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X-ray Mineralogy of the Parachute Creek
Member, Green River Formation, in the
Northern Piceance Creek Basin, Colorado

   

   

          

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X-ray Mineralogy of the Parachute Creek
Member, Green River Formation, in the

Northern Piceance Creek Basin, Colorado
By DONALD A. BROBST and JERRY D. TUCKER

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 803

A study of oil shale, marlstone, and tuff,
some containing dawsonite,
in three exposed sections

 

 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1973

 

 

UNITED STATES DEPARTMENT OF THE INTERIOR

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY

V. E. McKelvey, Director

Library of Congress catalog-card No. 73-600120

 

 

 

For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, DC. 20402 — Price $1.00 domestic postpaid or 75 cents GPO Bookstore
Stock Number 2401-00336

—+

 

 

 

CONTENTS

 

 

Abstract
Introduction
Piceance Creek basin
Lithologic terms
Tertiary stratigraphy
Older Tertiary rocks -----------------------
Wasatch Formation -------

Green River Formation ------------------
Douglas Creek Member ----------

Garden Gulch Member

Anvil Points Member ----------

Parachute Creek Member ------

Evacuation Creek Member ----------------------------------

Measured sections
Pipeline section
Lower Piceance Creek section -------------------------------------------

Rio Blanco section
Mineral composition --
Laboratory work
Procedures
Discussion

Oil shale and marlstone -------------------------------------------------
Vertical variation in composition -----------------------------
Fossiliferous oil shale and marlstone, pipeline

section --

 

 

 

 

  
 
 
  
 
  

 

 

 

 

 

 

 

 

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mammmmspshswwww

 

Mineral composition—Continued
Oil shale and marlstone—Continued
Vertical variation in composition—Continued
Marlstone and medium-brown oil shale, pipe-
line section ------------------------------------------------------
Oil shale from the Mahogany ledge, lower Pi-
ceance Creek section -------------------------------------
Massive marlstone from the Mahogany ledge,
lower Piceance Creek section ----------------------
Marlstone and laminated oil shale from the
Mahogany ledge, Rio Blanco section ---------
Lateral variation in composition ----------------------
Medium—brown oil shale, pipeline section --------
Dark, pyritic oil shale, Rio Blanco section -------
Dawsonitic rocks
Vertical variation in composition -----------------------------
Dawsonitic, pyritic oil shale, lower Piceance
Creek road --------------------------------
Lateral variation in composition ------------------------------
Tuff beds
Sandstone dikes
Cavities
Sedimentation and diagenesis -------------------------------------------------
References cited

 

 

 

 

 

 

 

ILLUSTRATIONS

 

FIGURE 1. Index map of the Piceance Creek basin and adjacent areas
2. Diagram showing correlation of three measured secti

Formation in the Piceance Creek basin

 

ons of the Parachute Creek Member of the Green River

 

gauge:

Map showing location of the measured section

p—A
owes

. Map showing locations of parts of the measure

. Photograph showing the lower part of the Parachute

units
ledge in the lower Piceance Creek section ----------------------------
ed oil shale from the Mahogany ledge in the lower Piceance
Creek section, as expressed by X-ray peak height in chart units

(1 section of the ParachutelCreek Member on lower Piceance Creek
Creek Member on lower Piceance Creek -----------------------------------
. Photograph showing upper part of the Parachute Creek Member on lower Piceance Creek ------------ --
Diagram showing nomenclature used for the Parachute Creek Member on lower Piceance Creek --------------------------
of the Parachute Creek Member near Rio Blanco--------------------- -----
Diagram showing nomenclature used for the Parachute Creek Member in the Rio Blanco section
. Photograph of fossiliferous laminated oil shale and marlstone from the pipeline section -------------------------------------------
. Histograms showing mineral composition of fossiliferous laminated oil shale and marlstone from the pipeline

section, as expressed by X-ray peak height in chart
11. Photograph of laminated oil shale from the Mahogany
12. Histograms showing mineral composition of laminat

   
  

 

 

13. Histograms showing mineral composition of massive marlstone from the Mahogany ledge in the lower Piceance

Creek section, as expressed by X-ray peak height in chart units

 

14. Photograph of marlstone and laminated oil shale from the Mahogany ledge in the Rio Blanco section -------------------
15. Histograms showing mineral composition of marlstone and laminated oil shale from the Mahogany ledge in

the Rio Blanco section, as expressed by X-ray

peak height in chart units

 

16. Histograms showing lateral variation in mineral composnion of medium—brown 011 shale from the pipeline section,

as expressed by X-ray peak height in chart units

 

III

Page

Page

13
14
15
22
23
25
34

35
37

38

39
40

41

42

 

 

FIGURE 17.

18—21.

22.

TABLE 1.

4-11.

 

CONTENTS

Page

Histograms showing lateral variation in mineral composition of dark pyritic oil shale from the Rio Blanco
section, as expressed by X-ray peak height in chart units 43
Graphs showing:

18. Abundance of analcime, albite, and quartz as a function of abundance of dawsonite in samples from

 

 

 

 

 

the Parachute Creek Member 44

19. Ratios of silicon to aluminum and of silicon to aluminum plus sodium in analcime from 91 samples
with and without dawsonite, Parachute Creek Member 45

20. Abundance of albite as a function of abundance of analcime in samples containing dawsonite, Parachute
Creek Member 45

21. Abundance of albite as a function of abundance of analcime in oil shale and marlstone, Parachute
Creek Member 50

Histograms showing mineral composition of dawsonitic, pyritic oil shale along lower Piceance Creek road, as
expressed by X-ray peak height in chart unit“ 51

 

 

TABLES

 

 

 

 

 

 

 

 

 

 

Page
Two-theta position of X-ray peaks measured for use in tables of mineral composition of rocks in the Green
River Formation 26
. X-ray data, expressed by X-ray peak height in chart units, from grinding experiments on dawsonitic rocks
from the lower Piceance Creek section. A, Peak height variation with grinding time; B, Peak height varia—
tion with size fraction and grinding time 27
. Ranges of X-ray peak height in chart units from four replicate scans of test samples ------------------------------------------------ 28
Mineral composition, expressed by X-ray peak height in chart units:
4. Rocks in stratigraphic succession from the pipeline section 29
5. Rocks in stratigraphic succession from the lower Piceance Creek section 30
6. Rocks in stratigraphic succession from the Rio Blanco section 32
7. Oil shale and marlstone from the three measured sections 34
8. A sequence of marlstone and medium-brown oil shale from the pipeline section -------------------------------------------- 36
9. Fifty-four dawsonitic rocks exposed on lower Piceance Creek 44
10. The dawsonitic oil-shale zone at six localities along lower Piceance Creek 46
11. Seventy-four tuffs above and below the Mahogany marker 48

 

 

X-RAY MINERALOGY OF THE PARACHUTE CREEK MEMBER,
GREEN RIVER FORMATION,
IN THE NORTHERN PICEANCE CREEK BASIN, COLORADO

By DONALD A. BROBST and JERRY D. TUCKER

ABSTRACT

Mineralogy of the Parachute Creek Member of the Green River
Formation (Eocene age) was studied by X-ray diffraction analysis
of about 650 samples of oil shale, marlstone, and intercalated thin-
bedded altered tuff collected from three measured sections along
the pipeline on the Cathedral Bluffs and along upper and lower
Piceance Creek, Rio Blanco County, Colo. The measured sections
are described in detail to provide a framework for the discussion of
vertical and lateral variation in mineral composition and to pro-
vide study sections for stratigraphic and mineralogic correlation
of exposed rocks with rocks obtained from drill cores in the deeper
parts of the basin.

Mineral composition of the oil shale and marlstone (expressed in
relative abundance of the minerals as a function of X-ray peak
height) generally is various mixtures of dolomite, calcite, quartz,_
potassium feldspar, albite, analcime, illite, and pyrite. Dolomite is
abundant in most of the rocks. Calcite occurs in more samples and
in greater abundance above the Mahogany ledge than below it.
Quartz content varies within narrow limits. Potassium feldspar
occurs in more samples and in slightly greater abundance than al-
bite. Analcime occurs in most of the rocks but is slightly more
abundant in rich oil shale than in marlstone. Small amounts of
illitic clay are common. Pyrite is a common accessory mineral that
is more abundant in rirh oil shale than in lean oil shale and
marlstone.

Dawsonite (NaA. 4,2003), of interest as a potential source of
aluminum and, prior to 1966 reported only from beds at depth in
the basin, was found disseminated in oil shale exposed below the
Mahogany ledge on lower Piceance Creek. The dawsonitic oil
shale contains considerably less analcime, dolomite, and calcite,
slightly less feldspar, about the same amount of illite, and more
quartz than oil shale that does not contain dawsonite. The
relations of analcime, dawsonite, and quartz in the exposed rocks
suggest that some dawsonite formed diagenetically from

. analcime. A zone of dawsonitic oil shale about 45 feet thick at its
emergence from the subsurface on lower Piceance Creek wedges
out about 1.5 miles to the north (shoreward).

Samples of oil shale and marlstone obtained with the use of a
dental drill from single laminae and groups of laminae a few
millimeters thick indicate a greater vertical variation in the com-
position than is indicated by composite samples from thicker in
tervals of the same rock. A unit of oil shale and marlstone about 1
meter thick has laminae containing more dolomite than calcite
that alternate with laminae containing more calcite than
dolomite. Changes in predominance of dolomite or calcite ap-
parently do not correlate with any obvious feature of the rock.

Tuff beds are abundant; many are less than 1 inch thick, but a
few are more than 1 foot thick. The beds weather creamy yellow or
orange brown and commonly form reentrants. The major

 

constituents of 74 tuffs studied were analcime, quartz, potassium
feldspar, and albite. Less abundant constituents were dolomite,
calcite, biotite, and illitic and chloritic clays. Dawsonite was
detected in four tuffs along lower Piceance Creek. The abundance
of volcanic material delivered to the basin seems to have in-
creased after deposition of the rocks in the Mahogany ledge.

Richly organic carbonate rock, with its small suite of constituent
minerals, that forms most of the Parachute Creek Member is con-
sidered to be the product of sedimentation and diagenesis in a
stratified lake containing fresh (or fresher) water at the top,
alkaline water at the bottom, and, at least occasionally, a zone of
mixed water in between. The lake waters were carbonated from
some decay of the organic matter. Most of the original sediment de—
livered to the basin yielded its constituents to form authigenic
minerals.

INTRODUCTION

Large deposits of oil shale and saline minerals in
the Green River Formation in adjacent parts of
Colorado, Wyoming, and Utah have drawn much
attention since Hayden (1869, p. 90) first described
these rocks of Eocene age along the Green River west
of Rock Springs, Wyo. Subsequent study has shown
that the formation is principally a sequence of com-
plexly related lacustrine deposits that is widely pre-
served in four basins (fig. 1): the Green River Basin
(Bradley, 1964; Culbertson, 1961, 1962, 1965); the Wa-
shakie Basin (Roehler, 1969); the Uinta Basin (Brad-
ley, 1931; Cashion, 1967); and the Piceance Creek
basin (Bradley, 1931; Donnell, 1961). Oil shale occurs
in all the basins but is most abundant and of high-
est grade in the Piceance Creek basin. Saline deposits
vary from basin to basin and include great com-
mercial deposits of trona (Na2CO'3-NaHC03-2H20)
in the Green River Basin, Wyo. (Culbertson, 1966;
Bradley and Eugster, 1969), and large resources of
nahcolite (NaHCOa) and dawsonite (NaAl(OH)2C03)
in the Piceance Creek basin, Colorado (Hite and
Dyni, 1967). Until recently, dawsonite was con-
sidered to be a rare mineral (Smith and Milton, 1966);
but its discovery in large amounts in the Piceance
Creek basin makes it of especial interest as a
potential source of aluminum, and research into its
origin, occurrence, and distribution has been
stimulated.

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

108°
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Piceance
Creek
basin _ 40o

 
 

Boundary of
area in large—

  
 
 
 
 

 

. Areas underlain by rocks of
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Grand Junction 0 39a

0 10 20 30 M LES
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FIGURE 1.-Index map of ‘the Piceance Creek basin and adj acent. areas.

 

 

PICEANCE CREEK BASIN 3

This report presents and discusses the data ob-
tained from an X-ray diffraction study of the
mineralogy of about 650 samples of rock, chiefly oil
shale, marlstone, and altered tuff, collected from ex-
posures of the Parachute Creek Member of the Green
River Formation on the periphery of the Piceance
Creek basin, Colorado. Vertical and lateral variation
of the mineral composition of the rocks is sum-
marized in terms of relative abundance of the various
minerals. Dawsonitic rocks, before 1966 known only
in drill cores from the deeper parts of the basin, are
described from exposures along lower Piceance
Creek. This study suggests that dawsonite is a pro-
duct of the diagenetic alteration of analcime.

Samples examined in this study were collected
from three measured sections of the Parachute Creek
Member (fig. 1): (1) along the pipeline on Cathedral
Bluffs, on the west side of Piceance Creek basin; (2)
along lower Piceance Creek, on the north side of the
basin; and (3) along upper Piceance Creek west of Rio
Blanco, on the east side. The sections are described in
detail to provide a framework for the discussion of the
X-ray data and to provide study sections for strati-
graphic and mineralogic correlation between out-
crops and drill cores taken from the interior of the
basin. Stratigraphic correlations of units described
here with those described by other workers also are
suggested.

PICEANCE CREEK BASIN

Piceance Creek basin is a structural basin that lies
between the Colorado and White Rivers and is mostly
in Garfield and Rio Blanco Counties, northwestern
Colorado (fig. 1). The basin forms an extensive, some-
what dissected plateau of about 1,600 square miles
that rises to 4,000 feet above the surrounding coun-
try. Good exposures of the Green River Formation are
common in the steep slopes and cliffs on the
periphery of the plateau. The average altitude of the
plateau is greater than 7,000 feet, and the highest
altitude is 9,400 feet, along the crest of the spec-
tacular cliffs west of Rifle, on the southeast side of the
basin. From the rim, the land surface slopes gently
downward to the central part of the basin, which is
characterized by rolling hills. The vegetation of this
semiarid region is sparse and consists mostly of sage,
pinion, and juniper. The principal industry is cattle
raising; some gas is produced from the Piceance
Creek gas field. The nearest commercial centers are
Rifle, Grand Junction, Meeker, and Rangely (fig. 1).

LITHOLOGIC TERMS

The lithologic terms discussed below are used in
this report to describe the general character of the
rocks in the various formations and the more specific

 

character of the beds and groups of beds in the
measured sections. The definitions used here closely
follow those of Bradley (1931, p. 6—8), who discussed
and explained many of the terms that have become a
part of the standard vocabulary used to describe the
Green River Formation.

Claystone, siltstone, mudstone, and sandstone are
all defined by particle size according to the Went-
worth scale (Wentworth, 1922). Mudstone has the
appearance of a fine-grained rock and contains an in—
definite mixture of clay—, silt-, and sand-sized
particles.

“Marlstone” is used in the manner of Bradley
(1931, p. 7), who designated the term for rocks that
consist principally of mixtures of calcite and
dolomite and that have textures intermediate
between those of mudstone and limestone. In follow—
ing this European usage, he avoided the need for
cumbersome multiword terms and firmly established
the term “marlstone” for these lacustrine carbonate
rocks.

Claystone, siltstone, mudstone, and marlstone in
the Piceance Creek basin generally are massive rocks
that are homogeneous in color and texture or, more
commonly, are distinctly bedded or laminated. In-
dividual laminae differ in color and thickness but
generally are only a few millimeters, or more rarely a
few centimeters, thick.

“Shale” categorizes fissile rocks made up of clay-
sized particles that weather approximately along
bedding planes into thin flakes, chips, plates, and
wedge-shaped fragments. The term “shaly” is used to
describe mudstone, siltstone, Claystone, and marl-
stone that have incipient fissility that is not
developed sufficiently to permit the rock to be called a
“shale.” “Paper shale” is applied to finely laminated
Claystone, siltstone, mudstone, and marlstone that
tends to part along closely spaced bedding planes.
Bradley (1931, p. 7) described paper shales as con-
sisting of very thin laminae of nonfissile rock
separated from one another by excessively thin
laminae that are fissile.

Oil shale is a special problem. Rocks rich in organic
material, commonly called oil shale in the Green
River Formation, have long been recognized as being
neither oily nor shaly (Bradley, 1931, p. 7, and 1964, p.
A19; Donnell, 1961, p. 864; Jaffe, 1962, p. 2; Cashion,
1967, p. 24; Smith, 1969, p. 185). Most of the oil shale is
dolomitic marlstone having various amounts of
organic matter that was derived chiefly from algae,
aquatic organisms, waxy spores, and pollen grains.
This organic matter is only slightly soluble in
ordinary petroleum solvents, but a large part is con-
vertible to a petroleumlike substance by destructive

 

 

 

4 X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

distillation. The shale part of the term undoubtedly

refers to the papery structure observed in many

weathered outcrops. (See Bradley, 1931, pl. 4B.)
Discussions in the literature reveal that “oil shale”

is a well-established term with economic implications.

As early as 1927, the Department of the Interior ruled
that any shale that yields oil when distilled will be re-
garded under the general mining laws as oil shale
(Bradley, 1931, p. 7). Standards for the minimum
amount of extractable oil to qualify the rock as oil
shale have not been set. The term, therefore, has been
used more qualitatively than quantitatively.

In the rock descriptions in this report, the term “oil
shale” was applied to those marlstones estimated by
reason of their color and weight to contain more than
3 gallons of shale oil per ton of rock. Generally the
darker the color and the lighter the weight, the higher
the oil content. A series of four color modifiers for the
overall appearance of the rock was established with
the counsel of experienced colleagues and applied on
the outcrop to estimate broad ranges of oil content:
light brown (lean rock, probably less than 15 gal of
shale oil per ton of rock); medium to dark brown
(lower and upper values, respectively, of a range of
about 15—30 gal of shale oil per ton of rock); and dark
red brown (rich rock, probably more than 30 gal of
shale oil per ton of rock).

The distinction between the lowest grade of oil
shale and “ordinary” marlstone (the barren
marlstone indicated by some workers) is a subjective
decision. Most marlstones contain some organic
matter and probably will yield some shale oil on dis-
tillation. According to D. C. Duncan (oral commun.,
1970), Fischer assays of some “barren marlstones”
indicated the presence of at least 5 gallons of shale
oil. Color is not an infallible criterion, but it can be a
useful one.

“Tuff” is used to describe any bed that consists
largely of volcanic ash, regardless of the degree of
alteration. Most of these rocks are analcime rich.

Following the definition of Fahey (1962, p. 18), the
adjective “saline” is applied to those minerals that
have sodium occupying one or all of the cation
positions and that have the carbonate radical sup-
plying all or part of the negative charge.

TERTIARY STRATIGRAPHY
OLDER TERTIARY ROCKS
A structural basin in the Piceance Creek region
had formed by early Tertiary time after deposition of
the marine and continental rocks of the Cretaceous
Mesaverde group (Bradley, 1931; Donnell, 1961). A 5-
to 20-foot unit of conglomerate and coarse sandstone
of Paleocene(?) age was deposited along the east
margin of the basin. This unit has been correlated

 

with the Ohio Creek Conglomerate found in areas to
the south (Donnell, 1961, p. 843).
WASATCH FORMATION

The Atwell Gulch Member of the Wasatch
Formation conformably overlies the Paleocene(?)
conglomerate. This member is a sequence of brown
sandstone and somber-colored shale of Paleocene
and Eocene(?) age which presumably underlies the
entire basin, although it thins from 500 feet on the
east side, near Rifle, to a vanishing point on the
southwest side (Donnell, 1961, p. 844). The Ohio
Creek and the Atwell Gulch were mapped with the
overlying Eocene part of the Wasatch Formation by
Donnell (1961, p. 844, pl. 48).

The upper part of the Wasatch Formation, of early
Eocene age, consists chiefly of fluviatile rocks, in-
cluding large amounts of clay, shale, and lenticular
sandstone accompanied by lesser amounts of lime-
stone, coal, and black carbonaeceous shale (Donnell,
1961, p. 846). Most of the rocks are brightly colored;
various shades of red, green, yellow, and purple are
common, but dull brown, tan, and gray generally pre-
dominate in exposures along the north and west sides
of the basin. The maximum exposed thickness, 5,300
feet, is 10 miles northwest of Rifle, and from this
point the formation generally thins westward. The
base of the unit is indefinite because of a zone tran-
sitional with the underlying beds. The contact with
the overlying Green River Formati‘on is also tran-
sitional.

GREEN RIVER FORMATION

The Green River Formation (Hayden, 1869, p. 90)
consists of sandstone, siltstone, shale, and several
kinds of carbonate rocks, some of which contain
saline minerals and abundant organic matter.
Although the original thickness is unknown, at least
3,000 feet of these rocks was deposited in the laws-
trine environment that persisted in this area during
much of middle Eocene time (Donnell, 1961, p. 847).

In a detailed study of the Green River Formation,
Bradley (1931, p. 9) divided the unit in the eastern
Uinta Basin, Utah, and the Piceance Creek basin,
Colorado, into four members, from bottom to top: the
Douglas Creek, Garden Gulch, Parachute Creek, and
Evacuation Creek Members. Donnell (1953) proposed
the name Anvil Points Member for the eastern equi-
valents of the Douglas Creek and Garden Gulch
Members and part of the Parachute Creek Member
exposed on the west side of the basin.

DOUGLAS CREEK MEMBER
The Douglas Creek Member is composed of cross-
bedded ripple-marked sandstone, algal and os-
tracodal limestone, oolitic sandstone and limestone,

x.

 

 

 

PICEANCE CREEK BASIN 5

and small amounts of gray shale. Donnell (1961, p.
848-849) reported that the member attains a max-
imum thickness of 800 feet in the southwestern part
of the basin and that it forms a recognizable unit in
outcrops on the south and west sides of the basin.
Cashion (1969) mapped about 500 feet of the member
along Cathedral Bluffs in the. Black Cabin Gulch
quadrangle (fig. 1, vicinity of the pipeline section).
On the south side of the basin, between DeBeque and
Grand Valley, the Douglas Creek Member merges
laterally with the Anvil Points Member (Donnell,
1961, pl. 48). Duncan and Belser (1950) reported a thin
Douglas Creek Member in the subsurface as far
northeast as the Piceance Creek gas field. The
Douglas Creek Member conformably overlies the
Wasatch Formation and is conformably overlain by
the Garden Gulch Member.

GARDEN GU LCH MEMBER

The Garden Gulch Member contains much papery
clayey (illitic) shale and marlstone—generally,
though not entirely, barren of oil—as well as thin
beds of sandstone, oil-shale breccia, and ostracodal,
oolitic, and algal limestone (Donnell, 1961, p. 849).
This member crops out in steep slopes between the
brown and buff benches of the underlying Douglas
Creek Member and the steep white cliffs of the transi-
tionally overlying Parachute Creek Member. The
unit is 700 feet thick at its type locality in Garden
Gulch (secs. 7 and 8, T. 6 S., R. 96 W.; fig. 1), a small
tributary of Parachute Creek on the south side of the
basin. A few miles east of the type locality the Garden
Gulch Member merges laterally with the Anvil
Points Member. Donnell (1961, p. 850 and pl. 48)
mapped the member on the west and north sides of
the basin to an area along the White River between
Yellow and Piceance Creeks, where he, too, found
that it apparently merges laterally into the Anvil
Points Member.

ANVIL POINTS MEMBER

The Anvil Points Member (Donnell, 1953) is a
heterogeneous sequence of gray shale, gray and
brown sandstone, siltstone, algal and oolitic lime-
stone, and some marlstone containing little or no oil.
The member crops out in cliffs and benches on the
east side of the Piceance Creek basin from Parachute
Creek on the south to within a few miles west of
Piceance Creek on the north (Donnell, 1961, pl. 48).
The member does not extend as far basinward as the
Piceance Creek gas field. It is considered to be the
eastern equivalent of the Douglas Creek and Garden
Gulch Members and part of the Parachute Creek
Member as exposed on the west side of the basin, and

it is probably the equivalent of the delta and shore

 

facies that Bradley (1931, p. 14) described in the Gray
Hills, north of the Piceance Creek basin. The Anvil
Points Member attains its maximum thickness of
1,870 feet along upper Piceance Creek.

The member interfingers with the underlying
Wasatch Formation and the overlying Parachute
Creek Member. Donnell (1961, p. 852) chose the top of
the Anvil Points Member at “the base of a series of
low-grade oil shales and at the top of the uppermost
sandstone bed in a sequence of barren marlstone
alternating with gray and brown sandstone.” The
base of the Anvil Points Member is established on a
criterion for the top of the Wasatch, that is, at the top
of the uppermost red shale bed which is at least 10
feet thick (Donnell, 1961, p. 852).

PARACHUTE CREEK MEMBER

The hallmark of the Parachute Creek Member is oil
shale. Bradley (1931, p. 11) noted, “It contains all of
the large groups of rich beds, most of the individual
rich beds, and a large proportion of the low-grade oil
shale.” The saline facies as well are most abundant
in the Parachute Creek Member. Bradley described
the member in detail at its type locality along
Parachute Creek, on the south side of the Piceance
Creek basin. The member, much of which commonly
is exposed in precipitous cliffs, has been mapped all
around the periphery of the basin, where it generally
is 500 to about 1,000 feet thick. In the subsurface it is
thicker; Donnell (1961, p. 852) reported a thickness of
1,700 feet in sec. 31, T. 1 S., R. 96 W.

Bradley (1931, p. 11—13) divided the member at its
type locality into three parts—lower oil-shale group,
transitional beds, and upper oil-shale group—each of
which was defined on characteristics of the included
oil shale. Revision of these groups was made at the
1,230-foot-thick section at Glover Point (sec. 22, T. 6
S., R. 96 W.) by Duncan and Denson (1949) and
Donnell (1961, p. 854). Donnell and Blair (1970, p. 76)
divided the member into a series of rich zones of oil
shale (designated R) separated by lean zones
(designated L), each zone being numbered from the
base of the section. This system of division was found
particularly useful on lower Piceance Creek and in
the pipeline section.

The richest oil-shale sequence in the member has
been called the Mahogany ledge in the surface sec-
tions and the Mahogany zone in the subsurface sec-
tions. The name is derived from the red-brown
mahogany color of the rich oil shales (Bradley, 1931,
p. 23). The Mahogany ledge or zone has been traced
throughout the basin and locally exceeds 200 feet in
thickness. Donnell (1961, p. 856-857), in summariz-
ing the geology of the ledge, reported that the richest
oil-shale bed (the Mahogany bed) ranges in thick-

 

 

 

6 X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

ness from 3 to 10 feet. In the thickest parts of the bed
in the deepest parts of the basin the average oil
content is 55 gallons per ton of rock. Most of the base
of the ledge is marked by a wavy-bedded tuff that at-
tains a maximum thickness of 18 inches. A second
characteristic tuff about 2 inches thick lies 8-10 feet
higher in the section. An analcimized tuff, generally
3-6 inches thick, that lies 3-14 feet above the
Mahogany bed has been called the Mahogany
marker. These and several other key beds with in-
formal names are referred to in the descriptions of the
measured sections. 'On some cliffs, the bottom and
top of the Mahogany ledge are accentuated by reen-

trants, or grooves, formed by the more rapid erosion
of marlstone that contains only small amounts of
organic matter. These grooves have been referred to
informally as the A- and B-groove in the upper and
lower positions, respectively.

Many cavities are found in the rocks exposed below
the Mahogany ledge. The cavities range in largest
dimension from a few inches to several feet and
presumably were once filled with saline minerals,
probably mostly nahcolite.

The Parachute Creek Member is characterized by
abundant intercalated beds of tuff which rarely at-
tain a thickness of more than a few inches. Many are
less than 1 inch thick, but a few are several feet thick.
The thicker beds commonly contain fragments of the
enclosing rocks. Most of the tuffs are analcime rich,
and they weather yellow or orange brown and com-
monly form reentrants between marlstone and oil
shale in the outcrops. The contacts are smooth to
wavy (undulating), and the natures of the upper and
lower contacts may differ. Some beds are dis-
continuous and podlike, but the lateral persistence of
many beds is remarkable.

The base of the Parachute Creek Member generally
is placed where rocks rich in carbonate (and organic
matter) become predominant upward through a tran-
sition zone from illitic shale, typical of the Garden
Gulch Member, or from the interbedded shales, silt-
stones, and fine-grained sandstones, typical of the
Anvil Points Member.

Bradley (1931, p. 11, pl. 7) placed the top of the
Parachute Creek Member at its type locality at the

base of a soft limy yellow-brown sandstone. Donnell

(1961, p. 857) placed the top of the Parachute Creek
Member at the base of the lowest sandstone or silt-
stone bed 10 feet or more thick that occurs above the
uppermost bed of a sequence of designated key beds.
In the northern parts of the Piceance Creek basin,
beds of brown tuffaceous sandstone unconformably
overlie truncated beds of marlstone. Scour channels
several feet deep in marlstone were filled with brown

 

sand of the Evacuation Creek Member in some areas
along Piceance Creek.

EVACUATION CREEK MEMBER

The Evacuation Creek Member, the uppermost
lithologic unit of the Green River Formation, was
named by Bradley (1931, p. 14) for about 530 feet of
marlstone and some shale and sandy rocks exposed
along Evacuation Creek in the eastern Uinta Basin,
Utah. In the vicinity of lower Piceance Creek (Rio
Blanco County, Colo.), Bradley (1931, pl. 3, loc. 8) as-
signed at least 500 feet of marlstone and some oil
shale and sandy rocks to the Evacuation Creek
Member. These rocks, he said, were overlain by about
400 feet of predominantly sandy beds, which he
tentatively correlated with the Bridger Formation in
the Uinta Basin. In the Piceance Creek basin,
Donnell (1961, p. 857 and pl. 48) later mapped the 400
feet of predominantly sandy beds as the Evacuation
Creek Member and included the marlstone sequence
of Bradley’s Evacuation Creek in the Parachute
Creek Member (fig. 6). Donnell’s usage is followed in
this report.

Sandstone abundance increases upward in the sec-
tion. The sandstones are commonly tuffaceous, mas-
sive, brown, and medium to coarse grained. In-
dividual beds cannot be traced very far along the out-
crop. These sandstone beds probably formed as
stream deposits in the lake basin.

MEASURED SECTIONS

Three excellent exposures of the Parachute Creek
Member along the northern periphery of the Piceance
Creek basin (fig. 1) were measured in detail; these
were the pipeline section along the Cathedral Bluffs,

. the lower Piceance Creek section, and the Rio Blanco

section along upper Piceance Creek. The descriptions
include some information on correlations between
our work and the work of others in the area of these
sections, as well as some possible correlations
between our sections. N o correlations between sec-

! tions are expressed or implied by the numbered units

of sedimentary rocks and tuff beds or groups of tuff

ibeds, called zones in each of the sections. Numbers

were assigned to units consecutively from bottom to
top in each section. A comparison of the three
measured sections is shown in figure 2.

X-ray data on the mineral composition of the rocks
collected from the measured sections are shown in
tables and figures and are discussed in later parts of
this report. Sampled units in the measured sections
are designated by an asterisk, and samples in the
tables and figures are correspondingly numbered for
the units from which they came.

 

MEASURED SECTIONS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PIPELINE SECTION LOWER PICEANCE RIO BLANCO
Sec. 34,T. 28., CREEK SECTION SECTION
R. 100 W. Secs. 11, 14,and 15 Secs. 5 and 6,
T. l N., R. 97 W. T.4S.,R.94 W.
' 25 MILES ' 30 MILES '
\/\ \/\ Evacuation Creek Member
// I Parachute Creek Member
/ Tuffaceous Tuffszzone
sandstone 1
Tuff 230 Unit 219
Tuff zones
207—208
Tuffaceous
TUff 210 marlstone
117
Tuff 163 7 7 Tuff 74
137 177 59 Top of Mahogany ledge
13C 169 46 Mahogany marker
124— 16/ 43 Mahogany bed
110 232' Base of Mahogany ledge
109 132
130
R—6
D
83
—6
L—5 R D
70 D
R—5 62 Tuff 94 D q
/‘ Parachute Creek Member
L—4 48 B 87 Unit 1
’\
L-5 / /\/ Anvil Points Member
78
R—4 D
D
R—5
25 —Tuff49
Dawsonite Anvil Points 200 FEET
Ln?) /". Member
L-3 B 21
- Garden Gulch
Unltl L-4 Member 100
50
Garden Gulch
Member R-4 0
Unit 1
M

 

FIGURE 2.—Correlation of three measured sections of the Parachute Creek Member of the Green River Formation
in the Piceance Creek basin. Numbered units refer to units described in each measured section. D indicates
occurrence of dawsonite. Numbers prefixed by R and L refer to zones rich or lean in oil shale, as applied
by Donnell and Blair (1970).

8 X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

PIPELINE SECTION

A nearly complete 909-foot-thick section of the
Parachute Creek Member was measured along a bull-
dozed pipeline right-of-way up the west face of the
Cathedral Bluffs near the center of sec. 34, T. 2 S., R.
100 W., Rio Blanco County, Colo. The geology of this
area in the Black Cabin Gulch (71/2-min) quadrangle
was mapped by Cashion (1969). A lithologic section
accompanied by a histogram showing Fischer as-
says of oil content was compiled by Trudell, Beard,
and Smith (1970, fig. 5).

Access to the pipeline section from the west is by
the paved Douglas Pass road and its subsidiary un-
paved roads shown on the 71/2-minute White Coyote
Draw and Black Cabin Gulch quadrangles. From the
east, the top of the section is reached by about 20
miles of unpaved access road beginning at the
junction of the Ryan Gulch and Piceance Creek roads
and shown on the 71/2-minute Square-S, Wolf Ridge,
Yankee Gulch, and Black Cabin Gulch quadrangles.
Use of four-wheel-drive vehicles is necessary for
access from the west and is recommended for access
from the east.

The lower contact of the Parachute Creek Member
is gradational but is placed where the illitic clay
shale of the underlying Garden Gulch Member gives
way upward to the predominant marlstone of the
Parachute Creek. The contact of the Parachute Creek
with the overlying Evacuation Creek Member is not
exposed but probably lies in the rounded slopes
within about 25 feet of the top of the measured sec-
tion.

The lithic details of the section are given below,
and the mineral composition of 71 samples from the
section is shown in table 4.

Nearly complete section of the Parachute Creek Member of the
Green River Formation along the pipeline in the center of
sec. 34, T. 2 S., R. 100 W., Rio Blanco County, Colo.

[Section measured by D. A. Brobst, J. D. Tucker, and J. R. Dyni. * indicates
sample data in table 4]

Thickness
(feet)
Top of exposed section.
Parachute Creek Member (part):
*230. Tuff, analcimic and feldspathic; weathers yel—
low brown. (Yellow T 88 painted on face of

 

 

 

 

outcrop below the tuff.) -------------------------------------- 1.7
229. Marlstone, light-brown, and some light-brown
oil shale 22.0
*228. Tuff, analcimic .2
227. Oil shale, laminated, medium— to dark-brown---- 5.3
*226. Oil shale, dark-red-brown, pyritic; weathers blue
gray 1.3
225. Oil shale; mostly light to medium brown ----------- 15.2
*224. Oil shale, dark-red-brown, pyritic; weathers blue
gray 1.0
223, Oil shale, medium- to light-brown ------------------------ 10.5

 

Nearly complete section of the Parachute Creek Member of the
Green River Formation along the pipeline—Continued
Parachute Creek Member (part)—Continued
Thickness
(feet)

Tuff, analcimic, weathers light yellow orange~-— 0.1
Oil shale; mostly medium to dark red brown.

Samples 1—10, collected at 20-ft lateral inter-

vals from a bed 3.1 ft below top of unit, were

222.
221.

 

 

studied in detail (fig. 16) ------------------------------------- 11.7
220. Marlstone, light-brown ------------------------------------------- 1.6
219. Oil shale, medium- to dark-brown ------------------------ 1.6
*218. Oil shale, medium-brown. Sample is from 2.6
ft above base. Samples from 96.8-cm-thick se-
quence from lower part of unit were studied
in detail (table 8) -------------------------------------------------- 10.6
217. Oil shale, medium- to dark-brown, with tuff zone
consisting of 6 thin, discontinuous, poddy an-
alcimic tuffs. (Yellow T 85 painted below up—
permost tuff of zone.) ------------------------------------------ 4.9
216. Tuff; discontinuous pods; weathers dark rusty
brown .1
215. Oil shale, light-brown, and interbedded marl-
stonc 4.6
214. Oil shale, dark-red—brown, pyritic ------------------------- .6
213. Oil shale, light- to medium-brown; laminated
beds. Contained remains of turtle tentatively
identified as a species of Echmatemys by G.
Edward Lewis (written commun., 1967) ---------- 9.5
212. Tuff, analcimic; pods and undulating bed; weath-
ers rusty brown ---------------------------------------------------- .1
*211. Oil shale, dark-red-brown, laminated, pyritic;
weathers blue gray ---------------------------------------------- 2.1
210. Oil shale, medium-brown; contains 4 thin rusty
brown tuffs 3.9

 

209. Tuff; relatively continuous bed 14 in. thick and
discontinuous pods as much as 2 in. thick
and 3 in. long .1
Oil shale, medium— to dark-brown. (Yellow

streak painted on dark-brown bed about 3 ft

 

208.

 

 

 

 

 

 

above base.) 8.5
207. Tuff .02
206. Oil shale, medium-brown --------------------------------------- .3
205. Tuff .01
204. Oil shale, mediumvbrown --------------------------------------- .2
203. Tuff .02
202. Oil shale, dark-brown --------------------------------------------- 1.5
201. Tuff, dark-rust-brown --------------------------------------------- .1
200. Oil shale; mostly medium brown; some light

brown 7.4
199. Tuff; mostly continuous undulating bed with

some pods as much as 1 in. thick --------------------- .1
*198. Oil shale, dark-brown, pyritic; weathers blue .

gray 3.0
197. Oil shale, light-brown, and some light-brown

marlstone. Samples 350—364, from a 12.15—cm-

thick sequence, are fossiliferous rock studied

in detail (figs. 9, 10) --------------------------------------------- 6.2

196.
*195.

Oil shale, medium- to dark-brown ------------------------ 2.4
Oil shale, light— to medium-brown. Continuous
zone of fossil insects—‘many similar to those
described by Bradley (1931, p.49—51, pls. 26—
28)—begins here and extends upward for about
40 ft. Sample is light-brown oil shale. Base
is 158 ft above top of Mahogany ledge and
is correlated with unit 155 ft above Mahogany

MEASURED SECTIONS 9

Nearly complete section of the Parachute Creek Member of the
Green River Formation along the pipeline—Continued
Parachute Creek Member (part)——Continued

194.

193.

192
191.
190.

189.
188.

*187.

*186

185.
184.
183.

182.

181.

180.
179.
178.
177.

176.
175.
174.
173.
172.
171.
170.

169.
168.

167.
166.
165.
164.

*163.

*162.

161.
160.

159.

 

 

 

 

 

 

 

 

 

 

 

 

 

Thickness
(feet)

ledge (Bradley, 1931, pl. 8). (Yellow BG painted

on outcrop 10.5 ft above base.)----~--—--------—-------- 13.0
Oil shale, medium- to dark-brown, pyritic-«mm- 1.6
Oil shale, light-brown, with tuff pods near top

and base of unit --------------------------------------------------- 3.7
Oil shale, medium-brown ------ 6.4
Oil shale, dark-brown, pyritic ------------------------------- 1.2
Oil shale, light-brown, and marlstone; weathers

conchoidally 7.8
Oil shale, dark-brown; weathers to blue p1ates-- 2.3
Oil shale, light-brown, and light-brown marl-

stone 6.7
Tuff, analcimic; weathers rusty brown inside

and white outside ------------------------------------------------ .1
Oil shale, dark-brown. (Yellow 13 painted be-

low the bed.) 1.3
Marlstone, light-brown, soft, tuffaccous(?) 6.6
Marlstone, light-brown ------------------------------------------- .9
Tuff, light-brown, analcimic; weathers blocky--- .2
Marlstone, light-brown ------------------------------------------- 6.5
Tuff, analcimic, light-pink—brown; weathers

light orange; undulating base with some in-

clusions of oil shale --------------------------------------------- 1.7
Oil shale, medium~brown --------------------------------------- 1.2
Tuff, weathered; 1/2 in. thick ---------------------------------- .05
Marlstonv .2
Tuff, analcimic, light-pink-brown; weathers

light orange .5
Marlstone, light-brown ------------------------------------------- .2
Tuff .2
Marlstone, light-brown ------------------------------------------- .4
Tuff, analcimic; weathers rusty brown --------------- .4
Marlstone, light-brown to yellow-------------------------- 3.5
Oil shale, medium- to dark-brown; weathers

platy; lower 3 in. contains 2 tuffs, each about

1 in. thick 1.5
Oil shale, light-brown, and light-yellow

marlstone 6.5
Oil shale, medium- to dark-brown ------------------------ 12
Oil shale, light-brown, and light-brown marl-

stone 5.0
Tuff, analcimic; weathers rusty brown .6
Oil shale, light-brown-----------------------—---------—--------~- .6
Tuff, analcimic; white smooth top; undulating

base; weathers light orange brown ------------------ 2.2
Oil shale; light brown near base to dark brown

near top 2.0
Tuff zone. Two tuffs split by 6 in. of light-

brown marlstone. Sample is from upper part

of upper bed. About 82 ft above Mahogany

ledge. Possibly correlates with tuff of unit 74

in Rio Blanco section ------------------------------------------ 2.4
Oil shale, light-brown to dark-red-brown; dark

shale weathers blue gray. Sample is from dark-

red-brown zone near base ----------------------------------- 4.8
Tuff, analcimic .5
Oil shale, dark-brown; upper 1 foot has irregu-

larly scattered pods of tuff 6 in. thick and as

much as 2 ft long ------------------------------------------------- 3.4
Tuff zone, Three thin tuffs (in light-brown oil

shale): at base, 8 in. above base, and at top--- 1.0

 

Nearly complete section of the Parachute Creek Member of the
Green River Formation along the pipeline—Continued
Parachute Creek Member (part)——Continued

Thickness
(feet)
158. Oil shale, light-brown, and yellow marlstone---- 6.9
157. Tuff, analcimic, white; weathers rust brown.
(Yellow T 62 painted above bed.) ---------------------- .2
156. Oil shale, medium- to dark-brown; includes a
zone of tuff pods 1%; in. thick 2.3 ft above base
and 2 red-brown tuff beds 1 in. thick at 5.3

 

and 5.5 ft above the base ----------------------------------- 5.5
155. Tuff, analcimic; weathers rust brown ------------------ .1
154. Marlstone, yellow, silty ------------------------------------------ 1,0
153. Tuff, analcimic; 1%; in. thick- - - 8.5
152. Marlstone, yellow, silty ------------------------------------------ 1.0
151. Oil shale, light-brown; some carbonate pods 1/2
in. thick and a few inches long ------------------------- 8.5
*150. Tuff, analcimic, dark-brown; weathers light
brown; sharp even contact at top; undulating
basal contact with relief of 2—3 in. Contains
many thin stringers of marlstone --------------------- 2.5
149 Oil shale, dark-red-brown -------------------------------------- 1.7

148. Tuff, analcimic, white; thickness varies from
0.2 to 0.4 ft; weathers blocky. (Yellow T 57
painted on outcrop above tuff)—- -3
*147. Oil 'shale; mostly dark red brown; some light
brown. Sample is dark-red-brown oil shale.
Contained a catfish skull of Ameriurus, Rhin-
eastes, or Pimelodus, as identified by D. H.

Dunkle (written commun., 1967) ----------------------- 5.1
*146. Tuff, analcimic; weathers light orange; persist-
ent bed, undulating contacts 0.4—1 ft thick ----- .5
145. Oil shale, dark-red-brown ----------- 1.7
144. Oil shale, light-brown, and some light-brown
marlstone; laminated ------------------------------------------ 4.7
143. Tuff; undulating contacts -------------------------------------- .02
*142. Oil shale, medium-brown, laminated. Sample is
from 2 ft above base -------------------------------------------- 2.6

141. Marlstone, light-brown; upper part contains
small pods of calcite. Zone of tuff pods 3 in.
long and 1%; in. thick 2.9 ft above base ------------- 4.1
*140. Oil shale, medium-brown. Sample is from 2.4
ft above base. (Yellow 11A3 painted on out-
crop.) 2.7
139. Oil shale, light-brown, and marlstone. 1.5 ft
above base is 2.2-ft-thick zone of tuff consist-
ing of 6 discontinuous layers of tuff pods 1
in. across and M; in. thick that is interbedded

 

 

with oil shale 6.7
138. Oil shale, dark-brown, and 3 thin tuffs at 1.2,
1.5, and 1.9 ft above base ----------------------------------- 1.9

*137. Marlstone, light brown. Marlstone sample is

from 10.6 ft above base. 8.6 ft above base is

zone 1.2 ft thick that contains pods of siliceous
material. Probable position of the A-grooven- 14.8

136. Oil shale, dark-brown; weathers blocky and blue

gray. Contains 10 thin beds of tuff in lower

4 ft. Sample is oil shale at top of unit. Top

of the Mahogany ledge. (Yellow 10 painted on

 

 

outcrop.) 9.1
135. Oil shale, dark-brown; fissile in lowermost 0.5

ft; weathers blue gray ......................................... 2_0
134. Tuff . .25
133. Oil shale, dark-brown; weathers blue gray --------- 1.5
132- Tuff; thin bed with undulating contacts---—--—--—- ,1

 

 

10

X—RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

Nearly complete section of the Parachute Creek Member of the
Green River Formation along the pipeline—Continued

Parachute Creek Member (part)-—Continued

131.
*130.

129.
128.

127.
126.
125.
*124.

123.
122.

121.
120.
119.

118.

*117.

116.
115.
114.
113.
112.

*111.

*110.

*109.

*108.

107.
106.
105.

104.
103.

102.
101.
100.

98.
97.
*96.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Thickness
(feet)
Oil shale, dark-brown 7.0
Tuff, gray, evenly bedded. The Mahogany
marker .5
Oil shale, medium- to light-brown. 3.8 ft above
base is 0.3 ft of contorted papery shale ---------- 8.5
Tuff, analcimic; persistent bed 0.1—0.4 ft tlfick
with smooth top and undulating base4--------—--- .2
Oil shale, dark-red-brown -------------------------------------- .95
Tuff .05
Oil shale, dark-red-brown -------------------------------------- 1.8
Oil shale, very dark red brown. The Mahogany
bed 1.9
Oil shale, medium- to dark-red-brown ---------- 2.0
Tuff, analcimic, brown; even contacts; persis-
tent .1
Oil shale, light- to dark-brown-------------~---------------- 10.3
Tuff .05
Oil shale, light- to dark-brown; weathers blue
gray 3.2
Tuff zone. Four tuffs; persistent beds 144/2 in.
thick, separated by 1/2—1 in. of oil shale. (Yellow
horizontal line painted on outcrop.)----------------- .4
Oil shale, medium- to dark-red-brown; weathers
blue gray. Sample is medium-brown oil shale
5.8 ft above base 13.8
Tuff, analcimic; wavy contacts~-——-------------—--------~- .1
Oil shale; contains thin tuff in upper 0.5 ft--—----- 3.7
Tuff, analcimic; 1/2 in. thick; persistent bed -------- .05
Oil shale 1.1
Tuff, analcimic, laterally persistent; smooth
contacts .3
Oil shale, medium- to dark-brown. Sample is
dark brown 10.9
Tuff, analcimic, light-yellow-gray; fragmental
appearance; very fine grained. Base of the
Mahogany ledge -------------------------------------------------- 2.1
Marlstone, gray-orange, laminated, soft; weath-
ers to slabby fragments; slope former; some
interbedded oil shale. At 17.4 ft above base,
cavities 1 ft in diameter along a persistent
zone possibly mark a saline zone. At 25 ft
above base is tuff 0.1—0.4 ft thick, lenticular.
Sample is medium-brown oil shale 17.4 ft
above base. Position of the B-groove 26.5
Oil shale, burned (‘1), soft, punky, crumbly. Top
of R6 zone 4.0
Tuff, analcimic, pink ---------- r ----------------------------------- .15
Oil shale .5
Tuff, analcimic; weathers reddish; wavy base;
smooth upper contact ------------------------------------------ .15
Oil shale 1.7
Tuff; weathers red brown; even contacts. (Paint- .

. ed yellow 36 on outcrop.) ------------------------------------ .25
Oil shale 4.3
Tuff; irregular contacts; poorly exposed-—*—-¢--------- .2
Oil shale, light-brown; weathers to fissile plates 2.4

. Oil shale; upper 0.5 ft contains cavities caused
by leached saline minerals(?) ---------------------------- 1.5
Tuff .05
Oil shale, light-brown; weathers to fissile plates 1.2
Tuff, analcimic; persistent bed, regular contacts. .05

 

Nearly Complete section of the Parachute Creek Member of the
Green River Formation along the pipeline—Continued

Parachute Creek Member (part)—Continued

95
94
‘93

*92.
91.

90.
89.

88.

*87.

*86.

85.

*84.

83.
82.
81.
80.
79.
78.

*77.
*76.

75.
74.

*73.

*72.

71.

70.
69.

68.

67.

  

 
 

 

 

 

 

Thickness
(feet)
. Oil shale, light-brown, fissile-mm- - ----- 2.7
. Tuff; irregular contacts ----------------- .15
. Oil shale, gray-brown, platy 7.5
Tuff, analcimic; weathers bright pink; persist-
ent bed; smooth contacts-----------------------—------------ .5
Oil shale, gray-brown, fissile 5.5
Tuff; weathers yellow ------------------------------------------ .6
Oil shale, dark-brown; weathers light yellow
brown, fissile to platy 10.9
Tuff, analcimic; weathers reddish brown. (Black
T 29 painted on outcrop.) .06
Oil shale, light- to dark-brown; weathers soft;
platy to subfissile. Sample is medium-brown
oil shale 26.5 ft above base------~-----------------—----- 33.8
Tuff analcimic; weathers red brown; persistent;
smooth contacts -~ .2
Oil shale. Lowermost 10 in. extremely weath-
ered and contorted, possibly marks a saline
zone. (Yellow 9 painted on slab of rock.) --------- 8.1
Oil shale, light-brown, marlstone. Partly con-
cealed. Some blue-gray-weathering oil shales
2—4 in. thick. (At 21.2 ft above base is black
44 painted on rock.) Sample is light-brown oil
Shale 19 ft above base ---------------------------------------- 39.3
Oil shale, with cavities as much as 0.4 ft in dia-
meter. Laterally persistent. Base of R—6 zone— 1.0
Marlstone, light-brown. Top of L—5 zone ------------ 1.0
Tuff .05
Marlstone, light-brown; has cavities 3.0 ft above
base 8.3
Marlstone, light-brown; contains cavities and
contorted beds, probably a solution breccia-n- 1.5
Tuff, light-gray; laterally persistent bed-----------—- .1
Marlstone, light-brown, tuffaceous 3.7
Marlstone, light-orangebrown; brecciated bed;
laterally continuous; many crystal cavities;
honeycomb structures. Sample is brecciated
marlstone .7
Marlstone, light-brown; weathers to brittle slabs 8.7
Oil shale, light-brown; weathers platy; solution
cavities as much as 1 ft in diameter are ir-
regularly distributed through unit--—----------~--~- 2.0
Marlstone, light-brown; weathers yellow, slab-
by. Sample is from 0.5 ft above base --------------- 16.4
Tuff, feldspathic, fine-grained; a distinctive >
white .3
Marlstone weathers light yellow orange; slab-
by; some light-brown oil shale. Several small
cavities from leached saline (?) minerals at
10.1 ft above base. Partly covered--------—-—--—--—-- 12.4
Tuff. Base of L—5 zone~~~ .1
Oil shale, light-brown; weathers blocky. (This
unit near a green and white metal fence post
and a wooden stake is marked 1%: on the pipe-
line right-of—way.) Top of R-5 zone-—----«-—-~~-—-— 40
Oil shale, medium- to dark-brown; weathers blue
gray; top is a sharp break with overlying unit.
Cavities 6-10 in. in maximum dimension
caused by leached saline minerals; broken
paper-thin brown septa-------—~-—---——-—~—-—~--—-—-— 2.4
Oil shale, light-brown; weathers blocky—--—-—~---- 5.3

 

Nearly complete section of the Parachute Creek Member of the

MEASURED SECTIONS 1 1

Green River Formation along the pipeline—Continued

Parachute Creek Member (part)—Continued Thickness
(feet)
66. Tuff 0.1
65. Oil shale 1.0
64. Tuff .1
*63. Oil shale, dark-brown; weathers blue gray; Brec-

62.

*61

60.
59.
58.

*57 .

56.

55.

*54.
53.
52.
51.
50.

. Marlstone, light-brown-gray; weathers slabby to

*48.

47.

*46.

45.

*44.

*43.

*42.

 

 

 

ciated. Cavities to 6 in. in maximum dimen-
sion caused by leached saline minerals. Heavy
films of hydrocarbon material along bedding
planes. Samples are dolomitic septum from
cavity and dark-brown oil shale-mm-
Oil shale. Base of R—5 zone -----------------------------------
Tuff, feldspathic; smooth contacts top and base;
laterally persistent. Top of L—4 zone ----------------
Marlstone, light-brovVn; weathers yellow ------------
Oil shale, light-brown----------------------—---------------------
Tuff zone. Five tuffs 71—1/2 in. thick with small
inclusions of oil shale. Tuffs interbedded with
oil shale
Oil shale, light-yellow-brown to light-brown-
gray; weathers platy and blocky in alternate
layers. Sample is from 1 ft below top---------------
Tuff, analcimic; laterally persistent; undulating
upper contact; basal contact irregular; inter-
fingers with underlying oil shale ----------------------
Oil shale, light-yellow-brown to light-brown-
gray; weathers platy and blocky in alternate
layers
Tuff, analcimic; laterally persistent; undulating
contacts
Marlstone, light-brown-gray; weathers platy to
blocky
Tuff
Marlstonv
Tuff

  

 

 

 

 

 

 

 

 

blocky
Tuff, analcimic; weathers orange brown; sandy
textured; lower contact smooth, upper contact
undulating. Base of L—4 zone ----------------------------
Oil shale, light-brown; weathers slabby. Top of
R—4 zone
Oil shale, dark-brown to red-brown; weathers
blue gray. Locally, beds are contorted and
have secondary coatings and pods of dolo-
mite. Possibly marks a zone leached of saline
minerals. Sample is dark-brown oil shale.
(Near top of unit is black 340 painted on out-
crop.) ‘
Marlstone, gray; hackly fracture -------------------------
Tuff, analcimic; weathers bright orange; lat-
erally continuous bed ------------------------------------------
Oil shale, light-brown, and some alternate lay-
ers of dark-brown oil shale a few inches thick.
Scattered gar-pike scales. Dark beds weather
blue gray. Unit weathers blocky in lower part,
platy in upper part. Several thin tuffs less
than 1A in. thick in upper 1.5 ft. Sample is
interlayered light- and dark-brown oil shale
from uppermost 1 ft. (Black 360 painted on rock
3 ft above base.) ---------------------------------------------------
Tuff zone. Uppermost tuff is 0.1 ft thick, anal-
cimic; has wavy lower contact, smooth upper

 

 

1.0
5.1

2.4
7.0

1.8

8.9

.15

8.8

3.5
.02

.04

5.9

2.8

1.2
6.2

13.6

 

Nearly complete section of the Parachute Creek Member of the
Green River Formation along the pipeline—Continued
Parachute Creek Member (part)—Continued ”301275288

22
contact. Lower 0.4 ft of unit contains 3 tuff
beds 1/ 16—1/8 in. thick about 1/2 in. apart sep-
arated by dark-brown oil shale. (Yellow square
painted on outcrop above tuff zone, and yellow
T—13 painted on outcrop face 3 ft above tuff

 

zone.) 0.5
41. Oil shale, medium- to dark-brown; weathers
mostly blue gray. Some gar-pike scales ----------- 9.7

*40. Tuff zone. Uppermost 0.6 ft consists of tuff (75
percent) and many platy inclusions of oil shale
(25 percent). Upper and lower contacts smooth.
Light-brown blocky-weathering oil shale 0.8
ft thick above lowermost tuff and 1A1 in. thick
at base of unit. Sample is lowermost tuff, dol-
omitic 1.42
*39. Oil shale, medium- to dark-brown; weathers blue
gray. Contains pods of dolomite that weather
light brown. Sample is medium-brown oil

 

 

shale from base of unit --------------------------------------- 3.5
38. Oil shale, light- to medium-brown, and some
gray marlstone --------------------------------------------------- 11.8
*37. Tuff, analcimic, evenly bedded; smooth contacts
at top and bottom ------------------------------------------------ .15
36. Oil shale 2.6

35. Tuff zone. Two tuffs. Lower is ”/8 in. thick, upper
is 1/8 in. thick; separated by ‘A in. light-brown
oil shale .06

*34. Oil shale; weathers gray; conchoidal fracture;
dark specks of organic matter. Sample is from
1 ft above base ----------------------------------------------------- 5.0
*33. Tuff, analcimic; weathers yellow; fine-grained;
undulating contacts. Intertongues with enclos-
ing oil shale. (Yellow T 9 painted on outcrop.)— 1.2

 

 

 

32. Oil shale 3.0
*31. Tuff, analcimic. (Yellow circle painted on out-

crop.) .08
30. Oil shale 17.7
*29. Tuff, analcimic, lenticular; discontinuous pods

as much as 1 in. thick ----------------------------------------- .08

*28. Oil shale, light- to medium-brown; contains dis-
seminated nodules of dolomite as much as 1
in. in diameter. Some beds of light-gray-brown
marlstone 0.1—2 ft thick. Sample is light-brown

oil shale 26.8 ft above base -------------------------------- 28.0
*27. Oil shale, light-brown; weathers blocky; contains
5—6 in. long and 3—4 in. thick of dolomite that
weathers white. Sample is from dolomitic pod.

(Black 450 painted at base of unit.) ------------------ 3.5

26. Oil shale, dark-brown; weathers blue gray --------- 1.0
*25. Oil shale, light- to medium-brown, fissile, and
blocky marlstone. Contact with overlying unit
is sharp. Sample is medium—brown oil shale

4 ft above base. Base of R—4 zone --------------------- 23.7
24. Marlstone, medium-brown; weathers blocky; con-
tains flakes of carbonaceous matter and pods

with iron-stained rims. Top of L—3 zone. --------- 3.5
23. Oil shale, gray-brown, fissile. Top 1 in. is ostra-
codal dolomite ------------------------------------------------------ 3.6

*22. Marlstone, light-brown. Intraformational con-
glomerate at base contains broken, flat, an-
gular fragments of carbonate rock. About 0.4

 

 

12

Nearly complete section of the Parachute Creek Member of the
Green River Formation along the pipeline—Continued
Parachute Creek Member (part)—Continued Thickness

_ _ (feet)
ft above is mass1ve bed of marlstone w1th

stringers and clusters of pyrite perpendicular
to bed. Above the pyritic part of unit are thin
pods of dolomite parallel to beds. Sample is
pyritic marlstone ~~
Marlstone, light-brown--—-----—-----»—~------------------------
Oil shale, light-brown; weathers gray; contains
lenticular tuffaceous marlstone as much as 1
in. thick. Marlstone sampled at 8.3 ft above
base
Marlstone, medium- to dark-brown
Marlstone, tuffaceous 1/2—1 in. thick ---------------------
Marlstone, light-yellow-brown, laminated; weath-
ers white. (2.5 ft below top is black 510 painted
on outcrop.)
Oil shale, medium-brown, fissile. Middle of unit
contains tuff zone 4, consisting of 3 tuffs 1A1
in. thick
Marlstone, yellow-brown; weathers white; blocky
Marlstone, light-brown; weathers gray; conchoi-
dal fracture; disseminated specks of limonite.
Samples from top of unit and 0.6 ft above base
are distinctive 1—in. and IA—in. dolomite-rich
beds that resemble tuffs --------------------------------
Tuff, analcimic
Marlstone, light-brown; weathers gray; concho-
idal fracture
Marlstone, light-brown; weathers white; blocky
Marlstone, light-brown; light-gray band in mid-
dle
Marlstone, light-brown, blocky --------------
Marlstone, light-brown, fissile ~
. Marlstone, light-yellow-brown, well-laminated,
blocky
Oil shale, brown; black specks of carbon. Some
yellow beds of dolomite 1 in. thick at 3 ft and
6 ft above base. First significant oil shale in
section. Sample is oil shale about 3 ft above
base. (Yellow circle painted on outcrop at base
of unit.)
. Marlstone, green, dolomitic, dense; conchoidal
fracture
. Marlstone, light-brown; weathers white; blocky;
resistant
. Shale, dark-yellow-olive, fissile to subfissile ------
.‘ Marlstone, light-yellow-brown; weathers white;
blocky. (Yellow circle painted at base of unit.)
. Marlstone, dolomitic, light—green-gray. Contains
fish teeth. Base of good exposures and design-
ated base of Parachute Creek Member ------------
Incomplete thickness of Parachute Creek
Member (rounded) --------------------------------------- 909

1.6
21. 4.9

*20.

 

17.1
7

19. .
.08

*18.
17.

 

11.5
16.

 

2.6
15. 7.5

*14.

1.2
*13. .04

*12.

 

 

8.8
11. 5.8
10.

 

5.3
1.0

 

7.5

6.9

 

5.5

 

3.6
4.5

 

9.3

1.0

Garden Gulch Member (part):

*Shale and siltstone, poorly exposed; mostly light
yellow brown to dark brown; conchoidal frac-
ture common. Weathers to lighter brown frag-
ments. Shales weather to small soft fragments
easily crushed by hand. Illitic clay abundant.
Some calcite and (or) dolomite common, espe-
cially near top; these carbonate beds increase

 

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

Nearly complete section of the Parachute Creek Member of the
Green River Formation along the pipeline—Continued
Garden Gulch Member (part)—Continued

Thickness
(feet)

in abundance upward and mark a transition
to rocks of the overlying member.

Sample of brown silty shale, taken about
60 ft below top of unit, is considered repre-
sentative of many beds in the upper part of
the member.

(Base of unit is in the cut bank along pipe-
line right-of-way about 200 ft uphill from in-
tersection of access road and pipeline. Yellow
I painted on trunk of pine tree just above cut

 

 

bank.) 90.0
Incomplete thickness of Garden Gulch
Member 90.0

LOWER PICEANCE CREEK SECTION

A complete section of the Parachute Creek Member
(1,185 ft) is exposed in the cliffs along lower Piceance
Creek in sections 11, 14, and 15, T. 1 N., R. 97 W., Rio
Blanco County, Colo. The area lies in parts of the
White River City and Barcus Creek SE 71/2-minute
quadrangles.

The base of the section is on the hill west of
Piceance Creek road 2.4 miles south of its junction
with Colorado Highway 64. Locations of the parts of
the section are shown in figure 3.

The base of the section is not well exposed but lies
in a transition zone between the predominantly clay
(illitic) Shales of the Garden Gulch Member below
and the carbonate-rich rocks of the Parachute Creek
Member above. The contact, placed where carbonate-
rich rocks become the predominant rock type, is
shown in figure 4. The top of the section has good ex-
posures of the upper part of the Parachute Creek
Member and the lower part of the overlying sandy
beds of the Evacuation Creek Member (fig. 5).

The mineral composition of 135 samples from this
section is given in table 5 and is discussed in detail
later. Rocks in this section are of especial interest
because they contain dawsonite. The lithic details of
this section follow.

Complete section of the Parachute Creek Member of the Green

River Formation along lower Piceance Creek in secs. 11,14, and
15, T. 1 N., R. .97 W., Rio Blanco County, Col .

[Section measured by D. A. Brobst and J. D. Tucker
tance of J. R. Dyni in 1966 and collaboration
in 1970. * indicates sample data in table 5]

with

Thickness
Evacuation Creek Member (part): (feet)
*Sandstone, tuffaceous, brown, fine to very fine
grained; lower contact unconformable. Base
of member (fig. 5). Two samples. (Yellow E
painted on rock at base of unit.)l-~--—----Unmeasured

Parachute Creek Member :

233. Marlstone, light-brown; weathers slabby and

platy
*232. Oil shale, dark-red-brown, pyritic -----------------------

 

5.0
.3

Complete section of the Parachute Creek Member of the Green

MEASURED SECTIONS

River Formation along lower Piceance Creek—Continued

Parachute Creek Member—Continued

231.

*230.

229.

*228.

*227.
*226.

225.

224.

223.

222.

221.
*220.

*219.

218.

217.

216.
215.

*214.

213.
212.
211.
210.
209.

208.

*207.

Marlstone, light-brown; weathers slabby and
platy. Partly covered -----------------------------------------
Oil shale, dark-red-brown, pyritic; weathers blue
gray and platy. Two samples
Marlstone, light-brown; weathers platy and slab-
by; forms ledges along the hill slopes --------------
Oil shales; mostly light brown; some medium
brown
Tuff, analcimic, gray; undulating contacts-—--—-
Oil shale, light-brown; contorted zone; some pods
of tuffaceous material. Sample is tuff --------------
Oil shale, medium-brown; weathers to thin
plates
Tuff, undulating contacts; pods as much as 6
in. thick
Oil shale, light- to medium-brown; weathers to
thin plates
Marlstone, thick-bedded, and some light-brown
oil shale near top. (Yellow X painted on rocks
near base of exposure.) ---------------------------------------
Section offset into next gully to , north.
Units 222—233 measured in second most
southerly gully which has exposures of
uppermost white-weathering zone.
Marlstone, light-brown; exposures p00r--------
Oil shale, medium- to dark-brown. Samples are
dark-brown oil shale at base of unit and med-
ium-brown oil shale 10 ft above base --------------
Marlstone, light-brown with thin protruding
ledges of very fine grained tuffaceous sand-
stone. Poorly exposed. Sample is tuffaceous
sandstone 15 ft above base --------------------------------
Sandstone, very fine grained; has organic de-
bris and rusty pinhead spots ----------------------------
Marlstone, brown; weathers platy; poorly ex-
posed. Base of a distinctly brown weather-
ing unit
Section offset to north.
Marlstone; poorly exposed -------------------------------------
Oil shale, light- to medium-brown, and white
marlstone; unit poorly exposed ------------------------
Limestone, white, crystalline, dolomitic; many
crystal cavities caused by removal of gyp-
sum(?). About 160 ft below top of member
and 240 ft above top of Mahogany ledge. Des-
cribed by Donnell (1961, p. 857)
Marlstone, light-brown; weathers platy and
slabby
Marlstone, light-brown; a massive bed ----—----
Marlstone; weathers to thin plates ----------------------
Marlstone, light-brown; massive bed; weathers
orange brown
Oil shale, medium- to dark-brown; weathers
platy
Tuff zone. Five thin tuff beds alternating with
light-brown oil shales. Poorly exposed. About
215 ft above top of Mahogany ledge. (Yellow
T 5 painted on marlstone above unit.)---—-—-—--——-
Tuff, analcimic; weathers rusty brown; weath-
ers to prominent reentrant on slopes -—---—----—-

 

 

 

 

 

 

 

 

Thickness

(feet)

12.0

9.0

12.0

2.0

2.6

6.0

6.0

10.0

11.0

29.0

12.0

13.0

30.0

1.0
15.0
2.0
5.0
2.4

2.4

3.5

1.0

 

108°15’

 

l

 

%

5 733

    

 

9%»

RCUS CREEK SE QUADRANG

WHITE RIVER CITY QUADRANGLE

(D

,_..

m

01
XBA

sopo

 

10

/ 1,3 Unit 1

  
  

/ /
V
/x

1/x

Units
113—119

/$ta 3X\' Base

   

5551.8. Bur. Mines cut

12

 

  
 
  
 

Viewpoint (fig. 4)

X Unit 119

\< Unit 133

Part of

15

Units 133—146X

 

Units 146—157lx
Units 178-195
X

l x—:Unit|s/lé5—2l7
l XUnits 217—222
I XLiDits 22é—233
l

Top of Parachute Creek Member

Mahogany ledge. Units 158—176

13

 

/
/

22 ‘ 23
/
/ l
5gigeazp|oint (fig.|5) (1) , , . .

 

.5
I

 

24

1M|LE -0
J

 

 

R97 W.

13

T.ZN.
T.lN.

40°
30”

FIGURE 3.—Locations of the measured section of the Parachute
Creek Member on lower Piceance Creek. Numbered units
refer to units described in the measured section. Station num-
bers refer to sample localities of data shown in table 10.

Complete section of the Parachute Creek Member of the Green
River Formation along lower Piceance Creek—Continued
Parachute Creek Member—Continued

Thickness

206. Oil shale, light- to medium-brown; weathers to

 

thick plates

205. Sandstone, light-brown, very fine grained --------
204. Oil shale, light-brown; intercalated with beds
of marlstone about 1A in. thick ----------------------

(feet)

4.6
.8

3.2

14 X—RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

 

FIGURE 4.—Lower part of the Parachute Creek Member on lower Piceance Creek. Lowercase letters refer to units of Bradley (1931,
pl. 4A). Numbers prefixed by R and L refer to zones rich or lean in oil shale. Numbers 14 and 113 refer to units described
in the measured section in this report. D marks the dawsonitic zone. X indicates the US. Bureau of Mines cut in the zone

of dawsonitic rocks. ng, Garden Gulch Member.

Complete section of the Parachute Creek Member of the Green
River Formation along lower Piceance Creek—Continued

 

  
 

 

  
 

Parachute Creek Member—Continued Thickness
(feet)
203. Oil shale; weathers platy-- --------------------------------- 1.0
*202. Tuff, analcimic, white to light-green; weathers
white with rusty spots- 1.5
201. Oil shale, medium-brown 3.0
200. Tuff, analcimic, yellow-brown- - .04
199. Oil shale, medium-brown; weathers to thin
plates 2.8
*198. Tuff, analcimic, light—yellow-brown, persistent;
weathers blocky --------------------------------------------------- .1
197. Oil shale, light—brown---- 10.0
196. Marlstone, light-brown» 23.0

*195. Oil shale, dark—brown; weathers platy, blue
gray 1.0
Section offset to north along this bed. Units
195-178 measured in gully that has a large
sandstone boulder at the mouth. Yellow
circle and UP painted on boulder
194. Marlstone; forms plate-covered slope ------------------- 6.0
193. Marlstone, light-brown; forms prominent ledge.

 

  

(Yellow 8A painted on ledge.) 3.0
192. Marlstone, light-brown; weathers white 2.7
*191. Oil shale, medium-brown ........................ 2 0

*190. Marlstone, light-brown, poorly exposed -------------- 11.0

 

Complete section of the Parachute Creek Member of the Green
River Formation along lower Piceance Creek—Continued
Parachute Creek Member—Continued Thickness
(feet)
*189. Marlstone, light-brown, and some tuffaceous
sandstone and sandy marlstone; unit poorly
exposed. Some mediumvbrown oil shale at base.
Samples are oil shale at base of unit; tufface-
ous sandstone 2.6, 3.6, and 5.6 ft above base;
and tuffaceous marlstone 7.6 ft above base-—— 165
*188. Marlstone; poorly exposed. Samples are tuff-
aceous marlstone 15 ft above base, light-yel-
low carbonaceous marlstone 21 ft above base,
and light-brown silty marlstone 0.4 ft below
top of unit 26.0
*187. Sandstone, red-brown, massive, tuffaceous,
very fine to medium-grained. Conspicuous
unit (fig. 5) 7.0
186. Marlstone, light-brown, and intercalated thin-
bedded red-brown sandstone. (Base about 85
ft above Mahogany ledge, but greater true
thickness of interval may be masked by slump-
ing.) 5.0
*185. Marlstone, light-brown, and some intercalated
light- to medium-brown oil shale. 15 ft below
top is tuffaceous carbonaceous siltstone and
very fine grained sandstone»-

 

 

 

 

MEASURED SECTIONS

 

FIGURE 5,—Upper part of the Parachute Creek Member on lower
section. Unit 187 is a distinctive sandstone. Interval between
brown. Tge, Evacuation Creek Member; Tgp. Parachute Creek

Complete section of the Parachute Creek Member of the Green
River Formation along lower Piceance Creek—Continued

 

 

 

 

 

 

 

Parachute Creek Member—Continued ”#75588
e
184. Oil shale, medium—brown 2.3
183, Oil shale, dark-brown; weathers blue gray. Over-
turned fold axis trends N.35°W., plunges 10°
NW .5
182. Marlstone,light-urown, weathers to brittle plates 11.7
181. Oil shale, medium-brown; weathers white---------- .4
180. Marlstone, light-brown ------------------------------------------ 16.1
179. Marlstone; weathers to brittle plates; poorly ex-
posed 5.5
178. Marlstone, light-brown; upper 1 foot has light-
brown oil shale 3.0
Section offset to north to good exposures
of Mahogany ledge.
*177. Marlstone, light-brown, and intercalated light-
brown oil shale 5 ft above base. Probable pos-
ition of the A-groove ------------------------------------------- 10-0
176. Oil shale, light- to dark-brown; lighter colors
increase upward. Top of the Mahogany ledge
(fig. 5) 5.0
*175. Tuff, analcimic, orange-brown; smooth lower
contact; undulating upper contact; persistent
bed. Informally referred to as the false mar-
ker bed. Mapped by G. N. Pipiringos and W.
J. Hail, Jr., as top of Mahogany ledge (oral
commun., 1970) ---------------------------------------------------- .7
*174. Oil shale, dark-brown. Sample is from 4.5 ft
above base 7.9
*173. Oil shale, platy, rust-brownf efflorescent salt
coatings 1.0

15

Top'ol‘
. Mahogany
led a

Piceance Creek. Numbers refer to units described in the measured
units 217 and 221 is a sequence of rock that weathers distinctively
Member.

Complete section of the Parachute Creek Member of the Green
River Formation along lower Piceance Creek—Continued

Parachute Creek Member—Continued Thickness
(feet)
*172. Oil shale, dark-brown, laminated; weathers

blocky and blue gray. (Black 40 painted on
outcrop 0.7 ft above base.) ---------------------------------
Tuff, analcimic; undulating upper and lower
contacts; persistent bed
Oil shale, dark-brown, laminated; weathers gray
Tuff, analcimic, orange-brown; persistent bed.
The Mahogany marker----
Oil shale, dark-brown to red-brown, laminated;
weathers gray; smooth face on outcrop. Sam-
ple is from 1 ft above base ---------------------------------
Oil shale, dark-red-brown, laminated; weathers
blue gray with rusty stains on outcrop. Sam-
ples are from base and 1 ft above base. The
Mahogany bed -------------------------------------
Marlstone, pale-yellowish-brown; massive bed
in which calcite predominates over dolomite;
darker brown discontinuous stringers of ana-
lcime- and dolomite-rich rock. Some beds of
clear analcime. Distinctive bed. Sample is
channel sample of massive brown marl-
stone. Samples 1-13, from this entire 31.25-
cm-thick sequence, were studied in detail (fig.
13)
*165. Oil shale, dark-brown; weathers to smooth sur-
face, blue gray. Samples are from 1, 3, and

4 ft above base -----------------------------------------------------

*164. Tuff, analcimic; pods 0.3 ft thick. Undulating
contacts

7.8
*171.

 

*170.
*169.

 

*168.
1.8
*167.

3.3
*166.

 

1.0

5.0

 

 

 

 

 

 

 

 

 

 

 

16 X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO
Complete section of the Parachute Creek Member of the Green Complete section of the Parachute Creek Member of the Green
River Formation along lower Piceance Creek—Continued River Formation along lower Piceance Creek—Continued
Parachute Creek Member—Continued Parachute Creek Member—Continued
Thickness Thickness
(feet) (feet)
163. Oil sha1n 0.3 142. Oil shale. Blue-gray-weathering ledge in upper
*162. Tuff, analcimic, orange-brown; smooth con- 2.4 ft with 2 tuffs 0.5 ft and 1.3 ft below top;
tacts .08 lower 3 ft medium brown and blocky--------------- 5.4
*161. Oil shale, dark-red-brown. Sample is from 2.5 141. Oil shale, dark-brown; weathers to thin plates
ft above base. Samples 200—218, from a 20.6- in rounded slope in upper part; forms blue-
cm-thick sequence beginning at base of unit, gray-weathering ledge in lower part ................ 2_2
were studied in detail (figs. 11, 12) ----------------- 6.1 140. Oil shale, medium-brown, papery; has small
*160. Tuff, analcimic; weathers light brown; smooth rusty concretions of dolomite(?) in top 0.4 ft. - 2.0
contacts .1 139. Oil shale, light-brown; conspicuous recess at
159. Oil shale, dark-red-brown, laminated; weathers top possibly caused by weathering of a tuff--- 3.0
to smooth gray face --------------------------------------------- 2.5 138. Oil shale, light- to medium-brown; weathers
158. Oil shale, dark-brown, laminated; weathers to blocky; has cavities 0.2—1 ft in diameter. Thin
alternating layers of light to dark blue gray. tuff at base 2.25
Thin discontinuous dolomite laminae weath- 137. Oil shale, dark-brown; forms ledge --------------------- 1.2
er to light orange brown. (Yellow 7P painted 136. Tuff, weathered; undulating contacts ----------------- .5
at base of fresh exposures in cut at curve 135. Oil shale, dark-brown; dolomite pebbles; forms
in the road.) 1.0 ledge 1.0
157. Tuff;‘undulating contacts ------------------------------------- .15 134. ’I‘uff pods, 0.4—1.2 ft thick ------------------------------------- 1.0
156. Oil shale, dark-brown; weathers blocky to slab- *133. Oil shale, dark-brown; weathers blue gray and
by 5.2 blocky. Has flat brown dolomite pods. Papery
155. Oil shale, dark-brown; weathers papery------ 1.1 where most intensely weathered. Good mar-
154. Tuff, Undulating contacts, persistent bed. ker bed. Marked 7 M in yellow paint----—----—----— 3.0
Makes groove in weathered outcrop. (Yellow Section offset to same bed on east side of
70 painted on outcrop.) --------------------------------------- .25 Piceance Creek valley from a point on
153. Oil shale; weathers slabby to blocky- 3.4 a nose 30 ft above Piceance Creek road.
152. Oil shale, laminated; weathers to smooth face» .6 132. Tuff, regular contacts; persistent bed. Base of
151. Oil shale, medium-brown; weathers blocky to the Mahogany ledge -------------------------------------------- .2
slabby 2.5 *131. Oil shale; mostly medium brown; weathers
150. Oil shale, dark-brown, laminated; weathers pa- slabby to blocky. 1 ft above base a cavity
pery 1.1 zone from leached saline material is overlain
149. Tuff zone. Four tuffs, 1/2—1 in. thick, weather by a 1-in. light bed of dolomite. Samples are
orange brown and are separated by dark- weathered material from near cavity: dark-
brown oil shale. Zone forms reentrant in ex- brown oil shale from cavity zone, and the
posure .5 light dolomite bed ------------------------------------------------ 3.9
148. Oil shale, dark—brown, laminated; weathers slab- *130. Marlstone, light~yellow-brown to brown; poorly
by 5.0 exposed; forms slope covered with brittle chips.
147. Oil shale, dark-brown, laminated; low specific Samples are marlstone and pod material from
gravity; weathers to white flat face on out— upper 1 ft of unit. Probable position of the B-
crop 1.3 groove 33.5
*146. Oil shale, dark-brown; weathers blue gray, with 129. Oil shale, poorly exposed; weathers more pa-
large solution cavities 1.5 ft in diameter; makes pery toward top. Top of R—6 zone --------------------- 6.0
projecting square-faced ledge; has a wavy thin 128. Oil shale, medium- to dark-brown; darkest beds
bed 0f tuff at top. Samples are residue and form blue-gray ledges ‘4—2 in. thick ------------------ 5.5
leached rosette material collected from cavity 127. Oil shale, leached; marks saline zone ------------------ .5
near yellow X. (Yellow X painted on cliffs that *126. Oil shale, dark-brown; weathers blue gray; ef-
are just north of curve in road.)----------------—------- 6.0 florescent salts abundant; thin beds give
Section offset 1,000 ft to north on west side outcrop fluted appearance. Middle of unit is
of road to same unit exposed on the north cavity zone. Sample is weathered oil shale
side of a tributary of Piceance Creek in at base of unit ------------------------------------------------------ 6.1
the Sl/zNWI/l sec. 14, Barcus Creek SE 125. Marlstone, light-brown; weathers platy and
(71/2-min) quadrangle. blocky 6.0
145. Oil shale; weathers blocky; conspicious leached 124. Oil shale, light-brown; weathers papery ------------ 1.0
cavities 15.5 123 Oil shale, light-brown; efflorescent salts; at
144. Oil shale, medium- to dark-brown. Tuff 0.1 ft top is dark-blue—weathering bed with flat
thick 1.5 ft above base. Vuggy zone above pods of dolomite-------------—-----------------------—-----—- 3.8
the tuff 3.25 122. Oil shale, dark-brown; weathers blue gray----—---- 2.6
143. Oil shale. Top and bottom light brown and fis- 121. Tuff; undulating lower contact, even upper con-
sile; middle part light brown and blocky. Re- tact; continuous bed. (Section offset to north
entrant 3 ft below top has irregular pinching from base of outcrop at spur of hill along
and swelling pods of analcimic tuff 0.02—0.5 irrigation ditch, where tuff is exposed and
ft thick 4.5 marlstone of unit 119 is just underground.)—--- .2

 

 

 

 

 

 

 

 

 

 

 

Complete section of the Parachute Creek Member of the Green

MEASURED SECTIONS

River Formation along lower Piceance Creek—Continued

Parachute Creek Member—Continued

*120.

Oil shale, medium— to dark-brown; some efflo-
rescent salt. Samples are dark-brown oil shale.
(Exposed on east side of the creek valley over
the jointed marlstone described below.)--—--—---

*119. Marlstone, light-brown. The jointed bed con-

*118.

*117.

116.

115.

*114.

*113.

112.
111.
110.
109.
*108.
107.
106.
105.
104.
103.

spicuously jointed 1-2 in. apart; joints strike
N. 48° W., dip 85° NE., and give blocky ap-
pearance. 1.9 ft above base is thin zone of
oval cavities 1/2—'% in. thick and 2 in. long filled
with mixture of quartz, calcite, dolomite, feld-
spar, and some analcime and dawsonite. Base
about 75 ft below base of Mahogany ledge.
Samples are cavity filling containing some
dawsonite, brittle marlstone 0.8 ft below cavity
zone. A good marker bed; marked by yellow
7F at cliffs on east side of irrigation ditch on
east side of Piceance Creek valley --------------------
Section offset to same bed on west side of
road west of Piceance Creek. Painted yel-
low 7F on outcrops at sample locality of
unit 119.
Oil shale, dark-brown; weathers papery; forms
ledge
Oil shales, medium-brown. Some weather to
blue-gray ledges; others weather to paper
ledges. A rubbly ledge-ribbed slope. Sample
is from a blue-gray ledge ------------------------------------
Oil shales, light- to medium-brown; weather to
gray, shaly, partly covered slope--------—---—-—-------
Oil shale, dark-brown; weathers blue gray; has
brown flat dolomite pods; forms ledge -------------
Oil shale, light- to medium-brown; weathers pa-
pery to slabby; forms poorly developed ledges.
A 1/2—in.—thick light dolomite at 21.7 ft. above
base. Sample is light-brown oil shale 6 ft above
base. Lower 3 ft is covered. A tuff 0.2-0.4 ft
thick is 9 ft above base of this unit in draw
to north
Oil shale, dark-brown; weathers blue gray; has
flat rusty brown dolomite pods. Sample con-
tains some dawsonite. (Yellow 6A painted
on this bed at base of outcrops west of and
about 50 ft above road, nearly on the bound-
ary of sees. 11 and 14, T. 1 N., R. 97 W., near
the east edge of the Barcus Creek SE quad-
tangle
Section offset to north, where a similar 3.5-
ft-thick bed is exposed above units 1-112
measured near center of sec. 11, T. 1 N.,
R. 97 W., White River City quadrangle.
Sample from unit 113 is from outcrop in
White River City quadrangle (fig. 4).

 

 

 

Tuff
Oil shale
Tuff
Oil shale
Tuff, analcimic, light-gray--------------—-----------—---—----
Oil shale
Tuff
Oil shale
Tuff, yellow-orange -------------------------------------------
Oil shale

 

 

 

 

 

 

 

 

Thickness

(feet)

0.5

5.7

4.0

15.0

20.0

6.0

25.0

3.5

*82

 

102.
101.

100.
*99.

98.
97.

*96.

95.

*94.

*93.

92.
*91.

90.
*89.

*88.

87.

86.

85.

84.

*83.

*81.

80.
*79.

78.

*77.

76.

74.

Complete section of the Parachute Creek Member of the
River Formation along lower Piceance Creek—Continued

Parachute Creek Member—Continued

 

 

 

 

 

 

 

 

 

 

 

17

Green

Thickness
(feet)
Tuff 0.01
Oil shale .25
Tuff, mottled .02
Oil shale; weathers gray blue. Sample contains
some dawsonite ---------------------------------------------------- 1.6
Tuff .02
Oil shale; mostly light to medium brown, with
some dark-brown beds -------------------------------------- 17.2
Tuff, yellow-brown; dark petroliferous stain;
very fine grained. (Yellow T 27 painted on
outcrop.) .06
Oil shale .5
Tuff, yellow-brown; contains albite and daw-
sonite; undulating contacts; persistent bed----- .02
Oil shale, medium- to dark-brown; some beds
weather blue gray; some beds form ledges.
Samples are dark-brown blue-weathering oil
shales 3 and 6 ft above base that contain
some dawsonite ---------------------------------------------------- 33.2
Marlstone, light-yellow-brown, sugary-grained .2
Oil shale, medium- to dark-brown; some weath-
ers blue gray. Sample is dark-brown oil shale
from middle of unit --------------------------------------------- 3.7
Tuff; weathers yellow orange; smooth contacts .02
Oil shale, light- to medium-brown; forms alter-
nating slopes and ledges. Samples are light-
brown oil shales 0.2, 4, and 9 ft above base.
Some dawsonite --------------------------------------------------- 10.5
Conglomerate; contains dolomite pebbles. (Yel-
low streak and 6A painted on outcrop.)----------— .5
Oil shale, light-brown, and fissile to platy and
locally papery marlstone; forms thin ledges.
Approximate base of upper oil shale group
(Bradley, 1931, pl. 4A, letter a). Base of R—
6 zone (fig. 4, this report) --------------------------------- 3.3
Oil shale, light-brown; weathers gray, fissile.
Approximate top of transitional beds (Brad-
ley, 1931, pl. 4A, letter b). Top of L5 zone
(fig. 4) 6.7
'I‘uff; weathers yellow brown; laterally persis-
tent .1
Oil shale, light-yellow-brown; forms thin ledges
and covered slopes; weathers fissile to p1aty-— 7.7
Oil shale; weathers papery, blue gray----------------- .5
Conglomerate. Angular pebbles of dolomite in
a coarse sand matrix ---------------------------------------- .17
Oil shale, light-brown. Sample is from 2 ft
above base 4.7
Tuff; weathers orange; smooth contacts .04
Oil shale, light- to medium-brown; weathers
fissile to papery, blue gray. Some thin or-
ange-weathering marlstone beds. Much cov-
ered slope. Sample is from marlstone bed ----- — 35.2
Oil shale, light-brown; weathers fissile. Base
of L-5 zone 14.8
Oil shale, dark-brown; weathers blue gray.
Sample is from top of unit. Approximate top
of lower oil shale group (Bradley, 1931, p1.
4A, letter C). Top of R—5 zone (fig. 4)..___.1_____.__ 1,7
Tuff; persistent bed; smooth contacts -------------- .02
. Oil shale, dark-brown——-—-----------------*—--- .3
Tuff; undulating contacts —-— .1

 

 

18

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

Complete section of the Parachute Creek Member of the Green
River Formation along lower Piceance Creek—Continued
Parachute Creek Member—Continued

73.
72.

71.
*70.

69.

68.
67.
66.

65.
*64.

63.

62.

61.

*60.

*59.
*58.

*57.

56.
*55.

*54.

53.
*52.

*51.

*50.

*49.

*48.

47.

*46.

45.
*44.

 

Thickness
(feet)
Oil shale, dark-brown; weathers papery, blue
gray 0.9
Tuff, yellow-orange; smooth contacts-—-......-.....--. .08
Oil shale, brown; forms slope-----~--~—----—-----. 5,0

  

Oil shale, dark-brown; weathers blue gray;
forms ledge. Sample contains dawsonite. Base
about 53 ft above tuff of unit 49 ---------------------- 3.5

Oil shale, light-brown, and light-brown marl-
stone; weathers fissile to platy and forms al-
ternating ledges and slopes every 0.2—0.3 ft-- 4.2

Tuff; sugary texture ------------------------------------------------ .04
Oil shale, light-brown; weathers platy--------------—- 3.8
Oil shale, dark-brown; weathers blue gray; con-

tains dolomite nodules; upper 4 ft is ledge ------ 6.2
Marlstone, light—yellow-brown --------------------------- .2

Oil shale, dark-brown; weathers blue gray.
Sample is from 1.5 ft above base and con-

 

 

 

 

tains dawsonite ---------------------------------------------------- 3.6
Tuff, oil-stained, dolomitic. (Yellow T 18 paint-

ed on a slab placed below the bed.) ------------------ .1
Oil shale; weathers blue gray, papery. Unit is

base of ledge 3.5
Oil shale, yellow-brown to dark-brown; incom-

pletely exposed ----------------------------------------------------- 5.4
Marlstone, tuffaceous; weathers yellow orange.

A tough rock 1.3
Tuff, analcimic, yellow-orange; sandy texture-—- .3
Oil shale, medium-brown; weathers papery.

Sample is from 1 ft above base ------------------------ 4.4
Tuff, analcimic; undulating upper and lower

contacts .2
Oil shale. Mostly covered slope --------------------------- 3.1
Oil shale, medium-brown; weathers blue gray,

papery. Sample is from 1 ft above base ----------- 4.2
Tuff, analcimic, orange-brown; has thin dolo-

mite bed near top ------------------------------------------------- .3
Oil shale .9
Tuff, analcimic; undulating contacts; discon-

tinuous bed. Sample contains dawsonite .2

Oil shale, light-brown; weathers fissile to pa—
pery; some blue gray. Sample is from 5 ft
above base 6.3

Oil shale, dark-brown; weathers blue gray; a
few very thin tuffaceous beds. Sample is from
4 ft above base and contains dawsonite ---------- 4.7

Tuff, yellow-brown, analcimic, coarsely crys-
talline; undulating contacts. (Yellow paint
on enclosing beds parallel to tuff.) Correlated
with tuff 13 of table 10 --------------------------------------- .3

Oil shale, light- to dark-brown; weathers platy;
contains gar-pike scales. Samples are from
2, 4.8, 5.8, 8.4, and 8.5 ft below tuff of unit
49, and all contain dawsonite. (Yellow 4 E1

 

 

 

painted at base of unit.) ------------------------------------- 8.5
Marlstone. Tuffaceous even bed, smooth con-

tacts .1
Oil shale, medium-brown, and light—brown marl-

stone. Sample is medium-brown oil shale ------- 4.4
Oil shale, medium-brown, poorly exposed ---------- 3.5
Tuff, analcimic, red; weathers white; undulat-

ing contacts .15

 

Complete section of the Parachute Creek Member of the Green
River Formation along lower Piceance Creek—Continued

Parachute Creek Member—Continued Thickness

(feet)

43. Oil shale, dark-brown; weathers fissile --------------- 3.5
*42. Oil shale, dark-red-brown; weathers to prom-
inent smooth-faced blue-gray ledge. Samples
are from top of unit (contains dawsonite);
0.5 and 1 ft below top; 2.5 ft below top (con-
tains dawsonite); and base of unit. (Yellow

circle painted on face of outcrop.)---——---------~----- 3.3

41. Oil shale, light-brown, poorly exposed ~ 8.0
*40. Oil shale, medium-brown; weathers blue gray;
forms thin ledge; contains dawsonite. Sam—

ples are from 1.7 ft above base and near base- 2.7
*39. Oil shale; weathers papery; distorted beds; prob-
ably marks a saline zone. Sample is from 2

 

 

 

ft above base 5.6
*38. Oil shale, poorly exposed. Sample is from 2.3
ft above base 4.7
*37. Tuff, analcimic .04
36. Oil shale; contains intraformational conglom-
erate in lower 2 ft ------------------------------------------------ 6.1

*35. Oil shale, dark-brown; weathers papery; dis-
tortedilower 0.5 ft. Samples are distorted oil
shale and dark-brown oil shale 0.9 ft above
base 2.8

*34. Tuff, orange; contains dawsonite------------------------- .7

*33. Oil shale, dark-brown; weathers papery. Top
1.2 ft of unit has efflorescent salts and may
mark a saline zone. Two samples from the

 

lowest 2.8 ft above base 6.2
*32. Oil shale, medium-brown. Sample is from 1.8

ft above base and contains dawgonite----__..-.-.. 4_0
*31. Marlstone, gray-green .08

*30. Oil shale, light- to medium-brown, with 0.08
ft olive-drab dolomite bed at base. Sample
is from dolomite bed 1.0
*29. Oil shale, dark-brown; weathers blue gray.
Conglomeratic with yellow-brown dolomite
blebs 3 in. in diameter and 1/16 in. thick.

Sample is from 3.9 ft above base ---------------------- 7.0
*28. Tuff; weathers yellow. (Yellow T 8 and streak
parallel to bed painted on rock.)--------------—-—---~- .1

*27. Oil shale, dark-brown; weathers papery. Sam-
ple is from 1 ft above base and contains daw-
sonite 2.0
*26. Oil shale, gray-brown, hackly; forms a slope.
Near top is a tuff zone consisting of thin tuff
and tuffaceous marlstone. Sample is marl-

 

 

 

stone and contains dawsonite------------------------—-- 3.6
25. Oil shale; has orange-weathering dolomite con-
cretions in upper 1 ft ------------------------------------------- 2.0
24. Tuffs. Two thin beds separated by oil shale ------ .1
23. Oil shale .55
*22. Tuff; weathers yellow; forms reentrant in out-
crop .2

21. Oil shale; weathers blue gray, papery. Base of
cliff-forming oil shales (fig. 4). Approximate
base of Parachute Creek Member (Bradley,
1931, pl. 4A). Base of R-5 zone ~ 1.0
*20. Oil shale and marlstone, light-brown. Sample
is marlstone 1.7 ft below top. Top of L-4 zone- 2.5
*19. Tuff, analcimic .02
18. Oil shale, light-brown; weathers fissile-—-------—----- 1.3
*17. Tuff, analcimic .04

 

 

MEASURED SECTIONS 19

Complete section of the Parachute Creek Member of the Green
River Formation along lower Piceance Creek—Continued
Parachute Creek Member—Continued Thickness
(feet)
*16. Oil shale, light- to dark-brown; weathers fissile;
forms slope littered with small shale plates.
Samples are dark-brown oil shale 2.7 ft below
top and light-brown oil shale near base of
unit
Oil shale; mostly covered mslope. Sample 15 med-
ium- -brown oil shale-u --- 6.0
14. Oil shale; forms ledge --------------------------------------------- 7.0
*13. Oil shale and marlstone; forms mostly covered
slope littered with small brown chips of brown
oil shale and plates of lightvbrown to orange
marlstone. Sample is light-brown oil shale 2
ft above base. Base of L4 zone -------------------------
12. Oil shale, medium- to dark-brown. Top of series
of ledge—forming shales. Top of R-4 zone. (Yel-
low 3 painted at top of ledge.) Base of unit
mapped by G. N. Pipiringos and W. J. Hail,
J r., as contact between Parachute Creek Mem-
ber and Garden Gulch Member -------------------------
11. Marlstone, light-yellow, silty, ostracodal--------—-—-
*10. Oil shale, dark-brown. Sample is from about
7 ft above base ----------------------------------------------------- 22.0
9. Marlstone, light-yellow-brown, silty -------------------- .3
*8. Oil shale, medium- to dark-brown; some weath-
ers blue gray. Forms alternating slopes and
ledges in 5-ft intervals. Sample is dark-brown
oil shale 19.5
7. Oil shale; weathers fissile; partly covered slopes 4.0
6. Oil shale, dark—brown; weathers blue gray; forms

27.9

 

*15.

30.0

15.0
3.5

 

 

 

ledge 3.0
5. Oil shale, medium- to dark-brown. 1 ft of dark-
brown oil shale at base --------------------------------------- 4.5

4. Marlstone; weathers to slope littered with light-
yellow-brown chips; poorly exposed -----------------
3. Marlstone and oil shale, light-brown; oil shale
increases toward top; forms a ledge ----------------- 9.0
2. Marlstone and oil shale, light-brown; forms

31.5

 

 

 

 

 

covered slope 12.2
*1. Oil shale, light- to dark-brown; darkest beds
weather blue gray; forms a ledge. Sample is
dark-brown oil shale ------------------------------------------- 10.1
Thickness of Parachute Creek Member
(rounded) 1,185.0
Garden Gulch Member (part):
Shale, olivegray, clayey but slightly dolomitic;
forms partly covered slope --------------------------------- 6.2
Oil shale, light-brown; weathers papery. (Yel-
low 1 painted on small outcrop.) ----------------------- 3.0
Shale, olive-gray, clayey; subfissile to hackly
fracture 25.0
Incomplete thickness of Garden Gulch Mem-
ber (rounded) ------------------------------------------------- 34.0

Other workers have chosen contacts of the
Parachute Creek Member on lower Piceance Creek
differently. Correlations of the data in this report
with those of earlier workers are shown in figures 4
and 6. Bradley (1931, pl. 4A) placed the basal contact
of the Parachute Creek about 210 feet higher strati-
graphically than we do. Donnell (1961, pl. 51) chose

 

the contact at the base of the lowest oil-shale-rich
zone, which coincides closely with our contact. G. N.
Pipiringos and W. J. Hail, Jr. (oral commun., 1970), in
geologic mapping of the White River City and Barcus
Creek SE quadrangles, respectively, have chosen the
bottom of a generally well exposed and easily map-
pable bench of dark-brown oil shale at the top of
smooth and rubble-strewn slopes as the base of the
Parachute Creek Member. This persistent bench is
about 120 feet above the contact we have chosen with
the aid of laboratory study.

. The position generally mapped as the base of the
Parachute Creek Member seems to lie above the
position chosen in drill cores or from detailed
laboratory study of rocks from measured sections.
This difference in selection of the contact may ac-
count for what has been interpreted in some areas to
be extreme basinward thickening of the Parachute
Creek Member within short distances.

The R and L designations shown in figure 6 were
used by Donnell and Blair (1970, p. 76) to describe
units of rich and lean oil shale, respectively. These
designations were easily applied to the section on
lower Piceance Creek and also correlate easily with
rock units described by Bradley (1931, pl. 4A). (See
figs. 4 and 6.)

From the data in the diagrammatic section on plate
3 and in photograph A on plate 4 of Bradley (1931), a
thin Parachute Creek Member was designated that
included only the most organic rich parts of the se-
quence of carbonate-rich rocks. He apparently used
the top of the oil-rich zone now called the Mahogany
ledge as the top of the Parachute Creek Member.
This, of course, automatically made the Evacuation
Creek of Bradley thicker than the Evacuation Creek
of later workers.

RIO BLANCO SECTION

A well-exposed complete section of the Parachute
Creek Member (764 ft) was measured in the cliffs
along the north side of Piceance Creek beginning at
the base of the member at the west end of the gravel
pit (NWlASWM; sec. 5, T. 4 S., R. 94 W.) and con—
tinuing westward to the draw intersected by the west
boundary of sec. 6, T. 4 S., R. 94 W., Rio Blanco Coun-
ty, Colo. (fig. 7). The gravel pit is 1.8 miles west of the
junction of the Piceance Creek road and Colorado
Highway 13 at Rio Blanco, Colo. The area is shown
on the Rio Blanco 71/2-minute quadrangle.

The contact between the Parachute Creek Member
and the underlying Anvil Points Member is
gradational. Eastward from the gravel pit, and down
section, the rocks become more silty and sandy and
contain less carbonate. The top of the Parachute
Creek Member is only moderately well exposed, but

20

the contact with the sandstones of the overlying Eva-
cuation Creek Member generally can be found to
within a few feet.

The lithic details of the section follow, and the

mineral composition of 98 samples is shown in table
6.

Complete section of the Parachute Creek Member of the Green
River Formation near Rio Blanco, in secs. 5 and 6, T. 4 S.,
R. 94 W., Rio Blanco County, Colo.

[Sech'on measured by D. A. Brobst and J. D. Tucker. ' indicates sample data in table 6]

Thickness
Evacuation Creek Member (part): (feet)
Sandstone, tuffaceous, light-brown; consists
chiefly of albite, quartz, analcime, and dolo-‘
mitic cement. Partly covered sldpe--—-—--—-~——--—
Incomplete thickness of Evacuation Creek
Member
Parachute Creek Member:
162. Marlstone, light-brown-----—------—--——-——-- --—--———-
*161. Oil shale, dark-red-brown, pyritic, laminated;
weathers blue gray; forms ledge -—-—---——--——
Oil shale; mostly light brown, with some dark-
brown beds a few inches thick; weathers platy- 6,8
Tuff, analcimic .02
Marlstone, light-brown, sandy, well-exposed-——- 14.5
Oil shale, dark-brown, pyritic; forms ledge. (Yel-
low line painted on bed.) —————————————————— .7
Section offset to same bed in next gully to
east, where yellow line and triangle are
painted on bed.
Oil shale, light- to dark-brown, laminated;
interlayered with light-brown marlstone. (This
unit better exposed on south side of road and
creek.)
Oil shale, dark-grayish-black, pyritic, laminated;
weathers blue gray and platy; forms ledge.
Samples 1—37, collected at 100-ft lateral inter-
vals, were studied in detail (figs. 7, 17)~-—--——--- _-3
Section offset to top of westernmost large
roadcut on north side of road. (See fig. 7.)
Oil shale, medium- to dark-brown, laminated,
poorly exposed
Oil shale, medium- to dark-brown. (Well exposed
in road cut.) 10
Oil shale, medium- to dark-brown; forms tuff zone
with nine analcimic tuffs 1%: to 1/2 in. thick.
Sample is tuff from lowest and thickest of nine
beds
Oil shale, medium— to dark-red-brown, pyritic;
laminated, but massive bedded on these fresh
exposures. Sample is dark-red-brown oil shale
from base of unit -——---—--------~-—-—~~—-—----——--——~
Sandstone dike, tuffaceous, light-brown to gray;
1 ft thick; strikes N. 75° E.; dips vertically» 0
Oil shale, medium» to dark-red-brown, laminated.
Massive beds. Deep blue gray weathered bed
near base of outcrop is base of unit. Sample
is dark-red-brown oil shale 5 ft above base of
unit
Section offset to next roadcut to east. (See
fig. 7.)
Oil shale, very weathered. Sample is light-brown
oil shale
Oil shale, medium-brown; weathers chippy ------
'I‘uff, analcimic, light-rust-brown-------~-—-------------— .02

50+

 

50+

7.5

2.3
160.

159.
158.
*157.

 

156.

 

20.0
*155.

154.
22.3

 

153.

 

*152.

 

6.0
*151.

7.2

*150.

*149.

13.5

 

*148.

 

147.
146.

 

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

Complete section of the Parachute Creek Member of the Green
River Formation near Rio Blanca—Continued
Parachute Creek Member—Continued

 

  
 

 

 

 

 

 

Thickness
(feet)
145. Oil shale, light- to medium-brown; weathers chip-
py 2.0
144. Tuff, analcimic, light-rust-brown-----~--~---------~—-- .02
143. Oil shale, medium-brown; weathers chippy ----- 7
*142. Tuff, analcimic, light-rust-brown -------------- ~ .02
*141. Oil shale, medium-brown, laminated—--- ----- ~ .4
140. 'I‘uff, analcimic, evenly bedded —~-— .04
139. Oil shale, medium- to light-brown, and 5 anal-
cimic tuffs 1/zs—‘/2 in. thick. (Yellow triangle paint-
ed on rock.) 4.9
138. Marlstone, light-brown, resistant; hard layer,
weathers to orange-brown sandy surface~~--- .5
Section offset to exposure on west wall of
an adit to the east.
137. Oil shale and marlstone, light— to dark-brown,
intercalated 1.3
*136. 'I‘uff, dark-brown, biotitic; has some organic de-
bris; weathers out in blocky fragments; con-
tacts undulate; maximum thickness 6 in ------- .3
135. Oil shale, medium»to dark-brown, massively
bedded, includes a light-brown marlstone. (Yel-
low M above a horizontal yellow stripe is
painted on marlstone.) ------------------------------------ 9.2
134. Marlstone, light-gray; beds 2 in. thick with some
intercalated light-brown laminated oil shale-- 1.5
*133. Oil shale, dark-brown, laminated. Sample from
top of unit. Zone of 3 thin tuffs in lower part- 2.3
132. Marlstone, light-brown. (Yellow circle 4 in. in
diameter painted on bed.) ---------------------------------- 2.0
*131. Oil shale; mostly medium brown. Sample of
medium-brown oil shale 3.1 ft above base.
Other samples are dark- and medium-brown
oil shale 7.4
130. Marlstone, light-brown; weathers orange brown .04
129. Oil shale, medium- to dark-brown ------------------------ 3.0
*128. Marlstone, light-brown; weathers to sandy sur-
face. Sample is whitish orange marlstone at
base 2.0
127. Sandstone dike, tuffaceous; about 4 in. thick;
strikes N. 20°W.; dips 65° NE. About 10 ft
above the road, dike is offset to right and ex‘
tends to top of outcrop. (Large yellow D paint—
ed on outcrop at road level just west of dike.)— 0
*126. Oil shale, dark-brown; thin pods and intercala-
tions of marlstone. Sample is dark-brown oil
shale 2 ft below top -------------------------------------------- 8.0
Section offset to gully to east.
*125 Marlstone, light-gray, tuffaceous ------------------------- .08
124. Oil shale, medium-brown; weathered plates form
partly covered slope -------------------------------------------- 11.1
123. Marlstone, light-brown ------------------------------------------ 2.0
122. Oil shale, dark~red~brown; weathers blue gray;
forms ledges a few inches thick --------------------- 4,1
121. Marlstone, light-brown, and medium-brown oil
shale _ 5.5
*120. Oil shale, dark-brown, well laminated; weath-
ers blue gray. Sample is from dark-brown ledge
-forming bed 6 in. thick ------------------------------------- 2.3
119. Oil shale, medium-brown, poorly exposed ------- 6.9
1 18. Oil shale, dark-red-brown to medium-brown;

weathers slabby and platy; forms ledges -------- 13.2

 

 

MEASURED SECTIONS

Complete section of the Parachute Creek Member of the Green
River Formation near Rio Blanca—Continued
Parachute Creek Member—Continued

Thickness
(feet)

*117. Marlstone, tuffaceous --------------------------------------------- .6
116. Oil shale, dark-red~brown; weathers blue and
slabby; has some interbedded light-brown

 

 

 

marlstone 6.0

1 15. Oil shale, light- to medium-brown; contains some
dark-brown beds -------------------------------------------- 4.8
*114- T “ff, light-brown, dolomitic ---------------- .2
113. Oil shale, red-brown, poorly exposed .................. 3_()
*112. Tuff .2
111. Oil shale, medium- to dark-brown~ 1.1

*110. Oil shale, dark-brown, pyritic; weathers blue;
forms ledge. (Yellow streak painted on rock.)- 6.3

 

*109. Oil shale, dark-red-brown, pyritic; forms ledge» .3
*108. Oil shale, medium- to dark-red-brown. Sample
is medium-brown oil shale ----------------------------- 4.4
107. Oil shale, dark-red-brown, pyritic; 1-ft-thick ledge
at top of unit 6.5
106. Covered unit 5.5

 

 
 
 

“105. Oil shale, dark-brown"-
104. Marlstone, gray, silty -------------------------------------------- .
103. Oil shale, medium- to dark-brown; weathers platy 7.7 '

 

 

 

*102. Tuff; consists of analcime in a deep-blue matrix- .17
101. Oil shale, dark-red-brown —~ .4
*100. Marlstone, tuffaceous, brown; resistant dense
bed .1
99. Oil shale, medium- to dark-brown ----------------------- 1.8
98. Marlstone, brown; resistant bed --------- .1
97. Oil shale, dark-brown ----------------------------------------- 2.1
96. Marlstone, gray; resistant bed ----------------------------- .2
Section offset to lowermost outcrop in gully
to east.
*95. Oil shale, dark-red-brown, laminated; weathers
blue gray 3.3

94. Marlstone, dark-brown, sandy, resistant; forms
ledges between layers of light-brown oil shale.
(Yellow streak on bed below at west end of
outcrop. ., 9.6

*93. Tuff, dark- brown, analcimic; even contacts; sat-

 

  

 

  
  

 

urated with petroliferous material- .1
92. Marlstone, light-brown ------------------------------------------- .8
*91. Marlstone, tuffaceous, sandy, gray; weathers
light orange brown ---------------------------------------------- .3
*90. Oil shale, dark-brown. Sample is from 2.2 ft
above base 4.3
89. Tuff, analcimic; undulating contacts ---------------- .05
88. Oil shale, medium-brown—— 1.2
*87. Tuff, analcimic, rust-brown, continuous; undu-
lating contacts -------------------------------------------------- .08
86. Marlstone, light-brown, thin-bedded; contains
chert pods 1—2 in. thick and as much as 6 in.
long. (Yellow P painted on outcrop.)-----------—---- 3.6
*85. Marlstone, light-gray, dolomitic; massive bed-- .4
84. Oil shale, medium- to light-brown ---------------------- 3.4
83. 'l‘uff, analcimic, light-brown ----------- - .02
82. Oil shale, light-brown -------------- .7
81. Tuff, analcimic, light-brown ------------------ .02
80. Oil shale, light- to medium-brown- ----- 3.2
79. Tuflf, analcimic, light-brown ------------------------------ .02
78. Oil shale, light- to medium-brown ----------------------- 2.2
77. Tuff .1
76. Marlstone, light—brown ---------------------------------------- 1.0

75. Oil shale, dark-red-brown; weathers blue gray -- 2.3

 

21

Complete section of the Parachute Creek Member of the Green

River Formation near Rio Blanca—Continued

Parachute Creek Member—Continued

*74.

*73.

72.

*71.

*70.
*69.

*68.
67.
. Sandstone, tuffaceous, dolomitic, laminated-~-
65.
*64.
*63.

62.

61.

60.
*59.

*58.

*57.

56.
*55.

54.
*53.
*52.
*51.

*49.

48.
*47.

Thickness

Tuff, analcimic; weathers brown; has inclusions
of oil shale and marl; undulating contacts; 84
ft above Mahogany ledge. Well exposed along
road (fig. 7). Possibly correlates with unit 163
in the pipeline section ------------------------------

Oil shale, medium- to dark-brown. Sample is
from top of unit -------------------------------------

Oil shale, interbedded medium— to dark-brown,
weathers platy. (Yellow circle painted on out-
crop at top of unit.) -------------------------------------- —

Oil shale, medium- to dark-brown. Sample is
dark-brown oil shale 2 ft below top of unit.
Top of unit contains discontinuous pods of
analcimic tuff as much as V2 in. thick. Tuff
and enclosing oil shale also sampled. (Yellow
triangle painted on outcrop about 15 ft above
road.)

Marlstone, lightbrown

Oil shale, dark-red-brown, laminated; contains
some tuff pods. Sample is dark-red-brown oil
shale. (Yellow dot on outcrop just below sam-
pled area.)

Sandstone, tuffaceous, light- to dark-brown -------

Oil shale, dark-red-brown, laminated ~—

 

 

Oil shale, dark-brown, laminated-----v-------—---———-
Sandstone, calcareous --------—---~-——-----—-——---—----——--
Oil shale, light- to medium- brown. Sampleis
light- brown oil shale ------------------------------------
'I‘uff, analcimic, rust- brown. (Painted yellow T
19 just above bed.) ----------------------------------- ~—
Marlstone, light-brown; poorly exposed in mid—
dle. (Forms base‘of outcrop that lies about
half way between 2 curves in road.) ----------- -
Covered slope
Marlstone, light-brown, and a few dark-brown
beds of oil shale a few inches thick; includes
4 layers of discontinuous pods of rust-brown
tuff about 1/2 in. thick at 6.3, 9.2, 9.5, and 11.5
ft above base. Top of unit is analcimic rust-
brown tuff about 1/2 in. thick. Sample is upper-
most tuff. Probable position of the A-groove--

 

Oil shale; mostly light brown with some thin
beds of dark-red-brown. Sample is light-brown
oil shale 4 in. below top. Small fold; axis trends
N 10° W. Top of the Mahogany ledge. (Yellow
5 painted on outcrop.)—--------------—------------------—----

Clay, white, chloritic and dolomitic.---

Marlstone, gray- to blueweathering -----------------

Marlstone, and 2 thin tuffs. Sample is marlstone

Marlstone, gray

Tuff, analcomic; weathers rust brown-------~—------

Marlstone, light-gray ------------------------------------------

Tuff, analcimic, medium-brown; some biotite —-—

Marlstone; laminated with tuff—-

'I‘uff, analcimic; weathers light brown. (Yellow
T9 painted under tuff in bend of road.) “The
false marker”

Oil shale, medium- to dark-red-brown --—-—--—-—----

Sandstone dike, tuffaceous, light-brown, fine-
grained, poorly sorted; 1 ft thick; strikes N,
70° E.; dips vertically; some organic debrisw-

 

 

 

 

(feet)

5.2

7.7

12.4

3.4
4.1

1.2

.01

6.9
26.4

12.3

16.3

 

 

 

 

22 X—RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO
Bradby(l93l, DonneH(l96l, Brobstand G.N.Pufinngos
pls. 3, 4A) modified by Tucker and W. J. Hail, Jr.
oralconvnun” (fiflsrepofl) (oralconnnun.,1970)

1970); Donnell
and Blair (1970)

 

      

 

  

 

 

 

 

 

 

     

 

 

 

 

 

 

 

     

 

    

 

 

 

 

 

 

 

 

 

 

 

   

"‘jB'rjifiéfl’?) .
Fermiaitién . ,4 ?
.._.,E"\_/'ac"uation
P a r a c h u t e
Evacuation
Creek
Member
Mahogany
marker
Upper
oil-shale Zone of B—groove
a; group D
.o
E
é’ _____________ _R-_6_ _T_0&f hill ________ _______
x in figure 4 B
8 . of this D
5 Unit a (pl. 4A) report D
B D
:: Transitional
'5 beds L—5
9 Unit b (pl. 4A)
N
o. D
Lower D
oil-shale R—5 Dawsonite—
group ML
D
't (pl 4A B
\\ L—4
\\ R—4
Parachute
100 FEET
50
0

FIGURE 6.—Nomenclature used for the Parachute Creek Member on lower Piceance Creek. D, occurrence of dawsonite. Numbers
prefixed by R and L refer to zones rich or lean in oil shale.

l.

 

 

MEASURED SECTIONS 23

T35. 36 31 )/ i 32 33 X

 

 

 
     
   
     
 

. I -
T' 4 S, Outcrop of Evacuation Creek Member' ) BM 7253 A\ .R10
x / Blanco
Samples of unit .' /

155 (fig. 17) '
x 15. 1
Un
1

  

Piceance

 

Cree/C

   
  
  

Unit 149 _.-Tuff of Sandy zone
xunlt 74 Units 16-27 Gra‘vel

X . It
25¢ 9

Base of Parachute Creek Member

 

Mahogany ledge
Units 38-58 (3.
88,9

0 .5 1 MILE
4|

 

 

12 7 8 9
R. 95 w. R. 94 w.

 

 

 

 

 

FIGURE 7. —Location of the measured section of the Parachute Creek Member near Rio Blanco. Numbers refer to units described
in the measured section.

Complete section of the Parachute Creek Member of the Green Complete section of the Parachute Creek Member of the Green
River Formation near Rio Blanco—Continued

 

Parachute Creek Member—C ontinued

*46.

45.
*44.
*43.
*42.
*41.

*40.
39.

38.

*37.

*36.
35.

*34.

*33.

Tuff, analcimic; lesser amounts of quartz and
alkali feldspar; minor amounts of illite in
weathered samples only. Samples of fresh and
weathered rock. The Mahogany marker. (Yel-
low + painted on tuff)

Oil shale, medium-brown

Marlstone, light-brown, dolomitic; massive beds
to 4 in. thick. Samples from a 9.5-cm-thick
sequence were studied in detail (figs. 14, 15) -

Oil shale, dark-red-brown; weathers blue gray.
The Mahogany bed --------------------------------------------

Dolomite; thin bedded in beds l11—1/2 in. thick -----

Oil shale, dark-brown ---------------------------------------------

Dolomite, brown ------------------------------------------------------

Oil shale, dark-brown; contains some marlstone
beds to 1 in. thick ------------------------------------------------

Oil shale, medium-brown; contains some light-
brown marlstone. (Yellow ML painted on out-
crop near road level.) ------------------------------------------

Section offset to 2 blue-gray beds exposed
beneath talus in gully to east.

Oil shale, medium- to dark-red-brown; laminat-
ed beds 1—2 in. thick; weathers blue gray and
platy. Samples are dark-brown oil shale 10.6
and 15.9 ft above base. (Ledge painted yel-
low.)

Oil shale, dark-red-brown; weathers blue gray --

 

Oil shale, medium-brown to red-brown; weath-
ers blue gray; strikes N. 90° W.; dips 10° SW-
011 shale; mostly light to medium brown. Sam-
ples are dark-brown oil shale in uppermost
bed (0.1 ft thick) and lowermost bed (0.2 ft
thick). Lowermost good unit of oil shales -------
Tuff, analcimic, biotitic. Base of the Mahogany
ledge

 

Thickness
(feet)

0.7
2.8

1.5
1.0

0.7

2.3

4.5

21.5

5.9

5.5

 

River Formation near Rio Blanca—Continued
Parachute Creek Member—Continued Thickness
(feet)
32. Marlstone, gray to brown. Probable position of

*31.
30.
*29.

. Marlstone 1.
*27.

26.
*25.

24.
*23.
*22.
*21.
*20.

19.
18.

*17.
*16.

*15.

 

B-groove 7.4
'I‘uff, analcimic, persistent bed; weathers dark

brown
Marlstone, thinly laminated .................................
Dolomite, sandy; weathers powdery ....................

 

Uni—‘53P

 

Sandstone, analcimic, very fine grained; weath-

ers rust brown. Sandstones in this part of sec-

tion chosen by Duncan and Belser (1950) as

uppermost beds of their lower sandy member.

This is 267 ft above the base of Parachute

Creek Member as defined by our measurement .7
Marlstone 1.2
Sandstone, dolomitic, light-brown, fine-grained,

thinly bedded .5
Marlstone, gray and brown, laminated; weath-

ers platy 6.9
Tuff, orange-brown. (Painted yellow T 4.) --------- .1
Marlstone, tuffaceous, thin- bedded, laminated-- 2.1
Marlstone, dark-brown ------------------------------------------- .5
Tuff; contains analcime, quartz, and alkali feld-

spar; weathers blocky. (Bed painted yellow. )—- .7
Marlstone, weathered, well- exposed ---------
Marlstone, partly exposed ------------------------------------- 16.5

Section offset to next gully east.
Marlstone, gray to light-brown; weathers

brown; strikes N. 15° W.; dips 10° SW ------------- 16.5
Sandstone, calcareous, gray, fine to very fine

grained, crossbedded ------------------------------------------- 3.9
Marlstone, light-chocolate—brown to gray, brit-

tle; weathers to rust—brown plates and slabs;

some tuffaceous material. Samples are tuff-

aceous marlstone at base of unit, brown marl-

stone 5.5 ft above base, and tuffaceous marl-

stone 25 ft above base ----------------------------------------- 32.5

 

 

 

 

 

 

 

24

Complete section of the Parachute Creek Member of the Green
River Formation near Rio Blanca—Continued
Parachute Creek Member—Continued
Thickness
(feet)
*14. Marlstone; various shades of brown. Unit con—
tains pyrite nodules, efflorescent salts, and
cavities (formerly occupied by saline miner-
als?). Common organic debris and fossils of
leaves, twigs, and insects. Eight samples.

 

 

(Yellow 3C at base of outcrop.) -------------------------- 10.0

13. Marlstone, platy weathering, poorly exposed 11.0
*12. Marlstone, gray to brown; somewhat siliceous
—dense, tough, and brittle. Samples are gray-
brown marlstone from basal beds and dark-
brown marlstone with insect impressions.

(Yellow 3A painted 3 ft above base.)--—-—----—-—---- 23.8

11. Poorly exposed sequence ---------------------------------------- 81.0
*10. Marlstone, gray, well-laminated. Sample is dense
marlstone near top of unit. Also sampled was
0.5-ft-thick tuff 2.1 ft above base. (Yellow paint

on sampled bed of marlstone.)-----------------------~- 16.8
*9. Marlstone, gray, and some silty beds; contains
tuffaceous pods ‘4; in. thick, especially in upper
8 ft. Samples are gray marlstone and tufface-

ous Siltstone 15.2

*8. Tuff, analcimic and dolomitic ------------------------------ .1

7. Marlstone, gray .3
6. Siltstone and very fine grained sandstone; con-

tains some asphaltite ------------------------------------------ .2

5. Marlstone, gray 2.4

4. Sandstone, fine-grained, poorly sorted, evenly
bedded; contains ostracodes and clay galls.
(Marked RB—1A in yellow.) -------------------------------- .5
3. Marlstone, gray, poorly exposed ---------------------------
2. Sandstone, gray-brown, fine-grained, poorly
sorted .7
*1. Marlstone, gray, laminated; weathers platy ------ 5.0
Section ends at base of exposures in ditch
along north side of Piceance Creek road at
west end of gravel pit. (See fig. 7.) Considered
to be the base of the Parachute Creek Member.
Eastward, the rocks are less well exposed, but
sandstone and Siltstone, characteristic of the
Anvil Points Member, increase in abundance.
Thickness of Parachute Creek Member __
(rounded) 764.0
Suggested correlations of our section with those of
earlier workers are shown in figure 8. Donnell (1961,
pl. 53) chose the lower contact of the Parachute Creek
Member at about the same stratigraphic position as
we did. Duncan and Belser (1950) placed the contact
at the top of sandstone beds (our units 25 and 27 in the
Rio Blanco section) about 270 feet abOve the base we
chose for the Parachute Creek (D. C. Duncan, oral
commun., 1970). Thus, they seemed to have a thinner
Parachute Creek Member—only 445 feet thick as
compared with 735 feet measured by Donnell (1961,
pl. 53) and 764 feet measured by us.

MINERAL COMPOSITION
The mineral fraction of most rocks examined in

 

 

this study of the Parachute Creek Member consists of 7

 

 

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

mixtures of dolomite, calcite, quartz, potassium
feldspar, albite, analcime, illite, and pyrite.
Dawsonite was detected only in oil shale on lower
Piceance Creek. Small amounts of chlorite occur in
some of the rocks, and biotite and (or) muscovite oc-
cur(s) in some of the beds of tuff. Thin coatings of
gypsum line some fractures.

Nearly all these rocks are extremely fine grained
and contain some tightly bound organic materials
that impregnate the rock, coating and masking the
mineral grains and making the physical separation
of the minerals from each other and from the organic
matter very difficult. Tisot and Murphy (1960) found
that oil shale from the Mahogany ledge near Rifle,
Colo., is composed of particles that are 90 percent silt
and clay size. They also reported that the mineral
fraction is 83.8 and 55.4 percent (by weight) in oil
shales which, respectively, assay 28.6 and 75 gallons
of shale oil per ton of rock. These features of the rock
make the study of the mineral composition by stan-
dard microscopic techniques unsatisfactory. X-ray
diffraction methods, although having certain
limitations, do provide a rapid means of acquiring
mineralogic data.

LABORATORY WORK
PROCEDURES

Samples weighing about 4 ounces (100 g) and taken
from about 1 inch (2—3 cm) of stratigraphic thickness
of the freshest both common and unusual rocks were
collected for X-ray study from the measured sections.
Samples of the tuffs generally represent the thinnest
stratigraphic intervals; many of these beds are less
than 1 inch thick. After initial sampling was com-
pleted in the three measured sections and the X-ray
results were examined, further sampling was done at
selected localities to provide material for study of the
details of vertical and lateral variation in the com-
position of selected units of rock, including the
dawsonite zone on lower Piceance Creek.

Samples from the three measured sections were
routinely prepared for X-ray study by being ground in
a hammer mill. The resulting powder was pelletized
at 22,000 pounds per square inch in a hydraulic press.
X-ray diffraction patterns of the pellets were made
with Norelco equipment (operated at 40 kv; 20 ma;
scale factor, 8; multiplier, 1; time constant, 4). Dif-
fraction data from CuKa1 radiation were recorded
from scans of the sample through an arc of 60° 29 on
100-unit chart paper at the rate of 2° 29 per minute.
Values for peak intensity, expressed as height of the
peak in chart units above base line, produced by the
N orelco equipment are summarized or shown in
tables 4—7 and 11 and in figure 21.

 

 

 

MINERAL COMPOSITION 25

Duncan and Donnell Brobst and cellulose backs. Diffraction patterns were made with

Belser (1950) (1961, pl. 53) TUCke" Picker-Nuclear equipment operated at the settings
(lh's legit”) described above.

     

 

 

_. . 'rjieje’k5
Creek

 

5Evéf<=.ja'ff\°“
Parachute

5 ft of tuff of unit 74

 

 

 

 

 

 

\T\__

Mahogany
ledge

' _ marker

 

 

 

 

 

 

 

 

 

lOO FEET

50

Creek
Points

Parachute IMemube

Afivil'

 

 

          

 

 

 

 

s 3's

FIGURE 8.—Nomenclature used for the Parachute Creek Member
in the Rio Blanco section.

Samples of dawsonitic and other rocks described in
tables 2 and 8—10 and in figures 16—19 were prepared
as described above, but diffraction patterns were ob-
tained by use of Picker-Nuclear equipment (operated
at 35 kv; 20 ma; scale factor, 3K; time constant, 1).
The diffraction patterns, also from CuKa1 radiation,
were recorded as described above.

Data compiled in figures 10, 12, 13, 15, 20, and 22
pertain to samples obtained by use of a dental drill
from sawed slabs of rock. The powder thus obtained
also was made into pellets as described above, but be-
cause of the small amounts of material available, the
pellets consisted of a thin coating of powder on

 

Diffraction patterns of all the rocks were examined
uniformly by measuring the height of the apex of the
peak above base line on chart paper divided into 100
units. One peak was measured for each mineral
detected; these selected peaks are shown in table 1.
The values thus obtained were compiled or sum-
marized in the tables and figures in this report.

DISCUSSION

Diagnostic peaks to be read for the minerals in a
given suite must be chosen to avoid use of 29
positions where the cumulative effect of the presence
of more than one mineral leads to ambiguity as to
how much of the peak height is attributable to any
one mineral. When possible, the most intense peaks
for each mineral are used, but this is not always pos-
sible or practical. In this study, the 20.9° 29 peak for
quartz was used rather than the more intense 266°
29 peak because illite enhances the latter peak. The
second highest peak for analcime occurs at 158° 29,
which is close to the 156° 29 major peak of dawsonite,
but our equipment was able to differentiate the two
peaks well enough for our purposes in this study.

Detection of dawsonite in the samples was con-
sidered of enough importance to conduct some grind-
ing experiments to determine the optimum method
of sample preparation for assuring the appearance of
the maximum peak height in the diffraction pattern.
Two samples of dawsonitic oil shale from the section
on lower Piceance Creek were crushed and then
ground and homogenized in a mixer mill. At various
timed intervals of 5—50 minutes, part of the sample
was removed and X-rayed. Results are shown in table
2. The data show that prolonged grinding reduces
the height of the dawsonite peak to a much greater de-
gree than the peaks of the other minerals. In the en-
tire length of the grinding time, the peak height of
carbonate minerals and illite was more affected than
was that of quartz and feldspar. Short grinding time,
to insure the recording of the maximum peak height
of the dawsonite, seemed desirable.

Another sample that contained both dawsonite
and analcime from outcrops on lower Piceance Creek
was crushed and passed through the hammer mill.
The sample was then split: half was sieved, and the
different fractions were X-rayed; the other half was
ground further in a mixer mill for 5 minutes and was
sieved, and the different fractions were X-rayed. The
results of these experiments are shown in table 23.
The X-ray data from the sample that was ground only
in the hammer mill show considerable uniformity;

 

 

 

26 X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

TABLE 1.—-Two-theta position of X-ray peaks measured
for use in tables of mineral composition of rocks in
the Green River Formation

 

Mineral Peak position

 

        
  
  
 

(degrees 29)
Chlorite .............................................. 6.3
Illite1 .......................... 8.8
Gyvsum ------------------------- 1 1,7
Dawsonite ...................... 15.6
Quartz ............................... 20.9
Analcime ............................ 26.0
Potassium feldspar ---------- 27.6
Albite ---------------------------------- 28.0
Calcite ---------------------------- 29‘ 5
Dolomite- ------------------- 3 1.0
Pyrite -------------------------------------------------- 33_ 1

 

‘Mica (biotite or muscovite) was distinguished from illite in tuffs by visual
examination of hand specimens.

slight variation is present, however, and the greatest
peak height for dawsonite was found in the finest size
fraction. The X-ray data from the sample processed
in both the hammer mill and the mixer mill show no
greater variation, but the peaks for dawsonite were
smaller in this half of the sample than in the other.
Thus, routine processing 0f the samples would seem
to only require crushing and grinding in the hammer
mill to provide a material in which dawsonite can be
detected with almost maximum sensitivity by X-ray
diffraction without sacrifice of sensitivity in
detection of the associated minerals.

Peak heights obtained for the finest fractions of the
samples shown in table 2B suggest that the values
measured for the samples obtained with the dental
drill should be similar. The data in table ZB also in-
dicate that the chances of detecting dawsonite are
enhanced in the finest fractions of the sample
without appreciable change in the peak of the other
minerals.

It would be ideal to demonstrate that the threshold
of detection is the same for all minerals and that
equal peak heights of various minerals indicate equal
amounts of those minerals. Such is not the case be-
cause of many factors affecting the response of
minerals to X-rays. Some of these factors are the time
of grinding and the particle size of the sample, the
presence of coatings of other substances onthe sur-
faces of the grains, the crystallinity of the mineral
and any variation in the composition, and the ten-
dency for minerals to lie in preferred orientation in
the sample. A detailed discussion of the factors is be-
yond the scope of this paper; the complexities of the
subject have been discussed by Jackson (1964) and
Schultz ( 1964).

Much effort in this study to translate X-ray dif-
fraction peak height directly to percentage of the

 

 

mineral, by the use of standards prepared from
minerals and matrices obtained from rocks of the
Parachute Creek Member, produced no satisfactory
scheme for achieving the highly desirable com-
bination of simple procedures and a short time for
routine application to a large number of samples.

Experiments with standards for quartz in a
dolomite matrix from the Parachute Creek Member
indicated that the value of the height of the 20.9° 29
quartz peak is about 80 percent of the value of the
amount of quartz in the standards, but these results
are semiquantitative at best. Jackson (1964, p. 256)
found that generally more than 10 percent quartz
must be present in a sample before the 20.9° 29 peak is
legible.

Fine-grained disseminated dawsonite could not be
separated from the other components of the rocks, so
satisfactory standards for quantitative evaluation of
X-ray peak heights could not be established. Smith
and Milton (1966, p. 1034) estimated, however, that as
little as 3 percent dawsonite can be detected by X-ray
diffraction. Comparison of X-ray data with chemical
determinations of acid-soluble aluminum has not
yielded satisfactory correlation. More involved and
time consuming procedures for the quantitative
determination of dawsonite, however, have been des-
cribed by Smith and Young (1969). .

Analcime seems to be highly sensitive to detection
by X-ray diffraction. Tuffs that contain about 50
percent analcime yielded a major peak whose apex
was not recorded at the standard settings of the X-ray
equipment. Preparation of standards was hindered
because the analcime in these rocks contains
myriads of small inclusions of other minerals.

Potassium feldspar and albite standards made
from materials in these rocks were not obtainable.
There is no reason to suspect, however, that the two
groups of feldspars have any significant differences
in sensitivity to X-rays. Equal peak heights of the two
feldspars in these samples probably do indicate
nearly equal amounts of the feldspars.

Dolomite and calcite seem to be similarly sensitive
to detection by X-rays. X-ray diffraction provides a
satisfactory and rapid method for distinguishing
between the two minerals and for estimating their
relative abundance in the sample.

Pyrite seems to be less easily detected in the X-ray
diffraction patterns than should be expected from its
high degree of crystal symmetry. Thin-section study
suggests that accessory amounts of pyrite are com-
monly disseminated in the rocks of the Parachute
Creek Member, but most legible peaks for pyrite are
restricted to those patterns from samples in which
pyrite is abundant and coarsely crystalline enough to
be seen easily by the unaided eye.

 

 

MINERAL COMPOSITION

27

TABLE 2,—X-ray data, expressed by X-ray peak height in chart units, from grinding experiments on dawsonitic
rocks from the lower Piceance Creek section

A. PEAK HEIGHT VARIATION WITH GRINDING TIME

 

Dark oil shale, unit 32

Dark oil shale, unit 50

 

 

 

 

Grinding time (min) —————————— 5 1o 20 30 40 5o 5 10 20 30 40 5o
Dawsonite -------------- 29 17 10 9 7 7 84 48 32 23 13 10
31 27 27 26 2s 27 38 32 37 37 29 29

14 14 14 14 14 17 13 14 14 11 1o

5 5 5 5 6 6 6 5 5 4 5

19 16 15 14 14 17 15 19 12 9 9

7 7 7 6 7 0 0 0 0 o 0

9 s 6 6 6 11 7 5 5 3 3

 

 

B. PEAK HEIGHT VARIATION WITH SIZE FRACTION AND GRINDING TIME

 

 

 

Method of - - Potassium ~ » - Wei ht
sample preparation Mesh Dawsomte Analoxme Quartz feldspar Albite Dolomite Illite per fe nt
Hammer mill only------—----‘ -28 71 14 31 9 10 34 7 100
Hammer mill and sieve--- +100 71 14 32 9 11 35 7 44
400 +200 64 14 30 1o 11 34 7 18
‘200 *% 71 13 31 9 11 37 s 7
_ 77 13 33 1 l 11 34 7 29
Hammer mill and
5-min mixer mill;
no sieve— ---------------------------------- 50 12 32 9 10 34 6 100
Hammer mill, 5-min
mixer mill,
and sieve ---------------------- +100 44 18 32 9 9 31 6 20
-100 +200 47 13 32 9 10 30 6 22
-200 +300 45 14 30 9 8 31 6 13
—300 51 12 31 ll 10 33 5 44

 

Most of the clay minerals in these rocks are illite
type. They tend to lie in a preferred orientation and to
yield the highest peak at 8.80 26. Muscovite and
biotite have their major peaks at the same position,
and examinations of hand specimens and thin sec-
tions were used to draw the distinctions noted in the
various tables.

Reproducibility of the X-ray data, a measure of
the precision of the method, is affected by some of the
factors already discussed. Some test pellets of
selected samples were prepared and scanned four
times —twice on each side—the second scan on each
side at 90° to the first scan. The ranges of the peak
height of the four scans of the test pellets are shown
in table 3. The ranges are small, although the range
of 2—4 chart units in the larger peaks is a smaller
variation than the spread of 3 chart units on smaller
peaks. The differences in the ranges cannot be
evaluated fully, but they are greatly dependent on the
homogeneity of the sample, physical and chemical
characteristics of the minerals—including any pre-
ferred orientation—and variation in the per-
formance of the X-ray generator, goniometer, and re-
cording systems. Test patterns were run frequently
during the periods of X-ray work to monitor variation
in the operation of the X-ray and recording equip-
ment. We consider the ranges of peak height to be suf-
ficiently small that they probably do not interfere
with the use of the data in the manner reported here.

The settings on the X—ray equipment previously
stated produced legible results on the chart from one

scan of the sample for most of the minerals detected.
Those peaks whose tops were not recorded on the
chart at the standard setting were reported in the
tables as values with a plus sign. The plus signs were
most frequently needed with values for analcime in
tuff beds and for dolomite in oil shale and marlstone,
but only about 7 percent of all values compiled in
tables 4, 5, and 6 had to be reported with plus signs.

We concluded from this study that peak heights ob-
tained by X-ray diffraction from these sam-
ples,which were uniformly prepared and exposed to
X-rays at similar settings of the equipment, do offer a
good means of not only determining the minerals
present but also comparing the relative abundance of
given minerals in different samples. More complex
methods requiring preparation of mineral standards
of questionable quality supplemented by chemical
analyses of the samples were rejected because of the
required time and because the final values expressed
as weight percent of the mineral are based on
mathematical manipulation that easily may make
them appear more precise and accurate than they
are.

A few further words of explanation and caution
about reading and interpreting the X-ray data in the
tables and figures of this report may be helpful. The
amount of a mineral in a sample is expressed by the
X-ray peak height in chart units in parts of 100. The
greater the value of the peak height, the greater the
abundance of the mineral. The peak height of a
mineral must not be read as percentage of that

 

 

 

28

 

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

TABLE 3.—Range of X—ray peak height in chart units from four replicate scans of test samples

 

Stratigraphic position

Potassium

 

 

 

 

 

 

     

and sample description Dawsomte Analcime Quartz feldspar Albite Dolomite Calcite
Norelco equipment
US. But. Mines cut:
Dark-brown oil shale 4.8 ft below tuff 13 (table 10)— ----- *- 33—36 41—44 30—34 17—20 21-25 43—46 --
Dark-brown oil shale 6.8 ft below tuff 13— -------------------- ~ 79—84 -~ 33-37 22-25 10-12 14—18 15—18
Lower Piceance Creek section:
Dnrk'brown oil shale 3 ft above base unit 93» ------- — 12—14 9—10 16-19 15—17 7—10 62-66 45-47
Dark-brown oil shale, unit 50 ------------------------------- 61—66 -~ 35-41 21—22 9—11 20-21 27—29
Picker-Nuclear equipment
U.S. Bur. Mines cut:
Dark-brown oil shale 4.8 ft below tuff 13-—-- 28—35 37—42 26—28 11-13 14-16 31-35 -—
Dark-brown oil shale 6.8 ft below tuff 13 --—- 89+ -~ 34-36 19—21 8—9 15—16 13-14
Lower Piceance Creek section:
Dark-brown oil shale 3 ft above base unit 93--~ 14-15 7-8 16-18 12—13 6-9 62—64 44—47
Dark-brown oil shale, unit 50 -------------------- —— 79—81 -- 39-43 16-19 6—8 17-18 26-28
Rio Blanco section:
Dark-brown oil shale, unit 16 ------------------------------------------- -—- 35—37 20-24 9—11 5-7 53-59 41-50

 

mineral in the sample. The values for the peak
heights, however, are a measure of the relative abun-
dance of different minerals in the same sample and
indicate variations in the mineral composition
between samples. The tables and figures of X-ray
data are, therefore, informative when read either
vertically or horizontally.

OIL SHALE AND MARLSTONE

The mineral fraction of the oil shale and marlstone
in the three measured sections is composed chiefly of
various mixtures of dolomite, calcite, quartz, potas-
sium feldspar, albite, analcime, illite, and pyrite.
Dawsonitic oil shale and marlstone, found only
along lower Piceance Creek, will be discussed
separately because of their potential economic value.
Relative abundance of the minerals in the oil shale
and marlstone determined from X-ray diffraction
patterns is shown in tables 4, 5, and 6. A summary of
the data from 196 samples of oil shale and marlstone
is shown in table 7. The values of peak height were
combined into groups, each consisting of a range of
10 chart units of peak height. From these groups, the
modal class (the group with the largest number of
values) and the median class (the group which in-
cludes the value of the middle sample of the entire
suite of samples) were determined for each mineral in
each rock type. The imbalance in the number of sam-
ples for each rock type merely reflects the distribution
of the samples collected.

Dolomite has long been recognized as the
predominant carbonate mineral of the marlstone and
oil shale (Bradley, 1931 , p. 20). Dolomite was detected
in all the samples, except one of oil shale on lower
Piceance Creek. According to the wide range of peak
heights recorded, the abundance of dolomite varies
greatly. Table 7 suggests a general decrease in abun-

 

dance of dolomite from the marlstones, which con-
tain lesser amounts of organic matter, to the dark oil
shales, which contain greater amounts of organic
matter.

Calcite is much more restricted in its occurrence
than dolomite. Nearly half of the 196 samples sum-
marized in table 7 do not contain detectable calcite,
and where present, calcite generally is less abundant
than dolomite. However, calcite was detected in more
samples and in greater abundance relative to
dolomite in samples above the Mahogany ledge than
below it in each of the three measured sections (tables
4, 5, and 6). In 69 samples taken above the Mahogany
ledge, calcite was detected in 59 samples and was
relatively more abundant than dolomite in 14 sam-
ples. In 127 samples taken below the Mahogany
ledge, calcite was detected in only 42 samples and
was more abundant than dolomite in only one.

Analcime is a common mineral in these rocks and
was detected in 85 percent of the 196 samples that are
compared in table 7. Dark oil shale contains more
analcime than lighter oil shale and marlstone. About
half the 196 samples of the four types of rock yielded
X-ray peak heights for quartz within the range of 1 1-
20 chart units, suggesting no great variation in the
relative abundance of quartz in many of these rocks.

Some potassium feldspar was detected in about 95
percent of the 196 samples of oil shale and marlstone.
In the three types of oil shale, nearly half the samples
are in the modal class, which coincides with the
median class of the medium and dark oil shales. The
potassium feldspar is mostly sanidine, but some sam-
ples contain microcline and orthoclase, according to
X-ray examination by the technique of Wright (1968,
fig. 3). Potassium feldspar was detected in more sam-
ples than was albite and occurs perhaps in slightly
greater relative abundance than albite.

 

 

MINERAL COMPOSITION 29

TABLE 4.—Mineral composition, expressed by X-ray peak height in chart units, of rocks in stratigraphic succession from the pipeline
section

ID, dark brown; M, medium brow-n; L, light brown; Cl ,chlorit/e; Py, pyrite; Gp, gypsum. Leaders (--—), not detected]

 

U 't t '
m Analcime Quartz P0 assmm Albite Dolomite Calcite Illite Remarks
sampled feldspar

 

 

PARACHUTE CREEK MEMBER
Rocks above Mahogany ledge

 

 

 

 

 

 

 

 

 

64 25 43 56 -- 4 Toff, micaceous (Cl, 5).

86+ 16 7 60 51 44 5 Tuff, micaceous.

23 25 18 10 52 — 5 Oil shale, pyritic (D) (Py, 5).

25 17 14 12 65 29 5 Oil shale (D).

29 14 9 11 70 51 3 Oil shale (M).

20 15 11 10 53 34 4 Oil shale, pyritic (D) (Py, 2).

48 19 17 -- 65 7 4 Oil shale, pyritic (D) (Py, 5).

45 15 14 13 81 13 7 Oil shale (L),

85+ 44 4 3 -- -' ‘- Tuff.

28 18 9 11 80 19 -- Oil shale (D).

59 37 29 —- -- 12 -- Tuff (Cl, 9).

27 19 16 15 ’75 20 -' Oil shale (D).

84+ 41 14 6 24 18 8 Tuff, micaceous (C1, 5).

26 13 9 12 63 44 5 Oil shale (D).

88+ 51 11 14 -- 8 8 Tuff, micaceous (Cl, 8).

11 17 12 8 82 48 4 Oil Shale (M).

12 16 12 9 74 58 3 Do.

17 17 11 12 88+ 29 -- Marlsmne,

22 90 ._ —- 21 6 -- Pod in marlstone.

Mahogany ledge

28 15 12 14 85+ -- -- Oil shale (D).

75+ 24 12 9 18 8 -- Tuff. Mahogany marker.

21 18 13 42 85+ ~ 9 Oil shale (D). Mahogany bed.

22 12 10 20 85+ 12 4 Oil shale (M).

17 15 14 25 72 38 7 Oil shale (D).

86+ 56 24 24 -- -- '- Tuff.

Rocks below Mahogany ledge

11 12 32 46 56 8 -— Oil shale (M).

—- 21 22 27 78+ ~ 9 Oil shale, bumed(?).

63 18 33 27 38 14 -- Tuff.

-- 13 18 -— 86+ — 4 Oil shale (M).

68+ 5 -- 70 -- — 3 Tuff, muscovitic.

30 14 <- 6 86+ 5 Oil shale (M).

83+ 32 15 30 -- -- -- Tuff.

14 12 19 14 80+ - -- Oil shale (L).

15 37 41 24 75 ~ 6 Marlstone, tuffaceous.

9 26 24 5 94+ 8 -- Mai-lstone, brecciated.
-- 26 32 -» 82+ - 3 Marlstone.

-- 45 65 27 -- -- Tuff (Cl, 8).

-- 12 6 5 87+ ~ 2 Cavity septum.

18 15 19 10 72 — 6 Oil shale (D) (G1), 3).
-- 43 57 55 -» —- 5 Tuff.

38 15 18 12 51 — 5 Oil shale (L).

44 15 10 37 24 -- -- Tuff.

80+ 45 10 -- 6 -- -' Do.

80+ 18 -- 8 -- -- —- Do.

12 12 5 4 21 6 4 Oil shale (D).

50+ 6 1 24 -- -- -- Tuff.

27 17 25 10 33 — 9 Oil shale (D).

78+ 27 20 15 57 -- -- Tuff.

7 10 12 -- 74+ — 1 Tuff, dolomitic.

11 8 4 4 35 - 4 Oil shale (M).

66 32 43 14 - —- 5 Tuff.

17 14 5 5 50 -— 8 Oil shale (M).

66 43 44 16 — 7 Tuff.

70+ 12 32 53 -- -- -- Tuff, micaceous (Cl, 8).

60+ 11 9 10 -- -- -- Tuff (C1, 7).

3 8 5 4 58 — 3 Oil shale (L).
8 14 8 7 88+ 15 5 Pod, dolomitic.

19 16 10 8 57 - 9 Oil shale (M).

15 18 16 -- 63 — 7 Marlstone (Py, 8).

4 9 7 15 85+ -- -- Marlstone, tuffaceous.

15 5 5 -» 80+ —- -- Marlstone, tuffaceous (magnesite, 15).
3 3 4 4 85+ -- -- Marlstone; at top of unit.
4 27 7 -- 75+ -- -- Marlstone; 0.6 ft above base.

60+ 8 27 5 -- ~ 6 Tuff.

15 12 4 5 86+ 6 Marlstone.

 

 

 

 

30 X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

TABLE 4.—Mineral composition, expressed by X-ray peak height in chart units, of rocks in stratigraphic succession from the pipeline
section—Continued

 

Unit Potassium

sampled Analcune Quartz feldspar Albite Dolomite Calcite 111m Remarks

 

PARACHUTE CREEK MEMBER—Continued
Rocks below Mahogany ledge—Continued

 

 

 

 

29 19 -- 10 84+ — 6 D0.
32 20 12 12 21 -— 16 Oil shale (M).
5 l5 -- 6 85+ — 8 Marlstone.
29 17 5 7 85 3 9 D0.
7 12 9 15 80+ ~ 5 Do.
GARDEN GULCH MEMBER
-- 35 14 17 14 13 21 Shale, silty.

 

TABLE 5.—Mineral composition, expressed by X-ray peak height in chart units, of rocks in stratigraphic succession from the lower
Piceance Creek section
1D, dark brown; M, medium brown; L. light brown; Cl,chlorite; Py, pyrite; Gp, gypsum. Leaders (~), not detected]

 

Unit , . Potassium . , , .
ssmpl ed Dawsomte Analcune Quartz feldspar Albxte Dolomite Calc1te Hhte Remarks

 

EVACUATION CREEK MEMBER

 

-~ 55 36 22 31 19 20 3 Sandstone, tuffaceous (Cl, 13).
-- 32 20 23 60 -- 85+ 5 Sandstone, tuffaceous (Cl, 3).

 

PARACHUTE CREEK MEMBER
Rocks above Mahogany ledge

 

 

 

 

.. 30 21 13 9 22 30 7 Oil shale, pyritic (D) (Py, 5).
-- 25 15 8 8 47 31 7 Oil shale, pyritic (D) (Cl, 3; Py, 2).
-- 32 14 11 10 54 27 5 Oil shale, pyritic (D) (Py, 2).
-- 90+ 6 5 4 -- 90+ 4 Oil shale (L).
-- 88+ 32 28 18 —— 43 22 Tuff.
-- 85+ 25 15 15 ~ -- 5 D0.
— 27 21 9 11 7O 64 5 Oil shale (M); 10 ft above base.
.1 17 13 12 10 64 76 4 Oil shale (D); at base.
-« 60 23 38 46 67 3 4 Sandstone, tuffaceous.
-- 3 15 16 9 63 80 5 Limestone.
. 68 39 26 28 43 3 - Tuff.
-— 73 73 14 10 —— -- ~ D0.
85+ 19 34 38 -- 62 — D0.
- 90* 4 6 14 73 ~ Do.
—- 36 10 75 65 71 57 3 Oil shale (D).
-- 27 12 6 -- 51 71 5 Oil shale (M).
18 7 5 5 51 90+ 4 Marlstone.
-~ 8 24 33 43 22 64 4 Marlstone, tuffaceous; 7.6 ft above base.
- 35 48 50 32 — 7 Marlstone, tuffaceous; 5.6 ft above base.
-- 17 31 41 78+ 34 14 5 Marlstone, tuffaceous; 3.6 ft above base.
-- 21 18 19 66 50 64 3 Marlstone, tuffaceous; 2.6 ft above base.
31 18 24 22 27 63 5 Marlsbone, tuffaceous; at base.
'- 9 26 30 36 44 58 3 Marlstone, silty; 0.4 ft below top.
16 16 5 9 62 78 6 Marlstone; 25 ft above base.
- 36 20 ~ 55 23 50 4 Marlstone; 21 ft above base.
37 26 28 50 25 15 5 Marlstone, tuffaceous; 15 ft above base.
-- 22 22 -- 77 67 11 4 Sandstone.
« 39 26 22 63 29 14 ~ Do.
- 24 11 8 7 71 14 3 Oil shale (L).
Mahogany ledge
-- 94+ 54 4 5 -- -- ~ Tuff. False marker.
22 11 9 5 63 25 3 Oil shale (D).
> 19 18 12 12 60 A- 8 Oil shale (M) (Gp, 10).
29 14 8 7 54 17 5 Oil shale (D) (Gp, 5).
12 35 - 83+ -- ~ — Tuff.
29 31 10 10 81 ' 8 Oil shale (D).
—» 79 29 -- 30 2O -- — 'I‘uff. Mahogany marker.
8 11 5 4 76 45 4 Oil shale (D).
-- 24 17 7 9 40 4 7 Oil shale (D); 1 ft above base. Mahogany bed.
26 23 7 8 50 12 8 Oil shale (D) (Py, 6); at base. Mahogany bed.

 

 

TABLE 5.—Mineral composition,

MINERAL COMPOSITION

31

expressed by X—ray peak height in chart units, of rocks in stratigraphic succession from the lower
Piceance Creek section—Continued

 

 

 

 

 

 

 

Um‘ Dawsonite Analcime Quartz ”1395‘“ Albite Dolomite Calcite 111m Remarks
sampled feldspar
PARACHUTE CREEK MEMBER—Continued
Mahogany ledge—Continued
.. 2 9 6 6 43 87 3 Marlstone,
—- 24 15 7 7 55 6 10 Oil shale (D); 4 ft above base.
w 11 18 3 5 95 ”l — - Oil shale (D) (Gp, 2); 3 ft above base.
-- 17 21 11 — 4O —- 10 Oil shale (D) (Py, 3); 1 ft above base.
-- 96+ 48 9 22 -- -- ~ Tuff.
-- 95+ 36 6 8 -- -- —- Do.
-- 15 17 8 10 82+ - 8 Oil shale (D).
-- 95+ 33 -- 8 —- 6 —- “ff.
-- 6 17 6 4 -- 90+ — Rosette in cavity (Gp, 5).
-— 7 29 11 10 68 78 3 Residue in cavity (Gp, 5).
-- 4 15 12 21 57 46 3 Oil shale (D) (Gp, 7).
Rocks below Mahogany ledge
-- 10 44 6 5 76+ — 2 Marlstone (Op, 3).
-- 26 14 17 20 85+ ~ 3 Oil shale (M); in cavity zone.
-- 38 25 - —- 90+ - — Material in cavity (G1), 2).
-— -- -— —— 26 80+ 6 3 Material in pod.
-— -— 13 25 27 65 ~ 5 Marlstone.
-- -- 13 26 16 50 20 4 Oil shale (D).
-« 23 21 5 9 60 -— 4 Do.
-— 21 14 12 10 83 3 6 D0.
10 12 20 32 —— 47 35 - Cavity filling (Gp, 8).
-- 9 37 13 6 60 —- 3 Marlstone.
-- 24 18 11 9 80 — 2 Do.
-- 17 18 6 14 55 ~ 9 Oil shale (D) (Gp, 12).
-- 8 14 10 10 62 —- 14 Do.
-- 38 19 27 13 40 - 7 Oil shale (L).
24 15 19 16 -— 52 - 6 Oil shale (D).
—- 33 20 24 17 61 ~ 7 T?“-
12 26 22 21 11 71 — 6 011 shale (D) (Gp, 4).
-- 16 35 16 -- 28 -— 5 'I‘uff.
35 15 25 16 8 -— -- - Do.
13 23 21 22 e 46 a 8 Oil shale (D); 6 ft above base.
13 10 20 17 4 59 45 5 Oil shale (D); 3 ft above base.
-- 28 27 16 ~ 70 -- 8 Oil shale (D) (Gp, 4).
<- 19 21 9 9 54 . 11 Oil shale (L); 6 ft above base.
11 6 22 25 ~ 62 - 7 Oil shale (L); 4 ft above base.
-- -- 27 34 — 32 — 9 Oil shale (L); 0.2 ft above base.
-- 22 15 11 85 -- —- Conglomerate, dolomitic.
-- -- 26 32 13 46 - 8 Oil shale (D).
-- 3 14 10 ~ 85+ ~ -- Conglomerate, dolomitic.
.. .. 20 27 — 70 ~ 6 Oil shale (L).
30 24 -- 85+ —- 8 Matlstone.
-- 19 51 13 10 85+ — 8 Oil shale (D).
18 8 21 17 11 43 4 6 Oil shale (D); 52.6 ft above unit 49.
20 23 26 14 8 40 ._ 6 Oil shale (D) (Py, 4); 36.1 ft above unit 49.
- 80 27 12 22 53 -- — Matlstone, tuffaceous; 25.6 ft above unit 49.
-- 92+ 38 29 12 -- 30 19 'I‘uff; 24.3 ft above unit 49.
30 23 16 1 73 —- 8 Oil shale (M); 20.9 ft above unit 49.
75+ 36 11 -— 65 - -- 'l‘uff; 19.7 ft above unit 49.
-- 14 20 12 .. 71 ~ 8 Oil shale (M); 13.4 ft above unit 49.
-- 31 90 41 ~ 50 11 6 Tuff; 12.1 ft above unit 49.
5 17 10 1 65+ -- ~ Toff; 11 ft above unit ‘49.
-- 13 17 10 10 81 — 8 Oil shale (L); 9.7 ft above unit 49.
47 »- 31 17 8 18 25 6 Oil shale (D) (Py, 4); 4 ft above unit 49.
~ 83 59 14 24 -~ 13 — Tuff, a key bed. Tuff 13 of table 101
13 9 33 17 8 66 - 6 Oil shale (D); 2 ft below unit 49.
53 7 31 18 7 17 — 5 Oil shale (D); 4.8 ft balow unit 49.
55 5 31 19 7 12 - 4 Oil shale (D); 5.8 ft below unit 49.
19 -» 21 13 4 86+ 5 Oil shale (D); 8.4 ft below unit 49.
42 5 30 12 1 45 - 6 Oil shale (M); 8.5 ft below unit 49.
31 6 25 18 6 61 3 Oil shale (M); 10 ft below unit 49.
~- 75+ 32 19 -- —- -- ’I‘uff; 16.5 ft below unit 49.
26 8 22 11 12 7 11 Oil shale (D) (Py, 5); 20 ft below unit 49.
-- 23 25 16 _ 42 10 9 Oil shale (D) (Py, 5; Gp, 6); 20.6 ft below unit 49.
3 18 27 17 10 35 - 8 Oil shale (D) (Py, 4); 21.1 ft below unit 49.
33 _. 28 17 10 24 12 8 Oil shale (D) (Py, 6); 22.6 ft below unit 49.
-- 23 24 12 9 49 9 6 Oil shale (D); 23.3 ft below unit 49.
24 -- 16 17 -— 48 8 5 Oil shale (D); 32.4 ft below unit 49.
-- 15 21 12 11 67 7 15 Oil shale (D); 34.1 ft below unit 49.
l 11 6 5 96 3 5 Oil shale (D); 37.4 ft below unit 49.
- 7 13 5 9 66 11 9 Oil shale (D); 42.4 it below unit 49.
- 41 22 26 6 26 13 6 Tuff; 44.4 ft below unit 49.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

 

 

32 X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO
TABLE 5.—Mineral composition, expressed by X-ray peak height in chart units, of rocks in stratigraphic successzon from the lower
Piceance Creek section —Continued
Unit D w 0 it An 1 ~ Quartz P°tassmm Alb'te D ' C 1 't '
sampled a s n e a tame feldspar l olomite a 01 e Ilhte Remarks
PARACHUTE CREEK MEMBER—Continued
Rocks below Mahogany ledge—Continued
-- 9 19 6 7 32 - 13 Oil shale (D); 52.4 ft below unit. 49.
3% 2 31 13 10 21 -- 13 Oil shale (D); 52.8 ft below unit 49.
-- 7 30 -- 49 ~ 2 ’hlff; 54.0 ft below unit 49.
-- 10 25 -- 9 48 5 11 Oil shale (D).
~- 8 20 15 7 28 -- 10 Oil shale (D); 57.4 ft below unit 49.
32-——~—~--- 29 g 31 16 8 22 8 14 Oil shale (D) (Py, 3).
- -— 2 5 2 2 93 - 2 Marlstorle; 64.2 ft below unit 49.
9 17 7 6 53 - 13 Marlstone; 65.2 ft below unit 49.
- 5 21 16 7 18 - 10 Oil shale (D); 68.4 ft below unit 49.
-- 23 38 12 -- -- 4 ’I‘uff; 72.3 ft below unit 49.
6 5 13 9 5 83+ 5 4 Oil shale (D); 73.3 ft below unit 49.
15 -- 50 25 18 57 — 6 Marlstone; 75.3 ft below unit. 49.
—- 5 43 40 -- -- — 6 Tuff.
-- 9 9 3 3 90+ 3 ~ Marlstone.
-- 64 5 11 16 ~ ~ — 'I‘uff.
-- 76 + 9 14 19 -~ — ~ Do.
-- <- 16 10 5 35 — 13 Oil shale (D); 2.7 ft below to .
-- 15 17 9 8 55 — 11 Oil shale (L); near base. p
—- 5 16 -- 9 33 ~ 13 Oil shale ( ).
-~ - -- 3 86 + 11 7 Oil shale (L).
-~ ~ - 6 8 70 + - 12 Oil shale (D).
-- 6 6 12 5 Oil shale (D) (Gp, 29).
0 Do.

[D, dark brown; M, medium brown; L, light brown; Py,

 

section

 

’T‘
l
l
|
x
- |..
. 1-1
M..
._.
m-
\I a:
b—‘D—I
mH
A01
ll'
. m
on»

pyrite; Cl, chlorite; Gp, gypsum. Leaders (---), not detected]

 

 

 

 

 

 

Uh“ Analcime Quartz Pmsm’" Albite Dolomite Calcite Illite Remarks
sampled feldspar
PARACHUTE CREEK MEMBER
Rocks above Mahogany ledge
35 20 12 9 60 41 10 Oil shale, pyritic (D) (Py, 2).
25 15 10 7 50 82 4 Do.
25 10 7 7 56 14 4 Oil shale, pyritic (D) (Py, 3).
81+ 36 23 19 -- ~ 5 'I‘uff, micaceous; lowest bed.
36 19 12 11 84 — 4 Oil shale, pyrih'c (D) (Py, 2).
83+ 41 16 34 -« 6 8 Sandstone dike, tuffaceous.
24+ 17 12 -- 80 22 5 Oil shale (D).
22 39 11 23 40 39 12 Oil shale (L).
6 25 27 80 -- — 11 Tuff pods.
11 34 11 18 87 + 19 15 Oil shale (M).
31 29 11 34 86 1‘ —— 4 Tuff.
32 15 8 8 74 13 5 Oil shale (D).
26 15 10 9 85+ 25 4 Oil shale (M) (Cl, 3); 3.1 ft above base.
9 26 5 3 55 88 + -- Oil shale (D).
28 17 13 10 61 28 5 Oil shale (M).
- 13 6 -- 85+ -- -- Marlstone.
18 15 12 - 72 23 3 Oil shale (D).
8 71 20 22 85+ 6 13 Marlstone.
18 12 9 - 55 72 3 Oil shale (D).
41 53 15 26 76 9 7 Marlstone, tuffaceous.

6 48 21 22 87+ 25 9 Tuff, muscovitie (Cl, 4).

7 41 25 19 84+ 14 11 Tuff, muscovitic.

-- 23 23 10 44 23 3 Oil shale, pyritic (D) (Py, 6).
40 13 10 8 40 10 5 011 shale, pyritlc (D) (Py, 3).
20 15 15 8 74 18 4 Oil shale (M).

68 21 17 9 35 7 5 Oil shale (D).
88+ 25 6 23 ~ 16 5 Tuff.

-- 44 12 48 85+ 15 11 Marlstone (Cl, 4).
16 43 11 -- 71 43 3 Oil shale (D).
83+ 24 7 23 -- 24 5 Tuff.

» 44 12 18 85+ 15 11 Marlsmne (Cl, 4).
17 86 -- -- 44 18 3 011 shale (D).
81+ 16 10 15 -- — 5 Tuff.

 

 

 

TABLE 6.-Mineral composition, expressed

MINERAL COMPOSITION

by X-ray peak height in

Blanco section —Continued

33

chart units, of rocks in stratigraphic succession from the Rio

 

 

 

 

 

 

 

 

 

Unit Potassium .
‘ Alb te ’ ' '
sampled Analmme Quartz feldspar 1 Dolomite Calmte Illlte Remarks
PARACHUTE CREEK MEMBER—Continued
Rocks above Mahogany ledge—Continued
85 -------- 7 37 13 22 86 15 13 Marlstonh
74.e__~.._~ 33+ 35 14 10 66 20 17 Tuff, weathered, biot’mc
85+ 41 23 13 50 22 17 Tuff, fresh, biotitic.
10 10 7 6 58 90+ 4 Oil shale (M).
9 21 22 -- 73 33 6 Oil shale (D); 2 ft below top.
39 80 10 7 42 - 5 Tuff (Cl, 3).
22 14 7 -- 75 -- 22 Oil shale (M); encloses tuff.
13 16 12 1 86+ 21 6 Marlstone.
28 11 7 13 43 39 3 Oil shale (D).
.. 14 -- 4 90+ — -- Sandstone.
1 - -- 2 91+ 70 .. Do.
10 18 18 -- 86 31 - Oil shale (L).
38 21 22 18 32 4 6 Tuff (C1, 5; Gp, 3).
Mahogany ledge
44 13 5 9 82+ -— 4 Oil shale (L).
4 5 -- -- 90+ 70 —- Clay bed (Cl, 31).
-- 26 -- 3 90+ -- Marlstone (Cl, 30).
78+ 20 10 10 30 -- 'I‘uff (Cl, 30).
20 24 9 14 86 Marlstone (Cl, 8).
13 64 35 39 43 — 7 Tuff, muscovitic (C1, 9).
85 + 37 7 34 40 ~ -- Tuff (Cl,3).
39 23 -- 75 + 27 ~ 4 Sandstone dike (Cl, 7).
78+ 22 10 11 <- - 5 Tuff, weathered.
78+ 17 14 9 - -- -< Tuff, fresh. Mahogany marker.
9 26 22 18 90+ ~ 9 Marlstone.
20 11 10 10 59 22 3 Oil shale (D). Mahogany bed.
12 7 2 4 95+ — 2 Dolomite
20 14 -— 8 96 21 5 Oil shale (D).
15 24 10 17 95+ 3 13 Dolomite.
—- 30 11 20 86+ 19 10 Oil shale (D); 15.9 ft above base.
8 16 -- 16 59 41 5 Oil shale (D); 10.6 ft above base.
13 14 9 16 67 18 -- Oil shale (D)
20 10 -- 12 79 — 4 Oil shale (D); uppermost bed.
14 11 10 -- 95+ 9 3 Oil shale (D); lowermost bed.
65 38 —» 53 33 —— 39 Tuff, biotitic.
Rocks below Mahogany ledge
89+ 20 16 77 74 — 3 'I‘uff.
5 11 -- 7 90+ 3 — Dolomite.
75+ 36 22 —- -- -- Sandstone, tuffaceous (Gp, 4).
2 4 . 7 90+ 3 -- Sandstone.
80+ 20 18 22 — -- 5
31 18 17 17 80 32 7 Marlstone.
12 22 12 11 86+ — 4 Do.
87+ 45 12 45 -- — -- Tuff.
25 17 31 25 58 6 6 Marlstone.
.. 37 25 18 74 82 4 Sandstone.
24 23 30 22 84+ — 5 Marlstone, tuffaceous; 25 ft above base.
42 16 17 28 73 18 5 Marlstone; 5 ft above base.
55 11 23 29 70 — 4 Marlstone, tuffaceous; at base of unit.
28 11 15 15 37 .. .. Cavity filling (Cl, 8; leonhardite, 23).
11 24 12 17 -- —- Noddule (Gp, 55).
49 14 27 25 73 -. . Marlstone (Py, 2).
22 6 -- 7 -- — -- Concretion, pyritic (Py, 27).
35 22 16 19 52 — 8 Marlstone (Gp, 17).
10 19 - 14 -- -- -- Concretion, pyritic (Py, 5; Gp, 29).
-- -- -- - - . Concretion, pyritic (Py, 17; szmolnokite, 28).
32 16 18 26 52 -— 4 Marlstone (Gp, 21).
8 10 13 11 59 56 —- Marlstone, fossiliferous (insects).
7 13 14 13 75 3 -- Marlstone.
16 8 7 7 74+ 5 D0.
47 17 18 14 61 — 5 Tuff.
10 31 24 12 76 — 5 Siltstone, tuffaceous.
12 27 20 12 85+ — 7 Marlstone (Cl, 3).
12 4 .. 6 84+ 4 -- Tuff (Cl, 17).
4 28 32 14 88+ — 3 Marlstone (Cl, 3).

 

 

 

 

34

 

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

TABLE 7.—Mineral composition, expressed by X—ray peak height in chart units, of oil shale and marlstone from the three
measured sections

[Numbers in parentheses indicate number of samples]

 

 

 

  

Marlstone (60) Light-brown oil shale (17) Medium-brown oil shale (33) Dark-brown oil shale (36)
Mineral .

Modal class Median class Modal class Median class Modal class Median class Modal class Median class
1-10 (20 11-20 1—10 (3) 11-20 11—20 (11) 11-20 21-30 (29) 11-20
11—20 (23) 21—30 11—20 (7) 11-20 11-20 (24) 11-20 11-20 (47) 11—20
11—20 (20) 11-20 1-10 (8) 11-20 11-20 (16) 11—20 11—20 (42) 11—20
1-10 (9) 11-20 1-10 (8) 1-10 1—10 (18) 1-10 1—10 (50) 1—10
81—90 (23) 71—80 81—90 (5) 61—70 81~90 (7) 61-70 51—60 (14) 51-60
— o (34) 0 0 (11) 0 0 (15) 1-10 0 (35) 1—10
Illite ------------------ 1-10 (42) 1-10 1-10 (12) 1-10 1—10 (26) 1-10 1-10 (71) 1—10

 

Some albite was detected in about 85 percent of the
196 samples of oil shale and marlstone. Albite peaks
in about half the samples of oil shale have heights in
the modal class (peaks of 1-10 chart units). The
modal class of peak heights for albite is the same in
the marlstone as in the oil shale, but the range of all
values is greater in the marlstone, as indicated by
only nine of 60 peaks being within the modal class
and by the median value lying in the class of 11—20
chart units. Most of the sodium feldspar is low-struc-
tured albite (Ab95_1oo) as determined by the X-ray
technique of Wright (1968, fig. 3). Low-structured
albite is considered to be of low-temperature origin,
and it has a high degree of order of the silicon and
aluminum atoms in the structure.

Small amounts of illite occur in many of the sam-
ples, and chloritic material occurs in a few of the sam-
ples.

Pyrite occurs as tiny disseminated grains and
streaks in many rocks—most commonly, the dark oil
shales.

Small amounts of some sulfate minerals derived
from the weathering of pyrite and other minerals oc-
cur mostly as coatings along bedding planes or as
fillings in fractures, or even as blooms of efflorescent
salts. The most common of these minerals is gypsum
(CaSO4-2H20), which occurs chiefly as thin white
coatings along bedding planes. The coatings of
gypsum are especially abundant in the outcrops
along lower Piceance Creek. Other sulfate minerals
detected by X-ray diffraction analysis are
szomolnokite (FeSO4-H20), starkeyite (MgSO4-
4H20), and bloedite (MgSO4-NagsO4-4H20) (B.M.
Madsen, written commun., 1968).

VER'I'ICAI. VARIA’I‘ION IN COMPOSITION

Data compiled in tables 4, 5, 6, and 7 characterize
the composition of the mineral fraction of units a few
inches thick of the generally laminated oil shale and
marlstone taken from various stratigraphic intervals
in the three measured sections. Further detailed
study of some differing units of these rocks was

 

 

undertaken to determine how similar a randomly
sampled inch or two of rock is to the next few inches
or feet above or below.

For this study, selected blocks of rocks were sawed,
and samples were obtained with the use of a dental
drill. Powdered samples thus obtained were
pelletized and were used to form a veneer of sample
on a backing of powdered cellulose. In the des-
criptions below, the letter and number symbols in
parentheses refer to colors in the standard “Rock-
Color Chart” by Goddard and others (1948).

FOSSILIFEROUS OIL SHALE AND
MARLSTONE, PIPELINE SECTION

A stratigraphic thickness of 12.15 cm of laminated
light-brown oil shale and marlstone rich in insect fos-
sils was selected for detailed study from unit 197 in
the pipeline section. The slab of rock, shown in figure
9, is 20 cm wide and has light laminae that are
yellowish gray (5Y 7/2) to light gray (N 7) alternat-
ing with dark laminae that are light olive gray (5Y
5/2) to medium gray (N5). Each sample consists of a
series of extremely thin light and dark laminae, but
each sample has a distinctly different color when
compared with the samples above and below (fig. 10).

 

FIGURE 9.—F0ssilifer0us laminated oil shale and marlstone from
the pipeline section (unit 197.) Dark spots show where samples
were taken. Numbers are sample numbers used in figure 10.

 

 

 

  

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_______ __________

 

 

 

 

36

 

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

TABLE 8.—Mineral composition, expressed by X-ray peak height in chart units, of a sequence of marlstone and medium-
brown oil shale from the pipeline section (unit 218)
(D, dolomite; c, calcite]

 

Number of samples

 

Thickness

 

Arithmetic average of peak height

 

 

Dark layers Light layers
(cm) Total P -
Analcime Quartz ““5““ Albite Dolomite Calcite Illite
D >0 0 >1) Total D 4 c c >D Total feldspar
26. 3 6 8 2 10 1 6 28 1 3 5 5 69 65 3
7. 3 3 0 2 2 5 20 13 3 4 58 80 3
15. 1 4 4 1 5 9 19 13 3 4 74 58 3
21. 8 8 2 13 15 23 20 1 1 4 4 69 74 3
1. 0 1 3 0 3 4 20 1 4 4 5 81 69 4
2. 1 1 0 2 2 3 22 1 2 3 3 73 87 3
4. 1 6 5 0 5 1 1 24 14 4 6 82 69 3
10. 1 9 0 9 9 18 14 10 4 4 84 75 0

 

 

The thickest individual lamina in this slab is about 1
mm thick, but commonly the total thickness of three
or four pairs of light and dark laminae is only 1 mm.
Even some of the thinnest laminae can be traced
laterally across the entire slab.

Clearly visible in figure 9 are structural features
that Bradley (1931, p. 29) called “loop bedding.”
In these, the normally even and regular lateral course
of the laminae in thin sequences generally a few
millimeters thick is interrupted irregularly by
constriction of some or all of the layers. In the short
interval of constriction, the inner laminae of the se-
quence commonly are pinched off, but the upper and
lowermost laminae are not. These features are more
common in the oil shale than in the marlstone, as
noted by Bradley (1931 , p. 29). The greater abundance
of these features in rocks rich in organic matter
suggests that they may be related to the algal life in
the lake.

The composition of the samples is shown in figure
10. Major minerals are dolomite and calcite that are
in association with analcime, quartz, feldspar, and
illite. The X-ray data indicate that the upper half of
the slab contains more calcite and less dolomite than
the lower half. No other differences in mineral com-
position are apparent, but the upper half of the slab
seems to be darker. The composition of a composite
channel sample of the entire slab is shown by the
broken lines in figure 10.

MARLSTONE AND MEDIUM-BROWN OIL SHALE,
PIPELINE SECTION
A stratigraphic thickness of 96.8 cm of marlstone
and medium-brown oil shale from unit 218 in the
pipeline section was studied in a series of slabs of

 

rock 5—22 cm wide. This sequence of rocks is well
laminated, and as in the slab described above, many
individual laminae are no more than 0.5 mm thick.
The lightest colored laminae in this sequence are
yellowish gray (5Y 7/2) to grayish yellow (5Y8/4).
The medium-colored laminae are light olive gray
(5Y 6/1 and 5Y 5/2) to dark yellowish brown (10 YR
4/2). The dark laminae contain the most organic
matter and range from olive gray 5 Y4/1 and 5Y3/ 2)
through dusky yellowish brown (10 YR 2/ 2) to
brownish black (5 YR 2/ 1).

The mineral composition of the suite of 89 samples
is summarized in table 8, which emphasizes some of
the characteristics of these rocks rich in dolomite and
calcite. A major feature of these rocks is the
stratigraphic variation in content of calcite and
dolomite; groups of layers rich in calcite alternate
with groups rich in dolomite. There is no apparent
correlation of the predominance of calcite or dolomite
with either light or dark layers. The relative content
of the other minerals does not vary greatly.

OIL SHALE FROM THE MAHOGANY LEDGE,
LOWER PICEANCE CREEK SECTION

A slab from a 20.6-cm-thick sequence of oil shale
from the Mahogany ledge was selected for study from
unit 161 in the lower Piceance Creek section. This se-
quence of rock, shown in figure 11, is well laminated,
but compared with the rock shown in figure 9, the
laminae in this sequence are more clearly defined
and form small units of rock with more distinctly con-
trasting color. As in the other rocks examined
in detail the individual laminae are extremely thin.
This slab is generally darker than the others de-
scribed in this part of the report, mostly because these

 

 

MINERAL COMPOSITION 37

rocks are richer in organic matter. The lightest
laminae in the oil shale are light brown(5 YR 6/4);the
intermediate—colored laminae are moderate brown
(5YR 4/4) to dark yellowish brown (IOYR 2/2) to
blackish red (5R 2/ 2). The tuff at the base of the slab
consists of two phases differing in color and texture.
The lower, coarser grained part (sample 200) is
moderate brown (5YR 4/ 4), and the upper, finer
grained part (sample 201) is pale yellowish brown
(10YR 6/ 2). The upper part easily could be mistaken
for marlstone in a casual examination.

The composition of 20 samples from this sequence
is shown in figure 12. Major minerals in the oil shale
are dolomite and calcite, but in this sequence the
dolomite peaks in general have twice the heights of
the calcite peaks. Analcime, quartz, potassium
feldspar, and albite are detectable in every sample.
Small amounts of illite are detectable in most sam-

ples.
The tuff has been altered to a rock consisting most-

ly of analcime and quartz. The total amount of feld-
spar probably is about equal in each tuff layer, but
the coarser grained layer contains only albite, and
the finer grained layer contains both potassium feld-
spar and albite.

MASSIVE MARLSTONE FROM THE MAHOGANY LEDGE,
LOWER PICEANCE CREEK SECTION

The entire 31.25-cm stratigraphic thickness of mas-
sive pale-yellowish-brown (10YR 6/ 2) marlstone of
unit 166 was studied in two slabs from the Mahogany
ledge of the lower Piceance Creek section. Some dis-
continuous, undulating thinly laminated brownish-
black (5 YR 2/ 1) lenses occur throughout the bed.

The mineral composition of the bed is shown in
figure 13. The rock is composed chiefly of calcite and
dolomite, with dolomite predominating only in the
thin discontinuous dark layers. The composition of
the bed is remarkably uniform, except for a slight
decrease upward in the content of analcime and for
the great variation of analcime, dolomite, and calcite
in the thin dark bed (sample 5, fig. 13).

l‘vIARLSTONE AND LAMINATED OIL SHALE FROM THE
MAHOGANY LEDGE, RIO BLANCO SECTION

A slab from a 9.5-cm-thick sequence of marlstone
and laminated oil shale in the Mahogany ledge was
selected for study from unit 44 in the Rio Blanco sec—
tion. This sequence of rock is shown in figure 14. The
lower 14 mm consists of thinly laminated oil shales.
The lightest layers are yellowish gray (5Y 7/2), and

 

FIGURE 11.—Laminated oil shale from the Mahogany ledge in
the lower Piceance Creek section (unit 161.) Dark spots show
where samples were taken. Numbers are sample numbers
used in figure 12.

the darkest layers are dusky yellowish brown (10 YR
2/ 2). The next 54 mm of pale-yellowish-brown (10 YR
6/ 2) marlstone consists of five massive beds in which
the lower parts are coarser grained and slightly
darker than the upper parts. Each of the five beds is
separated by a few thin undulating dark laminae
that appear to have more organic material than the
rock above and below. Above the five massive beds
are three thinner, but massive, beds separated by
dark layers that are thicker than those in the beds be-
low. These three beds have an aggregate thickness of
14 mm. The uppermost 1 3 mm of ' the sample consists
chiefly of thinly laminated beds of marlstone that
range from yellowish gray (5Y 8/ 1) to light olive gray

 

(5 Y 5/2).

 

 

38

2

217

216

215

214

213

212

211

210

209

208

207

206

205

204

203
202a

202

201

200 BASE

FIGURE 12.—Mineral composition of laminated oil

5 SAMPLE

 

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

POTASSIUM
ANALCIME QUARTZ FELDSPAR ALBITE DOLOMITE CALCITE ILLITE
CHi$go 10 20 30 4o 50 60 7080 90100 0 10 20 30 40 o 10 0 102050 60 7080 90100 20 3040 50 o 10
UNIIIIIIIIIIfiIIIIWFIIIfiIIIIIWIIIWr—I

 

 

I
V |
|
I

   

 

9J5

860

 

7.30

6.50

5.50

4.80
435

230

L30

OF
SAMPLE

 

 

l

 

shale from the Mahogany ledge in the lower Piceance Creek section (unit
161), as expressed by X-ray peak height in chart units. Dashed line indicates arithmetic average of values for each mineral
in a composite sample of units 202-218.

 

 

 

 

MINERAL COMPOSITION 39
111 g E “J
E N 7, n. '1 “J
—J 0: < O l: o o “J
2 5‘ 5 d m a :2 E
_l
CH < O n. “- < o o :'
UNl‘iR; 0 10 20 30 40 0 10 20 0 1o 0 10 20 30 4o 50 60 70 80 90100 20 30 40 50 60 70 80 90100 0 10
I_l_r__I'_-| I—T__| I'_I I—‘l I”—F I I I I I I I r I I I I I l I I (—1
SAMPLE CM
31.25
13
28.25
12
25.25
11
22.25
10
19.25
9
16.25
8
13.35
7
9.25
6
6.95
5 6.75
4
5.40
3 5.00
2
3.10
1
Base of
sample

FIGURE' 13.—Mineral composition of massive marlstone from the Mahogany ledge in the lower Piceance Creek section (unit
166), as expressed by X-ray peak height in chart units.

The mineral composition of these layers is shown
in figure 15. As in most of the rocks, the commonly
detected minerals include dolomite, quartz,
analcime, potassium feldspar, albite, and illite.
Calcite is conspicuously absent, in marked contrast
to the marlstone and oil shales in the comparable
stratigraphic position beneath the Mahogany
marker on lower Piceance Creek. The laminated rock

in the lower 14 mm of the slab contains a little more
feldspar and a little less dolomite than some of the oil
shales studied. The composition of the marlstone and
oil shale in the uppermost 13 mm of the slab varies
widely.

The middle 54 mm of the slab contains beds con—
siderably different than many noted elsewhere in
this study. The massive nature of the beds and the

 

 

 

40

variation in grain size, coarser on the bottom and
finer on the top, lend a distinctive appearance of
“graded bedding” to this unit of rock. Data in figure
15 indicate that the coarser grained part of the beds
contains more analcime and quartz, and less
dolomite, than the finer grained part. The thin dark
interlayers generally are more distorted than many
other layers and contain more dolomite—and
probably more organic matter—and less analcime
than the adjacent layers.

 

FIGURE 14.—Marlstone and laminated oil shale from the Mahoga-
ny ledge in the Rio Blanco section (unit 44). Numbers indicate
position of composite samples shown in figure 15.

LATERAL VARIATION IN COMPOSITION
MEDIUM-BROWN OIL SHALE, PIPELINE SECTION

Lateral variation in composition of a sequence of
medium-brown oil shale about 3 inches thick that lies
3.1 feet below the top of unit 221 in the pipeline sec-
tion was studied in a series of samples collected at 20-
foot intervals along 240 feet of continuous exposure.
The north end of the sequence is about 40 feet south of
a cattleguard. The rock is thinly laminated; the

 

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

lightest layers are pale yellowish brown (10 YR 6/2) ,
and the darkest layers are brownish gray (5 YR 4/1).

The mineral composition of the 10 samples is
shown in figure 16. The minerals detected include
dolomite, calcite, analcime, quartz, illite, potassium
feldspar, and albite. Dolomite is more abundant than
calcite in all the samples. These data indicate a
lateral consistence in composition.

DARK, PYRITIC OIL SHALE, RIO BLANCO SECTION

Lateral variation in mineral composition of a well-
exposed blue-gray-weathering dark pyritic oil shale
was studied in a suite of 37 samples collected at 100-
foot intervals along the continuous exposures of unit
155 in the Rio Blanco section. The samples were
collected from the middle of the 0.3-foot-thick bed that
is exposed as a rounded ledge 22.3 feet above the top
of the westernmost roadcut in the Rio Blanco section
(fig. 7).

The blue-gray weathered coating is very thin. The
rock is laminated on close inspection, but it has a
massive appearance because it is so dark—dark gray
(N 3) to grayish black (N2). The only mineral visible
to the unaided eye is pyrite, which is disseminated
throughout the bed. The pyrite is most easily seen on
fractures crossing the planes of lamination at low
angle.

The mineral composition of these samples is shown
in figure 17; the samples are numbered in horizontal
sequence eastward from sample 1. Dolomite,
analcime, quartz, potassium feldspar, albite, calcite,
illite, and pyrite were detected. A comparison of the
range and arithmetic average of the mineral content
of the various samples indicates a normal dis-
tribution of the values; that is, the data suggest a
laterally uniform composition for this bed.

DAWSONITIC ROCKS

Dawsonite (NaAl(OH)2C03) has been described
from drill cores in the Piceance Creek basin by Smith
and Milton (1966), and the potential resources of
dawsonite have been discussed by Hite and Dyni
(1967). In November 1966, we found dawsonite dur—
ing X-ray study of medium- and dark-brown oil
shales in the measured section on lower Piceance
Creek. The dawsonite occurs in scattered samples
from a stratigraphic interval of about 370 feet—from

 

FIGURE 15.—Mineral composition of marlstone and laminated oil shale from the ‘Mahogany ledge in the Rio Blanco

section (unit 44)

 

, as expressed by X-ray peak height in chart units.

 

 

 

ANALCIME

CHART UNITS O 10 20 30
r—r—rfi

SAMPLE MM
———#— 95.0

Base of sample

MINERAL COMPOSITION
QUARTZ POTASSIUM ALBITE
FELDSPAR

10203040506070 0102030 01020
r—fl—l—fififi

 

DOLOMITE

10 20 3O 4O 5O 6O 7O 80 90100

 

ILLITE

010
7—1

 

41

 

 

42
2
s a 2%
_ N (7, a.
o '— U) (0
_l 0: < Q
g at 5 a
< O 0. LL
CHART UNITS 0 10 20 30 O 10 20 O 10

SOUTH

10

SAMPLE

 

1

NORTH

FIGURE 16.

 

 

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

L|J
t Lu
Lu 2 ':
t o o if
m —J _| _
.4 O < -‘
< o o d
0 10 50 60 70 80 90 20 30 0 10

 

—Lateral variation in mineral composition of medium-brown oil shale from the pipeline section (unit

221), as expressed by X-ray peak height in chart units. Horizontal sample interval is 20 feet.

about 200 feet above the base of the Parachute Creek
Member upward to within about 70 feet of the base of
the Mahogany ledge.

A dawsonite-rich zone about 45 feet thick occurs
about 50 feet above the base of the R—5 zone (fig. 6).
This zone has been traced updip from its emergence
on lower Piceance Creek for about 1.5 miles
northwest to the edge of the plateau overlooking the
White River (fig. 3). As a result of this work, several
tons of rock from this zone were quarried for further
study by the US. Bureau of Mines. The rock was
taken from the exposures at the level of the Piceance
Creek road (fig. 4) in the SEIASWIA sec. 11, T. 1 N ., R.
97 W. (J. W. Smith, written commun., 1967).

A suite of 54 samples consisting of 47 dark- and
seven medium-brown oil shales was studied in de-
tail, and the mineral composition is summarized in

 

 

table 9. Quartz, potassium feldspar, dolomite, and
dawsonite occur in all the samples, and illite occurs
in 53 samples. Albite and analcime, however, occur in
only about half the samples; and pyrite and calcite, in
only about one-fourth.

X—ray analysis of the 54 samples of dawsonitic rock
from lower Piceance Creek shows that dawsonite
content increases as quartz content increases but
varies inversely with analcime content (fig. 18). Hay
(1970, p. 254) reported similar relations from drill
cores of rocks from the deeper parts of the basin; he
suggested that dawsonite and quartz could have
formed from analcime under a high partial pressure
of carbon dioxide, determined by equilibrium with
nahcolite, according to the following reaction:

NaAlSi206~H20+COZ->2Si02+NaAl(OH)2003

analcime —>quartz + dawsonite

 

 

POTASS

MINERAL COMPOSITION

IUM

CHART ANALCIME QUARTZ FELDSPAR ALBITE DOLOMITE
UNITS 0102030405060 0 102030 0 1020 0 1020 0 10203040506070 0 102030 01020 010
r-r-fl r—r‘I l—I—I r-r-r—r—r—r—r“! r—r—r—i r’r‘W (—1

SAMPLE

KOOONCDU'l-PQ’NH

NMHHI—nv—dp—nv—IHHHn—I
Hommxlmm-bwwwo

   

wwmwwwwmmmmmmmm
mmewmwommwmmbww

37

ARITHMETIC 34
AVERAGE

14

FIGURE 17.—Latera1 variation in mineral composi
expressed by X—ray peak height in chart units.
1. Locality is shown in figure 7.

40

tion of dark pyritic oil
Horizontal sample interval is 100 feet, be

 

  
 

CALCITE ILLlTE PYRITE

 

NfflMMfimmmmmmmmmmmwmmm

12 8.5

shale from the Rio Blanco section (unit 155), as

ginning on the west with sample

43

 

 

 

44

TABLE 9.—Mineral composition, expressed by X-ray peak height
in chart units, of 54 dawsonitic rocks exposed on lower Piceance
Creek.

 

 

 

   

Peak height
Mineral Number of ‘ ‘
samples Range Anthmetlc

average
Dawsonite ------------------------ 54 3—90 34
Dolomite 54 5—85 40
Quartz 54 8-40 25
Potass 54 6—35 13
Illite 53 2—1 1 6
Albite 34 4—25 9
Analcimen— 32 4—34 15
Pyrite ----- ~ 15 1—8 4
Calcite ------------------------------ 14 4—18 10

 

In a detailed investigation of the composition of
analcime by the X—ray method of Saha (1961) in 91
samples of oil shale and tuff with and without
dawsonite, we (Brobst and Tucker, 1972) found that
analcime in rocks containing dawsonite has a higher
silicon to aluminum ratio than analcime in rocks con-
taining no dawsonite. Data from this study, shown in
figure 19, indicate that analcime in dawsonitic rocks
is more siliceous and less aluminous than analcime
in rocks without dawsonite. This relation and the
relatively more abundant quartz in the dawsonitic

- rocks suggest that aluminum and silicon made
available in the diagenetic alteration and breakdown
of analcime were utilized in the formation of dawson-
ite and quartz.

 

X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

Figure 18 shows that most of the peak heights of
albite lie between 0 and 15 chart units regardless of
dawsonite content. The albite—analcime relation in
dawsonitic rocks is plotted in figure 20. There is no
apparent relation between the contents of albite and
analcime. A similar result is seen in figure 21, where
the data for the same pair of minerals are plotted for
190 samples of oil shale and marlstone that contain
no dawsonite.

Compared with the nondawsonitic oil shales and
marlstones, the dawsonitic rocks contain more
quartz, less analcime and dolomite, rarely any cal-
cite, slightly smaller amounts of feldspar, and about
the same amount of illite.

VERTICAL VARIATION IN COMPOSITION
DAWSONITIC, PYRI'I‘IC OIL SHALE,
LOWER PICEANCE CREEK ROAD

A stratigraphic thickness of 17.0 cm of dusky-
yellowish-brown (10 YR 2/ 2) to brownish-black (5 YR
2/ 1) dawsonitic, pyritic oil shale was selected for
study in a pair of slabs from the cut made by the US.
Bureau of Mines along the lower Piceance Creek road
(SEMISWl/t sec. 11, T. 1 N., R. 97 W.). The top of the
interval selected begins 4 feet below the base of a tuff
which is well exposed near the top of the cut. Shiny
black scales of gar pike are abundant in this sequence
of rocks. Laminae are laterally persistent in the

 

 

 

 

 

 

f2
— 50
z T‘fi I I I T
D
/
I— //
2E //
I _ // A
O 40 / o .
Z // o
_ /
r: // '
x
C, o . /// ' ' . ' //
U /
E 30 — O // .0 . // _
0: // . . . /./ O
< . X ' '/
D A 905 o /
O’ o x. /
A x o o /
2‘ o ' n o. // Quartz
v 20 — x x o . / _
A A
LL] Q 5x Q // /
E )2 o'x . X 'A/// \ Increase X
\

_| A A A / A .
< ox ° /X.// x X\\ \Dawsomte
32‘ 10 — /A x A A \\ A —
V A x x X \ A A

o .2 A A X x \\_ A A A A
“J A A AX AA A x A‘\A~\ A
E X X x X ‘\\
5 X A X \‘\A

\
_, A
A AA

<2: 0 LA_A—)%_LAX XJhQ‘A_d_Ax—§<A__iXA xx_|AX—x—><4_x__A_A)J_§XXX——i\m\i
< O 10 20 3O 4O 50 6O 70 8O 90 100

 

FIGURE 18.—Abundance of analcime,

 

DAWSONITE, IN CHART UNITS

albite, and quartz as a function of abundance
Parachute Creek Member.

of dawsonite in samples from the

MINERAL COMPOSITION 45

Si
A|+Na

33.5 s5

15 14.5 14

Oil shale
with
dawsonite;
10 samples

Oil shale

without 2 4
dawsonite;
22 samples

Tuff with
dawsonite;
3 samples

Tuff
without
dawsonite;
56 samples

ON
ow
CM

2.1 2.2 2.3 2.4

2.5

ATOMS PER UNIT CELL (0:96)

gas, 3_5 £5.51 a
13.5 13 12.5 12
2 2 2
O O O O. C O
2 2
O O O O O O O O O O
O O O
2 7 116 11 2
O O O O O O O O O O O
2.6 2.7 2.8 2.9 3.0
181
Al

FIGURE 19.—Ratios of silicon to aluminum and of silicon to aluminum plus sodium in analcime from 91 samples with and
without dawsonite, Parachute Creek Member. Numbers next to dots indicate number of samples plotted at that position.

rocks, but they are seen only on close inspection be-
cause the color contrast of adjacent layers is slight,
because of the abundance of organic matter.

The mineral composition of these rocks is shown in
figure 22. The data show a broad range in peak
heights of dawsonite—14-71 chart units. Dawsonite
content generally decreases upward, but analcime
content increases upward. Quartz content shows a
slight decrease upward. Amounts of other minerals
appear to be about the same in the upper and lower
halves of the sequence.

LATERAL VARIATION IN COMPOSITION

Lateral variation in the composition of the
dawsonite-rich zone on lower Piceance Creek was ex-
amined in a study of six suites of samples from
localities within 1.5 miles north of the cut made by
the U.S. Bureau of Mines (fig. 3). The mineral com—
position of these samples is listed in table 10. The tuff
of unit 49 in the lower Piceance Creek section,
referred to in this part of the report as tuff 13,
provided a datum for correlation. Tuff 13 is exposed
almost continuously north of station 3, as reported in

 

3O

20

ALBITE, lN CHART UNITS

     

0—” T 10_’_ 20 30 4o 50
ANALCIME, IN CHART UNITS

FIGURE 20.——Abundance of albite as a function of abundance of
analcime in samples containing dawsonite, Parachute Creek
Member. Numbers next to symbols indicate number of sam-
ples plotted at that position.

table 10. Data in table 10 indicate that the
dawsonite-rich zone is at least 20 feet thick at the
Bureau of Mines cut,where the base of the zone is not
exposed, and is at least 40 feet thick at stations 2 and

 

 

46 X—RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

TABLE 10.—Mineral composition, expressed by X-ray peak height in chart units, of the dawsonitic oil-shale zone at six localities
along lower Piceance Creek

[Station localities are shown in fig. 3. D, dark brown; M, medium brown; L, light brown; USBM, US Bureau of Mines. Leaders (--), not detected]

 

 

 

Distance
above or .
below Dawsonite Analcime Quartz Pffissmm Albite Dolomite Calcite Illite Pyrite Remarks
tuff131 9 51’”
(feet)
At USBM cut on lower Piceance Creek
35 12 -- -- 54 -- 5 ~ Marlstone (L); above the cut.
12 18 10 ~ 62 -- 6 ~ Marlstone, gray.
-~ 20 19 - 46 - 4 - Oil shale (D).
28 5 ~ 68 - 9 » Marlstone.
31 14 5 -- 69 -- 9 — Marlstone, gray.
19 19 12 -- 36 —- 5 — Oil shale, pebbly, blue-weathering.
13 33 45 64 - -- —- — 'I‘llff.
21 14 6 9 76 - 5 — Oil shale, pebbly, blue-weathering.
27 23 11 14 4O - 7 6 Oil shale (D).
1 7 1 1 6 7 74 -- 8 ~ 0,
80 40 10 8 - -- —- ~ Tuff 16.
1 7 ~~ 73 - —- — —- mff 14.
20 18 10 13 77 - 6 - Oil shale (D).
33 21 1 1 18 42 - 8 — Do.
20 22 13 8 85 -- 8 — Do.
25 25 10 8 39 -- 10 — D0.
*- 35 16 8 12 -- 9 - D0.
._ 23 9 6 29 -- 7 4 Do.
-~ 38 13 9 13 - 7 5 D0.
-- 40 12 7 17 , 9 6 D0.
16 48 1 43 -- »- ~ - Tuff 13;‘ top of cut.
42 33 16 18 43 —- 10 ~ Oil shale (D).
24 28 23 -- 47 -- 7 4 D0.
-» 37 22 9 15 15 9 7 Do.
15 41 53 43 -- -- 3 — Do.
13 23 14 -- 62 15 5 — Do.
-- 34 24 -- 22 17 6 ~ Oil shale (D); base of cut.

 

 

56 81 -- 44 13 2 — 'l‘uff 13.1

34 24 9 17 77 -» 9 — Oil shale (M),
17 33 20 -- 54 .. 5 - Oil shale (D).
-~ 34 19 10 14 15 8 — Do.

-- 29 12 10 60 -- 6 —— Do.

13 13 7 7 82 -- 3 — Do.

 

Station 2 (700 ft north of USBM cut)

 

 

 

 

 

17 21 15 14 36 -- 6 4 Oil shale (D), blueweathering.
35 18 30 84 -- -- 2 - 'l‘uff 18.
33 16 6 6 56 -- 6 ~ Oil shale (M).
90 29 8 12 47 -- — — Marlstone, tuffaceous.
87 14 16 42 52 1 1 —— Tuff 17.
20 16 8 8 55 -- 7 - Oil shale (M).
11 18 6 -- 52 -- 6 — Oil shale (D).
26 14 9 11 45 - 8 — Do.
15 16 7 6 63 - 7 —- Do.
18 22 9 6 14 -- 11 3 Do.
-~ 29 10 6 21 6 ~ Do.
-- 39 9 7 18 - 8 — D0.
-- 33 11 9 10 - 7 1 Oil shale (D), papery.
8 33 20 49 2 -- ~ - Tuff 13.1
20 17 16 8 53 -- 3 — Oil shale (D).
9 31 9 6 28 5 — Do.
-- 24 12 5 11 8 4 — Do.
-- 29 14 8 6 -- 4 — Oil shale (M).
- 25 11 6 18 8 5 ~ Do.
27 8 6 16 3 ~ Oil shale (D).
19 18 8 13 33 - 4 4 Oil shale (D), blueweathering.
23 16 7 13 45 1 5 .. Do.
7 21 13 10 30 -- 4 2 Do-
12 25 8 8 34 8 7 _ Marlstone, sandy.
16 30 8 9 35 12 10 -— 0-
12 s 10 25 . .. _ _ Tuff. dark-
Station 3 (2,200 ft north of USBM cut)
[See units 40—70 in table 5 for description]
Station 4 (about 1 mile north of USBM cut)
45 54 44 11 20 -- -- ~ .. Tuff 13.1
10 5 21 7 7 53 -- B — Oil shale (M).
— - 5 6 -- 90 -- » ‘ Oil shale (D).
9 . 16 6 —- 39 8 9 — Do.
3 4 12 B < 54 4 8 — Oil shale (M).
~ 8 15 4 5 62 4 10 — Dolomite, green.
- 27 15 6 -- 37 4 12 — Oil shale (D).

 

 

 

MINERAL COMPOSITION

47

TABLE 10.—Mineral composition, expressed by X-ray peak height in chart units, of the dawsonitic oil-shale zone at six localities
along lower Piceance Creek—Continued

 

 

Distance

 

 

above or Dawsonite Anal cime Quartz Potassium Albite Dolomite Calcite lllite Pyrite Remarks
below feldspar
tuff 131
(feet)
Station 5 (1.5 miles north of USBM cut)
0.0““ ------ — 19 35 32 .- - _ Toff 13.1
2.0 ———————— - -- 19 11 -- 59 4 7 — Oil shale (M).
4.8— — .. 14 9 -- 20 14 — Oil shale (L).
5.8--— — 16 9 -- 33 21 11 — Do.
6.6-~ — 5 16 11 ~ 11 10 12 — Oil shale (M).
8.5--—~ — 13 11 4 4 55 7 8 - Do.
10.0—— — 4 19 8 9 36 4 12 — Dolomite, green.
12.0-— - 12 4 4 51 3 10 — Oil shale (M).
12.5--— — 5 12 7 4 31 6 15 _ Do.

 

 

‘Tuff 13 is datum for these stations and is correlated with tuff 49 in the lower Piceance Creek section.

3. North of station 3, the oil shales are not as well ex-
posed as farther south, but the dawsonite zone seems
to have thinned to less than 10 feet at station 4 and is
absent at station 5. Northward thinning of the
dawsonite zone may be the result of deposition in a
more shoreward environment that was not conducive
to the formation of dawsonite or to the accumulation
of material that later could cause its formation. In
any case, the occurrence of dawsonite seems to cut
across time-stratigraphic units.

TUFF BEDS

Major constituents of nearly all the exposed tuffs
are analcime, quartz, potassium feldspar, and albite.
Less abundant constituents are dolomite, calcite,
micaceous minerals (including illite), and chloritic
clay. The mineral composition of 74 tuff beds sam-
pled in this study is shown in tables 4, 5, and 6 and is

summarized in table 11. _ _
Nearly all the samples contain analc1me, and all of

them contain quartz. Analcime content increases
slightly westward from Rio Blanco to the pipeline
section; it also tends to increase upward in both the
lower Piceance Creek and the pipeline sections.
Quartz content does not vary greatly but seems to in-
crease slightly upward in the three sections. Potas-
sium feldspar occurs in 66 of the 74 samples and
shows a slight decrease upward in both the lower
Piceance Creek and pipeline sections. Applying the
X-ray methods of Wright (1968), we determined that
the structural state of the potassium feldspar ranges
between maximum microcline and high sanidine, but
much is low sanidine. Albite also occurs in 66 of the
74 samples, and a few more samples from beds above
the Mahogany marker have albite than from below
the Mahogany marker. Again by applying the
methods of Wright (1968), we determined that most of
the sodium feldspar is albite in a low structural
state—that is, albite of low—temperature origin—

 

 

 

 

which suggests that it has been diagenetically
altered in the sedimentary environment.

Less than half the tuffs contain dolomite, and only
about one-third contain calcite. As in the marlstone
and oil shale, calcite occurs in a broader range and
commonly has higher values in the tuffs above the
Mahogany marker than below it. Only about half the
samples contain micaceous minerals. Dawsonite was
detected in the tuffs of units 94, 52, and 34in the lower
Piceance Creek section and in tuffs 13 and 18 (of table
10) in some other outcrops along lower Piceance
Creek.

SANDSTONE DIKES

Three gray to light brown sandstone dikes (units
150, 127, and 47) are exposed in the Rio Blanco sec-
tion. The dikes are about 4 inches to 1 foot thick, and
they fill irregularly but steeply dipping fractures in
the oil shale and marlstone sequence. The sandstone
is fine grained and consists of analcime, albite,
quartz, some potassium feldspar, and traces of
dolomite and calcite, suggesting that the original
material was tuffaceous. The sharp contacts of the
dikes with their enclosing rocks suggest that the
sand filled fractures in already consolidated sedi-
ments. The tops and bottoms of the dikes are not ex-
posed. Whether the dikes were formed by filling from
the top down or by squeezing from the bottom up
could not be determined.

CAVITIES

Many cavities were found in the rocks below the
Mahogany ledge in each of the three measured sec-
tions of the Parachute Creek Member. The cavities
range from a few inches to several feet across the
largest dimension. They presumably once were filled
with saline minerals, probably mostly nahcolite.

Many other details of structural features in the
rocks of the Green River Formation were reported by
Bradley (1929, 1931, 1964).

48

X~RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

TABLE 11.—Mineral composition, expressed by X-ray peak height

[A, samples above Mahogany marker;

 

 

 

 

 

 

 

 
  
 
 

 

Analcime Quartz Potassium feldspar
Stratigraphic
position and Number Arith- Number Arith» Number Arith-
number of of Range metic of Range metic of Range metic
samples samples average samples average samples average
Pipeline section:
A (7) .................................... 7 59—86 77 7 16—51 34 7 7-43 17
B (17) 15 0—86 60 17 5—56 24 15 0-65 23
Total (24) ................. 22 0—86 62 24 5-56 27 22 0—65 21
Lower Piceance Creek section:
A (9) ......................................... 9 12-94 75 9 4—73 34 7 0—34 14
B (18) ---------------- 18 5—96 52 18 5—90 32 17 0—41 18
Total (27) --------------------------------- 27 5—96 60 27 4—90 33 24 0—41 17
Rio Blanco section:
A (17) —- ------------------------------------------- 16 0—88 56 17 17—80 34 16 0—35 14
B (6).-----------------— ...... 6 12—89 63 6 4—45 24 4 0—18 10
Total (23) ------------------------------ 22 0—89 58 23 4—80 31 20 0—35 13
ummary:
A (33) -- 32 0-94 65 33 4—80 34 30 0-43 14
B (41)....-..------. 39 0—96 55 41 4-90 28 36 0-65 20
Total (74) ................................. 71 0-96 60 74 4-90 30 66 0—65 17

 

 

 

 

 

SEDIMENTATION AND DIAGENESIS

Sufficient information has been published to es-
tablish that in Eocene time the Piceance Creek basin
contained a large lake of fresh to alkaline-saline
water that was receiving detrital sediments from the
surrounding higher regions. Much of this detrital
sediment probably came from as much as 10,000 feet
of sedimentary rocks of Cretaceous age which
covered the region (Haun and Weimer, 1960). Many
falls of volcanic ash of Tertiary age also contributed
detrital sediment to the lake; this sediment
chemically charged the river and lake waters with
leached metals and silica and created a highly
alkaline environment.

Vertical and lateral variations in composition of
the rocks in the lower members of the Green River
Formation in the Piceance Creek basin reflect
differences in provenance of the materials delivered
to the fresh-water lake in the basin during pre-
Parachute Creek Green River time. By Parachute
Creek time, the environment of deposition in the lake
had changed from fresh to alkaline, and the bottom
sediments were especially rich in carbonate and
organic matter. In the late stages of deposition, dur-
ing Evacuation Creek time, the water freshened
again, and the sediments became more varied,
although sand and volcanic materials were most
abundant

The great body of laminated carbonate rocks, some
rich in organic matter, that comprise the Parachute
Creek Member is most likely the product of sedimen-
tation and diagenesis in the environment of an
alkaline lake. Field relations described in this report
suggest that the chemical composition of the lake

 

 

water changed from time to time, indicating a lack of
permanency of chemical stratification. Alkalinity of
the bottom waters was probably greater than pH 9
most of the time. This alkaline water was overlain
intermittently by fresher water. Between these two
layers, as postulated by Bradley and Eugster (1969, p.
B23), a zone of mixing of alkaline and fresh water un-
doubtedly existed at times; this zone allowed for the
widespread distribution of calcium, magnesium, and
bicarbonate ions and provided water fresh enough to
have supported the algal life required to form the oil
shale.

Large amounts of clay probably were delivered to
the Piceance Creek basin during Parachute Creek
time, but only small amounts of illite are detected
now. Clays of different kinds that were swept into the
alkaline lake yielded their constituents to form new
minerals, including feldspar, quartz, analcime, and
saline minerals. Whether the illite itself is detrital or
is an alteration product is not known.

According to Alderman and Skinner (1957) and
Alderman and von der Borch (1961), dolomite can
precipitate from warm, strong brine. Dolomite com-
monly forms diagenetically from preexisting cal-
cium-rich carbonate by the incorporation of mag-
nesium during recrystallization, but the extremely
fine grain of the dolomite in the rocks of the
Parachute Creek Member strongly suggests that the
dolomite is not a product of the recrystallization of
preexisting calcium carbonate. More likely, much of
the dolomite is a primary precipitate from the
alkaline lake water.

Calcite in the rocks of the Parachute Creek Member
also formed by precipitation from the lake water, but

—

 

SEDIMENTATION AND DIAGENESIS

in chart units, of 74 tuffs above and below the Mahogany marker

B, samples below Mahogany marker]

49

 

 

 

Albite Dolomite Calcite Illite Chlorite
Number Arith- Number Number Number Number
of Range metic of Range of Range of Range of Range
samples average samples samples samples samples
6 0-60 21 3 0-51 5 0—44 4 0—8 4 0—9
15 0—70 26 4 0—74 1 0—14 5 0-7 4 0—8
21 0—70 24 7 0—74 6 0-44 9 0-8 8 0—9
9 5—83 27 2 0—43 4 0—73 2 0—22 0 0
13 0—65 12 5 0—65 5 0—30 8 0—19 0 O
22 0-83 1 7 7 0—65 9 0—73 1 0 0-22 0 0
17 3—39 18 11 0—87 7 0—25 13 0-17 5 0—9
6 6—77 36 4 0—84 1 0-4 4 0-39 0 0
23 3-77 23 15 0—87 8 0—25 1 7 0-39 5 0—9
32 0—83 20 16 0—87 16 0-73 19 0-22 9 0-9
34 0-77 21 13 0—84 7 0-30 17 0—39 4 0-8
66 0-83 21 29 0—87 23 0—73 36 0—39 13 0—9

 

the water was probably fresher and lower in
magnesium than that giving rise to the dolomite.

The sample data in tables 4, 5, and 6 from the three
measured sections indicate that dolomite pre-
dominates greatly over calcite in rocks below the
Mahogany ledge, but that, above the Mahogany
ledge, calcite is more abundant and in some beds pre-
dominates over dolomite.

The bicarbonate chemical equilibrium system
evidently hung in delicate balance but shifted fre—
quently because of changes in such interrelated fac-
tors as climate, biological activity, and sedimenta-
tion. Interaction of these factors, causing turnover
and mixing of the water, as well as alteration of con-
ditions of the trophic levels of life and sedimenta-
tion, resulted in the accumulation of the thick se-
quence of laminated rocks of great lateral extent and
uniform composition in the Parachute Creek
Member. The changing chemical environments in
the lake promoted diagenetic alteration of the or-
ganic and inorganic fractions of the sediment.

Decay of organic materials—mostly algae and
pollen remains, according to Bradley (1970, p. 986-
987)—produced carbon dioxide in the chemical
system. The decay, however, was not complete, as in-
dicated by the high carbon to hydrogen ratios in the
oil shales (Smith, 1969, p. 186). Bacterial inhibitors,
such as lauric acid, have been reported (Bradley,
1970, p. 995; Miller, 1972, p. B10) from Florida in
modern sediments rich in organic matter. The
presence of such bacterial inhibitors in a sediment
would retard the oxidation of the enclosed organic
matter. If a bacterial inhibitor had been present in
the Piceance Creek basin, the dead algae ac-

 

cumulating on the bottom of the lake could have been
preserved after partial decay, despite the alkaline
(oxidizing) conditions prevailing there. This is not
the only means of preserving organic matter. The
organic matter literally could have been pickled at
the chemocline interface (Rolfe and Brett, 1969, p.
229). Whatever the mechanism of preservation, the
organic materials were involved in the diagenetic
processes active in the basin. These processes likely
resulted in the formation of various organometallic
complexes, by extraction of metals from the brine,
and polymers which evidently increased the stability
of the organic matter in the environment and re-
duced its solubility in common organic solvents.

Quartz in these rocks probably has a mixed origin.
Some is detrital, from both preexisting rocks and
falls of volcanic ash, and some formed diagenetically
from the breakdown of other minerals, such as anal-
cime and, especially, the clay minerals.

The presence of sanidine, orthoclase, and micro-
cline suggests that the potassium feldspars are of
mixed origin—volcanic, detrital, and diagenetic.
Orthoclase and microcline, neither of which is
especially common, are probably of detrital origin.
Sanidine is most likely of volcanic origin. Some
potassium feldspar may have formed diagenetically,
especially in the deeper parts of the basin. Authigenic
development of such feldspars would have required
extraction of potassium from the lake waters.

Plagioclases of different origins and compositions
were probably originally deposited in the basin, but
most of them are now albitic. Most of the albite
studied in detail from both carbonate-rich rocks and
tuff beds was determined by the methods of Wright

50 X—RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

 

 

 

 

70 I I I I I
o
60— EXPLANATION _
0 Dark oil shale
0 Medium oil shale
X A Light oil shale
x Marlstone
50— _
o
(I)
'2
Z 0
D 40* 1
l—
0:
<1:
5 O
E
Lu“
E 30— _
a x
0
<1: X x x
02 o x x
A
XX x O
20: . o O x _
X X o
X
s . o
o x o
I x x A O X : A A
x x o o o o o A
2 ): x o o o o o o
100_. g A o 0000. ..>< O. . _
I2 0 O O X 2 A O 20 g o A o
' x 0 0 A 00 o o o X o O
o g o o . o x x IA .
>|< x X0 X0 0
o o g x0 x 0X 0
o )8 Q 0 00X
1 ox
2 x
OOXiing—o olfixob o 0202—1—0 020—0 0 T I o I I
O 10 ‘ 20 3O 4O 50 6O 70

ANALCIME, IN CHART UNITS

FIGURE 21.—Abundance of albite as a function of abundance of analcime in oil shale and marlstone, Parachute Creek
Member. Numbers next to symbols indicate number of samples plotted at that position. _

(1968) to be in the low structural state, in which the
silicon and aluminum atoms are well ordered in the
framework structure. This state is characteristic of a
low temperature of formation and, therefore, a low
energy level. The uniform composition of the
plagioclase suggests that plagioclases of varied com-
positions and structural states that probably were
originally deposited in the lake from various sources
were altered diagenetically in the alkaline environ-
ment to a more sodium-rich albite in a lower struc-
tural state.

 

Analcime, which is a common, widespread
authigenic mineral in the exposed carbonate rocks
and tuffs of the Parachute Creek Member in the
Piceance Creek basin, formed at low temperatures in
moderately alkaline water from clays and zeolitic
precursors, themselves derived from volcanic glass.
Conditions fostering the formation of analcime from
other zeolitic minerals or the conversion of analcime
to feldspar in environments of higher alkalinity were
discussed by Hay (1966) and Sheppard and Gude
(1968, 1969), among others.

 

 

 

 

SEDIMENTATION AND DIAGENESIS 51
POTASSIUM
CHART DAWSONITE ANALCIME QUARTZ FELDSPAR ALBITE DOLOMITE CALCITE PYRITE ILLITE
UNITS 10203040506070 0 10 2030 O 10 20 30 40 O 10 20 O 1020 0 10 20 30 40 50 0 10 0 10 0 10
CM 1 l l fl F l | l W | | l l—l l—l F7
110

n—Ip—a l—‘p—I
94> P01
mm to;

r—u—d
99’
ON

12.25
11.95

11.4

10.5

9.3

8.4
8.0
7.6

6.4

5.80
5.25

4.4

 

 

FIGURE 22.—Mineral composition of dawsonitic, pyritic oil shale along lower Piceance Creek road, as expressed by X-ray peak
height in chart units.

s,

’ ‘3

Zeolitic precursors of analcime have not been
found in the Piceance Creek basin, but their absence
may be partly explained by the erosion of shoreward
deposits around all but the southernmost periphery
of the basin. Presumably the alkalinity of the water
in which the preserved beds were saturated was suffi-
ciently high to convert all earlier zeolites to analcime.
The data in figure 19 show that analcime in 40 of 56
tuffs that lack dawsonite has a composition (34.5-
35.1 atoms of silicon per unit cell) similar to that of
analcime derived from clinoptilolite in tuffs of the

 

Barstow Formation of California described by Shep-
pard and Gude (1969, p. 29). The close comparison
lends weight to the argument that at least some of the
analcime was derived from clinoptilolite. Where the
alkalinity increased further (pH>9), some analcime
reacted to form dawsonite and quartz. Rocks con-
taining both analcime and dawsonite are exposed
along lower Piceance Creek. Deeper in the interior of
the basin, all the analcime has been converted under
highly alkaline conditions to dawsonite and quartz
or to albite.

 

 

 

52 X-RAY MINERALOGY, PARACHUTE CREEK MEMBER, GREEN RIVER FORMATION, COLORADO

Most of the saline minerals are soluble under con-
ditions of weathering and have been removed from
rocks in the outcrops, except for the dawsonite, which
is tightly enclosed in rocks on lower Piceance Creek.
The presence of many zones of cavities in the three
measured sections suggests that some saline
minerals were deposited in pods and disseminated
crystals near the edges of the basin. Scattered pods
and crystals of nahcolite, dawsonite, and other saline
minerals probably formed diagenetically from
materials in the lake sediment that reacted with
trapped brine during burial.

In the lower part of the Parachute Creek Member in
the deeper parts of the basin are beds of nahcolite,
which contain some dawsonite, and some strati-
graphically higher beds of halite, which contain thin
interlayers of nahcolite and accessory amounts of
wegscheiderite (Na2C03'3NaHCO3), shortite
(NagCO3'2CaC03), northrupite (Na2C03'MgC03'Na
Cl), searlesite (NaBSi206'H20), and possibly trona
(N azCO 3'NaHCO3'2HzO) (Hite and Dyni, 1967).
Nahcolite 1n the Piceance Creek basin probably pre-
cipitated from brines in much the same manner as
did trona in the Green River basin. Nahcolite is the
major saline mineral in the Piceance Creek basin,
however, because the partial pressure of carbon di-
oxide at the critical temperature of the lake precluded
precipitation of trona (Bradley and Eugster, 1969, fig.
2 and p. B46—B58). The beds of halite in the Piceance
Creek basin also probably precipitated from brine,
very likely by brine mixing in the manner described
by Raup (1970). Bradley and Eugster (1969, p. B22-
B24) discussed the evidence for brine mixing rather
than evaporation to account for the origin of halite
and saline minerals in the Green River basin. The
same reasoning can be applied to the Piceance Creek
basin.

The possibility that the dawsonite in the nahcolite
beds in the deeper part of the basin is a primary
precipitate from alkaline water should not be
overlooked. Aluminum ions in preexisting alumino-
silicate gels and in minerals that were attacked by
highly alkaline lake water could have been available
to form dawsonite by direct precipitation from the
water at the same time as the nahcolite.

The formation of dawsonite by diagenesis and by
primary precipitation from alkaline lake waters and
the occurrence of dawsonite at the periphery of the
basin as well as at depth in the central part suggest
that greater amounts of dawsonite occur in this basin
than have previously been recognized. The amount of
aluminum potentially available in the dawsonite of
the Piceance Creek basin may be one of this nation’s
great resources of an industrially valuable com-
modity.

 

 

Sulfate minerals did not survive in the lake. Ac-
cording to Jones (1966, p. 196), sulfate is decreased in
the permanent lacustrine environment by bacterial
reduction. Sulfur from the sulfate ion becomes fixed
as pyrite or is lost to the air as hydrogen sulfide rising
from mudflats at the lake margins. Sulfate minerals
found in samples from outcrops are oxidation
products formed by weathering of the rocks.

REFERENCES CITED

Alderman, A. R., and Skinner, H. C. W., 1957, Dolomite sedimen-
tation in the south-east of South Australia: Am. Jour. Sci.,
v. 255, no. 8, p. 561—567.

Alderman, A. R., and von der Borch, C. C., 1961, Occurrence
of magnesite-dolomite sediments in South Australia: Nature,
V. 192, no. 4805, p. 861.

Bradley, W. H., 1929, The varves and climate of the Green River
epoch: U.S. Geol. Survey Prof. Paper 158—E, p. 87—110.

__l931, Origin and microfossils of the oil shale of the Green
River formation of Colorado and Utah: US. Geol. Survey
Prof. Paper 168, 58 p.

‘1964, Geology of the Green River Formation and associated
Eocene rocks in southwestern Wyoming and adjacent parts
of Colorado and Utah: US. Geol. Survey Prof. Paper 496—
A, 86 p.

__1970, Green River oil shale—Concept of origin extended:
Geol. Soc. America Bull., v. 81, no. 4, p. 985—1000.

Bradley, W. H., and Eugster, H. P., 1969, Geochemistry and
paleolimnology of the trona deposits and associated authi-
genic minerals of the Green River Formation of Wyoming:
US. Geol. Survey Prof. Paper 496—B, 71 p.

Brobst, D. A., and Tucker, J. D., 1972, Analcime—its composition
and relation to dawsonite in tuff and oil shale in the Green
River Formation, Piceance Creek basin, Colorado: Geol. Soc.
America Abs. with Programs, v. 4, no. 6, p. 369—370.

Cashion, W. B., 1967, Geology and fuel resources of the Green
River Formation, southeastern Uinta Basin, Utah and C010-
rado: U.S. Geol. Survey Prof. Paper 548, 48 p.

_1969, Geologic map of the Black Cabin Gulch quadrangle,
Rio Blanco County, Colorado: US. Geol. Survey Geol. Quad.
Map GQ—812.

Culbertson, W. C., 1961, Stratigraphy of the Wilkins Peak Mem-
ber of the Green River Formation, Firehole Basin quadran-
gle, Wyoming, in Short papers in the geologic and hydro-
logic sciences: U.S. Geol. Survey Prof. Paper 424—D, p. D170—
D173.

1962, Laney Shale Member and Tower Sandstone Lentil
of the Green River Formation, Green River area, Wyoming,
in Short papers in geology and hyrology: U.S. Geol. Survey
Prof. Paper 450—C, p. C54—C57. =

_1965, Tongues of the Green River and Wasatch Formations
in the southeastern part of the Green River Basin, Wyoming,
in Geological Survey research 1965: US. Geol. Survey Prof.
Paper 525—D, p. D139—D143. _

“1966, Trona in the Wilkins Peak Member of the Green
River Formation, southwestern Wyoming, in Geological Sur-
vey research 1966: US. Geol. Survey Prof. Paper 550—B, B159—
3164.

Donnell, J. R., 1953, Columnar section of rocks exposed between
Rifle and De Beque Canyon, Colorado, in Rocky Mtn. Assoc.
Geologists Guidebook, field conf. in northwestern Colorado,
May 14—16, 1953: 2d page facing p. 16.

 

 

REFERENCES CITED

 

1961, Tertiary geology and oil-shale resources of the Pic-
eance Creek basin between the Colorado and White Rivers,
northwestern Colorado: U.S. Geol. Survey Bull. 1082—L, p.
835—891.

Donnell, J. R., and Blair, R. W., Jr., 1970, Resource appraisal
of three rich oil-shale zones in the Green River Formation,
Piceance Creek basin, Colorado, in Gary, J. H., ed., Synthetic
liquid fuels from oil shale, tar sands, and coal—A sympo-
sium: Colorado School Mines Quart, v. 65, no. 4, p. 73-87.

Duncan, D. C., and Belser, Carl, 1950, Geology and
oil-shale resources of the eastern part of the Piceance Creek
basin, Rio Blanco and Garfield Counties, Colorado: U.S. Geol.
Survey Oil and Gas Inv. Map OM—119.

Duncan, D. C., and Denson, N. M., 1949, Geology of the Naval
Oil-shale Reserves 1 and 3, Garfield Countv, Colorado: U.S.
Geol. Survey Oil and Gas Inv. Prelim. Map 94.

Fahey, J. J ., 1962, Saline minerals of the Green River formation:
U.S. Geol. Survey Prof. Paper 405, 50 p.

Goddard, E. N., chm., and others, 1948, Rock-color chart: Wash-
ington, Natl. Research Council (repub. by Geol. Soc. Amer-
ica, 1951), 6 p.

Haun, J. D., and Weimer, R. J ., 1960, Cretaceous stratigraphy
of Colorado, in Weimer, R. J ., and Haun, J. D., eds., Guide
to the Geology of Colorado: Geol. Soc. America, The Rocky
Mtn. Assoc. Geologists, and Colorado Sci. Soc., Denver, Colo.
p. 58-65.

Hay, R. L., 1966, Zeolites and zeolitic reactions in sedimentary
rocks: Geol. Soc. America Spec. Paper 85, 130 p.

___1970, Silicate reactions in three lithofacies of a semiarid
basin, Olduvai Gorge, Tanzania: Mineralog. Soc. America
Spec. Paper 3, p. 237—255.

Hayden, F. V., 1869, Preliminary field report of the U.S. Geolog-
ical Survey of Colorado and New Mexico: U.S. Geol. and
Geog. Survey of the Territories ann. rept. 3, 155 p.

Hite, R. J ., and Dyni, J. R., 1967, Potential resources of dawsonite
and nahcolite in the Piceance Creek basin, northwest Colo-
rado, in Fourth symposium on oil shale: Colorado School
Mines Quart., v. 62, no. 3, p. 25-38.

Jackson, M. L., 1964, Soil clay mineralogical analysis, in Rich,
C. L, and Kunze, G. W., eds., Soil clay mineralogy—A sym-
posium: Chapel Hill, N. C., North Carolina Univ. Press,
p. 245-294.

J affe’, F. C., 1962, Nomenclature, uses, reserves and production,
pt. 1 of Oil shale: Colorado School Mines Mineral Industries
Bull., v. 5, no. 2, 11 p.

Jones, B. F., 1966, Geochemical evolution of closed basin water
in the western Great Basin, in Rau, J. L., ed., Second sym-
posium on salt, v. 1, Geology, geochemistry, mining: Cleve-
land, Ohio, Northern Ohio Geol. Soc., p. 181-200.

 

53

Miller, R. E., 1972, Normal fatty acids in estuarine and tidal-
marsh sediments of Choctawhatchee and Apalachee Bays
northwest Florida: U.S. Geol. Survey Prof. Paper 724-B, 13p.

Raup, O. B., 1970, Brine mixing—an additional mechanism for
formation of basin evaporites: Am. Assoc. Petroleum Geo-
logists Bull., v. 54, no. 12, p. 2246—2259.

Roehler, H. W., 1969, Stratigraphy and oil-shale deposits of
Eocene rocks in the Washakie basin, Wyoming, in Wyoming
Geol. Assoc. Guidebook 21st Ann. Field Conf.: p. 197—200.

Rolfe, W. D. I., and Brett, D. W., 1969, Fossilization processes,
chap. 8 of Eglinton, G., and Murphy, M. T. J ., eds., Organic
geochemistry methods and results: Berlin, Springer-Verlag,
p. 213—244

Saha, Prasenjit, 1961, The system NaAlSiO4 (nepheline)-NaAl
Si308 (albite)—HzO: Am. Mineralogist, v. 46, nos. 7-8, p. 859—
884

Schultz, L. G., 1964, Quantitative interpretation of mineralogical
composition from X-ray and chemical data for the Pierre
Shale: U.S. Geol. Survey Prof. Paper 391—C, p. Cl-C31

Sheppard, R. A., and Gude, A. J., 3d, 1968, Distribution and
genesis of authigenic silicate minerals in tuffs of Pleistocene
Lake Tecopa, Inyo County, California: U.S. Geol. Survey
Prof. Paper 597, 38 p.

___1969, Diagenesis of tuffs in the Barstow Formation, Mud
Hills, San Bemardino County, California: U.S. Geol. Survey
Prof. Paper 634, 35 p.

Smith, J. W., 1969, Geochemistry of oil shale genesis, in Wyoming
Geol. Assoc. Guidebook 21st Ann. Field Conf.: p. 185-190.

Smith, J. W., and Milton, Charles, 1966, Dawsonite in the Green
River Formation of Colorado: Econ. Geology, v. 61, no. 6,
p. 1029-1042.

Smith, J. W., and Young, N. B., 1969, Determination of dawsonite
and nahcolite in Green River Formation oil shales: U.S. Bur.
Mines Rept. Inv. RI—7286, 20 p.

'I‘isot, P. R., and Murphy, W. I. R., 1960, Physicochemical pro—
perties of Green River oil shale—Particle size and particle-
size distribution of inorganic constituents: J our. Chem. and
Eng. Data, v. 5, no. 4, p. 558-562.

Trudell, L G., Beard, T. N., and Smith, J. W., 1970, Green River
Formation lithology and oil shale correlations in the Pic-
eance Creek ‘ basin, Colorado: U.S. Bur. Mines Rept. Inv.
RI-7357, 14 p.

Wentworth, C. K., 1922, A scale of grade and class terms for
elastic sediments: J our. Geology, v. 30, no. 5, p. 377-392.
Wright, T. L., 1968, An X-ray method for determining the com-
position and structural state from measurement of two-theta
values for three reflections, pt. 2 of X-ray and optical study
of alkali feldspars: Am. Mineralogist, v. 53, nos. 1-2, p. 88-

104.

 

 

 

 

/EAm

“am? 7 MY
, Erosional and Depositional
g? Aspects of Hurricane: Camille in
Virginia, 1969

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 804

 

 

 

 

 

Erosional and Depositional
Aspects of Hurricané Camille in
Virginia, 1969

By GARNETT P. WILLIAMS and HAROLD P. GUY

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 804

 

 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1973

UNITED STATES DEPARTMENT OF THE INTERIOR

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY

V. E. McKelvey, Director

Library of Congress catalog-card No. 73-600265

 

For sale by the Superintendent of Documents US. Government Printing Office

Washington, DC 20402 — Price $1.80 (paper cover)
Stock Number 2401-02442

CONTENTS

 

 

Page Page
Abstract ________________________________________ 1 Erosion—Continued
Introduction _____________________________________ 1 Sediment yield—Continued
General description of study area __________________ 3 Estimated sediment-transport rates ________ 41
The storm ——————————————————————————————————————— 3 Depositional features ____________________________ 41
The fl°°d """"""""""""""""""""""""" 5 Channel deposits _____________________________ 42
Estimated storm-average discharges ___________ 5 . . . .
. . Sediment sampling, computation of size-
Estimated peak discharges ___________________ 6 f d‘ t 'b tion 44
Geomorphological features of drainage basins ______ 6 reouency 1s.r1 u. _s “j"""""". """"
Slopes of drainage areas ______________________ 7 Defimtlons of s12e-dlstr1but10n characteristics __ 47
Stream length and drainage area ______________ 7 Alluvial fans ________________________________ 47
Longitudinal profiles of stream channels _______ 10 Amount of deposition ____________________ 48
Topographic map data ___________________ 10 Cross-fan profiles ________________________ 51
Field measurements ______________________ 13 Grain-size characteristics _________________ 51
Erosion _________________________________________ 14 Highway deltas _____________________________ 54
Debris avalanches ____________________________ 14 Sedimentary features ____________________ 56
Source material __________________________ 17 Vertical variations in grain-size
General description of avalanche scars ____ 17 characteristics _________________________ 57
Geometry of scars _______________________ 19 Flood-plain deposits __________________________ 58
Methods of study ____________________ 19 Sedimentary features ____________________ 58
Longitudinal profiles _________________ 22 Vertical changes in grain size _____________ 62
Cross profiles ________________________ 25 Lateral variations in grain size ___________ 64
Possible causes of avalanches in Nelson Downstream changes in flood-plain deposits—
County ____________________________ 26 general _______________________________ 64
Theoretical considerations ____________ 27 Downstream changes in amount of deposition 65
Stream action at the base of the hill- Polly Wright Cove ___________________ 65
slope ______________________________ 27 Rucker Run ________________ , _________ 6 6
Depressions or troughs on the hillside __ 28 Downstream changes in average grain size__ 67
Orientation of hillside ________________ 28 Average particle size, local slope, and
Hillside gradients ____________________ 29 drainage area _________________________ 69
Length of hillslope ___________________ 30 Downstream variation in size of largest
Soil depth ___________________________ 31 stones ________________________________ 70
Summary ___________________________ 32 Downstream changes in sorting ___________ 71
Effect of debris avalanches on streamflow__ 33 Downstream changes in SkeWfleSS —————————— 71
Stream channels _____________________________ 35 Scarcity of coarse sand and gravel ________ 74
Sediment yield _______________________________ 38 Downstream changes in grain shape and
Volume of avalanche erosion ______________ 738 roundness _____________________________ 76
Sediment yield from stream channels ______ 39 Conclusions _____________________________________ 77
Total sediment yield and average denudation- 41 References ______________________________________ 79
ILLUSTRATIONS
Page
FIGURE 1 Map of study area __________________________________________________________________________ 2
2. Photograph showing upstream View of Wills Cove and Dillard Creek _________________________ 3
3. Map of rainfall distribution __________________________________________________________________ 4
4 Topographic maps of Ginseng Hollow, Polly Wright Cove basins, and headwaters of Wills Cove _- 8
5—10 Graphs:
5. Percentage of drainage-basin area steeper than a given slope, for basins of figure 4 ______ 10
6. Variation of stream length with drainage area for three Nelson County basins ___________ 11
7. Longitudinal profiles of stream channels ______________________________________________ 12
8. Longitudinal channel profiles plotted in the form of L/F' versus L _____________________ 13
9. Profiles of mountain channels and alluvial fans _______________________________________ 14
10. L/F versus L plot of longitudinal stream profiles _______________________________________ 15

III

IV

FIGURES 11—14.

15.
16.
17.
18.
19.

20.

21.
22—26.

27.
28.
29-32.

33.
34—36.

46—57.

TABLE 1.

2.
3.

CONTENTS

Photographs : ‘
11. Erosion and deposition ________________________________________________________________
12. Typical avalanche scars _________________________________________ 1 ___________________
13. Avalanche scar at Lovingston _________________________________________________________
14. Avalanche scars on sides of intermontane valleys _______________________________________
Contour maps of two avalanche scars, Polly Wright Cove __________________ ‘ ____________________
Profiles of hillslopes and their scars _______________________________________ l ____________________
Graphs of local gradient versus distance from hillt0p __________________________________________
Cross profiles of avalanche scars __________________________________________ 1 ___________________
Graphs showing relation of hillslope length to number of scars per acre and 110 average distance of
scarring per acre _________________________________________________________________________
Sketch of hypothetical drainage areas showing influence of hillslope length alnd drainage area on
avalanching ___________________________________________________________ ‘ ____________________

Sketch map of peak- flow study in Ginseng Hollow __________________________ ‘ ____________________
Photographs: i
22 Eroded mountam channels ________________________________________ l ____________________
23 Channel eroslon at S K Wllls home ________________________________ i. ___________________
24 Channel erosmn along hlghways __________________________________ l ____________________
25. Stream erosion under a railway trestle ____________________________ l ____________________
26. Channels showing both erosion and deposition _______________________ i ____________________
Diagram of orientation and relative volume of avalanches ____________________________________
Graph of volume of avalanche erosion with respect to average surface Slope ______________________
Photographs :
29. Boulders which probably were too large to be moved by floodwaters _____________________
30. Log jam in a mountain channel _______________________________________________________
31. Range of 'particle sizes in upstream deposits ____________________________________________
32. Imbricated boulders __________________________________________________________________
Graph showing typical particle-size distribution for a wide range of particle sizes ________________
Photographs : .
34. Alluvial fans __.___________..___._______________________.________4 ____________________
35. Bryant fan _____________________________________________________ _l ____________________
36. Eroded zone at apex of Campbell fan_______________________________; ____________________
Graph of amount of deposition with distance down fan ____________________ 1‘ ____________________
Cross-fan profiles _______________-__________________________--__________-_3 ____________________
Graph showing change in particle-size—distribution characteristics along alluvial fans _____________
Photographs:
40. Edes Hollow highway delta ___________________________________________________________
41. Dillard Creek highway delta ___________________________________________________________
42. Sedimentary features of a highway delta. _______________________________________________
43. Typical flood-plain deposits in headwater area _________________________________________
44. Common flood-plain deposits ___________________________________________________________
45. Close view of sandy flood-plain deposits ________________________________________________
Graphs:

46. Size-frequency characteristics of flood-plain sediments on Dillard Creek __________________
47. Size-frequency characteristics of flood-plain sediments on Rucker Run‘ ____________________
48. Volume of deposition per foot of channel length, Polly Wright Cove ______________________

49. Volume of deposition versus distance downstream on Rucker Run _______________________
50. Downstream changes in mean particle size of flood-plain deposits, for three streams ______
51. Average particle size versus local flood-plain slope _____________________________________
52. Average particle size versus drainage area ________________________ a ____________________
53. Downstream changes in size of largest stones _____________________ .l ____________________
54. Downstream changes in sorting of flood—plain deposits ___________________________________
55. Change in sorting with average grain size ______________________________________________
56. Downstream changes in skewness ______________________________________________________
57. Change in skewness with average grain size ____________________________________________

TABLES

Drainage area and average surface slope in tributaries and subbasins of Wills Cove, Ginseng Hol-

low, and Polly Wright Cove ____________________________________________ 1. ____________________
Hillside and scar dimensions and erosion volumes for measured avalanche scars ___________________
Factors contributing to instability of earth slopes _______________________________________________

Page

16
18
19
20

23
24
25

31

32
33

34
35
36
37
38
39

42
42
43
44
46

48
49
50

52
53

54
55
56
59
60
61

63

65
67

69
70
70
72
73
73
74

Page

7
23
27

CONTENTS V

 

Page
TABLE 4 Debris-avalanche scars per 1,000 feet of stream channel ________________________________________ 29
5 Effect of hillslope length and drainage area on frequency and amount of scarring _________________ 30
6. Estimated net sediment yields and storm—average transport rates _______________________________ 40
7. Computational procedure of combining a sieve analysis with a pebble count _______________________ 45
8 Vertical variations in grain-size characteristics in highway deltas ________________________________ 57
9. Volume and percentage of deposition by size classes in Polly Wright Cove _______________________ 66
10. Number of cases of deficiency in weight percent, for various particle-size classes __________________ 75
11. Average grain shape and roundness values in Polly Wright Cove _______________________________ 77
SYMBOLS
Dimensions Dimensions
a coefficient in the equation of longitudinal k constant in Hack equation for stream profile
stream-profile L horizontal distance from drainage divide ______ L
A cross-sectional flow area _____________________ L‘ n constant in Hack equation for stream profile
A; drainage area ______________________________ L2 Q discharge of water _________________________ Li‘T‘1
b coeflicient in various equations, representing 'rc average radius of curvature of a channel bend- L
slope of best-fit line Tl inside radius of curvature of a channel bend__ L
c coefficient representing portion of total rainfall 'ro outside radius of curvature of a.channel bend _ L
that runs off the ground surface S local slope (gradient)
C constant of integration in Hack (1957, p. 70) sic skewness of a sediment size-frequency
equation for stream profile distribution
d" average intermediate diameter of sediment So sorting of a sediment size-frequency
particles _________________________________ L distribution
dm grain size for which 10 percent of the V mean velocity of flow _______________________ LT‘1
distribution is finer _______________________ L W water-surface width of a stream _____________ L
dla average intermediate diameter of the five largest x distance downstream from start of deposition _- L
rocks at a site ____________________________ L a constant in equation of stream profile
e base of natural logarithms ,8 constant in equation of stream profile
F vertical fall from drainage divide ____________ L 'y constant in equation of stream profile
9 acceleration due to gravity __________________ LT'2 Ah elevation difference between high-water and
I rainfall intensity ___________________________ LT‘1 low-water marks around a channel bend ___ L

 

ENGLISH-METRIC CONVERSION TABLE

Length:
Inches X 0.0254 =meters
FeetX 0.3048:meters
Yards X 0.9144 :meters
Miles X 1.609 =kilometers

Area:
Square inches >< 0.0006452 : square meters
Square feetX 0.09290=square meters
Square yards X 0.8361 : square meters
Acres X 4047 : square meters
Square miles X 2,590,000 : square meters

Volume:
Cubic inches X 0.01639 =liters
Cubic feet X 28.32 :liters
Cubic yards X 764.6 :liters
Pints X 0.4732:1iters
Quarts X 0.9463 :liters
Gallon X 3.785 :liters
Acre-feetX 1233 = cubic meters

Weight:
Grains X 0.064802grams
Ounces (avoirdupois) X 28.35 : grams
Pounds (avoirdupois) X 453.6:grams
Tons (short) X 907.2 :kilograms
Tons (long) X 1016 =kilograms

 

Specific combinations :

Feet per secondX1.097:kilometer per hour
X0.3048:meters per second

Miles per hour>< 1.609 :kilometers per hour
X0.4470=meters per second

Pounds per square inch X 70.3: grams per square
centimeter

Pounds per square footX 0.4885:grams per square
centimeter

Tons (short) per square footX0.9765:kilograms per
square centimeter

Tons (short) per acreX 0.2241 :kilograms per square
meter

Tons (short) per square mileX0.0003502:kilograms
per square meter

Pounds per cubic footX0.01602:grams per cubic
centimeter

Cubic feet per secondX1.699=cubic meters per minute
X0.02832:cubic meters per second

Cubic feet per second for 1 dayX1.983:acre feet
X2446:cubic meters

Degrees Fahrenheit—32 X0.556:degrees Celsius.

 

 

EROSIONAL AND DEPOSITIONAL ASPECTS OF.
HURRICANE CAMILLE IN VIRGINIA, 1969

 

By GARNETT P. WILLIAMS and HAROLD P. GUY

 

ABSTRACT

Probably the worst natural disaster in central Virginia’s
recorded history was the flood resulting from an 8-hour deluge
of about 28 inches (710 mm) of rain on the night of August
19—20, 1969. This study examines some of the intensive sedi-
ment erosion and deposition that resulted from the storm
and flood.

Most of the 150 people whom the flood killed in this
mountainous area died from broken bones and other blunt—
force injuries, rather than by drowning. The transport of
sediment and other debris by the water therefore was very
significant in loss of life and in property damage.

Erosion resulted mainly from debris avalanches down the
mountain-sides and channel scour along streams and head-
water tributaries. Total amounts of sediment yield from
certain mountainous areas in Nelson County were about
3.2—4.6 million cubic feet per square mile, probably the equiva—
lent of several thousand years of normal denudation.

Characteristics of the debris avalanches were that (1)
they usually followed pre-existing depressions on hillsides
and occurred on slopes greater than 35 percent, (2) the
upslope tip of the avalanche scar tended to be located at
the steepest part of the hillside, where the convex slope
merged with the concave or planar zone immediately be-
low, (3) hillsides facing north, northeast and east were
more susceptible to avalanching than slopes facing other
directions, and (4) debris-avalanches caused rapid and dev—
astating surges of water and sediment in the mountain-
stream channels. Such surges in some instances temporarily
blocked the channel flow upstream.

Slightly more than half of the total sediment contributed
to the stream system was from erosion of stream channels.
Channel erosion was very irregularly distributed; some
ravines 10—20 feet wide and 5—10 feet deep were scoured
in places which formerly had only a very small channel,
whereas other channels only a few hundred yards away ex-
perienced little or no channel erosion.

By the use of figures for the total amount of sediment
removed from a drainage basin and the duration of the
storm, estimates were made of the storm-average sediment-
transport rate at the mouth of various basins. For drain-
age basins ranging up to about 1.5 square miles, the esti—
mated storm-average sediment—transport rates varied from
practically nothing to as much as 172,000 pounds per sec-
ond (7.4 million tons per day).

The types of sediment deposits were (1) debris-avalanche
deposits, rather rare, at the base of hillslopes, (2) moun-
tain-stream channel deposits, usually in scattered sediment
patches but locally occurring as large wedge-shaped deposits

 

behind debris dams, (3) alluvial fans, (4) delta-like deposits
at the junction of a stream and major highway, where
water backed up during the flood due to plugging of a cul—
vert, and (5) accretion deposits on flood plains. The highway
deltas and some downstream flood-plain sediments consisted
mostly of sand-sized grains, but the other types of deposits
usually contained particles ranging from silt or clay to
boulders 5—10 feet in diameter. Changes in grain size and
in volume of deposition with distance downstream were
measured, and sedimentary features of the various types
of deposits are described.

INTRODUCTION

On the night of August 19—20, 1969, the central
part of Virginia was deluged with some 28 inches of
rain from the remnants of Hurricane Camille. The
loss of life and property due to the flash floods, land-
slides and other sediment damage accompanying the
storm has been called the worst natural disaster ever
to strike Virginia. The storm was one of the most
severe ever recorded in the United States.

The region most affected was Nelson County, a
rural area midway between Charlottesville and
Lynchburg (fig. 1). About 150 people, 125 of them
in Nelson County, died in the storm and flood.
Damage in Nelson County alone amounted to $116
million worth of public and private property, includ-
ing about 150 homes and other buildings, 120 miles
of roads, 150 bridges and culverts, hundreds of cars
and trucks and 25,000 acres of cropland, including
orchards. About $150 million in public funds, mostly
federal, has been spent on recovery, including $8
million in debris clearance. Particularly heavy dam-
age occurred in Massies Mill, Woods Mill, Roseland,
Tyro, Lovingston, Norwood, Rockfish, and along
Davis and Muddy Creeks (fig 1).

On the basis of the extensive damage to life and
property, the Commonwealth of Virginia has made
recommendations for future land use in Nelson
County (Commonwealth of Virginia, 1970). Kuhaida
(1971) also offers some pertinent observations.

This report is a study of the extraordinary erosion

1

 

 

 

 

HURRICANE GAMILLE IN VIRGINIA, 1969

 

 

    

CHARLOTTE) VILLE
STUDY AREA

         
  
 

BRENT GAP

 

at / .
Q1 4311?,

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BRYANT FAN ““4“ e HGHWAY DELTA Rockflsh
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6‘34

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Lovingston

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HIGHWAY
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9" ‘3 . Shlpman

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172:2 -
2"” C}. Lowesville

Ripe;- Y‘ , ‘3
9 §

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be” .Norwood

 

 

3 MILES

0 2
##4##
3 4 KlLOMETERS

FIGURE 1.—Study area.

alluvial fans and many flood-plain deposits in the
weeks and months following the flood. Necessary
though this work was, it did limit the scope and
thoroughness of a study of the erosion and deposi-
tion. All of the data presented in this report were
obtained before man’s interference with the de-
posits. However, the writers would like to emphasize
that anyone wishing to study flood deposits should
act as soon as possible after the flood.

We acknowledge with thanks the many helpful
manuscript suggestions of Dwight R. Crandell, Luna

and deposition which the storm inflicted on parts of
Nelson County. Most of our field observations and
measurements were made within 3 months after the
flood. Erosion and deposition, somewhat less severe,
also occurred in regions bordering Nelson County,
but time limitations permitted only a brief recon-
naissance of these nearby areas.

Because much of the sediment deposition from the
flood interfered with the daily operations of man, a
massive sediment-cleanup campaign began soon after
the flood. Bulldozers effectively destroyed most of the

 

 

GENERAL DESCRIPTION OF STUDY AREA 3

B. Leopold, and John T. Hack. Jon W. Nauman pro-
vided valuable assistance with some of the field work.
Mr. and Mrs. S. K. Wills, Robert Bryant and Guy
Spencer, residents of Nelson County, allowed us to
roam at will over their land. Many excellent photo-
graphs were provided by the Virginia Division of
Mineral Resources, the Virginia Department of High-
ways, Ed Roseberry and others.

GENERAL DESCRIPTION OF STUDY AREA

The devastated area lies within the James River
drainage basin in the Blue Ridge geomorphic prov-
ince. Most of the region is mountainous (fig. 2), with
peaks towering as much as 1,200 feet above the val-
leys. The climate is temperate-humid. Trees, bushes,
small plants and dead leaves cover all of the hill-
slopes and ridges. Tree varieties include walnut,
poplar, oak, ash, locust, hickory, and sycamore.

 

Bedrock is mainly Precambrian gneisses, granites
and schists of the Lovingston and Marshall Forma-
tions (Bloomer and Werner, 1955). The geology is
very complex, with a variety of rock types. J ointing
is present in some places and apparently absent in
others. On hillslopes the bedrock generally lies from
a few inches to about 20 feet below the surface. The
soil, formed in place from the bedrock, is typically a
reddish or brown loam and generally contains some
rock fragments.

THE STORM

Hurricane Camille struck the State of Mississippi
on the Gulf of Mexico on August 17, 1969. As it
moved inland to the north and then curved eastward,
the hurricane weakened considerably. Eastern Ken-
tucky received only 1—2 inches of rainfall.

On the night of August 19 a rare combination of
circumstances brought about a rapid intensification

 

FIGURE 2.—Upstream view of Wills Cove and Dillard Creek, a typical drainage basin studied in this report. The photo-
graph, taken a few days after the flood, shows valley flood-plain deposits and hillside scars due to debris avalanches.
Main stream from Fortunes Cove enters from right foreground. (Photograph courtesy of Virginia Division of Min-

eral Resources.)

4 HURRICANE C‘AMILLE IN VIRGINIA, 1969

80°

78° 77°

 

EXPLANATION

/5
Line of equal total rainfall. in inches

39°——

 

 

 

38°

 

ROANOKE . 2

 

37°

20 O 20 40 MILES
J I 1 l I | /
Y
$ '
20 O 20 40 KILOMETERS G
LI_J_I_l—l____J '
Q7 ’5'
%

     

I
Lynchburg

, _
WASHINGTON, D.C. '

A

58\.
6

4/

RICHMOND

 

 

 

FIGURE 3,—Rainfall from noon August 19 to midnight August 20, 1969. Adapted from DeAngelis and Nelson (1969).

of the rainfall in the region just east of the Blue
Ridge Mountains, especially around Nelson County,
Virginia (Schwarz, 1970). The air in the region
southeast of Nelson County was nearly saturated
with moisture that had been accumulating for sev-
eral days before the storm. This moist air extended
up to an altitude of about 3,000 feet. The hurricane
itself contained a large amount of moisture at higher
elevations. As Camille arrived, the remnant circula-
tion of the hurricane created a flow of Wind in a
northwesterly direction at the lower levels. These
winds drew moist air from the southeast, and this
moisture moved under and joined that of the hurri-
cane to form a very deep layer of moist air. Thunder-
storms developed which, because of the unusual
thickness of the layer of moist air, were particularly
intense and persistent. Figure 3 shows the rainfall
distribution in central Virginia for the period cover-
ing the storm.

In some places the orography may have contrib-

 

uted to the intense rainfall by funneling the north-
west-flowing air into the mountain ridges. However,
the effect of orography on the rainfall is difficult to
determine. Over 21 inches of rain fell in a region
about 15 miles southeast of Charlottesville where the
terrain, while not flat, is devoid of any steep or high
mountains. Thus some areas received torrential rain
with little or no influence from nearby mountains.

The deluge was of catastrophic cloudburst propor-
tions. Rainfall of 12—14 inches was common in Nelson
County and nearby areas, with reliable reports of
27—28 inches in the central part of Nelson County
(Camp and Miller, 1970; Schwarz, 1970). Other
sources have reported unconfirmed amounts of as
much as 46 inches (Simpson and Simpson, 1970,
p. 31).

The storm lasted about 7 or 8 hours, from around
2030 hours August 19 until 0330 or 0400 August 20.
Except for a brief lull at about 2330 or 2400 hours,
the rainfall, thunder, and lightning were intense

THE FLOOD 5

during the entire storm. A particularly strong cloud—
burst struck about 0250, cutting off electricity and
telephones for many of the inhabitants. At this time
lightning—mainly sheet or horizontal lightning—
was so severe that the sky was virtually a continu-
ous bluish-white.

The staggering amount of rain easily ranks among
the largest quantities ever measured in the United
States. DeAngelis and Nelson (1969, p. 458), for
example, compare it to the following:

12 inches in 42 minutes at Holt, Mo., in 1947,

19 inches in 2 hours, 10 minutes at Rockport,
W. Va., 1889,

22 inches in 2 hours, 45 minutes at D’Hanis,
Tex., in 1935,

31 inches in 4 hours, 30 minutes at Smethport,
Pa., in 1942,

34 inches in 12 hours, at Smethport, Pa., in
1942.

Schwarz (197 0, p. 853) states that Camille’s rain-
fall in Virginia was within about 80—85 percent of
the estimated maximum possible rainfall, for areas
up to 1,000 sq mi over a 12-hour period. Yarnell
(1935, p. 50—51) presents figures showing that the
maximum 8-hour rainfall for central Virginia might
be 3.5—4.0 inches once every 10 years and 5.5—6.0
inches once every 100 years. After 25 years of addi-
tional data, Hershfield (1961) presented charts
which for the eastern U. S. are nearly the same as
Yarnell’s. Hershfield’s curves show that for central
Virginia a rainfall of 7 inches in 12 hours (no 8-hour
data given) would be expected only once in 100 years.
Thus the Camille rainfall in Virginia was about 3—4
times the amount expected once every 100 years,
for an 8—hour storm. Thompson (1969) reported that
for Virginia the amount of rainfall associated with
this storm occurs, on the average, only once in more
than 1,000 years!

THE FLOOD

Comparisons of this flood with previous floods in
the James River basin are diflicult because of the
different lengths of record at the gaging stations. A
comment by Camp and Miller (1970, p. 21) indicates
the magnitude of the 1969 flood: “The flow of the
James River at Richmond peaked at 222,000 cubic
feet per second and is considered to be the second
highest discharge on the James River since James-
town was settled in 1607.” Towns along the James
River and its main tributaries were inundated to
depths of as much as 14 feet.

At Buena Vista, a town about 15 miles west of

 

Nelson County on the Maury River, the measured
flood discharge of 105,000 cfs (cubic feet per sec-
ond) is not likely to be equaled or exceeded, on the
average, more than once every 130 years (Camp and
Miller, 1970). When one considers that the flow on
the James River at Richmond was the second high-
est since at least 1607, dis-charges as large as the
1969 flood occur at Richmond an average of about
once every 180 years. These estimates of 130- and
ISO-year floods provide a very rough idea of the
recurrence frequency of the Camille flood at stations
on two major rivers, the Maury and the James, near
Nelson County.

There are no streamflow records for most streams
in Nelson County, where much of the heaviest rain-
fall occurred. Data for the few sites where gaging
stations have been established go back only a few
decades. For the nine sites in the area at which a
peak discharge measurement was obtained (six
measurements were by indirect methods), the
August 1969 flood exceeded the previous record by
factors ranging from 1.5 to 8. The discharges in the
deluged upstream basins undoubtedly are less com-
mon in those basins than the 130- and 180-year
occurrences estimated for the Maury and James
Rivers.

This study unfortunately has no water-discharge
measurements in the upstream reaches of the drain-
age basins, where much of the sediment movement
occurred. Flow depths, according to eyewitness ac-
counts, sometimes changed radically within minutes.
One farmer described the flow in Cub Creek as in-
creasing in depth by intermittent jumps of as much
as 3 feet at a time. A resident of Woods Mill reported
that the water in his back yard rose about 5 feet in
20 minutes. Another Woods Mill resident estimated
that the water near his house rose about 8 feet in
less than 30 minutes. Even with allowances for
errors in estimates, the discharge of even the larger
streams undoubtedly changed rapidly, and in the
mountains the discharge of streams draining only a
few hundred acres probably changed even faster as
a result of the impact from the debris avalanches
(Guy, 1971) .

Even if the discharge at a given site had been
monitored closely throughout the flood, the investi-
gator would have the problem of what discharge to
relate to the resulting sediment deposits.

ESTIMATED STORM-AVERAGE DISCHARGES

Measured rainfall amounts can provide a rather
crude estimate of the average water discharge for

6 HURRICANE CAMILLE IN VIRGINIA, 1969

the duration of the storm for the smaller upstream
drainage basins. This method involves the so—called
rational formula

Q=cIAd

where Q is water discharge or surface runoff (in
acre-inches per hour, for this formula), 0 is a coeffi-
cient representing the proportion of total rainfall
that runs off the ground surface, I is average rain-
fall intensity in inches per hour and Ad is drainage
area in acres. Flow rate in acre-inches per hour is
about equal to flow rate in cubic feet per second. The
coeflicient c is usually estimated on the basis of pre-
vious experience with similar areas and reflects the
role of infiltration losses, surface detention, valley
and channel storage, and general physical character-
istics of the drainage basin (Foster, 1948, p. 343).
The effects of these factors probably were minimized
for this heavy storm, especially for the small steep
drainage basins in the study area. Reasonable values
for 0 therefore are taken to be about 0.90 for basins
of 100 acres or less, decreasing by 0.02 for each
additional 100 acres of basin size up to 2,000 acres.
In the upstream regions the flood probably lasted
from an hour or so after the onset of heavy rainfall
to an hour or so after the rain stopped, a period of
about 7 hours. According to the rainfall data men-
tioned above, plus the figures which Camp and Miller
(1970) listed, the average total rainfall over the gen-
eral study area can be taken as about 20 inches. If
20 inches accumulated during the 7-hour period, the
average intensity I was about 2.9 inches per hour.

The mountain drainage basins (fig. 1) studied in
some detail in this report, selected because they
showed some of the most widespread sediment
erosion and deposition, are Ginseng Hollow (drain-
age area Ad:0.667 sq mi), Polly Wright Cove
(Ad=0.953 sq mi), Wills Cove (Ad=1.577 sq mi),
and Freshwater Cove (4122.333 sq mi). (Some
neighboring regions, such as the Davis Creek area
and Fortunes Cove, also experienced considerable
erosion and deposition and might have been included
in the investigation had time permitted.) If one
uses the rational formula with the assumption just
mentioned, the approximate 7-hour average dis-
charges were 1,500 cfs for Ginseng Hollow, 1,400 cfs
for Polly Wright Cove, 2,100 cfs for Wills Cove and
2,700 cfs for Freshwater Cove.

ESTIMATED PEAK DISCHARGES

Investigations made after the flood usually, of ne-
cessity, deal with the peak discharge. Two ways to

 

estimate the peak discharge in the upstream reaches
of interest are (a) to extrapolate a best-fit line relat-
ing drainage area to measured discharges for down-
stream sites or (b) to measure the channel slope and
estimate the cross-sectional flow area for each study
reach, for use in the Gauckler-Manning formula.
Both of these attempts were fruitless in the present
case. A plot of drainage area versus peak discharge
per square mile, with data for the few downstream
sites measured, showed too much scatter to permit a
reliable extrapolation to small drainage areas. The
slope-area method faltered over a reliable estimate
of the resistance coefficient, as there was no way to
determine this value for a stream carrying and de-
positing particles ranging from clay to large boul-
ders, along with trees and other debris.

A third possible way to estimate the peak dis-
charge in the small upstream drainage basins is to
resort again to the rational formula Q=cIAd, in
which I represents a peak rate of rainfall intensity
and c and A, have the same values used above. If
one may judge from the data which Jennings (1950)
compiled, a reasonable estimate of the peak rate of
rainfall intensity in the basins studied here is about
25 inches per hour, even though such an intense
burst probably did not last for more than 5—10 min-
utes. If this peak intensity and the assumptions re-
garding c are valid, the rational formula yields ap-
proximate peak discharges of 9,100 cfs for Ginseng
Hollow, 12,200 cfs for Polly Wright Cove, 18,200 cfs
for Wills Cove and 23,100 cfs for Freshwater cove,
or about 6—9 times as large as the values "(estimated
above) for the 7-hour average discharge. These
peak values approximate the Myers rating of 100,
that is, the peak discharge per square mile is about
equal to 10,000/Ad°-5°. Some indirect measurements
which Camp and Miller (1970, p. 59) reported for
this storm also approach this rating; so the rational-
formula assumptions have some support.

All of the above discharge estimates are for water
alone, exclusive of the large amounts of sediment
and vegetative debris contributed by the hillsides and
stream channels.

GEOMORPHOLOGICAL FEATURES OF
DRAINAGE BASINS

The amount and extent of the erosion and deposi-
tion can be better understood if some background
information is provided on the landscape and stream-
channel characteristics of the study area. The fol-
lowing concerns selected geomorphological aspects
and their interrelations.

GEOMORPHOLOGICAL FEATURES OF DRAINAGE BASINS 7

SLOPES 0F DRAINAGE AREAS

Steep hillslopes provided excellent conditions for
mass wasting. Figures 2 and 4 indicate the general
steepness of the regions studied.

The areal distribution of slopes for the three drain-
age basins of figure 4 is shown in figure 5. These
slopes, listed in table 1, were obtained from the con-
tour maps (scale 1:24,000) by map measurements of
the local slope (50 ft upslope and 50 ft downslope)
at each of many grid points, shown as black dots on
figure 4 and spaced 400 feet apart. Subbasin drain-
age areas were outlined as in figure 4, and the areas
were measured by planimeter. The general slope

TABLE 1.—-Dra,inage area and average surface slope in tribu-
taries and subbasins of Wills Cove, Ginseng Hollow, and
Polly Wright Cove

 

 

 

 

 

Average
Drainage surface
Drainage basin area slope
(sq mi) (percent)
Wills Cove
West tributary _______________ 0.238 46.2
Middle tributary _____________ .145 46.5
Falls tributary
Subbasin 1 ______________ .040 ___
2 ______________ .037 ___
3 ______________ .029 ___
4 ______________ .068 ___
5 ______________ .046 ___
6 ______________ .030 ___
7 ______________ .026 -__
8 ______________ .052 39.5
9 ______________ .047 45.0
10 ______________ .033 41.4
11 ______________ .027 48.0
12 ______________ .024 40.0
13 ______________ .114 39.1
14 ______________ .060 41.5
15 ______________ .032 ___
16 ______________ .063 _-_
17 ______________ .064 ___
18 ______________ 014 ___
19 ______________ .022 ___
20 ______________ .006 -__
21 ______________ .008 ___
22 ______________ .038 ___
Subtotal (1—22) ________ 880 ___
Noncontributing __________ .314 ___
Total, Falls tributary 1.194
Average slope, basins 8—141 ____ 41.3
Total Wills Cove ______ 1.577 ___
Ginseng Hollow
Lower _______________________ 0.172 48.1
North tributary ______________ .086 42.7
South tributary ______________ .115 43.9
Main> 34002 _________________ .222 38.0
East bowl ___________________ .082 32.1
Total __________________ .677
Average slope, entire basin _______ 41.5

See footnotes at end of table.

 

TABLE 1.—--Drainage area and average surface slope in tribu-
taries and subbasins of Wills Cove, Ginseng Hollow, and
Polly Wright Cove—Continued

 

 

 

Average
Drainage surface
Drainage basin (sq mi) slope
(percent)
Polly Wright Cove
Tributary ___________ 1 ______ 0.043 49.3
2—5 ______ .086 38.6
6 _____ .037 39.3
7 ______ .026 40.0
8 ______ .069 45.8
9 ______ .060 45.5
10 ______ .034 53.0
11 ______ .037 54.2
12 ______ 043 47.5
13 ______ .024 52.0
Total (1—13) __________ .459
Average slope,
tributaries 1—13 ________________ 45.6
Lower _______________________ .130 37.7
Noncontributing ______________ .364 21.8
Total, entire basin ______ .953
Average slope, entire basin ________ 35.4

 

1 Weighted according to contributing drainage area.

2Refers to all drainage area upstream from a station 3400 ft up the
main channel, the measurement of this distance having begun at the
mountain front (apex of alluvial fan).

representing each such drainage area is the average
of all local slopes (grid points) within that area.

The terrain in Polly Wright Cove is virtually the
same as in the other basins, but the curve in figure 5
shows a lesser part of the total drainage area with
steep slopes for Polly Wright Cove because the map
measurements included more of the flood plains of
the basin.

Hillslope erosion appeared to be negligible or non-
existent in tributaries or subbasins having an aver-
age surface slope of about 35 percent or less.

STREAM LENGTH AND DRAINAGE AREA

The time for debris eroded near the stream head-
waters to arrive at a given downstream site depends
in part on the distance along the stream channel
which the debris must travel. Also, the amount of
water and sediment which a stream carries depends
partly on the stream’s drainage area. Thus, stream
length and drainage area are important factors in
the geomorphology of a flood-damaged region.

Various geomorphic studies have established that
stream length L is approximately related to drain-
age area Ad, where L is measured from topographic
maps (scale 1:24,000 in this case) as horizontal dis-
tance from drainage divide along the channel of the
longest stream above the station. Hack’s data (1957,

HURRICANE CAMILLE IN VIRGINIA, 1969

79" 55'

l

13

    
          
  
  

 

 

 

    

 

 

 

 
 

 

 

 

 

7/ 8
/ 7 / 6
/4
79° 55' 3— 1770'
30"
37°
47L— q
30"
D —a*‘
o 2
20
8 10 &
8 1
18 ;
19 %
Falls Tributary 9‘
d _
21 c—
Middle 79"55’ %
g Tributary 22
f
SUBBASINS IN HEADWATERS OF WILLS COVE
West Area of West Tributary: 0.238 square mile
Tributary - ~ Area of Middle Tributary=0. 145 square mile
79.55, 8 9 Area of Falls Tributary: 1.194 square miles
112 (I) 1/I2 1 MILE
I I 1 I |
5 o .5 1 KILOMETER
l 1 I I I l l I
Base from U.S. Geological Survey, CONTOU R INTERVAL 20 FEET
Horseshoe Mountain and Lovingston, 1967 DATUM Is MEAN SEA LEVEL

FIGURE 4.—Ab0ve and right. Contour maps of Ginseng Hollow, Polly Wright Cove and Wills Cove basins, showing loca-
tions of grid points (dots) used to determine average surface slope for tributaries and subbasins. Subbasins are out-
lined with solid lines. Arrow at mouth of each basin ShOWS flow direction. Notable hillslope erosion lacking in pat-

terned areas.

 

 

GEOMORPHOLOGICAL FEATURES OF DRAINAGE BASINS

    
   
 
          

North Tributary

 

Lower ,
37 ° A7 ' 30"

East Bowl

Main > 3400

37am 30"/

GINSENG HOLLOW

Area = 0.677 square mile

South Tributary

78° 52' 30”

 

 

 

 

 

 

 

 

 

 

 

 

 

16 17

 

Lower
10 6 POLLY WRIGHT COVE

‘ 9 7 Area=0.953 square mile
8 8 +37°47'3o"

2 3 4 5 5 7 78°52’30"
9

37° 47' 30"—

 

 

H
O

    
 
  
  
   

 

100 ‘

l l l | |

90
EXPLANATION

  

80 _ \. o— —o— —o —
\ Polly Wright Cove
\
\ x——x———x
70 — ‘\ Ginseng Hollow ‘7
k 13— —+——-A
60 — \\ Wills Cove _
\
h
50 — \ —

30—

10‘

PERCENTAGE OF BASIN AREA STEEPER THAN GIVEN SLOPE

 

 

 

0 10 20 30 40 5'0 60 70 80 90
SLOPE, IN PERCENT

FIGURE 5.—Percentage of drainage-basin area steeper
than given slope for Polly Wright Cove, Ginseng Hol-
low and headwaters of Wills Cove.

p. 64) for some 85 measurements in nearby Virginia
and Maryland showed that if all of the points are
viewed collectively, then L oc Ad”. Hack found this
same general relation for 400 observations reported
by Langbein (1947) for the northeastern United
States. Two other areas which Hack tested—one in
Arizona and one in South Dakota—also had power
relations but with an exponent of 0.7. Mueller (1972)
studied 65 large drainage basins (ranging from
5,000 to 5,000,000 sq mi) from various continents
and reported the general relation L oc Ad0-466.
Figure 6 is a plot of stream length versus drainage
area for three of the major streams studied here
(see fig. 1). A general relationship in which L varies
approximately with A,]‘)-6 probably could be fitted to
the complete group of points. But the scatter and
range of data are such that other exponents might
also apply. More interesting is the fact that the
points for any one stream show little scatter about
an eye-fitted line for the particular stream (values
of L from the equations in figure 6 can be determined
to within about $15 percent or better). The expo-
nents of lines drawn for individual streams show
considerable variation, ranging approximately from
0.4 to 0.7. Hack (1957) also found significant de-
partures from his general relation L oc Ad”. Con-
sequently, although general relations are often use-
ful and interesting, some attention also should be

 

HURRICANE C'AMILLE IN VIRGINIA, 1969

given to the extent to which individual streams de-
part from the general relation.

A low exponent means a lesser rate at which
stream length increases, for a given enlargement in
drainage area. Conversely, for given increments of
stream length, the stream with a lower exponent
drains relatively larger areas as distance increases.
Low exponents can reflect a lack of meandering
(smaller increases in stream length) for given in-
creases in drainage area, or they might suggest a
relatively rapid enlargement of drainage area down-
streamward. The latter is the reason for Dillard
Creek’s low exponent of 0.42.

LONGITUDINAL PROFILES 0F STREAM CHANNELS

The longitudinal profie of a stream, a plot of dis-
tance versus elevation, shows how the channel slope
changes with distance and is one of the basic char-
acteristics of a stream channel.

TOPOGRAPHIC MAP DATA

Longitudinal stream-profiles of five prominent
channels were measured from topographic maps
(scale 1:24,000) . The profiles extend for distances of
3—8 miles downstream from the drainage divide.

Figure 7 shows these longitudinal profiles (fall F
versus horizontal distance L) on arithmetic scales.
The characteristic concave-upward profiles are
smooth and regular for three of the streams (Camp-
bell Hollow, Rucker Run and Polly Wright), but the
other two (Ginseng Hollow and Wills Cove) include
a pronounced deviation or local steepening.

Many longitudinal profiles of streams and alluvial
fans plot as straight lines on semilog paper. For
some streams the elevation (ordinate) must be on
the log scale, whereas for others the distance (ab-
scissa) must be on the log scale. Krumbein (1937),
Shulits (1941), Yatsu (1959), Leopold and Lang-
bein (1962), and Fok (1971) dealt with the former
type; their studies were concerned mainly with
graded or well-developed rivers rather than moun-
tain streams. Semilog plots of the profiles shown in
figure 7, with elevation on the log scale, have a
strong curvature, and no constant could be found
(computed) to rectify the curves.

Hack (1957, p. 70; also Hack and Goodlett, 1960,
p. 11) and Leopold and Langbein (1962, p. A9) dealt
with the second type of plot, Where elevations vary
with the logarithm of distance. A diagram of this
sort, an exponential or depletion function, describes
the five profiles of figure 7 in a rather approximate
way. The plotted points, not shown here, have a
sinuous path, and a straight line fitted by eye pre-
dicts the altitude to Within about :17 percent.

 

 

GEOMORPHOLOGICAL FEATURES OF DRAINAGE BASINS 11

100

 

flllllll

L 211,800 A3“
(Dillard Creek)

10—

STREAM LENGTH (L), IN THOUSANDS OF FEET

L = 7800 A36"
(Polly Wright Cove)

 

1.0
DRAINAGE AREA (An), IN SQUARE MILES

o»
L.

 
    

| llllllll

L =6550 A3“
(Rucker Run)

    
 

 

I llllllll

FIGURE 6.—Variation of stream length with drainage area for three Nelson County basins.

For the range of elevations involved with these
stream profiles, the actual values of the elevations
are approximately proportional to the logs of the
elevations. Consequently a graph of elevation (not
vertical fall) versus L on log paper, not included
here, also shows an approximate straight-line rela-
tion. The alinement of points on such a logarithmic
graph is slightly better than on the semilog plot. A
straight line drawn by eye predicts the altitude to
within about :13 percent or better, with the possible
exception of the point nearest the drainage divide.
(Incidentally, plotting the fall F versus channel
length L on logarithmic paper did not produce a
straight line, nor could any constant be found to
rectify the curve.)

The type of plot which best expresses the elevation
or fall along the five streams is a hyperbolic equa-
tion, like the power law, and takes the form

F=L/ (a+bL)

Where a = the extrapolated value of the ordinate at
L = O and b is the slope of the best-fit line on the
graph. Rearranging the equation into the form
L/F=a+bL gives the type of diagram on which the
data plot as a straight line (fig. 8). (An alternative
way of rearranging the equation is 1/F=a (1/L) +b,
which indicates that a plot of l/F versus l/L, not
included here, also gives a straight line on arithmetic
scales. This variant of the plot is not practical be-
cause much of the stream length is squeezed into a
small section on the abscissa.)

 

12 HURRICANE CAMILLE IN VIRGINIA, 1969

 

 

TOTAL VERTICAL FALL FROM DRAINAGE DIVIDE (F), IN FEET

 

I l I I

o 5000 ' 10.000 15,000

20,000

I I | I

EXPLANATION

x Ginseng Hollow and Hat Creek

0 Campbell Hollow and East Branch Hat Creek
III Rucker Run

0 Polly Wright Cove and Muddy Creek

V Wills Cove and Dillard Creek

4|

I

\4
7“—

X

 

l I I I

25,000 30,000 35,000 40,000 45,000

 

TOTAL HORIZONTAL DISTANCE FROM DRAINAGE DIVIDE (L), IN FEET

FIGURE 7.—Longitudinal profiles of stream channels, based on data from topographic maps. Vertical exaggeration is
X 10.

 

One distinctive feature of this diagram is the
striking linearity of data points. Second, the local
steepening in Ginseng Hollow is quite apparent and
divides the profiles into two segments. This local
steepening was much less recognizable in the semi-
log and log plots. Last, the first data point on the
Campbell profile (100 ft from the drainage divide)
is markedly offset from the best-fit line. The ratio
L/F for this point is higher than would be expected,
so for this particular horizontal increment the fall
is less than would be expected. Probably the concave
profile is not as well-developed this close to the drain-
age divide.

After some algebraic manipulations, the equation
F=L/ (a+bL) assumes a form very close to one of
the equations which Hack (1957, p. 70, eq. 11) found
for stream profiles in nearby areas of Virginia and
Maryland. The pertinent Hack equation is for
streams in which the average size of the bed particles
decreased downstream, as is the case in the streams
studied here. Written in logarithmic form, Hack’s
equation is

10g(F—C)=10g(k/ (70+ 1)) -I— (71 + 1) logL

 

where C is a constant of integration and k and n are
also constants. The present equation, rearranged and
put in logarithmic form, is

log (F — a )=logv—log (L+B)
in which a=1/b, B=a/b and 'y= (—a/b9). This is
essentially Hack’s equation with ’I’L=—2 except that
the right-hand side has L + ,8, rather than L.

The coefficients a and b both reflect such features
as the channel steepness and do not lend themselves
to simple descriptive labels. Values of a in this study
ranged from 1.1 to 3.1, and b—values ranged from
0.000600 to 0.000870. Eye—fitted lines predict the fall
F to within about 9 percent error and usually to
much greater accuracy.

The appearance of the local steepening in Ginseng
Hollow on the L/F versus L diagram might seem to
suggest that this type of plot is sensitive to local
channel aberrations. This, however, is true only near
the drainage divide, where the distance L is still
rather short and F increases significantly. The ap-
parent sensitivity virtually disappears after L has
increased to about 2 or 3 miles, by which stage F
usually increases by relatively minor increments.

 

 

25

15

10

  

 

   

 

 

 

10

  

 

   

 

 

GEOMORPHOLOGICAL FEATURES OF DRAINAGE BASINS 13
I I l l l I
\ Ginseng Hollow and Hat Creek —
+ =1.7+o.00059 L
E
o o I I I I I I
p
<
n:
15 I I I I I I
\+ =1.2+0.00071L _
Campbell Hollow and East Branch Hat Creek _
l l I I I I
O 5000 10,000 15,000 20,000 25,000 30,000 35,000

TOTAL HORIZONTAL DISTANCE FROM DRAINAGE DIVIDE (L), IN FEET

FIGURE 8.—Longitudinal channel profiles plotted in the form of L/F’ versus L (topographic map data).

FIELD MEASUREMENTS

On three of the channels—Ginseng, Polly Wright
and Campbell—more detailed longitudinal profiles
were measured in the field with a stadia rod and
either a Zeiss level (for flatter reaches) or a hand
level. Distances along the channel are virtually the
same as horizontal distances and will be so treated
in the following discussion. The distance and fall
from the drainage divide to the uppermost channel
station were taken from the topographic map.

These longitudinal profiles of mountain channels
and, where present, their adjoining alluvial fans
have the usual concave-upward shape when plotted
on arithmetic scales (fig. 9). The local steepening in
Ginseng Hollow, discussed earlier, appears in the
upstream part of the Ginseng profile. The profiles
tend to consist of straight-line segments, a feature
which Bull (1964) pointed out for alluvial fans in
California. The present field data show that this seg-
mented characteristic applies to the channel up-
stream from a fan, in addition to the fan itself.
Furthermore, the profiles show no sudden change in
slope at a fan apex, and the location of the apex
cannot be found from studying the profile. This is
also a feature which Bull (1964, p. 101) noted for
his profiles in California. And Denny (1965, p. 55)

 

remarked that the mountain channels and alluvial
fans which he studied in California and Nevada have
a smooth profile with no break in slope at the fan
apex. As Morisawa (1968, p. 94) noted, the primary
cause of fan deposition therefore is not a sudden
flattening of channel gradient. Instead, such deposi-
tion most likely results from the sudden spreading-
out of the flow as it escapes the confining mountain
channel.

Profiles on semilog and log paper, not included
here, also consist of straight-line segments. The num-
ber of segments decreases progressively from arith-
metic to semilog to log plots. As with the topo-
graphic-map data, a straight line on the log diagram
is a better approximation of the longitudinal profiles
than a straight line on semilog paper. The L/F
versus L relation (fig. 10) describes the data most
accurately.

The equations for obtaining the vertical fall F
from the drainage divide, in feet, for a given hori-
zontal distance L from the drainage divide, in feet,
are:

F=L/ (2.52+0.00050L)
F=L/ (1.36+0.00075L)
F=L/ (1.20+0.00065L)

Ginseng-Bryant :
Polly Wright:
Campbell :

 

 

14 HURRICANE GAMILLE IN VIRGINIA, 1969

 

I I I

   
 
  
    
  
    

ELEVATION ABOVE SEA LEVEL, IN FEET

Apex of Ian/

End of fan

/

  

 

I I I I

I I |

EXPLANATION

X Ginseng Hollow and Bryant fan
0 PoIIy Wright Cove
0 Campbell Hollow and fan

/Apex of fan

End of fan

 
   

 

I I I

 

2000 3000 4000 5000 6000

|
7000 8000 9000 10,000 11,000

TOTAL HORIZONTAL DISTANCE FROM DRAINAGE DIVIDE (L), IN FEET

FIGURE 9.——Longitudinal profiles of mountain channels and, where present, adjoining alluvial fans. Data from field meas-
urements. Vertical exaggeration is X 10.

These equations were obtained graphically from fig-
ure 10, in which the best-fit lines have been drawn
by eye. Except for the local steepened reach in Gin-
seng Hollow, the equations predict the total fall from
the drainage divide to any station on the stream
channel to within :25 percent.

In summary, this section has presented measured
values of drainage areas, stream lengths and the
steepness of the terrain, together with some relation-
ships between these factors. A mathematical expres—
sion of the longitudinal profile has been found for
several of the main streams in the study area. Inas-
much as some kinds of erosion described in the fol-
lowing section are typical of mountainous regions,
future studies using more data may discover some
mathematical relation between the geomorphological
characteristics of the drainage basins, on the one
hand, and the amount and type of erosion expected to
result from a given quantity of rainfall. Similarly,
when more data are available it may be possible to
relate the geomorphological features to the down-
stream amount and pattern of deposition. Some ten-
tative steps toward these goals are taken in later
sections of this report.

 

EROSION
DEBRIS AVALANCHES

Measurements and estimates of amounts of ero-
sion presented later in this report suggest that nearly
half of all the storm-eroded sediment came from
downslope—trending strips on the hillsides. Many
scars (figs. 11 and 12) testify to the magnitude of
this hillslope degradation. The nature of these scars
and their association with the heavy rainfall indicate
that they were caused by a type of mass—movement
which Sharpe (1938, p. 61) called a debris ava-
lanche. A debris avalanche is a rapid down-hill flow—
age of soil, rock, trees and other vegetation (if
present) and water. According to Sharpe, “the typi-
cal debris-avalanche has a long and relatively nar-
row track, occurs on a steep mountain slope or hill—
side in a humid climate, and is almost invariably
preceded by heavy rains.” In Sharpe’s classification
debris avalanches differ from landslides in that land-
slides involve very little water. The Nelson County
avalanches included soil, trees and other plants,
water, and usually rocks ranging from gravel to
boulders up to 10 feet in intermediate diameter.

 

EROSION 15

 

3-0 I I I I
7.5 —
7.0 —
6.5 —

6.0 —

5.5 —

RATIO L/F

5.0 —
4.5 — \
End of fan

4.0 —

3.5 ’—

\

3_0 __ Apex of fan

I I I

 

   
  

End of fan

    

Apex of fan

EXPLANATION

X Ginseng Hollow and Bryant fan
0 PoIIy Wright Cove
0 Campbell Hollow and fan

I I

 

 

2.5 I
2000 3000 4000 5000 6000

| l
7000 8000 9000 10. 000 1 1,000

TOTAL HORIZONTAL DISTANCE FROM DRAINAGE DIVIDE (L), IN FEET

FIGURE 10.—Longitudinal profiles of figure 9 (mountain channels and, if present, adjoining alluvial fans), plotted in
the form of L/ F versus L. Data from field measurements. Every other point plotted.

A previous report (Williams and Guy, 1971) ana-
lyzed various aspects of the 1969 Nelson County
debris avalanches.

Hack and Goodlett (1960) described in consider-
able detail the important role of debris avalanches
in the overall adjustment among slope processes,
mountain form, and vegetation for a similar central-
Appalachian region in Virginia and West Virginia.

Eyewitnesses or survivors of debris avalanches
say that the entire event occurs very quickly. Obser-
vations during the present storm were obscured be-
cause of the darkness. Mr. S. O. Mawyer of Woods
Mill was almost swept away in a small avalanche
near his home and only saved himself by grabbing a
bush that was growing just beyond the slide border.
He said the ground started oozing slowly downhill
for a fraction of a second, and then the entire section
of the hillside suddenly slid quickly down the slope,
accompanied by a loud noise. Mr. B. R. Floyd, whose
Lovingston, Va., home (a few hundred yards down-
stream from the base of a long, high mountain) was
severely damaged by a 3,000-foot-long avalanche
(fig. 13), estimated the duration of the event in the
vicinity of his home to be about 3 minutes. Mr. W. E.

 

Davies, a geologist for the US. Geological Survey,
saw a debris avalanche in a 1949 West Virginia
storm and testified (oral commun., 1970) that the
whole strip of hillside started moving at about the
same instant. These subjective descriptions give
some indication of the short duration of a debris
avalanche.

Rapp (1963, p. 198—200) quoted an eyewitness
description of debris avalanches in western Norway:
“A mass of earth, boulders, trees and water moves
down the slope and a new slide track is formed * * *
The river (at the base of the hill) is filled with a
porridge of earth which flows downstream, mixed
with a crowd of naked birch stems, twisting and
whirling * * * New slides are coming down. It looks
like a wave of water that squeezes earth and trees
out of the ground and back again. The trees fall
down immediately (with their bases pointing down-
slope, according to Rapp). Then they are pushed
together with the earth and boulders on the way
downslope, so they reach the river naked, Without
twigs and bark. Water sprays out in small cascades
from the moving earth.”

People living in or near the mountains in Nelson

16 HURRICANE CvAMILLE IN VIRGINIA, 1969

 

FIGURE 11.-—Erosion and deposition caused by the torrential rainfall, Davis Creek area, Nelson County, Va. Scars on
hillsides mark locations of debris avalanches. Stream flood plain shows both erosion and deposition. (Photograph by
Ed Roseberry.)

County were unanimous in emphasizing the awful
roar they heard associated with both the debris
avalanches and the swollen streamflow. The noise
was variously described as sounding like a squadron
of airplanes warming up for takeoff; or continuous
discharges of dynamite, one charge right after the
other, sometimes overlapping; or many cannonballs
rolling along inside a bowling alley, with cracking,
popping, and explosions.

The slides occurred at intervals ranging from “one
right after the other” or “every few minutes” to
“every once in a while” (Simpson and Simpson,
1970, pp. 8—9). The accounts of local residents sug-
gest that the avalanching was more frequent toward
the end of the storm. Some slides occurred after the
rain had abated to a sprinkle or mist, at about 0400
hours on August 20.

At least the larger debris avalanches caused a very
noticeable quivering or trembling of the earth’s sur-

 

face for a radius of several miles.

There is no way to determine how many of the 125
people who lost their lives in Nelson County were
killed by debris avalanches. A number of missing
houses, particularly in the Davis Creek basin, origi-
nally stood in small hollows which were scoured by
avalanches. Other lives were lost when buildings and
property hundreds of feet downstream from hill-
slopes were ravaged by avalanche water and debris.
Dr. J. H. Gamble of Lovingston, who was in charge
of identifying and examining the flood victims, found
that almost none of the dead showed evidence of
drowning. “The vast majority were just multiple
fractures—rib . . ., spine . . ., large bone . . ., skull
fractures—from rocks and trees and so forth. Most
died from massive ‘blunt force’ injuries.” (Simpson
and Simpson, 1970, p. 270). Such testimony shows
that sediment damage during floods can be very im-
portant in terms of lives as well as property.

EROSION 17

SOURCE MATERIAL

The soil type on the mountainsides, according to
the US. Department of Agriculture classification, is
of the order inceptisol—a young soil that presumably
has formed rather quickly, mostly from alteration of
parent materials (here, the underlying crystalline
rocks) and which lacks horizons of marked accumu-
lation of clay, iron oxide, and aluminum oxide. The
subdivisions within the inceptisol order would be
ochrept and dystrochrept.

The soil usually is about 1—3 ft thick on the steeper
parts of the terrain. Logically, the thickness of the
profile should vary inversely with the long-term ero-
sion rate and (or) directly with the weathering rate
of the rocks. Most profiles on the hillslopes contain
some larger rock fragments, including a few of boul-
der size.

Two or 3 inches of dark-colored organic matter
cap the soil profile. Below this organic layer the soil
color is mostly red-brown. The texture is that of a
soil matrix, rather uniform in size-composition with
depth, containing a few larger fragments ranging
up to several feet in diameter. Soil samples from the
side walls of 10 scars—three in Polly Wright Cove,
five in Wills Cove, and two in Ginseng Hollow——
were analyzed for particle size. Such samples were
small (1 or 2 kilograms) and did not include parti-
cles larger than about 25 mm (millimeters). There
appears to be no significant difference in particle
size among the 10 soil samples. The average for the
10 samples was 15 percent gravel, 48 percent sand,
31 percent silt, and 6 percent clay-sized particles by
weight. The median size ranged from 0.08 to 0.28
mm. The larger fragments occur at diverse levels
within the soil profile and usually do not show any
pronounced trend of becoming larger with depth.
Some of these large fragments are on the top surface
and probably move downslope by creep. No repre-
sentative size-frequency distribution was obtained
for these large rocks.

GENERAL DESCRIPTION OF AVALANCHE SCARS

Typical avalanche scars range from about 200—800
feet in horizontal length, 25 to 75 feet in width and
1 to 3 feet in depth. Some scars are as short as 20
feet or as long as 1,000 feet, as wide as 200 feet, and
as deep as 15 or 20 feet. Average gradients are steep,
ranging in most cases from about 0.30 ft per ft (foot
per foot) (16 degrees) to 0.80 ft per ft (39 degrees).
The most common average gradients were 0.50—0.60
ft per ft. Based on 12 typical scars that were meas-
ured in detail, the average amount of sediment re-

 

moved in a single debris avalance was about 88,000
cubic feet or abut “'“X 4500 tons.
From the upslope tip, every debris avalanche con-

, tinued all the way down the hillside. Most scars be-

come slightly deeper with distance downslope.
Widths tend to increase downslope, as do avalanche
tracks in other areas (Swanston, 1969); however,
there are many exceptions where the width stays
about constant or decreases (fig. 12A). *

The heads of individual scars can be almost any-
where on a hillside, except that not one is located at
the crest of a hill. Some avalanches involved only the
foot of a hillslope, while others extend nearly to the
crest. Most scars originate in the middle third of the
slope between the ridge crest and the channel.

From a top View the break at the head of the scar
can be curved, irregular, or even a virtually straight
line, normal to the downslope direction.

Almost all avalanches removed the entire vegetal
cover in their path, including large trees. In many
cases the bedrock was exposed along the full length
of the scar. On other scars a foot or two of soil still
covers the bedrock, particularly in the lower reaches.
Some of the avalanches—probably those that oc-
curred near the end of the storm—removed only the
vegetation and part of the soil, so that no bedrock
was exposed. Many scars eroded to bedrock occur
next to scars which still have a partial soil cover (fig.
120).

The break between most slide areas and the adja-
cent unaffected ground is clean and sharp, especially
at the top of the scar. Many roots of the vegetation
which had been growing in the eroded soil were
broken and exposed. Most of these roots point down-
slope.

Mud deposits around the base of tree-trunks along
the edges of some scars suggest that the top surface
of the moving avalanche was as much as 3 feet
higher than the normal ground surface.

Nearly all the avalanches in the headwater areas
entered first- or second-order streams at the base of
the hillslope. These streams begin at the head of a
mountain ravine which itself experienced debris ava-
lanching or at least severe channel enlargement dur—
ing the storm. The streams wind through the moun-
tains for distances ranging from a few hundred feet
to as much as several miles, before emerging into
the broad intermontane valleys.

Along such mountain-stream channels the banks
opposite the scars rarely had deposits from the ava-
lanches, nor was any material left in the channel it-
self. Thus at some time between the avalanche and
the end of the flood, the stream removed nearly all

18

 

HURRICANE CAMILLE IN VIRGINIA, 1969

FIGURE 12 (above and right) .—Typical scars left by debris avalanches on hill-
slopes: A-C, headwaters of Wills Cove; D, drainage basin upstream from
Campbell fan; E, Ginseng Hollow.

 

EROSION 19

 

D

the dislodged material. Few, if any, of the avalanches
therefore occurred after the flood.

Avalanches on the sides of the broader intermon-
tane valleys continued beyond the base of the hill-
side for hundreds of feet and in most cases reached
the flooded zone in the center of the valley. After the
flood subsided, the path of these avalanches was
characterized by an incised channel and by sediment
deposition along each side of the channel (fig. 14) .

The huge volume of soil and rock eroded by debris
avalanches is discussed in the section on “Sediment
yield.”

GEOMETRY OF SCARS
METHODS OF STUDY

We measured the longitudinal profiles, cross pro—
files, widths, and depths of 12 scars which to the eye
appeared to be typical and representative of the
various types. For seven of these, the tools were a
hand level, tape, and surveyor’s rod. From the tops
of these seven scars to the base of the hillside, we
measured distance down the scar centerline with the
tape and read elevations at intervals of 10—«100 feet
(usually about 40—50 feet), depending on the steep-
ness of the slope. We estimated or measured widths

 

 

at intervals of 20—100 feet down the scar by extend-
ing the 25-foot rod from one edge of the scar toward
the opposite edge. At a few stations where the width
was not determined in this manner, we simply esti-
mated the total width by eye. We estimated erosion
in the center of the scar at all stations either by eye
or by holding the rod on one edge of the scar, point-
ing the other tip toward the opposite edge and assum-
ing that the rod represented the original surface.
The other five scars were mapped with an engi-
neer’s transit and surveyor’s rod in sufficient detail

 

FIGURE 13.-—Scar of major avalanche that penetrated Lov-

ingston, about 0300, August 20, 1969.
Ed, Roseberry.)

(Photograph by

 

 

20

HURRICANE C‘AMILLE IN VIRGINIA, 1969

 

A

FIGURE 14 (above and right).—Debris avalanches along sides of intermontane valleys. A, East Branch of Hat Creek. Creek
is at lower left foreground. Note deposition of logs, boulders and other particles along route from avalanche to creek.
B, Stevens Cove. Note damage to orchard. (Photographs courtesy of Virginia Division of Mineral Resources.)

that 10—foot contours could be drawn. With this
method the areal spacing of measurements was about
the same as with the hand-level method except that
additional readings were taken on the nearby undis-
turbed ground surface, both above the head of the
scar and on either side. Figure 15 presents maps of
typical scars and locations of cross sections. N0
depth-of—erosion estimates were made in the field for
scars mapped by transit; these depths instead were
estimated from the plotted cross profiles.

Elevations and distances from the drainage divide

 

to the head of the avalanche scar were taken from
the topographic map after we plotted the total hori-
zontal scar distance, as measured in the field, on the
map. The vertical distance from base of hillside
(usually taken as the channel edge) to top of scar,
as measured in the field, agreed very well with the
distance indicated by the contour lines on the map;
so for longitudinal—profile purposes the field and map
measurements could be combined with no significant
error.

A profile measured along the scar centerline in

 

21

EROSION

 

22 HURRICANE GAMILLE IN VIRGINIA, 1969

2

Polly Wright-A

     

EXPLANATION

0
Control point

l-H-H-t-H—l-l—l-d-l—l—l—H
Cross profile

Longitudinal profile

Edge of scar

 
   

Polly Wright-C

 

300
230
r/ ‘ J
l
» I
// \\ I \
\ 26o
b\ 9l \
/
Q
\ |
\9 \
\‘ 240
A l \
so 100 FEET 4"“ KH—
WM
. 220
CONTOUR INTERVAL 10 FEET /
ARBITRARY DATUM / \
I
v \
200
\

 

FIGURE 15.—Contour maps of two avalanche scars, Polly Wright Cove, showing locations of cross and longitudinal
profiles.

most cases does not exactly represent the longitudi—
nal profile before the avalanche because of the miss-
ing soil and rock in the scar. However, the overall
lengths (ranging from 560 to as much as 1,600 feet)
and vertical distances (240—599 feet) of the hillsides
studied are large compared to the estimated depth of
soil removed (generally less than about 5 feet). By
adding to the measured elevations the thickness of
soil and rock removed, as estimated in the field, we
were able to reconstruct the approximate pre-storm
profile for seven of the scars. These reconstructed
profiles closely approximated those measured in the
field. The only difference of any significance might be
near the base of those hillslopes from which a par-
ticularly large amount of sediment was removed.

 

This potential error might affect the apparent degree
of concavity of that region of the hillside. The post-
storm profiles as used here probably are quite close to
the original profiles, in most cases. The avalanches
certainly did not affect the profiles as far as the defi-
nition of convex and concave zones on the hillside is
concerned.

LONGITUDINAL PROFILES

Figure 16 shows the 12 scar and hillside profiles,
all of which have been standardized so that the units
of length and elevation are from zero to 1.0. The ab-
scissa is a sliding scale which we shifted systemati-
cally for plotting purposes, in order to put all of the

EROSION

 

1.0

0.9

0.8

0.6 —
0.5 —

0.4

PROPORTIONAL VERTICAL DISTANCE,
BOTTOM TO TOP OF HILL

 

0 ,7

 

 

 

 

0 0.1 0.2 0.3
l_ l l l

0.4
l

0.5 0.6 0.7 0.8 0.9 1.0
I l l . I I l

PROPORTIONAL HORIZONTAL DISTANCE, BOTTOM TO TOP OF HILL

FIGURE 16.—Longitudinal profiles of hillslopes, including avalanche scars. Vertical and horizontal distances have been

standardized to extend from 0 to 1.0. Table 2

gives actual scar and hillside dimensions. Arrow indicates position

of head of avalanche scar. See table 2 for profile numbers and scar designations.

profiles on one graph. An arrow on each profile
marks the head of the avalanche scar. Table 2 gives
the actual scar dimensions.

The profiles in figure 16 show a variety of shapes,
some details of which will be described in the para-
graphs below. The reader should look at each pro-
file, from base to hillside, and note (a) the general
hillside steepness in the region of the head of the
scar (arrow), and (b) the elevation of the head of
the avalanche relative to the vertical distance from
the bottom to the top of the hill. The scars generally
tend to begin in the zone where the local gradient is
steepest. In these profiles the steepest gradient is
located from about 0.3 to 0.95 of the horizontal dis-
tance and from about 0.3 to 0.95 of the vertical dis-
tance from base to hilltop. The head of the scar

TABLE 2,—Hillside and scar dimensions and erosion volumes
for measured avalanche scars

 

Hillside dimensions San- dimensions Erosion

 

 

Profile Scar
number designa- Length Full Length Fall ( 1,000
tion (ft) (ft) (ft) (ft) fta)
l ...... Ginseng—2,020 980 435 320 190 18
2 ______ Ginseng—East Br 620 240 260 120 67
3 ______ Ginseng—4 ,7 40 900 330 570 250 81
4 ______ Ginseng—Middle 646 310 500 250 144
5 ______ Ginseng—800 830 397 760 390 86
61 _____ Polly Wright—A 690 375 400 200 43
’I ______ Polly Wright—B 560 300 300 1'10 52
81 _____ Polly Wright—C 930 420 400 200 45
9 ______ Wills—5,850 880 505 260 17 0 32
10 ______ Wills—1,300 660 385 420 270 100
l 1 ______ Wills—1.100 1,200 600 870 390 162
12 ______ Wills-—7,550 1,620 565 860 380 233

 

1 Figure 15 shows contour mp of seals.

 

occurred on the average at 0.59 of the horizontal
distance and 0.62 of the vertical distance from base
to hilltop.

Hillslopes typically have a convex upper part and
a concave lower part. In some cases a middle section
of nearly constant gradient separates these two
zones; otherwise, the convex and concave portions
grade directly into one another. White (1966) has
shown that convex, straight, and concave profiles can
be most readily defined by plotting local hillslope
gradient as a function of horizontal slope distance,
on log scales. On such a diagram the convex profile
near the crest of a hill in many instances plots as a
straight line trending upward (positive exponent),
because the local gradient increases With slope dis-
tance. A horizontal line on the graph indicates that
the local gradient stays constant with distance away
from the crest: that is, the hillslope is straight. The
concave profile over the lower regions of a hillside
means that the local gradient decreases with hori-
zontal distance from the crest, and this type of pro-
file commonly plots on log paper as a straight line
sloping downward. All the slopes which White stud-
ied had smooth, regular profiles With prominently
convex upper regions and concave lower regions.

To examine the 12 profiles in more detail we plot-
ted the data on log paper using White’s method and
drew lines of best fit by eye. Figure 17 contains four
typical plots. Local gradient for any station was
reckoned from the arithmetic midpoints between the

 

 

24 HURRICANE CAMILLE IN VIRGINIA, 1969

1.0

 

l I I I I I I I I

_ A. POLLY WRIGHT-C

0.5 —~

 

 

 

I I \I I I | I I I

_ B. GlNSENG-4740 _

    

 

 

 

 

 

 

 

 

 

 

 

 

,_
o
0
LL
n:
LIJ
n.
I-
o
E 0.2
E
,;
Z 1.0
Lu I I I | I I I I I I I l l I
— L j _
o
E _ C WILLS—1100 / — D. POLLY gRIGHT-A _
3 " /” ‘
5 _//” —
o
_I
——O _.
02 I I I I I I I I I
100 500 1000 1500 so 100 500 1000

HORIZONTAL DISTANCE FROM DRAINAGE DIVIDE (L). IN FEET

FIGURE 17.——Variati0n in local hillslope gradient with distance from hilltop, for four typical hillsides on which debris
avalanches occurred. Arrow marks head of avalanche scar.

station of interest and the stations immediately
above and below. The corresponding value on the
abscissa is cumulative horizontal distance L from the
drainage divide to the station. The graphs presented
a wide variety of slope—types, as might be surmised
from figure 16. Some showed enough scatter that
various lines, straight or curved, might be fitted to
the points, and the difference between convex and
straight or between straight and concave segments
of the profiles sometimes became a subjective de-
cision.

What features do all the profiles have in common?
First, all have a convex zone beginning at the top of
the mountain. This upper convex zone varies Widely
in length—from the hilltop to about 0.1 or up to as
much as 0.7 of the horizontal distance to the base of
the hill. Some profiles showed two zones in this upper
convex region, corresponding to two straight lines
(both trending upward but at different rates) on the
gradient-versus-length graph (fig. 173).

Another common feature was that, with one ex-
ception, the profiles have a concave zone at the base
of the hillside. This zone may include as little as

 

about 0.1 or as much as 0.8 of the entire slope length.
Also, the concave zone often consists of two different
sections rather than one, as indicated by two down-
ward—trending straight lines on the graph (for ex-
ample, fig. 170) .

The profile pattern between the upper convex and
lower concave zones varies. In five cases these two
segments merged, with no intermediate zone (for
example, fig. 17 C ) . Two other profiles showed a
straight section between the convex upper slope and
the concave lower region. In the remaining five pro-
files the intermediate zone showed various combina-
tions of convex, straight and concave segments, with
no consistent pattern (fig. 17A,B,D).

The local gradient-versus-length plots verify the
deduction that the top of the scar is generally on the
steepest part of the hillslope. The plots also show
this point in relation to the convex and concave
zones. The persistent relation apparent from a study
of these gradient-length graphs is that the ava-
lanches in at least 9 of the 12 cases began at the
lower end of the upper convex zone on the hillside,
that is, at the junction where the convex upper zone

EROSION 25

merges with the concave or straight section imme-
diately below. This would in fact be the steepest
point on the hillside. More scar data should be ana-
lyzed to strengthen this conclusion, but the 12 scars
do include different slope lengths, heights, profile
shapes and degrees of erosion down their paths. In
spite of these and other differences, there is a pro-
nounced tendency for the head of the scar to be at
the steepest region on the hillside.

For the same hillslopes a previous report (Wil-
liams and Guy, 1971) examined gradient-length
graphs on which the origin of the profile was taken
as the top of the avalanche scar. Because those
graphs omitted the upper (convex) part of the hill-
side and began with the station several feet down
from the start of the scar, the graphs indicated that
the avalanches tended to form in the concave part
of the hillside. It was therefore not evident that the
convex upper slope of most profiles happened to ter-
minate about at the top of the scar. Thus, more use-
ful and accurate information is obtained by starting
the profile plot at the crest of the hill.

Another pertinent point in regard to the origin of
local-gradient plots is that because the abscissa is
horizontal distance on a log scale, the exponent or
slope of a best-fit line will vary Widely depending on
the origin, and consequently the magnitude, of the
horizontal measurement. Although local gradient is
fixed for any station on the hillside, the plotted points
can be spread horizontally to cover several log cycles
or compressed horizontally into a very short band,
depending on the abscissa-values being plotted.
White (1966) discussed other major problems asso-
ciated with the sensitivity of such diagrams to choice
of origin.

cnoss pnomms

Transverse measurements of avalanche scars were
made in the field; however, because the field profiles
vvere not obtained in true straight fines across the
scars and because the steep hillslopes would magnify
the error due to any such deviations, the cross pro-
files presented here (fig. 18) were obtained from
contour maps of the kind shown in figure 15. The
section was marked with a straight line on the con-
tour map and the elevation interpolated between
contours at 5-foot intervals, starting at the deepest
portion of the scar and proceeding to each side in
turn.

The shapes and dimensions of the cross profiles
vary considerably. Most scars are broad relative to
the depth.I¢ear the top of a scar,the profiles tend
to be rather flat. Toward the base of a hill, the pro-
files have a variety of shapes—flattish, for example,

 

 

LEFT BANK RIGHT BANK

‘x/ I 1 0.19

 

Wills-1100

 

 

Wills-1300

 

 

Polly Wright-A

 

  

Polly Wright-B

 

 

Polly Wright-C °

0 20 40 60 80 100 FEEV

 

 

 

FIGURE 18,—Typical cross profiles of avalanche scars, drawn
looking downslope. Number at edge of each profile indi-
cates proportional distance of profile section down hillslope
from start of scar. Vertical tick marks show edge of scar.
Dashed line=estimated pre-storm ground surface.

26 HURRICANE GAMILLE IN VIRGINIA, 1969

where the soil depth was shallow and bedrock is
exposed (fig. 18—Polly Wright B), or more U-
shaped where the soil was relatively deep (fig. 18—-
Polly Wright A). Flaccus (1958) found V-shaped
channels to be typical of the lower parts of ava-
lanche scars in the White Mountains of New Hamp-
shire.

The profiles also show typical trends of scar width,
with distance downslope.

The scar depths indicated by the cross profiles in
figure 18 seem to remain about constant or to in-
crease downslope, depending on the soil thickness.

POSSIBLE CAUSES OF AVALANCHES IN NELSON
COUNTY

The torrential rainfall undoubtedly was the pri-
mary cause of the debris-avalanches. But why did
avalanches occur down certain strips of hillside and
not on adjacent parts of the same slope or on other
hillsides only 50 yards or less away? One possible
reason is an uneven distribution of rainfall. A very
severely eroded stream channel commonly occurred
within a few hundred yards of a channel which ap-
peared to have carried only a small flow of water.
The most likely conclusion is that the rainfall intens-
ity was highly irregular, both in time at a given
spot and in area. Schwarz (1970) in fact affirmed
the complex nature of the rainfall for this extreme
event. He reported that a U. S. Weather Bureau sur-
vey team, investigating the various rainfall reports,
found that for each of four observations of over
20 inches total rainfall, less than 6 inches was meas-
ured at a location less than 5 miles away. Huff
(1967) states that multicellular patterns of precipi-
tation cause highly variable intensities and quanti-
ties near the centers of areas covered by heavy
storms.

Other factors which authors have mentioned as
possible influences on avalanching are steepness of
hillslope, vegetation type and density, kind of bed-
rock, attitude of stratified or jointed bedrock, ero—
sion or bombardment of the base of a slope by a
debris-laden stream, soil texture, orientation (as—
pect) of hillslope, length of hillslope, soil depth, sus-
ceptibility of soil to infiltration, ability of soil to
transmit water (hydraulic conductivity), the initial
presence of depressions or troughs along the hill-
slope, bolts of lightning, the vibrations of heavy
thunder, and the uprooting of trees due to strong
winds.

Although detailed measurements were not made,
vegetation type and density appear to be essen-

 

tially constant over the scarred area of the county,
even when differences in orientation and steepness
of slope and possibly in soil depth are considered.

Nearly all the bedrock of the area is rather imper-
vious. From exposures along scars and stream chan-
nels, it appears that the avalanches were more com-
mon over massive crystalline rocks than over schists,
but the former seems to be the predominant rock
type anyway. There is thus no evidence that the type
of bedrock influenced the likelihood of avalanching.
In some cases more than one rock type is exposed
along a scar. Some exposed bedrock is jointed,
whereas other exposures have no joints or cleavage.
Whether jointing increases the likelihood of ava-
lanching could not be determined in our study.

The possible influence of soil texture on the abil-
ity of soil to conduct water and to be susceptible to
infiltration cannot be sufliciently evaluated in a study
initiated after the avalanches have occurred. Soil
analyses at various stations on a hillside, before and
after the avalanches, would be the best way to find
any consistent associations. The same is true of the
internal shear strength of any layers in the soil pro-
file. Rapp (1963, p. 203) indicated that the main
slides at Ulvadal, western Norway, occurred along
planes mostly at or near the bottom of the podzolic
layer and the top of the fine-grained substratum in
the illuvial layer (the B horizon or layer accumulat-
ing clay for hundreds of years). Such a layer was
not readily noticeable along the avalanche walls in
Nelson County.

No large trees were found uprooted at the heads
of scars. Some scars began immediately downslope
from huge boulders, and the heads of other scars
were many times wider than the zone Which tree
roots would disrupt. Although the role of uprooted
trees in starting an avalanche could not be assessed,
this factor at most was probably of minor impor-
tance.

Some big slides were heard after the thunder and
lightning had stopped around 0400 August 20. Also,
the lightning during the storm was mainly the hori-
zontal type rather than vertical bolts which might
have struck the ground. These considerations suggest
that thunder and lightning probably were not major
factors in the initiation of debris avalanches.

The remaining possibilities which could be asso-
ciated with the Nelson County avalanches are stream
action at the base of the slope, depressions down the
hillslope, orientation of the hillside, the steepness of
the slope, the horizontal length of the hillside and
the soil depth. These factors are discussed in the
following pages.

EROSION

THEORETICAL CONSIDERATIONS

Immediately prior to an avalanche, slope stability
is in a delicate balance between shear force and shear
strength in the underlying materials. In soil mechan-
ics, the ratio of these two forces is used to express a
factor of safety that estimates the danger of sudden
slope failure:

Safety Factor=
sum of shear forces on critical surface

 

shear strength along the surface
A calculated factor of safety slightly greater than 1
in some cases may mean the possibility of slow yield-
ing or creep, instead of a slope failure.

The mode of deformation can be planar or rota-
tional. Except for some pockets of deep soil, the most
common types in Nelson County was planar, involv-
ing a relatively thin layer of “loose” soils or products
of weathering over an inclined bedrock surface.
Where evidence of rotational deformation was found
on deep soils, it was in some cases evident that a
larger planar deformation had occurred immediately
downslope.

Table 3 summarizes the various factors contribut-
ing to instability of earth slopes. Of the factors con-a
tributing to high shear stress, the weight of the rain-
water is considered by the authors to be the most
important in Nelson County. Bank-cutting by
streams is discussed in the paragraphs below. The
shear strength of the mantle probably was lowered
mainly by changes in intergranular forces due to
pore water.

 

27
STREAM ACTION AT THE BASE OF THE HILLSLOPE

Streams reportedly can cause avalanching by un-
dercutting the hillside (Wenner, 1951; Scott and
Gravlee, 1968; Rice and others, 1969). The mantle
along the base of a slope does provide some support
for the material uphill from it, so a slope would be-
come less stable if the base of the hillside were
eroded.

What is the field evidence for or against erosion
of the base of the hillslope causing avalanching in
Nelson County? The evidence in favor is that a
stream channel trending approximately perpendicu-
lar to the direction of the avalanche had eroded its
banks for as much as 20 feet along the base of some
avalanche scars. However, it is possible that, instead
of bearing a cause-and-effect relation, channel ero-
sion and debris avalanches are both independent
products of the torrential rainstorm.

Against erosion at the base of the mountain trig-
gering avalanching is, first, the important fact that
many debris avalanches occurred on hillsides which
were not touched by stream floodwaters (fig. 14).
Many avalanches, in fact, travelled overland for hun-
dreds of feet (fig. 14) before moving into the stream
channel, as for example, in the Hat Creek basin and
along highway US. 29. Second, some of the ava-
lanches were over a thousand feet long and only
about 25—75 feet wide. It is unlikely that a few feet
of erosion along the bottom of the hillside could
trigger such long, narrow slides, unless the ava~
lanching progressed upslope bit by bit. Testimony

TABLE 3.—Factors contributing to instability of earth slopes

[From Varnes. 1958]

 

Factors that contribute to high shear stress

Factors that contribute to low shear strength

 

A. Removal of lateral support
1. Erosion—bank cutting by streams and rivers
2. Human agencies—cuts, canals, pits, and so forth

B. Surcharge
1. Natural agencies—weight of snow and ice and
rainwater
2. Human agencies—fills, buildings, and so forth
C. Transitory earth stresses—earthquakes

Regional tilting

E. Removal of underlying support
1. Subaerial weathering—solutioning by ground
water
2. Subterranean erosion—piping
3. Human agencies—mining
F. Lateral pressures
1. Water in vertical cracks
2. Freezing water in cracks
3. Swelling
4. Root wedging

A. Initial state
1. Composition—inherently weak materials
2. Texture—loose soils, metastable grain
structures
3. Gross structure—faults, jointing, bedding
planes, varving, and so forth
B. Changes due to weathering and other physico—
chemical reactions
1. Frost action and thermal expansion
2. Hydration of clay minerals
3. Drying and cracking
4. Leaching
C. Changes in intergranular forces due to pore water
1. Buoyancy in saturated state
2. Loss in capillary tension upon saturation
3. Seepage pressure of percolating ground
water
D. Changes in structure
1. Fissuring of preconsolidated clays due to
release of lateral restraint
2. Grain structure collapse upon disturbance

 

28 HURRICANE GAMILLE IN VIRGINIA, 1969

presented earlier, however, indicated that the whole
strip probably came down as a single event. These
considerations suggest that stream erosion (or un-
dercutting at the base of a hillside) probably was
not a major cause of the avalanching, though it
might locally have been a factor.

A second theory (Kuhaida, 1971) regarding
stream action is that avalanching can be induced by
vibrations in the bedrock as a result of bombardment
of the slope-base by stream-transported debris. This
process would apply more commonly to slopes on the
outside of meander bends, where bombardment
would be more direct. Most streams flow at right
angles to the hillside, so there is some question as to
the intensity, as well as the role, of any Vibrations
produced by the sediment moving in the stream.
Also, as mentioned, many hillsides on which ava-
lanches occurred were hundreds of feet away from
a stream. Thus, while bombardment of a slope base
could conceivably produce vibrations strong enough
to trigger an avalanche, this probably was not a
major factor in the 1969 flood.

The avalanches themselves seem to have produced
the strongest vibrations during the» storm. As men-
tioned above, people miles from the slide areas inter-
mittently felt tremors, occurring at the same time as
a loud rumble, which they later attributed to ava-
lanches (Simpson and Simpson, 1970, p. 9). How-
ever, if vibrations caused debris avalanches, the lat-
ter probably would have occurred in groups rather
than being irregularly spaced through time.

DEPRESSIONS 0R TROUGHS ON THE HILLSIDE

Downslope—trending depressions or grooves on a
hillside collect water, and because they become
saturated sooner than the rest of the slope, they are
likely places for avalanching. Field observations and
photographs confirmed that many debris avalanches
did indeed take place where indentations or incipient
channels already existed on the hillside. In addition,
cross sections of the scar and the adjacent unaffected
ground, drawn from the transit surveys, commonly
showed that the projected original soil surface over
the scar definitely occupied a lower strip (fig. 18).
Furthermore, bedrock exposed along some scars
showed a weathered strip down the middle of the
scar where the color and surface texture were no-
ticeably different from the adjacent freshly exposed
bedrock. This suggests that such strips had served
as small incipient hillslope channels for many years
before the storm. Finally, moss that was about 5 or
more years old was growing on some of the exposed
bedrock in the moist depression along the center of

 

a few scars. Moss likes moisture, and moisture tends
to collect in a depression or trough. (A study of the
growth rate of moss on newly-exposed rock could
help date previous debris avalanches.)

In general, 85 percent or more of the debris ava-
lanches seem to have occurred along a previously
existing depression in the hillside.

In their study of a neighboring Appalachian re-
gion, Hack and Goodlett (1960, p. 44) observed that
“most of the chutes (scars) occupy former depres-
sions or groove-like areas, and the impression is in-
escapable that the chutes are indeed incipient hollows
or channelways that were partly obliterated during
the passage of time by falling blocks and mass move-
ment. They are, at rare intervals of time, flushed out
and deepened by heavy runoff and the avalanching of
debris.” Thus Hack and Goodlett felt that the hill-
side depressions where avalanches tend to occur are
themselves the scars of former avalanches or of simi-
lar rapid erosional processes. They further mention
(p. 56) that the avalanches represent a headwater
extension of the drainage network, that is, an in-
crease in the drainage density. Figure 11 shows this
feature.

Swanston (1969) found that debris avalanches in
southeast Alaska in many cases occur along local
drainage concentrations down the hillside.

ORIENTATION OF HILLSIDE

The aspect or orientation of the hillside could de-
termine (1) the amount of sun the slope normally
receives, which in turn influences the amount and
type of vegetation, the initial (prestorm) moisture
content of the soil, and consequently the depth and
character of the soil profile; and (2) the angle of the
attack and therefore the amount of rain on the slope,
in View of the wind direction during the storm. For
example, Tricart (1960) in the French Alps, Pippan
(1969) in the Austrian Alps, Diseker and Richard-
son (1962) in Georgia (USA), and Rice, Corbett,
and Bailey (1969) in southern California all found
erosion or mass movement to be more common on
slopes of a certain aspect. The preferred aspect, how-
ever, was not necessarily consistent among these
studies. Flaccus (1958), on the other hand, concluded
that the frequency of debris avalanches he studied in
New Hampshire had no relation to the direction in
which the hillsides faced.

In this study the amount and type of vegetation
did not appear to vary significantly with different
hillslope orientation. Visual examination along scar
edges revealed no apparent differences in the soil
profiles on slopes of different aspects. The angle of

EROSION 29

raindrop impact for a given rainfall intensity had
little or no effect on sheet erosion because the ground
surface was protected by an umbrella of trees, as
well as by a mat of decaying leaves and low-growing
vegetation. The angle of impact could, however,
affect the amount of water striking the hillslope, in
that more rain strikes a given area as the angle of
rainfall becomes more normal to the hillside. Thus
the chief potential importance of hillslope orientation
probably was in regard to (a) prestorm moisture
content of the ground, as influenced by the sun, and
(b) the amount of water which the hillslope received
during the storm, as influenced by the wind. The in-
tensity and direction of winds blowing at ground
level can vary dramatically during severe thunder-
storms.

Counts were made of the number of scars occur-
ring on hillsides facing each of the eight major
compass directions (N., NW., W. and so forth). This
was done by walking along selected drainage chan-
nels and marking, on a topographic map (scale
1:24,000), the location and extent of each scar. The
orientation and average gradient (base to head of
scar) were subsequently measured from the map.
The amount of territory covered ranged from 9,000
to 16,000 feet of distance along the stream channel
for each of the eight categories of hillside aspect, and
many different stream channels were involved. (A
given channel or reach serves two hillslope orienta-
tions, simultaneously.) The results (table 4) were
expressed in terms of average number of scars per
1,000 feet of mountain stream channel (base of hill-
side), for each different category of approximately
constant hillside (scar) gradient and aspect. A few
scars for slopes less than 0.30 and more than 0.79
are not listed. Most of this work was done in the
headwaters of Ginseng Hollow, Polly Wright Cove
and Wills Cove. However, scars for some combina-
tions of aspect and gradient (mainly on slopes less

TABLE 4.—Deb'ris avalanche scars per 1,000 feet

[Figures refer to average number of scars per 1,000 ft of reach inspected
along stream channel or base of hillside, for a given hillside orienta-
tion. A given channel distance or reach serves two orientations simul-
taneously. A few scars for slopes 185 than 0.30 and more than 0.79 are
not included]

 

Without With respect to slope (ft per ft)

 

 

Aspect respect
0 to 0.30 0.40— 0.50— 0.60— 0.70<

hillside slope 0.39 0.49 0.59 0.69 0.79 Total
(1) (2) (3) (4) (5) (6) (7)
3.4 4.0 2.1 3.0 3.6 5.4 18.1
2.8 1.6 .6 4.6 2.8 (1) 9.6
2.4 2.0 .7 4.9 3.4 5.2 16 2
1.5 (1) .5 2.3 .7 (1) 3.5
1.1 1.4 2.9 .6 .6 (1) 5.5
1.8 .8 1.6 1.4 2.0 (1) 5.8
1.4 1.0 .3 .3 (1) (1) 1.6
1.0 0 .8 .9 1.4 1.0 4.1

 

 

1 No avalanche scar observed for this slope and aspect.

 

than 0.40 and greater than 0.70 ft per ft) were
sparse, and additional observations were made in
Fortunes Cove (eight scars) and the Davis Creek
basin (16 scars) to supplement some of the defi-
cient classes.

The data in table 4, while sufficiently representa-
tive for the following analysis, may be incomplete or
faulty in several ways. Although 186 scars were re-
corded, involving some 103,000 feet measured along
mountain stream channels, the number of scars for
any one aspect and slope category ranged from 0 to
13, averaging about 3. The total distance along the
main stream for any one aspect and slope category
ranged from 0 to 6,300 feet, averaging about 2,300
feet. In a few cases the amounts examined may not
be enough to give a true picture of the avalanche
frequency distribution. Also, not every combination
of aspect and gradient was present to any significant
extent in the study area. Furthermore, in some cases
the determination of zones of constant slope and
hillside aspect from the topographic map involved
some subjectivity. Finally, plotting and measuring
avalanche scars on the map entails some error. From
the slopes of the 12 scars measured in the field, the
maximum error in measuring average scar slopes
from the map is judged likely to be about :010 ft
per ft, but usually the error is less than 0.05 ft per
ft. In spite of these possible errors, the data should
be reliable enough to indicate general trends.

Column 1 of table 4 shows the scar frequency for
different compass orientations, without respect to
the steepness of the hillside. If steepness and scar
dimensions are not considered, then column 1 sug-
gests that hillslopes facing north, northeast, and east
experienced several times as many avalanches as
slopes facing most other directions. Columns 2—6
give the number of scars for each slope category and
aspect. Although the data are not as conclusive as
might be desired, slopes facing north, northeast, and
east still tend to have more scars, for approximately
constant hillside gradient. Hence with most other
factors virtually constant, the susceptibility of a
hillside to debris avalanches in the study area tended
to be associated with the aspect of the hillside. Slopes
facing north, northeast, and east suffered the great-
est number of avalanches, probably because the ab-
sence of direct sunshine left these slopes with a
greater pre-storm moisture content and (or) the
Wind drove a greater amount of rainfall onto these
slopes during the storm.

HILLSIDE GRADIENTS

Avalanching, soil slippage and soil erosion should
occur more readily on steeper hillslopes, as reported

30 HURRICANE C‘AMILLE IN VIRGINIA, 1969

by Rice, Corbett and Bailey (1969) and Zingg
(1940). This is because the force required to start a
particle moving down a slope decreases as the slope
steepens.

The horizontal lines of table 4 show the frequency
of avalanching with increasing gradient, for a con-
stant compass direction. On the basis of these data
alone, and contrary to what might be expected, one
cannot conclude that avalanching in Nelson County
occurred more often on steeper slopes. Some hillside
aspects (N., SW.) show this relation, but others
(SE., S., W.) definitely do not.

If it is assumed that the data in table 4 are sufl‘i-
ciently representative, steeper slopes, beyond a mini-
mum of about 0.30 ft per ft (below which very few
avalanches occurred), do not seem directly related
to greater frequency of avalanching, for this storm.
Unlikely as this seems, there may be some undetected
factor or combination of factors contributing to this
conclusion. One possibility is that the gradient at the
head of the scar may be the pertinent slope, rather
than the average gradient as measured from head to
base of scar. Another possibility is that the steeper
slopes, say greater than about 0.70 ft per ft, do not
occupy a large enough distance along the stream
channel or a large enough hillside area to give a
statistically meaningful frequency of avalanching.

LENGTH OF HILLSLOPE

Longer hillslopes understandably can provide
greater quantities of sediment than short slopes
(Zingg, 1940). In addition, longer hillsides may en-
hance the likelihood of avalanching because the
downhill movement of water produces more water
on and in the soil with distance downslope. Data on
observed scars and topographic map measurements
of hillslope length were used to determine if debris

 

avalanching was more common and more extensive
on longer hillslopes.

The fieldwork consisted of marking on the topo-
graphic map the locations of avalanche scars and
estimating their lengths by eye. Only scars having
north, northeast, and east aspects were considered
because these aspects suffered more avalanching
than others. Gradient was ignored, on the basis of
the tentative finding that avalanching occurred with
about equal frequency for all slope categories be-
tween 0.30 and 0.80 ft per ft.

Topographic-map analysis consisted of measuring
the horizontal length of the hillslope, from ridge
crest to stream channel, at each scar location, and
measuring the distance along the stream channel,
for each category of hillslope length. Columns 1 and
3 of table 5 show the categories of hillside length and
the total channel distance inspected for each cate-
gory. The distances in column 3 are converted to per—
centages in column 4. (Hillslope lengths less than
200 ft represented only 2 percent of the drainage
area and had essentially no scars.)

In table 5 the number of observed scars for each
category of hillslope length (col. 7) does not truly
indicate any influence of slope length because all
slope lengths were not equally present. For example,
28 avalanches occurred on hillsides 400—500 feet
long, while only seven scars were found on hillsides
longer than 1,000 feet; however, slopes 1,000 feet
long were scarce, relative to those in the 400—599-
foot class. The number and (or) length of observed
slides in each category of hillslope length therefore
should be compared to the percentage of valley dis-
tance along the mountain stream channel (col. 4)
and also to the relative amount of drainage area
(col. 5) for each category. Because we inspected
nearly all channels in which the sideslopes had north,
northeast, and east aspects, column 4 in table 5 is

TABLE 5.—Efi’ect of hillslope length and drainage area on frequency and amount of scarring

 

 

 

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
Percent
of total
sample
area Average
Category Midpoint- Area 0: represented Total Relative length
0 average Valley Percent sample '_ by each length number of scars
hillslope length of distance of total wategory of Number of all of scars per acre
length hillside inspected valley 43,560 hillslope of scars scars1 per acre = (8)/ (5)
(ft) (ft) (ft) distance (acres) length observed (ft) = (7)/(5) (ft)
200—399 ___________ 300 27,800 28 192 14.0 20 3,540 0.104 18.4
400—599 ___________ 500 29,900 30 344 25.1 28 8,560 .081 24.9
600—799 ___________ 700 23,700 23 381 27.7 19 7,850 .050 20.6
800—999 ___________ 900 12,400 12 256 18.7 14 7,430 .055 29.0
arooo ____________ 1200 7,200 7 199 14.5 7 4,960 .035 24.9
Total _________________ 101,000 100 1,372 100.0 88 32,340

 

1Length of individual scars estimated during field inspections and summed for each hillslope category.

 

EROSION 31

representative of the entire drainage area of the
basins studied. Drainage area, as used in table 5, is
the product of the mean hillslope length (col. 2) and
the valley distance for the particular category (col.
3), in units of acres. The percentage of the total
area represented by each category (col. 6) was then
determined from column 5.

The number of observed scars (col. 7) is roughly
proportional to the percentage distance along the
mountain stream channel (col. 4), for a given cate-
gory. Therefore the number of scars is essentially
independent of the length of hillside, that is, the
length of the hillside probably had little or no influ-
ence on the likelihood of avalanching.

In regard to the effect of drainage area on the fre-
quency and amount (length) of scars, column 9 in
table 5 lists the relative number of scars per acre and
column 10 gives the average total length of scars per
acre. Figure 19 shows how these factors vary with
hillslope length. The relationships in figure 19 can be
reduced to a straight line by using the square root
of the hillslope length, but this would not improve
their accuracy. (See Wischmeier and Smith, 1965, p.
9.) While hillslope length is not an important factor
in the number of slides reaching a unit length of
stream valley, it is an important factor in the num-
ber per unit of drainage area and in the total length
of scars per unit drainage area. As length of hill—
slope increased, the number of scars per acre de-
creased (fig. 19A) and the total length of scars per
acre increased (fig. 19B). For example, about 10
scars occurred per 100 acres on 300-foot slopes in
contrast to only about three avalanches per 100 acres
on 1,200-foot slopes (fig. 19A). On the other hand,
the total length of scarring was about 1,600 feet per
100 acres on 300-foot slopes and 2,800 feet per 100
acres on 1,200-foot slopes.

These general conclusions regarding slope length
can be more readily visualized in a drawing of two
hypothetical sections of hillslope (fig. 20). Both sec—
tions have the same drainage area, but section B is
2.5 times the slope length of A. The unit distance
along the stream channel in figure 20 is distance X Y.
The number of avalanche scars encountered in walk-
ing along this unit reach is the same for both sec-
tions (five for this example), so that hillslope length
is not a factor in the frequency of avalanching per
unit distance along the stream channel. However, on
the basis of unit drainage area, section A has 12
scars whereas B has only five scars. This shows how
more avalanches occurred on the short than on long
slopes, for a given drainage area (col. 9 of table 5
and fig. 19A). Lastly, summing separately the scar

 

 

0.12
l l

0.06 — _

0.04 -— ‘T

NUMBER OF SCARS PER ACRE

0.02 —— ‘—

 

 

 

 

30

20-—

 

10— 'T

AVERAGE LENGTH OF SCARS PER ACRE, IN FEET

 

 

 

0 u I

O 500 1000
HILLSLOPE LENGTH, IN FEET

1500

FIGURE 19,—Relation of hillslope length to number of scars
per acre and to average distance of scarring per acre,
for hillsides having north, northeast, and east aspects.

lengths in sections A and B shows that the scars in
B amount to a greater total length. Since the acreage
of A and B are equal, the average length or distance
of avalanching per acre is greater on long than on
short slopes (col. 10 of table 5; fig. 19B). The latter
conclusion actually holds for unit distance along the
stream channel, as well as for unit drainage area.

SOIL DEPTH

The influence of soil depth on avalanching could
not be determined. Most of the avalanches began in
soil depths of about three feet or less, although minor
soil slips were common near the bottoms of hillslopes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FIGURE 20.—T0p (plan) View of two hypothetical drainage
drainage area on frequency and length of avalanching.
is 2.5 times that of A. Though the length of scarring is

where the soil depth was unknown and where the
slip may have been triggered by undercutting.

Soil depth may affect avalanching, in that water
can filter downward for greater distances in deep
soil, whereas a shallow soil would quickly become
saturated. The potential for soil slippage increases
with increasing saturation, which causes a greater
bulk weight. Thus from this viewpoint, one might
expect more avalanching in shallower soils, other
factors being equal.

On the other hand, the shear force would be pro-
portional to the depth of the soil and water. Deeper
soils, which also could contain more water, therefore
would be subjected to a greater shear force. There
would also be more possibilities for planes of weak
shear strength with deep soils. These considerations
suggest that avalanching might occur more readily

 

on deep soils, if other factors are equal.

32 HURRICANE CAMILLE IN VIRGINIA, 1969
A B
’6‘ Slope length ‘91 K Slope length ‘1
Avalanche scars’
A Stream channel at base of hillslopes
—\__
D. W
.=9 x
E
W, F
C M m
2
2 .8
E E
.2 .c
'5 no
as .8
2 m
E % §
0 .2
W ‘U
3’.)
2
Avalanche scars To
5
Y
Unit distance XY along stream channel
a

areas, A and B, showing influence of hillslope length and
Areas of A and B are equal, but the hillslope length of B
greater on B, the number of scars is greater on A.

If the effect of greater shear over deeper soils is
important, deep-soil avalanches might tend to occur
on flatter slopes than those in which shallow-soil
avalanches occur. Such a depth effect could explain
why we found as many avalanches on relatively flat
slopes (0.30—0.39 ft/ft) as on steep slopes (0.70—
0.79 ft/ ft).

SUMMARY

The head of a debris avalanche tended to be at the
steepest point on the hillside, that is, at the junction
between the upper convex slope and the straight or
concave section. The only factors associated with
greater frequency of debris avalanching for this
storm were depressions on the hillside, aspect of
hillside, and length of hillside per unit drainage area.
More avalanches occurred on slopes facing north,
northeast, and east than on slopes facing other direc-

 

EROSION 33

tions. Some factors, such as soil depth and various
soil properties, may affect the likelihood of avalanch-
ing, but their importance could not be assessed.
Other variables (for example, average steepness of
hillslope within the range of 30—80 percent gradient)
did not appear to be related to the occurrence of an
avalanche. Hillslope length did not affect the number
of slides reaching a unit length of stream channel;
however, on a unit-drainage—area basis more scars
occurred on short than on long slopes, whereas the
length of scarring was less on short slopes than on
long hillslopes. All the above conclusions depend on
the uncertain assumption that the rainfall intensity,
although probably varying in time and area, did not
affect any of the possibly relevant factors.

EFFECT OF DEBRIS AVALANCHES ON STREAMFLOW

The sediment deposited by a debris avalanche or
landslide can temporarily block or severely impede
the flow along a stream channel. Famous examples of
this phenomenon are the 1925 slide on the Gros
Ventre River in Wyoming and the 1959 landslide
into the canyon of the Madison River near Yellow-
stone National Park. In Nelson County channel
blockage probably occurred just upstream from a
sharp bend in the headwaters of Ginseng Hollow
(Guy, 1971) . The evidence for channel blockage here
is the very big difference between the maximum
water discharge attributable to precipitation rate
alone and the much higher discharge which actually
flowed through the bend as measured by indirect
methods. The large discharge through the bend
partly reflects the release of a volume of water stored
upstream of the avalanche as it was sliding across
the channel and partly reflects the volume of the slide
material that was added to the stream discharge.

An estimate of the channel discharge which would
result from the maximum rate of rainfall was made
in the same manner described earlier in the report,
using the rational formula. With 25 inches per hour
as the maximum probable rainfall intensity, the
measured drainage area as 20 acres, and a coefficient
of 0.90, the maximum discharge in the channel at-
tributable to rainfall would be about 450 cfs.

An actual peak flow of about 8,000 cfs in the chan-
nel was determined from topographic field measure-
ment at section B—B’ (see fig. 21). Because these
measurements were obtained by hand level, stadia
rod and pacing, the results are not precise and are
only approximations. The required measurements at
section B—B’ were (1) the superelevation Ah, that is,
the vertical distance between the high-water marks
on the inside and outside of the bend, (2) the cross-

 

Normal channel

North Tributary boundary

High-water line

      
  
   
 
  
 
   

  

Site of peak flow
determination
in channel

é-

low 450
cubic feet

per second
\ \
Debris avalanche area\\P \
. High-water line \ \\
Peak outflow 8000 N \ _,
cubic feet per second T

O 100 FEET
l_l__l_|._l

FIGURE 21,—Sketch of debris avalanche zone, normal channel
boundaries and high—water lines left by peak flow, north-
east branch of Ginseng Hollow.

sectional flow area A, (3) the outside and inside
radii of the bend (r, and m, respectively), (4) the
average radius of curvature r, = (1', + 1',)/2 and
(5) the water-surface width W.

The approximate mean flow velocity V in the
bend can be computed from an equation trans—
formed from Chow (1959, p. 448):

Ahgn ‘4
V=( >
W

where g=acceleration due to gravity. Inserting the
measured values gives

<13.5><32.2><80

80

A different method of computing V is through the
use of Grashof’s theory as given by Schoklitsch
(1937, p. 151):

 

‘29
> =21 ft per sec.

V2 1',
Ah=2.30— log —
9 Ti
Rearranging' the equation and inserting the field
data yields

13.5)(322 V2

V= 120
2.30 xlog—

40

which differs by less than 5 percent from Chow’s
more approximate equation. The computed peak
discharge Q is then Q=AV~ (390) (20)~8,000 cfs.

=20 ft per sec

34

HURRICANE GAMILLE IN VIRGINIA, 1969

 

FIGURE 22.—Examples of eroded mountain channels. Upper photograph is channel about 100 yards
upstream from apex of Campbell fan. Lower photograph shows headwaters of a tributary in
Ginseng Hollow.

 

 

EROSION 35

An error analysis of this calculated 8,000 cfs
should consider the effects of the measuring tech-
niques used, nonsteady flow, irregular velocity dis—
tributions, irregularly shaped channel boundaries,
imperfect circular shape of the bend, the effect of
sediment and other debris in the flow, and the possi—
bility that some channel enlargement may have
occurred after the peak flow. Also, a tributaryfrom
the north entered the channel just upstream from
the bend (fig. 19) ; however, near the junction the
high-water marks on this north tributary were much
lower than those on the study reach; so the flow
from the north tributary probably was stored be-
hind the rushing water—sediment mixture and did
not contribute to the peak flow in the bend. The many
indeterminates, plus the imprecise basic data meas-
urements, could amount to an error of about $3,000
cfs in thecomputed maximum discharge. Neverthe-
less, the peak discharge definitely was many times
(about 18 times, as estimated here) the discharge
reasonably attributable to an assumed very high
rate of rainfall runoff. The most likely explanation
for the high flow rate is that the 57,000 cubic-foot
avalanche moved through the reach in only a few
seconds, together with water which the slide had
temporarily blocked in the stream channel.

This case exemplifies one way in which a debris
avalanche could cause serious damage to man and
structures, especially in a small drainage area. By
temporarily disrupting normal runoff, a hillside
avalanche in the headwaters can trigger a chain
of events culminating in a tremendous surge of
sediment-laden water traveling at a very high
velocity. The large difference in discharge between
a relatively steady flood flow, though it may be at
record heights, and a big surge of water and debris
can mean the difference between minor damage and
devastation.

STREAM CHANNELS

Mountain streams in Nelson County commonly
range from 1 to 10 feet wide. During the flood the
stream channels were enlarged by severe erosion
and the removal of trees and shrubs (fig. 22). The
exact extent of such erosion could not be precisely
determined, as the dimensions and location of the
channel before the flood in most reaches were un-
certain. However, estimates and in some cases meas-
urements were made of the amount of channel ero-
sion for headwater streams, as discussed under
“Sediment Yiel .”

Figure 23 shows a channel which formerly was

 

only a few inches deep and narrow enough for a man
to step over. The magnitude of stream erosion in this
photograph was not uncommon in the mountainous
parts of the study area.

In some upstream reaches of mountain channels
the bedrock on the side slopes restricted the bank
erosion. In other areas bank erosion was evident
where vegetation such as trees and crops still clung
by a few tenacious roots to alluvium along the edges

'of stream banks. Many stretches of old logging

roads in the mountains and of paved highways in the
downstream valleys were partly or completely
washed away (fig. 24). Farmers along Indian Creek
and near the mountain ravine upstream from the
Campbell alluvial fan testified that the new channels
are at least twice as wide as the preflood channels.

Two factors restricted the downcutting of stream
beds. On the steeper mountain channels the resistant
bedrock was exposed either prior to the flood or soon
after the flood started, due to the thin mantle. Down-
stream in the broader valleys the overall gradient
was much flatter, and this limited the amount of
downcutting which the stream could accomplish
while still maintaining a slope steep enough to sat-
isfy the hydraulic and sediment—transport require-
ments.

Farther downstream, severe scour commonly oc-

 

FIGURE 23.—-Channel carved by the flood in the yard of S.
K. Wills, at the head of Wills Cove. Before the flood this
channel was but a few inches deep and so narrow that a
man could easily step over it.

 

 

 

36 HURRICANE CAMIL‘LE IN VIRGINIA, 1969

 

”a

FIGURE 24.—Channel erosion along highways. (Upper photograph courtesy of Virginia Division of Min-
eral Resources; lower photograph courtesy of Virginia Department of Highways.)

 

 

EROSION 37

 

FIGURE 25.—Scour of stream banks under a railroad trestle—Tye River at Norwood, Va. James River
in background. Bridge completely washed out in foreground. Note also floodplain deposition. (Photo-
graph courtesy of Virginia Department of Highways.)

curred next to bridges and railway trestles (fig. 25) .
In some localities as much as 20 feet of the original
stream bank was eroded, on each side of the stream.
The many trees carried by the raging streams prob-
ably contributed to this. The trees caught on bridge
piers and collected into huge debris jams that blocked
parts of the normal stream channel. Blockage of
parts of the flow cross section could cause faster
velocities in the unobstructed sections, thus increas-
ing the stream’s erosive power. The jams also en-
couraged overbank flooding which in some cases
resulted in erosion of the surface of the floodplain.

W. N. Whitehead (Simpson and Simpson, 1970,
p. 150) happened to observe the process by which a
roadway was eroded next to a bridge on Route 151
at Tye River.

“The river was up and passing over the roadway. As it
cascaded down the east (downriver) side of the fill, it began
to erode this, and we watched it as it kept digging back, with
the road collapsing bit by bit. The water ate its way back,
from the downriver side, all the way through the fill. Once
it got back thin enough the whole thing broke, and the water

 

just charged through. Then the gap between the bridge and
the edge of the road started getting wider and wider. This
was occurring on each side of the bridge.”

After the water broke through, the gaps accommo-
dated some of the flow and the level dropped. At its
peak, the water had been “well over the bridge
railings.”

Another type of channel erosion in some down-
stream areas was the caving or slumping of freshly
deposited sediment into the stream, along the banks
(fig. 25). This erosion probably occurred as the
flood was receding and involved sediment laid down
earlier by the same flood. The amount of sediment
eroded by bank caving is difficult to estimate.

Channel erosion, then, was certainly quite severe
in some places; however, other channels apparently
underwent little or no erosion. Thus the amount of
channel erosion varied Widely, even within areas as
small as an acre.

Bank erosion frequently exposed old alluvial
deposits. Some of these are 30 feet thick or more,
with particles ranging from sand to boulders in

 

 

 

38 HURRICANE CAMILLE IN VIRGINIA, 1969

size. Stratification is sometimes evident, but in other downstream valleys. Both erosion and deposition
cases all particles are completely mixed in a vertical occurred, in about equal amounts, in the apex region
section. Occasionally some lenses of imbricated par— of alluvial fans.
ticles appear. These alluvial deposits probably re-
sulted from ancient floods. SEDIMEN T YIELD

Along any given reach, a stream could exhibit
deposition as well as erosion (fig. 26) , but on balance
more erosion occurred in the headlands, whereas The volume of sediment removed by a debris
deposition predominated in the flatter and wider avalanche could not be measured precisely, and all

VOLUME OF AVALANCHE EROSION

 

FIGURE 26.—Channels showing both erosion and deposition. A, South Fork of Rockfish River. B, Ginseng Hollow. Note men
for scale. C, Small tributary to Hat Creek.

 

EROSION 39

of the data presented here are based on field esti-
mates of the prestorm ground configurations.

Table 2 lists the estimated erosion volumes for the
12 scars measured in detail. The amount of sediment
removed from these typical scars ranged from about
18,000 cubic feet to 233,000 cubic feet. The average
of the 12 is 88,000 cubic feet. The 12 examples se-
lected do not include the largest and smallest scars
in the entire storm area.

Figure 27 shows both the amount of erosion and
the compass orientation for these 12 scars. If the
orientations and volumes of the scars shown in
figure 27 are representative of the entire drainage
areas, the diagram strengthens the earlier con-
clusion that hillsides facing north through east were
most prone to sliding, not only in frequency of ava-
lanches but also in total amount eroded.

Field inspection was made of all of the upper part
of the Wills Cove drainage area (shown in figure 4),
all of Ginseng Hollow, and about 86 percent of
the Polly Wright drainage area. Visual estimates
were made of the length, average width and average
depth of each scar encountered. Column 2 of table 6
lists the total estimated amounts of avalanche ero-
sion for the various tributaries and subbasins. The
avalanches in Wills Cove produced about 2.60 mil—
lion cubic feet, those in Ginseng Hollow about 1.44
million cubic feet, and those in Polly Wright Cove
about 1.46 million cubic feet of sediment. The neigh-
boring Davis Creek, Fortunes Cove and adjacent
areas were also severely affected by avalanches; so
the total amount of sediment eroded by this process
was considerable.

Column 5 of the table shows that the volume of
avalanche erosion per square mile ranged from about
1.5 to 2.1 million cubic feet, with the greatest
amounts originating in Ginseng Hollow.

A very crude relation exists (fig. 28) between
the average slope of the ground surface, as deter-
mined from the the topographic maps (table 1),
and the volume of sediment eroded in debris ava-
lanches. The scatter prevents the determination of
a reliable regression curve, but the trend is from no
erosion at 32—35 percent average slope to 3 or 4
million cubic feet per square mile at 50 percent
average slope.

SEDIMENT YIELD FROM STREAM CHANNELS

As a part of the detailed studies made in Wills
Cove, Ginseng Hollow and Polly Wright Cove, esti—
mates were made of the net volume of channel ero-
sion in many of the tributaries and subbasins. These
estimates were based on visual field inspection of the

 

 

Z

4

 

FIGURE 27.—-—Orientation and relative volume of the 12
avalanches that were measured in detail. Scale: 1
inch:100,000 cubic feet.

complete lengths of most tributaries and on the
results of 18 surveyed channel cross sections which
compared prestorm and poststorm profiles. About
21/2 years before the storm the U.S. Geological Sur-
vey had taken aerial photographs of the entire area
for topographic map purposes. Using a Kelsh stereo-
scopic plotting instrument with these photographs,
we measured on the photographs 18 prestorm chan-
nel cross sections at locations which, judging from
the aerial photographs, would be easiest to locate
in the field. We then went to the field with a transit
and level rod and measured the post-storm cross
section at these 18 sites.

Although the poststorm profiles could be measured
quite accurately, the final erosion estimates include
several possible errors. The 1967 photographs may
not exactly represent the condition of the channels
just before the 1969 flood, but any channel erosion

 

 

 

 

8
I l I I

z
2 EXPLANATION A
g 0 Polly Wright Cove

LU

__. .
E 5 6 _ A WIHS Cove #

» x Ginseng Hollow L
Z Lu 4
9 g; '
8 a
E w A
m K 4 —— ——
a E X
Z Li
:5. r: '
A

i o x x

— AAX
u. m 2 — A __
o 3 A
m 0 A A x
2 x 8‘ X x A
3 °x
° #FJ/Jrrggl’fi
>

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30 35 4O 45 50 55
AVERAGE SURFACE SLOPE, IN PERCENT

FIGURE 28.——Volume of avalanche erosion with respect to
average surface slope.

 

 

40 HURRICANE CAMILLE IN VIRGINIA, 1969

TABLE 6.-—E'stimated net sediment yields and storm average transport rates

Net yield per square mile Aver- Weight Storm-average
Net yield (103 ft") (10“ ft?) age of sediment-
Drainage basin \ denuda- sediment transport rate
Ava- Channel Total Ava- Channel Total tion eroded
lanche lanche (inches) (104 tons) (104 tons (103 lb
per day) per sec)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)

 

 

 

 

 

Falls tributary:
Subbasins 1

 

Wills Cove, upper part
West tributary 908 873 1,781 3 . . . 104 357
Middle tributary 379 403 782 2 . 46 158
7
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2 52 23 75 .6 2:0 :9 4 14 3.2
3 2 4 6 .07 .14 .2 .1 .3 1 0.2
4 1 75 76 .01 1.1 1.1 .5 5 17 4.0
5 0 68 68 0 1.5 1.5 .6 4 14 3.2
6 28 56 84 .9 1.9 2.8 1.2 5 17 4.0
7 1 —'1 0 .04 ~.04 0 0 0 0 0
8 136 106 242 2.6 2.0 4.6 2.0 14 47 11.1
9 65 108 173 1.4 2.3 3.7 1.6 10 34 7.9
10 32 48 81 1.0 1.5 2.5 1.1 14 3.2
11 32 131 163 1.2 4.9 6.1 2.6 10 34 7.9
12 50 86 136 2.1 3.6 5.7 2.5 8 27 6 3
13 65 20 85 .6 .18 .8 .3 5 17 4.0
14 98 120 218 1.6 2.0 3.6 1.5 13 45 10.3
15 98 9 107 3.1 .3 3.4 1.5 6 21 4.8
16 60 81 141 1.0 1.3 2.3 1.0 8 27 6.4
17 30 20 50 .5 .3 .8 .3 3 10 2.4
18 120 0 120 8.6 0 8.6 3.7 7 24 5.6
19 45 96 141 2.0 4.4 6 4 2.8 8 27 6.4
20 4 7 11 .7 1.2 1.9 .8 5 17 4.0
21 0 24 24 0 3.0 3.0 1.3 2 7 1.6
22 81 42 123 2.1 1.1 3.2 1.7 7 24 5.6
a.
Subtotal (1—22) _______ 1,316 1,282 2,598 ___ _-_ ___ -_ 155 531 124.1
REE
Noncontributing ______________ o 0 o ___ ___ --_ __ 0 ___ ___-
Main channel ________________ -_-_ 965 965 __- ___ ___ __ 60 206 48
E
Total, Falls tributary -_ 1,316 2,247 3,563 215 737 172.1
%
Average, Falls tributary- -_-_ -__- ___- 1.1 1.9 3.0 1.3
Total, Wills Cove _____ 2,603 3,523 6,126 365
Average, Wills Cove ___ ___- ___- -___ 1.7 2.2 3.9 1.4
Ginseng Hollow
Lower subbasin .................. 523 712 1,235 3 0 4.1 7 1 3.1 73 250 58
North tributary ............. 104 152 256 1 2 1.8 3 0 1.3 15 51 12
South tributary _____________ 616 526 1,142 5 4 5.6 11 0 4.7 67 230 53
Main above sta. 3400 ____________ 197 303 500 9 1.4 23 1.0 30 103 24
East bowl (noncontributing) _-__ 0 0 O 0 0 0 0 0 0 0
\fi
Total, Ginseng Hollow _____ 1,440 1,693 3,133 ___ ___ ___ _- 185 634 147
Average, Ginseng Hollow _-_ -___ ___- -___ 25 4.6 0
Polly Wright Cove
85 114 199 2.0 2.7 4.7 2.0 12 41 9
180 194 374 2.1 2.3 4.4 1.9 22 75 17
80 211 291 2.2 5.7 7.8 3.4 18 62 14
40 90 130 1.5 3.5 5.0 2.2 8 27 6
133 268 401 1.9 3.9 5.8 2.5 24 82 19
156 230 787 2.6 3.8 6.4 2.8 23 79 18
248 86 334 7.2 2.5 9.7 4.2 19 65 15
204 105 309 5.5 2.8 8.3 3.6 18 62 14
187 128 315 4.4 3.0 7.4 3.2 18 62 14
28 92 120 1.2 3.8 5.0 2.2 7 24 6
Total, subbasins 1—13 ______ 1,341 1,518 2,859 ___ _-_ __- __ 169 -__ -_-..
Lower ___________________________ 115 123 238 1 5 1 6 3.1 .9 14 48 11
Noncontributing __________________ 0 0 0 0 0 0 0
Total, Polly Wright Cove _-_ 1,456 1,641 3,097 _-_ ___ -__ -_ 183
Average, Polly Wright Cove__ ___- __-_ _-_.. 1.5 1.7 32 1.4

during this Zl/é-year period probably was minor.
The plotting-instrument technique, probably one of
the smallest sources of error, was at best accurate
to within about $1 foot in elevation. Horizontal dis
tances, measured from the plotted Kelsh elevation
points with an engineer’s scale, were accurate to

 

within 1 percent. The major problem was locating
in the field the specific site that had been measured
on the photographs. (The photographic cross sec-
tions had to be measured first because of the limited
choice of suitable locations identifiable from the
photographs.) Numerous abandoned logging roads

 

 

DEPOSITIONAL FEATURES 41

along the ravines helped pinpoint the selected sites,
but several of the sections were difficult to locate in
the field because some of the roads, old cabins, and
other landmarks noted on the photographs were
washed away during the flood. The various sources
of error could amount to about 25 to 50 percent in
the amount of erosion attributed to any site. In addi-
tion, the visual estimates, the method used to meas-
ure poststorm profiles in most reaches, involve an
unknown amount of error.

While observations were being made of channel
erosion, attention was also given to any significant
channel deposition. Such deposition was notable and
persistent along some parts of the main channel in
the Falls tributary of Wills Cove and in Ginseng
Hollow. Deposition occurred mainly in reaches of
flatter gradient and less confined valley walls where
stream velocity probably decreased. The figures for
net sediment yield from channels (cols. 3 and 6,
table 6) represent the estimated erosion minus any
deposition.

Channel erosion, as near as can be determined
from these volume estimates, accounted for more
than half of the total sediment erosion (col. 3, table
6). The amounts of yield from individual tributaries
were as much as 5.7 million cubic feet per square
mile (col. 6, table 6). The average yield for the
three basins was 2.2, 2.5 and 1.7 million cubic feet
per square mile for Wills Cove, Ginseng Hollow and
Polly Wright Cove, respectively. The lower average
for Polly Wright reflects the effect of a rather large
part of the basin on which little or no erosion
occurred.

Net channel erosion apparently was slightly
greater than avalanche erosion, as far as volume of
erosion per square mile is concerned (cols. 5 and 6
of table 6) .

TOTAL SEDIMENT YIELD AND AVERAGE DENUDATION

If the amounts of yield from the separate sub-
basins or tributaries are added, the estimated total
yield from the headwaters of Wills Cove is 6.1 mil-
lion cu ft, from Ginseng Hollow about 3.1 million
cu ft, and from Polly Wright Cove about 3.1 mil-
lion cu ft. These volumes represent 3.9, 4.6 and 3.3
million cu ft per sq mi for the Wills (upper part),
Ginseng and Polly Wright basins, respectively.

If each of these amounts were imagined to be re-
moved uniformly from the entire area of the respec-
tive drainage basin, the denudation from Wills Cove
averaged about 1.4 inches, from Ginseng Hollow
about 2.0 inches, and from Polly Wright Cove about
1.4 inches. The average denudation for an individual

 

 

 

tributary or subbasin (col. 8 of table 6) ranged from
little or nothing to about 5.1 inches.

Judson and Ritter (1964) give estimates indicat-
ing that for central Virginia the average denudation
due to sediment removal by suspended load and bed-
‘load is in the range of about 0.6—1.4 inches per
thousand years. The 1.4—2.0 inches removed in one
storm for the drainage basins studied here show an
extent to which individual basins and rare events
can depart from the long-term average.

ESTIMATED SEDIMENT-TRANSPORT RATES

Although no measurements of sediment-transport
rate were made during the flood, a very rough idea
of the likely average rate at the mouths of some
tributaries can be obtained from the estimated total
sediment yield and the duration of the storm. As
transport rate customarily is expressed in weight
per unit time, the estimated volumes of sediment
yield must be transformed into weights. This trans-
formation (col. 9 of table 6) was made by using
110 lb per cu ft (pounds per cubic foot) for the
avalanche soils and 125 lb per cu ft for the coarser
channel material. Seven hours was the approximate
time during which the sediment moved in these
headwater areas. The storm-average sediment trans-
port rates (cols. 10 and 11 of table 6) ranged from
very little at the mouths of some subbasins to as
much as about 7,370,000 tons per day (172,000 lb
per sec) at the mouth of the Falls tributary in Wills
Cove. These estimated rates are for the full stream
width. Since the stream at the mouth of the Falls
tributary was about 100 feet wide during the storm,
the estimated rate of sediment movement at that
section may have averaged about 1,700 lb per sec
per ft of width for the 7-hour period. (By way of
comparison, laboratory flumes rarely exceed 1 or
2 lb per sec per ft width.) Such magnitudes reflect
the large quantities of rock and earth unleashed by
debris-avalanches and severe channel erosion. Be-
cause of this irregular rate of sediment introduc-
tion, the transport rate at any one place must have
varied considerably with time.

DEPOSITIONAL FEATURES

The floodwaters laid down extensive deposits of
sediment, often to the detriment of man and his
property. In some places the sediment came to rest
very close to its source, as at the foot of a hillslope
or on an alluvial fan at the mouth of a mountain
channel. At the other extreme, some of the small
particles eroded from the mountainsides undoubt-

 

 

 

42 HURRICANE CAMILLE IN VIRGINIA, 1969

edly moved all the way to Chesapeake Bay or the
Atlantic Ocean.

Five kinds of deposits were left after the flood:
(1) debris avalanche deposits at the base of hill-
slopes; (2) mountain-channel deposits, usually in
sediment patches scattered along the newly eroded
channel, but occasionally as large debris piles be-
hind a temporary dam; (3) alluvial fans where a
narrow mountain channel emerged into a relatively
broad intermontane valley; (4) deltas at the junc—
tion of a stream and major highway, where back-
water formed during the flood due to plugging of a
culvert; and (5) vertical accretion deposits on
floodplains.

Only rarely were debris avalanche deposits left
at the base of the hillside. Some of these particles
were probably too big to be moved by the floodwaters
(fig. 29). In other cases the slide probably did not
occur until after the peak flow, when the flow in
the ravine was no longer sufficient to carry away the
debris. Where no stream channel flowed past the
hillside, the momentum of the avalanche nearly
always transported most of the material away from
the base of the slope.

 

FIGURE 29.——Boulders which were dislodged in a
debris avalanche and which probably were too
large to be moved by the floodwaters (Ginseng
Hollow). Man on rock shows scale.

 

CHANNEL DEPOSITS

Some eroded material was left here and there
on the bed of the mountain channel after traveling a
distance ranging from a few feet to nearly a mile.
These channel deposits were either laid down by the
recession flow (since the peak flow probably could
have moved the particle sizes involved) or trapped
behind dams such as huge rocks or log jams (fig. 30) ,
in which case the deposition could have occurred at
various stages of the flood.

Deposits are sparse along the enlarged mountain
channels and generally absent near the heads of the
streams. As a stream approached its outlet into the
broad valley, the scattered deposits on some chan-
nels—those which became wider and flatter—became
more common, thicker (as much as 5 ft), and locally
continuous. Downstream reaches of mountain chan-
nels which did not become appreciably wider and
flatter usually had no sediment patches.

Particle sizes in channel deposits range from silt
to boulders 10 feet or more in intermediate diameter
(figs. 31 and 26). Some of these sediments were
measured to determine their size-frequency distribu-
tion, but this subject is discussed later in the report
because the deposits studied for grain-size distribu-
tion were continuous with downstream alluvial fan
and (or) floodplain deposits.

Most of the channel deposits were unsorted. Others

 

FIGURE 30.—-Upstream view of typical log jam in Ginseng
Hollow. Rocks of all sizes accumulate behind such dams.
Normal water flow, about 3 feet wide, can be seen in
foreground just to right of man.

 

 

3
4

DEPOSITIONAL FEATURES

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44 HURRICANE GAMILLE IN VIRGINIA, 1969

showed thin lenses or layers of well-sorted pebbles
or cobbles, often in an imbricated pattern. Such
well-sorted deposits in a few places formed minor
ridges along the edge of the channel, extending for
about 15*30 feet downstream parallel to the stream
direction. The ridges may be remnants of a deposit
that filled the channel bottom at some stage during
the flood, with the rocks from the central zone being
removed by recession flow. The ridges definitely
were formed after the peak flow because they were
on the channel bottom well within the maximum
cross-sectional flow area, and the peak flow would
have easily removed them.

Boulders as well as cobblestones accumulated in
imbricated patterns, as figure 32 shows. Such large
particles, although definitely moved by the flood,
probably were deposited during or soon after the
peak flow.

Debris piles behind dams in mountain channels
are as much as 200 ft long and extend all or most
of the way across the channel (up to 100 or even
200 ft). These wedge-shaped deposits are as much
as 20 ft deep at the downstream face. They show
little or no stratification or preferred orientation
of particles.

Deposits in the normal stream channel down-
stream from the mountains were under water at the
time of the investigation. These submerged sedi-
ments were not studied because they probably were
altered by the postflood streamflow to the extent that
they did not represent flood deposits. Valley sedi-
ments located on either side of the normal stream

 

FIGURE 32.—Downstream View of imbricated boulders left in
a stream channel in Edes Hollow.

 

are here treated as flood-plain deposits, except for
the alluvial fans and highway deltas.

SEDIMENT SAMPLING, COMPUTATION OF
SIZE-FREQUEN CY DISTRIBUTIONS

Except for the scattered debris piles in the moun-
tain channels the sediment deposits were inspected
for grain-size characteristics and other features.

For various reasons it was usually impossible to
define a sedimentation unit (a thickness of sediment
deposited under virtually constant physical condi-
tions). This fact, plus practical considerations, dic-
tated that in most cases only the surface material
was examined in regard to particle sizes.

The sediments laid down more than a mile or two
downstream from the alluvial fans or the head of the
main valley were mostly sandy. These fine-grained
deposits were sampled in a manner described below
and were analyzed by sieving.

In the upstream areas near the head of the valley
a typical flood deposit commonly included particles
ranging from fine silt to large boulders (fig. 31).
These deposits were measured by the “pebble-count”
method (Wolman, 1954). We stretched a measuring
tape perpendicular to the stream axis across the full
width of the deposit and recorded the intermediate
axis of the surface particle lying under every two-
foot tape increment. Grains smaller than about 10
mm were listed simply as “sand” for convenience,
and the intermediate axis of larger particles was
measured with a meter stick. The number of indi-
vidual particles counted ranged from about 30 to
more than 300, depending on the width of the de-
posit. At 5-foot intervals across the deposit a “sand”
sample was removed, except in those instances where
no fine material happened to occur at a given 5-foot
station. These samples represented the top inch or
two of sediment. All such sand samples for a given
section or reach were combined, and in the labora-
tory a single composite sieve analysis was made, re-
flecting an “average” size-frequency distribution for
this finer material. If the sand sample contained
about 10—15 percent less than 0.062 mm, a pipet
analysis of this part was also performed. In these
cases the results of the sieve and pipet analysis were
directly combined and recomputed as one distribu-
tion, on the assumption that the sieve diameter is
similar to the sedimentation diameter, within the
silt and clay range.

Ideally one would prefer a single size-frequency
distribution representing all the particle sizes pres-
ent in the deposit. Several factors had to be consid-
ered to achieve this goal.

 

DEPOSITIONAL FEATURES 45

Particles for a sieve and pipet analysis are usually
obtained with little thought as to possible size dif-
ferences between grains exposed on the top surface
of the deposit and those beneath the surface. The
sample usually contains both. The actual grain size
fortunately does not influence the quantity of each
size sampled, because the opening of the container
ordinarily is considerably larger than the grains.
The analysis yields percentages by weight, for each
size class. Particles in a pebble count or stone count,
however, represent particles lying only on the top
surface of the deposit and are selected with a definite
bias, namely in proportion to the exposed area of the
stone. Moreover, the recorded data give percentages
on a number basis rather than a weight basis. All of
these differences had to be resolved, at least as far
as possible, in order to combine the sieve and pebble-
count data into a single overall size-frequency dis-
tribution.

Kellerhals and Bray (1971) show that if the grain
sizes in a deposit are randomly dispersed the num-
ber-percentages for surface grains are equal to the
weight-percentages of a three-dimensional sample of
the deposit, on the assumption that all particles have
the same specific gravity. This means that for the
sediments analyzed here no conversion factor was
needed to transfer pebble—count (number) percent-
ages to sieve (weight) percentages. On this basis we
directly combined the pebble-count and sieve-analysis
percentages into one continuous frequency distribu-
tion, performing in the process an adjustment for
the relative proportions of large (pebble-counted)
stones and finer (sieved) particles.

The resulting frequency-distribution is a weight-
percent distribution representing all particles within
the three-dimensional body of the deposit. This dis-
tribution, incidentally, is approximately the same as
the percent of surface area each size class covers on
the top of the deposit. It is not a weight percentage
distribution of surface grains, that is, not the per-
centages that would result if all grains visible from
a top view were plucked from the surface and
weighed.

The assumptions involved are (a) homogenous
dispersal of all grain sizes throughout the body of
the deposit and (b) constant particle shape, specific
gravity, orientation and packing. Naturally these as-
sumptions are never completely true. Small grains
are often less abundant on the surface, as they tend
to hide in the voids or be winnowed away; however,
we believe we sampled most or all of the pertinent
flood sediments before any postflood erosion signifi-
cantly altered the surface of the deposits.

 

A simple example will show the computing proce-
dure. At a sampling site (cross section over the sur-
face) on an alluvial fan 59 entries were recorded in
a rock count: 14 large stones and 45 particles of
“sand.” Column 3 of table 7 shows the percentages
by number for the large stones, and column 4 lists
the percentages on a weight basis for the sieved
grains. Directly combining these two distributions
would imply that each of the two groups occupies 50
percent of the surface area of the deposits. However,
the stone count showed 14 tallies in the large-stone
range and 45 recordings of “sand.” Large stones, in
other words, covered only 1%9 of the surface area
of the deposit. The percentage in each size class for
large stones was therefore multiplied by 1%,, or
0.237, and the percentage in each size class of the
sieve analysis was adjusted by a factor of 4%,, or
0.763 (col. 5). This step produced a single weight-
frequency distribution for the entire deposit at the
sampling site, and the usual cumulative size-fre-
quency curve could then be drawn (fig. 33).

The sampling at each pebble-count site also in-
cluded a measurement of the intermediate axis of all
of the largest stones within about 10 feet upstream
and downstream of the tape section. The theory was
that these boulders would be proportional to the
stream competence, that is, to the stream’s ability to
transport sediment. They would represent a limiting
particle size showing what range of sizes the flow

TABLE 7,—Computational procedure of combining a sieve
analysis with a pebble count

Bryant fan, station 1,800. Adjustment factors:
0763 for

[Location of sample:
14/59 = 0.237 for large (pebble-counted) stones, 45/59 =
fine (sieved) particles]

 

(1) (2) (3) (4) (5) (6)
Cumula-
tive
percent
finer
than
upper
SIZE
limit

Percent
Percentages within by
subgroups weight,
entire
range
pipet of
analysis sizes

 

Number sieve<
Size class of

(mm) stones

large
stones

 

4,096-2,048
2,048—1,024 _-- -__ _-
1.024—512

  
   

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46 HURRICANE GAMILLE IN VIRGINIA, 1969

PERCENTAGE OF PARTICLES FINER THAN INDICATED SIZE

 

 

 

 

 

 

' 10 100

1000

PARTICLE DIAMETER, IN MILLIMETERS

FIGURE 33,—Typical particle size-frequency distribution, based on

percent by Weight, of a deposit that has a wide

range of particle sizes (Bryant fan, station 1800).

could and could not carry, in the region of the sam-
pling site (on the assumption that all sizes were
available for transport). Further reflection, how-
ever, suggests that the theory of competence is more
complicated than might seem at first glance. First,
the rate at which sediment entered the channel prob-
ably was unsteady, responding in part to the occur-
rence of debris avalanches on the hillsides upstream.
There is in fact no way of knowing (1) whether the
total volume or'weight rate of sediment introduction
was steady (it probably was not) or (2) which sizes
of rocks entered the channel at a given stage during
the flood. Besides these uncertainties regarding the
sediment introduction, there are several aspects of
the water discharge which could affect the stream’s
ability to transport sediment. The amount of water
entering the channel, for example, varied with time
in some unknown way because of the uneven distri-
bution of rainfall intensity throughout the storm.
Was the water discharge highest at the time the
largest stone arrived at the head of the study reach?
And did the discharge increase downstreamward, as
is common, thus increasing the stream competence
with distance? Against such a downstream increase

 

 

in competence would be the flatter channel or flood-
plain gradient with distance, which would reduce
the stream competence. In addition, the channel con-
figuration varied with distance, at some places caus-
ing the flow to become narrow and deep and at other
places wide and shallow. Such changes in flow cross
section can affect the sediment transport. “Stream
competence,” then, actually involves a number of
different factors, all of which might be important in
determining the stream’s ability to move the stones
delivered to it. The largest stones finally deposited
at a given section could have entered the channel at
different times and could have been deposited and
shifted a number of times during the flood. Thus the
final areal distribution of large stones represents the
combined effects of ( 1) some unknown rate of sedi-
ment introduction for each particle size throughout
the flood and (2) varying degrees of stream compe-
tence at different times and locations.

In most cases it was possible to tell whether a
given boulder had been transported and deposited
by this particular flood. However, as a safety factor
against any possible misinterpretation and freak
stone occurrence, the data on the following pages

DEPOSITIONAL FEATURES 47

represent the average size of the five largest stones
at each site, within 10 feet of either side of the cross
section line.

DEFINITIONS OF SIZE-DISTRIBUTION
CHARACTERISTICS

Cumulative particle size-frequency curves were
plotted on semilog paper as in figure 33, with per-
cent finer than a given grain size on the ordinate
(arithmetic scale). The following simple measures,
easily and quickly obtained graphically, were
adopted to describe the curves and are used in the
subsequent discussion.

The average particle size dm, was estimated by
averaging the grain sizes corresponding to the 10th,
50th, and 90th percentiles of the distribution (dm,
d50 and dgo, respectively). Since grain size is plotted
on a log scale, dm, is the antilog of the quantity (log
d10+10g d50+10g 90) /3-

The range, spread or sorting of particle sizes (8,)
is reflected by the percentile range dgo—dm. Because
of the log scale for grain sizes, this range is log
dgo—log dm, or log (dgo/dm). The (190 and d10 values
were selected because they cover the widest possible
definable range common to all curves. This measure
includes most of the distribution and is not affected
by the actual sizes involved. So=0 means “perfect
sorting” in the range between dgo and (110, that is, all
particles in this range have the same size. In such
case d90=d1o, the quotient is 1.0 and the log or sort-
ing is zero. So values of 1.0, 2.0, 3.0, and so on mean
that the percentile range deg—d10 covers one, two and
three log cycles of grain size, respectively.

The measure of asymmetry of the distribution or
skewness sis is (log d10+log d90—2 log d50)/(log
dgo—log d1o)- This is similar to the relative skewness
listed in Croxton and Cowden (1939, p. 254) but
deals with a distribution of the logarithms of par-
ticle diameters. Possible values of sk fall within
:10, and in a symmetrical distribution sk=0. A dis-
tribution having a preponderance of small grains
has a positive value of sk, whereas negative values
indicate a preponderance of large particles.

The average size (geometric mean) of the five
largest stones (d1,)is the antilog of (sum of logs of
intermediate diameters, divided by five). The geo—
metric mean, rather than the arithmetic mean, is
used because particle sizes customarily are treated on
a logarithmic scale.

ALLUVIAL FANS

Upon escaping the confinement of the rather nar-
row mountain channels, several of the swollen

 

streams deposited a large amount of sediment in the
form of alluvial fans (figs. 34 and 35). Such alluvial
fans or cones of debris seem to be common deposi-
tional features of floods in hilly areas (Eisenlohr,
1952; Jahns, 1947; Chawner, 1935). Fans actually
did not form on many streams, as the ground con-
figuration often did not favor the formation of fans.
For example, the mountain channel may have wid-
ened considerably before reaching the broad valley,
so that no sudden spreading out of the flow occurred.
In other cases the channel leaving the mountains was
deep enough to contain much of the flow for some
distance beyond the mountain front, so that only
typical flood—plain deposition resulted. Some drain-
age basins had very few debris avalanches in the
headwaters, so the streams in those basins carried
relatively little sediment.

Some of the more notable alluvial fans were
formed at the home of R. L. Bryant at the mouth of
the Ginseng Hollow (fig. 35), at the home of W. A.
Campbell near Shaeffer Hollow, at the home of S. K.
Wills at the head of Wills Cove, and at a downstream
site on Cub Creek (fig. 34). Fans ranged in length
from a few feet to nearly 0.4 mile. For example, the
Bryant fan was about 2,000 feet long, the Campbell
fan about 1,830 feet and the Wills partial fan about
850 feet. (Another stream eroded the downstream
part of the Wills fan.)

The cascade of water, rock and rubble that formed
an alluvial fan often caused considerable damage to
buildings and property, because fans usually occu-
pied areas of regular land use. At R. L. Bryant’s
home at the mouth of Ginseng Hollow, part of the
house was torn away, including the section in which
Mr. Bryant was sleeping at the time. (He rode 140
ft downstream on his mattress, along the edge of
the flow, sailed in through the open door of his barn
and spent the rest of the night sitting in the upper
part of his barn—a lucky survivor.)

Alluvial fan sediments were devoid of any recog-
nizable sedimentary features, such as bedding, lami-
nation, crossbedding, mud cracks, imbrication, or
other preferred orientation of particles. Except that
many rocks seemed to be lying on their long and
intermediate axes, the deposits looked as if they had
been shaken in a giant mixer and dumped.

Also dumped on fan surfaces were many trees and
branches, isolated or in piles. Isolated large trees
tended to be parallel to the flow direction, although
the roots could be pointing upstream or downstream.
(This tendency could be a useful aid in determining
flow direction in ancient sediments, if remains of

 

 

 

48 HURRICANE CAMILLE IN VIRGINIA, 1969

B

FIGURE 34,—Upstream

 

C

views of alluvial fans which formed where the stream escaped the confinement of the mountain

channel. A, Campbell fan. B, Wills partial fan (arrow points to man for scale). C, fan entering valley of Cub Creek

about 2 miles down from headwaters.

trees could be found.) Trees in log jams tended to
be oriented at oblique angles to the flow direction.
The flow depth over an alluvial fan should de-
crease proceeding downstream from the apex. There
was very little evidence to indicate the flow depth
over the Nelson County fans. From some high-water
marks on a hillside along the left-bank edge of the
Bryant fan, the peak flow depth about half way
down the fan was judged to be about 3—4 feet.

 

In all cases the stream at the fan apex, and occa-
sionally even further downstream on the fan, cut as
much as about 10 feet vertically into old alluvial
deposits and soil horizons (fig. 36). In fact the gen-
eral ground configurations reveal many old alluvial
fans where mountain channels enter the broad val-
leys in Nelson County. For example, all the fresh fan
deposits discussed here were formed on old alluvial
fans; so the 196%? storm was only one in a chain of

49

DEPOSITIONAL FEATURES

 

 

FIGURE 35.—Aerial ‘view of Bryant fan and lower part of Ginseng Hollow (Photograph courtesy of Virginia
Division of Mineral Resources).

similar major events in the geomorphic history of AMOUNT OF DEPOSITION

the area.

For a few weeks after the flood the creeks on the Sediment was transported to a fan over a period
fan tended to show a braided pattern, especially of time during which the discharge and sediment
toward the downstream part of the fan. transport rate undoubtedly varied considerably. The

 

 

 

50 HURRICANE CAMILLE IN VIRGINIA, 1969

 

FIGURE 36.—Eroded zone at apex of Campbell fan.

deposition or growth of the fan therefore proceeded
in stages. Due in part to the varying erosion and
deposition with time at the apex of the fan, the flow
arriving at the fan apex probably was diverted to
slightly different directions during the flood, and the
successive depositional stages probably manifested
themselves as “tongues” of deposit which varied in
areal location on the fan. As a result, the fan thick-
ness varies from one spot to another.

We analyzed amounts of deposition on the Bryant
and Campbell fans by setting up stations down the
fan centerline. At a number of these stations the
cross-sectional area of the deposit, in a plane normal
to the fan centerline (that is, roughly normal to the
flow direction) Was determined by stretching a meas-
uring tape over the full width of the fan and record-
ing the depth of fill along this cross section. The
depth varied from place to place, but usually it did
not exceed 1—2 feet. Depth was determined on the
basis of exposure of the original surface at some
points or by digging through the deposit. Along any
given cross section it was possible to define incre—
ments over which the depth of fill was approximately
constant, and the many subareas were summed to
get the total cross-sectional area of deposition, for
each downstream station.

The sediment deposited on a fan should depend in
part on the water discharge and fan slope. However,
the problems of which type discharge (for example,
storm-average or various instantaneous rates) and

 

 

 

slope (local slope or average slope from fan apex to
top) determine or indicate the final amount and dis-
tribution of the fan deposit are unresolved. These in
fact would be interesting subjects for future re-
search. As estimated earlier, the storm-average wa-
ter discharge at the apex of the Bryant fan was
roughly ,1,050 cfs. For the apex of the Campbell fan
the rational formula yields an estimate of only 134
cfs, owing to the much smaller drainage area (0.08
sq mi).’Average fan slopes (fig. 9) were 0.045 ft
per ft and 0.080 ft per ft for the Bryant and Camp-
bell fans, respectively. The product of discharge
times slope, roughly indicative of stream power, is
thus more than about four times greater for the
Bryant fan than for the Campbell fan. However,
aside from the fact that the storm—average discharge
and overall fan slope may not be the factors most
closely related to the volume of the deposit, the
sporadic nature of the amount and rate of sediment
supply to the two fans makes comparisons difficult.

Figure 37 shows how the cross-sectional area of
deposition varied with distance down two fans. The
actfial horizontal distance has been converted to pro-
portional distance from apex to downstream tip of
fan, in order to compare the two fans.

The apex or upstream region of an alluvial fan
typically showed both erosion and deposition. On
balance either process could predominate, depending
on the width of the upstream mountain channel rela-
tive to the width of the fan apex. At the Bryant
home the channel upstream was not very constricted
(fig. 35), and some deposition occurred before the
stream left the mountain channel. Consequently
deposition predominated over erosion around the fan
apex. The mountain channel upstream from the

 
 
 
 
 
 
  

350 fimr E
300 f' — ' “X -
E / \ Campbell
< 33 \ fan
32 m 250
< D:
f: 3‘ \\
2 g 200
9 z \
'— —
‘53) ,_- 150 X
”3 8
V) n.
8 Lu 100
U G
LI.
0 50 .
0 -. ,LALAJ_.,L-AJ_JA7 Er -JAJ

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8—0.9 1.0
PROPORTIONAL DISTANCE FROM APEX
TO DOWNSTREAM TIP OF FAN

FIGURE 37.——Amount of deposition with distance down fan,
for the Bryant and Campbell alluvial fans.

DEPOSITIONAL FEATURES 51

Campbell fan was deep and V-shaped (fig. 36), and
the fan had net erosion for about the upstream 0.1
of the length of the fan.

On the basis of figure 37, the Bryant and Campbell
fans each received about 300,000 cubic feet of sedi-
ment during the flood.

A striking similarity in the two curves of figure
37 is that the volume of deposition builds up abruptly
from very little at the apex to a peak amount and
then diminishes abruptly toward the downstream tip
of the fan. On the Bryant fan the peak deposition
occurs'about 0.3-0.4 of the way down the fan, while
on the Campbell fan the peak is about 0.5—0.7 of the
way along the fan.

CROSS-FAN PROFILES

Cross-fan profiles are surface profiles measured
normal to the long axis (centerline) of the fan, that
is, measured approximately parallel to the mountain
front. Such profiles normally would be convex owing
to greater deposition in the middle part (Bull, 1964,
p. 114).

Figure 38 contains cross-fan profiles for the Camp-
bell and Bryant fans. The Bryant profiles are convex
except for the first profile, which is 0.2 of the Way
down the fan. The original stream ran along the
south (left bank) edge of this fan; so the topography
is generally lower along that edge. In the down-
stream 0.4 of the fan length, the deposit splits into
two prongs (fig. 35). The apex of the Campbell fan,
as mentioned above, is mainly an erosional rather
than a depositional surface. Significant deposition
began around 0.17 of the way down the fan, but the
profile for that station generally reflects erosional
processes more than deposition. Cross profiles fur—
ther down the fan are only slightly convex. In the
downstream half of the fan, the main drainage is
along the left edge; therefore, as with the Bryant
fan, the surface is lower along that edge.

GRAIN—SIZE CHARACTERISTICS

On the Bryant, Campbell, and Wills fans particle-
size analyses were made across the full width of the
deposit, at various stations down the fan. Figure 39
is a graph of the various grain-size characteristics
as a function of distance down the fan. The grain—
size features at a given station down the fan center—
line represent the particles over the full width of the
fan, at that downstream station. Except for the
large-rock measurements, the sampling stations on
the Wills fan were too few in number (2) to warrant
plotting.

Average grain sizes range from about 2 to 6 mm.

 

Although one might expect the average grain size to
decrease with distance down the fan (Chawner,
1935) , such a trend is not very pronounced (fig. 39) .
The largest value of dav occurs not at the apex of the
fan but a short distance downstream—4.2 of the way
from the apex to the lower end of the Bryant fan and
about 0.4 to 0.5 of the way down on the Campbell
fan. Deposition did not begin as near the apex on
the Campbell as on the Bryant fan, as mentioned
above.

The geometric mean of the five largest stones
ranges from about 500 to 1,700 mm. On the Bryant
fan the size of the largest stones generally shows a
gradual decrease with distance of travel. Large
stones on the Campbell fan increase in size over the
upper 0.4 of the fan length, then gradually decrease
in size with further distance down the fan. The
trend in fact is quite similar to that of the average
grain size for the Campbell fan, but this is not the
case on the Bryant fan. Large stones on the Wills
partial fan show no particular tendency to increase
or decrease with distance, but this truncated fan
was less than half the length of the other two.
Pashinskiy (1964, p. 277) noted that on debris cones
bordering the Psezuapse River, near the Caucasian
Mountains, USSR, the coarsest material generally is
located in the middle part of the cone. Lustig (1965,
p. 145), on the other hand, found that large stones
on California fans were most abundant near the apex
region.

The largest stones on the Bryant fan are smaller
than those on the Campbell and Wills fans. This is
probably because the mountain ravines upstream
from the latter fans were confined, and practically no
channel deposition occurred. The Ginseng Hollow
channel upstream from the Bryant fan, on the other
hand, had a greater width/depth ratio and con-
tained debris jams and channel deposits (fig. 263,
30, 31A). These deposits included many of the large
boulders which otherwise would have been dumped
on the fan.

In general the alluvial fans are characterized by a
wide range of particle sizes—from clay or silt up to
boulders about 2 meters in intermediate diameter.
The sorting, in other words, is quite poor and was
probably affected by deposition of finer sediments at
the end of the flood. The dgo 1., range covers as much
as 3.7 log cycles of grain size along most of the
length of the fan (fig. 39) . Sorting on the Campbell
fan stays virtually constant at a value of about 3.4
along the entire study reach. On the Bryant fan the
upstream 0.6 of the fan length also has virtually
constant sorting, an S0 value of about 3.4 to 3.7, but

 

 

 

52 HURRICANE CAMILLE IN VIRGINIA, 1969

BRYANT

 

80

ELEVATION, IN FEET ABOVE ARBITRARY DATUM

CAMPBELL

 
  
 

DISTANCE FROM FAN CENTERLINE, IN FEET

 

ELEVATION, IN FEET ABOVE ARBITRARY DATUM

100 50 0 50
DISTANCE FROM FAN CENTERLINE, IN FEET

 

100 150 200

FIGURE 38.—Cross-fan profiles, looking down the fan, for the Bryant and Campbell alluvial fans. Num-
ber next to line of profile indicates proportional distance down fan, from apex to toe. Profiles re-
flect all pre—1969 deposition, in addition to Camille flood deposition.

the sorting improves with greater travel distance, so
that at 0.9 of the way down the fan the dgo—d10
ranges encompasses only about 2.3 log cycles of the
grain size—perhaps reflecting the fewer large stones.

All skewness values are positive, indicating a pre-

 

dominance of the smaller grain sizes. The weight of
the smaller grains in the fan, in other words, is
greater than that of the large boulders. With dis-
tance along the fan the skewness values change in-
versely with the average grain size (fig. 39). The

 

DEPOSITIONAL FEATURES 53
EXPLANATION

0 Bryant fan
x CampbelI fan
0 Wills fan

 

IN MILLIMETERS

.
avv

d

 

 

 

2000

 

1000

IN MILLIMETERS

dIs'

500

 

 

 

400

 

4.0

3.5

3.0

2.5

 

 

SORTING, IN LOG UNITS

 

 

+0.6

+0.4

+0.2

SKEWNESS, IN LOG UNITS

 

 

 

 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
PROPORTIONAL DISTANCE FROM APEX TO DOWNSTREAM TIP OF FAN

FIGURE 39.—Change in particle size-distribution characteristics with distance along alluvial
fans.

reason for this is that for a given range of grain weight than the large boulders, so that sk takes on
sizes a decrease in (in means the smaller grains are larger positive values. Conversely, given a distribu-
becoming relatively more abundant in terms of tion having a preponderance of smaller particles, an

54

increase in (1.. means that the larger stones are be-
coming more important is terms of weight. The dis-
tribution therefore tends to become more symmetri-
cal, that is, the sir, values tend toward zero. If the
large stones were to become more abundant than the
small grains, sic would be negative.

HIGHWAY DELTAS

Vast bodies of sediment accumulated in deposits
herein called highway deltas (figs. 40 and 41). Pas-
sageways under small bridges or highways became
clogged with vegetation and other debris, probably
early in the flood. In some cases the raging stream
scoured a new channel by eroding the highway next
to the bridge, but in other cases the highway became
an effective dam. A large body of water with a mean
flow velocity considerably slower than that of the
unaffected flow formed just upstream from the dam.
The stream filled sediment into the ponded water
until a sediment wedge or delta had build up to the
road level, after which time the water carried the
rest of its load across the highway and on to some

 

farther destination.
Where present, the highway deltas are within I

 

HURRICANE CAMILLE IN VIRGINIA, 1969

about 4 miles of the stream headwaters. Culverts or
bridges this close to the headwaters are rather small
and became plugged fairly easily. Farther down-
stream the streams are larger and flowed under
major bridges that washed out completely or that did
not become plugged with debris, so that deltas did
mot form.

‘ The dimensions of highway deltas are limited lat-
erally by the valley or floodplain walls and vertically
by the height of the roadway. Delta lengths often are
difficult to define because the deposit gradually
merges upstreamward with the regular floodplain
deposits. One of the smallest deltas is on route 151
about a mile south of Brent Gap. The deposit is about
200 feet wide at the highway, 150 feet long, 10 feet
deep at the thickest place on the downstream face,
and gradually thins laterally. The resident whose
house is only about 50 feet outside the edge of this
deposit testified that all of this sediment arrived
within about a 2-hour period. Other deltas (fig. 40)
are as much as about 700 feet wide and 10 to 12 feet
thick at the downstream face. Lengths are always

 

FIGURE 40.—Delta that formed where drainage from Edes
and Melton Hollows meets highway U.S. 29. A, Overall
upstream view looking up Melton Hollow. Edes Hollow
forks to the right at middle of picture. U.S. 29, a divided
four-lane highway, in foreground. Dotted linework indi-
cates boundary between grass and sand areas. (Photograph
by Ed Roseberry.) B, Closeup aerial view of downstream
part of delta. An inhabited house and two smaller build-
ings disappeared from this part of the delta during the
flood. House in center of photograph is nearly half buried
in sand. Construction crew at work unplugging culvert.
(Photograph courtesy of Virginia Department of High-
ways.) ‘

 

 

 

DEPOSITIONAL FEATURES 55

 

FIGURE 41.—Upstream View of delta deposited by Dillard
Creek at highway U.S. 29. Flow is from upper right to
lower left. One half of the four-lane highway is com-
pletely buried. (Photograph courtesy of Virginia Depart-
ment of Highways.)

greater than maximum widths and can be defined
conservatively as about 1,000 feet for the examples
shown in figures 40 and 41.

The large delta that formed Where Edes Hollow
meets highway U. S. 29 (fig. 40) has an estimated
cross-sectional area of 5,600 sq ft at the downstream
face (about 700 feet wide and an average of 8 feet
deep). If the volume is determined as approximately
V3 X area of downstream face >< length, the delta
contains an estimated 1.9 million cu ft of sediment.
The drainage basin upstream is about 1.3 sq mi, of
which about 0.9 sq mi experienced erosion that, from
aerial photographic and field inspection, seemed as
severe as that in Ginseng Hollow, Polly Wright Cove
and Wills Cove. In the latter three basins the severe
erosion contributed an average of about 4.9 million
cu ft of sediment per square mile. If the avalanche
and channel erosion in the Edes Hollow basin is
similar to that in these three basins, Edes Hollow
contributed about 4.4 million cu ft. The highway
delta therefore contained an estimated 39 percent of
the sediment eroded from the mountainous part of
the basin. Of the remainder, some was deposited up-
stream and some was carried downstream from the
delta.

Because the Edes Hollow delta is only about a mile
from the drainage divide, the flooding and deposition

 

 

in the delta probably did not last for more than 7 or
8 hours. A storm-average sediment-transport rate
for the region of the delta can be estimated from the
amount of sediment contained in the delta and the
period of accumulation. Actually the postflood delta
surface was filled to the lowest level of the highway
(fig. 403, upper left) and showed that some sediment
definitely moved across the highway. Consequently,
the volume of sediment left in the delta (about 1.9
million cu ft) divided by the period of deposition will
produce a minimum estimate of the average trans-
port rate. If 1.9 million cu ft accumulated in 8 hours,
the storm-average sediment-transport rate for the
apex of the delta was about 66 cfs, or 6,600 lb per
sec (285,000 tons per day). Field notes indicate that
the water surface in the vicinity of the apex of the
delta was about 200 feet wide. The approximate
storm-average sediment-transport rate at the apex of
the delta therefore was about 33 lbs per sec per foot
of channel width. Instantaneous rates may well have
been higher.

The estimated average transport rate in any case
represents just the delta region, rather than points
upstream from the delta. The transport rate into the
delta reflects the combined contributions of all up-
stream tributaries and debris avalanches, minus any
deposition occurring upstream from the delta.

The large delta that formed where Dillard Creek
meets highway U. S. 29 (fig. 41) has a cross-sec-
tional area at the highway of about 3,150 sq. ft.
(about 350 feet wide by an average of 9 feet deep).
It gradually merged with flood-plain deposits up-
stream. If 1,000 feet were considered the length, the
delta contained about 1 million cu ft of sediment.
The Dillard Creek basin has 3.3 sq. mi. of moun-
tainous area, 1.6 sq. mi. of which is in Wills Cove,
where the estimated yield was 4.9 million cu ft per
sq mi. We hiked extensively over the Fortunes Cove
area (the other part of the Dillard Creek basin) and
found it to be eroded to a similar degree as Wills
Cove. If the Wills Cove erosion yield of 4.9 million
cu ft per sq mi applies also to Fortunes Cove, the
Dillard Creek highway delta trapped an estimated
22 percent of the sediment yield. This figure is some-
what less than the 39 percent obtained for the Edes
Hollow delta because the Dillard delta is about 2
miles farther downstream from the sediment source,
and much of the eroded sediment was deposited on
flood plains upstream from the delta.

As the flood receded, the flow on the surface of
highway deltas began meandering and often assumed
a braided pattern (fig. 403, and 41). Toward the end
of the flood, the flow became very slow or even

 

 

 

56

stopped over much of the delta, as indicated by the
nature of the deposits, described below. When work-
men subsequently unplugged the culverts, the de-
posits in the central parts of the deltas were usually
eroded considerably as the stream worked its way
down to the culvert level.

From the relative elevations of the highway and
the floor of the delta, it appears that the water depth
in which these deltaic deposits were formed ranged
very approximately from 1 or 2 feet for the topmost
sediments to 10 or 12 feet for those deposited earli-
est. The 10—12-foot estimate is a maximum depth; in
all probability the water level rose as the sand lami-
nae accumulated, so that the water depth during
deposition was probably somewhat less than 10 feet.

A

FIGURE 42 Above and right—Sedimentary features of the
Dillard Creek highway delta. A, Sand laminae. Section
shown here is about 5 feet thick. Units on measuring tape
are feet and tenths of a foot. B, Sand laminae capped by
cross-bedded layer of fine sand, with mud layer on top
surface. This sequence probably reflects diminishing water
flow over the delta. Flow direction uncertain. C, Ripples
and mud cracks. ‘

 

HURRICANE GAMILLE IN VIRGINIA, 1969

SEDIMENTARY FEATURES

The sand deposits which make up nearly all of the
deltaic sediments have distinct layers, approximately
horizontal, ranging in thickness from a fraction of
an inch to about 1 inch (fig. 42A) . These laminae are
present from the base of the deposit to within a few
inches of the top surface, and exist over the entire
area of the delta. Single laminae cannot always be
traced very far laterally, and they are often nearly

 
 
 
  
   

 

 

 

DEPOSITIONAL FEATURES 57

inconspicuous in some areas and well defined in
others.

In addition to color differences, laminae in many
cases differ from one another in grain size. For ex-
ample, although most laminae are medium and fine
sand, some are noticeably coarse in texture. Lenses
as much as 6 inches thick, consisting of gravel or
pebbles, are present but are not very common. Such
lenses, where present, are usually at or near the
bottom of the deposit. Sometimes rocks up to 6 or 8
inches in diameter are found within a sand or gravel
matrix. These larger particles can occur singly, on
no common level, or they may occur in lenses which
extend varying distances—five to several hundred
feet in length.

The sand laminae in the delta on Dillard Creek at
U.S. 29 (fig. 41) are capped by a 3—6-inch layer of
fine sand that shows well developed small-scale cross-
bedding (fig. 423). These features are known to
form only during hydraulically tranquil (subcriti-
cal) flow and slow sediment-transport rates. They
probably are due to the braided streamflow that de-
veloped toward the end of the flood. Water depth at
the time of deposition probably was on the order of
one to three feet. Since the local flow direction in the
braided network probably varied considerably from
time to time, there is no assurance that a given ex-
posure is cut parallel to the flow direction. The cross-
stratification was not preserved in the center of the
delta, perhaps because such strata in this region
were eroded when the culvert was cleaned.

The top surface of most highway deltas was cov-
ered with a layer of mud (fig. 420) that ranged in
thickness from a fraction of an inch to about 1 foot.
This mud layer in most cases is missing along the
central part of the delta, so if originally present it
probably was swept away when the culvert was un-
clogged. The mud probably was deposited by slow-
moving or almost still waters, near the end of the
flood.

Ripples and mud cracks are common surface fea-
tures of highway deltas. Figure 420 shows mud
cracks in flat areas as well as superimposed on
ripple marks. The ripples may or may not be sym-
metrical, and it is quite difficult to determine from
them the current direction at the time of deposition.
Wavelengths of these ripple marks are commonly
about 0.25—0.5 foot, and heights are about 0.05 foot
or less.

In the days and weeks after the flood some settling
of deltaic deposits, especially the small grains, oc-
curred as water gradually escaped from the pore
spaces. The final thickness of such deposits therefore

 

 

 

 

is less, by some unknown factor, than the original
thickness.

VERTICAL VARIATIONS IN GRAIN-SIZE CHARACTERISTICS

Sediment samples at selected vertical intervals
were obtained at a total of four sites on the various
deltaic deposits. Two locations were on the delta
where Dillard Creek meets highway U. S. 29 (fig.
41); a third site was on the Edes Hollow—US. 29
highway delta (fig. 40); and the fourth was on a
small delta (about 200 ft wide by 150 ft long by a
maximum of 10 ft deep) in the headwaters of Hat
Creek on State route 151. Samplings at the latter site
and at one Dillard Creek site were on the front
(downstream) face of the delta. The second location
on the Dillard Creek delta was 200 feet upstream
from the front face, about 0.2 of the way from the
front face to the apex. On the Edes Hollow delta the
sampling was about 50 feet upstream from the front
face (about 0.05 of the distance from the front face
to the apex). The sites were approximately on the
center axis of the delta except for the spot 200 feet
upstream on the Dillard delta. This site was about
20 feet from the left-bank edge of the delta and was
chosen because of the good vertical exposure.

In all four vertical sections the deposited material
generally became finer as the flood progressed, that
is, the sediments became finer upward. Table 8 gives
the pertinent size-frequency characteristics. Depths
greater than 3.5 feet on State route 151 delta were
not sampled, but field notes emphasize that the lower
sediments were noticeably coarser than the overly-
ing ones. At the Edes Hollow site the lower half of
the deposit does not show a progressive coarsening
with depth, but the upper half definitely does. Thus

TABLE 8.—Vertical variations in grain-size characteristics in
highway deltas

 

 

Depth
below
Delta top
surface dav
(ft) (mm) 3.. sh
State route 151 _______________ 0.5—1.5 0.039 1.16 —0.11
2.5—3.5 .43 2.09 -.46
Edes Hollow __________________ .5 .22 .55 -.12
2.5 36 .84 .01
4.5 60 97 -.13
6.5 48 1.05 -.24
8.5 .40 1.01 —.32
Dillard Creek—front face ____ Top surface .09 .58 .02
.5 .11 .55 —.21
2.5 .18 .68 —.38
4.5 .19 79 -.42
6.5 .24 93 —.50
8.5 .30 88 —.45
Dillard Creek—200
ft upstream ______________ Top surface .01 1.47 —.58
.3 .07 59 —.06
1.0 .12 .71 —.17
2.0 .24 84 —-.32

 

 

58 HURRICANE CAMILLE IN VIRGINIA, 1969

during the depositional phase of the flood the coars-
est material dropped out earliest, with finer and finer
sizes being deposited as the flood progressed. The
rate at which the average grain size decreases varies
considerably from one sampling location to the next.

The average grain size seems to depend primarily
on how close the delta is to the sediment source
(mountain hillslopes). The State route 151 delta was
closest to the hills (about IA, mile) , and this site had
more gravels and pebbles than the other locations.
The Edes Hollow delta is about 1/2—11A), miles from
the sediment sources and had smaller average grain
sizes. Sediment in the Dillard delta probably had
traveled 34 miles and thus was the smallest of the
group. Changes in grain size with distance are dis-
cussed in more detail in the section on “Floodplain
Deposits.”

The first sediments deposited had the widest range
of grain sizes, and as deposition continued the sedi-
ments became better sorted (table 8). The only ex-
ception to this general trend was the top mud layer
at the site 200 feet upstream on the Dillard delta;
because of the clay sizes in this sample, the size curve
extends over a greater range. The mud layer at the
face of the delta was washed away before it could
be sampled, when highway crews unclogged the cul-
vert.

The actual values of sorting and the rate at which
the sediments became better sorted upward seem to
depend primarily on how close the delta is to the
sediment source (mountain hillslopes) . The State
route 151 delta was close to the hills (about IA, mile)
and consequently received a wider range of particle
sizes (more of the gravels and pebbles). The sedi—
ments in this delta are the most poorly sorted. Field
notes suggest that sorting improves upward most
rapidly at this site. At the Edes Hollow delta, which
is somewhat farther from its sediment source, sort-
ing is much better than at State route 151 and shows
less overall improvement upward. The sediments in
the Dillard delta had traveled the farthest, have the
best sorting, and improve upward at the slowest rate.

Skewness values are mostly negative, indicating a
preponderance of the coarser grains over the fines
(table 8). Sediments laid down first were the most
skewed, and the size distributions generally became
more and more symmetrical as the delta-building
progressed. There are no noticeable trends regard-
ing any effect of proximity of source material on
rate of change of skewness.

To summarize the trends in size-frequency distri-
bution with time: as the flood progressed, the sedi—
ments transported to and deposited in highway del-

 

 

tas became increasingly finer in size, better sorted,
and more symmetrical in weight-frequency distribu—
tion. Most of these trends also appeared, but often
were less pronounced, in the depth variations of
flood-plain deposits, as discussed below.

FLOOD-PLAIN DEPOSITS

Flood-plain deposits (figs. 43, 44) were laid down
on the gently sloping ground immediately adjacent
to the normal stream channel. As used in this report,
the term “flood-plain deposits” excludes particles left
in mountain channels and, where present, alluvial
fans. Thus flood-plain deposits begin at or just be-
low the mountain front at the head of the cove and
continue, in some places intermittently, for many
miles downstreamward.

The volume and grain sizes of flood-plain deposits
depend to some extent on local valley topography.
Where the valley narrows, the mean flow velocity
probably increased and less material was deposited.
Conversely, more sediment was deposited in wider
and flatter sections of a valley. In choosing the study
areas we tried to avoid either of these extremes.
Some reaches underwent both erosion and deposition.

Very little flood-plain deposition occurred in val-
leys which had few debris avalanches in the head-
waters.

Flood-plain deposits are as much as 5 feet thick
but generally are from about 0.2 foot to 3 feet. As
one would expect, at any downstream location they
tend to be thickest toward the center of the valley
and thinner near the edges. Flood—plain widths range
from a few feet to about 500 feet. The floods were
nearly everywhere many times wider than the origi-
nal channel.

SEDIMENTARY FEATURES

Flood-plain deposits within a mile or so of the
headwaters and avalanche areas have no discernible
sedimentary structures. Rather, they are quite simi-
lar to alluvial fan deposits in that all particle sizes,
ranging from silt to boulders, seem to have been
dumped all over the flood plain (figs. 43, 44A). Large
rocks and gravel in flood-plain deposits usually did
not accumulate in any distinctive way, such as in
bars or splays. '

Farther downstream the deposits consist mostly
of sand. From three sites studied in detail—one each
on Rucker Run, Dillard Creek and Muddy Creek—
and from other general observations, it appears that
such sandy flood-plain deposits in Nelson County
have several characteristics.

The laminations are a noticeable feature of nearly
all sandy flood-plain deposits (fig. 45). These lami-

 

 

DEPOSITIONAL FEATURES

FIGURE 43.———Upstream view of typical valley flood—plain deposits, headwaters of Davis Creek.
age to orchard. (Photograph courtesy of Virginia Division of Mineral Resources.)

 

Note dam-

 

 

60 HURRICANE GAMILLE IN VIRGINIA, 1969

nae are generally about 0.01 foot thick or less. Some-
times they appear to extend over the whole flood-
plain Width, but in other cases a single layer can be
traced only for about 5 feet before it pinches out
between other laminae. In addition to color differ-
ences, some laminae are distinguishable by a slightly
coarser texture. Also, some layers are different in
that they do not remain in the same plane as most of
the others; instead, these errant laminae may deviate
or dip by as much as 0.2 foot over a 2-foot horizontal
distance. They seem to be isolated, however, and are
rather rare.

The laminated sand often contains an occasional
1—2-inch pebble.

 

B

 

The exposure near the center of the valley on
Rucker Run :(fig. 45) has conspicuous pockets or
lenses of varying textures. The pockets usually in—
clude coarse sand and may have gravel and a few
pebbles. Normal laminae, on the other hand, seemed
to consist mainly of medium and fine sand. As figure
45 shows, the top and bottom surfaces of the pockets
are quite irregular and can rise or fall by as much as
a foot or so over about a 5-foot horizontal distance in
the approximate direction of flow.

No crossbedding was observed at any of the three
flood-plain sites studied in detail.

Ripple marks are common surface features of the
sandy flood-plain deposits and evidently formed as

0

FIGURE 44,—Common flood-plain deposits. A, Rucker Run about 0.3 mile downstream from head of valley. Circle around

man shows scale. B, Rucker Run about 0.75 mile upstream

from highway U.S. 29. C, Muddy and Davis Creeks about 0.2

mile south of Woods Mill, looking upstream (Photograph courtesy of Virginia Department of Highways.)

La

 

 

 

DEPOSITIONAL FEATURES

FIGURE 45.-—Sandy flood-plain deposits showing laminae, pockets,
(Rucker Run about 0.75 mi upstream from highway
and exposed thicknesses are about 2.5—3.0 feet.

lenses and coarse particles
US. 29). Tape is in feet and tenths,

 

 

61

 

 

 

62 HURRICANE CAMILLE IN VIRGINIA, 1969

the water receded. However, they tend to occur in
patches rather than covering the entire deposit, so
they may or may not be present at any given spot.
The ripple heights are rather low—about 0.01 or
0.02 foot. Wavelengths are only about 0.3 foot in
most cases, the range being from about 0.25 to 0.5
foot. Crests are oriented approximately normal to
the valley axis.

Mud cracks or shrinkage cracks also occur in
patches on the surfaces of flood plains. The thickness
of this mud layer can range from about 1 inch to a
foot or more. The greater thicknesses tend to be
found at longer distances downstream on the larger
streams, for example, at the confluence of two major
rivers or upstream from railroad embankments.
Such deposits probably suggest considerable back-
water during the flood.

The various sedimentary features listed above
seem to be similar to those 6f floods in other geo-
morphic regions (J ahns, 1947 ; Williams 1970, 1971;
McKee and others, 1967) .

VERTICAL CHANGES IN GRAIN SIIZE

Grain-size distributions conceivably could vary
with depth at a single location, lateral distance to-
ward the valley wall, and distance downstream. Size
variations in depth at a single location could not be
studied as far as large particles were concerned
because one large rock fragment in many cases occu—
pied the full thickness of the deposit. For finer grains
two flood-plain localities were examined in regard to
particle size-frequency characteristics with depth.
This of course reflects the sediment deposition with
time during the flood, at the sampling site. The 10-
calities, chosen mostly on the basis of accessibility
and undisturbed vertical sections, were on Rucker
Run, about 0.75 mile upstream from highway U. S.
29, and on Dillard Creek, about 1.3 miles downstream
from highway US 29. At the location of sampling,
the deposit on Rucker Run is about 2 feet thick, that
on Dillard Creek about 3 feet thick. Both locations
are about the same distance downstream (4—4.5 mi)
from the deposits at the heads of the valleys. A pos-
sibly important difference is that upstream from the
sampling site Dillard Creek had a large highway
delta, whereas Rucker Run had only a small or par-
tial delta. The Dillard Creek highway delta trapped
a very large amount of sediment, and this probably
occurred before deposition at the sampling site far-
ther downstream. Thus the grains at the Dillard
locality may represent material transported later in
the flood.

There is, unfortunately, no reliable way to deter-
mine the time of deposition relative to the peak

 

water flow, nor is there any way of knowing the
rates of sediment transport and deposition at vari-
ous stages of the flood.

Nearly all the flood-plain sediments investigated
for vertical changes in the grain size are sand-sized
or finer. At both the Dillard and Rucker sites the top
surface material was noticeably finer than that be-
low the surface (figs. 46, 47). These fine-grained top-
most sediments very likely were deposited in rela—
tively slow—moving water near the end of the flood.

Below the top surface the deposits at the Dillard
site are progressively coarser with depth. The aver-
age diameter at the base of the deposit was 0.37 mm,
and this average size gradually decreases to 0.11 mm
at the top surface. The sediments at this site also
became better sorted upward (fig. 46). The dgo—d10
range encompasses one log cycle of grain diameter
at the base of the deposit, and this range decreases
to about two-thirds of a log cycle for the sediments
deposited latest. The skewness shows no noticeable
trend. The bottom and top deposits have approxi-
mately symmetrical distributions. The middle layers
are also close to having symmetrical grain-size dis-
tribution but show a very slight tendency to include
a greater weight—percent of coarse grains than fine.

With the exception of the surface grains, the
Rucker Run sediments, in contrast to those on Dil-
lard, show no noticeable vertical trends. The average
grain size of the Rucker Run sediments fluctuates
between 0.15 and 0.45 mm throughout most of the
deposit and becomes finer only in the upper part.
Sorting stays about constant with depth. A possible
exception is the top surface, which is slightly more
poorly sorted than the sediments below. A more
poorly sorted surface material would represent the
opposite trend from the Dillard Creek site, where the
topmost material was better sorted than the under-
lying sediments. Skewness values at Rucker Run, as
with average size and sorting, did not vary widely
for the deposits below the surface. The skewness
range is about —0.13 to ——0.24, indicating a very
slight preponderance of coarser sizes. The surface
material, on the other hand, has a skewness of
+0.04, which means the size distribution is approxi-
mately symmetrical.

To sum up the main grain-size changes of these
flood-plain deposits with depth: at both the Dillard
and Rucker sites the top—surface (top inch or two)
grains are noticeably finer than the material below
the surface. The Dillard sediments become progres-
sively finer upward (that is, they become finer as
time progressed during the flood). Grain sizes at
the Rucker site, on the other hand, do not change

 

 

 

   
   
  

 

 

 

 

 

 

 

 

    
  
   
    

 

 

 

 

 

DEPOSITIONAL FEATURES 63
100 I I l I I
E1 90 — —
a) Top surface
g 80 _ 3 feet below top surface (base of deposit) _
<
g 1 foot below top surface
E 70 — -
z
E
,_ 60 _ 2 feet below top surface A‘
[I
l.|J
E
u‘ 50 — Grain-size characteristics —1
8
.J
9 Depth below dav k
E 40 — top surface (mm) so 5 —
0. (ft)
‘5 30 ~— _
Lu Top surface 0.11 0.64 —0.03
g 1 .15 .67 — .20
’2 20 — 2 .20 .81 — .24 —
“J 3 .37 1.03 — .04
o
E
m 10 — —
o l I I | I I I I I |
0.001 0.01 0.1 1.0 10.0 100
PARTICLE DIAMETER, IN MILLIMETERS
FIGURE 46.-—-Size-frequency characteristics of flood-plain sediments on Dillard Creek, about 4.5 miles downstream from
headwaters.
100 I I l I I
g 90 — _
U)
a Top surface 1.4 feet below top surface
E 80 — —
5 0'9 foot below top surface
E /
— 70 — 0.4 foot below top surface —
Z /
< 2.3 feet below top surface /\
I
|_ 60 H (base of deposit) 1.9 feet below top surface _
0:
DJ
E
"" 50 — _
8
DJ Grain-size characteristics
F‘ 40 — De th b I ~
0: p e ow d
E top surface (mars) 50 5k
u_ (ft)
0 30 ~ _
‘5 Top surface 0.088 0.98 0.04
E 0.4 .23 .75 -.15
z 20— .9 .45 .75 —.13 —
5 1.4 .17 .74 —.23
E 1.9 .22 .90 *.24
‘L 10 — 2.3 .15 .79 —.17 fl
0 l I l l l l l l | i
0.001 0.01 0.1 1.0 10 100

PARTICLE DIAMETER, lN MILLIMETERS

FIGURE 47,—Size-frequency characteristics of flood-plain sediments on Rucker Run, about 4 miles downstream from head-

waters.

64 HURRICANE CAMILLE IN VIRGINIA, 1969

significantly below the surface. Sorting differences
at the Dillard site indicate that as the flood pro-
gressed, the deposits became better sorted. At Rucker
Run, however, the sediments deposited last were a
bit more poorly sorted than those laid down earlier.
At both sites the distributions show a limited ten-
dency to be skewed (minor predominance of coarser
grains), except for the surface material which is
distributed approximately symmetrically, on a
weight basis.

The measured trends of grain-size distribution
with depth are probably a product of both the sizes
of particles offered to the floodwaters upstream from
the study sites and the transporting ability of the
stream. Thus, the deposition of finer and finer sizes
as the flood progressed (Dillard locality) could mean
that the larger particles were less frequently eroded
from the upstream hillsides and channels with time
and (or) the transporting ability of the flowing
water gradually diminished over the period of depo-
sition. Similarly, various possible combinations of
particle availability and stream power could account
for an absence of a distinct size-distribution trend
during deposition at the Rucker Run site.

LATERAL VARIATIONS IN GRAIN SIZE

For flood-plain deposits that include large ranges
in particle size the pebble-count data generally show
an apparently random distribution across the width
of the deposit. Sand-sized and finer grains in these
deposits tend either to form the matrix for the whole
deposit or to collect in scattered patches. Some of the
fringe areas along the outer edges of the deposits
tend to have more sand than larger stones. On the
other hand, stones up to 1 meter diameter occur in a
few places where no finer materials are deposited.

The sand deposit described above on Rucker Run,
about 0.75 mile upstream from highway U. S. 29,
was sampled to determine any lateral changes in
particle size of fine—grained deposits. The study area
was the right bank flood-plain deposit, which was
about 60 feet wide. Single laminae or strata were
either too difficult to trace laterally or too thin to
sample individually. Composite vertical samples rep-
resenting the entire thickness of the deposit (about
2 feet) were therefore taken at each of five sites—
15, 25, 35, 45, and 55 feet, respectively, away from
the present stream bank. The cumulative size-fre-
quency curves for these five samples very nearly
coincide. For a composite curve derived from all five
sieve analyses d,,=0.23 mm, S0=0.942 and 310:
—0.153. Comparing the individual curves to the av-
erage curve, the maximum deviations were i: 13 per-

 

cent for dav (i 0.03 mm), 1-8 percent for So and
t 34 percent for sk. The relatively minor differences
between curves could be due to actual differences in
the grain-size frequencies at the sampling sites, sam-
pling errors, or splitting of samples for sieve analy-
sis. Thus for the flood-plain deposits sampled there
was no significant lateral variation in grain-size
characteristics.

DOWNSTREAM CHANGES IN FLOOD-PLAIN DEPOSITS—

‘ GENERAL

Flo‘od-plain deposits of three streams—Polly
Wright, Rucker Run and Dillard Creek—were cho-
sen to study such features as changes in amounts of
deposition and in grain size with distance down-
stream. From one viewpoint the ideal stream for
studying such changes would have no tributaries at

‘all, and all of the deposited sediment would come

from a single upStream source. Unfortunately, Nel-
son County appears to have no such stream, particu-
larly since some deposited material undoubtedly
came from the bed and banks along the whole length
of the creeks.

The stream in Polly Wright Cove received sedi-
ment from three major tributaries near the middle
of the study reach. Rucker Run received sediment
from at least 13 debris avalanches or minor tribu-
taries within the upstream 8 percent of the total dis-
tance studied. Toward the downstream end, five
creeks join Rucker Run between the last two sam-
pling stations; however, of this group only Dillard
Creek contributed much sediment. Some minor
creeks also contributed sediment along other parts
of the Rucker study reach. Three tributaries joined
Dillard Creek, at about 0.2, 0.5 and 0.8 of the way,
respectively, along the 6.6-mile study zone.

The streams were less than ideal for sediment-
dispersion studies, also from the standpoint of time
of introduction of sediment. The exact times when
sediments emerged from the mountain ravine are
unknown. Sediment eroded from the banks and beds
of the mountain channels and higher order streams
probably was transported more or less continuously
during the flood, at a rate proportional to the stream
power. However, the large quantities dislodged by
the debris avalanches on the hillslopes entered the
channel at various times during the storm. Therefore
the resulting downstream deposits in small drainage
basins would reflect several stages and rates of sedi-
ment transport and deposition. Transport and depo-
sition would logically be more uniform with increase
in upstream drainage area.

The various types of source rocks on the hillsides
contain no distinctive and plentiful minerals which

 

DEPOSITIONAL FEATURES 65

would identify points of origin for particles in the
downstream deposits.

In spite of these possible disadvantages from the
viewpoint of ideal dispersion studies, the deposits
that remained after the flood subsided aré probably
typical of those left by other catastrophic ,floods in
similar environments. Lag deposits and material in
the stream channel prior to the flood were flushed
out or buried during the flood; so the sediments
sampled represent only material deposited by the
August 19—20 flow.

The upstream sampling stations were usually cho-
sen at approximately equal intervals of distance, al-
though sometimes the location was shifted slightly
to sample a deposit that seemed to be more
typical or that was not buried under piles of trees
and other debris. For at least the downstream half
of the flood-plain deposits investigated, the sampling
stations were selected on the basis of accessibility,
freedom from tributaries entering near the station,
and a subjective evaluation of how typical or repre-
sentative the deposits appeared to be. Some down-
stream reaches had little or no deposition, often due
to a local constriction in the channel.

The valley in Polly Wright Cove is only 0.8 mile
long. After emerging from Polly Wright Cove, the
stream merges with another sediment-bearing
stream (Muddy Creek). In reporting changes in
grain size with distance downstream, we will include
the mountain-channel deposits in Polly Wright Cove.
These deposits were continuous with the downstream
flood-plain deposits.

Within a week or two after the flood, the streams
had returned to their usual flow widths and depths,
these commonly being 1—20 feet wide and 0.1—0.6 foot
deep. These creek Widths were negligible or minor
compared with the widths of the flood deposits.
Nearly all the sampling was done on dry ground.

DOWNSTREAM CHANGES IN AMOUNT OF DEPOSITION
POLLY WRIGHT COVE

At 11 stations along Polly Wright Cove measure-
ments were made of the volume of the flood-plain
deposits, using the same techniques as on alluvial
fans. These data, expressed in volume of sediment
per unit (foot) of channel length, are shown in figure
48A. The downstream distance, x, was reckoned
from the first major deposits, excluding debris piles
and other scattered deposits in mountain ravines.
The volume of sediment decreases downstreamward,
although the scatter on the graph hinders determina-
tion of the precise relation. In an effort to reduce the
scatter, we combined the data for the 11 individual

 

A. Individual stations

 

 

 

 

 

 

1000
~ I I I :
I _ _
5 ‘ + _
z 500 —- —
LIJ
_l —- _
+
d _\ \ \ + -
E + \ \
< \+\
I — \ \ A
o \ \
”- + \ \ +
o + \ +\ \
}— \
O _. + \ _
o 100 _ \ _
I; __ _
I — + _
DJ
0. | —
p— 50
Lu
LIJ
LL.
9
m B. Averaged data
3 500
0 | I _‘
E _
:- » n
w
o
E _ 0 _
Lu
0
LL.
0 o
E 100 ~ —
3
_J
O
>
I I | l
0 1000 2000 3000 4000 5000

DISTANCE DOWNSTREAM FROM START OF DEPOSITS, IN FEET

FIGURE 48.—Volume of flood-plain deposition per foot of
channel length along Polly Wright Cove.

sections into four averages, consisting of the up-
stream three measuring stations, the second three,
the third two and the downstream three. With the
data combined into reaches about 1,000 feet long, the
scatter diminished considerably. Figure 483, a plot
of these results, shows that the volume of deposition
decreases exponentially with distance downstream.
According to the eye-drawn line, the volume of depo-
sition per foot of channel length at any downstream
site is equal to 370e—°’°°°25“, where e is the base of
natural logarithms. The deviations of data points
from the regression line range from +15 percent to
—12 percent.

The actual quantity deposited ranged from about
370 cu ft per ft at the upstream end to about 120
cu ft per ft at the downstream end of the 0.8 mile-
long deposit.

The total volume of sediment dumped in Polly
Wright Cove was about 0.97 million cu ft. An esti—
mated 3.1 million cu ft was eroded from the head-
waters (table 6). Sediment not accounted for in the
flood-plain deposits must have been transported com-
pletely out of the cove. Extrapolating the exponen-
tial equation just derived to a distance beyond the

66

cove is both risky and intriguing. If the equation
were applicable for as far as appreciable deposition
continued, the total amount deposited would be 370/
0.00025, or about 1.48 million cu ft, somewhat less
than the 3.1 million cu ft estimated to be eroded.
Nearly all of the 1.48 million cu ft, according to the
equation, would be deposited within three miles of
the upper end of the deposits. If the measurements
and the resulting equation for the 0.8-mile—long
study reach are accurate, either the equation should
not be extrapolated or the estimated 3.1 million cu
ft of erosion is too high.

Table 9 gives the volume of deposition by particle-
size categories and the size distribution by categor-
ies, for the four separate reaches along the 0.8-mile-
long cove. If the entire flood-plain deposit along the
length of the cove is considered, sand is by far the
most abundant size class. The cove received more
than twice as much sand‘ (449,000 cu ft) as any
other size group. The other outstanding feature is
the scarcity of silt and clay, this group contributing
only about 51,000 cu ft, or 5 percent of the deposi—
tion. The silt and clay, if eroded in substantial
amounts, could have been carried away as suspended
load. Most particles larger than sand, if eroded from
the headwater regions, probably would have come to
rest somewhere within the cove rather than moving
through the cove to some downstream site; the vol-
umes and percentages of these larger particles—
gravel, cobbles and boulders—dwindle noticeably
with distance along the cove, as table 9 shows. It
therefore appears that a much greater volume of
sand was eroded in the headwater regions, as com-
pared to larger particles.

In the reach farthest upstream, sand (31 percent
of the deposit at this site, or 90,000 cu ft) and boul—
ders (29 percent or 85,000 cu ft) are the most abun-
dant size classes. Boulders, if eroded from the head-
water regions in appreciable quantities, should be
abundant in this first reach because they would logi-
cally be deposited farther upstream than smaller
particles. In the next reach (about one-third of the
way along the cove’s flood-plain deposit) sand and
gravel are the most abundant groups, especially

HURRICANE CAMILLE IN VIRGINIA, 1969

sand. The volume and percentage of cobbles and
boulders are less than in the upstream reach, and
the amount of silt-clay is about the same. Sand be-
comes even more plentiful in the third reach and
amounts to 138,000 cu ft or 60 percent of the deposit.
The quantity and percentage of silt-clay are about
the same as in the two upstream reaches. Gravel is
still more plentiful than cobbles and boulders, but
these three categories, especially the latter two, are
scarcer than in the previous reach. Finally, in the
reach farthest downstream, sand comprises nearly
three-fourths (111,000 cu ft) of the total deposit.
Gravel is next in importance (18 percent), while silt-
clay, cobbles and boulders total only 10 percent
(16,000 cu ft) of the deposit.

In summary, the volumes and percentages of cob-
bles and boulders decrease steadily with distance
downstream and are practically negligible at the
end of the 0.8-mile study zone. Gravel everywhere
makes up about 16—25 percent of the sediment and
is more abudant about one-third of the way along
the cove than elsewhere. Sand consistently becomes
more important with distance, progressing from 31
percent to 72 percent of the deposit. Curiously, the
percentage of silt-clay remains virtually constant at
about 5 percent along the entire cove.

Later sections of this report examine other aspects
of grain-size trends with distance.

RUCKER RUN

Figure 49 shows how the volume of flood-plain
deposition varied with distance for the upstream
12.5 miles of Rucker Run. The somewhat erratic
nature of the deposit volume for the upper two or
three miles is due mainly to the addition of sediment
from small tributaries. The point labeled “partial
highway delta at U.S. 29” illustrates the amount of
sediment trapped by the highway. More sediment
probably would have accumulated here, that is, a
complete highway delta would have formed, if a
section of the highway had not washed out during
the flood. The volume of deposition at any given site

 

down to highway U.S. 29, about the first 4 miles, is

TABLE 9.—Volume and percentage of deposition by size classes with distance downstream in Polly Wright Cove

 

 

 

Volume

Proportional Length of deposi- Volume by size classes (1,000 fts) Percentages ‘in class

distance down- of tion in
stream to mid- reach reach Silt— Silt-

point of reach (ft) (1,000 ft3) clay Sand Gravel Gobble Boulder clay Sand Gravel Cobble Boulder
0.08 ___________________ 875 292 15 90 47 55 85 5 31 16 19 29
.32 ................... 1,233 288 14 110 72 40 52 5 38 25 14 18
.59 ___________________ 998 231 14 138 46 12 21 6 60 20 5 9
.89 ................... 1,254 155 8 111 28 5 3 5 72 18 3 2

 

4,360 966 51 449

193

 

 

DEPOSITIONAL FEATURES 67

1000

 

I I | I I |

500 I— —
/Partla| highway delta at US 29

X
/
K \X/x

._.
O
O

Confluence with Dillard Creek _

UI
O

FOOT 0F CHANNEL LENGTH
5
I
I

VOLUME OF DEPOSITION, IN CUBIC FEET PER
U1
I
I

 

 

I l | l I |
0 10 20 30 40 50 60 70
DISTANCE DOWNSTREAM FROM START OF DEPOSITS,

IN THOUSANDS OF FEET

i—I

 

FIGURE 49.——Changes in volume of flood-plain deposition
with distance downstream on Rucker Run.

in the approximate range of 150—300 cu ft per foot
of channel length.

Downstream from the partial trap at the highway
the amount of deposition dwindled rapidly. At the
confluence with Dillard Creek (approximately the
7-mile station) the volume of deposition was about
90 cu ft, and at 12.5 miles downstream from the
head of the cove the flood plain contained only 1 or
2 cu ft of sediment, a very thin layer.

The first 7 miles of the Rucker Run flood plain
received a total of about 7.8 million cu ft of sedi-
ment, according to figure 49.

Some of the silt and clay, and possibly sand too,
moved in suspension into the James River. Towns
and flood plains along the James, both upstream and
downstream from the junctions with tributaries
draining Nelson County, were covered with fine-
grained sediment to depths up to a foot. The source
of this material could be any place from the upper
reaches of avalanche scars in the headwaters to the
banks of the James River itself. Downstream from
Richmond the greatly increased concentration of
suspended load in the James River estuary reached
a maximum around Aug. 25, about 3—4 days after
the peak water discharge at Richmond (Maynard
Nichols, written commun, 1969).

One effect of the flood was to erode the mountain
hillslopes and aggrade the upstream parts of the
valleys. If rare catastrophic events produce most of
the erosion and deposition over a long period, the
results of this storm suggest a trend toward a pene-
plain, due to net hillside erosion and valley deposi-

 

tion. On the other hand, the storm may be a tempo-
rary deviation in a long-term trend which may in
time be established by more moderate erosional and
depositional processes.

Again, if this type of catastrophic event is domi-
nant, the Wills, Polly Wright and Freshwater Cove
flood plains, as well as certain others, are being con-
structed primarily by overbank deposition. They
would thus represent an exception to the mechanisms
which Wolman and Leopold (1957) proposed, Where-
by about 80—90 percent of a flood-plain thickness is
build by point-bar (lateral) accretion within a mi-
grating stream channel. In the present case the cru-
cial factor in determining the amount of overbank
deposition seems to be the quantity of sediment in-
troduced at the head of the valley. Where the moun-
tains underwent extensive debris avalanching, the
heads of the valleys received considerable overbank
deposition. This vertical accretion ranged from an
average of about 3 feet at the upstream ends of the
coves to 0.1 foot or less at a downstream distance of
1—8 miles. On the other hand, where few debris-
avalanches occurred in the mountains, as in the In-
dian Creek basin, the downstream-valley flood plains
received noticeably less sediment and may in fact
have undergone a net sediment loss due to lateral
erosion of the stream channel.

DOWNSTREAM CHANGES IN AVERAGE GRAIN SIZE

Most authors have found that average grain size
generally decreases downstreamward (Pettijohn,
1957), although exceptions have been reported
(McPherson and Rannie, 1969).

Figure 50 is a graph of the mean particle size d“
versus distance down-valley for Rucker Run, Polly
Polly Wright Cove and Dillard Creek. as before, at
is distance downstream from start of deposition. In
general, dav decreased with distance downstream. The
distribution of points on at least two of the three
plots is such that various lines can be fitted. For
example, either the solid or dashed lines can repre-
sent the relation for the Polly Wright Cove and
Dillard Creek sediments. The solid line for all three
streams suggests that given enough travel distance,
dav may become asymptotic toward some limiting
minimum value. The Rucker Run data are for a rela-
tively long study reach (12.5 mi) and tend to sup-
port this type of relation. The dashed lines for
Polly Wright Cove and Dillard Creek represent nega-
tive exponential functions, a type of relation rather
common in geomorphology and sedimentology.

The average particle size at the upper end of the
deposits was 1.6 mm for Rucker Run, 14.4 mm in

68 HURRICANE CAMILLE IN VIRGINIA, 1969

10.0

 

I I I I I I

CI RUCKER RUN

 

 

 

100.0

I +
10.0 1‘ +
+ \

\\ (013,214.46—
+<+~<+

\\
N-

+ \

 

POLLY WRIGHT COVE

0.0007”) _

1.0 —

 

_1 1 I I I
00

 

AVERAGE GRAIN SIZE (day), IN MILLIMETERS

1.0

 

  
   

~_
—~‘
~-‘
~~

01'- DILLARD CREEK ' -

l l I | I
0 4 8 12 16 20 24

DOWNSTREAM DISTANCE (x), IN THOUSANDS OF FEET

 

 

 

FIGURE 50.—Downstream changes in mean particle size
(dw) of flood-plain deposits.

Polly Wright Cove and 0.64 mm (extrapolated) for
Dillard Creek. This value depends on at least two
factors: the sizes of particles dislodged from the
hillsides and the sizes and numbers of particles
transported to the flood plains. Lithology and ero-
sional history undoubtedly influence the sizes of the
rocks dislodged from hillsides. Also, many (but not
all) large rocks were retained in mountain ravines
or alluvial fans and therefore were not included in
the flood plain analysis. This, however, was not the
case in Polly Wright Cove, where the deposits were
virtually continuous over the entire study reach and
Where no alluvial fan formed. The relatively large
value of dav (14.4 mm) at x=0 ft in Polly Wright
Cove reflects this condition.

Why does dav on Polly Wright decrease nearly 10
times as fast as on Rucker and Dillard? The answer
seems to lie in the sizes of particles introduced at
the head of the study reach and in the effect of
several side tributaries which supplied more large
rocks downstream. The upstream Polly Wright de-
posits were closer to the steep mountain hillslopes
which provided the debris. This fact, plus the ab-
sence of an alluvial fan, means that the upstream
deposits in Polly Wright Cove contained a greater
proportion of large boulders, thus contributing to a
larger average particle size. As mentioned elsewhere,

 

large rocks were not moved very far from the moun-
tainous areas during the flood (usually considerably
less than a mile). Thus the average particle size in
Polly Wright Cove decreased rather rapidly with
distance. On Rucker Run many slides and tributaries
furnished large rocks to the flood-plain deposits
along the study reach, so clav did not decrease as
rapidly as if large rocks had been introduced at a
single point source at the head of the reach. In the
Dillard Creek basin some deposition in mountain
ravines and in a fan trapped most of the large rocks
before deposition of the flood-plain sediments. Hence
the possible range of variation in dav along the Dil-
lard reach was much more restricted.

A decrease in grain size can result from selective
deposition, breakage of particles, and abrasion or
wearing down of the grain surface. Any of these
can be influenced by such factors as flow properties
(discharge, mean velocity, depth, width), channel
properties (gradient, roughness, sinuosity), par-
ticle characteristics (size, shape, specific gravity,
mineralogy), and erosional history or degree of
weathering. For two streams in the Black Hills area
of South Dakota, Plumley (1948) concluded that
selective deposition accounted for 75 percent and 84
percent of observed grain-size reductions, respec-
tively, with abrasion accounting for the remaining
small percentage. Scott and Gravlee (1968) reported
that for a flood surge on the Rubicon River in Cali-
fornia selective deposition caused more than 90 per-
cent of the measured size decline and that breakage
was not significant in the overall size reduction.
Bradley, Fahnestock, and Rowekamp (1972) con-
cluded that sorting processes caused 87 percent of
an observed reduction in the size of flood-transported
gravel along a 16-mile reach of the Knik River,
Alaska. The remaining small percentage in size re-
duction was attributed to abrasion.

Preflood weathering which could promote break-
ing during transport could be a minor factor with
the present sediments; however, on the basis of
field observations, most particles, at least those
visible on the surface and in cuts eroded through
the fresh deposits, seemed to be relatively fresh.
Breakage, however, could have occurred during
transport, especially with the larger rocks. Aside
from the possibility that some of the measured size
decline could be due to breakage, there is no firm
evidence to evaluate the extent to which breakage
during transport was important. Intuitively it would
seem to be a minor factor. Abrasion or wearing
down of the particle surface probably could not have
been significant, because the rock (igneous and

DEPOSITIONAL FEATURES 69

metamorphic) generally was hard and fresh, and the
distance of travel was quite short, ranging from a
few feet to about 12.5 miles for the data obtained
here. Thus the most likely reason for the progres-
sive decrease in size is selective deposition, with
breakage possibly affecting the trend to a minor
extent.

AVERAGE PARTICLE SIZE, LOCAL SLOPE, AND
DRAINAGE AREA

What factors might be most influential in deter-
mining the particle sizes that are left at a given
site? The two which appear most reasonable are
the local gradient and water discharge. For Rucker
Run and Dillard Creek local gradients were meas-
ured from topographic maps (1224,000). These
slopes equal the vertical distance on the maps be-
tween the contour line upstream'from the sampling
site and that downstream from the site, divided by
the horizontal distance along the channel between
the two contour lines. All slopes along Polly Wright
Creek were measured in the field with a Zeiss level
and stadia rod.

Average particle size shows some correlation with
local flood-plain slope S (fig. 51). The line fitted by
least-squares in figure 51 has the relation dav=
2,270 S138. Thus the average particle size decreased
as the slope became flatter. The deviations of data
points from the regression line range from +600
percent to —50 percent.

Hack (1957, p. 57) studied Virginia and Mary-
land streams near this area and included a much
greater variety of geologic environments and drain-
age-basin sizes. He found that with decrease in
slope the size of the bed material could increase,
decrease. or remain constant, depending on the sur-
face lithology of the drainage basin. Also, the sedi-
ments Hack studied had been extensively reworked
by normal streamfiows. (In fact, he felt that the
sizes of bed—material particles partly determined
the local slope, whereas the reverse probably was
true for the Hurricane Camille deposition.) Plumley
(1948) found power relations between median grain
size and local slope for ancient stream sediments
along three streams in the Black Hills of South
Dakota. Plumley’s three exponents, with slope the
independent variable, were 0.53, 0.53 and 1.25, and
(1,, decreased at a lesser rate as local slope decreased,
as compared with relations in Nelson County.

Water discharge, as mentioned, was not measured.
However, the drainage area usually shows a power
relation to water discharge. Consequently, drainage
area, as measured from topographic maps (1224,000)

 

100

 

I I l

_ + Polly Wright Cove
V Dillard Creek
[:1 Rucker Run

4

_ + _
+
+
10— fl
m El + _
+
+
L + _
D +

  
 

clav : 22705138

AVERAGE PARTICLE SIZE (dav),|N MILLIMETERS
S
l

Upstream —:>

 

 

 

0.01 1 l |
0.001 0.01 0.1 0.5

LOCAL SLOPE (S), IN FEET PER FOOT
FIGURE ESL—Change in average particle size» with local
flood-plain slope. The two points at steepest slopes for
Dillard Creek are alluvial fan sediments.

with a planimeter, was plotted against average grain
size. The drainage area for any sampling site in-
cludes the drainage area of all upstream tributaries
which enter the major stream.

Figure 52 indicates that with increase in drainage
area Ad, the average particle size decreased accord-
ing to the least squares relation dav=1.9Ad'1-34. This
equation pertains to all of the plotted points as a
group. Deviations of measured data from the regres-
sion line range from +300 percent to —26 percent.
Individual drainage basins may not follow the gen-
eral equation. In Polly Wright Cove, for example, the
average grain size decreases with the —2.8 power
(approximately) of drainage area, as suggested by
the dashed line in the diagram.

Since average particle size increases with the 1.98
power of local slope S and decreases with the 1.34
power of drainage area Ad, these relations can be re-
arranged and combined into the form S oc (dav0'25) /
Adm“). Writing the relation this way implies that
slope is the dependent variable, probably not the case

70 HURRICANE CAMILLE IN VIRGINIA, 1969

 

100-0 I | | I I I

\+ + Polly Wright Cove

" v Dillard Creek ‘
V: I: Rucker Run
\

10.0 —

AVERAGE PARTICLE SIZE (dav), IN MILLIMETERS

 

 

 

0‘01 1 I l I I
0.1 1.0 10 50

DRAINAGE AREA (Ad), IN SQUARE MILES

 

FIGURE 52.—Variation of average particle size with drain-
age area. Dillard Creek points include two alluvial fan
stations (coarsest values of div) and do not include
highway delta deposits.

in the present study, but the equation in this form
can be compared to Hack’s (1957, p. 58) relation
S cc (daVO-G) / (Adm). The differences in the exponents
are not very big, considering the amount of scatter
on the plots in both investigations. Hack’s equation
applies to streams in various rock types.

It will be interesting to see if future research
finds empirical relations of the sort discussed here
to be applicable to other physiographic regions.
Denny (1965) studied desert washes in California
and Nevada and could not find any correlation at all
between local slope, median particle size, and drain-
age area.

DOWNSTREAM VARIATION IN SIZE OF LARGEST
STONES

The largest stones at a site, if all sizes were avail-
able for transport, provide some indication of the
particle sizes the flow was able to move. Figure 53 is
a plot of the average size (intermediate diameter)

 

 

2000 I

I I I |
POLLY WRIGHT COVE

   
   

1000

d's :14246T0'00024X

IIIIIII

500 '—
I._

 

 

300 I I I I I
0 1 2 3 4 5

 

O)

 

  
 
 
    

DILLARD CREEK

INTERMEDIATE DIAMETER OF FIVE LARGEST
STONES ((1.5), IN MILLIMETERS

d|521230e7000013x :

MI I I I I

O 2 4 6 8 10 12
DOWNSTREAM DISTANCE (x), [N THOUSANDS OF FEET

 

    

 

FIGURE 53.——Downstream changes in average intermediate
diameter of the five largest stones at each station. Lines
fitted by least squares.

of the five largest stones (dls) as a function of dis-
tance downstream for Polly Wright and Dillard
Greeks. The Dillard Creek data include the Wills
partial fan at the head of the cove (five data points),
and the downstream distances begin at the fan apex
for this particular diagram. Only three pebble
counts—a number insufficient for plotting—were
taken on Rucker Run.

A negative exponential function, fitted here by
least squares, describes the data reasonably well. For
Polly Wright dls=1,420e—°-°°°m, with maximum de-
viations ranging from +135 percent to ——7 5 percent
of the regression value. For Dillard Creek dls=
1,330e—°-°°°13”, and maximum deviations range from
+145 percent to —70 percent of the regression value.
The Polly Wright exponent of —0.00024 means that
for every 1,000 feet of distance the geometric mean
of the largest stones decreases by 24 percent. Simi-
larly, along Dillard Creek the size at each 1,000-foot
station was about 13 percent less than that at the
previous 1,000-foot station. The exponents show that
the size of the largest stones decreases nearly twice
as rapidly along Polly Wright Cove as on Dillard
Creek. (Among other differences, the flood-plain
slope decreases more rapidly in Polly Wright Cove,
too.)

As a general trend the largest rock fragments
along Polly Wright Cove decreased from 142 cm in
the deposits farthest upstream to about 50 cm after
0.8 mile of travel. In Dillard Creek the average diam-
eter of the five largest stones was 133 cm at the up-

 

DEPOSITIONAL FEATURES 71

stream end of the creek and about 30 cm a little
more than 2 miles downstream.

The best-fit lines should not be interpreted as sug-
gesting that at any given downstream location the
average intermediate diameter of the five largest
stones would necessarily be the diameter indicated
by the line. At some intermediate locations no par-
ticles larger than pebbles or coarse sand appeared on
the surface. Considerations governing the selection
of sampling sites were mentioned earlier in the re-
port.

DOWNSTREAM CHANGES IN SORTING

The flood-plain deposits generally became better
sorted with distance down-valley (fig. 54). Again an
asymptotic relation seems to be the best fit to the
Rucker Run points, as is true for Dillard Creek. Most
of the boulders came to rest within a mile or so of the
upstream deposit so that the sorting has the largest
values and improves most rapidly in this zone. Sort-
ing on these creeks continues to improve with dis-
tance downstream but at a progressively lesser rate.
The sorting can only become zero when all grains
between d90 and d10 are the same size, a situation
extremely unlikely to occur. Thus the sorting prob-
ably should not continue to improve at a constant
rate with distance down valley; instead, a more
reasonable relation is a change by lesser amounts as
the possible range of improvement decreases, that is,
So should become asymptotic toward some limiting
minimum value.

A straight line fits the data points for Polly
Wright Cove, indicating a negative exponential re-
lation for the study reach. As explained above, this
relation probably could not continue indefinitely
with distance. For example, extrapolating the
straight-line suggests that about two miles down
from the upper end of the study reach, 8., would
have the unlikely value of zero, that is, all grains
from d90 to cl10 on the cumulative size frequency curve
would be the same size. In fact, the data for the
4,500-foot reach of Polly Wright Cove fit reasonably
well onto the points for Rucker Run and Dillard
Creek, as shown in the bottom part of figure 54. This
suggests that the So relation may be steep and linear
(exponential) within the first mile of emergence
from the mountainous area and then takes on a curve
approaching a limiting value some distance down-
stream.

In addition to a downstream limiting minimum
value, the sorting probably had a limiting maximum
value in the upstream deposits, due to the finite sizes
of boulders available for movement and movable by
the floodwaters. This value seems to be about 4, that

 

is, the range log dgo—log d10 for the poorest sorted
deposits did not encompass more than about 4 log
cycles of grain size. This range usually extended
from about 0.1 or 0.2 mm to about 1,000 or 2,000
mm. Sorting values higher than 4 could have been
restricted by a relative scarcity of larger boulders
available for transport or an inability of the flow to
move more than a few such boulders from the up-
stream areas to the valley flood-plain deposits.
Inspection of the stream channel upstream from
depositional areas revealed only a few really huge
boulders; so not many boulders larger than about
two meters in intermediate diameter were available.
A few boulders of such dimensions were moved by
the flood, for example in Ginseng Hollow, but proba-
bly only for short distances along the mountain
channel.

These probable limitations on sorting show up
more clearly in a plot of 8., versus dav (fig. 55). In
the upstream reaches d... is large, in spite of the
ubiquitous sand and silt, because of the presence of
the large rocks. The associated large value of sorting
tends to remain high, as d3, decreases from about
55 mm to 4 mm. With further decreases in dav, that
is, proceeding farther downstreamward, sorting im-
proves rapidly as the larger rocks become scarcer.
But in the downstream reaches, while d.“ continues
to decrease, So begins to level off, that is, the range
of sizes present in the deposits tends to become
constant. This suggests that in the downstream re-
gions the flow could easily transport all the available
grain sizes.

DOWNSTREAM CHANGES IN SKEWNESS

Along Dillard Creek and much of Rucker Run the
skewnesses are close to zero (fig. 56), indicating
approximately symmetrical distributions. Rucker
Run actually may show a very slight trend over the
full 12.5-mile study reach whereby the size distribu-
tions go from slightly positive (abundance of small
grains) at the upstream end to slightly negative
(preponderance of the larger grains within the dis-
tribution) at the downstream end; however, it is
difficult to say how much of this possible trend is
significant and how much could be due to chance
sampling. In Polly Wright Cove the deposits in the
upstream 1,000 feet had a preponderance of large
rocks (negative skewnesses), whereas the remaining
section of the study reach had slightly positive
skewnesses. Thus in these downstream areas of Polly
Wright Cove the smaller grains were more predomi-
nant than the large rocks in terms of weight-percent.

The skewness varies with the average grain size,
for the flood-plain and alluvial fan deposits, in a

72

= log dgo — log d10

SORTING (So)

HURRICANE C‘AMILLE IN VIRGINIA, 1969

 

I I | I I I

 

 

 

 

 

 

 

 

 

 

 

 

 

 

W
I I I I I

RUCKER RUN
D 1:]
I I I
40 50 60
I
+ + POLLY WRIGHT COVE
+ _
'1’ _
+
I | I |
1 2 3 4 5
I
DILLARD CREEK
V
v _
w
| I | I I
4 8 12 16 20 24
I | | I
-I++ +
+ RUCKER, DILLARD, AND POLLY WRIGHT DATA

 

 

4 8 12 16 20
DOWNSTREAM DISTANCE (x), IN THOUSANDS OF FEET

FIGURE 54.—Downstream changes in sorting 0f flood-plain deposits.

24

 

70

 

 

DEPOSITIONAL FEATURES 73
4.0
I I | I I | I I | I
D +
EXPLANATION o O
(X X+
+ Polly Wright Cove _ it? ’
v Dillard Creek } 1:“???
3‘0 1. CI Rucker Run po
27’ x CampbeII A“ . If
°° uwa an
_c|: 0 Bryant deposits
3 V WINS
‘0
3°
1 2.0 —'
6’
<5
E
I—
‘5
U’ 10 _ Upstream direction ————>
0 L I l I
0.01 0.1 1.0 10 100
AVERAGE GRAIN SIZE. IN MILLIMETERS
FIGURE 55.——Change in sorting with average grain size.
RUCKER RUN
+1.0
0 ____________________
.1.0 l l l l
o 0 10 20 30 40 50 60 70
‘6"
no
2 o
N ‘6‘
lo go POLLY WRIGHT COVE
:9“ T +1.0
no 8
2 ‘0 .
+ E," Preponderance of small particles
‘5‘ 0
(10
_o
Preponderance of large particles
II
9 ~1.
3 00 1 2 3 4 5
(I)
U)
UJ
z
E
g: DILLARD CREEK
<0 +1.0
l l l
_L
o T + T.
_1.0 I n I I I
o 4 8 12 16 20 24

 

     
 
  
  
 

 

    
 
  

 

    

 

 

 

 

 

 

 

 

 

 

 

 

DOWNSTREAM DISTANCE (x), IN THOUSANDS OF FEET

FIGURE 56,—Downstream changes in skewness of flood-plain deposits.

 

 

 

74 HURRICANE CAMILLE IN VIRGINIA, 1969

rather peculiar way (fig. 57). This graph should be
interpreted as showing a relation between d,., and
skewness, rather than as an implication that a
change in d... causes a change in skewness. Distribu-
tions that have a large average grain size are nega-
tively skewed, meaning the large boulders pre-
dominate as far as weight frequency is concerned.
As dav decreases to about 8 mm the distributions
gradually become more and more symmetrical. With
a further decrease in dav—down to about 2 or 3 mm
—the distributions become more and more skewed
in the opposite direction, that is, gain a preponder-
ance of smaller grains. The reason for this skewness
trend is the progressively smaller percentages of
large stones contained in the deposits. Average size
gets smaller, in other words, and the larger particles
within each sample become progressively less com-
mon. As d... decreases from about 2 mm, the sorting
improves rapidly (fig. 55), as the large stones begin
to disappear from the deposits. This means a trend
back toward more symmetrical distributions, as
shown in figure 57. Approximately symmetrical dis-
tributions are reached when dav has decreased to
about 0.5 mm. For smaller average grain sizes, the
distributions tend to be approximately symmetrical
or slightly negatively skewed.

SCARCITY OF COARlSE SAND AND GRAVEL

Geologists have long speculated on the curious
fact that many grain-size analyses show a dearth of
particles in the coarse sand or fine gravel ranges.

+ Polly Wright Cove
V Dillard Creek

D Rucker Run
0.6

0.4

    
 
  

+

0.2

SKEWNESS
O
O
\

’02

70.4

FIGURE 57.—Change in skewness with average grain size.

 

 

EXPLANATION

}Floodplaln deposits

V/""/

1.0 10.0
AVERAGE GRAIN SIZE, IN MILLIMETERS

This supposed scarcity of certain sizes causes the
histograms or size-frequency curves to show more
than one peak or mode, as long as the range of sizes
represented goes at least from medium sand to
coarse gravel. Pettijohn (1957, p. 44) gives a good
review of cases where such polymodality has been
reported in the literature. Russel (1968) goes into
the subject in some detail and concludes that grains
of about 1—6 mm diameters are deficient in fluvial
deposits because such grains are more readily en-
trained and more rapidly transported than larger
or smaller particles. The “missing” grain sizes, in
his View, are moved downstream beyond river
mouths and tend to be concentrated on beaches. The
following paragraphs summarize the Nelson County
flood deposits in regard to polymodality of size-
frequency distributions.

The first problem was how to define polymodality.
For example, if a class had a decrease of only one or
two percent below the percentages in the adjoining
size classes, it seemed unrealistic tc call such a slight
decrease a deficiency, because the minor differences
could easily be due to sampling or splitting (for sieve
analysis) errors. Then the question was how much
of a difference in weight percentage to require in
order to label the distribution poly modal.

To resolve this problem we measured the approxi-
mate error that could be attributed to laboratory
splitting of the field sample. This was done by sieving
the entire contents (1—4 lb) of 1) of the samples
brought from the field (called herein the field sam-

 

X Campbell
0 Bryant

} Alluvial fan deposits
V Wills

      
 

O
E]
12%;?
/ :Sxfi

Prepon ierance
T of small aartlcles

  
  

Preponc erance
of large articles

 

 

100.0

 

 

DEPOSITIONAL FEATURES 75

ple) and comparing the results to the corresponding
split samples. The field samples were split 1—3 times
in the laboratory, to obtain the split sample. The par-
ticular size classes of interest in the test were those
which were usually present in the field and which
were often involved in the apparent scarcity: 32—16,
16—8, 8—4 and 4—2 mm. For these four size classes

both the full field sample and the split sample were ‘

sieved, and the percent by weight in the total field
sample was compared to that in the split sample, for
a given size class. The largest discrepancy or differ-
ence was 5.3 percent, that is, one of the field sam-
ples had 5.3 percent by weight in one of the size
classes, whereas for the same class the split sample
had zero percent by weight. General agreement was
quite good, however, with the arithmetic average
discrepancy between full field sample and split sam-
ple amounting to 1.5 percent. Based on the data
from these sieve tests, we estimated the standard
deviation of the discrepancies or differences between
any two size classes of a given sample, using certain
simplifying assumptions. Two times this standard
deviation was 3.05 percent; that is, the chances were
about 95 out of 100 that within a size-frequency
distribution a difference of 3 percent or less between
any two size classes could be attributed to splitting
error. The criterion for polymodality therefore was
that at least one size class have at least 3 percent
by weight less than a coarser and finer class.

There were 63 grain-size analyses, involving two
flood-plain sites and four highway-delta sites, which
covered the complete range of sizes at a sampling
station. Of these analyses 27 dealt with a study of
grain size changes with depth. All such samples
were medium sand or finer and were analyzed by
sieving, occasionally including also a pipet treat-
ment. None of these 27 analyses was polymodal.

The remaining 36 analyses were surface sedi-
ments which usually involved a wide range of par-
ticle sizes, thus requiring in most cases a pebble
count in addition to the sieve analysis. Of these 36
cases, 24 showed a definite polymodality.

Table 10 shows the frequency with which each
size class was deficient, according to the 3 percent
rule described earlier. Particles which were espe-
cially scarce were those in the size range from 4 to
64 mm.

The polymodal samples have certain common
characteristics which are generally absent in the
unimodal distributions. As mentioned above, poly-
modality showed up markedly in surface samples
but did not appear in sediments below the surface.

 

TABLE 10.-—Number of cases of deficiency in weight-percent,
for the indicated particle size class
[Classes not listed had no instances of deficiency. Deficiency is at least

3 percent by weight less than a finer and a coarser size class, within
same sediment sample]

 

Size class, in millimeters

 

 

 

N

Stream or S ‘9 °°

study area «'4‘ 3 a 3 N ‘9 no
g 4. .2. g, “a ‘T a s N a '1“
v-7 {3 ‘fi H E a": 3 ob Jr all H

Polly Wright

(11 stations, 8

polymodal). _ 1 _ 2 7 5 6 6 3 2 2

Dillard Creek

(7 stations, 2

polymodal). 1 - - 1 2 1 2 2 _ _ _

Rucker Run

(6 stations, 2

polymodal). _ _ 1 1 1 2 1 1 _ - -

Campbell Fan

(5 stations, all

polymodal). - _ - 1 5 5 5 4 4 4 1

Bryant Fan

(7 stations, all

polymodal). _ _ 2 3 2 7 5 5 2 2 1

Sums: 1 1 3 8 17 20 19 18 9 8 4

36 stations 24,
having poly-
modal dis-
tributions

 

Deposits such as alluvial fans which had significant
proportions of boulders and cobblestones consist-
ently showed polymodal size distributions. Also, the
presence of such large rocks meant that the final
distribution represented a combined pebble count
and sieve analysis. (All 24 cases of polymodality
were combined pebble-count-sieve analysis distribu-
tions; an additional five such combined analyses did
not show polymodality.)

The scarcity of grains in the 4—64 mm range may
be either real or apparent. Apparent in this sense
means the scarce grains actually existed on the
surface of the deposit but were somehow missed
in the analysis. The possible ways they could have
been missed are: (1) failure to be tallied in the
pebble count; (2) failure to be included in the
scooping up of the “sand” sample; (3) erroneous
loss in percent by weight due to the mathematical
analysis of the data, that is, resulting from the
method of combining the pebble count with the sieve
analysis.

The pertinent sizes might be missed during a peb-
ble count in at least two ways. Due to the presence
of larger rocks, they may well have been sheltered
or overlapped by these rocks. Also, unless the in-
vestigator is particularly careful, he tends to select
large rocks in preference to smaller grains during
the pebble-counting.

In a few places, especially on flood plains down-
stream, a surface deposit contained only a few rocks
larger than gravel, so that the pebble count neces-
sarily had a small number of observations. However,

 

 

76 HURRICANE CAMILLE IN VIRGINIA, 1969‘

this possible source of sampling error would apply
in only a few of the 24 cases of polymodality. Fur-
thermore, such errors should apply equally to all size
classes rather than only to certain classes.

Failure to be scooped up with the “sand” sample
is a possible but not very probable source of error,
because most of the scarce sizes would not normally
be included in a sample of fine material. The field
sample almost always contained grains 8 mm in
diameter, often included pebbles up to 16 mm dia-
meter, and not uncommonly contained particles up
to 32 mm in diameter.

The method of combining the pebble count with
the sieve analysis certainly depends on several ques-
tionable assumptions, as explained earlier. However,
four size classes showed about an equally large fre-
quency of scarcity (table 10). A fault in the mathe-
matical treatment would more likely vary in some
way with the grain size.

If the scarcity of the particles in question is real,
the possible causes are that: (1) such grains were
never produced to any significant degree of abund-
ance; (2) the particles were either retained up-
stream (mountain channel deposits) or were carried
downstreamward beyond the deposits we inspected;
(3) the particles were laid down in the sediments we
inspected but were not abundant on the surface and
so were not sampled.

The theory that such grains were not produced in
significant quantities cannot be disproved but does
seem highly unlikely, inasmuch as particles ranging
from clay to 10-foot-thick boulders were eroded by
the floodwaters. The appearance of the polymodality
in deposits upstream from which no mountain-
channel deposits existed shows that the scarce grain
sizes probably were not retained upstream in the
headwater region. If particles ranging from 4 to
64 mm are particularly susceptible to entrainment,
they should nevertheless have been trapped in high-
way deltas like the one where Dillard Creek meets
highway US. 29. In fact, being scarce relative to
adjacent size classes upstream, they might even be
expected to be more abundant in highway deltas.
This, however, was not the case, nor could they be
located at greater distances downstream. The dis-
tances studied amounted to as much as 12 miles, by
which distance the deposits were strictly sand and
finer, with average grain sizes less than 1 mm
(fig. 50) and excellent sorting (fig. 54). These con-
siderations, especially the absence of excessive quan-
tities of the pertinent grains in highway deltas, cast
doubt on the theory that the missing grains were
moved all the way to the James River or farther.

 

 

 
  

It is quite possible that the pe tinent grain sizes
were present in the flood depo its but were not
abundant on the surface. This sit ation could result,
for example, if the floodwaters 1 id down rocks of
all sizes at one or more stages bu deposited medium
sands and finer grains in scatter (1 patches toward
the end of the flood. The scatt red sand patches
would tend to cover gravel and ebbles while leav-
ing the cobbles and especially the boulders exposed.
A surface sampling would then ecord a relatively
large number of big rocks and sand grains but
would miss many pebbles and gra el-sized particles.
If the deposits had not been dest oyed, this possible
cause of polymodality could be tes ed in the field.

In conclusion, flood deposits co sisting mainly of
grains smaller than coarse sand ere all unimodal.
Deposits which included a wide range of particle
sizes, however, were usually poly odal with a rela-
tively scarcity of particles 4—64 mm in diameter.
The most likely reason for this p lymodality is that
the scarce grains were covered p to a significant
extent by sands deposited during he recession stage
of the flood. Other possibilities ar that many of the
deficient sizes were hiding under the edges of the
larger rocks and that sampling bias favored the
selection of larger rocks during th pebble counting.

DOWNSTREAM CHANGES IN GRA N SHAPE AND
ROUNDNESS

The roundness of a grain is the egree of smooth-
ing or rounding, ranging from v ry sharp to per-
fectly rounded, of the edges or cor ers of the grain.
Particles become more rounded due to weathering
and to abrasion and wear, that is, with longer time
and greater distance of transport Observations on
grain roundness therefore might e helpful in esti-
mating distance of transport.

Grain shape, defined more speci cally below, is a
three-dimensional measurement 0 a particle’s gen-
eral form and is a separate concep from roundness.
Grain shape depends on amount 0 abrasion, initial
shape, cleavage and natural hard ess. The miner-
alogy generally influences these las three items. Be-
cause it affects settling velocity, th grain shape con-
ceivably could influence various a pects of particle
behavior in water, such as ease of entrainment and
mode and rate of transport. It c uld also provide
information on the hydrodynam'c conditions of
deposition.

Changes in grain shape and ro
tance downstream are still poorl
to scarcity of data, especially for
tions. Krumbein (1940) studied

ndness with dis-
understood due
iver flood condi-
California flood

 

——'i

CONCLUSIONS 77

/

gravels over a distance of about 7 miles. He found
that roundness increased from 0.28 at the l-mile
station to 0.44 at the 7-mile location (0.1 being very
sharp particle edges and 1.0 being perfectly rounded
edges) ; grain shape, however, showed no significant
change over this distance. Scott and Gravlee (1968)
found that a flood surge on a stream in the Sierra
Nevada mountains caused boulders to increase in
average roundness from about 0.25 to 0.40 over the
first two miles of travel. Studies of shape and round-
ness changes for other environments, such as
beaches, rivers at normal flow, and in laboratory ex-
periments, show various and even contradictory re-
lations (Pettijohn, 1957, p. 549).

We examined the deposits of Polly Wright Cove
for possible downstream changes in particle shape
and roundness. Most of these sediments orginated
in a reasonably localized area (about 0.6 sq mi). The
total distance of deposition along the stream unfor-
tunately was only about 0.8 mile, the upstream half
of which was subject to “contamination” from two
minor tributaries, as mentioned earlier. This 0.8-mile
distance might be considered too short to show any
shape and roundness changes, but laboratory experi—
ments (Krumbein, 1941a) have suggested that
roundness values during the first mile of travel can
increase from about 0.15 to 0.45, that is, roundness
increases considerably during the first mile or two
of transport.

The Polly Wright grains examined were in the
0250—0500 mm sieve class, from each of the 11
field stations. A colleague coded the 11 samples so
that the operator could not know the field location
of the grains being examined. Using a microscope,
the operator then measured the shape and estimated
the roundness of 50 randomly-chosen grains, for each
sample. Shape equals the short particle axis divided
by the square root of the intermediate times the
long axis, where all three axes are mutually perpen-
dicular (Schulz and others, 1954). Krumbein’s
(1941b) visual comparison chart served as the cri-
terion for roundness. Possible values of both these
definitions range from 0 to 1.0, where 1.0 is maxi-
mum possible shape or roundness. Owing to the com-
plex and varied mineralogy of the parent rocks it
was not possible to restrict the measurements to
only one mineral. The grains measured were two
unidentified translucent minerals that occurred the
most abundantly and consistently throughout all 11
samples.

Table 11 lists the average shape and roundness
values for each sampling station. All shape values
fall within the range 0.63—0.76. Grain corners and

 

 

 

 

 

TABLE 11.—Average grain shape and roundness values with
distance downstream in Polly Wright Cove

Average Average
Distance downstream grain-shape roundness
from first deposits (ft) value value

 

edges were quite sharp, and the low roundness values
range from 0.17 to 0.24. The data show no signifi-
cant change in either shape or roundness with dis-
tance downstream.

Krumbein’s (1940) and Scott and Gravlee’s
(1968) roundness studies showed a definite increase
in particle roundness over the first few miles of
travel. The use of gravel—to-boulder-sized particles
in those studies may be one reason why the present
roundness results differ from the previous work.
Also, the infusion of sediment from side tributaries
near the middle of the study reach may have con-
fused the present results slightly. Other possible
causes of discrepancy might be the range of grain
sizes of the transported and deposited materials, the
mineralogy and the physical conditions (hydrology
and geomorphology) of the floods. All of these dis-
crepancies warrant future study in both field and
laboratory.

The absence of an increase in grain shape agrees
with Krumbein’s field study (1940). His tumbling-
barrel experiments (1941a), which may not have
simulated catastrophic flood conditions, produced a
very slight increase in grain shape over the first
mile of travel.

CONCLUSIONS

The storm and flood of August 1969 in Virginia
was an extreme event (probably occurring no more
than once every several hundred years on the aver-
age) which caused enormous amounts of sediment
erosion and deposition. In the region most affected,
Nelson County, rainfall amounted to as much as 28
inches over the 8-hour storm. Peak streamflow was
estimated to be about 10,000—12,000 cfs per sq mi of
drainage area.

The longitudinal profiles of the five mountain
streams studied, including alluvial fans where pres-
ent, are very closely described by a hyperbolic equa—

 

78 HURRICANE CrAMILLE IN VIRGINIA, 1969‘

tion of the form F=L/ (a + bL) , where F and L are
vertical fall and horizontal distance respectively,
from the drainage divide, and a and b are coefficients.

Nearly half of the erosion took place in the form
of debris avalanches on upland hillslopes. Field ob-
servations and measurements on avalanche scars
reveal the following characteristics: (1) the scar
on the hillside usually extended up the slope to the
region where the local hillside gradient was steep-
est: (2) this upslope tip of the avalanche tended to
be located at the point on the hillside where the
convex upper zone merged with the concave or
straight section immediately below, a point which
could be from 0.3 to 0.95 of the horizontal distance
from base to top of hill: (3) debris avalanches
usually occurred down previously-existing grooves,
minor channels or depressions on the hillside, a
finding in agreement with other studies: (4) slopes
facing north, northeast and east had more debris
avalanching than hillslopes facing other directions;
and (5) on a unit drainage area basis, longer hill-
slopes had a greater total length of avalanche scars
but fewer scars than short hillslopes.

Slightly more than half of the erosion that oc-
curred was estimated to be from the enlargement
of stream channels.

The total volume of sediment eroded during the
storm was estimated to be about 6.1 million cu ft
(3.9 million cu ft per sq mi) from the headwaters
of Wills Cove, 3.1 million cu ft (4.6 million cu ft
per sq mi) from Ginseng Hollow and 3.1 million
cu ft (3.2 million cu ft per sq mi) from Polly Wright
Cove. These amounts correspond to average denuda-
tions of 1.4, 2.0 and 1.4 inches from Wills Cove
(upper part), Ginseng Hollow and Polly Wright
Cove, respectively, and are probably the equivalent
of several thousand years of “normal” denudation.

The types of deposits associated with the storm
and flood were: ( 1) debris-avalanche deposits, quite
rare, left at or near the base of hillslopes; ( 2) moun-
tain-channel deposits, in some cases in the form of
huge debris piles behind log jams; (3) alluvial fans
Where the narrow mountain channels entered the
open intermontane valleys; (4) deltas where a swol-
len stream’s path was temporarily blocked by a
highway embankment; and (5) flood-plain deposits.
The size-frequency distribution of the particles at
any locality on such deposits is described by com-
bining a sieve analysis with a pebble count in a
method which apparently has not heretofore been
used.

Except for highway deltas and some downstream
flood-plain sediments, the particle sizes in a deposit

 

 

 

generally ranged from clay or ilt to boulders. How-
ever, nearly all particles larger than about fine sand
were deposited after 5 or 10 1 iles of travel from
their source. Some of the Si] and clay probably
reached the James River and its estuary.

Two prominent alluvial fans ach contained about
300,000 cubic feet of newly dep sited sediment. The
average grain size on alluvial ans showed no dis-
tinct trend with distance down t e fan. Several other
authors have reported that particles tend to become
smaller with distance on a fan. Possible reasons for
this difference are the short lengths of the present
fans (up to about 2,000 ft) and the probably fast
velocity of the flow at the fan ‘pex, for this catas-
trophic event.

Highway deltas vary widely in size. One of the
largest contains an estimated 1, 00,000 cubic feet of
sediment. Such deltaic sediment consist mainly of
sand that has distinct laminatio s. Cross-stratifica-
tion near the surface and ripple marks and mud on
the top surface are also charact ristic. As the flood
progressed, the particles trappe in highway deltas
generally became finer in size, bet er sorted and more
symmetrical in weight-frequency distribution. The
storm-average sediment transport rate at the apex
of one major delta was estimated to be about 33 lb
per sec per foot of channel width.

Flood-plain deposits in the upland region have a
wide range of particle sizes an show no distinct
sedimentary features. The sand flood-plain sedi-
ments farther downstream commonly have lamina-
tions, ripple marks and mud cracks. Of two sites
chosen to study textural changes with depth (re-
flecting relative time of depositionl during the flood),
the particles at one site become finer and better
sorted toward the top surface, whereas at the other
site the grains show no noticeable trend except for
a layer of finer material on the surface.

The amount of deposition on flodd-plains decreased
with distance downstream, thou h at varying and
irregular rates. Side tributaries, h ghway deltas and
other factors influenced the measured rates at which
volume of flood-plain deposition diminished with
distance. Upstream deposition on‘Rucker Run was
about 150—300 cu ft per foot of channel length, but at
12.5 miles downstream the amount of deposition was
only minor. Beginning at the head of a valley just
beyond the mountain front, flood-plain sediments
show the following textural changes with distance
downstream: (1) average grain size decreases rather
systematically, reaching about 0.1 mm in about 5—7
miles of travel; (2) average gra'n size therefore
decreases with both a decrease in ltcal gradient and

 

 

 

————7

CONCLUSIONS 79

an increase in drainage area; (3) the average dia-
meter of the five largest stones, reflecting the stream
competence, decreases exponentially; (4) sorting
improves to the extent that the d90—d10 range de-
creases from about 2—4 log cycles of grain size to less
than one log cycle of grain size, over 5—7 miles of
travel; and (5) most size distributions are approxi-
mately symmetrical, a notable exception being the
deposits in Polly Wright Cove.

Some of the deposits apparently were polymodal,
being deficient, in fine gravel, a situation common to
many other sediments. The gravel particles in all
probability were as available as other sizes in the
headwaters, were not selectively retained upstream
from the floodplain deposits, and were not selectively
transported beyond the several miles of study reach.
The most probable reason for the supposed scarcity
of gravel-sized particles is the possibility that the
“missing” grains were mostly covered by sands de-
posited during the recession stage of the flood.

Particles from Polly Wright Cove in the 0.250—
0.500 mm sieve class showed no significant changes
in either shape or roundness, over about 0.8 mile
of travel.

REFERENCES

Bloomer, R. 0., and Werner, H. J., 1955, Geology of the
Blue Ridge region in central Virginia: Geol. Soc. Amer-
ica Bull., v. 66, p. 579—606.

Bradley, W. C., Fahnestock, R. K., and Rowekamp, E. T.,
1972, Coarse sediment transport by flood flows on Knik
River, Alaska: Geol. Soc. Am. Bull., v. 83, p. 1261—1284.

Bull, W. B., 1964, Geomorphology of segmented alluvial fans
in western Fresno County, California: U.S. Geol. Survey
Prof. Paper 352—E, p. 89-128.

Camp, J. D., and Miller, E. M., 1970, Flood of August 1969
in Virginia: U.S. Geol. Survey open-file report, 120 p.

Chawner, W. D., 1935, Alluvial fan flooding—the Montrose,
California, flood of 1934; Geog. Review, v. 25, p. 255—263.

Chow, V. T., 1959, Open—channel hydraulics: New York,
McGraw-Hill, 680 p.

Commonwealth of Virginia, 1970, Flood Disaster—Review
and Analysis: Richmond, Va., Division of State Plan-
ning and Community Affairs, 50 pp.

Croxton, F. E., and Cowden, D. J., 1939, Applied General
Statistics: New York, Prentice-Hall, Inc., 944 p.

DeAngelis, R. M., and Nelson, E. R., 1969, Hurricane Camille,
August 5—22: U.S. Dept. Commerce, ESSA’s Climatologi-
cal Data, National Summary, v. 20, no. 8, p. 451-474.

Denny, C. S., 1965, Alluvial fans in the Death Valley region,
California and Nevada: U.S. Geol. Survey Prof. Paper
466, 62 p.

Diseker, E. G., and Richardson, E. C., 1962, Erosion rates
and control methods on highway cuts: Am. Assoc. Agri-
cultural Engineers Trans., v. 5, p. 153—155.

Eisenlohr, W. 8., Jr., 1952, Floods of July 18, 1942 in north-
central Pennsylvania: U.S. Geol. Survey Water Supply
Paper 1134—B, p. 59—158.

 

 

 

 

 

Flaccus, Edward, 1958, White Mountain landslides: Appala-
chia, v. 32, p. 175—191.

Fok, Y. S., 1971, Law of stream relief in Horton’s stream
morphological system: Water Resources Research, v. 7,
no. 1, p. 201—203.

Foster, E. E., 1948, Rainfall and Runoff:
MacMillan C0., 487 p.

Guy, H. P., 1971, Flood flow downstream from slide: Am.
Soc. Civil Engineers, Proc., v. 97, no. HY4, p. 643-646.

Hack, J. T., 1957, Studies of longitudinal stream profiles in
Virginia and Maryland. U.S. Geol. Survey Prof. Paper
294—13, p. 45—97.

and Goodlett, J. C., 1960, Geomorphology and forest
ecology of a mountain region in the central Appala-
chians: U.S. Geol Survey Prof. Paper 347, 66 p.

Hershfield, D. M., 1961, Rainfall frequency atlas of the
United States: U.S. Dept. Commerce, Weather Bureau,
Tech. Paper No. 40, 115 p.

Huff, F. A., 1967, Time distribution of rainfall in heavy
storms: Water Resources Research, v. 3, no. 4, p. 1007—
1019.

J ahns, R. H., 1947, Geologic features of the Connecticut val-
ley, Massachusetts as related to recent floods: U.S.
Geol. Survey Water Sup-ply Paper 996, 158 p.

Jennings, A. H., 1950, World’s greatest observed point rain-
falls: Monthly Weather Review, v. 78, p. 4—5.

Judson, Sheldon, and Ritter, D. F., 1964, Rates of regional
denudation in the United States: Jour. Geophys. Re-
search, v. 69, no. 16, p. 3395—3401.

Kellerhals, Rolf, and Bray, D. 1., 1971, Sampling procedures
for coarse fluvial sediments: Am. Soc. Civil Engineers
Proc., v. 45, no. HY8, p. 1165—1180.

Krumbein, W. C., 1937, Sediments and exponential curves:
Jour. Geology, v. 45, no. 6, p. 577—601.

1940, Flood gravel of San Gabriel Canyon, Cali-

fornia: Geol. Soc. Am. Bull., v. 51, p. 639—676.

1941a, The Effects of abrasion on the size, shape and

roundneSS of rock fragments: Jour. Geology, v. 49, no.

5, p. 482—520.

1941b, Measurement and geological significance of
shape and roundness of sedimentary particles: Jour.
Sedim. Petrology, v. 11, no. 2, p. 64—72.

Kuhaida, A. J., Jr., 1971, Debris Avalanching as a Natural
Hazard in the Southern Appalachians: a Case Study of
the Davis Creek Watershed, Virginia: Johnson City,
Tenn., East Tennessee State Univ., Dept. Geography,
M.S. thesis, 69 p.

Langbein, W. B. and others, 1947, Topographic characteristics
of drainage basins: U.S. Geol. Survey Water Supply
Paper 968—0, p. 125—157.

Leopold, L. B., and Langbein, W. B., 1962, The Concept of
entropy in landscape evolution: U.S. Geol. Survey Prof.
Paper 500—A, 20 p.

Lustig, L. K., 1965, Clastic sedimentation in Deep Springs
valley, California: U.S. Geol. Survey Prof. Paper 352—
F, p. 131—192.

McKee, E. D., Crosby, E. J ., and Berryhill, H. L., Jr., 1967,
Flood deposits, Bijou Creek, Colorado, June 1965: Jour.
Sedim. Petrology, v. 37, no. 3, p. 829—851.

McPherson, H. J., and Rannie, W. F., 1969, Geomorphic
effects of the May, 1967 flood in Graburn watershed,
Cypress Hills, Alberta, Canada: Jour. Hydrology, v.
9, p. 307—321.

New York, The

 

 

 

 

t

80 HURRICANE CAMILLE IN VIRGINIA, 1969

Morisawa, Marie, 1968, Streams—Their Dynamics
Morphology: New York, McGraw-Hill, 175 p.
Mueller, J. E., 1972, Re-evaluation
master streams and drainage basins: Geol. Soc. Am.

Bull., v. 83, p. 3471—3474.

Pashinskiy, A. F., 1964, Experience of the study of alluvial
deposits of the Psezuapse River: Soviet Hydrology: Se-
lected Papers, no. 3, p. 276—290.

Pettijohn, F. J., 1957, Sedimentary Rocks:
per and Bros., 2nd ed., 718 p.

Pippan, T., 1963, Beitriige zur Frage der jungen Hangfor—
mung und Hangabtragung in den Salzburger Alpen:
Akad. der Wissenschaften in Géittingen, II. Math-Phys.
Klasse, Nachrichten Nr. 11, p. 163—183.

Plumley, W. J., 1948, Black Hills terrace gravels: a study
in sediment transport: Jour. Geology, v. 56, p. 526—577.

Rapp, Anders, 1963, The Debris slides at Ulvédal, western
Norway—an example of catastrophic slope processes in
Scandinavia: Akad. der Wissenschaften in Gottingen,
II. Math-Phys. Klasse, Nachrichten Nr. 13, p. 195—210.

Rice, R. M., Corbett, E. S., and Bailey, R. G., 1969, Soil
slips related to vegetation, topography and soil in south-
ern California: Water Resources Research, v. 5, p. 647—
659.

Russell, R. J., 1968, Where most grains of very coarse sand
and fine gravel are deposited: Sedimentology, v. 11, p.
31—38.

Schoklitsch, Armin, 1937, “Wasserbau” (Hydraulic Struc-
tures): New York, Amer. Soc. Mechanical Engineers,
v. 1, 488 p., translated from the German by Samuel
Shulits.

Schulz, E. F., Wilde, R .H., and Albertson, M. L., 1954,
Influence of Shape on the Fall Velocity of Sedimentary
Particles: U.S. Army, Corps of Engineers, Missouri
River Div. Sediment Series No. 5, Fort Collins, Colo.
161 p.

Schwarz, F. K., 1970, The Unprecedented rains in Virginia
associated with the remnants of Hurricane Camille:
Monthly Weather Review, v. 98, no. 11, p. 851—859.

Scott, K. M., and Gravlee, G. 0., Jr., 1968, Flood surge on
the Rubicon River, California—hydrology, hydraulics
and boulder transport: U.S. Geol. Survey Prof. Paper
422-M, 40 p.

Sharpe, C. F. S., 1938, Landslides and Related Phenomena:
New York, Columbia Univ. Press, 137 p.

Shulits, Samuel, 1941, Rational equation of river—bed profile:
Am. Geophys. Union Trans., 22d Annual Mtg., Pt 3,
p. 622—631.

New York, Har-

and

of the relationship of

I

Simpson, P. S., and Simpson, J. H., Jr., 1970, Torn Land:
Lynchburg, Va., J. P. Bell 00., Inc., 429 p.

Swanston, D. N., 1969, Mass wasting in coastal Alaska: U.S.
Dept. Agric. Forest Service Research Paper PNW—83,
15 p.

Thompson, H. J., 1969, The James River flood of August
1969 in Virginia: Weatherwise, Oct. 1969, p. 180—183.

Tricart, J., 1960, Quelques données au sujet du réle de la
neige dans la crue du Guil en juin 1957: Revue de
Géographie alpine, t. 48, no. 2, p. 333—344.

Varnes, D. J., 1958, Landslide types and processes: in
Eckels, E. B., ed., Landslides and Engineering Prac-
tice: NAS—NRC, Publ. 544, Highway Research Board
Spec. Report 29, p. 20—47.

Wenner, C. —G., 1951, Data on Swedish landslides: Geol.
Foren. Stockholm Fo'rhandlingar, v. 73, p. 300—308.

White, J. F., 1966, Convex-concave landslopes: a geometrical
study: Ohio Jour. Sci., v. 66, p. 592—608.

Williams, G. E., 1970, the Central Australian stream floods
of February-March 1967: Hydrology, v. XI, no. 2, p.
185—200.

1971, Flood deposits of the sand-bed ephemeral
streams of Central Australia: Sedimentology, v. 17, p.
1—40.

Williams, G. P., and Guy, H. P., 1971, Debris avalanches——
a geomorphic hazard in Coates, D. R., edit, Environ-
mental Geomorphology: Binghamton, N. Y., State Univ.
New York, p. 25—46.

Wischmeier, W. F., and Smith, D. D., 1965, Predicting rain-
fall-erosion losses from cropland east of the Rocky Moun-
tains: U. S. Dept Agric., Soil Conservation Service Hand-
book 282, 47 p.

Wolman, M. G., 1954, A method of sampling coarse river-
bed material: Am. Geophys. Union Trans., v. 35, no. 6,
p. 951—956.

and LeOpold, L. B., 1957, River flood plains: some
observations on their formation: U.S. Geol. Survey
Prof. Paper 282—C, p. 86—109.

Yarnell, D. L., 1935, Rainfall intensity—frequency data: U.S.
Dept. Agric. Misc. Pub. no. 204, 68 p.

Yatsu, Eiju, 1959, On the discontinuity of grainsize fre-
quency distribution of fluvial deposits and its geomor-
phological significance: Internat. Geographical Union,
Regional Conference Japan 1957, Proc., p. 224—237.

Zingg, A. W., 1940, Degree and length of land slope as it

affects soil loss in runoff: Agri. Engineering, v. 21, p.
59—64.

 

 

* U-S. GOVERNMENT PRINTING OFFICE: 1973*543—578/43

 

 

 

 

 

nrv 1""

 

 

 

 

 

 

 

Lower and Lower Middle Devonian
Rugose Corals 0f the N
Central Great Basin

 

 

 

 

 

 

 

 

 

 

 

 

 

Lower and Lower Middle Devonian
Rugose Corals of the
Central Great Basin

By C. W. MERRIAM

 

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 805

A stratigraphic—paleontologic study of
rugose corals as aids in age
determination and correlation of
Great Basin Devonian rocks with
those of other regions

 

 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1974

 

 

 

 

UNITED STATES DEPARTMENT OF THE INTERIOR

ROGERS C. B. MORTON, Secretary

 

GEOLOGICAL SURVEY

V. E. McKelvey, Director

Library of Congress catalog-card No. 73600011

 

 

For sale by the Superintendent of Documents, US. Government Printing Office
Washington, DC. 20402 — Price $52.85 (paper cover)
Stock Number 2401—02488

 

 

 

 

 

Abstract . ......................
Introduction .. ...............
Purpose and scope of investigation ..................................

 

History of investigation
Methods of investigation.
Acknowledgments ..............................................................
Stratigraphy of central Great Basin Devonian rocks ............
Great Basin Devonian facies belts and coral
reference sections ...................................................
Antelope-Roberts Mountains facies belt.
Lone Mountain reference section ......................
Nevada Formation, unit 1 ..........................
Nevada Formation, unit 2 .....
Nevada Formation, unit 3 ..........................
Nevada Formation, unit 4 ..........................
Nevada Formation, unit 5 .....
Devils Gate Limestone ................................
Southern Sulphur Spring Range
reference section ......................................
Beacon Peak Dolomite Member ...............
Nevada Formation, unit 1 ...........................
Nevada Formation, unit 2 ...........................
Sentinel Mountain Dolomite Member...
Woodpecker Limestone Member ..............
Bay State Dolomite Member .........
Devils Gate Limestone .......
Diamond Mountains facies belt ..........
Beacon Peak Dolomite Member .......
Oxyoke Canyon Sandstone Member...
Sentinel Mountain Dolomite Member ............
Woodpecker Limestone Member ..........
Bay State Dolomite Member .............
Devils Gate Limestone ...............
Monitor—Simpson Park facies belt ................
Rabbit Hill Limestone ........................................
Coral biostratigraphy of the central
Great Basin Devonian .....................................................
Early and early Middle Devonian coral zones.
Coral zone A ....................................................
Coral zone B .....
Coral zone C .....
Coral zone D ...................................
Middle Middle Devonian coral zones ..............................
Coral zone E ................................................................
Coral zone F .....
Coral zone G ........
Late Middle and Late Devonian coral zones ............
Coral zone H ................................................................
Coral zone I...
Biofacies aspects of Devonian coral distribution
and zonation ....................................................................
Syringaxon biofacies .
K obeha biofacies ................................................................
Papiliophyllum biofacies
Breviphrentis biofacies .....
H exagonaria-Sociophyllum biofacies ..............................
Phillipsastraea biofacies ....................................................

 

 

 

 

  
 
  
 
 
  
  

  
 
 
 

 
 

 
 
 

 

 

 
 

 

CONTENTS

 
 

 

 

 
 
 

 

 

 

 
 

 

 

  
 
 
  
 
  
 
 
 
  
 
  

Page
Coral succession and evolution as related to geologic
change and faunal migration ........................................ 25
Coral changes at close of Silurian .................................... 27/
Late Silurian and Devonian bursts of rugose
coral evolution ......................................................... 28
Zone D coral burst ........................ 28
Zone F coral burst .............................................. 28
Zone I coral burst ........................................................ 29
Age and correlation of Great Basin Early and early
Middle Devonian coral zones ........................................ 29
Age and correlation with distant regions. 29
Coral zone A ................................................................ 29
Coral zone B 29
Coral zone C ................................................................ 29
Coral zone D ................................................................ 30
Correlation with other areas in the Cordilleran Belt.... 30
North-central Great Basin ........................................ 31
Northern Sulphur Spring Range ......... 31
Southern Tuscarora Mountains ........... 31
Cortez Mountains ....................... .. 31
West-central Great Basin .......................................... 31
Toiyabe Range .................................................... 31
South-central Great Basin. 32
Hot Creek Range ................................................ 32
Southern Great Basin ................................................ 32
Ranger Mountains 32
Desert Range ...................................................... 32
Northern Panamint Mountains ........................ 32
Funeral Mountains ..................... 32
Northern Inyo Mountains .................................. 33
Systematic and descriptive paleontology ................................ 33
Classification of Great Basin Early and early
Middle Devonian Rugosa .............................................. 33
Taxonomic interpretation of rugose coral structure ...... 34
Exterior corallum features ........................................ 34
Taxonomic evaluation of corallum interior
structures ........................................................ 35
Septa ................. 35
Tabulae ..................................... 36
Dissepiments ..................................... 36
Stereoplasmic deposits ................. .. 37
Rugose coral symmetry and taxonomy .................... 37
Growth changes and reproductive features ............ 37
Variation and dimorphism ............................. 38
Descriptive terms ........................................ 38
Family Laccophyllidae ........................ 38
Genus S yringaxon ............. 39
Family Streptelasmatidae ......................................... 40
Subfamily Siphonophrentinae ......................... 41
Genus Siphonophrentis ............. 41
Subgenus Breviphrentis ..................... 42
Genus N evadaphyllum .................................. 44
Family Kodonophyllidae .................... 44
Family Stauriidae ................................................ 45
Genus Dendrostella .................. 45
Family Halliidae .................................. 46
Subfamily Halliinae ........................................ 46

 

 

IV CONTENTS

 
  
  
 
  

  

 

 

 

  
  
 
  

   

 

 

 

 

Page Page
Systematic and descriptive paleontology—Continued Systematic and descriptive paleontology—Continued
Family Halliidae—Continued Family Disphyllidae—Continued
Subfamily Halliinae—Continued Genus Hexagonaria .................................................... 60
Genus Aulacophyllum ............................... 46 Subgenus Pinyonastraea 61
Genus Odontophyllum ............................... 47 Genus Billingsastraea ...................................... 62
subfamily Papiliophyllinae 47 Family Cystiphylloidae ............................ 64
Genus K obeha ......................................... 47 Genus Cystiphylloides ..... 65
Genus Papiliophyllum ........................... 50 Family Digonophyllidae ............... 67
Genus Eurekaphyllum 52 Subfamily Digonophyllinae ...................................... 67
Family Bethanyphyllidae .................. 53 Genus M esophyllum .......................................... 67
Genus Bethanyphyllum .................................. 53 Subgenus M esophyllum sensu stricto ...... 68
Family Chonophyllidae ........................................... 55 Subgenus Arcophyllum ............................ 68
Genus Sinospongophyllum ...... 55 Subfamily Zonophyllinae ............................... 70
Family Endophyllidae ...................................................... 56 Genus Zonophyllum 70
Genus Australophyllum ............................................. 57 Locality register .......................................................................... 71
Family Disphyllidae ............... 58 Selected references 74
Genus Disphyllum ...................................................... 58 Index _______ ._ 79
ILLUSTRATIONS
[Plates follow index]
PLATE 1 Syringaxon.
2 K obeha and siphonophrentoid coral.
3 Kobeha.
4. Kobeha.
5. Kobeha.
6 Kobeha.
7 Papiliophyllum.
8. Papiliophyllum and Eurekaphyllum.
9. Odontophyllum, Aulacophyllum and Aulacophyllum-like rugose corals.
10. Bethanyphyllum.
11. Bethanyphyllum.
12. Bethanyphyllum.
13. (?) Kodonophyllum, Nevadaphyllum, Nevadaphyllum-like rugose coral, and Bethanyphyllum.
14. Siphonophrentis (Breviphrentis).
15. Siphonophrentis (Breviphrentis).
16. Siphonophrentis (Breviphrentis).
17. Sinospongophyllum and Siphonophrentis (Breviphrentis) .
18. Dendrostella and Disphyllum.
19. Cystiphylloides.
20. Cystiphylloides and Zonophyllum.
21. M esophyllum and M esophyllum (Arcophyllum).
22. M esophyllum (Arcophyllum),
23. Cystiphylloides and Hexagonaria (Pinyonastraea).
24. Billingsastraea.
25. Australophyllum, Billingsastraea?, and (?) Hexagonaria.
Page
FIGURE 1 Index map showing occurrences of Lower and lower Middle Devonian rugose corals in the central and
southern Great Basin 2
2 Map showing distribution of Lower and lower Middle Devonian marine facies belts in the central Great Basin... 7
3. Geologic map and cross section of part of Lone Mountain showing lithologic units in the Nevada Formation ......... 10
4 Geologic sketch map showing Silurian and Devonian units in southern Sulphur Spring Range .................................. 12
5 Geologic cross section showing Devonian stratigraphic units and coral zones in the southern
Sulphur Spring Range ....................................................................................................................................................... 13
6. Columnar diagram showing relationships of the Devonian reference sections of Lone Mountain and
Sulphur Spring Range to Devonian sections of the Monitor Range .......................................................................... 14
7. Columnar diagram showing relationship of the Devonian reference sections of Lone Mountain and
Sulphur Spring Range to that of the Diamond Mountains facies belt at Oxyoke Canyon .................................. 16

 

 

 

 

CONTENTS V
. Page
FIGURE 8. Diagram showing the Great Basm Devonian coral zones, equivalent rock units, coral biofacies, and
previously employed biostratigraphic designations ........................................................................................................ 18
9. Characteristic rugose coral genera of central Great Basin Late Silurian, Early Devonian, Middle Devonian, and
Late Devonian coral zones, showing known and inferred vertical ranges ................................................................ 26
TABLE
Page

TABLE 1. Evolutionary coral bursts in the Great Basin during the Silurian and Devonian Periods ............................................ 28

 

 

 

 

 

 

 

 

 

 

LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS
OF THE CENTRAL GREAT BASIN

 

By C. W. MERRIAM

 

ABSTRACT

Rugose corals of the Great Basin Devonian seaways under-
went three major bursts of evolutionary activity: (1) in late
Early to early Middle Devonian (early Eifelian) time; (2) in
the medial Middle Devonian (late Eifelian); (3) in Late
Devonian (Frasnian) time. No Rugosa are known in the
highest Devonian (Famennian) of this province. The product
of the first of these bursts of evolution is part of the subject of
this paper.

Devonian rocks of the central Great Basin occur in three
north-south facies belts of which the Antelope-Roberts Moun-
tains belt is the more important in terms of Early and Middle
Devonian coral distribution. No Rugosa were found in Early
and early Middle Devonian rocks of this age of the Diamond
Mountains facies belt on the east, where strata of this age are
barren dolomite and siliceous sandstone. Within the Monitor—
Simpson Park facies belt on the west, only the earliest Devon-
ian Rabbit Hill Limestone coral fauna is known.

Nine successive coral zones are defined in the Nevada For-
mation and overlying Devils Gate Limestone of the Antelope-
Roberts Mountains belt. These zones have been designated A
through I in ascending stratigraphic order. Described and illus-
trated herein are Rugosa and Early Devonian coral zones A,
B, and C and those of coral zone D, which is Early and early
Middle Devonian. Rugosa of coral zone A are best known in
the westerly Monitor—Simpson Park belt, where they charac-
terize the Syringaxon facies of the Helderbergian Rabbit Hill
Limestone.

The first great burst of Devonian coral activity is that of
coral zone D, followed by an even greater differentiation of
certain families in coral zone F, which is marked by spread of
the Disphyllidae and Digonophyllidae and disappearance of
Halliidae and Bethanyphyllidae of the older coral zones. Late
Devonian strata of coral zone I have few surviving rugose coral
families. However, the newly arrived and very distinctive
Phillipsastraeidae evolved rapidly and became abundant as
colonial and solitary forms here as in most of the Late Devon-
ian throughout the world. No Rugosa have been found in the
latest Devonian of the Great Basin.

Of 13 families of Rugosa in the Great Basin Silurian, 8 do not
continue on in the Devonian. Eleven Devonian rugose coral
families are described in the Great Basin province, of which
only the Laccophyllidae, Streptelasmatidae, and Chonophyl-
lidae carry over from the Silurian as major Devonian groups.
By early Middle Devonian time five new families have
appeared: Halliidae, Bethanyphyllidae, Disphyllidae, Cysti-
phylloidae, and Digonophyllidae. These may have evolved
from such Silurian stocks as the Lykophyllidae, Kyphophyl-
lidae, and Cystiphyllidae.

 

Halliidae are especially characteristic of Early Devonian
beds in coral zones B and C. The small solitary Syringaxon of
the Laccophyllidae is the only rugose coral in most deposits of
coral zone A. Locally, however, the compound genus Australa-
phyllum of the Endophyllidae carries over from Late Silurian
coral zone E to the Early Devonian Rabbit Hill of Devonian
coral zone A.

Of Early Devonian Halliidae, the endemic Kobeha and
Papiliophyllum are known only in the Great Basin province.
Corals of the subfamily Siphonophrentinae of the Streptelas-
matidae are abundant in coral zones C and D where they
paralleled the Onondaga and older members of this subfamily
in eastern North America. Billingsastraea nevadensis of coral
zone D is similar to species in somewhat older beds of eastern
North America. Coral zone D Digonophyllidae of the genera
Mesophyllum and Zonophyllum are significant ties with the
Rhine Valley Middle Devonian of western Europe.

INTRODUCTION

Corals are among the common fossils in Great Basin
Devonian rocks. Of the two extinct Paleozoic Orders,
Tabulata and Rugosa, the first is more abundantly
represented, but the Rugosa by reason of their mor-
phologic diversity, more complex internal features,
and greater evolutionary plasticity prove to be a more
rewarding subject for stratigraphic paleontology and
provide better material for taxonomic study and inves-
tigation of evolutionary trends through the Devonian
strata.

Like present-day Zoantharia, the extinct Rugosa
were beyond doubt highly sensitive to environmental
vicissitudes, and their geographic-stratigraphic dis-
continuities within the Great Basin Devonian clearly
reflect environmental control. Within the Great Basin
geologic province (fig. 1), the central Great Basin
Devonian includes a great diversity of marine rock
types or lithofacies and illustrates better than other
parts of the province a wide range of coral biofacies.
For example, the sandstones and dolomites of Early
and early Middle Devonian age in the Diamond
Mountains facies belt have yielded no rugose corals.
To the west, however, in the impure limestones of the
Antelope-Roberts Mountains facies belt (fig. 2), corals
become abundant and taxonomically diverse within

1

 

 

 

LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

 

  
  
 

 

 

 

 

    

 

 
   

 

 

 

 

 

 

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FIGURE 1.—Index map showing occurrences of Lower and lower Middle Devonian rugose corals in
the central and southern Great Basin. Symbols indicate Devonian coral zone.

 

INTRODUCTION 3

EXPLANATION
LOWER AND LOWER MIDDLE DEVONlAN
RUGOSE CORAL OCCURRENCES

Coral zone F, Middle Devonian (Eifelian)
Coral zone E, Middle Devonian

Coral zone D, late Early and Middle Devonian
Coral zone C, late Early Devonian

Coral zone B, Early Devonian (Oriskany)
Coral zone A, Early Devonian (Helderberg)

NUMBERED LOCALITIES

Lone Mountain map area (see fig. 3)

. Southern Sulphur Spring Range map area (see fig.4)

. Roberts Creek Ranch (M1042)

. Roberts Mts., Cooper Peak area (M1073)

Roberts Mts., Niel Creek area (M1072)

. Simpson Park Mts., Walti Ranch (M1074)

. Simpson Park Mts., Coal Canyon (M1075)

. Cortez Mts., (M1083)

. Mineral Hill area; McColley Canyon

10. Modoc Peak (M1071)

11. Combs Peak (M27)

12. Grays Canyon (M3; M51) '

13. Northern Antelope Range (M1035)

14. Northern Antelope Range (M1053)

15. Fish Creek Range (M1033)

16. Cockalorum Wash area, southeast of Eightmile Well
17. Rabbit Hill (M48; M187)

18. Northern Toquima Range, Petes Canyon area (M1150)
19. Toiyabe Range, west side south of Reeds Canyon (M1151)
20. Dobbin Summit (M1067; M1068; M1069)

21. Hot Creek Canyon (M1066)

22. Northern Panamint Range (M184; M1065)

23.‘ Funeral Mts. (M1059; M1060; M1061; M1062; M1063; M1064)
24. Ranger Mts. (M1034; M1058)

25. Desert Range (M1057)

Note: Numbers preceded by M are

USGS (Menlo Park) fossil localities

>00>ml

tom—ampwuscomga

about the same stratigraphic interval. Yet, farther
west, rugose coral faunas of limestones characterizing
the Monitor—Simpson Park facies belt are extremely
restricted taxonomically; most sections contain but a
single genus of small solitary coral.

In a time-rock sense a great part of the Devonian is
doubtless recorded by the 3,500—4,000 feet of marine
strata which make up the system in this province
(Merriam, 1940). Dolomite and limestone of shallow-
water shelf environments predominate. The Devonian
dolomite, which is mainly of diagenetic origin, espe-
cially characterizes the eastern Great Basin; for the
province as a whole, diagenetic dolomite occupies a
greater outcrop area than limestone. Where dolomite
and limestone facies come together in the central Great
Basin, the vertical and lateral changes are complex;
within this belt of unstable, fluctuating environment
the vertical range and geographic spread of coral
species were greatly affected by facies restrictions.

 

Corals are more conspicuous on the outcrop and are
seemingly more numerous in Devonian argillaceous
and silty limestones than in the cleaner carbonate
rocks. To some extent this seeming fossil abundance
may be misleading. The collector soon recognizes that
fossils weather free and are more easily obtainable on
the shaly, rubbly erosion surfaces formed by argilla-
ceous limestones than on the denser, less impure,
albeit fossil-rich carbonate rocks. In the past most
Great Basin Devonian fossil collecting by geological
exploring parties was from loose weathered material
of this nature.

Systematic fossil collecting during the 1930’s in
conjunction with geologic mapping of central Nevada
Devonian rocks demonstrated the stratigraphic utility
of rugose corals and was the initial inspiration for
this project. More recently the Cordilleran Rugosa of
Silurian and Devonian ages and those of eastern
North America became the subject of detailed re-
search by several coral specialists. Progress since 1940
in the light of world advances in the knowledge of
rugose coral structure, classification, stratigraphic dis-
tribution, and ecology makes possible a more mean-
ingful approach to continued study of western Rugosa
than would earlier have been possible.

PURPOSE AND SCOPE OF INVESTIGATION

The primary objectives of this study are the descrip-
tion, classification, and illustration of Great Basin
Lower and lower Middle Devonian Rugosa in accord-
ance with modern standards and techniques, together
with the interpretation of their evolutionary history
in the light of new knowledge of their stratigraphic
ranges and geographic occurrences. A proposed zona-
tion based on the corals is the chief product of these
paleontologic researches; in addition, geologic map—
ping and structural interpretation of the areas in
which the Devonian reference sections are situated
have been accomplished.

Study of the Devonian rugose corals and their eco-
logic associates has an important bearing upon geo-
logic correlation of the Great Basin strata with strata
elsewhere in the Cordilleran belt and with standard
Devonian sections in eastern North America and
Europe, especially in the Rhine Valley region. These
studies point up the endemic character of some Great
Basin coral genera and the more cosmopolitan nature
of others.

In this report the descriptive and taxonomic paleon-
tology includes only the rugose corals of the Rabbit
Hill Limestone and the lower half of the Nevada
Formation; the “barren zone” or coral zone E is an
appropriate cutoff horizon above which entirely dif-
ferent coral faunas were introduced.

 

4 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

HISTORY OF INVESTIGATION

Study of Great Basin Devonian rugose corals began
with Meek’s (1877, p. 25—33, pl. II) description of
Upper Devonian species collected in the White Pine
mining district, Nevada, by the 40th Parallel party.
Meek was guided in this modest contribution by the
memoirs of Edwards and Haime (1851; 1850—54),
whose works set high standards for coral research and
remained the authoritative references on this subject
for more than a half century.

Coral-rich Devonian strata, the subject of this re-
port, were discovered by pioneering geologists who
made the first topographic and geologic map of the
Eureka mining district, Nevada, in the 1880’s (Hague,
1892). Paleozoic coral research was at that time in a
static phase, largely because of technical difficulties in
thin-section preparation. Although large collections of
loose corals were zealously made by Walcott and his
field associates, it is not surprising to find that “Pale-
ontology of the Eureka District” (Walcott, 1884, p.
104—106), published an amazingly short time after
fieldwork, gave scant attention to the rugose corals.
None were illustrated.

The Eureka district Devonian coral material de-
posited in the U.S. National Museum was supple-
mented considerably during the 1920’s by the efforts
of Edwin Kirk of the U.S. Geological Survey, who
revisited many of Walcott’s localities and discovered
new localities in outlying areas. At Kirk’s suggestion,
the writer in 1933 began a program of sectioning and
study of Lower and lower Middle Devonian Rugosa
collected in the course of a geologic reconnaissance of
the Roberts Mountains. Comparisons were made with
the Eureka material and with Great Basin material
collected by earlier Great Basin exploring parties.
(The earlier material was also on deposit in the Smith-
sonian.) At the outset of this program it became evi-
dent that the older Eureka district collections had
limited stratigraphic value, because of the manner in
which collecting and reconnaissance geology were
done in the 1880’s. Some of the collections rather
certainly represent fossils taken from 100 feet to
several hundreds of feet of strata, but they are included
in a single lot; hence, cautious evaluation and sort-
ing is required for purposes of detailed stratigraphy
and ecologic association by present standards.1 '

Systematic thin-section study of American Devon-

‘According to Edwin Kirk (oral commun., 1935: written commun., 1954),
Walcott had described to him the manner in which some of the Devonian
fossil collecting was done at Lone Mountain and at the Eureka vicinity. Sev-
eral U.S. Naval Academy midshipmen attached to the Hague party for sum-
mer engineering experience were assigned to fossil collecting under Walcott’s
supervision. Large piles of corals and other fossils, found at central locations
on the outcrop about 1928, were believed by Kirk to be unretrieved caches of
the Annapolis trainees.

 

ian corals was little advanced at the inception of this
investigation in 1933. Few published descriptions were
accompanied by adequate illustration of internal
corallum structure, thus preventing meaningful com-
parison. Progress in Europe was more rapid. A mile-
stone in Paleozoic coral research was the burst of
activity at Marburg, Germany, by Rudolf Wedekind
and his colleagues during the 1920—36 period. De-
tailed descriptions and thin-section illustrations of
Rhine Valley Devonian Rugosa by these workers have
had special value in connection with identification and
classification of Great Basin and other American far-
western forms. Although the coral taxa of Wedekind
and his associates are keyed to stratigraphic units and
have value as zonal indices, their excessive generic
splitting is a controversial feature. Doubtless many
Wedekind genera will eventually be reduced in rank
or combined in synonymy by more conservative
workers (Birenheide, 1962a; 1964).

Stumm’s (1937; 1938; 1940) descriptive work on
Devonian rugose corals of the Eureka district and
adjacent areas dealt mainly with the Smithsonian col-
lections mentioned above. These contributions placed
on record previously unknown Early and Middle
Devonian genera and provided a foundation for con-
tinued taxonomic work upon these partly endemic
Great Basin forms.

Since 1940 general progress in the understanding of
the Rugosa has been great, with a rapidly expanding
world literature, some of which is referred to in the
section “Systematic and Descriptive Paleontology.”
Among indispensable compendia are:

(1) “Index of Paleozoic Coral Genera,” by Lang,
Smith, and Thomas (1940) . -

(2) “Revisions of the Families and Genera of the
Devonian Tetracorals,” by Stumm (1949) .

(3) “Rugosa,” by Hill (1956) in “Treatise on
Invertebrate Paleontology.”

To a considerable extent these Great Basin Silurian
and Devonian coral studies were a product of geologic
mapping and stratigraphy which were stimulated by
economic and resource factors. Search for petroleum
and metals in the Great Basin and successful oil explor-
ation in Devonian rocks of western Canada within the
past 25 years have encouraged study of all aspects of
the stratigraphy and paleontology. For the first time
meaningful comparison of Great Basin faunas with
those of the northern Cordilleran Belt has become
possible. Thus far close paleontologic similarities are
evident mainly among higher Middle and Upper
Devonian species, rather than among fossils of the
lower zones here dealt with.

Most of the corals described and figured herein

 

 

INTRODUCTION 5

were collected after 1947, during the course of geo-
logic mapping and stratigraphic investigation in the
Eureka mining district, Nevada, and adjacent areas
by the writer in conjunction with the detailed geo-
logic mapping program of T. B. Nolan. Central Great
Basin Devonian collections were supplemented from
time to time by coral material collected by US. Geo-
logical Survey mapping parties in other parts of the
province. In 1959 the mapping and stratigraphic
effort involving Silurian and Devonian rocks of six
15-minute quadrangles west of the Eureka mining dis-
trict was revitalized under the Kobeh Valley project
of Nolan and Merriam.

METHODS OF INVESTIGATION

Understanding the fossil distribution in the greatly
dislocated strata of the Great Basin Paleozoic requires
fairly detailed geologic mapping in order to set up
reliable reference sections. At best the standard
paleontologic column is a composite of stratigraphic
segments in disconnected structural blocks. Further
complexities are introduced by profound facies
changes, as for example the almost complete dis-
appearance of siliceous sandstone in the Lower Devo-
nian between the Diamond Mountains and Lone
Mountain. Dependable key beds with great lateral
continuity are uncommon in the Devonian rocks of
this vicinity. Attempts have been made to relate fossil
occurrences to structure sections prepared in the
advanced stages of the mapping procedure.

Stratigraphic data applicable to Devonian rugose
coral zonation have accrued from geologic mapping
since 1959 in the Whistler Mountain, Bartine Ranch,
and parts of the Garden Valley and Cockalorum Wash
quadrangles. Much light is shed upon the profound
Lower Devonian facies changes by the mapping of
T. B. Nolan near Eureka, especially in the southern-
most Diamond Mountains in the Pinto Summit quad-
rangle.

The more continuous measurable Devonian sections
within this region of thrust faulting occupy car-
bonate autochthons. Like the central mass of Lone
Mountain (fig. 3), these more rigid strata are little
deformed by thrusting, but they are cut by innumer-
able high-angle faults which break stratigraphic con-
tinuity. In this connection Lone Mountain, including
the primary Devonian coral reference section, has
been separately mapped.

Lone Mountain provides an excellent example of
highly complex Great Basin geologic structure where-
in stratigraphic sections unaffected by pervasive thrust
and normal faulting are indeed exceptional. The cen-
tral part of the mountain is a fairly straightforward

 

homocline of marine beds, mostly carbonate, ranging
in age from early Middle Ordovician to late Middle
Devonian. However, the lower or pediment slopes
reveal an entirely different and highly complex pattern
of thrusting which involves Ordovician graptolitic
beds, Permian limestones, and Devonian limestones.
Lone Mountain discloses to advantage the char-
acteristic structure pattern of the region — thrusting
followed by high-angle, mostly normal, faulting.

To the south beyond the limits of this study in the
Fish Creek Range occur Middle Devonian rocks of
coral zone F, lithologically quite different from the
normal autochthonous carbonates of this interval;
these highly deformed southern partly argillaceous
facies occupy what appear to be major thrust plates.

Coral collecting by the writer and associates during
the initial phase of this study (Merriam, 1940) was
in considerable part from loose weathered material,
precise stratigraphic horizon not being rigorously
determined. In later years more of the collecting was
done bed-by-bed on measured sections to secure in
situ associations, a procedure greatly facilitated by
new and accurate topographic maps. Whereas sections
were measured by tape and Brunton for collecting
purposes within the mapped areas, large-scale map
location of collecting sites was found to be more reli-
able because of pervasive faulting, which was difficult
to recognize or interpret where stratigraphic observa-
tions are confined to individual traverse courses.

Little progress has been made in biofacies study of
the Great Basin rugose corals and their ecologic asso-
ciates. Whereas Rugosa are dominant megafossils in
some lithologic units, in others they are numerically
less important elements of varied assemblages con-
taining corals, brachiopods, mollusks, and trilobites.
A good biofacies indicator is Syringaxon of the Early
Devonian Rabbit Hill Limestone, in which this abun-
dant small solitary genus is normally the only rugose
coral. By contrast coral zone F of the higher Middle
Devonian contains locally abundant large compound
genera in a potentially reef-forming biota.

With regard to relative age and correlation values
of the several phyla, it may be said that specialist
conclusions based upon independent study of sepa-
rate fossil categories have not always agreed with
those founded upon rugose coral research. Converging
and adjusted conclusions from research upon all the
major fossil categories are needed. Some corals are
perhaps better indicators of specific environments
than precise geologic age. In this work the associated
brachiopods have been utilized largely to support the
coral evidence for correlation and age.

 

 

 

6 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

ACKNOWLEDGNIENTS

Among Great Basin workers whose rugose coral
collections have added materially to this study are
the following: J. F. McAllister, Panamint Range and
Funeral Mountains; M. S. Johnson and D. E. Hib-
bard, Ranger Mountains; F. G. Poole, Ranger Moun-
tains; C. R. Longwell, Desert Range; F. J. Kleinhampl,
Monitor Range; H. E. Cook, Hot Creek Range; R. H.
Washburn, Toiyabe Range; J. H. Stewart and E. H.
McKee, Toiyabe and Toquima Ranges; T. B. Nolan,
Eureka mining district; and A. J. Boucot and J. G.
Johnson, northern Sulphur Spring Range and Cortez
Mountains.

An earlier draft of this report was read by the late
E. C. Stumm of the University of Michigan, whose
constructive suggestions regarding taxonomic matters
are appreciated. D. J. McLaren of the Geological
Survey of Canada has been most helpful in providing
information on the type species of Cystiphylloides and
other genera of Devonian rugose corals.

All photographic illustrations are the work of Kenji
Sakamoto of the US. Geological Survey, Menlo Park,
Calif.

STRATIGRAPHY OF CENTRAL
GREAT BASIN DEVONIAN ROCKS

Coral-bearing Devonian formations of the central
Great Basin are in ascending stratigraphic order as
follows: (1) Rabbit Hill Limestone of Early Devonian
(Helderberg) age; (2) Nevada Formation of Early and
Middle Devonian age; and (3) Devils Gate Limestone
of late Middle and Late Devonian age. Physical char-
acteristics of these formations have been described
in other reports (Merriam, 1940, 1963; Nolan and
others, 1956) together with details of their areal dis-
tribution and geologic structure. The Lone Mountain
and Sulphur Spring Range reference columns are
adopted as joint primary yardsticks for these rocks,
supplemented by partial sections in the Devils Gate
area and in the northern Monitor Range.

With reference to Early and early Middle Devonian
coral-bearing strata dealt with in this report, approxi-
mately correlative noncoralline rocks in the Diamond
Mountains to the east comprise entirely different
dolomite and sandstone facies. To the west in the
Monitor and Simpson Park Ranges, the Early Devon-
ian Rabbit Hill Limestone represents yet another
facies belt.

In the Sulphur Spring Range the Early and early
Middle Devonian beds most closely resemble, both
lithologically and faunally, those of the Lone Moun-
tain yardstick, but fortunately include westerly-
reaching quartzitic sandstone tongues from the
Diamond Mountains belt as well as easterly extending

 

 

beds which carry elements of the Rabbit Hill Helder-
bergian fauna of the Monitor—Simpson Park belt.
Hence in this key reference column of the Sulphur
Spring Range, lithologic and paleontologic features of
all these facies belts are rather satisfactorily united.

Most of the stratigraphic units and coral zones
treated in this report occur within the Nevada Forma-
tion of Early and Middle Devonian age, as earlier
redefined by Nolan, Merriam, and Williams (1956, p.
40—48). On the basis of lithology and fossils, this
formation has been subdivided vertically and laterally
in considerable detail. Its more characteristic facies
lie within the Antelope-Roberts Mountains belt, but
the easterly Diamond Mountains dolomite-arenaceous
facies are also included in the Nevada Formation. The
westerly Helderbergian Rabbit Hill Limestone is geo-
graphically separate and, except for its presence in
th northernmost Simpson Park Mountains, is not
known to be present in sections containing the Nevada
Formation. Beds with Rabbit Hill fossils earlier men-
tioned in the Sulphur Spring Range are more closely
allied lithologically to the Beacon Peak Dolomite
Member of the Nevada Formation as defined within
the Diamond Mountains facies belt.

GREAT BASIN DEVONIAN FACIES BELTS
AND CORAL REFERENCE SECTIONS

For purposes of this discussion, Devonian strata of
the central Great Basin may be treated in accordance
with its distribution in three subparallel facies belts
(fig. 2) as follows:

1. Antelope-Roberts Mountains facies belt,
2. Diamond Mountains facies belt,
3. Monitor—Simpson Park facies belt.

Each facies belt possesses distinctive lithologic, struc-
tural, and paleontologic characteristics. Whereas
north-south subparallel alinement of the belts is
today geomorphic-orographic, it may to some extent
reflect the predeformation distribution pattern of sedi-
mentation in shelf seaways of Devonian time.

ANTELOPE-ROBERTS MOUNTAINS FACIES BELT

The Antelope-Roberts Mountains belt stretches
south for about 90 miles from the Sulphur Spring
Range and Roberts Mountains, through the Fish
Creek Range and the Antelope Range. The strata of
this belt probably extend southward in the little-
explored Hot Creek Range. In a time-rock sense nearly
all the Devonian System as known in the Great Basin
is represented within the Antelope-Roberts Mountains
facies belt. A possible exception is the latest Devonian
of the upper Pilot Shale. Characteristic are the fossil-
rich silty and argillaceous limestones of Nevada

 

 

 

 

STRATIGRAPHY OF CENTRAL GREAT BASIN DEVONIAN ROCKS

 

40°—

39°

l
. I
Antelope—Roberts Mountains facies belt
Argillaeeous limestone with subordinate \

 
  
  
 
  
 
 
 
   

1 1 7 ° 1 1 6 °
‘7 l | 1’ l
EXPLANATION ' \K\ 1;} \
0 “ O’ \
7/ ‘4 Q\V“ A? U
//// §§ Mount Ml” m ,5 \
. ./ . Cortez Tenet” gm’ 9: ._ __ ELKO 09 __ ._
D1amond Mountains fames belt \ ~ 12. Railroad , Pass
Dolomite and siliceous sandstone. “in
No corals known I \

dolomitic limestone and calvarem'te; siliceous

sindfitonte interbeds on east side. Corals McClusky \ \
0’ ML (m Peak ‘ a Roberts Greek
4 tn Mulligan Gap
‘ . Garden Pass
. . , § . .Mount
Mon1tor—S1mpson Park fac1es belt \\ Hope
Limestone and calcareous shale; no dolomite. TyGrgge PH’LL’PS$UR
Syringaxon coral facies in Rabbit Hill \
I-IJ \

    
    

 

      
 

      
   

   

Limesume .Mount Callahan

  
  

DIAMOND

KOBEH VAL LEY

   
   
      
     
    
   
  

0
z Whistler Mtn,
< . Lone Mm _
Devils Gate
0:
Signal Peak .
mace Peak.
oAustin
M A H O G A N Y
H I L L S
lu
[D Antelope
\Peak
1'
A.
Reeds \
‘ Canyon
Ix
10 MILES
10 20 KILOMETERS
A

 

S

 

FIGURE 2.—Distribution of Lower and lower Middle D

 

I

evonian marine facies belts in the central Great Basin.

 

 

 

8 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

Formation, unit 2, which have not been recognized in
the other belts. Present along its eastern margin are
quartzitic sandstone and dolomite tongues interpreted
as westerly facies extensions from the Diamond Moun-
tains belt. Situated within this belt are the primary
coral reference sections for the Lower and lower Middle
Devonian at Lone Mountain and in the southern
Sulphur Spring Range.

LONE MOUNTAIN REFERENCE SECTION

Five lithologic units have been used in the detailed
geologic mapping of the Nevada Formation at Lone
Mountain (fig. 3), each characterized by distinctive
rugose corals and other fossils. The stratigraphy and
paleontology are better understood here than at
Modoc Peak, where the Nevada Formation type sec-
tion was earlier designated (Merriam, 1940, p. 15).
However, the Modoc section is in other ways some-
what more representative of the formation as a whole,
for it includes a quartzitic sandstone member of the
easterly Diamond Mountains facies, a tongue which
feathers out completely before reaching Lone Moun-
tain. The map divisions of the Nevada Formation at
Lone Mountain are designated units 1 through 5 in
ascending order.

The basal dolomite of unit 1 rests with a seemingly
gradational boundary upon the upper beds of the
Lone Mountain Dolomite. These lower Nevada dolo-
mites contain the Papiliophyllum fauna of coral zone
C, and the Acrospirifer kobehana fauna of about
Emsian age. No depositional record of the Rabbit Hill
Limestone or of the Beacon Peak Dolomite Member,
each with a Helderbergian fauna and coral zone A,
has been recognized here at Lone Mountain where
they would be expected just above the Lone Mountain
Dolomite. Likewise, coral zone B with Kobeha is not
represented by conclusively identifiable fossils. No
physical evidence of disconformity was found here
at the Lone Mountain Dolomite—Nevada Formation

boundary.
NEVADA FORMATION, UNIT 1

The lower unit of the Nevada Formation (fig. 3) is
about 260 feet thick in Coral Gulch on the south side
of Lone Mountain, where it consists of thick-bedded
blocky dolomite, dolomitic limestone, and limestone
of light-gray to mouse-gray color. Lower beds of unit
1 have much the same appearance as the underlying
Lone Mountain Dolomite, with which it appears to be
gradational at this locality. A disconformity separates
these two formations in the Mahogany Hills and in
the Diamond Mountains belt. Argillaceous matter is
present in the upper beds of this unit where it grades
into unit 2.

Unit 1 becomes less dolomitic traced northwest

 

toward Contact Gulch. Gray chert nodules flattened
parallel to the bedding are characteristic, and the
fossils are generally silicified. Chert and fossils weather
limonite brown.

The lowest identifiable fossils collected from unit 1
at Lone Mountain represent coral zone C. Poorly pre-
served large horn corals at the base may be in coral
zone B. In the Sulphur Spring Range calcarenite with
scattered rounded quartz grains occurs at the bottom
of unit 1 and contains the Kobeha fauna of coral zone
B with Cos tispirifer arenosus.

NEVADA FORMATION, UNIT 2

About 720 feet thick, unit 2 is well exposed in upper
Coral Gulch and upper Fossil Gulch. Because of its
partly argillaceous, thin-bedded, and banded char-
acter, the appearance of unit 2 contrasts sharply in
outcrop with underlying and overlying thicker bedded
units, being more resistant to weathering. The shaly
bands yield loose fossils in large numbers; most of the
collections first made from the Nevada Formation are
from outcrops of this nature. Corals, especially favo-
sitid heads, are abundant in many beds; some are in
their original upright growth position with their base
in a limestone layer, the upper part not uncommonly
having been buried by argillaceous sediment. Unit 2
contains the assemblages of coral zone D in which the
Rugosa reach a peak of abundance and diversity.

No siliceous sandstone was found in unit 2 at Lone
Mountain, but it was found at Combs Peak and Modoc
Peak. The eastward increase of siliceous matter, well
shown in the southern Sulphur Spring Range, reaches
a maximum in the Diamond Mountains southeast of
Eureka where the Oxyoke Canyon Sandstone Member
probably correlates with some part of unit 2.

NEVADA FORMATION, UNIT 3

About 285 feet thick, the dark-gray, well-bedded,
and relatively nonargillaceous limestone of unit 3 is
well exposed on the south side of Lone Mountain,
2,000 feet northeast of West Peak. Many beds and
lenses of crinoidal debris in it tend to be massive;
otherwise fossils are scarce in unit 3. Unit 3 has been
called the “barren zone” compared with the abun-
dantly fossiliferous units below and above. In the
Diamond Mountains at Oxyoke Canyon, the Sentinel
Mountain Dolomite Member, has yielded no fossils.
It is probably a facies equivalent of unit 3, but it is
completely dolomitized. No dolomite was recognized
in unit 3 at Lone Mountain.

NEVADA FORMATION, UNIT 4

A well-bedded division, unit 4, is about 675 feet
thick at Lone Mountain and crops out along the west

 

————7

STRATIGRAPHY OF CENTRAL GREAT BASIN DEVONIAN ROCKS 9

side of the main ridge between Reef Point and North
Peak. Unit 4 includes dense, resistant, fine-grained
limestone, dolomitic limestone, and dolomite. The unit
ranges in color from dull mouse gray to medium and
dark gray, and weathers light gray. These strata
include thin-bedded almost shaly intervals and thick-
bedded massive dolomite lenses. Rugose corals and
stromatoporoids are abundant locally within the thick-
bedded dolomitic bodies. Chert nodules weathering
limonite brown are fairly numerous, and fossils are
commonly‘ silicified. Unit 4, with numerous colonial
and solitary rugose coral genera, represents Devonian
coral zone F, the interval of greatest differentiation of
the colonial Rugosa in Middle Devonian time.

In the Fish Creek Range south of Eureka, Middle
Devonian beds correlative with the Nevada Forma-
tion, unit 4 include black shale and siltstone with
light-gray limestone bodies locally rich in rugose
corals like those of unit 4 at Lone Mountain. In both
places these loci of coralline proliferation suggest
incipient bioherms or patch reefs.

The Woodpecker Limestone Member of Nolan,
Merriam, and Williams (1956, p. 44) is the equivalent
of unit 4 in the Diamond Mountains, where it includes
more platy and shaly limestone, some of which is
pinkish in color. The thick-bedded dolomitic bodies
with a coral biota were not found in the Diamond
Mountains facies belt.

NEVADA FORMATION, UNIT 5

Unit 5, the uppermost unit of the Nevada Forma-
tion, is about 570 feet thick at Lone Mountain and
consists of thick-bedded and massive saccharoidal
dolomite and dolomitic limestone of dark-, medium-,
and light-gray color. Alternation of very dark gray
and light-gray thick dolomite beds is characteristic.
This resistant unit forms the summit ridge of Lone
Mountain between Flag Point and North Peak. It is
overlain by massive cliff-forming Devils Gate Lime-
stone, the lowest beds of which are crowded with
Amphipora, as is well shown on the first main spur
east of Section Ridge (fig. 3).

Unit 5 is sparsely fossiliferous at Lone Mountain.
There are scattered deposits of the large brachiopod
Stringocephalus. However, the organic structure of
brachiopods and stromatoporoids is largely destroyed
by dolomitization. The Bay State Dolomite Member
of the Diamond Mountains belt is the approximate
equivalent of the Nevada Formation, unit 5. Thick
beds with Stringocephalus are best shown in that belt.
Limestone beds near the base of the Bay State Dolo-
mite Member contain rugose corals of coral zone G
and the brachiopod Rensselandia.

 

DEVILS GATE LIMESTONE

The upper Middle and Upper Devonian Devils Gate
Limestone (Merriam, 1940, p. 16-17; 1963, p. 49—56)
is about 1,200 feet thick and rests conformably upon
the dolomites of Nevada Formation, unit 5 at Lone
Mountain. It consists mainly of limestone in most
localities; locally the lower part has been subjected to
patchy, irregular dolomitization (Merriam, 1963, p.
51) . At Lone Mountain the Devils Gate is the highest
unit of the central autochthon and consists of medium-
dark to dark-gray well-bedded limestone with scat-
tered massive, cliff-forming bodies. The topmost strata
are not exposed here; these abundantly fossiliferous
beds are best seen at Devils Gate or in the Newark
Mountain vicinity of the Diamond Mountains, accord-
ing to Nolan, Merriam, and Williams (1956, p. 48—
52), where both top and bottom are well exposed.

Clear-cut lithologic subunits are more difficult to
define and trace within the Devils Gate Limestone
than in the Nevada Formation because of greater rock
uniformity in the former. However, the upper 250—300
feet are quite readily separable by somewhat thinner
bedding, the presence of dark-gray Chert, large lenses
and beds of depositional mud-breccia, and the great
local abundance Of shell fossils. The lower half of the
Devils Gate everywhere includes a great deal of lime-
stone formed by massive concentric stromatoporoids
and Amphipora as at Lone Mountain, but in general
corals and shell fossils are abundant only in widely
scattered pockets. It has recently been found that the
large brachiopod Stringocephalus, thought previously
to be confined to the Nevada Formation, unit 5 (Bay
State Dolomite Member), ranges up into thick-bedded
massive limestones which characterize the lower third
of the Devils Gate at Lone Mountain.

SOUTHERN SULPHUR SPRING RANGE REFERENCE SECTION

Devonian rocks of the Nevada Formation underlie
most of the southern Sulphur Spring Range east of
the Mulligan Gap fault (fig. 4). The five Nevada
Formation units or their time-stratigraphic equiva-
lents described at Lone Mountain are present, but
the Devonian column is more inclusive in the Sulphur
Spring Range; stratigraphically beneath the Nevada
Formation, unit 1 are dolomites and dolomitic lime-
stones containing Helderbergian Rabbit Hill fossils.
These earliest Devonian beds (for this region) are
not found at Lone Mountain and are assigned to the
Beacon Peak Dolomite Member. In the Diamond
Mountains facies belt where the Beacon Peak is
described, it is the lowermost member of the Nevada
Formation. The overall lithologic makeup of the refer-
ence section of the Sulphur Spring Range Devonian

 

/

ction. Geologic cross

 

indicate Devonian coral zones.

 

 

 

ogic units in the Nevada Formation of this reference se

0 tain reference section. Letters

 

r?

STRATIGRAPHY OF CENTRAL GREAT BASIN DEVONIAN ROCKS 11

EXPLANATION

Devils Gate Limestone

Unit 5
(Bay State Dolomite Member)

 
 

 
 
 

 
   

  
 
   

 

g: f k\ \ v;
33 Unit 4 Undifferentiated Middle 0
E Devonian dolomite >
o [Ll
in D
65
2% Unit 3
>
Q3
Z
Unit '2
Unit-1‘
W
A 2
Lone Mountain Dolomite S
, , L DC
a 3
Roberts Mountain rmation (dolomitized) U)
with basal chert member
Hanson Creek Formation (dolomitized)
Z
E
. 0
Eureka Quartmte ;
WESTERN FACIES o
PALEOZOIC ROCKS E
O

   

Vinini Formation
Graptolite—bearing shale
and limestone

Contact
so 90
Fault, showing dip

Dashed where approximately located;
dotted where concealed

37

_L—

Strike and dip of beds

RUGOSE CORAL LOCALITIES

I E ‘M 29 .M 1 044

Coral zone F Coral zone E Coral zone D Coral zone C

Numbers preceded by'M are USGS
(Menlo Park) fossil locality numbers.
Devonian coral zones A ami‘B not
recognized at Lone Mountain

8
Fragmentary Silurian rugose corals

is somewhat intermediate between that of the Dia-
mond Mountains belt and the Antelope-Roberts

534-041 0 - 74 - 2

 

Mountains belt. In terms of Lower and lower Middle
Devonian stratigraphic paleontology, the Sulphur
Spring record is the most complete of the region,
comprising coral zones A through D in continuous
order. At Lone Mountain only zones C and D of this
interval were recognized.

BEACON PEAK DOLOMITE MEMBER

Thick-bedded, rather finely saccharoidal, prevailing-
ly light-gray dolomites of the Beacon Peak Dolomite
Member underlie the isolated Twin Hills near Tyrone
Gap, and crop out over a broader area at the south
end of the range between the Mulligan Gap and
Romano faults (fig. 4). Other outcrops occur to the
north in the vicinity of Wales Peak and the Prince of
Wales mine. Some 400 feet thick, the Beacon Peak of
this area passes upward without known break into
the arenaceous magnesian limestones and calcarenite
at the bottom of Nevada Formation, unit 1. As in its
type section in the southern Diamond Mountains at
Oxyoke Canyon, the Beacon Peak Dolomite Member
of the Sulphur Spring Range contains small lenses
of quartzitic sandstone. Here and there it changes
toward the top into dolomitic limestone.

Because of geomorphic and structural conditions in
gently dipping Silurian and Devonian strata of this
range the Lone Mountain Beacon Peak boundary has
not been revealed by erosion (fig. 5). However, typical
coarsely saccharoidal dolomite of the Silurian Lone
Mountain makes up East Ridge on the east side of
the Romano fault. In this footwall fault block the
Lone Mountain contains abundant Halysites and
pycnostylid corals of Silurian age, and may safely be
inferred to underlie the Beacon Peak in the west or
hanging-wall block of the high-angle Romano fault.

Fossils are scarce in most of the Beacon Peak
Dolomite Member of the Sulphur Spring Range,
especially at the south end and in the isolated Twin
Hills. Scattered deposits of well-preserved silicified
corals and brachiopods represent coral zone A and the
Rabbit Hill Helderbergian fauna. Because no identi-
fiable fossils were found in the Beacon Peak Dolomite
of the type area in the Diamond Mountains, the cor-
relation is based upon lithologic and stratigraphic
criteria.

NEVADA FORMATION, UNIT 1

Unit 1, which is defined at Lone Mountain, is repre-
sented by quite similar strata in the Sulphur Spring
Range (fig. 6). At Sulphur Spring Range, however, it
includes basal arenaceous magnesian limestones and
calcarenite unrecognized at Lone Mountain; these
lowermost beds contain in considerable abundance
the Costispirifer arenosus brachiopod assemblage of

 

 
   
 

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l
,,.
l
‘t
39" \ r \
55’ \

   

  
  

I?
4
I
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l
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///////A'
116'10'
Base from U.S. Geological Survey, 1:62 500
Garden Valley, 1949

9’ \uzmr
Geology by C. W. Merrlam and
T. B Nolan. 1952—68

1 MILE

 

2 KILOMETERS

 

 

 

 

 

 

 

EX P LA N ATl O N
+ + l + Z
+ v + S
Mount Hope igneous 02:
Garden Valley intrusive body Lu
Formation L'L
Dds
L.__
Devils Gate Limestone
with Amphipora
l %
Bay State Dolomite
Member
Woodpecker Limestone
Member
s: w
E Sentinel Mountain \. \
g Dolomite Member \ E
3 7 Undifferentiated -Z—
r: /. % Nevada Formation 0
”g ‘ including all units >
5 Nevada unit 2 Nevada unit 2 and members (“3]
Z Nevada unit 1 not quartz sandstone
mapped separately tongues in undif-
ferentiated Nevada
Formation
Nevada unit 1
Shown in section
only
’- I _ ‘
Beacon Peak Dolomite Quartzite and dolomite of unknown age;
l Member possibly Lower and Middle Devonian l
Z
M s
[I
Lone Mountain Dolomite 3
Contains Halysites and 2'
pycnoslylids 0')
WESTERN FAClES
PALEOZOIC ROCKS <2:
/ /////// —
////’/ y/// 9
Z 5157/0 >
Vinini Formation 8
Graptolite-bearing shale D:
. O
————— R U G O S E C O R A L
Contact

L O C A L l T l E S
Dashed where approximately located

 

Fault

Dashed where approximately located;
dotted where comealed

Coral zone D
Late Early and Middle Devonian

O
Coral zone C
JO Late Early Devonian
Strike and dip of beds 0
Coral zone B
Early Devonian (Oriskany)
A
Coral zone A

Early Devonian (Helderberg)

S
Silurian coral faunas

FIGURE 4.—Geologic sketch map showing Silurian and Devonian units in southern Sulphur Spring Range. Symbols indicate
Devonian coral zones. See figure 5, geologic cross section D—D’.

 

——’17

 

 

 

 

STRATIGRAPHY OF CENTRAL GREAT BASIN DEVONIAN ROCKS 13
B
ORDOVICIAN PERMIAN E DEVONIAN SILURIAN
Q)
P E L
5] g Nevada Formation Maintain
Garden Valiey Formation E g Dolomite
B
E E D - i—
g 0 g Unit 1 Unlt 2 _,
m cu Z) ‘ /
D E z m < D
8500’ B < C “- 8500’
m 0 8
'E :1 a West Sand East Sand g
_ ‘ ' 0
7500’ E Permian Ridge 5! m Peak Sandstone in Peak g 7500,
> I (1 unit 2
08 2 A B \ 0 East
6500’ iii \ \ A n: Ridge Qal 6500'
5500' WA \ 5500'
Note: Some Quaternary
1000 500 O 1000 FEET

deposits not shown
on geologic map (fig.4) .
1000

FIGURE 5.—Devonian stratigraphic units and coral

3000 4

6000 METERS

zones in the southern Sulphur Spring Range.

See figure 4 for location of section.

Oriskany age, together with the large new rugose coral
Kobeha which characterizes coral zone B. The basal
sandy beds with Costispirifer and Kobeha are exposed
at Wales Peak, Oriskany Peak, and Coral Ridge (fig.
4) where they are overlain stratigraphically by higher
beds of unit 1 containing the coral zone C assemblage

with-Papiliophyllum and Acrosplrifer kobehana as in
the Lone Mountain section.

NEVADA FORMATION, UNIT 2

Unit 2 is lithologically and faunally quite similar to
the type exposures at Lone Mountain, consisting of
argillaceous to silty limestones and siltstones with
abundant fossils of coral zone D, which everywhere
characterize the Antelope-Roberts Mountains facies
belt. However, unlike the exposures at Lone Moun—
tain, unit 2 contains in the Sulphur Spring Range
numerous tongues and lenses of light-gray to white
siliceous sandstone resembling the Oxyoke Canyon
Sandstone Member of the Diamond Mountains belt.
These sandstone bodies range in thickness from an
inch to more than 40 feet. Rounded quartz granules
also occur in some of the limestones. Sandstone beds
are present throughout unit 2 in this area, but the
thicker and laterally more persistent of these siliceous
sandstones are in the upper part of the unit. Buttes
like North Sand Peak and West Sand Peak (figs. 4,
5) are capped by these resistant sandstones, which
are underlain by the fossil-rich argillaceous limestones
characteristic of Nevada unit 2.

SENTINEL MOUNTAIN DOLOMITE MEMBER

The approximate stratigraphic equivalent of the
Nevada Formation, unit 3 at Lone Mountain, the beds
exposed between Oriskany Peak and Terrace Butte

 

 

(fig. 4) are largely unfossiliferous dolomite. At Lone
Mountain, unit 3 is limestone, much of it fine-grained
encrinite. Because it has few identifiable fossils, it is
referred to as the barren zone. Whereas the gross
bedding and textural features of these beds suggest
unit 3 at Lone Mountain, the dolomitic nature and
especially the alternation of thick light-gray and dark-
gray dolomite bands is more indicative of typical
Sentinel Mountain Dolomite in the Diamond Moun-
tains belt. The stratigraphic relationship to underly-
ing Nevada Formation, unit 2 appears to be normal
southeast of Oriskany Peak, but at Terrace Butte the
Sentinel Mountain Dolomite is in fault contact with
the overlying Woodpecker Limestone Member or
Nevada Formation, unit 4.

WOODPECKER LIMESTONE MEMBER

The limestones of the Woodpecker Member occupy
the interval of Nevada Formation, unit 4 at Lone
Mountain. However, they are lithologically more like
the typical Woodpecker Limestone of the Diamond
Mountains and, like the Woodpecker there, yield a
brachiopod fauna with abundant Leiorhynchus cas-
tanea. The prolific rugose coral assemblages of Nevada
Formation, unit 4 and coral zone F at Lone Mountain
are lacking, as is the case also in the typical Wood-
pecker Limestone Member.

BAY STATE DOLOMITE MEMBER

Thick-bedded light-gray and dark-gray dolomites
which form the upper part of Terrace Butte and rest
upon the Woodpecker Limestone Member are mapped
as the Bay State Dolomite Member. This unit in the
Diamond Mountains belt is the equivalent of Nevada
Formation, unit 5 at Lone Mountain. Its characteristic

 

 

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————7

STRATIGRAPHY OF CENTRAL GREAT BASIN DEVONIAN ROCKS 15

fossil is the large brachiopod Stringocephalus. In the
Diamond Mountains, coral zone G brackets the basal
beds of the Bay State and the topmost beds of the
Woodpecker Limestone Member. No other outcrops
of the Bay State were recognized in the southern
Sulphur Spring Range.

DEVILS GATE LIMESTONE

The Devils Gate Limestone is cut out by faulting in
the Terrace Butte vicinity. A fault sliver southwest
of Bailey Pass includes the only Devils Gate exposures
found in the Southern Sulphur Springs Range. Where
present along the Mulligan Gap fault, it lies between
conglomerate of the Permian Garden Valley For-
mation and lower beds of the Nevada Formation,
and consists partly of massive stromatoporoid and
Amphipora facies.

DIAMOND MOUNTAINS FACIES BELT

The geographic limits of the easterly Diamond
Mountains facies belt (fig. 2) are those of the Diamond
Mountains themselves. Between this belt and the
Antelope-Roberts Mountains belt to the west, great
lithologic and paleontologic changes are observed.
Facies changes are most impressive in the lower part
of the Devonian column. Within the 20 miles sepa-
rating Lone Mountain from the Diamond Mountains,
the normal Nevada Formation facies of units 1 and 2
disappear and their places are seemingly occupied by
dolomite and quartzitic sandstone, with consequent
eastward loss of faunas (fig. 7). The possibility of
major thrust displacement beneath the intervening
Diamond Valley introduces tectonic factors which
must be considered in this connection by the struc-
tural geologist. The greater part of the eastern Great
Basin Devonian is likewise dolomite, and nowhere
east of the Diamond Mountains have the lower faunas
of Nevada Formation, units 1 and 2 been found thus
far. No rugose corals of Early and early Middle
Devonian ages are known in the Beacon Peak or
Oxyoke Canyon Member of the Diamond Mountains
facies belt or, in fact, from Devonian dolomites any-
where to the east within the Great Basin province.

Passing east from the Antelope-Roberts Mountains
belt to the Diamond Mountains, the lithologic changes
are of lesser magnitude within the upper divisions
of the Nevada Formation. However, the faunas of
the Woodpecker Limestone Member corresponding to
Nevada Formation, unit 4 at Lone Mountain and
those of Nevada Formation, unit 5 (which is essen-
tially the Bay State Dolomite Member) reveal signi-
ficant eastward biofacies changes. For example, the
prolific coral assemblages of unit 4 (coral zone F) at
Lone Mountain do not appear in the approximately

 

correlative Woodpecker Member of the Diamond
Mountains.
BEACON PEAK DOLOMITE MEMBER

The Beacon Peak Dolomite Member is composed
of sparsely fossiliferous fine-textured dolomites with
subordinate siliceous sandstone intercalations and
lenses which rest disconformably upon more coarsely
saccharoidal Lone Mountain Dolomite, according to
Nolan, Merriam, and Williams (1959, p. 42). The
Beacon Peak Member is in turn conformably overlain
by the even more barren Oxyoke Canyon Sandstone
Member. Part of the Beacon Peak Dolomite Member,
ranging in thickness from 470 feet to about 1,000 feet,
is considered to be correlative with the Helderbergian
Rabbit Hill Limestone, although its higher beds may
be equivalent to arenaceous strata in the lower part
of Nevada Formation, unit 1 in the Sulphur Spring
Range. Poorly preserved ghosts of large high-spired
gastropods are the only fossils known in this member.

OXYOKE CANYON SANDSTONE MEMBER

The Oxyoke Canyon Sandstone Member consists
of thick-bedded quartz sandstone and orthoquartzite
with dolomite interbeds; the orthoquartzite resembles
white Eureka Quartzite but is less dense and locally
has carbonate cement, uncommon in the Eureka. In
places the Oxyoke Canyon Member is more than 400
feet thick. Fossils are very uncommon; only at the
Phillipsburg mine, 16 miles north of Eureka, were
poorly preserved brachiopods found in quartzitic sand-
stones of this unit. As noted above, the presence of
similar quartzitic sandstone as tongues and interbeds
within the Nevada Formation, unit 2 rather strongly
indicates that the Oxyoke Canyon Member is equiva-
lent to some part of that westerly unit in the Antelope-
Roberts Mountains facies belt. Westerly sandstone
tongues of Oxyoke character in unit 2 are numerous
in the Sulphur Spring Range, at Combs Peak, and at
Modoc Peak in the Mahogany Hills, and at Grays
Canyon and Eightmile Well in the Fish Creek Range.

SENTINEL MOUNTAIN DOLOMITE MEMBER

Thick-bedded generally unfossiliferous saccharoidal
dolo‘mites of the Sentinel Mountain Dolomite Member
exhibit alternation of light-gray and dark-gray dolo-
mite bands to a greater extent than the finer textured
Beacon Peak. The Sentinel Mountain Member occu-
pies the approximate interval of Nevada Formation,
unit 3 at LOne Mountain, which is limestone, a good
part being encrinite. Because of the scarcity of identi-
fiable fossils in both members, they are referred to in
paleontologic terms as the barren zone of the Nevada
Formation.

 

 

 

 

 

 

 

 

 

 

 

 

 

 
  

       
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

16 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN
g
S m g i m
E E < m z LONE MOUNTAIN SULPHUR SPRING RANGE DIAMOND MOUNTAINS
g g E: 8 S REFERENCE SECTION SOUTH END OXYOKE CANYON
m
S
Li
é Devils
3 Gate
Limestone ,I-
——————————— ?——————”’/
. Bay State Dolomite
Unit 5 (Bay State Bay State Dolomite Member 738 ft
Dolomite Member) Member
570 ft
,/—————? —————————
z ‘\
\ d k L' t
2 cu WOO pelcd:;lbellmes one Woodpecker Limestone
5 E Unit4 Member 387 ft
5 2 F 675 ft /// —————————————
// \
>
Ed
D . .
Nevada Sentinel Mountain
Formation . Dolomite Member Sentinel Mountain Dolomite
Umt 3 Member 610 ft
E 285 ft /_ _______ _\\
_ Oxyoke Canyon Sandstone
Unit 2 Member 400 ft
D 720 ft
’53
3
O
r-l .
. //’ Beacon Peak Dolomite
C Unit 1 B Umt 1 /’ Member 470 ft
<362£t _________ 4_\Aacon Peak
Z \\ Dolomite . .
3 Lone \\\\? A Member Dlsconformity
g Mountain \\\\ / Lone. Mountain
I—l Dolomite \\\ ___?___.__,/’/ Dolomite
D—t
m J

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FIGURE 7.—Relationship of the Devonian reference sections of Lone Mountain and Sulphur Spring Range to that of the
Diamond Mountains facies belt at Oxyoke Canyon.

WOODPECKER LIMESTONE MEMBER

Occupying the interval of Nevada Formation, unit
4 at Lone Mountain, the Woodpecker Limestone
Member consists of thin- to medium-bedded limestone
and calcareous shale or siltstone, some of which is of
slightly pinkish to purplish color. In certain beds,
fossils are abundant, especially the brachiopods, of
which the most diagnostic is Leiorhynchus castanea.
The rich coral assemblages of the dolomitic limestones
in Nevada Formation, unit 4 and coral zone F at Lone
Mountain do not occur in the Woodpecker.

 

 

BAY STATE DOLOMITE MEMBER

The uppermost member of the Nevada Formation,
the Bay State Dolomite Member, in this belt is thick-
bedded prevailingly dark gray saccharoidal dolomite.
Some beds are loaded with large Stringocephalus
shells, other beds contain much favositid coralline
material. Rugose corals are common only in the lower-
most beds, where they are locally associated with
Stringocephalus. Nevada Formation, unit 5 of the
Lone Mountain reference section is the approximate
equivalent of the Bay State. Great Basin Devonian

 

 

r—i

CORAL BIOSTRATIGRAPHY OF THE CENTRAL GREAT BASIN DEVONIAN 17

coral zone G brackets the lowermost strata of the Bay
State and the topmost beds of the Woodpecker Lime-
stone Member in the Diamond Mountains facies belt.

DEVILS GATE LIMESTONE

The Devils Gate Limestone, some 1,200 feet thick,
rests conformably upon the Bay State Dolomite
Member of the Nevada Formation and is overlain
without discordance by the Pilot Shale. As noted
under the Lone Mountain reference section, the lower
part of the Devils Gate includes much massive stroma-
toporoid and Amphipora limestone including coral
zone H. Thinner bedded upper limestones comprise
coral zone I of Late Devonian (Frasnian) age. Coral
facies are not well represented in the Diamond Moun-
tains exposures of this limestone.

MONITOR-SIMPSON PARK FACIES BELT

Lower Devonian limestones of the westerly Monitor—
Simpson Park facies belt have been traced southward
from the Tuscarora and Cortez Mountains (fig. 2)
through the Simpson Park, Toquima, and Monitor
Ranges to the Dobbin Summit area, a distance of
130 miles. Unlike the two subparallel facies belts on
the east, no dolomite is known in either the Devonian
or Silurian of the Monitor-Simpson Park belt. Over
most of this belt the Helderbergian Rabbit Hill Lime-
stone is the only Devonian unit identified by fossils.
Exceptional are outcrops of Nevada Formation, unit 2
(coral zone D) at the north end of the Simpson Park
Range near Coal Canyon. Coral-bearing strata of
probable Middle Devonian age are known on the west
side of the Monitor—Simpson Park belt in the Toiyabe
Range south of Austin. This occurrence near Reeds
Canyon is the westernmost exposure of Devonian in
this region. Underlying strata of possible Early
Devonian age at the Reeds Canyon locality have thus
far yielded no fossils within the stratigraphic interval
just above the Silurian where Rabbit Hill Limestone
would be expected.

RABBIT HILL LIMESTONE

In the type section of the Rabbit Hill Limestone
at Copenhagen Canyon, Monitor Range (Merriam,
1963, p. 42), about 250 feet of continuous section is
measurable. The dark-gray limestones and calcareous
shales of the type Rabbit Hill are deformed below a
thrust and rest without recognized stratigraphic break
upon graptolitic deposits of Silurian age. More com-
plete Rabbit Hill sequences occur at Dobbin Summit
(fig. 2) and at Coal Canyon, where in each case about
800 feet of the formation is exposed. At Coal Canyon

 

 

the underlying limestones of Silurian coral zone E
contain a large and diagnostic coral assemblage of
Gotlandian character; overlying Nevada beds have
yielded faunas of Nevada Formation, unit 2 and coral
zone D, but the stratigraphic contact is not exposed.
In the Dobbin Summit area, the subjacent Silurian
strata have yielded graptolites and brachiopods only.
The Rabbit Hill is overlain without recognized dis-
cordance by conodont-bearing limestones reported to
be of Mississippian age (John W. Huddle, oral com-
mun., 1966). Although no Rabbit Hill Limestone has
been found in the adjacent Antelope-Roberts Moun-
tains belt on the east, diagnostic elements of the
Rabbit Hill fauna occur in strata assigned to the
Beacon Peak Dolomite Member below Nevada For-
mation, unit 1 of the Sulphur Spring Range.

All the Rabbit Hill Limestone exposures that have
been studied represent the Syringaxon facies and
Devonian coral zone A. At Dobbin Summit upward
faunal changes are, however, observed within this
formation. The higher beds contain a large Costi-
spirifer cf. C. arenosus similar to that of lowermost
Nevada Formation, unit 1 and coral zone B.

CORAL BIOSTRATIGRAPHY OF THE
CENTRAL GREAT BASIN DEVONIAN

Rugose corals of restricted vertical range make pos-
sible biostratigraphic subdivision of the entire Great
Basin Devonian into nine successive coral zones labeled
by capital letters A through I in stratigraphic order
(fig. 8). Four of these time-stratigraphic divisions
correspond to mapped rock-stratigraphic units; the
remainder occupy rock units with two coral zones or,
as in the case of coral zone G, overlap the contact
separating two units (fig. 9). Field reference sections,
wherein the rocks have been mapped and the strati-
graphic section measured, are given for each coral zone.

Value of the proposed biostratigraphic zonation out-
side the Great Basin province remains to be demon-
strated. A possible disadvantage is the use in the
zonation scheme of endemic Halliidae like K obeha and
Papiliophyllum, not yet recorded in other provinces.
Other families and genera employed are more cosmo-
politan, like the Laccophyllidae, Siphonophrentinae,
Bethanyphyllidae, Disphyllidae, and the Old World
digonophyllids.

Initial biostratigraphic zoning of Great Basin
Devonian rocks (Merriam, 1940, p. 9) was based
largely on spiriferoid brachiopod ranges; the taxonomy
and geologic range of these have recently undergone
revision (Johnson, 1966a; 1966b, 1966c). Some earlier
adopted brachiopod markers continue to agree with
coral indices of the lettered zones. For example, the

*

 

 

 

 

 

 

    

 

 

 

 

 

 

 

     

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  
  

 

 

 

 

 

 

 

 

  
   

 

 

18 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN
2 RUGOSE _
ca 5 . COMPOSITE REAT BASIN CORAL PREVIOUSLY EURO
S E REFERENCE DEVONIAN COMMON RUGOSE CORALS EVOLU— CORAL BIOFACIES USED ZONE PEAN
; 53 SECTION CORAL ZONE TIONARY STAGE

BURST*
s 2 F ‘
L as nnia
5-: fl Lower part No rugose corals found ame n
h m Cyrtosm'm‘fer zone
8, r:
9% § 0)
E Ki Upper part Pachyphyllum, P hill’ipsastraea, * P hilljpsastraea Phillipsastraea zone F -
5 <5 Macgeea biofaCIes rasnlan
(D
q; r:
E Lower part H Rugose corals uncommon
Q
\
Givetian
Unit 5 G Acanthophgllum, Digonophyllum Stringocephalus zone
(Mochlophyllum)
.S
é‘ g Hexagonaria, Taimyrophyllum,
72 g Utaratuia, Sociophyllum, _ .

z 2 g Keriophyllum‘Acanthoznhyllum, * HWWWWW‘SWOP’WW’” “Martinia"k'£rki zone
5 Q, Digonophyllum, Mesophyllum, biofaCIes
g 5 Tabulophyllum

q
a *’ Eifelian
Q : Rugose corals uncommon
.2 (barren zone)
4;
a
E
3 Mesophyllum {Arcophyllurru
L“ . .
Brew}; rentzs, ethanyp 1/ um, . i ‘ I . ,, . .
" s Unit2 D D2 Pinyomstraea,Billingsastruea, * Brewphrentzs ‘Spmfer mnyonenm _____
§ Mesophyllum, Zonophyllum biofacies zone
E D1 Papiliophyllum, Breviphrentis
Emsian
C Papiliophyllum, Odtmtophyllum, Papiliophyllum Acrosm‘rifer kobehana
Breviphrentis biofacies zone
Unit 1
as *3
s s s C ,A W
-~ 4.. > as 7.31M er arenosus . ,
A E g g a, K059)” Kobebu zone (“Trematospi'm Siegeman
'5 E .n: : biofaCIes f ,, (Oriskany)
Q :- 0 u q auna )
.1 g 5 .E S
8—9 “a = 2 E a» I
a, ' .2"): ‘7-
2; a: a = m ° ‘ H Id
g a .a g D 3: ‘5 Syringaacan f Syflngzrxrm e er—
3 E S ,5 i? g g " blOfaCleS berg1an
g E E In 25 3 a? {5 I

 

 

 

 

 

       

 

 

 

 

 

 

 

 

 

 

 

 

 

FIGURE 8.—Great Basin Devonian coral zones, equivalent rock units, coral biofacies, and previously employed biostratigraphic
designations.

Acrospirifer kobehana zone is coral zone C, and that
of Costispirifer arenosus, or the “Trematospira fauna,”
is coral zone B. The zone of “Spirifer” pinyonensis
(now Eurekaspirifer pinyonensis) is essentially coral
zone D, although subzone D3 is considered Middle
Devonian and may be above the range of this spirifer.
In connection with rugose coral study, the associated
brachiopods and other diagnostic fossils remain to
be more fully evaluated stratigraphically. Tabulate
corals, actually the most abundant fossils in certain
Great Basin Devonian coral-brachiopod-trilobite beds,
are too little understood at present to have definitive
stratigraphic value in this province. Cephalopods,
other than straight-shelled genera, are uncommon in

 

these rocks. Age and correlation significance of the
rare ammonoids collected thus far are discussed below.

The proposed coral sequence is by nature com-
posite, for in no individual section are all nine zones
recognized in continuity. Lone Mountain has four in
sequence: C, D, E, and F; strata of zones G and H
are present, but thus far have yielded no Rugosa at
Lone Mountain. For the purposes of this report, the
Early and Middle Devonian section in the southern
Sulphur Spring Range is the most inclusive; coral
zones A, B, C, and D occur here in continuity. Devo-
nian coral zones G and H are best represented in the
southern Diamond Mountains. Zones H and I are
recognized in the Devils Gate vicinity, and in the

 

 

———i

CORAL BIOSTRATIGRAPHY OF THE CENTRAL GREAT BASIN DEVONIAN 19

adjacent northeastern part of the Mahogany Hills.
Late Devonian rocks that include the interval of coral
zone I are well exposed in the White Pine mining
district, especially along the west margin near the
Behnont mine and in the 10w hills west of Monte
Cristo.

Coral zones A, B, and C are of Early Devonian age;
coral zone D is Early and early Middle Devonian.
Zones E, F, G, and probably the lower half of H are
Middle Devonian. Coral zone I is Late Devonian,
including the» youngest Devonian rugose corals of this
province; none have been found in the high Devils
Gate Cyrtospirifer beds, or in the lower Pilot Shale
interval that probably correlates with European
Famennian.

For convenience, the lettered primary coral zones
are further divided by subnumbers as D1 and D2. In
this instance subzone D1 has a distinctive rugose coral
assemblage regarded as late Early Devonian, whereas
that of D2 is considered Early or early Middle Devo-
nian; subzone D3 is early Middle Devonian.

In summary, the mapped Devonian rock units con-
taining the zone corals remain to be equated with cor—
responding biostratigraphic coral range zones. Begin-
ning with the oldest, coral zone A is typified by the
westerly situated Rabbit Hill limestones but is present
also in the easterly Beacon Peak Dolomite Member
interval of the Sulphur Spring Range, beneath Nevada
Formation, unit 1 with coral zones B and C (fig. 9).
In the Lone Mountain reference section, only coral
zone C has been identified in Nevada Formation, unit
1; coral zones D, E, and F of this reference section
correspond to Nevada Formation, units 2, 3, and 4.
Coral zone G is found in a narrow band which brackets
the topmost beds of the Woodpecker Limestone Mem-
ber and the basal beds of the Bay State Dolomite
Member (Nevada Formation, unit 5) in the southern
Diamond Mountains. Coral zone H occupies the lower
half of the type Devils Gate Limestone wherein the
stromatoporoid-Amphipora biofacies is predominant.
At Devils Gate, coral zone I is typified by the
Phillipsastraea biofacies in the lower part of the upper-
most 250 feet of this formation below the Cyrtospirifer

beds.
EARLY AND EARLY MIDDLE
DEVONIAN CORAL ZONES

CORAL ZONE A

The type section of the Rabbit Hill Limestone in
Copenhagen Canyon, northern Monitor Range, is the
reference column for this Helderbergian Early Devo-
nian coral zone. Syringaxon foerstei n. sp., index fossil
of coral zone A and the Syringaxon biofacies, is com-
mon to abundant in a large brachiopod-coral fauna
throughout this formation, usually unaccompanied by

 

other Rugosa. Syringaxon as a genus ranges through
the Silurian and Devonian; it is represented by many
species throughout the world. The genus has been
recognized by fragmentary material in the Silurian
and Middle Devonian of the Great Basin.

The stratigraphic relationship of the Rabbit Hill
Formation and coral zone A to underlying and over-
lying zones of the Great Basin standard sequence can
not be determined at Rabbit Hill, where the sub-
jacent Silurian is a graptolitic facies and no younger
Devonian beds are exposed. Therefore elucidation of
the true position of these beds depends upon supple-
mentary study of correlative strata in other areas. At
Coal Canyon, northern Simpson Peak Range, lime-
stones of the Rabbit Hill rest conformably upon Upper
Silurian limestones of the Roberts Mountains Forma-
tion and Silurian coral zone E containing a rich
Ludlovian coral fauna of Gotlandian aspect. Upward,
however, the boundary with the Nevada Formation is
obscure because of faulting and poor exposure. In the
Dobbin Summit area of the southern Monitor Range,
the Rabbit Hill Limestone is conformably upon
Silurian limestone and is overlain with seeming ‘con-
formity by limestones of uncertain age, dated pro-
visionally by conodonts as Mississippian (J. W.
Huddle, oral commun., 1966).

Light is shed upon the true stratigraphic position
of the Rabbit Hill fauna and coral zone A as a result
of geologic mapping in the southern Sulphur Spring
Range. Here dolomite and dolomitic limestone, con-
sidered to be a northwesterly extension of the Beacon
Peak Dolomite Member, contain Syringaxon foerstei
and other elements of the Rabbit Hill fauna. In that
area the Silurian Lone Mountain Dolomite is below
the Beacon Peak above which lies Nevada Forma-T
tion, unit 1, whose lowermost beds contain Kobeha
walcotti and Costispirifer arenosus of coral zone B.
As elsewhere noted, the normal Beacon Peak—Lone
Mountain stratigraphic boundary is poorly exposed
in the southern Sulphur Spring Range; in the Diamond
Mountains it is a disconformity.

In the type section of the Rabbit Hill and coral
zone A, Syringaxon foerstei is associated with the
tabulate corals Striatopora, Pleurodictyum, and mas-
sive Favosites. Distinctive forms among associated
brachiopods are Levenea cf. L. subcarinata, H owellella
of. H. cycloptera and new species of Kozlowskiellina,
Leptocoelia, and Plethorhyncha. Leonaspis, Proetus,
and Phacops are the common trilobites. Large Costi-
spirifer resembling C. arenosus appears in higher Rabbit
Hill beds at Dobbin Summit. This early occurrence
of Costispirifer foreshadows its presence in coral zone
B, normally to be expected just above the Rabbit Hill.

 

 

*

20 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

Virtual absence of colonial Rugosa from the known
Great Basin Lower Devonian below coral zone D is
not easily explainable. Although the faunas of coral
zone A normally lack the compound genera, there are
two exceptions: the occurrence of Australophyllum
landerensis n. sp. in an otherwise typical Rabbit Hill
Syringaxon association of the northern Toquima
Range, and a Billingsastraea-like coral in a Rabbit
Hill assemblage on Maggie Creek northwest of Carlin,
southern Tuscarora Mountains.

CORAL ZONE B

Reference sections for this Early Devonian coral
zone are situated in the southern Sulphur Spring
Range, on the ridge 0.5 mile south-southeast of the
Prince of Wales mine and at hill 6927, 1.75 miles south-
southeast of Mulligan Gap (fig. 4). Along the main
ridge at hill 6927, the zone B strata are in places
loaded with large solit ry Rugosa, overlie beds of
coral zone A, and are ov rlain by beds containing the
fauna of coral zone C. ones B and C are within the
variable dolomitic limes one and limestone of Nevada
Formation, unit 1, which rests without break upon the
Beacon Peak.

The fauna of coral zon B and the Kobeha biofacies
contains Kobeha walcot i, Costispirifer arenosus, and
Gypidula cf. G. coeym nensis. The large solitary
Kobeha is abundant in eds and pockets, either by
itself or with the brachi pods. In places Costispirifer
is crowded in layers with ut the coral. Tabulate corals
are uncommon in the co al-rich beds. Other fossils of
this zone are a large Str phonella cf. S. punctulifera
and the large trilobite almanites. It is significant
that the fauna of coral one B contains but a single
rugose coral species and acks colonial Rugosa.

Another species of K beha, here named Kobeha
ketophylloides n. sp., occ rs in beds low in the Devo-
nian section 1.5 miles no th of Roberts Creek Ranch,
where it is associated wi Gypidula of G. coeyman-
ensis, Acrospirifer sp., an Pholidostrophia? sp.

 
   

CORA ZONE C

The reference section f r Early Devonian coral zone
C is at Contact Gulch on the northwest side of Lone
Mountain (fig. 3). A nor hwest-striking ridge on the
north side of this gulc is underlain by Nevada
Formation, unit 1, whic in this area has changed
laterally from dolomite nd dolomitic limestone to
the limestone here contai ing fossils of coral zone C.
Other excellent exposure of these beds are on the
southeast side of Lone Mountain, where Nevada
Formation, unit 1 is dolom te which is loaded in places
with silicified fossils. Cora zone B was not recognized

 

 

at Lone Mountain below coral zone C where it would
be expected. In the southern Sulphur Spring Range,
coral zone C occupies the higher beds of Nevada
Formation, unit 1 overlying the strata of coral zone B.

The large solitary Papiliophyllum elegantulum re-
places Kobeha walcotti of underlying zone B. Asso-
ciated with Papiliophyllum in this taxonomically more
diverse biota are Siphonophrentis (Breviphrentis)
kobehensis, Odontophyllum meeki, Aulacophyllum sp.
c, and Cystiphylloides lonense. Massive favositids are
common. No colonial Rugosa are present. The asso-
ciated brachiopod fauna is fairly large, including
Acrospirifer kobehana, Meristella cf. M. robertsensis,
Schuchertella cf. S. nevadaensis, Leptostrophia sp.,
and a large Cyrtina. This is the fauna of the Acro-
spirifer kobehana brachiopod zone of previous usage.

The genus Papiliophyllum is not restricted to coral
zone C; it reappears as an advanced form in coral
subzone D1, associated with a younger brachiopod
fauna.

CORAL ZONE D

The reference section of coral zone D lies on the
west side of Lone Mountain (fig. 3) between West
Peak and Central Peak, where it brackets the argil-
laceous limestones of Nevada Formation, unit 2. Coral
zone D corresponds to the “Spirifer” pinyonensis zone
of Merriam (1940). The Early and early Middle
Devonian coral and associated faunas of this zone are
taxonomically the most diverse of the Great Basin
Devonian, only those of Nevada Formation, unit 4
and coral zone F being comparable in this respect.
Because of the less compact shaly nature of much of
this unit, the abundant fossils weather loose and are
easily collected. Hence a large part of the previously
described Nevada Formation fauna came from these
beds. Coral zone D includes the lowest colonial Rugosa
found thus far in the Nevada Formation.

Using rugose corals, it is feasible to subdivide coral
zone D into three subzones, D1, D2, and D3, in ascend-
ing order. Most unit 2 exposures in the main outcrop
belt at Lone Mountain yielded D2 collections only.
Large collections representing D1 came from pediment
outcrops 5,500 feet south of Reef Point. Subzone D3
collections were made in the higher part of Nevada
Formation, unit 2 near the northwest end of Lone
Mountain at the head of Contact Gulch.

Subzone D1 is characterized by advanced Papilio-
phyllum elegantulum subsp. d, derived from P.
elegantulum of coral zone C. Associated large solitary
corals are Halliidae of a somewhat different type,
probably allied to Papiliophyllum. Among brachiopods
are Chonetes macrostriata, Gypidula loweryi, and
Strophonella cf. S. pustulosa, together with Leptaena,

 

 

————i

CORAL BIOSTRATIGRAPHY OF THE CENTRAL GREAT BASIN DEVONIAN 21

Schuchertella, and Meristella. Spirifers questionably
assigned to Eurekaspirifer pinyonensis are uncommon
in this assemblage. Chonetes macrostriata is abun-
dant, as it usually the case in lower beds of coral
zone D.

Subzone D2 includes among solitary Rugosa:
Bethanyphyllum lonense, B. antelopensis, Siphono-
phrentis (Breviphrentis) invaginatus, Sinospongo-
phyllum spp., Cystiphylloides robertsense, Mesophyl-
lum (Mesophyllum) sp. b, and Zonophyllum haguei.
The colonial corals are Disphyllum nevadensis, D.
eurekaensis, Dendrostella romanensis, Billingsastraea
nevadensis, and Hexagonaria (Pinyonastraea) kirki.
Associated fossils are those of the “Spirifer” pinyon-
ensis zone, as previously listed by Merriam (1940, p.
54—55) in which the commonest forms are Eureka-
spirifer pinyonensis, Atrypa nevadana, Gypidula
loweryi, Schizophoria nevadaensis, Schuchertella
nevadaensis, Chonetes macrostriata, Dalmanites
meeki, and Phacops cf. P. rana.

Subzone D3 includes the uppermost beds of Nevada
Formation, unit 2 in which the diagnostic coral is the
large solitary and structurally complex M esophyllum
(Arcophyllum) kirki. It is doubtful that Eureka-
spirifer pinyonensis survived into this early Middle
Devonian time-stratigraphic interval, and most of the
characteristic fossils of subzone D2 have not been
collected from subzone D3.

MIDDLE MIDDLE DEVONIAN CORAL ZONES

Profound changes in corals and all other shell-
bearing marine organisms took place in the interval
separating Nevada Formation, unit 2 and coral zone
D from Nevada Formation, unit 4 and coral zone F.
These changes are not recorded in starta of Nevada
Formation, unit 3, which has yielded few identifiable
fossils, hence being referred to as the barren zone.
None of the species cross the barren zone, and of five
rugose coral genera that survived to coral zone F,
three are different subgenerically.

CORAL ZONE E

Coral zone E occupies the interval of Nevada For-
mation, unit 3 at Lone Mountain (fig. 3). Crinoid
debris in thick beds and lenses makes up a consider-
able part of the unit. Poorly preserved bushy colonial
Rugosa from these beds are assigned questionably to
Disphyllum, and scrappy solitary coralla have char-
acteristics of Cyathophyllum.

CORAL ZONE F

The reference section for coral zone F is situated on
the south side of Lone Mountain, west of Charcoal

 

Gulch (fig. 3) and is the time-stratigraphic equivalent
of Nevada Formation, unit 4. The “Martinia” kirki
zone of Merriam (1940) corresponds to this interval.
The coral faunas of this zone at Lone Mountain are
best represented in dolomitic limestones occupying the
upper part of unit. 4

Coral zone F contains a large, diverse, and poten-
tially reef forming biota including both solitary and
colonial genera. The rugose corals of this zone are
mostly undescribed, such that generic assignments
are for the most part provisional. Among the more
abundant genera are: Taimyrophyllum, Hexagonaria,
Utaratuia, Sociophyllum, Acanthophyllum,Keriophyl-
lum, Digonophyllum, M esophyllum (Lekanophyllum),
Tabulophyllum, and Crystiphylloides. For the first
time in these Devonian rocks, the colonial Rugosa of
coral zone F outnumber the solitary forms. Nearly
all zone F species are unrelated to zone D species; none
appear to be ancestral to forms occurring in the higher
Devonian coral zones. Several of the diagnostic genera
like Taimyrophyllum, Utaratuia, and Sociophyllum
are represented also in correlative formations of
western Canada.

CORAL ZONE G

The reference section for coral zone G is situated in
the southern Diamond Mountains (fig. 2) at the head
of Oxyoke Canyon, west of Sentinel Mountain (Pinto
Summit quadrangle). It occupies a 30-foot interval
bracketing the uppermost beds of the Woodpecker
Limestone Member of the Nevada formation and the
lowermost beds of the overlying Bay State Dolomite
Member according to Nolan, Merriam, and Williams,
(1956, p. 45) . The lowest Bay State beds with S tringo-
cephalus fall within this coral zone, which also contains
the genus Rensselandia. Only in this zone are rugose
corals known to be associated with Stringocephalus.
Characteristic rugose coral genera of coral zone G are
Digonophyllum (Mochlophyllum), Mesophyllum,
Acanthophyllum, Cyathophyllum (Moravophyllum),
and Cystiphylloides. The colonial Rugosa of coral zone
F at Lone Mountain are not represented in the refer-
ence section for coral zone G.

At Lone Mountain the basal beds of Nevada Forma-
tion, unit 5, which is approximately correlative with
the Bay State, and the topmost beds of Nevada For-
mation, unit 4, correlative with the Woodpecker Lime-
stone Member, have not yielded the coral zone G
assemblage.

LATE NHDDLE AND LATE DEVONIAN CORAL ZONES

The rugose corals and stratigraphy of the Devils
Gate Limestone remain to be studied in detail and,
except for generalities, are beyond the scope of this

 

 

 

 

22 LOWER A D LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

report. Earlier investig tion of Rugosa from the upper
part of this formation y Stumm (1940) and by Mer-
riam (1940) confirme their Late Devonian age and
demonstrated that th-se higher coral faunas were
unrelated genetically tn those of the Middle Devonian
in coral zones F and l of present usage. Above the
Stringocephalus zone t e interval recorded by thick-
bedded limestones whi h make up the lower half of
the Devils Gate was semingly inhospitable to rugose
corals, as was the dolo itic Stringocephalus zone in
Nevada Formation, uni 5 and the Bay State Dolomite
Member. When Rugos reappearin force just below
the uppermost Devils ate Cyrtospirifer zone, they
include newly introducd genera, mostly of a single
family not yet discoveed in the Great Basin below
this horizon. For the I evils Gate time-stratigraphic
interval, two coral zon -s are proposed: coral zone H
below to include the lawer coral-poor thick-bedded
limestones, and coral 20 e I above for the upper coral-
rich beds. ‘

   
     
  
 
    
 
   
    
  
   
     
   
   
 
   
   
  
  
 
 
  
 
  

COR L ZONE H

Massive stromatoporo'ds and Amphipora are major
rock builders in the int-rval of coral zone H and as
such have masked and nbscured the contributions of
other lime-secreting org nisms. N o Rugosa were found
in these beds at Lon- Mountain. Rugose corals
assigned to Temnophyll m and Disphyllum were col-
lected from the lower 2I0 feet of the Devils Gate in
the southern Diamond ountains (Merriam, 1963, p.
53). The middle Devonin—Late Devonian transition
conceivably falls within he interval of coral zone H.

Reference section for L te Devonian coral zone I lies
in the Devils Gate Limetone type area on the north
side of Devils Gate Pass. I he dark-gray coralline lime-
stones below the Cyrtosprifer beds contain the locally
abundant Phillipsastraeiulae of this zone with only a
few solitary Rugosa of Other surviving families. Phil-
lipsastraeidae present are the colonial Phillipsastraea,
Pachyphyllum, and Phac llophyllum together with the
solitary MacGeea.

Other localities where t e coral faunas of zone I are
represented in the Devils 4 ate vicinity are on the ridge
east of Yahoo Canyon, W istler Mountain quadrangle.
In the White Pine mining district, these faunas occur
abundantly near the Bel ont mine mill and on the
ridge southwest of Monte risto, Green Springs quad-
rangle (Merriam, 1963, p. '4).

Limestones probably eq ivalent to the lower or Late
Devonian part of the Pilut Shale crop out at Devils
Gate above the Cyrtospiri 'er zone; like the Cyrtospiri-
fer beds, these highest De onian rocks have yielded no
Rugosa.

 
 

 

 

BIOFACIES ASPECTS OF DEVONIAN CORAL
DISTRIBUTION AND ZONATION

Ideally zone fossils may be environmental indicators
as well as stratigraphic guides. Patterns of coral distri-
bution in the Great Basin Devonian seaways and their
facies belts (fig. 2) give suggestive evidence of environ-
mental control. Rugose coral populations in these seas
formed only a part of much larger ecosystems whose
spread and survival as a whole were governed by inter-
play of ecologic factors, physical, chemical, and bio-
logic. Within the same time-stratigraphic interval,
entombing sediments of a specific kind may be viewed
as criteria of a fairly specific and stable bottom envi-
ronment where they contain about the same coral biota
in widely separated localities. In the section on “Great
Basin Devonian Facies Belts and Coral Reference Sec-
tions,” the broader aspects of rock facies distribution
were considered above in connection with physical
stratigraphy. There remains the ecologic evaluation of
coral zone indicators and their ecologic associates as
evidence of a particular biofacies.

From the viewpoint of the biological environment,
discontinuous lateral distribution of coral-rich Devo-
nian deposits indicates that optimum ecologic condi-
tions for vigorous coral growth were confined to rather
small patches of sea bottom separated by larger areas
of scarce shell-bearing benthonic life. Nearly all these
coral deposits circumscribed coral loci and thus were
not sites of true reef or bioherm building. N o biohermal
or patch reef complexes of persistent upward growth,
with initial sea bottom relief, altered reef cores, and
inclined flank beds like those of the Niagaran and the
Gotland Silurian were recognized in the Great Basin
Devonian. Only in the highest Silurian and in middle
Devonian coral zone F do loci of coral proliferation
suggest patch reef potential.

Carbonate rocks are generally the favored hosts of
rugose corals, especially the colonial forms. Moreover,
these Great Basin studies suggest an environmental
relationship between abundance and diversity of
Rugosa and certain petrologic characteristics of the
entombing carbonate. Taxonomically the most diverse
Devonian coral faunas of this province occur in the
Nevada Formation, unit 2 and coral zone D; the faunas
are found in impure nonmagnesian argillaceous lime-
stones with shale and siltstone interbeds. To these
varied coral faunas may be compared the more vigor-
ously proliferating coral associations of Nevada Forma-
tion, unit 4 (coral zone F) which occur in combinations
of limestone, dolomitic limestone, and dolomite having
a lower percentage of argillaceous matter. Coral faunas
of Nevada Formation, unit 4 consist of slightly fewer
species, but reveal a greater numerical concentration

 

 

 

BIOFACIES ASPECTS OF DEVONIAN CORAL DISTRIBUTION AND ZONATION 23

of individuals, especially colonial forms, and are thus
more important in rock building. On the contrary, the
pure or saturated coarsely saccharoidal Devonian dolo-
mites of this region, as distinguished from unsaturated
dolomitic limestones, seem to have been a diagenetic

facies singularly inhospitable to Rugosa. Among these ’

are the Sentinel Mountain and Bay State Dolomite
Members in the upper part of the Nevada Formation;
these have yielded few rugose corals. Rugosa are like-
wise scarce in diagenetic dolomites making up much
of the Devonian System of the eastern Great Basin,
that is, east of the Diamond Mountains. Easterly
rugose coral scarcity would appear to support these
paleoecological observations in the Nevada Formation
and suggests that Devonian shelf seaconditions favor-
ing extensive rugose coral growth like that of coral
zone F did not prevail in the eastern part of the Great
Basin province. To be eliminated in this connection
is the factor of possible coral destruction by dolomitic
recrystallization. However, in these Cordilleran pure
dolomites, where fossils were present in the initial sedi-
ments, they commonly escaped destruction locally by
early siliceous replacement.

Six biofacies of the Great Basin Devonian (fig. 9)
wherein rugose corals are important faunal constitu-
ents occur in the following stratigraphic order:

6. Phillipsastraea biofacies of coral zone I

5. H exagonaria-Sociophyllum biofacies of coral
zone F
Breviphrentis biofacies of coral zone D
Papiliophyllum biofacies of coral zone C
K obeha biofacies of coral zone B
Syringaxon biofacies of coral zone A

PPS”?

SYRINGAXON BIOFACIES

Coral-bearing medium- to dark-gray organic lime-
stones of the Rabbit Hill typify the Syringaxon bio-
facies and coral zone A. Separated by calcareous shaly
intercalations, these limestones commonly include a
high percentage of crinoid debris. Thick coarse-tex-
tured bioclastic lenses contain the remains of a large
brachiopod population, together with tabulate corals
of the genera Favosites, Striatopora, and Pleurodic-
tyum and the rugose coral biofacies indicator Syringa-
xon; this order indicates more or less their decreasing
order of abundance. Less numerous are the bryozoans,
trilobites, and the Mollusca other than small ortho-
ceratid cephalopods which are rather common. There
are no evidences of long transportation of the fossil
material; unbroken shells are present in the bioclas-
tic limestones, many brachiopods having articulated
valves. Stromatoporoids are a minor constituent. The
trilobites Leonaspis and Phacops are locally numerous

 

in platy limestone and calcareous shale interbeds
which are a subsidiary biofacies. Throughout the Rab-
bit Hill limestone the small, solitary Syringaxon is
common to abundant in most fossil beds, wherein it is
usually the only representative of the Rugosa.

No bioherms or patch reefs were found in the Rabbit
Hill Limestone of the Syringaxon biofacies, and the
corals had a minor role in rock building. No evidence
of dolomitization was recognized in the Rabbit Hill
Limestone of this biofacies. Complete silicification of
fossils is, however, widespread, a phenomenon which
in other formations is commonly associated with or
preceded dolomitic replacement. In the Rabbit Hill the
process of fossil silicification was clearly selective,
affecting brachiopods and corals; hard parts of other
organic groups were evidently less susceptible to this
kind of silicic additive replacement.

Colonial Rugosa are exceedingly uncommon in the
Rabbit Hill and Syringaxon biofacies, there being but
two known occurrences: that of Australophyllum
landerensis in the Toquima Range and a single Bil-
lingsastraea-like form in the southern Tuscarora
Mountains of northern Eureka County. Absent are
thick-walled solitary rugose coral genera of a possible
reef environment like those described from the roughly
correlative Coeymans Limestone of New York by
Oliver (1960a). Possibly significant environmentally
is the small amount of stromatoporoid material in this
biofacies, a characteristic also of the Breviphrentis bio-
facies and coral zone D. Its scarcity may be related to
frequent turbidity of the marine waters.

The Syringaxon biofacies is present also in the Bea-
con Peak Dolomite Member of the Nevada Formation
in the Sulphur Spring Range; here the fossils occur
in limestone beds which are somewhat dolomitic.

KOBEHA BIOFACIES

The Kobeha biofacies is in the strictest sense a
rugose coral biofacies in which the single species K.
walcotti predominates. This biofacies is best repre-
sented in the lowermost beds of Nevada Formation,
unit 1 (coral zone B) in the southern Sulphur Spring
Range. Here as at Lone Mountain, unit 1 changes
laterally in quite irregular fashion from dolomite to
dolomitic limestone to limestone. It is in lenses of cal-
carenite limestone with many rounded quartz granules
that the large solitary K obeha is most conspicuous and
is accompanied by few other fossils. Dolomitic lime-
stones are associated with these coralline facies. In
the same stratigraphic interval other calcarenite lenses
are loaded with the large shells of Costispirifer of the
C. arenosus type. Horn corals and brachiopods appear
to have been deposited in situ, but some of the large

 

 

 

 

24 LOWER A D LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

spirifer valves may ha e been sorted by current action
from the heavier corals to be concentrated in separate
bands. The corals h ve been silicified in varying
degrees.

   

PAPlLIOP LUM BIOFACIES

The large solitary apiliophyllum elegantulum of
the Halliidae is the mo t conspicuous fossil of this bio-
facies and in coral zon C, which occupies all but the
lowermost beds of Nev da Formation, unit 1. At Lone
Mountain and in the S lphur Spring Range, unit 1 is
laterally variable, cha ging in short distances from
limestone to dolomitic I mestone and to dolomite. Like
the Kobeha biofacies a d coral zone B at the base of
unit 1, this biofacies la ks colonial Rugosa; however,
the fauna as a whole is very much larger. The Hallii-
dae, now at their evolut onary peak, also include Aula-
cophyllum and Odonto hyllum; rugose corals of other
families are Cystiphyll ides and the earliest Brevi-
phrentis. Favosites in assive heads is the common
tabulate. As a whole, th fauna is a mixed association
containing many brachi pods, of which the most dis-
tinctive is Acrospirifer kobehana. Crinoid debris is
abundant. Gastropods a d clams are fairly numerous.
Papilophyllum succeeds Kobeha, from which it prob-
ably evolved, and conti ues to occupy the same eco-
logic niche. Within unit 1 there appears to be no special
preference of this fauna for either limestone or dolo-
mitic lithofacies. Corals and other fossils are silicified,
especially in the more dolomitic carbonate. Relative
abundance of stromatoporoids in the cleaner carbon-
ates of this biofacies has not been determined; prob-
ably they are numerous and, like the corals, of some
rock-building importance. No bioherms or patch reefs
were found in beds of the Papiliophyllum biofacies.

BREVIPHRE NTIS BIOFACIES

Following decline of the large Halliidae that char-
acterize the Kobeha and Papiliophyllum biofacies,
rugose corals of other families continued to increase
in numbers of genera and species. In terms of corals
and ecologically associated fossils, the Breviphrentis
biofacies of coral zone JD includes the largest and
taxonomically most varied faunas of the Great Basin
Devonian. The enclosing strata of Nevada Formation,
unit 2, to which this biofacies is confined, are im-
pure medium- and dark-gray argillaceous organic
limestones separated by shale and siltstone partings
and interbeds. Bottom faunas of this stratigraphic
interval were subjected periodically to abnormally
muddy water resulting from influx of current-trans-
ported clay or brought about by storm turbulence.
Favositids, solitary Rugosa, brachiopods, trilobites,
and Mollusca adapted well to the frequent turbid
water episodes. For the first time in the Devonian,

 

 

 

colonial Rugosa appear in this biofacies, but these
occur sporadically, are rather uncommon, and are far
outnumbered by solitary genera. Stromatoporoids are
quite scarce. It is suggested that stromatoporoid
scarcity and the small population of colonial Rugosa
may reflect inability of these organisms to withstand
turbidity. In the case of stromatoporoids such a likeli-
hood has been noted elsewhere by Rozkowska (1960,
p. 7).

Unlike cleaner carbonate rocks of Nevada Forma-
tion, unit 1, the impure limestones of unit 2 and the
Breviphrentis biofacies were not dolomitized diagene-
tically. Fossil silicification is, moreover, uncommon,
localized, and usually affects only the brachiopods of
unit 2. Beds with vast numbers of shells in a mixed
coral-brachiopod-trilobite assemblage show minimal
breakage of shells by wave or current action. Articu-
lated brachiopod valves are common and favositid
heads stand here and there in upright growth posi-
tions. The importance of the Rugosa as rock builders
is greatly overshadowed by the crinoids, massive
favositids, and brachiopods; the stromatoporoids play
an insignificant role. No biohermal bodies or incipient
patch reefs are known within this biofacies; mixed
faunal deposits with corals appear to have accumulated
as bands or beds in shallow water without appreciable
bottom relief.

Subordinate molluscan biofacies occupy shale or
siltstone interbeds of Nevada Formation, unit 2.
Clams and large gastropods are abundant locally in
these interbeds. Also present are the large heavy-
shelled benthonic tentaculites. Straight-shelled Ortho-
ceras-like cephalopods are fairly common in the
Breviphrentis biofacies, but the nautiloids and goni-
atites are quite uncommon.

Coralline beds with mixed faunas of the Brevi-
phrentis biofacies are usually dominated by massive
favositid heads. Numerically the most abundant
Rugosa are Breviphrentis, followed in order by Beth-
anyphyllum, the cystiphylloids, and the digono-
phyllids. Compound genera like Billingsastraea, Pin-
yonastraea, and Disphyllum are widely scattered in
relatively small pockets.

More detailed facies analysis of Nevada Formation,
unit 2 and the Breviphrentis biofacies will doubtless
lead to recognition of additional subsidiary biofacies
within which coral, trilobite, and other benthonic
associations may be discriminated. Biofacies com-
parison with the Onondaga Limestone of New York
which is approximately correlative geologically is
suggested. Unlike the Onondaga, no patch reefs or
extensive concentrations of colonial rugose corals were
recognized in the Breviphrentis biofacies. Oliver’s

 

 

CORAL SUCCESSION AND EVOLUTION 25

(1968, p. 31) New York Onondaga biofacies studies
call attention to five facies ranging in taxonomic
coral diversity from a high figure in patch reefs or
bioherms to a low figure in bedded coralline deposits.
Ecologically and taxonomically significant is Oliver’s
(1968, p. 30) observation that environmental factors
permitting high species diversity in Onondaga coral
faunas also favored greater variation within the
studied species.

HEXAGONARIA-SOCIOPHYLLUM BIOFACIES

Rugose coral assemblages of this predominantly
coralline biofacies in coral zone F occupy dolomitic
limestone, limestone, and dolomite of Nevada Forma-
tion, unit 4. The very great difference of coral faunas
from those of the Breviphrentis biofacies and coral
zone D is in harmony with the marked lithofacies
disparity, and the two are separated stratigraphically
by the barren zone of Nevada Formation, unit 3 and
coral zone E. For the first time in the Devonian,
colonial Rugosa outnumber the solitary forms in most
localities. The massive Favosites, so abundant in zone
D, is replaced by less numerous digitate favositids and
by Heliolites, a tabulate not found in the Devonian
below zone F. Patchy, discontinuous dolomitization is
similar to that in Nevada Formation, unit 1 and coral
zones B and C. Rugose corals and brachiopods of the
H exagonaria-Sociophyllum biofacies are strongly sili-
cified within the dolomitic carbonate. Rugose corals
together with stromatoporoids in situ are major car-
bonate builders in loci of thick-bedded massive and
more or less dolomitic limestone. Although this biota
is potentially reef forming, no true bioherms of large
dimensions were observed. The abundant rugose coral
genera in this biofacies at Lone Mountain and in the
Roberts Mountains are the colonial H exagonaria,
Taimyrophyllum, Cyathophyllum, Utaratuia, and
Sociophyllum together with the solitary genera Cysti-
phylloides, Mesophyllum, Digonophyllum, and Acan-
thophyllum.

PI-IILLIPSASTRAEA‘ BIOFACIES

The Phillipsastraea biofacies of Late Devonian age
occurs in relatively clean medium- to dark-gray lime-
stones in the upper part of the Devils Gate Limestone
and coral zone I. These upper beds have not been
diagenetically dolomitized, although the lower part of
the Devils Gate has been locally dolomitized in very
irregular fashion. Scattered concentrations of abun-
dant corals in the Devils Gate area and White Pine
district consist mainly of the colonial Phillipsas-
traeidae in bedded deposits. Stromatoporoids, so
abundant in stromatoporoid biofacies of coral zone H
in the lower Devils Gate Limestone, become incon-

 

spicuous in the Phillipsastraea biofacies. The tabulate
corals are almost unrepresented. Most of the diag-
nostic Rugosa of this biofacies are classified in the
single family Phillipsastraeidae and include the
colonial Pachyphyllum, Phillipsas traea, and Phacello-
phyllum together with the solitary MacGeea.

At Lone Mountain the upper beds of the Devils
Gate Limestone of this biofacies are not exposed above
the stromatoporoid-rich limestones in coral zone H.
They are present at Devils Gate and southward, but
they may best be observed in the White Pine district,
especially near the Belmont mine mill and in the low
range west of Monte Cristo.

CORAL SUCCESSION AND EVOLUTION AS
RELATED TO GEOLOGIC CHANGE AND
FAUNAL MIGRATION

Nearly 4,000 feet of geosynclinal marine strata in
the central Great Basin records much of the Devonian
Period, enclosing an unusually full succession of
rugose corals (fig. 9). Stratigraphically and in terms
of coral evolution, this succession is, however, far from
complete. Limestone or dolomite layers with abundant
corals and other fossils are separated by barren layers
of similar rock; between the coral-bearing units are
entire members hundreds of feet thick which yield
almost no Rugosa. How, these paleontologic gaps relate
to physical and biologic events of Devonian history
in the Great Basin province, and more generally in
the Cordilleran belt is a matter of some interest.
Worthy of consideration in this context is the possible
influence of a normal sea bottom ecologic succession
upon a coral biota. More important is the influence of
contemporaneous physical geologic change in the
surrounding terrane upon the accumulating layered
sediments.

Lateral spread and migration of the faunas was
influenced or compelled by a combination of such
physical and biologic factors. Corals of a particular
sedimentary facies were adapted to a sea floor environ-
ment which also affected or determined the character
of the entombing sediment. As with benthonic marine
organisms generally, the intricate fabric of rugose coral
evolution entails factors of species spread and migra-
tion, adaptation to available ecologic niches, isolation
of gene pools, mutation or gene recombination, and
above all survival or extinction by natural selection.
Classic paleontology sheds little light upon the under-
lying causative factors of evolution. Although the
fossil record is demonstrably incomplete, the study of
rugose corals frOm the more continuous sections of
this region makes possible the outlining of the broad
evolutionary trends and patterns, especially in the

 

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CORAL SUCCESSION AND EVOLUTION 27

hardier, more persistently adaptive lineages. In basins
of fairly continuous carbonate accumulation such as
these, coral lineages which survived for long periods
of progressive in situ evolutionary change may theo-
retically be distinguished from less adaptive stocks,
the fossil record of which is in this area brief. In the
central Great Basin Devonian, persistent lineages of
this kind are probably recognizable in the Laccophyl-
lidae with Syringaxon, in the endemic Papiliophyllinae,
in the Bethanyphyllidae, and among the Siphono-
phrentinae, as represented by Breviphrentis. Abun-
dant and ranging through considerable thicknesses of
strata, these evolutionary lineages may lend them-
selves eventually to bed-by-bed quantitative evolu-
tionary investigation.

The physical and biologic environment within a
given area of shallow Devonian sea bottom was under-
going constant fluctuating change. As recorded by
sediments and their entombed fossils, these changes
were to some extent repetitive and perhaps in some
instances cyclical. Exclusive of physical geologic fac-
tors, the normal ecologic succession of organisms upon
a growth site should be considered. Metabolic and
secretional activities of ecologically interdependent
colony-building organisms are capable of so modifying
their habitat as to inhibit continued occupancy by
the same biota. Hence upward disappearance of a coral
assemblage from a particular bed of in situ growth is
explainable. The succession of evolving coral assem-
blages in Nevada Formation, unit 2 provides good
examples of this situation.

Physical geologic changes have acted through
geologic time to keep the currents of life moving,
indirectly affecting the course of organic evolution.
Uplift, subsidence, mountain building, and erosion are
primary driving forces of biologic change. Evidences
of contemporaneous crustal deformation are difficult
to recognize and interpret within the stratified
Devonian rocks of the Great Basin. Although there
are no indications of contemporaneous folding or tilt-
ing, it is clear that upward sedimentary rock changes
were in some part controlled by crustal deformation
affecting the shelving sea bottoms and the adjacent
lands. Crustal movements brought local shifts in
marine and atmospheric circulation, changing the
direction and load capacity of debris-carrying currents.
Landward debris sources were modified to affect the
offshore character of accumulating marine deposits.

Convincing field evidences of unconformity within
the central Great Basin Devonian System are few
indeed, there being no recognized angular stratigraphic
discordances, major stratigraphic gaps, or erosion
intervals. Nonetheless there are many abrupt vertical

534-041 0 - 74 - 3

 

lithologic changes in seemingly parallel strata, accom-
panied by sudden faunal change. It is not, therefore,
unlikely that significant disconformities have been
overlooked. Within Nevada Formation, unit 2 may be
observed many repetitive vertical lithologic changes
with concurrent faunal change. In this unit fossil-rich
limestones characteristically alternate with silty and
argillaceous beds containing a somewhat different
fauna. Some of these changes appear to be more or ‘
less cyclical and may be partly the result of ecological
succession. More extreme rock changes in unit 2
followed local introduction of the white quartzitic
sands, bringing a facies usually barren of fossils. Sud-
den and permanent faunal change accompanied the
great rock change at the gradational boundary sepa-
rating unit 2 from unit 3; at this horizon the rich zone
D faunas disappear completely. Less abrupt is the
appearance of coral zone F assemblages above the
contact of unit 4 with the barren zone of unit 3.

CORAL CHANGES AT CLOSE OF SILURIAN

Resumption of limestone or dolomite deposition in
Early Devonian time was accompanied by abrupt and
profound change in corals (fig. 9). In the Great Basin
province, few rugose corals ancestral to Devonian
forms are known from either dolomite or limestone
facies of the Late Silurian. Change in the character
of carbonate deposition at this systemic boundary is
not great in several of the studied sections; physical
evidences of disconformity observable on the outcrop
are local and have been found thus far only in the
dolomite facies.

It is reasonable to link the major paleontologic
changes at the Silurian-Devonian boundary with the
“Caledonian Revolution,” a prolonged series of com-
pressive distubances which deformed Silurian and
older rocks in widely separated parts of the Northern
Hemisphere. Although angular discordance or indi-
cation of Caledonian compressive deformation is
unknown in the Great Basin, the mapping of the
Silurian-Devonian contact in several areas gives evi-
dence of disconformity. For example, in the Gold Hill
mining district of western Utah (Nolan, 1935, p. 18),
a disconformity is reported as separating Silurian
Laketown Dolomite from Early Devonian Sevy Dolo-
mite; this discordance is also recognized in the
Confusion Range (R. K. Hose, written commun.,
1958). Similarly, in the Diamond Mountains and in
the Mahogany Hills near Eureka, Nev., a mappable
disconformity separates Silurian Lone Mountain Dolo-
mite from the Lower Devonian beds, according to
Nolan, Merriam, and Williams (1956, p. 38). The
disconformity has not been traced laterally to the

 

 

 

28 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

Lone Mountain reference section, where the Silurian
dolomite is overlain with seeming concordance by
dolomite at the base of Nevada Formation, unit 1.
Unrecognized at this boundary zone are beds of the
Early Devonian Beacon Peak Dolomite Member,
which would be expected here, and the coral faunas
of Devonian coral zones A and B. Although the Lone
Mountain Dolomite—Nevada Formation boundary
appears gradational, the possibility of a depositional
gap here has not been entirely eliminated.

The beds in the Lone Mountain Dolomite Silurian
facies are characterized by the halysitids, pycnostylid
Rugosa, and Entelophyllum; none of these corals
reappear in the Devonian. Better understood are
boundary fauna] changes in limestone facies of the
Silurian Roberts Mountains Formation where it is
overlain without recognized depositional break by the
Early Devonian Rabbit Hill Limestone. For example,
in Coal Canyon, northern Simpson Park Mountains,
the limestones of Late Silurian coral zone E contain a
large Gotlandian type coral assemblage with Myco-
phyllinae, Kodonophyllidae, Chonophyllidae, Pycno-
stylidae, Goniophyllidae, and Endophyllidae. The
overlying Rabbit Hill has yielded only the solitary
Syringaxon in this area. A single occurrence of the
endophyllid Australophyllum is known elsewhere in
the Rabbit Hill. Clearly the rather unimpressive
lithologic change at the Silurian-Devonian boundary
is not commensurate with the profound change in the
coral fauna.

LATE SILURIAN AND DEVONIAN BURSTS 0F
RUGOSE CORAL EVOLUTION

From Late Silurian through Late Devonian time,
the history of the Rugosa in the Great Basin seaways
was characterized by bursts of proliferation and evolu-
tionary differentiation, separated by intervals during
which the Rugosa were restricted in taxonomic diver-
sity or poorly represented. Such bursts of coral activity
took place: ( 1) in Late Silurian coral zone E of the
upper Roberts Mountains limestones (fig. 9); (2) in
Early to early Middle Devonian coral zone D of
Nevada Formation, unit 2; (3) in Middle Devonian
coral zone F of Nevada Formation, unit 4; and (4) in
Late Devonian coral zone I of the upper Devils Gate
Limestone. Each burst involved taxonomically dif-
ferent coral groups which reached their peak in
evolution at that time (see table 1). During the
intervals of coral zones A and B, rugose corals were
little differentiated although they were locally numer-
ous; the rugose corals of zone C were becoming more
diverse. Coral zones E and H show a poor representa-
tion of the Rugosa; the beds carrying coral zone G are

TABLE 1.—Evolutionary coral bursts in the Great Basin during
the Silurian and Devonian Periods

 

 

 

 

 

 

 

 

 

 

 

 

 

Great Basin
Devonian European
coral zone Coral burst stage A ge
Rugose corals Famennian
unknown in latest q)
Devonian of 13
Great Basin .4
I I Frasnian
H ————'!—————-—‘.7-—- 5
G Givetian % ‘E
F F '5 g
Eifelian E o
E 7 D
D D ____'____'_T_
C ’ Emsian ,2.
A
B . . a
A Siegeman F11
Silurian I:
coral zone SE Ludlovian 3 .5
E a S
"l r:
(I)

 

 

 

 

 

introductory to an interval of dolomite facies unfavor-
able to the Rugosa.

Following the Late Devonian burst of coral zone I,
the Rugosa declined and seemingly disappeared in this
region before the close of the Devonian Period. When
Rugosa reappear in the Mississippian Joana Lime-
stone following an interval of extinction, they are
represented by entirely different families which are
unknown below this horizon.

ZONE D CORAL BURST

With deposition of impure argillaceous limestones
in Nevada Formation, unit 2 of the Antelope-Roberts
Mountains facies belt came the zone D burst of rugose
coral differentiation. This episode opened rather
abruptly after the interval of coral zones B and C in
which solitary Halliidae were dominant and coral
faunas were far less diverse. Siphonophrentinae,
Cystiphylloidae, and Bethanyphyllidae peaked in
coral zone D. Colonial genera, mainly Disphyllidae,
appeared, but these are subordinate to the solitary
genera. Large solitary Digonophyllidae arrived at this
time, reaching their acme later in coral zone F,
together with the Disphyllidae. Benthonic life was in
general favored by the shallow sea environment of
zone D; Tabulata were numerous and taxonomically
diverse, as were brachiopods, trilobites, and Mollusca.
In terms of genera and species, the zone D inverte-
brate faunas are overall the largest of the Great Basin
Devonian.

Except for poorly preserved disphyllids and solitary
coral species assigned to Cyathophyllum, the next
higher interval of Nevada Formation, unit 3 (coral
zone E) yields few Rugosa, and none from coral zone
D are known to carry over into this barren zone.

ZONE F CORAL BURST

Rugosa again became numerous and taxonomically

 

 

 

AGE AND CORRELATION OF CORAL ZONES 29

diverse within the interval of Nevada Formation, unit
4. Colonial genera are abundant for the first time in
the Devonian, being concentrated in growth sites
where corals predominate and where the limestones
are partly dolomitic. Away from these dolomitic lime-
stone loci, corals are scarce or absent, as in rocks of
this interval in the Diamond Mountains facies belt.
Families and subfamilies are not so numerous as in
coral zone D, but the Disphyllidae have differentiated
generically and the large solitary digonophyllids are
at their evolutionary peak. This was also an interval
of great rugose coral proliferation through the northern
part of the Cordilleran Belt in western Canada.

ZONE I CORAL BURST

Marine environments in which were deposited the
coarsely saccharoidal dolomite and thick-bedded stro-
matoporoid limestones of zones G and H were evi-
dently not conducive to rugose coral growth. When
next the Rugosa appear in force within Late Devonian
coral zone I, nearly all of the subfamilies and genera
of zones D and F have disappeared, their places being
taken by Phillipsastraeidae and one or two other sub-
ordinate families. Ancestry of the Phillipsastraeidae is
unknown. In coral zone F the genus Taimyrophyllum
superficially resembles Pachyphyllum, but a study of
internal structure does not bear out a genetic con-
nection.

In the upper part of the Devils Gate Limestone,
Phillipsastraeidae of zone I occur in scattered con-
centrations ecologically like those of coral zone F and
do not occupy laterally persistent coral beds. Similar
scattered loci of zone I coral proliferation occur in the
northern part of the Cordilleran Belt in Canada and
Alaska; this family also characterizes the Frasnian of
other continents.

AGE AND CORRELATION OF GREAT BASIN
EARLY AND EARLY MIDDLE DEVONIAN CORAL
ZONES

Early Devonian rocks were made known in the
central Great Basin during the geologic reconnais-
sance of the Roberts Mountains in 1934. At that time
beds containing Costispirifer similar to the eastern
Oriskany C. arenosus were discovered in a badly
faulted section. Stratigraphic studies in the Monitor-
Simpson Park belt during the 1950’s led to the recog-
nition of the Helderbergian age of the Rabbit Hill
Limestone (Merriam, 1963, p. 42—44). A review by
House (1962, p. 252) of cephalopod evidence in the
American Devonian led to the conclusion that the
“Spirifer pinyonensis zone” of Merriam (1940, p. 51),
initially called Middle Devonian, may also be of Early

 

Devonian age. In recent years research upon corals
and brachiopods allied to a broad program of geologic
mapping and stratigraphy in the Sulphur Spring
Range and areas adjoining the Eureka mining district
has shed light upon age and correlation problems.

AGE AND CORRELATION WITH DISTANT REGIONS
CORAL ZONE A

The Rabbit Hill rugose coral genera Syringaxon and
Australophyllum, because they occur in both Silurian
and Devonian strata of distant regions, have at present
no definitive correlation value. However, the Helder-
berg age of this formation is convincingly borne out
by associated brachiopods among which are: Levenea
of. L. subcarinata (Hall), Howellella cf. H. cycloptera
(Hall), Anastrophia cf. A. verneuili (Hall), and
Orthostrophia cf. 0. strophomenoides (Hall). Other
fossils of Helderbergian affinity are trilobites assigned
to Leonaspis and two species of the tabulate coral
Pleurodictyum. The closest known relatives of the
Rabbit Hill fauna thus occur in rocks of Helderbergian
age in New York, Oklahoma, and Tennessee (Mer-
riam, 1963, p. 43). Costispirifer foreshadowing the
New York Oriskany C. arenosus appears in higher
beds of the Rabbit Hill.

CORAL ZONE B

The large and abundant Kobeha walcotti of the
Halliidae occurs here without other rugose coral asso-
ciates; like Papiliophyllum of succeeding coral zone
C, Kobeha seems to be endemic in the Great Basin
Province and, as such, is of no distant correlation value
at present. Approximate Oriskany or Siegenian age is
indicated by the associated brachiopod fauna contain-
ing Costispirifer cf. C. arenosus and Gypidula with
affinity to G. coeymanensis. The “Trematospira fauna”
of Merriam (1940, p. 50), with C. arenosus and Tre-
matOSpira cooperi, is that of coral zone B. First recog-
nized within the intensely faulted terrane on the west
side of Roberts Creek Mountain (Merriam, 1940, p.
50—52, pl. 1), the fossils of this Oriskany interval have
in recent years been discovered during the mapping of
these deposits southward from the Old Whalen mine
area in the Sulphur Spring Range. In this range
several of the more complete stratigraphic sections
include all Devonian coral zones from A through D
in order.

CORAL ZONE C

The endemic halliid coral Papiliophyllum succeeds
Kobeha of underlying coral zone B. A larger coral
fauna accompanies Papiliophyllum, including the hal-
liid Odontophyllum meeki and Breviphrentis kobehen-
sis of the subfamily Siphonophrentinae. The Onondaga

 

 

 

30 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

and Hamilton Formations of eastern North America
are characterized by members of this subfamily
which appears earlier in the New York Coeymans
(Oliver, 1960a, p. 87). Siphonophrentis (Breviphren-
tis) kobehensis is less similar to Siphonophrentis
variabilis Oliver of the Coeymans than is Siphono-
phrentis (Breviphrentis) invaginatus of coral zone D.
Eastern species of Odontophyllum (Stumm, 1948b)
differ specifically from 0. meeki of coral zone C and
are reported to be of Middle Devonian age.

A preliminary appraisal of brachiopods in coral zone
C, the Acrospirifer kobehana zone (Merriam, 1940,
p. 50—53) , indicates that a provisional correlation with
the European Emsian appears reasonable.

CORAL ZONE D

Coral zone D brackets the interval of Nevada For-
mation, unit 2 in the Lone Mountain reference section
and corresponds to the “Spirifer pinyonensis zone” of
earlier usage (Merriam, 1940, p. 53). Vertical changes
in the rugose corals make it possible to further sub-
divide this zone into subzones D1, D2, and D3 in
ascending order. Initial appraisal of zone D coral,
brachiopod, and trilobite assemblages by the writer
in the 1930’s (Merriam, 1940) led to a Middle Devo-
nian age assignment, although underlying strata of
coral zone C, or the “Spirifer kobehana zone,” were
at that time considered Lower Devonian. The beds
of Nevada Formation, unit 2 were later assigned by
others to Early Devonian (Johnson, 1962a; 1962b;
1966b). Paleontologic support of the Early Devonian
interpretation comes in large degree at present from
the ammonoid succession as reviewed by House (1962,
p. 247—284). A well-preserved goniatite described by
A. K. Miller (1938, p. 46, pl. 6, fig. 1) as Agoniatites
nevadensis was collected by the writer in 1933 from
a locality near M29 on the southwest side of Lone
Mountain. The beds yielding the goniatite are Nevada
Formation, unit 2, within the range of coral zone D2;
associated fossils include Billingsastraea nevadensis.
This fossil is the only fairly complete goniatite known
from the lower part of the Nevada Formation; frag-
mentary material has been found at Bush Creek in
the Roberts Mountains and at Combs Peak by Wal-
cott. Restudy by House of the Miller type and the
only specimen of A. nevadensis, in the light of Erben’s
(1960) revision of European Early Devonian goni-
atites, led to reassignment of this species to Teicher-
ticeras, a genus considered indicative of the Emsian.

The conclusions of House and of Johnson regarding
the Early Devonian assignment of the entire “Spirifer
pinyonensis zone” or Nevada Formation, unit 2 are
only in part borne out by results of these coral investi-

 

 

gations. In harmony with an Early Devonian assign-
ment, the coral fauna of subzone D1 includes an
advanced Papiliophyllum elegantulum called sub-
species d. Upward in the section the preponderant
Rugosa are Siphonophrentinae of the species Brevi-
phrentis invaginatus, making these faunas similar to
the Onondaga faunas. The eastern Onondaga is analo-
gous, as it has an abundance locally of Siphonophren-
tinae; but the forms belonging to this family are mainly
Heterophrentis. Among other Rugosa of subzone D2,
Billingsastraea nevadensis shares many features with
the late Early Devonian Billingsastraea afi‘inis (Bill-
ings) of the Grande Greve, as refigured by Oliver
(1964).

Other Rugosa of subzone D2, the Family Bethany—
phyllidae, Family Digonophyllidae, and the Hexa-
gonaria, are less in accord with an Early Devonian age;
these Rugosa represent elements largely known from
starta of Middle Devonian age. The Halliidae, which
here characterized the Lower Devonian beds of coral
zones B and C, are uncommon above subzone D1, their
places being taken by the Bethanyphyllidae.

Digonophyllidae appear in subzone D2 with Meso-
phyllum and Zonophylglum. The Digonophyllidae in
these beds are greatly outnumbered by Siphonophren-
tinae and Bethanyphyllidae Zonophyllum haguei is
at least specifically distinct from Z. duplicatum
Wedekind of the early Middle Devonian “Nohner
Schichten” in the Eifel district, Germany. In Europe
and the Cordilleran Belt of North America, Digono-
phyllidae, are especially characteristic of the Middle
Devonian (Eifelian), peak in Great Basin coral zone
F. Bethanyphyllidae in this area are seemingly con-
fined to subzones D1 and D2. Hexagonaria of subzone
D2 is here placed in a new subgenus Pinyonastraea.
True Hexagonaria is known here only in coral zone
F, where it is locally the abundant genus.

Passing upward at Lone Mountain into subzone D3
and the uppermost beds of Nevada Formation, unit
2, the Digonophyllidae are represented by the struc-
turally complex Mesophyllum (Arcophyllum) kirki, a
species resembling Arcophyllum in the Middle Devo-
nian (Eifelian) in the Eifel district, Germany. Arco-
phyllum kirki has its nearest relatives in the zone of
“Cosmophyllum dachsbergi” at Gerolstein, Eifel dis-
trict (Wedekind, 1925, p. 71); following Wedekind’s
interpretation, this horizon is well within the Middle
Devonian.

In summary, these data appear to support the
ammonoid evidence for the Early Devonian age of
some part of the “Spirifer pinyonensis zone” of prior
usage, or Nevada Formation, unit 2. However, Middle
Devonian rugose coral elements are present in sub-

 

 

AGE AND CORRELATION OF CORAL ZONES 31

zone D2 together with those of latest Early Devonian,
and the digonophyllid Mesophyllum (Arcophyllum)
kirki of subzone D3 is, in the absence of conflicting
data, considered Middle Devonian. Accordingly, the
rocks of Nevada Formation, unit 2 and coral zone D
are here referred to as Early and early Middle
Devonian. Conclusions regarding age and correlation
of subzone D2 should await detailed description and
analysis of the large brachiopod and trilobite faunas,
together with the conodonts and tentaculites of this
interval. Likewise the ammonoid evidence is meager
at present. Rugose coral data suggest that the subjec-
tive Lower-Middle Devonian boundary lies figuratively
within a “gray band” of coral zone D and Nevada
Formation, unit 2.

CORRELATION WITH OTHER AREAS IN THE
CORDILLERAN BELT

Within the Cordilleran Belt, Early and early Middle
Devonian rugose coral-bearing rocks are almost un-
known outside the Great Basin. In the Canadian
Northwest, the oldest Devonian coral-bearing strata
thus far‘elucidated are the Eifelian or Givetian Hume
and Nahanni Formations, which contain faunas corre-
lative with Great Basin coral zone F. Billingsastraea-
like colonial Rugosa in these Middle Devonian forma-
tions are similar to Nevada Formation, unit 4 (coral
zone F) species. However, Billingsastraea verrilli
(Meek) of the Hume (Pedder, 1964), though speci-
fically distinct, possesses features of the older B.
nevadensis of coral subzone D2. Strata beneath the
Hume have yielded goniatites of the genus Teicher-
ticeras that are indicative of a possible Emsian age
(House and Pedder, 1963, p. 491); these older beds
are not known to contain Rugosa. The expected dis-
tribution of the Devonian System throughout the
Cordilleran Belt makes it seem unlikely that strata
correlative to Rabbit Hill and Oriskany of Lower
Devonian age are absent from these northerly regions.
Possibly the strata are represented as relatively unfos-
siliferous dolomites below the Hume and the Nahanni
Formations.

In Alaska Early Devonian rocks are likewise nearly
unknown. The well-understood Paleozoic sections of
the southeast Alaska panhandle include a very thick
Silurian column, and the Middle and Upper Devonian
are well represented, but the presence of Early
Devonian has not as yet been established.

Of interest in this connection is the occurrence of
glacial cobbles in the Chewelah area of Stevens
County, northeast Washington, that contain a fauna
resembling the Rabbit Hill Helderberg (F. K. Miller,
oral commun., 1965). Among the fossils are Syring-

 

axon sp., Pleurodictyum cf. P. lenticularis (Hall),
Levenea cf. L. subcarinata (Hall), and a species of
Leptocoelia.

NORTH-CENTRAL GREAT BASIN
NORTHERN SULPHUR SPRING RANGE

The Nevada Formation extends northward in the
Sulphur Spring Range through the Mineral Hill dis-
trict, where local names have been applied to lithologic
subdivisions (Carlisle and others, 1957; Johnson,
1962b). Fossil collections show that Devonian coral
zones B, C, and D are present. Zone B strata in
McColley Canyon contain a variety of Kobeha differ-
ing somewhat from typical K. walcotti. West of the
Old Whalen mine, lower beds of Nevada Formation,
unit 1 carry the Costispirifer arenosus brachiopod
assemblage but have not yielded Kobeha; these Costi-
sipirifer beds are calcarenites with quartz grains like
those in zone B which contains Kobeha and Costi-
spirifer in the southern Sulphur Spring Range. Beacon
Peak Dolomite Member with the Rabbit Hill fauna
and coral zone A has not been identified in the
northern part of this range.

SOUTHERN TUSCARORA MOUNTAINS

The northernmost known occurrence of Lower
Devonian beds in the Great Basin is at Maggie Creek,
8 miles northwest of Carlin, Nev. in the southern
Tuscarora Mountains. Limestones of Rabbit Hill age
at this locality contain a coral-brachiopod fauna
including Syringaxon, Pleurodictyum, and a Billings-
astraea-like colonial coral. This is one of two occur-
rences of a colonial rugose coral in Devonian coral
zone A. The Helderbergian limestones at Maggie
Creek are underlain by the Roberts Mountains
Formation.

CORTEZ MOUNTAINS

In the Cortez Mountains, strata carrying a Rabbit
Hill Helderbergian fauna occur 1.5 miles southeast
of Mount Tenabo summit (locality M1083). Pleuro-
dictyum together with abundant Syringaxon foerstei
indicate Devonian coral zone A.

WEST-CENTRAL GREAT BASIN
TOIYABE RANGE

Devonian limestone and calcareous shale correlative
with the Nevada Formation have recently been dis-
covered by R. H. Washburn (written commun., 1968)
on the west side of the Toiyabe Range 15 miles south-
west of Austin, Nev. (Stewart and McKee, 1968).
Exposures in the Reeds Canyon vicinity (locality
M1151) have yielded the compound Billingsastraea?

 

 

 

32 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

sp. T and a large H exagonaria-like form. Provisionally
compared to Billingsastraea and Hexagonaria (Pin-
yonastraea) of coral subzone D2, a restudy suggests
that the Billingsas traea-like form may be more closely
allied to undescribed Taimyrophyllum of coral zone
F. Accordingly, the age of this fauna remains some-
what uncertain, but it is more likely Middle than Early
Devonian. As the Toiyabe Devonian section is thick
and fairly continuous upward from underlying grapto-
litic Silurian, it is not improbable that other Devonian
fossil horizons, including the Rabbit Hill, may even-
tually be discriminated here.

SOUTH-CENTRAL GREAT BASIN

HOT CREEK RANGE

Corals suggesting zones C and D have been col-
lected in little-known Devonian beds of the Hot Creek
Range. Fragmentary specimens of probable Papilio-
phyllum come from locality M1066 in Hot Creek
Canyon (H. E. Cook, written commun., 1966) and an
Aulacophyllum-like coral comes from the Morey Peak
vicinity (H. W. Dodge, Jr., written commun., 1968).
Coral faunas of zone F are better known in this range,
suggesting that most or all of the Nevada Formation
interval is represented.

SOUTHERN GREAT BASIN

Southern Great Basin rugose coral-bearing beds of
Early and early Middle Devonian ages are known in
the Ranger Mountains, the Desert Range, the northern
Panamint Mountains, and the Funeral Mountains.
The occurrence of faunas at each place indicates a
southerly extension of the seaway in which the lower
part of the Nevada Formation of central Nevada was
deposited. No fossils with certainty as old as the
Rabbit Hill Helderbergian have thus far been dis-
covered in these southern mountain ranges.

RANGER MOUNTAINS

Dolomite, limestone, and quartzite, some 3,000 feet
thick and including beds rich in rugose corals, occur
in the Ranger Mountains and other ranges border-
ing Frenchman Flat, Nye and Clark Counties, Nev.
(Johnson and Hibbard, 1957, p. 350—356; F. G. Poole,
written commun., 1964). A quartzite about 90 feet
thick in the lower part of this section probably corre-
sponds to the Oxyoke Canyon Sandstone Member of
the Eureka district 200 miles north. The fauna occur-
ring in limestone beds 170 feet below the quartzite
and about 10 feet above a thick dolomite sequence
includes Siphonophrentis (Breviphrentis) invaginatus,
Zonophyllum sp., and Papiliophyllum elegantulum

 

 

subsp. d. Other fossils identified from this horizon
are Chonetes macrostriata, Dalmanites meeki, and a
Strophonella. The rugose corals suggest that this
fauna represents the lower part of coral zone D and
probably correlates with D1 of the Lone Mountain
column because of the presence of the advanced
Papiliophyllum. It is not unlikely that the underlying
dolomites include earlier Devonian as well as a Lone
Mountain Dolomite equivalent.

DESERT RANGE

Devonian beds at the south end of the Desert
Range, 30 miles east of Frenchman Flat (Locality
M1057, C. R. Longwell, oral commun., 1958) include
a fauna with Chonetes macrostriata, Strophonella,
Acrospirifer sp. and an incomplete corallum of either
Siphonophrentis (Breviphrentis) or Sinospongophyl-
lum. This assemblage suggests lower coral zone D,
possibly about the horizon of the Ranger Mountains
occurrence.

NORTHERN PANAMINT MOUNTAINS

Fossil collections from the upper part of McAllister’s
Hidden Valley Dolomite unit 3b (McAllister, 1952,
p. 17) in the southern Andy Hills of the Panamint
Mountains (Marble Canyon quadrangle, Calif.) in-
clude Acrospirifer kobehana, Costispirifer arenosus,
Papiliophyllum elegantulum, and Siphonophrentis
(Breviphrentis) cf. invaginatus. The spirifers and
Papiliophyllum indicate Early Devonian in the com-
bined intervals of coral zones B, C, and possible D1.
The genus Kobeha, which is to be expected with
Costispirifer arenosus, was not found here. Possibly
C. arenosus ranges upward in the Panamint Moun-
tains into beds with Acrospirifer kobehana and Papilio-
phyllum. In the lower part of the Nevada Formation
of central Nevada, the beds of coral zone B with C.
arenosus and Kobeha underlie those of coral zone C
with A. kobehana and Papiliophyllum elegantulum.
The Panamint beds in question appear to be older
than those in the Ranger Mountains and those in the
Desert Range that are discussed above which appear
to be correlative with the Nevada Formation, unit 2;
the Panamint Early Devonian strata are correlative
with Nevada Formation, unit 1 of the Lone Mountain
section.

FUNERAL MOUNTAINS

The upper part of the Hidden Valley Dolomite in
the vicinity of Pyramid Peak (Ryan quadrangle,
Calif), southern Funeral Mountains, contains coral
and brachiopod faunas resembling in part those of
the same dolomite unit in the northern Panamint
Mountains. Collections from six localities made by
J. F. McAllister include an abundance of a large

 

 

———’i

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 33

Meristella similar to M. robertsensis and abundant
Siphonophrentis (Breviphrentis) invaginatus. Less
common are Papiliophyllum elegantulum and Aulaco-
phyllum-like forms. These collections do not contain
Costispirifer arenosus or Acrospirifer kobehana as do
collections from the upper Hidden Valley of the Andy
Hills area, northern Panamint Mountains. Absence of
Early Devonian spirifers suggests that the Funeral
Mountains faunas may be somewhat younger than
the horizons of coral zones B and C, possibly being of
the age of coral zone D1 which contains the highest

Papiliophyllum.
NORTHERN INYO MOUNTAINS

Upper beds of the Vaughn Gulch Limestone at
Mazourka Canyon, northern Inyo Mountains contain
a species of Australophyllum similar to A. landerensis
of the Rabbit Hill. The upper Vaughn Gulch beds are
underlain by strata of Upper Silurian coral zone E
that also underlie the Rabbit Hill Limestone at Coal
Canyon, Simpson Park Mountains. Confirmation of
Helderbergian age of the upper Vaughn Gulch by other
fossils has not been achieved, and these beds are pres-
ently classified as Late Silurian or Early Devonian.

SYSTEMATIC AND DESCRIPTIVE
PALEONTOLOGY

CLASSIFICATION OF GREAT BASIN EARLY AND
EARLY MIDDLE DEVONIAN RUGOSA

Th classification adopted for Great Basin Rugosa
here described is for the greater part in accord with
that of Hill (1956), the most comprehensive and
authoritative classification published thus far. Depar-
tures from Hill’s arrangement of families and genera
involve content of certain families, status of sub-
families, and family or subfamily assignment of several
genera.

A new subfamily, the Siphonophrentinae, is pro-
posed to accommodate certain advanced Streptelas-
matidae. Because of uncertainties in the characteriza-
tion of Zaphrentis, the Family Zaphrentidae is not
used herein. The Disphyllidae are considered an inde-
pendent family not closely related to the Phillipsas-
traeidae, by reason of fundamental differences of
tissue structure. Stumm’s subfamily Papiliophyllinae
is restored for these seemingly endemic Halliidae; also
adopted is Stumm’s family Bethanyphyllidae, which
has a wide geographic distribution. For certain Great
Basin Silurian and Early Devonian species of Aus-
tralophyllum the Family Endophyllidae is adopted,
forms which might otherwise have been relegated to
the ill-defined Spongophyllidae. Stumm’s Family Cys-
tiphylloidae is restored to include Cystiphylloides, in

 

preference to placing it under Mesophyllum of the
Digonophyllidae.

Order RUGOSA Edwards and Haime 1850
I. Family Laccophyllidae Grabau, 1928
Genus Syringaxon Lindstrom, 1882
Syringaxon foerstei n. sp.
II. Family Streptelasmatidae Nicholson, 1889
(as Streptelasmidae)
Subfamily Siphonophrentinae new subfamily
Genus Siphonophrentis O’Connell, 1914
Subgenus B reviphrentis Stumm, 1949
(as genus)
Siphonophrentis (Breviphrentis)
invaginatus (Stumm)
Siphonophrentis (Breviphrentis)
kobehensis n. sp.
Genus Nevadaphyllum Stumm, 1937
N evadaphyllum masoni Stumm
III. Family Kodonophyllidae Wedekind, 1927
Subfamily Kodonophyllinae Wedekind, 1927
Genus Kodonophyllum Wedekind, 1927
(?)Kodonophyllum sp. a
IV. Family Stauriidae Edwards and Haime, 1850
Genus Dendrostella Glinski, 1957
(as subgenus of Favis tella)
Dendros tella romanensis n. Sp.
V. Family Halliidae Chapman, 1893
Subfamily Haliinae Chapman, 1893
Genus Aulacophyllum Edwards and Haime,
1850
Aulacophyllum sp. 0
Genus Odontophyllum Simpson, 1900
Odontophyllum meeki n. sp.
Subfamily Papiliophyllinae Stumm, 1949
Genus Papiliophyllum Stumm, 1937
Papiliophyllum elegantulum Stumm
Papiliophyllum elegantulum subsp.
d
Genus Kobeha new genus
K obeha walcotti n. gen., n. sp.
Kobeha ketophylloides n. gen., n. sp.
Genus Eurekaphyllum Stumm, 1937
Eurekaphyllum breviseptatum
Stumm
VI. Family Bethanyphyllidae Stumm, 1949
Genus Bethanyphyllum Stumm, 1949
Bethanyphyllum lonense (Stumm)
Bethanyphyllum antelopensis n. sp.
Bethanyphyllum sp. 6.
VII. Family Chonophyllidae Holmes, 1887
Genus Sinospongophyllum Yoh, 1937
Sinospongophyllum Sp. (1
Sinospongophyllum sp. e

 

fi

34 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

Sinospongophyllum sp. f
VIII. Family Endophyllidae Torley, 1933

Genus Australophyllum Stumm, 1949

Australophyllum landerensis n. sp.
IX. Family Disphyllidae Hill, 1939

Genus Disphyllum de Fromentel, 1861
Disphyllum nevadense (Stumm)
Disphyllum eurekaensis n. sp.

Genus Hexagonaria Giirich, 1896

Subgenus Pinyonastraea new subgenus
H exagonaria (Pinyonas traea)
kirki (Stumm)

Genus Billingsastraea Grabau, 1917
Billingsastraea nevadensis Stumm
Billingsastraea nevadensis subsp.
arachne (Stumm)

Billingsas traea? sp. T
X. Family Cystiphylloidae Stumm, 1949

Genus Cystiphylloides Chapman, 1893
Cystiphylloides robertsense
(Stumm)

Cystiphylloides lonense (Stumm)
Cystiphylloides sp. (1
XI. Family Digonophyllidae Wedekind, 1924
Subfamily Digonophyllinae Wedekind, 1924
Genus MeSOphyllum Schliiter, 1889
Subgenus Mesophyllum Schlfiter, 1889
Mesophyllum (Mesophyllum)
sp. b
Mesophyllum (Mesophyllum)
sp. c ‘
Subgenus Arcophyllum Markov, 1926
(as genus)
Mesophyllum (Arcophyllum)
kirki (Stumm)
Subfamily Zonophyllinae Wedekind, 1924

Genus Zonophyllum Wedekind, 1924
Zonophyllum haguei n. sp.
Zonophyllum sp. a
Zonophyllum sp. b

TAXONOMIC INTERPRETATION OF
RUGOSE CORAL STRUCTURE

Traditional gross comparative morphology of skele-
tal features is the basis for revised classification of
Silurian and Divonian Rugosa here adopted. Diagnos-
tic characters of families and genera are visible to the
unaided eye or under low magnification. Coral speci-
alists have long sought recognition of minute histologic
details as reliable taxonomic guides. Structures of this
kind, visible under a magnification range of 8—20 diam-
eters, have appropriately been called fine structure
(Kato, 1963). Although of value in the recognition of

 

certain families, fine structure is somewhat less diag-
nostic than the well-known minute wall features of

groupings are meaningful histologic characters of this
scale in wall tissue of Tryplasmatidae and Phillipsas-
traeidae (Ogilvie, 1897; Hill, 1936; Wang, 1950; Kato,
1963). None of the Early and early Middle Devonian
species here described disclose these minute features
convincingly. Silicificatron and other forms of additive
' ' most instances destroyed
original histologic structures or left them but vaguely
discernible in thin section through a veil of secondary
crystallization. Ideally a biologic classification based

At species and infraspecies levels, biometrics and
statistical analysis of variation have a definite place

The basic solitary rugose coral skeleton is an upside-
down conical platform strengthened internally by hori-
zontal, vertical, and diagonal supports and provided
externally with attaching processes. Within the
Rugosa generally there are limitless possibilities of
taxonomic subdivision using combinations of the more
stable megascopic exterior and interior characters. The
structural complexity varies from the simple Stauri-
idae to the very complex interior patterns of the
Digonophyllidae.

EXTERIOR CORALLUM FEATURES

Exterior surface characteristics of the rugosan coral-
lum have been adequately defined by Hill (1935; 1956)
and require little elaboration in this regard. Among the
solitary Devonian taxa here described, surface features
of taxonomic value given special attention are: (1)
median longitudinal profile of the modified cone, with
or without tendency to become elongate-cylindrical at
maturity; (2) strength and abundance of rugae; (3)
frequency and spacing of rejuvenescence flanges; (4)

 

 

————7

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 35

accentuation of septal grooves; and (5) development
of connecting or attachment processes.

Among colonial Rugosa generally the exterior fea-
tures of taxonomic value are growth habit or pattern,
which range from loosely fasciculate or bushy to mas-
sive cerioid. In the compact cerioid forms, shape and
size of the free-growing head are significant, as is the
extent of holothecal investment compared to area
occupied by the distal or calicular surface. The open
bushy forms reveal externally such features as lateral
and calice reproductive offsets and lateral connections,
which may be tubular as in Pycnostylidae or highly
irregular attachment excrescences like those of E ntelo-
phyllum.

Some of these gross external characteristics may be
viewed as adaptive, or they may be influenced by envi-
ronmental conditions, as, for example, the external
shape of a coral head.

Calice features are part of the corallum exterior, but
these also disclose much of the internal structure and
the character of reproductive offsets. The individual
calice profile in median longitudinal section reveals
calice shape and depth; such profiles may be V-shaped,
U-shaped, inverted bell-shaped, or squared. Other
calice features are: calice pit, median boss, distal calice
platform, and reflection of calice rim—all external
characters of taxonomic importance. Symmetry of the
calice viewed transversely is that of an adult transverse
section and shows to advantage the bilateral and quad-
rilateral features manifested by cardinal, counter, and
alar septa. Departures from complete radial symmetry
are clearly shown by pinnate arrangements of septa
contiguous to a cardinal fossula, present in many gen-
era. Septal edges projecting in from the sides and floor
of the calice may be denticulate or entire. The calice
rim may be narrow, acute, and unreflected as in
Syringaxon or Kobeha; in M ucophyllum, which has a
mushroom-shaped corallum, the calice rim is strongly
reflected, forming a wide upwardly convex marginal
platform. Digonophyllidae that have a wide dissepi-
mentarium also have correspondingly wide calice brims
or platforms with a conical median pit.

Compact thamnastraeoid and aphroid colonial gen-
era like Billingsastraea, although lacking a corallite
wall, commonly show false surficial walls or raised
intercalice polygonal ridges on a calicular surface;
other variants of this genus suppress the false wall but
develop elevated median cones, as in Pachyphyllum.
Such exterior calicinal features do not seem to have
more than subgeneric or species value. Characters of
the outer corallite wall, septa, biologic symmetry, and
reproductive offsets visible in the calice are treated
elsewhere.

 

Some normally solitary Rugosa are closely related
genetically to colonial species, calling for taxonomic
evaluation of growth habit in this respect. Among nor-
mally solitary taxa usually classified as Zaphrentidae,
the genus H eliophyllum, as demonstrated by Wells
(1937), produces compound adaptive groupings of fas-
ciculate to astraeoid form. Other families which include
closely related taxa of solitary to colonial habit are the
Tryplasmatidae and the Phillipsastraeidae. Among the
last, solitary Macgeea is commonly associated with
Phillipsastraea, Pachyphyllum, or Phacellophyllum,
and it seems not unlikely this genus is quite polyphy-
letic, possibly a solitary differentiate, or even a mani-
festation of dimorphism. Among corals described in
this report, there are partly phaceloid individuals of
otherwise cerioid Pinyonastraea.

TAXONOMIC EVALUATION OF CORALLUM
INTERIOR STRUCTURES

Chief internal structures of the rugose coral are
septa, tabulae, dissepiments, axial structures, and
stereoplasmic deposits. The septa and axial structures
are vertical elements, the tabulae are horizontal, and
the dissepiments are diagonal elements. Complexpat-
terns consisting of combinations of these elements lend
themselves to taxonomic evaluation.

SEPTA

In terms of fine structure, the two principal types
of rugosan septa are lamellar and acanthine. Somewhat
unsatisfactory attempts have been made (Wang, 1950)
to evaluate trabecular patterns of lamellar septa for
taxonomic purposes (Kato, 1963). In general these his-
tologic features are too poorly understood and the pres-
ervation of most Rugosa unsatisfactory for taxonomic
evaluation by this character. N0 Tryplasmatidae with
acanthine trabecular spines were found in the Great
Basin Early and Middle Devonian.

Of the eleven families of Great Basin Rugosa here
defined, nine possess lamellar septa; the remaining two,
Cystiphylloidae and Digonophyllidae, do not have
complete and continuous lamellar septa and are dealt
with separately.

Septum characters of special systematic importance
are: (1) septal count, (2) relative lengths of major
and minor septa, (3) vertical continuity of septa, (4)
radial continuity of septa, and (5) presence of true
septal carinae. Septal thickening by stereoplasm is
considered separately.

Evaluation of septal and other interior character-
istics at the species level is effectively expressed quan-
titatively by use of ratios, of which that involving
major septum count relative to mature corallite diam-

h

36 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

eter is the most widely used (Oliver, 1960a, 1968; Roz-
kowska, 1960).

Within the mature corallum, lamellar septa of most
families here defined have a modicum of vertical conti-
nuity. Nondissepimented forms like Siphonophrenti-
nae have amplexoid septa which lack this vertical
continuity except at the periphery; inward the partial
septa extend upward from distal surfaces of tabulae.
All genera with lonsdaleioid dissepiments have radially
discontinuous septa. This is true also of the Digono-
phyllidae in which septa tend to lose identity peripher-
ally within a complex mesh. Septal crests or septal
spines in these categories are radially alined seg-
ments growing toward the axis from inner dissepiment
surfaces.

True septal carinae are distinguished by continuity
in depth; as seen in longitudinal thin section a carina
passes diagonally downward and outward toward the
periphery, transacting dissepimental tissue. Carinae
are of three kinds: ( 1) crossbar or yardarm carinae,
(2) angulation or elbow carinae, and (3) strip carinae.
True carinae are readily distinguishable from minor
septal wiggles, unthickened angulations, and stereo-
plasmic lumps or bumps on septa which do not extend
downward from a given transverse plane. Strip carinae
are a derivative of crossbar carinae in the outer dissepi-
mentarium of Digonophyllidae like Arcophyllum,
wherein the septa are aborted, but the carinae occur
as diagonal strips viewed in longitudinal thin section.

TAB ULAE

A tabula is a supporting structure that occupies the
middle part of a corallum. Tabulae of more primitive
Rugosa extend from wall to wall, as in tabulate corals.
More advanced dissepimented rugose corals have the
interior differentiated into a middle tabularium and an
outer dissepimentarium. Tabulae are lamellar, simple,
and almost always thin, unlike septa which may be
stereoplasmically thickened. In the primitive condition
tabulae are nearly straight and horizontal. Modifica-
tion is by sag or axial inclination; in many advanced
genera the tabulae are domed and arched with a
peripheral inclination. Tabulae may be entire and com-
plete, or they may comprise short blisterlike domes
called tabellae with the appearance of flat dissepi-
ments. Edges of tabellae abut upon other tabellae, on
longer more nearly complete tabulae, or against inner-
most dissepiments.

The boundary separating tabularium from dissepi-
mentarium is discrete in some genera; in other genera
the two zones appear to blend. In general the inner
dissepiments are steeply inclined axially, whereas the
adjacent outer tabellae are inclined peripherally. With

 

genera having an aulos or inner ring, the tabulae may
be differentiated into a horizontal axial set and a peri-
axial set peripherally inclined, as in Syringaxon.

In forms with wide flat tabulae (like Kobeha) the
calice floor is a tabula which bends down abruptly at
the cardinal fossula.

Spacing of tabulae is rather uniform in some gene’i'a;
in others there is great irregularity. Sudden change
from close spacing to wide may be a response to envi-
ronmental change. Specimens have been observed
among solitary Rugosa in which the abrupt change in
attitude of tabulae was obviously a response to the
vertically attached corallum having fallen on its side,
resulting in a change in growth direction to maintain
horizontality of tabulae.

DISSEPIMENTS

As normal dissepiments, these blisterlike strength-
ening and space-filling elements occupy interseptal loc-
uli. Lonsdaleioid dissepiments are usually larger, occur
in the peripheral zone and are concave toward the out-
side. A single lonsdaleioid dissepiment opposes the
outer ends of several septa. Peripherally the septa
never transect lonsdaleioid dissepiments continuously;
they occur here only as radially alined crests.

Each normal dissepiment is three dimensionally a
spheroid segment with the basal plane axially inclined.
Transverse section traces of these dissepiments occur
in concentric, axially concave sets between pairs of
septa. Peripherally these traces may become angulo-
concentric or straight, or they may blend into an irreg-
ular herringbone or general cribriform tissue in which
the septa are suppressed.

In longitudinal section the overlapping dissepiments
form crude columns the number of which has taxo-
nomic meaning. Normal dissepiments may be globose
or elongate; lonsdaleioid dissepiments are always elon-
gate and, unlike the normal, dissepiments, are always
concave toward the outside, if viewed in transverse
section.

Average inclination of dissepiments has taxonomic
significance. In solitary and colonial forms with wide
corallites, the peripheral dissepiments are horizontal;
toward the axis the inclination always increases, such
that the innermost, usually smaller, dissepiments
stand nearly vertical. A character of considerable sys-
tematic value is discreteness or sharpness of the
boundary between these inner dissepiments and the
tabularium.

Digonophyllid species with complex peripheral pat-
terns may have small nontransverse or radial dissepi-
ments; all the edges of the dissepiments abut on a
single septum.

 

———i

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 37

Dissepiments are generally but not always absent
in Ordovician Rugosa and accordingly are viewed as
advanced structures in the evolutionary sense. Dis-
sepimented species appear abruptly and in some abun-
dance with the Early Silurian Lykophyllidae and
Arachnophyllidae. Nondissepimented Siphonophrenti-
nae are among the abundant forms in the Early and
early Middle Devonian rocks of the Great Basin. Dis-
sepiments undoubtedly arose independently in several
unrelated rugose coral lineages. With regard to corals
with lonsdaleioid dissepiments, this is fairly evident,
as they characterize several families among which are
the Spongophyllidae, Endophyllidae, Halliidae, and
Chonophyllidae. By themselves these lonsdaleioid fea-
tures are not regarded as indicative of genetic relation-
ship.

Columns of true horseshoe dissepiments are a special
category known in the Cordilleran Belt only in Late
Devonian Phillipsastraeidae. These features are nor-
mally associated with diagnostic trabecular bundles.

STEREOPLASMIC DEPOSITS

Septa ‘and other primary structures of the rugose
coral skeleton are thickened and added to in lamellar
fashion by secondary calcareous matter to which the
terms stereoplasm or stereome have been given. Within
a species certain of these stereoplasmic additions are
fairly regular and uniform. Deposits of this kind affect
mainly the septa; dissepiments may be so thickened
on the inner surfaces, but tabulae are generally not
thickened. Axial structures become a solid columella
when pervaded by stereome.

Taxonomically the most important stereoplasmic
deposits are the fairly uniform peripheral thickenings
of septa producing a septal stereozone. Certain genera
like Kodonophyllum and Nevadaphyllum always have
a wide septal stereozone. Stereoplasmically strength-
ened columellas do not occur in the Devonian corals
here described but are common in late Paleozoic and
Silurian genera. Some genera have either a general
stereoplasmic dilation of septa throughout their ta-
pered length or a uniform dilation only within the
tabularium.

Less significant taxonomically are the minor nonuni-
form lobose thickenings distributed irregularly along
septa or affecting only axial segments. True carinae are
not basically stereoplasmic, but may be supplemented
by this secondary material. Especially meaningful for
systematic purposes are the rather uniform lateral
swellings of septa that form an inner stereoplasmic
wall or aulos, as in Syringaxon.

Among rugose corals with a well-developed outer
wall, the thin epitheca may readily be distinguished

 

texturally in thin section from the contiguous septal
stereozone making most of the wall.

RUGOSE CORAL SYMMETRY AND TAXONOMY

Rugose corals have the underlying bilateral sym-
metry of the coelenterate. In most genera, however, the
more obvious symmetry is radial. In many solitary
Rugosa the primary bilateral symmetry is recognizable
externally or in the calice by means of the pinnate
arrangement of septa with reference to the cardinal-
counter plane. Biologic orientation is facilitated in
many solitary forms by the adult cardinal fossula
enveloping the cardinal septum. Well-defined counter
fossulae are less common. In the neanic stage of some
species there is a distinct quadripartite pattern defined
by cardinal, counter, and alar features; these become
less distinct in the ephebic transverse section. Gener-
ally the four symmetry quadrants are identifiable in
mature growth stages of solitary genera. With refer-
ence to the corallum exterior, the cardinal fossula may
lie either on the axially concave or the convex side;
whether this character is constant within a genus or
species is not known.

Contiguous cardinal quadrant septa tend to be pin-
nate or to become alined at maturity more or less
parallel to the cardinal septum and fossula in mature
stages. These septal features of symmetry, together
with the down—bending of tabulae, define the fossula.

Characters of bilateral symmetry are best shown by
solitary Rugosa; most cerioid colonial genera lack a
fossula and show little indication of anything but sec-
ondary radial symmetry in mature individual corallites.

GROWTH CHANGES AND REPRODUCTIVE FEATURES

Growth and reproductive features have an impor-
tant bearing upon rugose coral classification as in all
Orders of the Animal Kingdom. Sequences of develop-
ment change recorded in the corallum have, since the
inception of modern coral research, been made use
of in this regard. With Early Devonian taxa here
described, solitary Papiliophyllinae, when serially sec-
tioned, reveal progressive ontogenetic loss of septal
stereoplasmic thickening in more or less orderly fash-
ion. Syringaxon of the Laccophyllidae shows loss of
fossulae with development of the mature aulos.

Modes of asexual reproduction or so-called “in-
crease” among Rugosa have been dealt with exten-
sively (Lang and Smith, 1927; Hill, 1935, 1956) and are
readily discernible as axial, peripheral, and lateral off-
sets in solitary and fasciculate taxa (Oliver, 1968, p.
20). Reproductive offsets of compact colonial genera
like Hexagonaria and Billingsastraea are difficult to
deal with in this respect, calling for selection and spe-
cial preparation of suitable material.

 

i

38 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

Developmental study of colonial genera is intimately
related to manner of increase, for not only must onto-
genetic changes of corallites be considered, but the
colony growth pattern as well. Such patterns are a
three-dimensional arrangement of parts contingent
upon ways in which reproductive offsets develop from
parent corallites (Oliver, 1968; ROikowska, 1960).
Few developmental studies of cerioid rugose genera
have been carried out. Roz'kowska’s (1960, p. 14—28)
Hexagonaria investigations demonstrate calice offsets
from the dissepimentarium. Developmental patterns
involving reproductive offsets of more conveniently
handled phaceloid colonies are touched upon by Oliver
(1968, p. 26) in connection with statistical variation
analyses. In general too little is at present known of
these reproductive characters for them to figure sig-
nificantly in the taxonomy of Devonian compound
genera.

Small reproductive offsets, not found in most soli-
tary rugose coral species of the Great Basin Devonian,
have been recognized only in a single specimen of
Kobeha and in aberrant Breviphrentis. Characteristic
of Breviphrentis are rejuvenescence features produced
by growth of a single large daughter offset that largely
fills the parental calice.

Cone-in-cone growth of solitary Digonophyllidae
and Chonophyllidae evidently inspired Wedekind’s
(1924, p. 21) concept of the “septal cone.” In accord-
ance with this view, certain solitary genera with lamel-
lar but vertically discontinuous septa grew upward as
stacked-up increments or growth cones secreted by
the polyp basal ectoderm during successive growing
stages. Septa are represented by radial calice ridges or
radially alined septal crests separately secreted after
a resting interval.

VARIATION AND DIMORPHISM

Biometric analyses of individual variation are espe-
cially appropriate in connection with rugose coral spe-
cies discrimination. Studies by Oliver (1960a; 1968)
and Roikowska (1960) effectively present these data
graphically as ratio curves or scatter diagrams. The
most commonly used ratio is that of septal count rela-
tive to mature corallite diameter.

Biometry with statistical analysis of data is of value
in distinguishing continuous from discontinuous vari-
ation and, in connection with possibilities of gene or
somatic mutation, dimorphism, and intergrowth within
a colonial corallum complex of individuals from two or
more protocorallites (Oliver, 1968, p. 24—26). Dimor-
phism has been suspected but not always convincingly
demonstrated in numerous rugose coral species. Appro-
priate in this regard is reference to the “genomorph

 

concept” of Smith and Lang (1930) which was based
upon Carboniferous coral genera in which aberrant
corallites or parts of corallites have the appearance of
another genus. Critical reviews (RoZkowska, 1960;
Wilson, 1963; Oliver, 1968) have not encouraged use
of genomorph in a taxonomic sense as advocated by its
authors. Whereas observations leading to the geno-
morph idea with reference to Carboniferous Rugosa
are valid, the cited examples among Devonian species
appear to be founded upon misconceptions, as noted
by Roikowska (1960, p. 49) .

Likelihood of dimorphism has not been eliminated
in connection with certain Devonian species here
described, studies of large suites of associated individ-
uals on a population basis will be required. Siphono-
phrentis (Breviphrentis) invaginatus may bear such a
relationship to Nevadaphyllum and to associated indi-
viduals with sporadic dissepiments that are question-
ably assigned to Sinospongophyllum. Among the
Disphyllidae, Billingsastraea nevadensis and its sub-
species arachne, initially described by Stumm as Radi-
astraea, would also lend themselves to quantitative
appraisal with sufficient material. A similar situation
is found in H exagonaria (Pinyonastraea) kirki, whose
range overlaps that of Billingsastraea and which could
be interpreted as a genetically related cerioid disphyl-
lid possessing an outer wall.

DESCRIPTIVE TERMS

Descriptive terms applicable to the structure of the
rugose coral have been adequately defined and stabil-
ized by Hill (1935, p. 481—519; 1956, p. F234—F245)
and are now widely accepted. New and useful terms
have in recent years been proposed by Birenheide,
Glinski, Schouppé, and other European coral research-
ers. Hill’s terminology with minor modifications, is
adopted in this report.

Family LACCOPHYLLIDAE Grabau, 1928

Reference form—Syringaxon siluriensis (McCoy)
1850.

Small solitary trochoid to subcylindrical rugose
corals with very deep calice, straight smooth lamellar
septa, a narrow septal stereozone, and tubular stereo-
plasmic aulos. Tabulae partly complete, very strongly
uparched, nearly flat within aulos, steeply inclined
peripherally. N0 dissepiments.

These nondissepimented but otherwise specialized
corals are distinguished by the strong inner ring pro-
duced by swelling of septal tips and commonly rather
heavy addition of stereoplasm. Arching of tabulae is
pronounced. The Laccophyllidae occur in the Silurian
and Devonian wherein they may be abundant in a
facies with no other Rugosa. Nearly identical small

 

 

 

it

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 39

corals like Permia, which reappear in the Carboni-
ferous, may be homeomorphic (Hudson, 1944, p. 360;
Fliigel and Free, 1962, p. 232). Somewhat less con-
vergent are the Permian Polycoeliidae elucidated by
Schindewolf (1942, p. 55).

Syringaxon is the only member of this family recog-
nized in the Great Basin, where it is the characteriz-
ing rugose coral of the Helderberg Early Devonian
Syringaxon facies.

Genus SYRINGAXON Lindslrom. 1882

1882. Syringaxon Lindstrom, p. 20.

1900. Laccophyllum Simpson, p. 201.

1902. N icholsonia Poéta, p. 184. Cited in plate explanations as
Alleynia (N icholsonia).

1928. Laccophyllum Simpson. Grabau, p. 82.

1928. Alleynia Poéta (N icholsonia Poéta) Grabau, p. 82.

1935. Syringaxon Lindstrém. Butler, p. 117.

1938. S yringaxon Lindstrom. (in part). Prantl, p. 21.

1940. Syringaxon Lindstrém. Lang, Smith, and Thomas, p.
129.

1949. S yringaxon Lindstrom. Stumm, p. 10.

1956. S yringaxon Lindstrom. Hill, p. F258.

1962. S yringaxon Lindstrém (in part). Fliigel and Free, p.

224.

Type species.—By monotypy, Cyathaxonia siluri-
ensis McCoy, 1850 (p. 281); Silurian, upper Ludlow,
Underbarrow, Kendal, Westmorland, England. Accord-
ing to Butler (1935, p. 118) and Lang, Smith, and
Thomas (1940, p. 129), Lindstrém, in naming the
genus, gave no diagnosis; he merely used McCoy’s
species siluriensis under the new generic name Syring-
axon in his faunal lists of the Gotland Silurian
(Lindstrém, 1882, p. 20).

Diagnosis.—Small, solitary turbinate and ceratoid
to cylindrical rugose corals with deep calice and no
dissepiments. Axial ends of major septa dilated and
laterally in contact to form an aulos. Tabulae strongly
uparched distally, the aulos dividing them into inner
flat or slightly sagging segments and outer segments
which descend steeply to meet the outer wall (Fliigel
and Free, 1962, fig. 3); tabulae either continuous from
wall to wall through aulos stereozone, terminating
within the aulos, or abutting proximally as tabellae
against adjacent tabulae. Stereome usually abundant
as aulos thickening and general thickening or filling
in brephic and neanic growth stages. Narrow fossulae
commonly reveal quadrants in late neanic growth
stages.

Remarks.—-Simpson (1900, p. 201) called attention
to this distinctive rugose coral group in the American
Silurian upon proposal of Laccophyllum, with L.
acuminatum Simpson from the Niagaran of Perry
County, Tenn., as type species. Butler’s exhaustive
study (1935) determines that McCoy’s (1850, p.
281) “Cyathaxonia siluriensis” is the type species of

 

Syringaxon Lindstrom; later Lang, Smith, and Thomas
(1940, p. 129) concluded that the holotype of Lacco-
phyllum acuminatum Simpson is correctly assignable
to Syringaxon, thus making Laccophyllum Simpson
a synonym of Syringaxon Lindstrom.

Alleynia Poéta or Alleynia (Nicholsonia) Poéta (see
Lang and others, 1940, p. 15, 129) appears to be cor-
rectly regarded as a synonym of Syringaxon.

Barrandeophyllum Poéta (1902, p. 190) is similar
to Syringaxon. According to Prantl (1938, p. 34), who
studied Poéta’s cotypes of the type species, Barrande-
ophyllum perplexum, this genus is virtually identical
in habit, form, and general structure with Syringaxon,
from which it may have been derived. Barrandeo-
phyllum is distinguished from Syringaxon by irregu-
larities of the aulos, which is usually elliptical in
section, and by a sparing development of dissepiments.
Stereoplasm is always present but is not abundant.
The type species of Barrandeophyllum is reported
from the Lower Devonian Branik Limestone of
Bohemia. Syringaxon ranges from the Niagaran of
Tennessee through strata of Lower Devonian Helder-
berg age in western North America and is reported
in the Upper Devonian Independence Shale of Iowa
(Stainbrook, 1946, p. 402).

As noted by Hudson (1944, p. 360), other small and
rather simple corals closely resembling Syringaxon
range into the Carboniferous, where they are repre-
sented by the genus Permia Stuckenberg. According
to Hudson, Permia and Syringaxon are probable
homeomorphs.

In the Great Basin small solitary corals similar to
Syringaxon occur in the lower or Silurian part of the
Hidden Valley Dolomite of the northern Panamint
Mountains (McAllister, 1952, p. 15—17). Following
the great proliferation in the Great Basin Helder-
bergian these corals seemingly almost disappeared
from this region, although scarce and fragmentary
specimens which may belong either in Syringaxon or
Barrandeophyllum have been found at Lone Mountain
in the Nevada Formation, unit 2.

Springaxon Ioerstei n. sp.
Plate 1, figures 1—16
1963. Syringaxon acuminatum (Simpson). Merriam, p. 43.

Type material.——Holotype, USNM 159243; figured
paratypes, USNM 159245—159250 inclusive. Rabbit
Hill Limestone, Early Devonian, Central Great Basin;
Monitor Range, Nev.

Diagnosis .—Syringaxon has a very deep calice, thick
wall, prominent longitudinal grooves externally and
on interior of calice wall, and a high septal count for
this genus. Cardinal and alar septa are differentiated
in neanic stages.

fi

40 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

External features.—Corallum, large for the genus,
attains a length of 30 mm and maximal diameter of
27 mm at edge of calice; average length about 19 mm
and average diameter 16 mm. Calice very deep, in
large individuals as much as 16 mm or more than half
the corallum length. Average specimen is trochoid, but
ceratoid individuals are fairly common; turbinate and
nearly cylindrical individuals are uncommon. Septal
grooves are sharply defined and distinctly pinnate
with reference to the primary septa. Rugae are weakly
defined or absent, rarely prominent. A few individuals
have talons or attachment surface at apex. Septa
extend distally as low subequal ridges on inside of
calice and rarely become obsolete. Aulos is defined as
a ring-shaped boss at the bottom of the calice in many
specimens; in the others the aulos is ill defined, and
narrow fossulae may outline quadrants made by the
primary septa.

Transverse sections—Mature sections have 26 to
more than 30 major septa extending three-fourths of
the distance to the axis. Minor septa are normally
present, but in some individuals are not recognizable
at maturity; these septa range from mere stubs to
one-third the length of the major septa; in some
specimens the septa are buried within the peripheral
stereoplasm. Septa are usually dilated toward tips,
laterally in contact, and reinforced by stereoplasm to
produce an aulos. Entire septum may be somewhat
dilated. Individuals that have a poorly defined aulos
have pairs of contiguous septa meeting axially like a
tuning fork, and merged segments continue toward
axis; some of these specimens reveal quadrate trans-
verse symmetry. The thickness of the peripheral
stereozone in some specimens exceeds 1 mm, but is
usually not so thick as the aulos. There is consider-
able variation in the amount of stereoplasm; some
early ephebic sections show the entire aulos filled with
this material. The appearance of false dissepiments
possibly results from section-cutting bulbous distal
inflations of tabulae between the aulos and the outer
wall.

Longitudinal sections—Outer segments of tabulae
descend steeply, with upward inflection before
meeting the stereozone. Some complete tabulae are
vague within the aulos, others are traceable com-

 

pletely across. Some aulos segments of tabulae may
be thickened stereoplasmically. Some specimens have
complete tabulae with M-shaped curvature and near-
vertical outer segments. Tabular spacing is nonuniform
and usually is fairly wide.

Comparison with related forms—Butler’s (1935)
figures of Syringaxon siluriensis (McCoy) show a
maturely cerioid to subcylindrical form with fewer
septa and poorly developed minor septa. Syringaxon
foers tei includes externally similar subcylindrical vari-
ants, but the norm is a trochoid corallum. Both tend
to have heavy stereoplasmic deposits in the aulos and
a wide septal stereozone. Of several species figured by
Prantl (1938) from the Devonian of Czechoslovakia,
most have a lower septal count and elongate sub-
cylindrical coralla. Species described from the Greif—
ensteiner Kalk (Eifelian) of Germany by Flfigel and
Free (1962) have a weaker aulos and less arching of
tabulae.

Occurrence—Rabbit Hill Limestone of Helderberg
Early Devonian age; Devonian coral zone A. Northern
Monitor Range, Rabbit Hill vicinity: localities M48,
M49, M187. Middle part of the Monitor Range,
Dobbin Summit area: localities M1067, M1068,
M1069. Northern Simpson Park Mountains, Walti
Hot Springs area: locality M1074; Coal Canyon area:
localities M1032, M1075, M1076. Cortez Mountains,
Mount Tenabo area: locality M1083.

Beacon Peak Dolomite Member (Helderberg Early
Devonian age) of the Nevada Formation; Devonian
coral zone A. Southern Sulphur Spring Range:
localities M186, M197, M1081, M1082.

Family STREPTELASMATIDAE Nicholson, 1889
(as STREPTELASMIDAE)

Reference form—Streptelasma corniculum Hall.
Ordovician, New York.

These are solitary rugose corals with or without
fossula, normally without dissepiments but with a dis-
crete septal stereozone; tabulae are wide, flat or
domed, some complete. Septa of primitive forms are
thickened and laterally in contact through mid-neanic
stage; septa thin peripherally from axis; in some
genera septa reach axis and form with domed tabulae
axial complexes or columellae. Tabulae, obscure in
this genera, have a very wide stereozone.

Measurements of Syringaxon foerstei n. sp.

 

Calice bottom Ephebic section

 

 

  

 

USNM Corallum length Calice depth Outside diameter Number of Diameter Number of

No. restored (mm) (mm) (mm) major septa (mm) major septa
159243 (holotype) .............. 32 16 12 28 _ _
159244 (paratype) .............. 17 8 11.5 24 — _
159246 (paratype) ....... — — _ _ 9.5 26
159248 (paratype) .............. — —— — _ 13 24
159352 (pl, 1, figs. 9, 10)... — — — _ 15.6 26

 

 

 

 

f

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY

This diverse long-ranging family will probably lend
itself to further subfamily taxonomic subdivision
eventually. Great Basin Devonian representatives are
classified in a new subfamily, here designated as the
Siphonophrentinae.

Sublumily SIPHONOPHRENTINAE, new subfamily

Reference form—Siphonophrentis gigantea (Le-
sueur) 1821. Middle Devonian, New York.

These Streptelasmatidae have a narrow to wide
septal stereozone, amplexoid septa, and a weak to
prominent fossula. Tabulae are mostly complete,
straight or domed with axial and peripheral sag. Dis-
sepiments are lacking.

Included are the following genera and subgenera:
Siphonophrentis (Siphonophrentis) O’Connell, 1914
Siphonophrentis (Breviphrentis) Stumm, 1949 (as genus)
Heterophrentis Billings, 1875
Compressiphyllum Stumm, 1949
(?)Nevadaphyllum Stumm, 1937
(?) Homalophyllum Simpson, 1900

Breviphyllum Stumm, 1949 may belong here as a
synonym of Breviphrentis. Although defined as a genus
with dissepiments, Stumm’s holotype of the type
species of Breviphyllum (plate 17, figs. 12, 13) does
not reveal dissepiments. As noted by W. A. Oliver, Jr.
(written commun., 1970) , H omalophyllum has a well-
developed stereocolumella unlike the other genera here
included in this subfamily.

The significant generic characters are shape of
corallum, width of septal stereozone, prominence of
fossula, and rejuvenescence features. Mature corallum
shape ranges from elongate-subcyclindrical in Brevi-
phrentis to short and compressed laterally in Com-
pressiphyllum (Oliver, 1958). The septal stereozone
is relatively narrow in Siphonophrentis s.s. and some
species of Heterophrentis but wide in some species of
Breviphrentis and very wide in Nevadaphyllum. Septal
length and the spacing and evenness of tabulae are
characters of extreme variability within this sub-
family. Fossulae are prominent with Heterophrentis,
small or unrecognizable in mature coralla of some
Siphonophrentis s.s. and in Breviphrentis. Prominent,
shelving rejuvenescence flanges, and the narrow
elongate corallum set Breviphrentis apart from true
Siphonophrentis.

Solitary Rugosa that are here classified as Siphono-
phrentinae have from time to time been referred to
in the literature as zaphrentoid corals or assigned to
the Zaphrentidae, a family of uncertain characteriza-
tion to which they doubtfully belong (Hill, 1938, p.
23; Stumm, 1949, p. 11; Oliver, 1958, p. 816). Status
of the Siphonophrentinae with respect to Zaphrentidae
calls for evaluation of the type species of Zaphrentis,
usually cited as Z. phrygia Rafinesque and Clifford,

 

41

1820. Opinions vary widely regarding the characteriza-
tion of Z. phrygia, upon which the validity of the genus
and of the Family Zaphrentidae depends. Hill (1956,
p. 278, fig. 190, 3a—b) ascribes to Zaphrentis a narrow
dissepimentarium and crossbar carinae illustrated by
figures of Z. phrygia attributed to Schindewolf. Stumm
(1964, p. 34, pl. 27, figs. 1—7), on the contrary, regards
Z. phrygia as lacking dissepiments and notes the
possibility of confusion with carinate Heliophyllum
venatum Hall. Obviously, thin section study of topo-
type material is needed to resolve this taxonomic
problem.

Siphonophrentinae and stratigraphic indicators
within the early Middle Devonian beds (Onondaga
Limestone) of the New York area that are approxi-
mately correlative strata of the beds in the Great
Basin.

Associated with Siphonophrentinae in the Nevada
Formation coral zone D2 are solitary corals that
resemble Breviphrentis and Heterophrentis; they
differ in having sporadic dissepiments. These prob-
lematic individuals are assigned to Sinospongophyllum
of the Chonophyllidae, but for some individuals
aberrant development of lonsdaleioid dissepiments in
a siphonophrentid lineage cannot be entirely ruled out.-

Genus SIPHONOPHRENTIS O'Connell 1914

1914. Siphonophrentis O’Connell, p. 187, 190, 191.
1949. Siphonophrentis O’Connell. Stumm, p. 12—13.
1949. Breviphrentis Stumm, p. 13—14.

1950. Siphonophrentis O’Connell. Wang, p. 214.
1956. Siphonophrentis O’Connell. Hill, p. F271.
1960a. Siphonophrentis O’Connell. Oliver. p. 87—89.

Type species—By original designation Caryophyl-
lia gigantea Lesueur, 1821, p. 296, 297. Onondaga
Limestone, New York State.

Diagnosis.—Oliver’s (1960a, p. 87) diagnosis is as
follows:

Simple, ceratoid to cylindrical corals with amplexoid septa
withdrawn from axis except on and just above upper surfaces
of tabulae. Tabulae dome-shaped, flat or concave axially,
depressed at the fossula. No axial structure or dissepiments.

Remarks. —Siphonophrentis commonly develops
very elongate coralla and may attain large size.

Heterophrentis (type species Zaphrentis spatiosa
Billings, 1858) differs in having a curved ceratoid to
trochoid or almost turbinate mature corallum with
larger and better defined fossula on the convex side
and a narrow septal stereozone; the very elongate
cylindrical growth habit of Siphonophrentis is lacking.
Unlike Siphonophrentis, some mature individuals of
Heterophrentis have major septa reaching the axis,
where they may be loosely twisted and pervaded by
stereome, but not to the,extent of forming a discrete
axial structure. Tabulae'bf Heterophrentis are com-

 

 

—<—

 

42 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

monly more irregularly arched, less uniform, and more
widely spaced than are those of Siphonophrentis.
Immature and early mature growth stages of the two
genera are probably indistinguishable.

The genus Siphonophrentis lends itself to separa-
tion as two subgenera: Siphonophrentis s.s. and Brevi-
phrentis.

Subgenus BREVIPHRENTIS Stumm, 1949 (as genus)
1949. Breviphrentis Stumm, p. 13, 14, pl. 5, figs. 22—24.
1956. Breviphrentis Stumm. Hill, p. F271, fig. 183—6ab.
1960a. Siphonophrentis variabilis Oliver, p. 87—89, pl. 13.

Type species.—Amplexus invaginatus Stumm (1937,
p. 427, pl. 53, fig. 2, pl. 54, figs. 2a—c). Early Middle
Devonian, Nevada Formation, unit 2, coral zone D2;
Atrypa Peak, Eureka district, Nevada.

Diagnosis.—This narrow, elongate Siphonophrentis
is of markedly segmented appearance when fully
mature; the cylindrical corallum has deep lateral
shelving indentations and rejuvenescence flanges. The
cardinal fossula is commonly weak or unrecognizable
in the mature calice. The septal stereozone is medium
to wide.

Remarks—Oliver (1960a, p. 87) recognized the
morphologic resemblance of Breviphrentis invaginatus
to Siphonophrentis. Retention of Breviphrentis as a
subgenus seems warranted, as this group constitutes
a useful taxonomic unit differing from true Siphono-
phrentis in its more slender and markedly segmented
growth habit. Typical Siphonophrentis is a larger coral
when fully mature and lacks the pronounced rejuve-
nescence flanges; its septal stereozone is relatively
narrower.

Breviphrentis is especially characteristic of the
Great Basin Early and early Middle Devonian (coral
zones C and D). Stumm’s proposal of Breviphrentis
was made before the stratigraphic importance of
these corals was understood. In the New York Early
Devonian, Siphonophrentis variabilis Oliver (1960a,
p. 87, pl. 13, figs. 1—17) of the Coeymans Limestone
resembles Great Basin Breviphrentis more closely
than true Siphonophrentis.

Siphonophrentis (Breviphrentis) invaginatus (Slumm)
Plate 15, figures 1—11; plate 16, figures 1—13, 15, 16;
plate 17, figures 12, 13.
1937. Amplexus invaginatus Stumm, p. 427, pl. 53, fig. 2, pl.
54, figs. 2a—c.
1937. (?) Heterophrentis nevadensis Stumm, p. 426, pl. 53,
fig. 1, pl. 54, figs. 1a—c.
1937. (?) Amplexus lonensis Stumm, p. 428, pl. 53, fig. 4, pl.
54, figs. 4a—b.
1937. (?)Amplexus nevadensis Stumm, p. 53—54 (in part),
pl. 53, fig. 3, pl. 54, figs. 3a—b; not fig. 3c.
1940. Amplexus invaginatus Stumm. Merriam, pl. 16, figs. 3—
4.
1949. Breviphrentis invaginatus (Stumm), p. 13—14, pl. 5, figs.
22—24.

 

 

1949. (?)Breviphyllum lonensis (Stumm), p. 25—26, pl. 12,
figs. 4—5.

Type material.——Holotype, USNM 94443; paratype
USNM 94443a. Lower beds of the Nevada Formation,
Atrypa Peak, Eureka mining district, Nevada.

Figured specimens.—USNM 159296—159311 inclu-
s1ve.

Diagnosis.—This Siphonophrentis has an elongate
subcylindrical mature growth habit with several re-
juvenescence constrictions. Septal stereozone is nar-
row to fairly wide. The axial extensions of septa are
amplexoid, and the narrow cardinal fossula is either
vague or well defined in mature growth stages.

External features.—Neanic and early ephebic
growth is ceratoid like Heterophrentis and later
ephebic growth subcylindrical, elongate, and with re-
juvenescence constrictions. Calice rim flanges are com-
monly sharp and developed repeatedly at irregular
intervals; these flanges are usually broken off. Septal
grooves are well defined.

Transverse sections.—-Major septa, about 40, nor-
mally extend one-half to three-fourths the distance
toward the axis; though usually withdrawn from axis
in ephebic stages, some individuals have major septa
reaching the axis. Minor septa, long for this genus,
commonly exceed half the length of major septa. Indi-
viduals with a wide septal stereozone have a thickened
septa; 'in some, the complete stereoplasmic filling ex-
tends inward almost to the tips of minor septa. Septa
are fairly straight to minutely wavy. In some speci-
mens, the cardinal fossula may be defined by the

-shaped trace of the tabular downwarping, but others
reveal no evidence of this structure.

Longitudinal sections.—Calice rim rejuvenescence
flanges are sharp and project obliquely 8mm or more
from the coral body. Tabulae, mostly complete, arch
distally with a peripheral depression, and are either
straight axially and periaxially or have a median sag.
Tabellar loops or globose pockets develop near the
peripheral edges of the tabulae. Incomplete tabulae
are accompanied by flat peripheral tabellae. The regu-
lar specimens have more or less complete tabulae that
are commonly close spaced. Some irregular individuals
have widely spaced nonuniform tabulae. Aberrant indi-
viduals have closely spaced, nearly straight tabulae
almost unarched.

Comparison with related forms.—Siphonophrentis
(Breviphrentis) kobehensis of coral zone C lacks the
well-developed septal stereozone of most variants of
zone D invaginatus and has a lower septal count and
very short minor septa.

Siphonophrentis variabilis Oliver of the New York
Coeymans Limestone (Oliver, 1960a, p. 87, pl. 13, figs.
1—17) bears a rather close resemblance to invaginatus,

 

\

 

if

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY

from which it may differ only subspecifically. Both
include individuals with a wide septal stereozone; vari-
abilis is not known to have variants with nearly
straight tabulae as does the species invaginatus.

Remarks.—-A large suite Of Breviphrentis invagina-
tus from Nevada Formation, unit 2 at Grays Canyon,
Eureka district, illustrates the great variability of this
species. The highly variable characters are the arching
and evenness of tabulae, the spacing of tabulae, and
the width of the septal stereozone. Some individuals
have straight almost unarched tabulae. The narrow
cardinal fossula varies from vague or unrecognizable
to fairly well defined in the mature growth stages, simi-
lar to Heterophrentis. Local variants have a wide sep-
tal stereozone, suggesting that of Kodonophyllum or
Pseudoblothrophyllum.

Among variants of B. invaginatus at Grays Canyon
are individuals with the features of Stumm’s Amplexus
lonensis holotype, the type species of Breviphyllum.
As noted elsewhere, the generic diagnosis of Brevi-
phyllum (Stumm, 1949, p. 26) calls for a dissepimen-
tarium, but no dissepiments were found in the thin
sections of the holotype, Other individuals resemble
Stumm’s Heterophrentis nevadensis.

In longitudinal sections the axial extensions of
major septa rest in amplexoid fashion upon the upper
surfaces of tabulae.

Occurrence.—-Central Great Basin, Nevada Forma-
tion, unit 2, Devonian coral zone D. Lone Mountain
(D2): localities M55, M1036, M1048. Southern Fish
Creek Range (D2): locality M1033. Northern Fish
Creek Range, Grays Canyon (D2) : localities M3, M51.
Mahogany Hills (D2): localities M27, M1084. North-
ern Antelope Range (D2): locality M1035. Southern
Sulphur Spring Range (D2): localities M36, M198,
M1078.

Southern Great Basin, Devonian coral zone D.
Ranger Mountains: localities M1034, M1058. North-
ern Panamint Mountains: localities M184, M1065.
Funeral Mountains: localities M1059, M1060, M1061,
M1063, M1064. Desert Range: locality M1057.

Measurements of Siphonophrentis (Breviphrentis) invaginatus

 

Ephebic section Neanic section

 

 

Number of Number 0!
USNM Diameter major Diameter major
No. (mm) septa (mm) lento
159296 .............. 30.5 44
159298 .............. 29.3 40
159306 .............. 16 32 8.3 22
159309 .............. 26.6 42

 

Siphonophreniis (Breviphrentis) kobehensis u. up.
Plate 14, figures 1—15; plate 16, figure 14.
Type material.—Holotype USNM 159284; paratypes
USNM 159283, USNM 159285 to 159293 inclusive.

534-041 0 - 74 — 4

 

43

Lower part of the Nevada Formation, Lone Mountain,
Eureka County, Nev.

Diagnosis.—This Siphonophrentis has a ceratoid to
cylindrical growth habit that reflects frequent rejuve-
nescence and elongate curved corallites. Septa are
withdrawn from axis; minor septa are very short (or
unrecognizable). Tabulae are complete, occasionally
straight, but more commonly uparched distally and
either flat medially or with a slight sag. Tabulae are
usually rather widely spaced. The wall has a very nar-
row stereozone for this genus. There are no dissepi-
ments, but there are occasional looplike or globose
tabellae. The abrupt curvature changes on rejuvenes-
cence all caused by the resumption of upright growth
by the parent that had been recumbent.

External features.—The segmented appearance of
the corallum is caused by the marked constrictions
resulting from rejuvenescence. The rim of the parental
calice commonly remains a sharp flange distal to which
the single daughter corallite may differ in growth direc-
tion; for some individuals the direction may diverge
90°; but normally the change is only a few degrees.
There are a few weak transverse folds between the
rejuvenescence flanges. Septal grooves are well defined.

Transverse sections.—Major septa, about 40 in
ephebic stages, are withdrawn to about half the radius;
the septa are of fairly uniform width, little thickened
by stereoplasm, amplexoid, and resting upon the upper
surfaces of the tabulae. The outer wall has a thin septal
stereozone beyond which the minor septa project to a
distance only about one-fifth the length of the major
septa. In a late nepionic stage (diameter, 5 mm), the
septa number 22; most meet toward the axis but are
not otherwise in contact laterally; septa lateral to the
cardinal septum are subparallel. At an earlier nepionic
stage (diameter 3.5 mm) there are about 20 septa
within which the cardinal quadrants are recognizable,
and the two septa lateral to the cardinal bend inward
as they approach the axis, thus defining the primitive
fossula. The cardinal fossula, inconspicuous or unrec-
ognizable in later ephebic stages, is probably indicated
in transverse sections by a trace which appears to join
two major septa in U fashion and which probably
conforms to downwarping of a tabula. There are no
dissepiments.

Longitudinal sections.—Most tabulae are complete;
they vary from straight to uparched distally and
peripherally depressed; the axial part is slightly convex
distally to flat or sagging. Some individuals have a few
localized globose periaxial tabellae. The tabulae are
usually spaced rather wide. There are no dissepiments
and a very narrow marginal stereozone or none. The
tabulae are irregularly uparched where the corallum
makes a sharp bend at rejuvenescence.

 

 

a

 

44 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

Reproductive offsets—An abnormal corallum shows
a cylindrical, curving calice offset of slightly more than
half the diameter of the calice rim. This development
seems to be an abnormally small rejuvenescence offset
terminating growth of the parent after it began secre-
tion of the rejuvenescence shelf.

Comparison with related forms.——Breviphrentis
invaginatus possesses a wider septal stereozone and
longer minor septa. Siphonophrentis variabilis Oliver
of the New York Coeymans Limestone has a wide
stereozone and develops tabulae with M-shaped con-
figuration in longitudinal section; straight tabulae are
more characteristic of kobehensis.

Measurements of Siphonophrentis (Breviphrentis) kobehensis

 

Neanic section

Ephebic section (early)

 

 

Number of Number of
USNM Diameter major Diameter major
No. (mm) septa (mm) septa
1 59283 ( paratype) ............ 13.7 38
159291 (paratype) ............ 13.5 40
159294 (figured
specimen) ........................ 5.4 23

 

Occurrence—Lower Devonian (Emsian) , coral zone
C. West side of Lone Mountain, Eureka County,
Nev. localities M286, M74 in lower part of Nevada
Formation, unit 1 about 75 feet stratigraphically above
base.

Genus NEVADAPHYLLUM Stumm, 1937
1937. Nevadaphyllum masoni Stumm, p. 429, pl. 53, fig. 6, pl.
54, figs. 6a—b.
1949. Nevadaphyllum Stumm, p. 19, pl. 8, figs. 20—21.
1956. Nevadaphyllum Stumm. Hill, p. F271, fig. 183—5.

Type species.—Nevadaphyllum masoni Stumm (by
original designation). Nevada Formation, Lone Moun-
tain, Eureka County, Nev.

Diagnosis.—Large ceratoid to cylindrical solitary
rugose corals. Many of the very numerous long, smooth
major septa reach the axis, toward which they become
twisted. There is a wide peripheral stereozone and a
fossula. The tabularium is wide; the tabulae numerous,
crowded and incomplete, uparched periaxially with
axial and periaxial sag. Dissepiments are abnormal or
false; the dissepiments are obscured peripherally by
the stereozone.

Remarks.—Pseudoblothrophyllum Oliver (1960a, p.
91) has some features of N evadaphyllum. This Helder-
bergian genus, as represented by Pseudoblothrophyl-
lum helderbergium, has fewer major septa, a wider
stereozone, and a more regular tabularium. As with
Nevadaphyllum, the dissepiments are largely sup-
pressed within the wide stereozone.

Nevadaphyllum masoni Stumm
Plate 13, figures 3, 4

 

 

1937. Nevadaphyllum masoni Stumm, p. 429, pl. 53, fig. 6, pl.
54, figs. 6a—b.

Type material.——Holotype USM 94447; paratype
USNM 94447a. Lower part of the Nevada Formation,
Lone Mountain, Eureka County, Nev.

Diagnosis.—See generic diagnosis.

Transverse section.—Major septa, about 76; are
smooth and fairly straight for two-thirds of the radius
from the wall; they become increasingly wavy and
twisted toward the axis which most reach. There is
no axial thickening to form a discrete axial structure.
Minor septa, less than one-half the length of major
septa, become very thin axially. All septa thicken
peripherally; some show a very minute waviness. Most
of the wide stereozone is apparently infilled by stereo-
plasm between the septa. The well-defined fossula
extends from near the axis into the stereozone and con-
tains a shortened major septum that is assumed to be
the cardinal. Laterally the dissepiment traces cannot
be distinguished clearly from section plane intersec-
tions with the numerous irregular arched tabulae.

Longitudinal section—The tabularium is a complex
of close-spaced irregular tabulae and tabellae lacking
straight elements; tabulae are uparched periaxially
with a pronounced axial sag. Tabulae and tabellae are
poorly separated from elongate false dissepiments in
the zone of peripheral sag; axially inclined false
dissepiments are obscured peripherally by the wide
stereozone. In the axial zone, septal ends and crowded
tabulae form a plexus in which the structural details
are obscured.

Remarks—The types of Nevadaphyllum masoni
are the only known specimens with the full characteri-
zation of this genus. Probably this uncommon
multiseptate form with crowded irregular tabulae and
modified, obscured dissepiments represents an aber-
rant evolutionary development from the Breviphrentis
stock or perhaps the stock which produced the dissepi-
mented Nevada forms here assigned to Sinospongo-
phyllum. Of these, Sinospongophyllum Sp. f with a
wide stereozone, obscured nonuniform lonsdaleioid
dissepiments, and numerous axially twisted major
septa is the closest to N. masoni. In this form, how-
ever, the tabularium is much less complex.

Occurrence—Lower part of the Nevada Formation,
probably unit 2 and Devonian coral zone D2, early
Middle Devonian, Lone Mountain, Eureka County,
Nev.

Family KODONOPHYLIJDAE Wedekind, 1927
Reference form.—Kodonophyllum milne-edwardsi
(Dybowski). Silurian, Gotland.

These solitary and colonial rugose corals have long
lamellar septa, no fossula at maturity, no dissepiments,

 

 

 

—————7

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 45

and a very septal stereozone. The tabularium is com-
posed of flat tabulae or arched tabellae which may
combine with septal ends to produce an axial structure.

Two subfamilies are recognized: Kodonophyllinae
and Mycophyllinae.

These corals are largely confined to the Silurian
rocks; those rather characteristic of the Late Silurian
are the Great Basin Silurian coral zone E.

The Kodonophyllinae resemble the Siphonophrenti-
nae by having a wide stereozone; they differ in lacking
a mature fossula, in having on the whole a wider, den-
ser stereozone, and in possessing an axial structure
supported by arching tabulae and tabellae.

(?)Kodonophyllum sp. 1
Plate 13, figures 1, 2

An incomplete Kodonophyllum-like solitary coral
with an exceptionally wide septal stereozone was col-
lected from the lower part of the Nevada Formation in
the southern Fish Creek Range, where it was associ-
ated with'Siphonophrentis (Breviphrentis) invagina-
tus. This species of Siphonophrentis also has a wide
stereozone. Because this fragmentary specimen could
be prepared only as a transverse section, the possibility
of it being an extremely aberrant Breviphrentis or
N evadaphyllum is not eliminated.

A wide, dense stereozone exceeds one-half the coral-
lum radius. The septal count is approximately 66.
Major septa are withdrawn from the axis; minor septa
greatly exceed one-half the length of major septa and
extend far beyond the stereozone. All exposed septa
are thickened and wavy, with numerous protuber-
ances. Tabulae and axial structure are unknown.

The stereozone, similar to that of Pseudoblothro-
phyllum Oliver (1960a, p. 91, pl. 16), differs in having
long, smooth septa, some of which meet the axis. The
septa of Pseudoblothrophyllum differ in lacking lobes
and by being thinner in the tabularium.

Occurrence—Nevada Formation, unit 2, Devonian
coral zone D. Fish Creek Range, north end of Fenster-
maker Mountain: locality M1033.

Kodonophyllum, usually a Silurian genus, has a dis-
tinctive axial structure with a calice boss; it is other-
wise known only in Late Silurian coral zone E of the
Great Basin Province.

Family STAURIIDAE Edwards and Haime 1850

Reference form—Stauria astreiformis Edwards and
Haime, 1850. Silurian, Gotland.

These fasciculate and cerioid rugose corals have
slender corallites, narrow septal stereozone and thin
lamellar, nonamplexoid septa that commonly extend
to the axis. Tabulae are complete, straight or arched.
Dissepiments are commonly absent, but in some line-

 

ages arise as a single column or sporadically in a bro-
ken column.

Some species of Stauria reveal a quadripartite
mature transverse section in which four primary septa
are prominent and may meet at the axis. In the genus
Dendrostella, the four primary septa may exceed the
others in length, but usually they do not reach the
axis of a mature corallum.

Stauriidae include many Late Ordovician species of
Favistella Dana (or Favistina Flower), Cyathophyl-
loides Dybowski, and Paleophyllum Billings; these
genera carry over into the Silurian. Silurian Stauriidae
also include undescribed genera in addition to S tauria.
The Devonian representatives are Dendrostella, pos-
sibly Columnaria, and possibly Synaptophyllum Simp-
son, as revised by McLaren (1959 ) .

Genus DENDBOSTELLA Glinski, 1957

1886. Cyathophylloides rhenanum Frech, p. 93, pl. 3 (15),
figs. 19, 19a.

1892. Columnaria (Cyathophylloides) disjuncta Whiteaves,
p. 269, pl. 34, figs. 3, 3a, 3b.

1957. F avistella (Dendrostella) rhenana (Frech). Glinski, p.

88—90, figs. 1—4, 16.
Favistella (Dendrostella) praerhenana Glinski, p. 90—
91, figs. 5, 14.

Type species.——Cyath0phylloides rhenanum Frech
(by original designation, Glinski, 1957). Upper Middle
Devonian, Givetian, “Biicheler Schichten”, Paffrath
Basin, Germany.

Diagnosis.——These slender dendroid and phaceloid
rugose corals have a thick wall, no dissepiments,
smooth, simple, even, nonamplexoid and unthickened
septa; minor septa are short or lacking. Tabulae are
complete, either straight or with a slight doming or
sag,

Remarks.——Dendros tella was proposed by Glinski as
a subgenus under Favistella; however, it appears suffi-
ciently well characterized and distinctive to be consid—
ered a full genus. Denstrostella commonly has short
septa which are not truly amplexoid because they are
not developed only on the upper surfaces of tabulae.
Glinski states that the range is from Silurian (upper
Ludlovian) to Middle Devonian (Givetian). In the
Great Basin the only known occurrence is in Nevada
Formation, unit 2, possibly coral zone D3 which would
be about early Eifelian.

Dendrostella romunensis n. sp.
Plate 18, figures 1-4

Type material.——Holotype USNM 159318; Nevada
Formation, Devonian coral zone D. Locality M1031,
Sulphur Spring Range.

Diagnosis .—Dendros tella has relatively short major
septa and very short to completely suppressed minor
septa. There is no indication of transversely bilateral

 

46 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

   
 
 
 
 
 
 
 
 
 
 
   
   
 
 
   
   
  
 
 
 
 
  
  
  

pattern of septa.

External features.—Phaceloid colonies are many
centimeters wide with long, slender branching fairly
straight corallites loosely arranged. Surface has fine
longitudinal grooves and striae; transverse rugae are
weak. N o lateral connecting processes were observed.

Transverse sections—Major septa, about 20, com-
monly extending less than half the distance to the
axis. Minor septa pass only a short distance beyond
the wall or are represented only by roots within the
thick wall. The wall is divided circumferentially into
about 40 equal radial parts (segments) by dark hair-
thin lines, one segment for each septum root. Septa
have median dark lines.

Longitudinal sections.—Thickened wall has minor
undulations, but no sharp bends or angular rejuvenes-
cence features. Tabulae are all complete, not widely
separated, straight to undulant, but lack a persistent
axial arch or depression. There are no dissepiments.

Comparison with related forms—Dendrostella
romanensis n. sp. has shorter major septa than rhenana
(Frech) and praerhenana Glinski; unlike romanensis,
these west European forms have a suggestion of sym-
metry with primary septa distinguishable in mature
stages. Dendrostella disjuncta (Whiteaves) also has
long major septa and longer minor septa than
romanensis.

Measurements—Diameter (in mm) and major
septa, three corallites of holotype colony, USNM
159318:

These medium and large solitary rugose corals have
distinctly bilateral symmetry. Septa are numerous,
long and smooth; cardinal septum is in a prominent
fossula. Tabulae are wide, partly complete, normally
domed with an axial sag. Dissepimentarium is narrow
to wide; dissepiments are normal, globose, and lons-
daleioid. Septal thickening persists to adult growth
stages in cardinal quadrants.

The Halliidae are the abundant Rugosa of the Great
Basin Lower Devonian, where they characterize coral
zones B and C; they diminish in importance in coral
zone D.

Two subfamilies constitute the Halliidae: the Hal-
liinae of the Early and Middle Devonian, and the
Papiliophyllinae of the Early Devonian. The lykophyl-
lid corals of the Silurian, which have been classified
with the Halliidae by Hill (1956, p. F272), are here
regarded as a separate family, the Lykophyllidae of
Wedekind.

Sublamily HALLIINAE Chapman, 1893

Reference form.—Hallia insignis Edwards and
Haime, 1850. Devonian, Ohio.

The Halliidae have an especially well defined pin-
nate arrangement of septa in cardinal quadrants. The
dissepimentarium, narrow to wide, is made up of nor-
mal dissepiments only.

Genera of this widely occurring subfamily are H allia
Edwards and Haime, Aulacophyllum Edwards and
Haime, and Odontophyllum Simpson; of these, Aula-
cophyllum and Odontophyllum occur in the Great

Corallite ................ 1 2 3 . .
Diameter (mm) 9 8 7. 5 Basm Devonian coral zone C.
Major septa ---------- 20 20 20 Sublamily HALLIINAE Chapman, 1893

Occurrence.~In somewhat arenaceous limestone of
Nevada Formation, unit 2, Sulphur Spring Range,
northwest of Romano Ranch: locality M1031. The
coral-bearing bed lies about 150 feet stratigraphically
above sandy limestone with a large fauna including
Spirifer pinyonensis, Breviphrentis cf. B. invaginatus,
and Leonaspis sp.; this fauna probably represents coral
zone D2. The Dendrostella occurrence may be in coral
zone D3. The other North American occurrence of
Dendrostella recorded by Whiteaves (1892, p. 269-
270) apears to be in rocks of Givetian age, as suggested
by association with Stringocephalus at Lakes Mani-
toba and Winnipegosis. Glinski (1957, p. 105) records
D. praerhenana as Eifelian in the lower Nohner beds,
and D. rhenana as Givetian in the Bucheler beds, both
in the Rhine Valley region. The horizon of romanensis
is probably closer to Eifelian than Givetian.

Genus AULACOPHYLLUM Edwards and Haime, 1850
Aulacophyllum sp. c
Plate 9, figures 6—9

Medium and fairly large solitary corals of this kind
occur in coral zone C at Lone Mountain in association
with Papiliophyllum elegantulum and Odontophyllum
meeki. Unlike Papiliophyllum they do not possess lons-
daleioid dissepiments, and accordingly they seem more
appropriately assigned to Aulacophyllum. The strong
thickening of cardinal quadrant septa persists into
mature growth stages.

Occurrence—Nevada Formation, unit 1. Early
Devonian, coral zone C. Lone Mountain, Eureka
County, NeV.: Locality M74.

Other Aulacophyllum-like Rugosa of coral zone C
have thickened septa in contact laterally through the
neanic stage but are largely devoid of dissepiments.
These occur at locality M74 (pl. 9, figs. 10, 12) and in
the southern Sulphur Spring Range at locality M36
(pl. 9, fig. 11).

Family HALLIIDAE Chapman. 1893

Reference form. ——Hallia insignis Edwards and
Haime, 1850. Devonian, Ohio.

 

 

 

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 47

Genus ODONTOPHYLLUM Simpson. 1900

1882. Aulacophyllum convergens Hall, p. 22.

1833. Aulacophyllum convergens Hall, p. 281, pl. 17, figs. 1—2.
1900. Odontophyllum Simpson, p. 210.

1938. Odontophyllum Simpson. Stewart, p. 31, pl. 5, figs. 5—6.

1948b. Odontophyllum Simpson. Stumm, p. 51—59, pls. 1—2.

1949. Odontophyllum Simpson. Stumm, p. 16, pl. 7, figs. 13—
14.

1956. Odontophyllum Simpson. Hill, p. F273, fig. 186—2a-c.

1964. Odontophyllum Simpson. Stumm, p. 29-30, pl. 19, figs.

5—13.

Type species.——Aulacophyllum convergens Hall by
original designation. Middle Devonian; Beechwood
Limestone Member of the Sellersburg Limestone, Falls
of the Ohio, near Louisville, Kentucky (Stumm, 1964,
p. 4).

Diagnosis.—-These solitary curved turbinate and
curved trochoid to subpatellate Halliidae have a broad
and commonly very deep calice. Cardinal septum is on
the convex side in the long narrow fossula. Alar fossu-
lae are defined, but no counter fossula. Major septa ex-
tend to the axis; septa are denticulate at distal edges.
Some species have carinate septa. Tabulae are incom-
plete, distally arched. Dissepiments are present near
the periphery in the late growth stages.

Remarks.——Neanic stages of 0. convergens (Hall)
that are figured by Stumm (1948b, pl. 1, fig.11) show
their affinity with the Halliidae: having cardinal-coun-
ter bilateral symmetry, short cardinal septum, and
septa of cardinal quadrants subparallel bordering the
counter septum and bending inward toward the coun-
ter as the axis is approached. Longitudinal sections of
individuals with a very broad shallower calice have
tabularium with tabellae and a narrow dissepimen-
tarium. Specimens that are here described from the
lower part of the Nevada Formation have a deep calice
extending downward to the nepionic growth so that
transverse sections show little structure.

Odontophyllum meeki n. sp.
Plate 9, figures 1—5

Type material.——Holotype USNM 159261; paratype
USNM 159262. Lone Mountain, locality M74; Devo-
nian coral zone C.

Diagnosis.——This Odontophyllum has a curved tro-
choid to curved turbinate corallum and a wide, deep
calice extending downward to or almost to nepionic
growth. Cardinal and alar fossulae are well developed.
Cardinal septum are strongly developed and long in
mature calices. Septa of counter quadrants are shorter
and much less prominent in a mature calice than the
septa of the cardinal quadrants. Some septa are
slightly denticulate at the distal margins but have no
development of true carinae. The distal margins of the
calice are thin and sharp because there is no peripheral

 

platform as in some individuals of O. patellatum
(Holmes). The exterior has sharply defined septal
grooves.

Remarks.—This species shows extremely well the
pinnate arrangement of septa and septal insertion with
reference to primary septa. Associated with O. meeki
are other nondissepimented solitary trochoid rugose
corals having a deep calice and sharp rim, but with the
fossulae not so well defined (plate 9, figs. 13, 14).
These have narrowly cylindrical or ceratoid early
growth stages which may be elongate, stemlike, and
distorted. They differ from associated early growth
stages of Papiliophyllum; though lacking dissepiments
in the early growth stages, these have thickened septa,
especially in the cardinal quadrants.

Measurements.—Holotype: Diameter at calice rim
30 mm, corallum length 34 mm, calice depth 26 mm;
major septa at calice bottom 36.

Occurrence.-—Nevada Formation, Early Devonian,
coral zone C. Lone Mountain, Eureka County, Nev.:
locality M74.

Subiamily PAPILIOPHYLLINAE Stumm. 1949

Reference form. —Papiliophyllum elegantulum
Stumm, 1937. Lower Devonian, coral zone C, Great
Basin.

These large Halliidae have a peripheral band of Ions-
daleioid dissepiments; normal dissepiments are few or
absent. Septal thickening is commonly strong in ma-
ture cardinal quadrants.

Genera of this endemic subfamily are K obeha n. gen.
of coral zone B, Papiliophyllum Stumm of coral zones
C and D1, and Eurekaphyllum Stumm of coral zone C.

Genus KOBEHA. new genus

Type species.—Kobeha walcotti n. sp., here desig-
nated.

Diagnosis. —These large solitary Papiliophyllinae
have curved trochoid and curved ceratoid to subcylin-
drical shape. The calice is deep, rather flat bottomed
with nearly erect, straight walls and an acute margin
without platform. The outer wall has a narrow septal
stereozone. The cardinal fossula are well defined, usu-
ally on the convex side of the corallum. The major
septa of mature individuals number about 60, some of
which nearly reach the axis. Minor septa are short. In
nepionic and early neanic stages, septa that are thick-
ened by the stereome are laterally in contact, and
largely filling the interior. In mature stages the septal
dilation progressively decreases and becomes confined
mostly to cardinal quadrants. Advanced stages have
attenuate septa in counter quadrants and those of car-
dinal quadrants are also thinned, the attenuation is
progressively peripherally from the axis. Tabularium is

 

 

48

broad, 60—80 percent of mature corallum width; tabu-
lae are numerous, normally closely spaced. Some tabu-
lae are continuous with the axial sag, others are as
wide as the tabellae which are domed and discontinu-
ous. The dissepimentarium has one to three columns of
large steeply inclined dissepiments, some of which are
exceedingly large wall blasts.

Because of the large size and small number of wall
blasts and other large peripheral dissepiments, the
transverse sections through the mature corallum do
not show a conspicuous lonsdaleioid outer zone. The
peripheral zone of large dissepiments is well shown
only in longitudinal sections.

Remarks. —Kobeha has thus far been recognized
only in the central Great Basin. K. walcotti is the char-
acterizing species of the Lower Devonian K obeha zone,
which is coral zone B of the central Great Basin De-
vonian. Kobeha ketophylloides n. sp. is placed in this
new genus with reservation, but it seems to fit best
here. Kobeha precedes, and is conceivably ancestral to,
other Halliidae of this region, which include Papilio-
phyllum of coral zone C and Eurekaphyllum. Eureka-
phyllum is regarded as a synonym of Papiliophyllum
by some investigators (Hill, 1956, p. F273).

 

Kobeha walcotti n. gen., :1. sp.

Plate 3, figures 1, 2, 6; plate 4, figures 1—4;
plate 5, figures 1—7; plate 6, figures 8—10

1940. Zaphrentoid sp. cf. Papiliophyllum; Merriam, pl. 12,
fig. 5.

Type material.—Holotype USNM 159253; para-
types USNM 159251, 159252, 159256, 159257, 159260.
Nevada Formation, lower beds of unit 1; Devonian
coral zone B, Early Devonian. Southern Sulphur
Spring Range, Nev.

Diagnosis. — Kobeha without continuous lonsdale-
ioid dissepimentarium showing as a complete periph-
eral band in mature transverse sections. Longitudinal
sections show one to three columns of lonsdaleioid dis-
sepiments, most of which are large wall blasts. All
septa are thinned in late ephebic stages; major septa
are discontinuous peripherally, but the outermost seg-
ments are uniform and complete at their union with
the narrow septal stereozone. Major septa occur as
partly discontinuous septal crests on the upper sur-

 

 

LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

faces of tabulae. Tabulae are downwarped at the car-
dinal fossula, which is not confined in all individuals
to the convex side of the corallum. Calice is nonconical
with a broad bottom which is nearly flat to shallowly
concave distally.

External features.—Corallum is curved trochoid to
ceratoid in the neanic stages; it becomes nearly cylin-
drical in mature stages of large individuals. Septal
grooves are commonly separated by longitudinal
ridges with a minor secondary groove on the crest of
each ridge. Transverse features (rugae) vary from fine
growth striations to fairly prominent ring-folds at ir-
regular intervals. Regularly spaced rejuvenescence fea-
tures are absent, but irregular breakage and repair
structures are common and define the broken calice
rim. Bell-shaped to flowerpot-shaped calice has an
almost flat bottom and nearly erect sides below a
sharp rim. The tabular floor of the calice is down-
warped in the cardinal fossula, which may be situated
either on the convex side or laterally.

Transverse sections.—In advanced ephebic stages,
the major septa number at least 70, all of which may
be thinned. Stereoplasmic thickening of the septa in
the cardinal quadrants persists into the earlier ephebic
stages. The wall is a narrow septal stereozone. Some
major septa reach the axis in the early ephebic stages;
minor septa are short, usually less than one-seventh
the length 0f the radius. Traces of large wall blasts are
concave peripherally and encompass as many as six
major septa. Between septa where the section inter-
sects tabellae, the traces are usually concave periph-
erally; these features do not make a concentric pat-
tern.

Late neanic to early ephebic transverse sections usu-
ally show the cardinal quadrants filled with stereo-
plasmic deposits and the septa with thickening in the
counter quadrants. Septa are progressively thinned,
beginning axially in the counter quadrants. Thickened
septa in the cardinal quadrants are pinnate, but it is
difficult to ascertain which of two or three shortened
septa is actually the cardinal septum in some neanic
sections. Late nepionic and early neanic transverse
sections show stereoplasmic thickening of all septa;
septa in contact laterally completely fill the corallum.

Measurements of Kobeha walcotti n. sp.

 

 

 

 

  

Ephebio Neanic
Calice bottom section section
Corallum Number Number
length Calice Outside Number of of of
USNM restored depth diameter major Diameter major Diameter major
No. (mm) (mm) (mm) septa (mm) septa (mm) septa
159253 (holotype) ........ 19 52 68 —— — — ——
159251 (paratype).... 23 45 66 — — — —
159256 (paratype).... — — -— 53 64 27 50
159257 (paratype) ................ 22 57 — 46 58 —— —

 

 

 

 

 

———i

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 49

Longitudinal sections—The tabularium, wide in
mature longitudinal section, is as much as four-fifths
of the total diameter. Complete or nearly complete
tabulae commonly have a slight median sag, and wide
tabellae. Tabulae are closely spaced to widely sepa-
rated, downwarped at the tabularium margin, with a
pronounced sag at the cardinal fossula. Large lonsdale-
ioid dissepiments are normally in one or two columns,
steeply inclined to nearly vertical. Axial extensions of
major septa are carried on the upper surfaces of
tabulae.

Comparison with related forms—Kobeha ketophyl-
loides differs from K. walcotti by having larger less
uniform wall blasts as observed in mature transverse
sections, wherein these features are more prominent
and more irregularly distributed. The number of dis-
sepiment columns is greater in K. ketophylloides, and
the mature dissepiments are less steeply inclined than
in K. walcotti. In K. ketophylloides marked discontin-
uities of major septa where they meet wall blasts are
more numerous.

Occurrence—Lower part of the Nevada Formation,
basal beds of unit 1; Early Devonian, coral zone B with
Costispirifer arenosus. Southern Sulphur Spring
Range: localities M4, M56, M67, M69, M1041. North-
ern Roberts Mountains: locality M1072. Northern
Sulphur Spring Range, McColley Canyon: locality
M1018; specimens from this area differ subspecifically
from typical K. walcotti.

Kobeha kelophylloides n. sp.
Plate 3, figures 3—5, 8, 9; plate 6, figures 1—7

Type material.—Holotype USNM 159258; para-
types USNM 159254, 159255, 159259. Lower Devo-
nian, Nevada Formation, unit 1; coral zone B. South-
ern Roberts Mountains and Southern Sulphur Spring
Range, Nev.

Diagnosis.—Kobeha has very large and irregularly
distributed wall blasts and lonsdaleioid dissepiments
in mature transverse sections; these peripheral fea-
tures are circumferentially uneven and show marked
discontinuities of the major septa, segments of which
thicken in wedge fashion to terminate peripherally
against dissepiments or wall blasts. Individual wall

 

blasts subtend as many as 13 septa. Longitudinal sec-
tions have as many as seven columns of wall blasts and
lonsdaleioid dissepiments which decrease distally in
steepness of axial inclination to 40°.

External features—A large trochoid specimen with
deep bell-shaped, rather flat-bottomed calice shows
the cardinal fossula. Broken calice rim reveals the
cone-in-cone structure with wide irregular separations
making the characteristic wall blasts and lonsdaleioid
dissepiments.

Transverse sections—In advanced ephebic stages
major septa number 64. Minor septa are usually less
than half the radius but are longer than those of K.
walcotti. In advanced ephebic stages the septa are
thicker at the periphery in counter quadrants than in
K. walcotti and there are wide discontinuities where
major septa meet large dissepiments at which points
the septa thicken in wedge fashion locally. In later
ephebic stages septa in cardinal quadrants exceed in
thickness those of the counter quadrants; in earlier
ephebic stages all major septa are of about the same
thickness. Septa are thickened and laterally in contact
in later nepionic stages, separating in early neanic
stages; in late neanic stages septa of counter quad-
rants are thinner than those of cardinal quadrants.
The outer wall has a septal stereozone which in late
neanic stages is 2 mm thick. Large irregular dissepi-
ments and wall blasts are concave peripherally.

Longitudinal sections—Most of the wide and rather
closely spaced tabulae arched distally with a median
sag, and are for the greater part nearly continuous.
Short tabellae are uncommon. Large lonsdaleioid dis-
sepiments are fairly even and regular in curvature lon-
gitudinally though irregular transversely; dissepi-
ments decrease in steepness from early to late ephebic
stages where the axial inclination is about 40°. The
number of columns in the dissepimentarium increases
to seven at maturity; this fact distinguishes the species
from K. walcotti, the type species.

Reproductive offsets—A well-preserved silicified
specimen assigned to K. ketophylloides shows four
peripheral calice buds. The main corallite was itself
developed as a calicinal offset from the partially pre-
served parent.

Measurements of Kobeha ketophylloides n. sp.

 

Calice
bottom

Ephebic section

(early) Neanic section

 

 

Calice outside Number of Number of
USNM depth diameter Diameter major Diameter major
No. (mm) (mm) (mm) septa (mm) septa
159258 (holotype).... —— —- 55 70 30 50
159258 (holotype).... —— — 45 60 — —-
159259 (paratype)... —— —— 32.5 56' —- —
159254 (paratype)... 27 39 -— —- —— —-

 

 

 

i

50 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

Comparison with related forms.—Kobeha ketophyl- pl. 54, fig. 7a—e). Lone Mountain, Eureka County,
loides differs from K. walcotti in having a larger num- Nev.; lower part of Nevada Formation, unit 1, Lower
ber of mature dissepiment columns, in its more con- Devonian (Emsian), coral zone C.
spicuous lonsdaleioid separations in advanced ephebic Diagnosis.-—Solitary trochoid and ceratoid Hallii-
transverse sections, and longer minor septa. Heavy dae which grow to a large size have a deep flowerpot-
thickenings of septa in cardinal quadrants were not shaped, rather flat-bottomed calice with a cardinal
observed to persist ontogenetically into ephebic stages fossula. Peripheral zone has medium to large steeply
of K. ketophylloides as they do in some individuals 0i inclined lonsdaleioid dissepiments. Septa of cardinal
K. walcotti. The tendency for subcyclindrical growth quadrants are thickened in all the ephebic stages and
in advanced ephebic stages is greater than in K. wal- are laterally in contact in all the early ephebic stages.
cotti. Calice reproductive offsets were not recognized in Most septa are withdrawn from the axis and terminate
K. walcotti. peripherally at the inner margin of the lonsdaleioid

In mature pattern of construction Kobeha ketO- dissepimentarium. Minor septa are either suppressed
phylloides resembles the species of Ketophyllum from or inconspicuous as short discontinuous crests. In the
the Silurian of Gotland, that is figured by Wedekind neanic stages the cardinal septum is short within the
(1927) and the species from the Silurian 0f Czecho- fossula which is bordered by thick septa touching lat-
slovakia 0f Poéta (1902)- The septal discontinuities erally. Tabulae are mostly complete, wide, close to
of Ketophyllum are greater and lonsdaleioid separa- rather widely Spaced, and distally arched; in normal
tions more pronounced. Unlike Kobeha, the wide tab- mature stages tabulae are rather flat to Slightly sag-
ulae of Ketophyllum are usually rather flat, whereas ging axially and periaxially and are peripherally de-
those of K obeha are strongly arched distally and have pressed. Some individuals have tabulae that are rather
a median sag. Kobeha ketophylloides has thickened irregular and sharply arched distally in the neanic
septa in the neanic and earlier growth stages, espe- stages. Tabulae are bent sharply downward, funnellike
cially in the cardinal quadrants; the developmental at the cardinal fossula. Septa of the counter quad-
thinning 0f the septa begins peripherally in the neanic rants become thinned and lonsdaleioid dissepiments
growth within the counter quadrants, a characteristic develop in the early to mid-neanic stageS; the cardinal
feature 0f Kabeha and Papiliophyllum ontogeny. quadrants are bordered by lonsdaleioid dissepiments
Wedekind’s figures (1927, pl. 10, figs. 8—11) 0f the externally until late neanic or early ephebic stages.
neanic Stages 0f Ketophyllum elegantulum d0 hOt Remarks—The diagnosis here given is modified
show thickened septa and the septa are short neani- slightly from that of Stumm (1949, p_ 16). Of special
cally, Whereas in Kobeha ketophyllOideS the septa are significance is the seeming absence of minor septa in
thickened and approach the axis. These early develop- some mature transverse sections, although in some
mental differences by themselves are believed SUfll‘ specimens minor septa are recognizable as weak crests
cient to justify h0t assigning the Nevada forms to near the peripheral border of the tabularium. Also im-
Ketophyllum. portant taxonomically is the absence of lonsdaleioid

Occurrence—Lower part Of the Nevada Formation, dissepiments in the cardinal quadrants until the late
lower beds of unit 1. Early Devonian, coral zone B, neanic stage.
southern Roberts Mountains: type locality M1042. Papiliophyllum differs from Kobeha in having a bet-
At the type locality, K- ketophylloides is associated ter defined dissepimentarium with smaller and more
With a Gypidula that resembles G- coeymanensis,Acro- numerous lonsdaleioid dissepiments, especially in the
3P” if er sp., Leptocoelia sp., and a brachipod that re- mature transverse sections. In Kobe/2a the septa]
sembles the Pholidostrophia of the Rabbit Hill Helder— crests carry through to the outer wall; they do not in

berg. This horizon may be slightly older than the beds Papiliophyllum. Minor septa are better defined and
that contain specimens assigned to K. ketophyllozdes more continuous in Kobeha.

1n the Sulphur Spring Range. Southern Sulphur Papiliophyllum differs from Eurekaphyllum in pos-
Sp ring Range. localities M69’ M1039' sessing much more numerous and smaller lonsdaleioid

 

Genus PAPII-IOPHYI-I-UM Stumm: 1937 dissepiments. Eurekaphyllum shows widely spaced
1937. Papiliophyllum elegantulum Stumm, p. 430. tabulae with a pronounced axial-periaxial sag, whereas
1940. Papiliophyllum elegantulum Stumm, Merriam, p. 52,

 

Papiliophyllum usually shows distally arched com-

53, pls. 12, 16. l l t t b l
1949. Papiliophyllum elegantulum Stumm, p. 16, pl. 7. mon y C ose-se a u ae'
1956. Not Papiliophyllum Hill, p. F274, fig. 186, 4c, 4d.
Type species.—By original designation Papiliophyl- Papiliophyllum eleganiulum Siumm
lum elegantulum Stumm (1937, p. 430, pl. 53, fig. 7, Plate 7, figures 4—10; plate 8, figures 1—8

 

 

 

————7

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 51

1937. Papiliophyllum elegantulum Stumrn, p. 430; pl. 53, fig.
7, pl. 54, figs. 7a-e.

1940. Papiliophyllum elegantulum Stumm. Merriam, p. 52—53,
pl. 12, fig. 3, pl. 16, figs. 1, 2.

1949. Papiliophyllum elegantulum Stumm, p. 16; pl. ‘7, figs.
11, 12.

1956. Papiliophyllum elegantulum Stumm. Hill, p. F274, fig.
186—4a—4b.

Type material.——Stumm’s transverse thin section of
the holotype is similar to the transverse section of
Merriam (1940, pl. 16, fig. 1) made by cellulose peel.
The holotype is one of the fossils from the Nevada
Formation presented by Merriam to the US. National
Museum. Paratype, USNM 94448. Lower part of the
Nevada Formation, unit 1, Lone Mountain, Eureka
County, Nev.

Diagnosis.—This is a large Papiliophyllum. The
width of the mature lonsdaleioid dissepimentarium is
less than half the radius and consists of three to seven
columns of medium to large, steeply inclined dissepi-
ments. Some tabulae are complete, arched distally.
They are usually flattened axially and periaxially in
the ephebic stages and commonly are arched more
deeply and rather irregularly in the neanic stages. In
advanced ephebic stages the dissepimentarium is nar-
rowest at the cardinal fossula; the thickened septa
bounding the fossula invade this peripheral band.
Minor septa are weakly developed or unrecognizable.
Septa of the cardinal quadrants are heavily to mod-
erately thickened in the ephebic stages.

External features—These curved trochoid or curved
ceratoid corals usually have well-defined septal grooves
but commonly do not show very pronounced annular
folds or rugae; these features suggest fairly continuous
growth. The outer wall is commonly broken away in
the places where large wall blasts occur within. The
deep and rather flat-bottomed calice is bordered in
mature specimens by blisterlike lonsdaleioid dissepi-
ments; on the axial surfaces of these dissepiments lie
septal crests that become weaker toward the rim.
There is no calicular shelf.

Transverse sections.——Mature transverse sections
have an average of about 56 major septa, some of which
reach or nearly reach the axis. Minor septa occur as

 

thin discontinuous crests toward the peripheral edge
of the tabularium; some mature individuals show
almost no trace of minor septa. Septal crests are rarely
observed within the dissepimentarium and almost
never meet the wall. In advanced ephebic stages the
width of the dissepimentarium varies from less than
one-third to more than one-third of the radius. The
dissepiments lack uniformity, ranging in size from
small to very large and they subtend 12 or more septa.
In late ephebic stages septa of the counter quadrants
are always thinned; those of the cardinal quadrants
are thickened and commonly several remain laterally
in contact. The cardinal septum is shortened or
aborted in a fossula which encroaches peripherally
upon the dissepimentarium.

In the mid-neanic stages there are about 38 septa.
The septa vary from being all thickened and laterally
in contact with one another to being considerably
thinned in the counter quadrants, and some of those in
the cardinal quadrants are partly separated even
though they are thick. At the mid-neanic stage, but
usually a bit later, lonsdaleioid wall blasts begin to
develop in the counter quadrants only. The cardinal
septum roughly defines a plane of symmetry; on either
side of this plane the thickened septa are more or less
parallel near the periphery but bend laterally toward
this plane as they pass axially, some join near the axis
to produce a primitive fossula. Counter and alar septa
are not distinguishable with assurance. In early ephe-
bic stages lonsdaleioid dissepiments are generally not
developed or are just beginning to develop in the car-
dinal quadrants, and the thick septa are here largely
or partly in contact laterally.

Longitudinal sections.——In advanced ephebic stages
the tabularium width exceeds one-half the corallite
diameter. Sections parallel to the alar plane show
fairly uniform, distally arched tabulae, some of which
are complete and accompanied by wide tabellae. The
broad axial-periaxial part of the tabularium is flat or
has a slight sag, the peripheral part sags abruptly. In
neanic stages the tabular uparching is more pro-
nounced and axially convex to angular distally. Medial
sections through the cardinal fossula reveal the ex-

Measurements of Papiliophyllum elegantulum S tumm

 

Ephebic section Neanic section

 

 

Calice

 

Corallum bottom
length Calice outside Number of Number of
Figured restored depth diameter Diameter major Diameter major
specimen (mm) (mm) (mm) (mm) septa (mm) septa.
51 22 23 19.8 44
21 38
82 68
46 52

 

45 58

 

 

i

52 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

tensive stereoplasmic septal thickening and the pro-
nounced funnellike proximal sag of tabulae associated

with the fossula. Columns of lonsdaleioid dissepiments V

number seven or more in the advanced ephebic stages;
dissepiments vary greatly in size, and smaller ones are
scattered throughout. Very large wall blasts are com-
mon, but large dissepiments seen in some specimens
may also occur at the axial margin of this band.

Comparison with related forms. —Papili0phyllum
elegantulum seems to have evolved from the same
stock that also gave rise to Kobeha and Eurekaphyl-
lum, which are discussed elsewhere under their defini-
tions of genera. Papiliophyllum elegantulum differs
from Kobeha walcotti in having smaller and more nu-
merous lonsdaleioid dissepiments and in not having
septal crests within the dissepimentarium— the ab-
sence of these crests is a diagnostic feature of K. wal-
cotti. Eurekaphyllum breviseptatum differs in having
only a few very large wall blasts and lonsdaleioid dis-
sepiments and in having its very widely spaced tabulae
which are depressed proximally, not arched distally as
in P. elegantulum.

Occurrence—Lower part of the Nevada Formation,
unit 1; Devonian coral zone C of late Early Devonian
age, approximately Emsian. Associated with Acrospiri-
fer kobehana. Lone Mountain: localities M74, M286,
M1044. Southern Roberts Mountains: locality 18 of
Merriam (1940). Northern Roberts Mountains: locali-
ties 13, 94 of Merriam (1940). Southern Sulphur
Spring Range: locality M68. North end of Antelope
Range: locality M1035a. Hot Creek Range: locality
M1066?. Northern Panamint Mountains, California:
localities M184, M1065. Funeral Mountains, Califor-
nia: localities M1059, M1063.

Papiliophyllum elegantulum subsp. d
Plate 7, figures 1, 2

This subspecies is insufficiently known to character-
ize. It is an evolutionally advanced and a geologically
younger derivative of the elegantulum lineage with
very numerous lonsdaleioid dissepiments and crowded
fairly uniform wide tabulae that are only slightly
arched.

Measurements—Diameter of the late ephebic sec-
tion is 78 mm; the number of major septa is 62.

Occurrence.——-Lower part of the Nevada Formation,
unit 2. Devonian coral zone D1 of late Early Devonian
age. Lone Mountain: locality M1037; associated with
Sinospongophyllum sp. d, Chonetes macrostriata,
Gypidula loweryi, Spirifer pinyonensis, and Dalma-
nites meeki. Ranger Mountains, Clark County, Nev.;
a similar Papiliophyllum occurs here at locality M1034,
associated with a fauna which may be that of coral
zone D1.

 

 

 

Genus EUREKAPHYLLUM Stumm, 1937

1937. Eurekaphyllum breuiseptatum Stumm, p. 431, pl. 53,
fig. 8; pl. 54, figs. 8a—b.

1940. Eurekaphyllum Stumm. Lang, Smith, and Thomas, p.
58.

1949. Eurekaphyllum Stumm, p. 17, pl. 7, figs. 15—17.

1956. Papiliophyllum Stumm (in part). Hill, p. F273 (in

part), fig. 186—4c—d.

Type species. —— Eurekaphyllum breviseptatum
Stumm (by original designation). Lower part of the
Nevada Formation, Lone Montain, Eureka County,
Nev.

Diagnosis—Large curved trochoid Papiliophyllum-
like rugose coral with a peripheral zone of very large
irregular lonsdaleioid dissepiments and widely spaced
irregular wide tabulae which are axially depressed.
Inner ends of the septa are withdrawn some distance
from the axis; septa 0f the cardinal quadrants are
thickened. Septal crests are present in the dissepimen-
tarium.

Remarks.—Eurekaphyllum has the lonsdaleioid dis-
sepiments and thickened mature cardinal quadrant
septa of Papiliophyllum and Kobeha, but differs from
both in possessing exceedingly large irregular dissepi-
ments and in having a small number of tabulae, most
of which sag proximally. In transverse section, Eureka-
phyllum resembles Kobeha in having septal crests
within the dissepimentarium; Papiliophyllum com-
monly lacks these outer crests and differs in having
a much greater number of dissepiment columns.

Eurekaphyllum breviseplatum Stumm
Plate 8, figures 9, 10
1937. Eurekaphyllum breviseptatum Stumm, p. 431, pl. 53,
fig. 8, pl. 54, figs. 83—1).
1949. Eurekaphyllum breviseptatum Stumm, p. 17, pl. 7, figs.
15—17.

Type material. ——Holotype, USNM 94449. Lower
part of the Nevada Formation; Lone Mountain, Eu-
reka County, Nev. This is the only known specimen of
Eurekaphyllum.

Diagnosis.—See generic diagnosis.

Transverse section—Septa number about 64; all are
considerably withdrawn from the axis; minor septa,
if distinguishable, exceed half the length of the major
septa. Septa of the cardinal quadrants are thickened.
Some septa extend discontinuously to the outer wall
as thin crests. Width of the dissepimentarium is about
equal to the length of the major septa; most dissepi-
ments are very large, irregular and nonuniform; the
longest extends one-fourth of the circumference. Fos-
sula is indistinct.

Longitudinal section.—Tabulae are few; some are
complete, the more nearly complete are widely sepa-
rated and have a pronounced U-shaped sag with a

 

——7

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 53

somewhat flattened axial-periaxial segment. Large dis-
sepiments of irregular form are in one or two columns.

Occurrence—Lower part of the Nevada Formation,
Lone Mountain, Eureka County, Nev. The horizon
from which this form came is unknown; it probably
came from unit 1, coral zone C, which is the zone in
which Papiliophyllum is the abundant rugose coral.

Hill (1956, p. F273—F274) regards Eurekaphyllum
as a junior synonym of Papiliophyllum. Study of a very
large suite of specimens shows that the Eurekaphyl-
lum structure is not normal or modal for the type of
coral here placed in Papiliophyllum. As no additional
representatives of E urekaphyllum have been collected
from the beds which probably yielded the type and
only specimen, it seems likely that this form may be
an aberrant and uncommon development from the
Papiliophyllum stock. There are no intergradational
forms, morphologically speaking. Without knowledge
of the exact horizon or zone from which the type came,
it is believed desirable to let the genus in question
stand for the present. Like Kobeha it could well be
found to have stratigraphic as well as morphologic
significance.

Family BETHANYPHYLLIDAE Stumm, 1949

Reference form—Bethanyphyllum robustum (Hall)
1876. Middle Devonian, New York.

Medium and large trochoid to ceratoid rugose corals
with long, thin major septa and a cardinal fossula.
Multiple columns of medium to small normal globose
dissepiments occur in a wide dissepimentarium. Tabu-
larium is medium or wide, consisting of combinations
of straight, nearly complete tabulae and tabellae.
Septa of the cardinal quadrants are unthickened be-
yond the nepionic stages.

Bethanyphyllidae may have sporadic zigzag carinae,
but these are uncommon; in some species the fossula
is weakly developed. The dissepimentarium-tabularium
margin is usually not sharply defined. No lonsdaleioid
dissepiments are known.

This family designation is appropriate for a strati-
graphically important early Middle Devonian coral
group possibly evolving from the ancestral stock of the
Halliidae which precede Bethanyphyllidae in the De-
vonian of the Great Basin.

In a recent revision, the Family Bethanyphyllidae
has been abandoned, Bethanyphyllum being assigned
to the Zaphrentidae, together with Heliophyllum
(Stumm, 1963, p. 139; 1964, p. 38). Pedder (1965, p.
207) has emended the Bethanyphyllidae to accommo-
date Bethanyphyllum, Ceratophyllum, Moravophyl-
lum, Tortophyllum, and Stathmoelasma. In these gen-
era, septa are smooth or weakly carinate, unlike H elio-
phyllum which has strong yardarm carinae. The car-

 

dinal septum is relatively short. In mature stages it is
difficult to recognize the cardinal fossula of some spe-
cies; this is one of several features which distinguishes
Bethanyphyllidae from Halliidae.

Genus BETHANYPHYLLUM Stumm. 1949

1876. Cyathophyllum robustum Hall, pl. 22, figs. 1—14.

1937. Cyathophyllum? lonense Stumm, p. 435, pl. 55, figs.
3a—b.

1937. Grypophyllum giganteum Stumm, p. 433, pl. 54, figs.
9a—b.

1937. Grypophyllum curviseptatum Stumm, p. 433, pl. 55,
figs. 2a-b.

1937. Grypophyllum' nevadense Stumm, p. 432, pl. 53, fig. 9,
pl. 55, figs. 1a—b.

1937. Tabulophyllum nevadense Stumm, p. 434, pl. 55, figs.
4a—b.

1949. Bethanyphyllum Stumm, p. 18, pl. 8, figs. 1—4.

1956. Bethanyphyllum Hill, p. F278, figs. 189—6a—b.

1963. Bethanyphyllum Stumm, p. 139.

1965. (?)Stathmoelasma Pedder, pl. 31, figs. 1—5.

Type species.—Cyathophyllum robustum Hall,
1876, by original designation. Middle Devonian; Ham-
ilton Group of western New York State.

Diagnosis.——Medium to large solitary trochoid to
cylindrical rugose corals have numerous long, thin,
usually fairly smooth septa. The longer septa reach the
axis. Cardinal fossula is well defined to weak, without
pronounced pinnate arrangement of several bordering
septa. The dissepimentarium is wide, with multiple
columns of steeply inclined mostly small dissepiments.
The tabularium is wide or medium wide, consisting of
a variable complex of partial to nearly complete,
straight or bowed tabulae that are peripherally bor-
dered by large tabellae passing into dissepiments lat-
erally. Conspicuous vertical gaps commonly separate
the tabluae. Outer wall is thin, lacking a peripherally
continuous septal stereozone.

Remarks.—Bethanyphyllum lacks the more evident
bilateral arrangement of septa characterizing Aulaco-
phyllum and usually has no axial whorl like Torto-
phyllum. Some species assigned to Bethanyphyllum
have septal thickening in the initial cardinal quadrant
which persists well into the neanic stages (B. antelo-
pensis). In mature stages, however, the septa of Beth-
anyphyllum are normally unthickened in cardinal
quadrants alone, one of several features which distin-
guish this genus from the Papiliophyllum stock. If
there is septal thickening in the late stages of Bethany-
phyllum, it afiects especially the axial parts of major
septa in any or all quadrants. Bethanyphyllum also
lacks the large lonsdaleioid dissepiments of Papilio-
phyllum. Carinae are absent in most species of Beth-
anyphyllum; those species that do have scattered car-
inae, like B. antelopensis, are small and of the zigzag
thickening type rather than the true yardarm carinae.

 

—

54 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

Stathmoelasma, recently described by Pedder
(1965, p. 207, pl. 31, figs. 1—5, pl. 32, fig. 10) from the
Australian Devonian, is similar to Bethanyphyllum, of
which it may be a synonym. Pedder’s figures show
indications of a weak fossula, and the longitudinal
sections reveal nearly complete straight to slightly
bowed tabulae like those of Bethanyphyllum, with
conspicuous gaps. There is no septal stereozone.

Bethanyphyllum of coral zone D2 is preceded by
Papiliophyllum of coral zone C, which ranges up into
coral zone D1; Papiliophyllum has not been found in
association with the more typical Bethanyphyllum, as
exemplified by B. lonense (Stumm). However, in coral
zone D1 Papiliophyllum individuals with intermediate
features occur with advanced; these individuals reveal
minor mature septal thickening in the cardinal quad-
rant and in some specimens a few rather inconspicuous
lonsdaleioid dissepiments are present. Whereas these
specimens suggest development toward Bethanyphyl—
lum, they appear on the whole to be somewhat closer
to the Papiliophyllum stock.

Bethanyphyllum lonense (Stumm)
Plate 11, figures 1—4; plate 12, figures 3—10
1937. Cyathophyllum? lonense Stumm, p. 435, pl. 55, figs. 3a,
b

Tabulophyllum nevadense Stumm, p. 434, pl. 55, figs.
4a, b.
1940. Cyathophyllum sp. Merriam, pl. 12, figs. 2, 4.

Type material. —— Holotype, USNM 94453; lower
part of the Nevada Formation, Lone Mountain,
Eureka County, Nev.

Diagnosis. ——Bethanyphyllum has thin, commonly
rather wavy septa which may be slightly thickened
toward the axis. Tabulae varying from straight, wide,
and nearly complete to large and small tabellae. More
continuous straight tabulae and larger tabellae bound
the bigger longitudinal gaps. The dissepimentarium
has several columns of rather small and steeply in-
clined dissepiments. The fossula is generally unrecog-
nizable in mature growth stages.

External features—Poorly known. This form seem-
ingly does not become very large and tends to remain
trochoid with a very deep calice.

Transverse sections—Major septa of the advanced
growth stages average 36, some of which approach or
reach the axis in mature sections. Minor septa are
usually less than half the radius. Septa are thin and
wavy, never entirely smooth, with abrupt angular
bends. Some septa may be slightly thickened axially,
where they may be contorted but not twisted to form
an axial whorl. Between septa, the dissepiment traces
and tabellar intersections are concentric and either
evenly concave axially or occur as chevrons. The outer
wall is thin, without appreciable stereoplasmic thick-

 

 

ening. Neanic and ephebic sections show no fossula
or cardinal septum. No nepionic or early neanic sec-
tions are available, but presumably the septa of car-
dinal quadrants are thickened, to judge from the re-
lated species Bethanyphyllum antelopensis.

Longitudinal sections—The tabulariums of ephebic
stages vary considerably in width within the corallum;
they usually exceed half the diameter. The presence
of a few straight, wide, and nearly continuous tabulae
is characteristic, these tabulae separate longitudinal
intervals of tabellae and shorter tabulae and define
larger vertical gaps. Dissepiments, mostly small and
globose, are disposed in numerous columns bounded
axially by larger, less globose dissepiments or periph-
eral tabellae.

Comparison with related forms. — Bethanyphyllum
lonensis differs from B. antelopensis in having a wider
tabularium and shorter minor septa; major septa are
more sinuous in B. lonensis. Some mature individuals
of B. antelopensis have a cardinal fossula not observed
in lonensis. B. robustum (Hall) differs in having a
weakly defined ephebic cardinal fossula, more even
septa, and relatively larger peripheral dissepiments.

Measurements of Bethanyphyllum lonense Stumm

 

Ephebic section

 

 

Figured USN M Diameter N umber of
specimen N 0. (mm) septa
1 ................................ 159272 30 40
2 . .. 24 34
3 . 31.5 38
4 .. 124 134
1 59278 13 26

 

 

1Early ephebic.

Occurrence—Nevada Formation, unit 2. Devonian
coral zone D2; in association with Siphonophrentis
(Breviphrentis) invaginatus. Lone Mountain: locality
58 (Merriam, 1940), localities M55, M1036, M1048.
Northern Roberts Mountains: locality 11 (Merriam,
1940). Southern Sulphur Spring Range: locality
M1047. Northern Fish Creek Range, Grays Canyon:
localities M3, M51.

Bethanyphyllum antelopensis n. sp.
Plate 10, figures 1—7; plate 11, figures 5, 6;
plate 12, figure 11

Type material. — Holotype, USNM 159265; para-
types, USNM 159266—159269, 159274. Lower part of
the Nevada Formation, Combs Peak area, Eureka
County, Nev.

Diagnosis.——This Bethanyphyllum has long major
septa, commonly about two-thirds as long as the major
septa, usually with a correspondingly wide dissepimen-
tarium, and with several axially-periaxially straight
tabulae separated by wide vertical gaps. The septa are
thin except for the axial part which may be somewhat

———'

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 55

horizon about 270 feet stratigraphically above the base
of the Nevada Formation and just below a 15-foot
quartzite bed of Oxyoke Canyon type. The associated
fauna of the Spirifer pinyonensis zone includes abund-
ant “Martinia” undifera.

Similar corals provisionally assigned to B. antelo-
pensis (pl. 11, figs. 7-9) occur at Lone Mountain
(locality M1045) in the upper part of unit 2, possibly
as high as Devonian coral zone D3

thickened; septa show only moderate waviness or ir-
regularity. A fossula is present in some mature indi-
viduals.

External features—Inadequately known.

Transverse sections—Major septa average about 38
in mature sections. Septa are thin, only slightly wavy,
and for the greater part approach the axis toward
which they may be slightly thickened, especially in
the cardinal quadrants. Minor septa are long, in some
sections two-thirds the length of major septa. In some
specimens, a fossula may be defined by a bending of
pairs of septa at their axial ends toward the symmetry
plane of the cardinal septum, which, if correctly iden-
tified, remains fairly long in mature stages. Dissepi-
ments between septa appear to be axially concave, and
chevron features make a concentric pattern. Outer wall
appears to be thin and without stereozone. Septa of
cardinal quadrants are very much thickened and in
lateral contact through to mid-neanic stages. One
neanic section with 30 major septa shows thick cardi-
nal quadrant septa laterally in contact except near the
alar positions; the cardinal septa are arranged on
either side of a somewhat shortened cardinal septum.
Major septa are withdrawn slightly from the axis.
Within the tabularium, the counter quadrant septa
are also thickened slightly. There are rows of concen-
tric dissepiments in the counter quadrants, but none
were recognized in the cardinal quadrants. Minor septa
are slightly less than half the length of the majors. The
wall is unthickened by stereoplasm.

Longitudinal sections. —— The tabularium, usually
rather narrow, ranges from one-fourth to nearly one-
half the corallite diameter in the mature growth stages.
Nearly straight, almost complete tabulae define verti-
cal intervals separated by intervals of less complete
tabulae and peripheral tabellae. The more complete
straight tabulae commonly occur where the vertical
separation is greater. Dissepimentarium has numerous
columns of steeply inclined, small to medium and large
dissepiments, of which the smaller predominate.

Comparison with related forms—See Bethanyphyl-
lum lonense.

 
 
 
 
 
 
 
 
 
 
  
 
 
  
 
 
 
   
  
 
 
 
  
  
   
  
 

Belhanyphyllum 5p. d
Plate 10, figures 8—10; plate 13, figures 6,17, 9

Figured specimens.——USNM 159270, 159271,
159281, 159281a. Lower part of the Nevada Forma-
tion, Lone Mountain, Eureka County, Nev.

Specimens classified as Bethanyphyllum sp. (1 differ
from B. lonense and B. antelopensis in features of the
tabularium; they are wider, and the tabulae are more
closely spaced with a tendency toward distal arching.
The wide vertical gaps between some tabulae of lon-
ense and antelopensis were not found in sp. (1. It is
probable that sp. (1 lacks the very deep calice of some
individuals of lonense.

Occurrence—Lower part of the Nevada Formation,
lower beds of unit 2; Devonian coral zone D1. Lone
Mountain, locality M1037, where it occurs with the
fa ma including the advanced Papiliophyllum elegant-
ulum subsp. (1.

Family CHONOPHYLLIDAE Holmes, 1887

Reference form.—-Chonophyllum Edwards and
Haime, 1850.

These solitary rugose corals are of medium to large
size, dissepiments partly or wholly lonsdaleioid; some
tabulae are complete, flat or domed. Major septa are
lamellar, elongate, discontinuous peripherally, little
thickened. Fossula is weak or absent.

Genera included in this family are as follows:

Chonophyllum Edwards and Haime, 1850
Ketophyllum Wedekind, 1927
Tabulophyllum Fenton and Fenton, 1924
Sinospongophyllum Yoh, 1937
Diversophyllum Sloss, 1939

The Chonophyllidae are commonly quite rugate
externally because of their numerous rejuvenescence

 

Measurements of Bethanyphyllum antelopensis n. sp.
//Ephebicsection Neanicmfim flanges and cone-in-cone growth habit. The septal
/ . _
Number of Number of stereozone 1S usually not a conspicuous feature, and
US?! Digger '33:: D1133)" mfg the tabularium ranges from narrow in Chonophyllum
159265 (holotype) ________ 39 38 to wide or very wide in the other genera.
igggggflggiggggg '_'_'_'_jj_‘_ 35_ ‘f‘j 1'43 g5 Genus SINOSPONGOPHYLLUM Yoh, 1937
159274 (paratype ........ 29 32 1937. Sinospongophyllum planotabulatum Yoh, p. 56, pl. vi,
figs. 2—5.
Occurrence—Lower part of the Nevada Formation, 1940' Si’lwgpongophyllum Y°h~ Lang, Smith, and Thomas, D-
1 .

unit 2; Middle Devonian, Devonian coral zone D2.

. . 1949. Tabulophyllum Stumm, p. 27 (in part ; 1. 12, fi . 20,
Locality M27, 1.75 miles south of Combs Peak at a 21. ) p gs

 

fi

56 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

1956. Sinospongophyllum Yoh. Hill, p. F300, fig. 204, 5a—b.

Type species.—Sinospongophyllum planotabulatum
Yoh (by original designation). Upper part of the mid-
dle Devonian; Kwangsi, China.

Diagnosis—This ceratoid to subcylindrical Chono-
phyllidae has rather closely spaced, wide to very wide
tabulae which are either straight or sag axially and
peripherally. Septa are amplexoid, smooth or minutely
wavy, noncarinate, and usually withdrawn from axis.
Minor septa are well defined. Peripheral zone has sep-
tal crests, large irregularly distributed lonsdaleoid dis-
sepiments, and smaller normal dissepiments. Septal
stereozone is narrow to moderately wide. Fossula is
weak or absent.

Remarks.—Yoh’s figures and the type show very
steeply inclined dissepiments in a rather narrow band,
very wide, flattened tabulae, and no fossula.

Diversophyllum (Sloss, 1939, p. 65) differs in having
longer septa that reach the axis, more arched and
irregular tabulae, and less tendency to produce lons-
daleioid dissepiments.

Tabulophyllum, as typified by the Upper Devonian
T. rectum, differs from Middle Devonian Sinospongo-
phyllum in having weakly developed minor septa and
a less evident septal stereozone. However, the two
genera have much in common, and Sinospongophyllum
is regarded by Stumm ( 1949, p. 27) as a possible syno-
nym. For the present, however, it seems desirable to
retain Sinospongophyllum, pending more thin section
study of topotype material of both species. Externally
the eleven described Iowa Late Devonian species of
Tabulophyllum (Fenton and Fenton, 1924) show a
great variety of form, from turbinate to subcylindrical,
and some with wide dissepimentarium.

In the Cordilleran belt, corals assignable to either
Sinospongophyllum or Tabulophyllum are character-
istic of late Middle and Late Devonian rocks in the
Great Basin, southeast Alaska, and northwest Canada
(Smith, 1945). They occupy Great Basin late Middle
Devonian coral zone F in association with Hexagon-
aria. Those corals of lowermost Middle Devonian coral
zone D that are placed in SinOSpongophyllum have a
very wide tabularium, and some specimens have only
a few sporadic lonsdaleioid dissepiments. These coral
zone D specimens occur with Siphonophrentis (Brevi-
phrentis) invaginatus, variants of which they resem-
ble. Stumm’s (1949, p. 25) Breviphyllum that was
founded upon Nevada Formation material was pos-
\ sibly inspired by examination of such associated mate-
rial; the holotype is seemingly without dissepiments
and probably represents a specimen of invaginatus.
Possibly such sparingly dissepimented zone D corals
may be derived from the Breviphrentis invaginatus
stock by the aberrant development of dissepiments.

 

 

 

 

 

 

 

 

 

 

At present they are insufliciently known for specific
description and accordingly are designated informally
by letter.

Sinospongophyllum sp. d

Plate 17, figures 1, 2, 5, 6

Figured specimens.—USNM 159312, 159314; lower
part of the Nevada Formation, Lone Mountain and
northern Antelope Range, Eureka County, Nev.

The lonsdaleioid dissepiments are large, elongate,
and irregularly distributed in one or two columns. The
tabulae are closely spaced. The septal stereozone is
narrow.

Occurrence—Late Early Devonian, coral zone D1.
Locality M1037, south pediment of Lone Mountain,
Eureka County, Nev. Early Middle Devonian, coral
zone D2. Locality M1035, north end Antelope Range,
southern Eureka County, Nev.

Sinospongophyllum sp. e
Plate 17, figures 3, 4, 10, 11

1937. (?) Amplexus nevadensis Stumm, p. 427, pl. 54, figs. 3a—c.

northern Antelope Range, Eureka County, Nev.

The lonsdaleioid dissepiments are small and irregu-
larly distributed in one to several columns. The tabu-
lae are closely spaced. The septal stereozone is narrow.
Major septa are withdrawn from the axis.

Occurrence—Early Middle Devonian, coral zone D2.
LocalityM1038, Lone Mountain, Eureka County, Nev.
Locality M1035, north end Antelope Range, southern
Eureka County, Nev.

Sinospongophyllum sp. 1
Plate 17, figures 7, 8, 9

Figured specimens.—USNM 159315, 159316; lower
part of the Nevada Formation, Grays Canyon and
northern Antelope Range, Eureka County, Nev.

The lonsdaleioid dissepiments are small and irregu-
larly distributed in one to several columns. The tabulae
are closely spaced. The septal stereozone is narrow to
fairly wide. Major septa extend to the axis where they
are twisted together in an axial plexus.

Occurrence—Early Middle Devonian, coral zone
D2. Locality M3, Grays Canyon, southern Eureka
district, Nev.: Locality M1035, north end Antelope
Range, southern Eureka County, Nev.

Family ENDOPHYLLIDAE Torley, 1933
Reference forms.~Endophyllum bowerbanki
Edwards and Haime and E. abditum Edwards and

Haime, 1851. Devonian; Torquay, England.
These cerioid and aphroid rugose corals have wide

 

—————'

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 57

corallites, a broad marginarium of partly large lons-
daleioid dissepiments and a narrow to very wide tabu—
larium comprising closely spaced tabulae. There is no
axial structure.

Genera provisonally assigned to the Endophyllidae
are Endophyllum Edwards and Haime, 1851, Yassia
Jones, 1930, and Australophyllum Stumm, 1949.
Undescribed Late Silurian corals in the Great Basin
and the Klamath Mountains are related to Australo-
phyllum; the Klamath forms are a separate genus, and
those of the Great Basin a subgenus of Australophyl-
lum.

Some corals here regarded as Endophyllidae have
previously been assigned to Spongophyllum, a genus
not included in this family. It is proposed that the
term S pongophyllum be applied to species with slender
corallites agreeing in general structure and proportions
with the Devonian S. sedgwicki as originally illustrated
by Edwards and Haime (1853, pl. 56, figs. 2, 2a—c, 2e).

In addition to the wide lonsdaleioid marginarium,
Late Silurian representatives of Yassia and a subgenus
of Australophyllum manifest a decided tendency to
abbreviate and lose septa in mature growth stages.
These characteristics are not observed in S pongophyl-
lum.

Genus AUSTRALOPHYLLUM Stumm, 1949
1911. Spongophyllum cyathophylloides Etheridge, p. 7—8, pl.
A, fig. 3, pl. C, figs. 1—2.
1949. Australophyllum Stumm, p. 34, pl. 16, figs. 1—2.
1956. (?)Australophyllum cyathophylloides (Etheridge).
Hill, fig. 207—43—b.

Type species.-—Spongophyllum cyathophylloides
Etheridge; by author designation. “Lower Middle
Devonian”; Douglas Creek, Clermont, Queensland,
Australia.

Diagnosis. —— The cerrioid Endophyllidae have
medium wide to narrow, closely spaced, proximally
sagging tabulae. The wide to very wide dissepimen-
tarium has scattered to wholly lonsdaleioid dissepi-
ments, some of which are large.

Remarks. ——Australophyllum differs from Spongo-
phyllum in possessing multiple columns of elongate,
lonsdaleioid dissepiments, and more closely spaced
sagging tabulae which lack a peripheral depression.
Stumm’s diagnosis of Australophyllum includes carin-
ate septa, although his figures do not show these
convincingly. The wall of typical Australophyllum is
somewhat thickened stereoplasmically; septal crests
do not appear to be characteristic, as they are in the
Silurian subgenus.

Australophyllum landerensis n. sp.
Plate 25, figures 1—4

Type material.——I—Iolotype, USNM 159353; para-

 

type, USNM 159354. Lower Devonian Rabbit Hill
Limestone, Toquima Range, locality M1150.

Diagnosis—This Australophyllum has long minor
septa; all septa are thickened in the tabularium. The
outer dissepiments are steeply inclined for the genus;
the outer wall is thickened and beaded with wall
crests. The tabularium is medium wide; close-set tabu-
lae have a pronounced sag.

External features—Occurs in compact ceriod heads
up to 15 cm or more in diameter.

Transverse sections.——Septa are about 44, all of
which are long and usually thickened within the tabu-
larium; minor septa are more than one-half the length
of major septa. Some major septa reach the axis where
they are twisted. Some septa may be minutely wavy
and, where thickened, show minute nodes and lateral
bumps, but there are no true elbow carinae. The stere-
ome-thickened wall has a beaded appearance because
of the wall crests; other septal crests are sparse in the
lonsdaleioid band.

Longitudinal sections.——The tabularium, about one-
third the corallite width at maturity, is very sharply
set off from the dissepimentarium. The tabulae, 4 or 5
per millimeter, have a pronounced sag which may be
angulate axially. Large outer dissepiments are steep
for this genus; the smaller ones become vertical at the
tabularium margin. Dissepiment columns range from
7 to 12. Thickened axial segments of major septa
reveal minute lateral bumps.

Reproductive offsets—One mature corallite shows
three calice wall offsets internally situated.

Fine structure—Some thickened septa may have a
median clear trace; trabecular structure and lamina-
tion are poorly defined in the septal stereozone,

Comparison with related forms—Australophyllum
cyathophylloides, the type species, differs in having
fewer septa which lack thickening in the tabularium.
Australophyllum sp. (plate 25, fig. 5) from the upper
part of the Vaughn Gulch Limestone, Owens Valley,
Calif. (locality M1093), resembles landerensis but
lacks the thickened septa. The Vaughn Gulch form
occurs in beds of Late Silurian or Early Devonian age
that are immediately above the Late Silurian coral
zone E which contains an Australophyllum so different
that it is placed in a new subgenus. The form from
Silurian coral zone E has broader mature corallites
with a considerably smaller septal count and lacks
septal thickening; this form has outer lonsdaleioid dis-
sepiments inclined at a low angle, a larger number of
very large dissepiments and, unlike landerensis, tends
to reduce and lose septa at maturity.

Measurements. ——Mature corallite diameter and
septum count:

fi

58 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN
Ugfiftllgfi“ uflifitfia such as columns of true horseshoe dissepiments with

Corallites __________________________ A B C A B contiguous peculiar trabecular bundles or sheaves.

Diameter (in mm) ...13 14 10 13 10 ' ' ' '

Major septa ______________________ 22 22 22 20 22 Moreover, in the Great Basrn stratigraphic column the

Occurrence—Lower Devonian Rabbit Hill Lime-
stone, Petes Canyon, locality M1150 at north end of
Toquima Range, southern Lander County, Nev. At
locality M1150 this colonial coral is associated with a
typical Rabbit Hill fauna like that of the type locality.
Colonial corals of this kind are uncommon in the Rab-
bit Hill Limestone, which usually contains only the
small solitary rugose coral Syringaxon.

Family DISPHYLLIDAE Hill, l939

Reference form.—Disphyllum caespitosum (Gold-
fuss), 1826. Middle Devonian, Germany.

These phaceloid, cerioid, thamnastraeoid, and aph-
roid rugose corals have smooth or carinate, continuous
lamellar, and usually little-dilated septa. The tabular-
ium is wide, combining straight and slightly domed
tabulae with marginal tabellae. Dissepiments in sev-
eral columns are normal-globose or elongate; rarely
Ionsdaleioid. There are no horseshoe dissepiments.
Species with a wide dissepimentarium have bases of
outer dissepiments nearly horizontal.

This large complex Devonian family includes the
following genera and subgenera:

Disphyllum de Fromentel, 1861
Cylindrophyllum Simpson, 1900
Acinophyllum McLaren, 1959

Hexagonaria Giirich, 1896

Hexagonaria (Pinyonastraea) new subgenus
Billingsastraea Grabau, 1917
Taimyrophyllum Chernychev, 1941
Aphroidophyllum Lenz, 1961

Cerioid Hexagonaria-like genera are common in the
Silurian and Devonian; most of these do not fit well
in this family. Among these are the Australian X ystri-
phyllum Hill with wedge-thickened smooth septa and
a narrow dissepimentarium and Columnaria-like spe-
cies with few and irregularly distributed dissepiment
columns of the German Devonian (Glinski, 1955).
Certain other European Devonian species assigned to
Hexagonaria appear to be affiliates of the Family Phil-
lipsastraeidae (Rozkowska, 1960; Moenke, 1954).

The true spongophyllids and the Endophyllidae,
which include Endophyllum and Australophyllum, are
distinguished by a lonsdaleioid marginarium. How-
ever, this type of dissepiment arose independently in
several rugosan families and may be expected to
appear sporadically in Hexagonaria and other disphyl-
lid genera.

The Family Phillipsastraeidae as here interpreted
does not include the disphyllid corals (Hill, 1956, p.
F279-F282; Stumm, 1964). Phillipsastraeidae are
characterized by highly distinctive internal features

 

 

disphyllid forms are older, occurring in coral zones
D2 and F; the true Phillipsastraeidae are of Late
Devonian age, present only in coral zone I.

Genus DISPHYLLUM Fromentel, 1861

1826. Cyathophyllum caespitosum Goldfuss, p. 60, pl. XIX,
fig. 2b only; not pl. XIX, figs. 2a, 2c, 2d.

1846. Cladocora goldfussi Geinitz (in part), p. 569. New name
for Cyathophyllum caespitosum Goldfuss, 1826, p. 60,
pl. XIX, figs. 2a—d; not pl. XIII, fig. 4.

1935. Cyathophyllum caespitosum Goldfuss 1826 (p. 60, pl.
XIX, fig. 2b only). Lang and Smith, p. 545.

1940. Disphyllum de Fromentel. Lang, Smith, and Thomas,
p. 53.

1945. Disphyllum Fromentel. Smith, p. 20—21 (in part only).

1949. Disphyllum de Fromentel. Stumm, p. 32, pl. 15, figs.
1—5.

1956. Disphyllum de Fromentel. Hill, p. F280, fig. 191—10a—b.

fuss, 1826, p. 60, pl. XIX, fig.2b only (Lang and Smith,
1935, p. 545; Smith, 1945, p. 20—21). Middle Devo-

20—21).
Diagnosis—These bushy and phaceloid rugose cor-
als have fairly long slightly thickened major septa

dissepiments are nearly flat, but the axial ones steepen
to vertical in a border zone of small dissepiments.

. Some septa may have zigzag
carinae, but these are uncommon; there are no yard-

Remarks.—Disphyllum is here interpreted accord-
ing to illustrations of the type species of Smith ( 1945,
pl. 11, figs. 8a—c) and of Stumm (1949, pl. 15, figs.
1—5). Acinophyllum McLaren (1959, p. 2228) has a
narrower dissepimentarium and wider, straighter tabu~
lae without marginal tabellae. Some other phaceloid
rugose corals which might be confused with Disphyl-
lum have marginal horseshoe dissepiments; these
include Phacellophyllum Giirich and Peneckiella Sosh-
kina, possibly a synonym of Phacellophyllum (see

 

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 59

McLaren, 1959, p. 22—23; p. 28—29). Cylindrophyllum
Simpson has yardarm carinae; Eridophyllum has cari-
nate septa and an aulos. Sociophyllum, which is the
commoner coral of this general type in the Nevada
Formation, has a wide peripheral zone of lonsdaleioid
dissipiments and lacks carinae.

Disphyllum nevadense (Stumm). 1937
Plate 18, figures 7—10
1937. Spongophyllum nevadense Stumm, p. 435, pl. 53, fig. 10,
pl. 55, figs. 5a, b.
(?)Spongophyllum expansum Stumm, p. 436, pl. 53,
fig. 11, pl. 55, figs. 6a, b.
1940. not Spongophyllum cf. expansum Stumm. Merriam, p.
56—57.
not Disphyllum nevadense Stumm, p. 63.

Type material.— Holotype, USNM 94454; lower
part of the Nevada Formation, Lone Mountain,
Eureka County, Nev.

Diagnosis.—This slender Disphyllum has few dis-
sepiment columns, including both globose and narrow
elongate dissepiments; large, elongate dissepiments
are interseptal and not lonsdaleioid.

Transverse section—Major septa, 16 to 18, extend
to the axis in many corallites. Minor septa vary from
short to more than half the length of the major septa.
Septa, thin and wavy or straight, are more inclined
to waviness in the tabularium; they are noncarinate.
The wall is thin and lacks a stereozone.

Longitudinal section—The dissepiment columns
range from one to three. The dissepiments are either
small and globose or elongate. In places a nearly flat,
elongate dissepiment extends from the periphery to
the tabularium. Commonly there are one or two small
nearly vertical dissepiments at the inner margin. The
tabularium is wide; tabulae, mostly continuous or com-
plete, are usually uparched distally with a periaxial
sag; they are rarely straight.

Reproductive offsets—Lateral offsets are developed
at the calice periphery to form branches.

Comparison with related forms—Disphyllum eure-
kaensis n. sp. has larger corallites with zigzag carinate
septa and many more dissepiment columns lacking the
elongate individual dissepiments. Disphyllum goldfussi
(Geinitz) has more small dissepiment columns and
lacks the elongate dissepiments of D. nevadense.

Remarks—Disphyllum nevadense Stumm, (1940)
is a Late Devonian species of coral zone I and not
closely related to the form here reassigned to Disphyl-
lum.

Measurements.——Diameter and major septa, three
corallites of colony USNM 159320:

Corallites ......................... 1 2 3
Diameter (in mm) ........ 8.3 7.3 7
Major septa .................. 18 16 16

534—041 0 - 74 - 5

 

Occurrence—Nevada Formation, unit 2. Devonian
coral zone D2. Lone Mountain: Eureka County, Nev.
locality M1046; at this locality it is associated with
Disphyllum eurekaensis n. sp.

Disphyllum eurekuensis n. sp.
Plate 18, figures 5, 6

Type material—Holotype, USNM 159319. Nevada
Formation, unit 2; Devonian coral zone D2. Lone
Mountain locality M1046.

Diagnosis—This Disphyllum has corallites of large
diameter and multiple columns of predominantly small
dissepiments. The tabulae are mostly wide and fairly
straight; some specimens are complete and some have
peripheral tabellae and a tendency for peripheral
depression of tabulae. The septa are slightly thickened
in the dissepimentarium; some have weak zigzag
carinae.

External features.—- Longitudinal grooves are not
well shown; in places transverse rugae are fairly pro-
nounced. There are lateral mergings of corallites in
positions of marginal calicinal offsets.

Transverse sections—Major septa, which number
18 to 22 do not reach the axis; minor septa are about
two-thirds the length of the major septa. The septa
are minutely wavy to zigzag and have sporadic zigzag
carinae in the middle part of the dissepimentarium.
Outer dissepiments are rather irregular; some are
concave peripherally. All septa are continuous to the
wall. The wall is thin and lacks a stereozone. Some
are thickened slightly toward the inner edge of the
dissepimentarium.

Longitudinal sections. -—— Dissepiments, small and
medium size, are in as many as eight columns on each
side; outer three or four columns are medium, globose,
and nearly flat to low dipping axially; inner four col-
umns are small and steep to vertical. There are some
large elongate dissepiments in the outer zone. The
tabulae are rather closely set and for the most part
fairly continuous and straight; some are complete,
with large periaxial tabellae. Peripheral parts of the
tabulae are depressed in some specimens. Traces of
carinae appear in local patches.

Reproductive ofisets.—- The merging of corallites
laterally indicates reproductive offsets from calice
margins.

Comparison with related forms—Disphyllum eure-
kaensis differs from D. goldfussi (Geinitz) in having
more wavy and partly zigzag, weakly carinate septa;
the tabularium of D. goldfussi (see Smith, 1945, pl. 11,
figs. 8a—c; Stumm, 1949, pl. 15, figs. 2—3) is wider with
more tabellae at the tabularium margin. Disphyllum
nevadense (Stumm, 1937) has narrower corallites
lacking the zigzag carinae, fewer dissepiment columns,

 

 

60 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

and partly elongate dissepiments. Disphyllum nevad-
ense Stumm (1940, p. 63, pl. 7, fig. 10; pl. 8, figs. 11a—
b), a much younger species from the Devils Gate Lime-
stone, is more slender, has fewer columns of dissepi-
ments and a wide tabularium with medial flat tabellae,
and lacks the more nearly complete straight tabulae
of D. eurekaensis.

Measurements.——Diameter and major septa; three
corallites of colony USNM 159319:

 

Corallites .............................. 1 2 3
Diameter (in mm) ..... 19 16.6 17
Major septa ........................ 20 20 22

Occurrence—Nevada Formation, unit 2. Devonian
coral zone D2. Lone Mountain: locality M1046, associ-
ated with D. nevadense (Stumm, 1937).

Genus HEXAGONARIA Giirich, 1896
1900. Prismatophyllum Simpson, p. 218.

Type species. —— Cyathophyllum hexagonum Gold-
fuss; by subsequent designation (Lang and others,
1940, p. 69). Middle Devonian; Eifel district and Bens-
berg, Germany.

Diagnosis.—The colonies are spherical and mush-
room shaped; the polygonal corallites are separated by
a discrete, usually unthickened wall. Calices have a
flat or axially sloping peripheral platform and a deep
axial pit. Major septa are unbroken from the wall into
the tabularium and commonly reaching the axis; minor
septa end at tabularium margin. Septa are normally
thin, modified by waviness, minor zigzag elbow carinae
and strong yardarm carinae. Dissepimentarium, usu-
ally wide, has multiple columns in which peripheral
dissepiments lie nearly flat. There are no horseshoe
dissepiment columns and no associated trabecular
bundles.

Remarks.—Most species of true Hexagonaria have
long septa, some of which reach the axis. The septa
commonly thin abruptly within the tabularium. There
are, however, aberrant forms with all the septa short-
ened and an overly widened tabularium. The patterns
of tabulae are usually irregular and include variable
combinations of arched tabellae against inclined and
incomplete tabulae; straight complete tabulae are un-
usual. Thickened walls and septa are uncommon, al-
though there are species in which some individuals
have moderate radially extended dilation or sporadic
small bumpy or knobby swellings (Rozkowska, 1960,
figs. 9, 11, 12).

Most species presently interpreted as Hexagonaria
have carinae; usually yardarm carinae are in some but
not all corallites or are restricted to parts of a single
corallite. For example, Stumm’s figures of the type
species H exagonaria hexagona Goldfuss from the Eifel
district show definite and numerous yardarm carinae

 

(Stumm, 1948a, pl. VI, figs. 1, 2). However, Sorauf’s
(1967, p. 10, fig. 4) figures of a specimen assigned to
hexagona from Frasnes, Belgium, reveal no clear indi-
cation of yardarm carinae. It is assumed that the Eifel
district material from the Middle Devonian is more
nearly representative of the Goldfuss type species.

Unrelated Hexagonaria-like Rugosa.—Any family of
dissepimented rugose corals may theoretically give rise
to compact cerioid species by adaptive radiation.
Within the Phillipsastraeidae have evolved rather
closely related solitary, bushy, and lastly cerioid forms
which parallel H exagonaria. Convergent or homeomor-
phic cerioid corals of this sort are known in Paleozoic
strata from Silurian to Carboniferous. All share the
compact growth habit, by itself not a feature of over-
riding taxonomic importance. Five of these families
have cerioid radicles: (1) Kyphophyllidae, (2) Endo-
phyllidae, (3) Spongophyllidae, (4) Disphyllidae, and
(5) Phillipsastraeidae. Within a wide range of internal
structure combinations, each family gave rise to line-
ages paralleling or mimicking Hexagonaria of the
Disphyllidae.

Silurian rugose coral genera possessing the cerioid
growth habit of H exagonaria have received little atten-
tion from paleontologists. Undescribed corals from the
Klamath Mountains Gazelle Formation possess a nar-
row, weakly developed tabularium and are classified
with the Kyphophyllidae, Other western Silurian
forms are endophyllids with strong lonsdaleioid dis-
sepiments. Late Silurian Hexagonaria-like species of
eastern North America are members of the cerioid
genus Entelophylloides Rukhin, as are some Russian
species.

Stratigraphic range of Hexagonaria.—Hexagonaria
has been reported in Devonian rocks of western Europe
as old as Emsian and Siegenian (Sorauf, 1967, p. 24).
In general those species which are convincingly dis-
phyllid appear in the Eifelian rocks. In Europe the
highest known Hexagonaria is Frasnian Late Devo-
nian. The Hexagonaria from the Great Basin appears
as the subgenus Pinyonastraea in the Nevada Forma-
tion, unit 2 and coral zone D2, probably in earliest Eif-
elian. True H exagonaria peaks in coral zone F, which is
the higher Eifelian of this province. No coral zone I or
Frasnian H exagonaria is known with assurance in the
Great Basin; all cerioid species of zone I thus far iden-
tified are Phillipsastraeidae.

Hexagonaria systematics. — Characters by which
Hexagonaria may be subdivided taxonomically and
distinguished from Phillipsastraeidae and other fami-
lies have been reviewed by Stumm (1948a), Schouppé
(1958), and more recently by Sorauf (1967). At pres-
ent H exagonaria is a large morphologically diverse and

 

 

———i

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 61

complex genus of worldwide distribution in need of
descriptive study and taxonomic appraisal. Some
morphologically similar taxar within its scope are
doubtless products of convergent evolution. As with
Billingsastraea and other disphyllids, it is not unlikely
that similar internal structures developed in not very
closely related genetic stocks; in this light Hexago-
naria may be quite polyphyletic.

Current investigations of Hexagonaria differentia-
tion in Great Basin Devonian coral zones D and F sug-
gest that subgenera may be used appropriately. Ac-
cordingly the earliest H exagonaria of coral zone D is
discribed as subgenus Pinyonastraea.

Of uncertain relationship to H exagonaria are three
noncarinate Devonian groups of H exagonaria-like cor-
als: (1) the genus Xystriphyllum; (2) a group having
a few small sporadic lonsdaleioid dissepiments; and
(3) aberrant species structurally intermediate be—
tween Hexagonaria and Columaria.

Xystriphyllum, unlike H exagonaria, has a thickened
wall, thickened gradually wedge-tapering smooth
septa, narrow tabulae, and very steeply inclined or
vertical dissepiments. Group 2, with its scattered small
lonsdaleioid features, may conceivably be a Hexago-
naria derivative, for dissepiments of this kind clearly
arose in numerous genetically unrelated lineages. Aus-
tralophyllum of the Endophyllidae differs in possessing
a well-defined lonsdaleioid band.

Group 3, a heterogeneous, probably polyphyletic
form group, from the Devonian of Western Europe,
comprises thick-walled species with a very wide tabu-
lae, a reduced dissepimentarium having few columns,
and thick wedge-tapering, commonly short septa
(Glinski, 1955). Generic or subgeneric grouping may
eventually prove appropriate for these local differenti-
ates.

Certain Polish species of “Hexagonaria” described
by Moenke (1954) appear, on examination of the pub-
lished figures, to be better assigned to the Phillipsas-
traeidae. The origin of this family is unexplained.
Whether the distinctive horseshoe dissepiment col-
umns and trabecular bundles arose in a Middle Devo-
nian disphyllid line can only be inferred at present.
In the Central Great Basin, beds of coral zone F with
H exagonaria also contain disphyllids of the Taimyro-
phyllum type surficially mimicking Late Devonian
(coral zone I) Pachyphyllum of the Phillipsastraeidae.
These mimics lack the horseshoe dissepiment columns
and trabecular bundles.

Study of H exagonaria suites from coral zone F, sup-
plemented by review of the literature on Disphyllidae,
suggests that the following characters are of special
taxonomic value within this and allied genera.

 

1. Septal configuration: thin, smooth and
straight; or thickened, tapering gradually
from wall; or wavy, zigzag with elbow cari-
nae, yardarm carinae, or combination of
these.

2. Wall in transverse section: thin and wavy or
straight; or thickened stereoplasmically
with obtusely wedge-tapering septum bases.

3. Width of tabularium relative to dissepimen-
tarium.

4. Outer dissepiments in longitudinal section:
vertical to steeply inclined toward axis; or
nearly horizontal.

5. Outer dissepiments in transverse section: nor-
mal concentric, or irregular with herring-
bone pattern.

The width of the tabularium is a feature having a good
deal of latitude within a species and between species.
Normally about one-third the corallite diameter in
most species, the tabularium may broaden to exceed
one-half the corallite diameter, and the dissepiment
band narrows correspondingly as the septa shorten.
At the opposite extreme is Hexagonaria with narrow
tabularium and thin axial septum extensions which
meet in a twisted axial plexus accompanied by median
uparching of tabulae. A small raised median calice boss
may result, but no discrete axial rod or columella.

Subgenus PINYONASTRAEA. new subgenus
1937. Prismatophyllum kirki Stumm, p. 437; pl. 55, figs. 7a—b.
1940. “Prismatophyllum” kirki Stumm. Merriam, pl. 16, fig. 5.

Type species.—Prismatophyllum kirki Stumm, here
designated. Nevada Formation, unit 2, Devonian coral
zone D2; Lone Mountain.

Diagnosis.——This Hexagonaria has a thin wall and
thin minutely wavy septa lacking yardarm carinae.
The dissepimentarium is wide and has numerous col-
umns of globose dissepiments; the peripheral dissepi-
ments are nearly flat. The calice is shallow with a broad
brim platform and an axial pit.

Remarks. — The subgenus Pinyonastraea differs
from Hexagonaria (Hexagonaria) as typified by its
type species hexagona Goldfuss (Stumm, 1948a, p. 11—
15, pl. VI, figs. 1—2) in lacking crossbar or yardarm
carinae and other septal thickenings. Carinae, if de-
veloped in Pinyonastraea, are weak and of the zigzag
elbow or angulation type.

Stumm, in 1937 (p. 437), called attention to this
coral type as possibly having developed from ancestry
different from that of other “Prismatophyllum.” If it
has, study of more adequate material might justify
separate generic designation eventually.

Selected individuals of Pinyonastraea kirki resemble
internally the associated Billingsastraea nevadensis,

‘—

62 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

especially subspecies arachne; the principal difference
is lack of the outer wall. As elsewhere noted, it is con-
ceivable the two come from common ancestry.

Pinyonastraea is a relatively uncommon coral in the
higher part of Nevada Formation, unit 2, unlike the
local occurrence of H exagonaria s.s. which is abundant
in higher Middle Devonian coral zone F. The new sub-
genus has not been recognized outside of the Great
Basin Province.

Hexagonaria (Pinyonastmea) kirki (Stumm)
Plate 23, figures 5—10

1937. Prismatophyllum kirki Stumm, p. 437, pl. 55, figs. 7a—b.
1940. ”Prismatophyllum” kirki Stumm. Merriam, pl. 16, fig. 5.
1949. Hexagonaria kirki (Stumm), pl. 15, figs. 16, 17.

Type material.——Holotype USN M 94456; lower part
of the Nevada Formation, Lone Mountain, Eureka
County, Nev.

Diagnosis—This Pinyonastraea has large corallites,
minutely undulant, very weakly zigzag, thin carinate
septa and thin, even, commonly straight walls. Some
of the outer dissepiments are sublonsdaleioid in the
peripheral irregular zone of the dissepimentarium.

External features—This species occurs in large len-
ticular colonies 25 cm or more in greatest diameter. In-
dividual corallites are considerably larger than average
for Hexagonaria. A well-preserved distal surface (pl.
23, fig. 7) shows shallow calicinal pits with a weak
crateriform rim; the calicinal platform is concavely
depressed to almost flat, and the thin outer wall stands
sharply in relief.

Transverse sections—Major septa number 20—23;
these are uniformly thin, and for the greater part ex-
tend without discontinuity to the axial vicinity. Minor
septa are more than half to nearly as long as the major
septa, which extend to the tabularium margin. Some
minor septa are discontinuous, represented by crests,
or lacking; minor septa commonly do not pass periph-
erally to the wall. Septa range from straight and nearly
smooth to minutely undulant and zigzag carinate.
However, the carinae are not abundant; they are
minute, and in some specimens confined to a few septa,
in which they occur alternately in radial succession.
There are no yardarm carinae. The peripheral zone of
irregular dissepiments is wide; the outer sublonsdalei-
oid dissepiments, if present, usually are small.

Longitudinal sections—The flat-lying dissepiments
which make up most of the dissepimentarium show
little size regularity; they range from small to large,
the larger predominate. Significant features are nearly
straight, continuous, horizontal, and somewhat thick-
ened tabulae in parts of this zone.

Comparison with related forms. — In the Roberts
Mountains at locality M1054, a subcerioid variety with

 

 

 

corallite walls partly rounded transversely is associ-
ated with normal kirki; this fact suggests a phaceloid
tendency (Merriam, 1940, pl. 16, fig. 6). An Hexago-
naria-like species occurring in the Toiyabe Range at
locality M1151 near Reeds Canyon (plate 25, fig. 10)
has wide corallites and may be allied either to kirki
of coral zone D or to Hexagonaria flexum (Stumm) of
coral zone F.

H exagonaria (Pinyonastraea) kirki has no described
close relatives elsewhere. It is possible this form is
derived from the stock which produced the corals
assigned to Billingsastraea nevadensis.

Measurements—Holotype USNM 94456; diameter
of a mature corallite, 17 mm; major septa, 20. Figured
specimen USN M 159345: diameter of a mature coral-
lite, 17 mm; major septa, 23.

Occurrence—Lower part of the Nevada Formation,
unit 2. Devonian coral zone D2. Lone Mountain: local-
ity M1052. Northern Roberts Mountains: locality
M1054. Northern Antelope Range: locality M1053. At
Lone Mountain this coral may range into coral zone D3
at locality M1052.

Genus BILLINGSASTRAEA Grabau, 1917

1917. Phillipsastraea (Billingsastraea) Grabau, p. 957.

1937. Billingsastraea Grabau. Stumm, p. 437, pl. 53, fig.
13, pl. 55, figs. 8a—b.

1949. Billingsastraea Grabau. Stumm, p. 35, pl. 16, figs.
8—11, ?fig. 7.

1951. Billingsastraea Grabau. Ehlers and Stumm (in
part).

1953. Billingsastraea Grabau. Ehlers and Stumm, p. 1.

1956. Billingsastraea Grabau. Hill, p. F280, fig. 191—7.

Not 1958. Billingsastraea Grabau. Schouppé, p. 235—237.

1964. (?)Billingsastraea Grabau. Stumm, p. 43, pl. 40,
figs. 1—3.

1964. Billingsastraea Grabau. Oliver, p. B1—B5, pls. 1—2.

1964. Radiastraea Stumm. Pedder, p. 446—449, pls. 71—73.

Type species. —Phillipsastraea verneuili Edwards
and Haime, 1851 (by monotypy). According to Ed-
wards and Haime, the type occurrence is in the State
of Wisconsin; the type is now believed to have come
from glacial drift.

Diagnosis.—Oliver’s (1964) diagnosis is as follows:
Astraeoid, thamnastraeoid, or slightly aphroid corals with cal-
ices
peripheral platform. Septa are radially arranged and lightly
to heavily carinate with zigzag or crossbar carinae. Major and
minor septa extend from the periphery; minor septa terminate

composed of closely spaced, horizontal complete tabulae. The
dissepimentarium is composed of gently to strongly curved
dissepiments that are horizontally arranged except next to the
tabularia where they are inclined toward the corallite axes.

Remarks—Grabau (1917, p. 957) introduced the

 

——’i

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 63

name Billingsastraea in a subgeneric sense without
definitive treatment. Stumm first defined Billingsas-
traea as a genus in 1937. Redefining the genus in 1949,
Stumm (p. 35) in effect interpreted his genus Radias-
traea (Stumm, 1937, p. 439) as an objective synonym
of Billingsastraea, thus suppressing Radiastraea. As
noted by Oliver, the species Radiastraea arachne
Stumm (type species of Radiastraea) was regarded by
Stumm (1949, p. 35) as a weakly carinate species of
Billingsastraea. Oliver’s diagnosis above supplements
that of Stumm in taking into account the characters of
R. arachne.

Because the internal features of “Phillipsastraea”
verneuili Edwards and Haime, type species of Billings-
astraea, are unknown, the status of this genus remains
clouded. Pedder (1964, p. 447) regards certain species
assigned to Billingsastraea by Ehlers and Stumm
(1951; 1953) as constituting a separate but unde-
scribed compound H eliophyllum-like genus; these are
doubtless the strongly yardarm-carinate forms. He has
accordingly resurrected Radiastraea for the noncari-
nate to not so strongly carinate species of the arachne
type.

At present too little is known of the taxonomic sig-
nificance of prominent crossbar or yardarm carinae to
decide whether or not these features constitute a suf-
ficient basis for separating the species bearing them as
a genus distinct from the species presently in Billings-
astraea which have noncarinate septa or zigzag cari-
nae. The problem is similar to that in connection with
Hexagonaria.

In accord with Stumm’s 1949 review and the reeval-
uation of Oliver (1964), the term Billingsastraea is
provisionally retained for the Nevada forms here dealt
with, in the hope that eventually the type of verneuili
may be sectioned and studied.

Billingsastraea nevadensis (Stumm) and B. arachne
(Stumm) were both described from the lower part of
the Nevada Formation at Lone Mountain, Eureka
County, Nev. Both occur in the lower part of the Ne-
vada (in unit 2) and in coral zone D2; it is not im-
probable they are within the range of variation of a
single species. However, full confirmation of this iden-
tity will depend upon variation studies of more com-
plete suites of specimens from the same locality and
horizon than are at present available. Probably the
best course at this time is to consider B. arachne
merely a subspecies of B. nevadensis.

Billingsasiruea nevadensis (Stumm)
Plate 24, figures 1—3, 5, 6—8
1937. Billingsastraea billingsi nevadensis Stumm, p. 438, pl.
53, fig. 12, pl. 55, figs. 9a—b.
1940. Billingsastraea nevadensis Stumm. Merriam, pl. 12, fig.
1.

 

1949. Billingsastraea nevadensis Stumm, pl. 16, fig. 8.

Type and figured material. — Holotype USNM
94467; lower part of Nevada Formation, Lone Moun-
tain. Figured specimens: USNM 159346, 159347,
localities M1055, M1035, Antelope Range; USNM
159348—159350, locality M55, Lone Mountain. Devo-
nian coral zone D2.

Diagnosis.—This thamnastraeoid Billingsastraea
has uniformly thin finely wavy or zigzag septa and
numerous weak zigzag elbow carinae. Longer major
septa reach the axis; their waviness generally increases
as they approach the center. Minor septa are two-
thirds the length of the major septa; their axial tips
just enter the tabularium. Concentric dissepiment
traces, close-set at the inner margin of dissepimen-
tarium, form a false inner ring that normally has no
significant thickening. Tabulae are mostly irregular,
arched distally, and some of them are complete. Flat
outer dissepiments range in size from small to large;
inner steeply inclined dissepiments are small.

External features.——Ovoidal colonies that are 15 cm
or more in greatest diameter show polygonal outlines
resembling those of large corallites that have raised
margins with the external appearance of a wall. Calice
pits commonly lack the raised crateriform margin
characteristic of subspecies arachne.

Transverse sections.—-Major septa average about
16, most of them extend to the axis; in the tabularium,
major septa, wavy and irregular, commonly produce an
incipient plexus, join laterally or with their opposite
septa. Some individuals reveal a moderate thickening
of both major and minor septa only in those parts
where they pass from dissepimentarium to tabularium;
others show no such thickening. No wall separates
corallites, most septa pass into septa of adjacent
corallites peripherally. Dissepiment traces are usually
evenly concentric in the close-spaced periaxial area;
they become more irregular or nearly straight in the
more open peripheral area. Septal waviness varies con-
siderably from those with numerous small, even bends
without carinae to those with closely spaced, zigzag
bends having fine sharply projecting carinae at the
elbow angles. No crossbar (yardarm) carinae are pres-
ent. Astraeoid patterns are slightly developed periph-
erally, but no aphroid tendencies have been recognized
in this predominantly thamnastraeoid species.

Longitudinal sections.—The diameter of the tabu-
larium is about one-third of or slightly less than the
corallite diameter. In a broad zone of nearly flat lying
dissepiments, small to large dissepiments have irregu-
lar distribution; limbs of larger dissepiments subtend
as many as five small underlying ones. The innermost
column of small dissepiments stands near vertical. The

—

64 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

tabulae, rather closely spaced, commonly are arched
distally in an irregular fashion and have a periaxial
depression. A few tabulae nearly complete, most ter-
minate as large tabellae. Carinal traces show in scat-
tered patches. Horseshoe dissepiments are lacking.

Comparison with related forms. —Billingsastraea
nevadensis differs from B. verrilli (Meek) in the struc-
ture of its septa, which are thickened within the dis-
sepimentarium of verrilli (Smith, 1945, pl. 19, figs.
2b—c; and in cellulose peels of a Meek paratype); B.
nevadensis has uniformly thin septa in this region. B.
verrilli, figured by Pedder (1964, pl. 71, figs. 1—5; pl.
72, figs. 4—5), is less thickened here than is Meek’s
paratype specimen, but it has thicker than normal
nevadensis septa in the dissepimentarium.

Among the adequately illustrated species of Billing-
sastraea, the one under consideration bears a signi-
ficant resemblance to B. afl‘inis (Billings) as figured by
Oliver ( 1964). The differences are a greater number of
major septa (about 19 in afi‘inis, 16 in nevadensis) and
possibly in the vertical sides of calicular pits in afl‘inis.
Billingsastraea afl‘inis, reported by Oliver ( 1964, p. B3)
from the Grande Greve Formation of Coblenzian age,
is possibly not a great deal older than B. nevadensis
from the beds of coral zone D2.

Measurements.—The measurements of representa-
tive corallites of figured specimens are:

 

USNM No. ................................................. 159.946 159.947 15934.9
Diameter (in mm) ............ 16 14 11
Major septa .................................. 19 17 16

Occurrence—Nevada Formation, unit 2; Devonian
coral zone D2. Lone Mountain: localities 104 (Merri-
am, 1940), M55. Northern Roberts Mountains: local-
ity 3 (Merriam, 1940). Northern Antelope Range: 10-
calities M1035, M1055. At localities 3 and 104 (Mer-
riam, 1940) B. nevadensis is associated with subspecies
arachne.

Billingsastraecr nevadensis subsp. arachne (Stumm)
Plate 24, figure 4

1937. Radiastraea arachne Stumm, p. 439, pl. 53, fig. 13; pl.
55, figs. 8a—b.

1940. Radiastraea arachne Stumm. Merriam, pl. 13, fig. 5.

1949. Billingsastraea arachne (Stumm), p. 35, pl. 16, fig. 9,
10, 11.

1964. Radiastraea arachne Stumm. Oliver, p. B3.

1964. Radiastraea arachne Stumm. Pedder, p. 446—447, pl.

72, figs. 1—3, pl. 73, figs. 1—5.

Type material.—Holotype USNM 94458. Lower
part of the Nevada Formation, Lone Mountain.

Diagnosis.—This Billingsastraea has uniformly thin,
moderately wavy to only slightly wavy or nearly
straight septa, with a few zigzag carinae limited to a
few septa. The distal surface of type has prominent
raised crateriform rim at the edge of calicular pits.

 

Remarks—Stumm (1937, p. 439) defined Radias-
traea to contain species having these features, together
with an inner aulos or “tubular ring.” Later Stumm
(1949, p. 35) noticed that an aulos was not present;
accordingly he concluded that R. arachne is a weakly
carinate species of Billingsastraea. This appears to be a
reasonable interpretation. Pedder (1964, p. 446—449)
has reinterpreted Stumm’s Radiastraea as a genus and
has proposed its adoption to include arachne and ver-
rilli (Meek).

Occurrence—Lower part of the Nevada Formation,
unit 2. Devonian coral zone D2. Lone Mountain: locali-
ties 58, 104, 105 (Merriam, 1940). Northern Roberts
Mountains: localities 3, 36 (Merriam, 1940), M1073.
Southern Roberts Mountains: locality 15 (Merriam,
1940). At localities 3 and 104 this subspecies occurs
with typical Billingsastraea nevadensis.

Billingsastraeu? sp. '1'
Plate 25, figures 6—9

This Billingsastraea? has thamnastraeoid to aphroid
growth habit. Its thickened septa lack carinae but are
minutely wavy. Septal dilation is rather evenly dis-
tributed radially through the dissepimentarium; there
is a greater swelling of twisted axial segments in the
tabularium. Closely spaced tabulae, mostly incomplete
and irregular, have a slight proximal sag. In longitu-
dinal section this species resembles Billingsastraea
nevadensis (Stumm).

Billingsastraea? sp. T differs from B. nevadensis in
lacking septal waviness and angulation carinae and in
having thickened septa. Moreover, nevadensis nor-
mally is not aphroid.

The partly aphroid growth of this form is suggestive
of Billingsastraea-like corals with dilated septa occur-
ring in Nevada Formation, unit 4 (coral zone F) at
Lone Mountain. These undescribed coral zone F forms
are more appropriately classified as Aphroidophyllum
Lenz (1961, p. 505) or Taimyrophyllum Chernychev
1941, the relationships of which have recently been
discussed by Pedder ( 1964) .

Occurrence.——Toiyabe Range, Nev.; Austin quad-
rangle, locality M1 151, west range front 0.8 mile south-
southwest of mouth of Reeds Canyon. Lower part of
Devonian limestones correlative with the Nevada For-
mation. Middle Devonian within the interval of coral
zones D to F.

Family CYSTIPHYLLOIDAE Stumm. 1949
Reference form—Cystiphylloides aggregatum (Bil-
lings) 1859. Devonian; Ontario, Canada.
These compound and solitary Devonian cystimorphs
lack septa beyond initial growth stages, except for
traces or weak radiating septal ridges on mature calice

——’i

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 65

floor and wall. The transverse thin sections of some of which were supplied by McLaren), show corallites
species do not show septal crests. The calice is deep in neanic and mature growth stages. None have septal
and has a V-shaped profile. The tabularium is gener- crests, even at the periphery where they appear in
ally narrow, in keeping with the deep, conical calice. some cystiphylloids. Most of the dissepiments decrease
The dissepimentarium is not abruptly set off from the in size axially; they become less globose in the columns
tabularium. Straight tabulae are uncommon; the hori- bordering the wide tabularium where there is a rather
zontal structures consist of two or more tabellae with abrupt change to large tabellae.
bases nearly horizontal or axially inclined at a low Yoh’s Cystiphylloides (1937), from the Middle De-
angle. All the dissepiments are concave peripherally vonian of Kwangsi Province, South China, was pro-
in lonsdaleioid fashion. posed without reference to prior use of this generic
The Devonian Cystiphylloidae differ from the Silu- name by Chapman. Yoh’s excellent figures suggest
rian Cystiphyllidae in lacking the trabecular septal that it is a solitary coral with a wider dissepimentar-
spines that extend inward from dissepiment surfaces. ium and a narrower tabularium which is less abruptly
Transitional forms probably exist between the Cysti- set off from the former. Septal crests are present per-
phylloidae and the Digonophyllidae, which generally ipherally, a feature not noted in the Onondaga form.
have septal crests and ridges. Cystiphylloides, according to either Chapman’s or
Yoh’s definition, rather conclusively does not belong

Gem’s CYSTIPHYLLOIDES Chapman 1893 in synonymy with Plasmophyllum where it has re-

1859. Cystiphyllum aggregatum Billings, p. 137, text fig. 28. cently been placed by Birenheide (1964, p. 17).

118:3; Cyfgphxllziiis_gha§mfin’94:4 1 V fi _4 The cystiphylloid corals from the Nevada Forma-

1340: 22+. Ci} 88?; hi, ll: li d: $01.35;, ,Srfriitli, agilil'l‘homas, p. tion may be segregated as colonial or solitary and, on
48. the bas1s of septal crests, into two groups; one group.

1940. Cystiphylloides Chapman (in part). Stumm, p. 39 (in lacks septal crests entirely or has some scattered but
part); not pl. 19, figs. 1—7; not pl. 20, figs. 14—15. poorly developed, and the other group has well-devel-

1956- M esoPhylllfm (CyStiPhyUOideS) Chapman, 1893- Hill: oped peripheral septal crests. Within this morphologi-
T pe 2221222303325; 225;?fii6nit222regatum Billings cal range there is a great diversity of type with respect
185g Devonian' Onandaga near Simcoe Ontario, to features of the dissepimentarium and tabularium.
Canada Cystipliylloides Yoli 1937 is a honionym an d’ The term Cystiphylloides of Chapman is applicable to
' ’ some of these types, especially to the colonial forms.

is probably not congeneric with Cystiphylloides Chap- Other types, morphologically closer to Yoh’s Cysti-
man, although It has generally been so regarded phylloides may require a new generic name Generic
(Stumm 1949, p. 39). Unfortunately the internal '

structure of Billings’ type of Cystiphyllum aggregatum names such as Mesophyllum and Digonophyllum are
. . . . available for these cystlphy1101des w1th false septa or
is unknown, and the spec1men is lost. Accordlng to

D J McLaren (written commun Sept 1 1966) Bil- septal crests alined radially in the separate growth

. . . . cones.

llngs’ speCIes is almost certalnly the common Onon-

daga dendroid to phaceloid form, as suggested by Bil- Cystiphylloides rober’tsense (Stumm)

lings’ figure of the exterior. Sections of this species are Plate 23, figures 1_4

avallfible; the diagnos1s 18 base‘?‘ on them' ‘ 1937. M esophyllum robertsense Stumm, p. 440, pl. 53, fig. 14;
Diagnosts.—These are medium and large dendr01d p1, 55, figs, 10a_c.

to phaceloid and solitary cystiphylloid Rugosa; indi- Type material. —-Holotype USNM 94459, Frazier
vidual corallites range from trochoid to cylindrical. Creek, northern Roberts Mountains; paratype USNM
The mature dissepimentarium, of medium width, is 94460, Lone Mountain, Eureka County, Nev. Lower
composed mostly of small- and medium-sized, rather part of the Nevada Formation.
uniformly globose dissepiments. The border between Diagnosis. ——The mature corallites are cylindrical
the tabularium and the dissepimentarium is rather and narrow for the genus; probably colonial. A definite
well defined but not sharp; there is a change from peripheral zone of small dissepiments passes rather
small steep dissepiments to large axially inclined ta- abruptly into an inner band of large dissepiments that
bellae. The tabularium is medium wide to wide. Septa are not sharply set off from the tabularium.
and septal spines or crests are commonly absent. External features.——The cylindrical corallites have
Remarks.—A series of transverse sections of a den- rather coarse external longitudinal ribs. The parallel
droid, a moderately compact colony from the Onon- alinement of corallites in the matrix. A bushy colonial
daga Limestone of Hagersville, Ontario (Royal On- growth form, although no lateral connection was
tario Museum Collections No. 8950H), (photographs observed.

 

 

h

66 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

Transverse section. —The peripheral zone shows
about four columns of small dissepiments; at the axis
there is a fairly abrupt change to large dissepiments.
Within the outer band of small dissepiments there is
stereoplasmic thickening but septal crests, if present,
are indistinct. No septal crests were observed inter-
nally

Longitudinal section—The change from small dis-
sepiments to large ones in the peripheral zone is con-
spicuous, but the separation between the tabularium
and the large dissepiments is indistinct; the innermost
roughly horizontal arched features considered to be
tabellae occupy the axial part of the corallite that is
usually narrow.

Reproductive ofi’sets.—Stumm (1937, p. 440) notes
the presence of a calice offset in the holotype.

Comparison with related forms.—Other Great Basin
cystyphylloids become cylindrical when mature, but
this specimen is the only one I have reason to think
may be a phaceloid colonial.

Measurements—Figured specimen USN M 159343:
mature corallite diameter 22 mm; width of peripheral
band of small dissepiments 3 mm.

Occurrence—Lower part of Nevada Formation,
lower part of unit 2. Devonian coral zone D. Lone
Mountain: locality M1046. Northern Roberts Moun-
tains, Nev.; type locality of species on Frazier Creek.
At Lone Mountain locality M1046 this coral is associ-
ated with Disphyllum nevadense (Stumm) and D.
eurekaensis n. Sp.

Cystiphylloides lonense (Stumm)
Plate 19, figures 1—9
1937. M esophyllum lonense Stumm, p. 440, pl. 53, fig. 15; pl.
55, figs. 11a—b.

Type material and figured specimens. ——Holotype
USNM 94461, paratype USNM 94461a. Figured speci-
mens USNM 159322—159327: lower part of the Ne-
vada Formation, Lone Mountain, Eureka County,
Nev.

Diagnosis.—This medium-sized, solitary, ceratoid
Cystiphylloides has large tabellae not sharply set off
from large interior dissepiments; few recognizable sep-
tal crests are present in transverse sections, but the
deep calice has weak, raised, discontinuous radial stri-
ations. Both large and small dissepiments are in the
peripheral band.

Transverse sections.—About two-thirds the diame-
ter of the mature stages consists of larger dissepiments
and tabellae; a few large dissepiments are at the peri-
phery. There are a few scattered septal crests in the
peripheral band, and incomplete cones of stereoplas-
mic thickening occur at about the inner edge of the
dissepimentarium.

 

Longitudinal sections—Most dissepiments, includ-
ing those in the peripheral band, are steeply inclined.
The tabularium is commonly occupied by two large
tabellae, which are either nearly flat or axially inclined
at a low angle; in the early neanic stages there may be
a few complete and flat tabulae.

Comparison with related forms—The younger Cys-
tiphylloides robertsense of coral zone D2 has a greater
concentration of small dissepiments in the outer band
of the dissepimentarium and is cylindrical and prob-
ably colonial when mature. Cystiphylloides america-
num (Edwards and Haime) has a much wider dissepi-
mentarium with numerous columns, the outer columns
are nearly flat. Its tabularium usually shows several
laterally contiguous tabellae in a rather wide and fairly
discrete tabularium.

M easurements.—Three figured specimens (in mm) :

USNM No. ........................................................ 159.122 159.92.? 159.124
Length of corallum restored ............ 39 69 70
Diameter at calice edge .................... 22.5 31 31

Outside diameter at

calice bottom ................... 17 17 23
Depth of calice ....................... 16 35 29

Occurrence—Lower part of the Nevada Formation,
unit 1. Devonian coral zone C. In association with Pa-
piliophyllum elegantulum, Siphonophrentis (Brevi-
phrentis) kobehensis, and Acrospirifer kobehana. Lone
Mountain: localities M74, M286.

 

 

Cystiphylloides an. d
Plate 19, figures 10, 11

1884. (?) Cystiphyllum americanum Milne-Edwards. Walcott,
p. 106.

1937. (?)Mesophyllum flexum Stumm, p. 441, pl. 55, figs.
12a—b.

1938. (?)Mesophyllum vesiculosum (Goldfuss). Stumm, p.

483, pl. 59, figs. 8a—b.

These cystiphylloid rugose corals resemble Cysti—
phylloides americanum (Edwards and Haime). They
occur in the IOWer part of the Nevada Formation, prob-
ably ranging up through coral zone D to coral zone E.
In coral zone D these corals are represented by the
form here referred to as Cystiphylloides sp. d. There is
insufficient material to justify a specific name at
present.

Like C. americanum, this form grows to a large size
with numerous columns of medium and large dissepi-
ments that are not sharply set off from from tabellae
in the axial vicinity. In C. sp. (1 the dissepiments are in-
clined steeply and many are elongate, whereas in C.
americanum the peripheral dissepiments are less
steeply inclined. The calice of C. americanum is deep
and bellshaped, whereas the calice of C. sp. d may be
very deep and conical or funnel shaped. No septal
crests are noted.

 

——7

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 67

Occurrence—Nevada Formation, unit 2. Devonian
coral zone D2. Southern Sulphur Spring Range: local-
ity M36.

Family DIGONOPHYLLIDAE Wedekind. 1924

Reference form—Mesophyllum defectum Schliiter
1889. Middle Devonian, Germany.

Large, solitary, pervasively dissepimented rugose
corals have septa which tend to be discontinuous
lamellar plates, both vertically and radially. Bilateral
symmetry is obscure in mature growth stages; at the
mature stage the fossula is usually not clearly defined.

The Digonophyllidae include forms ranging from a
type with conspicuous septa to a type with greatly
reduced mature septa, which may appropriately be
called cystimorphs. The dissepimentarium is always
wide; the tabularium is narrow and may be poorly dif-
ferentiated. Many of these corals have a wide calice
brim or platform.

As noted by Wedekind (1924), the septal tissue of
the Digonophyllidae develops discontinuously in suc-
cessive growth cones (septal cones of Wedekind).

The family and generic classification of these corals
remains in a confused state. Multiplication of genera
by Wedekind and associates reflects the taxonomic
philosophy of the extreme “splitter,” although the
coral divisions appear to have been related to strati-
graphic units. Birenheide (1964) , in a painstaking and
detailed revision, eliminates many of the Wedekind
genera. Hill (1956, p. F314—F320) has adopted some
Wedekind genera as subgenera in a practical and rea-
sonably satisfactory scheme based on current under-
standing of this complex group.

For purposes of this study two subfamilies of the
Digonophyllidae are adopted: Digonophyllinae and
Zonophyllinae. In the Great Basin Province the Digo-
nophyllidae appear in Devonian coral zone D2 and are
not known above coral zone F. Here, as in Germany,
they are characteristic of Middle Devonian, especially
the Eifelian.

Subiamily DIGONOPHYLLINAE Wedekind, 1924

Reference form—Mesophyllum defectum Schliiter
1889. Middle Devonian, Germany.

The large Digonophyllidae have septa uniformly de-
veloped or sporadic and vestigal in growth cones. The
septa in the growth cones are either radially continu-
ous plates or radially alined ridges and crests. Strip
carinae are present in the marginarium of some genera.
Normal but irregular dissepiments of the periaxial
band change peripherally to irregularly lonsdaleioid.
The dissepiment pattern is highly complex and non-
uniform in the marginarium of species having periph-
erally suppressed septa.

 

 

 

 

 

In all Digonophyllinae the tabularium is relatively
narrow and poorly differentiated and lacks straight
tabulae. The calice is deep and conical, floored by two
or more tabellae; in those forms having a wide brim-
platform, the inner conical part of the calice is a
steep-sided pit.

Hill (1956, p. F317) and Birenheide (1964, p. 6)
note the presence of a fossula in some Digonophylli—
dae; however, no fossula is recognized in the Great
Basin species, and it. seems probable that symmetry
features of this kind are not generally conspicuous in
the Digonophyllinae.

No preparations of Great Basin material convinc-
ingly show vertical continuity of homologous septal
lamellae from one incremental growth cone to those
above and below, within successive nested cone
sequences.

The radially broken septa of some species commonly
have such closely spaced component crests that the
septa almost look continuous. Observed in transverse
thin section, each crest or spine is an outgrowth from
one or more tabellae or from one or more of the dissepi-
ments.

As noted elsewhere, it is probable that Digonophyl-
linae with almost wholly lonsdaleioid dissepiments in-
tergrade with the Cystiphylloidae.

Genera and subgenera classified with the Digono-
phyllinae are as follows:

Digonophyllum (Digonophyllum) Wedekind, 1923

Digonophyllum (Mochlophyllum) Wedekind, 1923

Mesophyllum (Mesophyllum) Schliiter, 1889

Mesophyllum (Arcophyllum) Markov, 1926
Arcophyllum is classified as a subgenus under Meso-
phyllum by Hill (1956, p. F318). Other possible sub-
genera of Mesophyllum are: Lekanophyllum Wede-
kind, 1923, Atelophyllum Wedekind, 1925, and Dialy-
tophyllum Amanshauser, 1925.

The Digonophyllinae appear in Early and early Mid-
dle Devonian coral subzones D2 and D3 of the Great
Basin with the genera M esophyllum and Arcophyllum.
Corals of this subfamily peak in the higher Eifelian
interval of coral zone F.

Genus MESOPHYLLUM Schluter, 1889
1956. Mesophyllum Schlu'ter 1889. Hill, p. F318.

Type species. — M esophyllum defectum Schliiter,
1889. Middle Devonian; Eifel district, Germany.

Diagnosis. — These Digonophyllinae have nonuni-
formly discontinuous septa which become obsolete
peripherally in a wide band of irregularly lonsdaleioid
dissepiments, with or without localized groups of strip
carinae.

Remarks. —— The corals assigned to M esophyllum
range in structure from maturely cylindrical cysti-'

 

i

68 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

morphs with only a few weak septal traces and scat-
tered or no bar carinae to those with numerous dis-
continuous and fairly strong continuous irregularly
thickened septa and abundant strip carinae.

At present the adoption of Mesophyllum as a genus
with subgenera, more or less in accord with the scheme
used by Hill (1956, p. F317—F320) seems to be a rea-
sonably satisfactory rationalization of the taxonomic
dilemma in this difficult and complex group. Biren-
heide’s detailed systematics (1964) are, on the other
hand, quite different; he classifies Mesophyllum as a
subgenus of Plasmophyllum.

Of the seven subgenera of Mesophyllum listed by
Hill, only two, Mesophyllum (Mesophyllum) and Me-
sophyllum (Arcophyllum) , are pertinent in this study.
Cystiphylloides Chapman is not here classified as a
subgenus of MeSOp/zyllum.

Subgenus MESOPHYLLUM sensu stricto
1956. Mesophyllum (Mesophyllum). Hill, p. F318, fig. 219—5.

Type species—Same as genus.

Diagnosis—This Mesophyllum has a highly discon-
tinuous, patchy, nonuniform, and unstable pattern of
prevailingly weak septa, with or without a few rather
poorly defined bar carinae.

Remarks.—On the one hand, this subgenus includes
cystimorphs resembling Cystiphylloides with only a
few weak septal traces; on the other, it probably grades
into the sugenus Arcophyllum with partly strong sep—
tal crests and numerous bar or strip carinae.

Corals of this general category occur in Nevada For—
mation, unit 2. Because they are known only from
fragmentary material, they are accordingly designated
provisionally by letter only.

Mesophyllum (Mesophyllum) sp. 13
Plate 21, figures 1, 2

Figured specimens.—USNM 159334. Lower part of
the Nevada Formation, Sulphur Spring Range, Nev.

Early ephebic transverse sections show many rather
stout septal crests of variable length; most of these are
concentrated in a zone halfway between wall and axis.
Inner dissepiments and tabellae are large. Carinae
were not recognized. In fully mature stages the septal
crests probably become thinner and more scattered.

Occurrence—Lower part of the Nevada Formation,
unit 2; Devonian coral zone D2. Southern Sulphur
Spring Range, Nevada; locality M36.

Mesophyllum (Mesophyllum) sp. 6
Plate 21, figures 3, 4
Figured specimens.—USNM 159335. Lower part of

the Nevada Formation, northern Antelope Range,
Nev.

 

 

 

 

Mature transverse sections show sporadic, mostly
vague septal traces in groups with widely scattered
short septal crests. Inner dissepiments and tabellae are
relatively smaller than in sp. b. In longitudinal section
all the rather small dissepiments in a very wide zone
are steeply inclined, the tabularium is very narrow,
and the septal cones and calice are acutely conical.
Thickened trabecular septal crests are developed at
the inner edge of the dissepimentarium. Carinae were
not recognized.

Occurrence. — Lower part of Nevada Formation,
unit 2; Devonian coral zone D. North end of the Ante-
lope Range, Eureka County, Nev.; locality M1035.

Subgenus ARCOPHYLLUM Markov, 1926 (as a genus)

1926. Arcophyllum Markov, p. 49—60, pl. 3.

1940. Arcophyllum Markov. Lang, Smith, and Thomas, p. 20,
41.

1949. Arcophyllum Markov. Stumm, p. 39, 43, pl. 21, figs. 1—3.

1922. Cosmophyllum Vollbrecht (not Blanchard, 1851), p. 17.

1925. Cosmophyllum Vollbrecht. Wedekind, p. 39.

1931. Cosmophyllum Vollbrecht. Wedekind and Vollbrecht,
pl. 28, figs. 1—6, pl. 32, fig. 8.

1931. (?)Pseudocosmophyllum Wedekind and Vollbrecht, pl.
19, figs. 1—4, pl. 20, figs. 1, 2, 5.

1931. ('2) Hemicosmophyllum Wedekind and Vollbrecht, pl.
31, figs. 1—12, pl. 32, figs. 1—7.

1932. Cosmophyllum Vollbrecht. Wedekind and Vollbrecht,
pl. 33, figs. 1—4.

1932. Hemicosmophyllum Wedekind and Vollbrecht, pl. 36,
figs. 1—8.

1932. (?) Pseudocosmophyllum Wedekind and Vollbrecht, pl.
38, figs. 1—5.

1937. Mesophylloides kirki Stumm, p. 441, 442, pl. 55, figs.
13a—b.

1956. Mesophyllum (Arcophyllum) Markov. Hill, p. F318,
fig. 219—1.

1956. ('2) Mesophyllum (Hemicosmophyllum) Wedekind and

Vollbrecht. Hill, p. F318, fig. 219—3a, b, c.

Type species.—Arcophyllum typus Markov, 1926
(by original designation). Middle Devonian; Calceola
beds, western slope of Ural Mountains, Russia.

Diagnosis. — The solitary Digonophyllinae have
large, commonly elongate subcylindrical mature
growth stages with thick external annulations and
rejuvenescence constrictions. The calice, deep and
inversely bell shaped to funnel shaped, is reflected
peripherally as a platform or brim, which is either
inclined axially, flattened, or broadly convex distally.
The brim surface is ornamented by numerous edges
of strip carinae. Septa are numerous, somewhat with-
drawn from axial tabellae, and range from continuous
to discontinuous as radially alined septal crests, the
more continuous septa predominate. Septa are thick-
ened locally in the tabularium; septa pass peripher-
ally into a wide band of irregular dissepiments, within
which some septa terminate short of the outer wall.
Concentric rows of strip carinae are vaguely defined

 

 

i

SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 69

peripherally in transverse thin sections; outermost
strip carinae are commonly detached from the septa
with which they are alined. Minor septa range from
about one—half to nearly full length of the major septa;
minor septa are more prone to discontinuity as alined
septal crests. The dissepimentarium is wide, is com-
monly three-fourths of corallum radius, and consists
of mostly small steeply inclined dissepiments which
pass axially without discontinuity into the narrow
medial zone of the tabellae. Outer dissepiments are
mostly lonsdaleioid; inner dissepiments form concen-
tric irregular chevrons and forks. Flat continuous tabu-
lae are few. In longitudinal thin section, prominent
isolated groups of diagonally inclined strip carinae
abut in the outer dissepimentarium against parts lack-
ing carinae.

Remarks.——Because of delay in publication, Voll-
brecht’s (1922) genus Cosmophyllum appeared in
print before Markov’s (1926, p. 49) Arcophyllum, with
which it is probably congeneric (Lang and others,
1940, p. 20). However, the generic name Cosmo-
phyllum, being an homonym, is superseded by Arco-
phyllum (Stumm, 1949, p. 43; Hill, 1956, p. F318).

Cosmophyllum-like digonophyllid Rugosa similar to
Arcophyllum are recorded by Wedekind (1924, p. 84,
85; 1925, p. 70, '71; 1926, table, p. 201) from the middle
part of the Middle Devonian, Eifel district, Germany.
The species in question are variously assigned to Cos-
mophyllum, Hemicosmophyllum, and Pseudocosmo-
phyllum. Further taxonomic revision of these Eifel
district genera is called for, in the light of field strati-
graphic occurrence, to establish their relationship to
Arcophyllum. Available illustrations of Hemicosmo-
phyllum and Pseudocosmophyllum suggest that these
corals may be closely related to, if not synonyms of,
Arcophyllum; detailed variation study is needed, not-
ing such features as presence of strip carinae in fully
mature individuals. Hill’s (1956, p. F317—F319) revi-
sion of the Digonophyllinae interprets Arcophyllum
and other genera of this subfamily as subgenera of
Mesophyllum Schlfiter. Arcophyllum-like corals from
southeastern Alaska have continuous septa, not the
radially broken septa of Mesophyllum, and may
accordingly be more closely allied to the genus Digono—
phyllum.

Mesophyllum (Arcophyllum) kirki (Stumm)
Plate 21, figures 5—7; plate 22, figures 1—6
1937. Mesophylloides kirki Stumm, p. 441, pl. 55, figs. 13a—b.

Type and figured material.——Holotype USNM
94463; figured specimens USNM 159336—159342.
Lower part of Nevada Formation, Lone Mountain,

Eureka County, Nev.
Diagnosis.—-This large Arcophyllum has a subcylin-

 

 

drical mature corallum. The wide dissepimentarium
consists of many columns of small steeply inclined dis-
sepiments; the relatively narrow tabularium has few
tabellae. The septa are withdrawn from the axis, some-
what thickened toward axis, and partly discontinuous
as septal crests. Strip carinae of the peripheral part of
the dissepimentarium are conspicuous in longitudinal
sections, inconspicuous or shadowy in. transverse sec-
tions. There is no stereozone, fossula, or other indica-
tion of bilateral symmetry in the mature corallum. The
funnel-shaped calice has a wide brim, which is distally
convex and proximally inclined toward narrow axial
pit.

External features.-—The epitheca is thin and is
absent over most of mature surface, possibly due to
wear. The complete coralla of some individuals are
very elongate and have annular folds and rejuvenes-
cence constrictions. Strip carinae project conspicu-
ously from the wide calice brim.

Transverse sections.——The septal count is 80;
this count includes minor septa, some of which are
nearly as long as the major septa; some reach the coral-
lum periphery, but most become unrecognizable
peripherally in the generally complex dissepiment tis-
sue. The septa are partly continuous and partly dis—
continuous as septal crests. Minute to small lonsdalei-
oid dissepiments compose a broad peripheral band; the
dissepiments increase in size axially and pass without
discontinuity into the tabellae of the narrow tabular-
ium. Inner dissepiments are composed of a complex
tissue which includes concentric but uneven traces,
herringbone chevrons, forks, and minute semiglobose
dissepiments that terminate against a single septum
at all edges. Septal thickenings are of the tapering
variety, without nodes and bumps of the acanthophyl-
loids. In transverse sections the strip carinae appear
as concentric radial rows of shadowy yet translucent
thickenings mainly within the peripheral lonsdaleioid
part of the dissepimentarium.

Longitudinal sections—The narrow tabularium
about one-sixth the diameter of mature growth stages,
consists of three or four axially inclined tabellae or less
commonly a single complete tabula. Small peripheral
dissepiments reveal a progressive size increase axially
and pass without break into the less steeply inclined
tabellae. Groups of prominent strip carinae, which
terminate abruptly against the normal dissepiments,
reveal an earlier growth stage calice brim.

Comparison with related forms.—Mesophyllum
(Arcophyllum) kirki of this report is, with some mis-
givings, assigned to Stumm’s species founded upon an
incomplete specimen from Nevada Formation, unit 2
at Lone Mountain; this unit is also the source of the

 

 

 

—<—

70 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

material here described. The holotype transverse thin
section of Stumm’s Mesophylloides kirki shows the
inner part of a corallum lacking the outer dissepimen-
tarium band which normally reveals strip carinae in
Arcophyllum. Stumm’s holotype has thinner, more
continuous septa with fewer septal crests than the
specimens here described.

The material referred to Mesophyllum (Arcophyl-
lum) kirki resembles M. (A.) dachsbergi (Vollbrecht)
and M. (A.) limbatum (Wedekind and Vollbrecht),
the first was originally placed in Cosmophyllum and
the second in Hemicosmophyllum. MeSOphyllum
(Arcophyllum) dachsbergi differs from M. (A.) kirki
in having a broader tabularium and more numerous
tabellae. These differences apply also to M. (A. ) limba-
tum. An undescribed Middle Devonian Arcophyllum-
like coral from the Alberto Islands, southeast Alaska,
has continuous septa, a wider tabularium with more
numerous tabellae, and a well-developed strip carinae
in the larger individuals.

Occurrence—Lower part of the Nevada Formation,
unit 2. Devonian coral subzone D3. Lone Mountain;
localities M29, M1036. The corals here assigned to
Mesophyllum (Arcophyllum) kirki characterize the
uppermost beds in the “Spirifer pinyonensis” zone of
previous usage. Comparison with Arcophyllum dachs-
bergi and A. limbatum suggests that coral subzone D3
is within the Middle Devonian. According to Wede-
kind and Vollbrecht (1931, pl. 28; 1932, pl. 36), Area-
phyllum dachsbergi and A. limbatum occupy the zone
of “Cosmophyllum dachsbergi” at Gerolstein, Eifel
district, Germany. Wedekind (1925, p. 71 table)
assigns the zone of “Cosmophyllum dachsbergi” to the
upper part of his coral zone “St-Stenophyllumstufe,”
which is shown by him as well up in the middle Middle
Devonian. Markov’s type of Arcophyllum, being
reported from Calceola-bearing beds of the Ural Moun-
tains, may be older. The comparable southeast Alas-
kan Arcophyllum-like coral from the Alberto Islands
is associated with Acanthophyllum, Australophyllum,
and Heliolites in a fauna which probably underlies
that containing Stringocephalus in this Alaskan strati-
graphic section.

Subfamily ZONOPHYLLINAE Wedekind, 1924

Reference form.—Zonophyllum duplicatum Wede-
kind. Early Middle Devonian; Germany.

The cystimorph Digonophyllidae lack continuous
septal lamellae; septal crests in growth cones that tend
to be greatly thickened stereoplasmically, form septal
wreaths or festoons where in contact laterally.

The Zonophyllinae range from cystimorphs with a
few sporadic septal crests to those with radially alined,
usually stout thickened crests and either a crescentic

 

 

festoon or a completely circular stereoplasmic septal
wreath.

Nepionic growth stages have thick stumpy septa in
lateral contact. The stereoplasm of septal wreaths
passes from one growth cone to those adjacent, as
revealed in longitudinal thin section.

In Germany and in the Great Basin, the Zonophyl-
linae are characteristic of the early Middle Devonian;
none have been recognized above coral zone D2.

Genus ZONOPHYLLUM Wedekind, 1924

1924. Zonophyllum Wedekind, p. 12—21, figs. 1—8.

1940. Zonophyllum Wedekind, Lang, Smith, and Thomas, p.
142.

1949. Zonophyllum Wedekind, Stumm, p. 46—47, pl. 22, figs.
16—22.

1956. Zonophyllum Wedekind, Hill, p. F314—F315 (in part),
fig. 216—1a—c.

Type Species.—Z. duplicatum Wedekind by subse-
quent designation, Lang, Smith and Thomas (1940 p.
142). Lower Middle Devonian; Nohner Schichten at
Nohn Eifel district Germany. From Wedekind’s (1924,
p. 85) zone D (Digonophyllumstufe), which is the
lowermost Middle Devonian as interpreted by him.

Diagnosis.—Medium-size and small solitary cysti-
phylloids of ceratoid to cylindrical growth habit have
thick stumpy to long septal crests in the peripheral
zone of mature individuals; in longitudinal section the
septal crests reveal thick trabecular spines which are
directed distally and axially. The peripheral zone of
small and medium-sized steeply inclined dissepiments
passes axially into a zone of large dissepiments and
periaxial tabellae. The axial zone has irregular, distally
convex tabulae, some of which may be almost flat and
wide. The ontogeny is distinctive. The late nepionic
stage has about twelve thick stumpy septa touching
laterally and has a suggestion of bilateral symmetry
though no specific cardinal septum may be recogniz-
able. In mid-neanic stage, there is a peripheral zone
of dissepiments with thinner septal crests and an inner
periaxial zone of thickened septal crests forming a sep-
tal wreath. In later growth stages, dissepiments and
tabellae are introduced between the two septal zones.
Septal crests are usually thick and numerous peripher-
ally in earlier ephebic stages. Advanced ephebic stages
are cystiphylloid with traces of septal crests.

Remarks.—Wedekind’s (1924) researches by means
of serial sections demonstrated that cystiphylloid
rugosa of the Zonophyllum group were distinct from
those of the true Cystiphyllum group. In this connec-
tion ontogenetic changes seem to be highly significant.
Cystiphyllum itself is a Silurian genus (Lang and oth-
ers, 1940, P. 48). The Devonian strata include descend-
ants and no doubt numerous homeomorphic strains,
such as Zonophyllum of the late Early and the Middle

 

—-’—7

LOCALITY REGISTER 71

Devonian. In accordance with Wedekind’s views
(1924, p. 29) , the early Middle Devonian Zonophyllum
group was possibly the ancestral stock whence came
the very numerous Digonophylloids of the ensuing
Middle Devonian, all of which include cystiphylloid

types.

Wedekind’s theory of the septal cone (septalkegel)
is set forth in connection with his description of Zono-
phyllum and its presumed evolutionary offshoots
(1924, p. 21). This theory is reviewed by Hill (1956,
p. F252, F314), who noted that in some of the rugose
corals under consideration, septal tissue is developed
only in successive inverse cones of thickening in which

large trabeculae are present.

Zonophyllum haguei n. sp.
Plate 20, figures 3, 4, 9, 10

Type material.——Holotype USNM 159333, paratype
USNM 159331; Grays Canyon, Eureka district,
Nevada. Lower part of the Nevada Formation; coral
zone D2.

Diagnosis.——Zonophyllum has a peripheral wreath
of thick septal crests in the dissepimentarium and
small very steep outer dissepiments. For part of the
septal wreath, thick crests are joined discontinuously
in a general stereoplasmic mass. The tabularium is
occupied by large axially inclined tabellae and rather
widely spaced tabulae which are, for the most part,
distally convex.

External features.——The mature corallum is rather
small and subcylindrical.

Transverse sections—All dissepiments and tabellae
are concave peripherally. There is progressive increase
in size from small outer dissepiments to the large tab-
ellae but no discrete border between dissepimentarium
and tabularium. Some thick outer septal crests origi-
nating at or near the outer wall penetrate two or more
rows of the small peripheral dissepiments. Stubby sep—
tal crests are sparsely developed within the tabularium.

Longitudinal sections.——The stereoplasmic deposits
in the outer septal wreath partly fill the dissepimen-
tarium. Large and elongate trabeculae extend inward
and distally; in some instances they penetrate columns
of smaller dissepiments. Dissepiments merge with size
increase into large less steeply inclined periaxial tab-
ulae. A few nearly flat tabulae may be more than one-
third the corallite diameter in the mature stages.

Comparison with related forms.—Zon0phyllum
haguei differs from Z. duplicatum Wedekind, the type
species, in lacking a well-defined inner wreath of thick-
ened septal spines; the outer wreath of spines in haguei
shows a more extensive deposit of stereoplasm. Other
forms assigned to Zonophyllum from the Great Basin
may represent distinct species but, being known from

 

 

insufficient material, are not formally described.

Occurrence—Nevada Formation, unit 2; Devonian
coral subzone D2. Grays Canyon, Northern Fish Creek
Range; localities M3, M51.

Zonophyllum sp. a
Plate 20, figures 5, 6

Figured specimens—USNM 159332; lower partof
the Devonian section, Ranger Mountains, Nevada.

Septal crests are short and scattered, not joined as
in haguei, to form a discrete septal wreath. The tabel-
lae are large in the wide tabularium.

Occurrence—Lower part of Devonian section; prob-
ably coral zone D1. Ranger Mountains, Nev.: locality
M1058. '

Zonophyllum sp. b
Plate 20, figures 11, 12

Figured specimens—USNM 159351, lower part of
the Nevada Formation; northern Fish Creek Range,
Nevada.

The few septal crests are largely confined to an inner
zone of diffuse stereoplasmic thickening which borders
the dissepimentarium.

Occurrence—Lower part of Nevada Formation, unit
2; Devonian coral zone D2. Grays Canyon, northern
Fish Creek Range; locally M51.

LOCALITY REGISTER
(see figs. 1, 2. 3, 4)
I. Southern Great Basin

1. Desert Range, Clark County, Nev.

Locality M1057. ——Army Map Service, Las Vegas, Nev.,
quadrangle; southwest edge of Desert Range east of
Braun’s Playa, in the W1/2 sec. 10, T. 16 S., R. 58 E.,
altitude 3,200 ft. Early Middle Devonian. Collected by
C. R. Longwell.

2. Ranger Mountains, east of Frenchman Flat, Clark County,
Nev.

Locality M1034. — Frenchman Lake SE quadrangle,
Nevada; lat 36°46’45” N., long 115°52’00” W. Between
10 and 25 ft above base of Nevada Formation. Collected
by F. G. Poole.

Locality M1058.—Frenchman Lake quadrangle, Nevada;
southeast side of Frenchman Flat, 1.5 miles east of Nye
County—Clark County line in higher part of the southern
Ranger Mountains; 1,500 ft northwest of summit 4907.
Limestone about 20 ft above base of Nevada Formation;
fossil zone 4 (Devonian unit A) of M. S. Johnson and
D. E. Hibbard (1957).

3. Northern Panamint Mountains, Ubehebe district, Calif.

Locality M184.——Marble Canyon quadrangle, California;
south side of Andy Hills in northwest corner of quad-
rangle, east side of Hidden Valley, on central ridge of
Andy Hills near summit 5612. Upper part of McAllister’s
(1952, p. 15—17) Hidden Valley Dolomite, unit 3b con-
taining Papiliophyllum and Costispirifer arenosus.

Locality M1.065.—-Marble Canyon quadrangle, California.
Andy Hills, south side; measured section across Mc-

 

i

 

 

72 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN
Allister’s unit 3b of the Hidden Valley Dolomite; in Nevada. Same as Locality M48 on southeast side of
same area as locality M184. Zoned collections A through Rabbit Hill. Rabbit Hill Limestone, Lower Devonian,

H by J. F. McAllister, April 1965. 2. Antelope Range, northern part ‘
4. Funeral Mountains, Calif. Locality M1035. — Bellevue Peak quadrangle, Nevada.

Locality M1059.—Ryan quadrangle, 1.8 miles N. 48° W. North tip of Antelope Range, west side of lower slope
of Pyramid Peak, Funeral Mountains. Uppermost part east of hill 6754, altitude 6,680 ft. Nevada Formation,
of Hidden Valley Dolomite with rugose coral fauna. unit 2.

Late Early Devonian. Collected by J. F. McAllister, Locality M1035a. — Same as Locality M1035, but a lower
June 1962. stratigraphic horizon.

Locality M1060.—Ryan quadrangle, 1.6 miles N, 58° W. Locality M1053. — Bellevue Peak quadrangle, Nevada.
of Pyramid Peak, Funeral Mountains. Uppermost part North end of Antelope Range, NEIA sec. 16, T. 16 N.,
of Hidden Valley Dolomite with rugose coral fauna. R. 51 E., 2,200 ft north-northwest of summit 7602, alti-
Late Early Devonian. Collected by J. F. McAllister, tude 7,000 ft. Nevada Formation, unit 2.

April 1962. Locality M1055. — Bellevue Peak quadrangle, Nevada.

Locality M1061. — Ryan quadrangle, northwest slope of North end of Antelope Range; top of spur, altitude 7,100
4298 hill, 4.5 miles S. 47° E. of Pyramid Peak, Funeral ft and 500 ft southwest of M1053. Nevada Formation,
Mountains, altitude 3,750 ft. Uppermost part of Hidden unit 2.

Valley Dolomite with rugose coral fauna. Collected by 3. Southern Fish Creek Range
J. F. McAllister, May 1964. Locality M1033. — Bellevue Peak quadrangle, Nevada.

Locality M1062.——Ryan quadrangle, 6.2 miles S. 71° E. of North tip of Fenstermaker Mountain, 3 miles southwest
Pyramid Peak, Funeral Mountains, altitude 3,450 ft. of Fish Creek Springs near top of range at altitude 6,700
Uppermost part of Hidden Valley Dolomite with rugose ft; 1,200 ft north of southern edge of quadrangle. Nevada
coral fauna. Collected by J. F. McAllister, November Formation, unit 2.

1963. Locality M1070.—Cockaloru_m Wash quadrangle, Nevada.

Locality M1063.—Ryan quadrangle, 4.7 miles S. 51° E. of First north-south ridge east of southern Fish Creek
Pyramid Peak, Funeral Mountains, altitude 3,700 ft. Range, near south boundary of Eureka County; 0.8 mile
Uppermost part of Hidden Valley Dolomite with rugose southeast of Eightmile Well near top of knob at altitude
coral faunas. Collected by J. F. McAllister, April 1965. 6,400 ft. Nevada Formation, unit 2.

Locality M1064.—Ryan quadrangle, 6.23 miles S. 72° E. of Locality M1043.—Cockalorum Wash quadrangle, Nevada.
Pyramid Peak, Funeral Mountains, altitude 3,450 ft. One mile south of Nyeka (BM 7352), on line between
Uppermost part of Hidden Valley Dolomite with rugose secs. 4 and 5, T. 14 N ., R. 52 E. Limestone conglomerate.

coral faunas. Collected by J. F. McAllister, March 1965. 4. Northern Fish Creek Range
Locality M3.—Pinto Summit quadrangle, Nevada. Near

11' South-central Great Baszn mouth of Grays Canyon, 1 mile south of Pinnacle Peak
1, Hot Creek Range, Nev.,middle part and 800 ft east of quadrangle boundary; east side of
Locality M1066.—— Army Map Service, Tonopah, Nev., canyon near bottom, altitude 7,250 ft. Nevada Forma-
sheet. Probably in Hot Creek Canyon about 4 miles tion, unit 2-
west-northwest of Hot Creek Ranch houses. Devonian Locality M51 .—Same as Locality M3-
including lower part of Nevada Formation with rugose 5. Mahogany Hills
corals. Collected by H. E. Cook (thesis, Univ. California, Locality M 2 7.—Bellevue Peak quadrangle, Nevada. Combs
Berkeley, 1966). Peak area, 1.7 miles south of Combs Peak on top of spur
2. Monitor Range, Nev., middle part in saddle at altitude 7,520 ft. Nevada Formation, unit 2.
Locality M1067. —Army Map Service, Tonopah, Nev. Locality M1071.—Whistler Mountain quadrangle, Nevada.
sheet. Dobbin Summit, northern Nye County, Nev.; 1 Mahogany Hills, east side (Mountain Boy Range) at
mile southeast of East Dobbin Summit Spring on east Modoc Peak; near quadrangle boundary at south side of
side of canyon; west edge sec. 32, T. 13 N., R. 49 E. MOdOC Peak. Nevada Formation, unitsl and 2.
Lower part of Rabbit Hill Limestone, Locality M1084. —— Bellevue Peak quadrangle, Nevada.
Locality M1068.—Dobbin Summit, northern Nye County, West side of Mahogany Hills, 1.75 miles west-southwest
Nev.; same as M1067, but a higher zone in Rabbit Hill 0f summit 0f Combs Peak. Lower part Of Nevada FOI-
Limestone. mation.
Locality M1069.—Dobbin Summit, northern Nye County, 6. Lone Mountain (see fig. 3)
Nev.; same as M1067, but upper part of Rabbit Hill Locality M1045.—Bartine Ranch quadrangle; Lone Moun-
Limestone. tain, northwest side, 2,200 ft S. 50" W. of U. S. Mineral

Monument No. 6828 and about 1 mile northwest of

”1' Central Great Basin summit of Lone Mountain, Nevada Formation, unit 2,

 

1. Monitor Range, northern part upper 250 ft.
Locality M 48. — Horse Heaven Mountain quadrangle, Locality M1052.——Bartine Ranch quadrangle; Lone Moun-
Nevada. West side Copenhagen Canyon, southeast slope tain, northwest side. Same as locality M1045.
Rabbit Hill, altitude 7,100 ft. Type section Rabbit Hill Locality M1048.——Bartine Ranch quadrangle; Lone Moun-
Limestone, Lower Devonian. tain, northwest side, 2,500 ft S. 33° W. of U. S. Mineral
Locality M49. — Horse Heaven Mountain quadrangle, Monument No. 6828, altitude 6,640 ft. Nevada Forma-
Nevada. One mile north of Locality M48, SEIASEIA sec. tion, unit 2.
35, T. 16 N ., R. 49 E.; in Rabbit Hill Limestone. Locality M286.—Bartine Ranch quadrangle; Lone Moun-
Locality M187. — Horse Heaven Mountain quadrangle, tain, northwest side, 2,700 ft S. 39° W. of US. Mineral

 

7—7'

LOCALITY REGISTER 73

Monument No. 6828, altitude 6,560 ft. Nevada Forma-
tion, unit 1.

Locality M1036.——Bartine Ranch quadrangle; Lone Moun-
tain, northwest side, 3,500 ft N. 62° W. of Lone
Mountain summit 7,936 at altitude 6,900 ft. Nevada For-
mation, unit 2 near middle.

Locality M1044.——Bartine Ranch quadrangle; Lone Moun-
tain, west side, 2,400 ft southwest of Lone Mountain
summit 7,936 at altitude 7,280 ft. Nevada Formation,
unit 1, upper beds.

Locality M29.—Bartine Ranch quadrangle; Lone Moun—
tain, west side; 2,000 ft south-southwest of Lone Moun-
tain summit 7,936, above altitude of 7,200 ft. Nevada
Formation, unit 2.

Locality M55.—Bartine Ranch quadrangle; Lone Moun—
tain, west side. Same vicinity and zone as locality M29.

Locality M74.—Bartine Ranch quadrangle; Lone Moun-
tain, south side, 3,800 ft S. 7° E, of Lone Mountain
summit 7,936 at altitude 7,020 ft. Nevada Formation,
unit 1.

Locality M1050.—Bartine Ranch quadrangle; Lone Moun-
tain, south side, 4,000 ft S. 16° E. of Lone Mountain
summit 7,936 at altitude 6,960 ft; 1,200 ft west of quad-
rangle boundary. Nevada Formation, unit 2, lowermost
beds.

Locality M1046.——Bartine Ranch quadrangle; Lone Moun-
tain, south side, 4,500 ft S. 23° E. of Lone Mountain
summit 7,936 at altitude 7,000 ft; 700 ft west of quad-
rangle boundary. Nevada Formation, unit 2.

Locality M1038.—Whistler Mountain quadrangle; Lone
Mountain, south side; at west edge of quadrangle, 2,500
ft S. 36° W. of summit 7,360 at altitude 6,890 ft, Nevada
Formation, unit 2.

Locality M1049.—Whistler Mountain quadrangle; Lone
Mountain, south side; 1,700 ft S. 34° W. of summit 7 ,360
at altitude 6,920 ft; 600 ft east of quadrangle boundary.
Nevada Formation, unit 2, upper beds.

Locality M1037.——Whistler Mountain quadrangle; Lone
Mountain, south side. Southeast pediment slope 1.5
miles north of Highway 50; 6,500 ft S. 11° E. of summit
7,360, altitude 6,420 ft. Nevada limestone in fault contact
with Permian beds.

. Southern Roberts Mountains
Locality M1042.——Roberts Creek Mountain quadrangle,

Nevada; 1.75 miles north of Roberts Creek Ranch house,

0.75 mile east of Roberts Creek and 1.25 miles northwest

of top of hill 7,504 (Pyramid Hill); top of knob, altitude

6,850 ft. Nevada Formation, unit 1.

. Northern Roberts Mountains

Locality M1072. ——Roberts Creek Mountain quadrangle,
Nevada. Near top of main spur south of Niel Creek, 1.4
miles S. 30° W. of Western Peak and 1,000 ft northeast
of summit 8,168, altitude 7,800 ft. Same as Merriam
(1940, pl. 1) locality 1 (R 24). Lower Devonian.

Locality M1073. —-Roberts Creek Mountain quadrangle,
Nevada. In saddle 1,500 ft southeast of Cooper Peak at
altitude 9,150 ft. Nevada Formation, unit 2. Same as
Merriam (1940, pl. 1) locality 11 (R 1).

Locality M1054.—Same as locality M1073.

. Northern Simpson Park Range

Locality M1074.——Walti Hot Springs quadrangle, Nevada.
Foothills 0.5 mile southeast of Walti Ranch and west of
McClusky Peak at middle of north edge sec. 4, T. 23 N.,
R. 48 E. Rabbit Hill Limestone; Lower Devonian. Col-

 

10.

lections by R. J. Roberts and R. E. Lehner, 1954.

Locality M1075.—Horse Creek Valley quadrangle, Nevada.
Near mouth of Coal Canyon, east side along ridge top of
summit 6,909, SE14 sec. 17, T. 25 N., R. 49 E. Rabbit
Hill Limestone, Lower Devonian.

Locality M1032.—Horse Creek Valley quadrangle, Nevada.
East side of Coal Canyon, NW1A sec. 21, T. 25 N., R.
49 E. Rabbit Hill Limestone.

Locality M1076.—Horse Creek Valley quadrangle, Nevada.
Near mouth of Coal Canyon, east side. Mostly float
below ridge top of summit 6,909 and down slope to west.
Rabbit Hill Limestone, Lower Devonian.

Southern Sulphur Spring Range (see fig. 5)

Locality M 4.—Garden Valley quadrangle, Nevada. Prince
of Wales mine area; 1,200 ft southeast of mine and
northwest of summit, 7,530, altitude 7,300 ft near old
charcoal pit. Nevada Formation, unit 1.

Locality M69. —— Garden Valley quadrangle, Nevada.
Prince of Wales mine area. Foat material near locality
M4.

Locality M1041.———Garden Valley quadrangle, Nevada.
Prince of Wales mine area. Measured section through
locality M4 southeast of mine, and northwest of summit
7,530. Nevada Formation, unit 1.

Locality M68. —— Garden Valley quadrangle, Nevada.
Prince of Wales mine area. Top of ridge east of mine at
signal station 7,530. Nevada Formation, upper part of
unit 1; Acrospirifer kobehana fauna.

Locality M67. —— Garden Valley quadrangle, Nevada.
East side of range 0.8 mile N. 65° E. of Bailey Pass at
altitude 6,520 ft, 0.1 mile south of road on top of spur.
Nevada Formation, unit 1.

Locality M36. —— Garden Valley quadrangle, Nevada.
South of Bailey Pass 0.9 mile at altitude 7,200 ft on
north side of knob. Nevada Formation, unit 2 with
S pirifer pinyonensis and Chonetes macrostriata.

Locality M198. -— Garden Valley quadrangle, Nevada.
Same as Locality M36.

Locality M197. —— Garden Valley quadrangle, Nevada.
S. 12° E. of Bailey Pass 0.8 mile on ridge top at altitude
7,080 ft; 1,000 ft northeast of Locality M36. Rabbit Hill
Lower Devonian fauna.

Locality M1031.—Garden Valley quadrangle; southern
Sulphur Spring Range, 0.5 mile north-northwest of
Romano Ranch house at east end of old lake terrace,
altitude 6,000 ft; 500 ft west of BM 5,836. Nevada For—
mation, unit 2 with rugose corals.

Locality M1078.——Garden Valley quadrangle; southern
Sulphur Spring Range 0.5 mile northwest of Romano
Ranch house, south side of old lake terrace at altitude
6,000 ft; 1,000 ft southwest of BM 5,836 and 500 ft south-
west of Locality M1031. Nevada Formation, unit 2.

Locality M1047. ——Garden Valley quadrangle; southern
Sulphur Spring Range about 0.5 mile west-northwest of
Romano Ranch house, altitude 6,000 ft; about 0.5 mile
southwest of BM 5,836. Nevada Formation, unit 2.

Locality M1'079.——Garden Valley quadrangle; southern
Sulphur Spring Range 1.5 miles N. 83° W. of Romano
Ranch house; 2,000 ft northeast of summit 6,933 at
altitude 6,560 ft. Nevada Formation, unit 2 with quartz-
ite interbeds and fossils.

Locality M1080.——Garden Valley quadrangle; southern
Sulphur Spring Range; S. 86° E. of Mulligan Gap 1.2
miles on top of northeast spur, altitude 6,885 ft; 2,500

L_________———---IIIIlIIIIIIll-IIIIIIIIIIIII'IIIIII

74 LOWER AND LOWER MIDDLE DEVONIAN RUGOSE CORALS OF THE CENTRAL GREAT BASIN

ft northeast of 7,446 summit. Lower Devonian with
rugose corals.

Locality M1081.——Garden Valley quadrangle; southern
Sulphur Spring Range. In ravine 600 feet west of
Locality M1080 at altitude 6,800 ft; 2,000 ft northeast of
7,446 summit. Lower Devonian with Rabbit Hill Helder-
berg fauna.

Locality M1040. —Garden Valley quadrangle, Nevada;
southern Sulphur Spring Range. South-southeast of
Bailey Pass 1.1 miles near range top and 750 ft north-
east of summit 7,378, altitude 7,240 ft. Lower Devonian
beds with Oriskany fossils.

Locality M56. — Garden Valley quadrangle, Nevada.
Southernmost Sulphur Spring Range, 1.6 miles S. 25°
E. of Mulligan Gap, east side of ravine on top spur at
altitude 6,690 ft. Nevada Formation, unit 1 with Oris-
kany fauna.

Locality M186. —— Garden Valley quadrangle, Nevada.
Southernmost Sulphur Spring Range, 1.7 miles S. 22°
E. of Mulligan Gap, east side of ravine, altitude 6,560
ft, and 750 ft southwest of Locality M56. Nevada For-
mation, Beacon Peak Dolomite Member with Rabbit
Hill Helderbergian fauna.

Locality M1039. — Garden Valley quadrangle, Nevada.
Southernmost Sulphur Spring Range. 1.5 miles south-
southeast of Mulligan Gap and 1,500 ft west of 6,927
summit on east side of ravine. Nevada Formation, unit 1.

Locality M1051.—-Garden Valley quadrangle, Nevada.
Southernmost Sulphur Spring Range. 1.25 miles south-
southeast of Mulligan Gap near top main spur at alti-
tude 7,150 ft; 2,700 ft south of summit 7,446. Nevada
Formation, unit 2.

Locality M1077. — Garden Valley quadrangle, Nevada.
Southernmost Sulphur Spring Range; 1.3 miles S. 25°
E. of Mulligan Gap on east side of ravine at altitude
6,720 ft. Nevada Formation, unit 1, with Lower Devon-
ian rugose coral fauna.

Locality M1082.—-Garden Valley quadrangle, southern-
most Sulphur Spring Range, east side. 1.2 miles due
west of BM 5,867 on top spur at altitude 6,440 ft; 1,400
ft east-northeast of summit 6,474. Lower Devonian
Beacon Peak Dolomite Member with Rabbit Hill
Helderberg fauna.

IV. N orth-central Great Basin

1. Northern Sulphur Spring Range

Locality M1018. —- Mineral Hill quadrangle, Nevada.
Northwest of Union Summit in McColley Canyon.
Lower beds of the McColley Canyon Member of the
Nevada Formation of Carlisle and others (1957), Lower
Devonian with rugose coral fauna.

Localities M1021 to M1025 inclusive—Mineral Hill quad-
rangle, Nevada. Same general areas as locality M1018,
in same stratigraphic unit. Lower Devonian with rugose
corals.

2. Cortez Mountains

Locality M1083.—Cortez quadrangle, Nevada. Southeast
side of Mt. Tenabo, east slope of the Cortez Mountains;
northeast side of upper Horse Canyon, 1,000 ft north,
700 ft west of SE cor. sec. 4, T. 26 N., R. 48 E., altitude
7,900 ft. Rabbit Hill Lower Devonian fauna with
S yringaxon and Pleurodictyum.

 

V. West-central Great Basin

1. Northern Toquima Range

Locality M1150. —Wildcat Peak quadrangle, Nevada.
SW14 sec. 16, T. 16 N., R. 46 E., top of spur 1,600 ft
south of summit 7,188 and 2,800 ft east of Petes Canyon
road. Rabbit Hill Limestone on Silurian graptolite-
bearing shale.

2. Toiyabe Range

Locality M1151.—Austin quadrangle, Nevada. SE14 sec.
36, T. 17 N., R. 42 E.; in first main canyon at range
front 1 mile south of Reeds Canyon. Devonian coral-
bearing limestone.

SELECTED REFERENCES

Billings, Elkanah, 1858, New genera and species of fossils from
the Silurian and Devonian formations of Canada: Cana-
dian Naturalist, v. 3, no. 6, p. 419—444.

1859, On the fossil corals of the Devonian rocks of

Canada West: Canadian Jour., n. s., v. 4, p. 97—140.

1874, On some new or little known fossils from the
Silurian and Devonian rocks of Ontario: Canadian
Naturalist, n. s., v. 7, p. 230—240.

Birenheide, Rudolf, 1962a, Die Typen der Sammlung'Wede-
kind aus den Familien Cyathophyllidae und Stringophyl-
lidae (Rugosa): Senckenbergiana Lethaea, v. 43, no. 2, p.
101422.

1962b, Revision der koloniebildenden Spongophyllidae

und Stringophyllidae aus dem Devon: Senckenbergiana

Lethaea, v. 43, no. 1, p. 41—99, 7 pls.

1964, Die “Cystimorpha” (Rugosa) aus dem Eifeler
Devon: Senckenbergischen Naturf. Ges., Abh. 507, p. 1—
119, 28 pls.

Butler, A. J., 1935, On the Silurian coral Cyathaxonia Siluri-
ensis M’Coy: Geol. Mag., v. 72, no. 849, p. 116—124, pl. 2.
Carlisle, Donald, Murphy, M. A., Nelson, C. A., and Winterer,
E. L., 1957, Devonian stratigraphy of Sulphur Spring and
Pinyon ranges, Nevada: Am. Assoc. Petroleum Geolo-

gists Bull., v. 41, no. 10, p. 2175—2191.

Chapman, E. J ., 1893, On the corals and coralliform types of
Paleozoic strata: Royal Soc. Canada Trans, v. 10, sec. 4,
p. 39—48.

Chernyschev, B. B., 1941, Silurian and Lower Devonian corals
from the Tareia River Basin (Southwest Taimir): Trud.
Arktick. Inst., v. 158, p. 9—64, 14 pls. (Russian and
English).

Dybowski, W. N., 1873, Monographie der Zoantharia sclero-
dermata rugosa aus der Silurformation Estlands, Nord-
Livlands und der Insel Gotland: Dorpat, Estonia. Also in
Archiv. Naturkunde LiV-, Ehst-, und Kurlands, ser. 1, v.
3, 274 p., 5 pls., v. 5, no. 3, p. 257—414, pls. 1, 2 (1873); no.
4, p. 415—532, pls. 3—5 (1874).

Edwards, H. M., and Haime, Jules, 1850—54, A monograph of
the British fossil corals: London, Paleontological Soc., 322
p., 72 pls.

1851, Monographie des polypiers fossiles des terrains
palaeozoiques précédée d’un tableau général de la classi-
fication des Polypes: Mus. Histoire Nat, Paris, Archives,
v. 5, 502 p., 20 pls.

Ehlers, G. M., and Stumm, E. C., 1951, Billingsastraea: Pt. 4
of Corals of the Middle Devonian Traverse group of
Michigan: Michigan Univ. Mus. Paleontology Contr., v.
9, no. 3, p. 83~92, pls. 1—3.

 

 

 

 

 

 

—'"———7

SELECTED REFERENCES 75

—————-1953, Species of the tetracoral genus Billingsastraea
from the Middle Devonian of New York and other re-
gions: Buffalo Soc. Nat. Sci. Bull., v. 21, no. 2, p. 1—11,
pls.1- .

Erben, H. K., 1960, Primitive Ammonoidea aus dem Unter-
devon Frankreiches und Deutschlands: Neues Jahrb.
Geol. 11. Palaontol., v. 110, p. 1—128, pls. 1—6.

Etheridge, Robert, J r., 1911, The Lower Palaeozoic corals of
Chillagoe and Clermont, pt. 1: Queensland Geol. Survey
Pub. 231, p. 1—8, Pls. A—D.

Fenton, C. L., and Fenton, M. A., 1924, The stratigraphy and
fauna of the Hackberry stage of the upper Devonian:
Michigan Univ. Mus, Geology Contr., v. 1, 260 p., 45 pls.

Fliigel, H., and Free, B., 1962, Laccophyllidae (Rugosa) aus
dem Greifensteiner Kalk (Eiflium) von Wiede bei Greis-
enstein: Palaeontographica, v. 119, no. A, (Palaozologie-
Stratigraphie) p. 222—247, pl. 41.

Frech, Fritz, 1886, Die Cyathophylliden und Zaphrentiden des
Oberdevons in Deutschland: Palaeont. Abh., v. 3, no. 3,
p. 115—234, 8 pls.

Fromentel, E. G. de, 1861, Introduction a l’étude des Polypiers
fossils: Paris, 357 p.

Geinitz, H. B., 1846, Grundriss der Versteinerungskunde:
Dresden, 815 p., 28 pls.

Glinski, Alfons, 1955, Cerioide Columnariidae (Tetracoralla)
aus dem Eiflium der Eifel und des Bergischen Landes:
Senckenbergiana Lethaea, v. 36, no. 1—2, p. 73—114.

1957, Taxionomie und Stratigraphie einiger Stauriidae
(Pterocorallia) aus dem Devon des Rheinlandes: Senck—
enbergiana Lethaea, v. 38, p. 83—108.

Goldfuss, G. A., 1826—33, Petrefacta Gerrnaniae, Bd. 1: Dussel-
dorf, Arnz and Co., 252 p., 71 pls.

Grabau, A. W., 1917, Stratigraphic relationships of the Tully
limestone and the Genessee shale in Eastern North
America: Geol. Soc. American Bull., v. 28, p. 945—958.

1928, Paleozoic corals of China, Part 1, Tetrasepta;
Second contribution to our knowledge of the streptelas-
moid corals of China and adjacent territories: Paleon—
tologia Sinica, ser. B, v. 2, fascicle 2, p. 1—175, 6 pls.

Giirich, Georg, 1896, Das Palaeozoicum im des polnischen
Mittelgebirge: Russ.-Kais. Min. Gesell. St. Petersburg,
Verhandl., ser. 2, v. 32, 539 p., 15 pls.

Hague, Arnold, 1892, Geology of the Eureka district, Nevada:
US. Geol. Survey Mon. 20, 419 p. (with an atlas).

Hall, James, 1876, Illustrations of Devonian Fossils; corals of
the upper Helderberg and Hamilton groups: New York
[State] Geol. Survey, Paleontology, 7 p., 136 pls.

1882, Description of the fossil corals from the Niagara

and upper Helderberg groups: 35th Ann. Rept. New York

State Mus. Nat. History, p. 407—464, pls. 23—30, (advance

sheets).

1883, Spergen Hill fossils, Paleontology: Indiana Dept.
Geol. Nat. History, 12th Ann. Rept. for 1882, p. 319-375,
32 pls.

Hill, Dorothy, 1935, British terminology for rugose corals:
Geol. Mag., v. 72, no. 857, p. 481—519, 21 figs.

1936, The British Silurian rugose corals with acanthine

septa: Royal Soc. London Philos. Trans, ser, B, no. 534,

v. 226, p. 189—217, 2 pls.

1938, Euryphyllum: a new genus of Permian zaphren-

toid rugose corals: Royal Soc. Queensland Proc., v. 49,

p. 23—38.

1939, The Devonian rugose corals of Lilydale and Loy—

ola, Victoria: Royal Soc. Victoria Proc., (new series), v.

 

 

 

 

 

 

 

534-041 0 — 74 - 6

___4-_

 

51, pt. 2, p. 219—256, 4 pls. ,

1956, Rugosa, in Moore, R. C., ed., Treatise on inverte-
brate paleontology, Part F—Coelenterata: New York and
Lawrence, Kansas, Geol. Soc. America and Kansas Univ.
Press, p. F233—F324.

Holmes, M. E., 1887, The morphology of the carinae upon the
septa of rugose corals: Boston, Bradlee Whidden, p. 7—31,
pls.1—16.

House, M. R., 1962, Observations on the ammonoid succession
of the North American Devonian: Jour. Paleontology, v.
36, no. 2, p. 247—284.

House, M. R., and Pedder, A. E. H., 1963, Devonian goniatites
and stratigraphical correlations in western Canada: Palae-
ontology, v. 6, pt. 3, p. 491—539, 8 pls.

Hudson, R. G. S., 1944, Lower Carboniferous corals of the
genera Rotiphyllum and Permia: Jour. Paleontology, v.
18, no. 4, p. 355—362, pls.56, 57.

Johnson, J. G., 1962a, Brachiopod faunas of the Nevada forma-
tion (Devonian) in central Nevada: Jour. Paleontology,
v. 36, no. 1, p. 165—169.

1962b, Lower Devonian-Middle Devonian boundary in

central Nevada: Am. Assoc. Petroleum Geologists Bull.,

v. 46, no. 4, p. 542—546.

1966a, Middle Devonian brachiopods from the Roberts

Mountains, central Nevada: Palaeontology, v. 9, pt. 1, p.

152—181, 5 pls.

1966b, Two new spiriferid brachiopod genera from the

Lower Devonian of Nevada: Jour. Paleontology, v, 40,

no. 5, p. 1043—1050, 3 pls.

19660, Parachonetes, a new Lower and Middle Devonian
brachiopod genus: Palaeontology, v. 9, pt. 3, p. 365—370,
2 pls.

Johnson, M. S., and Hibbard, D. E., 1957, Geology of the
Atomic Energy Commission Nevada Proving Grounds
area, Nevada: US. Geol. Survey Bull. 1021—K, p. 333—384.

Jones, 0. A., 1930, A revision of some Paleozoic coral genera
and species [abs]: Cambridge Univ., Abs. Dissert. Aca-
demical Year 1928—29, p. 35—36.

Kato, Makoto, 1963, Fine skeletal structure in Rugosa: Hok-
kaido Univ. Fac. Sci. Jour., ser. 4, v. 11, no. 4, p. 571-630,
3 pls., 19 text figs.

Lang, W. D., and Smith, Stanley, 1927, A critical revision of
the rugose corals described by William Lonsdale in Mur-
chison’s “Silurian system”: Geol. Soc. London Quart.
Jour., v. 83, p. 448—491,p1s. 34—37.

1934, Ludwig’s “Corallen aus Palaolitischen Forma—

tionen” and the Genotype of Disphyllum de Fromentel:

Annals and Mag. Nat. History, ser. 10, v. 13, no. 73, p.

78-81.

1935, Cyathophyllum caespitosum Goldfuss, and other
Devonian corals considered in a revision of that species
(with discussion): Geol. Soc. London Quart. Jour., v. 91,
no. 364, pt. 4, p. 538—590, pls. 35—37.

Lang, W. D., Smith, Stanley, and Thomas, H, D., 1940, Index
of Palaeozoic coral genera: London, British Museum
(Nat. History), 231 p.

Lenz, A. C., 1961, Devonian rugose corals of the lower Mac-
kenzie Valley, Northwest Territories, in Geology of the
Arctic, v. 1: Toronto, Ontario, Univ. Toronto Press, p.
500—514.

Lesueur, C. A., 1821, Description de plusieurs animaux appar-
tenant aux polypiers lamelliferes de Lamarck: [Paris]
Mus. Histoire Nat., Mém., v. 6, p. 271—299, pls. 15—17.

 

 

 

 

 

 

 

 

(1882), no. 3, p. 5—30.

McAllister, J. F., 1952, Rocks and structure of the Quartz
Spring area, northern Panamint Range, California: Cali-
fornia Div. Mines Spec. Rept. 25, 38 p.

McCoy, Frederick, 1850, On some new genera and species of
Silurian Radiata in the collection in the University of
Cambridge: Annals and Mag. Nat. History, ser. 2, v. 6, p.
270—290.

McLaren, D. J ., 1959, A revision of the Devonian coral genus
Synaptophyllum Simpson: Canada Geol. Survey Bull. 48,
p. 15—33, pls. 7—10.

Markov, K. V., 1926, Note sur Arcophyllum, un nouveau genre
de coraux Rugosa: Ann. soc. paleont. Russie, v. 5, p. 49—
60, pl. 3.

Meek, F. B., 1877, Paleontology: U.S. Geol. Explor. 40th Paral-
lel, v. 4, pl. 1—197, pl. 2.

Merriam, C. W., 1940, Devonian stratigraphy and paleontology
of the Roberts Mountains region, Nevada: Geol. Soc.
America Spec. Paper 25, 114 p., 16 pls.

1963, Paleozoic rocks of Antelope Valley, Eureka and

' Nye Counties, Nevada: US. Geol. Survey Prof. Paper
423, p. 1—67.

Miller, A. K., 1938, Devonian ammonoids of America: Geol.
Soc. America Spec. Paper 14, 262 p. 39 pls.

Moenke, Maria, 1954, Rodzaj Hexagonaria w dewonie Gor
Swietokrzyskich: Acta Geol. Polonica, v. 4, p. 445483,
2 pls.

Nicholson, H. A., and Lydekker, Richard, 1889, A manual of
paleontology [3rd ed.]: Edinburgh and London, 885 p.

Nolan, T. B., 1935, The Gold Hill mining district, Utah: US.
Geol. Survey Prof. Paper 177, 172 p.

Nolan, T. B., Merriam, C. W., and Williams, J. S., 1956, The
stratigraphic section in the vicinity of Eureka, Nevada:
US. Geol. Survey Prof. Paper 276, 77 p.

O’Connell, Marjorie, 1914, Revision of the genus Zaphrentis:
New York Acad. Sci. Annals, v. 23, p. 177—192.

Ogilvie, M. M., 1897, Microscopic and systematic study of
madreporarian types of corals: Royal Soc. London Philos.
Trans, ser. B, v. 187, p, 83—345.

Oliver, W. A., Jr., 1958, Significance of external form in some
Onondagan rugose corals: Jour. Paleontology, v. 32, no.
5, p. 815—837, pls. 104—106.

1960a, Rugose corals from reef limestones in the Lower

Devonian of New York: Jour. Paleontology, v. 34, no. 1,

p. 59—100, pls. 13—19.

1960b, Devonian rugose corals from northern Maine:

U.S. Geol. Survey Bull. 1111—A, p. 1—23, pls. 1—5.

19600, Coral faunas in the Onondaga limestone of New

York, in Geological Survey research 1960: US. Geol. Sur-

vey Prof. Paper 400—B, p. B172—B174.

1964, The Devonian colonial coral genus Billingsastraea

and its earliest known species: U.S. Geol. Survey Prof.

Paper 483—B, p. B1—B5, 2 pls.

1968, Some aspects of colony development in corals, in
Paleobiological aspects of growth and development, a sym-
posium:
no. 5, supp), p. 16—34.

Pedder, A. E. H., 1964, Correlation of the Canadian Middle
Devonian Hume and Nahanni Formations by tetracorals:
Paleontology, v. 7, pt. 3, p. 430—451, pls. 62—73.

1965, A revision of the Australian Devonian corals pre-

viously referred to M ictophyllum: Royal Soc. Victoria

 

 

 

 

 

 

 

 

 

Proc., v. 78, pt. 2, p. 201—220, pls. 30—34.
Poéta, Philippe, 1902, Anthozaires et Alcyonaires, v. 2 of Bar-
rande, Joachlm, Recherches Paléontologiques, pt. 1 of v.

p., pls. 20—118.

Prantl, Ferdinand, 1938, Some Laccophyllidae from the Mid-
dle Devonian of Bohemia: Annals and Mag. Nat. History,
ser. 11, V. 2, no. 7, p. 18—41, 3 pls.

Rézkowska, Maria, 1960, Blastogeny and individual variations
in tetracoral colonies from the Devonian of Poland: Acta
Palaeontologica Polonica, v. 5, no. 1, p. 1—64.

Schindewolf, O. H., 1942, Zur Kenntniss der Polycoelien und
Plerophyllen, eine Studie iiber den Bau der “Tetrakor-

v. 8, no. 4, p. 259465, pls. 1—16.

Schouppé, Alexander von, 1958, Revision des Formenkreises
um Phillipsastraea d’Orb., “Pachyphyllum” E.& H., Mac—
geea (Webst.),“Thamnophyllum” Pen, Peneckiella Soshk.
und verwandter Formen.: Neues J ahrb. Geologie u. Pala-
ontologie Abh., v. 106, no. 2, p. 139—243, pls. 5—6.

Simpson, G. B., 1900, Preliminary description of new genera of
Paleozoic rugose corals: New York State Mus. Bull. 39,
v. 8, p. 199—222.

Sloss, L. L., 1939, Devonian rugose corals from the Traverse
beds of Michigan: Jour. Paleontology, v. 13, no. 1, p. 52—
73, 4 pls.

Smith, Stanley, 1945, Upper Devonian corals of the Mackenzie
River region, Canada: Geol. Soc. America Spec. Paper
59, 126 p., 35 pls.

Smith, Stanley, and Lang, W. D., 1930, Descriptions of the
type specimens of some Carboniferous corals of the genera
“Diphyphyllum,” “Stylastraea,” Aulophyllum and Cha-
etetes: Annals and Mag. Nat. History, ser. 10, v. 5, p.
177—194.

Sorauf, J. E., 1967, Massive Devonian Rugosa of Belgium:
Kansas Univ. Paleont. Contr., Paper 16, 41 p., 19 figs.

Stainbrook, M. A., 1946, Corals of the Independence Shale of
Iowa: Jour. Paleontology, v. 20, no. 5, p. 401—427, pls.
57—61.

Stewart, G. A., 1938, Middle Devonian corals of Ohio: Geol.
Soc. America Spec. Paper 8, 120 p., 20 pls.

Stewart, J. H., and McKee, E. H., 1968, Favorable areas for
prospecting adjacent to the Roberts Mountains thrust in
southern Lander County, Nevada: US Geol. Survey
Circ. 563, 13 p.

Stumm, E. C., 1937, The lower Middle Devonian tetracorals
of the Nevada limestone: Jour. Paleontology, v. 11, no. 5,
p. 423—443, 3 pls.

1938, Upper Middle Devonian rugose corals of the
Nevada limestone: Jour. Paleontology, v. 12, no. 5, p.
478—485, 2 pls.

‘1940, Upper Devonian rugose corals of the Nevada lime-
stone: Jour. Paleontology, v. 14, p. 57—67, 2 pls.

1948a, Lower Middle Devonian species of the Tetra-

coral genus Hexagonaria of east-central North America:

Michigan Univ. Mus. Paleontology Contr., v. 7, no. 2, p.

7—49.

1948b, A revision of the aulacophylloid tetracoral genus

Odontophyllum: Michigan Univ. Mus. Paleontology

Contr., v. 7, no. 3, p. 51—61,pls. 1, 2.

1949, Revision of the families and genera of the Devo-

 

 

 

 

—

 

 

 

 

SELECTED REFERENCES 77

nian tetracorals: Geol. Soc. America Mem. 40, 92 p., 25 pls.

1963, Corals of the Traverse Group of Michigan—pt.

11, Tortophyllum, Bethanyphyllum, Aulacophyllum, and

Hallia: Michigan Univ. Mus. Paleontology Contr., v. 18,

no. 8, p. 135—155, 10 pls.

1964, Silurian and Devonian corals of the Falls of the
Ohio: Geol. Soc. America Mem. 93, 184 p., 2 figs, 80 pls.

Torley, K., 1933, Ueber Endophyllum bowerbanki M. Ed. u.
H.: Deutsch. Geol. Gesell. Zeitschr., v. 85, no. 8, p. 630—-
633, 1 pl.

Vollbrecht, E., 1922, Uber den Bau von Cosmophyllum nov.
gen.: Gesell. Beférd, gesamt. Naturwiss. Marburg Sit-
zungsber., v. 56, Jahrg. 1921, no. 1, p. 17—34, 14 text figures.

1926, Die Digonophyllinae aus dem Unteren Mittel-
Devon der Eifel: Neues Jahrb. Min., Geologie u. Pala-
ontologie Abh., v. 55, ser. B, p. 189—273, pls. 8—16.

Walcott, C. D., 1884, Paleontology '0f the Eureka district
[Nev.]: U.S. Geol. Survey Mon. 8, 298 p.

Wang, H. C., 1950, A revision of the Zoantharia Rugosa in the
light of their minute skeletal structures: Royal Soc. Lon-
don Philos. Trans, ser. B, no. 611, v. 234, p. 175—246, pls.
4—9.

Wedekind, Rudolf, 1923, Die Gliederung des Mitteldevons auf
Grund von Korallen: Gesell. Beftird. gesamt. Naturwiss.
Marburg Sitzungsber., Jahrg. 1922, no. 1, p. 24—35, 7 text
figures.

———1924, Das Mitteldevon der Eifel. Eine biostratigraph-

 

 

 

 

ische Studie. 1 Teil. Die Tetrakorallen des unteren Mittel-

devon: Gesell. Befbrd gesamt. Naturwiss. Marburg Schr.,

v. 14, pt. 3, p. 1—91.

1925, Das Mitteldevon der Eifel. 2 Teil. Materialen zur

Kenntnis des mittleren Mitteldevon: Gesell. Befiird. ges-

amt. Naturwiss. Marburg Schr., v. 14, pt. 4, p. 1—85.

1926, Die devonisch Formation, in Salomon, W., Grund-

ziige der Geologie: Stuttgart, v. 2, pt. 1, p. 195.

1927, Die Zoantharia Rugosa von Gotland (bes. Nord-
gotland): Sveriges Geol. Undersokning, ser. Ca, no. 19,
94 p., 30 pls.

Wedekind, Rudolf, and Vollbrecht, E., 1931, Die Lytophyllidae
des mittleren Mitteldevon des Eifel: Palaeontographica,
v. 75, p. 81—110,pls. 15—46.

1932, Die Lytophyllidae des‘ mittleren Mitteldevon des
Eifel: Palaeontographica, v. 76, p. 95—120, pls. 9—14.

Wells, J. W., 1937, Individual variation in the rugose coral
species, Heliophyllum halli M. E. & H.: Palaeontograph-
ica Americana, v. 2, no. 6, 22 p., 1 pl.

Whiteaves, J. F., 1892, The fossils of the Devonian rocks of the
islands, shores or immediate vicinity of Lakes Manitoba
and Winnipegosis: Canada Geol. Survey, Contr. Canadian
Paleontology, v. 1, p. 255—359.

Wilson, E. C., 1963, An evaluation of the genomorph concept:
Systematic Zoology, v. 12, no. 2, p. 83—90.

Yoh, S. S., 1937, Die Korallenfauna des Mitteldevons aus der
Provinz Kwangsi, Siidchina: Palaeontographica, v. 87, pt.
A, Lf. 1—2, p. 45—76, pls. 4—9.

 

 

 

 

 

 

 

 

 

 

  
  
  
   
 
  
  
 
 
  

Page
A

abditum, Endophyllum . .......................... 56
Acanthophyllum .. 21, 25, 70
Acinophyllum ..... 58
Acknowledgments .................... 6
acuminatum, Laccozzhyllum 39
Syringamon ....... 39
afi‘im‘s, Billinysastraea 30, 64
Age, coral zone B .......... 32
coral zone C ..... 30, 32

coral zone D ._ ..... 30
coral subzone D1

 

  
 
  
  
 
  
 
   
  
  
  

 

 

coral subzone D2 ....................... 31
coral zones, distant regions .. 29
Early Devonian ........ 29, 32, 33

Early middle Devonian 2.9

Late Silurian ................. 33

Nevada Formation, unit 2 31
uggregatum, Cystiphylloides 64, 65
Agtmiatites nevadensis 30
Alaska ............................. 29, 31, 56, 69
Alberto Islands, Alaska . 70
Alleym'a ................... 39
(Nicholsom'a) . 39
americanum, Cystiphylloides . 66
Ammonoids ..... 18, 30, 31
Amphipm‘a ...... . 9, 15, 17, 22
Amplexus invagmatus ,. . 42
lonensis ................. .1 42, 43
magnus . 56
'nevadensis 42, 56
Anastrophia verneuih‘ . 29
Andy Hills ......................... 32, 33
Antelope Range 6, 43, 52, 56, 62, 63, 68
Antelope-Roberts Mountains facies belt 1,
6, 13, 15, 17,29

antelopensis, Bethanyphyllum ...... 21, 33, 53, 51,
Aphroidophyllum ................. 58, 64
arachne, Billingsast’raea 64

 

Billingsastraea nevadensis.. 34, 38, 62, 63, 61,

  
 
  
 
 

 

Radiastraea ....... . 63, 64
Arachnophyllidae 37
Arcophyllum 30, 34, 36, 67, 68, 70

dachsbergi 70

kirki ....... 30

limbatum 70

typus ................ 68

(Arcophyllum) dachsbergi, Mesophyllum.. 70
kirki, Mesophyllum .......... 21, 30, 34, 69

 

  
 

 

  
 
 

 

 

 

  
 
 
 
  

limbatum, Mesophyllum .............. 70
Mesophyllum .................................... 67
Acrospirifer kobeham.... 13, 20, 24, 32, 33, 52, 66
fauna _ . 8, 20
zone 18, 30

51) ............................... 20, 32, 50
arenosus, Costispirifer 11, 1’7, 19
20, 23, 29,31, 32, 33,49

Assemblage, brachiopod ............ 31
coral-hrachiopod-tribolite 24
astreifo’rmis, Stauria ......... 45
Atelophullum ........ 67
Atrypu nevada‘na 21
Atrypa Peak ..... _ 42
Aulacophyllum . 24, 32, 33, 46, 53
convergens ................. 47

sp. 0 ............ 20, 33, 46

 

INDEX

___.——

[Italic page numbers indicate major references]

 

 
 

  
 

 

 

   

 

 
 
 
 
  
  
   
 
   
  
  

Page
Austin, Nev ........... . 17, 31
Austin quadrangle 64
Australophyllum ....... 28, 29, 33, 34, 57, 61, 70
cyathophylloides ..................... 57
landere’nsis ., 20, 23, 33, 34, 57
S13 ............................................... 57

B
Barrandeophyllum .. 39
perplexum ........ 39
Bartine Ranch quadrangle .. 5
Bay State Dolomite Member ............ 9, 18, 15, 16,
17, 19,21, 22, 23
lithology ......................................... 16
Beacon Peak Dolomite Member . 6, 8, 9, 11,
15, 17, 19, 23, 28, 31, 40
lithology ........ 15
type section .. 11
Beechwood Limestone .. .1 47
Belmont mine ......... 19, 22, 25
Bensberg, Germany .......... 60

Bethanyphyllidae .. 17, 27, 29, 30, 33, 53
Bethanyphyllum ..... 24, 33, 53, 54
antelopensis .. 21, 33, 53, 51,

 

 
 

    
 
  
  
  
 
    

lonense ...... .. 21, 33, 51,, 55
robustum .. 53, 54
sp. (1 ...... .. 33, 55
Billingsast'raea .. 20, 23, 24, 31, 32,
34, 35, 37, 38, 58, 61, 62

afi‘inis 30, 64
arachne 64
billingsi nevadensis ............... .. 63
nevadensis .......... 21, 30, 31, 34, 38, 61, 62, 6'3
arachne ,. ........ 34, 38, 62, 63, 64

verrilli . ....... 31, 64

sp. '1‘ ..... A 32, 34, 64
(Billinysastraea) , Phillipsastraea ...... 62

billingsi nevadensis, Billingsastmea.
Biofacies, Breviphre‘ntis ...................
H exagmwria-S ociophyllum
Kobeha
Papiliophyllum ..
Phillipsast'raea ..
Syringamrm ........ __
Biofacies aspects, Devonian corals
Biofacies indicator ..................

     
   

  
 

 

 

 

  
 
 

 

Bioherms
Biometrics .
Biostratigraphy, central Great Basin
Devonian ........ 17
Birenheide, Rudolf, cited 67, 68
bowerbanki, Endophyllwm .1 ..... 56
Brachiopods ....................... 5, 9, 13, 15, 16,
17, 18, 19, 20, 23, 24, 25, 29, 30, 50
spiriferoid ......................... ._ 17
Branik Limestone, Bohemia .. 39
Breviphre'ntis ....... 24, 27, 33, 38, 41, 1,2, 44, 45
inoaginatus ........ 30, 42, 43, 44, 46, 56
kobehenais 29
(Breviphrentis) invagimtus,
Siphanophre'ntis ....... 21, 30, 32,
33, 38, 42, 45,54, 56
kobehemis, Siphonophrentis .............. 20, 30,
33, 42, 43, 66
Siphanophrentis ...................................... 32, 41
Breviphyllum ............................................ 41, 43, 56

 

Breviphyllum—Continued

  
 
  

 

lo'nensis ..... 42
breviseptatum, Eurekaphyllum 33, 52
Bryozoans ................. 23
Biicheler Schichten . 45, 46
Bush Creek ............... 30

C
caespitosum, Cyathophyllum . .. 58
Disphyllum ,. 58

 
  
 
  
 
 
   
 
 
 
 
 
 
 
 
  
 
 
  
 
 
 

Calcarenite ........
Calceola beds, Russia
Caledonian Revolution
Canada, western .......
Carlin, Nev .................
Caryophyllia gigantea
castanea, Leiorhy'nchus .
Central Peak .
Cephalopods ..
orthoceratid .
Ceratophyllum
Charcoal Gulch
Chert nodules
Chewelah area ..
Cho’netes macrost'riata ..
Chonophyllidae ..
Canophyllum ......
Cladocora goldfussi
Clams .....................
Clark County, Nev ._
Clermont, Australia .
Coal Canyon ................
Cockalorum Wash quadrangle ...................... 5
Coeymans Limestone, New York 23, 30, 42, 44
coeymanemis, Gyzn'dula ......... : ..... . 20, 29, 50
Collection procedure
Calumnaria .................
(Cyathophylloides) disjuncta
Combs Peak ............
Compressiphyllum .
Confusion Range
Conglomerate .....
Conodonts ........
Contact Gulch
co’nverge‘ns, Aulacophyllum
Odontophyllum
Convergent genera .
cooperi, Trematospira _
Copenhagen Canyon ..................
Coral assemblage, Gotlandian
Coral assemblages, succession
Coral distribution, Devonian .....
Coral evolution, biologic factors
Devonian .............
geologic factors .
Late Silurian ......

  
   
  
  
 
 
 
 
  
 
 
 
  
 
 
  
 
 
 
 
  
 
  

 

 

related to faunal migration .. 25
related to geologic changes 25
Coral fauna, Ludlovian 19
Onondaga Limestone 25

Rabbit Hill ....... 19
Coral Gulch
Coral Ridge ..
Coral subzones ....................
Coral succession, related to

faunal migration
related to geologic change

25
25

 

 

79

 

fi

80

Coral zonation, Devonian ....................... .. 22
Coral zone A ........ 8, 11, 17, 18, 19, 23, 28, :29, 31
_ 8, 11, 17, 18, 19, 20, 23, 25, 28, 2.9, 32
....... 8, 11, 13, 17, 18, 19, 20, 23, 24, 25,

28, 2.9, 32, 42, 44, 47, 53
D .............. 8, 11, 13, 17, 18, 19, 20, 21,22, 23,

24, 25, 28, 80, 32, 42, 43, 44, 45

 

 

 

 

E ._ 3, 17, 18, 19, 21, 25, 28, 29, 33, 45
F _. . 5, 9, 13, 15, 16, 17,18, 19, 20, 21,
22, 23, 25, 28, 31‘

correlation .......................................... 31

G ...................... 9, 15, 16, 17, 18, 19, 21, 22, 28
H ._ ..... 17, 18, 19, 22, 25, 28

 
 
 
 

17, 18, 19, 22, 23, 25, 28
_ .. 5, 9, 23
Carboniferous _ ...... 38
colonial .............
dissepiments
favositid
horn 1.
internal structures .....

  
  
 
 
  
 
  

  

 
 

Paleozoic ................... 37
pycnostylid ............. l. 11
rugose 9, 13, 15, 16, 17, 19, 21, 22, 25
septa . 35, 37, 38
septal carinae ..... 36, 37
septa] stereozone . 37
Silurian ............... 37
skeletal features 34
solitary .......... 21, 24, 25, 35, 36, 37, 38
stereoplasmic deposits . 37
tabulae ......................................... 36', 37
tabulate ........ 18, 19, 20, 23, 24, 25, 29, 36

 

Cordilleran Belt .. ............ 25, 29, 30, 31, 37, 56

 

   
   
 
  
 
  

 

 

 

 

  
 
 
 
  
 
 
 
   

 

 

corniculum, Streptelasma 40
Correlation, coral subzone D2 .. 31
coral zones, Cprdilleran Belt .. 31
distant regions ._ .29

Cortez Mountains 31
Desert Range .. 82
Funeral Mountains 32
Hot Creek Range ....... 32
Hume Formation ....... 31
Nahanni Formation . 31
Nevada Formation 31
unit 1 32

unit 2 32
north-central Great Basin _. 31
northern Inyo Mountains .. 32
northern Panamint Mountains ..... 32
northern Sulphur Spring Range 31
Oriskany ..................................... 31
Rabbit Hill Limestone ,. 31
Ranger Mountains .92
south-central Great Basin 32
southern Great Basin . 32
Toiyabe Range ............. 31
Tuscarora Mountains, southern 31
west-central Great Basin .......... .. 81
Cortez Mountains .................. 31, 40
Cosmophyllum . 68, 69, 70
dachsbergi .. ................ 30, 70
Costispirifer _ 13, 19, 20, 23, 29

 

 

  
   
   

arenasus _ 8, 11, 17, 19, 20,

23, 29, 31, 32, 33, 49

Crinoids .......................................... 8, 21, 23, 24
curviseptatum, Grypophyllum .. 53
Cyathaxonia silurie‘nsis 39
Cyathophz/lloides .. 45
rhenanum ........................ 45

(Cyathophyllm‘des) disjuncta, Columnaria.. 45
cyathophyllaides, Australophyllum .
Spongophyllum
Cyathophyllum ............
caespitosum ..
hexagonum
lonense . __________
(Moravophyllum) .

 

 

 

 

 

INDEX

Cyathophyllum—Continued

  
   
  
 
 
   
  
 
 
 
  

  
  
 
 
 
 
  

robustum .. 53

sp ................. 54
cycloptera, Howellella 19, 29
Cylindrophyllum 58, 59
Cyrtina ................ 20
Cyrtospin'fer beds, Devils Gate 19, 22
Cyrtospirifer zone ..... 22
Cystiphyllidae ......................... 65
Cystiphylloidae _. 29, 33, 34, 35, 64
Cystiphz/llorides 6, 21, 24, 25, 33, 34, 65, 68

aggregatum _

americanum

lone'nse .............

robertse’nse ..

sp. d ...............
(Cystiphylloz’des) , Mesophyllum ..

Cystiphyllum ..... 70
Czechoslovakia . .......... 40, 50
D
dachsbergi, Arcophyllum ....................... .. 70
Cosmophyllum .. ..................... 30, 70
Mesophyllum (Arcophyllum) . 70

Dalmam‘tes
meeki .
defectum, M esophyllum

  
  
  
 
 
 
  
  

 

Dendrostellu ...............
disjuncta ........
praerhemma 46
rhenuna 46
romanenszs .. __ 21, 33, 45
(Dendrostella) praerhenamz, Favistella 45
rhenana, Favistella .......... 45
Descriptive paleontology ._ .93
Desert Range . 32, 43
Devils Gate 9, 18, 19, 25
Devils Gate Limestone _. ................. 6, 9, 15, 17,
21, 22, 25, 28, 29, 60
lithology ................................... .. 9, 17
type area _ 22
type section . 19
Devils Gate Pass 22
Dialytophyllum ........ 67

Diamond Mountains _ 5, 6, 8, 9, 13, 15,

18, 19, 21, 22, 23, 27

 

 

 

  
 
  

 

Diamond Mountains facies belt ............ 1, 6, 8, 9,

13, 15, 17, 29

Diamond Valley 15

Digonophyllidae ..... l. 17, 24, 29, 30, 33,

34, 35, 36, 38, 65, 67, 71

Digonophyllinae . ......... 34, 67, 68

Digonophyllum 21, 25, 65, 69

(Digonaphyllum) , .. 67
(Mochlophyllum) .

(Digonophyllum) , Diganophz/llum .
Dimorphism .....

   
  
 
  
  
 
 
 
 
   
  

Disconformity _. _ ...... 8, 19, 27
disjuncta, Columnarfa, (CyathophylloidesL 45
Dendrostella, .............................................. 46
Disphyllidae .............. 17, 29, 33, 34, 38, 58, 60, 61
Disphyllum ........... . 21, 22, 24, 34, 58
caespz‘tosum ............... 58
eurekaensis _ 21, 34, 59, 66

goldfussi ,,,,, 59
nevadense 34, 5.9, 60, 66
nevadensis .. ............... 21
Dissepimentarium 36
Dissepiments .......... . 86'
Diversophyllum ..... 55, 56
Dobbin Summit .. ..... 17, 19, 40
Dolomite ........... , 8, 9, 13, 15, 19, 20, 27, 28, 32
diagenetic . . 3, 23
recrystallization 23
saccharoidal ....... . 16, 22, 29
Douglas Creek, Australia 57
duplicatum, Zonophyllum ..... . 30, 70, 71

 

 

 

  
 
 
 

 
 
 
 
  
 
  

 

Page
E

Early Devonian coral zones 19
correlation ........................ 29
Early middle Devonian coral zones 1.9
correlation ._ 29
East Ridge ......... .. 11
Eifel district, Germany 30, 58, 60, 67, 69, 70
Eightmile Well .................. _. 15
elegantulum, Ketophyllum .. .. 50
Papiliophyllum l. 20, 24, 32, 33, 46, 47, 50, 66
Encrinite ................................................ 13, 15
Endophyllidae 28, 33, 34, 37, 56‘, 58, 60. 61

Endophyllum

abditwm
bowerbanki _ 56
Entelophglloides . 60
Entelophyllum 28, 35
Erben, H. K., cited 30
Eridophyllum .. 59
Eureka, Nev .................................. 27
Eureka County ........ 23, 43, 44, 46, 47, 50, 51, 52,

54, 55, 56, 59, 62, 63, 65, 68
Eureka mining district,
Nevada 4, 5, 29, 32, 42, 43, 56, 71

   

 

Eureka Quartzite ...................... 15
eurekaensis, Disphyllum . 21, 34, 5.9, 66
Eurekaphyllum .................. _ _ 33, 47, 50, 52

breviscptatum ................ 33, 5.2
Eurekaspirifer pinyonensis . 18,21
expansum, Sponyophyllum 59

 

F

Fauna, brachiopod ..

    

 

coral ....................
coral zone A ................. 19, 20, 28, 40
B _. 20, 28, 30, 31, 46, 47, 49, 50
C ., . 20, 30, 31, 46, 50, 52, 54, 66
D .............................. 20, 21, 27, 31, 32, 41,
46, 56, 61, 62, 64, 66, 68
E .. 21, 57, 64, 66
F .1 . 21. 27, 30, 32,

 
 

56, 58, 60, 61, 62, 64, 67

    

 

Onondaga .............. 30
Rabbit Hill .............. 29, 31, 50, 58
subzone D1 .. 20, 21, 30, 47, 52, 54, 55, 56, 71

 

subzone D2 ........ 21, 30, 46, 54, 55, 56, 58. 59,
60, 61, 62, 63, 64, 66, 67, 70, 71

 
 
 
   
  
 
  

subzone D3 ..................... 21, 30, 55, 62, 67, 70
Trematospira 29
trilobite ........... 31
Faunal migration, related to
coral evolution 25
Favistella ............................... 33, 45
(Dcndrostella) rhe’na’rw, 45
praerhenana ............ 45
Fa/uistina ..................
Favosites ............

   

Favositid heads .. 8, 24

  

 

Fenstermaker Mountain ....... .. 45
Fish Creek Range .......... 5, 6, 9, 15, 43, 45, 54, 71
fleamm, Hexagonaria. .. 62

M esophyllum ........ 66
foerstci, Syringaactm i. 19, 31, 33, 39
Foraminifera ........... 34
Fossil Gulch ....... 8

  
 
 
 

Fossils, silicified . .. 23, 24, 25, 34
Frasnes, Belgium
Frazier Creek .....
Frenchman Flat County, Nev ._
Funeral Mountains

Fusulinids ...............

 

 

 

 

 
 
 

 

 

Page
G

Garden Valley Formation ......... 15
Garden Valley quadrangle 5
Gastropods ............... 15, 24
Gazelle Formation . 60
Genomorph concept 38

Geologic change, related to
coral evolution ................ 25
Geologic structure, Lone Mountain .. 5

 

Germany ...............................
Gerolstein, Eifel district ..

 

 
  
  
 
 
 
 
 
 
  
 
  
 
  
  
 

gigantea, Caryophyllia i. 41

Siphonophrentia ...... 41
giganteum, Grypophyllum 53
Gold Hill mining district, Utah 27
goldfussi, Cladocora ......... 58

Disphyllum ..

 

 

Goniatites .......

Goniophyllidae

Gotland ................ _ 44, 45, 50

Gotland reef complex 22

Grande Greve Formation . 30, 64

Graptolite beds . , 17, 19, 32

Grays Canyon .. . 15, 43, 54, 56, 71

Great Basin, central .............. . 39, 43, 71
coral reference sections .. 6
correlation ................. . 31, 32
Devonian Facies belts b‘
faunas 24, 53, 56, 57, 60, 67, 71
north-central ....................... 74

 
 
 
 

Rugosa, classification
south-central ..
southern .......
west-central
Great Basin province 23, 25, 27, 29, 45, 62, 67

 

 

 
 
 
  
 
 
 

 

  
 

 

   
 
 

Green Springs quadrangle 22
Greifensteiner Kalk, Germany _ 40
Grypophyllum curviseptatum 53
giganteum ......................... 53
nevadense 53
Gypidula ................. 29, 50
coeymanensis 20, 29, 50
loweryi ................................... 20, 21, 52
H
haguei, Zonophyllum ......... 21, 30, 34, 71
Hallia .......... 46
insignia 46
Halliidae 17, 20, 24, 29, 30, 33, 37, 46, 53
Halliinae .. ..... 33, 46
Halysites 11
I-Ialysitids ....................... 28
Hamilton Formation 30

Helderbergian fauna ,

    
 

 

 
 

 

 

 

  
  
 
  
   
 

 

helderbergium, Pseudoblothrophyllum ........ 44
Heliolites ............................ 25, 70
Heliophyllum .. . 35, 53, 63
venatum

H emicosmophyllum .
(Hemicosmophyllum), Mesophyllum .......... 68
Heterophrentis ........ 30, 41, 42, 43
nevadensis ........ 42, 43
hexagona, Hewayonanu 60, 61
Hexagonan'a ...................... 21, 25, 30, 32,
34,37, 38,56, 58, 60,63
flexum ............ .. 62
hexagona ...... 60, 61
(Hexagomaria) 61
kirki ................. 62
(Pinyonastruea) .. . 32, 58
kirki ................ 21, 34, 38, 62
(Hexagonaria), Hexagonaria 61
hexagonum, Cyathophyllum 60
Hidden Valley .................. 33

Hidden Valley Dolomite
unit 3b ...............
Hill, Dorothy, cited .

 

 

 

 

——"'

INDEX

History of investigation .....

 

 
 
 
 
  
 

H omalophyllum ............ 41
Homeomorphic genera 34, 70
Hot Creek Canyon ....... .i 32
Hot Creek Range ..... 6, 32, 52

House, M. R., cited ..
Howellella cycloptera _

 

 

 

 

 

 
  
  
 
  
 
  
 
 

Hume Formation ......... 31
I, J

Independence Shale, Iowa .. 39

insignia, Hallia, .. 46

Introduction ...... 1

invaginatus, Amplexus . .. 42

Breviphrentis ................ 30, 42, 43, 44, 46, 56

Siphonophrentis (Breviphrentis) ...... 21, 30

32, 33, 38, 42, 45, 54, 56

Inyo Mountains 33

Joana Limestone 28
K

Keriophyllum .......................... 21

ketophylloides, Kobeha .. 20, 33, 48, 49

Ketophyllum ........ _ 50, 55

elegantulmn _ 50

Kirk, Edwin, cited 4

kirki, Arcophyllum .. 30

H exagonaria, ............
(Pinyonastrea)
Mesophylloides ............
Mesophyllum (A'rcophyllum) .. 21, 30, 34, 69
Prismatophyllum .. 61, 62

Klamath Mountains .. 5‘7, 60
Kobeha ...................... 8,13, 17, 20, 23, 24, 29,
31, 32, 33, 35, 36, 38, 47, 49, 50, 52, 53

 

  
 

 

 

 

fauna ..................... 8, 20
ketophylloides . 20, 33, 48, 49
walcotti 19, 20, 23,29, 31, 33, 48, 49, 52
zone 48
Kobeha Valley project . 5

 

kabehuna, Acrospirifer ,. 13, 20, 24, 32, 33, 52, 66

 

  
   
  
 
  

 

 
 
  
  

  
  

 

 
  
  
 
 
 

 

kobehensis, Breviphrentis .............................. 29
Siphonophrentis (Breviphrentis) ...... 20,

30, 33, 42, 43, 66

Kodonopbyllidae ...................... .. 28, 33, 44
Kodonophyllinae ....... 33, 45
Kodonophyllum _. 33, 37, 43, 45
milne-edwardsi 44

sp. a 33

sp. f .. 45
Kozlowskiellina ................. 19
Kwangsi Province, China 56, 65
Kyphophyllidae .. 60

L

Laccophyllidae .............................. 17, 27, 33, 37, 38
Laccaphyllum ....... 39
acuminatum . 39
Lake Manitoba ........ 46
Lake Winnipegosis 46
Laketown Dolomite 27
Lander County, Nev .............. ,. 58
landerensis, Australophyllum .. 20, 23, 33, 34, 57
Late Devonian coral zones ......................... 21
Late middle Devonian coral zones 21
Leiorhynchns castanea .......... 13, 16
Lekanophyllum ....................... 67
(Lekanophyllum), Mesophgllum . 21
lenticnlaris, Pleuradictyum ........... 31
Leonaspis 19, 23, 29
sp 46
Leptaena ...... 20
Leptocoelia 19, 31
sp ............ 50
Leptostrophiu sp .. . 20
Levenea subcarinata 19, 29, 31

 

 

 

 

limbatum, Arcophyllum .................
Mesophyllum (Arcaphyllum) 70
8, 9, 15, 16, 17,19, 22, 27, 32

     
 
  
 
 
   
 
 
 

Limestone ............
argillaceous . . 3, 13, 22, 24, 28
calcarenite
dolomitic
stromatoporoid _

Lithology, Bay State Dolomite Member ._
Beacon Peak Dolomite Member . . 15

Devils Gate Limestone .................
Nevada Formation, unit 1

 

unit 2 .. ....................
unit 3 1.
unit 4 .
unit 5 .................. .. 9
Oxyoke Canyon Sandstone Member 15
Rabbit Hill Limestone ............................ 17
Sentinel Mountain Dolomite Member. 15
Woodpecker Limestone Member . . 16
Locality register . 71

 

Lone Mountain ..

20, 22, 23, 24, 25, 30, 39, 43, 44, 46, 47,
50, 51, 52, 54, 55, 56, 59, 60, 61, 62, 63,
64, 65, 66, 69, 70
reference section 6, 8, 16, 17, 19, 28, 30, 32
Lone Mountain Dolomite ............ 8, 15, 19, 27, 28

Lone Mountain Dolomite—Nevada
Formation boundary ................ 28
lonense, Bethanyphyllum
Cyathophyllum ...........
Cysiiphylloides _
Mesophyllum
lonensis, Amplemus _
Breviphyllum ..
Louisville, Kentucky ..
Lower-Middle Devonian boundary .
loweryi, Gypidula, ..............
Lycophyllidae ....................

  
  
 
 
 
 

M

McAllister, J. F., cited
McColley Canyon
MacGeea ...................
macrostriata, Chonetes _
Maggie Creek .........
magnus, Amplexus
Mahogany Hills ........

 
 
 
 
  
 
 
 

 

 

Mapping procedures 5
Marble Canyon quadrangle, Calif 32
Martinia ki’rki zone . 21

undifera .................. 55
masoni, Nevadaphyllum 33, 44
Mazourka Canyon 33
meeki, Dalmanites

Odontophyllum . 20, 29, 30, 33, 46, 47
Meristella ............... 21, 33

robertsensis 20, 33

 

Merriam, C. W., cited .
Mesophylloides kirki ........
Mesophyllwm .............. 21, 25, 30, 33, 34, 65, 6‘7, 68

defectum ....................... 67

 
 

  
 
 
 
 
 
   
  
 
 
 
 
 
 

 

flexu’m .. 66
lonense 66
robertsense 65
vesiculosum . 66
(Arcophyllum) 67
dachsbergi .............. 70
kirki ............. 21, 30, 34, 69
limbatum .................. 70
(Cystiphylloides) . 65
(Hemicosmophyllum) 68
(Lekanophyllum) 21
(Mesophyllnm) ...... 67, 68
sp. b .
sp. c
(Mesophyllum), Mesophyllum 1
Methods of investigation ................................ 5

t

 

 
 
 
  
  
  

82

Page
Middle middle Devonian coral zones ............ 21
Miller, A. K., cited .............. 3O
milne-edwardsi, Kodonophyllum 44
Mineral Hill district ......................... 31
(Mochlophyllum), Digomophyllum . 21, 67

Modoc Peak .................
Moenke, Maria, cited ,
Mollusca .....
Mollusks ..... 5
Monitor Range u _ ............... 6, 17, 19, 39, 4O
Monitor—Simpson Park facies belt 3, 6, 17, 29
Monte Cristo ................................. n 19, 22, 25

  
  
 
  

M crow ophyllum ............................ 5 3
(Moravophyllum), Cyathophyllum _ 21
Morey Peak ................ 32
Mount Tenabo 31, 40
Mucophyllum 35
Mulligan Gap .......... 20
Mulligan Gap fault 15
Mutation .................. 38

Mycophyllinae .................

 

Nahanni Formation ..
Nautiloids ................................... 24
Nevada Formation ..... 6, 8, 32, 40, 47,

52, 54, 56, 59, 63, 65, 68, 71

 
 
  

 

barren zone ........................ 3, 8, 13, 15, 21, 25
Beacon Peak Dolomite Member .......... 6, 40
type section ......................................... 8
unit 1 ...................... 8, 9, 11, 15, 17, 19, 20, 23,

24, 25, 28, 31, 44, 46, 48, 49,

50, 51, 52, 53, 66

lithology .................................... 8
unit 2 ............. 6, 8, 1.9, 15, 17, 19, 20, 21,
22, 24, 27, 28, 29, 30, 31, 39, 42, 43,

44, 45, 46, 52, 54, 55, 59, 60, 61,

62, 63, 64, 66, 68, 69, 70, 71

 

 

   
 

 

 

 

   
 
  
   
  
 
 
  
  
  
 
  
   
 

 

lithology 8
unit 3 ............. . 8, 13, 15, 19, 21, 25, 27, 29
lithology . 8
unit 4 ............. _. 8, 13, 15, 16, 19,
20, 21, 22, 25, 28, 29, 31, 64
lithology . ...................................
unit 5 .............. 8, .9, 13, 15,16, 19, 21, 22
lithology ..... 9
nevadana, Atmpa 21
nevudaensis, Schizophoria . 21
Schuchertella ...... _ 20, 21
Nevadaphyllum 33, 37, 38, 41, 44
masom‘ ............................... 33, M
nevadense, Disphyllum .. 34, 59, 60, 66
Grypophyllum
Spongophyllum ..
Tabulophyllum
nevadensis, Agom‘atites .
Amplexus ...................

Billingsastraea .. 21, 30, 31, 34, 38, 61, 62, 65'
Billingsastraea bill-ingot
Disphyllum ......................
Heterophrentis ...........................
arachne, Billingsastraea, _ 34, 38, 62, 63, 64
New York .......................... .. 29, 53

 

Newark Mountain ......... 9
Niagaran reef complex 22
NichoLeom'a ............ 39
(Nicholsom‘a) Alleym'a . 39
Nohner Schichten .......... 30, 46, 70
North Sand Peak .. 13
Nye County, Nev .. 32

O

 

 
 
   

Odontophyllum .......................... 24, 30, 33, 46, 47
convergens 47
meeki ...... .. 20, 29, 30, 33, 46, 47
patellatu’m . 47

Ohio ......... 46

Oklahoma . ............. 29

 

 

 

 

 

 

 

 

INDEX
Page
Old Whalen mine area .................................. 29, 31
Oliver, W. A., Jr., cited _ 23, 24, 25, 38

 

quoted .......................... 62
Onondaga Limestone, New York _. 24, 29, 30, 41

 

    

 

 
  

 

Hagersville, Ontario 65
Orbitoids ............ 34
Oriskany Peak .. 13
Orthoceras .......... 24
Orthoquartzite .. 15
Orthostrophia strophomenm'des 29
Owens Valley, Calif . 57
Oxyoke Canyon .................................. 21
Oxyoke Canyon Sandstone Member 8, 13, 15, 32

lithology ..................................... 15

P
Pachyphyllum ............... 22, 25, 29, 35, 61
Paffrath Basin, Germany . 45
Paleophyllum ........................ 45
Panamint Mountains .. 32, 33, 39, 43, 52
Papiliophyllinae ........ _ 27, 33, 37, 47

Papiliophyllum 13, 17, 20, 24, 29, 32, 33, 47, 50, 53

 

     
 
   
  
 
 
 
   
 
 
 
 
   
 

 

 
 
 
 
 
 
 
 
 
  

 

 

 

 

 
 
 
 
 
 
 
  
    
  
   
 
 

 

 

elegantulum .. 20, 24, 32, 33, 46, 47, 50, 66
subsp. d ............ 20, 30, 32, 33, 52, 55
fauna .......................... 8
patellatum, Odcmtophyllum 47
Peneckiella ............................ 58
Permia 39
perplexum, Barrendeophyllum , 39
Perry County, Tenn 39
Petes Canyon ..... 58
Phacellophyllum . 22, 25, 35, 58
Phacopa ..... . 19, 23
rana ..... 21
Phillipsastraea 22 25, 35
(Billingsastraea) . ....... 62
biofacies .................. 19
verneuili l 62, 63
Phillipsastraeidae . 22, 25, 29, 33,
34, 35, 37, 58, 60, 61
Phillipsburg mine .. ...... 15
Pholidostrophz’a 50
sp .............. 20
phryyia, Zaphrentzs 41
Pilot Shale ................... 17, 22
lower .. 19
upper 6
Pinto Summit quadrangle ................... _ 21
Pinyonastraea ........................ 24, 30, 34, 35, 60, 61
(Pinyanustmea), Hexagonaria. ................ 32, 58
kirki, Hezayonaria .......... 21, 34, ,38, 6‘2
pinyonensis, Eurekaspin'fer ., ............... 18, 21
Spirifer ................................... .. 46, 52
planatabulatum, Sinosptmgaphyllum . 55, 56
Plasmophyllum ........................... . 65, 68
Plethorhyncha 19
Pleuradictyum . . 19, 23, 29, 31
lenticularis .. 31
Polycoeliidae . .. 39
Polyphyletic 35, 61
praerhenana, Dendrostella ...... 46
Favistella (Dendrostella) 45
Prince of Wales mine .. 11, 20
Prismatophyllum . 60, 61
kirki ,. 61, 62
Praetus ...... 19
Protocorallites .. .. 38
Pseudoblothrophyllum 43, 44, 45
helderbergium ._ ..... 44
Pseudocosmophyllum ._ 68, 69
punctuliferu, Strophonella, ............. 20
Purpose and scope of investigation . 3
pustulosa, Strophonella 20
Pycnostylidae .. 28, 35
Pyramid Peak ._ 32
Q, R
Quartz grains .................................... 8, 23, 31

 

 

 

 

 

 

 

 
 
   
 
  
 
  
   
 
  
 
 
 
 
  
 
 

Page
Quartzite ......................................... 32, 55
Queensland, Australia .. 57
Rabbit Hill .................. . 19, 40

Rabbit Hill Limestone . _ 5, 6, 8, 15, 17, 19,
23, 28, 29, 33, 39, 40, 57, 58

 

lithology ..... .. 17
type section 17, 19
Radiastraea . 38, 63, 64
arachne 63, 64
Tana, Phacops .......... .. 21
Ranger Mountains .. 32, 43, 52, 71
rectum, Tabulophyllum 56

 

Reeds Canyon _
Reef Point
Reefs, patch ...........................
Reference section, coral zone C
coral zone D .,
coral zone F
coral zone G
coral zone I ........
Lone Mountain .
Sulphur Spring Range ..
Reference sections .....
References selected
Rensselundia ..

 

 

  

 

rhenana, Dendrostella. 46
Ftwistella (Dendrostella) 45
rhenanum, Cyathophylloides _ 45
Rhine Valley ............................. 46
Roberts Creek Mountain . 29
Roberts Creek Ranch .................. 20
Roberts Mountains .............. . 6, 25, 29, 30,
49, 50, 52, 54, 62, 64, 65
Roberts Mountains Formation ............ 19, 28, 31
robertsense, Cystiphylloides
Mesophyllum ............

 
  
 
  
  
 
  
 
  
   

robertsensis, Meristella .
robustum, Bethanyphyllum _

Cyathophyllum ............
romanensis, Dendrostella,
Romano Ranch ..............
Rézkowska, Maria, cited

 

Rugosa ..................
calice features
Carboniferous ........... 38
classification .............. .93, 35
Coeymans Limestone 23

colonial 20, 21, 23, 24, 25, 31, 35, 36, 37, 38
Cordilleran
descriptive terms
digonophyllid
dissepimented
Early Devonian
Early Silurian .......
eastern North America
Eureka mining district
evolution .........
Devonian .
Late Silurian
zone D ..
zone F .
zone I
exterior corallum features
fine structure ..
Great Basin .
growth stages .............................
interior corallum structures .
Nevada Formation ......
Ordovician .....
pycnostylid
Rabbit Hill Limestone
reproductive features

  
 
 
   
   
  
 
 
 
  
 
 
 
  
 
 
 

   

Rhine Valley ............... 4
solitary .. 21, 24, 25, 35, 36, 37, 38
symmetry ............................ 37
taxonomy ,. 31,, 36, .97, 38
western North America ............. 3
Ryan quadrangle, Calif .................................. 32

 

‘

 

 

  
  
 
 

Page
S
Sandstone, quartzitic ................................ 8, 11, 15
siliceous .................... .8,13
Schizophm‘ia nevadaensis . 21
Schuchertella ______
nevadaensis

Section Ridge

 
  
  
    

sedgwicki, Spongophyllum 57
Sellersburg Limestone . 47
Sentinel Mountain ......... 21
Sentinel Mountain Dolomite
Member .......................... 8, 1.7, 15, 23
lithology .. . 15
Septa ............... 85, 37,38
Septal stereozone . ......... 37
Sevy Dolomite ...... 27
Silurian-Devonian boundary 27, 28
silurie’nsis, Cuathaxo’m'a .. .. 39
Syringuaum ............. .38, .99, 40
Simpson Park Mountains . 6 28, 33, 40
Simpson Park Range ., 6, 17

Simpson Peak Range ..

 

  
 
 

  

 

  

 

 
 
 
 
 
  

 

 

 

 

   

Sinosptmgophyllum ..... ,,
planotabulatum . ....... 55, 56
sp. (1 .. 33, 52, 56'
sp. e . ........ 33, 56
sp. f . 34 44, 56
spp .. 21
Siphonophrentinae .. 17,27, 29, 30, 33, 36,37, 45
Siphonophrentis. ................ 33, .61, 45
gigantea
oariabilis ..
(Breviph'rentis)
invaginatua
, 38, 42, 45, 54, 56
kabehemis ....... 20, 30, 33, 42, 43, 66
(Siphonophrentis) 41
(Siphonophre'ntis), Siphtmophrentis 41
Sociophyllum ............................................ 21, 25, 59
Southern Sulphur Spring Range,
reference section , 6, 8, 9
spatiosa, Zaph’rentis .................. 41
Spirifer kobehana zone .. 30
pinyo’nensis 46, 52
zone .. 18, 20, 21,29, 30, 55, 70
Spirifers .................... 32, 33
Spongophyllidae .. 33 37, 58, 60
Spongophyllum ............... 57
cyathophulloides . 57
w”, sum 59
"' U .. 59
sedgwicki ............................. . 57
Stathmoelasma . .53, 54
Stauriidae ......... 33, 34, 45
Stauria ..................... 45
astreifo‘rmis 45

534-0410 - '74 - 7

 

INDEX

Stereoplasmic deposits ..

  

 

  
 
 
  

 

 

 

 
  
 
   

Stevens County, Wash ..... 31
Stratigraphy, Central Great Basin
Devonian Rocks ................ 6
Streptelasmu corniculum 40
Streptelasmatidae .......... 33, 40
Streptelasmidae 33, 40
Striatopora ........................... 19, 23
Stringocephalus . . 9 15 16, 21, 46, 70
zone .............................................. 22
Stromatoporoid- -Amphipora biofac1es . 19
Stromatoporoids ..... ... .9 15, 17, 22, 23, 24, 25
strophomenoides, Orthostrophia 29
Strophonella ................................... 32
punctulifera, 20
pustulasa ...... ... 20
Stumm, E. C., cited .. 4, 22, 33, 51, 57, 66, 69
subcan‘nata, Leve’nea ..... 19,29, 31

Sulphur Spring Range... 6, 8, 9, 11, 13,
15. 17,18, 19, 20, 23,24, 29, 31,

40, 43, 45, 46,48, 49, 50, 52, 54, 67, 68
Synaptophyllum . 45
Syringaacon ..........

 

 
 
 

 

 

 
   
 
  

at ' “I'm 39
biofacies ....... 19
foe'rstei ...... ,. 19, 31, 33, 39
silun‘e’nsis . 38, 39, 40
sp ............... 31
Systematic paleontology ........ .93

T

  
 
  
  
 
   
 
  
 
 
 
 
 
  
  
   
   
 

Tabulae .........

Tabularium

Tabulata .......

Tabulophyllum .. 21, 55, 56
nevadense .. 53, 54
rectum ............... 56

Taimyrophyllum .. 21, 25, 29, 32, 58, 61, 64

Taxonomy, Rugosa . . 31,, 36, 37, 38

Rugosa, interior corallum .. 35
Teicherticeras 30, 31
Temnophyllum . 22
Tennessee .. 29
Tentaculites 24, 31
Terrace Butte 13, 15
Thrust plates 5

Toiyabe Range .
Toquima Range .

Torquay, England . 56
Tortophyllum ........... 53
Trematospira cooper-i . 29

fauna ................. 29
Trilobites ...... . 5, 19, 23, 24, 29, 30
Tryplasmatidae . 34, 35
Turbidity ............. 24

 

 

83

Page
Tuscarora Mountains .............................. 20, 23, 31
Twin Hills ................ .. 11

 

typus, Arcophyllum

 

 
 
   
   
 
 
 
 
 

Unconformity ......
undifera, Martinia .
Ural Mountains, Russm .
Utaratuia ........................
variabilis, Siphonophrentis
Variation ........................

statistical analysis
Vaughn Gulch Limestone
venatum, Heliophyllum
vernem'li, Anastrophia.

Phillipsastmea .....

verrilli, Billingsastraea ..
' 1 nan/vy- M rLur’

 

W,X

walcotti, Kobeha ...................................... 19, 20, 23,
29, 31, 33, 1+8, 49, 52
Wales Peak ......................... .. 11, 13
Walti Hot Springs area
Wedekind, Rudolf, cited
Well, J. W., cited ...............
West Peak ..........
West Sand Peak
Whistler Mountain quadrangle
White Pine mining district,
Nevada ............................ 4, 19, 22, 25
Wisconsin ............................................

 

  
 
  
 
 

 

Woodpecker Limestone Member .. .
15, 16, 17, 19, 21

lithology .....
Xystriphyllum

  
  
  
 
 
   
 
  
  

Yahoo Canyon .
Yassia .............
Yoh, S. S., cited ..
Zaphrentidae

 

Zaph’re’ntis .....
phrygia ______
spatiosa .

Zaphrentoid sp

Zoantharia ........ 1

Zonophyllinae .. , 70

Zonophyllum ....... 30, 34, 70
duplicatum ........ 30, ‘70, 71
haguei .......... 21, 30, 34, 71
sp. a .. 34, 71
sp. b 34, 71
sp ........................... 32

 

 

 

 

PLATES 1—25

[Contact photographs of the plates in this report are available, at cost, from US. Geological
Survey Library, Federal Center, Denver, Colorado 80225]

 

 

PLATE 1

FIGURES 1—8. Syringaxon foerstei n. sp.

P‘P‘WN!"

6.

Oblique calice View of holotype ( >< 11/2), USNM 159243.

Lateral view of paratype ( X 2) , USNM 159244.

Calice view of paratype ( X 1), USNM 159245.

Calice view ( x 2).

Early ephebic transverse thin section of paratype ( X 6), USNM
159246.

Longitudinal thin section of paratype ( X 6), USNM 159247.

7, 8. Mature transverse thin sections of two individuals ( X 2, x 4).
Early Devonian, Rabbit Hill Limestone; Devonian coral zone A. Locality
M187, Rabbit Hill, Copenhagen Canyon, Eureka County, Nev.

9—12. Syringaxon foerstei n. sp.
9, 10. Mature transverse thin section and longitudinal thin section

(X 3%), USNM 159352.

11, 12. Calice views of two silicified individuals ( X 2) .
Early Devonian; Devonian coral zone A. Locality M197, south of Bailey

Pass, Sulphur Spring Range, Nev.

13, 14. Syringaxon foerstei n. sp.
Mature transverse thin section and longitudinal thin section of paratype

(X 4), USNM 159248.

Early Devonian, Rabbit Hill Limestone; Devonian coral zone A. Locality

M1032, Coal Canyon, Simpson Park Range, Nev.

15, 16. Syringaxon foerstei n. sp.
15. Lateral View of paratype ( X 2), USNM 159249.
16. Lateral view of paratype ( X 2), USNM 159250.
Same horizon and locality as figures 1—8.

PROFESSIONAL PAPER 805 PLATE 1

GEOLOGICAL SURVEY

 

S YRIN GA X ON

PLATE 2

FIGURES 1—6. Kobeha cf. K. walcotti n. gen, n. sp.

1,2. Exterior and calice interior (X 1). Lower Devonian; Devonian
coral zone B. Locality M1021, McColley Canyon, Sulphur Springs
Range, Nev.

3. Exterior (X 1). Lower Devonian; Devonian coral zone B. Locality
M1018, McColley Canyon, Sulphur Spring Range, Nev.

4, 5. Longitudinal and transverse thin sections (X 11/2). Lower Devo-
nian; Devonian coral zone B. Locality'M1024, McColley Canyon,
Sulphur Spring Range, Nev.

6. Exterior of two attached corallites ( X 1). Lower Devonian; Devonian
coral zone B. Locality M1025, McColley Canyon, Sulphur Spring
Range, Nev.

7—9. Siphonophrentoid coral.

Lateral and calice views (X 1) and longitudinal thin section (X 3).
Lower Devonian; Devonian coral zone A (Helderbergian); locality
M186, southern Sulphur Spring Range, Nev.

——’1

PROFESSIONAL PAPER 805 PLATE 2

   
 
 

GEOLOGICAL SU RV EY

 

KOBEHA AND SIPHONOPHRENTOID CORAL

 

 

 

 

PLATE 3

FIGURES 1, 2, 6. Kobeha walcotti n. gen., n. sp.
1. Calice View of paratype ( X 1) , USNM 159251.
2. Lateral view of paratype ( x 1) , USNM 159252.
6. Lateral view of holotype ( x 1), USNM 159253.
Lower Devonian, Nevada Formation, unit 1; Devonian coral zone B. '
Locality M56, southern Sulphur Spring Range, Nev.
3—5, 8, 9. Kobeha ketophylloides n. sp.
3—5. Lateral, calice, and calice interior views of paratype ( X 1) ,
USNM 159254. Lower Devonian, Nevada Formation, unit 1; Devo-
nian coral zone B. Locality M1039, southern Sulphur Spring Range,
Nev.
8, 9. Oblique calice view ( x 1) and neanic transverse thin section
(X 2) of paratype USN M 159255. Lower Devonian, Nevada Forma-
tion, unit 1; Devonian coral zone B. Locality M69, southeast of
Prince of Wales mine, southern Sulphur Spring Range, Nev.
7. Kobeha cf. K. walcotti n. gen., n. sp.
Transverse thin section (x 2) of late neanic stage. Lower Devonian,
Nevada Formation, unit 1; Devonian coral zone B. locality M1040,
southern Sulphur Spring Range, Nev.

 

 

 

 

 

PROFESSIONAL PAPER 805 PLATE 3

GEOLOGICAL SURVEY

  
   

8
K OBEH A

 

 

 

 

 

PLATE 4

FIGURES 1—4. Kobeha walcottin.gen.,n.sp.

Early ephebic (x 2), late neanic (x 4), late ephebic (>< 11/2), and
longitudinal thin section (>< 11/2) of paratype USNM 159256. Early
Devonian, Nevada Formation, unit 1, Devonian coral zone B. Locality
M1041, southeast of Prince of Wales mine, southern Sulphur Spring
Range, Nev.

5, 6. Kobeha cf. K. walcotti n. gen., n. sp.

Longitudinal thin section (x 2), neanic transverse thin section (x 2).
Early Devonian, Nevada Formation, unit 1, Devonian coral zone B.
Locality M67, southern Sulphur Spring Range, Nev.

 

 

 

PROFESSIONAL PAPER 805 PLATE 4

GEOLOGICAL SURVEY

 

4 I
3’ '

  6’

 

K OBEHA

PLATE 5

FIGURES 1—7. Kobeha walcotti n. gen., n. sp.

1,2, Transverse and longitudinal thin sections of paratype ( >< 11/2),
USNM 159257. Lower Devonian, Nevada Formation, unit 1; Devonian
coral zone B. Locality M56, southern Sulphur Spring Range, Nev.

3—5. Transverse and longitudinal thin sections (x 1%) and transverse
thin section of late neanic stage (x 2). Lower Devonian, Nevada
Formation, unit 1; Devonian coral zone B. Locality M4, southeast of
Prince of Wales mine, southern Sulphur Spring Range, Nev.

6. Longitudinal thin section ( x 2). Lower Devonian, Nevada Forma-
tion, unit 1; Devonian coral zone B, Locality M67, northeast of Bailey
Pass, southern Sulphur Spring Range, Nev.

7. Longitudinal thin section of holotype ( >< 11/2), USN M 159253. Lower
Devonian, Nevada Formation, unit 1; Devonian coral zone B. Locality
M56, southern Sulphur Spring Range, Nev.

 

., a _ ., f. ,

5
E
T
A
L
P
5
0
8
R
E
P
A
P
L
A
N
O
I
S
S
E
F
O
R
P

 

GEOLOGICAL SURVEY

PLATE 6

FIGURES 1—7. Kobeha ketophylloides n. sp.

1—5. Longitudinal thin section (>< 2), transverse thin section (>< 1),
enlargement of previous thin section (>< 2), early ephebic transverse
thin section ( x 2), and neanic transverse thin section (>< 2), all of
holotype USNM 159258.

6. Neanic transverse thin section ( x 2).

7. Early ephebic transverse thin section of paratype (>< 2), USNM
159259.

Lower Devonian, Nevada Formation, unit 1; Devonian coral zone B.
Locality M1042, 1.75 miles north of Roberts Creek Ranch, Roberts
Mountains, Nev.

8, 9. Kobeha walcotti n. gen., n. sp.

Neanic transverse thin sections (>< 2), (>< 4) of paratype USNM
159260. Lower Devonian, Nevada Formation, unit 1; Devonian coral
zone B. Locality M69, southeast of Prince of Wales mine, southern
Sulphur Spring Range, Nev.

10. Kobeha walootti n. gen., n. sp.

Transverse thin section of late nepionic growth stage (>< 4), Lower
Devonian, Nevada Formation, unit 1; Devonian coral zone B. Locality
M56, southern Sulphur Spring Range, Nev.

 

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 805 PLATE 6

  

 

KOBEHA

 

 

 

FIGURES 1, 2.

5—7.

10.

 

PLATE 7

Papiliophyllum elegantulum subsp. d.

1,2. Transverse and longitudinal thin sections (x 1%). Late Early
Devonian, Nevada Formation, unit 2; Devonian coral zone D1. Local-
ity M1037, south pediment of Lone Mountain, Eureka County, Nev.

Papiliophyllum cf. P. elegantulum Stumm.

Lateral exterior (X 1). From limestone cobble, Locality M1043, Cobble

Hill, Cockalorum Wash quadrangle, Fish Creek Range, Nev.
Papiliophyllum elegantulum Stumm.

Calice interior (X 1). Early Devonian, Nevada Formation, unit 1;
Devonian coral zone C. Locality M286, Lone Mountain, Eureka
County, Nev.

Papiliophyllum elegantulum Stumm.

Lateral and calice interior views ( x 1) and early ephebic transverse
thin section (x 4). Early Devonian, Nevada Formation, unit 1;
Devonian coral zone C. Locality M74, Lone Mountain, Eureka County,
Nev.

Papiliophyllum elegantulum Stumm.

Neam'c transverse thin section ( X 4). Same locality as figures 5—7,
Papiliophyllum elegantulum Stumm.

Neanic transverse thin section (x 4). Same locality as figures 5—7.
Papiliophyllum elegantulum Stumm.

Late neanic transverse thin section (X 2). Same locality as figure 4.

 

 

 

 

PROFESSIONAL PAPER 805 PLATE 7

GEOLOGICAL SURVEY

 

PAPILIOPHYLL UM

534-041 0 - 74 - 8

 

PLATE 8
FIGURES 1—4. Papiliophyllum elegantulum Stumm.

Mature transverse thin section ( x 2), early ephebic thin section ( x 2),
longitudinal thin section ( x 2), mature transverse section ( x 11/2).
Early Devonian, Nevada Formation, unit 1; Devonian coral zone C.

Locality M286, northwest side of Lone Mountain, Eureka County,
Nev.

5, 6. Papiliophyllum elegantulum Stumm.

Longitudinal thin section (X 1), mature transverse thin section (X 1).
Early Devonian, Nevada Formation, unit 1; Devonian coral zone C.
Locality M1044, west side Lone Mountain, Eureka County, Nev.

7. Papiliophyllum elegantulum Stumm.

Longitudinal thin section ( X 1%). Early Devonian, Nevada Formation,
unit 1; Devonian coral zone C. Locality M68, east of Prince of Wales
mine, Sulphur Spring Range, Nev.

8. Papiliophyllum elegantulum Stumm.
Early ephebic transverse thin section ( x 1%). Early Devonian, Nevada

Formation. Locality M1035a, north end Antelope Range, southern
Eureka County, Nev.

9, 10. Eurekaphyllum breviseptatum Stumm.
Longitudinal and transverse thin sections ( x 1) of holotype; copies of

original figures (Stumm, 1937, pl. 54, figs. 8a, 8b). Nevada Formation,
Lone Mountain, Eureka County, Nev.

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 805 PLATE 8

 

PAPILIOPHYLL UM AND E UREKAPH YLL UM

FIGURES 1—5. ‘

6—9.

10.

11.

12.

13, 14.

PLATE 9

Odontophyllum meeki n. sp.

1—4. Calice view and two lateral views ( >< 11/2) , tilted calice view
( x 2) of holotype USNM 159261.

5. Lateral calice view ( X 1) of paratype USNM 159262.

Early Devonian, Nevada Formation, unit 1; Devonian coral zone C.
Locality M74, Lone Mountain, Eureka County, Nev.

Aulacophyllum sp. c.

6, 7. Calice view (X 1), early ephebic transverse thin section (x 3%).
USNM 159263.

8, 9. Calice view (x 1), ephebic transverse thin section (>< 31/2).
USNM 159264.

Same horizon and locality as figures 1—5.

Aulacophyllum-like rugose coral.

Lateral-interior of weathered specimen (X 1) showing down-bend of

tabulae at fossula. Same horizon and locality as figures 1—5.
Aulacophyllum-like rugose coral.

Mature transverse thin section ( X 2). Early Middle Devonian, Nevada
Formation, unit 1; Devonian coral zone D. Locality M36, south of
Bailey Pass, Sulphur Spring Range, Nev.

?Aulacophyllum sp.

Calice view ( X 1) . Same horizon and locality as figures 1—5.
?0dontophyllum sp.

Calice and lateral views ( X 1). Same horizon and locality as figures 1—5.

PROFESSIONAL PAPER 805 PLATE 9

GEOLOGICAL SURVEY

 

* ODONTOPHYLL UM, A ULA COPHYLL UM, AND A ULACOPHYLL UM—LIKE RUGOSE CORALS

PLATE 10

FIGURES 1—7. Bethanyphyllum antelopensis n. sp.

1, 2. Transverse and longitudinal thin sections of holotype (X 2),
USNM 159265.

3. Transverse thin section of paratype (X 2), USNM 159266.

4. Longitudinal thin section of paratype (x 2), USNM 159267.

5. Longitudinal thin section of paratype (x 2), USN M 159268.

6, 7. Late neanic thin section ( x 4) and ephebic thin section ( x 2)
of paratype USNM 159269. ’

Early Middle Devonian, Nevada Formation, unit 2; Devonian coral zone
D2. Locality M27, Combs Peak, southern Mahogany Hills, Bellevue
Peak quadrangle, Eureka County, Nev.

8—10. Bethanyphyllum Sp. d.

8, 9. Neanic transverse thin section ( X 4) and longitudinal thin section
(X 2), USNM 159270. Late Early Devonian, Nevada Formation;
Devonian coral zone D1. Locality M1037. Pediment slopes, south side
of Lone Mountain, Eureka County, Nev.

10. Neanic transverse thin section ( X 4), USNM 159271. Same horizon
and locality as figures 8, 9.

GEOLOGICAL SURVEY PROFESSIONAL PAPER 805 PLATE 10

 

J “
vi“

flwfig a:

BETHANYPHYLL UM

PLATE 1 1

FIGURES 1—4. Bethanyphyllum lonense (Stumm).

1, 2. Transverse and longitudinal thin sections ( X 2), USNM 159272.

3, 4. Transverse and longitudinal thin sections ( X 2) , USNM 159273.

Early Middle Devonian, Nevada Formation, unit 2; Devonian coral zone
D2. Locality M3, Grays Canyon, southern Eureka district, Nevada.

5, 6. Bethanyphyllum antelopensis n. sp.

Transverse and longitudinal thin sections of paratype (X 4), USNM
159274. Early Middle Devonian, Nevada Formation, unit 2; Devonian
coral zone D2. Locality M27, Combs Peak, southern Mahogany Hills,
Bellevue Peak quadrangle, Nevada.

7—9 Bethanyphyllum cf. B antelopensisn. sp.

Exterior (x 1), longitudinal thin section (X 2), transverse thin section
(X 2), USNM 159275. Middle Devonian, Nevada Formation, unit 2;
Devonian coral zone D3. Locality M1045, northwest side of Lone
Mountain, Eureka County, Nev.

GEOLOGICAL SURVEY PROFESSIONAL PAPER 805 PLATE 11

   
    

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PLATE 12
FIGURES 1,2. Bethanyphyllum cf. B. lonense (Stumm).
Transverse and longitudinal thin sections (>< 11/2), USNM 159276.
Early Middle Devonian, Nevada Formation, unit 2. Locality M1046,
Lone Mountain, Eureka County, N ev.
3—5. Bethanyphyllum lonense (Stumm).
Two transverse thin sections and a longitudinal thin section (x 2),
USNM 159277. Middle Devonian, Nevada Formation, unit 2; Devo-

nian coral zone D2. Locality M1047, east side Sulphur Spring Range,
Nev.

6—8. Bethanphyllum lonense (Stumm).
Longitudinal section, earl

Devonian coral zone D2. Locality M1048, northwest side of Lone
Mountain, Eureka County, Nev.

9—10. Bethanyphyllum lonense (Stumm).
Transverse and longitudinal thin sections (X 2), USNM 159279. Devo-
nian, Nevada Formation, unit 2; Middle Devonian coral zone D2.
Locality M3, Grays Canyon, southern Eureka district, Nevada.
11. Bethanyphyllum antelopensis n. sp.
Longitudinal thin section at calice ( X 2). Middle Devonian, Nevada
Formation, unit 2; Devonian coral zone D2. Locality M27, Combs
Peak, southern Mahogany Hills, Bellevue Peak quadrangle, Nevada.

 

 

 

PROFESSIONAL PAPER 805 PLATE 12

    

 

BE TH AN YPH YLL UM

  

GEOLOGICAL SURVEY

 

 

 

PLATE 13

FIGURES 1, 2. (?)Kodonophyllum sp. f.

3,4.

6, 7.

1. Transverse smoothed surface (X 1). Photographed in water.

2. Transverse thin section ( >< 3).

Early Middle Devonian, Nevada Formation, unit 2; Devonian coral
zone D. Locality M1033, north end of Fenstermaker Mountain, Fish
Creek Range, Nev.

Nevadaphyllum masoni Stumm.

3. Transverse thin section ( >< 11/2) of holotype, USNM 94447.

4. Longitudinal thin section ( x 3) of paratype, USN M 94447a.

Early Middle Devonian, Nevada Formation, unit 2; Devonian coral zone
D. Lone Mountain, Eureka County, Nev.

. Nevadaphyllum-like rugose coral.

Transverse thin section (x 2), USN M 159280. Early Middle Devonian,
Devonian, Nevada Formation, unit 2; Devonian coral zone D. Locality
M1049, Lone Mountain, Eureka County, Nev.

Bethanyphyllum sp. d.

Transverse and longitudinal thin sections ( X 2), USNM 159281. Late
Early Devonian, Nevada Formation; Devonian coral zone D1. Local-
ity M1037, pediment slopes, south side Lone Mountain, Eureka
County, Nev.

. Bethanyphyllum cf. B. lonense (Stumm).

Transverse thin section (x 1%), USNM 159282. Early Middle Devo—
nian, Nevada Formation, unit 2; Devonian coral zone D. Locality
M1050, Lone Mountain, Eureka County, Nev.

Bethanyphyllum sp. d.

Longitudinal section ( >< 11/2), USNM 159281a. Same horizon and local-

ity as figures 6, 7.

 

 

 

PROFESSIONAL PAPER 805 PLATE 13

GEOLOGICAL SURVEY
fl ». n ‘

     

) (?)KODONOPHYLL UM, NE VADAPH YLL UM, NEVADAPH YLL UM -LIKE
RUGOSE CORAL, AND BETHANYPHYLL UM

 

PLATE 14

FIGURES 1—15. Siphonophrentis (Breviphrentis) kobehensis n. sp

1. Lateral View of paratype (X 1) , USNM 159283.

2. Lateral view of holotype ( x 1) , USN M 159284.

Early Devonian, Nevada Formation, unit 1; Devonian coral zone C.
Locality M286, northwest side of Lone Mountain, Eureka County,
Nev.

3. Lateral View of paratype ( x 1) , USN M 159285.

Early Devonian, Nevada Formation, unit 1; Devonian coral zone C.
Locality M74, west side of Lone Mountain, Eureka County, Nev.

4. Lateral view of paratype ( x 1), USNM 159286. Same horizon and
locality as figures 1, 2.

5. Lateral view of paratype ( X 1), USNM 159287. Same horizon and
locality as figures 1, 2.

6. Calice view of paratype (>< 1), USNM 159288. Same horizon and
locality as figures 1, 2.

7. Calice View of paratype ( X 1), USNM 159289. Same horizon and
locality as figures 1, 2.

8. Longitudinal thin section of paratype ( X 2), USNM 159290. Same
horizon and locality as figures 1, 2.

9,10. Transverse and longitudinal thin sections of paratype (>< 4),
USN M 159291. Same horizon and locality as figure 3.

11. Longitudinal thin section of paratype (X 2), USNM 159292. Same
horizon and locality as figure 3.

12. Longitudinal thin section of paratype (>< 4), USNM 159293. Same
horizon and locality as figure 3.

13, 14. Two early neanic transverse thin sections ( X 7), USN M 159294.
Same horizon and locality as figure 3.

15. Nepionic transverse thin section (>< 7), USNM 159295. Same hori-
zon and locality as figure 3.

 

 

PROFESSIONAL PAPER 805 PLATE 14

SIPH ON OPHREN TI S (BRE VIPHREN TI S )

GEOLOGICAL SURVEY

PLATE 15

FIGURES 1—11. Siphonophrentis (Breuiphrentis) invaginatus (Stumm).

1, 2. Transverse thin section (>< 2) and longitudinal thin section
(X 4), USNM 159296.

Early Middle Devonian, Nevada Formation, unit 2; Devonian coral
zone D. Locality M1033, north end of Fenstermaker Mountain, Fish
Creek Range, Nev.

3, 4. Transverse thin section (>< 4) and longitudinal thin section
(X 2), USNM 159297.

Early Middle Devonian, Nevada Formation, unit 2; Devonial coral
zone D. Locality M198, southern Sulphur Spring Range, Nev.

5, 6. Transverse and longitudinal thin sections ( x 2), USNM 159298.
Devonian coral zone D. Locality M1034, Ranger Mountains, Nevada
Test Site.

7, 8. Transverse and lon tudinal thin sections (>< 2), USNM 159299.
Same horizon and locali y as figures 1, 2.

9. Transverse section (X 2), USNM 159300. Early Middle Devonian,
Nevada Formation, unit 2; Devonian coral zone D2. Locality M3,
Grays Canyon, southern Eureka district, Nev.

10. Longitudinal thin section ( X 2), USNM 159301. Devonian coral
zone D. Locality M1035, north end Antelope Range, Eureka County,
Nev.

11. Longitudinal thin section (X 2), USNM 159302. Same horizon and
locality as figure 9.

 

 

TE 15

  

PROFESSIONAL PAPER 805 PLA

   
 
 

’ GEOLOGICAL SURVEY

 

 

 

10 V
SIPHONOPHRENTIS (BREVIPHRENTIS)

 

 

 

534-041 0 - 74 - 9

 

 

PLATE 16

FIGURES 1—13. Siphonophrentis (Breviphrentis) invaginatus (Stmnm).

1, 2. Transverse and longitudinal thin sections (X 2), USNM 159303,

Early Middle Devonian, Nevada Formation, unit 2; Devonian coral
zone D2. Locality M55, Lone Mountain, Eureka County, Nev.

3. Transverse thin section (X 2), USNM 159304.

Early Middle Devonian, Nevada Formation, unit 2; Devonian coral
zone D2. Locality M3, Grays Canyon, southern Eureka district,
Nevada.

4. Longitudinal thin section (X 2), USNM 159305. Same horizon and
locality as figure 3.

5—7. Transverse thin section ( x 2), longitudinal thin section (X 2),
and transverse thin section of neanic stage ( x 4), USNM 159306.
Same horizon and locality as figure 3.

8. Transverse thin section ( X 2), USNM 159307. Same horizon and
locality as figure 3.

9. Transverse thin section (X 2), USNM 159308. Same horizon and
locality as figure 3.

10, 11. Transverse and longitudinal thin section ( X 2), USN M 159309.

Early Middle Devonian, Nevada Formation, unit 2; Devonian coral
zone D2. Locality M1033, north end Fenstermaker Mountain, Fish
Creek Range, Nev.

12,13. Transverse and longitudinal thin sections (x 2), USNM
159310.

Early Middle Devonian, Nevada Formation, unit 2; Devonian coral
zone D2. Locality M27, Combs Peak, southern Mahogany Hills,
Eureka County, Nev.

14. Siphonophrentis (Breviphrentis) kobehensis n. sp.

Transverse thin section of paratype (x 2), USNM 159283. Early
Devonian, Nevada Formation, unit 1; Devonian coral zone C. Local-
ity M286, northwest side of Lone Mountain, Eureka County, Nev.

15, 16. Siphonophrentis (Breviphrentis) invaginatus (Stumm).

Transverse and longitudinal thin sections (x 2), USNM 159311. Early
Middle Devonian, Nevada Formation, unit 2; Devonian coral zone
D2. Locality M1036, Lone Mountain, Eureka County, Nev.

 

 

 

V

 

GEOLOGICAL SURVEY

 

SIPH ON OPH REN TI S ( BRE VI PH REN TI S )

PROFESSIONAL PAPER 805 PLATE 16

FIGURES 1, 2.

3, 4.

5, 6.

8, 9.

10, 11.

12, 13.

PLATE 17

Sinospongophyllum sp. d.

Longitudinal and transverse thin sections (x 2), USN M 159312. Late
Early Devonian, Nevada Formation, unit 2; Devonian coral zone D1.
Locality M1037, south pediment slope, Lone Mountain, Eureka
County, Nev.

Sinospongophyllum sp. e.

Transverse and longitudinal thin sections (x 11/2), USNM 159313.
Early Middle Devonian, Nevada Formation, unit 2; Devonian coral
zone D2. Locality M1038, Lone Mountain, Eureka County, Nev.

Sinospongophyllum sp. (1.

Longitudinal and transverse thin sections (X 2), USNM 159314. Early ,
Middle Devonian, Nevada Formation, unit 2; Devonian coral zone
D2. Locality M1035, north end Antelope Range, southern Eureka
County, Nev.

Sinospongophyllum sp. f.

Transverse thin section ( X 2), USNM 159315. Early Middle Devonian,
Nevada Formation, unit 2; Devonian coral zone D2. Locality M3,
Grays Canyon, southern Eureka district, Nevada.

Sinospongophyllum sp. f.

Transverse and longitudinal thin sections (X 2), USNM 159316. Early
Middle Devonian, Nevada Formation, unit 2; Devonian coral zone
D2. Locality M1035, north end Antelope Range, southern Eureka
County, Nev.

Sinospongophyllum sp. e. .

Transverse and longitudinal thin sections (x 2), USNM 159317. Early
Middle Devonian, Nevada Formation, unit 2; Devonian coral zone D2.
Locality M1035, north end Antelope Range, southern Eureka County,
Nev.

Siphonophrentis (Breviphrentis) invaginatus (Stumm).

Transverse and longitudinal thin sections (x 2), USNM 94445. Holo-
type of Amplexus lonensis Stumm which is the type species of Brevi-
phyllum Stumm 1949. Nevada Formation, Lone Mountain, Eureka
County, Nev.

 

 

 

PROFESSIONAL PAPER 805 PLATE 17

BREVIPHRENTIS)

(

SIN OSPON GOPH YLL UM AND SIPH ON OPH REN TIS

GEOLOGICAL SURVEY

 

 

 

PLATE 18
FIGURES 1—4. Dendrostella romanensis n. sp.

Transverse and longitudinal thin sections of holotype (x 2), USNM
159318. Middle Devonian, Nevada Formation, Devonian coral zone D.
Locality M1031, southern Sulphur Spring Range, northwest of Romano
Ranch, Eureka County, Nev.
5, 6. Disphyllum eurekaensis n. sp.
Transverse and longitudinal thin sections of holotype ( x 4), USNM
159319. Early Middle Devonian, Nevada Formation, unit 2; Devonian
coral zone D2. Locality M1046, Lone Mountain, Eureka County, Nev.
7—10. Disphyllum nevadense (Stumm).
7—9. Transverse and longitudinal thin sections (x 4), USNM 159320.
Same horizon and locality as figures 5, 6.

10. Longitudinal thin section (x 4), USNM 159321. Same horizon and
locality as figures 5, 6.

 

 

 

GEOLOGICAL SURVEY

 

 

DEN DR OS TELLA AND DI SPH YLL UM

PLATE 19

FIGURES 1—9. Cystiphylloides lonense (Stumm).

1, 2. Calice and lateral views (x 1), USNM 159322. Early Devonian,
Nevada Formation, unit 1; Devonian coral zone C. Locality M74
Lone Mountain, Eureka County, Nev.

3,4. Lateral and calice views (X 1), USNM 159323. Early Devonian,
Nevada Formation, unit 1; Devonian coral zone C. Locality M286,
Lone Mountain, Eureka County, Nev.

5. Lateral view (X 1), USNM 159324. Same horizon and locality as
figures 3, 4.

6. Transverse thin section (X 2), USNM 159325. Same horizon and
locality as figures 1, 2.

7,8. Longitudinal and transverse thin sections (X 2), USNM 159326.
Same horizon and locality as figures 1, 2.

9. Longitudinal thin section (x 2), USNM 159327. Same horizon and
locality as figures 1, 2.

10, 11. Cystiphylloides Sp. (1.

Transverse and longitudinal thin sections (x 2), USNM 159328. Early
Middle Devonian, Nevada Formation, unit 2; Devonian coral zone
D2. Locality M36, Sulphur Spring Range, Nev.

12, 13. Cystiphylloides sp.

Transverse section and longitudinal section at calice (>< 11/2), USNM
159329. Early Middle Devonian, Nevada Formation, unit 2; Devonian
coral zone D2. Locality M1048, Lone Mountain, Eureka County, Nev.

)

 

 

PROFESSIONAL PAPER 805 PLATE 19

GEOLOGICAL SURVEY

 

 

C YS TI PH YLL OI DES

 

PLATE 20
FIGURES 1,2. Cystiphylloides sp.
Transverse thin section ( >< 11/2), longitudinal thin section ( x 2),
USN M M159330. Early Middle Devonian, Nevada Formation, unit 2;

Devonian coral zone D2. Locality M1051, south end Sulphur Spring
Range, Nev.

3, 4. Zonophyllum haguei n. sp.

Transverse thin section ( x 4), longitudinal thin section (x 2) of para-
type, USNM 159331. Early Middle Devonian, Nevada Formation,
unit 2; Devonian coral zone D2. Locality M51, Grays Canyon, south-
ern Eureka district, Nevada.

5, 6. Zonophyllum sp. a.

Longitudinal and transverse thin sections (x 2), USNM 159332. Early
Middle Devonian; Devonian coral zone D. Locality M1058, Nevada
Test Site, Frenchman Flat, Nev.

7, 8. Zonophyllum cf. Z. haguei n. Sp.

Longitudinal and transverse thin sections (X 2). Early Middle Devo-
nian, Nevada Formation, unit 2; Devonian coral zone D2. Locality
M1035, north end of Antelope Range, Eureka County, Nev.

9, 10. Zonophyllum haguei n. sp.

Transverse and longitudinal thin sections ( X 2) of holotype USNM

159333. Early Middle Devonian, Nevada Formation, unit 2; Devonian

coral zone D2. Locality M3, Grays Canyon, southern Eureka district,
Nevada.

11, 12. Zonophyllum Sp. b.

Transverse thin section ( x 2), longitudinal thin section ( x 4), USN M
159351. Same horizon and locality as figures 3, 4.

 

GEOLOGICAL SURVEY

PROFESSIONAL PAPER 805 PLATE 20

     

C YSTIPH YLLOIDES AND ZONOPHYLL UM

PLATE 21

FIGURES 1, 2. Mesophyllum (Mesophyllum) sp. b.

Two transverse thin sections (X 2), USNM 159334. Early Middle
Devonian, Nevada Formation, unit 2; Devonian coral zone D2. Local-
ity M36, southern Sulphur Spring Range, Nev.

3, 4. Mesophyllum (Mesophyllum) sp. 0.

Transverse and longitudinal thin sections (x 2), USNM 159335. Early
Middle Devonian, Nevada Formation, unit 2; Devonian coral zone D.
Locality M1035, north end Antelope Range, Eureka County, Nev.

5—7. Mesophyllum (Arcophyllum) kirki (Stumm).

Transverse and longitudinal thin sections (X 2) and enlarged trans-
verse thin section (X 4), USNM 159336. Middle Devonian, Nevada
Formation, unit 2; Devonian coral zone D3. Locality M29, Lone
Mountain, Eureka County, Nev.

 

PROFESSIONAL PAPER 805 PLATE 21

GEOLOGICAL SURVEY

 

 

MESOPHYLL UM AND MESOPHYLL UM (ARCOPHYLL UM )

 

 

 

 

 

PLATE 22

FIGURES 1—6. Mesophyllum (Arcophyllum) kirki (Stumm).

. Transverse thin section ( X 2), USN M 159337.

Transverse thin section ( x 2), USN M 159338.

Enlargement of transverse thin section ( x 4), USNM 159339.

Longitudinal thin section at calice (X 2), USNM 159340.

Longitudinal thin section ( x 4), USN M 159341.

. Longitudinal thin section ( X 2), USN M 159342.

Middle Devonian, Nevada Formation, unit 2; Devonian coral zone D3.
Locality M1036, northwest side of Lone Mountain, Eureka County,
Nev.

amewww

 

 

 

 

PROFESSIONAL PAPER 805 PLATE 22

GEOLOGICAL SURVEY

 

 

 

)

MESOPHYLLUM (ARCOPHYLL UM

 

 

 

PLATE 23

FIGURES 1—4. Cystiphylloides robertsense (Stumm).

Transverse, longitudinal, longitudinal, and transverse thin sections
(x 2), USNM 159343. Early Middle Devonian, Nevada Formation,
unit 2; Devonian coral zone D2. Locality M1046, Lone Mountain,
Eureka County, Nev.

5—10. Hexagonaria (Pinyonastraea) kirki (Stumm) n. subgen.

5,6. Transverse and longitudinal thin sections of holotype (x 2),
USNM 94456. Middle Devonian, Nevada Formation, unit 2;
Devonian coral zone D. Lone Mountain, Eureka County, Nev.

7. Upper surface of large colony (x 1), USNM 159344. Middle
Devonian, Nevada Formation, unit 2; Devonian coral zone D3.
Locality M1052, northwest side of Lone Mountain, Eureka
County, Nev.

8, 9. Transverse and longitudinal thin sections (X 2), USNM 159345.
Middle Devonian, Nevada Formation, unit 2; Devonian coral
zone D. Locality M1053, north end of Antelope Range, Eureka
County, Nevada.

10. Transverse print from stained cellulose peel ( x 2). Middle
Devonian, Nevada Formation, unit 2; Devonian coral zone D.
Locality M1054, south side of Cooper Peak, Roberts Moun-
tains, Nev.

 

GEOLOGICAL SURVEY

   
   

PROFESSIONAL PAPER 805 PLATE 23

 

10
CYSTIPHYLLOIDES AND HEXA GONARIA (PINYONASTRAEA)

FIGURES 1—3.

PLATE 24

Billingsastraea nevadensis (Stumm).

Longitudinal thin section (x 2), surface of colony (x 1), and transverse
thin section (X2), USNM 159346. Early Middle Devonian, Nevada
Formation, unit 2; Devonian coral zone D2. Locality M1055, north
end Antelope Range, Eureka County, Nev.

Billingsastraea nevadensis subsp. arachne (Stumm).

Upper surface of colony (X 1), USNM 94458. Early Middle Devonian,
Nevada Formation, unit 2; Devonian coral zone D2. Lone Mountain,
Eureka County, Nev. Copy of Stumm’s (1937, pl. 53, fig. 13) holotype
figure.

Billingsastraea nevadensis (Stumm).

Transverse thin section (x 3), USNM 159347. Early Middle Devonian,
Nevada Formation, unit 2; Devonian coral zone D2. Locality M1035,
north end Antelope Range, Eureka County, Nev.

Billingsastraea nevadensis (Stumm).

6. Longitudinal thin section ( X 4), USNM 159348.

7. Transverse thin section ( x 4), USNM 159349.

8. Longitudinal thin section ( x 4), USNM 159350.

Early Middle Devonian, Nevada Formation, unit 2; Devonian coral
zone D2. Locality M55, Lone Mountain, Eureka County, Nev,

24

 

          

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PROFESSIONAL PAPER 805 PLATE

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GEOLOGICAL E URVEY

 

BILLINGSASTRAEA

FIGURES 1—4.

6—9.

10.

PLATE 25

Australophyllum landerensis n. sp.
1, 2. Transverse thin section (X 2%) and longitudinal thin section
( >< 21/2) of holotype USNM 159353.
3, 4. Longitudinal and transverse thin sections ( x 2) of paratype
USNM 159354.

Early Devonian, Rabbit Hill Limestone. Locality M1150, north end of

Toquima Range.
Australophyllum sp.

Transverse thin section (X 2). Upper Silurian or lowermost Devonian
just above Silurian coral zone E, upper unit of Vaughn Gulch Lime-
stone. Locality M1093, Mazourka Canyon, northern Inyo Mountains,
Calif.

Billingsastraea? sp. T.

6, 7. Transverse thin sections ( X 2, X 3).

8, 9. Longitudinal thin sections ( X 3) .

All sections cut from same colony. Middle Devonian. Locality M1151,
Reeds Canyon area, Toiyabe Range.

('2) Hexagonaria sp. _
Transverse thin section ( x 2). Same locality and horizon as figures 6—9.

 

 
   

PROFESSIONAL PAPER 805 PLATE 25

 

 

A USTRALOPHYLL UM, BILLINGSASTRAEA?, AND (?)HEXAGONARIA

U. S. GOVERNMENT PRINTING OFFICE: 1974 O - 534-041

 

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LIBRARY

Geology of the
Chewelah—Loon Lake Area,

Stevens and Spokane Counties,
Washington

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 806

Prepared in cooperation with the
Washington Division of Mines and Geology

 

 

   
 
  
 

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Geology of the
Chewelah—Loon Lake Area,

Stevens and Spokane Counties,
Washington

By FRED K. MILLER and LORIN D. CLARK

With a section on POTASSIUM-ARGON AGES
OF THE PLUTONIC ROCKS

By JOAN C. ENGELS

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 806

Prepared in cooperation with the
Washington Division of Mines and Geology

 

 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1975

!__J

 

 

UNITED STATES DEPARTMENT OF THE INTERIOR

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY

V. E. McKelvey, Director

Library of Congress catalog-card No. 7 3-6003 14

 

 

 

For sale by the Superintendent of Documents, US. Government Printing Office
Washington, DC. 20402 — Price $2.15 (paper cover)
Stock Number 2401-02587

l_

CONTENTS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

     
  

 

 

 

   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Page Page
Abstract ...... 1 Paleozoic rocks—Continued
Introduction . 1 Carbonate rocks—Continued
Location and accessibility .................................................. 1 Devonian or Mississippian carbonate rocks—Con.
Previous work 2 Unit 2 . 30
Present work 3 Unit 3 . 31
Acknowledgments 3 Mississippian carbonate rock .................................... 31
Regional geologic setting ---------------------------------------------------- 4 Paleozoic carbonate rocks, undivided ...................... 32
Precambrian rocks ----------- 4 Mesozoic plutonic rocks . 33
Belt Supergroup . ------------ 4 Flowery ‘Trail Granodiorite .............................................. 34
Prichard Formation ---------------------------------------------------- 4 Starvation Flat Quartz Monzonite ............................... 38
Ravalh Group . - 6 Phillips Lake Granodiorite (and associated dikes).... 40
Burke Formation --------------------------------------------- 6 Two-mica quartz monzonite .............................................. 44
Revett Formation. -------- 7 Coarse-grained quartz monzonite ...................... 45
St- Regis Formation ----------- 8 Muscovite quartz monzonite ..................................... 46
Wffllafl‘l” FGormation """""""""""""""""""""""""""" 1i) Cenozoic plutonic rocks ................................. 47
Missgt 'apedroPupk F rmati 11 Silver Point Quartz Monzonite ........................................ 47
r1 ea ° on """""""""""""""""""""""" Granodiorite 50
Member a """""""""""""""""""" 12 Fine-grained quartz monzonite ........................................ 50
Member b """"""""""""""""""""""""" 12 Difierentiation of the plutonic rocks ........................................ 51
Member c ......................... 13 . .
Potassrum—argon ages of the plutomc rocks, by Joan C.
Member d ...................................................... 16
Deer Trail Group .- 16 Engels 52
Togo (-2) Formation __________________________________________________ 17 Cenolcficf:i hyiplabyssal, volcanic, and sedimentary rocks ........ 58
Edna Dolomite 17 A adc _ 1 es 58
McHale Slate 17 B” 55‘“ 2°
Stensgar Dolomite ...................................................... 17 L321}: F t’ 6(1)
Buflalo Hump(?) Formation ....................... 18 anglomfgg 1°“ 61
Deer Trail Group, undivided .................................... 18 . . . . .
Relation between the Belt Supergroup and the Glacial, alluvral, and talus depos1ts, undlfferentlated... 61
Deer Trail Group 18 Structure _ 62
Metamorphic rocks, undivided ________________________________________ 24 Structures in the Belt Supergroup block ........................ 62
Windermere Group .. .. 24 Folds 62
Huckleberry Formation ............................................ 24 Faults , ----- 64
Monk Formation ________________________________________________________ 26 Structures in the Deer Trail Group block .................... 65
Paleozoic rocks 27 Other differences between the two blocks ..... 66
Addy Quartzite 27 Structure separating the two blocks ................................ 67
Carbonate rocks 29 Other faults 69
Metaline Formation ............................................... 29 Mineral deposits 69
Devonian or Mississippian carbonate rock ____________ 30 References cited 71
Unit 1 . . 30 Index 73
ILLUSTRATIONS
Page
PLATE 1. Geologic map of the north half of the Chewelah—Loon Lake area, Stevens and Spokane Counties,
Washington In pocket
2. Geologic map of the south half of the Chewelah—Loon Lake area, Stevens and Spokane Counties,
Washington In pocket
FIGURE 1. Index map showing location of Chewelah—Loon Lake area 2
2. Map showing location of some geographic features referred to in the text 3
3. Generalized columnar section of the Prichard Formation . V 5
4. Generalized columnar section of member c of the Striped Peak Formation on Quartzite Mountain ....................... 14

III

IV

FIGURE 5.

10.

12—15.

16.
17—21.

22.

24.

TABLE

h

 

 

 

 

 

 

 

 

 

 

 

 

 

CONTENTS
Page
Photograph showing argillite and breccia from member 0 of the Striped Peak Formation .......................................... 14
Photograph showing soft-sediment breccia in the McHale Slate, probable correlative of member c of the
Striped Peak Formation . . ............................ 15
Columnar sections showing possible correlations between the Deer Trail Group and the Belt Supergroup ............ 21
Generalized geologic map showrng the dlstributron of the Belt Supergroup and Deer Trall Group In and
around the Chewelah—Loon Lake area .. ........ 22
Photograph showing the bold cliffs (dip slopes) of Addy Quartzite which form the west side of Quartzite
Mountain .............................................. . ...... 27
Photograph showing the contact between the Addy Quartzite and member (1 of the Striped Peak Formation .......... 27
Ternary plots of modes of plutonic rocks ................................................................................................................................ 34

Photographs showing:
12. Fine-grained dike-form mass of graphically intergrown rock that intrudes the Starvation Flat
' Quartz Monzonite ...................................................
13. Stained slab of Phillips Lake Granodiorite ..............
14. Stained slab of Silver Point Quartz Monzonite and granodiorite
15. Silver Point Quartz Monzonite .....................................................
Map showing potassium-argon sample localities ............
Graphs showing:
17. Changes in apparent ages of hornblende, biotite, and muscovite in an older pluton intruded by a

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

 

 

 

 

 

 

 

 

younger one .. .. ....... . 55
18. Apparent ages of hornblende and biotite from the Flowery Trail Granodiorite ............................................... 55‘
19. Apparent ages of muscovite and biotite from the Phillips Lake Granodiorite and associated dikes .............. 56
20. Relation of apparent ages to concentration of clean-clear hornblende in the fine-grained quartz
monzonite ......... 57
21. Plots of mafic dike modes .. .............................................................................. 58
Map showing location of major fold axes in the Belt Supergroup block ....................................................................... 63
Sketch map showing alternate interpretations of the relation of the Addy Quartzite to the
northwest-trending faults between Eagle Mountain and Jumpofl" Joe Mountain ................................................ 64
Cross sections showing possible interpretations of thrust relations between the Belt Supergroup
and Deer Trail Group ..... .. . . .. ........ . 68
TABLES
1. Chemical analyses and CIPW norms of basalt and one tufl'aceous rock from greenstone of the Page
Huckleberry Formation .. ............................. 25
Petrographic data on plutonic rocks ........................................................................... 35

 

 

Potassium-argon data on plutonic rocks ........ . __ 53
Mineral composition of selected mafic dikes . ......

 

 

FED.”

GEOLOGY OF THE CHEWELAH—LOON LAKE AREA,
STEVENS AND SPOKANE COUNTIES, WASHINGTON

By FRED K. MILLER and LORIN D. CLARK

ABSTRACT

The report area, two 15-minute quadrangles, is in the south-
ern part of Stevens County and the northern part of Spokane
County, about 30 miles north of Spokane. Much of the area is
underlain by two great Precambrian sections—the Belt Super-
group and the Deer Trail Group. The Deer Trail Group
appears to be equivalent to the upper part of the Belt Super-
group, although differences in thickness and stratigraphy sug-
gest that the sites of deposition of the two sections were much
farther apart than the sections are now. The Precambrian
Huckleberry Formation and Monk Formation unconformably
overlie the Deer Trail Group, but not the Belt Supergroup.
Both Precambrian groups are overlain by the Cambrian Addy
Quartzite. Cambrian, Devonian, and Mississippian carbonate
rocks are found above the Addy Quartzite where it overlies the
Belt Supergroup.

Nine plutons, representing three periods of plutonic activity,
intrude the Precambrian and Paleozoic rocks. They range in
composition from granodiorite to alkali-rich quartz monzonite.
The oldest is the Flowery Trail Granodiorite, an isolated pluton
near the center of the area. It appears to have been intruded
about 200 million years ago. Five others, mainly in the northern
part of the area, were intruded about 100 million years ago, and
intrusion of the remaining three, the Silver Point Quartz Mon-
zonite and two small satellitic plutons in the southern part of
the area, apparently climaxed plutonic activity about 50 million
years ago.

Andesite of Oligocene(?) age occurs in one small area south-
west of Chewelah. Yakima-type(?) flows of the Columbia River
Group are preserved at lower elevations in the southern part
of the area. Small patches of conglomerate, possibly of Tertiary
age, unconforrnably overlie the Huckleberry Formation south-
west of Chewelah and the Starvation Flat Quartz Monzonite
near Cliff Ridge. Quaternary glacial and alluvial deposits cover
large parts of the west half of the area at lower elevations.

The Belt Supergroup and the Deer Trail Group appear to
be confined to different structural blocks that are separated by
a major structural discontinuity. The chief structures of the
Belt Supergroup block, which underlies most of the eastern
part of the area, are a roughly north-south-striking anticline
and syncline. Both folds are overturned to the west in the
northern part of the area. Six large northwest-striking high-
angle faults appear to predate the folding and are probably
Precambrian. Although the sense of movement on these faults
is not well established, five show apparent left-lateral slip, and
one shows apparent right-lateral slip. The five could well be
dip-slip faults that have displaced rocks on the north sides
downward relative to the south sides.

The north-south folds and northwest faults of the Belt Super-
group block are apparently truncated by the Deer Trail Group
block, which underlies the western part of the area and strikes

 

N. 30°—40° E. The consistency of the different trends of, and
in, the two blocks and the apparent differences in facies and
thickness of probably equivalent rocks in each block suggest
that the blocks have been juxtaposed along a thrust fault.

High-angle faults, which are found in both structural blocks,
strike about N. 50°—60° E. and have displaced rocks on the
south sides downward relative to the north sides, These faults
may be contemporaneous with a set of approximately north-
south-striking faults which are inferred along the east side of
the Colville River valley.

The major thrusting is interpreted as having taken place less
than 100 million years ago. The inferred north-south faults on
the east side of the Colville River valley appear to cut the 50-
million-year-old Silver Point Quartz Monzonite but do not
offset the Miocene and Pliocene Columbia River Group.

INTRODUCTION
LOCATION AND ACCESSIBILITY

The report area, which coincides with the east half
of the Chewelah 30-minute quadrangle, covers about
400 square miles of Stevens and Spokane Counties in
northeastern Washington (fig. 1). Although the 30-
minute topographic map is now out of print, 7 1/2 -minute
topographic coverage is available for the entire quad-
rangle. The north half of the report area comprises the
Calispell Peak, Cliff Ridge, Chewelah, and Goddards
Peak 71/2-minute quadrangles, and the south half the
Nelson Peak, Valley, Springdale, and Deer Lake quad-
rangles. In addition, the north half is topographically
mapped at a scale of 1 : 62,500 and is named the Chewe-
lah Mountain quadrangle.

Figure 2 shows the location of the report area in
relation to Spokane, the nearest major city, and in
addition shows many of the geographic features fre-
quently referred to in the text. South of Chewelah, the
west edge of the area follows the west edge of the Col-
ville Valley, and the east border roughly follows the
divide separating the Colville and Pend Oreille River
valleys.

Most of the roads in the area are unsurfaced. Numer-
ous county, logging, and mining dirt roads provide easy
access to all parts of the area except the northeast
corner. The Burlington and Northern Railroad links
Chewelah, Valley, Springdale, and Loon Lake with

1

2 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

////:/ 16 49°
37/

   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Spokaneo

 

 

 

 

 

 

1 WASHINGTON I}

— ,._.—J

K/-———”

0 10 20 MILES

EXPLANATION

 

 

Completed work

 

 

 

 

Work in progress

Togo Mountain quadrangle — R. C. Pearson

Orient area — Bowman (1950)

Northport area — R. G. Yates

Deep Creek area — Yates (1964)

Kettle Falls area (west of river) — C. D. Campbell

Kettle Falls area (east of river) — J. W. Mills

Colville area -— W. A. G. Bennett

Twin Lakes quadrangle — G. E. Becraft

lnchelium quadrangle — A. B. Campbell

10. Bead Lake area — Schroeder (1952)

11. Wilmont Creek quadrangle — Becraft (1966)

12. Hunters quadrangle —Campbell and Raup (1964)

13. Turtle Lake quadrangle — Becraft and Weis (1963)

14. Mt. Spokane quadrangle — A. E. Weissenborn

15. Greenacres quadrangle — Weis (1968)

16. Metaline area — Dings and Whitebread (1965)

17. Magnesite belt — Campbell and Loofbourow
(1962)

18. Newport 30-minute quadrangle (includes remapping

area 10) — F. K. Miller

5953395999.“?

FIGURE 1.—Location of the Chewelah—Loon Lake area and surrounding areas for which geologic maps at a scale of 1: 62,500
or larger are available or mapping is in progress. Date indicates published report available; see list of references in

text.

Spokane to the south, and Nelson, British Columbia,
to the north.

PREVIOUS WORK

e

Weaver (1920), in a comprehensive report on the
mineral resources of Stevens County, published the
first geologic map of the area and attempted to estab-
lish a stratigraphic section. Jones (1928) mapped the
Chewelah 30-minute quadrangle in considerably more
detail than Weaver. He retained most of Weaver’s units,
difierentiated several more, and recognized the con-
glomerate at the base of the Huckleberry Formation.
Studies since Jones’ have concentrated‘mainly on the
northeastern Washington magnesite belt, immediately
west of the report area (fig. 2). The magnesite belt is
underlain by many of the Precambrian and lower Pale-
ozic units found in the report area.

Bennett (1941) prepared the first good geologic map
of the magnesite belt. He improved on earlier struc-
tural and stratigraphic interpretations, and he assigned
a Precambrian age to the thick section of fine-grained

 

elastic and carbonate rock beneath the Huckleberry
Formation. Besides mapping in the magnesite belt,
Bennett prepared a map of the south half of the Colville
30-minute quadrangle, a generalized version which
appeared in Mills and Yates’ report on high-calcium
limestone (1962, pl. 6).

Campbell and Loofbourow ( 1962) prepared a
detailed geologic map of the entire magnesite belt and
assigned all rocks beneath the Lower Cambrian Addy
Quartzite to the Precambrian. They also compared the
rocks of the Deer Trail Group with those of the Belt
Supergroup (p. F20).

Campbell and Raup (1964) mapped the Hunters
quadrangle, which covers most of the southwestern part
of the magnesite belt. Their map, although at a slightly
smaller scale than Campbell and Loofbourow’s, is more
detailed.

Schroeder (1952) mapped an area about the size of
a 15-minute quadrangle around Bead Lake, east of the
report area (fig. 2). He correlated parts of a thick sec-
tion of quartzites, argillaceous sandstones, and argil-

vv

 

INTRODUCTION 3

117°30'

METALINR
30' QUADRANGLE

1 18°00'

   
 
 
  
 
 
 
  
  
  
   

 

COLVlLLE
30' QUADRANGLE_
CHEWELAH NEWPORT
30' QUADRANGLE 30’ QUADRANGLE
‘ Calispell Peak
“if . .x
caidge Phctllzps Lake
i v .
c’ ewe” Johnson Mountain
>(6WIlson Mountain

48° 30'

   
 
 
 
    

 

  

Eagle Mountain
fijGoddards Peak

>< xChewelah Mountain
Quartzite Mountain

><Nelson Peak

 
 

0
st .
Jumpoff Joe Mountain
“V

JumpoffJoe Lake x LgDeerlLake «Horseshoe Lake

   

 

 

 

 

XD xBIue Grouse Mountain
. eer Lake Mountain
Spnngdale o x I “\Fan Lake
Loon Lakgfi Loon Lake x .
Mountain Elatka Lake
48° 00'
CLAYTON
QUADRANGLE
0 1O 20 MILES

 

 

Pertd

PACK SADDLE
MOUNTAIN
QUADRANGLE

CLARK FORK
QUADRANGLE

 

 

 

 
     
   
   
 

Coeur d’Alene

Lake WEST END

OF COEUR
D' ALENE
DISTRICT

 

FIGURE 2.—Location of some geographic features referred to in the text.

lites there with the Prichard Formation and the Ravalli
Group of the Belt Supergroup. This section of Belt
rocks is the nearest one to the report area that has been
relatively well studied. Pre-Tertiary sedimentary rocks
known to exist between the report area and the Bead
Lake area probably consist entirely or in part of Belt
rocks also (A. B. Griggs, oral commun., 1967).

PRESENT WORK

Work in the report area began in June 1962 as
a cooperative project of the Division of Mines and
Geology of the Washington Department of Natural
Resources and the US. Geological Survey. The authors
mapped most of the Chewelah Mountain quadrangle
in 1963 and 1964. Miller finished the mapping in 1965

 

with the help of J. C. Moore. Mapping of the southern
15-minute quadrangle was begun by Miller in 1966,
continued with the help of R. C. Reynolds in 1967, and
completed in 1968. Two preliminary geologic maps have
been published by the Washington Division of Mines
and Geology (Clark and Miller, 1968; Miller, 1969).

ACKNOWLEDGMENTS

The authors would like to thank Mr. Phillip P. Skok
for his cooperation and help during the study of the
mines in the Eagle Mountain area. Mr. Skok, repre-
senting several of the mine owners, very generously
allowed many of the company mine maps to be dupli-
cated in the Chewelah Mountain quadrangle prelimi-
nary report.

 

 

4 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

We are particularly indebted to Allan Griggs, of the
US. Geological Survey, who introduced us to the Belt
Supergroup in the Coeur d’Alene district and then
helped with many of the stratigraphic problems we
encountered in the Belt Supergroup in the Chewelah—
Loon Lake area. We are grateful for the professional
courtesies extended by Marshall Huntting, W. A. Ben-
nett, and Jerry Thorson of the Washington Division
of Mines and Geology, who helped in all aspects of the
project from the fieldwork to the final editing. Bennett’s
intimate knowledge of the region saved both authors’
time and effort on more than one occasion and several
times directed us to pertinent features we might other-
wise not have found. Finally, we would like to express
our appreciation to Robert G. Yates and the late Arthur
B. Campbell, of the US. Geological Survey, who helped
us to become acquainted with the regional geology of
northeastern Washington.

REGIONAL GEOLOGIC SETTING

In an excellent summary of the regional geology of
northeastern Washington, northern Idaho, and north-
western Montana, Yates, Becraft, Campbell, and Pear-
son (1966, p. 47) recognized an eastern and a western
geologic province, divided by the Columbia River val-
ley. They defined the eastern province as characterized
by Precambrian Belt and Windermere rocks and mio-
geosynclinal lower and middle Paleozoic rocks, and the
western province as composed of eugeosynclinal upper
Paleozoic and Mesozoic rocks. The report area lies
about 15—20 miles east of the boundary between the
two provinces.

Both provinces are underlain by numerous bodies of
Mesozoic plutonic rock, which Yates, Becraft, Camp-
bell, and Pearson (1966, p. 56) divided into two major
batholiths. As they have defined the boundaries of these
batholiths, the report area includes parts of both batho-
liths. Most of the extensive basalts of the Columbia
River Group lie south of the report area, although a few
prongs extend into the southern part.

Broad open folds and high-angle normal faults which
trend north-northwest are found in the Montana part
of the eastern province. The complexity of the structure
increases towards the west, and in Idaho west-north-
west-trending strike-slip faults and locally overturned
folds appear (Yates and others, 1966, p. 52).

In northeastern Washington, the folding and faulting
are noticeably more complex and irregular. In the
report area, strike-slip faults, thrust faults, and locally,
large overturned folds are cut by northeast- and north-
striking high-angle dip-slip faults. The major move-
ments probably occurred in the Precambrian, middle
and late Mesozoic, and early Tertiary.

 

PRECAMBRIAN ROCKS
BELT SUPERGROUP

The Belt Supergroup is a well-known section of Pre-
cambrian sedimentary rocks extensively exposed in
western Montana, northern Idaho, and eastern Wash-
ington. In Canada it is known as the Purcell Series.
It is generally divisable into a carbonate-rich eastern
facies and a more clastic western facies. Many forma-
tions, some of which are correlative, have been named
and delineated by various workers. The large number
of Belt units, confusing to many who have not studied
these rocks, is an indication of the complexity of the
internal stratigraphy of the group. Detailed strati-
graphic descriptions and measured sections of the Belt
rocks are difficult or impossible to obtain in the report
area because of poor exposures and extensive forest
cover.

The report area contains the westernmost exposures
of the Belt Supergroup. If the Deer Trail Group is cor-
relative with part of the Belt, however, the Belt terrane
extends about 15 miles further west.

PRICHARD FORMATION
DISTRIBUTION AND TOPOGRAPHIC EXPRESSION

The Prichard Formation is a thick sequence of inter-
bedded argillite, siltite, and fine-grained quartzite. It
underlies 38 square miles in the report area. An addi-
tional 12 square miles is covered by surficial deposits
or occupied by younger plutons. About 13,000 feet of
the formation is exposed in the core of a large, highly
faulted anticline, which occupies the entire east-central
part of the report area. Only the west half of the anti-
cline is found here, but reconnaissance of the rocks to
the east suggests that Belt strata continue in that
direction and that much of the other half may have
been replaced by plutons. The southeast limb of the
fold may be exposed along the west shore of Horseshoe
Lake about 7 miles east of Deer Lake. There, a thick
section of dark laminated argillite, strongly resembling
the upper part of the Prichard Formation, strikes north-
east and is truncated by plutonic rocks just north of
the lake.

The Prichard Formation was originally named the
Prichard Slate by Ransome (1905, p. 280—281) for the
exposures along Prichard Creek in the Coeur d’Alene
district, Idaho, where the unit, consisting chiefly of
argillite and well-indurated sandstone, was estimated
to be more than 8,000 feet thick. The base has not been
found in the report area or anywhere else.

The formation forms much of the higher mountain-
ous country along the east border of the area. Although
they do not crop out as well as the argillite, the quartz-

 

———7

PRECAMBRIAN ROCKS 5

itic parts of the formation are probably responsible for sum: of

the rugged topography formed by the unit. The road Burke Formation
along the high ridge crest between Chewelah Mountain ,
and Nelson Peak traverses quartzite for much of its
length. J oint-bounded blocks of all sizes litter the areas
underlain primarily by quartzite, but almost all have
been heaved, rotated, or otherwise moved by surface
or near-surface processes. In-place outcrops are abund-
ant in areas underlain by predominantly argillitic parts
of the formation, but topographic expression is more

subdued. EXPLANATION

Upper member

ll

STRATIGRAPHY AND THICKNESS

The Prichard Formation can be divided into at least
three members in the report area. Although they have
not been distinguished on the geological map because
of lack of time, for descriptive purposes they are inform-
ally referred to as the upper, middle, and lower mem-
bers in the following paragraphs. The upper member
(fig. 3) is predominantly dark-gray to black laminated
argillite, with a lesser amount of siltite, and contains

Argillite

  
 

 

Ouartzite

Middle member

 

 

only an occasional bed of quartzite. The middle member
consists of interbedded siltite, quartzite, and minor
argillite. The lower member probably consists of about
6,000 feet of interbedded siltite and argillite, although
information is available only from sparse outcrops and F330
float.
The upper member is locally divisible into three sub-
units, in descending order: 600 feet of argillite, 800 feet 3000
of siltite, and 3,000 feet of argillite. All the argillite in
the upper member is well bedded to laminated and light
to dark gray; locally it contains thin bleached zones, . Th‘ 2000
whose shape and orientation seem to be controlled by 2 52:31:):er
bedding. Very little quartzite or siltite is interbedded 0:. known and
within any of the argillite of the upper member. The 5 WOW exPOSedl 1000
siltite subunit is fairly distinctive owing to its color, 3 2:512:23: —re-
gray to dull yellowish gray, and its thick indistinct 'J petitive lithol-
bedding, vivid contrasts with the relatively dark lami- 09195 as {Ound
nated argillite zones above and below. The subunit also above 0
includes a number of quartzite and argillite beds. The
lower argillite subunit is generally darker than the l
upper one. It is the thickest relatively pure argillite Lg,
zone in the report area. Base ”0‘
The transition into the quartzitic middle member of ”posed
the Prichard Formation begins about 4,400 feet from FIGURE 3-‘Genel'alized mlumnar seetion 0f the

the top of the formation, where quartzite and siltite PriChard Fo’mation. in the Chewelah—hon
Lake area. Lower, middle, and upper members

beds start becoming thicker and more numerous (fig. are informal subdivisions and are not shown
3). The base is also a transition zone. The average on the geological maps.

thickness of the member is about 3,200 feet thick.

Although it probably consists of ab out 50 percent lighter colored than the argillite of the upper member.
quartzite, numerous zones within the member are simi— The quartzite is light gray to white, fine grained, and
lar to the transition zone at the top. Relatively pure vitreous. All gradations from quartzite to white siltite
argillite zones as much as several hundred feet thick are found. Beds of both quartzite and siltite average
also are found in this member, but most are distinctly between 1 and 5 feet in thickness and weather out in

 

fi

6 CHEWELAH-LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

large joint-bounded blocks. In general the more siltitic
to argillitic the rock, the thinner the beds.

The lower member only occurs east of the divide that
connects Chewelah Mountain and Nelson Peak. Scat-
tered outcrops, a few exposures in logging roadcuts, and
sparse float suggest that it is composed of the same
recurring lithologies as the other members but that
siltite and argillite are predominant.

The top of the Prichard Formation in the report area
is defined as the top of the highest 600-foot-thick argil-
lite zone beneath the quartzite, siltite, and argillite
transition beds of the Burke Formation. This is con-
trary to the placement of the Prichard-Burke contact
in most other Belt sections and should be taken into
consideration when the thicknesses of the Prichard and
Burke Formations are compared with those in other
sections, especially the relatively near well-studied
sections around Pend Oreille Lake and in the Coeur
d’Alene district. The upper part of the Prichard Forma-
tion in the report area appears to be more akin to that
at Pend Oreille than that around Coeur d’Alene.

Most workers agree that the bulk of the Belt Super-
group was deposited in shallow water (Ransome and
Calkins, 1908, p. 17; Yates and others, 1966, p. 47;
Hobbs and others, 1965, p. 33). Hobbs, Griggs, Wallace,
and Campbell (1965, p. 33) interpreted the relatively
clean, well-sorted quartzites at various levels in the sec-
tion to be suggestive of a nearshore environment. Others
have pointed out that-most of the sedimentary struc-
tures in the Prichard Formation are confined to the
uppermost part (Campbell, 1960, p. 552; Campbell and
Good, 1963, p. A8; Hobbs and others, 1965, p. 34).

In the report area, both ripple marks and mud cracks,
although not abundant, have been observed in the
upper part of the highest member. Cross laminations
and graded bedding on a fine scale are found through-
out the forrnation but are quite subtle. The pyrite
and pyrrhotite and accompanying stained surfaces
described by almost all investigators are also found in
the report area.

Several sills of greenish-black amphibolite are found
in the middle and lower members of the formation.
They have been thoroughly recrystallized, probably
from diabase, and the primary texture has been com-
pletely destroyed. Although they appear to have caused
only slight recrystallization of the host rocks, they seem
to have “set up” the rocks for metamorphism by later
intrusive bodies. In the vicinity of younger plutonic
rocks, the siltite and argillite adjacent to the sills show
pronounced recrystallization two to three times as far
from the plutonic contact as other rocks of comparable
composition not located near the sills. Most of the sills
appear to be strikingly concordant, with the possible
exception of the large body northeast of Chewelah

 

Mountain. This sill may be discordant, as it appears to
be higher in the section in the northern part of the area.
It is difficult to be certain, however, because of the
strong overturning in this area and because of the possi-
bility of additional undetected structures.

RAVALLI GROUP
BURKE FORMATION

DISTRIBUTION AND THICKNESS

The Burke Formation consists primarily of light-gray
siltite with lesser amounts of argillite and quartzite. It
crops out in patches along a belt extending from east
of Deer Lake northward to the South Fork of Chewelah
Creek. The belt is offset by many northwest-trending
faults.

The Burke Formation was named and first described
by Ransome (1905, p. 280—281) and Ransome and
Calkins (1908, p. 32) for the exposures around the
town of Burke in the Coeur‘ d’Alene district. They
reported a section about 2,000 feet thick “composed
of rocks that show all gradations from nearly pure
quartzite to siliceous shale.” Hobbs, Griggs, Wallace,
and Campbell (1965, p. 34) reported a similar thickness
but also found that it varied from place to place in the
district, generally thickening to the west.

The Burke Formation averages about 3,700 feet in
thickness in the report area. Miller (1969, p. 1) errone-
ously reported an average thickness of 4,500 feet, which
was calculated for the thickest exposed section of the
formation, located along the margin of the major valley
northeast of Deer Lake. Other thicknesses have been
calculated; the minimum, 3,100 feet, was calculated
for a section north of Goddards Peak. Although some
thickness variation may actually exist, most of it is due
to differences in where the contacts are placed, especi-
ally the upper one.

STRATIGRAPHY

The Burke consists mostly of light- to medium-gray
siltite. The basal zone, 150 feet of alternating argillite
and siltite, forms a transition between the argillite of
the underlying Prichard and the siltite of the Burke.
About 500 feet above the contact, the siltite grades into
a quartzite zone approximately 300 feet thick. This
quartzite zone, in turn, grades upward into a predom-
inantly siltite section. Zones of quartzite or argillite as
much as a few tens of feet thick are interlayered with
the siltite, mostly in the lower half of the formation.
The upper 400 feet is the only other part of the unit
that contains a significant proportion of quartzite.

About 3,000 feet above the base is a distinctive 100—
300-foot-thick zone of maroon to lavender argillite,
siltite, and quartzite, an almost perfect duplicate of

 

——————i

PRECAMBRIAN ROCKS 7

typical St. Regis lithology. The argillitic parts of the
zone contain mud cracks, mudchip breccias, and ripple
marks. The quartzite is very fine grained and in places
coarsely laminated. Laminations average about an
eighth of an inch thick and exhibit fine planar cross-
bedding internally.

Much of the Burke Formation, particularly the
siltite, is medium to light gray with a subtle, barely
noticeable purple cast. Some of the argillite beds in the
uppermost and lowermost parts of the Burke Forma-
tion have a gray- green cast, as does some of the siltite.
This coloration is restricted to specific parts of the
Burke here but appears to be typical of much of the
formation at Coeur d’Alene (Hobbs and others, 1965,
p. 35) and Pend Oreille (Harrison and J obin, 1963, p.
K10). The light-weathering rind on Burke siltite
described at both of the just-mentioned localities is
present in the report area but is not nearly as well
developed nor as extensive.

Beds range in thickness from less than 1 inch to more
than 10 feet but commonly are about 6—12 inches thick.
In general, the finer grained rocks form the thin beds,
and the relatively coarser grained rocks the thick beds.
Argillite, particularly in the uppermost and lowermost
parts' of the formation, appears to constitute a larger
proportion of the section than it actually does. This
is because thin argillite beds and partings form skins
on large exposures of bedding surfaces.

Oscillation and current ripple marks are loCally
abundant in the upper part of the formation. Some
quartzite strata at various horizons are crossbedded,
and much of the siltite is finely cross laminated. In
some layers the fine but somewhat indistinct lamina-
tions in the siltite are broken and disrupted, presum-
ably by slumping or some other form of contemporane-
ous deformation.

The mineralogy of the Burke Formation, like that of
the other Belt units, is relatively simple. Quartz, seri-
cite, plagioclase, potassium feldspar are the most com-
mon minerals, generally in that order of abundance.
Zircon, the most common heavy mineral, is found
throughout the formation. Small magnetite crystals
are also common.

REVE'IT FORMATION

DISTRIBUTION AND THICKNESS

The Revett Formation is predominantly white to
light-gray fine-grained quartzite. Within the report
area, the distribution of the Revett is similar to that
of the Burke Formation. It parallels the latter and is
disrupted about equally by the same cross-faults. East
of Deer Lake, the formation continues to the southeast,
but a few miles outside the area it bends to the east

 

 

 

 

and terminates against a crosscutting intrusive body.

The Revett Formation was initially named the Rev-
ett Quartz‘ite by Ransome (1905, p. 280—281) and
Ransom and Calkins (1908, p. 35) in the Coeur d’Alene
district, Idaho. Harrison and Campbell (1963, p. 1418) ,
in a discussion of correlation problems within the Belt
Supergroup, noted that the Revett is no more homo-
geneous than any other Belt formation in northern
Idaho or western Montana and suggested that the
name be changed to Revett Formation. Their observa-
tion regarding the inhomogeneity of the quartzite is
quite apparent in the report area, and the new name
they suggest will be used in this report.

Poor exposures prevent detailed measurement of any
Revett sections in the report area, although from out-
crop width the thickness of the formation appears to
vary little from an average of about 3,100 feet. As
Hobbs, Griggs, Wallace, and Campbell (1965, p. 37)
pointed out, however, at least part of the discrepancies
in thickness of the Revett Formation from place to
place may be due to differences in the way that its con-
tacts have been placed by different workers.

STRATIGRAPHY AND LITHOLOGY

Most of the Revett Formation in the report area is
composed of fine-grained conspicuously clean looking
vitreous quartzite. Although, as Harrison and Campbell
pointed out, the Revett Formation is probably as heter-
ogeneous as any other formation in the Belt Super-
group, the clean looking quartzite beds that character-
ize the Revett contrast rather strikingly with the pre-
dominantly impure clastics of the other formations.

In the report area, the depositional boundaries be-
tween all formations are transition zones, rather than
sharp contacts. The transition zone between the Burke
Formation and the overlying Revett Formation is the
widest in the Belt Supergroup in the report area. The
same criteria used by Hobbs and others (1965, p. 35)
to draw the contact in the Coeur d’Alene district are
used in this area; the base of the Revett Formation is
the horizon above which beds of vitreous quartzite pre-
dominate over siltite beds. In the south half of the
area, the transition zone has been reported to be about
200 feet thick (Miller, 1969, p. 1). In the northern half,
where the contact zone is better exposed, as on Jay
Gould Ridge east of Chewelah, this zone is closer to
400 feet thick.

The lower 200—300 feet of the Revett Formation
contains a fair proportion of siltite beds. These beds
decrease upward in number and, less consistently, in
thickness. Above the siltitic base is about 1,000 feet of
relatively pure vitreous quartzite. Even in this interval,
however, there are both single and multiple beds of
siltite.

t

8 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

Near the middle of the formation is about 500 feet
of interbedded siltite, siltitic quartzite, and quartzite.
The rocks of this zone are almost identical with the
bulk of the Burke Formation and, lacking continuity
with the more distinctive rocks above and below, could
easily be erroneously assigned to the Burke Formation.
Just below this zone is 50—100 feet of dark, banded
quartzite, some of which shows signs of crossbedding.
This quartzite is fine grained but coarser than most
in the formation.

The middle siltitic part of the Revett Formation is
overlain by a thick quartzite zone that contains rela-
tively few siltite beds. About 200 feet from the top of
the formation siltite beds are again noticeable and
become progressively more abundant toward the con-
tact with the overlying St. Regis Formation. In this
upper ZOO-foot interval, the quartzite and siltite have
a slight lavender tint, making the gradation into the
overlying St. Regis not only one of grain size but of
color also.

Beds range in thickness from less than 1 inch to more
than 20 feet; average thickness is about 1—2 feet. Exten-
sive talus composed of quartzite blocks commonly
accumulates at the foot of slopes underlain by the
Revett Formation.

Most of the quartzite is light gray to white. Siltite
beds commonly are the same color, but many are darker
gray, similar to the color of those in the Burke Forma-
tion. Thin bands of opaque minerals impart a faint
banding to the quartzite but are not abundant. Dissem-
inated dark minerals are common in most of the quartz-
ite but do not materially affect the color of the rock.
In places, quartzite beds contain pale-yellow roughly
spherical pea-sized areas in which part of the cementing
agent of the rock has been removed. Similar features,
mentioned by Hobbs, Griggs, Wallace, and Campbell
(1965, p. 38), appear to be more characteristic of the
formation in the Coeur d’Alene district than in the
report area. The weathered quartzite surfaces have a
pock-marked appearance where these small vuglike
features have been leached out by surface waters.

The siltite of the Revett Formation has virtually the
same mineralogy as the Burke Formation. The quartz-
ite is relatively pure but contains an unusually large
amount of heavy minerals, as much as a half of a per-
cent zircon and magnetite. Sericite and plagioclase are
the most common impurities, in that order of abund-
ance. Grains of potassium feldspar are common but not
abundant.

Crossbedding and ripple marks are the only common
sedimentary structures in the Revett Formation within
the report area. Neither structure appears to be as well
developed or as abundant as in the Coeur d’Alene dis-
trict. A few beds containing mud-chip breccias are found

 

in argillaceous beds on the mountain north of Deer
Lake, but these appear to be local.

ST. REGIS FORMATION
DISTRIBUTION AND THICKNESS

The St. Regis Formation consists of maroon and
green interbedded argillite and siltite. Numerous
quartzite beds are interlayered with the finer grained
rocks near the base. Good outcrops of the St. Regis
Formation occur in only a few places in the large area
underlain by the formation. Its distribution is roughly
the same as that of the Revett and Burke Formations,
except in the area around Wilson Mountain and the
area south of the Flowery Trail Granodiorite. Around
Wilson Mountain the formation is folded into a strongly
overturned syncline. The dips of both normal and over-
turned limbs are fairly low. The St. Regis Formation
is relatively thin for a Belt unit, but its outcrop width
is about 2 miles in that area because of the low dip of
the beds and the relatively subdued topography. (See
cross section A—A’, pl. 1.) From the south margin of
the Flowery Trail Granodiorite to Grouse Creek, most
of the St. Regis Formation is covered by glacial debris.

In the report area, the average thickness of the St.
Regis Formation is about 1,600 feet. No sections were
measured, and at only a few localities are both contacts
sufficiently well located so that a reasonably accurate
thickness can be calculated.

Ransome (1905, p. 280—282) named and first
described the St. Regis Formation in the Coeur d’Alene
district. Because of the excellent cliff exposures there,
Calkins (in Ransome and Calkins, 1908, p. 37) was
able to accurately measure the thickness of the forma-
tion. In the east-central part of the district he measured
996 feet of section but mentioned that the formation
appears to be thicker to the east and to the south.
Hobbs, Griggs, Wallace, and Campbell (1965, p. 39)
measured 1,400 feet for the same section but included
a green quartzose argillite zone in the St. Regis Forma-
tion which Calkins put in the overlying Wallace For-
mation. In the report area, the green beds are also
included in the St. Regis Formation.

According to Harrison and J obin ( 1963, p. K12) , the
St. Regis Formation is from 600 to 1,100 feet thick in
the Clark Fork quadrangle, 50 miles east of the report
area. However, they assigned the distinctive green argil-
lite beds, which are about 200 feet thick there, to the
lower Wallace Formation; thus the range in thickness
in the Clark Fork quadrangle can be increased to 800—
1,300 feet.

STRATIGRAPHY AND LITHOLOGY

The St. Regis Formation is one of the more distinc-
tive units in the Belt Supergroup because of its striking

 

 

PRECAMBRIAN ROCKS 9

color. It is typically red-purple or lavender, except for
several hundred feet of siliceous carbonate-bearing
argillite at the top of the section, which is a distinctive
yellow green.

The lower 50—200 feet of the St. Regis Formation is
transitional into the dominantly quartzitic Revett For-
mation below. The lower contact has been placed where
the red-purple argillaceous and siltitic rocks predomi-
nate over the relatively clean white and lavender
quartzite of the upper part of the Revett Formation.
Defining the contact in this manner makes its place-
ment relatively simple in the field because most of the
quartzite beds in the lower part of the St. Regis Forma-
tion are much more highly colored. White quartzite
and red-purple argillite and siltite beds are actually
interbedded in only about 50—100 feet of the transition
zone.

The lower three-fourths of the formation consists of
interbedded argillite, siltite, and quartzite. In general,
the finer grained. rocks are more highly pigmented. The
quartzites are pale lavender, and the argillites deep red-
dish purple; the siltite ranges from one color to the
other. In this part of the formation, the rocks grade
from predominantly quartzite and siltite near the base,
to predominantly argillite and siltite in the upper part.
The unit, as a whole, appears to be more quartzitic in
the report area than in the Pend Oreille or Coeur
d’Alene areas.

The upper quarter of the formation is composed of
alternating zones of red-purple elastic rocks and yellow-
green carbonate-bearing siliceous argillite, which are
10—50 feet thick. The red-purple zones are siltite and
argillite and are restricted to the lower two-thirds of
this part of the formation. The yellow-green argillite
in turn grades upward into the Wallace Formation,
mainly through an increase in carbonate-bearing
quartzite and black laminated argillite beds.

Individual beds range in thickness from 1 inch to
about 4 feet in the lower part of the formation. The
thicker quartzite beds are faintly banded by darker
purple layers. The maroon argillite and siltite in the
upper part of the formation are very thinly bedded and
in places laminated. Almost all siltite and quartzite
beds are separated by at least a film of red-purple argil-
lite. Bedding characteristics of the middle part of the
formation are not well known owing to poor exposure.

Mud cracks and mud-chip breccias are abundant
throughout the St. Regis Formation, especially near
the top. Even where the unit is mapped largely on the
basis of float, many chips and pieces of float have mud
cracks on them. Ripple marks and cross-laminations
are also common but not nearly as abundant as in the
Coeur d’Alene district, perhaps because exposures in
one area are so much better than in the other.

 

In the open, south-plunging syncline on Blue Grouse
Mountain, the maroon color of the St. Regis is com-
pletely bleached out in places. Along strike, the rocks
grade from maroon, through mottled white and maroon,
to white or pale green. The white and pale-green rocks
are poorly indurated and altered looking. All lithologies
are affected. The bleaching appears to be confined to a
restricted area of hydrothermal alteration, which affects
rocks underlying about half a square mile. The same
type of bleaching is present around some of the large
quartz veins on Blue Grouse Mountain, Deer Lake
Mountain, and Bald Mountain.

WALLACE FORMATION
DISTRIBUTION AND THICKNESS

The Wallace Formation is a thick unit made up of
argillite, quartzite, siltite, and carbonate rock. Much of
the quartzite and siltite are carbonate bearing. The
distribution of the Wallace in the report area is consid-
erably more irregular than that of most other Belt
formations. It forms a roughly linear but highly faulted
belt around the margin of the anticline in the east half
of the area, but also underlies part of Deer Lake Moun-
tain and Loon Lake Mountain in the southern part. In
the north half of the area, the formation forms part
of an up-faulted block on the west flank of Eagle
Mountain; the block extends northward to McDonald
Mountain.

The formation is divided into an upper and a lower
part in the report area. Hobbs, Griggs, Wallace, and
Campbell (1965, p. 41) divided it in the same manner
in the Coeur d’Alene district. Because the lower part
of the formation forms fewer outcrops than any other
Belt unit in the report area, it is difficult to obtain an
accurate estimate of its thickness. The average calcu-
lated thickness of the lower part of the formation at the
homoclinal section of the west flank of Bald Mountain
is about 3,500 feet. This is probably as accurate a figure
as can be obtained in this area.

A complete section of the upper part of the Wallace
Formation is not exposed in the report area, as a fault
marks the upper contact everywhere except on Deer
Lake Mountain, and the base of the upper part is not
exposed there. The thickest preserved sections are on
McDonald Mountain, Eagle Mountain, and just east of
Quartzite Mountain. The section on McDonald Moun-
tain is not as thick as the map seems to show, because
about one-third to one-half of the outcrop width is
made up of sills and dikes of leucocratic quartz mon-
zonite. A calculated thickness of 2,500—3,000 feet for
the section east of Quartzite Mountain probably repre-
sents a maximum for this part of the Wallace Forma-
tion. That section also is fault bounded, although it

 

 

 

10 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

appears to be relatively undisturbed internally. On
Eagle Mountain, the upper part of the Wallace Forma-
tion is highly sheared and may contain unrecognized
faults.

The formation was first named in the Coeur d’Alene
district by Ransome (1905, p. 280, 282). Calkins (in
Ransome and Calkins, 1908, p. 40) estimated the thick-
ness there to be at least 4,000 feet, but he did not divide
the formation. Hobbs, Griggs, Wallace, and Campbell
(1965, p. 42), who studied that area in greater detail,
found no well-exposed uninterrupted sections of the
formation. From measurements of several partial sec-
tions they concluded that the total thickness is between
4,500 and 6,500 feet.

STRATIGRAPHY AND LITHOLOGY
LOWER PART

The lower part of the Wallace Formation is composed
of argillite, siltite, quartzite, highly impure carbonate
rock, carbonate-bearing quartzite, and carbonate-
bearing siltite. It is varied in lithology, but is generally
easy to recognize not only because of the presence of
carbonate-bearing rocks but because of bedding char-
acteristics which are unique in the Belt Supergroup.

The lower contact of the Wallace Formation is
assigned on the basis of criteria that Hobbs, Griggs,
Wallace, and Campbell (1965, p. 43) used because
this part of the section is similar to that in the Coeur
d’Alene district. Hobbs drew the contact where the
alternating beds of quartzite and argillite of the Wal-
lace Formation became more numerous than the lami-
nated green argillitic rock of the St. Regis Formation.
In the report area, this transition zone is about 100 feet
thick and is well exposed below the upper Cottonwood
Road east of Parker Mountain and in the streambed
of Grouse Creek north of Bald Mountain.

Many of the transition beds are carbonate bearing,
as are some of the beds for several hundred feet below
and several thousand feet above the transition. The
lower part of the formation is one of the main carbon-
ate-bearing units in the western Belt Supergroup, but
in the report area almost none of this rock resembles
normal limestone or dolomite be cause the carbonate
minerals usually make up less than 50 percent (average
is about 20 percent).

As well as can be determined from the small isolated
outcrops, the lower part of the formation appears to
grade upward, with numerous local reversals, from pre-
dominantly carbonate-rich quartzite and siltite to silt-
ite or argillite and lesser amounts of quartzite. The
rocks in the upper part of the lower Wallace, particu-
larly near the transition into the predominantly argil-
litic upper Wallace, contain less carbonate minerals
than the lower part of the formation.

 

 

The unit is characterized by alternating beds of light-
colored quartzite and siltite and dark argillite. Carbon-
ate minerals are confined mostly to the quartzite and
siltite. The thickness of these relatively coarse grained
beds is highly variable not only from bed to bed but
within a single bed as well. The most striking lateral
changes in bed thickness appear to occur in carbonate-
bearing quartzite, which, in the extreme, thins from 5
feet to a few inches within a distance of less than 10
feet. Most of the quartzite beds are thinner, however,
and repeatedly pinch and swell. Hobbs, Griggs, Wal-
lace, and Campbell ( 1965, p. 44) suggested that this
boudinagelike appearance may be attributed to com-
paction adjustment and later deformation. The thicker
quartzite and siltite beds show almost no internal
stratification. Rarely do colored impurities define bed-
ding within these layers, although the upper part of a
coarser grained bed commonly grades into an overlying
argillite layer not only by a decrease in grain size but
more obviously by darkening in color.

The argillite layers, which contain most of the abun-
dant sedimentary structures in the lower parts of the
Wallace Formation, are dark gray to black and com-
monly finely laminated. Exposed bedding-plane sur-
faces generally have a blue-black phyllitic sheen. Unlike
the very even continuous laminations in other Belt
formations, the laminations in this part of the section
are commonly discontinuous, disrupted by other sedi-
mentary structures, or disrupted by differential com-
paction. Small discordant bodies of siltite or quartzite,
which look like miniature elastic dikes or filled mud
cracks, cut the laminated argillite, commonly at right
angles. These bodies are generally less than 1 inch long
and have been crenulated, probably by compaction.
They are found throughout the Wallace Formation and
in parts of the Striped Peak Formation, but are most
abundant in the lower part of the former. Desiccation
mud cracks and, to a lesser degree, ripple marks are
common throughout the unit, and in places mud cracks
are superimposed on ripple marks. Crossbedding was
not seen, although fine cross-laminations were found in
some of the darker fine-grained siltite beds.

UPPER PART

Partial sections of the upper part of the Wallace
Formation crop out best on Deer Lake Mountain, the
south flank of Parker Mountain, and the hill east of
Quartzite Mountain. At these localities the rocks are
predominantly composed of dark laminated argillite
but also contain zones of relatively pure looking limy
dolomite and beds of carbonate-bearing quartzite iden-
tical with those in the lower part of the formation. In
this respect the lithology of the upper part in this area
is intermediate between that at Pend Oreille Lake and

 

 

—————W

PRECAMBRIAN ROCKS 11

in the Coeur d’Alene district. Harrison and J obin
(1963, p. K13) divided the Wallace Formation into five
members in the Clark Fork and Packsaddle Mountain
quadrangles near Pend Oreille Lake. There, the transi-
tion from the lower calcareous member to the argillite
member, found about 2,500 feet above the base of the
formation, appears to represent roughly the same inter-
val as the transition from the lower part to the upper
part of the Wallace Formation in the report area and
in the Coeur d’Alene district. However, Harrison and
J obin (1963, p. K15) described additional beds resem-
bling those of the lower part in the member above the
argillite member, and a calcareous member above that,
which is composed principally of dolomitic limestone.
Although Hobbs, Griggs, Wallace, and Campbell (1965,
p. 44) mentioned a few hundred feet of carbonate-rich
beds in the upper part of the Wallace Formation, the
section they described at Coeur d’Alene is made up pre-
dominantly of dark laminated argillite.

On Eagle Mountain, 3 miles northeast of Chewelah,
the upper part of the Wallace Formation contains num-
erous beds, as much as 10 feet thick, of light-tan limy
dolomite. In the two fault-bounded blocks on the north-
east flank of the mountain, the unit is made up of about
equal parts of black laminated argillite, laminated car-
bonate-bearing argillite, and light-tan dolomite beds.
Here the various lithologies are repeated in groups from
a few feet to a few tens of feet in thickness. The aggre-
gate preserved thickness of this part of the unit is prob-
ably 800—1,000 feet. Although it is fault bounded, this
carbonate-rich zone probably occurs at least 3,000 feet
above the transition from the lower part of the forma-
tion because the zone is not found in the intervening
interval at the relatively well exposed section east of
Quartzite Mountain only 4 miles to the south.

East of Quartzite Mountain the unit is exposed bet-
ter than at any other place in the area and is fairly
similar to the upper part in the Coeur d’Alene district.
It is predominantly dark- gray to black laminated argil-
lite. There are a few quartzitic zones as much as 50
feet thick which are made up of individual quartzite
or siltite beds as much as 1 foot thick. Lensoidal seams
of brown siltite averaging about 0.1 inch in thickness
are common throughout the unit. Where these lenses
are thicker it is seen that they are channels cut in the
argillite and are commonly graded.

On the north flank of Deer Lake Mountain, the upper
part of the Wallace Formation is well exposed in large
roadcuts above the south shore of Deer Lake. The rock
there is highly quartzitic and carbonate bearing. It is
identical with that in the lower part of the formation
and was originally mapped by Miller (1969) as lower
Wallace. Natural exposures are slightly better on the
west flank than on the north. The carbonate-bearing

__4____—

 

 

quartzite beds on the west flank grade upward into
typical black laminated argillite of the upper part of
the formation. However, 200—300 feet above that the
lowermost member of the Striped Peak Formation rests
on the black argillite. If that contact is depositional, as
it appears to be, then the quartzitic rock exposed in
roadcuts along the south shore of the lake must be
an anomalous zone in the upper part of the Wallace
Formation.

Mud cracks, ripple marks, graded bedding, and, to
a lesser degree, cross-laminations are found in this part
of the section, although none are extensively developed.
The crenulated clastic dikelets or crack fillings so
abundant in the lower part of the formation are com-
mon but much less numerous. Slump structures and
preconsolidation deformation, which appear in some of
the similar looking argillites in the Striped Peak For-
mation, are not found in the upper Wallace Formation.

MISSOULA GROUP
STRIPED PEAK FORMATION

DISTRIBUTION AND COMPARISON WITH
OTHER NEARBY SECTIONS

The Striped Peak Formation in the report area is
confined for the most part to a narrow band on the
east side of the Addy Quartzite, which trends roughly
north to south from Eagle Mountain to J umpofi Joe
Mountain. Other outcrops are found on Deer Lake
Mountain and possibly beneath the Addy Quartzite on
the south flank of Blue Grouse Mountain.

The formation was originally named and described
in the Coeur d’Alene district by Ransome (1905, p. 280,
282). Calkins (in Ransome and Calkins, 1908, p. 44)
estimated the thickness of the preserved section to be
about 1,000 feet. Shenon and McConnel (1939, p. 5)
measured 1,500 feet of section about 1 mile southeast
of Striped Peak, the type locality.

Although not particularly thick, one of the best and
most complete sec ions of the Striped Peak Formation
is well exposed in :1 large part of the Clark Fork quad-
rangle, Idaho. Harrison and J obin (1963, p. K16)
divided the formation there into four rather distinct
units with a total thickness of about 2,000 feet. The
lowest member is about 600 feet thick and composed
predominantly of light-colored carbonate-bearing
siltite, quartzite, and argillite. The second member is
predominantly dolomite and is about 400 feet thick.
Member three is composed of about 300 feet of dark
well-laminated argillite and siltite, and the fourth,
uppermost member consists mainly of distinctive red
arkosic quartzite, about 700 feet thick. All but the low-
est member correlate well with similar divisions in the
report area.

 

h

12 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

STRATIGRAPHY AND LITHOLOGY

Although that part of the Belt Supergroup above the
Wallace Formation in the report area is similar to the
Striped Peak Formation at other places, the diflerences
that exist almost justify using a new name here. For
several reasons, however, not the least of which is the
confusion already existing in Belt nomenclature, the
rocks above the Wallace Formation in the report area
are assigned to the Striped Peak Formation. Facies
changes that are large and rapid relative to facies
changes in the lower Belt formations are recognized in
the Striped Peak Formation in western Montana and
northern Idaho. Most of the differences between the
Striped Peak Formation in the report area and the
formation in the Clark Fork quadrangle and the Coeur
d’Alene district can be explained by facies changes no
greate“ than those described between localities of com-
parable separation at other places in Montana and
Idaho.

The formation is divided into four members, which
are designated by letters to avoid confusion with the
numbered members in the Clark Fork quadrangle
(Harrison and J obin, 1963, pl. 1). A composite section
is illustrated here (middle column, fig. 7A) because no
complete and unfaulted section has been found in the
report area. Many of the members are fault bounded
in much of the area, and the contact between members
a and b is a fault wherever found.

MEMBER a

On J umpofl Joe Mountain and Deer Lake Mountain,
the lowest member of the Striped Peak Formation is
made up of thin- to medium-bedded siltite with inter-
laminated argillite partings. Another but smaller fault-
bounded section of siltite on the mountain south of
Beitey Lake is probably part of this member also. The
siltite appears to conformably overlie the black well-
laminated argillite of the upper part of the Wallace
Formation on Deer Lake Mountain. Although the com-
plete transition from one unit to the other is not
exposed anywhere, a composite of the transition zone
appears to be about 50—100 feet thick.

About 70 or 80 percent of the lower member is
medium-gray to olive-gray siltite. Except for about 100
feet of argillite near the top of the member, the other
20—30 percent of the unit is dark-gray to black argillite,
which occurs chiefly as thin bedding-plane partings and
in beds less than 1 inch thick. Although they some-
times tend toward pink or dull green, the siltite beds
do not vary much in color, perhaps because they have
been thermally metamorphosed in varying degree by
nearby younger plutonic rocks. On a weathered surface,
some siltite beds show faint internal laminations, which

 

are rarely seen on a fresh surface. Most siltite beds are
about %—% inch in average thickness, but a few
quartzitic beds are as much as 3 feet thick. Because
of its thin-bedded character, the unit forms platy talus
slopes below prominent outcrops.

Approximately the upper 100 feet on Deer Lake
Mountain is thinly laminated deep-reddish-purple or
maroon argillite and siltite with thinly interbedded
lensoidal layers of fine-grained quartzite. Interbedded
near the top of the maroon zone are several platy-
weathering light-gray to pale-lavender siltite layers 10
feet thick. The Addy Quartzite rests unconformably
upon the maroon zone, indicating that some of the for-
mation has been removed by erosion here. On J umpoff
Joe Mountain, pre-Addy erosion has removed the entire
maroon zone, and on the mountain south of Beitey
Lake the upper contact is a fault. The thickest section
of this member appears to be on Deer Lake Mountain,
where 900 feet of strata may be present.

Detrital mica is sparsely scattered through much of
the rock in both siltite and argillite layers. Large polyg-
onal mud cracks and thin zones of mud-chip breccia
are common in all parts of the member except for the
upper maroon zone. Small ripple marks are common
but not abundant. Salt casts are common in the lower
member of the Striped Peak Formation at other places
but Were not found in the report area.

Although many characteristics of this member are
similar to those of the lower member in the Clark Fork
quadrangle and in the Coeur d’Alene district, three
characteristics are notably different and make it diffi-
cult to correlate member a with the equivalent part of
the section at the other two localities. About 55 miles
east in the Clark Fork quadrangle and 75 miles south-
east in the Coeur d’Alene district, the lower member is
generally red, pink, or green, or it is light gray tinted
with one of these three colors (Harrison and J obin,
1963, p. K17; and Hobbs and others, 1965, p. 45). The
red color appears to be an important characteristic of
the unit over a very large area. Except for the maroon
zone in the upper part of the member on Deer Lake
Mountain, the rocks of member a are darker and less
colorful than those making up the lower member to the
east. In addition to a color difference, the lower mem-
ber in the Clark Fork quadrangle and in the Coeur
d’Alene district is characterized by small quartz and
calcite-filled vugs, and quartzitic layers which contain
carbonate minerals. Although these features were care-
fully searched for, only local traces of carbonate miner-
als could be found in member (1.

MEMBER b

Member b crops out in a narrow discontinuous belt
from Eagle Mountain south to the Loon Lake copper

¥

 

 

 

PRECAMBRIAN ROCKS 13

mine, but is well exposed only on Parker Mountain and
the mountain south of Cottonwood Creek. The unit is
chiefly medium- to thick-bedded dolomite containing
many argillaceous bedding-plane partings. Nowhere in
the area is a complete section of the member exposed,
as the lower contact is everywhere faulted. Because of
internal faulting, a reliable composite section can be
constructed for only part of the member. From the
available exposures, however, considerable lithologic
variety is obvious.

0n Quartzite Mountain and Parker Mountain the
contact with overlying member 0 is fairly well exposed
in places. Noticeable differences in the upper part of
member b are found along strike in the 1 V2 miles sepa-
rating these two localities. On Parker Mountain the
gradation down section from member c to b is from
gray argillite into purple argillite and subsequently into
purple or maroon dolomite. Locally, about 10—30 feet
of light-gray dolomite separates the purple argillite
from the purple or maroon dolomite. Lower in member
b at this locality, the maroon pigmentation of the car-
bonate is increasingly pale and tends toward gray.

On Quartzite Mountain, numerous thin beds of pale-
green carbonate-bearing siltite in zones as much as 10
feet thick are interlayered with the dolomite. The same
lithologies are found south of Parker Mountain, where
member b crops out about 1 mile north of Beitey Lake.
Here, however, beds of maroon dolomite and carbonate-
bearing siltite are interbedded with gray dolomite and
green carbonate-bearing siltite, and the contact with
member c is a fault.

From the south half of Parker Mountain to the
southernmost exposures of member b, the upper and
lower contacts of the unit are both faults. 0n the moun-
tain south of Parker Mountain, most of the dolomite
is medium gray and pale tan; maroon or green beds
occur only on the south flank. The gray and tan beds
probably represent the lowest part of the member
exposed and are also found in the easternmost expo-
sures of the member, near the top of Parker Mountain.
In general, the most intense maroon coloring appears
to be in the upper part of the member. The coloration
decreases in intensity down section into the more
abundant tan and gray beds. About half of the unit is
pale tan or gray on a fresh surface, weathers tan or red
brown, and forms a brick-red soil.

The thick carbonate beds contain closely spaced
laminae of silica. Some of these films of silica are nearly
perpendicular to bedding and on weathered surfaces
commonly exhibit a boxwork structure like that
described by Harrison and Jobin (1963, p. K18). In
the few places where stromatolites have been found,
the form of the fossil is commonly outlined and accen-
tuated by thin films of silica.

 

The dolomite beds in this member are considerably
purer as a whole than in any other Belt carbonate unit
in the report area, but contain, even so, several percent
sand, silt, and argillaceous material, in addition to the
silica already mentioned. On the west flank of Parker
Mountain, the dolomite contains an anomalously large
amount of sand about 7 00—800 feet below the top of the
member. The sandy zone is only about 100 feet thick
and grades downward again to relatively pure carbon-
ate beds with bedding-plane partings of argillite.

Calculated from outcrop width, the maximum thick-
ness of that part of the unit still preserved is about
1,750 feet. Although the least disturbed section was
chosen for the calculation, the figure may possibly be
too large owing to undetected faults. The preserved
part of the member is probably not less than 1,000 feet
thick, however, which is considerably thicker than the
400 feet reported by Harrison and J obin (1963, p. K18)
for member 2 in the Clark Fork quadrangle.

Because of stratigraphic uncertainties stemming
from the absence of a complete section of the Striped
Peak Formation throughout the area, the possibility
cannot be ruled out that the predominantly maroon
carbonate of member b is separated by member c from
the gray and tan carbonate. If member c were overlain
by a maroon carbonate unit and underlain by a gray
and tan carbonate unit, the stratigraphic section would
resemble that shown in figure 73. Although correla-
tions with other sections would not be impaired, and
might even be improved, this interpretation would
necessitate changing several structural interpretations.
As best as can be determined, however, all the relative-
ly clean carbonate rock is restricted to a single unit
and is overlain by member c.

MEMBER c

Member 0 is better exposed than any other member
of the Striped Peak Formation, and indeed better than
any unit in the area with the exception of the Addy
Quartzite. It is particularly well exposed on the south
and west slopes of Quartzite Mountain east of Chewe-
lah (figs. 4, 9). The member is composed chiefly of
medium- to dark-gray laminated argillite interlayered
with lighter gray siltite in beds generally less than 1
inch thick. The argillite beds are well laminated, but
in some parts of the unit the laminations are obscure
except on a weathered surface.

Most of the member is grayish argillite. About 500
feet above the base is 250—300 feet of light-gray, pale-
yellow, and pale-green siltite and siltitic quartzite.
Small flakes of detrital mica are found all through the
rock of this zone but especially along bedding planes.
Bedding averages 2—6 inches in thickness. The only
other lithology that is notably different from the argil-

 

 

 

14 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

  
 

 
 
   

THICK-
Ll H OGY DESCRIPTION
NESS T 0L

IN FEET

 
  

 
   

SUBUNIT

Addy Quartzite

 

Argillite and siltite, pale»gray-
green, faintly laminated;
shows decracks; minor
amount of soft-sediment
breccia; contains pale~pink
seams of coarser silt as
much as 1/8 inch thick

  
        
       
      
        
   
 

Argillite, dark-gray with light
laminations; zones of unit 1
a few feet thick; well
laminated; abundant mud-
cracks; abundant soft-sedi-
ment breccia, but confined
to individual beds

      
      
     
    
  

1 and 2 above mixed in about
equal proportions

Km

    
   
 
 

Covered
interval

 
 

215

  
 

 

 
 
 

Argillite, black with quartzitic

\ siltite. Slightly phyllitic

Siltite and siltitic quartzite,
light - gray; also yellow
and green; contains detrital
mica. Beds 2—6 inches
thick, nonlaminated; mud-
cracks and ripple marks. Near
base, alternates with medium-
gray laminated argillite

   
 
 
      
         
    
 
  

  
  

     

Quartzitic siltite, light-gray
with purple tinge; inter-
bedded with black laminated
argillite

      
     
   
   
 

Argillite and argillitic siltite,
dark-gray, well - laminated;
abundant; soft-sediment

  
  

  
  

 
 
 
 
  

    
     
  

 

 

 
 

 

Covered breccia
110 interval
Argillite, black and white;
Member b paper-thin laminations; looks
silty
1810
TOTAL

 

FIGURE 4.—Generalized columnar section of member c of the
Striped Peak Formation on Quartzite Mountain.

lite is about 300 feet of pale-gray-green argillite and
siltite in the uppermost part of the unit. The rock is
characterized by thin pink lensoidal seams of coarser
silt about one-eighth of an inch thick.

Sedimentary structures are abundant in this mem- '

ber. Mud cracks and small crenulated siltstone dikelets,
or filled desiccation cracks, occur throughout the mem-
ber. Graded bedding is well developed in the siltstone
beds, especially in the upper 500—1,000 feet of section
on Eagle Mountain, but most hand specimens show
only a gradation from light to dark gray because the
grain size is so small. Light-gray silt beds grade upward

 

 

into black argillite beds. Cross-laminations are common
but not obvious. Ripple marks are rare and confined
almost entirely to the siltite and siltitic quartzite zone.
Soft-sediment breccias are found throughout most of
the member (figs. 5, 6). They are apparently the result
of slumping or some other penecontemporaneous defor-
mation that occurred before lithification. Most of the
soft-sediment breccias on Quartzite Mountain are con-
fined to individual beds and truncated at top and bot-

 

FIGURE 5.—Argillite and breccia from member 6 of the Striped
Peak Formation. A, Laminated black argillite. Shows chan-
neling, elastic dikes, and graded bedding. Lighter layers are
graded from coarse to fine silt. Collected near top of Eagle
Mountain. B, Soft-sediment breccia showing disrupted bed-
ding and elastic dikes which presumably formed prior to
lithification of the argillite. Collected near the top of Eagle
Mountain about 100'feet away from specimens shown in A
and about 20 feet stratigraphically above it. '

 

PRECAMBRIAN ROCKS 15

torn by perfectly undisturbed beds, as if the disturbed
zones acted as a décollement before lithification. On
Eagle Mountain many of the beds bounding the soft-
sediment breccias are disturbed also and may have
formed under slightly different conditions. The dis-
turbed beds there range in thickness from about 1 inch
to more than 5 feet.

The two small hills south of the Loon Lake copper
mine provide the best exposures of the uppermost part
of member c and the transition into member d. The
contact is placed at the base of the lowest thick series
of maroon siltite beds. Some maroon siltite beds occur
below this, but they are confined to zones less than 3
feet thick and are separated by thicker zones of dark-
gray siltite and laminated argillite. Most of the beds
in the upper 200 feet of member c contain detrital mica.
Below the maroon rocks is a zone of finely laminated
olive-gray siltitic argillite about 50—100 feet thick.
These rocks appear to be highly susceptible to altera-
tion and weather out in large thin plates. Below the
laminated rocks is several hundred feet of interbedded
dark argillite and siltitic quartzite. Some zones of pure
poorly laminated black argillite are as much as 15 feet
thick, and some quartzite beds as much as 5 feet thick.

FIGURE 5,—Continued.

 

 

Below this, the rocks are similar to those that make up
member c on the mountain north of Beitey Lake.

The 1,810-foot-thick section on Quartzite Mountain
appears to be the thickest in the map area. On the
north flank of the mountain, the thickness may reach
2,000 feet where pre-Addy erosion did not cut so deep,
but the apparently thicker section could not be accu-
rately measured, as the rocks are very poorly exposed.
On Eagle Mountain incomplete exposure and possible
structural complications combine to prevent an accu-
rate estimate of the thickness of member c. The yellow-
and green-tinted siltite and siltitic quartzite zone found
on Quartzite Mountain could not be identified on Eagle
Mountain, but may have been cut out along the fault
bounding the unit on the east. Even so, the width of

 

FIGURE 6.—Soft-sediment breccia in the McHale Slate, probable
correlative of member c of the Striped Peak Formation. Loca-
tion is a few hundred feet west of the map area, about 4 miles
north of Chewelah. Photograph illustrates how soft-sediment
breccias are confined to distinct layers and are bounded by
undeformed laminated argillite. Compare with figure 5.

16 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

outcrop on the south flank of Eagle Mountain suggests
that the member is much more than 1,000 feet thick.
At least part of this section is stratigraphically higher
than the highest part of the member on Quartzite
Mountain. A composite thickness of the member on
both Quartzite and Eagle Mountains is probably 2,000—
2,500 feet. If the uppermost parts of the member, such
as found on the mountains north and south of Beitey
Lake, are added to this figure, the minimum thickness
of the composite section would be between 2,400 and
2,900 feet.

MEMBER d

The uppermost member of the Striped Peak Forma-
tion is exposed only on the mountains north and south
of Beitey Lake and on the two hills south of the Loon
Lake copper mine. (See fig. 10.) It is perhaps the most
easily identified of all the Striped Peak members
because of its deep-maroon to hematite-red color. The
only divergence from this color is on the north flank
of the hill south of Beitey Lake, where layers of black
faintly laminated argillite and siltite in zones as much
as 40 feet thick are interbedded with the maroon rock.
The chief rock type is siltite, but argillite is common
in thin layers and as bedding-plane partings. Thin beds
of quartzite also are found throughout the unit, but
they are not as abundant as'in member 4 in the Clark
Fork quadrangle. Bedding thickness ranges from about
%—3 inches and averages about three-fourths of an
inch. Internally some of the beds are faintly laminated.
Because it is thin bedded, this unit almost always
breaks into plates or chips.

A few feet of pale-green siltitic quartzite occurs in
the transition between this and the underlying member
c. These beds are similar to those between members
3 and 4 that Harrison and J obin (1963, p. K19)
described in the Clark Fork quadrangle.

The Cambrian Addy Quartzite unconformably over-
lies member d in the report area. The member is thick-
est, 500—800 feet, just southwest of Beitey Lake.

Ripple marks, mud cracks, and salt casts are well
developed and abundant throughout the member.
Cross-lamination, scour and fill, and graded beddings
are found locally and are relatively small scale features.

DEER TRAIL GROUP

The rocks assigned to the Deer Trail Group are
largely those that were originally called the Deer Trail
Argillite by Weaver (1920, p. 59). Bennett (1941, p. 7)
elevated the Deer Trail Argillite to group status, and
one of the carbonate zones in the section to formational
status. Campbell and Loofbourow (1962, p. F8), in
a more detailed report on approximately the same

 

region that Bennett studied, divided the Deer Trail
Group into the Togo Formation, Edna Dolomite,
McHale Slate, Stensgar Dolomite, and Buffalo Hump
Formation.

All the formations are extensively exposed in the
Huckleberry Mountain southwest of Chewelah. In
that area, the Deer Trail Group and younger rocks form
what has become known as the magnesite belt for its
large deposits of magnesite. This region is referred
to frequently in the following formation descriptions
because the various units are much more extensively
exposed there than in the report area. For a more com-
plete description of the Deer Trail Group, the reader is
referred to Bennett (1941), Campbell and Loofbou-
row (1962), Becraft and Weis (1963), and Campbell
and Raup (1964).

The assignment of rocks in the report area to the
Deer Trail Group is questionable because the rocks
closely resemble the upper part of the Belt Supergroup.
Without exception, however, all the rocks so assigned
are overlain or intruded by the greenstone of the
Huckleberry Formation. The greenstone has not been
found associated with the known Belt rocks east of the
main north-south belt of Cambrian Addy Quartzite.
Therefore, where considerable doubt exists, the pres-
ence of associated greenstone is used as a criterion in
assigning rocks to the Deer Trail Group.

Pronounced facies changes in the Deer Trail Group
over relatively short distances are well documented in
the magnesite belt by Campbell and Loofbourow ( 1962,
pl. 2) and Campbell and Raup (1964), and equally
large changes, but on a regional scale, are found in the
upper Belt Supergroup (A. B. Griggs, oral commun.,
1969; Harrison and Campbell, 1963, p. 1424). There-
fore, slight differences between the Deer Trail units
in the report area and the type formations in the mag-
nesite belt are less remarkable than would be similar
differences between two sections in the lower Belt
Supergroup.

All workers who have studied these rocks since
Weaver have considered both the Deer Trail Group and
Huckleberry Formation to be Precambrian in age.

The Deer Trail Group is truncated by intrusive rocks
north of Chewelah but continues on the other side of
the batholith in the Metaline quadrangle with the same
unvarying northeast trend that it has in the magnesite
belt. Possible correlatives of the Deer Trail Group in
the Metaline quadrangle have been called the Priest
River Group (Park and Cannon, 1943, p. 6), and the
same rocks in Canada have been called the Priest River
Terrane (Daly, 1912, p. 258). Becraft and Weis (1963,
p. 16) were the first to suggest a correlation between
the Priest River and Deer Trail Groups but were unable
to match individual units.

PRECAMBRIAN ROCKS 17

TOGO(?) FORMATION

Rock that may belong to the Togo Formation under.-
lies only one small patch in the report area, abOut 2
miles east of Valley. The rock is sheared dark-gray-
green argillite which looks identical with that found in
at least five other Precambrian formations in the area.
It is assigned to the Togo Formation only because it
appears to underlie the Edna Dolomite.

The lithology is similar to that making up part of
the type Togo Formation in the magnesite belt to the
west (Campbell and Loofbourow, 1962, p. F9). Camp-
bell and Loofbourow (1962, p. F8) named the unit for
the exposures around the Togo mine about 15 miles
due west of Springdale. There, the formation consists
of several thousand feet of dark-gray to black lami-
nated argillite. The upper part of the formation con-
sists of about 1,000 feet of relatively pure quartzite at
the latitude of Valley but thins to the north. Both
Campbell and Loofbourow (1962, p. F9) and Campbell
and Raup (1964) noted that the argillitic part of the
formation is carbonate bearing near the top. No accu-
rate estimate of the thickness of the Togo Formation
has been made because of inability to detect structure
in the monotonous section of argillite. Campbell and
Loofbourow (1962, p. F9) estimated that the unit is
at least 4,000 feet thick in the southern part of the area,
but it may be much thicker. Becraft and Weis (1963, p.
7) estimated the thickness from outcrop width in the
same general area to be about 20,000 feet.

EDNA DOLOMITE

Light-gray to tan dolomite crops out on three small
hills immediately west of the Togo ( ?) Formation in sec.
18, T. 31 N., R. 41 E., northeast of Valley. It is identical
in all respects with the type Edna Dolomite which was
named and described by Campbell and Loofbourow
(1962, p. F9). The rock is medium— to thin-bedded
impure dolomite, but it has a massive appearance. It
weathers light tan and forms a bright-hematite-red
soil. A completely fault-bounded discontinuous belt
that extends about 4 miles north from Chewelah also
is considered to be a part of the Edna. There, the lithol-
ogies are the same as those northeast of Valley, except
for a zone of vitreous quartzite about 300 feet thick in
the lower part of the exposed section and several zones
of argillite as much as 50 feet thick interbedded with
the dolomite. Only small partial sections are exposed
in the report area, and so the stratigraphy cannot be
described in detail.

Campbell and Loofbourow (1962, p. F10) reported
a zone of slate near the middle of the formation in the
magnesite belt and probably more than one zone of
vitreous quartzite. Campbell and Raup (1964) noted

 

several discontinuous quartzite zones in the Hunters
quadrangle, which covers most of the southern part of
the magnesite belt. In the report area quartzite and
argillite zones were found only northeast of Chewelah
and could not be matched unit for unit with those in
the magnesite belt.

The west boundary of the formation is a fault in this
area, and so only a minimum thickness can be esti-
mated. From outcrop width, the preserved section is
calculated to be 850 feet thick. Campbell and Loof-
bourow estimated that the thickness is between 1,500
and 2,500 feet in most of the magnesite belt but could
not accurately measure it because of poor exposures.

McHALE— SLATE

Black, gray, and green laminated argillite underlies
about half a square mile just east of Valley and is con-
sidered to be part of the McHale Slate. As with all units
of the Deer Trail Group in this area, the assignment is
not above question, but it is the best correlation based
upon available evidence. The argillite resembles the
type McHale Slate more closely than it does any other
formation in the Deer Trail Group and displays many
of the distinguishing characteristics of the formation.

The McHale Slate was named by Campbell and Loof-
bourow (1962, p. F11) for the exposures in McHale
Canyon, 4 miles west of Chewelah. There the unit is
between 1,000 and 1,500 feet thick, as it is in most of
the magnesite belt. The dominant lithology, which var-
ies little, is gray, green, and brown laminated argillite.
The McHale Slate contains numerous beds of soft-sedi-
ment breccia, which were not described by Campbell
and Loofbourow. The breccia resembles that found in
member 0 of the Striped Peak Formation. The unit also
contains numerous thin graded beds composed of silt-
and clay-sized particles.

In the report area the rocks of this unit are generally
phyllitic, although bedding is usually recognizable. The
formation is highly faulted, and so no section is com-
plete. One mile east of Valley about 2,000 feet of argil-
lite is preserved between two faults but is not well
exposed; it also may be faulted internally. This appar-
ently is the thickest possible section of McHale Slate
in the map area.

STENSGAR DOLOMITE

The Stensgar Dolomite crops out north of Valley and
southwest and north of Chewelah. The lowest contact
of the unit is nowhere exposed. It is either concealed
by younger rocks or cut off by faulting. The upper con-
tact on the hill north of Valley is gradational into the
argillite and siltite of the overlying Buffalo Hump(?)
Formation. In that area, the dolomite is predominantly
light gray or light tan with interbeds of maroon dolo-

18 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

mite, argillite, or siltite. Bedding thickness ranges from
1 inch to about 2 feet, and internal laminations or algal
structures are generally present in the thicker beds.
Maroon argillaceous partings occur between some beds
but are not numerous.

Weaver (1920, p. 58) named the Stensgar Dolomite
and included it in his Deer Trail Argillite. Bennett
(1941, p. 7) changed the name Deer Trail Argillite to
Deer Trail Group and elevated the Stensgar Dolomite
to a formation. The magnesite in the area is confined to
this formation, which is found almost the entire length
of the magnesite belt. Thickness ranges from 300 to
1,200 feet in the magnesite belt. There it is chiefly a
fine-grained light-blue or pinkish-gray dolomite, which
is thin bedded except where extensively recrystallized
(Campbell and Loofbourow, 1962, p. F13). Campbell
and Loofbourow (1962, F15) noted that a zone of red-
dish dolomitic slate is commonly found near the top
of the unit and that a similar zone about 100 feet thick
was also found at the base in a measured section at the
north end of the belt.

The thickness of the formation in the report area
cannot be accurately estimated, owing to poor expo-
sure. All the exposed sections are incomplete; 1 mile
southwest of Chewelah about 500 feet of the unit is
preserved. North of Valley a partial section of the unit
is about 1,000 feet thick, as calculated from outcrop
width, but is probably faulted internally.

BUFFALO HUMP(?) FORMATION

About 1,000 feet of argillite and siltite on the hill
north of Valley is questionably assigned to the Buffalo
Hump Formation. The name Buffalo Hump was given
by Campbell and Loofbourow (1962, p. F17) to a thick
section of argillite and quartzite that overlies the Stens-
gar Dolomite in the magnesite belt. They estimated
that as much as 3,000 feet of the unit is preserved near
the middle of the magnesite belt but found that it thins
to the northeast and southwest because of erosion prior
to deposition of the Huckleberry Formation.

The formation consists chiefly of quartzite and argil-
lite and exhibits striking facies changes in the magne-
site belt. Where it intersects the Hunters-Springdale
road, the unit is about 25 percent quartzite and 75
percent argillite. Only 5 miles along strike to the
southwest, the proportion of quartzite is 85 percent
(Campbell and Raup, 1964, calculated from their map).
Much of the quartzite is confined to zones and is vitre-
ous, medium to fine grained, and light colored. The
argillite is slaty and dark gray; much of it is not lami-
nated, unlike most of the argillite in the Deer Trail
Group (Campbell and Loofbourow, 1962, p. F18, F20).

In the report area, most of the rocks assigned to this
unit are well laminated or thin bedded; about 100 feet

 

of siltitic argillite is medium to thick bedded. The rock
is primarily medium to dark gray, but has a faintly red-
dish cast locally. Vitreous quartzite beds are not pres-
ent, and in this respect the rocks differ from those in
the magnesite belt. The rocks in the report area are
assigned tentatively to the Buffalo Hump Formation
chiefly because they conformably overlie the carbonate
unit containing maroon dolomite, which is considered
part of the Stensgar Dolomite.

On the hill north of Valley, the upper contact of the
unit appears to be faulted, but at least 1,000 feet of
section is preserved and fairly well exposed. This figure
is probably an accurate estimate of the thickness of the
unit preserved in the area.

DEER TRAIL GROUP, UNDIVIDED

Rocks presumably'belonging to the Deer Trail Group
crop out on the hill north of Springdale and north of
that on the mountain west of J umpofl Joe Lake. The
rock at both localities is not distinctive enough to assign
to any specific formation.

Black laminated argillite and some thin-bedded silt-
ite make up the section on the mountain west of J ump-
ofi Joe Lake. These rocks. most closely resemble the
McHale Slate or parts of the Togo Formation. The
rocks north of Springdale are about the same, except
for a much higher proportion of siltite to argillite.

RELATION BETWEEN THE BELT SUPERGROUP
AND THE DEER TRAIL GROUP

From the preceding descriptions it is apparent that
both the Belt Supergroup and Deer Trail Group are
thick Precambrian sections composed chiefly of fine-
grained elastic rocks which usually exhibit a very low
grade of metamorphism. Part of the Belt Supergroup
is strikingly similar to the Deer Trail Group and may
be an approximate time equivalent. There are, however,
obvious differences between these two sections, and
their proximity to one another necessitates either facies
changes or a large structural discontinuity.

The Belt Supergroup underlies many thousand
square miles and has been studied by many geologists,
a few of whom, such as Schroeder (1952, p. 19) and
Ross (1963, p. 88), briefly considered the relation
between the Belt and Deer Trail. In all previous stud-
ies, however, investigators were more handicapped than
us in attempting correlations, because the sections com-
pared were relatively far removed and, as a result, they
were unable to make unit-by-unit correlations.

Schroeder (1952, p. 18—20) compared the rocks in
the Bead Lake area With both the Deer Trail Group
in the magnesite belt and the Belt Supergroup in the
Clark Fork district. He recognized differences between

 

 

PRECAMBRIAN ROCKS 19

the two sections and correctly concluded that the rocks
in the Bead Lake area, which he named the Newport
Group, were more similar to the Belt Supergroup.
Campbell and Loofbourow (1962, p. F20) noted that
the similarity in lithology and sedimentary structures
and the great thickness of the Deer Trail Group com-
bined to make “the resemblance to the Belt Series
[Supergroup] striking.” Although they discussed the
problem more thoroughly than anyone had before, they
were unable to make unit-by-unit correlations. The cor-
relation of the two sections was also discussed, briefly,
by Becraft and Weis (1963, p. 17) .

We have drawn heavily on the valuable work by
these men and have combined it with our own data to
make tentative unit-by-unit correlation between the
Deer Trail Group and part of the Belt Supergroup.
The correlations proposed here are tentative, mainly
because of the composite nature of the Striped Peak
section in the report area, but also because of major
stratigraphic and structural differences between these
two thick sections and the units overlying them. Figure
7 summarizes the possible correlations between the
Deer Trail Group of the magnesite belt and the Belt
Supergroup of the report area and also shows the rela-
tion of the Belt of the report area to the Striped Peak
Formation of the Clark Fork quadrangle. The Striped
Peak units of the report area that are shown in figure
7 are pieced together as accurately as possible, but
faults that interrupt the section may introduce errors
in thickness and even in the order of superposition.
Figure 8 shows the present spatial relations between
the Deer Trail Group and the Belt Supergroup in the
report area.

In both the Belt Supergroup and Deer Trail Group,
the basal formation is considered at least twice as thick
as any other formation in that section. The Togo For-
mation has been estimated to be as thick as 20,000 feet,
and the only Belt unit to which it could possibly be
compared on the basis of both thickness and lithology
is the Prichard Formation.

Notably contrasting lithologic differences make cor-
relations between the Prichard and Togo Formations
suspect, even if the Togo is considered to be as thick
as the Prichard. Although both are made up of argillite,
siltite, and quartzite, the relative amounts in the two
formations are considerably different. The Togo For-
mation is composed chiefly of dark-gray argillite with
local, discontinuous carbonate zones and has a medium-
grained quartzite zone as much as 1,000 feet thick at
the top. The Prichard Formation has several distinct
argillite and quartzite zones; all the quartzite is fine
grained, and most of it is 4,000 feet or more below the
top of the unit (fig. 3). Both quartzite and siltite are
more abundant in the Prichard Formation, and iron

 

sulfides, which are characteristically found in the unit,
have not been described in the Togo Formation.

The obvious lithologic dissimilarities between the
formations above these basal units may have tended
to discourage previous attempts at unit-by-unit cor-
relation. Neither the Edna Dolomite nor the Stensgar
Dolomite, both relatively pure compared with Belt
carbonates, resembles any of the 10,000—18,000 feet of
Belt section between the Prichard and Striped Peak
Formations. The only other unit in the Belt Supergroup
that is lithologically comparable with the Togo Forma-
tion is the upper part of the Wallace Formation, which
is probably only slightly more than 2,500 feet thick,
thus considerably thinner than either the Prichard For-
mation or Togo Formation. Nevertheless, units over-
lying the Togo and upper Wallace Formations cor-
respond well. If this correspondence is meaningful and
the Togo Formation and the upper part of the Wallace
Formation are correlative, then the Togo Formation
may not be as thick as was estimated. Indeed, evidence
of another sort suggests that the Togo Formation is
considerably less than 20,000 feet thick.

Almost all estimates of the thickness of the Togo
Formation are based on the excellent work of Bennett
(1941), Campbell and Loofbourow (1962), Becraft
and Weis (1963) , and Campbell and Raup (1964) ,
who are chiefly responsible for the present understand-
ing of the Deer Trail Group. Although each of these
investigators has provided additional refinements on
earlier work, any study of the Togo Formation in the
magnesite belt is hampered by the incredibly poor expo-
sure and a lack of any traceable marker units other than
the quartzite at the top. This combination makes it im-
possible to systematically delineate structures in this
thick argillite unit. The result is well illustrated by the
wealth of complex structures which have been mapped
in the rest of the Deer Trail Group (Campbell and Loof-
bourow, 1962, pl. 1; Campbell and Raup, 1964) and the
almost total absence of faults and folds shown in the
Togo Formation, even where attitudes are locally
highly divergent. It would seem reasonable that faults
and folds are as numerous in the Togo Formation as in
the rest of the Deer Trail Group and that the formation
may therefore be thinner than previously estimated. If
the fault density in the rest of the Deer Trail Group is
superimposed on the Togo Formation, a thickness of
3,000 feet could more than adequately account for the
observed outcrop width.

The Togo Formation and the upper part of the Wal-
lace Formation are similar enough lithologically to be
considered correlative. Both are thick sections made up
chiefly of laminated dark-gray argillite, both contain
carbonate-rich zones, and both are overlain by sections
containing a significant proportion of relatively coarse

 

 

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CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

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———i

PRECAMBRIAN ROCKS 23

EXPLANATION

 

Tertiary and Mesozoic intrusive rocks

as

Paleozoic rocks, undivided

 

Cambrian rocks

Mostly Addy Quartzite and Gypsy Quartzite, but includes Maitlen
Phyllite and some Metaline Formation in places

V

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Mo k Formation

: :1

 

Huckleberry Formation, Leola Volcanics, and Shedroof Con-
glomerate

p€dt

Deer Trail Group and Priest River Group

 

Belt Supergroup

/-—’

Contact
______— __ _ _

Fault
Dashed where approximately located

WALLL...? ......... ?
Fault separating Deer Trail Group and Belt Supergroup

Dashed where approximately located; dotted and queried where
concealed or destroyed by younger rocks. Sawteeth on presumed
upper plate; hachured where fault is downdropped by younger

faults
___I__——_fi___

Normal Overturned
Axis of anticline, showing direction of dip of limbs
Dashed where approximately located

7__ __7_
Axis of syncline, approximately located
Quen‘ed where concealed
.... / _,
Deer Trail Group Belt Supergroup
Generalized strike of strata where reliable data are available

FIGURE 8.——-Generalized geologic map showing the distribution
of the Belt Supergroup and the Deer Trail Group in and
around the Chewelah—Loon Lake area. No postintrusive
rocks shown. Geologic data modified from Huntting, Bennett,
Livingston, and Moen (1961), Schroeder (1952), Park and
Cannon (1943), Bennett (1941), Campbell and Loofbourow
(1962) , and Campbell and Raup (1964).

 

 

clastics and carbonate rock. Unfortunately, distinguish-
ing internal characteristics are generally absent in both
units. Although only about 2,500—3,000 feet of the
upper Wallace Formation is preserved in the report
area, the unfaulted thickness before erosion could have
been somewhat greater.

The quartzite at the top of the Togo Formation has
a counterpart in member a of the Striped Peak Forma-
tion, although the lithologic correlation is not as close
as that between the other units correlated. The Togo
quartzite is chiefly light-colored medium- to fine-
grained quartzite with a small amount of interbedded
argillite. Member a, however, is predominantly darker
siltite interbedded with some argillite. The Togo
quartzite contains ripple marks and mud cracks similar
to those that are so abundant in member a, but the two
units difier from the others correlated in the two sec-
tions in that they are not look-alikes. However, the
Togo quartzite exhibits major facies and thickness
changes within the magnesite belt. Equal or larger
differences could exist between the magnesite belt and
the report area, especially since the Precambrian sec-
tions of the two areas appear to have been juxtaposed
by a thrust fault and thus were probably widely sepa-
rated when the rocks were deposited.

Member a does not closely resemble member 1 of the
Clark Fork and Coeur d’Alene sections either, even

though both are siltites. Rocks similar to those in mem-

ber 1 thin from a thickness of over 1,500 feet south of
the Coeur d’Alene district (Shenon and McConnel,
1939, p. 5) to about 600 feet in the Clark Fork quad-
rangle (Harrison and Jobin, 1963, p. K17), but the
units are lithologically similar at both localities. If
member 1 varies so greatly in thickness from north to
south, its lithologic character may possibly change
slightly to the west, and member a and the Togo
quartzite may be reflections of this change. Because
only part of member a is preserved in the report area,
it is also possible that the carbonate-bearing siltite,
which characterizes unit 1 to the east, was deposited
in the report area but because of faulting is no longer
exposed at the surface.

A remarkably good unit-by-unit match is evident
between the remainder of the Deer Trail Group and
the Striped Peak Formation. The Edna Dolomite is
indistinguishable from the light-tan and gray carbonate
that characterizes all but the upper part of member b.
The McHale Slate is almost identical with member c
and even displays the same type of soft-sediment defor-
mation that characterizes the member. Differences in
appearance result largely from the greater dynamic
metamorphism of the McHale Slate. Although no car-
bonate unit of significant thickness which could corre-
late with the Stensgar Dolomite is known to overlie

h

24 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

member 0, the maroon argillite, siltite, and quartzite
of member d might be compared with the maroon argil-
lite that bounds the Stensgar Dolomite and seems to
thicken toward the northeast end of the magnesite belt.

The Buffalo Hump Formation at the top of the Deer
Trail Group has no equivalent in the Belt section of the
report area, as the Cambrian Addy Quartzite rests un-
conformably on the eroded surfaces of member (1 and
older rocks. The Buffalo Hump Formation may be
roughly the same age as parts of the Missoula Group
that A. B. Campbell ( 1960, p. 560) described in the St.
Regis—Superior area to the east or as parts of the Libby
Formation. Either of these correlations would imply
considerable changes in facies and thickness. Within
the magnesite belt, the Buffalo Hump Formation
changes from predominantly argillite at the northeast
end to predominantly quartzite at the southwest end
(Campbell and Loofbourow, 1962, pl. 2; Campbell and
Raup, 1964) ; thus major facies changes do occur in this
part of the section.

METAMORPHIC ROCKS, UNDIVIDED

Deformed mica schist injected by leucocratic dikes
and sills occurs in several small areas in sec. 29, T. 34
N., R. 41 E., and sec. 34, T. 35 N., R. 41 E. These
highly metamorphosed rocks cannot be reliably as-
signed to any formation. In addition, they lie near the
boundary between the Deer Trail Group and Belt
Supergroup, and so they cannot even be assigned to one
or the other.

Highly recrystallized quartz-mica schist, quartzite,
and amphibolite underlie a narrow strip about 9 miles
long between Nelson and Goddards Peaks along the
east border of the report area. All the rock in this area
was derived from the Prichard Formation. It is mapped
separately from the Prichard Formation because a
short distance east of the report area it is not possible
to distinguish from which formation the metamorphic
rocks were derived. The metamorphic rocks, which are
intruded by many large and small bodies of two-mica
quartz monzonite, extend to the west side of Pend
Oreille Valley, 6 miles east of the report area. The
extreme recrystallization of the rocks was caused by
the numerous bodies of two-mica quartz monzonite.
The contact with the Prichard Formation cannot be
located precisely because a gradational zone as much
as 1 mile wide separates the units and because there
are very few exposures east of the divide separating
Nelson and Goddards Peaks.

WINDERMERE GROUP
HUCKLEBERRY FORMATION
A thick section of conglomerate overlain by an

 

 

equally thick section of greenstone constitutes the
Huckleberry Formation in the magnesite belt. The for-
mation rests unconformably on the Deer Trail Group
there. The two lithologies and their stratigraphic rela-
tion to the rocks above and below them were first
recognized by Jones (1928, p. 115), who referred to
them collectively as the greenstone phase of the Chew-
elah Argillite. Weaver (1920, pl. 1) earlier differenti-
ated small areas of greenstone locally but at most
places included both conglomerate and volcanic rock
in the Addy Quartzite. Bennett (1941), p. 8) divided
the conglomerate and greenstone and described them
in detail, but he assigned these rocks to the Lower
Cambrian. He recognized the major unconformity be-
tween the conglomerate and the underlying Deer Trail
Group and coined the names Huckleberry Conglomer-
ate and Huckleberry Greenstone. Campbell and Loof-
bourow (1962, p. F24) showed that the contact
between the greenstone and Addy Quartzite is also an
unconformity and assigned the conglomerate and
greenstone to the Precambrian. They gave these two
units member rank in a formation they named the
Huckleberry Formation. That usage is followed in this
report.

The Huckleberry Formation in the report area is
made up almost entirely of the greenstone member.
Conglomerate, which is found only on the hill southwest
of Chewelah, was not differentiated from the green-
stone on the geologic map. The largest area underlain
by the formation is about 8 miles due north of Chew-
elah. Here the greenstone is faulted against the Addy
Quartzite on the east and is unconformably overlain
by the Monk Formation on the west. It is not known
whether the absence of the conglomerate at this local-
ity is due to faulting or to nondeposition, but the latter
is suspected. On their geologic map of the magnesite
belt, Campbell and Loofbourow (1962, pl. 1) showed
the formation thinning toward the southeast, east, and
northeast, and as the formation is thin on the hill 1 mile
southwest of Chewelah, it may wedge out a few miles
north of the town.

The large area of greenstone north of Chewelah con-
sists of flows, breccias, and a minor amount of light-
colored tuff. Petrographically, much of it resembles
volcanic breccias and aquagene tuffs in British Colum-
bia that Carlisle described (1963, p. 57). Fine-grained
dark-green basalt appears to be the most common rock
type in the greenstone. Although these rocks are mildly
chloritized and epidotized, the primary igneous tex-
tures are perfectly preserved in many places. In several
specimens, pyroxene crystals (augite Ny=1.686, 2V:
54°) are completely unaltered, although almost all
plagioclase reflects a low-grade metamorphism in that
it is much more sodic (Anm) than an unaltered basalt

 

PRECAMBRIAN ROCKS 25

should be. The Na20 content of the rock, however, is
too low for a spilitic rock, although alkalies may have
been removed during metamorphism.

Analyses (table 1) of three samples considered to be
representative of the basalt flows and an analysis of a
fine-grained tuff show that the rock is chemically a
basalt but contains unusual amounts of a few compo-
nents. The total iron content is high, and the calcium
low. The analyses are most like those of a tholeiitic
basalt (Nockolds, 1954, p. 1030) , except that the silica
content averages 1 or 2 percent low. Normative quartz
is calculated in three of the specimens because of the
extremely low alkali content.

Whereas almost no planar structures, primary or
secondary, are developed in the greenstone north of
Chewelah, southwest of the town both the greenstone

TABLE 1.—-Chemical analyses and CIPW norms, in weight per-
cent, of basalt and one tufiaceous rock from the greenstone
of the Huckleberry Formation

[Analystsz P. L. D. Elmore, S. D. Botts, Lowell Artis]

 

1 2 3 4 5

 

Chemical analyses

 

 

 

 

 

 

 

 

 

 

 

 

 

42.6 43.8 44.8 47.5
12.7 12.0 13.2 13.4
.95 1.6 1.0 2.4
3.5 12.2 11.5 10.9
7.3 7.1 6.3 7.5
5.0 7.8 6.6 6.7
1.9 .95 2.8 2.1
.59 .28 .85 .9
.14 .15 .18 .43
5.0 5.7 4.8 4.4
3.5 3.2 2.8 2.3
.72 .54 .45 .25
20 .21 .21 .22
5 5 4 3 4.8 .24
Total ................................. 100.60 99.83 99.79 99.24
Chemical analyses (calculated on H20- and COz-free basis)
47.9 48.8 49.5 50.4 48.7
14.3 13.4 14.6 14.2 14.1
1.1 1.8 1.1 2.6 1.3
15.2 13.6 12.7 11.6 13.8
8.2 7.9 7.0 8.0 7.7
5.6 8.7 7.3 7.1 7.2
2.1 1.1 3.1 2.2 2.1
.66 .31 .94 .96 .64
3.9 3.6 3.1 2.4 3.5
.81 .60 .50 .27 .64
. .22 23 23 .23 .23
Total .................................. 99.99 100.04 100.07 99.96 99.91
CIPW norms (calculated on H20- and Gog-free bass)
6.3 ............ 2.0 ............
1.8 5.6
9.0 26.2
30.8 23.1
3.5 4.1
19.7 12.4
18.0 12.6
3.5
3.9
. 2.6 1.6
. 6.8 5.9
. 1.4 1.2
Total .................................. 100.0 99.9 100.1
Percent norm’ative
an in plagioclase ..................... 55.7 77.2 47.0 58.8 59.6

 

1. Fire-grained basalt, 700 ft E., 2,100 ft N. of SW cor. sec. 26, T. 34 N., R.
2. Fifie—isagied basalt, 1,050 ft E., 1,850 ft N. of SW cor. see. 26, T. 34 N.,
3. Fine-grained basalt, 1,500 it E., 1,550 ft N. of SW cor. sec. 26, T. 34 N.,
4. Fige-égagied tuft, 4,200 ft E., 1,700 ft N. of sw cor. sec. 26. T. 34 N.,
5

. Average composition of the three basalts.

 

 

 

and the conglomerate are cut by a well-developed cleav-
age which imparts a phyllitic character to the rock and
in most places masks any bedding or layering that may
have been present.

Attitudes in the large greenstone area north of
Chewelah are difficult to obtain because of the almost
complete lichen cover and the gradational character of
the contacts between flows and breccia horizons. At
the few locations where attitudes could be determined
with relative certainty, the sequence appears to strike
approximately north-south and to dip westward at low
angles. In at least one place in the eastern part of the
outcrop area, the greenstone dips eastward; thus the
great width of the outcrop may be due to a broad open
fold.

Because of the difficulty in determining attitudes in
the greenstone the thickness of this formation cannot
be accurately estimated. The few attitudes available
were used in drawing a cross section across the strike
of the large outcrop area north of Chewelah. If the cross
section is correct, the greenstone must be at least 1,200
feet thick to account for the outcrop width. As the base
is not exposed, the unit could easily be much thicker.

In several small areas 6 miles north-northeast of
Chewelah and at several places north and east of Val-
ley, greenstone appears to intrude the rocks of the Deer
Trail Group. Similar dikelike bodies of greenstone too
small to show on the map are found on the hill west of
J umpoff Joe Lake. All these intrusive bodies are prob-
ably related to the extrusive rocks of the Huckleberry
Formation. Some caution must be exercised in assign-
ing greenstone, whether intrusive or extrusive, to the
Huckleberry Formation, for similar-appearing green-
stone of Paleozoic age is present 17 miles southwest of
Chewelah in the Hunters quadrangle (A. B. Campbell,
written commun., 1965).

In the Metaline quadrangle, about 40 miles northeast
of Chewelah, Park and Cannon (1943, p. 7—11)
described some 5,000 feet of conglomerate that uncon-
formably overlies argillite of the Priest River Group.
The conglomerate is in turn overlain by some 5,000
feet of greenstone. They applied the names Shedroof
Conglomerate and Leola Volcanics to these two units
and correlated them with the formation Daly (1912)
named Irene Conglomerate (later named the Toby Con-
glomerate by Walker, 1926, p. 13) and Irene Volcanics
in Canada. Becraft and Weis (1963, p. 173) correlated
the conglomerate of the Huckleberry Formation with
the Shedroof and Toby Conglomerates, and the green-
stone with the Leola and Irene Volcanics.

The conglomerate northeast and southwest of the
report area is fairly thick, and its near absence within
the area suggests either nondeposition due to a topo-
graphic high or rapid thinning in a southeasterly direc-

 

 

26 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

tion. The basin in which the various conglomerate and
volcanic units were deposited appears to have been
fairly extensive in a northeast-southwest direction
(Becraft and Weis, 1963, p. 16), but little is known
about its extent, if any, to the northwest or southeast.

MONK FORMATION

The Monk Formation is poorly exposed in the report
area, except on the mountain west of Cliff Ridge and for
a distance of about 3 or 4 miles to the southwest (out-
side the quadrangle). The most distinguishing char-
acteristic of the formation is probably its heterogeneity.
Although predominantly slate and argillite, it contains
numerous beds of dolomite, conglomerate, and quartz-
ite.

The Monk Formation was named by Daly (1912, p.
148) for exposures of slate, phyllite, schist, and con-
glomerate along Monk Creek in southeastern British
Columbia. He measured a section about 5,500 feet
thick. Park and Cannon (1943, p. 11) estimated the
thickness of the formation to be about 3,800 feet in the
Metaline quadrangle. There, it is mostly fine-grained
phyllite with numerous interbeds of carbonate rock,
quartzite, and grit.

Rocks probably belonging to the Monk Formation
are found in the hills bordering Bayley Creek, on the
mountain west of Cliff Ridge, and on the hill 1 mile
southwest of Chewelah. The patchy occurrence of this
unit is due chiefly to faulting, but the variation in thick-
ness also results from Precambrian erosion. The upper
contact is everywhere an unconformity with the Addy
Quartzite. Some of the rocks, especially those east and
southeast of Bayley Creek, may not be part of the
Monk Formation, but were so assigned because they
are apparently underlain by the Huckleberry Forma-
tion.

On the mountain west of Cliff Ridge, dolomite of the
Monk Formation rests on greenstone of the Huckle-
berry Formation. The dolomite is pale yellow to pale
gray and highly recrystallized, and it occurs in beds
.as much as 5 feet thick. It is restricted to the lower 150
feet of the unit within the area and grades upward into
a section that consists predominantly of slate, some of
it carbonate bearing. About 1.5 miles to the southwest,
along strike, the lower carbonate zone thickens and is
overlain by rocks displaying an upward gradation
similar to that found to the north. From there, for
about 2 miles farther southwest, beds of conglomerate
and carbonate-bearing slaty argillite separate the car-
bonate rock and the greenstone. Although poor expo-
sures do not permit detailed stratigraphic observations,
the conglomerate part of the unit appears to become
progressively thicker to the southwest.

Park and Cannon (1943, p. 12) found a similar

 

 

sequence of units near the base of the formation in the
Metaline quadrangle, except that the thicknesses of
the individual units differ from those in the report area.
They reported that conglomerate forms the base of the
Monk Formation north of the headwaters of Gypsy
Creek and is overlain by 200—300 feet of limestone.
South of the Gypsy Creek headwaters, however, the
conglomerate is missing, and presumably the same
limestone rests on greenstone of the Irene Volcanics,
the Huckleberry greenstone equivalent. In and just
west of the report area, clasts in the conglomerate are
pebbles and cobbles of greenstone from the Huckle-
berry Formation, an andesitic-looking rock not found
in the area, and fine-grained white quartzite. The
matrix is metamorphosed but appears to have been
carbonate-bearing argillite or siltstone that was sandy
in places. The slate overlying the dolomite west of Cliff
Ridge is the most common lithology in the formation.
It is purple to maroon with thin pale-green beds which
range in thickness from about one-sixteenth inch to
about 2 feet. The purple beds are chiefly argillite, but
the pale-green layers are composed of slightly coarser
grained silt-sized material. Almost all the argillite is
finely laminated, although in much of it the lamina-
tions are quite subtle. Both the purple and green
layers are carbonate bearing. Higher in the section, the
slate contains progressively less carbonate, and in the
upper half of the unit almost no carbonate-bearing
rocks are found.

The small fault-bounded outcrops of this unit 4.5
miles due north of Chewelah are made up of both the
lower dolomite and the purple slate. At this locality,
however, the transition zone contains several tens of
feet of pisolitic sandy carbonate beds. The pisolitic
rock is light yellow brown and forms beds as much as
2 feet thick. It grades upward bed-by-bed into slaty
maroon argillite.

The Monk Formation west of Bayley Creek and on
the hill 1 mile southwest of Chewelah is made up, in
part, of lithologies not found in the more extensive sec-
tion west of Cliff Ridge and could be part of the Stens-
gar Dolomite. West of Bayley Creek, the Addy Quartz-
ite rests on about 100 feet of cream-colored dolomite.
The dolomite is faulted over about 150 feet of purple
to maroon argillitic dolomite and carbonate-bearing
argillite, which includes a 20-foot-thick bed of conglom-
erate and pebbly mudstone near the top. This pebbly
mudstone and the carbonate rocks below it may be part
of either the Monk Formation or the Stensgar Dolo-
mite.

The Monk Formation is overlain by the Lower Cam-
brian Addy Quartzite on the hill southwest of Chew-
elah. There the Monk consists of about 400 feet of
medium-gray slaty siltite and argillite and contains

 

PALEOZOIC ROCKS 27

beds of light-gray dolomite as much as 50 feet thick in
the lower 150 feet. The slaty rock and dolomite overlie,
or are faulted against, about 350 feet of highly sheared
conglomerate provisionally assigned to the Huckle-
berry Formation. This rock strongly resembles the
conglomerate member of the Huckleberry Formation
in the magnesite belt, but is also similar to the conglom-
erate found in the Monk Formation southwest of Clifl
Ridge. The conglomerate overlies the maroon argillite,
carbonate-bearing pebbly mudstone, and dolomite be-
lieved to be part of the Stensgar Dolomite.

PALEOZOIC ROCKS
ADDY QUARTZITE

The Addy Quartzite, first described and named by
Weaver (1920, p. 61—63), is a thick fine- to medium-
grained vitreous quartzite. It crops out at many places
in the west half of the report area and is one of the best
stratigraphic markers in the region. This unit and its
probable equivalent to the north, the Gypsy Quartzite,
underlie much of northeastern Washington.

The best exposures of the Addy Quartzite in the
report area are due east of Chewelah on the west flank
of Quartzite Mountain, where about 1,500 feet of the
unit forms spectacular, near-vertical cliffs (fig. 10).
Eagle Mountain marks the northern limit of an
approximately north-south discontinuous belt of Addy
Quartzite which extends southward to just beyond
Springdale. This belt is bounded on the west by a
fault of variable dip and unknown displacement. The
fault trace is covered by glacial and alluvial material
for the entire length of the belt.

A surface of low relief was eroded across rocks of the
Belt Supergroup after they had been faulted and
broadly folded. The Addy sediments deposited on this
surface therefore rest unconformably on several of the
Precambrian units. At most places in the area, however,
the angular discordance is so slight that it cannot be
reliably measured. On’ the west flanks of. Eagle Moun-
tain and Quartzite Mountain, the Addy rests on mem-
ber c of the Striped Peak Formation, and at various
places south of Quartzite Mountain, it rests on mem-
bers a, c, and d (figs. 9, 10). On the hill 1 mile south-
west of Chewelah, and on the mountain 10 miles north
of Chewelah, just west of the report area, the formation
rests on the Monk Formation. Southwest of Valley it
appears to have been deposited on the Buffalo Hump(?)
Formation of the Deer Trail Group.

The unconformity at the base of the Addy Quartz-
ite is well exposed on the west flank of Quartzite Moun-
tain and on J umpofl Joe Mountain. At both localities,
the basal 100-300 feet is a distinctive purple quartzite.
These beds are well stratified and generally are marked

 

 

FIGURE 9.—The bold clifl’s are dip slopes of Addy Quartzite
which form the west side of Quartzite Mountain. Member c
of the Striped Peak Formation underlies the quartzite just
beyond the lip of the cliffs. The exposures formed by member
c in the low swale near the center of the mountain and those
behind the most prominent cliff on the south flank of the
mountain are the best of any Belt formation in the area. The
steep slopes on the hill in the right background are underlain
by the Revett Formation. View east.

 

FIGURE 10.—Contact between the Addy Quartzite and member
d of the Striped Peak Formation is at the base of the bold
outcrops in the left center of the picture. The contact is well
exposed here, but the angular discordance between the two
units is so small that it cannot be measured. The base of
member d is near the break in slope at the right edge of the
photograph (arrow). Outcops are on the small hill immedi-
ately south of the Loon Lake copper mine. View north.

h

28 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

by a well-developed thin black striping which is easily
mistaken for bedding. From the basal beds the Addy
grades upward through pink quartzite over a strati-
graphic distance of about 100—200 feet into the white
and light-gray quartzite which characterizes most of
the formation. At several places in the area, the purple
quartzite is separated from the underlying Precambrian
rocks by as much as 500 feet of white, gray, or pink
quartzite and siltite (Reynolds, 1968, p. 11).

The bulk of the Addy Quartzite is white to light-gray
vitreous quartzite, although some beds have a pale-
yellow or pale-pink cast. Small pink quartz grains are
sparsely scattered throughout this rock and are a char-
acteristic of the formation. The beds range in thickness
from a few inches to over 20 feet but average about 3
feet. Although a poorly developed bedding-plane part-
ing is usually present and gives the rock a massively
bedded appearance, bedding, as defined by differences
in grain size or lithology, is not obvious owing to the
homogeneity of the formation. Real bedding in the
lower purple quartzite, as contrasted to the black strip-
ing, is defined by thin partings of argillaceous material
or by beds of coarser grained quartz. Beds of purple
quartzite average 1—2 feet in thickness, but massive
beds as much as 5 feet thick are common.

Reynolds (1968, p. 13, 15) studied the lower part of
the formation in detail, including the purple beds, and
found that the rocks consist of fine to medium sub-
rounded to well rounded moderately to well sorted
quartz grains. These observations also apply to the rest
of the formation. Small lenses of pebble conglomerate
are common in the lower 200—400 feet and are
abundantly exposed on Quartzite Mountain. Pebbles
of quartzite are the most common clasts. Pods of con-
glomerate and sedimentary breccia as much as 5 feet
thick occur locally at the contact with the underlying
Precambrian rocks, on Deer Lake Mountain, and
Quartzite Mountain. The clasts in these pods are com-
posed of the immediately underlying material and are
probably locally derived.

Small lensoidal pockets with a friable appearance are
another feature characteristic of the Addy Quartzite as
a whole but much more common in the lower 500 feet.
Much of the cementing material in these pockets has
apparently been leached out from between the grains,
but the grains are held together strongly by a small
amount of silica cement. Where numerous, the pockets
impart a vuggy appearance to the rock.

At least 50 feet of shale, some of it sandy, occurs
about 1,000 feet above the base of the unit on Quartzite
Mountain. This shale is well stratified and light gray,
pale green, and pale maroon. It is overlain by more
light-colored quartzite identical with that below. The
upper part of the formation is preserved only on the hill

 

 

1 mile south of Springdale. There, a few hundred feet
of medium- to thick-bedded white quartzite is overlain
by the Metaline Formation. An interval about 100 feet
Wide between argillaceous limestone of the lowest Met-
aline and quartzite of the highest Addy is covered, and
so it is not known if there is any slate or argillite
between the two units, as there is in sections north of
the report area.

The most complete section of Addy Quartzite in the
vicinity of the report area is just east of the town of
Addy (fig. 2), about 4 miles northwest of Chewelah.
There, a north-dipping, apparently homoclinal section
of Addy Quartzite about 4,000 feet thick overlies
Huckleberry greenstone and is reasonably well exposed.
The upper part of the quartzite contact appears to be
faulted against the Huckleberry Formation.

Only two fossil localities are known in the formation.
One is located about 2,500 feet above the base of the
section east of Addy. Fossils from this locality were
identified by A. R. Palmer (written commun., 1964)
and include Nevadella addyensis (Okulitch), Kutor-
gina?, and Hyolithes sp. Palmer concluded that the
trilobite indicates that the quartzite is very Early Cam-
brian. The other locality is about 1 mile to the south-
west, on the west side of Addy. Among those who have
examined fossils from this second locality, Okulitch
(1951, p. 405) seems to have made the most detailed
study. He reported finding the following fauna: M icro-
mitra (Paterina) sp.,Kutorgina cf. K. cingulata (Bil-
lings), Kutorgina sp., Rustella cf. R. edsoni Walcott,
Hyolithellus sp., Nevadia [:Nevadella] addyensis
Okulitch, olenellid fragments, and fucoids. Okulitch
concluded that “The fauna is undoubtedly Lower Cam-
brian in age; and the presence of the rare genus N evadia
[:Nevadella], with its very primitive characteristics,
suggests the lower portion of the Lower Cambrian.”

Lithologically, the fossil-bearing rock is not typical
of the formation as a whole. It is thin- to medium-
bedded fine-grained quartzite which is locally argilla-
ceous and contains detrital muscovite. Beds range in
thickness from 1 to 12 inches and are interbedded with
argillite bands as much as 4 inches thick. The argillite
is medium gray, black, and gray green. Some of it is
laminated, but most is not. In the upper part of the
fossiliferous zone are a few beds of dolomitic siltite.
Above the dolomitic zone are more thick to massive
quartzite beds typical of the formation. None of these
atypical lithologies have been recognized within the
report area.

The purple quartzite near the base of the Addy is
one of the most important stratigraphic markers in the
region, but appears to have been largely ignored by
previous workers. Bennett ( 1941, p. 9) briefly described
the formation, but did not mention the purple zone.

 

 

—’7 _

PALEOZOIC ROCKS 29

Campbell and Loofbourow mentioned a zone in which
the bedding planes are emphasized by thin purple
bands, but did not specify in what part of the section it
occurs. On a brief trip the authors found the purple
zone near the base of the formation on Stensgar Moun-
tain, which is about in the center of the magnesite belt.
Park and Cannon (1943) did not report a purple zone
in the Metaline quadrangle, nor did Yates (1964) in
the Deep Creek area.

Becraft and Weis (1963, p. 12) reported that the
Addy Quartzite is about 3,900 feet thick in the Turtle
Lake quadrangle, 30 miles southwest of Chewelah.
They correlated the formation with the Gypsy Quartz-
ite in the Metaline quadrangle. Forty miles northeast
of Chewelah, in the Deep Creek area, about 2,900 feet
of the Gypsy Quartzite conformably underlies the
Maitlen Phyllite (Yates, 1964), but the section is
faulted at the base. On Crowell-Sullivan Ridge near the
type section of the Gypsy Quartzite in the Metaline
quadrangle, the unit is 8,500 feet thick (Park and Can-
non (1943, p. 13). About 7 miles west of that, however,
the section is only about 5,300 feet thick.

CARBONATE ROCKS

Paleozoic carbonate rocks crop out discontinuously
from Eagle Mountain to south of Springdale. Only the
Cambrian, Devonian, and Mississippian Systems have
been identified, but other systems may have gone unrec-
ognized owing to the sparsity of fossils. Exposures in
the area are inadequate to construct a complete com-
posite section, and part of the section may not be
exposed owing to faulting or erosion. Thick sections of
Cambrian and Ordovician strata not found in the report
area occur to the west in the Hunters quadrangle
(Campbell and Raup, 1964) and to the north in the
Colville area (Bennett, pl. 6, in Mills, 1962), Deep
Creek area (Yates, 1964), and Metaline quadrangle
(Park and Cannon, 1943, p. 17-22). This distribution
may be due to rapid and large-scale facies changes;
however, it is equally possible that these units were
never deposited in the report area. Most of the Paleo-
zoic rocks here may have been deposited at a distant
location and brought in by large lateral movements.

Because of the discontinuous and patchy occurrence
of the Paleozoic carbonate rocks that are preserved, the
stratigraphic relations of these rocks are not well estab-
lished. Much of the carbonate rock, especially between
Loon Lake and J umpoff Joe Lake, is exposed only in
small, widely separated outcrops and had to be mapped
as undivided Paleozoic.

METALINE FORMATION

About 1.5 miles southeast of Springdale, carbonate
rocks of the Middle Cambrian Metaline Formation rest

 

 

 

with apparent conformity on the Addy Quartzite.
According to R. G. Yates, who examined these rocks
with the authors in the field, the rocks closely resemble
the lower and middle units of the Metaline Formation
in the Deep Creek area, about 60 miles north of Spring-
dale. There, the formation varies considerably from
place to place owing to both facies changes and large
lateral movements along faults; complete sections are
more than 5,000 feet thick and consist chiefly of lime-
stone and dolomite (Yates, 1964). In the northeastern
part of the Hunters quadrangle, 15 miles northwest of
Springdale, Campbell and Raup (1964) reported that
as much as 8,000 feet of limestone and dolomite overlies
the Addy Quartzite. They assigned these rocks to
Weaver’s (1920, p. 66) Old Dominion Limestone. Simi-
larities in lithology and faunal assemblages, and rela-
tionship to the Addy Quartzite, make at least part of
the Old Dominion a most likely correlative with the
Metaline Formation in the area.

In the Deep Creek area and in the Metaline quad-
rangle, the Metaline Formation is separated from the
Gypsy Quartzite (correlative with the Addy Quartzite)
by the Maitlen Phyllite, which is over 5,000 feet thick
in both areas. In the Hunters quadrangle and the report
area, the Old Dominion Limestone and the Metaline
Formation may rest directly on the Addy Quartzite. A
covered area about 100 feet wide separates the highest
outcrops of Addy Quartzite from the lowest Metaline
carbonate on the hill southeast of Springdale, and con-
ceivably that much phyllite could separate the two
units. As no phyllite float was found in the covered
area, the carbonate rock is assumed to rest directly on
quartzite.

The absence of the Maitlen Phyllite in the southern
part of Stevens County is apparently due to nondeposi-
tion rather than faulting. A major fault with large lat-
eral transport separates sections containing the phyllite
from those without it. The fault separating the Belt
Supergroup and Deer Trail Group may also divide the
Paleozoic section of the report area from that typified
by the Paleozoic rocks in the Deep Creek area.

Southeast of Springdale the base of the Metaline
Formation consists of gray to blue-gray limestone.
Irregularly shaped yellow-brown—weathering argilla-
ceous seams are distributed throughout the rock in an
interwoven network. The surface of the weathered rock
is typically grooved or fluted, resembling a rillenstein
like surface. The rock is thick to thin bedded and gener-
ally fine grained. About 4,000 feet northeast of the
Addy-Metaline contact, most of the lower part of the
Metaline Formation is repeated by a fault. There, num-
erous beds of black shale as much as 1 foot thick, which
are not exposed to the southwest, are interlayered with
the argillaceous limestone. Above the argillaceous lime-

 

 

i

30 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

stone thick- to thin-bedded tan to light-gray dolomite
is interlayered with a small number of thin dark-gray
shale layers. ,

The partial sections are very poorly exposed and may
be repeated more than once by faulting. The upper
contact is a fault, and so the thickness of the Metaline
Formation in the area is not known. Because of poor
exposures and uncertain structure, the thickness of
even the preserved part of the formation cannot be
accurately estimated. The part immediately above the
Addy Quartzite and southwest of the fault that repeats
the section may be homoclinal. If this portion of the
section is not faulted, it is about 2,000—2,500 feet thick.

Trilobites and brachiopods were collected in the
SW14 sec. 35, T. 30 N., R. 40 E. A. R. Palmer
examined two collections and identified the trilobites
as Peronopsis, Bathyuriscus, Olenoides, and undeter-
mined ptychopariods, and the brachiopods as Linnars-
sonia and Acrothele.

Palmer (written commun., 1968) stated that the col-
lections contain undoubted Middle Cambrian fossils
and also that “The * * * [fauna] * * * is most probably
of late Middle Cambrian age, and could be the same
age as the earlier faunas from the Metaline Limestone
[Formation]. Olenoides is a long-ranging genus and
precise placement * * * within the Middle Cambrian
on its own merits is not possible.”

DEVONIAN OR MISSISSIPPIAN CARBONATE ROCK

Some of the carbonate rocks in the Loon Lake quad-
rangle that Miller (1969, p. 3) described as Mississip-
pian( ?) may include strata as old as Devonian and are
here referred to as Devonian or Mississippian. Lime-
stone containing fossils overlies these rocks with no
apparent unconformity. The lower age limit is less pre-
cisely based on Upper Devonian fossils found in isolated
outcrops of carbonate rocks. The lower dolomite of the
earlier report is divided into two units, and the over-
lying dolomite and calcareous slate are retained as a
third.

UNIT 1

The lowest unit in this sequence is a dark-gray dolo-
mite that crops out discontinuously from the south
flank of Eagle Mountain to the mouth of Cottonwood
Creek. It also crops out in a small area along the Bur-
lington Northern Railroad tracks 1.5 miles northeast
of Springdale. Although not very extensive, the best
exposures of the unit are on the hill in sec. 19, T. 32
N ., R. 41 E.

The dolomite is uniformly dark gray, except for a
few zones which are a mottled light gray. N o limestone
beds were found in the unit, and in fact, very little of
the rock is even slightly limy. In places the dolomite
appears to be argillaceous, and it contains sparse sand

 

grains throughout. Bedding is well defined, ranging
from a few inches to 5 feet in thickness. The texture
varies from aphanitic to coarse grained.

Sedimentary structures are found throughout the
unit and along with the dark color serve to distinguish
the dolomite from all other carbonate units. Oolites are
common, usually confined to individual beds less than
1 foot thick but locally occurring as irregular patches.
Dolomitic conglomerate is also found throughout the
unit. It is composed of angular to slightly rounded
clasts as much as 1 inch across, which are almost
identical in appearance with the surrounding carbonate
matrix. Randomly oriented curved chips of white
coarse-grained dolomite scattered through most of the
unit may be recrystallized fossils. Some resemble the
curved cross section of a brachiopod shell, whereas
others are cylindrical and may be pelmatozoan remains.
The exposed portion of the unit is estimated to be
between 600 and 700 feet thick.

The lower contact is covered by surficial deposits
everywhere in the report area. Beneath the younger
cover unit 1 must be faulted against either the Addy
Quartzite or Metaline Formation. An exploratory oil
well drilled by the Empire Exploration Co. in the NE 14
sec. 30, T. 31 N., R. 41 E., penetrated carbonate rock,
most of it dolomite, for 2,192 feet. At 2,664 feet quartz-
ite was penetrated immediately below a fault zone,
although it is difficult to ascertain from the description
of well cuttings if the drill was in unit 1 before hitting
quartzite.

UNIT 2

The contact between units 1 and 2 is reasonably well
exposed on the hill in sec. 19, T. 32 N ., R. 41 E. Where
examined, it is marked by a rather abrupt change from
dark-gray to almost white dolomite. Like unit 1, unit
2 is internally homogeneous. The beds of white dolo-
mite at the base are representative of the unit as a
whole, except that large oolites or pisolites are found
only in the lower 10—20 feet. Other than bedding and
the oolites near the base, the unit contains no obvious
sedimentary structures, perhaps because of recrystalli-
zation. Although the units bounding it are predomi-
nantly fine-grained or aphanitic carbonate rock, unit 2
is almost uniformly coarse grained.

Bedding is less well defined than in unit 1. Beds
range from a few inches to about 5 feet in thickness; the
average is about 3 feet. The thickness of the beds gives
the rock a massive appearance, but close examination
of weathered surfaces shows that most of the thicker
beds are thinly laminated internally. A. K. Armstrong
of the U.S. Geological Survey examined specimens col-
lected from this unit and concluded that “Oolites and
coated carbonate lithoclasts in a matrix of smaller
pieces of the same material suggest a shoaling environ-

—

 

 

————7

PALEOZOIC ROCKS 31

ment for part of the carbonate” (oral commun., 1967 ).
These shoaling rocks alternate bed by bed with others
containing algal structures suggestive of an intertidal
environment (Miller, 1969, p. 3). No fossils other than
the nondefinitive algae have been found in the unit.
The unit is 500—650 feet thick on the hill in sec. 19,
T. 32 N., R. 41 E. The faulted section that is well
exposed along the Burlington Northern Railroad tracks
2 miles northeast of Springdale is nearly horizontal and
at least 550 feet thick. The rocks at this locality are
very light gray rather than white. Because most of the
units in this area are fault bounded, the rocks assigned
to unit 2 here could conceivably be a different part of
the section. They have been assigned to unit 2 because
they contain oolites, especially near the base, and are

underlain by dark- gray dolomite Wthh resembles unit 1.

UNIT3

Overlying the white dolomite is an extremely distinc-
tive unit which, unlike some of the carbonate units, is
recognized with confidence wherever mapped. It is not
internally homogeneous like the other two units but is
made up chiefly of light-colored dolomite, maroon slate,
and all gradations between the two. The base of the
unit is predominantly light-gray and cream-colored
dolomite and rests with apparent conformity on the
white dolomite of unit 2. About 40 or 50 feet above the
base, several beds as much as 2 feet thick of pale-gray-
green argillaceous dolomite and maroon slate are inter-
calated with the carbonate rock. The maroon beds
become thicker and more numerous upward in the sec-
tion. Two to three hundred feet above the base is a zone
of thin-bedded maroon slate about 100 feet thick. The
maroon rock grades into pale-green argillite both above
and below the zone. These color changes are especially
well displayed in the exposures northeast of Springdale.
The slate is generally well laminated and contains thin
seams of dolomite. It grades upward into light- gray and
cream-colored dolomite similar to that in the lower
part of the unit.

In the section northeast of Springdale, predominantly
light- gray to white dolomite that strongly resembles the
rocks of unit 2 is found 500—600 feet above the base
of unit 3. The contact between this rock and the under-
lying cream-colored dolomite of unit 3 is not exposed
but is thought to be a fault. If it is a fault, the preserved
part of unit 3 is between 500 and 600 feet thick.

Bedding thickness in the dolomite ranges from a few
inches to about 10 feet. Although the dolomite is cream
colored (described as tan or gray tan by Miller (1969,
p. 3) ) , the weathered color, which is almost pale orange,
is more characteristic of the unit. The texture is partly
saccharoidal, but some of the rock is sufficiently apha-
nitic to resemble chert.

 

MISSISSIPPIAN CARBONATE ROCK

Limestone and dolomitic limestone containing Mis-
sissippian fossils are found on the hill 1 mile north of
Springdale and on a smaller hill 1.5 miles east of Valley.
Most of the limestone is medium gray to blue gray. The
lower part of the unit contains a few zones of tan to
tan-gray dolomitic limestone, some of which are lami-
nated. Bedding thickness ranges from less than 1 inch
to more than 15 feet but averages about 2 or 3 feet.
Chert, in beds and nodules, is common but confined to
definite zones. On the small hill near the center of sec.
27, T. 30 N., R. 40 E., about 400 feet of limestone in
which cherty rock alternates with noncherty is well
exposed. The cherty zones are about 80 feet thick, and
the zones without chert about half that. Most of the
chert beds are only a few inches thick, but some are as
much as 10 inches. Slightly higher in the section to the
northeast, some of the thicker beds appear to have been
bioclastic limestone that has been locally replaced by
chert.

The grain size of the limestone on the hill north of
Springdale varies from coarse to fine and to some degree
may coarsen in the direction of the coarse-grained
quartz monzonite. Where dolomitic, the rock tends to
be slightly coarser than the limestone and ranges from
medium to coarse grained. Approximately 500 feet
above the base of the preserVed section there is about
10 feet of dark-gray to black aphanitic limestone which
serves locally as a marker within the unit. Both the very
fine grain size and the color of this zone distinguish it
from the other rocks in the unit.

Neither the upper nor the lower contact is exposed
in the area. Northeast of Springdale the upper contact
is a fault, and the lower part is concealed beneath surfi-
cial material. A thickness of 600—700 feet for the pre-
served part of the unit is calculated from outcrop width,
but this figure may be in error because of undetected
faults.

Fossils are found throughout the unit but are abund-
ant in only a few places. The tan to tan-gray beds in
the lower part of the unit contain abundant fenestellid
bryozoans and a few solitary corals. The medium-gray
to blue-gray beds in the same general part of the section
contain abundant pelmatozoan debris and a few fenes-
tellid bryozoans, but all are partly recrystallized. Near
the middle part of the exposed section northeast of
Springdale is a dolomitic limestone bed which contains
abundant corals, brachiopods, gastropods, and pelma-
tozoan debris. A. K. Armstrong of the US. Geological
Survey identified the following fossils (written com-
mun., 1967):

Coral:
Amplexizaphrentis sp.

 

i

32 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

Brachiopods:
Unispirifer sp. indet.
Spirifer sp. indet.
Pseudosyrinx? sp. indet.
Gastropod:
Platyceras sp.
Armstrong reported the following:

The fossils are poorly preserved as fragments which have
been replaced by coarse chalcedony within recrystallized
dolomitic limestone. Acid etching has yielded a small fauna.

ently devoid of a syrinx may possibly belong to the genus
Pseudosyrmx. The original shell structure was not pre-
served and the fragmentary nature of the material makes
positive generic identification impossible. Fragments of
pedicle valves strongly indicate the presence of both the
genus Spirifer and Unisperifer. The fauna suggests a
MiSSissippian age.

The limestone on the hill 1.5 miles east of Valley
presumably belongs to the same unit. A. J. Boucot
(written commun., 1966) recovered the following
brachiopods and suggested that the rocks were prob-
ably Mississippian in age:

Rhipidomella sp.
Composita sp.

indet. spirifer (fine ribs)
indet. spirifer (coarse ribs)
Crurithyris sp.

indet. brachiopods

Gilbert Klapper (written commun., 1966) examined
rocks from the same locality for conodonts. Samples of
a light-tan dolomitic limestone bed were collected about
30 feet stratigraphically below the gray limestone col-
lected by Boucot and yielded the following:

Siphondella isosticha (Copper)

Pseudopolygnathus multistriata Mehl & Thomas

Gnathodus sp.
Klapper concluded that “The * * * [age of the rocks]
* * * is definitely Mississippian. It contains about the
same fauna as that known from the basal Banif Forma-
tion of Crowsnest Pass, Alberta * * *. The fauna is one
zone higher than the fauna described from the basal
Lodgepole * * *”. (See Klapper, 1966, p. 5.)

Embysk (1954, p. 14) identified the following ostra-

codes from the same locality:
Graphiodactylus tenuis
Jonesina craterigera
Cavellina aff. C. corelli

Except for these sparse outcrops in the report area,
no Mississippian rocks have been reported in north-
eastern Washington or northern Idaho. The significance
of this fact cannot be competently evaluated by work

'in and around the report area, however, because the

 

entire Paleozoic is so incompletely exposed and poorly
understood.

PALEOZOIC CARBONATE ROCKS, UNDIVIDED

Much of the Paleozoic carbonate rock is mapped as
undivided because of the lack of distinguishing charac-
teristics needed to either assign the rock to established
units or define a new unit. In some of the areas shown
as bedrock on the geologic map, the exposure consists
of only a few widely separated small outcrops. Some of
the undivided carbonate rock undoubtedly belongs to
units already described, but much of it definitely does
not. Although lithologic descriptions of many indi-
vidual outcrop areas would serve little purpose, some
localities should be mentioned because the rocks there
contain a few fossils.

Jones (1929, p. 43) reported finding brachiopods in
a 2-foot-thick bed of purplish-red limestone in the SE
cor. sec. 22, T. 33 N ., R. 40 E. These were identified
by Branson (1931, p. 70) as Kutorgina cingulata (Bil-
lings) of Early Cambrian age. The limestone is enclosed
in light- to dark-gray dolomite, cream colored in places.
Most of the carbonate in this small area of outcrop is
highly brecciated dolomite—so brecciated that bedding
is difficult to recognize.

These fossil beds were searched for without success.
Exposures are good only locally, and stratigraphic rela-
tions are not clear in this area. Kutorgina cingulata
(Billings) is found in the upper part of the Addy
Quartzite, and Jones and Barnes may have collected
the fossils from a fault slice of that unit. The lithologic
descriptions by Jones and Branson are not detailed
enough to test this hypothesis, although Branson
( 1931, p. 70) mentioned that “the limestone is reddish
in color, dense, sandy, and bears thin lenses of impure
argillite.” Some of the fossiliferous beds in the Addy
Quartzite east of Addy would fit this description.

The rocks from which the fossils came may also be
part of the Old Dominion Limestone of Weaver ( 1920) ,
which overlies the Addy Quartzite north of Colville
(Bennett, in Mills, 1962, pl. 6). Although quite fossil-
iferous, the limestone there contains only Archaeocya-
tha, however.

R. H. B. Jones and J. P. Thompson collected Late
Devonian fossils from a rather nondistinctive medium-
gray limestone in the north-central part of sec. 19, T.
31 N., R. 41 E. The rock appears to be interbedded
with light-gray and cream-colored dolomite, but expo-
sures are not good enough to determine even local
stratigraphic relationships. The limestone is punky in
places owing to the presence of intricate solution
cavities. In addition to the brachiopods, the rock con-
tains solitary corals, which are poorly preserved, and
pelmatozoan debris.

 

 

——’i

MESOZOIC PLUTONIC ROCKS 33

J. T. Dutro and Helen Duncan of the US. Geologi-
cal Survey examined these fossils and identified the
brachiopod Cyrtospirifer sp., which, they remarked, “is
widely distributed in rocks of Late Devonian age in the
United States and elsewhere” (written commun., 1958).
Another collection was made from a locality a few hun-
dred yards farther north by R. G. Yates, J. C. Moore,
and F. K. Miller. The collection was examined by C. W.
Merriam of the US. Geological Survey, who stated
that the collection “probably is Upper Devonian as sug-
gested by Tenticospirifer which resembles Tenticospiri-
fer utahensis of the Devils Gate Limestone in Nevada
and other species of this genus in the Late Devonian
of Iowa. This fauna may be of about the same age as
those from the Devonian examined by Dutro and Dun-
can” (written commun., 1965).

In 1927, R. H. B. Jones and J. P. Thomson collected
fossils from a poorly exposed fine-grained medium- to
light-gray dolomitic limestone in the NW% sec. 23, T.
30 N., R. 40 E. These fossils were identified in 1958
by J. T. Dutro and Helen Duncan as follows:

Large crinoid columnals, indet.

Fenestella sp.

Cystodictya sp.

Leptargonia cf. L. analoga (Phillips)

productoid brachiopod, genus indet.

Tetracamera? sp.

camarotoechid brachiopod, indet.

spiriferoid brachiopod, indet.

Syringothyris? sp.
Dutro and Duncan concluded that “The association of
Leptargonia of. L. analoga (Phillips), Tetracamera?
sp., and Syringothyris? sp., together with productoid
and spiriferoid brachiopods, indicates an Early Missis-
sippian age. A reservation is placed on this assignment
only because the poor preservation of the fossils make
positive identifications difficult” (written commun.,
1958). The unit from which these fossils were collected
may be the same as the Mississippian limestone, but
lithologic differences are too great to map it as that.

Embysk (1954, p. 15) collected the following fossils
from limestone found in secs. 23, 26, and 27, T. 30 N.,
R. 40 E.:

Rhabdammina sp.
Ammobaculites? sp.
Endothyra sp.

M illerella sp.

Globovalvulina cf. G. bulloides
Trochammina sp.
Lophophyllidium cf. L. proliferum
Rhombopora nitidula

S pirifer aff. S. rockymontanus
? Squamularia transversa
Small Composita

 

 

 

 

 

 

Amphissites cf. A. centronotus

Amphissites cf. A. simplicissimus
She reported that the fauna is Pennsylvanian in age,
but she did not indicate exactly where in those three
sections the fossils were collected. Despite a concerted
effort to recover the locality, no Pennsylvanian fossils
were found. Unfortunately, four of the Paleozoic car-
bonate units in addition to the carbonate rocks mapped
as undivided are found in sections 23, 26, and 27.

MESOZOIC PLUTONIC ROCKS

Plutonic rock underlies a total of about 150 square
miles at the north and south ends of the report area
and intrude the complexly faulted and folded Precam-
brian and Paleozoic rocks. Eight'distinct plutonic bod-
ies, ranging in composition from granodiorite to alkali-
rich quartz monzonite, have been mapped. These plu-
tons are part of the Kaniksu and Colville—Loon Lake
batholiths, following the terminology of Yates, Becraft,
Campbell, and Pearson (1966, p. 56).

Geochronologic work by Joan C. Engels shows that
the plutons represent at least three periods of intrusive
activity, although they are not easily grouped on the
basis of mineralogical or physical characteristics. The
plutons range in area from about 1 square mile to more
than 60 square miles. Most are irregular in shape, and
the configuration of only a few appears to have been
controlled by preexisting structures.

Some plutons are not named because they are too
small to be of regional importance or are obviously an
early- or late-stage variant of a larger pluton. Four of
the plutons considered to be of regional importance
have been named.

The rock classification used is shown in figure 11.
Approximately 150 specimens were stained using the
method developed by Laniz, Stevens, and Norman
(1964) and were modally analyzed. The number of
specimens stained from any one pluton is a function of
the size of the pluton and the variation of mineral com-
position within the pluton. The greatest number of
modes were determined for the larger plutons and those
that showed noticeable variations in mineral com-
position. In most specimens for which accuracy was
checked, a total of 1,000—1,500 points insured no more
than a 2 percent error in any constituent. Point counts
were made with a glass plate imprinted with a grid of
points spaced 0.06 inches apart. The plate was placed
upon a stained slab, and the number of points falling
on each mineral was counted under a binocular micro-
scope.

Modes of some fine- grained rocks were obtained using
stained thin sections and methods described by Chayes
(1956). Almost all thin sections used for petrographic
descriptions were stained for potassium feldspar. All

 

 

34 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

Quartz

   

Quartz
monzonlte

      
  

     
     

Q
50 50
-m 0 I-__
10 35 65 K-feldspar P l. Flowery Trail Granodiorite K

. P 2. Starvation Flat Quartz Monzonite K
Plagloclase Boxed points are border zone specimens
Plutonic igneous rock classification used in this report (see text)

0 Q
1
3. Phillips Lake Granodiorite K P 4. Leucocratic dikes K P K

5. Two~mica quartz monzonite

 

        
  

.._|

P 6. Muscovite quartz monzonite K 7. Coarse-grained quartz monzonite P 8. Silver Point Quartz Monzonite K
Boxed point is composition of fine-grained

grou ndmass (see text)

    

Q Q
P 9. Granodiorite K P 10. Fine-grained quartz monzonite K P Average modes of all plutons K

FIGURE 11.—Modes of plutonic rocks in the Chewelah—Loon Lake area. Circle is the average for each pluton.
Modes recalculated to 100 percent quartz, plagioclase, and potassium feldspar.

mineral identifications are from hand specimen or FLOWERY TRAIL GRANODIORITE
thin section; no X-ray work has been done. Plagloclase LOCATION, EXTENT, AND T OPOGRAPHI C EXPRESSION
composrtlons were determlned by measurlng refractlve
indices using oil-immersion methods. The refractive The Flowery Trail Granodiorite, named by Clark and
indices of amphiboles were measured in the same man- Miller (1968, p. 3), is an elongate pluton about 10
ner. Although a small amount of overlap of indices was square miles in area, one of the few entirely within
noted, each pluton contains a hornblende of different the report area. The west end lies about 1 mile east of
refractiveindices and presumably difierentcomposition. Chewelah, and the long axis extends east-northeast
Table 2 summarizes the mineralogy and texture of from there for about 7.5 miles. The width nowhere

the major plutons in the report area. exceeds 2 miles. About 5 square miles is covered by

 

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i

36 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

glacial and alluvial material. The Flowery Trail road
traverses the length of the pluton and in the eastern
part provides excellent roadcut exposures.

A major canyon is incised along the length of the
pluton and owes its presence, at least in part, to the
nonresistant nature of the rock. Natural outcrops,
where present, are usually quite weathered. The best
exposures are found where the granodiorite is in con-
tact with more resistant metamorphic rocks.

INTERNAL FEATURES

The Flowery Trail Granodiorite is an even-grained
hornblende-biotite granodiorite. Although relatively
small, the pluton shows the largest compositional var-
iation of any in the report area. Modal analyses indi-
cate compositions ranging from granodiorite, through
quartz monzonite, to monzonite.

In contrast to normal zonation in a plutonic body, the
most quartz-rich specimens are found around the mar-
gins of this pluton. The quartz-rich rock at the margins,
however, contains about 15 volume percent more mafic
minerals than the rock in the center. This variation in
mafic minerals may reflect primary mineralogical zon-
ing, but the high quartz content of the border rock is
probably due to assimilation of the host rocks—quartz-
rich metasedimentary rocks of the Belt Supergroup.
Some modes of rocks from the interior of the pluton do
not indicate any zonal distribution of minerals.

If the zoning suggested by most of the modes is real,
itis too complex to be outlined by the few samples
whose modes have been determined. Unfortunately, in-
complete exposure due to heavy forest cover and glacial
deposits precludes sampling at the density needed to
reliably determine whether the zonation is real or
apparent.

CONTACT RELATIONS

Most of the contact is concealed by glacial and allu-
vial material or heavy forest cover. Even where the
granodiorite is shown on the map, outcrops are some-
what patchy. The best exposures of the contact are in
the west half of the pluton in the vicinity of the Jay
Gould mine, the Juno Echo mine, and the Blue Star
mine. At these three localities, which are on both sides
of the pluton, the contact with the metamorphic rocks
appears to be steeply dipping and is very irregular on
a small scale. Abrupt changes in direction every 10—100
feet are complicated by abundant, irregularly oriented
granodiorite dikes and sills which intrude the host rock.

The metamorphic aureole surrounding the Flowery
Trail Granodiorite varies in width. Along most of the
south border of the pluton, noticeable effects appar-
ently do not extend more than half a mile into the host
rocks. One of the outermost areas where discernible

 

 

 

 

 

 

effects are found is on the northeast flank of Quartzite
Mountain, about 1 mile south of the pluton. There,
carbonate-bearing rocks of the upper Wallace Forma-
tion have been recrystallized to calc-silicate hornfels
of the low albite-epidote-hornfels facies of Turner and
Verhoogen (1960, p. 511). North of the pluton, the
only place where the metamorphic effects can be dis-
tinguished from those of the Phillips Lake Granodiorite

unmetamorphosed rocks near the summit of Eagle
Mountain. Low on the north flank, the metamorphic
recrystallization again becomes apparent and increases
northward toward the Phillips Lake body.

On the north side of the pluton, mineral assemblages
characteristic of the hornblende-hornfels facies of Tur-

diopside-quartz-calcite-microcline and quartz-musco-
vite-biotite-plagioclase-andalusite. More than a few
hundred feet from the contact, host rocks at most places
are completely recrystallized, often with the formation
of large porphyroblasts, but with the formation of min-
erals characteristic of the albite-epidote hornfels facies.
Common assemblages include quartz-albite-muscovite-
chlorite-clinozosite-green biotite, quartz-muscovite-
tourmaline, and quartz-a1bite-muscovite-actinolite-
clinozoisite.

About half a mile east of the pluton, in the SW cor.
sec. 32, T. 33 N., R. 42 E., kyanite-bearing schist is
found in the upper part of the Prichard Formation.
Although this locality is not far from the Phillips Lake
Granodiorite, the kyanite probably crystallized owing
to the intrusion of the Flowery Trail Granodiorite. The
latter is considerably closer, and when it was intruded
the amount of cover was probably thicker than when
the Phillips Lake body was intruded. Abundant andalu-
site schist is found on the east and northeast flanks of
Goddards Peak in rocks of about the same chemical
composition as those forming the kyanite schist, but
these rocks are closer to the Phillips Lake Granodiorite
and were probably crystallized by that pluton.

PETROLOGY

Most of the Flowery Trail Granodiorite is medium to
fine grained. Locally the border rock is slightly foliate,
but most of it is structureless. Inclusions are common
though not abundant. Mafic minerals are abnormally
rich in irregular patches as much as several hundred
square feet, and these contrast strikingly with the more
leucocratic surrounding rock. If alpine exposures were
available, the rock would appear mottled on a large
scale, with the light and dark areas blending over a

 

 

————"

MESOZOIC PLUTONIC ROCKS 37

distance of a few feet or less. Its high color index dis-
tinguishes the Flowery Trail Granodiorite from all
other plutonic rocks in the area except for a granodio—
rite south of Springdale.

Plagioclase, the most abundant constituent of this
rock, occurs as subhedral to euhedral crystals that are
both normally and reversely zoned. Most of it is oligo-
clase; some rims are calcic albite, and some cores inter-
mediate andesine. In most sections the calcic cores are
obvious owing to large concentrations of small euhedral
clinozoisite crystals, calcite, and muscovite or sericite.
These minerals, especially the clinozoisite and calcite,
indicate that the plagioclase cores were probably more
calcic before alteration and recrystallization.

The potassium feldspar is microcline, although some
untwinned crystals may be orthoclase. All crystals are
anhedral and appear to have filled spaces between other
minerals. Where alteration of the granodiorite is obvi-
ous, especially near the Jay Gould mine, only the potas-
sium feldspar has been notably affected. There, the
mineral appears to have been preferentially removed
from the rock during mineralization. This relationship
is found only in the alteration zones around noticeably
mineralized areas.

Clear anhedral quartz is present as small interstitial
grains and less commonly as rims around plagioclase.
Some grains contain hairlike crystals of what may be
rutile, and some have undulatory extinction. Most
grains are 0.04 inch or less across and are difficult to see
in hand specimen. Because of this and the high mafic
mineral content, the rock is easily mistaken for a diorite
in the field.

Homblende, the most abundant mafic mineral, is
euhedral to subhedral, averages about 0.08 inch in
length, and is easily identified in all hand specimens.
Some crystals are corroded and embayed by biotite,
both around the edges and in the interior. Rounded
cores of monoclinic pyroxene (2V~60°) occupy the
centers of a few hornblende crystals. This is the only
known occurrence of pyroxene in the Flowery Trail
Granodiorite.

Biotite is present in all thin sections, but is always
less than half as abundant as hornblende. Crystals are
usually subhedral and closely associated with the hom-
blende.

Sphene is by far the most abundant accessory min-
eral and makes up as much as half a percent of some
specimens. Crystals range in size from 0.004 to about
0.12 inch. The characteristic wedge-shaped crystals are
visible in all hand specimens. Apatite is the only other
abundant accessory mineral in the Flowery Trail
Granodiorite, although it is not as abundant as sphene.
Zircon, magnetite, and ilmenite(?) are ubiquitous but
not abundant.

 

 

Minerals of the epidote group are the most common
alteration products in the granodiorite. Both epidote
and clinozoisite are present; highly birefringent epidote
(~0.35) is the most common. Epidote occurs as clus-
ters of small anhedral to euhedral crystals around
hornblende and biotite and within plagioclase crystals.
Some are slightly pleochroic: Z’::very light green,
X’=colorless. Pyrite, sericite or muscovite, tourmaline,
and carbonate minerals are the only other secondary
minerals in the granodiorite, and all but the sericite or
muscovite are rare.

Changes in the characteristics of some minerals, evi-
dent only under the microscope, suggest a mild
metamorphism that increases in an easterly direction.
Highly discordant apparent potassium-argon ages on
homblende-biotite pairs support this conclusion. (See
section “Potassium-Argon Ages of the Plutonic
Rocks”) In thin section, plagioclase crystals are free
of the cloudy haze of late-stage alteration products
almost always found in normal plutonic plagioclase. In
their place, scattered internally through the plagioclase,
are anomalous-looking small euhedral crystals of clino-
zoisite, epidote, and muscovite which were probably
formed by recrystallization of this late-stage alteration
haze. Although metamorphism did not proceed far
enough to erase zoning in the crystals, in plane-
polarized light they look like the clear unaltered plagio-
clase found in metamorphic rocks. These relations are
most noticeable at the east end of the pluton, suggest-
ing the source of the metamorphism was in that
direction.

Pleochroism and refractive indices of hornblende in
rock from the eastern part of the pluton are markedly
different from those in rock from the western part:

X Y Z ny
West ............ Tan ............ Olive green ........ Blue green ........ 1.679
East ........ Pale tan ........ Olive green ............ Green ............ 1.691

Eskola (1952, p. 166), Shido (1958, p. 171), and
Shido and Myashiro (1959, p. 86) reported a change in
pleochroism of hornblende from blue green to green
with advancing metamorphism. The changes they re-
ported were in regionally metamorphosed rocks, but the
comparison may be valid.

The metamorphism could have been caused by any
of several younger bodies to the east. The younger Phil-
lips Lake Granodiorite and leucocratic dikes lie to the
north and east but may not be the sole cause of meta-
morphism, as the former shows some of the same meta-
morphic features found in the Flowery Trail Granodio-
rite. Younger intrusives are found about 10 miles south-
east of the Flowery Trail Granodiorite. Although these
intrusive bodies are probably not close enough to have
affected the Flowery Trail, discordances in potassium-

 

t

38 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

argon dates suggest that other younger plutons may be
buried at shallow depth just east of the report area.

ENIPLACEMENT

The location and shape of the Flowery Trail Grano-
diorite appear to have been controlled by two or more
east-northeast-trending high-angle faults. Rocks and
preexisting structures which strike towards the pluton
are bent parallel to it near the contact and suggest that
the emplacement was, at least in part, forceful. Abun-
dant dikes and xenoliths and apparent contamination
by country rock near the contact, however, hint that
stoping and assimilation were at least as important as
forceful intrusion.

STARVATION FLAT QUARTZ MONZONITE
LOCATION, EXTENT, AND TOPOGRAPHIC EXPRESSION

Starvation Flat, located in the northwest corner of
the report area, is underlain almost entirely by a tex-
turally and mineralogically uniform quartz monzonite.
The rock was named by Clark and Miller ( 1968, p. 3) in
the preliminary report on the Chewelah Mountain
quadrangle, the north half of the report area. The
pluton occupies about 20—25 square miles within an
area extending on the south from the abandoned Cliff
Ridge Lookout to the north and west boundaries of the
quadrangle. Glacial debris covers much of the north-
west corner of the report area. The east side of the
pluton terminates at a high-angle fault of probably
large displacement, which places it against the Phillips
Lake Granodiorite. The quartz monzonite is found
in many of the roadcuts along State Highway 294 north
and west of the quadrangle and thus extends well out-
side the report area. Seventeen miles northeast of Calis-
pell Peak, quartz monzonite that is texturally, min-
eralogically, and modally identical with the Starvation
Flat Quartz Monzonite crops out in large roadcuts
along State Highway 31, just north of Lost Creek.

The pluton forms a topographic low in the general
landscape and attains significant relief only near con-
tacts with the more resistant metamorphic rocks. The
rather subdued topography around Starvation Flat is
typical of that underlain by the Starvation Flat Quartz
Monzonite. Although not mapped in detail, at least
part of the contact between the quartz monzonite and
the metamorphic rocks to the southwest can be inferred
from topographic differences.

CONTACT RELATIONS

On Blacktail Mountain, near the north border of the
area, intrusive relationships between the Starvation
Flat Quartz Monzonite, the Phillips Lake Granodiorite,

 

and highly metamorphosed sedimentary rocks are ob-
scured because leucocratic quartz monzonite dikes and
sills have intruded all three rock types. The configura-
tion of the contact between the Starvation Flat Quartz
Monzonite and the metamorphic rocks suggests a near-
vertical relation. At localities far distanct from the
quartz monzonite, the leucocratic dikes are closely
associated with the granodiorite and genetically related
to it. Since the quartz monzonite is intruded by the
dikes, it must be older than the granodiorite and pre-
sumably is intruded by it.

South from Blacktail Mountain the inferred contact
between the Starvation Flat Quartz Monzonite and the
Phillips Lake Granodiorite is buried under glacial de-
bris, but appears to be essentially straight. A contact
this long and straight could be a fault, or it could be
controlled by a preexisting fault. One well-located fault
and two inferred faults are alined with the contact from
the south and project toward it. Mylonite and cata-
clasite are developed for about 3 miles to the northeast
and southwest along the contact from the point where
it intersects Little Bear Creek.

Along the south border of the pluton, the quartz
monzonite intrudes the Huckleberry Formation. How-
ever, the contact is almost entirely covered by glacial
and alluvial sedmients, and its attitude is not known.
Just outside the west boundary of the area, the contact
swings south and roughly parallels the boundary of the
area for 2 miles. Here the contact is fairly well exposed
and quite irregular in configuration. The outcrop pat-
tern and narrow width of the metamorphic aureole sug-
gest that the contact is generally steeply dipping.

Pelitic, basic, and carbonate-bearing quartz-feld-
spathic rocks of the Monk Formation underlie the W1/2
sec. 27, T. 34 N., R. 40 E., at the west margin of the
map area. About 400 feet from the quartz monzonite
contact, the carbonate-bearing rocks are recrystallized
to plagioclase-diopside-grossularite-quartz hornfels,
and the basic rocks to plagioclase-diopside-hyper—
sthene-quartz hornfels characterizing the pyroxene
hornfels facies of Turner and Verhoogen ( 1960); in the
interval from approximately 400 to 1,500 feet, actin-
olite replaces the hypersthene resulting in an assemb-
lage characteristic of the hornblende hornfels facies.
Beyond about 1,500 feet metamorphic effects diminish
abruptly.

In contrast to the Monk Formation, noticeable re-
crystallization effects in the Huckleberry Formation
extend only a few hundred feet from the quartz monzo-
nite. At greater distances changes in the greenstone
are microscopic. The metamorphic effects of the Star-
vation Flat Quartz Monzonite and the Phillips Lake
Granodiorite on the host rocks between them cannot
be differentiated by source.

 

 

———"

MESOZOIC PLUTONIC ROCKS 39

P‘ETROLOGY

The Starvation Flat pluton consists of a medium- to
coarse-grained hypidiomorphic-granular hornblende-
biotite quartz monzonite. The rock is extremely uniform
in both mineralogy and texture. Modal analyses show
that the composition is also uniform, except along the
southwest border where the rock is contaminated ap-
parently by assimilation of Huckleberry greenstone or
by reaction with it. The average modal composition of
the noncontaminated. rock plots well within the quartz
monzonite field, but toward the granodiorite side. (See
fig. 11.)

In hand specimen the quartz monzonite is light gray
and commonly speckled with pink feldspar. White
plagioclase, pink or white potassium feldspar, clear or
smoky quartz, shiny black biotite, greenish-black hom-
blende, and golden-brown crystals of sphene are easily
seen without a hand lens. A distinguishing feature of
this rock is the ubiquitous occurrence of biotite in
euhedral pseudohexagonal tablets.

Plagioclase is the most abundant mineral in the rock.
Crystals are subhedral to euhedral and average about
0.15 inch in length, although some reach 0.4 inch. Aver-
age composition is An25. The most calcic plagioclase
core measured is A.n35, and the most sodic rim Ango.
Some crystals appear to be unzoned, whereas others are
highly complex and show both normal and reverse
zoning.

Most of the potassium feldspar appears to be ortho-
clase. Perthitic intergrowths are common but extremely
fine and difficult to see even under very high magnifica-
tion. Carlsbad twinning is present but rare. Crystals
are anhedral and occur interstitially to all other min-
erals of comparable grain size except quartz. Average
size is about 0.2 inch; some grains are as large as 0.6
inch. No compositional zoning was noted, but small
crystals of plagioclase, quartz, hornblende, biotite, and
apatite are oriented parallel to crystallographic direc—
tions in some crystals.

Quartz also occurs as anhedral grains, filling inter-
stices between plagioclase and the mafic minerals. Crys-
tals average about 0.14 inch in size. Undulatory extinc-
tion is present in. all grains but is not extreme. The
quartz is clear in thin section and contains only a few
almost submicroscopic inclusions.

Mafic minerals average 13 percent of the Starvation
Flat Quartz Monzonite. The hornblende to biotite ratio
averages about 0.7 except in the vicinity of the Huckle-
berry greenstone where hornblende is slightly more
abundant. Biotite occurs as subhedral and euhedral
crystals averaging about 0.12 inch across.

Hornblende is present in every specimen. Individual
crystals are from about 0.04 to 0.16 inch long. Crystals
are subhedral to euhedral and have reasonably consis-

 

tent optical properties throughout the pluton. They are
commonly partly altered to epidote or chlorite. Optical
properties and accessory minerals are g1ven in table 2.

Small rounded mafic inclusions composed mostly of
hornblende, biotite, and plagioclase are common,
though not numerous, throughout the pluton. Only
along the south border of the body where the quartz
monzonite intrudes greenstone of the Huckleberry For-
mation is the identity of these inclusions known. There
they are many times more numerous than in the inter-
ior and are demonstrably xenoliths. In specimens col-
lected within a few hundred yards of the contact, the
average plagioclase composition is more calcic by about
An10 than in the typical quartz monzonite, and mafic
minerals are almost 50 percent more abundant. Horn-
blende predominates over biotite in the border rock,
which is the reverse relationship of that in the bulk of
the pluton. The average modal composition of “normal”
and border-zone rock is as follows:

 
 
 

Normal Border zone
(nine specimens) (four specimens)
Plagioclase ...................................... 37 43
Potassium feldspar ......... 24 15
Quartz .......................................... 26 23
Mafic minerals .............................. 13 19

Mafic minerals in border specimens are concentrated
in small clusters, along with sphene, apatite, and
opaque minerals. In addition, clinopyroxene (ZAC:
37°) is present in the cores of some hornblende crystals.

During emplacement, chemical and physical condi-
tions in the magma apparently allowed rapid assimila-
tion of the greenstone. This is reflected not only by the
larger number of inclusions near the contact, but also
by compositional and mineralogical differences between
the contaminated marginal rock and the relatively
uncontaminated interior. The contamination effects
appear to extend less than 1 mile into the interior of
the pluton, and diminish most rapidly within the first
500 feet from the contact with the greenstone.

OTHER ROCKS INCLUDED WITH THE
STARVATION FLAT QUARTZ MONZONITE

A rock of unknown extent, which may be either a
porphyritic phase of the Starvation Flat Quartz Mon-
zonite or a separate plutonic mass, crops out due north
of Starvation Lake and for several miles along State
Highway 294 north of the area. Although its ground-
mass texture is similar to that of the Starvation Flat
Quartz Monzonite, the rock contains phenocrysts of
microcline as much as 3 inches long and almost no
hornblende. In all other respects, including optical
mineralogy and accessory minerals, the rock is similar
to the Starvation Flat Quartz Monzonite. If this rock
is not a phase of that pluton, the similarities suggest
that it may be at least genetically related.

t

40 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

A leucocratic dikelike body intrudes the Starvation
Flat Quartz Monzonite in secs. 34 and 35, T. 35 N ., R.
40 E., and the two sections immediately to the south.
In outcrop the rock resembles aplite and contains
small pod-shaped bodies of coarser grained material.
The coarser grained pods are less than 1 inch in diam-
eter, but some are as much as 4 inches long and crudely
tabular. In addition, the rock contains small miarolitic
cavities. Most of the rock is pale pink to light gray.
Biotite, the only dark mineral, makes up less than 1
percent of the body. The rock is unusual in that the
fine-grained part is a mass of graphic intergrowths of
quartz in albite and potassium feldspar (fig. 12). The
graphic texture, however, is not easily detected in hand

 

FIGURE 12.—Photomicrograph of the fine-grained dike-form
mass of graphically intergrown rock that intrudes the Starva-
tion Flat Quartz Monzonite. The texture is typical of the
entire rock, not just an isolated area. Long dimension of
photograph is about 2.5 mm. Crossed nicols.

specimens. None of the rock has the xenomorphic tex-
ture typical of aplitic dikes. The average modal compo-
sition of four specimens is as follows:

 

 

 

 

 

 

Albite ..... 28
Orthoclase (microperthite) .......................... 36
Quartz 36
Biotite ........................................................ Trace

The homogeneity of the rock is indicated by the indi-
vidual modes, none of which vary more than 2 percent
from the average. Although an unknown, but probably
small, amount of error is introduced, the mode can be
used to approximate a norm because the plagioclase
composition is only Anz, and the microperthitic potas-
sium feldspar contains few lamellae of albite. The mode
plots in the SiOg-NaAlSiSOS-KAlSiaog minimum trough
for 2,000 bars H20 pressure (Tuttle and Bowen, 1958,
p. 55), but falls about 10 percent off the ternary mini-
mum point for that pressure in the direction away from
the NaAlSi308 corner.

 

 

 

PHILLIPS LAKE GRANODIORITE
(AND ASSOCIATED DIKES)

LOCATION, EXTENT, AND TOPOGRAPHIC EXPRESSION

The name Phillips Lake Granodiorite is here coined
for the muscovite-biotite granodiorite exposed so well
around Phillips Lake, its type locality, in sec. 34, T. 34
N ., R. 41 E. This pluton underlies about 60 square miles
in the northeast corner of the report area. A plutonic
rock that is mineralogically, texturally, and modally
similar has been found 17 miles north of the area on
Huckleberry Mountain in the Spirit quadrangle (Yates
and Engels, 1968, p. D245). To the east, the granodio-
rite is found in the Tacoma Creek drainage in the
northwest quarter of the Newport 30-minute quad-
rangle. The full extent and configuration of this body
in the areas to the north and east have not yet been
determined, but the pluton appears to underlie a much
larger area outside the quadrangle.

Unlike other plutons in the report area, the Phillips
Lake Granodiorite underlies the highest elevations,
and it appears to be considerably more resistant than
any of the other plutons. However, this may be due
largely to the more resistant remnants of metamor-
phosed Precambrian roof rocks and the leucocratic
dikes which inject the pluton. The divide which runs
partly outside the east boundary of the area from north
of Calispell Peak south to Goddards Peak is capped by
small but numerous roof remnants of metamorphic
rock. Most of these appear to be less than 500 yards
long and in this part of the area consist of amphibolite
and mica schist.

INTERNAL FEATURES

The Phillips Lake Granodiorite is easily distinguish-
able from all other intrusive rocks in the report area. It
is dominantly a biotite-muscovite granodiorite but
varies greatly in composition (fig. 11). The interstitial
arrangement of the muscovite and biotite flakes among
the larger crystals of anhedral quartz and subhedral
plagioclase is distinctive in hand specimen as well as in
thin section (fig. 13). The micas in much of the rock
impart a slight foliation, which was probably formed
before the pluton totally solidified.

The granodiorite is intruded almost everywhere by
leucocratic dikes which fall into three general groups.
The most abundant are medium- to fine-grained equi-
granular quartz monzonite dikes from less than 1 inch
to over 200 feet thick. Where most numerous, in the
eastern part of the pluton, they average about 50 feet
thick and appear to be randomly oriented. The dike
walls are roughly parallel and relatively planar. The
quartz monzonite also forms irregular bodies, the larg-
est of which is a small cupola about 1 mile in diameter
that crops out northwest of Lenhart Meadows (sec. 23,

 

 

MESOZOIC PLUTONIC ROCKS 41

 

FIGURE 13—Stained slab of Phillips Lake Granodiorite. Feld-
spar is white, quartz dark gray, and biotite black. Even
though the specimen contains only about 5 percent potassium
feldspar, it is not foliate as is typical of most potassium feld-
spar-deficient parts of this body. The specimen shows the
interstitial occurrence of the biotite around the felsic miner-
als. Muscovite, although it does not show in the photograph,
has the same relation to the quartz and feldspar as the biotite.
Specimen is 3.5 inches long.

T. 34 N., R. 41 E). Concentrations of quartz monzo-
nite float suggest similar bodies may be present in the
northeastern part of the Phillips Lake Granodiorite.
The general distribution of the quartz monzonite dikes
is shown on the geologic map by an overprint. Where it
intrudes sedimentary or metamorphic rocks, this rock
invariably forms sills. Poor exposures prevent precise
calculations of the total area underlain by the equi-
granular quartz monzonite, but the area should be at
least a third of that mapped as Phillips Lake Granodio-
rite.

Dikes belonging to the other two groups are rela-
tively few in number and underlie probably less than

 

1 percent of the area shown as Phillips Lake Granodio-
rite. They consist of aplites and pegmatites of the more
typical varieties. Pure white aplite dikes, without bio-
tite, occur throughout the pluton but are especially
common around the margins. Although they have rela-
tively planar walls, these dikes are considerably more
irregular in shape than the quartz monzonite dikes. In
hand specimen, microcline, plagioclase, quartz, musco-
vite, garnet, and tourmaline are visible.

Pegmatities are irregularly intermixed with the
aplites and also, to about the same degree, with the
quartz monzonite dikes. The association with the latter
is largely restricted to the margin of the pluton. Most of
the pegmatites consist only of perthite, sodic plagio-
clase, quartz, and muscovite, but some also contain
biotite, garnet, tourmaline, and rarely beryl, or colum-
bite. Where associated with the biotite-bearing quartz
monzonite dikes, the pegmatites commonly contain
intergrowths of muscovite and biotite in the same
pseudohexagonal tablet. The three dike types are
found together in only a few places, but where they are,
the pegmatites and aplites both cut the quartz monzo-
nite dikes.

From Phillips Lake eastward to the border of the
report area, all three dike types become increasingly
more numerous, and in the vicinity of Calispell Peak,
the granodioritic country rock makes up probably less
than half the rock exposed. This increase in the ratio
of dikes to host rock is accompanied by a decrease in
the potassium feldspar content of the granodiorite from
an average of 15—20 percent near Phillips Lake to 0—5
percent along the east border. Also, the foliation in the
granodiorite, barely perceptible at Phillips Lake, be-
comes increasingly more pronounced toward the east
border.

The concentration of dikes thus may be related to
the degree of foliation and to changes in composition of
the host rocks. Several hypotheses were considered to
explain these relations. The most probable explanation
is that during the later stages of crystallization, when
the composition of the remaining melt was similar to
that of the dikes, the alkali- and volatile-rich melt was
removed from the interstices of the already crystallized
material, perhaps by filter pressing. The mobilized melt
formed the dikes; thus, the granodiorite is most defi-
cient in potassium feldspar where the dikes are most
numerous. The foliate texture results from the collapse
accompanying removal of the melt, which forced the
micas and remaining melt into interstices between the
larger quartz and plagioclase crystals.

The partitioning of potassium between microcline,
muscovite, biotite, and plagioclase is also interpreted
to mean that part of the melt was physically removed
from the granodiorite. Neither the muscovite nor biotite,

 

 

 

42 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

the only other two mineral phases in the granodiorite
containing appreciable amounts of potassium, system-
atically changes in amount with the decrease in potas-
sium feldspar content in the eastern part of the pluton.
Plagioclase composition does not change systematically
either.

The bulk composition of the original magma would
have been considerably more alkali rich than the com-
position of the Phillips Lake Granodiorite indicates if
all the dikes were originally derived from the Phillips
Lake magma as suggested. The presence of two micas
as characterizing minerals in the granodiorite supports
this suggestion. Muscovite and biotite are not the char-
acteristic minerals one would expect in a rock of this
composition, especially along the east border of the
area where the feldspar ratio of the host rock is that of
a quartz diorite. However, a theoretical composition
resulting from the combination of the magmas from
which the granodiorite and the leucocratic dikes crys-
tallized would be one from which muscovite and biotite
might crystallize.

To arrive at a weighted-average mode for the grano-
diorite and dikes combined, the ratio of dike rock to
pluton was estimated from surface exposure. As close
as can be estimated, about 35 percent of the area shown
as granodiorite on the map is underlain by dike rock.
By using this estimate, the average modal compositions
of the granodiorite and the dike rocks were weighted
proportionately, and the following mode calculated:

 
  

Plagioclase ...................................................... 40
Potassium feldspar ............. 17
Quartz ................................................... 30
Mafics (including muscovite) ...................... 13

This mode still plots in the granodiorite field, but near
the granodiorite-quartz monzonite boundary. If the
volume of dike rock is actually greater than that of the
granodiorite, an original magma from which they could
have crystallized would have a quartz monzonite com-
position.

Except for the large remnants of roof rock in the
eastern part of the pluton, almost no inclusions of any
kind have been found within the Phillips Lake Grano-
diorite or the associated dike rocks. Even near the
borders, the only perceptible difference from the rock
in the interior, with respect to foreign material, is an
increase in the amount of micas.

Brecciation and shearing resulting from faulting have
been recognized only along the northwest border of the
Phillips Lake Granodiorite and west and south of Bear
Canyon, where the rock is highly fractured in places
and recemented with quartz, chlorite, and epidote.

More than one set of joints is found in many outcrops
of the Phillips Lake Granodiorite. Mineralized joints

 

are cut by nonmineralized joints, suggesting more than
one generation. Joint attitudes were not systematically
measured and recorded on the map because most of the
rounded outcrops into which the granodiorite char-
acteristically weathers have obviously been rotated or
moved by frost heaving.

CONTACT RELATIONS

The contact between the Phillips Lake Granodiorite
and the metamorphosed host rocks is exposed only in a
few roadcuts, and in some of these, injection of the leu-
cocratic dikes has been so intense as to obliterate con-
tact relations. A few generalizations can be made,
however.

Possibly the most striking feature of the contact is its
generally shallow clip. The outcrop pattern on the map
shows a very low angle dip on the north flank of Wilson
Mountain and around Bell Meadow. The southeastern-
most 2 miles of the contact was drawn with very little
control because of poor exposure and heavy forest
cover. However, the presence of highly recrystallized
schist with porphyroblasts of andalusite as much as 4
inches long in the saddle north of Goddards Peak sug-
gests that the pluton underlies this area at shallow
depth and therefore that this segment of the contact is
indeed shallow. Almost all the roof remnants in the
eastern part of the pluton also have shallow-dipping
contacts. From the vicinity of Bear Canyon south to
The Tinderbox, the contact appears to be steeper.

Where exposed, the contact is highly irregular owing
to numerous dikes of both granodiorite and the leuco-
cratic rock. Along most of the contact the host rocks
appear to have reacted relatively passively; one excep-
tion is the large internal septum underlying McDonald
and Brewer Mountains, which was probably rotated in
a counterclockwise direction by the magma.

The Precambrian host rocks surrounding the Phillips
Lake Granodiorite show contact metamorphic effects
for several miles from the surface trace of the contact.
Because of the shallow dip of the contact, none of the
Precambrian rocks south of the pluton are very far
from the source of metamorphism. In the area between
the Phillips Lake Granodiorite and the Flowery Trail
Granodiorite, calc-silicate minerals have formed in all
the carbonate-bearing rocks except those on the west
flank of Eagle Mountain and at higher elevations on the
mountain. Contact metamorphic effects along the seg-
ment of the contact west of The Tinderbox but south of
the northwest-bordering fault do not appear to extend
as far into the host rocks as they do south of the pluton.
In the McHale Slate, which is intruded by the grano-
diorite at The Tinderbox and on the hill immediately
to the north, recrystallization is not apparent at dis-
tances greater than half a mile from the contact. This is

 

 

MESOZOIC PLUTONIC ROCKS 43

probably because the contact is steep here but may be
related to the greater distance from the Flowery Trail
Granodiorite. The latter, which is an older intrusive,
appears to have “prepared” the host rocks for the Phil-
lips Lake Granodiorite. Whether this “preparation”
consisted of preheating or was of a chemical nature is
not known, as potassium-argon dates suggest that the
Flowery Trail Granodiorite is about 100 my. (million
years) older than the Phillips Lake Granodiorite.

Along the south boundary of the Phillips Lake
Granodiorite, recrystallization of the host rocks at the
contact has developed mineral assemblages indicative
of the transition between the albite-epidote-hornfels
facies and hornblende-hornfels facies of Turner and
Verhoogen (1960, p. 511). Mineral assemblages in a
single thin section of a metamorphosed carbonate-bear-
ing rock typically include albite, epidote, clinozoisite,
quartz, biotite, microcline, diopside (rare), and abun-
dant medium-green amphibole that is highly birefring-
ent. Highly quartzose pelitic rocks form coarse-grained
quartz-mica schists that only rarely contain aluminum
silicates. A typical assemblage includes quartz, albite,
muscovite, biotite, tourmaline, and, in some specimens,
andalusite. The assemblages developed in pelitic rocks
are clearly indicative of the albite-epidote-hornfels
facies, but the appearance of diopside and a hornblende-
like amphibole in the carbonate-bearing rocks suggests
the transition to the homblende-homfels facies.

In the roof remnants. along the east border of the
area, the rocks are well into the hornblende-hornfels
facies. As most of the rocks were originally carbonate
bearing, a typical assemblage includes diopside, horn-
blende, quartz, and plagioclase of intermediate compo-
sition. On the spur trending northwest from Calispell
Peak, a small roof remnant contains the assemblage
vesuvianite, scapolite, diopside, quartz, calcite, clino-
zoisite, and plagioclase of intermediate composition.

At distances greater than 2,000 feet from any con-
tact of the Phillips Lake Granodiorite, all rocks are
well down into the albite-epidote-hornfels facies, but
almost all are, nevertheless, thoroughly recrystallized.
The difficulties in separating the contact metamorphic
effects of the Phillips Lake Granodiorite from those of
the Flowery Trail Granodiorite to the south have al-
ready been discussed. See section “Flowery Trail
Granodiorite, Contact Relations.” Pronounced meta-
morphic effects do not extend more than about half a
mile south of the Flowery Trail Granodiorite, and so
most of the metamorphic effects more than 1 mile north
of that pluton are probably due to the Phillips Lake
Granodiorite.

PETROLOGY

Plagioclase is by far the most abundant mineral in

 

the granodiorite. Crystals average 0.12—0.2 inch in
length and are mostly subhedral. Composition averages
about Ann. Normal zoning with minor reversals is
present, although it is not obvious in all crystals. The
most sodic zone measured is An16 and the most calcic
Any. The plagioclase is generally glass clear and free
of the normal haze of sericite and other late-stage alter-
ation products commonly found in plagioclase from
plutonic rocks, but it does contain small euhedral to
subhedral crystals of clinozoisite and epidote similar to
those in the Flowery Trail Granodiorite. These inclu—
sions and the highly discordant ages obtained from
potassium-argon analyses of muscovite and biotite sug-
gest that the granodiorite has been metamorphosed.

Potassium feldspar content averages about 11 per-
cent but ishighly variable, as the modes show (fig. 11).
Only microcline has been identified, but orthoclase may
also be present. The crystals vary in size but are about
the same as the plagioclase. Locally, the rock is notably
porphyritic, with microcline phenocrysts as much as 1
inch long. Smaller microcline crystals are mostly an-
hedral and appear to be interstitial to other minerals.
As with the plagioclase, no alteration is apparent other
than a slight clouding in some crystals. Small crystals
of muscovite are common within potassium feldspar
crystals in some thin sections and probably formed dur-
ing metamorphism.

The quartz is a very distinctive pale gray violet and
most commonly occurs in clusters of several grains
which look like one large crystal. Clusters are from 0.2
to 0.4 inch across and are roughly oval in cross section.
Inclusions are rare. Myrmekitic intergrowth of quartz
and plagioclase are common.

Biotite and muscovite crystals average about 0.04
inch in length and occur in clusters as much as 0.4 inch
across. Commonly both micas rim or mantle either
quartz or feldspar. All crystals are subhedral and show
almost no signs of alteration. Biotite is abundant and
Widespread, but muscovite is locally almost absent. The
total amount of mica averages about 15 percent of the
rock; the muscovite to biotite ratio averages about 0.3.

Epidote is found in all specimens but consistently
amounts to less than 1 percent of the rock. Crystals
are small, averaging about 0.008 inch. Some of the
epidote may be primary, as many of the larger crystals
have conspicuous cores of allanite.

Apatite, garnet, magnetite, zircon, and tourmaline
occur as accessory minerals, but only apatite and zir-
con are widespread. Apatite is most abundant, and some
crystals are as much as 1 mm long. Magnetite is rare
or absent in almost all specimens. Garnet and tourma-
line are present in only a few specimens and are
probably the product of metasomatism accompanying
instrusion of nearby pegmatites or aplites.

44 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

TWO-MICA QUARTZ MONZONITE
LOCATION, EXTENT, AND TOPOGRAPHIC EXPRESSION

The west edge of a two-mica quartz monzonite pluton
crops out on the east flank of Nelson Peak. An area of
about 2 square miles along the east border of the report
area is underlain by the pluton. The total extent is not
known, but anomalously gentle slopes continue for
about 4 miles to the southeast in the adjacent Newport
quadrangle and indicate a surface exposure consider-
ably greater than that within the report area. This
quartz monzonite, like most of the plutonic rocks in
the area, forms a topographic low and gentle slopes
except where in contact with more resistant metamor-
phic rocks.

INTERNAL FEATURES

Muscovite and biotite characterize this pluton. They
were found everywhere that the rock was examined.
The ratio of muscovite to biotite averages about 0.30
and varies only slightly from place to place. The Phil-
lips Lake Granodiorite and its associated dikes are the
only other rocks in the area that contain two micas.

The quartz monzonite has a hypidiomorphic-granular
texture and is uniformly coarse grained. It is almost
invariably deeply weathered and friable. The feldspars
have a bleached appearance, and biotite is commonly
surrounded by a brown stain of iron oxides.

Texturally and mineralogically the rock appears to
be quite uniform, but exposures are so poor that in-
ternal variations could easily go unnoticed. No dikes or
inclusions were found, and exposures are not such to
show joint development.

Modal analyses of seven specimens from different
localities scatter on both sides of the quartz monzonite-
granodiorite boundary (fig. 11); however, the average
composition, shown below, is on the quartz monzonite
side and is close to the calculated average modal compo-
sition of the Phillips Lake Granodiorite and associated
leucocratic dikes. (See section “Phillips Lake Grano-
diorite (and associated dikes), Internal Features”)

  

1 2
Plagioclase ........................................ 38 40
Potassium feldspar ..... 21 17
Quartz ................................................ 30 30
Mafics (including muscovite) ........ 11 13

1. Average modal composition of two-mica quartz mon-
zonite.

2. Calculated average modal composition of Phillips
Lake Granodiorite and associated leucocratic dikes.

If not just coincidental, the similarity suggests that the
two plutons are related or are disconnected parts of the
same pluton.

In the Rattlesnake Hills, 15—20 miles south-southeast
of Loon Lake, Griggs (1966) mapped another two-mica

 

quartz monzonite which is almost identical in modal
composition, texture, and appearance with the one in
the report area. If all three two-mica bodies are geneti-
cally related, they represent a widespread plutonic
entity in northeastern Washington.

CONTACT RELATIONS

The contact between the two-mica quartz monzonite
and the Prichard Formation is nowhere exposed, but
the relation of topography and inferred contact config-
uration suggests that it is steeply dipping.

Contact metamorphic effects are noticeable 1 mile
southwest of the pluton but cannot confidently be dis-
tinguished from those caused by the coarse-grained
quartz monzonite immediately to the south. Just east
of Nelson Peak, argillite 200 feet from the quartz
monzonite has been recrystallized to a quartz-musco-
vite-biotite hornfels with small porphyroblasts of chlor-
ite and garnet. The chlorite shows signs of reaction and
probably became unstable when the garnet began crys-
tallizing. Although a contact metamorphic occurrence,
the assemblage is most like the quartz-albite-epidote-
almandine subfacies of the greenschist facies (Fyfe and
others, 1958, p. 224).

PETROLOGY

The plagioclase in this rock is oligoclase. The crystals
are subhedral to euhedral and commonly have sodic
rims and calcic cores. Some plagioclase crystals contain
crystals of biotite and muscovite. Large parts of some
plagioclase crystals are replaced by irregular-shaped
grains of microcline.

All potassium feldspar appears to be microcline. The
characteristic grid twinning is well developed. The
potassium feldspar does not occupy interstices between
other minerals, as it would if it were a late-stage filling,
but occurs as subhedral crystals with the same relation
to surrounding minerals as the plagioclase. In this
respect it is different from that in most of the plutonic
rocks of the report area.

Large gray anhedral knots of quartz fill spaces be-
tween other minerals. The quartz contains inclusions
of all other minerals in the rock and shows little undula-
tory extinction.

Muscovite and biotite are randomly oriented and not
wrapped around felsic minerals as in the Phillips Lake
Granodiorite. They most commonly occur in patches in
which the two minerals are intergrown with one
another. Biotite has the pleochroic formula X=golden
tan, Y=Z=reddish brown.

Apatite and zircon are the only common accessory
minerals in the rock. Zircon is unusually abundant and
dots the biotite with pleochroic halos. Opaque minerals
are unusually scarce.

MESOZOIC PLUTONIC ROCKS 45

COARSE-GRAINED QUARTZ MONZONITE
LOCATION, EXTENT, AND TOPOGRAPHIC EXPRESSION

An area of about 15 square miles in the southern part
of the report area is underlain by coarse-grained biotite
quartz monzonite. The pluton has a highly irregular
outline and crops out in two separate areas divided by
a septum of Belt rocks just east of Deer Lake. The east-
ernmost of the two areas extends beyond the report
area for an unknown distance.

The pluton is a perfect example of how easily the
plutonic rocks in this region are eroded relative to the
metamorphic rocks. The part of the pluton northeast
of Deer Lake forms an open-ended basin, and a notice-
able break in slope marks almost the entire length of
the contact in this area. South of Deer Lake and north-
east of Loon Lake, almost the entire axis of this part
of the pluton is marked by prominent valleys. North
and west of Loon Lake the pluton forms low hills or
underlies flat alluviated areas.

Most of the rock is deeply weathered. In numerous
10—15-foot roadcuts, in all parts of the area, only loose
friable rock can be found. Natural exposures are rare,
and most of them are highly weathered. Only on State
highway 292, 31/2 miles east of Springdale, and on the
road between Loon Lake and Deer Lake is the rock
reasonably fresh.

INTERNAL FEATURES

The coarse- grained quartz monzonite is easily identi-
fied by grain size: The average size is greater than half
an inch. Grains of quartz and feldspar are about equal
in size, but grains of biotite are only about %—% inch
across.

Although most of the rock has a hypidiomorphic-
granular texture and is not obviously porphyritic,
phenocrysts of pink potassium feldspar as much as 2
inches long are locally common. Even where the rock is
nonporphyritic, the abundant potassium feldspar im-
parts a pink cast.

Locally, the distribution of potassium feldspar is not
uniform. In places, as much as a cubic yard of rock may
consist of 50—60 percent potassium feldspar. Pods of
potassium feldspar are irregular in shape and common
throughout the pluton. Textural relations and grain
size within these pods are the same as those in the rest
of the quartz monzonite. The pods may represent crys-
tal accumulates. Alternatively, they may have formed
by some sort of localized filter pressing process or may
be metasomatic.

The nonuniform mineral distribution makes it diffi-
cut to estimate the overall composition of the pluton
with accuracy. The average composition shown in figure
11, however, is probably reasonably accurate because

 

it represents modal analyses of several large samples
from each locality.

Samples from a number of places in secs. 18 and 19,
T. 30 N., R. 42 E., show a pronounced bimodal grain
size. Crystals of potassium feldspar, quartz, plagioclase,
and biotite averaging about 0.2 inch in size make up
about 65 percent of the rock and are set in a ground-
mass of the same minerals with an average grain size of
about 0.05 inch. This pronounced textural variation
may be due to thermal or pressure quenching of a crys-
tal-magma mixture. These textural variations could
not be mapped, but they have been found only on and
around the projections of preintrusion faults (pl. 2).
As thin sections show no cataclasis, the texture is pre-
sumed to be a primary feature and is probably due to
some deviation from the normal crystallization condi-
tions of the pluton. The melt may have intruded host
rock that was shattered enough so that it could not
retain the fluid pressure maintained by the rest of the
intrusive. Upon loss of fluid pressure, relatively rapid
crystallization took place locally and possibly sealed
the system from any further leakage.

Leucocratic muscovite-bearing bimodal rocks are
present at the outer margins of the pluton, near the
contact. These, however, are finer grained than the
bulk of the pluton.

Inclusions of any sort are not abundant in this plu-
ton, but dikes are common, especially around the mar-
gins. Some are normal-looking aplites and fine-grained
muscovite-bearing rocks with graphic texture. These
are probably genetically related to the quartz monzo-
nite because of their consistent spatial relationship.
Others, which consist of a dark-green rock, are highly
altered. They also out other plutons and may not be
related to this pluton.

CONTACT RELATIONS

The attitude of the contact could not be measured
directly, but the relationship of its configuration to
topography suggests that it dips outward between 40°
and 50° in most places.

Contact metamorphic effects of the quartz monzonite
are pronounced within a few hundred feet of the con-
tact but fade out rapidly beyond that. Good exposures
of metamorphosed siltite and argillite on J umpoff Joe
Mountain, Deer Lake Mountain, and on the ridge east
of Benson Peak furnish excellent control for determin-
ing the degree of metamorphism caused by the quartz
monzonite. At all three localities the range in chemical
composition of the host rocks is about the same. Other
physical and chemical conditions must have been uni-
form also, because the aureoles are nearly the same
width at all three localities and the minerals that crys-
tallized are almost identical. Less than 200—300 feet

46 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

from the contact, the most common mineral assemblage
is andalusite-cordierite-biotite-muscovite-quartz, in-
dicative of the hornblende-hornfels facies of Turner
and Verhoogen (1960, p. 513). Beyond 200—300 feet,
andalusite and cordierite are absent.

Quartz-albite-musc0vite-biotite of the albite-epidote-
hornfels facies is the typical assemblage in the interval
from 200 or 300 to about 600 feet. All the rocks in this
interval are thoroughly recrystallized but do not con-
tain any of the higher grade minerals. Beyond 600 feet,
chlorite porphyroblasts, fine-grained muscovite, incipi-
ent biotite, albite, and quartz are the characteristic
minerals. Much of the rock beyond 600 feet does not
appear to be thoroughly recrystallized. Beyond about
1,500 feet, few obvious metamorphic effects are observ-
able.

PETROLOGY

The mineralogy of the coarse-grained quartz monzo-
nite is relatively simple and uniform. Plagioclase, the
most abundant mineral, averages An20 and occurs as
white euhedral to subhedral crystals ranging in size
from about 0.2 to 0.8 inch. Most crystals show some
zoning, but it is not particularly pronounced. Locally
the plagioclase is sericitized and is pale green in hand
specimen.

Microperthitic orthoclase crystals are subhedral to
anhedral and range in size from about 0.2 inch to more
than 2 inches. One of the characteristics of the rock, the
significance of which is not understood, is the presence
of a thin hairline film of potassium feldspar around
most plagioclase crystals. No evidence was seen to indi-
cate whether this film resulted from exsolution or
from crystallization of the late-stage potassium-rich
solutions.

Biotite constitutes about 7 percent of the rock and
is the only mafic mineral. It is generally finer grained
than the other major minerals. The borders of most
crystals are slightly chloritized, but the centers are
unaltered.

Some sphene crystals are as large as a quarter of an
inch across and easily seen in hand specimen. The other
accessory minerals, given in table 2, are normally fine
grained and less abundant.

MUSCOVITE QUARTZ MONZONITE
LOCATION, EXTENT, AND TOPOGRAPHIC EXPRESSION

Leucrocratic muscovite quartz monzonite is exposed
in three areas in the southeastern part of the report
area and underlies a total area of about 2 square miles.
The largest exposure, in sec. 9, T. 30 N., R. 42 E., ex-
tends about 2.5 miles east of the report area and under-

 

lies as much as 3 square miles outside the area. A. B.
Griggs located small outcrops of muscovite quartz mon-
zonite at two localities just south of the report area.
One is 4 miles south of Clayton, the other 3 miles south-
east of Deer Park (oral commun., 1968). The rocks at
both localities are identical in every respect and are
undoubtedly genetically related to the muscovite
quartz monzonite in the report area. In addition, Griggs
reported that the same rock type crops out at various
places in the mountainous part of the Clayton quad-
rangle. Although individual plutons appear to be rela-
tively small, the rock type is apparently widespread in
the region.

Like most of the other plutonic rocks in the area, the
muscovite quartz monzonite forms topographic lows.
The contact of the pluton with the more-resistant
metamorphosed host rock generally is a break in slope.
Although exposures are generally poor, contacts can be
reliably mapped on the basis of this break in slope and
the presence in the soil of mica from the decomposed
plutonic rock.

CONTACT RELATIONS

Other than small variations in grain size, the musco-
vite quartz monzonite at the contact is identical with
that in the interior. As with some of the other plutons,
the metamorphic effects on the country rock are diffi-
cult to separate from those of other plutons nearby. On
Blue Grouse Mountain, which is almost 1 mile from any
any other pluton, the contact metamorphic effects are
very slight. At the contact, siltite has been recrystal-
lized into medium-grained quartz-muscovite schist.
However, hand specimens of host rock from more than
50 feet away show almost no metamorphic effects, and
thin sections of this rock show only slight recrystalliza-
tion.

The south border of the largest muscovite quartz
monzonite intrusion in the report area is cut by numer-
ous huebnerite-bearing quartz veins, as is the adjacent
host rock. Parts of the contact are greisenized, and the
quartzite and siltite as much as several hundred feet
from the contact are pock marked where limonite
psuedomorphs have been leached out. These veins and
the associated mineralization appear to be related to
the quartz monzonite.

PETROLOGY

On the basis of mineralogy, the rock is quartz monzo-
nite in composition and is referred to as such in this
report. However, because the plagioclase is sodic albite,
the rock could be classified as granite chemically. The
average mode, a chemical analysis, and CIPW norm of
an apparently representative sample are as follows:

CENOZOIC PLUTONIC ROCKS 47

Chemical amlysisi CIPW norm Average of 6 modes
(weight percent) (weight percent) (volume percent)

Q .......... 32.3 Plagioclase .......... 34
C .......... 1.4 Potassium
or ........ 27.2 feldspar ............ 33
ab ........ 34.7 Quartz .................. 27
an ........ 2.4 Muscovite ............ 6
en ........ .4 —
fs .......... 2 100
mt ........ 3
i1 .......... 1
cc ........ .1

99.1

 

100.01
1Analyzed sample collected in NE1/4, sec. 25, T. 30 N., R. 41 E. Analyzed

by P. L. D. Elmore, S. D. Botts, Lowell Artis, James Kelsey, Gillison Chloe,
James Glenn, and Hezekiah Smith.

The mineralogy of the rock varies little from place
to place. Although the proportion of the minerals varies
slightly, all specimens are made up of the same min-
erals. The only noticeable textural variations are slight
differences in grain size. Near the margins and in the
smaller intrusions, the grain size is only about 0.15
inch, compared with about 0.2 inch for the bulk of the
rock. The texture of the entire quartz monzonite is
hypidiomorphic-granular. Color is pink to cream, de-
pending on how altered the potassium feldspar is. Small
spots of limonite a few inches to a few feet apart are
present in most of the quartz monzonite. No dikes or
inclusions were found anywhere in the rock.

Average modal analyses of this rock indicate that
potassium and sodium feldspar contents are almost
equal. Miller (1969, p. 5) earlier reported the plagio-
clase composition to be about Anlo, but additional work
using immersion oils indicates an average composition
of Ang. Normative An of plagioclase calculated from
two analyses averages 3.5. The crystals are subhedral to
euhedral, well twinned, and almost devoid of zoning.
The rock does not appear to have been albitized.

Potassium feldspar is subhedral to anhedral pink or
cream-colored microcline. In thin section most crystals
show the characteristic grid twinning. Most of the
microcline is microperthitic, but the sodic phase appears
to have formed from normal exsolution rather than by
albitization. Along with quartz, the microcline occupies
interstices between other minerals.

Muscovite, the sole characterizing mineral, averages
about 6 percent of the rock. No textural features in
hand specimen or thin section suggest that any of the
muscovite is secondary.

The rock contains no mafic minerals other than
specks of magnetite, pyrite, or limonite. Accessory min-
erals, in order of abundance, are garnet, apatite, and

 

zircon. The garnet is pale brownish red and ranges from
a trace to 2 percent.

CENOZOIC PLUTONIC ROCKS
SILVER POINT QUARTZ MONZONITE
LOCATION, EXTENT, AND TOPOGRAPHIC EXPRESSION

The Silver Point Quartz Monzonite underlies about
30 square miles in the southernmost part of the report
area. It was named by Miller (1969) for exposures at
Silver Point on the west shore of Loon Lake. Although
its total extent is not known, this pluton apparently
underlies an extremely large area. The rock is exposed
in roadcuts along US. Highway 2 that are 15 miles
east-northeast of Loon Lake and may extend beyond
there. South of the area, the pluton extends at least 2
miles into the northern part of the Clayton quadrangle.
Rock similar in appearance to the Silver Point Quartz
Monzonite is found about 20 miles southwest of Loon
Lake on the west side of the Wellpinit quadrangle but
may not belong to the same plutonic mass (A. B.
Griggs, oral commun., 1968).

The Silver Point Quartz Monzonite forms areas of
moderate to low relief. Almost all exposures are deeply
weathered. Along US. Highway 395 near the south
border of the area, some new roadcuts 20 feet deep do
not penetrate unweathered rock. In the hills bordering
Ahren Meadows, however, most of the quartz monzo-
nite is relatively fresh, probably because of glacial ero-
sion. The least weathered and best exposures are along
the west and south shores of Loon Lake, where roadcuts
have recently been blasted into very fresh rock.

INTERNAL FEATURES AND PETROLOGY

The Silver Point Quartz Monzonite is a porphyritic
hornblende-biotite quartz monzonite. One of the most
striking features of the rock is its lack of internal varia-
tion, either in composition or texture. Modal analyses
(fig. 11) plot in a very small field that would probably
be even smaller if slightly larger slabs had been counted.
Several specimens collected 10—15 miles east of Loon
Lake do not vary more than 2 percent in any mineral
phase from specimens obtained around Loon Lake.
Near the borders, the pluton shows no obvious con-
tamination effects and no variability in modal compo-
sition. Color index ranges from 14 to 21, but for almost
all specimens it falls in a relatively narrow range be-
tween 14 and 18. The ratio of hornblende to biotite is
consistently between 0.75 and 1.0. g

The texture of the Silver Point Quartz Monzonite is
unlike that of any other plutonic rock in the report area.
The distinctive feature is the groundmass, which is

48 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

composed of two size groups of crystals (fig. 14): Crys-
tals of hornblende, biotite, plagioclase, potassium
feldspar, and quartz averaging 0.1—0.2 inch in size make
up about 40 percent of the rock; the rest of the ground-
mass consists of crystals averaging only 0.02—0.06 inch
in size and is composed of all mineral phases found in
the rock. This bimodal texture, like the modal compo-
sition of the quartz monzonite, varies little from place
to place. The greatest element of textural variability is
the size and content of potassium feldspar phenocrysts,
which range from 1A; to 1 1/2 inches and from less than 1
to about 5 percent.

FIGURE 14.—Stained slab of Silver Point Quartz Monzonite
(upper) and granodiorite from the small pluton southeast of
Springdale (lower). The Silver Point specimen is a perfect
example of the unusual texture found throughout that pluton.
The large felsic and mafic minerals are “floating” in a finer
grained interstitial mass of the same mineral types. Sparse
potassium feldspar phenocrysts are typical of the pluton. The
granodiorite specimen shows the high color index and equi-
granular texture typical of this body and contrasts sharply
with the texture of the Silver Point specimen to which it is
probably genetically related. Plagioclase is white, potassium
feldspar gray, and hornblende and biotite black. Quartz is
too fine grained to show well. The Silver Point specimen is
5 inches long, and the slabbed face of the granodiorite 3
inches long.

 

 

The table following compares the average modal com-
position of four specimens on the basis of the size range
of crystals:

 

Four
Four specimens,
Four specimens. groundmass
Entire specimens, groundmass recalculated
pluton. entire rock only to 100 percent
( a) ( b ) ( c) ( d ) d—b
Plagioclase ....40 42 13 21 —-21
Potassium
feldspar ....25 26 22 36 + 10
Quartz ............ 18 18 15 25 + 7
Mafics ............ 17 14 11 18 + 4
Large
crystals .......... 39

The specimens are from the southeast end of Loon
Lake. As the last column shows, the proportion of
plagioclase in the groundmass is considerably lower
than it is in the rock as a whole, whereas the proportion
of potassium feldspar, quartz, and mafic minerals is
higher. If the larger crystals are considered to be earlier
crystallization products, as they probably are, then the
different proportion of minerals in the two size grOups
would suggest that a normal but pronounced differen-
tiation occurred during crystallization. The average
modal composition of the . groundmass is plotted in
figure 11 for comparison with the average composition
of the rock as a whole. Some event, such as a rapid loss
of heat or volatiles, caused approximately the last 60
percent of magma to crystallize so rapidly that it could
not react with already crystallized minerals.

The Silver Point Quartz Monzonite shows none of
the features interpreted as recrystallization effects in
the Flowery Trail Granodiorite and Phillips Lake Gran-
odiorite. Mafic minerals appear to have the same optical
properties throughout the pluton, and the feldspars
contain the haze of alteration products normally found
in feldspar of plutonic igneous rocks.

Several north- to north-northwest-trending shear
zones have been recognized west of Loon Lake. The
largest zone, immediately west of the lake, is 500 feet
wide at one place and was traced for more than 4 miles.
In sec. 31, T. 30 N., R. 41 E., one of the zones intersects
the contact between the Silver Point Quartz Monzonite
and the fine-grained quartz monzonite, apparently
without offsetting it. The exposures are so poor in this
area, however, that the contact could be offset as much
as half a mile in an apparent right-lateral sense.

Within these zones, the rock is highly sheared and
displays cataclasis. Thin, anastomosing seams of silica
and chlorite bond the rock and make it extremely
strong. Small aplite dikes within the zones are highly
broken and are offset in a right-lateral sense along indi-
vidual shears. In thin section all minerals appear highly
granulated and almost all mafic minerals appear to
be ground up and chloritized (fig. 15). The highly

CENOZOIC PLUTONIC ROCKS 49

 

 

B

FIGURE 15.-——Photomicrographs of Silver Point Quartz Mon-
zonite. A, Typical undeformed Silver Point Quartz Monzon-
ite. Crossed nicols. B, Cataclastic Silver Point Quartz Mon-
zonite from the shear zone south and west of Loon Lake. Note
that all the mafic minerals, so abundant in A, are not present;
presumably they have been broken and altered to chlorite and
opaque minerals. Plane—polarized light. Long dimension of
both photographs is about 4 mm.

deformed rock in the shear zones grades into completely
undeformed rock over a distance of 20 or 30 feet.

Plagioclase, the most abundant mineral, occurs as
subhedral to euhedral crystals in both the fine- and
coarse-grained fractions of the groundmass. Average
composition is about Anzo, with zoning ranging from
An15 to An”.

Potassium feldspar, which appears to be microper-
thitic orthoclase, is the only mineral that forms pheno-
crysts. It does not show the microcline grid twinning,
but its crystal symmetry was not checked by X-ray.
Phenocrysts are euhedral, but groundmass minerals are
anhedral and fill intergranular spaces. In fresh speci-

 

mens it is pink and easily distinguished from the
plagioclase.

Quartz makes up about 18 percent of the rock but
is difficult to see without a hand lens, as most grains
are less than 0.04 inch long. It shows undulatory extinc-
tion and is interstitial to all other minerals.

Homblende occurs as subhedral to euhedral crystals
as much as 0.4 inch long. Average size is about 0.12
inch. Most shows no alteration. The optical properties
shown in table 2 were checked in six samples from vari-
ous localities, and little variation was noted.

Biotite, which is present throughout the pluton, is
closely associated with hornblende. More biotite is pres-
ent in the fine-grained groundmass than in the coarse.
Only a few biotite crystals are as much as 0.12 inch in
size, whereas most of the hornblende is this size or
larger.

Sphene is the most obvious accessory mineral and is
easily seen in hand specimen. Sphene, magnetite, and
less conspicuous apatite occur in about equal propor-
tions. Small zircon crystals are scattered throughout
the rock but are not abundant. Allanite, relatively rare,
occurs in crystals as much as 0.08 inch long.

CONTACT RELATIONS

Almost nowhere is the contact between the Silver
Point Quartz Monzonite and any other rock exposed.
Even where contacts are shown on the map, the actual
trace is almost invariably covered. Because of this, no
field evidence was found to ascertain the relative ages
between the Silver Point Quartz Monzonite and the
two smaller plutons adjacent to it west of Loon Lake.
Along this part of the contact, the quartz monzonite
exhibits no reduction in grain size, no foliation, and no
increase in the number of inclusions normally found in
the rock. Neither of the two adjacent plutons exhibit
these features either, and no apophyses or dikes were
found that might indicate relative age.

On the south flank of Loon Lake Mountain, the Silver
Point Quartz Monzonite intrudes the Revett, Burke,
and St. Regis Formations, and just east of Loon Lake
Mountain, it intrudes the lower part of the Wallace
Formation. The rocks are highly weathered here also,
and none of the contacts are exposed. However, small
but resistant outcrops of metamorphic rocks are found
within 100 feet of the most uphill occurrence of soil
containing decomposed granitic debris.

Most of the rock intruded ranges from silty argillite
to quartzite. Within a zone approximately 400 yards
wide next to the pluton, the argillitic rocks have been
converted to quartz-albite-muscovite-biotite schist.
Where the quartz monzonite intrudes the lower part of
the Wallace Formation in sec. 32, T. 30 N., R. 42 E.,
the carbonate-bearing siltstone is recrystallized to a

50 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

fine-grained quartz - albite - diopside - garnet - scapolite
hornfels. The presence of albite in this group of miner-
als probably indicates a disequilibrium assemblage.
Assuming an approximately constant pressure at the
particular level in the host rocks now exposed, during
the emplacement of the quartz monzonite the tempera-
ture could have increased through the stability range
of the albite-epidote-hornfels facies and into that of the
hornblende-homfels facies. However, because the albite
has not been converted to more calcic plagioclase, the
temperature probably did not remain high long enough
for a stable assemblage indicative of the hornblende-
homfels facies to form. At distances of more than half
a mile from the quartz monzonite, the host rocks show
almost no metamorphic effects.

GRANODIORITE

A small elongate body of hornblende-biotite grano-
diorite 2 miles southeast of Springdale underlies an area
of about 1 square mile. The rock does not occur any
other place in the report area and has not been reported
outside the quadrangle. Although this pluton and the
Flowery Trail Granodiorite are similar modally and
mineralogically, their ages are considerably different,
according to potassium-argon analyses.

INTERNAL FEATURES AND PETROLOGY

The granodiorite is easily distinguished from other
plutonic rocks in the report area by its high color index
and by the fact that it is equigranular. In addition, it
exhibits hypidiomorphic-granular texture and is com-
pletely unfoliated. The pluton is nearly uniform inter-
nally, with no obvious variations in mineralogy, grain
size, or texture.

The equigranular texture and high color index impart
a salt-and-pepper appearance (fig. 14). Both feldspars
are white, and quartz, although present, is not obvious.
Abundant specks of honey-brown sphene averaging
0.05 inch in length occur in all specimens and make
up as much as half a percent of some. Average grain
size of the major minerals is 0.1—0.15 inch.

Small aplite dikes as much as 6 inches wide cut the
pluton but are not common. Rounded mafic inclusions
from 0.5 to 6 inches in diameter are scattered through-
out the pluton. Irregular-shaped, wispy mafic segrega-
tions as much as 1 foot across are found from place to
place but are not abundant.

Plagioclase, the most abundant mineral, forms euhed-
ral to subhedral crystals, whose average composition is
between An25 and Anso. Crystals are normally zoned
from about An35 in the cores to about An20 at the rims.
In most specimens, 'both feldspars show very little
alteration.

 

Potassium feldspar appears to be microperthitic
orthoclase. No microcline twinning was observed, but
the crystals were not checked for symmetry by X-ray
methods. The potassium feldspar, along with quartz,
occupies interstices between other minerals.

Quartz is anhedral, clear of inclusions, and only
slightly strained. The granodiorite has less quartz than
any pluton in the report area.

The hornblende-to-biotite ratio is approximately 1:1.
Hornblende forms euhedral crystals, some of which
have partially altered pyroxene cores. Both mafic min-
erals occupy the same textural relationships to other
minerals, and neither is segregated from the other.

Sphene, by far the most abundant accessory mineral,
is obvious in all hand specimens. Apatite, zircon, and
magnetite are abundant but visible only in thin section.

CONTACT RELATIONS

The granodiorite is in contact with the Addy Quartz-
ite and three other plutonic rocks. Contacts are poorly
exposed, like those of most of the other plutons. On
the west and north sides of the body, the contacts with
the coarse-grained and the fine- grained quartz monzon-
ites are not exposed but were mapped on the basis of
float. The southeast segment of the contact with the
Silver Point Quartz MonZonite is locally exposed, but
evidence bearing on the relative age of the two plutons
is lacking. Because the configuration of the contact is
highly irregular, the dip is hard to estimate from the
relation of the surface trace to topography. Along a
small segment of the contact, the granodiorite intrudes
the Addy Quartzite, but because the quartzite contains
relatively few impurities, the pluton produced no obvi-
ous recrystallization effects. In the SW cor. sec. 2, T.
29 N., R. 40 E., almost half a mile from the contact,
the impure lowermost part of the Metaline Formation
contains needles of tremolite. These are the only obvi-
ous contact metamorphic effects attributable to the
granodiorite.

FINE-GRAINED QUARTZ MONZONITE

Fine-grained hornblende-biotite quartz monzonite
underlies about 1.5 square miles between Springdale
and Loon Lake. The pluton is irregular in shape but
crudely elongate in an east-west direction. Rock of this
type is not found at any other place in the report area
and appears to be confined to this single pluton.

In general, the rock is deeply weathered and very
poorly exposed. Roadcuts along State Highway 292
about 3.5 miles east of Springdale show that the rock
is highly weathered more than 10 feet below the sur-
face. Because of this deep weathering, part of the south
border was mapped on the basis of sparse float and is
not well located.

DIFFERENTIATION OF THE PLUTONIC ROCKS 51

INTERNAL FEATURES AND PETROLOGY

The fine-grained quartz monzonite has a rather uni-
form hypidiomorphic-granular texture throughout but
varies somewhat in grain size. In railroad cuts along the
tracks of the Burlington Northern Railroad about 3.5
miles east of Springdale, dikes of this rock have chilled
borders and cut the more extensively exposed coarse-
grained quartz monzonite. In this area and along the
nearby roadcuts on Highway 292, the grain size is 0.02—
0.05 inch, but at the northwest end of Loon Lake, it
is about 0.1—0.15 inch.

In hand specimen the rock is characterized by its
relatively fine grain size, a salt-and-pepper appearance
due to the interspersed light and dark minerals, and a
splotchy pink cast due to coloring of the potassium
feldspar.

Small aplitic dikes and dark-green aphanitic dikes
are common but not abundant in the pluton. Large
inclusions are rare, but the small inclusionlike clots are
almost everywhere in the finer grained parts of the
pluton.

The mineralogy appears to vary little in the few thin
sections examined. Average plagioclase composition is
about Anzo, but many of the crystals have pronounced
zoning. In all specimens examined, at least some of the
plagioclase crystals are noticeably larger than all other
crystals. Potassium feldspar is microperthitic ortho-
clase and together with quartz occurs as small irregular
grains interstitial to the other minerals.

Homblende is subhedral and commonly contains
cores of partially altered pyroxene. Its indices of refrac-
tion are considerably lower than in other plutons, and
its pleochroism is noticeably different: X = pale tan,
Y : pale olive green, Z = pale green. The homblende-
to-biotite ratio is about 1: 1, as in the granodiorite and
the Silver Point Quartz Monzonite. Biotite is similar
to that found in the other hornblende-biotite-bearing
plutonic rocks.

Homblende and biotite occur in about equal propor-
tions and make up about 18 percent of the rock. To a
noticeable degree, they occur in clots. The clots are
larger and more apparent at some places than at others
and may be partially resorbed mafic inclusions derived
from the Huckleberry greenstone or the Precambrian
sills of the Prichard Formation. This may explain the
highly discordant potassium-argon ages obtained from
the hornblende.

Sphene, by far the most abundant accessory mineral,
can be seen in most hand specimens. Apatite, magne-
tite, and zircon are common. Allanite is present but not
as abundant as the other accessory minerals.

CONTACT RELATIONS
The fine-grained quartz monzonite is in contact only

 

with other plutonic rocks. The southern contact is very
poorly exposed, and the relation of the age of this plu-
ton to that of the granodiorite and Silver Point Quartz
Monzonite is not known, nor is the attitude of the
contact.

On the other hand, the contact with the coarse-
grained quartz monzonite is locally well exposed and
appears to dip less than 50° N. The coarse-grained plu-
ton is clearly older than the fine-grained one. No con-
tact metamorphic eifects resulting from the intrusion of
the fine-grained quartz monzonite have been observed.

DIFFERENTIATION OF THE
PLUTONIC ROCKS

In the preliminary report on the north half of the
report area, the existence of an apparent differentiation
sequence in the plutonic rocks was suggested (Clark
and Miller, 1968, p. 3). A report on the south half
(Miller, 1969) suggested that two separate differentia-
tion sequences might exist and that it might be pos-
sible to separate rocks belonging to the Kaniksu and
Colville—Loon Lake batholiths on the basis of which
apparent differentiation sequence a particular pluton
belonged to (Miller, 1969, p. 4 and fig. 2A). Potassium-
argon ages since determined for most of the plutonic
rocks show that the ages of plutons thought to belong
to one apparent differentiation sequence span a period
of 150 my. Unless a differentiating magma can exist
for 150 my, it would appear that the previously pro-
posed differentiation sequences are more apparent than
real.

Most of the muscovite-bearing rocks appear to form
a crude trend, and all appear to belong to a 100-m.y.
period of plutonic activity. The Starvation Flat Quartz
Monzonite also belongs to this age group even though
it is a hornblende-biotite-bearing rock, and it plots
closer to the apparent differentiation sequence charac-
terized by hornblende and biotite. (See fig. 11.)

It seems more than just coincidental, however, that
the average modal compositions of the plutons plot on
such regular curves, that all the hornblende and biotite-
bearing plutons plot on one curve, and that all the
muscovite and two-mica plutons plot on another. To
postulate a differentiating melt existing for over 150
my. strains the credulity of even the most imaginative
geologist. However, a differentiation may have occurred
even though the parent material was not continuously
molten. It is possible that this parent material, regard-
less of whether it was derived from igneous, sedimen-
tary, or metamorphic rocks, melted more than once
without a change in the factors controlling difierentia—
tion. During the quiescent periods between melting,
differentiation of the parent material, and emplacement

52 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

of the individual plutons, chemical factors could have
been essentially constant. Then, when a new period of
melting occurred, differentiation could have begun
where it had left off at the end of the preceding period.

POTASSIUM-ARGON AGES
OF THE PLUTONIC ROCKS

By JOAN C. ENGELS

Seven of the eight major plutons in the report area
have been dated by the potassium-argon method, in
addition to several of the other plutonic rock types
associated with them. Although the apparent absolute
ages of two plutons have been determined and the
relative age relations between others are known, the
complete sequence of intrusion has not yet been estab-
lished with certainty.

Potassium determinations were made in duplicate
on Baird and Instrumentation Laboratories flame
photometers with a lithium internal standard. Argon
analyses were made on a 6-inch 60° Nier-type sector
mass spectrometer, using standard isotope dilution
techniques.

K40 decay constants:

Ae:0.585 >< 10—10yr'1

As=4.72 >< 10—10yr‘1

K‘°=1.19 X 10—2 atom percent
Errors (: values) have been assigned on the basis of
both experience with duplicate analyses and uncertain-
ties in the individual runs and represent 20.

Early in the study of the plutonic rocks by the potas-
sium-argon method, it was found that a pair of minerals
from a single rock often gave strikingly different ages.
Efi‘orts were then made to obtain rocks from which
more than one mineral could be extracted for dating.
By analyzing mineral pairs, an age disturbance could
be detected if the two minerals yielded different ages.
Of all the rocks dated, only two, the Starvation Flat
Quartz Monzonite and the Silver Point Quartz Mon-
zonite, appear to yield concordant ages on mineral
pairs.

Table 3 gives ages of the rocks analyzed, and figure
16 their locations. Examination of the two together
shows that the amount of discordance between indi-
vidual mineral pairs within other plutons generally
increases to the south and east. The discordances sug-
gest a widespread thermal disturbance about 50 my.
ago in the region just east of the report area. Although
the Silver Point Quartz Monzonite lies in this direction
and is among the youngest intrusive bodies in the area,
it is not known for certain if the thermal effects of this
pluton are widespread enough to have caused the dis-
cordances in the other plutons. If the Silver Point
Quartz Monzonite is the source of the discordances, the

 

effects extend several tens of miles from the surface
outcrop, or else part of the pluton underlies at shallow
depth the area north and northwest of Where it is pres-
ently exposed.

Hart (1961, 1964), Doe and Hart (1963), and Han-
son and Gast (1967) studied the effects of younger
intrusions on host rocks, using a number of dating
methods. They found that the apparent ages of the
host rocks range from their true age to the age of the
intrusion, and they plotted apparent age of the host
rock against distance from the contact. In any given
area, each mineral and each dating method employed
should have a distinctively shaped age-retention curve
which depends on a number of factors, including size
and composition of the units and pressure-temperature
conditions.

In general, hornblende has retained almost all argon
within a relatively short distance of the contact,
whereas biotite has retained argon only at much greater
distances. Muscovite is intermediate but is generally
closer to biotite than to hornblende. Figure 17 diagrams
these qualitative observations, without regard to dis-
tances involved or size of intrusions. The expected
distribution of apparent ages for each mineral type in
an older pluton can be obtained by projecting the curve
onto a line extending outward from the contact with
the younger body (fig. 17). The areal distribution of
apparent ages obtained by more than one method on
several mineral types may initially lead to confusion.
The scatter of apparent ages can range from the true
age of the host rock to the age of the younger pluton.
Thus, in an area where isotopic ages of plutonic rocks
show many discordances and apparent anomalies
because of a younger plutonic event, interpretation is
simplified by initially comparing ages obtained using
only one dating method on a single mineral type.

The unit which seems to best illustrate this qualita-
tive treatment of the effects of a younger plutonic event
is the Flowery Trail Granodiorite. Three biotite-hom-
blende pairs from this pluton show a progressive age
loss in an easterly direction. The oldest age obtained
for the pluton is 194 my on hornblende from a sample
(No. 1, fig. 16) collected in the western part of the body
near the Jay Gould mine. Biotite from the same rock
yields an age of only 98 my. Hornblende from another
sample (No. 2) collected about 1.5 miles farther east
gives an age of 183 my, and biotite an age of 84 my.
Sample 3, collected about 3.3 miles east of the first one,
yields ages of 143 my. for hornblende and 64 my. for
biotite.

The apparent age of these three samples is compared
with their location along an east-northeast—west-south-
west line in figure 18. Although more data would be
desirable, the graph at least suggests an approach to

POTASSIUM-ARGON AGES OF THE PLUTONIC ROCKS

53

TABLE 3.——Potassium—argon data on platonic rocks

 

 

 

 

 

 

 

 

 

 

i v ’3
a e g :3 .§ 5 :3
Egg Pluton or rock type Mineral :1 a 5% $3. 5 Location
:75 e “A g a g; g,
5% ‘4
1 Flowery Trail Granodiorite ................ Hornblende ...... 1. 44 4.348X 10‘10 11.2 194i7 NW1/40 sec. 9, T 32 N ,.R 41 E.
Biotite .............. 8. 71 1.283 X 10‘9 15.0 98 i 5
2 do Hornblende ...... 1. 41 4.007X 10'10 9.4 183+6 Center sec. 3, T. 32 N. ,.R 41 E.
Biotite .............. 8.175 1.041 X 10‘9 22.5 84— + 3 Do.
3 do Hornblende ...... 1. 39 3.042X 10‘10 11.4 143—— + 5 NW1/4 sec. 1, T. 32 N., R. 41 E.
Biotite .............. 8. 852 8.481 X 10‘10 69.9 64 i 3 Do.
4 Starvation Flat Quartz Monzonite....Hornblende ...... .6855 1.003 X 10‘10 20.1 97i 3 SVchS.}§W1/; sec. 3, T. 34 N.,
Biotite .............. 8.405 1 .254 X 10'9 7.8 98 i 3 Do.
5 Phillips Lake Granodiorite ................ Muscovite ........ 10.765 1.092X 10'9 24.0 671‘2 NEM; sec. 34, T. 34 N., R. 41 E.
Biotite .............. 9.360 7.922 X 10‘10 10.0 56 i 2 . Do,
6 do Muscovite ........ 10.64 1.356 X 10‘9 11.1 84 i4 SW14 sec. 8, T. 36 N., R. 42 E.
(Colville 30-min quadrangle) .
Biotite .............. 9.26 1 .089 X 10‘9 9.5 79 i 3 Do.
do Muscovite ........ 10.665 9.244X 10‘10 9.1 5st 2 NEM; sec. 12, T. 33 N. R 41 E.
Biotite .............. 9.448 7.259 X 10‘10 11.4 52 i 2
Leucocratic dike .................................. Muscovite ........ 10.72 1.366 X 10'9 11.1 84 i 2 NE% sec. 32, T. 35 N. R 41 E.
Biotite .............. 7.895 6.996 X 10‘10 45.4 59 i 2
do Muscovite ........ 10.68 1.438X 10'9 13.8 89i6 SWIAO sec. 21, T. 35 N. ,.R 41 E.
( Colv1lle 30- -min quadrangle) .
Biotite .............. 8.695 9.568 X 10‘10 29.8 74 i 2 Do.
10 Silver Point Quartz Monzonite .......... Hornblende ...... .817 7 .304X 10‘11 32.7 60: 2 NW% sec. 11, T. 29 N., R. 41 E.
Biotite .............. 8.70 6.502 X 10‘10 12.0 50 i 1 Do,
11 do Hornblende ...... .6078 4.642X 10‘11 37.5 51 1‘5 NW% sec. 5, T. 30 N., R. 44 E.
(Newport 30-min quad.).
Biotite .............. 8.45 6.016 X 10'10 21.8 48 i 1 Do.
12 Granodiorite ........................................ Hornblende ...... .874 8.231 X 10'11 26.6 63i2 NE1/4 sec. 11, T. 29 N., R. 40 E.
Biotite .............. 8.88 6.493 X 10‘10 10. 8 491' 2 Do.
13 Fine-grained quartz monzonite ........ Hornblende ...... .338 1.745X 1010 17. 51 320i23 NWIA sec. 32, T. 30 N., R. 41 E.
Biotite .............. 8.825 6.657 X 10‘10 1 1. 8 50— + 2 Do,
14 do Hornblende ...... .3555 1.671 X 10’10 35.0 294 i' 15 Do.
15 do Hornblende ...... .374 1.136 X 10‘10 38.7 195 i 8 Do.
Biotite .............. 8.455 6.445 X 10‘10 48 3 51 i 2 Do.
16 Muscovite quartz monzonite .............. Muscovite ........ 10.235 1.204X 10‘9 8.0 78i2 NWIA sec. 25, T. 30 N., R. 41 E.
17 Two-mica quartz monzonite .............. Muscovite ........ 10.745 9.042 >5'10‘10 21.7 56i 2 SEM; sec. 9, T. 31 N., R. 42 E.
Biotite .............. 9.12 7.568 X 10‘10 14.4 55 i 2 Do.
18 Aplite Muscovite ........ 11.00 1.033X 10‘9 9 5 631‘2 NEM; sec. 34, T. 34 N., R. 41 E.

 

 

finding the true age of the Flowery Trail Granodiorite.
The three biotites lie on a straight line which intersects
the 50-m.y. level approximately 2 miles east of sample
3, while a smooth curve drawn through the three horn-
blende points intersects the 50-m.y. mark at about the
same location. This construction is remarkably similar
to the curves depicted by Hart (1964). The projected
point of intersection may be the point at which an out-
crop of the pluton causing the disturbance would be
expected, or it may be the outer limit of complete argon
loss in the rocks that the pluton intrudes. Extrapolated
westward, the hornblende curve appears to flatten out,
which may indicate that the “true age” is not much
greater than the oldest age found for hornblende, 194
my.

These older hornblende ages do not appear to be due
to excess argon in low-potassium minerals, because the
homblendes have a relatively high potassium content,
averaging about 1.4 percent K20. Also, there is no cor-

 

relation between higher apparent excess argon and
lower potassium content, as might be expected in cases
of excess argon; in fact, the potassium values for these
three samples are remarkably similar (table 3).

Other plutons of early to middle Mesozoic age are
known from northeastern Washington and southern
British Columbia (Rinehart and Fox, 1972; Wanless
and others, 1965, p. 14), although, like the Flowery
Trail Granodiorite, each is associated with internal age
discordances. Clark and Miller (1968) assigned the
Flowery Trail Granodiorite a Mesozoic(?) age on the
basis of geologic relations. This assignment is here
refined to Late Triassic or Early Jurassic.

The next youngest pluton is the Starvation Flat
Quartz Monzonite, which appears to be unaffected by
the younger intrusive rock, at least where the dated
sample was collected. Hornblende from a specimen
collected on the west border of the area yields an age
of 97 my, which agrees well with an age of 98 my. on

54 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

6(10 miles)

 

t

\\"~) ‘4

\ \\ \
T. 35 Ni I'43” \\\\‘//\\\

\\ll/ \
“ \/"\\\

 

//
= II
I)

\\ ,
T.34N, U\\,, //
:~\\\“
=1

/
\\"\\//¢/
;,,///"\
\\n= //

 

T, 33 Ni

 

 

T.32 N.

 

 

T.31N.

CHEWELAH-LOON LAKE AREA

 

 

NEWPORT 30' OUADRANGLE

/

 

 

T.3O N.

 

T.Z9 No

 

 

 

 

 

 

R.40 E.

 

 

EXPLANATION

Silver Point Quartz
Monzonlte

 

   

\ l
r r L7 ’/\\/|/\,
AV h A \/\/

Fine-grained quartz Coarse-grained quartz

monzonite monzomte
.— . +

   

Granodiorite Muscovite quartz monzonite

   

Phillips Lake Granodiorite Two—mica quartz monzonite

Il‘ \\ =
\\ “(I \\

\\
,l/ \\\\\

Starvation Flat Quartz Monzonite Contact

   
 

0 4 8‘MILES

FIGURE 16.——Generalized map showing distribution of plutonic rocks in and around the Chewelah—Loon Lake area
and the potassium-argon sample localities. Numbers correspond to sample numbers in table 3.

POTASSIUM-ARGON AGES OF THE PLUTONIC ROCKS 55

 
 

 

  

 

 

 

 

 

 

 

u:
2
3:] l: 100 —
Lu g 90 ‘
u.
e E 80 —
° 3 70
‘3 o
< >- 60 '
m
3 Q 50 - ———————————
u:
“3‘; 40 —
H? 30 -
5'3? 20
g ‘ I
u, 10 — |
D- l
0 I
l Distance within an older plu-
l ton from the contact with
l a younger pluton
|
I
llllll | l I l |
ITITII I I | | 1
50 7
O 80 90 | Apparent ages of different minerals in map plan.
Hornblende | . .
l Shows graphically the relation between apparent
lfi I I I I l I I I I ages and why at any given distance from a
10 20 30 40 50 60 70 80 90 younger intrusive body, different minerals give
Muscovite different apparent ages
'4 I I I I I I I I I J
. _ 10 20 30 50 70 80 90
Biotite

PERCENTAGE OF AGE DIFFERENCE

RETAINED BY OLDER UNIT

FIGURE 17 .—-Changes in apparent ages of hornblende, biotite, and muscovite in an older pluton intruded
by a younger one.

West-southwest «———> East-northeast

   

Hornb/e
I7

100 —

m
o
I

 

APPARENT AGE (MILLION YEARS)

 

0 1 | l
1 2 3
Sample number

l<——1.5—-—>I<——1.8——>I
DISTANCE (MILES)

FIGURE 18,—Apparent ages of hornblende and biotite from the
Flowery Trail Granodiorite plotted against the distances sep-
arating specimen localities.

biotite from the same specimen. The potassium-argon

dates allow revision of the Mesozoic(?) age assigned

by Clark and Miller (1968) to Cretaceous.
Muscovite-biotite pairs from two samples of the Phil-

 

lips Lake Granodiorite collected within the area and
one sample collected about 10 miles north of the area
all yield discordant ages (table 9). Muscovite in the
northernmost sample (No. 6) gives an age of 84 m.y.,
and biotite 79 m.y.; muscovite in the intermediate sam-
ple (No. 5), 15 miles south-southwest of sample 6, gives
an age of 67 m.y., and biotite 56 m.y.; and muscovite
in the southernmost sample (No. 7), 18 miles south-
southwest of sample 6, gives an age of 58 m.y., and
biotite 52 my

Yates and Engels (1968, p. D245) reported similar
but less pronounced discordances from probably cor-
relative rocks in the Deep Creek area at a locality about
20 miles north of the report area. A rock which is mad-
ally, texturally, and mineralogically identical with the
Phillips Lake Granodiorite was mapped as part of the
Kaniksu batholith by Yates (1964) and gives a biotite
age of 92:3 m.y. However, muscovite from a pegmatite
associated with this rock gives an age of 99:3 m.y
(Yates and Engels, 1968). About 2 miles north of these
sample localities, the Spirit pluton, Which Yates and
Engels regarded as probably part of the Kaniksu batho-
lith, gives a similar discordance (muscovite, 96:3
m.y.; hornblende, 94:3 m.y.; biotite, 91:3 m.y.) , and

 

 

 

56 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

biotite from a rock collected about 14 miles to the west
gives a 100:3-m.y. age. They concluded that the bio-
tite in the eastern samples lost part of its argon and that
all these rocks were emplaced about 100 my. ago. If
the correlation of the Phillips Lake Granodiorite with
the Kaniksu rocks is correct, the probable age of the
granodiorite is then 100 m.y., much older than any of
the ages obtained so far for this rock in the report area.

Two of the leucocratic dikes that are associated with
the Phillips Lake Granodiorite and cut it in places were
also dated. A sample of the southernmost of the two
(No. 8) was collected on the west flank of Blacktail
Mountain where the dikes intrude the Starvation Flat
Quartz Monzonite. Biotite from this rock gives a 59-
m.y. age, and muscovite an 84-m.y. age. Sample 9,
which was also from a dike intruding Starvation Flat
Quartz Monzonite, was collected about 2 miles north
of sample 8 and yields a biotite age of 74 my and a
muscovite age of 89 my. Since leucocratic dikes of
this type cut the Phillips Lake Granodiorite, the maxi-
mum age obtained for the dike establishes a minimum
age for the pluton. Thus, even though 84 my is the
oldest date obtained on the Phillips Lake body, the
89-m.y. apparent age of the dike rock more closely
approaches the 100-m.y. age of the rocks to the north
with which the pluton is believed to be correlative.

The relative discordances within the Phillips Lake
Granodiorite and its associated leucocratic dikes point
to the same area of disturbance as the Flowery Trail
Granodiorite. A plot of the apparent muscovite and
biotite ages of both the Phillips Lake Granodiorite and
the associated leucocratic dikes versus distance between
projected sample locations (fig. 19) shows a pattern
similar to that predicted from figure 17.

A sample of the two-mica quartz monzonite north-
east of Deer Lake gives a muscovite age of 56 my and
a biotite age of 55 my. Despite the seeming accordance,
these ages are probably anomalous owing to the prox-
imity of the samples to a younger plutonic event. This
interpretation is supported by petrologic evidence that
the two-mica quartz monzonite is the same as, or
related to, the Phillips Lake Granodiorite.

Muscovite from a sample (No. 16) of the muscovite
quartz monzonite collected 2 miles south-southeast of
Deer Lake gives an age of 78 my. This sample was
dated before it was known that the pre-Tertiary plu-
tonic rocks had been disturbed by a later event. Because
of the proximity of the sample locality to the apparent
source of discordances noted in other units, the signifi-
cance of the 78-m.y. date is questionable.

The coarse-grained quartz monzonite was not sam-
'pled for potassium-argon dating in this area, because
it is highly susceptible to weathering and because the
only datable mineral in the rock, biotite, is slightly

 

100l—

North-northwest H South-southeast

 

25‘

APPARENT AGE (MILLION YEARS)

 

 

0 I | I I
9 8 5 7
Sample number
+1.5H‘E6fi-F—25—‘I
DISTANCE (MILES)

7 FIGURE 19.—Apparent ages of muscovite and biotite from the

Phillips Lake Granodiorite and associated dikes plotted
against the distances separating specimen localities.

chloritized. Even if a date that did not reflect the effects
of alteration could be obtained, its significance would
be difficult to evaluate because of the nearness of Terti-
ary plutonism. Field relations and spatial association,
however, indicate that this unit and the muscovite
quartz monzonite were probably emplaced during the
same general event, but a little later than the Phillips
Lake Granodiorite and its associated dikes and sills.

With the possible exception of the granodiorite and
fine-grained quartz monzonite, the Silver Point Quartz
Monzonite appears to be the youngest plutonic body
in the area on the basis of both potassium-argon dating
and crosscutting relationships found east of the area.
Hornblende from a sample (No. 11) collected 15 miles
east of Deer Lake in the Newport 30-minute quad-
rangle yields an age of 51 m.y., and biotite from the
sample an age of 48 my. Biotite from a second sample
from the Silver Point Quartz Monzonite (No. 10), col-
lected near the southeast end of Loon Lake, yields an
age of 50 m.y., whereas hornblende from this sample
gives an age of 60 my.

A greater discordance was found in a sample from
the small granodiorite pluton between Springdale and
Loon Lake. Biotite from this sample yields an age of
49 m.y., and hornblende an age of 63 my The most
striking discordance, however, is from a sample of the
fine-grained quartz monzonite (No. 13) collected
between Springdale and Loon Lake. Biotite from this
sample gives an age of 50 m.y., but the hornblende gives
an age of 320 my. A reanalysis of a split of the hom-
blende from the same rock yields an age of 294 my
Another sample of the rock was collected and processed

 

 

 

————'i

POTASSIUM-ARGON AGES OF THE PLUTONIC ROCKS 57

to check the large discordance, and a 195-m.y. age was
obtained on the hornblende and a 51-m.y. age on the
biotite.

Although potassium-argon dates appear to have been
lowered by thermal events in many of the other rocks,
the hornblende may give a misleading age for these
three plutons. The granodiorite and the fine-grained
quartz monzonite are thought to be genetically related
to the Silver Point Quartz Monzonite on the basis of
spatial associations and almost identical mineralogy. In
addition, biotite from all three plutons gives an age of
about 50 my, as does cogenetic hornblende from the
Silver Point Quartz Monzonite east of the area.

Thin sections show that the hornblende in the grano-
diorite and in the fine- grained quartz monzonite, which
yields ages in excess of 50 my, exhibits two character-
istics that differ markedly from the hornblende in the
sample of Silver Point Quartz Monzonite, collected east
of the area. While some of the amphibole in the two
smaller plutons occurs as isolated crystals, much of it
is clustered together into clots of crystals. The other
anomalous characteristic is the presence of pyroxene
cores in many of the crystals. In much of the rock, the
pyroxene has been partly altered to hornblende, and
its optical properties are not normal for either mineral.
Pyroxene cores and clotted hornblende have also been
observed in thin sections of samples of the Silver
Point collected near the southeast end of Loon Lake,
but both characteristics are much more sparsely devel-
oped than in the granodiorite and fine-grained quartz
monzonite. The hornblende clots may represent incom-
pletely digested material picked up by the Tertiary
plutons from either the Huckleberry Formation or the
amphibolite sills in the Prichard Formation. (See
“Fine-grained Quartz Monzonite, Internal Features
and Petrology”) .

Grain counts in immersion oils show that all three
samples of hornblende from the fine-grained quartz
monzonite consist mainly of pale-green crystals free of
alteration and inclusions. The remainder of each sample
consists of crystals that contain abundant opaque and
semiopaque material and may represent incompletely
altered pyroxene. Since all gradations between the two
types are present, the counts are somewhat subjective,
but a rough correlation between degree of purity and
age does seem to exist (fig. 20 and following table). The
higher proportion of crystals that appear to be altered
in the samples yielding older hornblende ages suggests
that these crystals may be the cause of the older ages
owing to incomplete outgassing of argon.

The data are not conclusive but do suggest that the
Silver Point Quartz Monzonite, along with its satellitic
plutons, is about 50 my. old. Whether this pluton or
others as yet unrecognized east of the area are responsi-

 

APPAR ENT AGE
(MILLION YEARS)

 

 

90 100
PERCENTAGE OF CLEAN-CLEAR HORNBLENDE

FIGURE 20.——Re1ation of apparent ages to concentration of clean-
clear hornblende in the fine-grained quartz monzonite.
Clean-clear taken to be all of ‘clean + 1/2 intermediate,

Composition of hornblende separates
used for potasstum-argon dating
Intermediate

hornblende2
( percent )

Apparent potassium-
argon age of
sample (m.y.)

I mpure
hornblendea
(percent)

Clean
hornblende1
(percent)

320 32 35 31 (also 2 percent
biotite)

294 40 42 15 (also 3 percent
biotite)

195 58 26 14 (also 2 percent
biotite)

1Pale green and clear.
2Alteration noticeable; contains inclusions of other crystals; also contains
fine-grained opaque material.

3Same as intermediate, but much more pronounced. Many crystals almost
opaque owing to alteration and opaque minerals.

ble for the pronounced discordances shown by the older
plutons is not yet known. Miller (1969) assigned the
Silver Point Quartz Monzonite a Tertiary age, which
is here referred to an Eocene age.

Hypabyssal dikes, some of which have petrologic
affinities to the Silver Point Quartz Monzonite, are
found throughout the report area and are especially
abundant in the area just east of the Flowery Trail
Granodiorite. Yates and Engels (1968, p. D246)
reported ages of about 50 my on lamprophyre dikes,
shonkinitic sills and dikes, and volcanic rocks from the
north half of the Colville 30-minute quadrangle. The
lamprophyre dikes, in particular, strongly resemble
some of the hypabyssal dikes in the report area and
may be related to the same period of igneous activity as
the Silver Point Quart Monzonite. If so, the intrusive
event represented by these 50-m.y.-old rocks may be
widespread in northeastern Washington.

The varied potassium-argon dates reported here can
be explained by as few as three main periods of plutonic
activity, if the dates are considered in conjunction with
the petrographic and field relations of the plutonic
rocks. The oldest, apparently involving only the
emplacement of the Flowery Trail Granodiorite,
occurred in Late Triassic or Early Jurassic time. The
Starvation Flat Quartz Monzonite and the Phillips
Lake Granodiorite and its associated dikes and sills
were emplaced in mid-Cretaceous time. The absolute
age of the muscovite quartz monzonite and coarse-

 

*—

58 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

grained quartz monzonite is uncertain. Field relations
and spatial associations suggest that they were prob-
ably emplaced during the mid-Cretaceous event, but
later than the Phillips Lake Granodiorite and its asso-
ciated dikes and sills. Plutonic activity in the area
apparently climaxed in the Eocene with the intrusion
of the Silver Point Quartz Monzonite, the granodiorite,
and the fine-grained quartz monzonite.

CENOZOIC HYPABYSSAL, VOLCANIC,
AND SEDIMENTARY ROCKS

MAFIC DIKES

Fine-grained dikes or dike-form bodies, rich in mafic
minerals, are scattered throughout the report area.
Almost all cut across bedding, but some are locally
concordant where they intrude Precambrian metasedi-
mentary rocks. Although they could be called lampro-
phyres, perhaps sodium-rich minette or vogesite, they
are referred to here simply as mafic dikes because they
do not fit well into any of the lamprophyre categories.

Although the dikes do not form an appreciable per-
centage of the bedrock anywhere, they are obviously
concentrated in some places. Three such places are in
and around the Silver Point Quartz Monzonite, the
Phillips Lake Granodiorite, and in the vicinity of Jay
Gould Ridge. Dikes are numerous though Widely scat-
tered throughout the area underlain by the lower part
of the Belt Supergroup, but almost none were found in
the Deer Trail Group, Huckleberry Formation, or the
Paleozoic rocks.

Most of the dikes are between 10 and 30 feet wide
and too small to map. The largest of the few that were
mapped are immediately south of Cottonwood Creek.
One is just over 1 mile long, and the other, although not
exposed along its entire length, is about 1.5 miles long.
They average about 300 feet in width, but the shorter

one bulges to about 1,000 feet near its north end. A

Another large dike, but one considerably different in
appearance, crosses Jay Gould Ridge in sec. 9, T. 32 N .,
R. 41 E. It averages about 150 feet in width and is
about half a mile long.

No preferred orientation common to even a majority
of the dikes is evident on a regional scale. Their orien-
tation appears to be controlled almost entirely by local
structural and sedimentary features such as foliation,
faults, joints, and bedding. The emplacement of the
two large dikes south of Cottonwood Creek was obvi-
ously controlled by bedding in the host rocks. At least
one dike, too small to be mapped, intrudes part of the
fault in sec. 9, T. 33 N., R. 41 E. If the dikes were
better exposed and more data available on the orienta-
tion of the smaller bodies, a regional trend might be-
come apparent.

 

The dikes vary greatly in appearance, even though
all are fine grained and most have approximately the
same mineral composition. Three dikes coarse grained
enough for modal analyses are of monzonite and quartz
monzonite composition (see following table and fig.
21); most of the others are too fine grained for modal

 

Modes of three mafic dikes
Specimen N o. .......................................... 2 8 9
Plagioclase:
Phenocrysts ...................... 19 20 12
Groundmass ...................... 25 23 28
Potassium feldspar .................. 25 26 28
Biotite ........................................ 9 6 14
Hornblende .............................. 11 11 7
Pyroxene ................................. 4 1 0
Quartz ........................................ 6 10 10
Apatite ...................................... Trace 1 Trace
Opaque minerals ...................... 1 1 1
Calcite ............................. 1 Trace
Sphene ........................... Trace Trace
Total ............................ 100 100

 

  

Plagioclase 35 65 K-feldspar

FIGURE 21.—Plots of mafic dike modes. Felsic minerals
recalculated to 100 percent.

analyses. Almost all the dikes are unusually fresh and
show little alteration. Because of this, they commonly
crop out even where the host rock is completely covered
by a thick layer of forest debris and soil.

Minerals found in the dikes are, in order of decreas-
ing abundance, plagioclase, potassium feldspar, horn-
blende, quartz, biotite, magnetite (or ilmenite), apa-
tite, Sphene, chlorite, epidote, calcite, hematite, zircon,
pyrite, allanite, and actinolite(?) . Not all these are
found in every dike. Table 4 gives the minerals of a
representative group from throughout the report area.

Phenocrysts are generally euhedral or subhedral and
consist of only plagioclase, potassium feldspar, quartz,
biotite, hornblende, and pyroxene. Plagioclase pheno-
crysts are found in most of the dikes and average 0.12—
0.2 inch in size. Their average composition is An“,

 

 

CENOZOIC HYPABYSSAL, VOLCANIC, AND SEDIMENTARY ROCKS

59

TABLE 4.—Mineral composition of selected mafic dikes
[X=mineral present; A=mineral present, but altered]

 

 

 

 

 

 

Phenocrysts Groundmass
a a
=9 a
I) '2 ,g a ‘H 0 S
. 3 E s g E E E 22 3 3 3 i g
”-1 u—. O In H up:
No. See. (N.) (E ) § .. 1? .3 g g 3 a ‘3 g a g g a g 'E: g -: g 3 g 2 Remarks
eggggg:§,sésaa2stafiiés
m a 0‘ :3 m n. m m o' m m S <: m 'in <: H o m m o 4: ,
32 41 X A X X X X X X X Aphanitic groundmass.
34 41 X A X X X X X X X X X X X X X See mode (table, p. 5 8 ).
34 41 A X A X X X X X X X X X X X Color index over 40.
82 41 X A X A X X X X X X X X X X Grfougdmass is high in potassium
e spar.
5 .. 28 84 41 X X X X X X X X X X X Even-grained large hornblende
phenocrysts.
32 41 X X A X X X X X X X X X X Grgéligdmass is high in potassium
spar.
33 41 X X X X X X X X X X X X X
33 41 X X X X X X X X X X X X X X X See mode (table, 1). 5 8 ).
32 41 X X X X X X X X X X X X X Do.
30 41 X X X X X X X X X X X X Gray aphanitic groundmass, pink
potassium feldspar phenocrysts.
29 41 X X X X X X X X X X X X X X Low color index, large potassium
feldspar phenocrysts.
29 41 X X X X X X X X X X X X X X X
29 41 X X X X X X X X X X X X X X X
29 41 X X X X A X X X X X X X X X Same as 10 in appearance.
29 41 X X X X X X X X X X X X X X X Same as 11 in appearance, but no
potassium feldspar phenocrysts.
29 40 X X A X X X X X X X X X X X Same as 11 in appearance.
80 41 X X X X A X X X X X X X X X X X Dark-gray even-grained
phenocrysts are small.
18 ............ 16 29 41 X X X A X X X X X X X X X X Same as 11 in appearance, but no
potassium feldspar phenocrysts.
19 ............ 1 29 40 X X A X X X X A X X X X X X X Roufiided pottaéssium feldspar
p enocrys .
20 ............ 6 29 41 X X A X X X X X X X X X X X Large potassium feldspar pheno-
crysts. Strong resemblance to
Silver Point Quartz Monzonite.
30 41 X X X X X X X X X X X Dull-pink groundmass.
30 41 X A X X X X X X X X X X X X X Same as 17 in appearance.
31 42 X X X X X X X X X High color index.
31 42 X A X X X X X X X X X
81 41 X X X X X X X X X X Dull-pink groundmass.
31 41 X A X A X X X X X X X X X X X Pink groundmass.
31 41 X A X A X X X X X X X X X X Dull-pink groundmass.
31 41 X A X A X X X X X X X X X X X Do.
31 42 A X X X X X X X X Same as 23 in appearance.

 

 

1Probably includes ilmenite.
2Margin of same dike as No. 2.

whereas average groundmass composition is An”. In
addition, potassium feldspar phenocrysts as much as
0.8 inch long are found in dikes in and around the Silver
Point Quartz Monzonite that may be related to that
pluton. Hornblende, the most common mafic pheno-
cryst, is found in about 90 percent of the dikes. Biotite
is found in about 80 percent, but in many of these it is
altered partly or completely to chlorite. In dikes that
contain phenocrysts of both biotite and hornblende,
one of the two minerals is always altered. In most, only
one of the mafic minerals is found in the groundmass,
and it corresponds to the unaltered mafic phenocryst.
Almost all the biotite in the dikes associated with the
Silver Point Quartz Monzonite is severely altered.
These crystals may not have been stable in the physical-
chemical conditions which produced the potassium
feldspar phenocrysts found in all these rocks. Pyroxene
phenocrysts are found only in the large dikes south of
Cottonwood Creek and in the chilled margins of an

unusually mafic dike about 2 miles west of Phillips
Lake. The borders of all pyroxene crystals examined
are altered to hornblende, biotite, or chlorite.

Groundmass grains are euhedral to anhedral and
range from 0.001 to 0.005 inch in size. The variation in
grain size is somewhat a function of the proximity to
the borders, although chilled margins are not obvious
in the field. Width of dike and grain size of groundmass
are generally related.

The groundmass is some shade of gray in all dikes
except the two large ones south of Cottonwood Creek.
The darker dikes contain a higher concentration of
mafic minerals in the groundmass than do the lighter
ones. The color of the dikes south of Cottonwood Creek
is a distinctive dull pink, which might be the result of an
abnormally large amount of small potassium crystals
in the groundmass. As with the feldspar-rich dikes
associated with the Silver Point Quartz Monzonite,

 

the biotite in all the pink rocks is highly altered.

60 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

The dikes are younger than any of the plutonic rocks.
Engels used potassium-argon methods to date several
dikes in the northeast quarter of the Colville 30-minute
quadrangle (Yates, 1964). Two lamprophyre dikes
which are similar to some of the mafic dikes in the
report area and may be related to them were dated as
49.9:15 my. and 51.7 :15 my. (Yates and Engels,
1968, p. D243).

ANDESITE

Relatively well exposed black andesite underlies an
area of about a quarter of a square mile, 3 miles south-
west of Chewelah. It is not found any other place in the
report area, but somewhat similar rocks have been
mapped in the Turtle Lake quadrangle to the south-
west by Becraft and Weis (1963) . They referred these
rocks to the Gerome Andesite (Weaver, 1920) and
assigned them to the Oligocene on the basis of plant
fossils in interbedded tufiaceous rocks (Becraft and
Weis, 1963, p. 37) . The Gerome Andesite has also been
mapped in the west half of the Hunters quadrangle, just
22 miles west of Valley, by Campbell and Raup (1964) ,
and in the adjacent Wilmont Creek quadrangle by
Becraft (1966). Becraft renamed the unit the Gerome
Volcanics.

The lithologic descriptions given by Becraft and
Weis partly fit the andesite in the report area, but they
differ in some important aspects. The andesite in the
Turtle Lake quadrangle is higher in SiO2 and A1203 but
is noticeably lower in FeO and MgO than the andesite
described here. Other constituents are about the same.

The andesite appears to rest on the Stensgar Dolo-
mite, but the exposures do not show whether the con-
tact is extrusive or intrusive. The top is not preserved,
and no flow structures were observed. If the andesite
is extrusive, and assumed to be near horizontal, it must
be at least 240 feet thick.

Phenocrysts of olivine, hornblende, and, to a lesser
degree, biotite are easily seen in hand specimen. Plagio-
clase and pyroxene crystals larger than the groundmass,
but smaller than the phenocrysts, are abundant al-
though obvious only in thin section. The mode in the
table that follows is representative of the andesite.
Hornblende is the most abundant mafic mineral. Al-
most all of it is highly oxidized and has thick rims of
magnetite or ilmenite finely disseminated in a semi-
opaque material. Inside the alteration rim the remain-
ing hornblende is slightly altered and highly zoned. It
is probably basaltic hornblende because of the oxida-
tion products, medium to high birefringence, and pleo-
chromism, X=1ight tan, Y=yellow brown, and Z:
deep golden brown. Olivine crystals are as much as 0.08
inch in size and are surrounded by fine-grained olive-
green to golden alteration products that have moderate

Chemical analysis, CIPW norm, and mode of andesite
southwest of Chewelah
[Analystsc P. L. D. Elmore, Hezekiah Smith. James Kelsey, Lowell Artis,

and James Glenn]

 

Chemical analysis CIP W norm M ode

(weight percent) (weight percent) (volume percent)
8102 .................... 58.3 Q .......... 8.0 Plagioclase .......... 8
A1203 .................. 14.7 or ........ 19.0 Homblende .......... 20
Fean .................. 2.5 ab ........ 25.6 Pyroxene .............. 3
F60 .................... 3.8 an ........ 17.0 Olivine .................. 1
MgO .................. 5.8 wo ........ 3.3 Biotite .................. 1
CaO .................... 5.8 en ........ 14.5 Groundmass ........ 67
Na20 .................. 3.0 fs .......... 3.7 __
K10 .................... 3.2 mt ........ 3.6 100
H20+ ............... 1.1 11 .......... 1.7
TiOa .................... .89 ap ........ 1.2
P205 .................... .51 cc ........ .2
MnO .................. .11 ——
CO, .................... .10 99.7

99.61

birefringence. The olivine has a 2Vx of about 80°~90°.
Biotite is much less abundant than the hornblende but
is surrounded by the same rims of fine-grained opaque
minerals. Its pleochroism is X=light yellow brown and
Y=Z:red brown.

Pyroxene is the second most abundant mafic mineral
but is not easily identifiable in hand specimen. It ranges
in size from about 0.12 inch down to microlites in the
groundmass and is the only mafic mineral that appears
to be relatively free of any alteration. The 2 V2 is about
45°—50° in some crystals, but about 0°—25° in others.
At least some of the pyroxene appears to be pigeonite,
and some augite. Plagioclase ranges in size from about
0.12 inch. down to microlites in the groundmass. It
appears to be andesine but is highly zoned.

The finer grained plagioclase and pyroxene, along
with opaque minerals and partially devitrified brown
glass, form an aphanitic groundmass with a pilotaxitic
texture. Much of the very fine grained material may be
devitrified glass. Although it is too fine grained to
identify in thin section and has not been X-rayed, its
alkali content (see preceding table) suggests that much
of it is quartz, potassium feldspar, and albite.

BASALT

About 10 square miles in the southwest part of the
area is underlain by basalt, but more than half of this
is masked by younger glacial and alluvial debris. The
basalt appears to be confined chiefly to elevations below
2,500 feet, except on the northwest slope of J umpofi
Joe Mountain, where it is found as high as 2,900 feet.
Individual flows and flow thicknesses could not be dis-
cerned, and so the attitude of the flows could not be
measured directly. Since the base is found at about the
same elevation in most places in the area, the flows must
be nearly horizontal, except around irregularities in the

 

—i

CENOZOIC HYPABYSSAL, VOLCANIC, AND SEDIMENTARY ROCKS 61

underlying surface. In the NE1/4 sec. 30, T. 31 N., R. 41
E., Empire Explorations Inc. drilled a test well which
penetrated 139 feet of basalt. Assuming that the basalt
is nearly horizontal, this is the most accurate measure-
ment of a partial section but probably does not repre-
sent a maximum thickness in the area.

The rock is black to dark gray, nonporphyritic, and
locally vesicular. Columnar jointing is well developed in
places but is not obvious because exposures are poor.
Petrographically, the rock has a hyalo-ophitic texture.
Plagioclase, pyroxene, and olivine crystals generally
constitute about 45 percent of the rock. Dark-brown
almost opaque glass with abundant disseminated mag-
netite and (or) ilmenite makes up the rest of the rock.
Several thin sections of rocks from different localities
showed little variation in mineralogy or texture. The
only notable variation was found in a specimen collected
in the NW% sec. 17, T. 31 N., R. 41 E., which contained
about a third more plagioclase and pyroxene than other
specimens and about a third less glass and olivine. The
following table gives the modes, in volume percent, for
specimens of this basalt:

One specimen from sec.

Specimens from three
17, T. 31 N., R. 41 E.

localities1

Plagioclase .............................. 26 35
Pyroxene ................................ 13 17
Olivine .................................... 6 3
Glass ........................................ 45 35
Opaque minerals .................... 10 10

Total ............................ 100 100

1Average of three modes; less than 3 percent variation in any constituent.

Weaver (1920,p. 99) and Jones (1929,p. 50) applied
the name Camas Basalt to all the Tertiary volcanic
rocks in the report area but recognized that the basalt
is largely continuous with the Columbia River basalts
to the south. They erroneously included the andesite 3
miles southwest of Chewelah with the basalt, however.
Griggs (1966) mapped basalt of the Columbia River
Group within 2 miles of the southwest corner of the
report area. Becraft and Weis (1963, p. 39-40) reported
at least 900 feet of Columbia River Basalt in the Turtle
Lake quadrangle, at least part of which appears to be
“Late Yakima flows.” D. A. Swanson, of the US. Geo-
logical Survey, examined several thin sections of basalt
from the report area and reported that they strongly
resemble Yakima Basalt, which is of Miocene and Plio-
cene age (oral commun., 1966).

LATAH FORMATION

Hosterman (1969, p. 56) assigned the clay-bearing
strata found in two small claypits in sec. 4, T. 29 N., R.
42 E., and sec. 32, T. 30 N., R. 42 E., to the Latah For-
mation of Miocene age. In an earlier report, Miller
(1969, p. 4) erroneously included these clay beds in the
Quaternary.

 

The formation was originally named by Pardee and
Bryan (1926, p. 1), who thought that the unit was
overlain by the Columbia River Basalt. Kirkham and
Johnson (1929, p. 483) showed that the Latah Forma-
tion actually interfingers with the basalt. The contact
between the basalt and Latah Formation is not exposed
in the report area.

In the two claypits the formation consists of sand-
stone, siltstone, silty clay, and what Glover (1941, p.
282) described as “bog iron.” The so-called bog iron
consists of rust-colored cohesive material which re-
sembles limonite and which cements elastic material
ranging in grain size from coarse sand to clay. The sur-
face of the bog iron is botryoidal in many places. The
bog iron may be confined to a single bed at both pits
and if so may prove an aid to prospecting for clay. (See
Miller, 1969, p. 6 and fig. 3.) The clay is unconform-
ably overlain by glacial material.

CONGLOMERATE

Small isolated patches of well-indurated unsorted
pebble to boulder conglomerate are found on the hill
southwest of Chewelah and on the south and east flanks
of Cliff Ridge. At both localities, the clasts are com-
posed of the unit on which the conglomerate is lying or
of nearby lithologies.

Southwest of Chewelah, the conglomerate appears to
cling to the side of the hill. Stratification is not obvious
in the rock, and so it is not known if this is a buttress
relationship. At Cliff Ridge, the conglomerate is uncon-
formably overlain by glacial material. Many of the
clasts in the conglomerate southwest of Chewelah are
fairly well rounded, but most of those in the unit at
Cliff Ridge are angular.

The age of the rock is not known. The conglomerate
at one locality may not even be the same age as at the
other. The unconformity at the base of the conglomer-
ate and the fact that the rock is well indurated lead us
to suspect a Tertiary age.

GLACIAL, ALLUVIAL, AND TALUS
DEPOSITS, UNDIFFERENTIATED

Glacial, alluvial, and talus deposits were mapped as
one unit. Alluvial material is confined to the beds and
flood plains of modern streams. Glacial debris consists
chiefly of sand and gravel and locally fine-grained
lacustrine deposits. The debris forms moraines, out-
wash plains, terraces, and thin mantles on hillsides.

The distribution of glacial erratics, striae, and
moraines suggests that ice covered the western two-
thirds of the report area and that a lobe moved east—
ward from the main body in Burnt Valley. The presence
of glacial debris on top of Quartzite Mountain led Clark
and Miller (1968, p. 3) to surmise that the glacial ice

h

62

in the Colville River valley must have been more than
2,000 feet thick. Chewelah Mountain does not appear
to be glaciated above the 5,000-foot elevation, although
bedrock is deeply frost riven. Similarly, that part of
Calispell Peak above this elevation must have pro-
truded above the continental glaciers, but two cirques
on the north side of Calispell Peak indicate local moun-
tain glaciation, presumably during the waning phase
of glaciation.

Moraines are common in the area, but many have
been eroded almost beyond recognition. A prominent
moraine is responsible for the sharp switchback in the
road in the NE% sec. 24, T. 33 N ., R. 41 E. Additional
small moraines are found at about the 3,600-foot level
on the slopes north of Burnt Valley.

The erosionally resistant north-south belt of Addy
Quartzite, Striped Peak Formation, and upper Wallace
Formation appears to have dammed westward-flowing
glacial streams and caused deposition of large volumes
of glacial debris in basins east of it. The largest of these
basins is now drained by Cottonwood Creek. Others
to the north are now drained by Sherwood Creek,
Thomason Creek, South Fork of Chewelah Creek,
North Fork of Chewelah Creek, and Bear Creek.

Poorly indurated lacustrine materials, probably de-
posited in ponded water behind ice dams or moraines,
are found at several places in the area. An excellent
example is exposed in small roadcuts at the top of the
divide which lies on the line between secs. 15 and 16,
T. 31 N ., R. 41 E. The sediments there are fine grained,
light gray to white, and thin bedded. Almost none of
the lacustrine deposits crop out in natural exposures.
Although they contain some clay minerals, these depos-
its do not have the high proportion of clay minerals
found in the lake sediments previously described by
Miller (1969, p. 4).

Talus deposits are found chiefly below bold outcrops,
formed mainly by the quartzite units.

STRUCTURE

Structural and stratigraphic interpretations are
closely interrelated in the report area because interpre-
tations involving one are almost invariably based on
the other. Much of the structure shown on the map and
cross sections is inferred or at best based in part on
indirect evidence because of the generally poor expo-
sure. This is particularly true for much of western part
of the area, where the structural complexity is greatest.
To a certain extent, the degree of interpretive freedom
is inversely proportional to the amount and quality of
exposure. During the mapping, as stratigraphic infor-
mation increased and interpretations became more re-
fined, the complexity of the structural history became
increasingly apparent. Because the amount of interpre-

 

CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

tation is so great and the structure so complex, the
authors have tried their best to distinguish observed
from interpreted structures in the following section
and, as much as possible, to point out the basis for
interpretations.

Two distinct structural blocks are evident in the
report area. (See fig. 8) The eastern block, which
underlies most of the area, consists largely of Belt rocks
that form the west limb of a large anticline. Numerous
faults cut this fold, and the northern part of the fold
is overturned toward the west. The western block is
underlain primarily by the Deer Trail Group, which
here forms the north end of the magnesite belt. Signifi-
cant differences in stratigraphy and structures within
the blocks suggest that a major fault separates them
and that a large but unknown amount of lateral move-
ment has occurred. The J umpoff Joe fault may be this
fault, but this possibly cannot be demonstrated con-
clusively. (See section “Structure Separating the Two
Blocks”) At the few localities where the fault is ex-
posed, it appears to dip shallowly to the west and
places Precambrian Deer Trail rocks on the west side
against Paleozoic rocks on the east side. Most of the
fault, however, is concealed beneath the surficial debris
filling the Colville Valley, and so it is not known for
certain whether the various segments mapped as the
J umpoff Joe fault are in fact parts of a single, con-
tinuous fault.

STRUCTURES IN THE
BELT SUPERGROUP BLOCK

FOLDS

The northerly trending west limb of a large anticline
is evident from the outcrop pattern and attitudes of
Belt rocks in the east-central partof the report area.
(See pls. 1, 2; figs. 8, 22). Southeast of Deer Lake the
flower part of the Belt Supergroup strikes northwest
and dips at moderate angles to the west. North of Deer
Lake the strike of the section swings progressively more
northward, and the dip becomes increasingly steeper.
At about the latitude of Grouse Creek, the section
strikes north-northeast and is overturned towards the
west. Northward it becomes progressively more over-
turned, but the strike remains fairly constant up to the
latitude of Quartzite Mountain. There, it begins to
swing farther eastward until in the vicinity of God-
dards Peak the section strikes east-northeast, and
locally east-west, and is then cut off by plutonic rocks.

The east limb of this anticline, east of the report
area, is not nearly as well defined. Attitudes of the Belt
rocks between Fan and Horseshoe Lakes (fig. 2) , about
7 miles east of Deer Lake, indicate that the rocks are
near the axis of the fold, as the strike swings to east-
west, and in places east-northeast. In this area all the

 

STRUCTURE 63

strata are right-side-up and dip gently to the south. If single structure. About 5 miles west of them, he mapped
the strike of the section continues to swing to the north- an anticline which Schroeder (1952, p. 26) had previ-
east, the strata will form the east limb of the anticline. ously named the Snow Valley anticline. This anticline
However, plutonic rocks may interrupt this continua- is en echelon with an unnamed anticline that Barnes
tion. mapped near the southwest end of Priest Lake, but is
This anticline, here named the Nelson Peak anticline, separated from it by about 8 miles of intervening
and the partially exposed syncline to the west, here younger granodiorite. All the folds are rather open, and
named the Chewelah syncline, are shown in figure 22. the strike of the axes varies somewhat. The general
They are the westernmost in a series of rather evenly strike, however, is about due north.

spaced generally north-south-trending folds extending In the Bead Lake area, Schroeder (1952, p. 25) map-
eastward almost to Pend Oreille Lake in Idaho. Barnes ped only the east limb of a fold that he called the New-
(1965, pl. 1) mapped two synclines, the Priest River port syncline and suggested that its axis lay to the
and the Peewee, in the Priest River valley in Idaho. The west, approximately in the position of the Pend Oreille
two folds project toward one another and may be a River. From the strike of the beds of the east limb, the

 

 

118000, “7°30, 117° 00
COLVILLE METALlNE\ !
30' UADRANGL‘ ’ :
48° 30' o a 30 QUADRANGLP '
CHEWELAH NEWPORT
30‘ QUADRANGLE 30’ QUADRANGLE ( ‘
CH EWELAH- «)2
LOON LAKE l g '
AREA l 1: '
I -° l
33 w
t}. 4 20
i I m; 2
.. ,9 §
I .\ 2 :2“
i“ . A
7
Z

 

 
  

CHEWELAH SYNCLINE
NELSON PEAK ANTICLINE

 

————-—-—_-———IDAHO

 

 

WASHINGTON

*3.
8

Note: Paleozoic and Precambrian
rocks in this area are covered

EXPLANATION

 

by surficial material or intrud- FOLDS
ed by p|utonic rocks —-+——? __H——_.7—.
Normal Overturned
Anticline
—-i—-+ —7—. —-H——?-——
Normal Overturned
Syncline

Showing trace of axial plane and direc-
tion of dip of limbs. Dashed and
queried where inferred

0 10 20 MILES

FIGURE 22.—Location of major fold axes in the Belt Supergroup block.

 

 

64 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

axis should have about the same strike as the Snow
Valley anticline.

The Priest River syncline, Snow Valley anticline, and
Newport syncline are all rather open folds with gentle
to moderately dipping flanks. The Nelson Peak anti-
cline and Chewelah syncline are noticeably tighter than
these three and are in part strongly overturned. There
is an equally noticeable increase in the intensity of
folding from south to north within the report area. Both
limbs of the Nelson Peak anticline at about the latitude
of Deer Lake are normal, but to the north, at the lati-
tude of Chewelah Mountain, the west limb is strongly
overturned to the west. The Chewelah syncline, al-
though ill defined and complicated by faulting in the
southern part of the area, is reasonably well developed
from the Jay Gould Ridge area north to Johnson
Mountain. Comparison of cross sections B—B’ and A—A’
(pl. 1) shows the change between these two areas.
Although strongly overturned, the syncline at the lati-
tude of B—B’ is rather regular. Along A—A’ however, the
limbs of the fold are attenuated, and the nose is con-
siderably thickened. The structural change in thickness
is due at least in part to the extreme development of a
closely spaced slip cleavage in this area. The cleavage
appears to be about parallel to the axial plane of the
fold and is so pervasive that'it has given the rocks a
highly sheared appearance. In the vicinity of B—B’ the
slip cleavage is relatively low dipping and roughly par-
allel to the axial plane of the syncline but is not nearly
as well developed as it is to the north. The right-side-up
part of the syncline is exposed on Johnson Mountain,
in Ten Mile Creek southeast of the Flowery Trail
Granodiorite, and in the vicinity of Deer Lake.

FAULTS

A group of northwest-trending faults offset the Belt
Supergroup rocks with rather large apparent displace-
ment, all but one in a left-lateral sense. Parts of the
traces of all of them are masked by glacial debris, and
so their position can only be inferred in many places.
The apparent movement along these faults could have
been strike slip or dip slip, probably the latter, and is
thought to be Precambrian in age. These faults are con-
sidered to predate the development of the major folds
in the Belt Series, as they do not appear to cut the
Cambrian Addy Quartzite, which is involved in the
folding (fig. 23). The fault east of Quartzite Mountain
(No. 2, pl. 1) has a minimum apparent displacement of
10,000 feet in an apparent left-lateral sense. At the
west end the displacement of the lower contact of the
Addy Quartzite is only about 1,000 feet and is inter-
preted as renewed post-Cambrian movement along a
Precambrian fault. Faults 3 and 4 do not cut the Cam-
brian quartzite, although they appear to be truncated

 

  

 

 

    
 

5-5;. 2

 

  

 
 
  

Reference line
523':Reference line

 

l
B C
O 2 4 6MILES

APPROXIMATE SCALE

FIGURE 23.—Sketch maps showing alternate interpretations of

the relation of the Addy Quartzite to the northwest-trending
faults between Eagle Mountain and J umpoff Joe Mountain.
A, Present mapped relation. B, Lower contact of Addy
Quartzite restored to position undisturbed by faults. Inferred
northeast-striking fault has been removed, C, Probable con-
figuration of lower contact of Addy Quartzite if movement on
northwest faults had all been post-Addy. Arrows indicate
apparent offsets only.

by a north-northeast-trending, perhaps roughly con-
temporaneous, fault before they reach the quartzite.
Fault 5, which has a minimum apparent offset of about
11,500 feet, passes through an area covered by glacial
drift, across which the Addy Quartzite has a roughly
comparable offset. The fault relations in this covered
area are largely interpretive and are complicated by
a well-documented large northeast-trending fault and
a small thrust fault, the existence of which is based
largely on interpretation. Most of the apparent left-
lateral offset of the Addy Quartzite in this area is prob-
ably caused by dip slip on the large northeast-trending
fault just mentioned. This fault clearly offsets the lower
contact of the Addy Quartzite and also offsets the in-
ferred contact between the quartzite and overlying car-
bonate rocks south of where it cuts fault 5.

The trace of fault 6 is covered for its entire length,

but the existence of the fault is inferred in order to
explain the juxtaposition of unlike Belt units to the
north and south of it. Because of the dips of the strata
involved, a prohibitively large dip slip would be required
to bring the rocks here from their original location.

 

 

STRUCTURE 65

Although broken by other faults, fault 6 appears to
strike northwest. The best reconstruction of premove-
ment paleogeology necessitates about 7 miles of right-
lateral slip along this fault. However, this distance may
bear little resemblance to the actual amount of move-
ment along the fault because of complications by other
faults in the immediate area and uncertainties in cor-
relation of offset features across the fault. The best
“matc ” across the fault appears to be the syncline on
Deer Lake Mountain with a similar syncline on the
south flank of Blue Grouse Mountain. Both folds have
the same axial strike, are rather open and involve the
same stratigraphic units. If they are offset parts of the
same structure and are related to the Nelson Peak anti-
cline and Chewelah syncline, then fault 6 must have
formed after the folding and is much younger than
faults 1 through 5 are considered to be.

Faults with approximately the same northwest strike
as fault 6, and with right-lateral offset as well, are
abundant and well documented in the Coeur d’Alene
district and in the Clark Fork quadrangle. The two
largest and most widely known of these are the Hope
fault in the Clark Fork and Libby areas, and the
Osburn fault in the Coeur d’Alene district. Harrison
and J obin (1963, p. K28) reported 16 miles of apparent
right-lateral offset on the Hope fault but estimated
that some of this is due to vertical movements. They
suggested that the major strike-slip movement took
place in the Precambrian and that the dip-slip move-
ment occurred in Laramide or post-Laramide to pre-
Pleistocene time.

Hobbs and his colleagues estimated as much as 16
miles of right-lateral strike-slip movement along one
segment of the Osburn fault. Detailed structural analy-
sis suggests that the major strike-slip movements along
this fault occurred after the intrusion of the 100-m.y.-
old monzonitic stocks in the vicinity but before the
extrusion of the Miocene Columbia River basalts
(Hobbs and others, 1965, pl. 10, p. 128). Even though
the major movement along this fault is probably Cre-
taceous, a zone of weakness approximately coincidental
with the present position of the fault may have existed
there much earlier (Hobbs and others, 1965) .

The probable strike-slip movement along fault 6 in
the report area may have occurred during the Creta-
ceous, when the Osburn fault was most active.

If the northwest-trending faults are folded, as the
cross sections indicate, their trace on plates 1 and 2
should be sinuous rather than straight, especially
where they pass from a slightly overturned to a more
tightly overturned part of the section and where they
cross areas of rugged topography. The faults probably
do have sinuous trace, but exposure is simply not ade-
quate to map actual fault traces. Locally, offset fea-

 

tures are exposed well enough that short segments of a
fault can be drawn. Most of the segments whose strike
can be determined with some reliability trend north-
west. Gross offsets such as those east of Quartzite
Mountain and in the vicinity of Cottonwood Creek are
obvious, but actual fault traces could be quite irregular
there as exposure is poor even in areas shown as bedrock.
To minimize interpretive prejudice, separated segments
along a fault have been connected by relatively straight
lines through areas of sparse outcrop or glacial cover,
even though the trace may actually be quite irregular.

Previously published cross sections (Miller, 1969)
show the faults unfolded. Neither interpretation can be
conclusively proved or disproved, but as the Addy
Quartzite is involved in the folding, the faults, which
apparently predate the quartzite, also must be folded.

Differential movement along preexisting faults dur-
ing folding, in addition to the later small-scale thrust-
ing, has created a locally complicated structural knot
where the Cottonwood Road intersects the Addy
Quartzite (sec. 5, T. 31 N., R. 41 E.). Much of the rock
in this small area is highly crushed, broken, or tightly
folded. If exposures were more complete, detailed study
here could help to better define the relations between
the various structures.

STRUCTURES IN THE
DEER TRAIL GROUP BLOCK

The Deer Trail Group block and most of the struc-
tures within it strike almost unvaryingly northeast-
southwest. Beds, faults, and, to a lesser degree, folds
diverge little from this trend. The trend is not well dis-
played in the relatively limited outcrops of the Deer
Trail Group in the report area but is excellently devel-
oped southwest and northeast of the area. North-south
and northwest-southeast trends within the Belt Super-
group block appear to be truncated by the Deer Trail
Group. The differences in trend and the truncation
distinguish one block from the other. No large struc-
tures in the Deer Trail Group block strike northwest-
southeast. A few faults strike northwest-southeast, but
none have large displacements or great extent (Camp-
bell and Loofbourow, 1962, pl. 1).

The rocks north of Chewelah form the northeast
end of the magnesite belt. Most of the rocks here are
covered by glacial and alluvial material, but the north-
east-southwest trends that characterize the magnesite
belt are better developed here than elsewhere in the
report area. Because exposure is so sparse in this part
of the report area, a small amount of reconnaissance
mapping was done just outside the west boundary, in
the Iron Mountains, where the rocks are fairly well
exposed. Structure and stratigraphy can be projected
from there into the report area. A series of four north-

 

 

66 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

east-southwest-trending moderate-angle reverse faults,
which project into the area, are well developed in the
Iron Mountains. Two more, not well defined in the Iron
Mountains, are found in the report area. Although they
appear to be steeper, almost all the faults that Camp-
bell and Loofbourow ( 1962, pl. 1) mapped in the mag-
nesite belt are reverse faults and have a similar strike
and trend.

In the north half of the magnesite belt, Campbell and
Loofbourow showed an inferred northwest-southeast
fault folded by a locally developed north-south-striking
anticline and syncline. Another anticline and another
syncline with the same axial strike are found on Gold
Hill and Deer Mountain 3 miles northwest of Chewelah.
There the folds appear to involve the Addy Quartzite
and are therefore post-Cambrian in age. Campbell and
Loofbourow suggest the sequence of structural events
in the magnesite belt began with development of the
northeast-southwest faults, followed by local folding
with subsequent development of the few northwest-
southeast faults. Presumably the northeast-southwest
strike of the entire magnesite belt was established dur-
ing or before development of the faults with that strike.

OTHER DIFFERENCES
BETWEEN THE TWO BLOCKS

The primary lithologic differences between the Deer
Trail Group and the upper part of the Belt Supergroup
are exaggerated by differences in degree of dynamic
metamorphism. Throughout most of the magnesite
belt, the argillites of the Deer Trail Group are to some
degree phyllitic and (or) slaty. This is especially true
of the Togo Formation and the McHale Slate. The
Edna Dolomite contains argillite zones as much as 600
feet thick and also bedding-plane partings of argillite.
Almost all the argillite is phyllitic; in places it even
imparts a phyllitic look to the dolomite. From recon-
naissance in the magnesite belt, the authors gained
the impression that the Deer Trail Group is noticeably
and consistently more phyllitic than the Belt Super-
group east of the Colville Valley. Deer Trail Group
rocks are relatively undeformed only in isolated pockets
—for example, the Stensgar Dolomite 4 miles north-
west of Chewelah on the north side of US. 395 and
the argillite in the SW cor. sec. 22, T. 33 N., R. 40 E.
(fig. 6). The McHale Slate within 20 feet of the Stens-
gar Dolomite at the locality just mentioned, however,
is converted almost to a phyllonite, as is argillite within
100 feet of the undeformed argillite in sec. 22. In con-
trast, the Belt Supergroup rocks east of the Colville
Valley are only locally phyllitic, and where they are
it is due to the extreme development of a slip cleavage,
particularly in the northern part of the area. In general,

 

 

however, the difference in dynamic metamorphism be-
tween the two sections is real and noticeable.

In addition to structural and stratigraphic contrasts,
a significantly different group of rocks overlie the Deer
Trail Group and Belt Supergroup blocks. The Addy
Quartzite rests on the Huckleberry and Monk Forma-
tions in the Deer Trail Group block, whereas it directly
overlies the Belt Supergroup in the other block.

There are only two localities in the report area where
the Huckleberry or Monk Formations possibly overlie
Belt rocks. In sec. 7, T. 33 N., R. 41 E., and in sec. 29,
T. 34 N., R. 41 E., small areas are underlain by green-
stone and amphibolite injected by many leucocratic
dikes. These localities are just east of what may be the
main structure separating the Deer Trail and Belt
blocks at this latitude. However, another fault which
also may be the main break passes just east of the
greenstone and amphibolite.

Across the international boundary, and on strike
with the Priest River Group, Rice (1941, map 603A)
showed a thick section of the Purcell Series (the Can-
adian correlative of the Belt Supergroup) overlain by
the Irene Volcanics and Toby Conglomerate (the Can-
adian correlative of the Huckleberry Formation). Al-
though the descriptions by Rice (1941, p. 8-13) fit the
Belt equivalent Purcell Series much better than the
Priest River Group, there is some doubt as to whether
the specific section in the southwest corner of the map
area fits the descriptions. Furthermore, it is not known
if the structure separating the Deer Trail and Belt
blocks in the report area extends this far north.

Along its strike length the Huckleberry Formation is
intermittently continuous for at least 90 miles. Near
the center of the magnesite belt, it is 4,500 feet thick
(Campbell and Loofbourow, 1962, p. F22, F23). Only
10 miles east, however, across the strike of the magne-
site belt, it is not found between the Cambrian and
Belt rocks. The basin in which the Huckleberry Forma-
tion and its equivalents were deposited may, therefore,
have been elongate in a northeast-southwest direction.
Even so, a basin this long might well have greater lateral
extent, and the narrow configuration preserved today
may be the result of structural shortening across the
basin. Erosion prior to the deposition of the Addy
Quartzite is known to have removed parts of both Pre-
cambrian sections and could have removed all or most
of the Huckleberry and Monk Formations from above
the Belt Supergroup now preserved east of the J umpoif
Joe fault.

There is a consistent difference in trend betWeen the
Deer Trail Group and the Belt Supergroup block. North
of Chewelah the northeast-trending Deer Trail rocks
abut younger plutonic rocks but continue with the
same trend on the other side of the batholith, in the

 

 

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIII----——————_______L

STRUCTURE 67

Metaline quadrangle. In the Metaline quadrangle they
are called the Priest River Group (Park and Cannon,
1943, p. 6), but are correlated by Becraft and Weis
(1963, p. 16) with the Deer Trail Group.

Just south of the Metaline quadrangle, in the Bead
Lake area, Schroeder (1952, pl. 1) showed the Newport
Group (Belt Supergroup) with a generally north-south
strike. Although the Newport and Priest River Groups
are separated over a distance of 15-20 miles by younger
plutonic rocks, their structural relationship appears to
be the same as that of the Belt Supergroup and Deer
Trail Group, respectively, in the report area. In both
areas the Deer Trail Group or its correlatives are con-
fined to the northeast-trending block, which appears to
truncate the less well defined north-south trend of the
Belt Supergroup and its correlatives. Only locally in
the northeastern part of Washington are the Belt rocks
known to have this northeast regional trend, and only
locally does the Deer Trail Group diverge from it.

STRUCTURE SEPARATING THE TWO BLOCKS

Stratigraphic differences between the Belt Super-
group and Deer Trail Group, structural differences be-
tween the two blocks to which they are confined, and
differences in the sections which overlie the two lead to
the conclusion that they are separated by a thrust fault
along which an undetermined, but possibly large,
amount of movement has occurred. This fault is
thought to be the Jumpofi Joe fault. However, subse-
quent faulting, possiblyiregional tilting, and conceal-
ment by glacial and alluvial debris combine to make
study of the fault contact difficult.

The J umpoff Joe fault is exposed at several localities
in the report area. It separates rocks of the Deer Trail
Group from those of the Belt Supergroup, but Whether
it juxtaposes the two sections or merely downdrops the
major structure is uncertain. The fault is well located
but poorly exposed on the hill immediately west of
J umpof‘f Joe Lake; here Paleozoic carbonate rocks dip
under argillite probably belonging to the Deer Trail
Group. South of there the fault is covered by younger
deposits for a distance of 2 miles but crops out on the
hill north of Springdale, where it again places presumed
Deer Trail argillite against Paleozoic carbonate rock.
Here the fault dips at a moderate to shallow angle
under the Deer Trail Group and is clearly a low-angle
reverse or thrust fault. The fault is covered from J ump-
off Joe Lake to Chewelah. It is exposed on Embry Hill
northeast of Chewelah and north of there on the west

, flank of Eagle Mountain. The actual fault plane or fault
zone is not exposed on Embry Hill but can be located
precisely enough to confidently show that the fault dips
shallowly to the west under the Deer Trail Group. The

 

fault is steeper on Eagle Mountain but may be slightly
downdropped by a younger, high-angle fault. North of
Eagle Mountain relations are obscured by glacial cover.

The fault appears to bend to the west at the north
end of Eagle Mountain and then continue northward
through The Tinderbox. The rocks in that areaare
extremely deformed and resemble those adjacent to the
fault on Eagle Mountain. From The Tinderbox the
fault must follow Bayley Creek for a short distance and
then continue to the northeast, forming the boundary
between the Starvation Flat Quartz Monzonite and the
Phillips Lake Granodiorite. Where it cuts through the
plutonic rocks, the fault forms a prominent mylonite
and cataclastic zone as much as 500 feet wide. How-
ever, from the south boundary of sec. 31, T. 34 N., R.
41 E., to the north edge of the area the identity of this
fault is uncertain. It may be the Jumpoff Joe fault, one
of the northeast-striking faults which project from the
southwest, or a combination of both. The mylonite and
cataclastic zone is thought to be part of the J umpofi
Joe fault because it dips from 30° to 45° NW. In addi-
tion, no extension of the J umpoff Joe fault is known on
the northwest side of the zone.

An inferred fault passes just east of The Tinderbox,
across the north fork of Chewelah Creek, and up Bear
Canyon (pl. 1) . It merges with the J umpoff Joe fault to
the south and with the mylonite and cataclastic zone
to the north. The fault is drawn through a number of
isolated but extremely contorted and brecciated out-
crops and may represent the main trace of the J umpofi
Joe fault.

If the J umpoff Joe fault is the major structure that
juxtaposes the two Precambrian sections, then the
Deer Trail Group has been thrust over the Belt Super-
group; but if it merely downdrops the major structure,
then, because of the distribution of the two sections,
the Belt Supergroup would be thrust over the Deer
Trail Group (fig. 24) . Although the field relations per-
mit either conclusion, the former is favored because it
is simpler and because the trends of the Deer Trail
block appear to truncate those of the Belt Supergroup
block. The fact that it is not even known with certainty
which section has overidden which, or for that matter if
one section is even thrust over the other, illustrates how
equivocal the data concerning this problem are. Re-
gardless of the exact form of the structure, however,
the obvious differences in trend, internal structures,
and stratigraphy of the two blocks indicate the exist-
ence of some sort of large-scale break.

Although there are significant facies changes, fairly
good stratigraphic correlations can be made between
the Belt Supergroup in the Coeur d’Alene district, at
Clark Fork, and in the report area. The facies changes
are not unreasonable, considering the distances in-

fi‘

68 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

E

Surface

  
  

 

Surface

Surface

 

EXPLANATION

 

Addy Quartzite Belt Supergroup Deer Trail Group

FIGURE 24.—Diagrammatic cross sections showing possible
interpretations of thrust relations between the Belt Super-
group and Deer Trail Group. A, Simple thrust relation-
ship. Deer Trail Group thrust eastward over the Belt
Supergroup. This is considered the most likely relation
and is the one shown on the geologic map and sections.
B, Belt Supergroup thrust westward over the Deer Trail
Group. Thrust later displaced by the Jumpofl' Joe fault
and upper part removed by erosion. C, Deer Trail Group
thrust eastward over the Belt Supergroup. Thrust is in
subsurface only and is displaced by the J umpoff Joe fault.
This interpretation assumes the thrusting is Precambrian

in age.

volved. No large-scale thrust faults are known in the
area between these localities, and so if the Belt section
of the report area had been thrust over the Deer Trail
Group, the rest of the Belt rocks east to the Clark Fork
and Coeur d’Alene areas would have had to move with
it. The thrust sheet would be tremendously large and
would contain no known imbricate thrusts, and the
thrust plane would be nowhere exposed at the surface.
If this is the case, however, the upper plate would be

 

thrust from east to west, as no section resembling the
Deer Trail Group is known east of Chewelah.

For the same reason, if the Deer Trail Group is
thrust over the Belt Series, as is suspected, the upper
plate must be thrust from west to east. Unfortunately
there are no exposures of the Deer Trail Group or Belt
Supergroup west of the relatively narrow magnesite
belt that would allow an estimate of how much move-
ment has occurred. The facies changes in the Belt sec-
tion between Clark Fork and the report area are more
pronounced than those between the report area and
the magnesite belt. This suggests that the amount of
thrusting may not be too great.

Unfortunately, a complete section of Addy Quartz-
ite resting on the Belt Supergroup is nowhere exposed
in the area. Because systematic differences in thick-
ness of the basal Cambrian quartzite are known to
exist in the region, comparison of the thickness of the
quartzite on the Belt Supergroup with that above the
Deer Trail Group might furnish information on how far
the two sections were originally separated. Addy
Quartzite overlying the Belt rocks east of the area
should be examined with this in mind.

Paleozoic rocks on Addy Quartzite appear to be
different above the two Precambrian sections, but the
Paleozoic carbonate rocks above the Belt Supergroup
are not well enough nor extensively enough exposed to
make meaningful comparisons with those above the
Deer Trail Group. In the Hunters quadrangle, which
includes the southern part of the magnesite belt, Camp-
bell and_ Raup (1964) showed several thousand feet of
limestone, slate, and chert of Ordovician age or older
above the quartzite, where it overlies the Deer Trail
Group. Yates (1964) also showed several thousand
feet of carbonate, phyllite, and slate of Ordovician age
or older above the quartzite, all of which apparently
overlies the Deer Trail or Priest River Group, but no
rocks corresponding to either of these thick sections
are found above the quartzite resting on the Belt Super-
group. Throughout the report area, Mississippian car-
bonate rocks are found above the Addy Quartzite where
it rests on the Belt rocks, but they have not been found
anywhere else in northeastern Washington.

The J umpoff Joe fault is thus presumably younger
than the Mississippian carbonate rocks and is probably
younger than the Starvation Flat Quartz Monzonite
and the Phillips Lake Granodiorite. This would indicate
that the thrusting took place less than 100 my ago.

Although it has been suggested here that the J ump-
oif Joe fault is the major structure separating the Deer
Trail and Belt blocks, it is possible that the large north-
east-striking faults that pass a few miles northwest of
Chewelah mark the division between the blocks and
that one of the faults in that system is significantly

 

 

 

 

MINERAL DEPOSITS 69

larger than the others. If this were the case, several
interpretations that have been proposed would have
to be altered: (1) The rocks west of the J umpoff Joe
fault that have been assigned to the Deer Trail Group,
primarily on the basis of their association with the
greenstone of the Huckleberry Formation, are actually
part of the Belt Supergroup, (2) the greenstone, al-
though thin, is present within the eastern structural
block, and (3) the J umpofi Joe fault, although a large
fault, has not had a significant amount of lateral move-
ment along it.

There are two significant reasons for suggesting that
this other fault system, and not the J umpoff Joe fault,
is the major structure separating the two structural
blocks: (1) All rocks and structures with the northeast
trend so consistently found in the Deer Trail block
would be restricted to that block. Most of the rocks in
the report area west of the J umpoff Joe fault and south
of Chewelah do not have this northeast strike. To sug-
gest stratigraphic assignments on the basis of struc-
tural evidence in this manner is ordinarily not justified.
However, the consistency of the northeast trends within
the Deer Trail block is so striking and is developed over
such a large area that any rocks assigned to this block
not having the northeast trend should be regarded with
some suspicion. (2) The topographic lineament formed
by faults of this zone within the report area continues
to the southwest outside the area. Campbell and Loof-
bourow (1962, pl. 1) mapped a fault along part of this
lineament, but the fault passes beyond the limits of
their mapping a short distance to the south.

Considering stratigraphic and structural relations
jointly, the following correlations and sequence of
events are tentatively proposed to explain the relation
between the Deer Trail Group and Belt Supergroup:
(1) The Deer Trail Group is roughly equivalent to the
upper Wallace Formation and the Striped Peak For-
mation; (2 ) the strata of the two blocks were deposited
at localities more widely separated than at present,
although information is not sufficient to accurately esti-
mate how far apart they were; (3) the two groups
underwent separate, though possibly related, deforma-
tion at their respective sites of deposition; and (4)
sometime after the extrusion of the Huckleberry vol-
canics and deposition of the Addy Quartzite, and prob-
ably after intrusion of the Starvation Flat Quartz Mon-
zonite, the two sections were brought together by thrust
faulting.

OTHER FAULTS

Several of the faults that have a general north-south
strike appear to be older than the Flowery Trail Grano-
diorite because the brecciated rocks in one of the fault
zones near the pluton are thoroughly recrystallized.

 

Most of these faults are not exposed, but are inferred
because of anomalous relationships across alluvium-
filled valleys. The faults immediately east and west of
the J umpofi Joe fault appear to belong to this group.
These faults may have been active at the same time as
the large northeast-striking faults, some of which are
interpreted as cutting the north-south faults and some
as being cut by them. The fault separating the Addy
Quartzite from the Paleozoic carbonate rocks southeast
of Chewelah probably belongs to this group.

Two sets of northeast-striking faults are found in the
Belt Supergroup block, but one set has a consistently
different strike (N. 50°—60°E.) from the faults in the
Deer Trail Group block. The large fault that passes
through the Upper Cottonwood Road area is repre-
sentative of that group. The other set, which approxi-
mates the N.30°—40° E. strike of the major faults in
the Deer Trail Group block, is not represented in the
report area. Three large faults with this trend are
found south of Horseshoe Lake, about 4 miles east of
Blue Grouse Mountain.

West of Loon Lake, three shear zones are found in
the 50-m.y.-old Silver Point Quartz Monzonite. These
zones strike about north-south to north-northwest.
Within the zones the rock is highly brecciated and has
been recemented by chloritic material and quartz.
Aplite dikes in the zones are both twisted and broken,
as if the process which formed the shear zones may have
been active when the dikes were intruded and con-
tinued active for some time after the dikes solidified.

Numerous smaller faults, some inferred, some ob-
served, are shown on the geologic maps. Most cannot
be dated by crosscutting relationships with closely
dated rocks or other structures.

MINERAL DEPOSITS

Commodities of economic interest in the report area
include copper, silver, lead, tungsten, barite, clay, silica
sand, and feldspar. Individual mine workings and pros-
pects that were accessible between 1963 and 1968 were
described in detail by Clark and Miller (1968, p. 4—5
and pl. 2) and Miller (1969, p. 6). Clark and Miller also
described from old company mine maps some workings
in the Eagle Mountain area that were not accessible
during the study period. Only general mine areas will
be discussed here. The reader is referred to earlier
reports by Weaver (1920), Patty (1921), Huntting
(1956), Clark and Miller (1968), and Miller (1969)
for individual mine descriptions.

In terms of total value of ore produced, the copper-
silver mines around Eagle Mountain are by far the
most important in the area. Of the 10,551,098 pounds
of recorded copper production from the report area,

 

 

 

70 CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

about 94 percent is accredited to the mines around
Eagle Mountain (Fulkerson and Kingston, 1958, p.
27—28). Almost 100 percent of the recorded silver pro-
duction also comes from these mines.

The copper-silver ore is found in quartz-carbonate
veins which range in thickness from a few inches to over
25 feet. Most are between 10—25 feet wide and are
within or near well-developed steeply dipping north-
northeast shear zones confined to the upper and lower
parts of the Wallace Formation. Sulfides are sparsely
disseminated in the veins and host rock and include
pyrite, chalcopyrite, tetrahedrite, pyrrhotite, covellite,
and chalcocite or digenite. Malachite and hematite are
also present. Most of the mines in the north half of the
report area, including those around Eagle Mountain,
are in country rock peripheral to the Flowery Trail
Granodiorite, and the mineralization may be related to
that pluton.

The sections accompanying the preliminary geologic
map by Clark and Miller (1968, pl. 1) show Eagle
Mountain to be underlain by a nearly horizontal thrust
fault. However, additional work since the publication of
that map and the delineation of individual Belt forma-
tions suggest that the mountain probably is not floored
by a thrust fault and that the shear zones which appear
to control the location of the veins are probably con-
tinuous at depth. Both the thrust and nonthrust inter-
pretations are based on poor exposure in critical areas,
however, and should be reevaluated if additional data
become available.

Only minor exploration has ever been attempted
below the main adit level in any of the mines in the
Eagle Mountain area. Regardless of whether the area
is floored by a thrust fault or not, the vein system
should be explored at depth by drilling. Patty (1921,
fig. 8) showed a rich streak of tetrahedrite continuing
350 feet below the main adit level in one mine and
widening with depth. In addition, old company maps
and records indicate an increasing silver-copper ratio
at depth. The ever-increasing demand for silver pos-
sibly warrants exploratory drilling of the lower parts of
the vein system.

Smaller deposits have been mined on Embry Hill,
about 1 mile southwest of the Eagle Mountain area.
These are also on the north side of the Flowery Trail
Granodiorite. They are roughly on strike with the Eagle
Mountain vein system, but whether the two are con-
tinuous is uncertain because faults and an area of poor
exposure separate the two localities. Only 4,011 pounds
of copper and 22 ounces of silver have been recovered
from the ore of the Embry Hill mines (Fulkerson and
Kingston, 1958, p. 28). The deposits differ from those
on Eagle Mountain in that they have a much higher
copper-silver ratio and also contain small amounts of

 

 

molybdenite. The Embry Hill veins may have been
emplaced within the southern continuation of the Eagle
Mountain shear zone or formed in Subsidiary breaks
related to the J umpoff Joe fault; the latter may border
the west margin of the mineral deposits at this locality.

A few deposits of lesser importance are found on the
south side of the Flowery Trail Granodiorite. Only the
Jay Gould mine has had recorded production. The
veins in the Jay Gould area are typified by lead and
silver-bearing minerals and thus differ from the Eagle
Mountain and Embry Hill ores. Argentiferous galena,
the major ore mineral, is found in quartz veins as much
as 10 feet wide.

The distribution of base metal deposits around the
Flowery Trail Granodiorite appears to exhibit a zona-
tion of sorts. The lead-silver deposits of the Jay Gould
area and the Blue Star mine of the Eagle Mountain
area occur within the margins of the pluton and in the
adjacent sedimentary rocks. Next and relatively near
the contact are the silver-copper deposits of Embry
Hill, in which the silver-copper ratio is relatively low.
The Eagle Mountain deposits, which have a high silver-
copper ratio, are farthest from the pluton.

The only other base metal deposit in the report area
which has had any significant production is the Loon
Lake copper mine, in .the NE% sec. 33, T. 31 N., R. 41
E. It has a production record of 622,555 pounds of cop-
per and 532 ounces of silver (Fulkerson and Kingston,
1958, p. 45). The production was recorded principally
for the period between 1916 and 1919 and came from
an individual ore shoot in a quartz vein from 4 to 20
feet wide. Most of the ore came from a secondary zone
of azurite, malachite, and cuprite. N 0 new shoots were
found by additional exploration. No other base metal
mines with any production are located within several
miles of the Loon Lake copper mine, although numerous
large quartz veins similar to the one on which the prop-
erty is developed are found in the mountains to the
east and southeast.

Several tungsten deposits have been found on Blue
Grouse Mountain east of Deer Lake. They consist of
sparsely disseminated huebnerite crystals in quartz
veins, greisen, and pegmatite segregations around the
periphery of the muscovite quartz monzonite. The min-
eralization appears to be related to this quartz monzo-
nite pluton.

Barite deposits have been found on Eagle Mountain,
the hills north and east of Valley, and a few hundred
feet southwest of the Loon Lake copper mine. Moen
(1964) described all the deposits, gave production
figures, and estimated reserves. All the barite occurs
in veins or a series of veins which range in Width from
less than 1 inch to several tens of feet. Moen reported
634 tons of barite shipped, reserves of 2,300 tons meas-

 

 

 

 

 

REFERENCES CITED 71

ured and indicated, and 24,750 tons inferred. The veins
are scattered and appear to be unrelated, but all are
restricted to the Striped Peak Formation or its probable
equivalent, the Deer Trail Group.

Two claypits in the Latah Formation are located
southeast of Deer Lake, near the south edge of the map
area. Similar deposits are found less than 1 mile east of
the report area at the same latitude as those southeast
of Deer Lake and just south of the area at the town of
Clayton. Hosterman (1969, p. 55, 56) studied the clay
deposits of Spokane County in detail. He described
the deposit just east of the area and gave analyses of
the clay. Miller (1969, pl. 1) prepared a highly general-
ized map which shows the possible location of addi-
tional clay in nearby areas.

The Addy Quartzite may in part be pure enough to
be a source for silica sand. Above the purple and pink
zones at the base of the formation, the sand is generally
white or light gray and probably almost pure quartz.
An extensive sampling program would be necessary to
block out an area of sufficient purity. On Lane Moun-
tain, a few miles west of the area, the quartzite is being
mined for the manufacture of glass. There, however,
the silica cement has been removed or was never depos-
ited, and the rock is extremely friable. All the Addy
Quartzite in the report area would require considerable
crushing.

Feldspar for use as a flux in glass manufacture may
be available from the 'muscovite quartz monzonite.
Analyses of this unit (see section “Muscovite Quartz
Monzonite, Petrology”) show that it contains very
little iron or manganese, two of the chief contaminants
in glass making. Abundant, easy-to-reach reserves are
available in the southeastern part of the area and just
east of the area.

REFERENCES CITED

Anderson, A. L., 1940, Geology and metalliferous deposits of
Kootenai County, Idaho: Idaho Bur. Mines and Geology
Pamph. 53, 67 p.

Barnes, C. W., 1965 Reconnaissance geology of the Priest River
area, Idaho: Wisconsin Univ., Madison, Ph.D. thesis, 145 p.

Bateman, P. 0., Clark, L. D., Huber, N. K., Moore, J _ G. and
Rinehart, C. D., 1963, The Sierra Nevada batholith—a
synthesis of recent work across the central part: U.S_ Geol.
Survey Prof. Paper 414-D, p. D1—D46.

Becraft, G. E., 1966, Geologic map of the Wilmont Creek quad-
range, Ferry and Stevens Counties, Washington: U.S. Geol.
Survey Geol. Quad. Map GQ—538, scale 1:62,500.

Becraft, G. E., and Weis, P. L., 1963, Geology and mineral
deposits of the Turtle Lake quadrangle, Washington: U.S.
Geol. Survey Bull, 1131, 73 p.

Bennett, W. A. G., 1941, Preliminary report on the magnesite
deposits of Stevens County, Washington: Washington Div.
Geology Rept. Inv. 5, 25 p.

Bowman, E. C., 1950, Stratigraphy and structure of the Orient

 

area, Washington: Harvard Univ., Cambridge, Ph.D.
thesis, 149 p.

Branson, C. C., 1931, New paleontological evidence on the age
of the metamorphic series of northeastern Washington:
Science, v. 74, no. 1907, p. 70.

Campbell, A. B., 1960, Geology and mineral deposits of the St.
Regis-Superior area, Mineral County, Montana: U.S. Geol.
Survey Bull. 1082—1, p. 545—612 [1961].

Campbell, A. B., and Good, S. E., 1963, Geology and mineral
deposits of the Twin Crags quadrangle, Idaho: U.S. Geol.
Survey Bull. 1142—A, p. A1—A33.

Campbell, A. B., and Raup, O. B., 1964, Preliminary geologic
map of the Hunters quadrangle, Stevens and Ferry
Counties, Washington: U.S. Geol. Survey Mineral Inv.
Field Studies Map MF—276, scale 1:48,000.

Campbell, Ian, and Loofbourow, J. S., 1962, Geology of the
magnesite belt of Stevens County, Washington: U.S. Geol.
Survey Bull. 1142—F, p. F1—F53.

Carlisle, D. 1963, Pillow breccias and their aquagene tuffs,
Quadra Island, British Columbia: Jour. Geology, v. 71,
no. 1, p: 48—71.

Chayes, Felix, 1956, Petrographic modal analysis—an elemen-
tary statistical appraisal: New York, John Wiley & Sons,
113 p.

Clark, L. D., and Miller, F. K., 1968, Geology of the Chewelah
Mountain quadrangle, Stevens County, Washington:
Washington Div. Mines and Geology Map. GM—5, scale
1:62,500.

Daly, R. A., 1912, Geology of the North American Cordillera
at the forty-ninth parallel: Canada Geol. Survey Mem. 38,
1-3, 857 p.

Dings, M. G., and Whitebread, D. H., 1965, Geology and ore
deposits of the Metaline zinc-lead district, Pend Oreille
County, Washington: U.S. Geol. Survey Prof. Paper 489,
109 p.

Doe, B. R., and Hart, S. R., 1963, The effect of contact meta-
morphism on lead in potassium feldspars near the Eldora
Stock, Colorado: J our. Geophys. Research, v. 68, no. 11, p.
3521—3530.

Embrysk, B. J ., 1954, Additions to the Devonian and Mississip-
pian paleontology of northeastern Washington: Washing-
ton State Coll., Pullman, Master’s thesis.

Eskola, Pentti, 1952, On the granulites of Lapland: Am. J our.
Sci., Bowen volume, pt. 1, p. 133—171.

Fulkerson, F. B., and Kingston, G. A., 1958, Mine production
of gold, silver, copper, lead, and zinc in Pend Oreille and
Stevens Counties,Washington, 1902—1956: U.S. Bur. Mines
Inf. Circ. 7872, 45 p.

Fyfe, W. S., Turner, F. J ., and Verhoogen, John, 1958, Meta-
morphic reactions and metamorphic facies: Geol. Soc.
America Mem. 73, 259 p.

Glover, S. L., 1941, Clays and shales of Washington: Washing-
ton Div. Mines and Geology Bull. 24, 368 p.

Griggs, A. B., 1966, Reconnaissance geologic map of the west
half of the Spokane quadrangle, Washington and Idaho:
U.S. Geol. Survey Misc. Geol. Inv. Map I—464, scale 1:
125,000.

Hanson, G. N., and Gost, P. W., 1967, Kinetic studies in con-
tact metamorphism zones: Geochim. et Cosmochim. Acta,
v. 31, p. 1119-1153.

Harrison, J. E., and Campbell, A. B., 1963, Correlations and
problems in Belt Series stratigraphy, northern Idaho and
western Montana: Geol. Soc. America Bull., v. 74, no. 12,
p. 1413-1428.

 

 

72

Harrison, J. E., and Jobin, D. A., 1963, Geology of the Clark
Fork quadrangle, Idaho-Montana: U.S. Geol. Survey Bull.
1141—K, 38 p.

Hart, S. R., 1961, Mineral ages and metamorphism, in Kulp,
J. L., ed., Geochronology of rock systems: New York Acad.
Sci. Annals, v. 91, art. 2, p. 192—197.

1964, The petrology and isotopic-mineral age relations
of a contact zone in the Front Range, Colorado: Jour.
Geology, v. 72, no. 5, p. 493—525.

Hobbs, S. W., Griggs, A. B., Wallace, R. E., and Campbell,
A. B., 1965, Geology of the Coeur d’Alene district, Sho-
shone County, Idaho: U.S. Geol. Survey Prof. Paper 478,
139 p.

Hosterman, J. W., 1969, Clay deposits of Spokane County,
Washington: US. Geol. Survey Bull. 1270, 96 p.

Huntting, M. T., 1956, Inventory of Washington minerals; pt.
2, Metallic minerals: Washington Div. Mines and Geology
Bull. 37, v. 1, 428; p. v. 2, 67 p.

Huntting, M. T., Bennett, W. A. G., Livingston, V. E., J r., and
Moen, W. S., 1961, Geological map of Washington: Olym-
pia, Washington Div. Mines and Geology, scale 1:500,000.

Jones, R. H. B., 1928, Notes on the geology of the Chewelah
quadrangle, Stevens County, Washington: Northwest Sci.,
v. 2, p. 111—116.

1929, The geology and mineral resources of the Chewe-
lah quadrangle, Washington: Washington State Univ.,
Seattle, Master’s thesis, 69 p.

Kirkham, V. R. D., and Johnson, M. M., 1929, The Latah for-
mation in Idaho: Jour. Geology, v. 37, no. 5, p. 483—501.

Klapper, G., 1966, Upper Devonian and Lower Mississippian
conodont zones in Montana, Wyoming, and South Dakota:
Kansas Univ. Paleo. Contr. 3, 43 p.

Laniz,rR. V., Stevens, R. E., and Norman, M. B., 1964, Staining
of plagioclase feldspar and other minerals with F. D. and
C. Red No. 2, in Geological Survey research 1964: US.
Geol. Survey Prof. Paper 501—B, p. B-152—B153.

Miller, F. K., 1969, Preliminary geologic map of the Loon Lake
quadrangle, Stevens and Spokane Counties, Washington:
Washington Div. Mines and Geology Geol. Map GM—6,
scale 1:62,500.

Mills, J. W. and Yates, R. G., 1962, High~calcium limestones
of eastern Washington: Washington Div. Mines and Geol-
ogy Bull. 48, 268 p.

Moen, W. S., 1964, Barite in Washington: Washington Div.
Mines and Geology Bull. 51, 112 p.

Nockolds, S. R., 1954, Average chemical composition of some
igneous rocks: Geol. Soc. America Bull., v. 65, no. 10, p.
1007—1032.

Okulitch, V. J., 1951, A lower Cambrian fossil locality near
Addy, Washington: J our. Paleontology, v. 25, no. 3, p. 405—
407.

Pardee, J. T., and Bryan, Kirk, 1926, Geology of the Latah
formation in relation to the lavas of the Columbia Plateau
near Spokane, Washington: US. Geol. Survey Prof. Paper
140—A, p. 1—16.

Park, C. F., Jr., and Cannon, R. S., Jr., 1943, Geology and ore
deposits of the Metaline quadrangle, Washington: U.S.
Geol. Survey Prof. Paper 202, 81 p.

Patty, E. N ., 1921, The metal mines of Washington: Washing-
ton Geol. Survey Bull. 23, 366 p.

 

 

 

 

 

CHEWELAH—LOON LAKE AREA, STEVENS AND SPOKANE COUNTIES, WASHINGTON

Ransome, F. L., 1905, Ore deposits of the Coeur d’Alene dis-
trict, Idaho: US. Geol. Survey Bull. 260, p. 274—303.
Ransome, F. L., and Calkins, F. C., 1908, The geology and ore
deposits of the Coeur d’Alene district, Idaho: US. Geol.

Survey Prof. Paper 62, 203 p.

Reynolds, R. L., 1968, Paleocurrents, petrology, and source area
of the Addy Quartzite (Cambrian), northeastern Washing-
ton: Undergraduate thesis, Princeton Univ., 48 p.

Rice, H. M. A., 1941, Nelson map-area, east half, British Colum-
bia: Canada Geol. Survey Mem. 228, Pub. 2460, 86 p.
Rinehart, C. D., and Fox, K. F., 1972, Geology and mineral
deposits of the Loomis quadrangle, Okanogan County
Washington: Washington Div. Mines and Geology Bull.

no. 64, 124 p.

Ross, C. P., 1963, The Belt series in Montana: US. Geol. Sur-
vey Prof. Paper 346, 122 p. [1964].

Schroeder, M. C., 1952, Geology of the Bead Lake district, Pend
Oreille County, Washington: Washington Div. of Mines
and Geology Bull. 40, 57 p.

Shenon, P. J ., and McConnel , R. H., 1939, The Silver Belt of
the Coeur d’Alene district, Idaho: Idaho Bur. Mines and
Geology Pamph. 50, 8 p.

Shido, F., 1958, Plutonic and metamorphic rocks of the Nakoso
and Iritono districts in the central Abukuma Plateau:
Tokyo Univ., Jour. Faculty Sci., sec. 2, v. 11, p. 171.

Shido, F., and Miyashiro, A., 1959, Hornblendes of basic meta-
morphic rocks: Tokyo Univ., Jour. Faculty Sci., sec. 2,
v. 12, p. 86.

Turner, F. J., and Verhoogen, John, 1960, Igneous and meta-
morphic petrology [2d ed.]: New York, McGraw-Hill,
694 p.

Tuttle, O. F., and Bowen, N. L., 1958, Origin of granite in the
light of experimental studies in the system NaAlSi308—
SiOZ—HZO: Geol. Soc. America Mem. 74, 153 p.

Walker, J. F., 1926, Geology and mineral deposits of Winder-
mere map area, British Columbia: Canada Geol. Survey
Mem. 148, 69 p.

Wallace, R. E., and Hosterman, J. W., 1956, Reconnaissance
geology of western Mineral County, Montana: US. Geol.
Survey Bull. 1027—M, p. 575—612.

Wanless, R. K., Stevens, R. D., Lachance, G. R., and Rimsaite,
R. Y. H., 1965, Age determinations and geological studies:
Canada Geol. Survey Paper 64—17 (pt. 1), 126 p.

Weaver, C. E., 1920, The mineral resources of Stevens County:
Washington Geol. Survey Bull. 20, 350 p.

Weis, P. L., 1968, Geologic map of the Greenacres quadrangle,
Washington and Idaho: US. Geol. Survey Geol. Quad.
Map GQ—734, scale 1:62,500.

Yates, R. G., 1964, Geologic map and sections of the Deep
Creek area, Stevens and Pend Oreille Counties, Washing-
ton: U.S. Geol. Survey Misc. Geol. Inv. Map I—412, scale
1:31,680.

Yates, R. G., Becraft, G. E., Campbell, A. B., and Pearson,
R. C., 1966, Tectonic framework of northeastern Washing-
ton, northern Idaho, and northwestern Montana: Canadian
Inst. Mining and Metallurgy Spec. Vol. 8, p. 47—59.

Yates, R. G., and Engels, J. C., 1968, Potassium-argon ages of
some igneous rocks in northern Stevens County, Washing-
ton, in Geological Survey research 1968: US Geol. Survey
Prof. Paper GOO—D, p. D242—D247.

 

 

 

 

 

Accessibility ......
Addy Quartzite ..
faults
folds
mineralization ..
relation to Belt Supergroup
relation to Deer Trail Group.
relation to glacial deposits.
relation to granodiorite ...... _.
relation to Huckleberry Formation... 24
relation to Striped Peak Formation. 11, 16

 
  
  
  
 
  

  
  
 
  
 
   

Ahren Meadows ....................... 47
Allanite ............. 49, 51
Alluvial deposits .. 61
Amphibolite 24
Andesite .. .................... 60
Apatite 43, 44, 47, 49, 50, 51
Aplite ................... 4, 43, 50, 69
Argillite . 2, 4, 6, 7, 8, 12, 13, 16,

17, 18, 19, 23, 26, 66

 

 
 
 
 
 
   
  
  
 
 
  
  
 
  
  
 
 
 
 

Armstrong, A. K., quoted... .................... 30, 32
B

Bald Mountain . . 8, 10
Barite ..... 69, 70
Basalt ..... 60
Batholiths . . 4, 16, 33, 51, 55
Bayley Creek ....... 26, 67
Bead Lake . , 18, 63, 67
Bear Canyon . 42, 67
Bear Creek 62
Beitey Lake . 12, 15, 16
Bell Meadow . 42
Belt Supergroup 2, 4, 65

dikes . 58

relation to Deer Trail Group.

structure .

Benson Peak ..
Blacktail Mountain
Blue Grouse Mountain .
Blue Star mine ..
Branson, C. C., quo
Breccia ..................
Brecciated rocks ..
Br ' h'nn

 

 

 

 

 

 

 

 

 
   
 
 
 
 
  
 
  

Brewer Mountain .............. 42
Buffalo Hump Formation 18
relation to Belt Supergroup.. 24
Burke Formation ........................... 6
relation to Silver Point Quartz
Monzonite . 49
Burnt Valley ..................... 61
C
Calispell Peak ..................... .. 38, 40, 41, 43, 62
Games Basalt ....... 61
Carbonate rock 8, 29, 80, 31, 32
Chewelah Argillite 24
Chewelah Creek ........ 67
Chewelah Mountain 5. 6, 62, 64
Chewelah syncline . 63, 64, 65
Clark Fork 67
Clay . 61, 69, 71

 

 

INDEX

 

[Italic page numbers indicate major references]

Page
Cliff Ridge .................
Clifl Ridge Lookout .
Coeur d’Alene district.

 

 
 

23, 65, 67
. 4, 61
. 33, 51

Columbia River Group .........
Colville—Loon Lake batholith..

 

 

 

 
  

Colville River .. 62
Colville Valley .. .. 62, 66
Conglomerate . 2, 24, 25, 26, 61
Copper ........................ 69, 70

 

 

   

Cottonwood Creek . 13, 30, 58. 66
Cr» ‘ “if"! 7, 10
Cross—laminations ........ 6, 7, 8, 10, 11, 14, 16
Crowell—Sullivan Ridge ...... 29

Crystallization ...........

  
 
 
 
 
  
  
  
 
 

Dating methods
Deep Creek
Deer Lake
Deer Lake Mountain
Deer Mountain ..
Deer Park ........
Deer Trail Group...

relation to Belt Supergroup ..

structure

undivided .
Defamation
Dikes
Dolomite
Duncan, Helen, quoted.

 

Dutro, J. T., quoted ........ 33
E

Eagle Mountain ................................................ 8,

11, 12, 14, 15, 27, 29, 30. 36, 42, 6'7. 69, 70

Edna Dolomite ................................................ 17', 66

relation to Striped Peak Formation ..

 

   

 

 
 

 

  
  
 
  

Fan Lake . ......... 62
4, 8, 38. 64, 67, 69
F ‘1 1r- 69, 71
Flowery Trail Granodiorite... .. 33, 52, 57
relation to mineralization" 70
relation to Phillips Lake
Granodiorite ...... 43
Flows .
Folds .
Fossils:
Acrothele ................... 30
Ammobaculites sp 33
Amphissites centro'notus . 33
simplicissimus ...... 33
Amplexizaphre’ntis an 31
Archaeocyatha .. 32
Bathyuriscua .. .. 80
Brachiopods 30 32, 33
Bryozoans ......... 31
Cavellina corelli . 32
Composite ......... 33

 

 

Fossils—Continued
Composite—Continued
sp ....................................
Conodonts
Corals ......
Crinoids ..
Crurithyria sp
Cyrtospin'fe'r sp
Cystodictya sp
Endothyra sp
Fe’nestella. sp
Fucoids
Gastropods .
Globo'valvuli'na bullm‘des .
Gnathodus sp ..
Graphiodactylus teams .
Hyolithes sp .......
Hyoh'thellus sp ..
J onesina crateriaera

  
 
 
 
  
 
 
 
 
 

 

 

 

  
  

 

 

 

  
 
 
  
 
 
    
  
 
  
 

 

 

 

 

Kuto'rgi'nu, .......

ci/ngulata .

sp ...............
Leptargom'a analoga 33
Linnarsstmia .. 30
Lophaphullidium pro iferum .. 33
Micromitra (Paten'mz) sp 28
Millerella sp .. 33
Nevadella, addyerms 28
Nevadia [=Nevadella] addyemus.. . 28
Olenellids . ............................ 28
Olenm'des . 30
Ostracodes . . 32
Pelmatozoan debris . 30, 31, 32
Peronopsis ......... . 30
Platycems sp .. 32
Pseudopolygnathus multistn'ata 32
Pseudosyrinm sp 32
Rhabdammina sp 83
Rhipidomella sp .. 32
Rhombopm‘a, m'tidula .. 33
" ‘ " edsom', 28
Siphondella isoaticha, .. ............ 32
Spirifer rockymontanus . 33

sp .............................. 32
Squumulan‘a transverse . 33
Stromatolites ....... 13
Sun'ngothyn's sp 33
Tenticospin'fer utahemn's . 33
Tetracamem sp . .. 33
Trilobites ............. 28, 30
Trachammina sp 33
Um'spififer sp ..... 32

 
  
   
  
 

Garnet .. 4‘7
Geologic setting ........ 4
Gerome Andesite 60
Glacial deposits . 61
Goddards Peak .. . 6, 24, 36, 40, 42, 62
Gold Hill ................................. 66
Graded bedding ..... 6, 11, 14, 16
Granodiorite ........ ...36, 40, 50, 56
relation to Silver Pomt Quartz

Monzonite ................................ 57

G1 ‘one 24

 

73

 

 

74

  
  
 

 

   

   

 

 
 
 
 
 
  
  
     
    
  

Page

Grouse Creek . 7, 10, 62
Gypsy Creek 26
Gypsy Quartzite .................. 27, 29

H
Hope fault ........... 65
Horseshoe Lake .. 4, 62, 69
Huckleberry Formation .. 2, 24. 66
relation to Starvation Flat Quartz
Monzonite 38
Huckleberry Mountain 16, 40
Huckleberry volcanics 69
Hydrothermal alteration 8
Hypabyssal rocks ................. 58
I, J, K

Ilmenite ....................... 37
Irene Conglomerate 25
Irene Volcanics 25, 66
Iron .................. 25, 61
Iron Mountains . ................ 65

36, 37. 52, 70
7, 58, 64
64
. 42
62, 66. 6‘7, 69, 70
...... 18, 25, 29, 67
11, 12, 27, 45, 60

Jay Gould mine...
Jay Gould Ridge ..
Johnson Mountain
Joints ..................

Jumpofi Joe fault
J umpofi Joe Lake...

 

 

 

Juno Echo mine. ....................... 36

Kaniksu batholith ............................. 33, 51, 55

Klapper, Gilbert, quoted ............................. 32
L

Lane Mountain ...... 71

Latah Formation 61

 
 
  
 
   

Libby Formation 24
Limestone . 31, 32
47

....................... 38

29, 46, 47, 48, 56, 57, 69
12, 15, 16, 70

  

 

 

 

     
    
  

Loon Lake Mountain . .................... 8
relation to Silver Pomt Quartz
Monzonite ............................. 49
Lost Creek ............ 38
M
McDonald Mountain . 8, 42
McHale Slate ........... . 17, 66
relation to Striped Peak Formation... 23
Magnesite belt . 2, 16, 17, 18, 24. 62, 65
Magnetite ...... 7, 37, 43, 47, 49, 50, 51
Maitlen Phyllite . 29
Merriam, C. W., quoted 33
Metaline Formation 29
Metamorphic rocks . ........ 24
Metamorphism 6, 37, 45, 66
Mineral deposits ........ 69
Missoula Group . ............................ 11
relation to Buffalo Hump Formation. 24
Monk Formation ............................................ 26, 66
relation to Starvation Flat Quartz
Monzonite ................................ 38

 

 

 

 

INDEX
Page
Mud-chip breccias ................................... 7, 8, 12
Mud cracks ............. .. 6, 7, 8, 10, 11, 12, 14, 16
N, 0
Nelson Peak ......................... 5, 6, 24, 44

  
 
  
 
 

Nelson Peak anticline.. 68, 64, 65
Newport Group ........... 19, 67
Newport syncline . ............. 63, 64
Old Dominion Limestone. .............. 29,32

  

 

  
 
   
   

  
    

 

 
     
  
 

 

  

 

 
  

Osburn fault .................. 65
P
Palmer, A. R., quoted... 30
Parker Mountain .. 10, 13
Peewee syncline ...... 63
Pegmatite ................ . 41, 43
Pend Oreille Lak . 6, 10, 63
Pend Oreille Valley... 24
Phillips Lake ................ 59
Phillips Lake Granodiorite. 40 55, 57
dikes ..................................... 58
relation to Flowery Trail

Granodiorite ............................ 36

relation to Starvation Flat Quartz
Monzonite ............... 38, 67
Plutonic rocks . 4, .98, $7, 51, 52
Previous work .. .. . 2
Prichard Formation . 3, «6
relation to Togo Formation. 19
Prichard Lake ...... 4
Priest Lake ......... . 63
Priest River Group . 16, 25, 66, 67
Priest River syncline.. 63, 64
Purcell Series .. 4, 66
Pyrite ............... 47

Q. R
Quartz monzonite ........... 39, 47
coarse~grained 45, 56, 57
fine-grained ...... 50, 56
relation to Silver Point Quartz

Monzonite ................................ 57
vite M 56, 57
two-mica ......... . M, 56
Quartzite .............. 2,

4, 6, 7, 8, 19, 23, 24, 26, 27
........ 8. 10, 11, 12, 14,
15, 27, 28, 36, 61, 62, 64, 65

Quartzite Mountain...

 

Rattlesnake Hills
Ravalli Group
Recrystallization .

44
3, 6'

 
 

. 6,
36, 37, 43, 44, 46, 48. 69
7, 49
. 6, 7, 8, 10, 11, 12. 14, 16

Revett Formation
Ripple marks .......

 

 

 

 

 

  

 

S

St. Regis Formation... . 7
relation to Burke Formation. 7

relation to Silver Point Quartz
Monzonite 49
Salt casts .. 12, 16
Sand ....... 69
Sandstone . ............................... 2, 61
“ l" 24
Scour and fill features .................................... 16
Sedimentary rocks 58

 

 

 
 
 
 
  
  
  

Page
Shale ........................ 28
Shearing ................ 42
Shedroof Conglomerate . 25
Sherwood Creek 62
Silica 69, 71

  
   

 

      
 

 

  
 
   
 

Sills .. 6. 8, 24, 36, 41
Siltite .. 4, 6, 7, 8, 12, 13, 16, 18. 19
Siltstone .. 61
Silver ...... 69, 70
Silver Point Quartz Monzonite. . 47, 52, 56, 57
dikes 58, 59
faults 69
relation to dikes... 57
relation to granodiorite 57
relation to quartz monzonite, fine-
grained . 57
Slate .......................... 17. 26
Snow Valley anticline... 63, 64
South Fork of Chewelah Creek .. 6, 62
Sphene ............ 49 50, 51
Spirit pluton .. .. 55
Starvation Flat Quartz
Monzonite .............. .98, 51, 52, 53, 57
relation to Belt Supergroup and
Deer Trail Group .......... 69
relation to Priest Lake Group. 67
Starvation Lake ............................... 39

Stensgar Dolomite ..........

 

 

relation to andesite. 60
relation to Striped Peak
Formation 23
Stratigraphic correlations 67
Striped Peak Formation... 11
relation to Belt Supergroup.. 19
relation to Deer Trail Group.. 69
relation to glacial deposits... 62
relation to Togo Formation. 23
Structure ......................................... 4, 62
T
Tacoma Creek .................................. 40

  
  
 
 
   

Talus deposits

Ten Mile Creek
The Tinderbox .
The m Creek
Thrusts ....................
Toby Conglomerate
Togo Formation

 

 

 

   
 

 

 

relation to Prichard Formation .. 19
relation to Striped Peak Formation... 23
Tourmaline
Tuif ..............
Tn ‘
V, W, Y, Z
Volcanic rocks .. 58
Wallace Formation .................................... 8, 69, 70
relation to glacial deposits .................... 62
relation to Silver Point Quartz
Monzonite ..................... . . 49
relation to Togo Formation. . 19
Wilson Mountain ...... 7, 42
Windermere Group 24
Windermere rocks ............................ 4
Yakima Basalt .................................. 61
Zircon .....

 

'7. 37. 43, 44, 47, 49, 60, 51

Zoning 34

 

 

 

 

 

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x‘ I 590 I It "a" ‘i ‘, ' /
x . . ~ 4 i W
Z ‘: 0 = \L OT _ kn. . ’ C 534gB ,
‘ = ' , == " ‘
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d, I: m.‘ \ -‘. l; 2725 —\ \\\\ g . / ,/ 69.
§ L 2 ~. 2 : o {”5 ‘\ / L ‘\\ “‘2 ‘3, " f/ 3%»
$/ g S rive. = K: i. \\ * II .~ , W
i,“ G 2 .175" u. I 1:. , . . 2:: = ‘1). f4 [I
J, 0...,_|J.q . ’ ~ -L '» ‘
mm > 24\~-.Ed -‘ \K ,I’ , //\ ‘11:? , mm».
is“ ' E in ii $qu ' [A ~ g/\ e
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E «56,, ' ' , .. . _ ' /. ff
48° 5 ‘1 I! , . "I 1,} Is . . W A .4 .. """ \J‘I " 48°19
117145 445 2 760 000 FEEr ~49 450 40' ‘51 ‘52 ‘53 Qag ‘54 ’ ‘55 ‘56 35’ .57 .59 ,60 ,6} «520% r; 117°30'
Base from US. Geologica Survey 91: SCALE 1:62,500 Geology by L. D. Clark and
Chewelah Mountain 1:62,5)0, 1966 1 1/2 0 1 2 3 MILES F.K.Miller,1963-64; F.K.Miller
1000-meter Universal Tranvrrse Mercator E H H H H ,_, assisted by J‘ 0 Moore, 1965
grid ticks g
i 1 5 0 1 2 3 KILOMETERS
; cu: H H H I——-—l l—l
" QUADRANGLE LOCATION
APPROX‘MME WAN CONTOUR INTERVAL 80 FEET
DECLINATION,1974 DOTTED LINES REPRESENT 40-FOOT CONTOURS
DATUM IS MEAN SEA LEVEL
'_ ___________
_, .
e 3
i.)
o E , ________________
E I/ c
.9 W
A , _ "I a a e »»»»» K A’
Glacral deposrts 0 Z O 1 fl P 4800'
4800 omitted in this area '3- L“ ”J ‘ -' """ \~ ,
, E m (I)
3 I
3200' ' h ‘33 PCm “ 3200'
1600’ 1600’
SEA LEVEL SEA LEVEL
1600’ 1600'
3200' 3200'
4800' 4800’
3200' 3200'
1600’ 1600'
SEA LEVEL SEA LEVEL
1500' 1600’
3200' 3200'
4800’ 4800’
117°45' 117°30'
48°30' .
EV: /
4800' C P91“ V C 0'
. . 7 pCh g 480
"E
3200' (3‘; P951) 3200'

     
   

  

Qag Qag p€sc Qag

III

  
  
 
 
 
 

V

 

  
 

    
   

 

 

1600,81 pee 1600' 48°19
. 7 #7
SEA LEVEL 7 ’ SEA LEVEL
Undifferentiated/- / Undifferentiated Belt Plate 2
1600' " Deer Trail, Belt/7. /S and plutonic rocks 1600’
and plutW1 /«

3200' ' ,

Interior-Geological Survey, Reston, Va.—1974 3200 48°00'

GEOLOGIC MAP OF THE NORTH HALF OF THE CHEWELAH-LOON LAKE AREA,
STEVENS AND SPOKANE COUNTIES, WASHINGTON

PROFESSIONAL PAPER 806
PLATE 1

CORRELATION 0F MAP UNITS

Qag > QUATERNARY

 

Unconformity

! > TERTIARYC’) CENOZOIC

Unconformity

\
> Eocene(?) TERTIARY

CRETACEOU S
Lower Jurassic or JURASSIC OR
Upper Triassic TRIASSIC
MISSISSIPPIAN

OR DEVONIAN

 

CAMBRIAN

 

Unconformity

 

Windermere
Group
Unconformity
Deer Trail . d
Group Missoula 8:21;:
Group Formation

 

Belt Supergroup

Ravalli
Group

 

 

 

DESCRIPTION OF MAP UNITS

GLACIAL, ALLUVIAL, AND TALUS DEPOSITS, UNDIFFERENTIATED
Chiefly unconsolidated gravel, sand, and clay
CONGLOMERATE — Well-indurated cobble to boulder conglomerate

MAFIC DIKES — Euhedral phenocrysts of hornblende, biotite, and feldspar in a
fine-grained matrix

 

PHILLIPS LAKE GRANODIORITE (Cretaceous) — Contains muscovite and
biotite, Medium to coarse grained. Double dash overprint indicates presence
of dikes associated with the Phillips Lake Granodiorite; wavy line overprint
indicates where metamorphic roof remnants are numerous in the unit

 

7 "Ks : ,: STARVATION FLAT QUARTZ MONZONITE (Cretaceous) — Contains horn-
blende and biotite, Medium to coarse grained

FLOWERY TRAIL GRANODIORITE (Upper Triassic or Lower Jurassic)
Contains hornblende and biotite. Has high color index

UNIT 3 — Light-tan dolomite and purple and green calcareous slate
UNIT 2 — White dolomite, in part oolitic

UNIT 1 w Dark-gray dolomite. Oolitic and conglomeratic
PALEOZOIC CARBONATE ROCKS, UNDIVIDED

ADDY QUARTZITE (Cambrian) — White to purple vitreous quartzite
WINDERMERE GROUP (Precambrian)
MONK FORMATION — Slate, dolomite, conglomerate, and quartzite
HUCKLEBERRY FORMATION — Slightly metamorphosed basalt and volcanic
elastic rocks. Minor conglomerate
DEER TRAIL GROUP (Precambrian)
STENSGAR DOLOMITE - Pink, tan, or gray dolomite, argillite, and siltite

McHALE SLATE — Black, gray, and green laminated argillite
EDNA DOLOMITE — Impure dolomite, argillite, and quartzite

METAMORPHIC ROCKS, UNDIVIDED — Schist and phyllite. Probably derived
from Belt Supergroup or Deer Trail Group

BELT SUPERGROUP (Precambrian)
MISSOULA GROUP
STRIPED PEAK FORMATION

Member c ~ Gray laminated argillite and siltite
Member b ~ Impure gray and maroon dolomite

WALLACE FORMATION
p€d
A

Upper part; dark laminated argillite
_7__ Contact — Approximately located; queried where doubtful

 

Lower part; carbonate-bearing siltite and quartzite, and argillite
RAVALLI GROUP

ST. REGIS FORMATION — Lavender and maroon argillite, siltite, and quartzite
REVETT FORMATION — White fine-grained quartzite
BURKE FORMATION — Light- to medium-gray siltite

PRICHARD FORMATION—Laminated argillite, siltite, and quartzite. pCd.
metadiabase sills

 

CD

_'__7.... Fault — Dashed where approximately located; dotted where concealed; queried

{a

 

>i

where doubtful. U, upthrown side; D, downthrown side. Arrows indicate
relative direction of lateral movement, or apparent lateral movement. T and A
on cross sections indicate movement toward and away from the observer.
Circled numbers indicate northwest-trending faults discussed in text

#7..” Thrust fault — Dashed where approximately located; dotted where concealed;
queried where uncertain. Sawteeth on upper plate

f —\, \iFL Shear zone

Fold, showing trace of axial plane— Dashed where approximately located;
dotted where concealed

____‘_ ......... Anticline

___._+ Syncline

—fi' .......... Overturned syncline

Strike and dip of beds

_|_ Inclined
~12)— Overturned
T79; Rotated more than 180°
_+_ Vertical
9 Horizontal
Strike and dip of schistosity
l Inclined
._.._ Vertical
+ Horizontal
Strike and dip of parallel beds and schistosity
70 Inclined
x Vertical
Strike and dip of cleavage
L Inclined
l-—-l Vertical
Strike and dip of parallel beds and cleavage — Where bedding is shown over-
turned, cleavage may or may not be overturned
1L Inclined
l—l—l Vertical
'-:)—-' Overturned
Strike and dip of slip cleavage
L Inclined
H—H Vertical
“BI—u Strike and dip of overturned beds and slip cleavage — Cleavage may or may not
be overturned
70.— Bearing and plunge of minor fold axis

. MESOZOIC

& PALEOZOIC

% PRECAMBRIAN

 

 

 

UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY

   

pCs 2 780 000 rear ‘17'37'30" SI 35' 11.41 E. rm: E. 2 510 000 rarer 117'30'

AE‘IS'

 

 

 

 

 

 

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48°00'
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Base from U.S. Geological Survey SCALE 1152.500 Geology by F. K. Miller, 1965-67;
1:24 000 advance sheets; Nelson Peak, , assisted by J. C. Moore, 1965, and
’ . 1 /2 0 1 2 3 MILES
Valley, Springdale, and Deer Lake,1965 g EEELl—i H H ,._—_—e R. L. Reynolds, 1967
lOOO-meter Universal Tranverse Mercator “3‘
grid ad“ 5 1EEEEE§E1::2‘E§ KILOMETE RS
APPROX‘MATE MEAN CONTOUR INTERVAL 40 FEET QUADRANGLE LOCATION
DECLINATlON,1974 DOTTED LINES REPRESENT 20'AND 40- FOOT CONTOUHS
DATUM iS MEAN SEA LEVEL
’R .-“ A/
. A g __
4800 ...... a
,. ,4 _
' b
' m
3200 Q Qag / Qag \
.\' L1\/»\\7/lfiy\/ A,
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1600' ’ . . ‘7 s ' '- . . i ;;\/),\7_\7-QQ\\/\://_\\v L
t \“ R10:/>’<I:.‘ms:‘ol - \:
. . . 1.‘ a“ ‘ . . /\’i<l\'/\j\/ '\ ’ l:
SEA LEVEL . :3 7 . z r 7/ " ’ >|<\§l:‘:\/\l‘/:C‘\ , <,
. .7 “ ',' .1. ‘ « L . l>]\/\‘/)\/i:’\/A\‘:g/l\\<l\l/:\/1L_
X’NLV/ (C’xD/TLUCTr
1600' ’S.‘I\/:/\T/\\//U\/\L\T\'//«\\l/\/—
\/_\/ \ (finl); \Q\ 1, \1‘ _
>\q\},’\: ¥<r\“a:'\":\i (9/ l
3200' <$:(\\/\\\J’\/ (JV/{Vi Q>F\/\ \_.
:.r\ 3159 (mm \ .-,;’,\\
4800 Interior—Geological Survey, Reston, Va.——1974

GEOLOGIC MAP OF THE SOUTH HALF OF THE CHEWELAH-LOON LAKE AREA,
STEVENS AND SPOKANE COUNTIES, WASHINGTON

Deer Trail Group

 

 

 

 

 

 

on

 

4800'

3200'

1600’

SEA LEVEL

1600’

3200'

4800'

CORRELATION 0F MAP UNITS

Qag

Unconformity

-. , a] #77.

 

 

    
 

   
 

Unconformity

Unconformity

ll

Unconformity

Winderm ere
Group

Unconformity

 

 

 

 

 

 

Missoula
Group
Belt Supergroup <
Ravalli
Group

}

RH

Pliocene and
Miocene

Oligocene(?)

Eocene(?)

Eocene

Striped
Peak
Formation

DESCRIPTION OF MAP UNITS

}QU ATERNARY1

TERTIARY

C RETACEOUS

MISSISSIPPIAN

MISSISSIPPIAN

OR DEVONIAN

CAMBRIAN

 

GLACIAL, ALLUVIAL, AND TALUS DEPOSITS, UNDIFFERENTIATED
Chiefly unconsolidated gravel, sand, and clay

fine-grained basalt of Yakima type (‘2)

a fine—grained matrix

Medium to fine grained

to coarse grained

acterizing mineral

acterizing mineral. Very coarse grained

UNIT 2— White dolomite, in part oolitic

to dark-gray

WINDERMERE GROUP (Precambrian)

elastic rocks. Minor conglomerate
DEER TRAIL GROUP (Precambrian)

AN DESITE — Hornblende-biotite-pyroxene-olivine andesite

UNIT 1 - Dark-gray dolomite. Oolitic and conglomeratic

PALEOZOIC CARBONATE ROCKS, UNDIVIDED

BASALT OF COLUMBIA RIVER GROUP (Miocene and Pliocene)—Black

LATAH FORMATION (Miocene) — Clay, silty clay, and sandy clay

MAFIC DIKES — Euhedral phenocrysts of hornblende, biotite, and feldspar in
GRANODIORITE - Contains hornblende and biotite. Equigranular texture
SILVER POINT QUARTZ MONZONITE (Eocene) — Contains hornblende and
biotite. Porphyritic with phenocrysts of orthoclase in bimodal matrix
FINE-GRAINED QUARTZ MONZONITE — Contains hornblende and biotite.
TWO-MICA QUARTZ MONZONITE — Contains muscovite and biotite. Medium
MUSCOVITE QUARTZ MONZONITE — Contains only muscovite as char-

COARSE-GRAINED QUARTZ MONZONITE — Contains only biotite as char—

LIMESTONE — Cherty medium -gray limestone and dolomitic I'mestone

UNIT 3 — Light-tan dolomite and purple and green calcareous slate

METALINE FORMATION (Cambrian) — Limestone and silty limestone, light-

ADDY QUARTZITE (Cambrian) — White to purple vitreous quirtzite

BUFFALO HUMP(?) FORMATION # Gray argillite, siltite, and quartzite

STENSGAR DOLOMITE — Pink, tan, or gray dolomite, argillite, and siltite

Mc HALE SLATE — Black, gray, and green laminated argillite

EDNA DOLOMITE — Impure dolomite, argillite, and quartzite

TOGO(?) FORMATION — Sheared gray and green argillite

DEER TRAIL GROUP, UNDIVIDED

METAMORPHIC ROCKS, UNDIVIDED — Schist and phyllite. Probably derived

from Belt Supergroup or Deer Trail Group

 

 

117°45' 117° 30'
48°30'
Plate 1
48° 15
Plate 2
48°00

 

 

 

L CENOZOIC

 

MESOZOIC

PALEOZOIC

>PRE—‘
CAMBRIAN

 

HUCKLEBERRY FORMATION — Slightly metamorphosed basalt and volcanic

 

 

 

?-—?—
ED ‘T

.A——L?_A.-A..

__t..__,
—_i ........
__g .........

70
._A_

70

tile

70

till

70"—

PROFESSIONAL PAPER 806
PLATE 2

BELT SUPERGROUP (Precambrian)
MISSOULA GROUP
STRIPED PEAK FORMATION

Member d — Maroon argillite, siltite, and quartzite
Member c — Gray laminated argillite and siltite
Member b ~ Impure gray and maroon dolomite

Member a — Gray siltite, argillite, and quartzite

WALLACE FORMATION
Upper part; dark laminated argillite

Lower part; carbonate-bearing siltite and quartzite, and argillite

RAVALLI GROUP
ST. REGIS FORMATION — Lavender and maroon argillite, siltite, and quartzite

REVETT FORMATION — White fine-grained quartzite

BURKE FORMATION — Light- to medium-gray siltite

PRICHARD FORMATION—Laminated argillite, siltite, and quartzite. pCd,
metadiabase sills

Contact # Approximately located, queried where doubtful

Fault — Dashed where approximately located; dotted where concealed; queried
where doubtful, U, upthrown side; D, downthrown side. Arrows indicate
relative direction of lateral movement, or apparent lateral movement. T and A
on cross sections indicate movement toward and away from the observer.
Circled numbers indicate northwest-trending faults discussed in text

Thrust fault — Dashed where approximately located; dotted where concealed;
queried where uncertain. Sawteeth on upper plate

Shear zone

Fold, showing trace of axial plane— Dashed where approximately located;
dotted where concealed
Anticline

Syncline
Overturned syncline
Strike and dip of beds

Inclined

Overturned

Rotated more than 180°
Vertical
Horizontal

Strike and dip of schistosity
Inclined

Vertical
Horizontal

Strike and dip of parallel beds and schistosity
Inclined

Vertical

Strike and dip of cleavage
Inclined

Vertical

Strike and dip of parallel beds and cleavage # Where bedding is shown over-
turned, cleavage may or may not be overturned

Inclined

Vertical

Overturned
Strike and dip of slip cleavage
Inclined

Vertical

Strike and dip of overturned beds and slip cleavage — Cleavage may or may not
be overturned

Bearing and plunge of minor fold axis

 

 

 

 

 

 

mgr :5 A "\5’

Geochemical Anomalies of a Claypit Area,
Callaway County, Missouri, and

Related Metabolic Imbalance '

in Beef Cattle

I

GEOLOGICAL SURVEY PROFESSIONAL PAPER 807

 

DOCUMEN

      

TS DEPARTMENT
AUG 13 1973

      

I I rut-ch-egfifsyu

. Ira-mp... ;

 

 

 

 

 

 

 

 

i

Geochemical Anomalies of a Claypit Area,
Callaway County, Missouri, and

. Related Metabolic Imbalance

in Beef Cattle

By RICHARD J. EBENS, JAMES A. ERDMAN, G. L. FEDER,
ARTHUR A. CASE, and LLOYD A. SELBY

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 807

A study of the concentrations of chemical elements
and compounds in samples of clays, soils, waters,
and plants, and an interference syndrome in

cattle, where mining activities have altered

the natural geochemical environment

 

 

 

   

 

UNITED STATES DEPARTMENT OF THE INTERIOR

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY

V. E. McKelvey, Director

Library of Congress catalog—card No. 73-600086

 

 

S. Government Printing Office

e Superintendent of Documents, U.
c GPO Bookstore

2 ~ Price 65c domestic postpaid or 45
Stock Number 240100337

For sale by th
Washington, DC. 2040

 

CONTENTS

 

  
 
 
  
  

 

 

   
   

 

 

 

 

 

Page Page
Abstract .................................................................................... 1 Methods of sampling and anlysis—Continued
Introduction ............................................................ 1 Analytical methods—Continued
Methods of sampling and analysis .................................... 2 Beef cattle ................................................................. 6
Sampling media and techniques ......... 2 Results and discussion ................................................................ 6
Surficial deposits ............................................... 3 Establishing typical geochemical values for
Efflorescent salts .................................................... 3 sampling media as bases for defining
Plants .................................................... 4 anomalous values .......................................................... 6
Water .......................................... 4 Surficial deposits ......................................................... 7
Beef cattle ............................................................. 4 Efflorescent salts ....................... 8
Analytical methods .............................. 5 Plants ............................................... 9
Surficial deposits ............................ 5 Water ......................................................... 14
Efflorescent salts ......................................... 5 Beef cattle ...................................... 17
Plants ................................ 5 Summary and conclusions .................... .. 20
Water ......................................................................... 6 References cited ....................................................................... 23
ILLUSTRATIONS
Page
FIGURE 1. Map of claypit area showing sample localities ................................................................................................................. 2
2. Aerial photograph of claypit area ................................................................................................... 3
3. Diagram showing movement of elements through the geochemical system .................................................................. 22
TABLES
TABLE 1. Approximate lower limits of detection for surficial deposits and plant materials
2. Compounds and elements in samples of surficial deposits and efllorescent salts f
3. Ash yield and elemental composition of plant samples from the claypit area ..............................................
4. Physical properties and chemical composition of surface water samples from the claypit study area ...................
5. Breeding and calving history of three distinct beef cattle herds on Ranch A for the 1970 and 1971 breeding
and calving seasons ............................................................................................................................................................... 15
6 Selected trace elements In whole blood samples from beef cattle hav1ng interference syndrome and from
those that were unaffected ................................................................................................................................................ 15
7. Concentrations of biochemic constituents in blood serum from beef cattle having interference syndrome
and from those that were unaffected ................................................................................................................................ 16
8. Mean chemical compositions, with central 95-percent range, of media that are comparable to those sampled
in the claypit area ................................................................................................................................................................ 16
9. Concentrations of selected elements and compounds in anomalous amounts in one or more samples of clay
from the claypit area, the average of these elements and compounds in soils in the vicinity of the claypit,
and the average for the Oak-Hickory Forest soil ............................................................................................................ 19
10. Elements and compounds that occur in anomalous concentrations in one or more samples of materials
from the claypit area .......................................................................................................................................................... 21

III

 

 

 

 

 

 

GEOCHEMICAL ANOMALIES OF A CLAYPIT AREA,
CALLAWAY COUNTY , MISSOURI, AND RELATED METABOLIC
IMBALANCE IN BEEF CATTLE

 

By RICHARD J. EBENS, JAMES A. ERDMAN, G. L. FEDER,
ARTHUR A. CASE, and LLOYD A. SELBY

 

ABSTRACT
Geochemical studies of waters, alluvial deposits, and vegeta-

tion revealed that aluminum, beryllium, cobalt, copper, molyb-
denum, and nickel occurred in anomalously high concentrations
in an area adjacent to a claypit in Callaway, County, M0. The
principal sources of these and other elements that were found
in anomalous amounts are believed to be the clay, shale, lime-
stone, coal, and pyrite that were exposed when the clay was

  
  
  
   
  
   
  

the health of beef cattle in nearby pastures.

The purpose of this report is to call the situation to
the attention of environmental scientists who may wish
to compare our findings and interpretations with those
resulting from future studies of situations that may be
similar. Only through continuing studies of this kind
will complete and final interpretation of the health
effects be possible.

and waters of the area. Pyrite, especially, affects the mobility
of some of these elements because, by weathering, it produces
sulfuric acid which increases the solubility of certain compounds.

On the two ranches studied, young beef cattle exposed to

lain by carbonate rocks of Mississippian and Ordovician
age. An oak-hickory forest constitutes the predominant
native vegetation in both areas. An abandoned claypit
several hundred feet wide, about 60 feet deep, and
partly filled with water is located at the “break” in the
topography near the west edge of the area (fig. 2). The
clay, which was mined for use in the ceramic industry,
occurred in a sink that had developed in the underlying
carbonate rock. McQueen ( 1943, p. 47) noted that in
this part of Missouri, fire clay commonly is mined from
deposits in sinks.

A large claypile and a smaller pile immediately north
of it are located on a ridge at the east margin of the pit.
The large pile consists of clay with abundant fragments
of both gray shale and carbonaceous shale, and smaller
amounts of pyritic material, gypsum, and carbonate
roc , whereas the smaller pile consists almost exclu-
sively of clay. Some surface runoff from the claypiles
drains westward into the claypit; the remainder drains
northward, eastward, and southward into Rocky Creek.

I

contributed to this syndrome.

Anomalous concentrations of elements may exist at many
other locations in Missouri and throughout the Midwest where
similar materials are brought to the surface by clay and coal
strip-mine operations (especially if pyrite is present).

INTRODUCTION

Claypits, with associated mounds of clay and debris
distributed about the ground surface, are anomalous
features compared to naturally occurring surficial mate-
rials. If such materials are suspected of contributing
unusual amounts of certain elements to the surround-
ings, the desirability of making detailed studies of their
chemical nature is apparent. One such situation in Cal-
raway County, reported to the Environmental Health
Surveillance Center, University of Missouri, was pos-
sibly contributing to breeding failures and growth sup-
pression in beef cattle that ranged nearby. The clay
deposit and its epidemiological implications were called
to the attention of US. Geological Survey personnel
who currently are engaged in a geochemical survey of

 

 

——’i

2 GEOCHEMICAL ANOMALIES OF A CLAYPIT AREA, MISSOURI

 

92° 02' 30"

MISSOURI

\

N
,K Ranch BB

0 ‘ .
B

O 1000 2000 3000 FEET

FIGURE 1.——Claypit area, Callaway County, Mo., showing locations of numbered sites where samples
vlillfre 1:03:30ng Base from US. Geological Survey, New Bloomfield (1969) and Osage City (1967) ,
0., : , .

Only the cattle that were pastured on land with direct Veterinary Medicine, University of Missouri—Colum-
access to Rocky Branch were reported to have meta- bia, for reviewing the manuscript. Messrs. David P.
bolic disorders. Hutcheson (nutritionist, School of Veterinary Medi-
Ebens (geologist), Erdman (botanist), and Feder cine, University of Missouri—Columbia), Larry Ed-
(hydrologist) of the US. Geological Survey conducted monds (Enviromental Health Surveillance Center, Uni-
the geochemical studies. Case (clinical veterinarian, versity of Missouri—Columbia), and Vincent Raaf
toxicologist) of the School of Veterinary Medicine, (Area Livestock Extension Agent) assisted in gather-
University of Missouri—Columbia, and Selby (epide- ing and interpreting data. We thank Messrs. Robert
miologist, veterinarian) of the Environmental Health Helzer and Byran Hungate (ranchers), and Merrill
Surveillance Center and the School of Veterinary Medi- Townley (veterinarian) for their cooperation in con-
cine, University of Missouri—Columbia, conducted the ducting the field studies.-
studies of metabolic imbalances of the beef cattle. Par-
tial support of these studies by Selby was provided by METHODS OF SAMPLING AND ANALYSIS
US. Public Health Service Grant No. E. s. 00082 to SAMPLING MEDIA AND TECHNIQUES
the Environmental Health Surveillance Center. Samples were collected to determine which elements
We express our appreciation to Messrs. Z. S. Alt- were present and in what concentrations in surficial
schuler, Hansford T. Shacklette, Richard W. White, deposits, vegetation, and water in order to characterize
and Mrs. Josephine G. Boerngen, all with the US. the geochemistry of the claypit area. Studies of meta-
Geological Survey, for their assistance in collecting and bolic imbalances of the beef cattle conducted at the
preparing samples, and in interpreting the data. We are ranches were supplemented by laboratory examinations
also indebted to Terrence M. Curtin of the School of and analyses of selected materials.

 

 

 

4...—

 

METHODS OF SAMPLING 3

 

FIGURE 2.—Aerial View of claypit area, Callaway County, Mo.
This view, looking south, shows the smaller claypile (left
foreground) and the larger claypile (left center) with diver-
sion ditches leading to the water-filled claypit (right center).
Before these ditches were constructed, some runoff from both
claypiles flowed to the left, and entered a branch of Rocky

SURFICIAL DEPOSITS

Surficial deposits, as defined in this study, consist of
clay and rock collected from the claypiles and the clay-
pit, alluvium collected from two forks of Rocky Branch
that drain slopes and small valleys below the claypiles
and claypit, and soils collected from plant-sampling
sites and from upland fields that are not affected by
drainage from the claypiles or pit. A total of 31 samples
of surficial materials from 14 sites was collected. The
locations of the sampling sites are given in figure 1.

Clay, rock, and some soil samples were collected at
depths ranging from a few centimeters to 15 cm by
using a mason’s hammer or a trowel. The eight samples
of loess soils were 1-inch-diameter cores obtained with
a stainless steel punch auger from depths of 2—15 cm.
Samples of both pyritic material and gypsum were
handpicked from the surface of the large claypile. All
samples were placed in waterproof paper containers,
dried in an oven with circulating air at 50°C, and pul-

 

Branch. Overflow from the claypit enters a branch of Rocky
Branch to the right of the wooded area, thence down the
valley to low areas of the livestock pasture shown in the left

background. Dump truck at lower right indicates scale.
Photographed February 1972.

verized in a ceramic mill to approximately minus-100-
mesh particle size.

EFFLORESCENT SALTS

Yellowish-brown efflorescent salts a few millimeters
thick at water seeps covered several tens of square feet
at the southeast side of the large claypile. Two samples
of this material were picked by hand from the ground
surface and placed in waterproof paper containers. It
was not possible to mechanically remove all clay par-
ticles from the efl‘lorescent salts. Therefore, in order to
obtain a better estimate of the elements present in each
component of the samples, the following separation
procedure was used: 43 g (grams) of one of the samples
( N o. 10, table 2) was placed in 1,600 ml (milliliters) of
distilled water at about 35°C for 24 hours. This mate-
rial was then filtered with a ceramic candle that had a
maximum pore radius of 0.6 micron, thus removing 16.5
g of insoluble residue from the 43-g samfle. The insol-
uble residue, sample 12, table 2, was dried at 90°C and

 

———”

4 GEOCI-IEMICAL ANOMALIES OF A CLAYPIT AREA, MISSOURI

pulverized in a ceramic mill to a grain size of minus-100

mesh. The filtrate was evaporated at 25°C and the

resulting evaporative residue, sample 11, table 2, was

air dried and pulverized in a ceramic mill to a grain

size of minus-100 mesh. -
PLANTS

A total of 36 plant samples, divided into four suites,
from 10 sites was collected and analyzed. The sampling
localities are indicated by the numbered sites in figure 1.

Two samples of redcedar trees that grew either in
native soil or in claypile material were collected on
May 7, 1971. One of these samples occurred near the
edge of the claypit west of the smaller claypile (fig. 1,
site 1) . The other sample was collected at site 3 where
some dead oak trees stood in clay deposits that resulted
from erosion and downslope movement from the larger
pile onto the native soil.

A second suite of samples consisted of grasses and
forbs (broad-leafed herbs) that were collected on June
17 in conjunction with water sampling, and their locali-
ties correspond to the water sampling sites shown in
figure 1, as follows: site 2, the south margin of the clay-
pit pond; site 9, streamside about 1,000 feet east-south-
east of the claypile; site 12, margin of a farm pond
northeast and across the valley from the claypile; and
site 18, streamside 0n Ranch B about 1.5 miles down-
stream from the claypit.

Woody native plant species sampled June 30 were
the same species as those sampled in an earlier study
which was made for the purpose of chemically charac-
terizing the vegetation—type areas of Missouri, and for
which we had already estimated typical concentrations
and ranges of selected elements in the plant species.
These samples were collected along the south fork of
Rocky Branch along a traverse downslope from the
claypile.

The final suite of plant samples, composed mostly of
white sweetclover, was collected in late September.
This plant species was believed, on the basis of an
earlier analysis, to concentrate molybdenum; moreover,
these plants showed evidence of having been grazed by
cattle. Certain species of plants associated with white
sweetclover also were found to contain anomalously
high concentrations of molybdenum, and were, there—
fore, included in this suite of samples.

Plant samples were cut with pruning shears, placed
in paper or cardboard containers, and dried in an oven
with circulating air at 50°C. Samples of forbs that were
used for separate analysesof roots and aboveground
parts were pulled from the ground and thoroughly
washed in tapwater before being dried. The 6- to 10-
inch terminal parts of deciduous tree and shrub stems
(branches) without leaves were used for analysis. The
redcedar samples were sim'lar, but included both stems

 

 

 

 

 

and scalelike leaves. Forbs and grasses were sampled
by cutting the plants near the ground, and the samples
included stems, leaves, and, if present, flowers and
seeds. These samples were not washed.

WATER

Water samples were collected from four sites (fig. 1,
sites 2, 9, 12, and 18) on June 17. The samples were not
filtered, in order to determine the trace elements that
were present in the water-sediment mixture that the
cattle might drink. Sites 9 and 18 were chosen because
adversely affected cattle had access to the water at
these sites. Even though cattle did not have direct
access to water in the claypit (site 2), during intense
rainfall the claypit overflowed and drained into streams
that flowed through the pastures. The farm pond at
site 12 was chosen as a control because it received no
drainage from the claypiles or claypit.

Samples were collected in acid-washed polyethylene
bottles by immersing them 1 foot below the surface of
the water. Each bottle was filled and drained twice with
sample water before collecting the final sample. The
trace-element samples were treated with 1.5 ml double
redistilled reagent grade concentrated nitric acid.
Samples for nitrogen-cycle determinations were col-
lected in 500-ml bottles, treated immediately with 30
mg mercuric chloride, and placed in an ice-filled cooler.
The samples in which the various forms of nitrogen
were to be determined were shipped in an ice-filled
cooler by bus to the US. Geological Survey laboratory
in Little Rock, Ark., where they were analyzed imme-
diately in order to minimize the effects of changes in
the nitrogen cycle components on the analyses. Field
determinations of pH, alkalinity, specific conductance,
the temperature were made at each sample site.

On July 16 a raw-water sample was collected for
microscopic determination of the presence and con-
centrations of potentially harmful microorganisms in
the claypit water. One liter of water was filtered
through a 50-mm-diameter 0.45-micron filter. The final
15 ml of unfiltered water and the filter were placed in
a petri dish. Within 2 hours of collection, Robert Lips-
comb, U.S. Geological Survey, St. Louis, Mo., prepared
a wet slide of an aliquot of the water sample which he
examined for the presence of microorganisms.

BEEF CATTLE

On two ranches, designated “Ranch A” and “Ranch
B” in this report, beef cattle were pastured in fields
adjacent to and downstream from the claypile area
(fig. 1). Ranch A is immediately adjacent to this area,
and cattle on this ranch were more intensively studied
than those on Ranch B located farther downstream
from the area. A thorough epidemiological workup of
the cattle on Ranch A was undertaken, and cattle on

 

 

METHODS OF SAMPLING AND ANALYSIS 5

both ranches were examined during numerous visits.

On Ranch A, in 1970, the cattle consisted of two
distinct herds—one composed of 54 Angus cows 7 years
old, the other, 66 Angus cows 4 years old. In 1971 an
additional herd of 24 Charolais cows 4 years old was
brought to the ranch. Both Angus and Charolais bulls
serviced the herds (table 5). Only the herd of 4-year-
old Angus cows showed signs of metabolic imbalance.
On Ranch B, one yearling and four older Charolais bulls
exhibited these signs. The yearling bull was purchased
from a ranch in southwest Missouri in April 1970.

Our first visit to observe the cattle was in May 1971.
Frequent visits to the ranches were made throughout
the summer and autumn of 1971 to examine the cattle,
to collect specimens, and to discuss the problem with
the ranchers, the local veterinarian, and the Area Live-
stock Extension Agent. Blood samples of the affected
and unaffected cattle were analyzed for selected trace
elements, blood serum enzymes, and macrominerals,
and the pH of rumen samples was determined. Cattle
were isolated from the claypit area and flood plain, and
rations were recommended to correct the interference
syndrome.

ANALYTICAL METHODS
SURFICIAL' DEPOSITS

Concentrations of elements in surficial deposits were
determined by analysis of pulverized samples in the
laboratories of the US. Geological Survey in Denver,
C010. and Washington, DC. Magnesium, sodium,
cadmium, lithium, and zinc contents were determined
by atomic absorption methods, arsenic by colorimetric
methods, fluorine by the fluorine selective ion electrode
method, and mercury by the mercury detector method
described by Vaughn (1967). Organic carbon concen-
trations were determined by making separate analyses
for total carbon and carbonate carbon and computing
the difference, according to the method described by
Tourtelot, Huffman, and Rader (1964). Silicon, alumi-
num, ferrous iron, calcium, potassium, phosphorus, and
selenium contents were determined by X-ray fluores-
cence methods.

Concentrations of the other elements were deter-
mined by semiquantitative spectrographic analysis.
The spectrographic method used is virtually that
described by Myers, Havens, and Dunton (1961), but
the analytical results are given in six, rather than three,
steps per order of magnitude. These results were
reported in geometric brackets having the boundaries
1.2, 0.83, 0.56, 0.38, 0.26, 0.18, 0.12, and so forth, per-
cent or parts per million (ppm); the brackets are iden-
tified by their respective geometric midpoints, such as
1.0, 0.7, 0.5, 0.3, 0.2, and 0.15. Thus, a reported value of
0.3 ppm, for example, identifies the bracket from 0.26
to 0.38 as the analyst’s best estimate of the concentra-

 

 

tion. The precision of a reported value is approximately
plus or minus one bracket at the 68-percent level of
confidence, and plus or minus two brackets at the 95-
percent level.

The approximate lower limits of analytical detection
for surficial deposits are given in table 1. Some combi-
nations of elements in a sample, however, affect these
limits. Concentrations somewhat lower than these
values may be detected in unusually favorable mate-
rials, whereas these limits may not be attained in unfav-
orable materials.

Surficial materials, except soils, were analyzed by
X-ray diffraction to determine their mineral content.

EFFLORESCENT SALTS

Efflorescent salts were analyzed for element concen-
trations by the same methods that were used for
samples of surficial deposits and, in addition, were
examined by X-ray diffraction to determine which min-
erals were present.

PLANTS

The plant samples were oven dried, then pulverized
in a Wiley mill. Wet digestion methods were used to
prepare the samples for determining the arsenic, mer-
cury, and selenium concentrations. For determining the
concentrations of other elements in the samples, the
pulverized plants were transferred to ceramic crucibles,

TABLE 1.—Approximate lower limits of detection for surficial
deposits and plant materials

[Analyses made by semiquantitative spectrographic method, except as indi-
cated. Dry surficial material was used for analyses of all elements. Dry plant
material was used for arsenic, mercury, and selenium analysesmlsnt ash was
used for analyses of all other elements. Limits are given in parts per million
............. no data available]

 

 

Lower limit of Lower limit of
detection (ppm) detection (ppm)
Element Element
Surficial Plant Surficial Plant
deposits materials deposits materials
A] ........................ 110,000 25 24
2300 50
1 2
3 '4
2100 2100
10 ..........
70 ..........
5 2
1300 '40
10 20
100 ..........
1.1 3.5
5 5
110,000 ..........
............... 20
5 10
100 ..........
2 5
‘7 5
10 20
1 2
10 ’25
10 20

 

 

 

1 Analysis by X-ray fluorescence method.

2 Analysis by atomic absorption method.

3 Analysis by colorimetric method.

4 Analysis by method of Tourtelot, Huffman, and Rader (1964) .
5 Analysis by fluorine selective ion electrode method.

3 Fe, total.

" Analysis by mercury detector method.

6 GEOCHEMICAL ANOMALIES OF A CLAYPIT AREA, MISSOURI

weighed, and burned to ash in an electric mufl‘le furnace
in which the heat was increased 50°C per hour to a
temperature of 550°C and held at this temperature
for about 14 hours. The ash was then weighed to deter-
mine the ash yield of the dry plant sample. Colorimetric
methods were used to analyze the ash for phosphorus
and molybdenum (Reichen and Ward, 1951), and the
atomic absorption method was used for cadmium, cal-
cium, cobalt, lithium, potassium, sodium, and zinc
determinations.

Concentrations of the remaining elements in ash
were determined by the same semiquantitative spectro-
graphic method described under “Surficial Deposits,”
except that the ash was diluted with an equal weight
of matrix composed of sodium silica (10 percent Na).

The lower limits of detection of the analytical
methods that were used for plant analyses are given in
table 1. Several samples did not contain enough mate-
rial for these lower limits to be attained; therefore, the
detection limits were higher for elements in these
samples.

WATER

Because of the possibility of changes occurring
rapidly in certain chemical properties of water after
sampling, determinations of pH, alkalinity, specific con-
ductance, and temperature were made at the sample
sites. Procedures for making these determinations were
given by Brown, Skougstad, and Fishman (1970).

All laboratory determinations, except those of nitro-
gen cycle components, were made in the US. Geological
Survey laboratories in Denver, Colo., under the super-
vision of Marvin W. Skougstad, The nitrogen cycle
determinations were made in the Survey laboratories
in Little Rock, Ark., under the supervision of Charles
T. Bryant.

Cadmium, chromium, cobalt, lead, zinc, mercury,
arsenic, and nitrogen cycle components were deter-
mined by methods given by Brown, Skougstad, and
Fishman (1970). All other determinations were made
by spectrographic methods described by Barnett and
Mallory (1971).

BEEF CATTLE

Whole blood samples from the beef cattle studied
were analyzed for trace-element content by the
Environmental Trace Substances Center, Research
Reactor Facility, Columbia, Mo., under the supervision
of Dr. James 0. Pierce. Whole blood samples were col-
lected by venipuncture in tubes containing 6 mg EDTA
(ethylenediamine tetraacetate) per 5 ml of blood, and
were wet ashed with a 5: 1 ratio of nitric and perchloric
acid. The residue was then dissolved in 1-percent nitric
acid and the sample analyzed by atomic absorption
spectrophotometry, using recommended methods ( Ker-
ber, 1971).

 

Blood serum analyses, using the methods of Tumble-
son(1969), were performed by Dr. David P. Hutche-
son, School of Veterinary Medicine, University of
Missouri at Columbia, for the determination of the
biochemic constituents cholesterol, total bilirubin,
glutamic-oxaloacetic transaminase, alkaline phospha-
tase, lactic dehydrogenase, total protein, creatinine,
blood urea nitrogen, calcium, inorganic phosphorus,
sodium, potassium, and chloride. The pH of rumen
samples was determined by Selby and evaluated by
Dr. Hutcheson.

RESULTS AND DISCUSSION
The results of laboratory analyses of surficial mate-
rials, efliorescent salts, plants, and water samples are
given in tables 2—4. The data and observations pertain-
ing to beef cattle are given in tables 5—7.

ESTABLISHING TYPICAL GEOCHEMICAL VALUES FOR
SAMPLING MEDIA AS BASES FOR DEFINING
ANOMALOUS VALUES

The substances that occur in anomalous concentra-
tions in various surficial materials must be identified
by evaluating the deviations of their concentrations
from typical concentrations in comparable materials
from other areas. Anomalous values can only be defined
as deviations from values that are considered typical
for the materials under consideration. Therefore, typi-
cal values must first be established for each category of
material; then a judgment must be made as to the
degree of deviation from the typical value that is
required to classify other values as “anomalous.” Devi-
ations above the typical values may, for convenience,
be designated “positive anomalies,” and those below,
“negative anomalies.”

The selection of criteria that are to be used in
distinguishing anomalous from normal concentrations
is a matter of judgment that must be made according
to the requirements of the study. We have chosen to
define normal concentrations as those that are within
the central 95-percent range of concentrations found
in comparable materials thought not to have been
affected by pollution; anomalous concentrations are
those that occur outside this range.

The geometric mean is a measure of central tendency
of the frequency distribution and, as such, is an esti-
mate of the typical or most common concentration for
the element or compound. Approximately 95 percent
of the values occur in the range whose limits are the
geometric mean divided by the square of the geometric
deviation and the geometric mean multiplied by the
square of the geometric deviation. The central 95-
percent ranges of the distributions of each element and
compound were computed on this basis (table 8), and
these ranges were used to define anomalous concentra-

 

 

RESULTS AND DISCUSSION 7

tions of the chemical constituents in samples from the
claypit area as given in table 10. If the concentration
of an element or compound was beyond the normal 95-
percent range in one or more samples of a given
material (table 10), this element or compound was
considered anomalous in that material. For example,
the geometric mean alumina content of B-horizon soils
from the Oak-Hickory Forest vegetation type area in
Missouri is 5.1 percent and the geometric deviation is
1.47 (table 8). Probably 95 percent of the samples have
alumina contents in the range 5.1 —:— (1.47)2 (2.4 per-
cent) to 5.1>< (1.47)2 (11 percent). These two limits
define the range against which the alumina analyses of
the clay samples from the claypit area were compared;
in this example, alumina concentrations in all five of
the clay samples were judged to be beyond the normal
95-percent range and are, therefore, anomalous with
respect to the B-horizon soils.

Typical values that were used to identify anomalous
values in sampling media from the claypit area are
given in table 8. This table gives geometric means and
geometric deviations for the concentrations of elements
and compounds in different categories of surficial
deposits and vegetation; they are believed to be the
best available data on typical concentrations of ele-
ments in the respective materials. The data in table 8
were developed from sampling programs that were
entirely unrelated to the claypit study. (See Shack-
lette, Erdman, and Keith, 1971.) The means and devi-
ations in this table are antilogs of the arithmetic means
and standard deviations, respectively, of the logarithms
of the analytical values. Where some of the element
concentrations were determined to be less than the
sensitivity of the analytical method (table 1) , the mean
and standard deviations of the logarithms were esti-
mated by means of a censored-distribution technique
devised by Cohen (1959) .

No reliable data were available for use as norms for
identifying anomalous concentrations of elements and
compounds in water.

SURFICIAL DEPOSITS

The concentrations of selected elements in 31
samples of surficial deposits collected from the claypit
area are given in table 2. Sample site numbers, dates
samples were collected, and a brief description of the
samples are included. The mineralogy, as determined
by X-ray diffraction analyses, is shown for all the
samples except those of soil.

In order to ascertain the possible effect that the
mined clay could have on the local environment, the
elemental composition of the clay was compared with
that of soils of the area, because both of these materials
influence the water in Rocky Branch and the supply of

 

elements available to plants. The elemental composi-
tions of clays from the claypiles and claypit differ
markedly from those of soils in the problem area and
from most B-horizon soils from the Oak-Hickory For-
est, the vegetation type which occurs throughout much
of southern Missouri and in which the claypit area is
located (table 9). The elements listed in table 9 are
those that were found to occur in anomalous concentra-
tions in one or more samples of clay. The four samples
of soil (Nos. 32—35, table 2) from the white sweetclover
sampling localities were composed mostly of clay on the
large claypile or of clay washed from the claypile, and
their elemental composition is similar to that of the
samples designated as clay.

Except for nickel in sample 21 (table 2), the concen-
trations of trace elements in a sample of dolomite ( N o.
19) and in two samples of carbonate residuum (Nos.
20 and 21, table 2) collected from the walls of the clay-
pit are not anomalously high with respect to the soils.
A sample of shaly coal (No. 4, table 2) collected from
the large claypile contained concentrations of beryl-
lium, lead, lithium, mercury, molybdenum, scandium,
vanadium, ytterbium, and zinc that are anomalously
high with respect to the soils, although apparently nor-
mal for this type of coal.

The elemental compositions of four samples of allu-
vium (Nos. 13, 14, 16, and 17, table 2) collected from
the beds of creeks that drain away from the claypiles
are similar to those of samples of clay from the clay-
piles. The clay-size fraction and the coarse-grained
fraction of the alluvium do not differ significantly in
trace-element composition. The amounts of clay and
shale particles which are derived from the claypiles and
carried by creeks, and the maximum distance that the
particles are carried, are not known. However, clay
similar to that found in the claypiles has coated rocks
in Rocky Branch and occurred as deposits (as much as
10 cm thick at sample site 5) in ephemeral pools in the
creekbed as far downstream as Ranch B, the farthest
downstream point in the study area. Clay and shale
particles similar to those found in the claypiles were
observed on parts of the flood plain several hundred feet
downstream from sample site 6 (fig. 1), the farthest
point downstream that the flood plain was inspected.

Gypsum (CaSOyHgO) was found to be widespread
on the surface of the large claypile and probably was
produced by the action of sulfuric acid solution on cal-
cium-bearing minerals in the claypile. Sample 8 (table
2), which is composed of gypsum, clay, quartz, apatite,
and crandallite(?), had anomalously high concentra-
tions of dysprosium, gadolinium, phosphorus, praseo-
dymium, samarium, and yttrium compared to those
found in the clays and the other gypsum sample that
were analyzed. In this sample these elements probably

8 GEOCHEMICAL ANOMALIES OF A CLAYPIT AREA, MISSOURI

occurred in the clay or in the phosphate minerals apa-
tite and crandallite. Barium, chromium, selenium, and
strontium were the only trace elements detectable in
gypsum sample 7 (table 2) although the concentra-
tions were low; other trace elements, if present, were
in concentrations below the detection limits given in
table 1.

Pyritic material was widely disseminated throughout
the large claypile; the presence of pyrite was verified
by X-ray diffraction of samples 5 and 6 (table 2).
Sample 5 was contaminated with clay, gypsum, and
calcite; hence, the chemical data for this sample reflect
the chemical composition of these materials. The con-
centration of cobalt was high in this sample compared
to that found in the clays. Sample 6, which was only
slightly contaminated with clay particles, contained no
abnormally high concentrations of trace elements com-
pared to the composition of normal soils from the area.

 

The presence of pyrite is important in geochemical sys-
tems, however, because the weathering of this material
results in the formation of sulfuric acid, which increases
the solubility of certain compounds. The mobilities of
constituent elements in these compounds, therefore, are
generally increased.
EFFLORESCENT SALTS

Chemical properties of the efflorescent salts are given
in table 2. X-ray diffraction analyses of sample 11
(table 2), which consisted of residue obtained by evapo-
rating the soluble fraction of the efllorescent salts, and
of sample 10 (table 2) indicate that alunogen, a
hydrous sulfate of aluminum having the formula
A12(SO4)3-nH20, is the dominant crystalline phase of
these salts. Palache, Berman, and Frondel (1951, p.
538—539) reported that alunogen occurs principally as
an efllorescence or crevice filling in coals, shales, and
slates that contain pyrite, and that the mineral is

TABLE 2.—Compounds and elements in samples of surficial

[Analystsz Leon A. Bradley, G. T. Burrow. Carroll Burton, J. P. Cahill, W. H. Ficklin, Larry D. Forshey, I. C. Frost, Johnnie Gardner, Roose-

velt Moore, M. W. S]
These elements.

ot, J. A. Thomas, R. L. Turner, and J. S. Wahlherg. Some elements were looked for in all samples but were not found.
analyzed by the semiquantitative spectrographic method. and their lower detection limits, in parts per million, are as fol-
lows: Antimony, 150; bismuth, 10: europium, 100: germanium. 10: gold. 20; hafnium, 100; indium, 10; palladium, 1:

platinum, 30; rhenium,

30; silver, 0.5; tantalum. 200; tellurium, 2,000; thallium, 50: thorium, 200; tin, 10; tungsten 100; and uranium, 500. If lanthanum or cerium

 

Site Date

Compound or element

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
 

 

  

 

 

 

Sample Labora- Material Total Fe
NO- 3.10. (3,13, 521%??? sampled Remark“ SiOz A1203 as Fean MgO
(percent) (percent) (percent) (percent)
Large claypile
1 D149910 1 Kaolinite; lesser amounts of illite and
mixed—layer clay .......................................................... i 48 30 2.2 0.8
2 D150439 1 d 45 29 2 .64
8 D150448 1 44 31 1.4 .6
4 D149912 1 . 13 8 16 .08
5 D149913 1 Contains clay, gypsum, and calcite. 8 4 35 .28
6 D150447 1 Slight clay contamination .................. 1 1 65 1
7 D150433 1 3 5 <.1 01
8 D150450 1 About 50 percent clay; contains quartz,
apatite, and crandallite ('I) ...................................... 35 24 2.2 .41
9 D150434 1 1—5 mm temporary salt crust (mostly alunogen)
on clay at seeps, base of large claypile
(south end); contains clay 23 20 6.5 1.04
10 D150435 1 ........ do 18 17 6.1 1.11
11 D150436 1 Evaporative residue (1.17 g residue per 100 ml of
. solution), obtained from sample 10 ........ .2 ........ .03
12 D150437 1 Insoluble residue obtained from sample 10 .. 43 24 7.3 .56
13 D154026 5 Clay, upper 3—10 cm of streambed deposit... 52 28 3.9 .97
14 D154027 5 Sand, silt, and clay collected in creekbed
immediately below sample 13 ...................................... 52 27 2.6 .71
Small claypile
15 D149911 1 Kaolinite: lesser amounts of illite and
mixed-layer clay .......................................... 46 34 1.5 0.55
16 D154024 10 Clay', upper 3—10 cm of streambed deposit 49 84 1.3 .56
17 D154025 10 Sand. silt, and clay collected in creekbed
immediately below sample 16 ...................................... 51 31 1.7 .54
Clayplt
18 D150445 2 June 30 Clay .............................. Kaolinite: lesser amounts of illite and
mixed-layer clay 41 33 1 0.42
19 D150446 2 ...... do ...... Silty dolomite .............. Collected from drainage dit
southeast part of claypi .. 5 1 2 16
20 D150442 2 ...... do ...... Carbonate residuum Collected from north wall 0 79 8 2.8 .45
21 D150449 2 ...... do ............ do ......................... d0 71 11 5.7 .64
Soils from Vicmlty of claypit
22 D149914 8 75 9 2.8 0.52
23 D149915 7 75 9 2.5 .48
24 D149916 11 70 11 4.7 .86
25 D149917 13 70 11 4.4 .78
26 D149918 14 82 7 2 .36
27 D149919 15 75 8 3.8 .47
28 D149920 16 77 8 3 .48
29 D149921 17 ' 82 7 1.7 29
30 D150440 6 Associated with white oak and buckbrush
sampling localities ....................................................... 77 8 2.9 .38
31 D150441 ........ .0 . 78 7 2.1 .33
32 D154028 1 Associated with white sweetclover
sampling localities ........ 47 32 1.4 .56
33 D154029 1 59 25 2.8 .89
34 D154030 2 50 30 1.7 .53
35 D154031 4 54 29 2.6 .90

 

 

 

————i

RESULTS AND DISCUSSION 9

formed by the action of sulfate solutions resulting from present, were in concentrations below the detection
the oxidation of the pyrite on aluminous minerals. limits given in table 1. The complete distance that
Analysis of the efl'lorescent salts served to identify these elements are moved in solution or in suspended
some of the elements that move in solution in the imme- solids by runoff from the claypile is not known. How-
diate vicinity of the claypile. Samples 9 and 10 (table ever, the crust of efflorescent salts that was sampled on
2) reflect, in part, the chemical composition of the clay June 30 was not observed during a visit to the claypit
from the large claypile because it was not possible to area on September 28. A 3-inch rainfall on September
remove all clay particles from the salts. The chemical 22 is thought to have washed the efflorescent salts from
. composition of the residue sample (No. 11) derived this area, and conditions conducive to the formation of
from the evaporated soluble material in sample 10 new crusts of salts were not in evidence.
reveals soluble elements in the efflorescent salts, plus
those that were released from the clay by the acid PLANTS
solution. Chemical analyses of the 36 plant samples from the
Aluminum, cobalt, copper, and nickel have the high- claypit area are given in table 3. Where several samples
est concentrations in sample 11, and barium, beryllium, of a species were collected and analyzed, the samples
chromium, gallium, lithium, manganese, scandium, that are considered to be more directly affected by the
ytterbium, yttrium, and zinc are present in lower con- chemical composition of the claypile generally are
centrations. Other trace elements analyzed for, if listed first in the table in order to facilitate examina-

 

deposrts and efi‘lorescent salts from the claypit area

were found in a sample, praseodymmm with a lower detection limit of 1 ppm was looked for in the same sample but was not found. If yttrium
concentration in a sample exceeded 50 ppm, the following elements, with their stated lower detection limits, were looked for in the same
sample, but were not found: Erbium, 50: holmium, 20; lutetium, 30: terbium 300; and thulium. 20. Asterisk, analysis by a semiquantitative
spectrographic method. Results are reported as geometric midpoints of geometric classes, in the series 1, 1.5, 2, 3, 5, 7, 10, 15, and so forth.
______________ , no data available]

Compound or element

 

 

 

 

 

 

  

 

 

 

 

 

 

 

Carbon-
CaO NazO K20 P205 Total C ate C Organic C As B" “ Be“ Cd Ce“ Co“I 01-"
(percent) (percent) (percent) (percent) (percent) (percent) (percent) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm)
Large claypile
0.3 0.13 3.6 0.5 0.6 0.06 0.5 ........ 70 500 3 <1 300 7 300
.1 .14 2.9 .3 .88 .01 .9 8 6 50 200 3 <1 150 3 150
.3 .09 2.9 .3 .6 .01 .6 6 4 50 150 2 <1 150 3 300
, < 1 .02 .4 .1 37.8 .06 37.7 ........ <20 30 3 .5 <150 3 70
16 .02 .5 .1 3.3 3 3 <.1 ........ <20 30 1.5 .5 <150 30 30
.4 .01 <.1 .3 7.24 7.2 .3 <20 30 <1 <1 <150 <3 7
32 <.01 <.1 <.05 .......................... <1 <20 10 <1 <1 <150 <3 2
5.9 .13 2.1 5.9 51 < 01 5 6.8 50 500 3 <1 300 <3 150
6 .04 1 3 6.7 20 70 5 <1 <150 50 70
6 .03 .9 2 13.4 20 100 7 <1 <150 70 50
........ .0001 <20 1.5 15 <1 <150 200 15
.2 .09 2.1 .5 12.9 50 300 3 <1 150 15 150
.2 .16 4.3 .2 8.0 70 300 3 <1 300 10 200
.5 .11 2.7 .3 .13 .9 9.1 70 300 3 <1 300 15 200
Small claypile
<0.1 0.36 2.5 0.2 0.71 0.09 0.6 200 2 <1 300 5 300
.2 .10 2.9 .2 .44 .01 .4 200 3 <1 300 7 300
2 14 2 7 2 2.99 <.01 3 0 200 3 <1 300 15 200
0.2 0.08 1.3 0.1 0.32 <0.01 0.3 30 2 <1 <150 15 200
29 .02 .3 <.05 11.8 11.3 .5 30 <1 <1 <150 5 7
4 .63 1.4 .05 .83 <.01 .8 500 <1 <1 <150 7 30
6 .75 1.6 1 37 <.01 4 700 1 5 <1 <150 7 70
Soils from v c
0.4 1.05 2 0.1 1.91 0.1 1.8 1.000 <1 <1 150 15 70
.5 1.08 1.8 .2 2.6 .11 2.5 70 1.5 <1 150 15 70
.5 .94 1.9 .2 1.88 .11 1.8 700 <1 150 15 70
.4 1.03 1.8 .2 1.25 .07 1.4 700 1 <1 150 15 70
.2 .94 2.1 .1 1.17 .08 1.1 700 <1 <1 150 16 70
.6 1.06 1.6 .2 1.82 .06 1.8 700 <1 <1 150 15 70
.5 1.01 1.8 .1 1.32 .12 1.2 700 <1 150 15 70
.2 .88 1.8 .1 2.05 .08 2 700 <1 <1 150 70
.5 .81 1.7 .1 1.48 .01 1.5 7.9 30 500 <1 <1 <150 15 50
.3 9 1.9 .3 1 16 <.01 1.2 5.5 30 700 <1 <1 <150 10 50
.3 .09 2.9 .3 .33 <.01 .3 1.2 70 300 3 <1 300 7 300
.4 .06 4.7 .07 3.41 .02 3.4 1.4 70 300 <1 150 7 300
.3 .08 2 .2 .46 <.01 .5 6.9 70 200 3 <1 700 30 200
.8 .11 4 .3 .53 .06 .5 2.7 70 300 3 <1 300 10 200

 

 

h

 

 

 

 

 

 

 

 

    

 

 

 

 

 

 

 

 

 

 

 

 

 
 
 

 

 

 

 

 

 

      

 

 

 

 

 

 

 

 

10 GEOCHEMICAL AN OMALIES OF A CLAYPIT AREA. MISSOURI
TABLE 2.—Compounds and elements in samples of surficial
Compound or ‘ t
Sample Laboratory Cu2 Dy2 F Ga" Gd‘ Hg La‘l Li Mn‘l M0‘
No. No. (ppm) (ppm) (percent) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm)
Large claypile
1 D149910..... ........ 50 0.08 150 153 30 < 3
2 D150439 .03 30 .17 70 242 20 3
3 D15o448 .11 50 .12 100 258 7 15
4 D149912 ........ 7 1.3 so 78 3 7
5 D149913 ........ <5 .75 30 22 60 <3
6 D150447 <.001 15 .48 <80 10 5 3
'7 D150433 <.001 <5 ........ .15 <30 <5 <1 <3
8 D150450 .084 50 50 <.01 150 195 3 <3
9 D150434 .11 20 <50 .34 30 180 30 <3
10 D150435 .17 20 <50 .27 30 156 50 <3
11 D150436 ........ 50 <50 ........ <30 1.6 100 <3
12 D150437 .096 50 <50 .25 100 210 15 5
13 D15402 .. .12 70 <50 .06 150 150 100 3
14 D154027.. .1 70 <50 .06 150 242 700 3
Small claypile
15 D149911 30 <50 ........ 50 <50 0.11 150 320 7 7
16 D154024... 50 ........ .098 70 ........ .03 70 284 30 3
17 D154025 50 ........ .084 70 ........ .02 70 280 300 3
Claypit
18 D150445... 150 0.084 50 0.06 70 338 50 7
19 10 .034 <5 <01 <30 <5 150 <3
20 10 .022 10 .. . .07 3o 22 500 <3
21 20 .052 20 ........ .04 30 27 150 <3
Soils from vicinity of claypit
22 D149914 15 15 0.04 50 24 1,000 <3
23 D149915 15 15 .07 70 24 1,500 <3
24 D149916 20 20 .06 70 25 500 <3
25 D149917 20 20 .05 50 24 700 <3
26 D149918 7 10 .04 50 21 500 <3
27 D149919 10 15 .05 70 20 1.000 <3
28 D149920 10 15 .06 60 23 1,500 <3
29 D149921 7 15 .07 30 20 200 <3
30 D150440 10 10 .09 50 22 1,500 <3
31 D160441 15 10 . .08 70 22 1.000 <3
32 D154028 100 70 <50 .02 150 246 15 3
33 D164029.. 70 70 .02 7o 41 20 3
34 D154030.. 50 50 .05 300 148 70 7
35 D154031.. 30 50 .02 150 144 70 3

    

 

 

 

 

tion of the table for anomalous element concentrations
in plants.

Plant species have inherent abilities to concentrate
certain elements in their tissues. This ability varies
among different species in such a manner that normal
levels of certain elements in one species may be highly
anomalous in another. Superimposed on this inherent
ability of species is their tendency to increase their
absorption of some of the elements that are unusually
abundant in the soil on which they grow. Both of these
characteristics of species must be taken into account
when seeking to identify anomalous element concentra-
tions in plant tissues that may be related to anomalous
levels of the same elements in the soil.

Ideally, data on the typical concentrations of ele-
ments in plants that are to be used for identifying
anomalous concentrations should be established for
each species, on the basis of analyses of plants that
grew in an environment that was typical for the species.
Because of the large number of plant species that may
be of interest in the geochemical study of a suspected
anomalous area, completely satisfactory data of this
sort are not commonly available. Therefore, the best
available data must be used, with the result that the
typical values that are established for each species or
group may range from highly reliable to doubtfully
applicable as bases for identifying anomalies. This var-

 

was found in our
11 the claypit area.

iation in reliability of typical values
study of the plant species that grewi
The data that were used for establishing typical values
(table 8), arranged in order of most reliable to least
reliable, are discussed in the paragraphs that follow.

In earlier biogeochemical studies in Missouri, we
established estimates of typical element concentrations
in three species of woody plants that are widespread in
the State, and that grow in the claypit area. These
species (white oak, buckbrush, and smooth sumac) are
common in the Oak-Hickory Forest, a vegetation type
mapped by Kiichler ( 1964) in which the Callaway
County claypit area is located. Typical ranges of ele-
ment concentrations for the three species are presented
in table 8.

Redcedar is another species which grows in the clay-
pit area and for which we have estimates of typical
element concentrations. These estimates (table 8) are
based on analyses of 10 samples from the Oak-Hickory
Forest area.

In certain species for which we do not have adequate
data, the normal element concentrations can be esti-
mated by using the analyses of closely related species;
this procedure is based on the assumption that the ele-
ment-concentrating ability among species is related to
their degree of taxonomic affinity, which may be gen-
erally, but not invariably, true. For example, data are

 

 

—’r

 

 

 

 

 

 

 

 

 

 

 

 

RESULTS AND DISCUSSION 11
deposrts and efl‘lorescent salts from the claypit area—Continued
Compound or element
Nb“ Nd* Ni' Pb“ Pr" Sc‘ Se Sm* Sr'l Ti* V" Y’I Yb‘ Zn Zr'l
(ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (percent) (ppm) (ppm) (ppm) (ppm) (ppm)
Large claypile
15 150 100 30 30 1 300 50 5 35 150
10 100 50 30 30 .3 300 70 7 31 150
10 100 30 50 30 .5 700 50 5 27 150
<10 <70 20 70 15 .15 500 50 7 132 30
<10 <70 150 15 10 .15 50 70 ........ 17 30
<10 ........ 15 <10 <5 .02 10 15 ........ 12 10
<10 ........ <5 <10 <5 .002 <7 (10 <1 <5 <10
<10 200 30 30 30 .5 200 150 7 20 100
<10 <70 300 15 15 .2 70 70 7 33 70
<10 <70 500 15 15 .15 70 100 7 31 70
<10 < 70 1,500 <10 10 <.0002 <7 150 15 1.7 <10
10 100 100 30 20 .3 200 70 7 48 100
15 150 100 50 30 7 300 70 7 47 150
15 150 100 70 30 5 300 70 7 32 150
15 150 70 50 .......... 5o 1 700 70 7 26 150
20 70 100 30 <100 30 7 500 50 5 30 150
20 100 100 50 <100 30 7 300 50 30 150
10 70 100 20 30 0.5 500 20 3 31 150
<10 ........ 20 <10 <5 .01 15 <10 <1 8 <10
10 <70 7 15 7 .3 5o 30 3 39 300
<10 <70 50 15 10 .2 100 30 3 77 200
10 70 15 15 10 0.3 <100 200 0.3 100 so 3 49 300
10 70 20 20 7 .6 <100 150 .3 7o 30 5 52 300
10 70 15 30 15 .6 <100 200 .5 150 30 3 67 300
10 70 15 30 15 .7 <100 200 .5 150 50 7 56 200
10 70 15 15 7 .2 <100 150 .5 7o 30 3 34 300
10 70 15 30 7 .4 <100 150 .5 70 30 3 44 300
10 7o 15 20 7 .2 <100 150 .5 100 30 3 43 300
10 70 15 15 7 .3 <100 150 .5 70 30 3 39 300
10 <70 15 20 7 .6 <100 150 .3 70 50 5 47 300
10 7o 7 15 7 .5 <100 150 .5 5o 50 5 29 500
20 200 70 7o 30 .7 <100 700 .7 700 70 7 31 150
20 70 70 30 20 .9 <10 500 .7 150 50 5 36 200
20 300 50 30 30 2.8 <100 1,000 .7 300 50 7 24 150
50 150 70 30 30 1.2 <100 1.000 .7 300 50 5 38 150

 

 

not available in our files or in the available literature
on which to establish typical element concentrations
in white sweetclover; however, we do have data on the
element content of 10 samples of yellow sweetclover, a
closely related species, from other parts of the United
States. In the absence of better estimates of the normal
values, these data are given in table 8 for use in evalu-
ating the element content of white sweetclover samples
from the claypit area.

Certain element-concentrating capabilities are char-
acteristic of many species within a plant family, and
somewhat predictable differences in these abilities may
occur among families. We have seven samples of grasses
from the claypit area, but have no highly reliable means
of estimating a corresponding norm for use in identify-
ing anomalous values. If we assume that members of
the Grass Family tend to concentrate elements simi-
larly, analytical data obtained for 18 samples of
meadow feScue from locations throughout Missouri,
as given in table 8, may be used for judging anomalies
in the claypit grass samples.

If corresponding analytical data for certain species
sampled in the claypit area are unavailable, there may
be no reliable basis for judging anomalous element con-
centrations in these species. Nevertheless, we do have
estimates of typical element values, and ranges in
values, for plants in general; these estimates are based

on about 1,100 plant samples, including many different
species, from throughout the conterminous United
States. These samples were collected in a nationwide
study of soils, described by Shacklette, Hamilton,
Boerngen, and Bowles (1971). The values, given in
table 8, may be used for identifying extremely high or
extremely low concentrations of elements in plant
samples from the claypit area if no better means for
such identifications are available.

Anomalies in the elemental compositions of the
plants growing in the claypit area are recognized by
comparing their analyses as given in table 3 to the
typical values (central 95-percent range) listed in table
8. The following discussion of these anomalies is organ-
ized by species or plant type, and the sample numbers
refer to those in table 3.

Five white oak trees were sampled on a traverse
extending from the margin of the larger claypile to the
wall of the claypit and down the drainage system to the
area in which cattle had been pastured. Cadmium was
unusually highly concentrated in all the samples except
No. 3, and sodium was abnormally low in all the
samples (table 3). Elemental compositions of the
samples from the trees most closely associated with the
claypile (Nos. 1 and 2) were the most divergent from
typical values. In general, these-samples had positive
anomalies in concentrations of aluminum, cadmium,

 

h

12

cobalt, copper, potassium, lanthanum, molybdenum,
nickel, ytterbium, and zinc. Negative anomalies were
apparent for barium, calcium, and sodium. Several
anomalies, unique to samples of white oak, were the
low calcium levels in the samples from site 1 near the
claypile, the only lanthanum anomaly (sample 1), and
the abnormally high zinc values in samples 1 and 4, col-
lected from the pasture site. The most extreme positive
anomalies were reflected in the cobalt, copper, molyb-
denum, and nickel concentrations in these samples.
Both samples of redcedar from near the claypiles con-
tained unusually high levels of aluminum, beryllium,
cobalt, and nickel, and unusually low levels of barium
and sodium. Sample 6, collected at site 3 where the
surficial deposits from the larger claypile were thick,

[Analysts: Harriet G. Neiman, Thelma F. Harms, and Clara S. E. Papp. ........

 

GEOCHEMICAL ANOMALIES OF A CLAYPIT AREA, MISSOURI

had additional positive anomalies in chromium, copper,
gallium, scandium, titanium, vanadium, and ytterbium.
The scandium anomaly in this sample is unique; no
other sample collected from the area contained detect-
able amounts of this element.

Of all the plants sampled, only redcedar contained
detectable beryllium. This element was found in
samples of the claypile, and analyses of water samples
and efflorescent salts showed that it was moving from
this source. Beryllium is not commonly detected in
plant samples. Of about 900 samples of various plant
species from throughout Missouri, only eight contained
2 ppm or more beryllium, and of these eight samples,
all were of shagbark hickory (Carya ovata) trees
except one which was of smooth sumac. No beryllium

TABLE 3.—Ash yield and elemental composition

..._, no data available. Ash, As, Hg, and Se reported as percent or ppm in dry

following equation: element (ppm) in dry material = element’ (ppm) in ash X “11 content (percent). Some elements were looked for in all samples but

0
follows: Antimony, 300; bismuth, 20; cerium, 300; europium, 200; germanium, 20; gold, 50; hafnium, 200; indium, 20; niobium, 20; palladium, 2; platinum,
sample, the following elements, With their stated lower detection limits, were looked for in the same sample, but were not found: Neodymium, 150;

geometric classes, in the series 1, 1.5, 2, 3, 5, 7, 10, 15, and so forth]

 

 

 

 

 

 

  
   

 

 

 

 

   

 

   

  

 

 

 

 

   

 

 

 

 

   
 

 

 

 

 

 

 

  

 

 

 

Sample Labora- Site Datled S A511 or element
tory No. samp e pecies Plant part sampled A h Al‘ A B* B 4 1-
No. s s a Be
N°- (fig' 1) (1971) (percent) (percent) (ppm) (ppm) (ppm) (ppm)
Trees
1 D415622 1 June 30 White oak (Quercus alba) ........ Branches, terminal 8—10 in ..... 2 0.7 (0.25 300 500 (2
2 D415623 1 d ....... do . ........ do 3 .7 <.25 200 1.000 <2
3 D415627 3.8 .3 <.25 200 3.000 <2
4 D415625 3.2 .2 <.25 200 3.000 <2
5 D415630 ........ o 3.5 .15 .25 150 2,000 <2
6 D415578 Redcedar
(Junipems virginiana) . 3.7 7 (.25 200 500 3
7 D415579 ........ o .......................................... 4.5 1 5 (.25 200 150 2
8 D415621 Buckbrush (Sympho-ricarpos
orbiculatus) .. 2.4 1.5 (0.25 200 5 000 <2
9 D415626 ........ do ..... 2.3 1.5 (.25 150 2,000 <2
10 D415624 2.2 .7 (.25 100 2,000 <2
11 D415629 2.5 1.5 (.25 150 3,000 <2
12 D415692 1 ........ do 2.2 3 (.25 200 3.000 <2
13 D415620 Stems, terminal 8—10 in 3 .2 (.25 200 7,000 <2
14 D415628 ........ do ........................................ 3.2 .5 (.25 200 3,000 <2
Grasses and sedges
15 D415641 2 June 17 Wood reed grass
(Cimm arundinacea) ............ Above-ground parts ................ 10 0.5 (0.25 50 200 <2
16 D415643 9 ...... do ...... Fowl meadow grass
(Glycerin atriata) ........ do ........................................ 7.4 .5 <.25 50 200 <2
17 D415642 9 ...... do ...... Common bullrush
(Scirpus atro’uirem) .. 7.4 5 <.25 100 300 <2
18 D415648 18 ...... do ...... Meadow fescue
(Festuca elatior) .................. 8.4 7 (.25 70 200 <2
19 D415649 18 ...... do ...... Timothy (Phleum pratense)
and Japanese chess
(Bromus japo'nicus) .............. 16 5 5 100 700 <2
20 D415651 18 _.do ...... Bluegrass (Poo pratensia) and
meadow fescue ........................ 9.7 1 <.25 70 500 <2
21 D415647 18 ...... do ...... Timothy, meadow fescue, and
redtop (Agrostz'a alba) .......... 11 7 <.25 50 1.000 <2
22 D415639 2 June 17 Goldenrod (Solidago sp.) .......... Above-ground parts ................ 11 1 (0.25 150 150 (2
23 D415644 9 ...... do ...... Common plantain
(Plantago major) ........ do 14 5 (.26 150 2.000 (2
24 D415650 18 ...... do .............. do ............... do 13 1 .25 150 700 (2
25 D415646 12 ...... do ......
(Eupatorium mgosum) ........ do ........................................ 18 1.5 (.25 100 1,500 (2
26 D415640 2 ...... do ...... White sweetclover
(Melilotus alba) 2d-yr. green stems and leaves 10 .1 <.25 150 1,000 (2
27 D415684 ........ do 2d-yr. dead stems and seeds.... 2.9 1 .25 300 1,000 (2
28 D415685 ........ do ......................... 2.3 1 (.25 700 300 (2
29 D415686 ........ do 2.1 1.5 (.25 300 500 (2
30 D415687 lat-yr. green stems 7.2 .7 (.25 300 70 (2
31 D415688 ........ do ............. 8 3 .25 300 200 (2
32 D415689 lst-yr. roots ..... 3.8 5 (.5 150 150 (2
33 D415690 1st-yr. green stems and leaves 7.2 3 ........ 300 150 (2
34 D415691
(Lespedeza striata) .............. Above-ground parts ................ 5.2 2 <.25 200 500 (2
Aquatic plants
35 D415638 2 June 17 Cattail (Typha- latifolia) .......... Leaves ........................................ 6.7 1 (0.25 70 70 (2
36 D415645 12 ...... do .............. do ........ do 10 1 <.25 70 3,000 <2

 

 

 

———7

RESULTS AND DISCUSSION 13

was found, however, in any of the 110 samples of red-
cedar collected from throughout Missouri in an earlier
study. If this plant is, in fact, a beryllium accumulator,
high soil concentrations of this element appear neces-
sary for the accumulation to occur.

Buckbrush samples, collected at the white oak
sampling sites, generally contained positively anoma-
lous concentrations of molybdenum and nickel, and
negatively anomalous amounts of sodium. Cadmium
occurred in unusually high concentrations in the two
samples (Nos. 8 and 9) from nearest the larger clay-
pile. Abnormally high concentrations of aluminum, cop-
per, gallium, tin, and vanadium were found in the single
sample that was collected in September (No. 12).
Anomalous concentrations of iron, potassium, manga-

of plant samples from the claypit area

 

nese, lead, and titanium occurred in other samples of
this species.

Smooth sumac, as indicated by the analyses on table
3, is much less sensitive to the element content of the
underlying soils than is white oak, an observation con-
sistent with the conclusions of Shacklette, Sauer, and
Miesch (1970, p. C25). In the two sumac samples, only
cadmium and cobalt occurred in unusually high con-
centrations, and sodium occurred as a negative anom-
aly. Molybdenum was abnormally high in sample 13
collected at the edge of the claypile, and magnesium
was anomalous in sample 14 collected from the wall of
the claypit.

Of the six samples of grasses that were collected in
the claypit area, only sample 19, from Ranch B, con-

material. Other elements reported as ppm or percent in ash; these values in ash can be converted to approximate values in dry material by using the

were not found. These elements, analyzed by the semiquantitative spectrographic method, and their lower detection limits, in parts per million, are as

70; rhenium, 70; silver, 1; tantalum. 500; tellurium, 5,000; thallium, 100; thorium, 500; tungsten. 200; and uranium, 1,000. If lanthanum was found in a

praseodymium, 200; and samarium, 200. Asterisk, analysis by a semiquantitative spectrographic method. Results are reported as geometric midpoints of

 

Ash or element

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ca Cd Co Cr“ Cu" Fe“ Ga‘ Hg K La‘ Li Mg" Mn“ Mo Na Ni‘l
(percent) (ppm) (ppm) (ppm) (ppm) (percent) (ppm) (ppm) (percent) (ppm) (ppm) (percent) (ppm) (ppm) (percent) (ppm)
Trees
22 10 60 7 500 0.3 <5 <0.025 13 70 20 3 30,000 10 0.04 200
26 11 60 3 200 .2 <5 <.025 9.8 <70 16 2 30,000 10 .04 200
30 6.2 4 5 150 .3 <5 <.025 6.4 <70 4 3 20,000 4 .04 70
31 7.4 4 2 150 .15 <5 <.025 7.4 <70 <4 3 10,000 4 .04 30
32 8.4 7 2 100 .1 <5 <.025 8 <70 1.5 20,000 <4 .03 50
22 9 20 50 200 1 7 025 11 <70 40 2 15,000 <5 .07 300
23 5 4 25 20 7o 5 <5 025 9 2 <70 18 3 15,000 <5 .08 300
Shrubs
16 45 6 15 300 0.7 <5 <0.025 17 <70 8 3 20,000 10 0.06 50
15 35 8 20 150 .5 <5 <.025 22 <70 16 2 15,000 10 .06 50
12 10 2 10 150 .2 <5 <.025 25 <70 <4 3 , 10 .06 7
12 28 8 3 100 1 <5 <.025 18 <70 12 5 20,000 <4 .11 50
15 14 5 50 1,000 .7 10 .025 17 <70 22 3 , 20 .22 30
23 5.2 9 5 150 .1 <5 <.025 15 <70 4 2 1,500 10 .03 30
21 4.8 5 5 50 .2 <5 <0.25 17 <70 <4 5 1.500 4 02 20
Grasses and sedges
3.4 0.4 2 7 50 0.15 <5 <0.025 17 <70 220 0.7 1.500 10 0.02 20
3.6 .3 1 7 30 .15 <5 .025 20 <70 4 3 700 10 .03 5
4.6 .9 1 7 50 .1 <5 <.025 24 <70 4 2 1.500 4 .03 7
3.2 .3 3 7 30 .3 <5 .025 26 <70 4 3 1.000 10 .12 7
6 3 7 50 50 2 7 .......... 14 <70 12 5 1,500 10 .09 7
4.4 1.2 2 7 50 .3 <5 .025 26 <70 <4 3 1,000 4 .07 10
2 4 5 1 5 50 3 <5 05 28 <70 14 2 1,000 <4 .12 20
Forbs
8 6 2 14 15 150 0.3 <5 <0.025 26 <70 12 2 2,000 10 0.03 50
15 1 2 3 100 .15 <5 .025 22 <70 <4 5 500 <4 03
........ .9 9 20 50 .5 <5 <70 <4 7 1.500 04 10
4.2 1.2 15 15 100 .5 <5 05 29 <70 <4 1.5 7,000 4 06 15
22 .8 4 2 50 .1 <5 <.025 17 <70 <4 5 300 60 .05 30
16 9.2 28 10 150 .2 <5 <.025 19 <70 22 3 500 10 .17 100
29 3.2 17 15 200 .3 <5 <.025 6 6 <70 6 3 500 60 .18 50
25 3.3 14 30 1,500 .5 <5 <.025 8 4 <70 12 5 500 750 27 7o
16 1.0 s 5 15 300 .15 <5 .025 21 <70 10 3 300 180 13 50
14 .8 8 50 1.000 .5 <5 .025 17 <70 16 3 700 40 19 30
4.3 ...... 15 70 200 .7 10 .......... 27 <70 28 5 500 250 1 8 70
11 ...... 10 50 200 .7 <5 <.05 20 <70 8 5 700 50 26 70
17 ...... <5 30 700 .7 <5 .025 12 <70 16 5 7,000 50 15 150
Aquatic plants
10 0.3 8 3 100 0 1 <5 <0.025 29 <70 4 2 15.000 10 0.88 30
6 8 .4 20 <2 50 <5 .025 30 <70 <4 3 20.000 10 .6 15

 

 

 

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14 GEOCHEMICAL ANOMALIES OF A CLAYPIT AREA. MISSOURI
TABLE 3.—Ash yield and elemental composition of plant samples from the claypit area——Continued
Ash or element
Sample Laboratory P Pb“ Sc' Se Sn“ Sr“ Ti“ V“ Y* Yb"l Zn Zr"
No. No. (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (percent) (ppm (ppm) (ppm) (ppm) (ppm)
Trees
1 D415622 300 <5 <05 <20 1,000 0.03 <5 <20 2 1,060 <20
2 D41562 200 <5 <.5 <20 1,000 .02 <5 <20 2 380 <20
3 D415627... 150 <5 <.5 <20 1,000 .02 <5 <20 <2 360 <20
4 D415625... 150 <5 <.5 <20 2,000 .015 <5 <20 <2 680 <20
5 D415630... 70 <5 <.5 <20 2.000 .01 <5 <20 <2 400 <20
6 D415578... 300 7 <.5 <20 1,000 .20 70 <20 5 440 50
7 D415579 ....... 100 <5 <.5 <20 500 .07 30 <20 <2 440 30
Shrubs
8 D415621... 18,000 500 <5 <0.5 <20 3.000 0.10 20 <20 <2 1,600 70
9 D415626 18,000 200 <5 <.5 <20 1,500 .10 30 <20 2 1,000 50
1o D415624 24,000 30 <5 <.5 <20 2,000 .05 10 <20 <2 1,500 20
11 D415629 24,000 300 <5 <.5 <20 2,000 .20 50 <20 2 2,100 70
12 D415692 24,000 500 <5 70 2 000 10 50 20 <2 1,550 70
13 D415620 18,000 50 <5 <.5 <20 5.000 .02 <5 <20 <2 1.000 <20
14 D415628.... 24,000 50 <5 <.5 <20 3,000 03 <5 <20 <2 680 30
Grasses and sedges
15 D415641.... 6.000 <20 <5 0.5 <20 200 0.02 10 <20 <2 240 50
16 24,000 <20 <5 <.5 <20 200 .02 10 <20 <2 240 <20
17 18,000 <20 <5 <.5 <20 300 .02 10 <20 <2 260 <20
18 18,000 <20 <5 <.5 <20 200 .02 10 <20 <2 160 20
19 12,000 20 <5 .5 <20 200 .20 70 <20 2 260 150
20 24,000 <20 <5 <.5 <20 200 .05 10 <20 <2 470 30
21 24,000 <20 <5 <.5 <20 300 .03 10 <20 <2 340 20
22 12,000 <20 <5 500 0.05 20 <20 <2 380 <20
23 18,000 <20 <5 1.500 .05 <5 <20 <2 360 50
24 24,000 <20 <5 700 05 20 <20 <2 280 50
25 18,000 <20 <5 1,000 07 20 <20 <2 300 70
26 12,000 <20 <5 1,000 007 <5 <20 <2 220 <20
27 18.000 70 <5 1,500 03 <5 <20 <2 270 20
28 12.000 150 <5 1,000 .05 <5 <20 <2 240 20
29 24,000 300 <5 1.500 .05 20 <20 <2 420 20
30 18.000 100 <5 700 015 <5 <20 <2 290 <20
31 24,000 200 <5 700 1 50 <20 <2 410 70
32 48,000 20 <5 1,000 3 100 20 2 520 50
33 18,000 20 <5 700 1 50 20 2 280 50
34 D415691... 45.000 200 <5 500 1 30 20 2 700 50
Aquatic plants
35 D415638 ....... 12.000 <20 <5 <05 <20 700 0.005 <5 <20 <2 220 <20
36 D415645 ....... 24,000 <20 <5 <.5 <20 2,000 .01 <5 <20 <2 220 <20

 

 

tained anomalous concentrations of elements, all of
which were positive. These anomalies were in alumi-
num, boron, cobalt, chromium, iron, gallium, titanium,
and ytterbium. Inasmuch as the mixture of grasses in
this sample did not include meadow fescue (the grass
species used to establish typical values), these un-
usually high concentrations may be due more to species
differences in absorption capability than to contamina-
tion of the soil.

White sweetclover is of special interest because it
is a known molybdenum accumulator, and because
molybdenum was found in anomalous concentrations
(3—15 ppm) in samples of clay, shale, and alluvium
from the claypit area. In parts of the Western United
States where soils contain high levels of molybdenum
(1.5 ppm or more), severe illness has occurred in cattle
that grazed this plant (Barshad, 1948) . In white sweet-
clover sample 26 (table 3), collected in June, 60 ppm
molybdenum was found in the ash (6 ppm in dry mat-
ter), and although this concentration is not considered
anomalous if judged by the central 95-percent range of
values for a closely related species (yellow sweetclover,
table 8), it exceeds the tolerance level of 5 ppm in dry
matter for cattle that was given by Webb and Atkinson
(1965). Molybdenum levels in another sample of white

 

 

sweetclover (No. 29, table 3) from the claypit area,
collected in September, exceeded this tolerance level
by a factor of three. In addition, samples of White
sweetclover contained anomalous concentrations of
aluminum, boron, chromium, cobalt, copper, gallium,
lead, manganese, nickel, tin, and titanium.

Japanese clover (sample 34, table 3) was the only
other forb (broad-leaved forage herb) sampled that
reflected the anomalous copper and nickel levels in sub-
strates of the claypit area. This species, like white
sweetclover, is a palatable forage plant and its element
content, therefore, is important in searching for causes
of the metabolic disorders of cattle at this site.

WATER

Chemical analyses of the four samples of water from
the claypit area are given in table 4. The chemical com-
positions of surface waters, as were sampled at the
claypit study area, are greatly influenced by meteoro-
logical conditions at a location both before and at the
time of sampling. Water samples from this area were
collected June 17, about 1 week after a mild thunder-
storm had occurred. During the previous few months,
however, very little rain had fallen; therefore, the prop-
erties of the samples were more representative of water

 

————i

RESULTS AND DISCUSSION 15

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TABLE 4.—Physical properties and chemical composition of TABLE 6.—-Selected trace elements in whole blood samples from
surface water samples from the claypit study area beef cattle having interference syndrome and from those
I [Analystst P. R. Barnett, 0. J..Feist, Jr., Darwin Golden, R. L. James, E. C. that were unaffected
Mallory, Jr., and R' D' McKIbben. All samples collected June 17' 1971] [Concentrations given as mg/ 100 g. Blood samples were drawn on the ranches
in the forenoon of June 17, 1971, and submitted immediately for analysis]
Origin of sample. Farm pond Claypit Email xfiml inh Rockfy Brhnlgh
Site No. (fig. 1)“. 12 2 cc 3 ranc on line Cattle having interference syndrome Unaggcltfidflgttle
PhYSical properties, at time of collection Labggtory Angus cows, Chg‘rllfilais Angus cows, Chlasnlallais
Appearance .......... Medium Bluish green, Light tan, Slightly Ranch A Rancli B Rana Ranch B
brown» With murky milky turbid 01—821 02-875 03—851 07—038 04—422 C5—456 06411068
muddy cast
Temperature °C.... 33.5 29.0 26.9 28.4
Specific conduct- 165 830 295 800 <0.25 <0.25 <0.25 <0.25 (0.25
ance (umhos/ <.05 <.05 <.05 <.05 <.05
cm at 25°) . .070 .067 .067 .071 .071
pH .......................... 7.50 4.27 7.73 8.22 1 84 2 04 2.04 2.04 2 04
, , . , _ 010 010 .010 010 010
Chemical composrtion (pg/l, except as indicated) .050 .050 .050 .050 .050
110,000 13,000 59,000 630 1‘22 ‘95 '95 2'04 '95
4 <1 <1 <1
250 19 110 14 . . .
1,622 $3 320 mg the only water 1n the creekbed occurred 1n Isolated
< .
<1: <3 <5 :5 pools. Therefore, water from the claypit pond and the
1; 1291 1; <é claypiles was not reaching Ranch B. However, during
83 $33 1,33% 8 033 44% periods of intense rainfall water from the claypit area
' <5 ’ 17 <5 does flow through this ranch, as indicated by the clay
<33 <11 <10 <11 . .
4 933 1 933 1 73(2) 10% coatings on many rocks in the streambed. Rocky
’<8 '<3 ’<2 <3 Branch is springfed at Ranch B, and at the time of
130 470 78 <11 . . . .
23;?) 3 fig <43 sampling was flowmg at an aproxunate rate of 1 cub1c
1 ggg 222 1 233 1go’ foot per second.
, , 7 . . . . .
00 212 133 3 The only bas1s available for Judglng any poss1b1e
0 1 20 . . . . .
gr . ' N 880 <11 120 <11 abnormal1t1es 1n the compos1t10ns of surface waters
Nr§3%1f1)/?§N ...... 31.1; 0.07 1.21 .34 collected from the claypit area is an analysis (table 4)
.......... . .0 0 ~
NH: (Tali/1) as N .7 .02 .01 0 of a sample from the farm pond at s1te 12 (fig. 1). The
N03 (mg/l) .......... 2.3 .3 1.3 .2 ‘
sample collected and analyzed contained a large quan-
tity of suspended silt and clay and, therefore, repre-
as it occurs during dry, rather than wet, periods. During sents stock water about as impure as it occurs under
wet periods the stream waters carry abundant sus- normal conditions. The pond, however, received no
pended material and, consequently, higher concentra- drainage from the claypit or the claypiles adjacent to it.
tions of the elements that occur in the clay. The acid water in the claypit, as is evident from the
The part of Rocky Branch that drains the claypiles data in table 4, contains unusually high concentrations
(fig. 1) was not flowing at the time of sampling, and of several elements, including beryllium, cobalt, copper,

TABLE 5.——Breeding and calving history of three distinct beef cattle herds on Ranch A for the 1970 and 1971 breeding and
calving seasons

[All cows were pasture bred: bulls remained in the pasture from June to September, therefore most cows calved during March and April of the following year.
Numbers in parentheses are percentages. Herd No. 2 ranged on pasture affected by the claypile; herds 1 and 3 were kept on unaffected pastures. The breed
of Herds 1 and 2, designated “Angus” m 1970, was changed to “Angus-Charolais" in 1971 because the sires were changed from Angus to Charolais]

 

 

 

 

 

 

 

 

 

 

 

Herd Sires Dams Cows Calves
No Breed B eed N b Age B eed Age B ed c 1 ed B 1' St‘llb C°mments
. 1‘ um er (yrs) 1' (yrs) 1‘ 8, V OI‘n a 1V8 1 cm
1970
1 Angus Angus 3 7 Angus 7 54 54 (100) 54 (100) 0 (0) Brought to ranch in 1966.
2 ...... do ............ do ...... 1 2 ...... do ...... 4 66 36 (54.5) 31 (86.1) 5 (13.9) Brought to ranch Oct. 1969

already bred; 7—8 cows

 

 

rebred.
1971
1 Angus-Charolais Charolais 1 9 Angus 8 54 54 (100) 54 (100) 0 (0) 01%;; callllf died soon after
irt .

2 ...... do ............ do ...... 1 5 ...... do ...... 5 66 24 (36.5) 23 (95.8) 1 (4.2) Undersized dam of still-
born calf died soon after
calving,

3 Charolais ...... do ...... 1 4 Charolais 4 24 24 (100) 24 (100) 0 (0) Two cows had difficulty

calving, but recovered.
Artificial insemination,
in addition to pasture
breeding, was used.

 

 

t

16 GEOCHEMICAL ANOMALIES OF A CLAYPIT AREA, MISSOURI

TABLE 7,—Concentrations of biochemic constituents in blood serum from

that were unafi‘ect

[Blood samples were drawn on the ranches in the forenoon of June 17, 1971, and submitted immediately for analysis. mg/100 ml=milligrams per 100 milliliters;
mEq/l=milliequivalents per liter; g/100 ml=grams per 100 milliliters]

bsef cattle having interference syndroms and from those
9

 

 

Cattle having interference syndrome Unaffected cattle (controls)

 

 

 

 

 

 

 

 

 
    
  

 

 

  

a o ai l, ' ,
Constituents of serum and reporting units Angus cows, Ranch A Ctharllcli Eu] Angus cows, Ranch A 0113:3113?“
01—821 CZ~875 03—851 07—038 04—422 05—456 06—11068
Cholesterol, mg/ 100 ml ........................... 154 128 126 95 170 128 87
Calcium, mg/ 100 ml... ......... 9.8 9.4 9.3 9.6 9.2 9.3 9.7
Chloride, mEq/l ................... 97 96 98 97 99 98 96
Total bilirubin, g/ 100 ml.. .4 .3 .3 .5 .4 .4 .5
Creatinine, g/ 100 ml .......... 1.0 1.0 1.0 .7 .3 .4 .9
Total protein, g/ 100 ml ............. 7.4 6.6 7.4 7.0 7.6 7.7 6.7
Inorganic phosphorus, mg/ 100 ml.... 7.2 5.9 6.2 7.9 5.9 5.5 7.0
lood urea nitrogen, mg/ 100 ml ........ 25 21 18 14 24 26 18
Lactic dehydrogenase, Wacker Units1 ..... 572 530 576 511 547 455 403
lkaline phosphatase, King-Armstrong
Units1 .. .. 19 18 17 28 20 16 27
Glutamic-oxaloacetic transaminase,
King Units1 .............................. 124 140 116 127 116 112 106
Sodium, mEq/l .. 149 143 150 152 146 149 147
Potassium, mEq/l .............................. 6.3 4.8 5.6 4.9 4.6 5.2 5.6

 

 

1 Tumbleson (1969).

nickel, and zinc. Samples coHected downstream from
the claypit, however, contained no concentrations of
elements that were notably high with respect to the
water in the farm pond at site 12.

Because samples of whole water were collected and
analyzed, it is not known whether the elements present

are in solution or in suspended particles. However, the
low pH (4.3) of the claypit water may cause many ele-
ments in the suspended particles to occur in soluble
form.

The question as to whether elements occur insoluble

form or within suspended materials may be important

TABLE 8.—Mean chemical compositions, with central 95-percent range,
[These data were used for establishing ranges in typical chemical compositions of certain sampling media. GM, geometric mean: GD, geometric deviation;‘rl‘latio,
per m1 ion.

 

B-horizon soils from Oak-Hickory Forest

vegetation type White oak stems

 

Element or compound

 

 

 

 

 

 

 

 

 

 

 

   
  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   

 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   

 

     

  

Central 95- Central 95-

GM GD percent range Ratio GM GD percent range Ratio
A], or A120,, percent;1 .......................................... 5.1 1.47 2.4—11 50:50 0.19 1.62 0.072—0.50 50:50
B 39 1.41 20—78 49:50 190 1.47 88—410 50:50
Ba ........ 390 1.78 120—1,200 50:50 4,200 1.58 1,700—10.000 50:50
Be .77 1.42 8—1.5 20:50 <2 . . 0:50
C, total, percent 1.1 1.72 37—3.3 50:50 ..........
C. carbonate, percent .. .054 4.14 .0032—.9 44:50 ..................
0, organic, percent .. .96 1.69 .34—2.7 50:50 ..................
Ca, 0,- 09.0, percentl .21 2.80 027—1.6 46:50 33 1.11
Cd <1 ............................ 0:50 3.7 1.33
Ce 78 1.45 37—160 6:50 <300 ........
Co ..... 10 1.71 34—29 49:50 2.2 2.33
Cr ..... 43 1.45 20—90 50:50 3.5 1.85
Cu _ 13 1.99 3.2—51 50:50 130 1.51
Fe, or total Fe as Fean, percent.1 .......................... 2.7 1.43 1.3—5.5 50:50 .14 1.38
Ga ........ 8.4 1.54 3.5—20 48:50 <5 ........
Hg __ .055 1.91 015—20 5050 ..................
K, or K20, percent1 ............... 1.3 1.61 .50—3.4 50:50 5.5 1.35
La. 35 1.37 19—66 46:50 <70 ........
'Li 18 1.33 10~32 50 50 .......... .. ..........
Mg, or MgO, percentI ............................................. .30 2.25 .059—1-5 50 50 1.8 .51—6.2 50 50
Mn 730 2.16 160—3,400 50:50 12,000 4,000—36.000 50:50
Mo ...................................... <3 ............................ 2:50 <5 0:50
Na, or NazO, percent1 .. .38 2.01 094—1.5 50:50 .15 17:17
Nb 8.0 1.38 4.2—15 22:50 <20 0:50
Nd 47 1.35 26—86 12:50 ....................
Ni . 12 1.82 3.6—40 47:50 21
P, or P205, percent‘ .076 1.88 022—.27 40:50 1.3
Pb 23 1.50 10—52 50:50 100
Sc .................... 5.4 1.49 2.4—12 37:50 <5
Se .31 1.90 086—1.1 48:50 ..........
Si. or SiOz, percent1 ......................................... 283 37.43 468—97 50:50 ....................
Sr 66 1.66 24—180 50:50 1,800 710—4,600
Ti, percent ......................................................... .35 1.44 17—.73 50:50 .016 .0057—.045
V 53 1.48 24—120 50:50 <5 ..
Y . 27 1.50 12—61 50:50 <20
Yb 2.8 1.44 1.4—5.8 50:50 <2 .................... 0:50
Zn 36 1.59 14—91 50:50 310 210—450 17:17
Zr ....... 300 1.63 110—800 50:50 <20 .................... 12:50

 

 

 

 

 

See footnotes at end of table.

 

 

—’7

RESULTS AND DISCUSSION 17

because it bears on the availability of the elements to
plants and animals. In other words, the environmental
significance of an occurrence of a trace element in water
cannot be ascertained from the magnitude of its con-
centration alone. The lead concentration in the sample
from the control farm pond, for example, is greater than
that in the other samples; yet the lead that is present
may be in a form that is not available to animal metab-
olism, whereas the lead of lesser concentrations in the
other waters may be readily available. Moreover, many
elements that were not present in high concentrations
in the waters from the claypit area at the time of
sampling may occur in high concentrations during per-
iods of heavy surface runoff. The elements found in the
precipitate at the base of the claypiles could be ex-
pected to occur in solution or as particulate matter in
waters running off the claypiles during and immediately
after periods of intense rainfall.

High concentrations of certain microorganisms that
may occur in water produce toxins to levels that can
be harmful or fatal to cattle. Some species of blue-green
algae are especially toxic. The concentration of micro-
organisms was found to be low in an aliquot of water
from the claypit; only a few objects that appeared to

of media that are comparable to those sampled in the claypit area

 

 

be unicellular green algae were found by microscopic
examination (Robert Lipscomb, oral commun., 1971).

BEEF CATTLE

The extent of the interference syndrome in the
breeding and calving history for the three herds on
Ranch A is given in table 5. Analyses for trace elements
in whole blood specimens from herds on both Ranch A
and. Ranch B are given in table 6; analyses for bio-
chemic constituents in blood serum are given in table 7.

We first observed the affected cattle on Ranch A and
Ranch B in May 1971, although the ranchers had
noticed interferences with growth, nutrition, and repro-
duction nearly a year earlier. We advised the ranchers
to exclude the cattle from the claypit area and the flood
plain below it by fencing; this was done on Ranch A
only. At the time of this visit we thought these cattle
were showing a favorable response to the better ration
that had been provided and to the spring grass. On
later visits, however, the cattle were noticed to be:
unthrifty and to be losing weight as the grass became
short under the influence of a drought in July and
August, despite supplemental rations that were pro-
vided.

number of samples in which detected : total number of samples; central 95—percent range is calculated as GM+GD2 to GMXGD’. Means are given in parts

except as indicated]

 

Buckbrush stems Smooth sumac stems

Redcedar stems and leaves Fescue grass, aboveground parts

 

 

 

 

   

  
   

 

Central 95- Central 95- Central 95- Central 95-
GM GD percent range Ratio GM GD percent range Ratio GM GD percent range Ratio GM GD percent range Ratio
1.2 1.33 0.12 2.11 0.026—0.53 50:50 0.47 1.61 0.18—1.2 10:10 0.56 2.53 0.087—3.6
180 1.35 200 1.26 130—320 50:50 210 1.30 120-350 10:10 48 1.24 31—74
3,800 1.63 1.400— 3,400 2.33 630-18,000 50:50 3,800 2 04 920—16,000 10:10 340 1.72 110—1.000
<2 ........ < ............. 0:50 <2 .. 0:10 <2 ........ ..

 

    

 

 

 
 

  

 

      
 

    

 

 

   

   

   

15
11
<300
5.2
21
180
.69
<5
"“15
<70
"""3.6 1.3-9.8” 49:49
10,000 1.62 3,800—26,000 49:49 moo-21,000 : . 310-2200
1. 2.49 .23-8.7 7:49 2. .29-18 3:10 8 2.47 .79-29
.24 1.21 .16-.35 22:22 . 10:10 .. ..........
<20 ........ .. 0:49 < 20 ........ 0:10 0:18
11 1.49 50-24 49:49 37 2.03 10:10 12:18
2.2 1.31 1.3-3.8 22:22 1.9 1.32 1.1-3.3 10:10 18:18
260 1.88 74-920 49:49 120 3. 5 11-1,300 10:10 18:18
<5 .. 0:49 <5 ........ .. 0:10 0:18
.................... <1 0:10
.1150?) "1196 ""3'901'5','8'00 4919 .2306 2161' ”570191300 10310 ""280 1. ' 120-680 "1"8":"1"8
. 2 1.73 040—.36 49 49 .030 2.00 .0075-.12 10:10 .037 2.23 .0074-.18 18:18
19 1.50 8.4-4.3 49 49 4.6 3. 5:10 2.0 5.99 .056-72 6:18
15 1.45 7 1—32 16 49 <20 0:10 <20 ............................ 0:18
1 4 1.42 69—2 13.49 <2 0:10 <2 0:18
1,800 1.40 660-2,500 22.22 430 10:10 ....................
79 2.16 17-350 49:49 29 3:10 44 15:18

 

See footnotes at end of table.

h

18 GEOCHEMICAL ANOMALIES OF A CLAYPIT AREA, MISSOURI

TABLE 8.—Mean chemical compositions, with central 95-percent range, of media th

. at are comparable to those sampled in the
claypit area—Continued

Yellow sweetclover, total plant

Parts of various species from throughout
t e conterminous United States

 

Element or compound

 

 

 

 

 

 

 

 

Central 95- Central 95-
GM GD percent range Ratio GM GD percent range Ratio
A], or A1203, percentl ................................................... 0.26 4.26 0.014—4.7 0.65 3.52 0.052—8.1 1,109:1,117
B ._ __ .. 160 1.56 66—390 240 2.10 64—1,100 1,133:1,150
Ba 27% 2.03 66—1,100 390 3.75 28—5,500 1,151:1,151
< ........ <2

 

 

Be
C. total, percent ............

   
 
 

C, carbonate, percent ..
0, organic, percent ..
Ca, or 0210, percent1
Cd

 

 

 

 

 

 

  
 
 
 
 
 
 

 

 

 

 

 

 

    

 

 

 

 

 

 

 

 

 

 

 

   

 

 

 

 

 

 

 

   

8: 1,153

          

 

           

 

 

.................... .94
80—26 9.6
38—270 100
Fe. or total Fe as Fean, percent1 ............ .21 029—1.5 .36
a. .................... .20
Hg ........................................................... u ....................
K, or K20, percent1 ..................... 13
En 1:10 <70
1 ........................................
Mg, or MgO, percent1 .............................................................. 10:10 3.0 1,120 1,153
Mn 110—560 10:10 1,000 4.38 57—21,000 1,153 1,153
o .......................................... 1.7—230 8:10 4.2 3.94 .2 — 5 45 ,124
Na, or N320, percent‘ ...... .......... .46 4.00 .029—7.4 277 277
Nb 0:10 ..........................................................
.......... 32 6.21 .83—1,200 11:47
1.63 16 2.84 2.0—130
2.83 2.0 2.27 .39—10
2.22 86 6.17 2.3—3.300
........ <5
Si. or SiOz. percent‘ ........................................................................................................................................................
Sr 1.89 250—3,100 10:10 880 3.78 62—13,000 1,145 1.152
Ti, percent .0091 2.39 .0016—.052 10:10 .026 3.49 0021—.32 1,122 1,148
V ........ .82 29.0 .00098—690 3:10 11 4.15 694 1,123
<20 ........ 1:10 <20 ........ 158 1,128
........ . 1:10 <2 101:1.108
........ .. 450 2.73 642 : 643
16.7 .0065—500 2:10 13 3.44 470:1,152

  

 

 

 

 

 

 

1Means given for plants are percentages of the element; means for

2Arithemtic mean.

3Standard deviation.

‘Central 95-percent range is calculated as arithmetic mean minus two stand

One herd, composed of 54 older Angus cows on Ranch
A, did not have access to the claypit area and in both
1970 and 1971 it produced 54 live calves (table 5). A
herd composed of 66 younger Angus cows that were
pastured adjacent to the claypit area produced 31 live
and five stillborn calves in 197 0, and 23 live calves and
one stillborn calf in 1971. A third herd, consisting of
24 Charolais cows 4 years old, was kept on pastures
unaffected by the claypit area, and in 1971 it produced
24 live calves.

On Ranch B one yearlin
bulls that had access to a
from the claypile develo

g and four older Charolais
pasture affected by runoff
ped the interference syndrome.
These bulls were unthrifty, grew slowly, and gained
weight at a very low rate, although they were on ade-
quate rations for normal develOpment. After being
removed from the part of the pasture that was affected
by runoff, the bulls slowly improved in condition, and
finally recovered without obvious signs of permanent
injury.

The yearling Charolais bull weighed approximately
1,100 pounds (500 kg) when purchased in April 1970.
During the following year he gained only 100 pounds
(45.4 kg). On being returned to the southwestern Mis-

soils are percentages of the compound.

ard deviations to arithmetic mean plus two standard deviations.

souri ranch from which he
than the normal ex

came, he gained even more
pected daily weight gain of 2—3
pounds (0.9—1.4 kg). Using this latter rate of gain, it
is estimated that a yearling Charolais bull could gain
730—1,095 pounds (331.1—497.7 kg) in 365 days.
Herds 1 and 3 on Ranch A (table 5), which were not
exposed to the pasture affected by runoff from the clay-
pile, produced excellent calf crops, and the calves were
normal and healthy. The breeding and calving record
of Herd 2 which grazed on the affected pasture (table
5) indicates that the interference syndrome greatly
reduced the reproductive capability of the herd. In
addition, the condition and growth rate of the cows
were affected; in 1971 these cows averaged about 600
pounds (270 kg) in weight, whereas normal Angus
cows of the same age should weigh about 1,100 pounds
(500 kg). After the 1971 calving season, all but 21 cows
of this herd were disposed of, as it was apparent that
they were not likely to reach the full size and weight
usual for mature Angus cows. The calves produced by
the 21 remaining cows were smaller and less growthy
than is usual for Angus-Charolais calves.
Interference syndromes are slow to develop,
corrective response to a change in environment is 1i

and
kely

 

 

 

———7

RESULTS AND DISCUSSION 19

TABLE 9.——Concentrations of selected elements and compounds
in anomalous amounts in one or more samples of clay from
the claypit area, the average of these elements and com-

ounds in soils in vicinity of the claypit, and the average
for the Oak-Hickory Forest soil

[Values are in parts per million, except as indicated]

 

 

    

 

s . 0' fl 6,. 5,. 5 u. _ has.
23 zg 23 z: z‘é 3,5 °:. gang's;
w W as at» as was 4.2””;
Element or as as 53 as 9.8 ass 5 sate
compound as 58 ES Ea Ea 22-23% >54 8:
775 53 (I) til (I) "‘ > 4 8mg
A1207, percent ...... 30 29 31 34 33 8 4 5 1
Ba . 500 200 150 200 30 700 390
3 3 2 2 <1 7
300 150 300 <150 <150 78
3 3 15 13 10
150 300 300 200 65 43
100 50 30 150 12 13
2 1 4 1.5 1 2.8 2 7
30 50 50 50 14 8 4
2 9 2 9 2.5 1.3 1 8 1 3
70 100 150 70 54 35
242 258 320 338 22 18
20 7 50 810 730
3 15 7 7 <3 <3
100 100 150 70 <70 47
50 30 100 100 14 12
.5 .3 .2 .1 .14 .076
so so so so 8.4 5.4
3.2 1.7 3 .4 .4 .31
45 44 46 41 76 83
700 700 700 150 160 66
.3 .5 1 .5 .43 .35
300 700 700 500 85 53
70 5o 70 20 35 27
7 5 7 3 3.8 2.8

 

 

1 Samples of clay from large pile east of claypit. Sample did not contain
visible amounts of coal or sulfide minerals.
2 Sample of clay from smaller pile immediatehy north of large pile.

l e13 Sample of clay from southwest wall of claypit about 5 ft above water
ev .

4 Geometric means of 10 samples of soil (Nos. 22—31 of table 2) from the
vicinity of the claypit. The samples were collected at depths of 2—15 cm and
were not visibly contaminated with clay from the claypit.

5 Geometric means of 50 B-horizon soil samples from Oak-Hickory Forest
areas in southern Missouri (Shacklette, Erdman, and Keith, 1971) .

to be slow. The syndromes represented by the two
groups of young cattle discussed in this report are not
instances of calculated and controlled experimental
procedures with known or predetermined factors.
Although the cows in Herd 2 had free access to rations
that were more than adequate for young beef cattle
during their first gestation, their health steadily deter-
iorated, with malnutrition, loss of weight, signs of
avitaminosis-A, and other evidence of starvation
becoming apparent. Yet these interference phenomena
were not fully appreciated for many months. Infectious
diseases and other possible causes for the deterioration
of the herd were ruled out insofar as was possible under
the circumstances.

Although the history of the animals, and their con-
dition as determined by observations, are of major
importance in the establishment of a diagnosis, anal-
yses from laboratory examinations provide very impor-
tant supportive evidence and often reveal hidden inter-
relationships. The blood samples reported in tables 6
and 7 were taken 8 months after the cattle had been
removed from the affected pasture, and their analyses
indicate a trend toward recovery of the animals. The
trace element content of whole blood and the macro-
mineral and enzyme values of the blood serum are

 

within the normal range for beef cattle, although the
ratios of concentrations of some elements may be
abnormal.

The effects of trace elements on human and animal
health have recently been discussed by Selby, Marien-
feld, and Pierce (1970). Deficiencies, as well as
excesses, of certain elements may result in imbalances
which disturb the normal nutrition and health of plants
and animals (Mills, 1970; Church, 1971). The disturb-
ance in animals may be so subtle as to suggest a minor
ration deficiency, or so pronounced that an obvious
toxicity is observed. We have worked with such inter-
ference phenomena before, and are of the opinion that
the syndrome shown by the young cattle on both
ranches discussed in this report is most likely a com-
plex imbalance of molybdenum, cobalt, sulfate, and
copper. Poole (1970) emphasized the fact that cyto-
chrome oxidase activity is depressed by copper defici-
ency in the presence of interference by molybdenum or
other trace substances. The copper values in blood
shown in table 6 may be within low normal ranges,
and are difficult to evaluate.

The severe depression of nutrition, growth, and
reproduction in Herd 2 best fits a diagnosis of chronic
molybdenosis as reported by Fleming, McCormick, and”,
Dye (1961) from Nevada, and by Barshad (1948) from
California. The changes in color and condition of the
hair coat and the abnormal thickening of the skin also,
fit cases of unthrifty animals seen at Our veterinary
clinics during the last 20 years, and resemble those
described by Muir (1941). Other workers have
described similar metabolic disturbances from many
places. (See Britton and Goss, 1946; Kretschmer and
Beardsley, 1956; Underwood, 1970, 1971; Dye and
O’Harra, 1959; Clarke and Clarke, 1967; Radeleff,
1970; and Mills, 1970.)

Our diagnosis of the problem as an interference syn-
drome is supported by the studies of the element con-
tent of the vegetation and other materials from the
area affected by drainage from the claypile, as given in
tables 2, 3, 4, 9, and 10 of this report. Data in these
tables suggest that in plants from the affected area,
certain elements other than those linked to molybdeno-
sis ocCur in concentrations greatly in excess of nutri-
tional requirements of cattle, as well as above the usual
ranges for such elements in Missouri plants (Pickett,
1955; Church, 1971) .

There could be many interrelations and imbalances
of major and minor elements in addition to those men-
tioned. Several workers have reported imbalances in
which phosphorus, calcium, or vital metabolic enzymes
were adversely affected by anomalously high or low
amounts of other substances ingested by cattle
(Thompson and others, 1971; Britton and Goss, 1946 ;

h

20 GEOCHEMICAL ANOMALIES OF A CLAYPIT AREA, MISSOURI

Davis, 1950; and Muir, 1941). Nickel may contribute
to interactions with other trace substances when pres-
ent in excessive amounts, and may reach interference
levels that correspond to the levels reported in tables
2 and 3 (especially the levels in sweetclover and lespe-
deza). O’Dell and Miller (1971) discussed various
aspects of nickel as it affects ruminant rations. Muir
( 1941) described the natural soil, pH, and related con-
ditions which promote mineral imbalances such as
anomalous concentrations of trace elements (especially
molybdenum), and he cited the work of pioneers such
as J. S. Watson who suspected the nature of the copper-
molybdenum-sulfate and other trace element inter-
relationships early in the present century.

We are of the opinion that the young Charolais bulls
on Ranch B farther down the valley were affected by
the same trace element imbalances that caused the
interference syndrome in Herd 2 of Ranch A. These
bulls were not as near the sources of the environmental
contamination as were the cows of Herd 2, and received
less exposure to the water and vegetation that con-
tained the anomalous concentrations of elements nearer
the claypit. These bulls made better recovery of health
than did the cows of Herd 2, when both were moved
from the affected pastures.

The toxic plants native to the flood-plain pasture
could make the imbalance of the trace elements worse,
but has, in our opinion, made only minor contribution
to the interference syndrome on Ranch A. The bulls on
Ranch B were confined to lots where they did not have
access to toxic plants, but grazed in a small pasture that
was flooded by Rocky Branch, and they depended on
a spring in the creek for their water supply. In our
opinion, white snakeroot (Eupatorium rugosum) is the
most dangerous of the toxic plants growing on either
farm. Plants of the Nightshade Family, some of which
are of known toxicity, are also present in the flood-plain
pasture. We believe that the principal contribution of
plants to the interference syndrome was not the organic
poisons of certain plants, but the concentration of ele-
ments that were found in certain plants, especially
sweetclover and lespedeza, that grew in the pastures.
Buckbrush also is browsed by cattle, and it contained
anomalous amounts of certain elements where it grew
in the contaminated area. Direct ingestion of the clay
and associated materials, or of water that carried these
materials, may also have affected the metabolism of
these animals.

SUMMARY AND CONCLUSIONS

Anomalous concentrations of elements in the claypit
area were due, in a large measure, to the chemical com-
position of the materials that have been exposed by the
mining operation. These materials include clay, shale,

 

coal, limestone, and pyrite. Pyrite is of special impor-

tance in effecting the release of certain elements into

the natural environment because, by weathering, it
produces sulfuric acid which is strongly reactive with
other materials in the claypiles.

Water that drained from the claypiles into the clay-
pit was highly acid and supported few aquatic organ-
isms. We believe that the principal importance of the
water in the local geochemical environment was its
downstream transport of elements in solution and in
particulate matter, and the subsequent deposition of
these materials in the flood-plain alluvium and in the
beds of the streams.

Plants that grow on the claypiles or in the alluvium
that was carried from the claypiles may concentrate
certain elements in their tissues as controlled by the
inherent characteristics of the different species; and the
concentrations present in the soil on which they grow.
Some of these elements probably produce no impor-
tant alteration of the natural environment, whereas
others, if concentrated, are known to be toxic to most
organisms.

In this summary, as in the report, element concentra-
tions in the clay and in other materials brought to the
surface by mining are regarded as anomalous wherever
they differ from the range of concentrations to be
expected in soils of the area.

Elements and compounds that are judged to occur
in anomalous amounts in sampling materials from the
claypit area are listed in table 10. Examination of this
table reveals that the elements and compounds may be
arranged in five groups, as follows:

1. Those that occur in anomalous amounts in the clay
or alluvium, or both, and that also were found in
anomalous amounts in many of the plant samples-—
aluminum, copper, gallium, molybdenum, nickel, so-
dium, and ytterbium. Special mention should be
made of cobalt, which is negatively anomalous in the
clay but positively anomalous in five kinds of plant
samples.

2. Those which occur in anomalous amounts in the clay
and alluvium, but which were found in anomalous
concentrations in none, or only a few, of the plant
samples—barium, beryllium, cerium, chromium, lan-
thanum, niobium, phosphorus, potassium, scandium,
titanium, vanadium, and yttrium.

3. Those that occur in typical, or lower, concentrations
in the clay and alluvium but, nevertheless, are ab-
sorbed in anomalous amounts by some plants—
boron, cadmium, calcium, and zinc.

4. Those which are anomalous in the clay or alluvium,
but for which we have no means of evaluating their
concentrations in plants—carbon, lithium, neodym-
ium, selenium, and silicon. Carbon is a major constit-

 

 

 
 

 

———’7

SUMMARY AND CONCLUSIONS 21

TABLE 10.-—-Elements and compounds that occur in anomaloas concentrations in one or more samples of materials from
the claypit area.
[+. anomalously high; 0, typical; —. anomalously low; .......... , no data available]

 

Materials sampled

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Clo. from Smooth Redcedar 31322113 White (full?!
Element or compound clayypiles asllttisildlr‘n Wgégfngak 3113,2253” sumac stems and abovege, 335:7 agdvzi
and claypit stems leaves ground total plant ground
parts‘ parts1
+ + + o +
o o o o o
_ o o o -
+ + o o +
_ o ..............................
o + .........................
o o ' o 6 i5 '
o o + + o
+ + O O O
— 0 o + +
+ + 0 0 +
+ + + o +
_ o — o o
+ + + o +
+ + + o o
+ + o o o
+ + ..............................
o o o + ._
_ ... — o o
+ + + + 0
_ O —. — .—
o + o o o
+ + ........................................
+ + + + o +
+ + o o o o
o + o — O O
+ + o o O +
+ + ........................................
+ + """ c3 """" '6 ""‘o """" '_.""
+ o o o o +
+ + o + o +
+ + o o o o
+ + + o o +
o o + o o 0

Zn .............................................................................

 

 

1Bluegrass, common bullrush, fowl meadow grass, Japanese chess, meadow fescue, redtop, timothy, and wood reed grass.

2Cattail, common plantain, goldenrod, Japanese clover, and white snakeroot.

uent of plants; the other elements are nonessential to

plant metabolism.

5. Those whose tendencies in concentrations and move-
ments through the local environment cannot be
readily categorized with the data that are now avail-
able—iron, lead, magnesum, manganese, and stron-
tium.

Elements in groups 1 and 3 potentially can influence
the metabolism of grazing animals because of their con-
centrations in plants, or their presence in deposits of
the clay on the plant surfaces. Elements in groups 1
and 2 can affect these animals if the clay or alluvium
is ingested directly, or if water is drunk in which these
elements are in solution or suspension, even if the vege-
tation is not grazed.

Plants that concentrate certain elements in high
amounts may be particularly important in contributing
to nutritional disorders of animals, especially (as in
sweetclover and Japanese clover) if the plants are very
palatable and therefore preferentially grazed. The im-
portance to the geochemical environment of certain less

 

palatable accumulator plants, such as the trees and
shrubs sampled in this study, may lie principally in
their ability to concentrate certain elements in the
upper soil horizons where they are readily available to
other plants.

In evaluating the total geochemical environment of
the claypit area, four elements (beryllium, copper,
molybdenum, and nickel) are seen to be conspicuously
anomalous in the clay, alluvium, and plant samples.
Moreover, the mobilities of certain elements (alumi-
num, beryllium, cobalt, copper, and nickel, among
others) are demonstrated by their high concentrations
in efl'lorescent salts and in the claypit water. Cobalt,
although not anomalous in the clay and alluvium
samples, is a common anomaly in the plant samples. Of
these elements, cobalt, copper, and molybdenum are
known to be metabolically significant; in trace amounts
they are essential to animals, but in high concentra-
tions may be toxic. Aluminum occurs in anomalously
high concentrations in all sampling media, and in an
acid environment such as may be provided by the oxida-

fi

22 GEOCHEMICAL ANOMALIES OF A CLAYPIT AREA, MISSOURI

tion of pyrite it is readily mobile. However, high con-
centrations of aluminum were found in plants only in
samples that were on or near the claypiles. If highly
concentrated, aluminum is thought to be toxic to
animals.

The interpretation of the movements of elements
and compounds through the local environment from
their principal source to grazing animals is summar-
ized in figure 3.

The interference with normal growth, nutrition, and
reproduction in the cattle was caused by the severe
imbalance of several elements that occur in anomalous
concentrations in both the drainage from the claypit
area, and in the vegetation contaminated by this drain-
age The most likely imbalance is in the complex rela-
tionship between copper and molybdenum, which is
possibly influenced by other elements that are present
in anomalous concentrations and that can, in them-
selves, influence metabolism of cattle. Similar inter-
ference syndromes (or toxicities) in which young cattle
are most seriously affected are known to occur in the
States of California, Florida, and Nevada, and in Can-
ada, Europe, Australia, and other places.

 
 
 

 

800
Q%)

Aquatic organisms in claypit
water killed by acid or ele-
ment content, or both

    
      
  

plain

available to grazing animals in:

2. Clay deposited on plant parts during flooding

certain elements

1

O 1000

 

92c 02' 30"

(\

CLAYPILES — SOURCE OF THE ELEMENTS THAT

MOVE IN ANOMALOUS CONCENTRATIONS INTO 700
THE STREAMS,ALLUV|UM, AND CLAYPIT WATER

 

Oxidation of pyrite forms sulfuric acid which increases
solubility of certain compounds in the clay pile

Element-concentrating plants grow on and around the
claypiles; when these plants decay, the elements are
released in a readily mobile form

Elements in particulate and soluble form are trans-
ported downslope by runoff

O Dilution of soluble elements in runoff.
Some elements, in both soluble form
and particulate matter, can be concen-
trated by plants growing on the flood \)O

. \
Certain elements, through chemical reactions and movement, are made / /

1. Water and water-clay mix in intermittent streams and ephemeral 700 Particulate and soluble
pools in the streambeds Lb elements carried

3. All parts of plants that grow on the flood plain and concentrate

  
 

2000

In field situations, some variables of the animals’
actual feed intake are not measurable—the amount of
any one plant that the animals eat, whether all animals
eat the same plants, the season of plant growth, and
the individual consumption of feed supplements. Unlike
laboratory experiments, the natural environment can-
not be treated as a rigorously controlled system. There-
fore, diagnosis of metabolic disorders must‘ employ
plausible inferences that are supported by observations
of the animals, study of the laboratory results, and
evaluation of the total environment to which the ani-
mals were subjected.

The clay and associated materials that were exposed
by the clay mining operation contain concentrations of
certain elements that can be considered anomalous in
the natural geochemical environment of plants and ani-
mals. Runoff from the claypiles transports these ele-
ments, either in solution or in suspended sediment, to
other parts of the area. These elements generally can
be absorbed by plants, and some of them may be con-
centrated to high levels. Of the elements studied, alumi-
num, beryllium, cobalt, copper, molybdenum, and
nickel generally were found to have the greatest mobil-

 

 
  

 
 

    
 
 

   

    
 
 
 

Claypit
area

  

    

MSSOUW

  
 
 
 

  

     
     
     
 

  

_/

We“
\Ranch BD 9}

._\”./.

   
 

  

O

ck);
1.;0. , .

     
  
    
     

   

downstream

V

3000 FEET

FIGURE 3.—Movement of elements through the geochemical system, claypit area, Callaway County, Mo.

 

 

————"

REFERENCES CITED 23

ity in the local environment and to occur most com-
monly in anomalous concentrations through the area.

Young beef cattle exposed to anomalous element
concentrations in the flood plain below the claypile
experienced a severe interference syndrome due to an
imbalance of minerals or other nutrients in their feed
or water, or both. The disturbance in metabolism of
cattle grazing on pastures affected by the claypile was
most similar to chronic molybdenosis. Imbalances of
copper and molybdenum, in addition to those of sul-
fate, nickel, cobalt, and other substances, may have
contributed to this syndrome.

Anomalous concentrations of elements that present
a hazard to livestock may exist at many other locations
in Missouri and throughout the Midwest where similar
materials are brought to the surface by clay and coal
mining, especially if the chemical mobility of elements
is increased under the acid conditions that may result
from the presence of pyrite.

REFERENCES CITED

Barnett, P. R., and Mallory, E. 0., Jr., 1971, Determination of
minor elements in water by emission spectroscopy; U.S.
Geol. Survey Techniques of Water—Resources’Inv., Book 5,
Ch. A—2, 31 p.

Barshad, Isaac, 1948, Molybdenum content of pasture plants in
relation to toxicity to cattle: Soil Sci., v. 66, no. 3, p.
187—195.

Britton, J. W., and Goss, H., 1946, Chronic molybdenum poison-
ing in cattle: Am. Veterinary Med. Assoc. Jour., v. 108,
no. 828, p. 176—178.

Brown, Eugene, Skougstad, M. W., and Fishman, M. J., 1970,
Methods for collection and analysis of water samples for
dissolved minerals and gases: U.S. Geol. Survey Tech-
niques of Water-Resources Inv., Book 5, Ch. A—1, 160 p.

Church, D. C., 1971, Nutrition, with chapters by Smith, G. E.,
Fontenot, J. P., and Ralston, A. T., v. 2, of Digestive physi—
ology and nutrition of ruminants: Corvallis, 0re., Oregon
State Univ. Book Stores, Inc., 801 p.

Clark, E. G. C., and Clarke, M. L., 1967, Garner’s veterinary
toxicology, [3rd ed.]: Baltimore, Williams & Wilkins Co.,
477 p.

Cohen, A. 0., Jr., 1959, Simplified estimators for the normal
distribution when samples are singly censored or trun-
cated: Technometrics, v. 1, no. 3, p. 217—237.

Davis, G. K., 1950, The influence of copper on the metabolism
of phosphorus and molybdenum, in McElroy, W. D., and
Glass, Bentley, eds., Copper metabolism—A symposium on
animal, plant, and soil relationships: Baltimore, Johns
Hopkins Press, p. 216—229.

Dye, W. B., and O’Harra, J. L., 1959, Molybdenosis: Nevada
Univ., Max C. Fleischmann Coll. Agriculture, Agr. Expt.
Sta. Bull. 208, 32 p.

Fleming, C. E., McConnick, J. A., and Dye, W. B., 1961, The
effects of molybdenosis on a growth and breeding experi-
ment: Nevada Univ., Max C. Fleischmann Coll. Agricul-
ture, Agr. Expt. Sta. Bull. 220, 15 p.

Kerber, Jack, ed., 1971, Analysis of cerium—determination of
calcium, magnesium, sodium and potassium [Biochemistry
supp, p. BC—1—BC—13], in Analytical methods for atomic

_____

 

absorption spectrophotometry: [Norwalk, Conn], Perkin-
Elmer Corp., 48 p.

Kretschmer, A. E., J r., and Beardsley, D. W., 1956, The molyb-
denum problem in the Florida Everglades region, in McEl-
roy, W. D., and Glass, Bentley, eds., A symposium on
inorganic nitrogen metabolism—Function of metallo-flavo-
proteins: BaltimorehJohns Hopkins Press, p. 471—491.

Kiichler, A. W., 1964, Potential natural vegetation of the con-
terminous United States: Am. Geog. Soc., Spec. Pub. 36,
116 p., map.

McQueen, H. S., 1943, Geology of the fire clay districts of east-
central Missouri: Missouri Geol. Survey and Water
Resources, 2d ser., v. 28, 250 p.

Mills, C. F., ed., 1970, Trace element metabolism in animals—
WAAP/IBP Internat. Symposium, Aberdeen, Scotland,
1969, Proc.: Edinburgh and London, E. & S. Livingstone,
550 p.

Muir, W. R., 1941, The teart pastures of Somerset: London,
Veterinary Jour., v. 97, p. 387—400.

Myers, A. T., Havens, R. G., and Dunton, P. J ., 1961, A spectro-
chemical method for the semiquantitative analysis of rocks,
minerals, and ores: U.S. Geol. Survey Bull, 1084—1, p.
207—229.

O’Dell, G. D., and Miller, W. J., 1971, Nickel in ruminant
rations: Feedstuffs, v. 43, no. 47, p. 41—42.

Palache, Charles, Berman, Harry, and Frondel, Clifford, 1951,
Dana’s system of mineralogy [7th ed., v. 2]: New York,
John Wiley and Sons, Inc., 1124 p.

Pickett, E. E., 1955, Mineral composition of Missouri feeds and
forages—I. Lespedeza: Missouri Univ., Coll. Agriculture,
Agr. Expt. Sta, Research Bull. 594, 24 p.

Poole, D. B. R., 1970, Cytochrome oxidase in induced hypocu-
prosis, in Mills, C. F., ed., Trace element metabolism in
animals——WAAP/IBP Internat. Symposium, Aberdeen,
Scotland, 1969, Proc.: Edinburgh and London, E. & S.
Livingstone, p. 465—471.

Radeleff, R. D., 1970, Veterinary toxicology, [2d ed.]: Phila-
delphia, Lea & Febiger, 352 p.

Reichen, L. E., and Ward, F. N., 1951, Field method for the
determination of molybdenum in plants: U.S_ Geol. Survey
Circ. 124, 4 p.

Selby, L. A., Marienfeld, C. J., and Pierce, J. 0., 1970, The
effects of trace elements on human and animal health: Am.
Veterinary Med. Assoc, Jour., v. 157, no. 11, p. 1800-1808.

Shacklette, H. T., Sauer, H. I., and Miesch, A. T., 1970, Geo-
chemical environments and cardiovascular mortality rates
in Georgia: US. Geol. Survey Prof. Paper 574—C, 39 p.

Shacklette, H. T., Hamilton, J. C., Boerngen, J. G., and Bowles,
J. M., 1971,.Elemental composition of surficial materials in
the conterminous United States: US. Geol. Survey Prof.
Paper 574—-D, 71 p.

Shacklette, H. T., Erdman, J. A., and Keith, J. R., 1971, Geo-
chemical survey of vegetation, in US. Geological Survey,
Geochemical survey of Missouri, plans and progress for
fourth six-month period (J anuary—J une, 1971) : U.S. Geol.
Survey open-file report, p. 27—46.

Thompson, U. D., Maddox, L. A., Jr., and Breuer, L. H., 1971,
Are your Charolais getting the minerals they need?:
Charolais Banner, p. 104—109.

Tourtelot, H. A., Huffman, Claude, J r., and Rader, L. F., 1964,
Cadmium in samples of the Pierre Shale and some equiva-
lent stratigraphic units, Great Plains region, in Short
papers in geology and hydrology: US. Geol. Survey Prof.
Paper 475—D, p. D73—D78.

Tumbleson, M. E., 1969, Modification of the Sequential Mul-

 

i

 

24 GEOCHEMICAL ANOMALIES OF A CLAYPIT AREA, MISSOURI
tiple Auto-analyzer (SMA—12/30) for use in animal 1971, Trace elements in human and animal nutrition
research studies: Clinical Biochemistry, v. 2, p. 357—367. [3d ed.] : New York and London, Academic Press, 543 p.
Underwood, E. J ., 1970, Progress and perspectives in the study Vaughn, W. W., 1967, A simple mercury vapor detector for geo-
of trace element metabolism in man and animals, in Mills, chemical prospecting: U.S_ Geol. Survey Circ. 540, 8 p.
C. F., ed., Trace element metabolism in animals—WAAP/ Webb, J. S., and Atkinson, W. J., 1965, Regional geochemical
IBP Internat. Symposium, Aberdeen, Scotland, 1969, reconnaissance applied to some agricultural problems in
Proc.: Edinburgh and London, E. & S. Livingstone, p. 5—21. Co. Limerick, Eire: Nature, v. 208, no. 5015, p. 1056—1059.

* u.s. GOVERNMENT PRINTING OFFICE: 1973—515—555/50

 

 

 

/ Paleontology and Stratigraphy of the
5%? Rabbit Hill Limestone and
' " 5’ Lone Mountain Dolomite of
Central Nevada

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 808

 

 

 

Paleontology and Stratigraphy of the '
Rabbit Hill Limestone and

Lone Mountain Dolomite of

Central Nevada

By C. W. MERRIAM

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 808

A comparative study of fossils from contrasting
carbonate facies near the Silurian-Devonian
boundary, and a review of stratigraphic relations

 

 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1973

 

 

UNITED STATES DEPARTMENT OF THE INTERIOR

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY

V. E. McKelvey, Director

Library of Congress catalog-card No. 73—600125

 

For sale by the Superintendent of Documents, US. Government Printing Office
Washington, D.C. 20402 — Price $1.75
Stock Number 2401—02379

 

CONTENTS

Abstract
Introduction ...........................
Purpose and scope of investigation
Acknowledgments .................................
History of investigation .........................................
Methods .
Silurian and Early Devonian depositional belts of
the Great Basin ...................................................................... 4
Areal distribution and stratigraphy of the

   
  

  
  
  
  
  

Rabbit Hill Limestone .................................................. 5
Rabbit Hill, northern Monitor Range . 6
Dobbin Summit, Monitor Range ..... ' 7
Northern Toquima Range ................................ 7
McClusky Peak area, Simpson Park Range ...... 8
Coal Canyon, northern Simpson Park Range 8
Cortez Mountains and Tuscarora Mountains 9
Beacon Peak Dolomite, Sulphur Spring Range ........ 10
Age and correlation of the Rabbit Hill Limestone .............. 10
Lone Mountain Dolomite ........................................................ 12

Lone Mountain Dolomite, Lone Mountain ................... 12

Lone Mountain Dolomite, southern Mahogany Hills .. 13
Lone Mountain Dolomite, southern

    

 
  

 
 

Fish Creek Range ........................................................... 15
Lone Mountain Dolomite, Sulphur Spring Range ........ 15
Age and correlation of the Lone Mountain Dolomite .......... 15
Conclusions regarding relation of Rabbit Hill Limestone
to Lone Mountain Dolomite ................................................ 17
Great Basin Silurian and Devonian coral zones ................. 18
Systematic and descriptive paleontology ............................. 18
Fossils of the Rabbit Hill Limestone and Beacon Peak
Dolomite Member of the Nevada Formation ................... 19
Order Tabulata Edwards and Haime .......... 19
Family Favositidae Dana ............ 19
Genus Favosites Lamarck ........................ 19
Favosites cf. F. helderbergiae Hall .. 19
Genus Striatopora Hall ............................ 20
Striatopora cf. S. gwenensis
Amsden ............................................. 2O
Genus Pleurodictyum Goldfuss ................. 20
Pleurodictyum nevadensis n. sp ...... 20
Pleudorictyum dunbari n. sp ............ 21
Order Rugosa Edwards and Haime ............ 21
Family Laccophyllidae Grabau ......... 21
Genus Syringaxon Lindstrom 21
Syringaxon foerstei n. sp. ................ 22
Family Streptelasmatidae Nicholson .............. 23
Genus Siphonophrentis O’Connell . .. 23
Siphonophrentis sp. B ...................... 23
Family Endophyllidae Torley ........................ 23
Genus Australophyllum Stumm ............ 23
Australophyllum landerensis n. sp .. 24
Australophyllum stevensi n. sp ........ 24
Australophyllum sp. v ...................... 25
Family Disphyllidae Hill ................... 25
Genus Billingsastraea Grabau .. 25

 

 

  

 
  

Page
Fossils of the Rabbit Hill Limestone and Beacon Peak
Dolomite Member of the Nevada Formation—Con.
Order Rugosa Edwards and Haime—Continued
Family Disphyllidae Hill—Continued
Genus Billingsastraea Grabau—Con.
Billingsastraea sp. m ........................ 25
Phylum Brachiopoda ........................................................ 25
Order Orthida Schuchert and Cooper .................... 25
Family Rhipidomellidae Schuchert . 25
Genus Rhipidomella Oehlert .................... 25
Rhipidomella rossi n. sp .................. 25
Family Dalmanellidae Schuchert ................... 26
Genus Levenea Schuchert and Cooper 26
Levenea subcarinata subsp
antelopensis n. subsp .................. 26
Family 0rthidae Woodward .................. 27
Genus Orthostrophia Hall ................. 27
Orthostrophia strophomenoides
subsp. newberryi n. subsp ............ 27
Order Strophomenida Opik .................................... 27
Family Stropheodontidae Caster .................. 27

Genus Leptostrophia Hall and Clarke 27
Leptostrophia sp. cf. L. becki

  

 

  
  

 

 

tennesseensis Dunbar ................... 27

Genus Pholidostrophia Hall and Clarke .. 28

(?)Pholidostr0phia sp. R ................. 28

Genus Strophonella Hall ......... . ..... 28

Strophonella of. S. punctulifera

(Conrad) .......................................... 28

Family Leptaenidae Hall and Clarke ........... 28

Genus Leptaena Dalman ........................ 28

Leptaena fremonti n. sp 28

Family Schuchertellidae Williams ................. 29

Genus Schuchertella Girty ...................... 29
Schuchertella cf. S. haraganensis

Amsden ............................................ 29

Order Pentamerida Schuchert and Cooper .......... 29

Family Parastrophinidae Ulrich and Cooper 29

Genus Anastrophia Hall .......................... 29

Anastrophia cf. A. verneuili (Hall) .. 29

Order Rhynchonellida Kuhn .................................. 29

Family Uncinulidae thonsnitskaya ............ 29

Genus Plethorhyncha Hall and Clarke 29

Plethorhyncha andersoni n. sp ........ 29

Order Spiriferida Waagen ..................................... 30

Family Meristellidae Waagen 30

Genus M eristella Hall ....................... 30

M eristella martini n. sp ............ 30

Family Ambocoeliidae George ..... 30

Ambocoelia sp. a ...................................... 30

Family Leptocoeliidae Boucot and Gill ........ 31

Genus Leptocoelia Hall .......................... 31

Leptocoelia occidentalis n. sp ,. 31

Family Retziidae Waagen ........... 31

Genus Trematospira Hall ........................ 31

III

IV CONTENTS

 

 

 

Page

 
 

 

 

 
 
  

 

 

 
  
  
  

 

 

P
Fossils of the Rabbit Hill Limestone and Beacon Peak age Fossils of the Rabbit Hill Limestone and Beacon Peak
Dolomite Member of the Nevada Formation—Con. Dolomite Member of the Nevada Formation—Con.
Phylum Brachiopoda—Continued Trilobites of the Rabbit Hill—Continued
Order Spiriferida Waagen—Continued Family Dalmanitidae Vogdes .................
Family Retziidae Waagen—Continued Fossils 0f the Lone Mountain Dolomite ...............
Genus Trematospira Hall—Continued Order Rugosa Edwards and Haime .........................
Trematospira mcbridei n. Sp .......... 31 Family Tryplasmatidae Etheridge ...................
Family Delthyrididae Waagen ................... 32 Genus Tryplasma Lonsdale .....
Genus Kozlowskiellina Boucot ................ 32 Tryplasma sp. f __________________________________
Kozlowskiellina nolani n. sp ---------- 32 Family Kyphophyllidae Wedekind ................
Genus Howellella KOZIOWSki ------------------ 33 Genus Entelophyllum Wedekind ............
Howellella cyelopterrz (Hall) Entelophyllum engelmanni n. sp
subsp. momtorensw n. subsp ....... 33 Entelophyllum engelmanni subsp. b
Genus Acrospirifer Helmbrecht and Entelophyllum eurekaensis n. Sp
Wedélfimd ---- . -------------- 33 Phylum Brachiopoda .
Acrosplrlfer klelnhampll 11- Sp ------ 34 Order Orthida Schuchert and Cooper ______________
Family Costispiriferidae Termier and Family Enteletidae Waagen _______________
Termler , """ """""""""""""""""""""""" 34 Genus Salopina Boucot ...........
Genus Costlsplrtfer Cooper ........................ 34 Salopina sp. f __________________
Costispirifer arenosus (Conrad) Order Rhynchonellida Kuhn
subsp. dobbinensis n. subsp ............ 35 . ”d """"""""""""""""""
Tentaculitids and conulariids of the Rabbit Familngfgfizrotoechu ae Schuchert and
H111 L‘meSt°?}e """" ,' """""""""""""""""""""""""" 35 Genus Camarotoechia Hall and Clarke ..
Order Conularllda Miller and Gurley 35 Camarotoechia pahranagatensis
Family Conulariidae Walcott ........................ 35 Waite
Genus Conularia Sp. cf. C. Camarotoechtaspb """""""""""
huntutna Hall. """"""""""""""""""""""" 35 Camarotoechia sp. f ..
Mollusca of the Rabblt Hlll leestone . 35 . . .
- . Order Splrlferlda Waagen ......................................
Family Platyceratldae Hall ............................ 36 . . .
Famlly Merlstellldae Waagen ........................
Genus Platyceras Conrad ........................ 36 . .
Pla Genus Hyattzdma Schuchert ._
tyceras sp. a """""" 36 ?Hyattidina sp f .................................
géatyceras Sp’ b """""" .' """"""""""" 36 Genus Hindella Davidson ........................
atyceras (Orthonychta) sp. 0 ....... 36 H' d ll
Trilobites of the Rabbit Hill .......................................... 36 F .1 Atm fad“ 53:1? """""""
Family Odontopleuridae Burmeister ............ 36 amay r132? ae D1 1 """"""""
Genus Leonaspis Richter and Richter 36 exit: t ry p a fa man """"
Leonaspis cf. L. tuberculatus (Hall) 36 , ry p a. S_p' """""""""
Genus M iraspis Richter and Richter ...... 37 Famlly Delthyrldldae Waagen
(?)Miraspis sp _______________________________ 37 Genus Howellella Kozlowskl ..................
Family Phacopidae Hawle and Corda .......... 37 Howellell“ Pa‘fc‘let? Walte --------
Genus PhaCOpS Emmrich _______________________ 37 - . Howellella Smlthl alte -------------------
Phacops sp. A, cf. P, logani Hall ______ 37 Locality register -- """""""""""
(7) Phacops sp. B, cf. P. canadensis Selected bibllography ------
Stumm .............................................. 37 Index .....................

 

 

 

ILLUSTRATIONS

[Plates follow index]

Striatopora, Pleurodictyum, Favosites, and Platyceras.
Syringaxon, (?)Phacops, (?)Miraspis, Leonaspis, and Conularia.

Leptostrophia, Orthostrophia, (?)Pholidostrophia, Stropheodonta, Strophonella, Schuchertella, and Leptaena.

Levenea and Rhipidomella.
Leptocoelia and Anastrophia.
Plethorhyncha, Trematospira, and Kozlowskiellina.

599°99‘97”“?!‘1t‘

Billingsastraea and Australophyllum.
Entelophyllum.

Hl-lD-l
N’s-‘9

Howellella, ?Hyattidina, and Hindella.

Costispirifer, Acrospirifer, Howellella, M eristella, and Ambocoelia.
Siphonophrentis, Schuchertella, Leptostrophia, Orthostrophia, Howellella, Rhipidomella, and Phacops.

Atrypa, Camarotoechia, Salopina, Tryplasma, Entelophyllum, pycnostylid coral, and Pycnostylus.

FIGURE 1.

TABLE 1.

 

 

 

 

 

 

 

CONTENTS V
Pa 6
Index map of part of the Great Basin showing location of Rabbit Hill Limestone and Lone Mountain 3
Dolomite fossils and approximate limits of Late Silurian—Early Devonian depositional facies belts ............. 5
Photograph showing view northwest across Copenhagen Canyon from Martin Ridge, showing Rabbit Hill
and overthrust Ordovician Antelope Valley limestone cliffs . 6
Photograph showing south side of Rabbit Hill, showing minor drag folds in west-dipping Rabbit Hill
Limestone of the type section ................... .. 7
. Correlation diagram showing stratigraphic relations of the Rabbit Hill Limestone and inferred equivalence
of Lone Mountain Dolomite to the Silurian Roberts Mountains Limestone ........................................................ 9
Diagram illustrating history and present usage of the stratigraphic name Lone Mountain Dolomite ...................... 13
Photograph showing south side of Lone Mountain, showing east-dipping stratigraphic section upward from
Ordovician Antelope Valley Limestone to Devonian Nevada Formation . ....... 14
Correlation diagram showing stratigraphic relations of the Lone Mountain Dolomite and its equivalence
to the Laketown Dolomite of Utah . 14
Correlation diagram showing stratigraphic relation of Rabbit Hill Limestone to Lone Mountain Dolomite
as interpreted . .......... . 17

 

 

 

TABLES

 

Page
Characteristic fossils of the Rabbit Hill Limestone and Beacon Peak Dolomite Member of the Nevada Formation 10
Characteristic fossils of the upper Lone Mountain—Laketown biofacies 16

 

 

 

 

 

 

PALEONTOLOGY AND STRATIGRAPHY OF THE RABBIT HILL
LIMESTONE AND LONE MOUNTAIN DOLOMITE
OF CENTRAL NEVADA

 

By C. W. MERRIAM

 

ABSTRACT

Lateral facies changes from diagenetic dolomite on the east
to limestone on the west greatly complicate stratigraphy and
paleontology of the Silurian and Devonian Systems in the cen-
tral Great Basin. Occupying the Silurian interval on the east,
the Lone Mountain Dolomite is nearly barren of specifically
identifiable fossils in its type section, but in the Fish Creek
Range and other parts of its type area it has recently been
found to contain well-preserved fossils. In the west-central
Great Basin, the highly fossiliferous Rabbit Hill Limestone of
Helderberg (Early Devonian) age overlies Silurian limestone
and calcareous graptolitic shale of the Monitor—Simpson Park
belt, in which no Lone Mountain dolomite has been discovered.

The Rabbit Hill Limestone lithofacies is unknown to the east
in the Antelope-Roberts Mountains belt, in which Lone Moun-
tain Dolomite occurs; however, Rabbit Hill fossils are present
locally in dolomite and dolomitic limestone of the Beacon Peak
Dolomite Member of the Nevada Formation. Southeast of
Eureka, Nev., in its type area, this member disconformably
overlies the Lone Mountian Dolomite, being the lowermost
member in that section of the Devonian Nevada Formation. In
the Sulphur Spring Range, fossiliferous Beacon Peak under-
lies Oriskany-age Nevada Formation containing Costispirifer
arenosus.

The Rabbit Hill fauna is far more diverse taxonomically
than the Lone Mountain Dolomite fauna. Its diagnostic fossils
include the corals Pleurodictyum nevadensis, Pleurodictyum
dunbari, and Syringaxon foerstei and the brachiopods Levenea
subcarinata subsp. antelopensis, Leptocoelia occidentalis, K02-
lowskiellina nolani, and Howellella cycloptera subsp. monito-
rensis. Upper beds of the Rabbit Hill Limestone at Dobbin
Summit, Monitor Range, contain the large spirifers Costi-
spirifer arenosus subsp. dobbinensis and Acrospirifer klein-
hampli, forms that foreshadow the Oriskany (Siegenian) age
faunas in the lower part of the Nevada Formation.

Species of Pleurodictyum, Levenea, Howellella, and Anas-
trophia, among others, indicate correlation of the Rabbit Hill
Limestone and Beacon Peak Dolomite with Helderbergian
rocks of New York and Tennessee. Whereas the westerly facies
Rabbit Hill Limestone was initially regarded as a possible
time-stratigraphic equivalent of the easterly Lone Mountain
Dolomite facies, paleontologic and stratigraphic evidence fails
to support this view. A remote possibility of a very early Devo-
nian horizon in topmost unfossiliferous beds of the Lone Moun-
tain is not entirely ruled out.

In areas recently mapped geologically within a few miles of
Lone Mountain, silicified corals and brachiopods characterize

 

 

 

 

 

dark-gray carbonaceous dolomite lenses in the upper part of
the Lone Mountain Dolomite. Of these Lone Mountain fossils,
the most diagnostic are species of the rugose coral Entelo-
phyllum and the brachiopod Howellella. The small spiriferoids
Howellella pauciplicata and Howellella smithi indicate a cor-
relation with the uppermost part of the Silurian Laketown
Dolomite in the Confusion Range, Utah. Entelophyllum is
unknown later than the Silurian.

INTRODUCTION

The stratigraphy and paleontology of the Silurian
and Devonian Systems in the central Great Basin is
complicated by lateral facies changes from diagenetic
dolomite on the east to limestone on the west. In the
Silurian, the principal direction of this change is north-
westerly, limestones on the west and northwest occupy-
ing stratigraphic positions in which dolomite comes to
prevail in the opposite directions. For example, at Lone
Mountain and in the Eureka mining district the Silu-
rian is entirely dolomite, whereas to the northwest in
the Roberts Mountains and adjacent parts of the Simp-
son Park Range it is largely limestone. Biofacies
changes accompanying westerly to northwesterly dis-
appearance of the Silurian diagenetic dolomite are com-
mensurate with enclosing lithofacies differences. Fauna]
disparity explainable by facies appears to be of such
magnitude as to eliminate or render uncertain a direct
paleontologic correlation of these two contrasting Silu-
rian carbonate facies.

In the central Great Basin, the Silurian limestones
and calcareous shales are more abundantly fossiliferous
than the easterly dolomites. Until recently, in fact,
identifiable fossils were unknown in the Lone Mountain
Dolomite in its type area, which includes Lone Moun-
tain and mountain ranges within and adjacent to the
Eureka mining district. Whereas the Silurian age of
much of the limestone and shale has now been fixed
paleontologically with Some confidence, dating hereto-
fore of the dolomite facies has remained inferential
because of the scarcity of determinable fossils.

 

 

2 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

The name Roberts Mountains Formation (Merriam,
1940, p. 11) was applied to the Silurian limestones and
calcareous shales of the westerly belt in this part of the
Great Basin. Limestones originally included as the
uppermost part of the Roberts Mountains Formation in
the Monitor Range (Merriam and Anderson, 1942, p.
1687 ) were found, in 1947, to be of probable Helderberg
(Early Devonian) age. In 1963 (Merriam, 1963, p. 42)
these lithologically distinctive and fossil-rich upper
limestones were described as a separate formation, the
Rabbit Hill Limestone. Rabbit Hill fossils described
here include those of the original list from the Monitor
Range type area (Merriam, 1963, p. 43).

PURPOSE AND SCOPE OF INVESTIGATION

The main objectives of this paleontologic report are
to describe and illustrate stratigraphically significant
megafossils from the Rabbit Hill Limestone in its type
area in the Monitor Range and the Lone Mountain
Dolomite in its type area in the vicinity of the Eureka
mining district, Nevada. Collections from the Rabbit
Hill in its type area are supplemented by material from
outlying areas in the Monitor Range, Toquima Range,
Simpson Park Range, Cortez Mountains, and the Tus-
carora Mountains, where the Rabbit Hill fauna was
discovered during the course of geologic mapping pro-
grams. Especially significant stratigraphically are Rab-
bit Hill fossils found in the lowermost part of the
Nevada Formation of the Sulphur Spring Range during
the Kobeh Valley program. Conclusions regarding rela-
tive geologic ages of the Rabbit Hill Limestone and the
Lone Mountain Dolomite, which as lithologic entities
do not occur in the same stratigraphic section, are
based upon paleontologic comparisons made in con-
junction with studies of the structure, stratigraphy, and
areal geology of their outcrop belts. Details of the stra-
tigraphy of both units have been dealt with in other
contributions (Merriam, 1940, 1963, 1973a, 1973b;
Nolan and others, 1956).

This comprehensive study of the previously unde-
scribed Rabbit Hill and Lone Mountain faunas is
intended to amplify and support stratigraphic-paleon-
tologic conclusions of monographic studies of rugose
corals in all Silurian and Devonian formations of the
central Great Basin (Merriam, 1973a, 1973b, 1973c).
Proposed zonation of Great Basin Silurian and Devo-
nian rocks by means of Rugosa (Merriam, 1973a,
1973b) takes into consideration the stratigraphic
occurrences of associated fossil groups, especially the
brachiopods. Several well-represented phyla remain to
be studied by specialists.

Conodont and graptolite investigations bearing upon
the complex interrelations of the Lone Mountain, Rab-
bit Hill, and Roberts Mountains Formations have, in

 

recent years, led to conflicting age results, conclusions
seemingly out of phase with those founded upon coral
and brachiopod research. A first step toward adjust-
ment of this confusion is theISystematic collection and
study of conodont material and graptolites, from beds
and sequences that also yield diagnostic corals, brachio-
pods, and other megafossils. Encouragement of such
unifying field and laboratory procedures is an ancillary
objective of this investigation.

Conodonts are abundant in the Rabbit Hill Lime-
stone in its type area and are briefly considered here
(Huddle, J. W., written communs., 1969, 1970). Mono-
graptid graptolites are reported from the type section
(W. B. N. Berry, oral commun., 1971), although none
were obtained during this study. In contrast, the Lone
Mountain Dolomite in its type area has yielded neither
conodonts nor graptolites during the course of this
study. Accordingly, a searching review is called for of
the somewhat circuitous and inductive stratigraphic
speculations of conodont researchers whose reasoning
leads to Devonian rather than Silurian age for the
greater part of the Lone Mountain Dolomite (Clark
and Ethington, 1966; Johnson, 197 0).

ACKNOWLEDGMENTS

Reconnaissance geologic mapping of counties in the
central Great Basin by geologists of the US. Geological
Survey has extended known areal distribution of the
Rabbit Hill Limestone and led to discovery of richly
fossiliferous exposures of this formation. Among con-
tributors to the map areas involved are F. J. Klein-
hampl, northern Nye County, Nev.; R. J. Roberts and
R. E. Lehner, northern Eureka County, Nev.; and E. H.
McKee and J. H. Stewart, Lander County, Nev. L. D.
Cress, US. Geological Survey, discovered the northern-
most known Rabbit Hill exposures at Maggie Creek
during geologic mapping in the vicinity of the Carlin,
Nev., gold mine. Geologic mapping by E. H. McKee in
the Wildcat Peak and Dianas Punch Bowl quadrangles,
Toquima Range, Nev., led to the finding of Rabbit Hill
fossils and has aided in clarifying the stratigraphic
relations of the Rabbit Hill Limestone to Silurian strata
correlative with the Roberts Mountains Limestone.

Correlation and age determination of the Lone
Mountain Dolomite were facilitated by mapping, strati-
graphic study, and fossil collecting by R. K. Hose, US.
Geological Survey, in the Silurian Laketown Dolomite
of the Confusion Range, Utah.

Glacial cobbles collected by F. K. Miller, U.S. Geo-
logical Survey, in Stevens County, northeast Washing-
ton, yielded silicified fossils suggestive of the Rabbit
Hill fauna.

A fossil collection from the Cortez Mountains, Nev.,
made by A. J. Boucot of Oregon State University has

 

V

 

INTRODUCTION 3

aided in establishing the relation of the Rabbit Hill to
the Wenban Limestone. C. H. Stevens, San Jose State
College, contributed a well-preserved colonial rugose
coral from the Sunday Canyon Formation of the Inyo
Mountains, Calif.

J. W. Huddle, US. Geological Survey, prepared
reports on Rabbit Hill Limestone conodonts, and Jean
M. Berdan, of the Survey, identified ostracods from the
same formation.

The writer gratefully acknowledges the critical read-
ing of the manuscript by G. Arthur Cooper, of the
Smithsonian Institution.

HISTORY OF INVESTIGATION

The “Lone Mountain Limestone” in its type area, as
described by Hague (1892, p. 57—62), included beds
now differentiated as Late Ordovician and Silurian. In
1892 the Ordovician or “Lower Silurian” had not been
fully adopted by the US. Geological Survey as a sys-
tem. Hague’s (1892, p. 324—325) initial “Upper Silu-
rian” assignment of the higher part of the Lone Moun-
tain was inferential at best and predicated upon the
position of these dolomites beneath strata of estab-
lished Devonian age (Walcott, 1884, p. 4, 99—211).

In redefining the “Lone Mountain Formation” at
Lone Mountain in 1940, Merriam removed the sepa-
rately mappable Late Ordovician dolomite as a lateral
equivalent of the Hanson Creek Limestone. Merriam
also concluded that an overlying medium-gray dolomite
of Hague’s original “Lone Mountain Limestone” could
reasonably be interpreted at that time as a southerly
dolomite equivalent of the Silurian Roberts Mountains

‘Limestone exposed 20 miles to the northwest. Still

undated by fossils, the restricted “Lone Mountain For-
mation” of Merriam (1940, p. 13) was viewed as resting
conformably upon the Silurian Roberts Mountains
Limestone in the Roberts Mountains, and upon its
inferred dolomitic counterpart at Lone Mountain. A
prominent chert marker unit occurs at the base of the
Silurian Roberts Mountains Limestone of the type area
and occupies the same position below the Silurian
dolomite at Lone Mountain. The chert unit has been
referred to as the Silurian basal chert, because in
subsequent years it was discovered at many widely
scattered localities in the Great Basin, where it lies
upon Late Ordovician strata of Hanson Creek Rich-
mondian age. In some areas where thick dolomites
above the chert marker have yielded no fossils, the
higher part of this dolomite sequence probably includes
beds of Early or even Middle Devonian age.
Reconnaissance geologic mapping and stratigraphic
investigation in the northern Monitor Range during the
1930’s (Merriam and Anderson, 1942, p. 1687) dis-
closed a Silurian graptolitic sequence comprising cal-

506—612 0 ~ 73 - 2

 

careous shale and platy limestone resting upon the
Silurian basal chert; these graptolitic beds are in the
area overlain by richly fossiliferous limestones later
mapped separately and designated as Rabbit Hill Lime-
stone. In 1942, all of these beds, including the Rabbit
Hill, were considered part of the Silurian Roberts
Mountains Limestone. In accordance with Merriam’s
1940 redefinition, the entire sequence appeared, there-
fore, to be older than the restricted Lone Mountain
Formation at Lone Mountain. Absence of dolomites in
this westerly Monitor Range column could be explained
by absence in the west of beds representing their time-
stratigraphic interval; more likely, the interval above
the Silurian basal chert recorded by dolomite at Lone
Mountain was occupied in the Monitor Range by lime-
stone and calcareous shale facies of deposition.

Paleontologic evaluation of the Rabbit Hill Lime-
stone by Merriam in 1947 led to the conclusion that it
was of Helderbergian (Early Devonian) age rather than
Silurian, encouraging search elsewhere for equivalent
Devonian strata at the top of the Roberts Mountains
Limestone. In the light of this disclosure and the theory
of lithofacies change from easterly dolomite to lime-
stone in the west, it now appeared not improbable that
the Lone Mountain Formation as restricted by Mer-
riam in 1940 might also be of Devonian age.

Progress toward eventual clarification of the Lone
Mountain—Rabbit Hill age relation was made after 1957
because of continued geologic mapping and strati-
graphic work under the Kobeh Valley project of T. B.
Nolan and Merriam. Discovery of Rabbit Hill fossils
in lowermost beds of the Nevada Formation and the
finding of Silurian faunas containing Entelophyllum
and H owellella in the upper 500 feet of the Lone Moun-
tain Dolomite in its type area convincingly suggested
that the Rabbit Hill Limestone was actually younger
than the restricted Lone Mountain. Beds containing
the lowest Nevada Rabbit Hill fossils are assigned to
the Beacon Peak Dolomite Member of the Nevada For-
mation which, in the Eureka mining district, rests dis-
conformably upon the Lone Mountain Dolomite as
mapped in that area (Nolan and others, 1956, p. 42).

Restudy of the thick dolomite sequence that overlies
the type section of the Roberts Mountains Limestone
at Roberts Creek Mountain gave no direct fossil evi-
dence of its age. These dolomites underlie the Nevada
Formation, and in the absence of fossils were assigned
in 1940 by Merriam to the Lone Mountain Formation.
In the present state of knowledge of these rocks, it
appears not unlikely that the upper part of the dolo-
mite may represent the Beacon Peak Dolomite Mem-
ber of the Nevada Formation, whereas the lower part is
conceivably a northwestward-extending tongue of the
Lone Mountain Dolomite. The underlying highest beds

 

 

4 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

of the Roberts Mountains Limestone contain the fauna
of Silurian coral zone D. The fauna of Silurian coral
zone E would be expected in the overlying dolomite,
conceivably followed upward by an Early Devonian
fauna of the Rabbit Hill Limestone within the upper-
most dolomite.

A forward step in unraveling the Late Silurian—Early
Devonian stratigraphic relation in the central Great
Basin was made in 1960 by Winterer and Murphy, who
found the Early Devonian Rabbit Hill Limestone rest-
ing conformably upon the Silurian Roberts Mountains
Limestone in the northern Simpson Park Range. At
Coal Canyon, 10 miles northwest of Roberts Creek
Mountain, the uppermost Roberts Mountains Lime-
stone contains Late Silurian coral zone E. No dolomite
is present in this Simpson Park section, which repre-
sents a westerly limestone and calcareous shale facies
of the Monitor— Simpson Park belt.

Description of Silurian brachiopods from the Lake-
town Dolomite (Waite, 1956; Johnson and Reso, 1964)
of the eastern Great Basin has facilitated study of the
Lone Mountain Dolomite faunas, which are much more
closely related to faunas of the Laketown than to
faunas of the Silurian limestone facies. Detailed geo-
logic mapping and stratigraphic study of the Laketown
Dolomite in the Confusion Range of western Utah by
R. K. Hose (written communs., 1954—1964) provided
the fossil collections and other data employed here.

lVIETHODS

Fossils described here were for the greater part
systematically collected in conjunction with geologic
mapping and structural study in a region of intense
deformation. Lateral facies change, thrusting, and per-
vasive normal faulting are features that require cooper-
ative effort of the geologist and the paleontologist in
the piecing together of compositereference columns
ever subject to critical revision. As a case in point, dis-
covery of Rabbit Hill fossils in the basal Nevada For-
fation above the Lone Mountain failed to support the
conclusion drawn from initial mapping of the Rabbit
Hill Limestone and the Lone Mountain Dolomite, that
these contrasting carbonate facies occupied separate
depositional belts and were mutually exclusive and
possibly correlative laterally in a time-stratigraphic
sense. Difficulty in continuous section measurement is
well illustrated in the Rabbit Hill Limestone in its type
area, where incompetent strata are folded and dragged
beneath a major overthrust; only a few hundred feet of
section is measurable at any one exposure. Regarding
true vertical order of the Silurian faunas, in particular,
uncertainties remain to be resolved by detailed geologic
mapping and interpretation of geologic structure and
lateral facies change.

 

These paleontologic studies place emphasis upon the
rugose corals. Systematic and descriptive research on
these abundant and commonly well-preserved fossils
makes possible their meaningful use in age determina-
tion, geologic correlation, and problems of depositional
facies. The Rugosa have been used in conjunction with
brachiopods as a basis for paleontologic zonation of
Silurian and Devonian rocks of the Great Basin (Mer-
riam, 1973a, 1973b). Because fossils are more abundant
and better preserved in the Silurian limestone facies
than in the dolomites, the rugose corals of these facies
have been more thoroughly investigated and are better
understood. Because of the biofacies differences, cor-
relation of Silurian faunal horizons across the inferred
lithofacies boundaries will doubtless remain quite
speculative.

This report deals mainly with silicified fossils pre-
pared by acid treatment. In the Rabbit Hill bioclastic
limestones, silicification was strangely selective; the
corals and brachiopods were replaced to a much greater
extent that associated Mollusca, Echinoderrnata, and
other organic groups, which evidently were chemically
less amenable to silica replacement. All identifiable
fossils from the Lone Mountain Dolomite are silicified.
Although the fossils from dolomite are well preserved
externally, the internal structures were commonly
destroyed in part by recrystallization.

SILURIAN AND EARLY DEVONIAN
DEPOSITIONAL BELTS OF THE GREAT BASIN

Silurian marine rocks in the southwestern part of the
Cordilleran geosyncline (fig. 1) are distributed in three
contrasting lithologic belts (Merriam, 1973a): (1) A
western graywacke belt of the Pacific Border, (2) an
intermediate limestone belt, and (3) an eastern dolo-
mite belt. The intermediate limestone belt traverses
the west-central Great Basin in a north to northeasterly
direction between the graywacke on the west and the
very extensive dolomite belt on the east. Passing from
one to another of these belts, faunas of about the same
age show biofacies differences that seem to be related
in part to change of depositional environment as well
as to features of paleogeography and faunal diSpersal.
Similar facies belts are recognizable in the Devonian.

The Silurian Roberts Mountains Limestone and
overlying Rabbit Hill Limestone occupy the inter-
mediate limestone belt; the Lone Mountain Dolomite
lies in the eastern dolomite belt. A diagenetic dolomite,
the Lone Mountain, occurs at the west border of a very
extensive dolomite sheet which, as the Laketown Dolo-
mite, includes all known Silurian strata of the east-
central and eastern Great Basin. The graywacke or
Pacific Border belt is preponderantly graywacke, vol-
canic rocks, and conglomerate with subordinate lime-

4

 

AREAL DISTRIBUTION AND STRATIGRAPHY OF THE RABBIT HILL LIMESTONE 5

EXPLANATION

 

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Rabbit Hill fossils (Helderbergian age)
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Coral-bearing limestone of possible Rabbit Hill
(Helderbergian) age

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Lone Mountain Dolomite with fossils of Silurian age,
and the upper Lone Mountain—Laketown biofacies

1. Type section of Rabbit Hill Limestone, northern
Monitor Range.
2. Rabbit Hill Limestone, Dobbin Summit, medial Monitor
Range.
3. Rabbit Hill Limestone, Petes Canyon area, northern
Toquima Range.
3a. Rabbit Hill Limestone, Ikes Canyon, Toquima Range.
4. Rabbit Hill Limestone, Walti Ranch, Simpson Park
Range.
5. Rabbit Hill Limestone, Coal Canyon, Simpson Park
Range.
6. Rabbit Hill Limestone, Cortez Mountains.
6a. Rabbit Hill Limestone, Maggie Creek, Tuscarora
Mountains.
7. Beacon Peak Dolomite Member, Bailey Pass area,
Sulphur Spring Range.
8. Beacon Peak Dolomite Member, South Mulligan
Gulch area, Sulphur Spring Range.
8a. Beacon Peak Dolomite Member, type section in
Oxyoke Canyon.
9. Lone Mountain Dolomite, type area at Lone Mountain.
10. Lone Mountain Dolomite, Mahogany Hills, southern part.
11. Lone Mountain Dolomite, Fish Creek Range, southern. part.
12. Lone Mountain Dolomite, Sulphur Spring Range.
13. Laketown Dolomite, Ibex Hills, Confusion Range, Utah.
14. Laketown Dolomite, Pahranagat Range.
15. Silurian dolomite, Ruby Mountains.
16. Vaughn Gulch Limestone (upper part), Inyo Mountains, Calif.
17. Sunday Canyon Formation (upper part), Inyo Mountains, Calif.

    
    
    
 

 

 

120° 116°

0 25 50 75 100 MILES

114°

FIGURE 1.—Index map of part of the Great Basin showing fossil localities of Rabbit Hill Limestone and Lone Mountain Dolomite
and approximate limits of Late Silurian—Early Devonian depositional facies belts.

stone; it contains no diagenetic dolomite. These west-
ernmost Silurian rocks occur at Taylorsville, Calif, just
north of the Sierra Nevada, but are best'exposed in the
Klamath Mountains and southeastern Alaska.

AREAL DISTRIBUTION AND STRATIGRAPHY
OF THE RABBIT HILL LIMESTONE

Within the major intermediate limestone belt (fig. 1)
of the southwestern part of the Cordilleran geosyncline,
the Rabbit Hill Limestone rests upon Silurian lime-
stones and calcareous shale; its exposures are confined
to the more localized Monitor-Simpson Park facies belt
in the west-central Great Basin. Scattered outcrops of
this formation are known from Dobbin Summit in the
Monitor Range northward 140 miles to the Tuscarora
Mountains. On the east, in the subparallel north-south
Antelope—Roberts Mountains facies belt, distinctive
elements of the Rabbit Hill fauna, but not the Rabbit

 

Hill Limestone itself, occur in dolomitic limestones
assigned to the Beacon Peak Dolomite Member at the
bottom of the Devonian Nevada Formation.

At Dobbin Summit in the medial part of the Monitor
Range, the Rabbit Hill Limestone overlies Silurian
limestone containing calcareous shale and is in turn
overlain by limestone of uncertain age yielding cono-
donts reported as Mississippian (J . W. Huddle, written
commun., 1966). Twenty miles north at the Rabbit
Hill type section, this formation rests upon Silurian
graptolite-bearing calcareous shale facies of the Rob-
erts Mountains Formation (Merriam, 1963, p. 42).
Because of faulting and erosion, no younger Paleozoic
strata are found here.

A key section with respect to stratigraphic relations
of the Rabbit Hill Limestone is that in the northern
Simpson Park Range, where this formation is conform-
ably underlain by the highest Roberts Mountains Lime-

6 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

stone carrying the Late Silurian faunas of coral zone E.
The Devonian Nevada Formation is here in fault con-
tact with the Rabbit Hill Limestone. Limestones con-
taining a Rabbit Hill fauna occur in the Toquima
Range (McKee and others, 1972), where they rest
conformably on the Roberts Mountains. Outlying areas
where this fauna has been collected from limestones
are Mount Tenabo in the Cortez Mountains and Maggie
Creek northwest of Carlin.

In terms of the major Silurian lithologic belts of the
Cordilleran geosyncline referred to above, the Beacon
Peak Dolomite containing Rabbit Hill fossils lies
areally within the eastern dolomite belt. Here strata of
Rabbit Hill Early Devonian age, but differing lithology,
underlie Nevada Formation unit 1, which contains
fossils of Oriskany (Siegenian) Early Devonian age.

RABBIT HILL, NORTHERN MONITOR RANGE

About 250 feet of Rabbit Hill Limestone is well
exposed at Rabbit Hill in Copenhagen Canyon, Horse
Heaven Mountain quadrangle (fig. 1). Here, in the
type section at the south end of this small isolated hill,
platy limestones and calcareous shales or siltstones
separate thick lenses and beds of bioclastic limestone
(pl. 8, fig. 15) containing abundant silicified fossils.
Throughout the Rabbit Hill type area (figs. 2 and 3)
these incompetent beds reveal evidence of drag folding
(Merriam, 1963, p. 10). Deformation of these strata is
sympathetic to the overthrust beneath which they lie
and as a result the Pogonip Group on the west overrode
the Roberts Mountains Formation and the Rabbit Hill.
Because of the nature of this lower plate dislocation, it

 

has not been determined whether the Rabbit Hill fossils
range through a thickness much greater than 250 feet
stratigraphically, as these beds are probably repeated
across the broad exposure by drag folding and sympa-
thetic slicing beneath the overthrust sole.

All fossils collected from the 250 feet of type section
of the Rabbit Hill Limestone are regarded as a single
fauna. Other collections of fossils within these deformed
strata of the type area north and west of Rabbit Hill
itself appear to represent about the same assemblage.

The largest fossil collections from the Rabbit Hill
Limestone, those listed in connection with the original
description of this formation (Merriam, 1963, p. 43)
and described here, came from the southeast side of
Rabbit Hill. Conodonts from the type section are listed
below under age and correlation. Monograptus has
been reported from the Rabbit Hill in its type area,
and according to W. B. N. Berry (oral commun., 1971) ,
graptolites have been found at Rabbit Hill. In connec-
tion with this study, no instance of interlayering of
M onograptus beds with established Rabbit Hill Lime-
stone was observed within the type area. Moreover, it
is not unlikely that the thrust slicing within the outcrop
belt might bring up slivers of graptolitic rock from
Silurian strata of the subjacent Roberts Mountains.

Most of the study fossil material from the Rabbit
Hill Limestone in its type area was silicified and was
prepared by the acid technique.

The fauna of the Rabbit Hill Limestone at its type
section is listed below:

Favosites cf. F. helderbergiae Hall
Striatopora cf. S. gwenensis Amsden

 

FIGURE 2.—View northwest across Copenhagen Canyon from Martin Ridge, showing Rabbit Hill (RH) right of center, and
overthrust Ordovician Antelope Valley limestone clifl's (0a) in distance. Dr—Rabbit Hill Limestone; S—Silurian grapto-
litic beds of Roberts Mountains; WC—Whiterock Canyon; CC—Copenhagen Canyon.

AREAL DISTRIBUTION AND STRATIGRAPHY OF THE RABBIT HILL LIMESTONE 7

 

FIGURE 3.—South side of Rabbit Hill, showing minor drag folds
in west-dipping Rabbit Hill Limestone of the type section.

Pleurodictyum nevadensis n. sp.

Pleurodictyum dunbari n. sp.

Syringaxon foerstei n. sp.

Rhipidomella rossi n. sp.

Levenea subcarinata subsp. antelopensis n. subsp.

Orthostrophia strophomenoides subsp. newberryi n.
subsp.

Leptostrophia sp. cf. L. becki tennesseensis Dunbar

(?) Pholidos trophia sp. R

S tropheodonta sp.

Leptaena fremonti n. sp.

Schuchertella cf. S. haraganensis Amsden

Plethorhyncha andersoni n. sp.

M eristella martini n. sp.

Ambocoelia sp. a

Leptocoelia occidentalis n. Sp.

Trematospira mcbridei n. sp.

K ozlowskiellina nolani n. sp.

H owellella cycloptera subsp. monitorensis n. subsp.

Platyceras sp. a

Platyceras sp. b

Platyceras sp. c

Orthoceras sp.

Leonaspis cf. L. tuberculatus (Hall)

(?)Miraspis sp.

Phacops sp. (large)

hexactinellid sponge spicules

crinoidal debris (abundant)

fucoids (pl. 8, fig. 14)

DOBBIN SUMMIT, MONITOR RANGE

Excellent exposures of Rabbit Hill Limestone were
discovered by F. J. Kleinhampl at Dobbin Summit
(fig. 1) in the middle part of the Monitor Range during
geologic mapping of northern Nye County, Nev. The
Rabbit Hill at this locality resembles that of the type
section 20 miles north but is less disturbed and occu-
pies a definable stratigraphic interval within a continu-
ous column. Silurian limestone and calcareous shale
conformably underlying the Rabbit Hill contain brach-

 

iopod and graptolite faunas. The overlying limestones,
which appear to be conformable, have yielded only
conodonts reported to be Mississippian (J. W. Huddle,
written commun., 1966).

Within the approximately 400 feet of Rabbit Hill at
Dobbin Summit the faunas change in character some-
what passing upward in the column with introduction
of the large spirifers Cos tispirifer and Acrospirifer, not
found in the Rabbit Hill Limestone in its type area.
The lower fauna is essentially that of the 250-foot
interval at the type section. Following is a partial list
of Rabbit Hill fossils from the lower 300 feet of the
Dobbin Summit exposures:

Favosites cf. F. helderbergiae Hall

Pleurodictyum nevadensis n. sp.

Syringaxon foerstei n. sp.

Levenea subcarinata subsp. an telopensis n. subsp.
Rhipidomella rossi n. sp.

Leptaena fremonti n. sp.

Plethorhyncha ,andersoni n. sp.

M eristella martini n. Sp.

Leptocoelia occidentalis‘n. sp.

K ozlowskiellina nolani n. sp.

Howellella cycloptera subsp. monitorensis n. subsp.
Leonaspis cf. L. tuberculatus (Hall)

In the upper 100 feet of the Dobbin Summit section,
the two large spirifers Cos tispirifer arenosus subsp. dob-
binensis and Acrospirifer kleinhampli appear; these
forms are precursors of the later Early Devonian fauna
of Nevada unit 1 and Great Basin Devonian coral zone
B. Most of the species in the lower fauna continue into
the upper interval.

NORTHERN TOQUllVIA RANGE

I kes Canyon—Limestones on the south side of this
canyon near its mouth contain a fauna of Rabbit Hill
age as follows:

Leptaena cf. L. fremonti n. sp.

Orthostrophia cf. 0. strophomenoides Hall
Levenea subcarinata subsp. antelopensis n. subsp.
Kolowskiellina nolani n. sp.

M eristella cf. M. martini n. sp.

Limestones underlying those of Rabbit Hill Early
Devonian age at Ikes Canyon contain a coral assem-
blage pertaining to Late Silurian coral zone E, below
which are beds containing Monograptus (McKee and
others, 1972). In this area, about 400 feet of limestone
section including these fossils represents a part of the
Roberts Mountains Formation overlain by the Rabbit
Hill Limestone equivalent given the local name “Mc-
Monnigal Limestone” by Kay and Crawford (1964).
Fossils listed from the “McMonnigal” by Kay and
Crawford (1964, p. 440) suggest that Lower Devonian
beds younger than Rabbit Hill may also be represented.

8 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

Petes Canyon area.—A small structurally disturbed
exposure of Rabbit Hill Limestone was discovered by
E. H. McKee in the Petes Canyon area during recon-
naissance geologic mapping of Lander County, Nev.
(fig. 1). At this locality (McKee and Ross, 1969, p.
428), a few feet of deformed Rabbit Hill limestone lies
in contact with Silurian graptolitic shales. The fossil
assemblage comprises species characterizing the Rab-
bit Hill type section in the Monitor Range 20 miles east,
differing only by the presence of a colonial rugose coral
Australophyllum landerensis n. sp. This is one of two
occurrences of colonial Rugosa discovered in the Rab-
bit Hill. Following is a partial list of the Petes Canyon
fossil assemblage (Locality M1150) :

Favosites cf. F. helderbergiae Hall

Striatopora cf. S. gwenensis Amsden
Pleurodictyum Sp. cf. P. nevadensis n. sp.
Syringaxon foerstei n. sp.

Australophyllum landerensis n. sp.

Levenea subcarinata subsp. antelopensis n. subsp.
Leptocoelia sp.

Kozlowskiellina nolani n. sp.

McCLUSKY PEAK AREA, SIMPSON PARK RANGE

A Rabbit Hill Limestone fauna containing abundant
trilobites was collected in the foothills east of Walti
Ranch (Walti Hot Springs quadrangle) by R. E. Leh-
ner and R. J. Roberts during reconnaissance geologic
mapping of Eureka County. No data are available on
the relations of these rocks to strata above and below.
Following is a partial list of the fossils from this locality
(M1074) :

Pleurodictyum cf. P. nevadensis n. sp.
Syringaxon foers tei n. sp.

Leptocoelia cf. L. occidentalis n. sp.
Leonaspis cf. L. tuberculatus (Hall)
Phacops sp. (large)

Proetus sp.

Conularia cf. C. huntiana Hall
Conularia cf. C. lata Hall
tentaculitids

COAL CANYON, NORTHERN SIMPSON PARK RANGE

An especially important reference section for the
Silurian and Early Devonian limestone facies of the
westerly Monitor- Simpson Park belt is near the mouth
of Coal Canyon, Horse Creek Valley quadrangle (fig. 1).
The stratigraphy was studied by Winterer and Murphy
(1960), who recognized the Rabbit Hill Limestone
overlying richly fossiliferous Late Silurian limestone
with lenses of coarse depositional limestone breccia.
Although this area is faulted considerably, the deposi-
tional relations of the Silurian Roberts Mountains For-

 

mation are in some ways better shown here than in the
type section of the Roberts Mountains Formation at
Roberts Creek Mountain, 12 miles to the southeast. In
order to elucidate the stratigraphy and geologic struc-
ture, the Coal Creek area was mapped in some detail
by Merriam as part of the geologic mapping of the
Horse Creek Valley quadrangle by the US. Geological
Survey.

On the east side of Coal Canyon the upper part of
the Roberts Mountains Formation is overlain con-
formably by 1,100 feet of the Rabbit Hill Limestone.
About 500 feet of the uppermost Roberts Mountains
along the east side of the canyon appears to be unfaulted
and it includes Late Silurian Coral zone E (fig. 4). The
west side of the Coal Canyon is within the north-south
Coal Canyon fault zone, which breaks the continuity
of the Silurian column, although no great amount of
the section appears to have been cut out by this defor-
mation. West of the Coal Canyon fault zone the lime-
stones of the Roberts Mountains contain a fauna simi-
lar to that of Silurian coral zone D.

One-half mile east of Coal Canyon, the Rabbit Hill
Limestone is repeated in a seperate fault block, greatly
broadening the exposure of this formation. About a mile
east of Coal Canyon, Nevada Formation unit 2 crops
out in another fault block. No normal stratigraphic
boundary of the Nevada upon the Rabbit Hill has been
found in this area.

As discussed below under age and correlation of the
Rabbit Hill Limestone, the results of this mapping and
stratigraphic-paleontologic work do not support the
conclusions of Johnson (1965), Johnson and Murphy
(1969), and Johnson (1970) regarding age and strati-
graphic sequence within the Roberts Mountains For-
mation of this area.

Rabbit Hill fossils listed below were collected from
beds high in the formation. It is probable that the unit
can be zoned here on the basis of bed-by-bed collecting.
As at the Walti Ranch locality west of McClusky Peak,
the Coal Canyon Rabbit Hill contains large trilobites
in some abundance:

Syringaxon foerstei n. sp.

Levenea subcarinata subsp. antelopensis n. subsp.
Leptostrophia cf. L. becki tennesseensis Dunbar
Strophonella cf. S. punctulifera (Conrad)
Leptaena fremonti n. sp.

Schuchertella cf. S. haraganensis Amsden
Plethorhyncha andersoni n. sp.

M eristella martini n. sp.

H owellella cycloptera subsp. monitorensis n. subsp.
(?)Acrospirifer kleinhampli n. sp.

(‘2) Costispirifer arenosus subsp. dobbinensis n. subsp.
(?)Coelospira sp. (small)

1

 

 

 

  

 

 

 

   
 
   
    

 

   
   
    

 

 

 

 

 

 

 

      

 

 
   
 

 

 
      

 

 

 

  

 

 

 

 

 

 

AREAL DISTRIBUTION AND STRATIGRAPHY OF THE RABBIT HILL LIMESTONE 9
1 2 3 4 5
Monitor Range Simpson Park Range Roberts Mountains Sulphur Spring Range Diamond Mountains
Rabbit Hill Coal Canyon Roberts Creek Mountain southern part nyoke Canyon
: Devrls Gate
.9 _ Limestone
DD E Units 1 and 2
_ ‘- L L _ _______ Bay State
r 0
Fault contact I, u. ' Thickness Dolomite Member
1 .u Beacon Peakl?) a o . (9 C
® Nevada / g Dolomitel ppr ximate '9
Formation 5 M ‘ ME ~
DD 1 1 Z ember, Woodpecker OF E Woodpecker
”:32 A» * “‘ ' “J “ E Limestone u? Limestone
a . .
1/ ”1,3 \\Do|0mi‘e|\ g Member . Member
/ I E \ y E Sentinel Mountain
Faulting and/ / —§ \\ ‘l E * Dolomite Member Sentinel Mountain
alluvrum /’ / D ‘\ i '—"*- @ Dolomite Member
/// r Dolomite/l : iy DD Unit 2
,’ l '5 , l % (limestone
/// / g Dolomite O 1 g facies) m Oxyoke Canyon
// I o l u: '0 t C
. Top / / ®DA Rabbit I 5 1% Lo \ D: “g; V,» Sands one Member 3
\t 5 “"“pmed Hill / :- ég’, Uni” 2 P k 0
\ 'E Limestone @E °5 7| DB Beacon ea 5
\ g ' ‘ 3 — - ‘ "'—‘ Beacon Peak Dolomite Member 0
‘ °’ DA Rabbit Hill Dolomite ® _
L 50 MiLEs :2 “menu“ so DA Dolomite Member Disconformiw _
Manhattano E Roberts Mountains Roberts g g g
117° 116“ 115° I.“ F°”“a"°" SE Mountains 5' g '-°"° M°Umain g
5 Calcareous grapto- “I _ D | 'te =
3) litic shaly facies Limestone 5 Do . o Oml w
Silurian basal chert Co | C so E Faulted section Faulted
Hanson a anyon in — " section
5, Creek SD W fault zone 5 ‘5
'E _ _Limestone g 23 Silurian Halysiter
0 Eureka I’
g Ouartzite MZ‘ZEZIFZS 2° Unit 2 and pymosw Ids 1000 FEET
Limestone E g
Q Overthrust relation; upper plate is Ordovician Pogonip Group. g 4
@ Sandstone resembling Oxyoke Canyon Sandstone Member. a: _ 500
® Coral zone SE unrecognized in dolomite facies. Silurian basal chert —_ ”rm 1
G) Rabbit Hill Helderbergian fossils in Beacon Peak Dolomite Member. Hanson Creek
6) Devonian and Silurian coral zones (DA, SD) shown on left of Base \Limestone Henson Creek 0
column. unexposed \\ Limestone
\ VERTICAL SCALE
' ' ‘ Eureka

 

‘ Ouartzite

FIGURE 4.—Correlation diagram showing stratigraphic relations of the Rabbit Hill Limestone and inferred equivalence of Lone

Mountain Dolomite to the

Orthoceras sp.

tentaculitids

Leonaspis cf. L. tuberculatus (Hall)
Phacops sp. (large)

( ?)Phacops sp. B, cf. P. canadensis Stumm
dalmanitid (very large)

CORTEZ MOUNTAINS AND TUSCARORA MOUNTAINS
Cortez Mountains—Rabbit Hill fossils occur in the
Wenban Limestone of Gilluly and Masursky (1965, p.
29) in the Cortez area 8 miles northwest of the Coal
Canyon section, northern Simpson Park Range. The
Wenban occupies large areas in the western Cortez
Mountains, where it rests upon the Silurian Roberts
Mountains Limestone. As described by Gilluly and
Masursky, this unit is probably more than 2,000 feet
thick and seems to include much of the Devonian. It
is fairly evident that a least the lower half represents
the Rabbit Hill interval as exposed in Coal Canyon,
whereas the upper half probably includes the Nevada
Formation, possibly capped by a Late Devonian equiva-
lent of the Devils Gate Limestone. Whether the Rabbit
Hill part of the Wenban can on a lithologic basis be
mapped separately from the Nevada in that area
remains to be demonstrated. Collections of poorly pre-
served fossils suggesting the Rabbit Hill fauna come

 

Silurian Roberts Mountains Limestone.

from localities along the west Cortez front. At locality

M1083 on the southeast side of Mount Tenabo, a col-

lection made by A. J. Boucot contains Syringaxon

foerstei n. sp. and Pleurodictyum cf. P. nevadensis n. sp.
Tuscarora M ountains.—Exposures of limestone con-

taining a Rabbit Hill fauna were discovered in the

southern Tuscarora Mountains by L. D. Cress during

the course of geologic mapping in the Carlin Gold mine

area. These disturbed limestones are in contact with

the Roberts Mountains Limestone, which in that Vicin-

ity contains Silurian Coelospira. At locality M1400 near

Maggie Creek, 9 miles northwest of Carlin, the follow-

ing fossils occur:

Favosites sp. (massive forms)

Pleurodictyum sp. cf. P. lenticularis (Hall)

Syringaxon foers tei n. sp.

Billingsastraea sp. m

Schuchertella sp. cf. S. haraganensis Amsden

Leptaena cf. L. fremonti n. sp.

Rhipidomella sp.

Leptocoelia sp. (shell fragments only)

Acrospirifer sp.

N ucleospira sp. cf. N. ventricosa (Hall)

M eristella sp.

phacopid trilobite pygidium (small)

10 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

Billingsastraea sp. m (pl. 9, figs. 1, 2) is the earliest
known coral of this genus in the Cordilleran belt and
is one of two known occurrences of colonial Rugosa in
the Rabbit Hill.

BEACON PEAK DOLOMITE,
SULPHUR SPRING RANGE

Geologic mapping of the southern Sulphur Spring
Range (fig. 1) under the Kobeh Valley project has dis-
closed many exposures of dolomite and dolomitic lime-
stone containing a fauna similar to that of the Rabbit
Hill Limestone in beds that conformably underlie
Nevada Formation unit 1, which carries the Oriskany
age (Siegenian) fauna of Devonian coral zone B.
Because of their stratigraphic position and lithologic
similarity to the Beacon Peak, lowest member of the
Nevada Formation in the Eureka mining district, these
beds are assigned to that unit (Nolan and others, 1956,
p. 42). In its type area, the Beacon Peak (fig. 1) rests
disconformably upon Lone Mountain Dolomite (fig. 4)
and has yielded no determinable fossils. Although Lone
Mountain Dolomite, where best exposed in the southern
Sulphur Spring Range, lies in fault contact with the
Beacon Peak and the higher Nevada, it is with some
confidence believed to directly underlie Beacon Peak
beds containing elements of the Rabbit Hill fauna.
Fossils from two of the Beacon Peak localities in this
area are listed below.

South Mulligan Gulch area (locality M186) :
Pleurodictyum sp. '

Favosites sp. (massive)

Syringaxon foerstei n. sp.

Siphonophrentis sp. B -

Levenea subcarinata subsp. antelopensis n. subsp.
Leptocoelia occidentalis n. sp.

Anastrophia cf. A. verneuili (Hall)

Strophonella sp. cf. S. punctulifera (Conrad)

Bailey Pass area (locality M197 ) :

Favosites sp. (massive)

Syringaxon foerstei n. sp.

Levenea subcarinata subsp. antelopensis n. subsp.
Leptocoelia occidentalis n. sp.

Leptaena cf. L. fremonti n. sp.

Anastrophia cf. A. verneuili (Hall)

M eristella sp. (large)

Acrospirifer sp. cf. A. kleinhampli n. sp.

AGE AND CORRELATION
OF THE RABBIT HILL LIMESTONE

The Rabbit Hill Limestone is of Helderbergian
(Early Devonian) age. When first examined in the type
area (Merriam and Anderson, 1942, p. 1687), these
beds were included with the Roberts Mountains For-
mation as a part of the Silurian System. Comparative

 

study of brachiopods in 1947 strongly favored an Early
Devonian age. Among its abundant and distinctive
brachiopod genera, Leptocoelia appears first in this for-
mation (table 1); so far as is known, this genus is con-
fined to the Devonian and is especially characteristic
of the Early Devonian. The genus Ambocoelia in the
Rabbit Hill confirms a Devonian age. Supporting

TABLE 1,—Characteristic fossils of the Rabbit Hill Limestone
and Beacon Peak Dolomite Member of the Nevada Formation

 

 

   

 

 
  

Simpson 0 5-
Monitor ark an 53
Range Range 5 g E
a: w °
a <0 mm:
IE $5 .= s: 5; £52
a :3 ES m 8 E E8
'5 '5 '5 9 33 ~ ”5.25"
g '8 8"; d 3 E = 3‘)
Cd a Bun B o m an.
Favosites cf. F.
helderbergiae Hall .................... X X X .. . .
Favosites sp. (massive) .................... X
Striatopora cf. S. gwenesis
Amsden ...................................... X X ..
Pleurodictyum nevadensis n. sp .. X X cf. cf. ..
Pleurodictyum sp ............................ ..
Pleurodictyum dunbari n. sp ...... X . ..
Syringaxon foerstei n. sp ............ X X X X
Australophyllum sp. r ................... X . ..
Rhipidomella rossi n. sp ............ X .
Levenea subcarinata subsp.
antelopensis n. subsp .............. X X X X
Orthostrophia strophomenoides
subsp. newberryi n. subsp ...... X
Leptostrophia sp. of. L. becki
tennesseensis Dunbar ...... X X
(?)Pholidostrophia sp. R _ X
Stropheodonta sp .......................... X
Strophonella sp. cf. S.
punctulifera (Conrad) ................ x x
Leptaena fremonti n. sp .............. X X X cf.
Schuchertella cf. S.
haraganensis Amsden .............. X X
Plethorhyncha andersoni n. sp __ X X X
M eristella martini n. sp ............ X X x
M eristella sp. (large)
Ambocoelia sp. a ............................ X
Leptocoelia occidentalis n. sp X X cf.
Leptocoelia sp ..................................
Trematospira mcbridei n. sp ...... X
Kozlowskiellina nolani n. sp ...... X
H owellella cycloptera subsp.
monitorensis n. subsp .............. X X X
Acrospirifer kleinhampli n. Sp ........ X cf. cf.
Costispirifer arenosus subsp.
dobbinensis n. subsp .................... X cf.
(?)Coelospira sp. (small) ................ X
Anastrophia of. A. verneuili
(Hall) ........................................ X
Platyceras sp. a .......... X
Platyceras sp. b ...... X
Platyceras sp. c ..... X
Orthoceras sp ................................ X X
Conularia cf. C. huntiana Hall X
Conularia cf. C, lata Hall ............ X
tentaculitids .................................... X x
Leonaspis cf. L. tuberculatus
(Hall) ........................................ X X X X
(?) Miraspis sp ................ X
Phacops sp. (large) ...................... X X x
(‘2) Phacops sp. B, cf. P.
canadensis Stumm .................... X
dalmanitid (very large) ........... X
Proetus sp ...................................... X

 

 

—__

 

AGE AND CORRELATION OF THE RABBIT HILL LIMESTONE 11

brachiopod evidence is provided by the presence of
Devonian types of Trematospira in the Rabbit Hill and
of Anastrophia related to A. verneuili in the correlative
Beacon Peak Dolomite Member. Moreover, Early Devo-
nian Acrospirifer and large Cos tispirifer of the Oriskany
C. arenosus type occur in higher Rabbit Hill beds. The
colonial rugose coral Billingsas traea sp. m of the Rabbit
Hill at Tuscarora Mountains further supports a Devon-
ian age, this genus not being recorded in older rocks.

Paleontologic comparison of the Rabbit Hill and
Beacon Peak faunas with Devonian faunas of eastern
North America demonstrates that several distinctive
western species and subspecies have near relatives in
Helderbergian (Early Devonian) strata of New York,
Tennessee, and Oklahoma. Among fossil indicators of
eastern Helderberg aflinity are two species of Pleura-
dictyum, the trilobite Leonaspis of the L. tuberculatus
type, and also the brachiopods Levenea subcarinata
subsp. antelopensis, H owellella cycloptera subsp. moni-
torensis, Anastrophia cf. A. verneuili, and Orthostro-
phia strophomenoides subsp. newberryi.

Evidence from study of Rabbit Hill conodonts also
supports an Early Devonian age. A conodont faunule
extracted from samples collected by the writer in the
upper 100 feet of the type Rabbit Hill Limestone at
Rabbit Hill is reported on by J. W. Huddle (written
commun., 1969) as follows:

***Your collections M1326—1 and M1326—2 from the upper
100 feet of Rabbit Hill Limestone at the Rabbit Hill type sec-
tion, Copenhagen Canyon, Horse Heaven quad., Nevada both
contain abundant specimens of I criodus latericrescens n. subsp.
B of Klapper 1969, I. latericrescens huddlei Klapper and Zieg-
ler and single cusp conodonts generally referred to Acodina
which seem to be associated with Icriodus latericrescens.

These forms are characteristic of Johnson-Boucot (1968)
Spinulosa-Zone I and Klapper et al in press Zone-5 (and Klap-
per, 1969) which is thought to be Siegenian.

Further permissive evidence of Siegenian age is pro-
vided by conodonts from the uppermost part of the
Rabbit Hill at Coal Canyon, Simpson Park Range
(locality M1310) , identified by Huddle as follows:
Belodella resimus Philip

I criodus cf. I. latericrescens n. subsp. B of Klapper

I criodus sp.

Ostracods from a locality near the base of the Wen-
ban Limestone near Cortez (Gilluly and Masursky,
1965, p. 31) have been reported on by Jean M. Berdan,
of the US Geological Survey. The lower part of the
Wenban is with assurance the lower part of the Rabbit
Hill Limestone of the neighboring Simpson Park
Range. Following are the ostracods listed by Berdan:
Mesomphalus sp.

Velibeyrichia sp.
n. gen. aff. Welleria
Saccarchites sp.

506-612 0 — 73 - 3

 

Aechmina? sp.

Acanthoscapha sp.

Tricornina sp.

Tubilibairdia sp.

Bairdia sp. aff. B. leguminoides

As several of the genera listed range upward from Late
Silurian into Early Devonian, it was not found possible
on the basis of ostracods alone to fix the age of these
beds.

Samples from the uppermost part of the Rabbit Hill
Limestone at Coal Canyon (locality M1310) yielding
Belodella resimus Philip and other conodonts reported
on by Huddle also contain ostracods, identified by Jean
M. Berdan as follows:

***The ostracodes include Thlipsura sp. afl’. T. furca Roth,
Parahealdia? aff. P.? convexoris Swartz and Whitmore, and
several unidentifiable species. Thlipsura furca was originally
described from the Haragan Limestone of Oklahoma. Para-
healdia? convexoris was described from the upper part of the
Manlius Limestone in southeastern New York; however, there
is an undescribed species in the Port Ewen Limestone in the
Hudson Valley which is even closer to the form from the Rab-
bit Hill. These two species suggest that this part of the Rabbit
Hill has affinities with the Helderbergian of the Appalachian
region.

Because of the high stratigraphic position of this ostra-
cod and conodont locality (M1310) , it is assumed that
these beds are younger than those in the Wenban Lime-
stone near Cortez that yielded ostracods identified by
Berdan.

On the basis of fossil evidence, the westerly Rabbit
Hill Limestone is correlated with the Beacon Peak
Dolomite Member in the more easterly Antelope-
Roberts Mountains facies belt (fig. 4). Fossils common
to the two differing carbonate facies are similar types
of Pleurodictyum, Syringaxon foerstei n. sp., Lepto-
coelia occidentalis n. sp., Levenea subcarinata subsp.
antelopensis, and similar Acrospirifer.

Limestones possibly correlative with the Rabbit Hill
occur in the Mazourka Canyon area, northern Inyo
Mountains, Calif. (fig. 1), where they lie in the upper
part of the Vaughn Gulch Limestone and in the upper
part of the more or less equivalent Sunday Canyon For-
mation (Ross, 1966, p. 31—35). These beds contain
species of the colonial rugose coral Australophyllum
similar to Rabbit Hill A. landerensis. The middle and
lower parts of both formations are Silurian (Merriam,
1973a). Late Silurian coral zone E underlies the upper-
most Vaughn Gulch division, which contains Australa-
phyllum sp. v of possible Helderbergian age. Australa-
phyllum stevensi in upper beds of the Sunday Canyon
Formation is also conceivably Early Devonian. As map-
ped by Ross (1966, pl. 1), the Vaughn Gulch Lime-
stone changes northward into the more shaly Sunday
Canyon Formation, in which Silurian graptolitic depos-

 

 

f

12 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

its predominate, a facies change comparable to that
noted elsewhere in correlative Roberts Mountains
Limestone of the major intermediate limestone belt.
With a single exception, there are no recorded occur-
rences of the Rabbit Hill fauna in western North
America outside of the Great Basin. Glacial cobbles
collected by F. K. Miller, of the US Geological Survey
(oral commun., 1965), in the Chewelah area, Stevens
County, northeastern Washington, contain a fauna of
Rabbit Hill affinity. Among the fossils are Syringaxon
sp., Pleurodictyum cf. P. lenticularis (Hall), Levenea
cf. L. subcarinata (Hall), and a species of LeptoCoelia.
Data from stratigraphic position of the Rabbit Hill
Limestone and correlative Beacon Peak Dolomite
Member have a bearing upon the age and correlation of
these units in a world sense. In the Sulphur Spring
Range the Beacon Peak occupies the interval between
the Lone Mountain Dolomite (below) and Nevada
Formation unit 1 (above) (fig. 4). Lower beds of
Nevada Formation unit 1 carrying Costispirifer areno-
sus and Acrospirifer as well as the rugose corals of
Devonian coral zone B are of Oriskany age, or Siegen-
ian of the European scale. Hence a pre-Oriskany or
Helderbergian age assignment of the Beacon Peak and
Rabbit Hill is appropriate. Presence in the topmost
part of the Rabbit Hill Limestone at Dobbin Summit
of the large Costispirifer arenosus subsp. dobbinensis
and the large Acrospirifer kleinhampli strongly sug-
gests that the fauna of these upper beds foreshadows
and may be little older than that of Nevada Formation
unit 1 in Devonian coral zone B with its Oriskany or
Siegenian elements. Moreover, the reported Siegenian
age of the uppermost Rabbit Hill based on conodont
evidence seems to be in harmony with these findings.
Fixing of the age of the base of the Rabbit Hill Lime-
stone is made possible by its conformable stratigraphic
relation to underlying coral-bearing limestones in the
northern Simpson Park Range. At Coal Canyon (fig. 1)
the topmost Roberts Mountains Limestone contains a
large and diverse coral assemblage of Gotlandian
aspect and Late Silurian (Ludlovian) age (fig. 4) . These
distinctive corals characterize Silurian coral zone E of
the Great Basin and include the Silurian rugose corals
M ucophyllum, Kodonophyllum, and Chonophyllum,
and pycnostylids. They are not known in Devonian
rocks, and, with the entire fauna of Silurian coral zone
E, do not reappear in the Rabbit Hill. Conclusions by
Johnson and others (Johnson, 1965; Johnson, 1970;
Johnson and Murphy, 1969) regarding a possible Devo-
nian age of the uppermost Roberts Mountains Lime—
stone at Coal Canyon are not confirmed by the rugose
coral and brachiopod studies of Merriam (1973a). The
Late Silurian fauna of coral zone E has been found in
the Toquima Range, Nev. (McKee and others, 1972) ,

 

where it underlies limestone with a probable Rabbit
Hill fauna. A similar relation is recognized (Merriam,
1973a) in the Vaughn Gulch Limestone of the northern
Inyo Mountains, Calif.

In summary, an Early Devonian (Helderbergian) age
for these Great Basin strata is supported by the strati-
graphic position of Rabbit Hill Limestone at Coal Can-
yon, Simpson Park Range, above Late Silurian (Lud-
lovian) beds of Silurian coral zone E, by the occurrence
of faunas of Rabbit Hill affinity below strata of Oris-
kany (Siegenian) age in the Sulphur Spring Range,
and most convincingly by paleontologic similarities of
the Rabbit Hill fauna to faunas of eastern Helderberg
formations.

LONE MOUNTAIN DOLOMITE

The name “Lone Mountain Limestone” originally
applied by Hague (1892, p. 57—62) to a more inclusive
section was later, as “Lone Mountain Formation,”
restricted by Merriam (1940, p. 13; 1963, p. 39) to
some 1,750 feet of blocky saccharoidal dolomite over-
lain by the Nevada Formation and underlain by a lower
darker gray dolomite unit. At Lone Mountain, Eureka
County, Nev., within the designated type area, there
has been previous to this report no fossil evidence appli-
cable to the restricted Lone Mountain Dolomite. Pre-
sumed Silurian age was predicated upon stratigraphic
position beneath Lower Devonian beds of Nevada unit
1, coupled with possible correlation of underlying
darker gray dolomite with Silurian limestones named
Roberts Mountains Formation by Merriam (1940, p.
11).

In other Great Basin areas, the name Lone Mountain
Dolomite has been adopted rather loosely in some
instances for lithologically comparable and usually
rather barren dolomites beneath an assumed Silurian-
Devonian boundary. Whereas the Lone Mountain Dolo-
mite was long assumed to be a westerly continuation of
the Laketown Dolomite of the eastern Great Basin,
there has previous to this report been no published
fossil evidence to bear out this View.

In recent years geologic mapping of areas within and
bordering upon the Eureka mining district has dis-
closed stratigraphic sections in which the Lone Moun-
tain Dolomite is quite fossiliferous, and where the
stratigraphic relations to contiguous formations may be
determined. These sections lie in the southern Diamond
Mountains, the southern Fish Creek Range, the
Mahogany Hills, and the southern Sulphur Spring
Range. '

LONE MOUNTAIN DOLOMITE, LONE MOUNTAIN

The “Lone Mountain Formation” of the type area as
redefined by Merriam in 1940 (p. 13, 19) included only

 

 

 

LONE MOUNTAIN DOLOMITE 13

the upper “1,570 feet” of Hague’s inclusive “Lone
Mountain Limestone” (Hague, 1892, p. 57). So
delimited, the Lone Mountain'of Merriam is underlain
by about 750 feet of darker weathering dolomite, at
that time considered to be a southerly dolomite facies
of the Roberts Mountains Formation, which in its type
area is mainly limestone rich in Silurian fossils (‘Mer-
riam, 1940, pl. 2, fig. 2).

Recent disclosures call for some realinement of the
dolomite units at Lone Mountain in the interest of
clarity and simplicity. Because of the dolomitic nature
of the entire section upward from the Silurian basal
chert member to the Devonian Nevada Formation, it
is here proposed to refer to the lower 750-foot darker
weathering dolomite in the Lone Mountain Dolomite
as Lone Mountain unit 1, designating the upper unit or
Lone Mountain Dolomite (restricted) of Merriam
(1940) as Lone Mountain unit 2 (fig. 5). So reappor-
tioned, Hague’s original “Lone Mountain Limestone”
comprises at the bottom a Late Ordovician dolomitic
facies of the Hanson Creek Formation overlain by Lone
Mountain Dolomite units 1 and 2. Of special strati-
graphic significance at Lone Mountain (fig. 6) is the
Silurian basal chert, which is as much as 80 feet thick
in places and forms the bottom member of Lone
Mountain Dolomite unit 1.

Although no positively identifiable fossils have been
collected from the type section of Lone Mountain
Dolomite during these investigations, poorly preserved
organic remains are not uncommon. Hague (1892, p. 59,
61) and Walcott ( 1884, p. 4, 273) make reference to
the presence at Lone Mountain of “Halysites catenu-
latus.” Because Hague gives its horizon as “within 50
feet of the quartzite,” it is likely this was an halysitid
normally occurring in the Late Ordovician Hanson

Merriam (this report)

Nevada Formation Early Devonian
unit 1 sis (early Emsian)

 

 

    

Haque (1892) Merriam (1940)

  
    
  

 

         

Nevada Limestone Nevada Formation

    

 

     
   
 

   
 
 
 
   
   

 
   

Lone Mountain
Dolomite

Lone Mountain
Formation
(restricted)

 

 

Silurian

    
   

 

    
 
 
 
 
 

    
  
  

Lone Mountain
Dolomite

Lone Mountain
Limestone

Roberts Mountains
Formation
(dolomite facies)

  

  

Hanson Creek
Formation
(dolomite facies)

Hanson Creek
Formation
(dolomite facies)

  
     

  
 
  

      

Ordovician

    
  

  
  

Eureka Quartzite Eureka Quartzite Eureka Quartzite

Pogonip Limestone Pogonip Limestone Pogonip Group

is Beacon Peak Dolomite Member unrecognized.
(I) Silurian basal chert marker red.

    

 

FIGURE 5.—Diagram illustrating history and present usage of
the stratigraphic name Lone Mountain Dolomite.

 

 

Creek and Ely Springs Dolomite. Walcott (1884, p. 4)
alludes to its poor preservation in stating that doubt
existed in the mind of James Hall, who examined the
fossil, as to the validity of the identification. Poorly
preserved tabulate corals were collected by Merriam
(1940, p. 13, 20) in the 1930’s at the base of Lone
Mountain unit 2. These corals were considered more
closely allied to Syringopora than Halysites.

Many exposures of dark-gray dolomite showing
conspicuous organic traces have been found in Lone
Mountain unit 2 during detailed mapping of the Lone
Mountain area by the US. Geological Survey. Car-
bonaceous dolomites containing the poorly preserved
fossils are most numerous in the upper 750 feet of the
Lone Mountain and appear to be lenses or pods sur-
rounded by lighter gray barren rock. The dark pods
appear to have been loci of especially prolific organic
activity within which the magnesian recrystallization
was somewhat less destructive of fossil structure than
in the lighter rock.

Definite rugose coral structures occur at two locali-
ties (M1122, M1122a) east of Charcoal Gulch on the
southeast side of Lone Mountain, probably within the
upper 500 feet of the Lone Mountain Dolomite. Mate-
rial from locality M1122 shows broken, partly macer-
ated Rugosa with fairly large subcylindrical corallites
of diameters up to three-fourths of an inch and lamellar
septa (pl. 11, fig. 32). These fossils suggest the Silurian
genus Entelophyllum, well represented in the higher
Lone Mountain Dolomite of the Mahogany Hills and
Fish Creek Range as discussed below.

LONE MOUNTAIN DOLOMITE,
SOUTHERN MAHOGANY HILLS

Dark-gray carbonaceous dolomites containing abun-
dant silicified fossils occur within the upper 500 feet of
the Lone Mountain Dolomite 11/; miles north of the
summit of Wood Cone Peak and 2 miles south-south-
west of Combs Peak (Merriam, 1963, p. 41). As at Lone
Mountain in the upper part of unit 2, these fossil-
bearing carbonaceous dolomites are lenticular within
the lighter gray barren dolomite and appear to occupy
about the same stratigraphic interval (fig. 7). At
locality M1112 the coral beds are quite extensive and
are occupied almost solely by the colonial bushy
Entelophyllum (pl. 10, fig. 11).

Southwest of locality M 1112, and presumably much
lower in the section, Halysites is present in dark-gray
dolomite that possibly represents Lone Mountain unit
1. Still lower, in considerably faulted range-front ter-
rane, are fossiliferous limestones of the Late Ordovician
(Richmondian) horizons representing the Hanson
Creek Formation (fig. 7). Walcott’s original locality for
the “Trenton” fauna, now known to be that of the Han-

 

 

14 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

   

 

FIGURE 6.—South side of Lone Mountain, showing east-dipping stratigraphic section upward from Ordovician Antelope Valley
Limestone (0a) on left to Devonian Nevada Formation (Dn) on right. Note color contrast differentiating darker gray Lone
Mountain unit 1 (811) from lighter gray Lone Mountain unit 2 ($12). Oe—Eureka Quartzite; Oh—Hanson Creek Dolomite
facies; Slb——Silurian basal chert; WP—West Peak; CP—Central Peak; FG—Fossil Gulch; CG—Charcoal Gulch.

 

 

 

 

 

 

 

 

 

 
  

 

 

    
    
  
 
 
   
   
    
   

   

 

 

 

 

 

 

 
   

 

 

 

 

 

  
 
   

 

1 2 3 4 5
Sulphur Spring Range Lune Mountain Mahogany Hills Diamond Mountains Confusion Range, Utah
southern part southern part Oxyoke Canyon Ibex Hills®
Devils Gate
Devils Gate __‘_ Limestone
Limestone S
: ‘5 Bay State
.9 m .
Thickness ; Unit 5 (Bay State E Dolomite Member
approximate g Dolomite Member) 3
Woodpecker u'
Limestone F F Woodpecker Limestone
Member Unit 4 Member
E g Sentinel Mtn '
3 Es Dolomite Member Sentinel Mountain
5 E Sandstgne E Dolomite Member
3 l2 em 9' Unit 3 (limestone facies)
D Unit 2 (limestone
g facies) '3 a Oxyoke Canyon
in D m . . . 1:; Sandstone Member
5 C 5 Unit 2 (Iimestonejgclej) ___________ g m
2 Unit 1 z // Thwkfless 2 Beacon Peak XE
B , apprDXImate _ Dolomite 5 o
B P k - . / Nevada Formation M b to 3
®A grammes ®— °"‘ ‘" °
93 ® ® Lone Mountain (9; 4s Howellella
E g Howells”: Dolomite E pauciplicm
o E pauczp zca a F o .
_. 2 o aulted 2 46 Vernczllopom,
8 'E Emelophyllum 3 Ente|0phv|lum section 0 Halysites, Huronia
Faulted section 0 beds 0 M1112 D 40 Halysites
.0 : t 2 ,7
; Llsxocoelma .
c Pycnastylux D : Faulted section 39,
E E Halysites Unit 2 E ‘5' 34 Halysite:
a a 5 g
25 E ”:2 2 Fish Haven Dolomite
c . . .

(D Sandstone resembling 0xvoke Canyon 8 a, [jalzsxtes Do|omrte facles

Sandstone Member. 2 Halysites S. g (Flax; Eureka
—- I 2

® Measured section R.K. Hose, U.S. GeoL Survey 3 Pycnostvlids -' o Quartzlte
(written commun. 1954): W -

' Fault contact W - Limestone , .

(9 Hanson Creek Limestone fauna (Richmondieni, S Unit1 x § ®facies’,~” 1000 FEET Devonian coral mnes (D' E)
Late Ordovician; locality of "Trenton fauna" " g; E ’1’” shown °" left °l column.
(Haque, 1892, p. 58: Walcott, 1884, p. 273]. g G) 5 2 Base unexposed

® Disconformitv at base of Devonian. : f; g SOTO—mitE—_ § § 500

(9 Beacon Peak Dolomite Member with Rabbit HiH E g g E fades E E
Helderbergian fossils in Sulphur Spring Range. 5%: in Eureka I :1

® No field evidence of disconformity. '9 Quartzite 0

0

FIGURE 7.—Correlation diagram showing stratigraphic relations of the Lone Mountain Dolomite and its equivalence to the
Laketown Dolomite of Utah.

son Creek limestone facies, is situated here near the following forms:
BM’7201, about nine-tenths of a mile north-northeast (‘2) Thamnopora sp.
of Wood Cone, and one-half mile southeast of Entelo- Entelophyllum engelmanni n. sp.
phyllum locality M1112. Camarotoechia sp.
Except for abundant Entelophyllum, the fauna of ?Hyattidina sp.f
locality M1112 is small and nondiverse, including only H owellella pauciplicata Waite

 

AGE AND CORRELATION OF THE LONE MOUNTAIN DOLOMITE 15

LONE MOUNTAIN DOLOMITE,
SOUTHERN FISH CREEK RANGE

Low-dipping, considerably disturbed Lone Mountain
Dolomite is in contact with the Nevada Formation 3 1/2
miles southwest of Fish Creek Springs, where these
Devonian rocks and overlying Devils Gate Limestone
make up the north end of Fenstermaker Mountain.
Blocky Silurian dolomites exposed here lie within the
upper part of the Lone Mountain Dolomite and yield
well-preserved silicified coral-brachiopod assemblages
(pl. 12, fig. 25) differing somewhat from the fauna of
locality M1112 in the southern Mahogany Hills.
Because of complex faulting not yet mapped out, the
relation to the Nevada Formation is not entirely clear.
It appears probable that these fossil-bearing dolomites
directly underlie the Nevada and occupy about the
same stratigraphic interval as the Mahogany Hills beds
of locality M1112 and the fossil-bearing dolomite lenses
at Lone Mountain locality M1122 (fig. 7).
. Lone Mountain Dolomite faunas from two Fish
Creek Range localities, both close to the south bound-
ary of the Bellevue Peak quadrangle, are described
here. The localities are M1 1 13, near the range crest, and
M1087, a quarter of a mile west. The fauna from
locality M1087 (pl. 12, fig. 25) is listed below:
slender ramose favositids (thin-walled)
Alveolites sp.
Entelophyllum engelmanni subsp. b
Tryplasma sp.
?Hyattidina sp. f
H indella sp. a
H owellella smithi Waite
The fauna collected at locality M1113 follows:
massive favositids (small colonies)
?Thamnopora sp.
Entelophyllum eurekaensis n. sp.
Entelophyllum sp. Cf. E. engelmanni subsp. b
Salopina sp. f .
Camarotoechia pahranagatensis Waite
Camarotoechia sp. b
Camarotoechia sp. f
Atry pa sp. f
?Hyattidina sp. f
H owellella smithi Waite

LONE MOUNTAIN DOLOMITE,
SULPHUR SPRING RANGE

Characteristic Silurian dolomites assigned to the
Lone Mountain form the large fault block at East
Ridge, south of Romano Ranch (fig. 1). The east-
dipping blocky dolomite is in contact on the west with
the Nevada Formation along the high-angle north-
south Romano fault. The areal geology and structure
as mapped in this vicinity strongly suggest that Lone

 

Mountain Dolomite also underlies the Early Devonian
Beacon Peak Dolomite Member between the Romano
fault and the parallel major Mulligan Gap fault 2 miles
west.

The Lone Mountain Dolomite of East Ridge is about
1,200 feet thick. Silicified corals were collected at
locality M1121 near the fault in lower strata of this
block and at locality M1148 on the east in the higher
beds. Both faunas represent a Halysites-pycnostylid
biofacies (fig. 7 ). That of the lower horizon contains a
large undescribed pycnostylid genus with flaring calice
(pl. 11, figs. 28, 29) in association with Halysites. The
upper fauna includes a great abundance of the slender
phaceloid Pycnostylus (pl. 11, fig. 30) together with
Halysites.

Corals of the East Ridge H alysites-pycnostylid bio-
facies are not related to those of the higher Lone Moun-
tain in the Mahogany Hills and Fish Creek Range,
which are the Entelophyllum-Howellella association
designated below as the upper Lone Mountain—Lake-
town biofacies. It is probable that these East Ridge
dolomites are a lower interval of the Lone Mountain
sequence, possibly including some of Lone Mountain
unit 1.

AGE AND CORRELATION
OF THE LONE MOUNTAIN DOLOMITE

All identifiable fossils collected during this investi-
gation from Lone Mountain Dolomite of the type area
are of Silurian age. They include the Entelophyllum-
H owellella assemblages of the Mahogany Hills and Fish
Creek Range and those of the Halysites-pycnostylid
facies of the Sulphur Spring Range (fig. 7). Rugose
corals of the genus Entelophyllum and the pycnostylids
are unknown in Devonian rocks; halysitids of the types
occurring in the Lone Mountain are not known to have
survived beyond the Silurian.

Whereas studies of the Lone Mountain Dolomite at
Lone Mountain itself have brought forth no unequiv-
ocal evidence of Silurian age in that immediate locality,
nearby exposures of this dolomite have yielded an
abundance of Silurian fossil material. The three
described E ntelophyllum-bearing faunas from localities
M1112, M1087, and M1113 have species in common,
and while differing somewhat in detail, probably all
represent a single stratigraphic interval corresponding
to the upper 500 feet of Lone Mountain unit 2 at Lone
Mountain. These faunas are of Late Silurian age and
characterize the upper Lone Mountain—Laketown bio-
facies (table 2). Moreover, discovery in the Lone
Mountain Dolomite at Lone Mountain of coralline
lenses comprising large volumes of comminuted rugose
corals suggesting Entelophyllum (pl. 11, fig. 32) seems
to bear out the possible equivalence of these beds in

16 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

TABLE 2.—Characteristic fossils of the upper Lone M ountain—
Laketown biofaces

 

Lone Mountain
Dolomite
JEQEEEEEL

Mahogany Hills M1112
Fish Creek Range
Confusion Range Utah

Unit 48
Pahranagat Range

Nevada

Laketown Dolomite
Silurian dolomite

M1087

X M1113

Massive favositids
(small colonies) ............................
Ramose favositids
(thin-walled) ......
?Thamnopora sp
Alveolites slp ..............
Entelophyl um engelmanm 9

 

n. sp ............................................
Entelophyllum engelmanni

n. sp
Tryplasma sp x
Salopina sp. f
Camarotoechia sp X
Camarotoechia pahranagatensis

Waite ..........................................
Camarotoechia sp. b
Camarotoechia sp. f ..........................
Atrypella carinata Johnson ............
Atrypa sp. f ..
?Hyattidina sp. f .......
?Hyattidina hesperal W te
H indella sp. a .................................... X
Howellella pauciplicata Waite x
Howellella smithi Waite .............. X X
?Meristina sp ....................................
Douvillina geniculata Waite ........
Lone Mountain unit 2 to the Late Silurian Entelo-
phyllum beds of the Mahogany Hills and Fish Creek
Range.

Comparison of the Entelophyllum-Howellella assem-
blages of the Lone Mountain Dolomite with Silurian
faunas of the higher Laketown Dolomite in the eastern
Great Basin provides good evidence of age and correla-
tion. A suitable Laketown reference section 'for present
purposes is that of the Ibex Hills, Confusion Range,
Utah, mapped and measured by R. K. Hose (written
communs., 1954—1964). The Ibex Hills Laketown (fig.
7) is about 1,200 feet thick, underlain by Late Ordovi-
cian Fish Haven Dolomite and overlain disconformably
by probable Early Devonian beds of the Sevy Dolomite.
Units 29 to 49 of the Hose measured section fall within
the Laketown. Laketown unit 48, about 60 feet below
the Sevy contact, contains the diagnostic Late Silurian
fauna of the upper Lone Mountain—Laketown biofacies,
whose key fossil is H owellella pauciplicata Waite. N0
Entelophyllum has yet been collected from unit 48 of
the Ibex Hills section, although generally in the eastern
Great Basin Laketown this rugose coral is present.

Upper Laketown beds correlative with unit 48 occur

 

 

«9X

 

   

 

gxxgxxx
2x2 xx:

xx-exéiiiiéi
Ex:

 

 

in the Pahranagat Range of southern Nevada (Waite,
1956; Johnson and Reso, 1964). In that area the char-
acterizing Howellella is the coarser ribbed species H.
smithi Waite, present also in the Lone Mountain of
Fish Creek Range, but doubtfully represented in unit
48 of the Confusion Range, where pauciplicata
predominates.

Other Silurian faunas characterize the greater part
of the Ibex Hills Laketown Dolomite below unit 48. The
faunas in units 29 upward to unit 47 have not yet been
found in the Lone Mountain Dolomite. Of special inter-
est is the abundance of the dasycladacean alga Verticil-
lopora in unit 46, a genus that reaches its peak in Late
Silurian coral zone D of the Silurian limestone facies of
the westerly Great Basin.

H alysites appears to be absent or very uncommon in
the Great Basin higher Silurian, not having been recog-
nized in the upper Lone Mountain—Laketown biofacies
or in Late Silurian coral zones D and E of the westerly
limestone facies. However, halysitids are clearly facies
controlled and generally through the Silurian and Late
Ordovician may be very abundant or totally lacking in
a given assemblage where other corals are common.

Pycnostylid Rugosa are distinctive Silurian corals,
seemingly also subject to some degree of facies control.
The Halysites-pycnostylid association of the Silurian
dolomite of Sulphur Spring Range has not yet been
identified in the lower Laketown, where it is to be
expected. In the Silurian limestone facies of the west-
erly Great Basin, the pycnostylid genera range upward
to coral zones D and E but, being absent from the
Rabbit Hill, are not known to survive into the Early
Devonian.

The Lone Mountain Dolomite is assumed to be cor-
relative for the most part with the Roberts Mountains
Limestone, an assumption based upon stratigraphic
position, but, because of biofacies differences, unsup-
ported by direct paleontologic evidence (fig. 4). Con-
clusive evidence of lateral intertonguing of the two car—
bonate facies is unavailable; however, within the type
section of the Roberts Mountains Limestone, interbeds
of dolomitic limestone and dolomite (Winterer and
Murphy, 1960) suggest the possibility of such a relation
in that area. In this type section, the uppermost beds
of the Roberts Mountains Limestone have largely
changed over to dolomite. These uppermost strata fall
in Late Silurian coral zone D. Above zone D, the section
is barren dolomite wherein highest Silurian coral zone E
would be expected; it is not improbable that these dolo-
mites may represent a northerly tongue of Lone Moun-
tain Dolomite unit 2, above which lies the Beacon Peak
Dolomite Member of Rabbit Hill (Early Devonian)
age (fig. 8).

RELATION OF RABBIT HILL LIMESTONE TO LONE MOUNTAIN DOLOMITE

1
Simpson Park

 

   

    
     

17

2
Roberts Mountains

 

 

 

 

 

 

   
 

 

 

 

 

 

 

 

 
 
   
   
   

 

 

 

 

   

 

 

 

 

Range Roberts Creek 3
Coal Canyon Mountain Lone Mountain
| l — 12 miles 20 miles
' I
\ | ‘ Elke g
I .
i,’_'_- Battle! t DF
/ Mountain DD Nevada
/' ' ‘ Formation
I E Nevada
E 1:; DE Formation
g; m / .7 ssssss t
-_ —— a FEUI‘WQ and 1,,” Beacon Peakl?) \\\ DD
( alluvru/rn// Dolomite Member \\ E
7 .7*-» ““““ Devonian \\\ —
\\\\\\ \ ‘ \oc
Rabbit Hill ~~~~~~~ \ Coral zones DA and DB unrecognized
\ DA Limestone ,/ Silurian ®
Austin °Eureka (30 Emelophyllum beds (Silurian)
o 569‘
i SE ® Lone Mountain
. unit 2
................... |\ Lone Mountain
‘\ : Coal Canyon Dolomite
‘\ (E fault zone
\ a
3 SD , Dolomite
U! Roberts Mountains SC [A Lone Mountain
0 25 50 MILES Limestone unit 1
o Silurian basal chert
Manhattan . Silurian basal chert Hanson Creek
E Dolomite Dolomite
Eureka
5 '3 Ouartzite
\\

\\

Ordovician

G) Coral zone SE unrecognized in dolomite facies.
@ Beacon Peak Dolomite Member contains Rabbit Hill fossils 10 miles
east in Sulphur Spring Range.
® Beacon Peak Dolomite Member unrecognized at Lone Mountaln.
Great Basin Silurian and Devonian coral zones (SA, DA) indicated
by capital letters on left of column

\‘\\ Hanson Creek
Limestone

Eureka . i
Ouartzite ' '-

 

 

  

 

   

Dolomite

1000 FEET

 

500

 

 

 

0

VERTICAL SCALE

FIGURE 8.—Correlation diagram showing stratigraphic relation of Rabbit Hill Limestone to Lone Mountain Dolomite
as interpreted.

Fossils have not been found in the uppermost Lone
Mountain Dolomite in its type area, that is, within the
300 feet or so between Late Silurian Entelophyllum-
Howellella beds and the Devonian Nevada Formation.
Accordingly, in a negative way it is not entirely possible
at present to rule out Early, perhaps pre-Helderberg,
Devonian age for the highest Lone Mountain. Factors
to be weighed are Helderbergian age of the lowest
Nevada member, the Beacon Peak Dolomite Member,
plus absence from the type Lone Mountain section at
Lone Mountain of the Beacon Peak. In that section
Nevada Formation unit 1 with post-Helderberg fossils
rests conformably upon the Lone Mountain as mapped.
In View of a seemingly gradational boundary, it is there-
fore not inconceivable that beds mapped as the highest
barren Lone Mountain may occupy the Helderbergian
time-stratigraphic interval.

On tenuous evidence, the Lone Mountain Dolomite
has in recent years been interpreted by several paleon-
tologists as at least partly Devonian, a View seemingly
inspired by earlier suggested lateral equivalence of the
Rabbit Hill Limestone to the upper part of the Lone
Mountain Dolomite (Merriam, 1963, fig. 7). A further
complication has been added by conodont, graptolite,

and brachiopod investigators (Clark and Ethington,
1966; Johnson, 1970), who conclude that a not incon-
siderable upper part of the Roberts Mountains Lime-
stone is also Devonian. These age conclusions are not
substantiated by Merriam’s (1973a) rugose coral and
brachiopod studies. Clearly an appraisal and adjust-
ment of these conflicting paleontologic findings is called
for, taking into account a review of the stratigraphic
ranges of all fossil groups represented in the light of
more recent structural and stratigraphic study of the
enclosing rocks.

CONCLUSIONS REGARDING RELATION 0F
RABBIT HILL LIMESTONE
TO LONE MOUNTAIN DOLOMITE

Among objectives of this investigation is elucidation
of age and stratigraphic relation of the Rabbit Hill
Limestone to the Lone Mountain Dolomite, the two
units having previously been viewed as locally occupy-
ing similar or overlapping stratigraphic positions and
never occurring in the same stratigraphic column (fig.
8). These paleontologic studies strongly indicate that
the Rabbit Hill fauna is of Helderbergian (Early Devo-
nian) age and is accordingly younger than the highest

 

18 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

known Lone Mountain Dolomite fossil horizon, which
is Late Silurian and lies no more than 400 feet below
the top of the dolomite formation. This factor greatly
narrows down the possibility of age equivalence of any
of the Rabbit Hill to the uppermost part of the Lone
Mountain.

Factors of stratigraphic significance bearing upon the
Rabbit Hill—Lone Mountain relation are: (1) probable
time-stratigraphic equivalence of Lone Mountain unit
1 and much of Lone Mountain unit 2 to the Roberts
Mountains Limestone of Silurian age as previously
demonstrated, and (2) the stratigraphic position of the
Beacon Peak Dolomite Member carrying a Rabbit Hill
fauna and overlying the Lone Mountain Dolomite
(figs. 4, 7).

Failure to discover fossils in the uppermost type area
Lone Mountain Dolomite leaves open the possibility
that the beds in unit 2 carrying the Silurian (Ludlo-
vian) upper Lone Mountain—Laketown assemblages
might conceivably be succeeded upward by a very Early
Devonian or Helderbergian fauna. However, the bio-
facies differences here might well eliminate a direct
fossil comparison. The Lone Mountain faunas of unit 2
include the spiriferoid genus Howellella and massive
tabulate corals, each represented by differing species
in the Rabbit Hill, but in general the biofacies differ-
ences are great. In fact, it would appear that the mag-
nitude of this faunal disparity, enhanced as it is by
facies, may be somewhat disproportionate to actual age
difference between the two formations.

GREAT BASIN SILURIAN AND DEVONIAN
CORAL ZONES

Rugose corals were used to zone Silurian and Devo-
nian strata of the Great Basin (Merriam, 1971a,
1971b). The five proposed Silurian zones are lettered A
through E in ascending stratigraphic order. Zone A is
of Early Silurian age (Llandoverian), B and C are
Middle Silurian (Wenlockian) , and D and E are Late
Silurian (Ludlovian). The nine Devonian coral zones
are lettered A through I; of these zones, A, B, and C are
Early Devonian, zone D is Early and early Middle
Devonian, zones E, F, G, and probably the lower half
of H are Middle Devonian, and coral zone I is Late
Devonian. In both systems, the coral zonation is best
shown in the limestone facies (figs. 4, 7, 8).

The Rabbit Hill Limestone is within Devonian coral
zone A, characterized by the Syringaxon biofacies.
There is a very profound discontinuity in rugose coral
history between Late Silurian coral zone E of the upper-
most Roberts Mountains Limestone and Early Devo-
nian coral zone A of the conformably overlying Rabbit
Hill. Following a great burst of coral evolution in
Silurian coral zone E, nearly all of the rugose coral

 

genera drop out abruptly. In most places the Rugosa
continue to be represented in coral zone A of the Rabbit
Hill by the one small solitary genus Syringaxon, which
is abundant. The next great burst of rugose coral evolu-
tion took place locally in Devonian coral zone D.
Knowledge of Rugosa in Silurian dolomite facies of
the Lone Mountain and the Laketown Dolomite is at
this time not sufficient for coral zonation. Rugosa are
locally abundant in several horizons of the Laketown,
ranging from beds with Palaeocyclus, possibly corre-
sponding to Silurian coral zone A (Merriam, 1973a) , to
those higher in the column containing Rhabdocyclus,
Tryplasma, lykophyllids, and Entelophyllum.

SYSTEMATIC AND DESCRIPTIVE
PALEONTOLOGY

This general paleontologic study of Rabbit Hill and
Lone Mountain faunas is concurrent with research
upon Great Basin Silurian and Early Devonian rugose
corals. Among its objectives are support for and
strengthening of conclusions based on the coral studies.

Questions of stratigraphic superposition, age, and
geologic correlation having to do with setting up of
reliable composite reference sections for the Great
Basin Silurian and Devonian require integration of all
lines of paleontologic evidence derived from study of as
much as possible of entire faunas. The rugose corals
are by themselves insufficient for achieving these objec-
tives. New genera and species of Great Basin Rugosa
are in some instances unknown in distant standard
sections of eastern North America and the Old World,
hence at present are of no direct comparative value in
this regard.

Among megafossils normally associated ecologically
with Rugosa, the brachiopods have been relied upon
for age conclusions within the Cordilleran mid-Paleo-
zoic. The determinative advantages of good brachiopod
interiors, where these shells, like those of the Rabbit
Hill and the Lone Mountain, are excellently preserved
by silicification are well known. Among rugose corals in
these environments, fine structures of wall and septa are
usually damaged or nearly destroyed by the same silici-
fication processes. Brachiopods named and described
are those silicified and most abundant in the Rabbit
Hill bioclastic limestones and in the dark-gray car-
bonaceous facies of the Lone Mountain. Other brachio-
pods are at this time insufficiently represented for
naming and full description, and much remains to be
done with the paleontology of this fossil group. System-
atics of the Rugosa are entered into more fully in
contributions dealing wholly with this Order (Merriam,
1973a, 1973b, 1973c). Of less commonly silicified
fossils, few have been touched upon. Mollusca, Echino-
derms, bryozoans, ostracods, and most of the trilobites

FAMILY FAVOSITIDAE DANA 19

remain to be described.

Rabbit Hill platy limestones and shaly-silty lami-
nated beds are locally rich in trilobite remains and in
places contain conularids and abundant tentaculites.
Near Walti Ranch (locality M1074) in the Simpson
Park Range, thin-bedded Rabbit Hill limestones yield
well-preserved Conularia comparable to Hall’s C. hunti-
ana of the eastern Helderbergian (pl. 2, figs. 18—20).

In the taxonomic sense, greater faunal differentiation
of the Rabbit Hill as compared with the upper Lone
Mountain is noteworthy. Of the Rabbit Hill silicified
bioclastic limestone fossils from the type section, some
26 taxa are listed here; these are only part of the total
preserved fossil assemblages in this facies. Fossils are
numerous in the restricted upper Lone Mountain dark-
gray carbonaceous dolomite facies, but the preserved
fauna is small and nondiverse. Only 11 taxa were recog-
nized in the most diverse of these faunas from the Fish
Creek Range. Some upward adjustment of this species
count would doubtless be called for, if unsilicified, and
therefore unrecovered, shell-bearing forms were known.
It is seemingly a safe assumption that the diagenetic
dolomite faunas of the higher Lone Mountain were
initially far less diverse taxonomically than the Rabbit
Hill Limestone bioclastic facies. Marine environmental
differences, little understood, would appear to be a
logical explanation for these disparities in faunal
diversity. In general, shallow-water marine conditions
during accumulation of the richly fossiliferous Rabbit
Hill Limestones must have been far more hospitable
than during deposition of the diagenetic upper Lone
Mountain dolomites. Except for the local carbonaceous
bodies, these magnesian carbonates are sparsely fossilif-
erous or completely barren.

FOSSILS OF THE RABBIT HILL LIMESTONE
AND BEACON PEAK DOLOMITE MEMBER
OF THE NEVADA FORMATION

Order TABULATA Edwards and Haime, 1850
Family FAVOSITIDAE Dana, 1346

Tabulate corals are the abundant and usually the
only colonial corals in the Early Devonian Rabbit Hill
Limestone. As limestone builders, the favositids con-
tributed much of the material in bioclastic facies, where
they are accompanied by the small solitary rugose
coral Syringaxon. Tabulates continue to predominate
in coralline facies to the early Middle Devonian beds
in the higher part of coral zone D, where colonial
Rugosa become fairly common. In Middle Devonian
coral zone F, colonial Rugosa outnumber Tabulata and
the favositids are no longer common in this region. The
local Devonian evolutionary peak of the Tabulata was
thus reached in argillaceous limestone facies of Nevada
Formation unit 2 and coral zone D, in which they out-
number Rugosa. As noted by earlier researchers in

506-612 0 - 73 - 4

 

corals the Paleozoic Tabulata throve better in muddy
seas than did colonial rugose corals, especially in turbid
bottom environments, where stromatoporoids are
absent. Similar argillaceous sediments are present as
interbeds in both Rabbit Hill Limestone and Nevada
unit 2. Tabulates are numerous in each case, and in
each the stromatoporoids are quite uncommon.

Three subfamilies of the Favositidae are present in
the Rabbit Hill Limestone: (1) Favositinae with the
genus Favosites; (2) Pachyporinae with Striatopora;
and (3) Micheliniinae with Pleurodictyum. Genera
that would be expected here, but have not been identi-
fied, are Emmonsia, Alveolites, Coenites, and Clado-
pora. There are no Heliolitidae or Syringoporinae in
the collections, and Halysitidae are absent.

Of special stratigraphic significance is the abundance
of Pleuro’dictyum of the P. lenticulare lineage; as noted
by several investigators, these corals characterize rocks
of about Helderbergian age in widely scattered parts of
the globe. Other and distinct Pleurodictyum lineages
occur in strata of Silurian age (Amsden, 1949, p. 100)
and range upward to the Middle Devonian (Fenton and
Fenton, 1936; Stumm, 1950, 1964). Neither Pleuro-
dictyum nor Striatopora have been recognized among
the abundant tabulate corals of Nevada unit 2 and coral
zone D.

Subiamily FAVOSITINAE Dana. 1846
Genus Favosites Lamurck, 1816

Favosites cl. 1". helderbergiae Hall
Plate 1, figures 16—19

The corallum of these massive favositids ranges from
large and globose or hemispherical more than 6 inches
in greatest diameter to elongate, digitate, and lobose.
Coralla with polygonal corallites 2—3 mm (millimeters)
Wide are distinguishable from those with small coral-
lites less than 2 mm. The wall is uniformly thin, a char-
acteristic of the genus; mural pores are moderately
large, disposed in either one or two vertical columns per
polygonal wall facet, have thickened rims, and may be
covered by a pore plate. Tabulae are usually rather
widely spaced, but in some coralla are closely set.
Septal spines are minute and very scarce. There are no
squamulae as in Emmonsia and certain species of the
Favosites alpenesis group of Swann (1947). Numerous
small reproductive offsets characterize some mature
coralla. These are usually but not always situated inter-
nally at wall facet junction angles.

At present there are no criteria by which these
Rabbit Hill massive favositids may be distinguished
from surficially similar species of Nevada unit 2 (coral
zone D). But available material of zone D Favosites
does not reveal the numerous reproductive offsets on
distal surfaces of mature coralla. Certain species of
Silurian Favosites like F. gothlandicus, the type species,

20 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

attain a uniformly much greater corallite width than
any of those in the Rabbit Hill or Nevada Formations.
Subiamily PACHYPORINAE Gerth. 1921

Genus Striatopora Hall. 1851 ‘
Striatopom cl. S. gwenensis Amsden

Plate 1, figures 1, 3—6
1963 S triatopora sp. cf. S. gwenensis Amsden. Merriam, p. 43.

Branching S triatopora with thick cylindrical coralla
tapering toward tips of branches. Septal ridges promi-
nent in polygonal calices. Corallite walls thickened
throughout by lamellar stereoplasm; greatly thickened
laterally around calices. Tabulae few and widely spaced,
visible in axial vicinity only, obscured by stereoplasm
peripherally. No mural pores or septal spines recognized.

Presence of large and small calices suggests corallite
dimorphism as recognized by Oliver (1966) for the type
species, S. flexuosa Hall. The type species appears to
be of more slender construction and internally the
“a-corallites” of Oliver (1966, p. 449) are much thinner
walled axially than in the Rabbit Hill species.

Associated with S triatopora in the Rabbit Hill Lime-
stone are slender ramose tabulates of similar external
appearance, but possessing thin walls, calices without
septal ridges, and large mural pores. Some of these
have an external holotheca covering calices of earlier
formed parts of a corallum.

Striatopora has not been recognized in Devonian
strata above the Rabbit Hill Helderbergian of the Great
Basin.

Sublumily MICHELINIINAE Waugen and Wentzel, 1886
Genus Pleurodictyum Goldiuss, 1329

Type species.——Pleurodictyum problematicum Gold-
fuss 1829. Lower Devonian, Coblenz and Eifel districts,
Germany. Known in the form of molds with supposed
worm tube in basal part.

Diagnosis.—Corallum round-ovoid transversely with
convex upper surface; base unevenly flattened, con-
cave or convex. Corallites large, radiating outward from
conical initial chamber, numbering from one to more
than 30, with thick hexagonal walls pierced by irregu-
larly spaced large communicating pores or canals. Walls
with as many as 36 rudimentary pseudosepta com-
posed of vertically arranged spines. Tabulae are usually
absent.

Remarks.—Like P. ploblematicum, the Lower Devo-
nian representatives of this genus are in part low,
laterally extended encrusting forms, the shape of whose
corallum base is more or less determined by the sub—
stratum. There are uncertainties about the structure
of problematicum because of its preservation as moulds.
Sardeson (1896, p. 292) interpreted this species as
lacking tabulae, but later workers (Stumm, 1950), p.
210; Hill and Stumm, 1956, p_. F466) regard Pleura-

 

dictyum broadly as having tabulae. Middle Devonian
large forms with numerous tabulae and radially elon-
gate corallites are assigned by some workers to M iche-
linia de Koninck 1841 (Sardeson, 1896, p. 294; Hill and
Stumm, 1956, p. F466). By others, Michelinia is
regarded as a synonym. According to Stumm (1964, p.
77—79), Pleurodictyum includes larger species with
abundant tabulae, and the genus is subdivided as two
subgenera; Pleurodictyum (Pleurodictyum) has walls
with strong septal ridges or spines and complete or
incomplete tabulae, and Pleurodictyum (Procteria)
Davis has smooth to faintly striate walls, cystose
tabellae in the larger species, and a thick papillose
peritheca. Some Middle Devonian forms such as “P.”
stylopora (Eaton?) from the Hamilton Group of North
America also are reported to have the tubular vermi-
form body of problematicum.

Simple species of Pleurodictyum having only a few
large corallites were present in the Silurian as repre-
sented by P. tennesseensis Amsden of the Brownsport
Formation (Amsden, 1949, p. 100, pl. XXIII, figs. 1—3).
Dunbar (1920, p. 118, pl. 1, figs. 5—7) has described P.
trifoliatum, another primitive more or less encrusting
species from the Lower Devonian Rockhouse Shale of
Tennessee.

If the new Rabbit Hill Helderbergian species Pleuro-
dictyum dunbari is correctly assigned generically, it
seems likely that these forms early developed two
growth habits, the low encrusting one like P. lenticulare
(Hall) of the New York Helderberg and the elongate
stalked form like P. dunbari, which appears to be
related to the Silurian P. tennesseensis and to the more
abbreviated trifoliatum.

Pleurodictyum nevudensis n. sp.
Plate 1, figures 7—12

1963 Michelinia sp., Merriam, p. 43.

Type material.—Holotype, USNM 159517; paratype
USNM 159518. Lower Devonian Rabbit Hill Lime-
stone, locality M404.

Diagnosis.—Pleurodictyum with large polygonal ra-
diating corallites having a deep calice. Base usually
shows conical apex of initial corallite and may be
flattened, convex, or concave. Pseudosepta, as many as
40, consist of longitudinal rows of close-set short spines.
Walls thick, pierced by large connecting pores in com-
mon wall of adjoining chambers, about 80 openings per
square centimeter. No tabulae, the deeper medial
calices extending almost to proximal (basal) wall.
Smaller newly added chambers near periphery.

Remarks.——-This form varies from encrusting indi-
viduals with roughly concave proximal surface and
thickened peritheca to erect forms with projecting

 

FAMILY LACCOPHYLLIDAE GRABAU 21

initial corallite and very deep calices. Larger encrusting
individuals have 36 corallites, but usually the erect
ones have many fewer.

Pleurodictyum nevadensis n. sp. resembles the Hel-
derbergian P. lenticularis (Hall). Hall’s figures (1887,
pl. III, figs. 1, 2, 3, 5) show large corallites that are
shallow with broad floor, not open nearly to the coral-
lum base as in P. nevadensis. It is not known whether
the broad corallite floor of lenticularis is actually a
tabula. Beecher’s (1893a, p. 211) studies of the devel-
opment of lenticularis imply that this primitive species
is nontabulate.

Occurrence—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality
M409. Dobbin Summit, Monitor Range, locality M1309
(cf.). Petes Canyon, Toquima Range, locality M1150
(cf.). Walti Ranch, Simpson Park Range, locality
M1074 (cf.). Mount Tenabo, Cortez Mountains,
locality M1083.

Pleurodictyum dunbari n. sp.
Plate 1, figures 13—15

1963 Pleurodictyum cf. P. trifoliatum Dunbar. Merriam, p. 43.

Type material.—Holotype, USNM 159522; paratype
USNM 159523. Lower Devonian Rabbit Hill Lime-
stone, locality M409.

Diagnosis.—Stalked, elongate, simply branching
Pleurodictyum with one to six thick-walled large coral-
lites with deep calice, a central calicinal boss, and about
22 prominent pseudosepta composed of longitudinally
alined spines. Peritheca thick, with a basal expanded
pedal attachment.

Remarks.—The mural pores are large and serve to
establish this aberrant form as a tabulate coral. A
transverse thin section of the stalk 1 cm above the
basal attachment shows parts of five closely appressed
thick-walled corallites; these have about 12 thick
pseudosepta or septal spines, some of which reach the
center and are for the most part laterally in contact.

The thick main stalk with expanded apical (or basal)
attachment appears to be that of the initial corallite
from which the others have budded off, more or less in
the manner described by Beecher for Pleurodictyum
lenticulare (Hall) (1893a, p. 207—212, pls. 9—13), but
after the primary corallite attained large size and was
growing erectly from its apical attachment disc. A
silicified specimen reveals no trace of tabulae in longi-
tudinal section. of the stalk, but these structures could
have been destroyed by the silicification.

Pleurodictyum trifoliatum Dunbar (1920, p. 118, pl.
1, figs. 5—7) of the Lower Devonian Rockhouse Shale
in Tennessee lacks the stalk and is an encrusting form,
but is otherwise similar to P. dunbari n. sp.; somewhat

 

closer perhaps is P. tennesseensis Amsden (1949, p.
100, pl. XXIII, figs. 1—3) of the Silurian Brownsport
Formation, which is erect but lacks the elongate stalk.

Occurrence—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.

Order RUGOSA Edwards and Haime. 1850
Family LACCOPHYLLIDAE Grabau, 1928

Reference form—Syringaxon siluriensis (McCoy),
1850.

Small solitary trochoid to subcylindrical rugose
corals with very deep calice, straight, smooth lamellar
septa, a narrow septal stereozone, and tubular stereo-
plasmic aulos. Tabulae partly complete, very strongly
uparched; nearly flat within aulos, steeply inclined
peripherally. No dissepiments.

These nondissepimented, but otherwise specialized
corals are distinguished by the strong inner ring pro-
duced by swelling of septal tips and commonly rather
heavy addition of extraneous stereoplasm. Arching of
tabulae is pronounced. The Laccophyllidae occur in
the Silurian and Devonian, wherein they may be abun-
dant in a facies lacking other Rugosa. Nearly identical
small corals like Permia, reappearing in the Carbonif-
erous, may be homeomorphic (Hudson, 1944, p. 360;
Flfigel and Free, 1962, p. 232). Somewhat less conver-
gent are the Permian Polycoeliidae as revised by
Schindewolf (1942, p. 55).

Syringaxon, the only member of this family recog-
nized in the Great Basin, is the characterizing rugose
coral of the Helderberg (Early Devonian) Syringaxon
facies.

Genus Syringaxon Lindstréim. 1882

1882
1900
1902

S yringaxon Lindstro'm, p. 20.

Laccophyllum Simpson, p. 201.

N icholsonia Pocta, p. 184. Cited in plate explanations as
Alleynia (Nicholsonia).

Laccophyllum Simpson. Grabau, p. 82.

Alleynia Poéta AN icholsonia Poéta). Grabau, p. 82

Syringaxon Lindstrom. Butler, p. 117.

Syringaxon Lindstrom (in part). Prantl, p. 21.

S yringaxon Lindstrom. Lang, Smith, and Thomas, p. 129.

Syringaxon Lindstrom. Stumm, p. 10.

Syringaxon Lindstro'm. Hill, p. F258.

Syringaxon Lindstriim (in part). Fliigel and Free, p. 224.

1928
1928
1935
1938
1940
1949
1956
1962

Type species.—By monotypy, Cyathaxonia silurien-
sis McCoy, 1850 (p. 281); Silurian, upper Ludlow,
Underbarrow, Kendal, Westmorland, England. Accord-
ing to Butler (1935, p. 118) and Lang, Smith, and
Thomas (1940, p. 129), Lindstrom, in naming the
genus, gave no diagnosis, merely using McCoy’s species
siluriensis under the new generic name Syringaxon in
his faunal lists of the Gotland Silurian (Lindstrom,
1882,p. 20). .

 

 

22 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

Diagnosis.—Small, solitary turbinate and ceratoid
to cylindrical rugose corals with deep calice and lacking
dissepiments. Axial ends of major septa dilated and
laterally in contact to form an aulos. Tabulae strongly
uparched distally, the aulos dividing them into inner
flat or slightly sagging segments and outer segments
that descend steeply to meet the outer wall (Fliigel
and Free, 1962, fig. 3); tabulae either continuous from
wall to wall through aulos stereozone, terminating
Within the aulos or abutting proximally as tabellae
against adjacent tabulae. Stereome usually abundant
as aulos thickening and general thickening or filling in
brephic and neanic growth stages. Narrow fossulae
commonly reveal quadrants in late neanic growth stages.

Remarks.—The genus Laccophyllrrm was proposed
by Simpson (1900, p. 201) with L. acuminatum Simp-
son from the Niagaran of Tennessee as type species.
Butler’s exhaustive study ( 1935) fixed McCoy’s ( 1850,
p. 281) “Cyathaxonia siluriensis” as the type species of
Syringaxon Lindstrém, following which Lang, Smith,
and Thomas (1940, p. 129) concluded that the holo-
type of Laccophyllum acuminatum Simpson is assign-
able to Syringaxon, making Laccophyllum Simpson a
synonym of Syringaxon Lindstrom.

Alleynia Poéta or Alleynia (Nicholsonia) Poéta
(Lang and others, 1940, p. 15, 129) appears to be cor-
rectly interpreted as a synonym of Syringaxon.

Barrandeophyllum Poéta (1902, p. 190) resembles
Syringaxon. According to Prantl (1938, p. 34), who
studied Pocta’s cotypes of Barrandeophyllum per-
plexum the type species, this genus is closely related to
Syringaxon. Barrandeophyllum is distinguished by
irregularities of the aulos, usually elliptical in trans-
verse section, and by a sparing development of dissepi-
ments. Stereoplasm is always present, though not
abundant. The type species of Barrandeophyllum is
reported from the Early Devonian Branik Limestone of
Bohemia. Syringaxon ranges from the Tennessee Niag-
aran through strata of Early Devonian (Helderberg)
age in western North America and is reported in the
Late Devonian Independence Shale of Iowa (Stain-
brook, 1946, p. 402).

As noted by Hudson (1944, p. 360), small, rather
simple corals resembling Syringaxon range upward to
the Carboniferous, where they are represented by
Permia Stuckenberg. According to Hudson, Permia
and Syringaxon are homeomorphs.

Small solitary corals resembling Syringaxon occur in
the Silurian part of the Hidden Valley Dolomite of the
northern Panamint Mountains (McAllister, 1952, p.
15—17). Following the great proliferation of this genus
in the Helderbergian of the Great Basin, it virtually
disappeared from this region; scarce and fragmentary
specimens that may belong either in Syringaxon or

 

Barrandeophyllum have been found in Nevada Forma-
tion unit 2 at Lone Mountain.

Syringaxon ioerstei n. sp.
Plate 2, figures 1—10
1963 Syringaxon acuminatum (Simpson). Merriam, p. 43.

Type material.—-Holotype, USNM 159243; figured
paratypes, USNM 159245—159250. Rabbit Hill Lime-
stone, Early Devonian, Central Great Basin, Monitor
Range.

Diagnosis.—Syringaxon having a very deep calice,
thick wall, prominent longitudinal grooves externally
and on interior of calice wall, and a high septal count
for this genus. Cardinal and alar septa differentiated in
neanic stages.

External features.—Corallum large for the genus,
attaining a length exceeding 30 mm and greatest dia-
meter of 27 mm at edge of calice; average length about
19 mm with maximum diameter 16 mm (see table).
Calice very deep, in large individuals 16 mm, or more
than half the corallum length. Average specimen
trochoid; ceratoid individuals fairly common; turbinate
and nearly cylindrical individuals uncommon. Septal
grooves sharply defined and distinctly pinnate with
reference to the primary septa. Rugae weakly defined
or absent, rarely prominent. Occasional individuals
with talons or attachment surface at apex. Septa
extend distally as low subequal ridges on inside of
calice, rarely becoming obsolete. Aulos defined as ring-
shaped boss at bottom of calice in many individuals; in
other specimens the aulos is ill defined and narrow
fossulae may outline quadrants made by the primary
septa.

Transverse sections.—Mature sections show from
26 to more than 30 major septa extending three-fourths
of the distance to the axis. Minor septa normally pres-
ent, but in some individuals not recognized at matu-
rity; these septa range from mere stubs to one-third
the length of major septa; in some instances, they are
buried within the peripheral stereoplasm. Septa usually

Syringaxon (foerstei) n. sp.
Table of measurements (in mm)

 

Holotype
USN M
1592 43
Paratype
USNM
159244
Paratype
USNM
159246
Paratype
USNM
159248
Figured
specimen
USN M
159352

 

Restored corallum
length
Calice depth ........ 16
Outside diameter
at calice
bottom .............. 12
Number of major
septa at calice
bottom .............. 28
Ephebic section:
Diameter .......... 9.5 13 15.6
Major septa 26 24 26

N
H
WK]

H
E"
01

N
A

 

 

 

 

n

FAMILY ENDOPHYLLIDAE TORLEY 23

dilated toward tips, laterally in contact and reinforCed
by stereoplasm to produce an aulos. Entire septum may
be somewhat dilated. Individuals with poorly defined
aulos show pairs of contiguous septa meeting axially
like a tuning fork, the merged segments continuing
toward axis; they may reveal quadrate transverse sym-
metry. The peripheral stereozone may exceed 1 mm,
but it is usually not as thick as the aulos. Amount of
stereoplasm varies considerably; some early ephebic
sections show entire aulos filled with this material.
Appearance of false dissepiments may result from sec-
tion cutting bulbous distal inflations of tabulae between
aulos and outer wall.

Longitudinal sections.—Outer segments of tabulae
descend steeply, with upward inflection before meeting
the stereozone. Some complete tabulae are vague
within the aulos; others are traceable completely
across. Aulos segments of tabulae may be thickened
stereoplasmically. In some individuals complete tab-
ulae have M-shape curvature with near-vertical outer
segments. Tabular spacing nonuniform, usually fairly
wide.

Comparison with related forms.——Butler’s (1935)
figures of Syringaxon siluriensis (McCoy) show a
maturely cerioid to subcylindrical form with fewer
septa and poorly developed minor septa. S. foerstei
includes externally similar subcylindrical variants, but
the norm is a trochoid corallum. Both species are
inclined to have heavy stereoplasmic deposits in the
aulos and a wide septal stereozone. Of several species
figured by Prantl (1938) from the Devonian of Czecho-
slovakia, most have a lower septal count and elongate
subcylindrical coralla. Species described from the
Greifensteiner Kalk (Eifelian) of Germany by Fliigel
and Free (1962) have a weaker aulos and less arching
of tabulae.

Occurrence—Rabbit Hill Limestone of Helderberg
(Early Devonian) age; Devonian coral zone A. North-
ern Monitor Range, Rabbit Hill vicinity, localities M48,
M49, M187. Middle part of the Monitor Range, Dobbin
Summit area, localities M1067, M1068, M1069. North-
ern Simpson Park Range: Walti Hot Springs area,
locality M1074; Coal Canyon area, localities M1032,
M1075, M1076. Cortez Mountains, Mount Tenabo
area, locality M1083.

Beacon Peak Dolomite Member of Helderberg (Early
Devonian) age, Devonian coral zone A. Southern Sul-
phur Spring Range, localities M186, M197, M1081,
M1082.

Family STREPTELASMATIDAE Nicholson, 1889

Genus Siphonophrentis O’Connell, 1914
Siphonophrentis sp. B

Plate 8, figures 1—3
Fragrnentary specimens of a nondissepimented coral

 

 

 

 

provisionally placed in Siphonophrentis were collected
from the Beacon Peak Dolomite Member in the south-
ern Sulphur Spring Range. A silicified individual with
restored corallum length of about 45 mm and greatest
diameter of 32 mm has about 60 straight, tapering
septa of medium length, poorly differentiated as major
and minor. An indefinite fossula lies on the convex side
of the corallum. The septal stereozone is narrow.

A smaller individual, possibly the tip of the above
described larger corallum, has short septa, a narrow
peripheral stereozone and rather close-set tabulae,
part of which are complete. Large elongate tabellae are
present peripherally.

Occurrence—Southern Sulphur Spring Range, local-
ity M186. Beacon Peak Dolomite Member of the
Nevada Formation, in Devonian coral zone A with a
Rabbit Hill Early Devonian (Helderbergian) fauna.

Family ENDOPHYLLIDAE Torley. 1933

Reference forms.—Endophyllum bowerbanki Ed-
wards and Haime and E. abditum Edwards and Haime,
1851. Devonian, Torquay, England.

Cerioid and aphroid rugose corals with wide coral-
lites, a broad marginarium of partly large lonsdaleioid
dissepiments and a narrow to very wide tabularium
comprising closely spaced tabulae. No axial structure.

Genera assigned to the Endophyllidae are:
Endophyllum Edwards and Haime, 1851
Yassia Jones, 1930
Australophyllum Stumm, 1949
Undescribed Late Silurian corals of the Klamath
Mountains, Calif, and the Great Basin also belong in
this family. These include an unnamed subgenus of
Australophyllum characterizing Great Basin Silurian
coral zone E and an unnamed genus related to Aus tralo-
phyllum in the Silurian Gazelle Formation of the
Northeast Klamath Mountains.

Certain corals here regarded as Endophyllidae have
previously been assigned to Spongophyllum, a homeo-
morphic genus not included in this family. It is pro-
posed that the term Spongophyllum be applied only to
species with slender corallites agreeing in general struc-
ture and proportions with the Devonian S. sedgwicki as
originally illustrated by Edwards and Haime ( 1853, pl.
56, figs. 2, 2a—c, 2e).

In addition to the wide lonsdaleioid marginarium,
Late Silurian representatives of Yassia and the unde-
scribed subgenus of Australophyllum manifest a decided
tendency to abbreviate and lose septa in mature growth
stages, characteristics not observed in Spongophyllum.

Genus Australophyllum Stumm, 1949
1911 Spongophyllum cyathophylloides Etheridge, p. 7—8, pl.
A, fig. 3, pl. C, figs. 1—2.
1949 Australophyllum Stumm, p. 34, pl. 16, figs. 1—2.

 

 

24 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

1956 (?)Australophyllum cyathophylloides (Etheridge). Hill,
fig. 207—4a—b.

Type species. — Spongophyllum cyathophylloides
Etheridge, by author designation. “Lower Middle
Devonian”; Douglas Creek, Clermont, Queensland,
Australia.

Diagnosis.——Cerioid Endophyllidae with medium
Wide to narrow, closely spaced, proximally sagging
tabulae and wide to very wide dissepimentarium com-
prising scattered to wholly lonsdaleioid dissepiments,
some large.

Remarks.——Australophyllum differs from Sponge-
phyllum by having multiple columns of elongate, lons-
daleioid dissepiments and more closely spaced sagging
tabulae without peripheral depression. Stumm’s diag-
nosis of Australophyllum includes carinate septa,
although his figures do not reveal these convincingly.
The wall of typical Australophyllum is thickened
stereoplasmically; septal crests do not appear to be
characteristic, as in the undescribed Silurian subgenus.

Australophyllum landerensis n. sp.
Plate 9, figures 3—6

Diagnosis .—Austral0phyllum with long minor septa,
all septa thickened in tabularium and outer dissepi-
ments steeply inclined for the genus; outer wall thick-
ened and beaded with wall crests. Tabularium medium
wide; close-set tabulae with pronounced sag.

External features—Occurs in compact cerioid heads
6 inches or more in diameter.

Transverse sections—Septa about 44, all of which
are long and usually thickened within the tabularium;
minor septa are more than one-half the length of major
septa. Some major septa reach the axis, Where they are
twisted. Septa may be minutely wavy, and where
thickened show minute nodes and lateral bumps, but
no true elbow carinae. Stereome-thickened wall with
beaded appearance because of wall crests; other septal
crests sparse in lonsdaleioid band.

Longitudinal sections .—Tabularium about one-third
the corallite width at maturity, very sharply set off
from dissepimentarium. Tabulae 4 or 5 per millimeter,
with pronounced sag that may be angulate axially.
Large outer dissepiments steep for this genus, the
smaller ones becoming vertical at tabularium margin.
Dissepiment columns range from 7 to 12. Thickened
axial segments of major septa reveal minute lateral
bumps.

Reproductive ofisets.—One mature corallite shows
three calice wall offsets internally situated.

Fine structure—Thickened septa may have a
median clear trace; trabecular structure and lamina-
tion ill defined in septal stereozone.

Comparison with related forms.-—Australophyllum

 

cyathophylloides, the type species, differs by having
fewer septa that lack thickening in the tabularium.
Australophyllum sp. v from the upper part of the
Vaughn Gulch Limestone, Owens Valley, Calif.,
resembles Australophyllum landerensis, but lacks
thickened septa; Australophyllum sp. v occurs in beds
of possible Early Devonian age immediately above Late
Silurian coral zone E, which contains a different sub-
genus of Australophyllum. The coral zone E subgenus
has broader mature corallites with a considerably
smaller septal count and lacks septal thickening; this
form has outer lonsdaleioid dissepiments inclined at
a low angle, a greater number of very large dissepi-
ments, and, unlike A. landerensis, tends to reduce and
lose septa at maturity. .

Measurements.—Mature corallite diameter and
major septum count:

Holotype Paratype
USNM 159353 USNM 159354
corallites corallites
A B C A B
Diameter (in mm) ........ 13 14 10 13 10
Major septa .................... 22 22 22 20 22

Occurrence—Lower Devonian Rabbit Hill Lime-
stone, Petes Canyon, locality M1150 at north end of
Toquima Range, southern Lander County. At locality
M1150 this colonial coral is associated with a typical
Rabbit Hill fauna like that of the type locality. Colonial
corals of this kind are uncommon in the Rabbit Hill,
which usually contains only the small solitary rugose
coral Syringaxon.

Australophyllum stevensi n. sp.
Plate 9, figures 8—13

Type material.——Holotype, USNM 165349; Sunday
Canyon Formation, locality M1401.

Diagnosis.—Australophyllum with few lonsdaleioid
dissepiments, many small dissepiments, septal thicken-
ing in tabularium moderate and nonuniform. Minute
septal spines present.

Transverse thin sections.—Septal count about 42 in
a corallite of 13 mm diameter; longer septa minutely
wavy and twisted near axis. Minor septa two-thirds
length of major septa. Carinae absent. Septa moder-
ately to slightly thickened in tabularium and innermost
dissepimentarium of parts of some corallites. Wall mod-
erately thickened stereoplasmically. Lonsdaleioid septa
present in some corallites, where they are irregular and
confined to small segments.

Longitudinal thin sections.—-Tabularium medium
wide to wide; tabulae close spaced and sagging. Dis-
sepiments mostly small, with as many as eight columns
on each side, many steeply inclined. Minute septal
spines scattered.

 

FAMILY RHIPILOMELLIDAE SCHUCHERT 25

Comparison with related forms.—Australophyllum
stevensi differs from A. landerensis by having fewer and
less uniformly developed lonsdaleioid dissepiments, a
less thickened wall, and less extensive septal thicken-
ing. The minute septal spines of A. stevensi were not
observed in A. landerensis. Australophyllum sp. v of the
higher Vaughn Gulch Limestone differs by having
unthickened septa and a somewhat more uniform pat-
tern of lonsdaleioid dissepiments.

Occurrence—Sunday Canyon Formation (Ross,
1966, p. 32), Mazourka Canyon area, northern Inyo
Mountains, Calif., locality M1401, east side of Al Rose
Canyon. The Sunday Canyon Formation as demon-
strated by Ross passes southward into the Vaughn
Gulch Limestone. A. stevensi came from beds that may
be of Early Devonian age about 40 feet stratigraphi-
cally below the top of the Sunday Canyon.

Study material is part of a single large corallum.

Australophyllum sp. v
. Plate 9, figure 7

Australophyllum sp. v. represented by a fragmentary
corallum from the upper part of the Vaughn Gulch
Limestone of the northern Inyo Mountains, Calif.,
shares some features of A. landerensis of the Rabbit
Hill and some characteristics of A. stevensi of the Sun-
day Canyon Formation.

Australophyllum sp. v has the thickened wall of A.
landerensis, but its septa are unthickened. The lons-
daleioid band is somewhat better developed than in A.
stevensi, and its septa are peripherally discontinuous
as septal crests.

Occurrence—Upper part of the Vaughn Gulch Lime-
stone, Mazourka Canyon area, northern Inyo Moun-
tains, Calif., locality M1093. The Vaughn Gulch Lime-
stone (Ross, 1966, p. 30) is largely Silurian, but its
upper unit is possibly of Early Devonian age like the
upper part of the Sunday Canyon Formation, which
passes laterally into the Vaughn Gulch beds. Late
Silurian limestones of coral zone E underlie the beds
that yielded Aus tralophyllum sp. v.

Family DISPHYLLIDAE Hill, 1939

Genus Billingsastraea Grabau, 1917
Billingsastraea sp. :11

Plate 9, figures 1, 2

Figured material.—Specimen USNM 165350; south-
ern Tuscarora Mountains, Maggie Creek, locality
M1400.

Diagnosis.—Billingsastraea with unusually small
corallites for the genus and smooth uniformly unthick-
ened septa.

Transverse thin sections.-—Septal count about 35 in
a corallite of 71/2 mm diameter; septa smooth, uniform
and unthickened, the major septa extending to axis;

 

minor septa more than three-fourths length of major
septa. Septa slightly wavy only in tabularium. Small
dissepiments crowded at inner edge of dissepimen-
tarium. ‘

Longitudinal thin section—Only available section
does not pass through tabularium. Some flat dissepi-
ments very elongate.

Comparison with related forms.——Corallites of this
species are about one-half the width of those of B.
nevadensis (Stumm) and B. affinis (Billings), both of
which have a larger septal count and minutely wavy
septa with small zigzag carinae not present in Billings-
astraea sp. m.

Occurrence—South end of the Tuscarora Moun-
tains, locality M1400 near Maggie Creek northwest of
Carlin. This coral is associated with a Rabbit Hill
Early Devonian fauna, and appears to be the oldest
known occurrence of Billingsastraea.

Phylum BRACHIOPODA Dumeril. 1807
Class ARTICULATA Huxley, 1869
Order ORTHIDA Schucherl and Cooper, 1932

Family RHIPIDOMELLIDAE Schuchert, 1913
Genus Rhipidomella Oehlert, 1890

1958 Rhipidomelloides Boucot and Amsden, p. 165, pl. XII,
figs. 5—9, pl. XIV, figs. 10—11, text figs. 9, 42.

The Rabbit Hill brachiopods placed in Rhipidomella
are most similar to species previously classified by
Boucot and Amsden (1958) as “Rhipidomelloides,” a
genus later placed in synonymy (Williams and Wright,
1965, p. 341).

Rhipidomella rossi n. sp.
Plate 4, figures 15—24
1963 Dalmanella sp. (small form); Merriam, p. 43.

Type material.—Holotype, USNM 159556; para-
types, USNM 159555, 159557—159561. Rabbit Hill
Limestone, locality M409.

Diagnosis.—Orthoid brachiopods with dorsal and
ventral valves about equally convex, rectimarginate;
dorsal valve Without sulcus. Ventral valve muscle field
moderately large, ovoid—fan-shaped, and lacking the
radial myophragms of some Rhipidomella. Dorsal valve
with stout brachiophores and large thickened cardinal
process.

Exterior.—Outline ovoidal to subcircular. Hinge line
about one-half maximum width of shell. Pedicle valve
interarea curved, concave, slightly apsacline, much
longer than dorsal valve interarea. Delthyrium large
and open. Both valves flattened toward commisure;
without trace of sulcus or fold. Fine radial ribs split
anteriorly.

Pedicle valve interior.—Delthyrial cavity large and
deep; teeth large, supported by abbreviated but stout
dental plates. The muscle field is bilobed, rounded
anteriorly, and has a median septum which is promi-

I

26 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

nent anteriorly at the union of the two large crescentic
diductor scars and faint or nonexistent posteriorly
between the adductors. The more or less heart-shaped
combined adductor areas are relatively large for the
genus. Radiating myOphragms that divide the muscle
field of some Rhipidomella species were unrecognized.
No pallial markings were observed. Crenulations at
internal shell margin reported (Boucot and Amsden,
1958, p. 165, 168) to characterize “Rhipidomelloides”
are too poorly preserved for meaningful comment.
Where recognizable on the silicified shells, they are
more suggestive of those of Rhipidomella than those of
rectangular cross section in “Rhipidomelloides.”

Brachial valve interior.—Median ridge varies from
very heavy to rather faint; extends to middle of valve.
Transverse ridge separating anterior from posterior
adductor scars well defined to faint; anterior scar is
larger. Stout shaft of cardinal process simple, may be
constricted beneath myophore that has one to several
tubercles.

‘ Comparison with related forms.—Rhipidomella
rossi appears to be related to both R. oblata (Hall) of
the Haragan Limestone and R. henryhousensis Ams-
den of the Henryhouse Formation (Boucot and
Amsden, 1958, pl. II, figs. 1—16; p1. XII, figs. 1—9; p1.
XIV, figs. 10—11). R. rossi seems to be more nearly
equivalved in transverse profile than oblata; the bra-
chiophores and cardinal process of henryhousensis are
less stout. Some specimens of oblata have well-defined
radiating myophragms in the ventral-valve muscle field
not noted in rossi, and the cardinalia of oblata are less
heavy.

Occurrence—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.

Family DALMANELLIDAE Schuchert, 1913
Genus Levenea Schuchert and Cooper, 1931

1931 Levenea Schuchert and Cooper, p. 246,
1932 Levenea Schuchert and Cooper, p. 123, pl. 18, figs. 19-23.,
25—32.

Type species.—0rthis subcarinata Hall, 1857 (by
author designation). Early Devonian (Helderbergian);
New York and Tennessee.

Diagnosis.—Dalmanellid brachiopods with subcircu-
lar outline, hinge line narrower than greatest width,
ventral interarea longer than dorsal; delthyrial cavity
of ventral valve deep, dental plates thickened on inside
to form fossette, diductor tracks deeply impressed.
Cardinal process prominent with lobate myophore;
adductor field or dorsal valve subcircular, or elliptical.

This genus, though reported from the Silurian, is
especially characteristic of the Early Devonian (Held-
erberg) rocks.

 

Levenea subcarinata subsp. antelopensis n. subsp.
Plate 4, figures 1—14
1963 Levenea n. sp. cf. L. subcarinata (Hall). Merriam, p. 43.

Type material.—-Holotype, USNM 159547; para-
types, USNM 159548, 159551, 159552, locality M409.
Paratypes, USNM 159549, 159550, locality M186.
Paratype, USNM 159553, locality M1309. Paratype,
USNM 159554, locality M1312. Rabbit Hill Limestone
and Beacon Peak Dolomite Member of the Nevada
Formation.

Diagnosis.—Large unequally biconvex Levenea with
well-defined brachial valve sulcus and medially sub—
carinate pedicle valve. Brachiophore blades thick.
Adductor scars of brachial valve large and deeply
impressed on shelly platform with medial ridge. Cardi-
nal process elongate and narrow to large with swollen
bifid termination at myophore.

Pedicle valve interior.—Delthyrial cavity deep;
diductor tracks deeply impressed in thickened shell
platform and separated by a wide flat-topped ridge
which may have a median groove. Diductor and adjus-
tor scars not differentiated. Teeth stout; dental plates
short and merging with anteriorly projecting wall of
delthyrial cavity. Dental plates may be thickened on
medial side above umbonally directed grooves in wall
of delthyrial cavity. Large rounded pit may develop
just anterior to muscle platform. Pallial markings not
well defined.

Brachial valve interior.—The large subquadrate,
quadripartite muscle field is sharply impressed in a
thickened shelly platform having prominent raised
rim; the median dividing ridge is usually stout and
rounded from the cardinal process shaft through the
posterior adductor pair, becoming more narrowly cari-
nate anteriorly. Brachiophores are thick blades joining
the raised outer muscle field rim dorsally. Sockets deep
and rounded. In some individuals there is a weakly
defined transverse lateral groove, the prolongation of
that between anterior and posterior adductor scars.

External features.—Subcarinate pedicle valve much
more deeply convex than sulcate brachial valve in this
biconvex shell. Valves ornamented by fine, close-set,
more or less equal radial costellae that split anteriorly.
Outline subrounded in commissure plane, greatest
width anterior to hinge line.

Comparison with related forms—Within its varia-
tion range, subsp. antelopensis includes individuals
whose brachial interior features may be matched
closely With those of typical subcarinata as figured by
Schuchert and Cooper (1932, pl. 18, figs. 19, 25, 31, 32) ,
and in general the new subspecies is morphologically
quite similar to the eastern Helderberg species. Typi-

 

FAMILY STROPHEODONTIDAE CASTER 27

cal subcarinata, unlike subsp. antelopensis, seemingly
does not have a marked tendency toward bifurcation of
the cardinal process, whereas antelopensis lacks the
secondary shaft of the cardinal process over the median
ridge (Schuchert and Cooper, 1932, p. 124) shown by
subcarinata s.s.

Occurrence—Early Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.
Dobbin Summit, Monitor Range, localities M1309,
M1311. Petes Canyon area, Toquima Range, locality
M1150. Coal Canyon, Simpson Park Range, locality
M1075. Early Devonian Beacon Peak Dolomite Mem-
ber. Southern Sulphur Spring Range, localities M186,
M197, M1312.

Family ORTHIDAE Woodward. 1852

Genus Orthostrophia Hall, 1883
Orthostrophia strophomenoides subsp. newberryi n. subsp.

Plate 3, figures 4, 5; plate 8, figures 6—9
1963 Orthostrophia sp. cf. 0. strophomenoides (Hall), Mer-
riam, p. 43.

Type material.—Holotype, USNM 159540; para-
types, USNM 159616, 159617. Rabbit Hill Limestone,
locality M409.

Diagnosis.—Orthostrophia of the strophomenoides
(Hall) type, large for the genus, with transverse out-
line, ventral fold, and dorsal sulcus. Sulcus well devel-
oped on posterior half only, becoming obsolete toward
the commissure in mature shells. Strength of radial
ornamentation medium to coarse for the genus. Dental
plates abbreviated as anterolateral rims of delthyrial
cavity.

External features.—Shell with biconvex lateral pro-
file; outline transverse-subquadrate. Hinge line wide
and straight. Ventral interarea apsacline, longer than
dorsal interarea, which is orthocline. Ornamentation
multicostellate with heavier radial ribs rather coarse
for the genus (5—7 ribs within 6 mm on mature part).
Concentric incremental ridges widely spaced and rather
subdued.

Pedicle valve interior.—Muscle field small, of tri-
angular outline, deeply impressed and terminating
anteriorly as an elevated shelf. The dental larnellae
develop as abbreviated anterolateral rims of the delthy-
rial cavity. Pallial markings and margins of adductor
and diductor scars indefinite on available silicified
specimens.

Brachial valve interior.—Brachiophores moderately
thick at edge of wide and fairly deep notothyrial cavity.
Sockets small. Cardinal process simple, swelling anter-
iorly to merge with prominent rounded medial ridge
that divides the muscle field. Adductor muscle scars
deeply impressed on a raised shelly platform. Trans-
verse ridges separating anterior from posterior adduc-

506-612 0 » '7': l :

 

tor scars weakly developed. Pallial markings poorly
shown.

Comparison with related forms.—Orthostrophia
strophomenoides newberryi resembles 0. strophomen-
oides (Hall) quite closely, judged by the illustrations
of Schuchert and Cooper (1932, p. 70—7 1, pl. 6, figs. 22,
24, 25, 27, 28) and of Hall and Clarke (1892, pt. 1, p1.
V, figs. 24—27). The hinge plate and brachial valve
muscle scar features are similar, but the available speci-
mens of newberryi do not reveal the strong pallial
markings of typical strophomenoides and the costellae
of newberryi seem on the whole slightly heavier.

Orthostrophia strophomenoides subsp. parva Ams-
den (1958a, p. 41—45, pl. 1, figs. 22—32) seems to be a
smaller subspecies, with somewhat less coarse radial
costellae than subsp. newberryi. Amsden’s illustrations
( 1958a, pl. 1, fig. 30, 31, 32) show a better separation of
anterior from posterior adductor scars of the brachial
valve than in newberryi and strongly developed vascu-
lar markings not known in the new species, possibly
because of preservation by silicification.

Occurrence—Early Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.

Order STROPHOMENIDA 6pik. 1934
Family STROPHEODONTIDAE Caster, 1939

Genus Leptosirophia Hall and Clarke. 1892
Leptostrophia sp. cf. L. becki tennesseensis Dunbar

Plate 3, figures 1—3; plate 8, figure 5

Fragmentary ventral valves of this genus from the
Rabbit Hill type section reveal interior details and sur-
face ornamentation. Ventral interiors have large tri-
angular diductor scars with bounding lateral ridges;
the ventral process is large and where widest shows a
median groove. Externally the ventral valve is slightly
convex near the umbo, flattening laterally and anter-
iorly. The surface is finely costellate, with about eleven
costellae per width of 5 mm. Concentric rugae weak,
recognizable only about halfway between umbo and
shell perimeter.

The Rabbit Hill shells resemble specimens from the
Bois d’Arc Limestone of Oklahoma and from the Bird-
song Shale of Tennessee referred by Amsden (1958a,
p. 78—80; pl. 3, figs. 15—20; pl. 6, fig. 1; pl. 11, figs. 27,
28) to this subspecies. Those illustrated by Amsden are
much less strongly rugate concentrically than the pos-
sibly aberrant representative of tennesseensis described
and figured by Dunbar (1920, p. 129, pl'. 3, fig. 18).

The Rabbit Hill Leptostrophia resembles more com-
pletely an undescribed species from the lower part of
the Nevada Formation (unit 1), where it occurs in
post-Rabbit Hill beds of Oriskany age. This form has
a less expanded ventral process with a less conspicuous
median groove.

28 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

Occurrence.-—-Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.
Dobbin Summit, Monitor Range, locality M1309.

Genus Pholidostrophia Hall and Clarke. 1892
(7)Pholidostrophia sp. R

Plate 3, figures 6, 7

This distinctive, possibly aberrant, stropheodont is
represented in the collections by a single silicified
pedicle valve. The outer surface is smooth and without
pseudonacreous texture, probably because of replace-
ment by siliceous matter. This valve is deeply convex,
with greatest width near hinge line; interarea wide,
short, orthocline, and denticulate. The poorly preserved
pseudodeltidium is thick, largely closing the delthy-
rium, and probably had a median fold.

The muscle field is rather deeply impressed; the large
fan-shaped diductor scars, unlike normal Pholido-
strophia, have strong lateral bounding ridges. Cardinal
process receiving pits are large and deep, suggesting
that the cardinal process of the brachial was thick. A
long ventral process is split by a median groove
throughout, this groove extending almost to the ante-
rior shell margin. Adductor scars unusually large and
oval. Pseudoteeth present.

This form differs markedly from normal Pholidostro-
phia by having diductor scar bounding ridges and a
very elongate median groove of the ventral process. It
may represent a distinct genus, but fuller characteriza-
tion must await collecting of more material.

0ccurrence.—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.

Genus Strophonella Hall, 1879
Strophonella cf. S. punctuliiera (Conrad)

Plate 3, figures 10, 11

A large S trophonella with exterior features inter-
mediate between S. punctulifera and S. bransoni Ams-
den occurs at several localities in the southern Sulphur
Spring Mountains in association with Rabbit Hill Hel-
derberg species. The resupinate curvature is within the
range of that illustrated by Amsden (1958a, p. 70) for
bransoni, but the radial ornamentation is perhaps more
like that of the New York Helderberg punctulifera
(Hall and Clarke, 1892, pl. XII, fig. 10), which reveals
finer costellae than the Haragan species bransoni.

Strophonella has been recognized only in the Lower
Devonian of Nevada, Where two other forms occur in
Nevada Formation, unit 1; of these, one occurs in the
Oriskany age beds of coral zone B and another slightly
higher in the beds of coral zone C together with Papilio-
phyllum and Acrospirifer kobehana.

This genus was not found in limestone facies of the
typical Rabbit Hill Limestone.

Occurrence—Lower Devonian, Beacon Peak Dolo-

 

mite Member of the Nevada Formation. Southern Sul-
phur Spring Range, localities M186, M197, M1081.
Family LEPTAENIDAE Hall and Clarke. 1894

Genus Leptaena Dalman. 1828
Leptaena fremonti n. sp.

Plate 3, figures 16, 17, 19

1963 Leptaena sp. cf. L. rhomboidalis (Wilckens). Merriam,
p. 43.

Type material.—Holotype, USNM 159544; para-
type, USNM 159545. Rabbit Hill Limestone, locality
M409.

Diagnosis.——Medium-sized Leptaena with fairly reg-
ular transversely subquadrate, moderately alate out-
line. Valves sharply geniculate anteriorly; externally
the valves have few medium to heavy concentric rugae
for the genus. Radial costellae may be subdued.

External features.—Proportions and outline of this
slightly alate, but not strongly mucronate shell, are
characteristic. The trail bears only radial ornamenta-
tion; ribs are coarse on the interior of both dorsal and
ventral valve trail surfaces. Concentric rugae of pedicle
valve exterior range from 6 to 9, few for this genus when
mature. The trail is usually long, fairly even, and bends
abruptly almost 90°, as shown on pedicle valve exterior.

Pedicle valve interior.—Muscle field deeply im-
pressed, with evenly rounded raised rim and median
septum; configuration like that of many species of
Leptaena.

Brachial valve interior.—-Lobes of the bifid cardinal
process of medium to large size, with extensive ovoid-
triangular myophore surfaces. Median ridge between
adductor scars may extend beyond valve middle as a
weak septum. Broadened radial ribs prominent on inner
trail surface. Inner valve surface may be strongly
postulose.

Comparison with related forms.—Leptaena fremonti
resembles Leptaena cf. L. rhomboidalis (Wilckens) of
Amsden (1958c, pl. II, figs. 12—15) from the Bois d’Arc
Limestone of Oklahoma, which has a more irregular out-
line. Leptaena acuticuspidata Amsden of the Oklahoma
Haragan (Amsden 1958a, pl. III, figs. 1—9) is also simi-
lar, but shows greater irregularities in and around the
muscle field of both valves. Leptaena ventricosa (Hall)
from the Frisco Limestone of Oklahoma as figured by
Amsden and Ventress (1963, pl. II, figs. 9—14) is more
elongate, less alate, and has a larger number of concen-
tric rugae.

Occurrence—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.
Dobbin Summit, Monitor Range, locality M1311. Coal
Canyon, Simpson Park Range, locality M1075. Speci-
mens compared to this species occur in the Southern
Sulphur Spring Range in the Beacon Peak Dolomite at
locality M197.

 

FAMILY UNCINULIDAE RZHONSNITSKAYA , 29

Family SCHUCHERTELLIDAE Williams, 1953
Genus Schuchertella Girty. 1904
Schuchertella cf. S. haraganensis Amsden

Plate 3, figures 12—15
1963 Schuchertella sp. (large form). Merriam, p. 43.

The genus Schuchertella is represented in the Rabbit
Hill collections by several silicified pedicle valves
resembling that of S. haraganensis; these are of medium
to large size for the genus, rather coarse ribbed and
lack dental lamellae. With the larger shells, the valve
is nearly flat or shallowly convex; the stout hinge teeth
are buttressed by a thickened ridge beneath the palin-
trope, but not projecting anteriorly along the floor as
dental lamellae. One smaller deformed individual is
much more convex and narrower at the hinge line, has
more elongate interarea, and shows evidence of possible
beak attachment (Stehli, 1954, p. 298).

Pedicle valves of the Rabbit Hill Schuchertella have
coarser ribbing than S. nevadensis Merriam from
Nevada Formation unit 2. An undescribed species
resembling nevadensis occurs in Nevada unit 1 with
Acrospirifer kobehana; this undescribed form has incip-
ient but very short dental lamellae in most but not all
individuals and accordingly might be assignable to
Schellwienella Thomas, rather than to Schuchertella
(Amsden, 1958a, p. 90—91).

Occurrence—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.
A similar Schuchertella occurs in these beds at Dobbin
Summit, Monitor Range, locality M1311.

Order PENTAMERIDA Schuchert and Cooper. 1931
Family PARASTROPHINIDAE Ulrich and Cooper. 1938

Genus Anasirophia Hall, 1867
Anastrophia cf. A. vemeuili (Hall)

Plate 5, figures 15—19

Several brachial valves of a possible new species of
Anastrophia were collected in the southern Sulphur
Spring Range at localities M186 and M197 in associa-
tion with a fairly large fauna of Rabbit Hill Helderberg
age. No pedicle valves were found. The internal features
of these shells are quite similar to those of verneuili as
illustrated by Schuchert and Cooper ( 1932, pl. 25, figs.
33, 36, 38, 39).

The Nevada species is of medium size to large, with
coarse radial costae and deeply convex brachial valve;
the fold is weakly defined in some individuals, well
defined in others. On the anterior part of large mature
shells, the number of costae occuping the fold ranges
from 5 to 7. The radial ornamentation of this form also
resembles that of Anastrophia grossa Amsden (1958a,
p. 65—68, pl. II, figs. 18—28).

Presence of Anastrophia is significant in fixing the
Helderbergian age of this fauna, because as in the New
York area, this genus is not known above that interval

 

(Amsden, in Amsden and Ventress, 1963, p. 194; text
figs. 10, 51).

Occurrence—Lower Devonian Beacon Peak Dolo-
mite Member of the Nevada Formation. Southern Sul-
phur Spring Range, localities M186 and M197.

Order RHYNCHONELLIDA Kuhn, 1949
Family UNCINULIDAE thonsnitskaya
Genus Plethorhyncha Hall and Clarke, 1894
Plethorhyncha andersoni n. sp.

Plate 6, figures 1—7

Type material.—Holotype, USNM 159574; para-
types, USNM 159575—159578. Rabbit Hill Limestone,
locality M409.

Diagnosis.—Large Camarotoechiacea with broad
shallow fold and sulcus; brachial valve more convex
than pedicle valve. N 0 dental plates. Rather small pos-
teriorly situated pedicle valve muscle field. Brachial
valve hinge plate (septalium) with median triangular
pit bordered by adventitious thickenings.

External features—Lateral profile biconvex; brach-
ial valve with greater convexity. Shape transversely
elliptical to subquadrate. Fold and sulcus broad and
flatly rounded at commissure of mature shells; width
one-half that of valves; these features developed only
in anterior half of mature individuals. Pedicle valve
flattened posteriorly. Shells ornamented by medium
to fine subequal radial ribs, of which there are 8—12 in
the sulcus at commissure of large individuals. Beaks
small and subdued.

Pedicle valve interior.—Hinge narrow; teeth are
modifications of wall and without dental plates. No del-
tidium covering recognized. Muscle field rather small,
moderately impressed and flabellate, with thin median
partition posteriorly; adductor scars partly differen-
tiated. Pallial markings indistinct.

Brachial valve interior.—Hinge plate and prominent
median septum united as a continuous element (sep-
talium). The hinge plate is thickened laterally to form
rims or ventral socket plates and has a triangular
median pit with lateral thickenings. In available speci-
mens there is no indication of a cardinal process or
myophore. The median septum extends about one-half
the distance to the anterior edge of the shell.

Comparison with related forms.—Plethorhyncha
andersoni differs from P. speciosum (Hall), the type
species (Amsden and Ventress, 1963, p. 94), by having
more numerous and finer radial ribs and a well-defined
fold and sulcus, these last being poorly developed in
speciosum. P. speciosum is more elongate anteroposte-
riorly. The hinge plate of some individuals of speciosum
carries a bifid cardinal process, although young speci-
mens are reported to lack this structure (Amsden and
Ventress, 1963, p. 95), in this respect resembling our
specimens of andersoni. Havlicek (1961, p. 127—131)

 

 

30 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

calls attention to progressive filling of the pit (“Septa-
liumholung”) during ontogeny by shell material. It is
possible that such a filling, together with the bifid
cardinal process and myophore, were destroyed in our
silicified specimens of andersoni, leaving only the pit.

Most species previously assigned to Plethorhyncha
such as P.? welleri (Stewart), P.? salinensis (Stewart),
and P. barrandi (Hall) have, like Speciosum (Hall), a
coarser pattern of radial ribbing (see Amsden and Ven-
tress, 1963, pls. III and XII). Such a pattern is present
in the foreign species P. diana (Barrande) and P. altera
Barrande as figured by Havlicek (1961, pls. XV and
XVI). Actually the surface ornamentation of P. ander-
soni is somewhat more suggestive of species placed in
Uncinulus and Costellirostra than Plethorhyncha (see
Amsden and Ventress, 1963, pl. III; Schmidt, 1941, pl.
1; Havlicek, 1961, pl. XXII), but the marked differ-
ences in internal structure do not support a direct rela-
tion. For example, Uncinulus as established by Schmidt
(1941, p. 15—25) and by Havlicek (1961, p. 139—149)
has in the mature growth stages a comblike structure
(Havlicek, 1961, p. 142, p. 56) that develops medially
on the ventral surface of the hinge plate, a feature not
known in Plethorhyncha.

Occurrence—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.
Dobbin Summit, Monitor Range, locality M1311. Coal
Canyon, Simpson Park Range, locality M1075.

Order SPIRIFERIDA Waagen, 1883
Family MERISTELLIDAE Waagen. 1883

Genus Meristella Hall. 1860
Meristella martini n. sp.

Plate 7, figures 23—27
1940 (?)Meristella cf. robertsensis Merriam, pl, 6, figs. 13—16.

Type material.—Holotype, USNM 159606; para-
types, USNM 159607, 159608. Rabbit Hill Limestone,
locality M409.

Diagnosis.—Of small to medium size. Outline of
pedicle valve umbo acutely angulate posteriorly; curva-
ture of wings in plane of commissure rather abrupt for
the genus. Lateral surfaces of pedicle valve slope
steeply just anterior to foramen and are not flattened
toward hinge line as a false interarea. Pedicle beak not
abruptly incurved or hooked.

External features.——Shell smooth except for concen-
tric incremental lines that are conspicuous only toward
front of mature individuals. Lateral profile subsequally
biconvex; some individuals have a deeper brachial valve
with convexity exceeding that of pedicle valve. Steep
sides are characteristic, pitching abruptly in front of an
acutely angulate pedicle valve beak. Outline in com-
missure plane more subtriangulate than subrounded,
with abrupt curvature at greatest shell width, which is
commonly anterior to middle. Brachial valve fold only

 

near front of mature shells, where it is evenly rounded
or slightly angulate at commissure. Pedicle valve sulcus
only on anterior third of valve, where it is shallow
except near commissure of larger individuals. Ventral
valve beak prominent for genus, but not hooked
anteriorly.

Pedicle valve interior.—Muscle field wide, striated,
and deeply impressed for this genus. Teeth large and
posteriorly hooked. Mature shells with dental plates
developed as short inconspicuous ridges which are sup-
pressed with umbonal thickening.

Brachial valve interior.—Hinge plate triangular,
merging in front with a high, sharp median septum
which usually extends more than one-half the valve
length. Socket large. The brachiophores converge
toward the beak outlining the large median triangular
pit characteristic of M eristella. Some specimens reveal
a process or thickening toward the apex that may be
cardinal process myophore. Others have bilobed shelly
fillings toward broader edge of pit, whereas some have
pit filled by shelly material.

Comparison with related forms.—Meristella n. sp.
differs from Meristella robertsensis in shape and pro-
portions of the pedicle valve, especially that part just
anterior to the beak; M. robertsensis is also a larger
form. Individuals figured by Merriam (1940, pl. 6, figs.
13—16) from Oriskany beds in the Lower Devonian of a
horizon lower than those yielding the typical robert-
sensis are quite similar to the new species and may be
assignable to it (see also Cooper, 1944, pl. 127, figs. 24,
25, but not fig. 23). Meristella atoka Girty (Amsden
1958a, p1. X, figs. 1—15) is similar to martini but
appears to differ in details of the hinge plate and
includes numerous variants with acute fold and sulcus
at the commissure. Meristella arcuata Hall and M.
laevis Hall are similar externally, but too little is known
of the internal features of these two species to make
comparison meaningful.

Occurrence—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.
Dobbin Summit, Monitor Range, locality M1311. Coal
Canyon, Simpson Park Range, locality M1075.

Family AMBOCOELIIDAE George, 1931
Ambocoelia sp. a

Plate 7, figures 28—31

Figured material.—USNM 159609—159612; Rabbit
Hill, Copenhagen Canyon, locality M409.

Several pedicle valves of Ambocoelia from the Rab-
bit Hill type section are of special interest in supporting
the Devonian age of this formation, as the genus is
unknown in older rocks.

The pedicle valve resembles that of A. umbonata
(Conrad), the type species, by having prominent

 

 

FAMILY RETZIIDAE WAAGEN 31

thickened hinge teeth unsupported by dental plates.
However, the teeth are buttressed by a shelly thicken-
ing beneath the delthyrium margin that merges toward
the beak with extensive umbonal filling by shell mate-
rial. The sulcus is broad and shallow for the genus.

Occurrence—Rabbit Hill Limestone. Rabbit Hill,
Copenhagen Canyon, locality M409.

Family LEPTOCOELIIDAE Boucot and Gill, 1956

Genus Leptocoelia Hall, 1857
Leptocoelia occidentalis n. sp.

Plate 5, figures 1-14

1963 Anoplotheca Sp. cf. A. acutiplicata (Conrad). Merriam,

.43.

(?))Leptocoelia sp. Boucot, Johnson, and Staton, pl. 125,
fig. 19.

Type material.—Holotype, USNM 159562; para-
types, USNM 159563, 159565—159570, locality M409.
Paratype, USN M 159564, locality M197.

Diagnosis.—Thick-shelled Leptocoelia with biconvex
lateral profile and well-defined sulcus and fold. Hinge
plate and cardinal process massive. Older shells have
prominent pit just anterior to strongly impressed
muscle field of pedicle valve.

External features.—Size, medium to large for this
genus; 3 or 4 prominent, rather sharply rounded radial
costae lateral to the brachial fold and 3 or 4 lateral to
the strong rib defining the pedicle valve sulcus. Outline
nearly round, with subdued beaks. Hinge line narrow.
The two strongest costea, which occupy the fold, rise
above the lateral rib as they approach the commissure;
fold not defined on posterior half of valve. Pedicle valve
with strong median rib in sulcus, opposing interspace
between the pair of fold ribs. Concentric incremental
frills strong and closely spaced toward commissure of
mature shells.

Pedicle valve interior.—Hinge teeth large, separated
from lateral walls by a rounded groove. Muscle field
large, fan shaped, and rather deeply impressed. Pair
of small ovoidal adductor scars separated by a narrow
ridge that thickens posteriorly. The usually large
rimmed pit in front of muscle field is distinctive.

Brachial valve interior.—Hinge plate broad and
thick, brachiophores merging basally with strong ven-
tral socket ridges that converge posteriorly at edge of
plate. Cardinal process thick and elongate-triangular in
outline with long, dorsally inclined posterior grooves
constituting the myophore. Heavy median ridge ex-
tends anteriorly from hinge plate, narrowing to form
dividing ridge of the large anterior adductor scars.
Sockets large and ovoidal.

Comparison with related forms.—Leptocoelia flabel-
lites (Conrad) Hall is regarded as the type species
(Amsden and Ventress, 1963, p. 178). The new species
differs from L. flabellites by having a highly convex

1964

 

brachial valve, whereas that of the former is flat; there
are also marked differences in hinge-plate structure.
Leptocoelia acutiplicata (Conrad) as figured by Kindle
(1912, pl. VI, figs. 1—15) is much less convex than
occidentalis and differs in hinge-plate structure. Lepto-
coelia infrequens (Walcott) is externally the closest to
occidentalis, but is less convex; its internal features are
not well enough known to make further comparison
possible (Amos and Boucot, 1963, pl. 63, figs. 5—9).
Leptocoelia occidentalis resembles species assigned to
Australocoelia Boucot and Gill, 1956, but differs with
respect to internal features, especially the cardinal
process by which the genus is distinguished from the
externally homeomorphic Leptocoelia (Boucot and
Gill, 1956, p. 1174).

Leptocoelia sp. (Boucot and others, 1964, pl. 125,
fig. 19) from lower beds of the Nevada Formation is a
brachial valve whose interior is quite similar to that of
occidentalis in nearly all structural details.

Occurrence—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.
Dobbin Summit, Monitor Range, locality M1311. Walti
Ranch, Simpson Park Range, locality M1074 (cf. occi-
dentalis). Beacon Peak Dolomite Member of the
Nevada Formation. Southern Sulphur Spring Range,
localities M186, M197.

Family RETZIIDAE Waugen. 1883
Genus Trematospira Hall. 1859
Trematospira mcbridei n. sp.

Plate 6, figures 8—15
1963 Trematospira sp. cf. T. equistriata Hall and Clarke. Mer-
riam, p. 43.

Type material.——Holotype, USNM 159579; para-
types, USNM 159580—159585. Rabbit Hill Limestone,
locality M409.

Diagnosis.——Finely, uniformly ribbed Trematospira
with well-developed sulcus; dorsal fold absent or very
weakly defined. Pedicle valve with narrowly flabellate
rather deeply impressed muscle field. Hinge plate sub-
quadrate, thick and prominent, projecting about 2 mm
posteriorly beyond beak. Sockets large.

External features.——Shape transversely elliptical,
with small subdued beaks. Lateral profile moderately
biconvex; hinge line narrow. No interareas. The sulcus
begins near the beak, remains shallow and fairly broad
to commissure of larger shells. Brachial valve convexity
changes anteriorly with slight medial swelling toward
front, but usually without development of a discrete
fold. Radial ribs close spaced, subequal, evenly rounded,
separated by interspaces of comparable width. Splitting
of ribs anteriorly uncommon. Concentric striations
inconspicuous. About 9 radial ribs in sulcus of pedicle
valve, with 18 to 21 ribs on each flank.

32 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

Pedicle valve interior.—Dental plates short and
inconspicuous. Muscle field triangularly flabellate and
rather deep, especially where its acute apex is
impressed medially in floor of delthyrial cavity, forming
wide lateral shelves. Adductor scars not differentiated.
Pallial markings unrecognized.

Brachial valve interior.—Thickened hinge plate var-
iable, invariably projects prominently beyond valve
edge in a posterior direction; this plate is a paired struc-
ture including stout brachiophores that merge antero-
dorsally with thick socket plates or brachiophore
support plates. The medial ridge may be either strong,
tapering anteriorly from the brachiophores along the
valve inner surface as a ridge, or subdued and narrow.
The cardinal process is a somewhat indefinite feature
without a well-defined shaft and is bordered laterally
by two posterior brachiophore projections.

Comparison with related forms—Externally T. mc-
bridei bears strong resemblance to T. equistriata Hall
and Clarke 1894, especially as figured by Schuchert
(Schuchert and Maynard, 1913, p. 430, pl. 73, figs.
8—9). The interior of equistriata is unknown but may
be related to T. deweyi (Hall) assigned by Hall and
Clarke (1894, p. 128, pl. 49, figs. 40—46) to Parazyga,
the interior of which has been figured. The hinge plate
of deweyi is similar to that of some individuals of
mcbridei, although this structure is quite variable.
Trematospira multistriata Hall has heavier radial rib-
bing than mcbridei, and there are differences in hinge-
plate details (Hall and Clarke, 1894, pl. 49, figs. 13, 14).

Trematospira mcbridei resembles T. cooperi Mer-
riam (1940, p. 82, pl. 6, fig. 12) externally and may be
a subspecies. Because the interior of cooperi is unknown,
however, the relation of these two Early Devonian
forms must await preparation of suitable material.

Occurrence—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.

I-‘amily DELTHYRIDIDAE Waagen, 1883
Genus Kozlowskiellina Boucot, 1958

1957
1958
1842
1857
1858
1963

Type species.—By original designation, Kozlowski-
ella strawi Boucot, 1957. Wenlock Limestone, Great
Britain; west of Wren’s Nest, Dudley, England, middle
nodular beds of the Wenlock Limestone.

Diagnosis.—Coarse-ribbed spiriferoid brachiopods
having frilled growth lamellae, uncomplicated fold and
sinus, a strong median septum in the pedicle valve, and
a large distinctive double cardinal process. Interarea of
pedicle valve long and extensive, that of the dorsal

Kozlowskiella Boucot, p. 318.

Kozlowskiellina Boucot, p. 1030.

Delthris raricosta Conrad, pl. 14, fig. 18.

Spirifer perlamellosus Hall, p. 57.

Kozlowskiella Boucot, Amsden and Boucot, p. 121.

K ozlowskiellina Boucot, Amsden and Ventress, p. 114.

 

valve insignificant.

Remarks.——As noted by Boucot (1957, p. 318—319),
the pedicle valve of K ozlowskiellina is more convex than
the brachial. The heavy ribs and interspaces are orna-
mented by fine radial riblets that project over the con-
centric lamellae as fringes of small spines. In mature
individuals, the deltidial plates are conjunct except for
an apical foramen. Dental plates are usually short but
stout; in older individuals, these become partly
embedded in secondary shell material deposited in the
umbonal and delthyrial cavities. The strong median
septum extends from one—half to two-thirds the dis-
tance to the anterior margin of the pedicle valve. The
double cardinal process may be deeply striated.

Hedeina Boucot, 1957 is externally similar to K02-
lowskiellina, but lacks the pedicle valve median sep-
tum; the cardinal process is not of the distinctive
double type found in Kozlowskiellina. Delthyris Dal-
man, 1828 possesses a thinner median septum in the
pedicle valve and differs from K 02lowskiellina by lack-
ing the frilly external lamellae, as well as the distinctive
double cardinal process and by having relatively longer
and thinner dental lamellae.

Kozlowskiellina occurs in rocks of Middle Silurian
age in England (Wenlock Limestone), in the higher
parts of the Roberts Mountains Formation of the type
section, which is either Middle or Upper Silurian, and
is especially characteristic of the Helderberg (Early
Devonian) beds of the Rabbit Hill Limestone.

Kozlowskiellinu nolani n. sp.
Plate 6. figures 16—24

1963 Kozlowskiellina Sp. a, Merriam, p. 43.

Type material.—Holotype, USNM 159589; para-
types, USNM 159586—159588, 159590, 159591, Rabbit
Hill Limestone, locality M409. Paratype, USNM
159592, Rabbit Hill Limestone, locality M1309.

Diagnosis.—Kozlowskiellina with narrow hinge line,
subquadrangular outline in plane of commissure, and
few heavy radial ribs. Ventral valve greatly thickened
by adventitious material in umbonal region. Dorsal
hinge plate large, with strong bifid cardinal process
flanked by thick brachiophore supports.

External features.—Size medium to large for this
genus. Hinge line width usually exceeds anteroposte-
rior length. Width of fold at commissure may be more
than one-third hinge line width. Fold and sinus broad,
deep and rather evenly rounded. Lateral profile
strongly biconvex; pedicle valve usually deeper than
brachial. Radial costellae limited to one on either side
of fold and one lateral to heavy ribs which border the
sulcus. Concentric frills usually well developed; thread-
like minor ribbing and spines at frill edges are not pre-
served. Pedicle valve interarea long and apsacline; del-

 

FAMILY DELTHYRIDIDAE WAAGEN 33

thyrial notch makes angle of about 28°. Brachial valve
interarea insignificant. Conjunct deltidial plates and
foramen not preserved.

Pedicle valve interior—Muscle fields not distin-
guishable in mature shells. Median septum high, usu-
ally extending more than half the distance from beak
to commissure. In early mature stages, septum thin,
following floor of delthyrial cavity as a low plate sepa-
rated from the dental lamellae; with older individuals
having umbonal adventitious deposits, the median
septum is much thickened posteriorly and merges with
thick, short dental plates to form a troughlike pseudo-
spondylium. The median septum commonly swells to
an elongate boss on floor of delthyrial cavity. One or
more pairs of apically trending grooves occur below
teeth along the walls of the delthyrium, converging
toward the beak.

Brachial valve interior.—Hinge plate large, slightly
less than one-third valve width at hinge line; a bifid
cardinal process, lateral to which are expanded brachio-
phore supports that make up most of the plate. Muscle
impressions poorly defined, small, with low dividing
ridge just anterior to hinge plate. Spiralia unknown.

Comparison with related forms.—Kozlowskiellina
nolani differs from K. strawi, the type species, in the
narrowness of the shell and convexity of the brachial
valve; the brachial valve of K. strawi is nearly flat.
Compared with K. nolani, most described species have
a more alate shell and are not known to have the exces-
sive thickening of the pedicle valve median septum on
the floor of the delthyrial cavity of older individuals.
Perhaps the most closely related is K. velata Amsden
(Amsden 1958a, p. 121, pl. VIII, figs. 1—13), though it
is more alate and has more major costellae and a more
angulate fold and sinus. An undescribed species of
Kozlowskiellina in the upper Roberts Mountains Silu-
rian is alate and has numerous major costellae and a
smaller hinge plate.

Occurrence—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.
Dobbin Summit, Monitor Range, locality M1309. Petes
Canyon area, Northern Toquima Range, locality
,M1150.

Genus Howellella Kozlowski, 1946
Howellella cycloptera (Hall) subsp. monitorensis n. subsp.

Plate 7, figures 17—22; plate 8, figure 10
1963 Spirifer sp. a, cf. “S.” cylopterus Hall, Merriam, p. 43.

Type material.—Holotype, USNM 159604; para-
type, USNM 159603; Rabbit Hill Limestone, locality
M409. Paratype, USNM 159605; Rabbit Hill Lime-
stone, locality M1311.

Diagnosis.—Howellella with evenly curved fold and
sulcus, lateral to which are 5 to 7 prominent evenly

 

rounded radial ribs on each flank. Dental plates short.
Ventral muscle field flabellate, usually impressed,
markedly striated, with low median partition. Interior
of pedicle valve pitted lateral to muscle field. Valve
surfaces ornamented by fine radial riblets that are
prominent and possibly spinose at concentric incre-
mental edges.

External features.—Lateral profile moderately bi-
convex, the two valves subequal. Hinge line width
usually exceeds length. Shape in commissure plane
subovoidal; cardinal extremities rounded. Fold and
sulcus uncomplicated. Pedicle valve interarea short,
concave-orthocline with hooked beak. Delthyrial notch
making angle about 550. Deltidial plates unknown.
Dorsal interarea very short.

Pedicle valve interior.—The fan-shaped impressed,
longitudinally striate muscle field undifferentiated
except for median ridge, which varies from broad to
weak or undefined. Dental lamellae short and ventrally
divergent. Pitting of inner valve surface strongest near
muscle field, but may extend to valve edge.

Brachial valve interior.—Hinge plate wide, divided
and open, with small cardinal process and thin, widely
divergent, bladelike brachiophore supports. Muscle
attachments weak or unrecognized.

Comparison with related forms.—The Nevada speci-
mens herein classified as a subspecies of cycloptera
(Hall) resemble Hall’s figures of the New York Helder-
bergian types rather closely and are quite similar to
the Oklahoma Bois d’Arc individuals figured by Ams-
den (Amsden 1958a, pl. VIII, figs. 14—26). The New
York specimens reveal the striated pedicle muscle field
and the pitting as in subsp. monitorensis and the exte-
rior pattern of fine surface ornamentation present upon
the Bois d’Arc individuals. The Bois d’Arc form reveals
a suggestion of a weak median sulcus on the dorsal fold
not recognized in subsp. monitorensis. The new sub-
species differs markedly from the Silurian Lone Moun-
tain Dolomite species Howellella smithi Waite, which
has a flattened fold and sinus near the commissure,
fewer lateral plications, and longer, more slender dental
plates. H owellella pauciplicata Waite, also of the Lone
Mountain, is smaller and has very weak lateral
plications.

Occurrence—Lower Devonian Rabbit Hill Lime-
stone. Rabbit Hill, Copenhagen Canyon, locality M409.
Dobbin Summit, Monitor Range, locality M1311. Coal
Canyon, Simpson Park Range, locality M1075.

Genus Acrospiriier Helmbrecht and Wedekind. 1923

1923
1944
1963

Acrospirifer Helmbrecht and Wedekind, p. 952.

Acrospirifer Wedekind. Cooper, p. 323.

H ysterolites (Acrospirifer) Helmbrecht and Wedekind,
1923. Amsden and Ventress, p. 105.

34 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

Type species.—Spirifer primaevus Steininger
(Cooper, 1944, p. 323; Amsden and Ventress, 1963, p.
108). Lower Devonian, Germany.

Diagnosis.—Cooper (1944) characterizes Acrospiri-
fer as follows: “***Subsemicircular to transversely
semielliptical, costate and lamellose spiriferoids; fold
and sulcus noncostate; dental plates strong, muscular
field large, elongate-oval; dorsal interior with thick
socket plates.”

Remarks.—Amsden and Ventress (1963, p. 105-111)
have reviewed the present status of Acrospirifer in con-
nection with the relations of A. murchisoni (Castel-
nau). These writers treat Acrospirifer as a subgenus of
Hysterolites Schlotheim 1820, following the usages of
Maillieux (1941) and Havlicek (1959).

Acrospirifer kleinhampli n. sp.
Plate 7, figures 9—12

Type material.—Holotype, USNM 159599; para-
type, USNM 159600. Rabbit Hill Limestone, locality
M1309.

Diagnosis—Large Acrospirifer with rather narrow
hinge line for the genus, short dental lamellae, and 6
or 7 radial ribs on either side of the ventral sulcus.
Mature individuals may show a tendency toward split-
ting of radial ribs anteriorly.

External features.—Cardinal extremities subrounded
to subangulate. Radial ribs rounded, rather closely
spaced and numerous for the genus. Pedicle sulcus deep
and usually subangular toward the commissure of
mature shells; brachial fold prominent and subrounded.
Concentric lamellae not prominent, obscured because
of silicification. Splitting or doubling of radial ribs
toward the anterior margin of large individuals appears
to be characteristic. Beak of pedicle valve slightly
hooked. Pedicle interarea well defined but less exten-
sive laterally than in other species of this genus. No
trace of deltidial plates was noted.

Pedicle valve interior.—Dental lamellae short and
obtuse for this genus. Muscle field large, rather deeply
impressed and striated.

Brachial valve interior.—Hinge plate with thin dor-
sally projecting flange medial to brachiophore as in
Acrospirifer kobehana (Merriam); flange does not
meet internal valve surface.

Comparison with related forms.—Acrospirifer klein-
hampli differs from A. kobehana (Merriam) by being
somewhat smaller, with narrower hinge line and later-
ally less extensive ventral interarea. The dental lamel-
lae of kobehana are longer and thinner. The radial ribs
of kobehana are heavier, fewer, and more widely spaced.
Acrospirifer kleinhampli resembles A. murchisoni
(Castelnau) but appears to be narrower (see Amsden
and Ventress, 1963, pl. VI) and less alate. The complex

 

pattern of concentric lamellae shown by murchisoni is
not known in kleinhampli, possibly because of preser-
vation by silicification.

Occurrence—Rabbit Hill Limestone. Dobbin Sum-
mit, Monitor Range, locality M1309 in the higher beds
of this formation.

Family COSTISPIRIFERIDAE Termier and Termier, 1949
Genus Costispiriler Cooper. 1942
1942 Costispirifer Cooper, p. 230.
1944 Costispirifer Cooper, p. 323, pl. 122, figs. 27—31.
1963 Costispirifer Cooper, Amsden and Ventress, p. 111—114,
pl. 5, figs. 3—11, text—fig. 35.

Type species.—Spirifer arenosus planicostatus
Swartz (1930, p. 56—57, pl. 9, figs. 13—15) by author
designation. From cherts in the upper part of the Giles
Formation near Saltville, Va. Lower Devonian. Cooper
(1942) regarded Costispirifer planicostatus (Swartz)
as a distinct species.

Diagnosis.—Large spirifers with costate fold and
sulcus. The costae are broad and flat with narrow inter-
spaces; costae ornamented with fine radial lines. Dental
plates strongly developed. In brachial valve, the crural
bases cup shaped and welded to sides of valve; noto-
thyrial cavity broad and moderately deep. Delthyrium
covered by a short convex pseudodeltidium.

Remarks.—Spirifers similar to the eastern Oriskany
Costispirifer arenosus (Conrad) are the most diagnos-
tic and abundant brachiopods of Early Devonian
(Siegenian) beds of the Great Basin, where they occur
with large horn corals belonging to the Subfamily
Papiliophyllinae. First recognized in the Roberts
Mountains (Merriam, 1940, p. 50, pl. 7, fig. 17, pl. 11,
fig. 17), these spirifers have been collected in large
numbers from arenaceous limestones of Nevada for-
mation unit 1 in the Sulphur Spring Range. Most speci-
mens are pedicle valves that exhibit flattening of ribs
toward the anterior margin of large shells; otherwise
the costae are rounded. Fine, delicate costellae were
not observed on ribs of unpeeled valves. A high per-
centage of these shells appear to be especially wide at
the hinge line as compared with more elongate figured
specimens from the eastern Oriskany (Schuchert and
Maynard, 1913, pl. 71, figs. 3, 8, 9).

In silicified pedicle valves from the upper part of the
Hidden Valley Dolomite, Panamint Mountains, Calif.,
the teeth are small and the short dental plates espe-
cially heavy where they form a buttress beneath the
interarea.

N0 far-western Costispirifers showing the very wide,
flattened costae of Costispirifer arenosus var. planicos-
tatus Swartz (1930, pl. 9, figs. 13, 14) have been rec-
ognized. Cooper (1942, p. 232) elevated Swartz’s
variety to a species separate from C. arenosus (Con-
rad) upon designating planicostatus as type species of

 

 

FAMILY CONULARIIDAE WALCOTT 35

Costispirifer.

Amsden and Ventress (1963, p. 111—114) have
reviewed the relations and distribution of American
Costispirifer, noting the taxonomic importance of flat
costae and narrower interspaces.

On the whole, differences in shell and ornamentation
are not great when the New York, Oklahoma, and
Great Basin forms are compared. The various geo-
graphic taxa might reasonably be regarded as sub-
species; some selected Nevada specimens are quite
similar morphologically to some of those from the
Appalachian belt as well as Oklahoma.

Appearance of Costispirifer of the arenosus type in
the higher Rabbit Hill fauna at Dobbin Summit,
Monitor Range, suggests that these beds are probably
little older than Nevada unit 1, in which very similar
brachiopods become dominant.

Costispirifer arenosus (Conrad) subsp. dobbinensis n. subsp.
Plate 7, figures 1—7

Type material.—Holotype, USNM 159594; para-
types, USNM 159593, 159595—159597. Rabbit Hill
Limestone, locality M1309.

Diagnosis.—Large Costispirifer arenosus with shal-
low to moderately deep pedicle valve sulcus, large
deeply impressed ventral muscle field, short dental
lamellae, and heavy dental lamella buttresses beneath
the palintrope. The convex pseudodeltidium beneath
the incurved beak is short and rather heavy.

Remarks—The Dobbin Summit pedicle interiors
reveal deeply impressed muscle scars and very short
dental plates, except for the greatly thickened buttress
beneath the interarea. The convex pseudodeltidium
beneath the beak is short and rather heavy.

This subspecies, judged by pedicle valve exterior
features, is specifically like C. arenosus from Nevada
unit 1. Wide individuals of subspecies dobbinensis
resemble wide shells of the Hidden Valley Dolomite
form, which have a somewhat more slender dental
lamella buttress.

The dorsal features of subspecies dobbinensis, like
the Nevada unit 1 form, are poorly known, because
most of the preserved shells are pedicle valves. Validity
of dobbinensis as a subspecies must therefore await
comparison of brachial valve features, likewise poorly
known in the Hidden Valley representatives. The like-
lihood that dobbinensis is ancestral suggests that dif-
ferences in the ventral interior may be borne out in the
rest of the shell when that is better understood.

0ccurrence.—Lower Devonian Rabbit Hill Lime-
stone. Upper beds of the Rabbit Hill Limestone, Dob-
bin Summit, Monitor Range, locality M1309. Frag-
mentary shells possibly belonging to this subspecies
have been collected from higher beds of the Rabbit

506»612 0 ~ 73 — 6

 

 

 

Hill Limestone at Coal Canyon, Simpson Park Range,
locality M1076.

TENTACULITIDS AND CONULARIIDS
OF THE RABBIT HILL LIMESTONE

Shells of Conularia are locally associated with abun-
dant tentaculitids in platy limestones and calcareous
shale interbeds of the Rabbit Hill Limestone. South-
east of Walti Ranch (locality M1074) in the Simpson
Park Range, such platy beds with Conularia contain
small slender tentaculitids (pl. 8, fig. 18) having the
ornamentation of Nowakia acuaria Richter. Trilobites
Leptocoelia, Pleurodictyum, and Syringaxon also occur
in this assemblage. Similar tentaculitids are present in
platy Rabbit Hill interbeds at Coal Canyon, northern
Simpson Park Range. In the Devonian of the Great
Basin, Nowakia-like shells are most abundant in the
Middle Devonian strata of Nevada Formation unit 4,
where smooth Styliolina also is common. No large
coarsely ribbed benthonic tentaculites like those of
shaly interbeds of Nevada Formation unit 2 were
observed in the Rabbit Hill.

Subclass CONULATA Moore and Harrington
Order CONULARIIDA Miller and. Gurley
Family CONULARIIDAE Walcott
Conularia sp. cf. C. huntiana Hall

Plate 2, figures 18—20

Figured material.——USNM 159536, 159537; Rabbit
Hill Limestone, locality M1074, Walti Ranch, Simpson
Park Range.

Flattened shells of this delicate Conularia range in
length from 30 mm to more than 400 mm. The sharply
sculptured transverse ribs are uniform, about 40 per
mm, and ornamented by close-spaced small tubercles.
In some individuals these tubercles are round, in others
elongate and drawn out longitudinally toward the
interspaces, but not to the extent shown in Hall’s figure
(1859—61, pl. 72A, figure 2b) of the Helderbergian C.
huntiana.

Similar Conularia occurs in the Early Devonian
Hunsriickschiefer of Bundenbach, Germany.

Occurrence.—Rabbit Hill Limestone, locality M1074
southeast of Walti Ranch, Simpson Park Range.

MOLLUSCA OF THE RABBIT HILL LllVlESTONE

Mollusca, greatly outnumbered by the brachiopods,
are generally not conspicuous in the Rabbit Hill Lime-
stone. Residues from hydrochloric acid solution of
Rabbit Hill bioclastic limestones yielded few lamelli-
branchs; their shells evidently were less amenable to
silicification than were those of brachiopods, corals,
and gastropods. Most gastropods so obtained are allied
to Platyceras. Fragrnentary straight Orthoceras-like
shells of small size were the only cephalopods recog-

 

 

 

36 RABBIT HILL LIMESTONE AND LONE MOU

nized. No identification of the fragmentary lamelli-
branchs was attempted.
Family PLATYCERATIDAE Hall
Genus Platyceras Conrad

Three kinds of Platyceras occur in the type Rabbit
Hill bioclastic limestones; these range in configuration
from nearly planospiral through openly planospiral to
somewhat helicospiral and disjunct. None of the large,
excessively spinose forms of Platyceras like those that
characterize lower beds of the Nevada Formation (unit
1) were found in the Rabbit Hill.

Platyceras sp. a
Plate 1, figures 20, 21
Platyceras Sp. a (USNM 159524) is nearly plano-
spiral, smooth, comprises two whorls and has an ovoidal
aperture and open umbilicus.
Occurrence.——Rabbit Hill Limestone. Rabbit Hill,
Copenhagen Canyon, locality M409.

Platyceras sp. b
Plate 1, figures 22, 23
Platyceras sp. b (USNM 159525) is more typical of
the genus, a small form with a single open whorl. The
aperture is nearly round with generating curve increas-
ing rapidly in diameter. Sinuosity of the growth line
conforms to an irregular aperture margin with five
minor embayments.
Occurrence.—Rabbit Hill Limestone. Rabbit Hill,
Copenhagen Canyon, locality M409.

Platyceras (Orthonychiu) sp. c
Plate 1, figure 24

Platyceras (Orthonychia) sp. c (USNM 159526) is
a small disjunct species comprising two whorls with the
character of the subgenus Orthonychia and having a
very elongate, straight body whorl. Growth lines and
aperture margin show two broad embayments.

Occurrence.—Rabbit Hill Limestone. Rabbit Hill,
Copenhagen Canyon, locality M409.

TRILOBITES OF THE RABBIT HILL LIMESTONE

Trilobites of the families Odontopleuridae and
Phacopidae are the common fossils at some exposures
of the Rabbit Hill Limestone. This is especially true of
the platy limestones in the Simpson Park Range west
of McClusky Peak and at Coal Canyon. In the type
area at Rabbit Hill, Monitor Range, and at Dobbin
Summit, trilobite remains are abundant in some beds,
whereas in the richly fossiliferous bioclastic lenses
where the brachiopods and corals are silicified, the trilo-
bites are not replaced by silica and do not appear in the
acid residues. Thin beds in which trilobite remains are
the common fossils yielded a few weathered specimens.
Some of these beds are a virtual “trilobite hash” from
which, by repeated splitting of large amounts of rock,
well-preserved but disarticulated fragmentary trilo-

 

NTAIN DOLOMITE OF CENTRAL NEVADA

bites may be prepared (pl. 8, figs. 12, 13). Most of these
are small spiny Odontopleuridae; it is unlikely that
articulated or complete specimens can be obtained
from these bioclastic beds.

Material available is not sufficient to justify more
than a cursory review of the Rabbit Hill trilobites,
referring the few kinds collected to the nearest de-
scribed species. Trilobite beds yielding better material
will doubtless be found by careful search of the Simp-
son Park exposures, in particular those at Coal Canyon
and near McClusky Peak (Walti Ranch), where frag-
mentary larger phacopids are abundant. It is probable
that most of the Rabbit Hill trilobites are undescribed
species, in View of the lack of study of far-western
Devonian trilobites.

Family ODONTOPLEURIDAE Burmeisier 1843

Spiny trilobites of this family predominate in some
trilobite beds of the Rabbit Hill Limestone. Leonaspis
is the abundant genus, long-forked structures indicate
the presence of other genera such as M iraspis and
Odontopleura. Trilobites of this family seem to be
uncommon in the Devonian section of this province
above the Rabbit Hill; none were found in the Lower
Devonian beds of Oriskany age in Nevada Formation
unit 1. Leonaspis occurs sporadically somewhat higher
in Nevada unit 2 of the southern Sulphur Spring Range
northwest of Romano Ranch, where it was found asso-
ciated with Spirifer pinyonensis in very sandy lime-
stones.

Genus Leonaspis Richter and Richter. 191']
Leonaspis c1. L. tuberculutus (Hall), 1859
Plate 2, figures 15—17
1859 Acidaspis tuberculatus Hall, p. 368—370; pl. 79, figs. 1—14.
1956 Leonaspis tuberculatus (Hall, 1859) . Whittington, p. 507—
509, pl. 57, figs. 1—9.
1963 Leonaspis Sp. cf. L. tuberculatus (Hall). Merriam, p. 43.

Collections from the Rabbit Hill Limestone in its
type section include a number of isolated free cheeks,
pygidia, and hypostomas of this form well enough pre-
served for identification. No cranidea were found. Free
cheeks have been identified at most Rabbit Hill collect-
ing localities.

The mature free cheek is similar to those illustrated
by Hall (1859), having 12 or 13 lateral spines, a mar-
ginal row of rather coarse tubercles and scattered
tubercles on the convex part of the cheek, these being
more numerous internally. The lateral spines are less
acute than on Hall’s illustrations and more like those
shown by Whittington (1956, pl. 57, fig. 7; pl. 58, figs.
3, 4) for Leonaspis tuberculatus and L. williamsi.

The pygidium has a general pattern quite similar
to L. tuberculatus as illustrated by Whittington (1956,
pl. 57, fig. 4), but the paired tubercles are smaller on
the Rabbit Hill specimens and the median tubercle at

 

FAMILY TRYPLASMATIDAE ETHERIDGE 37

the axial tip of L. tuberculatus is weak or absent. The
differences in the two pygidia suggest only subspecific
differences.

Genus Mimspis Richter and Richter. 1917
(?)Miraspis sp.

Plate 2, figure 14

Elongate paired or forked occipital ring spines are
associated with Leonaspis in trilobite beds of the Rab-
bit Hill Limestone. These spines probably came from
an odontopleurid genus such as Miraspis or possibly
Odontopleura, two genera believed to be limited to the
Silurian.

Family PHACOPIDAE Huwle and Corda. 1847

Trilobites of this family are common in certain beds
of the Rabbit Hill Limestone in its type section. In
some platy limestones of the Simpson Park Range,
phacopids are the most numerous fossils. Only one
genus, Phacops, has been recognized. There is some
specific diversity, as between those with a genal spine
and those lacking this feature. Although some of the
material is fairly well preserved, most of the specimens
are fragmentary. In this region phacopids are numerous
in the Lower and lower Middle Devonian through
Nevada Formation unit 2, but material available is
insufficient for detailed species comparison.

Genus Phacops Emmrich, 1839
Phacops sp. 11, cf. P. logcmi Hall, 1861
Plate 8, figures 16, 17

This form is represented at Rabbit Hill by fragmen-
tary small to medium-sized pygidia that are not con-
spicuously postulose and do not show a rim. The
cephalon is unknown. The pygidia also resemble those
of var. gaspensis and var. birdsongensis as figured by
Delo (1940, pl. 1, figs. 10—12, 13—15).

(?)Phacops sp. B, ci. P. canadensis Stumm
Plate 2, figures 11—13

Large phacopids with well-defined pygidia] rim occur
at Coal Canyon, Simpson Park Range. They are repre-
sented in the collections by a nearly complete articu-
lated specimen and by a partial crushed cephalon.

The inflated glabella and short pygidium indicate
that this form is probably related to the genus Phacops.
There are, however, decided differences, among them a
narrowness behind the swollen frontal glabellar lobe
and the presence of genal spines.

Among the described Phacopidae, Phacops canaden-
sis Stumm( 1954, p. 213, pl. IV, figs. 7, 15, 18) pos-
sesses a short genal spine but differs in features behind
the swollen frontal lobe. The thorax and pygidium of
P. canadensis are unknown.

Pygidia associated with the cephalon of this species
are of medium to rather larger size and have a narrow
rim not recognized in Phacops sp. A.

 

Family DALMANITIDAE Vogdes, 1890

The remains of larger trilobites from the Rabbit HiH
Limestone include a large incomplete dalmanitid ceph-
alon from the Coal Canyon section, Simpson Park
Range. This individual was about 60 mm wide in the
anterior part of the thorax. Although possibly a species
of Dalmanites, preservation is too imperfect for a defi-
nite generic assignment.

Order RUGOSA Edwards and Haime, 1850
Family TRYPLASMATIDAE Etheridge, 1907
Genus Tryplasmu Lonsdale, 1845

1845
1871
1894
1907
1927
1927
1927
1936
1940
1940
1940
1950
1952
1956
1960
1962

Tryplasma Lonsdale, p. 613.

Pholidophylum Lindstriim, p. 925.

Spiniferina Penecke, p. 592.

Tryplasma Lonsdale. Etheridge, p. 76—77.
Tryplasma Lonsdale. Lang and Smith, p. 461.
Pholidophyllum Lindstrom. Wedekind, p. 25.
Stortophyllum Wedekind, p. 30.

Tryplasma Lonsdale. Hill, p. 204.

Tryplasma Lonsdale. Lang, Smith, and Thomas, p. 135.
Pholadophyllum Lang, Smith, and Thomas, p. 99.
Tryplasma Lonsdale. Hill, p. 405.

Tryplasma Lonsdale. Schouppé, p. 80—84,
Tryplasma Lonsdale. Stumm, p. 841—843.
Tryplasma Lonsdale. Hill, p. F312.

Tryplasma Lonsdale. Oliver, p. 96.

Tryplasma Lonsdale. Oliver, p. 13.

Type species.—Tryplasma aequabile Lonsdale, 1845;
by subsequent designation (Etheridge, 1907, p. 42).
Silurian near Bogoslovsk; east of northern Ural Moun-
tains, Russia.

Diagnosis.—Solitary and fasciculate rugose corals
with acanthine septa that are vertical columns of tra-
becular spines. Corallites elongate or subcylindrical.
Septal stereozone medium wide to narrow. No dissepi-
ments. Tabulae mostly complete, commonly straight
and widely spaced.

Remarks.~——Tryplasma and related corals with acan-
thine septa have been the subject of special studies by
Hill (1936), Schouppé (1950), ‘ Stumm (1952), and
Oliver (1960). Species of this genus are characteristic
of Silurian deposits in Europe, Australia, and North
America; as noted by Duncan (1956, p. 226—227; figs.
3a—b) , they are among the common fossils in the Silu-
rian of western North America. Oliver (1960, p. 96)
notes that Tryplasma extends its range into the Lower
Devonian of Europe, Australia, and eastern North
America.

The genus Tryplasma as understood includes species
that differ considerably in growth habit, ranging from
solitary ones with elongate corallum showing repeated
rejuvenescence rims to bushy phaceloid colonies whose
slender branches are cylindrical and relatively smooth.

These corals are well represented in the Silurian
limestone facies of the west-central and southwest

38 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVP+DA

parts of the Great Basin but are poorly known in the
dolomite facies.

Tryplasma sp. 1
Plate 11, figures 24, 25

Isolated nondissepimented, cyclindrical corallites in
the upper part of the Lone Mountain Dolomite of the
Fish Creek Range are assigned to Tryplasma. The
complete tabulae range from straight to undulant and
sagging. Moderately long acanthine septal spines are
well shown in both transverse and longitudinal thin
sections.

Occurrence—Upper Silurian, upper part of the Lone
Mountain Dolomite. Southern Fish Creek Range,
locality M1087 in association with Entelophyllum
engelmanni and the H owellella brachiopod fauna.

Family KYPHOPHYLLIDAE Wedekind, 1927

Reference form.——Kyphophyllum lindstromi Wede-
kind. Silurian, Gotland, Sweden.

The Kyphophyllidae are mostly colonial phaceloid,
less commonly cerioid genera among which the fascicu-
late species with long subcylindrical corallites predomi-
nate. Long lamellar septa are characteristic, with one
to several dissepiment columns, the outer of which are
lonsdaleioid in some species. Tabulae are fairly wide,
arched in some genera; in a few species a flaring calice
rim is present.

Described genera provisionally included in this
family are:

Kyphophyllum Wedekind, 1927
Strombodes Schweigger, 1819
Petrozium Smith, 1930
Entelophyllum Wedekind, 1927
Entelophylloides Rukhin, 1938
Neomphyma Soshkina, 1937

At least two generic or subgeneric groups Within the
Kyphophyllidae of the Great Basin Silurian remain
undescribed. All members of this family appear to be
restricted to the Silurian System.

Genus Entelophyllum Wedekind. 1927

1927 Entelophyllum Wedekind, p. 22—24, pls. 2, figs. 11—12,
pl. 7, figs. 7—10, pl. 29, figs. 18—51.

1927 Xylodes Lang and Smith, p. 461—462, figs. 13—14.

1929 X ylodes Lang and Smith. Smith and Tremberth, p. 362—
367, pl. 7, figs. 1—6, pl. 8, figs. 2—4.

1933 Xylodes rugosus Smith, p. 516, figs. 6—7.

1940 Entelophyllum Wedekind. Lang, Smith, and Thomas, p.
57—58.

1940 Entelophyllum Wedekind. Hill, p. 411.

1940 Xylodes articulatus (Wahlenberg). Prantl, p. 10—13, pl.
1, figs. 1—3, pl. 2, figs. 1, 3, 4.

1956 Entelophyllum. Duncan, pl. 23, figs. 5c—d.

1956 Entelophyllum Wedekind, Hill, p. F275, fig. 187, 2a—c.

1962 Entelophyllum Wedekind. Oliver, p. 15, pl. 6, figs. 11—12.

 

1962 Entelophyllum Wedekind. Stumm, p. 2—3, pl. 1, figs. 6—8,
pl. 2, figs. 9—11. .
1964 Entelophyllum Wedekind. Stumm, p. 32, l. 22, figs. 9-21.

Type species.—Madreporites articulqitus Wahlen-
bergZEntelophyllum articulatum (Wahlenberg); by
subsequent designation, Lang, Smith, and Thomas
(1940, p. 57, 140). Silurian, Gotland, Sweden. Accord-
ing to Smith and Tremberth (1929, p. 366) , this species
occurs in strata of Wenlock and Ludlow ages on the
Island of Gotland and is recorded from the Wenlock
Limestone in England.

Diagnosis.—Phaceloid, possibly in part solitary
rugose corals With elongate subcylindrical corallites.
Major septa thin, slightly thickened near outer wall
only; longer septa approach the axis. Tabularium wide,
typically with close-spaced flat tabulae or tabellae and
narrow peripheral sag bordering dissepimentarium.
Dissepimentarium having few to many columns of small
steeply inclined globose dissepiments. Outer wall thin,
lacking a stereozone. No fossulae or other indication of
bilateral symmetry in mature stages. Septa slightly to
moderately wavy; well-developed elbow carinae not
present in typical form. Attachment wall outgrowths
characterize some species. Five or six reproductive olf-
sets, marginal to calice.

Remarks.—Not all Entelophyllum species have the
well-defined peripheral depressed zone of the tabu-
larium shown by the type species. Entelophyllum
pseudodianthus (Weissermel) of the English Wenlock
has zigzag thickened and carinate septa and less elon-
gate cylindrical corallites (Smith and Tremberth, 1929,
p. 361—362; Lang and Smith, 1927, p. 475, fig. 15); pos-
sibly subgenerically or even generically distinct from
Entelophyllum sensu stricto.

Disphyllum of the Middle Devonian resembles
Entelophyllum externally, but differs by having gen-
erally slender corallites that lack the thick attachment
outgrowths of Entelophyllum. Disphyllum also lacks
the peripheral depressed tabular zone of typical Entelo-
phyllum, has more even septa without carinae, and
commonly has a somewhat Wider tabularium. Trans-
verse sections of Disphyllum show a more uniform and
even concentric distribution of axially concave dissepi-
ment traces. Some species of Entelophyllum have a
cycle of reproductive offsets at the calice margin, a
characteristic not found in Disphyllum.

Entelophyllum engelmanni n. 5}).
Plate 10, figures 5—11

Type material.—Holotype, USNM 159413; para-
types, USNM 159414—159418.

Diagnosis.—Phaceloid Entelophyllum forming large
laterally extensive bushy colonies of nearly straight
cylindrical corallites joined by lateral outgrowths.

FAMILY KYPHOPHYLLIDAE WEDEKIND 39

Tabularium wide, tabulae mostly complete, subparallel,
usually lacking the peripheral sag of typical Entelo-
phyllum. Tabulae with axial-periaxial sag or slightly
arched distally. Tabellae uncommon. Major septa with-
drawn from axis, slightly wavy and without carinae;
minor septa short, usually less than one-half the length
of major septa. Septa thin toward axis, but with wedge
thickening peripherally. No stereozone.

External features .—Very elongate cylindrical mature
corallites, large for this genus, with well-defined septal
grooves crossed by annular incremental striations.
Coarse annular folds or rugae few. Some corallites have
thick irregular lateral attachment outgrowths dis-
tributed vertically along one side.

Transverse sections—Major septa about 28, thinned
axially and slightly withdrawn from the axis. Minor
septa less than one-half the length of major septa. All
septa thicken rather abruptly in wedge fashion toward
outer wall, which is very thin. Septa slightly wavy, lack
carinae. Dissepiments not numerous, somewhat irregu-
lar as chevrons, forks, and simple traces that are either
almost straight or slightly concave axially.

Longitudinal sections.—Tabularium Wide, about
two-thirds of corallite diameter. Tabulae mostly com-
plete, varying from straight or slightly arched axially
and periaxially with or without peripheral depression
to those with axial-periaxial sag and no peripheral
depression. A few broad, flat tabellae peripherally. Dis-
sepiments globose in one to three columns, steeply
inclined, and of small, medium, and large size.

Comparison with related forms—Entelophyllum
engelmanni differs from E. eurekaensis in the uneven-
ness of its tabulae, which usually lack the peripheral
depression. The extensively developed lateral connect-
ing excrescences of this species were not observed in
E. eurekaensis.

Occurrence—Late Silurian, upper part of the Lone
Mountain Dolomite; upper Lone Mountain—Laketown
biofacies. Southern Mahogany Hills, locality M1112.
Northern Fish Creek Range, locality M1087. A similar
Entelophyllum occurs in Silurian dolomite of the Ruby
Mountains.

Entelophyllum engelmanni subsp. 1)
Plate 10, figures 12, 13; plate 11, figures 26, 27

Entelophyllum engelmanni with subcylindrical coral-
lites attaining large size and having diameters exceed-
ing 1% inches or about twice normal for the species.
The large corallites have some 38 major septa, steeply
inclined dissepiments, no septal stereozone, and in
some instances unusually thick and prominent external
attachment processes. External rugae and protuber-
ances more prominent than in typical form.

 

Occurrence—Late Silurian, upper part of the Lone
Mountain Dolomite. Southern Fish Creek Range,
locality M1087 .

Entelophyllum eurekaensis n. sp.

Plate 10, figures 1—4

Type material.——Holotype, USNM 159412; para-
type, USNM 159419.

Diagnosis.—Subcylindrical to ceratoid Entelophyl-
lum with wide tabularium and closely spaced, straight,
nearly continuous tabulae and flat peripheral tabellae.
Peripheral zone of tabularium proximally depressed as
in typical Entelophyllum. Septa slightly thickened,
longer major septa approach axis. In transverse sec-
tions, the small to medium sized dissepiments show as
axially concave and chevron traces.

External features—This species, known only from
isolated pieces, is assumed to have been bushy and
phaceloid like E. engelmanni of the same beds. How-
ever, available specimens of eurekaensis are more
nearly ceratoid than cylindrical in shape.

Transverse sections.—Major septa about 30; most
are withdrawn, but a few approach the axis. Minor
septa range from short wedge stumps to about one-half
the length of major septa. Septa somewhat thicker than
in most Entelophyllum species and show only a little
waviness. No carinae recognized. Dissepiments include
herringbone and chevron traces as well as concentric
and axially concave. Septa thicken markedly in wedge
fashion toward outer wall, but there is no continuous
septal stereozone. Epitheca rather thin.

Longitudinal sections.—-—Tabularium width about
two-thirds corallite diameter. Most tabulae nearly
complete, axially-periaxially very flat, peripherally
depressed as in typical Entelophyllum. Flat peripheral
tabellae present. Dissepiments in as many as five
columns, of which the outer may have nearly horizontal
basal planes; larger dissepiments elongate.

Comparison with related forms—This species has
much flatter, more even tabulae than engelmanni;
tabulae are more closely spaced and have a well-defined
peripheral sag. Dissepiments of eurekaensis are on the
whole less steeply inclined, occur in more numerous
columns, and are less globose. The bushy and cylindri-
cal growth habit of engelmanni is not known in this
species. No individuals of eurekaensis with prominent
external attachment processes are known.

Occurrence—Late Silurian, upper part of the Lone
Mountain Dolomite; upper Loner Mountain—Laketown
biofacies. Southern Fish Creek Range, locality M1113;
associated with the H owellella-Camarotoechia-Atrypa
brachiopod assemblage of this facies.

40 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

Phylum BRACHIOPODA
Class ABTICULATA Huxley. 1869
Order ORTHIDA Schuchert and Cooper, 1932
Family ENTELETIDAE Waagen, 1884
Genus Salopina Boucot. 1980
Salopina sp. 1

Plate 11, figures 16—23

Small Dalmanellacea possessing an elongate ventral
palintrope and a variously extended dorsal valve
median septum are among common brachiopods in
Silurian and Early Devonian rocks of the Great Basin.
Need for taxonomic revision within this large and com-
plex orthoid group has recently been indicated by
detailed studies of dalmanellid morphology and syste-
matics (Williams and Wright, 1963). Recently pro-
posed generic names possibly applicable to certain of
these taxa in the Great Basin Province are Salopina
Boucot (1960), Protocortezorthis Johnson and Talent
(1967b) , and M uriferella Johnson and Talent ( 1967a).

Salopina sp. f is known mainly from silicified shells
with valves articulated and showing only external
features. Among newly described dalmanellid species,
the closest similarities appear to be with the Late Silu-
rian Salopina? sp. of Boucot (1960, pl. 1, figs. 1—5),
from Devon Island, Northwest Territories, Canada,
and Salopina cf. S. crassiformis (Kozlowski) of J ohn-
son and Talent (1967a) from the Roberts Mountains.
Better preserved interiors are required to fully estab-
lish these relations.

Occurrence.—Late Silurian, upper part of the Lone
Mountain Dolomite; Southern Fish Creek Range,
locality M1113.

Order RHYNCHONELLIDA Kuhn, 1949
Family CAMAROTOECHIIDAE Schuchert and Levene, 1929
Genus Camarotoechia Hall and Clarke. 1893

Brachiopods of the Camarotoechia group are among
the abundant and diverse fossils of the upper part of
the Lone Mountain Dolomite. At least three forms are
recognized, Camarotoechia pahranagatensis Waite, a
related form designated as C. Sp. b, and a finely ribbed
species resembling C. bieniaszi Kozlowski of the Polish
Borszczow beds to which the designation C. sp. f is
applied here. Camarotoechia-like brachiopods similar
to sp. b and pahranagatensis have been described by
Johnson and Reso (1964) from correlative Late Silu-
rian beds of the Pahranagat Range.

Camarotoechia pahranagatensis Waite
Plate 11, figures 7—9
1956 Camarotoechia pahranagatensis Waite, pl. 3, figures 1—5.

The shell assigned to this species agrees well in gen-
eral proportions, strength, and number of radial ribs,
and emargination of the anterior commissure with
Waite’s figures of the holotype.

Occurrence.—Late Silurian, upper part of the Lone
Mountain Dolomite; Southern Fish Creek Range,

 

locality M1113.
Camarotoechia sp. 13
Plate 11, figures 10—13

This form is characterized by a pair or, less com-
monly, three prominent radial ribs in the fold and
sulcus; these ribs are more pronounced than in C. pah-
ranagatensis. Ferganella? lincolnensis Johnson (John-
son and Reso, 1964, pl. 19, figs. 5—12) differs by having
three or more prominent ribs in fold and sulcus.

Occurrence—Same as C. pahranagatensis at locality
M1113.

Camarotoechia sp. 1
Plate 11, figures 5, 6

This finely ribbed form with weakly developed fold
and sulcus is with some hesitation referred to as Cama-
rotoechia; it is rather certainly unrelated to the other
brachiopods of the upper Lone Mountain fauna placed
in that genus, sharing some of its external features with

Trematospira and Atrypa. Externally similar brachio-

pods have been described by Kozlowski (1929, p. 158,
pl. V, figs. 12—14) as Camarotoechia bieniaszi from the
Borszczow beds of Poland.

Occurrence.—Same as C. pahranagatensis and sp. b
at locality M1113.

Order SPIRIFERIDA Waagen, 1883
Family MERISTELLIDAE Waagen, 1883
Genus Hyattidina Schuchert. 1913
?Hyaifidina sp. 1

Plate 12, figures 30—33

Small, smooth biconvex Hyattidina-like and N ucleo-
spira-like brachiopods, most less than 8 mm wide, are
very abundant in the upper Lone Mountain faunas.
Most of these articulated shells are probably immature
growth stages of such Spiriferacea as Hyattidina and
H indella. Brachial valves from Mahogany Hills locality
M1112 have hinge-plate features suggestive of H yatti-
dina congesta (Conrad); larger shells from locality
M1087 in the Fish Creek Range reveal spiralia with
lateral apices and pedicle valve muscle fields similar to
?Hyattidina hesperalis (Waite) of the Laketown Dolo-
mite. Larger and more robust shells in these Lone
Mountain faunas are assigned to the genus Hindella
and are described separately.

?Hyattidina hesperalis (Waite) was initially placed
in Protathyris Kozlowski (Waite, 1956) and later
referred to H yattidina Schuchert by Johnson and Reso
(1964). ?Hyattidina sp. f from the Lone Mountain
Dolomite has no well-defined fold and sulcus, differing
in this respect from mature Hyattidina congesta and
the Laketown hesperalis. The largest shells of ?H. sp. f
show a slight emargination of the commissure suggest-
ing incipient fold-sulcus development.

Externally very similar shells are described and
illustrated by Norford (1962) from the Silurian Sand-

if

FAMILY DELTHYRIDIDAE WAAGEN 41

pile Dolomite of Northern British Columbia. The
Sandpile species is assigned by Norford to Glassia
variabilis Whiteaves. ?Hyattidina sp. f has a spiralium
like that of the Meristellidae, with lateral apices of
cones; Glassia Davidson by definition has the spiralium
apices situated at the middle of the brachial cavity
(Schuchert, 1913, p. 409).

Occurrence—Late Silurian, upper part of the Lone
Mountain Dolomite; upper Laketown—Lone Mountain
biofacies. Southern Mahogany Hills, locality M1112, in
association with Howellella pauciplicata and Entelo-
phyllum engelmanni. Southern Fish Creek Range,
locality M1087, in association with Howellella smithi
and Entelophyllum engelmanni.

Genus Hindella Davidson. 1882
Hindella sp. a

Plate 12, figures 34—37

Hindella with valves about equally convex, length
but slightly greater than width. Anterior commissure
conspicuously bowed; fold of dorsal valve very weak
anteriorly, ventral valve with incipient sulcus. Shell
smooth except for incremental lines that are numerous
near the commissure. This species is relatively wider
than both H. prinstana and H. umbonata, and depth of
the dorsal valve is more nearly that of the ventral valve.

The interior of H. sp. a is unknown, leaving the
generic assignment uncertain. Some of the small and
possibly immature shells found in association and here
interpreted as belonging to ?Hyattidina sp. f may be
the young of H indella sp. a.

Atrypella carinata Johnson (Johnson and Reso,
1964) has similar features in the beak vicinity, a more
elongate shell with better defined fold and sulcus.

Occurrence—Late Silurian, upper part of the Lone
Mountain Dolomite, locality M1087, Southern Fish
Creek Range.

Family ATRYPIDAE Gill, 1871

Genus Atrypa Dalman, 1828
Atrypa sp.!

Plate 11, figures 1—4

Small to medium-sized Atrypa with coarse radial
costae, moderate even upward bowing of the anterior
commissure, and rather weakly defined growth lamellae
which produce small costal nodes. Costae may bifurcate
anteriorly. Convexity of brachial valve does not greatly
exceed that of pedicle valve.

Among described American Silurian atrypas, this
species appears closest to A. tennesseensis Amsden of
the Brownsport and Henryhouse, but differs by having
less prominent growth lamellae. Atrypa sp. of Johnson
and Reso (1964) from the Silurian of the Great Basin
has similar ornamentation and possibly represents the
same species as Atry pa sp. f.

 

 

 

 

Occurrence—Late Silurian, upper part of the Lone
Mountain Dolomite, Southern Fish Creek Range,
locality M1113.

Family DELTHYRIDIDAE Waagen. 1883
Genus Howellella Kozlowski, 1946

Small and medium-sized spiriferoids of this genus are
the most distinctive fossils of the Late Silurian dolo-
mites of the Great Basin. These shells have a conspicu-
ous fold and sulcus and strong dental lamellae, and
lack a ventral valve median septum. The coarse radial
costae which characterize this genus may become
nearly obsolete laterally in some species. Howellella
ranges from Late Silurian into the Helderbergian Rab-
bit Hill Limestone, where it is represented by a larger
species allied to H. cycloptera.

Howellella pauciplicalu Waite
Plate 12, figures 20—24
1956 Howellella pauciplicata Waite, p. 17, pl. 3, figs. 6—10.
1964 H owellella pauciplicata Waite. Johnson and Reso, pl. 20,
figs. 8, 10—12.
1964(?) M acropleura? sp. Johnson and Reso, p. 82, pl. 20, figs.
1—7.

This species is characterized by obsolete or nearly
obsolete ribbing on the flanks of the valves. A large
suite of individuals from Laketown Dolomite unit 48
of Hose in the Confusion Range, Utah (R. K. Hose,
written commun., 1954) show a range in dorsal valves
from those that are nearly smooth on either side of the
fold to those having the fold flanked by a single coarse
but subdued rib. In some individuals, the fold itself is
rather weak.

The upper Lone Mountain specimens have at least
one subdued rib lateral to the fold, and the shell flanks
are somewhat less smooth than in Waite’s holotype and
other Confusion Range specimens. There is no indica-
tion of continuous variation from the pauciplicata
lineage into coarsely plicated H owellella smithi, also of
the upper Lone Mountain.

Occurrence—Late Silurian, upper part of the Lone
Mountain Dolomite; southern Mahogany Hills, locality
M1112, associated with Entelophyllum engelmanni and
?Hyattidina sp. f.

Howellella smithi Waite
Plate 12, figures 1—19
1956 Howellella smithi Waite, p. 17, pl. 3, figs. 16—19.

This coarsely ribbed species, large for the genus, is
abundantly represented in two fossil localities of the
upper Lone Mountain Dolomite of the Fish Creek
Range. The hinge line is narrow and the shell width
considerably greater than the shell length. Fold and
sulcus are prominent, flattened medially toward the
commissure. Two coarse costae occupy the flanks of
both valves, lateral to which are one or more subdued

 

 

 

—‘—

42 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

ribs. Dental lamellae are well developed, but only mod-
erately long; there is no suggestion of a pedicle valve
median septum. In the brachial valve, the dental
rockets and other hinge-plate features are similar to
those of Howellella crispa (Hisinger) as illustrated by
Hall and Clarke (1894, pt. II, pl. 36, fig. 4). Some
individuals of this species, however, reveal a very weak
incipient median septum in the brachial valve not
known in crispa.

A suite of specimens in various growth stages gives
no indication of intergradation of Howellella smithi
with pauciplicata of about the same stratigraphic
horizon.

Occurrence—Late Silurian, upper part of the Lone
Mountain Dolomite; Southern Fish Creek Range,
localities M1087 and M1113. Waite’s holotype is
reported from Laketown beds “below the Sevy dolo-
mite” in the Pahranagat Range. Howellella smith was
not found in unit 48 of the Confusion Range, Utah,
Laketown Dolomite which yielded abundant H. pauci-
plicata.

LOCALITY REGISTER1

Fossils of the Rabbit Hill Limestone and correlative strata

Inyo Mountains, Calif.

Locality M1093.—Independence quadrangle, California.
NEIA sec. 8, T. 13 S., R. 36 E.; at mouth of Mazourka Can-
yon east of Kearsarge. At measured stratigraphic section
VG—l (Ross, 1966, pl. 1) 450 feet below top of Vaughn
Gulch Limestone.

Locality M1401.—Independence quadrangle, California. Ma-
zourka Canyon area, east side Al Rose Canyon, 6/10 mile
N. 78" E. of SE cor. sec. 36, T. 11 S., R. 35 E., on measured
section SC—5 (Ross, 1966, pl. 1) 40 feet below top of Sun-
day Canyon Formation.

Monitor Range, Nev. (middle part)

Locality M 1311 .—East side of Monitor Range near Dobbin
Summit, northern Nye County. East side of road east of
East Dobbin Summit Spring, altitude 8,500 ft (Army Map
Service, Tonopah sheet, NJ 11—5). Lower part of Rabbit
Hill Limestone. Same locality as M1067.

Locality M1068.—Same locality as M1311; in middle part
of Rabbit Hill Limestone.

Locality M I309.—Same locality as M1311; in upper part of
Rabbit Hill Limestone. Same locality as M1069.

Monitor Range, Nev. (northern part)

Locality M 409.—Horse Heaven Mountain quadrangle.
Southeast side of Rabbit Hill near junction of Whiterock
Canyon with Copenhagen Canyon; altitude 7,080 ft. Type
section of Rabbit Hill Limestone. Other locality numbers
same site: M48, M187, M1326.

Locality M 49.—Horse Heaven Mountain quadrangle; 8/10
mile north-northwest of Rabbit Hill; altitude 7,300 ft. Rab-
bit Hill Limestone with same fauna as type section.

Toquima Range, Nev. (northern part)

Locality M1150.—Wildcat Peak quadrangle. Petes Canyon

area, northernmost Toquima Range. SW14 sec. 16, T. 16

 

1Locality numbers with M prefix (for example M1093) used in this report
refer to US. Geological Survey fossil localities listed in the Paleozoic locality
ledgers of the Menlo Park, Calif. center.

 

N., R. 46 E.; on top of spur 1,600 feet south of summit
7,188, and 2,800 feet east of Petes Canyon road. Small iso-
lated exposure of Rabbit Hill Limestone in contact with
graptolitic shale. Same locality as M1147.

Simpson Park Range, Nev. (middle part)

Locality M1074.—-Walti Hot Springs quadrangle. Foothills
half a mile southeast of Walti Ranch and west of
McClusky Peak, altitude 6,000 ft. Rabbit Hill Limestone.

Simpson Park Range, Nev. (northern part)

Locality M1032.—Horse Creek Valley quadrangle. Coal Can-
yon area; east side of Coal Canyon in NWIA sec. 21, T. 25
N ., R. 49 E., altitude 6,600 ft. Rabbit Hill Limestone.

Locality M1075.—Horse Creek Valley quadrangle. Coal
Canyon area, near canyon mouth on east side. Limestone
beds near top of ridge 6909 on west side. Upper part of
Rabbit Hill Limestone.

Locality M1076.——Same as M1075, mostly float material
below ridge top 6909 down slope to west. Rabbit Hill Lime-
stone.

Locality M1310.—-Horse Creek Valley quadrangle. Coal Can—
yon area; SE14 sec. 17, T. 25 N., R. 49 E. West side of
ridge 6909 near top. Upper 200 feet of the Rabbit Hill
Limestone, in platy limestone with abundant trilobites.

Cortez Mountains, Nev.

Locality M1083.——Cortez quadrangle. Cortez Mountains,
southeast side of Mount Tenabo, near head of Horse
Canyon. 1,000 feet north, 700 feet west of SE cor. sec. 4,
T. 26 N ., R. 48 E.; altitude 7,900 ft. Rabbit Hill Limestone
fauna.

Tuscarora Mountains, Nev.

Locality MI400.——East side of Tuscarora Mountains near
south end (Army Map Service, Winnemucca sheet NK
11—11). Nine miles northwest of Carlin, near top of bluff
on east side of Maggie Creek; T. 34 N., R. 51 E. Rabbit
Hill Limestone overlying Roberts Mountains Limestone.

Sulphur Spring Range, Nev. (southern part)

Locality M186.—Garden Valley quadrangle. South Mulligan
Gulch area; east side South Mulligan Gulch near mouth;
2,000 feet southwest of summit 6927, altitude 6,560 ft.
Beacon Peak Dolomite Member with Rabbit Hill fauna
below beds with Oriskany-age fossils, and above probable
Lone Mountain Dolomite.

Locality M197.—Garden Valley quadrangle. Bailey Pass
area; 34 mile south of Bailey Pass on main ridge crest
1,000 feet southeast of summit 7107. Beds with Rabbit Hill
fossils below Oriskany-age faunas of the Nevada Formation.

Locality M1081 .—Garden Valley quadrangle. South Mulli-
gan Gulch area; east side of range 1 mile east of Mulligan
Gap, 2,600 feet northeast of summit 7446; altitude 6,800 ft.
Beacon Peak Dolomite Member with Rabbit Hill fauna.

Locality M1082.—-Garden Valley quadrangle. South Mulli-
gan Gulch area; due west of BM 5867, 12/10 miles on top of
spur, altitude 6,440 ft; 1,400 feet east-northeast of summit
6474. Beacon Peak Dolomite Member with Rabbit Hill
fossils.

Locality M1312.—Garden Valley quadrangle. Near M186.
Beacon Peak Dolomite Member with Rabbit Hill fossils.
Locality M1319.—Garden Valley quadrangle. Prince of

Wales mine area; southeast of Prince of Wales mine and
northwest of summit 7530; altitude 7,200 ft. Beacon Hill
Dolomite Member with Rabbit Hill fossils, below beds

with Oriskany-age fauna.

Fossils of the Lone Mountain Dolomite
Lone Mountain, Eureka County, Nev.

 

SELECTED BIBLIOGRAPHY 43

Locality M1122.—Whistler Mountain quadrangle. Southeast
side Lone Mountain, east side Charcoal Gulch, ‘1/10 mile
due south of summit 7360; altitude 6,840 ft on top of spur.
Dark-gray carbonaceous Lone Mountain Dolomite with
fragmentary rugose corals.

Locality M1122a.—Same area as M1122, 3,200 ft south-
southeast of summit 7360; altitude 6,600 ft. Dark-gray
Lone Mountain Dolomite with fragmentary corals.

Mahogany Hills, Nev, (southern part)

Locality M1112.—Bellevue Peak quadrangle. About 11/4
miles due north of top of Wood Cone Peak and half a mile
north—northwest of BM 7201; in foothill exposures of Lone
Mountain Dolomite. Altitude 7,300 ft. Dark-gray carbona-
ceous dolomite with silicified corals.

Fish Creek Range, Nev. (southern part)

Locality M1087.——Bellevue Peak quadrangle. North end of
Fenstermaker Mountain on west side at south boundary of
quadrangle; about 2,000 feet due south of summit 7232,
altitude 7,000 ft. Dark-gray Lone Mountain Dolomite with
silicified fossils.

Locality M1]13.——Bellevue Peak quadrangle. Same area as
M1087; 4/10 mile south-southeast of summit 7232. Altitude
7,080 feet. Dark-gray Lone Mountain Dolomite with silici-
fied fossils.

Sulphur Spring Range, Nev. (southern part)

Locality M1121.—Garden Valley quadrangle. East margin
of range in East Ridge, 2 miles south-southwest of Romano
Ranch, and 8/10 mile S. 60° W. of BM 5825; altitude 6,440
ft near top of ridge. Lower part of Lone Mountain Dolo-
mite with silicified corals.

Locality M1148.—Garden Valley quadrangle. East margin of
range, east slope of East Ridge in northeast corner sec. 35,
T. 23 N., R. 52 E.; half a mile north-northwest of BM
5867. Altitude 6,100 ft on top east-west spur. Lone Moun-
tain Dolomite with corals.

SELECTED BIBLIOGRAPHY

Amos, Arturo, and Boucot, A. J ., 1963, A revision of the brach-
iopod family Leptocoeliidae: Palaeontology, v. 6, pt. 3,
p. 440—457, pls. 62—65.

Amsden, T. W., 1949, Stratigraphy and paleontology of the
Brownsport formation (Silurian) of western Tennessee:
Yale Univ. Peabody Mus. Nat. History Bull. 5, p. 1—138,
34 pls., text figs.

1951, Brachiopods of the Henryhouse Formation (Silu-

rian) of Oklahoma: Jour. Paleontology, v. 25, p. 69—96,

pls. 15—20, text-fig.

1958a, Haragan articulate brachiopods, pt. 2 of Amsden,

T. W., and Boucot, A. J ., Stratigraphy and paleontology

of the Hunton group in the Arbuckle Mountain region:

Oklahoma Geol. Survey Bull. 78, p. 1—144, 14 pls., text figs.

1958b, Supplement to the Henryhouse brachiopods, pt.

3 of Amsden, T. W., and Boucot, A, J., Stratigraphy and

paleontology of the Hunton group in the Arbuckle Moun-

tain region: Oklahoma Geol. Survey Bull. 78, p. 145—157,

pls. 12, 14, text figs.

1958c, Stratigraphy and paleontology of the Hunton
group in the Arbuckle Mountain region, pt. V, Bois D’Arc
articulate brachiopods: Oklahoma Geol. Survey Bull. 82,
110 p., 5 pls.

Amsden, T. W., and Ventress, W. P. S., 1963, Early Devonian
brachiopods of Oklahoma; pt. 1, Articulate brachiopods of
the Frisco formation (Devonian): Oklahoma Geol. Sur-

 

 

 

 

 

vey Bull. 94, p. 9—140, pls. 1—12.

Beecher, C. E., 1893a, The development of a Paleozoic porifer-
ous coral: Connecticut Acad. Arts and Sci. Trans, v. 8,
pt. 2, p. 207—214, pls. 9—13.

1893b, Symmetrical cell development in the Favositidae:
Connecticut Acad. Arts and Sci. Trans, v. 8, pt. 2, p. 215—
218, pls. 14,‘ 15.

Boucot, A. J ., 1957, Revision of some Silurian and Early Devo-
nian spiriferid genera and erection of Kozlowskiellinae,
new subfamily: Senckenbergiana Lethaea, V. 38, no. 5—6,
p, 311—334, 3 pls.

1958, Kozlowskiellina, new name for K ozlowskiella Bou-

cot, 1957: Jour. Paleontology, v. 32, no. 5, p. 1030.

1960, Brachiopods, in Boucot, A. J ., Martinsson, Anders,
Thorsteinsson, R., Walliser, O, H., Whittington, H. B., and
Yochelson, Ellis, A Late Silurian fauna from the Suther-
land River Formation, Devon Island, Canadian Arctic
Archipelago: Canada Geol. Survey Bull. 65, 51 p., 10 pls.

Boucot, A. J ., and Amsden, T. W., 1958, New genera of brach-
iopods, pt. 4 in Amsden, T. W., and Boucot, A. J ., Stratig-
raphy and paleontology of the Hunton group in the
Arbuckle Mountain region: Oklahoma Geol. Survey Bull.
78, p. 159—170, pl, 14, text figs.

Boucot, A. J., and Gill, E. D., 1956, Australocoelia, a new
Lower Devonian brachiopod from South Africa, South
America, and Australia: Jour. Paleontology, v. 30, no. 5,
p. 1173—1178, pl. 126.

Boucot, A. J ., Johnson, J. G., Harper, Charles, and Walmsley,
V. G., 1966, Silurian brachiopods and gastropods of south-
ern New Brunswick: Canada Geol. Survey Bull. 140, 45 p.,
18 pls.

Boucot, A, J ., Johnson, J. G., and Staten, R .D., 1964, On some
atrypoid, retzioid, and athyridoid Brachiopoda: Jour.
Paleontology, v. 38, no. 5, p. 805—822, pls. 125—128.

Butler, A. J ., 1935, On the Silurian coral Cyathaxonia silu-
riensis M’Coy: Geol. Mag., V. 72, p. 116—124, pl. 2.

Clark, D. L., and Ethington, R. L., 1964, Age of the Roberts
Mountains formation (Silurian?) in the Great Basin:
Geol. Soc. America Bull., v. 75, p, 677—682.

1966, Conodonts and biostratigraphy of the Lower and
Middle Devonian of Nevada and Utah: J our. Paleontology,
v. 40, no. 3, p. 659—689, pls. 82—84.

Cooper, G. A., 1942, New genera of North American brachio-
pods: Washington Acad. Sci. Jour., v. 32, p. 228—235.
1944, Brachiopoda, in Shimer, H. W., and Shrock, R. R.,
eds, Index fossils of North America: Cambridge, Mass,
The Technology Press, Mass. Inst. Technology (New
York, John Wiley and Sons, Inc.) , p. 277—365, pls. 105—143.

Delo, D. M., 1940, Phacopid trilobites of North America: Geol.
Soc. America Spec. Paper 29, 135 p., 13 pls.

Dunbar, C. 0., 1918, Stratigraphy and correlation of the Devo-
nian of western Tennessee: Am. Jour. Sci., v. 46, p. 732—
755.

1920, New species of Devonian fossils from western
Tennessee: Connecticut Acad. Arts and Sci, Trans, v. 23,
p. 113—149, pls. 1—5.

Duncan, Helen, 1956, Ordovician and Silurian coral faunas of
western United States: US. Geol. Survey Bull. 1021—F,
p. 209—236, pls. 21—27.

Edwards, H. M., and Haime, Jules, 1850—1854, A monograph
of the British fossil corals: London, Palaeontographical
Soc., 322 p., 72 pls.

1851, Monographie des polypiers fossiles des terrains

palaeozoiques: Mus. Histoire Nat, Paris, Archives, v. 5,

 

 

 

 

 

 

 

 

 

 

44 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

502 p., 20 pls.

Etheridge, Robert, J r., 1911, The Lower Palaeozoic corals of
Chillagoe and Clermont, pt. 1: Queensland Geol. Survey
Pub. 231, p. 1—8, pls. A—D. [Australia]

Fenton, C. L., and Fenton, M. A., 1936, The “tabulate” corals
of Hall’s “Illustrations of Devonian fossils”: Carnegie
Mus. Annals, v. 25, art. 5, p. 17—56, pls. 1—7.

Fliigel, H., and Free, B., 1962, Laccophyllidae (Rugosa) aus
dem Greifensteiner Kalk (Eiflium) von Wiede bei Greifen-
stein: Palaeontographica, v. 119, no. A, p. 222—247.

Gilluly, James, and Masursky, Harold, 1965, Geology of the
Cortez quadrangle, Nevada: US. Geol. Survey Bull. 1175,
117 p.

Hague, Arnold, 1892, Geology of the Eureka district, Nevada:
US. Geol. Survey Mon. 20, 419 p. (with atlas), 8 pls.
Hall, James, 1859—1861, Organic remains of the lower Helder-
burg group and the Oriskany sandstone: New York Geol.

Survey, Palaeontology, v. 3, p. 1—532, pls. 1—120,

1887, Corals and Bryozoa: New York Geol. Survey,
Palaeontology, v, 6, p. 1—298, pls. 1—66.

Hall, James, and Clarke, J. M., 1892, An introduction to the
study of the genera of Palaeozoic Brachiopoda: Palaeon-
tology of New York, v. 8, pt. 1, p. 1—367, 20 pls., text figs.
[1893].

1894, An introduction to the study of the genera of
Palaeozoic Brachiopoda: Palaeontology of New York, v. 8,
pt. 2, p. 1—314, pls. 21—84, text figs.

Havlicek, Vladimir, 1959, Spiriferidae of the Silurian and
Devonian of Bohemia: Rozpravy Usti-ed. Ustavu Geol., v.
25, p. 1—218 (Czech text), p. 223—275 (English summary),
27 pls., text figs.

1961, Rhynchonelloidea des b'ohmischen alteren Palac-
zoikums (Brachiopoda): Roszpravy Ustred. Ustavu Geol.,
v. 27, p. 1—211, pls. 1—27.

Helmbrecht, W., and Wedekind, Rudolf, 1923, Versuch einer
biostratigraphischen gliderung der Siegener Schichten auf
grund von Rensselaerien und Spiriferen: Gliickauf, v. 59,
no. 41, p. 949—953.

Hill, Dorothy, 1935, British terminology for rugose corals:
Geol. Mag., v. 72, no. 857, p. 481—519.

1936, The British Silurian rugose corals with acanthine

septa: Royal Soc. London Philos. Trans, ser. B, no. 534,

v. 226, p. 189—217, 2 pls.

1940, The Silurian Rugosa of the Yass-Bowning District,

N.S.W.: Linnean Soc. New South Wales Proc., v. 65, pt.

3—4, p. 388—420, 3 pls.

1956, Rugosa, in Moore, R. 0., ed., Treatise on inverte-

brate paleontology, Part F—Coelenterata: New York and

Lawrence, Kansas, Geol. Soc. America and Kansas Univ.

Press, p. F233—F324,

1958, Distribution and sequence of Silurian coral
faunas: Royal Soc. New South Wales Jour. and Proc., v.
92, pt. 4, p. 151—173.

Hill, Dorothy, and Stumm, E. C., 1956, Tabulata, in Moore,
R. 0., ed., Treatise on invertebrate paleontology, part F—
Coelenterata: New York and Lawrence, Kansas, Geol. Soc.
America and Kansas Univ. Press, p. F444—F477.

Hudson, R. G. S., 1944, Lower Carboniferous corals of the
genera Rotiphyllum and Permia: Jour. Paleontology, v.
18, no. 4, p. 355-362, pls. 56, 57.

Johnson, J. G., 1965, Lower Devonian stratigraphy and corre-
lation, northern Simpson Park Range, Nevada: Canadian
Petroleum Geology Bull., v. 13, no. 3, p. 365—381.

1970, Great Basin Lower Devonian Brachiopoda: Geol.

 

 

 

 

 

 

 

 

 

Soc. America Mem. 121, 421 p., 74 pls.

Johnson, J. G., and Boucot, A. J., 1968, Brachiopods of the
Bois Blanc Formation in New York: US. Geol. Survey
Prof. Paper 584—B, p. 1—27, 8 pls.

Johnson, J. G., and Murphy, M. A., 1969, Age and position of
Lower Devonian graptolite zones relative to the Appala-
chian standard succession: Geol. Soc. America Bull., v. 80,
no. 7, p. 1275—1282.

Johnson, J. G., and Reso, Anthony, 1964, Probable Ludlovian
brachiopods from the Sevy dolomite of Nevada: Jour.
Paleontology, v. 38, no. 1, p. 74—84, pls. 19, 20.

Johnson, J. G., and Talent, J. A., 1967a, Muriferella, a new
genus of Lower Devonian septate dalmanellid: Royal Soc.
Victoria Proc., v. 80, pt. 1, p. 43—50, pls. 9, 10.

1967b, Cortezorthinae, a new subfamily of Siluro-Devo-
nian dalmanellid brachiopods: Palaeontology, v. 10, pt. 1,
p. 142—170, pls. 19—22.

Kay, Marshall, and Crawford, J. P., 1964, Paleozoic facies
from the miogeosynclinal to the eugeosynclinal belt in
thrust slices, Central Nevada: Geol. Soc. America Bull., v.
75, p. 425—454.

Kindle, E. M., 1912, The Onondaga fauna of the Allegheny
region: U.S. Geol. Survey Bull. 508, 144 p., 13 pls.

Klapper, Gilbert, 1968, Lower Devonian conodont succession
in central Nevada [abs]: Geol. Soc. America 64th Ann.
Mtg., Cordilleran Section, Tucson, 1968, program, p. 72—73.

Klapper, Gilbert, and Ormiston, A. R., 1969, Lower Devonian
conodont sequence, Royal Creek, Yukon Territory and
Devon Island, Canada; with a section on Devon Island
stratigraphy: J our. Paleontology, v. 43, no. 1, p. 1—27, 6 pls.

Kozlowski, Roman, 1929, Les brachiopodes de la Gothlandiens
de la Podolie Polonaise: Palaeontologia Polonica, v. 1,
p. 1—254, 12 pls., text figs.

1946, Howellella, a new name for Crispella Kozlowski
1929: Jour. Paleontology, v. 20, p. 295.

Lang, W. D., and Smith, Stanley, 1927, A critical revision of the
rugose corals described by W. Lonsdale in Murchison’s
“Silurian System”: Geol. Soc. London Quart. Jour., v.
83, p. 448—491, pls. 34-37.

Lang, W. D., Smith, Stanley, and Thomas, H. D., 1940, Index
of Palaeozoic coral genera: London, British Mus. (Nat.
History), 231 p.

Lindstrtim, Gustav, 1882, Silurische Korallen aus Nord-
Russland und Siberien: Kgl. Svenska Vetenskapsakad.
Handl., Bihang, v. 6, no. 18, 23 p., 1 pl.

McAllister, J. F., 1952, Rocks and structure of the Quartz
Spring area, northern Panamint Range, California: Cali-
fornia Div. Mines Spec. Rept. 25, 38 p.

McKee, E. H., Merriam, C. W., and Berry, W. B. N., 1972,
Biostratigraphy of the Tor and McMonnigal Formations,
Toquima Range, Nevada: Am. Assoc. Petroleum Geolo-
gists Bull., v. 56, no. 8, p. 1563—1570.

McKee, E. H., and Ross, R. J ., Jr., 1969, Stratigraphy of east-
ern assemblage rocks in a window in Roberts Mountains
thrust, northern Toquima Range, central Nevada: Am.
Assoc. Petroleum Geologists Bull., v. 53, no. 2, p. 421—429.

Merriam, C. W., 1940, Devonian stratigraphy and paleontology
of the Roberts Mountains region, Nevada: Geol. Soc.
America Spec. Paper 25, 114 p., 16 pls.

1963, Paleozoic rocks of Antelope Valley, Eureka and

Nye Counties, Nevada: US. Geol. Survey Prof. Paper

423, 67 p.

1973a, Silurian rugose corals of the central and south—

west Great Basin: U.S. Geol. Survey Prof. Paper 777, 65 p.

 

 

 

 

 

 

SELECTED BIBLIOGRAPHY 45

1973b, Lower and lower Middle Devonian rugose corals

of the central Great Basin: U.S. Geol. Survey Prof. Paper

805 (in press).

1973c, Middle Devonian rugose corals of the central
Great Basin: U.S. Geol. Survey Prof, Paper 799, 52 p.

Merriam, C. W., and Anderson, C. A., 1942, Reconnaissance
survey of the Roberts Mountains, Nevada: Geol. Soc.
America Bull., v. 53, p. 1675—1728.

Nolan, T. B., Merriam, C. W., and Williams, J. S., 1956, The
stratigraphic section in the vicinity of Eureka, Nevada:
US. Geol. Survey Prof. Paper 276, 77 p.

Norford, B. S., 1962, The Silurian fauna of the Sandpile group
of northern British Columbia: Canada Geol. Survey Bull.
78, 51 p., 16 pls.

Oliver, W. A., Jr., 1960, Rugose corals from reef limestones in
the Lower Devonian of New York: Jour. Paleontology, v.
34, no. 1, p. 59—100, pls. 13—19.

1962, Silurian rugose corals from the Lake Temiscouata

area, Quebec: U.S. Geol. Survey Prof. Paper 430—B, p.

11—19, pls. 5—8.

1966, Description of dimorphism in Striatopora flexuosa
Hall: Paleontology, v. 9, pt. 3, p. 448—454, pls. 68—71.

Poéta, Philippe, 1902, Anthozoaires et Alcyonaires, in Bar-
rande, Joachim, System Silurien du centre de la Boheme:
Prague, Recherches Paleontologiques, v, 8, pt, 2, 347 p.,
99 pls.

Prantl, Ferdinand, 1938, Some Laccophyllidae from the Middle
Devonian of Bohemia: Annals and Mag. Nat. History,
11th ser., v. 2, p. 18—41,pls. 1—3.

1940, Korallengattung Xylodes Lang and Smith im
béhmischen Silur: Czechoslovakia, Akad. Wiss. Mitt.,
Prague, 21 p., 3 pls.

Ross, D. C., 1966, Stratigraphy of some Paleozoic formations
in the Independence quadrangle, Inyo County, California:
US. Geol. Survey Prof, Paper 396, 64 p., illus.

Rukhin, L. B., 1938, The lower Paleozoic corals and stromato-
poroids of the upper part of the Kolyma river: U.S.S.R.,
State Trust Dalstroy, Contr. Knowledge of Kolyma-
Indighirka, Geol. and Geomorph., fasc. 10, 119 p., 28 pls.
[Russian, English summary].

Sardeson, F. W., 1896, Ueber die Beziehungen der fossilen Tab-
ulaten zu den Alcyonairen: Neues Jahrbuch fiir Mineral-
ogie, Geologic und Palaontologie, v, 10, p. 249—362.

Schindewolf, O. H., 1942, Zur Kenntniss der Polycoelien und
Plerophyllen: Abh. Reichsamt. Bodenf., Neue Folge, Heft.
204, 324 p., 36 pls.

Schmidt, Herta, 1941, Die mittel devonischen Rhynchonelliden
der Eifel: Abh. senckenberg. naturf. Gesell. 459, p. 1—79,
pls. 1—7.

Schouppé, Alexander, 1950, Kritische Betrachtungen zu den
Rugosengenera des Formenkreises Tryplasma L0nsd.,
Polyorophe Lindstr.: Osterreich. Akad. Wiss. Sitzungsber.
Math.-Naturw. Kl., div. 1, v. 159, p. 75—85.

Schuchert, Charles, 1897, A synopsis of American fossil
Brachiopoda including bibliography and synonymy: U.S.
Geol. Survey Bull. 87, p. 1—464.

1913, Brachiopoda, in Textbook of Paleontology: East-
man-Zittel, Macmillian and 00., p. 355—420.

Schuchert, Charles, and Cooper, G. A., 1931, Synopsis of the
brachiopod genera of the suborders Orthoidea and Penta-
meroidea, with notes on the Telotremata: Am. Jour, Sci.,
ser. 5, v. 22, p. 241—251.

1932, Brachiopod genera of the suborders Orthoidea and

Pentameroidea: Yale Univ. Peabody Mus. Nat. History,

 

 

 

 

 

 

 

 

Mem.,v. 4, pt. 1, p. 1—270, 29 pls., text figs.

Schuchert, Charles, and Maynard, T. P., 1913, Brachiopoda, in
Lower Devonian of Maryland: Maryland Geol. Survey, p.
290—450, pls. 1—98.

Simpson, G. B., 1900, Preliminary descriptions of new genera of
Paleozoic rugose corals: New York [State] State Mus.
Bull. 39, v. 8, p. 199—222; republished as New York State
Univ., New York State Mus. 54th Ann. Rept. of Regents,
1900, v.3.

Smith, Stanley, 1930, Some Valentian corals from Shropshire
and Montgomeryshire, with a note on a new stromatopo-
roid: Geol. Soc. London Quart, Jour., v. 86, p. 291—330,
pls. 26—29.

1933, On Xylodes rugosus sp. nov., a Niagaran coral:

Am. Jour. Sci., ser. 5, v. 26, no. 155, p. 512—522, 1 pl.

1945, Upper Devonian corals of the Mackenzie River
region, Canada: Geol. Soc. America Spec. Paper 59, 126
p., 35 pls.

Smith, Stanley, and Tremberth, Reginald, 1929, On the Silur-
ian corals Madreporites articulatus Wahlenberg, and
Madrepora truncata L: Annals and Mag. Nat. HiStory,
ser. 10, v. 3, p. 361—376, pls. 7, 8.

Soshkina, E. D., 1937, Corals of the Upper Silurian and Lower
Devonian of the eastern and western slopes of the Urals:
Akad. Nauk SSSR, Paleozool. Inst. Trudy, v. 6, pt. 4, 112
p., 21 pls. [Russian English summary].

Stainbrook, M. A., 1946, Corals of the Independence shale of
Iowa: Jour. Paleontology, v. 20, no. 5, p. 401—427, pls.57-61.

Stehli, F. G., 1954, Lower Leonardian Brachiopoda of the
Sierra Diablo: Am. Mus. Nat, History Bull. v. 105, art. 3,
p. 261—357, pls. 17—27, text figs.

Stumm, E. C., 1949, Revision of the families and genera of the
Devonian tetracorals: Geol. Soc, America Mem. 40, 921).,
25 pls.

1950, Corals of the Devonian Traverse group of Michi-

gan; pt. 3, Antholites, Pleurodictyum, and Procteria:

Michigan Univ. Mus. Paleontology Contr., v. 8, no. 8, p.

205—220, 5 pls.

1952, Species of the Silurian rugose coral genus Try-

plasma from North America: Jour. Paleontology, v. 26,

no. 5, p, 841—843, pl. 125.

1954, Lower Middle Devonian phacopid trilobites from

Michigangsouthwestern Ontario, and the Ohio Valley:

Michigan Univ. Mus. Paleontology Contr., v. 11, no, 11,

p. 201—221, 4 pls.

1962, Silurian corals from the Moose River synclinorium,

Maine, chap. A in Silurian corals from Maine and Quebec:

U.S. Geol. Survey Prof. Paper 430, p. 1—9, pls. 1—4 [1963].

1964, Silurian and Devonian corals of the Falls of the
Ohio: Geol. Soc. America Mem. 93 ,184 p., 2 figs, 80 pls.

Stumm, E. C., and Tyler, J. H., 1964, Corals of the Traverse
group of Michigan, Part 12, The small-celled species of
Favosites and Emmonsia: Michigan Univ. Mus. Paleontol-
ogy Contr., v. 19, no. 3, p. 23—26, pls. 1—7.

Swann, D. H., 1947, The Fauosites alpenensis lineage in the
Middle Devonian Traverse group of Michigan: Michigan
Univ. Mus. Paleontology Contr., v. 6, no. 9, p. 235—318,
pls. 1—17.

Swartz, F. M., 1930, The Helderberg group of parts of West
Virginia and Virginia: US. Geol. Survey Prof. Paper
158—C, p. 27—75, pls. 6—9, text figs.

1939, The Keyser limestone and Helderberg group, in

The Devonian of Pennsylvania: Pennsylvania Geol. Sur-

vey Bull., 4th sen, G19, p. 29—91, text figs.

 

 

 

 

 

 

 

 

 

 

46 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA

Waite, R. H., 1956, Upper Silurian Brachiopoda from the
Great Basin: Jour. Paleontology, v. 30, no. 1, p. 15—18,
pl. 4.

Walcott, C. D., 1884, Paleontology of the Eureka district
[Nevada]: US. Geol. Survey Mon. 8, 298 p., 24 pls.

Wedekind, Rudolf, 1927, Die Zoantharia von Gotland: Sveriges
Geol. Undersokning, ser. Ca, no. 19, p. 1—94, 30 pls.

Whittington, H. B., 1956, Type and other species of Odonto-
pleuridae (Trilobita): Jour. Paleontology, v. 30, p. 504—
520, pls. 57—60.

Williams, Alwyn, and Wright, A. D., 1963, The classification of
the “Orthis testudinaria Dalman” group of brachiopods:
Jour. Paleontology, v. 37, no. 1, p. 1-32, pls. 1, 2.

1965, Orthida, in Williams, Alwyn, and others, Brachio-
poda, pt. H, of Moore, R. C., Treatise on invertebrate pale-
ontology: Geol. Soc. America and Kansas Univ. Press, 927
p., illus.

Winterer, E. L., and Murphy, M. A., 1960, Silurian reef com-
plex and associated facies, central Nevada: Jour. Geology,
v. 68, no. 2. p. 117-139, 7 pls.

 

INDEX

_

[Italic page numbers indicate both major references and descriptions]

 

  
    
      
  

 

 

   
 
  
 
 
    
 

A Page
abditum, Endophyllum .................................... 23
Abstract .................. .. 1
Acanthoscapha sp.. 11
Acidaspis tuberculatus 36
Acknowledgements .. 2
Acodimz .......... .. 11
Acrospin'fer .. ........ 7, 11, 12, 33, 31,
kleinhamph 7. 8, 10, 12, .94; pl. 7
kobehana ........................ 28, 29, 34
murchisoni ..
sp. D
sp ..
(Acrospinfer), Hysterolztes
acuaria, Nowakia ....................... . 35
' hm, L v-1," 22
acuticuspidata, Leptaena.. 28
acutiplicata, Anoplotheca 31

Leptocaelia ..
Aechmi'mz sp ........
aequabile, Tryplasma .,
afi‘im’s, Billingsastraea

 

 

 

 

 

Alleym'a .......................
( N icholsonia ) .....
alpenesis, Favosites
altera, Plethorhyncha
Alveolites V
sp ..
AWL 1
umbonata 30
$1). a .. .. '7, 10, 30: pl. 7
Ambocoeliidae ....... .90
Anastrophia 10, 11, 29
grossa 29
vemeuili . 10, 11, 29; pl. 5

   
  

andersoni, Plethorhyncha . 7, 8, 29, 30; pl. 6

 

 

 

Anoplotheca acutiplicata . 31
sp ................................... 31
antelopensis, Levenea subcan'nata .......... 7, 8, 10,
11, 26; pl. 4

Antelope-Roberts Mountains facies belt... 5. 11
arcuata, Meristella 30
Areal distribution .. ~5
arenosus, Costispirifer 11, 12, 34, 35
dabbinensis, Costispinfer ......... 7, 8, 12,

planicostatus, Costispz‘rifer
Spirifer
Articulata .....

 
 
 
 
  

 

 

  
 
 
  
 
 
  
   
   
 

 

articulatum, Entelophyllum 38
articulatus, Madreporites ..... 38
Xylodes 38
atoka, Men‘stella . 30
Atrypa, .............. . 40, ‘1
* MM “sis 41

sp. f .
sp ......
Atrypella cari’natu .
Atrypidae .................
Australocoelia ......
Australophyllum
cyathophylloides .
landerensis
stevemi
sp r

. 24
8, 11, 24, 25; pl. 9
11, 2.6. 25, pl. 9
................. 11, 24. 25; pl. 9

 

  

Bailey Pass
Bairdia legumimn'des
sp ........
Barr " ,L

1

pair
barra/ndi, Plethorhy'ncha ..............
becki tennesseenais, Leptostrophia

 

 
 

 

 

 

Belodella resi‘mus ............
Berdan, Jean M., quoted
bie ' 07', Camar ‘ '"‘
Billingsastraea
afim’s ........
nevudensis
sp. m ............
birdsongemis, Phacops
Birdsong Shale, Tennessee .
Bogoslovsk, Russia ................. 37
Bois d’Arc Limestone, Oklahoma..
Borszczow beds, Poland ...................
bowerbamki, Endophz/llum
Brachiopoda .
brachiopods
Branik Limestone, Bohemia

  

 

 
   
 
  
 
 
 
  

 

 

2; 7, 10, 11, 17, 18, 35

 

   
  
 
 
 
  
  
 
 
 
  
 
   
 
  
  
 
  
 
 
  
  
 
 
 
  
 

bransoni, St’ropho'nella. .. 28
Brownsport Formation ............................. 21, 41
C
Camarotaechia . 40
biem‘aszi ..... 40
pahmnagatemis 15, 16, .60; pl. 11

sp. b .. . 15, 16. 40; pl. 11
sp. f . 15. 16, 40; pl. 11
sp ......... . 14, 16; pl. 11
Camarotoechiidae 40
canadensia, Phacops .. 9, .97, pl. 2
carinata, Atrypella ....... 41
catenulatus, H alusites 13
Chewelah area, Stevens County, Wash. 12

 

Chr rL n
Cladopora ..
Coal Canyon

fault zone .
Coblenz and Eifel districts, German
Coelospim

sp .........
Coenites .....
Conclusions ..
congesta, Hyattidina
conodonts ..

 

 

Conularia ..
huntia'na . 8, 10, 19, .95; pl. 2
lata .. ..................... 8, 10
sp . . 35:131. 2
Conulariidae 86
conularids ..... 19, .95
Conulata ......................... .95
convexoris, Parahealdia, . 11
Cooper. G. A., quoted. 34
cooperi, Tremutospira, 32
Copenhagen Canyon, Horse Heaven
Mountain quadrangle . 6
coral-brachiopod assemblages ........... 15

 

 

   
 
   
 
  

 

 

Page

corals .................. 2, 13, 15, 19
Coral Zones ....... 18
Cordilleran geosyncline . 4, 5, 6
Cortez Mountains . 2, 9, 21,42
Costellirostm .. ....... 30
Costispirifer .. 7, 11, .94, 35
arenosus ........... 11, 12, 34, 35
dobbi’ne'nsis . 7, 8, 10, 12, 85; pl. 7
pla'nicostatus 34
planicostatus . 34
Costispiriferidae . .94
crassiformis, Salopina . 40
crinoidal debris ......... 7
crispa, H owellella, 42

 

   
 
  
  
 

Cyathaxom‘a siluriensis

cyathophylloides, Austrulophyllum
Spongophyllum ............................

cycloptera monitorenais, H owellella

H owellella .............
cyclopterus, Spirifer

 

    
   

 

  

 

 

D

D ’ " sp 25
Dalmanellidae ............ 26
Dalmam'tes . 37
dalmanitid .. 9, 10
Dalmanitidae . 37
Delthyrididae .92, 41
Delthun’s ....... 32
raricosta .................. 32
Devils Gate Limestone. 9, 15

Devon Island, Northwest Territories,
Canada 40
deweyi. Trematoapim .. 32
din/nu, Plethorhyncha, .. 30
Disphyllidae 25
Die L," 38
dobbinensis, Costispirifer arenasus ........ 7, 8, 12.

Dobbin Summit ..........
Dauvilli’na gem‘culata
dunbari, Pleurodictyum

  
 

E

 
 

 

 

  
 
 
 

   
 

 

 

Ely Springs Dolomite 13
Emmmia .................... 19
Endophyllidae ................. 28
E .1 L 11 23
abditwm 23
bowe-rba'nlm 23
engelmzmm', Entelophyllum . 14, 38, 41;
pls. 10, 11

enyelmanm‘ b, Entellophyllum .................... 15. 89
Enteletidae ............... 40
Entelophyllm'des 38
Entelophyllum 3, 13, 14, 16, 18, 38
articulatum ................................ 38
enyelmamti 14, 16, .98, 41, pls. 10, 11

b .. 15, 16, 8.9
eurekaensis ............................ 10, 15, 39; pl. 10

r A ,1- +1.... 33

15

 

48

   

Page
Entelophyllum-Howellella assemblages 16, 16, 17
equistriata, Trematospira ............ 31, 32
eurekaensis, Entelophyllum 15, 39:11]. 10
Eureka mining district .. . 1, 2, 3, 10

 

  
 
 
 
  
   
   
 
 
 
 

 

F
Favoaites ...... 6, 7, 8, 10, 19
alpenesis 19
gothla'ndicus 19
helderberaiae . 6, 7, 8, 10, 19:1)1- 1
sp ..... 9, 10
Favositidae 19
favositids ..... 15, 16
Favositinae ........... _. 19
Fergwnella. lincolnensis . .......... 40

Fish Creek Range ......
Fish Haven Dolomite
flabellites, Leptocoelia .
flew-wow, Striatopora
foerstei, Sy-n‘ngaxon _
fremomi, Leptaemz

 

  

 

 

 

 
  
  
   

Frisco Limestone, Oklahoma ........... 28
fucoids .................. 7
furca, Thlipsura. 11
G
aaspensis, Phacops ............................. 37
Gazelle Formation, Klamath Mountains 23
geniculata, meillina. 16
Giles Formation, Virginia . 34
Glassiu variabilis ................... 41
gothlamlicus, Favosites 19
Gotland, Sweden . ..... 38

graptolites . 2, 3. 6, 7, 17
Great Basin .. ......... 1, 2, 4. 12, 18. 40
Silurian and Devonian depositional

 

systems of ............... 1, 2, 1,
Early Devonian coral zone B 7. 10, 12, 18, 28
Early Devonian coral zone C .............. 18, 28
Late Silurian coral zone D ........ 4, 8, 16, 18

Late Silurian coral zone E 4, 6, 7, 8, 11,
12, 16, 18, 19, 24
Middle Devonian coral zone F . 18, 19

 

 

 
  

Silurian basal chert .............. 3
Greifensteiner Kalk, Germany . 23
urosaa, Anastmphia ..... 29

awenensis, Striatopom

 

 
  
   

H
H alyaites ............
catenulatus
Halysites-pycnostylid biofacies
Halysitidae ...........

Hamilton Group

 

Hanson Creek Limestone ........... 3, 13
Haragan Limestone, Oklahoma . 26, 28
hamganensis, Schuchertella ...... 7, 8, 9, 29, pl 3
H " ' . 32
helderbergiae, Favosites ............ 6, 7. 8, 19; pl. 1
Heliolitidae ....................... . 19

 

Henryhouse Formation .
henryhouse'nsz’s, Rhipidomella

 

 

 

 

hespemlis, Hyattidina ............. 40
hexactinellid sponge spicules . 7
Hidden Valley Dolomite, Panamint
Mountains, Calif .............. 22, 34, 35
H‘ .1 n 40, 41
prinstana A.
umbo’nata

   

 

  
 

 

 

sp. a .......
History of investigation ...................... 8
Howellella 3, 15, 18, 33. 38, 41
crispa. ........ 42
cycloptera . .. 41
mmitorensis 7, 8, 10, 11, 38; pl. 8
pauciplicata 14, 16, 33, [,1, 42; pl. 12
amithi 15, 16, 33, .61, 42; pl. 12

 

 

INDEX

  
 

 

 

 
  

 

 

 

   
 
 
  

Page
Howellella-Cumarotoechia-A trypa.
brachiopod assemblage 39
huddlei, Icn'odus latericrescens 11
Huddle, J. W., quoted ................. 11
Hunsriickschiefer Formation, Germany 35
huntiana, Conulan‘a . 8, 19. .95; pl. 2
Hyattidina ................... 40
congesta 40
hespe‘ralia .............. 16, 40
sp. f ............. . 14, 15, 16, 1,0, 41; pl. 12
sp ................................. pl. 12
Hysterolites (Acrospi'rifer) .. 33, 34
I
Icriodus 11
latericresce'ns B . 11
huddlei 11
sp .......... 11
Ikes Canyon . 7
Independence Shale, Iowa 22
infrequens, Leptocoelia. . 31
Introduction .............. 1
Inyo Mountains, Calif. 42

 

K

kleinhampli, Acrospirifer . 7, 8, 10, 12, 34:1)1. 7

  
  

 

 

  
 
 

 

   

 

   
 

Kobeh Valley project ..... 2, 10
kobehana, Acrospin‘fer 28, 29, 34
Kodonophyllum .. 12
Kozlowskiella .. 32
strawi ........................................................ 32
KV 1 1 ' "'Mn 82
nolam‘ 7, 8, 10, 82, 33; pl. 6
strawi 33
uelata 33
sp. a .............. 32
Kyphophyllidae 3'8
Kyphophyllum 38
lindstromi 38
L

Laccophyllidae ........ 21
Lacvophyllum ...... 21
n ‘ him 22
laevis, Meristella ’ ........... 30

Laketown Dolomite, Confusion Range,
Utah .......................... 4, 16, 18, 40, 41
landerensia, Australophyllum ........ 8, 11, 24; pl. 9
lata, Conula'r’ia, 8
lateficrescens huddlei, Ic‘riodus , 11
B, Icriodus ........... 11
legumimn'des, Bairdia .. 11

lenticularis, Plewrodictyum .

 

 

 
 
 
 
 
  
 
  
   
  

 

 

 

Leonaspis 7, 8. 9, 10, 11, .96, 37
tuberculatus . 8, 9, 10, 11. 86
williamsi . .................. 36
sp .............. 36

Leptae’na . 7, 9, 10, 28
acuticuspidata
fremonti ......
rhomboidulis
ventricosa ..
sp ..............

Leptaenidae .. ..

Leptocoelia 8 12, 31, 35
acutiplicata A ......... 31
flabellites . 31
infrequens .. 31
occidentalis .. A 7, 8, 10, 11, 31:19]. 5
sp .............. . 8, 9, 10, 31, 35

Leptocoeliidae . ....... .91

Leptaatrophia .............. 8, 27
becki tennesseensis . '7, 8, 10, 27; pls. 3, 8
sp ..... 7, 10, 27; pls. 3, 8

   

 

L . 12, 26
subcarinata .............................................. 12, 26
antelopemis ............ ’ 7, 8, 10, 11. 26:1)1. 4

 

 

 
 

Page
lincolnensis, Ferganella .................. 40
lindstrb'mi, Kyphophyllum .. 38
Locality register .................... £2

 

' ,, ‘, Phacops 37
Lone Mountain .......................... 1, 3, 12, 13, 42
Lone Mountain Dolomite 2, 10, 12, 13, 15, 16,

17, 33, 38, 40

 

 

age and correlation of .......................... 3, 15
fossils of .......................... 4, 16, 17. 18, 19. 42
relation to Rabbit Hill Limestone 3, 17
Unit 1 ............................ 13, 15, 18

   
 

Unit 2 .................... . 13, 15, 16, 18

 

 

 

Lone Mountain Formation _ . 3, 12
Lone Mountain—Laketown biofacies . 15, 16,

18, 41
Lone Mountain Limestone . 3, 13
lykophyllids ......... 18

M

mcbn’dei, Trematospim . 7. 31, 32; pl. 6
McClusky Peak ..
Macropleura
Madreporites artwulatus .
Mahogany Hills .................
martini, Meristella, ..
Meristella .....
arcuata _
atoka A.
laem‘s ..
martini ......
robertsensia
sp .
Meristellidae
Meristina sp ,_
Mesomphalus sp

 
  
 
 
 
 
 
 
 
 
 
  
 
 
 
  
 
 
   

 

  
 
  
 
 
 
 
 
 

Methods ......
Michelinia ..
sp .................
Micheliniinae .
Miraspis . 35, 36, .97
S1) .. . 7, 10, 37; pl. 2
Mollusca 35
monitorensia, Howellella cycloptem 7, 8, 11, .93.
pl. 8
Monitor Range .................................. 2, 7, 21, 42
type area ......................... . 2
Monitor-Simpson Park belt 4, 5, 8
Monograptus 6, 7
Mucophullum 12
Mulligan Gap fault .. 15
Mulligan Gulch .................... 10
multistn'ata, Trematospira . 32
murchisoni, Acrospi-rifer ..... 34

 

Mum'fella ............................. _. 40
musculosa, Rhim’domella .

 

N
Neomphyma. .................................................... 38
Nevada Formation .................... 2, 6, 13, 17, 19, 31
Beacon Peak Dolomite Member 10, 15, 16,
17, 18
fossils .......................................... 3, 5, 6, 19

unit 1 6, 7, 10, 12, 17, 27, 28, 29, 34, 35, 36

 

 
  
 
  
 
 
 
 
  
 

unit 2 S, 19, 22, 29, 35, 36, 37
unit 4
nevadensis, Billingsastmea .
Pleurodictyum
Schuche'rtella .......

newber-ryi, Orthostrophia strophomenm'des
7, 11, 27; pls. 3, 8
Niagaran Formation, Tennessee .............
Nicholsom'a _____________________
(Nicholsom‘a), Alleymia
nolam', Kozlowskiellim
N owakia acuaria

Nu ' pira
ventricosa _

 

O Page

oblata, Rhipidomella ...................................... 26
accidentalis, Leptocoelia 7, 8, 10, 11, .91; pl. 5

 

  
   
  
  
 
  

Odontopleura. .. 36, 37
Odontopleuridae 86
Orthidae ....................... £7
Orthis subcari'nata. 26

Orthocems
sp .......

(Orthonychia) sp. c, Platyceras

01thastrophia ............

strophomenm‘dea .

newborn/1'

pawn. ..

sp ................

ostracods .......................

Pacbyporinae .................................................. 19, 20
pahmnagatensis, Camarotoechia .. 15, 1,0; pl. 11

 

 
  

 

 

 
 

 

 

 

  
 
 
 
  
    
  
  
  
  
 
 
 
 
  
 
 
 
  
  
 
 
 
   
  
  
  
 

Pahranagat Range 40
Palaeocyclus .......... 18
Papiliophullum 28
Parahealdia ..... 11
convexoris .. 11
Parastrophinidae . 29
Parazyga 32
purva, Orthost-rophia atrophomenoides 27
pauciplicata, Howellella 14, 16, 33, 41, 42; pl. 12
perlamellosus, Spirifer ........................ 32
Permit; .......................................... 21, 22
perplemum, Barrandeophyllum 22
Petes Canyon ............. 8
Pen ' .. 33
Phacopidae ......................................... .. 36. 87
Phacops ...... s7
birdsongemis 37
canadensis _. 9, 10, 37; pl. 2
gaspensis 37
loaam' ..... :7

sp. A 37; pl. 8

sp. B 9, 10, 87; pl. 2

sp .................... 7, 8, 9, 10
Pholadophyllum . 37
Pholidophylum . . 37
Pholidostrophia , ., :8
sp. R ........... 7, 10, 28; pl. 3
pinyonensis, Spirifer . 36
planicostatus, Costispirifer 34
arenosus ......... .. 34
Spirifer arenosua . 34
Platyceras . ............... 35, 86

7, 10, 86; pl. 1
_ 7, 10, .96; pl. 1
. 7, 10, 36:131. 1

sp. 3
sp. b ..............................
(Orthonychia) sp. c

Platyceratidae

Plethorhuncha .
altem .........
undersoni
ban-andi
diana _.
saline'nsts ‘
speciasum
welleri ..........

Pleurodictyum
dunburi .......
lenticulare
lenticularis
nevadensis
(Pleu'rodictyum)
problematicum
(Procteria)
stylopora. .....
tennesseenaia
trifoliatum ,
sp ..............

Pogonip Group

Polycoeliidne

 

 

 

 

 

 
 
 
 

 

 

 

  
 
 

INDEX

Page

primaevus, Spirife'r ........................ 34
primtana, Hindella. ....................... 41
prublematicum, Pleurodictywm _ 20
(Procten'a) Pleurodictyum ........ 20
Proetus sp 8, 10
Protathyris . _ 40
Protocortezo'rthis .......................... 40
pseudodianthus, Entelophyllum 38
punctulifera, Strophonella .......... 8, 10, 28:131. 3
Purpose and scope of investigation .......... 2
pycnostylids ........................... 12, 15, 16
Pycnostylus .. ..... 15
............ pl. 11

Rabbit Hill ...................
Rabbit Hill Limestone.
age and correlation of _.
areal distribution and stratigraphy of 5
type area .....
conularids of .
fossils of ..
mollusca of 35
relation to Lone Mountain Dolomite 3, 17
tentaculitids of
trilobites of
mricasta, Delthyris
resimus, Belodella .....

Retziidae ..................................
F“ n 'L J 1 a __

 
 
 

  
  

 

 

  
 
 
  
 
 
 
 
 
 
     
 
 
 

Rhipidomella ..
henryhousenszs
musculosa .........
oblata __
rossi ..
sp

Rhipidomellidae .....

Rhipidomelloides ..

rhomboidalis, Leptae'na . .

robertsensis, Men‘stella ........ 30

Roberts Mountains ......
Formation
Limestone

Rockhouse Shale, Tennessee

Romano fault ...........

rossi, Rhipidomella ..

 

2, 7, 10,13, 32
3, 4, 5,12, 18

  
  
 
 
 

 

  
  
   
 
 
  
 
 
 

   

 

 

rugosa, Xylodes .............................. 38
rugose corals .......... 2, 8, 11, 12, 13, 15. 16. 17, 18
S
Saccarchites sp ............................. 11
salinensis, Plethorhyncha . 30
Salopimz 1,0

crassifmmzs 40

sp. f ................ . 15, 16, 40; pl. 11

51) ............................................ 40
Sandpile Dolomite, British Columbia,

Canada ........................ 41
Schellwienellu 29
Schuchertellu 7, 8, 10, 29

haraganensis 8, 9, 10, 29; pl. 3
nevadensis _ .............. 29

sp ............... 9, 29; pls. 3, 8
Schuchertellidae ............................. 29
sedgwicki, Spongophyllum 23
Selected bibliography ............ 43
Sevy Dolomite ................... 16
siluriensis, Cyathaaco’nia 21, 22
Syringaxon .. . 21, 23
Simpson Park Range, Nevada ........ 1, 2, 4, 8, 21,
36. 37, 42

Siphonophrentis _ ........ 23
sp. B ......... . 10, 23; pl. 8
smithi, Howellella ., 15, 16, 33, 41, 42; pl. 12
speciosum, Plethorhyncha .. 29
Spiniferina ............................. 37

 

 

 

 

 
  
 
  
 
  
 
   

 

 

  
 

Page
Spinulosa ....................... 11
Spirifer arenosus planicostatus .. 34
cyclopterus ............................. 33
perlamellosus .. 32
pinyonensis
primaevus
sp. a .........
Spongophyllum
cyathophyllm'des
sedgwicki ..............
stevensi, Australophyllum .
Startophyllum
strawi, Kozlowskiella.
Kozlowskielli'na
Streptelasmatidae 23
Striatopma 6, 8, 10, 19, 20
f’ 20
gwenensis ................... . 6, 8, 10, 20; pl. 1
sp ...........
Strombades _
Strapheadonta sp
Stropheodontidae ......................................... 27

strophomenoides newber'rui,
Orthostrophia 7. 11, 27; pls. 3, 8

 

  
   
 
 
  

Orthostrophia ............... 7, 27
pawa, Orthostrophia . 27
Strophonella .. 8, 28
bransom’ _ . 28
punctulifem . 8, 10, 28; pl. 3
sp . 10
Stylioh’na 35
stylopo'ra, Pleuradictyum ..... 20

subcarinata antelope'nsis, Leveneu .. 7, 8, 10, 11,

Leveneu . ..
Orthis ..
Sulphur Spring Range 2, 10, 15, 28, 29, 36, 42, 43
Sunday Canyon Formation, Vaughn
Gulch Limestone, Mazourka
Canyon, Inyo Mountains,

 

 

     
  

 

Calif ...... 11, 12,24

Syringaxo'n 18, 19, 21, 35
foerstei 7, 8, 9, 10, 11, 22, 23; pl. 2
silurie‘nsis . 21, 23

sp ............ 12
Syringopam 13
Syringoporinae .. 19
Systematic and descriptive paleontology .. 18

T

Tabulata ....................... 19
tennesseensis, Atrypa 41

 
 
 
 
 
 
 
 
  
 
    
    
  
 
 
 
 
 
 
  
 
 
 
 

Leptostrophia becki
Pleurodictyum
tentaculitids .............

Thamnopom sp . 14, 15, 16

 

Thlipsura furcu 11
sp .......... . 11
Toquima Range . .......................... 2, 7, 12, 21, 42
Torquay Formation, England 23
Trematospira . . 11 81, 40
ooopen’ 32
deweyi .. . 32
equistn’ata ............. . 31, 32
mcbridei 7, 10, .91, 32; pl. 6
multistriata ‘
sp ................

Tricorm'na sp ..
trifoliatum, Pleurodictuum
trilobites
Tryplasma _
aequabile
sp. 1‘ ............
sp ...................
Tryplasmatidae .
tuberculatus, Acidaspis
Leanaspis
Tubilibai'rdia. sp

Tuscarora Mountains . 2, 9, 11, 25, 42

 

 

 

50

  
 

 

Page
U
umbonuta, Ambocoelia .................................. 30
Hindella, 41
Uncinulidae 2.9
Unci'nulus 30
V
variabilis, Glassiu _________ 41
veluta, Kozlowskiellina . 33

 

 

 

 
 
  
  

  
 

INDEX
Page
Velibeyn‘chia sp .............................................. 11
ventricosa, Leptae'na _ 28
Nucleospira ........ .. 9
verneuili, Anastrophia . 10, 11, 29; pl. 5
Verticillopo’ra ................ 16
W

Walti Ranch, Walti Hot Springs
quadrangle ............. 8, 35, 36
Welleria 11

Page
wellen‘, Plethorhy‘ncha ..
Wenban Limestone ........

 

. 32, 38

 

 

 

 
 
 

Wenlock Limestone, England ..
williamsi, Leonaspis ................... 36
X, Y
X37 4 38
articulatus ...... 38
rugosa, 38
Yassia. _____ 23

 

 

 

PLATES 1—12

[Contact photographs of the plates in this report are available, at cost, from the US
Geological Survey Photographic Library, Federal Center, Denver, Colorado 80225]

 

 

 

 

 

 

PLATE 1
FIGURES 1, 3—6. S triatopora cf. S. gwenensis Amsden.
1. Lateral view (X 11/2); USNM 159475.
3. Lateral view ( X 2); USNM 159476.
4. Transverse thin section ( X 2); USNM 159514.
5, 6. Longitudinal thin sections (X 2); USNM 159515, 159516.
Lower Devonian, Rabbit Hill Limestone; Rabbit Hall, Copenhagen Canyon, Nev. Locality M409.
2. Digitate favositid sp. a.
Lateral view (X 11/2) ; USNM 159513. Locality M409. (See figs. 1,3—6.)
7—12. Pleurodictyum nevadensis n. sp.
7, 8. Calice and lateral views of holotype (X 11/2); USNM 159517.
9. Lateral view of broken paratype (X 3); USNM 159518, showing pore distribution.
10. Interior view of wall (X 2); USNM 159519, showing pore pattern.
Locality M409. (See figs. 1, 3—6.)
11. Calice view (X 11/2); USNM 159520. Upper part of Rabbit Hill Limestone, Dobbin Summit, Monitor
Range, Nev. Locality M1309.

12. Calice view (X 1); USNM 159521. Lower Devonian, Rabbit Hill Limestone; Horse Canyon, Cortez
Mountains, Nev. Locality M1083.

tains, Nev. Locality M1083.
13—15. Pleurodictyum dunbari n. sp.
13. Lateral exterior of holotype ( X 11/2); USNM 159522.
14. Calice view of holotype (X 2%); USNM 159522.
15. Calice View of paratype ( X 2%) ; USN M 159523.
Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409.
16—19. Favosites cf. F. helderbergiae Hall.
16. Surface of massive colony ( X 1).
17. Longitudinal thin section (X 2).
18. Transverse thin section (X 2).
19. Longitudinal thin section (X 2).
Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409.
20, 21. Platyceras sp. a.
Umbilical and aperture views (X 1); USNM 159524. Lower Devonian, Rabbit Hill Limestone; Rabbit Hill,
Copenhagen Canyon, Nev. Locality M409.
22, 23. Platyceras sp. b.
Lateral and aperture views ( >< 11/2); USNM 159525. Locality M409. (See figs. 20, 21.)
24. Platyceras (Orthonychia) sp. c
Elongate surface of body whorl (X 1%); USNM 159526. Locality M409. (See figs. 20, 21.)

 

 

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GEOLOGICAL SURVEY

 

 

FA VOSITES, AND PLA TYCERAS

STRIA TOPORA, PLEUR ODICTYUM,

 

PLATE 2

FIGURES 1—10. Syringaxon foerstei n. sp.

11—13.

14.

15—17.

18—20.

1. Oblique calice View of holotype (x 11/2); USNM 159243. Lower Devonian, Rabbit Hill Limestone; Rabbit
Hill, Copenhagen Canyon, Nev. Locality M409.

2, 3. Lateral view (x 1%) and calice view ( X 1) of paratype USNM 159245. Locality M409, (See fig. 1.)

6. Transverse thin section of paratype (X 4); USN M 159246. Locality M409. (See fig. 1.)

7. Calice view (X 2); USNM 159528. Lower Devonian, Beacon Peak Dolomite Member of the Nevada For-
mation; southern Sulphur Spring Range, Nev. Locality M197.

8. Calice view of paratype (X 21/2); USNM 159244. Locality M409. (See fig. 1.) '

9, 10. Longitudinal thin section of two paratypes (X 4); USNM 159529, 159247. Locality M409. (See fig. 1.)

(?) Phacops sp. B, cf. P. canadensis Stumm.

11. Dorsal surface of nearly complete specimen ( x 1) ; USN M 159530.
12. Cephalon showing right genal spine (X 1); USNM 159531.
13. Latex impression of pygidium (x 1); USNM 159532. Rabbit Hill Limestone, Coal Canyon, Simpson

( ?) M iraspis sp.

Forked occipital ring spine (x 2), Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen
Canyon, Nev. Locality M409.

Leonaspis cf. L. tuberculatus (Hall).

15, 17. Pygidium (X 4) ; USNM 159533 and free cheek (X 4)‘ USNM 159534. Locality M409 (See fig. 14.)
16. Free cheek (X 2); USNM 159535. Lower Devonian, Rabbit Hill Limestone;
Range, Nev. Locality M1311.

Conularia sp., cf. C. huntiana Hall.

18. Lateral view (x 2) ; USNM 159536.
19. Surface of large individual ( x 2); USN M 159537.
20. Enlargement of part of fig. 19 ( x 8).

Lower Devonian, Rabbit Hill Limestone; southeast of Walti Ranch, Simpson Park Range, Nev. Locality
M1074.

 

 

PROFESSIONAL PAPER 808 PLATE 2

 

_f.«'.;.a:/W¥A

1,: x x 7 1,1,» m: smut?! f ’ .

SYRINGA XON, ('2) PHACOPS, (?) MIRASPIS, LEONASPIS, AND CONULARIA

 

 

 

FIGURES 1—3.

4, 5.
6, 7.
8, 9.

10,11.

12—15.

16, 17, 19.

18.

 

 

PLATE 3

Leptostrophia sp. cf. L. becki tennesseensis Dunbar.

1, 2. Exterior and interior of pedicle valve (x 2); USN M 159538.

3. Exterior of pedicle valve ( x 2); USNM 159539.

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev, Locality M409.
Orthostrophia strophomenoides subsp. newberryi n. subsp.

Exterior and interior (x 2) of holotype; USNM 159540. Locality M409. (See figs. 1—3.)
( ?) Pholidostrophia sp. R.

Exterior (x 1) and interior (X 2) of pedicle valve; USNM 159541. Locality M409. (See figs. 1—3.)
Stropheodonta sp.

Exterior (x 1) and interior (x 11/2) of same pedicle valve. Locality M409. (See figs. 1—3.)
Strophonella cf. S. punctulifera (Conrad).

10. Latex impression of probable pedicle valve ( x 2).

11. Latex impression of brachial valve exterior ( X 1).

Lower Devonian, Beacon Peak Dolomite Member of the Nevada Formation; southern Sulphur Spring Range

Nev. Locality M197.

Schuchertella sp., cf. S. haraganensis Amsden.

12—14. Pedicle valve exterior, interior and hinge views (x 1%); USNM 159542.

15. Pedicle valve exterior (x 11/2); USNM 159543. Locality M409. (See figs. 1—3.)
Leptaena fremonti n. sp.

16, 17. Pedicle valve exterior and interior ( x 1), holotype; USNM 159544.

19. Pedicle valve interior ( x 1), paratype; USN M 159545. Locality M409. (See figs. 1-3.)
Leptaena sp., cf. L. fremonti n. sp.

Pedicle valve exterior (x 11/2); USNM 159546. Lower Devonian, Beacon Peak Dolomite Member of the

Nevada Formation; southern Sulphur Spring Range, Nev. Locality M197.

y

PROFESSIONAL PAPER 808 PLATE 3

GEOLOGICAL SURVEY

 

 

v

S TR OPHE 0DON TA

EPTAENA

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LEPTOS TR OPHIA, 0R THOS TR OPHIA, (?) PHOLIDOS TR OPHIA

ANDL

STR OPHONELLA, SCHUCHER TELLA,

 

FIGURES

PLATE 4

1—14. Levenea subcarinata subsp. antelopensis n. subsp.

1—3. Exterior, interior, and umbonal views ( X 2) , holotype pedicle valve; USN M 159547.

4—6. Umbonal view (X 2), exterior and interior ( X 1%), paratype brachial valve; USNM 159548,

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409.

7. Brachial valve interior (x 2), paratype; USNM 159549. Lower Devonian, Beacon Peak Dolomite Mem-
ber of the Nevada Formation, southern Sulphur Spring Range, Nev. Locality M186.

8. Umbonal view of articulated shell (>< 11/2), paratype; USNM 159550. Locality M186. (See fig. 7.)

9. Dorsal interior (X 2), paratype; USNM 159551. Locality M409. (See figs. 1—6.)

10. Pedicle interior (x 2), paratype; USNM 159552. Locality M409. (See figs. 1—6.)

11, 12. Brachial valve exterior and interior (>< 11/2), paratype; USNM 159553. Rabbit Hill Limestone,
Dobbin Summit, Monitor Range, Nev. Locality M1309.

13, 14. Pedicle valve interior and exterior (>< 11/2), paratype; USNM 159554. Lower Devonian, Beacon
Peak Dolomite Member of the Nevada Formation, southern Sulphur Spring Range, Nev. Locality M1312.

15—24. Rhipidomella rossi n. sp.

15—17. Dorsal valve exterior, lateral and umbonal views (X 2), paratype; USN M 159555.

18, 19. Dorsal valve exterior and interior (X 2), holotype; USNM 159556.

20. Dorsal valve interior (>< 21/2), paratype; USNM 159557.

21. Ventral valve interior ( >< 21/2), paratype; USN M 159558.

22. Ventral valve interior (x 2), paratype; USNM 159559.

23. Ventral valve interior (>< 21/2), paratype; USNM 159560.

24. Dorsal valve interior (>< 21/2), paratype; USNM 159561.

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409.

 

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 4

22
LEVENEA AND RHIPIDOMELLA

 

 

 

PLATE 5
FIGURES 1—14. Leptocoelia occidentalis n. sp. ‘

1, 2, 4. Pedicle valve, brachial valve, and lateral exterior views ( x 2) , holotype; USN M 159562.

3, 5. Anterior (X 2) and umbonal (>< 11/2) views, paratype; USNM 159563.

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409.

6, 7. Brachial valve and pedicle valve exterior (x 11/2), paratype; USNM 159564. Lower Devonian, Beacon
Peak Dolomite Member of the Nevada Formation, southern Sulphur Spring Range, Nev. Locality M197.

8, 9. Brachial valve exterior (X 2) and interior (x 3), paratype; USNM 159565. Locality M409. (See
figs. 1—5.)

10. Pedicle valve interior (x 2), paratype; USNM 159566. Locality M409. (See figs. 1—5.)

11, 12. Pedicle valve interior of two paratypes (x 2); USNM 159567, 159568. Locality M409. (See figs. 1—5.)

13, 14. Brachial valve interior of two paratypes ( x 3) ; USNM 159569, 159568. Locality M409. (See figs. 1—5.)

15—19. Anastrophia of. A. verneuili (Hall),
9 15, 18, 19. Pedicle valve exterior (>< 11/2) and two views of interior of same individual; USNM 159571.

Lower Devonian, Beacon Peak Dolomite Member of the Nevada Formation; southern Sulphur Spring
Range, Nev. Locality M186.

16. Pedicle valve exterior (x 1); USNM 159572. Lower Devonian, Beacon Peak Dolomite Member of the
Nevada Formation; southern Sulphur Spring Range, Nev. Locality M197.

17. Pedicle valve exterior (x 11/2); USNM 159573. Locality M197. (See fig. 16.)

 

 

PROFESSIONAL PAPER 808 PLATE 5

GEOLOGICAL SURVEY

 

    

 

LEPTOCOELIA AND ANASTR OPHIA

 

FIGURE.

16—24. Kozlowskiellina nolani n. sp.

 

PLATE 6

1—7. Plethorhyncha andersoni n. sp.

1, 2. Brachial valve exterior and anterior view (x 1); holotype, USN M 159574.

3, 5. Pedicle valve exterior of two paratypes ( x 1); USNM 159575, 159576.

4, 7. Brachial valve exterior (x 1) and interior (x 2); paratype, USNM 159577.

6. Pedicle valve interior (x 1); paratype, USN M 159578.

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409,

8—15. Trematospira mcbridei n. sp.

8, 10, Pedicle valve exterior (x 1) and interior (x 2); holotype, USNM 159579.

9. Pedicle valve exterior (x 11/2); paratype, USNM 159580.

11. Pedicle valve interior (x 2); paratype, USNM 159581.

12. Pedicle valve interior (X 2); paratype, USNM 159582.

13—15. Brachial valve interior of three paratypes (X 2); USNM 159583, 159584, 159585, showing details of
the cardinal process.

Locality M409. (See figs. 1—7.)

16. Brachial valve exterior (>< 11/2); paratype, USNM 159586.

17. Brachial valve interior (x 11/2); paratype, USNM 159587.

18. Brachial valve interior (X 3); paratype, USNM 159588.

19. Pedicle valve exterior (x 2); holotype, USNM 159589.

20, 21. Pedicle valve interior of two paratypes (>< 11/2); USNM 159590, 159591.

Locality M409. (See figs. 1—7.)

22. Pedicle valve interior (>< 11/2); paratype, USNM 159592. Rabbit Hill Limestone; Dobbin Summit,
Monitor Range, Nev, Locality M1309.

23. Oblique posterior view (>< 11/2). Locality M409. (See figs. 1—7.)

24. Pedicle valve interior ( x 2); holotype, USNM 159589. Locality M409. (See figs. 1—7.)

 

—————7

GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 6

 

PLETHORHYNCHA, TREMA TOSPIRA, AN D KOZL OWSKIELLINA

 

FIGURES 1—7.

9—12.

13, 14.

15, 16.

17—22.

23—27.

28—3 1 .

PLATE 7

Costispirifer arenosus subsp. dobbinensis n. subsp.

1, 4. Pedicle valve exterior (x 1%,) and posterior View (X 1); paratype, USNM 159593.

2, 3. Pedicle valve exterior ( X 1) and interior ( >< 11/2); holotype, USNM 159594.

5. Brachial valve exterior ( X 1); paratype, USNM 159595.

6, 7. Pedicle valve exterior of two paratypes; USNM 159596, 159597.

Lower Devonian, Rabbit Hill Limestone; Dobbin Summit, Monitor Range, Nev. Locality M1309.
Acrospirifer sp.

Pedicle valve exterior (X 2); USNM 159598. Locality M1309. (See figs. 1—7.)
Acrospirifer kleinhampli n. sp.

9, 10. Pedicle valve exterior and interior (X 11/2); holotype, USN M 159599.

11, 12. Pedicle valve exterior and interior (>< 11/2); paratype, USNM 159600.

Locality M1309. (See figs. 1—7.)
Acrospirifer sp. D.

Brachial valve exterior and interior (>< 11/2); USNM 159601. Locality M1309. (See figs. 1—7.)
Acrospirifer cf. A. kleinhampli n. Sp.

Pedicle valve exterior and interior (x 1%); USNM 159602. Lower Devonian, Beacon Peak Dolomite Mem-

ber of the Nevada Formation; southern Sulphur Spring Range, Nev. Locality M197.

Howellella cycloptera subsp. monitorensis n. subsp.

17. Brachial valve interior (x 2); paratype, USNM 159603.

18, 19. Pedicle valve interior and exterior (X 1%); holotype, USNM 159604.

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409.

20—22. Pedicle valve, brachial valve, and anterior views (>< 11/2); paratype, USNM 159605.

Lower Devonian, Rabbit Hill Limestone; Dobbin Summit, Monitor Range, Nev. Locality M1311.
M eristella martini n. Sp.

23, 24. Pedicle valve exterior and interior ( X 1); holotype, USNM 159606,

25, 26. Pedicle valve interior (X 112) and exterior (x 1); paratype, USNM 159607.

27. Brachial valve interior (>< 11/2); paratype, USNM 159608.

Locality M409. (See figs. 17—19.)
Ambocoelia sp. a

28. Pedicle valve exterior ( X 3); USN M 159609.

29—31. Three pedicle valve interiors (x 3); USNM 159610, 159611, 159612.

Locality M409. (See figs. 17—19.)

 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 7

  

    

 

22 23 26

 
   

COSTISPIRIFER, ACROSPIRIFER, HOWELLELLA, MERISTELLA, AND AMBOCOELIA

 

 

 

FIGURES

6—9.

10.

11.

12, 13.

14.
15.

16, 17.

18.

1—3.

 

PLATE 8
Siphonophrentis sp. B
Calice and lateral views (x 1), and longitudinal thin section
Beacon Peak Dolomite Member of the Nevada Formation;

(X 3); USNM 159613. Lower Devonian,
southern Sulphur Spring Range. Locality

Schuchertella sp.
Brachial valve interior ( x 2); USNM 159614. Lower Devonian, Rabbit Hill Limestone; Dobbin Summit,
Monitor Range, Nev. Locality M1311.
Leptostrophia sp. of. L, becki tennesseensis Dunbar.
Brachial valve interior (x 2); USN M 159615. Lower Devonian, upper
Dobbin Summit, Monitor Range, Nev. Locality M1309.
Orthostrophia strophomenoides subsp. newberryi n. subsp.
6, 7. Brachial valve exterior and interior (>< 11/2); paratype, USNM 159616.
8, 9. Pedicle valve exterior and interior (x 11/2); paratype, USNM 159617,
Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409.
Howellella cycloptera subsp. monitorensis n. subsp.
Latex impression of shell bed (x 1). Lower Devonian, Rabbit Hill
Range, Nev. Locality M1311,
Rhipidomella of. R. musculosa (Hall).
Ventral valve muscle field (X 1). Lower Devonian, upper part of Rabbit Hill Limestone; Dobbin Summit,
Monitor Range, Nev. Locality M1309.
Laminated Rabbit Hill chert bed overlain by trilobite coquinite ( X 1).
12. Weather surface of coquinite showing parts of Leonaspis head shields.
13. Edge View showing chert layer overlain by trilobite coquinite.
Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409.
Weathered surface of platy calcareous siltstone showing “fucoids” ( x 1).
Weathered surface of coquinite composed mainly of bryozoans, brachiopods, and crinoidal debris (x 1),
Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409.
Phacops sp. A
16. Anteroventral edge of cephalon, showing glabella and one eye (>< 11/2).
17. Latex impression, showing dorsal surface of pygidium and several pleura (x 11/2).
Lower Devonian, Beacon Peak Dolomite Member of the Nevada Formation; southern Sulphur Spring
Range, Nev. Locality M197.
Weathered surface of a tentaculite (x 8). Early Devonian, Rabbit Hill Limestone; southeast of Walti Ranch,

Simpson Park Range, Nev. Locality M1074.

part of Rabbit Hill Limestone;

Limestone; Dobbin Summit, Monitor

 

#1

PROFESSIONAL PAPER 808 PLATE 8

GEOLOGICAL SURVEY

  

15
SIPHONOPHRENTIS, SCHUCHER TELLA, LEPTOSTROPHIA, 0R THOSTROPHIA,
HOWELLELLA, RHIPIDOMELLA, AND PHACOPS

 

 

FIGURES 1, 2.

3—6.

8—13.

PLATE 9

 

Billingsastraea Sp. m.
Transverse and longitudinal thin sections (X 3); USNM 165350. Early Devonian, Rabbit Hill Limestone,
south end of Tuscarora Mountains at Maggie Creek, locality M1400.
Australophyllum landerensis n. sp.

Australophyllum sp. v.
Transverse thin section ( x 2). Mazourka Canyon, northern Inyo Range, Calif.; locality M1093. Upper part
of Vaughn Gulch Limestone. From beds of possible Early Devonian age above Silurian coral zone E.
Australophyllum stevensi n. Sp.
8, 9. Transverse thin sections ( x 2) of holotype, USNM 165349.
10—13. Longitudinal thin sections ( X 2) of holotype, USNM 165349.
Mazourka Canyon area, northern Inyo Range, Calif.; locality M1401, east side of Al Rose Canyon, From beds
of possible Early Devonian age in upper part of the Sunday Canyon Formation.

PROFESSIONAL PAPER 808 PLATE 9

GEOLOGICAL SURVEY

 

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PLATE 10
FIGURES 1~4. Entelophyllum eurekaensis n. sp.
1, 2. Transverse and longitudinal thin sections of holotype (X 4); USNM 159412.
3, 4. Longitudinal and transverse thin sections of paratype (X 2); USN M 159419.
Late Silurian, upper part of Lone Mountain Dolomite, southern Fish Creek Range, Nev. Locality M1113.
5—11. Entelophyllum engelmanni n. sp.
5. Transverse thin section (x 4), holotype; USNM 159413.
6, 7. Longitudinal thin section ( X 2, X 3%), paratype; USNM 159415.
8. Longitudinal thin section (x 3), paraty ; USNM 159477.
9. Longitudinal thin section (x 4), paratype; USNM 159414.
10. Longitudinal thin section ( x 2), paratype; USNM 159478.
11. Lateral view of paratype (slightly reduced); USNM 159417.
Late Silurian, upper part of Lone Mountain Dolomite; southern Mahogany Hills, Eureka County, Nev.
Locality M1112.
12, 13. Entelophyllum engelmanni subsp. b.
12. Lateral View of attached corallites ( X 1); shows attached Howellella smithi.
13. Lateral View of attached corallites (>< 11/2).
Late Silurian, upper part of Lone Mountain Dolomite; southern Fish Creek Range, Nev. Locality M1087.

  
   

 

PROFESSIONAL PAPER 808 PLATE 10

GEOLOGICAL SURVEY

. ,1 "”i v

 
  
 
   

    

 

12

ENTELOPHYLL UM

 

 

FIGURES

1—4.

5, 6.
7—9.

10—13.

14, 15.

1 6—23.

24, 25.

26, 27.

28, 29.

30.

31.

32.

PLATE 11
Atrypa sp. f.
1—3. Ventral, dorsal, and lateral views (x 2); USNM 159479,
4. Dorsal view ( X 2); USN M 159480.
Late Silurian, upper part of Lone Mountain Dolomite; southern Fish Creek Range, Nev. Locality M1113.
Camarotoechia sp. f.
Dorsal and ventral exterior (X 2); USNM 159481. Locality M1113. (See figs. 1—4.)
Camarotoechia pahranagatensis Waite.
Dorsal, ventral, and anterior views (X 2); USNM 159482. Locality M1113. (See figs. 1—4.)
Camarotoechia sp. b.
10—12. Dorsal, ventral, and anterior views ( X 2); USNM 159483. Locality M1113. (See figs. 1—4.)
13. Dorsal view (X 2); USNM 159484. Locality M1113. (See figs. 1—4.)
Camarotoechia Sp.
Dorsal and anterior views (x 2); USNM 159485. Locality M1113. (See figs. 1—4.)
Salopina sp. f
16, 17. Oblique dorsal and ventral views (X 2); USNM 159486.
18, 19. Dorsal valve exterior and interior views (x 3); USNM 159487.
20. Dorsal valve exterior ( x 3); USN M 159488.
21, 22. Dorsal and ventral exterior ( x 3); USN M 159489.
23. Dorsal exterior (>< 21/2); USNM 159490.
Late Silurian, upper part of Lone Mountain Dolomite; southern Fish Creek Range, Nev. Locality M1087.
Tryplasma sp. f.
Transverse and longitudinal thin sections ( x 2); USNM 159491. Locality M1087. (See figs. 16—23.)
Entelophyllum engelmanni subsp. b.
Lateral exterior (>< 11/2) and transverse thin section ( >< 11/2); USNM 159492. Locality M1087. (See figs.
16—23.)
Pycnostylid coral.
Calice views of same corallite ( x 1, x 11/2). Silurian, lower part of Lone Mountain Dolomite; southern
Sulphur Spring Range, Nev. Locality M1121.
Pycnostylus sp.
Longitudinal thin section (x 11/2). Silurian, lower part of Lone Mountain Dolomite, southern Sulphur
Spring Range, Nev. Locality M1148.
Medium-dark-gray carbonaceous Lone Mountain Dolomite containing silicified Entelophyllum engelmanni
subsp. b ( X 1/2). Locality M1087. (See figs. 16—23.)
Dark-gray carbonaceous Lone Mountain Dolomite containing fragmentary rugose corals, probably Entelo-
phyllum (slightly reduced). Upper part of Lone Mountain Dolomite; east side of Charcoal Gulch, Lone
Mountain, Eureka County, Nev. Locality M1122.

    

 

PROFESSIONAL PAPER 808 PLATE 11

GEOLOGICAL SURVEY

ATR YPA, CAMAROTOECHIA, SALOPINA, TR YPLASMA, ENTELOPHYLLUM,
PYCNOSTYLID CORAL AND ? PYCNOSTYL US

 

FIGURES 1—19.

20—24.

25.

26, 27.

28, 29.
30—32.

33.

34—37.

PLATE 12
H owellella smithi Waite.
1—3. Oblique posterior, anterior, and dorsal views (>< 1%); USNM 159493.
4, 5. Dorsal and ventral views ( >< 11/2); USN M 159494.
6, 7. Ventral valve interiors showing dental lamellae ( X 2); USN M 159495.
8. Dorsal valve interior ( x 2); USN M 159496.
9, 10. Dorsal and ventral views ( X 1%); USNM 159497.
11, 12. Dorsal and ventral views ( x 2) ; USNM 159498.
13. Dorsal exterior ( X 2); USNM 159499.
14. Dorsal exterior ( x 2); USNM 159500.
15. Dorsal exterior ‘( >< 11/2); USNM 159501.
16. Dorsal exterior ( X 4); USN M 159502.
17. Dorsal exterior (>< 2); USN M159503.
18. Dorsal exterior (>< 2); USNM 159504.
19. Dorsal exterior ( X 3); USNM 159505.
Late Silurian, upper part Lone Mountain Dolomite; southern Fish Creek Range, Nev. Locality M1087.
Howellella pauciplicata Waite.
20—22. Dorsal, ventral, and posterior views ( X 2); USNM 159506.
23, 24. Dorsal and ventral views ( x 6); USN M 159507.
Late Silurian, upper part Lone Mountain Dolomite; southern Mahogany Hills, Nev. Locality M1112.
Medium—dark-gray upper Lone Mountain Dolomite containing abundant silicified Howellella smithi (>< 1/2).
Locality M1087. (See figs. 1—19).
?Hyattidina sp.
Dorsal and posterior views (>< 2); USNM 159508. Late Silurian, upper part of Lone Mountain Dolomite;
southern Fish Creek Range, Nev. Locality M1113.
?Hyattidina sp.
Dorsal and lateral views (>< 2); USNM 159509. Locality M1113. (See figs. 26, 27.)
?Hyattidina sp. f.
Dorsal, anterior, and lateral views (>< 3) ; USNM 159510. Locality M1087. (See figs. 1—19.)
?Hyattidina sp. f.
Ventral view of peeled shell ( X 4) showing part of spiralium with lateral apices. USNM 159511. Locality
M1087. (See figs. 1—19.)
Hindella sp. a.

Dorsal, ventral, lateral, and anterior views ( x 2); USNM 159512. Locality M1087. (See figs. 1—19.)

U. S. GOVERNMENT PRINTING OFFICE: 1973 O - 506-612

 

 

PROFESSIONAL PAPER 808 PLATE 12

GEOLOGICAL SURVEY

  
    

 

   

14 19
H0 WELLELLA, ? HYA TTIDINA, AND HINDELLA

 

13