Turonian (Eaglefordian) Stratigraphy of the Atlantic Coastal Plain and Texas By PAGE C. VALENTINE U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1315 A discussion of Turonian strata and the Cenomanian- Turonian boundary beneath the Atlantic and Gulf Coastal Plains. Revised ages of Upper Cretaceous stratigraphic units are presented UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1984 DEPARTMENT OF THE INTERIOR WILLIAM P. CLARK, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Catalogingi in Publication Data Valentine, Page C. | Turonian (Eaglefordian) stratigréphy of the Atlantic Coastal Plain and Texas. (Geological Survey professional fiaper ; 1315) Bibliography: p. | Supt. of Does. no. : I 19.16:1815 | 1. Geology, Stratigraphic-Cretaceous. 2. Geology-Atlantic Coast (U.S.) 3. Geology-Gulf Coast (U.S.) 4. Geologic-Texas-Gulf Region. I. Title. II. Series. QE688. V348 1984 551.770974 83-600335 For sale by the Distribution Branch, U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 CONTENTS Page Page Abstract 1 ; South Carolina Coastal Plain 7 INtPOGUCtOM | === cns 1 Fripp Island well 8 Acknowledgments .... 1 Layne Atlantic, Parris Island Test No. 2 well .........__._._._._._.. 9 Cenomanian-Turonian boundary 1 Clubhouse Crossroads corehole 1 ...... 9 Complexiopollis-Atlantopollis pollen zone st Ages of subsurface stratigraphic units in South Carolina .... 11 Age of calcareous nannofossil SDeCI@$ \ 5 | Georgia Coastal Plain 11 New Jersey Coastal Plain 6 Georgia Geological Survey wells 1197, 724, 1198 .................... 11 Toms River Chemical Co.:well 6 | Texas Coastal Plain 12 USGS Island Beach No.1 well A47 Socony Mobil corehole 16 12 New York, Rhode Island, and Massachusetts Coastal Plains ...... 7 | Correlation of Turonian age stratigraphic units of the Atlantic Fire Island State Park well 7 and Gulf Coastal Plains 16 Block Island outcrop 7 | Summary and conclusions 18 Martha's Vineyard and Nantucket Island wells ...... 7 | References cited 19 Virginia Coastal Plain 7 J and J Enterprises, E. G. Taylor No. 1-G well ....................... 7 ILLUSTRATIONS Page FIGURE 1. Turonian localities on the Atlantic continental margin 2 2-9. Diagrams showing: 2. Correlation of upper Cenomanian and lower Turonian stratigraphic units of France, the British Isles, the United States Western Interior, and the Gulf and Atlantic Coastal PIAIn§ 4 3. Upper Cenomanian and Turonian stratigraphy of the Toms River Chemical Co. well, New Jersey .:.... ...... 6 4. Stratigraphic interpretations of the Fripp Island well, South Carolina 8 5. Stratigraphic interpretations of Clubhouse Crossroads corehole 1, South Caroling ...........__................................... 9 6. Turonian stratigraphy of the Clubhouse Crossroads corehole 1, South CArOlin® ......_._.__....................................... 10 7. Reinterpreted correlation of Cretaceous stratigraphic units recognized in previous studies of coastal South Carolina with European and Provincial stages . 11 8. Upper Cenomanian, Turonian, and Coniacian stratigraphy of Socony Mobil corehole 16, Dallas, Texas ...:... : 19 9. Correlation of biostratigraphic and lithostratigraphic units of the Atlantic Coastal Plain and Texas ...... 14 10. Generalized correlation chart for upper Cenomanian to lower Campanian strata of the Atlantic and Gulf Coastal Plains 17 TABLE Page TABLE 1. Turonian localities on the Atlantic and Gulf Coastal Plains 3 IH TURONIAN (EAGLEFORDIAN) STRATIGRAPHY OF THE ATLANTIC COASTAL PLAIN AND TEXAS By PAGE C. VALENTINE ABSTRACT A stratigraphic analysis of 14 localities from New England to Georgia and of 1 well from the type area of the Eaglefordian Stage at Dallas, Tex., has resulted in a reevaluation of the ages of both formal and informal stratigraphic units previously established for the Atlantic and eastern Gulf Coastal Plains. Lower Turonian strata, once thought to be absent beneath the Atlantic Coastal Plain, are present. The study focused on a stratigraphic interval that is characterized by the presence of distinctive calcareous nannofossil and pollen floras. The Com plexiopollis-Atlantopollis pollen assem- blage zone, widespread throughout the Atlantic and Gulf Coastal Plains and previously dated as late Cenomanian, is now shown to be late Cenomanian-early Turonian on the Gulf Coast on the basis of its occurrence with calcareous nannofossils, planktic foraminifers, and mollusks of that age. On the Atlantic Coast, only the lower Turonian part of the Com plexiopollis-Atlantopollis zone is known to be pres- ent. Stratigraphic units that are now assigned to the lower Turonian include (1) the Woodbridge Clay and Sayreville Sand Members of the Raritan Formation, New Jersey; (2) the upper part of the Rari- tan equivalent beneath the eastern shore of Virginia; (3) the Tusca- loosa equivalent (informal units K2, E, and part of F) in the South Carolina and Georgia coastal region; (4) the Tuscaloosa Formation of eastern Alabama and western Georgia; and, beneath the Gulf Coastal Plain (5) the Coker Formation of western Alabama and (6) the upper Britton and lowermost Arcadia Park Formations at Dal- las, Tex. Cenomanian strata beneath the Atlantic Coastal Plain are now interpreted to be much thinner than previously supposed. The lower Turonian there is bounded by upper Turonian and uppermost Cenomanian hiatuses of regional extent, whereas the upper Ceno- manian-Turonian section is relatively complete at Dallas, Tex. INTRODUCTION Recent interpretations of the Upper Cretaceous stratigraphy of the Atlantic Coastal Plain have shown a relatively thick section of Cenomanian strata bounded above by a hiatus that encompasses at least early Tur- onian time in the Raritan Embayment of New Jersey and all of Turonian and Coniacian time in the South- east Georgia Embayment of South Carolina and Geor- gia (Gohn and others, 1978, 1980; Christopher, 19792, 1982). These conclusions have been based in part on the correlation of molluscan faunas of the Atlantic Coastal Plain with Cenomanian faunas of the Texas Gulf Coast (Stephenson, 1952, 1954) and partly on spores and pollen that have been compared with floras in Texas strata that have been dated as Cenomanian by using planktic foraminifers and mollusks (Chris- topher, 1982). In South Carolina and Georgia, the Cenomanian is reported to be 300 to 600 ft thick beneath the coast, and Turonian and. Coniacian strata are thought to be absent there (Gohn and others, 1978, 1980). In contrast, biostratigraphic studies of the COST No. GE-1 well offshore in the southeast Georgia Embayment (fig. 1, locality 14) have shown that Turonian and Coniacian limestone at least 600 ft thick overlies a thin, 150-ft interval of undated shallow-water, calcareous sand- stone of possible Cenomanian age (Valentine, 19792, b). This finding, and my observation of calcareous nanno- fossil assemblages of probable Turonian age in beds beneath the Atlantic and Gulf Coastal Plains that have been dated as Cenomanian in the reports cited above, has prompted a reevaluation of the age of this contro- versial stratigraphic interval. The present study is based on information from 13 wells and 1 outcrop on the Atlantic continental margin (fig. 1) and on 1 well from the Gulf Coastal Plain at Dallas, Tex. (table 1). The depths of samples and stratigraphic boundaries mentioned in the following discussion are given in feet as originally designated during drilling. The purpose of this report is (1) to delineate Turo- nian strata and the Cenomanian-Turonian boundary beneath the Atlantic Coastal Plain in New England, New York, New Jersey, Virginia, South Carolina, and Georgia and beneath the Gulf Coastal Plain at Dallas, Tex., by using calcareous nannofossils and by dating a distinctive pollen zone that is present throughout the region and (2) to revise the ages of some Upper Cre- taceous stratigraphic units that had been established previously for Atlantic and Gulf Coastal Plain deposits. ACKNOWLEDGMENTS I wish to thank W. V. Sliter and J. E. Hazel of the U.S. Geological Survey, Stefan Gartner of Texas A&M University, and J. D. Powell of Grand Junction, Colo., for critically reviewing the manuscript. I am particu- larly grateful to Joe Hazel and Dan Powell for the interest and insight they brought to our discussions of the problem. CENOMANIAN-TURONIAN BOUNDARY Until type sections are chosen for the Cenomanian and Turonian Stages, some controversy will exist regarding the identification and placement of the Cenomanian-Turonian boundary in the European and North American rock record. I have reviewed this problem (fig. 2; Valentine, 1982) and found that the workers who base their interpretation on the evolution 2 TURONIAN STRATIGRAPHY OF THE ATLANTIC COASTAL PLAIN AND TEXAS eram 0° O ( & 2, 4 E < Ei. FIGURE 1.-Turonian localities (numbered 1-14) on the Atlantic continental margin referred to in this study (see table 1). Line labeled 1,000 m is depth to basement. Shaded area is Cretaceous outcrop. of mollusks place the boundary either within an inter- val equivalent to the Seiponoceras gracile zone or at its lower or upper boundary (Basse, 1959; Hancock, 1959; Lecointre, 1959; Cobban and Scott, 1972; Kennedy and Juignet, 1973; Kennedy and Hancock, 1976; Juignet, 1976; Juignet and others, 1978; Rawson and others, 1978). Studies of coeval sections in Europe and North America have shown that the planktic foraminifer genus Rotalipora became extinct within the Sceiponoc- eras gracile zone or its equivalent (Magne and Pol- veche, 1961; Jefferies, 1962; Porthault and others, 1967; Robaszynski, 1971, 1976; Eicher and Worstell, 1970; Smith, 1975; Robaszynski and Caron, 1979), and I fol- low those stratigraphers who have adopted the Rotali- pora extinction event as a reliable datum for the prac- tical determination of the Cenomanian-Turonian boundary (van Hinte, 1976). The recognition of Turo- nian strata beneath the Atlantic and Gulf Coastal Plains depends primarily on the age of a pollen assem- blage zone and on the age of several distinctive calcare- ous nannofossil species. COMPLEXIOPOLLIS-ATLANTOPOLLIS POLLEN ZONE The Complexiopollis-Atlantopollis assemblage zone (Christopher, 19792) is a distinctive and wide- spread biostratigraphic unit that is used to identify Cenomanian strata beneath the Atlantic and Gulf Coastal Plains. This pollen zone is based on a previously described unit, pollen zone IV, that is present in out- cropping and subsurface strata of the middle and north Atlantic Coastal Plain (Doyle, 1969a; Doyle and Robbins, 1977). In outcrop, the Woodbridge Clay Member and the underlying Farrington Sand Member of the Raritan Formation in New Jersey were placed in pollen zone IV, as were correlative strata in wells in New Jersey and Virginia. Among the characteristics of zone IV is the occurrence of only two genera of the triporate Normapolles group of angiosperms, Complex- iopollis and Atlantopollis. These two genera occur together in the Woodbridge Clay Member, whereas lower in the zone only Complextiopollis is present. The age of pollen zone IV strata was considered to be middle and (or) late Cenomanian by some workers (Doyle, 1969a; Wolfe and Pakiser, 1971; Christopher, 19792) on the basis of European palynomorph biostra- tigraphy and on a molluscan fauna from the Wood- bridge Clay Member (Richards, 1943; Stephenson, 1952, 1954). However, Doyle (1969b) and Doyle and Robbins (1977) pointed out that Complexiopollis and Atlantopollis are important elements in the Turonian of Europe, and they speculated that the upper part of zone IV could be early Turonian in age. Christopher (19792) renamed pollen zone IV and redefined it to include only the Woodbridge Clay Member and the overlying Sayreville Sand Member of the Raritan Formation, thereby excluding the Far- COMPLEXIOPOLLIS-ATLANTOPOLLIS POLLEN ZONE TABLE 1.-Turonian localities on the Atlantic and Gulf Coastal Plains Locality Geographic location Elevation Total Measuring Ground level Depth Source of No. Name County and State Lat N. Long W. feet (meters) feet (meters) feet (meters) data' 1 ......USGS borehole 6001 ........ Nantucket, Mass. ...... 41°15'54.9" 70°02'16.72" 35.8 (10.9) 35.8 (10.9) 1,686 (514) 1 2 ...... Well ENW-50, Martha's Dukes, Mass. .............. 41°24" 70°35" 32.8 (10) 32.8 (10) 859 (262) 2 Vineyard. es Block Island outcrop ........ Washington, R.I. ...... Beach cliffs, eastern 3 shore of Block Island. 4 ...... Well $21091T, Fire Suffolk,; N.Y.... 40°37 278 :e78°Ib'40"_ | 12 (3.6) 2,014 (613.9) 3, 4 Island State Park. 5 ...... Toms River Chemical _ Ocean, N.J..........._..... 39°56" 74°12" elo erectors Ae .as 2,255 (687.3) - 4,5 Co. Well. (approx.) (approx.) 6 ...... USGS Island Beach |_ ...... 80°48'15" : 74°05'45!' :i 10 (3) 3,891 (1,186) 4,5 No. 1 well. 7 ......J and J Enterprises, Accomack, Va. ...... 87°598.3' 75°30.9' 52.5 (16) 42: | (12.8) 6,272 (1,011.7) 6 E. G. Taylor No. 1-G well. 8 ......USGS Clubhouse Dorchester, S.C. ...... 82°59'15" 80°21'25" 23 (7) 18 (5.5) 2,530 (771) 7 Crossroads corehole 1. 9 ......Fripp Island well ............. Beaufort, S.C. ............ s2°19'89" ag0°27/49" | | ... ...... as.... 5 (1.5) 3,168 (966) 8 (approx.) 10 ......Layne Atlantic, Parris |...... do:"... 2 32°19'40" - 80°41'50" 18. (6.5) 15 (4.6) 3,454 (1,053) 7 Island Test No. 2 well. 11 ......GGS 1197; Pan Ameri- - Glynn, Ga. ...... 81°22'20" - 81°383'54" 24° (7.8) A8 (4) _ 4,460 (1,359) 7T can Petroleum Union Camp No. 1. 12 ......GGS 724; Humble State- ................ 31°08'20" - 81°38'20" 20°: (8.8) 14 (4.3) 4,633 (1,412) T 1, Union Bag Camp. 13 ......GGS 1198; Pan Ameri- Camden, Ga. ...... 30°50'45" - 81°50'30" 28 (8.5) 14 (4.3) 4,710 (1,436) 7 can Petroleum, Union Camp No. 1-B. 14 ......Ocean Production Co., _ [Offshore] 30°37'08" - 80°17'59" 98 (80) 136 (41) 13,254 (4,040) 9 COST No. GE-1 well. - Ga.-Fla. (water depth) 15... Socony Mobil Field Dallas, Tex../......... 82°41'44" 06°54' 10" ; 666 (203) 591.2 (180.2) 10,11 Research Lab corehole 16. 'Sources of data: (1) Folger and others, 1978; (2) Hall and others, 1980; (3) Sirkin, 1974; (4) Brown and others, 1972; (5) Petters, 1976: (6) Robbins and others, 1975; (7) Brown and others, 1979; (8) Gohn and others, 1978; (9) Scholle, 1979; (10) Brown and Pierce, 1962; (11) Christopher, 1982. rington Sand Member. A necessary criterion of Chris- topher's new Complexiopollis-Atlantopollis assem- blage zone is the occurrence of the nominate genera and the absence of other Normapolles genera, and therefore the new zone does not include the lower part of pollen zone IV where only Complexiopollis is present. The stratotype of the new zone is the Woodbridge Clay Member exposed in the Raritan Bay region of north- ern New Jersey (Christopher, 19792, p. 100, fig. 4). The Complexiopollis-Atlantopollis assemblage zone was dated as middle to late Cenomanian on the basis of the first occurrence of Complexiopollis in middle Cen- omanian strata of Europe and of the Atlantic and Gulf Coastal Plains (Christopher, 19792, and references therein). This conclusion has influenced the most recent stratigraphic interpretations of the South Caro- lina and Georgia Coastal Plain (Gohn and others, 1978, 1980). The Woodbridge Clay Member of northern New Jersey, the stratotype of the Complexiopollis-Atlanto- pollis zone, was dated as Cenomanian on the basis of its dominantly molluscan macrofauna, which is poorly preserved, chiefly as molds and casts (Richards, 1943; Stephenson, 1954). The age of the Woodbridge fauna was addressed by Stephenson in 1952; after he studied a new fossil collection in 1954, he concluded that "the Raritan Formation, particularly in the lower part [Woodbridge Clay Member], corresponds approxi- mately in age to the Woodbine Formation (Cenoman- ian) of Texas * * *" (Stephenson, 1954, p. 25). The Cenomanian age of the Woodbine Formation is not in dispute as it is based on the presence of ammonite and bivalve species that are close relations or analogs of species found in the Cenomanian strata of France and England (Stephenson, 1952, p. 24). On the other hand, a comparison of the Woodbridge Clay Member fauna 4 TURONIAN STRATIGRAPHY OF THE ATLANTIC COASTAL PLAIN AND TEXAS WESTERN | GULF COASTAL ATLANTIC [09 "" | | PLAIN COASTAL PLAIN ISLES Ld & | southeast France| © batise texas (PUF {PE Y| 5 < &l § R § s & §| 3 3 ES g S| Bridge | 9 3+ 4+ §8 < o s a| Creek hase <- cames fares is as anl -l A] 3 5 £ ~ SI. $ S jel 3 9 fo S |Limestone | "S C| | gJC d c & S 8! member | & a = SS 5 1% ].. § R < 3 Sls 4 Is:. Shs s | 18 R = S | Sl - § | & S | §}|(Greenhorn| § § 8 fel O SI#€l § | 8 w S} - b 5 s C fra «ls $ |g € § |Limestone)] § € § § 3 2 8, as E $ S 3 3 E- & =| § < < § 8 g 1 5| § S $ 8 ze 3 s| 5 "1 Actino- |P S o S a §| s camax R p - pH S|& plenus s w 9 E S| = marls § o 3 8". 1% § = Fie S < | 18 [ =s 5 S T f S € (ae, ET- < -€ H =, ious authors; T (Turonian), C (Cenomanian). § §] *": (SI % o No vertical scale. At Dallas, Tex., J. D. Powell § S S/ a + + 1 1 t of Grand Junction, Colo., studied outcrops; R. t; % I| o © A. Christopher and Valentine studied the < *= * same core. COMPLEXIOPOLLIS-ATLANTOPOLLIS POLLEN ZONE 5 with that of the Eagle Ford Group (Cenomanian- Turonian) of Texas was not possible because the mol- luscan fauna of the Eagle Ford, which overlies the Woodbine Formation, had not been adequately studied and described (Stephenson, 1952, p. 25). Only two mol- luscan species from the Woodbridge Clay Member are definitely identified as occurring in the Woodbine Formation, while the rest are either related only to Woodbine forms or their identification is questioned by Stephenson. More significantly, a recent study by Christopher (1982) has shown that the molluscan correlation of the Woodbridge Clay Member and the Woodbine Formation is not valid because the Com- plexiopollis-Atlantopollis pollen assemblage of the Woodbridge Clay Member is not present either in the Woodbine Formation of Texas or in the Tarrant For- mation, the basal formation of the overlying Eagle Ford Group. However, the pollen assemblage is pres- ent higher in the Eagle Ford in the middle and upper part of the Britton Formation and in the lower part of the Arcadia Park Formation, and it is now interpreted by Christopher (1982, oral commun., 1981), to be late Cenomanian and possibly, in the uppermost part, early Turonian in age. The present study is based on the stratigraphy of wells on the Atlantic and Gulf Coastal Plains, and the results suggest that the Complexiopollis-Atlantopollis zone is early Turonian in age beneath the Atlantic Coastal Plain but that it ranges from late Cenomanian to early Turonian beneath the Gulf Coastal Plain at Dallas, Tex. (fig. 2). The distinctive Complexiopollis-Atlantopollis zone assemblage has been reported from many localities on the Atlantic margin including Martha's Vineyard and Nantucket Island, Mass. (Folger and others, 1978; Christopher, 1979a; Hall and others, 1980); Block Island, R.1I. (Sirkin, 1974); Long Island, N.Y. (Sirkin, 1974; Perry and others, 1975); New Jersey (Doyle, 1969a,b; Perry and others, 1975); Virginia (Robbins and others, 1975; Doyle and Robbins, 1977); North Carolina (Christopher and others, 1979); South Caro- lina (Gohn and others, 1978); and Georgia (Gohn and others, 1980). The assemblage also is present in the Tuscaloosa Group of Georgia and Alabama (Leopold and Pakiser, 1964; Phillips and Felix, 1971; Chris- topher, 19792, b) and in the Eagle Ford Group of Texas (Christopher, 1982). Offshore, it has been reported from the COST No. GE-1 well off Georgia. AGE OF CALCAREOUS NANNOFOSSIL SPECIES Establishing the ages of several key nannofossil species that are present in the stratigraphic interval under study here is important. In a worldwide study of Jurassic and Cretaceous strata, Thierstein (1976, fig. 7 and pl. 3, figs. 39, 40) concluded that Corollithion achylosum ranges from the Aptian to the latest Turo- nian. This species is restricted to rocks independently dated with planktic foraminifers as Turonian and older in the COST No. B-2, B-3, and GE-1 wells drilled on the Atlantic margin (Valentine, 1977, 1979b, 1980; Poag, 1977, 1980; Poag and Hall, 1979); a reevaluation of the COST No. B-2 well (Valentine, 1980) revealed a previous reference to C. achylosum (Valentine, 1977, p. 39) to be incorrect. On the Texas Coastal Plain, C. achylosum has not been reported from strata younger than Turonian (Gartner, 1968; Bukry, 1969; Smith, 1981). I found that in a core from the Eagle Ford and Austin Groups at Dallas, Tex. (Socony Mobil corehole 16; Brown and Pierce, 1962; Pessagno, 1969), the high- est occurrence of C. achylosum is in the upper part of the Arcadia Park Formation (upper Turonian); C. achylosum does not range into the overlying Atco Formation (Coniacian). In contrast, Verbeek (19772) reported that C. achylosum ranged as high as the Campanian, but this range appears to be based on an early paper by Thierstein (1973) and not on that author's later report (Thierstein, 1976). Moreover, Verbeek's (1976, 19772) studies in Tunisia and Spain showed that C. achylosum is restricted to Turonian and older strata except for a single occurrence in "Coniacian" beds that are probably Turonian in age (Valentine, 1982). Eiffellithus eximius was reported by Thierstein (1976, fig. 7 and pl. 5, figs. 28, 29) to range from the middle Turonian to the Campanian-Maestrichtian boundary, and Stover (1966) reported it as ranging throughout the Turonian. Wonders and Verbeek (1977) have shown that the first occurrence of E. eximius in the El Kef section of Tunisia is in the Turonian, above the extinction level of Rotalipora, and the same rela- tion exists in a section at Javernant, France (Verbeek, 19776; de Vries, 1977). Manivit and others (1977) indi- cated the initial appearance of E. eximius was in the upper Turonian, but subsequently, Manivit and others (1979) showed it first appeared in the middle Turo- nian. FEiffellithus eximius occurs with Corollithion achylosum in the Fripp Island and Clubhouse Cross- roads wells of South Carolina and in strata dated as Turonian in previous studies in the Dallas, Tex., core (Christopher, 1982; Powell, written and oral commun., 1981, 1982), in the Island Beach and Toms River wells of New Jersey (Petters, 1976), and in the COST No. B-2, B-3, and GE-1 wells offshore (Valentine, 1979b, 1980, 1982). A third stratigraphically important calcareous nannofossil species is Lithraphidites acutum. This species has been reported as ranging from middle Cenomanian to middle Turonian, although its last occurrence in the Turonian is not well documented 6 TURONIAN STRATIGRAPHY OF THE ATLANTIC COASTAL PLAIN AND TEXAS (Manivit and others, 1977, pl. 1, figs. 1, 7, 8). In the present study, L. acutum disappeared before the first appearance of Eiffellithus eximius, as reported by Manivit and others (1977). Lithraphidites acutum is present in the Fripp Island and Clubhouse Crossroads wells in South Carolina, in the Dallas corehole in Texas, and in strata dated as early Turonian with foraminifers (Petters, 1976) in the Toms River and Island Beach wells in New Jersey. Two distinct nannofossil assemblages have been identified in this study. They are present in, but are not confined to, the Complexiopollis-Atlantopollis pol- len zone, which is an important biostratigraphic unit that is found in the subsurface and in outcrops of the Coastal Plain from New England to Texas. The Lithraphidites acutum assemblage is present in the lower part of the Complexiopollis-Atlantopollis zone and contains Lithraphidites acutum, Corollithion achy- losum, Cretarhabdus lorei, Cruciellipsis chiastia, Par- habdolithus asper, and Podorhabdus albianus. The somewhat younger Eiffellithus eximius assemblage is found in the upper part of the Complexiopollis- Atlantopollis zone and contains Eiffellithus eximius, Corollithion achylosum, and possibly Cretarhabdus lorei. NEW JERSEY COASTAL PLAIN TOMS RIVER CHEMICAL CO. WELL The Raritan Formation exposed in northern New Jersey does not contain calcareous microfossils, but, 38 mi south of Raritan Bay, the formation, including the Woodbridge Clay Member, has been delineated in the Toms River Chemical Co. well through lithological, geophysical, and, most importantly, palynological cor- relations based on core samples (Perry and others, 1975). Pollen zone IV was recognized from about 1,300 to 1,500 ft, and the Woodbridge from about 1,300 to 1,430 ft (Perry and others, 1975, fig. 11). J. A. Doyle, who analyzed the spores and pollen in this well for the study by Perry and others, reported beds equivalent to the Woodbridge Clay Member and containing only Complexiopollis and Atlantopollis of the Normapolles group to be present at 1,298 to 1,300 ft and 1,369 to 1,371 ft and only Complexiopollis to be present at 1,487 to 1,439, 1,460, and 1,528 ft (Doyle, 1969b, oral com- mun., 1981). The interval from 1,298 to at least 1,371 ft in the Toms River well (figs. 2 and 3) correlates with the Complexiopollis-Atlantopollis zone of Christopher (19792). The age of the Complexiopollis-Atlantopollis zone can be determined because both planktic foram- inifers and calcareous nannofossils occur in this interval of the Toms River well. The extinction of Rotalipora is accepted here as marking the Ceno- Toms River Chemical Co. well , N.J. 4 u Locality No. 5 a &. & & @ A 2] § | € «| # , Calcareous Nannofossil & ir- "J 1 8) E) 5) §§) E species ranges :| ~€ € |- to | &.l € & A. 4 .S & S & = €:. & S s ${s§s §§ G $ 1200 - : °! |-- s t e SF § S : £3 s & \% WG §35 & 18. -- was % .S | S.o s «1350 -/ € | 5 | &§|8 C sS)|S e h S S<|g § E- __EN mum a x § s f. ¢ s c SE isl as § & & 7C 3 S5 |§ § s §§ & 1400 - S |g< s. ® .S J < (£5 ~a o e |4 wamn - vwvv-gw—wvr am han M60“ & S yr oc ~a a & & & § | ~R Eig fz 6 < §~ S & eN a ma /w &) & Ut 3234 "= S S 1500 5 5 S 1 |C a; & BJ %% & al os 3 & T FIGURE 3.-Upper Cenomanian and Turonian stratigraphy, calcare- ous nannofossil ranges, and the occurrence of the Complexi- opollis-Atlantopollis zone in the Toms River Chemical Co. well, New Jersey. Pollen stratigraphy adapted from the work of Doyle (1969b, oral commun., 1981). Planktic foraminifer stratigraphy from Petters (1976). Blacked-in areas represent cores studied for nannofossils. A hiatus (wavy line) is interpreted to exist between the upper Cenomanian and lower Turonian. Depth scale is origi- nal depth. manian-Turonian boundary, and Petters (1976, fig. 6) showed this datum to be at 1,440 ft at Toms River, below the Complexiopollis-Atlantopollis interval; he also recognized the lower Turonian Praeglobotrun- cana helvetica zone in the interval from 1,323 to 1,440 ft (1976, p. 96, fig. 6). I have identified calcareous nannofossil assemblages that corroborate the early Turonian age determination for the Woodbridge Clay Member (Complexiopollis-Atlantopollis zone) in the well. An analysis of four core samples (1,323-1,825, 1,345-1,347, 1,369-1,371, and 1,391-1,393 ft) revealed the age of this interval to be Turonian on the basis of the occurrence of Corollithion achylosum and Eiffelli- thus eximius. Lower in the section (1,415-1,417 and 1,437-1,439 ft), the highest occurrence of Lithraphi- dites acutum and Podorhabdus albianus at 1,415 ft and the presence of Corollithion achylosum and Podorhab- dus albianus at 1,437 ft suggest an early Turonian age NEW JERSEY COASTAL PLAIN 7 for these beds that lie above the Rotalipora extinction at 1,440 ft. USGS ISLAND BEACH NO. 1 WELL The USGS Island Beach No. 1 well is located about 10 mi southeast of the Toms River well, and the Cenomanian-Turonian biostratigraphy of the two wells is similar. Petters (1976, p. 93, fig. 6) delineated the lower Turonian Praeglobotruncana helvetica zone from 1,950 to 2,200 ft, the highest occurrence of Rotalipora. In the same interval, a Complexiopollis-Atlantopollis zone flora is present in sidewall cores from 2,004 and 2,200 ft (Christopher, oral commun., 1979), and I have identified calcareous nannofossils that I interpret to be Turonian in age from the same cores. The core from 2,004 ft contains Corollithion achylosum, Eiffellithus eximius, and other species. The nannofossil assemblage from 2,200 ft is similar, except that E. eximius is absent and Lithraphidites acutum is present. NEW YORK, RHODE ISLAND, AND MASSACHUSETTS COASTAL PLAINS FIRE ISLAND STATE PARK WELL The Atlantic Coastal Plain narrows in northern New Jersey as the continental margin turns eastward to New England. Cretaceous strata are confined to the subsurface in the coastal region from New York to Massachusetts except where they have been trans- ported southward and exposed by the advance of Pleis- tocene glaciers. The Complexiopollis-Atlantopollis zone assemblage is present in cores collected between 1,800 and 1,873 ft in a deep well drilled in Fire Island State Park (S21091T) off the south coast of Long Island, N.Y. (Sirkin, 1974). This interval has been correlated with the Woodbridge Clay Member of the Raritan Formation and pollen zone IV by Perry and others (1975, fig. 11). The Complexiopollis-Atlantopollis zone flora is from a part of the Fire Island well that was assigned to unit F by Brown and others (1972). BLOCK ISLAND OUTCROP Block Island off the coast of Rhode Island is the site of an exposure of Upper Cretaceous strata that were transported and tilted during a Pleistocene gla- cial advance. Sirkin (1974) reported the occurrence of Complexiopollis and Atlantopollis in lignite seams from beach cliffs there that indicates a correlation with the Complexiopollis-Atlantopollis zone of the Woodbridge Clay Member. MARTHA'S VINEYARD AND NANTUCKET ISLAND WELLS Two wells drilled on Martha's Vineyard and Nan- tucket Island, Mass., encountered beds that can be assigned to the Complexiopollis-Atlantopollis zone. In the ENW-50 well on Martha's Vineyard, R. A. Chris- topher identified the Woodbridge flora in three split- spoon samples from 550, 600, and 835.5 ft (Hall and others, 1980). On Nantucket Island, Christopher found the same flora in cores from 850.4, 940.0, 1076.1, 1083.0, and 1104.3 ft in the USGS borehole 6001 (Folger and others, 1978; Valentine, 1981). VIRGINIA COASTAL PLAIN J. AND J. ENTERPRISES, E. G. TAYLOR NO. 1-G WELL The Complexiopollis-Atlantopollis zone flora is present also in the E. G. Taylor No. 1-G well on the eastern shore of Virginia, the only reported occurrence of the flora from the Coastal Plain between New Jersey and North Carolina. The stratigraphy of the well has been studied by Robbins and others (1975) and Doyle and Robbins (1977) who studied the palynomorphs and also incorporated into their interpretation information provided by M. Ruth Todd about foraminifers from a 195-ft interval (1,83825-1,520 ft). Robbins and others (1975) examined cores and sidewall cores and delineated pollen zone IV from 1,450 to 1,560 ft. The pollen distribution presented in their report indicates that the Complexiopollis- Atlantopollis zone, as defined by Christopher (19792), is present in a short interval from 1,450 to 1,480 ft; foraminifer species in the same interval are not age diagnostic and could be Turonian or Cenomanian, but Rotalipora greenhornensis is present lower in the see- tion at 1,520 ft. Although Rotalipora occurs in a single sample, the pattern of stratigraphic succession, Rotal- ipora followed by Complexiopollis-Atlantopollis zone strata of early Turonian age, is similar to that observed in the Toms River, N.J., well. soOUTH CAROLINA COASTAL PLAIN Brown and others (1979) and Gohn and others (1978, 1980) have delineated the Upper Cretaceous stratigraphy beneath the South Carolina Coastal Plain on the basis of lithologic and electric log correlations that are supplemented by paleontological interpreta- tions. These authors studied many of the same wells, but their stratigraphic units often do not coincide. They also do not agree on the age of the lower part of the Upper Cretaceous section or on the placement of hiatuses. The results of the study of a deep stratigraph- ic test well (COST No. GE-1) on the Outer Continen- tal Shelf off Georgia (Valentine, 19792, b) prompted a reevaluation of the ages of Cretaceous strata that underlie the Georgia and South Carolina Coastal Plains. The three South Carolina wells treated here have been studied by other workers, and they are part 8 TURONIAN STRATIGRAPHY OF THE ATLANTIC COASTAL PLAIN AND TEXAS of a broader investigation (Valentine, 1982) to revise the Upper Cretaceous stratigraphic framework pre- viously established for the South Carolina-Georgia coastal region. FRIPP ISLAND WELL The Upper Cretaceous biostratigraphy of the Fripp Island well (fig. 4) has been studied in more detail than that of other wells in coastal South Caro- lina; the study involved the examination of 279 cut- tings samples at 94 levels in the approximately 1,700- ft Upper Cretaceous interval. There is a 263-ft sam- pling gap in the Campanian part of the section. Cuttings were collected over 10-ft intervals, and indi- vidual rock chips representative of each lithologic unit in a sample were examined. Calceareous nannofossils are, for the most part, abundant and well preserved, and the stratigraphy of the well is based on the ranges of the following selected species: Micula mura (1,507 ft); Tetralithus aculeus (1,507-1,907 ft); T. trifidus (1,527-1,970 ft); Broinsonia parca (1,527-2,427 ft); Eiffellithus eximius (1,808-8,147 ft, lowest sample); Lithastrinus grillii (2,263-2,867 ft); Chiastozygus cune- atus (2,427-3,007 ft); Lithastrinus floralis (2,457-3,147 ft, lowest sample); Marthasterites furcatus (2,457-2,857 ft); and Corollithion achylosum (3,057-3,147 ft, lowest sample). The Cretaceous-Tertiary boundary is at 1,437 ft, and the Maestrichtian-Campanian boundary is at 1,808 ft. The top of the Santonian is at 2,427 ft, and both Santonian and Coniacian cuttings are present down to at least 2,637 ft, where an unfossiliferous quartz sand appears that extends down to 3,057 ft. The 420-ft thick sand may be Coniacian in age, but, because I could not determine the boundary between the San- tonian and Coniacian Stages, the entire interval from 2,427 to 3,057 ft is treated as Santonian-Coniacian. Below the quartz sand, there is a marked change in lithology to gray, calcareous sandy or silty shale and gray limestone (Gohn and others, 1978). Three samples (3,057-3,067, 3,097-3,107, and 3,137-3,147 ft) from this unit contain a Turonian Hiffellithus eximius assemblage that includes, among other species, Ahmu- ellerella octoradiata, Corollithion achylosum, C. exi- guum, Eiffellithus eximius, and Lithastrinus floralis; two samples (3,097-3,107 and 3,127-3,137 ft) within this interval contain a Complexiopollis-Atlantopollis zone flora (R. A. Christopher, unpub. data, 1977). Planktic foraminifers dated as Turonian or Coniacian, but not older than Turonian, are present in a sample from 3,117 to 3,127 ft (C. C. Smith, unpub. data, 1977). Samples are not available from the lowest 21 ft of the section, and the well did not penetrate crystalline basement rocks (Gohn and others, 1978). Fripp Island well, S.C. Locality No. 9 Gohn and others (1978) _ |Valentine(1982) Provincial | European | European Stage Stage Stage 1400 - : Cenozoic 09?"ng (part) p 1437 ft ha KG Maestrichtian 18004 Navarroan- | Maestrichtian- Tayloran Campanian a 18 08ft s Lu «d ¥ > Ls & => 3 KS m 2200- g Campanian ayloran- _ E Auystinian Campanian LL. T 35" ed 5 K4 # 5 2427 ft neste | Contorler 2600-7 MAM/Ml K3 b Santonian - § Coniacian Eagle - = fordian 5 m 3000-7 o 8 -f 3057ftwrwnrnd Fagle- K2 Turonian ~ fordian r ete eS san a - 4 3168 ft TD - FIGURE 4.-Stratigraphic interpretations of the Fripp Island well, South Carolina. K2-K6 are unnamed stratigraphic units of Gohn and others (1978). Depth scale is relative to sea level; stratigraphic boundaries are given in original depths (for depth below sea level; subtract 5 ft). Wavy lines represent unconformities. My interpretation of the upper part of the Fripp Island section agrees with that of Gohn and others (1978). However, in the lower part of the well, those authors interpreted their units K2 and K3 to be Ceno- manian in age, and they recognized a major hiatus SOUTH CAROLINA COASTAL PLAIN 9 between units K3 and K4 that represents Coniacian and Turonian time. In contrast, I believe that unit K3 is Santonian-Coniacian in age and that unit K2 is early Turonian. LAYNE ATLANTIC, PARRIS ISLAND TEST NO. 2 WELL The Upper Cretaceous stratigraphic units of Brown and others (1979) and Gohn and others (1978, 1980) can be compared in the Parris Island Test No. 2 well; further, correlation is possible with the Fripp Island well, only 11 mi to the west, where the units of Gohn and others can be dated with nannofossils and pollen. Gohn and others (1978, 1980) based their corre- lation of the two wells on electric logs and paleontolog- ical analyses. Brown and others (1979) presumably used lithologic characteristics and the occurrence of key species of ostracodes and foraminifers to interpret the Parris Island well. The lowest units outlined in the well by these studies are physically the same, but Brown and others (1979) assigned them to unit E (Woodbinian) and Unit F (Washitan and Fredericks- burgian), whereas Gohn and others (1978, 1980) consid- ered them to be younger and placed them, respectively, in unit K2 (middle Eaglefordian) and unit K1 (Upper(?) Cretaceous). I have reinterpreted, in part, the electric logs pub- lished by Gohn and others (1978, sheet 2) to correlate strata in the Parris Island well with units I have dated at Fripp Island (Valentine, 1982). The beds in the lower part of the Parris Island well appear to be younger than the previous authors have indicated, and I inter- pret unit E (Cenomanian) of Brown and others (1979) and unit K2 (Cenomanian) of Gohn and others (1978, 1980) to be early Turonian in age. The age of thelowest unit in the Parris Island well is unknown at present. CLUBHOUSE CROSSROADS COREHOLE 1 The Clubhouse Crossroads corehole 1 (fig. 5) is 42 mi north of the Parris Island and Fripp Island wells. The lithology and paleontology of the core have been studied by Gohn and others (1977) and Hazel and others (1977), and this corehole has been incorporated into the stratigraphic frameworks of Gohn and others (1978) and Brown and others (1979). Their age inter- pretations are coincident down to the base of the Aus- tinian Stage. At that level, Gohn and others (1978) indicated the presence of a major disconformity be- tween units K4 and K3; Gohn and others (1980) assigned units K3 and K2 below the hiatus to the mid- dle Eaglefordian and assigned unit K1 to the Upper(?) Cretaceous. Brown and others (1979) interpreted the same interval to include strata of unit D (Eagleford- ian) separated by a hiatus representing unit E (Wood- binian) from the underlying rocks of unit F (Washitan and Fredericksburgian). Hazel and others (1977), by using planktic fora- minifers, have shown that the Tertiary-Maestrichtian boundary is at approximately 804 ft, that the Mae- strichtian-Campanian contact is at about 1,030 ft, and that Campanian strata extend down to approximately 1,706 ft. The interval from 1,706 to 2,342 ft is poorly fossiliferous, but spore and pollen flora typical of the Magothy Formation and the underlying South Amboy Fire Clay Member of the Raritan Formation of New Jersey are present down to 1,906 ft (Hazel and others, 1977). The Magothy and the South Amboy assemblages belong to the tripartite pollen zone V of Christopher (1977, 19792, and 1982) that is chiefly Santonian in age but that also includes strata of early Campanian and late Coniacian age (R. A. Christopher, oral commun., 1979). I have examined a sample from 1,752 ft that contains a rich Santonian nannofossil assemblage; a sample from 1,943 ft, however, contains only rare Clubhouse Crossroads corehole 1, S.C. Locality No. 8 Brown Gohn Hazel y and others | and others |_ and others Vaggg’e (1979) (1978, 1980) (1977) SEA LEVEL 300 - : Cenozoic 600 - 804 ft a A K6 MZ I2 © 900 - Navarroan MoektrichtHon Maestrichtian i Navarroan- 1025 ft 5 6 Tayloran 5 1200 - ad Tayloran ; If K5] _ Campanian Companion t Tayloran- as C Austinian # " Austinian iTostt & 1800 - Austinian _ K4] ~ santonian ? 3 D K3 ea antonian- Egrgdlfu-n & 6 5 Coniacian 2100 - * a £ € & 234211 Washitan, F [- ~z1 o han. tmni 2400 - Fredericksbur'gian /i up.(2) cre- K2 V7VT§£32WNM Triassic - Jurassic | basalt ce'g’fi’é'gfl?) ~-2530 ft TD -' FIGURE 5.-Stratigraphic interpretations of Clubhouse Crossroads corehole 1, South Carolina. Depth scale is relative to sea level; stratigraphic boundaries are given in original depths (for depth below sea level, subtract 23 ft). Wavy lines indicate unconformities. 10 TURONIAN STRATIGRAPHY OF THE ATLANTIC COASTAL PLAIN AND TEXAS nannofossils, and the presence of eximius, Tetralithus obscurus, and Lithastrinus grillii point to a Turonian age or younger, possibly Coniacian. Planktic foraminifers are sparse in the interval from 1,706 to 2,342 ft; two samples (1,922.5 and 2,308.8 ft) examined ~ by C. C. Smith (unpub. data, 1976) each contained a single species (G@lobigerinelloides caseyi and G. sp. ef G. caseyi, respectively) and were dated as Cenoman- ian. G. caseyi, however, is not restricted to the Ceno- manian; its highest occurrence is considered by Ascoli (1976) to be diagnostic of lower Turonian strata beneath the Scotian Shelf of Canada. It is present also in the upper Cenomanian and lower and middle Turo- nian of Kansas and Colorado (Eicher and Worstell, 1970). The beds from 1,706 to 2,342 ft are chiefly sand. and silt, and Gohn and others (1978, sheet 2) correlated this interval, which they identified as units K3 and K4, with a lithologically similar sequence in the Fripp Island well that I have determined to be Santonian- Coniacian in age. Lower in the Clubhouse Crossroads core, a spore and pollen flora characteristic of the Complexiopollis- Atlantopollis pollen zone and the Woodbridge Clay Member of the Raritan Formation of New Jersey is present at 2,342.83, 2.371.1, 2,375.0, and 2,404.8 ft (Hazel and others, 1977). On the other hand, samples from these beds (2,364.4, 2,83865.4, 2,369.4, 2,373.7, and 2,399.2 ft) contain planktic foraminifers interpreted to be Cenomanian in age (C. C. Smith, unpub. data, 1976). Guembelitria harrisi, Hedbergella brittonensis, and Heterohelix moremanti are the only species present, and the age is based on the presence of Guembelitria harrisi. The range of this species, however, is not pre- cisely known, and it is probably present in the Turonian as Eicher and Worstell (1970) have shown it to range higher than Rotalipora in sections in Colorado, Wyo- ming, and South Dakota. Three other samples (2,367.5, 2,370.5, and 2,396.0 ft) from this part of the core yielded only Guembelitria harrisi and Heterohelix moremant (C. W. Poag, unpub., data, 1981). Hattner and Wise (1980) studied nannofossils from the Upper Cretaceous of the Clubhouse Cross- roads core. Among four samples from the Com- plexiopollis-Atlantopollis interval, all but one are barren or contain nondiagnostic floras; at 2,373 ft, Ahmuellerella octoradiata, Lithraphidites acutum, and L. alatus are present in an assemblage they interpreted to be Cenomanian. I have examined the nannofossils from the same part of the core, and 38 of 80 samples in the 68.4-ft interval from 2,338.5 to 2,407.0 ft are fossiliferous (fig. 6). The ranges of biostratigraphically important spe- cies are Ahmuellerella octoradiata (2,375-2,407 ft); Corollithion achylosum (2,363.5-2,407 ft); Cruciellip- sis chiastia (2,364.5-2,406 ft); Eiffellithus eximius Clubhouse Crossroads - corehole 1, S.C. Locality No. 8 § | £ 8 3 A | g Calcareous nannofossil a &! a i S| € £ E species ranges & | 2] & | a € ~ = [=] "s 9 2340 -| 5 |- 2350 7 |- & $ ¢ 5 & § § s §§ ; § & a e s .$ NOE & $ £ 2360 - =' [(f. lm § &" & § S: |a" ] § saps F E3 (s & s s a y. W €: [%s Coy §. (J C | % | = " "& 8 $ 5 u 28 |- : §§ $ u § xo Q § S 20041 § | < | § | _- ¢ & - z 5 5 S | z € a s |= |x |= 1 1 12 .14€ |. * i- s | 1 ee ¥ }s% o = 2380 - | g §~ a. = '< Fd 5 | ® S s | € § 2 | 3% = S . § 5 - [ss N8 & S % 2390 - s § % E == 6 ~ == w . 2400 - s |- lak (tS EXPLANATION D core loss 2410 - - Q barren FIGURE 6.-Turonian stratigraphy, calcareous nannofossil ranges, and occurrence of the Compleziopollis-Atlantopollis zone in the Clubhouse Crossroads corehole 1, South Carolina. Pollen strati- graphy from Hazel and others (1977). Depth scale is original depth. (rare, 2,364 ft); Lithraphidites acutum (2,372.5-2,406 ft); L. alatus (rare, 2,894.5 ft); Microrhabdulus belgicus (rare, 2,373 and 2,406 ft); Micula staurophora (rare, 2,370-2,407 ft); and Podorhabdus albianus (2,364-2,406 ft). These strata are unit K2 of Gohn and others (1978) who have shown them to be coeval with K2 in the Fripp Island well that also contains a Complexiopollis- Atlantopollis zone flora and Turonian nannofossil assemblages. Brown and others (1979) indicated that their unit E is missing from the Clubhouse Crossroads section but that the older unit F is present. The evi- dence presented here and in the discussion of the Par- ris Island well suggests that unit F in the Clubhouse Crossroads core is equivalent to unit E at Parris Island SOUTH CAROLINA COASTAL PLAIN and that, in these two wells, they are correlative with unit K2 of Gohn and others (1978). Between these strata and basalt at 2,462 ft, there lies a thin, undated interval that is practically barren, which could be Cenomanian in age. AGES OF SUBSURFACE STRATIGRAPHIC UNITS IN SOUTH CAROLINA The analyses of the Parris Island, Fripp Island, and Clubhouse Crossroads sections are, in part (see Valentine, 1982), the basis for a reevaluation of the ages of previously described stratigraphic units in the subsurface of coastal South Carolina (fig. 7). I agree with the ages assigned by Brown and others (1979) to their units A (Navarroan) and B (Tayloran), but I observe some overlap of the two units at the Navarroan- Tayloran (Maestrichtian-Campanian) boundary. I re- strict their unit C (Austinian) to the upper Austinian (Campanian-Santonian), and I now assign their unit D (Eaglefordian) to the middle and lower part of the Austinian (Santonian-Coniacian) and unit E (Wood- binian) to the Eaglefordian (Turonian). Units E and F (Washitan and Fredericksburgian) may be delineated inadequately in South Carolina, because beds that are identified as Unit E in the Parris Island well are cor- relative, in my opinion, to unit F at Clubhouse Cross- roads (Brown and others, 1979). It appears that the upper part of unit F can be assigned to the lower Turonian (Eaglefordian) in this region. The ages of the stratigraphic units of Gohn and others (1978, 1980) that represent Maestrichtian, Cam- panian, and Santonian strata (units K6, K5, and K4) remain unchanged in my interpretation. Those authors, however, recognized a Coniacian-Turonian hiatus in the section, and they placed units K2 and K3 in the upper Cenomanian and placed unit K1 in the Upper(?) Cretaceous. In contrast, I believe that Santonian, Coniacian, and lower Turonian strata are present beneath the South Carolina coast. In my interpretation, unit K3 represents the Coniacian and possibly part of the Santonian (lower Austinian), whereas unit K2 is lower Turonian (middle and upper Eaglefordian). Unit K1 is present only in the lowest part of the sedi- mentary section and may be unfossiliferous; Ceno- manian beds, if present, are poorly represented in the interval just above pre-Cretaceous basement rocks. GEORGIA COASTAL PLAIN GEORGIA GEOLOGICAL SURVEY WELLS 1197, 724, 1198 In Georgia, three wells located in the center of the Southeast Georgia Embayment onshore (fig. 1) have penetrated strata near basement that contain floras characteristic of the Complexiopollis-Atlantopollis pol- len zone (Valentine, 1982). Brown and others (1979) South Carolina Coastal Plain 11 Brown s 3 f Gohn and others| Valentine | Provincial European | Valentine |and others (1979) | (1982) Stage Stage (1982) |(1978, 1980) A A Navarroan | Maestrichtian J— * K6 K6 Tayl B B A val Campanian K5 K5 C 55 fe ap piles C - |--" Austinian Santonian _?'LK4 K4 D Coniacian K3 p _E_:— C tige: Turonian K 2— fordian i Ne/ if AeA E Woodbinian | Cenomanian KL / F ? Washitan and F Fredericks- Albian burgian FIGURE 7.-Cretaceous stratigraphic units recognized in the subsur- face of coastal South Carolina by Gohn and others (1978, 1980) and by Brown and others (1979). Correlation of the units with Euro- pean and Provincial Stages, as shown by those authors, is com- pared to the interpretations of Valentine (1982) and the present: study. Crosshatched areas represent hiatuses. Dashed lines indi- cate uncertain delineation of unit boundaries with respect to European and Provincial Stages. and Gohn and others (1980) studied these wells as part of their stratigraphic interpretations of the region. Complexiopollis and Atlantopollis are present together in cuttings from 4,500 to 4,530 and 4,590 to 4,620 ft in Georgia Geological Survey (GGS) well 1198 (R: A. Christopher, unpub. data, 1978). These samples are from units E and F of Brown and others (1979) and from unit K 2-3 of Gohn and others (1980). A sample from 4,530 to 4,560 ft yielded nannofossils and planktic foraminifers that were interpreted to be Cenomanian in age (C. C. Smith, unpub. data, 1978). The nannofossil assemblage from this sample appears to me to be Tur- onian, on the basis of the presence of Corollithion achylosum, Eiffellithus eximius, Lithraphidites ala- tus, Parhabdolithus asper, and Podorhabdus albianus. The foraminifers of stratigraphic importance in the sample range across the Cenomanian-Turonian boun- dary; Guembelitria harrisi is present, but, as pre- viously mentioned, it is not a reliable marker for the Cenomanian. GGS 724 also yielded Complexiopollis and Atlan- topollis in cuttings samples 4,520 to 4,540 and 4,630 to 12 TURONIAN STRATIGRAPHY OF THE ATLANTIC COASTAL PLAIN AND TEXAS 4,640 ft (R. A. Christopher, unpub. data, 1978) from unit F (Brown and others, 1979) and from unit K2 (Gohn and others, 1980). In GGS 1197, a similar flora is present at 4,180 to 4,190 ft (R. A. Christopher, unpub. data, 1979) from units E and K2. TEXAS COASTAL PLAIN SOCONY MOBIL COREHOLE 16 The biostratigraphic relations from the Atlantic Coastal Plain are also evident in a core from the Gulf Coastal Plain at Dallas, Tex. (figs. 2 and 8, Socony- Mobil Field Research Lab corehole 16; Brown and Pierce, 1962; Pessagno, 1969; Christopher, 1982). In the Dallas core, a Complexiopollis-Atlantopollis zone flora is present in the middle and upper part of the Britton Formation and in the lower part of the Arca- dia Park Formation of the Eagle Ford Group, whereas, lower in the Eagle Ford Group, the pollen flora con- tains rare Complexiopollis but no Atlantopollis and is assigned to the post-zone III, pre-Complexiopollis- Atlantopollis zone interval (Christopher, 1982). A sim- ilar floral break occurs just above the Cenomanian- Turonian boundary in the Toms River well in New Jersey. My study of the calcareous nannofossils from the Dallas core shows that Eiffellithus eximius and Corol- lithion achylosum are present together in the upper- most part of the Britton Formation and range through the Arcadia Park Formation, indicating a Turonian age for these strata. The upper part of this interval (middle and upper Arcadia Park Formation) contains a post-Complexiopollis-Atlantopollis, pre-zone V flora and is late Turonian in age. The lower part of the interval (uppermost Britton Formation and lower- most Arcadia Park Formation) lies in the upper part of the Complexiopollis-Atlantopollis zone in this core and is early Turonian in age. Lithraphidites acutum, a species that ranges from the Cenomanian into the lower Turonian, is present in the middle and lower Complexiopollis-Atlantopollis zone (middle and upper Britton Formation). It is also present with the Norma- polles genus Complexiopollis in the lower Britton Formation, which is probably Cenomanian in age. In a previous study of the Dallas core based in planktic foraminifers, Pessagno (1969, pl. 9) concluded that the Britton and Arcadia Park Formations repre- sent upper Cenomanian and upper Turonian strata separated by a lower Turonian hiatus; he interpreted the Cenomanian-upper Turonian boundary to lie near the top of the Britton Formation, between about 213 and 223 ft. However, planktic foraminifers are not well represented in the core, and the stratigraphically important genus Rotalipora is present in only one sample at 444 ft (Pessagno, 1969, pl. 39b). J. D. Powell (in Christopher, 1982; oral and written commun., 1980, 1982) studied the mollusks and foram- inifers from an equivalent section in an outcrop near the Dallas core site and concluded that the upper 15 ft of the Britton Formation and possibly the lower 30 ft of the Arcadia Park Formation represent the Mytiloides "labiatus" zone of early Turonian age (fig. 9). Below this zone, in the middle and upper part of the Britton Formation, Powell delineated the Sceiponoceras gracile zone that I believe overlaps the Cenomanian-Turonian boundary. Regarding the range of Rotalipora, Powell (1970) found that the upper limit of abundant Rotali- pora is at the top of a chalky interval at outcrop locality D2 and that this level is also the base of the Sciponoce- ras gracile zone in outcrop and is coincident with the top of the bentonitic interval in corehole 16. Powell also found rare rotaliporids ranging up to the Metoic- oceras whitei and Inoceramus pictus level at locality D3. The Arcadia Park Formation at outcrop locality D3 and in the Dallas corehole several miles to the east is almost equal in thickness. The Britton Formation is not fully exposed at D3, but, assuming that the exposed section and an equal thickness of the Britton in the corehole are coeval, the top of the Rotalipora range should occur at about 270 ft in corehole 16. On the same basis, the top of the Mytiloides "labiatus" zone and the associated lower Turonian-upper Turonian boundary are placed provisionally 30 ft above the base of the Arcadia Park Formation (fig. 9). The placement of this datum is not well documented, and it probably lies higher in the section, above the top of the Complexiopollis-Atlantopollis zone. At present, a case cannot be made for extending the Complexiopollis- Atlantopollis zone into the upper Turonian. On the basis of the results of the studies on the Dallas core and the age established for the Complexi- opollis-Atlantopollis zone beneath the northern Atlan- tic Coastal Plain, I have concluded that upper and lower Turonian strata are present in the section that encompasses the upper Britton Formation and the Arcadia Park Formation. In a previous paper (V alen- tine, 1982), written before I knew the details of Powell's work on Rotalipora, I drew the Cenomanian-Turonian boundary at the base of the Complexiopollis-Atlan- topollis pollen zone in the Dallas core. Now I place the Cenomanian-Turonian boundary at the last occur- rence of Rotalipora in outcrop and at the equivalent level in the core as described above. This is somewhat below the boundary selected by Christopher (1982) at the top of the Sceiponoceras gracile zone, and it is above the boundary recognized by Brown and Pierce (1962). 183 TEXAS COASTAL PLAIN Socony Mobil corehole 16, Dallas, Tex. Locality No. 15 | | II | | | snag ubow jy =. > SNI "29 _ _ m . JY «mnie l 5 11/1115 j § 3. v1oydoino}s y - yer r snu1xg <7 < g zcnlw e ~9 C & | y ~ fe wnnbyxa "3 & "p » a ° 5 m wnsofp yap "3 . 2. wnyvuaubas 9 IN ig wninoo (7 <> 12dsD jf snp :; 194110] ~3 D1/s014I "9 ssua1q]D0 "4 $1/010/J "7 sajdung HH TBE ! TH THA IE» D10d1!/D {O} © 1 x suozr-g91d |. - guoz p- - aid guoz ualJOd | 'suor y- 9_4s04| 2 /270/0011p- 'It alo?" sod s Uj JID $j, - 4 uo!;pw104 | (1d)w4 oy hoof,“ foie M4103" gfi abo;g | (44) ub1aDju09 commas—“F cmfiwfih upiupwouay 1addp I I I I I I <> & & e & & LC) W) W) 1C) 1C) W) Tz ou ro l w 133;j NI 'H1'd30 and Coniacian stratigraphy, calcareous nannofossil ranges, and occurrence of the Complexi- FIGURE 8.-Upper Cenomanian, Turonian, igraphy from Christopher (1982). opollis-Atlantopollis and adjacent zones in the Socony Mobil corehole 16, Dallas, Tex. Pollen strati Single occurrence of Rotalipora from Pessagno (1969). Depth scale is original depth. 14 FIGURE 9.-Correlation of biostratigraphic and lithostratigraphic units of the Atlantic Coastal Plain and Texas. The Rotalipora extinction is a datum. Unit K2, a distinctive stratigraphic unit, is correlated in GGS 724, GGS 1197, Parris Island No. 2, Fripp Island, and Clubhouse Crossroads corehole 1 with the lower Turonian. The placement of the lower Turonian-upper Turonian boundary is uncertain, but it proba- TURONIAN STRATIGRAPHY OF THE ATLANTIC COASTAL PLAIN AND TEXAS bly lies above the top of the Complexiopollis-Atlantopollis zone in the Dallas corehole. The top of the Complexiopollis-Atlantopollis pollen zone is correlated with the top of the lower Turonian in Clubhouse Crossroads corehole 1 and in the E. G. Tavior No. 1-G, Toms River, Fire Island State Park, Martha's Vineyard, and Nantucket wells. Stratigraphic units are to scale at each locality. No horizontal scale. (4) & s + m Socony - Mobil corehole 16 Outcrop GGS 724 6GS : 1197 Parris Island n Dallas, Tex. Dallas, Tex. Ga. Ga. Test No.2,S.C. Locality 15 Locality 12 Locality II Locality 10 $x 3 . 3 SIlcEre a <. 9B 5 sl |<] = - E I 3 e[" |=] ars = g 9 co E 0 o g .< L g sed _< hog T| | 8 c | <] |S 8 4438 |-- 4151 4150 3140 FZ »| | € 3 §? fire 4180 S S C x C .9 Sla & Lu Lu 5 |- rel- S aszo | (9 £12 5 od F ~ wo O S t os C € & U ¥ had Bs SI [u s LL & & @ = o &: LL E £ S 3) |f a BIB S C ris - TH "iH LO— s Hiatus / 4630 |8 8 €] [«-] : 8 / Lis e m || @ «6 m (9) (M & C a |S / .S S / G I Sh / n € & 5 I |g Rs i2 € |S / E € & C s s § R | § / € = s € €a|§| / o "= y- s I ~SN 5 a S 2 :g N (8) | / S 5 5 € A / 3 o| | 4440 S CI- -= 12s <1 as + 460.6 f 5 ® (2) 1g m |- o. & 3 .o a 0 § * If E hs o = & & C - [_<] 526.7 543 Depths are original depths in feet. Sources of data are (1) Chris- topher, 1982; (2) Brown and Pierce, 1962; (3) Pessagno, 1969; (4) Powell, 1970; personal commun., 1981, 1982; (5) Christopher, unpub. data, 1978; (6) Gohn and others, 1980; (7) Brown and others, 1979; (8) Christopher, unpub. data, 1979; (9) Gohn and others, 1978; (10) Chris- CORRELATION OF TURONIAN AGE STRATIGRAPHIC UNITS 15 topher, unpub. data, 1979; (11) Hazel and others, 1977; (12) Robbins and others, 1975; (13) Christopher, oral commun., 1979; (14) Petters, 1976; (15) Brown and others, 1972; (16) Doyle, 1969b; oral commun., 1981; (17) Sirkin, 1974; (18) Hall and others, 1980; (19) Folger and others, 1978. & ( _ Fripp Island, Clubhouse Crossroads | | E.G. Taylor USGS Island Toms River S$21091T | |Eenw-50| | uses é $. C. corehole 1, S.C. No. 1-G, Va. Beach No. 1, N. J. Chemical Co.,N.J.| | Fire Island | [Martha's] | 6001 &n Locality 9 Locality 8 Locality 7 Locality 6 Locality 5 State Park, | |Vineyard,| [Nantucket] [~~ NY. Mass. | | Island, | | 7 Locality 4 | | Locality] | Mass. | | < 2 Locality | | 5 I .S 5 & s .S S Tad R 3057 23423 _ 2342 1450 1950 1298 1800 550 s504 | | 5 T- ; 1323 & 3097 23635 a | ~! ; - .5 S .S § § I & S| |Y) |., & Ho |S), i 2 S 6 is 3137 % o % 3147 <} - 24048 »a07 1480 | is_ 2 | | 1873 8355 | | moss] | 3 3168 [xl L- 1495 2200 % T 1437 < 10) (a | | un (9) (D (@ ® F3 1520 E- ® S 1528 a Pde) us» ua» __ us)] | der us umn ua] | us | |_ us) fl EXPLANATION Pollen _ zones Nannofossil assemblages Fiffellithus eximius @ ARotalipora occurrence Atiantopollis zone post -C-A zone, pre- zone Y Complex iopo'llis -Atlantopollis zone post- zone II1, pre- Comp/ex/opoliis - L ithraphidites acutum (§] pre -L/throphidites acutum 6 Rotalipora B - Basement last occurrence BN Barren interval (1) Source of data 16 TURONIAN STRATIGRAPHY OF THE ATLANTIC COASTAL PLAIN AND TEXAS CORRELATION OF TURONIAN AGE STRATIGRAPHIC UNITS OF THE ATLANTIC AND GULF COASTAL PLAINS The Complexiopollis-Atlantopollis zone is present in Coastal Plain strata extending from New England to Texas. This zone and its associated foraminifer and calcareous nannofossil assemblages play an important role in dating and revising the ages of formations beneath the Atlantic and Gulf Coastal Plains (fig. 9). At Dallas, Tex., upper Cenomanian and lower and upper Turonian strata are present in a seemingly uninterrupted section that lies unconformably beneath Coniacian beds of the Austin Group. Stratigraphic evidence based on the occurrences of mollusks and foraminifers from outcrops that are correlated with the corehole section indicates that the Complexiopollis- Atlantopollis zone and the Lithraphidites acutum nannofossil assemblage are present in the upper Cen- omanian and lower Turonian and that the Eiffellithus eximius assemblage succeeds the Lithraphidites acu- tum assemblage in the lower Turonian. Beneath the Atlantic Coastal Plain, in the Salis- bury and Raritan Embayments, pollen, foraminifers, and calcareous nannofossils from several localities have been studied. In the Toms River well, New Jer- sey, the pollen stratigraphy is incomplete, but the evi- dence suggests that the base of the Complexiopollis- Atlantopollis zone lies within the lower Turonian Praeglobotruncana helvetica zone, as does the boun- dary between the Lithraphidites acutum and Eiffel- lithus eximius assemblages. The stratigraphy at the Island Beach well is similar, except that a Complexi- opollis-Atlantopollis assemblage is present at the base of the P. helvetica zone where Rotalipora becomes extinct, and it is possible that the Complexiopollis- Atlantopollis zone extends below the Cenomanian- Turonian boundary here. In the E. G. Taylor well on the eastern shore of Virginia, the base of the Complexi- opollis-Atlantopollis zone lies in beds that have yielded poorly preserved planktic foraminifers tentatively dated as pre-Santonian to Cenomanian in age; Rotali- pora is present in the deepest sample studied, within the late Cenomanian post-zone III, pre-Complexiopol- lis-Atlantopollis zone interval. Therefore, the Complexiopollis-Atlantopollis zone appears to be early Turonian in age on the flanks of the Raritan and Salisbury Embayments. The upper Cen- omanian part of this pollen zone possibly is missing there, but it could be present in deeper areas of the basins. The Fire Island, Martha's Vineyard, and Nan- tucket wells are located near the landward edge of the Coastal Plain on the Long Island Platform, and, because the Complexiopollis-Atlantopollis strata lie at relatively shallow depths in these wells, I am assigning them an early Turonian age. South of the Cape Fear Arch, the Complexiopollis- Atlantopollis zone is present in a distinctive lithologic unit in a series of wells that transects the northern flank and central region of the Southeast Georgia Embayment (fig. 9). At Fripp Island, a Complexiopol- lis-Atlantopollis flora and the Turonian Eiffellithus eximius assemblage are present in an interval de- scribed as unit K2 by Gohn and others (1978, 1980). Unit K2 is lithologically variable, but it is a relatively thin unit of approximately formational rank near the base of the Upper Cretaceous sequence, widespread beneath the coasts of South Carolina and Georgia. At Clubhouse Crossroads, somewhat higher on the flank of the basin, the Complexiopollis-Atlantopollis, Eiffel- lithus eximius, and Lithraphidites acutum assemblages are all present in unit K2. I interpret unit K2 to be early Turonian in age, equivalent to the upper part of the Britton Formation and the lower part of the Arca- dia Park Formation at Dallas. In the Georgia subsur- face, the Complexiopollis-Atlantopollis zone is present in unit K2 in two wells in Glynn County. Along the Atlantic Coast from New York to Geor- gia, the lower Turonian correlates variously with "chronostratigraphic" units D, E, and F of Brown and others (1972, 1979). Unit F, in particular, has been recognized in many wells by the presence of an ostra- code fauna that includes the species Fossocytheridea lenoirensis, which has been reported from 38 wells in North Carolina and in 1 well in southern Virginia (Brown and others, 1972; Swain and Brown, 1972). At present, nannofossil, foraminifer, and pollen assem- blages from unit F in these wells cannot be compared, but some evidence indicates that beds containing F. lenoirensis are Turonian in age. In the Clubhouse Crossroads corehole 1, South Carolina, F. lenoirensis is present at 2,365 ft (Hazel and others, 1977), and I have observed it at 2,367.5 ft. Both occurrences are within the interval (2,342.3-2,404.8 ft) where calcare- ous nannofossils that I interpret to be Turonian in age are present with Complexiopollis-Atlantopollis pollen. In addition, a Complexiopollis-Atlantopollis flora is present in a core provided by P. M. Brown from unit F in a well from Halifax County, N.C., near the type section for unit F (Christopher and others, 1979; Christopher, oral commun., 1981). The foregoing biostratigraphic analysis has led to a new, albeit provisional, correlation of Coastal Plain formations and informal lithologic units with the Eaglefordian Provincial Stage (fig. 10). In the Raritan Embayment of northern New Jersey, the Complexi- opollis-Atlantopollis zone encompasses the Wood- CORRELATION OF TURONIAN AGE STRATIGRAPHIC UNITS -s ak Pollen Western Alabama-Georgia | South Carolina, J North Carolina, Virginia, New Jersey, _ |Pollen Stage zone Dallas, Texas Alabama area Clubhouse Crossroads Cape Fear Arch [Salisbury Embayment] Raritan Embayment | zone Stage 5 5 'c T Magothy Fm. & T § 5 o T equivalent o| & 5 es > Mooreville Blufftown . 9 E. 3 8 5 Chalk Formation _| Middendorf FM. | gor; Fry (7 Magothy G P.. [-- (part) (part) Aram _Formation IB -| _ No data p P and 5 |§ ~] 5 Cape Fear Fm. ~ 56 = |§ 3 Cape Fear Fm. 2 "= 2 el KG ml 0 s = s ® >i '< —————'?;’—— $ -513 § utaw >| -2 C '|# - & c & strata & 8 S [2] (part) (1) y 5 a 8 w [ILLIIT TLLTi { Calis: 9 2. Of : =| § I A §[ e ge )y T Arcadrs Fork 7 t/t 2 & |-. & Arcadia Par f til 40 .@ 5 Formation | &] , Gordo 3 ~|4 5 t) S 3| Formation > > 2 51 _L 5 __ 6 c (1) 9g : S SoysrevLIle a E & 2 p an e ? S| _ Coker Tuscaloosa fiscal-“$1 tFm‘ Raritan Fm. | E| _ Member (8) S| 5 2 §.g §z 5 9| Formation Formation Kgqup’? eat") equivalent | i2 W°° - ST | 16 S w ed Bb e & Jer's K1, F (part) Farrington |_; o | <2 s Hs U) eir a aie Sand - |8 §| § " |E < Tarrant Vick Raritan Fm. Member |& Q| S 3 |T :...... .s. l cain ogra oo 10 Sedimentary rocks.: ... 10 Plutonic rocks .._. ... .u. avlclel ave o 11 Volcanic rocks.... .. ""~... ch lrt a ol, 11 Faults Heracles . . len. oo. readin sain innate ases rie se 11 General characteristics ..... ...}... cu...... 11 Malor strike-slip faults . ...... ... ... 13 Pald Butte fault . . - .}. .cc sais s 13 Helena Valley fault.. .-.... ..} 0 15 Principal normal faults ... ................... 16 Silver Creek fault...... 2 ac 16 Northwest valley fault...... ... 16 Scratchgravel Hills fault .. .....:..... ..... 17 Spokane Benchdault .... ':....... . ~.. 17 Regulating Reservoir fault .............. . 18 Spokane Hillsfault . _ _................. 18 Secondary normalfaults..................... 18 Faults at Willit Ridge .. 19 Faults near Austin 19 Faults at Helena ._ ;-... _.. ven cl - 19 Faults west of Interstate Highway 15 and near Montana City ~...... .. m 19 Faults south of Louisville Station . .... ..... 19 Concealed zone of normal faulting in Helena Valley .oo. on .o ca f son aire antal . 19 _...... . not agua n cot aa ve 20 Eldorado thrust fault ..:... ~. ~ 20 Thrust fault subsidiary to the Eldorado ..... 20 Soup Creek thrust fault ...... 20 Minor thrust fault .--. suss nase, de 21 Nature of earthquakes.. 21 Seismic history of the Helena area .................. .. 283 calc csa. 23 Helenasearthquake of 1935. ...... ...............u.. 23 seismic activity .. . .....:.............. 25 -. >.. ..~ .. hole .R 28 Page Earthquake hazards .. . _. __.}... la na bae 29 Ground shaking ..' ...... .._ aman soe 29 Relation to magnitude and distance .... 29 Amplified shaking on surficial deposits . ...... .. 31 Shakine and damage :... ten. us 32 Ground failure .=. . ...s ..o etl su m o aan 34 Landsliding. ......... syc ee 34 Liquefaction-induced failure . ................. 37 Surface faulting ..... _.. scl. ll (bare le 38 Regional land displacement .................. 39 Settlement . .....}. f. _ cll. ule las eate 39 Ground cracking ..... ~~ mane dos 40 Rideing andfurrowling .. . .......... _ u g 40 (Ground churning ..... ...... sunil ue 40 Seiches and surges ...... .. ...u. ual adu. mamas 41 Local geologic conditions that may contribute to seismic hazards ; ...ll ls out l n ata aus aaa ate 41 Surficial deposits .. aoa e 41 Response to ground shaking in the 1935 carthquake ..:.... .... ull nl aa aat ns 42 Expected response to ground shaking in future carthquakes......... .ie. lc. roma al an 42 Medvedev's data .--. ..:: ~.. . 43 Correlation with Medvedev's basic classes of ground ...... ....:.. /O. opal onle 44 General response of surficial units .......... 44 Susceptibility to ground failure .............. 45 Deposits prone to landsliding ............. 45 Deposits prone to liquefaction .... 47 Deposits prone to settlement.............. 48 Deposits prone to cracking ...: .._ ....: 48 Steep bedrock slopes :...... = '..... 49 Faults _ ._. (sus s uc ao Apis san n ar 49 Potentially active faults ..... lll 49 Faults prone to reactivation .. ................ 50 Conditions conducive to regional ground displacement ......:.. ' 51 Hydrologic conditions ................ aarp B1 Land use and earthquake protection . .................. B1 General remarks... sa 51 Moderated motion on bedrock. ...: .... }. 52 Intensified motion on surficial deposits .. ...... ..... 52 Relative intensity on surficial units ............ 52 Water-saturated ground . .. .. ................ 53 Long-period motion in Helena Valley ... ........ 58 Ground failure on surficial deposits . ............... 54 Landsliding on steep bedrock slopes .... .... 54 Fault hazard abatement: . .... ..... ~. 55 Shorelineflooding ..... ./. mu. r aval. 55 Future assessment of seismic hazards.... ..... 55 Seismic microzonation and the need for quantitative earth-science data:... .... .... 9... aca 55 Role of the U.S. Geological Survey ................ 58 State and local involvement ..... .......... ...... 58 III IV CONTENTS Page References cited .. .} Naira 58 | Appendix-continued Appendix. -/ _ come l soll len pda aia d dis 61 Commentary on earthquake-resistant design ..... Modified Mercalli Intensity Scale of 1981 ... ...... .. 61 index: ss 09 -l l s ub an fac. o saan PLATE FIGURE TABLE 1. 1. w m 1a via t no - je 11. 12. 13. 6 fo to - ILLUSTRATIONS [Plates are in pocket] Map of the Helena quadrangle, Montana, showing distribution of surficial deposits and bedrock and traces of geologic faults. . Map of the East Helena quadrangle, Montana, showing distribution of surficial deposits and bedrock and traces of geologic faults. . Map of Helena, Montana, showing distribution of surficial deposits and bedrock, traces of geologic faults, and location of buildings heavily damaged in the earthquake of 1935. Map showing the location of the Helena area and the location of U.S. Geological Survey quadrangles mentioned in this report . . .. Portion of zoning map establishing building setback requirements along strands of the San Andreas fault in Portola Valley. California .. .......}.............. TABLES Selected strong-motion data for several earthquakes in the magnitude range 5.3-7.2 ................. .._. Seismic characteristics of basic types of ground as determined by Medvedev (1965). . . . . ...... ..... __ _. Correlation of rock units in the Helena area with Medvedev's (1965) basic categories of ground . ... .... ..... Rock units of the Helena area grouped according to relative seismic response .... ..... ...... > . Diagrams illustrating the principal types of faults in the Helena area . . .. ...... Map showing the traces of principal faults in and near the Helena area .. ....................... ._ . _. . Diagram showing the relation between epicenter, hypocenter or focus, and depth of focus of an earthquake .. ..... . Isoseismal map of the main shock of the Helena earthquake on October 18, 1985 . . . . . ... ___. . View of the north wing of Helena High School following the major aftershock on October 31, 19385 .. . . . . . . .. . Views of some damage in Helena caused by the earthquake of 1985 ..... . Portion of accelerogram of the October 31 aftershock of the Helena earthquake of 1985 . ... ............... . Photograph of ground crack in the floor of Helena Valley caused by the earthquake of 1935 .. ... . Map showing the location of some earthquake epicenters and the traces of principal faults in and near c Aa ts iv da o ria a l sane s chine nines Sketches of types of landslides classified according to their mechanism of movement. ...... ...... ...... .. Early microregionalization (microzonation) map of the Los Angeles basin and vicinity, California ........ ... nys.) 68 Page 12 14 22 25 26 27 28 29 30 35 56 57 Page se 08 : vou" 44 'Le 4G GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA-A REVIEW By Rosert Grorox ScHmiIDT! ABSTRACT The Helena area covers about 1,036 km? of the northern Rocky Mountains in west-central Montana and encompasses the Helena and East Helena 15-minute topographic quadrangles of the U.S. Geological Survey. Most of the area is in Lewis and Clark County. A portion at the south is in Jefferson and Broadwater Counties. The large, sediment-filled basin called Helena Valley, about 415 km? in extent, is the principal physiographic feature in the area. Broad slopes at the edge of this valley rise gradually toward and butt sharply against surrounding mountains. Helena, the State capital, lies at the southwest border of the valley; the Missouri River is at the northeast margin. Lake Helena in the northern part of the valley, Helena Valley Regulating Reservoir in the eastern part, and Hauser Lake on the Missouri River are the main bodies of surface water in the area. Drainage in the area is to the Missouri, chiefly through Helena Valley. Two main types of earth materials are present in the area: surficial deposits and bedrock. The surficial deposits, which mainly occupy the lowlands, include artificial fill, placer tailings, landslide deposits, stream deposits, slope wash, wind-laid deposits, glacial-lake deposits, and older gravel of Quaternary age and older stream and lake deposits of Tertiary age. In general, these materials consist of uncemented to weakly cemented gravel, sand, silt, and clay. Bedrock, which forms the mountains and hills and the substrate beneath the surficial deposits, is subdivided into sedimentary rocks of Cretaceous to Middle Proterozoic age, plutonic rocks of Tertiary and Cretaceous age, and volcanic rocks of Cretaceous age. Most of the bedrock is hard, firm, and permanently and strongly cohesive. Faults are numerous in the area. They are mainly located in and adjacent to a linear zone of crustal discontinuity known as the Lewis and Clark line, which extends northwestward through the area and encompasses most of Helena Valley. Several faults within the Lewis and Clark line are categorized as potentially active fractures. They are the Bald Butte fault, a strike-slip fracture at the southern boundary of the line; the Helena Valley fault, a strike-slip fracture at the northern boundary; and the Scratchgravel Hills, Spokane Bench, Regulating Reservoir, and Spokane Hills normal faults, which are smaller cross-fractures within the line. Most earthquakes are caused by sudden slippage along faults beneath the Earth's surface. The sudden rupture of a fault releases elastic energy stored in the adjacent rocks and produces seismic waves that travel rapidly through the Earth and excite its surface into vibrational motion. The focus or hypocenter of an earthquake is the point in the Earth's crust where fault rupture begins; the epicenter is the point on the Earth's surface directly above the 'Deceased, 1983. Information in this report is current to 1979; later illness pre- vented the author from continuing his investigations. Subsequent State and Federally funded research is refining information contained herein, and is applying observations and conclusions to land-use planning and earthquake-hazard mitigation in the Helena, Mont., area. focus. Magnitude, which is a rough measure of the size of an earthquake, is based on seismograph readings. Earthquakes of magnitude greater than about 5.0 may be destructive. The intensity of an earthquake is a measure of its local severity as determined by its effect on people, manmade structures, and the ground surface. On the Modified Mercalli Intensity Scale of 1931, which is widely used in the United States, earthquakes range from I to XII in order of increasing severity. Several hundred earthquakes have been felt in the Helena region since it was first settled in 1864. Most of these shocks have been of weak to moderate Mercalli intensity (II-IV ), but, in 1935, a destructive earthquake of intensity VIII caused extensive damage. The main shock of that earthquake was of magnitude 6%. In a recent study of seismicity in the area, Freidline, Smith, and Blackwell (1976) recorded 97 small earthquakes from June 25 to August 18, 1973. About half of the epicenters of these earthquakes cluster along the trace of the Bald Butte fault and suggest that it may be the locus of much of the current seismic activity in the area. Seismic activity at an intensity of I-V is almost certain to continue in the future, and the possibility exists that a damaging earthquake of intensity VI or greater might occur at any time. The area is in the highest risk zone (zone 3) on the seismic zonation map in the Uniform Building Code. Ground shaking is in most instances the chief hazard associated with earthquakes. Its severity largely depends upon earthquake magnitude and size of fault rupture and upon distance from the earthquake source. It also may be greatly influenced by the distribution of surficial deposits and bedrock at the earthquake site. In many earthquakes, the intensity of ground shaking has been reported to be greater on unconsolidated surficial deposits than on nearby bedrock. Damage from ground shaking is mainly caused by the horizontal component of movement and is closely dependent upon dynamic characteristics of the motion such as acceleration, velocity, displacement, duration, and frequency content. Secondary effects that involve sudden failure of the ground and movement of water surfaces commonly accompany strong earthquakes. These hazards, which can be highly destructive, include landsliding, liquefaction-induced failure, surface faulting, regional land displacement, settlement, ground cracking, ridging and furrowing, ground churning, and seiches (standing waves) and wave surges in surface waters. The severity of these effects generally correlates with the intensi- ty and duration of ground shaking and with the prevalence of geologic, topographic, and hydrologic conditions 'at the earth- quake site that can enhance these hazards. The surficial deposits in the area are capable of amplifying earthquake ground motion in future strong earthquakes. Enhanced shaking on these materials was probably a major cause of wide- spread damage in Helena during the earthquake of 1935. Data presented in the report suggest that the intensity of ground shaking generally can be expected to be least on bedrock; slightly greater on the bulk of the older stream and lake deposits; interme- diate on stream deposits, slope wash, wind-laid deposits, glacial- 2 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA lake deposits, older gravel, and older bentonitic clays; and greatest on artificial fill, placer tailings, and landslide deposits. The data further indicate that the intensity of shaking may increase sub- stantially on surficial deposits where the water table is close to the ground surface. The susceptibility of surficial deposits to ground failure contrib- utes to the potential seismic hazard in the area. Surficial materials prone to landsliding are present on hill and valley slopes; in streambank, lakeshore, and terrace and bench scarps; and in steep-sided manmade embankments and excavations. Old land- slide deposits also may undergo renewed movements during earthquakes, but, in the Helena area, these features are far from urban centers. Liquefaction effects are likely to occur in water-saturated sedi- ments in the lower part of Helena Valley and along the shores of Hauser Lake. Flood plains, irrigation-canal embankments, and earth dams also may include silt and sand that are susceptible to liquefaction. Artificial fill and placer tailings have the greatest potential for settlement and cracking in future strong earth- quakes, but these modes of failure also may occur on the broad expanse of stream deposits in the western part of Helena Valley and on flood plains. Steep bedrock slopes in the mountains and in escarpments along the Missouri River are potential sites of landsliding during future strong earthquakes. The flanks of Mount Ascension and Mount Helena, the slopes at the eastern front of the Scratchgravel Hills, and the declivities along the upper parts of Last Chance Gulch, Dry Gulch, and Tenmile Creek pose the chief threat to urbanized areas. Faults in the area that are potentially active constitute a seis- mic hazard. The Bald Butte and Helena Valley faults are probably capable of generating destructive earthquakes and have a high potential for surface rupture. The Scratchgravel Hills, Spokane Bench, and Spokane Hills faults also may have the capacity to produce damaging earthquakes and may be susceptible to reacti- vation and to surface breakage. Other faults in the area are a lesser hazard. The Helena Valley, Spokane Bench, and Spokane Hills faults have the potential to produce regional ground displacement that might affect surface waters. Hauser Lake on the Missouri River, Lake Helena, and the Helena Valley Regulating Reservoir are the principal bodies of surface water in the area on which earthquake-generated seiches or surges might form and flood the shoreline. The narrow portions of Hauser Lake, which would tend to constrict water oscillation, might sustain the greatest wave heights from earthquake- induced waves. Protection from earthquakes largely rests upon the engineering practice of making structures earthquake resistive. Land use is a supplemental means for seismic protection. It involves the siting of vulnerable structures and concentrations of people away from the places where the potential danger from earthquake hazards is greatest. The principal lands in the area on which it may be necessary to restrict structural development to achieve adequate seismic pro- tection include: (1) land that has a high potential for intensified shaking and ground failure-chiefly land underlain by thick artifi- cial fill and placer tailings and land underlain by surficial deposits in which the water table is at shallow depth; (2) steep slopes on surficial deposits and on bedrock that are prone to landsliding; (3) land along the trace of potentially active faults on which there is a risk of surface rupture; and (4) shoreline land susceptible to flood- ing from earthquake-induced water waves. Land underlain by stream deposits, slope wash, wind-laid deposits, glacial-lake deposits, older gravel, and older bentonitic clays, on which the water table is relatively deep (10 m or more) and on which landslide, fault, and flood hazards are minimal, is of interme- diate seismic risk to structures. On this ground, adequate protec- tion from earthquakes probably can be attained by a suitable combination of structural design requirements and land use. Bedrock terrain and, to a somewhat lesser degree, land under- lain by older stream and lake deposits (apart from older bentonitic clays), in areas not subject to landslide, fault, or flood hazards, generally present the lowest seismic risk to structures. From a seismic viewpoint, these lands are most suited for high-density structural development. The ideal objective in earthquake hazards assessment is to quantitatively define the level of earthquake effects that can be expected in any area during future earthquakes of specific magni- tude and location. The presentation of this information in map form is known as "seismic microzonation." The information in this report is not sufficiently accurate to estimate earthquake effects with the precision required for compre- hensive seismic zoning and engineering application. Additional quantitative data are needed on seismicity, on behavior of surficial deposits under conditions of earthquake loading, on physical char- acteristics of potentially active faults, on liquefaction potential, on slope stability, and on flood potential to formulate rational land-use and engineering policies that will effectively minimize seismic hazards in the area. An effective program to reduce earthquake hazards requires a major, long-term effort that enlists the expertise of many in- dividuals from a variety of professions. The responsibility for formulating and implementing a program of earthquake hazards reduction in Montana will largely rest with the State Earthquake Hazard Mitigation Committee. Much of the research required for earthquake hazards assessment under the aegis of the committee could be accomplished by State and local agencies, colleges, and universities. INTRODUCTION Earthquakes, which cause some of the greatest natu- ral disasters on Earth, are a serious problem in highly seismic regions of the United States, and elsewhere in the world; and concern about them has become more urgent as population increases and cities continue to grow. Accordingly, public officials and people concerned with land development in these regions have become increasingly attentive to the possible effects of future destructive earthquakes and to the ways in which damage and loss of life from them may be minimized. It is there- fore prudent that knowledge about earthquakes and their potential hazards be widely publicized. The effect that an earthquake may have in an area depends to a large extent on the local geologic conditions at the earthquake site. Consequently, basic geologic data are essential to realistically assess seismic hazards and to establish broad land-use practices that will help reduce future earthquake losses. This report treats the earth- quake problem in the Helena area from that standpoint. It describes the local geology, potential earthquake hazards, and local geologic conditions that may contribute to seismic hazards and briefly outlines the implications these factors have for land use and for earthquake protection. A brief account of the nature of earthquakes and a short summary of the seismic history of the area are included in GEOLOGY 3 the discussion. The future assessment of seismic hazards in the area, emphasizing the need for quantitative earth- science data, is examined in a concluding section of the report. The report is general in scope and nontechnical in approach. It is conceived as a useful first step toward the reduction of earthquake hazards in the Helena area. LOCATION The Helena area is in the northern Rocky Mountains in west-central Montana and, for the purpose of this report, is considered as the area encompassed by the Helena and East Helena 15-minute topographic quad- rangles of the U.S. Geological Survey (fig. 1). These quadrangles lie between long 111945" W. and 112915" W. and lat 46°30" N. and 46°45" N. and have a combined area of about 1,036 km. Most of the area is in Lewis and Clark County. About 207 km at the south is in Jefferson and Broadwater Counties. Helena, the State capital, which has a population of about 25,000, is in the south-central part of the area. The Missouri River flows across the northeastern part. PREVIOUS STUDIES Several earlier studies have focused upon the geology and earthquake activity of the Helena area. Knopf (1913) described the ore deposits in the region and provided information on regional geology. Pardee and Shrader (1933) also furnished data on metalliferous deposits and observed salient features of the geology, and Pardee (1950) discussed block faulting in the area. The ground- water resources of Helena Valley were studied by Lorenz and Swenson (1951). A geologic map of the southern and western parts of the area was compiled by Knopf (1963), and the geology of the southeastern part was mapped by Smedes (1966, pl. 1) in a study of the northern Elkhorn Mountains. Davis and others (1963) interpreted the sub- surface geologic structure in the eastern part of the area from gravity and aeromagnetic data. Most reports on earthquake activity have dealt with the destructive earth- quake that occurred at Helena in 1935; seismic data, geologic phenomena, and damage resulting from that quake were documented by Engle (1936), Scott (1936), Ulrich (1936), and Neumann (1937). Most recently, the results of an earthquake survey conducted in the Helena area in 1973 were described by Freidline and others (1976). FIELDWORK AND ACKNOWLEDGMENTS Most of the geologic information in this report was acquired during field studies in the summers of 1975, 1976, and 1977. The author was ably assisted in that work by William R. Trojan in 1975, D. Guy Waggoner in 1976, and Richard Hazelwood in 1977. Photographs of some of the damage sustained in the Helena earthquake of 1935 were provided by Sidney L. Groff of the Montana Bureau of Mines and Geology. Several colleagues on the staff of the U.S. Geological Survey have contributed ideas and information that have been helpful to the study: S. Warren Hobbs and William B. Joyner critically read an early draft of the report; Mitchell W. Reynolds provided unpublished data on the Helena Valley, Spo- kane Bench, Regulating Reservoir, and Spokane Hills faults in the East Helena quadrangle; and A. Frank Bateman, Jr. furnished information on a unique structur- al failure that occurred at the Kessler Brewery in Helena during the 1935 earthquake. GEOLOGY PHYSIOGRAPHY AND DRAINAGE The principal physiographic feature in the area is the broad, northwest-trending, oval-shaped basin called Hele- na or Prickly Pear Valley. This valley, which is largely ringed by mountains, is about 32 km long and as much as 19 km wide. Its area is about 415 km. The lowest part of the valley is occupied by Lake Helena, which is formed by back-up from Hauser Dam on the Missouri River. The lake covers an area of about 8 km? and has a surface elevation of about 1,113 m. The western part of the valley, which contains Lake Helena, is gently sloping and has a broad, flat floor. It is largely surfaced by young stream deposits and slope wash. The eastern part of the valley, which is higher, comprises low rolling hills and flat-topped benches. It is mainly underlain by older stream and lake deposits. The sides of the valley are marked by broad, gently inclined slopes that butt sharply against the surrounding mountains at elevations of about 1,160-1,280 m. At the south and southwest, Helena Valley is bordered by steep, rugged mountains that extend westward to the Continental Divide some 20 km away. The city of Helena is situated on the southern slope of the valley where it abuts this mountain front. Mount Helena and Mount Ascension, with altitudes, respectively, of about 1,664 and 1,632 m, rise abruptly above the southern margins of the city. On the west, the valley is bounded by the Scratchgravel Hills, which extend northward about 7 km and attain an elevation of about 1,601 m. They are connected on the west to the main range of the Rocky Mountains by a broad low ridge. The northern boundary of the valley is formed by a group of low hills whose summits are at altitudes of about 1,433-1,585 m. Over a short stretch on the northeast, the valley is bordered by Hauser Lake, on the Missouri River, beyond which are the Big Belt Mountains that attain a height of more than 2,400 m. The southeastern part of the valley is sand- wiched between the Spokane Hills on the east and the GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA y f y 111°00' (3 \\ I 66 \\\\\\ i cee 7 | 4,774, $ pe & Cascadeo M» \ * | et s Sole s «$ 73 " * f ; I ‘x‘ e I MONTANA 1 w - Ry i S CASCADE 47°00' | 7 i a Holter I, Lake | L I ~ fi—J s RM u 0/0 ~~]? Boxs 5 MEAGHER luser & ¢ e I at- t . § O45 CF 2 2 2 e-- oz?! xii A 46°30° 5 1 lancy % s $. Clancy Winston Of“ Lf/ Alhambra p Jefferson City ( BROADWATER / £4 OT ownsend Boulderg JEFFERSON L= "+m. Butte ) agcont|- 7 4 5 - &. a y Wa . & GALLATIN | olV’f/sz is x $ 4s... ~% 1 Whireohall & MADISON Bozeman 0 10 20 30 40 KILOMETERS 0 10 20 MILES FIGURE 1.-Map showing location of Helena area (shaded) and location of U.S. Geological Survey quadrangles mentioned in this report. SC, Silver City quadrangle; RM, Rattlesnake Mountain quadrangle; UHL, Upper Holter Lake quadrangle; E, Elliston quadrangle; H, Helena quadrangle; EH, East Helena quadrangle; CF, Canyon Ferry quadrangle. Circles mark epicenters of the Lombard earthquake of 1925 and the main shock of the Helena earthquake of 1935. GEOLOGY 5 steep northern flank of the Elkhorn Mountains on the south. A low divide between these ranges separates Hele- na Valley from Townsend valley. The Spokane Hills reach an altitude of about 1,682 m. The Elkhorn Moun- tains are high and rugged; far south of Helena Valley they culminate in Elkhorn and Crow Peaks at elevations above 2,740 m. Much of the area is drained by a network of perennial streams that lead into Helena Valley from the mountains to the south and west. The valley, in turn, is drained by the Missouri River, chiefly through Lake Helena. The principal streams that enter the valley are Spokane Creek, Prickly Pear Creek, Tenmile Creek, Sevenmile Creek, and Silver Creek. Spokane Creek, which drains the moun- tains to the southeast, flows northward along the south- eastern margin of the valley and empties into Hauser Lake on the Missouri River. Prickly Pear Creek, which drains a large area of mountains to the south, divides into several distributaries on entering the valley near East Helena. Its main branch flows northwestward across the valley to Lake Helena. Tenmile Creek, which drains the mountains to the southwest, enters the valley a short distance west of Helena and flows northeastward to join Prickly Pear Creek about 1% km southwest of Lake Helena. Sevenmile Creek drains the mountains to the west, flows eastward into the valley south of the Scratch- gravel Hills, and joins Tenmile Creek about 5 km north of Helena. Silver Creek runs southeastward through the northwestern part of the area and, on entering the valley north of the Scratchgravel Hills, flows eastward to Lake Helena. The mountains immediately south of Helena are most- ly drained by north-flowing, intermittent streams that lead into Helena Valley through Orofino Gulch, Grizzly Gulch, Last Chance Gulch, and Dry Gulch. The flow of these streams is ordinarily absorbed by the streambeds before it reaches the valley. Last Chance Gulch, which runs through the center of Helena, is formed by the mergence of Orofino and Grizzly Gulches a short dis- tance south of the city. Dry Gulch issues from the moun- tains along upper Davis Street in the eastern part of Helena. The mountains north of Helena Valley are drained by small intermittent streams that empty into the valley or into the Missouri River. The mountains in the north- eastern part of the area, on the east side of the Missouri River, are part of the Big Belt Range; they are large- ly drained by perennial streams that flow into the Missouri. The principal streams there are Trout Creek and Soup Creek. An elaborate system of canals and ditches extends around and across the central part of Helena Valley to supply water for irrigating crops. The irrigation water is mainly derived from Lake Helena and the Missouri River, and supplemental water is obtained from Prickly Pear, Tenmile, Sevenmile, and Silver Creeks. Water from the Missouri is pumped upward from a point just below Canyon Ferry Dam in the Canyon Ferry quadrangle to a tunnel that leads through the Spokane Hills and is im- pounded in a large regulating reservoir in the eastern part of the valley before it enters the main irrigation system. Altogether, about 130 km of land in the valley is under irrigation. About 36 km? of ground in the lower part of Helena Valley is periodically waterlogged due to the irrigation (Lorenz and Swenson, 1951, p. 39). This condition is caused by excessive ground-water recharge resulting from irrigation of higher lands in the valley. The irriga- tion water sinks into the ground and moves down along the water table toward the lower part of the valley. There the ground is unable to transmit the excess water, and so it is forced to the surface. The largest area of water- logged land, covering about 33 km, lies south of Lake Helena and extends up the main course of Prickly Pear Creek beyond Lake Stanchfield; a smaller area of water- logged ground, covering about 3 km, lies at the conflu- ence of Tenmile and Sevenmile Creeks. These areas are essentially bounded by the 6 ft (1.8 m) water-table line shown on plates 1 and 2. The water issues over a fairly continuous surface in the waterlogged areas, and the land is marshy, swampy, spongy, and highly unstable. Several years ago, in an attempt to reclaim the water- logged ground, drainage canals were dug to carry the excess water to Lake Helena and to Prickly Pear, Tenmile, and Sevenmile Creeks. This operation met with little success, however, for though the water table was lowered to normal levels near the canals it remained excessively high in the areas between them (K.R. Wilke, oral com- mun., 1977). ROCKS In a geological sense, the term rock signifies any natu- rally formed aggregate or mass of mineral matter that constitutes part of the Earth's crust. Therefore, in the broadest sense, rocks include not only the hard, firmly consolidated materials of the Earth's surface but also the soft, unconsolidated and weakly consolidated sediments such as clay, silt, sand, and gravel. In general, the firmly consolidated materials are categorized as bedrock, and the unconsolidated and weakly consolidated sediments are categorized as surficial deposits. In an engineering sense, the term rock is generally applied to firm, solid bedrock that cannot be excavated by normal methods alone, and surficial deposits and other soft earth materi- als are considered as soils. Surficial deposits and bedrock are widespread in the Helena area. The surficial materials, which comprise a cover of uncemented and weakly cemented sediments on the bedrock, mainly occupy the lowlands. Bedrock forms the mountains and hills as well as the substrate beneath the surficial deposits. A rather detailed subdivision of 6 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA the surficial deposits in the Helena area is presented in this study because ground motion and ground failure generated by earthquakes can vary significantly in differ- ent types of surficial materials. SURFICIAL DEPOSITS The surficial deposits are subdivided into nine units on the basis of differing physical characteristics and origin. These units include artificial fill, placer tailings, landslide deposits, stream deposits, slope wash, wind- laid deposits, glacial-lake deposits, and older gravel of Quaternary age (0-2 million years ago), and older stream and lake deposits of middle and late Tertiary age (2-38 million years ago). Some rocks in the older stream and lake deposits unit are hard and compact and could be classified as bedrock, but, because the bulk of the unit is composed of rocks that resemble the more orthodox surficial deposits, it is placed in the surficial category. The areal distribution of the surficial units is shown on the accompanying maps of the Helena and East Helena quadrangles (pls. 1, 2). The deposits cover an aggregate area of about 410 km. The boundaries of the units on the ground surface are covered in most places with soil and vegetation and their location generally must be inferred. The position of the boundaries shown on the maps is therefore approximate. Stream deposits and slope wash are combined as a single unit in areas where it is impracti- cal to separate them because of poor exposure or because of the map scale. The distribution and physical characteristics of the surficial deposits are important factors in evaluating seismic hazards in the Helena area. Data from many parts of the world show that damage to manmade struc- tures during earthquakes, and thus, presumably, the intensity of ground motion, is commonly greater on thick, soft sediments than on hard bedrock. Damage caused by the Helena earthquake of 1935 appears to have followed that pattern (Scott, 1936, p. 10). This aspect of the earthquake problem, as it relates to the Helena area, is examined more fully in the section on "Local geologic conditions that may contribute to seis- mic hazards." The descriptions of the surficial units that follow are based largely on visual inspection of the rocks in natural outcrops and are of a general nature. A few observations concerning the mechanical stability of the deposits are included in the descriptions; specific engineering prop- erties of the materials are unknown. ARTIFICIAL FILL The unit mapped as artificial fill (pls. 1, 2) includes a mass of earth fill along Last Chance Gulch between Neill Avenue and the Burlington-Northern Railway tracks in the city of Helena, the old city trash dump northeast of Helena, and slag piles at the American Smelting and Refining Company smelter in East Helena. The aggre- gate area covered by these deposits is about 24 ha (60 acres). Other bodies of artificial fill, not shown on the maps, include road and airport-runway foundations, earth dams at reservoir sites, irrigation-canal and railway embankments, pads of supportive gravel beneath some of the newer building and parking lots, and small masses of earth fill around manmade structures. The earth fill along Last Chance Gulch is as much as 4 m thick, the trash-dump fill is as much as 3 m thick, and the slag piles at East Helena are as much as 15 m thick. The other masses of artificial fill are mostly less than 2 m thick, but earth fill in some of the road approaches to Interstate Highway 15 is as much as 4 or 5 m thick. The earth fill along Last Chance Gulch and around manmade structures consists mostly of mixed soil and rock derived from local excavations. This material is coarse to fine grained, unsorted, unstratified, and loose- ly to moderately compacted. The earth fill in road and airport-runway foundations, on the other hand, is large- ly rounded gravel that was mined from local pits and screened to various sizes. This material, which has coars- er material at the base and finer at the top, is crudely stratified and firmly compacted. The pads of supportive gravel fill beneath buildings and parking lots also are mostly well sorted, rounded gravel. However, this materi- al is unstratified and is probably not as thoroughly compacted as the road and runway fill. The refuse fill in the old city dump consists of a heterogeneous mixture of metal, glass, wood, paper, and animal and vegetable matter covered with a thin layer of earth. In general, it is loosely compacted, unstratified, and unsorted. The slag piles at the smelter in East Helena are formed of angular fragments of fused rock (clinker) resulting from the ore-smelting process. This material is generally well compacted and is quite firm due to the interlocking arrangement of the clinker fragments. In general, artificial fill has a relatively low shearing resistance compared to natural surficial materials, espe- cially when saturated with water, and it is prone to dislocation by settlement, cracking, and slumping when subjected to strong earthquake ground motion. PLACER TAILINGS This unit constitutes waste rock resulting from placer mining. The largest body of tailings, produced by dredging, covers an area of about 2 km on the northern outskirts of Helena (pl. 1). Other large bodies of tailings, which together underlie an additional 1% km, are present along the upper part of Silver Creek (pl. 1); on Eldorado Bar, Gruel Bar, and Spokane Bar along the Missouri River GEOLOGY 4 (pl. 2); and along Holmes Gulch and Prickly Pear Creek south of East Helena (pl. 2). Smaller accumulations, not shown on the maps, are found along Sevenmile Creek above Birdseye (pl. 1), along Mitchell Gulch southeast of East Helena (pl. 2), and on McCune Bar and Danas Bar along the Missouri River (pl. 2). Much of the streambed of Last Chance Gulch that lies beneath the city of Helena also consists of placer tailings. The placer tailings, which are derived from stream and terrace deposits, mainly consist of large piles of coarse, washed gravel, commonly arranged in long rows. The maximum height of the piles, and thus the thickness of the deposits, is about 5 m. In general, the gravel is unsorted, unstratified, and loosely compacted ; it is com- posed of a mixture of boulders, cobbles, pebbles, and coarse sand. The chief rock constituents are quartzite, granite, volcanic rock (traprock), shale, and limestone. Some of the coarsest gravel is in the southern part of the tailings mass on the outskirts of Helena where a few boulders are as much as a meter across and many are as much as half a meter across. Because the placer tailings are extremely porous, water drains through them rapidly. In engineering terms, they probably can be classified as open-work gravel. The loosely compacted tailings are prone to slumping and internal movement if disturbed. Mechanically, they probably form the most unstable rock unit in the Helena area, but, in spite of this, several large structures have been built upon them. LANDSLIDE DEPOSITS Landslide deposits are rare in the area and are far from urban centers. They have been recognized only at the head of Park Gulch in the northwestern part of the Helena quadrangle (pl. 1) and along the northern front of the Elkhorn Mountains in the southeastern part of the East Helena quadrangle (pl. 2). The deposits consist of thick masses of coarse, jumbled, dislocated rock debris that broke away from steep cliffs and moved downward as gravity-propelled earthflows. The material is unsorted, unstratified, loosely compacted, and extremely porous. The surface of the deposits is rough and hummocky and has small closed depressions. The landslide deposit at the head of Park Gulch extends a short way into the adjoining Elliston quadrangle. It has an area of about 1 km and consists mainly of large blocks and smaller fragments of quartzite intermixed with soil. The land- slide mass along the front of the Elkhorn Mountains covers about % km? and consists of broken fragments of volcanic breccia, lava, and lavalike tuff intermixed with soil and slope wash. The maximum thickness of each deposit is about 12 m. A growth of tall trees on both of the landslides indicates that the deposits originated scores of years ago. Additionally, there is no evidence of recent movement, such as tilted trees, within or along the margins of the slides, which shows that they have been stabilized for many years. The material is, however, loosely compacted and prone to failure by landslip and settling if disturbed. STREAM DEPOSITS Stream deposits, the natural materials laid down in stream channels and on flood plains, occupy about 185 km of the land surface in the area. Most of the western floor of Helena Valley, encompassing an area of about 150 km", is covered by these deposits, and they are widely distributed on the floors of the major stream valleys and dry gulches in the area (pls. 1, 2). The stream deposits in Helena Valley comprise sediments brought in chiefly by Prickly Pear, Tenmile, Sevenmile, and Silver Creeks over the past several hundred thousand years. The stream deposits consist mainly of beds of rounded to subrounded pebble, cobble, and boulder gravel inter- layered with thin beds and lenses of sand, silt, and clay. The matrix of the gravels ordinarily consists of coarse sand. The deposits are generally well sorted, stratified (layered), and uncemented. The material in existing stream channels is ordinarily loose and weakly compacted ; older material on stream flood plains and beneath the land surface is generally well compacted. The rock constitu- ents of the gravels, which have been derived largely from upstream sources in the surrounding mountains, are mainly quartzite, granite, volcanic rock (traprock ), shale, and limestone. The sands are medium to coarse and consist chiefly of small grains of quartz, chert, feldspar, and magnetite, and tiny rock fragments. The silts are very fine grained and are composed of minute but visible grains of quartz and feldspar, flake-shaped particles of mica and chlorite, and small amounts of organic matter. The clays are mainly an aggregate of microscopic flakes of clay minerals. They are usually silty or sandy. Beds of gravel in the stream deposits range from % m or less to as much as 3 m thick. Beds of sand, silt, and clay are generally much thinner and range from less than a few centimeters to perhaps 1 m thick. Because of the constantly changing position and velocity of individual stream courses during deposition, the deposits vary great- ly from place to place in their sequential makeup and grain size. In general, the stream deposits in Helena Valley are coarser grained and thicker near the bordering mountains and are finer grained and thinner in the lower parts of the valley. A well drilled in the flood plain of Tenmile Creek at the Montana Club (now the Green Meadow Country Club) penetrated about 30 m of uncemented gravel and sand before entering older stream and lake deposits below (Lorenz and Swenson, 1951, p. 18). This 8 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA thickness is probably about the maximum for the stream deposits in Helena Valley. Along the major streams away from the valley, the deposits probably have a maximum thickness of about 12 m; in smaller valleys the deposits are mostly less than 3 m thick. Apart from loose, weakly compacted sediments in existing stream channels, the stream deposits are basi- cally quite stable in an engineering sense. For example, steep to vertical walls in some gravel pits have stood for years without appreciable slumping. On the other hand, water-saturated sands and silts in the deposits below the water table are probably susceptible to loss of strength and to failure by internal movement if disturbed by strong earthquake ground motion. This relation is exam- ined in further detail in the section on "Local geologic conditions that may contribute to seismic hazards." SLOPE WASH Slope wash comprises soil and rock material deposited on slopes by the action of gravity and by surface-water runoff not concentrated into channels. The material has been mapped only where it is of considerable extent and thickness. It is present chiefly on broad, gentle slopes along the southern, western, and northern margins of Helena Valley (pls. 1, 2). Altogether, about 50 km? in the area, including large parts of Helena and East Helena, all of the Helena Airport, and much of Fort Harrison, is underlain by these deposits. The slope wash was shed from bedrock outcrops on the steep slopes that rise above the deposits, and it thickens downslope away from the bedrock source. Its thickness ranges from a feather edge at the headward margins to a maximum of perhaps 6 m at lower elevations. The slope wash consists of beds of coarse gravel inter- layered with thin irregular beds and lenses of silt and clay. The gravel is composed of angular to subrounded fragments of bedrock in a matrix of sandy and silty clay whose volume usually exceeds that of the fragments. Along the southern margin of Helena Valley, the gravel fragments are chiefly quartzite, shale, and limestone; on the southern and eastern slopes of the Scratchgravel Hills, mainly granite and shale; along the northern mar- gin of the valley, mainly shale; and along the northern flank of the Elkhorn Mountains, in the southeastern part of the valley, mostly lava and lavalike volcanic tuff (traprock). Where the deposits are extensive, as along the southern and northern margins of Helena Valley, the gravel becomes progressively finer downslope. Near the bordering mountains it commonly contains blocks as much as half a meter across; at lower elevations the gravel fragments are mainly of pebble size. In general, the slope wash is composed of an uneven assortment of rock fragments, is poorly stratified, and is firmly compacted. It contains a large proportion of clay but little sand, and the majority of its contained rock fragments are angular. These features serve to distinguish the material from adjoining stream deposits. Most of the slope wash lies on inclined surfaces above stream levels and is well drained; the deeper parts of thick accumulations in the distal portions of some depos- its may be saturated with water. In general, the material is thoroughly compacted and appears to be quite stable mechanically, for slumping and subsidence of the depos- its were not observed. WIND-LAID DEPOSITS Wind-laid deposits include dunelike accumulations of sand and silt on lowland areas along the Missouri River and blanketing deposits of silt on upland surfaces in the Spokane Hills (pl. 2). The aggregate area covered by the deposits is about 10 km*. The wind-laid deposits along the Missouri River are found chiefly at the base of hillslopes at the inner mar- gins of terrace surfaces at Eldorado Bar, McCune Bar, Danas Bar, Spokane Bar, and Gruel Bar. This material was mainly derived as wind-blown sediment from terrace gravel and glacial-lake sediments that underlie the terraces, and it consists largely of fine, well-sorted sand made up of rounded grains of quartz and feldspar. The sand is unstratified, loosely to firmly compacted, and highly porous. Some of the wind-laid deposits along the Mis- souri contain large amounts of silt and clay and are much firmer than the well-sorted sands. A large area along York Road in the vicinity of Lakeside School, on the west side of Hauser Lake, is underlain by this material. The maximum thickness of the wind-laid deposits along the Missouri River is about 6 m. Deposits of silt are widely distributed on bench surfac- es along the north and west sides of the Spokane Hills in the southeastern part of the East Helena quadrangle (pl. 2) and also within the hills beyond (east of) the crest of the range in the adjoining Canyon Ferry quadrangle. In most places the silt is only a meter or so thick, but locally, where it has accumulated in ravines and depressions, it is as much as 5 m thick. It is well sorted, unstratified, and firmly compacted, and it stands in vertical walls as much as 5 m high. The silt, which consists of minute angular grains of quartz, feldspar, calcite, and mica in a binder of clay minerals, is commonly traversed by small, closely spaced, nearly vertical rootholes lined with organ- ic matter. In all aspects, the material is similar to the type of deposit called loess, which is of wind-laid origin. Distribution of the silt suggests that northwesterly winds swept the material off the floor of Helena Valley and deposited it on the windward and leeward sides of the obstructing crest of the Spokane Hills. GEOLOGY "9 In general, the wind-laid deposits are mechanically stable, although easily erodable. Because they generally lie on high ground above the water table, they are well drained. Where saturated with water, however, these deposits lose shearing resistance and become susceptible to failure by slumping, subsidence, and internal movement. Strong earthquake ground shaking tends to transform water-saturated sediments of this type into an essential- ly fluid state. GLACIAL-LAKE DEPOSITS Small patches of glacial-lake deposits are present on either side of Hauser Lake on the Missouri River, on the northeast shore of Lake Helena, and near the mouth of Spokane Creek (pl. 2). These materials were laid down in glacial lake Great Falls, which formed when the Missouri River was dammed by a continental ice sheet east of Great Falls, Montana, 20-30 thousand years ago. The deposits cover an area of about 3 km; their maximum thickness is about 12 m. The glacial-lake deposits consist of sand, silt, and clay in beds a few millimeters to as much as 30 ecm thick. In places the deposits are composed almost entirely of silt and clay in thin, alternating dark- and light-brown lami- nae 2-8 ecm thick. Each pair of light and dark laminae is called a "glacial varve." Commonly the varved deposits contain small oblate and tubular calcareous concretions. Locally, layers of fine-grained, well-sorted, weakly cement- ed sand form the bulk of the deposits. The sands are composed chiefly of subrounded grains of quartz and chert and less abundant grains of feldspar and mica. The glacial-lake deposits are firmly compacted. However, beds of sand and silt in the deposits are permeable, and the unit is highly unstable where saturated with water. For example, large-scale slumping of the deposits occurred along the shores of Hauser Lake as the waters rose behind Hauser Dam and submerged portions of these deposits. Strong earthquake ground motion would tend to reduce the shearing resistance of the water-saturated glacial-lake sediments and promote failure by slumping and subsidence. OLDER GRAVEL Older gravel lies on terrace surfaces along the major streams and in scattered patches along the southern and northern slopes of Helena Valley (pls. 1, 2). A few small masses of older gravel are present east of the Missouri River in the Big Belt Mountains (pl. 2), and the material covers an extensive area in the central part of Helena (pl. 1). The largest body of older gravel lies along the north- ern front of the Elkhorn Mountains in the East Helena quadrangle (pl. 2). Altogether, the older gravel covers an area of about 50 km. The maximum thickness of the deposits is about 20 m. The older gravel constitutes ancient flood-plain and alluvial-fan deposits that were laid down many thou- sands of years ago when the streams were at higher levels. The material is coarse, moderately well sorted, and irregularly stratified. It is made up largely of round- ed pebbles, cobbles, and boulders of granite, lava, weld- ed tuff, quartzite, shale, and limestone in a matrix of coarse sand. Boulders as much as 1 m across are pres- ent in the gravels; the bulk of the material, however, consists of pebbles and cobbles less than 10 em across. Thin lenses of sand, silt, and clay are locally present in - the deposits. The sands consist mainly of grains of quartz, chert, chalcedony, feldspar, magnetite, and fine-grained volcanic rock. The older gravels on terraces along the Missouri River and Silver Creek were in places extensive- ly mined for gold by placer methods. The larger areas of mined gravel are shown as placer tailings on plates 1 and 2. Most of the older gravel is well compacted. In places it is firmly cemented with calcium carbonate (caliche) and in other places with red iron oxide, especially at the base. The natural gravels are mechanically very stable and are subject to slumping only along the steep, stream- facing margins of terraces or where disturbed by placer mining. Most of the gravel is above the water table and is well drained. OLDER STREAM AND LAKE DEPOSITS Older stream and lake deposits are exposed over an area of about 120 km in the eastern part of Helena Valley (pl. 2). In the western part of the valley, these units are largely covered by younger stream deposits and slope wash, but their presence is known from small exposures in the city of Helena (pl. 1) and from cuttings in deep water wells drilled at the Green Meadow Country Club, Fort Harrison, the Masonic Home, and the Mon- tana State Vocational School. These occurrences sug- gest that the deposits are distributed over the entire western part of the valley at shallow depth. The northern two-thirds of Helena is probably underlain by older stream and lake deposits beneath a thin cover of younger surfi- cial material. The older stream and lake deposits presumably increase in thickness toward the central part of Helena Valley, but their maximum thickness is unknown. Knopf (1913, p. 94) reported a thickness of more than 365 m on the basis of wells drilled for artesian water, but he did not give the location of the holes. On the basis of a gravity survey conducted in the eastern part of the valley, Davis and others (1963, text, p. 3) concluded that the older stream and lake sediments in the vicinity of Lake Helena are more than 1,800 m thick. However, that thickness is 10 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA unconfirmed. East and southeast of Lake Helena, about 400 m of older, south-dipping beds at the base of the sequence are overlain by roughly 100 m of younger, flat-lying material. The older stream and lake deposits consist mainly of beds of clay, silt, sand, gravel, and volcanic ash that range in color from white through shades of gray, green, yellow, tan, brown, and red. The units generally contain large amounts of volcanic detritus, ranging in size from small ash particles to lava boulders a meter or more across, and most of the ash component is altered to clay. A few thin beds of dark-brown carbonaceous shale and lignite, which are as much as a meter thick, are present in the lower part of the unit in the northeastern part of Helena Valley west of Hauser Lake. The deposits were laid down along ancient stream courses and in lakes that existed in the valley 2 to 38 million years ago. Perhaps as much as half of the unit is made up of light- green, greenish-gray, gray, and light-reddish-gray clay in beds that are several centimeters to as much as 3 m thick. These clays represent altered volcanic ash and prob- ably consist largely of the clay minerals montmorillonite and beidellite. Such clays are called bentonite. Clays of this sort are exposed in the ravine east of St. Peter's Community Hospital, in the ravine north of the Fish and Game Commission Building, and on the east side of Dry Gulch along upper Davis Street in the city of Helena. The bentonitic clays form smooth, rounded outcrops and swell when wetted; they are soft and easily eroded. Weath- ered surfaces generally have a crinkled or popcornlike texture due to expansion and shrinkage of the clay. Beds of gray, brown, reddish-orange, and tan silt, sand, and gravel, which are interlayered with the clays at various horizons, form about 40 percent of the deposits. The sands are generally coarse and form beds as much as 3 m thick. They are mainly composed of grains of quartz, chert, feldspar, and rock fragments, but some are gravel- ly and contain scattered pebbles as much as 2 or 3 ecm across. In places the sands are cemented with calcium carbonate and are hard and compact. The gravels form lensing beds that range from about % m to 4 or 5 m thick. They are common in exposures in the southeastern part of Helena Valley south of York Road. The gravels consist of rounded pebbles, cobbles, and boulders of volcanic rock (traprock), granite, quartzite, shale, and rare lime- stone in a matrix of slightly cemented clayey sand. Prob- ably all of the rock constituents in the gravels were derived from nearby bedrock in the surrounding mountains. Boulders as much as a meter across are present in some beds, but large boulders are uncommon and the bulk of the gravels are formed of pebble- and cobble-size stones. In the area south and southwest of East Helena, the older stream and lake deposits consist mainly of white to light-gray, compact, siliceous volcanic ash. These rocks are well exposed in a road cut along U.S. Highway 12 about a kilometer west of East Helena. They are mainly composed of an aggregate of small pumice fragments and mineral grains -chiefly quartz, feldspar, biotite, and hornblende. In most places the pumice component is partly altered to clay, and the deposits are relatively soft and easily eroded. Some of the volcanic ash, however, is formed of coarse, angular volcanic rock fragments that are firmly cemented, and this material is hard and massive. The older stream and lake deposits, which are firmly compacted and moderately cemented, appear as a whole to be quite stable in an engineering sense. Road cuts in these materials have experienced little failure by slumping, and high natural scarps along the valleys of Spokane Creek and its tributaries, which are formed in the deposits, have stood for many decades without appreciable change. The bentonitic clays that form a large part of the unit are probably more prone to failure by slumping and internal movement than other rock types, especially where satu- rated with water. Strong earthquake ground motion would tend to reduce the shearing resistance of the clays and promote failure by slumping and subsidence. BEDROCK Bedrock, which forms the solid rock foundation beneath the area, consists of sedimentary, plutonic, and volcanic rocks. Sedimentary rocks are those that have formed by cementation and hardening of water- and wind-deposited sediments; plutonic and volcanic rocks, collectively known as igneous rocks, are those that have formed by solidifica- tion of molten or partially molten material called magma. The plutonic rocks are the result of intrusion and crystal- lization of magma beneath the Earth's surface, and the volcanic rocks are the result of extrusion of magma as lava and solidified lava fragments on the Earth's surface. The distribution of the three types of bedrock is shown on plates 1 and 2. Most of the bedrock is highly rigid, strongly and permanently cohesive, and of high shearing and compressive strength. Because of these characteristics, it is mechanically stable and, unlike the surficial depos- its, resistant to slumping, settling, or other types of ground failure. SEDIMENTARY ROCKS Sedimentary rocks occupy much of the mountain bor- der around Helena Valley and underlie the city of Helena beneath a thin cover of surficial deposits (pl. 1). Essentially, these rocks form a great layered sheet several thousand meters thick that rests on the so-called crystalline base- ment of the Earth's crust. The sedimentary bedrock ranges from middle Late Cretaceous age (about 86 mil- lion years ago) to Middle Proterozoic age (about 1,600 million years ago). GEOLOGY 11 The sedimentary rocks include sandstone, shale, limestone, and dolomite. The sandstone is composed mainly of small grains of quartz, feldspar, and mica that are cement- ed by silica or by calcium carbonate (calcite). Much of the sandstone in the Helena area is bonded with silica to form a hard, massive rock called quartzite. The shale consists largely of minute, clay-size particles of quartz, feldspar, mica, and chlorite bonded with silica or calcite. Most of the shale in the Helena region is hard, firm, and thinly layered and resembles slate. The limestone is formed mainly of calcium carbonate, and much of it consists of the fragments of shells of marine organisms in a cement of calcite. It is mostly hard, firm, and compact. The dolomite, which outwardly resembles limestone, con- sists largely of calcium-magnesium carbonate (dolomite), and some of it is made up of the skeletal remains of marine algae. It is generally hard and massive and forms most of the bedrock beneath Helena. All of the sedimentary rocks are characterized by a layered structure known as stratification. This structure is the result of deposition of the sediments in successive layers that vary somewhat in grain size, composition, and thickness. The surfaces between the layers are called bedding planes. The stratification of the sedimentary rocks in the Helena area is generally inclined at moderate to steep angles as a consequence of bending and tilting of the rocks by forces that formed the Rocky Mountains. Most of the sedimentary rocks are traversed by narrow joints that cut across the stratification. The rocks tend to split along these joints and along the bedding planes and commonly break down naturally at the surface into large and small fragments that in places veneer the solid rock. PLUTONIC ROCKS The plutonic rocks are mainly present in the high mountains along the southern border of the area where they form a great body of rock called the Boulder batho- lith (pls. 1, 2). Smaller masses are present in the terrain south and west of Helena Valley, such as the body that forms the center of the Scratchgravel Hills (pl. 1), and a small mass of plutonic rock is present beneath Carroll College in the city of Helena. Originally, these rocks were covered with great thicknesses of sedimentary and vol- canic strata. Deep erosion has since exposed them at the surface. The plutonic rocks range from early Tertiary age (about 45 million years ago) to Late Cretaceous age (about 78 million years ago). The plutonic rocks consist of an intergrown aggregate of crystalline minerals and are generally hard, massive, and compact. They range from silica-rich types called quartz monzonite and granite, composed mainly of quartz and potassium feldspar, to silica-poor types called diorite and gabbro, composed mostly of pyroxene and sodium- calcium feldspar. The silica-rich types are by far the more abundant. Most of the plutonic rocks are coarsely crystal- line, but some are fine grained and a few are glassy. In some places, especially in areas of gentle topography, they are deeply altered to granular soil as much as a meter or two thick. This material is soft and loose and has the con- sistency of sand or fine gravel. Beneath the soil a zone of partially weathered rock called saprolite is generally present that grades downward into solid rock. The sapro- lite is more than a meter thick in some areas. VOLCANIC ROCKS The volcanic rocks mainly cover areas in the Elkhorn Mountains to the southeast and areas along the upper part of Tenmile Creek to the southwest where they form layered piles as much as 600 m thick. They are of Late Cretaceous age and between about 74 and 80 million years old. The volcanic rocks consist mainly of hard, massive lava and lavalike rock called welded tuff, but include some volcanic breccia, tuff, and conglomerate formed of lava fragments. They range from silica-rich types called rhyolite and rhyodacite to silica-poor types called andesite and basalt. The rhyolite and rhyodacite, which are the most abundant, are formed chiefly of a fine-grained aggregate of quartz and potassium feld- spar. The andesite and basalt are made up largely of small crystals of pyroxene, sodium-calcium feldspar, and magnetite. FAULTS GENERAL CHARACTERISTICS Geologic faults are fractures in the Earth's crust along which there has been displacement of the rock on one side relative to the rock on the other side in a direction parallel to the fracture. The surface along which the rock masses have moved is called the fault plane, and the intersection of the fault plane with the ground surface is called the fault trace. Faults are generally classified on the basis of the relative direction of movement of the crustal blocks that bound them. In the Helena area, three principal types are present: normal faults, thrust or reverse faults, and strike-slip faults. The diagrams presented in figure 2 illustrate the main characteristics of each type. Normal faults (fig. 24 ) are those along which the block above the fault plane has moved downward relative to the block beneath the fault plane. Thrust or reverse faults (fig. 2B) are opposite and comprise those along which the block above the fault plane has moved upward relative to the block below. Normal faults are usually inclined more than 45° ; thrust or reverse faults 12 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA FIGURE 2.-Diagrams illustrating the principal types of faults in the Helena area. Arrows show relative direction of movement. A, Normal fault. Block to right of fault has moved downward with respect to block on left. B, Thrust or reverse fault. Block to right of fault has moved upward with respect to block on left. C, Strike-slip fault. Blocks have moved horizontally past each other along the fault. may be inclined more, or less, than 45°. Strike-slip faults (fig. 2C) are those along which blocks on either side of the fault plane have moved horizontally relative to each other. Such faults are generally vertical or steeply inclined. Movement on most faults, especially on the larger ones, takes place over a long period of time. On some faults the movement progresses slowly by a succession of small displacements separated by periods of inactivity; on others it occurs by imperceptibly slow, continuous movement called fault creep. Sudden breaks with sur- face displacements of a few meters and more have occurred on faults during strong earthquakes. Most faults are formed during periods of deformation that affect large regions of the Earth's crust; activity on the faults then ceases. In certain regions, however, faults have been rejuvenated after long periods of inactivity. Faults are often classified as active or inactive on the basis of their history of displacement. Active faults are those on which movement has taken place in the recent geologic past and on which movement is likely to occur in the future. The "recent geologic past" is commonly understood to mean the Holocene Epoch of geologic time between 0 and 10,000 years ago (Bonilla, 1970, p. 68-69). Inactive faults are those on which movement occurred in some earlier period of Earth history and which show no sign of displacement in Holocene time. Active faults may be marked by historic surface displacement, by the offset of surficial deposits or land- forms of geologically recent age, or by the presence of fault-produced topography such as recently formed scarps, offset stream courses, water-filled depressions, linear ridges, and narrow trenches. The absence of these fea- tures does not necessarily indicate that a fault is inactive, however, for geologic processes of erosion and deposition may effectively obliterate the physiographic evidence of fault displacement within a short period of time. Signifi- cant displacements that are not reflected at the Earth's surface also may occur on active faults at depth. In general, most faults are difficult to classify as active or inactive because the geologic record of their movement is incomplete. At the present state of knowledge, we can- not determine with certainty whether a given fault will undergo movement in the future. Earthquakes are commonly associated with faults and are generally considered to result from instantaneous rupture and movement on fault planes beneath the Earth's surface. In earthquakes of low to moderate magnitude, the rupture ordinarily is confined to a local area on the fault surface within the crust, but in shocks of high magnitude the rupture may extend widely over the fault surface and culminate in displacement at ground level. Additionally, ground motion generated by a large earth- quake on one fault has in some instances caused reactiva- tion of other adjacent faults and resulted in extensive breakage, warping, and subsidence of the land. Deforma- tion of that sort occurred during the Hebgen Lake, Montana, earthquake of 1959 (Witkind, 1964b). All faults, whatever their age and whether they are active or inactive, represent surfaces or zones of poten- GEOLOGY 13 tial failure in rocks of the Earth's crust. Accordingly, in highly seismic regions, every fault probably should be considered as a hazard. The degree to which an individu- al fault constitutes a hazard depends on such variables as the location, length, depth, and displacement of the fault and whether it is active or inactive. Long, active faults that extend to great depth are usually the most hazardous. Faults are abundant in the Helena area. Some are of very large displacement, but few are discernible on the ground, for they are largely covered with soil or loose rock or are concealed beneath surficial deposits. Most are confined to bedrock, chiefly sedimentary and volcan- ic bedrock, but some displace surficial deposits. Most of the faults have been recognized by the offset of rock formations on opposite sides of their trace; a few are marked by prominent topographic scarps resulting from displacement of the ground surface. Only a superficial study of the faults in the Helena area has been made by the author, and little quantita- tive data exist on the precise extent and time of the latest movements on them. At present we lack evidence that any of the faults have undergone surface movement in Holocene time (last 10,000 years), and, accordingly, none of them can be classified as active according to the definition previously outlined. However, two major strike- slip faults, which seem to be responsible for much of the seismic activity in the Helena area, and several large normal faults, which displace surficial deposits of pre- Holocene age and which are marked by well-defined scarps, are categorized as potentially active faults. Other faults in the area, which generally lack physiographic or other indications of Holocene movement and which appear on the basis of geological evidence to have orig- inated many millions of years ago, are considered to be inactive. The location of faults in the Helena area is shown on plates 1 and 2 on which the fault traces are represented by heavy lines. The larger faults, some of which continue far beyond the report area, are named after prominent geographic features. A small-scale map showing the traces of the principal faults in and near the Helena area is presented in figure 3. MAJOR STRIKE-SLIP FAULTS It has long been recognized that a zone of fundamental crustal discordance extends from the vicinity of Helena, Montana, northwestward across western Montana and northern Idaho to eastern Washington. This zone, known as the Lewis and Clark line (Billingsley and Locke, 1939, p. 36; Harrison and others, 1974, p. 9; Reynolds, 1977; Reynolds and Kleinkopf, 1977; Reynolds, 1979, p. 191-192), separates crustal blocks of profoundly contrasting struc- tural style and bulk rock composition that have been juxtaposed by a combination of large-scale vertical and horizontal fault movement. The term "line" was first applied to this structural feature by Billingsley and Locke (1939, p. 36) and is used for historical reasons. Actually, the "line" represents a zone 10-50 km wide that is charac- terized by faulting and other profound geologic discontinuities (Reynolds and Kleinkopf, 1977). Two major strike-slip faults that are believed to mark the eastern segment of the Lewis and Clark line are present in the Helena area. One, named the Bald Butte fault, forms the southern boundary of the line; the other, named the Helena Valley fault, forms the northern bound- ary of the line (fig. 3). The traces of the Bald Butte and Helena Valley faults are remarkable straight, and they are interpreted as steep fractures that extend far into the Earth's crust. South of the Bald Butte fault the land surface is mainly underlain by sedimentary, volcanic, and plutonic rocks. Large northeast- and northwest-trending folds and nor- mal faults in the sedimentary and volcanic rocks of that area end sharply against the Bald Butte fracture. North of the Helena Valley fault the land surface is mainly underlain by sedimentary rocks. Broad northwest-trending folds and thrust faults in the rocks of that area terminate abruptly against the Helena Valley fracture. Between the Bald Butte and Helena Valley faults is a linear crust- al strip 10-15 km wide that is composed mainly of sedi- mentary rocks. This strip is deformed into irregular folds and is broken by large normal faults, and it contains small, scattered masses of plutonic rock. Much of the seismic activity in the Helena area and in the adjoining region to the northwest appears to be concentrated along the Bald Butte and Helena Valley faults and within the deformed crustal strip between them, which constitutes the Lewis and Clark line (fig. 10). BALD BUTTE FAULT The Bald Butte fault, recognized during the course of this study, seems to have been the locus of many small earthquakes in 1973 and may be the most seismically active fracture in the area. The fault is named for Bald Butte, a prominent peak along the Continental Divide southwest of Marysville (fig. 3), where the fracture is well exposed. In the Helena area, the trace of the Bald Butte fault extends from the headwaters of Threemile Creek, at the northwestern boundary of the area, southeastward through the community of Birdseye to a point about 1 km north of Fort Harrison on the western outskirts of Helena (pl. 1). Southeast of that point the trace of the fault is covered by surficial deposits, but it is inferred to extend beneath those materials and to join a fault exposed 14 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA 112°30' 12915 y » 47°00" 3 =- 112°00 111945 7 o \,\ Hotter C, | DEARBORN 5 A Dam %o, Creek "$53? ~ C & Flesher Passy ») 0,7 AULT 'ad ”IQ 3 Us, /""‘\/ F401 t / C3 ) ELDORADO ®» Creek / THRUST #" FAULT Fauur / ( ,Stemple 9 Pass < - Virginia § Willow Creep E‘s” HOGBACK MOUNTAIN A a>. THRUST FAULT \ v4“ ilborn & EPN, moors as. . MOUNTAIN (BBS-fifléTE 5 * ts THRUST FAULT 0/Q \a s O \\ v Gravelly \p Marsh Ronge RATTLESNAKE F-. at C a Lake MOUNT AINA *riew cC N04 \‘:\ A694 \ 4 Upper Holter ‘ A a O Canyon *> a S=" (€ fa. “a 5 Creek *+, cA & % a CKLY PEAR\,.- U B, . \ Aur to iver * j BEAR TRAP‘Q' o \ VALLEY o FAULT t_ . a“ 4No \\ Silver \ flak“ 46045 |- 9 J f Marvwille * 0 City e C BALD s 28°. ~, S tan BUTre £4 BALD v? BELMON’ C24” == iB Lo m Uir\\ButtE } [northwest ~~ ~ $ & pe mex x Up VALLEY FAULT ,,~,\ ue D memes Mp C8 N > $19 a J 8 V j .* SCRATCHGRAVEL from CE *" j SILVER _>, HILLS FAULT! a GREENHORN CREEK C * S DJU fMOUNTAIN sl FAULT ?, \\;\‘ ——L| “é Oly Ul ® » €] \# § *-* *~ TALL & ""Tie reat f;( “Sign ‘S’QQS- “(6 % 1 Hauser D 6\ Birdseye MC l C C; ‘i‘ h’ls % i Lake l | Creek ( :\\ 4=-~ l'l: Helena \t, ~ c % u Mullan\ «e l\ \~’; “k: egulating ~ 70K Pass X egt \‘ \, Set * & QRPSF voir 0 \ Austin \ 0&2: Blossburg | \I I fix 4 Eis} mG El Fort Vi. niga ~ > Harrisont-- > U/ $4; R / % MOUNTA HELENA © 'ASCENSION FAULT 0 Unionville 46°30° 0 5 10 15 KILOMETERS esr e s-" 1 0 5 MILES EXPLANATION STRIKE-SLIP FAULT-Arrows show inferred relative direction of horizontal movement. Dashed where inferred; dotted where concealed NORMAL FAULT-U, upthrown side; D, downthrown side. Dashed where inferred; dotted where concealed _&__&A_.&A- THRUST FAULT-Sawteeth on upthrown side. Dashed where inferred; dotted where concealed —————— OUTLINE OF INTERMONTANE BASIN BOUNDARY OF HELENA AREA AS DEFINED IN THIS REPORT FIGURE 3.-Map showing the traces of principal faults in and near the Helena area. Northeast corner in part from unpub. mapping of M.W. Reynolds (1978). GEOLOGY 15 in bedrock about 6 km southeast of Helena (pl. 2). Farther east, the location of the Bald Butte fault is more speculative. Probably it extends eastward along the southern margin of Helena Valley, joins an east-west tear fault along the northern front of the Elkhorn Mountains described by Smedes (1966, p. 96; pl. 2, this report), and continues southeastward into Townsend valley. Northwest of the Helena area, the fault extends to Bald Butte in the Elliston quadrangle, continues westward across the Con- tinental Divide north of Black Mountain, and reaches the northwest border of Avon Valley where it is covered by surficial deposits. Beyond that point the location of the fault has not been accurately established, but recon- naissance studies suggest that it probably continues northwestward beneath the surficial fill in Avon Valley and joins a major northwest-trending fracture in the valley occupied by Nevada Lake. A prime characteristic of the Bald Butte fault is the large variation in apparent displacement of rock strata along its trace within relatively short distances. For example, at Bald Butte (fig. 3), the fault displays an apparent vertical separation of more than 4,400 m, yet a few kilometers to the west the apparent offset is 200 m or less. Similar variations in apparent vertical displace- ment occur elsewhere along the trace farther west and to the southeast. Furthermore, the sense of relative vertical displacement on the fault changes along its trace. East of the Continental Divide, rocks on the north side of the fault appear to be generally displaced upward relative to the rocks on the south, whereas west of the divide rocks on the north side of the fault appear to be displaced downward relative to the rocks on the south. This relation, together with the sharp change in regional geology across the fracture, strongly indicates that the main movement on the Bald Butte fault was strike slip, the rocks south of the fault perhaps moving west relative to the rocks on the north and the horizontal translation amounting to several kilometers. However, matching structures or matching rock strata on either side of the fault that might indicate the true sense of movement and absolute dis- placement on the fracture have not been identified. In places, rocks adjacent to the Bald Butte fault are steeply tilted, extensively shattered, traversed by close- ly spaced joints, and cut by numerous, steep secondary faults, some of which extend several tens of meters from the main fracture. These secondary structures were proba- bly produced by strike-slip movement. They are particu- larly well developed along the fault trace in the vicinity of Birdseye. Evidence of geologically recent or historic movement along the Bald Butte fault is lacking. Topographic fea- tures indicative of surface breakage have not been observed, and along much of its course the fault appears to be covered by surficial deposits of Holocene and Pleistocene age (0-2 million years ago) and by older stream and lake deposits of middle and late Tertiary age (2-38 million years ago). However, further work is necessary to deter- mine with certainty that these rocks have not been bro- ken by recurrent movement on the fracture. For example, it is possible that small displacements of the ground surface along the trace of the fault at the southern mar- gin of Helena Valley have been obliterated by the activi- ties of man. In general, geologic relations suggest that the principal movement on the Bald Butte fault predated the formation of the older stream and lake deposits and took place more than 38 million years ago. Despite its apparent geologic antiquity, the Bald Butte fault is considered to be potentially active, for low-magnitude earthquake activity, which was localized along it in 1973 (fig. 10), suggests that the fracture is undergoing contin- uous or renewed adjustments at depth. The coincidence of seismic activity with the fault is described in the section on "Seismic history of the Helena area." HELENA VALLEY FAULT The Helena Valley fault is well exposed along the northwestern margin of Helena Valley and in the low range of hills between Helena Valley and Silver Valley in the Rattlesnake Mountain and Silver City quadrangles, where it was discovered and mapped by M.L. Bregman and G.D. Robinson in 1970. Northwest of this exposure, the fault extends along the northeastern margin of Silver Valley, crosses the terrain northwest of the community of Canyon Creek, and continues to the Continental Divide near Stemple Pass (fig. 3). Beyond that point the loca- tion of the fault is uncertain, but satellite imagery sug- gests that it extends through a large area of volcanic rocks of probable Oligocene age (25-38 million years ago) north of Stemple Pass and continues northwestward to join the St. Marys fault (Harrison and others, 1974, fig. 3), which defines the northern limit of the Lewis and Clark line across much of northwestern Montana. To the southeast, the fault is poorly exposed, but geologic stud- ies indicate that it extends along the northern border of Helena Valley, traverses older stream and lake deposits west of Hauser Lake, crosses the Missouri River, leads up Market Gulch, and continues eastward into Townsend valley in the adjoining Canyon Ferry quadrangle. The type and amount of displacement on the Helena Valley fault probably compare with displacement on the Bald Butte fracture. Reynolds (1977) postulated that movement on the Helena Valley fault has varied through geologic time, from dominantly vertical between 1100 and 700 million years ago to dominantly strike slip during more recent geologic time. During the latter time, rocks north of the fault moved east relative to the rocks on the 16 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA south, the horizontal translation amounting to sever- al kilometers. However, the absolute displacement on the fault in the Helena area cannot be determined from existing geologic data. Pronounced breakage of the rocks along the trace of the Helena Valley fault was observed in Market Gulch and farther east in the Canyon Ferry quadrangle. At these places the fault is represented by a zone of sheared and broken shale as much as 50 m wide enclosing large exotic masses of quartzite and limestone. Physiographic features indicative of surface move- ment within the last few thousand years are lacking along the trace of the Helena Valley fault, and in places it is covered by stream deposits and slope wash of Holocene age (0-10,000 years ago). In the East Helena quadrangle (pl. 2), the fault cuts older stream and lake deposits of middle Tertiary age (25-38 million years ago), but the precise time of this movement has not been determined. The most recent movements on the Helena Valley fault in the Helena area are therefore bracketed between about 10,000 and 25 million years ago. The main movement on the fault is inferred to have taken place prior to the de- position of the Tertiary deposits more than 38 million years ago. The epicenter of the main shock of the Helena earth- quake of 1935 and the epicenters of several small earth- quakes recorded in 1973 lie near the trace of the Helena Valley fault (fig. 10), a relation that suggests these shocks originated on the fracture. Accordingly, although geolog- ic relations indicate that major displacement occurred far back in geologic time, it seems likely that the fault is now undergoing intermittent movement and may be considered an active break. PRINCIPAL NORMAL FAULTS The principal normal faults in the area are located in Helena Valley and west of the Scratchgravel Hills within the Lewis and Clark line (fig. 3). They include the Silver Creek, Northwest valley, Scratchgravel Hills, Spokane Bench, Regulating Reservoir, and Spokane Hills faults. The Silver Creek and Northwest valley faults appear to be old, inactive fractures. The Scratchgravel Hills, Spo- kane Bench, Regulating Reservoir, and Spokane Hills faults probably have undergone significant movement in Pleistocene time (10,000-2 million years ago). They are regarded as potentially active breaks. SILVER CREEK FAULT The Silver Creek fault is in the north-central part of the Helena quadrangle (pl. 1). It extends southward from Silver Creek through sedimentary bedrock west of the Scratchgravel Hills and terminates about 1% km north of Sevenmile Creek east of Birdseye. Northwest of its exposure at Silver Creek, the fault is covered by surficial deposits and its precise location is unknown, but probably it continues a long distance northeastward beneath the surficial materials along Silver Creek. The fault is inclined steeply southwest and is downthrown on the west and southwest. At Silver Creek, dolomite on the southwest side of the fault is dropped down against shale on the northeast and the displacement is at least 600 m. South of Silver Creek, displacement on the fault decreas- es progressively and becomes zero at its termination north of Sevenmile Creek. Where the fault crosses Coun- ty Highway 279 (Lincoln Road) near the center of sec. 16, T. 11 N., R. 3 W., on the north side of Silver Creek, the rocks on either side of the break are intensively sheared and shattered and form a zone of deformation about 3 m wide. It cannot be determined, however, whether actual movement was confined to one or the other of the bounding blocks or whether both were active during fault movement. The Silver Creek fault has no obvious association with contemporary seismic activity, displays no evidence of movement in Holocene time (last 10,000 years), and does not appear to cut surficial deposits northwest of its exposure along Silver Creek. Accordingly, it is consid- ered to be inactive. NORTHWEST VALLEY FAULT The Northwest valley fault extends northward along the western side of the Scratchgravel Hills, continues northeastward across the northwestern part of Helena Valley, and terminates against the Helena Valley fault (pls. 1, 2). The fault is concealed beneath surficial depos-. its over much of its length, is exposed only at its west and east ends, and is inferred to be offset by the Scratchgravel Hills fault. The fracture is steeply inclined and is downthrown to the south and east. It has a verti- cal displacement of at least 200 m and perhaps as much as 300 m, as indicated by the offset of rock formations along its trace. At the southwest, the fault presumably dies out in sedimentary bedrock west of the Scratchgravel Hills. The fault has no topographic expression, shows no evidence of movement in Holocene or Pleistocene time (last 2 million years), and has no apparent association with recent seismic activity. It is therefore regarded as an inactive break. A steeply inclined normal fault of northwest trend and a few kilometers long crosses secs. 3 and 11, T. 11 N., R. 4 W. north of the Northwest valley fault (pl. 1). This north- west-trending fault is inferred to end against the North- west valley fracture and is considered to be inactive. GEOLOGY 17 SCRATCHGRAVEL HILLS FAULT The Scratchgravel Hills fault extends along the east- ern front of the Scratchgravel Hills in the northeastern part of the Helena quadrangle (pl. 1). This fault was first identified by Pardee (1950, p. 382-383), who assumed that the steep, straight eastern face of the hills was a scarp produced by fault movement. The fracture presumably lies at the eastern foot of the hills where it is largely covered by stream deposits and slope wash. At the south, the fault extends an unknown distance into Helena Valley beneath the surficial materials. At the north, its location is also uncertain, but it is inferred to cut the Northwest valley fault and to continue a few kilometers northwestward in sedimentary bedrock. The fault proba- bly is steeply inclined to the east, is upthrown to the west, and is inferred to cut older stream and lake depos- its that lie beneath younger stream deposits and slope wash north and south of the Scratchgravel Hills (pl. 1). Pardee (1950, p. 383) estimated that displacement on the fault was at least 300 m, as measured by the height of the scarp along the Scratchgravel Hills, but precise geologic data are not available to determine the true slip on the fracture. The stream deposits and slope wash that cover the trace of the Scratchgravel Hills fault are of Holocene age (last 10,000 years). These materials show no evidence of movement along the line of the fault, which suggests that major fault displacement occurred prior to Holocene time. No additional geological data are available on the time of movement except that the fault probably cuts older stream and lake deposits of middle Tertiary age (25-38 million years ago). However, if the scarp at the east face of the hills was generated by the fault movement, the main displacement may have taken place in Pleistocene time, between 10,000 and 2 million years ago, for the scarp is in a youthful state of erosion. Furthermore, movement on the fault may not have ceased entirely, for the epicenters of two small earthquakes that occurred in 1973 lie at the south end of the fracture and another lies along the northern trace (fig. 10). These earthquakes may have originated on the fault. Accordingly, in view of its probable Pleistocene age and possible association with historic earthquakes, the Scratchgravel Hills fault may be considered an active break. SPOKANE BENCH FAULT The Spokane Bench fault trends northward through Helena Valley in the central part of the East Helena quadrangle (pl. 2). It extends west-northwest from its apparent southern limit near Clasoil, northward along the west side of the topographic highland known as Spokane Bench, northwestward across the east end of Lake Helena, and terminates against the Helena Valley fault north of the lake. It is about 20 km long. Over most of its length, the fault displaces older stream and lake deposits and follows the base of a low scarp that bounds Spokane Bench on the south and west. This scarp, which was produced by the fault movement, generally marks the fault trace. On the south side of the bench, the low, south-facing scarp interrupts the smooth, northwardly inclined surface formed along the southern margin of Helena Valley. On the west side of the bench, stream deposits of Holocene age (last 10,000 years) are laid down against the base of the scarp and the fault is concealed beneath them. To the north, in the vicinity of Lake Helena, the scarp is formed in bedrock. The Spokane Bench fault is steeply inclined, and pre- sumably it cuts and displaces the bedrock floor beneath Helena Valley. Displacement on the fracture appears to increase progressively northward along the fault trace from near Clasoil where it has zero displacement. Verti- cal displacement at the surface 5 km west of Clasoil is at least 20 m, as indicated by the height of the fault scarp at Diehl Lane. Along its midlength, west of the Helena Valley Regulating Reservoir, the vertical slip may amount to 30 m or more, as indicated by the scarp height. At the north, vertical displacement on the fracture is perhaps as much as 100 m where older stream and lake deposits are dropped down against sedimentary bedrock. As part of a seismic risk investigation undertaken by the U.S. Bureau of Reclamation in 1977, trenches were excavated a short distance east of and at the foot of the Spokane Bench fault scarp in the vicinity of the Helena Valley Regulating Reservoir. A detailed study of those trenches, which were as much as 80 m long and 2 m deep, was made by M.W. Reynolds of the U.S. Geological Survey and M. McKeown, U.S. Bureau of Reclamation. They observed that older stream and lake deposits of middle to late Tertiary age (2-38 million years ago) in the upper part of the scarp dip as much as 70° northeast (away from the scarp) and that sediments of probable early Pleistocene age (Pleistocene age = 10,000-2 mil- lion years ago) near the foot of the scarp are intensely folded, slumped along curving fractures, locally shattered, and in places invaded by sand dikes (M.W. Reynolds, written commun., 1977). Presumably, this deformation was caused by movement on a concealed, west-dipping fault at the base of the scarp -the Spokane Bench fault- during the middle or latter part of the Pleistocene Epoch. The Pleistocene displacement establishes the fault as a potentially active break. Conceivably, the fault is now undergoing displacement by slow creep. Although the Spokane Bench fault has no record of 18 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA historic seismic activity, the sand dikes in the deformed sediments of Pleistocene age, a short distance east of the concealed trace of the fracture, are probably related to strong earthquakes of local origin. These dikes, which are steeply inclined, of tabular shape, and as much as 20 cm wide, are believed to be the result of earthquake- induced liquefaction of sand at shallow depth and its injection into fractures in the overlying sediments (M. W. Reynolds, written commun., 1977). The age of the sand dikes could not be determined, but possibly they were formed during the destructive earthquake of 1985, at which time local residents saw water and sand spouting from cracks in the ground surface along the line of the fault north of the trenching site (M.W. Reynolds, oral commun., 1977). On the other hand, the dikes may relate to an earlier strong earthquake that took place in the Helena area long before the settlement of Montana. REGULATING RESERVOIR FAULT The Regulating Reservoir fault, which was recognized by M.W. Reynolds in 1975, trends northwest across the central part of Spokane Bench in the East Helena quad- rangle (pl. 2). It is about 6 km long, extends from the east side of the Helena Valley Regulating Reservoir at the north to Mitchell Gulch at the south, and crosses Can- yon Ferry Road. Along most of its length, the fault follows the base of a prominent, west-facing scarp pro- duced by vertical movement on the fracture. This scarp breaks the old land surface on Spokane Bench, and the displacement has produced a pronounced eastward tilt of the ground surface on either side of the fault trace. The offset of the land surface, as marked by the height of the scarp, ranges from 12 to 30 m, which is a rough measure of the minimum vertical displacement on the fracture. The age of the Regulating Reservoir fault cannot be accurately determined from existing geologic data. The fracture displaces older stream and lake deposits of prob- able Oligocene (middle Tertiary) age (25-38 million years ago) along much of its trace and extends beneath stream deposits of Holocene age (last 10,000 years) at Mitchell Gulch. Movement on the fault therefore occurred between 10,000 and 25 million years ago. It is probable, however, that the movement took place during the latter part of that interval, for the resulting fault scarp is a young landform little modified by erosion. Possibly the fault formed more or less simultaneously with the parallel- trending Spokane Bench fault, which cuts Tertiary stra- ta and displays evidence of Pleistocene activity. It seems advisable, therefore, pending the acquisition of more conclusive age data, to classify the Regulating Reservoir fault as a potentially active fracture. SPOKANE HILLS FAULT The Spokane Hills fault is in the northeastern part of the East Helena quadrangle (pl. 2). It extends northwest- ward along the west margin of the Spokane Hills, crosses Spokane Creek and the York Road, and ends against the Helena Valley fault. The Spokane Hills fault cuts sedi- mentary bedrock at the south, displaces older stream and lake deposits down against sedimentary bedrock along its midlength, and traverses older stream and lake deposits at the north. Between Canyon Ferry Road and Spokane Creek, the fracture follows the base of a remark- ably steep, straight scarp in the bedrock that probably was produced by a combination of fault movement and differential erosion on either side of the fault trace. The true displacement on the fault cannot be determined from current data, but geologic relations suggest that the minimum vertical movement on the fracture was several hundred meters. Major movement on the Spokane Hills fault apparent- ly occurred more than 20,000 years ago, for in places the fracture is covered by glacial-lake and wind-laid deposits of about that age, which show no evidence of displacement. However, the fault must have originated not long before the deposition of those sediments, for the scarp along its trace is little eroded and is in a youthful geologic state. Moreover, M. W. Reynolds (oral commun., 1977) has not- ed that the bedding is abnormally steep in newly formed, fan-shaped deposits of mixed stream and slope debris along the northern base of the scarp, which suggests that movement on this portion of the fracture may have continued into Holocene time (last 10,000 years). The fault is therefore regarded as a potentially active break. A splay from the Spokane Hills fault is inferred to extend southward beneath stream deposits along Spo- kane Creek (pl. 2). SECONDARY NORMAL FAULTS Many normal faults of shorter length and generally of smaller displacement than those just described are pres- ent in the area and are shown on plates 1 and 2. They are mostly formed in sedimentary and volcanic bedrock to the south and west of Helena Valley, and several are near Helena. All appear to be inactive, for they are deeply eroded faults that show no evidence of movement in geologically recent or historic time and are not known to be associated with seismic activity. Only a few of the faults cut plutonic bedrock, and several of them end against plutonic contacts. This relation suggests that most of them originated in response to intrusion of the Boulder batholith and its satellitic masses some 68-78 million years ago (Tilling and others, 1968, p. 688), and, GEOLOGY 19 accordingly, they are at least that old. On the other hand, even though these geologically ancient faults are consid- ered to be inactive, renewed movement on them in the future cannot be ruled out. FAULTS AT WILLIT RIDGE A prominent set of normal faults bounds a large wedge- shaped block of sedimentary bedrock in the vicinity of Willit Ridge in the northwestern part of the Helena quadrangle (pl. 1). The bedrock block is raised upward along these faults and is tilted downward against the Bald Butte fault, which bounds the block on the northeast. The normal faults may be second-order shears that devel- oped simultaneously with the Bald Butte fracture. The fault bounding the south side of the uplifted block cuts the north end of a large mass of plutonic bedrock that is probably of Eocene (early Tertiary) age (between 38 and 55 million years ago). The maximum displacement on the Willit Ridge fractures is about 600 m, as measured by the offset of rock formations along their trace. FAULTS NEAR AUSTIN A conspicuous group of fractures is present in the vicinity of Skelly Gulch and Sevenmile Creek near the community of Austin in the west-central part of the Helena quadrangle (pl. 1). These faults bound a series of rectangular blocks of sedimentary bedrock between the Boulder batholith and small outlying bodies of plutonic bedrock, and probably are the result of uplift and col- lapse that occurred during emplacement of the plutonic masses. The displacement along several of these faults is as much as 60 m. FAULTS AT HELENA Five normal faults in and near the city of Helena have been mapped and described by Knopf (1913, pl. 7, p. 98; 1963). The largest of these fractures, called the Mount Ascension fault, extends northeastward from Dry Gulch along the southeast flank of Mount Ascension and disap- pears beneath slope wash a short distance east of Helena. It has a vertical displacement of about 230 m. West of that fault and parallel to it is a long fracture that runs from Orofino Gulch along the northwest flank of Mount Ascension and extends beneath slope wash in the east- ern section of the city. It has a vertical displacement of about 70 m. Both of these fractures probably end against the Bald Butte fault. A small fault with a displacement of about 35 m splays off the fracture that runs along the northwest side of Mount Ascension, and this splay extends a short way into Helena beneath slope wash about a kilometer south of the State Capitol. Farther west, a fracture extends north-northeastward from the head of Last Chance Gulch along the eastern foot of Mount Helena to the reservoir on the west side of Helena, beyond which it is concealed by slope wash. The vertical displace- ment on this break is about 80 m. On the north slope of Mount Helena is a small fault with a vertical displace- ment of only a few meters. It disappears beneath slope wash at the southwestern margin of the city. FAULTS WEST OF INTERSTATE HIGHWAY 15 AND NEAR MONTANA CITY Several normal faults cut sedimentary bedrock in the hills west of Interstate Highway 15 and in the vicinity of Montana City in the southwestern part of the East Hele- na quadrangle (pl. 2). The largest of these fractures extends northward across the boundary between Lewis and Clark and Jefferson Counties and ends against the Bald Butte fault about a kilometer southeast of Helena. It is about 3 km long and has a maximum vertical displacement of about 200 m. Two small normal faults lie east of the southern trace of this fracture; other normal faults are found along the upper part of Holmes Gulch, between Clark Gulch and Jackson Creek, and south and east of Montana City. The displacement on these fractures ranges from a few meters to perhaps as much as 100 m. FAULTS SOUTH OF LOUISVILLE STATION A series of small normal faults, mapped initially by Smedes (1966, pl. 1), are distributed along the northern front of the Elkhorn Mountains south of Louisville Sta- tion in the southeastern part of the East Helena quadran- gle (pl. 2). These fractures mainly trend north and northeast and are of short lateral extent. They cut sedimentary, volcanic, and plutonic bedrock. The largest fracture fol- lows the north fork of Spokane Creek in the southeast corner of the quadrangle. Smedes (1966, p. 99) estimated the maximum vertical displacement on this break to be several hundred meters. Faults with a vertical displace- ment of 100 m or more also are present along Sheep Creek and along the upper part of Corral Creek. Other faults along the front of the Elkhorn Mountains are generally much smaller and have vertical displacements from a few meters to perhaps as much as 60 m. Several of the fractures, including the break along Sheep Creek, end abruptly against the Bald Butte fault. CONCEALED ZONE OF NORMAL FAULTING IN HELENA VALLEY On the basis of gravity measurements made in the eastern part of Helena Valley, a concealed zone of normal faulting has been postulated in the vicinity of Lake Helena (Davis and others, 1963). The location of the zone is shown on plate 2. The fault zone has not been verified 20 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA by drilling or by seismic techniques, however, and is problematical. If the concealed fault zone is real, it might represent an old, long-inactive splay from the Spokane Bench fault, for the zone curves southeastward toward that fracture. THRUST FAULTS Four thrust faults are present in the Helena area -the Eldorado thrust fault, a thrust fault subsidiary to the Eldorado, the Soup Creek thrust fault, and a minor unnamed thrust fault. All are confined to the mountain- ous terrain in the northeastern part of the East Helena quadrangle (pl. 2). Other large thrust faults are present north and northeast of the area, the largest of which are the Hoadley-Lyons and Moors Mountain thrust faults (fig. 3). The thrust fractures are situated in the Montana disturbed belt, a broad zone of intricately folded and faulted rocks that extends from the Canadian border southward along the eastern front of the northern Rocky Mountains. Large thrust faults in the western part of this belt (for example, the Hoadley-Lyons and Eldorado thrust faults) appear to terminate at the Lewis and Clark line (fig. 3). The disturbed belt was formed during the later stages of the crustal disturbance that created the Rocky Mountains some 50-80 million years ago. There is no indication that any of the thrust faults in the belt have been rejuvenated in Holocene or Pleistocene time (last 2 million years) or that they have been associated with historic seismic activity. Consequently, they are considered to be inactive. ELDORADO THRUST FAULT In the Helena area, the trace of the Eldorado thrust fault extends eastward in the bedrock hills north of Lake Helena, bends sharply to the southeast at Eldorado Bar (after which it is named), and continues down the west side of the Big Belt Mountains to Market Gulch where it sharply ends against the Helena Valley fault (pl. 2). The Eldorado fracture is exceptionally well exposed where it crosses the Missouri River south of Eldorado Bar and again near the mouth of Trout Creek, north of York Road. North of the Helena area the fracture has been mapped in the Upper Holter Lake quadrangle by Robin- son and others (1969), and a segment of the fault farther north has been described by Bregman (1976). Along the Eldorado thrust fault the rocks to the south and west have moved up and over the rocks to the north and east a distance of several tens of kilometers, and the fracture extends far westward in the subsurface in the region north of the Helena Valley fault. The mass of rocks above the fault plane is called the upper plate of the thrust or the thrust sheet, and the mass of rocks below the fault plane is called the lower plate. The rocks that constitute the upper plate are bent into broad, gentle folds, whereas those that comprise the lower plate are crumpled into tight, closely spaced folds and are broken by subsidiary thrust faults of large and small magnitude. Following emplacement of the thrust sheet, the entire mass was subjected to further stress and the fault sur- face itself was warped. As a result, the trace of the Eldorado is quite sinuous (fig. 3), and the inclination of the fault varies in places from 20° to 50°. In general, however, the fault trends northwest and dips at a relative- ly low angle to the southwest. At the fault trace, the upper plate of the Eldorado is formed of shale and the lower plate is formed of limestone, shale, sandstone, and quartzite. Along the east-west segment north of Lake Helena, the shale at the base of the upper plate is intensively crushed and shattered by the fault movement, forming a zone of breakage as much as 50 m wide, but along the southeast segment, between Eldorado Bar and Market Gulch, the rock at this horizon is sheared but not fragmented. This marked difference in style of deformation is probably related to the orienta- tion of the fault with respect to the rocks in the lower plate. On the east-west segment, the thrust sheet cuts sharply across the stratification in the lower plate; on the southeast segment, it is essentially parallel to the stratification. Greater resistance to the fault movement on the crosscutting segment may have set up stresses in the overriding rock that caused the fracturing. THRUST FAULT SUBSIDIARY TO THE ELDORADO A thrust fault subsidiary to the Eldorado is present north of the trace of the Eldorado thrust in the terrain north of Eldorado Bar. This fracture marks the leading edge of a mass of younger sedimentary rocks several hundred meters thick that has been dragged across the underlying rocks by the Eldorado thrust sheet, perhaps as much as 2 or 3 km. The subsidiary thrust is inclined 10°-20° south, and its trace, though very sinuous, is generally parallel to that of the Eldorado. The fault is well exposed on the west side of the Missouri River along the road that leads to Hauser Dam. At that locality, white limestone in the upper plate rests on red shale and sandstone in the lower plate. The limestone is tightly folded, is broken by closely spaced joints, and is more intensely deformed than the rocks in the lower plate. SOUP CREEK THRUST FAULT The Soup Creek thrust fault cuts sedimentary bedrock north and south of Soup Creek, east of the Eldorado thrust fault. It trends northwest, dips 30°-70° southwest, and has a maximum displacement of several thousand meters. At the north, the fracture is folded in a broad arc NATURE OF EARTHQUAKES 21 and is cut by the subsidiary thrust along the Eldorado; to the south, it extends into the valley of Trout Creek and continues southeastward into the Canyon Ferry quadrangle. The Soup Creek thrust fault may have origi- nated during a period of intense folding that preceded emplacement of the Eldorado thrust sheet. MINOR THRUST FAULT A small thrust fault about 2 km long and with a displacement of only a few hundred meters lies between the Eldorado and Soup Creek thrust faults. It appears to have resulted from breakage of a tightly compressed fold in the sedimentary bedrock and, like the Soup Creek fracture, may have formed before emplacement of the Eldorado thrust sheet. NATURE OF EARTHQUAKES Earthquakes are sudden vibrations of the ground sur- face caused by the passage of seismic waves through the Earth's crust. In most instances, the seismic waves are generated by slippage along geologic faults. The focus or hypocenter of an earthquake is the point in the Earth's crust where the fault rupture begins and from which the first seismic waves originate, the epicenter is the point on the Earth's surface directly above the focus, and the depth of focus (or focal depth) is the distance between the epicenter and the hypocenter. The relationship of these parameters is illustrated graphically in figure 4. Earthquakes generally occur in sequences that consist of one or more foreshocks, a main shock, and a large num- ber of aftershocks. The focal depth of earthquakes ranges from 0 to 700 km. Calculated focal depths of earthquakes in Montana range from near the surface to about 20 km. Two basic types of seismic waves are produced by earthquakes: body waves, which travel through the Earth, and surface waves, which travel along the Earth's surface. The body waves are the P or primary wave and the S or secondary wave. The P wave is compressional, like that of sound, in which each particle vibrates in the direction of propagation. It travels at a speed of about 5% km/s in the upper crust. The S wave is transverse, like a radio wave, in which each particle vibrates at right angles to the direction of propagation. It travels about half as fast as the P wave. The surface waves, called the L or long waves, include the Love, Rayleigh, and other types of waves. They are generally of greater wavelength and period than the P and S waves. The Love wave pro- duces lateral shear in the horizontal plane, and the Ray- leigh wave produces an elliptical motion like that of wind-driven ocean waves. Love waves travel at about 4 km/s, and the Rayleigh wave is somewhat slower. In general, stronger ground motion is produced by body waves near the earthquake source and by surface waves at greater distance. When seismic waves reach the Earth's surface they induce a highly irregular vertical and horizontal oscilla- tion in the ground that may last from a fraction of a second to several minutes. The severity of the oscillation generally decreases with increasing distance from the earthquake source and is less for small earthquakes than for large earthquakes. Earthquake ground motion or ground shaking is extremely complex, and, in the source region, its duration and character depend not only on the magnitude of the shock and the distance from the source, but also on the physical properties of the rock and soil through which the seismic waves travel and on the geolo- gical structure of the earthquake site. Ground shaking is usually responsible for most of the structural damage that occurs during earthquakes. It also can trigger land- slides and other types of ground failure such as settle- ment and cracking. Destructive waves in lakes, reservoirs, and rivers may also result from intense ground shaking. The vibrations produced by earthquakes are recorded and measured by sensitive instruments called seismographs, which make a permanent, continuous record of the wave motions as a function of time. The seismograph records are called seismograms. The epicenter of an earthquake can be computed from the arrival times of seismic waves at three or more seismograph stations to an accuracy that depends upon the number and distribution of the stations. If the distribution of the seismograph stations is geographically unfavorable with respect to the earth- quake source, the error in epicentral location may be as much as several tens .of kilometers. Strong-motion accelerographs are commonly installed in the basements of buildings in seismically active areas to measure the vertical and horizontal acceleration of the ground during earthquakes. These instruments record acceleration as a function of time, and it is usually expressed as a fraction of the acceleration of gravity (980 ecm/s*). The accelerograph records are called accelerograms. Veloci- ties and displacements of the ground can be obtained by integrating the acceleration-time curves on an accelerogram. Such data are used by engineers in the design of earthquake- resistant structures and in the evaluation of the earth- quake performance of structures. The size of an earthquake is generally expressed in terms of magnitude, its local severity in terms of intensity. The magnitude of an earthquake is a measure of the energy released. Intensity is a measure of the local destruc- tiveness of an earthquake. An earthquake therefore has only a single magnitude, but its intensity varies from place to place. Earthquake magnitude is determined by measuring the amplitude of the trace of seismic waves on a seismogram. The concept was first introduced by Richter (1935, p. 7), 2s GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA Earth's surface /ED|Cemer | | | | | | | | | | | | | | | F—Depth of focus: Focus or hypocenter (point on fault surface where rupture begins) FIGURE 4.-Diagram showing the relation between epi- center, hypocenter or focus, and depth of focus of an earthquake. No scale. who defined magnitude as the common logarithm of the maximum trace amplitude of seismic waves, in microme- ters (1 micrometer = 0.001 mm), recorded on a Wood- Anderson torsion seismograph 100 km from the epicenter. Observations at distances other than 100 km were cor- rected to convert them to the standard distance. Richter magnitude was designed to measure the size of local earthquakes in California and could only be applied to shocks of relatively shallow focal depth within about 600 km of a recording station. It is designated as local magnitude, or MJ,. Subsequently, two magnitude scales were evolved to compensate for distance and focal depth: the M5 scale, based on surface-wave amplitude and designed for earthquakes with geocentric distances of 20°-160° (station to epicenter) and with focal depths less than 50 km; and the Mp scale, based on body-wave amplitude and designed for earthquakes at geocentric distances greater than 5° and with focal depths between 50 and 700 km. In general, the M5 and Mp magnitude scales are reasonably consistent with Richter's MJ, scale. The standard surface-wave magnitude formula used by the U.S. Geological Survey is Ms = log:, (A/T) + 1.66 log;, D + 8.3, where A is the maximum horizontal surface-wave ampli- tude in micrometers, Tis the wave period in seconds, and D is the geocentric distance in degrees (station to epicenter). The M § scale is usually computed from Rayleigh surface waves in the period range of 18-22 s. The standard body-wave magnitude formula used by the U.S. Geological Survey is Mb m loglo (A/T) + Q(Dyh)5 where A is the trace amplitude of a particular wave in the P-wave group, Tis the wave period in seconds, and Q is a correction factor that is a function of geocentric distance (D) in degrees and focal depth (A) in kilometers. The Mp scale is generally computed from P waves having a peri- od of 1 s. Because magnitude scales are logarithmic, a unit increase in scale value is equivalent to a tenfold increase in the trace amplitude. For example, an earthquake of magni- tude 8.0 represents a trace amplitude 10 times greater than that of a magnitude 7.0 earthquake, 100 times greater than that of a magnitude 6.0 earthquake, and so on. Although there is no upper or lower limit to magn- itude, the largest ever recorded was 8.9 and the lowest about -3. The relationship between the magnitude of an earth- quake and the energy it releases is given by the equation (Richter, 1958, p. 366) Logie E = 11.4 + 1.5Mg¢, where M5 is the surface-wave magnitude and E is the energy in ergs. A difference of one whole unit in magni- tude therefore corresponds to a factor of 105, or 31.6, in the amount of energy released. Thus an earthquake of magnitude 8.0 represents an energy release that is about 32 times greater than that of a magnitude 7.0 earthquake and almost 1,000 times greater than that of a magnitude 6.0 earthquake. Intensity is a measure of an earthquake's local severi- ty as determined by its effect on people and manmade structures and the changes it induces in the Earth's surface. The principal intensity scale used in the United States is the Modified Mercalli Intensity Scale of 1931 (see appendix), in which the observed effects of earth- quakes are grouped into a series of categories ranging from I to XII in order of increasing intensity. In large earthquakes, the intensity is "barely perceptible" at the fringe of the area over when the disturbance is felt, but becomes progressively greater toward the earthquake source where it may reach a level of "total damage." Intensity assignments are quite subjective, however, because no precise or well-defined set of rules exists for establishing them. The level of earthquake intensity at any point is large- ly a function of distance from the earthquake source, earthquake magnitude, local duration of ground shaking, and soil conditions. Earthquakes that occur in remote, uninhabited regions generally cannot be evaluated in terms of Mercalli intensity. The distribution of intensity at earthquake sites is commonly shown on maps by isoseismal lines, which are the estimated boundaries between regions of different Mercalli intensity rating outward from the epicenter. The area bounded by the innermost isoseismal line is the area of an earthquake where ground shaking is strongest. The data necessary to construct isoseismal SEISMIC HISTORY OF HELENA AREA maps are usually obtained by a systematic canvas of the local population in the affected area. In the absence of instrumental data, such maps may be used to locate earthquake epicenters and to determine their approxi- mate magnitudes. These maps are also useful in defining broad differences in the shaking pattern in various areas and the relation of shaking to local earth structure- facts that are valuable in studies of earthquake hazards. The isoseismal map of the main shock of the Helena earthquake of 1935, shown in figure 5, is an illustration of this kind of map. Earthquakes of magnitude greater than about 5.0 may be destructive. A magnitude 5.0 shock usually affects a relatively small area within a few kilometers of the epicenter. Within this area the duration of the stronger shaking may be only 1 or 2 s, yet such ground motion can be damaging to structures not designed to resist earthquake forces. An earthquake of magnitude 6.0 can produce damaging motion over an area of many hundreds of square kilome- ters and strong shaking that lasts for as much as 10 s. Helena, Montana, for example, was severely damaged by shocks of 6 and 6% in October 1935 (see following section), and an earthquake of magnitude 6.3, centered near Long Beach, California, in March 1933, ranks as one of the most destructive shocks in the history of the United States. Earthquakes of magnitude 7.0 or greater generally affect areas of thousands of square kilometers. In such shocks, intense ground shaking may last for several tens of seconds, and extensive ground breakage and landsliding usually occur. They often result in major disasters, such as San Francisco (1906), Tokyo (1923), Alaska (1964), and Guatemala (1976). SEISMIC HISTORY OF THE HELENA AREA GENERAL SUMMARY In Montana, earthquakes occur chiefly in the western, mountainous part of the State. This area is part of a seismically active belt (the Intermountain Seismic Belt) that includes western Montana, southeastern Idaho, and western Utah. The belt generally parallels a series of large faults, some of which have undergone displacements in relatively recent geologic time. Most of the earthquakes that have occurred in Montana in historic time have been centered in four seismically active areas: the Flathead Lake area, the Helena area, the Townsend-Three Forks- Bozeman area, and the Virginia City-West Yellowstone- Lima area. Areas of lower seismic activity are scattered throughout western Montana. The plains region, in the eastern part of the State, is an area of very mild seismic activity. Only the earthquake history of the Helena area is considered here. 283 Several hundred earthquakes have been felt in and near the Helena area since it was first settled in 1864. The principal localities at which these earthquakes were noted include Helena, Kenwood (a Helena suburb), Fort Harrison, Rimini, Birdseye, Austin, Marysville, Silver City, Hauser Dam, East Helena, Montana City, Clancy, Alhambra, and Jefferson City. Most of the earthquakes have been of weak to moderate intensity (II-IV), but in 1935, a severe earthquake struck the area and caused extensive damage. The main shock and a strong aftershock in that earthquake were of intensity VIII. The first earthquake on record in the Helena area was a strong shock of intensity VI in 1869. Other strong earthquakes, apart from those that occurred in 1935, include a shock of intensity IV-V in 1910, a sharp shock of intensity VI in 1925 (probably related to the Lombard earthquake), a jolt of intensity VI in 1930, and a strong shock of intensity VI in 1940 that was felt over an area of about 18,000 km. A notable increase in the general level of seismic activity (the number of minor earthquakes per year) occurred in 1945, during which a record number of 117 shocks were reported. Most of these were of weak (II-III) to moderate (IV ) intensity, but a strong shock of intensity V on June 25, 1945, was felt over an area of 15,500 km. Most recently, the area was shaken by three sharp shocks on July 18 and 19, 1975. The strongest, which occurred on the 18th, had a magnitude of 3.9. The earthquake record in the area is much too short to identify or predict any cyclic recurrence of earthquakes. Activity at an intensity level of I-V is almost certain to continue in the future. The possibility exists that an earthquake of intensity VI or greater might occur at any time. HELENA EARTHQUAKE OF 1935 The destructive earthquake at Helena in 1935 resulted in four deaths, about 50 injuries, and property damage of about $4,000,000 (Engle, 1936; Scott, 1936; Ulrich, 1936; Neumann, 1937). It consisted essentially of a strong foreshock of intensity VII on October 12, 1935, a main shock of magnitude 6% (intensity VIII) on October 18, and a powerful aftershock of magnitude 6 (intensity VIII) on October 31. On the basis of calculations from aftershock records, an epicenter lying about 5 km northeast of the center of the city at lat 46°37" N. and long 111°58" W. was adopted as representing the central point of all activity (Neumann, 1937, p. 46). Recently, however, Dewey and others (1972, p. 888; fig. 5, p. 889) recomputed the epicenter of the main shock of October 18 using new techniques and found it to lie about 22 km north of the October 31 aftershock at about lat 46°48" N. and long 112°01' W. (fig. 10). The earthquake of 1935 was characterized by an exceptionally large number of shocks -2,281 were recorded 24 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA from October 3, 1935, to the end of 1936 (Neumann, 1937, p. 56). Of these, 62 were foreshocks and 2,218 were aftershocks. The strong foreshock on October 12 was felt over an area of 181,000 km, the main shock over an area of 596,000 km, and the powerful aftershock over an area of 363,000 km. Strong aftershocks of intensity VI on October 27, November 21, and November 28, 1935, and on February 13, 1936, also were felt over a wide area. An isoseismal map of the main shock of the Helena earthquake of 1935 is shown in figure 5. The shock was felt over most of Montana, in southern Canada, over much of Idaho, as far west as Washington and Oregon, and south into Wyoming. The two small areas of low intensity outside the main area of disturbance, one in northwestern Washington and the other in southeastern Montana, have no obvious geological explanation. The foreshock on October 12 caused damage of about $50,000 in Helena, East Helena, and Fort Harrison. It toppled chimneys, cracked windows and plaster walls, and threw objects from tables and shelves. The main shock of October 18 caused damage of about $3,000,000 in Helena and East Helena and resulted in two fatalities and a few score injuries. Altogether, about 300 buildings in Helena sustained some form of serious damage from this shock; the fall of chimneys and brick veneer, the failure of gables, the cracking of windows and plaster, and the overthrow of objects were common through- out the city. Gravestones were twisted and overthrown in the cemeteries. Many large structures were extensively damaged by the main shock. These included two buildings at Intermountain Union College, the newly completed Helena High School, the Bryant Elementary School, the National Biscuit Company building, St. Joseph Orphan Home, the County Hospital, and the Kessler Brewery. Damage was slight to the State Capitol, the Federal Building, the St. Helena Cathedral, and the old high school. The powerful aftershock on October 31 caused an additional several hundred thousand dollars' damage in Helena and East Helena and resulted in two fatalities. Many structures weakened by the previous shocks were further damaged by the aftershock, and the north wing of the new high school collapsed (fig. 6). Damage in all of the shocks was mainly the result of ground shaking. Ground cracking was minor; only one small landslide was triggered; and a few rocks were dis- lodged and rolled down slopes in the mountainous areas. A photograph of the new high school in Helena taken shortly after the October 31 aftershock is given in figure 6, and representative views of some of the other damage sustained in Helena during the earthquake are presented in figure 7. The most extensive type of damage to buildings was the collapse of brick, tile, and stone veneer and the collapse of walls made of these materials, which resulted in the fall of roofs. Solidly constructed wood buildings and steel-framed structures with walls built of heavy stone (for example, the State Capitol, the St. Helena Cathedral, the Federal Building) generally sustained the least damage. The drastic damage to the new high school was attributed to the fact that lateral earthquake forces were not considered in the design of the building (Scott, 1936, p. 10). The aftershock on October 31 produced a horizontal ground acceleration of 115 em/s?, or about 12 percent of gravity, as measured by a strong-motion accelerograph installed in the basement of the Federal Building at Helena a few days after the main shock (Neumann, 1937, p.72). The portion of the accelerogram covering the principal motion of the aftershock is presented in figure 8. The maximum acceleration was on the north-south component, the duration of strong shaking was only about 3 s, and the vertical component of acceleration was generally less than either of the horizontal components. The Federal Building at Helena is built on solid dolomite bedrock, and the recorded acceleration of 115 em,/s? probably applied only to that particular locality and type of rock. Ground-motion characteristics must have varied considerably from place to place during the major shocks, as indicated by the distribution of damage. The earthquake produced a few small fissures in the ground surface (Scott, 1936, p. 14). Small cracks as much as several centimeters wide, 1 m deep, and 90 m long opened in gravel-surfaced roads near Lake Stanchfield, and, along the south and east shores of the lake, smaller cracks formed from which water and sand issued. A few cracks also formed in the floor of Helena Valley about 3 km northeast of Lake Stanchfield, one of which is shown in figure 9, and several small cracks opened near Clasoil in the southeastern part of the valley. The earthquake had a pronounced effect on ground water. The flow of water from numerous wells and springs increased, and many new springs opened where none had previously existed. The flow of water in Sevenmile Creek and in Prickly Pear Creek increased by as much as 25 percent after the main shock (Ulrich, 1936, p. 331), but no record is available as to how long the abnormal flow lasted. Small stationary waves formed in the gravel surface of upper Davis Street in the city of Helena during the 1935 earthquake (Ulrich, 1936, p. 334). The main shock on October 18 produced a group of waves that were oriented parallel to the street direction. They measured 64-71 ecm from crest to crest and had a maximum trough depth of 5 cm. Following the major aftershock on October 31, the waves were more numerous and the troughs were enlarged to a maximum depth of 10 ecm. Visible ground waves were reported moving across the floor of Helena Valley by several persons during the strong earthquake shocks on October 18 and 31 (Ulrich, 1986, p. 334). Scott (1936, p. 12) reported that a man SEISMIC HISTORY OF HELENA AREA 25 14° I 112° 10° ‘|[l]B° 195° 20° ”18° H|6° 50° - BRITISH COLUMBIA Spokane ago |- IDAHO I-III anl OREGON © Gleichen I l p Wisdom iwift Curren c Swift Current SASKATCHEWAN MONTANA _ _fui ~ WYOMING Pocatello | | | 1 FIGURE 5.-Isoseismal map of the main shock of the Helena earthquake on October 18, 1935. From Neumann (1937, fig. 6). standing in a field near Lake Helena on October 31 saw waves coming rapidly toward him and that he was thrown to the ground when they passed beneath his feet. This phenomenon, which has been reported in other parts of the world during large earthquakes, is not well understood. The seismic waves generated by an earthquake travel at much too great a speed to be observed and the ground motion produced by them is not a regular wave motion. It has been suggested that the appearance of visible waves may be an optical illusion caused when seismic waves emerge from the ground and change the refractive index of the air sufficiently to deflect light rays reaching an observer, the rapid changes in the ray path giving the ground an apparent wave motion (Richter, 1958, p. 131). However, the optical theory does not account for the man being forcibly thrown to the ground. Conceivably, his fall was a reaction to illusory waves. LOCUS OF SEISMIC ACTIVITY During a recent study of the Helena area (Freidline and others, 1976), in which seismic activity was monitored with portable seismographs, 97 small earthquakes were recorded from June 25 to August 18, 1973. The magnitudes of these earthquakes ranged from 0.0 to 3.0, and focal depths ranged from near surface to about 17 km. Epicenters were located to an accuracy of +2 to +4 km. In the survey, it was found that most of the epicenters were clustered in two areas-one about 8 km northwest of Helena south of the Scratchgravel Hills and the other about 20 km northwest of Helena in the vicinity of Threemile Creek, at the northwest corner of the Helena quadrangle. Significantly, these areas of high seismic activity lie along the trace of the Bald Butte fault, and this relation strongly implies that the earthquakes originated 26 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA FIGURE 6. - View of the north wing of Helena High School following the major aftershock on October 31, 1935. This facility, newly completed in August 1935 at a cost of about $500,000, was severely weakened by the main shock on October 18. Photograph courtesy of the Montana Bureau of Mines and Geology. on the Bald Butte fracture and that it may represent the locus of much of the current seismic activity in the Helena area. A plot of hypocenters of the earthquakes clustered south of the Scratchgravel Hills suggests that the fault plane dips about 60°S. (Freidline and others, 1976, p. 87). The epicenters of some earthquakes that occurred in 1935 and 1973 and the traces of principal faults in and near the Helena area are plotted in figure 10. The remarkable concentration of epicenters along the trace of the Bald Butte fault south of the Scratchgravel Hills and at Threemile Creek is readily apparent, and several epicenters also lie near the trace of the fracture in the Elliston quadrangle farther west and in the East Helena quadrangle to the southeast. The destructive aftershock at Helena on October 31, 1935, also may have originated on the Bald Butte fault. As determined by Neumann (1937, p. 46), the epicenter of that shock lies about 3 km north of the fault trace, but, considering the margin of error inherent in the epicenter location, the aftershock may well have originated on the fracture. The epicenter of the main shock of the Helena earthquake of 1935, as recomputed by Dewey and others (1972, p. 888), is near the trace of the Helena Valley fault as are several of the epicenters determined in the 1973 survey (fig. 10). Some of the 1973 epicenters also lie near the traces of the North Fork, Beartrap, Granite Butte, Marsh Creek, Prickly Pear, Hilger Valley, and Spokane Hills faults. Accordingly, these fractures may be seismically active and undergoing intermittent adjustment at depth. However, the frequency of seismic disturbance on them, as indicated by the plot of the 1973 epicenters (fig. 10), appears to be much less than the frequency of activity on the Bald Butte fault. The epicenters determined in the 1973 survey are also significant from a regional standpoint, for they indicate that the earthquakes were mainly concentrated along and within the Lewis and Clark line (see section on "Major strike-slip faults"). West of the Helena area, historic earthquakes reaching as much as magnitude 5 have occurred along this zone in the vicinity of Helmville, Dalton Mountain, Greenough, Ovando, Bonner, Ninemile, SEISMIC HISTORY OF HELENA AREA 27 FIGURE 7. - Views of some damage in Helena, caused by the earthquake of 1935. A, Destruction of outer wall of County Hospital. B, Damage to brick wall of Bryant Elementary School caused by the main shock on October 18. Most of the remaining wall fell during the major aftershock on October 31. C, Collapse of building resulting from failure of walls. D, Outward fall of unbraced brick and tile walls and collapse of warehouse roof. E, Fall of stone gables. This type of failure was common. Photographs courtesy of Montana Bureau of Mines and Geology. 28 C <«-»GO rege |'—0.1g—-1 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA VERTICAL COMPONENT NORTH-SOUTH COMPONENT 7 SECONDS I EAST-WEST COMPONENT FIGURE 8.-Portion of accelerogram of the October 31 aftershock of the Helena earthquake of 1935. From Ulrich (1936, fig. 6). Superior, and St. Regis, and numerous microearthquakes (small, instrumentally determined earthquakes), which resemble the swarm activity at Helena in 1945, have recently been recorded in the region around Ovando (Qamar, 1977, p. 756). This documented earthquake activity, together with geologic data developed by Reynolds and Kleinkopf (1977), supports the concept that the Lewis and Clark line is a regional locus of much of the earthquake activity in northwestern Montana and that it is a funda- mental intracontinental crustal break along which active fault movement is now taking place. SEISMIC RISK Three destructive earthquakes of record have occurred in Montana besides the Helena earthquake of 1935. They include a magnitude 6% shock of intensity VIII in 1925 centered near Lombard in the northern part of Gallatin County, a magnitude 6% shock of intensity VIII in 1947 centered south of Virginia City in the southern part of Madison County, and a magnitude 7.1 shock of intensity X in 1959 centered near Hebgen Lake in the southern part of Gallatin County. The magnitude 6% shock near Lombard was felt strongly in Helena, where it caused minor damage and reached intensity VI. On the basis of this strong earthquake activity, a large part of west- central and southwestern Montana is included, along with parts of southeastern Idaho and western Utah, in zone 3 on the seismic zonation map in the Uniform Building Code (International Conference of Building Officials, 1976). Zone 3 includes areas in which earth- quakes of intensity VIII or greater are expected to occur in the future. Recently, a ground-acceleration probability map for the contiguous United States was prepared by Algermissen EARTHQUAKE HAZARDS FIGURE 9.-Ground crack in the floor of Helena Valley, about 3 km northeast of Lake Stanchfield, caused by the earthquake of 1935. Sand and water were forced from the crack as a result of liquefaction at shallow depth. Photograph courtesy of Montana Bureau of Mines and Geology. and Perkins (1976, fig. 4). It gives an estimate of the maximum horizontal ground acceleration (expressed as a percent of gravity) to be expected that has a 90-percent probability of not being exceeded in 50 years. The accel- erations are estimated for hard rock. On this map, the maximum expected horizontal ground acceleration indi- cated for the Helena area is 38 percent of gravity (0.38 g). That acceleration is more than three times the horizontal ground acceleration recorded in the basement of the Federal Building during the destructive aftershock of the Helena earthquake on October 31, 1935. 29 EARTHQUAKE HAZARDS Earthquakes produce movements of the Earth's surface. These movements, which can damage manmade struc- tures and the ground surface and result in fatalities, are called earthquake hazards. They include ground shaking, ground failure, and seiche and surge-induced flooding. The main characteristics and potential severity of these hazards are outlined in this section of the report. A series of integrated earth-science studies published as U.S. Geological Survey Professional Paper 941-A (Borcherdt, 1975) comprehensively define the nature of earthquake hazards in the San Francisco Bay region of California. That publication is commended to readers who wish to gain a more detailed understanding of the complexities of the earthquake process and the diversity of earthquake effects than can be obtained from this summary report. The studies in Borcherdt (1975), which are widely applicable to other areas of high seismic risk, include papers on faults and future earthquakes (Wesson and others, 1975), estimation of bedrock motion at the ground surface (Page and others, 1975), differentiation of sedimentary deposits for purposes of seismic zonation (Lajoie and Helley, 1975), response of local geologic units to ground shaking (Borcherdt, Joyner, and others, 1975), liquefaction potential (Youd and others, 1975), land- slides (Nilsen and Brabb, 1975), and predicted geologic effects of a postulated earthquake (Borcherdt, Brabb, and others, 1975). GROUND SHAKING Earthquake-generated ground shaking is the vertical and horizontal vibratory motion produced when seismic waves originate at a point of rupture on a fault surface and pass through the Earth's crust. This motion is extreme- ly complicated and highly irregular, for it is the sum of many different harmonic oscillations of the ground, each with its own frequency and amplitude. In most instances it is the chief cause of damage during earthquakes and is the principal hazard associated with them. The intensity and nature of ground shaking largely depend upon earth- quake source characteristics such as magnitude and size of fault rupture and upon distance from the source, but shaking also may be greatly influenced by surficial depos- its and soils, by discontinuities in rock strata, and by geologic structure at the earthquake site. RELATION TO MAGNITUDE AND DISTANCE The intensity of earthquake ground shaking generally increases with earthquake magnitude and decreases with distance away from the earthquake source. These rela- tions are indicated by the enlargement of the area of intense shaking and the enlargement of the area over 30 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA 47°00 1 12'°30’ 1 12|°1 5" 112°00" 111945" O 4645° Lake Helena | uy (@ 9 \ )_1 < / i- Z ( [r 46°30 - 2 )E Z O O 1 2 1 | 0 5 10 115 KILOMETERS | 1 1 T I I 0 5 10 MILES EXPLANATION O EPICENTERS LOCATED IN 1973-From --- STRIKE-SLIP FAULT-Arrows show inferred Freidline and others (1976, fig. 6) relative direction of horizontal movement; dashed where inferred; dotted where concealed NORMAL FAULT-Dashed where inferred; dotted where concealed; U, upthrown side; D, downthrown side O EPICENTER OF MAIN SHOCK OF 1935 EARTHQUAKE by Dewey and U others (1972, p. 888) Torna" 69 EPICENTER OF PRINCIPAL AFTERSHOCK OF 1935 EARTHQUAKE-From Neumann (1937, p 46) FIGURE 10. - Map showing the location of some earthquake epicenters and the traces of principal faults in and near the Helena area. Named faults: B, Beartrap; BB, Bald Butte; GB, Granite Butte; HEV, Helena Valley; HV, Hilger Valley; MA, Mount Ascension; MC, Marsh Creek; NF, North Fork; NV, Northwest valley; PP, Prickly Pear; RR, Regulating Reservoir; SB, Spokane Bench; SC, Silver Creek; SH, Scratchgravel Hills; SPH, Spokane Hills. which earthquakes are felt as magnitude increases and | intensity variation as a function of source distance for by the progressive lessening of earthquake effects, such | different earthquake magnitudes was made by Barosh as damage, away from the source. A detailed study of | (1969, p. 16-24). EARTHQUAKE HAZARDS pal The increase in intensity with magnitude is also appar- ent in the way in which ground motion is perceived by people in the source region of an earthquake. Small to moderate earthquakes (those with magnitude less than 5.0) are usually felt as a sudden tremor or sharp jolt that lasts for a second or less. Strong earthquakes (those with magnitude between 5.0 and 6.9) produce vibrations of much greater amplitude, and the shaking is felt as an intense jolting, rocking, or rolling motion that lasts for several seconds, followed by weaker tremors that may continue for as much as a minute. Major earthquakes (those with magnitude between 7.0 and 7.9) and great earthquakes (those with magnitude 8.0 or more) gener- ate motion that is characterized by oscillations of very large amplitude, and the shaking is perceived as a vio- lent tossing and lurching of the ground that may last for many seconds, followed by progressively weaker trem- ors that may continue for as much as several minutes. As a rule, the intensity of earthquake ground shaking decreases rapidly near the earthquake source and then more and more slowly as the distance increases. However, this decline in intensity usually varies with direction away from the source, and so isoseismal lines are rarely circular and either show an elliptical elongation in the direction of some major structural trend or are irregular. For example, the isoseismal map of the main shock of the Helena earthquake of 1935 (fig. 5) shows a weak but decided elongation parallel to the main structural grain of the Rocky Mountains. Locally, the pattern of shaking is strongly influenced by the distribution of surficial deposits at an earthquake site because ground motion is intensified in these materials. Consequently, isolated areas of intense shaking may occur on soft ground far from the earthquake source. The size of the fault rupture that produces an earthquake also may greatly affect the distance-intensity relations of ground shaking. If the fault breakage extends to the surface, heavy shaking is generally concentrated in a narrow region along the length of the ruptured fault, and isoseismal lines are highly elongated parallel to the fault trace. AMPLIFIED SHAKING ON SURFICIAL DEPOSITS Earthquake intensity has been reported to be greater on unconsolidated surficial deposits than on nearby bed- rock in many earthquakes. This relation is probably due, at least in part, to amplification of the ground motion in the surficial materials, particularly for longer period motion. It may also be due in part to increased duration of shaking on such materials. Other effects of the surficial deposits are perhaps to lengthen the period of the domi- nant vibrations and to increase the degree of periodicity in the motion. Quantitative data on ground-motion amplification in surficial deposits were obtained by Gutenberg (1957) in a study carried out in southern California in which the shaking characteristics of small, natural earthquakes in areas of alluvium (surficial deposits) were compared to the ground motion of the same earthquakes on crystal- line bedrock. In that study it was found that, for ground vibrations having periods of 1-1% s (long-period oscillations), the ratio of amplitudes at localities on fairly dry alluvi- um more than 500 ft (152 m) thick to amplitudes on bedrock was as much as 5:1 and ranged to as much as 10:1 on water-saturated ground; and it was further observed that vibrations with periods of about 4 s produced rela- tively heavy shaking in areas with a cover of alluvium only about 100 ft (30 m) thick (Gutenberg, 1957, p. 238). Perhaps even more significant than the amplification effects were the results concerning the duration of ground motion, which showed that relatively strong shaking on alluvium lasted several times longer than on crystalline bedrock and that shaking on deep alluvium lasted longer than on thin alluvium (Gutenberg, 1957, p. 235). Investigations in the San Francisco Bay region of California (Borcherdt, 1970; Borcherdt, Joyner, and others, 1975) have demonstrated that certain frequencies of ground shaking at low-strain levels are substantially amplified in some surficial geologic units. For example, recordings of low-intensity motions in that area produced by nucle- ar testing at the Nevada Test Site showed that horizon- tal ground velocities were five to eight times greater on the surface of bay mud than on nearby bedrock (Borcherdt, 1970, p. 35; Borcherdt, Joyner, and others, 1975, p. A56). Probably the ground-motion amplitudes measured for small earthquakes cannot be linearly extrapolated to the much stronger motions that are associated with destruc- tive earthquakes. Furthermore, the few comparative mea- surements of stronger motion that are available are insufficient to draw meaningful conclusions about the shaking behav- ior of surficial geologic units at high-strain levels. However, the distribution of Mercalli intensity for some earth- quakes suggests that some high-intensity motion pro- duced by large shocks is greatly magnified in surficial deposits, particularly longer period motion that is close to the fundamental vibrational frequency of the materials. In addition, strong-motion data obtained during the magnitude 6.5 earthquake at San Fernando, California, in 1971 appear to indicate that certain parameters of high-strain motion may be significantly amplified in soils or surficial deposits. Evidence of strongly amplified shaking in unconsolidated surficial materials has been documented for several large earthquakes. For example, Duke and Leeds (1959) noted in a study of the magnitude 7.5 Mexico earthquake of July 28, 1957, that the intensity of ground shaking in Mexico City, about 250 km from the earthquake source and 32 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA founded on deep alluvium of ancient Lake Texcoco, was much greater than at localities situated about 100 km from the source and founded on firmer deposits or on granite bedrock. The increased intensity at Mexico City, which contributed to extensive damage to taller structures, was attributed mainly to enhanced long-period vibrato- ry motion in the Lake Texcoco deposits. Similar ground- motion effects at Mexico City were induced by distant, strong earthquakes in 1962 (Zeevaert, 1964) and in 1978. Much of the heavy damage to buildings during the mag- nitude 6.4 Caracas, Venezuela, earthquake of July 29, 1967, also has been ascribed to destructive resonance effects that accompanied amplified shaking of surficial deposits in Caracas Valley (Seed and others, 1972, p. 787-806). Other earthquakes for which there is substan- tial evidence that damage to buildings was directly relat- ed to intensified shaking on underlying surficial materials are the magnitude 8.3 San Francisco, California, earth- quake of 1906 (Wood, 1908) and the magnitude 5.6 and 5.7 Santa Rosa, California, earthquakes of 1969 (Miller, 1970). Boore and others (1978, p. 17-18) compared strong- motion data recorded on rock (bedrock ) and soil (surficial deposit) sites during the 1971 San Fernando, California, earthquake over a distance range of 15-100 km. Their analysis showed that peak horizontal ground accelera- tion was not significantly different on the bedrock and soil sites, whereas peak horizontal ground velocity and peak horizontal ground displacement were significantly great- er on the soil sites. Accordingly, they "tentatively con- clude that amplification of velocity and displacement is a real effect associated with soil sites." The precise nature of the amplification mechanisms in the soils is unknown. SHAKING AND DAMAGE Almost all structures- single-family dwellings, high- rise buildings, powerplants, bridges, dams, smoke stacks, water towers, and other structures subject in some degree to damage from ground shaking during an earthquake. This damage is potentially hazardous to human beings, can be very costly to repair, and, if extensive, can affect the functioning of an entire community. In general, the degree of damage imparted to a structure by ground shaking depends to a large extent on its original engineer- ing design; consequently, earthquake provisions are incor- porated into building codes in many seismically active areas of the world. In the absence of proper engineering precautions, damage from large earthquakes can be almost total. The destruction of the high school at Helena on October 31, 1935, is an example (fig. 6). Most of the damage produced by earthquake ground shaking is caused by forces resulting from the horizontal component of motion, which is essentially unresisted by gravity. Provision against lateral forces is therefore of utmost importance in the design of buildings and other structures to make them earthquake resistive (Seismology Committee, Structural Engineers Association of California, 1975, p.1C-3C). All engineering structures are designed to resist the vertical force of gravity and are thus general- ly capable of supporting the additional vertical load of an earthquake. Only in great earthquakes, in which vertical displacement of the ground may reach many centimeters and in which accelerations may approach or even exceed the acceleration of gravity, is a vertical seismic overload likely to cause failure. Damage from earthquakes is closely dependent upon dynamic characteristics of the ground motion such as acceleration, velocity, displacement, duration, and fre- quency or wave-period content. The acceleration, velocity, and displacement of the earth motion are indicative of the force that is applied to the ground and to structures during shaking; duration is responsible for certain types of failure that are time-dependent and that result from long-continued vibrational stress; and frequency con- tent governs amplification and resonance effects in unconsolidated deposits. These parameters are impor- tant in earthquake engineering and in seismic hazards assessment, where quantitative estimates of ground shak- ing are necessary for design purposes and site evaluation. Only a few general observations concerning the influence of these factors on damage are given here. The acceleration, velocity, and displacement of earth- quake ground motion generally define the magnitude of the stresses and strains that the Earth's surface and structures undergo during an earthquake. Acceleration is directly related to the force induced on structures and thus to their structural response during shaking; veloci- ty determines input energy and thus tends to correlate with the severity of damage; and displacement is a mea- sure of the strain induced by the motion and is responsi- ble for damage resulting from excessive deformation. As a rule, acceleration, velocity, and displacement increase with earthquake magnitude at any given point from the earthquake source and decrease with distance away from the source, but the rate of decrease is somewhat less for velocity and displacement than for acceleration. In general, damage tends to increase as acceleration, velocity, and displacement increase, but this relation is complicated because of the variable response of surficial deposits and manmade structures to strong ground motions. Some representative values for horizontal acceleration, velocity, and displacement obtained from accelerograms for several earthquakes in the magnitude range 5.3-7.2 are listed in table 1. Strong-motion records from the source region of earth- quakes of magnitude greater than 6.0 are scarce. Data EARTHQUAKE HAZARDS 33 TABLE 1. - Selected strong-motion data for several earthquakes in the magnitude range 5.3-7.2 [From Boore and others, 1978, p. 33-40] Distance! - Horizontal Horizontal - Horizontal Earthquake Magnitude - Site (km) acceleration - velocity _ displacement Duration? E (cm/s) (cm) (s) Daly City, Calif.; 1971... ...... 5.3 Rock 8.0 0.127 4.9 2.3 1.6 Parkfield. Calif., 1966 :... ..... 5.5 Soil 6.6 0.509 78.1 26.4 12.1 Oroville, Calif.. 1975 ....;...... 5.7 Rock 8.0 0.110 5.0 1.6 0.0 Imperial Valley, Calif., 1940. . . . . 6.4 Soil 12.0 0.359 36.9 19.8 29.3 San Fernando, Calif., 1971. . . ... 6.4 Rock 3.2 31.251 113.2 87.7 13.5 Puget Sound, Wash., 1949. . . . .. 7.1 Soil 48.0 0.306 21.4 10.4 22.3 Kern County, Calif., 1952 ...... 7.2 Soil 42.0 0.196 17.7 9.1 19.6 !Shortest distance in kilometers to the surface of fault slippage. ?Time interval between first and last acceleration peaks equal to or greater than 0.05 g. ©Highest ever measured. have been obtained only in the magnitude 6.5 San Fernando, California, earthquake of 1971 and the magnitude 6.4 Imperial Valley, California-Mexico, earthquake of 1979. On the basis of considerations that allow for the effects of surface topography on the peak acceleration of 1.25 g, on the peak velocity of 113 cm/s, and on the peak dis- placement of 38 ecm recorded at a distance of 3 km from the causative fault during the 1971 San Fernando earth- quake (see table 1), Boore and others (1978, p. 25) con- cluded that "it is difficult to accept estimates less than about 0.8 g, 110 cm/s, and 40 em, respectively, for the mean values of peak acceleration, velocity, and displace- ment at rock sites within 5 km of fault rupture in a magnitude 6.5 earthquake." Significantly, those esti- mates generally appear to be substantiated by prelimi- nary strong-motion records obtained close to the source of the 1979 Imperial Valley earthquake (Porcella and Matthiesen, 1979, table B). Substantially higher values of acceleration, velocity, and displacement may be reached in the source area of larger shocks. For example, Page and others (1972, table 2) estimated that the values for maximum horizontal ground acceleration, velocity, and displacement, respectively, may reach 1.25 g, 150 cm/s, and 100 ecm within a distance of a few (3-5) kilometers of a causative fault in a magnitude 8.5 earthquake. The duration of ground shaking is an important factor in producing damage in large earthquakes, for failure in manmade structures and the initiation of certain types of ground failure are time dependent and result from a progressive weakening as earth vibration continues. The critical factor in severe earthquake damage is the num- ber of stress pulses imparted by the ground motion at potentially damaging levels of acceleration, velocity, and displacement. Accordingly, the incidence and degree of failure tend to become greater as the duration of shaking increases. An excellent example of the duration effect is provided by the Helena earthquake of 1935 in which many structures weakened by the main shock on Octo- ber 18 were subsequently badly damaged or collapsed by the strong aftershock that followed on October 31. The duration of strong ground shaking is commonly defined as the interval of shaking above a threshold acceleration value of 0.05 g recorded by a strong-motion accelerograph, or, stated somewhat differently, the interval on an accelerogram between the first and last acceleration peaks that have a value equal to or greater than 0.05 g. Duration so defined is called the "bracketed duration" of an earthquake. It increases with magnitude and decreases at a fairly rapid rate away from the earthquake source due to attenuation of the ground motion. The bracketed durations for some earthquakes in the magnitude range 5.3-7.2 are listed in table 1. Much higher values may be reached in the source region of larger shocks. The frequency content of earthquake ground motion is a vital factor in earthquake damage consideration. As previously noted, the amplification of ground shaking on surficial deposits is strongly dependent on frequency. In addition, resonance of surficial deposits and of manmade structures during earthquakes, which can be highly destructive, is directly related to frequency content. Resonance effects can occur in surficial materials or in structures if the fundamental vibrational frequency of the deposits or of the structures is close to frequencies contained in earthquake ground motion. Damaging oscil- lations caused by resonance are most likely to occur in a structure whose fundamental frequency coincides with that of the ground, for in that circumstance the effects of site resonance and structural resonance are additive. Accordingly, taller buildings may be stimulated into dangerous oscillation on thick accumulations of surficial deposits, whereas lower structures may respond with damaging oscillation on thinner bodies of unconsolidated materials or even on firm ground. Resonance of the ground and of structures during earthquakes is one of 34 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA the main reasons that damage increases with magnitude, for the stronger shocks produce a greater range of vibra- tion frequencies that may coincide with the fundamental frequencies of buildings and the supporting ground. In California, a site factor is usually included in seismic de- sign calculations to account for resonance effects (Seis- mology Committee, Structural Engineers Association of California, 1975, p. 26C-28C). GROUND FAILURE Large earthquakes commonly produce secondary effects that involve sudden, permanent failure of the ground surface. The most common types of failure are landsliding, liquefaction-induced failure, surface faulting, regional land displacement, settlement, ground cracking, ridging and furrowing, and ground churning. Any one of these effects can be damaging, even catastrophic, and an under- standing of their physical nature and of how and where they may originate is important in efforts to reduce earthquake hazards. The degree to which ground failure takes place during an earthquake generally correlates with the intensity and duration of ground shaking and with the extent of geologic features and materials at the earthquake site that are prone to failure. In Montana, ground failure was extensive in, for example, the Lombard earthquake of 1925 (Pardee, 1927, p. 8-10) and in the Hebgen Lake earthquake of 1959 (Hadley, 1964; Witkind, 1964a, 1964b). LANDSLIDING Landslides are produced by natural movement of rock and soil down slopes. They form in all types of rock materials and from many different causes, and they move by many mechanisms. In scale, they range from individual blocks of rock that tumble down steep slopes, through small earth slumps a few tens of meters across, to ava- lanches of rock that may travel several kilometers and involve millions of cubic meters of material. Strong earthquakes can effectively increase the forces acting to cause failure on slopes. Earthquake ground motion thus commonly triggers landsliding, chiefly on steep, marginally stable slopes where the downslope component of the force of gravity is high. Seismically induced landslides have caused great damage, numerous fatalities, and extensive disruption of travel in many parts of the world. A classic example was the catastrophic rock slide that plunged into the canyon of the Madison River during the major earthquake at Hebgen Lake, Montana, in 1959 (Hadley, 1964, fig. 54). In addition to obviously causing landslides associated with the period of shaking, earthquake ground shaking also may loosen and weaken deposits on slopes so much that another event may trigger a slide failure weeks or even months after the earthquake disturbance has ceased. The land- slide hazard associated with earthquakes therefore may persist long after the main seismic event. The enormous damage that earthquake-caused land- sliding may inflict is well illustrated by landslip effects that occurred during the great Indian (Assam) earthquake of 1897 (magnitude 8.7). In that earthquake, as described by Oldham (1899, p. 111-123), high, steep bedrock slopes in the hills in the area of major shaking were stripped bare of vegetation, soil, and loose rock, all of which plunged into the bottom of valleys and choked them with huge masses of debris. Significantly, considering slopes of comparable height and steepness, the landsliding was notably more severe in terrain underlain by sedimentary bedrock (sandstone and limestone) than in terrain formed of granitic (plutonic) and crystalline metamorphic rocks. Landslides can be described by the mechanisms that move them, by the type of material in which they develop, by their velocity, and by their displacement. Keefer (1984) studied 40 historical earthquakes and identified 14 types of landslides "caused by seismic events" (p. 420). Several common or representative landslide mech- anisms that can operate during earthquakes to produce slides are slump or rotational slip, earthflow, and rock- fall. Earth lurching, a type of movement characteristic- ally associated with earthquakes, also can produce slides in rock and unconsolidated material. Landslides produced by mechanisms like these are sketched in figure 11 and briefly described in the following paragraphs. Special kinds of landslides associated with liquefaction during earthquakes are discussed in the next section of the report. Slump and rotational slip (fig. 114) are common slide- producing processes. Slumps generally form on steep to moderate slopes in surficial deposits or other soft earth materials and are a common feature at the sides of val- leys, along stream embankments, and in deep roadcuts. Slumping ordinarily begins along a horseshoe-shaped fracture in the ground that curves beneath the slide mass; downward and outward rotational slip along this surface moves the slide. Commonly, steep transverse cracks form, which curve downward toward the front of the moving mass and may merge with the basal slide surface. Slump- ing can occur suddenly and rapidly, but more commonly it occurs gradually and the slide moves very slowly. Earthflows (fig. 11B) are not as common as slumps, but usually they are longer and cover a much larger area. They form on gentle, moderate, or steep slopes and generally originate in moist or water-saturated surficial deposits, soils, or other loose earth material, although some are formed in fragmented bedrock. In this type of slide, the boundary between the moving mass and the underlying stable rock is not a well-defined slip plane but instead is a transition zone in which movement gradually diminishes with depth. In a true earthflow, the entire sliding mass is mobilized as a viscous fluid that EARTHQUAKE HAZARDS 35 FIGURE 11. -Types of landslides classified according to their mechanism of movement. A, slump or rotational slip; B, earth flow; C, rockfall; D, slide caused by earth lurching. flows downslope; the velocity and displacement of the material are greatest at the surface of the mass and least at the base. Most earthflows move very slowly by the process referred to as creep, and they may move long distances if the slope characteristics are favorable. Some earthflows, composed of solid bedrock fragments, ac- tually resemble glaciers, where the flowing mass is fed by spalling off of rock at a headward scarp that con- tinually supplies new material to the flow. These slides, which commonly contain water or ice in void spaces, usually form in steep, mountainous terrain. Rockfalls (fig. 11C) are a common slide process on steep slopes formed of brittle bedrock, and Keefer (1984, table 4) listed rockfalls and rock slides as "very abun- dant" (his most abundant class) among earthquake- induced landslides. In such slides, the moving rock mass falls, rolls, bounces, or slips down a slope-generally rapidly -and has little or no coherent contact with the underlying stationary base. Rockfalls are of short lateral extent, although they may move considerable distances vertically (as when rocks are dislodged from high cliffs), and if they fall into a river or lake, their influence may travel far. Because they are largely confined to mountain- ous areas, damage caused by rockfalls may often be minimal, but when they cause damage-directly or in- directly -it can be severe. Earth lurching (fig. 11D) is characteristically asso- ciated with earthquakes. Earth lurching can produce a 36 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA peculiar wedging apart of surficial deposits or other soft earth materials by back-and-forth earthquake motion; slides due to lurching can take place at right angles to the margin of steep slopes such as are found along bluffs, streambanks, lakeshores, and artificial road and railway embankments. Such slides result from yielding of ground toward the unsupported face of a slope. First, a series of nearly parallel cracks or fissures form, separating the ground into rough blocks; as shaking continues, the outer block at the slope margin slides down as an intact mass. Successive slumping of other blocks can produce a slump form resembling a flight of stairs. Minor sliding of this sort may occur along banks and bluffs in strong earth- quakes, but extensive sliding due to lurching is asso- ciated with shocks of magnitude 8.0 or more in which the duration of strong shaking may be several-score seconds. In the magnitude 8.4 Bihar-Nepal (Indian) earthquake of 1934, earth lurching and the resulting landforms were especially common along lake shores, riverbanks, and embankments of artificial fill, and, in numerous instances, road and railway foundations as much as 2 and 3 m high were quickly reduced to the level of the surrounding country by the lurching process (Dunn and others, 1939, p. 38-39). Somewhat similar lurching occurred on water-saturated level ground in the Muzaffarpur district during the Bihar-Nepal earthquake (Ghosh, 1939). The presence of slope is a prerequisite of all landslides, for a tangential component of the force of gravity paral- lel to the surface of a sliding mass is necessary for movement to occur. In simple mechanical terms, land- slides result when the downslope component of the force acting on a rock mass exceeds the shearing strength of the material and causes it to separate from adjoining stationary rock and to move downward under the influ- ence of gravity. A slide therefore implies either that the force acting on the material was increased or that the shearing resistance of the material was lowered, and, because both of these conditions may be induced by ground shaking, landsliding is common during earth- quakes. Under normal conditions, most landslides result either from oversteepening of slopes by erosion or by man's activities, which increases the downslope com- ponent of force, or from a decrease in strength of the slope materials caused by heavy rainfall, removal of vegetation, or weathering. Many complex factors control the stability of slopes and their susceptibility to landsliding. Steepness is a primary factor -the larger the angle of slope, the greater the downslope component of gravity acting upon under- lying soil or rock. Landslides are therefore more abun- dant on steep slopes than on gentle slopes. For example, in the San Francisco Bay region of California, it was determined that landslides are common on slopes of more than 15 percent, few on slopes of 5 to 15 percent, and virtually absent on slopes of less than 5 percent (Nilsen and Brabb, 1975, p. A81). Landslide susceptibili- ty is also controlled by the types of rock or soil that underlie slopes and by the structural characteristics of the slope materials. In general, landslides are more abun- dant in thick soils, surficial deposits, and soft sedimenta- ry rocks such as clay and shale, but the largest slides occur in bedrock. Structures in rocks such as joints, fissures, bedding planes, and faults, and the orientation of these features with respect to slopes, can affect slope stability and the potential for landsliding. A particularly hazardous feature is the orientation of bedding planes parallel or nearly parallel to the slope of hillsides. The stability of slopes is also influenced by moisture content. The addition of water to surface rocks and soils lowers their resistance to sliding by increasing load weight, establishing pore-water pressure and dissolving mineral cement. The incidence of landsliding is therefore great- est in regions of wet climate. Other factors that affect slope stability are the amount and kind of vegetative cover; the degree to which slopes are steepened or undercut by erosion; and the extent of land modifications produced by man. Because the susceptibility of slopes to landsliding depends on so many variables, about which exact data are usually lacking, evaluation of regional landslide po- tential is generally imprecise. The incidence of landsliding tends to increase as earth- quake magnitude increases. The shocks of magnitude 6 and 6% in the Helena, Montana, earthquake of 1935 produced only minor landsliding in the form of a few rockfalls in the surrounding mountains and a small slump that covered part of U.S. Highway 91 in the valley of Prickly Pear Creek about 11 km south of Helena (Scott, 1936, p. 13). Landsliding was much more prevalent in the magnitude 6% Lombard, Montana, earthquake of 1925. It produced numerous rockfalls and small slides on steep slopes and cliffs and one large slide, estimated at about 30,000 m, that blocked the valley of Sixteenmile Creek and covered the railroad near Deer Park (Pardee, 1927, p. 8-10). The slides in the 1925 earthquake were most numer- ous within 20-24 km of the epicenter, but some rockfalls occurred as far as 65 km away (Pardee, 1927, p. 9). The magnitude 7.1 Hebgen Lake, Montana, earthquake of 1959 triggered extensive landsliding, ranging from innu- merable small rockfalls and slumps, through large slides down steep slopes, to the massive avalanche of some 30.5 million m of bedrock and loose slope debris that slid into the canyon of the Madison River below Hebgen Lake (Hadley, 1964, p. 107-121). All of the fatalities (28) incurred from the Hebgen earthquake were a direct result of landsliding. Timber and road damage caused mainly by slide processes exceeded $11,000,000 (Coffman and von Hake, 1973, p. 73). Major landsliding during the Hebgen quake was concentrated in a 2,600-km> area around the earthquake epicenter, but many smaller landslides and rockfalls occurred far outside this region, particularly in the northern part of Yellowstone National Park and in EARTHQUAKE HAZARDS 37 the canyon of the Yellowstone River near Gardiner, Mon- tana (Hadley, 1964, p. 122-123). LIQUEFACTION-INDUCED FAILURE Earthquake-generated liquefaction may be defined as the process whereby consolidated water-saturated sedi- ments are transformed into a fluid state as a result of build-up of hydrostatic pressure between the sediment grains. Silts and fine-grained sands are the sediments most susceptible to liquefaction, but the process also can occur in coarser materials and even in gravel. Liquefac- tion has been recognized as the underlying cause of many catastrophic landslides and of other types of destruc- tive ground failure during earthquakes, and a renewed focus on the problem in recent years has greatly advanced our understanding of the mechanical principles that gov- ern the process and the types of ground failure that are associated with it (Youd, 1973). Liquefaction occurs when earthquake vibrations cause the grains in a layer of water-saturated sediment to rearrange themselves into a more compact state. As grain reorientation takes place, grain-to-grain load stress is temporarily reduced, and part of the stress is transfer- red to the water that occupies the pores between the grains. This transfer of stress causes an increase in the hydrostatic pressure, which, in turn, reduces the shear strength of the sediment. If the hydrostatic pressure reaches a value equal to the confining pressure (the pressure exerted by the weight of overlying deposits), the sediment may transform into a viscous liquid and begin to flow. Other effects commonly occur in conjunc- tion with the liquefaction. When the ground vibrations cease, reconsolidation of the liquefied layer may cause pore water to move into overlying sediments, and this process may culminate in the ejection of water and sedi- ment at the surface in the form of sand boils or fountains, or even in a general condition of water seepage that leads to flooding of the ground surface. The overall degree to which liquefaction takes place in an earthquake depends upon the extent of sediment cover susceptible to the pro- cess and upon the intensity and duration of ground shaking in the affected area. Liquefaction itself does not present a serious problem during earthquakes unless it leads to movement or settling or flooding of the land surface. Ground dislocation associated with liquefaction may be grouped into three basic categories on the basis of the mechanics of the failure process: flow landslides, lateral- spreading landslides, and quick-condition failures (Youd, 1973; Youd and others, 1975). Flow landslides result when masses of loose granular sediment at and near the ground surface are liquefied and slope conditions permit a large amount of unrestrained flow. They generally form on moderate to steep slopes as liquefied flows or as slides composed of large, discrete blocks of cohesive sediment riding on liquefied flows (Youd, 1973, p. 7). Such slides may move long distances (as much as a kilometer or more) and cover wide areas of the land surface; they are by far the most damaging type of slide caused by liquefaction. Lateral-spreading landslides result when layers of loose to moderately dense material become liquefied at shal- low depth and movement is restricted to distances of a few tens of meters or less. These slides usually form on gentle slopes as slow-moving masses that spread laterally, and their surfaces commonly undergo cracking and dif- ferential settlement, especially at the margins (Youd and others, 1975, p. A72). Such slides can be very damaging to structures located on or in the moving mass. Quick- condition failures generally result when pore water in a liquefied layer rises into overlying near-surface sediments and they reach a condition resembling quicksand. This type of failure usually occurs in flat-lying areas under- lain by sediments of considerable thickness where the water table is close to the surface (Youd and others, 1975, p. A73). Damage in quick-condition failures can be very extensive owing to the settlement of structures into the soil or to the buoyant rise of buried structures, such as fuel tanks, through the liquefied sediment. The following examples illustrate the extreme destruc- tiveness that has resulted from various types of liquefaction- induced ground failure in some earthquakes of large magnitude. In Kansu Province, China, a large part of the land surface is formed by thick deposits of wind-laid silt called loess. A major earthquake in that area on Decem- ber 16, 1920, triggered great flow landslides in the loess, some of which moved at a relatively high velocity for distances of more than a kilometer. An estimated 200,000 people, including many that lived in excavations carved into the loess, perished in the slides. The Kansu landslides, and similar landslides triggered by an earthquake near Hsian in Shensi Province in 1556 in which almost a million people are believed to have died, were apparently caused by spontaneous liquefaction of the loess, but the exact mechanism of failure is unknown. The entrapment of air in the slides, especially at their base, may have greatly facilitated long-distance movement of the materi- al (Bolt and others, 1975, p. 187). At Anchorage, Alaska, in the magnitude 8.4 earth- quake of March 27, 1964, an area extending about 2.5 km along the coast and reaching inland as much as half a kilometer slid toward the ocean (Knik Arm), as a huge lateral-spreading landslide. This slide caused great dam- age to a residential area called Turnagain Heights, where some of the slide blocks moved as much as 300 m and houses actually slid into the chasms between them. That landslide has been attributed to liquefaction of thin layers of sand and silt in a near-surface clay (Hansen, 1965, p. A65). One of the most spectacular quick-condition failures of modern times took place in Niigata, Japan, during a 38 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA magnitude 7.5 earthquake on June 16, 1964, when sandy soil on which much of the city was built became liquefied and hundreds of buildings settled into the ground (Seed and Idriss, 1967, p. 83). Some structures, including sever- al large apartment buildings, settled more than 3 feet (1 m), and one of the apartment buildings tipped and rotat- ed through an angle of 80°. SURFACE FAULTING Sudden rupture and displacement of the ground sur- face along faults has occurred in many parts of the world during earthquakes. These displacements usually result from translation of the quake-generating rupture to the ground surface along a causative fault or from reactiva- tion of faults by strong ground motion. Large-scale sur- face faulting is typically limited to strong earthquakes, usually of magnitude greater than 6.5, but significant surface offsets have occurred during shocks of magni- tude 6.0-6.5 and even in smaller shocks whose magni- tudes were less than 5.5 (Bolt and others, 1975, p. 33-46). Large-scale surface fault rupture took place in the magni- tude 7.1 Hebgen Lake, Montana, earthquake of 1959. It is not known if surface faulting occurred in any of the other destructive shocks that have shaken Montana. The surface displacement and length of rupture that occurred along faults in several historic earthquakes are presented here to illustrate the degree of breakage that may take place on different types of faults at a wide range of earthquake magnitudes. During the magnitude 8.3 San Francisco earthquake of 1906, the horizontal slip on the San Andreas fault was as much as 5 m and breakage extended over a length of about 430 km (Wesson and others, 1975, p. A13, A38). The series of earthquakes that reached a magnitude of 5.5 in the Parkfield-Cholame area of California in 1966 produced a horizontal slip of a few centimeters along a 37.8-km segment of the San Andreas fault (Brown and Vedder, 1967, p. 11). Vertical displacement of more than 14 m-the greatest known - occurred on submarine faults during the magnitude 8.6 Cape Yakutat, Alaska, earthquake of 1899 and the mag- nitude 8.4 Alaskan earthquake of 1964, but the length of rupture on those fractures is unknown (Coffman and von Hake, 1973, p. 106-109). In the magnitude 8.7 Indian (Assam) earthquake of 1897 (Oldham, 1899, p. 138-152), vertical displacement was as much as 10.7 m and the rupture length was about 19.3 km along the Chedrang fault, and lesser faults underwent a vertical movement of as much as 3 m and had rupture lengths of as much as 11.3 km. In the Hebgen Lake, Montana, earthquake of 1959, vertical displacement was as much as 4.3 m and the rupture length was about 22.5 km on the Red Canyon fault, and vertical displacement was as much as 6 m and the rupture length was about 12 km on the Hebgen fault (Witkind, 1964b, p. 37). The magnitude 6.5 San Fernando, California, earthquake of 1971 produced a thrust or reverse displacement of about 1 m along a 15-km segment of the San Fernando fault zone at the foot of the San Gabriel Mountains (U.S. Geological Survey, 1971, p. 55). Surface fault ruptures may consist of a single, narrow main break, but, commonly, subsidiary branch and sec- ondary faults are formed on either side of the main fracture and the rupture forms a zone of disturbance of varying width. The principal displacement usually occurs along the main fault trace, but offsets on subsidiary faults, even at considerable distance from the main break, can be substantial and amount to as much as a meter or more. The degree of displacement and the width of the zone of deformation along surface ruptures generally increase with earthquake magnitude, and Bonilla (1970, p. 56) determined that zone width also varies with the type of faulting; it is narrowest for strike-slip faults and widest for normal and reverse faults at roughly equiva- lent levels of earthquake magnitude. Moreover, the rup- ture zones along reverse faults generally appear to be more complex and more irregular than those formed along normal or strike-slip faults (Wesson and others, 1975, p. A25). Some representative maximum fault-zone widths formed along earthquake-induced surface breaks in the United States are 100 m on the San Andreas strike-slip fault during the magnitude 8.3 San Francisco earthquake of 1906 (Lawson, 1908, p. 53), 60 m on the reactivated normal faults at Hebgen Lake during the magnitude 7.1 Montana earthquake of 1959 (Witkind, 1964b, p. 46), and 200 m on the reverse-fault rupture during the magnitude 6.5 San Fernando, California, earth- quake of 1971 (U.S. Geological Survey, 1971, p. 57). Although surface faulting is one of the most spectacu- lar effects of earthquakes, damage to manmade struc- ture and the land surface and fatality resulting from the process are usually small compared to that resulting from ground shaking or landsliding because fault move- ment is ordinarily confined to a fairly narrow zone alone the slipped fault trace. It is obvious, however, that a fault displacement of even a few centimeters beneath or across a structure may result in extensive damage, espe- cially if the fault movement is accompanied by intense ground shaking. Severe damage to several buildings astride the Hebgen fault occurred during the Hebgen Lake, Montana, earthquake of 1959 (Witkind, 1964b, fig. 26). Ground rupture along the San Fernando fault zone during the San Fernando, California, earthquake of 1971 caused severe damage to buildings, broke gas and water mains, and damaged roads (Lew and others, 1971, p. 25-26; Nichols and Buchanan-Banks, 1974, fig. 1). The Parkfield-Cholame, California, earthquake of 1966 caused ground fracturing that bent and cracked bridges, roads, fences, pipelines, a concrete canal, and a small earth-fill dam (Brown and Vedder, 1967, p. 22). EARTHQUAKE HAZARDS 39 REGIONAL LAND DISPLACEMENT Earthquake-induced surface faulting may result in sudden ground displacement that involves subsidence, uplift, and horizontal shifts of wide areas of the Earth's surface. These displacements range from a few centime- ters or less to many meters and may affect thousands of square kilometers of the land surface. The largest documented land displacement was that caused by the Alaskan earthquake of 1964, during which more than 250,000 km of the Earth's surface in south- central Alaska was measurably displaced by crustal defor- mation that included a maximum uplift of 11.6 m, a maximum subsidence of 2.3 m, and a maximum seaward horizontal shift of 19.5 m (Eckel, 1970, p. 11). In the conterminous United States, the most extensive chang- es in land level caused by an earthquake were those that occurred during a series of three powerful shocks cen- tered near New Madrid, Missouri, in 1811 and 1812. In those earthquakes, great blocks of land were raised and lowered as much as 3-4 m within an area of some 130,000 km; as a result, new lakes formed and extensive changes in the drainage pattern occurred (Coffman and von Hake, 1973, p. 43-46). At Hebgen Lake, Montana, widespread subsidence and warping of the land surface accompanied the reactivation of surface faults in the earthquake of 1959. The main dislocation covered a tract about 60 km long and about 22% km wide, and within that area about 155 km of the land surface that included Hebgen Lake dropped more than 3 m and the maximum subsidence was about 6.7 m (Myers and Hamilton, 1964, p. 55). Regional land displacement that involves vertical move- ment of the Earth's surface usually has a profound effect upon surface waters, and damage connected with this type of dislocation is mostly caused by sudden move- ments of water, changes in water level, and changes in drainage pattern. A spectacular effect of large earth- quakes in the marine environment is the generation of seismic sea waves, or tsunamis, which are produced by dislocation of the sea floor. Such waves, when they impinge on coastal areas, can cause extensive battering and flood- ing and were responsible for much of the damage sus- tained in the Alaskan earthquake of 1964. Inland, regional displacements may cause surges in lakes, reservoirs, rivers, and canals and permanent changes in water levels that result in flooding, erosion, and drowning of large areas of land. The cumulative effects of land-level changes in the New Madrid, Missouri, earthquakes of 1811 and 1812 destroyed more than 5,000 km of forest, principal- ly by flooding (Coffman and von Hake, 1973, p. 45). In the Hebgen Lake earthquake of 1959, differential subsi- dence of the lake bottom caused great surges of water that overtopped Hebgen Dam, flooded parts of the shore, and produced large slumps along the banks (Myers and Hamilton, 1964, p. 70-77). The wave surges were particu- larly damaging to boating facilities along the shore. Warping of the lake bottom caused displacement of the water surface and permanent submergence of a large area along the northeast side of the lake. Regional horizontal shifts of the Earth's surface, such as those that occurred in the Alaskan earthquake of 1964, produce little if any damage to the land or to manmade structures. SETTLEMENT Engineers have long known that masses of sand or gravel, which contain no significant component of clay, can be compacted very effectively by vibration. Thus, the intense shaking produced by earthquakes often leads to compaction of such materials and coincident settle- ment of the ground surface. In large earthquakes, the amount of settlement resulting solely from vibratory compaction, where liquefaction is not a factor, may amount to a meter or more, even over wide areas such as the floor of an alluvial basin. Quantitative measurements of settle- ment phenomena largely come from Alaska, where a large effort of scientific study was mounted following the great earthquake there on March 27, 1964 (Eckel, 1970). One of the most accurate measurements of settlement resulting from consolidation and compaction by heavy ground shaking during the Alaskan earthquake was made at Homer Spit, in the southwestern part of the Kenai Peninsula, Alaska, where natural surficial deposits sub- sided as much as 2% feet or about 76 ecm (Waller and Stanley, 1966, p. D22). Artificial earth fill is particularly susceptible to com- paction by vibratory earthquake motion, and much minor damage during large earthquakes, which in sum can be very disruptive and very costly, is caused by differential settlement of such material relative to adjoining ground or to an adjoining structure or is caused by differential settlement within the material itself. Masses of fill that are especially prone to such movements include railway embankments, road and highway foundations, bridge- abutment backfill, irrigation-canal levees, and support- ive pads of gravel or other earth fill beneath buildings and large paved areas such as parking lots and airport runways and aprons. During the magnitude 6.5 San Fernando, California, earthquake of 1971, extensive dam- age to streets and paved areas was caused by densifica- tion and differential settlement of the road foundations (Lew and others, 1971, p. 15). In the magnitude 7.1 Hebgen Lake, Montana, earthquake of 1959, compac- tion of the roadbeds caused extensive breakage and off- set of highway surfaces as well as settlement adjacent to bridge abutments, which lowered highways as much as 2 ft (60 cm) below bridge surfaces (Witkind, 1964a, p. 5-6, fig. 3). 40 GROUND CRACKING Ground cracks or fissures commonly form in the epi- central regions of large earthquakes and generally are most abundant in flat terrain underlain by surficial deposits, soft sedimentary rocks, or artificial earth fill. They are largely the result of intense ground shaking and may be considerably enhanced by differential settling. Cracks also form in bedrock along the margins of escarp- ments or cliffs as a result of shaking, and some fissures are formed in surficial deposits and in bedrock in response to slippage on faults. Primary cracks caused by ground shaking are in many instances difficult to distinguish from those that originate through other mechanisms such as liquefaction-induced movement of the ground surface. Ground cracks in soft earth materials commonly follow streambanks and flood plains, lakeshores, road and railway embankments, and irrigation levees, but in flat country devoid of such features they rarely show a preferred orientation and more generally are arrayed in irregular networks. The cracks mostly range in size from short hairline fractures to fissures 10-20 ecm wide and tens of meters long, but cracks of much larger dimension have formed in the source regions of large earthquakes. Generally, the cracks do not extend to depths of more than a few meters. Where formed in loose surficial materials, they are quickly filled with sediment. During the Helena earthquake of 1935, only a few small cracks opened in the floor of Helena Valley, as mentioned previously. Many ground cracks formed dur- ing the earthquake of 1925 near Lombard, Montana. They mainly opened in stream embankments and road foundations within 15-20 mi (24-32 km) of the epicenter (Pardee, 1927, p. 10). In the earthquake at Hebgen Lake, Montana, in 1959, cracking of the ground was wide- spread along the shores of the lake and in road founda- tions and road surfaces, and much of the road shattering was due to this cracking and contemporaneous settle- ment of the road fill (Witkind, 1964a, p. 5-11). RIDGING AND FURROWING Two distinct types of ridges and furrows formed in soft ground have been described in association with earthquakes of large magnitude: (1) parallel undulations resembling stationary waves, in which there is a differ- ence in level of as much as a meter between crest and hollow and in which the distance between crests is as much as several meters, and (2) lines of mound-shaped ridges raised along ground cracks. Ridges and furrows of the undulation type were produced on tidal flats in the San Francisco Bay region during the magnitude 8.3 California earthquake of 1906 (Nichols and Buchanan- Banks, 1974, fig. 22) and throughout large areas of the GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA epicentral tract of the magnitude 8.7 Indian (Assam) earthquake of 1897 (Oldham, 1899, p. 95). The undula- tions that formed in the Indian earthquake were highly disruptive to the agricultural economy of the region, for they were largely formed in ricefields, and extensive releveling of the land was necessary before crops could be grown again. Ridges and furrows associated with ground cracks were formed in a localized area of sandy soil on fairly level ground within the epicentral area of the Indian earthquake of 1897. These ridges were ascribed by Oldham (1899, p. 10-11, fig. 1) to the closing of ground cracks with great pressure, which forced the turf upward along the line of the cracks into distinct ridges. Oldham does not give the dimensions of the ridges, but judging from his illustration they were as much as a meter high. GROUND CHURNING Ground churning is a phenomenon associated with earthquakes, wherein parts of the ground and objects on it, such as loose stones, are overturned or thrown into the air with little horizontal displacement. This type of ground dislocation, which has occurred in the epicentral region of several earthquakes of magnitude 6.5 and above, is generally attributed to local ground motion having a | vertical acceleration approaching or exceeding that of gravity. Churned ground may form on the surface of solid bedrock, soft surficial deposits, or soils, and in sloping or level terrain ; but it is most common in bedrock at the crest of ridges or on other topographic prominences. In the magnitude 6% earthquake near Lombard, Montana, in 1925, a thin layer of soil on deposits of clay and sand was intensively shattered and broken into clods that were shifted about and overturned within a zone of ground cracks several feet (1-2 m) wide at the top of a slope above Roy Gulch (Pardee, 1927, p. 10; pl. 12A). Similar overturning of soil on a much larger scale, on fairly level ground, occurred in the magnitude 8.7 Indian (Assam) earthquake of 1897, and, over large areas of bedrock in that earthquake, stones from 25 cm to a meter across were thrown from the ground surface (Oldham, 1899, p. 10-11; p. 130-133). Shattering and overturning of sandstone, limestone, and quartzite occurred on several ridge crests and on other high ground in the vicinity of Hebgen Lake during the magnitude 7.1 Montana earthquake of 1959 (Hadley, 1964, p. 137), and extensive shattering and overturning of soil occurred on an isolated ridge crest in the magnitude 6.5 San Fernando, California, earthquake of 1971 (Nason, 1971, p. 97-98). Apparently, no damage to manmade structures has resulted from earthquake ground churning, but considerable disruption of wide tracts of land was caused by the overthrow of sod in the Indian earthquake of 1897. LOCAL GEOLOGIC CONDITIONS THAT MAY CONTRIBUTE TO SEISMIC HAZARDS SEICHES AND SURGES Seiches (pronounced sashes) are oscillations of the surface of lakes, ponds, rivers, reservoirs, and bays that travel back and forth across the water surface at regular periods determined by the depth and size of the water body. The oscillations are in the form of standing waves and may be likened to the sloshing of water in a container when it is suddenly jarred. Seiches usually originate from wind stress, unusual tides or currents, or sudden changes in atmospheric pressure, but in some instances they are produced by earthquake ground motion. Earth- quake shaking moves the water back and forth and sets up waves that can cause flooding of shoreline facilities and erosion of the land. In general, seiche waves generat- ed by earthquakes are of low amplitude and no more than a few tens of centimeters high, but waves as much as several meters high may result where water is constricted, as in the narrow arm of a lake, or where a body of water shallows abruptly near the shoreline. Waves as high as 20 ft (6 m) were produced in a constricted part of Kenai Lake, Alaska, during the earthquake of 1964 (McCulloch, 1966, p. A30). Damaging seiches may also occur in indus- trial or municipal storage tanks during earthquakes, and quasi-resonance between the ground vibrations and the oscillations of water can produce damaging water motion even at large distances from an earthquake source. Dur- ing the Nevada earthquake of December 16, 1954, weak ground shaking related to long-period motion produced damaging oscillations in the city reservoir and in indus- trial tanks in Sacramento, California, some 240 km from the epicenter (Steinbrugge and Moran, 1957, p. 338-348). Sudden regional warping or tilting of the land beneath bodies of water during earthquakes also may cause intense seiching of the water surface, as was mentioned earlier in the section on "Regional land displacement." The initial wave generated by warping may be as much as several meters high, and subsequent oscillations, which may continue for several hours after the initial disturbance, are of gradually diminishing intensity and amplitude. In the Hebgen Lake, Montana, earthquake of 1959, the water oscillations caused by subsidence of the lake bot- tom continued for at least 12 hours after the earthquake (Myers and Hamilton, 1964, p. 70). The large oscillations of water produced by land warping are generally called surges to distinguish them from ground-shaking-induced seiches, which ordinarily are of much smaller amplitude and destructive force. LOCAL GEOLOGIC CONDITIONS THAT MAY CONTRIBUTE TO SEISMIC HAZARDS Because seismic hazards involve movements of the ground surface, their level of severity is influenced to a large degree by the geologic setting at an earthquake 41 site. The potential location and size of destructive earthquakes, the potential level of damaging ground shaking, the potential for ground failure, and the potential for flood- ing are all closely determined by the nature and distribu- tion of geologic rock units and faults, the topography, and the size and extent of water bodies in the affected region. Moreover, owing to local differences in geology, the amplitude of ground motion and the extent of ground failure in any earthquake may vary widely from place to place, even at the same distance from the earthquake source. Like most seismically active regions of the world, the Helena area is host to a variety of geologic conditions that may contribute to seismic hazard. These conditions include: (1) the widespread occurrence of surficial depos- 'its prone to amplified shaking and ground failure, (2) the abundance of steep bedrock slopes prone to landsliding, (3) the occurrence of geologic faults susceptible to sur- face rupture, and (4) the presence of hydrologic features that create a potential for flooding. Geologic and seismologic data in the Helena area are not yet sufficient, however, to evaluate these conditions in other than a very general way; therefore, precise estimates or predictions of their potential effect in future earthquakes cannot be made. Nevertheless, the elementary assessment presented here- in should be useful in identifying problem areas and establishing broad land-use guides aimed at minimizing earthquake hazards. SURFICIAL DEPOSITS Surficial deposits underlie more than a third of the area, including most of the floor of Helena Valley, a broad tract of land at the south end of Silver Valley, and much of the low land along major streams (pls. 1, 2). In Helena Valley, large parts of Helena and Fort Harrison, the whole of East Helena, and much land undergoing rapid urban development in Lewis and Clark County are underlain by unconsolidated and weakly consolidated surficial units. The significance of the surficial deposits, insofar as earthquakes are concerned, is twofold: (1) ground motion tends to be amplified in these rocks, and (2) the deposits are susceptible to ground failure from landsliding, liquefaction effects, settlement, and cracking. It follows that the most widespread damage in a future destructive earthquake is likely to occur in areas under- lain by these materials. A general appraisal of the response of the surficial deposits to ground shaking during the Helena earth- quake of 1935, the expected response of the surficial deposits to ground shaking in future earthquakes, and the susceptibility of the surficial deposits to various types of ground failure is given following. 42 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA RESPONSE TO GROUND SHAKING IN THE 1935 EARTHQUAKE Structural damage in and near Helena during the earthquake of 1935 was largely confined to buildings constructed on surficial deposits; in most instances, it was very light or nonexistent in structures built on or anchored to bedrock. In general, the buildings that sus- tained severe damage on surficial deposits were compara- ble in size and type of construction to buildings that escaped damage on bedrock. The areas of worst damage, in which numerous buildings sustained fallen walls and roofs and other serious structural deformation, were along the northern margin of the city and in its northeastern, central, and south-central sections where structures were built on stream deposits, slope wash, and older gravel. The general correlation between extensive damage and surficial deposits is illustrated on plate 3, which shows the distribution of surficial deposits and bedrock, the traces of geologic faults, and the location of buildings heavily damaged in the earthquake of 1935. The correla- tion suggests that seismic shaking was intensified on the surficial materials. In the south-central part of the city, heavy building damage may have been related to amplified motion in accumulations of young surficial deposits that form a thin cover on bedrock over much of that area. The exten- sive damage in the upper part of Last Chance Gulch, for example, was attributed to amplified shaking in stream deposits that had been loosened and redistributed by early placer operations (Neumann, 1937, p. 47-48). East of the gulch, between Warren and Davis Streets, damage probably was caused mainly by intensified shaking of the older gravels that cap the low, flat-topped bedrock ridge running northward through that part of the city. Farther east, amplified motion in slope wash near bed- rock outcrop may account for the widespread damage to residential structures along Breckenridge, Hillsdale, and Highland Streets. The greatest incidence of damage to larger buildings from the 1935 earthquake occurred in the central and eastern parts of Helena and along its northern margin, which are underlain at shallow depth by older stream and lake deposits of Tertiary age (pls. 1, 3). These deposits, which consist largely of soft clay, overlap sedimentary and plutonic bedrock and underlie a thin veneer of younger surficial deposits. In Helena, the contact between the older strata and the bedrock, which is mostly concealed, winds through the city from St. Peter's Community Hospital on the east to the Kessler Brewery on the west and passes just north of the Capitol building and Carroll College. The contact represents the edge of the interface between the older stream and lake deposits and the bedrock, and presumably this interface dips gently north- ward and lies at moderate depth (0-200 m) beneath the city. The general restriction of major building damage to the area underlain by the older stream and lake sedi- ments may signify that ground shaking was significant- ly amplified in the wedge of older strata at the south margin of Helena Valley and was perhaps further height- ened in the overlying thin layer of younger surficial materials. However, because so many other factors were involved in producing structural damage, the influence of the older stream and lake deposits on ground shaking is problematical. A unique structural failure at the Kessler Brewery that was observed by A.F. Bateman, Jr. and the late C.E. Erdmann of the U.S. Geological Survey a few weeks after the 1935 earthquake may indicate that ground shaking was amplified at that locality. As described by Bateman (oral commun., 1977), round steel rest plates beneath vertical steel-plate supports at the ends of filled stainless-steel brewing tanks were driven downward as much as 7.5 cm into the concrete floor (ground floor) of the brewery by the force of the earthquake ground motion. The steel rest plates were about 2.5 cm thick and 30 cm in diameter, and the steel-plate supports were about 12 cm wide, 2.5 cm thick, and 40 cm long. The brewing tanks were cylindrical, about 2.5 m in diameter and 4 m long, and the concrete floor was about 85 cm thick. The mar- gins of the depressions formed beneath the rest plates were clean and sharp, which suggests that the plates were punched into the concrete surface. This phenome- non occurred only beneath filled tanks; the floor beneath empty tanks was not so affected. The brewery, which is on the far west side of Helena (pl. 3), stands on about 10 m of flood-plain gravel along Tenmile Creek. The gravel, in turn, rests on older stream and lake deposits, which are at least 100 m thick as indicated in water wells to the north and east. The force that drove the rest plates into the brewery floor may have resulted either from sudden, strong upward movements of the brewery floor and the inertial resistance of the tanks to such movement or from intense rocking of the tanks in response to intensified ground shaking at the brewery site. The stream gravel beneath the structure is normally saturated with water below a depth of about 2 m; the older stream and lake deposits that underlie the gravel also are water saturated. This condition may have contributed greatly to enhance shaking in the vicinity of the brewery, for observations show, generally, that earthquake ground motion is strongly amplified and has increased duration on water- saturated sediments. EXPECTED RESPONSE TO GROUND SHAKING IN FUTURE EARTHQUAKES Field studies at earthquake sites have shown that the intensity of ground shaking can vary greatly in different types of surficial deposits, and, in recent years, consider- LOCAL GEOLOGIC CONDITIONS THAT MAY CONTRIBUTE TO SEISMIC HAZARDS 43 able work has been focused on the development of quanti- tative techniques to predict the vibratory response of these materials under conditions of earthquake loading. The investigations of Gutenberg (1957); Borcherdt (1970); and Borcherdt, Joyner, and others (1975) concerning ground-motion amplification in surficial deposits have been mentioned in the preceding section on "Ground shaking." Other studies dealing with the dynamic response of surficial materials to earthquake ground motion, aimed mainly at establishing design criteria for engineering structures, have been made by Seed and Idriss (1969, 1971), Seed and Schnabel (1972), and Seed and others (1974), and a general treatment of the problem as it relates to earthquake-resistant design has been presented by Dowrick (1977, p. 44-79). Probably the most elaborate investigation of the subject is that of the seismologist Medvedev (1965, p. 38-55), who has quantified the effects of different rock types and other geologic factors on earth- quake intensity for the purpose of seismic microzonation (the delineation of geographical areas with different earthquake-hazard potential) in the U.S.S.R. Physical characteristics of surficial deposits, such as bulk density, seismic body-wave velocities, thickness, and degree of water saturation, as well as the effects on the deposits of small natural earthquakes and distant nuclear testing, have been used to analyze the shaking behavior of these materials. Because these factors are largely unknown for the surficial units in the Helena area, however, only a very simplified assessment of the expected response of the materials in future earthquakes, based mainly upon data from other areas, can be given here. The work of Medvedev (1965, p. 45-52) on the relation of seismic intensity to the character of the ground is particularly relevant in this regard, and a brief outline of his findings is provided here. MEDVEDEV'S DATA To introduce the factor of rock type in seismic micro- zonation, Medvedev (1965, p. 45-46) made use of relations termed the seismic-intensity increment and the seismic impedance of various basic categories of ground that he designated as (1) granites, (2) limestones and sandstones, (3) moderately firm ground, (4) coarse-fragmental ground, (5) sandy ground, (6) clayey ground, and (7) loose fill. The seismic-intensity increment, which is the increase in shaking intensity on a particular type of ground relative to the shaking intensity on granite, is based on the GOST intensity scale? used in the U.S.S. R. The intensity increments of the various types of ground were determined from field studies of earthquake intensities at numerous *The GOST intensity scale, which has 12 intensity ratings, is broadly similar to the Modified Mercalli Intensity Scale presented in the appendix to this report. localities in the Soviet Union where the effect of factors other than rock type was minimal. The seismic impedance of the ground is defined as the product of the velocity of the primary or longitudinal seismic waves (P waves) in the various classes of ground and the bulk density of the materials, or V pp, the component parameters having been ascertained from seismic prospecting data and from on-site density measurements. Table 2 shows the seismic- intensity increment P-wave velocity, bulk density, and seismic impedance of the basic types of ground as deter- mined by Medvedev (1965, tables 2.1 and 2.2, p. 46-47), and from this data he derives (Medvedev, 1965, p. 46) a mathematical relation between the seismic-intensity increment and the seismic impedance in the form n= 1.67 [log(Vpp granite) - log(Vpp ground)], where n is the seismic-intensity increment and 1.67 is an empirically determined correlation factor. The seismic-intensity increments listed in table 2 apply to ground in a natural state of moisture, but Medvedev (1965, p. 49) recognized from studies of earthquake effects that shaking intensity in unconsolidated deposits is mark- edly influenced by the water-table level in the ground. On the basis of observations of seismic intensity on sandy loams, loams, and fine sands and on the basis of other data, he concluded (Medvedev, 1965, p. 49) that (1) where the water-table depth is below 10 m the seismic intensity is not affected, (2) where the water-table depth is roughly 4 m the seismic intensity increases by about half a unit, and (3) where the water-table depth is 1 m or less the intensity is increased by one unit. From these relations Medvedev (1965, p. 49) obtained an equation expressing the increase in seismic intensity of a given area of ground as a function of water-table elevation such that np = 6-0.040, where np is the increase in seismic intensity, e is the base of the natural logarithm, and /A is the depth to the water table in meters below the ground surface. Taking water-table depth into account, he obtained a final for- mula (Medvedev, 1965, p. 49) for the seismic-intensity increment in the form n=1.67[log(Vpp granite) -log(Vpp ground)] + p-0.04h2 This equation has been used to compute seismic-intensity increments for common types of ground at earthquake sites in the U.S.S.R., where such factors are widely applied as a general standard for seismic microzonation and for adapting the design of engineering structures to natural foundation conditions. The standard seismic- intensity increments calculated for different types of ground are listed in Medvedev's report (1965, table 2.5, p. 50). 44 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA TABLE 2. -Seismic characteristics of basic types of ground as determined by Medvedev (1965) Seismic-intensity Vp p Vpp Ground increment (km/s) _ Bulk density Seismicimpedance (g/em?) Granites... _ . .ll cgl als 0 5.6 2.9 16.2 Limestones and sandstones ......... .. O-1 4.5-2.5 - 2.8-2.0 12.6-5.0 Moderately firm ground (gypsum, marl). . 1 3.0-1.7 - 2.4-1.7 7.2-2.9 Coarse-fragmental ground (rubble, pebble. gravel) ..... . . .. 1-2 2.1-0.9 - 2.0-1.6 4.2-1.4 Sandy ground.. ..... 1-2 1.6-0.6 _ 1.9-1.6 3.1-1.0 Clayey ground 1-2 1.5-0.6 - 2.0-1.6 3.0-1.0 [" "0 .._ fol o. 2-3 0.6-0.2 1.5-1.3 0.9-0.26 In general, Medvedev's data indicate that the intensi- ty of seismic shaking on unconsolidated surficial depos- its (coarse-fragmental, sandy, and clayey grounds) is markedly greater than the intensity of seismic shaking on firm rock or bedrock (granite, compact sedimentary rock ) and is greatest on loose fill. Specifically, his results predict that shaking intensity, as measured by the GOST intensity scale, may increase on coarse-fragmental ground by as much as 1.5 units, on sandy and clayey grounds by as much as 2 units, and on filled land by as much as 3 units over the intensity on adjacent granite, and that these intensities may further increase by a whole unit if the unconsolidated grounds are saturated with water. His studies also show that ground-motion intensity on compact sedimentary rocks (limestones, shales, sandstones) is somewhat greater than the intensity on granite and that shaking intensity on moderately firm ground such as marl may be as much as a whole unit higher than the intensity on granite. Moreover, his data demonstrate (table 2) that the intensity of seismic shaking on differ- ent types of ground generally increases as the seismic impedance of the rocks decreases and that seismic imped- ance broadly correlates with the overall firmness or hard- ness of the ground. The potential contrast in the shaking intensity of various rock units therefore can be deter- mined in a rough way on the basis of field observations. CORRELATION WITH MEDVEDEV'S BASIC CLASSES OF GROUND Some of the rock units in the Helena area have close counterparts among the basic classes of ground subject- ed to seismic analysis by Medvedey (1965). In particular, the plutonic and volcanic bedrock in the area probably corresponds rather closely to his granites; the sedimenta- ry bedrock to his compact limestones and sandstones; the older gravel to his coarse-fragmental ground; the wind-laid and glacial-lake deposits to certain of his sandy and clayey grounds; and the artificial fill, and placer tailings, and landslide deposits to his loose fill. The correlation of the stream deposits, slope wash, and older stream and lake deposits in the Helena area with Medvedev's ground types is less certain. The stream deposits unit consists mainly of gravel and, for the most part, probably can be equated with Medvedev's coarse-fragmental ground. Locally, however, this unit includes substantial amounts of sand and clay and, figuratively, is more or less a mixture of his coarse- fragmental, sandy, and clayey grounds. The slope wash unit is largely gravel with a matrix of sandy to silty clay, and the proportion of matrix in the gravel is usually greater than that of the rock fragments. The gravelly slope wash therefore corresponds to a mixture of Medvedev's coarse-fragmental and clayey grounds. The older stream and lake deposits unit consists largely of firm clay, weak- ly cemented sand and gravel, and compact volcanic ash, and the bulk of the unit therefore may broadly corre- spond to Medvedev's moderately firm ground in terms of seismic characteristics. In some areas, however, the rocks are less firm and include much soft bentonitic clay and clay-altered volcanic ash that probably correspond close- ly to Medvedev's clayey ground. The clayey rocks form a large part of the unit in the eastern and northern sections of the city of Helena and in the northwestern part of the Helena quadrangle. The general correlation of the Helena rocks with Med- vedev's basic categories of ground is shown in table 3. GENERAL RESPONSE OF SURFICIAL UNITS To a large extent, the amplification of ground motion in surficial deposits depends on the fundamental vibra- tional frequency of the materials, which is largely con- trolled by the thickness of and the seismic shear-wave (S-wave) velocity in the materials. Therefore, Medvedev's (1965) intensity increments for various classes of unconsolidated ground, which are based on seismic imped- ance values calculated from P-wave velocities and which do not take thickness into account, are not wholly accu- rate or reliable. It follows that estimates of intensity increments for surficial materials based on approximate comparisons with Medvedev's basic types of ground are even less reliable. Nevertheless, pending the acquisition of better data, the estimates based on such comparison and presented here for surficial units in the Helena area LOCAL GEOLOGIC CONDITIONS THAT MAY CONTRIBUTE TO SEISMIC HAZARDS 45 TABLE 3. - Correlation of rock units in the Helena area with Medvedev's (1965) basic categories of ground Medvedev's basic categories of ground Firm ground: Granites Limestones and sandstones Helena rock units, this report Plutonic and volcanic bedrock Sedimentary bedrock Moderately firm ground Older stream and lake deposits (bulk of unit) Coarse-fragmental ground Older gravel Sandy ground Clayey ground Wind-laid deposits Glacial-lake deposits Stream deposits Slope wash Bentonitic clays of the older stream and lake deposits unit Loose fill Artificial fill, placer tailings, landslide deposits serve as a rough guide to the potential seismic response of the deposits in future earthquakes. On the basis of the correlation with Medvedev's basic grounds, the rock units at Helena can be grouped into five categories according to similarities in potential seis- mic response as shown in table 4. The seismic-intensity increments assigned to each grouping roughly indicate the expected increase in potential shaking intensity from one category to another. These increments are based on the GOST intensity-scale values determined by Medvedev (1965, tables 2.3 and 2.5, p. 48, 50) for similar types of rock in the Soviet Union but are broadly interpreted to conform to the Modified Mercalli Intensity Scale of 1931, given in the appendix to this report. A rough estimate of the expected response of the rocks in future earthquakes can be made from the groupings in table 4. Generally, the data show that the intensity of ground shaking on the surficial rocks is expected to be substantially greater than the intensity of shaking on bedrock and that significant variations in shaking inten- sity can be expected among different categories of surfi- cial materials. More specifically, the groupings imply that ground-motion intensity will be weakest on plutonic and volcanic bedrock, slightly greater on sedimentary bedrock, intermediate on the bulk of the older stream and lake deposits, stronger on the uncemented surficial units, and greatest on loosely compacted artificial fill, placer tailings, and landslide deposits. In terms of Mercalli- scale units, the intensity of shaking relative to that on plutonic and volcanic bedrock is expected to increase by as much as 0.5 unit on sedimentary bedrock; by as much as 1 unit on the bulk of the older stream and lake deposits; by as much as 2 units on stream deposits, slope wash, wind-laid deposits, glacial-lake deposits, older gravel, and older bentonitic clays; and by as much as 3 units on artificial fill, placer tailings, and landslide deposits. These increases are in general accord with ground-motion effects that took place in the Helena earthquake of 1935, during which shaking on surficial materials was locally of inten- sity VIII but on bedrock was of intensity VI or less. As pointed out by Medvedev (1965, p. 49), the intensi- ty of earthquake ground shaking is enhanced in surficial deposits where the water-table level is close to the ground surface and may increase by as much as a whole GOST- intensity unit where the depth to water table is 1 m or less. Gutenberg (1957, p. 235) also noted a remarkable increase in shaking intensity on water-saturated ground. In the eastern part of Helena Valley, where the surface is covered by young stream deposits, the water table is generally within 12 ft (3.6 m) of the ground surface, and, over much of this area, it is at a depth of 6 ft (1.8 m) or less, especially during the period of summer irrigation. The general limit of the tract with shallow water table is shown by lines of equal water-table depth on plates 1 and 2. These lines apply to the month of September, but, because the water table fluctuates seasonally, a much larger area of valley ground may be saturated at shallow depth during the spring months when precipitation is greatest. Other bodies of surficial rock that are perma- nently saturated with water at shallow depth are present along perennial streams, lakes, and reservoirs in the region. Ground shaking in the areas of shallow water table can be expected to be intensified in future earth- quakes of destructive magnitude. SUSCEPTIBILITY TO GROUND FAILURE DEPOSITS PRONE TO LANDSLIDING Earthquake-triggered landslides are especially com- mon in surficial deposits and soils on steep slopes, but slides also may occur in these materials on low slopes, 46 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA TABLE 4. -Rock units of the Helena area grouped according to relative seismic response Seismic-intensity Category increment Rock units (range) 1 0 Plutonic and volcanic bedrock. 2 0-0.5 Sedimentary bedrock. 3 1 Older stream and lake deposits (bulk of unit). 4 1-2 Older gravel, stream deposits, slope wash, wind-laid deposits, glacial- lake deposits, and bentonitic clays of the older stream and lake deposits unit. 5 2-8 Artificial fill, placer tailings, and landslide deposits. even in terrain that is virtually flat, as a result of liquefac- tion of water-saturated ground. Surficial materials in the Helena area that are particularly susceptible to landslid- ing are present on steep hill and valley slopes, in streambank and lakeshore scarps, at terrace margins, and in artificial embankments and excavations. Old landslide deposits also may be subject to renewed movements during earth- quakes. The most prominent of these landslide-prone sites are broadly identified in this section of the report. Slope wash along the mountain front at the southern margin of Helena Valley locally mantles slopes that range from 15 to 40 percent. These materials may be highly susceptive to slumps and earthflows in a large earthquake, especially if their moisture content is high, as might result during periods of prolonged rainfall. The main masses of steeply inclined slope wash are at the north end of the Elkhorn Mountains (pl. 2), along the moun- tain front east of Helena near the Lewis and Clark County- Jefferson County boundary (pl. 2), on the upper west side of Helena (pl. 1), on hillsides south and west of Fort Harrison (pl. 1), and along the east flank of the Scratch- gravel Hills (pl. 1). Many smaller masses of slope wash on steep mountain slopes (not delineated on pls. 1 and 2) also may have a strong tendency to fail by landsliding in future earthquakes. Steep valley sides and steep slopes at the front of benches and terraces formed in surficial deposits are potential sites of slumping, debris sliding, and rockfall in future strong earthquakes. In the eastern part of the area (pl. 2), slopes as steep as 60 percent and more are present in surficial materials along Spokane Creek and its tributaries and along valleys and scarps cut into Spokane Bench, cut into the rolling terrain north of the Elkhorn Mountains, and cut into the broad benchland southwest of East Helena. The slopes along Spokane Creek and its larger tributaries are as much as 40 m high and along the other valleys as much as 25 m high. Other steep slopes, which are mostly less than 6 m high and in places almost vertical, are formed in surficial deposits along ravines in Helena Valley north and northwest of Lake Helena, on the northern flank of the Spokane Hills, and in the eastern outskirts of Helena. In the western part of the area (pl. 1), scarps with slopes of more than 60 percent and heights of as much as 4 m are locally present in surficial materials along the narrow ravine east of Sanders Street, along the east side of Dry Gulch north of Harlow Street, and along the east side of Last Chance Gulch west of Willard Avenue in the city of Helena; along ravines in the vicinity of Fort Harrison; and along ravines in the northwestern part of Helena Valley. Slopes of 60 percent and more and as much as 10 m high are locally formed in surficial deposits at the margins of the valleys of Silver and Threemile Creeks and tributary streams in the northwestern part of the area. Streambank and lakeshore scarps are prone to slump failure in large earthquakes and are frequently the site of earth lurching in shocks of high magnitude and long duration (see fig. 11D). Steep streambank scarps are locally formed in stream deposits along Spokane, Prick- ly Pear, Tenmile, Sevenmile, and Silver Creeks and, to a lesser extent, along smaller tributary streams. These scarps are generally 1-2 m high, but locally are as much as 5 m high. Commonly they are vertical. Much of the shoreline of Lake Helena is marked by a vertical or near-vertical scarp 1-2 m high formed in surficial deposits; steeply inclined to vertical scarps as much as 10 m high are locally present in glacial-lake sediments and other surficial units along the shores of Hauser Lake on the Missouri River, chiefly at Eldorado Bar, at the west side of the lake (river) south of the York bridge, at Metropoli- tan Bar, and near Lakeside (pl. 2). Gravel in the steep free face of river and stream ter- races might be dislocated by rockfall and debris sliding during strong earthquakes. In the eastern part of the area (pl. 2), slopes of this sort are common in older gravel along the Missouri River at Eldorado Bar, Danas Bar, McCune Bar, Spokane Bar, and Gruel Bar and to a lesser extent along McClellan Creek, Holmes Gulch, and Prick- ly Pear Creek. In the western part of the area (pl. 1), steep slopes are locally present at the margins of gravel- covered terraces along Sevenmile Creek and Skelly Gulch west of Birdseye, along the lower part of Park Creek north of Birdseye, and along Silver and Threemile Creeks. Steep embankments of artificial fill may be dislocated by slumping, settlement, and cracking during severe earthquakes and may be subjected to massive failure by earth lurching in shocks of high magnitude and long duration (fig. 110). In the Helena area, embankments of earth and rock fill are present along roads and railways, along irrigation and drainage canals, at earth dams, and at the Lake Helena causeway. The piles of smelter slag at East Helena, which are as much as 15 m high, also can be regarded as large embankments. The highest road embankments, which are elevated as much as 6 m above LOCAL GEOLOGIC CONDITIONS THAT MAY CONTRIBUTE TO SEISMIC HAZARDS 47 ground level, are along Interstate Highway 15 at a ravine- crossing about 1 km north of the area boundary, in ramps built at Lincoln Road and Sierra Road on the floor of Helena Valley, and in ramps built at Custer Avenue, Cedar Street, and Prospect Avenue (U.S. Highway 12) in the eastern outskirts of Helena. Railway embankments are generally low, but in places are as much as 3 m high. The earth embankments along irrigation and drainage canals are mostly 1-2 m high, but are as much as 6 m high at several places along the main irrigation canal where it crosses ravines in the eastern part of the area. The largest earth dams are at the Helena Valley Regulat- ing Reservoir in the eastern part of the area (pl. 2) and at the Gehring and Hardie Reservoirs on Threemile Creek in the western part of the area (pl. 1). The failure of embankments during earthquakes com- monly results in losses of impressive proportions, and care must be taken in the design of these features in seismically active regions to guard against earthquake damage. A broad summary of the types of earthquake- induced failure common to earth embankments and earth dams and a review of engineering methods used to ana- lyze and improve the stability of such structures have been presented by Okamoto (1973, p. 255-277; 427-490). Sherard (1967) has reviewed earthquake considerations that pertain to the design of earth dams; Chopra (1967) has investigated the response of earth dams to earthquake ground motion; and Seed and Martin (1966) have examined the use of seismic coefficients in earth dam design. Surficial materials in the walls of road and railway cuts, irrigation and drainage canals, and gravel pits commonly undergo slumping and rockfall during intense earthquakes. Most road cuts in the Helena area that are excavated in surficial units are shallow and between 1 and 2 m deep; a few cuts made in older stream and lake deposits along York Road and along U.S. Highway 12 in the eastern part of the area are as much as 5 m deep. The largest railway cuts, as much as 6 m deep, are in gravelly deposits along the Burlington-Northern tracks east of East Helena. The main irrigation and drainage canals in Helena Valley are as much as 3 m deep. Numerous steep- sided gravel pits, some with vertical walls as much as 6 m high, are excavated in stream deposits and slope wash in Helena Valley. The location of the principal pits is shown on plates 1 and 2. Reactivation and slumping of the margins, particularly the toe portions, of old landslide masses at the head of Park Gulch (pl. 1) and on the northern slope of the Elkhorn Mountains (pl. 2) might occur in a strong earthquake. DEPOSITS PRONE TO LIQUEFACTION Seismically induced liquefaction, which is responsible for some of the most striking and most damaging types of failure in surficial materials (see section on "Liquefaction- induced failure"), ordinarily occurs in layers and lenses of loose, well-sorted, water-saturated sand and silt with- in 30 m of the ground surface. In the Helena area, perma- nently saturated sand and silt in stream deposits on the floor of Helena Valley and on flood plains, in glacial-lake deposits and other surficial units along the shores of Lake Helena and Hauser Lake, and in some embank- ments of artificial fill have the highest potential for liquefaction. Sands and silt in the slope-wash unit, and wind-laid sand and silt, are rarely saturated with water and generally are not liquefiable during most of the year, but certain of these deposits may be highly susceptible to liquefaction if they are water saturated. Sand and silt in older gravel and in the older stream and lake deposits unit are unlikely to undergo significant liquefaction. A further assessment of the liquefaction potential of the surficial deposits and of the effects that liquefaction may induce in them during strong earthquakes is presented in the following discussion. Stream deposits on the floor of Helena Valley probably contain a large volume of potentially liquefiable sand and silt, for over much of this area the ground-water table is at a depth of 12 ft (3.6 m) or less (pls. 1, 2). A minor amount of liquefaction occurred on the valley floor near Lake Stanchfield and at a few other localities during the Helena earthquake of 1935, as evidenced by the issuance of water and sand from cracks in the ground (fig. 9), and very likely the process would increase mark- edly in an earthquake of larger magnitude. Conceivably, liquefaction could lead to damaging quick-condition effects on the valley floor, such as differential settlement of the ground, or even to a condition of general upward seepage and ejection of water at the land surface that might cause structures to settle into the soil. In some great earthquakes (magnitude >8.0), liquefaction of basin fill has produced intense fountaining of water and sand from fissures and vents that has flooded the land and has filled stream channels, drainage ditches, and other low areas with sediment. However, the possibility of such an extreme effect occurring on the floor of Helena Valley is remote. Beds of water-saturated sand and silt also may be present in the deeper portion of floodplain deposits along major streams. Liquefaction of these sediments in a strong earthquake might lead to quick-condition effects along those drainages. Glacial-lake deposits, stream deposits, and slope wash along the shores and beneath the waters of Lake Helena and Hauser Lake contain sand and silt that are potential- ly liquefiable. The glacial-lake deposits may be especial- ly susceptible to liquefaction, for they are largely composed of beds of clean, well-sorted sand and silt. Liquefaction of the near-shore and underwater sediments could cause lateral-spreading or flow landslides or both that would involve sizable tracts of shoreline land. Movement of flow landslides into the lakes or movement of underwa- ter flow slides might produce strong wave surges. 48 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA Fine-grained, water-saturated artificial fill also is prone to liquefaction, and, in many instances, slumping and settlement of earth embankments and other masses of loose fill during earthquakes have been ascribed to lique- faction. In the Helena area, irrigation-canal embankments and earth dams built largely of surficial materials may contain potentially liquefiable sand and silt. Road embankments and other bodies of earth fill that stand above the ground surface are ordinarily well drained and are not susceptible to liquefaction unless they become saturated with water during heavy or prolonged rain- fall or from snow melt. Railway embankments, which are mostly built of solid rock fragments, are generally not liquefiable. Sand and silt in the slope-wash unit have a low lique- faction potential, for this material mainly lies on well- drained sloping surfaces and is unsaturated with water during much of the year owing to the prevailing dry climate. During the wet spring months and during peri- ods of abnormally high rainfall, however, some slope wash is likely to become saturated, especially the distal parts of broad aprons of the sediment in the western part of Helena Valley -for example, the large accumulations that underlie the eastern and western sections of Helena (pls. 1, 2). Seismically induced liquefaction of saturated sand or silt in the slope wash conceivably could lead to the formation of lateral-spreading landslides over wide areas of ground on the gently inclined portions of these deposits. Masses of slope wash on steep to moderate slopes may occasionally become saturated from heavy rainfall or snow melt. Liquefaction of sand or silt in these materials might produce flow landslides. Wind-laid deposits on the flanks of the Spokane Hills and at localities along the Missouri River (pl. 2), much of which consist of the type of silt called loess, lie on high ground above the water table and ordinarily are not liquefiable. If these sediments became saturated with water from excessive rainfall or snow melt, however, they might be capable of extensive liquefaction and flow sliding in a strong earthquake. The potential for such behavior in loess is suggested by the widespread failure of the material in historic earthquakes, notably those that occurred in Kansu Province, China, in 1920 (Willis, 1922) and along the Mississippi River near New Madrid, Missouri, in 1811 and 1812 (Fuller, 1912, p. 59-61). Sand and silt in older gravel and in older stream and lake deposits are unlikely to become liquefied in future earthquakes. The older gravel, which lies above the water table, is rarely saturated; and sand and silt are not abundant in the unit. Furthermore, the older gravel is generally dense and well compacted and probably would resist dislocation even if liquefaction were to occur. Sand and silt in the older stream and lake deposits unit are mostly dense and partly cemented and generally may be incapable of significant earthquake-induced liquefaction. The water-table level in these deposits, apart from mate- rial at lakes and reservoirs and near flowing streams, is mainly at depths greater than 10 m, which further less- ens the possibility of liquefaction. Moreover, the com- pact and coherent state of the older stream and lake sediments probably would prevent much liquefaction- induced movement in them. DEPOSITS PRONE TO SETTLEMENT Intense vibration of the ground during strong earth- quakes commonly leads to compaction of loose surficial materials and to settlement of the ground surface. This kind of dislocation, which can occur either in dry or in saturated sediments and which can effect ground sub- sidences of as much as a meter or more, may produce damage to engineering structures supported on, or built of, the compacted materials. Substantial settlement of the land surface also can result from densification or from lateral spreading of liquefied sediments beneath the ground surface. Often, the precise cause of ground settlement cannot be determined. Surficial materials in the Helena area that may be particularly susceptible to seismically induced compac- tion and settlement include artificial fill, placer tailings, landslide deposits, and stream deposits. Slope wash, wind-laid deposits, and glacial-lake deposits are probably capable of densification to a lesser degree; older gravel and older stream and lake deposits are comparatively dense and firm and are unlikely to undergo significant compactive settlement from earthquake ground shaking. DEPOSITS PRONE TO CRACKING Horizontal oscillation of the ground during strong earthquakes commonly produces surface cracks that range from short hairline fractures to deep fissures many centi- meters wide and hundreds of meters long in loosely consolidated surficial deposits. This cracking, which may be accompanied by differential settlement of the ground surface, can cause serious damage to structures built of surficial materials and to structures buried in the deposits. Although only a few ground cracks were formed in surficial materials during the Helena earthquake of 1935 (magnitude 6%), a much greater incidence of cracking can be expected to take place in a future shock of larger magnitude. Surficial deposits in the Helena area that are most susceptible to earthquake-induced ground cracking are masses of artificial earth fill such as road and railway foundations, irrigation- and drainage-canal embankments, and earth dams. Placer tailings also may be highly sus- ceptible to this kind of dislocation. Other materials prone to cracking include stream deposits, slope wash, glacial- lake deposits, and wind-laid deposits of loess, particular- ly along streambanks and lakeshores. The older gravel and the older stream and lake deposits, which are general- ly firmer than the other surficial materials, probably LOCAL GEOLOGIC CONDITIONS THAT MAY CONTRIBUTE TO SEISMIC HAZARDS 49 would undergo significant cracking only in major or great earthquakes (magnitude >7.0). STEEP BEDROCK SLOPES Because landsliding takes place more readily and with greater frequency on steep slopes, it is most likely to occur in the mountainous parts of the Helena area in future earthquakes of destructive magnitude. Now, how- ever, it is not possible to predict precisely where, or at what specific level of earthquake ground shaking, land- sliding on the mountain slopes will occur, for quantita- tive data are not available on the stability of slopes in this region. Steep slopes on bedrock that are potential sites of earthquake-induced landsliding are especially common in the Scratchgravel Hills, in the mountains south and west of Helena, along the northern slope of the Elkhorn Mountains, on the west flank of the Spokane Hills, in escarpments along the Missouri River, and in the Big Belt Mountains (pls. 1, 2). The precipitous slopes on the flanks of Mount Ascension and Mount Helena, slopes at the eastern front of the Scratchgravel Hills, and slopes along the upper parts of Last Chance Gulch and Dry Gulch and the valley of Tenmile Creek pose a threat to urbanized areas. The north-facing limestone cliff near the summit of Mount Helena, which rises steeply above the western section of the city of Helena, may be particu- larly hazardous in terms of its potential susceptibility to earthquake-triggered landsliding. Although this preci- pice showed no evidence of dislocation during the earth- quake of 1935, it might be prone to rockfall or perhaps even to massive landsliding during a stronger earthquake, for example in the range of magnitude 6.5-7.0. Although steep slopes are common in the area, only two large landslides have been recognized: one at the head of Park Gulch in the northwestern part of the Helena quadrangle (pl. 1) and the other along the steep northern slope of the Elkhorn Mountains in the south- eastern part of the East Helena quadrangle (pl. 2). Tree growth indicates that these slides originated scores of years ago. The Park Gulch slide, which consists of a tonguelike mass of angular blocks of quartzite shed from the mountain mass that rises above it on the west, is doubtfully related to seismic shaking. The slide at the northern front of the Elkhorn Mountains is a large slump detached from a steep mass of volcanic bedrock. It might have been activated by earthquake vibrations, but other causes for its origin are equally plausible. FAULTS The earthquake hazard associated with faults is threefold: (1) earthquakes may originate on them, (2) surface rup- ture and strong ground shaking may occur along or near them, and (3) regional ground displacement may be asso- ciated with them. Geologic evidence indicates that earth- quakes generally occur on active faults and are rarely associated with inactive fractures (Bonilla, 1970, p. 68). The recognition of active or potentially active faults is therefore critical to the formulation of sound land-use practices and building ordinances that may be imple- mented to minimize the danger of future fault movement. Faults are numerous in the Helena area, but active faults that display evidence of movement in Holocene time (last 10,000 years) -have not been recognized. However, several faults in the area are categorized as potentially active fractures. They are confined to the Lewis and Clark line (figs. 3, 10), which appears to be the principal regional tectonic element in this part of Montana current- ly undergoing deformation. The crustal blocks north and south of the line, in the Helena area, are judged to be comparatively stable, and faults within those masses are believed to be inactive. POTENTIALLY ACTIVE FAULTS Six faults in the area are considered to be potentially active and likely to sustain future movement. They are the Bald Butte, Helena Valley, Scratchgravel Hills, Spokane Bench, Regulating Reservoir, and Spokane Hills faults. In most places, these faults are covered by soil, loose rock, and young surficial deposits; and little is known about their surface pattern, the subsidiary faulting asso- ciated with them, and the width of the zone of surface disturbance along them. Seismological data on the frac- tures are also sparse; only a few small earthquakes, whose epicenters were accurately determined in 1973 (Freidline and others, 1976), can be confidently related to specific faults. Accordingly, more detailed infor- mation on these faults must be obtained before any realistic estimate of their capability to produce earth- quakes can be made or the nature of ground deformation that may be associated with them during future move- ment can be predicted. The general characteristics of the potentially active faults have already been described. A summary of those data and a tentative evaluation of the earthquake-hazard potential of the faults based upon the limited informa- tion now available are given here. The Bald Butte and Helena Valley faults are many tens of kilometers long, extend far into the Earth's crust, and are many millions of years old. The principal move- ment on them was strike-slip and perhaps amounted to several kilometers. Deformation of stream deposits and slope wash along their traces has not been recognized, and it is uncertain that surface movements have occurred on the fractures in Holocene time (last 10,000 years). 50 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA However, the near coincidence of some earthquake epi- centers with the traces of these faults (fig. 10) suggests that the faults are active and, because of their large dimensions, potentially capable of producing future dam- aging earthquakes. Where the faults cross bedrock and can be examined, they consist of a main break bordered by a zone of small, branching subsidiary faults and subparallel fractures that extend as much as 50 m out- ward from the main line of rupture. If either of the two faults was to undergo sudden, large-scale surface breakage, as might occur in a powerful earthquake, the greatest displacement probably would occur in a narrow zone along the main break, but significant ground deforma- tion also might take place along the auxiliary faults and fractures that border the main fault line. Accordingly, earthquake-triggered surface breakage along either fault, in bedrock, might be distributed over a zone as much as 100 m wide. The effect of sudden fault rupture on surfi- cial deposits that cover the fault traces cannot be accu- rately predicted, but records of historic surface faulting (Bonilla, 1970, p. 58-59) indicate that much of the de- formation, especially larger displacements, probably would be transmitted upward through the surficial materials to the ground surface. The Scratchgravel Hills fault is a normal fault more than 12 km long. It has a maximum vertical displace- ment of about 300 m. Along the eastern front of the Scratchgravel Hills, the fault is marked by a high, steep scarp produced by the fault movement. The fault trace, which lies at the base of the scarp, is in most places covered by surficial deposits laid down in the Holocene Epoch (last 10,000 years), and the age of the fault is uncertain. However, the geologically youthful state of the scarp suggests that fault displacement probably took place in the Pleistocene Epoch, between 10,000 and 2 million years ago. Moreover, the proximity of the inferred trace of the fault to the epicenters of three small earthquakes recorded in 1973 (fig. 10) suggests that those shocks may have originated on the fracture. On the basis of these relations, the fault is regarded as a poten- tially active fracture, and its dimensions indicate that it may be capable of generating a future earthquake of destructive magnitude. Because the fault is poorly exposed, the extent of ground breakage that might result from sudden surface displacement on it is difficult to predict. It is possible, however, that deformation might occur within a zone many meters wide along the fault trace. The Spokane Bench fault is a normal fault about 20 km long. It has a maximum vertical displacement of about 100 m and probably extends into the bedrock floor beneath Helena Valley. Upthrow of older stream and lake deposits along the fault has produced a prominent scarp along the west and south sides of Spokane Bench. Over much of its length, the fault trace is covered by stream deposits of Holocene age (last 10,000 years), and major movement on the fracture predates those materials. However, trenching investigations across the fault near the Helena Valley Regulating Reservoir by the U.S. Bureau of Reclamation and the U.S. Geological Survey (M.W. Reynolds, written commun., 1977) have shown that the fracture deforms deposits of probable Pleistocene age (10,000-2 million years ago). Accordingly, the fault is regarded as a potentially active break. The length and displacement of the fault suggest that it is capable of generating future earthquakes, possibly of destructive magnitude. The zone of surface disturbance along the Spokane Bench fault, as determined by trenching, is as much as 50 m wide (M.W. Reynolds, oral commun, 1977); ground displacement triggered by an earthquake might be distributed over this broad strip of land. The Regulating Reservoir fault is a normal fault about 6 km long. It has a maximum vertical displacement of about 30 m. Because it may have originated simulta- neously with the parallel-trending Spokane Bench fault in Pleistocene time (10,000-2 million years ago), it is categorized as a potentially active fracture. However, the moderate dimensions of the Regulating Reservoir fault suggest that it is incapable of producing a destruc- tive earthquake. The Spokane Hills fault is a normal fault more than 11 km long. It has a minimum vertical displacement of several hundred meters and probably extends downward several kilometers in the Earth's crust. Upthrow of bed- rock on the northeast side of the fracture has produced a steep scarp along its midlength. Geologic relations indi- cate that major displacement on the fault took place not long prior to 20,000 years ago, and it is therefore classi- fied as a potentially active break. A low-magnitude earth- quake centered near the southern trace of the fault in 1973 (fig. 10) might have originated on the rupture, and small earthquakes probably will occur on the fault in the future. Whether the Spokane Hills fault is capable of producing a destructive earthquake is problematical, but the dimensions of the fracture suggest that it may have such a potential. The main fault break is straight and narrow, is only a meter or two wide, and is accompa- nied by little subsidiary fracturing in the adjoining rocks. Sudden surface displacement, however, might be distri- buted over a fairly wide zone along the fault trace. FAULTS PRONE TO REACTIVATION In the area of major shaking of powerful earthquakes, faults other than the causative fracture may undergo sudden reactivation and produce large surface displace- ment (Bonilla, 1970, p. 55, fig. 3.5). A classic example of this phenomenon was the reactivation of four normal faults northeast of Hebgen Lake during the Montana LAND USE AND EARTHQUAKE PROTECTION 51 earthquake of 1959, which produced scarps as much as 6 m high in the land surface (Witkind, 1964b, p. 37). Fault reactivation of this sort is most likely to occur on active faults, but large dormant faults also have undergone surface movement in strong earthquakes (Bonilla, 1970, p. 68). The faults in the Helena area that are most susceptible to reactivation are the potentially active fractures within the Lewis and Clark line; namely, the Bald Butte, Helena Valley, Scratchgravel Hills, Spokane Bench, Regulating Reservoir, and Spokane Hills faults. The Silver Creek and Northwest valley faults and the concealed fault in the vicinity of Lake Helena (pl. 2), which appear to be dormant fractures within the Lewis and Clark line, also may be capable of rejuvenation. Although geologic cri- teria indicate that the normal faults in the crustal block south of the Lewis and Clark line are inactive, some of these fractures, especially the larger ones, may have the potential to reactivate when subjected to intense earth- quake ground motion. Faults that are particularly sus- pect in this regard include the fractures at Willit Ridge, the fractures on either side of Mount Ascension that extend into the eastern section of Helena, and the large, north-trending fracture that ends against the Bald Butte fault about a kilometer southeast of Helena. The thrust faults in the Helena area, which lie in the crustal block north of the Lewis and Clark line (pl. 2), are very ancient; they are probably firmly healed and are unlikely to reactivate. CONDITIONS CONDUCIVE TO REGIONAL GROUND DISPLACEMENT In addition to ground displacement along the trace of faults, surface faulting also may produce regional warp- ing or tilting of broad areas of the land surface. These regional distortions, when they occur suddenly, can have an enormous effect on surface waters; commonly they produce rapid water movements, permanent changes in water level, or changes in drainage pattern that result in widespread damage. A potential for regional ground displacement in the Helena area is provided by the Hele- na Valley, Spokane Bench, and Spokane Hills faults. Conceivably, movements of a few meters along these fractures could cause warping or tilting of broad areas of land in Helena Valley. HYDROLOGIC CONDITIONS Large earthquakes can generate destructive seiches and wave surges in rivers, lakes, and reservoirs and in industrial tanks by strong ground shaking or by regional displacement of the land surface. The potential magni- tude of these effects is described in the section on "Seiches and surges." The principal bodies of water in the Helena area that are potentially susceptible to these hazards are Hauser Lake on the Missouri River, Lake Helena, and the Helena Valley Regulating Reservoir. The narrow portions of Hauser Lake north and south of Lakeside and in the lower canyon of Prickly Pear Creek, which would tend to constrict the oscillation of lake waters, might incur the greatest wave heights from seiching or surging. Other bodies of water in which earthquake- induced seiche effects might occur include Lake Stanchfield, the Northern Pacific Reservoir on McClellan Creek, the Hardie and Gehring Reservoirs on Threemile Creek, and the settling basin on Tenmile Creek. Damaging motions also might be produced in water-storage reservoirs and towers and in fuel-storage tanks in the area during a strong earthquake. LAND USE AND EARTHQUAKE PROTECTION GENERAL REMARKS Economic losses and casualties from earthquakes in populated areas mainly result from ground-vibration damage to manmade structures. Accordingly, protec- tion against earthquakes largely rests upon the engineer- ing practice of making structures earthquake resistive. A brief commentary on earthquake-resistant design, direct- ing attention to the seismic requirements in the Uniform Building Code and to earthquake engineering in general, is included in the appendix to this report. Lately, much thought also has been focused on the pos- sible effectiveness of land use as a supplement to engineer- ing design in providing protection from earthquakes- land use in this context being broadly defined as the siting of vulnerable structures and concentrations of people away from the places where the potential danger from earthquake hazards is greatest. Conceivably, informed land use, if implemented over a long period of time, could be a very effective means for preventing structural damage, saving lives, and minimizing social disruption during earthquakes. Its application is particularly important in areas of rising population and rapid urban growth. Land-use practice to counter earthquake effects must, of course, be undertaken judiciously. The proper goal is to establish a balance between the uses of land that satisfy the economic and functional needs of people and the uses that may provide appropriate public protection. Arbitrary land-use requirements that might unnecessari- ly discourage development should be avoided. Geologic conditions in the Helena area that may mod- erate or enhance seismic hazards have been described in the section on "Local geologic conditions that may con- tribute to seismic hazards." A review of those conditions and of their possible implications for land use and earth- quake protection is presented in the following discussion. 52 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA MODERATED MOTION ON BEDROCK In destructive earthquakes, the intensity of ground shaking can vary substantially depending on the type of rock or soil that underlies the ground surface. Probably the most important relation in this regard, insofar as earthquake safety is concerned, is the fact that damage, and thus presumably the intensity and duration of shaking, is ordinarily less on solid bedrock or on other types of firm ground than on unconsolidated surficial deposits. A rudimentary analysis of the expected response of local rock units in future earthquakes, given in the section on "Ex- pected response to ground shaking in future earthquakes," indicates somewhat more precisely that the intensity of ground motion on bedrock may be one or two and, in some instances, as much as three Mercalli-scale incre- ments less than the intensity on surficial materials. This estimate generally agrees with data accumulated at earth- quake sites in other parts of the world and with experi- mental results that show a marked lessening of ground-motion amplitude on bedrock. Accordingly, a large measure of protection from earthquake ground shaking may be real- ized by siting structures on or anchoring them to bed- rock or other firm ground. The ideal land-use practice to protect against earth- quake ground shaking probably would be to locate all new structures on bedrock sites that are not susceptible to landslide, fault, or flood hazards, but such a procedure is usually impractical. For example, in the Helena area, most of the bedrock terrain is steep and mountainous and does not easily lend itself to large-scale development, so that urban growth is mainly directed onto the flat alluvial floor of Helena Valley where construction and orderly planning are easier and where water is plentiful. Nevertheless, the potential for saving lives and property merits that serious consideration be given to building on solid ground. This is particularly true for vital facilities such as hospitals, fire and police departments, rescue- squad facilities, powerplants, and communication cen- ters as well as for high-occupancy structures such as schools, civic centers, theatres, office and apartment buildings, and large manufactories. A sizable area of bedrock terrain suitable for urban development is located immediately east of Helena, main- ly in sees. 27 and 34, but including portions of secs. 26, 28, 33, and 35 of T. 9 N., R. 3 W. Smaller areas of bedrock and of thinly covered bedrock near Helena, which are suited for some large-scale building purposes, are pres- ent west of Fort Harrison and on the south slope of the Scratchgravel Hills. Outlying areas of larger extent in which bedrock is at or near the ground surface, and in which the topography is generally favorable for construction, are located near Birdseye, south of Gearing (Gehring) station on Silver Creek, in the northwestern part of Helena Valley, and southeast of Montana City. Steep bedrock terrain at the southern margin of Hele- na and in the mountains to the south, as well as hilly bedrock terrain in other areas, is mainly suited for home construction. However, care must be taken in those areas, especially if dense development is planned, to protect against earthquake-induced landsliding. INTENSIFIED MOTION ON SURFICIAL DEPOSITS Data presented in the section on "Expected response to ground shaking in future earthquakes" show that a general enhancement of ground motion may take place on surficial deposits relative to bedrock, that significant variations in the intensity of shaking may occur on different types of surficial materials, and that shaking may be intensified on water-saturated sediments in future strong earthquakes. In addition, the amplification of long-period motion in thick accumulations of older stream and lake deposits in Helena Valley may constitute a potential hazard. In general, protection against earth- quake ground shaking on surficial deposits probably can be achieved through an appropriate combination of land- use and design measures. RELATIVE INTENSITY ON SURFICIAL UNITS Among the surficial units, it is expected that the intensity of ground shaking generally will be greatest on artificial fill, placer tailings, and landslide deposits; intermediate on stream deposits, slope wash, wind-laid deposits, glacial-lake deposits, older gravel, and older bentonitic clays; and least on the bulk of the older stream and lake deposits. The intensity of ground motion on artificial fill, placer tailings, and landslide deposits might be as much as three Mercalli-scale increments higher than the overall intensity on bedrock in a future strong earthquake. Furthermore, these surficial units are highly prone to settlement, cracking, and slumping during earthquakes. Artificial fill, placer tailings, and landslide deposits there- fore constitute some of the most seismically dangerous ground for building sites. The landslide deposits shown on plates 1 and 2 generally can be disregarded as a seismic risk, however, for they are in mountainous ter- rain far from populated areas. In the urbanized parts of the Helena area, masses of artificial fill and placer tailings that may pose a substan- tial seismic risk to development include: (1) the large body of placer tailings that covers about 170 ha (400 acres) of land north and south of Custer Avenue, (2) the mass of artificial fill that covers about 20 ha (50 acres) of land along the lower part of Last Chance Gulch north of Neill Avenue, and (3) the stream deposits that under- lie about 25 ha (60 acres) of land in the bottom of Last Chance Gulch, which were extensively worked for gold in earlier days and essentially constitute made land. The LAND USE AND EARTHQUAKE PROTECTION 53 distribution of these materials is shown on plates 1 and 3. The severe structural damage that occurred in the upper part of Last Chance Gulch during the earthquake of 1935 (pl. 3) was attributed mainly to intensified shaking on the made ground, although differential settlement of the land may have played a part in some of the structural failure. This area was the site of extensive urban renewal in the 1970's including con- struction of several large, high-occupancy brick- and concrete-walled buildings. Careful consideration should be given to future use of the land underlain by artificial fill and placer tailings. Before new structures are built on these deposits, the engineering and seismic characteristics of the materials should be thoroughly investigated to determine their potential dynamic response in future strong earthquakes, and appropriate design requirements should then be followed to effect proper protection against lateral earth- quake forces and ground settlement. Low-density develop- ment, entailing use of the land for parks, golf courses, recreation areas, parking lots, and the like, would pose the least risk to loss of life and property from a destructive earthquake. Serious thought should also be given to a review of the design of newly built, high-occupancy struc- tures sited on made land in Last Chance Gulch and on placer tailings along Custer Avenue to ensure that they meet building-code requirements for earthquake- resistant construction. The intensity of ground shaking on stream deposits, slope wash, wind-laid deposits, glacial-lake deposits, old- er gravel, and older bentonitic clays is expected to be as much as two Mercalli increments higher than the intensi- ty on bedrock in future strong earthquakes. Some of these surficial units also have a high susceptibility to ground failure, which increases the risk of building on them. Appropriate engineering investigations should there- fore be made to evaluate the increased risk to structures sited on these materials. In general, protection from earthquake shaking on these deposits probably can be gained by a suitable combination of design requirements and land use. Urban development in the Helena area now is concentrated in the western part of Helena Valley on land underlain by stream deposits and slope wash. The older stream and lake deposits (apart from benton- itic clays in the unit) constitute the firmest ground among the surficial materials, and the intensity of shaking on them in a strong earthquake ordinarily is expected to be no more than one Mercalli increment higher than the intensity on bedrock. Ground failure is also unlikely to occur on these materials. Accordingly, the bulk of the older stream and lake deposits generally present a lower seismic risk to structures and are from a seismic view- point more suited for high-density development than the other surficial units. A large area of older stream and lake deposits, covered in places by a thin veneer of older gravel, lies west and southwest of East Helena and extends to the vicinity of Montana City. Most of the eastern part of Helena Valley also is underlain by older stream and lake deposits (pl. 2). WATER-SATURATED GROUND A significant increase in the intensity of ground shak- ing may occur on unconsolidated surficial deposits in which the water table is near the ground surface. Medvedev (1965, p. 49) estimated that the intensity may increase one whole unit on the GOST intensity scale when the water table is within 1 m of the surface, and Gutenberg (1957, p. 235) determined that shaking may be greatly prolonged on water-saturated alluvial ground. Water- saturated sediments also are prone to earthquake- induced liquefaction, differential settlement, and cracking, which increase the seismic risk to structures built on those deposits. The largest area of shallow water saturation in the Helena region is on stream deposits in the western part of Helena Valley, mainly to the south of Lake Helena. This area, which is generally outlined by the 6- and 12-ft (1.8- and 3.6-m) lines of equal water-table depth shown on plates 1 and 2, covers about 90 km of the land surface. During the period of summer irrigation in the valley (June-September), the water table within much of the area bounded by the 6-ft (1.8-m) depth line reaches the surface and the ground is waterlogged, although drainage canals dug in the 1970's have partly alleviated this condition. Other areas underlain by surficial depos- its in which the water table is close to the surface are present along the shores of Hauser Lake on the Missouri River and adjacent to the Helena Valley Regulating Reservoir in the eastern part of the area (pl. 2). These areas are relatively small. Although most of the shallow-water-table land in Helena Valley is now in agricultural use and is thinly populated, significant urban development on the land has occurred locally and probably will continue in the future. Careful consideration should therefore be given to the practical steps that might be taken to reduce the increased risk of building on this ground. Before any comprehensive land- use program is devised for the area, however, the bound- aries of the water-saturated land should be more precisely defined and engineering data should be obtained to accurately assess the potential performance of the ground in future strong earthquakes. When that in- formation is available, appropriate design and land-use requirements can be formulated and implemented to effect seismic safety. LONG-PERIOD MOTION IN HELENA VALLEY In strong earthquakes, surface ground vibrations of long period (1.0-2.5 s) can be greatly amplified on thick accumulations of soft, loosely consolidated sediments 54 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA that underlie broad alluvial valleys and basins. This amplification, which occurs at a frequency near the natu- ral frequency of the deposits, causes the material to behave more or less like a shaken bow! of jelly during an earthquake. Shaking of this sort, which may be pro- duced by shocks that originate far from the earthquake source, is potentially hazardous to high-rise buildings whose fundamental period of vibration roughly coin- cides with that of the ground. Severe long-period shak- ing occurred on lake beds that underlie Mexico City during strong earthquakes in 1957, 1962, and 1978 and caused extensive damage to tall buildings in the down- town area. Those earthquakes were centered more than 200 km from the city. Helena Valley is underlain by a thick accumulation of older stream and lake deposits of Tertiary age. These deposits, which are physically similar to the lake beds beneath Mexico City, may have the potential to amplify long-period ground vibrations in future earthquakes. Accordingly, the potential earthquake performance of the older stream and lake sediments should be thorough- ly investigated before high-rise structures are built on the valley floor. Dynamic analysis of individual sites and structures probably will be necessary to ensure the adequacy of the design of tall structures in the valley-floor area. GROUND FAILURE ON SURFICIAL DEPOSITS Surficial deposits commonly fail by landsliding, lique- faction, settlement, and cracking during earthquakes, and such failure usually becomes more prevalent as earthquake magnitude increases. Surficial materials in the Helena area that may be highly susceptible to earthquake-triggered landsliding are present on steep hill and valley slopes; in streambank, lakeshore, and terrace scarps; and in steep-sided man- made embankments and excavations. Scarps and slopes with grades ranging from 60 percent to vertical have the greatest landslide potential, and structures should be sited a safe distance from these steeply inclined land- forms unless the hazard can be overcome by site prepara- tion or engineering design. Slopes with grades between 15 and 60 percent generally have less landslide risk, but locally they also may be highly unstable, especially if saturated with water, and their engineering characteris- tics and stability should be investigated prior to develop- ment. Slopes below 15-percent grade generally should have a low landslide potential under the prevailing dry climate, but liquefaction-induced slides might be triggered on these slopes by an earthquake if the slope materials are saturated with water, as might be the case during spring months or during periods of abnormally high rainfall. Liquefaction, which may produce lateral movement, settlement, cracking, and flooding of ground, is likely to occur in water-saturated sands and silts in the stream deposits that underlie the western part of Helena Valley and in glacial-lake and other surficial units along the shores of Hauser Lake. Water-saturated flood-plain depos- its along the major streams and water-saturated artifi- cial fill and placer tailings also may be highly susceptible to liquefaction processes. The high potential for liquefaction- induced failure in these deposits, coupled with the possi- bility that ground shaking may be significantly intensified on them, greatly increases the seismic risk to structures sited on the water-saturated materials. The dynamic properties and liquefaction potential of these sediments therefore should be carefully evaluated prior to exten- sive land development. Methods for determining the degree of liquefaction to be expected in unconsolidated surficial units during strong earthquakes are described by Seed and Idriss (1971) and by Youd and others (1975). Settlement and cracking of surficial deposits can be expected in a future strong earthquake. Artificial fill and placer tailings, the most weakly compacted of the surfi- cial materials, probably are most susceptible to this kind of dislocation, which adds to the risk of building on them. Stream deposits, slope wash, glacial-lake deposits, wind-laid deposits, older gravel, and older stream and lake deposits also may be prone to settlement and crack- ing locally. Features most likely to undergo cracking include artificial earth embankments, streambanks, lakeshore scarps, and terrace and bench margins. Structures gener- ally should be sited away from those landforms to avoid the cracking hazard, although locally it may be possible to alleviate the danger by site preparation. Widespread settlement and cracking might occur on the broad area of stream deposits in the western part of Helena Valley during a strong earthquake, especially in the area of shallow water saturation. The precise locale and severity of settlement and cracking on this wide expanse of land are largely unpredictable, however, and protection against these hazards is difficult by means other than earthquake- resistant design. LANDSLIDING ON STEEP BEDROCK SLOPES In major earthquakes, landslides in the form of soil slides, debris slides, and rockfalls are common on steep slopes underlain by bedrock, and, in rare instances, strong shaking may trigger large avalanches of solid rock on slopes that are unstable or marginally stable. Slides of this sort that occurred in the steep bedrock terrain around Hebgen Lake in the Montana earthquake of 1959 exten- sively damaged forests and roads and caused 28 fatalities. Bedrock slopes ranging from 60 percent to vertical are FUTURE ASSESSMENT OF SEISMIC HAZARDS 55 abundant in the mountainous terrain in the Helena area, and many of them are seismically unsafe and dangerous to structures built on them or sited near their base or crest. The bottoms of narrow, deep, steep-walled valleys and the base of high, steep cliffs are particularly hazard- ous as building sites because of their vulnerability to earthquake-triggered landslides. A thorough evaluation of the stability of valley slopes and cliff faces and the probability of landsliding at a particular site should be made before structural development is undertaken. FAULT HAZARD ABATEMENT Surface fault displacement, which might occur in the Helena area in a large earthquake, is most likely to take place along the potentially active Bald Butte, Helena Valley, Scratchgravel Hills, Spokane Bench, Regulating Reservoir, and Spokane Hills faults. Other faults in the area, which are classed as inactive, constitute a lesser hazard. Surface faulting is usually distributed over a small area compared to the broad expanses of land that are disturbed by other earthquake effects. Land-use and construction measures undertaken to counter the hazard of surface faulting must contend with the entire zone of deformation along a fault as well as with the main trace of the fracture, and fault hazard abatement generally has involved the adoption of build- ing easements and zoning ordinances along and within fracture zones where they are reasonably well located. Steinbrugge (1968, p. 11-20), in a consideration of earth- quake hazards in the San Francisco Bay area of California, suggested that three areas of different risk might be established in and near fault zones to guide land-use and construction practice. From lowest to highest risk, these areas are: (1) outside the fault zone, (2) within the broad fault zone but away from traces of active fault slip, and (3) on the main fault trace and on the trace of other ruptures in the zone that exhibit evidence of recent movement. Building easement and setback provisions adopted in 1971 by the town of Portola Valley, California, to deal with development on or near active strands of the San Andreas fault are described by Mader and others (1972, p. 845-857). This town and the city of Fremont, California, were the first communities officially to recognize the potential earthquake hazard of faults and to institute measures to cope with the danger. Figure 12 shows a portion of the zoning map establishing the setback pro- visions along the San Andreas fault at Portola Valley. Further field investigation is necessary to evaluate fault hazards in the Helena area properly. Data are lack- ing on the location of buried fault traces, the level of seismicity and of seismic risk associated with specific faults, the width of fault zones, and the distribution of branch and secondary faults along major fractures. When this information becomes available, the method of fault- hazard zoning adopted at Portola Valley, California, might be advantageously applied to the potentially active frac- tures in the Helena area. SHORELINE FLOODING Flooding along the shores of lakes and reservoirs in the area might result from seiches, wave surges, or per- manent submergence of land during future strong earth- quakes. However, these effects are largely unpredictable, and few measures can be taken to minimize them except to site structures-especially vital structures-away from the areas of potential flooding. FUTURE ASSESSMENT OF SEISMIC HAZARDS SEISMIC MICROZONATION AND THE NEED FOR QUANTITATIVE EARTH-SCIENCE DATA The ideal objective in earthquake hazards assessment is to obtain information that accurately defines the level of earthquakeeffects that can be expected in any area during future earthquakes of specific magnitude and location. The acquisition of this information and its presentation in map form constitute the practice of seismic microzonation or microregionalization. Such maps, which show in quan- titative terms the potentials for ground shaking, surface faulting, landsliding, liquefaction, settlement, cracking, and flooding in different geographic areas, can provide a meaningful evaluation of earthquake hazards that is directly applicable to engineering design and to the for- mulation of effective building codes and land-use policies for earthquake protection. Detailed microzonation maps, based mainly on intensity-increment techniques (Medvedev, 1965, p. 1-98), have been prepared for many years in the U.S.S.R., and extensive work on seismic zoning is under- way in other countries, including the United States. An early microregionalization (microzonation ) map of expect- ed maximum earthquake intensities in the Los Angeles basin of California is shown in figure 13. An extensive summary of microzonation research and methodology is given in the Proceedings of two Interna- tional Conferences on Microzonation for Safer Construc- tion Research and Application, the first held in Seattle, Washington, from October 30 to November 3, 1972, and the second held in San Francisco, California, from Novem- ber 26 to December 1, 1978. The earth-science information in this report provides a broad definition of the earthquake problem and a general evaluation of potential seismic hazards in the Helena area. However, the data are limited and do not furnish a proper basis for making the kind of quantitative esti- mates of earthquake effects that are necessary for com- prehensive seismic zoning and engineering application. 56 GEOLOGY, EARTHQUAKE HAZARDS, AND LAND USE IN THE HELENA AREA, MONTANA Area of figure 12 EXPLANATION FAULT TRACE LOCATION KNOWN e 175 ft setback 0 100 200 300 METERS --- FAULT TRACE LOCATION INFERRED 0 503 FEET FIGURE 12. -Portion of zoning map establishing building setback requirements along strands of the San Andreas fault by town ordinance in Portola Valley, California. New building is prohibited within 50 ft (15 m) of the well-located trace of the fault (within area of dark shading), and structures with an occupancy larger than single-family homes must be sited 125 ft (38 m) from the fault trace (beyond area of light shading). On the inferred strand of the fault (dashed line), setbacks of 100 ft (30 m) are required for single-family dwellings and 175 ft (53 m) for structures of higher occupancy. From Mader and others (1972, fig. 5) as modified by Nichols and Buchanan-Banks (1974, fig. 10). In particular, further studies are needed on regional and local seismicity, potential motions of local soils and surfi- cial deposits under conditions of earthquake loading, | 3. physical characteristics of active faults and the micro-: seismic activity associated with them, liquefaction poten- tial of water-saturated sediments, stability of slopes in urban areas, and flood potential along lakes and reservoirs. Only by broadening the earth-science information base in a very substantial way will it be possible to formulate rational land-use policies and reliable engineering cri- | 4. teria to minimize seismic hazards in the area effectively. Some worthwhile earth-science investigations that are likely to yield valuable data for future hazard assess- ment in the Helena area are the following: 1. - Monitoring microearthquake and small-earthquake | 5- earthquake source. potential ground-motion intensity. from earthquake forces. mediate, and greatest at sites equidistant from an Determining shear-wave (S-wave) velocity in differ- ent types of bedrock and surficial deposits. The studies of Borcherdt and others (1979) indicate that measure- ments of S-wave velocity are a promising means for determining seismic-intensity increments in rock units. Evaluating this parameter as a means for zoning Determining basic engineering properties (such as density, porosity, shearing resistance, and stiffness) and layering and grain-size characteristics of surficial units to estimate their potential for ground failure Measuring the thickness of surficial deposits above activity with portable seismographs to determine local seismicity (the level of earthquake activity) and to locate epicenters with respect to specific faults. 2. Recording and measuring ground motions generated on different surficial and bedrock units by small earth- quakes, distant underground nuclear tests, or quarry blasts to determine relative response of the rocks at low-strain levels and to delineate those geologic units on which ground shaking is likely to be least, inter- bedrock (depth to bedrock) which, along with S-wave velocity, can be used to determine the fundamental period of vibration of the materials in different geo- graphical areas. The fundamental vibration frequency of the surficial units must be known to properly eval- uate the problem of site-structure resonance in earth- quake-engineering design. 6. - Trenching across the trace of active faults at selected localities to determine the width of fault zones, the age FUTURE ASSESSMENT OF SEISMIC HAZARDS 57 118°00' 45" 11793730" 118030" 15" MOS o ' Z- € . t

vrea seers snare s 3, 19 Kansu Province, China, earthquake of 1920, flow 1 £. .». + 1s re repre ney 37 L T ANGNG rene bere pent 21 Lake Helena ............ .. 8, 17, 19, 20 seiches and surges . susceptibility of scarps to landslldmg Lake Stanchfield ...... Land displacement .... 4 Land use and earthquake protectlon Landslide deposits ..... and building .... Landsliding ...... ground failure ..... steepness of slopes ... Last Chance Gulch ...... damage in 1935 earthquake @APUA SALE 202.2200 0000000 ore deer vee s susceptibility of bedrock slopes to landsliding .... 49 Late UIRLACEOUS TOCK 10, 11 Lewis and Clark County . . 8, 19, 62 surficial deposits, reaction in earthquakes ...... 41 Lewis and Clark line ................. 13, 16, 26, 28, 49 potential for fault reactivation ...... 51 Liquefaction-induced failure . 47, 54 Lombard earthquake of 1925 . 28 ground churning ............................ . 40 ground cracking ..... . 40 landsliding .... . 36 LOHE WBVO cas ves er 21 Long-period wave motion, Helena Valley . . 54 LOVE WAVE recs reino rebs . 21 M M; scale ..... .s 26 Ms scale ... .. 26 McKeown, M., trench study .................... 7 Medvedev, equations of seismic intensity Mexico City earthquake of 1957, ground shaking on alluvium .......... nect Microregionalization ... ... 55 Middle and late Tertiary deposits ..... 15, 17 Middle Proterozoic rocks .... Middle Tertiary deposits .. Modified Mercalli Intensity Scale ...... See also Appendix ..................... Montana Bureau of Mines and Geology . [Montana] State Earthquake Hazard Mnugatxon Commit- ....... 58 Mount Ascension . 3, 19 Mount HeQH® x8 susceptibility of bedrock slopes to landsliding .... 49 N Natithe Of ORTEROURIEGS . ...... ... vie 233 els 21 New Madrid earthquakes of 1811 and 1812, crustal "1515. (3301s bes iva ther 39 Niigata, Japan, earthquake of 1964, quick-condition failure . .. 87, 88 Normal faults ..... Northwest Valley fault . Older gravel, and building ............. \;...» iehery placer gold contents ................... Older stream and lake deposits Sno buliding constituents ...... earthquake effect ... Oligocene deposits .. Orofino Gulch ........ P wave .. Park Gulch, large landslide ............ Parkfield-Cholame, Calif., earthquake of 1966, surface faulting ... Placer tailings ........ and building . constituents ..... Planning, State and local ............... Pleistocene deposits ....................... Pleistocene fault movement Plutonic rocks, constituents Potentially active faults .. Prickly Pear Creek ...................«. PIRCGF ...... ciss susceptibility of scarps to landsliding . Prickly Pear Valley. See Helena Valley . PIIMATY WBVG ... os 000 31-0 rin rer 21 Protection from earthquakes, engineering design .. 51 POGS . 50. oreo rev 10, 11 Quaternary deposits Quick-condition failure .. Rattlesnake Mountain quadrangle ... Rayleigh WaVe Regulating Reservoir fault .......... potential activity ...... Reynolds, M. W., trench study Richter magnitude .................. Richter relation between earthquake magnitude and released energy ...... 22 Ridging and furrowing ............... . 40 Robinson, G. D., mapped Helena Valley fault ...... 15 L4 35 Rock slides ... Rockfalls ......... § Wave ...........c.ss San Andreas fault . gs San Fernando earthquake of 1971, ground churmng strong-motion data San Francisco earthquake of 1906, building damage | 32 horizontal fault movement ..... Scratchgravel Hills ... epicenter of 1935 earthquake ROPMAL PMUIE® crse plutonic rocks .. slope wash ...... susceptibility of bedrock slopes to landsliding .... 49 Scratchgravel Hills fault ...... potential activity ...... SOCONORNY | NAVB L pes eros ererens in 21 Sedimentary rocks, Late Cretaceous age . 10 Middle Proterozoic age ...... 10 ;...... c+. 41, 51 Seismic hazards and geologic conditions ............... Pi Seismic history of the Helena area .. M8 Seismic microzonation ..................... . 55 vr U.S. GOVERNMENT PRINTING OFFICE:1986-676-047/26025 is sve is rr res +1 arr eBR oi 28, 52 Seismic sea waves ... sise 80 Seismic waves produced by earthquakes .............. 21 Seismic zonation ................... Seismographs, function Settlement .... Sevenmile Creek . susceptibility of scarps to landsliding ................ Shaking and damage ......... Shear wave ................ Silver City quadrangle Silver Creek ...... placer tailings .. susceptibility of scarps to landsliding Silver Creek fault ............. Size of earthquakes ........... Slope wash ...... and building . susceptibility to landsliding Slump landsliding .................... Slumping in steep embankments . Soup CrGGK Soup Creek thrust fault .... Spokane Bar, placer tailings . Spokane Bench fault ...... potential activity ...... CFGOK s susceptibility of slopes to landsliding Spokane Hills ...................... ¢ wind-laid deposits Spokane Hills fault .............. potential activity ...... State and local planning .... State Earthquake Hazard Mitigation Committee ... Stationary waves ... HE w a & a ! 4a Bak EES Ea ob SB ERE Stream deposits ..... and building .... Strike-slip faults . 18 Strong-motion accelerographs, function in recording earthquakes ..... 21 Strong-motion records ...... 33 Structural dynamic analysis . 0 Subsidence and warping .......... . 39 Surface faulting in historic earthquakes ............... 38 WAVCS \ cons 21 Surface-wave magnitude formula . . 2&8 Surficial deposits and seismic hazard . 41, 49 @TOUNC~TalIUPG 00000000084 een 3a vei ce 54 response to ground motion ... ¥ 52 is irs leve cours inv 41, 51 T TPEAMLIGOFOGK . cee 5, 42 susceptibility of bedrock slopes to landsliding .... 49 susceptibility of scarps to landsliding ... Tertiary fault movement ...... Tertiary rocks ............... response to earthquake ..... Threemile Creek, epicenter of epicenter of 1935 earthquake ... Thrust faults ... Townsend valley . Trout Creek ...... Tsunamis. See seismic sea waves U-Z Uniform Building Code ............... Upper Holter Lake quadrangle ... U.S. Public Law 95-124. See Earthquake Hazards Reduction Act of 1977. Virginia City earthquake of 1947 ........................ 28 Volcanic rocks, constituents ...... Water-surface oscillations Wave motion ... Wind-laid deposits and building ...... earthquake effect ... Zoning, fault-hazard .. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY 119005 B a W ( o- cle “WW“WQSM, , gain " e Surry BAN LIM TS ___ us-r4e(2) 7. BEG FAs RIE 454 y HELEN A 1 NAT | O N AL WRM SaD' h Worl o & } % 7 LEwis and |crark cdyity._ JEFFERSON 1COUNTY 4 34 Base modified from Urban Area Plat of Helena, 17%" Montana: Department of Highways, July 1976 TRUE NORTH APPROXIMATE MEAN DECLINATION, 1985 SCALE 1:25 000 MILE 1 2 KILOMETERS ] p- } \_ ® MONTANA d & mfam" MAP LOCATION Geology by R. G. Schmidt, 1975-76, assisted by W. R. Trojan, 1975, and D. G. Waggoner, 1976; and from Knopf (1963) MAP OF HELENA, MONTANA, SHOWING DISTRIBUTION OF SURFICIAL DEPOSITS AND BEDROCK, TRACES OF GEOLOGIC FAULTS, AND LOCATION OF BUILDINGS HEAVILY DAMAGED IN THE EARTHQUAKE OF 1935 PROFESSIONAL PAPER 1316 PLATE 3 EXPLANATION SURFICIAL DEPOSITS ) ARTIFICIAL FILL | PLACER TAILINGS STREAM DEPOSITS SLOPE WASH OLDER GRAVEL _|_ OLDER STREAM AND LAKE DEPOSITS BEDROCK SEDIMENTARY BEDROCK PLUTONIC BEDROCK APPROXIMATE CONTACT BETWEEN UNITS ************ INFERRED CONTACT BETWEEN OLDER STREAM AND LAKE DEPOSITS (OSL) AND BEDROCK (SB, PB) BENEATH COVER OF YOUNGER SURFICIAL DEPOSITS STRIKE-SLIP FAULT-Arrows show inferred relative direction of hori- zontal movement. Dotted where concealed; queried where location uncer- tain g NORMAL FAULT-Dotted where concealed; U, upthrown side; D,down- thrown side; queried where location is uncertain BUILDING DAMAGE IN EARTHQUAKE OF 1935 -Source of data: Ulrich (1936, figs. 10 and 11); Anderson and Martinson (1936) o Houses and small mercantile and public buildings having intermediate damage o Houses and small mercantile and public buildings having more than 50 percent damage (© Large mercantile and public buildings having more than 50 percent damage. 1, Kessler Brewery; 2, Transient Building, State Fair- ground; 3, County Hospital; 4, St. Joseph Orphan Home; 5, State Arsenal; 6, Helena High School; 7, National Biscuit Company; 8, Bryant School; 9, Intermountain Union College (two buildings); 10, City Hall CE 76 PC v. 1316 DEPARTMENT OF THE INTERIOR © PROFESSIONAL PAPER 1316 U.S. GEOLOGICAL SURVEY PLATE 2 112°00 ap § a , od "45 46°45 poommmmaap : rge r- " moe F g ; < oprat "pe oms : ~ z poe 11142945 I 1 a j - § v 2 4 } y y r ' _ M4 . . 4 3 2 _ EXPLANATION SURFICIAL DEPOSITS ARTIFICIAL FILL-Refuse fill in old city trash dump northwest C of Helena Airport and piles of smelter slag at East Helena. Refuse fill unsorted and unstratified, loosely compacted, uncemented, and as much as 3 m thick; smelter slag unsorted and unstratified, moderately well compacted, uncemented, and as much as 15 m thick PLACER TAILINGS-Piles of coarse, washed gravel, commonly arranged in rows, constituting waste rock from placer-mining operations; unsorted and unstratified; loosely compacted and l uncemented; maximum thickness about 6 m |, 0 ° LD o ®,} LANDSLIDE DEPOSIT-Coarse, jumbled mass of angular volcanic-rock debris and soil; unsorted and unstratified; loosely compacted and uncemented; maximum thickness about 15 m SD STREAM DEPOSITS-Gravel, sand, silt, and clay in stream beds, on flood plains, and in alluvial fans; mostly well sorted sandy gravel; loosely to firmly compacted; uncemented to weakly cemented; maximum thickness unknown but probably as much as 30 m ~SW | SLOPE WASH-Gravel, sand, silt, and clay on steep to gentle slopes; mostly poorly sorted clayey gravel; loosely to firmly compacted; uncemented to weakly cemented; maximum thick - ness unknown but probably as much as 6 m Collings Drive MIXED STREAM DEPOSITS AND SLOPE WASH, UNDIVIDED WIND-LAID DEPOSITS-Dune-like accumulations of fine sand, and blanketing deposits of silt, on lowlands along Missouri f River and on uplands east of Spokane Creek; well sorted and (a ( ) ) % f ) A unstratified; loosely to firmly compacted; uncemented to weakly /;\v hl, _d ( 7 bir £ ‘ z | ) y ' 7 ’ E cemented; maximum thickness about 6 m; silt constitutes loess (ee at 28 ok a ) \ : : ~~é2 R > t < _ m and locally stands in vertical walls as much as 4%/2 m high f .Q‘;'""?---_ L GLACIAL-LAKE DEPOSITS-Sand, silt, and clay along Missouri Z HA A TTSFR.V. River and lower reaches of Prickly Pear Creek and Spokane Creek; well sorted, thinly and evenly stratified; firmly compacted; uncemented to weakly cemented; maximum thickness about 12 m OLDER GRAVEL -Gravel, sand, silt, and clay on terrace surfaces above major streams, in ancient alluvial fans, and on remnants of old erosion surfaces; mostly poorly to moderately well sorted gravel; loosely to firmly compacted and weakly cemented; 140 maximum thickness about 20 m OLDER STREAM AND LAKE DEPOSITS-Gravel, sand, silt, clay, bentonite, lignite, and volcanic ash, well-sorted and evenly stratified , firmly compacted ,weakly to moderately well cement- N, nal 4. as [ f I PFI % \ \ 4 i - , ed; bentonite swells and becomes plastic when wetted; maxi- ffizfi?‘ Jus - /: | f f | 0 \ 3 / - I - a , 1 A \ | . i mum thickness unknown but probably more than 500 m thick $ ( | C 4 J Sl ‘ in central part of Helena Valley Ae € Ekrrl’g W. iS // g 3 PZ] Eff/-\§‘ j § | ? x at. ALi , | 4 Jy | & , $o " Lot ~~062 BEDROCK 6 // / Fas ( f. SEDIMENTARY BEDROCK -Limestone, dolomite, shale, and sandstone: hard, firm, and dense; permanently and strongly cohesive PLUTONIC BEDROCK -Mostly coarse grained crystalline granitic rock: hard, firm, and dense; permanently and strongly cohesive; locally weathered to loose granular soil VOLCANIC BEDROCK -Mostly fine grained crystalline lava and volcanic tuff; hard, firm, and dense; permanently and strongly cohesive " Stanchfielcé | 3 \ \ - $ B . --- _ APPROXIMATE CONTACT BETWEEN UNITS ------------- INFERRED CONTACT BETWEEN OLDER STREAM AND LAKE DEPOSITS (OSL) AND BEDROCK (SB, PB) BENEATH COVER OF YOUNGER SURFICIAL DEPOSITS -?- - STRIKE-SLIP FAULT-Arrows show inferred relative direction of horizontal movement. Dashed where inferred; dotted where concealed; queried where location uncertain t/m NORMAL FAULT-Dashed where inferred; dotted where concealed; U, upthrown side; D, downthrown side; queried where location uncertain ::%u:| CONCEALED ZONE OF NORMAL FAULTING POSTULATED BY DAVIS AND OTHERS (1963) FROM GRAVIMETRIC + , DATA-U, upthrown side; D, downthrown side BM, (her: 19 T Rt y } tes! a A I whem&_ - THRUST FAULT-Dashed where inferred; dotted where 338i; ) concealed; sawteeth on upthrown side X GRAVEL PIT APPROXIMATE LINE OF EQUAL DEPTH TO WATER TABLE-Datum is land surface; contour interval 6 ft. Measured September 1976; from Wilke and Johnson (1978) 0340 _ WATER WELL-Number indicates depth in feet C 10 N /‘ i R % . a\ comes C " ) ' a s tas ; d | | ack Lake Helena Drive y R stapes REFERENCES CITED -£ Davis, W. E., Kinoshita, W. T., and Smedes, H. W., 1963, Bouguer gravity, aeromagnetic, and generalized geologic map of East Helena and Canyon Ferry quadrangles and part of the Diamond City quadrangle, 39 "* i a - e opin- oil AB \ ys Is Ceres #5. t 3 i Lewis and Clark, Broadwater, and Jefferson Counties, Montana: U.S. ' y y, - , , I/ + acy? zz2 * # - ; je 1.991 chat al 3 y§ 35 Geological Survey Geophysical Investigations Map GP -444. f { , é ¢ i ( ) > Knopf, Adolf, 1963, Geology of the northern part of the Boulder batholith and adjacent area, Montana: U.S. Geological Survey Miscellaneous Geologic Investigations Map 1-381. Smedes, H. W., 1966, Geology and igneous petrology of the northern Elkhorn Mountains, Jefferson and Broadwater Counties, Montana: U.S. Geological Survey Professional Paper 510, 116 p. Wilke, K. R., and Johnson, M. V., 1978, Maps showing depth to water table, September 1976, and area inundated by the June 1975 flood, Helena Valley, Lewis and Clark County, Montana: U.S. Geological Survey Open-File Report 78-110, 2 sheets, scale 1:48,000. 1:9 N 46°30, . . . . - 4 r s 4 a 38 2 °, R. 3 W r A - % - t - e 1 83 16°30 112°00 55 CWM 50 : 111°45 Enggzglgféggologlcal Survey 1:62,500 mes SCALE 1:48 000 Geology by R. G. Schmidt, 1975-76, assisted h by W. R. Trojan, 1975, and D. G. Waggoner, Road f 1984 I o sss 0 $ an ofp .m n ann & g mites 1976; and from Knopf (1963) o u 1 .5 0 1 3 3 KILOMETERS * g png 144A QUADRANGLE LOCATION primed CONTOUR INTERVAL 40 FEET DecLINATION, 1985 NATIONAL GEODETIC VERTICAL DATUM OF 1929 MAP OF EAST HELENA QUADRANGLE, MONTANA, SHOWING DISTRIBUTION OF SURFICIAL DEPOSITS AND BEDROCK AND TRACES OF GEOLOGIC FAULTS @t 19 TL v. 13llb DEPARTMENT OF THE INTERIOR PROFESSIONAL PAPER 1316 PLATE 1 U.S. GEOLOGICAL SURVEY il 1 46°45 EXPLANATION SURFICIAL DEPOSITS ARTIFICIAL FILL-Earth fill along Last Chance Gulch in city of Helena and refuse fill in old trash dump northeast of Helena; unsorted and unstratified; loosely compacted and uncemented; maximum thickness about 4 m PLACER TAILINGS-Piles of coarse, washed gravel, commonly arranged in rows, constituting waste rock from placer-mining operations; unsorted and unstratified; loosely compacted and uncemented; maximum thickness about 6 m LANDSLIDE DEPOSIT-Coarse, jumbled mass of angular blocks of quartzite; unsorted and unstratified; loosely compacted and uncemented; maximum thickness about 15 m SD STREAM DEPOSITS-Gravel, sand, silt, and clay in stream beds, on flood plains, and in alluvial fans; mostly well sorted sandy gravel; loosely to firmly compacted; uncemented to weakly cemented; maximum thickness unknown but probably as much as 30 m SW SLOPE WASH-Gravel, sand, silt, and clay on steep to gentle slopes; mostly poorly sorted clayey gravel; loosely to firmly compacted; uncemented to weakly cemented; maximum thickness unknown but probably as much as 6 m MIXED STREAM DEPOSITS AND SLOPE WASH, UNDIVIDED OLDER GRAVEL-Gravel, sand, silt, and clay on terrace surfaces above major streams, in ancient alluvial fans, and on remnants of old erosion surfaces; mostly moderately well sorted gravel; loosely to firmly compacted and weakly cemented; maximum thickness about 6 m OSL OLDER STREAM AND LAKE DEPOSITS-Gravel, sand, silt, * clay, bentonite, lignite, and volcanic tuff, well-sorted and evenly stratified, firmly compacted, weakly to moderately well cemented; bentonite swells and becomes plastic when wetted; maximum thickness unknown but probably more than 500 m in central part of Helena Valley BEDROCK SB SEDIMENTARY BEDROCK -Limestone, dolomite, shale, and sandstone; hard, firm, and dense; permanently and strongly cohesive PLUTONIC BEDROCK -Mostly coarse grained crystalline granitic rock; hard, firm, and dense; permanently and strongly e * cohesive; locally weathered to loose granular soil :< AV? * 4 VOLCANIC BEDROCK -Mostly fine grained crystalline lava and volcanic tuff; hard, firm, and dense; permanently and strongly cohesive ------- - APPROXIMATE CONTACT BETWEEN UNITS ************** INFERRED CONTACT BETWEEN OLDER STREAM AND LAKE DEPOSITS (OSL) AND BEDROCK (SB, PB) BENEATH COVER OF YOUNGER SURFICIAL DEPOSITS %?— STRIKE-SLIP FAULT-Arrows show inferred relative direction of horizontal movement. Dashed where inferred; dotted where concealed; queried where location uncertain g ?- NORMAL FAULT-Dashed where inferred; dotted where concealed; U, upthrown side; D, downthrown side; queried where location uncertain X GRAVEL PIT ---6--- APPROXIMATE LINE OF EQUAL DEPTH TO WATER TABLE-Datum is land surface; contour interval 6 ft. Measured September 1976; from Wilke and Johnson (1978) 0510 WATER WELL-Depth, in feet REFERENCES CITED Knopf, Adolf, 1963, Geology of the northern part of the Boulder batholith and adjacent area, Montana: U.S. Geological Survey Miscellaneous Geologic Investigations Map 1-381. Wilke, K. R., and Johnson, M. V., 1978, Maps showing depth to water table, September 1976, and area inundated by the June 1975 flood, Helena Valley, Lewis and Clark County, Montana: U.S. Geological Survey Open-File Report 78-110, 2 sheets, scale 1:48,000. ing Basin hoffe a mae mane soe me thy pone mee aes ae nc fe e e e n 3 W 7 R n p w R R 3 22°15 ¥ 10 R. 4 W 5 R. 3 W 112°00 B. f U.S. Geological 174° : 1:Zszé5(r)(())mHelena (fggglca Survey S7 SCALE 1:48 000 Geology by R. G. Schmidt, 1975-76, assisted Roads as of 1984 t (2 o A by W. R. Trojan, 1975, and D. G. Waggoner, oads as of 1984 ; ere ef, _ 2 3 MILES 1976; and from Knopf (1963) o a 4 .5 0 1 2 3 KILOMETERS 3 --- Po- Ee bef bef ff bsd QUADRANGLE LOCATION eminence CONTOUR INTERVAL 40 FEET NATIONAL GEODETIC VERTICAL DATUM OF 1929 DECLINATION, 1985 MAP OF HELENA QUADRANGLE, MONTANA, SHOWING DISTRIBUTION OF SURFICIAL DEPOSITS AND BEDROCK AND TRACES OF GEOLOGIC FAULTS Field Relations, Crystallization, and Petrology of Reversely Zoned Granitic Plutons in the Bottle Lake Complex, Maine By Robert A. Ayuso U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1320 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1984 DEPARTMENT OF THE INTERIOR WILLIAM P. CLARK, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging in Publication Data Ayuso, Robert A. Field relations, crystallization, and petrology of reversely zoned granitic plutons in the Bottle Lake Complex, Maine. (Geological Survey professional paper ; 1320) Bibliography: p. 1. Batholiths-Maine. 2. Granite-Maine. I. Title II. Series. QE461.A888 1984 552.3 84-600000 For sale by the Distribution Branch, U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 CONTENTS Page Page List of geographic localities shown on plate 1 -------------- v | The Passadumkeag River Pluton-Continued Abstract 1 Petrography and mineral compositions-Continued Introduction 1 Alkali feldspar 29 Methods of study 2 Quartz 30 Acknowledgments 2 Sequence of crystallization ---------------__.____.- 30 Previous work 3 Summary of the bulk chemistry ~---------_-__________ 30 Physical setting 3 | Xenoliths in the Bottle Lake Complex -------------------- 40 Metamorphic rocks 3 Metasedimentary xenoliths -----_--------__--_-______ 40 Other granitic rocks in the region ----------------------- 4 Mafic xenoliths 40 The Bottle Lake Complex 5 | Comparison of granites in the Bottle Lake Complex --------- 41 The Whitney Cove pluton 6 | Felsic dikes 41 Field relations 6 | Amphibolite unit 42 The Topsfield facies 6 | Structures 48 The rim facies 6 | Estimate of intensive parameters during crystallization ----- 43 The core facies 7T Estimate of pressure 43 Petrography and mineral compositions --------------- 7 Estimate of water content las 44 Bioti‘te 9 Estimate of t, f 0, f occa oal o 44 Shaggrlgzclase Fl) General characteristics of the granite source region --------- 47 Akan feldspar 11 Geologic interpretation 48 Se P i Processes leading to reverse zoning ------------------ 48 quence of crystallization ---------------------- 11 Contamination 48 Summary of the bulk chemistry --------------------- 18 s oaks ary A itil Flow differentiation 49 The Passadumkeag River pluton ------------------------ 14 yp R Field relations 14 Intrusion of nonconsanguineous plutons -------------- 50 o . Late-stage recrystallization ------------------------- 50 The rim facies 14 a A i > Progressive melting and sequential emplacement ------- 50 The core facies 19 : har esa Petrography and mineral compositions --------------- 21 Chemlcal stratlflca‘t fol " det chambers ----------- 50 Amphibole 21 Fractional crystalhzatl'on ei hen eer eee ees 52 hll he Summary of mechanisms leading to reversely zoned Biotite 26 lutons in the Bottle Lake Complex --------------- 53 Interrelations between biotite, amphibole, and rock -- 29 Conclu siIZJns P 53 Plagioclase 29 References 55 ILLUSTRATIONS Page PuATE 1. Geologic map of the Bottle Lake Complex In pocket FIGURE 1. Map of Maine showing the Bottle Lake Complex and other plutons in the area 1 2. Photograph showing view from Almanac Mountain looking southeast toward the Bottle Lake Complex --------- 3 3. Photograph showing texture in the Passadumkeag River pluton 5 4. Photograph showing the texture and composition of the rim facies of the Whitney Cove pluton ---------------- 7 5. Modal ternary plot of the Bottle Lake Complex showing composition of the Passadumkeag River and Whitney Cove plutons and their respective facies 8 6. Photographs of stained slabs from two representative samples of the core facies of the Whitney Cove pluton ----- 8 7-9. Plots showing compositions of biotite from the core and rim facies in the Whitney Cove pluton as a function of: 7. Fel(Fe+ Mg) 15 8. SiO, content of the whole rock 16 9. Ti content 17 10. Graph showing range in composition of biotite as a function of the anorthite component in coexisting plagioclase in the Whitney Cove pluton 19 11. Generalized diagram of the crystallization sequence in the Whitney Cove pluton showing the early formation of the accessory minerals, plagioclase, and biotite 20 12. Variation diagrams of the Whitney Cove pluton showing core facies, rim facies, mafic xenoliths, and aplites ------ 22 13-15. Photographs of: 13. - Stained slab from the rim facies of the Passadumkeag River pluton 24 14. - Outcrop of the core facies of the Passadumkeag River pluton 24 15. - Stained slab from the core facies of the Passadumkeag River pluton 24 IV FiGuRE 16-17. TABLE 18. 19-21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 10. 11. 12. CONTENTS Plots showing compositions of amphibole from the core and rim facies in the Passadumkeag River pluton as a function of: 16. Fe/(Fe+Mg) 17. - SiO, content of the whole rO¢k Graph showing range in composition of amphibole as a function of the anorthite component in coexisting plagio- clase in the Passadumkeag River pluton Plots showing compositions of biotite from the core and rim facies in the Passadumkeag River pluton as a func- tion of: 19. Fe/(Fe+Mg) ratio 20. SiO, content of the whole rock 21. Ti content Graph showing range in composition of biotite as a function of the anorthite component in coexisting plagioclase in the Passadumkeag River pluton Graph showing composition of coexisting biotite and amphibole in the core and rim facies of the Passadumkeag River pluton Generalized diagram of the crystallization sequence in the Passadumkeag River pluton showing the early for- mation of the accessory minerals, plagioclase, biotite, and amphibole Variation diagrams of the Passadumkeag River pluton showing core facies, rim facies, mafic xenoliths, and aplites Bulk composition of the Bottle Lake Complex displayed on the AFM (A=Na,0+K,0; F=FeQ; M=MgO) dia- gram Normative quartz-albite-orthoclase-water diagram for rocks in the Bottle Lake Complex ---------------------- Plot of fez—t for the biotite in the Bottle Lake Complex Plot showing stability curves of biotite from the Bottle Lake Complex and the granite melting curve ----------- Generalized diagram showing a model for the reversely zoned plutons of the Bottle Lake Complex -------------- TABLES Average modal composition of plutons in the Bottle Lake Complex, Maine ---- Representative electron microprobe analyses of allanite, apatite, and sphene from the Bottle Lake Complex, Maine Representative electron microprobe analyses and structural formulae of magnetite from the Bottle Lake Complex, Maine 7 f Representative electron microprobe analyses and structural formulae of ilmenite from the Bottle Lake Complex, Maine a Representative electron microprobe analyses and structural formulae of biotite from the Whitney Cove pluton s f Representative electron microprobe analyses and structural formulae of plagioclase from the Whitney Cove pluton R § y Representative major and trace element analyses and norm compositions of granites from the Whitney Cove pluton . Representative electron microprobe analyses and structural formulae of amphibole from the Passadumkeag River pluton s Representative electron microprobe analyses and structural formulae of biotite from the Passadumkeag River pluton f Representative electron microprobe analyses and structural formulae of plagioclase in the Passadumkeag River pluton ; Representative major and trace element analyses and norm compositions of the Passadumkeag River pluton ----- Generalized features of normally zoned plutons compared to the reversely zoned plutons of the Bottle Lake Complex Page 25 28 29 32 34 35 35 35 38 42 46 47 54 Page 10 12 12 14 18 20 26 30 36 40 49 inla op- IO -E>lefol -A S LIST OF GEOGRAPHIC LOCALITIES SHOWN ON PLATE i Almanac Mountain Whitney Cove Mountains Passadumkeag Mountain Duck Mountain Getchell Mountain Topsfield facies Tomah Mountain Farrow Mountain East Musquash Mountain North Branch of Vickery Brook Mount Delight Pineo Mountains Sysladobsis Lake Area Whitney Cove Pork Barrel Lake Upper Sysladobsis Lake No. 3 Pond Lombard Mountain Bowers Mountain Moose Mountain Chain Lakes Pug Lake McLellan Cove Chamberlain Ridge Hasty Cove Orie Lake Junior Lake Farm Cove East Musquash Lake Mud Cove CONTENTS Jo a agp glove wos fiotk t Rs s ssw notulq d iero ofem stot dt & 3 1 1G : 6 & © FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF REVERSELY ZONED GRANITIC PLUTONS IN THE BOTTLE LAKE COMPLEX, MAINE By ROBERT A. AYUSO ABSTRACT The Bottle Lake Complex is a composite batholith of Middle Devo nian age that intrudes the core of the Merrimack synclinorium in east- central Maine. The batholith consists of the Whitney Cove and Passa- dumkeag River plutons. Both are granites and are petrographically and geochemically reversely zoned, having more mafic cores than rims. Primary sphene, magnetite, and abundant mafic xenoliths are characteristic of these plutons. The abundance and composition of amphibole, biotite, and plagioclase indicate that the most mafic rocks are concentrated in the core facies. The bulk composition of granites in the Bottle Lake Complex is also reversely zoned, from high SiO, in the rim facies (71-77 weight per- cent) to low SiO, in the core facies (67-72 percent). Higher contents of Al,;O, (14-16.5), Fe,0, (2.5-5.4), MgO (0.6-1.3), and TiO, (0.3-0.8) are characteristic of the core facies, compared to the abundance of Al;O, (12.0-14.5), Fe,0, (1.4-3.0), MgO (0-0.8), and TiO, (0.1-0.5) in the rim facies. Reverse zonation is also evident in the generally higher stron- tium, niobium, yttrium, and zirconium of the more mafic granites in the interior. Mafic xenoliths show more dispersed major and trace ele- ment variations compared to the host granites. Calculated biotite stabilities coupled with the granite minimum melting curve suggest that emplacement conditions were as follows: P=1-1.8 kbar, t=720-780°C, and {., slightly higher than the Ni-NiO but lower than hematite-magnetite buffer equilibrium curve. Reversely zoned plutons in the Bottle Lake Complex result from remobilization (resurgence) of the more mafic lower layers and of the accumulated and scavenged crystal mush into the upper, more felsic parts of the plutons modified by fractional crystallization (plagio clase, biotite, amphibole, apatite, zircon, magnetite-ilmenite). In the initial stages of evolution, each pluton was a convecting and chemical- ly stratified system with more mafic granitic magma at the base. Periodic influxes of more mafic granitic magma resulted in mixing of liquids and redistribution of minerals. Surges of more mafic granitic magmas or venting of the magma chamber may have triggered the remobilization of the lower layers into the upper, more felsic layers. Mafic xenoliths and their host granites are not related by fractiona- tion and probably represent foreign blocks obtained at depth. Granite magmas in the Bottle Lake Complex were emplaced con- secutively and were obtained from a compositionally variable source. The trend in isotopic composition becomes more radiogenic for stron- tium, lead, and oxygen from the Passadumkeag River to the Whitney Cove pluton. A volcaniclastic source (graywacke) that progressively became more continental in character accounts for the range of isotopic compositions in the Bottle Lake Complex. Although multiple injection of granite magmas occurred in the batholith, each pluton represents a closed geochemical system. Significant input of lead from reservoirs similar to the oceanic mantle, lower continental crust (granulite), or upper continental crust as represented by the metasedi- ments are ruled out by the isotopic tracers. INTRODUCTION The granitic rocks of the Bottle Lake Complex pro- vide an excellent environment for studying the field relations, petrography, and compositional distinctions within a composite batholith emplaced during the Aca- dian orogeny. The Bottle Lake Complex belongs to a group of Paleozoic intrusives forming a discontinuous trend that extends from coastal to north-central Maine (fig. 1). Plate 1 is a geologic map of the Bottle Lake Complex; letter symbols in parentheses are used herein to designate locations shown on the map. 100 MILES 100 KILOMETERS FIGURE 1.-Map of Maine showing the location of the Bottle Lake Complex and other plutons in the area. (1) Lead Mountain pluton; (2) Wabassus Quartz Monzonite; (3) Bottle Lake Complex, (4) Center Pond pluton. Traces of the Norumbega Fault Zone (NFZ) are also shown (modified from Louiselle and Ayuso, 1980). 1 2 FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX Detailed mapping and routine petrographic studies show that each pluton within the Bottle Lake Complex exhibits reverse zonation. This feature contrasts with typical mineralogic and geochemical zoning trends in calc-alkaline plutons in which higher color index and more mafic rocks from the outer rim surround felsic rocks in the interior (see Pitcher, 19792, b). This report presents the results of detailed mapping, petrographic, and mineral chemistry studies of the Bot- tle Lake Complex. A brief summary of the results ob- tained from geochronologic (Rb-Sr, U-Pb), isotopic (common Pb), and geochemical (major and trace element abundances) studies (Ayuso, 1982) is also included because it supplements the field observations. Such ob- servations place strong constraints on the sequence of intrusion, magmatic evolution accounting for the reverse zonation, and nature of the granitic sources within a Middle Devonian composite body. METHODS OF STUDY Because of limited access into the area, most of the field work consisted of pace-and-compass traverses to hilltops either from logging roads or from lakeshores. Hilltops are shallowly covered by glacial debris, soil, and vegetation, and outcrops are common. Outcrops along lakeshores are also common. In general, leuco- cratic granites are most exposed, and granites contain- ing abundant mafic minerals have fewer exposures because they weather and disaggregate more readily. The mafic mineral-rich rocks are concentrated on the western lobe of the Bottle Lake Complex. Rocks of lower color index (lighter colored) are predominantly in the eastern lobe of the Bottle Lake Complex and form numerous outcrops. Modal analyses of 150 granite samples (Ayuso, 1979, 1982) stained by the method of Boone and Wheeler (1968) were made in order to distinguish between plagio- clase, quartz, alkali feldspar, and total mafic minerals (biotite, hornblende, sphene, allanite, and so on). Mafic minerals were later apportioned by examination of thin sections. Routine point counting consisted of selecting up to three slabs per sample with minimum dimensions of 20X20 cm and counting 1,000-2,000 points using mainly a 0.3 X0.3-cm grid. This spacing was adequate for most rocks, especially the equidimensional granites. However, some of the slabs were smaller than statis- tically permissible for very coarse-grained rocks. The best estimate of the uncertainty in the modal analyses is +2 percent using the method of Van der Plas and Tobi (1965). Mineral compositions were determined using an auto- mated ARL nine-channel electron microprobe with an operating voltage of 15 kilovolts, 0.150 nanoampere emission current, and 2- to 10-micrometer spot size. Silicate and oxide minerals were employed as standards, which were checked against the composition of known silicates. Corrections were made by the method of Bence and Albee (1968). Seventy samples were analyzed for feldspar, biotite, amphibole, oxide minerals, sulfides, apatite, allanite, and sphene. A minimum of 10 analyses were made in the essential minerals of each sample to detect variations within and between grains. Opaque and accessory phases were similarly analyzed in selected samples. The maximum compositional varia tion estimated by microprobe analyses is given by the standard deviation. For biotite, the results show the fol- lowing maximum weight percent deviations: SiO, (0.6), Al;O, (0.3), FeO (0.7), MgO (0.4), MnO (0.02), TiO, (0.1), CaO (0.1), Na,0 (0.1), K,0 (0.3), F (0.4), and Cl (0.03). Plagioclase cores and rims, averaged separately, show similar deviations: SiO, (0.4), Al,O, (0.4), CaO (0.15), Na,0 (0.3), and K,0 (0.2). Finally, the typical variations in magnetite and ilmenite are as follows: magnetite, FeQ (0.50), TiO, (0.15), and MnO (0.10); ilmenite, FeO (0.7), TiO, (0.6), and MnO (0.5). Twenty alkali feldspar concentrates were homog- enized (sanidinized) and analyzed by X-ray powder dif- fraction techniques (Wright, 1968) to estimate their bulk composition and structural state. Analytical procedures of the X-ray fluorescence study followed the method of Norrish and Hutton (1969). Details and techniques concerning the geochronology and isotopic work on the Bottle Lake Complex are given in Ayuso and Arth (1983) and Ayuso (1982). Locations from which samples were used in this study are shown on plate 1. ACKNOWLEDGMENTS I am grateful to my assistants, S. T. Johnson and F. Bunky Wehr for their dedication. Special thanks are extended to D. R. Wones, who introduced me to the problems of granite petrogenesis and the geology of Maine. I am indebted to A. K. Sinha, whose steady criticism and pursuit of analytical excellence encourag- ed me throughout the study, and I thank M. C. Loiselle for helping during data collection and reduction and contributing in many stimulating discussions. I am especially grateful to my colleagues at Virginia Polytechnic Institute and State University: N. K. Foley, B. Hanan, J. D. Myers, and M. X. Wells for their encouragement and help. Many of the ideas expressed in this paper resulted from fruitful discussions with my colleagues at the Geological Survey. Comments of D. R. Wones, A. K. Sinha, D. A. Hewitt, F. D. Bloss, J. G. Arth, R. A. Bailey, W. F. Cannon, B. R. Lipin, R. L. Smith, and D. B. Stewart greatly improved the presen- tation and scientific content of the report. PHYSICAL SETTING 3 PREVIOUS WORK The area of this report is included within a reconnais- sance map by Larrabee and others (1965), who estab- lished the extent of the granitic plutons and attempted a regional correlation of the stratigraphy of the country rocks. Contacts between the plutons and country rocks are generally better defined for the northern contact based on aeromagnetic (Doyle and others, 1961; Boucot and others, 1964) and geologic studies (Larrabee and others, 1965; Ayuso, 1979; Ayuso and Wones, 1980) than for the more inaccessible and swampy terrane of the southern contact. Building on the pioneering effort by Larrabee and his coworkers, Ludman (1978a, b; 1981) presented a better understanding of the metamorphic rocks in the region concentrating on the area to the northeast and east of the Bottle Lake Complex. Detailed field work was done by Olson (1972), and reconnaissance mapping was done by Cole (1961) to the southwest and north of the Bottle Lake Complex, respectively. Recent work in the area has indicated anomalously high contents of molybdenum, arsenic, tungsten, and bismuth in stream sediment samples near the granite- country rock contact near Tomah Mountain (G) (Nowlan and Hessin, 1972; Post and others, 1967). In conjunction with those reports, molybdenite in granite bedrock was also reported. Subsequent work by Otton and others (1980) indicated that uranium and thorium were also present in anomalously high concentrations in stream sediment samples and concluded that U-Mo mineralization was likely as a result of vein or contact- metasomatic processes. Not enough observations were made, however, to properly evaluate the economic potential of the Tomah Mountain (G) area. PHYSICAL SETTING The Bottle Lake Complex is located between the towns of Topsfield and Lincoln in one of the popular recreational areas of east-central Maine. The region is characterized by low relief, numerous lakes and swamps, and abundant glacial debris (fig. 2). Several hills are about 500 m high, for example, Almanac Moun- tain (A), Whitney Cove Mountains (B), Passadumkeag Mountain (C), Duck Mountain (D), and Getchell Moun- tain (E) (pl. 1). The Madagascal and the Passadumkeag Rivers are the major streams that dominate the drain- age patterns in the area and connect extensive swamps (for example, 1000 Acre Heath). Mining and prospect- ing are notably absent in the region despite the concen- tration of pegmatites in several areas, the enrichment of sulfide minerals in the contact aureole between State Route 6 and the northern contact of the plutons (Doyle and others, 1961; Kleinkopf, 1960), and the potential for U-Mo mineralization near Tomah Mountain. METAMORPHIC ROCKS The Bottle Lake Complex intrudes greenschist facies metamorphic rocks of the Merrimack synclinorium. Country rocks are consistently low in metamorphic grade and show great differences in lithology and age (Larrabee and others, 1965; Olson, 1972; Ludman, 1978b). The age span represented by these rocks ex- tends from Cambrian(?) to Devonian with diverse lithol- ogies consisting of almost monomineralic sandstones to andesitic volcanics (Ludman, 1978b). Metasedimentary units generally show primary sedimentary features but have few fossils and are difficult to correlate regionally. Many faults occur between and within the metavolcanic and metasedimentary sections. All of these faults, however, are cut by the Bottle Lake Complex. The oldest rocks intruded by the Bottle Lake Com- plex are Cambrian(?) to Ordovician(?) green and maroon slates, argillaceous quartzo-feldspathic sandstones, and quartz-granule conglomerates. Larrabee and others (1965) suggested the age on the basis of the similarity to the upper Proterozoic and Lower Cambrian(?) Grand Pitch Formation and to parts of the Ordovician Teta- gouche Group in New Brunswick. Most units are thick bedded and exhibit penetrative cleavage and an early episode of isoclinal folding probably of pre-Acadian orogeny in age (Ludman, 1978b). This early folding episode was recognized only within these rocks. FicurE 2.-View from Almanac Mountain looking southeast toward the Bottle Lake Complex. Distance to the far hills, Whitney Cove Mountains , is about 15 km. 4 FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX Mineral assemblages show zoning as a function of dis- tance from the granite-country rock contact. Detailed traverses at right angles away from the pluton show zones of garnet, cordierite, and biotite hornfels. About 1 km from the contact, chlorite and white-mica-bearing argillaceous quartzo-feldspathic sandstones are typical country-rock lithologies. All of the rocks have tourmaline, epidote, calcite, sphene, and opaque minerals, as well as two feldspars. Albite (showing checkerboard texture) and alkali feld- spar are subordinate in abundance to quartz and sug- gest that the source was igneous in character. The Ordovician(?) or Silurian(?) metavolcanic and metasedimentary rocks form a band to the west of the Cambrian(?) and Ordovician(?) section. In addition, Lud- man (1978a) also mapped a thinner but similar section south of East Musquash Lake (CC) and north of the Bottle Lake Complex in the Scraggly Lake and Waite quadrangles respectively (pl. 1). Volcanic rocks exposed south of East Musquash Lake (CC) consist of hornblende-bearing andesite interbedded with minor sedimentary and volcaniclastic sandstones (Ludman, 1978a), while pelitic to quartzose rocks showing graded and fine-scale bedding characerize the tourmaline- bearing metasedimentary rocks. Contact metamor- phism is also evident in these rocks as noted by Cole (1961) and is indicated by the presence of garnet, cor- dierite, tremolite, and biotite as a function of distance from the plutonic contact. Garnet-cordierite hornfels are formed closest to the pluton and change to tremolite- epidote-biotite schists away from the contact. Contiguous to the granite-country rock contact, felsic pods, which mineralogically consist of two feldspars and of muscovite, quartz, garnet, allanite and biotite, are sometimes present. These pods are irregularly shaped, small (10-20 cm), and consistently show similar miner- alogy and cuneiform textures. Traces of relict and retro- graded aluminosilicate(?) minerals and muscovite are concentrated within alkali feldspar. In contrast to the felsic pods, the host country rock consists of finer grained, garnet-cordierite hornfels which also contain white mica and biotite. Silurian and Lower Devonian(?) rocks are designated as the Vassalboro Formation (Osberg, 1968) and are the most abundant country rocks intruded by the granites (pl. 1). Ruitenberg and Ludman (1978), Ludman (1978b), and Wones (1979) suggest that the Vassalboro Forma- tion is correlative to the Flume Ridge Formation (as used by Ludman and Westerman, 1977) to the south- east, the Kellyland Formation to the northeast, and the Bucksport Formation (as used by Wing, 1959) to the southwest of the Bottle Lake Complex. The Vassalboro is generally characterized in this area by calcareous siltstones interbedded with pelitic sedi- ments. Changes in bedding style, calcareous nature, color, and grain size are common in hornfels around the plutonic rocks. In the vicinity of the northern contact, near No. 3 Pond (Q) in the Winn quadrangle, the Vassal- boro is a pin-striped, shaly, slightly rusty, and intensely jointed rock. The stripes are generally centimeter-sized dark and light banks of contrasting mineralogy. Biotite- rich stripes are dark purple and alternate with light- colored stripes consisting of calcite and quartz. Throughout the rock, the assemblage diopside, am- phibole, epidote, and quartz coexists with biotite and calcite. Contact metamorphism in these rocks occurs as garnet-cordierite-biotite hornfels formed close to the contact. OTHER GRANITIC ROCKS IN THE REGION At least three other Paleozoic granitic plutons in addi- tion to the Bottle Lake complex are exposed in the area: the Center Pond pluton, the Lead Mountain pluton, and the Wabassus Quartz Monzonite (fig. 1; pl. 1). A brief summary of their characteristics is as follows. The Center Pond pluton was first studied by Larrabee and others (1965), but a more complete description is given in Scambos (1980). Field characteristics are given in Scambos (1980) and are summarized by Ayuso and Wones (1980), who noted the general similarity between the Passadumkeag River and Center Pond plutons. Although the Center Pond pluton is one of the smallest granites in this area (fig. 1), together with the Bottle Lake Complex it exhibits a characteristic mineral as- semblage (from amphibole: to biotite-rich) as well as bulk compositional variations (from quartz diorite and quartz monzonite to granite) which may be used to dis- tinguish granitic plutons intruding this part of the Merrimack synclinorium (Ayuso and others, 1980). As found in the Passadumkeag River pluton, the Center Pond pluton is cut by a right-lateral, northeast-trending fault zone. The Lead Mountain pluton is a large (1,000 km), com- posite body in which granite is the predominant rock type. Exposures of this pluton are found directly south of the Bottle Lake Complex, within fault-bounded blocks, and as a large granitic mass extending south toward the Atlantic coast (fig. 1). Recent mapping sug- gests that the pluton has an extensive lithological range from amphibole- and biotite-bearing granite to biotite and muscovite granites. Petrographic contrast (abun- dance of mafic minerals, ratio of magnetite to ilmenite, rock type variation) between the Bottle Lake Complex and the Lead Mountain pluton, which lie on either side of the Norumbega fault, argue against correlation of the two granites. The Wabassus Quartz Monzonite was first studied by Larrabee and others (1965) and is exposed only within THE BOTTLE LAKE COMPLEX 5 the blocks bounded by the Norumbega fault system (pl. 1) (Ayuso and Wones, 1980). Petrographic correlation with the Bottle Lake Complex or with the Lead Moun- tain pluton is not supported because the Wabassus is finer grained, more felsic, and texturally different from the other nearby plutons. Preliminary observations sug- gest that biotite is the predominant mafic phase. This rock is commonly exposed in intensely sheared and de- formed outcrops that show only traces of the original mafic mineralogy and felsic assemblage. THE BOTTLE LAKE COMPLEX The granitic plutons of the Bottle Lake Complex are exposed in an area of about 1,100 km in the Waite, Scraggly Lake, Springfield, Winn, Wabassus Lake, Nicatous Lake, and Saponac 15-minute quadrangles (pl. 1). The outline of the Bottle Lake Complex consists of two overlapping, subcircular intrusives arranged along an east-west trend, escept for the northeast exten- sion of the eastern intrusive-the Topsfield facies (F). The Bottle Lake Complex consists of the Passadum- keag River and Whitney Cove plutons. The Topsfield facies (F), which extends north of Mount Delight (K), is considered part of the Whitney Cove pluton because of the absence of sharp contacts between it and typical Whitney Cove rocks and because of similarity in petro- graphic characteristics. The two plutons are readily dis- tinguished from each other by differences in mafic min- eralogy (especially the ratio of biotite to amphibole), abundance of pegmatites and aplites, and abundance and types of inclusions (Ayuso, 1979). The intrusives in the Bottle Lake Complex are charac- terized by generally coarse-grained granitic rocks that consist of two feldspars, biotite and quartz, primary sphene, magnetite, ilmenite, zircon, apatite, allanite, and pyrite. Hornblende is abundant only in the Passa- dumkeag River pluton, where it occurs primarily in rocks of high color index also containing numerous mafic xenoliths (fig. 3). Larabee and others (1965) made no petrographic dis- tinctions between the granitic rocks of the Bottle Lake Complex, except for the possibility of an internal con- tact between the Topsfield facies and the main mass of the Whitney Cove pluton. Petrographic variation in the granites was ascribed to secondary processes, princi- pally to different degrees of country-rock assimilation. The Bottle Lake Complex is probably of Middle Devonian age, and its component plutons may differ on- ly slightly in age. Field observations show that the Whitney Cove pluton is cut by the Norumbega fault zone that disturbed Pennsylvanian sediments in south- ern New Brunswick (Wones and Stewart, 1976) but is younger than the Silurian to lower Devonian(?) country rocks it intrudes. Such structural and stratigraphic con- trols suggest that the Whitney Cove pluton must be older than Pennsylvanian and younger than Early Devonian. Previous geochronologic work on the Whitney Cove pluton by Faul and others (1963) indicated ages of 377 and 379 my., according to the International Union of Geological Sciences (IUGS) constants (Steiger and Jager, 1977), by the K-Ar method. This finding is in good agreement with a linear whole-rock Rb-Sr iso chron which resulted in an age of 379+10 (Ayuso and Arth, 1983). Zartman and Gallego (1979) suggested a zircon Pb-Pb age of 404+4 m.y. for a sample from the Topsfield facies, broadly in agreement with the range of 397 to 404 m.y. obtained by Ayuso (1982) on zircon samples from the main mass of the Whitney Cove plu- ton. Discordant zircons from the Whitney Cove pluton suggested a Concordia intercept age of 399+16 m.y., roughly similar to the Pb-Pb ages. Samples from the Passadumkeag River pluton were not dated by the K-Ar method, but a linear whole-rock Rb-Sr isochron consisting of xenolith-poor samples yielded an age of 381+8 m.y. (Ayuso and Arth, 1983). U-Pb analyses of discordant zircons resulted in Concor- dia intercept ages of 388+10 m.y. for samples contain- ing at least trace amounts of mafic xenoliths, while zir- cons from a large mafic xenolith gave ages of 415 and 117 m.y. The range of Pb-Pb ages in the Passadumkeag River pluton is from 374 to 406 m.y., while a range from 382 to 402 m.y. characterizes the mafic xenolith. The presence of distinct zircon populations in samples from the Bottle Lake Complex noted by Ayuso (1982) does not support a straightforward interpreta- tion of the U-Pb results. The youngest Pb-Pb age (374 m.y.) was obtained on a zircon fraction containing FicurE 3.-Photograph showing the massive texture and coarse grain size prevalent in the Passadumkeag River pluton. 6 FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX the least amount of the zircon type abundant in the mafic xenolith. Although the results from the whole- rock Rb-Sr and zircon U-Pb methods cannot be re- solved because of analytical uncertainty, Ayuso and Arth (1983) suggest that the ages might reflect the in- herited lead from older, discordant zircons of the mafic xenoliths that contaminated the newly developed zir- cons of the granitic magmas. Thus, although the Con- cordia intercept ages of the Passadumkeag River pluton suggest that it is younger than the Whitney Cove pluton, the crystallization ages obtained by the whole- rock Rb-Sr method are nearly the same for both plutons. Additional support for a slightly older age of the Whitney Cove pluton is given because the Passa- dumkeag River pluton is not cut by the fault zone that transects the Whitney Cove pluton and because rock types characteristic of the Passadumkeag River pluton intrude rocks typical of the Whitney Cove pluton. THE WHITNEY COVE PLUTON FIELD RELATIONS The Whitney Cove pluton covers an area of 400 km" and is characteristically granitic in mineralogy (IUGS classification of Streickeisen, 1973). It is easily recog- nized in the field because of its relatively low abundance of ferromagnesian minerals and its lack of amphibole. Other typical features include abundance of aplites and pegmatites and scarcity of mafic xenoliths. Three units are included in this pluton: the Topsfield facies, the rim facies, and the core facies (pl. 1). THE TOPSFIELD FACIES The geologic map of the Whitney Cove pluton does not show a contact between the Topsfield and the rim facies because of the gradual petrographic change bet- ween the two. The best exposures of the Topsfield facies are on Tomah Mountain (G), Farrow Mountain (H), and East Musquash Mountain (I) (pl. 1). These mountains form a scarp along the western and northern boundaries of the Topsfield facies. As Larrabee and others (1965) noted, granitic rocks exposed directly to the south of the mountains near the North Branch of Vickery Brook (J) progressively become more similar to the gray, coarser grained rocks typical of the rim facies exposed on Mount Delight (K). The Topsfield facies (F) is characterized by severe shearing and jointing. Most outcrops consist of inten- sely weathered granitic rocks ranging in color from moderate pink (5R 7/4) to moderate red (5R 5/4), accord- ing to the Rock-Color Chart of the Geological Society of America (Goddard and others, 1948 (1951)). Grain size is medium to coarse and the color index is generally less than 5. Pink alkali feldspar and plagioclase are phenocrysts in a matrix of felsic minerals and biotite. Zircon, apatite, allanite, opaque oxides (magnetite), and pyrite are not abundant. Most rocks exhibit aggregates of epidote, chlorite, and opaque oxides instead of primary biotite. Feldspars are commonly replaced by sericite and epidote. THE RIM FACIES Despite the similarity in mineralogy across the pluton, the most distinctive feature that separates the two facies is the characteristic seriate texture of the rim. The rim facies of the Whitney Cove pluton typically consists of grayish-pink (5R 8/2) to moderate-pink (5R 7/4) rocks. They are medium to coarse grained. Hypidio- morphic and seriate textures are developed on rocks of low color index (fig. 4). Two feldspars are present as phenocrysts, with alkali feldspar phenocrysts larger (up to 3.5 cm) and more abundant than plagioclase. Euhedral quartz pheno- crysts (up to 1 cm) and distinctive pseudohexagonal biotite books are characteristic of the pluton as a whole. Matrix minerals include two feldspars, quartz, biotite, allanite, sphene, apatite, and zircon. The opaque phases consist of magnetite, ilmenite, and pyrite. Magnificent outcrops are exposed in the Pineo Moun- tains (L) and in the Sysladobsis Lake area (M). Many of the outcrops contain aplites, pegmatites, granophyres, and quartz veins. Felsic dikes are variable in attitude and thickness and exhibit a tendency to subdivide and crisscross within individual outcrops. Modal mineral analyses indicate that the rim facies is uniformly granitic in mineralogy (table 1). The average mineral content of alkali feldspar (40.2 percent), plagio- clase (27.5 percent), quartz (28.1 percent), and the sum of the mafic minerals (biotite, opaque minerals, acces- sory minerals) (4.2 percent) attest to the felsic nature of this rock (Ayuso, 1979). Biotite is the predominant mafic phase, and the total abundance of the accessories and opaque minerals is characteristically less than 1 percent (figs. 4-5). Chlorite, epidote, and sericite have formed by alteration of biotite and plagioclase. THE WHITNEY COVE PLUTON T FIGURE 4.-Stained slab from the rim facies of the Whitney Cove pluton. Dark-gray areas are biotite, quartz, and accessory min- erals. Alkali feldspar is light gray, and plagioclase is white. THE CORE FACIES The core facies of the Whitney Cove pluton is best ex- posed along the shores of Whitney Cove (N) in the Wabassus Lake and Scraggly Lake quadrangles (pl. 1). Contacts between the core and rim facies are mostly gradational and poorly exposed. Large outcrops show- ing both rock types are exposed near Pork Barrel Lake (0). Distinction between the two facies strongly depends on the development of the typically porphyritic texture of the core rocks (fig. 6). Other characteristics of the core facies include the for- mation of a fine-grained matrix and the grayish-pink (5R 8/2) to grayish-orange-pink (10R 8/2) color. Large country-rock and quartz dioritic xenoliths are rare, but ovoidal clusters of fine-grained mafic minerals are more common. These clusters are small (up to 5 cm), widely disseminated, and consist principally of biotite with variable amounts of accessory minerals and plagioclase. The core facies typically has biotite as the predominant mafic phase in fine-grained clusters in the matrix and within the feldspars. Fine-grained biotite and feldspars impart a distinctive appearance to this facies. Despite the overlap in modal abundances across the pluton, the core facies is distinguished from the rim facies by its enrichment in plagioclase and depletion in alkali-feldspar and quartz (fig. 5). Modal examination of stained slabs (table 1) and thin sections indicates the following average mineralogy: alkali feldspar, 33.9 per- cent; plagioclase, 35.8 percent; quartz, 25.6 percent; total mafic minerals including the opaque and accessory suites, 4.7 percent. The modal analyses show that the core facies is generally enriched in mafic minerals com- pared to the rim. PETROGRAPHY AND MINERAL COMPOSITIONS The Whitney Cove pluton contains accessory phases, oxides, and sulfides as subhedral to euhedral grains mainly within biotite or near small clusters formed by plagioclase and biotite. Apatite is an example of a mineral that appears optically homogeneous but which is chemically heterogeneous (for example, F and MnO, table 2). Heterogeneity is exhibited even within individ- ual grains. Allanite is common as large (up to 1.5 mm), euhedral, and optically and compositionally zoned grains inter- grown with biotite and oxide minerals. Higher contents of titanium, iron, and in some cases flourine and calcium TABLE 1.-Average modal composition of plutons in the Bottle Lake Complex, Maine [Range is shown in parentheses] Mineral Whitney Cove pluton Passadumkeag River pluton Rim Core Rim Core Quartz 28.1 (20-48) 25.6 (20-31) 24.1 (22-30) 19.4 (13-29) Plagioclase 27.5 (21-42) 35.8 (24-50) 30.0 (20-41) 37.6 (26-52) Alkali feldspar --------------------______ 40.2 (29-55) 33.9 (24-53) 39.2 (28-50) 33.0 (20-46) Biotite 4.2 (1-6) 4.7 (1-12) 4.6 (1-9) 5.8 (1-12) Amphibole 0 0 2.1 (0-8) 4.2 (1-9) Others (sphene, apatite, magnetite, ilmenite, zircon, allanite) <0.5 <0.5 <0.5 <0.5 8 FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX Bottle Lake Complex Mafic Quartz Mafic minerals minerals 0A A Granite A o} o omy C 006 A 4 .. AK A 2&3” Quartz Alkali monzonite Plagioclase feldspar m 0 A EXPLANATION Passadumkeag River a Core A Rim Whitney Cove e Core o Rim Mafic minerals FIGURE 5.-Modal composition of the plutons of the Bottle Lake Complex. The four modal components illustrated are quartz, plagioclase, alkali feldspar, and the sum of the mafic minerals. Modal classmcatxon shown is from Strelckelsen (1973) Hye mad os rar pads “Mm WL B-43 Pine Fu we}; "ip) a a >> FIGURE 6—Stamed slabs from two representative samples of the core faces of the Wlutney Cove pluton Note the porphyntlc character of this rock and the euhedral shapes of the alkali feldspar (light gray) and subhedral plagioclase (white). THE WHITNEY COVE PLUTON 9 are characteristic in the cores of allanite compared to lower phosphorus in the rims (table 2). Sphene occurs as large primary grains (up to 4 mm) and as a product of biotite breakdown. No clear and consistent trend exists in the abundance or in the mineral chemistry of any ac- cessory phase across the Whitney Cove pluton (table 2). Magnetite and ilmenite form subhedral grains within biotite, plagioclase, and allanite. Intergrowths between biotite and magnetite are also common as are the anhedral concentrations of magnetite along biotite lamellae. Magnetite abundances show no trend across the pluton, and compositionally they contain less than 1 weight percent TiO, (table 3). Rounded pyrite grains are found preferentially within magnetite grains. Granular ilmenite forms individual grains, coexists with magne- tite, and also forms domains (Buddington and Lindsley, 1964) within it. Reequilibration of ilmenite at low temperature (Czamanske and Mihalik, 1972) is indi- cated by its manganiferous compositions (3.0 to 13.0 weight percent) (table 4). A trend is evident toward lower manganese in ilmenites of the rim facies of the pluton. BIOTITE Comparison of the chemical composition of biotite from the core and rim facies of the Whitney Cove pluton suggests that important contrasts exist within the granite (table 5). Biotite from the core facies is for the most part lower in the ratio of Fe/(Fe+ Mg) (0.48-0.58) compared to the rim facies (0.52-0.71) (fig. 7; table 5). The total Fe content of biotite from core to rim facies is positively correlated with SiO, content of the rock (fig. 8). The core facies generally contains biotites with the lowest manganese content (fig. 7; table 5). Results indi- cate that despite the absence of a strong gradient in abundance of biotite from rim to core facies, biotite shows compositional zoning in Fe/(Fe+Mg) ratios which readily facilitates distinguishing between the marginal and the interior portions of the pluton (fig. 7; table 5). The expected enrichment of titanium in early biotite and its correlation with higher phlogopite content (Robert, 1976; Czamanske and Wones, 1973) is not well developed in the Whitney Cove pluton (fig. 7). Biotites in the core facies contain about 0.19 to 0.23 Ti (atoms per 11 oxygens) and overlap with the range of 0.18 to 0.23 found in the rim facies (fig. 7; table 5). Corrosion and resorption of titanium-rich biotite suggest that early-crystallized biotites partially equilibrated with more felsic melt. The dispersal of titanium content is also evident in figure 8, where biotite composition is plotted against the silica content of the rock. Despite the clear distinction in the two facies for SiO,, biotites have similar titanium abundance and show no progres- sive or systematic gradient from the margin toward the interior rocks (table 5). Biotite from the Whitney Cove pluton shows no direct correlation between titanium and the silicon content (fig. 8) or between titanium and the mole fraction of iron in the octahedral layer (fig. 9). Similarly, no direct corre- lation exists between titanium content and the total abundance of the octahedral cations. However, the value for Fe/3 increases as a function of titanium within individual facies. Thus, biotite from the core facies has lower values for Fe/3 than those of the rim facies. At a given value of titanium, biotites from the core facies tend to be lower in Fe/3. (fig. 9). Aluminum in octahedral coordination (AIY') is charac- teristically widely dispersed with increasing Fe/(Fe+ Mg) ratios (fig. 7). Both the core and rim facies display a great deal of compositional scatter for AY! as well as for aluminum in tetrahedral coordination (ALY) (fig. 7). AlY, however, suggests a general increase as a function of the Fe/(Fe+Mg) ratio, so that higher Al values for the rim facies in some cases are correlated with higher Fe/(Fe+ Mg) ratios. The wide range in AlY! content and in the Fe/(Fe+ Mg) ratios in the Whitney Cove pluton suggests that these biotites record dif- ferent conditions during their crystallization. In figure 10, the biotites from the core facies with the lowest Fe/(Fe+Mg) ratios tend to have higher abundance of AIY' and coexist with the most calcic plagioclase. No correlations are evident between total aluminum and the alkali content of biotite in the pluton or between the sum of AIY' and Ti with the ratio of Fe/(Fe+ Mg). Total aluminum, Al, and AIlY' in these biotites also lack meaningful correlations with the silica content of the rock. Results for other constituents in biotites from the Whitney Cove pluton are summarized as follows: * The iron content and the Mg) ratio of biotite show the only systematic changes within the pluton. The iron content is directly related to the silica content of the rock (fig. 8). Higher iron in biotite is evident in rocks from the rim facies (table 5). Czamanske and others (1981) found decreasing or constant Fe/(Fe+Mg) ratios with increasing SiO, of the magnetite series granites in the J apan- ese batholith. According to Czamanske and others (1981), oxidation during magmatic differentiation resulted in such a trend. The generally decreasing Mg) ratio in biotite toward the interior of the Whitney Cove pluton is generally correlated with decreasing SiO, of the rock (fig. 8), and thus suggests that oxidation during differentiation can- not account for the change in Fe/(Fe+ Mg) ratios of the biotites. * The potassium abundance in biotite shows no gra- dient between the core and rim facies (fig. 8). 10 _- FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX TABLE 2.-Representative electron microprobe analyses of allanite, [Values are weight percent. Total iron as FeO; for allanite, cols. 1-3 are from the Passadumkeag River pluton; cols. 4 and 5 are from the Whitney Cove pluton; for apatite, cols. 6-15 are Column 1 2 3 4 5 6 j 8 9 10 11 12 13 14 Mineral Allanite Nap Apatite Sample number 240 25C BSR 490 93R 20C 250 290 75C 89C 105C 10R 12R 27R SIO, ----------------- 28.82 25.56 22.32 31.37 29.87 0.18 0.179 0.88 0.35 1.00 0.55 0.47 1.08 0.A7 THQ, ----------------- 3.39 3.68 5.09 2.62 2.40 .06 12 .06 .06 .00 04 00 .10 .07 AlyOg ---------------- 16.98 1248 15.08 1252 11.27 .00 .00 .00 00 00 .00 .00 00 .01 FeQ ----------------- 16.21 14.51 24.99 18.03 16.96 .50 15 .61 .38 97 .24 64 .66 .26 MnQ ---------------- .38 A4 25 A8 A5 .08 .09 .10 12 .20 .09 A17 18 12 MgO ---------------- 58 50 25 .92 1.31 11 12 14 .04 .10 12 .08 #1 12 CaO ----------------- 5.97 5.94 3.31 5.83 8.52 54.16 58.18 58.58 54.17 52.50 58.86 55.27 54.22 54.18 NaQ ---------------- 12 .24 A4 .07 .10 .00 .00 .00 .00 .00 00 00 00 .00 K,O ---------_------- .04 .07 .10 08 .06 .10 14 .08 .09 .00 .07 .00 47 .05 BaO --=-------------- .06 18 .00 .06 .00 .00 .08 .00 .03 .00 18 .06 .07 13 PO, ----------------- 58 .60 .00 .06 .00 40.66 40.09 40.28 39.58 41.14 40.25 38.96 40.23 39.68 SQ ---------_--------- .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 00 .00 00 00 F -_--------_----_-_---- A8 49 .00 .27 .00 4.03 4.44 3.12 4 Al 3.10 4 A2 3.63 3.45 4.21 €] --__------_-_-_______- .02 .08 .00 .08 .00 .00 .O1 .01 .01 .04 .01 .02 .00 00 Total ------------ 73.48 64.72 7183 72.26 70.94 99.88 99.81 99.46 99.24 99.65 99.78 99.30 100.22 99.85 e Manganese contents in biotites show a scattered but broadly increasing trend toward higher Mn con- tent with increasing Fe/(Fe+ Mg) (fig. 7); however, there is significant scatter for the felsic rim facies. e Although fluorine is always present in biotite, it shows no obvious trend when plotted against the Fe/(Fe+ Mg) ratio or the silica content of the rock (not shown). e Sodium, chlorine, phosphorus, barium, and stron- tium in biotite show no gradients across the plu- ton. Generally, these elements fall below the micro- probe detectability limit, or they exhibit random variations (table 5). PLAGIOCLASE Plagioclase was the first feldspar to crystallize in the Whitney Cove pluton. Several petrographic types are evident including plagioclase (1) as phenocrysts, (2) in the groundmass, (3) in clusters with biotite, and (4) con- centrated along the edges of other felsic minerals. Phenocrysts have distinct textures (kind and number of inclusions, associated contiguous mineralogy, resorp- tion features), and optical characteristics (zoning, twin- ning), even though they show the same range in compo- sition. At least two groups of phenocrysts are present. One group has a mottled appearance ("restite'" accord- ing to White and Chappell, 1977), is characteristically blotchy in extinction, and consists of cores enclosing many inclusions with thin, optically continuous rims. These phenocrysts are generally associated with clus- ters of biotite and contrast with the other phenocryst group which is distributed throughout the rock, has a more regular optical and chemical zoning, has wider rims, and tends to show more euhedral habits. A gra- dient exists toward calcic-rich plagioclase from rim (An,) to core (An,,) facies of the Whitney Cove pluton. The composition of plagioclase (table 6) across the plu- ton (fig. 10) agrees with the core to rim facies zoning suggested by the composition of biotite (table 5). In general, phenocryst cores and mottled plagioclase grains overlap in composition and are distinctly more calcic than plagioclase in the matrix. Within any single specimen, however, average core compositions of the two textural types may differ by up to 10 mol percent anorthite. Inclusions of plagioclase in alkali feldspar are typically at least as calcic as the phenocryst cores, ex- hibit similar compositional ranges, and are character- istically rimmed by a band of sodic plagioclase. The most calcic grains are sometimes found as inclusions in other phases. They differ by about 3-5 mol percent anorthite from the most calcic phenocryst cores of near- by rocks. Plagioclase cores are slightly zoned. Most zoning trends are in the normal fashion with a progressive de- crease in calcium from core to rim generally becoming more albitic by about 5 mol percent anorthite. Stron- tium concentrations are highest in the cores (up to 0.3 weight percent) but fall below the microprobe detec- tability limit in the rims. Barium, phosphorous, and other oxides were generaly undetectable. Iron was con- sistently present (up to 0.3 weight percent) in many THE WHITNEY COVE PLUTON apatite, and sphene from the Bottle Lake Complex, Maine 11 from the Passadumkeag River; cols. 16-26 are from the Whitney Cove; for sphene, cols. 27-31 are from the Passadumkeag River pluton; R and C represent rim and core facies, respectively] 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | Apatite 174 Sph BOR 31C 52R 53C 92C 58R 54R 5TR 85R 94R 104R 107R 13C 220 84C 105C 35R 0.67 - 0.42 - 0.50 - 0.41 1.85 - 0.32 - 0.52 0.44 0.650 0.59 0.46 0.59 29.86 30.61 31.12 30.95 30.18 .00 .00 00 .00 .00 .00 00 .00 .08 00 00 .00 34.35 32.25 33.24 33.80 31.69 00 .00 .00 .00 00 .00 00 .00 00 .00 .00 .00 2.06 2.18 - 2.13 2.05 - 2.67 .91 .39 .82 .61 1.58 .31 64 A5 A0 57 .68 58 2.05 2.11 2.00 - 2.21 1.88 14 A8 18 15 .19 .20 16 .26 22 14 27 18 19 19 A7 .22 .26 Al 10 12 .07 .39 .06 .06 .08 A1 10 .06 10 .07 13 .08 A1 .07 52.94 58.37 54.46 54.81 52.22 54.99 53.61 54.06 53.84 54.13 53.99 54.48 28.25 26.48 27.25 27.13 27.83 04 A41 00 00 00 .00 00 00 .00 .00 00 00 .02 .05 08 .06 .05 .01 03 .00 00 .00 00 .00 00 .06 00 .00 .00 .01 .02 .01 .02 03 00 .01 .08 .09 .02 .07 .08 .08 .06 00 .06 08 .02 13 10 09 0 41.11 41.23 39.51 39.50 41.07 40.54 40.24 39.06 40.42 41.87 40.71 39.81 04 .04 .08 04 0 .04 .01 00 .00 .00 00 00 .00 00 00 .00 00 04 .05 .04 _ 0 0 890 . 4.15 3.95, 3.566 3.57 - S.58 | 3.40 8608 _ 410 3.34 3.91 3.65 .84 .87 .67 80 0 .02 .02 .02 .01 .02 .02 .O1 .01 00 .01 .01 .02 .02 .01 .01 O01 . 0 99.89 100.27 98.94 99.21 100.91 100.09 98.72 98.07 99.89 100.75 100.15 99.39 97.82 95.72 96.88 97.49 94.66 phenocryst cores and rims. However, no compositional trend was evident. The composition of plagioclase in contact with large, euhedral biotite is typically calcic, normally within the compositional range of the phenocryst cores. In con- trast, the composition of plagioclase touching matrix quartz is characteristically sodic (An,,-An,,), typical of phenocryst rims and matrix plagioclase. The composi- tional range typical of granulated plagioclase in the mafic mineral-poor mortar (granular) texture is An, to Any,. Groundmass plagioclase forms subhedral grains up to about 0.5 cm with an average composition of Any,. Clusters of ferromagnesian minerals and plagioclase consist of large, stubby, mottled phenocrysts, and finer grained plagioclase which is compositionally similar to the groundmass. The most sodic plagioclase (An,) is found in the fine-grained matrix of the aplites and in the grains forming selvages (mortar texture) around other felsic minerals. QUARTZ Quartz forms inclusions near the rims of plagioclase phenocrysts and euhedral grains within alkali feldspar. It is also present as subhedral to euhedral grains in the matrix suggesting that it crystallized before alkali feldspar. Within the core of the pluton, quartz forms euhedral phenocrysts that in places coalesce to form clusters. Undulose extinction is a characteristic feature except near the faults where much of the quartz is com- pletely annealed. ALKALI FELDSPAR Alkali feldspar encloses all other phases, indicating that it crystallized late in the sequence. Microcline twins are commonly developed in the pluton, and these generally are embayed by perthite patches. Rapakivi (viborgite) texture is usually evident in most exposures. Alkali feldspar ranges in composition from Or;; to Org,, and its structural state resembles maximum microcline according to the scheme of Wright (1968) and Wright and Stewart (1968). Compositional zoning was not de- tected, although the composition of the albitic rims in the rapakivi texture ranged from almost pure Ab to Abs,-An;,. No gradients are evident across the pluton, probably because the consistently high orthoclase con- tent is indicative of substantial deuteric alteration. Alkali feldspar, however, was also out of equilibrium prior to the deuteric stage as indicated by the corroded and embayed alkali feldspar cores, by the intricate and irregular intergrowths of alkali feldspar and biotite, and by the irregular widths of the albite rims in the rapakivi texture. Edges shared by alkali feldspar and plagioclase show myrmekitic textures in which growth proceeded at the expense of plagioclase. Granophyre textures are for the most part constrained to between contiguous alkali feldspar grains. SEQUENCE OF CRYSTALLIZATION In accordance with the above observations, figure 11 presents a generalized crystallization sequence of the Whitney Cove pluton. Crystallization was initiated by 12 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX TABLE 3.-Representative electron microprobe analyses of structural formulae of magnetite from the Bottle [Calculated per four oxygen atoms; total iron as Fe; cols. 1-12 are from the Passadumkeag River pluton; cols. 13-20 are from the Whitney Cove pluton; R and Column 1 2 3 4 5 6 7 8 9 10 11 12 13 Sample number 5C 13C 17€ 28C 36C 78C BR 12R 23R TAR BOR 109R 440 Weight percent SIO, ------<-<<-------------- oi6 ois olf ois oos Ol6 Ol" ois 610 612 004 O12 0.05 TiOg ---------------------- 14 A1 .25 15 22 15 21 .28 .07 18 A7 .25 25 AQ, .03 .09 .03 AY .08 .01 .03 .03 .03 .06 .05 .05 10 FOO >- aie ian loc nme 91.47 89.650 9131 90.91 91.49 89.67 91.48 90.68 89.04 90.87 90.40 90.65 91.46 MBO 17 14 A12 18 19 .16 12 19 15 AT 15 21 25 MgO ---------------------- .00 .01 .00 .00 .05 .00 .04 .06 .00 .01 .07 .01 01 C&O -- E aaa mus uti ce o ce se 11 .16 14 15 15 .16 14 12 12 13 18 #i .20 N@,OQ ---------------------- .00 .00 .00 .01 .02 .01 .00 .00 .01 .00 00 00 00 K,Q .05 .05 .06 .05 .06 .07 .08 .04 .05 .06 .05 .06 07 BAO A1 .09 .10 A2 .28 .05 .10 .09 .06 .03 AZ A11 22 Total 92.24 90.45 92.14 91.85 92.62 91.04 92.383 O1.67 89.62 Q163 9128 91.57 92.61 Number of atoms " i a o 0.006 0.006 0.005 0.006 0.003 0.006 0.005 0.007 0.004 0.005 0.002 0.005 0.002 Pp J o ae ne 2 5 elec ie i us w on oe us o hea oa ce ta oi : 003 .oo7" Ooi '.o07 O22 ~.ob6 068 002 G05 005 007 ...007 Al oona «sss snus wor L001 doi ooc. ..o0os3 doi ool 001 001 002. 007 _ 005 C -or a e ee ans ho how irr make 2964 2.961 2961 2.955 2.953 2.928 2960 2.959 2974 2.962 2.965 2.957 2.953 MH woo dos '.004 . 006 ..o0o7 GOs :004 006.. 005 .006 O05 . 107 . 005 Mg ----------------------- moo. ~.d00. .ooo0o: doo .:.002z G00 002 . 004 .0006 ..000 .004 .:000 _ 001 (§ eo ar e ee hice ct me tee mm a e ne in r mee wos 007 . 006 006 007 006, 606 .oo5 Go6 .o06 L005 .00s Ng woo 000" ooo | dor doof 000 000 ..00!1' 000 . .000.. 000 fo rena er animes hace mae m aries ai tae bos. 003. 003. oor .o0o2. G04 ..o04 002 008 . .op3 .003. . 003. 003 BA -_e- sens moz dof. doz. 002 .o05 002 oof G01 - 001 008 002 - .00s TABLE 4.-Representative electron microprobe analyses and structural formulae of ilmenite from the Bottle [Structural formlae calculated for three oxygen atoms; total iron as FeO; R and C represent rim and core facies, respectively; cols. 1-15 are from the Passadumkeag Column 1 2 3 4 5 6 7 8 9 10 11 12 13 Sample number 3C 4C 5C 17€ 26C 28C TBR 111C 8R 12R 23R 74R SOR Weight percent SIO, ----<<<----------------- oor ofre boo olo ~o08 olo o06 pid 01% Oft 011 - 6.06 TiO, <--------------------- 51.10 490.54 50.48 S137 49.37 B0.81 49.74 50.07 48.68 5127 50.44 49.48 50.88 k ooo .00 .00 .00 .00 .00 .00 .00 .00 00 00 .00 00 00 FeO Een fees noncancer 43.86 44.49 42.63 43.32 44.70 42.75 44.750 40.21 45.46 41.94 48.45 41.35 39.38 MAO 197°" aar. 494 sa00 691 aat 847 506 544 bas ° Tob S97 MgO ---------------------- .03 .08 .03 .03 .04 .03 .04 .02 .08 .08 .05 02 .06 CaO execs arisen A1 .09 A2 13 15 A1 16 .10 15 .10 18 12 12 N@,Q ---------------------- .00 .01 .02 .00 .01 .00 .00 .O1 .00 .00 .01 .01 00 K,0 ----------------------- .04 .03 .05 .07 .04 .06 .05 .05 .04 .04 .04 .05 .08 BBO .23 124 .26 27 28 21 .20 21 15 .25 22 24 25 Total 99.71 99.01 99.23 100.22 98.54 100.46 99.45 99.20 99.72 99.25 100.32 99.28 99.15 Number of atoms M eam ana oo 0.002 0.003 0.001 0.003 0.003 0.002 0.003 0.002 0.003 0.003 0.003 0.003 0.001 T| _ noe bie s me 'os0 _ oes" 'lo74 loso 964 p68" 969 94s - os5 bol . 960 | 951 AT serem eron minum a man imine oaks oo 066 ldo0 ooo 000 000 odo 0006. 0006. 000 | 000 .:000 Toe "936 bt. 'ole 920 .o71. oil _ ' sep. 982 . Soo 990. 893 844 MH [i- oz L096 i293. loge - bso 149 006 fs5p i111 ils .1t6 ._ AM4 182 Mg -----------<=----<------ O15 00s. .00f looz. 002 Gof .o02 061 dos 065 002° 001! ~.002 (Cg erea n moon m bn an meanness ane mos. 00s ° 003. 064. gos '.0o02 00+ ' .003 wo 003 - 005 00s . 003 Na wooo, 006. -.oof Goo G01 . .000 ono.: 061 . O00 ..006 . 001 ..000 Jf Hee ea H a ee o inane nar ie in rele ao ele oor. dom oof 06s - .dort . 002 .ob2. 002 . dol . O01 . .001 ...001 . 001 Ba ------------------------ wos .o02 b0o3 bos 002 oozg oor: 002 .0b2z 00s - 002: 002 . 00s Lake Complex, Maine C represent rim and core facies, respectively] THE WHITNEY COVE PLUTON 13 0.06 0.18 0.19 0.25 0.33 0.33 0.10 17 .62 .29 12 A9 .28 14 12 .01 .00 .07 .21 "B1 .00 91.10 - 91.16 89.65 90.81 89.46 88.57 90.71 .28 32 15 12 .21 .30 22 .00 .07 .00 .08 .08 .02 .02 14 13 12 14 14 12 18 00 .00 .01 .01 .00 .01 .00 .05 .04 .05 .05 .06 .05 .06 24 .07 .03 .06 .24 .19 A1 92.11 92.60 90.49 91.71 91.22 90.08 91.49 0.002 0.007 0.008 0.010 0.013 0.013 0.004 005 .018 009 004 014 .008 .004 006 001 000 004 010 010 000 2.959 2.928 2.956 2.952 2.909 2.922 2.967 008 010 005 004 007 010 007 000 004 000 .005 005 001 001 006 005 005 006 006 .005 005 000 000 005 001 000 .001 000 003 .002 0083 003 003 003 003 004 001 .001 001 004 003 002 Lake Complex, Maine River pluton; cols. 16-21 are from the Whitney Cove pluton] 14 15 16 17 18 19 20 21 109R 114R 44C 92C 43R 53R 93R 108R 0.06 0.06 0.02 0.14 0.11 0.20 0.28 .08 49.98 - 47.56 48.96 48.71 51.91 49.07 52.12 51.28 .00 .01 .02 .00 .00 .00 .02 .00 42.19 44.15 42.26 36.20 35.32 38.38 35.51 40.83 6.14 TAL 8.11 13.37 10.46 10.92 10.15 7.61 .03 04 03 .06 .00 .08 .02 .10 10 .26 .26 .28 14 A7 .30 14 .00 .01 00 .00 .00 .00 .02 .01 .04 .05 .05 .05 .04 .05 .04 .06 22 A9 A6 .28 .26 .25 .26 .24 98.176 99.74 100.17 99.04 98.24 99.12 98.72 100.35 0.002 0.002 0.001 0.004 0.003 0.005 0.017 002 .971 932 949 950 999 954 .998 977 000 000 001 000 000 000 001 000 912 0.962 0.911 0.785 0.762 0.830 0.756 .865 134 182 ATT 293 227 .239 219 .163 001 001 001 002 000 004 .001 004 003 007 007 .006 004 .005 009 004 000 000 000 000 000 000 .001 001 001 002 002 002 001 .002 .001 002 003 005 005 003 003 0083 003 002 precipitation of the accessory phases generally in this order: zircon plus apatite, followed by oxides plus sulfides, and by allanite plus sphene. Biotite was the next phase to crystallize followed by plagioclase, quartz, and alkali feldspar. SUMMARY OF THE BULK CHEMISTRY The preceding sections demonstrated. that the Whitney Cove pluton was zoned mineralogically, tex- turally, and in the composition of its constituent minerals (Ayuso and others, 1982a). This zoning is also evident in the bulk composition of the granites from the rim and core facies (table 7). A summary of the geochemical characteristics follows in this section. The general gradient from core to rim facies occurs with decreasing CaO, MgO, Fe;,0,, TiO,, Al;O;, and P,0, as SiO, increases from 67.0 to 77.0 weight percent (fig. 12). These marked differences across the pluton take place at a uniform total alkali element abundance. Nor- mative compositions are corundum-poor for the pluton as a whole (table 7), but the sum of normative felsic minerals is highest in the rim facies. The most important observation derived from the bulk compositional change in the Whitney Cove pluton is that with the exception of the K,0 content, there is remarkable compositional colinearity from the margins to the interior (fig. 12). Compared to the mafic xenolith suite, the Whitney Cove pluton is more silicic. Rocks from near the trace of the major fault cutting the pluton generally also plot within the variation shown by the granite as a whole. Preliminary trace element determinations (U, Th, Pb, Rb, Sr, Y, Sc, Cr, Ta, Hf, Cs, Ba, Zr, and the rare earth elements) show irregular gradients within the pluton, except for the strong and consistent variations in zir- conium, strontium, and niobium (table 7). These three elements support the distinction between each facies and the geochemical zonation from core to rim. Higher abundances of strontium, zirconium, and niobium are concentrated in the interior of the Whitney Cove pluton. Rubidium shows no definite trend from core to rim facies. Barium and yttrium are somewhat lower in the most siliceous rocks but do not clearly separate the two facies. The process of fractional crystallization was evaluated using the least-squares computer program of Wright and Doherty (1970) for the major elements and the program developed by J. G. Arth (U.S. Geological Survey) for the trace elements in order to identify and quantify a fractionating assemblage capable of yielding the observed petrographic and bulk compositional variations. Ayuso (1982) suggested that crystallization 14 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX TABLE 5.-Representative electron microprobe analyses and structural formulae of biotate from the Whitney Cove pluton [Calculated per 11 oxygen atoms; total iron as FeO; R and C represent rim and core facies, respectively; nd, not determined] Column 1 2 3 4 5 6 d 8 9 10 11 12 13 14 15 16 Sample number 37C 44C 49C 51C 520 58C 92C 41R 53R 54R 5TR B5R 94R 104R 106R 107R Weight percent S10, ------- 36.66 37.05 36.88 36.90 37.65 37.57 37.20 35.51 37.98 37.15 37.23 38.16 36.78 35.94 36.85 37.81 TiO, ------- S91 892 411 S87 8.140 401 - $94 S61. $17 5.12 3.90 - 3.85 8.16 3.50 3.40 Al;O, ------ 14.92 14.92 14.34 14.05 14.42 14.14 14.05 13.31 14.01 13.93 15.23 14.47 13.28 14.70 13.95 13.93 FeQ ------- 20.18 18.72 21.89 20.78 21.10 21.89 21.04 26.02 20.94 23.67 23.52 20.99 24.42 24.62 21.04 20.93 MnO ------- .63 A8 59 58 .60 .61 .63 .65 .63 64 12 55 52 T7 55 .62 MgO ------- p48 1128 894 992 9490 9.72 007 6.25 10.210 8.91 7.61 10.84 7.91 774 - 9.95 10.40 CaO ------- .05 .07 .05 .10 18 .08 .04 .04 .09 .08 .06 .00 .04 04 04 .06 Na,0 ------- 18 .09 10 14 .09 *%. 11 .08 .08 AT 10 00 A1 .21 a .07 K,0 ------- 9.86 - 942 960 9.18 915 945 944 9.26 09.73, 940 943 991 9.28 9.35 9.238 - 9.55 BaO ------- .22 .28 .29 .36 18 19 .38 .20 .28 .20 .29 25 .28 .36 .25 A7 P,0, ------- .00 00 .00 .00 .00 .00 00 00 .00 .00 .00 .00 .00 .00 .00 .00 SrO -------- .00 .00 .00 .00 .00 _ nd 00 _ nd .00 .00 .00 .00 .00 .00 .00 .00 F ---------- 1.81 1.25 1.51 1.43 59 1.17 1.28 1.10 1.38 .99 .91 1.20 1.58 - 3.50 1.60 1.38 Cl --------- .09 .04 .06 .06 .06 .05 .06 .10 .09 11 .09 .07 .10 .08 .07 .09 Total 96.95 96.82 98.35 97.32 97.31 98.77 97.92 96.46 99.02 98.42 98.31 100.34 98.10 100.47 97.19 98.41 Number of atoms Si --------- BTI 218 211 2.19 284 281 280 2.19 282 2.81 2.81 219 281 208 270 282 Ti --------- 49 19 .28 28 22 .21 .23 .28 .20 .21 18 .21 22 18 .20 .19 Al --------- 1.33 1.32 1.27 1.25 1.28 1,24 1.25 1.23 1.23 1.24 1.36 1.25 1.19 1.29 1.24 1.23 Fe --------- 1.28 1.17 1.38 - 1.31 1.33 1.37 1.32 1.71 1.30 1.50 1.49 1.28 1.56 1.54 1.33 1.31 Mn -------- .04 .08 04 .08 04 .04 .04 .04 .04 04 .05 .08 .08 .05 .04 .04 Mg -------- 1.07 1.26 1.00 1.12 1.07 1.08 1.08 18 1.14 .94 .86 1.18 90 .96 1.12 1.16 Ca --------- .00 .01 .00 .01 .01 .01 .00 00 .01 .01 .01 00 .00 .00 .00 .01 Na -------- .08 .01 .01 .02 .01 .02 .02 .01 .01 .08 .01 00 .02 03 .02 .O1 K --------- .90 .90 .92 .88 .88 .90 .91 93 .92 .91 .91 .93 .90 .89 91 .92 Ba --------- .01 .01 .01 .01 .01 .01 .01 .01 .01 .01 .01 .01 .01 .01 .01 .O1 P ---------- .00 .00 .00 00 .00 .00 .00 .00 .00 00 .00 .00 .00 .00 .00 .00 Sr --------- 00 .00 .00 .00 .00 _ nd .00 _ nd .00 00 00 .00 00 00 00 .00 F ---------- Ad .30 .36 84 14 .28 .30 21 .24 22 .28 .38 .83 .39 .33 Cl --------- .01 .01 .O1 .01 .01 .01 .01 .01 .O1 .O1 .01 .01 .O1 .01 Kol .01 Fe/(Fet+ Mg) - 54 A8 58 54 55 .56 55 10 53 .61 .63 52 .63 .62 54 53 of 19 percent of the liquid in equilibrium with 13 percent plagioclase, 5 percent biotite, 0.5 percent apatite, and 0.5 percent magnetite-ilmenite accounted for some of the bulk chemical variation from representative rocks from the core and rim facies. The overall bulk chemical and petrographic variation of the internal subdivisions fo the Whitney Cove pluton, however, cannot be ex- plained by fractionation. In addition, the occurrence of more mafic granitic rocks in the interior of the pluton may be suggested to reflect processes other than frac- tional crystallization. THE PASSADUMEKEAG RIVER PLUTON FIELD RELATIONS The Passadumkeag River pluton is exposed in an area of about 700 km. It consists of rock types ranging in mineralogy from granite to quartz monzonite and shows an obvious change toward darker (more mafic-mineral- rich) rocks toward the interior. Euhedral, black horn- blende is a distinctive feature of the pluton as is a high abundance of mafic xenoliths. The Passadumkeag River pluton consists of the rim and core facies (pl. 1). THE RIM FACIES Rocks forming the rim facies are grayish pink (5R 8/2) to grayish-orange pink (10R 8/2). They are typically granitic in mineralogy (IUGS classification of Streickeisen, 1973) and show textures ranging from por- phyritic to equidimensional. The outcrop pattern of this facies suggests that it is variable in width. Near the area north of Upper Sysladobsis Lake (P) (Springfield quad- rangle), the rim facies is widest, but to the west, in the area near No. 3 Pond (Q) (Winn quadrangle), it is absent (pl. 1). THE PASSADUMKEAG RIVER PLUTON BIOTITE .052 | b Whitney Cove 0 o .044 |- = o (el e e @ (ol n ** o .036 |- 9 ~ % 6 o T T e I T | oure .230 |- he - - © 0 e 0. o $ ag 210 ~ Ti | e - 0 o & 7 190 je Le 0 - re t 170 | | | | | { I | I I T w a (5) o z .20|- ~ o & (L lo & 316 o I w 2 A|V| 0 O & o® 20 hg < 10 |- a e o o Fs & o o 05 - $ = 0 | | | | | I I | b | 1.21- *s 2s (el o a IV ® & Al b 1.17 |- P e ® EXPLANATION c o & 5 ® Core facies a L 0 Rim facies - % (el « E 113 | | I o | | 48 .52 .56 .60 .64 .68 72 Fe/(Fe + Mg) FigurE 7.-Compositions of biotite in the Whitney Cove pluton as a function of Fe/(Fe+ Mg). Each symbol represents the average obtained on at least 10 grains per sample. Note the different Fe/(Fe+ Mg) ratios of biotite from each facies of the pluton. See table 5 for specific titanium and manganese values. 15 16 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX BIOTITE .98 I E Whitney Cove .d4(- = .90 - % ~ 2° 7" MA .Y. o ~4 Ag ® sed ATOMS PER 11 OXYGENS A7 | | | | 1.7!- s 1.9)2- C o 541 Fe 1.3|+ LJ e - EXPLANATION (2 6 e Core facies _ - 0 Rim facies 11 | | | | 67 69 71 73 75 77 SiO, OF THE ROCK, IN WEIGHT PERCENT FIGURE 8.-Compositions of biotite in the Whitney Cove pluton as a function of SiO, content of the whole rock. Note the higher iron con- tent of biotite with increasing silica content. Detailed mapping and subdivision of this facies into | Many of these lithologic types (fig. 13) are evident in the different types is also possible using the abundance of | Springfield and Scraggly Lake quadrangles which con- amphibole, total ferromagnesian mineral content, and | trast with the predominantly amphibole-poor, equi- development of seriate, equidimensional and porphy- | dimensional rocks developed elsewhere in the rim facies, ritic textures (Ayuso, 1979; Ayuso and Wones, 1980). | for example, in the Nicatous Lake quadrangle. THE PASSADUMKEAG RIVER PLUTON es ; y BIOTITE I f 6 Whitney Cove o % o o 2.84 |- S o ® o g 6 a bed o % (oct) o o o @ 2.80 |- - 2.161 EXPLANATION - ® Core facies 0 Rim facies 272 | | § | | T 1 " .57- se -- 0 na- g o (5) 51 |- z o s _ o. I - e e 3 oo [ ® § (J @ 6. 45 |- C - g 5 s ® e @ & 0 > o 2 24 |_ < | & 39 | | | | 2.88 I I I I el L e o o o 2.84|- e & ma Si o: ® bt @ & o ® 2.80 |- d -I 6 o | o 1 | | 16 18 20 .22 24 .26 Ti, IN ATOMS PER 11 OXYGENS FIGURE 9.-Compositions of biotite in the Whitney Cove pluton showing the absence of clear correlations between differ- ent components as a function of titanium content of the biotite. Fe/3 in the rim facies is generally higher than for biotite in the core facies. See table 5 for specific silicon and titanium content. 37 18 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX TABLE 6.-Representative electron microprobe analyses and structural formulae of plagioclase [Calculated per eight oxygen atoms; total iron as FeO; R and C represent rim and core facies, respectively; Column 1 2 3 4 5 6 T 8 9 10 11 12 13 Sample number 370 44C 49C 51C 520 58C 92C 41R 43R 53R 54R B5R 93R Weight percent SIO, -------------------- 59.65 61.46 63.04 55.88 63.80 61.40 57.87 64.06 65.07 64.04 63.83 63.79 63.73 TiO, <------------------- .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 MK, 25.45 24.47 23.08 28.30 22.65 24.40 26.31 22.66 22.09 22.64 22.84 23.06 22.67 FeO A1 47 15 .29 15 14 Al .10 .06 A7 13 10 09 .01 .00 .02 .03 .01 .00 .00 .01 .01 .01 .00 02 00 MgO =< -at .02 .01 .02 .09 .02 .01 .02 .01 .01 .02 .02 .O1 00 CaQ 7456 545 459 ~ 998 400° 541 S11 S94 281 4st? 410 _ 386 s69 ------------------- 7.21 . B25 ' SBI bd4b 9.04 B12 G05 905 O41 872 BBG 808 9.54 KQ .25 37 .29 .24 .29 14 14 .36 .28 59 30 .20 25 SN) -~ Seer anc aka ae nd nd nd nd nd .00 A2 nd nd nd nd nd .07 Total 99.91 100.18 100.00 100.28 99.96 99.62 99.63 100.19 100.03 100.76 100.16 100.02 100.04 Number of atoms Sf -- =s - em a an an tainer eal e on ie hts 266-2789 240 251 gras 218 P61 S82 281 S81 281 gas Ti .00 .00 .00 .00 .00 .00 .00 .00 00 .00 00 00 00 .. palos Se l eee 184 128 121 -150° 148 128 140 lis i116 117" 119. i220 11s Fé nlm .00 .01 .01 .01 .01 .01 .01 .00 00 .01 .O1 00 00 MHA r ci n- .00 .00 .00 .00 .00 .00 .00 .00 .00 00 00 00 00 oin .00 .00 .00 .01 .00 .00 .00 00 00 .00 00 00 00 Oq) Aar e a a ole aa ae an a sale .34 .26 .22 A8 19 .26 .39 19 13 22 .20 18 18 Na .63 I1 16 A7 M17 10 .58 A7 .83 T4 16 T7 .82 o $e Pai rere eran .01 .02 .02 .01 .02 .01 .01 .02 .02 .02 .02 .01 .01 SF s a re r a ere ane ne i ine ane nd nd nd nd nd .00 .00 _ nd nd nd nd nd 00 Feldspar components, mol percent AR er ae enate oona els 35 26 22 50 19 27 40 19 14 22 20 19 17 AD on ank ams 64 72 76 49 79 72 59 79 85 76 78 80 81 OF 1 2 9 1 2 1 1 2 2 2 2 1 1 Additional petrographic heterogeneity in the rim facies is expressed by the progressive changes in fabric and mineralogy away from the granite-country rock contact. Rarely, porphyritic rocks are associated with aplites and tourmaline-bearing pegmatites at the con- tact, but within a few meters toward the interior they become medium-grained and equidimensional granites (fig. 13). Many of these changes are evident in the area of Getchell Mountain (E) and near Almanac Mountain (A) in the Springfield quadrangle. Forceful intrusion of the pluton is indicated by sharp contacts exposed north of No. 3 Pond (Q). Lit-par-lit disaggregation of country rock by aplites and pegma- tites, however, is a common contact phenomenon and is exemplified by outcrops west of Getchell Mountain (E) where the band of porphyritic rocks developed at the contact is poor in mafic minerals and pinkish gray (5YR 8/1) to grayish-orange pink (10R 8/2) in color. Am- phibole is the most important mafic mineral in the pluton as a whole but is typically uncommon near the contact; it increases in abundance and grain size, however, toward the interior of the pluton. Similar in- creases in the abundance of the accessory and varietal minerals are also evident. Mafic xenoliths are absent at the contact, and their change in abundance and size parallels that of amphibole. Although porphyritic rocks are generally massive, some of the seriate granites are foliated parallel to the contact. Preferred orientation of the feldspars, biotite and quartz argues for a granitic magma already satu- rated with respect to these phases during intrusion at this level. Exposures of foliated granites are common to the west of Lombard Mountain (R) and south of Bowers Mountain (S) in the Springfield and Scraggly Lake quadrangles, respectively. Other typical changes occurring within the rim facies as a function of distance from the country rock include the general decrease in schlieren, amorphous felsic inclu- sions, and country-rock xenoliths. All of these, except for the felsic inclusions, are alined with their apparent long dimensions horizontal and parallel to the contact. Many of the felsic masses show textures and miner- alogy similar to the porphyritic band developed at the contact with the country rock. The average modal composition of the rim facies is as follows: alkali feldspar, 39.2 percent; plagioclase, 30.0 THE PASSADUMKEAG RIVER PLUTON 19 in the Whitney Cove pluton nd, not determined] 14 15 16 17 18 94R 104R 106R 107R 108R 62.31 65.00 63.83 62.74 63.47 .00 .00 .00 .00 .01 24.04 22.18 23.01 23.50 22.85 14 .10 .10 14 15 .00 .01 .01 .00 .02 .01 .01 .01 .02 .01 4.60 3.52 4.26 4.68 4.44 8.59 9.12 9.03 8.65 9.01 A6 .85 .25 28 16 nd nd nd nd nd 100.15 100.24 100.51 99.97 100.11 2.16 2.86 2.81 2.18 2.80 .00 .00 .00 .00 .00 1.25 1.15 1.19 1.23 1.19 .01 .00 .00 .01 .01 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 B2 A7 .20 .22 B1 14 18 41 14 T7 .03 .02 .02 .01 .01 nd nd nd nd nd 22 17 20 23 21 75 81 78 76 78 3 va 2 1 i percent; quartz, 24.1 percent; biotite, 4.6 percent; and amphibole, 2.1 percent. The sum of opaque minerals and accessories accounts for significantly less than 1 per- cent of the mode. The trend in modal abundances within the Passadumkeag River pluton is clearly toward an in- terior facies rich in plagioclase and mafic minerals (fig. 5; table 1). THE CORE FACIES Granitic rocks representative of the core facies are coarse grained, very pale orange (10YR 8/2) to yellowish gray (5Y 8/1) in color, and contain numerous mafic xenoliths (fig. 14) and characteristic euhedral, black am- phibole prisms (Ayuso, 1979). Plagioclase content at- tains its highest value in this facies resulting in rocks properly termed quartz monzonite. The change between facies is in places abrupt, as in the area west of Upper Sysladobsis Lake (P), but is commonly unexposed and of unknown nature (pl. 1). The rocks are predominantly porphyritic to seriate and display euhedral alkali feldspar with rapakivi tex- ture (fig. 15). Plagioclase and amphibole are phenocrysts 60 I I Whitney Cove |_ *] 50 - = L % sel f ’—. Z s) oc 40 |- s ui a. wal O p3 z [ 24 m cC O O _,; 30 |- - & 5: o L.. q PM & o 0 o e o 0 o 20 |- o Nee o o i EXPLANATION | ® Core facies 0 Rim facies 10 | | | | | .06 10 14 18 Al Y' (BIOTITE), 10oNnS/11 0 FIGURE 10.-The normative anorthite (An) content of plagioclase cores plotted as a functon of the AlY' content of biotite in the Whitney Cove pluton. Higher anorthite component in plagio clase coexists with biotite containing the highest AlY' in the core facies. Rim facies have elagioclase with lower anorthite contents and biotite with lower AlYL. in a matrix of mafic and felsic minerals. The average modal composition of this facies is as follows: plagio- clase, 37.6 percent; alkali feldspar, 33.0 percent; quartz, 19.4 percent; biotite, 5.8 percent; amphibole, 4.2 per- cent; the sum of the accessory and opaque suites is less than 1 percent (table 1). The core contains about twice the total mafic mineral content of the rim. Additionally, reverse modal zonation is displayed by the antipathetic 20 Whitney Cove Sulfides | - -- Zircon Apatite Oxides Allanite Sphene Biotite Hornblende Pyroxene Plagioclase --- Quartz Alkali feldspar Liquid Rock FIGURE 11.-Generalized order of crystallization in the Whitney Cove pluton. Plagioclase, quartz, and alkali feldspar crystallized after the accessory and mafic minerals. FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX correlation between the sum of alkali feldspar plus quartz and that of total mafic mineral content plus plagioclase. Typical outcrops are exposed west of Sysladobsis Lake (M), on Moose Mountain (T), and around the Chain Lakes (U). The most distinctive feature of the rocks within the core facies is their heterogeneity in the regional sense. This heterogeneity results in the absence of smooth and linear trends in the modal abundances across the pluton. Typical core facies rocks consist of randomly distributed, fine-grained quartz-dioritic clusters, rich in mafic minerals interspersed with clusters made almost exclusively of feldspathic minerals. Similarly, the entire lithological diversity of mafic xenoliths is sometimes ex- emplified in individual outcrops by a great range in size, shape, and mineralogy. Xenoliths range in size from the small (5-10 cm), ovoidal, fine-grained, and randomly TABLE 7.-Representative major and trace element analyses and norm composition of the Whitney Cove pluton [R and C refer to rim and core facies, respectively; total iron as Fe,O;; LOI, loss on ignition] Column 1 2 3 4 5 6 7 8 9 10 Sample number 38R 3OR 41R 47R 31C 50C 51C 520 58C 60C Weight percent S10, --------------- 73.18 74.30 74.58 73.46 70.45 70.51 68.51 67.40 69.50 71.97 TiO, -------------- .34 .20 .26 .30 AT A9 54 .64 EB A7 13.94 13.25 13.44 13.60 14.70 14.30 15.00 15.20 14.64 13.61 g.11 1.78 1.84 2.40 2.93 3.07 3.27 3.97 2.983 242 MnQ «-s---..-..«... .05 .04 .04 .05 .10 .07 .06 .08 .06 06 MgO ---.-......._.- Eyl .34 .28 A2 Ti .81 92 1.02 .83 54 CaO -------------- 1.30 1.06 1.07 1.29 1.91 2.10 2.24 2.92 2.16 1.60 Na,O -------------- 3.23 2.97 3.08 1.32 3.23 3.57 3.44 3.66 3.45 8a7 KJ -_ 4.94 5.14 5.18 4.80 4.41 4.41 4.65 4.31 4.15 4.82 PG, 13 .09 .05 .08 15 15 18 22 A7 15 LOT -~. A8 A4 16 A9 A44 .92 1.21 1.58 .80 51 Total 100.07 99.61 99.98 100.21 99.56 100.40 100.02 100.58 99.73 99.57 Norm Q 32.49 34.97 34.28 32.55 30.10 27.67 24. 42 283.97 26.63 31.95 C s- fee = 1.23 1.09 .94 19 1.51 18 A2 .82 A4 87 Of 29.17 30.49 30.62 28.31 26.18 26.19 27.117 25.177 28.38 28.83 Al 27.01 25.23 26.07 28.03 27.45 30.45 30.70 31.42 28.84 26.172 AR 5.60 4.69 4.178 5.87 8.53 9.49 10.04 10.19 9.11 7.04 Ep -it .92 .85 10 1.04 1.93 2.03 2.32 2.57 2.09 1.36 HM 2.11 1.179 1.84 2.40 2.94 3.09 3.30 4.02 2.96 2.45 Ila ass mensen n A1 .09 .09 11 22 15 13 17 13 18 Th 2-2 .00 .00 .00 .00 .00 .00 .00 00 00 00 Ry .28 16 "22 .24 .36 Al A8 56 A2 "81 Ap .31 A1 12 19 .36 .36 Ad 53 Al .36 Trace elements in ppm Rb 165 160 197 148 193 158 164 171 152 186 Sr -___-ooormeakkaes 183 158 113 148 280 236 289 276 264 237 ¥ enact al 27 37 35 29 22 38 38 44 33 36 Ba e 527 564 352 424 755 509 703 527 584 497 IP Wer 195 164 162 159 177 203 227 281 195 185 NJ 17 16 17 10 20 24 25 26 20 19 THE PASSADUMKEAG RIVER PLUTON 21 oriented masses of biotite and plagioclase common throughout the Passadumkeag River pluton, to banded biotite-rich aggregates and to large (up to 1 m), disc- shaped and prominently porphyritic quartz-diorite rocks. PETROGRAHY AND MINERAL COMPOSITIONS Compositonal variation of the constituent phases within the Passadumkeag River pluton exceeds the ana- lytical uncertainty, supports the modal heterogeneity, and argues for distinct chemical differences even within each facies. The core facies of this pluton probably con- tains more accessories than the rim facies, especially as inclusions within mafic minerals and close to the mafic xenoliths. Zircon and apatite were the earliest phases to crystallize. Apatite in the Passadumkeag River pluton shows larger variations in fluorine (from 1.6 to 4.4 weight percent) and manganese (from the limit of de- tectability to 0.24 weight percent) than in the Whitney Cove pluton (table 2). Allanite (table 2) tends to form euhedral and smaller grains than in the Whitney Cove pluton, and these are also optically and compositionally zoned from core to rim. Primary sphene presents euhedral sides to all phases except apatite and zircon, while secondary sphene is generally anhedral and replaces amphibole and biotite. Representative analyses of sphene are given in table 1. Magnetite and ilmenite are generally enclosed in mafic minerals, occur as secondary reaction products in biotite and amphibole, and are scattered in the matrix. Rounded pyrite grains are rare and appear to concen- trate within magnetite. Magnetite contains less than 1.0 weight percent TiO, and shows no differences be- tween facies (table 3). Manganese in ilmenite is lower than in the Whitney Cove pluton but ranges up to 8.5 weight percent and suggests reequilibration at low tem- perature (table 4). Clinopyroxene(?) is an extremely rare phase in the Passadumkeag River pluton. It is found only in one sample of the core facies as very fine-grained inclusions within plagioclase phenocrysts. Although the pheno- crysts also enclose amphibole, no reaction rims between amphibole with the generally subhedral, monoclinic, and optically unzoned clinopyroxenes are evident. AMPHIBOLE Amphibole is heterogeneously distributed in this granite. Near the granite-country rock contact, am- phibole is absent. In a few areas within the core facies, amphibole and biotite are subequal in abundance, but more commonly, amphibole is subordinate to biotite. Two varieties of amphibole, a phenocryst and a matrix component, are present in the Passadumkeag River pluton. Amphibole phenocrysts (up to 0.7 ecm) are black prisms, invariably euhedral to all other silicates except biotite. Although amphibole generally precedes biotite in the crystallization sequence, inclusions of unalined biotite plates within amphibole suggest a stage of coprecipitation of these two phases. Crystallization of biotite prior to amphibole agrees with the suggestion of Wones and Dodge (1977) that in potassium-rich magmas, exemplified by the Bottle Lake Complex, a magmatic stage with low water activity promotes crys- tallization of biotite before amphibole. In accordance to the classification of Leake (1978), the amphiboles belong to the calcic group and range from edenite and edenitic hornblende to ferro-edenites and ferro-edenitic hornblende. The Fe/(Fe+ Mg) ratios range from about 0.51 to 0.75 (table 8) without a distinct trend in the pluton from rim to core facies (fig. 16). A gap in the Fe/(Fe+ Mg) ratio occurs at about 0.64 to 0.66, prob- ably as an artifact of sampling. Manganese displays a roughly increasing trend with higher Fe/(Fe+ Mg) ratios (fig. 16). The change in the total abundance in the A-site, and of potassium in the A-site, lacks a consistent trend in more iron-rich amphibole. Fluorine is positively cor- related with the silica content of the rock (not shown), and is in agreement with the change found in coexisting biotites. This relatively systematic change in fluorine content was not evident in biotite from the Whitney Cove pluton (table 5). The abundances of calcium, sodium, and titanium in amphibole are also typically scattered and show no distinctive gradient in the Passadumkeag River pluton (fig. 16). The total aluminum variation in amphibole shows a broadly in- creasing trend with Fe/(Fe+Mg) ratio. However, Al shows no correlation with increasing Fe/(Fe+ Mg) ratios (table 8), in contrast with the scattered but positively correlated change for AlY!'. The change in Mg) ratio of amphibole is not clearly correlated with the silica content of the rock (fig. 17) or with silicon in tetrahedral coordination (Si) of the amphibole (table 8). At a given Fe/(Fe+Mg) ratio, the amphiboles in the Passadumkeag River pluton are higher in Si'% than amphiboles from the Eagle Peak pluton (Noyes, 1978) and the Sierra Nevada batholith (Dodge and others, 1968). In contrast to the drastic decrease in Fe/(Fe+Mg) ratios of progressively more siliceous magnetite-series granitic rocks found by Czamanske and others (1981), amphiboles from the Passadumkeag River pluton are dispersed but do not show a decrease in Fe/(Fe+ Mg) ratios in more siliceous rocks (table 8). This observation strongly argues against 22 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX Whitney Cove Na;0 K0 2.0 - s OXIDES, IN WEIGHT PERCENT TiO; to o I I 1.0)- P;0s5 | | SiO,, IN WEIGHT PERCENT EXPLANATION e Core facies o Rim facies o Mafic xenoliths x Aplites FIGURE 12.-Variation diagrams of the Whitney Cove pluton showing the core and rim facies. The composition of the mafic xenoliths from the Passadumkeag River pluton and aplites are also plotted. Note the correlation of the oxides with the silica content of the rock, the absence of significant gaps in the trend, and the more silicieous character of the rim facies. Samples from the rim facies are lower in Al;O,, Fe,0,, MgO, TiO,, and CaO than the core facies. This compositional zoning of rocks from a single pluton is opposite to the arrangement in concentric and normally zoned plutons. OXIDES, IN WEIGHT PERCENT st 17{- 16 |- Al;Os 14 |- 13¢- 121 H1L._1 Whitney Cove THE PASSADUMKEAG RIVER PLUTON 14[- 121~ 10 |- Fezoa co I MgO t I =a I co © o | CaO petrel n 4 03 v2 _ a __ La 60 65 SiO,, IN WEIGHT PERCENT py- nemsor= "H.-.— , 3-017: q NL-B-15 Phe ft as ga Lx‘i‘v‘ui (% \ ) & u eRe FIGURE 13.-Stained slab of a characteristic sample from the rim facies of the Passadumkeag River pluton. Note the alkali feldspar (light gray) and plagioclase (white) form subhedral crystals and surround areas rich in mafic minerals (dark gray). FIGURE 14.-A typical outcrop of the core facies of the Passadumkeag River pluton. Mafic xenoliths have a large range in size in the core facies (knife is 7 cm long). Reaction bands are typically absent at the contact between the host granite and the mafic xenoliths. Note the grain size and the textural contrast between the xeno- lith and its host. significant oxidation during magmatic differentiation during the evolution of the Passadumkeag River pluton. The absence of gradual compositional changes in am- phiboles from the Passadumkeag River pluton suggests that during amphibole crystallization substantial chemical heterogeneity existed in the pluton. Also, am- phibole compositions argue against the existence of a systematic change in the silica activity of the rocks as represented by the core and rim facies. 24 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX Amphiboles from the rim facies range widely in titanium contents, from about 0.13 to 0.19 (atoms per 23 oxygens) in rocks with a minimum content of 70 weight percent SiO, in the rock. They are in contrast to amphibole from the core facies which attains abun- dances up to 0.23 but with a range in SiO, content from about 65 to 72 weight percent (fig. 17). Higher fluorine abundances in amphibole are correlated with higher SiO, content of the rock. Total aluminum, manganese, potassium (fig. 17), Al, and AlY"' are in contrast to this relation because they typically lack meaningful gra- dients with the SiO, content of the rock. Total aluminum, however, generally increases with the Fe/(Fe+Mg) ratio, while AIY' is uncorrelated with the anorthite component in coexisting plagioclase (fig. 18) from samples of the rim and core facies. Plagioclase from the core facies has a higher anorthite content than plagioclase in the rim facies at a given value of AlY' in the amphibole. Substitutions in amphibole involving Al for the sum of the total of the A-site occupancy +AIV'+2(Ti) were suggested by Czamanske and Wones (1973) and Robin- son (1971) to dominate the evolution of amphibole com- positions. Czamanske and Wones (1973) and Czamanske and others (1981) noted the slight deficiency of Al in granites from Finnmarka and Japan, respectively. Simi- lar deficiencies in aluminum were found in the am- phiboles from the Passadumkeag River pluton. Other substitutions including the coupling of Al for titanium are not evident in the amphiboles of the Passa- dumkeag River pluton, although there is a tendency for AlY'+Ti to increase with Mg). The change in io a Q} 36 5?in .t¥ a FIGURE 15.-Stained slab of a sample from the core facies of the Passadumkeag River pluton. Plagioclase (white) forms subhedral crystals subequal in size to alkali feldspar (light gray). Note the relative enrichment of plagioclase in this sample compared to that seen in figure 13. ATOMS PER 23 OXYGENS THE PASSADUMKEAG RIVER PLUTON AMPHIBOLE 9 | 7 I 3 ol- Passadumkeag River a A & A A A A A a S . I~ A*,, 'A ; A" a* AAMA A o * A A‘A A A i a & $2 . 8) A 4 aA Fr A J A 5 |- = 4 | | | | | 175 T T T T T A Mn .125|- *A a*" a I A #1 * {A * 4 a 4," A £ [fiat A A .075 ey | 4 \& a | | | I I T T T .5 |- - Yo s .3|- - K A A a a 2 tk 2A “A aga _ A A), _ AAA C .2 |- A A‘ A ~ A& A A A +o | | | | | r I I I I I A .6 |- i * 9a -f A a AA A A & A aA a A Na 5i- AA 4 g s A A 5 4 4 |- § A g AA . A ai A aA AA A aA 3 | | | | | 2.0 I I I I I A A A A A A i 4A (_ 4 A a 1.8 i. m*. * 1 gts F3 * ~ k A A A C Ca A 1.6 - EXPLANATION - A Core facies A A Rim facies 1.4 | | | L. | .25 | 1A I t I A A aA &A iy 4 R A .20 |- A A A - A A A ys A A\ A Ti A £ Ama k & & 15 |- A A A ail A A 10 | | | | | .54 .58 62 .66 .70 .74 78 Fe/(Fe+ Mg) FIGURE 16.-Compositions of amphibole in the Passadumkeag River pluton as a function of Fe/(Fe+Mg). Each symbol represents the average obtained on at least 10 grains per sample. Note the absence of clearly defined trends with increasing Fe/(Fe+ Mg) ratio. Only manganese shows a broad positive correlation with Fe/(Fe+ Mg) in the amphibole. The content of titanium, sodium and the total in the A-site shows large scatter. The compositions of amphibole in the core and rim facies are generally not significantly different. A gap in Fe/(Fe+ Mg) ratios from about 0.64 to 0.66 is probably an artifact of sampling. See table 8 for specific values. 25 26 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX TABLE 8.-Representative electron microprobe analyses and [Calculated for 23 oxygen atoms using the scheme of Czamanske and Wones (1973). Column 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Sample number 4C 9C 13C 17€ 210 240 25C 26C 200 31C 36C 15C 78C 790 84C Weight percent S10, ---------- 44.56 4446 43.48 43.76 41.85 42.83 4262 42.74 44.08 44.44 43.99 43.91 42.28 42.70 43.63 Al;O, ---------- 8.62 8.66 7.61 7.81 10.10 8.20 8.48 8.28 7.18 8.22 8.28 8.35 7.66 8.45 8.01 TiO, ---------- 1.68 1.66 1.77 1.85 1.39 1.96 1.88 1.12 1.71 1.66 1.91 1.68 1.60 1.37 1.62 FeQ ---------- 22.717 21.51 21.11 2046 25.63 24.28 26.06 22.25 21.39 22.89 22.04 22.41 21.34 25.22 23.59 MnO ---------- 18 14 .81 .69 87 .92 18 .86 10 10 12 19 16 19 .80 MgO ---------- 7.49 8.37 8.02 8.77 6.10 6.04 5.10 7.18 8.35 7.49 7.15 7.39 7.98 5.46 6.15 CaO ---------- 10.93 11.05 10.60 10.72 8.89 10.78 10.00 10.89 10.58 10.85 10.73 10.92 10.65 10.50 10.47 Na,0O ---------- 1.38 1.25 1.96 1.89 1.28 1.90 1.69 1.176 1.81 1.77 1.176 1.38 2.01 1.89 1.38 K,0 ----------- 1.12 1.12 1.03 1.00 2.11 1.11 1.16 1.13 87 .98 1.14 1.02 1.08 1.05 1.00 BaO ---------- .05 .04 .01 .00 .06 .02 .07 0+ . :nd 00 18 .05 .02 .00 .05 F ------------- Al 37 55 A8 711 38 58 .88 51 37 AO .31 .60 .61 .85 Cl ------------ 16 .16 11 £1 15 14 .29 14 A41 15 .20 A7 12 13 12 P,0, ---------- .00 .01 .02 .01 .01 .02 .01 .02 .20 .02 .00 .02 .O1 .01 .O1 SrO ----------- .01 .02 .O1 .01 00 .01 .04 .00 00 00 .00 .00 .02 .00 .01 Total 99.96 99.47 97.09 97.56 99.70 98.54 98.71 97.36 98.09 99.54 99.05 98.40 96.08 98.18 97.79 Number of atoms Si <----------- 6.1763 6.744 6.787 6.760 6.526 6.686 6.705 6.693 6.846 6.777 6.742 6.770 6.711 6.722 6.801 Al <----------- 1287 1.256 L218 1.240 OL474 1.314 1.2056 1.307 L154 1.228 1.258 1.230 1.280 1.278 1.199 (TET) ------ 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 Al <----------- .304 298 .188 183 398 195 2717 .221 247 254 .238 .287 148 290 272 Fe ------------ 2.811 2626 2.738 2583 3.025 3.170 3.304 2902 2.655 2853 2.772 2.813 2.792 3.268 2.971 Mg ----------- 1.694 1.892 1.866 1.019 1419 1.405 1.196 1.675 1.902 1.703 1.770 1.707 1.875 1.280 1.568 Ti <----------- 191 .189 .208 215 .163 .230 228 .202 .196 190 .220 193 190 162 .189 Mn ----------- 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 (M,-M,) ---- 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 Ca ------------ 11T1T L496 48s 1.802 loss lga? L482 1722 iljo2 LBO2 L812 1.772 1.1749 Mn ----------- 100 .095 107 090 115 131 097 115 090 .091 093 102 102 106 105 Fe ------------ 080 108 .018 .061 .318 000 128 018 .078 .067 .055 .067 040 069 105 Na ------------ 048 006 102 .075 .084 .067 095 .045 100 120 090 029 .046 .069 041 (M,) -------- 2000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 Na ------------ .364 .361 A92 A92 A59 508 A19 A89 A85 A083 A34 .393 572 509 974 K ------------ .216 .216 206 198 548 .221 .233 .226 .169 .191 222 197 219 210 199 Ba ------------ 0083 002 001 000 004 001 005 .001 000 000 .008 003 001 000 003 (A) -------- 583 579 .699 690 1.006 130 657 116 604 594 664 598 192 A19 576 Fe/(Fet+ Mg) ---- .631 591 596 567 102 .693 142 635 509 .632 615 .629 .602 122 .662 the sum of AlY and AIY' as a function of Al is consist- ent with the change found in the Japanese granites studied by Czamanske and others (1981). However, perhaps a result of the limited compositional variation in this pluton compared to the Japanese granites, am- phiboles from the Passadumkeag River pluton form an array along a steeper slope. BIOTITE Biotite is the predominant mafic mineral in the Passa- dumkeag River pluton. Several textural types are pres- ent including phenocrysts, groundmass, and biotite forming fine-grained clusters with other mafic minerals and plagioclase. Comparison of biotite compositions across the pluton from rim to core facies characteris- tically shows major overlap (table 9). The Passadum- keag River pluton is characterized by biotites with Fe/(Fe+Mg) ratios ranging from about 0.57 to 0.80 (table 9) and lacking a distinctive trend in titanium be- tween biotites from the core and rim facies (fig. 19). However, in spite of the overlap, at a given Fe/(Fe+ Mg) ratio, biotites from many of the samples from the core facies usually have higher titanium than those in the rim facies. Plotted against the Fe/(Fe+ Mg) ratio of the biotite, the titanium content shows no progressive gra- dient (fig. 19). Titanium content, however, is broadly correlated with the SiO, content of the rock (fig. 20), so that lower titanium in biotite occurs, in most cases, in the more silicic marginal facies of the pluton. Compared to the Whitney Cove pluton, the composition of biotite in the Passadumkeag River pluton shows a range for titanium from about 0.17 to 0.27 (atoms per 11 oxygens) (table 9), broadly in agreement with the range found in the Whitney Cove pluton. Biotite from the Passadum- keag River pluton suggests no correlations between titanium and the total abundance of the octahedral ca- THE PASSADUMKEAG RIVER PLUTON 27 structrual formulae of amphibole from the Passadumkeag River pluton Total iron as FeO; R and C represent rim and core facies, respectively; nd, not determined] 16 17 18 19 20 21 22 28 24 25 26 27 28 290 30 31 32 86C 89C 91C 105C 1100 1120 113C 1150 8R 10R 12R 23R 27R 35R T6R TTR BBR Weight percent-continued 48.27 44.52 42.77 44.23 43.37 42.92 44.57 43.67 44.06 43.73 44.25 43.00 44.15 4228 43.69 44.00 12.89 8.49 8.10 8.29 8.24 8.44 8.50 8.03 7.26 8.07 8.27 7.04 8.69 8.15 8.62 8.12 8.66 8.92 1.41 1.42 1.81 1.50 1.69 1.175 1.89 1.43 1.52 1.61 1.11 1.39 1.50 1.10 1.54 1.46 1.49 23.56 22.04 24.78 21.30 28.13 23.52 20.77 22.81 21.93 23.66 24.78 24.79 22.69 25.66 2243 22.53 25.02 .91 .69 .81 15 .98 .90 .65 .85 i 14 1.00 1.23 .62 1.28 10 10 .95 6.66 7.89 6.10 8.40 6.66 6.85 8.170 7.69 7.80 6.173 6.19 5.46 7.49 4.15 7.44 7.10 5.89 10.83 11.09 10.23 10.77 10.70 10.76 10.83 10.73 11.02 10.88 10.40 10.55 11.28 10.60 10.68 11.33 10.68 1.86 1.48 1.54 1.56 1.86 1.83 1.89 1.66 1.66 1.70 1.22 1.86 1.39 1.80 1.80 1.75 1.49 1.05 1.00 1.17 1.06 1.16 1.15 1.10 .99 1.13 1.14 .98 1.07 1.14 1.24 1.10 1.14 1.18 .01 .06 .04 .08 14 .10 A1 A1 14 14 .06 03 .02 .02 A41 .00 .04 A5 .31 51 57 Al A4 A5 51 A8 A6 .66 55 12 .63 AT 47 A9 .10 11 .31 11 .20 .20 37 A2 14 17 41 .20 11 .07 18 A12 15 .02 .00 .01 .01 .00 .00 .00 .00 .00 .00 .01 .03 .09 .02 00 .02 00 00 .00 .01 .00 .00 .00 .00 .00 00 .00 .00 .08 .08 .01 .00 .02 .00 98.62 98.71 98.98 98.53 98.74 98.92 99.16 97.83 98.69 99.23 97.81 98.88 99.38 98.08 98.35 99.80 99.19 Number of Atoms-continued 6.722 6.815 6.748 6.783 6.721 6.665 6.778 6.818 6.779 6.749 6.952 6.711 6.772 6.706 6.759 6.690 6.667 1.278 1.185 1.252 L217 1.279 1.886 12292 1.182 1221 L251 1.048 1.289 1.228 1294 1241 1310 1.333 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 217 2171 284 278 264 217 .216 154 248 254 256 309 245 817 239 248 301 3.040 2.759 3.166 2.637 2.997 2.966 2.580 2.889 2.791 3.012 3.164 3.236 2875 3.403 2.850 2.844 3.160 1.519 1.800 1.336 1.920 1.542 1.617 1.989 1.790 1.788 1.547 1.448 1.269 1.712 1123 1.716 1.746 1.365 164 164 214 170 197 200 215 167 178 187 1382 172 .168 181 195 167 174 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 1808 18190 1.728 1.710 1.778 1.797 1.764 1406 I1Bl17 1.815 L751 1.766 LB8&4 lsor i771 1.845 1.778 120 .089 107 .097 129 115 .083 112 108 .098 133 149 .081 145 100 090 126 022 .064 092 095 002 .051 .062 089 082 042 093 000 087 000 .052 055 .093 055 .028 .078 038 .091 037 .091 004 .048 045 028 .086 028 054 077 010 003 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 505 All .367 A26 A68 519 A67 529 A49 A65 347 A78 387 A98 A63 505 A47 207 195 234 208 228 .226 218 197 222 224 196 2183 222 250 .218 222 234 000 004 003 002 009 006 007 007 009 009 004 002 001 001 007 000 002 412 610 604 .636 105 151 .687 183 680 .698 547 .693 610 149 .688 127 .683 .668 611 109 587 .660 .651 571 625 612 664 693 118 .630 152 .628 624 104 tions, with the mole fraction of iron in octahedral coor- dination, or with the silica content (fig. 21). A dispersed but positive correlation exists between the Fe/(Fe+ Mg) ratio of biotite and of the rock. Despite this systematic change, however, biotite compositions cannot be used reliably to distinguish between the marginal and interior facies of the Passadumkeag River pluton (table 9). No correlation exists between the Fe/(Fe+ Mg) ratio of the biotite and the silica content of the rock. The absence of a compositional gradient of biotite and the composition of the rock distinguishes biotites of the Passadumkeag River pluton from those of the Whitney Cove pluton (tables 5, 9). The content of Fe in biotite does not show a correla- tion with the silica content of the rock (fig. 21), and thus despite the tendency for higher Fe at higher silica of the granite, biotites from the two facies cannot be properly distinguished. Higher fluorine contents may be evident in biotite from rocks with high silica in the Passadum- keag River pluton, although biotite from the core facies of the Whitney Cove pluton probably contains even higher fluorine content (tables 5, 9). The abundances of potassium (fig. 20), sodium, chlorine, phosphorous, barium, and strontium are uncorrelated with either the Fe/(Fe+Mg) ratio of the biotite or with the silica content of the rock. This obser- vation also applies to the manganese content which shows a wide and unsystematic range from core to rim facies. The distribution of AlY' in the biotite from the pluton is not correlated with the Fe/(Fe+ Mg) ratio (fig. 19); it forms, however, a band roughly correlated with the anorthite component in coexisting plagioclase from the rim facies (fig. 22). Overlap between the biotites of the two facies is a characteristic feature. Increasing Al! with higher Fe/(Fe+ Mg) ratios is the normal trend ex- pected for biotite coexisting with felsic liquid (Nockolds, 1947; Czamanske and Wones, 1973). 28 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX AMPHIBOLE 16 7 I | Passadumkeag River A A A Mn .12 |- - a A 4 % A A a & A 4 - aA A A A .08 A | __% | | A | 2.0 T T I I I A < g' 1.6 ~- l A A A 2 A aA * A AAA & $. 8 A Ay A 1.2 I | | | | T T | 'A I i y a. st ¥ 5 F 9 K z A * & A a aA & A 'A A pod 91.= A A A &' 'k A 3 | | % | | | mes T 1 | T | w A 5 A * A z . 21) A 4} 4 s a A A Ti A L # iR A 17 « A A A A 13 | | | Al | 16 I | a | Al I A A A & .68 |- - a ig B EXPLANATION A LL”, A C * AA A / &A A Core facies 12 60 |- A a A A Rim facies 3 A .52 | | | | | 64 66 68 70 72 74 76 SiO, OF THE ROCK, IN WEIGHT PERCENT FIGURE 17.-Compositions of amphibole in the Passadumkeag River pluton as a function of the SiO, content (in percent) of the rock. Note the large range in amphibole compositions at a given value of silica. Clearly defined trends from core to fim facies are absent. The most silicieous rocks (rim facies) may have amphiboles with lower titanium contents than those from the core facies. The Fe/(Fe+ Mg) ratio in the amphiboles shows quite a wide range and is not well correlated with the silica content of the rock. In general, however, some of the am- phiboles in samples from the rim facies have compositions that are somewhat higher in Fe/(Fe+ Mg) ratios than the majority of amphiboles from the core facies. THE PASSADUMKEAG RIVER PLUTON 29 - 40 T I I T | 7 Passadumkeag River & w A a. asd - < a) 30 : a - & a A F «fa / 4 A A C &' - a* A A AA y+ PS A A A a A "AA A A A sa CC 20|- C A a* EXPLANATION x 3 A A & A Core facies & A Rim facies §; SCC | | | | 15 .25 .35 AlY'(AMPHIBOLE), IONS/23 0 FicurE 18.-The anorthite content (An) of plagioclase cores ex- pressed as a function of the AlY' of amphibole in the Passadum- keag River pluton. Plagioclase in the core facies has a higher An content than plagioclase in the rim facies for a given value of AlY' in the coexisting amphibole. No compositional trend is evident for coexisting plagioclase and amphibole for the entire pluton, although samples from the rim facies suggest lower An contents of plagioclase in amphibole with higher values of AlY'. Results of biotite analyses for AlY form a wide band ranging from about 1.12 to 1.21 (atoms per 11 oxygens) (fig. 19). In contrast to the biotites from the core and rim facies in the Whitney Cove pluton, the most aluminous biotites from the rim facies of Passadumkeag River pluton are generally correlated with the most albitic plagioclase (fig. 22). Total aluminum shows no correlation with the total alkali content of biotite; total aluminum in biotite is roughly correlated positively with Fe/(Fe+Mg) ratio of the biotite and negatively with the silica content of the rock. The highest ratio of Fe/(Fe+ Mg) and the sum of AIY' and titanium occur in samples from the rim facies. However, the bulk of the pluton shows a lack of progressive variation expected from an idealized crystallization history. INTERRELATIONS BETWEEN BIOTITE, AMPHIBOLE, AND ROCK Both biotite and amphibole display similar ranges in Fe/(Fe+Mg) ratios, suggesting equilibrium partitioning during their crystallization (fig. 23). Samples that show the greatest deviations occur at the rim facies. The Fe/(Fe+ Mg) ratios of biotite and amphibole show wide scatter above the 1:1 line at values lower than 0.64. At values higher than 0.66, amphibole tends to have slight- ly higher ratios than coexisting biotite (fig. 23). In a plot of AIY' for biotite and hornblende (not shown), the most aluminous hornblende is positively correlated with biotite. This systematic change sug- gests that hornblende is enriched in AlY' at twice the rate of biotite. The variation (K,,) in in biotite and amphibole in relation to the sum of AIY' and titanium is very limited and lacks a positive correlation in the Passadumkeag River pluton. The distribution of titanium between coexisting biotite and hornblende is typical of granitic systems (Czamanske and Wones, 1973; Czamanske and others, 1977), showing a slight enrichment in favor of biotite (K,, amphibole/biotite=0.9). Also, as suggested by these authors and by Greenland and others (1968), manganese is concentrated in amphibole by a factor of about 4. PLAGIOCLASE The textural variation shown by plagioclase is signifi- cant. Plagioclase occurs forming two petrographic groups of phenocrysts, as groundmass grains, and in fine-grained clusters with mafic minerals. The composi- tion of plagioclase does not clearly relfect the modal zon- ing from the granitic rim facies toward the core (figs. 18, 22). Although plagioclase compositons of An,, occur within the inclusion-rich phenocrysts in the core facies, the average is An,, ,,. In general, plagioclase in the Passadumkeag River pluton shows large compositional variability within each facies (table 10). The only distinction is that the average compositon of plagioclase cores in the rim facies is constrained to less than An,, whereas plagioclase in the core facies is generally more calcic. In some cases, plagioclase inclu- sions within alkali feldspar are the most calcic composi- tions within a sample. Matrix plagioclase shows a range between An,, to Any,, overlapping the composition of the plagioclase phenocrysts. ALKALI FELDSPAR The composition of alkali feldspar shows insignificant variations between facies. This general compositional homogeneity probably resulted form deuteric alteration and reequilibration to compositions of Or,, ,,. Inclu- sions of all other phases are commonly enclosed within subhedral alkali feldspar, arguing for late crystallizaton of alkali feldspar. Euhedral faces are only observed when alkali feldspar shares faces with quartz. Rapakivi texture is uncommon in the Passadumkeag River pluton. In contrast with the Whitney Cove pluton, however, this texture is developed in a small number of alkali feldspar phenocrysts in most outcrops. 30 FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX TABLE 9.-Representative electron microprobe analyses and [Calculated per 11 oxygen atoms; total iron as FeO; R and Column 1 2 3 4 5 6 4 8 9 10 11 12 13 14 15 16 Sample number 3C 4C 5C 9C 13C 17€ 20C T5C 78C 79C 82C 84C 91C 105C 210 25C Weight percent S10, --------- 36.39 36.87 35.21 36.88 36.87 36.03 36.11 36.14 35.66 36.55 36.83 35.96 36.21 36.65 37.12 35.92 TiO, --------- 407 4.28 9.56 2.98 3.71 8.91 3.72 4.08 401 3.08 8.30 4.00 3.22 3.65 2.04 4.50 Al,O, -------- 18.57 14.00 13.47 14.42 13.43 13.14 14.00 13.86 13.03 14.13 13.82 13.72 13.89 13.45 14.29 13.49 FeQ --------- 24.77 25.14 23.98 23.04 23.33 23.13 24.80 24.65 23.69 26.82 23.66 25.76 26.59 22.76 26.35 26.68 MnO -------- A8 AT 54 AT 51 A8 51 A8 A2 A9 A9 A8 .36 Al .65 38 MgO -------- 767 - TBQ BB8 - 927 S814 1.46 760 670 C6.70 8.65 7.41 6745 940 7.22 5.10 CaO --------- .04 .00 .05 00 .06 04 .00 .08 .00 .00 .06 .00 00 .00 00 00 Na,0 -------- .08 00 .08 .00 12 .09 .00 14 00 .00 .08 .00 00 .00 .00 00 K,0 --------- 9.20 9.48 8.88 9.32 9.40 9.81 8.96 9.64 11.12 9.76 9.47 9.33 9.41 9.83 9.36 9.48 BaO --------- 18 15 .09 .18 .05 .09 .10 00 .08 14 .04 .07 .07 15 .08 .06 P,0, --------- Kul .00 .01 .00 00 .01 00 00 00 00 .01 .00 .00 00 00 .00 SrO --------- .02 .00 .08 00 00 .01 .00 .00 .00 _ nd .02 .00 .00 .00 .00 00 F -_---------- A6 .65 .82 .62 .86 .91 .63 .00 .89 12 18 49 A7 B7 1.09 .62 Cl ----------- .08 12 .06 18 58 .06 .06 .00 .07 .05 .07 .06 Al .06 82 .35 Total 96.97 99.00 95.11 97.76 97.79 96.40 96.65 96.67 95.76 98.53 97.32 97.23 97.68 97.27 99.42 97.22 Number of atoms Si ----------- 281 2740 277 280 281 2%0 280 281. 282 281 282 R70 260 ~2B0 261 280 Ti ----------- .24 .24 .21 19 21 .28 22 24 .24 18 .20 .23 19 .21 17 27 Al <---------- 1.24 1.25 120 1.21 120 i228 127 i121 128 125 1% 127 121 12%8 {1.24 Fe ----------- 1.60 1.50 1.585 146 1490 1.50 - 161 160 156° 142 lbl 1.67 172-146 L067 1.74 Mn ---------- .08 08 .04 .03 .08 .08 .08 .03 .08 .08 03 .08 .02 .08 04 .02 Mg ---------- .88 .89 .98 1.05 1.01 1.01 .90 .88 .80 18 .99 .86 18 1.08 .81 .66 Ca ---------- 00 00 .00 .00 .01 .00 00 .01 .00 00 .01 .00 .00 .00 00 .00 Na ---------- Kol .00 .01 00 .02 .01 .00 .02 .00 .00 .01 .00 .00 00 00 .00 K ----------- .91 .92 .89 90 .91 97 .89 .96 - 1.12 .96 92 92 .98 .96 90 94 Ba ---------- .00 .01 00 .01 .00 .00 .00 .00 .00 ud 00 .00 .00 .01 .00 .00 P ----------- 00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 00 .00 00 .00 Sr ----------- 00 00 .00 .00 .00 .00 00 .00 00 00 00 00 .00 00 .00 .00 F ----------- A11 16 .20 15 21 .22 15 00 .22 18 18 12 19 .21 .26 15 Cl ----------- .01 .02 .01 .02 .07 Kul .01 .00 .01 .01 Kul .01 .01 .01 04 .05 Fe/(Fe+ Mg) --- .65 64 .62 58 .60 .60 64 .65 .66 .69 .60 .66 .69 57 67 18 Granophyre is evident in samples close to the granite- country rock contact. These samples are commonly associated with other textures which include myrme- kitic intergrowths, with development of mortar or granulated texture, and with deeply embayed and cor- roded rims of biotite and opaques. QUARTZ Quartz is concentrated in the matrix, especially within the felsic clusters. Subhedral to anhedral grains, typically showing undulatory extinction and sutured borders are characteristic of this pluton. The absence of euhedral faces of quartz in contact with all other phases except alkali feldspars indicates that quartz is one of the latest phases to precipitate. SEQUENCE OF CRYSTALLIZATION Petrographic observations support the following se- quence of crystallization: zircon plus apatite; oxides, sulfides, and clinopyroxene(?); and allanite plus sphene. Hornblende, biotite, and plagioclase crystallized next, followed by quartz plus alkali feldspar (fig. 24). SUMMARY OF THE BULK CHEMISTRY The Passadumkeag River pluton is mineralogically and texturally zoned from rim to core facies, and this zoning is also shown in its bulk chemical composition (Ayuso and others, 19822) (fig. 25). Some of the most im- portant bulk chemical results are as follows: (1) The core facies is higher in CaO, MgO, Fe,0,, TiO,, P,0, and THE PASSADUMKEAG RIVER PLUTON structrual formulae of biotite from the Passadumkeag River pluton C represent rim and core facies, respectively; nd, not determined] 31 18 31C 19 34C 20 36C 21 730 22 1100 23 112C 24 113C 25 2R 27 10R 28 14R 26 BR Weight percent-continued 36.51 36.09 34.60 36.36 36.52 35.66 36.24 36.97 36.73 36.71 36.64 36.26 36.46 36.21 35.65 36.51 36.66 36.57 4.04 3.39 4.17 4.09 3.48 3.90 4.09 3.82 3.09 _ 3.02 3.46 3.55 3.55 3.03 3.16 3.44 8.37 3.28 13.54 18.84 1287 18.58 14.34 13.63 18.37 12.52 14.68 13.90 18.41 14.31 13.74 13.56 12.92 14.16 14.10 14.66 23.09 24.12 21.72 25.28 25.88 25.02 25.54 22.99 27.50 23.42 23.76 28.02 26.00 26.39 24.03 22.92 26.090 28.57 34 A2 A8 .50 A4 .51 AT A4 .85 A5 A8 11 AO .59 A9 .60 55 1.06 9.09 5.32 7.18 7.87 7.20 7.44 7.31 8.83 5.39 8.86 8.17 4.37 7.87 6.43 8.39 8.38 7.55 4.03 .02 00 .06 .07 00 .07 18 .28 .00 .08 .09 .00 00 .07 .07 .05 .00 00 .00 .00 12 .08 00 15 .09 .08 00 12 .08 00 .00 .05 A11 .06 .00 .00 9.44 _ 9.45 9.00 9.60 10.03 9.29 - 9.17 9.55 9.62 9.79 9.170 9.44 9.34 9.26 9.85 8.87 9.57 8.85 .09 .08 18 19 16 21 15 18 .08 18 A7 10 .07 .09 04 08 15 .06 .00 .00 .00 .00 00 .00 .00 .00 00 .00 .00 .00 .00 .01 .01 .01 .00 .01 00 .00 .00 00 .00 .00 .00 .00 .00 _ nd nd 00 .00 .00 .04 .05 .00 .00 67 55 15 A4 T4 57 .62 .81 92 nd 87 .85 .60 A0 94 .98 53 91 .09 .06 .08 13 .07 18 .08 .08 04 11 .08 .07 .10 .05 .05 .07 .06 .10 96.92 96.32 91.16 97.64 98.86 96.58 97.26 97.50 98.90 96.64 96.86 97.68 98.13 96.17 96.35 96.13 98.63 98.10 Number of atoms-continued 2.80 _ 2.80 2.83 2.81 2.19 2.18 2.81 2.82 2.82 2.84 2.83 2.83 2.80 2.85 2.18 2.81 2.80 2.83 28 .20 .26 .24 .20 .28 .24 .22 18 18 .20 .21 .20 18 .22 .20 .19 19 1.22 1.27 1.24 1.23 1.29 1.25 1.22 1.22 1.33 1.27 1.22 1.31 1.24 1.26 1.19 1.30 1.29 1.34 1.48 1.57 1.48 1.63 1.65 1.63 1.65 1.47 1.176 1.51 1.53 1.83 1.67 1.74 1.57 1.48 1.67 1.85 .02 03 .08 .03 08 .08 .08 .08 .06 08 .08 .05 08 .04 .03 .04 .04 .07 1.04 .96 87 .85 .82 .87 .84 1.00 .62 1.02 .94 51 90 15 .98 .96 .86 AT .00 .00 .01 .06 00 .01 .01 .02 00 .01 .01 .00 .01 .01 .00 .00 .00 .00 00 00 .02 .01 .00 .02 .01 .01 00 .02 .O1 .00 .01 .02 .01 00 .00 .00 .92 .94 94 95 .98 .93 .91 .93 .94 .97 .96 .94 .91 93 .98 .87 .98 87 .00 00 .01 .01 .01 .01 .01 .01 00 .01 .01 00 .00 .00 .00 .00 00 .00 .00 .00 .00 .00 .00 00 .00 .00 00 00 .00 .00 .00 00 .00 .00 .00 00 .00 .00 .00 .00 .00 .00 00 00 .00 .00 _ nd nd 00 .00 00 00 .00 00 16 14 .19 11 18 14 15 .20 22 nd .21 .21 15 .10 .28 .24 18 .22 .01 .01 .01 .02 .01 .02 .01 .01 .01 .01 .01 Kul .01 Kul .O1 .01 .01 .01 59 .62 .63 .66 67 .65 .66 .60 14 .60 .62 18 .65 10 .62 .61 .66 .80 Al;O;; (2) silica increases in a regular gradient from 65 percent in the core to 77 percent in the rim; and (3) the total alkali element content shows no significant enrich- ment in the more felsic rocks (table 11; fig. 25). Normative composition of this pluton shows that it is slightly corundum normative (less than 2 percent) and that it exhibits higher normative anorthite in the core facies. As in the Whitney Cove pluton, normative com- positions are not directly correlated with the abundance of silica. Preliminary analyses of the same suite of trace elements analyzed in the Whitney Cove pluton confirm the reverse zonation in the Passadumkeag River pluton. Higher zirconium, yttrium, and strontium abundances are characteristic of most of the interior rocks of the Passadumkeag River pluton; niobium shows little varia- tion in abundance from rim to core. More mafic granitic rocks tend to have higher barium than the more felsic rocks. With increasing silica, the variation of rubidium in the core and rim facies of the Passadumkeag River pluton suggests that each facies follows a slightly dif- ferent trend. The Passadumkeag River pluton has lower contents of strontium at a given silica value than the Whitney Cove pluton. The compositional diversity and field relations deter- mined from representative analyses of wall-rock xeno- liths argue for a minimum degree of interaction with the granitic melt. Control of the mafic xenoliths on the evolution of the granitic melt is uncertain, however, partly because of the petrographic diversity evident even within single outcrops. This diversity is indicated in the spread of compositions of the mafic xenoliths, as they are only broadly correlated to the trend defined by the granites. 82 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN TH « BOTTLE LAKE COMPLEX BIOTITE .046 | I I I | 3 *~ 4 I I I Passadumkeag River gt A A A .038|- s a A A Mn A a rs _ A * *' a .030 [- A A & ' z 78 a A A _ A A A A A g A | | | | | | | | 1 | | ars) .022 A A 27 I I I I I I I I I I I I I A A .25- -I 4 A a A A A A A wal" A A s A g A AA A Ti * A 21 m - waa A -I i A g A A A L A. & & i A u ( R yf 19 Kx [@] A A - a7 | | | | | | | | A* | | | CC wi I I I 3 I I I I I I | I I I , 14|- A A - ps3 A O a A A A *~ % = Z, A A. A. A +4 vi A Al A A A 'A § & A o6|- &A A * aA A # _ 4 A A A A A A 02 1 1 I oye 1 I & 1 | | | | T I I sars | y. Gs - I | T I 1.20|- A A gg A (> At a % A < A A A 1.18|- &A & i a A A ZI A # * A t a e Iv Al & 1.16- A A -] A A [7 A. A a A =I 114 _ __ EXPLANATION a f A A A Core facies a FZ A Rim facies ags 1 | | | | | | 2. _ 1 | | .58 .60 .62 .64 .66 .68 10 Fe/(Fe+ Mg) FIGURE 19.-Compositions of biotite in the Passadumkeag River pluton as a function of Fe/(Fe+ Mg). Note that biotite from the core and rim facies has similar contents of titanium. Biotite from the rim facies has a wide range in Fe/(Fe+ Mg) ratios. See table 9 for specific man- ganese, titanium, and Fe/(Fe+ Mg) values. THE PASSADUMKEAG RIVER PLUTON 33 BIOTITE 99 T T I T | I p" I "k Passadumkeag River .97 |- ka A 6 a S A -> .95 A A A a A A A K 93!- A A {2 A & / 91 |- &A A £2 a A .89 |- A 3 A .87 | | | | | | | | | | | | 27 I I I I fs I I I I I I I w e A cl { § X A O - * A A A T A - tC A 4 Ti s A a E 21(- P4 A A) S * A < A A 19 (- A -l pS A a7 | | | | | | | '% | | | s 1.9 I | | I | | | I I | | T Al 1.8 |- tal A A k a 1:71- fud # 'a A Fe i 16 A A A & A Jak & 94 A EXPLANATION A A A& Core facies 1.5 |- k A a A Rim facies _ c A A 1.4 | | | | | | | | | 65 67 69 71 73 75 77 SiO, OF THE ROCK, IN WEIGHT PERCENT FiGuRrE 20.-Compositions of biotite composition as a function of the SiO, content of the rock in the Passadumkeag River pluton. Note the general correlation between titanium and the silica content of the rock in samples from the core and rim facies. Potassium and iron show no clear correlation with the silica content of the rock. FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THT. BOTTLE LAKE COMPLEX BIOTITE 2.91 T T T I T T. T T T A Passadumkeag 4 River 2.89 |- ht * A 2.87 |- i 2 A A % (oct) £ aA A A A A A _ A A A A 2.85 A 2 *% - s A A A 2.83 A fl EXPLANATION 7 A A A Core facies 281!- A Rim facies C2 277- 223 | | | | | | | | | k- | "~ I I I I I I I I I | A <2 .59 [- - L L_ A A A Pes O o A S7 Ce O L* r: sae A A A an fra A A A H Fs 85m **" w 3 ek a A A g A A A, A C 53[-- a Ln = |-. iA A a 51 A = A a a A -I [=. A y* a .49 | | t &_" 1 e / | | | | | T T T T | I | I I 287- Fat \& A A A A. sa A 2.85 |- # A a] A A A g A Si s A val A & jue A &A A 2 A A - A A A A A p4 - A A A A 281!- a4 sel .> A & ] A A 2.179 | | | | | | | | 16 18 .20 .22 24 .26 .28 Ti, ATOMS PER 11 OXYGENS FIGURE 21.-Compositions of biotite in the Passadumkeag River pluton as a function of titanium content. Values are normalized to 11 oxygens. Note the lack of correlation between the total octahedral content, Fe/3, and silicon with the titanium content of biotite. See table 9 for specific titanium and silicon values. THE PASSADUMKEAG RIVER PLUTON 35 ( 40 | | | *T - Passadumkeag River - LL ( A t A "j 30 A S o A A A e- a AA a . a1 , aA, Aa aA r 4 {n i A A 2 ig A A AAA A cC A A AM 2 6 20 |- A 0 h : w EXPLANATION & A rg A Core facies aA < A Rim facies A 10 | I | g ql _ 0 .05 10 15 .216 Al V! (BIOTITE), IONS/11 O FicurE 22.-The anorthite content (An) of plagioclase cores ex- pressed as a function of the AlY' content of biotite in the Passa- dumkeag River pluton. Higher anorthite in plagioclase generally occurs in the core rather than in the rim facies at a given value of AlY' in biotite. No general trend is evident for the pluton as a whole. Lower An in plagioclase from the rim facies is broadly cor- related with higher contents of AlY"' in biotite. BIOTITE -AMPHIBOLE I I I Passadumkeag River 76- ~ A T2 z {> i A i- A o a A " .68 |- - on A = * Aa aA + A C. © 4.64 |- a 4. A S 12 A A /*A A A 60 ay x EXPLANATION] A A Core facies A A Rim facies .56 A _| | | | | 60 .64 .68 12 16 Fe/(Fe+ Mg) AMPHIBOLE FicurE 23.-Change in the Fe/(Fet+Mg) ratios of biotite coexisting with amphibole in the Passadumkeag River pluton. For compari- son, the 1:1 line is also shown. Note that the compositions scatter about the 1:1 line and that both biotite and amphibole have sim- ilar ranges in Fe/(Fe+ Mg). Passadumkeag River Sulfides | --- Zircon | -- --- | rw m h se oo t he NN i hee hoe mone ome hors ome fm hae Soe muse Oxides Allanite Sphene Biotite] - -- Hornblende - Pyroxene Plagioclase --- Quartz Alkali feldspar Liquid Rock FiGurE 24.-The generalized order of crystallization in the Passa- dumkeag River pluton. Plagioclase, quartz, and alkali feldspar crystallized after biotite, hornblende, and the accessory suite. Regular compositional variation in the Passadum- keag River pluton supports the contention that the core and rim facies are directly related. With the exception of the K,0 abundance, straight linear variations from the margins to the interiors are the norm. Overlap in bulk composition between the core and rim facies also sup- ports a comagmatic origin for the entire pluton in the same manner evident in the Whitney Cove pluton. Granitic rocks and their mafic xenolith hosts are strikingly different in bulk composition. Linear varia- tions shown by the granite hosts contrast with the dispersed spread of the xenoliths and argue that although a certain degree of reaction must have taken place, the granite magma and xenoliths did not re- equilibrate fully. Lower silica and a more mafic bulk composition is characteristic of the mafic xenoliths, although they also exhibit irregular variations in Al;O,, MgO, CaO, K,0, and P;,0, (fig. 25). The regression line obtained through the composition of the granitic rocks passes through the field defined by the mafic xenoliths. Given the dispersion of the bulk composition of the mafic xenoliths, it is difficult to relate them to the host rocks. Crystallization of about 25 percent of the liquid with removal of 17 percent plagioclase, 8 percent biotite (and amphibole), and 0.5 percent apatite (and zircon) may ac- count for the major and trace element variation from representative rocks from the core to rim facies. Results indicated, however, that the mafic xenoliths were not related to the host granites by any reasonable fractiona- tion mechanism. Thus, they cannot represent autoliths, and more logically the xenoliths may be thought of as unrelated and accidental blocks obtained at depth by 36 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX TABLE 10.-Representative electron microprobe analyses and [Calculated per eight oxygen atoms; total iron as FeO; R and C Column 1 2 3 4 5 6 v 8 . 9 10 11 Sample number 3C 4C 5C 9C 13C 17€ 200 210 220 240 250 Weight percent SIO, 64.17 63.03 - 64.67 63.05 62.28 - 65.02 56.30 61.87 63.65 63.81 64.24 TiOp <--------------------- .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 AlOg ---------------------- 29.59 S238 - saas - g4als6 - gai? 2800 28.50 22.70 2281 | 22.6 FAO -_ erea A11 18 A2 14 14 .10 15 18 12 18 10 MRO 2 =- neuen cet .01 .01 .01 .01 .02 .01 .00 .O1 .01 .01 .02 MgO .01 .02 .00 .01 .01 .00 .03 .01 .O1 .02 .01 Ca er erea asc oes a se meals 4.49 4.48 3.53 5.20 5.42 3.32 9.86 5.59 4.27 4.42 3.93 Nag 8.57 8.47 9.29 8.33 8.26 9.32 5.85 8.18 9.01 8.172 9.14 KQ -in _ _ ou oan nl .20 44 18 .31 .24 15 15 .20 22 30 24 SN nd nd nd nd nd nd 14 nd nd nd nd Total 100.44 100.11 100.13 100.43 100.93 100.09 100.48 99.63 99.99 100.22 100.44 Number of atoms S1 seres o hoe ne ma e ue mie ress as nie in ore 2.82 2.18 2.85 2.18 2.74 2.86 2.52 2.15 2.81 2.81 2.82 MNJ nene une on ce an nme rie o m m e Hn ha a mine .00 .00 .00 .00 .00 .00 .00 .00 .00 00 00 SAY e ae en em oon hese ice pm cain eme ae 1.18 1.23 1.16 1.22 1.27 1.15 1.48 1.24 1.18 1.19 1.18 Fp == os tems tn me de t Ie ae inon soe .00 .01 .01 .01 .01 .00 .01 .01 .00 .01 02 MA =s eee aan sens one nae .00 .00 .00 .00 .00 .00 .00 .00 00 00 00 Mg ----------------_-_____-- .00 .00 .00 .00 .00 .00 .00 .00 .00 00 00 Ca eee ee inne aan oem .21 .21 37 .25 .26 .16 AT 27 .20 .21 11 NA 22m :s re re d a ad ute inns me mo ae ie oa aa inm 73 13 19 T1 10 19 B1 T1 TT 15 18 Ree a enn onn inane .01 .03 .01 .02 .01 .01 .O1 .O1 .01 .02 01 SP e r dee o aie sii a has mour me meas re mere ce nd nd nd nd nd nd .00 nd nd nd nd Feldspar components, mol percent AM -- e 22 22 17 25 26 16 48 27 21 22 18 AT ee ee a aid a scn o cs arie mice meee aan 77 75 82 73 72 83 51 72 78 T7 81 ' i 1 3 1 2 1 1 1 1 1 2 1 TABLE 10.-Representative electron microprobe analyses and structrual Column 26 27 28 29 30 31 32 33 34 35 Sample number 89C 910 105C 110€ 111C 1120 113C 1150 8R 10R Weight percent SiO, 63.45 62.64 64.24 63.40 62.14 63.20 63.45 62.94 65.30 62.74 TiO, .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 Al;O; 23.05 23.44 22.80 22.96 23.69 28.23 22.15 23.26 21.91 24.15 FeO 14 "H 15 13 37 15 15 18 14 14 MnO .02 .01 .00 .01 .03 .01 .02 .01 .01 .00 MgO .01 .00 .01 .01 .00 .01 .01 .02 .01 .00 CaO 4.20 4.85 4. A1 4.06 5.23 4.13 4.32 4.57 8.17 5.94 Na,0 9.01 8.13 8.174 8.172 8.32 8.61 8.80 8.15 9.22 6.34 K,0 20 .28 .34 .37 .21 .30 .33 22 .38 37 Sro nd nd nd nd nd nd nd nd nd .00 Total 100.09 100.06 100.69 99.66 99.79 100.24 99.83 99.95 100.14 100.28 Number of atoms Si 2.80 2.17 2.82 2.81 2.16 2.19 2.81 2.19 2.87 2.16 Ti .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 Al 1.20 1.22 1.18 1.20 1.24 1.21 1.19 121 1.14 1.28 Fe .00 .00 .01 .01 .01 .01 .01 .01 .01 .01 Mn .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 Mg .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 Ca .20 23 .21 .19 .25 22 "al 22 15 .28 Na 44 15 T4 15 A2 T4 16 A5 19 54 K .01 .02 .02 .02 .01 .02 .02 .01 .02 .02 Sr nd nd nd nd nd nd nd nd nd nd Feldspar components, mol percent An 20 23 21 20 26 23 21 22 16 33 Ab 78 75 77 78 73 75 74 77 82 64 Or 1 2 2 2 1 2 2 1 2 2 structrual formulae of plagioclase in the Passadumkeag River pluton represent rim and core facies, respectively; nd, not determined] THE PASSADUMKEAG RIVER PLUTON 37 12 13 14 15 16 17 18 19 20 26C 28C 290 310 34C 36C 730 150 78C 790 81C 82C 84C 86C Weight percent-continued 62.98 63.15 61.40 63.81 62.43 65.09 62.40 63.90 64.57 63.19 62.10 62.85 63.37 62.89 00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 00 .00 23.04 23.20 23.80 23.24 23.26 21.66 23.40 22.77 22. 41 23.17 23.74 23.69 23.59 28.172 A1 15 47 A2 .08 18 13 .07 15 14 .16 .25 16 A7 .01 .O1 .00 .01 .00 .01 .01 .00 .83 .01 .02 .01 .02 .01 00 .01 .01 .02 .04 .01 .02 .02 .04 .01 .01 .03 .03 .02 4.07 4.37 5.18 4.34 4.87 8.17 4.66 3.94 2.93 4.48 5.21 4.94 4.48 5.22 9.25 8.81 8.01 8.83 8.95 9.44 8.74 9.20 9.14 9.03 8.62 8.48 8.94 8.48 18 .26 A4 21 .06 .21 .24 318 .19 .26 28 .30 32 Al nd nd nd nd .00 nd nd 12 nd nd nd nd nd nd 99.64 99.96 99.56 100.59 99.69 99.72 99.60 100.15 100.26 100.30 100.09 100.55 100.91 100.87 Number of atoms-continued 2.80 2.19 2.74 2.80 2.77 2.87 2.77 2.82 2.84 2.19 2.15 217 2.18 2 TT .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1.21 1.21 1.25 1.20 1.22 1.13 1.23 1.18 1.16 1.21 1.24 1.23 1.22 1.28 .00 .01 .01 .01 .00 .01 .01 .00 .01 .00 .01 .01 .01 .O1 .00 .00 .00 00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 00 .00 .00 .00 19 .21 .28 .21 .28 15 22 .19 18 .21 25 .23 "21 25 .80 16 .69 15 A7 .81 I5 19 18 T7 74 12 16 12 .01 .02 .03 .01 .00 .01 .01 .01 .O1 .02 .01 .02 .02 .02 nd nd nd nd .00 nd nd .00 nd nd nd nd nd nd Feldspar components, mol percent-continued 19 21 28 21 23 16 22 19 18 21 25 24 21 25 80 T7 70 78 T7 83 76 80 81 T7 74 74 27 73 1 2 8 1 0 1 1 1 1 2 1 2 2 2 formulae of plagioclase in the Passadumkeag River pluton -Continued 36 37 38 39 40 41 42 43 44 45 46 47 48 49 12R 14R 23R 27R 35R T4R T6R TTR SOR 88R 90R 109R 114R 117R Weight percent-continued 64.69 65.19 64.10 64.63 64.68 65.23 63.84 62.51 64.48 61.77 65.53 62.01 62.79 62.64 .00 .00 .00 .00 00 .00 .00 .00 .00 .00 00 .00 .00 .00 22.18 22.25 22.45 22.29 21.88 21.89 22.53 23.36 21.83 23.96 21.68 23.86 23.21 23.05 14 12 A18 A1 A2 15 15 13 12 .10 .10 AT 15 13 .01 .00 .02 .01 .00 .01 .01 .00 .00 .00 .01 .01 .01 .00 .01 .01 .01 .01 .01 .01 .01 .01 .00 .00 .01 .01 .01 .02 3.63 2.95 4.01 3.39 2.95 2.80 4.27 4.82 3.07 5.40 3.03 5.69 4.48 4.96 9.18 9.84 8.87 9.52 9.46 9.74 8.55 8.175 8.85 8.28 9.60 8.09 8.81 8.60 .26 .35 25 21 p 21 .32 .35 1.61 18 .31 .36 40 .26 nd nd nd nd nd nd nd nd nd .03 nd nd nd nd 100.10 - 100.71 99.84 100.23 99.82 100.04 99.68 99.93 99.98 99.74 100.27 100.20 99.86 99.66 Number of atoms-continued 2.85 2.85 2.83 2.84 2.86 2.87 2.83 217 2.86 2.15 2.88 2.15 2.19 2.178 .00 .00 .00 .00 .00 .00 .00 .00 .00 00 .00 .00 .00 .00 1.15 1.15 1.17 1.16 1.14 1.14 1.18 1.22 1.14 1.26 1.12 1.25 1.21 1.21 .01 .01 .01 .00 .00 .01 .01 .01 .00 .00 .00 .01 .01 .01 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 A7 14 19 .16 14 A8 .20 28 15 .26 14 721. 721 .24 18 .84 16 .81 .81 .83 13 15 16 T1 .82 10 16 14 .02 .02 .01 .02 .04 .01 .02 .02 .09 .01 .02 .02 .02 .02 nd nd nd nd nd nd nd nd nd .00 nd nd -- -- Feldspar components, mol percent-continued 18 14 20 16 14 14 21 23 15 26 15 28 22 24 81 84 79 82 82 85 77 75 76 73 84 70 76 75 2 2 2 2 4 E 2 2 9 J 2 2 2 2 38 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX Passadumkeag River Na20 I K,0 20 - wd OXIDES, IN WEIGHT PERCENT TiO; to o | | 1:01 P;0s | | 6 65 SiO,, IN WEIGHT PERCENT EXPLANATION a Core facies 8 Rim facies o Mafic xenoliths x Aplites FIGURE 25.-Variation diagrams in the Passadumkeag River pluton showing the core and rim facies. The composition of the mafic xenoliths and aplites are also plotted. Most of the oxides are highly correlated with the silica content of the rock. Note the absence of major compo sitional gaps, and especially the more siliceous nature of the rim facies. Samples from the rim facies are lower in Al;O,, Fe;,0,, MgO, TiO,, P,0, and CaO than the core facies. This compositional zoning of rocks from a single pluton is opposite to the arrangement occurring in con- centric and normally zoned plutons. Note the large fields defined by the composition of the mafic xenoliths, extending toward less silicieous compositions than the host granites. The generalized compositional field for the Mount Givens granodiorite (Bateman and Nokleberg, 1978) THE PASSADUMKEAG RIVER PLUTON Passadumkeag River 16|- Al2Os a 171 14 [|- 12 |- 8 a _- L-- 1 ] st - 124 41.42.14 _ L.. 1.1.1.1 - {_ LLL __ a h 12|- S 10 - As Fe203 co I | OXIDES, IN WEIGHT PERCENT I MgO t CaO 47 50 55 60 65 70 75 SiO,, IN WEIGHT PERCENT showing the core and rim portions of a typical normally zoned pluton is illustrated for contrast with the reversely zoned Passadumkeag River pluton. 39 40 FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX TABLE 11.-Representative major and trace element analyses and norm compositions of the Passadumkeag River pluton [R and C refer to rim and core facies, respectively; total iron as Fe,0;; LO1, loss on ignition] Column 1 2 3 4 5 6 1 8 9 10 11 12 Sample number 2R 6R 8R 10R 14R 15R 27TR 130 16C 170 200 210 Weight percent SIO, --------<-------------- T025 1070 608 T600 7259 G982 6§62 G827 C78! 7212 TiO, <--------------------- .19 Al .58 44 .16 14 .36 Al 52 .50 .67 .33 AlyO4 <--------------------- 13156 1404 19.66 l453 l21% list 18.56 1469 1489 1546 1481 13.70 Fe,O, ---------------------- 1.72 2.81 3.59 2.18 1.50 1.39 2.32 2.65 3.61 3.21 4.66 2.57 MnQ . .06 .05 .06 .03 .03 .03 .03 .05 .06 .06 11 .05 MgO 15 A6 .89 .67 .06 11 .38 .62 13 .10 87 .36 CHO .81 1.55 2.95 1.87 54 .69 1.17 1.175 2.02 2.10 247 1.28 N@,O ---------------------- 3.52 3.41 3.36 3.19 3.30 3.35 3.24 3.35 3.55 3.30 3.31 3.09 K,O --------------_-_____--- 4.80 4.173 3.98 4.77 5.13 5.18 5.22 5.40 4.16 5.53 4.03 5.27 P40, ---------------------- .04 .09 16 I1 .02 .01 .08 .10 14 AJ 18 .08 LOI ---------______________ Al .31 A7 A5 44 .33 33 A7 .56 .38 1.15 27 Total 100.02 99.58 99.35 99.63 100.28 100.04 99.28 99.31 99.36 99.64 100.07 99.12 Norm @ -z: 84.47 30.16 30.64 25.097 36.86 35.06 31.14 25.45 24.79 2282 27.03 31.20 ( eee ele ra er 19 T1 13 .03 .20 A6 .65 40 .56 54 94 18 -is 28.96 28.07 28.81. 28.26. 30.28 830.060 31.07 32.18 28.61 s2.80 28.80 31.492 AD er - 290.78 - 28.98 \ 27.16 31.98) 2785 28.934 2762 2854 30.28 2803 27.00 26.98 AME Piece cedc ~~ wann 3.16 7A9 10.156 8.58 2.54 3.36 5.32 8.08 9.17 9.60 - 11.07 5.88 EN :e .37 1.15 2.24 1.67 15 271 .92 1.56 1.83 1.175 2.17 .91 Him : 1.72 2.82 3.64 2.19 1.50 1.39 2.934 2.67 3.63 3.22 4.66 2.59 I ei- aos 13 A1 13 .06 .06 .06 .07 11 13 13 24 A1 M erin .00 .00 .00 .00 .00 .00 .00 .00 .00 00 00 00 RU re- 12 .36 .52 Al 13 A1 .33 .36 A6 EB 55 28 Ap esos .10 .21 .38 .26 .05 .02 .19 .24 38 31 EB 19 Trace elements in ppm RD ncs 266 129 132 137 229 170 178 170 184 152 151 230 SL 52 150 192 163 34 46 126 178 181 218 208 146 NY Ar Pee rac 26 36 34 33 32 20 24 33 44 31 44 35 l enas esen ae 160 426 541 509 62 90 524 594 497 897 477 309 eae eac amas 159 264 296 231 157 126 182 248 300 277 313 196 ND nck 27 19 22 17 18 19 13 18 24 18 23 17 the granite magmas. As in the case of the Whitney Cove pluton, fractional crystallization cannot fully explain the reverse zoning in the Passadumkeag River pluton. Furthermore, the wide range in petrographic features and the dispersal in modal and bulk chemical abun- dances are difficult to explain simply by fractionation. XENOLITHS IN THE BOTTLE LAKE COMPLEX The two plutons of the Bottle Lake Complex, the Whitney Cove and the Passadumkeag River plutons, are geographically closely associated, but each encloses different abundances and kinds of xenoliths (Ayuso, 1979). Two xenolith types are recognized in the Bottle Lake Complex: metasedimentary and mafic. METASEDIMENTARY XENOLITHS Metasedimentary inclusions are concentrated near the granite-country rock contact and are of limited im- portance in affecting the evolution of the Bottle Lake Complex. The size and abundance of these xenoliths decreases toward the interior of the granites. Also, they retain characteristic bedding styles, structural and petrographic features that match protoliths in the coun- try rock. MAFIC XENOLITHS Mafic xenoliths exhibit significant petrographic diversity among themselves as evidenced by their vari- able grain size, maximum dimension, abundance of XENOLITHS IN THE BOTTLE LAKE COMPLEX feldspar megacrysts, and wide range of biotite-to- amphibole ratios (Ayuso and Wones, 1980). The most abundant mafic xenoliths are porphyritic quartz-diorite rocks, fine to medium grained with prominent feldspar megacrysts. They are randomly distributed throughout the core facies of both granites but are especially abun- dant in the Passadumkeag River pluton. Mineralogic and size variability characterizes the xenoliths, as they range from mafic- to felsic-rich and from a few centi- meters to 1 m in length. Preliminary studies of the mineral chemistry in the mafic xenoliths show that the compositions of the mafic minerals are distinguishable from those in the host granite. This distinction is especially evident in biotite and to a lesser degree in amphibole. In contrast, the composition of plagioclase in the mafic xenoliths ex- hibits similar ranges (An,, to An,,) as those documented in the Passadumkeag River pluton. Biotite in the mafic xenoliths is generally higher in aluminum but lower in titanium and alkalies(?) com- pared to biotite in the host rocks. Both groups of biotite, however, show similar Fe/(Fe+Mg) ratios (0.50-0.70). Amphibole mimics the compositional change in biotite and shows progressively higher titanium, iron, and alkalies but lower magnesium in am- phibole of the granite coexisting with the xenolith. The compositions of mafic and country rock xenoliths are plotted on the granite variation diagrams (figs. 12 and 25) for comparative purposes. Although wall-rock xenoliths may exert control over the chemistry of a pluton, small-scale assimilation of such xenoliths by granitic liquids of the Bottle Lake Complex resulted primarily in dilution of the granitic components. This dilution is suggested by the broadly calc-alkaline nature of the Bottle Lake Complex compared to the strongly silicic and peraluminous compositions of most country rocks. Also, the variation from more mafic to felsic rocks in the plutons follows a well-defined trend despite the wide range of lithologies representative of the coun- try rocks. Finally, country rocks are significantly higher in 8°O (12.0-13.4 permil) compared to the granites (8.3-9.9 permil) and mafic xenoliths (6.8-9.0 percent) (A. Andrew, 1982, written commun.) arguing against major interaction between these rock types. COMPARISON OF GRANITES IN THE BOTTLE LAKE COMPLEX Because of the scatter in the abundance of the alkali elements, the calc-alkali indices for the Bottle Lake plutons are roughly constrained to between 53 and 57. The range is lower than expected for calc-alkaline suites 41 (60-64). Plotted on an AFM (A=Na,0+K,0; F=FeQ; M=MgO) diagram, the composition of the plutons defines a band trending away from the FeO-MgO side- line toward the alkalies (fig. 26). This trend suggests a broadly calc-alkaline trend. Wall-rock xenoliths are distinct from this trend, while mafic xenoliths are generally alined in agreement with the plutons and plot more closely to the FeOQ-MgO sideline. The composite nature of the Bottle Lake Complex, the circular or elliptical shape of the plutons, the develop- ment of an aureole by contact metamorphism, the range in the lithological variety of granitic rocks, and the pres- ence of mafic-rich inclusions in the Bottle Lake Complex are in agreement with the field relations outlined by Chappell and White (1974) characteristic of I-type granites. On the basis of petrographic observations, it is also reasonable to classify the plutons as belonging to the magnetite-series of Ishihara (1977). FELSIC DIKES Aplites are relatively uncommon in the Bottle Lake Complex. However, one of the differences between the two plutons is that the Whitney Cove pluton is com- paratively richer in felsic dikes (aplites, pegmatites, granophyres) than the Passadumkeag River pluton. Ad- ditionally, a few small miarolitic cavities (1-3 mm) are concentrated in the Whitney Cove pluton, west of Pug Lake (V) in the Scraggly Lake quadrangle, but appear to be absent in the Passadumkeag River pluton (pl. 1). The aplite dikes consist of fine-grained leucocratic rocks ranging from a few centimeters to 0.8 m in thickness. They often show diffuse contacts with the host granites, extreme variation in attitude, and mineralogical band- ing from felsic borders to thin biotite zones which culminate in a pegmatitic core. Muscovite is present in some of the aplites exposed within the plutons, especially in the core of the Whitney Cove pluton. Muscovite is best developed, however, in pegmatitic pods near granite-country rock contacts together with long blades (38-5 cm) of black tourmaline. These areas are exposed west of Almanac Mountain (A) and north of Bowers Mountain (S) in the Springfield and Scraggly Lake quadrangles (pl. 1). Within the Bottle Lake Complex, felsic dikes are com- mon east of Sysladobsis Lake (M) and along the shores of McLellan Cove (W), in Getchell Mountain (E) and south of Chamberlain Ridge (X). Felsic dikes are typical- ly low in mafic minerals, accessories, and plagioclase. Compositonally, they represent the most felsic rocks of each pluton and characteristically contain less stron- tium but more rubidium than the associated granites. 42 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX Bottle Lake Complex FeO Neo +/ V/ w Na;O EXPLANATION Aa Passadumkeag River A Core 0 Rim A 6 Core Whitney Cove x Aplite O Mafic xenolith 4 - Country rock xenolith Field of mafic xenoliths Field of country rock xenoliths MgO FIGURE 26.-AFM (A=Na,0+K,0; F=FeQ; M=MgO) diagram showing the Bottle Lake Complex, the mafic xenoliths, and aplites. The composition of the plutons defines an array trending toward the alkalies and is broadly calc-alkaline. Mafic xenoliths of the Passadumkeag River pluton plot closest to the FeQ-MgO sideline. AMPHIBOLITE UNIT An amphibolite unit crops out in the Scraggly Lake area, entirely confined within the cataclastic zone (pl. 1). This unit is best exposed in Hasty Cove (Y) and on islands near the southern shores of Mud Cove (DD). Most amphibolite outcrops are intensely sheared, jointed, and exhibit a strong northeast-trending foli- ation parallel to that of the granitic rocks. The predomi- nant rock type is a fine-grained, greenish-black (5 GY 2/1) unit with sparse plagioclase phenocrysts. Contacts with the granitic rocks of the Whitney Cove pluton are characterized by a hybrid zone where porphyritic greenish-gray (5 G 6/1) rocks are abundant. Felsic dikes cut the hybrid zone and the amphibolite. The mineralogy of the amphibolite consists of plagio- clase, amphibole, and biotite with minor amounts of quartz and alkali feldspar. Apatite, allanite, sphene, il- menite, magnetite, and zircon are also present. Apatite, however, is the most conspicuous accessory in this rock. STRUCTURES 43 STRUCTURES The generally massive fabric of the Bottle Lake Com- plex commonly persists outward to the granite-country rock contact. In foliated rocks, however, the feldspars are generally alined with (010) parallel to the contact. Extensive granite outcrops are developed on Lombard Mountain (R) and Getchell Mountain (E). Several areas within the granites also show foliated rocks consisting of the following: (1) zones within the core facies of the Passadumkeag River pluton; (2) foliated rocks of the rim facies of the Whitney Cove pluton developed in a cataclastic zone; and (3) rocks within the core facies of the Whitney Cove pluton. Foliation within the core of the Passadumkeag River pluton is alined to the northeast but is not accompanied by the strong cataclastic deformation characteristic of most foliated areas in the Whitney Cove pluton. Foliated areas within the Whitney Cove pluton are com- monly cut by bands of cataclastically deformed rocks. The two most important cataclastic areas are the northeast-trending fault zone of the Norumbega fault system and the fault zone which cuts the Whitney Cove pluton. Each of these zones is also characterized by foliated granitic rocks preferentially alined to the north- east in contrast with the apparent lack of regional aline- ment in the foliated rocks of the core facies in the Whitney Cove pluton. At least three fault zones are exposed in the Bottle Lake Complex: the wide band of shearing that cuts the Whitney Cove pluton; the Norumbega fault system; and the fault that cuts the Topsfield facies which was mapped by Ludman (1978b). The northeast-trending (N40-50°E) cataclastic zone that cuts the Whitney Cove pluton terminates against the Passadumkeag River pluton. This zone extends from Orie Lake (Z) to Junior Lake (AA) in a well-exposed, 1.5-3.0-km-wide band in the Scraggly Lak: quadrangle (pl. 1). Typical rocks are cataclastically deformed, sheared, and criss- crossed by quartz and epidote veins. Most outcrops in this zone show at least one set of mylonitic foliation to the northeast, although many show significant scatter in attitude. Spindle-shaped quartz grains are common in most exposures. Many outcrops also show evidence of right-lateral motion and up to 50 ecm of displacement in east-trending fractures across individual mylonitic zones. Granitic rocks are pervasively and massively altered. Feldspars are crisscrossed by thin, epidote-rich veins and show extreme alteration, disintegration, shearing, and displacement, especially within plastic bands of recrystallized quartz and biotite. The Norumbega fault zone is the major northeast- trending right-lateral system in the region and locally constitutes the southern contact of the Whitney Cove pluton (pl. 1). According to Wones (1979) the amount of displacement along the fault is unknown. Outcrops in Farm Cove (BB) of West Grand Lake in the Wabassus Lake quadrangle are good examples of intensely sheared, silicified and mylonitized granitic rocks. A left-lateral fault mapped by Ludman (1978b) along the southern shores of East Musquash Lake (CC) near State Route 6 separates the Topsfield facies from the main mass of the Whitney Cove pluton (pl. 1). The fault is oriented east-west and is characterized by epidotized and intensely sheared red granitic rocks. Mylonite veins are relatively common near the traces of the fault zones and also as randomly distributed and oriented features within the Whitney Cove pluton. Many of these veins are probably related to the iden- tified faults in the region. However, the preponderance of mylonites showing a pronounced east-west trend is suggestive of a distinct and possibly later deformation unrelated to the identified faults. Joints and fractures are common in most outcrops throughout the Bottle lake Complex. They often show large variation in attitude even within individual out- crops. On the basis of preliminary observations, no regional trend is displayed within the granitic rocks. Jointing is significantly increased with proximity to the areas of intense cataclastic deformation. ESTIMATE OF INTENSIVE PARAMETERS DURING CRYSTALLIZATION ESTIMATE OF PRESSURE A combination of textural, chemical, and geologic observations may be used to place constraints on pressure, temperature, fugacity of water, and oxygen fugacity during crystallization of the Bottle Lake Com- plex. Total pressure is among the most difficult param- eters to estimate. Plutons of the Bottle Lake Complex intruded country rock in the lower greenschist facies, almost certainly within the stability field of andalusite. Ludman (1978b) observed only andalusite in metamor- phic rocks in the area to the northeast, and contiguous to the Bottle Lake Complex. Depending on the choice of equilibrium curves, maximum pressure estimates based on andalusite stability range from about 3.5 kbar (Holdaway, 1971) to about 5.5 kbar (Richardson and others, 1969). Rast and Lutes (1979) estimated a pressure range of 1.5 to 3 kbar at the contact of the Pokiok-Skiff Lake granite (immediately to the northeast of the Bottle Lake Complex) on the basis of presence of 44 _ FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX coexisting garnet-cordierite-andalusite-biotite assem- blages. Similarly, the existence of garnet-cordierite- biotite assemblages (Hess, 1969) in the country rock in- truded by the Bottle Lake Complex suggests a pressure interval of 1.5 to 4.5 kbar. Rast and Lutes (1979) cite the estimate by Garland (1953) of about 2 kbar for the maximum thickness of cover north of the Bottle Lake Complex. This estimate is also consistent with P=2 kbar for the emplacement of the Center Pond pluton (Scambos, 1980) which lies im- mediately west of the Passadumkeag River pluton. Obvious signs of crystallization of the Bottle Lake Complex under water-saturated conditions are absent. It seems reasonable to suggest that because of the small number of aplites, pegmatites, and miarolitic cavities, only the most evolved rocks are equivalent to the syn- thetic Q@-Ab-Or-H,0 system (Tuttle and Bowen, 1958; Luth, 1969; James and Hamilton, 1968). Each of these units yields an estimate of pressure during emplace- ment. On this basis, and assuming that Pro=" uy: a range between 1.5 and 2.5 kbar probably existed during emplacement of the Bottle Lake Complex (fig. 27). Assuming that P;1,0=P.,,,.=2 kbar and that normative Ab/An=5.2 in the rock, a temperature of 685°C (+50°C) is estimated from the experimental data for granite minimum melts studied by von Platen (1965). ESTIMATE OF WATER CONTENT Water content in the original magmas of the Bottle Lake Complex was estimated by comparison of the order of crystallization with granodiorite experimental systems obtained by Naney (1978) and in conjunction with experimental systems documenting the paragen- etic sequence of mafic phases in K,O-rich magmas (Wones and Dodge, 1977). Early crystallization of euhedral hornblende together with euhedral biotite im- poses minimum water contents on these granitic magmas. In the case of relatively high water activity, amphibole precedes phlogopite in the crystallization se- quence. Such a sequence is present in the Passadum- keag River pluton, supporting the suggestion that water activity was relatively high during much of the crystallization of this granitic magma. Comparison of the mineralogy and order of crystallization observed in the Passadumkeag River pluton with pertinent systems studied by Naney (1978) suggests that water saturation occurred only in the latest stages of solidification. Water content probaby never exceeded 4 weight percent. The established order of crystallization for the Whitney Cove pluton also limits the water content of the magma. Vapor saturation occurred relatively late but at an earlier stage than in the Passadumkeag River pluton. Melts in this pluton probably never exceeded a maximum water content of 5 weight percent. Prominent alkali feldspar megacrysts are present in the core facies of this pluton because they grew faster than plagioclase and quartz (Swanson, 1977; Fenn, 1973), although this growth occurred relatively late in the sequence when water conditions in the pluton were still under- saturated. ESTIMATE OF 6 fop f,0 Although temperature of crystallization may be estimated from the equilibrium distribution of the albite molecule in coexisting plagioclase and alkali feldspar, the approach is not useful in the case of the Bottle Lake complex because of substantial feldspar reequilibration. Sanidization of alkali feldspar and use of powder diffrac- tion techniques (Wright, 1968; Wright and Stewart, 1968) suggest that the bulk composition is in the range of Or,, to Or,. Application of the feldspar geother- mometer (Stormer, 1975) yields a large spread in tem- perature from 450 to 800°C with most estimates clus- tered at about 450 to 550°C. These temperatures are lower than expected for a minimum melt at about 2 kbar (about 685°C) and result from the high ortho- clase content of the alkali feldspar, probably caused by secondary processes. Examination of coexisting oxides provides a way of simultaneously estimating fo, and ¢ (temperature in °C). Unfortunately, such estimates also yield unrealistically low temperatures (400-500°C) of equilibration of the Bottle Lake Complex. The composition of ilmenite is enriched in MnO probably making this phase untract- able by the Buddington and Lindsley (1964) scheme (Czamanske and Mihalik, 1972). Despite the coexistence of magnetite and ilmenite, the use of the geothermom- eter yields temperatures probably reflecting secondary processes. The modal abundance of magnetite and ilmenite displays significant variation in the Bottle Lake Com- plex. Either magnetite or ilmenite may be dominant in a sample. In at least one sample in the Whitney Cove pluton, inclusions within plagioclase were exclusively il- menite, while magnetite predominated in the matrix. Within the core of the Passadumkeag River pluton, many samples were dominantly of ilmenite rather than magnetite, but nearby rocks had subequal amounts of both phases. Coexistence of sphene and magnetite throughout the Bottle Lake Complex and essentially throughout the crystallization history marks the minimum fo, during crystallization. Wones (1966) suggested that this ESTIMATE OF INTENSIVE PARAMETERS DURING CRYSTALLIZATION 45 Bottle Lake Complex Q EXPLANATION 20 km in diameter) and probably sustained vigorous convection. Shaw (1974) suggested that convection of granitic magma resulted in efficient and systematic elemental gradients. This suggestion is in agreement with the results of Spera and Crisp (1981), who showed that chemical convection produces vertical composition gradients in magma chambers. Field and petrologic studies have suggested, for example, that in the Criffell- Dalbeattie pluton (Phillips and others, 1981) convection circulation was asymmetrical and occurred toward the end of the emplacement process. In the Bottle Lake Complex, both plutons probably established convective paths conducive to maintaining regular but vertically stratified bulk compositional gra- dients. However, mobilization of hotter, deeper granitic magma (thermal inputs), probably best characterized as a crystal mush, and upwelling into the higher convect- ing and fractionating systems, resulted in disruption of local equilibrium between liquid and crystals. Thus, significant mineral redistribution and mixing of liquids also occurred. Smith (1979) speculated on some of the 52 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX compositional and mechanical effects of thermal inputs (surges of new magma) into a crystallizing chamber and suggested that remelting and mixing of partially solidi- fied magma might be expected. Volcanic equivalents of the Bottle Lake Complex plutons are unknown. Thus, it is difficult to document the interplay between volcanism, with its attendant evisceration of the magma chamber, and resurgence as suggested by Bailey (1976) to explain the mechanism of resurgent doming. On the basis of available data, it can- not be demonstrated that remobilization of the core facies in the Bottle Lake Complex plutons was accom- panied by structural resurgence or by venting of the magma chamber. Nevertheless, it is interesting to note that the diameters (about 20 km), general shape, and ar- rangement of the plutons in the Bottle Lake complex are similar to those of the Toledo and Valles calderas in the Jemez Mountains of New Mexico. These calderas were described in the classic study of resurgence by Smith and Bailey (1968). According to their scheme, resurgent cauldrons pass through a number of stages beginning with a chemically stratified magma chamber. The intervening stages, which consist of volcanic events (ash-flow eruptions, caldera collapse, pyroclastic erup- tions, and so on) leading to resurgence, may be spec- ulated to have preceded the emplacement of the core facies of the plutons in the Bottle Lake Complex. Here again, however, the volcanic record of these processes has not been recognized. The relative timing of events in the Bottle Lake Complex is not well constrained. Although the core facies are in each case relatively younger than the rim, it is not possible to distinguish which pluton is younger by the Rb-Sr method. On the basis of field observations, however, the Whitney Cove pluton was suggested to predate the Passadumkeag River pluton. In comparison to the time necessary to complete the evolution of resurgent caul- drons in multiple calderas (for example, the Valles caldera), the evolution of the Bottle Lake Complex plutons may have taken at least as long as possibly longer to develop. For example, amphibole from the core and rim faces of the Passadumkeag River pluton differs by a minimum of about 2 m.y. in age as suggested by preliminary argon release studies (J. F. Sutter, 1983, oral commun.) FRACTIONAL CRYSTALLIZATION Fractionation of the phenocryst assemblage in the plutons of the Bottle Lake Complex is not the critical mechanism accounting for the reverse zonation but was superimposed on the original chemical zonation of the convecting magma chamber. Fractional crystallization may be accomplished by lateral accretion of crystals (Bateman and Chappell, 1979) with inward displace- ment of the melt and by gravitational settling. Rice (1981) considers gravitational settling unimportant in producing fractionation in felsic magmas because of the high-viscosity barriers. Shaw (1965), however, sug- gested that gravitational settling of mafic minerals and plagioclase was an adequate mechanism operating in granitic magmas. Emmeleus (1963) had previously ap- pealed to this mechanism to explain layering in granites from Greenland. More recently Robinson (1977) sug- gested that crystal settling resulted in the lithological zoning of the Tuolumne Intrusive Suite of the Sierra Nevada. For the Bottle Lake Complex, the relative im- portance of crystal settling compared to lateral accre- tion cannot be adequately judged with existing data, and it is likely that both were in operation. Neverthe- less, it seems evident that in the Bottle Lake Complex, the assemblage consisting of plagioclase, biotite, am- phibole, apatite, zircon, and magnetite-ilmenite partly controlled the change from some of the last fractionated to the most fractionated rocks (Ayuso, 1982). The core facies of both plutons represents a mixture of material from the lower parts of the chamber, new additions to the crystallizing chamber in the form of the crystal mush obtained from the new influxes of more mafic granitic magma, and of the accumulated fractionated assemblage. It should be emphasized, however, that although fractionation occurred during the evolution of the Bottle Lake Complex, this process by itself cannot account for the reverse zoning of the plutons. The Whitney Cove pluton shows a better defined gra- dient in its mineral abundances and mineral composi- tions coreward compared to the Passadumkeag River pluton. One dramatic result of mobilization and input of hotter granitic liquid into the chamber may be the more widely dispersed compositional variation of the miner- als, the lack of systematic mineral gradients, and abun- dance of mafic clots in the Passadumkeag River pluton. Such influx of more mafic granitic liquid, coupled with vigorous stirring in a convective system, may have mixed phases that originally crystallized and settled at the bottom or were eroded off the walls of the chamber with phases in equilibrium with liquids at different stages of fractionation, especially from new surges of magma. Thus, textural and chemical heterogeneity probably reflect processes related to the intrusion and mechanical mixing of different parts of the same crys- tallizing system and are not a direct result of frac- tionation. Especially in the case of the Passadumkeag River pluton, the abundance of mafic and felsic mineral clusters, the relict textures and compositional diversity of liquidus phases (biotite, plagioclase, and hornblende), CONCLUSIONS 58 and the abundance of a complex refractory suite sug- gest that the granite may have inherited some of its heterogeneity at the source. This suggestion is in agree- ment with observations by Marsh (1982), who indicated that diapiric movement probably involves motion of li- quids and remains from the source region. The presence of mafic xenoliths and mafic mineral clots in the Passadumkeag River pluton also suggests that some of the petrographic variation resulted from differential reaction between granitic magma and xenoliths. Mafic xenoliths were probably obtained at depth from the country rock. In contrast, mafic clots might represent aggregates of the fractionated assem- blage during earlier stages of crystallization. Also, it might be speculated that surges of hot, less differen- tiated or more mafic granitic magma into the crystalliz- ing chamber triggered the process of remobilization and autointrusion of the lower layers and of portions of the magma rich in mafic xenoliths, mafic clots, and mix- tures of the fractionating assemblages into the upper part of the chamber. SUMMARY OF MECHANISMS LEADING TO REVERSELY ZONED PLUTONS IN THE BOTTLE LAKE COMPLEX Reverse zoning in the Bottle Lake Complex is a result of remobilization (resurgence) of the deeper (hotter) parts of the system. The Bottle Lake Complex repre- sents a composite batholith derived from sequential melting, but each pluton evolved as an independent geochemical system. The initial state of the evolu- tionary path after the individual magma chambers were established was the development of chemical stratifica- tion, with hotter, more mafic magma at the base of the chamber (fig. 30). Convection in the magma chamber promoted the chemical gradients, which were aided by periodic influxes of more mafic granitic magma. Crystalliquid equilibria were of secondary impor- tance to explain the reverse zoning and were superim- posed on the original chemical zonation of the magma chamber (fig. 30). The stratification and division of the chamber into domains assured that the fractionating assemblage precipitated in these individual domains maintained equilibrium with only part of the chamber. Fractional crystallization by accretion and settling may have resulted, for example, in some accumulation of the most calcic plagioclase and the most magnesian mafic minerals. Periodic influxes of more mafic granitic magma at the base of the chamber would probably result in disruption of the convective cells, mixing of magmas at different stages of differentiation, and mix- ing of minerals of different compositions depending on their position in the magma chamber. Surges of hotter granitic magma into the base of the chamber resulted in resurgence or remobilization of the lower, more mafic crystal mush into the upper, more felsic layers. Alternatively, Bailey (1976) suggested that resurgent doming might occur from partially removing the top of the chamber as a result of volcanism. He sug- gested that isostatic equilibrium is restored by inward flow in the magma root zone leading to a rise in the sub- cauldron crustal column and magma chamber. In either case, field observations suggest that for both the Whitney Cove and Passadumkeag River plutons, the core facies were emplaced at this level of exposure subsequent to the rim facies (fig. 30). The plutons were intruded high in the crust, and this placement may explain the preservation of their reversely zoned features. This shallow level of emplace- ment together with decreased replenishment of hotter granitic magma at the base of the chamber might have resulted in a faster rate of cooling, less efficient convec- tion, and an increase in viscosity. As elemental diffusion became more sluggish and less systematic, the solidus temperature was reached. The granites consolidated and froze the reversely zoned features that are typically destroyed in plutons that have longer evolutionary paths. CONCLUSIONS The plutons in the Bottle Lake Complex constitute outstanding examples of reversely zoned granites. Mineral abundances as well as bulk compositions of each granite indicate that the interiors are enriched in mafic minerals and that they show higher contents of oxides typically expected to be concentrated along the margins. Remobilization (resurgence) and autointrusion of deeper parts of the system into the more felsic rocks of the margins explains the reverse zonation (fig. 30). Frac- tional crystallization was of secondary importance and probably accounts for the selective removal of the cumulative phases and mafic xenoliths. Convective transport resulted in redistribution and dispersal of the crystallizing assemblage in a chemically stratified system. Calculated biotite stabilities indicate a temperature range from 720-780°C and a total pressure from 1 to 1.8 kbar during the emplacement of the Bottle Lake Complex. The f,, conditions are characteristically higher than the Ni-NiO equilibrium curve as suggested by the assemblage of magnetite and sphene. The highly regular major oxide variations within each pluton, together with the Rb-Sr isotopic compositions resulting in linear isochrons, support the argument that 54 - FIELD RELATIONS, CRYSTALLIZATION, AND PETROLOGY OF THE PLUTONS IN THE BOTTLE LAKE COMPLEX THE BOTTLE LAKE COMPLEX 2 Present Surface "IGURE 30.-Generalized diagram showing a model for the reversely zoned plutons of the Bottle Lake Complex. The Whitney Cove and Passa- dumkeag River plutons evolved as independent systems. 1.-The initial stage of evolution was characterized by a chemically stratified system with more mafic granitic magma at the base (layer C) to more felsic granitic magma toward the top (layer A). 2. -The system passed through a stage of vigorous convection that promoted the chemical gradients. Fractionation by accumulation and lateral accretion may have been initiated at this stage. REFERENCES 55 each pluton behaved as an individual geochemical system. Oxygen isotopic compositions of the granites and country rocks are in agreement with the bulk com- positions gradients, suggesting that no significant interaction with country rocks occurred. The source of the plutons in the Bottle Lake Complex progressively changed to include more continentally derived debris. In the Passadumkeag River pluton, in- itial strontium, lead, and oxygen isotopic compositions are lower than in the Whitney Cove pluton indicating a less continental character of the source. Lead isotopic studies rule out a source similar to the upper oceanic mantle, lower continental crust, or upper continental crust as exemplified by metasediments intruded by the Bottle Lake Complex. The Bottle Lake Complex constitutes an example of reversely zoned plutons related by remobilization of more mafic but consanguineous magmas. Zoned gra- nitic plutons elsewhere have been explained by assim- ilation, late-stage reaction, multiple injection, or by frac- tional crystallization without remobilization and resurgence. Vigorous stirring with convective transport and large-scale upwelling occurred in the Whitney Cove and Passadumkeag River plutons leading to the present arrangement of rock types. Reversely zoned granitic plutons are unknown in east-central Maine apart from the Bottle Lake Complex. In general, plutons intruded near the core of the Merrimack synclinorium and ex- emplified by the Bottle Lake Complex are rich in mafic minerals and show a distinct geochemical composition (Loiselle and Ayuso, 1980) characteristic of plutons in- truded to the north of the Norumbega fault system. Reversely zoned plutons, in general, may be more numerous than recognized. It is conceivable that rem- nants of the reverse zoning become more difficult to discern as the plutonic rocks reach the latest stages of their evolution. In this case, the Bottle Lake Complex represents an earlier stage in the evolution of a felsic system that is usually represented by the final stages in normally zoned plutons. REFERENCES Ayuso, R. 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EDELEN, JR., K. V. WILSON, and JOE R. HARKINS, U.S. Geological Survey, and JOHN F. MILLER and EDWIN H. CHIN, National Weather Service, National Oceanic and Atmospheric Administration U.S. GEOROGICAL SURVEY PROFESSIONAL PAPER i131 9 Report prepared jointly by the U.S. Geological Survey and the National Oceanic and Atmospheric Administration UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1986 UNITED STATES UNITED STATES DEPARTMENT OF THE INTERIOR DEPARTMENT OF COMMERCE DONALD PAUL HODEL, Secretary MALCOLM BALDRIDGE, Secretary NATIONAL OCEANIC AND GEOLOGICAL SURVEY ATMOSPHERIC ADMINISTRATION Dallas L. Peck, Director Anthony J. Calio, Administrator Library of Congress Cataloging in Publication Data Main entry under title: Floods of April 1979, Mississippi, Alabama, and Georgia. (Geological Survey professional paper ; 1319) "Report prepared jointly by the U.S. Geological Survey and the National Oceanic and Atmospheric Administration." Bibliography: p. 45 1. Floods-Mississippi. 2. Floods-Alabama. 3. Floods-Georgia I. Edelen, George W. II. Geological Survey (U.S.) III. United States. National Oceanic and Atmospheric Administration. IV. Series. GB1399.4.M7F55 1984 551.48'0976 - 84-600097 For sale by the Books and Open-File Reports Section, U.S. Geological Survey, Federal Center, Box 25425, Denver, CO 80225 CONTENTS Page Page Glossary ------ ---- vill Reservoirs 28 Abstract -- 1 Major river basins of eastern Gulf of Mexico --------------- 29 Introduction ----------- 1 Coosa River basin 29 Acknowledgments 3 Tallapoosa River basin 29 Meteorological setting 4 Alabama River basin - 29 Antecedent CONGitiONs -------------<<-------------- 4 Tombigbee River basin ---------------------------- 30 Early spring storms -- 4 Tombigbee River upstream from Gainesville, Ala. ---- 30 March 3-4 ---------------------------__--___-- 4 Tombigbee River downstream from Gainesville, Ala. -- 31 March 10-11, 14, and 21 ------------------------ 5 Pascagoula River basin 33 March 23-24 --- 5 Pearl River basin - 33 April 1-4 7 Lower Mississippi River basin ----------------------- 39 April 8-9 ---------_-_________________-_____-.-_-~~ 9 Big Black River basin -------------------------- 39 Major storm event: April 11-18 ---------------------- 11 Flood-crest stages - 39 500-mb features ------------------------------- 11 Streamflow velocities 40 850-mb features 11 Velocity changes during peak discharges -------------- 40 Surface weather features ------------------------ 14 Velocity distribution through bridge openings ---------- 40 Satellite iMagery ------------------------------ 15 | Flood hydrograph data 41 Precipitation distribution ----------------------- 17 | Ground-water fluctuations 42 General description of floods 19 Numbering system for wells ------------------------- 44 Magnitude of floods --- 23 | Salinity and temperature data, Mobile Bay and Gulf of Mexico - 44 Flood damages ------ -- ---- - 28 | Aerial photography -- 44 FIOOG freqQU@ACy ------------------------------------- 24 | Selected references 45 ILLUSTRATIONS FRONTISPIECE. - Sequence of photographs showing the destruction of the bridge on State Highway 50 over the Tallapoosa River below Martin Dam near Tallassee, Ala., about 4:30 p.m., April 14, 1979. Page FIGURE 1. Area affected by floods on the Alabama, Big Black, Chattahoochee, Chickasawhay, Coosa, Pearl, and Tombigbee Rivers and their tributaries in April 1979 2 2. Significant meteorological features associated with the storm of March 3-4, 1979 =-------------<<<<<<<<-<<<-<-------- 5 3. Isohyetal analysis of storm rainfall March 3-4, 1979 6 4. Significant meteorological features associated with the storm of March 23-24, 1979 =-----------<----<<<-<-<---------- 7 5. Isohyetal analysis of storm rainfall, March 23-24, 1979 -----------------------___--___________<_<____--_------- 8 6. Significant meteorological features associated with the storm of April 1-4, 1979 ------------<----<---------------- 9 7. Isohyetal analysis of storm rainfall, April 1-4, 1979 10 8. 500-mb analyses: A. 0600 CST, April 11, 1979 12 B. 1800 CST, April 11, 1979 =& -== to e He aran nn csi m anne te e asa ut fa ae ie e oe me es e oe an he hama al ut ae oe ra se ae sa be 12 C. 0600 CST, April 12, 1979 12 D. 1800 CST, April 12, 1979 12 E. 0600 CST, April 13, 1979 ------ m ie oe ue ea He ae he ra ie ca ae od tn e ante oe me s s i ne ae in en me me as me o ae c Be me up or ie ha us an e oe he 12 F. 1800 CST, April 13, 1979 - s benim Sion eae oe to t o He an us ne m a ts an on m i t aad oe bo tine e ce to an it n lase ae ne ie se ae ce ese 12 9. 850-mb analyses: A. 0600 CST, April 11, 1979 13 B. 1800 CST, April 11, 1979 f th mn in in i me e a en tu she e Bn ae e ene he e te maniac on oe be A ue is as ae a ision an at se n ae ae e se c 13 C. 0600 CST, April 12, 1979 13 D. 1800 CST, April 12, 19709 13 E. 0600 CST, April 13, 1979 -- -== Pres 13 F. 1800 CST, April 13, 1979 s --as ru- 13 VI FicurE 10. 11: 12. 13. 14. 15. 16. yK 18. 19. 20-23. 24. 25-27. 28-31. 32, 33. 34. 35-43. 44, 45. 46. 47. CONTENTS Surface analyses: Page A. 0600 CST, April 11, 1979 ---- ai Emel reseed ti "16 B. 1800 CST.Apnil11. 1979 rir ober cc co agt 16 C. ©0600 CST, April 12, 1979 ---- «<- Ae i 16 D. 1800 CST, April 12, 1979 - - - - - - -. _ _. . 2 o non se oo o ens sn me m am a te m e e oe ae me me m me a s a on e a me s s me me me ms a os e one ho he as me me ae ma me meme 16 E. 0600 CST, April 18, 1979 -. - -- - - ~,... .. o os o une oso ne eee ee ee eme aem e ee e e m anm m me m a aie me me m ne anm me mme nie ie in mme mam m aus 16 F. 1800 CST, April 18, 1979 --- _._. _._ coco oe oon ooo een nere renner ee ie 16 Analysis of hourly observations at 1500 CST, April 12, 1979 ---------------_________________________________L 17 GOES visual image for 0730 CST, April 12, 1979, with major features of surface weather map superimposed ----------- 18 Enhanced GOES infrared images (Mb curve): A. 0000 OST, April 12, 10979 o 20 B. 0230 CST, April 12, 1979 - iss ibu 21 Radar summary map: A. 0535 CST, April 12, 1979 22 B. 1495 CST, April 192 1979 pein eases ience 22 Rawinsonde plot, 1800 CST, April 12, 1979: A. Jackson, Migs. Seo o s EE LEC LLL cum mnie co ol sal cme ao ce a ae ag m a h me an oe ie ue e ae e ue a e as oe tet us mass as an op e msi as a e eae he n inin nae 23 B. Centreville, Ala. -- - --- neem 23 Isohyetal analysis of storm rainfall, April 11-14, 1979 Toe eme meile be ae he H Hh us Tt we wi ma e e an n s e ag mle in ine nie he 24" Rainfall mass Curves - - > + +- = + = a o o am a ie ho os m me oue nee on me os mo as mm s an me us e i e ts an e m e m we me e me as us ts an ae ne t as im tn h ms me on Sn e on e e me mas or a he in hn he aa cn 25 Map showing location of fl00d determination Sites 26 Comparison of April 1979 peak discharges with maximum known flood peaks in Mississippi and Alabama -------------- 28 Hydrographs of discharge at selected gaging stations: 20. Coosa River basin in Alabama, April 1-16, 1979 29 21. Tallapoosa River basin in Alabama, April 3-22, 197Q 30 22. Cahaba River basin in Alabama, April 10-22, 1979 --------------------_-_-_________________________~- 30 23. Noxubee River at Macon, Miss., and near Geiger, Ala., and Sucarnoochee River at Livingston, Ala., April 2-23, 1979 - o + s a aoe o oce s a in he He oe he a t an an ae ne m as anos he ue el he ae in true oe noe an is as uae ae i e h e h ae H ie se 31 Photograph showing overflow of Tomblgbee River at Demopohs Ala., April 19, 10970 32 Hydrographs of discharge at selected gaging stations: 25. Valley Creek in the Black Warrior River basin in Alabama, April 2-21, 1979 - 33 26. North River and Black Warrior River in Alabama, April 2-21, 1979 ----------------------_-_--____-___-_--- 34 27. Pearl River basin at and upstream from Jackson, Miss., March 2 to April 28, 1979 -------<----------------- 34 Photographs showing: 28. Housing development in flooded area along Hanging Moss Creek in northern part of Jackson, Miss., April 16, 1979 --- ---- 35 29. Inundated residential area in the vicinity of Westbrook Road in northern part of Jackson, Miss., April 16, 1979 --- & Ree olen ut ines cab 36 30. Business district of J ackson, Miss., inundated by Pearl River overflow, April 16, 1979 ---------------------- 37 31. Flooded fairgrounds enclosed by levee, Jackson, Miss., near crest of Pearl River flood, April 16, 1979 ---------- 38 Hydrographs of discharge at selected gaging stations: 32. Pearl River near Monticello, Miss., and near Bogalusa, La., April 1-30, 1979 ----------------------------- 39 33. Big Black River at West, Miss., and near Bovina, Miss., April 1-30, 1979 -------------------------------- 39 Graph showing changes in point velocity, mean velocity, stage, and discharge of Alabama River near Montgomery, Ala., April 13-20; 1070 is ves r elo 40 Graphs showing velocity distribution and cross sections: 35. Alabama River at U.S. Highway 31 north, near Montgomery, Ala., April 15, 1979 ------------------------- 41 36. Mulberry Creek at highway bridge at Jones, Ala., April 14, 1979 41 37. Hashuqua Creek near Macon, Miss., April 12, 1979 -----------------------_-____________cc__________- 41 38. Noxubee River at U.S. Highway 45 bypass near Macon, Miss., April 14, 1979 ---------------------------- 42 39. Noxubee River at State Highway 17 near Geiger, Ala., April 15, 1979 42 40. Tombigbee River at Gainesville, Ala. (main channel), April 15, 1979 ------------------------------_------ 42 41. North River near Samantha, Ala., April 18, 1979 43 42. Pearl River at Interstate Highway 55 at Jackson, Miss., April 17, 1979 <-------------------------------- 43 43. Zilpha Creek at State Highway 35 near Kosciusko, Miss., April 12, 1979 43 Hydrographs of water levels in observation wells: 44. At Centreville, Ala. (Centreville Gin and Cotton Co.), March-April 1979 44 45. Near Pickensville, Ala., in the Tombigbee River basin, March-April 1979 -------------------------------- 44 Map showing location of specific-conductance sampling sites along the Intracoastal Waterway at the mouth of Mobile Bay, April 28-29, 1979 - aes ntr ctr t i a nent "" 45 Map showing location of flight lines along streams where aerial photographs were obtained on or near the crest of the flood, Apri ggg n_ nn nll _ tent t t MIC RL. ol redo sido nosen eae 46 TABLE CONTENTS VII TABLES [All tables appear at end of report] Page . Supplementary rainfall data, storm of April 11-13, 1979 ne wn ae m me n se He o m o m m as e me r os me e am ws an ar e h te te n as Se he e a as m a on me ne tos a e e e im 49 . Summary of fl00d Stages ANd GiSCharges 54 . Summary of flood damages on main streams and principal tributaries, March 1979 and April 1979 floods ------------------ 67 . Summary of stages and CONtentS Of StOFAGG M@S@rVOirS -----------------------------<-<_________=_----_------------- 69 . FIOOG-CTESt Stag@§ 80 . Streamflow velocities, Alabama River near Montgomery, Ala., Apn] 12 ce cat wos 111 . Gage height, discharge, and accumulated runoff, flood of April 1979 112 . Ground-water levels in selected observation wells in Alabama and Mississippi, April 1979 -------------------------~-~--- 197 . Specific conductance and temperature of samples at selected sites along the Intracoastal Waterway at the mouth of Mobile Bay, April 28-29, 1979 * o 209 . Aerial photographs obtained at or near the crest of the flood, April 1979 212 CONVERSION OF INCH-POUND UNITS TO INTERNATIONAL SYSTEM OF UNITS (S1) Most units of measure used in this report are inch-pound units. The following factors may be used to convert inch-pound units to the Inter- national System of Units (SI). Inch-pound to SI SI to Inch-pound Length inch (in.) = 25.4 mm millimeter (mm) an 0.03937 in. foot (ft) = 0.3048 m meter (m) = 3.2808 ft mile (mi) = 1.6093 km kilometer (km) = 0.6214 mi Area square mile (mi") im 2.5900 km? square kilometer (km) = 0.3861 mi? acre = 4046.86 m* square meter (m*) == 0.000247 acre Volume cubic foot (ft?) = 0.0283 m* cubic meter (m') z 35.3147 ft? acre-foot (acre-ft) rz 1233 m' m* i= 0.00081 acre-ft Velocity mile per hour (mph) == 1.6093 km/h kilometer per hour (km/h) = 0.6214 mph foot per second (ft/s) == 0.3048 m/s meter per second (m/s) = 3.2808 ft/s Flow rate cubic foot per second (ft's) 0.02832 m/s cubic meter per second (m/s) 35.3147 (ft"s)/mi? 0.01094 (m*/s)/km? (m*/s)/km? 91.40768 (ft'/s)/mi" Pressure [The National Weather Service uses millibar (mb) as customary unit for atmospheric pressure.] inch of mercury at 32°F (in. Hg) = 33.8639 mb mb ss 0.02953 in. Hg Temperature degrees Fahrenheit (°F) = 9/5(°C)+32 degrees Celsius (°C) m 5/9(°F-32) VIII GLOSSARY GLOSSARY Acre-foot (acre-ft). The volume of water required to cover 1 acre to a depth of 1 ft. It equals 43,560 ft? (cubic feet), 325,851 gal (gallons), or 1,233 m* (cubic meters). Aquifer. A water-bearing formation. Contents. The volume of water in a reservoir or lake. Content is com- puted on the basis of a level pool or reservoir backwater profile and does not include bank storage. Cubic feet per second (ft's). A rate of discharge. One cubic foot per second is equal to the discharge of a stream of rectangular cross sec 1 ft wide and 1 ft deep, flowing at an average velocity of 1 ft/s. It equals 28.32 L/s (liters per second) or 0.02832 ms (cubic meters per second). Cubic feet per second per square mile [(ft''s)/mi']. The average number of cubic feet per second flowing from each square mile of area drained by a stream, assuming that the runoff is distributed uni- formly in time and area One (ft's)/mi' is equivalent to 0.0733 (m*/s)/km'* (cubic meters per second per square kilometer). Cyclone. An atmospheric low-pressure system around which the wind blows in a counterclockwise direction in the Northern Hemi- sphere and clockwise in the Southern Hemisphere. Dewpoint (or dewpoint temperature). The temperature to which a given parcel of air must be cooled at constant pressure and con- stant water-vapor content in order for saturation to occur. Drainage area of a stream at a specific location. The area measured in a horizontal plane, bounded by topographic divides. Drainage area is given in square miles. One square mile is equivalent to 2.590 km (square kilometers). Fall line. A narrow zone between resistant rocks and the softer for- mations of the coastal plain, characterized by steepened gra- dients and by waterfalls, locally. Flood. Any high streamflow that overtops natural or artificial banks of a stream and overflows onto land not usually under water or ponding caused by precipitation at or near the point it fell. Flood peak. The highest value of the stage or discharge attained by a flood. Flood profile. A graph of the elevation of water surface of a river in a flood-plotted as ordinate; against distance-plotted as abscissa. Flood stage. The approximate elevation of the stream when overbank flooding begins. Front. The interface or transition zone between two airmasses of different density. Gage height. The water-surface elevation referred to some arbitrary gage datum. Gaging station. A particular site on a stream, canal, lake, or reser- voir where systematic observations of gage height or discharge are made. GOES. Geostationary Operational Environmental Satellite. GMT. Greenwich mean time. High. A center of high barometric pressure. Hydrograph. A graph showing stage, flow, velocity, or ground-water level of water, with respect to time. Instability. Areas of instability as referred to in this report are areas where the lifted index is less than four. Isohyet. A line connecting points of equal precipitation. K index. A measure of the airmass moisture content and stability. K=(Tsso=-Tso0)+*Tasso~(Tz0oo-Taroo where T and T,; are temperature and dewpoint, respectively, in degrees Celsius (°C); subscripts denote pressure levels. Knot. A velocity of 1 nautical mile per hour. Lifted index. Difference in degrees Celsius between the observed 500-millibar (mb) temperature and the computed temperature a parcel characterized by the mean temperature and dewpoint of the 50-mb-thick surface layer would have if it were lifted from 25 mb above the surface to 500 mb. Low. Center of low barometric pressure. Millibar (mb). A unit of pressure equal to 1,000 dynes per square centimeter. National Geodetic Vertical Datum (NGVD). Formerly called Sea Level Datum of 1929. A geodetic datum derived from a general adjustment of the first order level nets of both the United States and Canada. In the adjustment, sea levels from selected tide sta- tions in both countries were held as fixed. The year indicates the time of the last general adjustment. This datum should not be confused with mean sea level. Nautical mile. A distance of 6,080.20 feet (1.853 km]). Occluded front (occlusion). A composite of two fronts, formed as a cold front overtakes a warm front or a quasi-stationary front. This is a common process in the late stages of cyclone develop- ment. Planck's law. One of the fundamental laws of physics that gives the intensity of radiation emission at a specific wavelength as a func- tion of the temperature of a black-body. Precipitable water. The amount of water contained in an atmospheric column if all the vapor between two levels (usually the surface and 500 mb) were condensed. Radiosonde. A balloon-borne instrument package for measuring and transmitting meteorological data. Rawinsonde. A meteorological data-collection system including a radiosonde and reflectors for measuring winds by radar. Recurrence interval. As applied to flood events, the average number of years within which a given flood peak will be exceeded once. Runoff. That part of the precipitation that appears in surface streams. Sounding. A single complete radiosonde observation of the upper atmosphere. Specific conductance. The measure of the ability of water to carry an electric current and, therefore, an indication, within rather wide limits, of the dissolved-solids concentration or salinity of a solu- tion. Specific conductance is expressed in mhos/centimeter. In most waters, conductance is so low that micromho is used as the unit of expression. Stage-discharge relation. The relation between gage height and the amount of water flowing in a stream channel. Time of day is expressed in 24-hour time. For example, 12:30 a.m. is 0030 hours, and 1:00 p.m. is 1300 hours. Central standard time (CST) is used throughout this report unless stated otherwise. Trough. An elongated area of relatively low atmospheric pressure. FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA By GEORGE W. EDELEN, JR., K. V. WILSON, and JOE R. HARKINS, of the U.S. GEOLOGICAL SURVEY and JOHN F. MILLER and EDWIN H. CHIN of the NATIONAL WEATHER SERVICE, NATIONAL OCEANIC and ATMOSPHERIC ADMINISTRATION ABSTRACT A major storm brought large amounts of rainfall over the south- eastern United States April 11-13, 1979. Heaviest rain fell over north-central Mississippi and Alabama. Although the storm extended into the headwaters of the Chattahoochee River basin in northwest- ern Georgia, most flooding there was only moderate. A maximum of 21.5 inches was observed at a site 14 miles southeast of Louisville, Miss. Areal average rainfall exceeded 12 and 8 inches over the upper Pearl and upper Tombigbee River basins, respectively. Owing to a series of antecedent storms in March and April over the Mississippi- Alabama area, soils were saturated and many rivers were already bankfull. Additional rains April 21-23 in Mississippi and April 24-26 in Alabama averaged less than 2 inches over the flooded area. A max- imum of 6.4 inches was reported at Ruth, Miss., about 65 miles south of Jackson, where little or no rain fell during the major storm of April 11-13. Floods in Mississippi and Alabama caused by the series of storms were the maximum of record at 60 streamflow gaging stations in the Coosa, Alabama, Tombigbee, Chickasawhay, Pearl, and Big Black River basins. On the Pearl River, peak discharges at main stem gaging stations generally approached or exceeded those of the great flood of 1874, and recurrence intervals generally were greater than 100 years. On some streams, maximum stages and discharges produced by the March 3-4 storm, although greater than those previously ob- served, were exceeded during the April 11-13 storm. Other storms in April extended the flood duration and added materially to the flood volume. A comparison with the greatest known floods indicates that floods generally one-third greater than those in 1979 may occur in large basins and that floods two or three times greater may occur in small basins. Floods much greater than those observed in April 1979 or than the greatest known floods in the area are likely to occur if the probable maximum precipitation occurs. Nine lives were reported lost. Estimated damages from the March and April flooding totaled nearly $400 million. During April 1979, 75 percent of the total damage occurred in the Pearl River Basin, and 65 percent of the damage occurred in Jackson, Miss., and vicinity. Seventeen thousand people were driven from their homes in Jackson, Miss. The report presents analyses of the meteorological settings of the storms, the distribution of rainfall, and supplementary rainfall data that have not been published elsewhere. It also gives summaries of flood stages and discharges at 221 streamflow gaging stations, stages and contents of 10 reservoirs, flood-crest stages and hydrograph data (gage height, discharge, and accumulated runoff at selected times) at 46 gaging stations, ground-water fluctuations in 11 observation wells, and water salinity and temperature at 22 sites along the Intracoastal Waterway in Mobile Bay. The availability of aerial photography obtained during the flood is summarized, and flood damages are discussed. INTRODUCTION During March and April 1979, a series of storms in Mississippi and Alabama resulted in recordbreaking floods on streams in the Coosa, Alabama, Tombigbee, Chickasawhay, Pearl, and Big Black River basins. The first storm, March 3-4, produced maximum stages and discharges greater than previously observed on several streams in the Coosa, Tombigbee, and Chickasawhay River basins. Some of these floods were exceeded during the major storm of the series, April 11-13, which pro- duced most of the recordbreaking floods. The storms of March 23-24 and April 1-4 produced bankfull stages on many streams. A major rainstorm occurred April 11-13, 1979, over the Southeastern United States. Rain fell over large areas of Mississippi, Alabama, Georgia, South Carolina, Tennessee, and Arkansas. However, the heaviest rain fell in central and northern Mississippi and Alabama (henceforth referred to as "the two-State region"" or "the region"), over the Tombigbee and Pearl River basins. 1 2 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA #: p [ FN S A | GULF: OF -M E XIC O Area covered by this report o 0 100 200 IL | | I I I 100 200 300 300 MILES | I 400 KILOMETERS FiGuUrE 1.-Area affected by floods on the Alabama, Big Black, Chattahoochee, Chickasawhay, Coosa, Pearl, and Tombigbee Rivers and their tributaries in April 1979. Stages were still high on many streams when the ex- tremely heavy rains fell. The most severe flooding oc- curred in the middle reaches of the Tombigbee River and along the Pearl River at Jackson, Miss. Moderate flooding occurred along the Pascagoula River and the Yazoo River, a tributary to the lower Mississippi River. Although the storm extended into the headwaters of the Chattahoochee River basin in northwestern Georgia, most flooding there was only moderate. Minor storms, April 21-26, caused small streams in the lower Pearl River basin to rise coincidentally with the arrival of floodwaters from the April 11-13 storm. The April 21-26 runoff added materially to flood volumes and extended the duration of flooding along the lower Pearl River. Figure 1 is a map showing major rivers and areas affected by the floods. Peak flows in March and April at more than 60 streamflow gaging stations in Alabama and Mississippi were greater than those previously recorded. Maximum stages and discharges of record occurred along the main stems of the Coosa, Tombigbee, Pearl, and Big Black Rivers. Nine lives were reported lost. Damages estimated by the U.S. Army Corps of Engineers (1980a, b) totaled nearly $400 million. All rivers in Mississippi and Alabama drain into the Gulf of Mexico. The major rivers are the Alabama and ACKNOWLEDGMENTS 3 Tombigbee Rivers, which drain into Mobile Bay through the Mobile and Tensaw Rivers, and the Pasca- goula, Pearl, and lower Mississippi Rivers. The states of Mississippi and Alabama, bounded on the north by 35° N. latitude and on the south by the Gulf of Mexico, have ample rainfall. Mean annual total precipitation over the two-State region exceeds 50 in., and the number of days with appreciable rain (.01 in. or more) exceeds 100 each year. Rainfall is distributed throughout the year, with a maximum in March and a minimum in October. The Tombigbee River rises in the fall-line hills in northeastern Mississippi and flows southeastward to western Alabama and then southward to join the Ala- bama River to form the Mobile and Tensaw Rivers, which flow into Mobile Bay. The Tombigbee is 442 miles long; about 350 miles are navigable because of a series of improvements in the form of dams and locks. Unlike the Pearl River in Mississippi. the Tombigbee River is an important artery for manufactured goods; it can be accessed by the Birmingham industrial area through the Black Warrior River tributary. The Tom:- bigbee drainage basin is 22,100 square miles in area and is shaped like an inverted triangle. At the northernmost headwater region the drainage width is 170 miles; the width reduces to 80 miles at the midpoint of the river course near Demopolis, Ala., and narrows further as the river flows south, reaching a vertex near Mobile, Ala. Land use adjoining the Tombigbee River is predomi- nantly agricultural. There is no city along the Tombig- bee River main steam that compares in size with metropolitan Jackson, Miss., on the Pearl River. At Demopolis, Ala., the Tombigbee River crested April 18, at 37.03 feet, more than 24 feet above flood stage and 1.3 feet above the previous record, established in 1961. The Pearl River is the principal outlet for runoff from south-central Mississippi. Its watershed extends 240 miles from headwaters to the Gulf of Mexico and has a maximum width of about 50 miles. The total area drained is about 8,670 square miles. Except in its final 60-mile reach, where it forms the boundary between Louisiana and Mississippi, the Pearl River lies within the State of Mississippi. Its gradient is relatively flat, only about 1 in 5,000. It is mostly a shallow, meander- ing stream, nonnavigable except for recreational boat- ing. Land use along the Pearl River is predominantly rural, agricultural, and woodlands except for the Jackson, Miss., metropolitan area. Jackson is located on the west side of the Pearl River about two-fifths of the way from its source. It lies on a rolling upland dissected by some 14 tributary creeks which drain eastward to the Pearl River. These creeks pose a double threat to the adjoining metropolitan area: flash floods from urban runoff within each tributary watershed and backwater from the Pearl River main stem. The natural flood plain at Jackson, about 2 miles in width, has been modified extensively by levees. About 10 miles upstream from Jackson is the Ross Barnett Dam, built in 1962 to pro- vide water supply and recreation for Jackson. The reser- voir behind this dam is maintained at a high level, to within a foot or two of capacity, to provide maximum recreational benefits; therefore, the flood control capaci- ty of the system is minimal. The April 1979 Pearl River flood set a new stage record of 43.28 feet at Jackson. The levee was over- topped. Nearly 2,000 dwellings and 298 commercial buildings were flooded. Seventeen thousand people were driven from their homes. A new $54 million sewage treatment plant was damaged substantially and raw sewage flowed directly into the Pearl River. Vital public services-water supply, electric power, telephone, and fire protection-were curtailed or hampered. The purpose of this report is to present an analysis of the meteorological settings associated with the storm; stages, discharges, and accumulated runoff of the flood; contents of reservoirs, flood-crest elevations, and mag- nitude and frequency of peak discharges for comparison with previous large floods; ground-water levels; and a summary of flood damages. ACKNOWLEDGMENTS The meteorological and rainfall analyses contained in this report are based on data obtained by the National Weather Service and represent the collective effort of many professional people. The supplementary rainfall data were obtained by a field survey team that included Roy Roberts (National Weather Service Lower Mississippi River Forecast Center, Slidell, La.) Rovert Ellis and Robert Manning (National Weather Service, Southern Region), coopera- tive program managers from Mississippi, Alabama, and Arkansas, and personnel from the Mississippi Depart- ment of Natural Resources. Discharge records and other streamflow data appear- ing in this report were obtained as part of cooperative programs between the U.S. Geological Survey and the States of Alabama, Georgia, Mississippi, and Loui- siana; county and municipal agencies within those States; and agencies of the Federal Government. The cooperation of the Mobile and Vicksburg Districts of the U.S. Army Corps of Engineers in providing photog- raphy and information on reservoir operation, flood heights, salinity, temperature, and flood damages is gratefully acknowledged. Other Federal and State agen- cies, municipalities, universities, corporations, and indi- viduals assisted, financially or otherwise, in the data- 4 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA collection effort. Credit for this assistance is given in the appropriate places in the text. METEOROLOGICAL SETTING ANTECEDENT CONDITIONS The 1978-1979 winter season was much wetter than normal over the two-State region. The December 1978 precipitation over central and northern Mississippi and northwestern Alabama was more than one and one-half times normal. Jackson, Miss., had a monthly total of 8.4 in., or 3.4 in. above normal. Beginning in January 1979 a series of storms swept through the two-State region. The storm of January 1-3 was characterized by rapid movement of a Low from the lower Mississippi Valley to Quebec. The passage of the associated cold front caused precipitation to fall over the whole region. Jackson, Miss., had 2.74 in., and Bir- mingham, Ala., had 1.51 in. Subsequent storms that produced significant amounts of precipitation occurred during the periods January 6-8 and 18-21 and on January 24, 27, and 31. All of Mississippi, except the northernmost part, and western and southern Alabama had more than one and one-half times the normal pre- cipitation in January, and the midsection of the Pearl River drainage basin, centered around Jackson, had more than three times the normal January amount. Jackson itself received 14.1 in. in January 1979, com- pared with a normal of 4.4 in. Cyclogenesis occurred on February 5 and 6 off the Texas coast in the Gulf of Mexico. The surface Low moved eastward, and the southerly flow in advance of the center was lifted by the associated warm front, caus- ing rain to fall over Mississippi and Alabama on February 6 and 7. Other periods of appreciable pre- cipitation over the region were February 18-19 and 21-25. For the month, the central and southern parts of the two-State region had precipitation more than 50 per- cent above the February normal. Although departures were less for the northern half of Mississippi, precipita- tion was still above normal. Total February precipita- tion at Jackson, Miss., was 8.4 in., or 3.8 in. above normal. Thus, after three consecutive wet months in the winter season over the central part of the region, partic- ularly over the middle Pearl River basin, the soil was thoroughly saturated. Streamflows were more than am- ple in the Pearl River, in several headwater tributaries of the Pascagula River, and in the Tombigbee River, and reservoirs in the region were nearly filled even before spring season. EARLY SPRING STORMS The series of storms continued into the spring. Prior to the large storm of April 11-13 which produced the major flooding, there were seven spring storms that brought significant amounts of precipitation to the region. These storms occurred on March 3-4, March 10-11, March 14, March 21, March 23-24, April 1-4, and April 8-9. Among these storms, the more impor- tant rainfall periods were associated with the storms of March 3-4, March 23-24, and April 1-4. The weather situations accompanying each of these storms are dis- cussed briefly, with the three most significant storms discussed in some detail. MARCH 3-4 On February 28, a surface Low moved across the northern Pacific coast of the United States. Significant meteorological features associated with the storm are shown in figure 2. The surface system was over Nevada by the morning of March 1 and continued toward the southeast crossing the intermountain region. Aloft, at 500 mb, a deep short wave trough moved onshore the night of February 28-March 1 and continued its east- ward movement. By the evening of the 2d, the trough was over the eastern slope of the Rocky Mountains. The trough induced the re-formation of the surface Low in southeastern Colorado and the Oklahoma-Texas panhandle region. The Low stagnated briefly while its cyclonic circulation reorganized, then moved slowly eastward. By the morning of the 3d, the storm had become a well-organized system with a central pressure of 1,000 mb located over eastern Oklahoma. The warm front extended eastward from this system, across cen- tral Arkansas, southern Kentucky, and eastern Ten- nessee to western North Carolina. The cold front ex- tended southward along the Oklahoma-Arkansas and Texas-Louisiana borders. Across the Southeastern United States, warm moist air was advected from the Gulf of Mexico. At 0600 CST, March 3, the precipitable: water in this air flow was 1.56 in. at Boothville, La., and 1.48 in. at Jackson, Miss. These values compare with the climatological values of the semimonthly maxima of 1.91 in. at Boothville and 1.68 in. at Jackson. The K in- dex on the morning of the 3d was 30 at Boothville and 40 at Jackson, indicating thunderstorm probabilities of 50 percent at the former and near 100 percent at the latter. As warm maritime air from the Gulf of Mexico moved into the region, thundershowers were prevalent. From eastern Oklahoma, the Low turned northeastward and by the morning of the 4th was located over the east- central coast of Lake Michigan. The 500-mb trough con- tinued a steady eastward movement and passed over the region by the evening of the 4th. The eastward movement of these systems brought an end to the rain. The rain in the March 3-4 storm began over southern Mississippi during the evening of the 2d and then spread northeastward to large areas of the Pearl, Pasca- goula, Tombigbee, and Alabama River basins. Much of METEOROLOGICAL SETTING 5 \\ z \ t ‘~-\ y 030600 0 200 400 MILES f-++~- 0 _ 200 400 KILOMETERS 041800 EXPLANATION ®- - * Position and track of surface low «tk AA. Cold front \Narm front --- 500-mb trough position at indicated time 030600 Six-digit numbers denote date and time Example: 030600 is March 3d at 0600 CST FigurE 2.-Significant meteorological features associated with the storm of March 3-4, 1979. the rain fell on the 3d. The greatest rainfall total for the storm was 13.08 in., at the Hickory 1E, Miss., station. The largest single-day amount was 8.52 in. on the 3d at Codin, Ala., on the Gulf coast. The axis of heaviest rain- fall (fig. 3) extended between these two stations and con- tinued northeastward across Alabama. Rain was wide- spread over the two-State area. Areal average rainfall was greatest, amounting to more than 5 in., over the Chickasawhay and Tombigbee River basins. MARCH 10-11, 14, AND 21 Weak weather systems crossed the Southeastern United States on March 10-11 and March 14, and again on March 21. These storms caused rather widespread but light rain over Mississippi and Alabama. On March 10-11, rain over the coastal regions of Alabama aver- aged about 1 in., while over the rest of the two-State area rainfall averaged less than 0.5 in. The rainfall on March 14 and 21 was primarily centered over the north- ern portion of the two-State area and in each case aver- aged only about 0.25 in. Though the rainfall in these storms was light, it served to maintain a high level of soil moisture. MARCH 23-24 The second significant early spring storm occurred on March 23-24. The chain of events began when a Low crossed the California coast on March 18 and moved slowly eastward across Arizona and New Mexico. By late afternoon on March 21, the Low was in central New Mexico (fig. 4). At this time, it started to 'move in a northeasterly direction. The Low crossed southeastern Colorado, Kansas, and Missouri, and by the morning of the 23d it was centered in southeastern Iowa. The cold frontal system stretched southward from the surface Low. The primary front extended through Missouri, Arkansas, and Louisiana, crossing the Gulf of Mexico coast near Lake Charles. A secondary front and instabil- ity line/squall line existed in advance of the primary front. Most of the rainfall associated with the system 6 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA ‘.’,§‘ C\t& c giggg‘glsyfifig 3! W4 LAKE ~~ (powrcna RT?“ \ 87° 86° 85° 84° 83° IDAS : "4 $ + R + .) -K PALACHEE YA._ ~, 7 RAY % EXPLANATION Ie Lack Ac ARA l|||!||||! 50 100 o-- --4-- Isohyet showing total precipitation, March 3-4, 1979, in inches --2-- Supplementary isohyet, in inches 50 100 200 MILES | I 200 300 KILOMETERS FiguRE 3.-Isohyetal analysis of storm rainfall, March 3-4, 1979. was a result of the secondary front and instability line/ squall line. By the morning of the 24th, the Low had moved over central Lake Michigan and the frontal system had moved through the two-State region. The cold front extended from Lake Michigan through Michigan, Ohio, West Virginia, Virginia, North and South Carolina, crossing the coast near Charleston, S.C. Some lingering rainfall was occurring in northeastern Alabama, but the significant storm rainfall over the basin had ended. The 500-mb circulation had large meridional compo- nents prior to the storm. By the morning of the 22d, the flow aloft had split into two separate waves, with one re- maining offshore and the other centered over northern New Mexico. The easternmost 500-mb closed Low and trough were associated with the surface system that caused the rain over the two-State region. By the morn- ing of the 23d the Low had reached approximately 95° W. This position placed the two-State region under a trough-todownwind ridge flow pattern. Both mass and METEOROLOGICAL SETTING [f t © 221800 200 400 MILES I 0600 , 0 _ 200 400 KILOMETERS / 24 230600 230600 |230600 1 230600 EXPLANATION @®&- -» Position and track of surface low _ArAA. Cold front «aam. \Narm front --- 500-mb trough position at indicated time 220600 Six-digit numbers denote date and time Example: 220600 is March 22d at 0600 CST =-="=== Squall ling FiGURE 4.-Significant meteorological features associated with the storm of March 23-24, 1979. isobaric convergence (divergence) existed in a deep layer below (above) about 500 mb. This condition is very favorable for intensification of weather systems, and in fact both the surface and 500-mb Lows deepened as they moved to the northeast. In the warm, moist airflow in advance of the surface and upper air systems, precipitable water was only mod- erate. At Jackson, Miss., the observed amount from sur- face to 500 mb at 1200 GMT was 0.95 in. on the 22d and 0.43 in. on the 23d. These can be compared with the March mean at Jackson of .63 in. (standard deviation, .34). At Centreville; Ala., the observed amounts of pre- cipitable water for the same layer were 0.91 and 1.12 in. on those dates; climatological values are not available for Centreville. Rain began in the early morning of the 22d over a large part of Mississippi and spread to Alabama. The period of rainfall over Mississippi was March 22-23, with the 22d the rainier day, while the period of rainfall over Alabama was March 22-24, with the 23d the rain- iest day. A maximum storm precipitation of 4.42 in. fell at Dayton, Ala., (32°22 N, 87°39'W) in the Tombigbee River drainage basin. The average depth of rain was less than 1.0 in. over the Pearl River basin and approxi- mately 1.5 in. over the Tombigbee River basin. A gener- alized isohyetal map for this storm is shown in figure 5. APRIL 1-4 The third significant spring storm occurred during the period April 1-4. At 1800 on March 30, the 500-mb circulation over North America was characterized by a long wave trough over the Western United States, with the trough axis extending from western Montana to eastern Arizona. Meanwhile, off the west coast, a short wave impulse appeared and moved rapidly southeast- ward along the major trough. By the morning of April 1, this short wave trough was passing over the Oklahoma- Texas panhandle region (fig. 6), while the major long wave trough was still over the Rocky Mountains. The 8 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA 90° « C § EXPLANATION Isohyet showing total precipitation, March 23-24, 1979, in inches --0.5-- Supplementary isohyet, in inches 0 50 Le L. boat loa ’ E3 I £133 I 0 50 100 200 MILES | | A 200 300 KILOMETERS FIGURE 5.-Isohyetal analysis of storm rainfall, March 23-24, 1979. passage of the upper air short wave trough over an existing diffuse surface frontal system over the South- eastern United States triggered frontal wave formation and cyclogenesis. A weak depression located over north central Texas on April 1 intensified, and by that even- ing it had become a well-formed system centered on the Arkansas-Missouri border (fig. 6). The Low continued to deepen, and its cyclonic circulation expanded over an even larger region as it moved rapidly northeastward to the Great Lakes region and then to the Hudson Bay coast of Quebec by the evening of the 3d. Simultane- ously, the 500-mb short wave disturbance propogated rapidly toward Quebec. A section of the preexisting weak surface frontal system was already in place over northernmost Mississippi on the evening of March 31, with precipitation generally to the north of the front. As the frontal wave developed and the closed Low formed, a squall line was generated ahead of the cold front that extended from the center of the Low southward into the Gulf of Mexico. By the morning of the 2d, the cold front was moving through northwestern Mississippi while the squall line was already in western Alabama. The METEOROLOGICAL SETTING 9 __> 0 200 400 MILES [>- 0 _ 200 400 KILOMETERS EXPLANATION ®- - » Position and track of surface low _A.A.A. Cold front --- -- 500-mb trough position at indicated time 010600 Six-digit numbers denote date and time Example: 010600 is April 1st at 0600 CST -="=-= Squall line FicuRE 6.-Significant meteorological features associated with the storm of April 1-4, 1979. precipitable water in the warm, moist airflow in advance of the cold front was 1.46 and 1.13 in. at Jackson, Miss., and Centreville, Ala., respectively, at 1200 GMT on April 2, and 1.11 and 1.22 in., respectively, at 1200 GMT on April 3. These values at Jackson compare with 1.74 in. for the climatological April 1-15 semimonthly maximum. The K index was 38 at Jackson and 30 at Centreville on the 2d, indicating a thunderstorm prob- ability of 80 to 90 percent at the former and 40 to 60 per- cent of the latter. Rain started over northwestern Mississippi on the morning of March 31 and spread southeastward. Precip- itation fell over the whole two- State region during the period March 31-April 4. However, most of the rain fell between April 1 and 3 over Mississippi and between April 2 and 4 over Alabama. Maximum amounts for the storm were centered over the Alabama River basin, where an average of 5 in. was received. A point max- imum of 11.03 in. was observed at the Camden 3NW, Ala., station, on April 1-4; 8.06 in. of that fell on the 3d. The Tombigbee and Chickasawhay River basins re- ceived average rainfalls of 3.5 and 4 in., respectively. A generalized isohohyetal analysis for this storm is shown in figure 7. APRIL 8-9 The next period of rain over the region occurred April 8-9, with amounts considerably less than those contrib- uted by the three significant spring storms previously described. On April 6, a Low over the border region of British Columbia and Alberta in western Canada began to move southeastward, and by noon of the 7th it had reached the Dakotas. Once over the Iowa-Nebraska border region, the Low began to curve northeastward. It was over the Iowa-Illinois area on the morning of the 8th and over the Indiana-Ohio area on the evening of the 8th. Then it turned and moved toward New Brunswick. The associated 500-mb trough initially lagged behind 10 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA 87° 86° mars _ TEN NESSEE fx Nex Baran YA s I EXPLANATION . --$§-- Isohyet showing total precipitation, April 1-4, 1979, in inches v --]7-- Supplementary isohyet, in inches "F 29° 0 50 200 MILES (Led _ tta 1 ] rrr TT I 491 I l 50 100 200 300 KILOMETERS FiguRE 7.-Isohyetal analysis of storm rainfall, April 1-4, 1979. the surface Low and was over western Montana and Idaho when the surface Low was already over the Dakotas. But by the morning of the 8th, the upper level trough had caught up with the surface system. Much of the wave undulation of the 500-mb circulation pattern occurred to the north of the region of interest. The 500-mb flow over Mississippi-Alabama was predomi- nantly zonal and was only marginally affected by the passing of the short wave trough early on the morning of the 9th. This situation was in marked contrast to those associated with the three significant earlier storms, when the two- State region was under a pro- nounced 500-mb trough-to- ridge pattern sometime dur- ing the storms. The precipitable water in the southerly airflow over the region at 1200 GMT on April 8 was 1.22 in. and 0.75 in. at Jackson, Miss., and Centreville, Ala., respectively. As the Low turned toward the northeast on the morning of the 8th, the associated cold front moved eastward toward the two-State region. The distance of this sur- face system from the two-State region, the primarily zonal flow aloft over the region, and the lower moisture METEOROLOGICAL SETTING 11 content of the air than in the previous storms resulted in generally lower precipitation amounts. Scattered moderate rain began to fall over the northern two-thirds of the region on the morning of the 8th and continued intermittently throughout the day. At a few stations, the rain extended into the 9th. A maximum of 2.99 in. was observed at the Collinsville 7SE, Miss., station in the Chickasawhay River basin. MAJOR STORM EVENT: APRIL 11-13 The cumulative effect of these antecedent storms was to saturate the soil in the region. Many rivers were at high stages or exceeded bankfull along some sections before the outbreak of the major storm of April 11-13. For example, the Pearl River at Jackson, Miss., was already 10 feet above flood stage before heavy rain began on the 11th. The storm that was the direct cause of the floods on the Pearl and Tombigbee Rivers occurred on April 11-13. Precipitation was heavy through most of the two-State area but was concentrated primarily in the Pearl and Tombigbee River basins. The prolonged, large precipitation event resulted from a large, slow-moving weather system that for a period of several days brought warm, moist air over the Southeastern States. The discussion of meteorological conditions will proceed from the 500-mb to the 850-mb level, and then cover the surface features. 500-MB FEATURES Prior to the storm, on the evening of the 9th, a deep, long wave trough at the 500-mb level became estab- lished over the Western United States. This trough ad- vanced very slowly eastward, and by the morning of the 11th a cutoff Low was located on the Colorado New Mexico border at approximately 104° W (fig. 84). The associated downwind ridge extended southeastward from Michigan through Ohio and West Virginia to the Atlantic coast of North Carolina. This circulation pat- tern placed large portions of the Southeastern United States under a trough-to-ridge pattern and resulted in a southwesterly flow over the two State area. Wind- speeds were about 40 knots over the region, and dew- point depressions at the 500-mb level averaged about 5 degrees. The 500-mb pattern changed very little during the next 12 hours. The center of the cutoff Low moved northeastward to the Kansas-Nebraska border at a speed of only about 10 miles per hour, and the trough now extended southward from this locaton into extreme western Texas (fig. 8B). Over the two- State area, south- westerly winds still prevailed, with some increase in windspeed. The 500-mb Low continued to move north- ward, with very little eastward component. By the morning of the 12th, it was centered in east-central South Dakota (fig. 8C). During the next 12 hours move- ment slowed, and by the evening of the 12th the Low had moved to southern North Dakota (fig. 8D). From the morning of the 13th, the Low progressed slowly to eastern North Dakota, reaching the Minnesota- Manitoba border by the evening of the 13th (figs. 8E, 8F). The very slow progression of the Low and the pre- dominant northward (rather than northeastward) trajectory was matched by a corresponding slow pro- gression of the associated trough. From a position extending from the Kansas-Nebraska border to extreme western Texas on the morning of the 12th, the trough progressed very slowly eastward, reaching the Mississippi-Alabama regon on the night of the 13th. Therefore, the two-State region was under a prolonged 500-mb trough to downwind ridge pattern with a strong southwesterly flow-a most favorable prerequisite for flood-producing storms to develop. 850-MB FEATURES At the 850-mb level, the major feature associated with the deep 500-mb trough was a Low over Wyoming on the evening of the 9th. The Low progressed south- eastward through Colorado and brushed the Texas Pan- handle by the evening of the 10th before slowing down and beginning to turn northeastward. Prior to the storm period, the 850-mb wind over the two-State region was westerly. As the Low approached, the wind direction began to change and became predominantly southerly by the evening of the 10th. By the morning of the 11th, the 850-mb Low was located over the Colorado Kansas border region; it deepened as the circulation pattern over the Southeastern United States became more meri- dional (fig. 9A). Warm, moisture-laden air from the Gulf of Mexico was advected into the region by southerly winds reaching 40 to 45 knots as the 850-mb contour gradient tightened. The 850-mb Low continued to deepen, and by the evening of the 11th, when it was centered over the Kansas-Nebraska border (fig. 9B), its central height was 1,230 meters, a decrease of 110 meters in 2 days. A tongue of warm air extended north- ward from the Gulf of Mexico over the Pearl and Tom- bigbee River basins, with temperatures exceeding 16°C (shaded regon in fig. 9B). Dewpoint depressions in this tongue of warm air ranged between 2 and 6 degrees, in- dicative of the high moisture content. On the evening of the 11th, the 850-mb Low took a mostly northward track, with only limited eastward drift. By the morning of the 12th, the Low was centered over eastern South Dakota (fig. 9C), and 24 hours later it was over the North Dakota-Minnesota border (figs. 9D, 9F). By the evening of the 13th, it was over the Minnesota-Manitoba border (fig. 9F). The strong south- erly flow over the Mississippi-Alabama region persisted 12 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA EXPLANATION --570-- Isobar, in tens of meters L Center of low pressure --5-- Isotherm, in degrees Celsius (°C) H Center of high pressure FIGURE 8.-500-mb analyses. A, 0600 CST, April 11, 1979. B, 1800 CST, April 11, 1979. C, 0600 CST, April 12, 1979. D, 1800 CST, April 12, 1979. E, 0600 CST, April 13, 1979. F, 1800 CST, April 13, 1979. METEOROLOGICAL SETTING 13 EXPLANATION L Center of low pressure --153-- Isobar, in tens of meters H Center of high pressure --10-- Isotherm, in degrees Celsius (°C) % Temperature 16°C or higher FigurE 9.-850-mb analyses. A, 0600 CST, April 11, 1979. B, 1800 CST, April 11, 1979. C, 0600 CST, April 12, 1979. D, 1800 CST, April 12, 1979. E, 0600 CST, April 13, 1979. F, 1800 CST, April 13, 1979. 14 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA from the morning of the 11th until the morning of the 13th, when the circulation pattern began to change sig- nificantly. By the evening of the 13th, the region of int- erest came under a ridge-todownwind trough flow pattern and the 850-mb wind became northwesterly, signifying that the storm had ended. The average precipitable water over the two-State region increased from 0.6 in. on the morning of the 12th to more than 1.4 in. on the morning of the 13th. Then, as northwesterly flow replaced southerly flow, the precipi- table water decreased, to about 0.3 in. on the morning of the 14th. Specifically, the precipitable water in the airflow on the morning of the 13th was 1.47 and 1.55 in. at Jackson and Centreville, respectively. The 1.47 in. at Jackson can be compared with the mean of record there of semimonthly maxima of 1.29 (standard deviation, .21) and a maximum semimonthly value of 1.74. Com- parative statistics for Centreville are not available. The stability condition, as depicted by the daily lifted index analysis, indicated less than +4 (unstable condition) over the two-State region, from the morning of the 11th and throughout the duration of the storm. SURFACE WEATHER FEATURES On the evening of the 9th, the surface Low associated with this system was located over southern Montana, to the lee of the Continental Divide. By the evening of the 10th it had moved southward through Wyoming to eastern Colorado and deepened. The central pressure dropped from 992 to 985 mb. By the morning of the 11th, the Low was located in southeastern Colorado and had a central pressure of 982 mb (fig. 10A). By this time, occlusion of the frontal system had already occurred. The air near the center of the Low became well mixed with the occluded front, extending from the Center of the Low through Colorado, Kansas, and Oklahoma into Texas to the confluence of the warm and cold fronts. The warm front extended eastward through southern Oklahoma, Arkansas, central Mississippi, and south- western Alabama to northern Florida, while the cold front extended through east-central Texas southward into northern Mexico. The warm front, under the in- fluence of the strong southerly flow from the surface to above 500 mb, moved rapidly northward during the day. This was the same warm front that passed through the Red River Valley near the Texas-Oklahoma border region on the afternoon of the 10th, triggering severe thunderstorms and tornadoes that touched down at Veron and Wichita Falls, Tex., causing considerable destruction. The surface Low began a curvature to the northeast and by the evening of the 11th was centered in north-central Kansas (fig. 10B). The occluded front became indistinct near the center of the Low but was clearly defined from north of the Low into south-central Missouri. The cold front extended from this location southward through central Arkansas to eastern Texas. The warm front extended from the confluence of the fronts northeastward through southern Illinois, In- diana, and Ohio to West Virginia. The two-State area now was wholly within the warm sector of this storm and would remain in it until the rain ended with the passage of the cold front some 2 days later. As the cold front was progressing slowly eastward, a squall line had developed in advance of the front in the warm, moist, convectively unstable air in the warm sector. At 1800 CST on the 11th, the squall line extended from the Arkansas-Mississippi border to central Louisiana and was moving very slowly eastward across Tennessee and northern Mississippi and Alabama. Most of the rain during this storm was associated with this and other squall lines that developed in the warm sector of the storm. By the morning of the 12th, the Low had moved to southeastern South Dakota while the associated cold front, after reaching western Mississippi, had become a weak, quasi-stationary front (fig. 10C). Ahead of this front, a major squall line in the warm sector now ex- tended form central-eastern Mississippi to northeastern Alabama and northeastward. The movement of the Low slowed, and it had reached the North Dakota-Minnesota border region by 1800 (fig. 10D). The northern portion of the instability line had moved eastward more rapidly than the southern end during the day on the 12th. By 1800 it was oriented east-northeast to west-southwest from south of McComb, Miss., to just south of Atlanta, Ga. (fig. 10D). An analysis of hourly surface observations at 1500 on April 12 for the region is shown in figure 11. At this time, heavy rain was falling in central-western Alabama. A very inter- esting feature was the presence of a sharp surface trough oriented nearly east-west. The squall line was alined with this deep trough and took on the charac- teristics of a front, acting as a boundary between the warm maritime airmass to the south and the continen- tal airmass to the north. Most of the thunderstorms and rains occurred to the north of the trough as incoming maritime air was lifted along this line of low level convergence. The Low continued a very slow drift northward for the next 24 hours and was over the Minnesota-Canada border by the evening of the 13th (figs. 10, 10F). The two-State region was still in the warm sector of the pri- mary system as a weak Low developed in northern Mis- sissippi by the morning of the 13th and then moved northward along the cold front. The squall line, mean- while, persisted over the two-State region (fig. 10C). The southerly inflow weakened noticeably as the cold front started to sweep past the region. Beginning on the morning of the 13th, the upper air circulation pattern over the Southeastern United States gradually shifted from southwesterly to a more zonal METEOROLOGICAL SETTING 15 front. As the cooler and drier airmass from the interior of the continent replaced the maritime airmass, the 850-mb temperature at Jackson, Miss., decreased (from 16°C to 11°C) and the dew point dropped (from 15°C to 1°C) during the 12-hour period ending at 1800, April 13. At the surface, the cold front had moved across Missis- sippi and northwestern Alabama by then, and a High developed covering an area extending from central Texas to central Mississippi (fig. 10F). Surface winds became predominantly northerly over the Mississippi- Alabama as the storm ended and clear weather returned. SATELLITE IMAGERY A visible imagery photograph from GOES East taken at 0730 CST, April 12, with major features of the sur- face map superimposed, is shown in figure 12. The visi- ble range photograph is the result of reflected sunlight sensed in the 0.55-0.70 um band. Clouds, particularly large cumulonimbus towers with a reflectivity of 92 per- cent, appear very white on such photographs. Water surfaces, which are very poor reflectors, with a reflec- tivity of 9 percent, appear very dark. Between these two extremes are various shades of gray representing differ- ent surface reflectivity characteristics. It is evident that little active weather was associated with the stationary front that extended from Iowa, Illinois, Missouri, and Arkansas southwestward to the Texas coast. Most of the strong convective activity occurred along the squall line ahead of the front in the warm sector. At the time this satellite picture was taken, the very intense major burst of rain around Louisville, Miss., in the Pearl River headwaters was near its end, while heavy rain had just started to fall around Pickensville, Ala., in the Tom- bighbee River headwaters. As the thunderstorm downdrafts were chilled by the evaporation of raindrops and became colder than the environment, the denser and colder airmass gradually spread out from the squall line to form a boundary. Such a boundary could assume the characteristics of a cold front and provide the necessary lifting to a warm, moist, convectively unstable maritime airmass coming in from the Gulf of Mexico. This would lead to conden- sation and continuous replenishment of cloud material and thus would prolong the rainfall. The narrow clear strip just ahead of part of the squall line in figure 12 represents such a boundary created by squall line down- drafts and raindrop evaporation (in this case, the bound- ary was not obscured by higher clouds). Ahead of this major squall line but oriented similarly, in the central Alabama-Georgia region, is a less well-defined clear strip. This represents a secondary squall line whose associated thunderstorm clouds are much thinner than those along the main squall line. Two infrared pictures taken by the GOES East satel- lite are shown in figure 13. Every object having a temperature above absolute zero radiates electromag- netic energy in a spectrum that is a function of its tem- perature. The transfer of infrared radiation in clouds is dominated by water droplet absorption. If the liquid path through a cloud is greater than 30 gm~-~", which is the case for the great majority of clouds except thin cir- rus and clouds with very high base, the cloud is opti- cally thick. The intensity of the emitted radiation will be close to that given by the Planck's law at the cloud top temperature with no contribution from the underlying surface of the earth and internal cloud structure. The in- frared sensor aboard GOES measures the outgoing long wave radiation emitted from the surface of the Earth in a cloud-free area and from the tops of clouds in the at- mospheric transparent window band 10.5-12.6 um. This radiametric information is eventually transmitted to a central facility in Marlow Heights, Md., where it is converted by computer processing into shades of gray. The computer is capable of producing and recognizing 255 distinctive shades between black and white. This is far beyond the ability of human eyes to distinguish and digest properly in an operational environment. There- fore, the infrared image is usually enhanced to facilitate interpretation. In the enhancement process, any shade of gray may be assigned to any temperature when more contrast is needed to highlight a certain temperature range of specific interest. Thus, the enhancement proc- ess increases the contrast between features of interest and their backgrounds. There are different enhancement curves designed for hurricane detection, for viewing convective activity, for determining the extent of ice and snow covers, for viewing coastal upwelling, and so on. The two photos in figure 13 were enhanced accord- ing to the Mb curve, whose specification is listed in "The GOES/SMS User's Guide" (NOAA and NASA, undated). The Mb enhancement gives good definition to the low and middle clouds, but its main purpose is to highlight convective thunderstorms. Cloud-top temperatures between -42° and -52.2°C are shown in light gray, between -53.2 and -58.2°C in dark gray, between -59.2 and -62.2°C in black, between -63.2 and -80.2°C in medium gray, and below -80.2°C (characteristic of overshooting cumulonimbus turrets) in vivid white. The relationship between cloud-top temperature of convective thunderstorms and the amount of precipita- tion is complex and depends on many concurrent meteorological factors. Scofield and Oliver (1977), using the Mb-enhanced GOES infrared images, developed an empirical technique for estimating rainfall from short- lived isolated thunderstorms that produce heavy rain because of large updrafts. For thunderstorms in a satu- rated environment that is stationary over an area for more than 1 hour, as was the case for the storm over Louisville, Miss., on April 12, the rainfall rate will be EXPLANATION Isobar, in millibars Center of low pressure Center of high pressure Cold front Warm front Occluded front Stationary front Squall line £: H ridin -A __... witn my- FIGURE 10.-Surface analyses. A, 0600 CST, April 11, 1979, B, 1800 CST, April 11, 1979. C, 0600 CST, April 12, 1979. D, 1800 CST, April 12, 1979.5, 0600 CST, April 13, 1979. F, 1800 CST, April 13, 1979. greater than that expected from a short-lived storm, and adjustments must be made (Scofield and Oliver, 1980). Qualitatively, an estimate of the amount of convec- tive rainfall depends on cloud-top growth, the existence of any overshooting top cloud, the merge factor, the saturated environment factor, and the observed surface to 500-mb precipitable water. Heavy precipitation is associated with expanding, overshooting cold top, with the merging of cold tops, with persistent white contour over a geographical area, and with high precipitable water content in the atmospheric environment. Each of these empirical factors has its meteorological basis. For example, a convective storm with rapidly expanding cold top indicates strong rising motion and vigorous growth and, consequently, heavy rainfall. Another storm of exactly the same size but with contracting cold top is in a stage of dissipation. Rainfall rates of the two storms could differ by a factor of 20. At 0000 CST on April 12, there were two cumulonim- bus overshootings with cloud-top temperature less than -80°C over the State of Mississippi (fig. 134). A smaller top in the northern part of the State covered areas of Yalobusha and Calhoun Counties. Sarepta 1NNE (34°08' N., 89°17 W.), in Calhoun County, had 2.1 in. of rain during the first hour of April 12. The much more extensive overshooting tops were in north-central Mississippi and covered Winston, Attala, and Holmes Counties and adjacent areas to the north. By 0230 these two tops had merged and expanded northeastward into northwestern Alabama (fig. 13B). At this time, Louisville, Miss. (33°08 N., 89°04" W.), in Winston County had already received 3 in. of rain, while at Pickensville 1E, Ala. (33°14' N., 88°16 W.), rain had just begun to fall. The great expansion of the white top area in the 2%%-hour period indicates vigorous growth of convective storm activity as the Pearl, Noxubee, and Tombigbee River headwaters were inundated with heavy rainfall. PRECIPITATION DISTRIBUTION Rain began to fall over western Mississippi on the evening of the 11th. As warm, moist maritime air con- a t X, j“ —’9,,” csv tvs o - 2 - BNA sym smv §! U; o: ~ o ~ 00 o § # a Ler het 1, % -- / ( 7 & , 4 AHN 0 ANB BHM 132 55 8 "C s to. ** EXPLANATION 1008 --- Isobar, in millibars. Interval 2 mb --- Surface trough T‘— Stationary front For other symbols, refer to specimen station model in daily weather maps published by National Oceanic and Atmospheric Administration FIGURE 11.-Analysis of hourly observations at 1500 CST, April 12, 1979. The deep surface trough extending across the central region of Mississippi and Alabama is a major feature. verged into the warm sector and was lifted, numerous thundershowers occurred in the unstable environment, and some cumulonimbus turrets reached to a height of 15 km along the squall line. By midnight, the rain had extended over central and northern Mississippi. Heavy rains were falling over the headwaters of the Pearl, Nox- ubee, and Tombigbee Rivers, and by the morning of the 12th, rain had spread to adjacent areas of Alabama. The time distribution pattern demonstrates that two differ- ent rainfall intensities existed over the Pearl River head- waters. Starting late on the night of the 11th, and main- ly during the early morning of the 12th, extremely intense rain fall; this was followed by prolonged heavy rain ending early on the morning of the 13th. For exam- ple, Louisville, Miss., in a 31-hour period ending at 0400 on April 13, had a total of 18.7 in. of rain, but 9.1 in. of this fell during a 5-hour period ending at 0600 on the 12th. Over the Tombigbee and Alabama Rivers head- waters farther to the east, rain began and ended later, 'pasodumadns deur 1ayjeam Jo saimmjea; 10few U ms «Jail e 2 O m O sal O & my m a a £ p + p 4 A g c- 3 S m [+n bas fn O _ A Q O p- l GENERAL DESCRIPTION OF FLOODS 19 and differences in the rainfall intensity pattern became less distinguishable. Radar summary maps of the United States east of 100° W. for 0535 and 1435 CST, April 12, are shown in figures 144 and 14B. At 0535 CST, a solid line of echoes in intensity 5, corresponding to a rainfall rate of 4.5- 7.1 in./hour, extended from southeast of Louisville, Miss. (38°08' N., 89°04' W.), through north-central Alabama. This was near the end of the period when tor- rential rain had been falling at Louisville 14SE, Miss. At 1435, a closed area with echo intensity 3, represent- ing a rainfall rate of 1.1-2.2 in./hour, over east-central Mississippi and north-central Alabama corresponded to the area north of the trough line in figure 11 where rain was prevalent. A cumulonimbus tower having a cloud- top height greater than 15 km was located near the maximum precipitation center just to the southeast of Louisville, Miss. As the heavy rain progressed eastward into north- western Alabama, by 0600 CST, April 12, the squall line reached a position extending from northeastern Ala- bama to southwestern Mississippi. By 0800, precipita- tion had reached all of Alabama except the southeast and coastal areas. The headwaters of the Black Warrior, Coosa, and Tallapoosa Rivers in central Alabama had been receiving considerable rain. By late morning, mod- erate rain began to spread over northwestern Georgia. Rawinsonde observations for Jackson, Miss., and Centreville, Ala., for 1800 on April 12 are shown in figures 15A and 15B. The K indices associated with the soundings were 38 and 39 for Jackson and Centreville, respectively, indicating a thunderstorm probability of 80-90 percent. The wind shears through the cloud layer for both soundings were weak, a condition favoring a longer mature stage once a thunderstorm formed. At 1800 on the 12th, storm precipitation had occurred and was near its end at Jackson but was still in progress around Centreville. Most of the rain of the storm fell on the 12th and was a consequence of thundershowers associated with a ma- jor squall line. The rain continued over the entire north- central portion of the two-State region throughout the 12th, with only occasional respite before tapering off. Rain essentially ended in Mississippi by noon of April 13, but continued into the afternoon over some areas of Alabama. Heaviest rain occurred in east-central Missis- sippi near Louisville, Miss., in the headwater region of the Pearl and Noxubee Rivers. Isohyetal analysis of the total storm rainfall is shown in figure 16. The maximum point rainfall of more than 21.5 in. in about 32 hours was located 14 miles east-southeast of Louisville, Miss. Areal average rainfall over the Pearl River headwaters above Carthage amounted to more than 12 in. Louisville itself, which is 80 miles northeast of Jackson, Miss., re- ceived a storm total of 18.7 in. Jackson recorded a storm total of 8.60 in., of which 4.16 in. fell in the 1-hour period ending at 2300 on April 11. The monthly total rainfall of 14.38 in. was 9.73 in. above normal and made April 1979 the wettest April on record for Jackson. To the south of Jackson, the storm rainfall decreased rapidly, dropping to.3 in. about 35 miles southward and to only 0.7 in. at Brookhaven, 52 mi. south by west from Jackson. Very little rain fell over the southern one-third of the Pearl River basin. A secondary precipitation maximum of 17.3 in. was located 1 mile east of Pickensville, Ala., in the headwaters of the Tombigbee River, just across the Mississippi border in central Alabama. The areal aver- age rainfall over the Tombigbee River basin above Liv- ingston exceeded 8 in. It should be pointed out that both the primary and secondary point maxima of 21.6 + in. and 17.3 in. far exceeded the 100-year 4-day rainfall of 13 in. over the region (Miller, 1964). In figure 16, it is seen that the axis joining the primary precipitation center at Louisville 14 SE, Miss., and the secondary center at Pickensville 1E Ala., was nearly zonal and took a direction southwest-northeast. So was the orientation of the area receiving 6 in. or more of rain. This phenomenon could be explained by the fact that during the early morning of the 12th, the very in- tense thunderstorms that brought heavy rain over Louisville, Miss., took a nearly eastward track. Further- more, the instability line over central Mississippi and Alabama, along which the incoming maritime air was lifted and processed into rainfall, was alined along a sur- face trough that had a zonal orientation throughout the late morning and afternoon of the 12th. Selected rainfall mass curves are shown in figure 17. Time distributions of rainfall for the two reported rain- fall maxima at Louisville 14 SE, Miss., and Pickensville 1E, Ala., were estimated using data from the nearest recording gages. Supplementary rainfall data for the storm of April 11-13 are published in table 1 (at end of report) for convenient reference. Later in the month rain fell again, over Mississippi during the period April 21-23 and over Alabama on April 24-26. The area receiving the most rain was the lower Pearl River drainage basin, where very little or no rain fell during the major storm of April 11-13. A max- imum of 6.4 in. was reported at Ruth, Miss., about 65 miles south of Jackson. However, when averaged over the still-flooded areas of the two-State region, less than 2 in. was added. The main effect of this postflood rain was to retard floodwater recession and thus to prolong the period of flooding. The Pearl River at Monticello, Miss., was above flood stage for 27 days during the month of April, returning to its normal channel in early May. GENERAL DESCRIPTION OF FLOODS The area affected by the floods of March-April 1979 in Alabama, Mississippi, and adjacent parts of Georgia and Louisiana is shown in figure 1. Streams throughout the area were high in early March as a result of storms 20 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA FIGURE 134-GOES infrared images enhanced by Mb curve: 0000 CST, April 12, 1979. centered over the Chunky River basin in east-central Mississippi and the Satilpa Creek basin in west-central Alabama. Successive storm periods in March and April over central Alabama and Mississippi increased soil moisture conditions favorable for high runoff yields and culminated in widespread, recordbreaking floods in mid- April. Data at 221 streamflow gaging sites are presented in table 2 (at end of report). The first column in table 2 lists a number assigned to each site, for use only in this report. For convenience, these site numbers are used throughout this report in illustrations, tables, and discussions. Flood data in table 2 are presented in the downstream order used in the annual water-resources data reports. Gaging station records are listed in a downstream direc- tion along the mainstream, and stations on tributaries are listed between stations on the mainstream in the order in which those tributaries enter the mainstream. Stations on tributaries entering above all mainstream GENERAL DESCRIPTION OF FLOODS 21 FicurE 13B-GOES infrared images enhanced by Mb curve: 0230 CST, April 12, 1979. stations are listed before the first mainstream station. Stations on tributaries to tributaries are listed in a simi- lar manner. Each gaging station has been assigned a permanent station number (column 2) conforming to the down- stream order. The 8-digit permanent station number (for example 02441500) includes a 2-digit part number ("02") plus a 6-digit "downstream order number" ("441500"). In this report, the records are listed in downstream order by part. The part number refers to an area whose boundaries coincide with certain natural drainage lines. Records in this report are in Part 2 (South Atlantic slope and Eastern Gulf of Mexico basins) and Part 7 (Lower Mississippi River basin). Datum of gage above National Geodetic Vertical Datum (NGVD) is the elevation of the "zero'' reading of the gage. The location of each gaging station site is shown in figure 18. The site numbers on that map correspond to those in table 2. FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA 22 '6L61 'st tudy 'Lso sert 'g '6161 "st tudy 'Ls9 sge0 'y :'dew Arewrums xepey-p1 sunolg auayd 19mOYSuIe1 _ my Aq umoys Buisearsag -sougy pue atuesop jeuonep Aq poysijgnd sdew mols PUE ISH 98 saut) Aq umoys Buiseaiouj jayjeam Ajlep u: japow uewidads 01 19j31 pljoss: HM“ r 1991 j0 uo dod editon P } \ ---417 $001 sageoiput 1aqwnp Aq umoys sasegq 001 Aq pasn saweu uone»s 01 1331 sogudAs 19naj-a914| | wis xoq yo1em 19u12e9M | _ _ _| 199} 10 Bujuayeam Apuaiedde unojsiapuny] -ma Buisearsop (-) pue 10 mau +ms - $,001 Sozeoipui 1aquunp 'auljiapun Aq umoys sdojp __ ow wojsiapuny} Amgeap +m (+) 'Ausuopur jo aBueyo pue 'sianaj 'adA; uon \ % wuojsiapuny} me _ -eridioaud 'aaquunu 'paads :Bummoys | or 'g-£-]| sonyisugul je 'seaie Oyoy3 V d380H FLOOD DAMAGES 28 | 1 --+ \ \ | % | \ 4 | \ | \ \ | 105 \ \ \ w c e c [.. G 2 3 y ) \ /| < \| Y pl \ ui --- I cs | | > +74 \ \ A u \ ~ Ye o_ h 1 \ \ \ \ \ \ | L.4 \\ 7 \ /\\ o ~40 -30 -20 -10 0 10 20 3 A TEMPERATURE, IN DEGREES CELSIUS (°C) 400 i ¥ 500 | 2 ¥] g | I I 600 \ 2 \ S \ z \ j L g 700 f +7 A % \\ x \ \ A | \ § ...! yo - s 3 \ a_ | \‘ \\\ N ‘J ases * K | \ \ X \ 3 §7 ts .t % O} \ goo) [\ 5 &" X \\\ \\\\‘ \\‘ {x2 { J ‘ 1000 10 o‘ I x ay 3 A \\ 5-50 ~40 -30 -20 -10 0 10 20 30 B TEMPERATURE, IN DEGREES CELSIUS (°C) V Direction and speed of wind. Pennants and barbs on shaft indicate wind speed. Pennants=50 knots, long barb=10 knots, short barb =5 knots. North is at top. Example shown indicates 60-knot northeasterly wind FIGURE 15.-Rawinsonde plot, 1800 CST, April 12, 1979. A, Jackson, Miss. B, Centreville, Ala. MAGNITUDE OF FLOODS Peak discharges at about one-fourth of the stream- flow stations were the greatest recorded since the sta- tions were established. In the Pearl River basin above Jackson, record floods occurred at most gaged sites. Figure 19, which relates flood discharge rates to corre- sponding drainage areas, provides a comparison of flood discharges in 1979 with those of the greatest known floods in the area. Curves A and B (fig. 19), developed by Crippen and Bue (1977), are defined by the greatest known floods through September 1974, in areas above and below the fall line, respectively, in the regions that include the area of this report. The curves provide a guide for estimating potential maximum floodflows. Curve C (fig. 19) is an enveloping curve through the greatest discharge rates during the 1979 floods. The curves indicate that floods generally about one-third greater than those in 1979 may occur in large basins and that floods two or three times greater may occur in small basins. However, the all-season probable max- imum precipitation (PMP) over the central Mississippi- Alabama region is 27 in. in 72 hours over a 5,000-square- mile area (Schreiner and Riedl, 1978). Therefore, poten- tial floods much greater than those observed in April 1979 or those indicated by an envelope curve of historic floods are likely to occur if precipitation is near or equal to the magnitude of the PMP. FLOOD DAMAGES Flood damages provide a measure of the relative mag- nitude of floods. Exact amounts of flood damage for this flood, which extended over a wide area, are not known. Estimates of flood damage were obtained from the U.S. Army Corps of Engineers, Mobile District (19802), and Vicksburg District (1980b). Summaries of estimated damages on main streams and principal tributaries for the floods of March and April 1979 are shown in table 3 (at end of report). In the area of this report, estimated flood damages were $41,916,000 for March 1979 and $344,239,000 for April 1979. During April 1979, 75 percent of the total flood damage occurred in the Pearl River basin, and 65 per- cent of the total damage occurred in Jackson, Miss., and vicinity (Hinds and Rankin Counties). At least nine lives were lost. The Federal Emergency Management Agency re- ported that within the areas declared eligible for Federal disaster relief assistance, 5,549 flood insurance policies were in force in Mississippi, with $130,076,100 of cov- erage, and 1,450 flood insurance policies were in force in Alabama, with $45,853,000 of coverage, prior to the April 1979 flood. 24 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA 90° ' % EXPLANATION -- 4-- _ Isohyet showing total precipitation, April 11-13, 1979, in inches 0 er stea ar t a aa ni [IIX|IIIIT] | 0 I 50 100 200 300 KILOMETERS 50 100 200 MILES ] FIGURE 16.-Isohyetal analysis of storm rainfall, April 11-14, 1979. FLOOD FREQUENCY Frequency of flooding was derived from a statistical evaluation of historical records of floodflows from a net- Knowledge of the magnitude and probable frequency work of streamflow gaging stations distributed of recurrence of floodflows is useful in designing and | throughout the flood area (fig. 18). The techniques gen- locating structures to be situated on the flood plain so erally used to determine flood-frequency relations are as to minimize flood losses and in providing a technical | those described by the U.S. Water Resources Council basis on which to develop criteria for flood-plain | (1977). Recurrence intervals at most sites in Mississippi management. were obtained from flood-frequency relations described 25 'soamo ssew [ TUNOLA Cl Tl Bl CL 90 T I €1 T1¥dVi Cl T1¥dV I 90 O0 S1 CL 90 00 I I I I T €1 T1HdV) 90 00 I I Cl THHUdV I B1 iL 90 090 T T T €1 T1¥dV) | eL 90 90 I T $1 j 90 00 I 90. 00 Bi T I I FLOOD FREQUENCY 'ey 'O41SM weyBuruirg 1 1 1 1 1 'ey 'weq pue 1207 Joie» 1 1 . 1 1 *ssip 'uosepj T 1 1 1 1 'ssip 'uosyoer 1 1 €1 TH¥dVI Zl 1H¥UdV €1 1HdVi Tl T1IMdV 90 00. BL _ _IL 90 T T I I I 'eIVy '3 1 1 1 T 1 T 90 00 sL ZL 90 T T I I [fey 'weq 1aajo esoojeasn| | 1 1 T 1 €1 Cl T1IYdV €1 TI¥UdV) Tl T1IUdV 81 6l 90 _ 90 SL _ ZL 90 00 I T I T T H q tec... 3 '395 1 ailiasino7 1 T 1 1 1 90 00 I T 'ssip 'ajiasino7 T 1 90 I 1 © * ~~ o NI 7W¥INIVH FJAILYINWNJD OL al PL 91 81 OC CC OL Cl 2 9L 81 OT CC SSHON! NI 7V4NIVH FJAILVINWNJ 26 25° 33° o 31 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA 91° 90° 89° 88° MAR‘N Acs (C33 I ) r‘.___-s_l___ L H—_;§_’,!_7J,_ ARK K swumm, o a 7 £ ”x R f REHOUS? west / CAR BATON roUcE. 24 Jt An 2s .. C . fe a I“ Q u\ 4, | | eg _ [* ___ bed 3 s | CyA zz" s bowie 2 C ‘ c y (3s vil 4 wR gensiony, "/; Fy LAKE Cys £ o % # Pon & 3 -G mie | SC | 1% & ) Ck £1 g BENTON - accern I/ ( §./ H \ Q Y isan { e} +1 & I FJT‘nPPAH I‘T‘""‘i § 2 12> 2 MARSHALL | /* A | AC vumm _F-aANI. £7 U TN J' -> \ ofp ; Aege dne c mag's \ Ser o 14051, Ten fiPRENTISSI a '(:R__vh_9 f gib NY . $¥ 5p Cre £ \ al 9 4 j o L fill va \Jf If"/Qt‘*““ efan Ritn/l K . ATs ¢ eX Faz } LAFAYE I> 1 Seme a? ~ gOAHOEwAL +4. {% f he fl? ii | i \\/ “WEWAmiA‘ Af‘k/J—bqrw, “_)_ a J’QUH NF ”TM“, j‘m"jl\#OM/‘TBYGQKL§E\‘I \"/ P JWA‘EJON I 3 |- L g'." 19-1 - 24, g- ALJYALOBUSHA‘ /,"'§7“ L C3 ato 1-777 I | ! afe! l_ ! ~ CALHOUN ehkmstw, f- $9 bh“ A T _c." \ X i [7 [ ] d J ,\_-J !> f c f t 87 LAWRI 192 1 aR E na D a J—“———J“ I A,. | | @apertrp | FLET G=; wesster | (fei aw -~ /e". } 1007. @ f He"! 3&4}; \% s % -_ *y ¢ h t rCARRS‘KLLl x: s= E 1278 ; - _ &=, {okt BEHA LOWN 1s 1 ( § s # ir! T-." Ble 5 fiffiomw #103 I Ede € j P ~ C ,- w - ~A ) A 102 TU y $* * " f 98" Ced oc m eAbiger 1 (3&1an Yage snd .* Ug FAs >-, A 17 1 2164 1b6¢ hed 9 140 m RLE w/ h f 0 .1 J I 99 We“ W 39 Tag -- 1820 0 ®"* iw s 1 3 ag YS =£207® i ea 167 S163 108 110) rou J;~- / x 72 L E {C59 HMBC 0 1844 $99 TL. 1s o n 5 a-- ____'\1 = -- 1474 if aa o a $3 wo 220, 193.195 If I COTT “DALE "T ,H’\9’Ds £1fi j NEWTON‘ E 158 s | * 93) 1188 § 189 , 1550 50- ~ “k J5&-_ RANKlN Ax 16k}: 160 | I *% gy" a_ R sagpen | C RKE & Wie be vans as e mt chuAr—c ‘,,/ [3 Bk 3 2d % sfmpqowlfifl e ‘”7_“__/}_‘,L__, E e ra ( aAa r afa x "- % Crud ~- er (C, Fogx 25af d 1 f (12 hy o Nes *j, {7 L\ X A $ i a { LINEDLN JEFFERSON \ "O) f f w A ¥An : Z ‘LAWRE cer *\ ‘ DAVIS S) 4. 31 Fa e., i w' /: 1 [ FRANKLIN ang . £ L + —-1r—--—-_TL_ i gig L_;~ ) ; J 1s i% e 1; ( % AY \ RANIDOLPH \ % J C 7 * >w0RTHii§ =#.1 [hm/“N; \povengety{ _ {Tjrxf fiifib; --=: | \ I '_“'J; _T (gr—mam»: $ ’4r®c ————————— CQuQmTT )COOK ”kg?“ e J.. wa \ 4 te, 5 || ¥ F ase _x -Os eyi| aia Toral H MAS., i GRADY\ Th E 8“,sz EXPLANATION .84 Flood determination point. Number corresponds to that in table 2. prabata x" mr 0 200 MILES g fare + ire cho of A Aires Lan coiled | 0 I 50 100 200 300 KILOMETERS 27 28 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA 10,000 ---; I TTT f F F3THI FFT] [ITH I $5? 1s * "° A l o =] 0 C \& /, A AAACU’VG C N I tf T FTA ¢ TAH f FASTA pA [ 11 112 o 216 s el JAJ NTL 100 EX PLANATIO N - A - Maximum discharge known in the flood area ® 0 Maximum discharge in April 1979 e181 Number corresponds to flood determination point in table 1 Curve A: Enveloping curve through greatest known discharge rates in area above the fall line through September 1974 (Crippen and Bue, 1977, figure 7) poet eet es Seem tome cf F 1 ii DISCHARGE, IN CUBIC FEET PER SECOND PER SQUARE MILE Curve P 0 I IHIIHI FHF FC ETVIA Curve greatest known discharge rates in area 0 @ below the fall line through September 1974 (Crippen and Bue, 1977, figure 5) greatest discharge rates during flood of April 1979 oe (go B: Enveloping curve through 0 C: Enveloping curve through {3-13 111] y " f f ___ j. _| L1 {111 0.1 1 10 100 1000 10,000 100,000 DRAINAGE AREA, IN SQUARE MILES FIGURE 19.-Comparison of April 1979 peak discharges with maximum known flood peaks in Mississippi and Alabama. by Colson and Hudson (1976), and in Alabama by Olin and Bingham (1977). At sites where the 1979 flood events significantly affected flood-frequency relations, 1979 peak discharges were combined with those of other floods to determine the floodflow potential. Recurrence interval, as applied to flood events, is the average number of years within which a given flood peak will be exceeded once. Frequencies of floodflows may also be stated in terms of their probabilities of oc- currence, which for large floods are virtually the reciprocals of the recurrence intervals. Thus, a flood with a 25-year recurrence interval would have a 4-percent chance of being exceeded in any given year, and a flood with a 100-year recurrence interval would have a 1-percent chance of being exceeded in any given year. Recurrence intervals are average figures-the average number of years that will lapse between occur- rences of floods that exceed a given magnitude. The occurrence of a major flood in one year does not reduce the probability of that flood being exceeded in the next year, or later in the same year. sx In the area of this report, the lengths of available streamflow records generally are adequate to reliably define flood-frequency relations for recurrence intervals of up to 100 years. The 100-year (1-percent chance) flood discharges at most sites are shown in table 2 for com- parison with the discharges of the March-April 1979 floods. The 100-year flood discharge is not shown for sites with less than 10 years of record or for sites on streams materially affected by regulation or diversion. Estimates of 100-year discharges for some streams in small drainage basins were based both on observed peak discharges and on synthetic discharge data generated with a calibrated rainfall-runoff model. Peak discharges based on modeling techniques are identified in table 2 by appropriate footnote. RESERVOIRS Many reservoirs are located on the main stems of the Coosa, Tombigbee, and Alabama Rivers. A summary of stages and contents of selected reservoirs in the Coosa, Tallapoosa, Black, Warrior, Chickasawhay, and Pearl River basins is presented in table 4 (at end of report). Many relatively small Soil Conservation Service flood-control reservoirs are located in the Tombigbee, Pearl, and Black River basins. Emergency spillways of some of these reservoirs were overtopped. The Soil Con- servation Service reports that substantial reductions of peak stages existed in the reaches just below the reser- voirs. Storage in the reservoirs in the Pearl River basin, about 18,000 acre-feet, had little effect on Pearl River at Jackson, which discharged about 250,000 acre-feet per day for several days. MAJOR RIVER BASINS OF EASTERN GULF OF MEXICO 29 100,000 Ia TTT I1 T TIT r L“ Choccolocml) Creek at Jackson Shoals, Ala. CZ Station No. 02404400, Site No. 30 |- co>++Big Canoe Creek at Ashville, Ala. = [- Station No. 02401390, Site No. 24 10,000 I A e l \ Lg ige grea, 484) mi' x (y __ x> TTTH Qaina [ -= J fLKII‘ainage area, (148 mi* I \ Df N] g Note: Site number corresponds to flood determination point in table 2 Too t= 13°11 0100 SOL (OLA T (T (113 1 ca 4 jc l a 152190 4 5 6 7 8s : 9. 10 11 12:13. 14.15 16 APRIL 1979 Ficur® 20.-Discharge at gaging stations in the Coosa River basin in Alabama, April 1-16, 1979. Bluff and Loakfoma Lakes, adjacent lakes in the Nox- ubee National Wildlife Refuge, 38 miles upstream from Macon, Miss., were washed out near the crest of the flood. They are shallow lakes located on the Noxubee River flood plain. Estimated total storage is less than 5,000 acre-feet. Levees surrounding the two lakes developed six crevasses during the flood. Storage in Okatibbee Reservoir on Okatibbee Creek near Meridian, Miss., during both the March and April floods caused substantial reductions in peak stages along Okatibbee Creek and upper Chickasawhay River, according to the U.S. Army Corps of Engineers. Okatib- bee Reservoir crested March 5 at elevation 350.7 feet (table 4), fell to 341.9 feet April 1, and crested again April 15 at 355.2 feet (3.8 feet below the crest of the emergency spillway). The peak inflow of 15,100 ft"s April 13 was reduced to an outflow of 1,240 ft*/s, accord- ing to the U.S. Army Corps of Engineers. The Ross Barnett Reservoir on the Pearl River just upstream from Jackson, Miss., is primarily a water- supply and recreation reservoir with a relatively small capacity for storing floodflows. On April 14, prior to the arrival of the flood crest, the reservoir was drawn down to pool elevation of 296.5 feet. Floodwaters were stored in the reservoir, and on April 16 the pool elevation crested at 299.8 feet. This represented an increase in storage of about 120,000 acre-feet during the passage of the flood wave. T T 1000 DISCHARGE, IN CUBIC FEET PER SECOND T MAJOR RIVER BASINS OF EASTERN GULF OF MEXICO COOSA RIVER BASIN Recurrence intervals of peak discharges in the Coosa River basin in Georgia, upstream from Weiss Reservoir, were in the 10- to 20-year flood range. Little River, just upstream from Weiss Dam in Alabama, had a peak dis- charge slightly less than that of the 100-year flood. Severe flooding occurred along the Coosa River and its tributaries downstream from Weiss Dam near Cen- tre, Ala., to its confluence with the Tallapoosa River near Montgomery, Ala. Along the Coosa River main steam, recurrence intervals of peak flows were approxi- mately 5 years at Gadsden (site 22), 50 years at Chil- dersburg (site 35), and more than 100 years at Jordan Dam (site 48). Tributaries to the Coosa River between Weiss Dam and Jordan Dam near Wetumpka, Ala., recorded peak discharges generally approaching 100-year floods. An exception was Hatchet Creek basin, where peak flows were nearly double those of a 100-year flood. Hydrographs of discharge April 1-16, 1979, at streamflow gaging stations on Big Canoe Creek at Ash- ville, Ala. (site 24), and Choccolocco Creek at Jackson Shoals, Ala. (site 30), are shown in figure 20. TALLAPOOSA RIVER BASIN The flood of April 1979 in the Tallapoosa River basin was characterized by heavy rainfall and high runoff yields. The combination of high antecedent streamflow, saturated soils, and intense rainfall resulted in wide- spread flooding. At the gaging station, Tallapoosa River at Wadley, Ala. (site 57), a new maximum (period 1924-79) occurred on March 4, 1979, and that in turn was exceeded by the April 14, 1979, flood peak. Lesser peaks occurred April 3, 4, and 9. In the Alabama counties of Clay, Randolph, and Tallapoosa, peak discharges were in the 100-year flood range. The high unit runoff in this part (middle third) of the basin is documented at two discontinued gaging sta- tions. Harbuck Creek near Hackneyville, Ala. (site 59), and Hillabee Creek near Hackneyville, Ala. (site 60). Along the main stem Tallapoosa River, the peak dis- charge at Heflin, Ala. (site 51), was that of a 25-year flood, and at Wadley, Ala. (site 57), was greater than the 100-year flood. The peak discharge passing Martin Dam (site 63), 142,000 ft"/s, attenuated to 128,000 ft*s at the gaging station Tallapoosa River below Tallassee, Ala. (site 64), which equaled the February 1961 flood and was exceeded only by the December 1919 flood (the highest since 1886). Hydrographs of discharge of the Tallapoosa River, April 3-22, at gaging stations near Heflin, Ala., and at Wadley, Ala., are shown in figure 21. ALABAMA RIVER BASIN The combined flows of the Coosa and Tallapoosa Rivers resulted in a peak discharge in the 50-year fre- quency range on the Alabama River at Montgomery, 30 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA 100,000 1f\l \Drainage area, ‘mii /°‘ 10,000 / \ (= --> Tallapoosa River at Wadley, Ala. mini?!“ mi* Station No. 02414500, Site No. 57 ! co00 Tallapoosa River near Heflin, Ala. 1 ‘ 1 }‘1 I T 96m T TTM s § 7 § | Led 1/1111 1000 L Station No. 02472000, Site No. 51 DISCHARGE, IN CUBIC FEET PER SECOND Note: Site number corresponds to flood determination point in table 2 1 111‘x‘x‘l151i1l‘1‘xgi J 22 1 1 7 § g Cig on (12 A9 14/156 16 17° 18 10) 20 21 APRIL 1979 100 1 1 1 « <6. 6 to - FicurE 21.-Discharge at gaging stations in the Tallapoosa River basin in Alabama, April 3-22, 1979. Ala. (site 68). The April 1979 peak discharge at the gag- ing station near Montgomery (site 69) was exceeded only by the April 1, 1886, March 3, 1888, and February 26, 1961, floods. The April 1979 flood was the fourth highest flood since 1833. Discharge of the Alabama River was measured near the peak on April 18, 1979, at Selma, Ala. (site 74). The measured discharge (less than the peak discharge) was within 10 percent of the 50-year flood at Selma. This dis- charge was exceeded only by the floods of March 1, 1961, and April 8, 1886. Peak discharge at the most downstream gaging sta- tion at Claiborne, Ala. (site 85), was the fourth highest peak since 1886 and was in the 25-year flood range. In the Cahaba River basin, in central Alabama, flood magnitudes varied widely. Recurrence intervals of peak discharges on Shades Creek, a tributary to the Cahaba River upstream from Centreville, draining part of the urban and industrial areas of Birmingham, ranged from about 10 years in the upstream part of the basin to 100 years downstream from Greenwood in the lower part. Peak discharges on the Cahaba River at Centreville (site 79) and Marion Junction (site 81) were the fourth greatest floods during the period of record (1902-1979) and were in the 25-year flood range. Hydrographs of discharge at gaging stations on the Cahaba River near Cahaba Heights, at Centreville, and near Marion Junction, Ala., were shown in figure 22. TOMBIGBEE RIVER BASIN TOMBIGBEE RIVER UPSTREAM FROM GAINESVILLE, ALA. In the Tombigbee River basin, the greatest rains fell in the middle third. Severe flooding occurred along the Tombigbee River from Columbus, Miss., downstream to the mouth and on tributaries upstream from Choctaw County, Ala. Upstream from Columbus, Miss., flooding was not severe. Tributaries in northern Alabama flow- ing westward into Mississippi, the Buttahatchee River and Luxapallila Creek, experienced only minor flooding in the upstream reaches. Recorded peak discharges on the Buttahatchee River were in the 2-year frequency range. In the adjacent basin to the south, Luxapallila Creek, a major left-bank tributary of the Tombigbee River at Columbus, Miss., had a peak flow of 40,400 ft*s, with a recurrence inter- val greater than 50 years at the gaging station near Columbus (site 96). Yellow Creek, which flows into Luxapallila Creek just downstream from the Steens, Miss., gaging station contributed substantially to the floodflow. Along the main stem Tombigbee River, peak dis- charges upstream from Cochrane, Ala., were in the 10-year range. In contrast, the peak discharge at Gainesville, Ala., augmented by inflow between Cochrane and Gainesville, exceeded that of a 100-year flood and was the greatest known since at least 1892. Tributary inflow between Cochrane and Gainesville was documented at two gaging stations-Sipsey River near Elrod, Ala. (site 101), and Noxubee River near Geiger, Ala. (site 109). 100,000 (- T T T T T T T T T T T 3 50,000 |- w | 3 [ / \%inage‘area, 1768 mi2 | o + - Z o L- al s ws (5 10,000 |- 2 & E Px \\ 4 | sot m £ H 5000 - \ \ Drainage area, 1029 mi*- L. L. \\\ o o E- -- - ad D-, [r- __] o - = 4 (“5 1000 > \ § E - Drainage area, 201 mi - A [.. =I ia A. # a |- mm | Too lt _L £ -L L s L OE c _L (ean -ed -L 10. 11 A2 19 14 45. 16 17 ~18 19 20 21 '92 APRIL 1979 Cahaba River near Marion Jt., Ala. Station No. 02425000, Site No. 81 - Cahaba River at Centreville, Ala. Station No. 02424000, Site No. 79 o>>>> Cahaba River near Cahaba Heights, Ala. Station No. 02423425, Site No. 75 Note: Site number corresponds to flood determination point in table 2 Ficur® 22.-Discharge at gaging stations in the Cahaba River basin in Alabama, April 10-22, 1979. MAJOR RIVER BASINS OF EASTERN GULF OF MEXICO 31 $000,000° 1 -t- 1-1: I ft -E t 1T -T- } fT t --- Noxubee River at Macon, Miss., Station No. 02448000, Site No. 107 ------------ Noxubee River near Geiger, Ala., C- Station No. 02448500, Site No. 109 Sucarnoochee River at Livingston, Ala., Station No. 02467500, Site No. 148 I $1.00 40A 100,000 {A- Drainage area, 768 miq'; \ \\ *_Drainage area, \ = 1410 mi? | 10,000 #T Ax I TTT DISCHARGE, IN CUBIC FEET PER SECOND 1000 |- af ~a (3 Note: Site number corresponds to flood # as determination point in table 2 =I {Tr -L f- _L {l- A ad j. . J 1 4 4. 4 100 2 5 10 15 20 23 APRIL 1979 FicurE 23.-Discharge at gaging stations on the Noxubee River at Macon, Miss., and near Geiger, Ala., and on the Sucarnoochee River at Livingston, Ala., April 2-23, 1979. Sipsey River, located between the Tombigbee and Black Warrior Rivers, flows southwestward to the Tom- bigbee River. The peak discharge of the Sipsey River at the gaging station near Elrod (site 101) was the second highest known flood since 1900 and was exceeded only by the flood of February 23, 1961. The recurrence inter- val of the peak discharge April 13, 1979, was about 25 years. Noxubee River, which flows southeastward from Mississippi to its confluence with the Tombigbee River in Alabama, experienced the heaviest rainfall of the storm, over most of its drainage area. At the gaging sta- tion at Macon, Miss. (site 107), the stream reached a stage of 38.97 feet (discharge 125,000 ft/s), which is 6 feet higher than the flood of March 1951, the previous maximum of record. At Geiger, Ala. (site 109), near the mouth, the runoff resulted in a peak discharge more than four times the maximum known flood and more than double that of a 100-year flood. Tributaries to the Noxubee River had lesser floods, with peak discharges having recurrence intervals generally ranging from 20 to 100 years. Hydrographs of discharge for the period April 2-23, 1979, at gaging stations on the Noxubee River at Macon, Miss., and Geiger, Ala., and on the Sucarnoo chee River at Livingston, are shown in figure 23. TOMBIGBEE RIVER DOWNSTREAM FROM GAINESVILLE, ALA. In the reach of the Tombigbee River between Gaines- ville and Demopolis, Ala., the flood was the highest known at Epes, Ala. (site 115), since 1892. The Black Warrior River flows into the Tombigbee River just upstream from Demopolis. The combined flow of the Tombigbee and Black Warrior Rivers produced the maximum known flood since 1874, and probably since 1812, on the Tombigbee River at Demopolis lock and dam gaging station (site 143) (fig. 24). The April 1979 peak discharge at Demopolis exceeded that of a 100-year flood by nearly a third. The lower half of the Black Warrior River basin re- ceived the heaviest rainfall, and severe flooding oc- curred along the Black Warrior River and its tribu- taries. In the Tuscaloosa-Oliver lock and dam area at Northport, Ala. (site 138), the flood on Black Warrior River was the greatest since 1900 and the peak dis- charge (272,000 ft*/s) exceeded that of the 100-year flood by 9 percent. Peak discharges on tributaries of the Black Warrior River approached those of a 100-year flood. Hydrographs of discharge of Valley Creek, April 2-21, 1979, near Bessemer (site 128) and near Oak Grove, Ala. (site 129), are shown in figure 25. Hydrographs of discharge of North River near Samantha, Ala. (site 137), and Black Warrior River at Northport, Ala. (site 138), for the period April 12-21, 1979, are shown in figure 26. The flood on the Tombigbee River from Demopolis downstream to Coffeeville, Ala., was the greatest known since 1874 and exceeded the 100-year flood dis- charge at Demopolis (site 143) and at Coffeeville, Ala. (site 151). Sucarnoochee River, a large right-bank tribu- tary flowing into the Tombigbee River near Demopolis, Ala., had peak discharges with recurrence intervals greater than 100 years at all gaged sites downstream from State Highway 16 near Dekalb, Miss. The April 1979 peak flow of the Sucarnoochee River at Livingston, Ala. (site 148), was nearly double that of the maximum known flood (1939-79) in February 1961 and a third greater than the 100-year flood discharge. A hydrograph of the discharge of the Sucarnoochee River at Livingston, Ala., is shown in figure 23. Pawticfaw and Ponta Creeks, right bank tributaries to Sucar- noochee Creek, had peak discharges with recurrence intervals in excess of 100 years at their crossings of U.S. Highway 45 (sites 146 and 147, respectively). FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA 32 argopy 'sreaum3u;g ;o sdio; Auury Jo 4saqmod ydeiSoj0ug '6161 '61 "ery 'sodowag 12 10ary JO MAJOR RIVER BASINS OF EASTERN GULF OF MEXICO 38 100,000 I’{‘1{IIII[ (] *--» Valley Creek near Oak Grove, Ala. (- Station No. 02462000, Site No. 129 |- o-o-o Valley Creek near Bessemer, Ala. Station No. 02461500, Site No. 128 o Note: Site number corresponds to flood determinatipn poiht in table 2 10,000 £- 113 T7 A =a {SJA | Drainage area, 145 mi? =. 1000 |- \\\P/ 1 \ DISCHARGE, IN CUBIC FEET PER SECOND I LL! FT] - | * Drainage area, 51 mi? 100 1! 12-43 -14 15 a46 17 18": 19 20-21 APRIL 1979 FiGurE 25.-Discharge at gaging stations on Valley Creek in the Black Warrior River basin in Alabama, April 2-21, 1979. PASCAGOULA RIVER BASIN In the Pascagoula River basin the March floods gen- erally were greater than those in April. The heaviest rains, March 3-4, were centered over the upstream part of the Chickasawhay River. The peak discharge of Chunky Creek, head of Chickasawhay River, March 4, near Chunky, Miss. (site 156), was the greatest since records began in 1939, exceeding the 100-year flood discharge. The stage of the flood on Sowashee Creek at Meridian, Miss. (site 158), on April 13 was the highest since records began in 1939, but it was only 0.8 foot higher than that reached on March 4. The March 5 flood on Chickasawhay River at Enterprise, Miss. (site 160), was a foot lower than the previous maximum (since 1900) flood in 1961 and was equaled a few weeks later, April 14. PEARL RIVER BASIN Pearl River is formed by the confluence of Tallahaga, Nanih Waiya, and Bogue Chitto Creeks about 10 miles - east of Philadelphia, Miss. Recurrence intervals of peak discharges on most streams in the northern and eastern parts of the basin were much greater than 100 years. Exceptions were Tuscolameta Creek and eastern tribu- taries downstream from Tuscolameta Creek, where flood peaks generally had recurrence intervals of less than 10 years. Floods on Pearl River at all gaged sites from Burn- side, Miss. (site 169), downstream to Jackson (site 194) were the greatest known since at least 1874. Recurrence intervals of peak discharges near Monticello (site 196), and Columbia, Miss. (site 197), and near Bogalusa, La. (site 198), were equal to or greater than 100 years, although the April 1979 flood may not have exceeded the great flood of 1874. On Lobutcha Creek and Yockanookany River, right- bank tributaries to the Pearl River upstream and down- stream, respectively, from Carthage, Miss., (site 178), peak flows were two to three times those of a 100-year flood. The three gaging stations that measure most of the in- flow into Ross Barnett Reservoir immediately upstream from Jackson-Pearl River at Carthage (site 178), 34 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA 1,000,000 - ; Drainage area, 4828 mi U Drainage Tea, 219 mi? y z 100,000 f T g HL 3.11 4 | fix } | 10,000 {iu 1 1 1 J DISCHARGE, IN CUBIC FEET PER SECOND 1000 |- \5\ E, #. E ”\D\( +-»-* Black Warrior River at Northport, Ala. Po Station No. 02465000, Site No. 138 o-o-o North River near Samantha, Ala. Station No. 02464000, Site No. 137 Note: Site number corresponds to flood de- 1 Ijlllll } termination point in table 2 y | I i | | | | | | | | 12 13 14 15 16. 17 -18 - 19 20 . 21 APRIL 1979 100 Ficur® 26.-Discharge at gaging stations on North River and Black Warrior River in Alabama, April 2-21, 1979. Yockanookany River near Ofahoma (site 184), and Tusco- lameta Creek at Walnut Grove (site 179), had peak discharges of 102,000 ft*s, 46,500 ft's, and 23,600 ft's, respectively. A near-peak discharge of 143,000 ft's was measured in Ross Barnett Reservoir at State Highway 43 about 10 miles upstream from the Ross Barnett Reservoir dam. A peak discharge of 145,000 ft's in the vicinity of Jackson, representing natural flow of the Pearl River without the effects of storage in Ross Barnett Reservoir, was estimated on the basis of reservoir inflow and discharge measurements made at State Highway 43 and at the gage at U.S. Highway 80. The exceedance probability of a peak discharge of 145,000 ft/s estimated from a frequency relation based on the period of known floods, 1874-1980, is about 0.2 percent-equivalent to an average recurrence interval of about 500 years. The peak flow at the gaging station at U.S. Highway 80 (site 194) in Jackson, based on a series of discharge measurements, attenuated to 128,000 ft's on April 17, 1979. Hydro graphs of discharge at gaging stations on Pearl River, Tuscolameta Creek, and Yockanookany River are shown in figure 27. The Pearl River at Jackson, Miss. (site 194), crested at 43.28 feet April 17, nearly 6 feet higher than the previous record stage of 37.5 feet in 1902. The 43.28-foot stage resulted in extensive flooding along the Pearl River and its tributaries in Jackson, Miss., and vicinity, both in the business district and in residential areas (figs. 28 to 31). At Monticello, Miss. (site 196), the Pearl River crested on April 20 with a peak discharge of 122,000 ft'/s at a stage of 34.08 feet, a foot higher than the flood of April 1902. At Columbia, Miss. (site 197), the Pearl River crested with a discharge of 120,000 ft"s at a stage of 27.8 feet, nearly as high as that of a flood in 1900 but 1 to 3 feet lower than the extreme flood of 1874. Water- surface differentials of 4 feet developed between the up- stream and downstream sides of the U.S. Highway 98 crossing of the east flood plain at Columbia, and the highway embankment was cut in two places by the floodflow. The Pearl River at Bogalusa, La. (site 198), crested April 24 at a stage of 23.2 feet and a discharge of 129,000 ft's. The increase in discharge between Co- lumbia and Bogalusa resulted from moderately heavy rain in the vicinity (3.41 in. at Bogalusa) April 21-23. The flood at Bugalusa exceeded the previous maximum (records since 1938) of April 17, 1974, by 1.1 feet. 1,000,000:II|I|lIIH|l||'||l|||||||||II|\UlllllIII||IIIII||VHI|IIIIIIE |- -- - Tuscolameta Creek at Walnut Grove, Miss., 500,000 |- Station No. 02483000, Site No. 179 ---------- Yockanookany River near Ofahoma, Miss., Station No. 02484500, Site No. 184 Pearl River near Carthage, Miss., Station No. 02482550, Site No. 178 127 lll| dl 100,000 |-- -- Pearl River at Jackson, Miss., E Station No. 02486000, Site No. 194 [ 50,000 |- Note: Site number corresponds ~~~ _ to flood determination point |(I| o Z O O LLJ (O CC LJ o. J- 6 \ in table 2 Io \ a A ' [2] | 9 10,000 -f § 3 s000 -~ \\ 2 -1 \ IJJ —d ll‘. e \ 2 CC \ 4 1000 |- 5 E 5° soof _ ~ \A 5 ® 100 IIIIIIIIIIIIIIIIIIHIIIIIIHH IIllIIIIHHIIIIIIHIIIIIIIL a 10 20 30 10 20 30 MARCH 1979 Ficur® 27.-Discharge at gaging stations in the Pearl River basin at and upstream from Jackson, Miss., March 2 to April 28, 1979. APRIL 1979 35 MAJOR RIVER BASINS OF EASTERN GULF OF MEXICO '40L98sI( arqojy 'seoutgu; ;o sdio;p Auury gp Jo 4Asaqinoo yde1soj0uq '6161 '91 judy "sstpy 'uosyoep Jo qred wayiou ut yaa1q ssopy SuSuep1 Suore eare popooy; ut quatudofamap Sutsnop; -'8Z THNOI FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA yde1Soj0uq '6L61 '91 Iudy © arqgopyt Jo 'g' Jo 4saqin0o 'sstpy 'uosyoep Jo qred ut peoy { JO Ajrutota ay ut eare feruoptsai1 pagepunuy - '6z aunoly 37 MAJOR RIVER BASINS OF EASTERN GULF OF MEXICO 4ou9sI( oiigopy jo sdao;y Auury 'g' Jo 4saqinoo ydeaS0j0ug '6161 '91 [Udy 'moff1940 19Aty Lreaq 4q paepunut "sstpy © uosyoe p Jo joLuystp ssauisng-'0€ HHNOD1A FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA 38 argo, Jo sdiop 4uuy 'g' Jo yde1S0j0uq '6L61 '91 [GV 'POOJJ 19AIY [rea JO 189.10 xeau "sstpy 'uosyoep Aq pasojpus spuno8.te} papoo[[-'Tg FLOOD-CREST STAGES 39 1,000,000 HET E ETT TT tit t f 1 fa -t- 11 13 Pearl River near Bogalusa, La., in Station No. 02489500, Site No. 198 #: --- Pearl River near Monticello, Miss., = Station No. 02488500, Site No. 196 " I 100,000 (CT T HIH x 2\_ \_ Drainage area, 6630 mi 10,000 RZ - Lt f 1103 Note: Site number corresponds to flood determina- tion point in table 2 i DISCHARGE, IN CUBIC FEET PER SECOND $2 3C A1 _L CA- AAL T 3 11-13. 1A JLL L_LJ_L _| 5 10 15 20 25 30 APRIL 1979 1000 1 FiGuRE 32.-Discharge at gaging stations at Pearl River near Monti- cello, Miss., and near Bogalusa, La., April 1-30, 1979. Hydrographs of discharge of the Pearl River, April 1-30, 1979, at gaging stations near Monticello, Miss. (site 196), and Bogalusa, La. (site 198), are shown in fig- ure 32. A discharge of 155,000 ft*s was measured at the Interstate 59 crossing of Pearl River near Pearl River, La. (site 199), on April 26 near the crest. A discharge of 152,000 ft'/s was measured at the Interstate 10 crossing of Pearl River near Slidell, La. (site 200), on April 26. LOWER MISSISSIPPI RIVER BASIN BIG BLACK RIVER BASIN The major flood along the Big Black River, which flows into the Mississippi River about 25 miles down- stream from Vicksburg, Miss., occurred April 12-16, 1979. Runoff from tributaries in the central part of the basin contributed substantially to the flood. Extreme floods occurred on medium-sized tributaries draining up to 160 square miles. Zilpha Creek near Kosciusko (site 204) had a peak discharge approaching that of a 100-year flood, and Doaks Creek near Canton, Miss. (site 210), had a peak flow more than twice that of a 100-year flood. Major floods occurred also on Long Creek near Kosciusko (site 207) and Bear Creek near Canton, Miss. (site 213). Recurrence intervals of peak flows on the main stem of Big Black River ranged from about 25 years at the gaging staton at West, Miss. (site 205), to more than 100 years downstream near Bovina, Miss. (site 219). Big Black River at West (site 205) crested at a stage of 24.27 feet (discharge 48,000 ft/s). Big Black River at Pickens (site 208) crested at a stage of 23.6 feet and at State Highway 16 near Canton (site 211) crested at an elevation of 193.22 feet (discharge 85,800 ft"s). The increase in flood magnitude resulted from extreme trib- utary inflow from Big Cypress and Doaks Creeks be- tween Pickens and Canton. At the U.S. Highway 80 gage near Bovina, Miss. (site 219), Big Black River crested at 40.56 feet (discharge 81,200 ft/s), the great- est flood since at least 1912. Hydrographs of discharge of the Big Black River, April 1-30, 1979, at gaging stations near West (site 205) and Bovina, Miss. (site 219), are shown in figure 33. FLOOD-CREST STAGES Flood-crest elevations at many ungaged points along streams were obtained by leveling to floodmarks iden- tified during or immediately following the floods. Flood- crest stages provide a means to determine the extent of overflows and are useful in land-use management of flood-plain lands. Both the U.S. Geological Survey and the U.S. Army Corps of Engineers (Mobilé and Vicksburg Districts) participated in flagging the floodmarks. Most of the elevations were determined by the Corps of Engineers. Records of flood-crest stages in the Mobile, Pasca- goula, Pearl, and Big Black River basins are presented in table 5 (at end of report). Data on both main-stem streams and several tributaries are included. Points of measurement are referred to distance in miles upstream from the mouth of the stream. River mileage was determined by the U.S. Army Corps of Engineers (1972) unless otherwise noted. Flood-crest 100,000 firm- {/ % T TTM] Drainage area, 2810 mi pL 14 T *% \\ im I | 10,000 Drainage area, 985 mi? \ E DISCHARGE, IN CUBIC FEET PER SECOND 1000 |- prams - m Big Black River near West, Miss., X [ Station No. 07289350, Site No. 205 ig I -- -- Big Black River near Bovina, Miss., 3 Station No. 07290000, Site No. 219 Note: Site number corresponds to flood g determination point in table 2 10011111Illlllllllllllllllllllil 1 5 10 15 20 25 30 APRIL 1979 FicurE 33.-Discharge at gaging stations on Big Black River at West, Miss., and near Bovina, Miss., April 1-30, 1979. 40 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA sem. 19 1 I | 1 | | 1 280 % [~ > o 55g > 9 JMM-k a $3.ng 260 CZ) | C f 8s -I ® W, D _. a / ey % 240 cc f So ~ B ip |- / ks. ~ > sol- 3 7 Co gp 220 8 C o |- /5’! \ 322 24 i w \ he ea a / j & lid (e] A O Me 7 l Is: F x \ KER z aise f mes. _|_ a Li * ag- o s Mes --- 180 ° u; [LE / e* T s. eeg Ve/Oclt a“ W . :| z. |- / velocity" ~~==~.., 'I 5 - 2 if} M > g 4 Z \ i 3x h 160 (E + xix = O 6 A % T a2 |- g 3 \- 140 i- A L > Ls A g / 40 __. 7 120 9 331 / / 4 2% L 38g! - -- | 4 1090 § | z / wage. | | | | | | | | 36 -- 80 & 8 13 14 15 16 17 18 19 20 APRIL 1979 FIGURE 34.-Changes in point velocity, mean velocity, stage, and discharge of Alabama River near Montgomery, Ala., April 13-20, 1979. Meter location for point velocity is at stage 15.0 ft, 25 ft above streambed at upstream side of the center bridge pier on U.S. Highway 31. elevations are water-surface elevations in feet above National Geodetic Vertical Datum of 1929 (NGVD of 1929). Flood-crest elevations at U.S. Geological Survey gaged sites may be determined from Table 2, "Sum- mary of Flood Stages and Discharges" by adding the gage height of the flood to the datum of the gage (NGVD of 1929), where the datum is known. Additional records of flood-crest stages and other de- tailed information may be obtained from the U.S. Corps of Engineers and the U.S. Geological Survey. STREAMFLOW VELOCITIES VELOCITY CHANGES DURING PEAK DISCHARGES Velocity changes with respect to time and stage dur- ing the passage of a flood wave are of great interest to hydrologists. The gaging station, Alabama River near Montgomery, Ala. (site 69), records a point velocity that has been calibrated to the mean velocity in the cross sec- tion at the gage (table 6) (at end of report). The relations of point velocity, mean velocity, stage, and discharge, to time every 6 hours for the period April 13-20, 1979, are shown in figure 34. VELOCITY DISTRIBUTION THROUGH BRIDGE OPENINGS Velocity distribution through channel constrictions during peak flows is of great interest to designers of bridges, culverts, and other hydraulic structures. The distribution of velocities is an integral part of a velocity- meter discharge measurement of flow. Stream velocities obtained at or near the crest of the floods exceeded 10 feet per second at some sites. Velocities at bridges were far from uniform, varying greatly both in vertical and horizontal directions. Max- imum velocities were 1 1/2 to 2 times the average veloci- ties at the bridge openings. Variations were related to bridge and channel geometry and to the extent of chan- nel (or flood plain) contraction at the bridge. Velocity distribution diagrams are shown for nine se- lected bridges, five in Alabama and four in Mississippi FLOOD HYDROGRAPH DATA 41 a o o o —,Sur1v"ace gr ot‘zher 'obse;‘vatiron .00} _ A 0.2 observation oo [ __ A 0.6 observation *""[ - 80.8 observation .00 - .oo} G .oo}. woo s "*, T1 j A, poles fei o ©:-0 6 o 6 VELOCITY, IN FEET PER SECOND o ie n c A a o_ w c w L deena NENE t r t u r u t 150.0 © Ground surface elevation a a 0 o aper- 130.0 a ho o o 110.0} r o o o GEODETIC VERTICAL DATUM 90.0} ELEVATION, IN FEET ABOVE NATIONAL 80'00 200 400 0 800 1000 1200 60 DISTANCE FROM LEFT ABUTMENT, IN FEET FIGURE 35.-Velocity distribution and cross section: Alabama River at U.S. Highway 31 north, near Montgomery, Ala., April 15, 1979. Water-surface elevation, 151.50 ft; total discharge, 261,000 ft's. (figs. 35-43). The velocity diagrams for the highly con- tracted bridges (Hashuqua and Zilpha Creeks and Nox- ubee River in Mississippi) show higher velocities in the overflow areas (on the flood plain) than in the channels. Moderately contracted bridges (Noxubee, Tombigbee, and Alabama Rivers in Alabama) show fairly high velocities near one abutment but not as great as those in the channels. Velocities near the abutment are low on Mulberry Creek and North River in Alabama. FLOOD HYDROGRAPH DATA Gage height, discharge, and accumulated runoff at se- lected times during the flood at 47 gaging stations in Alabama, Mississippi, and Louisiana are shown in table 7 (at end of report). The period begins prior to the major rise and extends to the end of the gaged record or to an arbitrary cutoff point on the recession, when the dis- charge approaches that of the antecedent flow. The period for some gaging stations starts March 1, 1979, to define flow conditions prior to the floods of March 1979, whose peak flows exceeded those in April 1979 at some stations. The intervals selected for presenting momen- tary stage and discharge information provide sufficient detail to define the flood hydrograph. Runoff in inches shows the depth to which the drainage basin would be a o .00 § .oo} .oo} .oo} .oo} .oo .oo} .00 .00 - .00 00 R 1 a R al A0.2 observation 80.8 observation REE VELOCITY, IN FEET PER SECOND Hon u A a o ~ co w a $... o 190.0 r r t r r ~ t r i 9 Ground surface elevation 185.0} 180.0 a be on o 170.0} - o &n o GEODETIC VERTICAL DATUM 160.0} ELEVATION, IN FEET ABOVE NATIONAL i i i il 155.00 & 5b 150 200 250 100 DISTANCE FROM LEFT ABUTMENT, IN FEET FIGURE 36.-Velocity distribution and cross section: Mulberry Creek at highway bridge at Jones, Ala., April 14, 1979. Water-surface elevation, 186.35 ft; total discharge, 15,600 ft's. ome mere seme oppo mormon porne nar m ca 11.00 .(10C A0.2 observation 4 F A0.6 observation 00} 80.8 observation oo} .oo oof .oo} .oo oo} .oo 'OO:_L.LA......T,4. 100. 98. 96.0} 94.0} 92. 90.0} 88 86.0} 84 82.0} so. D e VELOCITY, IN FEET PER SECON =] o eam em e amer mnm cng © Ground surface elevation GEODETIC VERTICAL DATUM ELEVATION, IN FEET ABOVE NATIONAL o ooo o e- ooo oe o r-r u -r o Keese. oot ule 524 . 8 400 coot aleve ie ite tiate cs 3004, 20 40 60 B0 i106 i120 ido iso i8o 200 220 240 260 DISTANCE FROM LEFT ABUTMENT, IN FEET FiGURE 37.-Velocity distribution and cross section: Hashuqua Creek near Macon, Miss., April 12, 1979. Gage height, 97.85 ft; total discharge, 13,900 ft's. 42 FLOODS OF APRIL 1979. MISSISSIPPI. ALABAMA, AND GEORGIA 10.00 t r t r t r r r r u - A 0.2 observation 4 A 0.6 observation 4 0.8 observation VELOCITY, IN FEET PER SECOND a o o 180.0 u r t r u r t r u r o Ground surface elevation # a i o s 0 o o o a on 0 o ELEVATION, IN FEET ABOVE ASSUMED VERTICAL DATUM ra o 00 00 f 00 } A0.2 observation A0.6 observation 80.8 observation 140'00 f 260 g 460 600 800 1000 DISTANCE FROM LEFT ABUTMENT, IN FEET FiGURE 38.-Velocity distribution and cross section: Noxubee River at U.S. Highway 45 bypass near Macon, Miss., April 14, 1979. Water-surface elevation, 36.25 ft; main channel discharge, 69,400 ft''s; total discharge, 81,700 ft's. covered if all the runoff during a given period were uni- formly distributed. The runoff for the March or April storm can be roughly approximated by subtracting the accumulated runoff at the beginning of the flood from the runoff at the end of the flood period. GROUND-WATER FLUCTUATIONS Descriptions of selected ground-water observation wells influenced by the storm of April 1979 are shown in table 8 (at end of report). These wells tap unconsolidated aquifers of Late Cretaceous and Quaternary age in the Black Warrior and Tombigbee River basins and consol- idated aquifers of Late Cambrian, Early Ordovician, and Early Mississippian ages and metamorphic rocks in the Coosa and Tallapoosa basins. The water-level fluctuations, shown on the hydro- graph of well 1 W (fig. 44) and other wells, during the storm of April 1979 were influenced by local precipita- tion and direct infiltration and loading effects from nearby streams. An absence of rises in the water levels in wells 3W and 5W until several days after the storm may indicate a lag in recharge to the aquifer from the outcrop area to the vicinity of the wells. The variations in water level in these observation wells are shown in table 8. oo} | 00: - oo} .oo} woof .oo .00 .00 VELOCITY, IN FEET PER SECOND mo m co A on o w co to ++ o 135.0 r - t t r r t l t r © Ground surface elevation r ho &n o v- er &n o 105.0f GEODETIC VERTICAL DATUM w &n o ELEVATION, IN FEET ABOVE NATIONAL $>: Yo 2000 3000 1000 5000 DISTANCE FROM LEFT ABUTMENT, IN FEET 6000 FicurE 39.-Velocity distribution and cross section: Noxubee River at State Highway 17 near Geiger. Ala., April 15, 1979. Water- surface elevation, 133.62 ft; total discharge, 125,000 ft's. 10.00 --- .oo} A0.2 observation - a 0.8 observation o o v Jie ca png 0 ues VELOCITY, IN FEET PER SECOND p e om tm A in o ow & w o 6 2 MMM at fop mmm -or cnr erige cog aran rege cognomen vag ming mg tcc cn cor a Ground surface elevation 1 a o 0 o 90.0 } GEODETIC VERTICAL DATUM L \ aP { ELEVATION, IN FEET ABOVE NATIONAL 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 DISTANCE FROM LEFT ABUTMENT, IN FEET 50.0 FicurE 40.-Velocity distribution and cross section: Tombigbee River at Gainesville, Ala. (main channel), April 15, 1979. Water- surface elevation, 113.88 ft; total discharge, 124,000 ft's. GROUND-WATER FLUCTUATIONS 43 r 0 o o us r .00: A0.2 observation F A0.6 observation 00 [- 80.8 observation 00 F .oo} .00: .oo} .005 st _ {|| 265.0 t r t t t r r v r t t VELOCITY, IN FEET PER SECOND Ld bo to 4s &n o ~ co wo o a Ground surface elevation 260.0 ¢ 255.0} ho on 0 o ba ro J & o &n o o GEODETIC VERTICAL DATUM 235.0} ELEVATION, IN FEET ABOVE NATIONAL 0 $ 100 150 200 250 DISTANCE FROM LEFT ABUTMENT, IN FEET FIGURE 41.-Velocity distribution and cross section: North River near Samantha, Ala., April 13, 1979. Water-surface elevation, 262.84 ft; total discharge, 18,500 ft's. Water-level fluctuations in observation wells near the Tombigbee River were influenced primarily by the stage of the river during the flood, and this influence de- creased with distance from the river. The rise in water levels in response to high river stages and to local pre- cipitation during the flood and resultant recharge to the adjacent alluvial deposits of Quaternary age is shown on the hydrograph for observation well 15W (fig. 45). The decline of water levels March 5 to April 1, and April 13-30, resulted from water draining from the alluvial deposits subsequent to lowering of the stage of the river. The water levels in observation wells tapping the Eutaw Formation of Late Cretaceous age near the Tom- bigbee River were influenced during the flood in part by direct infiltration from the river to the aquifer, in part by recharge on outcrop areas, and in part by loading ef- fects from high river stages. Wells 8W, W, 11W, and 12W, which tap the Eutaw Formation, are separated from the river by the relatively impermeable Mooreville Chalk of Late Cretaceous age, suggesting that the fluc- tuations shown on the hydrographs are caused prin- cipally by loading effects from an increase in the volume of water in the river and in the adjoining alluvial deposits. r- o - Surface or other observation 00 [ _ A 0.2 observation oo} A 0.6 observation L 4 0.8 observation .00 + 00 00 00 . 00 . 00 . 00, 00 +00 p- pede ad 3 4 VELOCITY, IN FEET PER SECOND oN c B orn o w c w ate o 280.0 --- ; © Ground surface elevation GEODETIC VERTICAL DATUM ho ro o ~ 0 fs s 6 No ho ho wo PA on o 0 o o o o ELEVATION, IN FEET ABOVE NATIONAL i i a a 0 100 200 300 400 500 600 700 860 s 960 AIOIOO DISTANCE FROM LEFT ABUTMENT, IN FEET 220.0 FIGURE 42.-Velocity distribution and cross section: Pearl River at Interstate Highway 55 at Jackson, Miss., April 17, 1979. Gage height, 43.21 ft; total discharge, 128,000 ft's. r o 00 r t r t t + - - L - Surface or other observation .00 A 0.2 observation F A 0.6 observation .00 a 0.8 observation .00 } .00 } .00 } .00 . 00 . 00 . 00 .00 i R 1 i 40 4s 0000 Ke 000 uite ccie VELOCITY, IN FEET PER SECOND 0 m to 4> _ o ~ co to goog aug. go aa gat dl a o 300.0 t r - © Ground surface elevation ho to &n o ho co &n o v ELEVATION, IN FEET ABOVE NATIONAL GEODETIC VERTICAL DATUM C o o 489-8, 100 200 300 40 DISTANCE FROM LEFT ABUTMENT, IN FEET FIGURE 43.-Velocity distribution and cross section: Zilpha Creek at State Highway 35 near Kosciusko, Miss., April 12, 1979. Water surface elevation, 291.41 ft; total discharge, 21,400 ft's. 44 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA C0 meam erp ~-_ Site No; 1 W |- Site number corresponds - to that in table 8 reopen itt] N N NQ t ho & ho & D bad Le herefor rrd 25 30 WATER LEVEL, IN FEET BELOW LAND SURFACE DATUM ho $ ho co Dead tha rut 1 5: 10 15 -- 20 25 30 5 10. 15 20 MARCH 1979 APRIL 1979 FIGURE 44.-Water level in observation well 3256220870755501, at Centreville, Ala. (site 1 W) (Centreville Gin and Cotton Co.), March- April 1979. NUMBERING SYSTEM FOR WELLS The wellnumbering system of the U.S. Geological Survey is based on the grid system of latitude and longi- tude. The system provides the geographic location of the well and a unique number for each well. The number consists of 15 digits. The first 6 digits denote the de- grees, minutes, and seconds of latitude, the next 7 digits denote degrees, minutes, and seconds of longitude, and the last 2 digits (assigned sequentially) identify the wells within a 1-second grid. SALINITY AND TEMPERATURE DATA, MOBILE BAY AND GULF OF MEXICO The U.S. Geological Survey, in cooperation with the Corps of Engineers, Mobile District, collected salinity and temperature data along the Intracoastal Waterway in Mobile Bay during the flood period April 28-29, 1979. The data are summarized in table 9 (at end of report), and the locations of sites are shown in figure 46. Specific conductance readings indicate that salinity, ranging from 20 to 3,000 micromhos per centimeter, is relatively low in the waterway sampled except for the Mobile Ship Channel. The specific conductance in the ship channel (site 16, fig. 46) at a depth of 35 feet was 45,000 micromhos per centimeter (compared with about 55,000 micromhos per centimeter in the Gulf of Mexico). Specific conductance readings from 10 feet to the sur- face at site 16 were about 300 micromhos per centi- meter, indicating the "wedge" effect of freshwater floodflow over the more saline Gulf water. The temperature was relatively constant from water surface to the floor of the waterway. Generally, tem- peratures at the surface were higher, 0.5° to 1.0° (Celsius), than the temperatures near the floor of the waterway. AERIAL PHOTOGRAPHY Aerial photographs were taken April 14-19, 1979, at or near the crest of the flood on several streams in the Mobile and Pearl River basins. The photographs are useful in identifying inundated areas and analyzing hydraulic conditions. Flight lines along streams where aerial photographs were obtained are listed in table 10 (at end of report). The table furnishes information on date the photo- graphs were taken, flight heights, and type of film used. The date, time, and altitude are also shown on each photograph. The approximate locations of the flight lines are shown in figure 47. The photographs listed in table 10 were obtained by the U.S. Geological Survey or the Corps of Engineers and are on file in the U.S. Geological Survey District Offices in Tuscaloosa, Ala., or Jackson, Miss. Aerial photographs were obtained near the crest of the flood at 15 highway and railroad crossings of Pearl River (5 on April 14 and 10 on April 19). These photo- graphs, together with stage and discharge data, are use- ful in analyzing the hydraulics at these crossings. O mmm | ~- Site No. 15 W 2] |___ Site number corresponds to that in table 8 JAG/flame f C MM 3 o WATER LEVEL, IN FEET BELOW LAND SURFACE DATUM p I & cu ou Mou rou Hou 10 15 : 20 25 30 APRIL 1979 7 t 5 10 15 20 25 30 5 MARCH 1979 FIGURE 45.-Water level in observation well 331426088192202, at site 3.4 miles west of Pickensville, Ala. (site 15W), at river mile 292.0 above the mouth of the Tombigbee River, March-April 1979. SELECTED REFERENCES 45 88°07'30" 88°00 45) 87°35" 30°22'30" -n- Mobile & j / | Bay ta wyo€:L ET L hFAs min pood paepure3§ *Ut-g WYOE:L ZT 86°C LT »88 i€T 66 (T) @Ttrasuoyofd *u3gt uo wy 9 popus pure y1izt uo yy € uegaq ufey poog san; asap 'ufeg = .= Os 1€S »L48 i161 E6 (z) opa03 *Y1¢T uo y g popua pur y3zT uo wy g ueSoq ufry 2004 aqnp 1891 'uf-y inclaiited 00 °'8 SS »48 i61 .€€ (t) opa03 *suof3ra1iasqo +00 ° OT. 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'o1 I14dv s/44 O0L'éy eseeje1 wunw;xey *weq ssjeM 40 uopjon44su09 Of JOj4g *Aep jed puoses ued jee; ojgno puesnoy; uj »weessdn upseq u; sijoaseses 4q pereinbey +4joAajesey Aq «dew opydesbodo; wou; epnil41y +wep uor;einbes-os pue eye7 sjequeq Aq *sejueq Aoup;g exeq7 4q egen (5161 youew 40 poop; sepnjou| s o 0 b 6 + me- % E c a go L a + 3 > ® x > N 6L61 O8p'Z £99 o05'1 0 "86 zi *adv _ o6l'1 91 "L6 gost '6 - Aem - "01-0961 - CrArd +*****ss/p 'uo;j0g seeu yeeuq peweuun 1106210 122 6L61 * 69-0961 cke 9C o0¢ 't 9r°CZ zi *adv _ oor's 6r°CZ oget "zz *bny = 1°CL ****ssy 'uo4jog jeeu yeeuy poo4ee!; 011062L0 OcZ 00# " £L 6 o0z ' 18 95 0p 91 *adv _ €s0or i961 "oz *>e0 _ 61-961 £6*ve ****ssiw 'eupmog seeu jeajy orig 51g 000062L0 61z 6L61 = \ 000 "91 86 "61 €1 *adv _ 00012 gg "oz €sel 'og *ady _ "ou-ZS61 v6 "691 K1 «+«+****ssm 'esopy seeu oriy;p enbog 0G868ZL0 _ 81Z Nfl— ODOs— Q—— ace N— at< OQ— N'oh “5-0— qfl cg Ohl'oaw a FO- o-onto-conoaoo-nnnooonuaoooooonflfl-I fesoy eeu yee49 JeyiuRj; 1§968ZL0 LZ penu1 4u0Q-NISVE8 M3A IX NOVIG 918 (§/g4) (19 (§/g44) (44) e4eq (5/4) (44) e4eq spoo} ; (44) (1) uojjeujujezep 30 eve1d pue wees sequnu - sequinu poo 13 aed 44 61 oy efuey> 44 61 oy wouy 6Z61 30 wnjeq _ eoue | aeeA-o01 _ $/g4) efeq -s10 efeg 40 eo 440A obe queu 30 ebjey>s1 q POL 49g 21 4°poeq -ujeaqg -ouseg efuey> jeuopgey ex0ge -s10 eL61 11 2dy poop; buj inp wnw;xew ebeb jo wnyeq ponumnuoy-saSmyasip pun safn3s poot] Jo Linuwung-'7 WIYV I, TABLES TABLE 3.-Summary of flood damages on main streams and principal tributaries March 1979 flood 67 Basin and Stream Alabama-Coosa River Basin Alabama River Coosa River Tallapoosa River Total Escambia-Conecuh River Basin Escambia River Conecuh River Total Tombigbee River Basin Tombigbee River Total Choctawhatchee River Basin Choctawhatchee River Total Coastal (Baldwin and Santa Rosa Counties) Total Pascagoula River Basin Pascagoula River Total Pearl River Basin Pearl River Total TO TAL Flood damages in dollars Roads and Agriculture _ Railroads _ Urban & Other Total 110,000 91,700 4,300 206,000 1,514,300 1,313,000 11,989,700 14,817,000 200,000 1,285,000 25,000 1,510,000 1,824,300 2,689,700 12,019,000 16,533,000 53,000 674,500 13,189,000 13,916,500 -- 55,500 -- 55,500 53,000 730,000 13, 189;000 13,972,000 50,000 335,000 203,000 588,000 50,000 335, 000 203,000 588,000 -- 250,000 -- 250,000 Tsay 250,000 S= 250,000 2,023,000 1,020,000 3,750,000 6,793,000 2,023, 000 1,020, 000 3,750,000 6,793,000 11,000 177,000 182,000 370,000 11 , 000 177,000 182,000 370, 000 921,000 1,038,000 1,451,000 3,410,000 921,000 1,038,000 1,451,000 3,410,000 4,882 , 300 6,239,700 30,794,000 41,916,000 68 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 3.-Summary of flood damages on main streams and principal tributaries-Continued April 1979 flood Basin and Stream Alabama-Coosa River Basin Alabama River Coosa River Tallapoosa River Apalachicola River Basin Apalachicola River Chattahoochee River Flint River Tombigbee River Basin Tombigbee River Black Warrior River Mobile River Basin Mobile River Pascagoula River Basin Pascagoula River Leaf River Chickasawhay River Pearl River Basin Pearl River Big Black River Basin Big Black River and southwest Tributaries Total Total Total Total Total f Total TO TAL Flood damages in dollars Roads and Agriculture _ Railroads _ Urban & Other Total 2537 3,900 1,148,300 13,503,500 17,025,700 1, 365,000 2,014 , 300 5,261,900 8,641,200 425,000 1,484,000 1,446,800 2,355,800 4,163,900 4,646,600 20,212,200 29,022 , 700 0 0 0 0 0 276,700 1,075,700 1,352,400 50,000 410,000 205,000 665,000 50, 000 686 , 700 1,280,700 2,017,400 9,346,100 _ 11.854,200 17,031,300 38,231,600 750,000 879,900 4,543,700 6,173,600 10,096,100 - 12,734,100 21,575,000 44 , 405 , 200 0 580,000 1,609,800 2,189,800 0 580,000 1,609,800 2,189,800 _- 304,000 216,000 520,000 82,000 143,800 468,500 694 , 300 637, 000 1, 387,800 1,167,800 3,192,600 719,000 1,835,600 1 , 852 , 300 4 , 406 , 900 5,147,000 12,236,000 239,914,000 257,597,000 5,447,000 12,236,000 239,914,000 257,597,000 3,360,000 1,240,0001/ _ 4,600,000 23,836,000 32,719,000 287,684,000 344,239,000 l/ Includes Roads and Railroads TABLES 69 TABLE 4.-Summary of stages and contents of storage reservoirs [Measurements taken at 2400 CST on indicated dates] Weiss Lake near Leesburg, Ala. 02399499 March 1979 April 1979 Elevation Elevation 1/ NGVD Change in 1/ NGVD Change in of 1929 Contents storage of 1929 Contents storage Day (feet) g/(ft3/s/day) 2/ (ft3/s/day) (feet) 2) (fte/siday) 2/ (ft3/s/day) 1 563.26 143,510 567.60 134,160 +550 2 563.22 142,930 -580 562.30 130,050 -4,110 3 563.87 152,490 +9, 560 562.24 129,230 -820 4 567.38 210,960 +58, 470 563.36 144,960 +15,730 5 569.50 252,050 +41 ,090 563.40 145,540 +580 6 570.41 271,080 +19,030 563.28 143,800 -1, 740 7 570.42 271,300 +220 563.22 142,930 -870 8 570.89 281,460 +10,160 562.78 136,670 -6, 260 9 569.57 253,490 -27,960 562.56 133,610 -3,060 10 568.94 240,760 -12,730 562.36 130,860 -2, 750 11 568.10 224,410 -16, 350 562.40 131,410 +550 12 566.95 203,160 -21, 250 562.99 139,640 +8 , 230 13 565.54 178,850 -24, 310 566.78 200,130 +60, 490 14 564.31 159,190 -19,660 569.10 243,950 +43,820 15 563.54 147,540 -11,600 570.07 263,870 +19,920 16 563.05 140,490 -7,100 570.31 268,950 +5 ,080 17 562.56 133,610 -6, 880 570.16 265,770 -3,180 18 561.95 125, 340 -8, 270 569.89 260,100 -5,670 19 561.57 120, 360 -4,980 569.43 250,620 -9, 480 20 562.06 126,810 +6, 450 568.80 237,990 -12,630 21 561.74 122,580 -4, 230 567.92 221,000 -16,990 22 561.32 117,160 -5,420 566.76 199,780 -21, 220 23 561.69 121,920 +4, 760 565.50 178,190 -21, 590 24 562.38 131,140 +9, 220 564.46 161,510 -16,680 25 562.50 132,780 +1, 640 563.66 149, 360 -12,150 26 562.46 152,230 -550 563.26 143,510 -5, 850 27. 562.36 130,860 -1, 370 5635.30 144,080 +570 28 562.44 131,960 +1,100 563.39 145, 390 +1, 310 29 562.28 129,770 -2,190 $65.22 142,930 -2,460 30 562.40 131,410 +1,640 563.46 146,420 +3,490 31 562.56 133,610 +2, 200 / National Geodetic Vertical Datum of 1929. / One cubic foot per second per day is equivalent to 1.9835 acre-feet. Note: Records furnished by Alabama Power Co. 70 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 4.-Summary of stages and contents of storage reservoirs-Continued H. Neely Henry Reservoir near Ohatchee, Ala. 02401620 March 1979 April 1979 Elevation Elevation 1/ NGVD Change in 1/ NGVD Change in of 1929 Contents storage of 1929 Contents storage Day (feet) 2/(ft3/s/day) _ _2/ (f£t5/s/day) (feet) 2/ (ft35/s/day)y 2/ (ft35/s/day) 1 SoS. 00 45,610 504.83 44 , 840 +1 ,780 2 504.96 45,430 -180 503.92 40,660 -4,180 3 503.74 40,100 -5 , 330 504.41 42,970 +2, 310 4 502.50 35,160 -4 , 940 502.49 35,120 -7,850 5 502.54 35,310 +150 502.64 35,700 +580 6 502.41 34,820 -490 504 . 36 42,750 +7,050 7 502.43 34,900 +80 SoS 45,660 +2,910 8 502.58 35 , 470 +570 SoS. 00 45,610 -50 9 502.51 35,200 -270 504.97 45,480 -130 10 502.42 34,560 -640 504.83 44 , 840 -640 11 502.49 35,120 +560 504.47 43,230 -1,610 12 502.44 34,930 -190 502.50 35,160 -8, 070 13 502.38 34,710 -220 502.57 35 , 430 +270 14 502.54 35, 310 +600 502.53 35,270 -160 15 S05 .00 45,610 +10, 300 502.40 34,780 -490 16 505.00 45,610 0 502.50 35,160 +380 17 504.92 45,290 -320 502.58 35,470 +310 18 504.57 43,670 -1,620 502.54 35,310 -160 19 504.51 43,410 -260 502.64 35,700 +390 20 501.31 30,840 -12,570 502.56 35,590 - 310 21 503.635 39,640 +8 , 800 502.58 35,470 +70 22 503.18 37,810 -1, 830 502.44 34 , 930 -540 23 504.43 43,060 +5, 250 503.36 38 , 540 +3,610 24 504.25 42,270 -790 504.99 45,570 +7 ,030 25 504.63 43,940 +1,670 506.50 52,860 +7, 290 26 504.42 43,010 -930 506.56 53,170 +310 27 503.81 40, 390 -2,620 507.36 57, 380 +4, 210 28 503.78 40,270 -120 507.59 58,640 +1, 260 29 503.42 38,750 -1, 520 507.56 58,470 -170 30 503.63 39,640 +890 507.47 57,980 -490 31 504.48 43,060 +3, 420 1/ National Geodetic Vertical Datum of 1929. 2/ One cubic foot per second per day is equivalent to 1.9835 acre-feet. Note: Records furnished by Alabama Power Co. TABLES TABLE 4.-Summary of stages and contents of storage reservoirs-Continued Logan Martin Reservoir near Childersburg, Ala. 02405200 71 1/ National Geodetic Vertical Datum of 1929. 2/ One cubic foot per second per day is equivalent to 1.9835 acre-feet. 3/ Forebay elevation for 0100 hours on Mar. 24. Note: Maximum outflow discharge, 115,200 cubic feet per second, Apr. 15. furnished by Alabama Power Co. Records March 1979 April 1979 Elevation Elevation 1/NGVD Change in 1/NGDV Change in of 1929 Contents storage of 1929 Contents storage Day ___ (feet) 2/ (£t3/s/day) __ 2/(£t5/s/day) (feet) 2/(£t3/s/day) __ 2/(ft3/s/day) 1 459.94 105,370 __ _ _ ....... 459.95 103,430 +1,600 2 459.91 103,190 -180 459.81 102,600 -830 'e 460.55 107,070 +3, 880 461.53 113,260 +10,660 4 468.79 169,790 +62,720 463.74 128, 390 +15, 130 5 471.83 199,910 +30,120 464 . 84 136,570 +8 , 180 6 472.16 203,430 +3, 520 464.68 135,350 -1,220 7. 470.86 180,840 -13,590 463.23 124,750 -10,600 8 468.87 170,530 -19, 310 461.74 114,630 -10, 120 9 467.09 154,720 -15,810 461.24 111,400 -3, 230 10 465.94 145,200 -9, 520 461.37 112,230 +830 11 464.70 135,500 -9, 700 461.41 112,490 +260 12 463.57 127,170 -8 , 330 464.61 134,820 +22, 330 13 462.60 120, 300 -6, 870 471.95 201,180 +66, 360 14 461.75 114,690 -5,610 474.04 224,540 +23, 360 15 460.64 107,630 -7, 060 472.83 210,760 -13, 780 16 460.40 106,150 -1,480 470.77 188,930 -21 , 830 17 459.77 102, 360 -3,790 469.09 172,580 -16, 350 18 459.77 102, 360 0 467.62 159,290 -13, 290 19 459.75 102,240 -120 466.36 148,610 -10,680 20 459.68 101,830 -410 465.43 141,120 -7,490 21 459.47 100,590 -1, 240 464 . 32 132,650 -8,470 22 459.08 98 , 340 -2, 250 463.52 126,810 -5 , 840 23 - 3/459.99 103,670 *+5,330 463.16 124,260 -2, 550 24 "~ 460.06 104,090 +420 463.26 124,960 +700 25 459.82 102,650 -1,440 463.46 126,380 +1,420 26 459.87 102,950 +300 466.13 146,730 +20, 350 27 459.81 102,600 -350 466.33 148, 370 +1,640 28 459.52 100,890 -1,710 465.54 142,000 -6, 370 29 459.35 99,900 -990 463.94 129,850 -12,150 30 459.33 99,780 -120 463.84 129,120 -730 31 459.68 101, 830 25000 _ .f ~ "° _ . C . __" 72 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 4.-Summary of stages and contents of storage reservoirs-Continued Lay Lake near Clanton, Ala. 02407950 March 1979 April 1979 Elevation Elevation 1/NGVD Change in 1/NGVD Change in of 1929 Contents storage of 1929 Contents storage Day (feet) 2/(ft3/s/day) - 2/(ft3/s/day) (feet) _2_/(ft3/s/day) 2/ (ft35/s/ day) 1 396.24 153,910 - _ . ....... 395 . 80 131, 300 -700 2 396.27 134,090 +180 396.07 132,890 +1, 590 3 396.15 153,570 -720 396.02 132,600 -290 4 396.02 132,600 -770 395.73 130,880 -1, 720 5 395.33 128,560 -4 , 040 395.84 131,530 +650 6 395.76 131,060 +2, 500 395.90 131,890 +360 7 395.85 131,590 +530 396.18 133,550 +1,660 8 395.85 131,590 0 395.90 131,890 -1,660 9 $96.13 133,250 +1, 660 396.29 134,210 +2, 320 10 395.90 131,890 -1, 360 396.16 133,430 -780 11 395.82 131,410 -480 396.07 132,890 -540 12 396.07 132,890 +1, 480 395.78 131,180 -1,710 13 396.06 132,840 -50 395.95 132,180 +1, 000 14 396.03 132,660 -180 395.75 131,000 -1,180 15 395.81 131,350 -1, 310 395.94 132,120 +1,120 16 395.96 132,240 +890 396.07 132,890 +770 17 396.03 132,660 +420 395.85 131,590 -1, 300 18 395.69 130,650 -2,010 395.79 131, 240 -350 19 395.89 131,830 +1, 180 396.10 133,070 +1, 830 20 396.06 132,840 +1,010 396.06 132,840 -230 21 396.21 153,730 +890 396.13 133,250 +410 22 396.01 132,540 -1, 190 396.12 133,190 -60 23 396.39 134,820 +2, 280 396.15 133,370 +180 24 395.93 132,060 -2, 760 396.04 132,720 -650 25 396.15 133,370 +1, 310 396.00 132,480 -240 26 396.39 134,820 +1,450 395.79 131,240 -1, 240 27 396.23 133,850 -970 395.92 132,000 +760 28 396.24 133,910 +60 395.74 130,940 -1,060 29 396.27 134,090 +180 396.21 133,730 +2 ,790 30 396.40 +34 , 880 +790 396 . 34 134,520 +790 31 395.92 132,000 --' .yat. 'o O : n o 1/ National Geodetic Vertical Datum of 1929. 2/ One cubic foot per second per day is equivalent to 1.9835 acre-feet. Note: Maximum outflow discharge, 197,000 cubic feet per second, Apr. 13. by Alabama Power Co. Records furnished TABLES 73 TABLE 4.-Summary of stages and contents of storage reservoirs-Continued Mitchell Dam near Verbena, Ala. 02409400 | March 1979 April 1979 Elevation Elevation 1/ NGVD Change in 1/ NGVD Change in of 1929 Contents storage of 1929 Contents storage Day ___ (feet) 2/ (ft"/s/day) 2/ (f£t5/s/day) (feet) 2/ (ft5/s/day) 2/ (ft5/s/day) 1 311.8 87,930 -600 310.8 84,990 -3, 540 2 311.9 88,230 +300 312.3 89,420 +4 , 430 3 312.2 89,120 +890 311.9 88 , 230 -190 4 311.5 87,040 -2,080 311.8 87,930 -300 5 312.1 88,820 +1,780 312.8 90,920 +2,990 6 312.2 89,120 +300 312.1 88,820 -2,100 7. 312.2 89,120 0 312.0 88,530 -290 8 311.9 88 , 230 -890 312.2 89,120 +590 9 311.8 87,930 -300 312.0 88,530 +590 10 312.0 88 , 530 +600 312.0 88,530 0 11 512.2 89,120 +590 312.0 88,530 0 12 $12.2 89,120 0 312.2 89,120 +590 13 311.8 87,930 -1,190 316.2 101,460 +12, 340 14 312.2 89,120 +1 ,190 512.2 89,120 -12 , 340 15 312.2 89,120 0 312.1 88,820 -300 16 311.9 88 , 230 -890 311.9 88,230 -590 17 311.9 88 , 2 30 0 311.8 87,930 -300 18 312.2 89,120 +890 312.2 89,120 +1,190 19 312.2 89,120 0 311.8 87,930 -1,190 20 311.9 88,230 -890 312.1 88,820 +890 21 312.0 88 , 530 +300 $11.9 88,230 -590 22 311.9 88,230 -300 312.0 88,530 +300 23 312.0 88 , 530 +300 312.1 88,820 +290 24 311.9 88,230 -300 312.2 89,120 +300 25 312.0 88 , 530 +300 312.2 89,120 0 26 311.9 88 , 230 -300 311.8 87,930 -1,190 27. 212.2 89,120 +840 312.1 88,820 +890 28 311.8 87,930 -1,1 90 312.0 88,530 -290 29 312.35 89,420 +1,490 s 312.1 88,820 +290 30 312.1 88 , 820 -600 SF1 .9 88 , 230 -590 31 312.0 88 , 530 -290 1/ National Geodetic Vertical Datum of 1929. z] One cubic foot per second per day is equivalent to 1.9835 acre-feet. Note: Records furnished by Alabama Power Co. 74 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 4.-Summary of stages and contents of storage reservoirs-Continued Jordan Lake near Wetumpka, Ala. 02414000 l] National Geodetic Vertical Datum of 1929. 2/ Includes Walter Bouldin Reservoir 3] One cubic foot per second per day is equivalent to 1.9835 acre-feet. Note: Maximum outflow discharge, 316,000 cubic feet per second, Apr. 13. by Alabama Power Co. March 1979 April 1979 Elevation Elevation 1/NGVD Change in 1/NGVD Change in of 1929 2/Contents storage of 1929 2/Contents storage Day _ (feet) 3/(ft3/s/day) _ 3/(ft3/s/day) (feet) 3/(ft3/s/day) _ 3/(ft5/s/day) 1 251.90 118,750 _ . - =....... 250.22 113,280 -3,030 2 2951.31 116,800 -1,950 250.90 115,460 +2,180 3 2582.77 121,680 +4 , 880 291.53 117,520 +2,060 4 251.78 118, 350 - 3, 330 291.71 118,120 +600 5 251.90 118,750 +400 251.86 118,610 +490 6 2951.95 118,910 +160 2591.81 118,450 -160 7 281.77 118, 310 -600 251.74 118,210 -240 8 251.80 118,410 +100 291.76 118,280 +70 9 291.70 118,080 -330 251.71 118,120 -160 10 251.60 11735750 -330 251.84 118,550 +430 11 251.90 118,750 +1, 000 251.40 117,090 -1,460 12 251.82 118,480 -270 2§1.77 118, 310 +1,220 135 251.85 118,580 +100 256.71 135,960 +17,650 14 251.91 118,780 +200 251.90 118,750 -17,210 15 251.79 118, 380 -400 251.93 118,850 +100 16 251.90 118,750 +370 251.92 118,810 -40 17 251.82 118,480 -270 291.93 118,850 +40 18 251.86 118,610 +130 251.95 118,910 +60 19 251.74 118,210 -400 251.72 118,150 -760 20 251.84 118,550 +340 251.81 118,450 +300 21 251.90 118,750 +200 251.71 118,120 -330 22 251.70 118,080 -670 251.89 118,710 +590 23 251.78 118, 350 +270 251.81 118,450 -260 24 251.72 118,150 -200 251.75 118,250 -200 25 251.57 117,650 -500 251.86 118,610 +360 26 251.87 118,650 +1, 000 291.71 118,120 -490 27 251.94 118,880 +230 251.73 118,180 +60 28 291.75 118,250 -630 2591.74 118,210 +30 29 291.91 118,780 +530 251.82 118,480 +270 30 261.82 118,480 -300 ° 251.86 118,610 +130 31 351.16 116, 310 cr ATO _ se l ~! e dae. amintae "00 oP Cas a Records furnished TABLES TABLE 4.-Summary of stages and contents of storage reservoirs-Continued Lake Martin near Tallassee, Ala. 02417500 1/ National Geodetic Vertical Datum of 1929. Z] One cubic foot per second per day is equivalent to 1.9835 acre-feet. Note: Maximum outflow discharge, 128,000 cubic feet per second, Apr. 14. by Alabama Power Co. March 1979 April 1979 Elevation Elevation 1/NGVD Change in 1/NGVD Change in of 1929 Contents storage of 1929 Contents storage Day (feet) g/(ft3/s/day) g/(ft3/s/day) (feet) g/(ft3/s/day) g/(ft3/s/day) 1 482 . 24 675,620 _. _._. -..r.... 486.49 752,440 +3 , 360 2 482.21 675,100 -520 486.30 748,890 -3, 550 3 482.40 678,420 +3, 320 487.17 765,230 +16, 340 4 484.70 719,440 +41,020 489.16 803,450 +38 , 220 d 487.78 776,820 +57, 380 489.92 813, 360 +9,910 6 489.15 803,250 +26, 430 490.05 820,920 +7, 560 7. 489.83 816,580 +13, 330 489.94 818,750 -2,170 3 489.86 817,170 +590 489.75 815,010 -3, 740 9 489.61 812,250 -4,920 489.63 812,650 -2, 360 10 489.39 807,940 -4, 310 489.39 807,940 -4,710 5 489.12 802,670 -5, 270 489.24 805,010 -2,930 12 488.88 798,000 -4,670 489.32 806,570 +1, 560 13 488.64 793, 350 -4,650 490.80 835,840 +29, 270 14 488.45 789,680 -3,670 490.52 830,250 -5, 590 15 488.23 785,440 -4 , 240 490.10 821,910 -8 , 340 16 487.92 779,490 -5,950 490.05 820,920 -990 17 487.68 774,910 -4 , 580 490.02 820, 330 -590 18 487.40 769,590 -5, 320 489.90 817,960 -2, 370 19 487.13 764,470 -5, 120 489.78 815,600 -2, 360 20 486.93 760,700 -3, 770 489.88 817,570 +1,970 21 486.90 760,140 -560 489.37 807,550 -10,020 22 486.44 751,510 -8,630 489.16 803,450 -4, 100 23 486.45 751,700 +190 489.19 804,030 +580 24 486.50 752,630 +930 489.15 803,250 -780 25 486.65 755 , 440 +2,810 489.75 815,010 +11 ,760 26 486.55 753,570 -1,870 490.00 819,940 +4 , 930 27 486.49 752,440 -1,130 490.03 820,530 +590 28 486.58 754,130 +1,690 489.98 819,540 -990 29 486.29 748,710 -5,420 489.87 817,370 -2,170 30 486.12 745,540 -3,170 489.78 815,600 -1,770 31 486.31 749,080 t3,940 __ -_ _ ¢. ~. <0. or c_ ll in rss Records furnished 76 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 4.-Summary of stages and contents of storage reservoirs-Continued Lewis Smith Reservoir near Jasper, Ala. 02451950 March 1979 April 1979 Elevation Elevation 1/ NGVD Change in 1/ NGVD Change in of 1929 Contents storage of 1929 Contents storage Day (feet) g/(fts/s/day) 2/(£t3/s/ day) (feet) g/(ft3/s/day) Z/(ft3/s/day) 1 507.81 ©98,;700 °- - 509.36 693,970 +3, 380 2 509.96 700, 360 +1 ,600 509.87 699,400 +5,430 3 512.64 729,640 +29, 280 510.45 705,620 +6, 220 4 515.33 760, 320 +30, 680 510.55 706,700 +1,080 5 $15.55 762,880 +2 , 560 510.38 704,870 -1, 830 6 516.12 769,580 +6, 700 510.14 702,290 -2,580 7 515.84 778,120 +8 , 540 510.12 702,070 -220 8 $15.30 759,970 -18, 150 510.06 701,430 -640 9 514.68 752,780 -7, 190 509.94 700,150 -1, 280 10 514.16 746,810 -5,970 509.89 699,610 -540 11 513.61 740, 550 -6, 260 509.90 699,720 +110 12 513.01 733,780 -6, 770 512.61 729,310 +29,590 13 512.70 730, 310 -3,470 517.18 782,190 +52,880 14 512.35 726,410 -3,900 518.20 794,520 +12,330 15 511.99 722,420 -3,990 518.67 800,270 +5,750 16 511.60 718,130 -4 , 290 518.43 797, 330 -2, 940 17 511.20 715,750 -4 , 380 517.89 790,750 -6, 580 18 510.74 708,750 -5, 000 517.32 783,870 -6, 880 19 510.35 704,540 -4, 210 516.63 775,620 -8, 250 20 510.60 707,240 +2, 700 $15.95 767,570 -8, 050 21 $09.60 696,520 -10, 720 515.25 759,380 -8, 190 22 509.16 691,860 -4 , 660 514.54 751,170 -8, 210 22 so9.50 695,460 +3, 600 513.81 742,620 -8, 550 24 509.82 698,860 +3,400 513.10 734,790 -7, 830 25 510.04 701,220 +2 , 360 512.55 728,640 -6, 150 26 509.77 698 , 330 -2,890 $12.53 726,190 -2,450 27 509.48 695,250 -3, 080 511.95 721,980 -4, 210 28 509.353 693,650 -1,600 $11.57 717,800 -4,180 29 S09 692,180 -1,470 511.16 713,320 -4, 480 30 509.04 690,590 -1, 590 $10.75 708,860 -4 , 460 31 S09. 04 690,590 0 1/ National Geodetic Vertical Datum of 1929. 2/ One cubic foot per second per day is equivalent to 1.9835 acre-feet. Note: Maximum outflow discharge 9,100 ft3/day April, 21,23. April 13 and 14 no outflow; April 15, 1,400 ft5/s. Records furnished by Alabama Power Company. Outflow April 12, 2,700 ft5/s; TABLES 77 TABLE 4.-Summary of stages and contents of storage reservoirs-Continued Okatibbee Reservoir near Meridian, Miss. 02475976 March 1979 April 1979 Elevation Elevation 1/ NGVD Change in 1/ NGVD Change in of 1929 Contents storage of 1929 Contents storage Day (feet) 2/(ft3/s/day) __ 2/ (ft5/s/day)_ (feet) 2/ (ft5/s/day) 2/ (ft5/s/day) 1 344.07 23,385 sigle 341.92 19,265 -142 2 344.15 23,543 158 342.15 19,674 408 3 347.33 30,976 7,433 342. 80 20,879 1,204 4 350.05 38,567 7,591 343.71 22,649 1,770 5 350.66 40, 435 1,867 344, 27 23,802 1,152 6 350.51 39,982 -453 344.35 23,985 182 7 350.27 39 , 244 -737 344. 31 23, 892 -92 8 349.99 38,363 -880 344.68 24,697 804 9 349.66 37,399 -963 345, 33 26,134 1,436 10 349.36 36, 524 -875 345.62 26, 802 667 t! 349.04 35,608 -915 345.75 27,092 290 t 348. 71 34,673 -934 349. 41 36,686 9,593 13 348.38 33,715 -898 353. 81 50,970 14,283 14 348.02 32,783 -991 355,24 56,293 5,323 15 347.64 31, 791 -992 3955.20 56,134 -159 16 347.26 30, 802 -988 354.98 53,297 -836 17 346.85 29,764 -1,037 354.73 34,359 -938 18 346. 46 28,799 -965 354.46 53,371 -987 19 346.06 27,817 -982 354.18 32,321 -1,049 20 345.66 26,897 -919 353.88 51,239 -1,081 21 345.36 26,203 -694 353.58 50,174 -1,065 22 345.23 25,899 -304 353.30 49,157 -1,017 22 345.05 25,493 -406 353.02 48,187 - 970 24 344.73 24,790 -702 352.76 47,290 - 897 25 344, 31 23, 896 -893 352.49 46,363 - 926 26 343.86 22,945 -950 352.23 45,482 -' 880 27 343. 39 22,016 «929 351.94 44,530 - 952 28 342.90 21,055 =961 351.62 43,494 -1,035 29 342. 40 20,135 =920 351.29 42,405 -1,089 30 _ 342.12 19,622 5513 350.94 41,292 -1,112 31 342.00 19,407 -214 1/ National Geodetic Vertical Datum of 1929. 2/ One cubic foot per second per day is equivalent to 1.9835 acre-feet. Note: Furnished by U.S. Army Corps of Engineers 78 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 4.-Summary of stages and contents of storage reservoirs-Continued Ross Barnett Reservoir near Jackson, Miss. 02485600 March 1979 April 1979 Elevation above Elevation above Day National Geodetic g-/E1evation above National Geodetic g/Elevation above ngtical Datum at National Geodetic ngtical Datum at National Geodetic -'Meeks Bridge Vertical Datum at -'Meeks Bridge Vertical Datum at (feet) dam (feet) (feet) dam (feet J 29771 297.2 297.4 297.4 2 297.2 297.2 297.4 297.3 3 297.3 297.3 297.6 297.6 4 297.4 297.3 297.9 297.9 9 297.6 297.6 297.9 297.9 6 297.3 297.3 297.8 297.8 7. 297.4 297.2 297.7 297.7 8 297.7 297.6 297.8 2097.8 9 297.9 297.9 297.8 297.8 10 297.5 297.5 297.6 297.7 11 297 12 297.2 297.6 297.5 12 297.3 297.3 298.1 298.1 13 297.53 297.5 298.2 298.2 14 297.4 297.5 297.1 296.6 13 297.3 297.3 297.9 296.9 16 297.3 297.4 299.1 2598.8 17 297.3 297.3 300.0 299.7 18 297.3 297.4 299.2 299.1 19 297.3 297.3 297.9 297.8 20 297.3 297.4 297.2 297.2 21 29713 297.4 296.6 296.6 22 297.4 297.4 296.2 296.3 23 297.3 297.4 296.1 296.1 24 297.4 297.4 ois 296.0 25 297.4 297.4 296.0 26 297.3 297.4 296.0 27 297.4 297.4 296.1 28 297.4 297.4 296.2 29 297.4 297.4 296.2 30 297.4 297.4 296.3 31 297.4 297.4 I I U At State Highway 43, 7.6 miles upstream from dam. 2/ Data furnished by Pearl River Valley Water Supply District (rounded to tenths). J Crest elevation 299.8 feet, 2300 hours April 16 to 0100 hours April 17. TABLES TABLE 4.-Summary of stages and contents of storage reservoirs-Continued Ross Barnett Reservoir near Jackson, Miss. 02485600-Continued Discharge measurements of (02485000) Pearl River at Meeks Bridge near Canton, Mississippi, (State Highway 43). Mean elevation National Geodetic Vertical Datum Discharge Date Mean time (feet) (ft /s§ April 15 1740 298.3 128,000 April 16 1330 299.4 143,000 April 17 1730 299.3 102,000 April 18 1550 298.5 73,200 April 19 1420 297.2 43,700 80 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) COOSA RIVER BASIN Coosa River: Jordan Dam near Wetumpka, Ala. (upstream) 18.9 2956.8 LCeft rss sy ...s 18.7 191.9 U.S. Geological Survey gaging station (02411000) on right bank 0.5 mi downstream from Jordan Dam, near Wetumpka, Ala...... 18.6 189.3 Right 17.7 186.0 Right Dank.....i.rn«rvas vcs 60s rss warr. 15.8 182.9 Right sears s 14.6 178.9 Right 15.95 1748 Right ¥2.2 170.9 U.S. Geological Survey gaging station (02411600) on downstream side of bridge on State Highway 14, in Wetumpka, Ala.... 11.4 169.6 Right sos 6.4 163.1 Mouth, at Alabama River, mile 314.4 (confluence of Coosa and Tallapoosa Rivers) near Montgomery, Ala............. 0.0 _ : .' _." TALLAPOOSA RIVER BASIN Tallapoosa River: Alabama Power Co. gage (02418500) on left bank, 1.5 mi downstream from Benjamin Fitzpatrick Highway bridge at Thuriow Dam, at Tallassee, Ala........... 48.0 212.6 right 46.8 211.8 Left DANK. is y iis. r 44.1 209.5 U.S. National Weather Service gage (02419500) on Atlanta and West Point Railroad bridge at Milstead, Ala......... 39.8 203.5 Upstream side of Alabama Highway 229, 0.4 mi northeast of main channel, right bank.: :i i aar d ta ry als ain ain 6 na ni e a a 39.8 203.8 Right ccc cans ise ssg anns . 39.8 202.9 Downstream side of Alabama Highway 229, 0.4 mi northeast of main channel, right Dank. ...... l sae ck kr 39.7 203.0 Right sss esos 29.7 202.7 Left ien 29.6 202.4 See footnotes at end of table. TABLES TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) TALLAPOOSA RIVER BASIN--Continued Tallapoosa River--Continued Left Dank... ...... .se ove sice s s a eas eis elsie s 39.4 200.4 Left bank.. ...... .l sv suf Sale a aie a ee er the aie a % 37.1 197.1 Left bank...... .. ...he f aht diy sie cs an ecs a 33.0 189.0 Left bank. ...... .. clarisa anale sir an near aan ss 28.0 182.0 Left i ss cea aliens. 24.8 174.9 Left bank.: 21.0 194. 3 Left eras aisles 19.5 170.1 Left bank;... ...a iis a y aisi s. ae nov a arian ade ala 'o BPE 168.0 Neft sa ¢ 9.8 163.9 Neft ibank.y.i....... aie r esse.. t sn visiabs n are a 9.6 163.4 Left .f sie issa rs wa 4.8 163.0 Mouth, at Alabama River mile 314.4 (confluence of Coosa and Tallapoosa Rivers) near Montgomery, Ala............. 0.0 .... ._". g ~<<<~~- ALABAMA RIVER BASIN Alabama River: Confluence of Coosa and Tallapoosa Rivers near Montgomery, Ala.............. 314.4 _. -.. .i. __ Right L Dank. ... . sks s a ne ane sir wishes 3H1.1 162.1 eft Dank....... .s nel sise nn s saisle misc a slates 304.8 159.4 Right -Dank.. ;.... .ie essense son nece al scaisivie"sliece's 301.8 157.6 U.S. National Weather Service gage (02419988) on left bank in abandoned pumping station of the Riverview Manufacturing Co. at 715 Shady St., Montgomery, Ala................ ssa vi a. 269.9 2! 156.2 Right «. nl. a fein 's 291.2 155.0 U.S., Geological Survey gaging station (02420000) at bridge on U.S. Highway 31, Montgomery. Ala................. .... 287.6 152.4 Left Danky:.. .;. evil. Alice vor c rs is son ele a ates 277.6 147.6 Right DARK... ..«...... /+ asl 261.2 139.5 Left sn} 255.0 JS7 .5 U.S. Army Corps of Engineers gage (02421351) at downstream end of Jones Elut? dock and dame. 245.4 Wiss.: See footnotes at end of table. FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) ALABAMA RIVER BASIN--Continued Alabama River--Continued Right seers. 6s cc srs 244.9 133.1 Left e sia ar rs aon riva 'r a's se aks af 243.0 132.0 Right Dank. slates nes os s s 239.5 150.3 Left bank...! wow.... race cls a n+ sa ana a). s 237.8 127.7 Left sires sys r 6s sa sie rs ros 294.5 128.1 Richt: Dank... ...l elses. raisers .s «lass nna sels 227.4 124.4 Right bank: ias « ql sinn 1 sis s + a a s 219.4 119.3 U.S. Geological Survey gaging station (02423000) at bridge on U.S. Highway 80, at, SEiMa, 214.8 116.8 Right a+ ren cla) fis s so wie a +s 2135.4 116.2 Right so 205.4 112.9 Cahaba RMVET ai. Wasa an ias rossi srs rr ¢. 198.1. a.. c Right .z tis} s cnn re sar 197.4 108.5 Right ss enne cn sigs bia n 6 + . 187.8 104.0 Left es s. 180.2 98.9 fi'ecft bank....... { seria trs as aik s a ne bor a ais a 169.4 93.9 RACht .la? .s 156.0 87.8 Left sie s as s a ak 5. as 133.0 78.2 Left bank...... aks aura: h; - as. 124.4 $/ 95.2 fight bank. ...ll. ad. ah.. irk... 119.5 & 73.9 Left bank. ...... .. ras nin t w s sles a a shales - 114.8 71.8 peft bank. ...ne... si cen a asin soa anale aie a 110.5 68.2 Right: bank. lll ok alla «ace a a 105.2 66.0 Right 80.0 53.5 Right sa. 79.2 52.0 U.S. Geological Survey gaging station (02429500) downstream side of bridge e] on U.S. Highway 84, at Clarborne, Ala. ... 76.1 -- 51.6 RSAC rak a r s sone a y s es 74.9 50.9 Right bank...... ia. nn aces s eons a+ s 70. 7. 49.5 Right bank.. ..... h n r ror a o «a wince ringe) a' 68.9 47.8 Right bank.. ..... «allele aks . r acs ainlaon + s 68.8 47.8 Right .l .. sive alah aon b aisle sae nor a n .s 's 63.2 44.0 Might «al ra or as ais n Sikes Fiklk a 62.6 43.6 Left ne cele S20 t a s in a a cna isl nr 61.5 42.6 Right: bank...... fine. «sks ce.. ecs}. 61.1 42 .4 ...l s. i ates s < aa sain a a s sla gk ais 58.7 41.8 Left .. . .es .s r siv aris sis n s o an a none a a a a a + a 55.9 39.4 See footnotes at end of table. TABLES TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) ALABAMA RIVER BASIN--Continued Alabama River--Continued Left rics ssa slvr oir a n ooo 52.5 37.0 Right. Dank. . ...s. rl. ac ri s wore 's s ails s ti f 51.6 35.8 Raght Dank... .nl .s sels a ns s his.: n a n ner alta ois 50.1 34.6 Right Dank... =a sa 48.0 38.3 Left Dank. .... ae brie a ao as ani nia ai aig a s 43.4 31.2 Right ne sig ces r 12.1 31.1 Left Dank? <6 6 sigle a ait cltisiE s sin's 41.8 30.6 Right DANnK. ... .+ ... .aole sles a ain a n ei mls is sll 39.8 30.5 Right: iDank; ..... ...es e rts een se o wis a a a hae 38.1 28.0 Right cl mia lk els} rnb a eine ans nin a a Ble n iain +a 31.0 24.9 Mouth, 'at Mobile River mile 45.0 (confluence of Alabama and Tombigbee Rivers) near Calvert, Ma...........«..... 0.0: >= -. :~:. seases CAHABA RIVER BASIN Shades Creek: Left bank 200 ft upstream from 5-barrel culvert and 100 ft north of U.S. Highway 76 in Irondale, Ala............«.«w¢«..» . 53.2 707.0 Right bank at downstream end of 5-barrel culvert and 100 ft north of U.S. Highway 76 in Irondale, Ala.........:....««@* sis ««: 535.2 706.5 Right bank 100 ft upstream from U.S. Highway 78 in Ilrondale, Ala.............. 53.1 706.4 Left bank 60 ft downstream from U.S. Highway 78 in Irondale, Ala.............. 53.0 TOS .9 Right bank at downstream side of bridge on Elder Street in Birmingham, Ala....... 51.6 688.1 Right bank at upstream side of culvert on Old Leeds Road in Mountain Brook, Ala.... 49.0 675.1 Left bank S0 ft downstream from Old Leeds Road in Mountain Brook, Ala.............. 49.0 675.2 Left bank 5 ft upstream from abutment of bridge on Beachwood Road in Mountain Brook, Ala. ...x aha «ia s 48.5 670.0 Left bank 100 ft downstream from Beachwood Road in Mountain Brook, Ala.... 48.5 669.4 Left bank on downstream side of Beachwood Road in Mountain Brook, Ala.... 47.9 664.6 See footnotes at end of table. 84 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) CAHABA RIVER BASIN--Continued Shades Creek--Continued Right bank 20 ft upstream from Lakeshore Drive in Mountain Brook, Ala............. A7 .3 654.5 Right bank at downstream end of bridge on Lakeshore Drive in Mountain Brook, MAL alate fia sr anc tonsa s ss s 47.3 651.5 Right bank 100 ft downstream from Lakeshore Drive in Mountain Brook, Ala... 47.2 650.9 Left downstream wingwall at bridge on old U.S. Highway 31 near Homewood, Ala... 45.1 637.9 Right bank at upstream side of bridge on Green Spring Highway in Homewood, Ala.... #248 626.4 Right bank at downstream side of bridge on Green Spring Highway in Homewood, Ala. 42.8 626.4 Right bank at Shades Creek filter plant near Homewood, 41.1 616.4 Right bank at downstream side of bridge f on Oxmoor Road near Homewood, Ala........ 40.2 611.9 Right bank 35 ft upstream from gravel road 0.1 mile east of Shannon Road (E':SE»q sec. 33, T. 18 8.,. R.. 3 -W.) near Homewood, *39.2 601.2 Right bank 35 ft, downstream from gravel road 0.1 mile east of Shannon Road (EHSEZ sec. 33, T. IO S.. R. 5 W.) near Homewood, 30:2 601.2 Right bank 25 ft upstream from Alabama State Highway 150, 0.6 mile southeast of Parkwood, 31.5 553.1 Right bank at downstream side of Alabama State Highway 150, 0.6 mile southeast of Parkwood, cs sass ss 31.5 553.0 Right bank at upstream side of county road 0.8 mile southwest of Parkwood, Ala...... 30.4 538.6 Right bank at downstream side of county road 0.8 mile southwest of Parkwood, Ala. 30.5 538.6 Left bank upstream side of Morgan Road near Hopewell, 25.2 510.6 Left bank downstream from Morgan Road near Hopewell, }% 20,2 510.4 See footnotes at end of table. TABLES TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) CAHABA RIVER BASIN--Continued Shades Creek--Continued U.S. Geological Survey gage (02423630) on left bank on downstream side of bridge on Dickey Spring Road near Greenwood, Ala....:......;«« 1+ «s +s sje cies . 20.8 493.6 Mouth (at Cahaba River mile 104.2)........ 0;0 __ _ ~'. ° . TOMBIGBEE RIVER BASIN Tombigbee River: U.S. Geological Survey gaging station (02441500) on left bank, 1200 feet downstream from bridge on U.S. Highway 45E and 82, at Columbus, Miss............ 319.7 164.4 Left bank at sediment range 10 B l.... 219.3 164.0 Right bank near sediment range 9 B h.... 318.5 1635.8 Creck,..;............n«. «k++... SJ. _ ___. / _ Right ;; sawa sa st risa (age anld : 317.1 163.2 Right bank near sediment range 20 A C.:... 316.0 162.6 Left bank near sediment range 19 A S..... 315.0 161.0 Right bank at sediment range sA 172 £/..... 312.7 158.4 Left bank at sediment range 17 A $ os 312.2 157.3 Right bank at sediment range 16 A C...... 311.2 156.0 Right bank near sediment range 15 A £/.... 309.6 153.8 Right bank near sediment range 13 A £/.... 307.8 1952.7 Left bank at sediment range 11 HB $A .as. 307.3 1152.7 Left bank at sediment range 8 HB £7 ,,,,,,, 306.0 152.1 Right bank at sediment range 3 HB £/...... 302.6 /150.6 Right bank at sediment range 8 A £/....... 300.2 150.7 Right bank near Southern Natural Gas pipeline near Forreston, Miss............ 297.8 148.8 Right bank at sediment range 4 A 4 ss 295.0 345.0 Right bank near sediment range 3 A £/..... 292 ,0 143: Left bank on staff gage at Pickensville Eanding, ias 290.1 143.0 Left bank at sediment range 1 A f/f ....... 288.0 111.1 Left bank at sediment range 15 AG &..: 286.2 199.7 Right bank near sediment range BCD *.}... 285.0 1390 :5 Left bank near sediment range 15 A $...... 285.0 140.0 Left bank at sediment range 14 A /F": 281.8 139.6 See footnotes at end of table. FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of: 1929 Stream and location (miles) (feet) TOMBIGBEE RIVER BASIN--Continued Tombigbee River--Continued U.S. Geological Survey gaging station (02444500) near left bank, downstream side of bridge on State Highway 17, near Cochrane, Ala............... $7° :: ->> 271.4 1335.1 Right bank at sediment range 10 A —] ...... 271.1 131.7 Left bank near sediment range 9 A img... 264.8 130; 2 Right bank near sediment range 8 A f] ..... 261.4 1350.5 Right bank at sediment range 7 A £/.m.%.n2 2090 129.3 Left bank at sediment range 6 A ias 2595.0 127.5 Right bank at sediment range 5 A ...is 282.1 124.8 Left bank near sediment range 4 A .c 248.1 123.2 Right bank near sediment range 3 A &..... 244.5 122.6 Right bank near sediment range 2 A .... 241.0 120;}2 U.S. Geological Survey gaging station (02449000) near right bank on downstream side of bridge on State Highway 359 at Gainesville, Ala........... 234.4 119.6 Right bank at sediment range I1 C t... 232.8 117.5 Fet aas saris ao, - aisle is ain s 229.4 116.2 Left bank at sediment range 3 C a.. 229.0 116.2 Left Bank.......... «ivete ale seine srs ao sisle's a's 226.5 115.4 Left bank near sediment range 5 C Air.. 221.3 111.7 Right bank near sediment range 6 C A s 218;1 111.5 U.S. Geological Survey gaging station (02449500 discontinued) at bridge on U.S. - Highway 11 .at Epes, Ala......,...... 215.2 108.9 Left bank near sediment range 7 C E] ...... 212.9 107.4 Left bank near sediment range 8 C £4 ...... 207.9 106.8 Left bank near sediment range 9 C - ...... 204.2 104.3 Left bank, Bluffport, Ala............,. ... 202.0 102.5 Right bank near sediment range 10 C ... 200.5 101.5 Right bank near sediment range 11 C ff.... 198.3 100.7 Right bank near sediment range 12 C ff.... 193.0 96.4 Right bank near sediment range 12 CAf§/... 191.2 a/ 95.5 Right bank near sediment range RB 5 - .... 189.8 ~ +995.7 Left bank at sediment range RB 10 €£/...... 185.0 95.4 Right bank near sediment range RB 12 /... 1835.0 gs .s Right bank near sediment range 12 CE §... 180.8 95. 2 Left bank near sediment range 13 C £/7..... 179.9 95.2 Left bank 100 feet upstream from Black Warrior RIVEI....«ria @@@ sls 175.0 93.9 See footnotes at end of table. -<¥<- Sowashee Creek at Meridian, Miss. Hawkins Crossing road bridge, highwater mark on upstream and downstream curb Of axes +0 10.6 5354 Southern Railroad bridge, highwater mark on second bent from left bank abutment on downstream .. 10.0 3821 U:S. Highway 11 and 80 bridge, highwater mark on upstream end of right bank concrete abutment....;.......;.1 @.... 9.8 531.0 U.S. Geological Survey gaging station (02476500) upstream side of bridge on U.S. Highway 45 at Meridian, Miss...... 9.5 328.8 Meridian and Bigbee Railroad, highwater mark on downstream piling of first bent from left abutment.......;..%... . 8.2 $18.3 18th Avenue bridge, highwater mark on Fight bank abutment...........;....... 8.1 347.0 --Highwater mark on first creosote piling on left bank upstream wingwall. 8.1 316.7 U.S. Highway 45 (business route) bridge highwater mark on 14-inch creosote sign pole 40 feet east of southeast corner of .s. 776 316.2 Grand Avenue bridge, highwater mark on power pole, 130 feet right of- bridge, 25 feet upstream from centerline of a. tholll sales ale Pele an s aa 7.4 --Highwater mark on upstream right bridge %... 1.94. *% TiL 313.2 --Highwater mark on downstream wall of concrete block building, 130 feet downstream and 200 feet right of right bridge T/A 312.7 See footnotes at end of table. 92 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued (Data furnished by Corps of Engineers, Mobile District) Elevation above Distance National geodetic upstream vertical datum f from mouth of 1929 Stream and location (miles) (feet) PASCAGOULA RIVER BASIN--Continued Pascagoula River tributary streams--Continued Sowashee Creek at Meridian, Miss.--Continued 31st Avenue bridge, highwater mark on concrete guardrail post at right bank bridge abutment pile cap......... ..... 6.6 310.7 --Highwater mark on rear of church about 120 feet from right bank abutment, 80 feet downstream from centerline of ssa s sales r 0s s 6.6 310.5 Gulf Mobile & Ohio Railroad, highwater mark on upstream piling of fifth pile bent from right abutment.............. 6.5 208.3 I-20 frontage road bridge, highwater mark on upstream concrete pile of second pile bent from left bank saints + 5.6 502-6 49th Avenue bridge, highwater mark on 18-inch oak tree about 50 feet up- stream and 60 feet left of left bank bridge abutment................«...~.. 4 .8 301.4 --Highwater mark on 14-inch power pole 50 feet downstream and 130 feet from left bank bridge abutment............. 4.8 301.1 Mouth, at Okatibbee Creek mile 84.4..... 0.0 >> =: ' PEARL RIVER BASIN Nanih Waiya Creek: Near Louisville, Miss., upstream side of State Highway 14, 150 feet right of main-channel bridge................... g/458.5 4656.3 --At downstream right abutment of main- channel g/458.5 466.4 Near Fearns Springs, Miss., upstream side of State Highway 490, 1800 feet right of main-channel bridge.......... g/446.2 434.6 --Downstream side of State Highway 490, 1800 feet right of main-channel .. ry .r l s 4a . g/446.2 433.9 See footnotes at end of table. TABLES TABLE 5.-Flood-crest stages-Continued 93 Stream and location PEARL RIVER BASIN--Continued Nanih Waiya Creek--Continued Near Handle, Miss., upstream side of State Highway 397, L300 feet right of main-channel --Downstream side of State Highway 397, 1000 feet left of main-channel bridge... Pearl River: Near Burnside, Miss., upstream side of State Highway 15, 1700 feet left of main-channel bridge...............~.r../. --Downstream side of State Highway 15, 150 feet left of main-channel bridge.... Near Philadelphia, Miss., upstream side of State Highway 19, 4800 feet right of main-channel «« --Downstream side of State Highway 19, 300 feet right of main-channel bridge... Edinburg, Miss., upstream side of State Highway 16, 1300 feet left of main- channel U.S. Geological Survey gaging station (02482000) right bank, 20 feet down- stream from bridge on State Highway 16, at Edinburg, Near Edinburg, Miss., left bank, 1.5 miles downstream from State Highway 16, FEeFt Dank... .. rere h.. Near Sunrise, Miss., upstream side of county highway, 2100 -feet right of main-channel bridge.... --At Corps of Engineers profile point No. 17, left bank, in SW4NE4 sec. 1, T: ION. Rr O - «ears ssn sw ies ss Near Freeny, Miss., at State Highway 488 crossing of Standing Pine Creek......... Near Carthage, Miss., upstream side of State Highway 35, 7000 feet right of main-channel bridge.................s.}. See footnotes at end of table. Distance upstream from mouth (miles) g/442.9 g/442.9 g/416.2 g/416.2 g/412.9 g/4a12.9 g/387.5 387.5 h/ 386.4 g/378.5 276.0 i/371.8 g/366.3 Elevation above National geodetic vertical datum of 1929 (feet) 430.6 430.2 401.3 399.0 395.2 394.1 37. 371.7 h/ 370.0 362.0 h/355.7 h/352.0 344.7 94 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) PEARL RIVER BASIN--Continued Pearl River--Continued --~Downstream side of State Highway 35, 7000 feet right of main-channel bridge.. g/3565.3 MA3:3 U.S. Geological Survey gaging station (02482550) right bank on downstream side of bridge on State Highway 35, near Carthage, r> esse esr ar : 366. 3 344.0 Near Carthage, Miss., 5.8 river miles downstream from bridge at State Highway 35, right bank of main channel.......... 360.5 h/35355.7 Near Wiggins, Miss., 4.3 river miles up- 3 stream from bridge at State Highway 13, left bank of main channel............ ... 358.4 h/$35..2 Near Wiggins, Miss., upstream side of C State Highway 13, 2000 feet left of main-channel bridgg....................s. g/354.1 382.8 --Downstream side of State Highway 13, left bank at end of main-channel bridge. g/ 354.1 h/331.7 Near Wiggins, Miss., t.8 river miles downstream from State Highway 13, right bank of main 3852.3 h/ 330.4 Near Ofahoma, Miss., 6.3 river miles up- = stream from Ross Barnett Reservoir low- head dam, right bank 1400 feet right on right bank of GCoge Lake...............~.. 348.8 h/327.8 Ross Barnett Reservoir low-head dam, Fight - bank, 250 feet 342.6 h/352L.3 Near Ross Barnett Reservoir low-head dam 1.5 river miles downstream, right bank 2000 feet right of main channel, on Fight bank of Alligator Lake........../.. 341.4 h/319.5 Near Ratliff Ferry, 7.8 fiver miles up: * stream left bank, 1000 feet upstream from Rankin-Scott County line........... 3386.2 317,353 Near Ratliff Ferry, 5.9 river miles up- stream, right bank, 200 feet right of main Channel... 1% ra «kaas hs r«rs ra rr sss 536.5 Rat1iff Ferry, right bank, 200 feet right of nain ss 330.4 213.1 River Bend, right bank, 60 feet right of main 11s sas sss}: 328.5 310.4 See footnotes at end of table. TABLES TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) PEARL RIVER BASIN--Continued Pearl River--Continued Near River Bend, 2.8 river miles down- stream right bank 2000 feet right, of main channel at Natchez Trace crossing Brown CIEEK...'. +++ rss . 226.8 305.8 Near Canton, Miss., along Natchez Trace, 2.0 miles north of State Highway 43..... 321.0 301.3 Near Canton, at State Highway 43, up- stream side of State Highway 43, 3500 feet left of main-channel bridge........ g/319.4 301.3 --Downstream side of State Highway 43, 50 feet left of main-channel bridge..... g/319.4 299.9 U.S. Geological Survey gaging station 5. (02485000 discontinued) downstream side of left main pier of Meeks bridge on State Highway 43 near Canton, Miss...... 300.0 Ross Barnett Reservoir dam, upstream side of dam at Control House gage............ 301.8 299.8 --Downstream side of dam, 10,500 feet Tight of .s 301.6 288.2 Jackson, Miss., north side of Jackson Country Club at maintenance buildings... 299.6 2987 Jackson, Miss., southeast side of St. Andrews Drive, 400 feet northeast from intersection with St. Haylake Drive... .. 298.0 28718 ~-Old Canton Road at Purple Creck......... 296.6 286.8 Near Jackson, Miss., near north edge of sec. 23, T. 6 N., R. 2 E., 600 feet west Of railroad........./.../....¢....¢@@a .. 2096.5 286.9 Near Jackson, Miss., on gravel road 0.5 miles west of Luckney, Miss............. 295. 286.4 Jackson, Miss., at intersection of East Northside Drive and East Cheryl......... 295. 286.1 Jackson, Miss., at Hanging Moss Creek at interstate Highway 295. 286.4 Near Jackson, Miss., at intersection of State Highways 25 and 475 in NE4 sec. Pos Te 6 N:, R. 2 ° E..: ls vins ses .. 294 . 285.6 Near Jackson, Miss., at State Highway 475, at Hog «=,; 294 . 284.7 At Jackson, Miss., in SEG sec. 19, T. 6 N., 'R. 2 E., -at Lake Circle.........,.... 293.35 285.2 See footnotes at end of table. 96 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) PEARL RIVER BASIN--Continued Pearl River-Continued Near Jackson, Miss., in SE4 sec. 29, T. 6 N., R. 2 E.. upstream side of State Highway 25, at B-Line Caspline-Jiffy Stop, 4200 feet left of mnain-channel .s 2035.2 2085.2 --Downstream side of State Highway 25 across from B-Line Station...........,... . . 293.2 284.5 Jackson, Miss., upstream side of State Highway 25, 150 feet northwest of Lelia Drive intersection, 35500 feet west of main-channel bridge............. 292.9 284.6 --Downstream side State Highway 25, 100 feet south of Lelia Drive intersection.. 292.5 283.6 Jackson, Miss., upstream side of State Highway 25, 1500 feet left of main- channel g/292.4 285.1 --Downstream side of State Highway 25 at 1eft ADULMCNL. 1a ric s. g/292.4 294.1 Near Jackson, Miss., at intersection of x State Highway 468 and GM&O Railroad north of Flowood ss 291.9 284.1 Jackson, Miss., State Highway 25, at smith-Wills 291.5 283.1 Jackson, Miss., upstream side of GM§O Railroad, right bank, 800 feet right main channel.....}1.. ccr g/290.6 282.35 --Downstream side of GM§&O Railroad, right bank, 800 feet right of main channel.... g/290.6 281.8 Jackson, Miss., Interstate Highway 55 in NEY see. 2, T. 5 N., R. 1 FE.. about 1000 feet north of Fortification Street...... 289.6 281.8 Jackson, Miss., on west side of building at corner of Noody and Harris Streets, 800 feet southwest of Fortification Street inside fairgrounds levee......... 269.2 279.4 Jackson, Miss., upstream side of Inter- state Highway 55, left bank, 200 feet left of main-channel bridge............. 288.4 279.9 --Downstream side of Interstate Highway 55 at left abutment of main-channel sia nabs cs 1s ss g/288.3 279.3 See footnotes at end of table. TABLES TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) PEARL RIVER BASIN--Continued Pearl River--Continued Jackson, Miss., on Tombigbee Street, 200 feet east of Jefferson Street across from northeast corner of Mississippi Power & Light Company building inside fairgrounds nance sane s a 288.2 279.4 Jackson, Miss., downstream side of Woodrow Wilson bridge at right abutment... .r icra a «se a's late siace's g/287.6 278.7. Jackson, Miss., upstream side of I. C. Railroad,; right ;» g/287.2 2781 --Downstream side of I. C. Railroad at right end of bridge.................. g/287.2 277.8 Jackson, Miss., upstream side of U.S. Highway 80, right bank, 800 feet right of main-channel bridge................. . g/287..0 277.08 U.S. Geological Survey gaging station (02486000) on left bank at downstream side of bridge on U.S. Highway 80 at TACKSON, MASS......1 .. ««« ars r aaa altec ss 267.0 277.0 Downstream side of U.S. Highway 80, right bank at end of main-channel bridge 2867.0 276.9 Jackson, Miss., upstream side of Inter- state Highway 20, right bank, 800 feet Fight Of a ahaa . g/286.7 276.8 --Downstream side of Interstate Highway T 20, right bank, 800 feet right of main *s tisk 60%. g/286.6 276.2 Jackson, Miss., GM§O Railroad at <. McDowell Road at abandoned landfill, right bank, 1000 feet right of main channel. ariens rats sss . 265.6 275.5 Jackson, Miss., along GM§&O Railroad about 300 feet south and 300 feet west of abandoned landfill entrance.......... 13/284 2735.6 Jackson, Miss., along GM§&O Railroad, 2000 > feet north of Savannah Street inter- change, right bank, 1500 feet right of river at north levee of Wastewater Treatment . 282.4 272.06 --1500 feet south of Savannah Street inter- change, 400 feet east of railroad at south levee of Wastewater Treatment .. ress scr rosie a s r rcs hia aly s soe a seine vor r 281.4 270.8 See footnotes at end of table. 98 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) PEARL RIVER BASIN--Continued Pearl River--Continued Elton, Miss., downstream side Elton Road, right bank, east side of railroad at FItONn.... .% +.. alt as bin cin ele s Sin ais s 279.1 26977 Richland, Miss., upstream side of Sloan Drive, left bank, 4500 feet left of main 2785 269.1 Byram, Miss., downstream side of county highway, right bank, 700 feet right of main g/270.2 264.4 Near Rosemary, Miss., upstream side of > county highway, right bank. 9000 feet right of g/259.2 256.9 --Downstream side of county highway, near left end of main-channel bridge......... g/259.2 256.8 Near Moncure, Miss., upstream side of county highway, right bank, 3600 feet right of main g/254.9 2527. --Downstream side of county highway, right £. bank, at end of main-channel bridge..... g/254.9 252.0 Near Gatesville, Miss., 300 feet upstream from county highway, left bank, 300 feet left of -main chamnel.;.......;.......... g/246.2 249.4 --Downstream side of highway, left bank, left end of main-channel bridge......... g/246.2 249.3 Near Hopewell, Miss., downstream side of county highway, left bank at end of main-channel bridge..:;:.................. g/241.4 244.2 --Right bank, at end of main-channel ara sir € . g/241.4 244.3 Near Hopewell, Miss., along county road on east bank, 24 miles south of Hope- well - rss pires s Gins + 3/236.2 241.7 Georgetown, Miss., 200 feet upstream from main-channel bridge at State Highway 28 left bank 200 feet Ileft................. g/231.7 231.7 --Downstream side of State Highway 28, left bank, at end of main-channel briadge............ter.hnrer redes. reese... €/231.7 231.4 Near Georgetown, Miss., at Copiah Creek, right bank, 1300 feet right of main reacts rss as ans 1/228.2 228.6 See footnotes at end of table. TABLES TABLE 5.-Flood-crest stages-Continued Elevation above See footnotes at end of table. Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) PEARL RIVER BASIN--Continued Pearl River--Continued Near Rockport, Miss., at Keys Creek, Tight bank, 2100 feet right of main rs « 1Jj/222.6 224.2 U.S. Geological Survey gaging station e- (02448000 discontinued) downstream side at right end of bridge on county highway near Rockport, Miss., (in abandoned gage house)................... 221.7 223.0 --Downstream left bank at end of bridge... 221.7 222.9 Near Rockport, Miss., at Dry Creek, loft bank 3000 ft sng ss... 1/220.3 220.8 --At Pegies Creek, right bank, 2300 feet R ment coors nie r bins c ale dele s C a 1/216.4 217.5 --At Saddlebags Creek, right bank, 600 & fect Tight... rere 1/204.8 209.4 Near Ferguson, Miss., at St. Regis Paper C Company pumping station, left bank...... 205.4 208.2 Wanilla, Miss., 7700 feet right of river, at State Highway 27 crossing of Bear san a. ri rita's tor van y a a % £1j/202. 206.3 Near Rosella, Miss., upstream side of C county highway, left bank, 800 feet Upstream... s saale sae as riviera 's g3/200.0 202.4 --Downstream side of county highway, under reference point near center of main-channel gi/200.0 201.9 Near Monticello, Miss., at tributary, 1 mile north of intersection of U.S. Highway 84 and county highway, left bank,; 2400 feet J/ 197.0 198.6 Monticello, Miss., at old bridge site, > 1.1 miles upstream from U.S. Highway 84, Fight bank. ........,....«sacalses age sise . 191.9 195.0 Monticello, Miss., upstream side U.S. Highway 84, left bank, 700 feet left.... g/190.8 193.9 --400 feet downstream from U.S. Highway 5 84, left bank,-300 feet left............ g/ 190.8 192.3 U.S. Geological Survey gaging station (02488500) downstream side of left pier of bridge on U.S.. Highway 84 near Monticello,. sis ant + 190.8 192.6 99 100 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Stream and location Distance upstream from mouth (miles) Elevation above National geodetic vertical datum of 1929 (feet) PEARL RIVER BASIN--Continued Pearl River--Continued Near Monticello, Miss., at State Highway 587 crossing Halls Creek, right bank, 4500 fect s sonra sir c ss Near Monticello, Miss., at GM§O Railroad crossing Coopers Creek, 4000 feet right of Pearl River channel............ Near Robinwood, Miss., at GM&O Railroad crossing tributary, 2500 feet right of main .r... 2% «.s «re cls's aa Near Tilton, Miss., at State Highway 587 GM§O Railroad crossing Tilton Creek, 2700 feet right of main- Near White Bluff, at GM§O Railroad crossing small tributary, 3500 feet Tight of main channel................... Morgantown, Miss., along north side of county road, 500 feet east of State Highway 587... «@ Near Goss, Miss., at State Highway 13 crossing Holliday Creek, left bank, s500 feet left of main channel.......... Near Columbia, Miss., at forest road along Twitty Creek, left bank, 500 feet left of main channel................ .... Near Morgantown, Miss., at State Highway 587 crossing of small tributary, 72.8 miles southeast of Morgantown ........... Near Columbia, Miss., upstream side of State Highway 35 Bypass, 8300 feet left of main-channel bridge..;............... Near Columbia, Miss., upstream side of State Highway 35 Bypass, about 1000 feet left of main channel............... --Downstream side of main-channel bridge at left Columbia, Miss., upstream side of GM§O Railroad right bank, 1000 feet right of main --Downstream side of GM&O Railroad at yfight end of main-channel bridge........ See footnotes at end of table. i/189.8 i/184.3 1835.5 i/166.3 157.8 151.5 i/149.8 147.6 146.1 gi/143.5 5/141.6 g/141.6 g/138.7 g/138.7 192.4 187.1 184.3 172.9 167.1 160.0 157.9 155.5 154.9 1952.2 150.4 148.7 146.7 145.0 TABLES 101 TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) PEARL RIVER BASIN--Continued Pearl River--Continued Columbia, Miss., upstream side of U.S. Highway 98, right bank about 500 feet right of g/157.8 144.8 National Weather Service gaging station (02489000) downstream side of upstream bridge on U.S. Highway 98 near Columbia, Miss., wire-weight gage }... g/137.8 143.5 --Downstream side of U.S. Highway 98 at right abutment of main-channel bridge... g/1357.8 1428 Near Lampton, Miss., at State Highway. crossing of Upper Little Creek, 2.2 miles left of river, half a mile south Of 125.8 153.6 Near Hub, Miss., at State Highway 43 crossing of Lower Little Creek, 1.8 miles southwest of Hub, 1.2 miles left Of: 121.9 125.9 Near Sandy Hook, Miss., 1800 feet east of railroad at upstream side of county :.: +- «a+ r arn 111.9 1165.2 Near Marion-Pearl River County line, at State Highway 43 crossing tributary, left bank, 4000 feet left of main s sels y eve rink rirce s r aa aon wonks 3/103.4 106.6 Near Bogalusa, La., gaging station near right bank at downstream side of State Highway 10, 2 miles east of Bogalusa.... 78x2 I/ 78.3 Near Bogalusa, La., at Richardson's Land- ing on 5-inch tree, 300 feet upstream from 74.8 h/.. 74.5 East Pearl River near Nicholson, down- stream side Interstate Highway 59 near left downstream abutment................ 35.6 h/ 24.0 West Pearl River at Pearl River, La., on power pole 20 feet upstream from ..... r. ¥ sath asi r rig's oon ane s a 22.1 h/ 19.8 East Pearl River near Gainsville, Miss., on 24-~inch tree on left bank............ 20.7 h/ 12.9 See footnotes at end of table. 102 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Elevation above Pistance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) PEARL RIVER BASIN--Continued Pearl River--Continued West Pearl River at Davis Landing transferred to power pole downstream right bank end of boat ramp............. 16.6 h/ 11.8 East Pearl River near Slidell, La., down- stream side Interstate Highway 10, near left abutment «« sr 15.4 10.2 East Pearl River near Pearlington, Miss., at U:S-~ Highway 9.0 h/ *S 70 West Pearl River near Pearlington, Miss., at U.S. Highway 80 near downstream right abutment......;.............6r%.s. TO n/ 5.6 Pearl River tributary streams: Tallahaga Creek: Néar Louisville, Miss., upstream side of State Highway 25, left bank, 500 feet .s g/ 15.9 480.5 --Downstream side of State Highway 25 at right end of main-channel bridge... g/ 15.9 478.2 Near Noxapater, Miss., upstream side of State Highway 15, right bank, 1450 feet vox ss sss g/ 19.7 445.1 --Downstream side of State Highway 15, at right end of main-channel bridge... ofa" 90.7 4435.7 Noxapater Creek: Near Louisville, Miss., upstream side of State Highway 25, left bank, 700 feet >is. s sind. g/ 21.6 183.7 --Downstream side of State Highway 25 at right end of main-channel bridge... 216 479.5 Near Noxapater, Miss., upstream side of State Highway 15, right bank, 1000 feet ss ss g/. 10.9 450.8 --Downstream side of State Highway 15, left end of main-channel bridge.... ... 10.9 429.2 See footnotes at end of table. TABLES 103 TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of- 1929 Stream and location (miles) (feet) PEARL RIVER BASIN--Continued Pearl River tributary streams--Continued Lobutcha Creek: Near Zama, Miss., upstream side of county highway (Massy Crossing), left bank, 2900 feet left of main channel.. 57.1 424.2 --Downstream side of county highway right bank, 150 feet right of main- channel 3r¥1 422.8 Zama, Miss., upstream side of State Highway 19, right bank, 75 feet right of main-channel bridge................ 31.8 415.2 --Downstream side of State Highway 19, S00 feet right of right end of main- channel 31.8 414.2 Near Renfroe, Miss., upstream side of State Highway 25, right bank, 500 feet Tight of main channel...........;...... 16.7 385.9 --Downstream side of State Highway 25 at right end of main-channel bridge... 16.7, 383.9 Near Carthage, Miss., upstream side of washed out county highway (Scotts Crossing), left bank, 50 feet right of main channel............../l.¢rn;... 1049 569.0 Near Carthage, Miss., upstream side of State Highway 16, left bank, 4400 feet left of main channel........;.... 4.2 356.9 --Downstream side of State Highway 16 at right end of main-channel bridge... 4.2 555.0 Yockanookany River: Ackerman, Miss., upstream side of State Highway 15, left bank, 100 feet left of tributary and 200 feet south of Illinois Central Gulf Raril- TOAdY s+ vs ria na son ne a aige nv te a re sors 5a 74:7 515.6 Near Fentress, Miss., upstream side of county road., left bank, G650-feet siva a vin cir n init acre n nnis ain t aon e's s elds 71 488.1 --Downstream side of county road at right end of main-channel bridge... ... 711 485.3 See footnotes at end of table. 104 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Elevation above See footnotes at end of table. Airstance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) PEARL RIVER BASIN--Continued Pearl River tributary streams--Continued Yockanookany River--Continued Weir, Miss., upstream side of county road, right bank, 900 feet right...... 66.7 460.4 --Downstream side of road at left end of main-channel bridge................ 66.7 459.8 Weir, Miss., upstream side of State Highway 413, right bank, 50 feet Fight va ran ain sr rir sone s ande = + 66.0 458.3 --Downstream side of State Highway 413 at right end of main-channel bridge... 66.0 457.0 McCool, Miss., upstream side of State Highway 411, left bank, 1200 feet left of main channel:................. 60.1 437.9 --Downstream side of State Highway 411 at left end of main-channel bridge.... 60.1 437.0 Near Ethel, Miss., upstream side of county highway east of Ethel, right bank,; 1400 feet fTight................. 51.6 122.3 --Downstream side of county road, 100 feet right of main-channel bridge..... 51.6 4241: Near Ethel, Miss., upstream side of county highway, south of Ethel, left bank, 1000 fect left.................. 50.6 418.8 --Downstream side of county highway, 700 feet left of main-channel bridge.. 50.6 416.7 Near Kosciusko, Miss., upstream side of county highway (Munson Crossing), 3 miles east of Kosciusko, right bank, 2200 feet .. 45.3 402.4 --Downstream side of county highway, right bank, 3600 feet right........... 45.3 40270 Near Kosciusko, Miss., 400 feet upstream from left end of bridge at State High- way 35, and about 300 feet left of main 41.9 398.9 --Downstream side of State Highway 35 at left end of bridge................. 41,9 397.0 U.S. Geological Survey gaging station (02484000) left bank on downstream side of bridge on State Highway 35 near Kosciusko, Miss.................. 41.9 397.4 TABLES 105 TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) PEARL RIVER BASIN--Continued Pearl River tributary streams--Continued Yockanookany River--Continued Near Kosciusko, Miss., at crest-stage gage site 5-C, right bank, 600 feet right of main channel.. ...... is j/ 40.9 394.0 --At crest-stage gage site 4-D, right bank, 1000 feet right of main Channels. sas an airs as s scmie'e rie wie J/: 40.1 389.1 --At crest-stage gage site 3-D, right he bank, 1800 feet right of main Channel.. .... ..}. crt ans eon aie a dig J/ - 38.4 384.7 --At crest-stage gage site 2-D, right "G bank, 3200 feet right of main channel. 3/ 37.2 381.2 --At crest-stage gage site 1-D, right w bank, 2800 feet right of main channel. 3/ 55.9 379.1 Near Thomastown, Miss., downstream side of county highway, 4 miles northeast of Thomastown, right bank, 2000 feet right of main channe1l............... .. 28.2 368.8 Near Thomastown, Miss., upstream side of State Highway 429, right bank, S00 feet-right of main channel...... ... 22.2 361.2 --Downstream side of State Highway 429 at leftrend of 22.2 359.2 Near Ofahoma, Miss., upstream side of county highway (Red Dog Road), 8.6 river miles upstream from State High- way 16, 500 feet right of main- channel s. 12.6 346.4 --Downstream side of main-channel bridge at left abutment................ 12.6 346.2 Near Ofahoma, Miss., upstream side of State Highway 16, right bank, 5800 feet right of main channel............ 4.0 335.3 U.S. Geological Survey gaging station (02484500) near center of span on downstream side of bridge on State Highway 16 near Ofahoma, Miss......... 3:0 334.4 --Downstream side of State Highway 16 near right +4 3.0 353.1 See footnotes at end of table. 106 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Stream and location Distance upstream from mouth (miles) Elevation above National geodetic vertical datum of 1929 (feet) BIG BLACK RIVER BASIN Big Black River: Near Tomnolan, Miss., downstream side of county highway, left bank............... Near Stewart, Miss., upstream side of county highway, right bank, about 90 feet from main-channel bridge........ Near Kilmichael, Miss., downstream side of State Highway 413, right bank........ Near Vaiden, Miss., downstream State Highway 35, right bank, 1300 feet right of main-channel bridge............ West, Miss., upstream side of State High- way 19, right bank, 1700 feet right of main CHaNRCI . .. .. ce vin avs ae nln sisal a sain + --Downstream side of State Highway 19 at right end of main-channel U.S. Geological Survey gaging station (07289350) downstream side of left pier of bridge on State Highway 19 at West, Durant, Miss., upstream side of State Highway 12, right bank, 6000 feet Tight... nos a isl ain a Pin aon alsin e ns ns --Downstream side of State Highway 12, at left end of main-channel bridge...... Near Goodman, Miss., upstream side of State Highway 14, right bank, 500 feet right of nain channel........%...... --Upstream side of State Highway 14, right bank, 6700 feet right of main- channel --Downstream side of State Highway 14 at left end of main-channel bridge......... U.S. Geological Survey gaging station (07289500 discontinued) downstream side of bridge on 'old (abandoned) U.S. Highway 51 at Pickens, Miss., 220:feet right of bridge...........;.... Pickens, Miss., upstream side of U.S. Highway 51, right bank, 3200 feet Fight of nain .... See footnotes at end of table. 265.6 258.5 250.8 225.2 209. 0 209.0 209.0 190.8 190; 8 175.2 176.0 1760 162.7 161.2 h/ 341.9 309.9 h/288.2 274.6 275.6 274.0 256 :1 2535.0 236.7 257.0 235.1 h/219.9 218.7 TABLES TABLE 5.-Flood-crest stages-Continued 107 Distance upstream from mouth Stream and location (miles) BIG BLACK RIVER BASIN--Continued Big Black River--Continued --Downstream side of U.S. Highway 51 at left end of main-channel DFIORC...2.. ...... valr a wik kin alain a as nle aon nl er 161.2 Way, Miss., upstream side of Illinois Central Railroad, left bank, 4500 feet left of main 145.8 --Downstream side of Illinois Central Railroad, left bank, 4500 feet left of main 145.8 Near Way, Miss., upstream side of Inter- state Highway 55, right bank, 3800 feet right of main 144.5 --Downstream side of Interstate Highway 55 at left end of main-channel bridge...... 144.5 Near Canton, Miss., upstream side of State Highway 16, right bank, 3000 feet right of main-channel bridge.................. 139.6 --Downstream side of State Highway 16 at right end of main-channel bridge........ 139.6 Near Bentonia, Miss., upstream side of U.S. Highway 49, right bank, 1000 feet right of main-channel bridge............ 106.0 --Downstream side of U.S. Highway 49 at right end of main-channel bridge........ 106.0 U.S. Army Corps of Engineers crest-stage gage (07289730) on downstream side of left pier of bridge on U.S. Highway 49 near Bentonia, MISS..................y.. 106.0 Near Bentonia, Miss., at county highway at Turkeyfoot Branch, right bank, 1300 feet 98.3 Near Nevada, Miss., at abandoned Coxs Ferry Road, right bank, 4000 feet right of main 92.8 Near Nevada, Miss., at abandoned Coxs Ferry Road, left bank, 3500 feet left of main 92..1 Near Nevada, Miss., at county highway near King Solomon Church, right bank, 5000 feet 89.8 See footnotes at end of table. Elevation above National geodetic vertical datum of 1929 (feet) 247.6 201.5 200.4 19916 198.4 194.5 192.9 162.9 161.6 161.6 h/156.1 h/154.2 153.3 h/153.6 108 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Stream and location BIG BLACK RIVER BASIN--Continued Big Black River--Continued Near Nevada, Miss., at county highway near center of sec. 28, T. 8 N., R. 3 W., left bank, 4500 feet:left................ Near Youngton, Miss., at end of county highway in sec. 10, T. 1 N., R. 4 W., left bank, 1000 feet left of main ss Near Youngton, Miss., at county highway at Halls Creek, left bank, 3700 feet left of main channel..............;..... Near Edwards, Miss., at county highway at Rocky Creek, left bank, 4500 feet left of main ag. Near Edwards, Miss., at county highway at Askew Bridge (abandoned), left bank, 2500 feet left of main channel.......... Near Edwards, Miss., at upstream side of Interstate Highway 20, right bank, 2800 feet right of main channel......... --Downstream side of Interstate Highway 20, at left end of main-channel bridge.. Near Bovina, Miss., upstream side of U.S. Highway 80, left bank, 500 feet left of main .. ssi wks sls --Downstream side of U.S. Highway 80 at left end of main-channel bridge......... U.S. Geological Survey gaging station (07290000) downstream side of left pier of bridge on U.S, Highway 80 near Bovina, Near Bovina, Miss., downstream side of Illinois Central Gulf Railroad at Fright end of main-channel bridge........ Near Bovina, Miss., at county highway in NWNW! sec. 20, T. 15 N.. R. 5 E., at Tee road north near Markham Creek, right bank, 5800 feet right of main ..... ..a sre eas ss bers s r ras acres Near Ufica, Miss., upstream side of State Highway 27, right bank, 900 feet right of main ss See footnotes at end of table. Distance upstream from mouth (miles) 89.3 $1.0 76.3 729 o 69.8 69.8 614.7 61:7 61.7 61.2 54.8 S1..7 Elevation above National geodetic vertical datum of 1929 (feet) h/152.7 h/148.0 h/145.4 h/143.8 140.2 125.5 124.1 h/116.2 113.8 TABLES TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) BIG BLACK RIVER BASIN--Continued Big Black River--Continued --Downstream side of State Highway 27, at right end of main-channel bridge..... $1.7 112.4 Near Utica, Miss., upstream side of Fishers Bridge, right bank, 6000 feet right of main 39.4 105.5 --Downstream side of Fishers Bridge, 50 feet downstream from left end of main- channel DridgG............ .s} sales . 39.4 104.4 Near Rocky: Springs, Miss., at end of county highway in NW4SE4 sec. 37, T. 14 N., R. 4 E., left bank, 100 feet feft of main channel................sg.. 33.8 h/ 99.4 Near Port Gibson, Miss., at Hankinson io Bridge, left bank, 100 feet left of pain Channel ss 25.0 h/ 94.3 --Right bank, 1300 feet right of main <- «11 sash cules aoe rans s 23.0 93.8 Near Port Gibson, Miss., upstream side of left abutment of U.S. Highway 61 ...i ants ba bon a aa siv aos sigle & 16.0 h/ 90.6 --Downstream side of U.S. Highway 61 at & right abutment of main-channel bridge... 6.0 90.3 Near Port Gibson, Miss., at Karnac Lake Ferry, left bank, 200 feet left of main ss 8.3 h/ 87.4 Big Black River tributary streams: Bear Creek: Near Gluckstadt, Miss., downstream side of U.S. Highway 51, right bank........ g/ 20.0 255.2 Near Canton, Miss., upstream side of g U.S. Highway 51, left bank, 1000 feet iawn vn vins bans ata a a+ bons ib x a g/ 12.0 224.0 --Downstream side of U.S. Highway 51, at right end of main-channel bridge... g/ 12.0 222.9 Canton, Miss., upstream side of State Highway 22, left bank, 200 feet left.. g/ 10.0 217.4 --Downstream side of State Highway 22 5 at right end of main-channel bridge... g/ 10.0 216.4 See footnotes at end of table. 109 110 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 5.-Flood-crest stages-Continued Elevation above Distance National geodetic upstream vertical datum from mouth of 1929 Stream and location (miles) (feet) BIG BLACK RIVER BASIN--Continued Big Black River tributary streams--Continued Bear Creek--Continued Near Canton, Miss., upstream side of Interstate Highway 55, left bank, 200 GEE ;... .is ss cei a + g/ . 9.3 215.1 --Downstream side of Interstate High- way 55 at right end of main-channel ...s ials rv a n s aa nik an nd te n a nce s g/ 9.3 212.9 Near Canton, Miss., upstream side of county highway (old Yazoo City Road) left bank, 400 feet g/ 3.4 197.9 --Downstream side of county highway at right end of main-channel bridge...... a/ :: 3.4 197.8 Oscurred April I6, 1979. Occurred April 17, 1979. Gecurred April 18, 1979. Possible meander effect. Gecurred: April 22, 1979. River mile at main channel bridge. River mile at mouth of tributary. wo 'go h 0 QA O CG ® River mile assigned by U.S. Geological Survey. Sediment range lines, U.S. Army Corps of Engineers sediment surveys. Furnished by U.S. Army Corps of Engineers (rounded to nearest 0.1 foot}. TABLES TABLE 6.-Streamflow velocities, Alabama River near Montgomery, Ala., 02420000, April 12-20, 1979 Point* Average velocity velocity Stage Discharge Nate Time (ft/s) (ft/s) (ft) (ft3/s) 4-12 2400 332 3.46 3210 £3,000 4-13 0600 4.16 8.15 34.60 108,000 4-13 1200 4.73 4.59 36.90 129,000 4-13 1800 5. O0 4.76 39. 40 142,000 4-13 2400 5.30 4.96 42.00 159,000 4-14 0600 5.60 5.15 45.30 183,000 4-14 1200 5.81 5.29 48.10 210,000 4-14 1800 5.92 5.36 50.00 229,000 4-14 2400 & 00 5,40 51.70 245,000 4-15 0600 6.02 5.42 52.63 254,000 4-15 1200 5.92 5. 36 53. 37 258,000 4-15 1800 5.85 5.32 53.87 260,000 4-15 2400 5.74 5.24 54. 20 259,000 4-16 0600 5.66 5.19 54.40 258,000 4-16 1200 5.50 5. 09 54. 50 254,000 4-16 1800 5.40 5.02 54.41 250,000 4-16 2400 & 20 4.87 54.22 241,000 4-17 0600 5.10 4.83 53.82 236,000 4-17 1200 5.00 4.76 53. 36 229,000 4-17 1800 4.84 4.66 52.92 221,000 4-17 2400 4.72 4.58 52.29 212,000 4-18 0600 4.60 4.50 51.70 204,000 4-18 1200 4.50 4, 44 51.00 197,000 4-18 1800 4.48 4.43 50.00 189,000 4-18 2400 4.40 4.37 48.99 180,000 4-19 0600 4.30 4.31 48. 00 170,000 4-19 1200 4.28 4. 30 47.08 163,000 4-19 1800 4.26 4.28 46.02 158,000 4-19 2400 4.25 4.28 45.01 151,000 4-20 0600 4.20 4.24 43.80 143,000 4-20 1200 4.18 4.23 42.75 138,000 4-20 1800 4.12 4.19 41.60 133,000 4-20 2400 4.10 4.18 40, 40 128,000 *From continuous velocity meter at stage of 15 feet, about 25 feet above stream bottom, at upstream end of center bridge pier on U.S. Highway 31 near Montgomery. $19 112 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979 [Includes data for flood of March 1979, where significant. Gage height, in feet; discharge, in cubic feet per second; accumulated runoff, in inches] Site 02400100, Terrapin Creek at Ellisville, Ala. [Maximum discharge occurred on March 4, 1979] ea w un ue ue ae we 2 oo ul un un ae an on ue mn me ae ae ae me an me me mn un mn mn an mn an mn un me an mn an me mn an me un ae mn an an an an ms we as me un ms an an me mn mn uo ou ol on me on ms ae me ae me me me m me ue me m oe me oe e mn a ne oa me me n me oe ne on me GAGE HEIGHT DISCHAR GE ACCUM. RUNOFF GAGE HEIGHT DISCHARGE ACCUM. RUNOFF 3*03 3-03 3-03 3-03 3-03 3-03 3-03 3-063 3 3-03 3=03 3-03 3-04 3-04 3-04 3-04 3-04 3-04 3-04 3-04 3-04 3-05 305 3~05 3~05 3-05 3-05 3-06 3-06 3-06 6.19 6.35 6.49 6.75 7.38 7.67 8.79 9.99 11.51 13.04 14.19 16.26 18.21 19.49 19.72 18.71 18.25 17.99 16.41 15.98 15.52 15.00 14.12 13.77 12.95 12.05 11.91 10.82 10.08 10.02 590 475 455 489 510 562 670 955 1,180 1,600 2,240 3+260 3,890 5,530 8,730 14,100 18,400 19,600 15,600 14,200 13,400 9,080 8 +090 T +340 6+500 5,440 4 +960 3,820 3+610 3540 2,780 2 +300 2 +260 0 . 03 0.05 0.05 0.09 0.19 0.20 0.21 0.21 0 . 22 0.23 0 » 23 0.24 0.26 0 . 28 0 . 30 0 . 33 0 . 47 0 . 76 1.17 1.40 1.92 c 2.09 2.28 2.32 2.37 2.41 2.55 2.61 2.19 2.99 3.01 3.22 3tl‘o 3-16 3-16 3-16 3-16 3-16 3-17 3-17 840 149 745 705 623 558 4B5 475 412 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02400100, Terrapin Creek at Ellisville, Ala. -Continued GAGE HEIGHT 371 352 350 334 334 321 319 304 304 289 289 334 415 514 835 1 +030 1,170 1,190 978 1 +020 1,060 1 +060 740 674 666 558 496 492 418 ACCUM. DATE TIME 0100 2400 0100 2400 0200 2400 0200 2400 0800 2400 1500 1900 2400 1100 1700 2000 2100 2200 2300 2400 0100 0200 0400 0500 0600 0700 1000 1400 1700 2200 2400 0600 1000 GAGE He I GHT 6.06 5.92 415 374 374 347 345 326 326 311 311 306 311 306 304 301 301 332 352 402 489 661 1,000 1,680 3+540 3,820 4,990 5,780 7,360 8,380 8,010 4,800 3,820 3+650 3930 113 ACCUM. RUNOFF 7.26 1.36 114 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 0240100, Terrapin Creek at Ellisville, Ala. -Continued tn o ae a ae as wn an an ae me me an me me we ue we oe on an mn un an a mn an an me an me an os un on me mn n me as ue om me me m an am mn m un me me me me mm me me oe me me oe me m me te m oe oe me me mn me me m te m on me h c om me n me ne ne me t te me he ne me e DATE TIME GAGE DLSCHARGE ACCUM. DATE _ TIME GAGE DISCHARGE ACCUM. HEIGHT RUNOFF HE I GHT RUNOFF 4=04 1200 13.47 4,520 7.41 4-13 0900 17.68 12,400 10.29 4-04 1400 13.57 4,670 7.46 4=13 1600 17.19 11,000 10.77 4=04 1700 13.21 4, 140 7.54 4=13 2000 17.26 11,300 11.04 4-04 1800 12.98 3,830 7.57 4-13 2200 11T.12 10,800 11.18 4-04 2300 11.83 3 +480 7.68 4-13 2400 16.72 9,810 11.30 4-04 2400 11.64 3,350 7.70 4-14 0100 16.43 9,130 11.35 4-05 0100 11.46 31220 7.71 4-14 0400 15.32 7,020 11.49 4-05 0600 10.80 2770 7.80 4-14 0600 14.68 6,120 11.56 4-05 1900 9.93 2210 7.99 4-14 1100 13.13 4,900 11.72 4-05 2400 9.67 2+070 8.06 4#=14 1800 12.93 3,810 11.90 4-14 2400 12.39 3,690 12.04 4-06 0100 9.64 2,050 8.07 4-06 2400 9.02 1+710 8.33 4-15 0100 12.32 3,670 12.06 4=l15 0700 11.81 3,470 12.19 4-15 2100 10.51 2,580 12.44 4-07 0100 9.00 1 +700 8.34 4-15 2400 10.30 2,450 12.48 4-07 2400 8.63 1,530 8.56 4-16 0100 10.24 2+410 12.50 4-08 0100 8.62 1,530 8.57 4-16 2200 9.52 1,990 12.77 4-08 2200 8.41 1,430 8.75 4-16 2400 9.49 1 970 12.79 4-08 2400 8.46 1,450 8.77 4-17 0100 9.47 1,960 12.81 4-09 0100 8.58 1,510 8.78 4-17 2400 9.15 1,780 13.06 4-09 0200 8.92 1 +660 8.79 4-09 0400 9.68 2 +070 8.81 4-09 0500 9.80 2+140 8.83 4-18 0100 9.14 1,780 13.07 4-09 1200 6.81 1 +610 8.90 4-18 2400 8.88 1,640 13.31 4-09 2400 8.02 1 +250 9.01 4-19 0100 8.87 1,640 13.32 4-10 0100 7.97 1 230 9.01 4-19 2400 8.63 1,530 13.54 4-10 1300 7.57 1 +040 9.09 4-10 2400 7.35 941 9.16 4-20 0100 8.61 1,520 13.55 4=20 2300 8.31 1 , 380 13.74 4-l1l 0100 7.33 932 9.16 4-20 2400 8.24 1 , 350 13.75 4-11 2400 7.08 817 9.28 4-21 0100 6.18 1 320 13.76 4-21 0700 7.99 1 +240 13.80 4-12 0700 7.03 194 9.32 4-21 2400 7.81 1,150 13.93 4-12 0900 7.27 904 9.33 4-12 1100 7.33 932 9.34 4-12 1200 7.67 1 +090 9.35 4-22 0200 7.79 1 140 13.94 4-12 1300 6.33 1 +390 9. 35 4-22 2400 7.61 1 , 060 14.09 4-12 1400 9.20 1,810 9.37 4-12 1600 11.44 3,210 9.40 4-23 0200 1161 1 +060 14.10 4-12 1700 12.13 3,630 9.42 4-23 1500 1.46 992 14.18 4-12 1800 12.79 3,780 9.44 4-23 2400 7.27 904 14.23 4-12 2000 14.29 5,650 9.51 4-12 2400 16.22 8,640 9.69 4-24 0100 7.25 895 14.24 4-24 1600 7.06 806 14.31 4=13 G400 17.14 10,900 9.93 4-24 2400 7.00 780 14.35 4-13 0800 17.52 12,000 10.21 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02401390, Big Canoe Creek at Ashville, Ala. 115 wn w we oe me wn me me me ms me me oes mn me on mn an mn an an on mn mm an an me am mn me an am mn on an an un am mn m an on un me an an an an an an am me an ap an an mn am me on ae an an an an mn an an an an mn an on an an an an an on an an as mn an ae an an an on an an an an an DATE TIME GAGE HEIGHT DATE TIME GAGE HE IGHT DISCHARGE ACCUM. RUNOFF we wn ue an me mn os mn me mn mn ae me me me mn me oe on me on an mn ap an an an an on an an an me an me an mn an ae am an an an an mn an an ae an an an an an me mn an an an mn an an me an an an ms n an an an on an an un an an an an ae an an an an an an an an an an an an an an an 3-01 3-01 3=01 3~01 3-01 3-01 3-02 3-02 3-02 3-03 3-03 3~03 3~03 3-03 3~03 3-03 3-04 3-04 3-04 3-04 3-05 3~95 3-05 3-06 3-06 3-06 3-06 0200 0600 1300 1700 2200 2400 0100 1500 2400 0800 1200 1500 1800 1900 2100 2400 0700 1500 1800 2400 0100 1300 2400 0100 0800 1600 2400 0100 2400 0100 2400 0100 2400 5.99 6.52 8.13 8 . 30 1.97 7.73 71.59 6.31 6.00 6.00 6.89 8.40 10.84 11.55 13.04 14.89 16.95 17.39 17.32 16.80 16.66 14.80 13.43 13.24 11.53 9,70 8.37 DISCHARGE ACCUM. RUNOFF 4719 566 0.03 820 0 . 09 B45 0.12 196 0.16 760 0.18 7139 0.19 531 0.28 480 0 . 32 480 0 . 36 631 0 . 39 860 0.41 1310 0.45 1,530 0.46 2,790 0.52 5,140 h. 65 8900 1.20 9940 2.01 9,770 2.31 8,580 2.89 8,290 2.98 5000 3.77 39210 4.24 3+010 427 19510 4 . 43 1 +080 4.53 856 4.61 838 4 62 634 4.79 631 4.80 496 4 93 490 4.94 404 5.04 3-10 3-10 3~11 3-11 3-11 3-12 3-12 3~13 3~13 3-14 3-14 3~15 3415 3-16 3-16 3-17 3-17 3~18 3-18 3~19 3-19 3-20 3-20 3-21 321 0100 2400 1100 1800 2400 0100 2400 0100 2400 0100 2400 0100 2400 0100 2400 0100 2400 0100 2400 0200 2400 0100 2400 0500 2400 403 380 400 382 356 352 302 301 274 273 267 266 237 235 219 218 202 202 190 190 178 178 170 170 162 116 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02401390, Big Canoe Creek at Ashville, Ala -Continued DATE TIME GAGE DISCHARGE ACCUM. DATE TIME GAGE DISCHARGE ACCUM. HEIGHT RUNOFF HE I GHT RUNOFF 3-22 0300 3.52 162 5.82 4-02 1900 3.67 180 6.53 3-22 2400 3.46 156 5.85 4-02 2200 3.82 198 6.53 4-02 2400 4 . 44 268 6.54 3-23 0600 3.53 164 5.86 3-23 0800 3.90 208 5.86 4-03 0100 5.03 344 6.54 3-23 1100 4 . 83 318 5.87 4-03 0200 5.87 461 6.55 3-23 1300 6.08 493 5.88 4-03 0500 9.00 950 6.57 3-23 1600 7.72 758 5.90 4-03 0900 11.32 1,430 6.63 3-23 2000 8.34 B51 5.94 4-03 1200 12.25 2+)180 6.69 3-23 2100 8.29 844 5.95 4-03 1800 12.71 2,520 6.84 3-23 2400 7.80 770 5.97 4-03 2400 12.31 2,220 6.99 3-24 0100 7.58 7137 5.98 4=04 0100 12.21 2,150 7.01 3-24 1000 5.82 454 6.03 4-04 0700 11.45 1,470 7.12 3-24 2200 4 . 95 334 6.08 4-04 2400 11.17 1 390 7.38 3-24 2400 4.87 323 6.09 4-05 0100 11.06 1 +370 7.40 3-25 0100 4.84 319 6.09 4-05 1900 71.93 790 7.59 3-25 2400 4 . 33 256 6.16 4-05 2400] 7.39 709 7.63 3-26 0100 4 . 32 255 6.16 4-06 0100 7.30 695 1.64 3-26 2400 4 » 03 223 6.22 4-06 2400 6.07 491 7.78 3-27 0100 4.02 222 6.22 4-07 0100 6.04 487 7.78 3-27 2400 3. 85 202 6.27 4-07 2400 5.37 390 1.88 3-28 0100 3.85 202 6.27 4-08 1900 5.12 356 7.96 3-28 2400 3.71 185 6.32 4-08 2300 5.84 457 1.97 4-08 2400 6.16 506 7.98 3-29 0200 3.70 184 6.32 3-29 2400 3.59 171 6.36 4-09 0500 8.18 827 8.02 4-09 0900 8.64 896 8.05 4-09 1000 8.58 887 8.06 3-30 0200 3.58 170 6.37 4-09 2400 6.28 526 B8. 17 3-30 2400 3.48 158 6.41 4-10 0100 6.18 510 8.17 3-31 2400 3.51 161 6.44 4-10 1400 5.44 399 8-23 4-10 2400 5.19 365 6 27 4-01 2400 3.88 206 6.49 4-11 0100 5.18 364 8.27 4-11 2400 4 . 82 317 8.36 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02401390, Big Canoe Creek at Ashville, Ala. -Continued 117 wn wn on hn me on mee on me m me oe oe me me e ms n me me me me ae me me mm an an mn me am as e me e an ae os am an an an an an me un an an an an an an ots ab oif on uh as us an an an un an as an an ap an an an an an an as as an an an an an an an as an an as an an an an an wun DATE 4-12 4-12 4-12 4-12 4-12 4-12 4-13 4-13 4-13 4-14 4-14 4-14 4#*15 4=15 4-15 4-15 4-16 4=~16 4-16 TIME 0600 0700 1200 1500 1800 2400 1100 1800 2400 0100 1600 2400 0100 1500 1700 2400 0100 1300 2400 GAGE HEIGHT 4 e 73 5.01 8.94 11.35 13.28 15.02 17.81 18.74 18.45 18.35 15.47 IQOQI 14.31 12.04 11.55 9.98 9.79 8.13 7.35 DISCHARGE 305 341 941 1 +440 3+050 5,330 11 +000 13600 121800 12 +500 61060 4 +440 4 + 310 2+030 1530 1130 1090 820 703 ACCUM. RUNOFF 8.37 8. 38 8.41 8.45 8.53 8.81 9.76 10.70 11.54 11.67 13.06 13.48 13.53 13.99 14.02 14.12 14.13 14.24 14.33 DATE 4-17 4-17 4-18 4-18 4-19 4-19 4-20 4-20 4-21 4-21 4-22 4-22 4-23 4~-23 4-24 4-24 TIME 0100 2400 0100 2400 0100 2400 0100 2400 0100 2400 0100 2400 0100 2400 0100 2400 GAGE HEIGHT 7.27 6.24 DISCHARGE 691 519 513 423 420 364 361 319 318 288 287 268 266 255 254 246 ACCUM. RUNOFF 118 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02404400, Choccolocco Creek at Jackson Shoals, Ala. GAGE ACCUM. GAGE ACCUM. DATE____TIME___ _HEIGHI______ DISCHARGE______._ ByUSQOFFE.__ .._... DATE____TIME____HEIGHI______ DISCHARGE_______ RUNOEE 3- 2 2400 19.49 955 0.00 4- 3 1300 33.80 19700 0.78 4- 3 1400 33.70 19500 0.84 >- 3 1500 19.45 933 0.04 4- 3 2400 30.53 13400 1.27 3- 3 1700 19.63 1040 0 . 05 3- 3 2000 20.56 1640 0.07 4- 4 0100 30.10 12800 1.31 3- 3 2100 21.21 2130 0.07 4- 4 0500 29.24 11500 1.46 3- 3 2200 22.87 3550 0.09 4- 4 1600 29.71 12200 1.89 3- 3 2300 24.76 5570 0.10 4- 4 2400 27.76 9460 2:13 3- 3 2400 26.81 8150 0.13 4- 5 0100 27.49 9090 2.16 3- 4 0500 34.03 20200 0.45 4- 5 1300 25.49 6450 2.41 3- 4 1400 37.76 30100 1.32 4- 5 2400 24.43 5180 2.59 3- 4 2400 35.55 23800 2.08 4- 6 0100 24.32 5060 2.61 3- 5 0100 35.19 22900 2.16 4- 6 2400 22.97 3640 2.88 3- 5 1000 32.56 17300 2.65 3- 5 2400 28.24 10100 $.11 4- 7 0100 22.94 3620 2.89 4- 7 2400 22.20 2950 3.10 3- 6 0100 27.98 9770 3.14 3- 6 1000 26.78 8110 3.37 4-10 2400 21.45 2320 0.00 3- 6 2400 25.81 6850 3.68 4-11 0200 21.44 2310 0.01 3- 7 0100 25.76 6790 3.70 4-11 2400 24.11 2050 0.16 3- 7 2400 24.24 4970 4.07 4-12 0800 21.16 2090 0.21 3- 8 0100 24.18 4910 4.08 4-12 1200 22.09 2860 0.25 3- 8 2000 22.84 3530 4. 30 4-12 1300 22.60 3310 0.26 3- 8 2100 22.00 2780 4.31 4-12 1500 24.70 5500 0.30 3- 8 2200 22.75 3450 4 , 32 4-12 2200 33.32 18700 0.71 3- 8 2400 22.57 3280 4 . 34 4-12 2400 34.15 20400 0 . 84 3- 9 0100 22,52 3248 4.35 4-13 0900 35.52 23800 1.53 3- 9 2400 21.79 2600 4.54 4-13 1900 37.76 30100 2.49 4-13 2400 36.92 27600 2.94 4- 1 2400 18.99 685 0.00 4-14 0100 36.79 27200 3.02 4- 2 1900 18.98 680 0.04 4-14 2100 30.59 13500 3.89 4- 2 2000 19.09 735 0.04 4- 2 2100 19.36 883 0.05 4-15 0100 29.54 12000 4.04 4- 2 2200 19.96 1240 0.05 4-15 0600 28.76 10900 4.22 4- 2 2300 21.42 2300 0.06 4-15 2400 26.68 7980 4.68 4- 2 2400 23.60 4270 0.07 4-16 0100 26.58 7850 4.70 4- 3 0400 30.20 12900 0. 24 4-16 2400 24.57 5340 5.09 4- 3 0800 32.82 17800 0.46 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02407000, Coosa River at Childersburg, Ala. 1419 ta ta 1 U NESE SP SY a a a a w un n &n un ta 1 Co co do co ta 1 w w w w 117000 119000 116000 111000 111000 107000 107000 101000 98400 95600 95000 91900 91200 91600 91800 87100 88800 88400 88700 84100 76900 76700 75688 70500 68800 70100 71100 69100 68100 67700 68800 64700 62400 63500 63300 62600 60300 59600 60200 59900 50000 58600 0 0 0 o Hoo o 0 0 0 o WG N D b ND N N N ND N N N Leaf aul alll wed Roder papa bls tnt $4.06 4 £3. 8 090) e 405050 00606000000 k k 0% t tr ta ta w ur or ta w u tr ta B BBA t 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1500 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 31800 19000 43700 77400 84400 93300 115000 132000 146000 150000 148000 149000 148000 148000 145000 141000 138000 134000 133000 127000 118000 110000 101000 97400 87700 84500 82100 77100 74400 74500 74200 70500 64700 65900 65000 64700 64600 64500 64400 63400 60000 58900 59700 59600 60200 60200 59300 49100 50200 40700 0 0 0 o lenflenfl ent @] 0 0 0 o 10% aos a out 4". % Doge N ND N N «0.0. w N N b w tr ta ta w ur ta ta w tr ta ta B B A p B A A p B B A p ACCUM. 120 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02411000, Coosa River at Jordan Dam GAGE ACCUM. GAGE ACCUM. pATE____TIME____UBIGCHIL_____ DISCHARGE_______ BUNQEF...__.__._- DATE____TIME____HEIGHI______ DISCHARGE_______ RUNOEE 3- 2 2400 c 40700 0.00 4-12 0600 c 32600 0.03 4-12 1200 ¢ 39900 0.07 3- 3 0400 ¢ 40700 0.02 4-12 1800 c 80000 0.14 S- 3 0600 ¢ 34000 0.04 4-12 2400 € 191000 6.31 3- 3 1200 c 34000 0.07 3- 3 1400 c 49000 0.08 4-13 0400 c 195000 0.43 3- 3 1600 c 56200 0.10 4-13 0900 c 199000 0.58 3- 3 1800 c 65100 0.12 4-13 1200 c 215000 0.68 3- 3 2400 c 146000 0.25 4-13 1500 c 267000 0 . 80 4-13 1800 c 305000 0.94 3- 4 0600 ¢ 251000 0.48 4-13 2000 c 316000 1.04 3- 4 0800 c 253000 0.56 4-13 2100 ¢ 301000 1.08 3- 4 1000 c 253000 0.63 4-13 2200 c 308000 1.13 3- 4 1200 € 251000 0.71 4-13 2300 ¢ 311000 1.18 3- 4 1800 c 227000 0.92 4-13 2400 € 308000 1.22 3- 4 2400 ¢ 190000 1.09 4-14 0400 c 298000 1.41 3- 5 0600 € 163000 1.24 4-14 0800 M 264000 1.57 3- 5 1200 ¢ 158000 1.38 4-14 1200 € 239000 1.71 3- 5 1800 c 136000 1.51 4-14 1800 h 211000 1.90 3- .5 2200 c 101000 1.57 4-14 2400 ¢ 186000 2.07 3- 5 2400 c 110000 1.60 4-15 0600 c 174000 2.28 3- 6 0100 € 114000 1.62 4-15 0900 c 147000 2.30 3- 6 0200 h 120000 1.64 4-15 1200 ¢ 155000 2.37 3- 6 0600 c 114000 1.71 4-15 1800 c 149000 2,50 3- 6 1200 c 114000 1.81 4-15 2400 c 148000 2.64 3- 6 1800 c 101000 1.90 3- 6 2100 C 92500 1.94 4-16 0600 e 147000 2.77 3- 6 2400 ¢ 99700 1.99 4-16 1200 c 137000 2.90 4-16 1800 c 136000 3.02 3- 7 0200 e 99700 2.02 4-16 2400 ¢ 119000 3.13 3- 7 0300 c 105000 2.04 3- 7 1200 C 96200 2.17 4-17 0600 € 115000 3.24 3- 7 1800 c 93000 2.25 4-17 1200 c 115000 3.34 S- 7 2400 c 95000 2.34 4-17 1800 c 105000 3.44 4-17 2400 c 96700 3.52 4-11 2400 ¢ 35600 0.00 4-18 0600 i 99900 3.62 4-18 1200 c 79100 3.69 4-18 1800 c 79900 3.76 4-18 2400 c 82000 3.84 c No gage height record. TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued TABLES 02412000, Tallapoosa River near Heflin, Ala. DATE _ TIME GAGE DISCHARGE ACCUM. DATE _ TIME GAGE DISCHARGE ACCUM. HEIGHT RUNOFF HEIGHT RUNOFF 3-01 - 0100 5.77 905 3-06 1200 - 26.24 18,600 4.13 3-01 - 2400 5.48 818 0.07 3-06 2400 - 23.87 13,400 4.80 3-02 - 0100 5.47 815 0.07 3-02 - 2400 5.22 740 0.13 3-07 0100 _ 23.61 12,900 4.85 3-07 1300 - 16.51 6,010 5.24 3-07 1600 _ 11.38 3,280 5.29 3-03 - 1700 5.31 767 0.18 3-07 1800 8.90 2,160 5.31 3-03 - 1800 5.49 821 0.18 3-07 2100 7.72 1,630 5.33 3-03 - 1900 5.98 968 0.19 3-07 2400 7.44 1,500 5.35 3-03 - 2000 6.97 1,310 0.19 3-03 - 2100 8.37 1,930 0.19 3-03 2400 - 14.47 4,780 0.23 3-08 0100 7.38 1,480 5.35 3-08 2400 6.65 1,190 5.46 3-04 - 0400 _ 20.68 9,060 0.33 3-04 - 0900 _ 26.26 18,700 0.57 3-09 0100 6.63 1,180 5.46 3-04 - 1200 - 26.62 19,600 0.77 3-09 2400 6.21 1,040 5.55 3-04 2400 - 26.59 19,500 1.59 3-10 0100 6.19 1,030 5.56 3-06 - 2000. . 27.13 20,800 2.99 3-10 2400 6.04 987 5.64 3-05 2400 - 27.13 20,800 3.28 3-11 1900 6.23 1,050 5.70 3-06 - 0500 _ 27.14 20,900 3.65 3-11 2400 6.17 1,030 5.72 121 122 DATE TIME FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02412000, Tallapoosa River near Heflin, Ala -Continued GAGE HEIGHT 584 659 824 1 +140 1,580 4 » 100 6+230 7+200 7260 9 +200 10,600 10,600 10,200 10 +100 T+1l10 6+930 5,070 2970 2+280 1,720 1,700 1 +660 1,280 1 »270 ACCUM. RUNOFF DATE TIME GAGE HEIGHT 20.62 24.89 27.07 27.17 26.88 26.78 23.29 23.08 17.84 11.19 9.37 B. 44 DISCHARGE 9,000 15,300 20,700 20,900 20 +200 20,000 12,400 12,100 6,890 3,190 2,370 1,950 DISCHARGE ACCUM. RUNOFF TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02413300, Little Tallapoosa River near Newell, Ala. 123 we wn e wn me on wn on me am me an on me me ae on m me mm me mn an mn mn mn on an mn an me mn me m mn n an me mn as an me an as an as an an an an an an an as mn as an n an an on an an an an an an an an an an an an ap an an an an an an as an an an an an an as as an an an an ao DISCHARGE 634 134 1 +090 1,440 2 +670 5,520 7+800 8 +050 7+630 5110 5+000 4,890 4,010 3960 3+210 3,150 2 +250 2+220 1,670 1 +650 1 340 1 +330 1,150 1+150 938 938 162 DATE 4-02 4-02 4-02 4-03 4-03 4=0 3 4-03 4-03 4-03 4-03 4-04 4-04 4-04 4-04 4-05 4=05 4=06 4-06 4-07 4-07 4-0 7 4-08 4-08 4-08 TIME 2200 2300 2400 0100 0300 0400 0700 1000 1200 2400 0400 0800 2300 2400 0100 2400 0100 2400 0100 2000 2400 0100 2000 2400 GAGE HEIGHT 3.42 3.52 3.77 4.38 6.27 6.85 12.46 12.91 12.70 10.67 11.13 13.66 12.11 12.13 12.09 11.53 11.46 8.70 8.60 7.03 6.83 6.78 6.16 6.55 DISCHARGE 750 654 646 614 430 436 476 578 822 1,670 3,110 5,520 5,840 5,690 4 +270 4 +590 6,430 5,280 5290 5 +260 4 +870 4,820 3 +020 2,960 2,050 1,950 1,920 1,610 1,810 ACCUM. RUNOFF 0 . 08 0.08 0.08 0.08 0 . 09 011 0.16 0 23 0 27 0 50 0.56 0.65 0.98 1.00 1.85 2.03 2.06 2.07 2,20 2.22 124 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02413300, Little Tallapoosa River near Newell, Ala. -Continued DATE 4-11 4=11 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4=13 4-13 4-13 4-13 TIME 0100 2400 0100 2400 0100 2400 1000 1700 1800 1900 2000 2200 2300 2400 0500 1000 1400 1500 GAGE HEIGHT DISCHARGE 1,850 1,490 1 470 1,190 1,190 998 974 1,190 1 1430 2050 3+060 3,890 3,800 5,170 6920 9,950 12,700 12,700 ACCUM » RUNOFF DATE TIME GaGE HEIGHT DISCHARGE ACCUM. RUNOFF un an un ws on un an as an an me an an oe ae an as un me o as an an an an m an an me an m an as mn mn mn un an m me an an an mn am an am an me an n a an a on an me on mn an 2.23 2.38 2. 38 2,50 2.51 2-60 2.64 2.67 2.67 2.68 2.69 2.72 2.7“ 2.76 2.88 3.04 3.23 3.28 1800 2400 0700 2400 0100 2400 0100 1800 2400 0100 2400 0100 2400 0100 2400 16.66 16.10 16.20 15.81 15.79 12.78 12.61 9.43 6.75 9930 6,940 9,100 6 +490 8,470 S+,750 5,630 3,460 3,050 3,000 2,380 2+360 1 920 1,880 1,560 3.40 3.61 TABLES 125 TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02414500, Tallapoosa River at Wadley, Ala. B A A B A D p A D t w w Co co co NENE S a a o w m n un t o t tr Gt ta tr £ A A A w un 0015 2130 0915 0930 2400 0030 1045 1745 0900 0915 2400 2400 0200 0600 1000 1200 1400 2000 2400 0345 1200 1945 2400 1209 2400 0900 2400 GAGE Accum. GAGE Accum. ________________ HEIGHT______DISCHARGE_______RUNOFF__________DATE____TIME____HEIGHT______DISCHARGE_______ RUNOFF 5.581 3500 0.00 4- & - 2000 7:37 6630 2.44 a- 8 2400 7.67 7240 2.47 5.5% 3530 0.06 6:06 4350 0.07 4- 9 _ 0100 7.78 7420 2.47 6.98 5890 0.09 a- 9 _ 0900 8.57 9280 2.54 4- 9 . 2400 7.67 7240 2.64 7.99 7950 0.10 13.01 19500 0.19 4-10 _ 2400 7.10 6110 2.78 15.67 25700 9.26 16.90 28700 0.28 4-11 _ 2490 6:61 5250 2.90 26-67 67600 0.55 28.23 76200 0.83 4-12 . 1200 6.47 5010 2.95 28.12 75600 0.85 4-142 - 1700 6.88 5710 2.98 26:17 64900 1.18 4-12 . 2100 8.89 10000 3-902 417 2400 11.81 16700 3:07 26.03 64100 1.19 28.85 51500 1.38 413 0100 1s.41 20400 3.08 21.84 43300 1.62 4-13 0600 . 17.55 30400 3.23 18.84 33800 2.06 4-13 _- 1200. 22.04 40100 3.45 413 - 1800 | 27.75 73600 3.86 18.76 33600 2.07 4-13 - 2800 _ 30.29 87500 4.27 17.52 30300 2.35 4-13 - 2400 - 30.35 87800 #485 16.39 27400 2.63 4-14 : ©6200- 30.57 89100 4.52 1s. 71 25800 2:92 4-14 _ 0400 _ 29.94 85600 4.68 15.67 25700 2.92 4-14 12006 36.77 68200 5.19 13.94 21600 3.322 4-14 0 2400 - 22.02 44000 5.68 13.84 21400 $:.23 4-15, 0300 _ 21.37 41500 5.80 11.62 16300 3.38 4-15 - 0900 _ 20.50 38800 6.02 8.55 9240 3.44 4-15 | 2400° i9.0s 34400 6.50 Z'gg 2223 g'gj 4-16- . 1200 _ 17.44 30100 6.83 & * 4-16 - 1800 - 46.31 27200 6.99 6.92 5790 3.62 4-16 - 2400 _ 15.08 24300 7.42 4-88 2610 0,00 4-17" 14:02 21800 7.24 4-17 - 1200 12.63 18600 t g:?g fggg 8.8; 4-17 - fso0o - 10:13 12900 7.42 12 52 19100 G+ 4-17 - 2400 8.85 9920 7.48 14.67 23300 0.14 (e er rego S 4-18 __ 2400 8.01 7990 7.66 18.39 32600 0.37 17.62 30600 0.48 4-19 _ 0100 7.96 7880 7.66 4-19 _ 2400 7.45 6790 7.81 16.30 27200 $:s7 17.77 31000 0. 82 4-20 __ 2400 7.08 6070 7.94 18.94 34100 1.06 1822 o 1719 4-21 _ 0100 7.04 6000 7.95 4-21 _ 2400 6.73 5450 8.07 15.35 24900 1:47 14.35 22600 tis 4-22 _ 2400 6.53 5110 8.18 13.85 21400 1.91 11.81 16700 2.14 7.96 7880 2.32 2400 126 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.--Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02420000, Alabama River near Montgomery, Ala. GAGE co co co co ~ESE SPS a a o a w wn on un L B B A w U Gt G w w w 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 77700 74600 72000 68700 66400 62400 60300 58100 59800 58600 60500 60600 71000 100000 127000 143000 160000 172000 179000 185000 183000 181000 179000 176000 174000 171000 169000 167000 163000 160000 156000 154000 151000 148000 146000 144000 ...... ...... ...... ...... ...... ...... ...... ...... ...... 3-10 3-10 3-10 3-10 3-11 3-11 3-11 3-11 3-12 3-12 3-12 3-12 3-13 3-13 3-13 3-13 3-14 3-14 3-14 3-14 3-15 3-15 3-15 3-15 3-16 3-16 3-16 3-16 3-17 3-17 3-17 ..... ..... 142000 138000 135000 132000 129000 126000 124000 120000 118000 117000 116000 115000 112000 110000 109000 108000 105000 102000 101000 100000 97300 94100 94100 89900 86200 84300 79700 75600 73000 67300 65600 63000 61600 58000 53700 53400 ...... ...... ...... ...... TABLES 127 TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02420000, Alabama River near Montgomery, Ala. -Continued GAGE ACCUM. GAGE ACCUM. DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 3-18 2400 . ..... $2100 - |: ...... 3-27 1800 |_ ..... 29000 . . |...... 3-27 2400 . ..... 28500 .. . . \ 3-19 0600 . ..... $1600 . [- ...... 3-19 $200 _ ...;, 50300 - - - ...... 3-28 0600 ...... ©4500 : ;.. ...... 3-19 1800 | ..... 49400 | ___ ...... 3-28 1200 - ..... 29500 ._ | . ...... 3-19 2400 |_ ..... 47200 - | = ...... 3-28 1800 - ...... 27900 __ _ ...... 3-28 2400 _ = ..... $6000 __ _. ...... 3-20 9600 '..... 45400 | __ == ...... 3-20 1200 - -..... 45200 | - ...... 3-29 0600 - ...... $2800 _ .. _ | ...... 3-20 1800 - ..... 45500 _ = ...... 3-29 1200 | ..... 31400 .. ;...... 3-20 2400 - ..... 47400 -' _ ...... 3-29 1800 |_ ..... 28400 __ | ...... 3-29 2400 __ ..... 26800. - | |..) ...... 3-21 9600 ..... 40800 _ | _. ...... © 3-21 1200 - ..... 59200 [| ...... 3-30 0600 __ ..... $3200 _| | ....+. 3-21 1800 . ..... 41400 |___ === ...... 3-30 1200 | ..... 28800 | _ | | ...... 3-21 2400 | ..... 40200 sas sas 3-30 1800 - ..... 29700 ... . _ ...... 3-30 2400 - _.... 28600 ' _ ' . ...... 3-22 0600 - ..... 40200 |__ ...... 3-22 1200 - _ ..... §2400 __ | | ...... 3-31 0600 - ..... 21800 . _ _ ...... 3-22 1800 -...... 45400 |_ - =...... 3-31 1200 - ..... 27500 '>. _| ..... 3-22 2400 - ..... 45800 | | - = ...... 3-31 1800 _ ...... 22400 | - . ...... 3-31 2400 |_ ..... 18500 ___. . . ...... 3-23 0600 ..... 46900 |__ ...... 3-23 1200 - ..... 49400 -| =...... 4- 1 0600 __ ..... 16800 . . | ...... 3-23 1800 - ..... 51900 | - ...... 4- 1 1200 - ...... 18500 _ © -/ ...... 3-23 2400 | ..... $2600 | - _ ...... 4- 1 1800 |_ ..... 16800 __.: | ...... 4- 1 2400 | ..... 17800 | ' ; ...... 3-24 0600 __ ..... $2200 . | _.. ...... 3-24 1200 -..... $1000 - - =...... 4- 2 0600 ° ..... 16600 _ ... | ...... 3-24 1800 - -..... $0000 -'! .. : ...... 4- 2 1200 - ..... 16600 _._ . ...... 3-24 2400 ° ;.... 46200 | __ === ...... 4- 2 1800 - ..... 17200 ___ _ - ...... 4- 2 24008 ..... 23300. __ . ...... 3-25 0600 . ..... 43700 |__ = ...... 3-25 1200 _ ..... 40400 |___ === ...... 4- 3 6600 | -..... 43600 | -_ _ ...... 3-25 1800 - ..... 41400 -_ ...... 4- 3 $200: ;.... 80800 .. ...1.% 3-25 2400 _ ...;... 29100 [° - ...... 4- 3 j800 ;.... 105000 -. '.: ...... 4- 3 2400 36.50 121000 ._. _ _ ...... 3-26 P600 - ..... 28300 - | ° ...... 3-26 1200 - ..... 22000 | | ...... 4- 4 0600 38.10 118000 ... _ ...... 3-26 1800 - ..... 29100 _ - ...... 4- 4 1200 39.70 118000 . - | - | ...... 3-26 2400 |_ ..... 35400 | - = ...... 4- 4 1800 40.95 119000 | | _.. ...... 4- 4 2400 42.05 121000 _- _.. . ...... 3-27 0600 _ _ ..... 35200 | | | | ...... 3-27 1200 | ..... $2100 - -| - ...... 4- 5 0600 42.55 125000 __ :i ...... 128 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02420000, Alabama River near Montgomery, Ala. -Continued GAGE ACCUM. GAGE ACCUM DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 4- 5 1200 43.02 128000 | _ (...... 4-14 0600 45 . 30 183000 __... ...... 4- 5 1800 43, 32 126000 ___ -...... 4-14 1200 48.10 210000 < -_ -_ 4- 5 2400 43.35 126000 _ ° -' ...... 4-14 1800 50.00 229000. _ :... ..1..s 4-14 2400 51.70 245000 -... .....% 4- 6 0600 43.30 126000 - _ _ | '...... 4- 6 1200 43.25 151000 _ <_ [...... 4-15 0600 52.63 254000 - .= _ _.....% 4- 6 1800 42.82 142000 |__ (...... 4-15 1200 53.357 258000 : _ ...... 4- 6 2400 42.46 144000 |___ ___ ...... 4-15 1800 53.87 260000 . _.: ._ ...«.4 4-15 2400 54.20 259000 __.. ..... 4- 7 0600 42.42 142000 __ __ |...... 4- 7 1200 41.45 140000 |__ ___ ...... 4-16 0600 54.40 258000 - -= : si...; 4-*7 1800 41.05 140000 |__ - = ...... 4-16 1200 54.50 254000. . _- _ ...... 4- 7 2400 40.38 140000 |- - ...... 4-16 1800 54.41 250000 - :...... ..... 4-16 2400 54.22 241000 . ._.. - ...... 4- 8 0600 39.75 135000 __ | ...... 4- 8 1200 39.15 150000 :- __ >_ {...... 4-17 0600 53.82 256000 . -. . ...... 4- 8 1800 38.52 126000 |___ ___ ...... 4-17 1200 53.36 229000 _ _-. ...... 4- 8 2400 37.87 1235000 ___ | [...... 4-17 1800 52.92 221000 . .s . ...e. 4-17 2400 52.29 242000 ;>: : ....% 4- 9 0600 37.20 120000 -_ _ __ '...... 4- 9 1200 36.69 116000 -__ _ [...... 4-18 0600 $1.70 204000 |...... ...... 4- 9 1800 36.00 112000 - .. _. [...... 4-18 1200 51.00 197000 | =. ...... 4- 9 2400 35.52 108000 - - - ...... 4-18 1800 50.00 189000 . .- ... ...... 4-18 2400 48.99 1890000 . -.. .....% 4-10 0600 34.90 104000 -- - =. (...... 4-10 1200 34.40 99400 ._. -...... 4-19 0600 48.00 170000 _ .._ ;.... 4-10 1800 33.89 $6100 - _ | ...... 4-19 1200 47.08 165000 __ - - ...... 4-10 2400 33.30 92500 . - ° ...... 4-19 1800 46.02 1988000 - - - - ...... 4-19 2400 45.10 151000 ~=>_ 4-11 0600 32.82 $6700 | _ _- ...... 4-11 1200 32.48 $3300 - - _ - ...... 4-20 0600 43.80 145000 - _. ___ ...... 4-11 1800 32.10 §0600 _ _ ° _ ...... 4-20 1200 42.75 138000 _. . ' _ ....... 4-11 2400 32.72 73700 ._ ° i...... 4-20 1800 41.60 1335000 _ _-_ 4-20 2400 40.40 128000 |-... _ ...... 4-12 0600 32.38 75000 -- _ __ ...... 4-12 1200 31.00 68800 _ _. ° ...... 4-21 0600 39.50 125000 _ -_ - 4-12 1800 30.92 69400 ___ == ...... 4-21 1200 38.26 124000 ..- _ ___ i..... 4-12 2400 32.10 $3000 _: -...... 4-21 1800 37.50 116000 :-/... i...+, 4-21 2400 36.20 112000 _ '- _. ' 4-13 0600 34 . 60 108000 . _ - ...... 4-13 1200 36.90 128000 | - ...... 4-13 1800 39.40 142000 _ __ ° ...... 4-13 2400 42.00 159000 - _ _ ...... TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02422500, Mulberry Creek at Jones, Ala. 129 m B B BoB B ote of tf O4 G4 O4 G4 Ga a oa a ~ NPS 0100 2100 2400 0100 2000 2400 0100 2400 0100 2400 374 625 1510 2640 3640 5140 8660 13100 14200 16000 15600 12000 10700 5910 3640 2980 2000 1890 1788 1330 1290 1280 1110 1090 1080 914 908 782 & ta B A 0 0 0 0 0 00 0 @ o o Of ta ho N N N - O t Or ta w ur to 4-12 4-12 4-12 4-12 4-12 4-12 4-13 4-13 4-13 4-13 4-14 4-14 4-14 4-14 4-15 4-15 4-15 920 902 980 1100 1200 5070 7260 8060 9850 10500 13500 18500 20900 6128 4000 2920 2770 2160 1610 1580 1180 1170 962 950 800 794 695 w in 0 0 0 0 0 0 o BBB u 0 o fin} B A A ACCUM. «78 94 . 95 . 09 10 21 130 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02423425, Cahaba River near Cahaba Heights, Ala. GAGE ACCUM. GAGE ACCUM. DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 4-10 2400 2.41 516 0.00 4-14 2230 12.27 4430 6.95 4-14 2400 11.19 4060 6.99 4-11 0600 2.42 523 . 02 4-11 1200 2.36 470 . 05 4-15 0600 7.29 3060 7.16 4-11 1800 2.33 439 .07 4-15 1015 4.80 2550 7.25 4-11 2400 2.32 433 09 4-15 1100 4. 36 2200 7.26 4-15 1130 4.12 1910 7.27 4-12 0700 2.53 439 11 4-15 1145 4.06 1830 7-27 4-12 0900 2.58 791 A11 4-15 1200 2.93 1690 7.28 4-12 1100 3.45 1630 14 4-15 1245 3.91 1660 7.29 4-12 1300 4.38 2360 «18 4-15 1330 3.82 1560 7.30 4-12 1500 8.00 3230 23 4-15 1530 3.79 1530 7.32 4-12 1700 13.86 5080 . 30 4-15 1545 3.58 1310 7.52 4-12 1900 17,25 7960 43 4-15 1600 3.71 1450 7.52 4-12 2100 18.80 9580 157 4-15 1615 3.73 1470 7.5% 4-12 2300 20.05 11000 & 74 4-15 1700 3.65 1390 7.34 4-12 2400 20.67 11800 . 83 4-15 1745 3.62 1350 7.34 4-15 1800 3.58 1310 755 4-13 0200 21.65 13100 1.04 4-15 1815 3.62 1350 7.35 4-13 0400 22.74 14500 1.26 4-15 1830 3.49 1230 7.35 4-13 0600 23.58 15600 1.50 4-15 1915 3.951 1250 7.36 4-13 0800 24.45 16800 1.76 4-15 1930 3.46 1200 7.36 4-13 1000 26.00 19000 2.05 4-15 1945 3.46 1200 7.36 4-13 1200 27.81 21000 2.38 4-15 2000 3.55 1290 7.36 4-13 1400 28.00 22000 2.72 4-15 2100 3.49 1230 7.97 4-13 1600 28.31 22500 3.06 4-15 2115 3.84 1590 7.38 4-13 1800 28.67 23100 3.42 4-15 2200 3.88 1630 7.39 4-13 2000 28.85 23400 3.78 4-15 2215 3.83 1580 7.39 4-13 2100 28.86 23500 3.96 4-15 2230 3.85 1600 7.39 4-13 2200 28.84 63400 4.14 4-15 2245 3.80 1540 7.40 4-13 2400 28.73 23200 4.50 4-15 2400 3.78 1520 7.41 4-14 0100 28.39 22700 4.76 4-16 0015 3.82 1560 7.41 4-14 0200 28.43 22800 4.94 4-16 0145 3.74 1480 7.43 4-14 0300 28.00 22200 5.11 4-16 0345 3.70 1440 7.45 4-14 0630 26.47 19900 5.68 4-16 0530 3.66 1400 7.47 4-14 1100 22.21 13800 6.25 4-16 1030 3.50 1240 7.52 4-14 1115 22.09 13600 6.28 4-16 1115 3.49 1230 7.53 4-14 1200 20.99 12100 6.35 4-16 1315 3.43 1170 7.55 4-14 1445 18.39 9090 6.57 4-16 1445 3.43 1170 7.56 4-14 1715 16.37 7070 6.73 4-16 1730 3.35 1100 7.59 4-14 1800 15.85 6550 6.77 4-16 2000 3. 34 1090 7.61 4-14 1930 14.55 5450 6.83 4-16 2215 3.28 1030 7.63 4-16 2330 3.25 990 7.64 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02423425, Cahaba River near Cahaba Heights, Ala. -Continued 131 ACCUM. GAGE ACCUM. DATE TIME GAGE HEIGHT N o o u G UG G t t a seit Son Cc lin o ll wlan N N IN N N N N ND N N N N N N N N N N ND ND a Nea ao ail uae a oe (a C n ao an oan a nn a io ann or N ID N N D N N N N N non c a w ol onl con t oe n oa rls coe 1030 1010 1020 963 865 865 833 857 824 738 738 715 685 692 655 634 641 613 592 585 571 585 558 552 512 456 437 444 431 424 418 431 437 424 437 431 444 437 450 450 NESE NESE SEN NESE S NESN SNES SI SIE SESE SESE SIE SE SIE SI SI SE SDS a 11 n o cem n c C ha an cin 0 l a ca ia ion coa oa oa a 20g ve c ® NESS SENE NENE SP SPS £ oe Luk (oal c lie role i a c og 4-19 4-19 4-19 4-19 4-19 4-19 4-19 4-19 4-19 4-19 4-20 4-20 4-20 4-20 4-20 4-20 0745 0815 0845 1215 1530 1630 2130 2200 2215 2400 04 30 0530 0745 0800 0900 0915 1045 1115 1145 1215 1500 1715 2015 2400 0245 0345 0900 0915 1045 1115 1415 1445 2345 2400 0500 0745 0845 0900 0930 1030 N N N N N N N N N N N N ND N N N N N ND N sine elle CC ai a mantis N N N N N ND NN ND N N N ND N N N N N N N oo Waa % 437 437 405 392 374 386 368 374 362 362 368 392 399 380 374 351 351 339 339 327 327 322 311 311 311 322 322 316 305 295 289 278 278 284 295 305 305 289 289 268 NESNESNE NENE NOSE SES S Co 0s oo co to co to co bo do Co Co ~1 ~1 aan ce Sn o e o e ooc a a n oe 1 a L aioe Co co 00 to to co to co co co nove ole one Pe roa ie ao og co co co co to co sisi so ae) % 132 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02423425, Cahaba River near Cahaba Heights, Ala. -Continued GAGE ACCUM. GAGE ACCUM. DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 4-22 1200 2.19 268 8.12 4-24 2200 2.18 263 8.24 4-22 1215 2.16, 254 8.12 4-24 2330 2.20 273 8.24 4-22 1615 217 259 8.13 4-24 2400 2.21 278 8.24 4-22 1745 2.20 273 8.13 4-22 , 1945 2.21 278 8.14 4-25 0130 2.22 284 8.24 4-22 2000 2.23 289 8.14 4-25 0445 2.26 305 8.25 4-22 2400 2.22 284 8.15 4-25 0600 2-31 222 8.25 4-25 0745 2.32 339 8.26 4-23 0145 2.22 284 8.15 4-25 1000 2.33 345 8.26 4-23 0215 2.20 273 8.15 4-25 1015 2.36 362 8.27 4-23 0500 2.19 268 8.16 4-25 1115 2.36 362 8.27 4-23 0545 2.235 289 8.16 4-25 1230 2.39 380 8.27 4-23 0730 2.25 289 8.16 4-25 1415 2.45 418 8.28 4-23 0800 2.22 284 8.16 4-25 1700 2.61 519 8.29 4-23 0900 2.19 268 8.17 4-25 1830 2.76 620 8.29 4-23 0930 2.19 268 8.17 4-25 1930 2.92 738 8.30 4-23 0945 2:16 254 8.17 4-25 1945 2.93 745 8. 30 4-23 1215 2.14 244 §.17 4-25 2015 3.05 841 8.30 4-23 1715 2.12 235 8.18 4-25 2145 3.36 1110 8.32 4-23 1730 2.13 239 8.18 4-25 2300 3.66 1400 8.33 4-23 1830 2.12 235 8.18 4-25 2400 3.94 1700 8 . 34 4-23 1845 2.13 239 8.19 4-23 2200 2.11 230 8.19 4-26 0045 4.14 1930 8.35 4-23 2315 2.12 235 8.19 4-26 0100 4.25 2060 8.35 4-23 2400 2:13 239 8.19 4-26 0145 4.35 2190 8.37 4-26 0345 5.06 2630 8.40 4-24 0745 2.13 239 8.21 4-26 1000 6.87 2970 8.54 4-24 0900 2.11 230 8.21 4-26 1715 6.50 2910 8.71 4-24 1230 2.12 235 8.22 4-26 1745 6.68 2940 8.72 4-24 1330 2.13 239 8.22 4-26 1800 6.05 2830 8.72 4-24 1445 2.18 263 8.22 4-26 1815 6.84 2960 8.73 4-24 2045 2.17 259 8.23 4-26 2015 8.47 3330 8.78 4-24 2130 2.16 254 8.24 4-26 2100 8.54 3340 8.80 4-26 2400 8.06 3230 8.87 DISCHARGE TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued GAGE HEIGHT W W W W J~ B- N - Ww Ww wi w W W w W O - Woe N N N - - ; ci nwuwuwvaa - cacy y w o w 4 N N N N or cow 02424000, Cahaba River at Centreville, Ala. DISCHARGE ACCUM. RUNOFF N N N -i -a -a J- EW W N wi in in ia GAGE HEIGHT A7 «65 «13 99 - 94 . 85 < 18 . 66 . 26 «93 . 62 - 31 +69 17 86 . 63 34 ZH 98 . 88 ~ Sw _ w o a o o a ao o dC 48 AP # 0% a a ao o o ow o o ACCUM, RUNOFF 133 134 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02425000, Cahaba River near Marion Jct., Ala. GAGE ACCUM. GAGE ACCUM. DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 4-10 2400 15.59 8770 0.00 4-16 0100 40.77 69500 2.97 4-16 2400 39.05 48900 3.96 4-11 0100 15.47 8690 0.01 4-11 2400 12.31 6470 0.14 4-17 0100 38.96 47800 4.00 4-17 2400 37.24 35200 4.71 4-12 1300 11.66 6070 0.21 4-12 1800 11.88 6220 0.23 4-18 0100 37.15 34900 4.74 4-12 2100 15.94 9360 0.26 4-18 2400 33.81 27600 5.38 4-12 2400 19.56 12000 0.29 4-19 0100 33.60 27300 5.32 4-13 2400 27.44 19500 0.70 4-19 2400 28.16 20300 5.73 4-14 1800 35.91 31000 1.19 4-20 0100 27.89 20000 5.75 4-14 2200 38.01 39200 1.33 4-20 2400 22.48 14500 6.04 4-14 2400 38.97 47900 1.41 4-21 0100 22.30 14300 6.05 4-15 0600 40.64 68000 1.77 4-21 2400 18.60 11400 6.28 4-15 1400 41.13 73900 2.29 4-15 1800 41.08 73300 2.54 4-15 2400 40.82 70100 2.91 TABLES 185 TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02429500, Alabama River at Claiborne, Ala. GAGE Accum. GAGE ACCUM. DATE _ TIME _ HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 2-28 2400 41.60 118000 0.00 3-14 0600 48.30 169000 3.49 3-14 1200 48.00 165000 3.56 3- 1 0600 41.70 118000 . 05 3-14 1800 47.70 162000 3.63 s- 4 1200 41.73 117000 .10 3-14 2400 47.40 156000 3.70 $- 1 1800 41.70 116000 15 3- A 2400 41.62 114000 .20 3-15 0600 47.00 152000 3.76 3-15 1200 46.65 150000 3.82 3- 2 0600 41.50 111000 .24 3-15 1800 46.20 144000 3.88 3- 9 1200 41.25 109000 .29 3-15 2400 45.85 141000 3.94 3-:2 1800 40.90 103000 .33 3-2 2400 40.45 101000 .38 3-16 0600 45.40 137000 4.00 3-16 1200 44.98 131000 4.06 3- 3 0600 40.00 96300 .42 3-16 1800 44.50 127000 4.11 3- 3 1200 39.33 93300 .46 3-16 2400 44.00 123000 4.16 3- 3 1800 39.20 102000 .50 3- 3 2400 39.50 115000 .55 3-17 0600 43.46 119000 4.21 3-17 1200 42.95 114000 4.26 3- 4 0600 40.16 119000 . 60 3-17 1800 42.40 110000 4.31 3- 4 1200 40.80 125000 . 65 3-17 2400 41.85 106000 4.35 3- 4 1800 41.52 128000 . 70 3- 4 2400 42.20 132000 «76 3-18 0600 41.20 103000 4.40 3-18 1200 40.55 98200 4.44 3- 5 0600 42.70 134000 «82 3-18 1800 39.80 93300 4.48 3- 5 1200 43.20 138000 . 88 3-18 2400 39.00 91800 4.52 $- 5 1800 43.70 142000 .94 3- 5 2400 44.20 145000 1.00 3-19 0600 38.30 87700 4.55 3-19 1200 37.45 82000 4.59 3-6 0600 44.62 148000 1.06 3-19 1800 36.62 77500 4.62 S- 6 1200 45.02 150000 1.12 3-19 2400 35.74 75500 4.65 $- 6 1800 45.40 154000 1.19 3- 6 2400 45.75 158000 1.25 3-20 0600 34.90 71900 4.68 3-20 1200 34.15 68900 4.71 S- 7 0600 46.10 162000 1.32 3-20 1800 33.50 67100 4.74 2-7 1200 46.40 165000 1.39 3-20 2400 32.92 64800 4.77 $- 7 1800 46.70 168000 1.46 3- 7 2400 46.95 171000 1.54 3-21 0600 32.20 61300 4.79 $-21 1200 31.35 56900 4.82 3- 8 0600 47.18 173000 1.61 3-21 1800 30. 20 51700 4.84 3- 8 1200 47.45 175000 1.68 3-21 2400 29.18 50800 4.86 3- 8 1800 47.65 175000 1.76 $m . 2400 . armas 176000 1-85 3-22 - 0600 _ 28.65 51400 4.88 8 0600 48.10 180000 1.91 3-22 1200 28.28 51800 4.90 3- 9 1200 48 . 30 183000 1.98 3-22 1800 27.95 50800 4.93 s- 9 1800 48.50 185000 2:06 3-22 2400 27.82 53000 4.95 S-99 2400 2:44 3-23 0600 28.05 56500 4.97 3-10 - 0600 48.85 190000 2.22 3-23 - 1200 28.65 62600 5.00 3-10. 1200 49.00 192000 2.30 3-23 - 1800 29.25 £52000 5-05 3-23 2400 29.90 66500 5.05 3-10 1800 49.25 197000 2.39 3-10 2400 49.36 196000 2.47 y $600 sosa £75900 $08 3-11 -: os00 49.48 196000 2.85 3-24 - 1200 30.85 69800 5.11 S-11 | 1200 49.57 197000 2.64 3-24 _ 1800 31.25 71000 8.14 Self. 49.58 195000 2.72 3-24 - 2400 31.72 71700 5.17 3-11 2400 49.60 193000 2.80 $25 0500 7i%60 $320 3-12 - 0600 49.58 191000 2.88 3-25 - 1200 32.10 720600 5.23 3-12 -- 1200 49.55 191000 2.96 3-25 - 1800 32.20 69700 5.20 3-12 1800 49.50 188000 3.04 3-25 2400 31.95 65800 5.29 3-12 2400 49.37 185000 3.12 s-se 0806 62400 5.52 3-13 - 0600 49.20 183000 3.20 3-26 _ 1200 31.52 61500 5.34 3-13 - 1200 49.00 180000 3.27 3-26 - 1800 31.00 26200 aval 3-26 2400 30.02 53600 5.39 3-13 1800 48.80 176000 3.35 *t 3-13 2400 48.55 172000 3.42 136 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02429500, Alabama River at Claiborne, Ala. -Continued GAGE ACCUM. GAGE ACCUM. DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 3-27 0600 29.18 50300 5.41 4«- :p 0600 47.45 171000 7.30 3-27 1200 28.25 47400 5.43 4- 9 1200 47.62 173000 7.37 3-27 1800 27.63 45600 5.45 4-9 1800 47.75 175000 7.45 3-27 2400 26.88 43400 5.47 4- 9 2400 47.85 176000 7:52 3-28 0600 26.60 46600 5.49 4-10 0600 47.90 176000 7.60 3-28 1200 26.38 45400 5.51 4-10 1200 47.95 173000 7.67 3-28 1800 25.75 40800 5.52 4-10 1800 47.95 172000 7.74 3-28 2400 24.80 36900 5.54 4-10 2400 47.90 171000 7.81 3-29 0600 24.25 35500 5.55 4-11 0600 47.85 171000 7.89 3-29 1200 23.60 37800 5.57 4-11 1200 47.72 168000 7.96 3-29 1800 23.37 38400 5.59 4-11 1800 47.55 166000 8.03 3-29 2400 23.45 47300 5.61 4-11 2400 47.40 162000 8.10 3-30 0600 23.75 41100 5.62 4-12 0600 47.15 158000 8.16 3-30 1200 23.88 41900 5.64 4-12 1200 46.80 153000 8.23 3-30 1800 24.25 43400 5.66 4-12 1800 46.50 150000 8.29 3-30 2400 24.35 42500 5.68 4-12 2400 46.15 147000 8.35 3-31 0600 24.40 42600 5.70 4-13 0600 45.75 141000 8.41 3-31 1200 24.43 42300 5.71 4-13 1200 45.30 137000 8.47 3-31 1800 24.43 42300 5.73 4-13 1800 44.90 132000 8.53 3-31 2400 24.22 38300 5.75 4-13 2400 44.45 128000 8.58 4-1 0600 23.75 34600 5.76 4-14 0600 44.05 126000 8.63 4- 1 1200 22.95 32600 5.78 4-14 1200 43.70 125000 8.69 4- 1 1800 22.05 31900 5.79 4-14 1800 43.50 125000 8.74 4- 1 2400 21.25 29900 5.80 4-14 2400 43.35 126000 8.79 4- 2 0600 20.72 29300 5.81 4-15 0600 43.30 128000 8.85 4- 2 1200 20.42 29800 5.83 4-15 1200 43.32 130000 8.90 4- 2 1800 20.15 29700 5.84 4-15 1800 43.40 132000 8.96 4- 2 2400 20.90 42700 5.86 4-15 2400 43.55 133000 9.01 4- 3 0600 & 60000 5.88 4-16 0600 43.75 136000 9.07 4- 3 1200 c 73000 5.91 4-16 1200 44.00 139000 9.13 4- 3 1800 c 84000 5.95 4-16 1800 44.25 142000 9.19 4-3 2400 c 96000 5.99 4-16 2400 44.50 144000 9.25 4- 4 0600 c 103000 6.03 4-17 0600 44.83 149000 9.31 4- 4 1200 c 110000 6.08 4-17 1200 45.20 152000 9.38 4~ 4 1800 c 118000 6.13 4-17 1800 45.55 157000 9.44 4- 4 2400 c 125000 6.18 4-17 2400 45.94 162000 9.51 4- 5 0600 42.00 131000 6.24 4-18 0600 46. 30 167000 9.58 4-5 1200 42.60 136000 6.30 4-18 1200 46.75 172000 9.66 4- 5 1800 43.20 140000 6.35 4-18 1800 47.25 177000 9.73 4- 5 2400 43.75 145000 6.42 4-18 2400 47.65 182000 9.81 4- 6 0600 44.25 147000 6.48 4-19 0600 48.05 185000 9.89 4- 6 1200 44.75 151000 6.54 4-19 1200 48.45 190000 9.97 4- 6 1800 45.10 153000 6.61 4-19 1800 48.80 195000 10.05 4- 6 2400 45.40 154000 6.67 4-19 2400 49.10 198000 10.15 4= J 0600 45.70 158000 6.74 4-20 0600 49.45 201000 10.22 4- 7 1200 46.00 161000 6.81 4-20 1200 49.75 205000 10.30 4~:7 1800 46.25 162000 6.87 4-20 1800 50.00 208000 10.39 4 7 2400 46.45 164000 6.94 4-20 2400 50.25 209000 10.48 4~ 8 0600 46.67 166000 7.01 4-31 0600 50.50 212000 ~ 10.57 4- 8 1200 46.85 166000 7.08 4+. % 1800 47.10 169000 7.16 4- $ 2400 47.30 170000 7.25 c - no gage height record TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02429500, Alabama River at Claiborne, Ala. -Continued 137 GAGE HEIGHT 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 212000 214000 216000 216000 217000 216000 214000 214000 213000 210000 207000 205000 200000 195000 190000 183000 175000 169000 162000 4-28 4-28 4-28 4-28 4-29 4-29 4-29 4-29 4-30 4-30 4-30 4-30 TIME 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 . 2400 0600 1200 1800 2400 0600 1200 1800 2400 155000 149000 143000 137000 132000 127000 126000 125000 124000 123000 123000 124000 124000 126000 126000 127000 127000 128000 128000 128000 138 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02439400, Buttahatchie River near Aberdeen, Miss. ACCUMULATED ACCUMULATED GAGE _ GAGE DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 04-12 0100 11.30 2, 630 0.00 04-15 2400 15. 62 9, 500 2.16 04-12 0600 12.91 3, 920 O. 03 04-12 1200 14.08 S, 7920 0.03 04-16 1200 14.99 7, 840 2. 36 04-12 1800 14. 09 S, 810 0.15 04-16 2400 14.47 6, 610 =. 53 04-12 2400 14.97 7, 780 0.23 04-17 2400 13. 34 4, S20 2.80 04-13 1200 16.01 10, £00 0.45 04-13 2400 17.13 14, 200 Q.75 04-18 2400 1%. 25 3, 320 2.98 04-14 0600 17.591 16, 700 0.974 04-19 2400 11. 35 2, 660 3.12 04-14 1200 17.70 17, 700 1.14 04-14 1400 17.74 17, 200 1.21 04-20 2400 10. S52 2, 210 3. 24 04-14 1800 17.71 17, 700 1.33 04-14 2400 17.48 16, 600 1.55 04-21 2400 9.82 1, 870 3. 34 04-15 1200 16.53 12, 500 1.920 04-22 2400 7.39 1, 680 3. 42 04-11 04-12 04-12 04-12 04-12 04-12 04-12 04-13 04-12 04-13 04-13 04-13 04-13 04-13 04-14 04-14 04-14 2400 0130 0300 0600 az200 1200 16400 2000 2400 0300 0£00 1200 1800 2400 0600 1200 2400 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued GAGE HEIGHT 12.17 12.01 13.47 17.93 20.16 21.47 22.82 23.74 24.66 25.58 26.51 27.29 27.51 27.37 PJ I TJ U1 O. 0. O G -o C 0 \ 02441000, Tibbee Creek near Tibbee, Miss. 139 ACCUMULATED GAGE ACCUMULATED DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 2, 760 0.00 04-15 1200 23.85 11, S00 2.493 2, 700 0. 00 04-15 2400 23.10 7, 270 2. 467 3, 430 0.01 S, 070 0.03 04-16 1200 22.27 7, 800 2.33 6, 140 0.046 04-146 - 2400 20.973 &, S60 2.97 6, 260 0.07 8, £70 0.14 04-17 1200 18.99 5, §70 3. 09 11, 100 0.20 04-17 2400 6.97 4, SSQ 3. 13 14, 500 0.2: 04-18 1200 13.82 3, S560 3. 24 179, 000 0. 34 04-18 2400 10.70 2, 420 3.31 24, £00 0.46 30, 300 0.72 04-172 1200 H. 33 1, 570 3. i353 32, 100 1.02 04-19 2400 &. 45 764 B . SB% 30, 700 1.32 04-20 2400 4.97 566 3.41 27, 800 1.59 23, 800 1.34 04-21 2400 4. é£1 477 3. 42 16, 000 2.2.2 04-232 2400 4. 36 422 3. 44 140 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02441500, Tombigbee River at Columbus, Miss. GAGE ACCUMULATED GAGE ACCUMULATED DATE T IME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 04-11 0100 15. 04 15, 400 0. 00 04-11 1200 14.47 14, S00 0.095 04-146 1200 33. 43 64, 100 2.33 04-11 2400 13. 67 13, 400 0.11 04-16 2400 32. 68 57, 200 2.53 04-12 0300 13.82 13, £00 0.12 04-17 1200 31.88 57, 200 2.82 04-12 0600 16.38 17, 400 0.14 04-17 2400 30.82 52, 800 3. 05 04-12 0700 18.93 21, 600 0.16 04-12 1200 21.13 25, S00 0.18 04-18 1200 29.91 47, 800 3.26 04-12 1800 24.85 33, 100 0.24 04-18 2400 27.98 42, 800 3.45 04-12 2400 27.63 40, 800 0.32 04-19 1200 26. 08 37, 800 3.61 04-13 ©0600 30.53 49, 800 0.42 04-19 2400 23.83 32, 600 3.76 04-13 1200 32.50 S8, 100 0.53 04-13 1800 33. 85 67, 000 0.66 04-20 1200 21.30 27, 300 3.33 04-13 2400 34. 62 72, 9200 0.30 04-20 2400 18.72 22, 500 3.99 04-14 0600 35.16 78, 100 0.96 04-21 1200 16. 25 18, 200 4.07 04-14 1400 39. 33 80, 400 1.18 04-21 2400 13.89 14, S00 4. 14 04-14 1800 35.21 78, 800 1.29 04-14 2400 39.10 77, 300 1.45 04-22 1200 11.26 10, 800 4.12 04-22 2400 9.22 8, 090 4.23 04-15 1200 34.64 73, 000 1.76 04-15 2400 34.07 68, 500 2.05 04-23 2400 7.79 6, 250 4.29 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02443500, Luxapallila Creek near Columbus, Miss. 141 GAGE ACCUMULATED GAGE ACCUMULATED DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 04-11 2400 11.68 1, 382 0. 00 04-15 0600 29.87 30, 700 4.13 04-12 0300 12. 45 1, 720 0. 00 04-15 1200 28.80 26, 800 4.50 04-12 0600 13. 68 2, 300 0.02 04-15 1800 27.47 22, 300 4.81 04-12 0900 15. 25 3, 140 0.04 04-15 2400 26.11 18, 100 S. 07 04-12 1200 17.71 4, 630 0.06 04-12 1500 19.96 6, 170 0.09 04-16 0600 24.65 13, 200 S. 23 04-12 1800 21.89 8, 260 O. 14 04-16 1200 23. 28 10, 700 S. 44 04-12 2100 23. 35 10, 800 0.20 04-16 1800 21.94 8, 320 5.56 04-12 2400 24.41 13, 300 0.28 04-16 2400 20.74 6, 930 S. 65 04-13 0300 25. 38 15, 900 0.37 04-17 1200 19. 02 S, 510 5.81 04-13 0600 27.17 21, 400 0.49 04-17 2400 17.795 4, 660 S. 94 04-13 0900 28.74 26, 600 0. 65 04-13 1200 29.98 31, 100 0.83 04-18 1200 16. S57 3, 920 6.05 04-13 1500 30. 89 34, 800 1.04 04-18 2400 15. 40 3, 230 6.15 04-13 1800 31.61 37, 300 1.27 04-13 2100 32.07 39, 200 1.52 04-19 2400 13. 44 2, 180 6.283 04-13 2400 32. 30 40, 200 1.77 04-20 2400 12.43 1, 710 6.383 04-14 0100 32. 35 40, 400 1.34 04-14 0300 32.31 40, 200 2.03 04-21 2400 11.92 1, 483 6.47 04-14 0600 32. 31 40, 200 2.29 04-14 1200 31.92 38, 600 2.73 04-22 2400 11.99 1, 340 6.54 04-14 1800 31.32 36, 200 3. 27 04-14 2400 30.69 33, 700 3.72 04-23 2400 11.36 1, 250 6.60 142 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02446500, Sipsey River near Elrod, Ala. DATE TIME GAGE DISCHARG ACCUM. DATE TIME GAGE DISCHARGE ACCUM». HEIGHT RUNOFF HE IGHT RUNOFF 3-01 0200 13.88 3+210 3-16 0200 12.35 1 +280 4 . 64 3-01 1700 14.06 3+680 0.17 3-16 2400 12.17 1 +190 4 » 72 3-01 2400 14.20 4+» 100 0 . 25 3-17 0100 12.16 1,180 4 72 3-02 0600 14.23 4» 190 0 « 33 3-17 2400 11.93 1 090 4. 80 3-02 2200 14.09 3+770 0.52 3-02 2400 14.06 31680 0.54 3-18 0100 11.92 1,080 4.80 3-18 2400 11.66 1,010 4. 87 3-03 1200 14.10 3+800 0.67 3-03 1800 14.41 4+) 730 0 . 75 3-03 2400 14.99 7 +250 0.86 3-19 0100 11.64 1,000 4 . 88 3-19 2400 11.35 943 4.94 3-04 0800 15.46 9,600 1.07 3-04 1000 15.48 9 +700 1.13 3-20 0100 11.33 939 4.95 3-04 2400 15.21 8 , 350 1.51 3-20 2400 11.06 891 5.01 3-05 0100 15.19 8 +250 1.53 3-21 0100 11.06 891 5.01 3-05 2200 14.93 6,950 2.00 3-21 2400 10.92 866 5.07 3-05 2400 14.92 6900 2.04 3-22 0100 10.90 862 5.07 3-06 0100 14.92 6900 2.06 3-22 2400 10.65 817 5.13 3-06 2000 14.71 5850 2.42 3-06 2400 14.81 6,350 2.49 3-23 2400 11.12 902 5.19 3-07 1000 15.06 7600 2.70 3-07 2400 14.86 6600 3.01 3-24 1200 11.19 914 5.23 3-24 2400 11.14 905 5.26 3-08 0100 14.85 6+550 303 3-25 0200 11.13 903 5.26 3-08 2400 14.40 4,700 3.40 3-25 2400 11.05 B89 5.32 3-09 0100 14.38 4,640 3.41 3-26 2400 11.21 918 5.39 3-09 2400 14.04 3.70 3-27 2400 11.86 060 <4 3-10 0100 14.03 3+590 3.71 B i Soke 3-10 2400 13.77 2990 3.93 3-28 2400 12.56 1+410 5.55 3-11 0100 13.76 2+970 3.94 gr A951 21910 4113 3-29 2100 - 12.76 1+570 5.64 3-29 2400 12.15 1,570 5.66 3-12 0100 13.49 2,470 4 . 13 3-30 0100 12.74 1 +560 5.66 3-12 2400 13.20 2 +030 4 . 29 3-30 2400 12.42 1 +320 5.76 3-13 0100 13.19 2,020 4.29 3-31 0100 12.40 1 +310 5.76 3-13 2400 12.89 1,690 4 . 42 3-31 2400 12.09 1 +150 5.85 3-14 0100 12.87 1 670 4 » 43 4-01 0100 12.09 1 150 5. 85 3-14 2400 12.59 1,430 4.53 4-01 2400 12.02 1 120 5.93 3-15 0100 12.58 1,430 4.54 4-02 2300 12.14 1 »170 6.00 3-15 2400 12.36 1 +290 4 63 4-02 2400 12.18 1 +190 6.01 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02446500, Sipsey River near Elrod, Ala. -Continued 143 vean en on wn an an an an ceesess sss wn an an n an an as at an an un ar en am an a an an an ain an a a an on an an an as ar an e n an on av an an ar en an wo us us ms as ms me an on an ae an n as an an an an an an an an an mn we o on o o e an ««« DATE TIME GAGE HEIGHT DISCHARGE ACCUM . RUNOFF DATE TIME GAGE HEIGHT DISCHARGE ACCUM. RUnoF F wo as an as un un as an as an on un am an an ms me on an on m an ae an am mn oe un un an an an an an an an un an an on an an as an n an as an an an an mn n an ap an an an an an me an an on an n me an an an an an an an an as me an an an an an an an an an on an as an an an an an 4-03 4-04 4-05 4=05 4-06 4=07 4-08 4-09 4-09 4-09 4-10 4-10 4-11 4=11 4-12 4-12 4-12 4-12 4-12 4-13 4-13 4=13 4-14 4-14 2400 2400 0100 2400 2400 2400 2400 0800 2000 2400 0100 2400 0100 2400 0400 1000 1400 1700 2400 0800 0900 2400 0100 2400 12.85 13.06 13.06 12.83 12.97 13.21 13.50 13.54 13.42 13.36 13.35 13.02 13.00 12.62 12.55 13.30 13.99 14.95 17.07 17.85 17.81 17.32 17.28 16.86 1 1660 1 +870 1 +870 1 +640 1 +770 2+040 2,490 2,560 2,360 2270 2250 1,820 1,800 1 +460 1 )410 2,170 3,480 7,050 18,400 23+100 22900 19,900 19,700 17,200 6.85 6.93 6.96 6.97 711 1.24 71.27 731 1.36 1.64 8.16 8.23 9.18 9.24 10.48 4-15 4-15 4-15 1200 2300 2400 0100 2400 0100 2100 2400 0100 2400 0100 2400 0100 2400 0100 2400 0100 2400 0100 2400 0100 24080 0100 2400 16.86 16.59 16.56 16.52 15.36 15.31 14.65 14.59 14.57 14.17 14.16 13.85 13.85 13.55 13.54 13.24 13.23 12.91 12.89 12.56 12.54 12.34 12.33 12.15 17,200 15,500 15,400 15,100 9,100 8,850 5,600 5,360 5 +280 4 +010 3,980 3+150 3150 2580 2560 2090 2,070 1,710 1,690 1,410 1,400 1 +270 1,270 1,180 11.10 11.63 11.68 11.72 12.54 12.57 12.98 13.03, 13.05 13.36 13.37 13.62 13.63 13.82 13.83 13.99 13.99 14.12 14.13 14.23 14.24 14.33 14.33 14.42 144 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02448000, Noxubee River at Macon, Miss. GAGE ACUOUMULATED GAGE ACCUMULATED DATE TIME _ HEIGHT DISCHARGE RUNOFF DATE _ TIME - HEIGHT _ DISCHARGE RUNOFF 04-01 - 2400 7.63 421 0.00 04-12 1800 31.22 25, 700 1.42 04-12 2000 32.81 39, £00 1.95 04-02 0100 7.63 421 0.00 04-12 2200 34.23 55, 400 1.73 04-02 04600 7.60 414 0.90 04-12 2400 $5.57 72, 400 1.97 04-02 2400 7.86 476 0.02 04-13 ©200 36.45 £4, 800 2.283 04-03 0600 9.23 818 0.02 04-13 0400 87.12 974, 800 2.62 04-03 1200 11.785 1, 450 0.04 04-13 04600 37.65 103, 000 3. 00 04-03 - 1800 13.21 1, 810 0.05 04-13 0800 38. 06 109, 000 3.40 04-03 - 2400 14.53 2, 140 0.023 04-13 1000 38. 346 114, 000 3.383 04-13 1200 38. 61 118, 000 4.27 04-04 - 0600 17. 835 2, 850 0.11 04-13 - 1500 38. 85 122, 000 4.96 04-04 - 1200 18.92 3, 240 0.14 04-13 - 1800 38.95 124, 000 5.46 04-04 - 2200 19.23 3, 320 0.20 04-13 1900 38.97 125, 000 5.720 04-04 - 2400 19.23 3, 320 0.22 04-13 2100 38. 90 123, 000 £. 237 04-13 2406 38.71 120, 000 7.07 04-05 1200 18.98 3, 250 0.29 04-05 1800 18. 64 3, 170 0.33 04-14 04600 38.06 109, 000 2.38 04-05 2400 18.07 3, 030 0.34 04-14 - 0900 37.58 102, 000 3.989 04-14 1200 37.00 93, 000 7.54 04-06 1200 16.47 2, 630 0.43 04-14 1800 36.00 78, 000 10.82 04-06 - 2400 18.20 2, 310 0.43 04-14 - 2400 34.97 64, £00 11.34 04-07 - 1200 14.82 2, 220 0.54 04-15 - 0600 33.96 52, 100 12.01 04-07 - 2400 14.99 2, 260 0.529 04-15 1200 32.98 41, 300 12.54 04-15 1800 31.99 31, 400 12. 26 04-08 - 0800 15.28 2, 320 0.42 04-15 2400 31.04 24, 3200 13. 28 04-08 1600 17.15 2, £00 0. 66 04-08 - 2400 19.06 3, 280 0.71 04-16 1200 29.39 15, 400 13.73 04-16 2400 28.08 10, 700 14.03 04-09 0800 20.19 3, 580 0.74 04-09 1600 20.41 3, £60 0.32 04-17 - 1200 27.146 8, 890 14.25 04-09 2400 20.48 3, £90 0.87 04-17 2400 26.50 7, 760 14.44 04-10 1200 20.31 3, 620 0.26 04-18 1200 25.94 7, 150 14.61 04-10 - 1800 19.98 3, 510 1.00 04-18 - 2400 25.37 6, 630 14.77 04-10 - 2400 19.38 3, 360 1.04 04-19 1200 24.54 5, 930 14.92 04-11 1200 17.21 2, 810 1.11 04-192 2400 23.27 5, 040 15.04 04-11 2400 14.42 2, 120 1.16 04-20 1200 21.30 4, 040 19.195 04-12 0400 18.71 1, 240 1.18 04-20 2400 17. 36 2, 850 185.22 04-12 0600 16.723 2, 690 1.192 04-12 0800 21.88 4, 300 1.20 04-21 - 0800 13.91 1, 990 15. 26 04-12 1000 24.51 5, 210 1.22 04-21 1600 11. 24 1, 320 15. 29 04-12 1200 26.93 8, 470 1. 25 04-21 - 2400 9.95 998 15. 30 04-12 1400 28.60 12, 200 1.29 00 04-12 1600 29.76 17, 200 1. 34 04-22 2400 . 93 742 15. 34 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02448500, Noxubee River near Geiger, Ala. 145 D 1 SCHARGE ACCUM- RUNOFF ------------------------------------------------------------------------------ w o w vlawww t 1 0 0 o o Jp pe U 0 0 0 0 0 o in un wn «n wn n W W W W w w w w 1 0 o o o 3-06 3-06 3-07 3-07 3-07 307 3-08 3-08 3-08 3-08 3-09 3-09 3-09 3-09 3-10 3-10 3+ 10 3- 10 3° 11 3411 3-11 3711 3-12 3-12 3-12 3~12 «51 17,800 17,000 16, 400 15,700 15,200 14,700 14,200 13,700 13,200 12,800 12, 300 11,800 11,400 10,900 10, 400 9,870 9,370 8,830 8, 330 7,770 7, 180 6, Lho ow pp CP p- IIW w W W Ww wo w@ Nn tD min a- p 0 0 0 0 0 0 0 o 0 0 0 o ma ea ea 2a sa cl - - 0 0 N N N ho 00 O4 . 08 £13 17 22 27 32 37 42 47 «54 66 81 . 96 12 . 28 +39 . 50 «59 «84 95 13 28 4 59 . 75 .90 . 04 18 «32 «L4 «57 . 69 . 80 . 92 . 02 «13 4 «32 «42 +51 «59 «67 «75 . 82 «89 ©95 01 . 06 NNW w aaa aaewy w o o o in wn un un 11. 11. 12. 12. 12, 12, 12. U in un wn wn in wn un ence l g AP Arde w co w on ¥ 090% 5.34 5.34 5.35 5.35 5.36 5.36 5.37 in wn W to co ~ wi in wn un EW W w O w w co U www ww uw o nnn - - 00 w « p t 5.44 in 8 p tn 5.4 / . 48 50 52 «53 55 «57 «59 in wi w» _ w wn un un 146 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02448500, Noxubee River near Geiger, Ala -Continued DATE Time GAGE DISCHARGE ___ Accum- dATE | Fimg Gace DISCHARGE ___ ACCUm- HEIGHT RUNOFF HETGHT RUNOFF 3-26: - 0600 . 11.57 1,970 5.62 4-07: _ 6600. - 18.62 3,850 6.58 3-26 1200. 11.19 1,830 5.64 4-07 $700. . 17.4% 3,450 6.61 3-26 1800 10.72 1,670 5.65 4-07 1800 16:33 3,090 6.63 3-26 - - 15.51 1,580 5.66 4-07: -- 2400 - 45:43 2,790 6.66 4-08 - 0600 _ 14.84 2 3=27 0600 __ 10.39 1.550 5.68 4-08 1200 - 15.14 2'238 2'§§ i-g; 11000 10.8 ie g.§g 4-08 1800 _ 18.10 3,530 6.73 e 1800 _ 10.30 ¢ $ 4-08 2400 , : A 3-27 . / gh0o. » 1,620 5.72 §9:75 4, 520 6.77 4-09 0600 _ 22.68 3-28 0600 10.38 1,650 5.73 4-09 1200 24.01 5,388 23; 3-28 f200 | 19.45 1, 660 5. 7h $599. - thes as s sl 3-28 _ 1800 _ 10.49 1,690 5.76 4-09 _ 2400 _ 24.78 6,110 6. 3-48 - - 2400 ~ 10.45 1,690 5.77 . f 'he 4-10 __ 0600 % 3-29 _ 0600 _ 10.42 1,680 5.78 hel tooo Hoi 2'323 $ 9% 3-29 1200 _ - 10.18 1,690 5.80 4-10 1800 _ 23.57 5,650 g'lg 3=750.. 1800 _ 9.76 1,620 5.81 4-10° © - 9460 © 23.54 5,390 7.14 3-29 ._ g400o - 9.21 1, 480 5.82 > - L-11 0600 | 22.04 5,110 7.18 3-30 _ 8600 . 9.59 yn g'gfi 4-11 1209 - <21.26 4 , BLO 7:22 5:33 (ago 3-2; Sre 5.85 4-11 1800 _ 20.50 4 , 580 7.26 eke o. Shoo ioe s +: 4-11 2400 __ 19.65 4 , 300 7.30 s 4-12 ' 0600 18.85 4,060 7.33 §_§: $388 2:32 £3; 2:2? h- 12 6900 - 22.89 5,410 7.34 3731 1800 6.25 629 5.88 b- 12 1200 - 30.09 8,660 7.39 A 8 os # u- 12 1600 - 356.87 14,800 7.47 333 2400 18 5 5+ L-12 2000 __ 39.65 25,600 7.61 13] debe e pB h- 12 2400 _- 41.28 33, 700 7:79 2 a if Of :f eno as inn o gos o pS ro tage t big tea e+ 4-13 -- 0800 / - 42.14 Lo , 500 £.21 f § L- 13 1200 _ 42.90 48 , 500 &. 48 u- 13 1600 _ 44.08 62,800 8.82 S e 2 9 f 4-13" 34600 ~ 95, 500 5.77 u- 02 1300 6.19 624 5.91 4-02 1800 2'1“ 532 fia] h- 14 o4oo _ 47.00 113,000 10.38 h- 02 2l°° ‘23 598 5.91 b- 1h 0800 _ 47.60 127,000 11.07 h- 02 2400 6.7 73 5.92 b- 14 1200 _ 48.10 141,000 11.83 b- 14 1600 _ 48.50 154,000 12.68 2'03 $§88 19-7‘ éjsgg 5-93 h-14 1800 _ 48.58 156,000 13.10 “jg; (egs 12.22 3'380 g'g7 b-14 -_ 2000 _ 48.58 156,000 13.52 : ) j k-t4 _ 2400 - 48. 46 150,000 1h. 34 4-03 ~ . 17.72 3,720 6.01 { 4-15 - - 48.;6 144,000 15.13 i on ce Phe: ig th ay 4-15 _ 0800 _ 47.90 135,000 15.86 '> (20s. sae 3" 680 6.03 4-15 1200 _ 47.50 124,000 16.53 Nea (ege -. a meo a+ 4-15 1600 _ 46.90 111,000 17.13 s > § 4-15 _ 2000 _ 46.20 92, 400 17.63 hgh .. 7ooo. 6,160 6.16 ls _ | beige pes (2 u-04 2400 __ 25.28 6,310 6.19 + » > 4-16 0600 Lh .50 63,900 18.59 0300 _ 25.45 2,380 2-25 4-16 1200 - 43.60 51,200 19.01 h-05 0600 _ 25.43 6'3Z0 6.5 4-16 1800 _ 43.00 L4 , 200 19.37 h-05 1290 _ 25:1! to ©29 4-16 _ 2400 _ 42.40 37,800 19.68 4-05 1800 _ 24.62 6,050 6.34 205 : 2800 . 20:92 aa $:59 4-17 __ 0600 _ 41.80 32,600 19.94 b-17 1200 - 41.18 28,800 20.18 u-06 _ 0600 _ 23.04 5, 460 6.43 17 f s od f args 4-06 1200 _ 22.00 5,100 6. 48 5100. ims obo 4-06 j800 - 306.97 4,740 6.51 § > 3 4-06 2400 19.82 4,290 6.55 TABLES 147 TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02448500, Noxubee River near Geiger, Ala -Continued DATE _ TIME GAGE DISCHARGE ___ Accum- DATE _ TIME __ GAGE DISCHARGE ___ Accum- HELGHT RUNOFF HEIGHT RUNOFF 4-18 _ 0600 _ 39.48 21,200 20.75 4-25 __ 0600 7.97 1,180 22.66 4-18 1200 __ 38.98 19,500 20.91 4-25 1200 | 8.15 1,290 22.67 4-18 1800 38.49 18,000 21.06 4-25 1800 8.35 1, 360 22.68 #-18 - z400 - 38.02 16,600 21.19 4-25 _ 2400 __ 8.48 1,420 22.69 ly . 9600 . 17.54 pois Pik 4-26 __ 0600 __ 8.58 1,490 22.70 floe . 37:07 11,200 21:98 k-26 - 1200 - 8.64 likig 22.72 hla. 1800 36.69 121000 Bi 22 4-26 _ 1800 _ 81.66 1,510 22.73 4-19 __ 2400 _ 36.14 12,900 21.65 - . 9.62 11750 52.7% #30 " 1200 - 35.2: 11,5600 21.85 u-z; miss 3'43 z'ggg er ;7 4-20 1800 _ 34.72 11,000 21.94 N27 1200. $.22 1 tes at' =30 - 2B9o - 34.20 10,500 22.02 heap ~. choo - Slag 1 509 ago 4-21 0600 __ 33.66 9,930 22.60 _ op o orf 4-21 1800 32.41 8,810 22.25 4-28 1800 8.13 1'380 22.83 4-22 _ 1200 _ 29.06 6.430 __ 22.44 - Phage 594 Neigh. . 55.87 h-22 1800 _ 27.30 5,680 22.48 : | J.2% 1; 4p $2.87 4-23 - - 25.71 4,960 22.52 hees | 2400 ° $p; 72.85 [0-23 0600 22-75 39930 22.55 l‘_3o 0600 6.88 1,050 4-23 _ 1200 _ 20.01 3,210 22.58 | 4200) Sipp 1 22.99 4-23 1800 _ 16.95 2,400 22.60 ' 4-23 2400 13.92 1,710 22.61 4-30 1800 6.57 955 22.91 4-30 __ 2400 __ 6.44 916 22.92 b-24 __ 0600 __ 11.46 1,300 22.62 b-24 1200 __ 9.65 1,200 22.63 4-24 1800 _ 8.46 1,130 22. 64 4-24 00 2400 00 7.98 1,110 22.65 148 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02449000, Tombigbee River at Gainesville, Ala. GAGE ACCUM GAGE ACCUM. DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 2-28 2400 31.58 46200 0. 00 3-17 1200 16.38 12700 3.88 3- 1 1200 30.68 46900 10 3-18 1200 15.58 10700 3.93 3- 2 1200 30.49 46900 . 30 3-19 1200 14.50 8490 3.97 3- 3 1200 31.67 49000 . 51 3-20 1200 14.45 8240 4.01 3~ 3 2400 37.18 63800 65 § 3-21 1200 13.93 7270 4.04 3- 4 0600 39.06 72900 15 3- 4 1200 41.57 87400 . 82 3-22 1200 14.28 8050 4.07 3- 4 1800 42.34 91300 «92 3- 4 2400 42.80 93800 1.02 3-23 1200 15.67 11400 4.12 3- 5 0600 43.12 94700 1.12 3-24 1200 19.29 20200 4.21 3- 5 1200 43.26 95600 1.22 3- 5 1600 43.15 96100 1.29 3-25 1200 21.95 25700 4.32 3- 5 1800 43.35 95700 1.32 3- 5 2400 43.40 96000 1.42 3-26 1200 22.44 27000 4.44 3- 6 0600 43.44 96200 1.52 3-27 1200 22.74 27400 4.56 3- 6 1200 43.32 95400 1.62 3- 6 1800 43.29 95100 1.72 3-28 1200 21.74 25100 4.67 3- 6 2400 43.21 94600 1.82 3-29 1200 19.37 18800 4.75 3- 7 1200 42.87 91600 2.02 3-30 1200 16.75 13800 4.81 3- 8 1200 41.78 86700 2.59 3-31 1200 16.34 13000 4.87 3- 9 1200 40.86 81600 2.74 4- 1 1200 15.07 10500 4.91 3-10 1200 38.96 71900 3.03 4- 2 1200 15.57 12400 4.96 3-11 1200 35.69 60000 3.29 4- 3 1200 21.48 23500 5.06 3-12 1200 31.79 46100 3.49 4- 4 1200 27.20 37000 5.22 3-13 1200 26.80 31600 3.63 4- 5 1200 29.01 41400 5.40 3-14 1200 21.34 20700 3.72 4- 6 1200 28.84 40900 5.57 3-15 1200 17.79 14000 3.78 4- 7 1200 28.15 38900 5.74 3-16 1200 16.36 12300 3.83 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02449000, Tombigbee River at Gainesville, Ala. -Continued 149 GAGE ACCUM. GAGE 4-13 4-13 4-13 4-13 4-13 4-14 4-14 4-14 4-14 4-14 4-14 4-15 4-15 4-15 4-15 4-15 4-15 4-15 4-16 4-16 4-16 4-16 4-16 4-16 4-17 4-17 4-17 4-17 1200 1200 1200 1200 2400 0600 1200 1600 2000 2400 0400 0800 1200 1600 2000 2400 0400 0800 1200 1600 2000 2400 0400 0800 1200 1300 1600 2000 2400 0400 0800 1200 1600 2000 2400 0600 1200 1800 2400 40000 46200 42000 35400 34000 33300 44900 61900 78200 87400 102000 114000 126000 138000 149000 161000 176000 190000 204000 220000 232000 243000 251000 259000 260000 261000 260000 255000 251000 247000 241000 234000 227000 219000 213000 203000 193000 183000 175000 o o o a a a a a NON _ OG o co 00 NI NPN S t w co co co co co alone L of an oie o ane te «91 A11 . 29 17. 18. 17. 15 69 08 46 .49 94 168000 158000 151000 144000 135000 129000 123000 116000 112000 107000 101000 95700 89000 83200 77900 72600 69300 65800 60400 51600 47800 37600 32700 29300 27400 19000 14000 12300 12600 13300 14400 13000 10800 9760 13. 68 13.74 13.80 13.85 13.89 150 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02449245, Brush Creek near Eutaw, Ala. DATE TIME GAGE DISCHARG «ACCUM. DATE TIME GAGE DISCHARGE ACCUM. HEIGHT RUNOFF HEIGHT RUNOFF 3-01 0030 5.02 AJ 3-08 0015 5.49 121 4 01 3-01 0215 5.17 92 0.01 3-08 2400 5.17 92 4 » 10 3-01 0700 6.01 167 0 . 03 3=0l1 1215 6.20 188 0.06 3-01 2400 5.54 125 0.13 3-09 0015 5.17 92 4 » 10 3-09 2400 5.00 77 4.17 3-02 0015 5.53 124 0.13 3-02 1245 5.19 94 0.18 3-10 1745 4.93 72 4 22 3-02 2400 5.10 86 0.22 3-10 2400 5.21 96 4.24 3-03 0245 5.19 94 0 22 4-10 0015 6.16 183 0 . 00 3-03 0345 5.47 119 0 . 23 4-10 1245 5.67 137 0 . 07 3-03 0430 6.03 169 0.23 4-10 2400 5.43 115 0.12 3-03 0715 8.86 S11 0-27 3-03 1015 9.87 655 0 . 34 3=03 - 1145 10.36 1728 0 . 37 4-11 0015 5.43 115 0.12 3-03 1600 15.88 1 +550 0.56 4-11 2400 5.13 89 0.21 3-03 1815 17.41 2+110 0 . 70 3-03 1915 18.31 2+650 0 . 79 3-03 2115 19.69 4 030 1.05 4-12 0715 5. OS 81 0 23 3-03 2215 19.79 4,150 1.20 4-12 0745 5.16 91 0.24 3-03 2400 19.51 3+810 1.45 4-12 0800 5.43 115 0.24 4-12 0815 5.92 159 0.24 4-12 0830 6.86 260 0.24 3-04 0015 19.46 3+750 1.48 4-12 1000 14.37 1,320 0 . 29 3-04 - 0445 19.09 3+310 t 4-12 1100 17.09 1,950 0 . 35 3-04 1100 18.19 2 +550 273 4-12 1230 18.47 2,780 0 . 48 3-04 1800 15.50 1,490 3.22 4-12 1500 18.23 2,580 0 . 74 3-04 2230 11.82 952 3.42 4=12: 1115 17.87 2 +340 0 93 3-04 2400 10.31 721 3.47 4-12 1830 18.62 2+900 1.05 4-12 2200 21.81 6,900 1.70 4-12 2400 22.23 7,660 2.24 3-05 0015 10.09 688 3.47 3-05 0230 8.51 464 3.52 3-05 - OS4S 71.59 346 3.56 4-13 0445 22.68 8,560 3.65 3-05 1500 6.79 252 3.66 4-13 - O0S54S 22.58 8,360 3.96 3-05 2400 6.45 215 3.74 4-13 0900 21.93 7,090 4 . 85 4-13 1145 22.15 7,500 5.60 4-13 1645 20.16 4 +590 6.66 3-06 0015 6.44 214 3.74 4-13 2115 18.55 2,840 7.25 3-06 1900 5.92 159 3.86 4-13 2400 17.67 2240 7.49 3-06 2400 5.82 150 3.89 4-14 0015 17.59 2200 7+51 3-07 0015 5.82 150 3.89 4-14 0530 15.39 1,470 7.85 3-07 2400 5.50 122 4 0 1 4-14 1230 9.47 598 8.11 4-14 1530 8. 39 448 8.17 4-14 2130 8.10 409 8.26 DISCHARGE DaTE TIME TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02449245, Brush Creek near Eutaw, Ala -Continued GAGE HEIGHT 151 ACCUM. RUNOFF DATE TIME GAGE HEIGHT DISCHARGE ACCUM. RUNOFF 4-14 4-15 4-15 4-16 4-16 4-17 4=17 2400 2200 2400 0745 2400 0015 2400 8.22 425 631 637 641 573 572 389 8.29 8.73 8.77 0015 2400 0015 1715 2400 0015 0830 2400 7.93 6.25 6.25 5.17 4 . 85 4.84 4.68 4.59 387 193 193 92 67 66 55 49 152 DATE 4=10 4-10 4=10 4-11 4-11 4-11 4-12 4-12 4-12 4-12 4-12 4-12 4=12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-13 4-13 4-13 4-13 4-13 4-13 4-13 4-13 TIME 0030 0900 2400 0730 1415 2400 0545 0600 0615 0630 0645 0700 0730 0745 0830 0930 1200 1345 1915 1615 1845 1945 2045 2345 2400 0545 0830 1315 1330 1515 1645 1745 1830 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued GAGE HEIGHT 7.70 7.70 7.67 7.68 71.64 7.61 7.63 7.67 7.78 7.95 8.21 8.70 9.72 10.09 11.32 12.32 12.58 12.36 11.97 12.54 14.23 14.37 14.13 14.24 14.30 15.79 15.44 17.06 17.06 16.50 14.25 12.12 11.19 02461500, Valley Creek near Bessemer, Ala. DISCHARGE ACCUM. RUNOFF 160 160 0.04 153 0.11 1895 0.15 145 0.18 138 0 . 22 143 0.25 153 0 . 25 180 0 . 25 245 0 . 25 364 0 . 25 616 0.26 1,340 0.27 2+050 0 . 29 2820 0 . 35 3870 0.46 4 » 140 0.76 3+910 0 . 98 3+510 1.14 4090 1.26 6+170 1.67 6,390 1.86 6+010 2.05 6,180 2.59 6,280 2.64 8,820 3.99 89190 10.68 11,300 6.15 11 +300 6.23 10,100 6.81 6200 7.18 3+660 7.32 2690 7.38 DATE 4-13 4-13 4~13 4-13 4-14 4-14 4-14 4-14 4-15 4-15 4-16 4-16 4-17 4-17 4-17 4-18 4-18 4-18 4-19 4-19 4-19 4-20 4-20 4-20 TIME 2030 2045 2230 2400 0015 0615 2000 2400 0015 2400 0115 2400 0300 2230 2400 0045 2215 2400 0330 1900 2400 0345 1445 2400 GAGE HEIGHT 10.10 9.97 9.57 9.39 9.37 8.96 8.52 8.45 7.85 7.80 7.82 7.83 7.74 7.74 DISCHARGE 2,050 1,540 1,220 1,090 1,070 767 512 477 477 345 340 265 270 237 241 241 201 205 205 185 193 197 170 170 ACCUM. RUNOFF 71.52 71.53 7.60 7.66 7.66 7.83 8.09 8.14 8.68 8.84 8.85 8.99 9.00 9.02 9.11 9.14 9.16 9.22 9.27 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02462000, Valley Creek near Oak Grove, Ala. 153 DaTE I IME GAGE ht IGnT bATk Time bAGE nc lGhT DISCrArRGt A CCUM» KUNUF F oo e ae ee we me me oe me oe me ee me me oe m me e me me me e m me me me an m m mn am me om m om an oe an me me me me me mn oe n me me me me me oe me me me me an me mn me me me me me o m on me oe me oe ne me oe me oe mo ae an on an on an 3.91 3.97 4. U5 3.62 3. 75 3. 74 3+ 1¢ 3. 70 3.05 3.74 3.b5 3.92 4 » UC 4.69 4.44 5.b1 9.68 9.67 4 » 13 5.0% 500° 6.25 t. 95 4. UC 1.57 6.16 5:13 5.12 5. U / 4.5 7 4 . 44 4 , 44 4 » 3 7 4 » 3 7 4. CY 4.20 4.1% ulSCrarGE ACCUm. KUNOF r 360 420 0 .ul 49% 0 » 0 1 293 0 . v4 £64 £36 0 » u ( ceo 0 . uo 212 0 .us 185 (+4 1 23d 0.12 $1 7 0 » 13 375 U » 1 3 466 0 » 1 3 1 %u 70 U e 1 4 1 +el0o t» 14+ 1,590 0.18 3+ 350 0 « su 3) 440 ( » 3.3 3+ 1 Gu U . 44 1,540 U.O> 1 +ec50 U » (2 11280 Q. 183 1,000 U. 3+020 U .o 3050 U » 91 2+930 (0.9Y0 1s 760 1 .u / 1.280 1.18 1 +280 1.19 1 +260 1.19 Ybb 1.37 6 76 1.45 676 1.40 £12 1.49 «lz 1.951 (36 1.97 669 1.63 640 1.05 4-U 7 4=U 7 4=U / 4-0 7 4=U 7 4-U / 4-U e 4= Ui 4-00 4-Uo 4- Ub 4= U & «- Uo 4-00 4- Ui =U iz 4-06 4- Uy 4=UY in duck hd £4 wi} by 4- U9 4=~ U % 4-19 4= U % 4s t &= UI dut 2d ndd th J in dut Ci 4-10 4-10 4=1u indude A7 t= 1 v «- 10 a- 1uV 4-10 4= 10 4-10 4-10 Uuls u50 u 1245 140 U 1445 c40 u uluo vilos vi4o5 ub5l5 Vb4S 1345 1600 cU45 2345 2400 0 i 30 U33V u>uu bel5 1230 1430 170u 1745 1B63G c luu e 130 £619 cec45 2400 Uulo U 300 #315 b53UG u (30 Uel5 1200 cllo 2300 £315 C400 4.21 4 . 1 7 4.12 4.09 4.11 4. 06 '+. 08 4.04 4 «VO 4 » U 3 4. U4 4» 0 3 4. 04 'a . 06 4» 1 7 4.24 4» C ( 4. 3 7 4.66 4, 6 7 4 . 48 4.28 4.23 4.20 4.15 4.15 4.10 4» 13 4. UY 4.11 4» 10 4.10 4. 0b 4.05 4. 06 4 & U / 4.05 4.01 4 » 00 4.0 1 3.90 4 » 0 0 1 % 1s abe Sub 6 (i Cbo 6 (6 4b0 50% 620 CBo 117 cle Uu5U 060 §1¢ 126 6TY lat- 10 uo 600 FSU SoU 540 Sou Pou "bu ayy 5u9 5i9 499 45 7 44 [ 457 429 44 f 154 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02462000, Valley Creek near Oak Grove, Ala. -Continued Se oe ue we oe oe an ue me mn me on me we am n me nn me mn me me ae on me me me on on mn me me mn me m me on mn me me wn me mn ae mn mn an me an me me me mn an an ms un me me an ne me on oe me me me m me ne oe me me me me an me me me me me me mm oe me oe e me ne oe me oe ae me vaAlt _ vault UlSCnakGt mCCUM. valet - TiMk uabGt UIstrarut ACULUM » he lon f rUNur F he 1 Gn T F a-l1l - v430 4 » 0 0 447 l 4-18 - Uil>s 4. 2 [ 111 10 .c3 4-=1l 1230 3.97 420 2+31 4-18 - ciclo 4.13 58 u 10 . 37 4-11 1630 3.44 343 2. 3C - c245 4+» 12 5 (0 10V . 37 4-11 - 1945 3.95 4uUu2 2 « 34 4-16 _- c40u 4.14 seu 10.36 4-11 - 2s00 3.53 364 230 4-l1y - Uu245 4% 13 seu 1v.40 4-12 uvcza5 3.91 366 2% 3! 4-19 - us45 4 . U7 54 U lv «40 4-12 ve45 J.Y1 366 2.306 «-19 4.11 Sou lv .«1 u~12 0715 a . u4 486 4-19 - 4. Ub 529 lv .42 4-12 Uusuu 120 c.34 4-19 - vo3U 4. lu 250 1v «43 #=-i12 0915 4 » CY 136 2% 41 4-19 - 1945 4.05 499 10.4 7 4-12 1000 «4.40 a%4 2641 4-1y - 1630 4 » 0 7 51% 10.48 4=l¢ 1130 5.00 1520 2.43 4-1y - 2u45 4. U5 ayy 1u.50 4-12 1215 1.44 easel 2 s 44 4-19 - 2400 4% U 3 = (6 1v.5¢ 4-12 1400 14. 9 +340 «-12 - 1s0uv 6s 250 2.02 4-le 2400 esl ( 10, 3.41 4-20 - U130 4. 04 aBso 1v.5¢ 4-20 _ 4. 0 U 44 / 10.59 «-2u - 1000 4» UC «bb 1v.57 4-13 - 0430 cS5.vs 12+ 100 3.95 «=c20 - 150u 4. 0U 44 7 1v.59 4-13 - 26.0 i 143500 4 . 4 3 4-20 lel5 4. 0 U 44 { 10.61 «- 13 i215 cy. 14 24s UGO 5.40 4-¢v - 1030 4 . U 3 a 1b 10.61 4=13 loi5 29.80 26+ 300 6.49 «-z2U - 2u00 4. U 1 45 7 1uv.61 4-13 1730 24.10 26° 000 b. b 3 4-20 - 2400 3.40 611 10.03 4-13 2345 co. 16 16,400 b. co 4-13 24800 2b. 55 10+ i » 32 «-2l - b83uv 4% 0 U 44 7 10.6 / 4-2 l 1vuo 3.99 430 10.60 4-l4 - uul5 26.36 15%500 b. 39 4-21 _ 2400 3.95 4249 10.74 4-14 - 0315 £¢x iv 9% 210 be (% e-l4 - 0730 10.6 / 381 U 9 % U 3 4-14 - 19445 b. 64 2+070 9.11 a=ce UT0L 3.90 629 10.7 ( 4-14 0 1730 6. 18 2% 030 9. 30 4-ee2 1100 3.94 393 1V . 7/9 «-l4 - 2400 5.60 1.620 4 . 4 3 «-c¢c i615 3. 9.3 304+ 1v.b61 4-¢¢ - 1630 3.96 611 1uv.6c «-£2 - 2400 4» 0 U a4 7 104.55 4-15 UulS 5.45 1,610 9.43 4-15 - 1345 4.99 1 +230 9.03 4-15 2400 4.75 1+l10 9.16 4=es3 - Usl5 4» 10 550 1v.b67 «=c3 0 ull5 4.15 Fu u 10.09 4-23 Ubu 4.14 590 1 V «40 4-16 - 0045 a. 16 1 +120 9 . 7 7 4=23 0 1400 3.98 429 1v «93 - 24800 4 » 64 6 76 10 .u 1 4-23 £300 3.93 304 lu. 97 4-~23 - e400 3.91 366 1v.9 {( «=17 Ull5 4.45 885 10 .u 3 4-17 - 2400 4.20 Tu 7 10.¢c 4-24 0 1/15 3.91 366 11.04 4-24 - culo 3.94 3493 11.05 4-24 _ c400 4» U 1 aoi 11.0 / TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02462000, Valley Creek near Oak Grove, Ala. -Continued 155 ue we ue we me me un me me me me me e mn oe mn m me me me mn me an me an me me me on nn an on o me me me me mn me me ue e m mn mn me an mn an me me oe mn me me me mn oe m oe mn me ue oe me ue ae ue me oe me oe oe oe me me me oe me me an on e me me me ae ae me ee ae ae ae an GaGE HEIGHT DISCHARGE ACCUM. RUNOFF DATE TIME GAGE ht 1GHT ACCUM. RUnOF F 4-25 4-25 4-25 4-25 4-25 4-25 4-25 4-25 4-26 4-26 4-26 4-26 4-26 4-26 4-26 4-26 0300 0500 1100 1315 1730 2015 2345 2400 0400 0615 1400 1900 2130 2300 2315 2400 4.01 4.08 3.97 3.99 4.15 4.28 4.49 4 . 48 4.93 5.54 4.51 4.35 4 . 39 4.39 4 . 44 95.44 457 529 420 436 600 7126 921 912 1 +200 1 )470 936 793 631 831 876 1 +420 11.08 11.09 11.12 11.13 11.15 11.17 11.21 11.21 11.25 11.29 11.38 11.43 11.45 11.46 11.47 11.48 707 600 630 620 529 529 499 468 438 429 156 DATE TIME FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued GAGE HEIGHT 02464000, North River near Samantha, Ala. DISCHARGE 500 500 385 385 335 321 594 1 +530 3+040 4 +060 4,570 5,990 13,700 17,900 18,100 19,400 18,900 18,700 18,600 15,100 10 +900 ACCUM. RUNOFF 0.00 0 . 07 DATE 4-15 4-15 4-15 4-15 4-15 4-15 4-16 4-16 TIME 0100 0400 0700 0900 1100 2400 0100 2400 0100 2400 0100 2400 0100 2400 0100 2400 0100 2400 GAGE HEIGHT 20.13 15.34 8.90 6. 85 6.22 5.06 DISCHARGE 10,200 7060 3+680 2+550 2+200 1,580 1,570 1 120 1,090 836 830 654 649 517 511 423 418 365 ACCUM. RUNOFF 7.49 7.67 71.77 7.81 7.84 i » 01 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02465000, Black Warrior River at Northport, Ala. 157 GAGE HEIGHT GAGE HEIGHT D 1 SCHARGE 173000 199000 209000 214000 230000 269000 272000 265000 245000 239000 231000 209000 197000 188000 175000 169000 162000 ACCUM- RUNOFF 0 0 0 0 o N N -a a la a u - o w W W w w NJ . 02 . 08 21 «43 . 68 95 23 . 30 39 . 48 «56 . 88 18 . 48 . 88 26 38 «49 . 60 73 DATE TIME 2200 2400 0600 1200 1800 2400 0600 1200 1800 2400 0200 0400 0600 1200 1400 1600 1800 2000 2200 2400 60. 60. 59. 58. 57. 55. 54. 52. 51. 48. 47. 46. 45. 45. 45. 45. 4 , L4, 44 , 150000 144000 136000 123000 117000 99500 90000 74800 66600 46300 39400 31000 30400 31400 31900 34500 48500 29800 24900 24000 4 in &n q= w w in in n wn un wn un un wn un wi wn in a- aome e lon a o ) 9 £0 so £0 ls 158 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02465286, Cribbs Mill Creek at 2d Avenue in Tuscaloosa, Ala. GAGE ACCUM. GAGE ACCUM. DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 4-11 0030 0.52 4.0 0.00 4-12 2015 4.86 412 2.75 4-11 1400 .52 4.0 .03 4-12 2045 4.01 301 2.85 4-11 2400 51 3:7 .05 4-12 2115 3.70 264 2.92 4-12 2145 3.63 256 3.00 4-12 0600 .59 5.7 .07 4-12 2200 3.67 260 3.03 4-12 0615 1:17 31 . 07 4-12 2230 3.47 237 3.10 4-12 0630 1.94 85 . 08 4-12 2300 3.00 185 3.16 4-12 0645 2.02 92 .10 4-12 2315 2.80 165 3.18 4-12 0700 2.83 168 12 4-12 2330 2.68 153 3.20 4-12 0715 3.19 206 15 4-12 2345 2.77 162 3.23 4-12 0745 3.40 229 .21 4-12 2400 2.74 159 3.25 4-12 0800 3.77 272 .25 4-12 0830 4:12 316 . 34 4-13 0015 2.99 184 3.27 4-12 0845 4.01 301 . 38 4-13 0030 4.07 309 3.32 4-12 0915 3.48 238 .45 4-13 0045 5.22 463 3.38 4-12 0945 2.63 148 . 50 4-13 0115 5.92 576 3.54 4-12 1000 2,47 132 .52 4-13 0200 5.67 534 3.77 4-12 1015 2.93 178 .54 4-13 0215 4.95 424 3.83 4-12 1030 3.43 232 .57 4-13 0230 3.81 277 3.87 4-12 1100 5.02 433 . 68 4-13 0245 3.26 214 3.90 4-12 1115 5.25 468 175 4-13 0300 2.97 182 3.92 4-12 1200 4.81 405 .93 4-13 0330 2.88 173 3.97 4-12 1215 4.18 323 .97 4-13 0345 2.92 177 4.00 4-12 1230 3.39 228 1.01 4-13 0430 2:73 158 4.07 4-12 1245 2.90 175 1.03 4-13 0515 2.32 119 4.12 4-12 1300 2.58 143 1.05 4-13 0530 2.24 112 4.14 4-12 1330 2.16 104 1.08 4-13 0600 2.16 104 4.17 4-12 1345 2.01 91 1.10 4-13 0615 2:21 109 4.18 4-12 1430 1.71 67 1.13 4-13 0630 2.20 108 4.20 4-12 1445 1.78 72 1.14 4-13 0645 2.26 113 4.22 4-12 1500 1.91 83 1.15 4-13 0700 3.31 219 4.25 4-12 1515 1.78 72 1.16 4-13 0730 6.24 633 4.40 4-12 1530 1.94 85 1.17 4-13 0745 7.50 870 4.52 4-12 1545 2.02 92 1.18 4-13 0800 8.29 1040 4.66 4-12 1600 2.94 179 1.21 4-13 0815 8.83 1160 4.83 4-12 1615 3.%2 278 1.25 4-13 0845 9.27 1270 5.17 4-12 1630 4.95 424 1.31 4-13 0900 9.21 1250 5.35 4-12 1645 6.05 599 1.39 4-13 0915 8.77 1150 5.51 4-12 1715 7.24 818 1.61 4-13 0930 7.62 894 5.64 4-12 1730 7.68 906 1.74 4-13 1000 5.47 501 5.81 4-12 1800 7.86 942 2.00 4-13 1015 4.19 325 5.85 4-12 1830 7 A7 804 2,24 4-13 1030 3.50 240 5.89 4-12 1900 6.15 617 2.42 4-13 1045 3.12 198 5.92 4-12 1945 5.10 445 2.63 4-13 1100 2.81 166 5.94 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02465286, Cribbs Mill Creek at 2d Avenue in Tuscaloosa, Ala -Continued 159 GAGE ACCUM. ered ROH N} NJ N) noni ele e al a e aS al % a aaa ona ooo w 1300 2400 1200 2400 1200 2400 1300 2400 . 80 «77 &74 «73 70 18 15 13 11 10 w t o o 6.47 6.57 6.66 6.74 6.82 6.89 6.96 160 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02465493, Elliotts Creek at Moundville, Ala. DATE TIME GAGE HEIGHT 4-10 4=10 4-10 4-10 4=11 4-11 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-12 4-13 4-13 4=13 0030 0015 1645 2400 0030 2400 0730 0800 0815 0900 0930 1315 1645 1715 1745 1815 1915 1930 2000 2030 2045 2230 2400 0215 0800 0945 “D67 4.67 3.87 3.69 DISCHARGE ACCUM. RUNOFF 126 126 0 . 00 83 0 . 08 74 0.11 74 0.11 62 0.19 61 0.21 68 0 . 22 76 0.22 149 0.22 223 0 . 23 298 0 . 28 280 0 . 33 343 0 . 33 477 0 . 35 835 0 . 36 1190 0.42 1 +410 0.44 2+240 0 . 49 2 +440 0 . 55 2,360 0.58 1 780 0.75 1,440 0.87 1 +290 1.02 1 460 1.41 1.60 DATE TIME GAGE HEIGHT 4=13 4-13 4=13 4-13 4-13 4-14 4-14 4-14 4-14 4-15 4-15 4-16 4=~16 4-17 4-17 4-18 4-18 1015 1145 1345 1615 2400 0030 1000 1730 2400 0045 2400 0045 2400 0045 2400 0015 2400 0015 2400 7.40 7.29 7.10 6.97 6.77 6.76 6.33 6.13 6.00 DISCHARGE 3,000 2,560 1,850 1,460 1,160 1 +140 552 403 333 330 215 213 154 153 121 121 100 100 8T ACCUM. RUNOFF 1.67 1.88 2.09 2.29 2.78 2+81 3.19 3.37 3.48 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02467000, Tombigbee River at Demopolis lock and dam, Ala. 161 GAGE a a a a w wn n in L B A A w u tr ta NESE SES Co co co co 104000 111000 117000 120000 125000 130000 133000 141000 145000 147000 151000 152000 155000 158000 160000 165000 166000 168000 169000 170000 s r- w beret par geal leni aul alll sed ~I o 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 170000 170000 171000 170000 169000 164000 165000 160000 156000 154000 151000 145000 140000 133000 125000 114000 105000 96200 86800 78200 70000 62600 56000 51300 46800 43700 39100 35900 33300 32000 31400 31000 31000 A w @ n N t tr ta ta A A A m B u ur ur w ur r ta £104 al is aln Coss e Hol- B B p pm L B p A 162 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02467000, Tombigbee River at Demopolis lock and dam, Ala. -Continued GAGE ACCUM GAGE ACCUM DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 3-17 1200 20:12 30600 4.37 3-26 0600 20.85 42400 4.98 3-17 1800 20.09 30200 4.39 3-26 1200 20.83 42000 5.00 3-17 2400 19.99 28600 4.40 3-26 1800 20.83 42000 5.03 3-26 2400 20.89 43000 5.05 3-18 0600 20.01 29000 4.42 3-18 1200 19.94 27900 4.44 3-27 0600 20.85 42400 5.08 3-18 1800 19.91 27400 4.45 3-27 1200 20.86 42500 5.10 3-18 2400 19.78 25500 4.47 3-27 1800 20. 84 42200 5.13 3-27 2400 20.80 41500 5.15 3-19 0600 19.72 24600 4.48 3-19 1200 19.64 23400 4.50 3-28 0600 20.77 41000 5.18 3-19 1800 19.67 23800 4.51 3-28 1200 20.75 40600 5,20 3-19 2400 19.68 24000 4.53 3-28 1800 20.72 40100 5.23 3-28 2400 20.73 40300 5:25 3-20 0600 19.73 24800 4.54 3-20 1200 19.72 24600 4.56 3-29 0600 20.70 39800 5.28 3-20 1800 19.73 24800 4.57 3-29 1200 20.65 39000 5.30 3-20 2400 19.61 23000 4.59 3-29 1800 20.51 36700 5. 32 3-29 2400 20.28 33000 5 . 34 3-21 0600 19.52 21700 4.60 3-21 1200 19.50 21400 4.61 3-30 0600 20.11 30400 5,36 3-21 1800 19.51 21500 4.62 3-30 1200 19.98 28500 5.38 3-21 2400 19.56 22200 4.64 3-30 1800 20.03 29200 5.40 3-30 2400 20.00 28800 5.41 3-22 0600 19.60 22800 4.65 3-22 1200 19.61 23000 4.67 3-31 0600 19.95 28000 5.43 3-22 1800 19.56 22200 4.68 3-31 1200 19.90 27300 5.45 3-22 2400 19.59 22700 4.69 3-31 1800 19.82 26100 5.46 3-31 2400 19.66 23700 5.48 3-23 0600 19.64 23400 4.71 3-23 1200 19.77 25400 4.72 4- 1 0600 19.54 22000 5.49 3-23 1800 19.94 27900 4.74 4- 1 1200 19.39 19900 5.50 3-23 2400 20.17 31400 4.76 4- 1 1800 19.13 16200 5.51 4- 1 2400 19.00 14500 5.52 3-24 0600 20.33 33000 4.78 3-24 1200 20.43 35400 4.80 4- 2 0600 19.25 17900 5.53 3-24 1800 20.60 38100 4.82 4- 2 1200 19.44 20600 5.54 3-24 2400 20.79 41300 4.85 4- 2 1800 19.62 23100 5.56 4- 2 2400 19.91 27400 5.57 3-25 0600 20.89 43000 4.87 3-25 1200 20.90 43200 4.90 4- 3 0600 20.70 39800 5.60 3-25 1800 20.88 42900 4.93 4- 3 1200 21.10 46800 5.63 3-25 2400 20.78 41200 4.95 *4- 3 1800 21.35 51300 5.66 4- 3 2400 21.73 58100 5.69 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02467000, Tombigbee River at Demopolis lock and dam, Ala. -Continued 163 ACCUM. GAGE J 1 w n on &n & 1 a a a a A& 1 NESS » 1 co co co co & 1 t w w w 0600 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 65300 70800 75900 79200 81200 82800 83600 84200 84200 84000 84200 84200 83400 82800 79900 77400 75400 74800 74000 75400 76700 76300 75400 74600 73300 70600 69100 66800 64300 61600 59800 58500 57200 58000 66400 89400 a a u u NESS S ~ o oa a £0. 0.0% "he on 0 NOPD S «0k 0.0% 0600 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 24.23 24.85 25 . 34 25.78 26:29 26.96 27.54 28.17 28.85 29.64 30.49 31.42 32.357 33.31 34.18 34.93 35.53 36.03 36.45 36.72 36.90 37.00 37.03 36.95 36.83 36.66 36.42 36.15 35 . 85 35.57 35.20 34.82 34.42 34.01 33.59 33.14 107000 119000 129000 138000 146000 158000 168000 175000 183000 192000 202000 212000 242000 261000 271000 286000 298000 306000 320000 335000 341000 343000 340000 325000 311000 298000 286000 285000 282000 279000 275000 267000 257000 247000 242000 234000 co N ~ w co co co co w co co co 164 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02467000, Tombigbee River at Demopolis lock and dam, Ala. -Continued GAGE ACCUM. GAGE ACCUM DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 4-22 0600 32.70 224000 12.79 4-26 1800 20.83 42000 14.16 4-22 1200 32.22 214000 12.92 4-26 2400 21.00 45000 14.19 4-22 1800 31,77 212000 13.05 4-22 2400 $1.25 193000 15:17 4-27 0600 21.07 46300 14.22 4-27 1200 21.03 45500 14.24 4-23 0600 30.72 187000 13.28 4-27 1800 20.97 44500 14.27 4-23 1200 30.12 174000 13,39 4-27 2400 21.03 45500 14.30 4-23 1800 29.45 169000 13.49 4-23 2400 28.74 160000 13.59 4-28 0600 21.09 46600 14.33 4-28 1200 21.14 47500 14.36 4-24 0600 27.90 146000 13.67 4-28 1800 21.06 46000 14.38 4-24 1200 27.01 141000 13.76 4-28 2400 21.02 45400 14.41 4-24 1800 25.97 128000 13.84 4-24 2400 24.83 114000 13.90 4-29 0600 21.02 45400 14.44 4-29 1200 20.98 44600 14.46 4-25 0600 23.67 94700 13.96 4-29 1800 20.97 44500 14.49 4-25 1200 22.75 77200 14.01 4-29 2400 20.90 43200 14.52 4-25 1800 22.06 64100 14.05 4-25 2400 21.58 55400 14.08 4-30 0600 20.80 41500 14.54 4-30 1200 20.70 39800 14.57 4-26 0600 21.21 48800 14.11 4-30 1800 20.57 37600 14.59 4-26 1200 20.93 43700 14.14 4-30 2400 20.39 34700 14.61 wn wo we ao we on an an m ms mn me an me on me a an as an an un an as an us mn an an me an ms an as an me un an an me an an an m an as an on mn an un on un an an an an an an an an an an an an DISCHARGE DATE TIME TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02467500, Sucarnoochee River at Livingston, Ala. GAGE HEIGHT ACCUM . RUNOFF DATE 3-01 3-01 3-01 0200 0100 2400 0100 2400 0400 1300 2000 2400 1300 2400 0800 1900 2200 2400 0 100 2400 0 100 1500 2400 0100 2400 0100 2400 0100 1800 2400 0100 1700 2400 20.44 20.44 17.35 17.16 13.40 13.69 17.38 21.46 22.90 24.54 24.87 26.01 217.64 27.69 21.64 217.59 24.46 24.32 22.86 22.16 22.08 20.03 19.91 15.85 15.60 11.36 10.47 10 . 35 9.34 9.31 5070 5 +070 3540 3 +460 2,320 2+410 3+550 5,840 T+430 11,600 12+600 16,300 22900 23+100 22900 22 +100 11+400 11 +000 T +350 61490 6,410 4 +820 4,750 3+060 2980 1 , 740 1 +520 1490 1 +240 1 +230 3~12 3-12 3-13 313 TIME GAGE HEIGHT 165 DISCHARGE ACCUM. RUNOFF 0400 2400 0 100 2400 0100 2400 0100 2400 2400 1100 1700 2000 2100 2200 2400 0300 0500 2400 0800 2400 1300 2400 0100 2400 0900 2400 9 . 30 9.04 6.33 7.92 8.78 9.38 10.57 14.02 16.75 17.01 16."S 18.25 19.34 19.78 19.64 19.63 19.49 19.50 19.23 1 +230 1,160 1,150 1,000 994 890 886 808 590 621 934 1,250 1,540 2+510 3+330 3+400 3+240 3900 4 +410 4,670 4,580 4,580 4 )490 4 +500 4 » 360 0 . 05 0.06 0 . 0 7 0 . 09 166 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02467500, Sucarnoochee River at Livingston, Ala. -Continued DATE TIME GAGE DISCHARGE ACCUM. DATE _ TIME GAGE DISCHARGE ACCUM. HEIGHT RUNOFF HEIGHT RUNOFF 4-08 1200 186.92 4 +200 1.50 4-14 2400 32.04 50 , 700 1.44 4-08 1800 19.72 4,630 1.57 4-08 2000 19.65 4,590 1.59 4-08 2400 19.36 4,420 1.63 4-15 0100 31,84 49,100 71.57 4-15 1700 271.7172 23,200 8.98 4-15 2400 25.95 16,100 9.32 4-09 0100 19.30 4 » 390 1.65 4-09 2400 18.60 4 , 040 1.89 4-16 0100 25.73 15,200 9.36 4-16 1100 23.90 9,760 9.66 4-10 0100 18.59 4 , 040 1.90 4-16 2400 22.62 6950 9.93 4-10 2400 18.06 3,820 2+ 13 4-17 0100 22.54 6,870 9.95 4-11 0100 18.04 3,820 2.14 4-17 2400 20.81 5,330 10.30 4-11 2400 17.90 3,760 2.36 4-18 0100 20.73 5,270 10.31 4-12 0900 18.25 3+900 2.45 4-18 2400 17.92 3,770 10.58 4-12 2000 20.36 5020 2.58 4-12 2400 22.71 7,050 2.64 4-19 0100 17.75 3,700 10.59 4-19 2400 12.51 2»050 10.76 4-13 0600 25.24 13,700 2.61 4-13 1000 26.41 17,900 2.98 4-13 2200 30.03 35,600 3.80 4-20 0100 12.30 1990 10.76 4-13 2400 30.68 40 +200 4.00 4-20 1700 9.89 1,370 10.83 4-20 2400 9.35 1,240 10.85 4-14 1000 33.31 60,900 5.36 4-14 1300 33.47 62,200 5.63 4-21 0100 9.29 1 220 10.85 4-14 2000 32.179 56,700 6.90 4-21 2400 8.53 1 +060 10.92 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02468500, Chickasaw Bogue near Linden, Ala. [Maximum discharge occurred on March 4, 1979] 167 ACCUM. w Or G Gr Gt tr tr ta B B A A p p w un n in b + 0 w t w a a nu ae le oi a ae canning te 0 0 0 0 000 0 £ w n- o o B B p A 2400 1400 1500 1600 1900 2000 2100 2200 2300 2400 0300 0900 1300 1600 2400 0100 1800 2300 2400 rvs a'm o y oun aw 162 116 113 122 243 625 1430 2990 5050 9050 16800 18200 17800 14800 14300 4070 2080 1880 0 0 00 0000 0 ni- o 0 N N ND n 168 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02475500, Chunky Creek near Chunky, Miss. [Maximum discharge occurred on March 4, 1979] GAGE ACCUMULATED GAGE ACCUMULATED DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 03-02 2400 5.37 828 6.24 03-01 0100 5.54 924 0.00 03-01 1200 5.69 1, 000 0.04 os-10 - 2400 s.i5s 730 &. 32 03-01 2400 6.598 1, 510 0.10 oO3-11 2400 5.38 828 &. 40 03-02 1000 6.76 1, 610 6.17 03-02 2400 6.34 1, 370 0.26 o3-12 2400 5.04 £30 &.47 03-03 0600 6.99 1, 740 0.30 os-13 2400 4.76 551 6.53 03-03 1200 8.32 2, 430 0.35 03-03 1500 9. 68 3, 200 Q. 38 03-14 - 2400 4. 6Z 486 6.59 03-03 1800 10. 99 4, 030 0.43 03-03 2100 12.59 S, 140 0.49 les 5 rs R 03-03 2400 13.21 5, 8790 0.56 pearls 240" § #35 616" 03-16 2400 4. 33 373 6.67 03-04 0300 15.03 7, 020 O. 64 03-04 0600 19.16 10, 700 0.75 os-17 - 2400 4.26 349 6.71 03-04 - 0900 24.952 24, 300 0.97 03-04 1200 25.77 34, 200 1.34 o3-18 2400 4.21 333 £.785 03-04 1500 26.99 40, 400 1.81 03-04 1700 26.64 40, 200 2.15 o3-i192 2400 4.13 305 6.73 03-04 2100 26.19 36, 300 2.80 03-04 2400 25.79 32, 600 3.24 o3-20 - 2400 4.06 284 6.981 03-05 0800 24.20 22, S00 4.17 03-21 2400 4.02 270 & .84 03-05 14600 22.06 14, 200 4.78 03-05 2100 19.88 11, 400 5. 05 03-22 2400 4.12 299 4.846 03-05 2400 18. 28 9, 860 8.19 03-23 2400 5. 88 1, 060 6.93 03-Oé 0600 14.96 £, 960 S. 40 03-06 1200 12.61 S, 150 5.99 03-06 1800 11.14 4, 120 8.467 03-06 2400 10.16 3, 490 03-24 0400 5.97 1, 100 4.95 O3-O7 0600 7.31 2, 980 5. 85 Oo3-24 2400 5. 34 787 7.03 03-07 1200 8.45 2, 4920 5.92 03-07 1800 7.47 1, P80 8.97 03-25 2400 4. 46 409 7.99 03-07 2400 6.68 1, 590 6.02 03-26 2400 4.15 302 7.13 03-08 1200 6.03 1, 170 6.09 03-08 2400 5.81 1, O50 6.14 O3-27 2400 4.01 262 7.16 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02475500, Chunky Creek near Chunky, Miss.-Continued 169 GAGE ACCUMULATED GAGE ACCUMULATED DATE TIME HEIGHT DISCHARGE DATE TIME HEIGHT DISCHARGE RUNOFF 03-28 2400 3. 93 240 7-18 04-12 0400 5.81 979 7.959 04-12 1400 5. 63 890 F.61 03-29 2400 3. 86 220 7.20 04-12 2400 9. 88 3, 320 7.70 03-30 2400 3. 83 213 7.23 04-13 0100 10. 23 3, S30 4.72 04-13 0300 12. 07 4, 760 47.75 O3-31 2400 3. 82 210 7. 25 04-13 0600 13.26 5, 630 9.82 04-13 0900 15. 20 7, 160 7.90 04-01 2400 3. 85 #15 7.21 04-13 1200 20. 07 11, 600 10. 02 04-13 1500 24.12 22, 100 10. 23 04-02 - O8B00 3. B9 255 7.23 04-13 1800 25. 38 27, 500 10.56 04-02 1600 4.85 3998 7.29 04-13 2100 25. 99 34, 400 10.96 04-02 2400 5.17 700 7.31 04-13 2400 26.14 35, 800 11.40 04-03 1200 7.43 1, P10 7.38 04-14 0100 26.17 36, 100 11.956 04-03 2400 8. 09 2, 270 7.48 04-14 0300 25.96 34, 100 11.85 04-14 0600 25.98 30, 800 12.26 04-04 1200 9.34 2, 780 7.62 04-14 25.10 27, 700 12.63 04-04 2400 10. 06 3, 430 7.78 04-14 1200 24. 60 24, 800 12.96 04-14 1500 24.16 22, 300 13.26 04-05 1200 11.80 4, S70 7.98 04-14 1800 23.91 17, 000 13.852 04-05 2000 12. 32 4, P40 8.14 04-14 2100 22.78 16, 100 13.74 04-05 2400 12.19 4, 850 £. 22 04-14 2400 21.69 13, S00 13.93 04-06 0600 11.72 4, 520 8.34 04-15 ©0600 17.00 10, 500 14.23 04-06 1200 10. 84 3, P30 8.45 04-15 1200 15.74 7, 610 14.46 04-06 1800 10. 07 3, 430 04-15 1800 13.23 5, 610 14.63 04-06 2400 7.91 2, 760 8. 62 04-15 2400 11.56 4, 410 14.746 04-07 1200 7 AZ 1, 770 8.74 04-1464 0600 10.49 3, 700 14.34 04-07 2400 5. 62 895 04-16 1200 7.61 3, 140 14.94 04-16 2400 7. 62 2, 000 19.07 04-08 0700 5.27 774 8.83 04-08 1200 5.54 852 8.85 04-17 1200 6. 20 1, 180 15.15 04-08 2400 6.96 1, £40 8.91 04-17 2400 S. 64 385 15.21 04-09 1200 7.82 2,110 9.01 04-18 1200 5.33 739 15.25 04-0? 1800 8. 08 2, 250 9.06 04-18 2400 5.13 6SS 15. 23 04-02 2400 8. 34 #2, 390 7.12 04-12 1200 4.96 573 15.31 04-10 1000 8.51 2, 490 9.22 04-19 2400 4. §4 S20 15. 24 04-10 1700 8.41 2, 430 7. 30 04-10 2400 8.19 2, 310 7.37 04-20 1200 4.74 478 5.27 04-20 2400 4.66 446 15. 39 04-11 0600 7. 88 2, 140 9.42 04-11 1200 7.54 1, 260 9.47 04-21 1200 4.40 420 15.41 04-11 2400 6.27 1, 230 9.56 04-21 2400 4.54 3798 15.43 04-22 1200 4.48 376 15. 45 04-22 2400 4. 45 366 15.47 170 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02476500, Sowashee Creek at Meridian, Miss. GAGE ACCUMULATED GAGE ACCUMULATED DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 04-11 ©0100 3. 49 177 0. 00 04-14 1200 S. 68 414 3.791 04-11 ©4600 3. 45 170 0.02 04-14 2400 4. 36 273 4.03 04-11 1200 3.41 164 0. oS 04-11 - 1800 3. 36 150 0. 08 04-15 1200 3.90 224 4.12 04-11 2400 3.31 148 0.11 04-15 2400 3. 61 190 4.19 04-12 0600 3. 29 145 0.13 04-16 2400 3. 40 1958 4.32 04-12 1200 6.30 490 0.19 04-12 1800 7.84 693 0.29 04-17 2400 3. 26 1395 4. 42 04-12 2400 16.11 2, 400 0.57 04-18 2400 3.17 119 4.51 04-13 0730 22. 87 7, 270 1. 65 04-13 0900 22.50 6, 900 1.97 04-19 2400 3.11 108 4.59 04-13 1200 21.12 S, 630 2.53 04-13 1500 19.195 4, 110 2.97 04-20 2400 3.10 106 4.67 04-13 1800 16.61 2, 620 3.27 04-13 2100 13.97 1, 750 3. 47 04-21 2400 3. 06 98.0 4.74 04-13 2400 11.72 1, 280 3.40 04-22 2400 3. 14 109 4.82 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02476600, Okatibbee Creek at Arundel, Miss. TM GaASE ACCUMULATED Gace TIME - HEIGHT _- DISCHARGE RUNOFE "timg -- 0100 11.07 1,740 0.00 2400 11.19 2400 11.17 17/770 bis (2400 (ease 1200 10.70 1, £30 0.27 oz > 2400 10. 34 1,530 0.34 240) a 04600 10.69 1, 430 0.40 os-17 2400 10.73 1200 11.86 2, 000 0.45 E a in 1800 _ 14.19 2, 820 0.51 ele sadn . 2100 18.93 8, 380 0.59 a s > 2400 19.84 11, £00 5.73 03-12 2400 10.53 0300 20.02 12, 400 0.87 02-20 2400 10.47 0600 20.15 13, 000 1.04 $2 a u ists 1200 - 20.469 | 15, 600 1.45 filo . 0.00 1330 20.71 15, 700 1.54 a cause s 1800 20.35 13, 200 1.846 03-22 2400 7. 48 2400 19.37 9, 85s 2.189 9 2400 9.47 0600 18. 29 6, 58o 2.41 L f 1200 17. 29 4,510 2.54 03-24 2400 7.91 1800 16. 48 3, 850 2.67 ck" >a. is 2400 15. 82 3, 500 2.77 o3-25 2400 10. 29 1200 14.77 3, 050 2.95 2400 10. 40 a s 2, 780 3. 2400 14.07 2, 780 2.A1 paz» | hace 1200 13.51 2, 570 3.25 aida) . 2400 13.11 2,420 3.39 03-28 2400 10. 30 1200 12.85 2,330 3.52 or-29 2400 10. 22 2400 12.59 2, 240 3. 64 oz-30 - 2400 10.15 2400 12.12 2, 080 3.83 os-31 2400 7.99 2400 12.00 2, 040 4.10 A, . 04-01 2400 &.50 3 32 2400 11.83 1, 980 4.3 pas0e "2406 Braz 2400 11.56 1, 200 4.53 04-03 1200 12.67 2400 11.26 1, 830 4.73 04-03 2400 14. 10 ACCUMULATED DISCHARGE RLUNOFEE 1, 780 4.993 1, 720 8.12 1, £70 2.30 1, 640 S. 43 1, £10 S. 64 1, 580 5.133 1, S60 6.990 1, 540 6.17 1, 280 6.33 1, 280 6.47 1, 400 6.61 1, 510 6.77 1, 540 6.94 1, 530 7.10 1,810 7.27 1, 490 7. 43 1, 470 7.99 887 7.72 585 7.80 1, 270 7.99 2, 280 2, 790 8.14 172 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02476600, Okatibbee Creek at Arundel, Miss.-Continued 04-04 04-04 04-04 04-04 04-05 04-05 04-04 04-06 04-09 04-09 04-02 04-09 04-10 04-10 04-11 04-12 04-12 04-12 04-12 04-12 04-12 04-12 Q£00 1200 1730 2400 1200 2400 1200 2400 2400 1200 1800 2400 O&£O0 , 1130 1800 #400 1200 2400 2400 O£00 1200 1400 1400 1800 2000 2400 GAGE ACCUMULATED GAGE ACCUMULATED HE LGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 15. 09 3, 180 g. 22 04-13 0400 15. £2 3, 400 10.17 164.17 3, 680 8.31 04-13 Q600 18.78 7, 720 10.22 16.44 3, 820 8.40 04-13 0800 1%. 39 7, 320 10. 30 14. 38 3, 790 8.52 04-13 1200 19. 86 11, 700 10.50 04-13 1500 20.78 16, 100 10. 69 14.71 3, 020 8.70 04-13 1830 21.91 20, S00 10.93 12. 36 32, 160 8.84 04-13 2400 20. 80 16, 200 11.43 10.56 1, 5790 8.94 04-14 - O£00 19.995 10, S00 11.80 2.91 1, 400 2.03 04-14 1200 18. 54 7, 240 12.04 04-14 1800 17.85 4, 380 12.20 m.iSs 1, 190 2.17 04-14 2400 14.78 4, 040 1%. 32 9.74 1, 350 9.293 04-15 1200 15.85 3, 270 12.52 11.96 3, 030 9.96 04-15 2400 14.51 2, 950 12.70 13.01 2, 370 9.34 04-164 2400 13. 03 2, 400 12.99 14. 00 #, 750 7.41 14.44 2, 720 9.43 04-17 2400 12.24 2, 120 13. 23 14.01 2, 760 7.57 13.195 2, 440 7. 64 04-18 2400 11.83 1, 780 13.46 10. 40 , S40 9.74 04-12 2400 11.83 1, 890 13.47 2. 85 1, 110 9.32 8.46 1, 020 9.9.3 04-20 2400 11.34 1, 830 13.87 8. £1 1, OSO 7.94 04-21 2400 11.18 1, 780 14.07 1, 340 9.99 11.14 1, 760 10.01 04-22 2400 11.12 1, 760 14.246 11.995 2, O20 10. 02 12.54 2, 22 10.04 13.12 2, 430 10.06 14. 24 2, 840 10.11 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02477000, Chickasawhay River at Enterprise, Miss. GAGE ACCUMULATED DATE _ TIME _ HEIGHT _ DISCHARGE RUNOFF DATE _ TIME 03-08 - 1200 03-01 0100 17.31 4, 400 0.90 03-08 - 7400 03-01 1200 16.74 4, 160 0.07 03-01 2400 16.55 4, 080 0. 14 o3-09 - P400 03-02 1200 16.12 3, 200 0.24 03-10 - 2400 03-02 2400 15.84 3, 780 0.32 03-11 2400 03-03 0600 18.55 4, 940 0.34 0900 20.89 6, 130 0.39 2400 03-03 1200 25. 68 10, 000 0.43 03-03 1500 27.44 11, 200 0.42 03-13 2400 03-03 1800 29.37 14, 200 0.55 03-03 2400 30.53 15, 800 6.71 oB-14 - 2400 03-04 0300 30.97 16, 400 0.72 o3-15 72400 03-04 0600 31.12 16, 600 0.87 03-04 - 0900 32.62 19, 000 0.946 03-16 2400 03-04 1200 33.80 20, 200 1.97 03-04 - 1500 35.23 23, 800 1.18 0OB-17 2400 03-04 - 1800 37.03 28, 600 1.31 03-04 2100 38. 82 34, 600 1.47 O3-18 2400 03-04 2400 40. 39 40, 200 1.67 03-19 2400 os-05 0300 41.37 46, 300 1.89 03-05 0700 41.88 49, 700 2.21 03-20 2400 o3-05 41.85 49, 500 2.33 03-05 1200 41.61 47, 900 2.63 OB-21 2400 o3-0s 1500 41.35 46, 200 2.87 03-05 1800 40.20 43, 500 3.10 2400 03-05 2100 40.25 40, 200 3.31 03-05 2400 397.50 37, 100 3.51 2400 o3-06 0600 37.76 31, 000 3.84 o3-24 2400 03-06 1200 35. 24 23, 800 #4. 13 03-06 1800 32.69 19, 100 4.35 o3-25 2400 03-06 2400 30. 39 15, £00 4.53 - 7400 o3-07 04600 28.10 12, 600 4. 67 03-07 1200 246.00 10, 300 4.73 Oo3-27 2400 03-07 1800 23.43 8, 190 4.83 03-07 2400 21.75 6, 790 4.946 or-28 2400 GAGE HEIGHT 14.78 14. 09 13.44 13. 08 12.74 12.41 12. 22 12.06 11.76 11.64 11.64 13. 02 13.17 12. 20 11.959 11.47 DISCHARGE 173 ACCUMULATED RLNOFEF 0 0 & « ta NJ Ui C 4 B 174 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGI TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02477000, Chickasawhay River at Enterprise, Miss.-Continued DATE 13-27 03-30 04-01 04-02 04-02 04-02 04-04 04-04 04-05 04-05 04-05 04-04 04-06 04-07 04-07 04-08 04-082 04-09 04-09 04-10 04-10 04-11 04-11 T IME 2400 2400 2400 2400 1200 1800 2400 0300 0£00 1200 1800 2400 1200 2400 1200 2100 2400 1200 2400 1200 2400 1200 2400 1200 2400 1200 2400 1200 2400 GAGE HEIGHT 11.31 11.21 10. 63 7.10 10. SO 14.01 14. 00 18. 08 17.07 20. 60 21.54 17.98 18. S 17.26 15.81 ACCUMULATED DISCHARGE RUNOIEE DATE 2, 040 7.48 22:13 2,025 7.54 1, 790 7.64 oal 1, 200 7.79 22:13 4 04-13 Z‘74 04-13 7.74 x:. 7274 04-13 } 04-14 oa-14 A+ oa-14 #4 04-14 B 7.99 a 8, 540 8.13 paty 7, 300 8.31 04-14 9, 440 ”ySéO 04—15 5: S30 o4-i5 04-15 8, 850 2. 8: a 7; 140 9.04 04-16 04-146 5, 540 2.17 04-16 4,260 oa-17 3, 590 9.34 04-17 4, 270 9.44 04-18 5, 180 9.53 5, 580 2.64 04-19 5, S790 4,79 04-20 4, 790 9.84 $ 04-21 4, 380 9.946 3, 770 10.04 04-22 TIME GAGE HEIGHT DISCHARGE ACCUMULATED RUNOFF wane w gn n onn o onn en een e e e e ee eme e e ne einem 1200 1800 2400 0300 0£00 0200 1200 1500 1800 2100 2400 0300 0600 0200 1200 1500 1800 2100 2400 0400 1800 2400 0600 1200 2400 1200 2400 2400 2400 2400 2400 2400 13.63 14.65 17.82 21.21 22. 60 24.00 25. 00 26.47 28. 00 31.84 34.00 36.00 37.05 40.04 41. OS 41.81 41.90 41.68 41.17 397. 80 36.00 33.80 31.20 28. 83 24.04 20.71 18.84 16.57 14.90 13.90 13.42 13. 08 2, 710 3, 300 4, £20 £, 360 7, 490 8, 700 9, 480 10, 800 12, S00 17, 800 21, 200 25, S00 35, 400 39, 200 44, 300 47, 200 49, 800 48, 300 45, 000 38, 200 25, S00 20, 200 16, 800 13, 500 8, 730 6, 020 S, 070 4, 080 3, 400 3, 010 2, 830 2, 700 10.11 10.14 10.13 10.21 10.24 10.23 10. 23 10. 393 10.44 10.52 10.42 10.74 10.89 11.03 11.30 11.53 11.79 12.04 12. 27 12.70 13.39 13.58 13.77 13.93 14.15 14.30 14.42 14. 60 14.746 14.89 15. 01 15. 12 TABLES 175 TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02478500, Chickasawhay River at Leakesville, Miss. GAGE ACCLIMLLATEL GAGE ACCLIMLIL_ATELC DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RLNOCFF $1 : O10 24.75 18, £00 0.00 1 _ 2400 24. 36 17, 700 0.24 1200 oO3-O2 2400 24. 23 17, S00 0.48 400 2400 , 700 oO3-O% 1200 24.82 2, 800 0. £0 2400 #7.%2 27, 400 6.7% o3-15 159500 17, 000 om-18s 2400 PF. 3% 14, ono 03-04 1200 32, 800 0.97 03-04 2400 33, 700 1.20 1200 20.53 10, 200 5.77 2400 17.40 9, 730 £ 03-05 1200 29.06 35, 200 1.44 O3-0O5 2400 29.23 34, 200 1.49 03-17 2400 18.34 7, 740 &. 76 03-046 1200 297. 30 34, £00 1.94 2400 17.74 £, 780 7.04 O3-0Oé£ 2400 27,30 346, £00 2.19 O3-12 2400 17.237 £, 400 7x15 o3-07 1200 27. 28 346, S500 2.44 o3-O7 - 2400 79.32 36, 700 2« 70 2400 16.92 5, 9760 7.24 o3-08 1200 27.91 37, 700 o3-O8 2400 29.81 40, 000 03-21 2400 16.42 S, £10 7.32 G P) I) Q () O or-33 2400 14.70 5,710 7.379 oe00 30. 1200 30. 1800 30. #400 30. 41, 200 4%, £00 43, 700 44, 7400 () ~ 1200 17.75 7, 000 7.44 2400 17. S5 7, 440 7.50 th t Ct 60 « o .On O. 2400 20.70 11, 200 7. £44 0600 20.93 45, 400 1200 30, 99 #00 1800 30. £6 44, 300 « $ ~ 3 03-25 2400 19.46 9, 310 7. 78 . (s B B B G3 nd o 03-10 2400 30, £6 44, 300 «45 2400 18. 32 7, 740 7.70 QO3-11 0800 45, 700 03-37 7400 17.51 £, 480 &. 00 03-11 _ 1400 44, £00 U p p O3-11 2400 42, 400 O O3-78 - 2400 16. £9 5, 700 S,. O8 O3-12 1200 29.72 300 S. 35 2400 16. 08 5, 000 8.14 o3-12 2400 29.28 346, 200 2.41 O3-30 2400 19, 73 4, £250 &. 22 03-12 - 1200 28.70 33, 000 s.85 03-132 2400 28.12 27,700 &. 07 oB-31 - 2400 15.51 4, 430 R. 29 176 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02478500, Chickasawhay River at Leakesville, Miss.-Continued 04-02 04-02 04-O3 04-04 04-04 04-05 04-OSZ 04-04 04-06 04-07 04-07 04-08 04-08 04-09 04-07 04-10 04-10 O4-11 04-12 04-13 awn nn nnn ee mee ene nene e ne ge e ee e ee ee ee e ee e e e e ne e ne e he e e e ee eee ee ee ne e e ne e nee e ae en ae on ee e GAGE ACCUMLILATEL GAGE ACCLIMULATED TIME HEIGHT DISCHARGE RLINOFF LATE TIME HEIGHT CISCHARGE RLINCFF 2400 s. 35 04-14 2400 22. 22 13, 700 12.62 0100 8.35 04-19 2400 21.39 12, 300 12. 80 2400 8.41 N4-14A 2400 21.70 12, 800 12.97 2400 04-17 2400 14, 700 13.14 1200 2400 04-18 2400 24.24 17, S00 13. 38 1200 7.11 04-19 2400 259.70 21, 100 13.45 2400 oa-320 - 2400 26. 85 24, £00 13.97 OS00 I. 498 2400 9.91 04-21 2400 27.03 =S, 100 14.31 1200 10.17 oa-p3 - Pano 26.91 22, 400 14. £4 10.41 1200 TS. A% 19, £00 14.7% 1200 31,100 2400 TS. 15, 100 14.91 2400 29, 200 04-24 - 2400 197.16 &, 870 15.07 1200 27.644 27, 500 11.04 2400 274. 25 25, P00 11.27 04-25 2400 18.44 &, 190 19.17 1200 11.40 - 2400 18. 72 {9.30 2400 14.96 4-97 - H4OOD 18. 59 &, o8BO 15. 42 2400 29.99 22, 000 04-28 - 2400 18.19 7, 550 15.52 2400 24.95 179, 100 12.16 04-229 2400 17. S0 &, 779 15.69 2400 22.65 16, 300 12.41 04-30 2400 16. 2T 5,170 195.71 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02482000, Pearl River at Edinburg, Miss. 177 GAGE ACCUMLILATED GAGE ACCUMULATED DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 03-03 0100 20. 26 S, 450 0.00 03-146 - 1200 11.99 1, 700 4.71 03-03 0800 20.76 5, 8790 0.04 0B-1é6 2400 11.67 1, 410 4.94 03-03 1600 21.97 7, 170 0.195 0O3-O3 2400 23.06 8, 770 0.246 03-17 1200 11.39 1, 530 4.997 03-17 2400 11.14 1, 470 5.90 03-04 0800 23.71 10, 100 0.39 03-04 1600 24.32 11, 700 0.54 03-18 1200 10. 82 1, 400 5.03 03-04 2400 25. 45 17, 200 0.74 2400 10.41 1, 330 2.06 03-05 0800 26. OS 22, 100 1.02 03-12 1200 10. 30 1, 260 5.09 03-05 1600 26. 33 25, 000 1.34 03-12 2400 10. 00 1, 180 5.11 03-05 2100 26. 45 26, 300 1.54 03-O5 2400 26.40 25, 800 1.790 03-20 1200 7.67 1, 110 S. 14 2400 7.37 1, OSO 5.16 03-06 0800 26. 37 25, 400 2.05 03-06 1600 26.14 23, 000 2.39 03-710 1200 9.06 984 5.13 03-06 2400 25.81 20, 000 2.49 03-21 2400 8.76 g24 5.20 03-07 0800 25.43 17, 100 2.94 03-37 1200 8.50 873 5.22 03-07 14600 24.91 14, 000 2.19 03-32 2400 8.53 879 5.24 03-07 2400 24. 35 11, 800 3. 22 1200 7.85 1, 1950 95.26 03-08 1200 23.91 ?, 62 2s 913 2400 7.75 1, 130 5. 29 03-08 2400 22.40 S, 040 3.74 03-24 1200 10.19 1, 230 - 31 i390 P1. 66 4, B00 3.99 o=- 2400 &, - 5.3: 03-0? P400 - 20.585 5, 970 4.02 SAs Raon 10.57 S28 9-33 j ag 03-25 1200 10.51 1, 310 5.36 03-10 1200 20.06 5, 290 4.14 3-25 ye 03-10 2400 19.41 4, 840 4.24 Pr 2400 i948 1, 230 5.39 03-26 1200 9.81 1, 140 5.41 03-11 1200 18. 46 4, 380 4.34 03-26 2400 9.60 1, 100 5.43 PB-11 - 2400 17.91 3, 780 4.42 03-27 2400 9.39 r M o3-12 1200 17.18 3, 590 4.50 1, 050 5. 48 03-12 2400 16. 30 3, 230 4.57 03-28 2400 9.37 1, 050 5.52 93-13 1260 15.46 2, 880 4. £4 03-29 2400 9.40 1, O50 5.57 03-13 2400 14. 48 2, SSO 4.69 03-30 2400 9.38 1; * os-14 1200 13. 99 2.830 4.74 oso 5.61 OB-14 2400 13.2379 2, 130 4.7» 03-31 2400 9.20 1, 010 5.65 0B-15 O200 12.83 1, P50 4.80 a 0OB-15 2400 12.38 1, #10 4.37 24080 9:96 Pas 9:62 178 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02482000, Pearl River at Edinburg, Miss.-Continued ACCUMULATED Gace ACCUMULATED DATE - TIME - HEIGHT _ DISCHARGE __ RUNOFF DATE - TIME - HEIGHT _ DISCHARGE ___ RUNOFF - e 04-02 1200 3.79 930 5.71 4-15 | 2p.4r 68,100 13.01 04-02 2400 9.21 1, 010 5.73 o4-i5s ikbo. 28.87 - 60,200 13.90 04-18 P400 - - 53,200 14.63 o4-0o3 1200 11.84 1, £60 5.74 . pa-03 2400 12.40 1, 830 5.80 pa-1% A300 s7.82: . 40,800 15.65 pazoa' tane (s.as »:870 s.ga 2400 Se.es 16.37 ©a-0t «4090. 16.01 3, 100 5.91 o4-17 1200 - gs.7s | 19,500 16. 87 dazoe 456 Cie» 94-17 $400 24.76 13, 300 17.21 04-0: 3 pmos S400 - 17.44 2, 790 «. 05 p4a-18 1200 | PB.%8 0 10,000 17.45 04-06 1200 17.66 3, 860 6.13 pa<12 2400 Groo 17°84 04-06 - 2400 17.44 3, 750 £.21 pa 34 1 ++ oc 0 & I 1200 #400 a300 1100 1200 1300 1400 1500 14600 1700 1800 15,29 5. fits 18.46 t G omen « a. ik an 18. 460 17. 08 17.951 19. 88 20, 26 £20 210 820 400 100 10, 800 11, £00 12, 500 13, £00 14, £00 16, 200 17, 800 17, 200 p 7 a C: & q H & < C On C. 0 x ka va & C « (as -G C+ x oro G i 6 7.15 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02482550, Pearl River at Carthage, Miss.-Continued 181 04-12 04-12 04-17 04-12 04-13 04-13 04-13 04-13 04-13 04-13 04-13 04-13 04-14 04-14 04-14 04-15 04-15 04-15 04-15 04-15 04-146 04-14 04-14 04-146 04-16 04-16 04-14 04-17 04-17 04-17 04-17 04-17 04-17 04-17 04-17 04-18 04-18 17200 2000 2100 2200 2300 2400 0100 0200 0300 0400 0é£00 0800 1100 2400 0200 1300 2400 0700 1200 1600 2000 2400 0400 0800 1200 1500 1800 2100 2400 0300 0400 1000 1300 1600 19200 2200 2400 0300 0600 GAGE HEIGHT 23.34 age | am 23.48 24. 09 24.57 25.06 285.56 25. mas 2G 3 PQ To PJ NN (A (. B+ L BQ Op PJ PJ PJ « 790 BJ TY BJ ~ ~ [Pull doll du 0) 00 00 $ O+ 8.49 28. 21 27.74 27.695 27.38 27.07 246.80 246.591 24. 28 24.04 25.81 25. £0 25.40 25.18 24.94 24.77 24.58 24.41 24.24 24.13 x7 « 7 BX DJ tr G3 ~o on DISCHARGE #1, 200 23, 700 28, 200 33, £00 39, 800 45, 200 S2, 000 27, 5090 £1, 700 £5, 700 72, 800 77, 400 70, 800 76, 200 102, 000 76, 800 71, S00 86, 700 81, 200 77, 700 73, 100 4&7, 100 64, 200 £1, £00 S8, 200 SS, 000 S2, 100 47, 300 46, 300 43, 100 40, 800 38, 300 36, 000 33, 800 32, 400 30, 200 28, 400 ACCLIMULATED GAGE ACCUMULATED RLINQEF DATE TIME HEIGHT DISCHARGE RUNOFF 7.18 04-18 0900 23. 63 26, 700 17.83 7.20 04-18 1200 23. 48 2595, 200 17.92 7.23 04-18 1500 23. 32 23, 800 18. 00 7.2 04-18 1800 23.18 22, 600 18. 03 7 04-18 2100 23. 00 21, 200 18.16 7.34 04-18 2400 22.84 20, 200 18. 23 7.42 04-179 0300 22. 65 19, 100 18. 30 7.43 04-19 - 0600 22.48 18, 100 18. 36 7.99 04-19 1000 22. 20 16, 200 18. 44 7.62 04-17 1300 21.97 15, 200 18.50 7.73 04-19 1700 21.66 15, 000 18. 57 7.95 04-19 2000 21.41 14, 200 18. 62 8.23 04-19 2400 21.06 13, 300 18.68 7. 43 04-20 0300 20.79 12, 600 18.73 10. 39 04-20 0700 20.45 11, 700 18.79 10.82 04-20 1100 20.12 11, 000 18.84 12.08 04-20 1400 17. 80 10, 400 18. 87 04-20 1800 19.48 7, 860 18. 92 04-20 2300 17. 08 ?, 240 18. 983 04-20 2400 19. 00 9, 120 18. 99 F3 2 04-21 1200 18.11 7, 850 19.10 14.53 04-321 2400 17.22 £, 880 19.21 14.93 04-22 1200 16.40 6, 070 19.29 15. 24 04-22 2400 15. 65 S, 380 19.37 15. 57 15.79 04-23 1200 15. 04 4, 840 19.44 15.99 04-23 2400 14.36 4, 280 19.51 16.19 146.37 04-24 1200 13.73 3, 820 19.56 04-24 2400 13. 23 3, 490 19.61 16.99 16.71 04-25 1200 12.81 3, 220 19. 66 16.92 04-25 2400 12.48 3, 030 19.70 17.06 17.20 04-26 1200 12.18 2, 850 19.74 17.23 04-26 2400 11.93 2, 710 19.78 17.45 17.92 04-27 1200 11.67 2, 570 19.82 04-27 2400 11.42 2, 440 19.85 17. 6:3 17.73 04-28 1200 11.14 2, 300 19.89 04-28 2400 10. 87 2, 170 19.92 182 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02483000, Tuscolameta Creek at Walnut Grove, Miss. GAGE ACCUMULATED GAGE ACCUMULATED DATE _ TIME _ HEIGHT _ DISCHARGE RUNOFF BATE _ TIME _ HEIGHT _ DISCHARGE RUNOFF 03-02 0100 19.74 1, 830 0.00 oz-08 - 0800 17.87 1, 070 4.72 os-oz2 0800 18.791 1, 580 0.04 1400 12.76 §64 4.81 o3-02 1600 18.39 1, 400 0.03 o3-o8 - 2400 ¥ 7347 4.83 os-o02 2400 19.38 1, 640 0.13 § 03-09 1200 15.10 Spx 4.84 03-03 0300 22.14 2, 720 0.146 o3-09 - 2400 14.63 519 4.29 oz-03 04600 24.05 3, 670 0.12 03-03 0200 25.02 4, 320 0.24 03-10 1200 14.34 473 4.391 03—03 1200 26. 01 5; 920 0. 30 c,:‘__‘:_ 1 0 2400 15 F 07 5:34 4 5,4 os-03 1500 26.33 6, 800 0.37 1800 26.50 7, 410 0.45 1200 1s. 3f £40 A.os 03-03 2100 26.48 7, 450 0.953 2400 15.14 az 4.99 oz-03 2400 26. 36 7,240 0.62 1200 14.; S98 5.02 oz-04 0300 24.62 s, 070 9.70 2400 (4.: #17 =.05 03-04 04600 27.10 2, 600 0.80 03-04 0900 27.68 11, 600 0.72 1200 14.05 456 £.07 03-04 1200 28.19 14, 100 1.07 2400 13.80 473 5.09 oz-04 1500 28. 69 16, 500 1.24 03-04 1800 29.22 19, 700 1.45 os-14 - 1200 aps 4 03-04 2100 27.62 22, £00 1.69 03-14 72400 3.55 375 5.12 o3-04 2400 29.79 23, 900 1.95 $3-18 - 1200 12. 38 339 5.14 o3-O5 0200 29.82 24, 100 2.123 oB-150 2400 13.13 312 5.15 oz-o05 0500 29. 69 23, 200 2.40 03-05 0800 27.91 21, 700 2.65 02-14> 1200 1.95 P87 5.17 oz3-os 1100 729.22 19, #00 2.89 eae a 3 oB-08 i406 |- 28.90 17, 800 3.10 03-16 . £400 12.52 €7€ =. 1% oz-os 17090 28.55 15, 800 3.27 a * s 3 a pB-0s P100 - P8B.08 | 13,500 7.51 paris _ 48:55 yue 252 2400 27.748 11, 800 8.664 o3-17 2400 12. 67 '49 5.20 paob 27.31 10, 100 3.82 1200 ( ten 247 a "1 oz-0464 0800 26.94 8, 870 3.97 2496 o 2440 5. 2:3 03-06 - 1200 26. 62 7. 820 4.09 fe aa ue 2s o 62-06 15006 . 26.78 7, 050 4. 20 els" 2400 12-27 S22 tS2 sono - 6, 400 4.31 b2-if 2400 t«-20 ZSS Sr =% 2-06 < 3 = oz-06 2400 25.99 5, 870 4.40 - i208 (oras 39% e oz-07 ©4600 25.64 s, 080 4.52 - £400 14.42 221 =. 27 p3-07 : 13600 74.47 3, 820 4;43 *% 3 2 % F y wa-07. - s2.0i 2, 460 4. 67 lars Mee ites ate a's} 03-07 - 2400 19.93 1, 640 4.74 2 l 182 a": TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02483000, Tuscolameta Creek at Walnut Grove, Miss.-Continued on-26 ol-26 3-27 DB-27 oz-28 oz-28 oz-29 or-29 O: O3- O ( G C O os-31 O3-31 04-01 04-01 04-03 04-07 04-02 04-03 04-03 04-03 04-04 04-04 TIME 1200 2400 ogoo 1400 1700 ©2400 1200 2400 1200 2400 1200 2400 1200 2400 1200 2400 1200 2400 1200 2400 1200 2400 1200 2400 0800 1600 2400 OsO0 1600 2400 1200 2400 GAGE HEIGHT 1%. 14.3 17.5 18. 17.9 17. 17. 16. 183 ACCUMULATED ACCUMULATED DISCHARGE ___ RUNOFF DATE _ TIME - HEIGHT _ DISCHARGE ___ RUNOFF 219 i. 30 pov ois, oa-o0s 13200 __ &, £70 6.894 04-05 3400 _- 24.08 &, 2320 7.13 = 0m 1:3;8 5:52 04-04 - 1200 25.84 5, 5290 7.40 (1 asp 2. s, 04-04 - 2400 25.10 4, 370 7.62 Sy 4 04-07 og0o0 _- 2, 700 7.73 , 360 5.47 04-07 - 14600 19.20 1, 440 7.79 1. 120 e; 04-07 - 2400 16.69 863 7.83 73 oa-o0s - 0800 15.46 667 7.85 Sz S.io 04-08 1400 -- 20.04 1, 840 7.89 04-08 2400 - 21.98 2, 650 7.95 188 5.42 31. 5163 04-09 1200 _- ar.os 3. 140 8.09 04-09 3400 _ 22.82 3, 160 8.23 281 5.45 asl §. z.; 04-10 1200 _- 3, 190 8.37 04-10 2400 _ 22.04 2, 8320 8.51 232 719 5.63 04-11 1200 __ 20.29 1, 280 8.62 04-11 - 2400 17.88 1, 210 8.69 221 5.49 aCe 2.73 o4-12 oz0o 18. 49 1, 300 8.70 04-12 0600 19.26 1, 460 8.72 {2% 5.974 04-12 0800 -- 21.54 2, 590 8.73 T2 5.73 04-12 0900 _ 23.30 3,350 8.75 04-12 1000 _ 24.43 3,910 8.74 #7 5.73 04-12 i100 - 25.17 4, 460 8.73 74 2 04-12 1200 - 4,910 8.79 04-12 1300 -- 25.79 5, 320 s.81 (597 5.594 04-12 1400 _ 25.84 5, 480 8.83 2s 517% 04-12 1500 - 25.82 5, 430 8.85 04-12 14600 - 25.462 5,110 8.87 s £.94 04-12 1706 - 25.35 4, £40 8.832 ys Fig? 04-12 1800 - 26.10 6, 240 8.91 15538 Simo 04-12 1900 - B6.4i 7,140 8.94 04-12 2000 - 26.65 7,870 8.97 2,970 5.84 04-12 2100 _ 26.37 8, 560 2.00 3.330 5.94 04-12 2200 - 27,00 8, 280 9.03 4, 430 6.097 o4-1i2 2300 - 27.02 9, 070 9.04 04-12 2400 - 26.99 9, 000 9.10 5, 200 6.29 €, 170 £. 95 184 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02483000, Tuscolameta Creek at Walnut Grove, Miss.-Continued GAGE ACCUMULATED GAGE ACCUMULATED DATE _ TIME - HEIGHT _ DISCHARGE _ RUNOFF DATE - TIME - HEIGHT _ DISCHARGE |_ RUNOFF 04-13 0100 26.98 9, 010 2.13 04-19 0300 13.97 405 13.73 04-13 0200 26.94 8, 950 4.17 04-19 - 0600 13. 87 392 13.78 04-13 300 26.94 9, 010 97.20 04-19 1000 13.78 380 13. 79 04-13 0400 26.93 9, 020 9.22 04-19 1300 13.46 345 13.79 04-13 04600 24.96 7, 170 9.30 04-192 1700 13. 34 332 13.80 04-13 0800 27.12 7, 700 7.37 04-19 2000 13. 28 324 13.80 04-13 1100 27.62 11, 400 9.49 04-19 2400 13. 22 317 13.81 04-13 2400 27.74 23, 300 10.34 04-20 0300 13. 20 313 13.81 04-14 0300 27.76 23, £00 10.61 04-20 0700 13.16 307 13.82 04-14 1300 29.40 21, 000 11.45 04-20 1100 13.10 299 13. 82 04-14 2400 28.379 14, 200 12.19 04-20 1400 13. 07 294 13.82 04-20 1800 13. 02 289 13. 83 04-15 0700 27.69 11, 500 12.54 04-20 2300 12.97 282 13.83 04-15 1200 27.24 9, 810 12.74 04-20 2400 12. 97 282 13.83 04-15 1600 26.72 8, 760 12.83 04-15 2000 26.67 7, 920 13.01 04-21 1200 12. 87 271 13.85 04-15 2400 26.45 7, 230 13.12 04-21 2400 12.73 2595 13.84 04-16 0400 26.26 6, 630 13.23 04-22 1200 12. 65 245 13.87 04-146 0800 26.11 6, 160 13. 32 04-22 2400 12. 65 246 13.83 04-16 1200 25.90 S, 580 13.41 04-146 1500 25.64 5, 020 13. 47 04-23 1200 12.76 262 13.89 04-16 1800 25.11 4, 280 13.53 04-23 2400 12.97 291 13.91 x- 2 a ; 4 ® seee Hi P96. 195 oa-24 1200 _ 13.28 $7 12.9% 04-24 2400 13. 48 397 13.94 04-17 0300 21.52 2, 160 13.63 << 04-17 0600 20.27 1, 700 13. 65 04-25 120¢ 13.51 420 13.95 04-17 1000 19.01 1, 310 13.63 04-25 2400 13. 46 415 13. 97 04-17 1300 18.13 1, 100 13. 69 04-17 1600 17.37 950 13.70 04-26 1200 13.31 400 13.99 04-17 1900 16.75 832 13.71 04-26 2400 13. 29 371 14.01 04-17 2200 16. 28 750 13.72 04-17 2400 16.01 703 13.73 04-27 1200 13. 28 415 14.03 04-27 2400 13.06 428 14.05 tals been | 57s 0 12174 os-28 1200 _ 12.79 #a2 - 14.04 04-18 1200 14.63 498 19.759 04-18 1500 14.47 474 13.76 04-18 1800 14.33 454 13.76 04-18 2100 14. 20 438 13. 77 04-18 2400 14. 08 421 13.77 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02484000, Yockanookany River near Kosciusko, Miss. 185 Gage ACCUMULATED Gace ACCUMULATED DATE _ TIME - HEIGHT - DISCHARGE __ RUNOFF DATE _ TIME - HEIGHT _ DISCHARGE ___ RUNOFF oz-o3 0100 9.87 898 0.00 1200 os-os3 0800 _ 11.56 1, 490 0.04 fais sane Blg] 5s s 03-03 1600 - 123.42 3, 510 0.12 g * 03-03 2400 | 14.31 5, 070 0.30 i260 c.es s.A§ 03-04 0700 _ 14.58 5, 600 0.49 2400 972 Pes Seo 03-04 14600 - 14.42 5, 280 0.73 3 03-04 2400 _- 14.43 5, 300 0.94 (lee 1m0n 2.71 214 3.22 os-is 2400 5.64 206 3.353 os-os 0800 _ 14.91 6, 300 1.17 u 03-05 1600 _ 15.20 6, 970 1.43 8§_:Z £388 g'gg $22 3.24 os-05 2400 - 15.05 6, 610 1.76 i Sre? 03-20 1200 5.51 192 3.27 o3-046 o800 - 14.48 5, 800 1.94 = 03-06 1600 _ 14.21 4, 870 2.18 o pase ¢? 3.28 03-06 2400 | 13.71 3, 970 2:33 Os~B1: A200 Slat (87 03-07 0800 | is.i6 3, 130 2.47 tors! S400 s 183 3. 30 03-07 1600 - 12.38 2, 150 2.57 y n 03-07 2400 | 11.35 1, 380 2.64 ss 1209 $-2¢ 187 3.31 os-22 2400 7.71 ase 3.38 os-os 1200 9.29 768 2.71 03-08 2400 s. 58 ess 2.75 area (Pon 9.82 886 3.36 03-23 1600 - 11.62 1, 520 3. 40 babe: 1200 sito sap 5.98 03-33 2400 - 12.76 2, 610 3.49 03-09 2400 7.69 483 2.81 oz-24 oé00 _ 12.92 2, 810 3.57 os3-10 1200 7.39 436 2.84 03-24 irh0 - 12.80 Fe 3.65 03-10 2400 7.79 499 2.87 or-z4 padGb - igr.se 3310 h 03-11 1200 8.57 633 2.90 oO3-25 1200 12.42 2, 190 3.93 03-11 2400 8.95 703 2.94 om-2s p40OG | 12.17 1, 930 4.05 03-12 1200 8.52 624 2.98 03-26 0800 11.47 1, 440 4.12 03-12 2400 7.96 527 3.02 o3-26 1600 9.93 212 4.16 oz-26 2400 s. 24 575 4.19 os-13 1200 7.51 ass 3.04 f f 03-13 2400 7. ts 397 3.07 o3-27 1200 7.09 372 4. 22 oz-27 2400 6.61 324 4.24 os-14 1200 6.86 359 3.09 a 03-14 2400 6.63 327 3.11 oO3-28 1200 6.32 285 4.26 oz-28 2400 6.09 ase 4. 28 os-1s 1200 6.40 297 3.12 os-15 2400 6.17 268 3.15 oz-29 1200 5.92 238 4. 29 oz-29 2400 5.79 223 4. 30 186 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02484000, Yockanookany River near Kosciusko, Miss.-Continued GAGE ACCUMULATED GAGE ACCUMULATED DATE TIME HEIGHT DISCHARGE DATE TIME HEIGHT DISCHARGE RUNOFF oz-30 1200 5.67 2t2 4.32 oA-11 o800 9.66 #49 5.70 oz-30 2400 5.62 204 4.33 04-11 1600 8.83 680 5.93 04-11 2400 8.24 S75 2.99 03-31 13200 178 4.34 or-31 . 2400 197 4.35 04-12 ©0200 10.93 1, 2 B. 946 04-12 0500 14.70 3, 2 &. 01 $4-01 1200 P36 4.37 04-12 1000 1L.4h 19, 3 6.21 04-01 2400 275 4. 38 04-12 1300 14, 800 £. 40 04-12 1700 18, £00 «73 04-02 327 4.39 04-12 2100 20, 200 7 _ 3A 04-02 1600 420 4.41 04-12 - 2400 21, 700 7.42 04-02 2400 570 4.43 04-13 - Q300 20. 28 24, 000 7.7% 04-03 o800 9.99 924 4.46 Q4-13 0600 21.058 27, 800 3.14 04-03 14600 11.07 1, 260 4.50 04-13 0900 21.76 ~1,900 & . $08 04-03 2400 11.97 1,780 4. 56 04-13 1200 22.47 34, 400 2.02 04-13 1500 24.91 37, £00 7.65 04-04 - oBoo I. 44 2, 220 4. 64 04-13 19200 23.06 40, 700 10.45 04-04 - 1400 12.53 3, 32°20 4.73 04-13 2200 22.98 40, 100 11.04 04-04 - 2400 12.4642 2,430 4.82 04-13 2400 22. 88 37, 400 11.44 o4a-0s - 0800 12.87 2. 370 4.972 ba-18 ..O40O 22. 23 12.19 04-05 1400 12.40 2,170 5.01 04-14 0800 22.01 12.88 04-05 2400 12. 28 2, 040 5. 09 04-14 1200 21.45 13.51 04-14 1600 20. 85 14.07 04-06 1200 12.07 1, 860 9.21 04-14 2000 20.23 14.57 04-06 - 2400 11.82 1, 470 5.30 04-14 - 2400 19.91 15. 00 04-07 - 0soo 10.44 1, 050 5.35 04-15 0600 18. 36 16, 300 15. 55 04-07 1600 3.76 705 5.37 04-15 1200 17.28 12, 700 15.98 04-07 - 2400 7.96 527 5.41 04-15 1800 14. 33 7, 7180 16.31 04-15 2400 1T. 9¢ 73.7299 16.98 04-08 - O§500 7 _. L6 472 5.43 04-08 1200 I. 64 845 5.45 04-16 )c.c &, 100 16.78 04-08 2400 10.43 1, 040 5.50 hb4-14 120 4, T30 16.94 04-16 180 4, O00 17.08 04-02 - 0800 11.59 1, 500 T. 04-16 ~4J0 3, 240 17.18 04-02 129200 12.00 1, 780 S. 64 04-072 - 2400 11.978 1,740 5.69 04-17 ©£600 12.62 2, 430 17.27 04-17 1200 11.987 1, £70 17.33 04-10 - 0800 11.74 1, 580 5.75 04-17 1800 10. 89 1, 200 17.g7 04-10 - 14600 11.27 1, 360 5.8 04-17 2400 9. 62 840 17.40 1 04-10 2400 10. S8 i, 070 5. 86 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02484000, Yockanookany River near Kosciusko, Miss.-Continued 187 Gace ACCUMULATED case ACCUMULATED DATE - TIME - HEIGHT _ DISCHARGE __ RUNOFF DATE _ TIME - HEIGHT _ DISCHARGE __ RUNOFF o4a-z4 - 7.06 387 17.65 § s s. - s Paste. too a Fos 17 ce 04-24 1200 t 380 17.62 a ' 2400 Aye (l 17.42 04-24 2400 6.90 364 17. 63 3 04-25 1200 6.95 371 17.70 oa4-1i2 1200 £i73 341 17.49 2 Prsi> " 2490 tap hed (7 iE] 04-25 2000 7.14 399 17.72 f 04-25 2400 7.16 393 17.73 04-20 1200 6.29 283 17.53 04-20 2400 £:13 263 17.54 Seno Tos 22+ o 92 £ oa-26 2400 £.77 346 17.77 oa- 2 s. 2 ® soit ff m dif) amiss son a . ih 04-27 2400 &. 03 251 17.91 oa-22 1200 5.79 223 17.59 04-22 2400 5.98 245 17. 60 loss (1800 i> p 17 23 oa-28 2400 5.45 186 17.83 oa-23 1200 6.63 327 17. 62 04-23 2400 7.03 383 17.64 188 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02484500, Yockanookany River near Ofahoma, Miss. GAGE ACCUMULATED GAGE ACCUMULATED DATE _ TIME _ HEIGHT _ DISCHARGE RUNOFF DATE - TIME - HEIGHT _ DISCHARGE RUNOFF os-03 0100 14.15 3, 440 0.00 03-03 1200 15. 40 4, 520 0.14 03-17 1200 5.32 466 3.71 oz-0o3 2400 16.50 6, 110 0.34 03-17 2400 5.01 414 3.73 oz3-04 1200 16.65 £, 420 0.53 os-18 1200 A«#7 378 3. 75 os-04 1700 16. 66 6, 440 0.63 os-18 2400 4.61 351 03-04 - 2400 16. 60 6, 320 0.83 & os-19 1200 4.46 329 2.77 oz-os5 1200 16.55 6, 210 1.07 os-19 2400 4. 33 310 3.79 o3-05 2400 16.59 é, 300 $.21 03-20 1200 4.22 294 3.80 03-06 1200 16.87 6, 260 1.95 03-20 2400 4.12 281 3.31 03-06 2400 16.76 6, 660 1.80 f os-21 1200 4.05 271 3.82 03-07 1200 16.93 7, 040 2.06 o3-21 2400 3.96 259 3.33 o3-07 2400 16.77 é, 680 2.32 03-232 1200 3.93 255 3.94 03-08 1200 16.29 5, 700 2.54 03-22 2400 S. 77 547 3. 85 os-0o8 2400 15.55 4, 680 2.76 03-23 1200 s.18 1, 080 3.39 oz-09 1200 14.60 8.770 2.92 os-23 2400 8.86 1, 240 3.93 03-09 2400 13.54 3, 020 3.05 03-34 1200 8.30 £,. 110 3.98 03-10 - 1200 ta.az 2, 410 3.146 03-24 2400 8.07 1, 050 4.02 03-10 2400 11.34 1, 970 3. 24 1200 8.42 1, 140 4.046 03-11 1200 10. 29 1, 630 3.31 03-25 2400 9.26 1, 350 4.11 03-11 2400 9.32 1, 360 3.37 03-36 1200 10. 49 1, 690 4.17 03-12 1200 8.43 1, 140 3.42 03-26 2400 11.37 1, 990 4.24 03-12 2400 7.75 974 3.46 03-27 1200 11.67 2, 090 4.31 03-13 1200 7.32 871 3.49 03-27 2400 11.55 2, 040 4.39 os-13 2400 7.18 839 3.53 om-28 1200 11.11 1, 890 4. 47 03-14 1200 7.13 828 3.54 03-28 2400 10. 32 1, 640 4.54 03-14 2400 7-07 814 3.59 03-29 1200 9.14 1, 320 4.59 os-15 1200 6.87 770 3. 62 o3-29 2400 7.77 979 4. 64 os-15 2400 6.52 695 3.65 03-30 1200 6.41 672 4.67 03-16 1200 6.08 606 3.67 03-30 2400 5.47 492 4, 69 03-16 2400 5.68 530 3.70 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02484500, Yockanookany River near Ofahoma, Miss.-Continued 189 GAGE ACCUMULATED GacE ACCUMULATED DATE | TIME - HEIGHT - DISCHARGE __ RUNOFF DATE _ TIME _ HEIGHT _ DISCHARGE ___ RUNOFF 03-31 1200 4.93 401 4.71 o4-12 0200 11.58 2, 060 6.23 03-31 2400 4. 63 354 4.72 04-12 0300 11.71 2, 110 6.24 04-12 0400 - 12.01 2, 240 6.24 04-01 1200 4.45 327 4. 74 04-12 0500 12.37 2, 390 6.25 04-01 2400 4. 32 308 4.75 04-12 04600 12.74 2, 580 6.26 § 04-12 9700 - 13.19 2, 820 £.27 04-02 1200 4. 37 316 4.746 04-12 og800 13.78 3, 170 6.23 04-02 2400 4176 345 4.77 04-12 9900 - 14.58 2;7850 6.23 04-12 1000 - is.s2 4, 650 6.30 04-03 1200 6.76 746 4.30 04-12 ii06 . is.38 5, 620 6.32 04-03 2400 7.64 947 4.83 94-12 1200 _- 1.78 6, 700 6.34 04-04 1200 8.94 1, 260 4.87 ae cline. -. (hez reno ae 04-04 2400 9.44 1, 390 4.92 4 a i f T * r 3 04-12 i890 - is.04e - 10,300 6.42 04-05 1200 7.62 1, 440 4.98 a ives {amit cas 04-05 2400 _ 10.25 r 5.03 e tE - 12" eos Sf r 04-12 1800 _ - 15,800 6.55 pasos lizoo _ ii.s pce Slap 1900 . i9.%8 - 17,400 w 04-06 2400 | 11.95 2, 210 5.18 fite (ofan _ oa-t2z 310060 .fo.i2 . _ (s;800 6.72 Caspr igoo - iz.is o 04-12 2200 . 20.31 . 21,000 6.78 ned? Maico - a ea g. ba-i> 2300 - 20.48. 22,p06 6.85 r 04-12 Javo . Solse _ 25,500 6.92 ba-bd8e i200 - 12.04 2, 250 5.44 ; r > $2-13 p1oo . zs,s00 7.90 o4a-os 2400 _ 14.08 3, 390 5.55 oasis Bago Bores ca.400 7197 04-09 1100 _ is.27 4, 380 5.69 ime hom Sino $ he he 9s 64-13 9400 - 2i.oe - 28,800 7.23 r 64-13 bz0o0 - si.ls. 32),800 7.40 04-10 0100 __ 14.09 3, 390 5.84 ie [ad flos" . Steno a Taz 94-13 ii06 . - 27,800 7.84 04-10 0300 - 13.84 3, 220 5.833 C 04-13 1400 - Sil.at - §s.:.fi o4-10 weoo - 13.48 2, 990 5.91 f 2 04-13 1900 | 2il.8s9 - 36, i060 8.53 04-10 0900 _ 13.14 2. 790 5.94 iis saoe - sp (on 04-10 1200 - 12.83 2, £20 5.97 i 3s a3 of-10 Leno . 12.49 ar aso 6-90 04-14 0400 _ pr.08 _ 34,300 9.51 wa-10 . ts.is 2, 300 6.04 acto | {ings o eg cos o4a-14 0700 _ - 36,300 9.34 r 04-14 o900 _ 22.48 - 38,000 10.03 pati lbevo - 11.48 s r408 £.10 Q4-14 1000 | 0 38,500 10. 20 $4-14 13090 - 22.74 - 30,700 10.59 oa-i1 12006 -_. i1.42 2, 000 6.14 cs ori (Bage "ilig. rays agen b4-14 1700 . S3.08 | a3,700 11.13 04-14 P100 - 0 45,900 11.70 ga-14 3300 _ 23.3 46,400 12. 00 04-14 2400 - P3.35 - 46,200 12.14 190 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02484500, Yockanookany River near Ofahoma, Miss.-Continued GAGE ACCUMULATED GAGE ACCUMULATED DATE - TIME - HEIGHT - DISCHARGE RUNOFF DATE - TIME - HEIGHT _ DISCHARGE __ RUNOFF o4a-1s 0700 23.12 44, 800 13.14 oa-18 1200 16.24 S, 430 18.07 42s." a900 53.81 a ( 22as 04-18 1500 16. 00 5, 080 18.12 64—15 1200 Zg'34 41,700 13's, 04-18 1800 15.72 4, 710 18.17 & ® r « 30 acte" 1206 anos at (36 (2.33 o4-18 2100 15.46 4, 400 18.21 Yas 2. f * 04-18 2400 15.17 4, 060 18. 25 o4-15 14600 22.56 38, 800 14.37 r o4- 9 22. a . Jf 4 nere sos tener 95 os-19 o300 _ i4.ss 3, 810 18.29 E a £4» \r a O+ a ¥ yor os 04-12 0600 14.59 3, 570 18. 33 oa-1s 2200 P2.03 33.800 15.07 04-18 P466 - gi.se _ 322,000 15.23 pais i000 _ 11-1" 3, 250 18.37 04-192 1300 13.90 3, 040 18.40 o4-16 0300 21.52 29, 500 15.53 0A-19 1700 13.91 2, 810 18. 44 naco Toa; aeon (e 04-19 2000 13. 20 2, 640 18.47 21. $ 5. -19 2400 _ 12.80 2, 430 18. 50 04-16 0500 21.30 27, 800 15.74 04715 * r 04-146 0700 - - 26,000 15.93 O800 - 20.96 - 28, 200 16.01 na-zo omoo 12.91 redo Ns 2% 04-16 0900 _ 20.83 _ 24,400 16.09 9700 _ 1s O2 A has A" an = } 04-20 1100 11.65 1, 960 18.583 o4-16 1100 20.61 22, 800 16.25 a =Te - 1200 SLS a 12.92 04-20 1400 11.29 1, 840 18.59 s r 6.32 > 5 04-20 1800 10.81 1, 690 18. 62 04-16 - 1300 70.40 - 21,590 16. 39 s C 324 04-20 2300 10.21 1, 510 18. 64 04-16 - 1500 20.19 _ 20,300 r a oo h i teo tia 64-16 1790 19.94 18, 800 16.65 04-20 240 10. r » 6! 82:12 1388 {3'33 13'233 12'32 04-21 1200 8.66 1, 110 18.70 s * * - 73 04-16 21060 19.50 16, 500 16.37 04-21 2400 7.36 gos 18. 04-16 - 2300 19.27 15, 400 16.97 04-16 2400 19:16 14, 800 17.02 oa-22 1200 6.36 596 18.76 04-22 2400 5.82 496 18.73 o4- s 4 ® s ir esa onine ra add A 04-23 1200 5.99 528 18. so o4-17 0300 18s. 85 13, 500 17.1% nees - 2400 ward 291 (alg: 04-17 ©0400 18.73 13, 000 17.20 * Baud o4-17 0600 18.51 12, 100 17. 23 o 04-17 o8co - | is.32 - 11,300 17.36 acai 2409 a ppv te o4-17 1000 18.13 10, 600 17. 43 £ 3 04-17 1300 17. 87 9,760 17.52 G ©a=i7 soo ~' 17.72 9, 270 17.53 n 2200 a igy es rane 04-17 1600 17.65 9, 050 17.61 * = o4-17 1700 17.57 8, 800 17.64 os-17 i90oo - 17.44 8, 420 17.70 nar ©2390 ras 34 ( oa 04-17 2000 17. 38 8, 240 17.72 3 * 04-17 2200 17.24 7, 840 17.78 o4-17 2300 17; to 7, 680 17.80 oA-27 1200 5. 40 430 12-3; 04-17 2400 17.11 7, 490 17.82 04-27 2400 5.36 424 - 9° oa-i8s 0300 16.91 6. 970 17.89 04-28 1200 5.32 419 18.97 o4a-18 0600 16. 69 6, 440 17.96 04-28 2400 5.21 401 18.99 o4-18 0900 16. 47 5, 930 18.02 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02486000, Pearl River at Jackson, Miss. ACCUMULATED 101 GAGE GAGE ACCUMULATED DATE _ TIME _ HEIGHT _ DISCHARGE RUNOFF DATE _ TIME _ HEIGHT __ DISCHARGE RUNOFF 03-02 0100 21.67 27, 000 0. 00 93-02 1030 30.89 24, 600 o. 12 03-19 1200 11.81 3, 800 5.1» 03-02 2400 31.30 25, 800 0.29 03-192 2400 16.75 2; G10 5.24 03-03 1200 32.27 29, 000 0.45 03-20 1600 10.12 2, 720 8.2% o3-03 2400 33.12 32, 100 0.64 o3-20 2400 2.22 2, 320 8.24 03-04 - 2400 32.857 33, 800 1.03 03-21 2400 8.71 2, 090 5.27 oz-0s 2400 33.99 35, 500 1.45 o03-22 1200 8.83 32, 150 5.23 or-22 2400 10.21 3, 760 5.30 03-06 1600 24.81 38, 500 1.74 03-046 - 2400 34.33 37, 400 1.89 03-33 1200 10. 29 2, 800 5.31 03-23 2400 12. 88 4, 010 5.33 o3-07 0300 24.223 36, 800 1.95 o3-07 2400 34.41 37, 700 2.34 03-24 - 1200 13.69 4, 400 5.36 03-34 2400 15.65 5, 340 B. 39 03-08 14600 34.63 39, 200 2.65 a s o3-08 2400 34.58 38, 9700 2.81 os-35 2400 16.83 5, 720 5.446 03-09 2400 34.66 39, 400 3.28 03-26 0900 17.00 6, 000 5.43 03-26 2400 15.10 5, 080 5.52 03-10 2400 34.40 37, 800 3.74 03-27 2400 13.81 4, 460 5.592 03-11 2400 32.11 28, 400 4.14 oz:-28 2400 t3r6e1 , 4,360 5.63 03-12 1200 30.31 23, 700 4.29 os-12 2400 28.87 18, 7200 4.42 o3-22 1200 13.46 4, 290 5.66 o3-29 2400 12. 66 3, 200 5.469 2400 26.99 15, 300 4. 62 o3-30 2400 11.06 s, 180 5.73 03-14 1200 26.17 14, 100 4.74 03-14 2400 25. 37 13, 100 4.79 03-31 2400 9.72 2, 540 5.76 os-15 1200 24.37 13, 100 4.87 04-01 1200 8.79 2, 130 5.78 os-15 2400 22.86 10, 300 4.94 04-01 2400 7.19 1,450 5:79 0OB-16 2400 19.21 7, 310 S. oS 04-02 1200 7.78 1, 4680 5.80 04-02 2400 9.01 2, 220 5.81 os-17 0800 18.11 6, 570 8.07 03-17 14600 16.73 5, 870 5.10 04-03 1200 13. 14 4, 130 5.83 03-17 2400 14.85 4, 960 5.12 04-03 2400 15.921 5, 470 5.84 03-18 1200 12.72 3, 930 5.15 04-04 - 1200 18. 86 7, 070 5.39 03-18 2400 12. 13 3, 650 5.17 04-04 2400 21.17 8, 740 5.94 192 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02486000, Pearl River at Jackson, Miss.-Continued ACCUMULATED 04-10 2400 1400 2400 2400 1700 2400 2300 2400 0600 1200 1800 2400 0é£00 1200 1800 2400 04600 1200 1800 2400 ©£600 1200 1800 2400 04600 1200 1800 2400 GAGE GAGE ACCUMULATED HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 23. 62 11, 000 6. 00 04-17 0300 43. 07 125, 000 11.79 25.953 13, 300 6.07 04-17 43.16 126, 000 11.93 04-17 0200 43.23 127, 000 12.17 26.67 14, 800 6.146 04-17 1200 43. 28 128, 000 12.34 26.79 15, 000 6.25 04-17 1500 43. 28 128, 000 12.53 04-17 1800 43.22 127, 000 12.74 26.15 14, 100 &. 42 04-17 2400 42.98 123, 000 13.12 25.78 13, £00 6.52 04-18 04600 42.60 118, 000 13.43 s 14, 000 6.99 04-18 1200 42.16 112, 000 13.82 04-18 1800 41.70 106, 000 14.15 vases 15, 500 6.76 04-18 2400 41.31 102, 000 14.46 27. 64 16, 300 6.90 04-19 0600 40.94 77, 300 14.746 27.78 16, 500 &.96 04-192 1200 40. 54 72, 800 18.03 04-192 1800 37.89 SS, 700 18. s 27.61 16, 200 7.14 04-192 2400 37.11 77, 100 15.54 28. 44 17, 200 7 AY 04-20 0800 38.15 £7, 400 18.83 30. 05 22, 100 7.21 04-20 1600 37. 28 S9, 200 16.10 31.10 25, 200 7. 23 04-20 2400 36.16 49, 700 16.32 32. 98 31, 500 7. §7 33.78 35, 200 7.47 04-21 0800 C5.27 43, 400 16.50 04-21 14600 34.57 38, 200 16.67 41, 700 7.99 04-21 2400 33.995 33, 700 16.81 45, 600 7.72 48, 300 7.846 04-22 1200 3%. 17 28, 700 17.00 53, 00G 8.01 04-232 2100 21.79 27, 400 17.13 04-22 2400 31.96 27, 700 17.17 37. 64 62, S00 8.18 38. 70 74, 700 £. 37 04-23 1200 30. 58 23, 600 17.92 379. 67 83, 200 8. 63 04-23 2400 29.32 20, 100 17.45 40. 42 971, 500 8.89 04-24 1200 28.51 18, 000 17.57 41.20 100, 000 7.17 04-24 2400 27.91 16, 100 17.67 41.83 108, 000 7.49 42.25 113, 000 7.82 04-25 1200 26.50 14, £00 17.74 42. 49 116, 000 10.14 04-25 2400 25.07 12, 700 17.85 42.62 118, 000 10.51 04-26 1200 23.56 11, 000 17.92 42.78 121, 000 10.87 04-26 2400 21.63 7, 100 17.989 42. 85 122, 000 11.24 42.995 123, 000 11.60 04-27 1200 19.76 7, 680 18.03 04-27 2400 17.32 £, 160 18.07 04-28 1200 15. 08 5,070 18.10 04-28 2400 13.91 4, 210 18.13 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02488500, Pearl River at Monticello, Miss. 193 GAGE ACCUMULATED GAGE ACCUMULATED DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 04-01 2400 11.19 6, 330 0.00 04-16 1200 25.51 43, 800 2.15 04-02 1200 10.97 6, 070 0.02 04-16 2400 26.66 52, 200 2.33 04-02 2400 12.50 7, 950 0.04 04-17 1200 28.23 64, 700 2.34 04-03 1200 15.77 12, 400 0.08 04-17 2400 29.79 78, 400 2.81 04-03 2400 18.91 16, 900 0.14 04-18 1200 31. 22 91, 9200 3.12 04-04 1200 21.14 21, 300 0.21 04-18 2400 32. 41 104, 000 3.48 04-04 2400 21.77 22, 800 0.29 04-19 1200 33. 40 114, 000 3.388 04-05 2400 21.84 23, 000 0.46 04-19 2400 33.95 120, 000 4.31 04-06 2400 21.00 21, 000 0.62 04-20 1200 34.08 122, 000 4.76 04-20 2400 33.87 120, 000 5.21 04-07 2400 20.23 19, 300 0.77 04-21 2400 32.77 108, 000 6.05 04-08 2400 19.94 18, 700 0.91 04-22 2400 31.56 95, 300 6.30 04-09 2400 19.54 17, 9200 1.04 04-23 2400 30. 37 83, 700 7.46 04-10 2400 19.23 17, 400 1.17 04-24 2400 29.06 71, 800 8.03 04-11 2400 19.27 17, 400 1.30 04-25 2400 27.87 61, 700 8.953 04-12 2400 19.77 18, 300 1.43 } 04-26 2400 26. 895 53, 600 8.95 04-13 1200 20. 42 19, 700 1.50 04-13 2400 21.27 21, 600 1.58 04-27 2400 25. 80 45, 800 9.32 04-14 1200 22. 12 24, 200 1.66 04-28 2400 24. 32 35, 800 9.62 04-14 2400 22.93 27, 500 1.76 04-29 2400 21. 49 22, 000 9.93 04-15 1200 23.78 32, 400 1.87 04-15 2400 24.56 37, 300 2.090 04-30 2400 16.18 11, 400 9.96 194 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 02489500, Pearl River near Bogalusa, La. GAGE ACCUMULATED GAGE ACCUMULATED DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 04-02 2400 14. 36 8, 280 0.00 04-19 2400 19.67 40, 200 2.94 04-03 0600 14.74 8, 930 0.01 04-20 1600 19.90 45, 000 3.110 04-03 1200 15.83 10, 100 0. 02 04-20 2400 20.10 49, 400 3.19 04-03 1800 17.25 15, 000 0.04 04-03 2100 17.87 17, 800 0. 05 04-21 1200 20.53 S9, 400 3. 34 04-03 2400 18. 85 22, 900 0.06 04-21 2400 21.23 76, 400 3.993 04-04 0600 19.18 31, 200 0.10 04-22 1200 21.97 95, 000 3.77 04-04 1400 19.67 40, 200 0.17 04-22 2400 22.61 112, 000 4.04 04-04 2000 19.82 43, 300 0.23 04-04 2400 19.85 44, 000 0.27 04-23 0600 22.80 117, 000 4. 22 04-23 1600 23.15 127, 000 4.51 04-05 2400 19.70 40, 800 0.51 04-23 2400 23. 20 128, 000 4.795 04-06 2400 19.56 38, 000 0.73 04-24 0300 23.23 129, 000 4.84 04-24 1600 23. 20 128, 000 5.23 04-07 2400 19.44 35, 800 0.93 04-24 2400 23. 04 124, 000 S. 46 04-08 2400 19. 35 34, 100 1.13 04-25 1200 22.75 116, 000 5.80 04-25 2400 22. 40 106, 000 6.11 04-09 2400 19. 25 32, 400 1.32 04-26 2400 21.60 85, 700 6.65 04-10 2400 19.10 29, 9700 1.49 04-27 2400 20.95 69, 500 7.99 04-11 2400 18. 92 27, 300 1.65 04-28 2400 20.57 60, 400 7.495 04-12 2400 18. 80 25, 700 1.80 ¢ 04-29 2400 20.32 54, 500 7.77 04-13 2400 18. 66 24, 100 1.94 04-30 2400 20.15 50, 600 8.06 04-14 2400 18. 65 24, 000 2. 08 os-01 2400 19.97 46, 500 8.34 04-15 2400 18. 80 25, 700 2.21 os-02 2400 19.65 39, 800 8.58 04-16 2400 19.01 28, 600 2.27 05-03 2400 18.52 22, 600 8.75 04-17 2400 19.23 32, 000 2.54 05-04 2400 16.74 13, 400 8.86 04-18 2400 19.46 36, 100 2.73 os-05 2400 16.29 12, 200 8.93 TABLES TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 07289350, Big Black River at West, Miss. 195 GAGE ACCUMULATED GAGE ACCUMULATED DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 04701 0100 7.58 798 0.00 04-12 1500 20. 20 13, 800 1.37 04-01 2400 8. 25 928 0.03 04-12 1800 21.68 22, 600 1.46 04-12 2400 23.12 35, 200 1.73 04-02 1200 10. 57 1, 440 0.05 04-02 1800 12. 43 1, 220 0.06 04-13 0600 23. 89 43, 500 2.10 04-02 2400 13. 45 2, 220 0.08 04-13 1200 24.21 47, 200 2.53 04-13 "1600 24.27 48, 000 2.83 04-03 0600 14. 28 2, 470 O. 11 04-13 1800 24.27 48, 000 2.99 04-03 1200 14.77 2, 630 O. 13 04-13 2030 24.20 45, 400 3.17 04-03 1800 15.06 2, 730 0.16 04-13 2400 24.14 46, 400 3. 42 04-03 2400 15. 35 2, 850 0.13 04-14 0600 23.79 42, 400 3. 34 04-04 1200 15.91 3, 070 0.24 04-14 1200 23. 42 38, 300 4.22 04-04 2400 16.41 3, 330 0.30 04-14 1800 23. 08 34, 800 4.56 04-14 2400 22.71 31, 100 4.987 04-05 1200 16.97 3, 730 0.36 04-05 2400 17.36 4, 230 0.44 04-15 1200 21.93 24, 400 3. 40 04-15 2400 20.99 18, 000 5.980 04-06 1200 17.47 4, 420 0.52 04-06 1400 17.49 4, 450 0.54 04-16 2400 19.53 10, 700 6.34 04-06 2400 17.48 4, 440 0.61 04-17 2400 18.38 6, 670 6.67 04-07 2400 17.09 3, 850 0.76 04-18 2400 17.20 3, 970 6.87 04-08 2400 16.70 3, 520 0.70 04-19 2400 15. 83 3, 040 7.90 04-09 2400 16.23 3, 230 1.03 04-20 1200 14.26 2, 460 7.05 04-10 2400 15.11 2, 750 1.14 04-20 2400 11.39 1, 620 7.09 04-11 2400 14.50 2, 540 1.24 04-21 1200 8.76 990 7.12 04-21 2400 7.72 781 7.13 04-12 0300 15.91 3, O70 1. 25 04-12 0600 17.395 4, 210 1. 27 04-22 1200 7.27 696 7.195 04-12 1200 18.44 6, 850 1.32 04-22 2400 7.22 687 7.16 196 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 7.-Gage height, discharge, and accumulated runoff, flood of April 1979-Continued 07290000, Big Black River near Bovina, Miss. GAGE ACCUMULATED GAGE ACCUMULATED DATE TIME HEIGHT DISCHARGE RUNOFF DATE TIME HEIGHT DISCHARGE RUNOFF 04-02 2400 15.13 3, 580 0.00 04-16 0600 40.42 80, 200 3. 00 04-03 1200 18.77 3, 890 0.02 04-16 1200 40.50 82, 000 3. 27 04-03 2400 18. 30 5, 190 0.95 04-16 1900 40.56 83, 300 3. 58 04-16 2400 40.51 82, 200 3.81 04-04 1200 22.10 7, 310 0.99 04-04 2400 23.06 7, 890 0. 14 04-17 0600 40.52 82, 400 4.09 04-17 1100 40. 44 80, 700 4.31 04-05 0600 23.12 7, 920 0.17 04-17 1800 40.32 78, 000 4.62 04-05 2400 22.87 7, 770 0. 25 04-17 2400 40.23 76, 100 4.87 04-06 2400 22. 46 7, 530 0.39 04-18 1200 39.97 70, 400 5.34 04-18 2400 39.67 64, 100 5.80 04-07 2400 21.93 7, 210 0.44 04-19 1200 39.33 56, 900 6.20 04-08 2400 22. 10 7, 310 0.54 04-19 2400 38.97 49, 700 6.59 04-09 1200 23.47 8, 130 0.59 04-20 2400 38. 32 36, 900 7.13 04-09 2400 24.06 8, 490 0.45 04-21 2400 37. 48 28, 400 7.56 04-10 2400 24.66 8, 850 0.76 04-22 2400 36.33 24, 000 7%91A 04-11 1200 24.95 9, 020 0.832 04-11 2400 26.72 10, 100 0. 38 04-23 2400 35. 03 20, 500 8.20 04-12 ©0600 28.59 11, 300 0.92 04-24 1200 34. 23 18, 800 8.33 04-12 1200 29.88 12, 400 0.26 04-24 2400 33. 37 17, 100 8. A45 04-12 1800 32.84 16, 200 1.01 04-12 2400 34.10 18, 500 1.046 04-25 1200 32.59 15, 800 8.56 04-25 2400 31.89 14, 700 8.66 04-13 0600 34.64 19, 600 1.13 04-13 1200 35. 28 21, 100 1.19 04-26 1200 31.23 13, 800 8.75 04-13 1800 35. 80 22, 500 1.27 04-26 2400 30. 60 13, 100 8.84 04-13 2400 36. 65 25, 100 1.34 04-27 1200 29.99 12, 500 8.93 04-14 0600 37.69 29, 400 1.43 04-27 2400 29.26 11, 800 9.01 04-14 1200 38. 42 38, 700 1.99 04-14 1800 38. 85 47, 300 1.49 04-28 1200 28.56 11, 300 9.09 04-14 2400 39.25 SS, 300 J .: 04-28 2400 27.74 10, 700 9.16 04-15 0600 39.53 61, 100 2.95 04-29 1200 26. 32 9, 760 9.23 04-15 1200 39.79 66, 600 2.24 04-29 2400 23.13 7, 770 9.23 04-15 1800 40.04 71, 900 2.49 04-15 2400 40.25 76, 500 2.74 04-30 1200 18. 99 5, 240 9.33 04-30 2400 15.79 3, 580 9.34 TABLES 197 TABLE 8.-Ground-water levels in selected observation wells showing effects of flood of April 1979 in Alabama and Mississippi (sand and gravel) and recharge from Tombigbee River Site 1 Cased Depth Well Depth Formation and | Factors influencing Number Location and Well Number | (feet) (feet) Lithology | ground-water condition: | I | iw | Bibb County, AL 325622087075501 | 80 404 Cambrian and Ordovician| Infiltration and I | I | (dolomite) | loading from I | I I f | Cahaba River [ | I I | I | 2w | Elmore County, AL 323757086013901| 63 I 402 Augen gniess | Local precipitation | | | | | (metamorphic rocks) | | | I | | | J- "34 | Greene County, AL 325005087532001| 395 | 407 | Eutaw Formation (sand)| Local precipitation I I I | | I | sw | Hale County, AL 324205087352801 I 258 I 278 | Eutaw Formation (sand}| Local precipitation I | I | | - 6w | Jefferson County, AL | | | I | | 332605086523001 | 68 | 140 | Bangor Limestone | Local precipitation 1 I | | | (limestone) | | Iw | Marengo County, AL | 860 | 900 | Eutaw Formation (sand)| Loading from I I 323055087504101 I I I | Tombigbee River | | - 8w | Pickens County, AL I 71 I 91 | Eutaw Formation (sand)| Loading from I I 330116088113101 I I I I Tombigbee River | - 9w | Pickens County, AL | 117 | 137 | Eutaw Formation (sand)| Loading from I I 330117088180301 I I I I Tombigbee River | 11W _| Sumter County, AL 325212088121601| 370 | 390 | Eutaw Formation (sand)| Loading from | | | I | | Tompigbee River, | | I | | | 1.35 miles west of [ | | I | | River | | | | | I | 12W | Sumter County, AL 325215088111301| 350 | 370 | Eutaw Fommation (sand)| Loading from | I | I I | Tombigbee River, I | | I | | 0.35 mile west of I | | | | | River | | | I | I | 15W | Noxubee County, Miss. (near I | | | | | Pickensville, AL) 331426088192202| 20 | 30 | Alluvial Deposits | Local precipitation | | | | I I | | | I | | I | | I | I 198 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 8. -Ground-water levels, flood of April 1979-Continued Site 1 W (325622087075501), Well at Centreville, Ala. (Centreville Gin & Cotton Co.) [Water level, in feet, below land-surface datum at indicated time, 1979] Water level (feet) Water level (feet) 3- 2 3- 2 3- 3 3- 3 3- 4 3- 4 31 S 3- S 3- 6 3- 6 3- 7 3- 7 3- 8 3- 8 3- 9 3- 9 3-10 26.01 26.24 26.37 26.49 26.54 26.56 25.18 23.25 22.39 22.12 22.07 22.20 22.80 23.48 24.03 24.48 24.85 25.11 25.35 25.54 25.72 25.86 25.95 26.05 26.14 26.23 26.31 26.45 26.58 26.67 26.72 4- 3 4-3 4- 4 4- 4 2400 2400 2400 2400 2400 1200 2400 1200 2400 1200 2400 2400 2400 2400 2400 2400 2400 2400 1200 2400 1200 2400 1200 2400 26.83 26.91 26.98 27.06 27.16 27.26 27.23 26.96 26.63 26.39 26.39 26.46 26.63 26.84 26.98 27.11 27.19 27.28 27.33 27.30 27.36 27.26 26.42 24. 85 24 .02 23.43 2400 2400 2400 1200 2400 1200 2400 1200 2000 2400 1200 2400 1200 2400 1200 2400 2400 2400 2400 2400 2400 25.26 25.49 25.75 25.81 23.90 22.04 21.04 20.56 20.42 20.44 20.51 20.66 21.20 22.02 22.77 23.19 23.78 24.21 24.55 24.84 25.02 2400 2400 2400 2400 2400 2400 TABLES TABLE 8. -Ground-water levels, flood of April 1979-Continued Site 2W (323757086013901), Well at Elmore County High School, Eclectic, Ala. [Water levels, in feet, below land surface datum (altitude 557.5 feet) at indicated time] 199 Water level Water level Water level Water level Date __Time (feet) Date _ Time (feet) Date _ Time (feet) Date __ Time (feet) 2-28 - 2400 8.20 3-15 2400 7.96 3-30 - 2400 8.01 4-14 _ 2400 7.37 3- 1 - 2400 8.18 3-16 2400 7.96 3-31 2400 8.00 4-15 _ 2400 7.34 3- 2 2400 8.15 3-17 2400 7.94 4- 1 _ 2400 7.99 4-16 2400 7.35 3- 3 2400 8.02 3-18 - 2400 7.92 4- 2 2400 8.02 4-17 2400 7.37 3- 4 - 2400 7.97 3-19 2400 7.94 4- 3 2400 7.81 4-18 _ 2400 7.39 3- 5 - 2400 7.95 3-20 2400 7.95 4- 4 _ 2400 7.70 4-19 2400 7.42 3- 6 2400 7.92 3-21 2400 7.98 4- 5 _ 2400 7.73 4-20 _ 2400 7.47 3- 7 2400 7.91 3-22 - 2400 8.00 4- 6 2400 7.72 4-21 - 2400 7.51 3- 8 2400 7.97 3-23 2400 7.94 4- 7 2400 7.70 4-22 2400 7.55 3- 9 2400 7.98 3-24 - 2400 7.97 4- 8 2400 7.61 4-23 - 2400 7.57 3-10 - 2400 7.97 3-25 - 2400 8.02 4- 9 ©2400 7.64 4-24 _ 2400 7.51 3-11 2400 7.97 3-26 - 2400 8.04 4-10 _ 2400 7.64 4-25 - 2400 7.28 3-12 2400 7.96 3-27 - 2400 8.04 4-11 2400 7.64 4-26 - 2400 7.23 3-13 - 2400 7.94 3-28 - 2400 8.04 4-12 - 2400 7.59 4-27 - 2400 7.21 3-14 - 2400 7.97 3-29 2400 8.02 4-13 - 2400 7.41 4-28 _ 2400 7.21 4-29 _ 2400 71.21 4-30 _ 2400 7.25 200 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 8. -Ground-water levels, flood of April 1979-Continued Site 3W (325005087532001), Well at Eutaw, Ala. (Greene County warehouse) [Water level, in feet, below land-surface datum (altitude 110.1 feet NGVD) at indicated time] Water level Water level Water level Water level Date _ Time (feet) Date _ Time (feet) Date _ Time (feet) Date _ Time (feet) 2-28 - 2400 44.12 3-15 2400 43.53 3-31 2400 43.71 4-15 2400 43.63 3-1 2400 44.08 3-16 - 2400 43.58 4-1 2400 43.63 4-16 - 2400 43.58 3-2 1200 44.07 3-17 2400 43.60 4-2 2400 43.63 4-17 2400 43.58 3-2 2400 44.08 3-18 - 2400 43.62 4-3 2400 44.05 4-18 _ 1200 43.54 3-3 1200 43.91 3-19 - 2400 43.66 4-4 2400 44.18 4-18 _ 2400 43.57 ‘3-4 2400 43.81 3-20 - 2400 43.72 4-5 2400 44.19 4-19 2400 43.57 3-5 2400 43.83 3-21 2400 43.73 4-6 2400 44.14 4-20 - 2400 43.54 3-6 1200 43.84 3-22 - 2400 43.66 4-7 2400 44.00 4-21 2400 43.50 3-7 2400 43.80 3-23 2400 43.58 4-8 2400 43.77 4-22 2400 43.42 3-8 2400 43.73 3-24 - 2400 43.57 4-9 2400 43.69 4-23 - 2400 43.38 3-9 2400 43.72 3-25 - 2400 43.57 4-10 _ 2400 43.69 4-24 2400 43.39 3-10 - 2400 43.69 3-26 - 2400 43.63 4-11 ©2400 43.74 4-25 - 2400 43.38 3-11 - 0500 43.68 3-27 2400 43.65 4-12 0700 43.176 4-26 - 2400 43.37 3-11 2400 43.63 3-28 - 2400 43.67 4-12 2400 43.73 4-27 - 2400 43.40 3-12 - 2400 43.58 3-29 - 2400 43.70 4-13 1400 43.59 4-28 _ 2400 43.40 3-13 - 2400 43.54 3-30 - 2400 43.74 4-13 2400 43.61 4-29 - 0500 43.44 3-14 - 2400 43.51 4-14 _ 2400 43.67 4-29 - 2400 43.42 4-30 _ 2400 43.42 TABLE 8.-Ground-water levels, flood of April 1979-Continued Site 5W (324205087352801), Well at City of Greensboro, Ala. [Water level, in feet, below land-surface datum (altitude 257 feet) at indicated time] TABLES 201 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 55.99 55.97 55.95 55.94 55.93 55.93 55.91 55.91 55.91 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 55.88 55.88 55.87 55.87 55.88 55.88 55.88 55.89 55.89 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 55.86 55.85 55.85 55.84 55.83 55.81 55.80 55.78 55.77 55.74 55.72 55.71 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 55.65 55.65 55.65 55.64 55.64 55.63 55.62 55.61 55.61 55.61 202 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 8.-Ground-water levels, flood of April 1979-Continued Site 6W (332605086523001), Well near Oxmoor, Ala. (at County Road 42) [Water level, in feet, below land-surface datum at indicated time] 3- 2 3- 2 3- 3 3- 3 3- 3- a a 3- 3- 3- 3- o o w un 3- $- bbd 3- 8 3- 8 3- 9 3- 9 3-10 3-10 4- 2 4- 2 4- 3 4- 3 4- 4 4- 4 4- 4- wn in 4- 4- o o 4> 4 sis 4- 8 4- 8 TABLES TABLE 8.-Ground-water levels, flood of April 1979-Continued Site TW (323055087504101), Well at J. C. Webb Compress Co., Demopolis, Ala. Nater level Water level Date - Time (feet) Date _ Time (feet) Date 2-28 2400 14.67 3-16 1200 15,41 3-31 3-16 2400 15. 36 3- 1 1200 14.81 3-17 2400 15. 38 4- 1 3- 1 2400 15.02 3- 2 2400 15,26 3-18 2400 15.13 4- 2 3- 3 2400 15.33 3-19 2400 14.89 4- 3 3- 4 2400 15.05 3-20 2400 14.75 4- 4 3- 5 2400 14.46 3-21 2400 14.65 4- 5 3- 6 2400 14.19 3-22 2400 14.65 4- 6 3- 7 2400 13.70 3-23 2400 14.41 4- 7 3- 8 2400 13.40 3-24 1600 14.41 4- 8 3-24 2400 14.54 3- 9 2400 13.36 3-25 1200 14.58 4- 9 3-25 2400 14.49 3-10 - 2400 13.61 3-26 2400 14.28 4-10 3-11 2400 13.93 3-27 2400 14.27 4-11 3-12 2400 14.31 3-28 - 2400 14.61 4-12 3-13 2400 14.79 3-29 2400 15.01 4-13 3-14 2400 15. 37 3-30 2400 15.07 4-14 3-15 2400 15.46 4-15 Time 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 [Water level, in feet, below land-surface datum (altitude 110 feet) at indicated time] Water level (feet) 14.88 14.63 14.41 14.04 13.92 14.31 14.12 14.03 14,00 14.12 14.18 14.38 13.89 13.43 12.67 11.78 10.14 Date Time 2400 1200 2400 2400 0300 2400 1200 2400 2400 2400 2400 2400 2400 2400 2400 2400 2400 Water level (feet) 8.34 7.95 7.68 7.58 7.57 7.176 7.95 8.16 8.70 9.96 11.42 12.23 12.61 12.73 13.07 13.10 13.53 208 204 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 8.-Ground-water levels, flood of April 1979-Continued Site SW (330116088113101) (USCOE), Well on Tombigbee River approximately halfway between Aliceville and Gainesville lock and dam at river mile 259.2 above mouth of Tombigbee River [Water level, in feet, below land-surface datum (135.6 feet NGVD) at indicated time] Water level Water level Water level Water level Date _ Time (feet) Date __Time (feet) Date __ Time (feet) Date _ Time (feet) 2-28 - 2400 17.36 3-15 2400 17.42 3-30 - 2400 17.34 4-15 2400 14.02 3-1 2400 17.34 3-16 - 2400 17.42 3-31 2400 17.32 4-16 2400 13.96 3-2 2400 17.36 3-17 2400 17.42 4-1 2400 17.32 4-17 2400 14.00 3-3 2400 17.04 3-18 - 2400 17.44 4-2 2400 17.23 4-18 _ 2400 14.13 3-4. 2400 16.78 3-19 2400 17.44 4-3 2400 17.14 4-19 2400 14.34 3-5 2400 16.49 3-20 - 2400 17.43 4-4 2400 17.06 4-20 _ 2400 14.62 3-6 2400 16.40 3-21 2400 17.42 4-5 2400 16.99 4-21 2400 15.03 3-7 0300 16.39 3-22 2400 ° 17.36 4-6 2400 16.95 4-22 - 2400 15.57 3-7 1800 16.39 3-23 1300 17.31 4-7 2400 16.90 4-23 2400 15.93 3-7 2400 16.41 3-23 - 2400 17.33 4-8 2400 16.77 4-24 _ 2400 16.18 3-8 2400 16.47 3-24 - 2400 17.30 4-9 2400 16.80 4-25 - 2400 16.29 3-9 2400 16.59 3-25 - 2400 17.29 4-10 _ 2400 16.84 4-26 - 2400 16.34 3-10 - 2400 16.73 3-26 - 2400 17.27 4-11 2400 16.89 4-27 - 2400 16.40 3-11 2400 16.91 3-27 2400 17.28 4-12 2400 16.16 4-28 _ 2400 16.46 3-12 2400 17.09 3-28 - 2400 17.31 4-13 2400 14.80 4-29 2400 16.49 3-13 - 2400 17.24 3-29 - 2400 17.36 4-14 _ 2400 14.21 4-30 _ 2400 16.53 3-14 - 2400 17.37 TABLES 205 _ TABLE 8. -Ground-water levels, flood of April 1979-Continued Site OW (330117088180301), Well 0.7 mile west of Tombigbee River, 3.5 miles southwest of Pickensville at river mile 286.0 above mouth of Tombigbee River [Water level, in feet, below land-surface datum (139.80 feet NGVD) at indicated time] Water level Water level Water level Water level Date _ Time (feet) Date _ Time (feet) Date _ Time (feet) Date __ Time (feet) 3-21 2400 4.08 4-2 2400 4.06 4-12 - 1800 2.92 4-19 2400 3.25 3-22 2400 4.01 4-3 2400 3.96 4-12 _ 2400 3.04 4-20 - 2400 3.59 3-23 - 2400 4.02 4-4 2400 3.99 4-13 - 0600 2:77 4-21 2400 3.68 3-24 - 2400 4.04 4-5 2400 4.03 4-13 1200 2.21 4-22 2400 3.68 3-25 - 2400 4.05 4-6 2400 4.04 4-13 _ 2400 1.44 4-23 - 2400 3.68 3-26 - 2400 4.09 4-7 2400 4.04 4-14 _ 1200 1.13 4-25 - 2400 3.66 3-27 2400 4.10 4-8 2400 3.90 4-14 _ 2400 1.06 4-26 - 2400 3.64 3-28 - 2400 4.11 4-9 2400 3.94 4-15 1200 1.05 4-27 2400 3.67 3-29 2400 4.12 4-10 _ 2400 3.96 4-15 2400 1.15 4-28 - 2400 3.69 3-30 - 2400 4.11 4-11 2400 3.97 4-16 2400 1.55 4-29 2400 $72 3-31 2400 4.12 4-12 0600 3.81 4-17 2400 2.09 4-30 _ 2400 3.75 4-1 2400 4.11 4-12 1200 3.51 4-18 _ 2400 2.67 206 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 8.-Ground-water levels, flood of April 1979-Continued Site 11W (325212088121601), Well 1.35 miles west of Tombigbee River, 4.2 miles northwest of Gainesville at river mile 240.9 above mouth of Tombigbee River [Water level, in feet, below land-surface datum (140.6 feet) at indicated time] Water level Water level Water level Water level Date _ Time (feet) Date _ Time (feet) Date _ Time (feet) Date _ Time (feet) 2-28 - 2400 14.55 3-14 - 2400 14.27 3-30 2400 14.45 4-15 - 2400 13.62 3-1 2400 14.54 3-15 2400 14.30 3-31 2400 14.39 4-16 - 2400 13.55 3-2 2400 14.51 3-16 - 2400 14.31 4-1 2400 14.40 4-17 2400 13.56 3-3 1200 14.40 3-17 2400 14.30 4-2 2400 14.32 4-18 2400 13.57 3-3 2000 14.25 3-18 - 2400 14.30 4-3 2400 14.36 4-19 _ 2400 13.58 ‘3-3 2400 14.35 3-19 - 2400 14.30 4-4 2400 14.40 4-20 _ 2400 13.59 3-4 2400 14.44 3-20 - 2400 14.30 4-5 2400 14.45 4-21 - 2400 13.60 3-5 2400 14.43 3-21 2400 14.32 4-6 2400 14.45 4-22 - 2400 13.60 3-6 2400 14.37 3-22 2400 | 14.24 4-7 2400 14.42 4-23 - 2400 13.64 3-7 2400 14.32 3-23 0300 14.19 4-8 2400 14.31 4-24 _ 2400 13.63 3-8 2400 14.31 , 3-23 2400 14.26 4-9 2400 14.36 4-25 - 2400 13.62 3-9 2400 14.29 3-24 - 2400 14 . 30 4-10 ©©2400 14.36 4-26 - 2400 13.68 3-10 - 2400 14.27 3-25 - 2400 14.35 4-11 2400 14.36 4-27 - 2400 13.75 3-11 2400 14.27 3-26 - 2400 14.38 4-12 1800 14.01 4-28 - 2400 13.83 3-12 2400 14.24 3-27 - 2400 14.40 4-12 2400 14.17 4-29 - 2400 13.88 3-13 1900 14.20 3-28 - 2400 14.42 4-13 2400 14.13 4-30 _ 2400 13.94 3-13 2400 14.22 3-29 2400 14.42 4-14 _ 2400 13.89 TABLES 207 TABLE 8.-Ground-water levels, flood of April 1979-Continued Site 12W (325215088111301), Well 0.35 mile west of Tombigbee River, 3.7 miles northwest of Gainesville at river mile 240.9 above mouth of Tombigbee River [Water level, in feet, below land-surface datum (162.82 feet, NGVD) at indicated time] Water level Water level Water level Water level Date _ Time (feet) Date __ Time (feet) Date __ Time (feet) Date __ Time (feet) 2-28 - 2400 37.42 3-18 - 2400 37.41 4-4 2400 37.32 4-16 2400 35.66 3-1 2400 37.43 3-19 2400 37.40 4-5 2400 37.35 4-17 1200 35.62 3-2 2400 37.42 3-20 - 2400 37.40 4-6 2400 37.38 4-17 - 2400 35.59 3-3 2400 37.25 3-21 2400 37.39 4-7 2400 37.36 4-18 _ 2400 35.62 3-4 2400 37.33 3-22 - 2400 37.31 4-8 2400 37.24 4-19 _ 2400 35.73 3-5 2400 $7.32 3-23 2400 37.31 4-9 2400 37.29 4-20 _ 2400 35.89 3-6 2400 37.27 3-24 - 2400 37.35 4-10 _ 2400 37.30 4-21 _ 2400 36.11 3-7 2400 37.23 3-25 - 2400 37.41 4-11 _ 2400 37.32 4-22 2400 36.30 3-8 2400 37.30 3-26 - 2400 37.44 4-12 - 0700 37.32 4-23 - 2400 36.47 3-9 2400 37.33 3-27 2400 37.46 4-12 - 1200 $7.21 4-24 _ 2400 36.57 3-10 - 2400 37.34 3-28 - 2400 37.48 4-12 2400 37.14 4-25 - 2400 36.62 3-11 2400 37.34 3-29 - 2400 37.47 4-13 1200 36.98 4-26 - 2400 36.72 3-12 2400 37.36 3-30 - 2400 37.46 4-13 - 2400 36.82 4-27 2400 36.80 3-13 2400 37.36 3-31 - 2400 37.38 4-14 _ 1200 36.62 4-28 - 2400 36.87 3-14 - 2400 37.43 4-1 2400 37.36 4-14 _ 2400 36.34 4-29 2400 36.93 3-15 2400 37.43 4-2 2400 37.28 4-15 1200 36.11 4-30 _ 2400 36.97 3-16 - 2400 37.42 4-3 1900 37.31 4-15 2400 35.90 3-17 2400 37.41 4-3 2400 37.25 208 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 8.-Ground-water levels, flood of April 1979-Continued Site 15W (331426088192202), Well 3.4 miles west of Pickensville, Ala. (Noxubee County, Miss.) at river mile 292.0 above mouth of Tombigbee River [Water level, in feet, below land-surface datum (146.64 feet) at indicated time] Water level Water level Water level Water level Date _ Time (feet) Date _ Time (feet) Date _ Time (feet) Date _ Time (feet) 2-28 - 2400 4.30 3-18 - 2400 4, 32 4-4 2400 4.63 4-14 1200 1,29 3-1 2400 4,20 3-19 2400 4.39 4-5 2400 4.56 4-14 _ 2400 1.44 3-2 2400 4.17 3-20 2400 4.46 4-6 2400 4.56 4-15 1200 1.57 3-3 2400 3.17 3-21 2400 4.52 4-7 2400 4.58 4-15 2400 1.70 3-4 1700 3.05 3-22 2100 4.57 4-8 2400 4.51 4-16 _ 2400 1.93 3-4 2400 3.08 3-22 2400 4.52 4-9 2400 4.50 4-17 2400 2.19 3-5 2400 3.19 3-23 0200 4.50 4-10 _ 2400 4.49 4-18 _ 2400 2.44 3-6 2400 3.30 3-23 2400 4.56 4-11 _ 2400 4.54 4-19 2400 2.66 3-7 2400 3.43 3-24 - 2400 4.61 4-12 - 0500 4.57 4-20 _ 2400 2.84 3-8 2400 3.56 3-25 - 2400 4.67 4-12 - 1200 4.00 4-21 2400 3.01 3-9 2400 3.66 3-26 2400 4.72 4-12 - 1800 1.68 4-22 - 2400 3.13 3-10 2400 3.72 3-27 2400 4.77 4-12 2400 1.03 4-23 - 2400 3.26 3-11 2400 3.79 3-28 - 2400 4.82 4-13 0600 0.89 4-24 _ 2400 3.35 3-12 2400 3.86 3-29 2400 4.86 4-13 0800 0.52 4-25 2400 3.45 3-13 2400 3.93 3-30 2400 4.92 4-13 1000 0.71 4-26 - 2400 3.58 3-14 2400 4.04 3-31 2400 4.95 4-13 1200 0.82 4-27 2400 3.70 3-15 2400 4.11 4-1 2400 4.98 4-13 1800 1.04 4-28 2400 3.81 3-16 - 2400 4.18 4-2 2400 5.01 4-13 2400 1.15 4-29 2400 3.92 s-17 _ 2400 4.26 4-3 2400 4.85 4-20 _ 2400 4.03 TABLES 209 TABLE 9.-Specific conductance and temperature of samples at selected sites along the Intracoastal Waterway at the mouth of Mobile Bay, April 28-29, 1979 Stat ion Location Date Time Weather Depth Specific Water number 1979 (hours)| conditions (feet) conductance temperature (micromhos per (degrees centimeter) Celsius) 1 Marker 18 in Bon Secour April 28 1510 |Calm, warm, Surface 2,400 23.5 River near Mimi's clear 5 2,600 21.5 Restaurant 6 2,600 21.8 2 Post with staff gage in April 28 1500 |Calm, warm, Surface 2, 700 22.5 Bon Secour River out clear 5 2,900 21.5 from lower end of boat dock on right bank 3 Buoy 136 on Intracoastal April 28 1420 |Calm, clear, Surface 3,200 22.5 Waterway warm 5 3,200 22.0 10 3,200 22.0 12 3,200 21.5 4 State Hwy. 59 crossing April 28 1350 |Calm, warm, Surface 3,000 22.0 Intracoastal Waterway clear 5 3,000 22.0 10 3,000 22.0 12 3, 000 22.0 5 Buoy 147 on Intra- April 28 1320 |Calm, warm, Surface 3,200 22.5 coastal Waterway clear 5 3,200 21.5 10 3,200 21.5 14 3,200 21.5 6 Buoy 159 on Intracoastal April 28 1300 |Calm, warm Surface 2,900 21.5 Waterway--Mobile Bay clear 5 2,900 21.5 10 3,000 21.0 7 Buoy 167 on Intracoastal April 28 1255 |Calm, warm, Surface 2, 800 21.5 Waterway--Mobile Bay clear 5 2,8pN 21.5 6 2,850 21. 8 Buoy 175 on Intracoastal April 28 0915 |Calm, warm, Surface 1,700 21.5 Waterway--Mobile Bay clear 5 1,700 20.5 10 1,750 20.5 14 1,800 20.5 April 28 1245 |Calm, warm Surface 1,700 21.0 clear 5 1,750 21.0 8 1,750 21.0 9 Buoy 183 on Intracoastal April 28 0950 |Calm, warm, Surface 1,350 21.0 Waterway--Mobile Bay clear 5 1,350 20.5 10 1,400 20.5 12 1,400 20.5 9 April 28 1235 |Calm, warm, Surface 1,500 21.0 clear 5 1,500 21.0 8 1,500 21.0 9 April 29 1120 |Windy, cool, Surface 2,400 20.5 cloudy 5 2, 450 21.0 10 2, 400 21.0 13 2, 400 21.0 210 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 9.-Specific conductance and temperature of samples at selected sites along the Intracoastal Waterway at the mouth of Mobile Bay, April 28-29, 1979-Continued Station Location Date Time Weather Depth Specific Water number 1979 (hours )| conditions (feet) conductance temperature (micromhos per (degrees centimeter) Celsius) 10 Buoy 191 on Intracoastal April 28 1225 |Calm, warm, Surface 1, 300 21.0 Waterway--Mobile Bay clear 5 1, 300 21.0 f 8 1,300 21.0 11 Buoy 195 on Intracoastal April 28 1010 |Calm, warm, Surface 1,550 20.5 Waterway --Mobile Bay clear 5 1,500 20.5 10 1,600 2n.0 12 1,600 20.0 11 April 29 1030 |Windy, cool, 1,400 20.5 cloudy 5 1,400 20.5 10 1,400 20.0 14 1,400 20.0 12 Buoy 205 on Intracoastal April 28 1020 |Calm, warm, Surface 200 20.5 Waterway--Mobile Bay clear 5 200 20.5 10 200 20.0 11 200 20.0 12 April 29 0945 |Windy, cool, Surface 1,800 20.5 cloudy 5 1,800 20.5 10 1,800 20.5 14 1,800 20.5 13 Buoy 215 on Intracoastal April 28 1030 |Calm, warm, Surface 500 20.5 Waterway --Mobile Bay clear 5 500 20.5 10 600 20.0 12 600 20.0 14 Buoy 223 on Intracoastal April 28 1045 |Calm, warm, Surface 400 21.0 Waterway--Mobile Bay clear 5 400 20.5 10 500 20.5 13 600 20.0 15 Buoy 231 on Intracoastal April 28 1055 |Little windy, |Surface 250 20.5 Waterway Bay warm, clear 5 250 20.5 10 300 20.0 14 300 20.0 16 Between tower (oil April 28 1120 |Little windy, |Surface 300 20.0 derrick) at Dauphin warm, clear 5 300 20.0 Island and tower at Fort 10 300 20.0 Morgan on Intracoastal 15 2,000 19.5 Waterway Bay 20 40,000 20.5 25 41,000 20.5 30 43,000 20.5 35 45,000 20.5 17 2.2 Miles north of April 29 0955 |Windy, cool, Surface 150 19.5 Buoy 205 on Intracoastal cloudy 5 150 19.5 Waterway--Mobile Bay 10 150 19.5 11 150 19.5 18 2.2 Miles south of April 29 1015 |Windy, cool, Surface 2 , 200 20.0 Buoy 205 on Intracoastal cloudy 5 2,200 20.0 Waterway--Mobile Bay 10 2,250 20.0 TABLES 211 TABLE 9.-Specific conductance and temperature of samples at selected sites along the Intracoastal Waterway at the mouth of Mobile Bay, April 28-29, 1979-Continued Station Location Date Time Weather Depth Specific Water number 1979 (hours)| conditions (feet) conductance temperature (micromhos per (degrees centimeter) Celsius) 19 2.2 Miles north of Ruoy April 29 1040 |Windy, cool, Surface 200 20.0 195 on Intracoastal cloudy 5 250 20.0 Waterway--Mobile Bay 10 250 20.0 20 2.4 Miles south of Buoy April 29 1055 |Windy, cool, Surface 1,300 20.0 195 on Intracoastal cloudy 5 1, 300 20.0 Waterway--Mobile Bay 9 1,300 20.0 21 2.2 Miles north of April 29 1130 |Windy, cool, Surface 500 21.0 Buoy 183 on Intracoastal cloudy 5 550 20.5 Waterway--Mobile Bay 10 550 20.5 22 2.1 Miles south of April 29 1145 |Windy, cool, Surface 2,150 20.5 Buoy 183 on Intracoastal cloudy 5 2,200 20.5 Waterway--Mobile Bay 8 2,150 20.0 212 FLOODS OF APRIL 1979, MISSISSIPPI, ALABAMA, AND GEORGIA TABLE 10.-Aerial photographs obtained at or near the crest of the flood, April 1979 Flight line Date Flight 1/Type number April height or in figure 47 Stream and location 1973 (feet) film MOBILE RIVER BASIN Black Warrior River Basin 1-2 Black Warrior River, Oliver Lock and Dam at Tuscaloosa to Interstate Highway 59 at Fosters 14 3,000 B/W TOMBIGBEE RIVER BASIN 3-4 Tombigbee River, Cochrane to Epes 16 6,000 B/W 5-6 Noxubee River, Ala.-Miss. State line to mouth at Tambigbee River 16 6,000 B/W 7-19 Demopotis, confluence of Black Warrior and and Tombigbee Rivers 18 6,000 B/W ALABAMA RIVER BASIN 20-21 Alabama River, confluence of the Coosa and Tallapoosa Rivers to Jones Bluff Lock and Dan 16 8,500 B/W 22-31 Alabama River, Jones Bluff Lock and Dam to mouth of Cahaba River 18 6,000 B/W PEARL RIVER BASIN 32 Pearl River-Burnside (SR 15), Philadelphia (SR 19), Edinburg (SR 16), Carthage (SR 35), Wiggins (SR 13) 14 6,000 B/W 33-35 Pearl River-Ross Barnett Reservoir to Byram 16 5,000 B/W IR 36-38 Pearl River-Ross Barnett Reservoir to Byram 17 3,000 B/W IR 39-40 Pearl River-Ross Barnett Reservoir to Byram 17 12,000 B/W IR Al Pearl River-Byram, Rosemary, Moncure, Gatesville, Hopewell (all county highways); Georgetown (SR 28); Rockport (county highway); Wanilla (Illinois Central Railroad and county highway); Monticello (U.S. 8) 19 6,000 B/W IR 1/ B/W denotes black and white film. B/W IR denotes black and white infrared film. *#U.S. GOVERNMENT PRINTING OFFICE: 1986-491-409:40010 Palynology of Selected Coal Beds in the Proposed Pennsylvanian System Stratotype in West Virginia By ROBERT M. KOSANKE U_S.:. GEOLOGICAL SURVEY PROFESSIONAL PAXPEK 13 18 A description of palynomorph assemblages, range zones, and coal correlations of selected coals from the proposed Pennsylvanian System stratotype of West Virginia and adjacent States UNITED STATES GOVERNMENT PRINTING -OFFICE,.- WASHINGTON :- 1984 UNITED STATES DEPARTMENT OF THE INTERIOR WILLIAM P. CLARK, Secretary GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging in Publication Data Kosanke, Robert M. (Robert Max) Palynology of selected coal beds in the proposed Pennsylvanian System stratotype in West Virginia. (Geological Survey professional paper ; 1318) Bibliography: 44 p. Supt. of Docs. no.: I 19.16:1318 1. Palynology-West Virginia. 2. Paleobotany-Pennsylvanian. 3. Coal-Geology-West Virginia. I. Title. II. Series. QE993.K633 1984 561'.13'09754 83-600376 For sale by the Branch of Distribution, U.S. Geological Survey 604 South Pickett Street, Alexandria, V A 22304 CONTENTS Page Page Abstract 1 | Palynomorph assemblages-Continued Introduction fu 1 Middle Pennsylvanian Series ------------------------ 8 Previous work 3 Kanawha Formation -------------------------- 8 Acknowledgments 5 Charleston Sandston'e ————————————————————————— 15 Sample methods, preparation, and localities ---------------- 5 Upper Pennsylvanian Series oo ra t oes 21 s Conemaugh and Monongahela Formations --------- 31 Palynomorph assemblages from the proposed Pennsylvanian Palynomorph assemblages from part of the Pottsville Forma- stratotype section of West Virginia --------------------- 7 tion of Ohio and the Lee Formation of eastern Kentucky ---- _ 35 Upper Mississippian and Lower Pennsylvanian Series ---- 7 | Summary 39 Bluestone and Pocahontas Formations ------------ 7 | References cited - he 42 New River Formation ------------------------- 7 ILLUSTRATIONS Page FiGuURE op a m o eke po - TABLES - 1-19. 20-22. Location map for outcrop and mine samples, and proposed Pennsylvanian System stratotype --------------------- Diagram of Upper Mississippian and Lower Pennsylvanian Stratigraphic Units <-------<---<<------------------- Chart of abundance of dominant and ACCeSSOry G@M@A 2 3 Diagram of Middle and Upper Pennsylvanian Stratigraphit UMits 3 4 8 Stratigraphic section at Bluefield, West Virginia Stratigraphic section near Garwood, West Virginia --- 9 Generalized section of Pottsville FOMMtiOn, Ohi0 35 London dock section, Kentucky, and a generalized section for Sawyer quadrangle, Kentucky ---------------------- 40 Diagram showing occurrence of SeléCted taxa ------------------------_____________________-__________---- 41 TABLES Page Percentage of palynomorphs in West Virginia coals: 1. Sewell coal ~~~ ax 10 2. Lower DOuglas(?) COB 11 + s.. y " o i i e 12 4. Cedar Grove coal o Wet. e 13 5. Winifrede coal EC er abla acte -a ues. 14 6. Stockton coal as de. 16 7. Little No. 5 Block cool, series 5B 2 - --= -~ -- - a o ae > aes mee oo oo ce mee aco ms mm me on me or me e fea e r oe Sang na m m h me ne me me m me i as m e to noe en 18 8. Little No. 5 Block coal, series 484 ----------------------------------- 20 9. - Lower No. 5 Block coal, series 553 e Norm he fn on u a oe nine e n ca ne an an i o Sele He al e mes on Aune ss hn an 22 10. Lower No. 5 Block coal, series 485 a a eme ae fics Whe ae m ie be a ale mele ach oe 23 11. Lower No. 5 Block coal, series 446 Cenk steam 24 12. Upper No. 5 Block(?) coal, series 447 nemen el mane -n animais snes tos ank 26 13. Upper No. 5 Block coal, series 554 27 14. Upper No. 5 Block coal, series 572 =e, sess =s 28 15. Upper No. 5 Block coal, series 486 ------------------------ e 4% 5+ -' 80 16. Upper No. 5 Block coal, lower bench «ex hes Ae as % 32 17. Upper No. 5 Block coal, upper bench -- & a 33 18. No. 6 Block coal o 34 19. Pittsburgh No. 8 @O@l 34 Percentage of palynomorphs in Ohio coals: 20. Sharon No. 1 COB ----~-------~---=___ -- __ lolol cl 36 21. Anthony coal =s of 22. Quakertown No. 2 coal 38 HI PALYNOLOGY OF SELECTED COAL BEDS IN THE PROPOSED PENNSYLVANIAN SYSTEM STRATOTYPE IN WEST VIRGINIA By ROBERT M. KOSANKE ABSTRACT The usefulness of Pennsylvanian palynomorphs, spores, and pollen grains, as an aid in coal-correlation investigations in the Ap- palachians, has been known for many years. However, much of this and subsequent information was scattered in the literature or was not from the proposed stratotype area of West Virginia. Investigation of coals from sections of the proposed Pennsylvanian System stratotype provided the opportunity to examine changes in palynomorph con- tent through a number of coals from the New River Formation to the basal part of the Monongahela Formation. The rank of most coals of the Pocahontas and New River Forma- tions of West Virginia does not permit extraction of palynomorphs with current laboratory maceration techniques. Because of this, the data of some possibly equivalent lower rank Pennsylvanian coals from adjacent parts of southern Ohio and eastern Kentucky have been included. The coals examined from the Kanawha Formation, Charleston Sandstone, and Monongahela Formations of West Virginia have yielded abundant and well-preserved palynomorphs. Attention has been focused on the Charleston Sandstone, which is a massive, complex unit lacking marine fossils and composed primarily of sandstone. The coal is a significant resource in Pennsylvanian rocks, and the correlation of coals is an important consideration in the area of the stratotype in West Virginia and in adjacent States. As a result of this preliminary examination, the approximate range zones of some important taxa have been established. These range zones together with abundance data are used to correlate the coals. The range zones of some important taxa from Lower to Upper Penn- sylvanian coals are: Densosporites irregularis Hacquebard and Barss, Stenozonotriletes lycosporoides (Butterworth and Williams) Smith and Butterworth, Schulzospora rara Kosanke, Laevigatosporites spp., Radiizonates spp., Torispora securis Balme, Zosterosporites triangularis Kosanke, Thymospora pseudothiessenii (Kosanke) Wilson and Venkatachala, Schopfites dimorphus Kosanke, and Thymospora thiessenii (Kosanke) Wilson and Venkatachala. Some of the range zones are relatively short and extremely useful for correla- tion studies. For example, in the Charleston Sandstone, T. pseudo- thiessenii (Kosanke) Wilson and Venkatachala is present in the Upper No. 5 Block coal (upper bench) and the No. 6 Block coal, whereas Schopfites dimorphus Kosanke is restricted to the No. 6 Block coal. Thymospora thiessenii (Kosanke) Wilson and Venkatachala is not restricted to the Pittsburgh No. 8 coal, but it is the only coal known in which this taxon is so dominant (more than 70 percent of the palynomorph assemblage). This preliminary report has provided a framework for the correla- tion of a selected number of coals occurring in Ohio and eastern Ken- tucky with those of the proposed Pennsylvanian System stratotype of West Virginia In other studies, additional samples from the stratotype would be examined for ultimate correlation with rocks of Pennsylvania and in adjacent States and elsewhere. INTRODUCTION The need for a stratotype section of Pennsylvanian rocks has been indicated by boundary and correlation problems. Theoretically, an ideal stratotype section would contain a complete depositional sequence of rocks from oldest to youngest. This requirement was met in West Virginia despite the fact that the alternation of marine and nonmarine deposition does not extend throughout the stratotype section. The presence of widespread coals in the stratotype section suggested that palynomorphs have an important role to play in defining the stratotype. Many of the coals in West Virginia are exposed in the rocks of the proposed Penn- sylvanian System stratotype (fig. 1). Pennsylvanian rocks of the proposed stratotype section start with the Lower Pennsylvanian Series near Bluefield, W. Va., at the position of the Bramwell Member of the Bluestone Formation, and continue north-northwest through the Middle and Upper Pennsylvanian Series into the Dunkard Basin of northwestern West Virginia, south- eastern Ohio, and southwestern Pennsylvania. Although coal is abundant in West Virginia, not all of the coal is amenable to maceration because it is of high rank. Palynomorphs are altered by coalification from translucent to opaque entities in high-rank coal, so they have little value for palynological studies. Palyno- morphs in coals in the Pocahontas Formation and the lower half of the New River Formation generally appear to be in this category. Figure 2 illustrates some of the Lower Pennsylvanian strata from the stratotype examined for palynomorphs. Lower Pennsylvanian strata that may be in part equiv- alent to the lower part of the stratotype section occur in adjacent southeastern Ohio and eastern Kentucky. Coal 1 2 PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA in these two areas is of lower rank and is readily | some of these data to correlate with the stratotype sec- amenable to maceration, so that excellent assemblages | tion. These data are discussed subsequently under of palynomorphs were recovered. I decided to include palynomorph assemblages from Ohio and Kentucky. co &n 84° 83 82° 81° | | | / | -" A ey Vila—1:5 l/j " _ I 7 LLL J WEST VIRGINIA JACKSON | ~7f\ - 4 | -| OHIO 39° GALLIA f \ ©06023 ~ he" I ' I g sC. —\,L 7 y LAWRENCE f L/\ INDIANA / 7 * 06040 | 38 Déi12 10. \ [% péoso x>}D6036 f ‘> "1 pt FAYETTE | D6034 X D6113 x fix 3 | Dsus5 x D6115 xD6041 | x 035 D6111 xD6038 ©. x ae Cirratriradites sp =< £- == e- s x o= Crassispora kosankei (Potonié and Kremp) Bharadwaj X -- -- -- X Cristatisporites sp ---- =« he x ¥. & ae Densosporites annulatus (Loose) Schopf, Wilson, and Bentall --------<----------------- F o= re x ee D. sinuosus Kosanke ------------------- x x x x x D. spp -- - o-- -- X X -- -- Granulatisporites pallidus Kosanke -- 2+ X % a= - G. tuberculatus Hoffmeister, Staplin, and Malloy -- - - - =~ == xX & se G. cf. G. verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall ——————————————————————— e -- X =- X ? Laevigatosporites sp ke -% 3s x a> as Leiotriletes sp -- aix =< = ere x 22 Raistrickia sp -------- -- ew lke sree ag mu ss tl ha g e e i m e me nee aas s bu ot anos us me ae ar ie on ewe e me se 22 Ca E> x 28 Reinschospora speciosa (Loose) Schopf, Wilson, and Bentall ----------<---------~------ X X X -- -- Reticulatisporites sp - ag bre a+ he € Savitrisporites nux (Butterworth and Williams) Smith and Butterworth ------------------ -- -- X X -- Schulzospora rara Kosanke ## X 9 R e Spencerisporites sp <+ bre as fe ast Monosaccate xX xX Fe ws => DESCRIPTION OF MATERIAL IN MACERATIONS 4831-A, 8.9 cm roof shale. 431-B, 35.5 cm coal (weathered). 431-C, 35.5 em coal (weathered). 431-D, 431-E, 35.5 em coal (weathered). 8.9 em seat rock. PALYNOMORPH ASSEMBLAGES FROM PENNSYLVANIAN STRATOTYPE 11 by Smith and Butterworth (1967), and by Clayton and others (1977). Gillespie and Pfefferkorn (1979), based on their studies of plant megafossils, placed the Westphalian A-B boundary just above the Sewell coal bed in the New River Formation, somewhat below the Gilbert coal. Procoronaspora sp. and Stenozonotriletes bracteolus are not abundant, and only a few specimens have been identified. The top of their stratigraphic range in Europe is reported by Smith and Butterworth (1967) to be in the upper half of the Namurian; definite information about its range in the United States is lack- ing. Additional samples from this part of the proposed Pennsylvanian System stratotype should be investi- gated in order to provide a better understanding of these taxa. The Cedar Grove coal from the type locality in the Cedar Grove quadrangle is not a part of the proposed Pennsylvanian System stratotype. The Cedar Grove coal occurs about in the middle of the Kanawha Forma- tion (fig. 3, samples of macerations 122-A-D). Three coal samples were collected (table 4). Densosporites is the dominant taxon in the coal samples (122-A-C) as TABLE 2.-Palynomorphs from the Lower Douglas(?) coal bed in West Virginia [Maceration series 432; USGS Paleobotanical loc. No. D6032; 750 specimens counted; X, present but not observed in count] Taxon 432-A 432-B 432-C (percent) Ahrensisporites guerickei (Horst) Potonié and Kr@Mp -- 0.8 X Calamospora hartungiana Schopf in Schopf, Wilson, and Bentall ------------------ -- -- 0.8 C. parva Guennel 1.2 -- 1.6 C. sp --- 5s i" 2.4 a 1.6 Convolutispora florida Hoffmeister, Staplin, and Malloy -- -- --- -- 8 -- Crassispora kosankei (Potonié and Kremp) Bharadwaj - -- 1.2 2.4 -- Cristatisporites sp A -- -- Densosporites annulatus (Loose) Schopf, Wilson, and Bentall -------<<<---<--------------------~- 9.2 37.6 -- D. spp - wes ap 2.0 #. &' Dictyotriletes castaneaeformis (Horst) Sullivan -- 1.2 -- -- D. bireticulatus (Ibrahim) Potonié and Kremp 4 -~ -= Endosporites sp ----- --- --- -- -- .8 Florinites sp -------------- _-_-_---------- - -- -- X Granulatisporites pallidus KO8@RKke 4.4 .8 1.6 G. verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall -- -- 5.6 .8 1.6 G. spp -- ---- - 8.4 .8 2.4 Knoxisporites triradiatus Hoffmeister, Staplin, and Malloy - --- 1.6 -- -- Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall ---------------------------- -- f .8 L,. I@tUus KOS§@MKke -- X 8 L. OValis 4.0 4.0 6.4 L. sp -- A -- -- Lophotriletes cf. L. gibbosus (Ibrahim) Potonié and Kremp 1.2 -- -- Lycospora granulata Kosanke A -- .8 Lycospora micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall ---- A 1.6 8.8 L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata KOS@Ake ---------------------------- 22.4 12.8 25.6 Tispp- -_- -- 2g =A ovo 1 344. 384 Raistrickia prisca Kosanke ------ -- X -- R. SDPp A 1.6 8 Savitrisporites nux (Butterworth and Williams) Smith and Butterworth X -- -- Stenozonotriletes bracteolus (Butterworth and Williams) Smith and Butterworth -------------------------- A -- -- Triquitrites sp 4 Re 3a Wilsonites sp -- -- .8 Monosaccate -- 3.2 1.6 5.6 Unassigned - 1.6 Total 100.0 100.0 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 432-A, 432-B, 432-C, 7.6 em roof rock. ° 7.6 em coal. 10.8 cm coal-bone. 12 PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLV ANIAN STRATOTYPE, WEST VIRGINIA shown in the summary of most abundant taxa: Densosporites 40.5 percent Granulatisporites 6.0 Laevigatosporites 25.83 Lycospora 20.2 92.0 percent Laevigatosporites is second in abundance to Den- sosporites with 25.3 percent of the assemblage. This is significantly higher than the 5 percent recorded for Laevigatosporites in the Gilbert(?) coal below. The presence of L. ovalis accounts for much of the increase in abundance of the genus. Although Densosporites is the dominant taxon, especially in 122-B, many of the specimens are poorly preserved and identification to the species level is impossible. Poor preservation is also noted for Lycospora, which accounts for 20.2 percent of the assemblage. Accessory taxa of the Gilbert(?) coal, Procoronaspora, Stenozonotriletes, and Schulzospora are not present in these samples of the Cedar Grove coal from the type locality. Acanthotriletes cf. A. echinatus (Knox) Potonié and Kremp, Punctatisporites obesus (Loose) Potonié and Kremp, and P. sinuatus (Artuz) Neves are present in limited numbers. The Winifrede coal, in the upper half of the Kanawha Formation (fig. 3), was collected from the type locality in the Belle quadrangle and assigned to maceration 121 (table 5). This locality is considered to be outside the geographic area of the stratotype. Laevigatosporites is clearly the dominant taxon for the first time strati- graphically, with one-half the assemblage assigned to this genus in coal samples 121-A-B and D-E as follows: Densosporites 9.0 percent Granulatisporites 12.3 Laevigatosporites 51.6 Lycospora 217 84.6 percent Laevigatosporites globosus Schemel is an important member of the assemblage inasmuch as it represents 24.2 percent of the population of the coal samples. In the clay parting (No. 121-C), L. globosus Schemel represents 65.6 percent of the assemblage. This taxon is an important member of many younger Pennsylvanian coal assemblages in the United States. Seven species of Laevigatosporites are present in this set of samples of TABLE 3.-Palynomorphs from the Gilbert(?) coal bed in West Virginia [Maceration series 433; USGS Paleobotanical loc. No. D6033; 500 specimens counted; X, present but not observed in count] Taxon 433-A 433-B 433-C (percent) Calamospora ¢f. C. liquida KOS@MK@ X 2.4 -- C. parva Guennel X 1.6 -- C. Sp -- -- -- Densosporites annulatus (Loose) Schopf, Wilson, and Bentall ---------------------------------_--_-_--_---- 28.8 .8 -- D. triangularis KOS@MK@ X -- -- D. Sp -- 2.4 -- Granulatisporites pallidus KOS@NKke X 1.6 -- G. Sp .8 2.4 -- Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall ---------------------------- 1.6 -~ -- L. latus KOS@Ake ----------------------- 1.6 -- -- L. OValis KOS@MK@ 5.6 .8 -- LOPhOtrilete@$ Sp -- 3.2 -- Lycospora granulata KOS@NKG .8 2.4 «- L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulat@a KOS@nke --------<------------------- 23.2 19.2 X L. spp ------ 30.4 53.6 X Sp -----------------------_--__-__----- --- .8 2.4 -- PUMCtAtISPOMIt@S SDD 3.2 4.0 X Raistrickia Sp ----------------- ---- X -- ~~ Schulz08pOra rara KOS@MAKG 2.4 1.6 -- Stenozonotriletes bracteolus (Butterworth and Williams) Smith and Butterworth --------------------~------ X f -- .8 1.6 -- Total -- rat ere an ege io cep i on. c elin i se als ada nepal of a mia ia he dee ara an ae a a in Pr s 100.0 - 100.0 _ 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 433-A, 433-B, 433-C, 22.2 em coal. 22.2 em coal. 7.6 em seat rock. PALYNOMORPH ASSEMBLAGES FROM PENNSYLVANIAN STRATOTYPE 13 the Winifrede coal (table 5). The primary differences be- tween the Winifrede and Cedar Grove coals, from their respective type localities, are the presence of L. globosus Schemel and the dominance of Laevigato- sporites in the Winifrede coal (see tables 4 and 5). The Stockton coal, in the upper part of the Kanawha Formation (fig. 3), contains a parting similar to the Winifrede coal; this is shown in tables 5 and 6. Samples of the Stockton coal were collected from the Valley Camp Coal Company mine located north of Mammoth, W. Va., and assigned to macerations 566-A-G. Two im- portant genera, Radiizonates and Torispora, are present TABLE 4.-Palynomorphs from the type locality of the Cedar Grove coal bed in West Virginia [Maceration series 122; USGS Paleobotanical loc. No. D6035; 1,000 specimens counted; X, present but not observed in count] Taxon 122-A 122-B 122-C 122-D (percent) Acanthotriletes cf. A. echinatus (Knox) Potonié and Kremp -- e -- 12 0.4 Ahrensisporites sp ---- ---- -- 1.2 X 4 Apiculatisporis sp - --- -- --- -- 0.4 -- -- Calamospora breviradiata Kosanke - ---- --- 1.6 -- -- <- C. 8p ------------------_-__-_________- 0.4 A -- -- Cirratriradites maculatus Wilson @Ad CO@ -----------------------________________________--- A -- A .8 Convolutispora sp -- -- ---- -- -- X -- Crassispora kosankei (Potonié and Kremp) Bharadwaj -- <--- -- -- A -- Cristatisporites spp ---- 2.0 2.4 1.2 .8 Densosporites annulatus (Loose) Schopf, Wilson, and Bentall ---------------------------------- ~- -- 4.4 ~- D. sphaerotriangularis Kosanke -------- 4 1.6 A 4 D. triangularis Kosanke -- a ~- 1.6 3.2 -- D. SDp -------------------- ---- 3.2 76.8 29.2 4.4 Dictyotriletes bireticulatus (Ibrahim) Potonié and Kremp -------------------------------____--- 1.6 A 1.6 A D. castaneaeformis (Horst) Sullivan seco mene snene ann n nn arn me nm nmn mme mmm nemen as -- -- -- K Endosporites cf. E. globiformis (Ibrahim) Schopf Wilson, and Bentall --------------------------- A -- -- .8 Florinites antiquus Schopf in Schopf, Wilson, and Bentall ------------------------------------- -- A -- .8 F. Sp -- -- .8 -- Granulatisporites pallidus Kosanke -- 2.0 8 2.0 1.6 G. verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall ----------------------------------- .8 -- -- A G. SDP 3.6 3.6 4.8 9.2 KnOXiSPOrItes Sp .8 -- -- -- Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall -------------------- 3.6 -- 1.2 -- L. latus Kosanke ------ ---- -- -- X -- L. medius Kosanke --------- 2.8 .8 2.4 .8 L. ovalis Kosanke ---- 37.6 8.2 18.0 9.6 L. vulgaris (Ibrahim) Alpern and Doubinger ------------- ---- -- --- 2.0 X 6.4 -- Lycospora granulat@ KOS@MAKk@ 2.8 A 9.6 6.0 L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke -------------------- 18.8 A 10.4 12.0 L. SDD ------------------_--__---____- 8.4 2.0 A 44.0 Punctatisporites obesus (LOOSe) POtONIG @Ad Kr@Mp -------------------------_--_____________- -- -- .8 A P. SINUatus Neves -- ~- X s PBa cy -_ _sclle ap desde 2.8 2.4 .8 2.0 RQiStricRki@ Sp ----------------------- he le wag me he ra m e u m m han s ie an tn r he aie te ve ce a es eee x x x se ReticUul@tiSPOrites SD -- -- -- .8 Savitrisporites nux (Butterworth and Williams) Smith and Butterworth -------------------------- -- -- -- X Simozonotriletes intortus (Waltz) POtORIG @Ad Kr@Mp -- -- X s Vestispora sp -------- --- -- -- X -- Wilsonites delicata (KOSANKe) KOS@MAK@ 1.2 A A A ------------------------ 2.4 .8 -- 3.6 Unassigned --- --- A -- -- -- frotal --- o eee ras sn % 1090.0. 100.0 100.0 1060.0 DESCRIPTION OF MATERIAL IN MACERATIONS 122-A, 26.7 em coal. 122-C, 32.8 cm coal. 122-B, 27.8 cm coal. 122-D, 12.7 em seat rock. 14 PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA TABLE 5.-Palynomorphs from the type locality of the Winifrede coal bed in West Virginia [Maceration series 121; USGS Paleobotanical loc. No. D6035; 1,250 specimens counted; X, present but not observed in count] Taxon 121-A 121-B 121-C 121-D 121-E (percent) Acanthotriletes cf. A. echinatus (Knox) Potonié and Kremp =m 2.0 0.4 0.4 0.4 0.4 Apiculatisporis sp -~ 1.2 -- a .8 Calamospora breviradiata Kosanke -- --- -- 2.0 -- 1.6 X C. hartungiana Schopf in Schopf, Wilson, and Bentall --------------------------------- -- A -- A A C. sp -- -- A -- -- -- Cirratriradites maculatus Wilson and Coe ---- -- -- -- A .8 SD -- X -- -- x Crist@tiSPOMIt@S SD -- A -- A X Densosporites annulatus (Loose) Schopf, Wilson, and Bentall -------------------------- 9.2 6.4 -- -- -- D. sphaerotriangularis Kosanke - -- A -- -- -- -- D. triangularis Kosanke -- 1.2 ~- X 5.6 A D. SDD ccc cc e 3.6 1.2 7.2 27.6 3.2 Dictyotriletes bireticulatus (Ibrahim) Potonié and Kremp ----------------------------- -- .8 s -- .8 Endosporites ornatus WilsON @Ad CO@ ----------------____________________________-- X X -- -- X E. globiformis (Ibrahim) Schopf, Wilson, and Bentall --------------------------------- X -- -- -- 1.2 E. sp -- -- -- A -- -- Florinites antiquus Schopf in Schopf, Wilson, and Bentall ----------------------------- .8 A -- -- A F. triletes Kosanke ---- _-_ccccc__c______~ X -- -- -- -- F. Sp -- -- -- ~- X Granulatisporites pallidus Kosanke ---- .8 9.2 ~- -- 4.0 G. spp ---- -- - -- ---- 1.2 15.2 1.2 3.6 14.0 Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall ------------- 1.6 -- A A A L. globosus Schemel -------------- ---- 17.2 27.2 65.6 36.0 18.0 L. latus Kosanke -- ---- ---- .8 .8 -- -- -- L. medius Kosanke --- 1.6 2.0 .8 A 1.6 L. minutus (Wilson and Coe) Schopf, Wilson, and Bentall ------------------------------ 10.4 4.4 11.2 3.6 6.4 L. ovalis Kosanke --- --- -- -- 24.8 10.4 8.4 6.4 13.2 L. vulgaris (Ibrahim) Alpern and Doubinger ---------------------- ---- -- 4.8 2.8 .8 3.2 1.6 LycospOr@ KOSAMKG 5.2 12 -- .8 3.6 L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall ------------------------- 4A -- -- 1.6 -- L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke ------------ A 2.4 A .8 8.0 -- > yee 10.0 3.6 &. 2.4 6.8 Punctatisporites obesus (Loose) Potonié and Kremp ---------------------------______- -- -- -- A X P. sinuatus (Artuz) Neves -= w h m a on me us ae me a a moe ae as n a a sa a sn ae t ae eae a an X s e += <= P. spp -- ---- o 2.0 8.2 2.8 2.0 6.8 Raistrickia sp --- - -- -- -- -- -- A 1.6 Reticulatisporites sp -- A -- -- A .8 Savitrisporites nux (Butterworth and Williams) Smith and Butterworth ------------------ -- -- -- -- 2.0 Triquitrites cf. T. pulvinatus Kosanke ----- h X -- -- -- T. sculptilis Balme -- -- A -- X X T. $p -----<-----<-----_- __ ccc oren nen emm eee enemee nme mmm nnn nmn nm mensen ene. -- .8 A -- .8 Verrucosisporites sp ----------- -- A -- -- X Wilsonites cf. W. vesicatus (Kosanke) Kosanke -- ---- A -- -- -- -- e ime o i coe Ez x as x x MONOSACCAt@ .8 2.4 -- 12 2.0 Total --- ---- 100.0 100.0 100.0 100.0 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 121-A, 40.6 cm coal. 121-D, 24.1 cm coal. 121-B, 40.6 cm coal. 121-E, 22.9 cm coal. 121-C, 10.2 em parting (clay). PALYNOMORPH ASSEMBLAGES FROM PENNSYLVANIAN STRATOTYPE 15 in this coal that help differentiate the Stockton from the Winifrede coal below. Laevigatosporites and Lycospora are the most abundant taxa in the coal samples (566-A-C and E-F): Densosporites 11.4 percent Laevigatosporites 30.2 Lycospora 30.7 Radiizonates 12.5 84.8 percent The presence of Radiizonates in the coal samples at the rate of 12.5 percent is of interest because it was not observed in the Winifrede coal below. Radiizonates tenuis (Loose) Butterworth and Smith in Butterworth and others (1964) and R. cf. R. faunus (Ibrahim) Smith and Butterworth contribute significantly to this per- centage as well as specimens assigned to R. sp. Radiizonates is also present in many of the block coals of the Charleston Sandstone as shown in tables 7-18. Kosanke (1973) reported Radiizonates present in the Richardson-Skyline coals from their respective type localities in eastern Kentucky. Torispora is present only in the top coal sample (566-A), but not in sufficient abundance to occur in the abundance counts. Trihyphaecites triangularis Peppers was originally described from the Carbondale Formation of Illinois and has been identified from the Stockton coal (566-C). This is an unusual taxon because it is considered to be of fungal origin and produces septate hyphae at each of its three corners. I have also identified this taxon from several coals in eastern Kentucky including the Whitesburg, Fire clay rider, and Francis, all from the Breathitt Formation. CHARLESTON SANDSTONE The terminology employed by Englund and others (1979) for stratigraphic units previously included in the Allegheny Formation is used in this report. Additional modifications suggested by T. W. Henry (written commun., 1980) and by H. H. Arndt (oral commun., 1981) have helped to interpret the palynomorph data and to better utilize the stratigraphic and palynomorph data in an effort to understand the geologic history of the Charleston Sandstone. The samples from the Charleston Sandstone are from exposures, mines, and diamond drill holes in the vicinity of Charleston, Kanawha County, W. Va. The coals ex- amined are the Stockton A, Little No. 5 Block, Lower No. 5 Block, Upper No. 5 Block, and the No. 6 Block coal. Arndt (1979) summarized the geology of the Charles- ton Sandstone. From this summary and from field work it is clear that the coals of the Charleston Sandstone were deposited without marine deposition having oc- curred between the coals; terrestrial deposition followed by marine deposition did not occur in the area of the stratotype. The possible influence of this type of deposi- tion on the palynomorph assemblages is potentially great. The Stockton A coal (maceration series 571) occurs a short distance above the Kanawha black flint. Palyno- morphs are abundant and well preserved in the Stockton A coal, especially in sample 571-A. In this sample Lycospora is most abundant, and Laevigato- sporites and Emdosporites are well represented. Also, Florinites, Raistrickia, Verrucosisporites, Cyclograni- sporites, Crassispora, Densosporites, Cirratriradites, Acanthotriletes, Wilsonites, and Spackmanites have been identified in this sample. Spackmanites has not been identified from older coals in this study. Torispore securis Balme, which is present in one sample of the Stockton coal (566-A) of the Kanawha Formation, has not been identified in the samples of the Stockton A coal. The Little No. 5 Block coal (macerations 552-A-G and 434-A-H) was examined for palynomorphs. Sam- ples for macerations 552-A-G were collected from a highwall of the Harewood strip mine located east of Car- bondale, Fayette County, W. Va. The taxa identified and their abundance are shown in table 7. The dominant and accessory genera are shown on figure 4. The coal samples yielded abundant and well-preserved paly- nomorphs, but neither the roof nor seat samples yielded sufficient palynomorphs to make abundance counts worthwhile. The most abundant genera in the Little No. 5 Block coal (552-B-F) are as follows: Densosporites 10.5 percent Laevigatosporites 35.5 Lycospora T1 Torispora 14.1 Radiizonates 76.7 percent Laevigatosporites is the most abundant genus, and eight species have been identified (table 7). Laevi- gatosporites is, in a large measure, uniformly abundant in all the coal samples. Densosporites, especially D. triangularis Kosanke, is numerically important in two coal samples (552-C-D). Torispora securis Balme is the most abundant in the three coal samples (552-B-D), whereas Radiizonates tenuis (Loose) Butterworth and Smith in Butterworth and others is abundant only in 16 PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA one coal sample (552-E). Lycospora is numerically im- portant only in the bottom coal sample (552-F). Preser- vation of specimens assignable to Lycospora is poor and a number of these specimens could not be identified to the species level, especially in the bottom coal sample (552-F). What I have classified as L. pellucida-L. pseudonnulata in table 7 is most abundant. The second set of samples taken from the Little No. 5 Block coal (maceration 434-A-H) were collected from the Semet-Solvay mine at Harewood northeast of Boomer, Montgomery quadrangle, Fayette County, W. Va. Analyses of these samples are shown in table 8 and on figure 4, and they are very similar to the other set of Little No. 5 Block coal samples (552-A-G) except for the leader coal sample (434-H). The same species of Laevigatosporites are present in the leader coal in approximately the same abundance, but Lycospore represents nearly 50 percent of the assemblage. Lycospora is present at the rate of only 11.5 percent in the main part of the coal (434-A-E) as shown: Densosporites 3.9 percent Laevigatosporites 36.1 Lycospora 11.5 Radiizonates 15.3 Torispora 21.0 87.8 percent Radiizonates and Torispora are greatly reduced in the leader coal (434-H), as shown in table 8. Stratigraphic and palynological evidence suggests an equivalence be- tween these two samples of the Little No. 5 Block coal (maceration series 552 and 434). Spencerisporites gracilis (Zerndt) Winslow has not been found below the Little No. 5 coal (434-B). This is of interest because Winslow (1959) reported that the old- est occurrence of this taxon in Illinois was the upper part of the Tradewater Group, a term no longer used in TABLE 6.-Palynomorphs from the Stockton coal bed in West Virginia [Maceration series 566; USGS Paleobotanical loc. No. D6036; 1,750 specimens counted; X, present but not observed in count] Taxon 566-A 566-B 566-C 566-D 566-E 566-F 566-G (percent) Apiculatisporites sp -- -x -- -- i o 0.8 -- Calamospora breviradiata Kosanke - 1.6 -- X X -- .8 -- C. hartungiana Schopf in Schopf, Wilson, and Bentall ----------------- -- -- -- X X .8 xX C. parva Guennel ---- -- -- -- -- 1.6 X 2.4 2.4 C. pedata Kosanke -------- -- -- -- -- -- 8 -- Csp mec. sct ce o i." ous =% 0.8 0.8 *s a> az Cirratriradites maculatus Wilson and Co@ -------------------------- -- -- -- -- -- 8.2 -- C. Sp -------------- 0.8 -- .8 X X .8 X SD ------------------__________ccc_c_cccc_______- _- 0.8 -- -- -- 1.6 -- Crassispora kosankei (Potonié and Kremp) Bharadwaj ---------------- e ~- 1.6 -- 2.4 4.0 0.8 Densosporites annulatus (Loose) Schopf, Wilson, and Bentall ----------- -- 1.6 -- -- -- 1.6 .8 D. sphaerotriangularis KOS@Ake ------------------________________- X -- -- f ~- <- -- D. triangularis Kosanke -- 4.0 20.8 .8 a -- -- -- ec in then one 7.2 _.. Tie 8." a se 3 Dictyotriletes bireticulatus (Ibrahim) Potonié and Kremp -------------- .8 X -- -- -- .8 X Endosporites ornatus Wilson and Coe ---- - X X -- X -- -- -- E. sp ------------ X -- -- -- X -- -- Florinites antiquus Schopf in Schopf, Wilson, and Bentall ------------- -- -- .8 2.4 X -- .8 Granulatisporites verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall -- -- -- -- -- -- 1.6 1.6 8 G. SDD ---------------------- ---- X -- 1.6 4.0 3.2 -- 8.2 Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall -- 5.6 1.6 1.6 1.6 -- 1.6 8 L. globosus Schemel ------------- - 5.6 11.2 8 8.2 -- 8.2 8 L. latus Kosanke --------------- - i X -- -- 1.6 X 1.6 L. medius Kosanke ------------ 2.4 .8 4.0 1.6 3.2 4.0 4.0 L. minutus (Ibrahim) Schopf, Wilson, and Bentall -------------------- 4.0 13.6 4.0 4.0 3.2 3.2 1.6 L. ovalis Kosanke 12.8 4.8 8.8 7.2 1.6 10.4 15.2 L. punctatus Kosanke s 4.8 13.6 -- 1.6 -- ~- -- L. vulgaris (Ibrahim) Alpern and Doubinger ------------------------- -- .8 -- .8 ~- -- .8 Leiotriletes sp f -- 8 f -- X 1.6 Lophotriletes spp 1.6 X -- 1.6 3.2 -- -- PALYNOMORPH ASSEMBLAGES FROM PENNSYLVANIAN STRATOTYPE 17 Illinois. Its rocks are now called the Spoon Formation. The presence of S. gracilis in the Little No. 5 coal may indicate approximate equivalence with the Illinois occurrence. Torispora securis Balme is a prominent taxon of the assemblages of the Little No. 5 Block and the Lower No. 5 Block coals of West Virginia. Torispore was pro- posed by Balme (1952) for spores that were basically elliptical in proximo-distal orientation, and distinctly monolete, with a pronounced thickening at one extremi- ty of the spore that may be expanded into a crescentic or rectangular projection. The outer layer of some sporangia contains specimens of Torispore securis Balme, which Horst (1957) considered were sporangial cells. For these Horst proposed the binomial Bicoloria gothanii Horst. Because Horst considered these to be sporangial in origin he did not recognize the presence of any proximal apertures. Subsequently, Doubinger and Horst (1941) emended the genus Torispore and recognized the presence of various types of proximal apertures. Guennel and Neavel (1961) summarized the development of Torispora and recognized Bicoloria for intact sporangia and Torispora for isolated dispersed spores. I have observed these peculiar thickenings on specimens I would identify with a number of monolete taxa, and in one instance on a trilete palynomorph. It is not relevant to this paper to be concerned with the proper classification of Torispore securis except to recognize that the range zone does not necessarily repre- sent the range zone of an individual taxon, but rather a collection of taxa that possess thickenings. I prefer to regard Torispora as representing a monolete taxon with a thickened condition that occurred on certain paly- nomorphs for a period of geologic time. Torispora is present in coals of the proposed Pennsylvanian System stratotype from near the top of the Kanawha Formation through the Charleston Sandstone. It should be noted that the abundance of Torispora varies greatly, ranging TABLE 6.-Palynomorphs from the Stockton coal bed in West Virginia-Continued [Maceration series 566; USGS Paleobotanical loc. No. D6036; 1,750 specimens counted; X, present but not observed in count] Taxon 566-A 566-B 566-C 566-D 566-E 566-F 566-G (percent) Lycospora granulata Kosanke 1.6 -- 22.4 8.0 0.8 8.0 14.4 L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall ————————— -- -- 4.0 5.6 16.8 .8 4.0 L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata KOS@Nk@ --------------------------- -- -- -- 2.4 16.0 10.4 8.0 10.4 L. punctata Kosanke --------- - -- -- .8 2.4 4.8 2.4 3.2 L. SDP ------------<---------- -- .8 2.4 26.4 28.8 36.0 23.2 28.0 Microreticulatisporites cf. M. concavus Butterworth and Williams ------ X -- -- -- -- -- M. sulcatus (Wilson and Kosanke) Smith and Butterworth ------------- -- -- X 1.6 1.6 -- -- Punctatisporites spp ------------- -- -- 3.2 1.6 .8 .8 .8 Raistrickia sp ------ -- 8 .8 .8 -- -- -- Radiizonates tenuis (Loose) Butterworth and Smith in Butterworth and Others 1964 ------------------__________-__-_________-_---- 8.8 -- 1.6 -- -- .8 -- R. cf. R. faunus (Ibrahim) Smith and Butterworth -------------------- 7.2 f -- f -- .8 -- R. Sp ----------------------- -- 29.6 4.8 7.2 .8 -- 8.2 1.6 Torispora securis Balme - X -- f -- -- -- -- Trihyphaecites triangularis Peppers -- -- X -- -- -- -- Triquitrites crassus Kosanke -- -- X -- -- .8 .8 T. sculptilis Balme -- X -- -- 2.4 -- -- .8 T. sp ---- -- - - -- .8 -- -- -- .8 -- Verrucosisporites sifati (Ibrahim) Smith and Butterworth ————————————— .8 2.4 -- X X: -- -- V. 8p -- -- -- X -- 1.6 -- Vestispora costata (Balme) Spode in Smith and Butterworth ----------- -- -- .8 -- -- 3.2 -- V. fenestrata (Kosanke and Brokaw) Spode in Smith and Butterworth ---- -- -- .8 -- 4.8 .8 -- V. cf. V. magna (Butterworth and Williams) Smith and Butterworth ----- -- -- -- -- -- .8 -- V. sp - - -- -- .8 -- .8 2.4 .8 Monosaccate --- -- .8 1.6 1.6 2.4 -- -- UNASSIgMed -- .8 -- -- .8 -- -- Total 100.0 100.0 100.0 100.0 100.0 100.0 _ 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 566-A, 30.5 cm coal. 566-E, 26.17 cm coal. 566-B, 30.5 cm coal. 566-F, 26.17 cm coal 566-C, 30.5 cm coal. 566-G, 15.2 em seat rock. 566-D, 38.1 cm parting. 18 PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLV ANIAN STRATOTYPE, WEST VIRGINIA from zero to 31 percent in adjacent levels of the same coal (434-D-E). The Lower No. 5 Block coal (macerations 553-A-E) occurs approximately 18 m above the Little No. 5 Block coal (macerations 552-A-G) in the highwall of the Harewood strip mine, east of Carbondale, Fayette County, W. Va. The coal at this locality is 91.2 em thick. Three equal coal samples were taken in addition to the roof and seat rock samples (table 9). Laevigatosporites is codominant with Torispora; both occur at the rate of 32 percent in the coal samples (553-B-D) as shown: Densosporites 9.6 percent Laevigatosporites 32.2 Lycospora 3.8 Radiizonates 9.2 Torispora 87.5 percent Densosporites and Radiizonates occur at about the same rate as they occur in the Little No. 5 Block maceration series (552). Lycospora decreased in abun- dance to less than 4 percent, largely because it was almost absent from the upper part of these samples of the Lower No. 5 Block coal. Crassispora kosankei (Potonié and Kremp) Bharadwaj reached 7.6 percent abundance in the bottom coal sample (553-D). Zos- terosporites triangularis Kosanke is present in very limited quantities in part of the Lower No. 5 Block coal (macerations 553-A-B)., A second set of the Lower No. 5 Block coal (macer- ation series 435) was collected from the Semet-Solvay strip mine located east of Smithers, Fayette County, W. Va. The coal at this locality is somewhat thicker than that sampled for the previous set of Lower No. 5 Block coal samples (553-A-E); the palynological analyses are given in table 10. The dominant and ac- TABLE 7.-Palynomorphs from the Little No. 5 Block coal bed in West Virginia, series 552 [Maceration series 552; USGS Paleobotanical loc. No. D6038; 1,250 specimens counted; X, present but not observed in count] Taxon 552-A 552-B 552-C 552-D 552-E 552-F 552-G (percent) Alatisporites hexalatus Kosanke -----------------_________________ -- -- 0.8 -- -- -- -- A. triglatus --------------________________c_c_c__________ -- -- -- -- X -- -- ApiCUIQtiSPOPIt@S SD -- -- -- -- 0.4 -- -- Calamospora breviradiata KOS@AKk@ -------------------_____________ -- -- -- -- -- 0.8 -- C. hartungiana Schopf in Schopf, Wilson, and Bentall ----------------- -- -- -- -- X -- -- C. parva Guennel -- -- -- -- X .8 X C. Sp -- 1.6 .8 -- 2.4 A -- Cirratriradites annulatus Kosanke --------------_-__________________ -- 1.2 X 0.4 .8 A -- Crassispora kosankei (Potonié and Kremp) Bharadwaj ---------------- -- 0.4 -- -- A 1.6 <- Cristatisporites indignabundus (Loose) Potonié and Kremp ------------ -- A -- -- -- -- f Densosporites annulatus (Loose) Schopf, Wilson, and Bentall ----------- -- A -- -- -- -- -- D. sphaerotriangularis -----------------________________- -- -- -- 2.4 -- -- -- D. triangularis ----------------________________________- X -- 10.4 9.2 ~- -- -- D. SDD X 2.0 16.8 9.2 2.4 -- -- Dictyotriletes bireticulatus (Ibrahim) Potonié and Kremp -------------- -- -- 1.6 X A -- -- Endosporites ornatus Wilson and Coe - X 4 -- -- -- A -- Florinites antiquus Schopf in Schopf, Wilson, and Bentall ------------- -- ~- -- X A 1.2 -- Granulatisporites pallidus KOS@AKk@ ------------------------------- -- -- -- -- 1.2 1.2 -- Granulatisporites verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall -------- -- -- 1.2 -- -- -- «-- -- G sp sem -s - cel ete ec --f #2 1.2 2.4 3 2.8 4 <3 Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall -- 2.0 -- .8 2.8 3.2 -- L. globosus Schemel -- 5.6 6.4 8.0 2.8 5.6 -- L. I@tUs KOS@MK@ -- A -- -- A -- -- L. medius Kosanke <<------------ X 4.0 4.0 2.8 1.6 1.6 -- L. minutus (Ibrahim) Schopf, Wilson, and Bentall -------------------- X 9.2 8.0 9.2 6.8 8.0 f L. ovalis Kosanke -- -- X 15.6 13.6 8.4 9.6 20.4 -- L. punctatus Kosanke -- -- --- ---- -- A -- 8.2 9.6 .8 -- L. vulgaris (Ibrahim) Alpern and Doubinger ------------------------- -- -- a -- 1.6 .8 -- Lycospora granulate Kosanke ---- -- 1 .6 X -- .8 3.2 <- PALYNOMORPH ASSEMBLAGES FROM PENNSYLV ANIAN STRATOTYPE 19 cessory genera are given on figure 4. These analyses are similar to those of the Lower No. 5 Block coal already discussed (maceration series 553), although minor dif- ferences exist. For example, in the coal samples of maceration series 435, Laevigatosporites and Lycospora are more abundant and Torispore is somewhat less abundant than in the coal samples of maceration series 553. Once again, Zosterosporites triangularis Kosanke and Crassispora kosankei (Potonié and Kremp) Bharadwaj are present, the latter species constituting 8 percent (435-B). Another set of Lower No. 5 Block coal samples (maceration series 446), identified on the basis of stratigraphic position, were collected from the Can- nelton Coal Company strip mine near the head of Bullpush Fork, Fayette County, W. Va. The coal is very thick at this locality (238 em) and contains two partings (table 11). The identified palynomorphs of maceration series 446 are shown in table 11, and the abundant and accessory genera are shown: Densosporites 6.8 percent Laevigatosporites 41.7 Lycospora 11.4 Torispora 26.5 86.4 percent The preservation of palynomorphs is poor in Lower No. 5 Block coal (maceration series 446) compared to other block coals studied in this report. This is shown by the fact that many specimens of Densosporites could not be identified to the species level and are classified either as Densosporites sp. or as D. "rings." The designation '"rings'' means that only the thickened equatorial structure remains. The number of specimens of Lycospora and Torispora not identified to the species TABLE 7.-Palynomorphs from the Little No. 5 Block coal bed in West Virginia, series 552-Continued [Maceration series 552; USGS Paleobotanical loc. No. D6038; 1,250 specimens counted; X, present but not observed in count] Taxon 552-A 552-B 552-C 552-D 552-E 552-F 552-G (percent) L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall --------- -- 1.6 -- -- .8 2.0 -- L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke ---------------- -- ---- -- 2.0 -- -- 1.2 15.2 -- L. SDP X 6.8 X X .8 23.2 «-- Microreticulatisporites sulcatus (Wilson and Kosanke) Smith and BUtt@rwOrth -------------------------------- -- -- X -- -- -- -- -- Punctatisporites spp ------ ---- -- X 4.0 4.0 8 -- 1.6 -- Radiizonates tenuis (Loose) Butterworth and Smith in Butterworth and others, 1964 ------- ---- -- -- -- -- 10.4 32.8 A -- R. cf. R. faunus (Ibrahim) Smith and Butterworth -------------------- -- -- X -- -- -- -- Rip '' aay. s 4 .8 € * A 2s ¥. Torispora securis Balme -- X 30.0 30.4 32.4 9.2 2.0 -- Triquitrites protensus Kosanke X A -- -- -- 4 -- T. sculptilis Balme ------------------- -- -- -- ~- -- A -- Verrucosisporites sifati (Ibrahim) Smith and Butterworth ------------- -- -- -- 2.0 2.0 -- -- V. Sp ---------------<--------___--- -- -- -- 4 -- -- -- Vestispora costata (Balme) Spode in Smith and Butterworth ----------- -- £2 -- -- -- .8 -- V. fenestrata (Kosanke and Brokaw) Spode in Smith and Butterworth ---- - -- 2.4 -- -- 1.2 1.6 -- Wilsonites vesicatus (Kosanke) Kosanke --------------------------- -- 8 -- -- -- i_ -- Wisp ---- Sl :. ~ x Ss 4A aL s Monosaccate ---- -- 2.0 .8 A .8 .8 -- Total --------- -- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 552-A, 7.6 em roof rock. 552-B, 25.4 cm coal. 552-C, 25.4 cm coal. 552-D, 25.4 cm coal. 552-E, 25.4 cm coal. 552-F, 25.4 cm coal. 552-G, 7.6 em seat rock. 20 PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA level is further proof of poor preservation (maceration series 446). The preservation of palynomorphs in the parting sampled is also poor, preventing a worthwhile abundance count. Basically the same taxa are present in maceration series 446 as are present in the other Lower No. 5 Block coal samples previously discussed. Crassisporae Rkosankei (Potonié and Kremp) Bharadwaj is present at the rate of 8.8 percent in the bottom coal sample (446-K) corresponding to similar abundances in the other samples of the Lower No. 5 Block coal (553-D and 435-B). The most abundant genera occurring in the coal samples of maceration series 446 (table 11) are: Densosporites 22.3 percent Laevigatosporites 37.7 Lycospora 12.1 Torispora _9.4 81.3 percent Zosterosporites triangularis Kosanke, which was pres- ent in the first two sets of Lower No. 5 Block coal samples, has not been identified from samples of mac- eration series 446. On the basis of overall abundance, it is questionable whether or not samples of maceration series 446 correlate with those of the Lower No. 5 Block coal (maceration series 553 and 435). A separate evalua- tion of the three coal benches of maceration series 446 suggests that the lower bench (446-I-K) is more closely related to the Lower No. 5 Block coal samples (553 and 435). Thick and somewhat variable in occurrence, the coals of the Charleston Sandstone may represent rapid ac- cumulation and burial as a result of the absence of disruptive marine incursions between coals. The amount of elapsed geologic time might not be as great as one might expect. Similarity of palynological as- semblages may very well be a measure of similarity of paleoecologic conditions. TABLE 8.-Palynomorphs from the Little No. 5 Block coal bed in West Virginia, series 434 [Maceration series 434; USGS Paleobotanical loc. No. D6037; 1,500 specimens counted; X, present but not observed in count] Taxon 434-A 434-B 434-C 434-D 434-E 434-F 434-G 434-H (percent) Alatisporites hexalatus Kosanke --------------------______- -- X X -- -- -- -- A. sp -- l -- -- -- -- n -- Calamospora hartungiana Schopf in Schopf, Wilson, and Bentall -- - 0.4 -- X =- 0.8 -- -- -- C. parva Guennel -- --- -- -- -- 2.0 -- -- 0.4 C. spp -- 4 -- -- -- A -- -- 1.6 Cirratriradites annulatus Kogsanke -------------____________ 1.2 X -- X e -- -- -- Convolutispora sp -- X -- -- -- -- -- Crassispora kosankei (Potonié and Kremp) Bharadwaj -------- 4 -- -- -- 1.2 -- X 8:2 Densosporites sphaerotriangularis Kosanke ----------------- 4 -- 0.8 -- 8 -- X -- D. triangularis Kosanke 1.2 6.0 0.8 -- f X -- D. sp 1.6 5.2 2.4 £8 x x 4 Dictyotriletes bireticulatus (Ibrahim) Smith and Butterworth -- ~- X A -- f -- -- Endosporites globiformis (Ibrahim) Schopf, Wilson, and Bentall 2.0 -- X -- -- -- -- -- E. ornatus Wilson and Coe 2.0 -- -- -- 8 -- -- -- E. sp -- -~ a. == &= == X £- Florinites antiquus Schopf in Schopf, Wilson, and Bentall ----- 1.2 X -- -- 4 -- -- 8 F. triletus Kosanke -- -- -- A -- -- -- Granulatisporites pallidus Kosanke ----------------------- X -- -- -- -- -- 8 G. verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall ---- -- -- A 2.0 -- -- 1.2 G. spp 2.8 1.2 1.6 "4 8 x x 4 Knoxisporites sp -- -- -- -- ~- X -- Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall .8 1.2 A 1.2 .8 -- f 1.2 L. globosus Schemel -- 5.2 5.2 10.8 8.0 12.8 X X 8.0 L. latus Kosanke 3.2 0.8 .8 X A -- -- A L. medius Kosanke - -- - 1.6 1.6 .8 A A -- -- 1.6 L. minutus (Ibrahim) Schopf, Wilson, and Bentall ------------ 14.8 12.0 8.8 5.2 10.0 X X 7.2 L. ovalis Kosanke 14.4 2.4 11.2 4.4 9.6 X X 14.4 L. punctatus Kosanke - -- 6.0 5.6 10.8 6.8 1.6 -- «~ 1.2 L. vulgaris (Ibrahim) Alpern and Doubinger ----------------- X -- -- -- -- -- -- Lycospora brevijuga KoSsanke -------------------_________ -- -- -- -- -- ~- 4 L. granulata Kosanke 2.4 4 -- -- 4.4 -- -- 7.4 PALYNOMORPH ASSEMBLAGES FROM PENNSYLVANIAN STRATOTYPE Wanless (1939) correlated the No. 5 Block coal, which is mined extensively in the Kanawha River Valley, with the Lower Kittanning coal of Pennsylvania and Ohio. In the current nomenclature of the block coals, the No. 5 Block coal of Wanless is probably the Lower No. 5 Block coal. The Lower No. 5 Block coal does not cor- relate with the Lower Kittanning coal, but is older, and this will be taken up subsequently with the discussion of the Upper No. 6 Block coal. The Upper No. 5 Block coal occurs in benches, coal separated from coal by non-coal layers, and the correla- tion of these separate benches may be difficult. The cor- relation of these coal benches is based on palynological evidence such as abundance, or guide fossils, or a com- bination of these factors. For example, the thin coal (maceration 554-A) does not contain Thymospore pseudothiessenii (Kosanke) Wilson and Venkatachala and as a result is not correlative with samples of mac- eration series 573, but is older. 21 Upper No. 5 Block(?) coal (maceration series 447, table 12) was collected from the Union Carbide 7C mine located near Sanderson, Kanawha County, W. Va. A parting 12.7 ecm thick separates the bottom 40.6 cm of coal from the top 100.8 ecm of coal. The overall abun- dance is similar to that of the Lower No. 5 Block(?) coal (maceration series 446, table 11). However, Crassispora kosankei (Potonié and Kremp) Bharadwaj does not ex- ceed the 2 percent level in any of the segment samples, and Zosterosporites triangularis Kosanke is present in the parting sample (447-D). Preservation of palynomorphs extracted from coal samples of maceration series 447 is better than that of coal samples of maceration series 446. The non-coal samples of maceration series 447 did not yield sufficient or well-preserved palynomorphs to make abundance counts. The majority of the specimens that were iden- tified from this parting are thought to be herbaceous. The same is true of the parting samples of the 446 TABLE 8.-Palynomorphs from the Little No. 5 Block coal bed in West Virginia, series 434-Continued [Maceration series 434; USGS Paleobotanical loc. No. D6037; 1,500 specimens counted; X, present but not observed in count] Taxon 434-A 434-B 434-C 434-D 434-E 434-F 434-G 434-H (percent) L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall - 4.8 A 2.0 4 9.6 X -- 2.8 L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoan- nulat@ KOS@MAKk@ -----------<-----__-__-________________- 8.8 -- 1.2 -- 11.6 -- X 13.6 L. punctata Kosanke ---- -- -- -- -- 4.0 X -- 2.0 M --- --_----- ec anl buen _o dnl l Bull 7.2 t> 2.0 A4. . 18.0 2s x 22.4 Microreticulatisporites sulcatus (Wilson and Kosanke) Smith and Butterworth ------ -- -- -- -- -- -- A -- -- -- Murospora kosankei Somers -- -- - -- X -- -- -- X -- -- Punctatisporites obesus (Loose) Potonié and Kremp ---------- -- -- -- X -- -- -- 1.2 P. quasiarcuatus KOS@Ake ------------------_____________ -- -- -- .8 -- -- X 8 P. spp ---> ees. teen tent _ Loan 1.6 2.0 2.8 1.2 1.6 2- £= 4 Radiizonates tenuis (Loose) Butterworth and Smith in Butter- worth and others, 1964 -----------------_____________-- 2.4 22.8 -- 28.0 8 -- -- 4 R. spp -- " m rad l RQStrICRIQ Sp 4 -- -- -- -- -- -- 4 Reinschospora sp --------- -- -- 4 -- -- -- -- -- Reticulatisporites Sp ----------------------___________-- -- 4 A -- -- -- -- -- Spencerisporites gracilis (Zerndt) Winslow ------------------ -- X -- -- -- -- -- -- Torispora securis BAlMe 13.6 28.0 31.6 31.6 -- X X .8 Triquitrites cf. T. exiguus Wilson and Kosanke -------------- A -- -- -- ~- -- -- A T. pulvinatus KOS@Ake -------------------_______________ A -- 1.2 -- -- -- -- .8 T. Sp 4 -- -- -- 4 X X A Vestispora fenestrata (Kosanke and Brokaw) Spode in Smith and Butterworth ------------------___________________ -- -- -- -- 1.2 -- X 1.2 V. sp - -- --- e---cccc_____-_- -- -- X -- -- -- -- -- WilsOMites Sp =---------------------_-__________________ -- -- X -- -- -- -- -- MonOS@CCate --------------------------______- A -- 8 -- .8 -- X 4 Unassigned ----------------------______________________ A -- -- -- -- -- -- -- Total --------- ---- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 434-A, 30.5 cm coal. 434-E, 30.5 cm coal. 434-B, 30.5 cm coal. 494-F, 12.7 em seat rock 434-C, 30.5 cm coal. 434-G, 7.6 em seat rock. 434-D, 30.5 cm coal. 4934-H, 15.2 em coal. 22 PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA TABLE 9.-Palynomorphs from the Lower No. 5 Block coal bed in West Virginia, series 553 [Maceration series 553; USGS Paleobotanical loc. No. D6110; 750 specimens counted; X, present but not observed in count] Taxon 553-A 553-B 553-C 553-D 553-E (percent) Acanthotriletes sp -- X -- 0.4 -- Ahrensisporites sp ---- - -- a -- X -_ Alatisporites sp f 0.4 -- -- ~- Calamospora breviradiata Kosanke -- -- -- X -- C. hartungiana Schopf in Schopf, Wilson, and Bentall - -- -- -- 2 -- C. parva Guennel ---- -- 2 -- -- -- C. sp -- .6 0.4 1.0 -- Cirratriradites annulatus Kosanke -- A A A -- Crassispora kosankei (Potonié and Kremp) Bharadwaj -- -- -- 7.6 X Cristatisporites sp - -- 2 -- -- -- Cyclogranisporites cf. C. multigranus Smith and Butterworth --------------------<----- -- A X -- -- Densosporites annulatus (Loose) Schopf, Wilson, and Bentall -------------------------- -- % -- -- f D. sphaerotriangularis Kosanke - -- 2.0 A -- -- D. triangularis Kosanke -- -- 6.6 3.2 -- -- D. spp - -- 122 4.8 Au -- Dictyotriletes bireticulatus (Ibrahim) Potonié and Kremp ----------------------------- == == x == e Endosporites globiformis (Ibrahim) Schopf, Wilson, and Bentall ------------------------ -- -- A -- -- E. sp ------ ---- -- e -- -- -- 1.0 -- Florinites antiquus Schopf in Schopf, Wilson, and Bentall ----------------------------- -- -- -- 1.0 -- Granulatisporites verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall --------------- -- -- -- 2.4 -- a+ e .8 ¥ 1.6 Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall ------------- -- 2 -- .6 -- L. globosus Schemel ---- - -- --- X 12.2 7.6 9.6 -- L. latus Kosanke --- -- X -- .6 -- L. Medis -- 1.2 1.6 2.6 -- L. minutus (Ibrahim) Schopf, Wilson, and Bentall ------------------<----------------- a 4.8 6.4 5.4 X L. ovalis Kosanke ---- -- 2.4 2.4 16.0 X L. punctatus Kosanke - --- ---- --- -- 8.0 6.0 8.0 -- L. vulgaris (Ibrahim) Alpern and Doubinger ----------------------- ---- -- -- 1.2 .8 X L. sp -- ---- -- -- -- -- v2 -- Lycospora granulata Kosanke ----- -- -- -- 2.6 -- L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall ————————————————————————— -- -- -- 1.4 % L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke ------------ -- -- -- -- X L. punctata Kosanke -- -- A 72 X L. spp -------- ---- -- --- -- 2 A .8 X Punctatisporites obliquus Kosanke -- 1.2 -- 1.6 -- P. spp --- ---- -- -- - -- -- 2.2 2.4 1.2 -- Radiizonates cf. R. tenuis (Loose) Butterworth and Smith in Butterworth and others, 1964 --- -- -- 12.0 1.4 -- R. sp -- -- A 12.4 1.6 «~ Raistrickia cf. R. aculeata Kosanke - --- X X -- -- -- R. cf. R. crocea Kosanke -- -- -- 2 -- -- -- Ri sp -==- es s a> x" # s x Torispora securis Balme -- -- --- X 40.2 34.4 21.8 -- T. Sp -- .8 A -- -- Triquitrites sculptilis Balme ------- ---- ---- -- A -- .6 -- T. sp o> e €> 2g 4 4 A sp Verrucosisporites sifati (Ibrahim) Smith and Butterworth =--------------<-------------- -- X -- 1.6 -- V. sp ----- ~- ~- 2.0 2.4 -- Vestispora fenestrata (Kosanke and Brokaw) Spode in Smith and Butterworth ------------- f -- -- .6 X Zosterosporites triangularis Kosanke --- -- X X -- 2? -- Monosaccate -- X 1.4 -- 2.0 -- Unassigned -- -- A -- X X Total -- 100.0 100.0 100.0 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 553-A, 15.2 em roof rock. 553-B, 30.4 cm coal. 553-C, 30.4 cm coal. 553-D, 30.4 cm coal. 553-E, 7.6 cm seat rock. PALYNOMORPH ASSEMBLAGES FROM PENNSYLVANIAN STRATOTYPE TABLE 10.-Palynomorphs from the Lower No. 5 Block coal bed in West Virginia, series 435 [Maceration series 435; USGS Paleobotanical loc. No. D6111; 1,000 specimens counted; X, present but not observed in count] 23 Taxon 435-A 435-B 435-C 435-D 435-E (percent) Acanthotriletes cf. A. echinatus (Knox) Potonié and Kremp ~~ 1.2 -- -- -- Ahrensisporites guerickei (Horst) Potonié and Kremp -- -- X -- -- -- Anapiculatisporites spinosus (Kosanke) Potonié and Kremp --------------------------- -- -- X 0.4 -- Calamospora breviradiata Kosanke ---- -- 0.8 -- -- -- C. hartungiana Schopf in Schopf, Wilson, and Bentall ---- -- -- 0.4 X -- C. parva Guennel ----- -- -- A «- X -- C. sp ----- 0.8 1.6 X 1.2 -- Cirratriradites annulatus Kosanke -- X -- .8 -- C. Sp ------<--------- ---- e X X -- X Convolutispora sp ---- .8 -- -- -- -- Crassispora kosankei (Potonié and Kremp) Bharadwaj -- -- 8.0 -- 5.2 X Densosporites sphaerotriangularis Kosanke - -- A -- -- -- D. triangularis Kosanke 4.0 f X -- -- D. spp -- -- 8.4 A .8 1.2 -- Florinites antiquus Schopf in Schopf, Wilson, and Bentall - ~- -- -- .8 -- Granulatisporites pallidus Kosanke A -- -- 1.2 -- G. verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall 12 .8 X .8 X G. spp 2.4 .8 .8 4.0 -- Knoxisporites sp - -- -~ A -- -- Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall ------------- -- 3.6 -- 4 -- L. globosus Schemel 6.4 4.8 12.8 10.8 -- L. medius Kosanke --- 2.0 2.8 A 1.2 X L. minutus (Ibrahim) Schopf, Wilson, and Bentall -----------------------_-___________- 10.4 4.8 42.8 30.0 X L. ovalis Kosanke 6.8 10.0 X 5.6 -- L. punctatus Kosanke 11.2 2.8 1.6 1.2 -- Lophotriletes cf. L. gibbosus (Ibrahim) Potonié and Kremp -- -- ~- A -- Lycospora granulata Kosanke -- 1.6 -- 2.0 X L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall ------------------------- -- 3.2 -- 7.6 X L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke ------------ -- 6.4 -- X X L. punctata Kosanke -- ---- A 9.2 «~- 1.2 -- L. SDD ------------------------ 2.4 21.2 A 10.8 X Microreticulatisporites sulcatus (Wilson and Kosanke) Smith and Butterworth ------------ -- 1.6 ~- 12 -- Punctatisporites cf. P. obesus (Loose) Potonié and Kremp ----------------------------- A A -- -- -- P. obliquus Kosanke -- -- X X .8 .8 == P. spp -------------- ---- 3.6 1.2 2.0 A -- Radiizonates cf. R. tenuis (Loose) Butterworth and Smith in Butterworth and others, 1964 --- X -- 1.6 1.2 -- R. sp - -- -- ---- -- X -- -- -- Raistricki@ CrOC@Q KOS@MK@ -- -- -- X -- R. imbricata Kosanke -- A -- ~- -- R. Sp -- =- X X -- Reticulatisporites sp ---- -- -- -- A -- Torispora securis Balme 30.4 1.6 6.8 .8 -- T. sp -- 3.2 X 28.4 4.4 -- Triquitrites cf. T. arculatus Wilson and Coe -- --- 1.6 -- -- A -- T. prOt@nSUS KOSAMK@ -- -- -- X -- T. pulvinatus Kosanke A A -- .8 -- T. sculptilis Balme ---- -- .8 -- e -- T. spp ------- -- 4.0 -- 2.4 -- Verrucosisporites sp -- .8 -- -- -- Vestispora fenestrata (Kosanke and Brokaw) Spode in Smith and Butterworth ------------- -- 2.4 -- A X Zosterosporites triangularis Kosanke 1.2 -- X -- -- Monosaccate -- A ~- -- -- Unassigned 1.2 12 -- -- -- Total ----- --- 100.0 100.0 100.0 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 435-A, 30.4 cm coal. _ 435-B, 30.4 cm coal. 435-C, 30.4 cm coal. - 435-D, 30.4 cm coal. 435-E, 7.6 em seat rock. 24 series. Both the 447 and 446 maceration series have a higher proportion of Densosporites and a lower concen- tration of Torispore than was found in either set of samples of the Lower No. 5 Block coal (maceration series 553 and 435). The abundant genera in 447-A-C and E are as follows: PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA Block coal (553 series). Samples 554-A-B and D were productive; the data are shown in table 13 and on figure 4. The coal sample 554-D, occurring 12 m above the Lower No. 5 Block coal (553 series), has Laevigato- sporites as the dominant taxon of the assemblage and Lycospora as the subdominant as shown: Densosporites 26.6 percent 554-A 554-B 554-D Laevigatosporites 34.6 Densosporites - 283.2 0.8 5.6 percent Lycospora 9.9 Laevigato— Torispora 270 sporites 24.0 22. 4 44.8 78.1 percent Lycospora 13.6 52.4 25.4 Torispora 8.0 .8 16.0 Upper No. 5 Block coal (maceration series 554) was < 2 2 collected starting about 12 m above the Lower No. 5 68.8 78.8 91.3 - percent TABLE 11.-Palynomorphs from the Lower No. 5 Block coal bed in West Virginia, series 446 [Maceration series 446; USGS Paleobotanical loc. No. D6039; 1,750 specimens counted; X, present but not-observed in count] Taxon 446-A - 446-B - 446-C - 446-D - 446-E 0 446-F _ 446-G -- 446-H - 446-1 _ 446-J _ 446-K (percent) Acanthotriletes echinatus (Knox) Potonié and Kremp ---- -- -- X -- -- -- -- -- - -- -- -- -- Ahrensisporites cf. A. guerickei (Horst) Potonié and Kremp ------------------------_-_-_---- -- X -- -- -- X - -- -- -- -- Sp ---------------------------- -- -- -- -- -- X - -- -- 0.4 -- Anapiculatisporites spinosus (Kosanke) Potonié and Kremp - ts -- 63 *: E. * 92 < # ms *- x Calamospora pedata Kosanke ----------------- -- -- -- -- -- -- - -- -- X -- C. SDP ----------------------_-____________- -- A -- -- -- X - -- -- 1.6 1.6 Cirratriradites maculatus Wilson and Coe ------- X -- -- -- a A - -- -- -- 0.8 ConvolutispOr@ SPP ------------------------- -- -- =-- -- -- A - -- 0.8 1.2 -- Crassispora kosankei (Potonié and Kremp) Bharadwaj ------------------------------ -- -- E X -- -- - -- .8 -- 8.8 Densosporites triangularis Kosanke ------------ -- 16.4 X 28.0 5.6 39.2 - f -- 19.2 1.6 D. spp §- 16. ~ 52." fs :n as .x x §: 548 8 D. "fringes at ce ® 22 x 3.2 §°* 20... *> g . 280 . =- Dictyotriletes bireticulatus (Ibrahim) Potonié and Kremp -- X -- -- -- -- -- - -- -- 3.2 _ -- Endosporites formosus Kosanke -------------- X -- ~- -- ~- -- - -- e -- -- E. globiformis (Ibrahim) Schopf, Wilson, and Bentall --------------------------------- -- -- -- -- -- X - -- -- -- -- E. OMAtUS ---------------------_--_--------- X -- -- -- -- -- - -- .8 -- -- E. sp -- -- <-. x -- -- -- X $" ~ -- 8 _ -- -- Florinites antiquus Schopf in Schopf, Wilson, and BeNtall --------------------------------- -- -- X -- 4.4 A - X 112 4 2.4 Granulatisporites pallidus Kosanke ------------ -- -- X X X -- - -- 4.0 -- 8 G. verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall ------------------------------ X -- X -- 2.4 1.6 X X -- 1.2 3.2 G. spp - -- A -- 1.2 2.4 7.6 - -- 8.8 4.0 3.2 Knoxisporites cf. K. rotatus Hoffmeister, Staplin, and Malloy -- -- -- -- -- -- -- X - -- -- -- -- Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall ----------------- -- A -- -- -- A - X .8 1.6 X L. globosus Schemmel ------------------------ X 13.6 X 12.8 9.2 6.8 - -- 8.8 6.0 : 12.8 L. latus KOS@AKk@ --------------------------- -- -- -- 0.4 _ -- 18s < '+ -- e -- -- L. medius KOS@NKk@ ------------------------- -- 2.8 -- 1.6 4.4 1.2 - -- 3.2 2.4 3.2 L. minutus (Ibrahim) Schopf, Wilson, and Bentall - -- 20.8 X 15.2, 24.0 6.8 - -- 112 - 11.2 2.4 PALYNOMORPH ASSEMBLAGES FROM PENNSYLV ANIAN STRATOTYPE Coal sample 554-B, occurring about 5 m above 554-D, has Lycospora as the dominant genus and Laevigato- sporites as the subdominant. The bone coal sample 554-A, occurring about 2.5 m above 554-B, has Den- sosporites and Laevigatosporites as codominant genera. The codominance of these two genera together with specimens assigned to Verrucosisporites differentiates this sample (554-A) from the other two coal samples of this series (554-B and 554-D). A set of samples of the Upper No. 5 Block coal (maceration series 572-A-F) was collected from above the 12-A of the Valley Camp Coal Company northwest of Mammoth, Kanawha County, W. Va. The paly- nological data are shown in table 14, and the abundant genera of the coal samples (572-B-E) are: 25 Densosporites 4.3 percent Laevigatosporites 43.3 Lycospora 16.0 Torispora 21A 85.0 percent Laevigatosporites is clearly dominant; Lycospora, Torispora, and Densosporites are present at approx- imately the same rate as in another sample of the Upper No. 5 Block coal (554-D). Another coal sample that is thought from paly- nological evidence to be related to the Upper No. 5 Block coal (maceration series 436) was collected about 20 m above the Lower No. 5 Block coal (maceration series 435). The palynomorph analyses are shown in TABLE 11.-Palynomorphs from the Lower No. 5 Block coal bed in West Virginia, series 446-Continued [Maceration series 446; USGS Paleobotanical loc. No. D6039; 1,750 specimens counted; X, present but not observed in count] Taxon 446-A - 446-B _ 446-C _ 446-D _ 446-E - 446-F _ 446-G - 446-H - 446-1 - 446-J _ 446-K (percent) L. ovalis KOS@NKk@ -------------------------- -- 10.8 -- 3.6 7.6 6.4 -- -- 12.0 7.2 9.6 L. punctatus ----------------------- -- 3.6 -- 8.0 4.0 2.4 -- X 2.4 -- 3.2 Lophotriletes microsaetosus (Loose) Potonié and KreMp --------------------------_-_------- -- -- -- -- -- 8 -- ~- -- -- -- Lycospora granulata Kosanke ---------------- -- 1.2 -- A 1.2 .8 -- -- .8 -- 72 L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall ----------------------- -- A -- -- 4.4 -- -- -- 8 -- 4.0 L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke ---------- -- 3.6 -- f X -- f -- 2.4 -- -- L. punctata KOSanke ------------------------ -- 7.6 -- -- 5.2 1.2 -- -- -- A -- L Sp ---------------<---_________-_-_------ -- 11.2 X 4 5.6 9.6 X X 8.8 28. 12.8 Microreticulatisporites sulcatus (Wilson and Kosanke) Smith and Butterworth ------------ X .8 -- -- 3.6 -- -- -- 2.4 X -- Punctatisporites obliquus Kosanke ------------ -- A -- -- 8 A -- -- .8 -- 4.0 P. SDD -------------------__-____________--- X -- -- X -- £2 -- X 6.4 2.4 3.2 Radiiz0nates Sp ---------------------------- -- -- -- -- -- X -- wo - -- -- Raistrickia crinita Kosanke ------------------- -- -- -- -- -- -- -- -- -- -- 8 Reticulatisporites Sp ------------------------ -- -- -- -- -- -- -- -- -- -- 8 Torispora securis Balme --------------------- X 3.2 -- -- 10.8 1.6 -- X -- 2.4 -- T. gp ------------- ---- ---- -- -- -- 16.8 1.2 1.6 -- -- -- 1.2 6.4 Triquitrites protensa Kosanke ---------------- X -- -- 2.4 1.2 -- -- -- 4.0 _ -- 3.2 T. Sp se - o ool an e H % <2 #s 4 =% R s4 #7 s x" Verrucosisporites sifati (Ibrahim) Smith and BUtt@erworth ----------------------------- -- X -- -- -- ~- -- -- -- -- -- Vesicaspora wilsonii (Schemel) Wilson and Venkatachala ---------------------------- -- -- -- -- -- -- -- -- X -- -- Vestispora fenestrata (Kosanke and Brokaw) Spode in Smith and Butterworth ------------- -- -- -- -- -- -- -- -- 3.2 -- -- WilsOnites Sp ------------------------------ -- -- -- -- -- -- -- -- 8 -- -- MONOSACCAt@ ------------------------------ -- -- -- -- -- -- -- X 2.4 -- -- UN@SSigned ------------------------------- -- .8 X .8 -- A X -- -- A 3.2 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 446-A, 5.1 em roof rock. 446-B, 34.3 cm coal. 446-C, 2.5 cm parting. 446-D, 34.3 cm coal. 446-E, 34.3 cm coal. 446-F, 34.3 cm coal. 446-G, 25.4 cm parting. 446-H, 25.4 cm parting. 446-1, 33.6 cm coal. 446-J, 33.6 cm coal. 446-K, 33.6 cm coal. 26 PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA TABLE 12.-Palynomorphs from the Upper No. 5 Block(?) coal bed in West Virginia, series 447 [Maceration series 447; USGS Paleobotanical loc. No. D6040; 1,000 specimens counted; X, present but not observed in count] Taxon 447-A 447-B 447-C 447-D 447-E (percent) Alatisporites hexalatus Kosanke -- -- -- 1.2 -- -- A. Sp. -- -- 0.4 -- -~ Calamospora hartungiana Schopf in Schopf, Wilson, and Bentall ------------------------ X -- -- -- -- C. spp -- -- 0.4 1.2 2.4 -- 0.4 Cirratriradites maculatus Wilson and Coe -- ---- s 0.8 1.6 -- A Crassispora kosankei (Potonié and Kremp) Bharadwaj --- 2.0 -- 2.0 -- -- Densosporites annulatus (Loose) Schopf, Wilson, and Bentall -------------------------- -- -- -- -- A D. triangularis Kosanke 10.4 34.8 32.0 X 11.6 D. spp -- --- 6.8 7.2 2.4 -- 4.8 Dictyotriletes bireticulatus (Ibrahim) Potonié and Kremp ----------------------------- .8 4A A -- 4 Endosporites ornatus Wilson and Coe occ cC X -- 2.0 -- -- E. sp A s 1.6 x .8 Florinites antiquus Schopf in Schopf, Wilson, and Bentall .8 .8 -- -- -- F. Sp -- .8 .8 «~ 1.2 Granulatisporites verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall --------------- A -- 2.8 X A G. spp X 3.6 1.6 -- A Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall ------------- .8 .8 1.6 -- 2.8 L. globosus Schemel -- ---- 8.4 11.6 4.0 X 8.4 L. latus Kosanke -- -- --- A -- ~- ~- A L. medius Kosanke -- -- -- 4.0 .8 A X 5.2 L. minutus (Ibrahim) Schopf, Wilson, and Bentall 14.8 8.4 2.4 X 1.2 L. ovalis Kosanke 31.2 2.4 10.8 -- 9.2 L. punctatus Kosanke -- 2.0 2.0 2.4 X 4.0 Lycospora granulata Kosanke .8 1.2 2.8 X 1.6 L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall ------------------------- 1.6 3.2 .8 -- 2.0 L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke ------------ 3.6 .8 2.8 -- 2.4 L. spp 5.2 4.0 7.2 -- 3.2 Microreticulatisporites sulcatus (Wilson and Kosanke) Smith and Butterworth ------------ A -- -- -- -- Punctatisporites obesus (Loose) Potonié and Kremp ---------------------------------- f -- .8 -- .8 P. quasio@rcuatus KOS@AK@ «~ 2.4 -- -- 1.2 P. spp ---- 2.0 4.8 3.6 -- 4.8 Radiizonates tenuis (Loose) Butterworth and Smith in Butterworth and others, 1964 ------- -- -- -- -- 14.0 R. cf. R. faunus (Ibrahim) Smith and Butterworth «-- -- -- -- X Raistrickia sp X -- -- X -- Reticulatisporites cf. R. polygonalis (Ibrahim) Loose -- -- .8 1.6 -- -- Torispora securis Balme 2.4 4.8 4.0 X 15.2 Triquitrites cf. T. sculptilis Balme -- -- a A -- -- T. sp €. g 1.6 A4 ~- a- Vestispora sp -- --- A -- -- -- -- Zosterosporites triangularis KOS@MAK@ ----<--------------______________c____________- -- -- -- X -- Monosaccate -- .8 2.8 -- 2.4 Unassigned -- f -- -- A Total -- 100.0 100.0 100.0 100. DESCRIPTION OF MATERIAL IN MACERATIONS 447-A, 33.6 em coal. 447-D, 12.7 cm parting. 447-B, 33.6 cm coal. 447-E, 40.6 cm coal. 447-C, 33.6 cm coal. PALYNOMORPH ASSEMBLAGES FROM PENNSYLVANIAN STRATOTYPE 27 TABLE 13.-Palynomorphs from the Upper No. 5 Block coal bed in West Virginia, series 554 [Maceration series 554, USGS Paleobotanical loc. No. D6041; 750 specimens counted; X, present but not observed in count] Taxon 554-A 554-B 554-C 554-D (percent) Ahrensisporites guerickei (Horst) Potonié and Kremp ------ -- -- 0.4 -- -- Calamospora breviradiata Roganke -- A -- -- C. hartungiana Schopf in Schopf, Wilson, and Bentall 0.8 .8 -- -- C. parva Guennel ------------------ -- A -- -- C. 8p 1.6 .8 -- X Cirratriradites sp ------- .8 A -- -- Crassispora kosankei (Potonié and Kremp) Bharadwaj - -- .8 X 0.4 Cyclogranisporites sp ------- -- -- -= .8 Densosporites sphaerotriangularis Kogankée -- -- -- A D. triangularis Kosanke --- 8.0 X -- 4A D sp -* ze n an PINAL AA oo 14.4 .8 + 4.4 Dictyotriletes bireticulatus (Ibrahim) Potonié and Kremp -----------------<------------------- -- 8 -- 4 D. sp ----- .8 -- -- -- Endisporites cf. E. globiformis (Ibrahim) Schopf, Wilson, and Bentall ---------------------------- -- 4.4 -- -- E. ornatus Wilson and Co@ ---------------------- ---- -- X -- -- E. 8p -- 1.6 -- 1.2 Florinites antiquus Schopf in Schopf, Wilson, and Bentall -- 8 2.4 -- 1.6 Granulatisporites pallidus KOS@NKke .8 -- -- X C --- --54 cn deme _ .8 1.6 x x Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall -------------------- 8 1.2 -- 2.4 L. globosus Schemel ---- -- 8 6.0 X 6.0 L. latus Kosanke -- X -- 12 L. medius Kosanke ---- 2.4 2.8 -- 3.6 L. minutus (Ibrahim) Schopf, Wilson, and Bentall -------------<-----------<------------------- 2.4 1.6 -- 5.2 L. ovalis Kosanke ------------ ---- 14.4 10.4 X 16.0 L. punctatus Kosanke 2.4 1.2 X 8.2 L. vulgaris (Ibrahim) Alpern and Doubinger - -- .8 .8 -- 2.0 Lycospora granulata KOS@MAKke 4.0 2.8 -- 1.6 L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall ------------------<--<------------ 1.6 -- X -- L,. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke -------------------- 1.6 26.4 f 6.4 LI; PURCHALQ KOSBNKe --- -- 1.6 -- .8 L. spp --- --- -- 6.4 21.6 -- 15.8 Microreticulatisporites sulcatus (Wilson and Kosanke) Smith and Butterworth -------------------- 1.6 -- ~- -- Murospora kosankei Somers 1.6 -- -- A Punctatisporites sp ---------- 5.6 .8 -- -- RQdi{z0N@te§ 8p 3.2 X -- 8 Reinschospora sp eccccccececcecccecccc~~-- -- -- X -- Raistrickia cf. R. aculeata Kosanke ---- .8 -- -- -- Torispora $ecuris BAlMe 8.0 .8 X 16.0 Triquitrites protensus Kosanke ----------- -- ---- -- X -- -- T. pulvinatus Kosanke .8 2.4 -- 4 Vestispora fenestrata (Kosanke and Brokaw) Spode in Smith and Butterworth -------------------- -- 1.6 X -- V. levigata Wilson and Venkatachala -- A -- -- Verrucosisporites sifati (Ibrahim) Schopf, Wilson, and Bentall --------<----<<<------------------ .8 -- -- -- V. verrucosus (Ibrahim) Ibrahim --- 2.4 -- -- .8 V. Dp 5.6 A -- 2.4 Wilsonites sp -- -- A -- -- --- 1.6 1.2 X 4 Unassigned ------------------------- --- 1.6 -- a -- TObAL 100.0 _ 100.0 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 554-A, 12.7 em bone coal, 2.5 m above 554-B. 554-C, 7.6 cm shale 1 m below 554-B. 554-B, 35.5 cm coal, 5 m above 554-D. 554-D, 35.5 em coal 12 m above 553. 28 table 15, and the bottom two samples (436-B-C) were productive. Analyses of these samples suggest a sim- ilarity to other samples of the Upper No. 5 Block coal (554-D and maceration series 572). Radiizonates is pre- sent although not abundant in all sets of the Upper No. 5 Block coal (maceration series 436, 554, and 572). Zosterosporites triangularis is present in the seat-rock sample of the 436 maceration series. The numerically important genera of coal sample 436-B are: Laevigatosporites 53.2 percent Lycospora 15.2 Torispora 13.2 81.6 percent Another set of samples of the Upper No. 5 Block coal (574-A-C) were collected adjacent to a pipeline north- west of Marting, east of the Kanawha-Fayette County line, in Fayette County, W. Va. The sample breakdown and palynomorph analyses are given in table 16. These PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA samples appear to be related to those of maceration 554-B because each coal sample has Lycospora as the dominant taxon. However, Triquitrites and Granulatisporites are notably more abundant in coal sample 574-A. Zosterosporites triangularis Kosanke has been iden- tified from both the Lower and Upper No. 5 Block coals, but it is not abundant and does not occur consistently. This type of range zone was observed in some coals of the Princess Reserve District of eastern Kentucky by Kosanke (1973). The abundant genera of coal sample 574-A are: Granulatisporites 6.4 percent Laevigatosporites 13.6 Lycospora 40.0 Torispora 5.6 Triquitrites 8.8 74.4 percent TABLE 14.-Palynomorphs from the Upper No. 5 Block coal bed in West Virginia, series 572 [Maceration series 572; USGS Paleobotanical loc. No. D6112; 1,250 specimens counted; X, present but not observed in count] Taxon 572-A 572-B 572-C 572-D - 572-E 572-F (percent) Acanthotriletes cf. A. triquetrus Smith and Butterworth ------------------------ 0.8 -- -- -- X -- Alatisporites trialatus Kosanke --- ---- -- .8 0.8 -- -- -- -- Anapiculatisporites spinosus (Kosanke) Potonié and Kremp --------------------- .8 X -- -- -- -- Calamospora breviradiata KOS@MK@ -------------------_____________________- -- 3.6 0.4 -- 0.4 -- Cp se e rien le -<. ecus. #2 1.6 F «3 4 %> Cirratriradites annuliformis Kosanke and BrOKkaw ----------------------------- -- -- A 0.4 1.2 -- C. sp ---- 1.6 A -- -~ 4 =-- Crassispora kosankei (Potonié and Kremp) Bharadwaj -------------------------- 4.8 1.6 A 8 -- == Cristatisporites sp --------- f -- - -- -- 1.2 -- f -- Densosporites triangularis Kosanke -- 4.0 -- 3.2 4" -- =- D. SDPp 2.4 X 10.8 1.6 8 X Dictyotriletes bireticulatus (Ibrahim) Potonié and Kremp ----------------------- X 4 el -- -- f Endosporites ornatus Wilson and CO@ ------------------------______________- 2.4 3.2 -- -- -- -- E. Sp 2.4 12 A -- A -- Florinites antiquus Schopf in Schopf, Wilson, and Bentall ----------------------- 4.0 .8 A .8 2.0 -- F. Sp -------------------____-- - 1.6 -- A -- .8 ««- Granulatisporites pallidus Kosanke .8 -- f -- «-- -- G. verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall --------------------- -- 4 -- -- 1.2 -- G. spp ------------ - 1.6 1.2 A 4 A =- Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall ------ 1.6 .8 A .8 A -- L. globosus Schemel -- 6.4 8.8 6.8 9.6 4.4 X L. latus Kosanke --. 1.6 -- A A -- L. medius Kosanke -- 5.6 2.8 3.6 2.4 3.2 -- L. minutus (Wilson and Coe) Schopf, Wilson, and Bentall ------------------------ 4.8 3.6 9.2 11.2 1.2 X L. ovalis Kosanke 12.8 31.2 14.4 12.8 9.2 X L. punctatus Kosanke f 8.0 9.2 12.4 4.4 -- L. vulgaris (Ibrahim) Alpern and Doubinger .8 -- ~- X «-- -- Leiotriletes sp -- X -- -- X X Lycospora brevijuga Kosanke ~- -- A -- X -- PALYNOMORPH ASSEMBLAGES FROM PENNSYLVANIAN STRATOTYPE The exact palynological placement of maceration 554-A is not certain, but it most likely would fall be- tween maceration series 574 and 573 of the Upper No. 5 Block coal. Four samples (573-A-D) were collected from the highwall of the Cannelton Coal Company Mine, located northwest of Marting and east of the Kanawha-Fayette County line in Fayette County, W. Va., but only the coal sample 573-B-C contained sufficient palynomorphs to make abundance counts (table 17). Most significant is the occurrence of Thymospora at the rate of 11.4 percent together with the presence of Punctatisporites obliquus Kosanke and P. minutus (Kosanke) Peppers, because this must place the samples of maceration series 573 very close to the position of the Lower Kittanning coal. In Illinois, the range zone of 7. pseudothiessenii starts below the Colchester (No. 2) Coal Member according to Kosanke (1950) and Peppers (1970) and is present throughout the Carbondale Forma- tion and the lower part of the Modesto Formation. 29 Kosanke (1973) reported that the range zone of T. pseudothiessenii, in the Princess Reserve District of northeastern Kentucky, started in the Princess 5B coal, which is stratigraphically just below the Princess No. 6 coal and is present above in the Breathitt and Conemaugh Formations. Kosanke (1973) correlated the Princess No. 6 coal with the Lower Kittanning coal of western Pennsylvania and eastern Ohio. Gray (1967) reported on the palynomorph content of coals in the lower and middle Allegheny of western Pennsylvania and eastern Ohio. Thymospora pseudothiessenii was identified from the Lower Kittanning and younger coals but not from the Lawrence coal, a thin coal occurring below the Lower Kittanning coal. The presence of Thymospora in coal samples of maceration series 573 suggests that the coal is near the position of the Lower Kittanning coal. A comparison of the assemblage of palynomorphs from the Lower Kittanning coal (Habib, 1966; Gray, 1967) with those of series 573, however, suggests that series 573 is older, TABLE 14.-Palynomorphs from the Upper No. 5 Block coal bed in West Virginia, series 572-Continued [Maceration series 572; USGS Paleobotanical loc. No. D6112; 1,250 specimens counted; X, present but not observed in count] Taxon 572-A 572-B 572-C 572-D | 572-E 572-F (percent) L. granulat@ KOS@NKke 2.4 1.2 1.6 4 " 15.6 X L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall ------------------- -- .8 -- -- .8 X L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke ------ -- -- 2.4 -- 2.8 X L. punctata Kosanke ----------------- -- X 1.6 .8 -- 6.4 X L. spp ------ - -- ecccccccc_____-_-_----- 8.8 4.0 9.2 16. 14.0 -- Microreticulatisporites sulcatus (Wilson and Kosanke) Smith and Butterworth ------ .8 .8 12 -- -- -- Murospora kosankei Somers .8 X -- -- X -- Punctatisporites minutus (Kosanke) Peppers ---- 1.6 -- -- 8 1.2 f P. obesus (Loose) Potonié and Kremp X -- 4 A A a= P. sp - z 2.8 2.4 1.3. 2.4 s Reticulatisporites lacunosus Kosanke -- -- -- A -- -- f R. sp --- ---- -- -- 4 -- -- -- -- Radiizonates sp -------------- -- - .8 -- -- X X -- ReinschOSpOra Sp ----------------------- .8 -- -- -- -- -- Torispora securis (Balme) Alpern, Doubinger, and Horst ------------------------ 12.0 11.2 15.2 39.6 19.6 X Triquitrites protensus Kosanke X .8 A .8 .8 -- T. pulvinatus Kosanke --- X .8 «-- -- -- -- T. sculptilis Balme - 8.2 .8 -- -- -- X T. sp ----- --- ---- .8 -- A -- -- -- Vestispora fenestrata (Kosanke and Brokaw) Spode in Smith and Butterworth ------ .8 1.2 e A A -- V. sp -------- -- .8 12 .8 8 .8 -- Wilsonites sp -- 3.2 -=- A -- 2.0 -- Monosaccate - 3.2 A .8 f 1.6 X Unassigned n X .8 -- X -- Total 100.0 100.0 100.0 100.0 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 572-A, 15.2 em roof. 572-D, 33.0 cm coal. 572-B, 33.0 cm coal. 572-E, 33.0 em coal. 572-C, 33.0 cm coal. 572-F, 15.2 em seat rock. 30 PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA TABLE 15.-Palynomorphs from the Upper No. 5 Block coal bed in West Virginia, series 436 [Maceration series 436; USGS Paleobotanical loc. No. D6042; 500 specimens counted; X, present but not observed in count] Taxon 436-A 436-B 436-C (percent) Alatisporites various Kosanke <--- -~~--- -_- _... ooe eo ou on cannon gine LEC SEL LLCO X 0.4 -- Calamospora $p -- --- --- - -- - _. _. c cs n cns so o ooo oe ae w e n n n a m ne m m m m me m o n m a m m mm m m m noe me m me mem meee oe meme mnie an meme ae aem Awe, 1.2 x Cirratriradites annulatus Kosanle ---~-- --- _ 222000800 2.0.0.0 Li nna ao ae o nmn ne mnm ne nemen rene x x az ConvolttigpOra Bp - <== -== == = s n H m H ao nene a me t e ne co ne we me w us ms ae me H s ae ae me me meme li m mi s ma e me ar me a me fot haine r me ms ine m be B me hn me an he hea oe a 4 <2 Crassispora kosanket? (Potonie and Kremp) Bharadw af - -==--- --- s- - -s - 2 ou on oo o ee ne o oem anne a in mnm oie arie a atin a m a =a .8 x C. sp ---- a -- X Densosporites sphaerotriangularis Kosanke airmen. sige - x ers x D. triangularis Kosanke ----- ois s Be ane b ne he o age as ie to oe oe an ae e os che ee maladie ae oo ma o in ant n he a males a oo Ht whe .8 x D, SDP ofa o ee ee ee ee e s o e ee eee me eee meee meee e meee e e eme eee ee nece ec X A 1.6 Dictyotriletes bireticulatus (Ibrahim) Potonié and Kremp a 4 ke Endosporites cf. E. globiformis (Ibrahim) Schopf, Wilson, and Bentall ----------------------------------- x x s E. ornatus Wilson and Coe ----- ---- pea o eee r t e alien ie cs une maul mn he tn t maine me Te me hink moss he an pain io he i fai te cs x .8 a E. sp - -- == .8 =c Florinites antiquus Schopf in Schopf, Wilson, and Bentall ————————————————————————————————————————————— -- 4.0 1.6 F. $p -----<----- --< < spp--<-< s - x 9.2 12.8 Microreticulatisporites sulcatus (Wilson and Kosanke) Smith and Butterworth ---------------------------- -- A 1.6 Punctatisporites obesus Potonié and Kremp ccc a x a+ P. spp g==- o --- X 2.8 3.2 Radiizonates sp Cn oe ewe we to an el ma oe me me whle Bn he he ne ne pa h r an n es l oe n t tied ane n i . x o as Reinschospora sp ------------ = sus- ae x - Torispora securis Baliye --- --- --- -. 2. 2 222 n 2 n cll c dln lll ll oc o o e ne me me me ae a ae me me me we f a me a m e te a m m me m ie m m m me me ie ae eae ie ie a> 12.4 4.8 T. sp -- e-cccccccccccccccccececenecccececec_~ -- - -- .8 .8 Triquitrites cf. T. arculatus Wilson and Coe oon nees ens 1.2 16%. Monosaccate -- -- .8 .8 -- Total =-- Hebe -- ane 100.0 _ 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 573-A, 19.0 em roof rock. 573-D, 1.9 cm seat rock. 573-B, 19.0 cm coal. 573-C, 19.0 em coal. 34 TABLE 18. -Palynomorphs from the No. 6 Block coal bed in West Virginia [Maceration 603; USGS Paleobotanical loc. No. D6115; 250 specimens counted; X, present but not observed in count] PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA Taxon 603 (percent) Calamospora breviradiata Kosanke - -- 1.2 C. sp 2.0 Cirratriradites annuliformis Kosanke and Brokaw 0.4 Cyclogranisporites sp ---- A Endosporites sp ---- A Florinites antiquus Schopf in Schopf, Wilson, and Bentall A Granulatisporites verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall - A G. sp ---- .8 Laevigatosporites globosus Schemel -- 12.8 L. medius Kosanke 1.6 L. minutus (Ibrahim) Schopf, Wilson, and Bentall -- 13.2 L. ovalis Kosanke 4.8 L. punctatus KOGAMKG ------ --- -- _. _. ___no ooo nooo o o nnn n onn n n n o nn n m mma onn nm mannn mmm mmm 2.8 L. vulgaris (Ibrahim) Alpern and Doubinger -- ---- - .8 Leiotriletes sp ---- --- .8 Lycospora brevijuga Kosanke - 4.0 L. granulata Kosanke ---- ---- he- 11.2 L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall 1.6 L. spp -- 10.0 Punctatisporites obliquus Kosanke --- 1.6 P. sp --- ---- .8 Raistrickia cf. R. imbricata Ko#sanke - -~ -->> = s. cool o ne o oon se s a Bee ae os os o a a o c as a a haf fm me m mto m mee me me me ume c me mo h a ne oe we me me no me me mo h me ae me me ae A Schopfites dimorphus --- - --- - -. -. -. - =-. . 2 coll ooo on lo o onn ae e n t n nn n oe a a a a r m a a n m mn mo ne mme m mme m mme een emi mmm mem X Thymospora pseudothiessenii (Kosanke) Wilson and Venkatachala --- ---- ---- 21.6 Torispora securis Balme -- -- 1.2 Triquitrites pulvinatus Kosanke -- .8 T. sp -- -- --- .8 Vestispora fenestrata (Kosanke and Brokaw) Spode in Smith and BUtt@erworth #>. Verrucosisporites sp -- -- ---- - A Wilsonites sp 1.2 Monosaccate -- -- -- ---- 1.6 Total -- 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 603, one lump of coal. TABLE 19.-Numerically important palynomorphs from the Pittsburgh No. 8 coal bed in West Virginia [Maceration series 428; USGS Paleobotanical loc. No. D6043; 750 specimens counted; X, present but not observed in count] Taxon 428-A 428-B 428-C - 428 A-C (percent) Laevigatosporites medius Kosanke --- -- 3.2 2.0 7.2 4.1 L. minutus (Ibrahim) Sthopf, Wilson, and Bentall -- 4.0 2.8 6.0 4.2 L. ovalis Kosanke -------- -- 3.6 3.2 6.4 4.4 Thymospora thiessenii (Kosanke) Wilson and Venkatachala 84.4 88.0 72.4 81.6 Total --- -- - 95.2 96.0 92.0 94.3 DESCRIPTION OF MATERIAL IN MACERATIONS 428-A, _ 35.5 cm coal. 428-B, _ 35.5 cm coal. 428-C, _ 35.5 cm coal. PALYNOMORPH ASSEMBLAGES FROM POTTSVILLE AND LEE FORMATIONS 35 PALYNOMORPH ASSEMBLAGES FROM PART OF THE POTTSVILLE FORMATION OF OHIO AND THE LEE FORMATION OF EASTERN KENTUCKY The Pennsylvanian rocks of Ohio and eastern Ken- tucky are not highly metamorphosed; therefore, recov- ery of palynomorphs is relatively easy and preservation is generally excellent. Figure 7, modified from Stout (1939), records the presence of four coals within the basal 30.4 m of the Pottsville Formation of Ohio. The oldest coal is the Sharon No. 1 coal, which occurs a short distance above the Sharon Conglomerate Member (Stout, 1939; Collins, 1979). Above this, in this 30.4 m interval, Stout recorded the presence of the Anthony, Huckleberry, and Quakertown No. 2 coals. The Sharon No. 1 and the Quakertown No. 2 coals were mined and prized for their low sulfur content. For a discussion of the lithostratigraphy, biostratigraphy, and coal re- sources of this part of the Pottsville of Ohio, see Collins (1979). Two sets of samples of the Sharon No. 1 coal have been collected, prepared, and examined. These sets of samples (maceration series 469 and 542) are from Byer quadrangle, Jackson County, in southern Ohio. The coal of maceration series 469 is 83.7 cm thick. The paly- nological data are shown in table 20, and the abundant genera are: Densosporites 40.2 percent Granulatisporites 5.6 Lycospora 44.8 90.6 percent Lycospora and Densosporites are codominant taxa and represent 85 percent of the assemblage. Both of these genera are related to the Lycopsida. Chaloner (1958) reported that the spores of Lycospore have been associated with arborescent lycopods, whereas the spores of Densosporites are associated with herbaceous lycopods. Six species of Densosporites have been identi- fied (table 20) and Lycospora pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke is the dominant taxon assigned to that genus. No specimens assignable to Laevigatosporites were observed. The sec- ond sample, maceration 542, is only 52.7 ecm thick and was collected as a single unit. A somewhat smaller assemblage of similar taxa was observed in sample 542, except that Densosporites is the dominant taxon and Lycospora is subdominant. Densosporites covensis Berry and D. irregularis Hacquebard and Barss are present, and these taxa occur elsewhere in the United States in Lower Pennsylvanian coals. The Anthony coal (maceration 540) is thin and not mined. The sample prepared and examined was 27.9 cm thick and came from the Sciotoville quadrangle in southern Ohio. Lycospora is the dominant taxon (table 21), and Densosporites is subdominant. Lycospora pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseu- doannulata Kosanke represents 33.6 percent of the palynomorph assemblage. This assemblage is similar to the sample from the Sharon No. 1 coal in that Den- sosporites covensis Berry and D. irregularis Quakertown No. 2 coal (468-A-D, 541-A-B) Huckleberry coal Anthony coal (540) Sciotoville flint clay 30.5 METERS Sharon ore Sharon No. 1 coal (469-A-F, 542) Sharon Conglomerate Member Harrison ore EXPLANATION o: - -] SanDsTOoNE, :" '6n.) congLOMmERaAtic .*.'| SsANDSsTONE [-=-] SILTSTONE [:: --=] OR MUDSTONE SHALE OR CLAYSTONE ja) co« FIGURE 7.-Generalized section of the basal 30.5 m of the Pottsville Formation of Ohio, from Stout (1939). Maceration numbers in parentheses mark position of samples studied. 36 PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA TABLE 20.-Palynomorphs from the Sharon No. 1 coal bed in Ohio [Maceration series 469; USGS Paleobotanical loc. No. D6027; 1,500 specimens counted; X, present but not observed in count] Taxon 469-A 469-B 469-C 469-D - 469-E 469-F (percent) Ahrensisporites guerickei (Horst) Potonié and Kremp -------------------------- «- 1.6 ~ 0.8 -- 1.6 Anapiculatisporites minor (Butterworth and Williams) Smith and Butterworth ------ 0.4 -- -- -- -- X Apiculatisporites spp --- -- A -- -- -- 0.8 X Calamospora breviradiata ROoganke loo eigen eden en. -- -- 1.6 -- -- -- C. hartungiana Schopf in Schopf, Wilson, and Bentall -------------------------- -- A A -- -- -- C. SDD --- ono n onne anna nan ee eee eee oo eee meee eee enn nem m mnm mn nanan nmn s -- .8 -- .8 1.6 2.4 Camptotriletes bucculentus (Loose) Potonie and Kremp ------------------------- -- -- -- -- -- 8.2 Cirratriradites cf. C. maculatus Wilson and Coe -------------__________________ -- -- -- ~- -- X Convolutispora florida Hoffmeister, Staplin, and Malloy ------------------------ -- -- -- -- X -- C. SDD <--- <--- --- . 19.2 81.2 D. irregularis Hacquebard and Barss 1.6 2.4 9.6 5.2 5.6 -- D. spinifer Hoffmeister, Staplin, and Malloy -------------_-_____________________ -- -- -- -- .8 -- D. triangularis Kosanke ---- -- -- 4.4 13.6 -- -- D. variabilis Felix and Burbridge - 2.0 15.6 3.2 8.4 .8 9.6 D. SDp 2.4 4.0 22.0 12.0 - 12.0 11.2 Dictyotriletes castaneaeformis (Horst) Sullivan -------------___________________ 1.2 -- -- -- -- 3.2 Endosporites sp ----- -- -- -- -- -- X -- Granulatisporites pallidus Kosanke --- ---- 1.2 -- .8 .8 7.2 6.4 G. verrucosus (Wilson and Coe) Schopf, Wilson, and Bentall ————————————————————— ~- A -- -- -- f G SBD # erat _i .8 2.8 1.6 44 6.4 5.6 Knoxisporites rotatus Hoffmeister, Staplin, and Malloy ------------------------ X -- -- -- -- -- Lycospora granulata Kosanke -- - ---- 6.0 -- .8 12 4.0 -- L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall ——————————————————— X -- -- -- 1.2 -- L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke ------ 32.0 42.4 30.0 21.6 18.8 9.6 L. spp ---- ---- --- I ---- 32.8 21.6 18.0 9.6 8.4 6.4 Potonieisporites elegans (Wilson and Kosanke) Wilson and Venkatachala ---------- -- X -- -- A -- Punctatisporites sinuatus (Artuz) Neves --- -- -- -- -- -- -- -- X P. spp -------------- -- 2.0 .8 .8 .8 1.6 .8 Raistrickia spp --------- - X A -- .8 .8 .8 Reinschospora speciosa (Loose) Schopf, Wilson, and Bentall ————————————————————— -- -- -- -- X -- Savitrisporites nux (Butterworth and Williams) Smith and Butterworth ----------- -- .8 A 2.8 4A 4.0 Schulzospora rara Kosanke --- -- -- A -- -- -- -- S. sp -- ---- --- A -- -- -- -- -- Simozonotriletes intortus (Waltz) Potonié and Kremp ------------------_-_____-- X X -- -- -- -- Stenozonotriletes lycosporoides (Butterworth and Williams) Smith and Butter- worth -- -- ---- Innintnininininininiaiaiaiainiateteretainiatateteteteietetetetetetetate 13.6 -- -- .8 -- -- Waltzospora priscus (Kosanke) Sullivan -- o A 1.2 1.2 -- 2.8 -- Monosaccate --- a A A -- -- A -- Unassigned ------------ -- --- 1.2 1.2 .8 -- X -- TOt@l ---- 100.0 100.0 100.0 100.0 100.0 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 469-A, 15.2 em roof rock. 469-D, 27.9 cm coal. 469-B, 25.4 cm coal. 469-E, 15.2 em coal. 469-C, 15.2 em coal. 469-F, 16.2 em seat rock. PALYNOMORPH ASSEMBLAGES FROM POTTSVILLE AND LEE FORMATIONS 37 Hacquebard and Barss are present along with other species of the genus reported previously in the Sharon No. 1 coal, but dissimilar in that Densosporites is sub- dominant to Lycospora in abundance. The most abun- dant genera of the Anthony coal (maceration 540) are: 26.8 percent 66.8 93.6 percent Densosporites Lycospora The single specimens Anaplanisporites sp., Apiculatisporis ef. A. aculeatus (Ibrahim) Smith and Butterworth, Convolutispora florida Hoffmeister, Staplin, and Malloy, Grumosisporites cf. G. varioreticulatus (Neves) Smith and Butterworth, and others were observed as shown in table 21. No speci- mens assignable to Laevigatosporites were observed. The Huckleberry coal is thin and occurs above the Anthony coal and below the Quakertown No. 1 coal. No samples of this coal were available for study, so it is not known whether or not Laevigatosporites first occurs in the Huckleberry or in the Quakertown No. 2 coal. The occurrence of Laevigatosporites is well established in the Quakertown No. 2 coal (table 22; fig. 4); this is the start of the consistent occurrence of Laevigatosporites range zone in Pennsylvanian coals of Ohio. Poorly pre- served single specimens of what were questionably assigned to Laevigatosporites were observed in both sets of the Sewell and Sharon No. 1 coal. Both sets of samples of the Quakertown No. 2 coal are from the Byer TABLE 21.-Palynomorphs from the Anthony coal bed in Ohio [Maceration 540; USGS Paleobotanical loc. No. D6029; 250 specimens counted; X, present but not observed in count] Taxon 540 (percent) Ahrensisporites guerickei (Horst) Potonié and Kremp Anaplanisporites sp Mpiculatisporis cf. A. aculeatus (Ibrahim) Smith and Butterworth Apiculatisporites spp -- - Calamospora parva Guennel ------- C. sp --------- Convolutispora florida Hoffmeister, Staplin, and Malloy C. cf. C. meltia Hoffmeister, Staplin, and Malloy ------ Crassispora kosankei (Potonié and Kremp) Bharadwaj Cyclogranisporites Sp ----------------- Densosporites annulatus (Loose) Schopf, Wilson, and Bentall --- D. covensis Berry ------ = 2.0 Grumosisporites varioreticulatus (Neves) Smith and Butterworth -- X -- -- Knoxisporites rotatus Hoffmeister, Staplin, and Malloy -- -- -- .8 K. sp -- -- ~- 1.2 Laevigatosporites desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall -------=-«-__._..____ -- -- f 1.6 L. latus Kosanke -- X 1.6 -- L. medius Kosanke X 1.2 -- 2.8 L. ovalis Kosanke X 4.8 11.2 4.4 Lycospora granulata Kosanke X 26.0 13.6 2.8 L. micropapillata (Wilson and Coe) Schopf, Wilson, and Bentall X 2.0 .8 13.2 L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke -------------------- X 44.0 24.0 25.2 L. spp -- 16.8 32.8 22.4 Potonieisporites elegans (Wilson and Kosanke) Wilson and Venkatachala ------------------------ -- -- .8 -- Punctatisporites spp X A 3.2 1.2 Raistrickia sp - -- -- A 1.6 -- Savitrisporites nux (Butterworth and Williams) Smith and Butterworth -------------------------- X -- -- -- Schulzospora sp X -- -- -- Vestispora sp -- -- -- .8 Monosaccate -- -- 1.2 1.6 2.8 Unassigned --- -- .8 .8 A Total 100.0 100.0 100.0 DESCRIPTION OF MATERIAL IN MACERATIONS 468-A, 10.2 em roof rock. 468-C, 25.4 cm coal. 468-B, 25.4 cm coal. 468-D, 5.1 em seat rock. SUMMARY 39 fied include Schulzospora sp. Lycospora is clearly domi- nant in 468-B-D as shown below: 9.4 percent 79.6 89.0 percent Laevigatosporites Lycospora L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke is the most abundant taxon (table 22). In addition, L. granulate Kosanke is numerically important in the top half of the coal (468-B). The following species of Laevigatosporites have been identified: L. desmoinensis (Wilson and Coe) Schopf, Wilson, and Bentall, L. latus Kosanke, L. medius Kosanke, and L. ovalis Kosanke. Densosporites is poorly represented in the Quakertown No. 2 coal, which contrasts markedly with the abundance of this taxon found in both the Sharon No. 1 and Anthony coals. Maceration series 541, the Quakertown No. 2 coal, is 65 cm thick and was sampled as the top half of the coal (541-A) and the bottom half of the coal (541-B). Lycospora is the dominant genus in both samples with L. granulata Kosanke the most abundant species fol- lowed by L. pellucida (Wicher) Schopf, Wilson, and Bentall-L. pseudoannulata Kosanke. Laevigatosporites is present at about the same rate as was found in maceration series 468 (9.4 versus 9.7 percent), and an additional species, L. vulgaris (Ibrahim) Alpern and Doubinger, is present. The bottom sample (541-B) con- tains specimens which I assigned to Endosporites cf. E. zonalis (Loose) Knox. Endosporites is present in maceration series 468, but not this species. The palynomorph content of three coals occurring within the basal 30 m of the Pottsville Formation of Ohio has been examined in detail. Representatives of both arborescent (Lycospora) and herbaceous (Den- sosporites) lycopods dominate the assemblages of these coals. The start of the consistent occurrence of Laevigatosporites is found in the Quakertown No. 2 coal. No palynological information is available on the Huckleberry coal; the start of the range zone of Laevigatosporites in Ohio should be clarified. The basal Pennsylvanian formation in eastern Ken- tucky is the Lee Formation. The lower portion of this formation is well exposed along the London boat dock in the Sawyer quadrangle, Laurel County, Ky. Six sets of samples were collected along the road leading to the London boat dock (maceration series 129-134). Kilburn (1956) gave the measured thickness as 100.2 m. The sec- tion begins near BM B-202 at the dock at the Pennington-Lee contact and continues along the road to the top of the plateau in the Sawyer quadrangle. (For additional information see Puffett, 1962, and Rice and others, 1979.) Abundant and well-preserved spores and pollen grains were common to the upper five sets of coal samples (maceration series 129-133). The basal coal sample (maceration 134) contains a number of paly- nomorphs, but the sample is weathered and preserva- tion of palynomorphs is poor so that abundance counts are not reliable. Lycospora is the most abundant taxon found in the other five sets of coal samples from the Hudson through the Barren Fork coal near the top of the section (fig. 8). The Barren Fork coal is the most diversified of the coals with respect to palynomorph content. Schulzospora rara Kosanke occurs in all six sets of the London boat dock section. Densosporites ir regularis Hacquebard and Barss ranges from the Mississippian rocks below through the Beaver Creek coal in the Lee Formation (fig. 8). Stenozonotriletes lycosporoides (Butterworth and Williams) Smith and Butterworth occurs in the unnamed coal, the Hudson coal, and the Stearns 1% coal, but Trinidulus diam- phidious Felix and Padden is present only in the Stearns 1% coal. Punctatisporites sinuatus (Artuz) Neves apparently first appears in the Hudson coal, Dic- tyotriletes bireticulatus (Ibrahim) Smith and Butter- worth first appears in the thin unnamed coal (macera- tion series 130) just above the Hudson coal, and Laevigatosporites is known to occur first in the Barren Fork coal. The Schulzospora range zone is continuous through all of the coals exposed in the London boat dock section of Kentucky and is known to terminate in the lower part of the Middle Pennsylvanian. In Ohio Schulzospora is known to be present in the Sharon No. 1, Anthony, and Quakertown No. 2 coals The start of the Laev- igatosporites range zone in eastern Kentucky is at the Barren Fork coal, and we know this genus is present in the Quakertown No. 2 coal of Ohio. SUMMARY Coals occurring in the upper half of the New River through the Monongahela Formations of the proposed Pennsylvanian System stratotype of West Virginia are amenable to the chemical maceration process allowing palynomorphs to be extracted. However, although coals occurring in the lower half of the New River and Pocahontas Formations react to the chemical macera- tion process, they do not consistently yield paly- nomorphs, so meaningful analyses are not possible. For this and other reasons, some Lower Pennsylvanian coals from Ohio have been incorporated into this report together with remarks on the occurrence of palyno- morphs from some Lower Pennsylvanian coals from eastern Kentucky. Figures 4 and 9 summarize the abun- dance and occurrence of taxa useful in correlation 40 PALYNOLOGY OF COAL BEDS IN THE PROPOSED PENNSYLVANIAN STRATOTYPE, WEST VIRGINIA London dock section Sawyer quadrangle, Kentucky Sawyer quadrangle, Kentucky Rockcastle Conglomerate Member Beave! Creek gos! 132 Lee Formation 86-127 METERS 91.4 METERS 131 ----------- Stearns No. 1% coal 1 130 I 129________’_._~—H udson coa 134 (Kilburn, 1956) Pennington Formation (Modified from Puffett, 1962) EXPLANATION sd *conccomninic [=-] share sity """ SANDSTONE --] umestone SiLTSsTONE SHALE, [ ess oR MUupsToNe CARBONACEOUS Bs Cio ie -- FiGurE 8.-London dock section, Sawyer quadrangle, Kentucky, as reported by Kilburn (1956), and a generalized section for Sawyer quadrangle as reported by Puffett (1962). The named coal beds have been examined as well as two thin coal beds occurring just above the Pennington Formation and above the Hudson coal. Maceration numbers 129-134 are shown. SUMMARY studies. It should be noted that the scope of this in- vestigation is the occurrence of palynomorphs of selected coal beds. Therefore, because every coal has not yet been examined, gaps remain in our knowledge con- cerning the precise range zones of some taxa. The following are some of the taxa that have re- stricted or otherwise useful range zones (fig. 9), and are useful in biostratigraphic studies: Densosporites annulatus (Loose) Schopf, Wilson, and Bentall D. irregularis Hacquebard and Barss Laevigatosporites globosus Schemel L. punctatus Kosanke Radiizonates spp. Savitrisporites nux (Butterworth and Williams) Smith and Butterworth Schopfites dimorphus Kosanke Schulzospora rara Kosanke OHIO 41 Thymospora pseudothiessenii T. thiessenii (Kosanke) Wilson and Venkatachala Torispora securis Balme Lower Pennsylvanian coals from Ohio are dominated by lycopsid plants as evidenced by the abundance of Lycospora and Densosporites (fig. 4). The same is true for the Lee coals of eastern Kentucky. The Lower Douglas(?), Gilbert(?) and Cedar Grove coals from the lower part of the Kanawha Formation of West Virginia are dominated by lycopsid palynomorphs. Above the Cedar Grove coal in the Kanawha Formation of West Virginia, a significant change is noted in palynomorph assemblages by the dominance of Laevigatosporites in the Winifrede coal (maceration series 121). Changes were occurring rapidly by the time the Stockton coal (maceration series 566) was deposited somewhat below the Kanawha black flint, although some of these changes may have their roots in the Coalberg coal WEST VIRGINIA Camptotriletes bucculentus Densosporites irregularis Stenozonotriletes lycosporoides Waltzospora prisca Schulzospora rara Savitrisporites nux Densosporites annulatus Grumosisporites cf. G. varioreticulatus Convolutispora ampla Laevigatosporites spp. Stenozonotriletes bracteolus Procoronaspora sp. Punctatisporites obesus Laevigatosporites globosus Radiizonates spp. Verrucosisporites sifati Vestispora fenestrata Laevigatosporites punctatus Microreticulatisporites sulcatus Murospora kosankei Zosterosporites triangularis Vesicaspora wilsonii Mooreisporites inusitatus Thymospora pseudothiessenii Schopfites dimorphus Thymospora thiessenii LOWER PENNSYLVANIAN 469 540 468 432 433 FiGurE 9.-Stratigraphic occurrence of selected taxa from Lower 122 MIDDLE PENNSYLVANIAN UPPER PENNSYLVANIAN L? o . XL l 22 on cer - aie a a ae o a elle anl ol n in a hin rain fe in ie in ie ie in ie an onle be malar ie 23 References Cited ans na snes = te sl aln 24 Supplemental information n 27 Comparison of the porphyritic granodiorites of Point Reyes and Monterey ___ 27 Comparison of the granitic rocks near the Pinnacles and Neenach Volcanic Formations of Matthews (1976) . .... _. 31 ILLUSTRATIONS Page 1. Index map of central and southern California, showing selected geologic and geographic features __________ 2 2. Map showing postulated realinement of some basement-rock units along the San Gregorio-Hosgri fault zone 3 3. Generalized geologic map of the Gualala area 4 4. Generalized geologic map of the northern Salinian block 6 6. Generalized geologic map of the central Salinian block 7 6. Generalized geologic map showing location of a possible north-south-trending fault connecting the Ben Lomond and La Honda faults uanks aia s aln -am ans. -is s 8 7. Map showing probable offset of the west margin of the Salinian block by the San Gregorio-Hosgri fault zone 8 8. Map showing locations of wells to basement between the Chalone Creek and San Andreas faults __________- 9 9. Generalized geologic map of the southernmost Sierra Nevada and the westernmost Mojave Desert ________ 10 10. Generalized geologic map showing locations of sheared rocks along the Vergeles fault. 11 11. Map showing extrapolation from well-core data of some basement-rock units in the central Salinian block -_- 15 12. Generalized geologic map of the southern Salinian block __ 17 13. Triangular diagram showing comparison of modally analyzed specimens of the porphyritic granitic rocks of Thermal Canyon and the porphyritic granodiorite-granite of the La Panza Range____________-__-__-__. 18 14. Maps showing possible reconstructions of the northern and central Salinian block before San Andreas fault movement-.......2 _- ons onle Rime nes sls nites cen srs ss t als 22 15. Generalized geologic maps showing locations of modally and chemically analyzed samples of the porphyritic granodiorites of Point Reyes and 27 16. Triangular diagrams showing modes of the porphyritic granodiorites of Point Reyes and Monterey 28 17. Histograms showing chemical analyses of the porphyritic granodiorites of Point Reyes and Monterey ______. 28 18. Triangular diagrams showing chemical compatibility of the porphyritic granodiorites of Point Reyes and MORtETEY .. . ..- «acer an -- au ns on aol ball ain ahs an nle Ml a ao a mine tie Sik ene ma ae a an e o ale ~ = a lp o in a al m an od on ace alle 30 19. Triangular diagrams showing modes of the Tomales Point and Inverness granitic bodies ___________--___.- 30 20. Maps showing locations of granitic rocks of the Pinnacles and Neenach areas and of modally and chemically analyted samples. cules suns baw ss an b a an - oms tens ns soe 31 21. Triangular diagrams showing modes of granitic rocks of the Pinnacles and Neenach areas ______________.-.- 34 22. Histograms of chemical analyses of samples of granitic rocks of the Pinnacles and Neenach areas _________- 35 23. Triangular diagram showing modes of chemically analyzed samples of granitic rocks of the Pinnacles and Neenach areas ...'s n 22221. __ lll ell inl le eae bad ain ale an ala in a me alee ar nl a tn ine haces iam han as ie in ance i in in in in hn n he in ale 36 24. Triangular diagrams showing chemical compatibility of granitic rocks of the Pinnacles area with those of the Neenach area ll =i ned ons eae rns an mer medi nn ss caw e sss m 36 IH IV CONTENTS Page FIGURE 25. Histograms showing semiquantitative-spectroscopic-analysis "midpoints" of trace-element concentrations in samples of the tonalite and granodiorite of Johnson Canyon, the granodiorite of the Fairmont Reservoir, the granite of Bickmore Canyon, and the felsic variant of the Fairmont Reservoir body _______-_____-_- 37 TABLES Page TABLE - 1. Chemical analyses of selected granitic rocks from the Point Reyes and Monterey areas, California_________ 29 2. Modes of selected granitic-rock samples from the Neenach area, 88 3. Chemical analyses of selected samples of the tonalite and granodiorite of Johnson Canyon, the granodiorite of the Fairmont Reservoir, the granite of Bickmore Canyon, and the felsic variant of the Fairmont Reservoir ¢.... L- cL. cer. Peal bien an meas bus nls'n oe on Rink s ain an an oo o ao 35 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS THE SAN ANDREAS, SAN GREGORIO-HOSGRI, AND RINCONADA-RELIZ-KING CITY FAULTS, CALIFORNIA By C. Ross ABSTRACT A reconstruction that treats the Salinian block as a south- ward extension of the Sierra Nevada is supported by (1) the possible correlation of several basement-rock features of the central Salinian block and the south end of the Sierra Nevada, and (2) reversal of right-lateral movement on the San Gregorio- Hosgri fault zone that significantly telescopes and shortens the north end of the Salinian block. However, currently accepted and documented movements on the San Gregorio-Hosgri and San Andreas fault zones are not great enough to allow either the Barrett Ridge slice or the K-feldspar-rich Cretaceous and lower Tertiary sedimentary rocks of the Gualala area to be derived from the southern Sierra Nevada. Additional fault dis- placement or transportation of exotic blocks from considerable distances would seem to be required. A model that treats the Salinian block solely as a fault-derived fragment of the southern Sierra Nevada does not appear to completely resolve the re- construction problem. Yet the similarities between the base- ment rocks of the Salinian block and the southern Sierra Ne- vada are great enough that strong data would be required to support alternative models of Salinian-block origin. INTRODUCTION During the past several years, I have gathered considerable information on the distribution, pe- trography, and chemical composition of the gra- nitic and metamorphic rocks of the California Coast and Transverse Ranges, particularly in the Salin- ian block. On the basis of that information, I pre- viously noted (Ross, 1978) that a parent terrane for the Salinian block is not evident and that the south- ernmost Sierra Nevada is not a likely source ter- rane from which the Salinian block could have been derived. Three strong objections were made (Ross, 1977a, 1978) to a reconstruction that would place the Salinian block adjacent to the southern Sierra Nevada. First, hornblende-rich high-grade meta- morphic rocks, which are widespread in the south- ernmost Sierra Nevada, appear to be absent from the Salinian block. Second, the Salinian block is practically barren of metallic mineralization, whereas metallic-mineral deposits are common in the southern Sierra Nevada. Third, there is no evi- dence in the Salinian block of metasedimentary rocks that could be correlative with the thick quartzite and marble units of the Cordilleran mio- geocline-units that almost certainly reach the San Andreas fault southeast of the Sierra Nevada. Two recent developments, however, lend support to a reconstruction model that would derive the Salinian block from the southern Sierra Nevada region. First, my mapping in the east-west-trend- ing tail of the Sierra Nevada (San Emigdio Moun- tains) has revealed a major structural break that juxtaposes oceanic basement' on the north against continental basement on the south. The Vergeles- Zayante fault zone in the central Salinian block may be a continuation of that fault zone in the Sierra Nevada. Second, Graham and Dickinson (1978a) and, more recently, Clark and others (1984) have suggested that significant right-lateral offset may have taken place along the San Gregorio-Hosgri fault zone. A reconstruction that took account of such offset could significantly telescope the northern part of the Salinian block (Bodega Head to Ben Lomond) and help resolve the longstanding contrast be- tween suspected offsets on the San Andreas fault in southern and northern California. About 300 km of right-lateral offset on the San Andreas fault is documented by the offset of several Tertiary and basement-rock units across the fault in central and southern California. More than 500 km of right- lateral offset has been suggested in northern Cal- ifornia on the assumption that the northernmost granitic outcrops in the Salinian block were once adjacent to granitic terrane on the northeast side of the San Andreas fault. The telescoping effect of the San Gregorio-Hosgri fault zone, inferrable from the the data of Graham and Dickinson (1978a, p. 17) and Clark and others (1984), removes more than half of the offset discrepancy. In this report, I review data from selected base- ment-rock units in the Salinian block, the south- 'As used in this report, "oceanic basement" includes not only greenstone, basalt, and gabbro derived from oceanic crust, but also the Franciscan assemblage and associated rocks, most of which were deposited on, and are closely associated with, oceanic crustal material. 1 2 ernmost Sierra Nevada, and nearby areas in re- lation to the problem of offset on the San Gregorio- Hosgri, San Andreas, and Rinconada-Reliz-King City fault zones. I also discuss problems concerning the Barrett Ridge slice and the Gualala granitic clasts-problems that are difficult, if not impossi- ble, to resolve on the basis of 300 to 350 km of base- ment movement between the central Salinian block and the southern Sierra Nevada. By their very nature, basement-rock correlations are equivocal; for this reason, I place little faith in one-to-one" basement-rock correlations. The com- parison of several basement-rock units to several similar basement-rock units is much more con- vincing, and such a comparison is more apt to pro- POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA however, the correlations of Cordilleran granitic suites and their surrounding metamorphic rocks are particularly difficult because in this region sim- ilar rocks are widespread and recurrent. The work then becomes a search for unusual rock types that may be, if not unique, at least rare enough to be regionally significant. The younger, fossiliferous rocks, whose correlation parameters (such as shorelines and lithofacies pinchouts) are more de- finitive, give us a better chance for unequivocal correlations, but these younger rocks cannot be used to resolve fundamental offset problems con- cerning events that predate their existence. Thus, I have for the most part consciously ignored the vide a genuine contribution to a correlation model; 122° ' A Point /\ & Arena N \\ Area of G \, \, Figure 3 el 3.1 A\ ~ \ i= 4 Xs Head x Area of | Point Reyes I y Figure 4 \ t \ \ % > \ 3 ¢ 77/0, Montara : Mogmin '.- __\\ 14x Ario Nuevo Point, « T.». younger sedimentary, volcanic, and alluvial units that are inherently part of any reconstruction | anat \\\‘“\ \ a < wth 4 116° -- _- Stes SL. .A T. FAULT Figure 9 -) 0C PC Tehachapi \ San! Emigdio +g MOJAVE C fitmalm I ~ DESERT 35° MW?) s Portal-Ritter 6 ~~ Rid j}; «1 ° Holcomb and _ Frazier "4" @ /Wn9htwood area Mountain - Com 0 ng T‘Wflfi S/ aing = Ap 2G 9704 MADRE elles aflzfi' Chocolate and Orocopia _,, n, Mountains / ne, /‘ 100 KILOMETERS FIGURE 1.-Index map of central and southern California, showing selected geologic and geographic features and locations for figures 3, 4, 5, 9, and 12. SAN GREGORIO-HOSGRI FAULT ZONE 3 model; my studies have been concerned solely with the basement rocks and with the maximum move- ments of fault blocks, as recorded by these rocks. A series of generalized geologic maps of parts of the Salinian block, the southern Sierra Nevada, and nearby related areas is included in this report to show the distribution of those basement-rock units that are pertinent to the discussion. Figure 1 shows the areas covered by these geologic maps. SAN GREGORIO-HOSGRI FAULT ZONE Graham and Dickinson (1978a, b) suggested as much as 115 km of right-lateral slip along the north- ern part of the San Gregorio-Hosgri fault zone, on the basis of correlation of several features across the fault zone, including: similar Cretaceous and Tertiary sedimentary sections, two similar anom- alous K-feldspar-bearing tectonic slabs of the Fran- ciscan assemblage, a matching pair of Mesozoic ophiolite patches, an offset gravity feature, and a tectonic contact of the Franciscan terrane against Salinian-block basement between Bodega Head and the Gualala Basin (see fig. 4) that has been observed to match certain relations along the Pi- larcitos fault. If these Cretaceous, Tertiary, and ophiolite correlations are valid, then the northern Salinian-block basement rocks must also have been dismembered and moved a comparable distance. Graham and Dickinson (19782) noted that their pairs of offset geologic features are not "tightly constrained" and that they "show probable offset ranges." More recent work by Clark and others (1984) indicates that a larger right-lateral offset on the San Gregorio fault of about 150 km is called for by the present distribution of Tertiary sedimen- tary rocks of the Point Reyes, Santa Cruz Moun- tains, and Monterey areas. The granitic basement of this same region is also compatible with such an offset (see supplementary section below entitled "Comparison of the Porphyritic Granodiorites of Point Reyes and Monterey"). A basement reconstruction using either the 115- km offset of Graham and Dickinson (1978b) or the 150-km offset of Clark and others (1984), is permis- sible, considering the vagaries of shapes of granitic bodies. The larger offset, however, in my opinion, permits a better "onstrike" alignment of a number of possibly related tonalitic bodies, as well as an alignment of the porphyritic granodiorites of Point Reyes and Monterey (fig. 2). Either reconstruction would place the granitic rocks of Bodega Head op- posite Montara Mountain-a permissible correla- tion because both masses are dominantly horn- blende-biotite tonalite. This adjustment would also place all known onshore and offshore outcrops of the northern Salinian block (Bodega Head, Point Reyes area, Cordell Bank, and the Farallon Is- lands) to the south of the Pilarcitos fault (see fig. 4). Furthermore, it follows that if, as Silver and others (1971) suggested, the Gualala Basin is un- derlain by Franciscan basement, then a blunt- ended Salinian block rests against Franciscan basement on the north. The presence of Franciscan basement is suggested by a small fault-bounded outcrop of spilite (fig. 3) near Black Point (Went- worth, 1968). Such spilitic basement rocks are un- known in the Salinian block but are found in the Franciscan basement. Even if the Gualala area is underlain by Fran- ciscan basement, granitic basement rocks must be relatively close by to have supplied a source ter- rane for a thick section of Cretaceous and lower Tertiary K-feldspar-bearing arkose and conglom- erate that is rich in clasts of granitic rock. If the Gualala Basin is floored by the Franciscan assem- blage, then this basin cannot be too wide because granitic basement must be present to the west or south; that is, the Salinian block probably extends northward from its exposures at Bodega Head and Cordell Bank, possibly as far as Point Arena (fig. 3). EXPLANATION Tonalite of Montara PILARCITOS Mountain A/ rauut SAN GREGORIOHOSGRI Porphynie aracodiont FAULT ZONE A Pe e an es of Monterey and Point Reyes ~ Tonalites of Tomales Point, Ben Lomond, and Vergeles Monterey Peninsula 0 20 40 60 KILOMETERS borg lick. FIGURE 2.-Postulated realignment of some basement-rock units along the San Gregorio-Hosgri fault zone. 123°%45° Plagioclase arkos POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA 123°30' 1 39°00 ¥ A K-feldspar arkose - (Tertiary) (Cretaceous) 123°15' Ay K-feldspar arkose (Cretaceous) 123°00' sd s - 38°30 15 KILOMETERS __ _L _ __LL____J | 38°15 FIGURE 3.-Generalized geologic map of the Gualala area (modified from Wentworth, 1968). SAN GREGORIO-HOSGRI FAULT ZONE 5 Instead of the large block (sphenochasm) that Silver and others (1971) suggested for the Gualala Basin, there may be only a thin sliver of the Fran- ciscan that is bounded by a fault on the west-just offshore, as Wentworth (1968) suggested. This fault could well be an extension of the Pilarcitos fault- that is, a San Andreas fault strand. If the Pilarcitos fault correlates with a structural contact north of Bodega Head and south of Fort Ross, as suggested by Graham and Dickinson (1978a), then granitic basement rocks may extend as much as 70 km northward of Bodega Head and offshore of Gualala (fig. 3). It would be interesting to know whether any of the Eocene rocks east of Montara Mountain between the Pilarcitos and San Andreas faults re- semble the K-feldspar arkoses of the same age in the Gualala area; such a resemblance would be ex- pected if the offset suggested by Graham and Dick- inson (1978a) is valid. Placing Bodega Head opposite Montara Moun- tain would leave granitic rocks north of probable oceanic basement. Both geologic and geophysical evidence suggest that oceanic basement may be present between the Vergeles-Zayante fault and the Butano fault (figs. 4, 5). The only basement outcrop between these two faults is the hornblende quartz gabbro and anorthositic gabbro near Logan (fig. 5). These basement-rock types are unlike any granitic basement in the Salinian block, and their chemistry and petrography suggest that they are probably oceanic (Ross, 1970). West of the Logan outcrops (fig. 5), the occurrence of a gravity high (Clark and Rietman, 1973) sug- gests that gabbroic rocks extend westward of the present outcrop, possibly to the Vergeles fault. Also, Hanna and others (1972) and Brabb and Hanna (1981) noted that the Boulder Creek aero- magnetic anomaly north of Ben Lomond Mountain between the Zayante and Butano faults is one of the largest magnetic features in the vicinity of the San Andreas fault. The Boulder Creek high and the somewhat less impressive Corralitos aeromag- netic high (fig. 4) are most likely caused by gabbroic rocks similar to those exposed near Logan, where there is also an impressive aeromagnetic anomaly (Hanna and others, 1972). Seismic-refraction veloc- ities of about 5.5 km/s have recently been obtained from the basement between the Zayante and Bu- tano faults. These velocities are compatible with those obtained elsewhere in the region from Fran- ciscan graywacke (A. G. Lindh, written commun, 1982). Graywacke in this block would be as com- patible as gabbro with an oceanic basement. Seis- mic-refraction profiles obtained recently north of the Vergeles-Zayante fault zone suggest that the Logan-type gabbroic rocks may be less extensive than had previously been believed. The only other basement-rock data for the area between these two fault zones are from the Union Hihn #2 oil well (fig. 4). This well is east of Ben Lomond, and its plotted position is just east of the Zayante fault (Ross and Brabb, 1973). The core material from the well is much like that from the basement outcrop just west of the Zayante fault. The Union Hihn #2 may actually bottom west of the Zayante fault-if the fault dips steeply east, or if the well is some- what deflected or either the well or the fault are slightly mislocated. Union Hihn #1, a few hundred feet northeast of Union Hihn #2, bottomed at 7,747 ft in Miocene beds, whereas the basement samples from Union Hihn #2 are from depths of 3,400 to 3,500 ft (Ross and Brabb, 1973). These data suggest some discordance (the Zayante fault?) between the two holes. Nevertheless, Salinian basement in the block between the Vergeles-Zayante and Butano faults cannot be ruled out on the basis of the pres- ent data. I first suggested (Ross, 1970) that the 'gabbroic rocks at Logan composed a thin fault sliver along the San Andreas fault, but later grav- ity and aeromagnetic data (Clark and Rietman, 1973; Hanna and others, 1972) have suggested that the gabbroic rocks are much more extensive; none- theless, the seismic-refraction velocity of 5.5 km/s seems to contradict all these older data. Clearly, more data are needed to delineate the basement of this block. If the block between the Butano and Vergeles- Zayante faults is oceanic, the Vergeles-Zayante fault zone may be an old strand of the San Andreas system, as Dibblee (1980) suggested. Alternatively, the terrane between the Butano and Vergeles-Za- yante faults could be an exotic sliver that was caught up in the Salinian block. The problem with considering the Vergeles-Zayante fault zone to be a major oceanic-continental break is that the Mon- tara Mountain granitic massif would then be ma- rooned east of the westernmost fault of the San Andreas fault system. On the basis of the presence of the Montara mass (fig. 4), the basement between the Butano and Pilarcitos faults is generally thought to be granitic. A northward continuation of the Ben Lomond fault that would tie into the La Honda fault (fig. 6) was suggested by C. M. Wentworth (oral com- munication, 1982) on the basis of an abrupt change in the geologic grain and attitude of bedding in Tertiary sedimentary-rock units across this zone. The occurrence of such a fault would suggest that 6 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA granitic basement underlies the block of country between the proposed La Honda-Ben Lomond fault and the San Gregorio fault from Montara Moun- tain south to Ben Lomond (fig. 6). Such a north- south-trending fault and the accompanying block of granitic basement would contradict my current suggestion that a suture of oceanic basement be- tween the Zayante-Vergeles and Butano faults ex- 123°30' 123°15° Tonal 122%45° onalite of 04 & Tomales Point bent Tomales: Point Granodiorite and granite of Inverness Tonalite of Cordell Bank sa («indo- hauls sites:m) # Tx l ®:A \ a \ <2 a } Porphyritic granodiorite Rr of Point Reyes P: A4 C Y4AF -L C Granodiorite of \ ~,_the Farallon Islands \ $!N 0 .C E Aa N Tonalite of Montara Mountain 0 5 10 15 KILOMETERS tends westward to the San Gregorio fault. Granitic rocks and metasedimentary rocks ex- posed east of the Ben Lomond fault are grossly similar to the basement rocks of the Ben Lomond Mountain area; that similarity suggests that the Ben Lomond fault is not a significant basement break and that displacement of the basement is modest. However, an impressive aeromagnetic 37°45" 12215° 121°45° Ben Lomond *T, ¢,)" ,¢ \ 4 4/744’7?‘ cap ing" ** f. Ad \ amp Texaco Poletti #1" **;, G2 ll i %\ (porphyritic grano- *, $7 (b Union #2 diorite of Monterey?) '. Hihn i a.. & W‘Q“ 37°00 *. Granite of ¢(’(} Smith Grade _ Granitic rocks, L | \ | undivided FIGURE 4.-Generalized geologic map of the northern Salinian block. Well symbol (4+) shows location of undivided granitic rocks in the subsurface. SAN GREGORIO-HOSGRI FAULT ZONE 7 high between the Zayante and Butano faults (fig. 6), which suggests the presence of gabbroic rocks there similar to exposed rocks near Logan (Brabb and Hanna, 1981), appears to terminate near the line of the proposed fault. The aeromagnetic-anom- aly gradient drops off rapidly west of the proposed fault, but it is questionable whether the gradient change is enough to allow the interpretation that granitic basement is faulted there against gabbroic basement. Information provided by present exposures and geophysical data do not appear to be sufficient for a unique solution to the problem of a possible north- south-trending fault and an accompanying strip of granitic basement. Closer examination of the area near the junction of the Ben Lomond and Zayante faults might resolve whether the Ben Lomond 121°30' 122°00° f Minimum offshore extent of the porphyritic granodiorite of Monterey {based on dredging) ‘_ f: *« \ ( $ R ~.. BAY Texaco Davies. well {tonalite _ \_ of Vergeles?) ~ I \_ _ Granite of «Fremont Peak ba C Monterey Porphyritic granodiorite tonalite of Compton (1960) Porphyritic \ granodiorite ~ e! Monterey fault is truncated by the Zayante fault or vice versa, but probably nothing short of additional sub- surface basement data can resolve this dilemma. Because of similar gravity patterns near Ano Nuevo Point (west of Ben Lomond) (fig. 1) and off- shore from Point Sur (fig. 5), Silver and others (1971) suggested an offset of only some 90 km on the San Gregorio fault. They interpreted these data to indicate offset on the west margin of the Salinian block (the Nacimiento fault zone). More recent data, however, suggest that the Franciscan assemblage of the Point Sur area has been dis- placed from similar rocks near Cambria (fig. 1) along the San Gregorio-Hosgri fault zone (Graham and Dickinson, 1978a). Thus, the Sur fault is most probably a segment of the San Gregorio-Hosgri fault zone and not part of the Nacimiento fault 36°30 36°15° 7 20) & Schist of Siovva/s de Salinas (subsurface) (g \\ San Ardo \@@ oil field - 36°00° 20 25 KILOMETERS | | | FIGURE 5.-Generalized geologic map of the central Salinian block. 8 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA zone. If so, the offset on the Nacimiento fault zone is about 130 to 135 km (fig. 7). The question then arises whether the gravity pattern off Point Sur (Silver and others, 1971) is related to the gravity expression of the Farallon Ridge to the north. Note that this offset on the Nacimiento fault zone is somewhat less than the 150-km offset indicated by data of Clark and others (1984) for the San Gregorio fault. The structure is complex where the Naci- miento fault intersects the shoreline south of Mon- terey, and more San Gregorio-Hosgri slivers may exist there that are analogous to the one at Point Sur. Thus, the seeming discrepancy may be less than the present figures suggest. Recent dredging in Ascension Canyon (off the coast west of the Ben Lomond area) (fig. 7) has brought up specimens of spilitic basalt and serpen- tinite that are considered to be inplace Franciscan (Mullins and Nagel, 1981). This dredged material provides a definite tie point to limit the westward extent of the Salinian block at that latitude. SAN ANDREAS FAULT ZONE Matthews (1976) presented compelling evidence that his Pinnacles Volcanic Formation in the south- # Tonalite of / / ¥ PILARCITOS Fauuy $%, Granitic 6 N &, N G ho Tonalite of ." A Ben Lomond -~ 3 Metasedimentary rocks 40 KILOMETERS MONTEREY BAY VA & Nl FIGURE 6.-Generalized geologic map showing location of possible north-south-trending fault (hachured line) connecting the Ben Lomond and La Honda faults. ern Gabilan Range and his Neenach Volcanic For- mation on the opposite side of the San Andreas fault (see fig. 20) are correlative and were contig- uous 23 m.y. ago, in Miocene time. To directly jux- tapose the Neenach and Pinnacles volcanic areas, Matthews suggested that the Chalone Creek fault (fig. 8) is an early Miocene trace of the San Andreas fault. He based this suggestion on the alignment of the Chalone Creek fault with Peach Tree Valley and on the absence of granitic outcrops in the sliver between the Chalone Creek and San Andreas faults. Oil wells have penetrated granitic basement at 2,000 to 4,300 ft within this sliver, however, and the core material suggests ties with the central Salinian block (Ross, 1974). Core samples 34 and 45 (fig. 8) are probably of the schist of Sierra de Salinas. These cores are lo- cated very near the extension of the Chalone Creek fault proposed by Matthews, but the fact that the samples were recovered at depths of 5,300 and 5,800 ft suggests that they are east of the Chalone Creek fault, because surface outcrops are present no more than 5 km to the west. If samples 34 and 45 are of the schist of Sierra de Salinas and if sample 27 is of the tonalite and granodiorite of Johnson Canyon, as its lithology suggests, it is unlikely that 124° I Point Arena © Y ej yA A -A el Cordell s. Point 38° |- Be"«~!_'neyes Possible extension Dy of Nacimiento ie. " anllon/(J Islands fault zone Sedimentary rocks of Pigeort‘n. Point (Cretaceous)-'* 6+ Point Sur 4-‘7 0 __ 40 _ 80 __ 120 kilometers fi'flngefflé (BE.. ALL ___| 0; | | 36° |- FIGURE 7.-Probable offset of west margin of the Salinian block (Nacimiento fault) by the San Gregorio-Hosgri fault zone. SAN ANDREAS FAULT ZONE 9 the Chalone Creek fault has had significant strike- slip displacement, and it may be dominantly dip slip, as Andrews (1936) suggested. The general con- figuration of the slice between the Chalone Creek and San Andreas faults more closely resembles a sliver along the San Andreas fault, and the well- core data are admittedly sparse. Even if the Cha- lone Creek fault is not a strike-slip fault, Matthews' (1976) correlation is still valid. The present sepa- ration of these two volceanic-rock units compares well with earlier estimates of San Andreas base- ment offsets by Crowell and Walker (1962) and with various Tertiary offset features described by Ad- dicott (1968) and Grantz and Dickinson (1968). These offsets would bring the Gabilan Range (fig, 5) up against the Sierra Nevada tail (San Emigdio Mountains) (fig. 1). I am skeptical of this correla- tion for several reasons, mainly because there is no evidence in the Salinian block of counterparts 121°15¢ to the hornblende-rich high-grade metamorphic rocks of probable oceanic affinity that underlie large areas of the Sierran tail. However, the recent realization that the Pastoria fault zone (fig. 9) of Crowell (1952) may extend westward to intercept the San Andreas fault has caused me to speculate that the Pastoria fault zone may have a counter- part fault in the Salinian block-the Vergeles-Za- yante fault zone. The Pastoria fault zone and, by much inference, the Vergeles-Zayante fault zone may indicate a major structural discordance (strike-slip or reverse fault movement, or both) that juxtaposes oceanic and continental terranes. Cer- tainly, the gabbroic rocks at Logan (see figs. 5, 14) and Eagle Rest Peak (see fig. 9, 14) near these two fault zones are petrographically and chemically compatible with each other (Ross, 1970; Ross and © others, 1973). The absence north of the Vergeles- Zayante fault zone of representatives of the horn- 36°30 |- Pinnacles Volcanic Formation of Matthews (1976) Granitic rocks; undivided Schist of Sierra de Salinas 0 5 10 15 KILOMETERS 1 Tonalite and granodiorite of Johnson Canyon(?) Basement penetrated at about 3000'; no samples 46 Dark gneiss, like gneissic rocks at Red Hills (?) Hornblende-biotite tonalite FIGURE 8.-Locations of wells to basement between the Chalone Creek and San Andreas faults, showing rock types penetrated, sample numbers, and depths to basement. Modified from Matthews (1976, fig. 18); basement core data from Ross (1974). POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA 10 #. oatfop; qsourrojsom pus epeaop qsouuroyjnos ay} Jo deut 21801038 00o81 L | | | e6pry sony ;jeu0g 40 m-------------G SH3L3WO7!X OZ or 0 4 «31k & Ing zueny 10A1989y juouniey Jo squoipoueiy } Q ye9q ing c seung adojequy 10 $HIGIPOUSIO _. s jo cueig (9461) smeynew jo uonewnoy ouedjoAa ydeusay uoneunoy uoAuey useg cigwfinhuhm-VEQ 1103007 € k ’ uregunop ysnug uofey jo auueig jo euuey _ $9994 v y, 24200!) i 4 2° $ 3 0 p y» -Z cD 3 A ¥ F 0 W 4 Gequounpes'© ~-" 7 & < _ je gu000lp 01 aue303 ; A ang N ~ th—‘u-=-. uoneunoy g Bu ot Cys" uoAue3 useg, .~ < 3a r /- r "ry \ s=." yeeq soy 00o§E 40 c1gge9 pepiaipun X... 'syoo: onueig is flab? "a> ..... AC A+% 1 1 YA F \\ N- -n 0 -v) 0 f Tk \\W/ N v S 4 47. 777 459 - .S10S€ 147 #7 q / f f 's Fy ¢ #4 F *. ly 4445 #3=, n Ger 4 13 = (e* w Tees ~- “MN“ u n. 7 “\ Sopue isiyosueaig eujoguydwe wfltnu *s r 14 f /, 7 >-pue isyosueangy a* es 7 \\\\\ / <.\\\\ ; a= 374, 3 ai LP Z #2 Cig $24, MPPA x x Fest rrr rg {5 *+ 1 # a 4 Ififl\\\ < \\\\“ \% *s tei"? c Teunersoy;s puse F an. & - maasd A# "" Syg Geunersouy pus ./ \.. ) ( j mre? hel egamg pormung sowee i, .. C > Ull‘M.\\\ a I§§\a \ #1 I\\\I\\\ Mate =~ sae ca “SWZEWm-floul/ml Ie C \\t§ A /Q =" -An, sere =I ,:» | DESE SLe81 L ,OEc81 L L 0061 L L SAN ANDREAS FAULT ZONE 11 blende-rich high-grade metamorphic rocks may simply indicate more overlap by Eocene and Oli- gocene sedimentary rocks and Miocene volcanic rocks there than to the north of the Pastoria fault zone. The outcrop belt of the hornblende-rich meta- morphic rocks thins markedly north of the Pastoria fault zone near the San Andreas fault, and so the absence of such rocks along the north side of the Vergeles-Zayante fault is not surprising. On an earlier map of the Vergeles fault area, Allen (1946) showed a sliver of granitic rocks north of the Vergeles fault about 5 km south of San Juan Bautista (fig. 10). My examination of this area re- vealed marble, mica schist, the tonalite of Vergeles, and medium- to coarse-grained granite, all sparsely exposed along a ridge that extends from the Ver- geles fault northward to the Old Stage Road, where tonalite and granite are exposed in a roadcut. These granitic rocks might have been emplaced Pliocene and Holocene sedimentary deposits TO SAN JOSE Eocene tur v- e. k "e and oj; Sedimenty re !ig0cene across the Vergeles fault zone, and they may have a relation analogous to that of the granite of Brush Mountain to the Pastoria fault zone (fig. 9). How- ever, the granitic rocks that appear to be on the north side of the Vergeles fault zone are more likely a sliver along the fault. Cursory examination of the rocks at several lo- calities along the Vergeles fault zone has revealed only a modest amount of shearing that can be re- lated to the fault (fig. 10). Several thin slickensided shear zones were observed in Tertiary sandstone immediately northeast of the Vergeles fault zone at its west limit of exposure east of U.S. Highway 101. There, the fault takes a more northerly trend, and shears that strike about N. 20° W. are aligned with the mapped fault trend. The slickensided zones dip 60-70° S. and flake off in flattened ovoid plates that have the appearance of paper shale. Sparsely exposed granitic rocks just southwest of EXPLANATION _a65 Strike and dip of foliation 36°47'30" San\Juan Bautista 121°30' TOCks A x ** AN NT \\\Sed,~ Aste Xx < \\\\\\§\ | | ) U.S. HIGHWAY 101 7 3 ~ h Ka Mip pals NAGA J shee cn -~] solr. yq} ~~~ 19 , Sheared metased~," ~~ /- imentary rocks\ | With: d \% \ ~ * TO SALINAS TO SALINAS 4 KILOMETERS 'm, Sms Pema ato lShears IP XSA A4 sandstone 2 QOD SA “‘§§\Protomylonitized all a tonalite) yy -&" a AIN eries "_ » c 5 : Z\72., /| ~~, - Mylonite clast I o -_ " associay A UC y # a /\,‘\7s\s_o\Cl/aréd ION/f/jd % l'\ N fOR Iss -felsic granitic ro s " I/C Retreat ** p SAYA 477 Marais. FIGURE 10.-Generalized geologic map showing locations of sheared rocks (circles) along the Vergeles fault. Geology simplified from Clark and Rietman (1973) and Dibblee (1980). 12 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA the faultline are deeply weathered and show no obvious evidence of shearing. Slickensides were ob- served, however, in some granitic float. Shearing also occurs in Tertiary sandstone and in micaceous schist on both sides of the Vergeles fault along the San Juan Grade Road between Sa- linas and San Juan Bautista (about 8 km east along the fault from the U.S. Highway 101 locality). Slick- ensided shear zones, as much as 0.3 m wide, cut Tertiary sandstone beds that are in, or just north of, the Vergeles fault zone. The shear zones trend N. 70° W. and dip about 85° S. About 0.2 km south of the fault zone, shearing and granulated lenses are evident in micaceous schist in a roadcut. These shear zones also strike N. 70° W., but they dip some- what less steeply at 70° S. Some of this so-called shearing, parallel to the schistose foliation, may merely be weathered metamorphic foliation. The granulated zones, however, observed in thin see- tion, definitely postdate the metamorphic foliation and reflect later deformation. Shear zones were also seen in granitic rocks about 0.2 km south of the Vergeles fault zone, di- rectly south of the St. Francis Retreat (fig. 10). A few thin red shear zones cut the granitic rocks and trend N. 65° W. and dip about 80° S. Very near the mapped trace of the Vergeles fault in San Juan Canyon (about 2 km to the west of the previous locality), a roadcut on the south side of the canyon exposes Tertiary sandstone. This sandstone con- tains many angular quartz grains, as much as 4 mm across, that are strongly undulatory, granu- lated, and (or) slivered; some of these grains may be fragments of mylonite. Other clasts are poly- crystalline and consist of plagioclase and deformed quartz. The general clast lithologies suggest that the source rocks were cataclastically deformed, probably felsic granitic rocks. Most of the sand- stone that I sampled near the Vergeles fault in the Tertiary section probably is locally derived. By analogy, the sandstone containing the clasts of cat- aclastic(?) quartz and granitic fragments was ap- parently derived from deformed granitic rocks along the Vergeles fault. Just south of the Old Stage Road, biotite grano- diorite is exposed on a ridge on the north line of sec. 16, T. 13 S., R. 4 E., just south of the trace of the Vergeles fault (about 4 km west of the mylonite clast locality, fig. 10). These granitic rocks have a protomylonitic texture in thin section; they include strung-out, mosaicked, and slivered quartz as well as streaked-out biotite that gives an anastamosing fabric to the rocks. These rocks seem to be deformed more pervasively than are the outcrops previously described, in which deformation is localized along discrete shear zones. Because of poor exposures, relations are unclear there, but I suspect that the deformed granitic rocks are in or very near the Vergeles fault zone. These protomylonitized gra- nitic rocks are a likely source for the Tertiary sand- stone in San Juan Canyon that contains myloni- tized grains of granitic composition. The clues of mylonitization at these latter two localities suggest that strong compression is part of the deformational pattern of the Vergeles fault. Mylonite would also seem to be more compatible with a strongly compressional strike-slip fault zone than with a largely extensional dip-slip fault zone, which the Vergeles fault had previously been con- sidered to be. However, the basement is certainly downdropped north of the Vergeles fault; seismic- refraction lines across the fault suggest a down- drop of several thousand feet (W. D. Mooney, writ- ten commun., 1982). Coppersmith (1979), in a detailed study of the Vergeles-Zayante fault zone, noted slickensides in trenches across the fault zone whose orientations indicated a significant horizontal component in most recent movements. He also noted that several streams crossing the fault trace had clearly been diverted in a right-lateral sense. Coppersmith fur- ther noted that fault-plane solutions of several seis- mic events that most probably were associated with the Vergeles-Zayante fault zone show strike- slip focal mechanisms with little or no vertical com- ponent of movement. Dupré (1975) observed that the Sangamon-age Watsonville terrace complex (100,000 years old) is deformed by faulting and that Holocene activity is evident in the fault-controlled geomorphology. He cited these observations as evi- dence that the Vergeles-Zayante fault zone is ac- tive and has undergone late Pleistocene and Ho- locene movements. Dupré (1975) also cited current seismic activity in the Vergeles-Zayante region as indicative of ongoing fault movement. These two fairly recent studies support the view that the Ver- geles-Zayante fault zone is an active strike-slip fault zone. Coppersmith (1979) also notéd that along much of the more than 80-km trace of the Vergeles-Za- yante fault zone, a main fault is difficult or impos- sible to identify and that there are many relatively short fault segments without much lateral conti- nuity. It is difficult to reconcile this statement with my contention that the Vergeles-Zayante fault zone is a major throughgoing strike-slip fault zone. Poor exposures may explain the apparent absence of a mappable main fault; nevertheless, if Cop- # SAN ANDREAS FAULT ZONE 13 persmith's interpretation is correct, it creates dif- ficulties for my suggestion that the Vergeles-Za- yante fault zone is a major strike-slip fault zone. Miocene volcanic rocks directly north of the Ver- geles fault have a radiometric age of 22 m.y., which is the same as the age of similar volcanic rocks just north of the Pastoria fault zone in the San Emigdio Mountains (fig. 9) (Huffman and others, 1973). The suggestion that these two volcanic areas were once part of one volcanic field is strengthened by lith- ologic and petrologic similarities (Bazeley, 1961), and by similarities of both bulk chemical analyses of the volcanic rocks and trace-element concentra- tions in garnet and biotite from the two areas (Turner, 1968). Numerous workers, the earliest of whom were Hill and Dibblee (1953), have noted stratigraphic similarities between the Eocene to Miocene sedi- mentary section in the western San Emigdio Moun- tains (fig. 9) and the interconnected depositional area that received sediment of the same age in the northern Santa Lucia Range and the northern Ga- bilan Range north of the Vergeles fault (fig. 5; see sources cited by Clarke and Nilsen, 1973, and Nil- sen and Link, 1975). In all, there is abundant evidence from such di- verse groups of rocks as oceanic gabbroic rocks, Miocene volcanic rocks, and Eocene to Miocene sed- imentary rocks for a firm tie between the north- ernmost Gabilan Range and the westernmost San Emigdio Mountains (Sierra Nevada tail). In view of this tie, as well as the compelling similarity be- tween the Pinnacles Volcanic Formation in the southern Gabilan Range and the Neenach Volcanic Formation southeast of the San Emigdio Moun- tains, the question should be asked: Can the Salin- ian block basement units of the Gabilan Range be fitted to the basement units in the San Emigdio Mountains on the east of the San Andreas fault? I have long been intrigued by the close resem- blance of the granodiorite of Natividad in the Ga- bilan Range to the granodiorites of Lebec and Gato- Montes in the Sierran tail (figs. 5, 9); in fact, I com- monly referred to the granodiorites of Lebec and Gato-Montes early in my Sierran work as "Nativ- idad type." All three granodiorites are medium-fine grained and contain distinctive scattered coarse biotite flakes. All three masses are distinguished by scattered hornblende crystals with red cores that indicate the presence of skeletal clinopyrox- ene remnants. Modally and chemically, the three masses are also virtually identical. Coarse-grained biotite granite, of the typical and common "low melting trough" granitic rock type, is associated with all three granodiorites-the granites of Fre- mont Peak (Gabilan Range), Tejon Lookout, and Brush Mountain (Sierran tail). Neither the tonalite of Vergeles nor the tonalite and granodiorite of Johnson Canyon of the Gabilan Range (fig. 5) appear to have counterparts in the Sierra Nevada tail (fig. 1) (San Emigdio Moun- tains). The granodiorite of the Fairmont Reservoir, however, which crops out near the Neenach Vol- canic Formation, is similar lithologically, modally, and chemically to the Johnson Canyon body, which crops out near the Pinnacles Volcanic Formation. Both the Fairmont Reservoir and Johnson Canyon granitic bodies contain much sphene with inclu- sions of opaque material in shapes resembling ar- abic- to runic-written characters. I have observed this feature in other plutonic masses in the Cali- fornia Coast and Transverse Ranges, but it is un- common there, and so its abundance in both the Fairmont Reservoir and Johnson Canyon masses may be significant. More detail on the similarity of those two granitic masses is presented in the supplementary section below entitled "Comparison of the Granitic Rocks near the Pinnacles and Neen- ach Volcanic Formations of Matthews (1976)." The presence in the Sierra Nevada tail of equivalents to the Johnson Canyon and Vergeles bodies would greatly strengthen correlation of the tail with the central Salinian block, but considering the common shape and distribution vagaries of granitic bodies, the absence of such equivalents is not devastating to the proposed correlation. Strontium-isotopic data available for the central Salinian block and the Sierra Nevada tail enable a general comparison between these two areas. Relatively high initial strontium-isotopic ratios (approx 0.7082) have been determined for several granitic samples from the Gabilan and Santa Lucia Ranges (Kistler and Peterman, 1973). More de- tailed work by J. M. Mattinson (written commun, 1982) indicates that not all the Gabilan Range plu- tons are cogenetic and that there is some variance in initial strontium-isotopic ratios; nevertheless, all are relatively high. Similar high initial stron- tium-isotopic ratios (0.7079-0.7085) have been de- termined in one sample of the granodiorite of Lebec and in several samples of the granodiorite of Gato- Montes in the Sierra Nevada tail (R. W. Kistler, written commun., 1981). One granitic sample from the La Panza Range has an initial strontium-iso- topic ratio of 0.7080 (Kistler and others, 1973). These data, though admittedly sparse, point to strontium-isotopic compatibility between the cen- tral Salinian block and the Sierra Nevada tail. 14 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA Doe and Delevaux (1973) determined the lead- isotopic compositions in seven granitic samples from the length of the Sierra Nevada for the Late Cretaceous part of the Sierra Nevada batholith. Of particular interest in their studies is the *"*®Pb/2"Pb ratio, which is a measure of the uranogenic or "ra- diogenic (J-type)" lead. The two southernmost sam- ples analyzed from the batholith (lat approx 35°45 N., near Isabella Lake, fig. 1) are two of the three Sierran samples with the highest *"*®Pb/2"Pb ratios (19.37 and 19.15). Doe and Delevaux (1973) reported similar relatively high *"®*Pb/%*Pb ratios from the Santa Lucia Range (19.53 and 19.11) and Point Reyes (19.44) in the Salinian block. They suggested that these data support the contention that the Salinian block is a faulted-off part of the Sierra Nevada batholith. This conclusion, though permis- sible, is admittedly based on very limited data. Another feature that seems to relate the two areas is their anomalous structural grain. The gra- nitic contacts, and the trend and strike of much of the metamorphic pendant material in the northern part of the Gabilan Range, are generally east-west, markedly different from the north-southward to northwestward trend of most California basement. If the Gabilan Range is placed alongside the Sierra Nevada tail and if the Vergeles and Pastoria faults and the Neenach and Pinnacles Volcanic Forma- tions are lined up, the combined block will have a generally east-west-trending grain. Another correlation between these two areas has already been suggested, on the basis of the simi- larity of the schist (metagraywacke) of Sierra de Salinas (figs. 5, 11) to the schist of Portal-Ritter Ridge (Pelona Schist?) (fig. 9); (Ross, 1976). The ex- posed schist of Sierra de Salinas, together with sim- ilar schist in well cores, composes a rather impres- sive belt that appears to be cut off by the San Andreas fault. If the Gabilan Range is placed next to the Sierra Nevada tail, this belt aligns with out- crops of the schist of Portal-Ritter Ridge. The strong physical and chemical similarity of the schists in these two areas has already been established (Ross, 1976); similarity of their struc- tural settings remains to be shown. The schist of Sierra de Salinas in the Gabilan Range is intruded by granitic rocks and has some migmatitic mar- ginal zones. In addition, dikes and sills of volcanic rocks (probably related to the Pinnacles Volcanic Formation) are conspicuous near the south end of the large outcrop area of schist in the Gabilan Range. By contrast, the only known intrusions into the schist of Portal-Ritter Ridge (fig. 9) are dark diabasic dikes composed of labradorite, horn- blende, clinopyroxene, and minor quartz. The source of these dikes is unknown. The contact along the north margin of the schist of Portal-Ritter Ridge has been mapped as a fault- the Hitchbrook fault of Dibblee (1960, 1961). How- ever, this fault does not cleanly separate granitic rock on the north from schist on the south. For example, the large mass of schist at Quartz Hill is north of the fault, and the Hitchbrook fault, as mapped, passes through a spur of schist in the main Portal-Ritter Ridge body (Dibblee, 1961). Further- more, Evans (1978) showed a small outcrop of gra- nitic rock south of, and adjacent to, the Hitchbrook fault. This outcrop, immediately south of a dis- tinctive hill of lithic lapilli tuff, is not shown as fault-bounded against schist; however, no mention of this outcrop is made in Evans' text. The contact between the schist and the granitic rocks is covered with alluvium along much of its length. In my brief examination of the rocks along the Hitchbrook fault in a few localities, I saw sheared granitic rock and no granitic apophyses into the schist. Never- theless, I am not convinced that the Hitchbrook fault is a tectonic break between the schist of Por- tal-Ritter Ridge and the granitic terrane to the north. I suggest that a thorough search along this contact be made for intrusive relations whose oc- currence would support the thesis that the schist terranes of the Sierra de Salinas and Portal-Ritter Ridge are correlative and were once contiguous. Together with the Tertiary correlations, the pos- sibility of basement-rock correlations suggests that the Gabilan Range (figs. 5, 11) may have orig- inated opposite the area of the present Sierra Ne- vada tail (fig. 9). Important to this correlation is my interpretation that the Pastoria and Vergeles- Zayante fault zones represent a tectonic contact between oceanic and continental terranes. If it can be determined that the basement between the Ver- geles-Zayante and Butano faults is largely oceanic, and if similar rocks underlie the block north of the Butano fault, these facts would suggest a major break between continental and oceanic terranes that would greatly strengthen the correlation be- tween the Gabilan Range and the Sierran tail. A reconstruction that attaches the Gabilan Range to the Sierran tail would probably carry the Santa Lucia Range along with the Gabilan Range. The gneissic and tonalitic rocks (with associated migmatite of the Santa Lucia Range) might have their onstrike equivalents in the gneisses and ton- alites of the Holcomb and Wrightwood area (fig. 1); (Ross, 1972a). Correlation of these two gneissic ter- ranes was suggested to me several years ago by P. } P9 SAN ANDREAS FAULT ZONE 15 Ehlig, and the idea still seems to have merit. At | that the correlation would fit with the Gabilan- present, such a correlation must remain specula- | Sierran correlations. One possible reason to reject tive because much of the basement between the | this correlation is the fact that the route from the Santa Lucia Range and the San Andreas fault is | Santa Lucia Range to the San Andreas fault seems covered by younger rocks, but it is worth noting | to be blocked by granitic rocks and schist similar 36° 121° EXPLANATION e Location of well from which basement core was studied * sgh a . «% : , xox wox xox Limits of extrapolation from well-core data A3 e - San - -e i Ardop [8\ e ,* |_ bearing e “(Q < -*e* / | granodiorite- e \\>// ./. _. A _ tonalite fist] Peppery-- ,%.1\“ '' % \ Quartz-poor granite . \/ bah a l? _, ~A hornblende -rich © : met #A tonalite 30 KILOMETERS bnet heard e rier ca charac tine crone FIGURE 11.-Extrapolation from well-core data of some basement-rock units in the central Salinian block (modified from Ross, 1974). 16 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA to the échist of Sierra de Salinas that are evident in well-core material from the San Ardo oil-field area (figs. 5, 11). Hypersthene-bearing tonalite and associated hy- persthene-bearing granulite-grade metamorphic rocks ire found in both the southernmost Sierra Nevada and the Santa Lucia Range. The tonalites and associated metamorphic rocks of both terranes have middle Cretaceous U-Pb radiometric zircon ages. In addition, coarse red garnet is character- istic of both terranes. The occurrence of granulite- grade metamorphic rocks also implies greater crus- tal depths than is common for batholithic terranes in California. At the least, these two unusual, coe- val terranes appear to reflect a similar metamor- phic and tectonic setting. The correlation of the two terranes is speculative but plausible. Further details of the comparison of these two terranes were discussed by Ross (1983). Another large area of basement rock in the cen- tral Salinian block is the porphyritic granodiorite- granite of the La Panza Range (fig. 12). This body of rock probably extends southward, possibly dis- continuously, from the San Ardo area to the La Panza Range and presumably even farther south (fig. 11), although no basement outcrops or sub- surface data indicate its presence there (Ross, 1974). Much of this large and relatively homoge- neous mass is distinctly porphyritic, and I have suggested (Ross, 1978) that it is correlative with the porphyritic granodiorite of Monterey (figs. 4, 5). A body of porphyritic granitic rock in the Ther- mal Canyon area (fig. 1) was believed by Smith (1977) to be a possible correlative of the La Panza mass. I was also informed by S. E. Joseph (oral commun., 1979) that the rubidium-strontium data for the Thermal Canyon and La Panza rocks are similar. I have examined and sampled the granitic rocks in Thermal canyon and made modal analyses of seven stained slabs. In the field, these rocks strikingly resemble the granitic rocks of the La Panza Range. In modal composition (fig. 13), the Thermal Canyon samples are generally lower in quartz than the La Panza rocks, and the two fields are somewhat distinct, although they overlap. It is hard to evaluate the relation between these two bodies because I sampled only a small area in Ther- mal Canyon. More data are needed to confirm (or deny) the correlation between these two masses. The present distance between the Thermal Can- yon rocks and the nearest La Panza Range granitic outcrops is more than 400 km; this distance exceeds the amount of displacement required on the San Andreas fault if the Gabilan Range is to be refitted against the Sierra Nevada tail. However, for a con- siderable distance south of the La Panza Range no basement rocks are exposed, and the extent of the Thermal Canyon mass is also unknown. Thus, the separation may be somewhat less than 400 km. It seems unlikely, however, that the discrepancy in separation can be completely compensated for in this way. Smith (1977) has noted the problem and proposed some 175 km of right-lateral offset on a fault within the Salinian block, but I have trouble reconciling the basement-rock data with such a fault. One additional obstacle stands in the way of a La Panza-Thermal Canyon correlation. The Ther- mal Canyon region seems to have a framework of Precambrian metamorphic and granitic rocks (Rogers, 1965; Jennings, 1967), whereas no Precam- brian rocks have been found in the central Salinian block. However, small outcrops of an unusual gneiss have been noted in American Canyon (fig. 12) just south of the La Panza granitic outcrop. I have examined these outcrops and studied some thin sections and stained slabs from the specimens collected. The gneiss appears to be of relatively high grade and in part to have a distinctive purple color in weathered outcrop; at least in part, it ap- pears to be an orthogneiss. These gneissic rocks resemble some of the gneissic rock at Red Hills or some of the "dioritized" gneiss of Mount Abel- Mount Pinos; their appearance is out of character for the central Salinian block. Further study of these rocks, particularly isotopic age dating, is needed. At this latitude, these gneisses may very well be Precambrian because a Gabilan Range- Sierran tail reconstruction would place the La Panza Range adjacent to known Precambrian ter- ranes in the San Bernardino Mountain area (fig. 1). RINCONADA-RELIZ-KING CITY FAULT ZONE In previous reconstructions, the Rinconada fault has been considered to be a favorable structure along which to sliver and attenuate the Salinian block. For example, Smith (1977) called for some 170 km of right-lateral offset on this fault zone. Dibblee (1976), in a carefully documented study of the Rinconada and related faults, called for a more modest offset of Upper Cretaceous and lower Ter- tiary units, of about 60 km. Graham (1978), in a detailed study of Tertiary units and structures in the central Salinian block, postulated 45 km of right-lateral movement on the basis of offset shore- 17 RINCONADA-RELIZ-KING CITY FAULT ZONE .SPoPE 'reuarew aoa ;o uorjd11osap OJ ($161) ssoy 2998 ueluljeg [E1jua0 oy} UI som oy} 0}; syooI quaWoaseq ayi[un ore YoIYM JO Yj0q 'syoo1 ol}lue1s ots[o; pue sstous st aolfs aSpTy yolreg ay} ut [ELUajEW qUaWaseq adam ajouap sop Yor[q 'Y20]q Uelulreg ayq ;o dew 130f0a8 HHNDLI mor tte ~ m SH31L3WOTX O€ Oc OL 0 guo|@q S¥oBL L ,§Lo61 L L L 1S1oSE IIH POY Jo o1ggeg ,1SLe0Z L 18 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA lines and other features. He also believed that the distribution of the schist of Sierra de Salinas sup- ports such an offset. On the basis of the present distribution of schist in the subsurface in the San Ardo oil field and in outcrops in the Sierra de Sa- linas (fig. 5), offsets of much as 50 km are possible. I have noted that the major schist bodies in the Sierra de Salinas and in the Gabilan Range, to- gether with all the other schist localities (except the isolated San Ardo area), form a somewhat dis- continuous, relatively regular west-northwest- trending belt of schist that extends from the Sierra de Salinas to the San Andreas fault. I see no com- pelling reason to believe that this schist belt was significantly faulted or offset by the Rinconada fault zone. I have long been perplexed by the isolated schist of the San Ardo area and its relation to the rest of the schist belt. The San Ardo rocks may be some- thing other than the schist of Sierra de Salinas, but physically they are certainly similar. Given Graham's (1978) data on Tertiary shorelines, the basement may have been offset by the Rinconada- Reliz fault, though by no more than some 45 km. Interestingly enough, reversal of that amount of movement across this modest crack in the Salinian block would bring the porphyritic granodiorite of Monterey and its offshore continuation much closer to the northernmost outcrops of the por- phyritic granodiorite in the Gabilan Range-a cor- relation I had suggested before Graham's study (Ross, 1978). ~, 3\- Biotite content ranges from R 2 to 12 percent in the La a* Panza body. Less than 1 percent hornblende in some specimens Biotite 69 EXPLANATION + La Panza O Thermal Canyon K-feldspar - Plagioclase FIGURE 13.-Comparison of modally analyzed specimens of the porphyritic granitic rocks of Thermal Canyon and the porphyritic granodiorite-granite of the La Panza Range. Presumably, the Rinconada-Reliz fault zone con- tinues northwestward along the course of the much-discussed and sometimes controversial King City fault (Ross and Brabb, 1973). It may continue across Monterey Bay along one of several north- west-trending faults of the Monterey Bay fault zone of Greene and others (1973). Then, to the north, the Rinconada-Reliz-King City fault zone probably merges with the San Gregorio-Hosgri fault west of the basement outcrops in the Ben Lomond area (Ross and Brabb, 1973, fig. 4). PROBLEMS OF SALINIAN-BLOCK RECONSTRUCTION THAT STILL REMAIN Many basement-rock correlations seem to make good sense or, at least, provide compatible ties if the Bodega-Point Reyes basement is pulled south- ward along the San Gregorio-Hosgri fault zone to the Ben Lomond area and then the central block of the Salinian block is pulled southward along the San Andreas fault to the general area of the Sierra Nevada tail (San Emigdio Mountains). However, the following basement problems still persist, unresolved. CORDILLERAN MIOGEOCLINAL ROCKS The upper Precambrian and lower Paleozoic sed- imentary rocks of the Cordilleran miogeocline have been traced southward from Nevada, through east- ern California, across the Mojave Desert, and into the San Bernardino Mountains. Although the pres- ervation of this belt is spotty and near its south limits is much disrupted by intrusive rocks and covered by younger rocks, there seems to be little doubt that it reaches, and is cut off by, the San Andreas fault zone. The distinctive rock types of this section-thick pure quartzite and thick lime- stone-have not been found in the Salinian block. If the Gabilan Range-Sierran tail correlation is valid, then such rocks might be expected to appear at about the latitude of the La Panza Range (figs. 11, 12). The La Panza Range basement is almost entirely granitic; it contains only traces of biotite schist and marble, as well as a small amount of unusual-ap- pearing gneiss just south of the main granitic base- . ment outcrops. Admittedly, vast areas to the north and south of the La Panza Range granitic outcrops are covered by younger deposits that conceal the composition of the basement; nevertheless, it would have been reassuring to see at least a few quartzite or marble pendants in the exposed base- PROBLEMS OF SALINIAN-BLOCK RECONSTRUCTION THAT STILL REMAIN 19 ment. Of considerable interest are the strikingly distinctive pure quartzite (orthoquartzite) cobbles and pebbles that are common in the Cretaceous beds which lap up on the south side of the La Panza granitic basement. These pure quartzite cobbles and pebbles are of a rock type that is virtually unknown in the Salinian block basement. Howell and Vedder (1978) speculated that both the concentration of quartzite in the erosional product of the basement and its rarity in the pres- ent basement may reflect differential magmatic stoping. They proposed that the relatively light quartzite is selectively floated to the upper parts of the magma chamber, where it becomes an early erosional product, leaving the pluton relatively im- poverished in quartzite, even though quartzite may have been abundant in the original metamor- phic framework. Their mechanism suggests that upper Precambrian and lower Paleozoic Cordil- leran miogeoclinal rocks may once have been pres- ent in the central Salinian block. BEAN CANYON FORMATION The Bean Canyon Formation forms discontin- uous pendants for almost the entire length of the granitic outcrop south of the Garlock fault, from the San Andreas fault east for about 60 km (fig. 9) The Bean Canyon contains distinctive metavol- canic-rock layers and dark schist that, in part, is rich in coarse andalusite crystals. If the Gabilan Range is moved up against the Sierran tail, the Bean Canyon Formation might be expected to oc- cur in the central or southern Gabilan Range; how- ever, no metavoleanic or dark andalusite-bearing rocks have been seen there. Note, however, that the westernmost large exposure of the Bean Can- yon is dominantly marble and contains neither metavolceanic-rock layers nor dark andalusite schist, and that the next most easterly marble-rich area of outcrop contains very minor amounts of andalusite-bearing schist and thin layers that may, or may not, be metavolceanic rocks. These volcanic and andalusite layers are probably absent to the west because of a facies change and so would not be expectable in the Gabilan Range. Scattered mar- ble inclusions throughout the granitic terrane of the central and southern Gabilan Range may rep- resent the Bean Canyon, but no distinctive asso- ciated lithologies occur to make a convincing tie. TEMBLOR CLASTS Directly related to the discussion of the Bean Canyon Formation is the problem of the Temblor clasts. Bouldery beds in the Miocene Santa Mar- garita Formation in the Temblor Range (fig. 1) ap- pear to be cut off on the west by the San Andreas fault. Huffman (1972) suggested that the most plau- sible source terrane for these clasts is the northern Gabilan Range. In examining the Temblor clasts, I noted many metavolceanic and dark andalusite- bearing rocks (Ross, 1980). I have seen neither rock type in the Gabilan Range or anywhere in the Sa- linian block, but these two rock types generally characterize the Bean Canyon Formation. This di- lemma will persist until these two rock types are found in the Gabilan Range basement. My studies, which admittedly were scattered and concentrated on the granitic rocks, leave much room for more detailed investigation, particularly of the meta- morphic rocks of the Gabilan Range. SIERRAN QUARTZITES Within the metasedimentary rocks of the south- ern Sierra Nevada, pure quartzite (orthoquartzite) is distinctive and abundant enough to be noted and mapped in various localities. I have suggested that the absence of pure quartzite in the Salinian block was one of the reasons for questioning a match between the Salinian block and the southernmost Sierra Nevada. However, I have come to think that this distinction may have been overemphasized. Certainly, only minor amounts of pure quartzite occur near the San Andreas fault in pendants and inclusions in the granodiorite of Lebec and in the Bean Canyon Formation, whereas more seems to occur in the Kernville and Isabella Lake areas (fig. 1) farther to the north and east. The difference may be solely a matter of facies change or is an indi- cation of irregular variation in a discontinuously exposed sedimentary section. I no longer think that the difference between the metasedimentary rocks of the Gabilan and Santa Lucia Ranges and those of the southernmost Sierra Nevada is great enough to argue against correlating these two terranes. METALLIC-MINERAL DEPOSITS In an earlier report (Ross, 1978), I noted the abun- dance and variety of metallic-mineral deposits in the southernmost Sierra Nevada, in contrast to the virtual absence of such deposits in the Salinian block. The Salinian block still appears to be anom- alously barren.However, the number of developed and productive properties drops off sharply south of the latitude of Tehachapi (fig. 1), and mineral deposits are notably sparse in the Sierran tail- 20 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA that is, in the area where the proposed correlative join with the barren Gabilan Range would be. The difference in the amount of mineralization is con- siderably less if the Sierran tail alone is compared with the Salinian-block rocks. The normal vagaries of distribution of mineral deposits in similar ter- ranes may also be a factor here. The problems discussed thus far can all be ac- commodated, at least in part, by the proposed re- construction. Four more serious problems remain, involving: (1) the Barrett Ridge slice (fig. 12), (2) Montara Mountain and the K-feldspar-rich sedi- mentary rocks of the Gualala area (figs. 3, 4), (3) a europium-anomaly contrast between the Salinian block and the southernmost Sierra Nevada, and (4) the unlocated west margin of the Salinian block. BARRETT RIDGE SLICE The Barrett Ridge slice (Ross, 1972a)-the anom- alous basement terrane east of the Red Hills-San Juan-Chimeneas fault (fig. 12)-poses possibly the greatest problem for a fault-reconstruction model based only on reversal of currently acceptable dis- placements on the San Andreas and San Gregorio- Hosgri fault zones. A recapitulation here of the data from the Red Hills, Barrett Ridge, Mount Abel-Mount Pinos, and several well cores should help explain why the Barrett Ridge slice presents a problem. In the Red Hills, a few square kilometers of gneis- sic basement rocks pokes up through the Cenozoic cover and appears to be truncated on the west against the Red Hills-San Juan-Chimeneas fault. Most of these outcrops consist of hornblende-bio- tite gneiss of tonalitic composition that is, in part, homogenized to a massive granitic rock. Less com- mon are outcrops of augen gneiss, biotite-rich gneiss, hornblende schist, amphibolite, marble, and metasiltstone. Barrett Ridge is an elongate rib of basement made up largely of quartzofeldspathic gneiss that is locally rich in biotite but poor in hornblende. The gneiss is thinly layered and strongly folded, in part ptygmatically. Near the south end of the ridge, a thick interbed of relatively pure quartzite and a plug of alaskite are present. Alaskite-aplite dikes are common in the gneiss and, at least in part, appear to be sweated out of the gneissic rocks. Sev- eral wells drilled north and south of Barrett Ridge have pierced the basement. Studies of core mate- rial from these wells (Ross, 1974) show the base- ment to be dominantly dark gneiss and granofels, with lesser amounts of amphibolite and felsic gran- ite. In other words, the suite of subsurface samples generally resembles the outcrop areas of Barrett Ridge and Red Hills. The inferred south end of the Barrett Ridge slice, and the southernmost basement exposure of the Salinian block, is the massif of Mount Abel-Mount Pinos (fig. 12). Although the geology is complex in detail, the overall pattern is simple. A southern belt is dominated by felsic granitic rocks. A central belt of high-grade banded gneiss, augen gneiss, migmatite, and amphibolite is characterized by gradations of the gneiss to homogeneous granitic rocks of tonalite and granodiorite compositions, much like those of the Red Hills. The central belt overlies a northern belt of the Pelona Schist along a thrust contact marked by an impressive mylonite zone which may be the westernmost exposure (on the southwest side of the San Andreas fault) of the Vincent thrust (Ehlig, 1968). It is clear from this description that the Barrett Ridge slice differs significantly from the central Salinian block to the west. Plutons of tonalite and granodiorite seem to be absent to rare in the Bar- rett Ridge slice, and the granitic rocks generally contain patches of ghost gneiss and grade into gneissic rocks. Kistler and others (1973) obtained an anomalously high initial "Sr/*Sr ratio of 0.7164 from a sample of homogenized gneiss from Mount Abel; they concluded that the gneiss is probably Precambrian. They also obtained an initial "Sr/*"Sr ratio of 0.7095 from homogenized gneiss from the Red Hills-a value significantly higher than from samples from the central Salinian block (west of the Barrett Ridge slice), but comparable to those obtained from gneissic samples from the San Ga- briel Mountains to the southeast. These data con- firm what the petrography had suggested-that a strong discordance exists between the Barrett Ridge slice and the rest of the Salinian block. If 2n attempt is made to slide the Barrett Ridge slice back along the San Andreas fault zone, find- ing a parent terrane poses a real problem. South- eastward from the Portal-Ritter Ridge area (fig. 1) on the northeast side of the San Andreas fault, the Holcomb and Wrightwood basement rocks (Ross, 1972a) might be able to accommodate part of the Barrett Ridge slice, but surely the large plutonic bodies of the San Bernardino Mountains (fig. 1) and their probable Cordilleran miogeoclinal roof pen- dants would be strange company for the Barrett ridge slice. The basement sample from the Barrett Ridge slice is small; however, a good petrographic sample is available from the Red Hills along the west side of the slice to the Mount Abel-Mount Pi- PROBLEMS OF SALINIAN-BLOCK RECONSTRUCTION THAT STILL REMAIN 21 nos area (fig. 12). These rocks are relatively similar and are distinctive over a large area. If, instead of pushing the Barrett Ridge slice back along the San Andreas fault, that slice and the adjacent Mount Frazier area were to be pushed back along the south side of the San Gabriel loz- enge and molded around it along the San Gabriel- Sierra Madre fault zone (fig. 1), a better match of rock types would be obtained. Also, the Pelona Schist at Mount Abel-Mount Pinos would end up south of, and almost adjacent to, the main outcrops of the Pelona Schist in the eastern San Gabriel Mountains. Although this reconstruction makes good lithologic sense, it brings about a structural problem that is virtually insurmountable. If the San Gabriel basement block originated opposite the Chocolate and Orocopia Mountains before San Andreas fault movement, as Crowell and Walker (1962) convincingly demonstrated on the basis of a correlation of several basement-rock units, then, to reach its present position, the Barrett Ridge slice would have had to travel some 200 km farther than the central block of the Salinian block. This movement would be necessary for both the corre- lations of Crowell and Walker (1962) and the one proposed here for the Gabilan Range-Sierra Ne- vada to be satisfied, and clearly it is implausible. Howell and others (1980) suggested that the Red Hills-San Juan-Chimeneas fault is part of an old collision zone between two basement terranes that were accreted to the North American Continent at a latitude somewhere in southern Mexico. These two terranes drifted northward as a structural. unit, beached in southern California, and subse- quently were transported some 300 km by move- ment on the San Andreas fault system. This pro- posal nicely solves the apparent need for additional movement on the Barrett Ridge slice, but it sug- gests that we should see evidence of an impressive collision in the area of the Red Hills-San Juan-Chi- meneas fault zone. Small samples of basement rocks from the Red Hills, San Juan Canyon, and Barrett Ridge have not revealed the types of major contortions and cataclastic deformation that I would expect to find associated with such a struc- tural event. Nonetheless, it seems reasonable to view the Red Hills-San Juan-Chimeneas fault zone as a major structural discordance (possibly a strike-slip fault) that predates the San Andreas fault. The Barrett Ridge slice and its west-bound- ing fault present a serious-if not insurmount- able-problem for a simple 300 to 350 km of base- ment reconstruction. MONTARA MOUNTAIN AND GUALALA GRANITIC CLASTS The proposed reconstruction that places the Ga- bilan Range opposite the Sierra Nevada tail also presumes that oceanic basement is present north of the Vergeles-Zayante fault. This reconstruction ' (fig. 14) leaves the granitic basement of Montara Mountain marooned considerably north of the Bo- dega Head-Ben Lomond granitic basement. This anomaly calls for the Montara mass to be either a structurally isolated block or an intrusion into oceanic basement. The K-feldspar arkose of Gualala (fig. 3), with its coarse granitic debris, must have been derived from a continental source. According to my recon- struction, however, these sedimentary rocks are also cut off from a granitic basement source. Both the granitic rocks of Montara Mountain and the K- feldspar-rich sedimentary rocks of the Gualala area can be accommodated more easily if the base- ment is continental north of the Butano fault; how- ever, such a situation would cast considerable doubt on the correlation of the Pastoria and Ver- geles-Zayante fault zones. EUROPIUM-ANOMALY CONTRAST Trace-element patterns for the granitic rocks of the Salinian block and the southernmost Sierra Nevada present possibly significant contrasts. Eu- ropium anomalies in the rocks of the southernmost Sierra Nevada not only occur in the granites, as they do in most granitic suites, but also are sur- prisingly common in the granodiorites and even in some of the tonalites. In the Salinian block as well as in the central Sierra Nevada (Dodge and others, 1982), pronounced europium anomalies are found only in the granites. A graphic comparison of the trace-element patterns of these three regions was shown by Ross (1982). The Salinian-block data, though sparse (14 sam- ples), cover a wide range of chemical compositions and a wide geographic range, and so they are prob- ably representative. The sampling in the south- ernmost Sierra and, even more so, in the central Sierra is much more extensive and surely reflects an actual difference in trace-element patterns. The contrast in trace-element patterns between the Salinian block and the southernmost Sierra Nevada is incompatible with the correlation of these two terranes. At present, however, the full significance of this contrast is not fully understood. More trace-element data for the gap between the central and southernmost Sierra Nevada are POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA 22 'C(6-6 '34 '08et) staeq pue wou; ';[n¥g} seaipuy ueg ay} uo alojoq ya0[q ay} Jo syo01 juaWwaseq Jo sealer pajoatas Jo UoIinglLI}sIP ay1 Jo Iloy} pu® (0861) SIAEG puse foyyoing 4q pasodoid puaq jeutfoodo aofepy 'g are sauoz jng] 11Ssop[-o1103a1in) ueg puse seaipuy ueg ay} uo squawmaiowu sq1un 40x ;o 'y 'quaWwaAouw jing] seaipuy Ueg alojaq yo0]q UeIUITES pUB UJaYjI0U ay} JO suofonJ}suod3d HHNDILI U 7 abeiquesse ueosiouesy 3NOZ 11NV4 OLN3IWIOVN aBuey sion equeg x aBuey ueitqey a ~* Bq g ueg \ \ 1 i ~ 1 -soAoy w10d I eieng */ | o18 u¢o abeiquesse 1 1, cueosiouesy juaweseq ueuerg 10 \ A wur I I | \ a1aym payop 'prju0} »6pry 1onpy-jeiog pue seueg ap euarg Jo yeod soy 2i8eq pur 'ueBo7 'my prog Jo sosgqeqy \ # sajeB12q pue 'puowo7 usg '"ujo4 sarewo}, jo sayfeuo1 safey jujog pure Aaiajuop Jo oppufydiog (9161) smaynem jo suopeumioy Jjueofoq yoeusopy pue sapeuuq NOLLVNVTIdX3 wIOM1 ViNyg LNV1 VIHOLSYd fara fur c" Op OT 0 VYH31IS PROBLEMS OF SALINIAN-BLOCK RECONSTRUCTION THAT STILL REMAIN 28 needed to determine the geographic extent of eu- ropium anomalies and their values over a broad range of granitic rock compositions. UNLOCATED WEST FLANK OF THE SALINIAN BLOCK The Salinian block, as presently exposed, is no- tably thinner than other parts of the Cordilleran plutonic are, from which are it is generally assumed to have been derived. For example, in comparison with the southern California batholith or the cen- tral Sierra Nevada batholith, the Salinian block appears to lack a west flank that elsewhere in the Cordilleran plutonic are includes abundant tonal- ite, trondhjemite, and gabbro as well as metamor- phic framework rocks rich in volcanic material and voleanoclastic debris. Page (1982), in his compre- hensive review of the migration history of the Sa- linian block, emphasized its anomalous thinness and suggested that the disappearance of the west flank is the result of either (1) megatransport at the Earth's surface or (2) destruction by piecemeal subduction (tectonic erosion). If the present west limit of the Salinian block (the Nacimiento fault) marks a zone where oceanic material has collided with a continental margin, the surviving continental-margin rocks would be expected to preserve some evidence of this strongly compressive event. However, the westernmost gra- nitic exposures in the La Panza Range, adjacent to the Nacimiento fault zone, do not appear to be strongly deformed or melanged, and Page (1982) noted that Salinian granite, essentially in contact with oceanic and pelagic sedimentary rocks, shows no evidence of interaction. It seems unlikely that piecemeal subduction of lighter continental ma- terial downward into denser oceanic material could have occurred here (or anywhere) on a large scale without leaving evidence of such an impressive event. The abrupt west termination of the granitic base- ment of the Salinian block against oceanic mate- rial, seen in both the La Panza and Santa Lucia Ranges, more likely reflects a strike-slip fault zone. If the missing western part of the original Salinian block has, indeed, been stripped away by mega- transport to a site as yet unknown, it is plausible that-as Howell and others (1980) proposed-the east margin of the block may also have undergone megatransport, of which modest movements along the San Andreas and San Gregorio-Hosgri fault zones are only the most recent events. However, the possibilities of correlation between the central Salinian block and the southernmost Sierra Ne- vada cannot be lightly dismissed. As we continue to search for the source of the Salinian block, so also must we continue to search for its sheared-off west margin. CONCLUSIONS Figure 14A, which shows selected key units of basement rock of the Salinian block reconstructed along the southwest side of the present San An- dreas fault, indicates a possible distribution of basement before movement along the San Grego- rio-Hosgri and San Andreas fault zones. Figure 14B shows a similar reconstruction, including the oroclinal bend proposed by Burchfiel and Davis (1980). Their reconstruction connects the Naci- miento fault around the oroclinal bend with the contact, now buried, between Sierran basement on the east and the Franciscan-assemblage basement on the west. Note that the reconstruction by Burch- fiel and Davis (1980) places the Santa Lucia Range about 50 km south relative to the Gabilan Range, so as to take account of the movement proposed by Graham (1978) across the Rinconada-Reliz-King City fault (fig. 5). Either way (fig. 144 or 14B), there is a good juxtaposition of the schists of Sierra de Salinas and Portal-Ritter Ridge. The combined Pastoria and Vergeles-Zayante fault zone would presumably bend southward, with the oroclinal flexure somewhere seaward of Bodega Head and Cordell Bank to join the Nacimiento fault zone. However, the dilemma of the isolation of the Gual- ala area and Montara Mountain north of the other continental (granitic) basement remains, and its solution demands more data on the characteristics of the basement at the north end of the Salinian block. A reconstruction that depends on some 300 to 350 km of right-lateral offset on the San Andreas fault and some 130 km of similar movement on the San Gregorio-Hosgri fault brings into alignment several basement-rock units and structures in the central Salinian block with similar features in the southernmost Sierra Nevada. Correlations of in- dividual granitic and metamorphic basement rocks can never be truly unequivocal because similar basement-rock types and textures are apt to recur. However, the occurrence of a cluster of correlative basement-rock units in the Gabilan-Santa Lucia Ranges and the southern Sierra Nevada region cannot be dismissed lightly. In summary, that cluster of possibly correlative units and features includes (1) an unusual and dis- tinctive metagraywacke (schists of Sierra de Sali- 24 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA nas and Portal-Ritter Ridge), (2) mineralogically unusual hornblende quartz gabbros and coarse an- orthositic gabbros (in the Logan, Gold Hill, and Ea- gle Rest Peak areas), (3) several granitic units, (4) a similar east-west structural grain, and (5) a struc- tural break between oceanic and continental base- ment terranes (the Vergeles-Zayante and Pastoria fault zones). j The reconstruction that fits the central part of the Salinian block to a potentially correlative ter- rane is far more uncertain for the northern part of the Salinian block. There, the composition of the basement rocks is of critical importance, but large areas are now covered by sedimentary rocks and ocean water. Furthermore, whether this northern basement is oceanic or continental, some correla- tion problems still remain. To the south is an even greater problem-the Salinian block-Sierra Ne- vada reconstruction places part of the Barrett Ridge slice opposite the San Bernardino Moun- tains in an untenable juxtaposition of dissimilar basement rocks. By themselves, movements on the San Andreas and San Gregorio-Hosgri fault zones do not seem to resolve the problem of the origin of the Salinian block. Such movements solve some problems, but they create other, greater ones. As already dis- cussed, Howell and others (1980) proposed much larger movement for a composite block of coastal California that includes the Salinian block. This movement, premised in part on the paleomagnetic studies by Champion and others (1980), would pre- date San Andreas movement. Early in the prepa- ration of this report, when I first heard this model described, I was nearly convinced that data on off- sets of the San Gregorio-Hosgri fault zone (Graham and Dickinson, 19782, b), my new ideas concerning an ancient ocean margin in the Sierra Nevada tail, and the conventionally accepted amounts of move- ment on the San Andreas fault zone would enable a resolution of the origin of the Salinian block. Therefore, I gave the model of Howell and others (1980) short shrift. However, as I pursued the prob- lem, it became apparent that my initial model was inadequate and that theirs might be right. Nevertheless, the match of several basement- rock units and features in the central Salinian block with the southern Sierra Nevada region (fig. 14) cannot be readily dismissed. Are all of those correlations only the fortuitous superpositions of undiagnostic features? Or do all of the correlative features occur within a large, composite, exotic coastal block that was offset only by the later San Andreas movement? For example, the schists of Sierra de Salinas and Portal-Ritter Ridge could both be part of a composite coastal terrain that was split apart by later San Andreas movement. However, the granitic rocks, structures, and struc- tural grain in the Sierran tail are firmly tied to the main Sierra Nevada block and are separate from any composite coastal block. The presence, which I have suggested, of correlatives of these features in the central Salinian block could pose problems for the model of Howell and others (1980). Their model would then call for the present Gabilan Range to be beached (after its long journey from southern Mexico) adjacent to some nearly identical rocks and structures in the southern Sierra Ne- vada-and that would imply a degree of coinci- dence that is hard to credit. : In conclusion, the problem of the origin of the Salinian block does not seem to be resolved. I had hoped that this study would resolve the problem; instead, these reconnaissance studies have merely provided tantalizing clues that need to be pursued. Neither the model that calls for some 300 km of San Andreas fault movement supplemented by San Gregorio-Hosgri fault movement, nor the model of Howell and others (1980), which calls for a pre-San Andreas movement of a large composite terrane, provides all the answers. Both models create some new problems even as they appear to solve others. Further detailed basement-rock studies of both the central Salinian block and the Sierran tail should help decide whether there is a valid correlation between these two areas or merely a juxtaposition of several of similar-appearing but unrelated base- ment-rock units. REFERENCES CITED Addicott, W. O., 1968, Mid-Tertiary zoogeographic and paleo- geographic discontinuities across the San Andreas Fault, California, in Dickinson, W. R., and Grantz, Arthur, eds., Proceedings of conference on geologic problems of the San Andreas fault system: Stanford University Publications in the Geological Sciences, v. 11, p. 144-165. Allen, J. E., 1946, Geology of the San Juan Bautista Quadrangle, California: California Division of Mines Bulletin 133, 112 p. Andrews, Philip, 1936, Geology of the Pinnacles National Mon- ument: University of California Publications, Department of Geological Sciences Bulletin, v. 24, no. 1, p. 1-38. Bazeley, W. J. M., 1961, 175 miles of lateral movement along the San Andreas fault since Lower Miocene: Pacific Petroleum Geologist Newsletter, v. 15, no. 5, p. 2-8. Brabb, E. E., and Hanna, W. F., 1981, Maps showing aeromag- netic anomalies, faults, earthquake epicenters, and igneous rocks in the southern San Francisco Bay region, California: U.S. Geological Survey Geophysical Investigations Map GP- 932, scale 1:125,000. Burchfiel, B. C., and Davis, G. A., 1980, Mojave Desert and en- virons, in Ernst, Gary, ed., The geotectonic development of REFERENCES 25 California (Rubey volume 1): Englewood Cliffs, N.J., Pren- tice-Hall, p. 217-252. Champion, D. E., Grommé, Sherman, and Howell, D. G., 1980, Paleomagnetism of the Cretaceous Pigeon Point Formation and the inferred northward displacement of 2500 km for the Salinian block, California [abs.]: Eos (American Geophysi- cal Union Transactions), v. 61, no. 46, p. 948. Clark, J. C., Brabb, E. E., Greene, H. G., and Ross, D. C., 1984, Geology of Point Reyes peninsula and implications for San Gregorio fault history, in Crouch, J. K., and Bachman, S. B., eds., Tectonics and sedimentation along the California margin: Los Angeles, Society of Economic Paleontologists and Mineralogists, Pacific Section, p. 67-86. v. 38 Clark, J. C., and Rietman, J. D., 1973, Oligocene stratigraphy, tectonics, and paleogeography southwest of the San An- dreas fault, Santa Cruz Mountains and Gabilan Range, Cal- ifornia Coast Ranges: U.S. Geological Survey Professional Paper 783, 18 p. Clarke, S. H., Jr., and Nilsen, T. H., 1973, Displacement of Eocene strata and implications for the history of offset along the San Andreas fault, central and northern California, in Ko- vach, R. L., and Nur, Amos, eds., Proceedings of the con- ference on tectonic problems of the San Andreas fault sys- tem: Stanford University Publications in the Geological Sciences, v. 13, p. 358-367. Compton, R. R., 1960, Charnockitic rocks of Santa Lucia Range, California: American Journal of Science, v. 258, no. 9, p. 609- 636. Coppersmith, K. J., 1979, Activity assessment of the Zayante- Vergeles fault, central San Andreas fault system, Califor- nia: Santa Cruz, University of California, Ph.D. thesis, 216 p. Crowell, J. C., 1952, Geology of the Lebec quadrangle, California: California Division of Mines Special Report 24, 23 p. Crowell, J. C., and Walker, J. W. R., 1962, Anorthosite and related rocks along the San Andreas Fault, Southern Calif.: Uni- versity of California Publications in Geological Sciences, v. 40, no. 4, p. 219-288. Dibblee, T. W., Jr., 1960, Geologic map of the Lancaster quad- rangle, Los Angeles County, California: U.S. Geological Sur- vey Mineral Investigations Field Studies Map MF-76, scale 1:62,500. 1961, Geologic map of the Bouquet Reservoir quadrangle, Los Angeles County, California: U.S. Geological Survey Mineral Investigations Field Studies Map MF-79, scale 1:62,500. 1967, Areal geology of the western Mojave Desert, Cali- fornia: U.S. Geological Survey Professional Paper 522, 153 p. 1976, The Rinconada and related faults in the southern Coast Ranges, California, and their tectonic significance: U.S. Geological Survey Professional Paper 981, 55 p. 1980, Geology along the San Andreas fault from Gilroy to Parkfield: California Division of Mines and Geology Special Report 140, p. 3-18. Dibblee, T. W., Jr., and Chesterman, C. W., 1953, Geology of the Breckenridge Mountain quadangle, California: California Division of Mines and Geology Bulletin 168, 56 p. Dodge, F. C. W., Millard, H. T., Jr., and Elsheimer, H. N., 1982, Compositional variations and abundances of selected ele- ments in granitoid rocks and constituent minerals, central Sierra Nevada batholith, California: U.S. Geological Survey Professional Paper 1248, 24 p. Doe, B. R., and Delevaux, M. H., 1973, Variations in lead-isotopic compositions in Mesozoic granitic rocks of California: A pre- liminary investigation: Geological Society of America Bul- letin, v. 84, no. 11, p. 3513-3526. Dupré, W. R., 1975, Quaternary history of the Watsonville Low- lands, north-central Monterey Bay region, California: Stan- ford, Calif., Stanford University, Ph. D. thesis, 232 p. Ehlig, P. L., 1968, Causes of distribution of Pelona, Rand, and Orocopia schists along the San Andreas and Garlock faults, in Dickinson, W. R., and Grantz, Arthur, eds., Proceedings of conference on geologic problems of the San Andreas fault system: Stanford University Publications in the Geological Sciences, v. 11, p. 294-306. Evans, J. G., 1978, Postcrystalline deformation of the Pelona Schist bordering Leona Valley, southern California: U.S. Geological Survey Professional Paper 1039, 17 p. Graham, S. A., 1978, Role of Salinian block in evolution of San Andreas fault system, California: American Association of Petroleum Geologists Bulletin, v. 62, no. 11, p. 2214-2231. Graham, S. A., and Dickinson, W. R., 1978a, Apparent offsets of on-land geologic features across the San Gregorio-Hosgri fault trend: California Division of Mines and Geology Spe- cial Report 137, p. 13-23. 1978b, Evidence for 115 kilometers of right slip on the San Gregorio-Hosgri fault trend: Science, v. 199, no. 4325, p. 179- 181. Grantz, Arthur, and Dickinson, W. R., 1968, Indicated cumula- tive offsets along the San Andreas fault in the California Coast Ranges, in Dickinson, W. R., and Grantz, Arthur, eds., Proceedings of conference on geologic problems of the San Andreas fault system: Stanford University Publications in the Geological Sciences, v. 11, p. 117-120. Greene, H. G., Lee, W. H. K., McCulloch, D. S., and Brabb, E. E., 1973, Faults and earthquakes in the Monterey Bay region, California: U.S. Geological Survey Miscellaneous Field Studies Map MF-518, scale 1:200,000. Hanna, W. F., Brown, R. D., Ross, D. C., and Griscom, Andrew, 1972, Aeromagnetic reconnaissance along the San Andreas fault between San Francisco and San Bernadino, Califor- nia: U.S. Geological Survey Geophysical Investigation Map GP-815, scale 1:250,000. Hill, M. L., and Dibblee, T. W., Jr., 1953, San Andreas, Garlock, and Big Pine faults, California: A study of the character, history, and tectonic significance of their displacements: Geological Society of America Bulletin, v. 64, no. 4, p. 443- 458. Howell, D. G., and Vedder, J. G., 1978, Late Cretaceous paleo- geography of the Salinian block, California, in Howell, D. G., and McDougall, K. A., eds., Mesozoic paleogeography of the western United States: Pacific Coast Paleogeography Symposium 2: Los Angeles, Society of Economic Paleontol- ogists and Mineralogists, Pacific Section, p. 523-534. Howell, D. G., McLean, Hugh, and Vedder, J. G., 1980, Late Cretaceous suturing and translation of the Salinian and Nacimiento blocks, California [abs.]: Eos (American Geo- physical Union Transactions), v. 61, no. 46, p. 948. Huffman, 0. F., 1972, Lateral displacement of Upper Miocene rocks and the Neogene history of offset along the San An- dreas fault in central California: Geological Society of Amer- ica Bulletin, v. 83, no. 10, p. 2913-2946. Huffman, O. F., Turner, D. L., and Jack, R. N., 1973, Offset of Late Oligocene- early Miocene volcanic rocks along the San Andreas fault in central California, in Kovach, R. L., and Nur, Amos, eds., Proceedings of the Conference on tectonic 26 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA problems of the San Andreas fault system: Stanford Uni- versity Publications in the Geological Sciences, v. 13, p. 368- 373. Jennings, C. W., compiler, 1967, Salton Sea sheet of Geologic map of California: California Division of Mines and Geology, scale 1:250,000. Kistler, R. W., and Peterman, Z. E., 1973, Variations in Sr, Rb, K, Na, and initial in Mesozoic granitic rocks and intruded wall rocks in central California: Geological Society of America Bulletin, v. 84, no. 11, p. 3489-3512. Kistler, R. W., Peterman, Z. E., Ross, D. C., and Gottfried, David, 1973, Strontium isotopes and the San Andreas fault, in Ko- vach, R. L., and Nur, Amos, eds., Proceedings of the con- ference on tectonic problems of the San Andreas fault sys- tem: Stanford University Publications in the Geological Sciences, v. 13, p. 339-47. Matthews, Vincent, III, 1973, Geology of the Pinnacles Volcanic Formation and the Neenach Volcanic Formation and their bearing on the San Andreas fault problem: Santa Cruz, University of California, Ph.D. thesis, 214 p. 1976, Correlation of Pinnacles and Neenach volcanic for- mations and their bearing on San Andreas fault problem: American Association of Petroleum Geologists Bulletin, v. 60, no. 12, p. 2128-2141. Moore, J. G., 1959, The quartz diorite boundary line in the west- ern United States: Journal of Geology, v. 67, no. 2, p. 64-68. Mullins, H. T., and Nagel, D. K., 1981, Franciscan-type rocks off Monterey Bay, California: Implications for western bound- ary of Salinian block: Geo-Marine Letters, v. 1, no. 2, p. 135- 139. Nilsen, T. H., and Link, M. H., 1975, Stratigraphy, sedimentology and offset along the San Andreas fault of Eocene to lower Miocene strata of the northern Santa Lucia Range and the San Emigdio Mountains, Coast Ranges, central California, in Weaver, D. W., Hornaday, G. R., and Tipton, Ann; eds., Paleogene Symposium and selected technical papers: Con- ference on Future Energy Horizons of the Pacific Coast: American Association of Petroleum Geologists-Society of Exploration Geophysicists-Society of Economic Paleontol- ogists and Mineralogists, Pacific Sections, Annual Meeting, Long Beach, Calif., 1975, Proceedings, p. 367-400. Page, B. M., 1982, Migration of Salinian composite block, Cali- fornia, and disappearance of fragments: American Journal of Science, v. 282, p. 1694-1734. Rogers, T. H., compiler, 1965, Santa Ana sheet of Geologic map of California: California Division of Mines and Geology, scale 1:250,000. Ross, D. C., 1970, Quartz gabbro and anorthositic gabbro: Mark- ers of offset along the San Andreas fault in the California Coast Ranges: Geological Society of America Bulletin, v. 81, no. 12, p. 3647-3662. 1972a, Petrographic and chemical reconnaissance study of some granitic and gneissic rocks near the San Andreas fault from Bodega Head to Cajon Pass, California: U.S. Geo- logical Survey Professional Paper 698, 92 p. 1972b, Geologic map of the pre-Cenozoic basement rocks, Gabilan Range, Monterey and San Benito Counties, Cali- fornia: U.S. Geological Survey Miscellaneous Field Studies Map MF-357, scale 1:125,000. 1974, Map showing basement geology and locations of wells drilled to basement, Salinian block, central and south- ern Coast Ranges, California: U.S. Geological Survey Mis- cellaneous Field Studies Map MF-588, scale 1:500,000. 1975, Modal and chemical data for granitic rocks of the Gabilan Range, Central Coast Ranges, California: National Technical Information Service Report PB-242 458/AS, 42 p. 1976, Metagraywacke in the Salinian block, central Coast Ranges, California-and a possible correlative across the San Andreas fault: U.S. Geological Survey Journal of Re- search, v. 4, no. 6, p. 683-696. 1977a, Pre-intrusive metasedimentary rocks of the Salin- ian block, California-a tectonic dilemma, in Stewart, J. H., Stevens, C. H., Fritsche, A. E,, eds., Paleozoic paleogeog- raphy of the western United States: Pacific Coast Paleo- geography Symposium 1: Los Angeles, Society of Economic Paleontologists and Mineralogists, Pacific Section, p. 371- 380. 1977b, Maps showing sample localities and ternary plots and graphs showing modal and chemical data for granitic rocks of the Santa Lucia Range, Salinian block, California Coast Ranges: U.S. Geological Survey Miscellaneous Field Studies Map MF-799, 3 sheets. 1978, The Salinian block-a Mesozoic granitic orphan in the California Coast Ranges, in Howell, D. G., and Mc- Dougall, K. A., eds., Mesozoic paleogeography of the western United States: Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 2, p. 509-522. 1980, A tectonic mystery-basement rock clasts in the Temblor Range, San Luis Obispo and Kern Counties, Cal- ifornia: California Geology, v. 33, no. 7, p. 153-157. 1982, Results of instrumental neutron activation analyses for selected plutonic samples from the Salinian block, Cal- ifornia Coast Ranges: U.S. Geological Survey Open-File Re- port 82-935, 6 p. 1983, Hornblende-rich, high-grade metamorphic terranes in the southernmost Sierra Nevada, California, and impli- cations for crustal depths and bathlith roots: U.S. Geological Survey Open-File Report 83-465, 51 p. Ross, D. C., and Brabb, E. E., 1973, Petrography and structural relations of granitic basement rocks in the Monterey Bay area, California: U.S. Geological Survey Journal of Re- search, v. 1, no. 3, p. 273-282. Ross, D.C., Wentworth, C. M., and McKee, E. H., 1973, Cretaceous mafic conglomerate near Gualala offset 350 miles by San Andreas fault from oceanic crusutal source near Eagle Rest Peak, California: U.S. Geological Survey Journal of Re- search, v. 1, no. 1, p. 45-52. Silver, E. A., Curray, J. R., and Cooper, A. K., 1971, Tectonic development of the continental margin off central Califor- nia: Geological Society of Sacramento Annual Field Trip Guidebook, p. 1-10. Smith, D. P., 1977, The San Juan-St. Francis fault and the Rin- conada-Jolon fault: proposed middle Tertiary right-lateral faults in southern California: Geological Society of America Abstracts with Programs, v. 9., no. 4, p. 501-502. Turner, D. L., 1968, Potassium-argon dates concerning the Ter- tiary foraminiferal time scale and San Andreas fault dis- placement: Berkeley, University of California, Ph.D. thesis, 99 p. Wentworth, C. M., 1968, Upper Cretaceous and lower Tertiary strata near Gualala, California and inferred large right lat- eral slip on the San Andreas fault, in Dickinson, W. R., and Grantz, Arthur, eds., Proceedings of conference on geologic problems of the San Andreas fault system: Stanford Uni- versity Publications in the Geological Sciences, v. 11, p. 130- 143. SUPPLEMENTAL INFORMATION 27 SUPPLEMENTAL INFORMATION COMPARISON OF THE PORPHYRITIC GRANODIORITES OF POINT REYES AND MONTEREY The granitic rocks at Point Reyes and on the Monterey Peninsula (fig. 15) are generally similar in appearance. Both contain conspicuous euhedral K-feldspar phenocrysts, but the rocks are not 123° 0 100 KILOMETERS _..____J 38° 0 5 KILOMETERS i_] Tonalite of Tomales Point everywhere porphyritic (seriate). The phenocrysts in the Point Reyes granitic rocks do not exceed 5 cm in length, whereas those in phenocrysts of the Monterey granitic rocks are as much as 15 em long. This extreme development of coarse phenocrysts, however, occurs only locally in the Monterey mass; commonly, the phenocryst size in both masses is similar. The modal mineralogies of the two masses are also similar (fig. 16); the variations are well within the limits found in normal plutonic units. \ (Offshore extent based on dredging) 121945" 10 KILOMETERS Granodiorite of Cachagua Porphyritic grano' diorite of Monterey _ pr. 1973 Granodiorite and granite of Inverness sso |- [ 1 L of Point Reyes 380 - 0 1 KILOMETER borin mcse d C FIGURE 15.-Locations of the porphyritic granodiorites of Point Reyes and Monterey. A, Locations of study areas at Point Reyes and Monterey. B, Locations of modally analyzed samples (dots) and chemically analyzed samples (circles) of the porphyritic granodiorite of Monterey. C, Location of the porphyritic granodiorite of Point Reyes. D, Locations of modally analyzed samples (dots) and chemically analyzed samples (circles) of the porphyritic granodiorite of Point Reyes. Numbers refer to samples listed in table 2. 28 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA One possibly significant difference is that the spec- imens of the Point Reyes mass that I have exam- o ined contain about 1 percent of hornblende, $ +36 2 whereas I have seen no hornblende in the Mon- 'terey mass. Also, the Monterey mass has what ap- & pears to be primary muscovite, which is absent in the Point Reyes mass. However, the granodiorite g

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Mig gree togo. puro" orsgo ~ poo uerse . fife g:te -: ols - 9/G-40 _ ELGT-40O _ SS§T-4G pT9-40 68b-40 S6§-40 209-40 afesamy gt-9 _ b8S-40 OLS-40 ----- a| dues Kpoqg s roadasay quouJLPj ayj 40 quBLJPA 915 [aj uofue) auowyoig 40 ariuguy JIlOAdJasay quoWJirj ayq 40 aqi40ipouruy uofuey uosuyop 30 arisoipoues6 pure arif ardwes QZ aunbl; aas *(SL61) ssoy 'sadwes [1° ssoY 'pT9-40 pue '20O9-40 'E6S-40 'O6§-40 '68t-40 saidwes :rjep [eoiwayo jo sapunog Rpoqg quomuimf ay, fo qunina orsfaf ay; pun 'uohuny auomyoarg fo aqrunib ay3 'moarasay quouuin y ay fo aqriorpounib ay; 'uohun; uosuyopr fo aqmorpounib pun ammnuo; ay; fo sardiuns fo sashmun pouuay)-'g HIIVIL *quapu4ad qjubram ut san[eA {1Y] Bickmore Canyon Johnson Canyon Fairmont Reservoir 089 1N3943d LHOI3M NI 'LN3LNOY 30IXO 16 |- 5 oS Felsic variant of Fairmont Reservoir FIGURE 22.-Comparisons of chemical analyses of samples of the tonalite and granodiorite of Johnson Canyon with those of samples of the granodiorite of Fairmont Reservoir, and of chemical analyses of one sample of the felsic variant of the Fairmont Reservoir body with those of samples of the granite of Bickmore Canyon. 36 POSSIBLE CORRELATIONS OF BASEMENT ROCKS ACROSS FAULTS IN CALIFORNIA plots, Q-Or-(Ab+An) and Or-Ab-An, clearly show grouping and separation of the two pairs of bodies. The ternary diagrams accentuate the picture of chemical compatibility that was evident in the his- togram (fig. 22). The trace-element abundances for the chemi- cally analyzed samples are plotted here on a his- togram for easy reference and comparison (fig. 25). The data were derived from semiquantitative spec- troscopic analyses. The data plotted in figure 25 are arbitrary midpoints of the steps shown, from which the actual concentration may vary by one or two steps. The comparison of values between the Johnson Canyon and Fairmont Reservoir masses clearly shows similarity. Levels of nickel (Ni) and, to a lesser extent, secandium (Se) and chro- mium (Cr) are somewhat higher in the Johnson Canyon samples. This relatively high concentra- tion probably reflects the generally higher mafic- mineral content of the Johnson Canyon mass-Ni, Se, and Cr are all relatively concentrated in mafic minerals. Expectably, the samples from the Bick- more Canyon body and the one felsic sample from the Fairmont Reservoir area are generally about the same, or somewhat lower, in most trace ele- ments than are the granodiorite samples. Excep- tions are barium, which is slightly higher in the granites (probably because they contain relatively more K-feldspar), and lead, which is also slightly higher in the granite specimens. Such differ- ences-of one or, at most, two steps-are probably not- significant in semiquantitative spectroscopic Other 2 (Number of superposed samples) EXPLANATION o Johnson Canyon o Fairmont Reservoir a Fairmont Reservoir (felsic) A Bickmore Canyon lef oue a La ls | \ NEX K-feldspar 90 65 35 10 - Plagioclase FIGURE 23.-Modes of chemically analyzed samples of the granodiorite of Fairmont Reservoir, the granite of Bick- more Canyon, the tonalite and granodiorite of Johnson Canyon, and the felsic variant of the Fairmont Reservoir body. F (FeO +2 Fe,O,, +MnO) EXPLANATION © Johnson Canyon o Fairmont Reservoir @ Fairmont Reservoir (felsic) a Bickmore Canyon Alk (Na,0 +K,0) 50 M (MgO) Normative minerals Ab 50 An Normative minerals 50 Or 50 Ab +An FIGURE 24.-Chemical compatibility of the tonalite and gran- odiorite of Johnson Canyon with the granodiorite of Fair- mont Reservoir, and of the granite of Bickmore Canyon with the felsic variant of the Fairmont Reservoir body. SUPPLEMENTAL INFORMATION 37 CONCENTRATION, IN PARTS PER MILLION ‘ c00000 9 us co00e0cecee0000 : omecccemeecceneeoss (LALA 101, 1914 T (of dxf St 4 ECE 1 ET -C ‘ Cr 2r N 5 w ec | m: Yb | -A | | c Y mi- V | me was © a r-B <6 4 ER cl: o Sc Clem Go P8 -B Fairmont Fleservoir\B m N: I Johnson Canyor \- -C «--] 8 o Nb f) La Tmt oor: Ga o - mts 8A C Cu |_ MH am as an un Cr G G -- :A = -B Co G n wi Be 8 m ==] Fai 4 Felsic airmont Reservoir Ia‘variam Bickmore Canyon o Ba Johnson CanyonHZHq - ino e-cce0e-e0000-cc00 seos- o © _ CONCENTRATION, IN WEIGHT PERCENT FIGURE 25.-Histograms showing semiquantitative-spectro- scopic-analysis "midpoints" of trace-element concentrations in samples of the tonalite and granodiorite of Johnson Canyon, the granodiorite of the Fairmont Reservoir, the granite of Bickmore Canyon, and the felsic variant of the Fairmont Res- ervoir body. data. Nevertheless, comparison of the trace-ele- ment concentrations in the Johnson Canyon and Fairmont Reservoir masses, and of the Bickmore Canyon mass with felsic specimens from the Fair- mont Reservoir area, supports the contention that these two pairs are correlative. Sparse Rb/Sr data suggest compatibility between the granitic rocks of the Neenach and Pinnacles areas, although, clearly, more work is needed. Three samples from the Johnson Canyon body and one from the Bickmore Canyon unit give an initial strontium-isotopic ratio of 0.7082 (R. W. Kistler, in Ross, 1972b). A single sample from the Fairmont Reservoir mass gives an initial strontium-isotopic ratio of 0.7083 (Kistler and others, 1973). Dikes of Tertiary volcanic rocks that are almost certainly satellitic to the main intrusive center of the Pinnacles Volcanic Formation are abundant and widespread in granitic rocks of the Pinnacles area. The relation leaves little doubt that the vol- canic rocks intruded the surrounding granitic rocks. By contrast, I have seen no volcanic dikes in granitic rocks of the Neenach area. I do not know the reason for this anomaly. Could it be caused by structural discordance between the volcanic and granitic rocks of the Neenach area? The pattern that is apparent on the map (fig. 20C) does not suggest an abrupt break between the two rock types. However, exposures in this area are very poor-for example, most of the area underlain by granitic rocks and surrounded by volcanic rocks near the west end of the Neenach map area is a low rolling grassy slope with seattered felsic gra- nitic rock fragments and a small exposure of the granodiorite of Burnt Peak at its south tip. Mat- thews (1973) noted that poor exposures hindered delineation of the volcanic and granitic units, and he resorted to showing vertical fault contacts on a cross section. This expedient fails to solve the prob- lem; it merely points out that a problem exists. My reconnaissance work with the granitic rocks sug- gests that they are relatively cohesive and that the faults shown within them (Dibblee, 1967) do not seriously disrupt the granitic rocks. Nevertheless, the question of why volcanic dikes are absent in the granitic rocks of the Neenach area needs an answer! In conclusion, the granitic rocks near the Pin- nacles Volcanic Formation are compatible, both modally and chemically, with the granitic rocks near the Neenach Volcanic Formation. The expect- able uncertainties of correlating granitic masses persist, but the further work suggested in this re- port may reduce these uncertainties considerably. GPO 587-044/10016 RETURN - EARTH SCIENCES LIBRARY "M -»wmip _ 230 Earth Sciences Bldg. 642-2997 ETH C T ' ~ f DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY 68°30' 25° 45°30' r : 68°00' f Pond _ (Dbpe Mw , l wth rfrgizzxj N GRAND me \ pnt m \ ACZ i j : " Hore \ J st ( J 7 . . % Nap A I at \ "CB ? ies agfigu ( | + \~\\\\\\/ ( o / 411 / /y e & Tl p s+. yop & %, I ‘ ‘ w ) W \ PROFESSIONAL PAPER 1320 PLATE 1 Lamb Piace L__s _s 45°15" 35" 67°30' INTERIOR-GEOLOGICAL SURVEY, RESTON, VA.-1984-G83654 SAMPLE LOCATIONS 79 o DSv Dbpr 5 MILES 5 KILOMETERS Saponac Nicatous Lake 68°15" 68°00° 67°45" SOs Springfield Scraggly Lake Wabassus Lake 45°05 45°05" t/ «#" " _- 68°30' Base from U.S. Geological Survey, 1:62,500 Winn, 1960; Springfield, 1931; Scraggly Lake, 1941; Waite, 1940; Saponac, 1931-57; Nicatous Lake, 1932; Wabassus Lake, 1941-63 ~ bras Geology by R. A. Ayuso and others (1977-79); based on fieldwork by D. Larrabee and others (1965), A. Ludman (1978), D. R. Wones (1979), and T. Scambos (1980) 68°00' SCALE 1:125 000 1 0 5 MILES r-- =- m= == 10 KILOMETERS 23 BEDROCK GEOLOGIC MAP OF THE BOTTLE LAKE COMPLEX, MAINE CORRELATION OF MAP UNITS BOTTLE LAKE COMPLEX DESCRIPTION OF MAP UNITS PLUTONIC ROCKS Bottle Lake Complex Passadumkeag River pluton Coarse-grained biotite-hornblende core facies; generally has quartz monzonitic composition, high color index, euhedral amphibole prisms, and abundant mafic inclusions Coarse-grained biotite-hornblende granitic to quartz-mon- zonitic rim facies; commonly heterogeneous in texture; quartz forms large mosaic textures, generally poorer in mafic minerals and mafic xenoliths than rocks in the interior Amphibolite Fineweimned, greenish black with sparse plagioclase and amphibole phenocrysts; found near the cataclastic zone only Whitney Cove pluton Medum- to coarse-grained - granite biotite core facies; hemogeneous, typically porphyritic, and low color index Dbwe ) Coarse-grainéd biotite granite rim facies; equidimensional % texture, low color index, biotite in pseudohexagonal books. Pattern shows area of Topsfield facies PLUTONIC ROCKS Other than Bottle Lake Complex Center Pond pluton; medium-grained rock ranging from dio- rite to biotite granite and containing abundant hornblende Undifferentiated granites in the Lead Mountain pluton; usu- ally coarse-grained and biotitic to hornblendic Medium-grained Wabassus Quartz Monzonite found only within Norumbega fault zone; lower mafic-mineral content than Bottle Lake Complex METAMORPHIC ROCKS DSy | Vassalboro Formation-Calcareous siltstones and pelites showing prominent mineralogic zonation from contact metamorphic effects imposed by the Bottle Lake Complex - Undifferentiated volcanic rocks with rusty pelitic beds Undifferentiated pelitic siltstones containing graded beds Graywackes, siltstones, slates MIDDLE DEVONIAN LOWER DEVONIAN(?) AND SILURIAN SILURIAN AND ORDOVICIAN(?) ORDOVICIAN(?) AND CAMBRIAN(?) Inclined bedding Vertical bedding Inclined cleavage Vertical cleavage Inclined joint Vertical joint Joint having variable strike Joint having variable dip Massive rock having no foliation Inclined cataclastic surface Vertical cataclastic surface Cataclastic surface having variable strike Cataclastic surface having variable dip Inclined foliation Vertical foliation Foliation having variable strike Foliation having variable dip Inclined leucocratic dike Vertical leucocratic dike Leucocratic dike having variable strike and dip Leucocratic dike having variable dip Abundant leucocratic dikes Fault Contact Locality referred to in text Note: Some symbols on map show strike and variable dip