Nonmarine Ostracodes in the Lakota Formation (Lower Cretaceous) From South Dakota and Wyoming By I. G. SOHN GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069 Revision of nonmarine Lower Cretaceous ostracode genera from the Black Hills, and description of two new genera and four new species. On the basis of this revision, the Lakota Formation is considered to be pre-Aptian in age UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON:1979 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataloging in Publication Data Sohn, Israel Gregory, 1911— Nonmarine ostracodes in the Lakota Formation (Lower Cretaceous) from South Dakota and Wyoming. (Geological Survey professional paper ; 1069) Supt. of Doc. No. : SD 119.16:1069 Bibliography: p. Includes index. 1. Ostracoda, Fossil. 2. Paleontology—Cretceous. 3. Paleontology—Black Hills, S. Dak. and Wyo. I. Title. II. Series: United States. Geological Survey. Professional paper ; 1069. QE817.Q8S583 565’.33 77—608326 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, DC. 20402 Stock Number 024—001—03155-6 Family Cyprideidae Martin, 1940 ________________________________________ CONTENTS Key to the species __________________________________________ Limnocypr’idea mowisonensis (Roth, 1933) ______________ L.? albe’rtensz's (Loranger, 1951) ________________________ Page Abstract _____________________________________________________________________ 1 Introduction _________________________________________________________________ 1 Acknowledgments ____________________________________________________________ 2 Age of the rocks ____________________________________________________________ 2 Paleoecology _________________________________________________________________ 4 USGS Mesozoic collection localities __________________________________________ 5 Systematic descriptions _____________________________________________________ 8 Family Trapezoidellidae, n. fam. ________________________________________ 8 Key to the genera __________________________________________________ 8 Genus Trapezoidella. n. gen. ____________________________________ 8 Trapezoidella, trapezoidalis (Roth, 1933) ____________________ 9 T. rothi n. sp. ________________________________________________ 9 Genus Limnocypridea Liibimova, 1956 ____________________________ 10 11 11 12 12 12 12 Key to the genera ___________________________________________________ Genus Cypridea Bosquet, 1852 ___________________________________ Subgenus Cypridea Bosquet, 1852 _____________________________ 13 Subgenus Pseudocypridina Roth, 1933 _______________________ 13 Cyp'ridea, (Pseudocypridina) piedmonti Roth, 1933 _______ 15 Cypridea (P.) inornata (Peck, 1941) _____________________ 15 Cypridea (P.) laeli n. sp. ________________________________ 16 Cypridea (P.) henrybelli n. sp. __________________________ 17 New genus undescribed ___________________________________________ 18 “Cypridea” sp. 1 ____________________________________________ 18 Genus Longispinella n. gen. ______________________________________ 18 Longispinella asymmetrica n. sp. ____________________________ 18 L. longispina (Peck, 1941) __________________________________ 19 References cited _____________________________________________________________ 20 Index ________________________________________________________________________ 23 PLATE FIGURE ILLUSTRATIONS [Plates follow index] Trapezoidella, Limnocypridea. Limmocypridea?, Trapezoidella. Cypridea (Pseudocypridina), Limnocypridea, Candona. Longispinella. Longispinella. Cypridea (Pseudocypridina) . Cypridea (Pseudocypridina), Longispinella, “Cg/prided.” Cypridea (Pseudocypridina) . Page Probable stratigraphic position of the Lakota Formation __________ 3 2. Map showing the collection localities ______________________________ 3. Shell morphology of Cyprideidae __________________________________ III 7 13 IV CONTENTS TABLE TABLE 1.-—USGS Mesozoic collections represented by each number on the locality map ____________________________________________ Page NONMARINE OSTRACODES IN THE LAKOTA FORMATION (LOWER CRETACEOUS) FROM SOUTH DAKOTA AND WYOMING By I. G. SOHN ABSTRACT The stratigraphic age of the Early Cretaceous Lakota Formation in the Black Hills of South Dakota and Wyoming is Barremian or older rather than late Aptian as previously considered. This age is based on the study of certain ostra- codes in 46 collections and the revision of several previously described taxa in North America. The new genera Trapezoidella and Longispinella, and the new species T. rothi and L. asymmetrica, as well as Cypri- dea (Pseudocypridina) laeli and C. (P.) hem‘ybelli, are de- scribed and illustrated. “Cypridea” sp. 1 is illustrated as an example of an as—yet—undescribed genus to which many of the species previously referred to Cypridea s.l. should be referred. Subgenera of Cypridea Bosquet, 1852, are elevated to generic status except Gym-idea (Cypridea) and C. (Pseu- docupridi’na) Roth, 1933. Species previously referred to the Paleozoic marine subgenus Bythocypris (Bairdiocypm's) Kegel, 1932, are illustrated and referred to the new family Trapezoidellidae in the genera Trapezoidella and Limno- cypridea Lfibimova, 1956. Dimorphism similar to that in the living genus Candona Baird, 1845, is proposed for Limnocypridea mowisone'nsis (Roth, 1933), which, unlike most nonmarine ostracodes, is demonstrated to be variable in lateral outline. A lectotype is designated for Bairdiocy- pris albertensis Loranger, 1951, from the Blairmore Forma- tion (Aptian-Albian) in Alberta, Canada, and one for Limnocypm'dea equalis (Harper and Sutton, 1935), from the Lakota Formation, South Dakota. The Canadian species is reillustrated and questionably referred to Limnocypridea. INTRODUCTION Because of the presence of uranium, the Meso- zoic sedimentary deposits in the southern Black Hills, S. Dak. and Wyo. (Gott, Wolcott, and Bowles, 1974, and references therein), have been mapped by the US. Geological Survey in cooperation with the US. Atomic Energy Commission. N onmarine ostra- codes are the most common fossils in the Upper Jurassic (Morrison Formation) and in the Lower Cretaceous sedimentary rocks (Robinson, Mapel, and Bergendahl, 1964, and references therein). I re- ceived ostracode collections during the early stages of field work, and I joined the field parties in 1957 to obtain additional collections. The nonmarine ostracodes from the Black Hills were described and illustrated as faunules from the Morrison Formation of Late Jurassic age by Roth (1933) and later by Harper and Sutton (1935). Roth (1933) described, among other species, Bythocypm's (Bairdiocypm’s) morm’sonensis, B. (B.) trapezoidalis, and Pseudocypridina piedmonti as part of the nonmarine fauna. Harper and Sutton (1935, p. 627) added to the faunule from a second locality, B. (B.) celtz'formis, B. (B.) morrisonens'is var. equalis, and Darwinula dakotensis. Loranger (1951, p. 2360; 1954, p. 286) described Bythocypm‘s (Bairdiocypm's) albertensis from the Lower Creta- ceous Blairmore Formation in central and southern Alberta, Canada. Howe and Laurencich (1958, p. 79) stated that Loranger’s description does not fit Bairdiocypm's. I demonstrated that the sedimentary rocks in South Dakota from which Roth, and also Harper and Sutton, described the ostracodes are actually from the Lower Cretaceous Lakota Formation (Sohn, 1957, 1958). In that study I was able to differentiate between the Jurassic and Lower Creta- ceous sedimentary rocks in the Black Hills, because the Jurassic Morrison Formation contains Them’o- synoecum Branson, 1936, and does not contain notched forms that belong in the Cyprideidae Mar- tin, 1940. In contrast, the Lower Cretaceous sedi- mentary rocks do not contain Theriosynoecum and do contain notched forms. I was not able, however, at that time to correlate the Lower Cretaceous rocks in the Western United States with the cosmopolitan stratigraphic scheme which is based primarily on marine faunas. During the past two decades, publications on Lower Cretaceous stratigraphy of the Black Hills and on nonmarine Early Cretaceous ostracodes abroad (see references cited) have made it possible to suggest a tentative correlation. On the basis of selected taxa discussed in this paper, the Lakota Formation is inferred to be pre-Aptian in age. When Post and Bell (1961) defined the Chilson Member of the Lakota Formation in the southern 2 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING Black Hills, they recognized the Minnewaste Lime- stone Member above the Chilson Member and below the Fuson Member of the Lakota Formation. The Minnewaste Limestone Member is present only in the southern and southeastern Black Hills in Custer and Fall River Counties, S. Dak. (Waagé, 1959, fig. 7), and where it is absent, the Chilson Member is disconformably overlain by the Fuson Member (Post and Bell, 1961, figs. 349.1, 349.2). Rocks equivalent to the Chilson Member of the Lakota Formation thin westward and pinch out beneath rocks equivalent to the Fuson Member west of a line that approximately bisects R. 63 W. in Crook and Weston Counties, Wyo. (Post and Bell, 1961, p. D178, fig. 349.2; Robinson, Mapel, and Bergendahl, 1964, p. 25). For this reason, Mapel and Pillmore (1963, p. M17, pl. 1) mapped the rocks in Wyoming as Lakota Formation. Map localities 5—7 of this report are in Wyoming in rocks considered to be equivalent to the Fuson Member of the Lakota Formation in the southern Black Hills in South Dakota (Post and Bell, 1961, p. D178), rather than to the Chilson Member. How- ever, the ostracodes in eight collections from the Fuson Member in Fall River and Custer Counties, S. Dak., although low in diversity (three genera), differ on the generic level from the high-diversity (eight genera) ostracodes in the Chilson Member of South Dakota (Sohn, 1958, unpublished reports on referred collections, MD—57—60, MD—57—61), and also from those in Wyoming. The ostracodes from map localities 5—7 in Wyoming (pls. 1, 3, 7, and 8), as well as some not included in this report, are identical on the species level with those from the Chilson Member. Because of the short period of absolute time involved, the ostracodes of the Chilson member may have extended into the Fuson Member during similar environmental conditions northwest of Inyan Kara Creek in Wyoming, and the differ- ence on the generic level between the ostracodes of the two members in South Dakota may have been due to different environments. It cannot be stated with certainty that the similarity of ostracodes on the species level between the Lakota Formation undifferentiated in Wyoming and the Chilson Mem- ber of the Lakota Formation in South Dakota indi- cates a time equivalence. All the previously de- scribed ostracode species (Roth, 1933; Harper and Sutton, 1935) and the newly described species, with the possible exception of those from Wyoming, are from the Chilson Member of the Lakota Formation. The Mesozoic nonmarine species previously re- ferred to Bythocypm's (Bairdiocypris) are rede- scribed, lreillustrated, and referred to Mesozoic genera, and the Middle Devonian marine genus Bairdiocypris Kegel, 1932 (see Sohn, 1960, p. 83), is restricted to Paleozoic rocks: Silurian (Lundin, 1965, p. 37; Pranskevichius, 1972, p. 139), Carbon- iferous (Green, 1963, p. 99; Buschmina, 1965, p. 83; 1968, p. 94; 1970, p. 28), and questionably Per- mian (Willey, 1970, p. 130). ACKNOWLEDGMENTS I wish to thank the following colleagues in the US. Geological Survey for guiding me in the field and (or) sending me collections from the Black Hills: Henry Bell III, M. H. Bergendahl, W. R. Braddock, J. J. Connor, W. J. Mapel, C. L. Pillmore, C. E. Price, C. S. Robinson, D. E. Walcott, and V. R. Wilmarth. Prof. K. M. Waagé, Yale University, guided me to some critical localities, Prof. R. E. Peck, University of Missouri, donated specimens of Cypridea longispina Peck, 1941, and Dr. D. M. Loranger made available the types of Bairdiocypm‘s albertensz’s Loranger, 1951. Without the aid of these scientists, this study could not have been made. AGE OF THE ROCKS The nomenclatural history of the Lower Creta— ceous formations was discussed by Waagé (1959, p. 18) and later by Wolcott (1967, p. 433). The Lakota Formation consists, in ascending order, of the Chilson Member, the Minnewaste Limestone Member, and the Fuson Member. Post and Bell (1961, p. D173) divided the Chilson Member into tWo units. The lower (Unit 1) consists mostly of fine-grained yellowish-gray sandstone interbedded or interfingered with highly carbonaceous siltstone and mudstone layers and ranges in thickness from zero to about 400 feet (122 m). Unit 2 unconfor- mably overlies the older unit. It consists of len- ticular bodies of grayish-yellow or reddish-orange to reddish-brown fine-grained well-sorted sand- stones that are interbedded with and finger later- ally into varicolored siltstone or claystone. Unit 2 ranges in thickness from zero to 437 feet (133 m). The mudstone and sandstone are calcareous in many places; consequently, it is inferred that Roth’s as well as Harper and Sutton’s collections came from this unit. The exact stratigraphic position of the Lower Cretaceous continental deposits in the Western In- terior of the United States in terms of the European stages is as yet uncertain. I (Sohn, 1958, p. 122) suggested that the basal part of the Lakota Forma- AGE OF THE ROCKS 3 TIME EUROPEAN ( M,Y. SOHN, 1958 THIS PAPER STAG ES SUBSTAGES ALBIAN 108 — 7 -’ LAKOTA FORMATION APTIAN 7 ? (I) 3 115 —— 8 O < l- LU 5 BARREMIAN D: I.“ E 121 — _, LAKOTA FORMATION HAUTERIVIAN 126 — z S 2 8 VALANGINIAN 0 Lu 131 —— Z . _, BERRIASIAN 135 PORTLANDIAN Z 2 1 ? 138.5 — 3, A S S a: '— z o < E ‘x’ -* I: 9: t g MORRISON 2 I- -— KIMMERIDGIAN FORMATION 141.5 —— FIGURE 1.—Probable stratigraphic position of the Lakota Formation. Absolute scale from van Hinte (1976b). tion may prove to be older than Aptian (1958, fig. Western Interior and concluded that the boundaries 2, p. 124). Lane (1963, p. 232) summarized the within the formations were still highly conjectural. previous work on the Lower Cretaceous of the Anderson (1973, fig. 1) extended the Lower Cre- 4 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING taceous of South Dakota to the approximate base of the Middle Valanginian but noted that the North American ages are subject to considerable revision. Cook and Bally (1975, p. 206) showed the Lakota Formation of South Dakota as starting in the Middle Aptian(?), extending through the Barre- mian, and questionably terminating at the top of the Hauterivian. Because the Early Cretaceous ostracodes in the Black Hills of South Dakota and Wyoming are en- demic, all the known species and those described here as new offer no clues to intercontinental cor- relation. However, some idea as to the probable stratigraphic position of the rocks might be obtained ' by recording the ranges of related species in Europe, Asia, and South America. Figure 1 shows the probable stratigraphic position of the Lakota Formation on the basis of such a comparison. The Lakota Formation contains, among other species, Cypridea, (Pseudocypridina) piedmonti Roth, 1933, C. (P.) henrybelli n. sp., and C. (P.) laeli n. sp. The resemblance of C. (P.) piedmonti to C. (P.) um'costata Galeeva, 1955, from the Barre- mian of Mongolia, as shown in the discussion of the species, suggests that the Lakota Formation is probably not younger than the Barremian. C. (P.) henrybelli is shown in the discussion of the species to belong, on the basis of lateral outline and ros- trum, to the Cypridea, parallela-line of Wolburg that has a stratigraphic range of Wealden 4 to Wealden 6 Beds in Germany. The Wealden Beds 4 t0 6 were considered to be Valanginian in age by Anderson (1973, fig. 1) but van Hinte (1976b) re- garded these beds as Berriasian in age. The lateral nodes relate this species to C. (P.) binodosa (Mar- tin, 1940) from the middle Purbeckian of Germany, and to C. (P.) salvadorensis nodifer (Krommelbein, 1962) as well as to C. (P.) subtilis (Krommelbein, 1965), both from Brazil. The Brazilian species are considered to be at least partly younger than the Wealden Beds of Germany, and are probably of approximate Valanginian Age. C. (P.) laeli is shown in the discussion of the species to resemble the Purbeckian Cypm'dea fasciculata-group of Wolburg and also the late Purbeckian-Berriasian C. alta- group of Wolburg. Certain structures on the sur- face of the carapace could have developed from similar structures on species described from Pur- beckian through Berriasian Ages. On the basis of the resemblances and postulated evolutionary stages of development in relation to the known species outside of North America, C. (P.) henry— belli and C. (P.) laeli suggest that the plausible age for the Lakota Formation is younger than Berri- asian and possibly also younger than early Valan- ginian. According to van Hinte’s proposed absolute time scales for the Jurassic (1976a) and for the Creta- ceous (1976b) , the time involved between the under- lying Morrison Formation (Kimmeridgian) and the base of the Aptian is approximately 26 my, of which 6 my. are in the Jurassic and the remaining 20 my. in the Early Cretaceous. On the basis of the estimates of the timespan in the standard section, the Lakota Formation should fall somewhere with- in the 16-m.y. span between the Berriasian and the base of the Aptian. As the ostracodes dealt with in this paper are from the Chilson Member, the lowest of three members of continental deposits, I estimate the timespan of the rocks represented by the ostra- codes to be less than 10 my, somewhere between 118 my. and 128 my. before the present. PALEOECOLOGY The Lower Cretaceous sedimentary rocks in the Black Hills represent limnic and fluviatile deposits, and the ostracodes in those rocks belong to genera described from nonmarine environments in other parts of the world. The one possible exception is presented in a study by Allen and others (1973) on the basis of isotopic ratios of the carbonate in fos- sils from the Lower Cretaceous Wealden clay in Europe (England and Germany). They concluded that two species of Cypridea: C. bispinosa sut- tingem's [sic] = C. bispinosa suthringe‘nsis Ander- son, 1967, and C. recto, tillsdenensis Anderson, 1967, “might be marine” (Allen and others, 1973, p. 619), and that other species of Cypridea used in their study may be freshwater. It is known that non- marine ostracodes have been transported into brackish and also marine environments. I have re- covered from the same samples (Sohn, 1967 , p. 123) Cypridea specimens and charophytes associated with typically marine ostracodes as well as the foraminifer Chofatella, decipiens Schlumberger, 1905. However, the paleogeographic framework of the European Lower Cretaceous differs from that in the Black Hills. In Europe, the Lower Cretaceous sedi- ments were deposited during a marine-freshwater transgressive and regressive sequence (Anderson and others, 1967, p. 174—175), whereas no evidence exists in North America of a marine incursion in Wyoming and South Dakota during Early Creta- ceous time (Lane, 1963, fig. 2). The population dynamics of the limnic ostracodes USGS MESOZOIC COLLECTION LOCALITIES 5 in the Black Hills area must have been such as to induce an unusual variety in the shell morphology. The development of lateral ridges on the valves, asymmetrical on the carapace as on Trapezoidella (pl. 1, figs. 5, 8, 16; pl. 2, figs. 14, 16, 18, 20-24, 28, 30, 36), and on Cypridea (Pseudocypridina) (pl. 3, figs. 1, 4, 9, 10, 13; pl. 6, figs. 1, 5, 8, 10, 13, 16, 21, 23, 32, 41, 42; pl. 8, figs. 29, 30) on which they are developed only on the left valves, and the asymmetri- cal structure on the left valve only in Longispinella (pl. 4, figs. 9, 13, 16, 17, 18; pl. 5, figs. 7, 13,20, 21; pl. 7, figs. 5, 7) probably reflects some functional response to their ecology. Sohn (1962) and Sohn and Anderson (1964) demonstrated that the presence and position of every spine and node in the Mesozoic freshwater cypridacean ostracode Them‘osynoecum Branson, 1936, are genetically controlled, and later workers (Benson, 1972; Liebau, 1975) showed that the same is true for marine cytheraceans. Some of the species in the Black Hills show a variation contrary to this principle, as illustrated in this paper in Cypridea (Pseudocypm'dina) henrybelli (pl. 3, figs. 14—17; pl. 8, figs. 1—25). Although similar struc- tures have been recorded on other limnic cyprida— ceans, nobody has proposed an explanation for their presence. At the present state of knowledge, such structures cannot be ascribed to a definite ecological factor. USGS MESOZOIC COLLECTION LOCALITIES [Map locality numbers refer to figure 2] USGS 25460. Chilson Member of Lakota Formation. Unit 2, Buck Canyon, SE14, sec. 15, T. 8 S., R. 4 E., Flint Hill quadrangle, Fall River County, S. Dak. Colln. H. Bell, 1954, (MD—5541, field No. HBP470—54). Map 10c. 17. USGS 25643. Lakota Formation, NElA .sec. 9, T. 50 N., R. 64 W., Crook County, Wyo. Colln. W. J. Mapel, 1956 (F— 56—32, field No. MP—41—23). Map loc. 6. USGS 25644. Lakota Formation, NW14 sec. 21, T. 51 N., R. 65 W., Crook County, Wyo. Colln. W. J. Mapel, 1956 (F—56—32, field No. MP—48~19). Published in error as USGS 24644 by Robinson, Mapel, and Bergendahl (1964, p. 37, unit 13), see USGS 31001. Map loo. 5. USGS 25645. Same locality as USGS 25644. Colln. W. J. Mapel, 1956 (F—56—32, field No. MP—48-20). Published in error as USGS 24645 by Robinson, Mapel, and Bergen— dahl (1964, p. 37, unit 14), see USGS 31001. Map Ice. 5. USGS 25646. Lakota Formation, approximately 80 feet (24.4 m) above base. Sec. 16, T. 6 N., R. 4 E., Lawrence County, S. Dak., vicinity of Sturgis. Colln. W. J. Mapel, 1956 (F—56—32, field No. MP—119—9). Map loc. 2. USGS 25647. Lakota Formation, Nl/z sec. 30, T. 6 N., R. 5 E., Meade County, S. Dak., Colln. W. J. Mapel, 1956 (F—56—32, field No. MP~119—10). Map loc. 4. USGS 26098. Chilson Member of Lakota Formation, Unit 2, Buck Canyon measured section, 56 to 63 feet (17 to 22 m) above base. SE14, sec. 15, T. 8 S., R. 4 E., Flint Hill quadrangle, Fall River County, S. Dak. Colln. H. Bell, 1954 (MD—56—6, field No. HBP—51—54). Map 10c. 17. USGS 26100. AEC Diamond Drill Hole RE—17 (Bell and Post, 1971, p. 557, pl. 32), same as USGS 30988, core at 267.0 feet (81 m). Colln. H. Bell, 1955 (MD—56—6, field No. RE—17B). Map 10c. 16. USGS 26468. Lakota Formation, measured section in SE14 sec. 1, T. 8 S., R. 3 E., elevation 4,170 feet (1,271 m), Fall River County, S. Dak. Colln. V. R. Wilmarth, 1956 (MD—57—11, field No. MK—S—56). Map 10c. 10. USGS 26469. Same locality and section as USGS 26468 at elevation 4,200 feet (1,280 m). Colln. V. R. Wilmarth, 1956 (MD—57—11, field No. MK—T—56). Map 10c. 10. USGS 26939. Lakota Formation, 20 feet (6 m) above base, SW14 sec. 9, T. 50 N., R. 64 W., Crook County, Wyo. Colln. W. J. Mapel and C. L. Pillmore, 1957 (F——57—31, field No. 213—6). Map 10c. 6. USGS 26940. Lakota Formation, basal part, sec. 29, T. 50 N., R. 64 W., Crook County, Wyo. Colln. W. J. Mapel and C. L. Pillmore, 1957 (F—57—31, field No. 216—1). Map loc. 7. USGS 26941. Lakota Formation, limestone bed, 1 foot (0.30 m) above USGS 26940. Colln. W. J. Mapel and C. L. Pillmore, 1957 (F—57—31, field No. 21642). Map Ice. 7. USGS 30985. Chilson Member of Lakota Formation, upper part, mudstone, dark greenish gray, somewhat sandy, Unit 2, SE14 sec. 11, T. 8 S., R. 3 E., Flint Hill quad- rangle, Fall River County, S. Dak. Colln. H. Bell, 1954 (field No. HB—1—54:Station B436). Map 10c. 13. USGS 30986. Chilson Member of Lakota Formation, upper part, thin sandstone in Unit 2 (Bell and Post, 1971, p. 520), SW14 sec. 12, T. 8 S., R. 3 E., Flint Hill quad- rangle, Fall River County, S. Dak. Colln. H. Bell, 1954 (MD—55—11, field No. HB—2—54). Map 10c. 13. USGS 30987. Chilson Member of Lakota Formation, white clay, Unit 2, 1.8 miles (2.9 km) southeast of 30986. Flint Hill quadrangle, Fall River County, S. Dak. Colln. H. Bell, 1953 (MD~53—55, field No. HB—14—53). Map 10c. 16. USGS 30988. Chilson Member of Lakota Formation, Unit 2, AEC Diamond Drill Hole RE-17 (Bell and Post, 1971, p. 557, pl. 32), corner common to secs. 14, 15, 22, 23, T. 8 S., R. 3 E., Flint Hill quadrangle, Fall River County, S. Dak. Core at 289.5 feet (88 m) interbedded mudstone and sandstone. Colln. H. Bell, 1955 (MD—56v6, field No. RE717I). Map loc. 16. USGS 30989. Chilson Member of Lakota Formation, Unit 2. AEC Diamond Drill Hole RE—14 (Bell and Post, 1971, p. 555, pl. 32), SW1/48W1/1 sec. 11, T. 8 S., R. 3 E., Flint Hill quadrangle, Fall River County, S. Dak. Core at 346.0 feet (105 m), siltstone, dark-gray, carbonaceous; some dark-greenish-gray claystone. Colln. H. Bell, 1955 (MD—56—6, field No. RE—14J). Map 10c. 13. USGS 30990. Chilson Member of Lakota Formation, Unit 1, mudstone about 10 feet (3 m) above base of section, Upper Chilson Canyon, Marty’s Ranch, T. 8 S., R. 3 E., Flint Hill quadrangle, Fall River County, S. Dak. Colln. I. G. Sohn and H. Bell, 1957, field No. 8/15/10/57. Map 10c. 14. USGS 30991. Chilson Member of Lakota Formation, Unit 1, same locality as above, limestone below and between paper shale sequence. Colln. I. G. Sohn and H. Bell, 1957, field No. 8/15/18/57. Map 10c. 14. 6 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING USGS 30993. Lakota Formation, core in NE% sec. 33, T. '7 S., R. 3 E., Edgement quadrangle, Fall River County, S. Dak. Colln. W. B. Braddock, 1953 (MD—53—33, field No. BB—45—33). Map Ice. 9. USGS 30994. Chilson Member of Lakota Formation, mud- stone below typical Lakota sandstones and above the Unkpapa Sandstone. Sec. 4, T. 8 S., R. 4 E., Minnekahta quadrangle, Fall River County, S. Dak. Colln. H. Bell, 1953 (MD—53—33, field No. HB—9—53a). Map 10c. 11. USGS 30995. Lakota Formation, 95 feet (29 m) below top, center NW1A sec. 17, T. 8 N., R. 1 E., Butte County, S. Dak. Colln. W. J. Mapel, 1957 (F—57—35, field No. 253— 13a). Map loo. 1. USGS 30996. Lakota Formation, gray silty claystone, car- bonaceous, approximately 150 feet (45.7 m) below top of formation, 4,300 feet (1,311 m) N. 35° E. from com- mon corner secs. 11, 12, 13, 14, T. 8 S., R. 5 E., Cascade Springs quadrangle, Fall River County, S. Dak. Colln. J. J. Conner, 1957 (MD—57-60, field No. AS—58). Map 10c. 15. USGS 30997. Chilson Member of Lakota Formation, probably Unit 2, coquina at Roth’s (1933) type—locality, sec. 28, T. 4 N., R. 6 E., Meade County, S. Dak., 3 miles (4.8 km) north of Piedmont. Colln. I. G. Sohn, 1957 (field No. 8/10/2/57). Map loc. 8. USGS 30998. Lakota Formation, laminated ostracodal clay, Harper and Sutton’s (1935) type-locality, NW1/1. sec. 29, T. 6 N., R. 4 E., Lawrence County, S. Dak. Colln. I. G. Sohn and H. Bell, 1957 (field No. 8/11/2/57) Map loo. 3. USGS 30999. Lakota Formation, shale with ostracodes, about 3 feet (0.9 m) below the sandstone, same locality as above. Colln. I. G. Sohn and H. Bell, 1957 (field No. 8/11/4/57). Map 10c. 3. USGS 31001. Lakota Formation, near top, shale above lime- stone, near Corral Creek, NE1/2 sec. 20 and NW% sec. 21, T. 51 N., R. 65 W. Crook County, Wyo. Colln. I. G. Sohn and W. J. Mapel, 1957 (field No. 8/20/21/57), same as USGS 24645225655 (see Robinson, Mapel, and Ber- gendahl, 1964, p. 37, unit 14). Map loc. 5. USGS 31002. Chilson Member of Lakota Formation, Unit 2, mudstone, gray to green calcareous, core at 314.5 feet (96 m) in same drill hole as USGS 30989. Colln. H. Bell, 1955 (MD—5646, field No. RE—14A). Map 10c. 13. USGS 31003. Same unit, formation and drill hole as above, core at 321.8 feet (98.1 m). Colln. H. Bell, 1955 (MD— 56~6, field No. RE—14D). Map 10c. 13. USGS 31004. Same unit, formation and drill hole as above, core at 334.0 feet (102 m). Colln. H. Bell, 1955 (MD— 56—6, field No. RE—14G). Map loc. 13. USGS 31005. Same unit, formation and drill hole as above, siltstone, dark—gray, carbonaceous, core at 345.0 feet (105 m). Colln. H. Bell, 1955 (MD—56-6, field No. RE— 14I). Map 10c. 13. USGS 31006. Chilson Member of Lakota Formation, Unit 2. Same drill hole as USGS 30988. Mudstone, dark-olive- gray, carbonaceous, core at 283.5 feet (86 m). Colln. H. Bell, 1955 (MD-56—6, field No. RE—17H). Map 10c. 16. USGS 31007. Chilson Member of Lakota Formation, Unit 2, Buck Canyon, SE14 sec. 15, T. 8 S., R. 4 E., Flint Hill quadrangle, Fall River County, S. Dak. Mudstone, brownish gray, silty; bedding irregular, unit 10 of Bell and Post (1971, p. 531), 52 feet (15.8 m) above base. Colln. H. Bell, 1955 (MD-56—6, field No. HB-23—54). Map 10c. 17. USGS 31008. Same unit as above, slightly higher. Colln. H. Bell, 1955 (MD—56—6, field No. HB—24—54). Map 10c. 17. USGS 31009. Lakota Formation, variegated clay just below USGS 30998. Colln. I. G. Sohn and H. Bell, 1957 (field No. 8/11/3/57). Map loc. 3. USGS 31129. Chilson Member of Lakota Formation, Unit 1, same location as USGS 30990, about 5 feet (1.5 m) below USGS 30990, Fall River County, S. Dak. Colln. I. G. Sohn and H. Bell, 1957 (field No. 8/15/11/57). Map loc. 14. USGS 31130. Chilson Member of Lakota, Unit 1, sandy layer, just above USGS 31129. Fall River County, S. Dak. Colln. I. G. Sohn and H. Bell 1957, (field No. 8/15/12/ 57). Map 10c. 14. USGS 31153. Lower part of the Lakota Formation, shale, sec. 32, T. 7 S., R. 6 E. Channel sample of upper one- half of 15—foot (4.6-m) lens in cut on north side of Fall River Road, 3.2 miles (5.1 km) southeast of city limits (1940) of Hot Springs, Fall River County, S. Dak. Same locality as Peck (1957, p. 11) 10c. D286. Colln. I. G. Sohn, D. E. Wolcott, and C. E. Price, 1957 (field No. 8/16/1/57). Map Ice. 12. USGS 31154. Same locality as above, channel sample of lower one-half of the same lens to contact with underlying Unkpapa Sandstone (Upper Jurassic). Colln. I. G. Sohn, D. E. Wolcott, and C. E. Price, 1957 (field No. 8/16/2/57). Map 10c. 12. USGS 31171. Chilson Member of Lakota Formation, probably Unit 2, shale, about 3 feet (0.9 m) above USGS 30997, and approximately 33 feet (10 m) above base. Sec. 28, T. 4 N., R. 6 E., Meade County, S. Dak. Colln. I. G. Sohn, 1957 (field No. 8/10/1/57). Map loc. 8. USGS 31172. Chilson Member of Lakota Formation, prob- ably Unit 2 shale, about 25 feet (7.6 m) below USGS 30997, and approximately 5 feet (1.5 m) above base. Sec. 28, T. 4 N., R. 6 E., Meade County, S. Dak. Colln. I. G. Sohn, 1957 (field No. 8/10/3/57). Map loc. 8. USGS 31237. Chilson Member of Lakota Formation, same locality as USGS 30990, shale, Unit 1, about 3 feet (0.9 m) lower in the section than USGS 31129. Colln. I. G. Sohn, and H. Bell, 1957 (field No. 8/15/13/57). Map 10c. 14. USGS 31238. Same locality as above, 2 feet (0.6 m) below USGS 31237. Colln. I. G. Sohn and H. Bell, 1957 (field No. 8/15/14/57). Map 10c. 14. USGS 31239. Lakota Formation, gray, silty claystone ap- proximately 150 feet (45.7 m) below top, 5,400 feet (1,646 m) N. 45 E. from common corner of secs. 11, 12, 13, 14, T. 9 S., R. 5 E., Cascade Springs quadrangle, Fall River County, S. Dak. Colln. J. J. Conner, 1957 (MD— 57—60, field No. AS—33). Map 10c. 18. The geographic location of the samples in Wyo- ming and South Dakota is shown in figure 2. Col- lection localities that are too close to each other to be shown on the map are lumped under one number. Table 1 shows the USGS Mesozoic localities under each of the location numbers on the map. USGS MESOZOIC COLLECTION LOCALITIES Ruchvflllyo Ihomen lumy Pods Rarity F‘mw‘ w: I ’2 I-Eflflfii‘: ’1‘ V I 20 MILES ' .0 s: 30KILOMETERS Blue from US. Geological Survey State buss K A Wyoming, 1964 and South Dakota, 1961, 1:500,000 FIGURE 2.—Map showing the location of the collection localities in South Dakota and Wyoming. 8 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING TABLE 1.——USGS Mesozoic collections represented by each number 07L the locality map (fig. 2) Map Zowtion No. l'SGS .llcsozoir mllertitm No. 1 30995 2 25646 3 30998, 30999, 31009 4 25647 5 25644, 25645, 31001 6 25643, 26939 7 26940, 26941 8 30997, 31171, 31172 9 30993 10 26468, 26469 11 30994 12 31153, 31154 13 30985, 30986, 30989, 31002, 31003, 31004, 31005, 31129 14 30990, 30991, 31129, 31130, 31237, 31238 15 30996 16 26100, 30987, 30988, 31006 17 25460, 26098, 31007, 31008 18 31239 SYSTEMATIC DESCRIPTIONS Class OSTRACODA Latreille, 1802 emend. 1804 Order PODOCOPIDA Sars, 1865 Superfamily CYPRIDACEA Baird, 1845 Family TRAPEZOIDELLIDAE Sohn, n. fam. Diagnosis—Medium to large (between 0.75 mm and 21/2 mm or larger), thick walled, with straight to curved dorsal margin. Surface smooth or tubercu- late, with or without ventrolateral ridge or node on larger valve. Overlap strong along dorsal and ven- tral margins, variable on end margins. Duplicature Wide on end margins, hingement ridge and groove, with or without anterior toothlike widening on ridge. Dimorphism unknown. Discussion.——Galeeva (1955, p. 26) described Limnocypridae Mandelstam, 1948, for the genera Dsunbaina Galeeva, 1955, Cypridea Bosquet, 1850, Mongolianella “Mandelstam in litt. 1948,” and “Cyprideamorphella,” but did not describe, illus- trate, or cite a reference to Limnocym'idea. the type- genus. Because Limnocypridea Liibimova, 1956, had not been validated in 1955, the family Limnocypri- dae is a nomen nudum, and does not compete with the Trapezoidellidae. Howe (1962, p. 134) discussed the Limnocypridae, and stated that “As used this family is more or less equivalent to the Cyprideinae Martin, 1940 * * * .” Liibimova (1956b, p. 9) transferred Limnocy- pridea Liibimova, 1956, and Mongolianella Mandel- stam, 1955, to the Cyprideinae, and Mandelstam and Schneider (1963, p. 106) added to the subfamily the genera Latom’a Mandelstam, 1963, Zefaina Man- delstam, 1963, and Ilyocypromorpha Mandelstam, 1955. The Cyprideinae were elevated to family status, the Cyprideidae Martin, 1940, by Hartmann and Puri (1974, p. 57) who stated that all the genera in this family possess a “rostrum-like” in- cisure at the border of the anterior and ventral margins. Because none of the genera except Cypri- dea discussed above has an anteroventral incisure, I am referring them to the new family Trapezoi- dellidae. Key to the genera in the Trapezoidellidae 1 Left valve larger than right __________________ 2 1a Right valve larger than left __________________ 5 2(1) Ventrolateral ridge and dorsolateral groove on left valve ________________________ Trapezoidella 2a Without ventrolateral ridge and dorsolateral groove on left valve ________________________ 3 3(2a) Dorsal margin overreaches right valve ________ _________________________________ Limnocypridea 3a Dorsal margin does not overreach right valve __ 4 4(3a) Dorsoposterior margin pointed __________ Zefaina 4a Dorsoposterior margin rounded ____ Mongolianella 5(la) Dorsal margin round ____________________ Latom'a 5a Dorsal margin straight ______________________ 6 6(5a) Lateral surface tuberculate ______ Ilyocyprimorpha 6a Lateral surface not tuberculate Cyprideamorphella Genus TRAPEZOIDELLA Sohn, n. gen. Type-species.—Bythocypris (Bairdiocypm’s) trap- ezoidalis Roth, 1933. Diagnosis—Large, to 1.6 mm in greatest length, trapezoidal, with straight or convex dorsal margin. Surface smooth, with ventrolateral ridge near ven- tral margin, and dorsolateral thin groove sub- parallel to dorsal margin of left valve. Overlap and overreach of left valve over right. End outline sub- triangular, ridge and overlap forming almost straight base, dorsal outline subelliptical, greatest width at approximate midlength, posterior wider than anterior. Discussion—This genus is established for the type-species, T. trapezoidalz's (Roth, 1933), and T. rothz’ n. sp., both from the Lower Cretaceous La- kota Formation in the Black Hills. Harper and Sut- ton (1935, p. 627) stated in their discussion of Bythocypris (Bairdiocypm's) morrisonensis Roth, 1933 (= Limnocypridea), “A semi-false keel paral- leling the dorsal margin of the left valve is the only surface ornament,” and Loranger (1951, p. 2360) stated in her description of Bairdiocypris alberten- sis Loranger, 1951 (= Limnocypridea?), “Surface ornamentation commonly consists of straight ridge or false keel on left valve parallel with the ventral margin.” Both of the above species do not have the diagnostic ventrolateral ridge and are discussed under Limnocypridea Liibimova, 1956. Krommel- bein (1963, p. 387) described and illustrated Salva- SYSTEMATIC DESCRIPTIONS ' 9 doriella redunca subsp. comitans from the upper part of the Ilhas Formation of Bahia, Brazil, that is trapezoidal in lateral outline and has a ventrolateral ridge on both valves, which, combined with the lateral outline, differentiates it from the nominate subspecies, the type-species of Salvadoriella. Be- cause Krommelbein did not mention a dorsolateral groove, I do not know whether the Brazilian taxon belongs in the new genus. Salvadoriella Krommel- bein, 1963 (type-species Candona? redunca Krom- melbein, 1962) differs from Trapezoidella in having a concave ventroanterior, is smaller in size, has a relatively narrow overlap, and lacks the ventro- lateral ridge and dorsolateral groove on the larger left valve. Stratigraphic range—Lower Cretaceous. Trapezoidella trapezoidalis (Roth, 1933) Plate 1, figures 6—9, 12—17; plate 2, figures 30—32 Bythocypris (Bairdiocypris) trapezoidalis Roth, 1933, Jour. Paleontology, V. 7, no. 4, p. 402, pl. 48, figs. 6a~d. Lakota Formation, Meade County, S. Dak.; Harper and Sutton, 1935, Jour. Paleontology, v. 9, no. 8, p. 628, pl. 76, figs. 16, 17 (orientation reversed 180°). Lakota Formation, Lawrence County, S. Dak. Diagnosis—Straight backed, with straight ven- trolateral ridge near middle of larger valve. Discussion—The holotype (USNM 74470) is a young individual about one-half the size of available specimens (compare pl. 1, figs. 6—9 with figs. 16, 17). The species is distributed in the Chilson Member of the Lakota Formation in South Dakota and Wyo— ming. Geographic distribution.—South Dakota; Butte County; map loc. 1. USGS colln. 30995, USNM 242910. Meade County; map 10c. 4, USGS colln. 25647, USNM 242921; map loc. 8, Roth’s type-locality, pl. 1, figs. 6—9, and USGS colln. 30997, USNM 242911, associated with Limnocypridea morrisonensis (Roth, 1933) and Cypridea (Pseudocypridina) piedmontz’ (Roth, 1933). Lawrence County; map loc. 3, Harper and Sut- ton’s type-locality and USGS colln. 30998, USNM 242912, associated with Cg/prz'dea (Pseudocypr'i- dina) piedmontz’ (Roth, 1933); USGS colln. 30999, USNM 242913, associated with Limnocypridea morrz'sonensis (Roth, 1933); USGS colln. 31009, USN M 242914. Fall River County; map loc. 13, USGS colln. 30986 (‘2 identification), USNM 242915, associated with Cypridea (Pseudocyprz’dina) piedmonti (Roth, 1933); map 100. 17, USGS colln. 31007, USNM 242916, associated with T. rothi. n. sp., and Cypridea (Pseudocypridina) hehrybellz' n. sp.; map 10c. 16, USGS colln. 30987, USNM 242916. Wyoming, Crook County; map loc. 6, USGS colln. 25643, pl. 1, figs. 12—17, USNM 242917; USGS colln. 26939 (? identification), USNM 242918; map loo. 7, USGS colln. 26940, USNM 242919; 26941, pl. 2, figs. 30—32, USNM 242920. Trapezoidella rothi Sohn, n. sp. Plate 1, figures 1—5, 10; plate 2, figures 7—29, 33, 34—36 Name—In honor of Dr. Robert Roth, Wichita Falls, Tex., who was the first to describe the Meso- zoic ostracodes from the Black Hills, S. Dak. Holotype.——USNM 242861. Paratypes.—USN M 242836442838, 242860, 242862—242864. Type-locality.—Map 10c. 13, 813%, sec. 11, T. 8 S., R. 3 E., Flint Hill quadrangle. Fall River County, S. Dak. Other localities—See geographic distribution. Type leoel.—Upper part of the Chilson Member of the Lakota Formation, USGS colln. 30985. Diagnosis—Convex dorsal margin and gently curved lateroventral ridge on left valve, smaller right valve with shallow horizontal lobe below and subparallel to straight hingeline, delineated ven- trally by a horizontal shallow sulcus. Description—The lateral outline of the carapace is subhemicircular, with a convex dorsal margin, a straight to slightly concave ventral margin, curved end margins with the posterior margin more broad- ly rounded than the anterior margin. The left valve overlaps the right, and overreaches it along a straight-hinge margin; it bears a gently curved ridge near its ventral margin, and a narrow groove subconcentric to the curved dorsal outline. This groove gives the impression of the dorsal margin having been pinched along its perimeter. The smaller right valve is subtrapezoidal in lateral out- line, with a straight-hinge margin that is over- reached by the left valve, and with a shallow hori- zontal lobe below the hinge margin. This lobe has below it a shallow sulcus that sets it off from the convexity of the valve. Discussion—This species was called “Genus F” in my reports to the field geologists who were map- ping in the Black Hills and appears as such in their fauna] lists. Geographic distribution—South Dakota, Fall River County; map loc. 9, USGS colln. 30993, pl. 1. figs. 1, 2, pl. 2, figs. 34—36; map loc. 10, USGS colln. 242851— ‘ 26468, pl. 2, fig. 21, USNM 242922; USGS colln. 26469, USNM 242923; map loc. 11, USGS colln. 30994, pl. 2, fig. 23, associated with Cypridea 10 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING (Pesudocypm'dina) piedmonti (Roth, 1933); map loc. 13, USGS colln. 30985, pl. 2, figs. 7—9, 22, 24—29, 33, USNM 242924; USGS colln. 30989, USNM 242025; USGS colln. 31002, USNM 242928; USGS colln. 31003, USNM 242929, associated with C. (P.) henrybelli n. sp.; USGS colln. 31004, USNM 242930; USGS colln. 31005, USNM 242987, associated with C. (P.) inornata (Peck, 1941) ; map 10c. 14, USGS colln. 30990, pl. 2, figs. 10, 11, USNM 242926; USGS colln. 30991, USNM 242927; USGS colln. 31237, USNM 242959, associated with C. (P.) inor- nata (Peck, 1941), and C. (P.) henrybelli n. sp.; USGS colln. 31238, USNM 242960, associated with C. (P.) mornata (Peck 1941); map 10c. 16, USGS colln. 26100, USNM 242933, associated with C. (P.) inomata (Peck, 1941); USGS colln. 30988, pl. 2, figs. 12—15, USNM 242934; USGS colln. 31006, pl. 2, figs. 16, 17, USNM 242935; map 10c. 17, USGS colln. 31007, pl. 2, fig. 20, associated with T. trap- ezoidalis (Roth, 1933) and C. (P.) hem'ybellz' n. sp.; USGS colln. 31008, USNM 242932. Genus LIMNOCYPRIDEA Liibimova, 1956 Limnocypm'dea Liibimova, 1956a, in Kiparisova, Markovsky, and Radchenko, Materialy po paleontologii, VSEGEI, Materialy, new ser., no. 12, p. 106; Liibimova, 1956b, VNIGRI, Trudy, no. 93, p. 9; Liibimova, Mandelstam, and Schneider, 1960, Osnovy paleontologii, v. 8, p. 353; Swain and others, in Moore, 1961, Treatise on inverte- brate paleontology, Part Q, Arthropoda 3, Crustacea, Ostracoda, p. Q237; Mandelstam and Schneider, 1963, VNIGRI, Trudy, no. 203, p. 112. Bythocypm's (Bairdiocypris) Kegel. Roth, 1933, Jour. Paleontology, v. 7, p. 401; Harper and Sutton, 1935, Jour. Paleontology, v. 9, p. 627; Loranger, 1951, Am. Assoc. Petroleum Geologists Bull., v. 35, no. 11, p. 2359; Loranger, 1954, Western Canada sedimentary basin—A symposium, p. 286. Type-species (original designation).—Limnocy- pridea abscondida Liibimova, 1956a, p. 108, pl. 26, figs. 2a—c, text figs. 27a, b. Dzunbain Formation (Barremian), SE Mongolia, U.S.S.R., nonmarine. Diagnosis.——Carapace thick walled, subtriangular, suboval or trapezoidal, with rounded ends, greatest convexity in middle or ventral part of valves. Left valve overlaps right, greatest overlap along venter, dorsal margin overreaches; hingeline approximately straight, of variable length. Vestibule large, radial pore canals straight or slightly curved; surface smooth or pitted, with or without elongate nodes on ventral part. Discussion—The following description is modi- fied from the original description and discussion, which has been translated from Liibimova (1965a, p. 106), and from that given in Moore (1961, p. Q237). Carapaces large (length 1.2 to 1.8 mm), thick walled, suboval to trapezoidal with rounded corners, with the greatest convexity in the middle or posteroventral part of the valve. The left valve markedly larger than right and overlaps the latter all around: particularly strong overlap is expressed on the dorsal and ventral margins. Occasion- ally the dorsal part of the left valve is noticeably raised above the dorsal margin of the right valve and markedly overlaps [overreaches] longitudinally the entire dorsal margin. Anterior and posterior margins of equal height or the anterior is slightly higher than the posterior. Both ends are bevelled in their upper part and are roundly curved below, somewhat lower downward. Dorsal margin straight. Ventral margin concave in the middle. Valves pitted, with one or two [nodes] protuberances in the ventral part, sometimes smooth. Inner margin of the valves does not coincide with the outer. Pore—canal zone wide, well developed on anterior and posterior ends, and on the ventral side. Pore canals straight or somewhat curved, extend [from the] sinuous line of concrescence. Sometimes branched pore canals are ob- served. On the anterior and posterior ends are well developed structureless plates [calcified part of the inner lamella]. Hinge straight—ridged, equaelemental, of sufficiently simple construction. The right valve has a ridge, widening towards the ends [particularly toward the front] and curving in its own marginal parts, tapers [merges] imperceptibly to an- terior and posterior ends. Hinge of left valve has the opposite structure, i.e., consists of a shallow groove, also slightly widening towards the ends and dying out at the anterior and posterior where it flattens out. Reason for separating genus: Hinge of described genus is generally similar to the hinge of the genus Cyprideamor- phella erected by Mandelstram for Lower Cretaceous repre- sentatives from eastern Zabaikal. Differs from it in simpler construction, namely: absence in the anterior portion of the ridge, the thickened curved tooth, and in the anterior portion of the groove and expanded socket that opens into the groove. In addition, the arrangement of the hinge elements of the described genus are reversed: ridge on right valve and groove on left, and in the related genus Cyprideamorphella the ridge on the left valve and the groove on the right. The overlap is also different in the two genera. Members of the genus Limnocypridea are characterized by left overlapping valves, well-developed pore-canal zone, peculiar hinge structure, and also characteristic trapezoidal outline of the carapace and elevated margin of the dorsal part of the valve, which characterize the new genus. The type-species, L. abscondida Liibimova, 1956, is nonreticulated and has no nodes or ridges; in the same year, Liibimova (1956b) described four additional species, two of which, L. tumulosa and L. bitumulosa, have subventral nodes and are finely reticulated, and two, L. subplcma and L. grammi, are smooth. Several species in North America that belong to Limnocypm'dea conform with the original concept of the genus as defined in the USSR. There are, however, additional species that do not fit within the genus as originally defined. This situ- ation is not unique because, in practice, genera are SYSTEMATIC DESCRIPTIONS 11 usually erected before all the species that belong to the taxon are known. Van Morkhoven (1963, p. 61) considered Limno- cypm'dea as a synonym of Lineocypris Zalanyi, 1929. The two genera differ in type and amount of over- lap on the dorsal margin and in details of the muscle-scar pattern. Key to the species of Limnocypridea 1 Lateral surface with nodes or ridges ________ 2 1a Lateral surface without nodes or ridges ________ 3 2(1) One subventral node on each valve ____________ ____________________ tumulosa Lfibimova, 1956b 2a Two subventral nodes on each valve __________ ____________________ bitumulosa Liibimova, 1956b 3(1a) Dorsal margin straight ________________________ 4 3a Dorsal margin curved ________________________ 8 4(3) Ventral margin concave ______________________ ___________________ absco'ndida Liibimova, 1956a 4a Ventral margin straight ______________________ 5 5(4a) Height of left valve one half or less greatest length ____________ albertensis (Loranger, 1951) 5a Height of left valve more than one half greatest length ______________________________________ 6 6(5a) Greatest height of right valve anterior to mid— length ______________________________________ 7 6a Greatest height of right valve at midlength __ ______________________ grammz’ Liibimova, 1956b 7(6) Anterior margin of right valve broader than posterior margin ____________________________ __________ celtiformis (Harper and Sutton, 1935) 7a Anterior margin of right valve narrower than posterior margin ____ subplana. Liibimova, 1956b 8(3a) Greatest height behind midlength ______________ _____________________ morrisonensis (Roth, 1933) 8a Greatest height in front of midlength __________ ______________ equalis (Harper and Sutton, 1935) The divisions shown in the key are tentative be— cause some of the species described from Mongolia may be conspecific. Cypridopsz's parallela Hanai, 1951, from the Middle and Upper Cretaceous of cen- tral Manchuria may belong in Limnocypridea but is not included in the key because of the uncertainty. L. equalis (Harper and Sutton, 1935) is recog- nized here as a valid species, and the variation in lateral outline of L. morrisonensis (Roth, 1933), is described and illustrated. Limnocypridea morrisonensis (Roth, 1933) Plate 1, figures 11, 18730; plate 3, figures 26729 Bythocypris (Bairdiocypris) morrisonensis Roth, 1933, Jour. Paleontology, v. 7, no. 4, p. 401, pl. 48, figs. 4aec; Harper and Sutton, 1935, Jour. Paleontology, v. 9, p. 627. Bythocyp'ris (Bairdiocypris) mm'm'sonensis var. equalis Harper and Sutton, 1935 (part), Jour. Paleontology, v. 9, no. 8, p. 627, pl. 76, figs. 2223 (not fig. 21:L. cqualis). Diagnosis—Large, as much as 2.7 mm or more in greatest length; smooth; lateral outline of left valve varies from subtriangular to subovate, dorsal mar- gin curved to acuminate; greatest height behind approximate midlength, greatest length below mid- height; hingeline straight, one-half or less greatest length, closer to posterior than anterior end, below overreaching left valve; anterior margin always narrower than posterior, dorsoanterior margin al- ways longer than dorsoposterior, ventral margin straight to gently concave; dorsal margin coincides with hingeline. Discussion—Harper and Sutton (1935, p. 627) described the new variety equalis because “Roth did not mention variations in B. morrisonensis * * *.” They illustrated three specimens, the first of which (pl. 76, fig. 21) is here designated as the lectotype of L. equalis (Harper and Sutton, 1935), and the other two (pl. 76, figs. 22, 23) are syno- nyms of L. morrisonensis. Specimens from Roth’s type-locality (topotypes) (pl. 1, figs. 18, 24) that are undoubtedly conspecific with the holotype (pl. 1, figs. 22, 25—28) are 2.3 mm in greatest length. Other topotype specimens range in greatest length from 2.2 mm (pl. 1, fig. 21) to 2.7 mm (pl. 1, fig. 20). The smallest representative of this species that I found is 1.8 mm long in a group of nested valves (pl. 1, fig. 11). I cannot explain the absence of younger instars because the nesting indicates quiet water that would preclude size sorting by currents. Specimens of T. trapezoidalis (Roth, 1933) as small as 0.85 mm are associated with this species. I consider all the specimens illustrated on plate 1, figures 11, 18—30, to be conspecific. The variation in lateral outlines of the specimens illustrated on figures 18—29 is gradational; the specimen illus- trated on figure 30, and the one on plate 3, figures 26—29, differ from the rest in lateral outline and are considered to be males of the species. This inference is based on the dimorphism found in living Can- dona Baird, 1845 (McGregor and Kesling, 1969a, b) in which the valves of the females as determined by soft parts have a dorsoposterior truncation (pl. 3, fig. 30). This truncation is similar to the speci— mens illustrated on plate 1, figures 18—29. The valves of male Candona have a rounded posterior (pl. 3, fig. 31) similar to those specimens of L. morrisonen- sis illustrated on plate 1, figure 30; plate 3, figures 26—29. The magnification of plate 1, figure 28, is approximately x 30 in order to compare the size of this species with the sizes of the other species illustrated on this plate that are also approximaely x 30. Geographic distribution—South Dakota, Meade 12 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING County; map loc. 4, Roth’s type-locality, pl. 1, figs. 22, 25—28, and map loc. 8, USGS colln. 30997, pl. 1, figs. 11, 1821, 23, 24, 29, 30; pl. 3, figs. 26—29, USNM 242936, associated with Trape‘zoidella tra- pezoidalis (Roth, 1933), and Gym-idea (Pesudo- cypridina) piedmonti (Roth, 1933). Lawrence County; map 10c. 3, Harper and Sut- ton’s type—locality and USGS colln. 30999, USNM 242937, associated with T. trapezoidalis (Roth, 1933). Limnocypridea? albertensis (Loranger, 1951) Plate 2, figures 1—6 Bairdiocypris albertensis Loranger, 1951, Am. Assoc. Petro— leum Geologists Bull., v. 35, no. 11, p. 2360, pl. 2, figs. 7, 8, 16, 17, 21, 28, 36, 37. Blairmore Formation (Aptian- Albian), Alberta, Canada; Loranger, 1954, Western Canada sedimentary basin——A symposium, p. 286, pl. 2, figs. 7, 8, 16, 17, 21, 28, 36, 37; Howe and Laurencich, 1958, Introduction to the study of Cretaceous Ostracoda, p. 78. Diagnosis—Small, less than 0.9 mm in greatest length, smooth, dorsoanterior margin longer than dorsoposterior margin. Discussion.—Loranger included in her description of this species the following: “Surface ornament commonly consists of straight ridge or false keel on left valve parallel to the ventral margin.” She very kindly sent me four out of the five illustrated specimens. The four syntypes that I examined do not have a ventrolateral ridge; consequently, this species is referred here to Limnocypridea? rather than to Trapezoidella. The original of Loranger’s figure 28 (pl. 2, figs. 4—6) is here designated as the lectotype; it and the three paralectotypes are deposited in the Geological Survey of Canada (nos. 48735—48738). I am grate- ful to Dr. F. L. Staplin, Imperial Oil Limited, for permission to deposit these specimens with the Geo- logical Survey of Canada. According to Stelck (1975, p. 438, fig. 10), the Blairmore Formation is late Aptian—early Albian in age. Family CYPRIDEIDAE Martin, 1940 I agree with Hartmann and Puri (1974, p. 57) in elevating the Cyprideinae to family category. My discussion of this subfamily (Sohn, 1969, p. B3) would now be applicable to the family. More than 300 species have been recorded in the genus Cypridea Bosquet, 1852, and its subgenera, making this an unwieldy taxon with which to deal. For practical purposes, it would be easier to deal with this group if it were divided into smaller taxonomic units; the elevation of some of the subgenera to generic category would accomplish this. In a previous study (Sohn, 1969, p. B4), I pro- posed a key to the subgenera of Cypridea in which I differentiated the subgenus Pseudocypridina from the subgenus Cypridea on the basis of the presence of a ventrolateral ridge on the left valve of the former and the absence of such a ridge on the latter. I now know that this was not a valid cri- terion. Although some species that I now refer to Cypridea (Pseudocypridma), do have a ventrolat- eral ridge in common with the type-species, C. (P.) piedmonti Roth, 1933, other species do not have that ridge. The other subgenera in that key are here elevated to generic status. Key to the genera in the Cyprideinae 1 Nonsulcate ____________________________________ 2 1a Sulcate ________________________________________ 6 2(1) Left valve larger ____________________________ 4 2a Right valve larger ____________________________ 3 3(2a) Lateral outline ovoid, rostrum insignificant, alveolus obsolescent, surface without nodes or spines ______________ Paracypm'dea Swain, 1946 3a Lateral outline subtriangular, rostrum and alveolus well developed ______________________ ______________________ Ulwellia Anderson, 1939 4(2) Lateral outline subovoid 4a Lateral outline subrectangular 0r subtriangular, rostrum, alveolus, and cyathus well developed, surface with subcentral spine, with or with- out tubercles ________________________________ 8 Surface with or without nodes or ridges, without tubercles or spines, rostrum reflexed, alveolus obsolescent, cyanthus lunate ________________ ________ Cypridea (Pseudocypm'dina) Roth, 1933 5a Surface with tubercles or spines, without nodes or ridges, rostrum, alveolus, and cyathus usually well developed ______________________ ____________ Cypridea (Cypridea) Bosquet, 1852 6(1a) One sulcus ___________________________________ 7 6a Two sulci ____________ Bisulcocypridea. Sohn, 1969 7(63) With two nodes ________ Morim'a Anderson, 1939 7a With three nodes _ Morininoides Krommelbein, 1962 8(4a) Lateral outline subrectangular, surface with tubercles or small spines ____________________ ______________________ n. gen. (“Cypridea” sp. 1) 8a Lateral outline subtriangular, surface without tubercles or small spines _- Longispinella n. gen. 5(4) Genus CYPRIDEA Bosquet, 1852 Cypridea Bosquet, 1852, Belgium, Acad. Royale Sci., Lettres, Beaux-Artes, Mem. Courronés et Mem. Savantes Etrangérs, v. 24, p. 47; Sylvester-Bradley, 1949, Geologists’ Assoc. Proc., v. 60, pt. 2, p. 130. Cypridea (part) of authors. Type-species (subsequent designation).— Cypris granulosa Sowerby, 1947, p. viii. 1836, by Sylvester-Bradley SYSTEMATIC DESCRIPTIONS 13 Discussion.——Sylvester-Bradley (1949) redefined the genus and designated a neotype for Cypridea granulosa (Sowerby, 1836), the type—species, from the lower part of the middle Purbeckian of Eng- land. On the basis of Sylvester-Bradley’s descrip- tion and illustrations, Cypridea is closer to Pseudo- cypm'dina Roth, 1933, than to a large number of species that have been described as or referred to the genus Cypridea. His assignment of both as sub- genera is accepted in this study. The major differ- ences between the two sub‘genera are: (1) well- developed rostrum, and alveolus in Cypridea. and reflexed rostrum, obsolescent alveolus in Pseudo- cypm’dina; and (2) the presence of relatively large tubercles on the lateral surface of Cypridea and of fewer and smaller tubercles on Pseudocypm‘dina. Most of the species that have been assigned to Cypridea differ from Cypridea as redefined "by Sylvester-Bradley in size, lateral outline, surface ornament, and sculpture, and in the development of the alveolus and the cyathus (fig. 3). In this paper I am illustrating in open nomen- clature as “Cypridea sp. 1” a carapace from the Lakota Formation that shows many of the above differences. The reason for the open nomenclature is that I have found only one good carapace in one collection and five very poorly preserved carapaces in a second collection. Although I had previously stated (Sohn, 1969, p. B2) that dimorphism in Cypridea is unknown, I have since observed dimorphism in width of pos- terior in cypridinid ostracodes (this paper, pl. 5, figs. 9, 12). Hanai (1951, p. 411, figs. 2—7) discussed and illustrated males and females of Cypridea sub- valdensis Hanai, 1951, from the Middle Cretaceous of Manchuria, and Andreev (in Andreev and Man- delstam, 1968, p. 80) illustrated dimorphism in Cypridea gissarensis Andreev, 1968, from the upper Aptian of Tadzhikistan. Anderson (in Anderson, Bazley, and Shephard— Thorn, 1967, p. 202) established the basis for dis- criminating between the genera in the Cyprideinae by naming and illustrating characters in the shell morphology of “Cypridea” (fig. 3). This major con- tribution provides criteria to split the taxon into component genera. Such a revision. however, is be- yond the scope of this paper. Subgenus CYPRIDEA Bosquet, 1852 emend. Sylvester- Bradley, 1949 Type-species.——Same as the genus. Diagnosis—Relatively large cypridinids, to about 2 mm in greatest length, subovoid, with or without FIGURE 3.——Some of the characters in the shell morphology of Cyprideidae used in this paper, modified from Ander- son (in Anderson, Bazley, and Shephard-Thorn, 1967, p. 202). distinct angulation at junction of dorsal and an- terior margins; surface finely punctate, with large tubercles, without reticulations or large spines; rostrum well developed, cyanthus usually lunate; hinge margin incised. Stratigraphic range—Upper J urassic-Upper Cre— taceous. Subgenus PSEUDOCYPRIDINA Roth, 1933 Pseudocypridina Roth, 1933, Jour. Paleontology, v. 7, no. 4, p. 404; Howe and Laurencich, 1958, Introduction to the study of Cretaceous Ostracoda, p. 480. Langtom'a Anderson, 1939, Annals Mag. Nat. History, ser. 11, v. 3, no. 15, p. 304. Cypridea (Pseudocypridina) Roth. Sylvester—Bradley, 1949, Geologists’ Assoc. Proc., v. 60, pt. 2, p. 146; Swain in Moore, 1961, Treatise on invertebrate paleontology, Part Q, Arthropoda 3, Crustacea, Ostracoda, p. Q242; Kneuper-Haack, 1966, Beih. Geol. Jahrb., v. 44, p. 187. Type—species (monotypy). —— Pseudocypridina piedmonti Roth, 1933, Lakota Formation (Lower Cretaceous), South Dakota. Diagnosis—Relatively large cypridinids, to about 2 mm in greatest length, subovoid, without distinct angulation at junction of dorsal and anterior mar- gins on larger left valve; surface finely punctate, , with or without scattered tubercles, smaller than combined diameters of two punctae, usually near end margins, never with large spines or tubercles; with or without nodes or lateral ridges; rostrum poorly developed, alveolus obsolescent, cyanthus 14 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING lunate or indistinct; hinge margin incised. Stratigraphic range—Upper Jurassic—Upper Cre- taceous. Discussion—The holotype of P. piedmonti Roth, 1933, is probably a male; it is here reillustrated (pl. 6, figs. 23—27). Many of the species assigned to Cypridea Bosquet, 1852, should be referred to the subgenus C. (Pseudocypridina). The following species have been described in, referred to, or are here referred to Pseudocypridina: Cypridea acutituberculata Galeeva, 1955, Barremian (Lower Cretaceous), Asia. Cypridea (Pseudocypridina) alacarama‘e Kneuper-Haack, 1966, upper Purbeckian (Upper Jurassic), Europe. Cypridea alta. alta Wolburg, 1959, upper Purbeckian and Valanginian (Upper Jurassic~Lower Cretaceous), Europe. C. alta formosa Wolburg, 1959, middle and upper Wealden 3 (Upper Jurassic—Lower Cretaceous), Europe. C. altissz'ma Martin, 1940, Wealden (Lower Cretaceous), Europe. C. altissima rotunda Wolburg, 1959, lower to middle Wealden 2 (Upper Jurassic), Europe. C. amisia Wolburg, 1959, Wealden 2 (Upper Jurassic), Europe. C. baida’rensis Bischofi', 1963, probably Hauterivian- Barre- mian (Lower Cretaceous), Asia Minor. C. binodosa Martin, 1940, Purbeckian (Upper Jurassic), Europe. C. brevirostrata Martin, 1940, Wealden (Lower Cretaceous), Europe. C. consulta. Mandelstam in Liibimova, Kaz’mina, and Reshetnikova, 1960, Barremian (Lower Cretaceous), Asia. C. (Pseudocypridina) demandae Kneuper-Haack, 1966, up- per Purbeckian (Upper Jurassic), Europe. C. dolabrata angulata (Martin). Wolburg, 1959, Wealden 3 (Upper Jurassic), Europe. C. dolabrata dolabrata (Anderson). Wolburg, 1959, Wealden 3 (Upper Jurassic), Europe. ?C. (Pseudocypridina) ellipseloides Hou, 1958, Lower Cre- taceous, China. ?C. (P.) extender Hou, 1958, Lower Cretaceous, China. C. fasciata Anderson, 1967, Wealden (Lower Cretaceous), Europe. C. fasciculata (Forbes in Lyell). Wolburg, 1959, Wealden 1 & 2 (Upper Jurassic), Europe. C. inaequalis Wolburg, 1959, Wealden 2 & 3 (Upper Juras- sic), Europe. C. laevis Galeeva, 1955, Barremian (Lower Cretaceous), Asia. C. laevigata fairlightensis Anderson, 1967, Wealden (Lower Cretaceous), Europe. C. laevigata hawkhurstensis Anderson, 1967, Wealden (Lower Cretaceous), Europe. C. laevigata leonardi Anderson, 1967, Wealden (Lower Cretaceous), Europe. C. laevigata philpottsi Anderson, Cretaceous), Europe. C. laevigata subquadrata Anderson, 1967, Wealden (Lower Cretaceous), Europe. C. laevigata wadhurstensis Anderson, 1967, Wealden (Lower Cretaceous), Europe. 1967, Wealden (Lower C. lata Martin, 1940, Purbeckian-Wealden (Upper Jurassic— Lower Cretaceous), Europe. C. (Cyamocypris) latiovata Hou, 1958, Lower Cretaceous, China. C. (C.) sp. A Hou, 1958, Lower Cretaceous, China. C. (C.) sp. B Hou, 1958, Lower Cretaceous, China. C. (Pseudocypridina) magna. Hou, 1958, Cretaceous, China. C. (P.) moneta Kneuper-Haack, 1966, upper Purbeckian (Upper Jurassic), Europe. C. (P.) moneta logronana. Kneuper-Haack, 1966, Purbeckian (Upper Jurassic) Europe. C. nannorostrata Krommelbein, 1962, Lower Cretaceous, South America. ?C. obesa Peck, 1951, Cloverly Formation taceous), Wyoming, U.S.A. C. (Cyamocypris) ovatiformis Hou, 1958, Lower Cretaceous, China. C. parallela. Martin, 1940, Wealden (Lower Cretaceous), Europe. C. (Pseudocypm'dfina) parallela Hou, 1940) Lower Cretaceous, China. C. posticalis Jones, 1885, Purbeckian (Upper Jurassic), Europe. C. prognata Liibimova, 1956, Barremian(?) taceous), Asia. C. profusa Liibimova, 1956, Upper Cretaceous, Asia. ?C. quadrata Peck, 1951, Cloverly Formation (Lower Cre- taceous), Utah and Wyoming, U.S.A. C. rotundata Anderson, 1967, Wealden (Lower Cretaceous), Europe. C. salvadorensis nodifer Krfimmelbein, (Lower Cretaceous), South America. C. salvadorensis salvadorensz's Krémmelbein, 1962, Wealden (Lower Cretaceous), South America. Pseudocypridina sambaensis Grekofl’, 1957, Wealden (Lower Cretaceous), Africa. Cypridea, (Pseudocypridina) setina (Anderson, 1939), upper Purbeckian (Upper Jurassic), Europe. C. (P.) setina, acerata Anderson, 1962, Wealden 5 (Lower Cretaceous), Europe. C. (P.) setina, camelodes Anderson, 1962, lower and middle Wealden 4 (Upper Jurassic), Europe. C. (P.) setina dotica Anderson, 1962 Wealden 3 (Upper Jurassic), Europe. C. (P.) setina erumna Anderson, 1962, Wealden 3, (Upper Jurassic), Europe. C. (P.) setina fiteriensis Kneuper-Haack, 1966, middle Pur- beckian (Upper Jurassic), Europe. C. (P.) setina rectidorsata Sylvester-Bradley, 1949, upper Purbeckian (Upper Jurassic), Europe. C. sowerbyi Martin, 1940, Purbeckian (Upper Jurassic), Europe. ?C. spinigera Liibimova, 1956 (:C. lubimovae Sohn, 1969), Barremian (Lower Cretaceous), Asia. C. (Pseudocypridina) subcentrinoda Hou, 1958, Cretaceous, China. C. subtilis Krémmelbein, 1965, Wealden (Lower Cretaceous), South America. C. subvaldensis Hanai, 1951, Cretaceous, Manchuria. C. tenuis Anderson, 1967, Wealden (Lower Cretaceous), Europe. C. trite Liibimova, ceous), Asia. upper (Lower Cre- 1959 (not Martin, (Lower Cre- 1962, Wealden 1956, pre-Barremian (Lower Creta- SYSTEMATIC DESCRIPTIONS 15 C. unicostata Galeeva, 1955, Barremian (Lower Creta- ceous), Asia. C. (Cypridca) mzinorla Hou, 1958, Lower Cretaceous, China. C. valdensis (Sowerby, 1836). Anderson, 1967, Wealden (Lower Cretaceous), Europe. C. 'vidrana Wolburg, 1959, Wealden 2 (Upper Jurassic), Europe. C. vitimcnsis Mandelstam in Liibimova, 1956, Barremian and older (Lower Cretaceous), Asia. C. (Cypridea) yumenensis Hou, 1958, Lower Cretaceous, China. C. (Pseudocypridina) spp. Hou, 1958, Lower Cretaceous, China. . Some of these species may be synonyms of each other, but without comparative specimens, it would be imprudent to classify them as such. Cypridea (Pseudocypridina) piedmonti Roth, 1933 Plate 6, figures 1—47 Pseudocypridina piedmomi Roth, 1933, Jour. Paleontology, v. 7, no. 4, p. 404, pl. 48, figs. 7a—h; Peck, 1951, Jour. Paleontology, v. 25, no. 3, p. 319, pl. 48, figs. 16—18; Sohn, 1958, Wyoming Geol. Assoc., Guidebook, Thirteenth Ann. Field Conf., p. 123, pl. 1, figs. 578. Cypridea picdmonti (Roth). Harper and Sutton, 1935, Jour. Paleontology v. 9, no. 8, p. 625, pl. 76, figs. 12—15. not Cypridca (Psaudocypridina) pz'cdmrmfi Roth. Swain, 1946, Jour. Paleontology, v. 20, no. 6, p. 550, pl. 83, figs. 10~12=Cypridea? salwfldormisis salvadorcnsis Krtim- melbein, 1962. not Cypridca (Pscudocypridina) picdmonti (Roth). Wicher, 1959, Geol. Jahr., v. 77, p. 47, pl. 9, fig. 6 (juvenile? of indet. sp.). Diagnosis—A species of Pseudocypridina with a ventrolateral ridge on left valve, with few, small (less than twice the diameter of punctae), subdued, scattered tubercles, near end margins. Discussion—This species is similar to C. (P.) unicostata (Galeeva, 1955), described from the Barremian of Mongolia, from which it differs in having a higher posterior margin, and a less de- fined rostrum. The holotype of P. picdmonti has a narrower posterior in dorsal outline than Galeeva’s species. Although I do not consider the two species to be conspecific. this feature is interpreted to represent a male carapace and Galeeva’s speci- men, a female carapace. A ventrolateral ridge on the overlapping valve is present in several other species in the subgenus Pseudocypridina as well as in some species belonging to other taxa in the Cypridininae. All the ventrolateral ridged species in Pseudocypridina differ from C. (P.) piedmonti and C. (P.) unicostata in lateral outline and lack the scattered small tubercles. Three species from the Barremian of Mongolia and Siberia have small tubercles but lack the ventrolateral ridge: C. (P.) acutituberculata (Galeeva, 1955), C. (P.) consulta (Mandelstam) in Liibimova, Kaz’mina, and Reshet- nikova, 1960, and C. (P.) vitimensis (Mandelstam) in Liibimova, 1956b. Stratigraphic age—Roth (1933) assumed that the ostracode assemblage that includes P. pied- monti was from rocks in the Morrison Formation. However, as previously indicated, the faunule is from Lower Cretaceous rocks and belongs in the Chilson Member of the Lakota Formation, prob- ably Unit 2. Geographic distribution—South Dakota, Mead County; map loo. 8, Roth’s type-locality, pl. 6, figs. 23—27, and USGS colln. 30997, pl. 6, figs. 5—7, 10—13, USNM 242938, associated with Trapezoidella trap- ezoidalis (Roth, 1933), and Limnocypridea mor— m'sonensis (Roth, 1933); USGS colln. 31171, pl. 6, figs. 1—4, 8, 9, USNM 242939; 31172, USNM 242940. Lawrence County; map loc. 3, Harper and Sut- ton’s type-locality and USGS colln. 30998, USNM 242957, associated with T. trapezoidalis (Roth, 1933). Fall River County; map loc. 13, USGS colln. 30986, USNM 242041, associated with T. trape- zoidalis (Roth. 1933); map 10c. 11, USGS colln. 30994, USNM 242958. associated with T. rothi n. sp. ; map loc. 17, USGS colln. 26098, pl. 6, figs. 28—37, 41—47, USNM 242942, associated with Cypridea (Pseudocypridina) inornata (Peck, 1941), “Cyp- ridea.” sp. 1, and Longispinella asymmetrica n. sp. Cypridea (Pseudocypridina) inornata (Peck, 1941) Plate 3, figures 18723; plate 7, figures 24 Cypridea inornata Peck, 1941, Jour. Paleontology, v. 15, no. 3, p. 301, pl. 44, figs. 33—36. Kootenai Formation, Montana. Pseudocypridina inornata (Peck). Peck, 1951, Jour. Paleon- tology, v. 25, no. 3, p. 319, pl. 48, figs. 8711. Minnewaste Limestone Member of the Lakota Formation, Fall River County, S. Dak., and Kootenai Formation, Montana. Cypridea inornata? Peck. Sohn, 1958, Wyoming Geol. Assoc. Guidebook, 13th Ann. Field Conf., pl. 1, figs. 17, 18. Lakota Formation, Crook County, Wyo. Diagnosis—Differs from C. (P.) piedmonti Roth, 1933, in lacking a ventrolateral ridge on the larger valve. Discussion—Peck (1951, pl. 48, fig. 9) illustrated a carapace from the Lakota Formation of South Dakota that differs from the carapace that I am illustrating (pl. 3, fig. 22) in that the anterodorsal curvature on Peck’s specimen meets the dorsal mar- gin at a point farther back from the anterior mar- gin than in my specimen, but the holotype, from the Kootenai Formation of Montana, illustrated by Peck (1941, pl. 44, fig. 33), more closely resembles the same View of my specimen (pl. 3, fig. 23). 16 Geographic distribution—South Dakota, Fall River County; map 10c. 13. USGS colln. 30985, USNM 242968, associated with T. rothi n. sp.; USGS colln. 31005, USNM 242988, associated with T. rothi n. sp.; map 10c. 14, USGS colln. 31237, USNM 242964, associated with T. rothri n. sp. and Cypridea (Pseudocypridina) hem‘ybcllz’ n. sp.; USGS colln. 31238, USNM 242965. associated with T. rothri n. sp.; map 10c. 15, USGS colln. 30996, USNM 242982; map 10c. 16, USGS colln. 26100. USNM 242963, as- sociated with T. rotki n. sp.; map loc. 17, USGS colln. 26098, USNM 242962, associated with C. (P.) piedmonti (Roth, 1933), “Cg/prided” sp. 1, and Longispinella assymetrica n. sp.; USGS colln. 25460. USNM 242976, associated with C. (P.) henrybelli n. sp., “Cypridea” sp. 1, and L. assymctrica n. sp.; map loc. 18, USGS colln. 31239, USNM 242983. as- sociated with L. longispina (Roth, 1941). Lawrence County; map 100. 2, USGS colln. 25646. USNM 242986. Wyoming, Crook County; map 100. 5, USGS colln. 25645. pl. 3, figs. 1823, pl. 7, figs. 244. USNM 242961, associated with C. (P.) laclz’ n. sp.; USGS colln. 25644, USNM 242968, associated with L. longispina (Peck, 1941). Cypridea (Pseudocypridina) laeli Sohn, n. sp. Plate 3, figures 1—13, 24, 25, 32; plate 7, figure 1; plate 8, figures 26—30 Name—In honor of Master Lael Schooler. Wash- ington. DC. a budding young scientist. Holotype—USNM 129644 Paratypes.—USNM 2428654242871, 242908 Type-locality.—-Map loc. 5. USGS colln. 25645. NEl/L sec. 20, and NWl/l. sec. 21, T. 51 N.. R. 65 W., Crook County, Wyo. Other localities—See geographic distribution. Type level.— Lakota Formation, shale near top. Diagnosis—Subovate. with arched dorsal margin. ventrolateral ridge and dorsoanterior node on larger left valve; right valve with curved irregular ridge subparallel and slightly removed from dorsal mar- NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING cal node at the dorsoanterior. In ventral View. this ridge has an abrupt posterior termination (pl. 3, fig. 13). In most specimens, the surface of the valve is smooth along the dorsal margin; in some. a crude delineation of a thin ridge borders the dorsal edge of the valve (pl. 3, figs. 2. 11). The right valve has an irregular ridge subparallel and slightly removed from the hinge contact. In some specimens. this ridge is variable and starts as a subelliptical node approximately opposite the node on the left valve and becomes stronger as it extends backward to just before the approximate junction of the posterior and dorsal margins. In other specimens. it has a series of constrictions along its backward route. The hingeline is slightly incised; a straight double ridge on the right valve fits into a groove and ridge on ' the left valve (pl. 3. fig. 32). The surface is finely punctate. The left valve overlaps on all margins. . The overlap along the venter is straight along the posterior two-thirds of the length; at that point it has a distinct bend towards the rostrum. Dorsal and ventral outlines are subelliptical: the greatest width is at or slightly behind the midlength. The end outlines are subelliptical. truncated along the venter by the ridge on the left valve. and along the dorsum by the ridge and incised hinge; the greatest width is at the approximate midheight. D2'scussi0n.~—C. (P.) laeli resembles in lateral outline and surface ornament the Cypridea fasci- culata-group of Wolburg (1959. p. 243) from the middle and upper Purbeckian, and also the Cypridea 1 alta-group of Wolburg (1959, p. 262) from the . upper Purbeckian-Berriasian, both from Germany. gin. Surface finely punctate, with scattered minute . _ ] ridge closer to the rostrum and in tapering back- spinelets more common on anterior and posterior quarters than on center. Description—The carapace is subovate. with an arched dorsal margin. gently convex ventral margin. broadly rounded end margins, and a distinct rostral incisure on both valves. The left valve has a distinct ridge near the ventral margin that starts behind the rostrum and expands posteriorly along the valve surface for about three—fourths of the greatest length, and a distinct but low moundlike subellipti- The node on the left valve and dorsal ridge on the right valve could have evolved from similar struc- tures on C. (P.) alta formosa (Wolburg. 1959) of Purbeckian age (Wolburg. 1959, p. 264. pl. 3. figs. 2a—c. 11. 12). The ventrolateral ridge on the left valve is present on a specimen illustrated by Wol- burg (1959. pl. 2, fig. 5) as a tuberculate variety of C. (P.) (Zolabrata angulafa (Martin. 1940) from the lower or middle Wealden 3 (Purbeckian). This specimen differs from C. (P.) Iaeli in having the wards. An almost identical dorsal ridge on the right valve is present on C. (P.) fasciculata, (Forbes in Lyell. 1855). illustrated by Wolburg (1959. pl. 1. fig. 3) from the middle Purbeckian; this species has nodes that are much larger than the spinelets on C. (P.) laeli scattered on the anterior and posterior surfaces of the punctate valves. Wolburg (1962, pl. 29) illustrated a gradational series beginning with the tuberculate C. (P.) fasci- SYSTEMATIC DESCRIPTIONS 17 culata. in the Jurassic Wealden 1, through less tuberculated individuals of the same species in Wealden 2, to a nontuberculated species in Wealden 2, which he identified as Cypridea altissima Martin. He illustrated two specimens (pl. 29, figs. 7, 8) that are not conspecific with C. (P.) altissima (Martin, 1940, pl. 4, figs. 45, 47) recorded by Martin from the Lower Cretaceous (Martin, 1940, pl. 13). The reduction in number and ultimate loss of nodes through time in this species group and the affinities of C. (P.) laeli enumerated above suggest that C. (P.) laeli may be younger than the lower Valan- ginian. Geographic distribution—Wyoming, Crook Coun- ty; map loc. 5, USGS colln. 31001, pl. 3, figs. 1—9, 24, 25, 32; pl. 7, fig. 1; pl. 8, figs. 26—30, USNM 242966; USGS colln. 25645, p]. 3, figs. 10—13, USNM 242967. Cypridea (Pseudocypridina) henrybelli Sohn, n. sp. Plate 3, figures 14717; plate 8, figures 1—25 Name—In honor of Henry Bell 111, US. Geo- logical Survey, who introduced me to the ostracodes from the Black Hills. Holotype.—USNM 129645. Paratypes.—USNM 242901—242907. Type-locality.—Map loc. 17, Buck Canyon, SE14 sec. 15, T. 8 S., R. 4 E., Flint Hill quadrangle, Fall River County, S. Dak. USGS colln. 25460. Other localities—See geographic distribution. Type-level.—Chilson Member of Lakota Forma- tion, Unit 2, about 5 feet (1.5 m) above the base. Diagnosis—Straight backed. with anterodorsal angulation, finely punctate; commonly with distinct nodes at midheight on anterior and posterior quar- ters of each valve; sometimes one or both nodes may be smaller, more subdued, or entirely missing on the right valve. Description—The carapace is elongate-ovate, with a straight dorsal margin that is one-half or slightly less than one-half the greatest length, a gently convex ventral margin, 21 distinct beak, a rounded anterior margin that is higher than the rounded posterior margin and that meets the dor- sal margin at a distinct angulation at about one- third the greatest length. The hinge is incised. The dorsal outline is elliptical with the greatest width at approximately midlength; the lateral nodes, when present, cause the dorsal outline to have a hexagonal appearance, with convex lateral sides. The left valve overlaps on all margins except the hingeline. The lateral surface is finely punctate. The lateral nodes vary in size, shape, and height among specimens (compare pl. 8, figs. 1, 4, 7, 10, 12, 21); the right valve of some specimens does not have any nodes. Discussion—On the basis of the lateral outline and rostrum C. (P.) henrybelli belongs in the parallela-line of the Cypridea valdensis-parallela- group of Wolburg (1959, p. 267). The Cym‘idea parallela-line was recorded by Wolburg (1959, p. 227, fig. 2) as ranging stratigraphically from Weal- den 4 to Wealden 6 (Berriasian~lower Valanginian). The lateral nodes relate C. (P.) hehrybelli to C. (P.) binodosa (Martin, 1940) from the middle Purbeckian of Germany, and to C. (P.) salvadoren- sis nodifer (Krommelbein, 1962) from the upper part of the Candeias and the lower part of the Ilhas Formations of Brazil. The species differs from C. (P.) binodosa in lacking a ventrolateral ridge on the left valve (Martin, 1940, pl. 3, fig. 42), and from C. (P.) salvadorensis nodifer in that the nodes are closer to the end margins and in having a more dis- tinct rostrum. C. (P.) subtilis (Krommelbein, 1965) from the middle to upper part of the Can- deias Formation of Brazil also has two lateral nodes and a well-developed rostrum, but the nodes on C. (P.) henrybelli are closer to the end margins as well as to the ventral margin. Krommelbein (1966, p. 115) considered the Candeias and Ilhas Formations to be at least partly younger than the Lower Cretaceous Wealden Beds of Europe. It may be significant that C. (P.) salvadorensis nodifei' (Krommelbein, 1962) is associated with C. (P.) salvadorensis salvadorensis (Krdmmelbein, 1962), from which it differs only in having lateral nodes, and that the typeseries of C. (P.) henrybelli contains specimens without nodes on the right valve. C. (P.) baidarensis (Bischoff, 1963), from the Lower Cretaceous (probably pre-Hauterivian to Hauterivian-Barremian) of southern Lebanon, was described and illustrated as having a single node near the posterior of the left valve. These morpho- logically related species suggest an age younger than lower Valanginian for the new species. Geographic distribution—South Dakota, Fall River County; map 10c. 13, USGS colln. 31003, USNM 242971, associated with Trapezoidella i'othi n. sp.; map 100. 14, USGS colln. 31129, USNM 242985; USGS colln. 31130, pl. 8, figs. 1-25, USNM 242970, associated with Longispinella asymmetrica n. sp.; USGS colln. 31237, USNM 242973, asso- ciated with T. i'othi n. sp. and Cym'idea (Pseudo- cym'idina) inm‘nata (Peck, 1941); map 10c. 17, USGS colln. 25460, pl. 3, figs. 14—17, USNM 242975, associated with C. (P.) inornata (Peck, 1941), “Cg/prided” sp. 1, and L. asymmetrica n. sp.; USGS colln. 31007 (? identification), USNM 242972, asso- 18 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING ciated with T. trapezoidalts (Roth, 1933) and T. rothi n. sp. New genus undescribed “Cypridea” sp. 1 Plate 7, figures 8—12 Discussion—A single well-preserved carapace (USNM 242900) about 0.9 mm in greatest length was found in a collection from the Lakota Forma- tion, Fall River County, S. Dak. (USGS colln. 26098, map loc. 17). This specimen is reticulated, has a large subcentral spine, numerous surface tubercles, and resembles Cypridea (C.) propunctata Sylvester-Bradley, 1949, in lateral outline and in the development of the rostrum, alveolus, and cy- athus. Although five additional, poorly preserved carapaces were found in the same area (USGS colln. 25460 (USNM 242978)), the available ma- terial is inadequate to describe the taxon. This taxon differs markedly from Cypridea Bosquet, 1852, as represented by Gym-idea granulosa (Sowerby, 1836), and also from Pseudocypridina Roth, 1933, as illustrated in this paper. Species described in Gym-idea that are similar to “Cg/prided” sp. 1 should be segregated in a separate genus. The speci- mens described and illustrated by Swain and Brown (1972, p. 14, pl. 1, figs. 19, 20; pl. 3, fig. 1) as Cypm’dea (C.) wyomingensis Jones, 1893, from the Lower Cretaceous of the Atlantic Coastal region are referable to this genus, probably as a new species. Genus Longispinella Sohn, n. gen. Type-species—Longtspinella asymmetrica Sohn n. sp. Name—For the long lateral spine on each valve. Diagnosis—Relatively small, to 1 mm in greatest length, subtriangular in lateral outline; surface punctate, with one subcentral large spine, without nodes, small spines or ridges; rostrum and alveolus well developed, cyathus usually subtriangular. Di- morphic in width of posterior. Discussion—This genus is established for those species previously referred to Cypridea Bosquet, 1852, that have a robust lateral spine on each valve and that do not have accessory smaller spines. The following additional species are here assigned to Longispinella: C. armata Krtimmelbein, 1962, Lower Cretaceous, Brazil. C. longispina Peck, 1941, Kootenai Formation, Lower Cre- taceous, Montana. C. tucanoensis Krommelbein, 1965, Lower Cretaceous, Brazil. Stratigraphic range—Lower Cretaceous. Longispinella asymmetrica. Sohn, n. sp. Plate 4, figures 7—20; plate 5, figures 1—7, 13-16 Name.——Asymmetrical ornament on left valve. Holotype.——USNM 242882 Paratypes.——USNM 242877—242881, 242883 Type-locality.—Map locality 14, Upper Chilson Canyon, T. 8 S., R. 3 E., Flint Hill quadrangle, Fall River County, S. Dak. USGS colln. 31130. Other localities—See geographic distribution. Type-level.—Sandy layer above paper shale in Chilson Member of Lakota Formation, about 5 feet (1.5 m) above base of member. Diagnosis.—Subtriangu1ar, with well-developed rostrum, alveolus, and triangular cyathus; with robust lateral spine in approximate center of pos- terior third of each valve; short perpendicular shal- low sulcus bounded anteriorly by a rounded ridge at approximate midheight, just behind the upper part of the alveolus on left valve. Description—The carapace is small, less than 0.9 mm in greatest length. The lateral outline is subtriangular; the anterior and dorsoanterior mar- gins form a continuous curve from the tip of the rostrum to the approximate mid-length. The hinge line is straight, incised; it slopes downward to a point about halfway between the curve of the pos- terior margin and the lateral spine. The posterior margin is gently curved; it extends as the outside of the triangular downward-pointing cyathus. The ventral margin of the right valve is straight; the ventral margin of the left, overlapping, valve is gently curved to straight. The dorsal outline is sub- elliptical, with the posterior end wider than the anterior end, but the greatest width is subcentral. The rostrum is well defined; it points straight down to below the ventral margin, and it is separated from the valve surface by a subdeltoid-shaped al- veolus. The alveolus extends upwards about half- way to the curve of the anterior margin; it has a horizontal ridge at its base. This rounded ridge con- nects the rostrum to the valve surface. A single robust lateral spine is about one third of the greatest length from the posterior margin, and about halfway between the ventral and dorsal margins. The valves are punctate, except the areas of the rostrum and alveolus. The left valve has a smooth, shallow, vertical, short sulcus, whose bot- tom is at approximately the same distance above the ventral margin as the spine. This sulcus is sepa- rated from the alveolus by a rounded smooth ridge. The right valve does not have this sulcus and ridge, but the area in that position is smooth. The left SYSTEMATIC DESCRIPTIONS 19 valve overlaps the right along all the margins ex- cept the incised hinge margin. Discussion—This species belongs in a group of species previously assigned to Cypridea that have in common a robust lateral spine and a subtriangular lateral outline. It differs from L. longispina (Peck, 1941) by having the peculiar sulcus bounded by a ridge on the left valve. Peck (1951, pl. 48, fig. 12) illustrated a specimen from the lower 15 feet of the Lakota Formation, Fall River County, S. Dak. as C. longispina. The illustration of this specimen suggests that it does not belong in L. longispina, but because the right side of the carapace is illus- trated, it cannot be referred to L. asymmetrica. Peck (1941, p. 301) related C. longispina with C. brevicomis Peck, 1941, from the Draney Formation (upper Aptian) of Idaho and Wyoming and to C. spinigem (Sowerby, 1836) from the Wealden (Low~ er Cretaceous) of England. The latter two species are not subtriangular in lateral outline; conse- quently, they are not included in Longispinella. Geographic distribution—South Dakota, Fall River County; map 10c. 12, USGS colln. 31153, USNM 242979, associated with L. l0ng1spz'na (Peck, 1941); map 10c. 14, USGS colln. 31130, pl. 5, figs. 1—7, 13—16, associated with L. longispina (Peck, 1941); map loc. 17, USGS colln. 26098, pl. 4, figs. 7—20, USNM 242974, associated with Cypridea (Pseudocypm'dina) piedmonti (Roth, 1933), C. (P.) inmmta (Peck, 1941), and “Cypridea” sp. 1; USGS colln. 25460, USNM 242977, associated with C. (P.) inornata (Peck, 1941), C. (P.) henm/be'llz' n. sp., and “Cypridea” sp. 1. Longispinella longispina (Peck, 1941) Plate 4, figures 1—6; plate 5, figures 8712, 17—23; plate 7, figures 57 Gym-idea. longispina Peck, 1941, Jour. Paleontology, v. 15, p. 300, pl. 43, figs. 679. Kootenai Formation, Montana; Peck, 1951, Jour. Paleontology, v. 25, p. 312, pl. 48, figs. 12—15. Lakota Formation, Fall River County, S. Dak., Cloverly Formation, Fremont County, Wyo. Cypridca longispina? Peck. Sohn, 1958, Wyoming Geol. As- soc. Guidebook, 13th Ann. Field Conf., pl. 1, figs. 14. Lakota Formation, Crook County, Wyo. Diagnosis—Differs from L. asymmetm'ca in smaller and narrower size. in more pointed end in dorsal outline, and in either having a smaller per- pendicular shallow sulcus bounded anteriorly by a rounded ridge behind the alveolus of the left valve, or not having that structure. Discussion—Peck (1941) illustrated the left view of the holotype, and two right views and the ventral View of three paratypes. The same view of the holotype was republished by Peck (1951, pl. 48, fig. 15), as well as a right view of a carapace from the Lakota Formation and the right and ventral views of a carapace from the Cloverly Formation. I obtained from Dr. Peck three specimens from the type-locality in Montana and am illustrating two presumed males mainly to show the dorsal and ven- tral outlines and the poor state of preservation (pl. 4, figs. 1—6). One of these specimens (pl. 4, fig. 4) has a faint suggestion of the ridge and sulcus on the left valve, although Peck’s drawing of the holo- type does not show that feature. The specimens illustrated here from Crook County, Wyo. (pl. 7, figs. 5, 7), and from Peck’s locality in Fall River County, S. Dak. (pl. 5, figs. 20, 21), have that struc- ture, which is smaller than that on L. asymmetrica. Other specimens, however, do not have that struc- ture (pl. 5, figs. 11, 18). Dimorphism in width of posterior in dorsal and ventral outlines is inferred in this species because the specimen illustrated by Peck in 1941 (pl. 43, fig. 9) is narrower in ventral outline than is the carapace illustrated by him' 1n 1951 (pl. 48, fig. 14) , likewise, the carapaces illustrated here in pl. 4, figs. 3, 5; pl. 5, figs. 9, 19; pl. 7, fig. 6 are narrower in dorsal and ventral outlines than are the specimens illustrated herein on pl. 5, figs. 12, 22. Presumably the ones with the wider posteriors represent fe- males, and those with narrower posteriors represent males. It is noteworthy that the left valve of the holo- type from the Kootenai Formation, Montana, has a knoblike structure near the posterior end of the left valve and that a somewhat similar structure, not quite as well defined, can be seen on the left valve of the specimen from the Lakota Formation, Wyoming, illustrated he1e (pl. 5, figs. 18 and 20). This structure is absent on all the other specimens illustrated; consequently, it is probably of no diag- nostic significance, but it lends a certain amount of credence to my identification of this species. I have no data to confirm that the stratigraphic age of the Kootenai Formation in Montana and the Cloverly Formation in Wyoming, both of which have been assigned to the Aptian, are older than Aptian, although I now consider the Lakota For- mation to be pre Aptian in age. Geographic dist1 ibut1o11.—Montana, County; Peck’ s (1941, p. 288) loc. 23. South Dakota, Fall Rive1 County; map loc.12, USGS colln. 31154, pl. 5, figs. 8— 12 ,USNM 242980; USGS colln. 31153, pl. 5, figs. 17, 23, USNM 242981, associated with L.asym1nct11'ca n. sp.; map 10c. 18, Cascade 20 USGS colln. 31239, USNM 242984, associated with Cypridea (Pseudocypridea) inornata (Peck, 1941). Wyoming, Crook County; map 10c. 5, USGS colln. 25644, p]. 7, figs. 5—7, associated with C. (P.) inor- nata (Peck, 1941). 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Page A abscondida, Limnacrypridca -___ __- 10, 11 acerata, Cypridca (Pseudocyprzdma) sctina ____________________ 14 acutituberculata, Cypridca _____________ 14 Cypridcu. (Pscudncypridina) _______ 15 Age of the rocks ____________________ 2 alacaramac Cypridca (Paeudocrypri- dina) ____________________ 14 albertcnsis, Bairdiocyp'ris _____________ 12 Limnocypridca _______________ 11, 12; pl. 2 alta, Cypridca __________ 16 Cypridca alta _______ _ 14 Cypridea (Pseudocypndma) _______ 17 alta, Cypridca. ____________ 14 formosa. Cypridca. ________________ 14 altissima, Cypridca ___________________ 14, 17 Cypridca (Pscuclocyprz'dina) ______ 17 rotunda, Cypridca ________________ 14 amisia, Cypridca ______________________ 14 angulata, Cypridca dolabrata __________ 14 Cypridca (Pseudocypridina) dola- brata _____________________ 16 armata, Cum—idea, _____ . ________ 18 asymmetrica, Longispinclla _____ 15, 16, 17, 18; pls. 4, 5 B baidarensis, Cypridea ___ 14 Cypridca (Pseudocypruizna) 17 Bairdiocypris albcrtensis ______________ 12 (Buirdz'ocypris) morrisancnsis, Byfho- cypris ____________________ 11 morrisoncnsis cqualz’s, Bythocypris 11 trapezoidalz's, Bythocyp‘ris _________ 8, 9 Bythocypris ______________________ 10 binadosa, Cypridm ____________________ 14 Cypridca (Psaudocypridina) _______ 17 Bisulcocz/pridcu. _______________________ 12 bitumulosa, Limnocym‘idca ____________ 10,11 brcvicornis, Cum—idea _________________ 19 brevirostrata, Cypridea _____ 14 Bythocyp'rz's (Bairdiocypris) 10 (Buirtliocypris) morrisoncnsis 11 morrisoncnais cqualz's __________ 11 trapezoidalis __________________ 8, 9 C camclodcs, Cypridca (Pseudocyridina) sctina _ Candona _______________ rcdunca ___________ sp. cultifor'mis, Limnocyp'ridca _____________ 11 comitans. Saluadorizrlla rcdunca ________ 9 consulta, Cypridca ____________________ 14 Cypridca (Pacudocypridina) ______ 15 (Cyamocypris) latiovatn, Cypridca _.__ 14 ovatiformis, Cypridca _____________ 14 Cypridacea ___________________________ 8 Cypridca. ________________________ 8,13, 18,19 acutitubcrrulata 14 (1,211 16 INDEX [Italic page numbers indicate major references] Page alta __________________________ 14 formosa ______________________ 14 altisaima _________________________ 14, 17 rotunda. ______________________ 14 amisia ___________________________ 14 armata ___________________________ 18 baidarcnsis 14 binodosa ____ 14 brovicornis . __ 19 brevirostratu __________ 14 consulta ______________ 14 dolabrata angulala ________________ 14 dolabrata ____________________ 14 fasciata __________________________ 14 fasciculata _______________________ 14 16 gissarcnsis ________________________ 13 granulosa ________________________ 18 inacqualis ________________________ 14 inornuta _________________________ 15 lacvigatn. fairlightcnsis ___________ 14 haw/churstcnsis _______________ 14 lcvnardi _- _________ 14 philpottsi ___ 14 subquadrata 14 warlhursfcnsis ________________ 14 Icavia 14 [um 14 longispina ________________________ 18, 19 lubimovac ________________________ 14 umznorosfratu. 14 011030. __________________ 14 parallcla _________________________ 14, 17 picdmonti _ 15 posticalia ______ 14 profusa 14 prognuta 14 quadrata 14 rotuntlata 14 srllmulorcnsis nodifcr ______________ 14 salvadorcnsis _________________ 14, 15 sowr’rbyi _________________________ 14 spinigcra. ________________________ 14, 19 aubtilis ___________________________ 14 subvuldcnsis ______________________ 13, 14 tennis ____________________________ 14 trim _ _________________ tuca nocnszs u n {ma tn ((1 valdcnsis vidrana. __________ viti'mcnsis sp. 1 _____________________ 13,15, 16, 17, 18, 19; p]. 7 (Cyamocypris) latiovata __________ 14 nvnfiformis ___________________ 14 (Cypridl‘u) _______________________ 12, 13 propmlctata 18 uninmln ______________________ wyom innmzsis ynmmulusz's ___________________ sp. A ________________________ (Pscudocypridinrz) acul itulu’rculu Ia Page alacaramac 14 alta formosa 16 altissima 17 baidarcnsis 17 binodosa 17 consulta 15 demandac ____________________ 14 dolabrata angulatu. ____________ 16 cllipscloidcs 14 cxtcnda. __-_ 14 fasciculata ___________________ 16 hcnrybclli __________________ 9, 10, 16. 17, 19; pls. 3, 8 inornata ____________ 10, 15, 17, 19, 20; pls. 3, 7 lacli __________________ 16; pls. 3, 7, 8 mugna _______________________ 14 moncta _______________________ 14 logronann ________________ 14 parallcla picdmonti salvado'rcnsis nodifcr _ salvadorcnsis sctinu accrata ___________________ camclodcs (lotion. crumna fitcricnsis rcctidorsata subcontrinoda subtilis _______________________ unicostata __ vitimcnsis spp ______________________ (CI/milieu) propmzctata, Cypridca ___- uninoda, Cypridcu. ________________ wuomingcnsis, Cynridca ___________ yumcncnsis, Cum—idea, _____________ 51’). A, Cypridca ___________________ sp. B, Cypridw __________________ Cypridca Cyp'ridcumorphclla Cypx'ideidae _, Cym'ideinae __ ....... Cz/p'rz'dopsis para/Ida ___ Cypris {Iranulosa (Pseudocypridina) _ _ (Iolabrara. Cypritlr'a dolabrata _________ domanduc, Cyridcu "nan/(11a, Cypridca ______ _ Cypridca (Psmdacypridiua) -._ dolabram, Cyprirlva _______________ (Intica, Cypridca (Psz‘uducyprz'dhm) sc- tinu. ______________________ Dsu nbaina ____________________________ «Ilipsrlaidm, Cypridca (Psoudncypridina) limhorypris (Bairdiocypris) morrisoncnsis mum/is, 14 11 24 Page Limnocypridea ____________________ 11 erumna, Cypridea (Pseudocypridina) setina ____________________ 14 extenda, Cypridea (Pseudocypridina)__ 14 F fairlightensis, Cypridea laewigata __ _ 14 fasciuta, Cypridea ...... 14 fasciculata, Cypridea _________________ 14, 16 Cypridca (Pseudocypridina) _______ 16 fiteriensis, Cypridea (Pseudacyprindina) setina __ 14 formosa, Cypridea alta ____________ __ 14 Cypridca (Pseudooypridina) alta ._ 16 G gissarensis, Cypridca __________________ 13 grammi, Limnocypridea _______________ 10, 11 granulosa, Cypridca __________________ 18 Cypris ___________________________ 12 H hawkhurstensis, Cypridea, lacvigata ,___ 14 henrybclli, Cypridca (Pseudocypridina) 9, 10, 16, 17, 19; pls. 3, 8 I Ilyacyprimorpha ______________________ 8 inacqualis, Cypridea __________________ 14 inornata, Cypridea ____________________ 15 Cypridea (Pseudacypridina) __ 10, 15, 17, 19, 20; pls, 3, 7 Pseudocypridimz __________________ 15 L lacli, Cypridca (Pseudocypridinu) __ 16; pls. 3, 7, 8 lacvigata fairlightcnsis, Cypridca. ______ 14 hawkhurstcnsis, Cypridea. _________ 14 lconardi, Cypridca ________________ 14 philpottsi, Cypridca -__ _ 14 subquadrata, Cypridea ____________ 14 wadhurstcnsis. Cypridca ___________ 14 laem's, Cypridcu. ______________________ 14 Langtonia 13 lata, Cypridea ___ 14 latiovata, Cypridca (Cyamocypris) ___, 14 Latam'a ______________________________ 8 leonardi, Cypridca laevigata ___________ 14 Limnocypridae _______________________ 8 Limnocypridea ____________________ 8, 9, 10, 12 abscondida _ albcrtensis __________________ 11, 12; pl. 2 bitumulosa __ celtifo’rmis ___ cqualis grammi __ _ morrisoncnsis ___________ 9, 11, 15; pls. 1, 3 subplana _________________________ 10, 11 tumulosa _________________________ 10, 11 Lincocypris __________________________ 11 logronana, Cypridca (Pseudocypridina) moncta longispz'na, Cypridea. Longispinclla __ 16, 19; pls. 4, 5, 7 Longispinclla ______________________ 12, 18, 19 asymmetrica, ______________ 15, 16, 17, 18; pls. 4, 5 longispz'ml _____________ 16, 19; p15. 4, 5, 7 lubimovac, Cypridca __________________ 14 M magna, Cypridca. (Pseudocypridina) __- 14 moneta, Cyp’ridca (Pseudocyprz'dina) __ 14 logronana, Cypridca (Pseudocypri- dina) ____________________ 14 INDEX Page Mongoliancllu ________________________ 8 Morinia ______________________________ 12 Morininoidcs __________________________ 12 morrisoncnsis, Bythocyzwis (Buirdio- cypris) __________________ 11 Limnocyzn‘idca __________ 9, 11, 15; pls. 1, 3 equalis, Bythocypris (Buirdiocypris) 11 N nmmorostrata, Cypridca _______________ 14 nodifcr, Cypridca (Pseudocypridina) salvadorcnsis _____________ 17 Cypridca salvadorcnsis ____________ 14 O obesa, Cypridca ______________________ 14 ovatiformis, Cypridca (Cyamacypris) __ 14 P Paleoecology __________________________ 1, Paracypridca _________________________ 12 parallola, Cypridca __ _________________ 14, 17 Cypridca (Psoudocypridina) ______ 14 Cg/pridopsis ______________________ 11 phi/pottsi, Cypridca laevigata __________ 14 ])i(’(177107lti, Cypridca __________________ 15 Cyp'ridca (Pscudocypridina) ______ 9, 12, 15,16, 19; pl. 6 Psaudocyp’ridina __________________ 13, 15 posticalis, Cypridca ______ 14 profusa, Cypridea ____________________ 14 prognata, Cypridea ___________________ 14 propunctata, Cypridca (Cypridca) _____ 18 Psmtdocypridina ___________________ 12, 1.1, 18 inornata _________________________ 15 picdmonti sambacnsis (Pscudocypridina) acutimbcrculata, Cy- pridca ___________________ 15 alacarumac, Cypridca _____________ 14 (11811 formosa, Cypridca ____________ 16 altissima, Cym'idca _______________ 17 haida'rensis, Cypridca _ 17 binodosu, Cypridca ________________ 17 consulta, Cypridca ______ 15 dcmundac, Cypridea 14 dolabrata angulata, Cypridca ______ 16 cllipscloidcs, Cypridcu. _____________ 14 (’xtcnda, Cypridca _ 14 fasciculata, Cypridm ___ _ _____ 16 lzcnrybclli, Cypridca. ______ 9, 10, 16, 17,19; pls. 3, 8 inornata, Cypridca _________ 10, 15, 17, 19, 20; pls. 3, 7 lacli, Cypridca ............. 16‘; p15. 3, 7, 8 magna, Cypridea ________ 14 moneta, Cypridca __________ 14 moneta logronana, Cypridca _______ 14 parallcla, Cypridca _______________ 14 picdmonzi, Cypridca _________ 9, 12, 15, 16, 19; pl. 6 salvadorcnsis nodifcr, Cypridca __-- 17 salvadorcnsis, Cypridca _______ 17 scntina, Cypridca _________________ 14 accrata, Cypridea __ _ 14 camclodcs, Cypridca _ 14 dotica, Cypridca. __- _ 14 crumna, Cypridca 14 fitc’ricnsis, Cyp‘ridca ___________ 14 rcctidorsata, Cypridca ________ 14 subcontrinodu. Cypridca ___________ 14 subtilis, Cypridca _________________ 17 unicostata, Cypridca ______________ 15 vitimcnsia, Cypridea ______________ 15 spp ______________________________ Cypridca -. Q quadrata, Cypridca ___________________ 14 Page R rcctidorsuta, Cypridea, (Pseudocypri- dina) sclina ______________ 14 redunca, Candona ____________________ 9 comitans, Salvadoricllu ____________ 9 rothi, Trapezoidella _________ 8, 9, 15, 16, 17, 18; pls. 1, 2 rotunda, Cypridca altissima ________ _ 14 rotundata, Cypridca ___________________ 14 S aalvadorcnsis nodifcr, Cypridca ________ 14 nodifcr, Cypridca (Psoudocypridina) 17 salvadorcnsis, Cypridca ............ 14 Cypridca (Pseudocypridina) ___ 17 Cypridca (Pseudocypridinu) sala- dorcnsis __________________ 1‘7 Cypridca salvadorensis ____________ 14, 15 Salvadoricllu ___________ 8, 9 rcdunca comitans _. 9 samlzacnsis, Pscudocypridina __________ 14 suntina, Cypridca (Pscudocypridina) __ 14 uremia, Cypridca (Pscudocypridina) 14 ramclodcs, Cyprideu (Pseudocypri- dina) ____________________ 14 crumnn, Cypridca (Pseudocypri- dina) ____________________ 14 fitcricnsia, Cypridca (Pseudocypri- dina) ____________________ 14 rcctidorsum, Cypridca (Pseudocypri- dina) ____________________ 14 smvcrbyi, Cypridca ______________ 14 spinigcra, Cypridca ___________________ 14, 19 subcontrinoda, Cypridca (Pseudocypri— dina) ____________________ 14 subplana, Limnocypridea ______________ 10, 11 subqundrata, Cypridva laevigata _______ 14 subtilis, Cypridca _____________________ 14 Cypridca (Pseudocypridina) ______ 17 subvaldcnsis, Cypridca ________________ 13, 14 Systematic descriptions _______________ 8 T tennis, Cypridca ______________________ 14 trapezoidalis, Bythocypris (Bairdiacy- pris) ____________________ 8, 9 Trapezoidclla _______ 8, 9, 10, 11, 12,15, 18: pls. 1, 2 Trapvzoz'dclla _________________________ 8, 12 rothi ___________ 8, .9, 15, 16, 17, 18; pls. 1, 2 trapezoidalis ________ 8, 9, 10, 11, 12, 15, 18; p15. 1, 2 Tl'apezoidellidae 8 trita, Cyp'ridca ,___ 14 tumnacnsis. Cypridca _________________ 18 tumulosa, Limnocyprideu U Ulwcllia. ______________________________ 12 unicostata. Cypriclca __________________ 15 CypTidCa (Pseudocypridina) ______ 15 uninoda, Cypridca (Cypridca) _________ 15 USGS Mesozoic collection localities _.-_ 5 V valdcnsis, Cypridca ___________________ 15,17 vid'raml. Cypridca __- 15 viti'mcnsis, Cypridca ___________________ 15 Cz/pridca (Pacudocypridina) 15 W wadhurslcnsis, Cypridea. lacvigata _____ 14 u'yomingcnsis, Cypridca (Cypridca) ___ 18 Y yumcncnsis, Cypridcu (Cypridea) _____ 15 Z Zcfaina ______________________________ 8 PLATES 1-8 Contact photographs of the plates in this report are available at cost, from US. Geological Survey Library, Federal Center, Denver, Colorado 80225 PLATE 1 FIGURES 1—5, 10. Trapezoidella rothi Sohn, n. sp. (p. 9). 1, 2. Outside and inside views of right valve approx. X 30. Paratype USNM 242836, Lakota Formation, Edgemont quadrangle, Fall River County, S. Dak. USGS colln. 30993, map Ice. 9. 3—5. Right, posterior, and left views of carapace approx. x 30. USNM 242837, Chilson Member of Lakota Formation, Flint Hill quadrangle, Fall River County, S. Dak. USGS colln. 30986, map. 10c. 13. 10. Outside view of right valve approx. x 30. Paratype USNM 242838, same collection as above. 6—9, 12—17. Trapezoidella trapezoidalis (Roth, 1933) (p. 9). 6—9. Right, dorsal, left, and posterior views of juvenile carapace approx. X 30. Holotype USNM 74470. Lakota Formation, 3 miles (4.8 km) south of Piedmont, Meade County, S. Dak. 1245. Right, dorsal, left, and posterior views of larger carapace approx. X 30. Figured specimen USNM 242839. Lakota Formation, Crook County, Wyo. USGS colln. 25643, map loo. 6. 16, 17. Left and posterior views of still larger carapace approx. X 30. Figured specimen USNM 242840. Same as collection above. 11, 18—30. Limnocypridea morr'isonensis (Roth, 1933) (p. 11). 11. Inside view of nested valves, approx. x 15. Figured specimen USNM 242841. Probably topotypes from Roth’s type-locality, USGS colln. 30997, map loc. 8. 18—21, 23, Right views of eight carapaces showing variation in lateral outlines ap- 24, 29, 30. prox. X 15. Figured specimens USNM 242842—242849. Lakota Formation, probably topotypes from Roth’s type-locality, 3 miles (4.8 km) south of Piedmont, S. Dak. USGS colln. 30997, map loc. 8. 22, 25-28. Right, dorsal, ventral, and left views of holotype approx. x 10, and right view approx. x 30 for relative size to other species on plate. Holotype USNM 74469. Roth’s type-locality. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069 —PLATE 1 TRAPEZ OI DELLA , LI MN OC YPRI DE A FIGURES 1—6. 4—6. 7729, 33. 10, 11. 12—15. 16, 17. 18, 19. 20. 21. 22. 23. 24, 25. 26—29. 33. 30—32. 34—36. PLATE 2 {SEM means scanning electron micrograph] Limnocypridea? albertensis (Loranger, 1951) (p. 12). 1—3. Ventral, left, and right views of carapace approx. X 30, original of Loran- ger's pl. 2, fig. 21. Paralectotype, Geol. Survey of Canada No. 48736. Blairmore Formation (Aptian-Albian), Imperial’s Deville No. 1 well, 3,402—3,416 feet (1,037—1,041 m). Dorsal, right, and left views of carapace, approx. x 30, original of Loran- ger’s pl. 2, fig. 28. Lectotype, Geol. Survey of Canada No. 48735. Blair- more Formation (Aptian-Albian), Imperial’s Looma No. 1 well, core at 3,947—3,978 feet (1,203—1,212 m). Trapezoidella rothi Sohn, n. sp. (p. 9). 7—9. Dorsal, right, and left views of carapace, SEM approx. X 30. Paratype USNM 242851. Upper part of Chilson Member of Lakota Formation, Fall River County, S. Dak. USGS colln. 30985, map 10c. 13. Inside and outside views of right valve, approx. X 30. Paratype, USNM 242852. About 10 feet (3 m) above base of Chilson Member of Lakota Formation, Fall River County, S. Dak., USGS colln. 30990, map 10c. 14. Dorsal, right, left, and ventral views of carapace, approx. X 30. Paratype USNM 242853. Unit 2 of Chilson Member of Lakota Formation, AEC Diamond Drill Hole RE—17, core at 289.5 feet (88 m), Fall River County, S. Dak. USGS colln. 30988, map 10c. 16. Left and right views of crushed carapace, approx. X 30. Paratype USNM 242854. Same unit and drill hole as above, core at 283.5 feet (86.4 m). USGS colln. 31006, map 10c. 16. Left and right views of partly broken carapace, approx. X 30. Paratype USNM 242855. Unit 2 of Chilson Member of Lakota Formation, Fall River County, S. Dak. USGS colln., 30986, map 10c. 13. Left view of crushed carapace, approx. X 30. Paratype USNM 242856. Unit 2 of Chilson Member of Lakota Formation, Fall River County, S. Dak. USGS colln. 31007, map 10c. 17. Left view of carapace, approx. X 30. Paratype USNM 242857, Lakota Formation, Fall River County, S. Dak. USGS colln. 26468, map 10c. 10. Left view of carapace, SEM approx. X 30. Paratype USNM 242858. Upper part of Chilson Member of Lakota Formation, Fall River County, S. Dak. USGS colln. 30985, map 10c. 13. Left view of carapace, approx. X 30. Paratype USNM 242859. Chilson Member of Lakota Formation, Fall River County, S. Dak. USGS colln. 30994, map 10c. 11. Outside view of left valve SEM approx. X 30, hinge view, SEM approx. X 100. Paratype USNM 242860. Same collection and locality as fig. 22. Posterior, dorsal, left, and right views of carapace, SEM approx. X 30. Holotype, USNM 242861. Same collection and locality as fig. 22. Right View of carapace, SEM approx. X 75. Paratype USNM 242862. Same collection and locality as fig. 22. Trapezoidella, trapezoidalis (Roth, 1933) (p. 9). Left, dorsal, and right views of carapace, approx. X 30. Paratype USNM 242863. Lakota Formation, Crook County, Wyo. USGS colln. 26941, map loc. 7. Trapezoidella, rothi Sohn, n. sp. (p. 9). Detail of adductor muscle attachment scar, SEM approx. X 180, inside and outside views of fragment of left valve approx. X 30. Figured specimen USNM 242864. Lakota Formation, Fall River County, S. Dak. USGS colln. 30993, map Ice. 9. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069 —PLATE 2 LIMNOC YPRIDEA .7, TRAPEZOIDELLA PLATE 3 [SEM means scanning electron micrograph] FIGURES 1—13. Cypridea (Pseudocypridina) laeli Sohn, n. sp. (p. 16). 1—4. Ventral (anterior to left) dorsal (anterior to right), right, and left views of four carapace approx. x 30. Paratypes USNM 242865—242868. La- kota Formation, Crook County, Wyo. USGS colln. 31001, map loc. 5. 5—7. Dorsal (anterior to left), right, and ventral (anterior to left) views of carapace, SEM approx. x 30. Paratype USNM 242869. Same collection as above. 8, 9. Dorsal (anterior to right), and left views of carapace, SEM approx. x 30. Paratype USNM 242870. Same collection as above. 10—13. Left, dorsal (anterior to left), right, and ventral tanterior to right), views of carapace. Holotype USNM 129644. Lakota Formation, Crook County, Wyo. USGS colln. 25645, map loo. 5. Same specimen as Sohn, 1958, p. 1, figs. 9—12. 14—17. Cypridea (Pseudocypridina) hem'ybelli Sohn, n. sp. (p. 17). Left, dorsal (anterior to right), right, and ventral (anterior to right) views of carapace, approx. x 30. Holotype USNM 129645. USGS colln. 25460, map 10c. 17. Same specimen as Sohn, 1958, pl. 1, figs. 13—15. 18-23. Cyprz'dea (Pseudocypridina)ino'mata (Peck, 1941) (p. 15). 18,19. Dorsal (anterior to right) and right views of carapace, instar, approx. X 30. Figured specimen USNM 242873. Same collection as figs. 179. 20, 21. Dorsal and right views of carapace, adult, approx. x 30. Figured specimen USNM 129647. Same collection as figs. 10—13. Same specimen as Sohn, 1958, pl. 1, figs. 17, 18. 22, 23. Right and left views of carapace, approx. x 30. Figured specimen USNM 242874. Same collection as figs. 1—9. 24, 25. Cypridea (Pscmlocypridina) Iaeli Sohn, n. sp. (p. 16). Ventral (anterior to left), and left views of carapace, SEM approx. )< 30. Paratype USNM 242871. Same collection as figs. 149. 26—29. Limnocypridea mowisonensis (Roth, 1933) (p. 11). Dorsal (anterior to right), left, posterior, and right views of presumed male carapace, approx. x 15. Figured specimen USNM 242850. Lakota Formation, Roth’s type locality, Meade County, S. Dak. USGS colln. 30997, map 10c. 8. 30, 31. Candona sp. (p. 11). Left lateral views of female and male valves, approx. X 30. Figured speci- mens USNM Crustacea 168192, 168193. Collected alive in Kenilworth Aquatic Gardens, Washington, DC. 32. Cypridea (Pseudocypridina) Iaeli Sohn, n. sp. (p. 16). Left valve hinge approx. x 130. Paratype (broke during removal from stub) USNM 242872. Same collection as figs. 1—9. GEOLOGICAL SURVEY " YAL PAPER 1069—PLAT C YPR IDEA (PS E UDOC YPR I DI N A ), LI M N GO YPRI DE A , CANDONA PLATE 4 [Scanning electron micrographs (SE31) approx. X 90, except fig. 14 which is approx. X 200, reduced 1/3 for publication] FIGURES 1—6. Longispinella longispina (Peck, 1941) (p. 19). 1-3. Left, right, and dorsal views of carapace, presumed male. Figured specimen, topotype USNM 242875. Kootenai Formation, T. 18 N., R. 4 E., Cascade County, Mont. Peck’s colln. 23 (1941, p. 288). 4-6. Left, ventral, and right views of carapace, presumed male. Figured speci- men, topotype USNM 242876. Same collection as above. 7—20. Longispinella, asymmetrica. Sohn, n. gen., n. sp. (p. 18). 7—9. Right, ventral (anterior to left), and left views of carapace. Paratype USNM 242877. Unit 2 of Chilson Member of Lakota Formation, Fall River County, S. Dak. USGS colln. 26098, map. loc. 17. 10—13. Posterior oblique, dorsal, right, and left views of carapace. Paratype USNM 242878. Same collection as above. 14—17. Right, ventral, detail of left anterior, and left views of carapace. Paratype USNM 242879. Same collection as above. 18—20. Left, dorsal, and right views of carapace converted to fluoride. Paratype USNM 242880. Same collection and locality as above. GEHLWHUAL SURVEY PROFESSIONAL PAH-IR 1069~PLA E 1 FIGURES 1—7. 8—12. 13—16. 17—23. PLATE 5 [Scanning electron microgruphs approx. X 90, except fig. 20 which l.\' approx. X 250, reduced 1/3 for publication] Longispinella asymmetrica Sohn, n. sp. (p. 18). 1—3. Dorsal, right, and ventral views of carapace. Paratype USNM 242881. Unit 1 of Chilson Member of Lakota Formation, Fall River County, S. Dak. USGS colln. 31130, map 10c. 14. 4—7. Right, ventral, dorsal, and left views of carapace. Holotype USNM 242882. Same collection as above. Longispinella lovtgispina (Peck, 1941) (p. 19). 8—10. Left, dorsal, and right views of carapace, presumed male. Figured speci- men USNM 242884. Lowermost part of Lakota Formation, Fall River County, S. Dak. USGS colln. 31154, map loc. 12. 11,12. Left and dorsal views of carapace, presumed female. Figured specimen USNM 242885. Same collection as above. Longispinella asymmetrica Sohn, n. sp. (1). 18). Left, ventral, dorsal, and right views of carapace. Paratype USNM 242883. Same collection as figs. 1—7. Longispinella Iongispina (Peck, 1941) (p. 19). 17—19. Right, left, and dorsal views of carapace, presumed male. Figured speci- men USNM 242886. Lower part of Lakota Formation, Fall River County, S. Dak. USGS colln. 31153, map 10c. 12. 20—23. Detail of anterior of left valve, left, dorsal, and right views of carapace, presumed female. Figured specimen USNM 242887. Same collection as above. ’JLOGICAL SURVEY PROFESSIONAL PAPER 10659‘1’ LONG] S PI NELLA FIGURES L47. Cypridca 1—4. 5—7. 10—13. 14-17. 18f20. 21, 22. 23—27. 28—33. 34437. 38~40. 41—47. PLATE 6 [Scanning electron micrographs (SEM) taken approx. x 60, and when: indicated larger, reduced 1/2 for publication] (Pseudocypridina) piedmonti Roth, 1933 (p. 15). Left, posterior, right, and dorsal (anterior to right) views of carapace. Figured specimen USNM 242888. Probably Unit 2 of Chilson Member of Lakota Formation, Meade County, S. Dak. USGS colln. 31171, map ice. 8. Left, dorsal (anterior to right), and posterior views of carapace. Figured specimen topotype USNM 242889. Probably Unit 2 of Chilson Member of Lakota Formation, Meade County, S. Dak. USGS colln. 30997, map loo. 8. Left valve and posterior of carapace. Figured specimen USNM 242890. Same collection as figs. 174. Left, posterior, right, and ventral (anterior to left) views of carapace. Figured specimen, topotype USNM 242891. Same collection as figs. 5—7. Right, dorsal (anterior to right), left, and posterior views of carapace. Figured specimen USNM 242892. Same collection as figs. 1—4. Dorsal, posterior, and right views of carapace. Figured specimen USNM 242893. Same collection as figs. 1—4. Left and posterior views of carapace. Figured specimen USNM 242894. Same collection as figs. 1—4. Left (anterior imbedded in mounting medium), posterior, right, dorsal (an— terior to left), and ventral (anterior to left) views of carapace. Holo- type USNM 74473. Probably Unit 2 of Chilson Member of Lakota Forma— tion, Meade County, S. Dak. Roth’s type-locality, map loc. 8. Detail of dorsoanterior approx. X 50, left, posterior, right, ventral (an- terior to left), and dorsal (anterior to right) views of carapace. Figured specimen USNM 242895. Unit 2 of Chilson Member of Lakota Formation, Fall River County, S. Dak. USGS colln. 26089, map 10c. 17. Right valve, detail of binge approx. x 50, inside, outside, and dorsal views. Figured specimen USNM 242896. Same collection as figs. 28—33. Left valve, detail of binge approx. x 75, outside and inside views. Figured specimen USNM 242897. Same collection as figs. 1—4. Ventral oblique, left, posterior, dorsal oblique (anterior to left), right, ven- tral (anterior to left), and dorsal (anterior to right) views of carapace. Figured specimen USNM 242898. Same collection as figs. 28—33. GEOLOGICAL SURVEY PROFESSIONAL PAPER Hum—PLATE ‘7 C YPRIDEA (PSE UDOCYPRIIHNA) PLATE 7 [Scanning electron micrographs (SEM) not reduced for publication] Cypridea (Pseudocypridina) laeli Sohn, n. sp. (p. 16). Dorsal view of carapace, approx. x 75. Same specimen as pl. 3, figs. 24, 25. Chilson Member of Lakota Formation, Crook County, Wyo. 2—4. Cyp'r'idea, (Pseudocypridina) {momata (Peck, 1941) (p. 15). Ventral (anterior to left), posterior, and right views of carapace, approx. x 60. Figured specimen USNM 242899. Lakota Formation, Crook County, Wyo. USGS colln. 25645, map 10c. 5. 5—7. Longispinella longispina (Peck, 1941) (p. 19). Detail of anterior portion of left valve, approx. X 300, dorsal and left views of carapace, approx. x 90. Figured specimen, presumed male, USNM 12943. Limestone near middle part of Lakota Formation, Crook County, Wyo. USGS colln. 25644, map Ice. 5. The same specimen was illustrated by Sohn (1958, pl. 1, figs. 1—4). 8-12. “Cypridea” sp. 1 (p. 18). Dorsal, posterior, anterior, left, and right views of carapace, approx. x 90. Figured specimen USNM 242900. Unit 2 of Chilson Member of Lakota Formation, Fall River County, S. Dak. USGS colln. 26098, map 10c. 17. FIGURE 1. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069 —PLATE 7 CYPRIDEA (PSE OCYPRIDINA), LONGISPINELLAy “CYPRIDEA” PLATE 8 [All scanning electron micrographs (SEM), photographed approx. X 90. reduced 1/2 for publication] FIGURES 1—25. Cypridea 1—3. 4—6. 10—12. 13—16. 17—20. 21—25. (Pseudocypridina) hem'ybelli Sohn, n. sp. (p. 17). Left, dorsal (anterior to right), and right views of carapace with two nodes on each valve. Paratype USNM 242901. Unit 1 of Chilson Member of Lakota Formation, Fall River County, S. Dak. USGS colln. 31130, map 10c. 14. Left, dorsal (anterior to right), and right views of carapace with two nodes on each valve. Paratype USNM 242902. Same collection as above. Left, dorsal (anterior to left), and right views of carapace with two nodes on each valve. Paratype USNM 242903. Same collection as above. Left, dorsal (anterior to right), and right views of carapace with two nodes on each valve. Paratype USNM 242904. Same collection as above. Left, dorsal (anterior to left), ventral (anterior to right), and right views of carapace with two nodes only on left valve. Paratype USNM 242905. Same collection as above. Left, dorsal oblique (anterior to right), posterior, and right views of cara- pace with two nodes only on left valve. Paratype USNM 242906. Same collection as above. Left, ventral (anterior to right), posterior, dorsal oblique (anterior to right), and right views of carapace with one node only on anterior part of left valve. Paratype USNM 242907. Same collection as above. 26—30. Cypriden (Pseudocypridina) Iaeli Sohn, n. sp. (p. 16). Right, posterior, dorsal (anterior to right), ventral (anterior to left), and left views of carapace. Paratype USNM 242908. Lakota Formation, Crook County, Wyo. USGS colln. 31001, map loc. 5. GEOLOGICAL SU {VEY PROFESSIONAL PAPER IUGB—PLATE 8 CYPRIDEA (PSE UDOCYPRIDINA) fiU.$. GOVERNMENT PRINTING OFFICE: 1979 O— 28l-359’l2 Oramlrnfera froatheKara ‘ Rewew 0f mIicStudies Foraminifera from the Kara and Greenland Seas, and Review of Arctic Studies By RUTH TODD and DORIS Low GEOLOGICAL SURVEY PROFESSIONAL PAPER 1‘070 Sparse and erratic fauna (111 species) of low diversity and strong dominances from the Continental Shelf of both seas and from slopes, basins, and rises of the Greenland Sea UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1980 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVE Y H. William Menard, Dire "tor Library of Congress Cataloging in Publication Data Todd, Ruth, 1913— Foraminifera from the Kara and Greenland Seas, and review of Arctic studies. (Geological Survey professional paper ; 1070) Bibliography: p. Includes index. Supt. of Docs. no.2 I 19.16:1067 1. Foraminifera—Kara Sea. 2. Foraminifera—Greenland Sea. 1. Low, Doris, joint author. II. Title. III. Series: United States. Geological Survey. Professional paper ; 1070. QE772.T592 563’.1 77-608327 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, DC. 20402 Stock Number 024—001—03287—2 PLATE FIGURE TABLE 1. D—I NH CONTENTS Abstract Introduction Previous studies in the area Analyses of faunas Kara Sea Greenland Sea Comparison of the Kara and Greenland Seas faunas Diversity and density Summary Faunal reference list References cited Index ILLUSTRATIONS [Plates 1 and 2 follow index] Arenaceous Foraminifera from Kara and Greenland Seas. Calcareous Foraminifera from Kara and Greenland Seas. Page 12 18 18 19 19 20 21 29 Page Index map 2 Map of Kara Sea 3 TABLE S Page Distribution of species in the Kara and Greenland Seas 4 Locality and depth of bottom-sediment samples from the Kara Sea 13 Locality and depth of bottom-sediment samples from the Greenland Sea 13 iii FORAMINIFERA FROM THE KARA AND GREENLAND SEAS, AND REVIEW OF ARCTIC STUDIES By RUTH TODD and DORIS Low ABSTRACT Analyses of the Foraminifera found in 83 bottom sediment samples from the Kara and Greenland Seas showed a com- bined fauna of 111 species. All the Kara samples and half the Greenland samples were taken on the Continental Shelf at depths between 82 and 640 m. The samples from deeper parts of the Greenland Sea were taken from continental slopes, basins, and rises, at depths mostly between 2,195 and 3,340 m. The sparse fauna is erratic in distribution and has a low diversity but a uniformity of character over large areas. Many of the species appear to be eurybathyal. Many samples are strongly dominated by one or more species. Large robust arenaceous and porcellaneous species constitute a significant part of the population. INTRODUCTION Two lots of bottom sediment samples—47 from the northern and western parts of the Kara Sea and 36 from the northern part of the Greenland Sea—were selected for Forarninifera analysis from collections made during oceanographic surveys in the late sum- mer of 1965 (fig. 1 and table 1). These surveys were conducted by personnel from the US. Naval Oceano- graphic Oflice on board the US Coast Guard Cutter N orthwind (WAGE—282) in the Kara Sea from July 25 to September 29, 1965 and the USS. Edisto (AGE—2) in the Greenland Sea from August 23 to September 12, 1965. Most of the 47 Kara Sea samples were concen- trated in an area between about lat 77 °30’ and 81°30’ N. and between about long 67° and 88° E., but a few were taken from east of Novaya Zemlya as far south as lat 72° N. (figs. 1, 2, and table 2). Depths sampled in the Kara Sea ranged from 82 to 640 m; most of them were between 188 and 541 m. Because the depths did not vary extremely and because depth did not seem to affect the foraminifer assemblages, we have arranged the samples in approximate order of geographic sequence from northeast to southwest. On table 1 we have grouped the samples from Kara Sea as follows: Arctic Ocean, northeast of Severnaya Zemlya (North Land) (1 sample at 265 m) Ofi' Taymyr Peninsula, between Taymyr Peninsula and North Land (1 sample at 82 m) West of North Land (11 samples ranging in depth from 188 to 412 m) East of Franz Josef Land (18 samples ranging in depth from 216 to 640 m) South of Franz Josef Land toward Novaya Zemlya (7 samples ranging in depth from 251 to 485 m) Bordering Novaya Zemlya (9 samples ranging in depth from 223 to 499 m) These groupings in the Kara Sea have little to unite them and set them apart from each of the other regional groupings except that the more southerly samples, toward Novaya Zemlya, show a lack or a decrease of Reophax nodulosus, Hyperammina elon— gata, Cribrostomoides subglobosus, and Aschemonel— la scabra. In general, each individual fauna is small in num- ber of species, and most faunas are dominated by one or several species. The overall picture does not show a consistent presence of many species, such as is characteristic of warmer waters. The most persistent species on the Continental Shelf are Psammosphaem fusca, Reophax scorpiurus, and Trochammz‘na name, and the first two of these are in positions of domi- nance in most of the samples. Cm'brostomoides crassimargo and Saccorhiza ramosa are fairly con- sistent but very scattered east of Franz Josef Land; they are not dominant, except that S. mmosa shares dominance with other species in several of the south- ern samples along Novaya Zemlya. A total of 36 samples from the Greenland Sea were studied, most of them found between approxi- mately lat 71° and 78° N. and long 20° and 1° W. (table 3). Three others were found near Spitsbergen at about lat 80° N. and between long 1° and 4° E. Depths sampled range from 45 to 1,825 fathoms (about 82 to 3,340 m). Those taken on the Conti- 1 2 FORAMINIFERA FROM THE KARA AND GREENLAND SEAS GREENLAND (Denmark) Base from Central Ixntalli‘ggnoe Agency FIGURE 1.—Index map of the north polar region showing place names mentioned in text. 80 75° 70° 0 INTRODUCTION 50° 55° 60° 55° 70° 75° 80° 85° 90° 95° 100° 80° 105° 110° \ \ \ l \ 106 8600/ w 1100 d" (0\ 108 .107 O {71% 3‘ ©5‘ 110, ‘ AYA 59‘“ § C c 12 122 ’123 Q (North \’ “P? 105 ~1 ' Cheluskma 114. .113 O .124 - 131' FRANZ 0 Q115 117 .125 JOSEF Q0 115. ' 135 .134 .126 - LANDQ ' ° . 9 100° 0 $00 0 137 136 .144 \ Q G .143 4 $72 Go 0 139 141.12' “47,153 ‘ /0 /Do D Q o 1.49. 148 91 0 Tikhaya Bay .151 . 154 ><75° .156 77 ' 95° .155 ' TAYMYR -157 .53 K A R A .54 90° 41 S E A Sverdrup ' \Island .29 Dickson 850 / 70° 800 W 75° \ \ \ 50° 55° 60° 65° 70° FIGURE 2.—Map of the Kara Sea showing the location of bottom sediment samples. 4 FORAMINIFERA FROM THE KARA AND GREENLAND SEAS TABLE 1. —Distribution of species in the Kara and Greenland Seas Kara Sea South of Franz Josef Land Bordering West of North Land East of Franz Josef Land toward Novaya Zemlya Novaya Zemlya 90 Off Taymyr Peninsula 106 Arctic Ocean X X X X X Adercot'ryma glomemtum (Brady). Ammodiscus gullmarensis Hoglund. Anguloge'm'naflms Todd x Aschemonellascabm xxxx?xx xx xxxx xxxx xxx xxxxx x xx Brady. Astacolus planulatus Galloway and Wissler. Astrononion gallowayi x x x x Loeblich and Tappan. Biloculinella globula x (Bornemann). Bolivina rhmbo'idalis (Millett). Bmcella inusitata x x x x x x x x Andersen. Bulimina emilis Brady _____ x x x x x x Cassidul'ina norc'rossi x x x Cushman. subglobosa Brady _______ Cibicides bradfi (Tolmachofi). lobatulus (Walker and x x x x x x x x Jacob). Comuspim involvens x x (Reuss). Lacunosa Brady ......... planarln's Schultze _____ Cribrostomoidescmssi- x xxxxxxxxx x x x x x xx xxxxxx marge (Norman). jeflreysi (Williamson) . subglobosus(G.O. xxx? xxx xxxxxxxxx xx xxxx xxx Sars). Cmc'ilowlina e'm'csom' x Loeblich and Tappan. Dentalina baggi Galloway x and Wissler. decepta (Bagg) ........... frobisherensis Loeb- x x x lich and Tappan. Egge'rella advent), x x (Cushman). X X X X X X X X X X X X INTRODUCTION TABLE 1. —Distr’ibution of species in the Kara and Greenland Seas-Continued Greenland Sea Greenland Continental Shelf 2 Flank mid-oceanic ridge 4 Flank Jan Mayen fracture zone Greenland Continental Rise 5 Greenland Basin 23 24 25 26 27 28 29 3O 34 15 16 17 GBGDOGOOH v—‘r—4N 35 3 22 Greenland Continental Slope 14 21 37 11 12 13 10 7 32 Spitsbergen Continental Slope 33 Wall mid-oceanic rift 31 Ade'rcotryma glommtum (Brady). Ammodiscus gullmarensis Hoglund. Angulogerinafluens Todd ___________ Aschemonella scabm Brady. Astacolus planulatus Galloway and Wissler. Astronomion gallowayi Loeblich and Tappan. Bilocul'inella globula (Bornemann). Bolivina rhomboidalis (Millett). Buccella inusitata Andersen. Bulimina exilis Brady ................ Cassidulina norcrossi Cushman. subglobosa Brady __________________ Cibicides Irradii (Tolmachofl') ._ lobatulus (Walker and Jacob). Cmuspira involvens (Reuss) ..... lacunosa Brady .................... planorbis Schultze ................ Cribrostomoides crassimargo (Norman). jefireysi (Williamson) ____________ . subglobosus (G. O. Sars) ________ Cmciloculina ericsoni Loeblich and Tappan. Dentalz'na baggi Galloway and Wissler. decepta (Bagg) ...................... frobisherensis Loeblich and Tappan. Egge’rella advena (Cushman) ....... X X X X X X X FORAMINIFERA FROM THE KARA AND GREENLAND SEAS TABLE 1,—Distribution of species in the Kara and Greenland Seas —Continued Kara Sea West of North Land East of Franz Josef Land South of Franz Josef Land toward Novaya Zemlya Bordering Novaya Zemlya 106 Arctic Ocean 90 Off Taymyr Peninsula 107 108 109 110 102 122 123 124 131 125 126 112 113 114 115 116 117 137 136 135 134 139 141 142 143 144 147 148 149 Elphidiella arctica (Parker and Jones). hannai (Cushman and Grant). Elphidium bartletti Cushman. clavatum Cushman frigidum Cushman orbiculare (Brady) Epistominella exiguu (Brady). Epom'des repandus Montfort. tene’r (Brady) ............ cumidulus homathi Green. Fischer'ma Sp _________________ Fissurina kerguelenensis Parr. marginata (M ontagu) serrata (Schlum- berger). x Florilus lubrador’icus (Dawson). Globigem'na bulloides d’Orbigny. pmhydema (Ehren— berg). quinqueloba Natland Globigerim'ta glutinata >< (Egger). Globobulimina auricu- lata (Bailey). Glolmlina glacialis Cushman and Ozawa. H emisphaerammina marisalbi (Stschedrina). H omosina sp. of Parker _ Hyperammma elongata Brady. friabilis Brady __________ Islandiella, helenae Fey- ling-Hanssen and Buzas. islandica (Norvang) .. J aculella acuta Brady ..... Lagena disto'ma Parker X X X X X and Jones. INTRODUCTION TABLE 1.—Dist7‘ilmtion of species in the Kara and Greenland Seas—Continued Greenland Sea Greenland Greenland Continental Shelf Continental Rise Flank Jan Mayen fracture zone 2 Flank mid-oceanic ridge 22 Greenland Continental Slope 23 24 25 26 27 28 29 30 15 16 17 19 8 0 9 8 1 3 4 14 12 13 10 7 35 34 21 37 11 32 Spitsbergen Continental Slope 5 Greenland Basin 33 Wall mid-oceanic rift 31 Elphidiella aretica (Parker x and Jones). hannai (Cushman and Grant). Elphidium bartletti Cushman. clavatum Cushman ............ x x ? x x ? frigidum Cushman ............ orbiculare (Brady) ............. x Epistominella exigua x x x x x x (Brady). Epom'des repomdus x Montfo'rt, tene’r(Brady) ..................... >< xxxxxxxxxxx tumidulus homathi x x x x x X Green. Fische’rina sp __________________________ Fissum'na kerguelenesis x x x Parr. marginata (Montagu) _________ serrata (Schlumberger). Flo'm'lus labradom'cus .............. X (Dawson). Globigem'na bulloides d’Orbigny. pachyderma (Ehrenberg)__._ x x x x x x x X x x x x x x x x x x x x quinqueloba Natland __________ x x x x x Globigerim'ta glutinata (Egger). Globolmlimina auriculata (Bailey). Glolmlina glacialis Cushman and Ozawa. H emisphaemmmina marisalbi (Stschedrina). H ormosina sp. of Parker x Hyperammina elongata x x x x x x x x x x x x Brady. friabilis Brady ___________________ x x x x Islandiella helenae Feyling- x x x x x x Hanssen and Buzas. islandica (Navang) ___________ x x x x x J aculella acuta Brady .............. X Lagena distoma Parker and x Jones. X X X \7 XX XX XX X X X X XX X FORAMINIFERA FROM THE KARA AND GREENLAND SEAS TABLE 1. —Distribution of species in the Kara and Greenland Seas —Continued Kara Sea West of North Land East of Franz Josef Land South of Franz Josef Land toward Novaya Zemlya Bordering Novaya Zemlya 90 Off Taymyr Peninsula 106 Arctic Ocean 107 108 109 110 102 122 123 124 131 125 126 112 113 114 115 116 117 137 136 135 134 139 141 142 143 144 147 148 149 151 153 156 154 157 155 77 57 55 53 54 41 29 23 13 X Lagena hispidula Cushman. laevis (Montagu) ________ Lamngosigm hyala- scidia Loeblich and Tappan. Melom's zwndamue (van Voorthuysen). Nom'onella turgida digi- tutu, N¢rvang_ Oolina hexagona (W il- liamson). lineata (Williamson) melo d’Orbigny __________ >< Parafissum'na groen- landica (Stschedrina). tectulosto’ma Loe- blich and Tappan. sp .............................. X Patellina comgata x Williamson. Pateoris hamnoides (Rhumbler). Pelosina sp ...................... Placopsilina bradyi Cush- man and McCulloch. Planispz'rinoides buccu- x lentus (Brady). Protoschista sp ................ Psammatodendron arbo- rescens Norman. Psammosiphonella ems- satina (Brady). Psammosphaem fusca Schulze. Pseudononion sp ______________ Pullem‘a bulloides (d’Orbig'ny). Pyrgo fomasimi Chap- x man and Parr. rotalam'a Loeblich and Tappan. vespe'rtilio (Schlum- berger). un'lliamsoni (Sil- vestri). X INTRODUCTION TABLE 1. —Distm'bution of species in the Kara and Greenland Seas— Continued. Greenland Sea Greenland Continental Rise Greenland Continental Shelf 4 Flank Jan Mayen fracture zone 14 22 Greenland Continental Slope 32 Spitsbergen Continental Slope 2 Flank mid-oceanic ridge 33 Wall mid-oceanic rift 23 24 26 27 28 29 30 34 15 16 17 19 8 20 3 5 Greenland Basin 31 moo—l 25 35 21 37 11 12 13 10 7 6 X ‘7 Lagena hispidula x Cushman. laem’s (Montagu) _______________ Lamngosig'ma hyala- scidia Loeblich and Tappan. Melomls zaandamae (van x x x x x x x x Voorthuysen). Nonionella turgida digi- tata Norvang. Oolina hexagona, (W il- x liamson). limata (Williamson) x x mlo d’Orbigny _________________ x x x Pamfissum'na groen- x x x x x x x landica (Stschedrina). ‘ tectulostoma Loe- x x x x x blich and Tappan. sp _____________________________________ x x x x x x Patellina comgata Williamson. Pateo'r'is haue'r'moides (Rhumbler). Pelosina sp ............................. x Placopsilina bradyi Cush- man and McCulloch. Planispim'noides buccu- Lentus (Brady). Protoschista sp _______________________ Psammatodendron arbo- x rescens Norman. Psam’mosiphonella cras- ? satina (Brady). Psammosphaemfusca x x x x x x x x x x x x x Schulze. Pseudononion sp ____________________ x x x Pullem'a bullm'des x x x (d’Orbigny). Pyrgo fomasinii Chap- man and Parr. rotalam‘a Loeblich x x x and Tappan. vespe'rtilio (Schlum- x x x x x x x x x x x x x x ? berger). williamsoni (Silvestri) _____ 10 FORAMINIFERA FROM THE KARA AND GREENLAND SEAS TABLE 1. —Distribution of species in the Kara and Greenland Seas —Continued Kara Sea West of North Land East of Franz Josef Land Josef Land toward South of Franz Novaya Zemlya Bordering Novaya Zemlya 90 Off Taymyr Peninsula 107 106 Arctic Ocean 108 109 110 102 122 123 124 131 125 126 151 153 156 154 157 155 77 X Pyrgoella sphaera (d’Orbigny). Quinqueloculina akne’r’i- ana d’Orbigny. Recumoides laevigatum Hoglund. Reophax arctica Brady..._ dentalim'fomis Brady. guttifer Brady ........... nodulosus Brady ........ scomiums Montfort Rhabdammimz abyssmm M. Sars. discreta Brady ........... X Robertina arctz'ca x d’Orbigny. Rosalimz globulam's x d’Orbigny. Saccammina difilug’i or- mis (Brady). sphaewlca M. Sars ...... Smcwhiza ramosa (Brady)- Spim'llina vivipara x Ehrenberg. Spiroplectammina bifor— mis (Parker and Jones). Stetscrm'a hmathi Green Textulama earlandi Parker. torquata Parker _________ Thura'mmma papillata Brady. Tolypammina schaudimn' Rhumbler. Triloculina t’m'hedra Loeblich and Tappan. Trochammina com'ca Earland. cf. T. gm'sea Earland..- cf. T. japomlca Ishiwada. nana (Brady) .............. quadriloba Héglund sp ______________________________ Turrispirillma arctica (Cushman). X X X X X X X X X X X X X X ~¢ INTRODUCTION TABLE 1. —Distm'bution of species in the Kara and Greenland Seas —Continued Greenland Sea Greenland Continental Shelf Greenland Continental Rise 5 Greenland Basin 4 Flank Jan Mayen fracture zone 14 22 Greenland Continental Slope 32 Spitsbergen Continental Slope 2 Flank mid-oceanic ridge 33 Wall mid-oceanic rift 3 OSWH 23 24 25 26 27 28 29 30 35 34 15 16 17 19 8 20 21 37 11 12 13 10 7 6 31 Pyrgoella sphaera (d’Orbigny). Quinqueloculina akmri- x ana d’Orbigny. Recurvoz'des laem'gatum x x Hoglund. Reophax arctica Brady ___________ dentalimfomls Brady. guttzfer Brady __________________ x x nodulosus Brady .............. scorpiums Montfort x x x x x x x x x x x x x Rhabdammina abyssorum x x x x x x x x x x x x x x x x x M. Sars. discreta Brady __________________ x x x Robertina arctica d’Orbig'ny. Rosalina globular-is d'Orbigny. Saccammina difilungor- x x x x x x x mis (Brady). sphaem’ca M. Sars ............. Saccorh’iza ramosa x x x x x x x x x x (Brady)- Spim‘llina m'm'para Ehrenberg. Spiroplectammma bifor- mis (Parker and Jones). Stetsonia hmwath’i Green x x x Textulam'a earlamii x ? ? ? Parker. torquata Parker ________________ x x x Thurammim papillata Brady. Tolypammma schaud'inni x x x Rhumbler. Triloculina trihedra x x x x x x x x x x x Loeblich and Tappan. Trochammina com'ca x Earland. cf. T. g’risea Earland.-. x x cf. T. japom'ca >< Ishiwada. nam(Brady) ____________________ x ?xx xxxxx >< quadriloba Hbglund x x x sp ..................................... Tunispir'illimz arctica x (Cushman). 12 FORAMINIFERA FROM THE KARA AND GREENLAND SEAS nental Shelf came from depths between 45 and 194 fathoms (about 82 and 355 m). Those taken on con- tinental slopes, basins, and rises came mostly from depths between 1,200 and 1,825 fathoms (about 2,195 and 3,340 m). On table 1 we have grouped the samples from Greenland Sea as follows: Greenland Continental Shelf (19 samples ranging in depth from 45 to 194 fathoms [approx 82 and 355 m]) Flank of mid—oceanic ridge (1 sample at 360 fathoms [approx 660 m]) Flank of Jan Mayen fracture zone (2 samples, at 1,225 and 1,230 fathoms [approx 2,240 and 2,250 m]) Greenland Continental Slope (2 samples, at 900 and 1,060 fathoms [approx 1,645 and 1,940 m]) Greenland Continental Rise (8 samples ranging in depth from 1,200 to 1,825 fathoms [approx 2,195 and 3,340 m]) Greenland Basin (1 sample at 1,560 fathoms [ap- prox 2,855 m]) Spitsbergen Continental Slope (2 samples, at 640 and 1,380 fathoms [approx 1,170 and 2,525 m]) Wall of mid-oceanic rift (1 sample at 1,750 fath- oms [approx 3,200 m]) Samples from the Continental Shelf off northeast— ern Greenland, between approximately lat 71° and 78° N., contain faunas similar to, although sparser than, those from the Continental Shelf areas of the Kara Sea. Kara and Greenland Seas Continental Shelf faunas are comparable except for Reophax nodulosus, which was not found on the Greenland Sea shelf. The three species found most often in the Kara Sea were like- wise found most often on the Continental Shelf of the Greenland Sea—namely Psammosphaera fusca, Reophax scorpiurus, and Trochammma mma. Comparatively deep areas of the Greenland Sea are inhabited by a distinctly different fauna from that observed at shelf depth. This change is due in part to the disappearance or the decrease of some of the Continental Shelf species, such as Hyperammina elongata, Psammosphaera fusca, Saccorhiza ramosa, Reophax scorpiurus, Rhabdammma abyssorum, and Trochammina mma and to the increase in abundance (that is, percentage at individual stations) of others, such as Cribrostomoides subglobosus and Globiger- ina. pachyderma, plus other planktonic species. In addition, this distinction is enhanced by the addition of the following deep-water species: Cibicides bradii Epistominella exigua Eponides tener E. tumidulus horvathi Fissurina kerguelenensis Parafissum'na groenlandica P. tectulostoma P. sp. Py'rgo vespertilio Triloculina trihedm Stetsom'a horvathi Finally, three deep-water samples collected west of Spitsbergen are generally similar to those from the deep-water samples of the Greenland Sea. Acknowledgments.-—We are grateful to the US. Naval Oceanographic Office for the opportunity of studying these samples. Many colleagues contributed advice and criticism in the course of our work, in particular, David L. Clark of the University of Wis- consin, C. Wylie Poag of the US. Geological Survey, and Charles T. Schafer of the Bedford Institute of Oceanography. Robert H. McKinney photographed the larger specimens. The smaller ones were photo- graphed by Ruth Todd, and all illustrations were re- touched by Doris Low. PREVIOUS STUDIES IN THE AREA Foraminifera have been studied from isolated areas in the Arctic regions for nearly 100 years. In an early assessment of foraminiferal faunas of the Arctic, Brady wrote, “The facts * * * appear to indi- cate that there is no very striking diminution in the number and variety of the Rhizopoda as we approach the North Pole” (Brady, 1878, p. 439). Three years later, in describing and listing the faunas from 6 samples from the west side of Novaya Zemlya and 10 samples from the shores of Franz Josef Land, he reported a total of 71 species (Brady, 1881). In the six samples from the west side of Novaya Zemlya, at depths between 100 and 400 m, a total of 54 species was reported, but no more than 32 species were ob- served in a single sample. In the 10 samples from around Franz Josef Land, taken at depths between 163 and 265 m, the combined fauna consisted of 51 species, and the richest sample there had 30 species. The assemblages reported by Brady contained many species as well as combinations of species identical with those found in the present suite of samples. One of his samples (sample G from 230 m, off Franz Josef Land) consisted almost entirely of specimens of Saccammma sphaem’ca. This feature is also char- acteristic of several of our Kara Sea samples. In these samples, however, the abundant form is Psam- PREVIOUS STUDIES IN THE AREA 13 TABLE 2.—Local'ity and depth of bottom-sediment samples from the Kara Sea, July 25—September 29, 1965 TABLE 3.—Locality and depth of bottom-sediment samples from the Greenland Sea, August 23—September 12, 1965 8:112?“ Latitude Longitude (12:5:12) 1 ____________ 72°11.0’ N. 57°10’ E. 499 13 ____________ 73°44.7’ 59°37’ 315 23 _______ _ 74°29.5' 62°06’ 320 29 _______ -_ 75°13.4' 68°34’ 362 41 ____________ 75°50.1’ 71°36° 223 53 ____________ 77“32.5' 71°36’ 223 _ 76°44.5’ 70°24’ 443 _ 77°32.0’ 67°00’ 356 57 ____________ 77°31.0' 61°50' 265 77 ____________ 78°03.4' 74°39' 362 90 ____________ 77°29.7’ 98°37' 82 102 ____________ 81°04.1' 87°32’ 340 106 ____________ 81°27.5' 97°34’ 265 107 ____________ 81°30.5' 87°39’ 420 108 ____________ 81°30.5’ 84°54’ 410 109 ____________ 81°30.6’ 82°15’ 423 110 ____________ 81°34.8' 79°52’ 203 112 ____________ 81°37.0' 75°20’ 421 113 ____________ 81°36.0’ 73°00’ 640 114 ____________ 81°42.3' 70a46' 631 115 ____________ 81°35.5' 67°32' 567 67°08’ 475 69°34' 566 82"05’ 268 83°58’ 298 83°59’ 315 84°01' 204 84°02’ 217 82°13’ 202 74°32’ 243 71°43’ 593 69"10' 549 66°48’ 498 64°15' 228 66°55’ 520 69°47’ 564 80°00.0’ 72°11’ 538 80°00.0’ 74°36’ 215 79°34.9’ 72°00’ 521 79°35.0’ 69°27’ 532 79°35.2’ 66°57’ 526 79°06.2’ 64°06’ 260 79°05.0’ 74°09’ 366 78°37.3’ 71°41’ 485 78°12.6’ 69°00’ 443 78°50.7’ 66°39’ 374 157 ____________ 78°33.0’ 63°38’ 346 mosphaem fusca, a species superficially similar to Saccammiha sphaem’ca. Shortly following Brady’s work, Goes prepared an illustrated catalog of the Arctic and Scandinavian species known at that time (Goes, 1894) and in- cluded with his synopsis a chronological summary of the various cruises and dredging excursions that had been carried out in the Arctic seas until that time. He pointed out that, even in spite of the various localities that had been searched, many new forms remained to be discovered. For a report on the Norwegian—North Atlantic Ex- pedition of 1876—78, Kiaer examined more than 100 samples, among which were 12 bottom samples from around Spitsbergen and 4 from near Jan Mayen Is- Sample Lati- Longi- Approx. Depth No. tude tude depth from 10g (meters) (fathoms) 70°54.8' N. 20°29.7' W. 330 180 70°56.8' 12°51' 660 360 71°53' 12°14' 2,250 1,230 72°21' 11°56’ 2,240 1,225 73°14.2' 11°42.5’ 2,855 1,560 73°16.5' 12°30.5’ 2,655 1,450 73°14’ 13°30’ 2,545 1,392 73°23' 18°03' 230 125 73°25.3’ 17°03' 330 181 73°26.5' 15°22' 2,195 1,200 74°15' 07°03’ 3,340 1,825 74°30’ 08°55’ 3,295 1,800 74°48' 10°34’ 3,110 1,700 75°17’ 11°22’ 1,940 1,060 75°35' 12°50’ 230 126 75°43' 13°27’ 240 132 75°51' 14°21' 260 142 75°48’ 15°16' 240 131 75°52' 15°17' 165 90 75°43.8’ 15°56’ 165 90 78°20.2' 00°42.5' 2,965 1,620 78°20.5’ 04°12' 1,645 900 78°18.5’ 05°40' 355 194 78°18.5’ 06°53’ 265 145 78°20’ 08°13’ 196 107 78°22’ 09°15' 248 135 78°21’ 10°43’ 205 112 78°19' 11°56’ 152 83 78°20’ 13°40’ 132 72 78°21.5' 14°26’ 82 45 80°00’ 04°15’ E. 1,170 640 80°00' 03°03’ 2,525 1,380 80°01’ 01°07.5' 3,200 1,750 76°57.5’ 08°01' W. 308 168 35 ____________ 76°51’ 07°10’ 322 176 37 ____________ 76°10.6’ 05°04' 2,930 1,600 land (Kiaer, 1899). From the composite of his 12 Spitsbergen samples, Kiaer reported 42 species, and from the 4 Jan Mayen samples, he found 39 species. His quantitative list of 166 species is typical of what is now known of the Arctic population; that is, sparse, erratic, and with a tendency toward strong dominance of certain species. He mentioned such dominating species as Saccammina sphaerica, Rhab- dammina abyssomm, and Truncatulina [= Cibicldes] lobatulus. Many of Kiaer’s species are undoubtedly identical with our species, though some appear under different generic names and a few under different specific names. Awerinzew (1911) reported the Foraminifera found in two samples from rather shallow water from the southern and eastern parts of the Kara Sea. His samples 2 and 3 from 37 and 38 m respectively are taken from much shallower water than any of our Kara Sea samples. Both his samples contained meager faunas, six and nine species respectively. Al- though reported under different generic or specific 14 FORAMINIFERA FROM THE KARA AND GREENLAND SEAS names, the following species probably appear in both Awerinzew’s and our assemblages: Species of chrinzew (1911) Species of this paper Reophax scarpiu'rus Montfort. Trochammina nana (Brady) . Flarilus labrudoricus (Dawson). Astrononivn gallowayi Loeblich and Tappan. Reophux scorpiurus Montfort _____ Haplophragmium nanum Brady ___ Nonionina scapha Fichtel and Moll_ Nonionina stelligcra d‘Orbigny ___ Haplophragmium cana’riensc d’Orbigny ______________________ Crihrastomoidcs jcffrcysi (Williamson). Palystomclla striatopmwtata Elphidium clavatum Cushman. Fichtel and M01] var. inccrta Williamson. Cassidulina lac’vigata d’Orbigny ___ Islandiella helenac Feyling-Hanssen and Buzas. Psammatodendron arborescc’ns Norman. Trochammina cf. T. grisea Earland. Hyperummina arboresccns Normani Trochammina nitz’da Brady ________ Stschedrina, in a number of papers, reported on the distribution of species in the Kara Sea (1936, 1938, 1958), Greenland Sea (1947, 1964a), and Arctic Basin (1964b). In a pioneer study of the Kara Sea foraminiferal fauna, Stschedrina (1936) summarized the results of analysis of the rich collections made during the years from 1929 to 1936 by two Russian expeditions into the region. She presented an annotated listing of 43 species found in the Polar Seas and included quantitative tables, in broad terms, showing their occurrences around North Land (nine samples be- tween 24 and 52 m) ; in the southeastern Kara Sea between Sverdrup Island and Dickson (six samples between 17 and 28 m) ; Shokalsky Strait, within the island group called North Land (six samples between 43 and 276 m) ; at Cape Cheluskina, the northern- most point of Taymyr Peninsula (two samples at 47 m); and Vilkitsky Strait between Cape Chelus- kina and North Land (eight samples between 100 and 206 m) . As is true of our present samples, most of these Kara samples had few species; those bordering North Land and from shallow depths around Sver— drup Island and Dickson averaged only slightly more than two species per sample. The richest samples were found in the two straits, but even there the assemblages were not very diverse, the maximum number of species per sample being 16 in Shokalsky Strait and 10 in Vilkitsky Strait. The dominating species were mostly agglutinated, with one excep- tion; namely the richest sample from a shallow loca- tion in Shokalsky Strait, where Planispim'na sphaem [Pyrgoella sphaem] and Cibicides sp. share dominance. Besides cosmopolitan species, the following species recorded by Stschedrina (1936) seem to be identical with those we have observed, though sometimes un- der different names: Hyperammina elongata Brady Rhabdammma abyssorum M. Sars Hyperammina arborescens Norman Reophax dentaliniformis Brady R. scorpiums Montfort Triloculina bucculenta (Brady) Planispi’rina sphaera d’Orbigny Cornuspira involvens (Reuss) E'lphidz'um incertum (Williamson) Cassidulina laevigata d’Orbigny Cibicides lobatulus (Walker and Jacob) In a summary report, Stschedrina (1938) judged that the Kara Sea foraminiferal fauna consisted of 102 species and divided her study area into eight regions, each characterized by certain species or groups of species from the three complexes of forms which compose the general population of the Kara Sea, namely: (1) species characteristic of shoal areas of cold seas, littoral zones and mouths of rivers, including species that can withstand consid— erable reduction of salinity; (2) cold-water arctic species widespread in the Kara Sea, including cosmo— politan species; and (3) boreal-arctic, boreal, and northern Atlantic species, as well as abyssal species from the Pacific and Atlantic Oceans, a group of species referred to as the “Atlantic complex.” In a preliminary summary of the foraminiferal fauna of the northern part of the Greenland Sea, Stschedrina (1947) recorded quantitatively the oc- currence of 91 species at 11 stations ranging in depth from 225 to 3,000 m. She recognized two complexes: (1) her previously described “Atlantic complex” of species, most of them abyssal, peculiar to the Green- land Sea and to certain other Arctic regions and (2) the “Arctic complex” of species, most of them eury- bathyal and widespread all over the Arctic. The samples upon which Stschedrina’s analyses were made include some from depths shallower than any of our samples. Nevertheless, the fauna she re- ported is very similar to our listing herein. Most of the species in our assemblages are those typical of the “Atlantic” and “Arctic” complexes. In 1958 Stschedrina reported on a. core of 97.8 cm of sediment obtained from the Kara Sea, the lower two-thirds of which contained Late Cretaceous and Paleocene Foraminifera. In the upper one-third of the core a typical Arctic fauna provides evidence of a thin layer of modern sediment overlying the bedrock. Two of her papers in 1964 list the faunas found in the northern part of the Greenland Sea (114 species) and in the Arctic Basin (162 species). PREVIOUS STUDIES IN THE AREA 15 In the Greenland Sea paper (Stschedrina, 1964a), the species are also recorded in separate check lists of agglutinated and calcareous species from around Spitsbergen, the Continental Shelf (5 samples from 130 to 225 m) and the Continental Slope (6 samples from 659 to 1,825 m) ; from the central part of the Greenland Sea (7 samples from 2,581 to 3,835 m) ; and from off Greenland, the Continental Shelf (12 samples from 51 to 259 m) and the Continental Slope (6 samples from 368 to 1,840 m). In her Arctic Basin paper, Stschedrina (1964b) divided the species into three ecologically significant groups: sublittoral, eulittoral, and abyssal-bathyal. The first two groups contain, respectively, 8 sparsely represented species and 27 well-represented species and constitute the “Arctic complex.” The abyssal- bathyal group of species includes 25 well-represented species of the “Atlantic complex.” She also plotted the occurrences of these 60 species in shelf and slope habitats around Spitsbergen and around Franz Josef Land and in lower flat and ocean-floor habitats of the central part of the Arctic Basin. Her “Arctic complex” of species is that main- ly occupying the sublittoral and eulittoral zones, and the “Atlantic complex” of species is that mainly oc- cupying the abyssal-bathyal zone. But in this group- ing of species there is much overlap; that is, not all the sublittoral species, such as Spiroplectammina bi— formis and Pateoris hauerinoides, are unknown on the continental slopes. Nor are all the eulittoral spe- cies, such as Saccorhizu, ramosa, unknown in both the shelf areas and the lower parts of the Arctic Ocean. Moreover, representatives of the abyssal-bathyal group of species are found at shallow depths as well as the deepest, but only four species are found ex- clusively on the floor of the Arctic Ocean. Nearshore species of several coastal areas of Spits- bergen were well documented by Nagy (1963) and Rouvillois (1966) and illustrated in the former re- port. Nagy reported 60 species from 45 samples at depths between 0 and 51 m. Rouvillois found 32 spe- cies between depths of 0 and 25 m. Distribution is erratic and patchy. Among species dominating in various samples were Astrononion gallowayi, Buccella frigida, Cas- sidulina crassa, C. islandica, Cibicides lobatulus, Elphz’dz’um clavatum, Pateom's hauem‘noides, Spiro- plectammma biformz's, and Tholosina bulla. Green (1960) discussed the ecology of Arctic For- aminifera and based his conclusions on cores of the central Arctic Ocean, taken between 433 and 2,760 In. His total assemblage consisted of 105 species of which he found 20 to be useful in depth zonation. He recognized four depth zones—shelf, slope, apron, and abyssal—and listed a few species as diagnostic of each zone. Those we have in common with his cen- tral Arctic Ocean material are: Cassidulina teretis, C. islandica, Cibicides lobatulus, and Elphidium bart- letti from the shelf; Troohammz’na mama and Cassidu- lina norcrossi from the slope; Epom'des tumidulus horvathi and Triloculina trihedm from the apron; and Epom'des tener, Quinqueloculma aknem‘ana, Stet- som‘a horvathi, and Cibicz’des wuellerstorfi [our C. bradii] in the abyssal zone. The above-mentioned species are not in all in- stances separable into the same depth zones. For example, Trochammina name is found chiefly in our shelf fauna; Quinqueloculz’na akneriana is absent from our deeper samples and is present only sparsely in our shelf fauna; and Epom'des tener and E. tu- midulus horvathi are found together in our samples from the deepest water. Because of its greater depth and its basinal rather than shelf origin, Green’s fauna (1960) has only a small proportion of its elements in common with our assemblages. Androsova (1962) reported quantitatively on the species present in a part of the Polar Basin, between the North Pole and northern Greenland and Spits- bergen. Seven short cores were studied, ranging in length from 4 to 20 cm, taken at depths between 3,767 and 4,395 m. The fauna is meager, consisting of 13 benthonic and 6 planktonic species, and the population is predominantly planktonic. Only five of the benthonic species are the same as those that we have from the deeper parts of the Greenland Sea. Some bottom sediments from the Kara Sea and around Franz Josef Land, obtained by several Rus- sian ships between 1953 and 1958, were quantitative- ly analyzed and their Foraminifera assemblages com- pared with those in some outcrops and Well drillings in the northern part of western Siberia (Basov and Slobodin, 1965). Pie diagrams (Basov and Slobodin, 1965, text figs. 2—18) show graphically the abun- dance, diversity, species composition, and dominance for several areas. For the three sampled depths around Franz Josef Land, results were as follows: Between 24 and 27 m Cibicides rotundatus Stsche- drina [probably equivalent to our C. lobatulus] is dominant and is accompanied by several species of Elphidium in the sublittoral zone. These two groups together compose nearly three-quarters of the abun- dant fauna. A much less abundant but more varied fauna was sampled between 20 and 80 m in the Tik— haya and Yuri Bay areas where Spiroplectammina biformis and H aplophragmoides sp. are dominant 16 FORAMINIFERA FROM THE KARA AND GREENLAND SEAS and are accompanied by various other agglutinated forms as well as by a few specimens of Cibicides, Cassidulz'na, and Elphidium. In the upper bathyal zone around Franz Josef Land, a moderately abun- dant and diverse fauna sampled between 220 and 500 m is not strongly dominated by any species, but Ade’rcotryma glomeratum, Haplophmgmoides sp., Proteom'na difllugiformis, and Spiroplectammma bi- formis combine to make up 59 percent of the assem— blage. The balance consists mostly of other aggluti- nated forms and of species of Elphidium, Cassidu- Zinc, and N om'onellimi [our Florilus]. In the northeastern part of the Kara Sea, bottom samples from 350, 70, and 40 m vary in abundance, but all show low diversity (seven, five, and eight species, respectively) but little uniformity. In the most northern sample, at 350 m, four species in the family Elphidiidae make up more than half the population; the balance is divided almost equally among species of Cassidulina, [our Islandiella], Vir- gulina, Globulimt, and Haplophmgmoides. The sam- ple from 70 m was moderately abundant in, and strongly dominated by, Eggerella advena (nearly 85 percent) . In the sample from 40 m, two species share dominance—Trachammma karica Stschedrina [our T. mama] and Globigem’na pachyderma (Ehren- berg) together making up 78 percent of the total population. Two bottom samples in the southwestern part of the Kara Sea at 90 and 63 m showed moderate di- versity (12—14 species), but no strong dominances. In both samples, Elphidium clavatum was the most abundant species. The other chief components of the faunas were additional species of Elphidium plus species in the genera Cassidulma [our Islandz'ella] and N onionelh’na [our Florilus]. In a sparse fauna represented by three bottom samples taken at depths of 23 to 40 m in the sublit— toral area of the southeastern part of the Kara Sea, the assemblage was moderately dominated by El- phidium orbiculare, and most of the remaining spe- cies fell under the genera Elphidium, Cassidulina, Trochammina, and Globigerina. This assemblage has developed in response to the outflowing of fresh- water from the Ob’ and Yenisey Rivers. The foraminiferal fauna of the Laptev Sea was sampled in 1963 and briefly recorded (Todd and Low, 1966). In the analysis of 33 bottom-sediment sam- ples, ranging in depth from 10 to 54 m, 16 arenace- ous and 24 calcareous species were found. Most of the samples contained a sparse fauna of between 1 and 5 species. The two richest samples, one at 22 m and another at 53 m, contained 18 and 19 species respectively. The assemblage of 40 species represents Stsche- drina’s sublittoral group of species, which she de- scribed (1959) as characteristic of the Continental Shelf, subject to seasonal fluctuations that are re- lated to a reduction in the salinity of bottom water. More than half the species are the same as those we have observed from the Kara Sea, but, of the domi- nating species in the Kara Sea, only three (Cribros- tomoides crassimargo, Reophax scorpiurus, and Trochammina mama) are present in the Laptev Sea. In general, the Laptev fauna lacks the large robust forms that are typical of the deeper water of the Kara Sea. Vilks (1969) studied the Foraminifera in the ice- covered seas of the Canadian Arctic, between ap- proximately lat 75°30’ and 77°30’ N. and long 109° and 116° W. In his quantitative analysis of samples taken between 17 and 458 m, he found two bathy- metric zones on the Continental Shelf. Their common boundary at about 200 m separated the upper zone of Arctic surface water, inhabited principally by arena- ceous species, from the lower zone of warmer and more saline water of Atlantic origin, inhabited prin- cipally by calcareous species. His combined assemblage of 78 species contained many species in common with our assemblages from the Kara and Greenland Seas but lacked, or had only rare representatives of, several of our larger and more robust arenaceous and porcellaneous species, such as Aschemonella scabm, Pelosina cylindrica, Planispim'noides bucculentus, Psammosphaera fusca, Pyrgo vespertilio, and Rhabdammina abyssomm. In a report on the Barents Sea, Digas (1971) studied the foraminiferal fauna of a small area in the central part of the sea. The study included 17 sta- tions located between about lat 74° and 76° N. and long 30° and 411/;0 E., at depths between 153 and 335 m. Fifty-four calcareous species and 25 arena- ceous ones are recorded, the arenaceous species being more abundant. The richest samples contain from 35 to 42 species (25 to 30 calcareous species and 10 to 12 arenaceous ones). Each of the samples is strongly dominated by one or several species, mostly by arena- ceous species. One sample (No. 19) consisted of 70 percent Adercotryma glomemtum. Conversely, one of the rich samples (No. 7) contains conspicuously fewer arenaceous species and specimens——21 calcare- ous and 11 arenaceous species—and the dominance is shared among Buccella frigida, Quinqueloculina sp., and Cibicides sp. PREVIOUS STUDIES IN THE AREA 17 In general, this Barents Sea fauna contains many species in common with the Kara and Greenland Sea faunas of comparable depths and, like them, is high- ly variable from station to station. Slobodin and Tamanova (1972, tables 2—7 on p. 25—30) made quantitative studies of the foraminifer- al assemblages in six Kara Sea cores ranging in length from 2.44 to 5.37 m. Four of these cores were from east of the southern end of Novaya Zemlya at depths between 108 and 372 m, and two were from the northern part of the Kara Sea between North Land and Franz Josef Land at 304 and 482 m (Slo- bodin and Tamanova, 1972, map on p. 31). Hence, these cores may be compared to our present samples. Analyses of these cores show rich assemblages in the top sample of each core, with but one exception, and these quantitative records give a fairly detailed pic- ture of the bottom fauna characteristic of this part of the Kara Sea, covering a distance of about 1,200 km. From these cores we can see the predominance of agglutinated forms, elphidiids, and cassidulinids, and the widespread dominance of Trochammma lcarica Stschedrina [our T. mama]. This species has a strong position of dominance in two of the cores, shares dominance with another species in two more of the cores, and is present but rare in the other two cores. Other species well represented in this part of the Kara Sea, as reported by Slobodin and Tamanova (1972) and present in our samples though some less abundantly, are: Adercotryma glomeratum Cassidulina islandica [:Islandiella] C. norcrossi Eggerella advena Elphz’dium clavatum Labrospira crassimargo [:Cm’brostomoides] Nom'onellma labmdorz’ca [:Flom'lus] Recurvoides lacvigatum Reophax scorpiurus Rhabdammina abyssorum Spiroplectammina bifo'rmis Textularia to’rquata The major species found by Slobodin and Tama— nova (1972) that were not found by us (or not identified by these names) are Alveolophragmium karaensis Stschedrina, Hyperammina bradyz’ Stsche- drina, Proteom'na atlantica ‘Cushman, Trochammm- ella bullata Hoglund, and Trochammmula fissum- perta Stschedrina. The number of species found by these authors, as well as their diversity, is compar- able with our present samples. In the same report, Slobodin and Tamanova also set down salinity and temperature tolerances for 44 selected nonagglutinated species. They then drew graphs representing interpreted changes in salinity, depth, and temperature in the upper (unconsoli- dated) parts of the cores they studied, and, for two cores, the lower (consolidated) parts as well. These graphs (Slobodin and Tamanova, 1972, text figs. 2 and 3, p. 32, 33) represent change from a shallow brackish sea to the present normal marine environ- ment of the shelf sea accompanied by cooling tem- peratures. All but one of the core graphs show this change to have been fluctuating. The indications of these earlier periods of shallow and brackish deposi- ' tion are chiefly a decrease of the species at the tops of the cores accompanied by significant differences in their proportions. Iqbal (1973) studied the sediments and Foraminif- era in 40 grab samples from M’Clure Strait, mostly at depths between 250 and 400 m. He recognized three thanatotopes: one exclusively arenaceous that decreases in number away from shore and that seems to prefer finer grained substrates; one predominant- ly calcareous that increases away from shore and is found on silty and sandy substrates; and a third thanatotope Characterized by a mixture of calcareous and arenceous species. Iqbal concluded that the distribution of the 74 indi- vidual species that he found did not fall into any definite patterns but was more typical of mixing such as might have resulted from extensive turbidity cur- rents and ice-rafting, which are the dominant means of sediment transport on the shallow continental shelf areas of the Arctic. Finally, in an unpublished 1967 University of Wisconsin master’s thesis by Sarah Stoll that was summarized by Andrew and Kravitz (1974), 34 of the same samples that we studied were analyzed statistically for their foraminifer content. These samples were restricted to the northern part of the Kara Sea (north of 76° N). All were taken within two north-trending open-ended troughs—St. Ann Trough near Franz Joseph Land and Voronin Trough near Severnaya Zemlya—that are separated by the shallow Central Kara Plateau upon which two small islands rise above the sea surface. Stoll based her analyses on the 19 most abundant species found in the samples, and our subsequent findings agree in general with her results: arena- ceous species are predominant over calcareous ones; individual samples are characterized by low diversity and high dominance of a single species, such domi- nant species being different from sample to sample. In addition, she noted that. in the deep troughs she studied, abundance appears to be directly propor- tional to bottom temperature and pH and inversely related to oxygen content, free nitrogen, and organic 18 FORAMINIFERA FROM THE KARA AND GREENLAND SEAS carbon. She concluded that other conditions, includ- ing depth, have no linear relationship with abun- dance and that this variable relationship may be due to the complexity of current patterns, which prevent bottom temperature from being inversely proportion— al to depth in the troughs. ANALYSES 0F FAUNAS KARA SEA In the Kara Sea we noted 85 species, only 10 of which were found as major components in more than one sample: Aschemonella scabra Cribrostomoides crassimargo C. subglobosus Globigerina pachyderma Hyperammina elongata Psammosphaera fusca Reophax nodulosus R. scorpiurus Saccorhim ramosa Trachammina nana Twelve additional species were found in signifi- cant numbers but each species was found in only one sample: Cornuspira involvens meiloculina ericsoni Dentali‘na baggi Elphidium orbiculm‘e Globigerina bulloides Globigc’rinita glutinata N om’onella turgida digitata Patellina corrugata Psammosiphonella crassatina Pullem'a bulloides Robertina arctica Trachammina contact The following 28 species have scattered occur- rences, as shown in table 1, and, with a few excep- tions (indicated by asterisks), are not abundant or dominating: Adercotryma glomeratum Ammodiscus gullmarensis Astronom'on gallowayi Buccella inusitata Cassidulina norc‘rossi *Cz'bicides lobatulus Cribrostomoides jeflreysi Elphidium clavatum Florilus labmdom‘cus *Islandiella helenae *I. islandica Jaculella acuta Melom’s zaandamae *Pelosina cylindm'w *Plam’spim’noides bucculentus Pyrgo williamsom' *Pyrgoella sphaera Recurvoides laevigatum Reophax arctica *Rhabdammina abyssorum R. discreta Saccammina difllugiformis Spiroplectammina biformis *Textulam'a earlandi T. torquata Trochammz'na cf. T. grisea T. cf. T. japom'ca T. quadriloba The remaining 35 species were found as single or rare specimens in one or a few stations in the Kara Sea: Angulogerina fluens Biloculinella globula Bulimina em'lz's Cornuspira planorbis Dentalina frobisherensis Eggerella advent), Elphidiella hannai Elphidium bartletti E. frigidum Fissum'na kerguelenensis F. marginata F. serrata Globobulimina auriculata Globulina glacialis H emisphaerammina marisalbi Hormosina sp. Hyperammina friabz'lis Lagcna hispidula L. laem‘s Laryngosigma hyalascidea Oolina melo Pateom’s hauerinoides Placopsilina bradyi Protoschista sp. Psammatodendron arborescens Pyrgo fornasinii Quinqueloculina aknem'oma Reophax dentali‘nifo'rmis R. guttifer Rosalind globularis Saccammina sphaerica Spirillina. vivipam Thurammina papillata Triloculina trihedra Trochammina sp. GREENLAND SEA In the Greenland Sea we noted 75 species, only 8 of which were found as major components in more than one sample: Cibicides bradii (deep) CribTOstomoides subglobosus Epom'des tener Globigem’na pachyde'rma Psammosphaera fusca (shallow) Pyrgo vespertilio ANALYSES 0F FAUNAS 19 Rhabdammina abyssorum Saccorhiza ramosa Found in significant numbers, but mostly in single samples, are Pelosma cylindrica, Pyrgo rotalaria, and Rhabdammina discreta. The following 29 species have scattered occur- rences, as shown in table 1, and, with a few starred exceptions, are not abundant or dominating: Ade’rcotryma glome’ratum Ammodiscus gull‘marensis Angulage’rina fluens Aschemonella scabm Buccella inusitata *Cibicides lobatulus *Cm’brostomoides crassimargo C. jeflreysi Elphidium clavatum E. frigidum E. orbiculare Epistominella em’gua (confined to deep area) Epom’des tumidulus lzorvathi (confined to deep area) Fissurina kerguelenensis Globigerina quinqueloba (confined to deep area) *Hyperammina elongata Islandz’ella helemze I. islandica Jaculella acute *Melom's zaandamae Pamfissurina groenlandica (confined to deep area) P. tectulostoma (confined to deep area) P. sp. (confined to deep area) *Reophacc scorpiurus Saccammina difi‘lugiformis (confined to shallow area) Stetsom’a howathi Triloculina trihedra (confined to deep area) *Trochammina mma (confined to shallow area) T. quadriloba (confined to shallow area) The remaining 35 species from the Greenland Sea were found as single or rare specimens in one or a few stations: - Astacolus planulatus Astronom'on gallowayi Bolivina rhomboidalis Cassidulina norcrossi C. subglobosa Cornuspira lacunosa Dentalina baggi D. decepta D. frobishe'rensis Elphidiella arctic!» Epom’des repandus Fischerina Sp. Fissu'rina marginata Florilus lab’radoricus Hormosina sp. Hyperammina, friabilis Lagena distoma L. hispidula Oalina hexagona 0. lineata 0. melo Psammatodendron arborescens Psammosiphonella crassatina? Pseudonom'on sp. Pullem‘a bulloides Quinqueloculina akneriana Recumoides laevigatum Reophaw guttife’r Textularia earlandi T. torquata Tolypammina schaudinm‘ Troohammina com'ca T. cf. T. grisea, T. cf. T. japom'ca Turrispz'rillina arctica COMPARISON OF THE KARA AND GREENLAND SEAS FAUNAS The combined faunas total 111 species, the two faunas having 50 species in common plus 36 species found exclusively in the Kara Sea and 25 exclusively in the Greenland Sea. Two comparatively abundant species (Reophax nodulosus and Spiroplectammina biformis) were among those found only in the Kara Sea. On the other hand, the Greenland Sea contains two different faunas, the one from shallower water is quite similar to that of the Kara Sea, and the one from deeper water comprises in large part several species not found, or found only rarely, in the Kara Sea, such as Epistominella exigua, Epom'des tener, E. tumidulus Izorvathi, Cibicides bradii, Pyrgo ves- pertilio, Triloculina trihedra, and the three species of Pamfissurina. The fauna in the Kara Sea seems not to be signifi- cantly different from that of comparable depths re- ported from other parts of the Arctic. It is, as al- ready pointed out, very similar to that of the shal- lower samples from the Greenland Sea. The assem— blages in the deeper samples from the Greenland Sea, likewise, are typical of those from comparable depths in the Arctic Basin. Comparisons with Antarctic assemblages of com- parable depths, however, show some generic simi- larities, but few species, other than cosmopolitan ones, are the same in the two regions. DIVERSITY AND DENSITY Diversity can be taken as a measure of different features of a fauna. Most simply, it can be measured as the number of species in an assemblage; that is, 5 species or 50 species. But this measure of diversity does not take into account different abundances and is extremely dependent upon size of sample. Gibson and Buzas (1973) gave as an example one assem- blage of five species having its species in the propor- tions of 0.90, 0.04, 0.03, 0.02, and 0.01 and another 20 FORAMINIFERA FROM THE KARA AND GREENLAND SEAS having proportions of 0.46, 0.26, 0.16, 0.09, and 0.03. The second example would be regarded as having a greater diversity. A sample in which individuals are evenly distributed among the species gives a higher diversity value than a sample strongly dominated by one species, and the addition of rare species changes the diversity value only slightly. Although the total number of species is the sim- plest measure of diversity, such a measure is ex— tremely dependent upon size of the sample. For pre- cise measurement of diversity, such as discussed by Buzas and Gibson (1969), it is necessary to work with a standard-size sample (or one that can be pro- rated to a standard size) and to determine, by split- ting if necessary, the total population. An approximate measure of diversity can be taken as the number of species whose proportions total 95 percent of the total population (Walton, 1964, p. 213) or 90 percent (P-oag, 1975, oral commun.) Al- though our samples are not of uniform size and have not been picked clean, we have chosen to record a crude approximation of diversity by the latter meth- od for several of our samples. Most of our samples are moderately to strongly dominated by one or sev- eral species. The few that are not so dominated usually have a larger numb-er of species, as well as a greater diversity. The following tabulation lists five of the samples of greater diversity in order of num— ber of specimens mounted: Number of species making up 90 percent of the population Total number of species Samples of this study Kara 77 _________ 22 15 Kara 122 ________ 21 11 Greenland 3 ______ 19 10 Kara 106 ________ 25 15 Greenland 16 ____ 24 19 Slobodin and Tamanova (1972) recorded quanti- tatively the specimens they found in six cores in the Kara Sea. With only one exception, they found their richest assemblages in the top sample of each core. For comparison with our samples, we have calcu- lated an approximation of the diversity for the top sample of each of their cores, tabulated below: Number of species Samples of Slobodin . making up and Tamanova (1972) T°ta1 “umber (c... .0... “f .. .12. amt... 5 __________ 22 11 27 __________ 26 12 40 __________ 24 13 104 __________ 7 5 153 __________ 21 13 175 __________ 21 11 D. L. Clark (Jan. 6, 1977, written commun.) pointed out that density figures can be strongly bi- ased by shock waves preceding piston coring devices that blow away 10 to 25 cm of sediment from the surface where the coring device makes contact, so that the modern living population of the sea bottom is not represented in the core tops. This bias has been recognized by comparison between core tops from piston cores and those from box cores where the effects of shock waves are not felt. Even with this allowance, foraminifer populations on the floor of arctic seas are less dense than those in most other regions. In discussing Foraminifera population densities of the Arctic Ocean, Clark and others (1975, p. 63) calculated an approximate figure of 63 benthonic in- dividuals per square meter as an average. Further speculations regarding lifespan, under conditions not conducive to reproduction of Foraminifera, led these authors to arrive at the figure of two live individuals per square meter during times of faunal scarcity (Clark and others, 1975, p. 64). They further sug- gest that this population density may be approxi- mated spatially by one cow in 1,440 acres of pastureland. During times of maximum population the figure may rise to as much as 280 live individuals per square meter, still far from an abundant count when compared with the average density of 10,000 tests per square meter on the outer shelf of the Gulf of Mexico (Loeblich, Tappan, and others, 1964, p. C119). Thus, the Arctic regions appear to be very sparsely settled with Foraminifera. This general rule of increase in density and di- versity has exceptions from the Arctic to the tropics. Gibson and Buzas (1973, p. 217) found low diversi- ties south of Nova Scotia, in the Gulf of Maine, and on Browns and Georges Banks as well as in delta areas of the Gulf of Mexico; they attributed the anomalous figures to the environmental regimes be- ing different from adjoining areas. SUMMARY The typical fauna known from shelf seas of the Arctic regions is well represented in the northern and western parts of the Kara Sea and in the north- ern part of the Greenland Continental Shelf. Its dis— tinguishing characteristics are its sparseness, its erratic distribution, its low diversity, and the strong dominances present in many of the samples. The benthonic Foraminifera that compose the bulk of the fauna are almost exclusively agglutinated and most— ly large and robust. In addition, the ubiquitous FAUNAL REFERENCE LIST 21 planktonic species of the Arctic (Globigerma pachy- derma) and various large robust miliolids make up most of the balance of the assemblage. The faunas in 17 samples from the deeper areas beyond the Continental Shelf in the Greenland Sea, on the other hand, are distinctly different from the Continental Shelf faunas. Although they share sparseness, erratic distribution, and low diversity with the shelf faunas, and have half of their species in common, their individual samples seem not to be as strongly dominated by one or several species as the shelf samples are. Moreover, the large aggluti- nated Foraminifera do not occupy as prominent a position in these deeper sediments. Instead, smaller calcareous forms are characteristic. FAUNAL REFERENCE LIST The following alphabetical list of species will fa- cilitate reference to the original description or to a descriptive or systematic treatise where each species is discussed. For each species that is illustrated, a reference to the plates is included. The samples in which each species was found may be determined by referring to table 1. Adercotryma glomeratum (Brady). Loeblich and Tappan, 1953, p. 26, pl. 8, figs. 1—4. (Pl. 1, fig. 8). Relatively small compact form distinguished by its longer dimension being parallel with its axis of coiling, and its aperture scarcely discernible. Ammodiscus gullmarensis Hoglund. Todd and Low, 1967, p. 14, pl. 2, fig. 9. (P1. 1, fig. 4.) A minute and fragile species. orange in color. Angulogerina fluens Todd. Todd and Low, 1967, p. 30, pl. 4, fig. 5. Aschemonella scabra Brady, 1879, p. 44, pl. 3, figs. 6, 7. (Pl. 1, fig. 20.) In this genus the axis of the test is branching and ir- regular. The chambers are irregularly bulbous. The wall is relatively thin and fragile, coarse and rough or fine and smooth, depending on the coarseness of the sediment in which the animal lived. Each chamber has multiple aper- tures, or broken—off connections to other chambers. The species is most often represented by disjointed segments. Brady (1884, p. 272—273) mentioned that the long, many jointed tests are flexible in the fresh condition but become brittle, especially at the stoloniferous tubes between cham- bers, upon drying. Bathymetry rather than geography ap- pears to be the governing factor in the distribution of Aschemonella. Brady reported the genus in the North and South Atlantic and the North and South Pacific at an average depth of 1,800 fathoms (extremes were 210 and 2,900 fathoms). Astacolus planulatus Galloway and Wissler. Todd and Low, 1967, p. 22, pl. 3, fig. 5. Astrononion gallowayi Loeblich and Tappan, 1953, p. 90, pl. 17, figs. 4—7. Biloculinella globula (Bornemann). Todd and Low, 1967, p. 20, pl. 2, fig. 14. A large glossy brown specimen with an apertural flap that fills the aperture. Balim’na rhomboidalis (Millett). Cushman, 1937, p. 138, pl. 18, fig. 7. A cosmopolitan species. Buccella inusitata Andersen, 1952‘, p. 148, pl., figs. 10, 11. Bulimina exilis Brady. Loeblich and Tappan, 1953, p. 110, pl. 20, figs. 4, 5. (P1. 2, fig. 3.) This minute glassy species looks quite similar to speci- mens in the Arctic that have been referred to Virgulina cf. V. complanata (Phleger, 1952, pl. 14, figs. 15, 16) and to Cassidella complanata (Vilks, 1969, pl. 3, fig. 18) and, in fact, all three may be the same. The critical structural difference is that Bulimina is triserial throughout; Cassi- della is triserial initially, becoming biserial and slightly twisted; and Virgulina is biserial and twisted throughout. These are transitional distinctions that may not hold true. Cassiduh‘na norcrossi Cushman. Todd and Low, 1967, p. 37, pl. 5, fig. 11. At a superficial glance, this species can be confused with a species of Lenticulina. However, the loop-shaped aperture is diagnostic. Cassidulina subglobosa Brady, 1884, p. 430, pl. 54, fig. 17. A cosmopolitan species. Cibicides bradii (Tolmachofi‘). Planulina bradii Tolmachofi'. Barker, 1960, p. 192, pl. 93, fig. 8. Similar to Planulina wuellcrstorfi (Schwager) but thick- er and not evolute on the umbilical side. Compared to Cibi- sides rugosa (Phleger and Parker, 1951, p. 31), which Barker suggested might be a synonym, these are less convex 0n the nonspiral side, and the rugose ornamentation is less strongly developed. The generic distinction between Plann- li’rza and Cibicides appears to be that the former is par- tially evolute rather than involute on the umbilical side, and that it is more strongly compressed than Cibicides. But both these morphologic features are gradational, and even some specimens of a single species could be placed in either genus. The present specimens are closer to Cibicides than to typical Planulina. Cibicides lobatulus (Walker and Jacob). Todd and Low, 1967, p. 34, pl. 5, figs. 1, 2, 4. Cornuspira involvens (Reuss). Todd and Low, 1967, p. 21, pl. 2, fig. 11. (Pl. 2, fig. 18.) Cornuspi’ra lacunosa Brady, 1884, p. 202, pl. 113, fig. 21. (Pl. 2, fig. 19.) This species striations. Cornuspira plano'rbis Schultze. Todd and Low, 1961, p. 15, pl. 1, fig. 9. A cosmopolitan species, but more characteristic of shal- low than deep water. Genus Cribrostomoides Cushman, 1910 The most comprehensive history of the genus Cribrosto- moides was given by Frizzell and Schwartz (1950). In addition to outlining the complex taxonomic problem, they illustrated the range of variation in the aperture. We agree that typically the aperture is an elongate slit near the base, but within the face, of the last-formed chamber. Later irregularities may develop in the apertural lip, or within the elongate slit, simulating multiple apertures. This phenomenon occurs commonly in the type species Cribrostomoides subglobosus (G. O. Sars) but has not is characterized by crude longitudinal 22 been reported in other species such as C. crassimargo (Norman). Cribrostomoides Cushman, emend. Todd and Low Test free, involute, planispiral-streptospiral, symmetri— cal to asymmetrical; periphery rounded; chambers simple, increasing in size as added; wall nonalveolar, arenaceous, fine to coarse grained; aperture interio-areal, elongate slit with upper and lower lips of finer material which may touch at intervals making a series of irregular openings. The principal refinement to our emendation is the test’s inclination to be asymmetrical. The original designation of Crib’rostomoides Cushman (1910, p. 108) differed from Haplophragmoides Cushman (1910, p. 99) only in its aper- tural characters. Loeblich, Tappan, and others, (1964, p. C225) also gave this as the only distinguishing feature with no further diagnosis. However, all species we have studied within the genus have a lack of symmetry in their coiling. The asymmetry grades from a slight warping tendency in the axis of coiling in specimens of C. crassima’rgo (Norman) to strep— tospiral coiling in end forms of C. subglobosus (G. O. Saris), the type species. This is evident not only in thin section (Henbest, 1931, pl. 12, fig. 2 [Cushman Colln. No. 24771]) but also in exterior appearance of the umbilici, which may be unequal. In the more twisted individuals, one umbilicus is flush and the other is slightly depressed. In his 1931 study of wall structure, Henbest illustrated thin sections of “Cribrostomoides bradyi Qushman” (pl. 12, figs. 1, 2), and his figure 1 has been republished several times to illustrates the lack of subdivision of the chambers (Maync, 1952, text fig. B2; Loeblich, Tappan, and others, 1964, text fig. 136.2). Although Henbest’s figure 2 revealed the tendency to streptospiral coiling, this feature was neglected by subsequent authors in their consideration of generic characters of Cm'brostomoides. Echols (1971, p. 162) noted the coiling abnormalities in his suite of specimens of Cribrostomoides subglobosus from the Antarctic. We do not agree, however, that the degree of twist in Cribrostomoides warrants suppressing the more contorted genus Recurvoidcs Earland, 1934, as was recom- mended by Echols. Our reason for maintaining both Cribrostomoidcs and Recurvoz'des as distinct genera is that the type of coiling is fundamentally difl’erent. Recurvoides was originally de- scribed as consisting of two planispiral and partially em- bracing convolutions set at approximately 90° from each 'other so that the edge of the earlier whorl remains as a bulge from one umbilicus of the later whorl. Good illustra- tions of the type species of both genera by Loeblich, Tappan, and others, (1964)—-Cribrostomoidcs subglobosus (fig. 136.1, USNM 12657a) and Recurvoides contortus (fig. 136.9, USNM 640980)—c0nvincingly show their distinctions. Cribrostomoides crassima’rgo (Norman). Todd and Low, 1967, p. 15, pl. 1, fig. 24. Some of our specimens are attached to Psammosphaera fusca, or it may be that specimens of P. fusca were incor- porated in the wall as sand grains would be. Cribrostomoides jeflreysi (Williamson). Todd and Low, 1967, p. 15, pl. 1, fig. 21. (Pl. 1, fig. 3.) A delicate, thin-walled species with inflated chambers, strongly depressed umbilicus, and broad low aperture. Cribrostomoides subglobosus (G. O. Sars). (Pl. 1, fig. 7.) Synonymy: FORAMINIFERA FROM THE KARA AND GREENLAND SEAS Cribrostomoides bmdyi Cushman. Henbest, 1931, pl. 12, figs. 1, 2. Recumoides subglobosus (G. O. Sars). Uchio, 1960, p. 52, pl. 1, figs. 26, 27. [See complete synonymy.] Cribrostomoidcs subglobosum (G. O. Sars). Loeblich and Tappan, 1964, p. 225, figs. 136.1, 136.2. Echols, 1971, p. 162, pl. 3, figs. 8, 9. Haplophragmium latidorsatum Bornemann. Flint, 1899, p. 276, pl. 20, fig. 1. Test free, nearly circular, involute, planispiral-strepto- spiral, umbilical area may be slightly deeper on one side depending on degree of twist, periphery rounded; cham- bers simple, not subdivided, increasing in size as added, about six visible in last coil; sutures straight, mostly flush in early part, slightly depressed between later chambers; wall generally of firmly cemented fine sand and a few coarser clear quartz grains, surface irregular but smoothly finished; aperture an interio marginal slit, short, curved, with lip composed of fine cementing material, slit becoming longer in larger specimens with tendency of lip to seal intermittently, simulating multiple apertures. Cruciloculina em’csoni Loeblich and Tappan, 1957, p. 234, pl. 74, figs. 34. (P1. 2, fig. 13.) Dentalina baggi Galloway and Wissler. Todd and Low, 1967, p. 22, pl. 3, figs. 10, 11. Dentalma decepta (Bagg). Todd and Low, 1967, p. 22, pl. 3, fig. 6. Dentalma frobisherensis Loeblich and Tappan, 1953, p. 55, pl. 10, figs. 1—9. Eggerella advena (Cushman). Loeblich and Tappan, 1953, p. 36, pl. 3, figs. 8—10. This shallow-water species is rare in our samples, most of which were taken from water too deep for it. Elphidiclla arctica (Parker and Jones). Todd and Low, 1967, p. 34, pl. 4, fig. 15. Elphidiella hamwi (Cushman and Grant). Cushman, 1941, p. 35, pl. 9, figs. 5, 6. The taxonomy of this species, of which we have only one worn and orange-stained specimen, is not firmly estab- lished (see Hopkins and others, 1974, p. 459, 461). Their suggestion (table 3 on p. 454) that it is presently re- stricted to the Pacific side of the Arctic is not supported by the occurrence of the similar if not identical species Elphidiella tumida Gudina in middle and late Pleistocene beds of western Siberia (Gudina and Evserov, 1973, p. 107, pl. 14, fig. 3; pl. 15, figs. 1, 2). Elphidium bartletti Cushman. Loeblich and Tappan, 1953, p. 96, pl. 18, figs. 10—14. Elphidium clavatum Cushman. Todd and Low, 1967, p. 33, pl. 4, figs. 16, 17. Elphidium frigi’dum Cushman. Todd and Low, 1967, p. 33, pl. 4, figs. 9, 10. Elphidium orbiculare (Brady). Loeblich and Tappan, 1953, p. 102, pl. 19, figs. 1-4. Epistominella exigua (Brady). Todd, 1965, p. 30, pl. 10, fig. 1. (PI. 2, fig. 11.) This minute species appears to be widespread in deep waters of both polar and equatorial regions. Eponidcs repandus Montfort. Todd, 1965, p. 20, pl. 7, figs. 3, 4. The one specimen we have of this widespread species is the compact repandus-form. It is broken and shows the effect of some boring predator. FAUNAL REFERENCE LIST 23 Epom'des tenor (Brady). Vilks, 1969, p. 50, pl. 3, fig. 16. (PI. 2, fig. 10.) This widespread species is characteristic of deep waters. It is smooth and polished, unornamented, and very neatly constructed. The sutures meet in a star pattern at the center of the ventral side. The dorsal sutures, also, are radiating, not slanted. The aperture is bordered by a raised rim. Epom'des tumidulus homathi Green, 1960, p. 71, pl. 1, fig. 5. (P1. 2, fig. 7.) Test minute for the genus, dorsally high spired, ven- trally open at the umbilicus; periphery rounded and lobu— lated; chambers inflated, very gradually increasing in size as added, six to eight composing the final whorl; sutures distict, slightly indented, radiating, not oblique; wall smooth, polished, brownish-orange in color, irridescent; aperture inconspicuous under the ventral edge of the final chamber. Greater diameter 0.11—0.23 mm; height 0.06— 0.10 mm. This Arctic form seems closely related to Brady’s species described as Truncatulina tuvmidulus from 2,740 fathoms, off the Canaries. It is similar in almost all respects, even to the brownish color. It differs chiefly in having more chambers per final whorl, in the ventral umbilicus being more widely open, and in lacking limbation of the early dorsal sutures. Fischerina sp. (Pl. 2, fig. 12.) The generic separation of Fischcrinella from Fischcrina on the basis of the coiling being trochospiral instead of planispiral seems inappropriate to us. Hence, We place the involute-evolute specimen we have in Fischerina. It is a thick but fiat-coiled form in which only a small bulge of the initial coil shows at the center of the evolute side. Seven chambers comprise the final whorl. Fissurina kerguclenensis Parr, 1950, p. 305, pl. 8, fig. 7. (Pl. 2, fig. 9.) This Antarctic species is found also in the Arctic. Fissurina marginata (Montagu). Loeblich and Tappan, 1953, p. 77, pl. 14, figs. 6—9. Fissum'na serrata (Schlumberger). Loeblich and Tappan, 1953, p. 78, pl. 14, fig. 5. Florilus Iabradoricus (Dawson). Todd and Low, 1967, p. 35, pl. 5, fig. 9. Globigerina bulloides d’Orbigny. Parker, 1962, p. 221, pl. 1, figs. 1—8. Globigerina pachyderma (Ehrenberg). Parker, 1962, p. 224, pl. 1, figs. 26—35; pl. 2, figs. 1—6. Globigerina qui'nqueloba Natland. Parker, 1962, p. 225, pl. 2, figs. 7—16. Globigcrinita glutinata (Egger). Parker, 1962, p. 246, pl. 9, figs. 1—16. Globobulimina auric‘” (Bailey). Todd and Low, 1967, p. 26, pl. 3, fig. 38. Globulina glacialis Cushman and Ozawa. Cushman, 1948, p. 50, pl. 5, figs. 15, 16. Hemisphaerammina marisalbi (Stschedrina). Iridia maris— albi Stschedrina, 1962, p. 57, text figs. 4, 5. Specimens formerly called Webbinella are placed in the genus Hemisphavrammina that was erected when it was found that the type species of Webbinella was in reality an attached polymorphinid. H. marisalbi, described from the White Sea, was originally placed in the genus Iridiella, which, like “Webbinella,” consisted simply of a thick- Walled, agglutinated hemispherical chamber attached to a rigid support. Our material consists of two adjacent speci- mens, orange and rather coarse grained, attached to a broken fragment of an arenaceous tube. Hormosina sp. of Parker, 1952, p. 395, pl. 1, figs. 8, 9. (Pl. 1, fig. 15.) Parker reported and illustrated a rare species found ofl" Portsmouth, N.H., consisting of 3 or 4 chambers. We believe We have the same species occurring very rarely in both seas. Its two or three globular chambers are joined by tightly constricted necks, and the neck of the final chamber is slightly drawn out. This species is similar to Reophaw guttifer, but its chambers are more globular and less separated from one another, and the wall is built of finer grains. Hyperammz‘na elongata Brady. Loeblich and Tappan, 1953, p. 19, pl. 1, fig. 6. (P1. 1, fig. 18.) Most of our specimens of this species lack the bulbous initial end. But the smoothly finished wall in which angular and moderately coarse grains are set in a fine orange matrix is easily recognizable even in small broken fragments. In his discussion of this species in the Chal- lenger Report, Brady (1884, p. 257, pl. 23, figs. 4, 7—10) included both rough-surfaced and smooth, polished ones in his concept of the species. Since then, others have sepa— rated these two kinds into H. elongata for the rough—sur- faced ones and H. laevigata for the smooth, polished ones. Hoglund (1947, p. 66—68, text figs. 22—31) presented a convincing argument for distinguishing between these two species. Our present material seems inadequate for clear separation. Hence, We use H. elongata for this slender tubular species that has a thin hard wall. Hyperammina friabilis Brady, 1884, p. 258, pl. 23, figs. 1—3, 5, 6. This species is large, stout, and has a thick Wall of rough and friable texture. Genus Islandiclla Norvang, 1958 The distinction between Cassidulina and Islandiella has been clarified by Feyling-Hanssen and Buzas (1976); namely, that Islandiella possesses a free tongue, the exten- sion of the internal tooth, that projects out of the aper- ture, rather than a platelike lip attached to the base of the aperture from which there is no connection back to the aperture of the preceding chamber. Islamliella helenae Feyling-Hanssen and Buzas, 1976, p. 155, text figs. 1—4. Studies by Feyling—Hanssen and Buzas (1976) show that the widespread Arctic species reported as Cassidulina teretis Tappan (Loeblich and Tappan, 1953, p. 121, and many other authors) is not the same as the types of Cas— sidulina teretis from the Pleistocene of northern Alaska The modern Arctic species belongs in Islandiella, but the Pleistocene one is a true Cassidulina. Islandiella islandica (Norvang). Loeblich and Tappan, 1953, p. 118, pl. 24, fig. 1. Our specimens, ranging from 0.16 to 0.19 mm, are some- what smaller than normal for this species. Vilks (1969, p. 49) found this species absent in depths shallower than about 200 m. Jaculella acuta Brady, 1884, p. 255, pl. 22, figs. 14—18. (Pl. 1, fig. 17.) Jaculella differs from Hyperammina in being tapering rather than cylindrical. Otherwise, they are quite similar and have the same kind of smooth and hard wall surface. In some specimens the axis of the test is arcuate; in others, straight. 24 FORAMINIFERA FROM THE KARA AND GREENLAND SEAS Lagcna distoma Parker and Jones. Todd and LOW, 1967, p. 24, pl. 3, fig. 18. Lagena hispidula Cushman, 1913, p. 14, pl. 5, figs. 2, 3. This cosmopolitan species differs from L. laem's in that the greatest diameter is midway of the chamber rather than toward the base and the body of the test does not merge into the long slender neck. From the Arctic species, L. flatulenta. Loeblich and Tappan, it dilfers in its Wall surface being finely hispid instead of smooth hyaline. Lagena laevz’s (Montagu). Todd and Low, 1967, p. 24, pl. 3, fig. 17. (Pl. 2, fig. 1.) Laryngosigma hyalascidia Loeblich and Tappan, 1953, p. 83, pl. 15, figs. 6—8. (Pl. 2, fig. 2.) Melom's zaandamae (van Voorthuysen). Nonion zaandamae (van Voorthuysen). Loeblich and Tappan, 1953, p. 87, pl. 16, figs. 11, 12. (Pl. 2, fig. 8.) Nonionella turgida digitata Norvang. Todd and Low, 1967, p. 36, pl. 5, fig. 8. Oolma hexagona (Williamson). Loeblich and Tappan, 1953, p. 69, pl. 14, figs. 1, 2. Oolina lineata (Williamson). Loeblich and Tappan, 1953, p. 70, pl. 13, figs. 11—13. Oolina melo d’Orbigny. Loeblich and Tappan, 1953, p. 71, pl. 12, figs. 8—15. Parafissm'ina grocnlandica (Stschedrina). Androsova, 1962, p. 108, text fig. 3. (Pl. 2, fig. 6.) Parafissurina tectulostomu Loeblich and Tappan, 1953, p. 81, pl. 14, fig. 17. (Pl. 2, fig. 5.) Parafissurina sp. (Pl. 2, fig. 4.) Test compressed, circular in outline except for the pro- truding aperture, moderately inflated; periphery subacute; wall smooth, opaque; aperture hooded, as typical of this genus. At first glance this could be one of the several species of Fissm'ina that are characteristically found in the Arc-tic seas. Patellina corrugata Williamson. Loeblich and Tappan, 1953, p. 114, pl. 21, figs. 4, 5. Pateom‘s hauerinoides (Rhumbler). Loeblich and Tappan, 1953, p. 42, pl. 6, figs. 8—12; text figs. 1A, B. A quinqueloculine Miliolinella (:Scutuloris) without an apertural flap. In classifying miliolids, apertural char- acters seem to be more important than type of initial coiling. Pelosina sp. Rare specimens, in which a thin flexible chitinous lining of an elongate tube, coated loosely with sand, collapses when dry into a sandy ribbon. Placopsilina bradyi Cushman and McCulloch, 1939, p. 112, pl. 12, figs. 14, 15. A cosmopolitan species. Planispirinoides bucculentus (Brady). Parr, 1950, p. 287, pl. 6, figs. 1—6; text figs. 1—5. (Pl. 2, fig. 17.) Protoschista sp. A branching Reophax, our specimen is large, rugged, and coarse grained. Psammatodendron arborescens Norman. Barker, 1960, p. 58, pl. 28, figs. 12, 13. Slender, irregular, finely arenaceous tubes. Psammosiphonella crassatina (Brady). Astro‘rhiza Massa- tina Brady, 1884, p. 233, pl. 20, figs. 1—9. Avnimelech (1952, p. 64) erected Psammosiphonella to include certain species formerly placed in the tubular genera Bathysiphon, Marsipella, Astro’rhiza, and Rhab- dammina. Psammosiphonella differs from the first two of these genera in that the wall is composed of mineral grains, mostly quartz, instead of sponge spicules. It differs from the other two genera in lacking radiating arms. Whether or not these distinctions are valid remains to be seen, but that question is beyond the scope of this study. Nevertheless, it seems convenient to use this generic name for the friable species originally included under Astrorhiza, which was described from dredg‘ings at 640 fathoms in the Faro'e Channel. This species differs from other species of Astrorhizar in lacking distinct arms. Our specimens are large (4—5 mm), coarse-grained, and so loosely cemented and fragile that it is impossible to determine the size of the living cavity, the wall thickness, and Whether the wall was solid or labyrinthic‘, and whether both ends of the tube were open. Psmmnosphaera fusca Schulze. Brady (part), 1884, p. 249, pl. 18, figs. 1, 5—8. This species normally consists of a single arenaceous sphere, but specimens may be attached to foreign objects or even to each other. Its rough but firm surface, smoothly finished inside, is like that of Saccammina sphaerica M. Sars from which it difi’ers in lacking a defiinite aperture. It appears to be cosmopolitan in deep waters. Pscudononion sp. This tiny, compact but inflated form of about seven chambers has a depressed and open umbilicus. Greater dimension 0.17—0.23 mm. Pullem‘a bulloides (d’Orbigny). Todd, 1965, p. 48, pl. 18, fig. 6. Py’rgo fornasinii Chapman and Parr. Barker, 1960, p. 4, pl. 2, fig. 7. (Pl. 2, fig. 16.) This circular Pyrgo has a Wide and almost noncurving flap filling the aperture that results in a narrow elongate apertural slit. The test is large, well-rounded, and plump. Pyrgo rotala‘ria Loeblich and Tappan, 1953, p. 47, pl. 6, figs. 5, 6. (Pl. 2, fig. 20.) Pm’go vcspertillio (Schlumberger). Todd and LOW, 1967, p. 21, pl. 2, fig. 24. (Pl. 2, fig. 21.) Pyrgo williamsoni (Silvestri). Loeblich and Tappan, 1953, p. 48, pl. 6, figs. 1—4. (Pl. 2, fig. 14.) Pyrgoclla sphaera (d’Orbigny). Todd and Low, 1967, p. 21, pl. 2, fig. 20. (Pl. 2, fig. 22.) Quinqueloculina akneriana d’Orbigny. Todd and Low, 1967, p. 18, pl. 2, fig. 22. Recurvoides laevigatum H6glund, 1947, p. 150, pl. 11, fig. 6; text figs. 117—119. Test minute for the genus, compressed, periphery rounded, not lobulated; chambers indistinct, not inflated, five or six making up the final whorl; sutures indistinct, straight not much indented; wall composed of rather large grains for the small size of the entire test, smoothly finished, polished orange in the early part of the test, clear later; aperture not observed in the unbroken final chamber, a very small opening into the penultimate chamber is ob- servable near the base of the septa in two specimens in which the final chamber is broken. Greater diameter 0.20 mm; thickness 0.10 mm. Reophax arctica Brady. Loeblich and Tappan, 1953, p. 21, pl. 1, figs. 19, 20. Reophax dentaliniformis Brady, 1884, p. 293, pl. 30, figs. 21, 22. A more delicate species than R. scorpiu’rus Montfort and having a straight, not curved, axis. FAUNAL REFERENCE LIST 25 Reophax guttifer Brady. Brady, 1884, p. 295, pl. 31, figs. 10—15. (Pl. 1, fig. 14.) Reophax nodulosus Brady, 1884, p. 294, pl. 31, figs. 1—9. (Pl. 1, fig. 16.) Reopham scorpiurus Montfort. Todd and Low, 1967, p. 14, pl. 1, figs. 13, 14. Rhabdammina abyssorum M. Sars. Brady, 1884, p. 266, pl. 21, figs. 1-13. (Pl. 1, figs. 13, 19.) Built of fine to coarse sand grains, the surface is rough but firmly cemented. Rhabdammina discreta Brady, 1884, p. 268, pl. 22, figs. 7—10. (Pl. 1, fig. 12.) The surface is identical with that of R. abyssorum M. Sars but the test shows constrictions. Robertina arctica d’Orbigny. Cushman, 1948, p. 61, pl. 6, figs. 16—18. Rosalina globula’m’s d’Orbigny. Douglas and Sliter, 1965, p. 155, pl. 2, fig. 2; pl. 3, figs. 1—5; text fig. 2. Saccammina difj‘lugiformis (Brady). Reophaoc difflugiformis Brady, 1884, p. 289, pl. 30, figs. 1—5. Our specimens are built of moderately coarse grains. Saccammina sphaerica M. Sars. Brady, 1884, p. 253, pl. 18, figs. 11—17. Characterized by its produced aperture. Saccorhiza ramosa (Brady). Hyperammina ramosa Brady, 1884, p. 261, pl. 23, figs. 1549. (P1. 1, figs. 21, 22.) Spirillina vivipara Ehrenberg. Loeblich and Tappan, 1953, p. 112, pl. 21, figs. 2, 3. Spiroplectammina biformis (Parker and Jones). Loeblich and Tappan 1953, p. 34, pl. 4, figs. 1—6. Stetsom’a horvathi Green, 1960, p. 72, pl. 1, fig. 6. A minute rotaliform species having a transparent wall. Five chambers separated by opaque suture lines comprise the final whorl. Tcxtularia carlandi Parker. Phleger, 1952, p. 86, pl. 13, figs. 22, 23. Textularia torquata Parker, 1952, p. 403, pl. 3, figs. 9—11. (Pl. 1, fig. 11.) Thu’rammina papillata Brady, 1884, p. 321, pl. 36, figs. 7—18. (Pl. 1, fig. 10.) Tolypammina schaudinm’ Rhumbler. Parker, 1954, p. 485 pl. 1, fig. 15. (Pl. 1, fig. 9.) Triloculina trihedra Loeblich and Tappan, 1953, p. 45, pl. 4, fig. 10. (Pl. 2, fig. 15.) Genus Trachammina Parker and Jones, 1859 This genus is fairly consistently present in our material, but all the species are relatively small and fragile. Trochammina com'w Earland. Phleger, 1952, p. 86, pl. 13, figs. 35, 36. Originally described from the Antarctic. Diameter 0.2 mm. Troohammina cf. T. grisea Earland. (Pl. 1, fig. 1.) Our specimens, although much smaller, compare well with this flat-spired species described from the Antarctic (Earland, 1934, p. 100, pl. 3, figs. 35—37). Trochammina cf. T. japom'ca Ishiwada. (Pl. 1, fig. 2.) Our specimens are moderately high-spired, and five chambers (or rarely four) make up the final whorl. They seem close to T. japom'ca described from Toyama Bay (Ishiwada, 1950, p. 190, p1., fig. 2). Trochammina nana (Brady). (Pl. 1, figs. 5, 6.) Haplophragmium nanum Brady, 1884, p. 311, pl. 35, figs. 6—8. Trochammi’na lobata Cuchman, 1944, p. 18, pl. 2, fig. 10. Trochammz'na karica Stschedrina, 1946, p. 147, pl. 3, fig. 16. Test small for the genus, trochoid, composed of 2 to 21A; whorls, dorsal side flat, ventral side convex but depressed toward the umbilicus, periphery subacute, entire in the early part, lobulated in the later part; chambers, six to eight in the final whorl, depressed dorsally, inflated ven- trally and progressively more so as added, the final one extending inward with a large lobe that fills the umbilicus; sutures distinct, dorsal ones flush, curved, and oblique, Ventral ones incised, straight, and radial; wall thin, built of large sand grains for the size of the test but smoothly finished and glossy, orange in color; aperture under the umbilical lobe of the final chamber and extending to the periphery. Diameter 0.25 to 0.60 mm; thickness 0.10 mm. This appears to be a highly variable species in which several different forms have been given different names. Large suites of specimens show the unity of the variants. The features that serve to unite this large plexus of mor- phologic types are, first, the extreme flatness of the dorsal surface; second, the lobulation of the latter part of the adult whorl; and, third, the lobate extension of the final chamber as a flat tongue into the umbilicus. The variable features seem to be chiefly the irregularity in shape and disposition of chambers and the degree to which the chambers expand as added. Gradual expansion results in a nearly circular test, and rapid expansion re- sults in an oblong shape. Trochammi‘na quadriloba Héglund. T‘rochammma pusilla Héglund, 1947, p. 201, pl. 17, fig. 4; text figs. 183, 184 (renamed T. quadriloba because of homonymy). Characterized by a pointed dorsal spire and rough surface. Trochammina sp. A tiny attached flake, having many chambers. The sutures are straight, n‘ot slanted. Turm‘spim‘llina arctica (Cushman). Loeblich and Tappan, 1953, p. 113, pl. 21, fig. 1. REFERENCES CITED Andersen, H. V., 1952, Buccella, a new genus of the rotalid Foraminifera: Washington Acad. Sci. J0ur., v. 42, no. 5, p. 143—151, figs. 1—13. Andrew, John A., and Kravitz, Joseph H., 1974, Sediment distribution in deep areas of the northern Kara Sea, in Herman, Yvonne, ed., Marine geology and oceanog- raphy of the arctic seas: New York, Springer Verlag, p. 231—256, figs. 1—16, tables 1—6. Androsova, V. P., 1962, Foraminifery donnykh otlozhenij zapadnoj chasti polyarnogo bassejna [Benthonic For- aminifera of the western part of the Polar Basin], in Issledovaniia po programme Mezhdunarodnogo Geofizi— cheskogo goda, L. G. Vinogradova, ed.: Vses. Nauchno- Issled. Inst. Morskogo Ryb. Khoz. i Okean. (VNIRO), Trudy, v. 46, p. 102—117, figs. 1—17, tables 1—4. Avnimelech, Moshé, 1952, Revision of the tubular Monotha- lamia: Cushman Found. Foram. Research Contr., v. 3, p. 60—68, 1 pl. Awerinzew, S., 1911, Zur Foraminiferen-Fauna des Sibiri- schen Eismeeres: Acad. Imp. Sci. St. Pétersbourg, Cl. 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Page A abyssorum, Rhabdammina ___ 12, 13, 14, 16, 17, 18, 19, 25; pl. 1 acuta, Jaculella __ __________ 18, 19, 23,; pl. 1 Adercotry'ma glomeratum 16, 17, 18, 19, 21: pl. 1 advenu, Eggerella. _______________ 16, 17, 18, 22 akneriana, Quinqueloculina _____ 15, 18, 19, 24 Alveolophragmium karaensis __________ 17 Ammodiacua gullmarensia ___- 18, 19, 21; pl. 1 Angulogerina fluens ________________ 18, 19, 21 arborescens, Hyperammina ____________ 14 Psammatodend'ron __________ 14, 18, 19, 24 arctica, Elphidiella ___________________ 19, 22 Reophaa: __________________________ 18, 24 Robertina. ________________________ 18, 25 Turrispirillina ____________________ 19, 25 Aschemonella scabra ____ 1, 16, 18,19, 21; pl. 1 Astacolus planulatus __________________ 19, 21 Astrononitm gallowam’ ______ -14, 15, 18, 19, 21 Astrorhizu ____________________________ 24 crassatina ________________________ 24 atlantica, Proteom'na _________________ 17 uuriculata, Globobulimina _____________ 18, 23 B baggi, Dentalimz ___________________ 18, 19, 22 bartletti, Elphidium ________________ 15, 18, 22 Bathysiphon __________________________ 24 biformis, Spiraplectammina _______ 15, 16, 17, 18, 19, 25 Biloculinella globula ___________________ 18, 21 Bolivimz rhomboidalis _________________ 19, 21 bradii, Cibicidea ________________ 12, 18, 19, 21 Planulina ________________________ 21 bradyi, Cribrostomoides _______________ 22 Hyperammimv. ______________ _ 17 Placopsilina ________________ _ 18, 24 Buccella frigida __________ ___ 15, 16 inusitata ______________ _- 18, 19, 21 bucculenta, Triloculina ________ 14 bucculentus, Planispirinaides __ 16, 18, 24; pl. 2 Bulimina exilis __________________ 18, 21; pl. 2 bulla, Tholosina ___________ 15 bullata, Trocha’mminella _ _ 17 bulloides, Glabigerina ___ - 18, 23 Pullenia _______________________ 18, 19, 24 C carnariense, H aplophragmium _________ 14 Cassidella complanuta ___- _ 21 Cassidulina, ___________ _ 16, 23 crassa ________ 15 islandica __ _ 15, 17 laevigata __ 14 norcrossi ___ 15, 17, 18, 19, 21 subgloboaa -_ ___________ 19, 21 teretis ___ ___________ 15, 23 Cibicides __ bradii lobatulus _ ________ 14, 15, 18, 19, 21 rotundatus _____________________ 15 rugosa -__ ________________ 21 sp ________________________________ 14 INDEX Page clawatum, Elphidium __ 14, 15, 16, 17, 18, 19, 22 complanata, Cassidella. ________________ 21 Virgulina ____________ ___- 21 conica, Trachammina ___ 18, 19, 25 contortua, Recurvoides _ _______ 22 Cornuspira involvens __ 14, 18, 21; pl. 2 lucunasa __ __ 19, 21; pl. 2 planorbis ___- ___ 18, 21 carrugata, Patellina _ _ 18, 24 crassa, Cassidulina __ _ 15 crassutina, Astrorhiza . 24 Psammosiphonella ________ 19, 24 crassimargo, Cribrostomoidea __ 1, 16, 18, 19, 22 Labraspira _______________________ 17 Cribrostomoides ___________________ 17, 21, 22 bradyi ____________________________ 22 crassimarao _______________ 1, 16, 18, 19, 22 jcffreyai _______________ 14, 18, 19, 22; pl. 1 subglobosum ______________________ 22 subglobosue ____—____ 1, 12, 18. 21, 22; pl. 1 Cruciloculina. cricsom’ ____________ 18, 22; pl. 2 cylindrica, Pelosina ________________ 16, 18, 19 D decepta, Dentalina - ._ 19, 22 Dentalina baggi _ _ 18, 19, 22 decepta ____ _.- 19,22 frobisherensis _________ _ 18, 19, 22 dentaliniformis, Reophax _ ___- 14, 18, 24 difl‘lugz'formis, Proteonina _ 16 Reophaw __________________________ 25 Saccammina ___________________ 18, 19, 25 digitata, Nonionella turgida __________ 18, 24 discreta, Rhabdammina ______ 18, 19, 25; pl. 1 distoma, Lagena ______________________ 19, 24 E earlandi, Textularia _______________ 18, 19, 25 Eggerella advena. ________________ 16, 17, 18, 22 elongata, Hypera/mminu _____ 1. 12, 14, 18, 19, 23; pl. 1 Elphidiella arctica ____________________ 19, 22 hannai ___________________________ 18, 22 tumida ___________________________ 22 Elphidium ___________________________ 15, 16 bartletti _______________________ 15, 18, 22 clavatum _ 14, 15, 16, 17, 18, 19, 22 frigidum __ ___ 18, 19, 22 incertum ____________ 14 crbiculare ________ __ 16, 18, 19, 22 12, 19, 22; pl. 2 _ _______ 19, 22 _ 12, 15, 18, 19, 22:13]. Epistaminella exigua. _ Epom'des repandus _. tener 2 ' tumidulus horvathi ___- 12, 15, 19, 22; pl. 2 ericaoni, Cruciloculina ___________ 18, 22; pl. 2 exigua, Epistominella ________ 12, 19, 22; pl. 2 exilis, Bulimina __________________ 18, 21; pl. 2 F Fischerinu ____________________________ 23 sp __________________________ 19, 23; pl. 2 Page Fischerinella __________________________ 23 fissuraperta, Troohamminula ___- 17 Fiasurina ____________________________ 24 lcerguelenensis ________ 12, 18, 19, 23; pl. 2 marginata _____________________ 18, 19, 23 serrata. ___________________________ 18, 23 flatulenta, Lugemz ____________________ 24 Florilus _______________________________ 16, 17 labradmicus ________________ 14, 18, 19, 23 fluens, Angulogerina ______________ 18, 19, 21 fornasinii, Pyrgo _______________ 18, 24; pl. 2 friabilis, Hyperammina ____________ 18, 19, 23 frigida, Boccella ______________________ 15, 16 frigidum, Elphidium _______________ 18, 19, 22 frobisherensis, Dentalina ____________ 18, 19, 22 fusca, Psammosphaera _____ 1, 12, 16, 18, 22, 24 G gallowayi, Astrononion ______ 14, 15, 18, 19, 21 glacialis, Globulina ____________________ 18, 23 Globigerina ___________________________ 16 bulloides __________________________ 18, 23 pachyderma ____________ 12, 16, 18, 21, 23 quinqueloba ______________________ 19, 23 Globigerinita glutinata _______________ 18, 23 Globobulimina auriculata ______________ 18, 23 globula, Biloculinella __________________ 18, 21 globularia, Rosalina __________________ 18, 25 Globulina _____________________________ 16 glacialis __________________________ 18, 23 glomeratum, Adercot'ryma 16, 17, 18, 19, 21; pl. 1 glutimta, Globigerinita _______________ 18, 23 grisea, Trochammina ______ 14, 18, 19, 25; pl. 1 groenlandica, Parafiseurina ___ 12, 19, 24: pl. 2 gullmarensis, Ammodiscus ___- 18, 19, 21; pl. 1 guttifer, Reophaa: ________ 18, 19, 23, 25; pl. 1 H hannai, Elphidiella ____________________ 18, 22 Haplophragmium canariense __________ 14 latidorsatum ______________________ 22 nanum ___________________________ 14, 25 Haplophragmoides ____________________ 16, 22 sp _______________________________ 15, 16 hauerinoides, Pateoris _____________ 15, 18, 24 helenae, Islandiella ______________ 14, 18, 19, 28 Hemisphaerammina ___________________ 23 marisalbi _________________________ 18, 23 hexagona, Oolina _____________________ 19, 24 hispidula, Lagena _________________ 18, 19, 24 Hormosina. sp ________________ 18, 19, 23; pl. 1 horvathi, Eponides tumidulus ..... 12, 15, 19, 22; pl. 2 Stetsonia ______________________ 12, 19, 25 hyalaacidea, Laryngosigma _______ 18, 24; pl. 2 Hyperummina ________________________ 23 arborescens ______________ 14 bradm' ____________________________ 1‘7 elongata _ 1, 12, 14, 18, 19, 23; pl. 1 friabilis ________ -_ 18, 19, 23 laeviguta _ _ 23 ramosa. ___________________________ 25 30 Page I inccrtum, Elphidium __________________ 14 inusitata, Buccella __________________ 18, 19, 21 involvens, Cornuspira ________ 14, 18, 21; pl. 2 Iridia. marisalbi _______________________ 23 Iridiellu ______________________________ 23 islandica, Cassidulina __________________ 15, 17 Islandiella. _____________________ 18, 19, 23 Islandiella __________________________ 16, 17, 23 helenae _____________________ 14, 18, 19, 23 islandica _______________________ 18, 19, 23 J Jaculella ______________________________ 23 acuta __________ 18, 19, 23; pl. 1 japom'ca, Trachammina ______ 18, 19, 25; pl. 1 jeffreysi, Cribrostomaides __ 14, 18, 19, 22; pl. 1 K kamensis, Alveolophragmium __________ 17 karica, Trachammina ______________ 16, 17, 25 kerguelcncnsis, Fissurina ___ 12, 18, 19, 23; pl. 2 L labradorica, Nonionellina ______________ 17 labradaricus, Florilus ____________ 14, 18, 19, 23 Labrospi'ra crassimargo ________________ 17 lacunosa, Cornuspira ____________ 19, 21; pl. 2 laevigata, Cassidulina _________________ 14 Hyperammina ____________________ 23 laevigatum, Recurvoides _________ 17, 18, 19, 24 laevis, Lagena. ____________________ 18, 24; pl. 2 Lagena distoma _______________________ 19, 24 flatulenta _________________________ 24 hispidula. ______________________ 18, 19, 24 laevis _______________________ 18, 24; pl. 2 Laryngosigma hyalascidea ....... 18, 24; pl. 2 latidorsatum, Haploph'ragmium _______ 22 Lenticulina ___________________________ 21 lineata, Oolina. _______________________ 19, 24 lobata, Trochammz'na _________________ 25 lobatulus, Cibicides __________ 14, 15, 18, 19, 21 Truncatulina. ______________________ 13 M marginata, Fissurina ______________ 18, 19, 23 marisalbi, Hemisphaerammina ________ 18, 23 Iridia _____________________________ 23 Marsipella ____________________________ 24 melo, Oolina ______________________ 18, 19, 24 Melanie zatmdamae ____________ 18, 19, 24; pl. 2 Miliolinella ___________________________ 24 N nana, Trochammina ___ 1, 12, 14, 15, 16, 17, 18, 19, 25; pl. 1 mmum, Haplophragmium _____________ 14, 25 m'tida, Trochammina __________________ 14 noduloaus, Reophax _____ 1, 12, 18, 19, 25; pl, 1 Nonion zaandamae _______________ _ 24 Nonionella turgida. digitata. ___ _- 18, 24 Nonionellina ______________ - 16 labmdorica ________ _ 17 Nonionina. acapha, _____ _ 14 stelligera, ______________________ 14 norcrosai, Cassidulina ________ 15, 17, 18, 19, 21 Page 0 Oolina hexagona _____________________ 19, 24 lineatu __________ __ 19, 24 melo _______________ __ 18, 19, 24 orbicula‘re, Elphidium _ _ __ 16, 18, 19, 22 P pachydcrma, Globigcrina ____ 12, 16, 18, 21, 23 papillata, Thurammina __________ 18, 25; pl. 1 Parafissurina _________________________ 19 groenlandica ______________ 12, 19, 24: pl. 2 tectulostama _____________ 12, 19, 24; pl. 2 sp _______________________ 12, 19, 24; pl. 2 Patcllina corrugatu ____________________ 18, 24 Pateoris hauerinoides ______________ 15, 18, 24 Pelos‘ina cylindrica ________________ 16, 18, 19 sp ________________________________ 24 Placopsili’na bradyi ___________________ 18, 24 Plam‘spirina. sphaera __________________ 14 Planispirinoides bucculentus __ 16, 18, 24; pl. 2 planorbis, Cornuspiru ................ 18, 21 planulatus, Astacolus __________________ 19, 21 Planulina bradii ______________________ 21 wuellerostorfi _____________________ 21 Polystomella striatopunctata __________ 14 Proteonina atlantica __________________ 17 difiiugiformis ____________________ 16 I'rotoschista sp _______________________ 18, 24 Psammatodend'ron arborcsccns __ 14, 18, 19, 24 Psammosiphonella ____________________ 24 crassatinu _____________________ 18, 19, 24 Paammosphaera. fuscu. 1, 12, 16, 18, 22, 24 Pseudononion Sp -__ _-__ 19,24 PuIlenia bulloidcs _____ 18, 19, 24 pusilla, Trochammina. _ _ _ _ 25 Pyrgo fornasinii _____ _ 18, 24; pl. 2 rotularia ____________________ 19, 24; pl. 2 vcspertz’lio __________ 12, 16, 18, 19, 24; pl. 2 williamsoni __________________ 18, 24; pl. 2 Pyrgoella. sphacra ____________ 14, 18, 24; pl. 2 Q quadriloba, Trovhammina _________ 18, 19, 25 quinqueloba, Globigerina ______________ 19, 23 Quinquclaculina akneriana ______ 15, 18, 19, 24 sp ________________________________ 16 R ramosa, Hyperammina ________________ 25 Saccorhiza _______ 1, 12, 15, 18, 19, 25; pl. 1 Rccurvoides __________________________ 22 contortus ________________________ 22 laevigatum _________________ 17, 18, 19, 24 subglobosus _______________________ 22 Reophux ______________________________ 24 arctica, ___________________________ 18, 24 dentaliniformis difllugiformis guttifer ______________ 18, 19, 23, 25; pl. 1 nodulosus ___________ 1, 12, 18, 19, 25; pl. 1 scorpiu‘rus _, 1, 12, 14, 16, 17, 18, 19, 24, 25 repandus, Eponides _______ 19, 22 Rhabdammina __________________ 24 abyssorum ____________ 12, 13, 14, 16, 17, 18 19, 25; pl. 1 discreta __________________ 18, 19, 25; p]. 1 rhomboidalia, Bolivina ______ 19, 21 Robertina, arctica _- _________________ 18, 25 Rosalina globularia ______________ 18, 25 rotalaria, Purge _______________ 19, 24; pl. 2 rotundatua, Cibicides _________________ 15 rugosa, Cibicides _____________________ 21 Page S Saccammina dirflugiformis _________ 18, 19, 25 sphaericu. _______________ 12, 13, 18, 24, 25 Saccorhz'za ramosa ___- 1, 12, 15, 18, 19, 25; pl. 1 scabra, Aschcmonclla ___- 1, 16, 18, 19, 21; pl. 1 scapha, Nonionina ____________________ 14 schaudinni, Tolypammina ________ 19, 25; pl. 1 scorpiurus, Reophax ______ 1, 12, 14, 16, 17, 18, 19, 24, 25 Scutuloris ____________________________ 24 serrata, Fissurina. _____________________ 18, 23 sphaera, Planispirina __________________ 14 Pyrgoclla _________ __ 14, 18, 24; pl. 2 sphuerica, Succammina _ 12, 13, 18, 24, 25 Spirillina. viviparu ____________________ 18, 25 Spiroplcctammz'na. biformis 15, 16, 17, 18, 19, 25 stelligera, Nonionina. __________________ 14 Stetsvm‘u. horvathi 1.-- _ 12, 19, 25 striatopunctata, Polystomella __ 14 subglobosa, Cassidulina _________ _ 19, 21 subglobosum, Cribrostomoz’des _________ 22 subglobosus, Cribrvstomoidcs ___. 1, 12, 18, 21, 22; pl. 1 Recu-rvoides ______________________ 22 T levlulostoma, Purafissurina ___. 12, 19, 24; pl. 2 toner, Epom‘dca ________ 12, 15, 18, 19, 22; pl. 2 teretz‘s, Cassidulina _____ ___- 15, 23 Textularia. earlandi _________ 18, 19, 25 torquuta ___- -_ 17, 18, 19, 25; pl. 1 Tholosina. bulla. ______________________ 15 Thurumminu papillata _ 18, 25; pl 1 Tolypammina. schaudinm' _ _______ 19, 25; pl. 1 torquata, Textularia ______ 17, 18, 19, 25; pl. 1 trihed‘ra, Triloculina. .___ 12, 15, 18, 19, 25; pl. 2 Triloculina bucculenta _________________ 14 trihedra ___________ 12, 15, 18, 19, 25; pl. 2 Trochammina __________ 14, 16, 18, 19, 25; pl. 1 conicu. ________________________ 18, 19, 25 grisea ________________ 14. 18, 19. 25; pl. 1 japonica _________________ 18, 19, 25; pl. 1 karica _________________________ 16, 17, 25 lobata ____________________________ 25 'na'na. _._ 1, 12, 14,15, 16, 17, 18, 19, 25.” pl. 1 nitida ____________________________ 14 pusilla ____________________________ 25 quadriloba _____________________ 18, 19, 25 SD _______________________________ 18, 25 Trovhamminella bullata _______________ 17 Trochamminula. fissuraperta ____________ 17 Truncatulina Iobatulus ________________ 13 tumidulus _________________________ 23 tumida, Elphidiella ____________________ 22 tumidulua hor’vathi, Eponides ______ 12, 15, 19, 22; pl. 2 Truncatulina. ______________________ 23 turgida digitata, Nonionella __________ 18, 24 Turrispirillina arctica ................ 19,25 V vespertilia, Pyrgo ______ 12, 16, 18, 19, 24; pl. 2 Virgulina _____________________________ 16, 21 complanam _______________________ 21 vivipara, Spirillinu. ___________________ 18, 25 W Webbinella ___________________________ 23 williwmsoni, Purge ______________ 18, 24; pl. 2 wuellerstorfi, Planulina ________________ 21 Z zaandamac, Melanie .......... 18, 19, 24; pl. 2 Nonion __________________________ 24 fir U.S. GOVERNMENT PRINTING OFFICE: I980 O— 311-344/26 PLATES 1 AND 2 Contact photographs of the plates in this report are available, at cost, from US. Geological Survey Library, Federal Center, Denver, Colorado 80225 FIGURE 1. 10. 11. 12. 13, 19. 14. 15. 16. 17. 18. 20. 21, 22. PLATE 1 Troohammi’na cf. T. grisea Earland (p. 21). USNM 241897, )< 80; Kara Sea, sta. 77. a, Dorsal View; b, ventral View. Trooharmmina. cf. T. japom'ca Ishiwada (p. 21). USNM 241898, x 80; Kara Sea, sta. 77. a, Dorsal View; b, ventral view; 6, edge View. Cribrostomm‘des jefireysz’ (Williamson) (p. 18). USNM 241900, X 30; Kara Sea, sta. 102. a, Side view; b, edge View. Ammodiscus gullmarensis H6glund (p. 17). USNM 241921, x 50; Greenland Sea, sta. 5. Trochammz'na nana (Brady) (p. 21). 5. USNM 241899, x 80; Kara Sea, sta. 77. a, Dorsal View; I), ventral View. 6. USNM 241913, x 80; Kara Sea, sta. 143. a, Dorsal View; I), ventral View. Crib’rostomoides subglobosus (G. O. Sars) (p. 18). USNM 241920, x 30; Greenland Sea, sta. 4. Edge View to show aperture. Adercot’ryma glomemtum (Brady) (p. 17). USNM 241929, x 50; Greenland Sea, sta. 30. Tolypammina schaudinm' Rhumbler (p. 21). USNM 241914, x 50; Greenland Sea, sta. 2. Thummmina, papillata Brady (p. 21). USNM 241909, X 30; Kara Sea, sta. 135. Broken specimen. Textulowia torquata Parker (p.21). USNM 241896, x 80; Kara Sea, sta. 77. Rhabdammina discreta Brady (p. 21). USNM 241926, x 15; Greenland Sea, sta. 23. Rhabdammina abyssomm M. Sars (p. 21). 13. USNM 241910, X 15; Kara Sea, sta. 137. 19. USNM 241911, x 15; Kara Sea, sta. 137. Reophax guttife‘r Brady (p. 21). USNM 241906, x 50; Kara Sea, sta. 109. Hormosina sp. of Parker, 1952 (p. 19). USNM 241915, x 50; Greenland Sea, sta. 2. Reophax nodulosus Brady (p. 21). USNM 241895, x 15; Kara Sea, sta. 77. Jaculella acuta Brady (p. 19). USNM 241890, x 15; Kara Sea, sta. 1. Hyperammina elongata Brady (p. 19). USNM 241894, x 15; Kara Sea, sta. 77. Aschemonella scabra Brady (p. 17). USNM 241912, X 15; Kara Sea, sta. 141. Saccorhiza ramosa (Brady) (p. 21). 21. USNM 241891, x 7; Kara Sea, sta. 41. 22. USNM 241925, x 15; Greenland Sea, sta. 19. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1070 PLATE 1 »&‘~$fiz‘ a?» A“ .5 ha» ARENACEOUS FORAMINIFE RA FROM KARA AND GREENLAND SEAS FIGURE 1. 2. 3. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 21. 22. PLATE 2 Lagena laevis (Montagu) (p. 20). USNM 241892, x 30; Kara Sea, sta. 53. Laryngosigma hyalascidia Loeblich and Tappan (p. 20). USNM 241905, x 50; Kara Sea, sta. 106. ‘ Bulimina- exilis Brady (p. 17). USNM 241893, x 50; Kara Sea, sta. 53. Parafissurina sp. (p. 20). USNM 241924, x 30; Greenland Sea, sta. 13. at, Front View; b, side view. Parafissurina tectulostoma Loeblich and Tappan (p. 20). USNM 241931, x 50; Greenland Sea, sta. 33. Parafissurma grocnlandica Stschedrina (p. 20). USNM 241932, x 50; Greenland Sea, sta. 33. a, b, Views 90° apart. Epom'des tumidulus horvathi Green (p. 19). USNM 241923, x 80; Greenland Sea, sta. 11. a, Dorsal view; b, ventral View; 0, edge View. Melom's zaandamae (van Voorthuysen) (p. 20). USNM 241928, x 30; Greenland Sea, sta. 30. a, Side View; b, edge view. Fissu’rina kerguelenensis Parr (p. 19). USNM 241917, x 80; Greenland Sea, sta. 3. Epom'des tene’r (Brady) (p. 19). USNM 241919, X 80; Greenland Sea, sta. 3. a, Dorsal view; b, ventral view; c, edge view. Epistominella exigua (Brady) (p. 18). USNM 241918, x 80; Greenland Sea, sta. 3. a, Dorsal View; b, ventral view; c, edge View. Fischerina sp. (p. 19). USNM 241930, x 50; Greenland Sea, sta. 32. a, Dorsal view; b, ventral View; 0, edge View. Cruciloculina ericsoni Loeblich and Tappan (p. 18). USNM 241908, x 30; Kara Sea, sta. 112. Apertural View. Pyrgo williamsom’ (Silvestri) (p. 20). USNM 241907, x 30; Kara Sea, sta. 110. a, Front view; 1), side View. Triloculina trihcdra Loeblich and Tappan (p. 21). USNM 241916, X 50; Greenland Sea, sta. 3. Pyrgo fornasim'i Chapman and Parr (p. 20). USNM 241904, x 15; Kara Sea, sta. 106. 0., Front view; b. top view. Planispirmoides bucculentus (Brady) (p. 20). USNM 241903, x 15; Kara Sea, sta. 106. (1, Front view; b, side view. Cornuspim involvens (Reuss) (p. 17). USNM 241901, X 15; Kara Sea, sta. 106. a, Side view; b, edge View. Cornuspira lacunosa Brady (p. 17). USNM 241927, x 15; Greenland Sea, sta. 29. Pyrgo rotalam'a Loeblich and Tappan (p. 20). USNM 241933, x 30; Greenland Sea, sta. 37. Top View. Pyrgo vespertilio (Schlumberger) (p. 20). USNM 241922, x 15; Greenland Sea, sta. 6. Top View. Py'rgoella sphaera (d’Orbigny) (p. 20). USNM 241902, X 15; Kara Sea, sta. 106. Top View. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1070 PLATE 2 CALCAREOUS FORAMINIFERA FROM KARA AND GREENLAND SEAS » v ' a L ‘ " ‘ , 4 . i < 1 . r . . . ' l 4 , v r m \ J w" Reconstruction of Crustal Blocks Of California on the Basis of Initial Strontium Isotopic Compositions Of Mesozoic Granitic Rocks By RONALD W. KISTLER and ZELL E. PETERMAN SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 1071 A study of regional variation of initial strontium isotopic composition of Mesozoic granitic rocks in California UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1978 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Catalog-card Number 78-600103 For sale by the Superintendent of Documents, US. Government Printing Office Washington, DC. 20402 Stock No. 024-001-03109-4 FIGURE 1. 2. 3. 4. 5. 99°.“ 10. TABLE 1. CONTENTS Page Abstract ——————————————————————————————— =— — — 1 Introduction ————————————————————————————————— 1 Fault block reconstruction ——————————————————————————— 4 Development of the continental margin ————————————————————— 7 Trace element variations ———————————————————————————— 10 Source materials for the granitic rocks —————————————————————— 11 Summary and conclusions ——————————————————————————— 13 Rock type and locality description of rocks investigated —————————————— 15 References cited ——————————————————————— ‘ ———————— 16 ILLUSTRATIONS Page Index map showing specimen localities of granitic rocks investigated ____________________________ 3 Map of California showing boundaries between different crustal types ___________________________ 4 Map showing distribution of ri of Mesozoic granitic rocks and mafic Cenozoic volcanic rock with late Cenozoic lateral displacements removed from San Andreas and Garlock fault systems _______________ 6 Location and configurations of lines ri = 0.7040 and 0.7060 in the western United States ________________ 8 Position of Salinian-western Mojave terrane after 800 km of left-lateral displacement is removed along the discontinuity in ri in the central Mojave Desert ___________________________________ 9 Diagram of model of continental rifting used to account for present configurations of lines ri = 0.7040 and ri = 0.7060 _________________________________________________________ 10 Plots of: Rb concentration against ri _______________________________________________ 11 Plots of: Sr concentration against ri _______________________________________________ 11 Rubidium concentration relative to strontium concentration in California granitic rocks with ri less than 0.7060 ___________________________________________________________ 12 Plots of: Rb/Sr against ri _____________________________________________________ 13 TABLES Page Strontium analytical data ____________________________________________________ 2 Chemical analyses of granitic rocks ________________________________________________ 2 Potassium-argon dates ______________________________________________________ 2 III RECONSTRUCTION OF CRUSTAL BLOCKS OF CALIFORNIA ON THE BASIS OF INITIAL STRONTIUM ISOTOPIC COMPOSITIONS OF MESOZOIC GRANITIC ROCKS By RONALD W. KISTLER and ZELL E. PETERMAN ABSTRACT Initial 8’Sr/“éSr was determined for samples of Mesozoic granitic rocks in the vicinity of the Garlock fault zone in California. These data along with similar data from the Sierra Nevada and along the San Andreas fault system permit a reconstruction of basement rocks offset by the Cenozoic lateral faulting along both the San Andreas and Garlock fault systems. The location of the line of initial 67Sr/“Sr = 0.7060 can be related to the edge of the Precambrian continental crust in the western United States. Our model explains the present configuration of the edge of Precambrian continental crust as the result of two stages of rifting that occurred about 1,250 to 800 my. ago, during Belt sedi- mentation, and about 600 to 350 my. ago, prior to and during the development of the Cordilleran geosyncline and to left-lateral trans— lation along a locus of disturbance identified in the central Mojave Desert. The variations in Rb, Sr, and initial B7Sr/‘fi‘Sr of the Mesozoic granitic rocks are interpreted as due to variations in composition and age of the source materials of the granitic rocks. The variations of Rb, Sr, and initial a7Sr/BéSr in Mesozoic granitic rocks, the sedi— mentation history during the late Precambrian and Paleozoic, and the geographic position of loci of Mesozoic magmatism in the west- ern United States are related to the development of the continental margin and different types of lithosphere during rifting. INTRODUCTION The isotopic composition of strontium was deter- mined for specimens of granitic rocks in the vicinity of the Garlock fault, in the southern Sierra Nevada, and in the northern Mojave Desert of California. Values for Rb, Sr, K/Sr, K/Rb, 87Sr/ESSr, initial 87Sr/BGSr, and age for each specimen are given in table 1. Chemical analyses of some of these rocks are given in table 2, and K-Ar ages of some are listed in table 3. Locations of specimens investigated are shown in figure 1, and petrographic descriptions and sample locations are given in the Appendix. Analytical techniques for Rb, Sr, and 87Sr/‘M‘Sr are the same as those described in Kistler and Peterman (1973), and those for K-Ar dates are the same as those described in Kistler (1968). Previously, we found (Kistler and Peterman, 1973) that initial 87Sr/fiSSr (hereafter called ri) values in Mesozoic granitic rocks to the north of the Garlock fault in California show a systematic areal variation, independent of age, and that the ri of superjacent up- per Cenozoic basalts and andesites in that area show the same areal variation. We suggested that the boundary between granitic rocks with ri less than 0.7060 and greater than 0.7060 was coincident with the seaward edge of marine miogeosynclinal sedimen- tation during the late Precambrian and Paleozoic in California, that is, the edge of the Paleozoic continen- tal shelf. Armstrong, Taubeneck, and Hales (1977) es- tablished that the ri of Mesozoic granitic rocks and Cenozoic volcanic rocks had the same relation in Washington and Idaho to Precambrian and Paleozoic sedimentation. - One goal of the present study was to extend to the vicinity of the Garlock fault distinctive pattens of ri previously established in the Sierra Nevada north of the Garlock fault by us (Kistler and Peterman, 1973) and along the San Andreas fault system (Kistler and others, 1973). Offsets of the pattern of ri along these fault systems could then be used to help establish lim- its of Cenozoic displacements along them. The pattern of variation of strontium isotopes of Mesozoic granitic rocks in California appears to indi- cate that the State is composed of four fundamentally different types of crust. The boundaries between these crustal types where presently known are indi- cated in figure 2. The first type is crust that has been intruded by Mesozoic granitic rocks that are princi- pally granodiorite and quartz monzonite and that have ri greater than 0.7060. The second type is crust that has been intruded by Mesozoic granitic rocks that are principally tonalite and granodiorite and have ri greater than 0.7040 but less than 0.7060; this can be subdivided into two types on the basis of trace- elements abundances in Mesozoic granitic rocks that intrude it. The third type is crust intruded by Meso- zoic granitic rocks that are principally quartz diorite l INITIAL. STRONTIUM ISOTOPIC COMPOSITIONS OF MESOZOIC GRANITIC ROCKS Table 1.—Strontium analytical data [n.d. = not determined K20 and N920 determined by L.B. Schlocker. Rb and Sr determined by W.P.Doering 87Sr/""Sr determined by R.A. Hildreth and R.W. Kistler] Specimen Wt percent Rb Sr Weight ratios Atom ratios Age No. Map No. K20 N920 (ppm) (ppm) Rh/Sr K/Rb K/Sr “Sr/“Sr ti (m.y.) Sr 1—73 ——————— 1 1.79 3.16 77.2 360 0.215 193 41.4 0.7048 0.703 ' 120 Sr 2-73 ——————— 2 1.76 4.02 57.7 399 .145 253 36.6 .7050 .7043 "V 120 Sr 3—73 ——————— 3 1.71 3.45 44.0 514 .086 323 27.6 .7036 .703 4' 120 Sr 4—73 ------- 4 3.01 2.96 146. 249 .586 171 100.4 .7089 .7061 D 120 Sr 5—73 ——————— 5 3.40 2.81 154. 238 .646 183 118.5 .7084 .705 9‘ 120 Sr 6—73 ——————— 6 3.38 4.00 140. 349 .401 201 80.5 .7073 .7058 ' 90 Sr 8—73 ——————— 7 2.87 3.82 98. 737 .133 243 32.3 .7080 .7075 ’ 90 Sr 9-73 ——————— 8 2.39 3.91 81.8 695 .118 242 28.5 .7084 .7080 9 90 Sr 10—73 —————— 9 2.84 3.70 89.6 634 .141 263 37.2 .7076 .7070 5‘ 90 Sr 11—73 —————— 10 4.92 3.13 118. 609 .193 346 67.0 .7084 7077 90 Sr 12—73 —————— 11 2.45 4.56 80.1 612 .131 253 33.2 .7062 .7058 81 Sr 14—73 —————— 12 2.00 3.91 55.0 347 .159 302 47.8 .7055 .7050 80 Sr 15—73 —————— 13 1.70 3.68 53.8 341 .158 262 41.3 .7060 .7055 81 Sr 16—73 —————— 14 3.83 3.50 98.1 382 .257 324 83.2 .7062 .7042 210 SR 17—73 ————— 15 2.45 4.33 72.0 848 .085 282 23.9 .7069 .7066 90 Sr 18-73 —————— 16 3.29 4.50 108. 731 .148 253 37.3 .7092 .7081 180 , Sr 19—73 —————— 17 3.03 3.32 105. 350 .301 239 71.7 .7065 .7041 200 Sr 20—73 —————— 18 4.76 3.45 132. 339 .390 299 116.5 . .7089 .7060 180 COS 10—2 ————— 19 n.d. n.d. 80.1 485 .165 — — .7057 .7041 200 COS 13—42-2 - — — 20 n.d. n.d. 10.3 664 ' .016 — -— .7062 .7060 180 A3 ————————— 21 n.d. n.d. 169. 261 .548 — — .7106 .7064 184 A6 ————————— 22 n.d. n.d. 57.7 686 .084 — — .7047 .7041 200 D15 ————————— 23 n.d. n.d. 146. 489 .299 — — .7094 .7070 210 D16 --------- 24 n.d. n.d. 203. 311 .653 — — .7130 .7070 210 E12 ————————— 25 n.d. n.d. 89. 592 .150 — — .7083 .7070 210 C—203 ——————— 27 3.63 3.62 144. 345 .417 225 89.1 .7182 — p C (7) C—204 ——————— 28 4.33 3.17 180. 219 .824 211 174. .7174 —- pC(?) C-201 ——————— 29 1.58 3.97 27.7 970 .029 473 13.5 .7063 .7063 13 E10 --------- 26 n.d. n.d. 139. 171 .815 — — .7107 .7070 100 Table 2.—Chemical analyses of granitic rocks [Analyst, H. Smith] Spec. No. 1—73 2—73 3—73 4—73 5—73 6—73 8—73 9—73 10—73 11—73 12—73 15—73 16—73 17—73 18—73 19—73 20—73 SiOz - — - 63.2 68.7 65.8 65.8 65.1 68.1 65.8 63.8 63.8 72.7 59.0 61.8 71.9 62.1 68.4 65.8 70.3 A1203 - — 16.5 15.7 15.9 15.1 15.2 15.9 16.2 17.1 16.3 14.0 16.8 16.8 14.5 15.6 16.3 15:8 15.2 Fe203 — 0.7 1.1 1.6 0.3 1.0 1.3 1.5 1.3 1.7 0.90 1.4 1.2 0.90 0.40 1.8 2.1 1.5 FeO — — — 4.3 2.2 2.6 3.8 3.8 2.0 2.6 3.5 3.4 0.96 4.5 4.7 1.2 4.5 1.3 2.5 1.3 Mg0 —— 2.8 1.2 2.1 2.0 2.2 0.9 1.2 1.3 2.1 0.30 2.6 2.2 0.36 1.8 0.70 2.0 068 C30 — — — 5.8 3.8 5.0 4.2 3.9 2.4 3.5 3.9 4.5 1.5 5.2 4.6 2.0 4.9 2.7 4.3 1.9 Na, - — 3.3 4.2 3.8 3.1 2.9 4.1 4.0 4.1 3.7 3.1 4.7 4.1 3.5 4.5 4.6 3.5 3.4 K20 - — - 1.8 1.8 1.8 3.0 3.6 3.3 2.9 2.5 2.8 5.0 2.6 1.7 3.8 2.5 3.4 3.1 4.8 1120+ — — 0.53 0.54 0.52 0.49 0.45 0.64 0.52 0.81 0.45 0.27 0.75 0.79 0.33 0.52 0.25 0.57 0.58 1120— — — 0.25 0.26 0.28 0.29 0.23 0.27 0.38 0.29 0.28 0.25 0.35 0.31 0.36 0.28 0.33 0.28 0.27 'I‘iO2 — - 0.62 0.44 0.52 0.57 0.66 0.52 0.77 0.82 0.87 0.20 1.2 0.91 0.19 1.1 0.35 0.56 0.36 P205 — — 0.15 I 0.14 0.16 0.12 0.11 0.21 0.23 0.25 0.23 0.06 0.38 0.22 0.08 0.35 0.15 0.14 0.13 Mn0 —— 0.07 0.04 0.08 0.06 0.06 0.04 0.04 0.04 0.06 0.00 0.10 0.09 0.06 0.06 0.04 0.08 0.05 C02 — — — 0.03 0.05 0.04 0.02 0.05 w 0.03 0.02 0.04 0.06 0.08 0.08 M __0‘24 __0_.0§ 0. 4 m Sum 100 100 100 99 99 100 100 100 100 99 100 100 99 99 100 101 101 TABLE 3.-—-Potassium-argon dates [K20 determined by L. B. Schlocker. Moles “Arrad determined by R. W. Kistler ] K2o ”Afrad ”Afraid Map No Mineral (wt percent) (x 10‘" moles/gm) (percent) Age (m.y.) 6 ——————————————————— Biotite 8.81 88.71 77 67.1 i 1.7 7 ——————————————————— —do— 9.36 110.99 94 78.7 1- 2.0 8 ——————————————————— —do— 9.16 103.07 70 74.8 t 1.9 10 ___________________ ——do— 7.22 77.22 75 71.1 1- 1.8 15 ——————————————————— ——do—— 8.77 23.67 50 18.2 x 0.5 Hornblende 1.62 18.12 44 74.2 i 1.9 17 ———————————————————— Biotite 8.64 184.40 91 139.5 : 3.5 Hornblende .55 10.72 28 127.4 i 8.0 18 ——————————————————— Biotite 8.48 95.48 87 74.8 i 1.9 27 ——————————————————— —do— 8.11 138.98 79 112.7 1 2.8 28 ___________________ —do— 6.90 92.83 92 89.0 1 2.3 INTRODUCTION 3 and trondjhemite and have ri less than 0.7040; this third type is also characterized by the principal expo- sures of ophiolites in California. The fourth type is Franciscan melange. In our original study of ri in Mesozoic granitic rocks (Kistler and Peterman, 1973), we found not only that a simple pattern of variation in chemistry and ri of Mesozoic and Cenozoic igneous rocks exists in Califor- nia, but that variations in chemistry and ri could not 118° be related to depths of magma generation along sub- duction zones or to the age of the igneous activity, However, the variation was dependent on geographic position of specimens investigated and was correlated with long-lived crustal features. Granitic rocks with ri greater than 0.7060 were intruded into regions with a crust as much as 50 km thick and in many areas with exposures of Precambrian crystalline rocks (Oliver, 1977). Similar studies (Early and Silver, 1973; Kistler 117° I- , ~Q ’ I \ ~,/.:_\.:.K,L,..-:,~.\,;~: , , I"‘L‘LVIYKI,:I\,\I(I‘—“— ’\ \I‘uv -‘i’ru /I_\/ -/ ~» \I Iw~ I~x ' -’., I\ ll— ,/ l"-/ \I\-l‘~‘/'\\,\,\ "\r‘/\’/|/_/ <’\,\l:l—-lz / z \ ’\— _ ’/ ’lxlz\/\>"\’ V a \r a \/ , .- ~‘ _ «\I/DLQ’IxD—‘lls‘qf‘l‘ \C‘pl‘K-j"(I\L\'."I\Cv’\\7—y- ’ \a ’ _ ~ ‘ \ _ , (PI: >I<‘\’.l\l\,_|1‘\’/I 8 1‘ I) -x:- \_/’|/’ ~ C\ .I ""3"" \I‘IL‘" ;’ \1‘! I \’/\'I 7|‘\7(\\Q/f ‘Ll/\Cl:\ ‘,|/“I/,I\/‘-\’ I _ I"l’|,‘l."|7 (DC; ”I I ’ / —\,\/‘_,\/_‘\J/ ‘, ' .\ I\'\,\’ l\ \ 4,], ‘ \- m r \\~/‘ I I r — - I; r \ >1 - Lp J’/\/\_/I\\./ - :IPUECPWI \ \ / ~\ ,— \ WI" ‘ ’/\/:, -n’F ‘ r ‘ _ \ <“‘,’-II/\\1’I\-’/‘ 113‘] ‘4 KW l EXPLANATION Cenozoic volcanic and sedimentary rocks and alluvium | . . . \ \/_\ ”>9 Mesozorc granitic fix“ rocks 7 . _ /////% Metamorphic rocks Contact —- Fault-Dashed where inferred; dotted where concealed o Speciman locality —- For analysis of numbered samples see tables 1—3 0 25 50 KILOMETERS L-_|_|_1_|_L__.—_l FIGURE 1.—Generalized geologic map of vicinity of Garlock fault zone, California (modified from Dibblee, 1960) showing specimen local- ities of granitic rocks investigated for present study. Unnumbered sample localities are from Kistler and Peterman (1973) and Kistler, Peterman, Ross, and Gottfried (1973). 4 and others, 1973; Kistler, 1974; Armstrong and others, 1977; Peto and Armstrong, 1976; Le Conteur and Templeman-Kluit, 1976) have simply reinforced this observation. As a consequence, we conclude that areas in the western United States intruded by Mesozoic granitic rocks with ri greater than 0.7060 are under- lain by ensialic crust. Considering the line ri = 0.7060 as a reflection of limits of Precambrian continental crust and the edge of the paleozoic continental shelf gives further insight into the reasons for the location of loci of magmatism of different ages and into the nature of the source ma- terials for the granitic rocks. This insight is especially clear after the disrupted boundaries of the isotopic pattern are restored along the San Andreas and Garlock fault systems and the resultant pattern is re- lated both to a known Precambrian aulocogen in the Death Valley region and to the age and type of sedi- ments deposited in the Paleozoic cordilleran geosyncline along the margin of the western United States. EXPLANATION _ 42° %" WU] r,> 0.7060 % V////j 0.7040< ri< 0.7060 M3321? E Ii < 0.7040 E Franciscan rocks 38° I \ \\\\\\\\\\ U! > Z FAULT 34° a SEAL cov — -—_. SAN GREGORIO — FAULT RINCONADA ANDREAS FAULT "Illlif/ HIIHI 150K I GFAULTK /|/ 9 .nmlllil‘l @J/I \\§\\\\\\\‘\ ISAgNFGABRmL -='II AULT ILOMETERS FIGURE 2.—-Generalized geologic map of California showing boundaries between four different crustal types characterized by Mesozoic granitic rocks with distinctive ri. INITIAL STRONTIUM ISOTOPIC COMPOSITIONS OF MESOZOIC GRANITIC ROCKS FAULT BLOCK RECONSTRUCTION In order to test suggested offsets of basement rocks to the west of the San Andreas fault, Kistler, Peterman, Ross, and Gottfried (1973) determined the ri of Mesozoic granitic rocks in the vicinity of the San Andreas fault zone from the Gualala area in the north into the southern California batholith in the south. Two stages of motion of basement terrane were uti- lized to bring the granitic rocks with distinctive ri to the west of the San Andreas fault zone into a reason- able prefault configuration adjacent to granitic rocks in the Mojave Desert east of the fault. For the first stage, which is required to restore about 320 km of post-lower Miocene offset, the entire length of the present-day San Andreas fault (fig. 2) and the San Ga- briel fault zone was considered the break between lithosphere blocks (Anderson, 1971; Crowell, 1968). After this restoration, granitic rocks from Ben Lo- mond to Bodega Head remain in an apparently anomalous position to the west of the Great Valley. Stratigraphic studies indicate these rocks arrived in this position during Late Cretaceous and Paleocene time and provided debris to Eocene submarine fan de- posits, some of which are now out by the San Andreas fault (Nilsen and Clarke, 1975). The second stage, along a proto-San Andreas fault, utilized the San Andreas fault north of the Garlock fault, the southern part of the Sur-Nacimiento fault, and the Reliz- Espinosa-San Marcos-Rinconada fault zone to restore granitic rocks from Ben Lomond to Bodega Head to a possible pre-Late Cretaceous position to the south (Kistler and others, 1973). The second-stage restoration of Kistler, Peterman, Ross, and Gottfried (197 3) indicated about 150 km of pre-middle Eocene, post-Late Cretaceous motion along the Reliz-Espinosa-San Marcos-Rinconada fault zone in the interior of the Salinian block. How- ever, only about 60 km of pre-Miocene lateral dis- placement is likely along the south end of this fault zone (Dibblee, 1972, 1976), and the new strontium isotopic data indicate that the Ben Lomond region is not in an anomalous position. An additional fault or process is necessary, however, to remove granitic rocks from Montara to Bodega Head from their anomalous position west of the Great Valley. Up to 100 km of late Cenozoic right-lateral displacement is suggested for the Seal Cove-San Gregorio fault zone, a western branch of the San Andreas fault system (Silver, 1975; Graham, 1975; Dibblee, 1976). If 100 km of right-lat- eral displacement is removed along the Seal Cove-San Gregorio fault zone, however, the granitic rocks from Montara to Bodega Head would no longer be in a posi- tion suitable to shed debris into lower Tertiary sub- FAULT BLOCK RECONSTRUCTION 5 marine fans in the location shown by Nilsen and Clarke (1975). Early Cenozoic lateral displacement of up to 50 km in the interior of the Salinian terrane along the San Juan fault and the Rinconada fault zone of Dibblee (1976) is possible, but the configuration of the isotopic pattern does not require any pre-Miocene Cenozoic lateral displacement of continental base- ment rocks along this segment of the California bor- derlands. Smith (1962), on the basis of apparent offsets of dike swarms in Mesozoic granitic rocks, suggested about 64 km of Cenozoic left-lateral displacement along the Garlock fault. Subsequent geologic studies in the vicinity of the fault have supported Smith’s conclusion, as summarized by Davis and Burchfiel (1973). Troxel, Wright, and Jahns (1972), Davis and Burchfiel (1973), and Garfunkel (1974) concluded that the Garlock fault is a continental transform re- lated to Cenozoic crustal extension in the Great Basin and that displacement along it is not everywhere the same. Offsets in the strontium isotopic pattern in the vicinity of the Garlock fault zone indicate a maximum of about 52 km of displacement along the fault. In figure 3, major post-Miocene right-lateral dis- placements of continental rocks along the San Andreas and San Gabriel fault zones have been re- moved from the California borderlands (Kistler and others, 1973). In addition, 52 km‘ of left-lateral dis- placement has been removed along the Garlock fault. Post-Late Cretaceous and Pre-middle Eocene dis- placement of 50 km could be removed from the Reliz- Espinosa-San Marcos-Rinconada fault zone of Dibblee (1972) and its extension, the King City fault zone of Ross and Brabb (1973), but this displacement provides no improvement in alinement of ri and is not shown. The sliver of basement bounded by the San Gabriel and San Juan fault zones may be shown in a too southerly position in figure 3, because geologic evi- dence indicates a right-lateral offset of only 40 km on the San Gabriel fault zone (Crowell, 1952; Dibblee, 1968). If the geologic estimates of displacement along the San Gabriel fault zone are correct, the sliver bounded by the San Gabriel and San Juan fault zones would have to lie further to the north. If this were the case, considerable right-lateral slip along the San Juan fault zone would have to be removed to place the rest of the Salinian block in the position shown. As much as 37 km of post-lower Tertiary right-lateral slip has been suggested for this fault, and earlier move- ments with the same sense may also have occurred along it (Dibblee, 1976, p. 21). The strontium data do not uniquely define a position for this sliver in the in- terior of the Salinian block, and its position in figure 3 is established only if there is no internal deformation within the block, an unlikely possibility (Garfunkel, 1974). The continuity of ri across the San Andreas fault zone to the south of Ben Lomond and across the Garlock fault zone after the indicated restoration is remarkable. An 80-km restoration along the Seal Cove-San Gregorio-Palo Colorado fault zone would juxtapose granitic rocks with similar ri (0.7061 to 0.7068) at Bodega Head, Point Reyes, Montara, and the Farallon Islands. These granitic rocks still appear to be in an anomalous position relative to sedimentary rocks of the Great Valley sequence of late Mesozoic to Tertiary age. However, moving them further south laterally along a fault does not produce a post-Late Cretaceous pre-middle Eocene juxtaposition of ri that is any better than that in the position shown. The po- sition of these granitic rocks shown in figure 3 places them just west of the junction between Franciscan melange and the Great Valley sequence—the Coast Range thrust. The projection of this junction south lines up with a zone of ultramafic rocks in the western part of the northern Santa Lucia Range (Ross, 1976). We believe that the Coast Range thrust and the zone of Ultramafic rocks may be related. If so, the granitic rocks under discussion could have arrived from the west to their apparently anomalous position prior to the Paleocene and early Eocene and, in effect, could be part of the Franciscan melange. It should be noted that their ri values are derived on the assumption that these granitic rocks are about 110 my. old (Mattinson and others, 1972; Kistler and others, 1973). However, this age has never been established unequivocally, as zircon ages from these rocks are discordant and indi- cate a pre-Mesozoic component (Mattinson and oth- ers, 1972) in the zircon populations. Plotting the raw RbSr data from granitic rocks from Bodega Head, Point Reyes, and Farallon Islands (Kistler and others, 1973) on a strontium evolution diagram yields an ap- parent age of about 200 my. and a common ri of 0.7058. If the pluton at Montara is assumed to have the same ri, its age is about 320 my. These calcula- _ tions are not meant to indicate real ages; they are meant to show that the granitic rocks are possibly older than Mesozoic and possibly have an ri less than 0.7060. The small exposures of granitic rocks from Montara to Bodega Head are the isotopically unusual rocks of the Salinian block. The oldest strata of the Gualala basin to the north of Bodega Head lie on spilitic vol- canic rocks similar to those of the Franciscan Forma- tion and with oceanic affinities (Wentworth, 1966). The other basins of early Tertiary sedimentation are INITIAL STRONTIUM ISOTOPIC COMPOSITIONS OF MESOZOIC GRANITIC ROCKS 118° EXPLANATION ‘i 0.70404“~ Granitic >0.7030 < 0.7040 A >o.7040 < 0.7050 X >o.7050 < 0.7060 v >0.7060 < 0.7070 —o— —o— >0.7070 < 0.7080 0 o >0.7080 < 0.7090 I :1 <1 I> Volcanic >0.7090 + \ A-V \ \ \ \ \ V \ \ \ \ \ V \ 2 \\ \ 3 M\\ V ‘. \ -o‘—‘ 35° —- Limit of granitic exposure -L -L 4- Boundary of aulacogen .‘ ———---- Contact - Dashed where approximate; dotted where inferred ‘ —— Fault - Dashed where approximate; dotted where inferred -‘--‘-— Thrust fault - Dashed where approximate FIGURE 3.—Distribution of ri of Mesozoic granitic rocks and mafic Cenozoic volcanic rocks with late Cenozoic lateral displace- ments removed from San Andreas and Garlock fault systems. Stippled area is where 0.704 < ri < 0.706. Locations of geo- graphic features mentioned in text are: (1) Gualala area, (2) Bodega Head, (3) Point Reyes, (4) Farallon Islands, (5) Mon- tara, (6) Ben Lomond, (7) Santa Lucia Mountains, '(8) El Paso Mountains, (AA)—Amargosa aulacogen. Faults mentioned in text are: (A) Coast Range thrust, (B) Seal Cove-San Gregorio, (C) Rin- conada, (D) San Andreas, (E) San Gabriel, (F) San Juan, (G) Gar- lock. Thin lines outline areas of Mesozoic granite rocks (see fig. 1). leeco‘nstruction along faults is made relative to a fixed Mojave oc . DEVELOPMENT OF THE CONTINENTAL MARGIN 7 suggested to have formed by slicing and fragmenta- tion of continental crust along transform boundaries, and some may be floored by oceanic crust (Nilsen and Clarke, 1975). With these facts in mind and because there is no compelling reason to shift to the south the granitic exposures from Montara to Bodega Head, we suggest these grantitic rocks may represent the deeply exposed rocks of a volcanic arc terrane that were emplaced from the west into their positions shown in figure 3 during the Late Cretaceous and Paleocene. DEVELOPMENT OF THE CONTINENTAL MARGIN Another noteworthy feature of the pattern of ri after these major fault displacements are removed is an area in the southern Sierra Nevada and central Mojave Desert characterized by Mesozoic granitic rocks and late Cenozoic volcanic rocks with ri between 0.7040 and 0.7060 between terranes intruded by Mesozoic granitic rocks with ri greater than 0.7060. The ri of Mesozoic granitic rocks in this area indicates a discontinuity underlain by ensimatic crust between two areas underlain by ensialic crust. The northern (eastern) terrane characterized by Mesozoic granitic rocks with ri greater than 0.7060 we will call Sierran, and the southern (western) terrane characterized by Mesozoic granitic rocks with ri greater than 0.7060 we will call Salinian—western Mojave. The time of forma- tion of the discontinuity between the Salinian-west- ern Mojave and the Sierran ensialic terranes is only surmised from geologic features in its vicinity; these features are discussed below. The systematics of the isotopic data from granitic rocks in the discontuinuity are compatible with the timing inferred from the geo- logic considerations. A trough that controlled the Pahrump Group and subsequent Precambrian sedimentation, named the Amargosa aulacogen (Wright and others, 1974), oc- curs within the Sierran terrane (fig. 3) immediately east of the discontinuity between the ensialic terranes. The basal sedimentary unit in the trough, the Crystal Spring Formation, is intruded by basaltic dikes and sills of probable 1,200 my age and lies unconformably on crystalline basement of approximately 1,700 my. age. The proximity of the aulacogen to the discontinu- ity between ensialic terranes suggests that these fea- tures are related: the aulacogen would be the failed arm of a triple junction (Burke and Dewey, 1973; Hoffman and others, 1974) with the other arms repre- sented by the ensimatic terrane in the southern Sierra Nevada and central Mojave Desert now characterized in part by Mesozoic granitic rocks and Cenozoic ba- salts with ri less than 0.7060. These relations suggest the discontinuity could have formed as long as 1,200 my ago. The time of the formation of the discontinuity be- tween the Sierran and Salinian-western Mojave ter- ranes is also limited by the oldest crystal rocks within the discontinuity; these old rocks unfortunately are known only poorly. The oldest of these known include metamorphosed Paleozoic sedimentary rocks and vol- canic rocks. Ordovician oceanic sedimentary rocks oc- cur in the El Paso Mountains (fig. 3), but because these strata have affinities to western-facies eugeo- synclinal rocks of the Cordilleran geosyncline, they are considered by some workers to be allochthonous and emplaced from the west (Poole, 1974). Other me- tamorphosed carbonates and eugeosynclinal rocks of Paleozoic age lie in the discontinuity south of the Garlock fault in the central Mojave Desert (Jennings and others, 1962). These rocks are flanked on both the east and the west by outcrops of Precambrian crystal- line basement of approximately 1,700 my age and by miogeosynclinal rocks of Paleozoic age (Stewart and Poole, 1975). The strontium isotopic systematics of Mesozoic granitic rocks in the discontinuity with ri less than 0.7060, as discussed below, are compatible with the development of the discontinuity during Precambrian continental rifting at the time of formation of the au- lacogen. However, geologic evidence indicates that parts of the discontinuity were reactivated or became active during renewed rifting of the North American continent immediately prior to sedimentation in the Cordilleran geosyncline. If the interpretations above are correct, the Salinian-western Mojave terrane was a continental mass that lay west of the site of Paleozoic eugeosynclinal sedimentation in the Cordilleran geo- syncline. Its present position in southern California is the result of subsequent Mesozoic convergence along the western margin of North America; it may result in part from about 800 km of middle Mesozoic left- lateral displacement along the extension of the zone of disruption of Precambrian basement, as described by Silver and Anderson (1974). Figure 4 shows the configuration, where presently known, of the lines r1 = 0.7040 and ri = 0.7060 on an outline map of the western United States after re- moval of lateral displacements along the San Andreas and Garlock fault systems. The configuration of these lines in Idaho and Washington is from Armstrong, Taubeneck, and Hales (1977). The line ri = 0.7060 marks the boundaries of ensialic crust and the sea- ward edge of late Precambrian and Paleozoic marine miogeosynclinal sedimentation along the Sierran ter- rane. The north-south trend of the edge of ancient 8 INITIAL STRONTIUM ISOTOPIC COMPOSITIONS OF MESOZOIC GRANITIC ROCKS continental crust in central Idaho and northern Ne- vada changes abruptly at about lat 38° N in central Nevada to westward, running into eastern California. At about long 120° W, the trend of the margin changes abruptly again to about north-south as far as the dis- continuity between Sierran and Salinian-western Mojave terranes. Lower Paleozoic strata in northern California, Oregon, and Idaho can be divided into three stratigra- phic belts (Churkin, 1974). The western volcanic rock and graywacke belt occupies the region where the ri of Mesozoic granitic rocks are less than 0.7040. The east- ern belt of carbonate rock and quartzite occupies the 120° 115° | I SOUTHERN CALIFORNIA 0 100 . 200 300 400 KILOMETEHS BATHOLITH l I FIGURE 4.—Location and configurations of lines ri = 0.7040 and 0.7060 in western United States. Displaced basement rocks along San Andreas and Garlock fault systems have been restored to positions shown in figure 3. region where rj is greater than 0.7060. The central belt of graptolite shale and chert occupies the region where ri of Mesozoic granitic rocks are between 0.7040 and 0.7060. In the Mojave Desert, the geologic history of base- ment rocks and the record of Paleozoic sedimentation is only poorly known. This lack of knowledge is princi- pally because of poor exposures of basement rocks and the poor fossil control in those rocks that are exposed. However, the remarkable correspondence between strontium isotopic ratios in Mesozoic granitic rocks and late Cenozoic mafic volcanic rocks and lower Paleozoic stratigraphy to the north suggests to us the following: the discontinuity between the Salinian- western Mojave and Sierran terranes defined by ri be- tween 0.7040 and 0.7060 in its Mesozoic granitic rocks is an indication of a Paleozoic sedimentation history in this discontinuity like that in the two belts of eu- geosynclinal rocks to the north. If this postulate is cor- rect, a puzzling exception in plate-tectonic models of Mesozoic igneous activity in California, Nevada, and Arizona can be resolved. A locus of Jurassic magmatic activity along a north- west-southeast trend extends from southern Arizona to northwestern California and is crossed in the cen- tral Sierra Nevada by a locus of Cretaceous magmatic activity with a more northerly trend (Kistler and oth- ers, 1971, fig. 2; Kistler, 1974, fig. 2). These loci place older Mesozoic igneous rocks to the west of younger ones in Northern California and Nevada and younger Mesozoic igneous rocks to the west of older ones in southern California and Arizona. Of the many existing plate-tectonic models for the Mesozoic magmatic ac- tivity in California (Hamilton, 1969), none has ac- counted for the inland locus of Jurassic magmatism, extending from southern Arizona across the eastern Mojave Desert and into the Inyo-White Mountains in eastern California. In fact, the Jurassic magmatic ac- tivity in Arizona cuts the Precambrian craton and was hundreds of kilometers inland from the present conti- nental margin. This fact led Kistler, Evernden, and Shaw (1971) to account for it as simply a locus of mag- matism manifesting a linear zone of high heat flow in the mantle that had characteristics like present-day oceanic rises. Continued geologic, geochronologic, and isotopic tracer studies have now identified other features asso- ciated with the inland locus of Jurassic magmatism. A zone of disruption that extends S 50° E from the southern Inyo Mountains into the Sierra Madre Occi- dental of Sonora offsets Precambrian crystalline rocks 1,725—1,800 my. old some 500 km in a left-lateral sense and lies along the locus of Jurassic magmatism; 700—800 km of left-lateral offset of Paleozoic deposi- DEVELOPMENT OF THE CONTINENTAL MARGIN 9 tional trends occurs near the same structure (Silver and Anderson, 1974). The discontinuity between the Sierran and Salinian-western Mojave terranes lies along the western margin of the Jurassic magmatic locus. The apparent left-lateral shear zone identified by Silver and Anderson (1974) led these investigators to suggest that the locus of Jurassic magmatism marks the position of a former plate boundary. The coinci- dence of the discontinuity between the continental Sierran and Salinian-western Mojave terranes with the western margin of the Jurassic intrusive locus strengthens this concept. Figure 4 shows the relative positions of the ensialic Salinian-western Mojave and Sierran terranes after removal of lateral displacements along the San An- dreas and Garlock fault systems. Stewart and Poole (1975) have correlated two miogeosynclinal Precam- brian and Paleozoic sections in the Salinian-western Mojave terrane with two similar stratigraphic sections in the Sierran terrane. This correlation requires that these two terranes have been in the same relative posi- tions since the late Precambrian (Stewart and Poole, 1975). On the other hand, Silver and Anderson (1974) suggest a correlation of Precambrian and Paleozoic strata in the Sierran terrane with strata on the west side of the zone of disruption in the Precambrian basement about 800 km to the south. To us these dif- fering interpretations indicate that individual strati- graphic sections do not uniquely define relative positions of deposition of sedimentary strata in the Cordilleran miogeosyncline. Apparent truncation and offset of ancient basement terrane, however, are pro- vocative. Therefore, we tested where the Salinian- western Mojave terrane would lie in the early Mesozo- ic if its position shown in figure 4 resulted from a left— lateral displacement during the middle Mesozoic along the extension of the zone of disruption of Pre- cambrian basement described by Silver and Anderson (1974). The position is shown in figure 5. Similar shapes and juxtaposition make it possible to speculate that the Salinian-western Mojave terrane once occu- pied the wide region between the ri = 0.7040 and ri = 0.7060 lines in northwestern Nevada. We envision the configuration of the margin of con- tinental crust, indicated by the line ri = 0.7060 in the western United States (fig. 4), as developing in the fol- lowing way. During the time of development of intracontinental basins that received the Belt Super- group sediments, about 1,200 to 850 my ago (Obrado- vich and Peterman, 1968), a true continental separa- tion occurred along a locus now marked by the line ri = 0.7040 (fig. 6A). Burke and Dewey (1973) propose a continental separation at this time, but their locus of separation is indicated to be well to the east of the line ti = 0.7040. The western continental plate moved away, and its present location is unknown. This rifting event died out probably about 850 my ago. Just prior to the Early Cambrian, rifting began again. The initial locus of the new separation is marked by the line ri = 0.7060. In Washington and Idaho, the new locus of rifting coincided with the earlier locus and the lines ri = 0.7 040 and 0.7060 are essentially coincidental (Arm- strong and others, 1977). In Nevada and California, the new locus of rifting extended into the continental terrane. As a consequence, the western plate consisted of both mafic lithosphere made 1,200—850 m.y. ago 120° 115° Salinian-westem Mojave terrane 4o“ — O 100 200 300 400 KILOMETERS |_L__l—__L.___._l—l | l FIGURE 5.—Position of Salinian-western Mojave terrane after 800 km of left-lateral displacement is removed along extension of zone of dislocation in Precambrian basement described by Silver and Anderson (1974). 10 INITIAL STRONTIUM ISOTOPIC COMPOSITIONS OF MESOZOIC GRANITIC ROCKS and older continental fragments, including the Salin- ian-western Mojave terrane (fig. 63). During Mesozo- ic convergence along the western margin of North America, the continental fragments in the western plate were returned close to their former positions. Accepting the rifting history as indicated in figure 6, material intruded into the rift zones would produce mafic (oceanic) lithosphere. We prefer to use the term mafic lithosphere because modern oceanic lithosphere is defined on the basis of seismic characteristics, and even though this ancient rift filling was probably oce- anic crust, it is no longer identified as such seis- ~ 600 - 350 m.y. FIGURE 6.—Diagram of model of continental rifting used to ac- count for present configurations of lines ti = 0.7040 and ri = 0.7060. A, Continental separation 1,200—850 m.y. ago during de- velopment of Precambrian aulacogens of Belt age. Locus of sepa- ration is now marked by line ri = 0.7040. B, Continental separation during early Paleozoic beginning about 600 m.y. ago. Note that western rifting plate is made up of both continental and mafic lithosphere. Initial locus of rifting is now marked by line ti = 0.7060 (edge of Precambrian continental crust). mically. This mantle-derived material would have dif- ferent Rb, Sr, and r1 than the Precambrian lower con- tinental crust. In the discussion that follows, we will show that the strontium isotopic systematics are com- patible with deriving Mesozoic magmas west of the line ri = 0.7060 from the lithosphere produced during the two rifting events in our model. TRACE ELEMENT VARIATIONS Two values of ri, 0.7040 and 0.7060, mark natural separations of Mesozoic granitic rocks in the Sierra Nevada into three types on K-Rb, K-Sr, and Rb/Sr- Rb variation diagrams (Kistler and Peterman, 1973). Using the alkali-lime index of classification of sili- ceous plutonic rocks (Peacock, 1931), calcic plu- tonic rocks have ri less than 0.7060, and calc—alkalic granitic rocks have ri values greater than 0.7060 (Kistler, 1974). Enough Rb, Sr, and r1 data now exist for California granitic rocks to make some general statements about elemental abundances in them rela- tive to ri. Rubidium concentration and ri (fig. 7) correlate in almost all the samples. For samples with ri greater than 0.7040, Rb and Si02 are also positively cor- related. Tie lines between some points join samples from mapped cogenetic granitic rock sequences. SiOg does not fall below 60 weight percent in the rocks in- vestigated that have ri greater than 0.7080 or below 55 weight percent in the rocks investigated that have ri between 0.7040 and 0.7080. In granitic rocks with ri greater than 0.7040, rubidium reaches a maximum concentration of about 200 ppm and the maximum Si02 content is about 75 weight percent. Three sam- ples that plot in an anomalous position relative to other specimens with ri less than 0.7040 are trondjhemites with Si02 that average 71 weight per- cent but contain lower Rb concentrations than any other specimens investigated. Strontium concentration is plotted against ri in fig- ure 8 for each granitic rock specimen. Granitic rocks with ri greater than 0.7060 have maximum values of about 800 ppm strontium in the most mafic speci- mens, and those with ri less than 0.07060 have maxi- mum values of about 650 ppm Sr in the most mafic specimens. Concentration of strontium in the most felsic rocks is about 100 ppm regardless of ri. When rubidium is plotted against strontium (fig. 9) for all granitic rocks investigated with ri less than 0.7060 as well as for average oceanic basalts (Hart and others, 1970), points can be separated into three dis- crete groups. Points representing granitic rocks with ri between 0.7030 and 0.7040 from the western Sierra Nevada lie along the oceanic basalt line and trend into SOURCE MATERIALS FOR THE GRANITIC ROCKS 11 °'7‘2° I I I I I I I I I I I I I I I I I I I I I 0.7100 — _ {I _ I _ 0.7080 — I 'I I'- f I .1 H I I __ I I - - — - I. I .I I I _ I I I I I I I I I -: 0.7060 — I 5—H I I I I I {-1 I — _ I. I I I _ III fu—H' _II -I_l—lI—————.. 0.7040 — -. I I I I _ I _ I I I H I——-———I _ 0.7020 — _ Q7000 I I i I I I I I I I I I I l I I I o 100 200 RUBIDIUM CONTENT, IN PARTS PER MILLION FIGURE 7.—Rb concentration plotted against initial 86Sr/87Sr values for specimens of Mesozoic granitic rocks in California. Lines join samples, from mapped cogenetic granitic rock sequences. the group of points representing Sierran granitic rocks with ri between 0.7040 and 0.7060.Th0se specimens with Rb and Sr abundances equivalent to oceanic ba- salts are trondjhemites, and the others are tonalites. Points representing other granitic rocks with ri less than 0.7060 define two fields in figure 6. Granitic rock specimens from the southern California batholith, two specimens from the southern Sierra Nevada near Te- hachapi, and the single specimen from Ben Lomond in the Salinian block lie in a field that does not overlap the field for granitic rocks in the Sierra Nevada with comparable ri. The separation of granitic rocks into groups on the diagram that can have similar ri but grossly different strontium concentration for any giv- en rubidium concentration suggests that source mate- rials for the southern California batholith and several of the granitic rocks in the southern Sierra Nevada had trace-element compositions different from the source materials that yielded granitic rocks with simi- lar ri in the Sierra Nevada. The difference could also reflect a different history for the source materials or simply result from a different depth of magma genera- tion in a similar source. These granitic rocks lie at the south and north ends of the Salinian-western Mojave terrane. Points representing granitic rocks with ri greater than 0.7060 form a field that overlaps the field of granitic rocks in the Sierra Nevada with ri between 0.7040 and 0.7060. These points are not shown in figure 9. SOURCE MATERIALS FOR THE GRANITIC ROCKS In order to account for the observed variation in ri of Mesozoic granitic rocks north of the Garlock fault in California, Kistler and Peterman (1973) adopted a model in which the melts that resulted in the granitic rocks with ri greater than 0.7060 were derived from a lower continental crust that acquired its chemical and isotopic characteristics about 1,700 my. ago and had a ri of 0.7020 and Rb/Sr values that regionally varied between 0.06 and 0.10. If the source for the granitic rocks with ri less than 0.7060 was assumed to have ac- 0.7100 . I . | . I. .... o I I _ 00 o o . I” . '.:0°. :0. _ o o o o. . .0 o o 0 . .-: 0.7060 —— ... 0 .0 . E‘~.s’. ° I ‘° ° ° — C _ ° ”"o':.¢-°. . 0 _ .0 .0 $00 0 °_7020 1 4i L l 41 d l l I 0 400 800 STRONTIUM CONTENT, IN PARTS PER MILLION FIGURE 8.-——Sr concentration plotted against ri values for speci- mens of Mesozoic granitic rocks in California. 12 INITIAL STRONTIUM ISOTOPIC COMPOSITIONS OF MESOZOIC GRANITIC ROCKS quired its Rb—Sr characteristics at the same time, the ratios required to produce the presently observed ri variation range from 0.02 to 0.06. It was pointed out, however, that as the ri values of the Mesozoic granitic rocks approach 0.7030, it becomes increasingly more difficult to decipher a possible pre-Mesozoic history for the source material on the basis of ri data alone. We will refine our model for the pre-Mesozoic history of the source region for the Mesozoic granitic rocks with ri less than 0.7060 on the basis of our model for development of the configuration of the western mar- gin of ensialic crust (fig. 6). We plotted Rb/Sr against ri for Mesozoic granitic 100 10 TB EXPLANATION Sierra Nevada and Central Mojave El 0.7030 < ri < 0.7040 0 0.7040 < ri < 0.7050 0 0.7050 < ri < 0.7060 Southern California batholith A 0.7030 < ri < 0.7040 A 0.7040 < 'i < 0.7050 Northern boundary Salinian — W. Mojave terrane V 0.7050 < r5 <70.7060 RUBIDIUM CONTENT, IN PARTS PER MILLION L I Average oceanic basalts (Hart and others, 1970) OFB = Ocean floor basalt LKT = Low potassium tholeiitic TB = Tholeiitic basalt AB = Alkali basalt 1 I l I l | I 100 1000 STRONTIUM CONTENT, IN PARTS PER MILLION FIGURE 9.-—-Rubidium concentration relative to strontium con- centration in California granitic rocks with ri less than 0.7060. rocks in California (fig. 10). An isochron with ri equals 0.7020 and 1,600—my age (1,600 my. reference isoch- ron used to account for the average 100 my age of the granitic rocks investigated) is also shown on the dia- gram. With the data available only from the granitic rocks north of the Garlock fault (Kistler and Peter- man, 1973), all points fell to the right of a 1,600-my. isochron on a similar diagram. This distribution was compatible with an increase in Rb/Sr in melts derived during partial 'melting and subsequent differentiation from a 1,600 m.y.-old source with ri = 0.7020 and Rb/Sr between 0.02 and 0.10. The new data also fit this distribution except for two specimens with ri greater than 0.7080. However, the most mafic speci- mens with ri less than 0.7060 have Rb/Sr about twice that implied by the 1,600 m.y.-old source, and the most mafic specimens with ri greater than 0.7060 have Rb/Sr only slightly higher than that implied by the source. We feel that these Rb/Sr differences are sig- nificant and bear on the history of the source materi- als for the granitic rocks. If the source for all the Mesozoic granitic rocks in California formed 1,700 my ago and had ri of 0.7020 at that time, the relatively high values of Rb/Sr in the granitic rocks with ri less than 0.7 060 could be due to a lesser degree of partial melting of these source materi- als than the degree of partial melting of similar source material for granitic rocks with ri greater than 0.7060. Rb/Sr is higher in the initial melt than in the granite source and would vary inversely with the degree of melting. However, in terms of major-element chemis- try, granitic rocks with ri less than 0.7060 are calcic, and those with ri greater than 0.7060 are calc-alkalic (Kistler, 1974). This fact suggests that different abun- dances and ratios of large-ion lithophile elements in the groups of granitic rocks are due to processes other than degree of melting of similar sources, because less- er degrees of melting should, in terms of major ele- ments, yield more alkalic rather than more calcic magmas. We will elaborate below. Our model (fig. 6) indicates that the ensimatic lith- osphere to the west of the Sierran terrane formed be- tween about 600 and 350 my. ago. In figure 10, we have drawn a 500 my. isochron (500 my. isochron is used to account for the average 100 my. age of the granitic rocks investigated) with ri of 0.7030. The ri of 0.7030 was selected because this is the lowest mea- sured by us in any Mesozoic and younger igneous rocks to the west of the 0.7060 line. All points for gran- itic rocks with ri less than 0.7060 lie to the right of this isochron, a feature that is compatible with deriving the magmas represented by these granitic rocks from a source terrane about 600 my old and characterized by Rb/Sr between 0.012 and 0.10. Granitic rocks with SUMMARY AND CONCLUSIONS 13 0.7100 l l l l 0.7080 ' ' 0 ° ' a o o 0 _ o 0 e 0 0.7060 0 . o — O . . — o o L“ 0.7040 l — I _ EXPLANATION I Southern California batholith, 0'7020 Ben Lomond and Tehachapi Mountains _ samples 0 All other samples — 0.7000 - — I l I I l l l l l 0 0 1 0.2 0.3 O 4 0.5 0.6 0.7 0.8 0.9 1.0 Fib/Sr FIGURE 10.—Isochron plot for California granitic rocks. Rb/Sr plotted against ri the 1,600-m.y., 1,100-m.y., and 500-m.y. isochrons shown for reference with regard to possible age of source material of granitic rocks as discussed in text. ri greater than 0.7060 could not be derived from a source terrane with these characteristics. Southern California batholith specimens, located in an area extending south from the south edge of the Salinian-western Mojave terrane, and the four speci- mens with ri less than 0.7060 along the north edge of the Salinian-western Mojave terrane (fig. 9), have generally lower Sr for any given Rb abundance than other California granitic rocks with equivalent ri. This fact indicates that the source for these granitic rocks could have been depeleted in Sr relative to the source for the granitic rocks with similar ri in the northern and western Sierra and in the eastern part of the dis- continuity. The indicated depletion is compatible with a different source history and composition than that for the source of Sierran granitic rocks with simi- lar ri. The terrane into which these granitic rocks are intruded would be mafic lithosphere formed between 1,200 and 850 my. ago that became part of the west- ern plate during the second rifting stage beginning in the Cambrian (fig. 6B). The lithosphere source mate- rial for these granitic rocks is older than that for grani- tic rocks with similar ri in the Sierra Nevada, and it possibly formed with a ri of around 0.7010. A 1,000- m.y. isochron (1,000-m.y. isochron used as an average age for the source) with this ri lies close to the left of those points (shown as black squares in fig. 10) repre- senting these granitic rocks. SUMMARY AND CONCLUSIONS Kistler, Evernden, and Shaw (1971) and Armstrong, Taubeneck, and Hales (1977) interpreted values of ri greater than 0.7060 in Mesozoic granitic rocks in the western United States as being due to contamination of magmas with less radiogenic strontium by radio- genic strontium from the host rocks. We (Kistler and Peterman, 1973) tested the possibility of contamina- tion by intruded wallrocks of granitic magmas for rocks with similar ri and rejected the possibility. With the additional data available, including those of Arm- strong, Taubeneck, and Hales (1977 ), we still reject contamination as a dominant cause of isotopic vari- ation and consider variation in ri as time dependent and reflecting Rb/Sr differences established much earlier in the source materials for the granitic mag- mas. Ages inferred for the source materials from the systematics of relation between Rb, Sr, and ri in the granitic rocks are consistent with ages inferred for the sources from geologic considerations. This interpreta- 14 tion implies that the pattern of ri of igneous rocks maps a lithosphere zone of melting, probably at a depth of 30 to 50 km, that intersects ancient crust of different ages and compositions. An alternative to the constant depth zone of litho- sphere melting to explain the variation in ri has to be considered. The granitic rocks with ri greater than 0.7060 also have the highest strontium concentrations (fig. 8). Partial melting of ensialic crust is not neces- sarily a unique source for increased Sr relative to par- tial melting of ensimatic crust. Also, a mixing model (mixed source, not mixed magmas) with basaltic (oce- anic crust) and granitic (continental crust) end mem- bers should show a negative correlation between ri and Sr. However, Hart and others (1970) showed a positive relation between depth to seismic zone and Sr concentration in overlying volcanic rocks in the major active subduction zones of the Pacific. Their model to account for this relationship utilized the concept of large-ion-lithophile “depleted” versus “undepleted” mantle as source materials for the eruptive magmas. The model could be modified to include “suboceanic” versus “subcontinental” mantle sources, and the depth aspect would not be ignored when the Sr con- tents of the samples most distant from the trench are so high. Even though the granitic rocks with high ri are not alkalic, this may not be a discriminating fac- tor. Many Cenozoic mafic lavas with high ri are alka- lic. With strontium concentration being a function of depth of melting, our major argument, the necessity of continental crust associated with the plutons having ri greater than 0.7060 is unaffected. The ri variation shows that the source yielding high—ri magmas must have older and (or) higher Rb/Sr material than that yielding low—ri magmas. Whether the ri = 0.7060 con- tour reflects an “edge” or simply an intermediate de- gree of melting of the two end members that accomplished the same thing does not much affect the plate-tectonic interpretation. The low—ri areas still re- flect the contribution of the low—Rb/Sr end members and require some interpretation such as a rift that re- moved the high—Rb/Sr and (or) older parent. Both the constant-depth zone and variable-depth zone of lithosphere melting to account for the observed vari- ation in ri and Sr abundance in the Mesozoic granitic rocks in California are within regions of granitic magma generation considered possible according to experimental evidence summarized by Wylie, Huang, Stern, and Maalae (1976). The strontium isotope data support the concept of rifting of the western margin of North America during the time of Belt sedimentation (Burke and Dewey, 1973) and again at the inception of sedimentation in the Cordilleran geosyncline (Stewart, 1972; Churkin, INITIAL STRONTIUM ISOTOPIC COMPOSITIONS OF MESOZOIC GRANITIC ROCKS 1974). Churkin’s model of the early Paleozoic sedi- mentation history of western North America involves migration of frontal arc systems away from the conti- nent and creation of interarc basins and marginal ocean basins that were sites of deposition of the sedi- ments in the graptolite shale-chert belt. Churkin’s concept requires the derivation of thick quartzite se- quences in the graptolite shale-chert belt from the craton far to the east. The petrography and age of some of the quartzites in this belt have led other work- ers (Ketner, 1966; Gilluly and Gates, 1965) to deny the possibility of an eastern source and to appeal to an un- known continental source to the west to provide the materials for these units. Westward rifting of a conti- nental fragment, possibly the Salinian-western Mo- jave terrane, from the area between lines ri = 0.7040 and 0.7060 in northwestern Nevada and northeastern California beginning in the Cambrian (fig. GB) would support the latter view. Strontium-isotope studies of granite plutons have proved to be useful in tectonic studies. Investigations of possible offsets along transcurrent faults in the past have relied on apparent displacements of sedimentary rocks, because igneous and metamorphic basement rocks seldom have distinctive physical characteristics that can be correlated unequivocally over long dis- tances. Current methods of classification of igneous rocks restrict their use as indicators of transcurrent fault displacement—granodiorites around the world look pretty much alike. However, in granodiorites in- vestigated so far in California, ri ranges from about 0.7040 to 0.7095. Strontium isotope ratios, therefore, provide an easily determined parameter in basement terrane with enough variation to test transcurrent off- sets suggested by apparent displacement of superjacent sedimentary strata or other geologic fea- tures. Our test of the suggestion of Silver and Anderson (1974), that a minimum of 500 km of left-lateral dis- placement during the middle Mesozoic occurred along the trend of the Jurassic locus of magmatism extend- ing from California to Sonora, supports but does not prove the concept. We do not know where the locus of dislocation could be to the west of the Sierra Nevada nor its exact location in southern California; any or all of the faults in the Foothills fault system (Clark, 1960; Duffield and Sharp, 1975) are possible candidates in the Sierra Nevada. Clark (1960), Baird (1962), and Cebull (1972) have presented evidence for possible strike-slip displacement along the components of the Foothills fault system. The model of two-stage rifting of the western mar- gin of North America during the Precambrian and early Paleozoic not only helps to resolve the problem ROCK TYPE AND LOCALITY DESCRIPTION OF ROCKS INVESTIGATED 15 of source materials for quartzites in Paleozoic eugeo- synclinal assemblages in northwestern Nevada and northern California but also helps to account for a se- quence of lower Mesozoic quartzites, marbles, and pe- litic schists exposed discontinuously in a belt of roof pendants in the western Sierra Nevada south of lat 38° N. The position of these rocks has been consid- ered anomalous because they are separated from stra- ta of similar age and lithology to the east by a belt of volcanic and sedimentary strata of similar age (Stan- ley and others, 1971). Source materials for the quart- zite-carbonate sequence in the roof pendants would have to lie to the west, where none now exist. The western plate that encroached on North America dur- ing the early Mesozoic, however, was made up of both oceanic and continental material (fig. GB). An ophio- lite-melange sequence of Permian and Triassic age oc- curs in a belt parallel to and west of the western belt of lower Mesozoic sedimentary rock (Saleeby, 1975). This situation places the lower Mesozoic sedimentary rocks in the western belt in a trench of early Mesozoic ‘ age (Schweikert and Cowan, 1975). Continental frag- ments in the plate encroaching from the west would provide a source for the quartz sands in this sequence. The proposed minimum of 500 km of left-lateral mid- dle Mesozoic disruption along this plate boundary (Silver and Anderson, 1974) would place the continen- tal rocks of the western plate in a position that is now far to the south of the site of deposition of western belt lower Mesozoic sedimentary rocks. Thus, the early Mesozoic trench associated with the converging plates lay to the east of the Salinian-west- ern Mojave terrane and along the western margin of the Sierran terrane. Magmatic activity associated with this stage of convergence occurred along the northwest-southeast locus extending at least from northern California to south-central Arizona (Kistler and others, 1971). When continental parts of the west- ern converging plate reached the trench, subduction was no longer possible. Continued convergence had to be relieved in a new trench developed to the west of the Salinian-western Mojave terrane, a trench now re- presented by Franciscan rocks. The late Mesozoic and Tertiary Great Valley sequence was deposited in the shadow of the Salinian-western Mojave terrane. The granitic rocks exposed discontinuously from Montara to Bodega Head (fig. 3) could have been brought to their apparently anomalous position west of the Great Valley sequence on the plate subducting beneath the Franciscan melange. Our model (fig. 6) requires two stages of rifting of the western margin of North America and molds into compatibility modern tectonic theory and geologically determined sedimentation history. The configuration of the plate boundaries as indicated by the strontium isotopic pattern is a crucial factor in the development of the model. In addition, geochronologically deter- mined magmatic history and isotope geochemistry permit a model to be developed for this same marginal configuration when it changed from accretionary to convergent. Reactivation of continental rift zones is apparently a common phenomenon (McConnell, 1972; Garson and Krs, 1976). A triple junction associated with continental rifting is inferred to be active now in southern Idaho (Prostka and Oriel, 1975), centered on the line ri equals 0.7060. A geophysically defined axis of symmetry for the Great Basin (Eaton, 1976) ex- tends from about lat 42° N to 34° N. The northern part of this axis lies near the line ri = 0.7060, but the southern part is entirely in crust characterized by Mesozoic granitic rocks with ri greater than 0.7060. If the axis is the locus of spreading under the Great Ba- sin (Eaton, 1976), it is a modern analogy of the rifting that occurred along the line ri = 0.7060 prior to depo- sition in the Cordilleran geosyncline (fig.6B)_ ROCK TYPE AND LOCALITY DESCRIPTION OF ROCKS INVESTIGATED Hornblende quartz diorite, specimen locality 124 of Evernden and Kistler (1970). Hornblende-bearing biotite quartz monzonite, specimen locality 125 of Evernden and Kistler (1970). Foliated quartz diorite, 2.6 km east of Glennville on California Hwy. 155. Sphene-bearing biotite-hornblende granodiorite, specimen locality 129 of Evernden and Kistler (1970). Foliated biotite-hornblende granodiorite, speci- men locality 130 of Evernden and Kistler (1970). Porphyritic biotite quartz monzonite, 13.0 km south from junction of California Hwy. 178 on Kelso Valley Road. Biotite quartz monzonite, 12.2 km south of local- ity Sr 6—73 on Kelso Valley Road. Biotite quartz monzonite, on Jawbone Canyon Road, 5.5 km east of junction with Kelso Valley Road. Biotite-hornblende granodiorite, on Jawbone Canyon Road, 12.6 km east of junction with Kelso Valley Road. Biotite quartz monzonite, on California Hwy. 58, 18.7 km east of Mojave Calif. In small quarry on north side of road. Biotite—hornblende quartz diorite, 17.4 km north of Willow Springs turnoff on Willow Springs- Tehachapi Road. Biotite granodiorite, on road to Kern County Park, 3.2 km from park entrance. Biotite-hornblende granodiorite, on California Hwy. 58, 13.2 km west of Tehachapi Railway Station. Sr 1—73 Sr 2—73 Sr 3—73 Sr 4—73 Sr 5—73 Sr 6—73 Sr 8—73 Sr 9—73 Sr 10——73 Sr 1 1—7 3 Sr 12—73 Sr 14—73 Sr 15—73 16 INITIAL STRONTIUM ISOTOPIC COMPOSITIONS OF MESOZOIC GRANITIC ROCKS Sr 16—73 Biotite quartz monzonite, first granitic rock outcrop on east side of Last Chance Canyon Road in El Paso Mountains. Triassic age for this granite (table 3) is from Armstrong and Suppe (1973). Hornblende-biotite granodiorite, on county road, 1.2 km south of Randsburg, Calif. Biotite quartz monzonite, 19.2 km north of junc- tion with U.S. Hwy. 395 of county road, 0.4 km south of Johannesburg, Calif. on county road that intersects with California Hwy. 178. Hornblende-biotite granodiorite, on road 2.3 km north of location of specimen Sr 18—73. Foliated porphyritic biotite quartz monzonite, outcrop on east side of U.S. Hwy. 395 at Little Lake turnoff on road to lower Little Lake Ranch. Biotite granodiorite, outcrop at center of south edge of sec. 10 T. 21 S., R. 38 E., Haiwee Reser- voir, Calif. quadrangle. Hornblende quartz diorite, outcrop in center of sec. 34, T. 21 S., R. 38 E., Haiwee Reservoir, Calif. quadrangle. A3 Fine—grained porphyritic alaskite, outcrop at cen- ter of west edge of sec. 10, T. 30 S., R. 43 E., Cuddeback Lake, Calif. quadrangle. A6 Sphene-bearing hornblende quartz diorite, outcrop on small hill, 0.4 km east of hill 3699 near center of north edge of T. 30 S., R. 44 E., Cuddeback Lake, Calif. quadrangle. Biotite-hornblende granodiorite, outcrop 305 in east of BM 2745 on Randsburg Road, Quail Mountains, Calif. quadrangle. Medium—grained biotite quartz monzonite, outcrop at 792 m on northwest—trending ridge in northeast corner of sec. 16, T. 17 N., R. 2 E., Quail Mountains, Calif. quadrangle. Biotite quartz monzonite, outcrop at Two Springs, Camp Irwin Military Reservation, Leach Lake, Calif. quadrangle. Medium—grained biotite quartz monzonite, outcrop at Desert King Spring, Camp Irwin Military Reservation, Leach Lake, Calif. quad- rangle. Gray biotite granite, outcrop at Black Magic Mines, Owlshead Mountains, Leach Lake, Ca- lif. quadrangle. Gray biotite granite, outcrop on hill 3342, Owlshead Mountains, Leach Lake, Calif. quad- rangle. Trachyandesite, outcrop on south edge near west corner of sec. 32, T. 19 N., R. 3 E., Leach Lake, Calif. quadrangle. REFERENCES CITED Anderson, D., 1971, The San Andreas fault: Scientific Am., v. 225, p. 51—67. Armstrong, R.L., Taubeneck, W.H., and Hales, P.O., 1977, Rb-Sr and K-Ar geochronometry of Mesozoic granitic rocks and their Sr isotopic composition, Oregon, Washington, and Idaho: Geol. Soc. America Bull., v. 88, p. 397—411. Armstrong, R.L., and Suppe, J., 1973, Potassium-argon geochronometry of Mesozoic igneous rocks in Nevada, Utah, and southern California: Geol. Soc. America Bull., v. 84, p. 1375-1392. 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