Paleontological Contributions
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THE UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS October 23, 1975 Paper 78 QUATERNARY FRESHWATER OSTRACODA FROM THE GREAT SALT LAKE BASIN, UTAH' KENNETH H. LISTER Department of Geology, The University of Kansas, Lawrence; present address: 317 Via Anita, Redondo Beach, California ABSTRACT Ostracodes are described from two cores, each more than 200 m long taken in Quater- nary sediments of the Great Salt Lake Basin, Utah. Thirty-one species of Ostracoda in thirteen genera have been identified. Most species belong to typically freshwater genera: Candona, Cyclocypris, Physocypria, Cyprinotus, Eucy pris, Cypridopsis, Potamocy pris, Ilyocy pris, Pelocypris, Cytherissa, Litnnocythera, and Dartvinula. One species of the genus Cyprideis is more typical of brackish water. Three new species are named: Candona camuramarginis, C. adunca, and C. pronopa. INTRODUCTION As part of a study concerned with changes in and Hoff (1942). The literature on Pleistocene relative abundance of ostracode taxa, two long freshwater ostracodes is somewhat less extensive cores taken in Quaternary sediments of the Great than that on living forms. Lack of soft parts has Salt Lake Basin, Utah, were sampled. About 700 made identification difficult in some cases and has samples were examined and from these a large allowed some confusion between adults and im- number of specimens were procured. Descrip- mature instars. Revisions of the genera Candona tions of thirty-one species of Ostracoda in 13 and Limnocythere are badly needed. genera make up the bulk of this work. Although During the late Cenozoic, freshwater ostra- descriptions of many of the species have been codes were, in general, evolutionarily conservative. previously published, some based on Recent speci- All of the previously described species from the mens lack details of carapace morphology. New Great Salt Lake Basin occur in Recent and species are described herein: Candona camura- Pleistocene ostracode faunas. The climatic fluc- marginis, C. adtinca, and C. pronopa. tuations of the Pleistocene apparently had little The volume of recent work on the systematics effect on the evolution of North American species of freshwater ostracodes is not great. Delorme of freshwater ostracodes. This probably was a (1970a, b, c, d; 1971) prepared an excellent mono- consequence of the fact that many freshwater graph of freshwater ostracodes of Canada that ostracodes were able to migrate with relative ease builds on the pioneering work of Furtos (1933) from one lake or stream to another (Van Mork- Manuscript received September I, 1974. 2 The University of Kansas Paleontological Contributions—Paper 78 hoven, 1962, P. 139). Migration throughout the most times the basin was occupied by a fairly Pleistocene in response to changing climatic con- large lake with extensive shallow areas whose ditions most likely caused genetic homogeniza- waters contained low to moderate amounts of tion within species, and thus worked against dissolved minerals. The regional climate at times speciation, which probably requires initially iso- of high lake level was probably cool, and the area lated, small populations (Eldridge and Gould, probably received more moisture than it does 1972). today. Moist, cool periods are thought to be cor- Current knowledge of the environmental tol- relative with glacial stages in the Pleistocene erances of freshwater ostracode species is rather (Eardley and Gvosdetsky, 1960) that alternated limited. Some data on Recent occurrences of the with drier periods during which the lake shrank species found in the Great Salt Lake Basin fauna or completely disappeared. The nature of the are summarized in Table 1. The most common ostracode fauna indicates that at certain times the members of the Quaternary assemblage from the lake waters were more saline than usual. During cores studied are: Candona rawsoni, Cyprinotus these times, Cyprideis salebrosa and Limnocythere glaucus, Cypridopsis vidua, Limnocythere friabil- is, Limnocythere itasca, Physocypria pustulosa, staplini were common. More details of the eco- Ilyocy pris biplicata, and Ilyocypris gibba. The logical history of the basin have been described abundance of these species may indicate that at elsewhere (Lister, 1974). STUDY AREA AND SAMPLING PROCEDURE During glacial stages, as moist climates re- Bonneville, and Provo as members, comprises placed prevailing arid conditions in most of south- gravel, sand, silt, and clay and is up to 100 m western North America, lakes developed in many thick. It is bounded stratigraphically by soils: the closed basins. The Great Salt Lake is a remnant Dimple Dell below and the Graniteville above, the of what was, at times, the largest of these lakes. latter separating the Little Cottonwood Forma- The area which encompasses Salt Lake Valley, tion from the Draper Formation. The Draper Utah Valley, the Bonneville Salt Flats, and Sevier Formation consists of sand and gravel tongues Valley was the site of successive Pleistocene lakes interbedded with lacustrine silt and clay and is up which developed during glacio-pluvial periods. to 50 m thick. The Draper Formation is overlain The latest and probably the most extensive of by the Midvale Soil, which in turn, is overlain by the Pleistocene lakes to occupy the Great Salt Recent alluvium and lake deposits. Formations Lake Basin was named Lake Bonneville by Gil- older than the Little Cottonwood have not been bert (1890), and the sediments deposited in this named. These older formations make up the bulk lake, Lake Bonneville Group. Hunt (1953) di- of the strata sampled in the present study. vided the Lake Bonneville Group into three for- In five places lacustrine sediments of the mations: Alpine, Bonneville, and Provo. Morri- Great Salt Lake Basin were cored under the son (1965) noted that as originally defined these direction of the late Armand J. Eardley. The formations were: 1) based on inferred lake his- cores are: Saltair (depth 200 m, taken 1956), tory rather than on lithology; 2) not tied to any section 28 (236 m, 1960), Wendover (171 m, specific type localities; 3) not separated by un- 1960), Knolls (152 m, 1960), and Burmester (307 conformities; 4) correlated with a given lake m, 1970). Only the Saltair core taken in the stage (water level) and thus did not include SE 1/4 sec. 25, T. 1 N., R. 3 W., at an elevation of volumetrically important transgressive and regres- 4,205 feet and the section 28 core taken in SE 1/4 sive deposits. Morrison expanded the Lake Bonne- SW IA sec. 28, T. 1 N., R. 2 W., at an elevation ville Group to include two major lacustrine epi- of 4,218 feet were sampled for the present study. sodes and named two corresponding formations: Their location in Utah and in relation to the Little Cottonwood and Draper. The Little Cot- shoreline of the Lake Bonneville high-stand is tonwood Formation, which includes the Alpine, shown in Figure 1. The Saltair and section 28 Lister—Quaternary Ostracoda from Utah 3 TABLE 1. Summary of Environmental Preferences of Recent Representatives of Species of Ostracodes Found in Great Salt Lake Basin Sediments. From Various Sources, Including Delorme (1970a, b, c, d; 1971). • ‘Solt Lake City SPECIES FIAS ITATS Section 28 Candona acutula Shallow water, lakes, nearctic. Û tah Lake C. camuramarginis Temporary ponds, nearctic. C. caudata Streams and deeper parts of lakes, cosmopolitan. C. crogmaniana Permanent and temporary ponds, nearctic. C. atittnca C. pronopa Shoreline Lake Bonneville C. ratcsoni Ponds and lakes, tolerant of moderately high amounts of dissolved minerals, nearctic. Cyclocypris ampla Wide tolerance, ponds and lakes, nearctic. C. serena Wide tolerance, ponds and lakes, ncarctic. Physocypria pustulosa Lakes and ponds, not found in very cold water, holarctic. Cyprinotus glane us Lakes, not found in very cold water, holarctic. FIG. I . ImIcx niap of Utah showing location of cores use 1 Etteypris serrata Lakes and ponds, not found in in this study (designated by stars) and the shoreline of very cold water, holarctic. Lake Bonneville at its maximum extent. Cypridopsis Ticitta Lakes and ponds, in weeds, cosmopolitan. Potamocypris granulosa Lakes and ponds, holarctic. P. pallida Springs, holarctic. The type of sediments within the cores indi- P. smaragdina Lakes and ponds, not found in cates that lacustrine conditions prevailed in the arid regions, holarctic. basin alternating with periods during which the P. unicatidata Lakes and ponds, holarctic. ilyocypris biplicata Streams and lakes, holarctic. lake shrank and dried. Since major lake episodes I. gibba Streams and lakes, holarctic. and associated silty sediments probably correlate Pelocy pris tuberculata Playa lakes, nearctic, possibly to times of glacial advance in northern continental neotropical. North America, periods of soil formation most Cyprideis salebrosa Tolerant of saline water, lakes likely correspond to interglacial stages. However, and ponds, neotropical and nearctic. some soils may have formed during short-term Cytherissa lacustris Cold, deep lakes, holarctic. glacial retreats or developed locally during moist Lim nocyt here ceriotuberosa Lakes, nearctic. periods. Low water levels may also be recognized L. friabilis Lakes, nearctic. by the presence of plant root tubes, coarse elastics, L. illinoisensis Cool lakes, nearctic. reddish coloration of sediments, brine shrimp fecal L. itasca Cool lakes, nearctic. L. paraornata Streams, nearctic. pellets, and ooids (Eardley and Gvosdetsky, 1960; L. parascutariense Streams and lakes, ncarctic. Eardley, et al., 1973). L. psendoreticulata Lakes and permanent ponds, For the present study samples 2.5 cm long nearctic. were sawed from the 2 cm diameter Saltair and L. staplini Lakes, tolerant of moderate to high salinities, nearctic. section 28 cores. Samples taken from the Saltair Darwinula stevensoni Large, cool lakes, cosmopoli- core were spaced 10 to 20 cm apart where core tan. recovery was complete, whereas samples from the section 28 core were spaced 20 to 40 cm apart. The sediment was soaked in a cold, dilute solu- cores are the most complete and longest of the tion of sodium carbonate and most samples had four cores taken before 1970 and available at disaggregated within a day.