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Introduction
Pleistocene fresh-water ostracodes have been described from very few parts of the world and have never been previously studied from the central High Plains. The sinkhole country around Meade County, Kansas, (Fig. 1-2) affords a unique opportunity for study, inasmuch as ostracodes are found in several Pleistocene rock units exposed on the flanks of the stream-dissected sinkholes. Samples from these beds and additional samples from Pleistocene strata in Texas, Oklahoma, and Missouri and from Pliocene and Recent deposits in Meade County were studied in order to determine whether ostracodes could be used as guide-fossils for the Pleistocene Epoch or its stages and also to extend knowledge of this poorly known group of the Ostracoda.
Previous work--Published taxonomic analyses of Recent living fresh-water ostracodes have been carefully examined during the study of Pleistocene and Pliocene ostracodes, as the fossil forms are similar to or identical with living species. These descriptions of living species from widely separated areas in the United States and from Europe are primarily concerned with the soft parts of the animal, which are not preserved as fossils. The lack of adequate descriptions of the carapaces of these forms has been a considerable handicap in the present study.
Figure 1--Generalized map of the High Plains area showing sample-collecting localities.
Turner (1895) published the first important study of living ostracodes in the United States. Later, Sharpe (1918) diagnosed the known North American species and formulated a key for their identification. Sars (1926) described a few Canadian species; Furtos (1933) described ostracodes from Ohio; Dobbin (1941) described several species from Washington; and Hoff (1942) described the ostracodes of Illinois. Tressler (1947) compiled another checklist of known species of North American fresh-water ostracodes. Swain (1955) described the Recent fresh-water ostracodes living in the saline waters of San Antonio Bay, Texas, many of which have been found also in the Pleistocene fresh-water deposits of southwestern Kansas and the High Plains. Ferguson (1958) published a supplementary checklist for the period 1947-1957. Winkler (1960) described, from cave deposits in Michigan, an early Recent fauna that shows a similarity to the fauna described herein. Swain (1961) published the most recent revision of the classification of the cypridacean ostracodes, which is used in the present report, as part of Treatise on Invertebrate Paleontology, pt. Q, Arthropoda 3 (Moore, ed., 1961).
Figure 2--Map of Meade County, Kansas, showing localities sampled.
Relevant European studies referred to in this report include: Jones (1857), a study of the Tertiary and Pleistocene Ostracoda of England; Sars (1925), an extensive study of Recent Ostracoda from Norway and other parts of Europe; Klie (1938), a complete review of the Recent fresh-water ostracodes of Germany; Bronstein (1947), a study of fresh-water ostracodes of the Soviet Union, and Wagner (1957), a study of the ostracodes of the Pays-Bas region of Holland.
One of the first reports of ostracodes in Pleistocene deposits of North America was that by Baker in 1920. Staplin (1953) described the morphology and ecology of Pleistocene ostracodes from Illinois. Ostracodes were found in Meade County, Kansas, by Smith (1940) and by Frye and Hibbard (1941).
Methods--Specimens from the Pleistocene deposits of the High Plains were collected during the summer of 1956 and during the spring and summer of 1957. At most localities, samples of sand, clay, and silt were obtained at 1- to 3-foot intervals from outcrops for which measured sections had been published. Particular attention was paid to strata containing noticeable aquatic sedimentary structures or aquatic gastropod faunas. In a few outcrops ostracodes could be seen with a hand lens, but generally the samples were collected "blind" from well-sorted sands and silts. Where ostracodes were present in these samples they were found to be very abundant.
In the laboratory the samples were dried thoroughly in an oven, placed in beakers of water containing a small quantity of liquid detergent, heated to boiling, and the suspension decanted through 35- and 60-mesh screens. Samples free of clay and coarse sand were not heated but were washed under a stream of running water and sieved through 18-, 35-, and 60-mesh screens.
Acknowledgments--Gratitude is expressed to the following persons: Dr. C. W. Hibbard of the Museum of Paleontology of the University of Michigan for aid in the field and for obtaining some of the samples used in this study; Dr. A. B. Leonard of the Department of Zoology at the University of Kansas for a sample from Missouri used in this study; and to Professor J. Hughes of the Panhandle Plains Historical Museum for material from Texas used in this study. Gratitude is expressed to G. Lloyd Foster, former graduate student of the Department of Geology, the University of Kansas, who was helpful during the time of this study.
Repository--All of the types have been retained in the collections of the Department of Geology, the University of Kansas.
Stratigraphic Classification
The names and classification of stratigraphic units as used in this report (Fig. 3) are those of Hibbard (1958) for Meade County, Kansas. Dr. Hibbard accompanied us on most of our collecting trips and pointed out the placement of beds from which our samples were obtained relative to his stratigraphic classification. The classification of the Pleistocene currently used by the State Geological Survey (Jewett, 1959), is also shown in Figure 3.
Fig. 3--Southwest Kansas Pleistocene classification, modified after Hibbard (1958) and Jewett (1959).
Hibbard (1955, p. 183), with reference to classification based on the vertebrate fauna, stated:
"Only tentative correlation exists at the present time in North America between the glacial and interglacial deposits of the glacial region and the nonglacial deposits of the Ice Age (Pleistocene) outside of the glaciated regions. If only four major glaciations and three major interglacial intervals occurred in North America, then a direct correlation can be made between the nonglacial Pleistocene deposits in southwestern Kansas, and the known glacial section, on the basis of cyclic erosion, deposition, and successive Pleistocene faunas. Until more work is done and a better correlation exists between these regions it is considered best to treat the assignment of Pleistocene faunas from southwestern Kansas to definite glacial or interglacial ages as only tentative."
This consideration is especially true for a relatively unknown fossil group such as the ostracodes of the Pleistocene.
The ostracodes from the Pleistocene stages of the unglaciated High Plains.area cannot be adequately correlated with those of the glaciated region until more ostracode faunas have been described from the glacial type areas.
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Kansas Geological Survey, Geology
Placed on web November 2005; originally published June 1962.
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