by Edwin D. Gutentag and Richard H. Benson
Originally published in 1962 as Kansas Geological Survey Bulletin 157, Part 4.
This online version has been created because the published version is currently out of print. This is, in general, the original text as published in 1962. The information has not been updated.
Water wells are drilled or dug in unconsolidated sand and clay, which differ in character from one location to the next to such an extent in some areas that mapping a water-producing zone solely on the basis of similarity of rock type is very difficult. Fossils can be very helpful in correlating water-bearing strata of the same age or strata formed in similar depositional environments. Microfossils (those too small to identify with the unaided eye) are particularly useful for this purpose, as undamaged specimens can be recovered from well cuttings. The most abundant microfossil in the surficial water-yielding strata of Kansas is the microscopic fresh-water relative of the lobster, the ostracode.
The ostracode abounds in almost every aquatic habitat but it is not commonly known to the layman. To the geologist the ostracode represents an important form of past life found in rocks of all ages, extending back from the Recent for more than 500 million years, and deposited in environments ranging from deep ocean to lakes and streams. The Germans call the ostracode "muschelkrebs" or mussel-shrimp, because it resembles a tiny shrimp contained in the shell of a fresh-water mussel. Illustrated within this report are ostracode shells, which are the sole remains of an otherwise very complicated form that has lived in the High Plains area from some time before the Ice Age to the present.
Richard H. Benson
Pleistocene deposits in southwestern and central Kansas, western Oklahoma, and northern Texas have yielded eleven species of fresh-water ostracodes. Pliocene and Recent deposits have each yielded one species. Genera represented are Cypricercus, Eucypris, Cypridopsis, Potamocypris, Candona, Ilyocypris, Cyprideis, and Limnocythere. Four species are new: Eucypris meadensis, Candona nyensis, C. renoensis, and Limnocythere staplini. Nine species described previously from living forms were found as fossils: Cypricercus tuberculatus (Sharpe), Cypridopsis vidua (O. F. Müller), Potamocypris smaragdina (Vávra), Candona caudata Kaufmann, C. crogmaniana Turner, C. fluviatilis Hoff, Ilyocypris bradyi Sars, I. gibba (Ramdohr), and Cyprideis littoralis Brady.
All genera represented and two of the new species (Eucypris meadensis and Candona nyensis) are living today. The existing classification of living ostracodes, based on appendages, is used for the Pleistocene forms, although the fossil ostracodes were necessarily described on the basis of their carapace features.
Candona nyensis n. sp. seems to be restricted to deposits of Pleistocene age, and can be used locally in southwestern Kansas to distinguish Pleistocene from Pliocene sediments.
Cyprideis littoralis Brady, which normally lives in brackish water, seems to have become adapted to the fresh-water environment of Pleistocene sinkholes.
Kansas Geological Survey, Geology
Placed on web November 2005; originally published June 1962.
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