COLLABORATIVE RESEARCH: Plio-Pleistocene Mammal Faunas and Environmental Change in the Meade Basin of Southwestern Kansas: A Combined Stratigraphic, Faunal, and Isotopic Approach

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The primary purpose of this project is to determine the effects of abiotic and biotic factors on the community structure and morphology of small mammals, especially rodents, during the past 5.0 million years in the Meade Basin of southwestern Kansas. The Meade Basin is a unique natural laboratory, as more than 100 fossiliferous localities (representing at least 40 superposed intervals) spanning the entire later Cenozoic are found within a small area of approximately 45 km2. Three radiometrically dated ashes at 2.1, 1.2-1.5, and 0.67 Ma provide calibration points for part of the sequence, and a magnetostratigraphic chronology will be developed that will add considerable refinement to the basic stratigraphic framework. Further field mapping will hopefully solve a few remaining thorny stratigraphic problems, especially in the upper part of the Rexroad Formation. Systematic studies at appropriate museums will refine the rodent database. A preliminary stable isotope study of paleosol carbonate nodules and caliche beds in Pliocene sediments has revealed significant habitat and climatic gradient changes, reflecting the expansion of tropical grasses throughout the Great Plains during this time. The isotopic studies will be extended to additional localities and to mammalian tooth apatite, to better refine the record of environmental change and to examine the response of small mammal diets to environmental gradients. Finally, appropriate analytical methods will be used with the rodent database to examine the dynamics of community assembly and anatomical change within lineages. The Meade Basin rodent database and stable isotopic record will generate one of the most detailed historical records of habitat, climatic, and faunal change in a terrestrial animal community anywhere in the world, and the stratigraphic model resulting from this project will provide the primary source of late Cenozoic stratigraphic information for the Great Plains region of North America.