Two New Pleistocene (Kansan) Molluscan Local Faunas from Trego County, Kansas

Two new Pleistocene local faunas, the cedar Bluff and the Lone Tree, are reported from Trego County, Kansas. Twenty- three taxa were collected from the Cedar Bluff l.f. along the Smoky Hill River. The Lone Tree l.f. contains twenty-one taxa which were collected just below an ash bed. The mollusks associated with the ash and the topographic position of the deposits suggests a Kansan age. The stratigraphic position of the local faunas and the mollusks indicate the cedar Bluff l.f. is older than the Lone Tree l. f. Mollusks from both local faunas suggest temporary pools, surrounded by grass and some scattered shrubs and trees, existed on the floodplain of the ancestral Smoky Hill River. The climate, during the time the mollusks lived, combined cooler summers with winters which were probably slightly cooler than the present winters in Trego County, Kansas. A shift in mollusks susceptible to climatic change between the local faunas indicates the Cedar Bluff l.f. was cooler than the Lone Tree l.f. The presence of Gastrocopta cristata and G. procera only in the Lone Tree l.f., whose distribution is primarily southern, and the presence of an extant Arctic-Alpine taxa, Vertigo modesta, only in the Cedar Bluff l.f., indicates a slight warming trend in the area between the time the two faunas lived.