Paleontology and geology of the Badwater Creek area, central Wyoming. Part 16. The Cedar Ridge local fauna (late Oligocene)

Abstract

Upper Oligocene strata unconformabiy overlying upper Eocene sediments outcrop along Badwater Creek, in central Wyoming.The fauna from the underlying Eocene sediments has been collected and studied by Carnegie Museum of Natural History since 1962.Late Oligocene mammals were first recognized in the overlying sandy facies during the 1964 field season by field parties of Carnegie Museum.Intensive collecting and use of screen washing techniques have resulted in the recognition of 26 mammal genera.Most of the fossils recovered are fragmentary, and are generally less than 3 mm in size, which indicates considerable transport of the material.This assemblage of animals is biased by two major factors.First, due to stream sorting, only small teeth and bones were deposited so that larger mammals, which surely lived near the site of deposition at that time, are not represented in the fauna.And second, the local climate was dry and of moderate temperature.This is indicated by the presence of calcic feldspars and gypsum crystals throughout the section.Due to the dry climatic conditions, only land mammals, which were adapted to this ecological situation, could live there and consequently these animals are represented in the present fauna.On the other hand, the animals, which required a more mesic condition, could not have lived there and consequently they are not represented in the