The Stratigraphy and Mammalian Paleontology of the Wasatch Formation (Eocene), Fossil Butte National Monument, Lincoln County, Wyoming

The National Park Service conducted a study of the Fossil Butte area and decided that its scientific value and importance was sufficient to propose that the area be included in the National Park System both for public use and the preservation of the fossils located there. As a result of this study, a detailed paleontological reconnaissance of the early Eocene Wasatch Formation at Fossil Butte National Monument was conducted, with special emphasis placed on prospecting in outcrops that would be disturbed by construct ion activity, to determine if the destruction of paleontological sites would result, Additional localities with potential for the recovery of significant fossil specimens were determined during a general survey of other Wasatch exposures on the monument. There were six localities in the main body of the Wasatch Formation that produced identifiable fossil specimens. In the Fossil Basin, Oriel and Tracey (1970) have subdivided the Wasatch and Green River formations into several units. The Wasatch Formation has been divided in to seven units: the basal conglomerate member, the lower unnamed member, the main body, the sandstone tongue, the mudstone tongue, the Bullpen member, and the Tunp Member. The Green River Formation has been divided into the Fossil Butte Member and the overlying Angelo Member. The sediments of the main body of the Wasatch Formation suggest a fluviatile origin for these sediments. Depositional environments include streams, floodplains and swamps. Paleontological evidence supports this origin. Fifteen families are represented by the specimens collected during this reconnaissance. These specimens along with previous collections from Fossil Butte and nearby surrounding areas are identifiable to eighteen vertebrate species. Fourteen are mammals from the following families: Family Leptictidae, Family Adapidae, family Microsyopidae, Family Stylinodontidae, Family lschyromyidae, Family Hyaenodontidae, Family Miacidae, Family Hyopsodontidae, Fami ly Mcniscorheriidae, Family Coryphodontidae, Family Equidae, Family Helaletidae and Family Dichobuinidae. The specimen of Cynodontomyslatidens is a record for Fossil Butte National Monument. Correlation of the fauna with seven other local faunas places the Fossil Butte National Monument local fauna in middle early Eocene (Lysitean) age. Exposed beds at the proposed site appear rather unfossiliferous: however, a paleontologist or ranger naturalist should monitor fresh exposures for fossil specimens