Abstract

The Tate Museum Field Locale 1 (TMFL1), first discovered in 2002, has since yielded many interesting geological and paleontological finds. Though TMFL1 is situated on a large private ranch outside of Casper, only two relatively small areas are fossil-bearing, producing from outcrops in the Eocene Wind River Formation. Other than a few pieces of petrified wood, no fossils have been discovered in the Paleocene Fort Union Formation in the area.

TMFL1 is located near the edge of the Wind River Basin, with the Fort Union outcrop showing a 30 degree northeast dip. The contact between the Fort Union and Wind River formations is buried, and the Wind River Formation is nearly horizontal on top. Based on descriptions of the Wind River Formation from other areas in the basin, it appears that both the Lysite and Lost Cabin members are present, though an exact boundary between the two has not yet been determined.

Fossil finds are mainly micro-sites, with the majority or the fossil material comprising broken bits and pieces of bone and teeth. Mammal teeth of fauna ranging from small primates to large Coryphodon tusks have been found. Crocodile, turtle and gar remains are common in both producing areas. The fossils in the first area seem to originate from a few thin sandstone lenses between variegated siltstone layers similar in coloration to the Lysite Member as described by other studies. Fossils in the second area are found in buff-colored siltstones similar to the Lost Cabin Member, and the sites in this area produce more complete fossil remains.

Further exploration will help to determine why these two fossil-bearing sites are the only ones in TMFL1, and also to explain an occurrence of hematite-cocooned fossils in one section of the first site.