NO. 4 GEOLOGY, WIND RIVER BASIN—TOURTELOT 9 
dant in some of the finer grained rocks. The minerals occur mostly 
as anhedral to euhedral crystals and the rocks would be classified as 
crystal tuffs, for the most part, except for their deposition in running 
water. Lithic fragments are common in most rocks, however, and 
are the major constituent in some. The lithic fragments are sub- 
rounded and are most abundant in association with strata that con- 
tain roundstones of volcanic rock. 
The green and brown member is fairly uniform in its gross litho- 
logic characteristics, being readily recognizable by its colors alone at 
most places. On the north side of Badwater Creek (loc. I and vicinity, 
fig. 2), the rocks consist of light-gray to grayish-brown hard ledgy 
fine-grained limy andesitic volcanic sandstone and siltstone some- 
what different in gross appearance from most beds in the Tepee Trail. 
A fragmentary tooth identified as Amynodon?, characteristic of the 
Tepee Trail of this area, suggests that this sequence is only a locally 
different facies of the Tepee Trail formation. 
The abrupt lithologic changes, on a bed-by-bed basis, that charac- 
terize the green and brown member of the Tepee Trail are shown 
by two sections in adjacent parts of secs. 22 and 27, T. 4o N., 
R. 90 W. (fig. 4), near the mouth of Sagebrush Draw. Green colors 
are striking in the rocks at the exposures in sec. 27 but are entirely 
missing in the section only about half a mile to the north. Both sec- 
tions have more yellow and gray colors than is common along the 
south end of the Big Horn Mountains. The only feature that appears 
to be common to the two sections is a conglomerate zone 40 to 50 
feet below the base of the gravel that caps the pediment surface 
below which the two sections are exposed. The conglomerate zone, 
however, is not continuous between the two sections. 
Gypsum and crystalline selenite are abundant on the weathered 
surface of these exposures. Selenite also forms on the weathered 
surface of Tepee Trail strata in other parts of the area but is particu- 
larly conspicuous here. The siltstone and claystone have no obvious 
pyrite content and the origin of the selenite is not known. It is pos- 
sible that these outcrops are the “deeply disintegrated clays... 
and much gypsum” mentioned by Granger (Sinclair and Granger, 
IQII, p. 105). 
At several places, rocks of the green and brown member contain 
abnormally large amounts of selenium, as much as 187 parts per 
million being found in one bed in sec. 3, T. 39 N., R. 91 W., Fremont 
County (Beath, Hagner, and Gilbert, 1946, p. 11). At this place, 
the rocks are red, white, ocher, green, and brown, and range from 
coarse grained to fine grained. The red colors are anomalous in the 
