22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
change as the eastern border of the Wind River Basin is approached, 
and it is concluded that the basin was open to the east during at least 
the later part of early Eocene time. 
Conditions of deposition of the Tepee Trail formation were quite 
different. First, the bulk of the sediment being deposited was derived 
from the volcanic centers in the Absaroka-Yellowstone region. 
Second, very little material was being eroded from the mountain 
ranges in contrast to the vast amount of debris that had been shed 
by them during early Eocene time. There is little or no evidence of 
any marked general climatic change, although the local climate prob- 
ably was somewhat modified by the seemingly great volcanic activity 
no more than 70 miles or so to the west. 
The well-developed bedding and rounded pebbles, cobbles, and 
grains of volcanic material indicate that the final agent acting on most 
of the material in the Tepee Trail formation was running water. 
Pond or quiet-water environments certainly existed, as is indicated 
by the fresh-water limestone and beds of claystone, but these seem 
to be minor in the environment as a whole. It is possible that the 
pebbles and cobbles of volcanic material were carried from their 
source to the northeastern part of the Wind River Basin entirely by 
streams. The presence of cobbles, however, seems to imply streams 
of great carrying power. Other evidence for such streams, such as 
channeling and relatively thick accumulations of conglomerate, are 
largely lacking. Also, it is difficult to imagine streams with such 
carrying power having courses essentially parallel to the mountain 
fronts and as close to them as the distribution of cobbles would 
indicate. 
At present, the volcanic breccia, tuff, and minor intrusive rocks of 
the Tepee Trail formation in the Absaroka Range form steep escarp- 
ments above the Wind River Basin on the south and the Big Horn 
Basin on the east. These erosional escarpments clearly have little 
relation to the possible former extent of the materials into the Wind 
River and Big Horn Basins. Squaw Buttes, in the southwestern part 
of the Big Horn Basin, is an isolated remnant of the Early Basic 
Breccia (Van Houten, 1944). Although the pieces of the rock have 
been somewhat rounded, and the mass should be called a volcanic con- 
glomerate (R. L. Hay, personal communication, 1956), the rock is 
similar in appearance and physical characteristics to the breccias of 
the Absaroka Range. Squaw Buttes thus appears to be a remnant of 
volcanic material in the deposition of which running water was not 
the dominant agent. Probably masses of volcanic material once ex- 
tended much farther into the Wind River and Big Horn Basins than 
