24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
derived from the pre-Tertiary rocks. It is difficult to imagine how 
the volcanic material could have been placed almost within the canyon 
mouth by streams flowing eastward or northeastward in the Wind 
River Basin, even though a source for the volcanic material might 
have been a mudflow 50 or even 20 miles away. A similar topographic 
setting for Tepee Trail deposition is shown in figure 6, a cross sec- 
tion along Clear Creek, and a contrasting section along the ridge a 
mile west of the creek. 
In considering this anomalous distribution of volcanic conglom- 
erate, it should be recalled that both the Wind River Basin and the 
Big Horn Basin to the north were being filled at about the same time. 
Inasmuch as the Wind River Basin is believed to have been open to 
the east, and the Big Horn Basin was either closed or open to the 
north, there is no reason for the two basins to have filled at the same 
rate. Quite the contrary seems much more reasonable, in fact, when 
it is considered that volcanic material could enter the Wind River 
Basin chiefly through a relatively narrow passage at the northwest end 
of the basin. The middle and late Eocene volcanic material had ac- 
cess to the Big Horn Basin, obviously, all along the west side of the 
basin, 70 miles or so long. It seems logical to believe, therefore, that 
the Big Horn Basin was filled to the lowest topographic point be- 
tween the Owl Creek and Big Horn Mountains at a time when the 
floor of the Wind River Basin on the south side of the mountains 
was still several hundred feet below this point. The lowest point be- 
tween the ranges probably is concealed by the Tepee Trail strata along 
Bridger Creek (T. 41 N., R. 91 W.). As successively higher low 
points in the mountains were reached, such as the upper part of Sage- 
brush Draw, material would flood down the canyons to the south. 
Some downcutting of the canyons probably took place at this time 
and soon erosion into the Big Horn Basin fill permitted volcanic 
cobbles to move down the canyons and be deposited in their mouths. 
The white clastic facies of the Tepee Trail formation clearly repre- 
sents erosion of the mountains during Tepee Trail time. At very 
few places, however, do the rocks of the white clastic facies indicate 
as much vigorous sedimentational activity as suggested by the coarse 
volcanic sediments in the Tepee Trail. The general lack of sorting 
and possible mudflow deposition of some of the white clastic facies 
have been mentioned. The white kaolinitic appearance of some parts 
of the white clastic facies, particularly adjacent to areas underlain 
by granite, may be the result of leaching of iron from the early Eocene 
residual soils that were suggested by Van Houten (1948). Further 
investigation of this possibility would be interesting. 
