NO. 4 GEOLOGY, WIND RIVER BASIN—TOURTELOT 2I 
genic uplift had its major pulsation, or reached its culmination, prob- 
ably in Pliocene time, as pointed out by Love (1939). It is believed 
that faulting, represented by the Cedar Ridge fault, and others men- 
tioned by Love, by which the relations between mountain ranges and 
basins were again changed, took place at this time. 
The sedimentational history of Eocene rocks in the northeastern 
part of the Wind River Basin can now be discussed against this back- 
ground. The rocks of the Tepee Trail formation present two interest- 
ing sedimentational problems. One is the mode of transport of such 
large volumes of volcanic material. The other is the conditions that 
permitted the accumulation of volcanic material directly adjacent to 
a rugged topography in the pre-Tertiary rocks and prevented the ero- 
sion of them and the incorporation of the debris with the volcanic 
material. 
Discussion of these problems necessarily is speculative in large 
part. Perhaps a somewhat imaginative reconstruction of events and 
conditions will stimulate the gathering of data bearing on such 
problems. 
The Wind River formation in the northeastern part of the Wind 
River Basin represents a complex of depositional conditions. Ex- 
tremely coarse debris was shed by the mountains into the basin, as 
evidenced by the boulder conglomerate in Cedar Ridge and in the 
western part of the area included in figure 2. These conglomerate 
masses did not extend far into the basin, however, and at the time 
they were accumulating near the mountains red-banded fine-grained 
sediments were being deposited no more than 4 or 5 miles to the 
south. Apparently these were derived from the uplands, large areas 
of which were covered with red residual soil according to Van Houten 
(1948). The manner of deposition of the conglomerate has not been 
studied. The great size of some of the boulders suggests that mud- 
flows may have been important in moving the coarse material out of 
the mountains. Mudflow structures were not recognized in the con- 
glomerate, though, perhaps because they had been obscured by re- 
working of the mudflow masses by streams. 
In the Boysen area, west of that shown in figure 2, the mountain 
debris, none as coarse as that in the northeastern part of the Wind 
River Basin, was moved southeast from the mountain front by rela- 
tively short tributaries to a generally eastward-flowing master drain- 
age system (Tourtelot and Thompson, 1948). The locus of succes- 
sive levels of the master drainage system seems to lie about along the 
south margin of figure 2. The depositional pattern of the numerous 
channel sandstones that mark the locus of the drainageway does not 
