20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
Near the mountains, the Tepee Trail strata dip at low angles away 
from the mountains. Some part of this angle of dip may represent 
original depositional slope; the rest is the result of the southward 
tilting of the mountain block in response to the movement on the 
Cedar Ridge fault. Near the Cedar Ridge fault, the strata dip north- 
ward at many places, the strata having been dragged upward by move- 
ment along the major fault. 
The age of the Cedar Ridge fault and associated structures cannot 
be placed more closely than post-late Eocene. It seems likely, how- 
ever, that the Cedar Ridge fault is as young as Pliocene, to conform 
with the pattern of normal faulting that resulted from epeirogenic 
uplift of the Rocky Mountain region, as pointed out by Love (1939, 
p. II4). 
SEDIMENTATIONAL HISTORY 
The sedimentational interpretation of the Eocene strata in the 
northeastern part of the Wind River Basin can contribute to the re- 
construction of the geologic history of the Wyoming basins, which 
has been reviewed by Van Houten (1952). This history, briefly 
stated, applies chiefly to the Wind River and Big Horn Basins and 
is one of mountain and basin formation in late Cretaceous and early 
Tertiary time, with the rising mountains shedding much debris into 
the basins by early Eocene time. Much of the present mountain 
topography had been shaped by the end of early Eocene time, which 
seems also to mark the end of differential movement between the 
mountain ranges and the basins until much later in Tertiary time. 
From middle Eocene time through at least some part of Miocene 
time, and perhaps into the Pliocene, the basins were progressively 
filled, chiefly with volcanic material from the Absaroka-Yellowstone 
volcanic region. As the basins were filled the mountain ranges were 
buried, and eventually a broad constructional plain resulted from 
which are inherited many of the features of the present drainage 
system. 
The process of basin filling was essentially continuous but it was 
interrupted locally from time to time (Love, 1952). During Paleo- 
cene and early Eocene time, the surfaces of deposition in the basins 
were not far above sea level, the increasing amount of sediments in 
the basins being accommodated by differential movements between 
the mountains and the basins. From middle Eocene time on, the 
surfaces of deposition were gradually raised higher and higher, in 
part because the sediments accumulated without basin sinking and 
perhaps in part because of progressive epeirogenic uplift. Epeiro- 
