LARAMIE REGION, WYOMING 431 
had been completed and static conditions reached. From the entire 
absence of exposures of Eocene sediments in southeast Wyoming, 
we may suspect that the chief activity of the region throughout the 
Eocene epoch was denudation. The abundance of pebbles of pre- 
Cambrian schists and granites in the basal gravel of the Oligocene 
series shows that the cover of stratified rocks had been entirely 
removed from the arches, and that the ancient rocks themselves were 
deeply eroded during the Eocene cycle. The folds were therefore 
truncated during Eocene time." 
Just what the final topographic result of this epoch of erosion was 
is now difficult to discern. ‘There is some evidence, however, that 
it was not the complete planation of the district. Along the eastern 
border of the Laramie uplift the Oligocene deposits lie in valleys which 
had previously been cut through the limestone ridge. The inter- 
vening “hog-backs,” which mark the outcrops of the Carboniferous 
limestone, stand 300-500 feet above these buried valleys. The 
relief just previous to the making of the Oligocene deposits must 
therefore have been at least as great in some parts of the district as 
that of the present. 
On the other hand, the Oligocene deposits are notably fine and 
well stratified. They are not such formations as accumulate along 
the flanks of high mountains where streams have steep descents. 
From such facts as these it seems probable that by the close of the 
Eocene epoch the district in general was relatively low, but that the 
Laramie anticline was a hilly belt, while perhaps more rugged moun- 
tains were left farther west. 
This uneven Eocene surface is preserved where it is still covered 
by the Oligocene strata, but over the rest of the area it seems to have 
been very largely destroyed by later cycles of erosion. 
The Medicine Bow ranges west of the Laramie basin are essen- 
tially a maturely dissected plateau of schistose rocks with an average 
elevation of 10,000 feet. The plateau is topped by the rugged 
glaciated peaks locally called “the Snowy range,”’ and by some lesser 
monadnocks. Farther east along the Laramie arch the nearly level 
1 Since this article went to press, my attention has been called by Mr. Bailey 
Willis to evidence indicating that the arches were partly uplifted in earlier Mesozoic 
times, and that the Paleozoic cover was removed from them before the Cretaceous 
sediments were laid down. 
