434 ELIOT. BLACKWELDER 
alluviation to the Oligocene and early Miocene times. This also 
gives us a convenient datum point to which we may refer some of the 
later events of the district. 
Later Tertiary peneplain.—One of the most striking peculiarities 
of the Sherman uplift is its monotonous and relatively even surface. 
No imposing range of mountains, like that of the Uinta arch, marks 
its site. Roads run in almost every direction; and the Union Pacific 
Fic. 3.—Subdued crest of the Laramie uplift, near Tie Siding. Undissected Sher- 
man peneplain. 
Railroad crosses the divide, not through a deep pass, but across an 
open plateau. At the station of Sherman one may look for miles in 
almost any direction, and it is with difficulty that he realizes that his 
t That this was not a time of constant conditions is indicated by the fact that the 
Arikaree is a coarse formation and lies unconformably on the finer sediments below.- 
The significance of these facts has been commented on by Darton (U. S. G. S. Profes- 
sional Paper 32, pp. 185, 186) and, as I am not in a position to add to his interpretation, 
they are passed over at this time. 
