254 proceedings: geological society 



rated by a marked unconformity which permits the upper part of 

 that formation to transgress across all of the older formations exposed. 



There are no structural evidences of the supposed unconformity 

 between the "Upper and Lower Laramie" as defined by Veatch. No 

 angular or erosional discordance or apparent evidence of overlap be- 

 tween the two formations was noted. Furthermore both seem to have 

 been equally affected by diastrophic disturbances. The only apparent 

 evidence in support of an unconformity at this horizon is the presence 

 of a conglomeratic zone, the base of which has been taken as the bound- 

 ary between the two formations. Recent petrographic studies seem, 

 however, to indicate that this conglomerate was not derived from the 

 surrounding mountains but was obtained from a more remote source — 

 apparently that which furnished the sediments of the "Lower Lara- 

 mie." The conglomerate seems to have been deposited before the 

 orogenic disturbances which gave rise to the present mountain ranges 

 surrounding the Hanna Basin and without any great physical break 

 between it and the underlying formation. 



These observations seem to indicate that the great post-Cretaceous 

 orogenic disturbance and resultant unconformity occurred about the 

 middle of the so-called "Upper Laramie" epoch rather than preceding- 

 it; that is, it is pre- Wasatch instead of pre-Fort Union. 



Carroll H. Wegemann: The discovery of Wasatch fossils in so-called 

 Fort Union beds of Powder River Basin, Wyoming, and its bearing on the 

 stratigraphy of the region. 



The rocks overlying the Fox Hills in the region southeast of the 

 Bighorn Mountains of Wyoming have been divided by most writers 

 into two formations, — the Lance or Triceratops beds below and the 

 Fort Union above. The Fort Union is separable, on lithologic grounds, 

 into two divisions; the lower carries abundant fossil leaves and con- 

 sists of shale and fine-grained bluish-white sandstone, together with 

 numerous thin beds of highly ferruginous sandstone; the upper is 

 composed of gray shale and rather coarse-grained yellow and buff 

 sandstone (the color of the whole formation being predominantly 

 yellow), ferruginous beds are lacking, and fossil leaves are not abun- 

 dant. During the past season specimens were obtained, by R. W. 

 Howell and the writer, of teeth of Coryphodon molestus from beds near 

 the top of the upper disvision of the Fort Union as exposed in the 

 Pumpkin Buttes, and from beds near the middle of the formation. 

 Coryphodon molestus is known only from the Wasatch, and the finding 

 of its remains in the upper division of the Fort Union appears sufficient 

 evidence for the correlation of that division with the true Wasatch. 

 Former collections, near the base of the upper division of the so-called 

 Fort Union, of small mammal teeth resembling species collected from 

 the Torrejon of New Mexico and the Silbcrling Quarry of Montana 

 are not considered by Dr. J. W. Gidley as necessarily establishing 

 the correlation of the beds in which they were found with the Fort 

 Union, since recent discoveries in the Clark Fork and Sand Coulee 

 beds of Wyoming and in the Ignacio beds of Colorado have proved 



