-^^o 2.] PEALE ON THE LARAMIE GKOUr. 199 



In the more central and eastern localities of the group, tlie overlying 

 Tertiaries are conformable to the Post-Cretaceous, and the whole of the 

 latter may probably be present, although even there there have been 

 unconformities noted in the strata of the Laramie itself by Dr. AYhite 

 and others, so that, as Bannister remarks in the American Journal of 

 Science and Arts for March, 1879 (p. 245): "The evidence" "indicates 

 that the Laramie epoch was throughout one of stratigraphic disturb- 

 ance rather than that there was only one great orographic change at its 

 close." 



In Western Wyoming and adjacent regions there was intense oro- 

 graphical disturbance after the deposition of the beds that there rei)re- 

 sent the group. Then also occurred the folding that resulted in the for- 

 mation of Meridian fold and the Wyoming and Salt Eiver ranges, which 

 was accompanied by the faulting seen along the eastern sides of the two 

 ranges. The region westward from what is now the Green Eiver Basin 

 was lifted above the level of the sea and added to the land area which 

 was farther west, and had been defined at the end of the Carboniferous. 

 This uplift included the Wahsatch region of our district that lies 

 north of latitude 11° 45'. In this region there are a number of isolated 

 monoclinal ranges, which are the eroded remnants of anticlinal folds. 

 The faults that are found farther south in the areas explored by the For- 

 tieth Parallel Survey have in this region become ordinary folds. Speak- 

 ing of these monoclinal ridges, Eang says :* " The frequency of these 

 monoclinal detached blocks gives abundant warrant for the assertions 

 of Powell and Gilbert that the region is one prominently characterized 

 by vertical action j yet w^hen we come to examine with greater detail 

 the structure of the individual mountain ranges, it is seen that this ver- 

 tical dislocation took place after the w^hole area was compressed into a 

 great region of anticlinals with intermediate synclinals. In other words, 

 it was a region of enormous and complicated folds, riven in later tune 

 by a vast series of vertical displacements, which have partly cleft the 

 anticlinals down through their geological axes, and partly cut the old 

 folds diagonally or perpendicularly to their axes." 



In regard to the monoclinal ridges within the limits of the district 

 examined by me, the evidence is not difficult to obtain that they are 

 simply the eroded fragments of anticlinals. The erosion forming tliem 

 took place in the period which began with the Post-Cretaceous uplift, 

 and has continued ever since. The faulting in the Wyoming and Salt 

 River Eanges, as I have already stated, was probably synchronous with 

 folding that occurred there. 



Everywhere in the district there is ]^erfect conformability from the 

 Cambrian to the top of the Laramie as it is exposed in the district. 

 This Laramie, as already stated, probably only represents the older por- 

 tions of the group. Its fossil remains appear to indicate this. The fos- 

 sils of the more eastern Laramie Group are not found in it, nor have the 

 * Report Geol. Expl. Fortieth Parallel, vol. i, Systematic Geology, p. 735. 



