WASATCH EPOCH. 7 



The preceding remarks I have quoted from the report of Dr. C. A. 

 White to Dr. Hayden,* as expressive of the position of this important for- 

 mation. In hthological character, the Wasatch consists of a mixed arenaceo- 

 calcareous marl, alternating with beds of white or rusty sandstone. The 

 more massive beds of sandstone are in New Mexico, Colorado, and Wyo- 

 ming, at the base of the formation. The mai-ls readily weather into the 

 fantastic forms and canyon labyrinths of bad-land scenery. The marls 

 often contain concretionary masses of a highly silicious limestone, which 

 cover the banks and slopes of the bluffs with thousands of angular frag- 

 ments. It is' characteristic of this formation that the marls contain brightly 

 colored, usually red, strata ; and in many localities the colors are various, 

 giving the escarpments a brilliantly banded appearance. 



Petrographically, this formation has two divisions, the Wasatch proper 

 and the Green Eiver beds ; the latter name having sometimes been given to 

 the entire formation as well as the former. Dr. White thus describes it:t 



Eesting immediately and conformably upon the Wasatch are the strata of the 

 Green Eiver Group. Although intimately connected with the former by continuous 

 sedimentation and specific identity of molluscan species, they differ considerably from 

 those of that group in general aspect, and in composition also. The group is, Uthologi- 

 cally, at least, separable into two divisions, but they are not regarded as severally of 

 co-ordinate value with the other recognized Tertiary groups. The lower division consists 

 mainly of silicious and sandy shales and laminated and thin-bedded sandstones, with, 

 in some places, especially in the western part of this district, frequent layers of hard, 

 dark-colored carbonaceous shales. In some places the strata are also quite calcareous, 

 occasional layers being nearly pure, compact, finely-laminated limestone. Others of 

 the calcareous layers are sometimes oolitic in textui-e. The general aspect of the strata, 

 as seen exposed at a distance, is light gray. 



The upper division consists mainly of sandstones that are coarser, as well as less 

 thinly and distinctly bedded, than those of the lower division. In some parts it is shaly 

 and in others carbonaceous. Much of its sandstone is ferruginous in aspect, instead 

 of having the gi'ay tint that the lower division has. Sometimes certain beds of its 

 sandstones are eailhy aud easily disintegi-ated, often lea\dng, weathered out of the 

 mass, spherical concretions of hard sandstone that vary in size from a fraction of 

 an inch to two or three feet in diameter. Other beds sometimes present buttress-like 

 masses in the brow of bluifs, which form conspicuous and somewhat remarkable fea- 

 tures in the landscape. Such features are very characteristic of this division in the 

 bluifs of Green Eiver, in the vicinity of Green Eiver City, Wyo., and, to a less extent, 

 they also appear in the bluifs which border the canon and valley of White Eiver, in 

 the southwest portion of this district. 



•Aiiuunl Report, 1876 (1H78), p. 35. 



t Annual Report U. S. Geol. Surv. Terrs., 1876 (1878), p. 35. 



