iSNDLicH.] TERTIARY WASATCH GROUP. 79 



gard that and the results thereby produced as sufficient ground for sub- 

 division. Besides this, I have not found any other feature or charac- 

 teristic upon which to base a separation. 



In speaking of the Tertiary groups below, the older one — Wasatch — 

 "will first be discussed, and then will follow the Green Eiver, which com- 

 prises very nearly the entire district, and even extends beyond its limits 

 into the regions examined by Drs. White and Peale. Of more interest 

 than the geognostic are the orographic features of this area, inasmuch 

 as they aflbrd an excellent example of the enormous influence that long- 

 continued erosion can produce where it takes place under favorable con- 

 ditions. The general and even slope of the plateau and the softness of 

 the strata form a combination that must be productive of the most com- 

 plete results. 



Wasatch Group. — Again we begin with the region of the Grand Hog- 

 back, as affording the most typical occurrence of beds belonging to this 

 group. A series of low, bluff-like hills, covered with cedars and scat- 

 tering i)inons, occurs west of the hogback slope in the vicinity of White 

 Eiver. They extend northward into Professor White's district. Sand- 

 stones and generally light-colored shales compose them, and weather 

 readily into ever-changing forms that keep fresh the colors exhibited 

 by the strata. Continuing in a southerly direction, they gradually get 

 narrower, being encroached upon by the Green River beds setting in 

 from the west. South of Station 4 the minimum width is reached, 

 where the hogback allows the formation of but a narrow valley between 

 Itself and the eastern edge of the Book Cliffs. These latter swing around 

 to the southwest soon however, and a comparatively low area of triangu- 

 lar shape is enclosed between them, the Grand Eiver on the south, and 

 the southern end of the hogback. Strata belonging to the Wasatch 

 Group form the bluff's and low tables within this area. Viewed from 

 Station 5, on one of the prominent points of the hogback, southeast of 

 Eifle Creek Canon, the appearance of the low portion of country thus 

 enclosed is a very characteristic one. Leaning against the steeply-dip- 

 ping strata of the Laramie Group are the Wasatch beds, which very 

 rapidly lose their steep dip, however, and spread out in narrow ridges, 

 hogbacks, and tables in the valley. Upon first sight the general ap- 

 pearance strikingly resembles that of the Puerco' marls in Southern 

 Colorado.* Variegated sandy and marly shales, interstratified with 

 sandstones, form the hills. Colors varying from white to grey, yellowish, 

 greenish, pink, red, brown, and purple, and exhibiting many shades, 

 tend to enliven the monotony of the otherwise dreary scenery at that 

 locality. Piiions and cedars cover the hills, representing the only green 

 vegetation that can flourish in the poorly watered spot. A general dip 

 off' from the hogback, i. e. toward the southwest, veers more to the west 

 as we approach the edge of the Book Cliffs, and as the Wasatch strata 

 dip under them, they acquire the gentle northerly dip that is prevalent 

 among the Green Eiver beds. All along the base of the cliff's, so far as 

 within our district, the variegated beds may be traced ; they cover but 

 a very small area, and most frequently appear only in the lower portion 

 Qf the precipitous face shown by the cliffs. Dr. Peale has found Lara- 

 mie occurring there also. I did not observe this latter group within my 

 area, although it is possible that it may exist some distance down the 

 Grand, and there be obscured either by the drift or by the Wasatch beds. 

 Laramie no doubt dips under, together with the Wasatch, but does not 

 appear clearly. 



*Comp. Eep. U. S. Geol. Surv., 1875, p. 189. 



