384 GEOLOGICAL EXCURSION TO THE BOCKY MOUNTAIN'S. 



several), are less readily defined and are apparently rather local in their 

 nature. In places, especially on the immediate Hanks of the mountain 

 massives, the elsewhere horizontal Tertiary beds are (bund to he 



upturned ar considerable angles, in the great Tertiary basin of Green 



river, east of the Wasatch and north ot the Uinta mountains, there is 

 evidence of dynamic movement, and Ot a limited amount of erosion, at 

 the close of each of the three Focene epochs there represented. 



The principal plication of the Wasatch range mast have taken place 

 at the close of the Cretaceous, and at this time also was Conned the 

 great east and west anticline' of the linta Mountains, which stretches 

 160 miles eastward from the eastern Hank of the Wasatch, opposite the 

 great granite mass of Little Cottonwood canyon. That the movement 

 of uplift of this range has been, in a measure, continued in Tertiary 

 times, is proved by the fact that the Tertiary beds resting upon its 

 thinks are also bent upwards; bat the angle at which they are upturned, 

 even in the lowest and most disturbed of these Eocene series, is much 

 lower than that of the Cretaceous beds, while those of the two upper 

 series often pass in a nearly horizontal position completely over the 

 eroded edges Of the upturned Oretaceous strata. 



Erosion, since the deposition of the Eocene Tertiary beds, has carved 

 out many interior valleys to the east of, and generally parallel with, the 

 main crest of the Wasatch range, and this erosion has exposed por- 

 tions of the underlying upturned beds. Over the greater part of the 

 plateau region immediately west of the crest, however, the Tertiary 

 covering still remains and masks their structure. 



The broad general features Of structure of the older part of the 

 range, as far as it has been made out, are as follows: 



At the north is a great syneline trending to the west of north, in 

 whose eroded axis lies the great depression of Cache valley. The west- 

 ern Hank of this syneline forms the front of the range from "The dates" 

 south to Brigham city. Prom here south to beyond Farmington 

 stretches the Farmington Archean body, one covered by an arch of 

 sedimentary beds. The western portion has been cut Off by the great 

 Wasatch fault, and the remainder in great measure denuded of its cov- 

 ering of sedimentary beds. Southeast of Salt Lake city is the great 

 granite body of Little Cottonwood canyon, assumed to be of post- Archean 

 age, though the crystalline rocks through which it was intruded are now 

 considered Algonkian. The position of the overlying sedimentary beds, 

 and the fact that their lowest members contain fragments of granite in 

 the immediate vicinity of that body, prove that it is certainly pre- 

 Oambrian. Included between the Farmington and the Cottonwood 

 masses is a syneline of beds ranging from Cambrian to Cretaeeous, 

 whose axis runs nearly east and west. These upturned beds wrap round 

 either of the older masses on the east; that is, the strikes of beds form- 



