66 



ANNALS NEW YORK ACADEMY OF SCIENCES 



Fig. 23. — Section of the 

 Morrison and adjacent 

 formations in the es- 

 carpment north of Bell 

 Ranch, Neic Mexico. 



1. — Purgatoire - D a - 

 kota ; 2. — Morrison ; .3. — 

 Exeter ; 4. — Red Beds. 

 Scale, 125 feet to 1 inch. 

 (Lee.) 



Morrison" Formation in Western Colorado 

 AND Eastern Utah 



A series of variegated clays and shales occur in 

 many localities in western Colorado and eastern 

 Utah, which correspond lithologically and strati- 

 graphically with the Morrison formations east of 

 the Eocky Mountains. The meager invertebrate 

 fauna of these clays and sands agrees with that of 

 the eastern Morrison, and the discovery by Riggs 

 in 1900 of a vertebrate fauna in these beds, con- 

 sisting of practically the same forms as the fauna 

 of the eastern Morrison, proves that some part, at 

 least, of these western clays corresponds to all or 

 certain parts of the Morrison formation east of the 

 Rocky Mountains. 



The clays under discussion have been referred to 

 in different localities as the Gunnison formation, 

 McElmo formation, Flaming Gorge formation, 

 "Lower Dakota" and "Jurassic beds." The strata 

 included under some of these terms undoubtedly 

 contain beds that do not correspond with any part 

 of the eastern Morrison formation. This fact does 

 not preclude the probability that in general these 

 beds correspond with the eastern Morrison. 



The western representatives of the Morrison for- 

 mation occur in isolated areas preserved by fault- 

 ing, as at Crested Butte; in hog-backs, as in the 

 exposures east of Vernal ; and in the walls of river 

 canyons as at Grand Junction. Detailed descrip- 

 tions of the formation at some of the better known 

 localities are given below. 



The following description of the Gunnison for- 

 mation in the Crested Butte quadrangle is given 

 by Eldridge (1894, 3) : 



In the Anthracite-Crested Butte quadrangles the 

 Gunnison formation rests unconformably on the 

 maroon and older formations. It consists of 

 quartzites and shales, with a minor amount of 

 limestone. Its thickness is from 300 to 450 feet. 

 At the base of the formation is a heavy white 



