816 C. C. MOOK ORIGIN AND DISTRIBUTION OF THE MORRISON 



are all given to parts of the same formation, and it is best to drop tliem, 

 in a general discussion, in favor of the name Morrison. 



Distribution and Thickness of the Morrison' 



Tlie Morrison, in tlie Ijroad sense, is widely distributed. At the type 

 locality in Colorado it is poorly exposed. It occurs in (lie hog-backs 

 along the eastern border of the Eocky Mountain front range, from the 

 Laramie Mountains south to the central parts of New ]\Texico : in the 

 Grand River Valley and tributaries in western Colorado and Ftali ; in 

 the canyons of streams tributary to the San .Tnan tvivor in southwestern 

 Colorado; south of the T'inta ^Fountains ami in the (Jrand Tfoo--1)ack in 



A 



B 



C 



D 



Figure 1. — Diagramiaatic Rein c\tutuli(.n uf the TJiickncss of the Muni.soii Formation 



in various Areas from Houth to North 



A, maximum thickness in the Telluride quadrangle, Colorado ; B, thickness near Mack, 

 Colorado; C, thickness near Tensleep, M'yoraing: D, thickness near Belt Creek, Montana. 

 Scale, 400 feet to 1 inch. 



western Colorado and eastern Utah; in a few isolated areas in Montana, 

 around the flanks of the Bighorn. Owl Creek, and A\'ind River ]\[ountains; 

 in local u])lifts and faulted blocks in eastern and central Wyoming, and 

 ai'ound most of the rim of the Black Hills. 



In the southwestern areas the Morrison, or McElmo, has a considerable 

 thickness; near Green River, Utah, it is over 1,000 feet thick, accoi-ding 

 to lAipton ; in the Telluride quadrangle it is reported l)y Cross to be 900 

 feet thick; near Grand Junction and Mack, in the Grand River Valley, 

 it is about 700 feet thick; south of the Uinta Mountains it is about 650 



