NO. 4 PHYSIOGRAPHY OF ROCKY MOUNTAINS — LEE 1 5 



and to lower La Plata. Still lower in the sections are beds litho- 

 logically like the Shinarump conglomerate and the Chinle formation. 



East of the Uinta Mountains the rocks of Jurassic age are cov- 

 ered for many miles. But near Medicine Bow, Wyo., the variegated 

 beds ( Morrison) lie with apparent conformity on marine Jurassic 

 (here called Sundance), and this in turn on Chugwater or typical 

 " Red Beds." Apparently the La Plata- group has no representative 

 here unless the Sundance be included in that group. 



In the Laramie Basin, Wyo., Morrison and Sundance are pres- 

 ent. The Sundance is described as resting in some places on typical 

 Chugwater, but in other places on beds which, although included in 

 the Chugwater formation, are described 1 as not like Chugwater. 

 Special attention is called to these because similar beds in several 

 places farther south will be compared with them. 



The section east of the mountains, near Cheyenne, differs from the 

 Laramie Basin section only in the apparent absence of the beds 

 between Sundance and Chugwater. 



NORTHWEST COLORADO TO NORTHEAST COLORADO 



Attention is next directed to a group of sections a few miles south 

 of those last described, starting with northwest Colorado. Farther 

 east, near Meeker, the variegated beds, which are doubtless equiva- 

 lent to the Morrison, are separated from the typical " Red Beds " by 

 sandstones, which Gale 2 regards as probably equivalent to his White 

 Cliff (Nugget of Schultz), but no marine beds of Jurassic age were 

 found. 



In the vicinity of Encampment, Wyo., 3 and a little farther south, 

 near Hahns Peak, Colo. (Encampment section), the Sundance lies 

 between Morrison and typical " Red Beds." There seems to be no 

 representative of the La Plata sandstone. Still farther to the east in 

 North Park, Colo., no representative of the Sundance was found, 

 but a sandstone of variable thickness, which corresponds in character 

 with the La Plata sandstone and with the unnamed beds between 

 Sundance and Chugwater in the Laramie Basin section, occurs near 

 the base of what Beekly " classed as Morrison. In the foothills 



1 Darton, N. H., et al., U. S. Geol. Survey Geol. Atlas, Laramie-Sherman 

 folio (No. 173), 1 910. 



2 Gale, H. S., U. S. Geol. Survey Bull. 340, 1008. 



3 Spencer, A. C., U. S. Geol. Survey Prof. Paper 25, 1904. 



4 Beekly, A. L., U. S. Geol. Survey Bull. 596, 191 5. 



