402 N. H. DARTOtf STRATIGRAPHY OF THE BLACK HILLS, ETC. 



of the slopes the older formations are covered by later Tertiary deposits. 

 The following list sets forth the principal features of the formation in 

 southeastern Wyoming. 



Cretaceous •< 



Jurassic 



Triassic (?) or 

 Permian. 



Carboniferous ( 

 (Pennsylva- -J 

 nian). ( 



Cambrian (?)... 



Archean or Al- 

 gonkian. 



Formations. 



Laramie 



Fox Hills 



Pierre 



Niobrara 



Benton 



Dakota- Lakota 



Morrison 

 Sundance. 



Chug water 



Tensleep. . 



Principal characters. 



Sandstones, with coal and 



shales. 



Sandstones 



Dark shales 



Calcareous shale 



Dark shales and sandstones . 

 Buff massive sandstone and 



conglomerate, with shale 



intercalations. 

 Light colored massive shale 



and gray sandstone. 

 Greenish shales and buff 



sandstones ; local gypsum 



beds. 

 Red shales and red sand- 

 stones, with gypsum and 



limestone. 

 Gray massive sandstone . . 

 Gray massive limestone ; 



some sandstone. 

 Coarse, hard, massive, gray 



conglomeratic sandstone. 

 Granites and schists. 



Thickness. 



Feet. 



500 or more 



200 ± 

 1,000 or more 

 100 ± 



800 d= 

 200 =b 



}■ 200-475 

 580-800 



60 

 200-1,000 



0-100 



CAMBRIAN 



» 



In Casper mountain and associated ridges at the northern end of the 

 Laramie range the basal member of the sedimentary series is a gray to 

 brown sandstone, conglomeratic at the base, which is supposed to be of 

 Cambrian age, although no organic remains were discovered in it. It 

 has a thickness of 100 feet for some distance, but soon thins out to the 

 eastward. 



PENNS YL VA NIA N 



There extends along the east slope of the Laramie range a series of 

 limestones, with some local beds of sandstone, all of which appear to be 

 of Upper Carboniferous age. Fossils of this age have been reported by 

 F. V. Hayden on Boxelder and La Prele creeks, and by A. Hague in the 

 region west and northwest of Cheyenne. These remains were not found 

 in the lowermost beds, so there is a possibility that earlier Carboniferous 

 or even older sediments are represented ; but this is thought to be exceed- 

 ingly improbable. The limestones have a thickness of about 250 feet at 



