168 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



"The predominant rock is white to buff sandstone in thick massive beds, 

 cross-bedded and often weathering into irregular pinnacled forms. * * * On the 

 west side of the range, in the vicinity of Paintrock and Tensleep creeks, the forma- 

 tion varies in thickness from 75 to 150 feet, and in its thicker portions its lower 

 part includes some softer, fine-grained sandstones and the upper member is 

 strongly cross-bedded. * * * The upper portion of the Tensleep sandstone often 

 is calcareous and at many points there are one or two beds of a mixture of sand 

 and lime sediments." 



The Tensleep sandstone is said in this paper to represent the upper 

 portion of the Minnelusa of the Black Hills. 



(Page 35.) " The Embar Formation. In the southern part of the Bighorn 

 uplift between the red beds and Tensleep sandstone is a limestone with some 

 associated shaly and cherty beds, which, with gradual increase in thickness, is 

 continued westward in the Bridger Range and Owl Creek Mountains. Appar- 

 ently it is neither a development of the basal portion of the Red Beds nor of the 

 calcareous sandstone which sometimes occurs at the top of the Tensleep sand- 

 stone in the region north. * * * On the east side of the Bighorn Mountains the 

 formation first appears near the West Fork of Powder River, and, on the west 

 side, in the slopes south of Redbank. It finally attains a thickness of about 200 

 feet on the ridge south of Thermopolis, where it constitutes an extensive dip 

 slope several miles wide, extending along the north slope of the Bridger Range. 

 Prominent exposures appear in the upper canyon of the Bighorn River, which 

 cuts deeply into this slope. Here the formation consists of 50 feet of massive 

 limestone, underlain by calcareous shale filled with nodules and lenses of chert, 

 a member which merges down into sandy shales and impure limestones. At the 

 base there is a thin mass of sandstone breccia lying on the massive Tensleep 

 sandstone. Owing to extensive faulting, the formation appears only at one point 

 on the south side of the Bridger Range, but it outcrops prominently at the south- 

 western termination of the Bighorn uplift, 3 miles east of Deranch. Here the 

 limestone constitutes a line of low hogback ridges, at the base of which appear 

 sandy and cherty shales of buff color lying on the Tensleep sandstone. A thick 

 mass of the limestone appears in the 7,ooo-foot knob 6 miles northeast of Deranch, 

 which at first sight might be mistaken for Madison limestone. Two miles south 

 of No Wood, at the northern end of a short, deep gorge of No Wood Creek, a 

 partial section is exposed in which the Embar limestone is seen to be 10 feet 

 thick, somewhat cherty, and lying on 10 feet of cherty shales, which extend to 

 the top of the Tensleep sandstone. The limestone is overlain by a yellowish 

 sandy bed, which may constitute the base of the Red Beds. At the head of 

 West Kirby Creek the limestone is underlain by gray and reddish sands, in all 

 about 30 feet thick. A short distance north of No Wood post-office the following 

 section is presented: 



Section on No Wood Creek I mile northeast of No Wood, Wyoming. 



Feet. 



Red beds, with lo-foot bed of limestone 100 feet from base (Chugwater). 

 Limestone, light yellow, weathers in thin beds, has a layer of flint near the center, and occasional 



flinty concretions 10 



Shale, light yellow 25 



Limestone, massive, of light-gray color, with chert concretions and layers of black chert between 



bedding planes 20 



Buff shale o to 2 



Soft white sandstone (Tensleep). 



