CARBONIFEROUS SYSTE^r 415 



In the iipper limestone member, 5 miles southeast of Leo, which is in 

 Amsden formation, the following species were found: Clionetes fleniingi, 

 Produchis nehrasl-cnsis. P. cora, Aviculipecten occidentalism and Allerisma 

 terminale. In limestone of about the same horizon, just above red shale, 

 11/2 miles southwest of Shirley post-office, or 15 miles north-northwest of 

 Difficulty, the fossils obtained are Archceocidaris, aff. megastylus, Clio- 

 netes flemingi, ? Productus cora, P. portJocliianus, and Seminula sub- 

 tilita. 



TENSLEEP SA^'DSTONE 



General relations. — In most portions of Wyoming the Carboniferous 

 limestones are overlain by a thick body of sandstone which generally gives 

 rise to a flanking ridge of considerable prominence. It has been desig- 

 nated the Tensleep sandstone from the typical locality in the Bighorn 

 mountains and probably represents the upper sandstone of the j\Iinnelusa 

 formation in the Black hills. It is conspicuous in the Owl Creek, Wind 

 Eiver, and Eattlesnake uplifts and the ranges constituting the northern 

 extension of the Laramie mountains, but locally in Laramie basin and 

 eastward it is less distinct. 



Owl Creel' mountains. — The thickness of the Tensleep sandstone is 

 uniformly 200 feet or slightly more in Owl Creek mountains. In the 

 east end of the uplift it outcrops at or near the top of the mountains and 

 it extends far northward in the canyon of Bighorn river. In the low 

 divide, where the Lander road crosses the mountains, the formation pre- 

 sents a complete arch, constituting the summit. Farther west the sand- 

 stone extends along the flanks of the moimtains, and extensive exposures 

 occur south of Middle fork of Owl creek, in the anticlinal ridge east of 

 longitude 109° and on the east slope of Black mountain. Most of tlie 

 rock is white to buff sandstone, in thick massive beds, in greater part 

 cross-bedded. Locally the color of the weathered surface is very dark, 

 particularly near the Lander road and in the vicinity of Middle fork of 

 Owl creek. 



Wind River mountains. — The Tensleep sandstone constitutes a promi- 

 nent ridge extending along the slope of the limestone footliills of the 

 Wind Eiver range. In the canyons of the many streams flowing out of 

 the mountains the formation is marked by cliifs of considerable beight 

 presenting very massive ledges. The rock is cross-bedded, massive sand- 

 stone locally iron-stained and averaging 350 feet thick. Its thickness 

 near Circle is estimated at 550 feet. 



Rattlesnal-e mountains. — Much of the upper slope on the northeast side 

 and northwest end of Eattlesnake mountain consists of Tensleep sand- 

 stone, which is about 150 feet thick. Most of the rock is quartzitic and 

 n-eathers dark. 



