CARBONIFEROUS SYSTEM 421 



principal members: An upper sandstone, doubtless representing the Ten- 

 sleep sandstones ; limestones averaging about 200 feet thiclv, apparently 

 representing the Amsden and Madison limestones; and. a basal sandstone 

 which in the western part of the area probably represents the Deadwood 

 formation. The Tensleep sandstone is especially conspicuous in a high 

 peak 5 miles north of Difficulty and in the anticline just north and north- 

 west of Difficulty. It appears also in two anticlines east of that place 

 and in the "Flat Top," a ridge 5 miles north of ]\Iedicine Bow. A sec- 

 tion measured by Mr Woodruff, 2 miles southwest of Shirley post-office, 

 is as follows : 



Section on No'rthcant Slope of Shirley Hills, 15 Miles Northwest of Difficulty, 



Wyoming P^^^ 



Sandstone (Teusleep) '. 125 



Limestone ( fossiliferous) 80 



Red shale (basal Amsden ?) 25 



Limestone, hard, massive, fossiliferous (Madison ?) 75 



Conglomerate, some limestone pebbles 200 



Granite. 



On the south side of the same uplift, at a point 9 miles west-northwest 

 of Difficulty, the rocks under the Chugwater red beds are 150 feet of sand- 

 stone (Tensleep), 200 feet of gray limestone with some sandstone and 

 purplish slabby limestones, 40 feet of red shale (basal Amsden ?), 400 

 feet of limestone resembling Madison limestone, and 30 feet of sandstone 

 and conglomerate lying on pre-Cambrian. ISTear longitude 107°, on the 

 south side of the uplift, the basal sandstones are 100 feet thick. South- 

 east of Leo the Tensleep sandstone is underlain by 55 feet of limestone, 

 shaly in the lower part, 80 to 100 feet of red shale, and 110 feet of hard 

 limestones. The latter are separated from the granite by 50 feet of hard, 

 brown, cross-bedded sandstone, conglomeratic in its lower portion. 



Laramie iasin. — The Casper formation outcrops along the east side of 

 Laramie basin, and near Laramie it extends up the long slope to the sum- 

 mit of Laramie mountains. It occupies the south end of the basin and 

 extends to and along a portion of the outlying ranges of Medicine Bow 

 mountains as far as Laramie river. Farther north it is cut out by the 

 great fault, but a small area remains west of this in Centennial valley. 

 The formation is over 1,000 feet thick near Laramie, but it thins to the 

 southwest to 500 feet on Sand creek and 608 feet on Red mountain. It 

 is 850 feet thick in Centennial valley and 1,000 feet on Ijaramic river at 

 the Colorado state line. Northwest of Laramie the middle portion of 

 the formation is mostly limestone, but farther south most of this rock 

 gives place to sandstone in part of reddish color. The principal features 



b 



