440 N. H. DAKTON PALEOZOIC AND MESOZOIC OF WYOMING 



hills of the Eattlesnake mountaiiis, where the thickness is about 300 feet, 

 there are gray sandstones at the top, and part of the medial sandy shales 

 are of pronounced reddish tint, as in the Black hills and some other dis- 

 tricts in Wyoming. 



Platte valley to EocTc river. — The Sundance formation presents most of 

 its usual features along the south side of Casper moiftitain, in Muddy 

 Creek valley, and on Wagonliound creek and North Platte river south of 

 Douglas. In tlie extensive exposures in the big bend of the river south 

 of Douglas, there are 30 feet or more of massive gray sandstone overlain 

 by 30 feet of pale greenish, sandy sliale, 5 feet of soft, greenish, massive 

 sandstone, 40 feet of soft sandstones of bright reddish tint, 15 feet of 

 massive buff sandstone, and about 200 feet of green shale with 3 hard beds 

 of fossiliferous limestone. In the high ridge southeast of Hammond the 

 basal sandstone is 50 feet thick, massive, cross-bedded, moderately fine- 

 grained, and of pale orange color. It is overlain by 50 feet of buff sand- 

 stone, mostly slabby ; 30 feet of pale red, soft sandstone ; 100 feet of shale 

 with hard layers, and at the top a few feet of buff sandstone. The red- 

 dish sandstone continues for some distance to the south and west and is 

 conspicuous 1% miles east of Freeland, about Alcova, and along the south 

 side of Shirley hills. In the Alcova region and southward the basal 

 member is white, massive, cross-bedded sandstone in places 40 feet thick 

 (see plate 28). West of Difficulty there is also a body of white sandstone 

 in the overlying shale member, together with the usual hard, fossiliferous, 

 limy layers. The following section is typical for the Alcova region : 



Section of Sundance Formation near Alcova, Wyoming 



Feet 



Green shale 65 



Slabby, hard limestone 10 



Green shale 10 



Limestone 10 



Green shale 75 



Sandstone 5 



Shale, part pink, part green 100 



Sandstone, white (on Chugwater red beds) 25 



Total 300 



In the Freezeout hills and Eock Eiver region the lower beds of the for- 

 mation are predominantly sandy, while the upper part consists largely of 

 green shales with hard, fossiliferous layers. In an extensive exposure 

 east of Medicine Bow the strata are as follows : 



