THE GEOLOGICAL SUCCESSION 391 



80 feet of beds comprising green shales above and thin-bedded sand- 

 stones below, the former containing abundant fossils. 



Sqaaiv Creek locality. — On Squaw creek, southwest of Herniosa, the for- 

 mation comprises a thin sandstone at the base, then a mass of shales of 

 dark color, and a top member of buff and yellow slabby sandstone. 



Spring Creek locality. — On Spring creek the following features are ex- 

 posed : 



Unkpapa sandstone. 



Buff sandstone, massive above, slabb}' below 25 feet thick. 



Green shales with three fossiliferous layers and some 



thin sandstones 75 " " 



Pale greenish, soft, massive, argillaceous sandstone. . . 25 " " 



Pinkish, massive, soft sandstone 6 " " 



Talus 50 " " 



Buff slabby sandstone, ripple-marked 12 " " 



Talus 20 " " 



Greenish shale 5 " " 



Buff sandstone 3 " " 



Red beds. 



The sandstone at the top of this section is a very conspicuous member 

 for some miles on either side of Spring creek, and it appears to have 

 developed out of the sandy beds which usually overlie the upper green 

 shales southward. It is possible, however, that it is a representative of 

 the lower portion of the Unkpapa sandstone which is thin in this 

 vicinity. 



Rapid Creek area. — Three miles southwest of Rapid the upper buff sand- 

 stone above referred to has a thickness of 25 feet, and it is underlain by 

 a thick mass of green shales containing belemnites and other fossils. 



In the vicinit}^ of the gap on Rapid creek west of Rapid and for some 

 miles north the exposures of the Sundance beds are not continuous so 

 as to give a satisfactory section. Shales of buff, gray, and green color, 

 with intercalated beds of sandstones and fossiliferous limestones, are the 

 principal features. 



Locality at Cascade. — Returning to the region south of Hot Springs, 

 there is found at Cascade a fairly complete section of the Sundance beds 

 having a thickness of 400 feet. They comprise from the top a succes- 

 sion of green shales with fossil-bearing layers, a considerable thickness 

 of red sandy shales, the usual heavy bed of buff, slabb}'-, ripple-marked 

 sandstone, 60 feet of green shales, and a basal, red, massive sandstone 

 lying on the Red beds. 



LVI— Bull. Geol. Soc. Am., Vol. 10, 1898 



