THE HEART MOUNTAIN OVERTHRUST, WYOMING 551 



S.piriferina soliderostris, Cliothyridina crassicardinalis , Eumetria 

 Verneuliana, Platyceras sp. 



South Peak lies about 8,000 feet southeast of Middle Peak and 

 is formed by the conjunction of three smooth ridges that extend 

 northwest, southwest, and east, respectively. The space between 

 these two peaks is a smooth, rolling flat covered with sagebrush, and 

 no rock outcrops were recognized in it. Just below the summit of 

 this peak and well distributed around it there are sLx rugged 

 outcrops of cream-colored limestone, each from 50 to 75 feet long. 

 The limestone outcrops do not exhibit bedding but are highly 

 shattered and several are entirely made up of angular fragments of 

 limestone, one to ten inches in diameter, which are imbedded in a 

 fine sand of similar material. The only fossils noted in these 

 outcrops are a few crinoid stems, but the texture resembles that 

 of the Madison limestone blocks on Middle Peak. 



The best evidence of the character of the beds under the lime- 

 stone is obtained at the head of a ravine on the northeast side of 

 the peak, where the smooth surface near the summit merges with 

 bad lands that show horizontal Wasatch material. No fossils 

 were found at this locaHty. The evidence at South Peak indicates 

 that a triangular cap of crushed Madison limestone, about 600 feet 

 long and 400 feet across the base and about 80 feet thick, overlies 

 horizontal Wasatch beds. 



The summit of South Peak lies at the -northwest end of an area 

 about 3,000 feet in diameter within which there are eleven smaller 

 and lower hills each of which shows outcrops of limestone breccia 

 more than 50 feet long. Figure 4 shows one of the largest of these 

 outcrops, in which the bedding is still preserved. It is 200 feet 

 long, about 25 feet thick and, although it yielded no fossils, the 

 texture indicates that it is probably part of the Bighorn limestone 

 (Ordovician) . Farther southeast these low hills merge with gravel- 

 covered flat terraces that extend to the east and southeast toward 

 the center of Bighorn Basin. Near the center of the hifls, capped 

 by limestone, there is a flat depression 500 feet in diameter at the 

 northwest edge of which is Markham Spring, at an elevation of 

 5,850 feet. Even at the end of August, in the dry season of 1919, 

 it yielded about two gallons a minute of clear non-alkaline water. 



