520 abstracts: geology 



through Thermopolis, where it has some large hot springs and travertine 

 deposits near its crest. The antidine is not symmetrical, since the 

 dips are about 45° on the south side and 7° on the north side. The 

 rock formations involved belong to the Cretaceous, Jurassic, Triassic, 

 and Carboniferous systems. In the Warm Springs domes about 4 

 miles east of Thermopolis the Chugwater, a Triassic formation, is 

 exposed at the surface, and the oil sand is reached in the Carbon- 

 iferous-Embar group. In the Hamilton dome the rocks exposed at 

 the surface are Cretaceous, and the productive sand is in the Triassic- 

 Chugwater formation. Unlike the light high-grade Cretaceous oils 

 found in Wyoming the oil from the Warm Springs domes is heavy and 

 dark. Its specific gravity is about 19.1° Baume. That produced in 

 the Hamilton dome is of a little better grade than the Warm Springs 

 oil, having a gravity of nearly 23° Baume. The production of the 

 Warm Springs domes is given as about 1000 barrels per day. No 

 production is given for the Hamilton dome, as the oil had been struck 

 too recently to justify an estimate. A. J. C. 



GEOLOGY. — Gas in the Big Sand Draw anticline, Fremont County, 

 Wyoming. A. J. Collier. U. S. Geol. Survey Bull. 711-E. 

 Pp- 9 (75-83), pi. I, figs. 2. 1920. 



The Big Sand Draw anticline, 18 miles southeast of Riverton, Fre- 

 mont County, Wyoming, is so largely concealed by overlying rocks 

 that it was impossible to say whether it was a pitching fold or one of 

 the most promising anticlines of the region. 



The rocks involved are the Tertiary, White River and Wind River 

 formations which unconformably overlie the Cretaceous, Mesaverde, 

 Steele, Niobrara, Carlile, and Frontier formations. At the north end 

 of the anticline the Mesaverde formation and Steele shale are exposed, 

 showing on the west limb a dip of 43° and on the east limb a dip of 

 25°. Farther south there are occasional exposures of the Steele shale 

 showing dips to the east. The overlying Wind River formation is 

 apparently also folded into an anticline but with very low dips. 



In 19 1 8 two wells were put down, striking gas rated at 7000 and 10,000 

 cubic feet per day. The gas is contained in one of the Frontier sands 

 locally called the Wall Creek sand. 



The field will be tested further to determine whether or not oil may 

 be found either in the wells already drilled or in wells lower down on the 

 flanks of the anticline. A. J. C. 



