538 abstracts: geology 



GEOLOGY. — The Salt Creek oil field, Wyoming. Carroll H. Wege- 

 MANN. U. S. Geol. Survey Bull. 670. Pp. 52, with maps and 

 illustrations. 1918. 

 This report describes the rock formations from Jurassic to Tertiary 

 in age that are exposed in the field, and depicts the structure in detail. 

 The oil is found in Upper Cretaceous sandstones and was probably 

 derived from the remains of small sea plants or animals which were 

 buried in the thick beds of Cretaceous mud that formed the shales 

 lying below the sandstones in which the oil now is stored. The distri- 

 bution of oil in the Salt Creek, Shannon, and Teapot pools are given, 

 and the future output is estimated. 



R. W. Stone. 



GEOLOGY. — Gravel deposits of the Caddo Gap and De Queen quad- 

 rangles, Arkansas. Hugh D. Miser and A. H. Purdue. U. S. 

 Geol. Survey Bull. 690-B. Pp. 15, with maps and illustrations. 

 1918. 

 The gravels are of Lower Cretaceous, Upper Cretaceous, and Quater- 

 nary age, and are composed mainly of pebbles of novaculite (a variety 

 of chert) derived from the Arkansas novaculite exposed in the Ouachita 

 Mountain region, which is north of the Gulf Coastal Plain. The main 

 reasons for the preparation of this report are to present a description 

 of the gravels and to indicate the possibility of their use in tube mills. 



R. W. Stone. 



GEOLOGY. — Quicksilver deposits of the Phoenix Mountains, Arizona. 

 Frank C. Schrader. U. S. Geol. Survey Bull. 690-D. Pp. 15, 

 with maps. 1918. 

 The quicksilver deposits here described are 10 miles northeast of 

 Phoenix and about the same distance east of Glendale, the nearest 

 railway stations, in the southwest slope of the range. They occur in 

 schist belts, in zones of shearing or fracture that parallel the lamination 

 in the inclosing schist. The deposits consist mainly of portions of the 

 country rock which have been more than normally crushed and madje 

 schistose and later mineralized. They contain numerous specks, 

 veinlets, films, small bodies, and crystals of cinnabar and metacinna- 

 barite. A few globules of native quicksilver associated with the cinna- 

 bar ore have been reported. The gangue minerals, the chief constit- 

 uents of certain stringers and veinlets, are quartz, calcite, hematite, 

 and limonite. Kyanite and tourmaline are locally abundant in the ore. 



R. W. Stone. 



