584 EDWARD STEIDTMANN 



Turner^ describes the complex of pre-Cambrian granite-gneiss, 

 quartz-monzonite gneiss, granite augen schists, calcareous augen 

 schists, and small lenses of hydrous mica-schists of the Silver Peak 

 district of Nevada. Certain dolomites, quartzites, and green 

 knotted schists underlying the Olenellus fauna may be Algonkian, 

 but have been provisionally referred to the Lower Cambrian. 



Walcott^ finds the following succession of pre-Cambrian 

 sediments exposed below basal Cambrian conglomerate in the Bow 

 River valley of Alberta, Canada: Hector formation — -shales 

 1,300-2,150 feet; Corral Creek formation — -sandstones 2,600 feet, 

 base not found. He correlates them with the Camp Creek and 

 Sheppard series of arenaceous rocks which lie beneath the Cambrian 

 and above the Siyet limestone in Montana, southwestern Alberta, 

 and southeastern British Columbia. 



Weeks^ finds that the oldest rocks of the Osceola district are 

 granites and schists, with intruded porphyry, which he believes are 

 probably Archaean. 



' Winchell"* finds that the lowest rocks exposed in the Ruby range, 

 about 60 miles south of Butte, Mont., are quartz schists and slates, 

 probably of pre-Cambrian age. 



' H. W. Turner, " Geology of the Silver Peak Quadrangle," Bull. ofGeol. Soc. Am., 

 XX (1909), pp. 223-64, 4 pis., I fig. 



^C. D. Walcott, "Pre-Cambrian Rocks of the Bow River Valley, Alberta, 

 Canada," Smith. Misc. Coll., LIII, No. 7 (August, 1910), pp. 423-31, 3 pis. 



3 F. B. Weeks, "Geology and Mineral Resources of the Osceola Mining District, 

 White Pine County, Nevada," Bull. 340, U.S. Geological Survey, 1907, pp. 117-33. 



4 Alexander N. Winchell, "Graphite near Dillon, Montana," Bull. 470, U.S. 

 Geological Survey, 191 1, pp. 528-32. 



