0. H. Ilershey — Belt and Pelona Series. 267 



Thus we may have a total thickness (including 1,000 feet of 

 Cataldo quartzite) in the Belt group of strata remaining in the 

 Wardner District of 19,800 feet. A geologist, whose past expe- 

 riences with other alleged thick formations entitle him to take 

 a critical view of the subject, has expressed the conviction that 

 Calkins' estimates of the thickness of the Coeur d'Alene rocks, 

 which were evidently derived by the measuring of sections at 

 right angles to the bedding planes, are far too high. My esti- 

 mates are based on a knowledge of the value that must be given 

 to individual formations in making up the mass of certain fault 

 blocks and are not dependent entirely on the original attitude 

 of the bedding planes. I am not certain that the Prichard 

 formation attains the 8,000 feet thickness assigned to it, but I 

 am confident that the estimates of thickness of the other forma- 

 tions will in a general way stand the test of the most intensive 

 study. 



Elsewhere in the Belt area higher members of the series 

 occur, and in the Belt Mountains and Mission Range of Mon- 

 tana they are nonconformably overlaid by Cambrian sediments. 

 In the " Geologic Map of North America," * besides the main 

 area lying chiefly in Idaho, Montana, and British Columbia, a 

 small area of Belt rocks is indicated in the Wasatch Range 

 north of Ogden, Utah. The central portion of the Uinta 

 Range is also mapped as Belt. The Wasatch area is presum- 

 ably that which has been discussed recently by Mr. E. Black- 

 welder.f The prevailing rocks are variously colored quartz- 

 ites or quartzitic sandstones. There are many thin beds of 

 conglomerate and at several horizons hard shales and slates, 

 chiefly dark purplish brown and bright green, though some are 

 distinctly black and others rich maroon. A few thin beds of 

 brown dolomite occur. Cross-bedding, ripple marks and sun- 

 cracks are prevalent. These strata are referred to the Algon- 

 kian and are presumed to be overlaid nonconformably by 

 Lower Cambrian quartzite 1,000 to 1,500 feet thick, and this 

 by Olenellus-bearing shales and limestones. The base of the 

 Cambrian quartzite is placed at a well-marked conglomerate. 



During the first six months of 1905, I made an extensive 

 geological reconnaissance of a portion of Eureka, White Pine 

 and Elko counties in Eastern Nevada, particularly of the ranges 

 on both sides of Steptoe Valley. I find in my notebook under 

 date of May 16, 1905, the following generalized section : 



*Pro£. Paper U. S. Geol. Survey No. 71, plate 1, 1911. 

 f New Light on the Geology of the Wasatch Mountains, Utah ; Bull. Geol. 

 Soc. Am., vol. xxi, 1910. 



