O. II. Ilershey — Belt and Pelona Series. 271 



they do not impress me as typical river sediments. Rivers 

 meandering on a plain leave channels which become filled with 

 sediments and preserved. Nothing even remotely suggesting 

 such a fossil channel has ever come to my attention in the 

 Coeur d'Alene District. Furthermore, in my description of 

 the Belt formations in the Wardner District I have taken pains 

 to mention the existence in some of the formations of frequent 

 hands of practically pure, white quartzite. These were origi- 

 nally beds of nearly pure fine-grained sand comparable with 

 the St. Peter sandstone in the Mississippi basin. They prove 

 a nearly perfect assortment of materials at frequent intervals 

 ranging from late Prichard time to the close of the Revett 

 period. They are not typical river sediments. It is difficult 

 to understand how a river might deposit over a considerable 

 area a bed of nearly pure quartz sand 100 feet thick. For 

 these reaso*ns I consider the fluviatile origin of the Belt terranes 

 not yet satisfactorily proved. Indeed, I am inclined to support 

 the hypothesis that the sediments were deposited in a vast 

 inland sea or lake into which large rivers carried great quan- 

 tities of fine sediment, some of which was precipitated without 

 perfect sorting, while some was brought under the action of 

 currents that formed the white sand beds. 



The Oro Grande series of marble, quartzites and slates in the 

 Mohave Desert in Southeastern California* was correlated on 

 lithologic grounds with the Lower Cambrian strata of Inyo 

 County, California^ At that time I had not seen the latter, 

 but I have since visited the White Mountain Range and con- 

 tinue to hold the impression that the Oro Grande series is the 

 correlative of part of the Lower Cambrian of Inyo County. I 

 want to call attention to the fact that the Oro Grande sediments 

 have been altered by regional metamorphism to the same 

 degree as the Lower Cambrian and Belt quartzites and slates 

 of Eastern Nevada, excluding the lower two members of my 

 section. They have a somewhat more altered appearance than 

 the Belt sediments of the Coeur d'Alene District of Idaho ; 

 for instance, the slates are, roacroscopically, more evidently 

 micaceous. 



At the Yellow Butte, about 12 miles by the California North- 

 eastern railroad from Weed, and hence north-northwest of Mt. 

 Shasta in Northern California, there is an "island" of older 

 rocks rising through the Tertiary lavas. It consists mainly of 

 a fine-grained hard white and gray quartzite in which are thin 

 micaceous schists, the whole being unlike anything in the Kla- 



* Notes on the Later Cenozoic History of the Mohave Desert Region in 

 Southeastern California; Univ. Calif. Publ., Bull. Dept. Geol., vol. vi, pp. 

 336-337, 1911. 



f Some Crystalline Rocks of Southern California; Am. Geol., vol. xxix, 

 pp. 286-287, 1902. 



