92 GEOLOGY OF THE EUREKA DISTRICT. 



of calcareous and sandy beds; in others, of tine grits and shales; and, again, 

 of nearly pure siliceous sediment, varying from fine to coarse grained, de- 

 ])endent largely upon the distance from any land area and depth of water in 

 which it was deposited. Here at Eureka the material is exceptionally coarse 

 with abundant evidence of shallow water deposition and the existence of a 

 land surface not very far remt)ved at the time the beds were liiid down. 



Two large bodies represent the Weber conglomerate at Eureka, one 

 directly east of Carbon Ridge and the other overlying the Alpha Ridge 

 west of Hayes Canyon. The former is not shown in its full development, 

 the upper members being cut off hj the Pinto fault, but the geological 

 position of tlie latter is admirabh" Ijrought out by the underlying and over- 

 lying limestones. Across their broadest development the beds have a 

 thicknes.s estimated at about 2,000 feet. They are well shown in long par- 

 allel ridges inclined at liigh angles, with a synclinal followed bv an anti- 

 clinal fold. Foi- tlie most part the formation is made up of coarse material 

 of both angular and rounded fragments of red, brown and Avhite grits, 

 together with jasper, brown hornstone, and green chert}' pebliles firmh^ 

 held together by a siliceous cement. Interstratified in the coarse material 

 are occasional beds of fine, yellow white sandstone, which has been used as 

 a lining for the large smelting furnaces at Eureka. In certain beds the 

 angular ])ebbles predominate, and in others the rounded, but in general there 

 is a fair admixture of both varieties. Near the sununit of the horizon a 

 single belt of blue limestone comes in, which, liowever, in its lateral exten- 

 sion, may not be persistent. Considering the thickness and nature of these 

 conglomerates, they present an exceptionally uniform appearance through- 

 out, with almost no shale and but little limestone. No subdivisions need 

 be drawn. Although the formation has yielded no fossils, its structural 

 relations permit of its being easily correlated with the Weber conglomerate 

 of northern and eastern Nevada. With the coarse conglomerates of the 

 Weber at Agate Pass', in the Cortez Range, there is the closest resemblance; 

 both areas mu.st have been near the shore line of the Paleozoic sea, in cen- 

 tral Nevada. 



'U. S. Geological Exploration of the Fortieth Parallel, vol. 2, Descriptive Geology, p. 574. 



