POTASH SALTS AND OTHER SALINES IN THE GREAT BASIN REGION. 



Pre-Tertiary rocks embrace a comparatively large area of the basin region. The chief 

 formations are: Cambrian, Silurian, Devonian, Carboniferous, Triassic, and Jurassic. 

 Pre-Cambrian formations have been described by King, Spurr, and Ball, but are rela- 

 tively unimportant. The eastern and southeastern part of Nevada is characterized 

 by Cambrian, Silurian, Devonian, and Carboniferous rocks. These rocks are quartz- 



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Fig. 1. — Diagrams showing tlie proportion of mountain and intermomitain area in the several districts. 



ites, slates, limestones, and sandstones. Triassic and Jiu-assic formations are rela- 

 tively less abundant and occur in widely distributed patches in the west-central and 

 southwest portions of the basin region. They consist of limestones, slates, shales, 

 and thin beds of quartzite. In the Triassic are also found beds of gypsum. 



Post-Jurassic orogenic movement, accompanied by granitic intrusions, ushered in 

 a period Of land elevation and erosion, which continued throughout Cretaceous time. 



