156 



EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



Tabic enumerating the various formations and groups, (jx. — Continued. 



II 



Fossils. 



Orthistritonia, Corals, Dicel- 

 locephalus, and others. 



Character of strata. 



Blue and whito limestones, partly ooilitic. 

 Thinly banded shales. Greatest thick- 

 ness north. 



100 

 to 

 280 



"53 § 



Lingula, Obolus, Obolella. 



"White and yellow, mostly red quartzites. 

 Sometimes thinly bedded, and again 

 heavily stratified. Greatest local devel- 

 opment at Rawliugs. 



220 

 to 

 COO 



Granites, composed of orthoclase, oligo- 

 clase, quartz, and dark-colored micas. 

 The latter substituted by hornblende 

 and chlorite. 



30, 000 



g S 



Schists, composed of quartz, feldspar, horn- 

 blende, and mica. Metaliferous. 



«w 



Massive, structureless granites, composed 

 of orthoclase, large masses of white 

 quartz and muscovite. 



18, 000 



Indef- 

 inite. 



"We find that in the Sweetwater district the total maximum thickness 

 of sedimentary deposits amounts to more than 16,000 feet. The esti- 

 mates upon which the thickness of Archaean groups are based must ne- 

 cessarily be incomplete, but I believe that the figures given approach to 

 true dimensions as closely as is possible. Were the structure of chains 

 and ranges perfectly open, more reliable results could be obtained. 



