552 DESCRIPTIVE GEOLOGY. 



activity of the Tertiary age is well shown in the broad areas of both acidic 

 and basic rocks. 



PALiEozoic FoEMATioNS OF THE PiNON Range. — South of Dixie Pass, at 

 its extreme northern end, the range rises in an elevated group of peaks, the 

 highest of which has been called the Raven's Nest. This is formed of a 

 heavy body of grayish-blue limestones, with included strata of buif lime- 

 stone, which trend diagonally across the Piiion Range, with a strike of 

 about north 25° east and a dip of from 25° to 35° to the northwest. 

 Directly north of the Railroad Mining District, the ends of this limestone belt 

 are covered by an overflow of trachyte. At the east base of Raven's Nest 

 Peak, these beds are conformably underlaid by a thin bed of granular 

 saccharoidal quartzite, which closely resembles the gray limestone above it, 

 the one passing gradually into the other. The whole body of limestone is 

 between 3,000 and 4,000 feet in thickness, and is made up of remarkably 

 heavy beds. Toward the bottom, it is prominently siliceous, but toward the 

 top is a very pure crystalline limestone, which has been much altered into 

 marble, and, where imaltered, is reticulated with seams of calcite. This 

 formation is overlaid by about 1,200 feet of finely-laminated and iron- 

 stained quartzites. The material of this formation is exceedingly fine : it 

 carries no conglomerates; it has no gritty grains, but shows throughout a 

 uniform compact texture. West of Raven's Nest Peak, it is much traversed 

 by jointing planes, with a strike of northwest and southeast. It is altogether 

 similar to the great quartzite formation which appears south of Pinto Peak 

 in the region of Pinon Pass, and from the trend of the two bodies there is 

 little doubt that they are the same. Directly south of Pinon Pass, the 

 quartzite is overlaid by a heavy limestone, which contains Devonian fossils. 

 West of Raven's Nest Peak, the quartzite body is also overlaid by a high 

 conical hill composed of heavy dark beds of limestone, conformable with 

 the quartzite, and dipping west at about 40°. A few crinoidal stems were 

 all the fossil remains found in this upper series of beds. Its thickness is 

 entirely unknown, but there are exposed at least 4,000 feet of strata. How 

 much more lies to the west under the Humboldt Pliocene is, of course, 

 uncertain. 



From its position over the quartzite, from the heavy character of its 



