570 DESCRIPTIVE GEOLOGY. 



SECTION VI. 



COETEZ EANGE. 



BY S. F. EMMONS. 



Tenabo Peak Eegion. — The Cortez Range lies next west of the Pifion 

 Range, and is separated from it by the narrow Pliocene basin of Pine Valley. 

 It has a northeast and southwest trend; but, owing to the great accumulations 

 of intrusive rocks, its boundaries are less clearly defined than are those com- 

 posed mainly of sedimentary strata. To the south, the range terminates 

 abruptly in Tenabo Peak, but to the north it stretches out in broad, irreg- 

 ular fields of rhyolite. The Cortez exhibits a marked contrast to the Pinon 

 Range, the latter being formed of longitudinal uplifts of Palaeozoic strata 

 bordered by volcanic outflows, while the former, exposing but little of sand- 

 stone and limestone, show§ intense activity of igneous rocks, not only in the 

 broad accumulations of volcanic material, but in the great variety of rocks 

 represented from quartz-propylite to the latest flows of basalt. 



Tenabo Peak, at the extreme southern end, stands out somewhat 

 prominently from the rest of the range, separated by the marked depression 

 of Agate Pass. This peak, the highest in the range, has an elevation of 

 9,240 feet above sea-level, and rises boldly over 4,000 feet above the Qua- 

 ternary plains of Crescent Valley. Tenabo, in the language of the Sho- 

 shone Indians, is said to signify "Lookout", a very appropriate name, as the 

 peak aflbrds one of the broadest and most commanding views to be found in 

 Central Nevada. The greater part of the mountain is made up of. a heavy 

 body of granite, extending from the base up to within 900 or 1,000 feet of 

 the summit, where it is overlaid by a limestone 'body referred to the Upper 

 Coal-Measure series. This granite also forms the lower 2,000 feet of the 

 precipitous western wall of the mountain down to Shoshone Wells, stretch- 

 ing westward so as to include the body making the divide between Cres- 

 cent and Cortez Valleys. 



Mill Creek and other lesser canons cut deeply into the formation, and 



