494 DESCRIPTIVE GEOLOGY. 



SECTION II. 



OMBE MOUNTAINS TO EAST HUMBOLDT EANGE. 



BY ARNOLD HAGUE. 



Ombe Mountains. — To the north of the Ibenpah Mountains, the Great 

 Desert extends to the westward for several miles, with long, dreary slopes 

 toward the Gosi-Ute Range; but farther northward, it is again cut off 

 by the Ombe Mountains, which rise abruptly above the level plain of 

 Lower Quaternary. The mountains are about 30 miles in length by not 

 more than 4 or 5 in width, with a trend a few degrees east of north and 

 west of south. The 114th meridian, the boundary-line between Nevada 

 and Utah, runs just east of the main crest of the mountains, while the 41st 

 parallel crosses the lower slopes of Pilot Peak, at the extreme southern end. 

 Pilot Peak, its most prominent elevation, forms one of the most commanding 

 summits in this region of country, reaching an altitude of over 10,000 feet 

 above sea-level, and rising at least 6,000 feet above the Desert. From its 

 great elevation, abrupt slopes, and isolated position, it has always been, 

 from the times of the earliest explorers and emigrants, a noted landmark in 

 their journeys across the country; and, as it lies just west of the Great 

 Desert, midway between the Humboldt and "VVahsatch Ranges, the summit 

 affords one of the broadest and most instructive views to be obtained in 

 Western Nevada. 



Within the limited area occupied by this narrow range, there are 

 found represented the older highly crystalline granites, heavy massive 

 quartzites and limestones, which have been referred to the Carboniferous, 

 thinly-bedded, upturned calcareous and silicQous shales of the Green River 

 Eocene Tertiary, and still later a considerable outburst of rhyolites and 

 basalts, finally followed by the deposition of horizontal beds of Pliocene 

 age. By reference to the geological map, it will be seen that there is only 

 one body of granite represented, situated near the central portion of the 

 range; other bodies occur, but they are too small to be indicated. 



