FAULT BASINS. 27 



than 5,000 or 6,000 feet. The eastern slope is comparative!)" gentle, and 

 conforms in a general way with the inclination of the beds of volcanic rock 

 composing a large part of the mountains. The bold western mountain face 

 is in reality an eroded fault scarp; the thrown block underlies Quinn River 

 Vallev. 



In the case of the Jackson Range the principal fault follows its western 

 base ; the eastern base of the Pine Forest Mountains is also a precipitous 

 fault scarp; the Black Rock Desert, intervening between these ranges, is a 

 depressed area, which has been deeply buried beneath the sediments of 

 Lake Lahontan. An ideal section from east to west, tlirough these ranges, 

 is shown in the following diagram: 



Fig. 2. — Ideal section through the Black Kock Desert, Nevada. 



The Pahute Range, on the eastern border of the Carson Desert, has a 

 well defined line of displacement along both the eastern and the western 

 base, as indicated in tlie following generalized section : 



Pajruxe nayige 



■^^=^=^^ ■ ^ ^ 



Fig. 3. — Ideal section of the Pahnte Kauge, Nevada. 



Great faults may also bo traced along the western bases of the West 

 Humboldt and Star Peak ranges. The eastern shores of both Pyramid and 

 Winnemucca lakes are likewise determined by fault scarps, as indicated 

 below. 



P/rsm/d Uke /SJ!S«~^ W,nnen,^^ca. Lake. 



Fig. 4. — Ideal section through Pyramid and "Winnemncca lakes, Nevada. 



In Walker Lake Valley the orographic structure so typical of the Great 

 Basin is again repeated ; the main displacement in this instance follows the 

 western border of the vuUe}^ and determines the abrupt eastern face of the 

 Wassuck Mountains. The topography of the valley is well shown on 

 Plate XV. 



