The Mo}ave Desert 127 



portion of the Great Basin plateau. In the north, in the Death 

 Valley region, mountain ranges trend in somewhat parallel lines 

 in a generally north-northwest and south-southeast direction. 

 Faults in many cases mark the boundaries of the ranges and 

 valleys. Death Valley, lying west of the Amargosa Range 

 (Funeral and Black mountains) , is a sunken basin in which the 

 floor dips to the east and north toward the great fault scarp 

 which marks the mountain side. The structure of Panamint 

 Valley, lying west of the Panamint Range, suggests that it is a 

 down-faulted block with the greatest depression on the east side 

 of the valley. What is thought to be a fault-plane appears in 

 the abrupt wall of the mountain range on the east. Hot springs 

 at the north end of the valley, and the springs near Ballarat, 

 indicate a zone of faulting along this edge of the valley. The 

 parallel arrangement of the mountains and valleys is generally 

 believed to be due to a series of parallel faults, the valleys repre- 

 senting large blocks that have been lowered relatively with 

 respect to the blocks that have been elevated or tilted to form 

 the mountains. 



Very ancient rocks, granites probably of Archaean age, 

 occur in some of the mountains. Whatever rocks may have 

 been deposited over them have been removed by erosion. Dur- 

 ing the early part of the Palaeozoic era (Cambrian period) some 

 parts of the region were submerged beneath the sea. This is 

 shown by beds of limestone and other sea sediments in which 

 fossils have been found. If the sea covered the entire region 

 during Cambrian time the formations that were laid down 

 have been removed by erosion from most of the region. During 

 the long Ordovician, Silurian, and Devonian periods it is 

 thought that the region was land, as no fossils of these ages have 

 been found. Small patches of rocks containing fossils of Car- 

 boniferous age have been found, showing that the sea covered 

 parts of the region at least during Cambrian time. Through- 

 out the Mesozoic era the region is thought to have been land, 

 and was greatly eroded. In the early part of the Tertiary 



