114 



University of California Publications. [Geology 



Detailed Description of the Fault Zone. 



The three topographic divisions of the Carson Range have 

 been described. The structure of these in detail will be given, 

 beginning with the central portion, which contains the old river 

 channel and therefore admits of the definite establishment, by 

 means of stratigraphic evidence, of faulting and of the topo- 

 graphy due to faulting. 



The Carson Area. — The Carson topographic area of the Car- 

 son Range is characterized by three quite well denned north- 

 south ridge lines. These are most clearly shown along an east- 

 west section through Marlett Peak. They may be referred to 

 for convenience as the west summit ridge, the east summit ridge, 

 and the low east ridge. The west summit ridge forms the main 

 crest, and bears the two highest points, Snow Valley Peak and 

 Marlett Peak. The east summit ridge rises to elevations nearly 

 as high as the other, and is separated from the main crest by a 

 persistent line of depressions or valleys. The low east ridge rises 

 about 1,500 feet above the Nevada valley, and consists of a series 

 of hills separated by the cross valleys or canons of the range. 

 The main west summit ridge is complex in detail. On an east 

 west section through Snow Valley Peak this crest is composed of 

 the main peak and two sub-crests to the west. The down-dropped 

 block underlying Marlett Lake also belongs with this topographic 

 division. The east summit ridge and the low east ridge are both 

 comparatively simple. The long slope leading down from the one 

 to the other, however, is again complex, far more than the map 

 indicates. It is strongly characterized by a succession of flats 

 with steep shoulders rising to the west, giving the whole a step- 

 like profile. On this section the slopes rising from Lake Tahoe 

 are steeper than at any other point directly above the water. 

 Huge blocks of granodiorite are continually becoming loosened 

 and roll down to the lake shore. Just northwest of Marlett Peak 

 one can stand nearly 2,500 feet almost directly above the water 

 and obtain a view not to be equalled at any place on the lake. 

 The east-west profile of the Carson Range across this section is 

 quite serrate in character. The three principal ridge lines are 

 persistent, the sub-ridges are not always so. All strike north 

 and south. 



