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University of California Publications. 



[Geology 



ized by no such peculiarities of the topography. Lastly, there 

 is no evidence of stream erosion on any side of this particular 

 sub-crest. These peculiar sub-crests, or the apices of fault- 

 blocks, are so striking and important a feature of the topog- 

 raphy that further discussion here is not amiss. A good example 

 is found south of Marlett Peak. The unequivocal fault-plane 

 that bounds Marlett Lake on the east passes north just west of 

 Marlett Peak, faults the river gravels, and extends further to 

 the north for about a mile before its traces become lost. The 

 west wall is dropped relatively to the east. North of Marlett Peak 

 a sub-ridge has been formed, and on this are situated two crests. 

 The southernmost of these two crests is on the old river channel ; 

 the northern one is all in granodiorite. The nature of the first 

 is plainly evident from stratigraphic evidence. The other then 

 becomes likewise clear. Each crest is separated from the higher 

 crest to the west by a narrow valley or col, in which are found 

 products of deep rock disintegration. No stream has ever flowed 

 in these cols, and no running streams are near either of these 

 sub-crests. The movement along the fault-plane appears in all 

 eases to have so fractured the bounding walls that rock disinte- 

 gration has been comparatively rapid and atmospheric erosion 

 correspondingly great. But there is a further characteristic of 

 these sub-crests, viz : their buttress form. The question is in- 

 stantly forthcoming : If these sub-crests are due to north-south 

 faulting, why is the crest not a ridge line instead of a dome? 

 To answer this, attention must be called to the intense east-west 

 faulting and fracturing. The major faulting has always been 

 along north-south lines, but much induced secondary movement 

 has taken place at right angles. The latest large central move- 

 ments appear to have been concerned with the north-south tilting 

 of a few large blocks and the elevation of others. These will be 

 discussed in the proper place. Actual dislocation in an east-west 

 direction is proved by hypsometric discordance of plateau rem- 

 nants, river gravels, and volcanics, the presence of typical fault- 

 scarps, and stratigraphic discordance in the schist areas. While 

 in many cases the buttress form of the sub-crests or lesser fault- 

 blocks can at once be proved to be due to faulting in any one of 

 the above ways, it also is a fact that in all cases with the facts 



