SIERRA N VALLEYS OF THE KLAMATH REGION 1 63 



in this relatively depressed area and has an elevation of about 

 1,400 feet. I am inclined to the belief that before the derange- 

 ment of the drainage the Trinity and Klamath rivers had inde- 

 pendent courses across the area now occupied by the South Fork 

 Mountain, and that this mountain gained topographic promi- 

 nence by faulting or folding so rapidly that the drainage was 

 deflected toward the northwest along the line of the fault or 

 fold. 



The later system of valleys in the Klamath region is com- 

 parable to the Sierran valleys of the Sierra Nevada region. In 

 the latter area only in very exceptional instances has the erosion 

 since the uplift of the peneplain exceeded 3,000 feet in depth. 

 The resulting valleys are equally as narrow, when in a formation 

 of like resistant properties, as in the more northern region. 

 Indeed, the evidence of age is rather in favor of the Klamath 

 than the Sierra Nevada region, for the valleys or gorges or can- 

 yons, as we may choose to call them, more thoroughly dissect 

 the surface in the former area. However, the contrast is not 

 great when the comparison is made with the Sierra Nevada region 

 south of the Tuolumne river. The latter is more thoroughly 

 dissected than the northern Sierra region because the average 

 slope of the surface is greater. The slopes in the Klamath 

 region, by reason of the arching, were at least as great as in the 

 southern Sierra region, and the remarkable similarity in the 

 nature of the dissection, and the depth and width of the valleys 

 eroded, unmistakably point to a like age. To assert that the 

 inception of the last great uplift of the Klamath region occurred 

 at a time materially antedating or succeeding the inception of 

 the last great uplift of the Sierra Nevada region, one must disre- 

 gard the most positive evidence to the contrary. I want to 

 emphasize very strongly that there is the best of reason for cor- 

 relating the last great arching of the Klamath region, which 

 deranged the drainage and caused the erosion of the new valleys, 

 with the westward tilting of the Sierra Nevada region which 

 initiated the canyon cutting. 



As already intimated, I consider the arching of the Klamath 

 region as contemporaneous with and merely a portion of the last 



