3§4 



University of California. 



[Vol. i. 



Valley to its present form, our present imperfect knowledge of the 

 geology of its bounding mountain ranges, more especially of the 

 eastern portions of the Coast Ranges and Klammath Mountains, is 

 a serious obstacle. It is very doubtful whether anything at all 

 comparable with the present valley existed during Cretaceous times. 

 According to Mr. Diller,* the Klammath Mountains formed an 

 island during the early part of this period at least, but our knowl- 

 edge of these mountains is too slight for anything like a positive 

 statement to be made. At Paskenta, on the west side of the Sacra- 

 mento Valley, there is a great thickness of Cretaceous strata ex- 

 posed, dipping steeply toward the valley. Mr. Diller, referring to 

 these strata, speaks of over 29,000 feet of sediments (Shasta-Chico 

 Series) being laid down in the Sacramento Valley, but he probably 

 hardly means to convey the impression that there was then any 

 distinct valley. No such thickness of Cretaceous rocks is found on 

 the eastern or Sierra Nevada side of the valley, and we should 

 rather suppose that the sediments observed at Paskenta thin out 

 under the present valley, and that their greatest thickness, and 

 therefore the deepest depression in which the Cretaceous sedimen- 

 tary lens was deposited, was either at the above-named place, or 

 even at some place west of it, over the site of the present Coast 

 Ranges. In the latter case the strata have probably been largely 

 removed by denudation. Throughout the Coast Ranges the Cre- 

 taceous strata are so widely spread, and so considerable in volume, 

 as to indicate that the region occupied by these mountains was not 

 only submerged at that time, but was probably more deeply sub- 

 merged than was the area of the present Great Valley. 



During the Eocene (Tejon), according to Mr. Diller, f northern 

 California and a large part of Oregon were above sea and being 

 degraded, no Eocene deposits being known in California above the 

 40th parallel. There was probably a gradual subsidence, as shown 

 by the thinning out of the Tejon northward in California. But so 

 much being granted, there is nothing to indicate that any step had 

 been taken toward the initiation of the Upper Sacramento Valley, 



*Loc. cit., p. 423. 



"("Topographic Revolution on the Pacific Coast, 14th An. Rept. U. S. Geol. 

 Survey, p. 424. 



