260 W. LINDGREN — TWO NEOCENE RIVERS OF CALIFORNIA. 



and westward from a crest which was probably situated along a line just above the 

 Yosemite and Hetch-Hetchy valleys, for there the erosive biting into the granite 

 axis seems to be deepest. The rivers, by long work, had finally reached their base- 

 levels and rested. The scenery has assumed all the features of an old topography, 

 with gently flowing curves. The continental elevation" — previously described in 

 the same paper — " of the Pliocene did not greatly affect the river slopes of this part. 

 At the end of the Tertiary came the great lava streams, running down the river 

 channels and displacing the rivers; the heaving up of the Siena crust-Mock on its 

 eastern side forming the great favdt cliff there and transferring the crest to the ex- 

 treme eastern margin; the great increase of the western slope and the consequent 

 rejuvenescence of the vital energy of the rivers; the consequent cutting down of 

 these to form the present deep canyons, and the resulting wild, almost savage, 

 scenery of these mountains." 



Mr J. S. Diller, who has studied the geology of the northern end of the 

 Sierra Nevada north of the fortieth parallel, holds similar views as to the 

 age and elevation of the range. They were first set forth in his " Notes 

 on the Geology of northern California,*'* which, however, does not in- 

 clude any detailed discussion of the Tertiary river deposits on the west- 

 ern slope. His conclusions may he best stated by quoting from a later 

 paper on the " Geology of the Lassen peak district: "f 



"During the whole of the Cretaceous and the Tertiary the great belt of country 

 lying east of the present Sacramento valley, embracing the region now occupied by 

 the Sierra and a large portion of the Great Basin, was above the sea, and subjected 

 to great degradation, which reduced it almost to its base-level of erosion. This 

 gentle plain swept westward toward the ocean directly across the site of the present 

 Sierra. That the north end of the Sierra country was a lowland during the Miocene, 

 as already shown, is rendered perfectly evident by the character of its flora; and 

 the relation of the Miocene conglomerate to the eastern escarpment north of Honey 

 lake is such as to demonstrate that during the Miocene the Sierras were not yet in 

 existence. Similar conditions continued through the Pliocene, for the Pliocene 

 gravels on the western slope of the Sierras were evidently deposited while its in- 

 clination was very gentle, before the Sierra region had attained any considerable 

 elevation, and apparently also while it was yet a part of the Great Basin platform. 

 * * * The faulting, by means of which the Sierra Nevada range was separated 

 from the Great Basin platform, took place, in a geologic sense, very recently. The 

 eastern escarpment of the range, at least in its northern portion, was evidently 

 formed after the conclusion of the volcanic activity in its immediate vicinity." 



Since the above was written, Mr Diller has published a paper on the 

 -• Geology of the Taylorville region,"^ in which he shows the Taylorville 

 fault to be an overlhrust instead of a normal fault, as he had previously 



supposed. This change necessarily modifies his earlier views to some 

 extent. 



♦ Bulletin 33, U. S. Geol. Survey, L886. 



t Eighth Ann. Rep. V. 8. Geol. Survey, 1889, p. 128. 



| Bull. Geol, Soc. \m., vol. 3, p, 369. 



