Geol.— Vol. I.] TURNER— ORIGIN OF YOSEMITE VALLEY. 267 



formed by folding, and probably at this time much worn 

 down; but that the fault-scarp of this portion of the range 

 was initiated previous to the deposition of these beds 

 seems not improbable. 



In the south-central Sierra Nevada there is also some 

 evidence tending to show that the crest-line of the range 

 was in Tertiary time where it now is. Thus the gravel 

 deposits of the Tertiary Tuolumne River have been traced 

 from the foothills to Mt. Dana, the course of the stream 

 substantially coinciding with that of the present Tuolumne 

 taken in a general way, as will be more fully noted here- 

 after. There is, also, some evidence that the Pleistocene 

 canyons of the southern Sierra are the greatly deepened 

 valleys of Tertiary time, and these Tertiary valleys show 

 every evidence of ending west of the present crest of the 

 Sierra. 



II. Orogenic Movements in the Pleistocene. 



For the sake of convenience, the orogenic disturbances 

 are treated of in one section, although they probably 

 occurred at various times and in each of the subdivisions of 

 the Pleistocene. 



From the preceding section it will be seen that the main 

 displacements are regarded as having occurred within and 

 at the close of the Tertiary Period. Until the geology of 

 the eastern slope of the Sierra Nevada is better known it 

 will not be possible to estimate to what extent such dis- 

 placements have occurred within Pleistocene time. Mr. 

 Walcott^ has brought forward good evidence to show that 

 in the neighborhood of Big Pine, the Inyo Mountains, the 

 range lying im.mediately east of the southern Sierra Nevada 

 has undergone an elevation in Pleistocene time of 3,000 

 feet. This elevation probably occurred during the middle 

 of Pleistocene time, as the lake beds of the Waucoba em- 

 bayment southeast of Big Pine are regarded by Mr. Walcott 

 as probably of early Pleistocene age. It may have occurred 



1 Journ. Geol., Vol. V, 1897, pp. 340-348. 



