48 THE JOURNAL OF GEOLOGY. 



Peak, beneath whose lavas it disappears, makes it very probable 

 indeed that they are connected with the lone formation that dis- 

 appears under the opposite edge of the same lavas bordering 

 upon the eastern side of the Sacramento valley. If this could be 

 definitely established it would show that the northern end of the 

 Sierra Nevada has been elevated 7,000 feet since the gravel 

 period of that region. It is possible that the increased elevation 

 does not extend far to the southward, for beyond the 40th par- 

 allel the eastern crest of the railge retreats to the escarpment of 

 the main block of which the Sierra Nevada is composed. 



In connection with the upheaval of the northeastern portion 

 of the range a fault was formed along the eastern base at least 

 beyond Honey Lake. A short distance above Janesville the 

 gravels are displaced by a fault in which the throw is about 3,000 

 feet. On the very crest of the range, seven miles northwest of 

 Janesville, the gravel rises to 7,400 feet, while at the foot of the 

 steep slope which it caps the same gravel occurs in Mr. Weisen- 

 berger's mine at an elevation of about 4,300 feet. To the north- 

 westward the fault runs out apparently in a monoclinal arch, later 

 than the volcanic eruptions on the crest of the range at that 

 point, ^ but before the final eruptions of the Lassen Peak region 

 were completed. Mr. Lingdren has shown "" that further south 

 the eastern slope of the range was formed before the eruption of 

 the andesitic lavas. ' There is some evidence of a similar 

 character in the Honey Lake Region. 



ORIGIN OF THE EARLIER AURIFEROUS GRAVELS. 



The Tejon epoch appears to have been brought to a close, 

 and the Niocene initiated, in northern California, without any 

 marked change of level, unless a general subsidence, 3 so that the 

 influences in operation during the Tejon continued into the 

 Miocene. The old streams still carried on their enfeebled 

 erosion, and in some places the land was completely reduced to 



'See also Eighth Annual Report U. S. Geological Survey, p. 429. 

 - Bull. Geol. Society of America, Vol. 4, pp. 257-298. 

 3Dall and Harris : U. S. Geol. Survey, Bull. 84, p. 278. 



