Diller — Klamath Mountain Section, California. 361 



5. Tuff, 6 miles northeast of Paskenta, Tehama County, Cal. 



Analyst, George Steiger. 1893. 



6. Another portion of same mass as 5. Analyst, E. T. Allen. 



1903. 



7. Tuff, Redding Creek Basin, Trinity County, Cal. Analyst, 



E. T. Allen. 1903. 



8. Tuff, Hyampom, Trinity County, Cal. Analyst, George 



Steiger. 1893. 



A number of chemical analyses of Lassen Peak lavas, includ- 

 ing both andesites and dacites, were made some years ago and 

 average examples are given in 1 and 2 of the accompanying 

 table. The dacites have a glassy base which, as shown by 

 analysis 3 is richer in silica and potash than the lava. The 

 tuff 40 miles southeast of Lassen Peak (4) is supposed to 

 have resulted from a late eruption of that peak and was put in 

 for comparison with the tuff of the Sacramento Valley (5 and 

 6) from the same source, and afford a basis for comparison with 

 that west of the Sacramento Valley on Redding Creek (7) and 

 at Hyampom (8) in the Klamath Mountains. The last two are 

 certainly not of the same eruption, for they are widely differ- 

 ent in age. The tuff of Hyampom, so rich in particles of 

 clear volcanic glass, contains Miocene leaves, while that of Red- 

 ding Creek and Hay Fork basins is much later, overlying the 

 Miocene shales, and of much more recent appearance. The 

 leaf-bearing shales of Hay Fork have been Pound rich in 

 infusoria and as far as seen, although like tuff in appearance, 

 contain no particles of glass which could be identified with 

 certainty. 



Becker* called attention to much volcanic material in Lake 

 County, and Hersheyf suggested that the prevailing winds of 

 that region being from the south the tuff in the Neocene basins 

 of the Klamath Mountains may have come from Lake County. 



As to the age of the tuffs in Hay Fork and Redding Creek 

 basins, from the fact that they occur between the Pleistocene 

 gravel and Miocene shales and sandstones they may be regarded 

 in general as being Pliocene. 



Pleistocene. 



The Pleistocene of the Klamath Mountains embraces numer- 

 ous elevated beaches along the coast as well as glacial and flu- 

 vial deposits among the mountains, but for our present purpose 

 these have been sufficiently treated in U. S. Geological Survey 

 Bulletin 196, page 24, and by Hershey in the Journal of Geol- 

 ogy, volume viii, page 42. 



* U. S. Geol. Survey Monograph xiii. 

 fJour. Geol., x, 391. 



