416 University of California Publications in Geology [Vol. 9 



A study of Knowlton 's list as given in Lindgren 's ' ' Tertiary Gravels 

 of the Sierra Nevada" shows that most of the forms mentioned by 

 him above as showing a subtropical climate were found in the bench 

 gravels or the rhyolitic tuffs. 



The mixture of plants of the lowlands and plants of the high- 

 lands to which Knowlton refers is explained in part by the facts 

 that his fauna is a mixture of forms obtained from the andesites and 

 from the bench gravels and rhyolite, and in part by Lindgren 's clear 

 picture of a mountainous region of fairly great relief bordering a 

 coastline. The fact that many of the species are subtropical is not 

 contrary to the conclusions concerning Eocene climate which the 

 writer derived from the study of the marine invertebrates of the 

 Tejon Eocene. In fact a subtropical climate is inferred from both 

 studies and hence there is nothing in the floras which would reject 

 an Eocene age determination for the bench gravels and the rhyolite. 



In addition to this, some direct evidence concerning Eocene floras 

 was obtained by Diller. Several of the species listed by Knowlton 63 

 have also been reported from a known Tejon locality in Oregon. 

 Among these were Magnolia lanceolata and Aralia ivhitneyi. Con- 

 cerning this flora Knowlton remarks that "they have both been 

 reported from the Fort Union formation as well as from the lone 

 formation of Shasta County, California, and other localities ... a 

 fact which undoubtedly robs them of the significance they might 

 otherwise have as tending to prove the Eocene age of all the aurifer- 

 ous gravels". Knowlton assumed a proven Miocene age for the lone. 

 This assumption may be due to the determination of some poorly 

 preserved marine fossils from the supposed lone of the Marysville 

 Buttes as Miocene. Better material obtained from this locality 

 demonstrates the Eocene age of these beds. It has, been shown 

 above that the age of the lone is Eocene and hence this evidence 

 supports an Eocene age for the auriferous gravels most decidedly. 

 Thus far there is no evidence which can not be legitimately inter- 

 preted as indicating an Eocene age for the deep gravels and most 

 of the rhyolite of the superjacent series of the Sierra Nevada. 



SUMMARY OF GEOLOGICAL EVENTS ALONG THE WESTERN 

 FOOTHILLS OF THE SIERRA NEVADA 



The historical geology of the east side of the Great Valley border 

 from Chico time to the Recent is in summary: 



65 Knowlton, F. H., in Professional Paper No. 73, p. 64, 1911. 



