222 .!. S. DILLEK — GEOLOGY OF CALIFORNIA AND OREGON. 



amorphism of the Klamath mountains and Sierra Nevada occurred soon 



after the close of the Taylorville Jurassic. 



How long a time interval is represented by the great unconformity 

 between the Taylorville Jurassic and the Shasta-Chico series is not yet 

 known, hut that the upheaval took place in the earlier part of the inter- 

 val is most probable. 



The relation of the Mariposa beds to the Taylorville Jurassic, on the 

 one hand, and to the Shasta-Chico scries, on the other, is yet a matter of 

 doubt, but will soon be resolved by Mr Becker and his assistants, Messrs 

 Turner and Lindgren, who are now making a thorough survey of the 

 Gold belt of the Sierra Nevada. It is already evident from the researches 

 of Mr Becker and Dr White that the faunas of the Mariposa and Knox- 

 ville beds are closely related, and on this account the great fauna! and 

 stratigraphic break corresponding to the great unconformity between 

 Shasta-Chico series and the Taylorville Jurassic on Pit river might be 

 expected at the base of the Mariposa beds. That an upheaval occurred 

 at the close of the Jurassic of Taylorville is indicated by the distribution 

 of Auccllu in northern California and Oregon. Accordingly the disturb- 

 ance in the Mariposa beds would have to be referred* to a later epoch, 

 either within the Aucella-beaxing series or to the close of the Chico or 

 Miocene. 



Inter-Cretaceous-Tertiary Upheaval of the Klamath Mountains. 



The lower portion of the Shasta-Chico series is in general more dis- 

 turbed than the upper or Chico portion. This is due to various causes, 

 the principal of which is to be found in the fact that, as now exposed, 

 the Shasta beds are nearer the centers of disturbance than the Chico. 

 The Chico has been removed from the disturbed areas by erosion. 



On the western side of the Sacramento valley, along Elder creek, 

 where the Shasta-Chico series is exposed, the whole series is tilted, but 

 the Shasta beds in the western portion toward the Coast range arc some- 

 what more disturbed than the Chico beds in the eastern portion ; yet 

 the difference is not great and the change so gradual through a number 

 of miles of well-exposed strata that we looked in vain for any break in 

 the stratigraphy or fauna. 



The character of the strata had much to do in determining the amount 

 of deformation. The shales of the Shasta-Chico series are generally more 

 deformed than the sandstones and conglomerates of the same locality, 

 1 lecause less rigid. They predominate in the lower portion of the Shasta- 



*See paper by Mr S. F. Kmmons "On Orographic MmvuiniN in the Roeky Mountains," Hull. 

 Oeol, Soc. Am., vol. 1, \>. 27'J. 



