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University of California Publications in Geology [Vol. 9 



comprising the core of the present range. The character of the contact 

 of the Trabueo formation with the basement complex, as shown in 

 detail and by areal mapping, indicates a land surface of low relief, 

 but the character of the sediments contradicts this in a measure, for 

 streams of considerable gradient must have existed in order to have 

 transported the coarse sediments characterizing these strata. This 

 apparent conflict may possibly be reconciled upon the assumption of 

 a rather narrow coastal plain, adjacent to a mountainous country of 

 considerable relief. If no land existed west of this shore-line, as seems 

 probable, the physical environment of this region differed considerably 

 from that of the present Sacramento Valley region. 



The Upper Cretaceous beds of northern California were deposited 

 in an inland sea protected from the open ocean by an archipelago, 

 occupying the region of the present Siskiyou Mountains and the 

 northern end of the Coast Ranges. Regarding this Diller and Stanton 

 say 



The attenuation of the Shasta-Chico Series westward from the Sacramento 

 Valley and the overlapping of the newer beds upon older crystalline rocks of 

 the Coast Range shows that the Coast Range was formed before the deposition 

 of the Shasta-Chico series, and probably at the close of the Jurassic when the 

 Mariposa beds were upturned. 29 



Such a distribution of land might have had a marked effect upon 

 the local oceanic currents, thereby producing temperature differences 

 sufficiently great to account in part for the faunal dissimilarities noted 

 above. Such a factor accompanied by others of lesser rank, concerning 

 which but little is as yet known, is perhaps of sufficient importance 

 to make it unnecessary to consider that the faunal peculiarities of the 

 Santa Ana Mountains and northern California basins of deposition 

 are due solely to different faunal stages. 



RELATION TO FOREIGN CRETACEOUS FAUNAS 



Various writers, including Gabb, White, Smith, Stanton, Hamilton, 

 Whiteaves, and Anderson, have expressed opinions regarding the 

 ecptivalents of the Chico group. This problem is complicated; there- 

 fore, only a few of the more recent, views upon this subject will be 

 considered in this discussion. 



Anderson, following in part the conclusions of Gabb and Whit- 

 eaves, considered that "the Chico, the Nanaimo, and the Phoenix and 



29 Diller, J. S., and Stanton, T. W., op. Git., p. 464, 1894. 



