458 DILLER ANT) STANTON— THE SHASTA-CHICO SERIES. 



the great unconformity that if ever found in contact they will probably 

 not be conformable. 



This view is supported by the latest investigation concerning the pale- 

 ontologic relation of the two sets of beds. The Geological Survey of Cali- 

 fornia recognized the fauna of the Mariposa beds as Jurassic and distinct 

 from the Cretaceous of the Shasta group in the Coast range, although it 

 should be said that the Aucella-bearing portion of the Knoxville had at 

 that time yielded very few fossils other than Aucella and Belemnites im- 

 pressus. 



The studies of Dr White led him to regard the Aucellse of both beds as 

 essentially the same species.* Dr Becker according!}^ made the Mari- 

 posa beds equivalent t to the Knoxville, and finally J placed the post- 

 Jurassic (Whitney) but pre-Chico upheaval of the Sierra Nevada and 

 Coast range after the deposition of the Horsetown beds. 



The complete faunal and stratigraphic intergradation which, as we§ 

 have shown, occurs -wherever the Horsetown and Chico beds are found 

 in contact, precludes the existence of a great tinconformity between them 

 at any point in northern California and renders it certain that the great 

 upheaval took place before the deposition of the Shasta-Chico series. 



Professor Hyatt, who has recently studied the fauna of the Mariposa 

 beds and compared with it the Ammonites and Aucellse of the Knoxville 

 beds, authorizes us to say that in his opinion " the fauna of the Knox- 

 ville beds, on the one hand, is decidedly Cretaceous and clearly related 

 to that of the Horsetown beds, but, on the other hand, is entirely distinct 

 from that of the Mariposa beds." 



This conclusion corroborates those drawn from the stratigraphic evi- 

 dence and establishes upon a firmer basis the view long since entertained 

 by Whitney that the upheaval and metamorphism of the Sierra Nevada 

 occurred at the close of the Jurassic. 1 1 



* Ibid., Bulletin no. 15, p. 24. 



flbid.. Bulletin no. 19, p, 18. 



X Bull. Geol. Soc. Am., vol. 2, p. 20G. 



g Bull. Geol. Soc. Am., vol. 4, pp. 207-211 and 249-257. 



I The Aucella beds of the Sierra Nevada are confined, as fur as yet certainly known, to the lower 

 portion of the western slope, and their general trend would carry them across the Sacramento 

 valley to the Klamath mountains and Coast range just north of the 40th parallel, where the northern 

 limit of the Knoxville beds in California is known to occur. The Aucella beds are not yet known 

 in contact with the Taylorville Jurassic, which occurs not only upon the northern end of the Sierra 

 Nevada, but also well developed in the Pit river region of Shasta county, California, as well as in 

 southwestern Nevada and the Blue mountains of eastern Oregon (Bull. Geol. Soc. Am., vol! 4, p. 

 221; also vol. 5, p. 400). There may have been an upheaval of the Sierra Nevada either before or 

 immediately after the deposition of the Taylorville Jurassic by which the Aucellse were limited to 

 the western part of that range, but the change of level may have been gentle and not accompanied 

 by folding and metamorphosing of the involved strata. 



