BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 2, pp. 201-208. February 20, 1891 



NOTES ON THE EARLY CRETACEOUS OF CALIFORNIA 

 AND OREGON. 



BY GEORGE F, BECKER. 



[Rtadbefore the Society December 31, 1890.) 



CONTENTS. 



Page. 

 The Shasta Group 201 



Original Definition and Fauna of the Group 201 



Importance of the Subject 202 



Exposures at Riddles 203 



Eossils from Riddles 204 



Inferences from the Relations at Riddles 205 



Confirmatory Evidence from Canada 205 



Conclusions on the Shasta Group 206 



The Post-Triassic Upheaval 206 



Discussion 207 



The Shasta Group. 



Original Definition and Fauna of the Group. — Messrs. Gabb and Whitney- 

 described two groups of lower Cretaceous beds in California, the relations 

 of which to one another they left doubtful. One of them is extensively 

 represented in the Coast ranges of California, and is especially character- 

 ized by the presence of Aiicella accompanied by a few other shells, which, as 

 it happens, throws little light on the true horizon. The age suspected was 

 Neocomian. The other set of beds occurs on Cottonwood creek, near Horse- 

 town, in Shasta county. These do not contain Aucella, but carry Ammonites 

 batesii, A. traskii and a considerable number of other fossils, which led Gabb 

 to suggest that they belonged to the Gault. It Avas evidently his opinion 

 that -they were younger than the Aucella-hesiring beds, but the two sets were 

 provisionally classed together as the Shasta group. ''"^ Professor Jules Marcou 

 recognized only the beds at Horsetown as Cretaceous. Professor J. F. 

 Whiteaves also discussed these beds in connection with their supposed equiv- 

 alents in British Columbia, referring the Aueella-hea,r'ing series to the Neo- 



* Pal. Cal., vol. II, 1869, p. xiv. 



(201) 



