1918] 



Davis: The Franciscan Sandstone 



13 



The Galice series is lithologically like the Mariposa slates and 

 contains an Upper Jurassic fauna similar to that of the Mariposa. 

 These facts have led to its correlation with the Mariposa. 



The Dothan series is believed by Diller to be younger than the 

 Galice series. The Galice is spatially above the Dothan, but these 

 relations have been interpreted as due to overturning'. 30 



The work of Diller is in apparent agreement with the earlier ob- 

 servations regarding the Franciscan in the Coast Ranges of Cali- 

 fornia. According to his work, the Franciscan must be regarded as a 

 group intermediate between the Mariposa and the Knoxville. If the 

 Mariposa be uppermost Jurassic and the Knoxville lowest Cretaceous 

 the Franciscan rocks fill the gap between the Jurassic and the Cre- 

 taceous and represent a period hitherto unrecognized in sedimentation. 



This would be in agreement with the peculiarity of the fauna and 

 the flora at Slate 's Springs, which have been referred by some paleon- 

 tologists to the Jurassic, by others to the Cretaceous, and by still 

 others to an intermediate transition period. It would agree with the 

 interpretation of a Cretaceous age for the Franciscan made by Whit- 

 ney and others on the basis of an Inoceramus found on Alcatraz 

 Island. Also, if the Franciscan sandstone be a continental deposit, 

 as suggested later, this indicates a wide extension of land in Fran- 

 ciscan time. 



This interpretation is opposed to the ideas of C. II. Davis, and the 

 recent opinion of Knowlton. However, these differences of opinion 

 may be due to the unusual nature of the fauna and the small number 

 of species. The flora, moreover, does not appear to be characteristic 

 of the Jurassic, judging from the great differences of opinion among 

 those who have studied it. 



Uncertainty as to the Age of the Knoxville 



The independent evidence presented by Diller, pointing to the 

 Franciscan as an intermediate group, post-Jurassic and pre-Creta- 

 ceous in age, would be almost conclusive if it were not for certain 

 ideas regarding the age of the Knoxville. If the lower Knoxville be 

 the equivalent of the Mariposa, Diller 's correlations are wrong, since 

 there is then no room for the Dothan series at the point in the geolog- 

 ical column where he would place it. The exact stratigraphic rela- 

 tion of the Knoxville to the Mariposa has never been determined and 

 no locality is known where they are in contact. 



so Diller, J. S., Am. Jour. Sci., vol. 23, p. 410, 1907. 



