44 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



FORMATIONAL DISTRIBUTION IN CALIFORNIA 



The Chico. — A review of the Cretaceous generally has been 

 well presented by Messrs. Diller, Stanton, Anderson, Smith, 

 Crandall, Packard, and others. The Cretaceous record of Cali- 

 fornia has been kept exclusively by the Pacific, so naturally we 

 may expect to find faunas from southern California closely re- 

 lated to faunal assemblages from northern California, Vancou- 

 ver Island, Alaska, Japan and India. Comparing southern 

 faunas with those from these regions, one is impressed with the 

 large number of genera which occur elsewhere around the 

 North Pacific. The Chico of California is confined primarily 

 to the Coast Ranges, with smaller areas on the northeastern 

 border of the Great Valley from which it was originally de- 

 scribed. These deposits are not confined to the flanks of the 

 Coast Ranges, but are often found as remnants resting uncon- 

 formably on the older metamorphosed sediments. Most of our 

 Eocene deposits are closely associated with the Chico and are 

 often apparently confomiable with it, although an unconformity 

 usually exists. The area covered by the Chico rocks in Cali- 

 fornia is not great, but its stratigraphic limits have been very 

 difficult to determine, where it is associated directly with the 

 Horsetown below or with the Martinez above. When either of 

 these formations is absent a rather distinct unconformity is 

 apparent. The Chico epoch, wherever its record has been ob- 

 served in California, has been one of rapid sedimentation. 

 Especially is this true in the lower Chico which is made up 

 almost entirely of sandstones, and its fauna are those adapted 

 to littoral conditions. 



The Martinez. — North of Mt. Diablo, "the Martinez forma- 

 tion is represented areally by a strip averaging a quarter of a 

 mile wide, which extends from lower Oil Creek westward for 

 four miles. Its west end is terminated by a cross fault, while 

 its eastern end is cut off by the Tejon conglomerate."* The 

 Martinez has been found in southern California only in the 

 Calabasas sheet, east of Santa Ana® and east of Los Angeles in 

 the Rock Creek quadrangle. The formation in the Calabasas 



♦Dickerson, R. E., Univ. of Calif. Publ. Bull. Dept. Geol., vol. 6. p. 175, 

 1910-11. 



^ Martinez and Tejon are reported on the west_ flank of the Santa Ana 

 mountains by the class in paleontology from the University of California in 1913. 



