230 



RALPH ARNOLD 



It is a noteworthy fact that with one exception wherever the line 

 between the marine Eocene formations (Martinez, Arago, Tejon, etc.) 

 and the Cretaceous beds is marked by an angular unconformity, the 



underlying beds are either of lower 

 Cretaceous (Knoxville) or middle 

 Cretaceous (Horsetown) age, and 

 that wherever the Eocene rests on 

 the Chico, or upper Cretaceous, ex- 

 cluding the case at San Diego, the 

 unconformity is not angular, and as 

 far as the stratigraphic evidence 

 goes, the two formations represent 

 an apparently uninterrupted period 

 of sedimentation. 



The apparent conformability of 

 the Eocene on the Cretaceous, to- 

 gether with the superficial similarity 

 of their faunas, led Gabb and 

 Whitney of the early California 

 Survey to class the Martinez and 

 Tejon formations with the Cre- 

 taceous. White, Stanton, and Mer- 

 riam have, however, shown the 

 Eocene age of the Martinez and 

 Tejon. Of the relationships existing 

 between these two and the Chico, 

 or upper Cretaceous, Dr. Merriam 

 has the following to say: 



The Martinez group, comprising in 

 the typical locality between one and two 

 thousand feet of sandstones, shales, and glauconic sands, forms the lower part 

 of a presumably conformable series, the upper portion of which is formed by 

 the Tejon. It contains a known fauna of over sixty species, of which the greater 

 portion is peculiar to itself. A number of its species range up into the Tejon 

 and a very few long-lived forms are known to occur also in the Chico. Since 

 the Martinez and Chico are faunally only distantly related it is probable that an 

 unconformity exists between them.' 



I Jour. Geol., Vol. V, 1897, p. 775. 



EoCENJ E 



Fig. I. — Map showing hypothetical 

 distribution of land and water on the 

 Pacific Coast of the United States 

 during Eocene time. 



