1914] Dickerson: Fauna of the Martinez Eocene of California 117 



TIME-INTERVAL BETWEEN DEPOSITION OF MARTINEZ AND TEJON 



The time-interval which elapsed between the deposition of these 

 gray-green Tejon shales and the uppermost Martinez strata~rrrast have 

 been very great. During this time many characteristic Martinez 

 species entirely disappeared. A portion of this time-interval is prob- 

 ably represented by unconformity between the lowermost Tejon strata 

 and the Martinez, although there is no one place yet discovered at the 

 type locality which proves this fact. A marked change in lithology, 

 a considerable difference in dip throughout the field, and a very 

 abrupt change in fauna suggest unconformity at the type locality. 



CORRELATION OF MARTINEZ WITH EOCENE OF THE 

 ATLANTIC AND GULF STATES 



Dr. W. H. Dall 29 first attempted a correlation of the Pacific Coast 

 Eocene with that of the eastern states. In this general correlation 

 paper, the Martinez and Tejon were correlated with the lower portion 

 of the Eocene. Weaver, 30 in his paper on the palaeontology of the 

 Martinez Group, correlates the Martinez with the Midway of the Gulf 

 States region. He says : 



"For comparison with the Martinez fauna, the following important locali- 

 ties have been selected: the Gulf States, the Atlantic States, the London and 

 Paris Basins, and the Sind district of western India. 



"Compared with these the fauna of the Martinez Group seemed to be a 

 distinct unit. Of the forty-nine genera listed only twenty-two could be found 

 in the literature on the Eocene of the Gulf and Atlantic States. No species 

 were found in common yet several were somewhat similar. This fauna has its 

 closest affinities with that represented in the Midway of the Gulf States and 

 the Aquia stage of Maryland and Virginia. The correspondence to the Aquia 

 is however less marked than to the Midway. . . . The fauna of the Tejon 

 Group bears a closer similarity to both the Aquia and Chickasawan than does 

 the Martinez." 



Weaver also concludes from a comparison with the London Basin 

 and Paris Basin faunas that the Martinez is more nearly related to 

 the fauna of the Thanet Sands and the Bracheux Beds. He states: 

 ' ' the Martinez may represent some portion or all of the lower quarter 

 of the Eocene." 



29 Ball, W. H., 18th Ann. Eept. U. S. Geol. Surv., pt. 2, pp. 327-328, 1898. 

 so Op. cit., pp. 111-113. 



