64 University of California Publications in Geology [VOL. 8 



INTRODUCTION 



The discovery of several new areas of Martinez rocks and the secur- 

 ing of large additions to the fauna in them have led to further investi- 

 gation of the stratigraphy and fauna of the lower Eocene of the Pacific 

 Coast. That the Martinez is separated from the Chico (Cretaceous) 

 below and from the Tejon (upper Eocene) above by well-marked 

 unconformities are the principal conclusions from stratigraphic 

 studies. Faunal studies prove that the Martinez fauna of approxi- 

 mately two hundred species is quite distinct from the Chico and the 

 Tejon faunas. The great increase in the fauna makes correlation with 

 the lowermost Eocene of the Gulf and Atlantic states more certain. 

 The proposed correlation made in this paper fixes a portion of the 

 Martinez as the equivalent of the lowermost Eocene of the Gulf 

 States, the Midway, and the rest as the representative of an earlier 

 Eocene time than has been recognized elsewhere in the United States. 



REVIEW OF THE LITERATURE 



W. M. Gabb 1 first used the term Martinez Group to describe strata 

 which he thought were transitional between the Chico-Cretaceous and 

 his Cretaceous "B," the Tejon of the present nomenclature. Dr. 

 T. W. Stanton 2 next investigated this group. He proved that a portion 

 of the Martinez Group of Gabb was Chico and placed the upper portion 

 as a distinct faunal zone of the Tejon, designating it as lower Tejon. 



Dr. Stanton 's admirable review was followed by a short, decisive 

 paper by Merriam 3 who worked at the type locality. Merriam 

 described the conditions at the type locality as follows : 



In the following discussion the name Martinez is applied to that portion 

 of Gabb's Martinez Group which remains, after the removal of the Chico- 

 Cretaceous element. The writer's statements are based on observations, extend- 

 ing over a period of several years, made in the typical region for the group, 

 viz., that adjacent to the town of Martinez. 



In the hills to the southwest of Martinez, strata of unquestionable Chico 

 age, containing a characteristic fauna, occur over a considerable area. In a 



1 Gabb, W. M., Kept. Geol. Surv. of California, Palaeontology, vol. 2, p. 13 of 

 preface, 1869. 



2 Stanton, T. W., The Faunal Relations of the Eocene and Upper Cretaceous 

 on the Pacific Coast, 17th Ann. Kept. U. S. Geol. Surv., pp. 1011-1060, 1895-6. 



s Merriam, J. C., The Geological Relations of the Martinez Group of Cali- 

 fornia at the Typical Locality, Jour, of Geology, vol. 5, pp. 767-775, 1897. 



