460 STUDIES FOR STUDENTS 



quadrangle more than mere traces of coal do not occur, and 

 strata containing brackish-water fossils are rare." * 



THE MARINE FORMATIONS 

 THE MARTINEZ FORMATION 



The name Martinez was first applied by Gabb 2 to a division 

 of Cretaceous rocks of California. The name comes from the 

 town Martinez, near which typical exposures occur. In recent 

 years the formation has been studied critically by Stanton 

 and by Merriam. " Mr. Stanton has shown the Martinez of 

 Gabb to consist of two parts, one characteristic Cretaceous and 

 inseparable from the Chico group, the other being more closely 

 related faunally and stratigraphically to the Tejon-Eocene than 

 to Chico." 3 The latter was called Lower Tejon by Stanton. 

 Merriam observes that at numerous points on the Pacific coast 

 where the Tejon has been found it always contains an easily 

 recognized fauna. From studies of the faunas in the vicinity of 

 Martinez he proposes (following a suggestion of Stanton) to 

 apply the name Martinez to the Lower Tejon of Stanton. 



In the vicinity of Martinez, the Martinez and Tejon groups form an, 

 apparently conformable series between two and three thousand feet in thick- 

 ness and about equally divided between the two. The faunas, though over- 

 lapping, are in the main quite distinct. . . . While some intermingling of 

 species exists, it is not greater than we should expect to find in adjoining 

 groups or periods. . . . The two sets of strata, or two faunas, while belong- 

 ing perhaps to the two series, represent different periods in the geological 

 history of California, periods quite as distinct so far as faunal evidence is 

 concerned, as the Miocene and Pliocene, or the Pliocene and Quaternary. 4 



The Martinez formation is characterized as " comprising, in 

 the typical locality between one and two thousand feet of sand- 

 stones, shales and glauconitic sands," forming " 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 



x DlLLER : loc. cit., p. 320. 



2 Cf. Merriam : Jour. Geol., Vol. V, p. 767, 1897. 



3 Merriam : loc. cit., p. 768. 4 Merriam : loc. cit., p. 774. 



