PREVIOUS LITERATURE OF xMOUNT DIABLO EOCENE 283 



age of these deposits was still questioned by many geologists, and Whit- 

 ney's original statement that here was a continuous and conformable 

 series, extending from the center of the mountain mass out to the valley 

 and including beds from Lower Cretaceous to uppermost Tertiary, re- 

 mained unchallenged. 



T. W. Stanton,* in 1896, made a special study of the Eocene beds of 

 California in order to determine if possible their stratigraphic and f aunal 

 relationships to the Upper Cretaceous deposits of this general region. 

 His work showed conclusively that there was a decided faunal break 

 between these two horizons. Stanton at this time studied the Eocene sec- 

 tion on the north side of Mount Diablo, and in his paper are given several 

 lists of fossil invertebrates. With regard to the position of this fauna 

 he states:^ "The fauna represented by these lists is clearly the original 

 Tejon fauna, that occurs in the neighborhood of Fort Tejon, New Idria, 

 and elsev^here along the Coast Ranges of Washington. Its Eocene char- 

 acter has been recognized by Conrad, Marcou, Heilprin, White, and 

 others.'' 



R. E. Dicker son^ has described in considerable detail the stratigraphy 

 and fauna of the Martinez Group of this section. He described the un- 

 conformity between the Martinez and the Chico (Upper Cretaceous) and 

 also an unconformity at the top of the Martinez, which he believed to be 

 the contact between the Martinez and the Tejon. It will be shown in this 

 paper that this latter unconformity is not between the Martinez and the 

 Tejon, as he believed, but between the Martinez and a series of beds, here 

 referred to as the Meganos Group, which are intermediate between the 

 Martinez and Tejon, and separated also from the Tejon by an uncon- 

 formity. 



Meganos Group North of Mount Diablo 



STRATIGRAPHY AND LITHOLOGY 



The area under consideration. — The principal area under discussion is 

 a strip extending from about one mile to the west of the old coal-mining 

 town of Nortonville, east and a little to the south of the eastern edge of 

 the Mount Diablo quadrangle. The outcrops, including the Martinez, 

 Meganos, and Tejon groups, dip to the north, the angle of dip varying 



* T. W. Stanton: Faunal relation of the Eocene and Upper Cretaceous on the Pacific 

 coast. Seventeenth Ann. Kept. U. S. Geol. Surv., pt. 1. 1896, pp. 1011-1059. 



"Op. cit, p. 1021. 



« R, E. Dickerson : The stratigraphic and faunal relations of the Martinez formation 

 to the Chico and Tejon, north of Mount Diablo. Univ. of Califoi-nia Publ. Bull. Dept. 

 Geol., vol. 6. no. 8, 1011, pp. 171-177 ; Fauna of the Martinez Eocene of California. 

 Univ, of California Publ. Bull. Dept. Geol.. vol. 8, no. 0, 1914, pp. 01-180. 



