132 BRUCE CLARK 
THE MEGANOS GROUP IN THE VICINITY OF MOUNT DIABLO 
Mount Diablo is a much faulted anticline of which the Fran- 
ciscan series forms the core. The Shasta-Chico series (Lower and 
Upper Cretaceous) is represented in this section by more than 
ten thousand feet of shales and sandstone, on top of which, on 
either side of the anticline, are Eocene strata having a maximum 
thickness of nearly four thousand feet. These beds in turn are 
overlain by beds referable to the Oligocene, Miocene, and Pliocene. 
The two Eocene sections, the one on the north side of the Mount 
Diablo anticline and the other on the south side, will be considered 
separately as their outcrops are disconnected. 
MEGANOS TO THE NORTH OF MOUNT DIABLO 
The type section of the Meganos is on the north side of the 
Mount Diablo anticline. In this paper, the description of that 
section is largely a repetition of the data presented in the former 
paper, but adds some details. 
The section extends 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 Mount Diablo Quadrangle. These beds, 
including the Martinez, Meganos, and Tejon groups, dip to the 
north, the angle of dip varying from 15° to 4o.. The greatest 
width of the outcrops is about two and a half miles. 
Stratigraphy and lithology—The beds of the Meganos Group in 
this area rest unconformably on those of the Maitinez Group. 
This unconformity, as stated above, was first described by Dicker- 
son. The lower Tejon, as recognized at that time, is the base 
of the Meganos, as described in this paper. The Meganos beds 
in this area have a maximum thickness of about three thousand 
feet. The section may be roughly divided into five lithologic 
members. Beginning at the base, these will be designated divisions 
ANS VAC, 1D), Buaiel 10, 
1R. E. Dickerson, ‘‘The Stratigraphic and Faunal Relations of the Martinez 
Formation to the Chico and Tejon North of Mount Diablo,” Univ. Cal. Pub. Bull. 
Dept. Geol., Vol. VI (1911), No. 8, pp. 174-76. 
2 The lower part of this section, that is, the Martinez and divisions A, B, and C 
of the Meganos, are best exposed in the section just to the west and south of the old 
town of Stewartville. The upper Meganos beds are best exposed on the ridge just 
to the north of Deer Valley and to the north of that ridge. The best Tejon section is 
to be found in the vicinity of the old town of Nortonville; also a very good section 
may be seen in the vicinity of the old town of West Hartley. 
