FAUNAL RELATIONSHIPS OF THE MEGANOS GROUP 141 
This species is one of the most important markers of Dickerson’s 
Balanophyllia variabilis zone.t 
EOCENE SECTION SOUTHEAST OF MOUNT DIABLO 
The Meganos and Tejon beds of the section just described can 
be followed continuously eastward, barring some cross-faulting, 
from the area on the Concord Sheet, to that in the Mount Diablo 
Quadrangle in which Dickerson made his study. In this section data 
were obtained for the establishment of three of his faunal zones. 
The typical Tejon is represented throughout this area by 
heavy, massive, buff-colored quartzose sandstones, the outcrops 
of which form a prominent feature of the landscape. The Meganos 
beds of the more eastern area are composed for the most part of 
shale and shaly sandstone, with sandstones at the base, a section 
which is very similar to that just described, about ten miles to 
the west. 
Detailed mapping has failed to show any marked difference in 
dip and strike between the Meganos and the Tejon in this southern 
area, such as occurs to the north of the mountain. At a few 
localities there is an apparent difference in dip between the beds 
of the two horizons; this, however, could not be verified with 
certainty, the division being recognized by a sharp change in 
lithology, and by faunal evidence. . 
Faunal zones.—The locality at which Dickerson did most of 
his work in the “Tejon” of Mount Diablo is southeast of the moun- 
tain, in the vicinity of Cave Point and Riggs Canyon. Dickerson 
divided his (so-called) Tejon into three horizons, the faunas of 
which were referred to as: (1) the Turbinolia zone; (2) the Rimella 
simplex zone; and (3) the Balanophyllia variabilis zone.* 
tR. E. Dickerson, “Stratigraphy and Fauna of the Tejon Eocene of California,” 
Univ. Cal. Pub. Bull. Dept. Geol., Vol. TX (1916), No. 17, pp. 373-79- 
2JIn the former paper referred to above, the writer stated that in this section 
thereis a marked difference in strike between the Meganos beds and those of the 
Tejon, and the difference was taken as one of the evidences of the unconformity 
between the beds of these two horizons. Later work, however, has shown that this 
apparent difference in strike is, in part at least, the result of faulting. Also it was 
stated that to the east of this area the Meganos disappeared due to this unconform- 
ity. At that time the writer had not recognized that the so-called Tejon beds to the 
east, as described by Dickerson, were in part Meganos. 
