I40 BRUCE CLARK 
MEGANOS TO SOUTH AND SOUTHEAST OF MOUNT DIABLO 
SECTION NEAR EAST EDGE OF CONCORD QUADRANGLE 
When the first paper on the Meganos was published, compara- 
tively little work had been done on the Eocene section south of the 
Mount Diablo anticline. A brief description was given in that 
paper of the beds exposed near the east border of the Concord 
Quadrangle which joins the Mount Diablo Quadrangle on the 
west. Here a typical Meganos fauna was found stratigraphically 
below beds containing a Tejon fauna. 
Lithology.—In this section the Meganos beds have an approxi- 
mate thickness of 2,000 feet. At the base there is between 150 
and 200 feet of medium-fine yellow-brown sandstone beginning 
with about 20 feet of basal conglomerate which contains angular 
bowlders of fossiliferous Chico (Upper Cretaceous) sandstone, 
together with angular fragments of shale which is very similar to 
that found immediately below the contact. The upper 1,800 
feet of the Meganos consists principally of dark-colored shales, 
fine shaly sandstone, and fine sandstone. Some of these shales are 
almost black and contain considerable lignitic material; they are 
identical in character with the dark-colored shales in the Meganos 
_ north of Mount Diablo. 
There is a very marked lithological change between the Tejon 
beds of this section and those of the Meganos. The Tejon beds 
consist of 2,000 feet of massive, buff-colored quartzose sandstones 
which weather into cavernous bluffs on the north side of Pine 
Canyon a little farther east. At what appears to be the base of 
the Tejon is a narrow band of fine conglomerate made up of quartz 
and black and red chert, together with angular fragments of shale 
similar to the shale member immediately below. 
Coal has been found at a number of localities in the basal 
beds of the Tejon, indicating the same general conditions as those 
recorded by the sediments on the north side of the mountain. 
In the sandstones near the base the species Balanophyllia variabtlis, 
a coral which is common in the beds above the coal in the Tejon 
on the north side of Mount Diablo, was found in abundance. 
