586 BRUCE L, CLARK 
does not enable one to show the exact location of the shore lines of 
all the seas that have occupied this general area. However, it 
is believed that the plates show the approximate distribution of 
the seas and will give the reader some conception of the location 
of the most important land masses, the degree of isolation of the 
basins, and the present known extent of the Tertiary horizons in 
California. 
TERTIARY DIVISIONS 
There are at least five major divisions of the Tertiary of the 
West Coast which in the writer’s estimation might be recognized 
as representing true periods. Each one of these five major divisions 
is composed of more than one epoch of deposition. Each epoch 
is represented by distinct faunas which lived in distinct seas. 
The deposits belonging to each of the major divisions will be 
referred to as a “‘series’’; thus, the Eocene, Oligocene, Lower- 
Middle Miocene, Upper Miocene, and Pliocene series. To the 
deposits of each epoch of deposition the term “group” has been 
applied. The term “formation” is reserved for the lithologic 
member within the group. 
EOCENE 
During the Eocene period of the West Coast there were at least 
three epochs of deposition, as indicated in the correlation table, 
and there is a suggestion that there were four and possibly five. 
At the present time, however, only three distinct stratigraphic 
divisions have been definitely separated. ‘These are the Martinez 
(Lower Eocene), Meganos (Middle Eocene), and the Tejon (Upper 
Eocene). Crustal movements of considerable magnitude separated 
these epochs. In the region of Mount Diablo, middle California, 
there is a difference in dip and strike between the Martinez and 
Meganos groups. Over large areas along the coast where beds of 
the Meganos and Tejon deposits occur in contact, there is an 
angular unconformity separating the two. ‘The marine faunas 
of these three divisions of the Eocene differ greatly from each 
other, further substantiating the stratigraphic evidence of marked 
