588 BRUCE L. CLARK 
The Meganos and the Tejon seas (Figs. 3 and 4) were some- 
what similar in outline. In middle California the deposits of these 
epochs were laid down in a great trough of which the present 
Great Valley of California is a remnant. The Meganos sea was 
the wider of the two Eocene seas that occupied this depression 
Fic. 1.—A key map showing the general distribution of positive and negative 
areas in California during the Tertiary. Of all the positive areas outlined, No. 6, 
the Santa Monica Mountain area, is the most problematical. (1) Sierra Nevada 
area; (2) Klamath Mountain area; (3) Coast Range area; (4) Tehachapi Peninsula; 
(5) Sierra Madre, San Bernardino, San Jacinto Mountain area; (6) Santa Monica 
Mountain area. 
and was connected with an east and west trough in southern Cali- 
fornia in the region of the present Santa Ynez Mountains. These 
two general areas of deposition existed throughout the Tertiary. 
They were bordered by areas or zones of uplift which have also 
been more or less permanent. East of the great north and south 
trough was the Sierra Nevada block which dates back to the Upper 
