728 N. H. DARTON 
TERTIARY SYSTEM 
EOCENE 
General relations.—1 found that on the shore of the Pacific 
Ocean the earlier Tertiary deposits began at the mouth of the Rio 
San Vicente in latitude 31° 30’ and extended south to about latitude 
29° 25’, south of Punta Canoas. In this area they underlie a narrow 
coastal plain mostly from 8 to 10 miles wide, but broadening to 
nearly 20 miles near latitude 30°. They lie on the Chico beds but 
to the east abut against the metamorphic pre-Chico rocks, and the 
termination of the crop to the north and south is due to the west- 
ward extension of the latter to the ocean shore. Throughout the 
area the strata dip at very low angles to the west, and local flexures 
are rare and slight. Some general relations are shown in sections 
Tt, [SON ES) 2 
The rocks are shales and sandstones mostly of light-gray to 
buff color, 1,200 feet or more thick near latitude 30°. To the south 
they contain fossils of the Martinez or Middle to Lower Eocene 
age, but in the region north of latitude 30° most if 10t all of the beds 
appear to be Tejon or Upper Eocene, although the lower formations 
may exist beneath the surface. There are promiient exposures 
along the lower parts of the valleys of the Rio Rosario, Arroyo 
San Vicente, Rio San Fernando, and Arroyo Santa Caterina, near 
Rosario and southward, and in bluffs along the ocean near Cabo 
Colnett and Punta Camalu and near Bluff Point and Punta Canoas, 
the two latter southwest of Santa Caterina. As shown in section 5, 
Figure 2, the thick succession .of beds exposed in the bluffs along 
the ocean at Bluff Point is preserved by the heavy lava cap of 
Mesa San Carlos. 
Fossils—Fossils were collected at several localitities in the 
Eocene beds and kindly determined for me by Dr. Julia A. Gardner. 
On the shore of the Pacific Ocean, a mile south of the mouth of the 
Arroyo San Antonio, latitude 31° 05’, the following were found: 
Cylichna sp.; Turritella n.sp., cf. T. uvasana Conrad; Amauropsis 
sp.; Leda sp.; Cucullaea matthewsont, Gabb?; Cardium, cf. C. 
brewert Gabb; Cardium sp.; Tellina? sp.; and Semele sp. 
On the ocean shore a half-mile south of Colnett Creek, 5 miles 
southeast of Cabo Colnett, were collected Omphalius sp.; Cardium 
