A 2,265-ft conformable sequence of marine conglomerate, sandstone, and mudstone crops out along continuous sea-cliff exposures on southwestern Santa Cruz Island. Disconformably overlying rocks of late Eocene age, the Vaqueros Sandstone, the Rincon Formation, the San Onofre Breccia, and the Monterey Formation contain mollusks and foraminifers, which indicate the presence of a Miocene sequence of Zemorrian through Mohnian (?) ages.

The southwestern corner of the island is structurally represented by a doubly plunging anticline trending approximately N40°W. Outcrops of the Vaqueros, Rincon, and San Onofre formations are on both the southwestern and northeastern limbs of the fold enveloping a Paleocene-Eocene core. The Monterey Formation is exposed only on the southwestern limb and, although this unit is not lithologically identical to the typically siliceous Monterey Formation on the mainland, it can be correlated with these mainland exposures on the basis of fossil Foraminifera. Paleoecologic and paleotopographic studies based on field relations and foraminiferal paleoecology indicate that the shallow part of the basin was on the east or northeast, and that the deeper areas extended westward and perhaps sou hward.

End_of_Article - Last_Page 469------------