M. L. Natland, 1950. "1940 E. W. SCRIPPS CRUISE TO THE GULF OF CALIFORNIA: Part IV Report on the Pleistocene and Pliocene Foraminifera", 1940 E. W. Scripps Cruise to the Gulf of California, Charles A. Anderson, J. Wyatt Durham, Francis P. Shepard, M. L. Natland, Roger Revelle
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Sixteen samples were collected from outcrops exposed on North San Lorenzo, Carmen, Monserrate, and Coronados islands. Two samples were taken from exposures at Santa Ynez Bay. All these localities are in the Gulf of California and were collected by C. A. Anderson and J. Wyatt Durham during the 1940 cruise of the E. W. Scripps. Seventy-two species of Foraminifera were found in beds thought to be of Pleistocene age, and 83 species were found in beds considered to be Upper Pliocene. In general, the Pleistocene fauna suggests a clear-water tropical environment with a depositional depth of less than 50 meters, since it is practically identical with the Recent shallow-water fauna in the Gulf. The Upper Pliocene fauna was probably laid down in water ranging from 275 to 500 meters deep, since it is very similar to the Recent fauna which is not found beyond this range off the west coast of Central America. The Upper Pliocene fauna correlates with that found in the Charco Azul Pliocene formation of Panama and with Uvigerina peregrina beds of the Los Angeles and Ventura basins. These beds lie beneath those containing Cassidulina limbata Cushman and Hughes, and above those which contain Bulimina subacuminata Stewart and Stewart.
The collection contains five species which are considered new and two species to which new names have been assigned.