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The Jalama formation of Late Cretaceous age is exposed along both sides of the Pacifico fault in Jalama and Santa Anita canyons in the Western Santa Ynez Mountains. It consists of 2275± feet of alternating sandstones and silty shales that have been divided into seven members. The base is nowhere exposed but the geologically older Espada formation in Salsipuedes Canyon is Late Jurassic in age, which suggests an unconformity at the Espada-Jalama contact. The relationship between the Jalama and overlying Anita formations is uncertain at the type locality but an unconformity exists beyond this area.
Approximately 133 species of Foraminifera, of which the majority are calcareous perforate forms, have been identified from nineteen localities. Three separate foraminifer faunules of characteristic composition can be distinguished. Forty-four localities have yielded 58 molluscan species that have been treated systematically; 12 pelecypod species and 5 gastropod species are new. The megafauna can not be broken down into stratigraphic faunules but may be subdivided into 2 ecologic groups.
Both the foraminifer and molluscan assemblages indicate a late Campanian age for the Jalama formation. The Foraminifera correlate with Goudkoff's Tracian and upper Weldonian stages and with the lower Navarro of the Gulf Coast.
The megafauna is most closely related to the molluscan assemblage of the upper Chico formation, but is slightly younger, and is very close in age to the Cretaceous sediments in Bee Canyon, Orange County, California, in the Sucia Islands, Washington, and in the lower horizon in the Simi Hills, Ventura County, California.
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