Paleocurrent Patterns Along Continental Margin of Central California During Cretaceous Time: ABSTRACT

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Cretaceous turbidites exhibiting numerous paleocurrent features crop out across a 300 sq mi area long the northeastern flank of the Diablo Range in central-western California. More than 400 pieces of data on sole marks, sandstone and conglomerate grain fabrics, carbonaceous fragment orientation, and parting lineation were used to deduce the trend and sense of the ancient turbidity currents which deposited the beds. In the northern part of the area the sense of current movement was from northwest to southeast (same as Ojakangas farther north in the Sacramento Valley), though some data indicate an opposite sense of movement. In the central part of the area the sense of movement was northeast-southwest and southeast-northwest. In the southern part of the area the sense of current movement was northwest-southeast and northeast-southwest. Possible source areas include an ancient craton on the east and an offshore island arc, such as that visualized by Kay, or possibly Klamath Island, Mohavia, and Salinia as visualized by Reed. Coalescing submarine fans with apexes pointing north, east, and southeast toward an ancient craton seem to fit best the observed paleocurrent pattern. The paleocurrent data provide no evidence for a Cretaceous source area, such as Salinia or an island arc, west or southwest of present-day central-western California. The sequence of beds studied is more than 20,000 ft thick, and ranges in age from Aptian to Maestrichtian; older strata may be present. Current trends show little variation with stratigraphic position. End_of_Article - Last_Page 712------------