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  • Surface and subsurface data indicate that Cretaceous strata in the southern Ventura basin are part of the northward prograding Chatsworth submarine fan. The fan extends westward as far as Trancas Beach in the Santa Monica Mountains and wells in the Oxnard Plain and on Oak Ridge. The eastern edge of the fan is constrained by wells in western San Fernando Valley which contain fine-grained strata which may have been deposited east of the Chatsworth fan. The Nonmarine Simi Conglomerate overlies the Cretaceous and is itself overlain by Paleocene marine beach sandstone and siltstone. These marine strata do not extend eastward into the San Fernando Valley. The lower Paleocene and Cretaceous strata were overlapped by the upper Paleocene Santa Susar1a and middle Eocene Liajas Formations. Sedimentation patterns for the Santa Susana and Llajas may be explained by two models: (1) A northwest-trending submarine ridge on which muds and silts were deposited, was flanked on the northeast and southwest by troughs receiving deep-water sands. (2) Both formations were deposited on a southwest-facing shelf, slope, and turbidite trough. Subsurface data important in basin analysis include 1) bathyal paleo- bathymetry for the entire Santa Susana, 2) sand channels in the Santa Susana which possibly funneled sediment westward down a submarine slope, 3) shelf-facies(?) Eocene strata with neritic to upper bathyal paleobathymetry in Oxnard Plain, and 4) Llajas fades in northern Simi Valley suggesting gradation upward from a shallow marine to outer shelf or slope environment. Facies correlations across the Simi fault indicate no large-scale post- Paleogene strike-slip displacement. If these sequences were rotated, as suggested by paleomagnetic data, the restored Cretaceous fan would come from the east and the restored Paleocene shoreline would face south. Thus paleogeography for the Cretaceous is simplified by the rotation hypothesis, but Paleocene paleogeography is made more complicated.
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