Abstract

In the Ventura region approximately 47,000 feet of exposed Cenozoic sedimentary rocks provide a nearly complete record of the later events in the sedimentational history of the southern Coast Ranges. The Pleistocene history may be divided into four episodes: (1) the deposition of 6000 feet of marine and terrestrial strata; (2) folding and faulting of all the formations; (3) stream erosion which carved a surface of late maturity, and; (4) intermittent regional uplift which started the present erosion cycle, now in the stage of early maturity. Differential erosion has conspicuously controlled the topography. Active faulting and warping occur widely. The drainage diversion of the Upper Ojai Valley by Santa Paula Creek is a large-scale example of stream capture, and numerous other examples of drainage adjustment have taken place. Late Pleistocene uplift is recorded by terraces in the Ventura River valley, and by marine terraces bordering the Pacific Ocean. Both series of terraces are warped, and both reach their maximum elevation where the rocks are intensely deformed.

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