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Hemipelagites and Associated Facies of Slopes and Slope Basins |
Laboratoire de Geólogie, Université de PAU, Avenue Philippon, F.64000 PAU, France
Department of Geological Sciences, University of Southern California, Los Angeles, California 90007, USA
Plio-Pleistocene slumps, debris-flow deposits, turbidites and hemipelagic sediments accumulated in the Ventura Basin to thicknesses of almost 2 km. The section exposed along Santa Paula Creek, California, contains at least six units of thick sandstones and conglomerates that represent fan lobes deposited at times of either tectonic pulses or minor climatic changes. Sections exposed in Adams Creek about 5 km west of the Santa Paula section suggest that the Santa Paula section was located on the fringes of these lobes. Gross sedimentation rates for the entire section are of the order of 1 m/1000 yrs. This is similar to the accumulation rates in the contemporary Santa Barbara Basin. The bulk of the intervening mudstones, siltstones and fine sandstones are thin-bedded (less than 10 cm thick) and represent interdistributary and basin plain facies. Mudstones are often laminated and the relatively sparse evidence of bioturbation suggests that the basin bottom waters were anoxic. Open connection over sills is evidenced by the discovery of the skeletal parts of a whale. The section illustrates the structures and associations of fine-grained sediments in a deep-water turbidite basin of high accumulation rate.
