--> Holocene Organic Rich Slope-centered Mudrock Deposition, Santa Barbara Basin, California Continental Borderland: El Nino Flood-Induced Suspended Sediments, Turbidites, Syntectonic Sedimentation & Mass Flows during Greenhouse Eart

AAPG Pacific Section and Rocky Mountain Section Joint Meeting

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Holocene Organic Rich Slope-centered Mudrock Deposition, Santa Barbara Basin, California Continental Borderland: El Nino Flood-Induced Suspended Sediments, Turbidites, Syntectonic Sedimentation & Mass Flows during Greenhouse Eart

Abstract

Santa Barbara Basin (hereafter SBB), the offshore extension of the onshore Ventura Basin, is the northernmost basin in the California Continental Borderland. The basin is unique in that it is the only canyonless basin in the inner borderland. It is a slope-centered mudrock depositional system with a much studied anoxic, or dysaerobic basin floor. The slope comprises 96% of the basin and the basin floor, only 4% of the basin area. Basin sediments on the slope and basin floor in the Holocene reflect a diverse group of sedimentary processes including hemipelagic rain of microfossils, mass movement, fine-grained turbidite deposition, flood-borne deposition from hyperpycnal (surface plumes), metaxypycnal (water column plumes along density interfaces) and hypopycnal (bottom hugging) plumes overprinted by current winnowing by the Anacapa Current. Two major rivers act as point source of terrigenous clastic input during the rainy season, the Santa Clara River-Ventura River Influx (hereafter SCRVRI). The SCRVRI injects fine grained sediments into these 3 plume types, as well as sand onto the shelf. The SDRVRI produces gray flood layers during particularly rainy periods. During greenhouse earth in the SCRVRI drainage basin, predominant textural input is silt, rather than sand in icehouse earth periods. However, on the eastern limit of the basin, the Hueneme Sill, the vigorous Anacapa Current generates a large current-winnowed sandy dune field. High sedimentation rates, measured as 173 cm/1000 yr in one piston core, result from the sediment pathways from the NW, NE and East, resulting in extensive sediment creep, slumps, gravity faulting and debris flows. Syntectonic sedimentation is pervasive in the zone between the Pitas Point and Oak Ridge faults coupled with massive deformation from the Goleta Slide area. The basin serves as a modern alalog to unconventional reservoir exploration and exploitation, particularly for California's Monterey Formation.