Distribution and character of sedimentary facies in a 196.5-m core from Ocean Drilling Program (ODP) Site 893 in Santa Barbara Basin (southern California) reflect global and regional controls during the latest Quaternary. Stratigraphic trends in grain size, sediment composition, sedimentary fabric, and degree of bioturbation record changes in oceanic deep-water circulation, climate, sea level, basin geometry, sediment sources, and transport pathways through the last two glacial and interglacial episodes (~160 k.y.). The sedimentary sequence in Hole 893A is divided into six facies: four record varied levels of bottom-water oxygenation by the degree of bioturbation of primarily laminated olive-gray hemipelagic mud, whereas two reflect coarse- and fine-grained event deposition. Varved sediments typical of the Holocene Santa Barbara Basin compose only 21% of the entire latest Quaternary sequence.
An ultra-high-resolution record (<10-yr sample spacing) of bottom-water oxygenation, as shown by the preservation or destruction of annual varves, reveals cyclic variation over decadal to Milankovitch time scales and apparently reflects the changing age and ventilation of Pacific Intermediate Waters. Over the past ~75 k.y., bioturbation and basin oxygenation correspond closely to glacial-interglacial oscillation, with warm intervals being oxygen-depleted and laminated and cold intervals being oxygenated and bioturbated. Preliminary results suggest a correlation between basin stratigraphy and deep-water circulation proxy records from elsewhere in the Pacific and Atlantic oceans, indicating that sediments of Santa Barbara Basin are a sensitive recorder of global and regional paleoceanographic and paleoclimatic change.
Date of initial receipt: 8 September 1994
Date of acceptance: 3 April 1995
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