Stratigraphies of carbonate (CaCO₃) organic carbon (C_org), CaCO₃ and C_org mass accumulation rates (MAR), and paleoproductivity were determined with a sampling interval of 100 to 150 yr/sample for Ocean Drilling Program (ODP) Hole 893A from Santa Barbara Basin. Variations in CaCO₃ with time do not show the typical Pacific pattern (higher during glacial periods), nor any pattern that can be related to glacial-interglacial cycles. Variations in total C_org with time show four peaks of high values that occurred during Oxygen-Isotope Stage (OIS) 5 and earliest OIS-3. There is a moderate correlation between CaCO₃ and C_org mass accumulation rates. The fluxes of total sediment, CaCO₃, and C_org are all an order-of-magnitude higher than occurred on the adjacent open continental margin. Paleoproductivity values, a proxy derived from an empirical correlation with C_org MAR, approached 250 gC/m² yr during OIS-5 and OIS-1, and were less than or equal to 200 gC/m² yr during all other times. Surprisingly, only percentage C_org shows a response to global climatic forcing with a precessional periodicity of 23 k.y./cycle, but only during OIS-5. Basin isolation during periods of lowered sea levels appears to have regulated C_org and CaCO³ deposition by a mechanism related to the advection of California Current and California Counter Current waters. Fluctuations in strength or dissolved-oxygen content of the basin's bottom water are documented in lamination cycles, but did not significantly affect the preservation of CaCO₃ and C_org.

Date of initial receipt: 11 July 1994
Date of acceptance: 13 February 1995

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