Geochemical and sedimentologic variations in inter-annually laminated sediments from Santa Monica Basin

Laminated sediments were recently discovered in the center of Santa Monica Basin, California Continental Borderland and extend from the present day to at least the Little Ice Age (ca. 1600 A.D.). Unlike the annual varves observed in Santa Barbara Basin, the light-dark lamination couplets observed in ‘l”Pb-dated cores from the center of Santa Monica Basin occur at 3 to 6 year intervals, very similar in length to the El Nifio Southern Oscillation (ENSO) phenomena. The mechanisms that control the temporal patterns of laminations in this basin are unknown. Potential causal mechanisms of lamination formation in Santa Monica Basin include: (1) changes in the flux of terrigenous vs. marine organic carbon and detritus; (2) surface water processes which affect marine productivity and organic carbon flux to the sediments; and (3) deep water processes which affect oxygen renewal and preservation of organic matter within the basin. A box core from the central portion of Santa Monica Basin was analyzed using a suite of geochemical, sedimentary, and micropaleontologic techniques in order to: (a) investigate which, if any, of these mechanisms has contributed to the occurrence of laminations; and (b) reconstruct proxy records of climate change. Samples were extracted from this core at 1 mm increments and provide a temporal resolution of l-3 years per sample, a resolution which is comparable in length to the thickness of individual laminae within the core. Geochemical and micropaleontologic analyses of cor