ABRUPT AND MILLENNIAL-SCALE CLIMATE AND OCEAN CHANGE SINCE THE MID-PLEISTOCENE TRANSITION IN SANTA BARBARA BASIN, CALIFORNIA

We have discovered evidence for abrupt ocean/climate change and millennial-scale oscillations distributed through the past ~735 kyr in Santa Barbara Basin, California. As part of an integrated seismic acquisition and piston coring campaign in 2005, we acquired thirty-two 2-11 m long piston cores that provide ~2-9 kyr high-resolution windows into past climate behavior. High-frequency climatic oscillation is recorded in 8 of these cores by variations in massive to laminated sedimentary fabric, oxygen and carbon isotopes, % total organic carbon, % carbonate, % biogenic silica, abundance of redox and productivity sensitive elements, or planktonic foraminiferal assemblages. In general, warm interstadials are represented by laminated, organic-rich sediment deposited under highly productive surface waters. During this interval, rapid decadal-scale climatic/oceanographic transitions occur within different climatic states, such as, MIS 3-like intermediate conditions, deglacial transitions, and glacial episodes. To date, no Dansgaard-Oeschger-like interstadials have been found to occur during otherwise fully interglacial conditions. These results indicate that the California margin has been sensitive to climatic forcing and experienced rapid climatic fluctuations since at least the Mid-Pleistocene Transition when predominance of 41-kyr climate cycles shifted to a 100-kyr climate cycle regime. Sedimentation rates are of sufficient magnitude (70-130 cm/kyr) to obtain data at sub-decadal sample intervals, permitting analysis of the rate of change and climate/ocean phasing at human time scales. We were able to obtain these cores by identification of distinctive seismic stratigraphic horizons related to climatic and sea-level fluctuations on deep-penetration industry multichannel seismic (MCS) reflection data and in high-resolution MCS and towed chirp data acquired during 2005 and 2008 research cruises. These horizons were mapped in 3D to seafloor outcrop, where they are accessible to piston coring. Ages of horizons and cores were determined by interpolation between ODP Site 893, a previously published 1-Ma horizon, dated tephra, biostratigraphic markers, and climate states and transitions identified from oxygen isotope records from the recovered cores.