High Resolution Paleomagnetic Secular Variation and SedimentHistory in Sediments from the Gulf of California: DSDP Site 480 and Atlantis II Cores

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Anoxic, varved sediments are accumulating along the margins of the Gulf of California at especially high rates. The temporal and spatial distribution of these sediments remains to be determined, and consequently a full understanding of their origin is uncertain. Dr. Karlin has studied the geochemical and paleomagnetic character of these materials at DSDP Site 480. The present award is to resample this Site and to participate on a coring cruise in June '90 to augment this data set. He has five objectives: 1) refine the paleomagnetic time scale at Site 480, calibrating to a delta O18 record that will be measured at WHOI, and to an automated varve-counting technique in collaboration with similar work by A. Soutar (Scripps) on box cores to be collected in June; 2) reconstruct the last 250 Kyrs of productivity, ocean circulation , and continental climate from XRF and LECO geochemical analyses from Site 480; 3) examine the last 20Kyrs of paleomagnetic secular variation recorded in the upcoming piston cores, dating with AMS C14, delta O18 and varve counting; 4) combine rock magnetic, sedimentological and geochemical studies to evaluate the effects of diagenesis upon the fidelity of paleomagnetic signals recorded in rapidly deposited sediments; and 5) use similar rock magnetic and geochemical analyses to characterize the last 20Kyrs of spatial and temporal variations in productivity and terrigenous input to the Gulf of California.