Magnetic susceptibility measurements were made on whole-core, split-core, and discrete samples from Ocean Drilling Program Site 893, located in the central Santa Barbara Basin. These measurements are presented and preliminary evaluations are made regarding the relationships between magnetic susceptibility, index properties (density, porosity, and water content), and geochemical variables (weight percentage of calcium carbonate and total organic carbon) over the past 160,000 yr.
"Gray beds" in the sediment column, which are faithfully identified by magnetic susceptibility profiles, are most abundant and best preserved within Holocene intervals of laminated sediments and during oxygen isotope Stage 5. The preservation of these gray beds is associated with intervals of lowered sea level and increased global ice mass, as determined from oxygen isotopes.
Calculations of the magnetic susceptibility flux for Hole 893A have been made using an age model based on both accelerator mass spectrometer 14C age dates and the oxygen isotope stratigraphy presented in this volume. The magnetic susceptibility flux may provide a proxy indicator of the relative intensity of terrigenous input into the Santa Barbara Basin and/or may reflect changes in the geochemical environment of the basin through time.
Preliminary observations suggest that magnetic susceptibility measurements may be sensitive to changes in the weight percentage of sedimentary components (e.g., organic matter and to a lesser extent calcium carbonate). It is not yet clear whether this is caused solely by dilution effects or whether this indicates magnetite dissolution during sediment diagenesis.
Finally, we evaluate the Site 893 data using available (regional and global) paleoclimatic records and the results of Holocene modeling runs, in order to assess the possible significance of the susceptibility data as a proxy recorder of paleoceanographic and/or paleoclimatic processes along the western margin of North America.
Date of initial receipt: 1 September 1994
Date of acceptance: 7 March 1995
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