HR: 0830h
AN: OS31B-0212    [PDF]
TI: Climatic and Environmental Controls of Organic Carbon Accumulation on the California Continental Margin: a Comparison of Deep and Shallow Sites in the Late Quaternary Santa Barbara Basin
AU: * Zeleski, C M
EM: cathzeleski@aol.com
AF: California State University, Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840 United States
AU: Behl, R J
EM: behl@csulb.edu
AF: California State University, Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840 United States
AB: The Quaternary sedimentary sequence of the Santa Barbara Basin presents a unique opportunity for testing the relative importance of different environmental criteria for the preservation of organic carbon. New piston cores obtained during the IMAGES MONA Cruise (2002) from a central/ deep (569 m) and marginal/ shallow (481 m) location in the Santa Barbara Basin lie within and above the intermediate water mass and have been deposited within more consistently dysoxic (deep core) and consistently oxygenated (shallow core) settings. This study correlates total organic carbon (TOC) with C/N ratios, carbonate and grain size. Our results will help evaluate the relative significance of local environmental versus regional oceanographic/climatic variation in the preservation of organic matter. Initial sample spacing analyses were acquired at 40 cm ($\sim$275 y). TOC ranges from 3.4 to 1.0 wt.% (shallow) and 4.1 to 1.3 wt.%(deep). C/N ratios vary from 10.5 to 8.4 (shallow) and from 13.3 to 8.7 (deep). Gross trends in TOC and C/N are well correlated between core MD 2503 (deep) and core MD 2504 (shallow). The TOC profile in both has a typical "burned-down" pattern decreasing downcore from 4.1 and 3.4 wt.% respectively to $\sim$1.5 wt.% at 12 - 14 mbsf at the base of the Holocene. The C/N ratios show an inverse relationship to TOC suggesting a downcore decrease in the preservation of marine organic matter. Below the most dramatic effects of burial diagenesis C/N ratios in both cores are highly correlated with TOC, suggesting that the relative contribution of organic matter is controlling TOC. In cores MD 2503 and MD 2504, mean CaCO$_{3}$ sharply drops from higher values during the glacial (3.7 and 6.3 wt.%, respectively) to lower values during the Younger Dryas and Bolling Allerod (2.0 and 4.5 wt.%). After initially increasing at the base of the Holocene, both locations record a gradual decrease in CaCO$_{3}$ to the present. Higher (20 cm, 130 y) resolution TOC and C/N data is being produced to strengthen correlations with other proxy data. Grain size analysis for both cores is being completed to determine the role of fine-grained material. From data provided by co-workers stable isotopes of planktonic and benthic foraminifera, Mg/Ca ratios, faunal and floral (nannoplankton and pollen) assemblages, and clay mineralogy are also being correlated with TOC to determine the relative significance of provenance productivity, ventilation and substrate composition in the accumulated preservation of organic matter.
DE: 4243 Marginal and semienclosed seas
DE: 4267 Paleoceanography
DE: 4806 Carbon cycling
DE: 4825 Geochemistry
DE: 4863 Sedimentation
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting