Patterns and Rates of Organic Carbon Accumulation in Recent Pelagic and Hemipelagic Marine Environments

D. Cwienk, M. S. Leinen, M. A. Arthur

Maps were constructed for the global distribution of percent organic carbon, sedimentation rates, bulk sediment accumulation rates, and organic carbon accumulation rates (OCARs), exclusive of the continental shelves, on the basis of both published and some new data from sediment cores. The OCAR data base uses only cores in which stratigraphic resolution is sufficient to define a mean sedimentation rate for the last 12,000 years and from which bulk density measurements are available or can be calculated using established relationships to carbonate content. Data coverage was adequate for much of the Pacific Ocean basin but was somewhat sparse for the Atlantic, Indian, and Southern oceans. Nonetheless, basic patterns of organic carbon accumulation can be observed from the ma s. As expected, the OCARs are highest in the equatorial Pacific, where surface-water productivity is highest, and low under the central gyre regions where surface organic carbon flux and total sediment flux are both low. Higher OCARs also occur in more rapidly accumulating sediments near the continental margins, partly as a function of the enhanced preservation of labile carbon that results from higher sedimentation rates and, in some cases, from higher productivity in surface water masses or increased flux of terrigenous organic matter. The patterns of OCAR are similar, in general, to patterns of accumulation of biogenic opal, thereby reinforcing the link between biological productivity and OCARs.

An analysis of the global impact of pelagic-hemipelagic OCARs, using this data base, suggests that no more than 0.21 × 10¹⁴gOC/year accumulate over the deep-sea floor at present--only about 16% of the estimated global annual organic carbon burial. However, the deep-sea organic carbon sink may have been more important in the past.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.