Organic Carbon Preservation in the Present-Day Ocean

Richard A. Jahnke

Over the last decade, studies of sediment diagenesis have significantly improved our understanding of the processes controlling the remineralization and preservation of organic matter reaching the sea floor. In situ benthic flux chamber incubation, pore water and sediment studies in the California Borderland basins indicate that input, rather than diagenetically-driven preservation factors, is most closely correlated with organic carbon burial rates. Because organic carbon input rates and total sediment deposition rates are in most instances correlated, these results also support the role of sediment surface area in determining burial rates. Preservation efficiency, that is the proportion of the total organic carbon deposited that is buried to a prescribed depth, does not correlate with bottom water oxygen or the dominance of oxic remineralization. Similar correlations are observed on the central California continental margin and in the central basins of the Atlantic and Pacific Oceans suggesting that these results may have wide applicability.

Studies of organic matter remineralization in turbidites, however, provide convincing evidence that factors that control diagenetic processes, such as the availability of oxygen, can influence burial rates. These seemingly contradictory lines of evidence can be reconciled if it is postulated that preservation factors control remineralization only after the most labile portion of the deposited organic matter is remineralized.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California