Interrelationships of organic carbon and submarine sediment geotechnical properties

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Abstract
Total organic carbon content (TOC) and selected geotechnical properties were measured in submarine sediments of the U.S. central east coast and the Mississippi Delta. TOC values in the near‐surface Delta sediments were approximately 1% (dry weight). TOC in surficial sediments from the U.S. east coast outer continental shelf, upper slope, and upper rise was generally less than 1%, but between the upper slope and the upper rise, values ranged from 1 to 3% and exceeded 3% in patches associated with Norfolk and Washington Canyons. TOC displayed positive linear correlations with water content, liquid limit, plastic limit, plasticity index, and the amount (percent) of fine‐grained material. Nevertheless, there appeared to be no strong dependence of geotechnical properties on TOC in these sediments. This was in accord with previously reported studies on terrestrial soils with TOC values of less than 5%. Carbohydrate content was strongly correlated with water content and plasticity index, suggesting that measurement of individual components of the organic material may provide more sensitive indications of the effects of organics on geotechnical properties than measurement of bulk TOC. Selected geotechnical properties and TOC content of U.S. continental margin surficial sediments displayed regional trends related to water depth and morphological setting. These trends are probably related to recent biological, sedimentological, and ocdeanographic processes active on the outer shelf, slope, and rise.