ORGANIC-MATTER CONTENT IN US ATLANTIC CONTINENTAL-SLOPE SEDIMENTS - DECOUPLING THE GRAIN-SIZE FACTOR

Decoupling organic content in sediments from grain size can help define spatial variations in biological productivity, transport or preservation in continental margin sediments. Upper slope and upper rise sediments off the eastern United States have organic nitrogen contents similar to or lower than those predicted by grain size, whereas mid-slope sediments between Norfolk Canyon and Cape Fear have much higher organic contents. These elevated values probably result from off-shelf transport, combined with rapid burial and correspondingly reduced rates of remineralization. Low organic contents on the upper slope partly reflect higher rates of remineralization, while lower values on the upper rise presumably result from low input of organic matter and low rates of burial and increased oxic degradation.