General descriptions, organic contents and geolipid ratios at DSDP Leg 72 Holes

Organic matter in sediments from Sites 515, 516, and 517 reflects a history of low marine productivity and of oxygenated bottom waters in the western South Atlantic since the Pliocene. Organic carbon contents are low, averaging 0.26% of sediment weight. Distributions of n-alkanes, n-alkanols, and n-alkanoic acids show evidence of microbial reworking, and n-alkanes contain important terrigenous contributions, presumably of eolian origin.

Organic geochemistry from different DSDP Holes in the subtropical South Atlantic Ocean

Organic matter has been characterized in samples of Pleistocene, Pliocene, and Miocene sediments from seven Deep Sea Drilling Project sites in the subtropical South Atlantic Ocean. Organic carbon concentrations average 0.3% for most samples, and n-alkanoic acid, n-alkanol, and alkane biomarkers indicate extensive microbial reworking of organic matter in these organic-carbon-lean sediments. Samples from the easternmost parts of the South Atlantic contain an average of 4.1% organic carbon and reflect the high productivity associated with the Benguela Current. Lipid biomarkers show less microbial reworking in these sediments. Eolian transport of land-derived hydrocarbons is evident at most of these oceanic locations.