Organic biomarker compound concentrations in sediments from DSDP Hole 96-619

Organic carbon-normalized concentrations of total long chain (C37-C39) alkenones and some individual C27-C29 desmethyl sterols were determined to be useful proportional indicators (tracers) of preserved marine and terrigenous organic carbon, respectively.

The alkenones, whose only known source is marine phytoplankton of the class Prymnesiophyceae, generally occurred in higher concentrations in interglacial isotope stages 1 and 5a-b than in the intervening glacial stages. Sterols (C27-C29), apparently of a dominantly terrigenous origin, occurred in lower concentrations during interglacial stages than in glacial stages. Tracers of both terrigenous and marine organic matter appear to be affected by the differential diagenetic alteration of the biomarker/Corg ratios, as indicated by a simple, first-order kinetic model.