Dr. Pearson's study presents the first comprehensive suite of compound-specific carbon isotopic (d13C and D14C) data for lipid biomarkers isolated from marine sediments. Isotopic compositions of individual biomarkers representing phytoplanktonic, zooplanktonic, bacterial, archaeal, terrestrial, and fossil carbon sources are reported for Santa Monica Basin and Santa Barbara Basin surface sediments. The data show that the carbon source for most of the biomarkers is marine euphotic zone primary production or subsequent heterotrophic consumption of this biomass. Two lipid classes represent exceptions to this finding. D14C values for the n-alkanes are consistent with mixed fossil and contemporary terrestrial plant sources. The archaeal isoprenoid lipid data reflect chemoautotrophic growth below the euphotic zone. The biomarker class most clearly representing marine phytoplanktonic production is the sterols, indicating that these compounds could serve as paleoceanographic tracers for surface-water dissolved inorganic carbon. The isotopic data are used to construct algebraic models for quantitative estimation of contributions from the different sources to sedimentary organic carbon.