Biogeochemical Applications of Compound-Specific Radiocarbon Analysis
Abstract
Compound-specific carbon isotopic (delta 13C and delta 14C) data are reported for lipid biomarkers isolated from Santa Monica Basin (SMB) and Santa Barbara Basin (SBB) surface sediments. These organic compounds represent phytoplanktonic, zooplanktonic, bacterial, archaeal, terrestrial, and fossil carbon sources. The lipids include long-chain n-alkanes, fatty acids (as FAMEs), n-alcohols, C(30) mid-chain ketols and diols, sterols, hopanols, and ether-linked C(40)-biphytanes of Archaca. 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. Delta 14C values for the n-alkanes are consistent with mixed fossil and contemporary terrestrial plant sources. The archaeal isoprenoid data reflect chemoautotrophic growth below the euphotic zone. The biomarker class most clearly representing marine phytoplanktonic production is the sterols. It is suggested, therefore, that the sterols could serve as paleoceanographic tracers for surface-water DIC. The isotopic data are used to construct two algebraic models. The first calculates the contributions of fossil and modern vascular plant carbon to SMB n-alkanes. This model indicates that the delta 14C of the modern component is +235% (post-bomb) or 0% (pre-bomb). The second model uses these values to determine the origin of sedimentary TOC. The results are comparable to estimates based on other approaches and suggest that approx. 60% of SMB TOC is of marine origin, modern terrestrial and fossil sources contribute approx. 10% each, and the remaining approx. 20% is of unknown origin.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 2000
- Accession Number
- ADA380195
Entities
People
- Ann Pearson
Organizations
- Woods Hole Oceanographic Institution