Abstract
Carbon isotopic compositions (δ13C values) of sterols in various geochemical samples were analyzed and their usefulness as a biomarker was evaluated. δ13C values of algal derived sterols ranged from -25.3 to -22.1‰ in Holocene sediments, while they ranged from -29.7 to -24.2‰ in glacial marine sediments, suggesting that the δ13C values are mainly depend on the primary productivity. The δ13C values of 24-methylcholesta-5,22-dien-3β-ol in Japan Sea sediments ranged from -25.2 to -23.1‰. This sterol is derived from bacillariophyceae (diatom) and haptophyceae. However, the carbon isotopic compositions of unsaturated C37 ketones (C37 alkenones) are largely different from that of 24-methylcholesta-5,22-dien-3β-ol. The δ13C values of cholesterol which is produced partly by zooplankton ranged from -24.5 to -21.5‰. The δ13C measurements of C29 sterols are valid for the discrimination of their sources (marine and/or terrestrial) and this would provide a powerful tool for discussing the paleo-climatic changes in the Japan Sea.
