PALEOCLIMATE OF THE LATE OLIGOCENE ARCTIC OCEAN: MOLLUSCAN ISOTOPIC AND BIOTIC EVIDENCE

Molluscan isotopic and biotic evidence was used to determine the paleotemperature of the Late Oligocene Arctic Ocean during an important period of climate change. Molluscs were collected from the Nuwok Member type section on the Arctic coast of Alaska. A systematic analysis was conducted to determine the position of Late Oligocene Arctic molluscs within a context of marine Cenozoic evolution and diversification. Oxygen stable isotope ratios of five fossil genera were used to calculate paleotemperatures and analyze growth histories. Taxa were selected to check for compatibility of results between fossil genera from the same environment. Oxygen stable isotope ratios of four recent high-latitude genera were analyzed for comparative purposes. Isotopically derived paleotemperatures represent the first documented quantitative temperatures for the Late Oligocene Arctic Ocean. Isotopic and systematic results give great insight into the extent and degree of Arctic cooling by the Late Oligocene and the origin of modern Arctic molluscs.