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. Mollusks 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 mollusks 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 modem Arctic mollusks.