Abstract

The Bermuda Islands preserve carbonates recording many past changes in sea level, including multiple warm and cool geologic intervals. Several localities expose shell-rich deposits from the Last Interglacial (~125,000 years ago), a time broadly similar to climate today that can potentially serve as an analog for future conditions. Here, we use δ18O analyses of fossil mollusks to estimate past temperatures and seasonality and compare our data with those from other species.

Eight Dendostrea frons oysters were sampled along their growth axes to reconstruct seasonal temperature curves. We report a mean δ18O value of -0.51 ± 0.17‰, corresponding to a temperature of ~23°C. These temperatures are similar to modern Bermuda (~16 to ~31°C), suggesting that North Atlantic circulation may have been similar to today. Grape Bay and Bird Island Glycymeris americana mollusks, well known in isotopic work, were utilized for interspecies analysis and report similar temperature reconstructions, ~22°C and ~24°C, respectively. The Dendostrea frons oysters require further evaluation to verify biologic effects as well as determine its oceanic depth environment. In comparison to other Last Interglacial temperature reconstructions these data could reflect a Gulf Stream current roughly as strong as today, in contrast to colder temperatures described in other studies.