Exploring Early Eocene Hyperthermals on the New Jersey Paleoshelf (ODP 174AX)

Abstract

Abstract We investigate early Eocene hyperthermals by complementing foraminiferal and bulk carbonate isotopes with benthic foraminiferal assemblages from three marine coreholes located along a paleoshelf transect on the New Jersey coastal plain (ODP 174AX Bass River, Double Trouble, and Ancora). Distinct negative δ13C and δ18O excursions likely correspond to the globally documented ETM-2, H2, I1, I2, and J events. Foraminiferal stable isotope data at Bass River reveal greater warming in benthic and thermocline communities compared to the surface dwellers during these excursion events. During the largest excursion event (ETM-2), thermocline-dwelling Subbotina not only experienced greater overall warming, but also recorded lower δ18O values than Morozovella (–5.1‰ vs. –4.3‰). This suggests either greater warming in the thermocline, habitat depth restructuring, or possibly a change in calcification season. We also demonstrate a potential biotic threshold, providing the first comprehensive evaluation of the sensitivity of shallow-marine taxa in response to these transient warming events.