A NEW RECORD OF THE PALEOCENE-EOCENE THERMAL MAXIMUM FROM THE SALISBURY EMBAYMENT OF THE U.S. ATLANTIC COASTAL PLAIN

The Paleocene–Eocene Thermal Maximum (PETM) is an ancient (~56 Ma) global warming event associated with the rapid release of massive amounts of isotopically-light carbon to the ocean-atmosphere system, making it an informative analog for anthropogenic climate change. Here we report the findings of an ongoing study being conducted on a coastal PETM record recovered in a sediment core drilled at Surprise Hill, Virginia. A global hallmark of the PETM is a carbon isotope excursion (CIE) that is manifested in the geological record as a conspicuous interval of decreased carbon isotope (δ¹³C) composition of marine carbonates. Our benthic foraminifer δ¹³C record constrains the CIE to a 12.6-meter interval encompassing the Marlboro Clay, with the CIE onset signaled by an abrupt ~3‰ decrease across the contact between the Marlboro Clay and underlying Aquia Formation. Complementary benthic foraminifer δ¹⁸O values show a ~2‰ decrease contemporaneous with the CIE onset, indicating ~8ºC warming assuming a constant seawater δ¹⁸O composition. We find that the local marine ecosystem was profoundly perturbed by PETM conditions. Such macro-invertebrates as scleractinian corals and bivalved molluscs, as well as relatively large benthic foraminifers, associated with the Aquia Formation were locally extirpated and thus absent in the overlying Marlboro Clay. As a result, the macro- and microfossil faunas of the Marlboro Clay are typified by pyritized gastropod steinkerns, relatively small benthic foraminifers, pulsed increases in dinoflagellate and planktic foraminifer abundances, and an increased frequency in serpulid worm tube encrustations. We posit that biotic change across the CIE onset was chiefly driven by the combined effects of ocean warming, deoxygenation, and acidification. The change in substrate sedimentology from glauconitic sands of the Aquia Formation to pelitic mudstones of the Marlboro Clay likely reflects increased riverine input into the Salisbury Embayment driven by an accelerated hydrological cycle and is believed to have been a synergistic stressor under the greenhouse climate state known as the PETM.