High Resolution Middle Eocene Marine Stable Isotope - Southern Ocean Sites

At sites on Maud Rise and the Kerguelen Plateau, a distinct negative shift in d18O values (~1.0‰) is observed ca. 41.5 Ma. This excursion is interpreted as primarily a temperature signal, with a transient warming of 4C over 600 k.y. affecting both surface and middle-bathyal deep waters in the Indian- Atlantic region of the Southern Ocean.

This isotopic event is designated as the middle Eocene climatic optimum, and is interpreted to represent a significant climatic reversal in the midst of middle to late Eocene deep-sea cooling. The lack of a significant negative carbon isotope excursion, as observed during the Paleocene–Eocene thermal maximum, and the gradual rate of high-latitude warming suggest that this event was not triggered by methane hydrate dissociation.