Carbon and oxygen isotopic compositions of Cibicidoides spp. and fine fraction separates (<10 µm) from ODP Holes 113-689B, 119-738B, and 120-748B, supplement to: Bohaty, Steven M; Zachos, James C (2003): Significant Southern Ocean warming event in the late middle Eocene. Geology, 31(11), 1017-1020

• Main Authors: Bohaty, Steven M, Zachos, James C
• Format: Article in Journal/Newspaper
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2003
• Subjects: Drilling/drill rig; Leg113; Leg119; Leg120; Joides Resolution; Ocean Drilling Program ODP; Indian; Kerguelen; Maud Rise; Southern Ocean; Methane hydrate
• Online Access: https://dx.doi.org/10.1594/pangaea.713540; https://doi.pangaea.de/10.1594/PANGAEA.713540

A prominent middle Eocene warming event is identified in Southern Ocean deep-sea cores, indicating that long-term cooling through the middle and late Eocene was not monotonic. At sites on Maud Rise and the Kerguelen Plateau, a distinct negative shift in d18O values (~1.0 per mil) is observed ca. 41.5 Ma. This excursion is interpreted as primarily a temperature signal, with a transient warming of 4°C 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. Rather, a transient rise in pCO2 levels is suspected, possibly as a result of metamorphic decarbonation in the Himalayan orogen or increased ridge/arc volcanism during the late middle Eocene.