34 Paleontology

Wednesday, 11 March 2026
8:30 AM - 10:00 AM
RCC, 103

Redox Conditions during the Middle Eocene Climatic Optimum in the Mentelle Basin, Southern Ocean

Paper number: 34-5
Program: Technical Sessions
Time: 9:45 AM – 10:00 AM

Authors

Abstract

The Middle Eocene Climatic Optimum (MECO) represents one of the most significant transient and unique warming events in Earth’s climate history, interrupting the long-term cooling trend that followed the Early Eocene Climatic Optimum. Unlike earlier hyperthermals, MECO lacks a globally coherent carbon isotope signature, suggesting the involvement of biogeochemical processes beyond simple carbon-cycle perturbation. However, the identity of these processes and their impacts on ocean redox conditions and nutrient cycling remain poorly constrained. To investigate redox and nutrient cycle responses to sustained warming during MECO in the Southern Ocean, we generated a high-resolution downcore record of sedimentary trace metal (U, Re, Mo) concentrations and bulk organic nitrogen isotopes (δ¹⁵N) from Hole U1514A (IODP Expedition 369) in the Mentelle Basin. Prior to the MECO, proxy records indicate predominantly oxic water conditions. During the MECO, trace-metal enrichments and δ¹⁵N values suggest reduced oxygen availability, but likely not persistent anoxia or euxinia, followed by a return to fully oxic conditions in the post-MECO interval. Not all proxies seem to agree, however, which may indicate the occurrence of biogeochemical processes that influenced only particular proxies or that the change in oxygen concentration was not significant enough to impact all redox proxies on a basin scale. Overall, the proxy data indicate that sustained MECO warming at this site was associated with predominantly suboxic conditions rather than persistently oxic waters or sustained anoxia/euxinia.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411515

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