[M-IS15] Paleoclimatology and Paleoceanography

[MIS15-03] Chemical characterization of multiple hyperthermal events in the early Paleogene Hothouse reconstructed from seafloor sediments of the Campbell Plateau, South Pacific Ocean

*Kazutaka Yasukawa¹, Erika Tanaka^2,3, Ann G. Dunlea⁴, Ingrid Hendy⁵, Bryan Niederbockstruck⁶, Ursula Röhl⁶, Minoru Ikehara², Kentaro Nakamura^1,3, Yasuhiro Kato^1,3 (1.School of Engineering, The University of Tokyo, 2.Center for Advanced Marine Core Research, Kochi University, 3.ORCeNG, Chiba Institute of Technology, 4.Woods Hole Oceanographic Institution, 5.University of Michigan, 6.MARUM - Center of Marine Environmental Sciences, University of Bremen)

Keywords:Paleogene, IODP, hyperthermals, PETM, South Pacific

During the early Paleogene, Earth’s mean surface temperature was considerably higher than at present day, which is recently described as “Hothouse” climate state in the Cenozoic era [1]. Superimposed on the millions-of-years global warmth, multiple transient global warming events occurred. These early Paleogene “hyperthermals” are commonly characterized by rapid and distinct negative carbon isotope (δ¹³C) excursions in both terrestrial and marine realms, suggesting massive injections of ¹³C-depleted greenhouse gas(es) into the ocean-atmosphere system.
International Ocean Discovery Program Expedition 378 “South Pacific Paleogene Climate” was conducted from January to February 2020. One of the major targets of this expedition was to recover a continuous sedimentary sequence including the early Paleogene hyperthermals [2]. In this study, we investigated Holes U1553C and U1553D, drilled at ~1,222 meters of water depth on the southern Campbell Plateau, south of New Zealand [2]. We analyzed major- and trace-element compositions, δ¹³C, δ¹⁸O, and CaCO₃ contents for 364 bulk carbonate samples. The downhole δ¹³C profile clearly demonstrates multiple negative excursions corresponding to the Paleocene-Eocene Thermal Maximum (PETM), the most prominent environmental perturbation in the early Paleogene, and other modest hyperthermals such as the Eocene Thermal Maximum (ETM) 2 and ETM3. In the presentation, we will discuss multi-elemental features of the bulk sediment composition and their time-series variations during the studied interval.

[1] Westerhold et al. (2020) Science 369, 1383-1387. [2] Röhl et al. (2022) Proceedings of the IODP. 378.