Abstract

Early Paleogene hyperthermals,including the well-studied Paleocene-Eocene thermal maximum (PETM; ~55.5 Ma) were transient global warming phases, associated with massive injection of 13C-depleted carbon that marked the event with a negative carbon isotope excursion (CIE) in sedimentary components. Recent studies on high accumulation rate marginal marine sections have shown that biotic change (poleward migration of the dinoflagellate Apectodinium) and, at least regional, warming preceded the CIE. Recent work has focused on deposits from the Southwest Pacific Ocean (~65°S paleolatitude; ODP Site 1172). TEX86 analyses indicate that the long-term Paleocene-Eocene surface ocean temperature evolution in this region was strikingly similar to that of the global deep ocean. Surface waters at this site were Antarctic-derived; nevertheless, the Apectodinium acme is recorded at the PETM and is also here found to lead the CIE. TEX86 values indicate that sea surface temperatures (SST) rose by ~9°C during the PETM to a maximum well over 30°C. Dinocyst assemblages are consistent with sea level rise as well as significant changes in hydrology across the PETM. If time allows, I will present dinocyst and organic geochemical results from the PETM of continental margin deposits from the US Gulf Coast. Documentation of hyperthermal Eocene Thermal Maximum 2 (ETM2, ~53.5 Ma) is limited, hampering evaluation of its global nature and pattern of change. New data from the ETM2 section recovered from the Lomonosov Ridge, Arctic Ocean (IODP Expedition 302) shed new light on this hyperthermal. The \u03b413C of total organic carbon (TOC) shows a ~3.5\u2030 negative CIE at its onset. Dinocyst assemblages show a freshening and eutrophication of Arctic Ocean surface waters. TEX86-derived SSTs and MBT-derived atmospheric temperatures show a ~3-4 °C rise. Pollen of palms imply coldest month mean temperatures >8°C, which is challenging for the current generation of fully-coupled climate models. Laminated sediments and the absence of organic foraminiferal linings suggest that anoxia persisted at the sediment-water interface. Biomarker analyses also indicate euxinic conditions in the photic zone during ETM2. All trends, including those recorded using XRF core scanning t echniques, mimic those recorded for the PETM but generally exhibit a slightly smaller magnitude. Our findings corroborate the notion that ETM2 was indeed a true global warming phase, associated with the rapid injection of light carbon. Moreover, TEX86 and palm pollen suggest that maximum ETM2 temperatures in the Arctic may have been warmer than those during the PETM.