Deep-sea benthic foraminiferal response to the Late Lutetian Thermal Maximum at Demerara Rise (ODP Site 1260, equatorial western Atlantic)

Abstract. The Late Lutetian Thermal Maximum (LLTM) was a short-lived warming event recorded in the middle Eocene, at ∼ 41.52 Ma. It has been linked to the highest insolation values of the last 45 million years on Earth's surface. In order to understand the effects of the LLTM warming in deep-sea ecosystems, the benthic foraminiferal response to the LLTM is documented at Ocean Drilling Program (ODP) Site 1260 in Demerara Rise, equatorial western Atlantic. Previous studies at this site reveal the LLTM is defined by a negative excursion in carbon and oxygen stable isotopes, minimal %CaCO3, elevated X-ray fluorescence (XRF) Fe, and a dark clay-rich layer, indicating CaCO3 dissolution. Our analyses reveal changes in the benthic foraminiferal assemblages and in the sediment components across the LLTM. Carbonate dissolution during the LLTM is supported by the decrease in planktic foraminifera, an increase in siliceous components and in the number of fish teeth, poor preservation of the benthic foraminiferal tests, and increased relative abundance of CaCO3 corrosion-resistant taxa (e.g. Nuttallides truempyi, Oridorsalis umbonatus). The lowest benthic foraminiferal accumulation rates and diversity of the assemblages during the peak LLTM warming may be indicative of lower export productivity and environmental stress; alternatively, they may result from a taphonomic bias due to CaCO3 dissolution. The comparison of these results with the available benthic foraminiferal studies in the Atlantic and Pacific oceans leads to the conclusion that the environmental response to the LLTM was strongly influenced by the palaeogeographic and palaeoceanographic setting.