Integrated record of the Late Lutetian Thermal Maximum at IODP site U1508, Tasman Sea: The deep-sea response

Abstract

The Late Lutetian Thermal Maximum (LLTM) was a transient and brief global warming event recorded in the middle Eocene, at 41.52 Ma. The biotic response to the LLTM has been documented at only a few marine sites so far. Here, we present the first record of deep-sea benthic foraminiferal assemblage changes during the LLTM in the southwest Pacific at International Ocean Discovery Program Hole U1508C (1609 m water depth) in the Tasman Sea. The LLTM coincides with a negative excursion in bulk sediment δ¹³C (0.47‰) and benthic foraminifera δ¹³C (0.36‰), with changes in the relative abundance of benthic foraminiferal species and in the deep-water organic geochemistry. The decrease in diversity of the assemblages indicates environmental stress during the event, potentially linked to oxygen deficiency, as evidenced by the occurrence of dysoxic taxa (e.g. Lenticulina spp., Turrillina brevispira). Although calcareous taxa dominate, the presence of corrosion-resistant species and poorly preserved foraminiferal tests suggest slightly CaCO₃-corrosive bottom waters, but no dissolution was evident. We suggest the shallowing of the thermocline and enhanced water column stratification at this site during the LLTM.