Low-latitude climate evolution during the Paleocene: a biogeochemical and palynological study of ODP Leg 171B

Abstract

Paleocene climate is characterized by a reversal from multi-million year cooling to warming and additionally contains the first evidence for occurrence of transient hyperthermal events, including the Early Late Paleocene Event (ELPE). While these long-term temperature trends are mainly known from deep ocean and high latitude temperature records, this study provides one of the first Paleocene low latitude records, from Ocean Drilling Program (ODP) Site 1051 and 1052, a continental slope setting in the North Atlantic. Long-term sea surface temperature reconstructions based on the TEX86 paleothermometer reveal early Paleocene cooling of comparable magnitude as has previously been recorded for the deep ocean and Southern ocean. However, a temperature minimum is reached ~3 Myrs earlier than in the aforementioned records, after which late Paleocene – early Eocene temperatures are remarkably constant. This seems to correspond to sparse temperature reconstructions from low latitude Tanzania. This indicates that while early Paleocene cooling seems to have been global, the following long-term warming was focused on the high latitudes, reducing the meridional temperature gradient. Secondly, a paleoenvironmental reconstruction based on dinoflagellate cysts (dinocysts) reveals no major changes in coastal proximity during the early Paleocene, but some third-order sea level fluctuations were tentatively reconstructed. Thirdly, high-resolution organic geochemical analyses over the ELPE interval reveal a large increase in abundance of methanotrophic archaea, providing tentative evidence for methane hydrate dissociation, which could causally couple changes in the carbon cycle to warming. This highlights a worthwhile area of further research.