New insights into hyperthermal events during the late Paleocene to early Eocene

The late Paleocene and early Eocene climate was punctuated by several warming events known as hyperthermals. These events reflect perturbations in the carbon cycle, identified by the negative carbon isotope excursions, including the prominent Paleocene-Eocene Thermal Maximum. Under the high carbon emission scenario of RCP8.5, the climate is predicted to most closely resemble early Eocene conditions within the next hundred years, making it a promising analog to study the possible long-term environmental changes that we have to face in the near future. High-resolution geochemical records from the Atlantic and Pacific provide astronomically calibrated age models of the early Paleogene. However, these sites are located in the equatorial- to subequatorial regions, so the high-latitude climate changes of the early Paleogene still remain elusive. IODP Expedition 378 recovered new Paleogene sediments at Site U1553 in the high-latitude Southwest Pacific.

Here, we present a novel late Paleocene to early Eocene age model spanning ~7 million years, which will be essential for future paleoceanographic studies of this site. To construct the age model, we used a combined chemostratigraphic and biostratigraphic approach. Our results show that the shape and pattern of the U1553 bulk sediment δ¹³C record generally match the orbitally-tuned records, which is reflective of a global trend. However, the nannofossil events at site U1553 exhibit a striking delay compared to lower latitude sites, suggesting that these commonly-used datums are not applicable at the high latitudes.