The Impact of Tasman Gateway Opening on Early Paleogene Climate and Oceans: New Results from IODP Expedition 369, Site U1514

The high latitudes are of critical importance for the regulation of global climate, oceanographic currents and biogeochemical cycles both today and in the past. Yet, the history of these regions is poorly known particularly from past high-CO₂ intervals such as the early Paleogene ( 34-66 Ma). This dearth represents a fundamental gap in our understanding of how high-CO₂ worlds operate and ultimately hinders our ability to predict current and future anthropogenic change.

In 2017, International Ocean Discovery Program (IODP) Expedition 369 cored IODP Site U1514 in the Mentelle Basin (offshore southwest Australia; Indian Ocean). This site recovered several hundred metres of relatively (temporally) complete early Paleogene clayey nannofossil oozes and chalks that are rich in carbonate microfossils well suited to assemblage and inorganic geochemical analyses. As such it is one of the few continuous high southern latitude sites available and provides an opportunity to investigate this oceanographically sensitive region during the opening of the Tasman Gateway (between Australia and Antarctica).

Here we present a suite of new bulk sediment and foraminiferal stable oxygen and carbon isotope (δ¹⁸O and δ¹³C) data from IODP Site U1514, spanning the Paleocene through Eocene ( 60-34 Myrs) including the short-lived global warming event, the Paleocene-Eocene Thermal Maximum ( 56 Ma). Our studies will shed new light on the thermal and oceanographic evolution of surface and deep waters in the southeast Indian Ocean through this critical interval of Earth history, and ultimately allow us to address key outstanding questions regarding the mechanisms, feedbacks and consequences of tectonic changes at high southern latitudes and, thus, the dynamics of past high-CO₂ worlds.