Nannofossil assemblag and geochemistry of IODP Site 356-U1463

International Ocean Discovery Program Site U1463 provides a record of local surface water conditions and Australian climate in relation to changing ITF connectivity. Modern analogue‐based interpretations of nannofossil assemblages indicate that ITF configuration culminated ~3.54 Ma. A decrease in warm, oligotrophic taxa such as Umbilicosphaera sibogae, with a shift from Gephyrocapsa sp. to Reticulofenestra sp., and an increase of mesotrophic taxa (e.g., Umbilicosphaera jafari and Helicosphaera spp.) suggest that tropical Pacific ITF sources were replaced by cooler, fresher, northern Pacific waters.

This initial tectonic reorganization enhanced the Indian Oceans sensitivity to orbitally forced cooling in the southern high latitudes culminating in the M2 glacial event (~3.3 Ma). After 3.3 Ma the restructured ITF established the boundary conditions for the inception of the Sahul‐Indian Ocean Bjerknes mechanism and increased the response to glacio‐eustatic variability.