Late Neogene nannofossil assemblages as tracers of ocean circulation and paleoproductivity over the NW Australian shelf

Abstract. Late Miocene to Pliocene sediments from the NW Australian shelf, drilled by International Ocean Discovery Program (IODP) Expedition 356, provide unique records of paleoclimatic variations under warmer-than-present conditions. During period 6 3.5 Ma, area was dominated warm, tropical waters supplied an intensified, uninterrupted Indonesian throughflow and characterised prevailing humid conditions, including increased precipitation river runoff. Despite available information regarding general little is known about concurrent regional ocean circulation patterns relative strength seasonally flowing boundary currents, such as Leeuwin Current. In this study, we investigate two astronomically tuned calcareous nannofossil time series IODP Sites U1463 U1464 track long-term changes in water column stratification, which influences availability nutrients upper photic zone considered be a primary control on (paleo)productivity marine phytoplankton. By documenting shifts dominant species within assemblages comparing these paleotemperature gradients between shelf eastern Indian Ocean, identify significant change ecological oceanographic regime that occurred across Miocene–Pliocene (5.4–5.2 Ma), can attributed overall intensification mixing over shelf. Significant abundance composition reflect broader-scale processes evolutionary events, termination late early biogenic bloom (4.6–4.4 Ma) extinction Sphenolithus spp. (∼3.54 long after shift.