Biomarkers (TEX86), planktic isotopes and XRF records of IODP Site 356-U1459 (Perth Basin)

The Indonesian Throughflow (ITF) operates as an important link in global thermohaline circulation and ITF variability probably modulated Pliocene climate change. Yet, whether ITF variability accounted for oceanographic change south of Northwest Cape remains controversial. Here, we present a multi-proxy oceanographic reconstruction from the Perth Basin and reconstruct the Pliocene history of the Leeuwin Current (LC). We affirm the LC to be active throughout the Pliocene, albeit with fluctuations in intensity and scope. Three main factors control LC strength. First, a tectonic ITF reorganization caused an abrupt and permanent LC reduction at 3.7 Ma. On shorter time-scales, eustatic sea-level and direct orbital forcing of wind patterns hamper or promote the LC. At 3.3 Ma, for instance, LC intensity plunged in response to a eustatic ITF restriction. At that time, Site U1459 fell outside the extent of a weakened LC and the latitudinal sea surface temperature gradient became significantly steeper.