IODP Exp 361 SAFARI Moratorium: Glacial terminations of the Plio-Pleistocene

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The last 5Myr or so witnessed significant global cooling and the development of ~100kyr glacial/interglacial cyclicity. The Mid-Pleistocene transition (MPT; ~1250-700ka) marks a shift from glacial cycles dominated by obliquity forcing (the '40kyr world') to the much larger amplitude cycles that characterise the Late Pleistocene. The so-called '100kyr problem' stems from the fact that orbital forcing at ~100kyr (eccentricity) is too weak to explain the observed glacial cyclicity. Furthermore there was no apparent change in insolation forcing across the MPT that could explain the change from 40kyr to ~100kyr periodicity. Recent studies have implicated the influence of sub-orbital climate oscillations in the timing and amplitude of glacial terminations during the Late Pleistocene. Here we propose to test for the presence and amplitude of sub-orbital scale events associated with glacial terminations over the past 5 Myr.Specifically, we will focus on the role of the Agulhas Leakage (warm and salty waters entering the Atlantic Ocean from the Indian Ocean) in propagating the recovery of interglacial mode circulation within the Atlantic basin during deglacial transitions.We will employ an integrated approach, using multiple measurement techniques and core sites. Our approach will be to identify glacial terminations based on ship-board measurements and the results of XRF core scanning prior to the sampling party. We will then perform high resolution measurements (e.g. XRF scans, foraminiferal stable isotopes and planktonic foraminiferal faunal counts) across a selection of terminations to assess the magnitude of millennial-scale perturbations and their timing, relative to the specific termination in question (as determined by benthic foraminiferal d18O). We will also investigate conditions bracketing each deglacial sequence (i.e. the preceding glacial and subsequent interglacial intervals) in order to assess potential linkages between the magnitudes of millennial-scale perturbations and the termination itself. Surface temperature reconstructions (from foraminiferal fauna) would be compared with XRF scans of Fe/Ti/Al/Ca to proxy riverine runoff, in order to assess the compound effects of frontal movements associated with abrupt changes in ocean circulation. Benthic foraminiferal d13C will be employed to assess corresponding changes in ocean circulation associated with the surface changes we reconstruct.Glacial terminations to be investigated will include T2, 5 and 7 and a selection of earlier transitions. Specific terminations will be identified during the cruise as material is collected and initial screening / age model development proceeds.