Description: Determining the age of marine sediments is essential to reconstruct past changes in oceanography and climate. The oxygen isotopes of benthic foraminifera record long-term changes in global ice volume and deep-water temperature, and are commonly used to construct age models. However, continental margin settings often display much higher sedimentation rates due to regional input by rivers. Here, it is necessary to create a regional framework to allow precise dating of strata. We created such a framework for the Northwest Shelf (NWS) of Australia, which was cored by International Ocean Discovery Program (IODP) Expedition 356. We used oxygen and carbon isotopes in benthic foraminifera to construct an astronomically-tuned age model for IODP Site U1463. The natural gamma radiation (NGR) variations for IODP Site U1463 were then correlated to those of other IODP sites and industry wells in the area. The IODP Site U1463 age-depth model thus provides a reference for other archives on the NWS allowing to assign ages to regional seismic reflectors and the timing of sediment input via rivers. This age model is also used to determine first and last occurrences of foraminifera showing that the Indonesian Throughflow (ITF) blocked the migration of foraminifera from the Pacific to the Indian Ocean after 5 Ma.

Description: 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.

Description: A new MATLAB algorithm for the quantification of NGR spectra that is transparent and accessible to future NGR users. Here, we share the results of this MATLAB algorithm for all holes drilled by DV JOIDES Resolution since Exp. 317.

Description: During International Ocean Discovery Program (IODP) expeditions, shipboardgenerated data provide the first insights into the cored sequences. The natural gamma radiation (NGR) of the recovered material, for example, is routinely measured on the ocean drilling research vessel DV JOIDES Resolution. At present, only total NGR counts are readily available as shipboard data, although full NGR spectra (counts as a function of gamma-ray energy level) are produced and archived. These spectra contain unexploited information, as one can estimate the sedimentary contents of potassium (K), thorium (Th), and uranium (U) from the characteristic gamma-ray energies of isotopes in the 40K, 232Th, and 238U radioactive decay series. Dunlea et al. [2013] quantified K, Th and U contents in sediment from the South Pacific Gyre by integrating counts over specific energy levels of the NGR spectrum. However, the algorithm used in their study is unavailable to the wider scientific community due to commercial proprietary reasons. Here, we present a new MATLAB algorithm for the quantification of NGR spectra that is transparent and accessible to future NGR users. We demonstrate the algorithm's performance by comparing its results to shore-based inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma-emission spectrometry (ICP-ES), and quantitative wavelength-dispersive X-ray fluorescence (XRF) analyses. Samples for these comparisons come from eleven sites (U1341, U1343, U1366-U1369, U1414, U1428- U1430, U1463) cored in two oceans during five expeditions. In short, our algorithm rapidly produces detailed high-quality information on sediment properties during IODP expeditions at no extra cost.

Description: Global climate underwent a major reorganization when the Antarctic ice sheet expanded ~14 million years ago (Ma) (1). This event affected global atmospheric circulation, including the strength and position of the westerlies and the Intertropical Convergence Zone (ITCZ), and, therefore, precipitation patterns (2-5). We present new shallow-marine sediment records from the continental shelf of Australia (International Ocean Discovery Program Sites U1459 and U1464) providing the first empirical evidence linking high-latitude cooling around Antarctica to climate change in the (sub)tropics during the Miocene. We show that Western Australia was arid during most of the Middle Miocene. Southwest Australia became wetter during the Late Miocene, creating a climate gradient with the arid interior, whereas northwest Australia remained arid throughout. Precipitation and river runoff in southwest Australia gradually increased from 12 to 8 Ma, which we relate to a northward migration or intensification of the westerlies possibly due to increased sea ice in the Southern Ocean (5). Abrupt aridification indicates that the westerlies shifted back to a position south of Australia after 8 Ma. Our midlatitude Southern Hemisphere data are consistent with the inference that expansion of sea ice around Antarctica resulted in a northward movement of the westerlies. In turn, this may have pushed tropical atmospheric circulation and the ITCZ northward, shifting the main precipitation belt over large parts of Southeast Asia (4).

Description: An unusually short glaciation interrupted the warm Pliocene around 3.3 Ma (Marine Isotope Stage (MIS) M2). Different hypotheses exist to explain why this glaciation event was so pronounced, and why the global climate system returned to warm Pliocene conditions relatively quickly afterwards. One of these proposed mechanisms is a reduced equator-to-pole heat transfer, in response to a tectonically reduced Indonesian Throughflow (ITF). The ITF is a critical part of the global thermohaline ocean circulation, transporting heat from the Indo-Pacific Warm Pool to the Indian Ocean. When ITF connectivity is reduced, the water and heat supply for the Leeuwin Current, flowing poleward along Australia's west coast, is also diminished. To assess the possible relationship between mid-Pliocene glaciations and latitudinal heat transport through the Indonesian Throughflow, we constructed a multi-proxy orbital-scale record for the 3.7–2.8 Ma interval from International Ocean Discovery Program (IODP) Site U1463, off northwest Australia. The comparison of the Site U1463 record with paleoclimate records from nearby Site 763 and West Pacific Warm Pool Site 806 allows for a detailed regional reconstruction of Pliocene paleoceanography and thus for testing the proposed hypothesis. An astronomically-paced decrease in potassium content characterizes the late Pliocene interval of U1463. This record documents the increasing aridity of northwest Australia, periodically alleviated by reinforced summer monsoon precipitation under summer insolation maxima. The d18O record of the planktonic foraminifer Globigerinoides sacculifer correlates exceptionally well with the sea surface temperature (SST) record from Site 806 in the West Pacific Warm Pool, even during MIS M2. Hence, Site U1463 preserves an uninterrupted ITF signal even during Pliocene glaciations. However, the U1463 d18O G.sacculifer record exhibits a 0.5‰ offset with the nearby Site 763A record around MIS M2. This implies that Site 763A, about 500 km west of U1463, more closely tracks Indian Ocean SST records across MIS M2. The U1463 data reveal that heat-transport through the Indonesian Throughflow did not shut down completely during MIS M2, but rather its intensity decreased prior to and during MIS M2, causing Site 763A to temporarily reflect an Indian Ocean, rather than an ITF signal. We conclude that ITF variability significantly influenced latitudinal heat transport by means of the Leeuwin Current and hence contributed to the relative intensity of MIS M2. We propose the ITF valve between the Pacific and Indian Ocean as a positive feedback mechanism, in which an initial sea level lowering reduces ITF heat transport, in turn amplifying global cooling by advancing the thermal isolation of Antarctica.

Description: Late Miocene to mid‐Pleistocene sedimentary proxy records reveal that northwest Australia underwent an abrupt transition from dry to humid climate conditions at 5.5 million years (Ma), likely receiving year‐round rainfall, but after ~3.3 Ma, climate shifted toward an increasingly seasonal precipitation regime. The progressive constriction of the Indonesian Throughflow likely decreased continental humidity and transferred control of northwest Australian climate from the Pacific to the Indian Ocean, leading to drier conditions punctuated by monsoonal precipitation. The northwest dust pathway and fully established seasonal and orbitally controlled precipitation were in place by ~2.4 Ma, well after the intensification of Northern Hemisphere glaciation. The transition from humid to arid conditions was driven by changes in Pacific and Indian Ocean circulation and regional atmospheric moisture transport, influenced by the emerging Maritime Continent. We conclude that the Maritime Continent is the switchboard modulating teleconnections between tropical and high‐latitude climate systems.