The sedimentary imprint of Pleistocene glacio-eustasy: Implications for global correlations of seismic sequences

We evaluate lithofacies, chronology, and seismic sequences from the Canterbury Basin, New Zealand passive continental slope (Integrated Ocean Drilling Program [IODP] Expedition 317 Site U1352 and environs) and compare this with slope sequences from the New Jersey passive margin. Our goal is to understand continental slope sedimentation in response to glacio-eustasy and test the concepts of sequence stratigraphy. High-resolution geochemical elemental and lithostratigraphic analyses were calibrated to a chronology constructed from benthic foramininferal oxygen isotopes for the past ~1.8 m.y. We identify lithofacies successions by their unique geochemical and lithologic signature and correlate them with marine isotope stages (MIS) at Milankovitch 100 k.y. (MIS 1–12) and 41 k.y. (MIS 13–63) periods. Eight seismic sequence boundaries (U13–U19) were identified from high-resolution multichannel seismic data, providing a seismic stratigraphic framework. Except for MIS 1–5 and MIS 54–55, there are 2–16 MIS stages and a comparable number of lithofacies contained within each seismic sequence, indicating that it took one to several glacio-eustatic cycles to build each seismic stratigraphic sequence. These findings support prior results obtained by the Ocean Drilling Program (ODP) Leg 174A on the New Jersey continental slope. On both margins, there is a strong correlation between seismic sequences, lithofacies, and MIS, thus linking them to glacio-eustasy. However, the correlation between MIS and seismic sequences is not one-to-one, and Pleistocene seismic sequences on the two margins are not synchronous. Local conditions, including differences in sedimentation rates and creation of accommodation space, strongly influenced sediment preservation at each location, revealing that high-frequency Pleistocene seismic sequences need not correlate globally

Timing and Pacing of Indonesian Throughflow Restriction and Its Connection to Late Pliocene Climate Shifts

drier conditions. This shift fundamentally reorganized Earth\u27s climate from the Miocene state toward conditions similar to the present. During the Pliocene, the progressive restriction of the Indonesian Throughflow (ITF) is suggested to have enhanced this shift toward stronger meridional thermal gradients. Reduced ITF, caused by the northward movement of Australia and uplift of Indonesia, impeded global thermohaline circulation, also contributing to late Pliocene Northern Hemisphere cooling via atmospheric and oceanographic teleconnections. Here we present an orbitally tuned high‐resolution sediment geochemistry, calcareous nannofossil, and X‐ray fluorescence record between 3.65 and 2.97 Ma from the northwest shelf of Australia within the Leeuwin Current. 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

Indonesian Throughflow drove Australian climate from humid Pliocene to arid Pleistocene

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

Compositional results from the Late Miocene and Pliocene of Sites U1514 and U1516: X-ray fluorescence and grain-size measurements

Late Miocene and Pliocene marine sediments were cored at Sites U1514 and U1516 in the Mentelle Basin offshore Western Australia, as part of the International Ocean Discovery Program Expedition 369. Core samples were investigated to assess the chemical and physical compositional of these unconsolidated sediments, using X-Ray Fluorescence (XRF) and Grain-size analysis. XRF measurements on discrete samples (WD-XRF) were performed at the University of Oldenburg with a Panalytical AXIOS Plus spectrometer, in 63 samples from Site U1516 (Table S1) and 16 samples for Site U1514 (Table S2). Sediment sample splits were ground and homogenized in an agate ball mill. Glass beads were prepared from the sample powder after pre-oxidation with 1 g of ammonium nitrate using di-lithium tetraborate as a flux (700 mg sample, 4.2 g flux). Calibration of the XRF instrument was based on 52 international reference samples and in-house standards. Precision was determined from the pooled standard deviation of several duplicates and is better than 3% for major elements and better than 5% for trace elements when concentrations were above the detection limit. Grain-size measurements were conducted in 153 samples from Site U1516 (Table S3) using a Mastersizer 3000 laser diffraction particle analyzer at the Institute for Geophysics at the University of Texas at Austin. Dry samples were disaggregated and homogenized in water under sonic dispersion using a Hydro LV cylinder, mixing at 2800 rpm. Samples were added to the solution until obscuration values remained stable. Three measurements were performed on each sample and the median spectra were then processed