Trace metal concentrations are reported in micrograms per gram of sediment in core C012-PC05 (64⁰ 40.517’ S, 119⁰ 18.072’ E, water depth 3104 m). Each sediment sample (100-200mg) was ground using a pestle and mortar and digested following an initial oxidation step (1:1 mixture of H2O2 and HNO3 acid) and open vessel acid on a 150 degree C hotplate using 2:5:1 mixture of concentrated distilled HCl, HNO3 and Baseline Seastar HF acid. After converting the digested sample to nitric acid, an additional oxidation step was performed with 1:1 mixture of concentrated distilled HNO3 and Baseline Seastar HClO4 acid. A 10% aliquot of the final digestion was sub-sampled for trace metal analyses. Trace metal concentrations were determined by external calibration using an ELEMENT 2 sector field ICP-MS from Thermo Fisher Scientific (Bremen, Germany) at Central Science Laboratory (University of Tasmania). The following elements were analysed in either low (LR) or medium resolution (MR): Sr88(LR), Y89(LR), Mo95(LR), Ag107(LR), Cd111(LR), Cs133(LR), Ba137(LR), Nd146(LR), Tm169(LR), Yb171(LR), Tl205(LR), Pb208(LR), Th232(LR), U238(LR), Na23(MR), Mg24(MR), Al27(MR), P31(MR), S32(MR), Ca42(MR), Sc45(MR), Ti47(MR), V51(MR), Cr52(MR), Mn55(MR), Fe56(MR), Co59(MR), Ni60(MR), Cu63(MR), Zn66(MR).

Sediment cores were collected from the East Antarctic margin, aboard the Australian Marine National Facility R/V Investigator from January 14th to March 5th 2017 (IN2017_V01; (Armand et al., 2018). This marine geoscience expedition, named the “Sabrina Sea Floor Survey”, focused notably on studying the interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles. The cores were collected using a multi-corer (MC), were sliced every centimetre, wrapped up in plastic bags, and stored in the fridge. Back at the home laboratory (IMAS, UTAS, Hobart, Australia), sediment samples were dried in an oven at 40°C. Three hundred mg of dry sediment was then homogenised and vortexed for 10-sec with 12 mL of a reductive solution of 0.005M hydroxylamine hydrochloride (HH) / 1.5% Acetic Acid (AA) / 0.001M Na-EDTA / 0.033M NaOH, at pH 4 (Huang et al., 2021). The sediment was then leached a second time (to ensure the removal of all oxides and excess minerals, i.e. to isolate the detrital fraction) with 15 mL of 0.02M HH, 25% AA solution and agitated using a rotisserie (20 rpm) overnight (Wilson et al., 2018). Samples were then centrifuged, rinsed with Milli-Q water 3 times, and dried in an oven at 50°C. About 50 mg of resulting dry (detrital) sediment was ground, weighed into a Teflon vial, and digested with a strong acid mixture. First, the sediment was oxidized with a mixture of concentrated HNO3 and 30% H2O2 (1:1). Samples were then digested in open vials using 10 mL HNO3, 4 mL HCl, and 2 mL HF, at 180°C until close to dryness. Digested residues were converted to nitric form before being oxidised with a mixture of 1 mL HNO3 and 1 mL HClO4 at 220°C until fully desiccated. Samples were finally re-dissolved in 4 mL 7.5 M HNO3. A 400 μL aliquot was removed from the 4 mL digest solution and diluted ~2500 times in 2% HNO3 for trace metals analysis by Sector Field Inductively Coupled Mass Spectrometry (SF-ICP-MS, Thermo Fisher Scientific, Bremen, Germany) at the Central Science Laboratory (UTAS, Hobart, Australia). Indium was added as internal standard (In, 100 ppb). 88Sr, 89Y, 95Mo, 107Ag, 109Ag, 111Cd, 133Cs, 137Ba, 146Nd, 169Tm, 171Yb, 185Re, 187Re, 205Tl, 208Pb, 232Th, 238U, 23Na, 24Mg, 27Al, 31P, 32S, 42Ca, 47Ti, 51V, 52Cr, 55Mn, 56Fe, 59Co, 60Ni, 63Cu and 66Zn were analysed using multiple spectral resolutions. Element quantification was performed via external calibration using multi-element calibration solutions (MISA suite, QCD Analysts, Spring Lake, NJ, USA). Raw intensities were blank and dilution corrected. References Armand, L. K., O’Brien, P. E., Armbrecht, L., Baker, H., Caburlotto, A., Connell, T., … Young, A. (2018). Interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles (IN2017-V01): Post-survey report. ANU Research Publications Huang, H., Gutjahr, M., Kuhn, G., Hathorne, E. C., and Eisenhauer, A. (2021). Efficient Extraction of Past Seawater Pb and Nd Isotope Signatures From Southern Ocean Sediments. Geochemistry, Geophysics, Geosystems, 22(3), 1–22. Wilson, D. J., Bertram, R. A., Needham, E. F., van de Flierdt, T., Welsh, K. J., McKay, R. M., … Escutia, C. (2018). Ice loss from the East Antarctic Ice Sheet during late Pleistocene interglacials. Nature, 561(7723), 383.

Marine sediments often represent an important reservoir of carbonate minerals that will react rapidly to changing seawater chemistry as a result of ocean acidification. Ocean acidification (the reaction of CO2 with seawater) lowers the saturation state with respect to carbonate minerals and may lead to dissolution of these minerals if undersaturation occurs. There are three main carbonate minerals found in marine sediments: 1. aragonite 2. calcite (also referred to as low-magnesium calcite, containing less than 4mol% MgCO3) 3. high-magnesium calcite (greater than 4 mol% MgCO3) Due to the different structure of these minerals, they have different solubilities with high-Mg calcite the most soluble, followed by aragonite and then calcite. As seawater CO2 increases and the saturation state with respect to carbonate minerals decreases, high-Mg calcite will be the first mineral subject to undersaturation and dissolution. By measuring the carbonate mineral composition of sediments, we can determine which areas are most at risk from dissolution. This information forms an important baseline with which we can assess future climate change. The effect of ocean acidification on carbonates in marine sediments will occur around the world, but due to the lower seawater temperatures in Antarctica, solubility is much lower so the impacts will occur here first. This dataset is a compilation of carbonate mineralogy data from surface sediments collected from the East Antarctic margin. The dataset includes sample metadata, bulk carbonate content, %calcite, % aragonite and mol% MgCO3 (i.e. the magnesium content of high-Mg calcite). This dataset was compiled from new (up to 2020) and archived sediment samples that contacted sufficient carbonates (typically greater than 3% CaCO3)/

Sediment cores were collected from the East Antarctic margin, aboard the Australian Marine National Facility R/V Investigator from January 14th to March 5th 2017 (IN2017_V01; Armand et al., 2018). This marine geoscience expedition, named the “Sabrina Sea Floor Survey”, focused notably on studying the interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles. The cores were collected using a multi-corer (MC) and a Kasten corer (KC). The MC were sliced every centimetre, wrapped up in plastic bags, and stored in the fridge. The KC was sub-sampled using an u-channel; and sliced every centimetre once back the home laboratory (IMAS, UTAS, Hobart, Australia). This dataset presents concentrations of major and trace elements measured in bulk multi-cores sediment samples collected during the IN2017_V01 voyage. The data include the sampling date (day/month/year), the latitude and longitude (in decimal degrees), the seafloor depth (in meter), the sediment core ID, the sediment depth (in cm), and the concentrations (in ppm or μg/g) of a suite of elements. This dataset presents concentrations of major and trace elements measured in bulk sediment samples collected during the IN2017_V01 voyage. The data include the sampling date (day/month/year), the latitude and longitude (in decimal degrees), the seafloor depth (in meter), the sediment core ID (KC14), the sediment depth (in cm), and the concentrations (in ppm or μg/g) of a suite of elements. About 200 mg of dried and ground sediment were weighed into a clean Teflon vial and oxidized with a mixture of concentrated HNO3 and 30% H2O2 (1:1). Samples were then digested in open vials using an acid mixture comprising 10 mL HNO3, 4 mL HCl, and 2 mL HF, at 180°C until close to dryness. Digested residues were converted to nitric form before being oxidised with a mixture of 1 mL HNO3 and 1 mL HClO4 at 220°C until fully desiccated. Samples were finally re-dissolved in 4 mL 7.5 M HNO3. A 400 μL aliquot was removed from the 4 mL digest solution and diluted ~2500 times in 2% HNO3 for trace metals analysis by Sector Field Inductively Coupled Mass Spectrometry (SF-ICP-MS, Thermo Fisher Scientific, Bremen, Germany) at the Central Science Laboratory (UTAS, Hobart, Australia). Indium was added as internal standard (In, 100 ppb). 88Sr, 89Y, 95Mo, 107Ag, 109Ag, 111Cd, 133Cs, 137Ba, 146Nd, 169Tm, 171Yb, 185Re, 187Re, 205Tl, 208Pb, 232Th, 238U, 23Na, 24Mg, 27Al, 31P, 32S, 42Ca, 47Ti, 51V, 52Cr, 55Mn, 56Fe, 59Co, 60Ni, 63Cu and 66Zn were analysed using multiple spectral resolutions. Element quantification was performed via external calibration using multi-element calibration solutions (MISA suite, QCD Analysts, Spring Lake, NJ, USA). Raw intensities were blank and dilution corrected. References L.K. Armand, P.E. O’Brien and On-board Scientific Party. 2018. Interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles (IN2017-V01): Post-survey report, Research School of Earth Sciences, Australian National University: Canberra.

Amery Ice Shelf AM06 borehole drilled early January 2010. Sub-shelf water profiling measurements conducted over a period of a few days. Partial video recording of borehole walls and sea floor benthos. Collection of targeted ice core samples. Sediment sample collected from sea floor. Long term monitoring instruments installed (thermistors in ice, 3 x CTD in ocean cavity). This is a parent record - see the child records for further information, and access to the data. Some general readme documents are available for download from the provided URL.

Although oceanic crust covers about 60% of the Earth, relatively little is known of its geology and the processes that have created it. Macquarie Island represents a unique subaerial exposure of the seafloor, and an exceptional environment for active study and research into the ocean crust. We plan to utilise geological and geophysical techniques to help us better understand the lithological complexity and evolution of the oceanic crust. Project objectives: Our primary objective is to conduct coordinated ground- and air-based magnetic and electromagnetic surveys of the oceanic crust that comprises Macquarie Island and the surrounding seafloor for ~ 5 km from the island. We will integrate these geophysical data with the results of our recent studies of the Island and additional follow-up geological investigations. Together these data will improve our understanding of the tectonic and hydrothermal evolution of Macquarie Island ocean crust and through it, the evolution of oceanic crust in a more general sense. We believe the acquisition of these data will allow us to: (1) better resolve the complex geologic structure of the island; (2) determine the three-dimensional extent of the hydrothermal alteration of this example of oceanic crust; (3) map active fault zones across the island; and (4) correlate the geology of the Island with the offshore geology, linking it to regional data sets and the nearby active plate boundary. The dataset has two forms. The main dataset is magnetic field data recorded in the Bauer Bay to Boot Hill area of Macquarie Island, on 200 m line spacings (csv file). The subsidiary dataset are sample locations for the same area for a small set of rock samples obtained to check on magnetic character (word file). Data were collected using a GEM Systems GSM-19 Overhauser Magnetometer. The fields in this dataset are: Easting Northing Sample Rock Type Magnetic Intensity (nT) Taken from the 2008-2009 Progress Report: Progress against objectives: This project was in abeyance for the 2007-8 season due to our scientific field program being postponed as a necessity of the rabbit eradication program on Macquarie Island. A detailed study of the formation of specific magnetic lows from our regional ground magnetic survey, with the aim of determining their cause, and gaining insight into interpretation of magnetic lows in ocean crust in general. Hydrothermal alteration in ocean crust typically results in magnetic lows because it involves magnetite destruction. However, it is apparent that on Macquarie Island this is not the only cause of magnetic lows. There are 5 principal study sites: (1) Prion Lake to Brothers Point, and including the Mt Tulloch summit and slopes; (2) Waterfall Lake and surrounds; (3) Hurd Point to the coast immediately east of Mt Jefferies; (4) East Ainsworth area, east of the Caroline Cove protection zone; (5) Whisky Creek area, cutting through the eastern escarpment ~ 5 km north of Hurd Point. The 2008-9 season has involved (1) compiling of geological mapping from each site and rectification with the available topographic base and most recent satellite imagery; (2) processing of magnetic data from each of the detailed surveys; (3) extraction of field observations into a digital database that can be accessed within his GIS platform; (4) petrographic description of ~100 polished thin sections to evaluate magnetite behaviour; and (5) a brief return to Macquarie Island to attempt to infill areas of geological data/sample deficiency. In terms of the objective of correlating the geology of the island with the offshore geology, this has been in process within the USGS under the supervision of Dr Carol Finn. This part of the project is employing heli-magnetics obtained with the cooperation of AAD during resupply, using a USGS instrument The data was partly processed at Utas by Dr Michael Roach, and then transferred on for more detailed processing at the USGS.

Metadata record for data from ASAC Project 2592 See the link below for public details on this project. The Southern Ocean is one the most significant regions on earth for regulating the build up of anthropogenic carbon in the atmosphere, and the capacity for carbon uptake in the region could be altered by climate change. The project aims to use repeat ocean sections to detect anthropogenic carbon storage, identify key processes regulating the amount of storage, and to test models that predict future uptake. The data are broken down by season and voyage, and a word document providing further details about the project is also available as part of the download file.

These dataset files (2 tables) are supplementary material to: Halpin, J.A., Daczko, N.R., Direen, N.G., Mulder, J.A., Murphy, R.C., Ishihara, T., 2020. Provenance of rifted continental crust at the nexus of East Gondwana breakup. Lithos 354-355. https://www.sciencedirect.com/science/article/pii/S0024493719305237?via%3Dihub https://doi.org/10.1016/j.lithos.2019.105363 They include: Supplementary Table 1. Zircon U-Pb datasets Supplementary Table 2. Zircon Lu-Hf datasets Sample details from Halpin et al. (2020): Ishihara et al. (1996) made initial reports of the dredge sites from which our analyses have been made. Dredging at four sites on the eastern margin of the Bruce Rise was undertaken during cruise TH-94 of the R/V Hakurei-Maru during the austral summer of 1994/5, along with other geophysical data acquisition reported in Ishihara et al. (1996). Of the four sites dredged, sites D1502, D1503 and D1504 all recorded hauls of basement rocks, including crystalline basement fragments. These dredge sites and hauls are summarised in Table 1. The recovered dredge samples have variable shapes, but the samples analysed here (two granites from D1502; Fig. 3) contain sharp and unweathered faces consistent with dredging from in situ basement. The interpretation of composite seismic profiles TH94/21 and GA-229/19 from the eastern flank of the Bruce Rise (Fig. 1b) shows a folded and faulted syn-rift sequence that thickens towards the south and is separated from flat-lying post-rift sediments by a prominent erosional unconformity (Stagg et al., 2006). The outermost ridge, flanked by the Vincennes Fracture Zone, is interpreted to comprise exposed crystalline basement, and we interpret the granitic samples studied here to represent parts of this basement complex. Sample D1502-A is a medium to coarse-grained (~2–4 mm) red granite, whereas sample D1502-B is a fine to medium-grained (~1–1.5 mm) cream-grey granite (Fig. 3a). Both samples comprise quartz, plagioclase, alkali feldspars (including microcline), biotite and accessory magnetite and zircon. Sample D1502-B additionally contains minor biotite-amphibole-rich schlieren. Biotite is variably orientated suggesting weak magmatic foliation. The low-strain character of the samples is supported by very limited undulose extinction of some grains, minor development of sub grains in quartz, and preserved igneous microstructures that include subhedral feldspar grains presenting some crystal faces (red lines, Fig. 3b), quartz-feldspar interstitial textures (blue ‘i’, Fig. 3b), low dihedral angles (double blue arrow heads, Fig. 3b), elongate mineral films along grain boundaries that are inferred to have pseudomorphed former melt, and growth twinning in plagioclase. Minor low-temperature alteration of feldspar and biotite to sericite ± chlorite is observed in sample D1502-A. High resolution whole thin section photomicrographs are available at https:// imagematrix.science.mq.edu.au/. Details of analytical methods from Halpin et al. (2020): Initial sample preparation including zircon separation and mounting was performed at Curtin University. Zircon grains were imaged via cathodoluminescence (CL) on a FEI Quanta 600 SEM at the Central Science Laboratory, University of Tasmania, to reveal internal structure in order to optimise and contextualise U-Pb analyses. U-Pb zircon analyses were performed on an Agilent 7500cs quadrupole ICPMS with a 193nm Coherent Ar-F gas laser and the Resonetics S155 ablation cell at the Discipline of Earth Sciences, University of Tasmania. Each analysis was pre-ablated with 5 laser pulses to remove the surface contamination then the blank gas was analysed for 30 s followed by 30 s of zircon ablation at 5 Hz and ~2 J/cm2 using a spot size of 29 μm. Isotopes measured include 49Ti, 56Fe, 91Zr, 178Hf, 202Hg, 204Pb, 206Pb, 207Pb, 208Pb, 232Th and 238U. The down hole fractionation, instrument drift and mass bias correction factors for Pb/U and Pb/Th ratios on zircons were calculated using the primary standard (91500, Wiedenbeck et al., 1995) and secondary standards (TEMORA 1, Black et al., 2003; Plešovice, Sláma et al., 2008) analysed at the beginning of the session and every 15–20 unknowns using the same spot size and conditions as used on the samples to provide an independent control to assess accuracy and precision. The correction factor for the 207Pb/206Pb ratio was calculated using 17 analyses of the international glass standard NIST610 analysed throughout the analytical session and corrected using the recommended values (Baker et al., 2004). All data reduction calculations and error propagations were done within Microsoft Excel® via macros designed at the University of Tasmania (see Halpin et al., 2014; Sack et al., 2011). No common Pb corrections were applied. However, time-resolved isotopic ratios for each analysis were scrutinised on concordia diagrams to investigate the presence of common Pb and/or ancient Pb-loss and/or mixing of age zones, and analyses (or parts of analyses) were excluded from the dataset where a combination of these trends was detected. Uncertainties quoted in Supplementary Tables and in figures are the internal measured uncertainty only (i.e., those from random based sources of error, e.g., counting statistics). External sources of uncertainty (i.e., from systematic sources of uncertainty, e.g., decay constant uncertainty, uncertainty in the age of the primary zircon standard) calculated after Horstwood et al. (2016) and Thompson et al. (2018) are quoted in parentheses for the standard data below (see also Supplementary Table 1). 206Pb/238U ages for the secondary zircon standards Plešovice and TEMORA 1 over the course of this study (at 95% confidence) are 333.6 ± 2.7 (4.3) Ma (n = 7, MSWD = 1.3) and 415.1 ± 3.2 (5.3) Ma (n = 6, MSWD = 0.4), compared to the published TIMS zircon ages of 337.13 ± 0.37 Ma (Sláma et al., 2008) and 416.8 ± 1.1 Ma (Black et al., 2003), respectively. Although Plešovice is slightly outside 2σ of the internal uncertainties, it is well within the published values when considering the external uncertainties. The primary zircon standard 91500 yields a 207Pb/206Pb weighted mean age of 1065.3 ± 8.8 (10.5) Ma (n = 27, MSWD = 0.71) within error of the recommended value of 1065.4 ± 0.3 Ma (Wiedenbeck et al., 1995). Tera-Wasserburg diagrams and age calculations were made using Isoplot v4.11 (Ludwig, 2003). Uncertainties for individual analyses as quoted in text and as error bars on U\\Pb plots have been calculated to the two-sigma level. Weighted mean and intercept ages are reported at 95% confidence limits. Hf isotope analyses were performed in situ on a subset of the same grains analysed for U-Pb using a Photon Machines Excimer 193 nm Ar-F laser ablation micro-probe attached to a Nu Plasma multi- collector (MC)-ICPMS system at Macquarie University GeoAnalytical (MQGA)(see Griffin et al., 2004 for a detailed methodology). A gas blank was analysed for 30 s followed by up to 120 s of ablation at a beam diameter of 40–50 μm, 5 Hz and ~7.5 J/cm2. Zircon CL images were used to ensure that Hf isotope analyses overlapped the same do- main analysed for U-Pb. The Mud Tank and Temora-2 zircon standards were used as a reference standard for Hf analysis; our weighted average 176Hf/177Hf values for these standards are 0.282526 ± 41 (n = 17, MSWD = 1.6) and 0.282678 ± 10 (n = 7, MSWD = 2.1), respectively, within error of the published values of 0.282523 ± 43 (Mud Tank; Griffin et al., 2006) and 0.282680 ± 24 (Temora-2; Woodhead et al., 2004). Uncertainties quoted are the internal measured uncertainty and do not include any propagation of error from the reference standard. The initial 176Hf/177Hf value (Hfi) in zircon is calculated using the measured 176Lu/177Hf, 176Hf/177Hf and apparent 207Pb/206Pb age and the 176Lu decay constant of Scherer et al. (2001) of 1.865 x 10-11. Model age calculations (TDM) are based on a depleted-mantle source with Hfi = 0.279718 and 176Lu/177Hf = 0.0384. This provides a value of 176Hf/177Hf (0.28325) similar to that of average mid-ocean ridge basalt over 4.56 Ga. The calculated TDM ages use the measured 176Lu/177Hf of the zircon and give a minimum age for the source material of the magma from which the zircon crystallised. Two-stage model ages (TDM2) are calculated assuming that the parental magma was derived from the average continental crust (176Lu/177Hf = 0.015), which in turn was originally derived from the depleted mantle.