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Data files for rock magnetic data collected on discrete samples at the Institute for Rock Magnetism, University of Minnesota on a Quantum Designs Magnetic Properties System 3 (MPMS3) and Lakeshore Model 8600 Vibrating Sample Magnetometer (VSM). Data include Field Cooled (FC), Zero Field Cooled (ZFC), and Low Temperature Cycling of Room Temperature Saturation Isothermal Remanent Magnetization (LTC-RTSIRM) curves measured on the MPMS and Hysteresis Loops, Direct Current Demagnetization Curves, and Hysteresis Loops collected on the VSM. 

{"Abstract":["Supplementary tables in support of "Antarctic response to orbital forcing during the intensification of extensive bipolar glaciation (1.75-3.30 Ma) from relative paleomagnetic intensity (RPI) stratigraphy of the Dove Basin, Scotia Sea, in Iceberg Alley.""]} 

Abstract The Antarctic ice sheet blankets >99% of the continent and limits our ability to study how subglacial geology and topography have evolved through time. Ice-rafted dropstones derived from the Antarctic subglacial continental interior at different times during the late Cenozoic provide valuable thermal history proxies to understand this geologic history. We applied multiple thermochronometers covering a range of closure temperatures (60–800 °C) to 10 dropstones collected during Integrated Ocean Drilling Program (IODP) Expedition 318 in order to explore the subglacial geology and thermal and exhumation history of the Wilkes Subglacial Basin. The Wilkes Subglacial Basin is a key target for study because ice-sheet models show it was an area of ice-sheet retreat that significantly contributed to sea-level rise during past warm periods. Depositional ages of dropstones range from early Oligocene to late Pleistocene and have zircon U-Pb or 40Ar/39Ar ages indicating sources from the Mertz shear zone, Adélie craton, Ferrar large igneous province, and Millen schist belt. Dropstones from the Mertz shear zone and Adélie craton experienced three cooling periods (1700–1500 Ma; 500–280 Ma; 34–0 Ma) and two periods of extremely slow cooling rates (1500–500 Ma; 280–34 Ma). Low-temperature thermochronometers from seven of the dropstones record cooling during the Paleozoic, potentially recording the Ross or Pan-African orogenies, and during the Mesozoic, potentially recording late Paleozoic to Mesozoic rifting. These dropstones then resided within ~500 m of the surface since the late Paleozoic and early Mesozoic. In contrast, two dropstones deposited during the mid-Pliocene, one from the Mertz shear zone and one from Adélie craton, show evidence for localized post-Eocene glacial erosion of ≥2 km. 

Glacial-marine sediments from the Antarctic continental margin provide a record of depositional environment, oceanographic variability and ice dynamics that is tapped with scientific ocean drilling. This study focuses on Ocean Drilling Program Core 693A-2R, a 9.7 m sediment core retrieved from near the continental margin of the Archean Grunehogna Craton in Dronning Maud Land (DML), East Antarctica. The results contribute to a better understanding of ice-shelf behavior in DML during the mid-Pleistocene transition (MPT), a well-known transition from 40-kyr to 100-kyr cycle periods. The age model, constructed based on Sr isotope stratigraphy and geomagnetic reversals, indicates that the core spans 1.20 to 0.65 Ma. The dynamic behavior of DML ice shelves with periodic iceberg calving is revealed by the glacial–interglacial variation in sedimentation patterns, with interglacials characterized by higher concentrations of ice-rafted debris (IRD) associated with enhanced paleo- productivity than glacial intervals. The responses of DML ice shelves to warm climates are represented by a prolonged interglacial period at 1.0–1.1 Ma (MIS 31–27) and significant interglacial expressions during MIS 19 and 17. The 40Ar/39Ar ages of individual ice-rafted hornblende grains are compared with the on-land geology of DML and neighboring regions to determine the provenances of IRD. Specifically, 40Ar/39Ar results record pri- marily late Neoproterozoic to Cambrian ages (600–400 Ma) with a predominant peak of 520–480 Ma. This Pan- African/Ross orogeny signature is very common in East Antarctica but is not found in the most proximal margin of the Grunehogna Craton, and is instead associated with the region of DML several hundred kilometers east of the deposition site. This indicates that significant discharges of icebergs occurred in the remote DML, which were then transported by the westward-flowing Antarctic Coastal Current to deposit IRD at the studied site during the MPT. This study establishes a confirmed MPT sedimentary sequence off DML, against which future MPT proxy records from the Weddell Sea embayment and other sectors in Antarctica can be compared and correlated, and provides a basis for more detailed analyses of the response of DML ice sheet to Pleistocene climate variations. 

{"Abstract":["Rock magnetic data from IODP Exp. 382 Sites U1537 and U1538 to support Reilly et al. "A geochemical mechanism for >10 m offsets of magnetic reversals inferred from the comparison of two Scotia Sea drill sites"\nExcel Files:\n\nU1537_CubeSummary_Zenodo.xlsx : Summary of NRM, ARM, IRM, and magnetic susceptibility investigations on U1537 cube samples\nU1538_CubeSummary_Zenodo.xlsx : Summary of NRM, ARM, IRM, and magnetic susceptibility investigations on U1538 cube samples\nZip Files:\n\nFORC_Data.zip : First order reversal curve data files in MicroMag format for samples discussed in paper\nDCD_Data.zip : DC Demagnetization curve data files for samples discussed in paper\nHysteresis_Data.zip : Hysteresis Loops for samples discussed in paper\nMPMS_Data.zip : Data collected on Magnetics Property Measurement System 3, including Field Cooled/Zero Field Cooled Curves, Low Temperature Cycling of Room Temperature IRM, and AC Susceptibility\n \nNRM = Natural Remanent Magnetization; ARM = Anhysteretic Remanent Magnetization; IRM = Isothermal Remanent Magnetization"]} 

Paleomagnetic, rock magnetic, or geomagnetic data found in the MagIC data repository from a paper titled: A Geochemical Mechanism for >10 m Apparent Downward Offsets of Magnetic Reversals Inferred From Comparison of Two Scotia Sea Drill Sites 

Abstract Over the last 3.3 million years, the Antarctic Ice Sheet (AIS) has undergone phases of ice sheet growth and decay, impacting sea level and climate globally. Presently, the largely marine‐terminating AIS loses mass primarily by iceberg calving and basal melt of ice shelves. Quantifying past rates and timing of AIS melt is vital to understanding future cryosphere and sea level changes. One proxy for past ice sheet instabilities is iceberg rafted debris (IRD) fluxes. However, traditional methods of IRD quantification are labor‐intensive. Here, we present a new method of identifying IRD grains in sediment core X‐ray images using a convolutional neural network machine learning algorithm. We present a 3.3‐million‐year record of AIS IRD melt events using sediment cores from International Ocean Discovery Program Sites U1536, U1537, and U1538 in the Southern Ocean's “Iceberg Alley.” We identify two increases in the IRD fluxes throughout this period, at ∼1.8 and 0.43 Ma. We propose that after 1.8 Ma, the AIS expanded and transitioned from a primarily terrestrial‐terminating to a primarily marine‐terminating ice sheet. Therefore, after 1.8 Ma, glacial terminations and AIS iceberg discharge are associated with variations in global ice volume, presumably through the mechanism of sea level and, therefore, grounding line change. The second AIS regime change occurs during the Mid‐Brunhes Event (∼0.43 Ma). After this time, there are heightened and continuous IRD fluxes at each glacial termination, indicating increased AIS size and instability after this time. 

Abstract We document an apparent downward displacement of the Matuyama‐Brunhes magnetic reversal by ∼20 m at Scotia Sea International Ocean Discovery Program Site U1538 (Pirie Basin) by comparison with the well‐defined paleomagnetic record at nearby Site U1537 (Dove Basin). Detailed stratigraphic correlation between the two sites is possible due to similar lithologic variations. However, the two sites have distinctly different porewater geochemistry. Notably, Site U1538 indicates a greater demand for electron acceptors to oxidize organic carbon and Fe²⁺enrichment below the depth of SO₄²⁻depletion. Magnetic parameters indicate enrichment of an authigenic magnetic mineral with strong remanence properties around the depth of SO₄²⁻depletion (∼46 m at Site U1538) relative to magnetic parameters at correlative depths at Site U1537. Fe²⁺enrichment below the depth of SO₄²⁻depletion is not predicted based on the energetically favorable order of electron acceptors for microbial respiration but is documented here and in other depositional settings. This indicates Fe²⁺production exceeds the production of H₂S by SO₄²⁻reduction, providing a geochemical environment that favors the production and preservation of ferrimagnetic remanence‐bearing iron sulfides over paramagnetic pyrite and, thus, a mechanism for deep chemical remanent magnetization acquisition at depths of tens of meters. The influence of authigenic ferrimagnetic iron sulfides on paleomagnetic signals can be difficult to demonstrate with magnetic properties alone; therefore, this finding has implications for evaluating the fidelity of magnetostratigraphic records with complementary geochemical data. Such situations should be considered in other depositional environments with similar porewater Fe²⁺accumulation below the SO₄²⁻reduction depth.