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{"Abstract":["This dataset consists of detrital zircon U-Pb data from samples from the Amundsen Sea Embayment. The data are a product of the publication: "Reconstructing Eocene Antarctic river drainage from provenance analysis of Amundsen Sea Embayment sediments".\n\nIncluded are data from three Holocene sediment samples strategically located around the embayment to help characterise the detritus currently being eroded and deposited in the Amundsen Sea. Samples comprise of locations proximal to Pine Island Glacier and Thwaites Glacier, with a further sample to the north of Thwaites Glacier. A fourth sample consists of Cretaceous mudstone from a drill core from site PS104_20-2 in the Amundsen Sea Embayment.\n\nA second file contains a compilation of selected detrital zircon U-Pb dates from potential source areas around West Antarctica. These include the sedimentary rocks of the Swanson Formation and Ellsworth-Whitmore Mountains, as well as all published West Antarctic subglacial till data. Data from moraines in the Transantarctic Mountains are also included."]} 

List of sample locations and fission track data produced at the University of Arizona under NSF Proposal 1917009 "Collaborative Research: ICe sheet erosional Interaction with Hot geotherm (ICI-Hot) in West Antarctica 

List of supplementary data produced at the University of Arizona under NSF Proposal 1917009 from publication Marschalek, J.W., Thomson, S.N., Hillenbrand, C.-D., Vermeesch, P., Siddoway, C., Carter, A., Nichols, K., Rood, D.H., Venturelli, R.A., Hammond, S.J., Wellner, J., Van De Flierdt, T., 2024. Geological insights from the newly discovered granite of Sif Island between Thwaites and Pine Island glaciers. Antarctic Science 36, 51–74. https://doi.org/10.1017/S0954102023000287 

List of supplementary data produced at the University of Arizona under NSF Proposal 1917009 from publication Marschalek, J.W. et al., 2024a, Byrd Ice Core Debris Constrains the Sediment Provenance Signature of Central West Antarctica: Geophysical Research Letters, v. 51, p. e2023GL106958. 

Sedimentary records can illuminate relationships between the climate, topography, and glaciation of West Antarctica by revealing its Cenozoic topographic and paleoenvironmental history. Eocene fluvial drainage patterns have previously been inferred using geochemical provenance data from an ~44– to 34–million year deltaic sandstone recovered from the Amundsen Sea Embayment. One interpretation holds that a low-relief, low-lying West Antarctic landscape supported a >1500-kilometer transcontinental river system. Alternatively, higher-relief topography in central West Antarctica formed a drainage divide between the Ross and Amundsen seas. Here, zircon U-Pb data from Amundsen Sea Embayment sediments are examined alongside known regional bedrock provenance signatures. These analyses suggest that all observed provenance indicators in the Eocene sandstone derive from West Antarctic rocks. This implies that a local river system flowed off a West Antarctic drainage divide, helping constrain the mid-Late Eocene evolution of West Antarctic topography with implications for the history of rifting and the characteristics of sediments infilling interior basins. 

In 2019, International Ocean Discovery Program (IODP) expeditions to offshore West Antarctica recovered deep ocean sediment cores in the outer Amundsen Sea (Exp. 379) and Dove Basin (Exp. 382). These cores are characterized by numerous ice-rafted detritus (IRD) intervals, including dropstone cobbles released by icebergs calved from past glaciers/ice streams that incised the subglacial bedrock of West Antarctica. We selected nine dropstones from latest Miocene through mid-Pliocene sediment from IODP Sites U1532C, U1533B (Exp. 379) and U1536E (Exp. 382), comprising sandstone, diorite, granitoid, basalt, and rhyolite, for petrologic characterization and multi-method geo-thermochronology. Dating methods applied include U-Pb zircon (UPbZ) geochronology, and apatite fission-track (AFT) and (U-Th)/He (AHe) low-temperature thermochronology, to reveal dates and rates of geologic events with bearing on their crustal provenance and source region bedrock thermal history. Comparison to published data reveal dropstones to be of both local and distant origin. Notable discoveries are: 1) From U1536E, a ~1200 Ma [U-PbZ] diorite cobble, with ca. 130 Ma AFT and 65-50 Ma AHe ages that most resembles cratonic crust of Queen Maud Land (East Antarctica). 2) Three granitoid rocks from U1533B with ca. 174-179 Ma (UPbZ) ages. The only known rocks of similar age and lithology in West Antarctica are described in the Whitmore Mountains (WM). AFT ages of 114 Ma, 91 Ma, and 81 Ma may thus provide the first thermochronology data from the WM. 3) A 27±1 Ma (UPbZ) diorite of from U1533B records 25.6 Ma AFT and 10.6 Ma AHe ages, suggesting origins in the western Antarctic Peninsula. 4) Two very similar distinctive green quartz arenite dropstones were recovered from latest Miocene core at U1533B and U1536E, locations separated by 3270 km. Multivariate statistical comparison of their UPbZ age populations with published data indicates a common provenance in the Ellsworth Mountains (Antarctic interior). When placed within geotectonic and paleoclimate context, discoveries from IRD-dropstones promise to advance understanding of crustal and landscape evolution of evolution of glaciated continents, variations in icesheet extent during warm periods, and ocean/atmospheric current circulation. 

The Cenozoic tectonic history of Marie Byrd Land (MBL), West Antarctica, is dominated by uplift of the MBL dome, a ~800 by ~300 km topographic swell thought to be supported by a hot mantle anomaly, and normal faulting accompanying extension of the West Antarctic rift system (WARS). Additionally, glaciation beginning at 34 – 20 Ma resulted in deeply incised glacial troughs with up to 5km of relief. This study investigates the timing, magnitude, and spatial relationships of these tectonic and erosional events by determining a regional exhumation history of western MBL through thermo-kinematic modeling of low-temperature thermochronologic data. New apatite (U-Th)/He (AHe) analyses include ages between 46 – 63 Ma, significantly younger than previously determined ages between 80 – 100 Ma. 3D thermo-kinematic modeling reveals focused glacial incision alone is incapable of producing this young population of AHe ages, indicating additional exhumation processes have been at work since ~80 Ma. Differential exhumation across western MBL is required to produce the range of observed AHe ages, with laterally variable exhumation ranging from little to none on the Edward VII Peninsula to ~0.04 km/myr in the eastern Ford Ranges. This spatial pattern is consistent with enhanced exhumation related to uplift of the MBL dome in the eastern Ford Ranges, with this effect diminishing westward to the Edward VII Peninsula. A sharp change in exhumation rate in the western Ford Ranges suggests recent motion on inferred normal faults consistent with WARS extension and down-dropping of the Edward VII Peninsula. Models based on available bedrock data provide little insight into the timing and magnitude of glacial incision due to the present inability to directly sample bedrock in deep glacial troughs. However, model predictions of bedrock low-temperature age distributions within glacial troughs are useful as a point of comparison for detrital age distributions. New detrital AHe ages from Sulzberger Bay, offshore western MBL, range from 49 – >100 Ma and are consistent with model age distributions. These model results support a complex, spatially heterogeneous exhumation history for western MBL tied to its position between the MBL dome and the WARS and provide insight into the impact of glacial incision across the regional landscape. 

Marie Byrd Land (MBL), West Antarctica, is poorly studied geologically due to its ice cover and remoteness. As a result, the timing and magnitude of tectonic and erosional events, such as the tectonic uplift of the Marie Byrd Land dome and the incision of the DeVicq Glacial Trough, are debated. When faced with problems difficult to study and solve through in-person field work, it becomes necessary to turn to modeling. Pecube is a thermo-kinematic modeling program that uses topographic and crustal thermal data to calculate thermochronologic ages across a landscape. Thermochronology uses radiometric dating of mineral systems that are sensitive to specific temperatures and can be used to track cooling related to the tectonic and exhumation history of a region. Model predictions can be compared to observed ages to test the viability of tectonic or geomorphic scenarios. Observed ages used here include dates derived from apatite fission track analysis (AFT; closure temperature ~ 110 °C) and apatite (U-Th)/He dating (AHe; closure temperature ~ 60 °C) of detrital material recovered from offshore MBL that presumably originated from the DeVicq Trough region of MBL. Ongoing modeling efforts will determine how closely calculated bedrock ages compare to new detrital AHe ages, ranging from 23.5-82.8 Ma, and AFT ages, ranging from 49.7-83.6 Ma. These ages broadly correspond to late breakup of Gondwana (~100-85Ma), erosion during and after the uplift of the Marie Byrd Land dome (~30Ma), and glacial incision (beginning at 34 or 20Ma). In light of these new data, alterations were made to existing Pecube models for the DeVicq Trough region to rule out and narrow down the timings and rates possible for both glacial incision at the DeVicq Glacial Trough and exhumation of the Marie Byrd Land dome. Preliminary results suggest that varying glacial incision start time between 34 and 20 Ma, dates proposed for the initiation of the West Antarctic Ice Sheet, does not change resulting bedrock ages significantly. However, varying background exhumation rates results in ages that are broadly consistent with observed ages. Ongoing modeling efforts seek to refine this range further to give insight on the exhumation history and tectonic processes of this region. 

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.