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This dataset contains uranium and thorium isotopic compositions (U-234, U-235, U-238, Th-230, Th-232) and major element compositions (Al, K, Na, Ca, Fe, Mn, reported as oxides) for silicate sediments from glaciogenic drifts associated with advances of Taylor Glacier in Taylor Valley, Antarctica. Isotopic measurements were obtained by ID-TIMS in the Keck Isotope Facility at UC Santa Cruz and elemental measurements were obtained by ICP-OES in the Plasma Analytical Laboratory. All measurements include fully propagated analytical and systematic (e.g. isotopic tracer) uncertainties. Chemical index of alteration was calculated from major element data. Prior to measurements, sediments were sieved to ≤125 μm grain sizes, separated into quartz-feldspar-rich and clay-rich aliquots by hydraulic settling, and subjected to sequential chemical extractions ("leaching") prior to silicate digestion.
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Uranium-series isotopes as tracers of physical and chemical weathering in glacial sediments from Taylor Valley, Antarctica
The McMurdo Dry Valleys of Antarctica formed by extensive glacial erosion, yet currently exhibit hyperarid polar conditions canonically associated with limited chemical and physical weathering. Efficient chemical weathering occurs when moisture is available, and polythermal subglacial conditions may accommodate ongoing mechanical weathering and valley incision. Taylor Valley, one of the MDV, hosts several Pleistocene glacial drift deposits that record prior expansions of Taylor Glacier and sediment redistribution, if not sediment production. We present U-series isotopics of fine-grained sediments from these drifts to assess the timescales of physical weathering and subsequent chemical alteration. The isotopes 238U, 234U, and 230Th are sensitive to both chemical and physical fractionation processes in sedimentary systems, including the physical fractionation of daughter isotopes by energetic recoil following radioactive decay. By comparing U-series isotopic measurements with models of U-series response to chemical weathering and physical fractionation processes, we show that Pleistocene drift sediments record histories of significant chemical alteration. However, fine-grained sediments entrained in the basal ice of Taylor Glacier record only minor chemical alteration and U-series fractionation, indicating comparatively recent sediment comminution and active incision of upper Taylor Valley by Taylor Glacier over the Pleistocene. In addition, the results of this study emphasize the utility of U-series isotopes as tracers of chemical and physical weathering in sedimentary and pedogenic systems, with particular sensitivity to radionuclide implantation by α-recoil from high-U authigenic phases into lower-U detrital phases. This process has occurred extensively in >200 ka drifts but to a lesser degree in younger deposits. U-series α-recoil implantation is an important physicochemical process with chronometric implications in other hyperarid and saline sedimentary systems, including analogous Martian environments.
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- Award ID(s):
- 2102591
- PAR ID:
- 10560400
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Chemical Geology
- Volume:
- 671
- ISSN:
- 0009-2541
- Page Range / eLocation ID:
- 122463
- Subject(s) / Keyword(s):
- Uranium-series geochemistry Chemical weathering Comminution McMurdo Dry Valleys Antarctica Glacial erosion
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.chemgeo.2024.122463
