Single-grain and multigrain luminescence dating of on-ice and lake-bottom deposits at Lake Hoare,Taylor Valley,Antarctica |
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| Authors: | GW Berger PT Doran KJ Thomsen |
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| Institution: | 1. Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA;2. Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA;3. Radiation Research Department, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, P.O. 49, DK-4000 Roskilde, Denmark |
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| Abstract: | The large radiocarbon (14C) reservoir effect in Antarctica varies regionally and with settings. Luminescence sediment dating has potential as an alternate geochronometer. Extending our earlier tests of the effectiveness of resetting of photon-stimulated-luminescence (PSL) that employed only multi-aliquot analyses of fine-silt grains, we applied single-aliquot multigrain, and single-grain-quartz (SGQ) PSL procedures to a variety of samples from on and under the meters-thick perennial ice cover at Lake Hoare. These procedures yielded quartz sand age estimates for ice-surface sand (the source of the lake-bottom sand) of 10–80 a. Sand within a small dune on the perennial lake ice in front of Canada Glacier gave an SGQ age estimate of 48 ± 23 a. These methods produced realistic age estimates in lake-bottom short cores that are at least 5–20 times younger than comparable (uncorrected-for-reservoir) 14C results. Near-core-top PSL age estimates ranged from zero to ～500 a, depending on the core site. Four of the 7 short cores revealed clear linear age-depth trends for the upper few cm of core. These results demonstrate that for such lake-core deposits, single-aliquot and single-grain PSL dating can replace 14C dating, at least in Lake Hoare, because PSL dating lacks a significant ‘zero-point’ offset such as the 14C reservoir effect, and because PSL dating of quartz is applicable to samples as old as ～150 ka under normal sedimentary conditions. Moreover, these results imply that isolated paleo-lake-bottom deposits (e.g., microbial-mat sand mounds above present lake levels) throughout the McMurdo Dry Valleys can now be dated directly. |
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