Single-grain and multigrain luminescence dating of on-ice and lake-bottom deposits at Lake Hoare, Taylor Valley, Antarctica

The large radiocarbon (C-14) 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) C-14 results. Near-core-top PSL age estimates ranged from zero to similar 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 C-14 dating, at least in Lake Hoare, because PSL dating lacks a significant 'zero-point' offset such as the C-14 reservoir effect, and because PSL dating of quartz is applicable to samples as old as similar to 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. (C) 2010 Elsevier B.V. All rights reserved.