Surmounting luminescence age overestimation in Alaska-margin Arctic Ocean sediments by use of 'micro-hole' quartz dating

Because of several difficulties with the application of radiocarbon (C-14) dating to Arctic Ocean sediments, numeric dating techniques are needed that can complement, supplant and reach beyond the C-14 method. However, large age overestimates (often >7 kyr) for near-sediment-water-interface horizons from Arctic Ocean cores have been almost universal when luminescence dating has been applied to multigrain aliquots of fine silt (4-11 mu m) quartz and feldspar grains. Here micro-hole quartz-grain photon-stimulated-luminescence (PSL) dating is applied to the 0.5-2.0 cm horizons of multicores from high-sedimentation-rate sites spanning depths from 87 m to 1140 m at the Alaska margin of the Arctic Ocean. Expected near zero ages (0-200 a) result when grains larger than similar to 11 mu m are used, demonstrating that fine-silt age overestimations here and perhaps elsewhere in the Arctic Ocean are a function of grain and aliquot size. At the 87 m site, the micro-hole PSL approach revealed no significant gradient in age estimates over the 1-26 cm horizon range, implying that bioturbation reached to at least 26 cm. Micro-hole PSL dating of 25-62 mu m quartz grains from trans-ocean sea-ice sediment also produced expected near zero ages, in contrast to earlier reported long-bleach multigrain PSL results from 4-11 mu m fractions of the same samples. The micro-hole PSL approach thus surmounts the age overestimation problem associated with the use of multigrain silt fractions, and overcomes limitations of the C-14 method in this region. Finally, results unexpectedly suggest the potential of micro-hole quartz PSL for use in provenance studies of Arctic Ocean sea-ice sediment. (C) 2011 Elsevier Ltd. All rights reserved.