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

Abstract

Because of several difficulties with the application of radiocarbon ( 14C) dating to Arctic Ocean sediments, numeric dating techniques are needed that can complement, supplant and reach beyond the 14C 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 μm) 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 ∼11 μm 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 μm 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 μm 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 14C 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.