Dating ice shelf edge marine sediments: A new approach using single-grain quartz luminescence

摘要

To develop an alternative dating tool for the Antarctic Peninsula (where the ~(14)C method requires large, spatially variable reservoir corrections), we tested the clock-zeroing assumption of photon-stimulated luminescence (PSL) dating using a variety of PSL procedures. At ice shelf edges around the Antarctic Peninsula, sediment-water-interface ("zero-age" analogs), silt-rich short cores were collected in 2001-2003, originally only for fine silt dating tests. Later access to suitable instrumentation also permitted testing the potential of single-grain quartz (SGQ) dating of sand grains from these cores. For the fine silt grains we employed multiple-aliquot and single-aliquot methods to obtain last daylight exposure age estimates from near-core-top material. With the sand fraction we employed automated SGQ PSL methods to isolate the youngest grains. Five of six fine silt samples gave unreasonably large age estimates (>20 ka), with the sixth sample yielding a multiple-aliquot short-bleach age estimate of 1.1 ± 0.6 ka. In contrast, five of seven sand samples yielded geologically reasonable last daylight exposure ages of 0.2-0.6 ka. These SGQ results are also remarkable when compared to published ~(14)C ages of 1 ka to 9.7 ka from core top living calcite and acid-insoluble organic matter. These SGQ results establish the likely utility of this single-grain dating approach in such settings to provide chronologies for calving line histories of ice shelves. To take advantage of this utility, core collection should employ large-diameter coring devices (e.g., Kasten and multicorers), A caveat is that large numbers (e.g., ～10,000) of quartz grains may need analysis to provide acceptable statistics for useful age calculations.