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

Abstract

To develop an alternative dating tool for the Antarctic Peninsula (where the 14C 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 14C 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.