Reassessment of the record of linear dune activity in Tasmania using optical dating

Abstract

Stabilized linear dunes in northeastern Tasmania have previously been dated using luminescence signals from quartz (Duller G.A.T, Augustinus, P., 1997 Luminescence studies of dunes from north-eastern Tasmania. Quaternary Geochronology (QSR) 16, 357–365.) and gave ages from 44±4 to 29±3 ka. Unexpectedly, no evidence was found for dune activity at the last glacial maximum (LGM). The ages were obtained using analytical methods available at the time, including multiple aliquot methods. In recent years the single aliquot regenerative dose (SAR) procedure has been developed, and this method gave ages from 23.8±1.6 to 21.8±1.3 ka for the same samples. A further seven samples from other linear dunes in the area gave ages from 16.8 to 19.7 ka. These ages are strong evidence that linear dunes in northeastern Tasmania were last active at, or immediately after, the LGM, consistent with evidence for enhanced aridity through large parts of the Australian continent at that time. Earlier methods of optical dating using quartz did not explicitly check for changes in luminescence sensitivity and thus their reliability must be suspect. For samples measured here, the largest discrepancy in equivalent dose between the sensitivity corrected and non-sensitivity corrected data is 84%, while for the remainder it is much smaller. These results demonstrate the importance of checking the validity of previously published optical dating results which were obtained using methods that did not explicitly check for sensitivity change.