Thermoluminescence Dating of Alluvial Sequences in Coastal Valleys of Southern New South Wales: problems and potential

Because of its potential for establishing chronologies far beyond the range of C¹⁴ thermoluminescence (TL) dating has made a significant contribution to the study of the Quaternary history of many Australian landscapes. But, as the reliability of the technique requires the removal by sunlight of any residual TL from quartz grains during transport, inadequate bleaching may yield ages for depositional events that are too old. Inadequate bleaching often can be detected by the shape of curves showing the ratio of natural TL vs laboratory-induced TL with increasing temperature. We use this technique here, together with C¹⁴ dating and pedogenic evidence, to assess the reliability of TL determinations for alluvium in the valleys of the Clyde River and Termeil Creek. The Pleistocene TL ages from these valleys seem reliable, but Holocene dates do not. However, we demonstrate that, even where inadequate bleaching is demonstrable, TL analysis can still yield important insight to depositional processes.