Thermoluminescence dating on gypseous dunes of Lake Amadeus, central Australia

Abstract

The formation of shoreline gypseous dunes is a major event in the Quaternary history of many playas in central Australia. The dunes probably were formed during a period of high regional water table when abundant gypsum was deposited in a near‐shore groundwater seepage zone and deflated on to the shoreline dunes. Ten samples from two sites at Lake Amadeus, a major playa in the region, provided coarse (90–125 μ) quartz grains for thermoluminescence (TL) dating. Both regeneration TL and additive TL were measured. A well defined regeneration curve is basically consistent with the additive curves. Three methods, alpha counting, analyses of radioactive isotope concentrations and on‐site gamma scintillometer measurements, were used to evaluate the dose rates, giving consistent results. Although the equivalent doses of the samples scatter from 25 Gy to 71 Gy, the TL ages of all samples from the two sites cluster in the range 45–60 ka.