Single-aliquot and single-grain optical dating confirm thermoluminescence age estimates at Malakunanja II rock shelter in northern Australia

The earliest direct ages for human occupation of Australia are 50-60 ka from Malakunanja II and Nauwalabila I rock shelters in the Northern Territory (Roberts, 1997). These ages were obtained from unheated quartz sediments using thermoluminescence (TL) dating at Malakunanja II (Roberts et al., 1990a, 1990b) and optical dating at Nauwalabila I (Roberts et al., 1994). At both sites, a combination of additive- dose and regenerative-dose multiple-aliquot procedures was used to estimate the palaeodoses, while the dose rates were determined principally from high-resolution gamma-ray spectrometry analyses (which showed that a condition of secular equilibrium presently exists in the 238 U and 232 Th chains).