Preliminary Luminescence Dates for Archaeological Sediments on the Nullarbor Plain, South Australia

Human occupation of the Nullarbor Plain in South Australia has been known to extend into the Pleistocene since a series of major archaeological excavations was begun in the 1950s and 1960s. An antiquity of more than 20,000 years BP for human presence in the region was established on the basis of 14 C chronologies at Koonalda Cave and Allen's Cave (also known as site N145). The oldest date reported for traces of human activity was -22,000 years BP (or -26,000 years BP after calibration) from Koonalda Cave. Here we present preliminary results of our luminescence dating investigations at Allen's Cave and Koonalda Cave, and also report some new 14 C age determinations on associated charcoal. The wind-blown quartzose sediments deposited in Allen's Cave were dated by optically-stimulated luminescence (OSL) and thermoluminescence (TL). A near-modern age was obtained for a near-surface sample and good agreement was obtained between the calibrated 14 C ages of a well-preserved -10,000 year-old hearth and the optical (OSL) and TL ages of the underlying sediments. An optical date of -40,000 years was obtained for the sediments immediately overlying the lowest artefacts at Allen's Cave, thereby extending the period of human occupation of the southern Nullarbor by 14,000 years. Optical dating was not successful at Koonalda Cave however, due to the probable intermittent storage and fluvial remobilisation of sediments en route to the cave floor in this deep karst system. An apparent optical age of -9000 years was obtained for alluvium deposited recently on the cave floor close to the Gallus Site, and substantial optical age overestimates were obtained for lacustrine sediments collected from the -20,000 years BP levels of the archaeological excavation. The validity of the 14 C age determinations made in the 1960s was confirmed using state-of-the-art 14 C methods to date two charcoal samples collected in 1991.