Luminescence dating at Border Cave: attempts, questions, and new results

Border Cave hosts a rare Middle and Early Later Stone Age sequence of deposits that extends as far back ca. 250 thousand years (ka). The site's chronology has been built mainly on Electron Spin Resonance (ESR) ages obtained from teeth, conducted at the end 1990s, radiocarbon dating for more recent layers. In order to refine sequence's chronology, several materials were selected luminescence dating, including 34 siliceous lithic artefacts, quartz feldspar grains extracted 10 sediment samples. Since radioisotopic contents cave sediments are abundant in volcaniclastic host rock (about 2% K, ppm 232Th, 2 238U sediments) lower layers over 40 ka, high (>150 Gy) equivalent doses (De) expected most saturated thermoluminescence (TL) signals artefact samples suggested either they had not heated past, or already too old be dated. presence 40–63 ?m dominated by fast Optically Stimulated Luminescence (OSL) component with apparent D0 values (200–1000 suggested, priori, could appropriate measuring Des. However, systematic drop De these was observed fully understood corrected accordingly. recently proposed pIT protocol, together global growth curve (GGC) approach, applied 63–80 data suggest IR225 signal likely bleached time deposition. Nonetheless, two age estimates, assumed bracket target age, have calculated each sample. These estimates consistent previous ESR ESR/C14-based Bayesian models. Further improvements can considered future - GGC method, which would allow both increased accuracy precision.