Dating stone arrangements using optically stimulated luminescence and fallout radionuclides

Abstract

Buildings and monuments constructed from stone provide some of the best-preserved surface archaeology, but their construction ages can be difficult to determine using radiocarbon techniques. In Australia, stone arrangements are recognised as architectural or symbolic features belonging to Aboriginal societies. The structures are predominantly inorganic with shallow infill, hampering attempts to determine their antiquity. Optically stimulated luminescence (OSL) techniques have the potential to date these features, but their complex geometry requires careful consideration of the background radiation. Here, we present the first ages for Australian Aboriginal stone construction using single-grain OSL techniques on quartz from stone arrangements in central Australia. Beta and gamma dose rates and the cosmic ray dose have been estimated from mapping the gross geometry of stone and sand courses. The resulting OSL ages are internally consistent and, together with fallout radionuclides ¹³⁷Cs and ²¹⁰Pb, indicate a minimum age for construction between 1959 and 1981 AD. We demonstrate that single-grain OSL techniques can be used to determine the age of emplaced sand between stones and, assuming a stable substrate, can be used to date stone building construction as well as building occupation, providing chronologies for sites where organic material for radiocarbon analysis is limited or unavailable.