Radiocarbon and luminescence age estimate database for the Willandra Lakes Region World Heritage Area: a reliability-assurance assessment

The legacy of geochronological data gathered within the Willandra Lakes Region World Heritage Area over more than 60 years has produced a corpus of age estimates that are now of varying reliability as a result of improvements in laboratory, measurement, analytical, and reporting procedures. A database of all known radiocarbon and luminescence age estimates was compiled and the reliability of each age estimate was ranked from A (most reliable) to C (least reliable). A total of 128 of 269 radiocarbon, 138 of 339 optically stimulated luminescence (OSL), and 0 of 53 thermoluminescence ages were given a Rank A score. Using only Rank A OSL age estimates, a Bayesian modelled chronostratigraphic framework for the Lake Mungo lunette was developed for the Lower Mungo (56.2 ± 3.0 to 37.7 ± 1.0 ka), Upper Mungo (36.4 ± 1.1 to 34.1 ± 1.7 ka), Arumpo (25.1 ± 0.6 to 18.2 ± 0.5 ka), and Zanci (18.2 ± 0.5 to 17.2 ± 0.7 ka) Units. Three lacustrine phases were identified using Rank A radiocarbon ages on otoliths and mussel shell: system-wide high water ∼55–35 ka cal BP (continuing in the north until ∼30 ka cal BP); a short pulse reaching to Lake Outer Arumpo ∼29–24 ka cal BP; and a final saline phase at Lake Mungo ∼21–17 ka cal BP, whilst freshwater conditions were maintained throughout this period at Lake Mulurulu. Only 62 of 143 radiocarbon ages associated directly with archaeological features were given a Rank A score and because they are derived from a restricted range of site types, some with restricted temporal distributions, they are not a reliable basis for documenting the history of land use and occupancy. Continued research is needed to increase the number of reliable age estimates from depositional, palaeohydrological, and archaeological contexts in different landforms to produce a clearer understanding of both palaeoenvironmental change, and the history of land use and occupancy of this enduring cultural landscape.