The first successful application of Optically Stimulated Luminescence dating to a colonial era (<0.25 ka) archaeological site in Australia

Abstract

While exploration of Australian post-colonial (≤0.25 ka) OSL dating is well established in a range of natural sedimentary contexts (e.g. fluvial, aeolian, coastal), to date there have been no successful examples of the technique applied to archaeological sediments of this era. Here we present the results of a multi-phase compliance-based archaeological excavations of a new bridge crossing the Hawkesbury-Nepean River (northwest Sydney). These works identified a Last Glacial Maximum (LGM) aeolian deposit through which a colonial era drainage system had been excavated. Historical documents reveal the construction of the system occurred between 1814 and 1816 CE. An opportunistic range-finding Optically Stimulated Luminescence (OSL) sample was obtained from anthropogenic trench backfillcomposed of reworked LGM depositsimmediately above the drainage system. Minimum and Finite Mixture age models of single grain quartz OSL provided a date of 1826 CE (1806-1846 CE), in close agreement with the documented age of construction. These findings provide the first evidence of a colonial structure reliably dated using OSL, and demonstrate the feasibility of wider deployment of OSL dating to other archaeological sites of the recent era (≤0.25 ka). We propose that such environments associated with large volumes of sand-rich backfill, in particular, likely heighten OSL dating success. We propose that well-documented historical archaeological sites in Australia also have the potential to provide a robust testing ground for further evaluating the accuracy of OSL dating in a range of young archaeological sedimentary contexts, potentially to sub-decadal levels.

Was Aboriginal population recovery delayed after the Last Glacial Maximum? A synthesis of a terminal Pleistocene deposit from the Sydney Basin, New South Wales, Australia

“…These findings correlate well with established models for the region (Barry et al, 2020;McDonald, 2008;White, 2017;Williams et al, 2014), as well as providing new insights into the wider Sydney Basin, and southeast Australia more broadly. Prior to the terminal Pleistocene, archaeological evidence in the Sydney Basin is sparse and indicates the presence of highly mobile groups whose lithic resources are provisioned by the Hawkesbury-Nepean River gravels (Kohen et al, 1984;McDonald, 2008;White, 2017White, , 2021Williams et al, 2014Williams et al, ,2017Williams et al, ,2019, one of southeast Australia's major rivers. The IMTC raw material sources that dominate these earlier Parramatta assemblages derive only from gravels sourced in the Hawkesbury-Nepean River corridor, although it is possible that there may be drowned sources downstream of Parramatta in this smaller river system.…”

Tracking an exotic raw material: Aboriginal movement through the Blue Mountains, Sydney, NSW during the Terminal Pleistocene

“…These sites generally reflect brief, or intermittent visits, with increasing artefact numbers and technological attributes, indicative of longer occupation times, only in the last few thousand years. To the east, numerous academic and cultural heritage management (CHM) projects along the Hawkesbury-Nepean River corridor show fairly intense use of the region since c.35 ka continuing throughout the Last Glacial Maximum (LGM) and Holocene (Attenbrow 2010;Kohen et al 1984;McDonald 2008;Nanson et al 1987;White 2017;White and McDonald 2010;Williams et al 2012Williams et al , 2014Williams et al , 2017Williams et al , 2019. Excavations at Pitt Town (PT-12) and Windsor (South Bank PAD W-SP #45-5-3581) (Figure 1) suggest that the elevated terraces associated with the Hawkesbury-Nepean River were an ecological refuge through the LGM (21 ± 3 ka), with unchanging artefact attributes indicating economic and social behaviour adopted during this climatic downturn remained constant well into the Holocene period (AAJV 2017; Williams et al 2012Williams et al , 2014.…”