Tending to tradition: Dating stone arrangement maintenance in northwest Australia using optical methods

• Published in: Journal of archaeological science, reports Vol. 49; p. 104053
• Main Authors: Gliganic, L.A., Slack, M., Meyer, M.C.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-06-2023
• Subjects: Australian archaeology; Luminescence; Minimum age model; Single-grain OSL; Stone arrangements; Minimum age model; Australian archaeology; Stone arrangements; Single-grain OSL; Luminescence
• ISSN: 2352-409X
• DOI: 10.1016/j.jasrep.2023.104053

•Single-grain optically stimulated luminescence (OSL) can be used to date construction and maintenance of stone arrangements.•Single-grain OSL measurements from 39 samples used to date stone arrangement in Pilbara region of Australia.•Comparison of stone arrangement OSL samples with natural soil OSL samples shows that stone arrangement samples retain a record of boulder emplacement.•The Pilbara stone arrangement complex was constructed at least 1,360 years ago and was subsequently maintained until ca. 380 years ago.•The maintenance of the stone arrangement complex over at least 900 years demonstrates a strong connection between people, the landscape, and their imprint on the landscape.
Despite the ubiquity of Aboriginal stone arrangements around the Australian continent, there is very little data-driven information about the antiquity or development of these sites. The lack of chronological controls for these sites has limited our understanding of the timing, development, and functions of stone arrangement culture. Here, we present geochronological investigations of a stone arrangement complex near the Packsaddle Valley in the Pilbara region of Western Australia using optically stimulated luminescence (OSL) dating. Sedimentary OSL samples were collected from directly beneath the boulders that comprise the stone arrangements to estimate the timing of their emplacement. The process of boulder erection by Aboriginal people involved partial removal of the topsoil, which would only have provided the sediments with brief periods of sunlight exposure. Hence, the OSL signals of our samples were not expected to have been fully bleached during boulder erection. Consequently, the single-grain OSL equivalent dose (De) data were modelled using the unlogged Minimum Age Model to identify those grains that reflect boulder emplacement. The OSL characteristics (proportion of zero-dose grains, skewness of De distribution, and Central Age Model De) from the stone arrangement OSL samples were compared to those from natural soil samples taken adjacent to the boulders, and results show that the stone arrangement samples retain a record of boulder emplacement and do not simply reflect natural soil processes. Consequently, ages for all samples were calculated to generate a chronology for boulder emplacement at the site.
Boulder emplacement proceeded from ∼1,410 years ago until ∼420 years ago, with data from four recumbent boulders indicating they collapsed ∼380 years ago. The data clearly clusters into three discrete, self-consistent phases of boulder emplacement occurring at 1,360 ± 90 years ago, 800 ± 30 years ago, and 480 ± 20 years ago. We conclude that (i) the stone arrangement complex was constructed at least 1,360 years ago, (ii) the boulders tend to fall down by natural processes and, thus, the site was subsequently visited and maintained at least twice (800 and 480 years ago) when the fallen boulders were re-emplaced, and (iii) this process ended ca. 380 years ago after which the site has not been maintained. The maintenance of the stone arrangement complex over at least 900 years demonstrates a strong connection between people, the landscape, and their imprint on the landscape.