Temporal variability in shell mound formation at Albatross Bay, northern Australia

Abstract

We report the results of 212 radiocarbon determinations from the archaeological excavation of 70 shell mound deposits in the Wathayn region of Albatross Bay, Australia. This is an intensive study of a closely co-located group of mounds within a geographically restricted area in a wider region where many more shell mounds have been reported. Valves from the bivalve Tegillarca granosa (Linnaeus, 1758) were dated. The dates obtained are used to calculate rates of accumulation for the shell mound deposits. These demonstrate highly variable rates of accumulation both within and between mounds. We assess these results in relation to likely mechanisms of shell deposition and show that rates of deposition are affected by time-dependent processes both during the accumulation of shell deposits and during their subsequent deformation. This complicates the interpretation of the rates at which shell mound deposits appear to have accumulated. At Wathayn, there is little temporal or spatial consistency in the rates at which mounds accumulated. Comparisons between the Wathayn results and those obtained from shell deposits elsewhere, both in the wider Albatross Bay region and worldwide, suggest the need for caution when deriving behavioural inferences from shell mound deposition rates, and the need for more comprehensive sampling of individual mounds and groups of mounds.

Report on excavation of a shell mound site at Mandjungaar, western Cape York Peninsula

“…A local ΔR value of -103±16 radiocarbon years (Ulm 2010) is used here in preference to other values (e.g. Petchey et al 2013;Rhodes et al 1980) and as per other recent work in the region (Holdaway et al 2017;Morrison 2014). All calibrated radiocarbon ages are presented at the 2σ (95% confidence) level and individual ages are given as calibrated age-ranges.…”

“…In an intensive study of four shell matrix sites located at the Wathayn outstation, they determined a high degree of variability existed between shell matrix sites, including hiatus periods in the formation of some mound sites. An expanded program of research focused on shell mound features followed, and sought to understand the temporal and spatial variability of a large number of sites at one locality, encompassing both shell matrix deposits (Fanning et al 2018;Holdaway et al 2017) and earth mounds (Brockwell et al 2017). This required a major program of field sampling to obtain stratigraphic profiles, column samples and radiocarbon determinations from 70 shell matrix features within a study area with at least 158 identified sites and some 212 radiocarbon determinations (Holdaway et al 2017).…”

“…An expanded program of research focused on shell mound features followed, and sought to understand the temporal and spatial variability of a large number of sites at one locality, encompassing both shell matrix deposits (Fanning et al 2018;Holdaway et al 2017) and earth mounds (Brockwell et al 2017). This required a major program of field sampling to obtain stratigraphic profiles, column samples and radiocarbon determinations from 70 shell matrix features within a study area with at least 158 identified sites and some 212 radiocarbon determinations (Holdaway et al 2017). This work demonstrated that mound building commenced on the southern Weipa Peninsula at ~4000 cal BP and through until the past 500 years, but with little consistency in mound accumulation rates between mounds or within particular phases (Holdaway et al 2017:18).…”

“…Although undertaken as a cultural heritage management project, this study contributes new datasets relevant to understanding late Holocene settlement patterns, economies and occupation chronologies on the Weipa Peninsula. Mandjungaar is approximately mid-way between two other intensively studied areas, the well-known Kwamter mound (Bailey 1977;Stone 1992Stone , 1995Wright 1971), as well as large mound complexes near Wathayn and Ndhinggwulung (Figure 1), that have been the focus of a recent and ongoing major research program (Brockwell et al 2017;Fanning et al 2018;Holdaway et al 2017;Shiner et al 2013). This paper reports on the research design and results of work at Mandjungaar, before considering these in relation to other work undertaken on the Weipa Peninsula, and across the Albatross Bay catchment more generally.…”

“…Over 500 mound sites have been documented in the Weipa area across a wide range of geomorphic and ecological settings (Bailey 1994;Morrison 2013b), with a temporal range of approximately 4000 cal BP to the late 1800s (Holdaway et al 2017;Morrison 2014). Yet despite intensive research, there remain many localities where shell mounds are known to exist, but where little or no sampling has taken place.…”