Bayesian re-evaluation of Lapita settlement in Fiji: radiocarbon analysis of the Lapita occupation at Bourewa and nearby sites on the Rove Peninsula, Viti Levu Island

Abstract

80 radiocarbon dates are presented for Lapita-era sites on the Rove Peninsula, southwest Viti Levu Island, Fiji.  Of these, 67 are from the Bourewa site which is the largest and probably the earliest in the area.  Of these, 10 are rejected as not being demonstrably associated with its Lapita occupation.

Constraints on date interpretation arising from sample materials are highlighted.  In particular, charcoals that have not been identified to short-lived tree species, twigs or seeds are evaluated according to observed contextual associations and established understanding of inbuilt age offsets using Bayesian outlier analysis.  It is concluded that many of the dates on charcoal are imprecise indicators of settlement age and have an average offset of 150 years.  Shell radiocarbon results are similarly evaluated and it is concluded that the majority have ¹⁴C values that are in equilibrium with the marine radiocarbon reservoir and therefore yield ages that are accurate indicators of Lapita occupation of Bourewa.

Results suggest that initial occupation at Bourewa occurred 2814±25 calBP (2837-2786 calBP [68.2% prob.]; 2865-2770 [95.4% prob.]) and ended 2657±20 calBP (2677-2641 calBP [68.2% prob.]; 2690-2614 calBP [95.4% prob.]).  Similar analyses applied to other dated Lapita sites in Fiji shows that, while Bourewa is among the earliest, the Matanamuani (VL 21/5) site on Naigani Island remains the earliest to be securely dated.