Fig 1.
Map of the central subtropical gyre waters and associated island groups.
Insert: Sāmoan Archipelago showing sites mentioned in text.
Fig 2.
Map of the south eastern coast flat of Ofu Island showing location of excavations conducted in 1986, 1987, and 1989.
Numbered circles represent excavation units (reproduced from [35] fig 5.8).
Fig 3.
Map of the 1987 excavation area showing locations of Main Excavation and Unit 10 (reproduced from [35] fig 5.3).
Table 1.
New and extant radiocarbon dates from earliest layers at To’aga, Ofu Island.
Fig 4.
Change in delta R (ΔR) value across the Pacific over the last 3500 years.
Red circles = U/Th coral samples from Va’oto and Coconut Grove (Ofu Island). Black trendline based on a 4-point moving average.
Fig 5.
Bayesian sequence model for the To’aga site.
This model uses a ΔR value of -160±48 14C years for samples that date between 2600 and 2250 cal BP (i.e., “Main Excavation Layer IIA-C”) and -48±82 14C years for earlier phases. The period between 2600 and 2250 cal BP is indicated by the grey bar. 68% and 95% error margins are indicated by bars under each age distribution. The notation [O:2/5] indicates a 2% posterior probability of being an outlier in the model.
Table 2.
Radiocarbon Bayesian model results for To’aga depending on ΔR used.
Table 3.
Results from Bayesian single phase outlier analysis for Ofu Island (Coconut Grove, Ofu Village and Va’oto).
Fig 6.
Regional chronology for Tonga and Sāmoa.
A. Old regional chronology based on Clark et al. [26] for Sāmoan Polynesian Plainware sites (short-lived material only), Mulifanua [16], and Burley et al. [28] for Tongan Lapita and PPW sites. The range for To’aga is as reported by Kirch [20], pg 91). The approximated 95% age range for To’aga, as determined by [21] using shell dates, is 2700–2400 cal BP (upper estimate represented by dashed line on the To’aga bar). Lapita start and end arrows mark U/Th dates considered to represent the most secure age for Lapita start and end on Tongatapu and Vava’u respectively ([28] pg 10–11). B. New regional chronology using age-appropriate ΔR for To’aga, Mulifanua (NZA-5800 only), and PPW dates from Ofu [26] (excluding To’aga). Intcal13 has been used for all charcoal calibrations and dates from Burley et al. [44] have been incorporated into the PPW Tongan ranges. ? symbols represent the possible early (Model #1) age range for Ofu Island. The solid dark grey bar for To’aga represents the earliest phase of activity at the site only, with the whisker extensions representing the oldest and youngest end of the age range obtained for the earliest deposits depending on whether a ΔR of -48 or -160 is used. L = Lapita sites; PPW = Polynesian Plainware sites.