The SE-SZ-8 site of Nanggu is a large Lapita site in the Reef/Santa Cruz group of the Southeast Solomon Islands. This paper provides a detailed discussion of its geomorphological and environmental context on Santa Cruz and the within site position of four marine shell dates from it, followed by a Bayesian analysis of the radiocarbon dating of the site. The analysis includes two new marine shell dates on additional species to overcome possible problems due to species selected for dating. Together these data indicate that despite recent critique of the sequence of the three excavated decorated Lapita sites (SE-SZ-8, SE-RF-2, SE-RF-6) proposed by Green (1991a) for the Reef/Santa Cruz Group there is little basis to suggest the Nanggu site is not both the oldest dated Lapita site in the sequence, but also earlier than any other so far identified within the period of early Lapita colonization of Remote Oceania.
Keywords: Lapita, Bayesian chronology, geomorphology, environment
The Lapita settlement of the Reef/Santa Cruz Islands in the southeast Solomon Islands represents the first major open ocean crossing into previously uninhabited Remote Oceania (Green 1991b) and crossing from Near Oceania required nothing more than sailing due east with the seasonally prevailing winds along a zenith star path (Irwin 2006:73). As such the nature and timing of this settlement is of considerable importance to our consideration of the colonization of Oceania (Sheppard and Walter 2006). Recent critique of the dating and interpretation of the chronology of the Reef/Santa Cruz Lapita sequence with implications for our understanding of regional change in ceramic sequences (Best 2002, Felgate 2003) makes it imperative that we review and enhance, where possible, the basic data available on the sites in question. The SE-SZ-8 has long been considered the best candidate for the oldest investigated site in the Reef/Santa Cruz site sequence (Green 1991a). However, it has been recently suggested, based on possible overlap in the age of SZ-8 with RF-2 and theories of ceramic change, that this site is possibly the youngest (Best 2002:93) in the series of three Lapita sites (SZ-8, RF-2, RF-6) reported by Green. Best (2002:90) has also called for the publication of more detailed information on the excavation context of all published dates in order to evaluate their "integrity". This report collects together data, including new and revised data, on the geological and environmental context of the site, its relationship to local tephrachronology, site layout, stratigraphy, site sampling and a basic calibration of new and previously available SZ-8 radiocarbon data. It also reports a Bayesian analysis designed to estimate the timing and duration of the occupation associated with the SZ-8 archaeological record.
From 1976 onwards (Green 1976, 1979, 1991a: Table 3) two Tridacna marine shell radiocarbon determinations have been available as an indication of the approximate age of the SE-SZ-8 dentate-decorated Lapita site of Nanggu, on the island of Nendo or Santa Cruz, in the Outer Eastern Islands of the Solomons. However, a more precise calibrated date has never been possible, although general estimations have been published using a default [DELTA]R value of zero or a composite one of 100 (Kirch and Hunt 1988: Table 2.3, Spriggs 1990:11, Table 1). Thus the most cautious assessment of the site's age, using those [DELTA]R marine values, had been set out by Green (1991a:201) along the following lines.
1. The four charcoal dates for the SE-RF-2 Nenumbo Lapita site make it the most securely dated site in the Reef/Santa Cruz region. The spatial distribution of excavated artifacts and features suggested the occupation was of short duration.
2. The two then available SZ-8 marine shell dates overlapped statistically at 1 standard deviation with the RF-2 site when the SZ-8 DR was estimated at 0 or 100. …