The importance of shell: Redating of the To’aga site (Ofu Island, Manu'a) and a revised chronology for the Lapita to Polynesian Plainware transition in Tonga and Sāmoa
The importance of shell: Redating of the To’aga site (Ofu Island, Manu'a) and a revised chronology for the Lapita to Polynesian Plainware transition in Tonga and Sāmoa
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贝壳的重要性：托阿加遗址（马努阿奥富岛）的重新定年以及汤加和萨摩亚拉皮塔到波利尼西亚平器过渡的修订年表
DOI：
10.1371/journal.pone.0211990
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发表时间：
2019
期刊：
影响因子：
3.7
通讯作者：
P. Kirch
中科院分区：
文献类型：
--
作者：
F. Petchey;P. Kirch
放射性碳测年太平洋考古遗址充满了困难。这些地点通常位于沿海的海滩山脊或沙丘上，表现出水平和垂直的扰动，木炭等可测定的材料通常高度降解，可能来自老树或漂流木，除非特别确定为寿命短的材料，而骨胶原很少在热带条件下存活。因此，贝壳是确定太平洋遗址年代最合理的材料，因为它不易改变，可以取样以确保只代表最后几个生长季节，而且往往与人类经济活动密切相关。然而，贝壳放射性碳（14C）定年一直受到解释问题的困扰，这主要是由于我们对近岸海洋和河口环境中14C循环的了解有限。因此，在区域时间计量评估中，贝壳日期通常被忽略，近年来，贝壳日期经常被完全避免。我们对贝壳14C来源的最新了解，以及第一个南太平洋环流海洋14C随时间变化模型的发展，结合贝叶斯统计模型，现在为我们提供了这些贝壳放射性碳定年的价值。在这里，我们对奥富岛上的To’aga遗址的年代进行了修订，这是一个与Sāmoa波利尼西亚平原时期有关的早期居住遗址，我们将其最早的使用日期定在2785至2607 cal BP之间（68%的可能性）。
Radiocarbon dating Pacific archaeological sites is fraught with difficulties. Often situated in coastal beach ridges or sand dunes, these sites exhibit horizontal and vertical disturbances, datable materials such as wood charcoal are typically highly degraded, may be derived from old trees or driftwood unless specifically identified to short-lived material, while bone collagen rarely survives in tropical conditions. Shell, therefore, is the most logical material for dating Pacific sites since it is resistant to alteration, can be sampled to ensure only the last few seasons of growth are represented and is often closely tied to human economic activities. However, shell radiocarbon (14C) dating has been plagued by interpretive problems largely due to our limited knowledge of the 14C cycle in nearshore marine and estuarine environments. Consequently, shell dates are typically ignored in regional chronometric evaluations and in recent years shell is often avoided for dating altogether. Recent advances in our understanding of the source of shell 14C as well as the development of the first South Pacific Gyre model of changing marine 14C over time, combined with Bayesian statistical modelling, now provide us with insight into the value of these shell radiocarbon dates. Here we present a revision of the age of the To’aga site on Ofu Island–an early occupation site associated with the initial Polynesian Plainware period in Sāmoa, the earliest use of which we date to between 2785 and 2607 cal BP (68% probability).