Developing 230Th/U Dating of Coral Artifacts for High-Precision Cultural Chronologies in Eastern Polynesia

为东波利尼西亚高精度文化年表开发珊瑚文物的 230Th/U 年代测定

• 批准号: 1521133
• 负责人: Warren Sharp
• 金额: $ 16.9万
• 依托单位: Berkeley Geochronology Center
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-15 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1521133&HistoricalAwards=false
• 关键词: Developing; 230Th; Dating; Coral; Artifacts

Researchers wish to understand the tempo of the rise of complex, populous societies from small founder groups and the pace of accompanying environmental change. Archaeological study of Polynesian cultural sequences created on island ecosystems is well suited to such investigations. Beginning with small bands of pioneering settlers, the first humans on the landscape of each newly discovered island, Polynesian societies of increasing size and hierarchical complexity developed over time. This development was accompanied by environmental changes including profound modifications to native flora and fauna, landscapes, and marine resources. However, the timing of initial settlement and the tempo of ensuing cultural and environmental change remain highly uncertain despite nearly 70 years of research. In the current project, Drs. W. Sharp and P. Kirch and their collaborators Drs. M. Allen and G. Molle will further develop a novel approach to dating Polynesian cultural sequences. The expected improvements in dating will, for the first time, provide a clear picture of the speed of cultural and environmental change in these Polynesian societies. Better dates in key Eastern Polynesian archipelagoes will also help resolve a longstanding debate over the timing of the extraordinary trans-Pacific dispersal of the Polynesians. Developing the capability to precisely date coral artifacts will help Pacific archaeologists erect refined chronologies for human occupation and human-ecosystem interaction elsewhere in Oceania. Polynesian archaeologists have traditionally depended almost solely upon radiocarbon dating (i.e., 14C dating) to provide a quantitative temporal framework for colonization of islands and subsequent evolution of island cultures and environments. Despite significant improvements in the radiocarbon technique through the years, radiocarbon dating has severe inherent limitations when applied to the past ~1000 years, the time frame of cultural development in eastern Polynesia. An alternative dating technique that has already demonstated considerable success in applications in Polynesia is 238U-234U-230Th dating of corals, herein referred to as 230Th coral dating. The technique is based on decay of naturally occurring uranium in corals, and reliable 230Th coral ages with precisions of 1-2% are readily attainable. For example, for 500-year old corals this translates into dates with uncertainties of only five to ten years. In the current project, Sharp, Kirch and their collaborators will apply 230Th coral dating to coral abraders made from pieces of Acropora or other corals used by Polynesians to shape fish hooks made from shell. Such coral abraders are common in Polynesian archaeological sequences and have been shown to be highly suitable for 230Th dating. In sum, the project will provide chronologies for cultural sequences in key archipelagoes of Eastern Polynesia of unprecedented accuracy and precision, thereby substantively advancing our understanding of Polynesian prehistory.

研究人员希望了解复杂的、人口众多的社会从小创始群体崛起的速度以及随之而来的环境变化的速度。 对岛屿生态系统上创造的波利尼西亚文化序列的考古研究非常适合此类调查。 从一小群开拓者定居者开始，他们是每个新发现的岛屿上的第一批人类，随着时间的推移，波利尼西亚社会的规模不断扩大，等级制度也越来越复杂。 这一发展伴随着环境变化，包括对本土动植物、景观和海洋资源的深刻改变。然而，尽管经过近 70 年的研究，最初定居的时间以及随后的文化和环境变化的速度仍然高度不确定。在当前的项目中，博士。 W. Sharp 和 P. Kirch 以及他们的合作者 Drs。 M. Allen 和 G. Molle 将进一步开发一种新颖的方法来测定波利尼西亚文化序列的年代。 约会方面的预期改进将首次让人们清楚地了解这些波利尼西亚社会的文化和环境变化的速度。东波利尼西亚群岛的更准确日期也将有助于解决关于波利尼西亚人跨太平洋非同寻常的扩散时间的长期争论。发展精确测定珊瑚文物年代的能力将有助于太平洋考古学家为大洋洲其他地区的人类占领和人类与生态系统相互作用建立精确的年表。 波利尼西亚考古学家传统上几乎完全依赖放射性碳测年（即 14C 测年）来为岛屿殖民以及随后岛屿文化和环境的演变提供定量的时间框架。 尽管多年来放射性碳技术取得了显着进步，但放射性碳测年法在应用于过去约 1000 年（波利尼西亚东部文化发展的时间框架）时仍存在严重的固有局限性。 另一种测年技术已在波利尼西亚的应用中取得了相当大的成功，即珊瑚的 238U-234U-230Th 测年，本文称为 230Th 珊瑚测年。 该技术基于珊瑚中天然存在的铀的衰变，并且可以轻松实现精确度为 1-2% 的可靠的 230Th 珊瑚年龄。 例如，对于 500 年历史的珊瑚来说，这意味着日期的不确定性只有五到十年。 在当前的项目中，Sharp、Kirch 及其合作者将应用 230th 珊瑚年代测定法来研究由鹿角珊瑚或波利尼西亚人用来塑造贝壳制成的鱼钩的其他珊瑚碎片制成的珊瑚研磨器。 这种珊瑚研磨器在波利尼西亚考古序列中很常见，并且已被证明非常适合 230 年代测定。 总之，该项目将以前所未有的准确性和精确性提供东波利尼西亚主要群岛文化序列的年表，从而实质性地增进我们对波利尼西亚史前史的理解。