Radiocarbon Dating of Calcined Bones: Insights from Combustion Experiments Under Natural Conditions
Radiocarbon Dating of Calcined Bones: Insights from Combustion Experiments Under Natural Conditions
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煅烧骨头的放射性碳测年：自然条件下燃烧实验的见解
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
C. Moreau
中科院分区：
文献类型：
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作者：
A. Zazzo;J. Saliège;M. Lebon;S. Lepetz;C. Moreau
对煅烧骨中残留的碳酸盐进行放射性碳测年被广泛认为是一种可行的替代方法，可以在胶原蛋白不再存在的情况下确定骨骼残留物的日期。然而，在煅烧过的骨头中测得的δ 13 C值非常低，这引发了人们对用于测年的碳的来源的质疑。本研究的目的是量化在自然条件下煅烧的骨骼的骨碳酸盐和环境CO2之间的碳同位素交换的幅度。在新石器时代和中世纪时期之间的四个考古骨骼在单独的明火上燃烧长达4小时，每小时取一次煅烧骨骼的子样品。所有骨骼的IRSF值均显著增加，碳酸盐含量和δ 13 C值均显著降低。在煅烧良好的骨的碳酸盐部分中测量的14C年龄表明，骨碳酸盐中存在的67 ± 3%至91 ± 8%的碳被燃烧气氛中的碳取代。这一发现证实了先前在实验室条件下获得的结果，并对考古背景下发现的煅烧骨的14C测年产生了严重影响。如果骨头和木炭之间的年龄差异可以忽略不计，那么在煅烧的骨头上获得的14C年龄将仅反映骨头样品的真实年龄。研究结果还表明，煅烧骨的δ 13 C值可以用来估计C交换的程度和对埋藏后成岩蚀变的控制。
Radiocarbon dating of the carbonate remaining in calcined bones is widely regarded as a viable alternative to date skeletal remains in situations where collagen is no longer present. However, anomalously low δ13C values measured in calcined bones prompted questions about the origin of the carbon used for dating. The goal of this study was to quantify the magnitude of carbon isotope exchange between bone carbonate and environmental CO2 for bones calcined under natural conditions. Four archaeological bones ranging in age between the Neolithic and the Medieval period were combusted on a separate open fire for up to 4 hr and subsamples of calcined bones were taken every hour. All the bones experienced a significant increase in IRSF values and decrease in carbonate content and δ13C values. 14C ages measured in the carbonate fraction of well-calcined bones indicate that 67 ± 3% to 91 ± 8% of the carbon present in bone carbonate was replaced by carbon from the atmosphere of combustion. This finding confirms previous results obtained under laboratory conditions and has serious implications for 14C dating of calcined bones found in archaeological contexts. The 14C age obtained on a calcined bone will only reflect the true age of the bone sample if the age difference between the bone and the charcoal can be neglected. Our results show also that δ13C values of calcined bones can be used to estimate the degree of C exchange and control for post-burial diagenetic alteration.