An Icelandic freshwater radiocarbon reservoir effect: Implications for lacustrine 14C chronologies
An Icelandic freshwater radiocarbon reservoir effect: Implications for lacustrine 14C chronologies
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DOI：
10.1177/0959683611400466
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发表时间：
2011-11-01
期刊：
影响因子：
2.4
通讯作者：
Dugmore, A. J.
中科院分区：
文献类型：
--
作者：
Ascough, P. L.;Cook, G. T.;Dugmore, A. J.
淡水放射性碳（C-14）库效应（FRE）是大气和淡水碳库之间的C-14年龄偏移。在极端的例子中，FREs可以达到10 000 C-14 yr的量级，这是对古环境和考古样品进行C-14定年的一个重要考虑因素。如果FRE和样品中受FRE影响的碳的比例可以准确量化，则可以对FRE进行校正。然而，尽管这种校正对于受影响的样品是期望的，但是为了产生有用的时间顺序信息，这种校正是准确的是必要的。FRE校正的准确性可能会受到淡水系统内FRE空间变化的限制，但尽管如此，目前仍缺乏信息来确定和量化受影响系统内的这种变化。在这里，我们提出了一项研究的结果，调查的影响，空间FRE变化后测年精度在Myvatn湖，北方冰岛的淡水系统。大量的FRE（>10 000 C-14年）以前已被确定在考古和现代样品从该地区，这表明相当大的空间变异的潜力。该研究还评估了Δ C-13和Δ N-15在受影响样品的年龄校正中的使用。结果表明，底栖碎屑和生物在初级营养水平的位置内的湖泊受到影响的FRE至少3500 C-14年，具有明显的空间变化导致的C-14年龄差异高达7670 14 C年样品之间。稳定同位素值与数据集内的FRE之间存在广泛的相关性。然而，大相关的不确定性，目前排除了高度准确和精确的稳定同位素为基础的定量的比例，自由基影响的碳在考古和古环境样品Myvatn和周边地区。
A freshwater radiocarbon (C-14) reservoir effect (FRE) is a C-14 age offset between the atmospheric and freshwater carbon reservoirs. FREs can be on the order of 10 000 C-14 yr in extreme examples and are a crucial consideration for C-14 dating of palaeoenvironmental and archaeological samples. Correction for a FRE may be possible, provided the FRE and the proportion of FRE-affected carbon within a sample can be accurately quantified. However, although such correction is desirable for affected samples, it is essential that such correction is accurate in order to produce useful chronological information. Accuracy of FRE correction can be limited by spatial variation in FRE within a freshwater system, but despite this there is currently a paucity of information to identify and quantify such variability within affected systems. Here we present results of a study that investigates the effects of spatial FRE variation upon dating accuracy within the freshwater system of Lake Myvatn, northern Iceland. A substantial FRE (>10 000 C-14 yr) has previously been identified in archaeological and modern samples from the region, which shows the potential for considerable spatial variability. The study also assesses the use of delta C-13 and delta N-15 in age correction of affected samples. The results show that benthic detritus and organisms at primary trophic levels from locations within the lake are affected by a FRE of at least 3500 C-14 yr, with clear spatial variation resulting in C-14 age differences of up to 7670 14C yr between samples. There is a broad correlation between stable isotope values and FRE within the data set. However, large associated uncertainties currently preclude highly accurate and precise stable isotope-based quantification of the proportion of FRE-affected carbon within archaeological and palaeoenvironmental samples from Myvatn and the surrounding region.