Bulk sediment 14C dating in an estuarine environment: How accurate can it be?
Bulk sediment 14C dating in an estuarine environment: How accurate can it be?
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河口环境中的大量沉积物 14C 测年：准确度如何？
DOI：
10.1002/2016pa002960
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
L. Zillén
中科院分区：
文献类型：
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作者：
B. Lougheed;S. Obrochta;C. Lenz;Anette Mellström;B. Metcalfe;R. Muscheler;Maja Reinholdsson;I. Snowball;L. Zillén
摘要 由于波罗的海河口的许多沉积岩芯中缺乏海洋大型化石，研究人员常常被迫对大量沉积物样品进行 14 C 测定。然而，导致大量沉积物形成的碳源路径的模糊性给基于这些样本的 14C 地质年代学带来了很大的不确定性，并且在以前的波罗的海研究中可能没有充分考虑到这种不确定性。我们通过分析来自波罗的海中部两个独立测年的全新世晚期沉积物序列中密集间隔的大量沉积物 14C 测定来量化这种不确定性。我们的结果显示，两个岩心位置之间的中位沉积物储层年龄或 R(t)bulk 存在约 600?14C?yr 的差异（一个岩心约为 1200?14C?yr，另一岩心约为 620?14C?yr），表明空间变化较大。此外，我们还发现两个核心的下核心（即时间）R(t)整体变化至少约为 200?14C?yr。我们还发现取自同一核心深度的两个样本之间存在 585?14C?yr 的差异。我们建议，在大型咸水水体中使用沉积物 14C 测年的研究在评估不确定性时应考虑 R(t) 体积的时空变化，从而得出更大但更准确的校准年龄范围。 （较少的）
Abstract Due to a lack of marine macrofossils in many sediment cores from the estuarine Baltic Sea, researchers are often forced to carry out 14C determinations on bulk sediment samples. However, ambiguity surrounding the carbon source pathways that contribute to bulk sediment formation introduces a large uncertainty into 14C geochronologies based on such samples, and such uncertainty may not have been fully considered in previous Baltic Sea studies. We quantify this uncertainty by analyzing bulk sediment 14C determinations carried out on densely spaced intervals in independently dated late-Holocene sediment sequences from two central Baltic Sea cores. Our results show a difference of ~600?14C?yr in median bulk sediment reservoir age, or R(t)bulk, between the two core locations (~1200?14C?yr for one core, ~620?14C?yr for the other), indicating large spatial variation. Furthermore, we also find large downcore (i.e., temporal) R(t)bulk variation of at least ~200?14C?yr for both cores. We also find a difference of 585?14C?yr between two samples taken from the same core depth. We propose that studies using bulk sediment 14C dating in large brackish water bodies should take such spatiotemporal variation in R(t)bulk into account when assessing uncertainties, thus leading to a larger, but more accurate, calibrated age range. (Less)