Mapping Fluid‐Filled Inclusions in Stalagmites Using Coupled X‐Ray and Neutron Computed Tomography: Potential as a Water Excess Proxy
Mapping Fluid‐Filled Inclusions in Stalagmites Using Coupled X‐Ray and Neutron Computed Tomography: Potential as a Water Excess Proxy
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DOI：
10.1029/2018gc008140
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发表时间：
2019-06
期刊：
影响因子：
3.7
通讯作者：
B. Wortham;I. Montañez;D. Rowland;M. Lerche;A. Browning
中科院分区：
文献类型：
--
作者：
B. Wortham;I. Montañez;D. Rowland;M. Lerche;A. Browning
应用新的代理，如稳定同位素组成和惰性气体浓度的化石滴水被困在石笋中的包裹体，有可能提供独特的限制过去的水文气候状态和表面温度。然而，包裹体沃茨的地球化学分析需要了解给定石笋中主要为液体与空气填充的包裹体的三维空间分布。在这里，我们结合中子计算机断层扫描和中高分辨率X射线计算机断层扫描，绘制出三维方解石密度和分布的液体与空气填充的包裹体在塞拉利昂内华达州石笋（ML-1），形成于末次冰消期（18.5至11.7 ka）。中子计算机断层扫描-X射线计算机断层扫描结果与石笋方解石组构时间序列的比较表明，尽管最高密度的方解石含有丰富的液体（流体）填充的包裹体，但方解石密度和组构总体上是液体包裹体分布（LID）的次要控制因素。此外，石笋时间序列的多元统计评估表明，LID和方解石δ 18 O和δ 13 C之间在多世纪至千年尺度上存在显着关系，这表明LID和洞穴水供应之间存在潜在联系。
Application of novel proxies, such as the stable isotope compositions and noble gas concentrations of fossil drip water trapped as inclusions in stalagmites, have the potential to provide unique constraints on past hydroclimate states and surface temperatures. Geochemical analysis of inclusion waters, however, requires an understanding of the three‐dimensional spatial distribution of dominantly liquid‐ versus air‐filled inclusions in a given stalagmite. Here we couple neutron computed tomography and medium‐ to high‐resolution X‐ray computed tomography to map out the three‐dimensional calcite density and distribution of liquid‐ versus air‐filled inclusions within a Sierra Nevada stalagmite (ML‐1), which formed during the last deglaciation (18.5 to 11.7 ka). Comparison of coupled neutron computed tomography‐X‐ray computed tomography results with a time series of stalagmite calcite fabrics indicates that although highest density calcite contains abundant liquid (fluid)‐filled inclusions, calcite density and fabric overall were secondary controls on the liquid inclusion distribution (LID). Furthermore, a multistatistical evaluation of the stalagmite time series indicates a significant relationship at the multicentury‐ to millennial‐scale between LID and calcite δ18O and δ13C that suggests a potential link between LID and water availability to the cave.