High-resolution records of rainfall events from clay bands in tufa
High-resolution records of rainfall events from clay bands in tufa
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DOI：
10.1130/g20736.1
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发表时间：
2004-09-01
期刊：
影响因子：
5.8
通讯作者：
Ihara, T
中科院分区：
文献类型：
--
作者：
Kano, A;Kawai, T;Ihara, T
个别降雨事件被记录为薄粘土带每年层压，淡水碳酸盐石灰华。降雨事件的径流夹带粘土，然后粘附到石灰华表面。从日本西南部采集的一个样本展示了1988年至2002年15年间形成的100多个粘土带。粘土带的年代学是通过使用碳酸盐中氧同位素比值的温度依赖性循环来确定的，粘土含量是通过电子探针微区分析Si X射线强度来量化的。所得的Si X射线强度曲线与实际降雨记录的模式几乎一致。各带粘粒含量与降雨量有关。>50 mm/周的降雨量产生了足够数量的悬浮洞穴粘土，从而在石灰华中产生粘土带。由于粘土带在沉积后的蚀变中幸存下来，这种新方法可以应用于古老的石灰华沉积物，并具有很大的潜力，作为一个高分辨率的降雨记录用于气候研究。
Individual rainfall events are recorded as thin clay bands in annually laminated, freshwater-carbonate tufa. Runoff from rainfall events entrains clay that then adheres to the tufa surface. A specimen collected from southwest Japan exhibits >100 clay bands formed during a 15 yr period from 1988 to 2002. The chronology of the clay bands was determined by using the temperature-dependent cycle of oxygen isotope ratios in the carbonate, and the clay content was quantified by electron-probe microanalysis Si X-ray strength. The obtained Si X-ray strength curve and actual rainfall record follow a nearly identical pattern. The clay content of each band correlates with rainfall amount. Rainfall of >50 mm/week produced sufficient amounts of suspended cave clay to produce clay bands in the tufa. Because the clay bands survive postdepositional alteration, this new method can be applied to ancient tufa deposits and has great potential as a high-resolution rainfall record for use in climate studies.