Small dynamic mountainous rivers in Taiwan exhibit large sedimentary geochemical and provenance heterogeneity over multi-spatial scales
Small dynamic mountainous rivers in Taiwan exhibit large sedimentary geochemical and provenance heterogeneity over multi-spatial scales
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台湾小型动态山地河流在多空间尺度上表现出巨大的沉积地球化学和物源异质性
DOI：
10.1016/j.epsl.2018.10.012
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发表时间：
2019
影响因子：
5.3
通讯作者：
Xie Xiaolei
中科院分区：
文献类型：
--
作者：
Deng Kai;Yang Shouye;Bi Lei;Chang Yuan-Pin;Su Ni;Frings Patrick;Xie Xiaolei
台湾河川因构造活动及台风频繁，具有快速的物质流失及沉积物转移的特徴。各种方法已被用来限制影响其沉积物源汇路由的过程。在大多数情况下，由于沉积物路径较短（<200 km），出口处的沉积物被认为是整个上游流域的代表性平均值。然而，这种假设可能是不适当的，因为巨大的成分异质性，甚至可以存在于这样的小动态河流系统。为了揭示其站内和全流域的地球化学不均匀性，我们收集了沿着浊水溪和里雾溪在台湾的沉积物样品。在每个站点收集了多个沉积在不同位置或不同粒度的样品，并测量了<63 μm组分的元素和Sr-Nd同位素组成。首次将元素比值和降维技术应用于沉积物物源判别。他们表明，大元素的异质性存在于同一站的样品之间，也站之间沿着每条河流，可变的沉积物混合和当地岩性的异质性解释。当我们的Sr-Nd同位素数据与台湾河流的文献数据相结合，可以区分五个离散的河流沉积物集群，反映了流域间的沉积物源区在台湾岛的异质性。我们还应用了Sr-Nd同位素混合模型与蒙特-卡罗模拟相结合，以量化两条河流的物源异质性。西山麓/台陆科带的沉积物的贡献浊水/里务下游之间的沉积物样品，被认为是空间或时间的复制，可以变化的系数为0.02。结合野外原位观测资料，提出了暴雨或台风频繁袭击下的动态山区小河流，泥沙输移方式的快速变化导致了其物源异质性。不同事件搬运的不同物源沉积物在各站得以保存，导致站内和全盆地的地球化学不均一性。研究表明，“小型”动态山区河流在多空间尺度上具有“大型”地球化学和物源异质性，“自然平均化”的普遍假设在这类河流中应谨慎对待。为此，提出了几种适用于山区小河流的泥沙采样方法，以供参考。未来的研究依赖于碎屑沉积物，例如应用宇宙成因核素或锂同位素，还应该意识到在小型山区河流的异质性，因为快速变化的物源可以同时偏置的风化和侵蚀信号，并导致不具有代表性的结果。
Taiwan rivers are characterized by extremely rapid mass wasting and sediment transfer due to active tectonics and frequent typhoons. Various methods have been applied to constrain processes affecting their sediment source-to-sink routing. In most cases, the sediment at the outlet is considered to be a representative average of the whole upstream basin due to the short sediment routes (<200 km). However, this assumption may be inappropriate because huge compositional heterogeneity can exist even within such small dynamic river systems. To reveal their intra-station and basin-wide geochemical heterogeneity, we collected sediment samples along the Zhuoshui and Liwu Rivers in Taiwan. Multiple samples deposited in different locations or with different grain-sizes were collected at each station, and the <63 μm fractions were measured for their elemental and Sr–Nd isotopic compositions. Elemental ratios and dimension-reducing technique were firstly applied to discriminate the sediment provenances. They show that the large elemental heterogeneity exists between samples at the same station and also between stations along each river, explainable by variable sediment mixing and local lithological heterogeneity. When combining our Sr–Nd isotopic data with literature data from Taiwan rivers, five discrete clusters of river sediments can be distinguished, reflecting the inter-catchment heterogeneity of sediment provenance in Taiwan Island. We also applied a Sr–Nd isotopic mixing model coupled with Monte-Carlo simulations to quantify the provenance heterogeneity in both rivers. The sediment contribution of the Western Foothills/Tailuko Belt to the Zhuoshui/Liwu downstream can vary by a factor of ∼2 between sediment samples that were considered as spatial or temporal replicates. Combined with field in-situ observations, we propose that fast-changing sediment transport modes cause the provenance heterogeneity in small dynamic mountainous rivers attacked by frequent heavy storms or typhoons. Sediments transported during different events and with different provenances can be preserved at each station, which leads to the intra-station and basin-wide geochemical heterogeneity. This study shows that “small” dynamic mountainous rivers can exhibit “large” geochemical and provenance heterogeneity over multi-spatial scales, and thus the common assumption that “let nature do the averaging” should be treated cautiously in this kind of river. Therefore, we propose several effective sediment sampling approaches on small mountainous rivers for reference. Future studies relying on detrital sediments, e.g. applying cosmogenic nuclides or Li isotopes, should also be aware of the heterogeneous nature in small mountainous rivers, because fast-changing provenances can simultaneously bias the weathering and erosion signals and lead to unrepresentative results.
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影响因子：
5.3
作者：
Garzanti, Eduardo;Ando, Sergio;Lupker, Maarten
通讯作者：
Lupker, Maarten
台湾浊水河流域晚第四纪硅酸盐风化强度与古环境变化重建
影响因子：
2.2
作者：
Zhao Yun;Yang Shouye;Liu James T.;Fan Daidu;Yang Rick J.;Bi Lei;Chang Yuan-pin
通讯作者：
Chang Yuan-pin
DOI：
10.1016/j.cageo.2013.05.015
发表时间：
2013-09
期刊：
Comput. Geosci.
影响因子：
--
作者：
A. Resentini;M. Malusà;E. Garzanti
通讯作者：
A. Resentini;M. Malusà;E. Garzanti
影响因子：
2.9
作者：
J. Warrick
通讯作者：
J. Warrick
影响因子：
2.9
作者：
L. Carter;L. Carter;A. Orpin;S. Kuehl
通讯作者：
L. Carter;L. Carter;A. Orpin;S. Kuehl