A robust chemical weathering index for sediments containing authigenic and biogenic materials
A robust chemical weathering index for sediments containing authigenic and biogenic materials
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DOI：
10.1016/j.palaeo.2022.111288
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
Tenichi Cho;T. Ohta
中科院分区：
文献类型：
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作者：
Tenichi Cho;T. Ohta
化学风化是地球表面的一个重要过程。鉴于沉积物的化学成分反映了它们产生的风化环境，这可以深入了解过去风化的强度和风格。由沉积岩全岩地球化学组成计算出的风化指标被广泛应用。然而，这些指标有局限性，如非硅酸盐矿物的污染。为了建立一种广泛适用于各种条件下形成的沉积岩风化指标，我们利用成分数据和多元统计对一个火成岩数据集及其风化剖面进行了分析。从数据集中独立提取了火成岩的化学变化和风化趋势，并提出了一种新的风化指数（鲁棒风化指数）。利用腐岩剖面和地带性土壤评价了RW指数的适用性。我们进一步将RW指数应用于富含碳酸盐的古土壤，以测试其在古气候研究中的应用。RW指数即使对于含有大量非硅酸盐物质的沉积物也是稳健的，因此可以比较各种沉积岩的风化强度。将RW指数应用于陆相和海相沉积物，可以提高古风化条件的时空重建能力。
Chemical weathering is an important process at Earth's surface. Given that the chemical composition of sediments reflects the weathering environment in which they were generated, this can provide insights into the intensity and style of weathering during the past. Weathering indices calculated from the whole-rock geochemical compositions of sedimentary rocks are widely used. However, these indices have limitations, such as contamination by non-silicate minerals. To develop a weathering index widely applicable to sedimentary rocks formed under various conditions, we used compositional data and multivariate statistics to analyse a dataset for igneous rocks and their weathering profiles. The chemical variations of the igneous rocks and weathering trends were independently extracted from the dataset, and a new weathering index (the robust weathering (RW) index) is proposed. The applicability of the RW index was assessed using saprolite profiles and zonal soils. We further applied the RW index to a carbonate-rich paleosol to test its use in studies of paleoclimate. The RW index is robust even for sediments containing a large amount of non-silicate materials, and thus enables comparison of the weathering intensity of a wide range of sedimentary rocks. Spatial–temporal reconstructions of paleo-weathering conditions will be improved by applying the RW index to terrestrial and marine sediments.