Chemical weathering outputs from the flood plain of the Ganga
Chemical weathering outputs from the flood plain of the Ganga
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DOI：
10.1016/j.gca.2018.01.003
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发表时间：
2018-03-15
影响因子：
5
通讯作者：
Ahmad, Talat
中科院分区：
文献类型：
--
作者：
Bickle, Michael J.;Chapman, Hazel J.;Ahmad, Talat
河流漫滩的沉积物运输贡献了显着的，但不受约束的一部分，从快速侵蚀的山区带，这对海洋的化学通量和造山带对长期气候的影响具有重要意义的总化学风化通量。我们报告的水和泥沙化学分析从恒河泛滥平原，一个主要的过境水库的沉积物从喜马拉雅造山带。我们的数据包括6个主要的南部支流的恒河，31个额外的分析主要河流在尼泊尔的喜马拉雅山前，79个样本的恒河收集接近口以下的法拉卡拦河坝，每两个星期超过三年和67个水和8个泥沙样本的支流局限于恒河洪泛平原。河漫滩支流的特点是一个浅三角洲O-18三角洲D阵列，相比，大气水线，与低三角洲D-过量从蒸发损失的河漫滩，这是反映在较高的三角洲D-过量的山区河流在尼泊尔。稳定同位素数据证实，在洪泛平原支流的沃茨主要来自洪泛平原降雨，而不是从山上的沃茨的再分配。洪泛平原的支流在化学上与喜马拉雅山脉的主要河流不同。他们可以分为两类。来自科西河周围小区域的支流的Sr-87/Sr-86比值> 0.75，Na/Ca摩尔比值高达6。其余河漫滩的支流具有Sr-87/Sr-86比值
Transport of sediment across riverine flood plains contributes a significant but poorly constrained fraction of the total chemical weathering fluxes from rapidly eroding mountain belts which has important implications for chemical fluxes to the oceans and the impact of orogens on long term climate. We report water and bedload chemical analyses from the Ganges flood-plain, a major transit reservoir of sediment from the Himalayan orogen. Our data comprise six major southern tributaries to the Ganga, 31 additional analyses of major rivers from the Himalayan front in Nepal, 79 samples of the Ganga collected close to the mouth below the Farakka barrage every two weeks over three years and 67 water and 8 bedload samples from tributaries confined to the Ganga flood plain. The flood plain tributaries are characterised by a shallow delta O-18 - delta D array, compared to the meteoric water line, with a low delta D-excess from evaporative loss from the flood plain which is mirrored in the higher delta D-excess of the mountain rivers in Nepal. The stable-isotope data confirms that the waters in the flood plain tributaries are dominantly derived from flood plain rainfall and not by redistribution of waters from the mountains. The flood plain tributaries are chemically distinct from the major Himalayan rivers. They can be divided into two groups. Tributaries from a small area around the Kosi river have Sr-87/Sr-86 ratios > 0.75 and molar Na/Ca ratios as high as 6. Tributaries from the rest of the flood plain have Sr-87/Sr-86 ratios