FLUVIAL-EOLIAN INTERACTIONS IN SEDIMENT ROUTING AND SEDIMENTARY SIGNAL BUFFERING: AN EXAMPLE FROM THE INDUS BASIN AND THAR DESERT
FLUVIAL-EOLIAN INTERACTIONS IN SEDIMENT ROUTING AND SEDIMENTARY SIGNAL BUFFERING: AN EXAMPLE FROM THE INDUS BASIN AND THAR DESERT
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DOI：
10.2110/jsr.2015.42
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发表时间：
2015-06-01
影响因子：
2
通讯作者：
VanLaningham, Sam
中科院分区：
文献类型：
--
作者：
East, Amy E.;Clift, Peter D.;VanLaningham, Sam
大型河流近海海洋地层记录中的沉积物产生及其随后的保存通过复杂的沉积物转移系统联系在一起。为了解释地层记录，关键是要了解环境信号是如何从沉积源区转移到沉积汇的，特别是要了解缓冲在掩盖气候或构造信号方面的作用。在干旱地区，信号缓冲可以包括沉积物在相连的河流和风沙系统中的循环。我们研究了印度河和塔尔沙漠之间的泥沙输送连通性，那里的河流和风沙系统在大空间尺度(数百公里)上交换沉积物。夏季风将来自印度河下游和三角洲的沉积物向东北方向循环，即顺风和逆流，进入沙漠。印度河沉积物的远场风沙循环足够重要，足以控制沙漠下风末端的沉积物来源，尽管不同时代的印度河沉积物在沙漠中的比例在不同地区有所不同；塔尔沙漠西北部的沙丘沙类似于全新世晚期-最近的印度河三角洲，需要较短的运输和返工时间。在塔尔沙漠北部河流河道较小的空间尺度(1-10米)上，也有来自当地河流的河流和风沙沉积物重新作用的地层学证据。就沉积量而言，我们估计塔尔沙漠的沉积储量可能比印度河盆地所有其他已知缓冲区的总和还要大。因此，自全新世中期以来，当沙漠随着夏季季风降雨量的减少而扩大时，河流风沙循环一直是缓冲向海洋输送沉积物的一个重要但鲜为人知的过程。类似的河流-风沙连通性也可能影响全球其他旱地地区的沉积物路线和信号传输。
Sediment production and its subsequent preservation in the marine stratigraphic record offshore of large rivers are linked by complex sediment-transfer systems. To interpret the stratigraphic record it is critical to understand how environmental signals transfer from sedimentary source regions to depositional sinks, and in particular to understand the role of buffering in obscuring climatic or tectonic signals. In dryland regions, signal buffering can include sediment cycling through linked fluvial and eolian systems. We investigate sediment-routing connectivity between the Indus River and the Thar Desert, where fluvial and eolian systems exchanged sediment over large spatial scales (hundreds of kilometers). Summer monsoon winds recycle sediment from the lower Indus River and delta northeastward, i.e., downwind and upstream, into the desert. Far-field eolian recycling of Indus sediment is important enough to control sediment provenance at the downwind end of the desert substantially, although the proportion of Indus sediment of various ages varies regionally within the desert; dune sands in the northwestern Thar Desert resemble the late Holocene-Recent Indus delta, requiring short transport and reworking times. On smaller spatial scales (1-10 m) along fluvial channels in the northern Thar Desert, there is also stratigraphic evidence of fluvial and eolian sediment reworking from local rivers. In terms of sediment volume, we estimate that the Thar Desert could be a more substantial sedimentary store than all other known buffer regions in the Indus basin combined. Thus, since the mid-Holocene, when the desert expanded as the summer monsoon rainfall decreased, fluvial-eolian recycling has been an important but little recognized process buffering sediment flux to the ocean. Similar fluvial-eolian connectivity likely also affects sediment routing and signal transfer in other dryland regions globally.