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Late Quaternary aeolian sand deposition sustained by fluvial reworking and sediment supply in the Hexi Corridor - An example from northern Chinese drylands

机译:河西走廊河流改造和沉积物供应维持第四纪晚期风沙沉积-以中国北方旱地为例

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Aeolian deposits are frequently used for palaeoenvironmental change studies. Their formation depends on an array of requirements: the supply of material suitable for aeolian transport and favorable conditions of sediment availability and wind strength. In order to infer palaeoenvironmental information from aeolian sand deposits these factors need to be carefully evaluated. We present a study from northern Chinese Hexi Corridor, based on 11 optically stimulated luminescence (OSL) dated sediment sections. These represent interchanging aeolian and alluvial deposits under gravel surfaces and aeolian sand in dune fields interrupted by interdunal flood deposits. Investigations in two subareas reveal contrasting geomorphologic and sedimentary histories: (1) sediment deposition during the Pleistocene-Holocene transition (similar to 12 ka) followed by deflation during the Holocene and (2) frequent sediment recycling revealed by a wide spectrum of ages throughout the Holocene. The late glacial sediment pulse recorded in the western Hexi Corridor is attributed to high sediment supply, generated by efficient (peri-)glacial sediment production during glacial times in the adjacent Qilian Shan (<5700 m asl) and a moisture increase inducing the reworking of those (glacio-)fluvial deposits during the Pleistocene-Holocene transition. The absence of a powerful reworking agent preserved these late glacial deposits in the western Hexi Corridor in contrast to moister eastern parts where Holocene sediment reworking prevailed.
机译:风沙沉积物经常用于古环境变化研究。它们的形成取决于一系列要求:适合风沙运输的材料供应以及沉积物可利用性和风强度的有利条件。为了从风沙沉积物中推断古环境信息,需要仔细评估这些因素。我们基于11个光学激发发光(OSL)过时的沉积物剖面,提出了一项来自中国北方河西走廊的研究。这些代表了砂砾岩表面下的风沙和冲积沉积物交换以及沙丘中的风沙被间断洪水沉积打断。对两个分区的调查揭示了相反的地貌和沉积历史:(1)更新世-全新世过渡(类似于12 ka)期间的沉积物沉积,然后在全新世期间放气,(2)整个沉积时代的广泛年龄揭示了频繁的沉积物再循环全新世河西走廊西部记录的晚冰期沉积物脉动归因于高的沉积物供应,这是由于邻近祁连山(<5700 m asl)的冰期有效(围产期)产生了冰质沉积物,以及水分增加导致了对河床的改造。更新世-全新世过渡期的那些(冰川)河床沉积物。与新世沉积物改造盛行的潮湿东部地区相比,河西走廊西部地区晚期冰川沉积的缺乏保留了强大的改造剂。

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