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首页> 外文期刊>Palaeogeography, Palaeoclimatology, Palaeoecology: An International Journal for the Geo-Sciences >Alluvial sequence in the north piedmont of the Chinese Tian Shan over the past 550 kyr and its relationship to climate change
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Alluvial sequence in the north piedmont of the Chinese Tian Shan over the past 550 kyr and its relationship to climate change

机译：过去550年中国天山北麓的冲积层序及其与气候变化的关系

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摘要

A new division of Middle and Late Pleistocene alluvial sequence in the north piedmont of the Chinese Tian Shan based on geomorphologic, stratigraphic, and chronologic criteria provides a framework for examining their relationship to climate change during glacial-interglacial transitions. Over the past 550 kyr at least four major alluviation episodes occurred within the piedmont. Along the major river valleys in this region, each episode of alluvial fan deposition morphologically correlates with a major river terrace. These correlations create a regionally applicable framework for subdivision of the Quaternary alluvial sequence in the study area, where seven stepped river terraces are defined. Our new chronology of this fluvial sequence suggests that, following intervals of aggradation, three highest river terraces and equivalent alluvial fans were abandoned at similar to 530 ka, similar to 300 ka and similar to 10 ka, respectively. Paleosols at the base of the loess sequences that directly overlie the older terraces and fans suggest that episodes of aggradation occurred late in the glacial cycles. The subsequent incision that caused abandonment/stabilization of these terraces and fans occurred near to glacial-interglacial transitions. A relatively high degree of synchrony in major river incision events across the piedmont, despite disruption by several discrete structure zones with asychronous tectonic activities, supports the dominant control exerted by climatic conditions on alluvial deposition and terrace creation during the Quaternary across the north piedmont of the Chinese Tian Shan.
机译：根据地貌，地层学和年代学标准，在中国天山北麓的中更新世晚期冲积层序的新划分提供了一个框架，以检验它们与冰川-冰川间过渡期与气候变化的关系。在过去的550年里，山麓地区至少发生了4次主要冲积事件。沿着该地区的主要河谷，冲积扇沉积的每个事件在形态上都与主要河床阶地相关。这些相关性为研究区域中的第四纪冲积层序的划分创造了区域适用的框架，该区域定义了七个阶梯状河阶地。我们对这种河流序列的新的年代顺序表明，在不断凝结之后，三个最高的河流阶地和同等的冲积扇被抛弃了，分别为530 ka，300 ka和10 ka。黄土层序底部的古土壤直接覆盖在较早的阶地和扇形上，表明在冰川周期的晚期发生了凝集事件。随后导致这些梯田和扇形体放弃/稳定的切口发生在冰川-冰川间过渡附近。尽管整个山麓地区的主要河流切割事件发生了相对高度的同步，尽管被几个具有不同步构造活动的离散结构带破坏了，但仍支持了气候条件对北山麓第四纪第四纪冲积沉积和阶地形成的主要控制作用。中国天山。

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