Alluvial plains formation in response to 100-kyr glacial–interglacial cycles since the Middle Pleistocene in southern Tian Shan, NW China
Alluvial plains formation in response to 100-kyr glacial–interglacial cycles since the Middle Pleistocene in southern Tian Shan, NW China
复制标题
中国西北部天山南部中更新世以来冲积平原的形成对100 kyr冰期-间冰期旋回的响应
DOI：
10.1016/j.geomorph.2019.05.013
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发表时间：
2019
期刊：
影响因子：
3.9
通讯作者：
张玲
中科院分区：
文献类型：
--
作者：
Weiliang Huang;杨晓平;Jessica A. Thompson Jobe;李胜强;杨海波;张玲
米兰科维奇理论的原则是，北方半球夏季的日照，部分地受地球轨道偏心率的控制，在更新世中期和晚期驱动了100 kyr的气候变化周期。虽然有大量的证据表明，100 kyr的气候波动驱动的冰川间冰期周期的节奏，它仍然是复杂的识别之间的因果关系的强迫机制和景观响应，特别是在多千年的时间尺度。中亚天山东南部的焉耆盆地保存了至少7代的冲积面，为研究气候波动导致地貌沉积演化提供了重要的资料。利用焉耆盆地南天山皮埃蒙特两条新的宇宙成因10 Be深度剖面和四条冲积废弃地表暴露年龄资料，对已有的年代学资料进行了补充。在过去的0.6百万年中，这些表面的连续废弃，10万年的周期在5.1±0.9到~550 ka之间，表明有多个加积切割周期。叠加的100 kyr周期的加积切割是最好的解释偏心驱动的气候变化。在这些循环中，沉积物是在冰川作用期间由冰川和冰缘侵蚀产生的，然而，由于中亚冰川期的干燥和寒冷条件，几乎没有水排放可用于将它们从山谷中运输和撤离。后来，在冰期到间冰期的过渡期间，由于冰川融水导致的较高的降水量和高排放量导致河流的运输能力超过了撤离沉积物的阈值。随后的快速下切发生在上游沉积物库耗尽之后，其时间也对应于我们研究区域的冰期到间冰期的过渡期。与天山北麓皮埃蒙特受西风带控制的加积和下切作用相比，焉耆盆地南天山皮埃蒙特的沉积体系主要受偏心驱动的冰期-间冰期旋回控制。
The tenet of the Milankovitch theory is that Northern Hemisphere summer insolation, partly controlled by Earth’s orbital eccentricity, drives 100-kyr periodicity in climate change during the middle and late Pleistocene. Although abundant evidence exists for 100-kyr rhythmic climatic fluctuations driving glacial-interglacial cycles, it is still complicated by the identification of causal links between forcing mechanisms and landscape response, especially over multi-millennial timescales. The intermontane Yanqi Basin in the southeastern Tian Shan, Central Asia, preserves at least seven generations of alluvial surfaces, providing insights into the record of climatic fluctuations leading to morpho-sedimentary evolution. We complement existing chronologic data with two new cosmogenic 10Be depth profiles and four surface exposure ages of alluvial surface abandonment in south Tian Shan piedmont within Yanqi Basin. Over the last 0.6 Myr, the successive abandonment of these surfaces with a 100-kyr cyclicity between 5.1±0.9 to ~550 ka, indicating that there were multiple aggradation-incision cycles. The superimposed 100-kyr cycles of aggradation-incision are best explained by eccentricity-driven climate change. Within these cycles, sediment is produced during the glaciation by glacial and periglacial erosion, however, due to the dry and cold conditions of the glacial periods in central Asia, there is little water discharge is available to transport and evacuate them from valley. Later, during the glacial to interglacial transition, higher precipitation and high discharge due to glacial melt water resulted in higher transport capacity of the river past a threshold to evacuate sediment. Subsequent fast incision occurs after the upstream sediment reservoir is depleted and its timing also corresponds to the glacial to interglacial transition period in our research area. Compared with the aggradation and incision of the north piedmont of Tian Shan governed by the Westerlies, the sedimentary systems of South Tian Shan piedmont within Yanqi Basin are mainly controlled by eccentricity-driven glacial-interglacial cycles.