Morphodynamics and lake level variations at Paiku Co, southern Tibetan Plateau, China
Morphodynamics and lake level variations at Paiku Co, southern Tibetan Plateau, China
复制标题
DOI：
10.1016/j.geomorph.2015.07.007
复制
发表时间：
2015-10
期刊：
影响因子：
3.9
通讯作者：
B. Wünnemann;D. Yan;R. Ci
中科院分区：
文献类型：
--
作者：
B. Wünnemann;D. Yan;R. Ci
青藏高原湖泊的代理记录通常用于推断第四纪晚期与季风相关的气候变化。流域过程的具体影响及其与湖盆的相互作用很少被利用。基于实地形态调查，结合遥感分析，结合古岸线和阶地湖泊序列的放射性碳测年沉积物数据，我们可以证明藏南派库错冰川动态、河流冲积扇/阶地的形成与湖泊水位和面积变化之间存在着密切的关系。我们的研究结果表明，大规模河流冲积扇（F1）的形成早于西夏邦马冰川的最大推进。后者在 42-21 卡路里 BP 的当地末次盛冰期 (LLGM) 期间，在现有冰川以北形成了一个独特的终端冰碛复合体。 LLGM到全新世晚期，出现了年轻的扇代（F2），伴随着湖泊水位波动，总体呈下降趋势。形态可追踪的最高湖泊水位为 4665 m asl，存在于 25 cal BP 之前，并导致潜在的溢流流入邻近的廊强错和彭曲河。 LLGM 期间也存在高水平，随后略有下降，直到大约 12 月。 15 cal BP，由于在寒冷和干燥的气候条件下融水排放减少。在冰川晚期/全新世早期 11.9 至 9.5 卡BP 之间恢复到之前的水平可能是由于气候变暖、融水排放增加和印度夏季季风 (ISM) 水分供应增加造成的。此后，派库错逐渐缩小到目前的水平，而最年轻的扇（F3）一代在全新世中期至今的短暂放电条件下演化为个体小尺寸个体。四个阶地（T4-1）的形成可能是由于湖泊水位降低而导致平均侵蚀率为 50 cm/ky 的扇代连续切入的结果。不能完全排除构造影响。自1976年以来，冰川消失了约。面积减少了 15%，并伴随着 1972 年至 2014 年 6 月期间湖泊面积损失约 3.7%。夏季季风降雨导致湖泊水位高度发生约 1-2 m 的季节性变化。我们的数据显示，在过去 25 cal BP 期间，冰川动态、河流过程、阶地形成和水收支变化之间存在密切的相互作用，以响应众所周知的、日照驱动的、ISM 有效的水分供应。晚冰期和全新世时期。温度驱动的融水动态是派酷公司水平衡变化的控制因素。
Proxy records from lakes on the Tibetan Plateau are commonly used to infer monsoon-related climatic changes during the late Quaternary. Specific influences of catchment processes and their interaction with the lake basin are seldom utilized. Based on morphological field investigations, supported by remote sensing analyses in combination with radiocarbon-dated sediment data from lacustrine sequences along paleoshorelines and terraces, we can demonstrate that close relationships exist between glacier dynamics, fluvial–alluvial fan/terrace formation and lake level and lake area changes of Paiku Co, southern Tibet. Our results show that the formation of large-scale, fluvial–alluvial fans (F1) predates the maximum advance of the Xixiabangma glaciers. The latter formed a distinct terminal moraine complex north of the present glaciers during the local LGM (LLGM) at 42–21 cal ky BP. A younger fan generation (F2) developed from the LLGM to the late Holocene, which was accompanied by lake level fluctuations with a generally decreasing trend. The highest morphologically traceable lake level at 4665 m asl existed prior to 25 cal ky BP and induced a potential overflow to the neighboring Langqiang Co and Pengqu River. A high level also existed during the LLGM, followed by a minor decline until ca. 15 cal ky BP, owing to reduced meltwater discharge under cold and dry climatic conditions. A return to the previous level during the late-glacial/early Holocene period between 11.9 and 9.5 cal ky BP is likely caused by climate warming, increased meltwater discharge, and enhanced Indian Summer Monsoon (ISM) moisture supply. Afterwards, Paiku Co shrank gradually toward its present level, while the youngest fan (F3) generation evolved as individual small-sized bodies under ephemeral discharge conditions from the mid-Holocene to the present.The formation of four terrace levels (T4-1) is likely the result of sequential incision into the fan generations with a mean erosion rate of 50 cm/ky, caused by lake level lowering. Tectonic impact cannot be completely ruled out. Since 1976, the glaciers lost ca. 15% in area, accompanied by lake area loss of ~ 3.7% between 1972 and June 2014. Seasonal lake level variations of about 1–2 m in height occur in response to summer monsoon rainfall.Our data show a close interaction between glacial dynamics, fluvial processes, terrace formation, and water budget changes throughout the last 25 cal ky BP in response to the well-known, insolation-driven, ISM-effective moisture supply during the late-glacial and Holocene period. Temperature-driven meltwater dynamics were the controlling factors for variations in water balance of Paiku Co.