Late Pleistocene outburst floods from Issyk Kul, Kyrgyzstan?
Late Pleistocene outburst floods from Issyk Kul, Kyrgyzstan?
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DOI：
10.1002/esp.4109
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发表时间：
2017-08
影响因子：
3.3
通讯作者：
Swenja Rosenwinkel;A. Landgraf;W. Schwanghart;Friedrich Volkmer;A. Dzhumabaeva;S. Merchel;G. Rugel;F. Preusser;O. Korup
中科院分区：
文献类型：
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作者：
Swenja Rosenwinkel;A. Landgraf;W. Schwanghart;Friedrich Volkmer;A. Dzhumabaeva;S. Merchel;G. Rugel;F. Preusser;O. Korup
伊塞克湖是世界第二大山湖，它周围的高海岸线和湖泊沉积物记录了第四纪时期湖泊水位的波动。这些标志物与测深和地球化学数据一起记录了湖泊闭合和外部排水的交替阶段。湖泊沉积物的最高层需要通过Boam峡谷对湖泊西部出口进行前坝。我们测试以前假设的冰或滑坡坝故障，探索晚第四纪湖泊水位和爆发之间的可能联系。我们审查和重新编制的年表报告的变化，在湖泊网站，并提供新的年龄废弃的海岸线使用14 C在双壳类和腹足类贝壳，植物碎屑，以及砂透镜体在三角洲和河流沉积物中使用红外线激发发光。我们的日期是一致的湖泊水位升高之间~45万年和22万年。宇宙成因的10 Be和26 Al暴露年龄的风扇阶地包含不稳定的巨石（>3米）下游的峡谷限制洪水的时间为20.5-18.5万年，晚于伊塞克湖的高点。水流能力分析给出了夹带和运输这些漂石的峰值流量>104 m3 s-1。然而，古冰川模型表明，与伊塞克湖无关的天然堰塞湖可能在突然排空时产生如此高的排放量。因此，尽管我们的数据与灾难性突发洪水的假设一致，但在过去150年中，平均湖平面变化高达90 mm yr-1，在没有任何突发的情况下变化很大，因此，仅使用沉积档案将湖平面下降与灾难性溃坝联系起来仍然是模糊的。这种限制可能很容易适用于其他地方的其他第四纪湖泊。尽管如此，我们重建的更新世洪水是世界上最大的报告之一，并激励进一步研究中亚的古水文。版权所有© 2017约翰威利父子有限公司
Elevated shorelines and lake sediments surrounding Issyk Kul, the world's second largest mountain lake, record fluctuating lake levels during Quaternary times. Together with bathymetric and geochemical data, these markers document alternating phases of lake closure and external drainage. The uppermost level of lake sediments requires a former damming of the lake's western outlet through the Boam gorge. We test previous hypothesised ice or landslide dam failures by exploring possible links between late Quaternary lake levels and outbursts. We review and recompile the chronology of reported changes in lake site, and offer new ages of abandoned shorelines using 14C in bivalve and gastropod shells, and plant detritus, as well as sand lenses in delta and river sediments using Infrared Stimulated Luminescence. Our dates are consistent with elevated lake levels between ~45 ka and 22 ka. Cosmogenic 10Be and 26Al exposure ages of fan terraces containing erratic boulders (>3 m) downstream of the gorge constrain the timing of floods to 20.5–18.5 ka, postdating a highstand of Issyk Kul. A flow‐competence analysis gives a peak discharge of >104 m3 s–1 for entraining and transporting these boulders. Palaeoflood modelling, however, shows that naturally dammed lakes unconnected to Issyk Kul could have produced such high discharges upon sudden emptying. Hence, although our data are consistent with hypotheses of catastrophic outburst floods, average lake‐level changes of up to 90 mm yr–1 in the past 150 years were highly variable without any outbursts, so that linking lake‐level drops to catastrophic dam breaks remains ambiguous using sedimentary archives alone. This constraint may readily apply to other Quaternary lakes of that size elsewhere. Nonetheless, our reconstructed Pleistocene floods are among the largest reported worldwide, and motivate further research into the palaeoflood hydrology of Central Asia. Copyright © 2017 John Wiley & Sons, Ltd.