李晓花^1,,
胡振波^1,,,
潘保田¹,
李梦昊¹,
莫钦鸿¹,
董子娟¹,
王军^1,2
1. 兰州大学资源环境学院, 西部环境教育部重点实验室, 甘肃 兰州 730000
2. 甘肃省地质调查院, 甘肃 兰州 730000

基金项目: 国家自然科学基金重点项目（批准号：41730637）和高等学校学科创新引智计划项目（批准号：BP2018001）共同资助


详细信息

作者简介: 李晓花, 女, 25岁, 硕士研究生, 第四纪地质学专业, E-mail:xhli18@lzu.edu.cn

通讯作者: 胡振波, E-mail:zhbhu@lzu.edu.cn

中图分类号: P931.2;P542

收稿日期:2020-05-27
修回日期:2020-08-13
刊出日期:2021-01-30

Migration process of the Beida River channel within the Jiudong Basin as a result of the climate fluctuation and rapid tectonic activity in the Holocene period

LI Xiaohua^1,,
HU Zhenbo^1,,,
PAN Baotian¹,
LI Menghao¹,
MO Qinghong¹,
DONG Zijuan¹,
WANG Jun^1,2
1. College of Earth and Environmental Sciences, Lanzhou University, Key Laboratory of Western China's Environmental Systems, Ministry of Education, Lanzhou 730000, Gansu
2. Geologic Survey Institute of Gansu Province, Lanzhou 730000, Gansu


More Information

Corresponding author: HU Zhenbo,E-mail:zhbhu@lzu.edu.cn

MSC: P931.2;P542

--> Received Date: 27 May 2020
Revised Date: 13 August 2020
Publish Date: 30 January 2021


摘要
摘要:位于青藏高原东北缘的祁连山与外围的金塔南山分别限定了酒东盆地的南北边界，构成了盆山耦合的宏观地貌体系。起源于祁连山的北大河北流进入酒东盆地后，沿近东西走向的金塔南山南麓发育了系列与山体平行的纵向河道，然后径直转向北流经鸳鸯峡谷出盆地，形成了贯通水系格局。野外地貌与沉积追踪考察发现，沿金塔南山南麓分布3条被遗弃的河道，它们东西向延伸，两端与北大河现代河床靠拢，为该河流的古河道。根据年代由老到新的原则，依次将它们命名为古河道1至3，并对其主槽沉积的上覆泥炭样品进行加速器¹⁴C测年。结果显示，古河道1至3分别在7471 cal.a B.P.、7434 cal.a B.P.和5706 cal.a B.P.被遗弃。基于此，论文初步重建了北大河沿金塔南山南麓的迁移过程，并进一步与区域冰芯气候记录和金塔南山北缘断裂的古地震数据对比，发现河道面向山体北移发生在气候变暖和构造相对平静期，而背向山体快速南移则主要对应于气候变冷和构造相对活跃期。因此，在活动构造区河道迁移可能是河流综合响应亚轨道时间尺度气候波动和流域快速构造活动的结果。结合区域活动构造的研究成果，论文进一步揭示北大河河道迁移可能反映了青藏高原中全新世以来向东北缘的扩展。
关键词: 酒东盆地/
北大河/
废弃河道/
金塔南山

Abstract:The Jiudong Basin is restricted by the Qilian Shan(Shan=Mountain in Chinese), uplifted as the northeastern margin of the Tibetan Plateau, to the south, and by the Jintanan Shan to the north. The landscape across this basin is thus characterized by an alternation between basin and mountain. The Beida River deriving from the Qilian Shan debouches into this basin, and excavating a series of longitudinal channels in an east-west direction, along the southern front of the Jintanan Shan, until it turns northward and flows through the Jiudong Basin via the Yuanyang Gorge. Based on preliminary field investigation, a total of three abandoned channels were identified along the southern front of the Jintanan Shan. Moreover, they extend in an east-west direction, nearly parallel to the Jintanan Shan, and then connect with the current riverbed of the Beida River at their both tips. The sedimentary characteristics of the three abandoned channels can also be correlated with the Beida River. Therefore, their formation was probably attributed to the Beida River diversion. The study on the formation process of the three abandoned channels can provide excellent insight into the fluvial response to the climatic fluctuation and tectonic activity. In order to establish a chronological sequence for them, the AMS ¹⁴C dating has been employed to constrain the basal ages of the peat bed overlying directly the main-channel-bed sediment. Obtained result shows that the three channels were abandoned by the Beida River at 7471 cal.a B.P., 7434 cal.a B.P., and 5706 cal.a B.P., respectively. They are named here as paleo-channels 1, 2, and 3 according to above chronological sequence. Under the constrain by this chronological framework, the migration process of the Beida River channel along the southern front of the Jintanan Shan has been reconstructed. Further comparison with the paleo-seismic data along the Jintanan Shan fault and the climatic record in suborbital timescale from the ice core at the northeastern Tibetan Plateau, we found that the channel of the Beida River tended to move toward north near to the Jintanan Shan when the climate was warmed and the tectonic activity was in a relative quiet state, while its fast southward migration away from the mountain mainly occurred in a tectonic active period combined with climate cooling. The Beida River originates from the glaciers in the Qilian Shan, meltwater thus contributes most of its runoff. In the warming climate, the increasing runoff, combined with the decreasing sedimentary flux on account of increasing vegetation coverage, may lead to a high energy for the Beida River in hydrological force. Therefore, the relative quiet tectonics coupled with warming climate enables this river to move further toward north near to the Jintanan Shan. On the contrary, the Beida River has to turn back and even further southward migration away from this mountain in a tectonic vigorous and cold climatic period.
Therefore, we concluded that the channel abandonment in the Jiudong Basin may be attributed to the fluvial response of the Beida River to the climate fluctuation in suborbital timescale and the rapid tectonic activity of the Jintanan Shan. Previous works on the active tectonics over the northeastern Tibetan Plateau have revealed that the growth and extension of the Jintanan Shan is controlled by the Jintanan Shan fault, whose activity may be linked with the northeastern extrusion of the Tibetan Plateau. Therefore, the migration process of the Beida River channel reconstructed in this paper may imply a further northeastward extrusion of the Tibetan Plateau in mid-Holocene.
Key words:Jiudong Basin/
Beida River/
abandoned channel/
Jintanan Shan



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