Miocene to Early Pleistocene Depositional History and Tectonic Evolution of the Issyk‐Kul Basin, Central Tian Shan
Miocene to Early Pleistocene Depositional History and Tectonic Evolution of the Issyk‐Kul Basin, Central Tian Shan
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DOI：
10.1029/2020gc009556
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发表时间：
2021-03
期刊：
影响因子：
3.7
通讯作者：
S. Roud;M. Wack;S. Gilder;A. Kudriavtseva;E. Sobel
中科院分区：
文献类型：
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作者：
S. Roud;M. Wack;S. Gilder;A. Kudriavtseva;E. Sobel
位于天山山脉中部的伊塞克湖盆地（吉尔吉斯斯坦）拥有中亚最大、最深的山湖。周围Terskey和Kungey山脉的侵蚀导致邻近凹陷处堆积了长达4公里的沉积物。区域缩短和隆起可能在渐新世-中新世开始形成盆地，但精确的年龄控制很少。为了更好地理解这些过程的时间，我们获得了对伊塞克湖以南暴露的化石贫乏的河湖沉积物的磁性地层年龄限制，这与伊塞克湖盆地以外的等效地层的先前年龄限制非常一致。两个500-650 m厚的剖面主要由楚群沉积物组成，其年代为6.3-2.8 Ma和7.0-2.4 Ma（晚中新世-早更新世）。结合重新解释的下伏地层的磁性地层学约束，我们发现，同构造沉积开始于1.22亿年前，平均沉积速率<10 cm/ka。沉积速率增加到10-30厘米/ka在7马，同时加速隆起的Terskey山脉南部。一个剖面（Kaji-Say）在5 ~ 3 Ma之间发生变形事件，同时整个盆地的沉积中心发生位移，这表明Kungey山脉在1.55 Ma开始向北大幅隆起。这种隆起和变形将伊塞克湖地区变成了一个封闭的盆地，促进了深湖的形成。大约3 Ma的湖相沉积标志着伊塞克湖的存在。
The Issyk‐Kul Basin (Kyrgyzstan), situated in the central Tian Shan Mountains, hosts the largest and deepest mountain lake in Central Asia. Erosion of the surrounding Terskey and Kungey ranges led to the accumulation of up to 4 km of sediment in the adjacent depression. Creation of the basin from regional shortening and uplift likely initiated around the Oligocene‐Miocene, yet precise age control is sparse. To better understand the timing of these processes, we obtained magnetostratigraphic age constraints on fossil‐poor, fluvio‐lacustrine sediments exposed south of Lake Issyk‐Kul, that agree well with previous age constraints of the equivalent strata outside the Issyk‐Kul Basin. Two 500–650 m thick sections comprised mainly of Chu Group sediments were dated at 6.3–2.8 Ma and 7.0–2.4 Ma (late Miocene to early Pleistocene). Together with reinterpreted magnetostratigraphic constraints from underlying strata, we find that syn‐tectonic deposition commenced at ∼22 Ma with average sedimentation rates <10 cm/ka. Sedimentation rates increased to 10–30 cm/ka at 7 Ma, concurrent with accelerated uplift in the Terskey Range to the south. A deformation event in one section (Kaji‐Say) between 5 and 3 Ma together with concurrent shifts of depositional centers throughout the basin signal the onset of substantial uplift of the Kungey Range to the north at ∼5 Ma. This uplift and deformation transformed the Issyk‐Kul area into a closed basin that facilitated the formation of a deep lake. Lacustrine facies deposited around 3 Ma mark the existence of Lake Issyk‐Kul by that time.