青藏高原北部新生代构造演化在柴达木盆地中的沉积记录
摘要: 青藏高原形成和演化过程中经历的构造活动，在高原的盆地中均有相应的沉积记录。柴达木盆地位于青藏高原北部，盆地新生界地层详细地记录了这些构造—沉积响应。对野外剖面和钻井岩心的新生界沉积物进行了多方面研究，其结果显示，柴达木盆地保存了青藏高原北部三个阶段的构造活动信息：①E1+2的红色粗碎屑沉积物指示了始新世早期的强烈活动构造背景，沉积记录具有低ZTR指数和低重矿物稳定指数的特征，记录了全盆地范围内的造山活动和构造隆升事件，是印度—欧亚板块碰撞所致的远程响应。在这次广泛的大面积的造山活动后，区内迅速遭受剥蚀、夷平，自中—晚始新世时期起，接受沉积。因而此时柴达木盆地与可可西里盆地、乃至塔里木盆地为连通的湖盆体系。②阿尔金山前N1和N21的粗碎屑沉积物记录了渐新世—早中新世阿尔金山的构造隆升事件，而柴北缘和柴西南的大范围三角洲—湖泊细粒沉积物，具有较高的重矿物稳定指数，反映了平静的构造背景，与阿尔金断裂快速走滑以及盆地总体稳定向北推移的时间相对应。大量的侧向走滑活动消减了来自印度板块的挤压应力，使得柴北缘和柴西南的沉积源区（即祁连山和东昆仑造山带）处于构造平静期。③中中新世以来全盆地向上变粗的粗碎屑沉积物，具有较低的重矿物稳定指数，记录了青藏高原北部整体强烈的地壳缩短、加厚和快速构造隆升事件。此外，综合物源分析显示，柴达木盆地新生代沉积源区性质随时间并没有发生明显的改变。
The Cenozoic Sedimentary Record in Qaidam Basin and Its Implications for Tectonic Evolution of the Northern Tibetan Plateau
Abstract: The tectonic events and climatic changes during the formation and evolution of the Tibetan Plateau could be recorded in the sedimentary succession in adjacent basins. Qaidam Basin, which is located in the northern sector of Tibetan Plateau, preserves a set of thick and continuous Cenozoic sediments. These sediments are the reliable materials for investigation on tectonic evolution of the Tibetan Plateau. Here, we present an integrated study of the Cenozoic sediments from outcrops and drilling well cores. The results indicate that Qaidam Basin has recorded three phases of tectonic evolution. The details can be described as follows. (1) The red coarse detrital sediments of Lulehe Formation which are characterized by low abundances of (Zircon, Tourmaline Rutile) minerals and low heavy mineral stability index. These sediments recorded an event of orogenic movement and tectonic uplift in the whole basin scale, which can be explained as the farfield effects of India-Eurasia collision. Furthermore, after this orogenic event, the region of Altyn and East Kunlun areas was rapidly denudated and flattened, and then became to depositional areas since Middle-Late Eocene. Therefore, it is concluded that Qaidam, Tarim and Hoh Xil Basins may have been parts of a single topographic depression at that time. (2) The Shang Ganchaigou Formation and Xia Youshashan Formation coarse sediments in front of the Altyn Mountains formed in response to the uplift of the Altyn area, whereas the dominated fine-grain sediments with high heavy mineral stability index of other vegions of the Qaiclam Basin can be interpreted as delta-lake facies, suggesting a stage of quiet tectonic background. This quiet setting can be caused by the large-amplitude lateral extrusion along the sinistral strike-slip Altyn Tagh Fault which accommodated the continuing indentation of India into Eurasia. (3) The Shang Youshashan Formation and Shizigou Formation upward-coarsening sediments with low heavy mineral stability index were deposited in high-gradient depositional systems. These sediments recorded the event of crustal shortening and thickening and the intense, rapid uplift of the whole northern Tibetan Plateau. Furthermore, the integrated provenance analysis results indicate the Cenozoic source compositions for the Northern Qaidam Basin did not have significant changes over time.
青藏高原北部新生代构造演化在柴达木盆地中的沉积记录[J]. 沉积学报, 2013, 31(05): 824-833.
| 引用本文: |
青藏高原北部新生代构造演化在柴达木盆地中的沉积记录[J]. 沉积学报, 2013, 31(05): 824-833.
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The Cenozoic Sedimentary Record in Qaidam Basin and Its Implications for Tectonic Evolution of the Northern Tibetan Plateau[J]. Acta Sedimentologica Sinica, 2013, 31(05): 824-833.
| Citation: |
The Cenozoic Sedimentary Record in Qaidam Basin and Its Implications for Tectonic Evolution of the Northern Tibetan Plateau[J]. Acta Sedimentologica Sinica, 2013, 31(05): 824-833.
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