| 引用本文: | 张 飚，李乐意，刘向东，贺宁强，
杜 彪，宋院利，常 宏.2016.晚中新世以来帕米尔高原生长过程及其与塔里木盆地气候变化可能的联系[J].地球环境学报,(4):346-356 |
| ZHANG Biao, LI Leyi, LIU Xiangdong, HE Ningqiang,
DU Biao, SONG Yuanli, CHANG Hong.2016.Link between development of the northeast Pamir Plateau and climate changes in the Tarim Basin[J].Journal of Earth Environment,(4):346-356 |
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| 摘要: |
| 帕米尔高原是我国极端干旱区 —— 塔里木盆地的西部边界，也是青藏高原西部构造结所处的位置，所以，它的构造演化过程对于研究青藏高原生长过程及塔里木盆地的干旱化历史具有重要的意义。本文通过帕米尔高原东北部正断裂活动的空间展布、活动性质及运动时代的分析，结合最近构造观测结果，提出帕米尔高原在晚中新世已经隆升到了能够影响西风气流通过的高度。尽管高原在晚中新世已经存在东西向的拉张应力，木吉-塔什库尔干谷地可能最终形成于早-中更新世。这一事件奠定了作为喜马拉雅山到南天山之间过渡的帕米尔高原的现今地貌形态及塔里木盆地的气候特征背景。本文结合西昆仑北部及南天山的古地理演化及构造运动证据分析，提出帕米尔高原晚中新世以来的构造地貌演化可能是塔里木盆地晚中新世干旱化加剧的主要原因，中更新世气候代用指标解释复杂性可能也与此密切相关，全球变冷和特提斯海西退可能对晚中新世以来的气候变化也有一定的贡献。 |
| 关键词: 帕米尔高原 谷地 正断裂 走滑断裂 构造隆升 干旱化 |
| DOI：10.7515/JEE201604003 |
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| 基金项目:国家自然科学基金项目（41420104008，41572166，41290252） |
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| Link between development of the northeast Pamir Plateau and climate changes in the Tarim Basin |
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ZHANG Biao, LI Leyi, LIU Xiangdong, HE Ningqiang,
DU Biao, SONG Yuanli, CHANG Hong1,2,3
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1. Shaanxi Central of Geological Survey, Xi’an 710068, China;2. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China;3. University of Chinese Academy of Sciences, Beijing 100049, China
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| Abstract: |
| Background, aim, and scope The Pamir Plateau, the west syntaxis of the Tibetan Plateau, is located in the west to the Tarim Basin where climate is extremely arid. So, its evolution plays an important role to the growth of the Tibetan Plateau and aridification process in the Tarim Basin. Based on the studies of spatial distributions, activity and age of the normal fault in the northeastern Pamir, and observations on tectonics in the past several years, it is deduced that westerly wind was obstructed when flowing through directly since the Late Miocene when the Tibetan Plateau had been uplifted to a certain elevation. Tectonic events in the Pamir Plateau have been researched on volcanism, sedimentology, metamorphism, deformations of the geological materials, low temperature chronology, and Global Positioning System (GPS). Evolution of climatic changes also has been carried out because the high-resolution drilling cores obtained from the eastern Tarim Basin. Comparison possible elevations of the Pamir Plateau and the significant climatic changes in the Tarim Basin in special time windows since Late Miocene can shed light on their correlation. Materials and methods In this study, we calculate probable elevation in different geologic times according to GPS data and low temperature measurements published in recent decades. Field works in the Muji-Tashkorgan valley in northeastern Pamir show that normal faults have initiated at least since Late Pleistocene. This suggests that obviously uplift occurred in this region since that time. The elevations of the Pamir Plateau were estimated when the significant climate change occurred in Late Miocene. Results The results of the GPS and low temperature thermochronologies showed that even if the east-west extensive stress occurred in the Pamir since late Middle Miocene, uplift occurred in the northeastern Pamir Plateau. Paleoelevation of the Pamir Plateau was lower than 3000 m on the base of the data from these observations since transition of the Late Miocene and Early Pliocene, calculated from shortening amount of the crust stemmed from recent GPS data (10 — 12 mm ∙ a−1). The similar result is obtained on the base of the uplift rate came from the low temperature thermometers (0.5 — 0.4 mm ∙ a−1). The oldest sediment observed in hanging wall of the normal faults in Muji-Tashkorgan valley is composed of the Early-Middle Pleistocene. So, Muji-Tashkorgan valley developed at least since the Early-Middle Pleistocene on the setting of pressure stress state in the north of the Pamir Plateau. Discussion If these are the cases, the west wind could reach the Tarim Basin directly before Late Miocene. Because the elevation of the Pamir Plateau uplifted in Late Miocene, the west wind weakened and part of it cannot reach the Tarim Basin directly. This process can decrease the moisture and enhance the aridification in the basin. Elevation increased attributed to the progressively tectonic uplift since Late Pleistocene triggered development of the mountain glacial, and most of the amount of the water reached the basin would block in the high mountains, rivers and lakes in the basin. The variation made amount of the water volume increase in lakes on the background of enhanced aridification in whole basin. It makes climate proxies of index complicated, which came from different sedimentary documents, especially the eolian deposits. These tectonic and climatic events shaped the geomorphology of the Pamir Plateau since Late Miocene which is located between the Himalaya and South Tianshan. And since Late Miocene, climate feature of the Tarim Basin was mostly influenced by the decrease of moisture because of the uplift of the Pamir Plateau and the migration southward of the west wind drove by increasing ice volume in the north hemisphere, even through retreat of the Paratethys Sea play minor role. We argue in this study that evolution of the tectonic geomorphology of the Pamir Plateau caused the enhancement of aridification and complicated interpretation to climatic proxies in the Tarim Basin since Late Miocene. Conclusions Growth of the Pamir Plateau has started since Oligocene-Miocene, and activities were observed along several fault belts inner and around the plateau. The normal faults along the eastern Muji-Kashkorgan valley suggested that east part of the plateau has still uplifted since early-middle Pleistocene. Height of the plateau can influence climate changes in the Tarim Basin because it may be obstruct the westerly circulation. Recommendations and perspectives The results about the evolution of the Pamir remained controversial, for an example, the development age from Eocene to Pleistocene. Detail process (including elevations and rates in different geologic times) of its uplift should be study on the top plateau and in the surrounding basins. |
| Key words: Pamir Plateau valley normal fault slip fault tectonic uplift aridification |
