| 柴达木盆地北缘第四纪左旋斜冲推覆构造运动 |
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| 引用本文： | 吴珍汉,胡道功,吴中海,叶培盛,周春景.柴达木盆地北缘第四纪左旋斜冲推覆构造运动[J].第四纪研究,2009,29(3):599-607. |
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| 作者姓名： | 吴珍汉 胡道功 吴中海 叶培盛 周春景 |
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| 作者单位： | 中国地质科学院地质力学研究所,北京,100081 |
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| 基金项目： | 科学技术部国际合作重点项目，中国地质调查局地质调雀项目，国际合作INDEFTH-Ⅳ项目 |
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| 摘 要： | 柴达木盆地北缘第四纪发育比较强烈的左旋斜冲构造运动，形成长达百余公里、宽度超过30km的大型推覆构造，由斜冲断层、逆冲岩席和褶皱构造等组成。根据野外观测相关资料，柴达木盆地北缘第四纪发生两期构造变形： 早更新世不同规模的逆冲岩席如中新元古代中深变质岩、古生代浅变质岩与中生代沉积地层沿北西西－北西向断层发生左旋斜冲构造运动，导致下伏中新统和上新统湖相沉积地层强烈褶皱变形，上覆不同规模的逆冲岩席； 晚更新世中晚期构造运动导致中晚更新世砾石层发生宽缓褶皱变形。估算柴达木盆地北缘第四纪斜冲推覆构造运动产生的最小缩短量约为 17～18km，平均缩短速率约为 6.6～6.9mm/a。柴达木盆地北缘第四纪斜冲推覆构造运动是青藏高原北部新生代逆冲推覆构造运动自南向北扩展迁移的重要表现形式。
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| 关 键 词： | 逆冲推覆构造 左旋斜冲断层 缩短速率 第四纪 柴达木盆地北缘 |
QUATERNARY SINISTRALSLIP THRUSTING IN NORTH MARGIN OF QAIDAM BASIN |
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| Wu Zhenhan,Hu Daogong,Wu Zhonghai,Ye Peisheng,Zhou Chunjing.QUATERNARY SINISTRALSLIP THRUSTING IN NORTH MARGIN OF QAIDAM BASIN[J].Quaternary Sciences,2009,29(3):599-607. |
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| Authors: | Wu Zhenhan Hu Daogong Wu Zhonghai Ye Peisheng Zhou Chunjing |
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| Institution: | Institute of Geomechanics|Chinese Academy of Geological Sciences|Beijing 100081 |
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| Abstract: | Thrust systems had been discovered in the north margin of the Qaidam Basin by geologic mapping and seismic profiling. However，the time and tectonic mechanism of the thrusting are still in argument. Trench and field survey as well as ETM image in Xitieshan，Luliangshan，and Qaidamshan Mountains give evidences for two periods of Quaternary sinistralslip thrusting in the north margin of the Qaidam Basin，providing key data for a better understanding of Cenozoic tectonic evolution and crust shortening of Northern Tibetan Plateau. Quaternary sinistralslip thrusting in the north margin of the Qaidam Basin formed a largescaled thrust system of more than 100km long and 30km wide in Dachaidam area which is mainly composed of sinsitralslip thrust faults，tectonic slices，and folds. Tectonic slices of Proterozoic gneiss，Ordovician green schist，Jurassic coalbearing formation，and Cretaceous conglomerate were thrusted over the folding Cenozoic sandstone，conglomerate，marl，and mudstone along front sinistralslip thrust faults，and sinistral offset as large as ca.5km of Ordovician green schist slices occurred along major thrust fault in Southern Xitieshan Mts. Two unconformities were identified in the folded Cenozoic strata beneath the major sinistralslip thrust faults along a trench as deep as 6m in the west bank of the Bagachaidam Lake，northwest of Xitieshan Mts. One occurred between the Miocene marl and the Middle Pleistocene pebbles，and another between the Middleearly Late Pleistocene pebbles and the Holocene deposits of pebbles and soil，indicating two periods of Quaternary sinistralslip thrusting in north margin of Qaidam Basin, i．e. the Early Pleistocene and the middlelate Late Pleistocene. The Early Pleistocene sinistralslip thrusting of the Proterozoic gneiss，Ordovician green schist，Mesozoic strata，and Early Cenozoic red beds overlying Miocene marl and Pliocene conglomerate. The sinistralslip thrusting in the middlelate Late Pleistocene caused formation of syncline and anticline in the Middle Pleistoceneearly Late Pleistocene fluvial sands and pebbles. The minimal shortening distance and average shortening rate caused by the sinistralslip thrustings in Quaternary are estimated to be ca.17～18km and ca.6.6～6.9mm/a，respectively in the north margin of the Qaidam Basin. Quaternary sinistralslip thrustings in the north margin of the Qaidam Basin were closely related to sinistral slip of the Altyn Tagh fault and compression caused by the northward subduction of the Indian continental plate. They can also be regarded as the result of the northward growth of Cenozoic thrusting and crust thickening in Northern Tibetan Plateau. |
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| Keywords: | thrust system sinistral slip thrusting shortening rate Quaternary north margin of Qaidam Basin |
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