ABSTRACT

The Cenozoic sedimentary infill of the Qaidam Basin in the northern Tibetan Plateau provide significant insights into the uplift history and the tectonic evolution of the basin-bounding mountain ranges. Along the SW basin margin, a continuous record is preserved in the ~3000-m-thick Cenozoic succession at the Changweitai area. An up-section switch from marginal and deep lacustrine sedimentation to lacustrine delta-alluvial fan deposition indicates progradation and increasingly basinward advance of sediment transportation systems. Provenance data from sandstone petrology, palaeocurrent analysis and zircon U-Pb geochronology suggest that the Eastern Kunlun Range has been consistently providing material to the SW Qaidam basin since the deposition of the upper Xiaganchaigou Formation, indicating its latest uplift episode prior to the Late Eocene (before 35.5 Ma). However, variation in depositional systems indicates a clear shift in sediment provenance between the deposition of the Xiayoushashan Formation and the Shangyoushashan Formation. We propose that the Cenozoic Eastern Kunlun Range experienced a northward encroachment of shortening into the Qaidam Basin. During the Early Miocene, extensive topographic growth of the Altyn Tagh Range caused by reactivation of the Altyn Tagh strike-slip fault, provided the main source of sediment for the western Qaidam basin. Subsequently, a new source for the basin was provided by the uplifting Qimen Tagh subrange since ~15 Ma.

摘要

青藏高原北部柴达木盆地的新生代沉积充填物对盆地抬升历史和盆地边界山脉的构造演化提供了重要的见识。沿西南盆地边缘，昌威台地区约3000米厚的新生代陆续保留了连续记录。从边缘和深湖相沉积向湖三角洲冲积扇状沉积的向上转换表明，沉积物输送系统逐渐发展并向盆地方向发展。来自砂岩岩石学，古流分析和锆石U-Pb年代学的物源数据表明，自下夏格岔沟组上部沉积以来，东部昆仑山脉一直为柴达木西南盆地提供物质，表示其晚始新世（35.5 Ma之前）的最新隆升事件。然而，沉积系统的变化表明，夏游沙山组沉积与上游沙山组沉积之间的物源明显转移。我们认为，新生代东部昆仑山脉经历了向北缩短到柴达木盆地的侵占。在中新世早期，由于阿尔金塔格走滑断层的复活而引起的阿尔金塔格山脉广泛的地形生长，为柴达木盆地西部提供了主要的沉积物来源。随后，自约15 Ma以来，起义的祁门塔格次子带为该盆地提供了新的资源。沉积系统的变化表明，下游沙山组沉积与上游沙山组沉积之间的物源明显转移。我们认为，新生代东部昆仑山脉经历了向北缩短到柴达木盆地的侵占。在中新世早期，由于阿尔金塔格走滑断层的复活而引起的阿尔金塔格山脉广泛的地形生长，为柴达木盆地西部提供了主要的沉积物来源。随后，自约15 Ma以来，起义的祁门塔格次子带为该盆地提供了新的资源。沉积系统的变化表明，下游沙山组沉积与上游沙山组沉积之间的物源明显转移。我们认为，新生代东部昆仑山脉经历了向北缩短到柴达木盆地的侵占。在中新世早期，由于阿尔金塔格走滑断层的复活而引起的阿尔金塔格山脉广泛的地形生长，为柴达木盆地西部提供了主要的沉积物来源。随后，自约15 Ma以来，起义的祁门塔格次子带为该盆地提供了新的资源。阿尔金塔格走滑断层的复活导致阿尔金塔格山脉的广泛地形生长，为柴达木盆地西部提供了主要的沉积物来源。随后，自约15 Ma以来，起义的祁门塔格次子带为该盆地提供了新的资源。阿尔金塔格走滑断层的复活导致阿尔金塔格山脉的广泛地形生长，为柴达木盆地西部提供了主要的沉积物来源。随后，自〜15 Ma以来隆起的Qimen Tagh子范围为盆地提供了新的资源。