【摘要】 青藏高原东缘的大渡河中游泸定—石棉段呈深切河谷地貌,发育岩崩、滑坡、古地震堰塞湖、冲洪积扇等不同类型的堆积物、沉积物。基于野外调查、遥感解译、剖面测量和光释光测年(OSL)发现,这些沉积物记录了龙门山断裂带西南段——冷碛镇断裂2万年来的两期活动,可能是2次古地震事件。第一期发生在18ka左右,冷碛镇断裂切割了晚更新世的角砾状砂层和岩崩堆积物,显示右行走滑特征。这期变形促使大渡河堵塞,形成得威乡古堰塞湖,其堵江位置位于加郡乡—得妥乡的V型深切河谷段。第二期活动冷碛镇断裂切割了湖相地层,并破坏了堰塞湖,可能发生在11ka左右。新发现对于全面认识龙门山断裂带的活动历史、序列及方式具有重要意义。更多还原

【Abstract】 In the deep-incised valleys along the middle reaches of the Dadu River,field investigation led to the discovery of several types of sediments,which include rockfalls,landslides and paleo-dammed lake sediments. These sediments have preserved the activity records of the Lengqizhen fault,which is the southernmost segment of the Longmen Mountain fault zone. Two strike-slip events were determined on the basis of high resolution SPOT imagery interpretation,field observations,and stimulated luminescence dating(OSL). The early event occurred at 18 Ma and the later at 11 Ma. During the early deformation event,right slip faulting of the Lengqizhen fault cut into a brecciated sand and a suite of massive blocks. This deformation caused a damming event in the Dadu River and formed the Dewei paleo-dammed lake. The dammed lake lasted for 8ka and eventually broke about 11 ka ago. The position of the damming event occurred in the main valley,from Jiajun Township to Dewei Township,along the V-shaped stream of the Dadu River. The late deformation event of the fault cut into the lacustrine deposits. This study has a great significance for understanding the history,activities and the full sequence of the Longmen Mountain fault zone.更多还原