大盈江断裂晚更新世以来活动的地质证据

GEOLOGICAL EVIDENCE OF ACTIVITY ALONG THE DAYINGJIANG FAULT SINCE LATE PLEISTOCENE

大盈江断裂新构造活动特征明显,断层三角面、线性山脊、断层槽地等断层地貌发育,卫星影像上线性特征清晰,断裂对梁河、盈江盆地、桑岗、西帕河等第四纪盆地具有明显的控制作用。根据近年来境内外野外调查结果,大坪子、丙辉村、老新寨、热水塘、广云村等多处断层露头显示错断了晚更新世或全新世地层。丙辉村被错地层年龄为(56.56±4.81)kaBP,断面上发育松软的断层泥;老新寨被错地层年龄为(24.80±2.11)kaBP和(28.80±2.45)kaBP;缅甸境内西帕河T2阶地上发育断层沟槽,长500m,宽12～16m,深5～8m,T2级阶地形成时代为(10.13±0.86)kaBP。断裂最新活动时代为晚更新世—全新世,以水平左旋滑动为主,NE段滑动速率1.5～2.5mm/a;SW段滑动速率1.2～1.6mm/a。

There are evident neotectonic characteristics along the Dayingjiang Fault,with fault landforms developed,such as fault facet,linear ridges,fault troughs etc.,and clear linear features in satellite images.The Quaternary Basins of Lianghe,Yingjiang,Sanggang and Xipahe are obviously controlled by the fault.Based on field investigation results at home and abroad in recent years,the fault has displaced the Late Pleistocene or Holocene strata,as revealed by the outcrops at Dapingzi,Binghui,Laoxinzhai and Guangyun.At Binghui village,the age of the displaced stratum is（56.56±4.81）ka BP,and on the fault plane,loosely consolidated gouge is developed.The ages of the displaced strata at Laoxinzhai village are（24.80±2.11）kaBP and（28.80±2.45）ka BP.At Xipahe of Myanmar,there is a fault trench developed on T2 terrace,with 500m in length,12～16m in width and 5～8m in depth,and the terrace formation age is（10.13±0.86）kaBP.It means that the latest active time of Dayingjiang Fault is late-Pleistocene to Holocene,and the fault has been dominated by left-lateral slip,with an average left-slip rate of 1.5～2.5mm/a along the northeastern segment and 1.2～1.6mm/a along the southwestern segment.