Cosmogenic nuclide burial age of the Sanying Formation and its implications  

作　　者：ZHENG Yong JIA Jun NIE XiKe KONG Ping 

机构地区：[1]Key Laboratory of the Earth's Deep Interior,Institute of Geology and Geophysics, Chinese Academy of Sciences

出　　处：《Science China Earth Sciences》2014年第6期1141-1149,共9页中国科学（地球科学英文版）

基　　金：supported by the"Strategic Priority Research Program"of the Chinese Academy of Sciences(Grant No.XDB03020300);National Natural Science Foundation of China(Grant Nos.41173067&41021063)

摘　　要：The Pliocene fluvial/lacustrine sediments of the Sanying Formation lie along the Red River fault and its northwest extension;their majority outcrops appear around Eryuan.The Sanying Formation is characterized by multiple intercalated coal layers and its unconformities contact with the underlying Triassic limestone and the overlying Quaternary coarse sediments.Cosmogenic nuclide burial dating confirms the Pliocene age of the Sanying Formation.The burial ages of the overlying Quaternary sediments provide the lower age limit of the Sanying Formation:2 Ma.Detrital zircon U-Pb age distribution suggests provenance of the Sanying Formation traced to the Songpan-Ganzi flysch belt.From the spatial distribution as well as sedimentary and fault ages,we found a strong connection of the Sanying Formation with the Red River and the Jianchuan faults.We therefore propose that activation of the Red River and the Jianchuan faults during the Late Miocene resulted in subsidence of basins in the extensional areas around Eryuan and in the middle to south segments of the Red River fault.The basins were filled with water carried by the Jinsha River and overflow-lakes formed within the basins where the Sanying Formation was deposited.Most of the lakes were dried and sedimentation of the Sanying Formation ceased due to the uplift of the Yunling Mountains,which forced rerouting of the Jinsha River at the beginning of Quaternary.The Pliocene fluvial/lacustrine sediments of the Sanying Formation lie along the Red River fault and its northwest extension; their majority outcrops appear around Eryuan. The Sanying Formation is characterized by multiple intercalated coal layers and its unconformities contact with the underlying Triassic limestone and the overlying Quaternary coarse sediments. Cosmogenic nuclide burial dating confirms the Pliocene age of the Sanying Formation. The burial ages of the overlying Quaternary sediments provide the lower age limit of the Sanying Formation： 2 Ma. Detrital zircon U-Pb age distribution suggests provenance of the Sanying Formation traced to the Songpan-Ganzi flysch belt. From the spatial distribution as well as sedimentary and fault ages, we found a strong connection of the Sanying Formation with the Red River and the Jianchuan faults. We therefore propose that activation of the Red River and the Jianchuan faults during the Late Miocene resulted in subsidence of basins in the extensional areas around Eryuan and in the middle to south segments of the Red River fault. The basins were filled with water carried by the Jinsha River and overflow-lakes formed within the basins where the Sanying Formation was deposited. Most of the lakes were dried and sedimentation of the Sanying Formation ceased due to the uplift of the Yunling Mountains, which forced rerouting of the Jinsha River at the beginning of Quaternary.

关 键 词：Sanying Formation burial age cosmogenic nuclide Red River fault Dali fault system 

分 类 号：P542[天文地球—构造地质学]