In southeast Chongqing City,the Nanhuan System is only found in Xiushan and Youyang County and can be divided into three Formations:Nantuo Formations,Datangpo Formations and Qianzimen Formations,of which Nantuo Formations and Qianzimen Formations are Drift sheet,and their ssedimentary enviroment is glacial ground moraine-tillite facies,Lensatis sand-condlomerate facies in englacial channel,proglacial littora facies,forming a large managanese deposit,Nanhuan Period climate has the typical three-stage structural features:the upper and lower glacial,sandwhiched between an interglacial,i.e.Natuo glacia stage,the interglacial of Datangpo and Qianzimen glacial.