Abstract:

Jurassic System developed in the east part of Junggar Basin could be divided into six sedimentary sequences and two tectonic sequences.The sedimentary sequences inclose alluvial fan,braided river,braide river delta and lake sedimentary systems Seatimentary environment includes wetland fan,braided river,braided river delta meandering stream,normal delta,slump turbidite fan,lake shore and shallow lake.The distribution and evolution of the sedimentary systems possess distinct inheritance.There were two provenances in the study area.In sequence I,the north provenance was rich in source materials and formed alluvial fan braided river-braided river delta sedimentary system;in sequence Ⅱ～Ⅲ,lake basin extended and the north provenance receded and formed meandering stream normal deta slump turbidite fan lake sedimentary system;sequences Ⅳ～Ⅴ were controlled by south provenance and small meandering stream deltas formed,the basin rapidly shrank away and meandering stream sediments developed well and distributed extensively.The coal bearing formations in Changji Sag and the slope area,especially the mudstone resulted from lake ingression in sequence Ⅲ are potential source rocks of the study area.The main reservoirs are the sandbodies deposited in the meandering streams and the deltaic sandbodies in sequence Ⅲ in Cainan and the slope area,the sondbodies developed in delta front subaqueous distributive channels of sequences Ⅰ,Ⅲ,Ⅴ in Santai and north Santai areas,the meandering stream sand bars of sequence Ⅵ.

Key words: east Junggar Basin, Jurassic, sedimentary system, depositional environment, hydrocarbon significance