THE SEDIMENTARY ENVIRONMENT ANALYSIS OF THE UPPER PART OF THE SHASI MEMBER IN BONAN SUBSAG

Detailed studies of structure feature and sedimentary facies of the upper part of the Shasi member in Bonan subsag are carried out by means of the combination of geology and geophysical prospecting,and by the combination of macroexamination and microexamination.It is confirmed that the sedimentary environment of the upper part of the Shasi Member in Bonan subsag is littoral facies,semideep lacustrine facies and sublacustrine fan,on the basis of sedimentary cycle and rhythm characteristics. The authors have studied sedimentary facies of the upper part of the Shasi Member in Bonan subsag, divided sublacustrine fan into inner,middle,outer fan,and further divided them into five microfacies, in the light of sedimentary characteristics ,the marks of logging and seismic facies.The characteristics of the distribution of sublacustrine fan,are presented and the sedimentary pattern of sublacustrine fan is established.