Genetic Model of the Deep Water Salt Lake of the Paleogene Sha-4 Member in Dongying Sag

Key words: 
• the Paleogene /
• Sha-4 member in Dongying sag /
• salt lake

Abstract: There were cyclothems consisted of evaporite rocks,deep color mudstones or shales and deep water turbidity sediments of Peleogene Sha-4 member in Dongying sag,which was salt lake sedimentary assemblage with more than 1000m in thickness.The evaporite rocks consisted of halite and anhydrite rocks mainly existed in north and centre of Dongying sag where the deep fractures developed.The fossil assemblage indicated that the climate was semi-dry and semi-moist in Paleogene Sha-4 member in Dongying sag.Analyzed the sedimentary characteristics and depositional conditions,the authors considered that the brine in deep water was the substance basis of the salt sediment,the salt in deep strata was the source of brine and the deep fractures in the north of the sag were the paths where the salt substance entered the developing sag.The deep water genesis model of salt lake in Dongpu sag which can be compared with that of Lake Kivu,was put forward after the discussion.The new field in subsalt strata exploration can be found on the basis of the lithofacies assemblage of source rock and evaporite rock.