Abstract:

Shallow-water delta depositswere generally developed during the sedimentation of the second member of the Shahejie Formation in the Chezheng sag of Jiyang Depression with a relatively flat topography.A systematic study of the sedimentary characteristics and models of these delta depositswas performed by integrating core observation and relevant testdatawith logging data.The shallow-water delta front subfacies dom inates the second member of the Formation and can be divided into the inner front and the outer front.It is characterized by large width of facies belt，highly developed underwater distributary channel and largescale distribution of sheet-like sandbody.The shallow-water delta sandbodies are dom inated by medium-to-fine sandstone，siltstone/fine sandstone and siltymudstone.The grain size probability curves present patterns of“rolling+skip+suspension”，“1skip+1suspension”and“2skip+1suspension”.Several types of sedimentary structures were developed，including various fluviatile beddings and wave beddings and marks aswell as bioturbation.

Key words: shallow-water delta, sedimentary characteristic, sedimentary model, Shahejie Formation, Chezhen Sag, Jiyang Depression