Sequence Stratigraphy And Sedimentary Characteristics Of The Linyi Delta Sand Bodies In The Upper Of The Third Member Of Shahejie Formation In The Huimin Sag

Linnan Subsag is located in the southwest of Huimin Sag in the west of Jiyang Depression.It is a graben basin which was controlled by north-leaning Xiakou Fault and south-leaning Linshang Fault.Linyi Delta developed in the north of Linnan Subsag in the upper of the third member of Shahejie Formation.In this paper,based on the drilling core,logging data,seismic data,analysis of test data,through the methods of seismic interpretation,core observation and grain size analysis,a systematic research of sequence stratigraphy,the direction of provenance system,sedimentary characteristics and distribution pattern of the Linyi Delta sand bodies were carried on.According to seismic data interpretation and the applying of logging data,and on the basis of the tracking reflection of the top and bottom surface(T3,T4)of the upper of the third member of Shahejie Formation,four subsequence interface from bottom to top(Q1-Q4)and five parasequence sets were identified.The parasequence sets prograde forward sequentially from west to east during the overall subsiding progress of base level of the upper part of the third member of Shahejie Formation.Parasequence set 1-3 were mainly located in the central and western regions.Those parasequences were characterized by the rising half cycle and falling half cycle of the base level,and dominated by the falling half cycle.Parasequence set 4 and Parasequence set 5 located in the eastern region,dominated by the falling half cycle of the base level.According to topographical features and seismic progradation reflection,the palaeocurrent direction,sandstone percentage,heavy mineral analysis,the source of sediment in the upper third member of Shahejie Formation of Linyi Delta was the western Chengning Heave.The whole area was divided into two parts by the Panhe Heave,which is distributed in Pan 27-Pan 22-Pan 214-Shang 643.The south part was sourced from NWW,while the north part was sourced from SWW,with the direction from west to east totally.Delta and turbidite fan deposits are common in the research area and the delta front sedimentary sand bodies were most developed.The delta plain deposits mainly developed in the rising plate of LinShang fault,of which the distributary channel and interdistributary subfacies are most developed.Delta front was extensively developed in the central and west region,mainly developing underwater distributary channel and mouth bar deposits with obvious progradational characteristics.Delta front sand bodies slumped under the volcanic or earthquake activities which triggered turbidite sand bodies in the deep water in front of it.On the basis of sequence stratigraphic framework,taking Parasequence sets as constraints,the studied area was subdivided into five period of periodic delta-turbidite sedimentary bodies.The deposition sequentially prograde forward in each period and the delta sedimentation took the main role as the turbidite locally distributed(from 1-3 period).Locally,in the north,the water depth was relatively shallow and containing less turbidites.On the contrary,the water depth incersaed company with aboundabt turbidite added in the south.The sand body-Parasequence set 3 was slected to analysis the internal farmwork of their deposits.It was concluded that three different lobe sediments were distinguished.The 3 period lobes continued moving.Lobe 1 formed previously in the south lower region.Lobe 2 and 3 gradually developed after the evening of the south lower region while the channel changed northward.The lobe deposited corresponding turbidites in the deep water at their front respectively.Based on the above observations,the sedimentary model of Linyi delta that the single delta lobe continued moving was established.