The Research Of The Characteristic Of Sedimentation-sequence Filling During Paleogene Dongying Formation In Southern Liaoxi Sag

This paper is based on the Dongying Formation of southern Liaoxi Sag,Liaodong Bay Depression.According to the interpretation of drilling cores and the interpretation of geophysical data,the writer uses the techniques of sedimentology,sequence stratigraphy,geophysics,structural geology,the sedimentary facies characteristics and the sequence stratigraphic characteristics during the research.In this paper,three major sedimentary systems,lakes,braided river delta and fan delta,in the study area during Dongying Formation of Paleogene are analyzed.Upon the former study,comprehensive analysis of logging data and seismic profile data,the writer divided the Dongyin Formation,which in the study area,into three third-order sequences,SQd₃,SQd₂ and SQd₁.SQd₃ is mainly composed of semi-deep lake facies.During the SQd₂,the study area gradually turned to braided river delta sedimentary facies.Moreover,a smallscale shoreline sedimentary facies can be found in the study area.When the SQd₃ was deposited,the lake sediments were rarely found in the study area,instead,multi-period braided river delta can be noticed everywhere.All these above,can be the prove of the changing of study area during Dongying Formatiom.During the period that the SQd₃ deposited,the Liaodongyan Basin was in its rapid fracture period.In the study area,the basin area was increasing and the scale of lake was developing.The tectonic activity was weakened and the basin subsidence was mitigated,for the come of late rapid fracture period.At the same time,the western provenance,including Liugu River's magmatite and metamorphic rock mixture provenance and Dashi River magmatite rock provenance,was providing abundant sediments.So,the lake sediments becoming braided river delta sediments in this area.As the provenance comes from the west,the writer construct high-resolution sequence frameworks parallel to the source and perpendicular to source.And the sedimentation-controlling factors are discussed in five ways,which is,A/S ratio,sequence boundary,fault,palaeo-geomorphology and slope break.