Study on the Sedimentary System of Paleogene in Changdi Region of Zhanhua Sag

Key words: 
• Zhanhua Sag /
• Changdi region /
• Paleogene /
• sedimentary system /
• sedimentar subfacies /
• sedl&mdash

Abstract: Changdi region is situated in the eastern part of Zhanhua sag in Jiyang depression．It belongs to one part of the Zhuangxi-Gudong buried hill belt in Structure．with area an about 160 km²．Based on the synthetical analysis the geologieal,log,seismic and chemical analysis data,the authors believe 5 types of sedimentary system were developed in this area in Paleogene,that is,subsurface fan,beach and dam,fan delta,turbidity current and braided river. Subsurface fan can be divided 3 types of sub-facieses,i,e,root-fan,middle-fan and fan edge by core and conglomerate distribution and etc．the middle-fan can be divided 3 micro-facies-braided channel．space between channel and front-edge zone．In the braided channel,sediment grain is coatse．And it shows positive rhythm,SP curve with box type and atc．Surface of scour can be seen at the bottom of the channel． Beach and bar system were formed at the edge of lake．shallow platform and etc．They can be divided into 2 types,i．e．,terrigenous debris type and carbonate rock type．The terrigenous debris type was distributed mainly over the west edge of the study area．and carbonate rock type was distributed mainly in the middle part．About the fan delta system．there were prodelta and delta front in the area．The delta front subfaces consists of embranchment channel,channel mouth bar and etc．Judged by distribution of the sedimentary system,during the third member of Shahejie formation,researching area belongs to subsurface fan system．From the early stage to metaphase,the sediment range were widened gradually．In the later period,the range of lake and size of subsurface fan diminished．During the second member and the early stage of the first member of the Shahejie Formation,this area belonged to beach and bar system．In the third member of Dongying Formation,the study area belonged to fan delta system,and it stretched gradually from southeast to north．duing the later period,the southeast part developed the fan delta plain．The delta front subfaces consisted of embranchment channel,channel mouth bar and etc． During the second member and the first member of the Dongying Formation,this area belonged to braided river system as a whole．There were a series of channel bar deposits． It was thought by synthetically analyzing the regularity of vertical evolution of sedimentary system was stinct．During the third and second member of the Shahejie Formation．the type of sedimentary system was subsurface fan near bank,the sediments came from Changdi lower upheaval．During the first member of the Shahejie Formation．it belonged to beach and bar system,while later period of the member,it was deep lake．From the third member of the Dongying Formation to the second and first member。the sediment system was fan delta,braided river,sediments mostly came from the Kendong—Qingtuozi upheaval．