Sedimentary System And Evolution Of Neogene In East Liaodong Area

Based on the previous research results,regional structures,and sedimentary backgrounds,this paper makes full use of core,logging and seismic interpretation data on the basis of sedimentology and sequence stratigraphy,and carries out a comprehensive study of sequence stratigraphy and sedimentary system in the Neogene Guantao formation and the lower Minghuazhen formation in the east of Liaodong area.Firstly,based on the core sequence observation,well log interpretation and seismic reflection sequence stratigraphic interpretation,the sequence and system boundary were identified.sequence stratigraphy was divided,and a sequence stratigraphic framework of the entire region was established.The results show that three tertiary sequences were identified in the Guantao Formation and the lower Minghuazhen Formation in the Neogene.The Guantao Formation corresponds to a three-level sequence(SQ1),and the lowstand system tract(LST),the transgressive system tract(TST)and the highstand system tract(HST)can be identified internally.The lower Minghuazhen Formation is divided into two third-level sequences(SQ2,SQ3),and the lower part corresponds to SQ2,which can further identify TST.and HST,the upper part corresponds to SQ3 and TST and HST can also be identified.Secondly,through the identification of phase markers,the comprehensive analysis of single well facies,wells,logging facies and seismic facies,combined with paleogomorphology,paleowater system and paleoclimate,5 sedimentary facies are identified in the Guantao Formation and the lower Minghuazhen Formation in the east of Liaodong area: braided river,braided river delta,meandering river delta,shallow water delta and lakes.Among them,the braided river mainly developed in the early stage of the lower section of the Guantao Formation,and the braided river delta mainly distributed in the middle and late stages of the lower section of the Guantao Formation.The meandering river delta mainly develops in the upper section of the Guantao Formation and the lower part of the lower Minghuazhen Formation,while the shallow water delta is mainly distributed in the upper part of the lower Minghuazhen Formation,and the lake phase develops in the low-lying areas during each depositional period.Based on the analysis of the drilling and logging data deposition environment,the spatial distribution of sedimentary systems in different system domains was implemented based on the results of paleogeomorphic restoration and seismic attributes analysis.According to the analysis,the paleogeomorphological evolution and paleoclimate change are the main factors controlling the sedimentary evolution of this area.In the early stage of SQ1 development,after the Dongying movement,the landform slope was large,and the surface undulations affected the development of braided river sediments;with the deposition slowing down and the climate shifting to temperature and humidity,SQ1 evolved into braided river delta and meandering river delta in the middle and late stages of development.During the development period of SQ2,the landforms gradually became flat,and the sedimentary background inherited the characteristics of SQ1.The development of the meandering river delta was the main feature.By the time SQ3 was developed,on the basis of further landform slowing,the cold-warm,dry-wet changes of the climate were frequent,and the level of lake level rises and falls,resulting in the development of the meandering river delta in its early estuary dams that evolved into the development of branch channels.shallow water delta.