Sedimentary Character And Evolution Of Mesozoic Jiyang Depression

According to the comprehensive interpretation of seismic data andthe analysis of balanced section ,the properties of kinematic andgeometry of Mesozoic in Jiyang depression were anatomised.The resultsshow that intermountainous basin developed in Jurassic Jiyang depressin,andwasinternallybuiltupbyanumberofsubbasinsofvariousscales.Thebasin system experinced three evolution stages of contractive basinbeing controlled by compressional enviroment, depression basin and faultbasin being controlled by extensional enviroment.And that contractivestructual styles developed in compresson-subsidence stage, tectonicactivities were sleep in depression stage and half grabens developed infaultstage.According to representative outcrop in environs of Jiyang ,coreobservation, a lot of well logging,seismic data and tectonic location, manysedimentary facies,such as river,delta,fan delta,lake and swamp, areidentified ,and their sedimentary facies model are built. After the analysisofthedistributoncharacterof gravellysandstone, thecontent ofstationaryand non- stationary mineral and trace element, it is found that the detritalmaterials in sedimentary areas are mainly derived from the West-Northside and the East-South side,and partial detrital materials derived frominteralpartialprominence.The research of geodynamic setting of the basin evolution andsedimentry systems shows that alluvial fan-river-lake sedmentary systemswere dominant in Mosozoic of Jiyang depressin, and lake facies was also semi-deep lake subfacies .The sedimentation of Jurassic Jiyang provincewas mainly controlled by convergence of Siberia plate ,Yangtze plate andNorth China plate in Eurasian tectonic system, and the sedimentation ofCretaceous Jiyang province was mainly controlled by the activity ofsinistralshearofTanlufaultzone.Being primarily controlled by the more strong activities ofNorth-West overthrusts, intermountainous contractive basin , which wasinternally built up by a number of sometimes isolated and sometimeslinked subbasins of various scales, developed in Early-middle Jurassic,sedimentation and subsidence centers were situated on the East-Northsides of overthrusts and the difference of both was subtle,and the maindeposit is composed of dark fine clastic rock and red coarse clasticrockstructure.Beingprimarilycontrolledbypaleogeographyandclimate,intermountainous depression basin , which was internally built up by anumber of isolated subbasins of various scales, developed in late Jurassic,thelocationofsedimentationandsubsidencecenters was thesame,andthemain deposit is composed of red coarse clastic rock and grey coarseclastic rock structure . Being primarily controlled by the strong activitiesof North-West faults, intermountainous fault basin , which was internallybuilt up by a number of sometimes isolated and sometimes linkedsubbasinsofvariousscales,developedatearlyperiodofEarlyCretaceous ,sedimentation and subsidence centers were situated on the South-Westsides of faults and the difference of both was great,and the main depositis composed of red coarse clastic rock and grey coarse clastic rockstructure . Being primarily controlled by the poor activities of North-Westfaults, intermountainous fault basin , which was internally built up by anumber of isolated subbasins of various scales, developed at late period ofEarly Cretaceous , the locational difference of sedimentation andsubsidence centers was dwindled, and the main deposit is composed ofthevolcanicrocks.Based on the research of the Sedimentary-Tectonic evolution,the distribution character of coal seam, source,reservoir and cap rocks wereanalyzed. The results show that there are two source rocks,which are coalseam and dark argillaceous rock at early-middle Jurassic and darkargillaceous rock at earlyperiod of earlyCretaceous,and that the river anddelta facies sandstones of low Cretaceous ,which are at the vicinitiy offaultszones,arethefavourableexplorationtargets.