库车坳陷中生界陆相层序地层格架与盆地演化

PATTERN AND EVOLUTION OF MESOZOIC CONTINENTAL SEQUENCE STRATIGRAPHYIN THE KUQA DEPRESSION

根据库车坳陷野外露头和钻井地层对比与沉积相分析 ,建立了库车坳陷中生界陆相层序地层的格架 ,总结了陆相盆地层序地层发育的特点 ,指出了多期叠合盆地陆相层序发育和横向对比的复杂性。将库车坳陷中生界划分了 5个二级构造层序 ,每个层序分别由低位、湖侵和高位体系域组成。低位体系域多为巨厚的冲积扇、扇三角洲和辫状河三角洲沉积体系 ,代表较强烈的造山活动期的沉积响应。湖侵体系域主要为辫状河三角洲前缘—滨浅湖沉积体系 ,代表造山运动间歇期的沉积响应。高位体系域多为冲积扇—辫状河三角洲平原沉积体系 ,代表较弱的造山活动期的沉积响应。根据库车坳陷层序演化 ,建立了陆相盆地的 3种盆地模式 ,即强挤压沉陷盆地 ,以早_ 中三叠世和晚第三 第四纪为代表 ;弱挤压沉陷盆地 ,以晚侏罗 早白垩世为代表 ;造山后剥蚀反弹盆地 ,以晚三叠世 早。

Basedonstratigraphicalcorrelationandsedimentaryfaciesoftheoutcropsandthedrilling wells,thesequencestratigraphicpatternofMesozoicintheKuqadepressionwasestablished ,and thecharacteristicsofsequencestratigraphyincontinentalbasinssummarized .Thereoccurredcom plexityonthedevelopmentandcorrelationofcontinentalsequencestratigraphyinthemanyperiods ofsuperpositedbasins.Fivesecond ordertectonicsequencesofMesozoicintheKuqadepression weredivided .Eachsequencewascomposedoflowstandsystemtracts ,transgressivesystemtracts andhighstandsystemtracts.Thelowstandsystemtractsweremostlyhugethicknessalluvial,fan deltaandbraideddeltadepositonalsystemsrespondedtointensiveorogenesis.Thetransgressivesys temtractsweremostlybraideddeltafronttoshoreandmereoflakerespondedtointermittentoforo genesis.Thehighstandsystemtractsweremostlyalluvialandbraideddeltaplaindepositonalsys temsrespondedtoweaklyorogenesis.BasedonthesequenceevolutionsoftheKuqacontinental basin,threeevolutionmodelswereconcluded ,namely,high flexiblebasinduringEarly Middle TriassicandNeogenetoQuaternary ,weakly flexiblebasinduringLateJurassictoEarlyCretaceous, andreboundbasinafterorogeniccollisionduringLateTriassictoEarly MiddleJurassicandPaleo gene.