【作者】 段凯波；

【导师】 梅冥相；

【作者基本信息】 中国地质大学（北京） ， 矿产普查与勘探， 2011， 博士

【摘要】 为全面系统建立中扬子及其邻区晚三叠世至中侏罗世三级层序地层格架,以及摸清沉积相迁移展布规律、沉积古地理演化格局和确定中扬子盆地性质等沉积学问题,以达到对晚印支—早燕山中扬子沉积盆地的较全面认识,为扬子板块和秦岭—大别山造山带组成的盆山体系演化提供重要的沉积学线索,进一步丰富该区大地构造学、沉积学、盆地分析和油气成藏等学科理论体系,同时对中扬子油气资源勘探也具有指导意义。以露头、钻井、测井和古生物等资料为基础,应用现代沉积学理论和陆相层序地层学原理,划分和对比晚三叠世至中侏罗世中扬子及其邻区沉积盆地三级层序地层,以及研究其沉积相（微相）、物源、沉积—构造古地理、盆地性质等方面的特征,得出以下一些结论:①通过对三级层序界面识别,可将晚三叠世至中侏罗世中扬子盆地充填序列共划分为12个三级层序。其中上三叠统大致可识别出3个三级层序T₃S₁、T₃S₂和T₃S₃,下侏罗统可划分为3个三级层序J₁S₁、J₁S₂和J₁S₃,而中侏罗统可识别出6个三级层序J₂S₁、J₂S₂、J₂S₃、J₂S₄、J₂S₅和J₂S₆,部分分区因地层缺失而只能识别出更少的三级层序,不同的三级层序或不同地区的同一三级层序的沉积特征存在一定的差异;②晚三叠世沉积体系主要为一套网状河+曲流河及其三角洲和残留陆表海（湖泊）组成的沉积相组合。而早、中侏罗世主要为曲流河+辫状河及其三角洲和新生湖泊沉积相组合,其中辫状河体系占主导,局部发育冲积体系和扇三角洲体系;③印支晚期在中扬子北缘陆壳向北俯冲碰撞的挠曲沉降作用下,中扬子前陆盆地及其邻区具有相对稳定的古地理背景,沉降沉积主体中心位于中扬子北缘秭归盆地和荆当盆地及西缘分区,地势上具东高西低、南高北低的特征,曲流河及其三角洲和残留湖泊相组合占主导,而网状河体系组合仅分布于鄂东盆地和荆当盆地。而燕山早期中扬子及其邻区除继续受北缘俯冲作用的影响外,还受控于中扬子陆内强烈的挤压变形,存在多沉降沉积中心且沉降幅度更大,区内地势地貌更为复杂,除鄂东盆地和西缘邻区为曲流河体系组合以及南缘为冲积体系或扇三角洲外,中扬子前陆盆地其它各分区沉积体系为占主导的辫状河及其三角洲和新生湖泊沉积相组合;④依据中扬子沉积—构造特征,将晚三叠世至中侏罗世中扬子盆地厘定为陆相磨拉石前陆沉积盆地;更多还原

【Abstract】 To establish 3^rd-order sequence stratum framework fully and systematically, and to make clear sedimentological issues about sedimentary facies distribution and migration, palaegeographical background and evolvement, and the basin attribution for Middle Yangtze and its adjacent areas from Late Triassic to Mid Jurassic, some studies have been determined and worked on. The results are useful for comprehensive understanding of Middle Yangtze Basin from Late Indosinian to Early Yanshanian, and provide important sedimentological clues for further research in basin-orogen evolvement of Yangtze and Qinling-Dabieshan system, and enrich geological theory such as Tectonics, Sedimentology, Basin Analysis and Hydrocarbon Reservoir Forming, meanwhile, the results are guidance for Middle Yangtze hydrocarbon prospecting. On the base of information from outcrops, well drilling, well logging and paleontology and under the guidance of principles from Modern Sedimentology and Continental Sequence Stratigraphy, 3^rd-order sequence strata are divided and correlated, and the sedimentary facies（sub-facies）, provenance, sediment-tectonic paleogeography and basin attribution are analyzed and studied for Middle Yangtze and its adjacent from Late Triassic to Mid Jurassic. The conclusions and results are showed as following:①By identification the third-order sequence stratum boundaries, the Middle Yangtze Basin sedimentary filling sequence from Late Triassic and Early Jurassic can be totally divided into 12 third-order sequence stratum units, in which the 3 of T3S1, T3S2 and T3S3 belongs to Upper Triassic, and the 3 of J₁S₁, J₁S₂ , J₁S₃ and the 6 of J₂S₁, J₂S₂, J₂S₃, J₂S₄, J₂S₅, J₂S₆ belong to Lower Jurassic and Mid Jurassic respectively, but some subareas in Middle Yangtze and its adjacent get less 3^rd-order sequence stratum units because of stratigraphic lacunae. The sequence sedimentary features are different from one to one and from subarea to subarea;②The Late Triassic sedimentary system is characteristic by the sedimentary facies assemblage of Anastomosing River + Meandering River and their Delta + Residue Lake, while the Lower and Mid Jurassic is characteristic by the assemblage of Braided River +Meandering River and their Delta + Newly Lake, which the Braided River system is dominant, and Alluvial system or Fan-Delta system develops partly;③On the influence of flexuring subsidence resulted from subduction to north of Middle Yangtze North Edge, the Middle Yangtze Foreland Basin and its adjacent in Late Triassic keeps a stable paleogeographic background and the center of subsidence and sediment locates in the north edge such as Zigui Basin and Jingdang Basin, and also west edge. The physiognomy is characteristic by“higher east and lower west, higher south and lower north”and the sedimentary system is dominated by Meandering River and its Delta + Residue Lake, while Anastomosing River system distributes in Edong Basin and Jingdang Basin only. Except the impact of flexuring subsidence which has the same mechanism with that in Late Triassic, the Middle Yangtze Area in Early Indosinian is controlled by inland strong compression and deforming, so it has some different centers of subsidence and sediment and has diversiform and complicated physiognomy. During this period, the foreland basin sedimentary system is dominated by assemblage of Braided River and its Delta + Newly Lake, while Meandering assemblage distributes in Edong Basin and Adjacent of West-Edge, and Alluvial system and Fan-Delta system exists in the South Edge;④By analysis Sedimentology and Tectonic features, Middle Yangtze Basin from Late Triassic to Mid Jurassic is a Continental Molasse Foreland Sedimentary Basin probably.更多还原