准噶尔盆地乌夏逆冲断裂带三叠纪-侏罗纪构造控扇规律及时空演化  

Regularities of Triassic-Jurassic Structural Movements Controlling Fans Development in the Wuxia Thrust Belt of Junggar Basin

作　　者：刘华[1] 陈建平[1] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《大地构造与成矿学》2010年第2期204-215,共12页Geotectonica et Metallogenia

基　　金：中石油总公司重点攻关项目"准噶尔盆地西北缘滚动精细勘探项目"资助

摘　　要：通过研究准噶尔盆地西北缘乌夏逆冲断裂带三叠系-侏罗系构造层序、沉积相及断裂特征,认为三叠纪-侏罗纪时期是在二叠纪前陆盆地完全消亡、洋壳俯冲彻底结束后发育的板内挤压陆内坳陷盆地,主要发育冲积扇-扇三角洲-辫状河-湖泊沉积体系,其中扇体发育代表了最典型的沉积特征,反映了构造活动的期次和强度,具有"构造指相性",从下至上划分为三叠系亚构造层序、侏罗系八道湾组-西山窑组亚构造层序和侏罗纪头屯河组-齐古组亚构造层序。分析表明三叠纪-侏罗纪扇体叠置迁移的总体趋势为:T1b-J1b期在扇体总体由盆内向盆缘退缩的背景下,呈现并夹杂两个短期内由盆缘向盆内再盆缘的进退波动变化(T1b-T2k1期、T3b2-J1b1期),即三叠纪-侏罗纪扇体的沉积展布具后退式夹短暂推进式叠置迁移特点。相应地,三叠纪-侏罗纪以形成近东西向和东西向断裂为主,并从盆地内向山前方向依次后展式发育,其间夹杂短暂的前展式发育特征,构造活动强度逐渐由南向北、由西向东迁移。因此,绝大多数同生断裂控制了扇体的沉积边界和分布,部分控制了其厚度和发育方向,扇体的迁移与控扇断裂的活动迁移具有很好的吻合性,断裂活动是控制乌夏地区沉积的主要因素。最终建立了三叠纪-侏罗纪构造控扇响应模式,并划分为三个发育阶段:早三叠世坳陷初期旱地扇发育阶段、中晚三叠世坳陷鼎盛期湿地扇发育阶段、扇三角洲发育阶段和侏罗纪的坳陷填充期陆上平原发育阶段,从早至晚,气候经历了一个由干旱到潮湿,由潮湿变干旱再到潮湿的旋回过程。By the study on Triassic-Jurassic tectonic sequences,sedimentary facies and faults in the Wuxia thrust belt of the Junggar basin,the authors believe that the Wuxia area was an intracontinental depression,experienced Permian foreland basin and oceanic crust subduction. There mainly developed fluvial fans,fan deltas,braid rivers and lakes,among them,the fans are the typical sedimentation,with fine directive property to reflect phases and intensity of structural movements. Thus,from low to up,the sedimentation can be divided into three subsequences：Triassic,J1b-J2x and J2t-J3q. The study indicates that on the whole,the Triassic-Jurassic is characterized by a model of a backward thrusting movement from the interior of basin to the edge of mountainous region with gradual withdrawing migration of fan bodies from strongly to weakly,mingled with two smaller advancing-backing fluctuant processes,that is to say,from T1b to J1b,with the backward thrusting movement of fan-controlling synsedimentary faults from the edge of the Junggar Basin to mountainous region,the intensity of thrusting movement gradually weakened until vanished from the edge to the interior of the basin. At the same time,from the Triassic to Jurassic,there mainly formed approximately east-west and east-west faults,gradually developing from the interior of the basin to the edge of mountainous region,which can be called a backward thrusting movement,sometime reflecting a reverse developing manner,which can be called a forward thrusting movement,so intensity of structural movements migrated from south to north,from west to east gradually,and in different periods most synsedimentary faults controlled edge and distribution of fans,partly controlled their thickness and growth direction,there is an excellent coupling between them. Finally,a structural fan-controlling mode is set up：obvious sedimentary response of gradual retrograde migration from the edge of the basin to mountainous area controlled by the backward thrusting movement,mingled with the smaller f

关 键 词：乌夏逆冲断裂带 三叠纪-侏罗纪 扇体发育 同生断裂 

分 类 号：P542[天文地球—构造地质学]