【作者】 徐胜林；

【导师】 陈洪德；

【作者基本信息】 成都理工大学 ， 沉积学， 2010， 博士

【摘要】 论文以沉积学,层序地层学,古生物学,地球化学和地球物理学等学科理论为指导,通过对川西前陆盆地上三叠统-侏罗系野外露头,钻井岩心,测井资料、地震资料和地球化学资料的综合分析,研究了川西前陆盆地上三叠统至侏罗系的沉积体系特征,层序地层学特征,在此基础上进一步分析了川西前陆盆地与龙门山造山带盆山耦合过程中的沉积充填特征,主要认识如下:1.根据岩石组合、沉积组构、沉积序列、生物组合以及沉积机理等因素,并综合运用前人已有工作成果,本文认为川西前陆盆地沉积演化过程中可识别出3个沉积体系组和8个沉积体系;大陆沉积体系组,海陆沉积体系组和海洋沉积体系组;大陆体系组:主要包括冲积扇沉积体系、河流沉积体系,湖泊三角洲沉积体系和湖泊沉积体系;海陆过渡体系组:主要有三角洲、河口湾沉积体系;海洋体系组:主要有滨岸沉积体系、浅海陆棚沉积体系,并详细研究了各沉积体系在川西地区的发育特征。2.通过野外露头与钻井岩心观测,结合测井和地震资料,晚三叠世-侏罗纪川西前陆盆地层序界面表现形式有以下7种:不整合面,古喀斯特作用面,大型底冲刷面,间歇暴露面,超覆面,岩性岩相转换面,最大(海)湖泛面;且以此为根据认为晚三叠世-侏罗纪川西前陆盆地可以识别出6个构造层序,14个三级层,较为深刻的研究了各级层序发育特征,并详细探讨了影响层序发育的因素。3.通过对晚三叠世-侏罗纪川西前陆盆地沉积充填特征分析,发现:①晚三叠世至侏罗纪川西前陆盆地沉积环境经历了从海相沉积环境到海陆过渡沉积环境,并最终演变为陆相沉积环境,海陆转换的关键时刻为安县运动。②同一时期,川西前陆盆地北部地区,中部地区和南部地区的沉积充填特征具有差异性;不同时期,川西前陆盆地北部地区,中部地区,南部地区各自垂向沉积充填特征同样具有差异性;并依此建立了相应的沉积学模式。③TS1BE马鞍塘期,龙门山造山带整体尚处于构造活动初期,川西前陆盆地以发育混积陆棚沉积环境为特征,且在安县地区见有生物礁沉积;TS1BW小塘子期龙门山造山带北段最先发生构造隆升,海相三角洲沉积体系发育于川西前陆盆地西北部。TS2BE期龙门山造山带北段再次经历了较为强烈的造山运动,形成快速充填的沉积结构,而龙门山造山带中段和南段构造活动不显著,前者于盆地形成自西而东的海相三角洲-滨浅海沉积,后者则表现为自西而东滨浅海-海相三角洲沉积;TS2BW期,龙门山造山带南段也发生了构造隆升,同龙门山造山带北段一起为川西前陆盆地提供沉积物质,而龙门山造山带中段地区构造活动尚不显著,毗邻的川西前陆盆地中部地区仍与广海连通。安县运动后(TS2BW顶,TS3BE底)龙门山造山带中段完成了最后的隆升,海水从此退出了川西前陆盆地,盆地进入陆相沉积盆地演化阶段。TS3-TS6期,川西地区开始进入前陆盆地的陆相沉积演化阶段,主体发育河流三角洲-湖盆沉积环境。④侏罗纪川西前陆盆地为陆相湖盆演化阶段,在盆地扩张体系域(BE),龙门山造山带构造活动剧烈,盆地以发育冲积扇沉积体系为特点,三角洲沉积体系不发育,在盆地收缩体系域(BW),龙门山构造活动相对较弱,盆地以发育三角洲沉积体系为特征,冲积扇沉积体系不发育;侏罗纪各时期总体表现为龙门山造山带北段和南段较为活跃,中段活性较差。⑤退积体系域(RST)发生于构造推覆作用增强阶段,以发育冲积扇沉积体系为特征,三角洲沉积体系不甚发育;进积体系域(PST)在构造推覆减弱至停息阶段,以发育三角洲沉积体系为特征,冲积扇沉积体系不发育。更多还原

【Abstract】 Guided by sedimentology, sequence stratigraphy, paleobiology, geochemistry, geophysics and so on, Integrated researhed the outcrops, cores ,logging data ,seismic data and geochemistry data from the late Triassic to Jurassic in the western Sichuan foreland Basin, realized the charaters of depositional system, sequence stratigraphy, depositional charaters within Tectonic Sequence, discussion the realationship between the western Sichuan foreland basin and Longmenshan orogenisc belt from late Triassic to Jurassic. The main achievements as follow were obtained:1.According to the petrofabric, depositional fabric , sedimentary sequence, life assemblage and so on, combined with predecessor’s research, 3 sedimentary system groups and 8 sedimentary system were recognized. Continental sedimentary system group contain alluvial fan sedimentary system, fluvial sedimentary system and lake sedimentary system; transition sedimentary system group contain delta sedimentary system and gulf sedimentary system; marine sedimentary system group contain beach sedimentary system and mixed shelf sedimentary system.2.According to the outcrops and cores ,combined with logging data and seismic figures ,7sequence typical surfaces were found,which were surface of unconformity, surface of ancient karst, surface of erosion, surface of weather crust, surface of onlap,transition surface of rock character and facies and flooding transgressive surface. And then 6 tectonic sequence and 14 sedimentary sequence were recognized,the characters of eace tectonic sequence and sedimentary sequence detailed researched, and the elements which controled or impacted the development of tectonic sequence and sedimentary sequence were discussed at the same time.3.sedimentary-filling graphs within tectonic sequence system tract from late Triassic to Jurassic built up, found that:①From late Triassic to Jurassic, the environment of western Sichuan foreland basin was difference ,at the beginning ,the setting was marine, then changed to transition ,finally changed to continental environment, and the key stage was Anxian tectonic movement. ②The tectonic movement of Longmenshan orogenisc belt was eposide, the movement of each part of Longmenshan orogenisc belt was different form late Triassic to Jurassic, and the adjacent area’s setting was different too.So the sedimentary models built up in different place or at the different time was difference.③During the Ma’antang Stage(TS1BE), tectonic movement of Longmenshan orogenisc belt was weak and entire underwater ,mixed shelf is the mainly setting of the western Sichuan foreland baisn and sponge reefs found in the Anxian district. During the Xiaotangzi Stage(TS1BW), the north part of Longmenshan orogenisc belt uplifted firstly and marine delta found in the corresponding place of western Sichuan foreland basin.During the stage of TS2BE, tectonic movement of the north part of Longmenshan orogenisc belt rivived , which led sedimentary structures with rapid filling characters forming in the north-west part of western Sichuan foreland basin, and tectonic movement of the middle part and the south part of Longmenshan orogenisc belt remainly quiet. In this situation ,form west to east, marine delta to coastal-shallow sea setting formed in the north-west Sichuan foreland baisn ,and coastal-shallow sea to marine delta setting formed in the other place. During the stage of TS2BW, the south part of Longmenshan orogenisc belt uplifted ,too. The fragmentary material stripped form the south part and the north part of Longmenshan orogenisc belt were transported into the western Sichuan foreland basin. During this time ,tectonic movement of the middle part of Longmenshan orogenisc belt was not obvious, the environment of western Sichuan foreland basin remain transition.When the time come to the end of TS2BW and the begin of TS3BE, the middle part of Longmenshan orogenisc belt uplifted ,and the sea water dismiss form the western Sichuan foreland basin.After that, fluvial delta and lake were the mainly setting of western Sichuan foreland basin.④During the stage of Jurassic,the tectonic movement mainly occurred at the stage of basin expansion(BE) ,and the stage of basin withdrawal(BW) is quiet. So we could find alluvial fan sedimentary system in the stage of BE and delta fan sedimentary system in the stage of BW.⑤The RST system tract occurred during the stage of tectonic movement happened, which lead to alluvial fan sedimentary system, PST system tract occurred during the stage of tectonic movement quiet , and mainly developed delta fan sedimentary system , alluvial fan sedimentary system hardly found.更多还原