【作者】 张成弓；

【导师】 陈洪德；

【作者基本信息】 成都理工大学 ， 沉积学， 2010， 硕士

【摘要】 黔南-桂中地区地处上扬子地台南缘,受古特提斯洋演化的影响,在二叠纪-中三叠世期间,在其独特的构造-沉积演化过程中,发育的海相地层具有良好的油气勘探前景。本论文在前人研究成果的基础上,以构造地质学理论、沉积学理论、层序地层学理论为指导,以盆地演化-沉积演化-层序演化为主线,通过研究钻井及野外露头剖面,采取宏观观测与室内微观分析相结合,对该区的沉积体系、层序地层、层序岩相古地理及盆地演化进行综合研究。通过对野外露头剖面、钻井岩芯和测井等资料的综合分析,认为黔南-桂中地区二叠纪-中三叠世发育海岸体系、碳酸盐台地体系、台盆体系和混积陆棚体系等4类沉积体系,详细研究了各沉积体系的特征,建立了海岸沉积模式、碳酸盐台地沉积模式及陆棚沉积模式。在重新厘定黔南-桂中地区二叠纪-中三叠世不同相区的地层划分对比方案的基础上,对野外露头、钻井剖面进行了层序界面识别和层序地层分析,将黔南-桂中地区二叠纪-中三叠世划分为2个超层序,19个三级层序,其中在二叠纪中识别出12个三级层序,下、中三叠世识别出7个三级层序。详细讨论了各三级层序及其体系域的发育特征,并建立了层序地层格架。在沉积体系研究、层序地层学研究的基础上,用构造-层序岩相古地理编图方法,以超层序体系域为编图单元,编制了7张构造-层序岩相古地理图,系统揭示了黔南-桂中地区二叠纪-中三叠世不同时期的相带展布规律。总体上,SS1至SS2早期高位,黔南地区以开阔-局限台地为主,向南至桂中地区则呈现台-盆相间的沉积格局;SS2晚期高位以发育碎屑岩沉积。综合盆地演化动力背景、海平面变化等因素,分析了黔南-桂中地区二叠纪-中三叠世三个盆地演化阶段(被动陆缘裂谷盆地阶段,弧后裂谷盆地阶段,前陆盆地阶段)的沉积充填演化过程。被动陆缘裂谷盆地阶段:早二叠世晚期,由于受到北西、北东两组方向的同沉积断裂控制,形成了典型的破裂型克拉通边缘,同时由于海平面下降的影响,研究区大部分地区暴露剥蚀,仅在地堑区充填SS1超层序的低位体系域;中二叠世早期,由于海平面的上升,黔南地区以开阔-局限台地为主,向南至桂中地区则呈现台-盆相间的沉积格局,形成了SS1超层序的海侵体系域;中二叠世晚期,海域进一步扩大,成为晚古生代的最大海泛期,由于台地的镶边作用,台盆相间格局明显,形成了SS1超层序的高位体系域。弧后裂谷盆地阶段:晚二叠世早期,由于东吴运动的影响,地壳剧烈上升,海平面下降,研究区大部地区隆升暴露,仅在西南部的深水台盆区发育SS2超层序的低位体系域;晚二叠世中晚期,随着海平面上升,隆升暴露区再次被海水侵没,重新呈现台-盆相间格局;早三叠世,沉积格局并没有出现大的变化,海平面持续上升,至奥伦尼克期达到最大,形成了SS2超层序的早期高位体系域。前陆盆地阶段:中三叠世,受印支运动的影响,海平面下降,研究区沉积了一套巨厚的陆源碎屑浊积岩,形成了SS2超层序的高位体系域。更多还原

【Abstract】 South Guizhou and middle Guangxi located in south edge of Upper Yangtzee platform, influenced by the evolution of Paleo-Tethys ocean, from Permian to middle Triassic, within the unique tectonic-sedimentary evolution, there developed marine stratum with good exploration prospects. Based on the predecessors’research achievements, guided by the theory of tectonic geology, sedimentology, sequence stratigraphy, taking the main line of basin evolution, sediment evolution and sequence evolution, according to the study on drilling and outcrop, with the method of macro-observation and indoor analysis on microfacies, this thesis have comprehensively studied on depositional system, sequence stratigraphy, sequence lithofacies paleogeographic and basin evolution.Through comprehensive analysis on outcrop, drilling core and logging data, it is believed that there developed 4 depositional systems from Permian to middle Triassic in south Guizhou and middle Guangxi, which are shore, carbonate platform, platform basin and mixed shelf. The characteristic of each depositional system have been studies in detail, the depositional model of shore, carbonate platform and shelf were established.After regularizing the division and comparison plan of Permian to middle Triassic in south Guizhou and middle Guangxi, sequence boundary identification and sequence stratigraphy analysis are studied on section of outcrop and drilling. It can be divided into 2 super sequence and 19 third-order sequence of Permian to middle Triassic in study area, there are 12 third-order sequence in Permian and 7 third-order sequence in lower to middle Triassic. Each sequence and its characteristic of system tracts were discussed in detail, and the sequence framework has been established.Based on research of depositional system and sequence stratigraphy, taking super sequence system tracts as compilation unit, seven tectonic-sequence lithofacies paleogeographic were drew, which show the depositional facies distribution pattern of different stage from Permian to middle Triassic. Overall, the SS1 and early highstand period of SS2, the open and restricted platform developed in south Guizhou, and the pattern of platform interleaved with basin developed in middle Guangxi, the clastic rocks developed in late highstand period of SS2.Combined with evolution dynamics setting and eustasy, it is analyzed the filling process of three evolution stage from Permian to middle Triassic in study area, which are stage of rift valley basin of passive margin, stage of rift valley basin of back-arc, stage of foreland basin. In the stage of rift valley basin of passive margin, controlled by synsedimentary faulting of NW and NE in late Permian, which formed the typical fractured craton edge, and influenced by the fall of sea level, most of study area exposed to denude, the SS1 lowstand system tracts only filled in graben. In early middle Permian, with the rose of sea level , open platform and restricted platform developed in south Guizhou, and the pattern of platform interleaved with basin developed in middle Guangxi, which formed the SS1 regression system tracts. Then in late middle Permian, regression expanded further, it was the maximum flooding period of late Paleozoic, and due to the rim of platform, the pattern of platform interleaved with basin was more obvious , which formed the highstand system tracts of SS1. In stage of rift valley basin of back-arc, during early late Permian, Dongwu movement reached the climax, crust rose strongly, sea level fell, most of study area rose to expose, the SS2 lowstand system tracts only developed in southwest deep water platform basin, from middle to late of late Permian, with rose of sea level, upheaval zone submerged by water again, the pattern of platform interleaved with basin appeared again. During early Triassic, the depositional pattern didn’t changed much, sea level rose continuously and reached highest at Olenekian stage, which formed the early highstand system tracts of SS2 super sequence. In stage of foreland basin stage, influenced by Indosinian movement, sea level fell, a set of thick epicontinental clastic turbidite deposited in study area, which formed highstand system tracts of SS2 super sequence.更多还原