【作者】 纪占胜；

【导师】 姚建新；

【作者基本信息】 中国地质科学院 ， 古生物学与地层学， 2006， 博士

【摘要】 研究了西藏及滇西地区石炭纪一三叠纪沉积体系和古生物群的时空演化规律、讨论了成因及其地质学意义,最终对羌塘盆地油气地质勘探的区域和层系提出了建议。在地层学方面,进一步完善了拉萨地区旁多群的地层序列、厘定了申扎地区德日昂玛一下拉剖面的岩石地层序列、在冈底斯一念青唐古拉地层区发现了三叠系的碳酸盐岩地层剖面,新建了三叠系江让组、指出敌布错组和坚扎弄组的地层时代不是晚二叠世,而是晚三叠世一早中侏罗世。在青藏高原和滇西地区,共考察10余条剖面,通过系统分析,进一步完善和修订了石炭系一三叠系的地层格架。在古生物学方面,初步建立了青藏高原冈底斯一念青唐古拉地层区晚石炭世一晚三叠世的牙形石序列。发现了晚石炭世的Neognathodus动物群、中二叠世Vjalovognathus动物群和Rabeignathus动物群、中二叠世中后期的Mesogondolella动物群、晚二叠世长兴阶的Clarkina动物群,在阿里狮泉河地区的左左剖面的左左组中上部发现了早三叠世的牙形石化石。此外,在措勤敌布错的江让组中识别出了早三叠世一晚三叠世的多个牙形石带。在微古植物学上,在申扎地区德日昂玛一下拉剖面的永珠组下部发现了混生孢子组合、在敌布错组和坚扎弄组中发现了晚三叠世一早侏罗世的孢粉组合。系统采集了申扎地区德日昂玛一下拉剖面的腕足类化石,首次建立了腕足类和牙形石化石带的对比关系。发现了牙形石和腕足类在晚石炭世一早二叠世地层划分的意见分歧,指出现在的冈瓦纳相和特提斯相晚石炭世一早二叠世地层划分的主导门类之间还存在着巨大矛盾,有待于进一步解决。并在理论上初步探讨了存在矛盾的原因和解决方法。对冰海相杂砾岩、含砾板岩的特点、成因、大地构造背景和时空演化的规律进行了研究。通过对申扎地区德日昂玛一下拉剖面的珊瑚、腕足类和牙形石类在形态、结构和古生物地理区系的分析,总结出早石炭世一中二叠世生物群性质暖一冷暖混生一冷一冷暖混生一暖的变化规律,通过对沉积特征、沉积相的分析得出了相同的规律。在沉积和古生物特征研究的基础上,探讨了石炭一二叠纪冰期和冈瓦纳大陆冰川、冈瓦纳大陆北缘裂谷系、生物群性质三者之间的相互作用。指出冈瓦纳一特提斯过渡相区是在早石炭世末期冈瓦纳大陆北缘形成的裂谷系基础上发展起来的,在晚石炭世一早二叠世为大陆边缘裂谷,在中二叠世时期裂谷作用增强,发展成陆表浅海,一直持续到晚二叠世末期,而羌南和羌北在晚二叠世末期已经拼合到劳亚大陆,三叠纪早中期,又一次大规模伸展,三叠纪末期受喜马拉雅块体的俯冲碰撞,冈底斯以北隆升成陆地。构建了一个与以往完全不同的构造演化模型。在沉积体系和古生物群分布规律的研究基础上,指出羌南和羌北地区在晚石炭世一早二叠世时期,隶属于冈瓦纳大陆的北缘,经过中二叠世和晚二叠世的冈底斯以南地区的裂谷作用的加强和强烈的伸展运动,在晚二叠世末期已经拼贴在劳亚大陆的南缘,在三叠纪时期羌南和冈底斯以南地区又一次强烈的伸展,在雅鲁藏布江一带形成具有洋盆性质的深水盆地,在班公湖一怒江断裂带在附近拉伸出大陆边缘的裂谷,晚三叠世末期,雅鲁藏布江一线俯冲碰撞,冈底斯及以北地区强烈隆升,形成陆地。通过三叠纪时期的沉积体系的时空演化序列,分析出三叠纪在冈底斯北缘、羌南地区形成了有利的生储盖的岩相配置,通过盆地热演化史和牙形石有机变质成熟度的分析,指出冈底斯一念青唐古拉地层区北缘和羌南的三叠系具有良好的油气勘探前景。更多还原

【Abstract】 The spatio-temporal distributions and evolutions of the Caboniferous-Triassic sediment and biota in Tibet and West Yunnan are studied. And their origins and geological implications are discussed too. The sequence of the Pangduo Group in the Lhasa area was further described; the lithostratigraphic formations at the Deriangma-Xiala section in Xainza area was clarified; A new Triassic section was discovered at Dibucuo in Cuoqin area, and the Jiangrang Formation was suggested to it; The Dibucuo Formation and the Jianzhanong Formation was revised to be the Late Triassic -Early Jurassic instead of the Late Permian previously. Based on the investigation and analyse on more than 10 sections on the Qinghai-Xizang(Tibet) Plateau and West Yunnan, the sequence through the Carboniferous to the Triassic was revised.The conodont sequence from the Late Carboniferous to the Late Triassic was primarily established in the Gongdise-Nyainqentanglha Stratigraphic Region. The Late Carboniferous Neognathodus fauna, the Middle Permian Vjalovognathus fauna and Rabeignathus fauna, the Late Permian Clarkina fauna were discovered. The Triassic conodont was found in the Zuozuo Formation in Shiquanhe area. Sereral conodont zones through the Early Triassic to the Late Triassic were recognized in the Jiangrang Formation in the Cuoqin area.The mixed palynological assemblage of the lower part of the Yongzhu Formation, Xianza District, Northern Xizang (Tibet) was found. The Late Triassic-Early Jurassic palynological assemblage was found from the Dibucuo Formation and the Jianzhanong Formation, which were thought to be Late Permian previously. The brachiopod fossils were systemically collected at the Deriangma-Xiala section in Xainza area, and its correlation with conodont zones was recognized too. And based on the correlation between the conodonts and brachiopods, the conflict of the division of the Late Carboniferous-Early Permian between the Gondwana and Tethys was discovered. The reason and solution of the conflict was discussed theoretically too.The characteristics, the spatio-temporal distributions, origin and tectonic backgroud of the glaciomarine deposition, diamictite, pebbly slates were studied too.Based on the analyse of the form, structure and their provincilism of the coral, brachiopod and conodont at the Deriangma-Xiala section, the biota through the Early Carboniferous to the middle Permian displayed a series of the Warm fauna-mixed fauna-Cool fauna-mixed fauna-Warm fauna. The analyse on the characteristic of the deposition and sedimentary facies showed the same evolutionary trend. Based on the spatio-temporal distributions and evolutions of the Caboniferous-Triassic sedimentary assemblage and biota, the relationships and effects among the Caboniferous-Permian Ice Age, the Gondwana glacier, and the rift system at the northern margin of the Gondwana were discussed.Based on the spatio-temporal distributions and evolutions of the Caboniferous-Triassic sedimentary assemblage and biota, the Qiangtang Block was thought to be at the northern margin of the Gondwana Continent during the Late Carboniferous to the Early Permian. It was pushed northwards during the Middle and early of Late Permian by the rift of the South tethys. At the end of the Late Permian, it was collided to be the southern margin of the Euro-Asia Continent. During the Triassic, it underwent the the transgression and regression of the sea-level, at the end of the Triassic it was uplifted to be land again with the Gondise Block. Based on the analyse of the stratigraphic sequence of the Triassic and its covering strata and the Index of the Organic Metamorphic Maturity of conodont, the Triassic of the northern margin of the Gongdise-Nyainqentanglha Stratigraphic Region and the South of the Qiantang Stratigraphic Region was a promising target for the oil exploration.更多还原