【作者】 孙立新；

【导师】 万晓樵； 丁林；

【作者基本信息】 中国地质大学（北京） ， 古生物学与地层学， 2005， 博士

【摘要】 班公湖——怒江缝合带是青藏高原上一条重要的构造带。与其相邻的羌塘盆地是中生代特提斯洋盆形成与演化的忠实记录者,它是研究特提斯洋陆转换、盆山藕合的理想地区之一。本文运用碰撞构造理论、造山带与盆地分析方法,研究了班公湖—怒江中段安多地区晚中生代碰撞作用过程的沉积响应。 本文首先确定了安多地区晚中生代地层序列,自下而上由晚侏罗世安多组、邦爱组;早白垩世东巧组;晚白垩世阿布山组构成。并建立了晚中生代岩石地层格架。其次,对晚中生代地层进行了沉积相和火山岩相的划分,在安多组中识别出扇三角州相、辫状河相、冲积扇相、火山碎屑流相、火山泥石流相、溢流相。邦爱组中识别出碳酸盐岩开阔台地相、局限台地相、蒸发台地相和碎屑潮坪相、泻湖相。东巧组中识别出冲积扇—扇三角洲、局限海、干旱浅湖相、三角洲相。阿布山组中识别出干旱冲积扇相、辫状河相和干盐湖相。在沉积相研究的基础上,分析了各组的源区构造背景,安多组物源来自岛弧造山带,邦爱组来自北部克拉通,东巧组具有双向物源,阿布山组物源来自周围的造山带。 在岩相—相序组合分析的基础上,运用层序地层理论,在晚中生代地层中划分出三个二级构造层序,8—9个三级层序。其中晚侏罗世—早白垩世构成一个二级层序包含3—4个三级层序;早白垩世构成一个构造层序,包含3个三级层序,晚白垩世构成一个构造层序,包含3个三级层序,反映盆地不同演化阶段的地层响应。 首次对安多—聂荣一线发育的晚侏罗世玄武安山岩、安山岩、英安岩、流纹岩等火山岩进行了系统的岩石学、地球化学、同位素年代学研究,研究表明该火山岩具岛弧火山岩的性质,并进一步证实班公湖—怒江洋壳具有向北俯冲的特征。运用地层古生物和火成岩同位素年代学方法,对班公湖—怒江洋盆闭合时限进行了探讨,初步得出了闭合时限为早白垩世,大约131—124.5Ma。 从洋盆演化阶段出发,通过对晚侏罗世—白垩纪盆地充填特征分析,结合区域大地构造背景,得出了J₃—K₁盆地属于弧后前陆盆地,K₁为背驮式盆地,K₂为山间磨拉石盆地的认识,它们反映了一个连续的碰撞作用过程的沉积响应。更多还原

【Abstract】 Bangonghu-Nujiang Suture Zone (BNSZ) is an important tectonic zone in the Qinghai-Tibet Plateau. The Bangonghu-Nujiang Suture Zone (belt) and Qiangtang Basin recorded the formation and evolution of Tethys in the Mesozoic times. It is one of the ideal areas to study the ocean-land conversion and basin-range coupling. Based on the theory of collision tectonics, orogenic blet and basin analysis, this paper studies the sedimentary response of collision process in the mid-Bangonghu-Nujiang Suture Zone.Firstly, the stratigraphic sequence has been divided into Late Jurassic Anduo and Bangai Formations, Early Cretaceous Dongqiao Formation, Late Cretaceous Abushan Formation in ascending order, and a late Mesozoic litho-stratigraphic framework has been established in the Anduo area.Secondly, sedimentary facies have been studied from the sequence. In the Anduo Formation, fan delta, braided river, alluvial fan, pyroclastic debris flow, lahar and lava flow are illustrated. In the Bang’ai Formation, carbonate open platform, restricted platform, evaporate platform, lagoon and clastics tide flat are recognized. In the Dongqiao Formation, alluvial fan-fan dealt, restricted sea, coastal-shallow lake and delta are discussed. In the Abushan Formation, alluvial fan, braided river and shallow salt lake facies are recognized. According to the sedimentary facies, the sediments of Anduo Formation in the basin mostly came from the island arc belt in the south of basin. The detrital composition and the geochemistry characters imply that the island arc is the tectonic background of the source area. The sediments of Dongqiao Formation in the basin came from two ways; the Abushan sediments were from adjacent of the orogenic belt. Based on sequence stratigraphy, late Mesozoic strata have been divided into three two-order megasequences and eight or nine three-order cyclic-sequences. The Late Jurassic-Early Cretaceous tectonic sequence includes 3 or 4 three-order sequences. The Early Cretaceous tectonic sequence includes 3 or 4 three-order sequences. The Late Cretaceous tectonic sequence includes 3 or 4 three-order sequences. These sequences show a stratigraphic response to the collision processes.The island arc belt is composed of volcanic rocks of Anduo Formation. The volcanic rock sequence belongs to a basic -intermediate -acidic rock series. Geochemistry analysis更多还原