雅鲁藏布江缝合带沉积混杂岩放射虫生物地层研究

发布时间：2018-04-01 23:29

本文选题：混杂岩　切入点：放射虫　出处：《中国地质大学(北京)》2015年硕士论文

【摘要】：西藏南部雅鲁藏布江缝合带以南发育有一套砂泥质沉积混杂岩,对于碰撞启动时间及新特提斯洋闭合的研究具有重要意义。本次研究获得了雅江缝合带混杂岩中的放射虫化石组合,探索了其所属时代与分布情况,恢复了古地理面貌,进而重建了其形成过程与机制,为印-亚板块碰撞过程与特提斯演化提供新的证据。本次对位于特提斯喜马拉雅北亚带的江孜床得-北家剖面与吉隆桑单林剖面进行了地层研究工作,并发现丰富的放射虫化石。经过系统鉴定研究,在床得-北家剖面宗卓组中发现放射虫化石72属,121种,并将其划分为Holocryptocapsa fallax-Tethysetta boesii组合带,Holocryptocanium barbui-Trimulus fossilis组合带,Guttacapsa gutta带,Diacanthocapsa brevithorax-Excentropylomma cenomana组合带,Pseudoacanthosphaera spinosissima-Pseudodictyomitra pseudomacrocephala组合带,Acaeniotyle starka-Immersothorax cyclops组合带共6个化石带;在桑单林剖面中发现放射虫化石58属,91种,同时划分出Rhopalosyringium magnificum带,Immersothorax cyclops带,Homeoarchicorys eiformigum带,Mita regina-Phaseliforma subcarinata组合带,Diploplegma somphum-Phormocyrtis turgida组合带共5个化石带。床得-北家剖面基质是砂泥质沉积组合,所产放射虫化石指示其年代为晚白垩世Campanian期;岩块成分主要有砾岩、砂岩、碳酸盐、硅质岩,所产放射虫化石指示其年代为早白垩世Aptian期-晚白垩世Turonian期。该套地层为特提斯喜马拉雅沉积北亚带晚白垩世宗卓组砂泥质混杂堆积。桑单林剖面分为不整合的下部不含硅质成分砂泥质沉积宗卓组(化石年龄为晚白垩世Campanian期)与上部含大量硅质成分砂泥质沉积桑单林组(化石年龄为晚古新世Thanetian期)。桑单林组中混入的早期地层分子指示其并非正常沉积地层,而是在印-亚版块碰撞下早期地层混入Thanetian期沉积形成的混杂岩。江孜地区甲查拉组与桑单林地区桑单林组为两套同期异相地层,说明古新世晚期,在藏南东部印-亚版块发生陆陆碰撞的同时,西部的桑单林地区两侧陆壳尚未进入碰撞阶段。西藏境内印-亚版块碰撞沿雅江缝合带自东向西发生。
[Abstract]:To the south of the Yarlung Zangbo River suture zone in southern Tibet, there is a set of sandy and muddy sedimentary melange. It is of great significance to study the initiation time of collision and the closure of the Neo-Tethys Ocean. In this study, the fossil assemblage of radiolarian in the melange rocks in the Yagang suture zone was obtained, and the age and distribution of the assemblage were explored, and the paleogeographic features were restored. And then it reconstructs its formation process and mechanism, This paper provides new evidence for the process of Indo-subplate collision and Tethys evolution. The stratigraphic study of the Jiangzi bed De-Bei Jia profile and the Jilong Sangdan Forest profile located in the northern Tethys Himalayan Asian belt has been carried out in this paper. Through systematic identification, 121 species of radiolarian fossils belonging to 72 genera were found in the Zongzhuo formation of the Bende-Baijia profile. It is divided into 6 fossil belts in the Holocryptocapsa fallax-Tethysetta boesii assemblage belt, Holocryptocapsa fallax-Tethysetta boesii barbui-Trimulus fossilis assemblage belt, Guttacapsa gutta belt, Diacanthocapsa brevithorax-Excentropylomma cenomana assemblage belt and Pseudoanthosphaera spinosissima-Pseudodictyomitra pseudomacrocephala assemblage belt, and there are 91 species of radiolarian fossils 58 genera and 91 species found in the mulberry forest profile, including the Pseudoanthosphaera spinosissima-Pseudodictyomitra pseudomacrocephala assemblage belt and the Pseudoanthosphaera spinosissima-Pseudodictyomitra pseudomacrocephala assemblage belt. At the same time, there are 5 fossil belts in the Rhopalosyringium magnificum Rhopalosyringium magnificum Immersothorax cyclops cyclops eiformigum eiformigum Mita regina-Phaseliforma subcarinata somphum-Phormocyrtis turgida assemblage. The matrix of the bed to Beijia section is the sandy muddy sedimentary assemblage, and the radiolarian fossils indicate the late Cretaceous Campanian age. The rock block mainly consists of conglomerate, sandstone, carbonate, siliceous rock, The age of radiolarian fossils indicates that the age is early Cretaceous Aptian and late Cretaceous Turonian. This set of strata is the late Cretaceous muddy mixed deposit in the northern subbelt of Tethys Himalayan Sediment.Sangdan forest profile is divided into unconformity. Zongzhuo formation (fossil age is late Cretaceous Campanian period) without siliceous composition, and Sundanlin formation containing a large amount of siliceous composition in upper part (fossil age is Thanetian period of late Paleocene). The early mixed formation in Sangdan forest formation. The stratigraphic molecules indicate that it is not a normal sedimentary formation, The formation of Jiachara formation in Jiangzi area and that of Sangdan Lin formation in Sangdan forest area are two sets of synchronal heterogeneous strata, indicating the late Paleocene, the late Paleocene, the late Paleocene, and the late Paleocene. At the same time, the continental crust of the Sangdan forest area in the west has not entered the collision stage. The collision occurred from east to west along the Ya Jiang suture belt in Tibet.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：Q915;P535

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