本文選題：混雜巖　切入點：放射蟲　出處：《中國地質(zhì)大學(北京)》2015年碩士論文

【摘要】：西藏南部雅魯藏布江縫合帶以南發(fā)育有一套砂泥質(zhì)沉積混雜巖,對于碰撞啟動時間及新特提斯洋閉合的研究具有重要意義。本次研究獲得了雅江縫合帶混雜巖中的放射蟲化石組合,探索了其所屬時代與分布情況,恢復了古地理面貌,進而重建了其形成過程與機制,為印-亞板塊碰撞過程與特提斯演化提供新的證據(jù)。本次對位于特提斯喜馬拉雅北亞帶的江孜床得-北家剖面與吉隆桑單林剖面進行了地層研究工作,并發(fā)現(xiàn)豐富的放射蟲化石。經(jīng)過系統(tǒng)鑒定研究,在床得-北家剖面宗卓組中發(fā)現(xiàn)放射蟲化石72屬,121種,并將其劃分為Holocryptocapsa fallax-Tethysetta boesii組合帶,Holocryptocanium barbui-Trimulus fossilis組合帶,Guttacapsa gutta帶,Diacanthocapsa brevithorax-Excentropylomma cenomana組合帶,Pseudoacanthosphaera spinosissima-Pseudodictyomitra pseudomacrocephala組合帶,Acaeniotyle starka-Immersothorax cyclops組合帶共6個化石帶;在桑單林剖面中發(fā)現(xiàn)放射蟲化石58屬,91種,同時劃分出Rhopalosyringium magnificum帶,Immersothorax cyclops帶,Homeoarchicorys eiformigum帶,Mita regina-Phaseliforma subcarinata組合帶,Diploplegma somphum-Phormocyrtis turgida組合帶共5個化石帶。床得-北家剖面基質(zhì)是砂泥質(zhì)沉積組合,所產(chǎn)放射蟲化石指示其年代為晚白堊世Campanian期;巖塊成分主要有礫巖、砂巖、碳酸鹽、硅質(zhì)巖,所產(chǎn)放射蟲化石指示其年代為早白堊世Aptian期-晚白堊世Turonian期。該套地層為特提斯喜馬拉雅沉積北亞帶晚白堊世宗卓組砂泥質(zhì)混雜堆積。桑單林剖面分為不整合的下部不含硅質(zhì)成分砂泥質(zhì)沉積宗卓組(化石年齡為晚白堊世Campanian期)與上部含大量硅質(zhì)成分砂泥質(zhì)沉積桑單林組(化石年齡為晚古新世Thanetian期)。桑單林組中混入的早期地層分子指示其并非正常沉積地層,而是在印-亞版塊碰撞下早期地層混入Thanetian期沉積形成的混雜巖。江孜地區(qū)甲查拉組與桑單林地區(qū)桑單林組為兩套同期異相地層,說明古新世晚期,在藏南東部印-亞版塊發(fā)生陸陸碰撞的同時,西部的桑單林地區(qū)兩側(cè)陸殼尚未進入碰撞階段。西藏境內(nèi)印-亞版塊碰撞沿雅江縫合帶自東向西發(fā)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.
【學位授予單位】：中國地質(zhì)大學(北京)
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：Q915;P535

【參考文獻】

相關期刊論文 前4條

1 張宏飛,Nigel Harris,Randall Parrish,張利,趙志丹,李德威;北喜馬拉雅淡色花崗巖地球化學:區(qū)域?qū)Ρ�、巖石成因及其構造意義[J];地球科學;2005年03期

2 蔡福龍;丁林;王厚起;岳雅慧;來慶洲;;特提斯喜馬拉雅帶江孜地區(qū)古近紀地層源區(qū)分析——對造山帶早期地殼加厚的制約[J];地質(zhì)科學;2013年02期

3 李亞林;王成善;胡修棉;M.Bak;王進軍;陳蕾;李祥輝;;西藏南部始新世早期放射蟲動物群及其對特提斯閉合時間的約束[J];科學通報;2007年12期

4 李紅生,吳浩若;西藏南部白堊系沖堆組的一些放射蟲化石[J];微體古生物學報;1985年01期

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