西藏江孜床得白垩纪介形虫生物地层

发布时间：2018-06-26 14:54

本文选题：上白垩统 + 介形虫　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：青藏高原南缘地处特提斯—喜马拉雅构造域的东段,是印度板块与欧亚板块碰撞的前锋地带,地质构造极其复杂。西藏南部地区发育有良好的海相白垩纪地层,地层中含有的微体古生物化石(有孔虫、放射虫及介形虫等)较为丰富。白垩纪是新特提斯演化的一个关键时期,藏南白垩纪微体古生物地层的研究,可为探讨新特提斯洋演化及白垩纪时期古地理、古环境提供重要依据。本文的研究重点为藏南江孜床得地区介形虫生物地层。藏南地区白垩纪特提斯-喜马拉雅沉积分带明显,以定日—定结—岗巴大断裂为界,分为特提斯喜马拉雅北亚带和特提斯喜马拉雅南亚带。北带(康马—江孜一带)整体上为大陆斜坡—大洋盆地的沉积环境,沉积水体相对较深,浮游类生物化石(浮游有孔虫、放射虫及箭石等)丰富,大洋红层(CORBs)分布广泛;南带(岗巴—定日—札达一带)为印度板块北缘被动陆缘盆地,整体上属于大陆架沉积环境,沉积水体相对较浅,化石门类相对减少,尤其以放射虫极为罕见为特征。本文主要对位于特提斯喜马拉雅北亚带的江孜地区床得西剖面进行了详细的介形虫生物地层研究,其中床得组紫红色页岩(红层)中化石含量较为丰富。通过对床得西剖面所含介形虫化石的系统研究及鉴定,共鉴定出24属41种,划分出5个生物组合:①Xestoleberis eximia—Talicypridea ventricosa组合,②Schuleridea shalayiensis—Candona longireniformis组合,③Uroleberis inflata—Candoniella subcurvata—Argilloecia组合,④Talicypridea occultaca—Bairdia acrocaudalis—Xestoleberis组合,⑤Cypridopsis zhungaerensis—Cyclocypris cf.calculaformis组合。根据介形虫化石生物属种及所在层位浮游有孔虫的代表属种,将江孜床得西剖面地层的时代厘定为三冬晚期—马斯特里赫特早期。其中,床得组红层的时代推测为坎潘期至马斯特里赫特早期。论文同时还对床得西剖面的岩石特征及沉积环境进行了初步探讨,由分析推断该地区在白垩纪时期的沉积环境为大陆斜坡至深水洋盆。
[Abstract]:The southern margin of the Qinghai-Xizang Plateau is located in the eastern part of the Tethys Himalayan tectonic domain and is the front zone of the collision between the Indian plate and the Eurasian plate. The geological structure is extremely complex. There are good marine Cretaceous strata in southern Tibet, which contain abundant micropaleontological fossils (foraminifera, radiolaria, ostracoda, etc.). The Cretaceous is a key period of the Neo-Tethys evolution. The study of the Cretaceous micro-paleostratigraphy in southern Tibet can provide an important basis for the study of the evolution of the Neo-Tethys Ocean and the paleogeography and paleoenvironment of the Cretaceous period. This paper focuses on the ostracod biostratigraphy in Jiangzi bed area, southern Tibet. The Cretaceous Tethys Himalayan Sedimentary zonation is obvious in the south of Tibet and is divided into the Tethys Himalayan North Asia Zone and the Tethys Himalayan South Asia Zone. The northern belt (Kangma-Jiangzi area) is the sedimentary environment of continental slope and oceanic basin, the sedimentary water is relatively deep, the planktonic fossils (planktonic foraminifera, radiolaria and quiver) are abundant, and the oceanic red beds (CORBs) are widely distributed. The southern belt (Gangba Dingri Zanda area) is a passive continental margin basin in the northern margin of the Indian plate. It belongs to the sedimentary environment of the continental shelf on the whole, with relatively shallow sedimentary water bodies and relatively reduced fossils, especially characterized by the extremely rare radiolaria. In this paper, a detailed study on the western section of the bed in Jiangzi area, located in the northern subzone of Tethys Himalayas, has been carried out, in which there are abundant fossils in the purple red shale (red bed) of the bed formation. A total of 24 genera and 41 species were identified by systematic study and identification of ostracia fossils in the Dexi section of the bed. The species were divided into 5 assemblages: 1 Xestoleberis eximia-Talicypridea ventricosa (2Schuleridea shalayiensis-Candona longireniformis) and 3Uroleberis inflata-Candoniella subcurvata-Argilloecia assemblage. 4Talicypridea occultaca-Bairdia acrocaudalis-Xestoleberis assemblage. According to the species of fossil ostracia and the representative genera of planktonic foraminifera in the strata, the stratigraphic age of the west section of Jiangzi bed is determined to be the late three-winter to the early Maastricht. Among them, the age of the bed formation red layer is supposed to be from the Kampan period to the early Maastricht period. At the same time, the rock characteristics and sedimentary environment of the western section of the bed are discussed. The sedimentary environment of the area during the Cretaceous period is from continental slope to deep water ocean basin.
【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】：Q913;P534.53

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