藏北荣玛乡亚丹地区下二叠统曲地组的厘定及大地构造意义
发布时间：2018-11-04 17:19
【摘要】：西藏羌塘中部增生杂岩的不断解体对于该区古生代—三叠纪地层格架的厘定及特提斯洋演化研究具有重要的指示意义。对西藏荣玛乡亚丹地区的增生杂岩进行实测剖面时,发现一段早二叠世大陆斜坡相深水重力流形成的海底扇细碎屑岩沉积,北侧被新生代康托组红层覆盖,南侧与玄武岩等基性岩块呈断层接触,沉积序列不完整,主体为一套海底扇中扇-外扇厚层粉砂岩夹水道砂岩透镜体。碎屑岩层中垮塌沉积的生屑灰岩夹层含Parafusulina,Pseudofusulina,Schwagerina,Chalaroschwagerina parampla共4属10种■类化石,指示地层时代为早二叠世亚丁斯克期。1∶25万日干配错幅区域地质调查将该地层归为吞龙共巴组,主要为混积陆棚相沉积。依据岩石地层及化石组合时代,厘定本套海底扇沉积为下二叠统曲地组。结合前人报道的早—中二叠世含■灰岩建造,以及羌塘中部晚石炭世—早二叠世基性岩的大陆裂谷背景,认为羌塘中部早二叠世沉积代表了中特提斯洋演化的初始阶段,并推测在空谷阶之后发育小规模洋盆。
[Abstract]:The continuous disintegration of the accretive complex in the central Qiangtang, Tibet, is of great significance for the determination of the Paleo-Triassic stratigraphic framework and the study of the evolution of the Tethys ocean. When the accretive complex in Yadan area, Rongma Township, Tibet, was measured, it was found that the subsea fan fine clastic deposits formed by deep-water gravity flow in the early Permian continental slope were covered by the red beds of the Cenozoic Kangto formation on the north side. The southern side is in contact with basalt and other basic rock blocks, the sedimentary sequence is incomplete, and the main body is a set of sandstone lens in the channel between the thick siltstone of the fan and the outer fan of the submarine fan. The intercalation of bioclastic limestone deposited in clastic strata contains 10 species and 4 genera of Parafusulina,Pseudofusulina,Schwagerina,Chalaroschwagerina parampla. The stratigraphic age is the early Permian Adinsk period, and the regional geological survey of the 1: 250 000 dry fault block classifies the formation as Tunlong Gongba formation, which is mainly a mixed continental shelf facies deposit. According to the age of lithostratigraphy and fossil assemblage, this set of submarine fan deposits is determined to be the lower Permian curved formation. Combined with the early and middle Permian limestone formation reported by predecessors and the continental rift background of the basic rocks of the late Carboniferous and early Permian in the central Qiangtang, it is considered that the early Permian sediments in the central Qiangtang represented the initial stage of the evolution of the Middle Tethys Ocean. It is speculated that a small scale ocean basin is developed after the empty valley terrace.
【作者单位】： 中国地质大学地球科学与资源学院;
【基金】：中国地质调查局项目《西藏荣玛乡南地区1∶5万四幅区域地质调查》(编号:121201103000150004) 中央高校基本科研业务费项目《西藏羌塘中部蓝岭高压变质带变质、变形作用过程及构造意义》(编号:2652014004)
【分类号】：P534.46
本文编号：2310597
[Abstract]:The continuous disintegration of the accretive complex in the central Qiangtang, Tibet, is of great significance for the determination of the Paleo-Triassic stratigraphic framework and the study of the evolution of the Tethys ocean. When the accretive complex in Yadan area, Rongma Township, Tibet, was measured, it was found that the subsea fan fine clastic deposits formed by deep-water gravity flow in the early Permian continental slope were covered by the red beds of the Cenozoic Kangto formation on the north side. The southern side is in contact with basalt and other basic rock blocks, the sedimentary sequence is incomplete, and the main body is a set of sandstone lens in the channel between the thick siltstone of the fan and the outer fan of the submarine fan. The intercalation of bioclastic limestone deposited in clastic strata contains 10 species and 4 genera of Parafusulina,Pseudofusulina,Schwagerina,Chalaroschwagerina parampla. The stratigraphic age is the early Permian Adinsk period, and the regional geological survey of the 1: 250 000 dry fault block classifies the formation as Tunlong Gongba formation, which is mainly a mixed continental shelf facies deposit. According to the age of lithostratigraphy and fossil assemblage, this set of submarine fan deposits is determined to be the lower Permian curved formation. Combined with the early and middle Permian limestone formation reported by predecessors and the continental rift background of the basic rocks of the late Carboniferous and early Permian in the central Qiangtang, it is considered that the early Permian sediments in the central Qiangtang represented the initial stage of the evolution of the Middle Tethys Ocean. It is speculated that a small scale ocean basin is developed after the empty valley terrace.
【作者单位】： 中国地质大学地球科学与资源学院;
【基金】：中国地质调查局项目《西藏荣玛乡南地区1∶5万四幅区域地质调查》(编号:121201103000150004) 中央高校基本科研业务费项目《西藏羌塘中部蓝岭高压变质带变质、变形作用过程及构造意义》(编号:2652014004)
【分类号】：P534.46
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