豫西汝州罗圈组杂砾岩及上覆东坡组的成因及时代探讨
发布时间：2018-07-25 15:29
【摘要】：位于华北地台南缘、以杂砾岩沉积为特征的罗圈组自命名起就一直倍受地质学界的关注。关于其是否为冰川成因以及形成时代的问题,一直没有得出统一的意见。而罗圈组杂砾岩之上的东坡组,普遍为一套以成熟度较高的细碎屑岩为主的地层,该地层与具有生物地层依据的寒武纪地层呈不整合接触关系。本文在野外剖面考察以及室内的砾石数据统计分析的基础上,可以认为层状及纹层状杂砾岩中含有的特殊“上凸下绕”现象为冰筏沉积的坠石构造,特别是发现了微观砂级碎屑的“坠石”现象,能够反映当时为寒冷的冰川环境。加上罗圈组地层中其他与冰川作用相关的现象和证据,如漂砾现象,以及砾石的形态特征等,再结合地层本身的层位、分布规律,可以认为罗圈组应为冰川作用所形成。而于东坡组发现的Skolithos、Arenicolites、Treptichnus、Palaeophycus、Planolites等遗迹化石,表明东坡组不低于早寒武世的第一个遗迹化石带,为晚于Treptichnus(Phycodes)pedum生物带的寒武纪沉积。可认为东坡组的形成年代应晚于震旦纪,为寒武纪早期。而其下伏的罗圈组与东坡组整合接触,形成时代应为寒武纪早期或震旦纪晚期(埃迪卡拉纪末期或之后)。
[Abstract]:The Luohuan formation, which is located in the southern margin of North China platform and characterized by complex conglomerate deposits, has been paid close attention to since its naming. There has been no unified opinion as to whether or not it was a glacier and the age of its formation. The Dongpo formation above the complex conglomerate of Luohuan formation is generally a set of fine clastic rocks with high maturity, which is unconformable with the Cambrian strata based on biostratigraphy. On the basis of field profile investigation and statistical analysis of gravel data in the laboratory, it can be concluded that the special "upwelling and underwinding" phenomenon contained in layered and lamellar conglomerates is a falling stone structure of ice raft deposition. In particular, the "falling stone" phenomenon of micro-sand clastic is found, which can reflect the cold glacial environment at that time. In addition, other phenomena and evidences related to glaciation, such as boulder phenomenon and gravel morphology, in the strata of Luohuan formation, combined with the stratigraphic layer and distribution law, can be considered to be formed by glaciation. However, the fossils such as Skolithoso Arenicolitesus Treptichnus Palaeophycus-Planolites found in the Yudongpo formation indicate that the Dongpo formation is not lower than the first trace fossil belt of the early Cambrian and is a Cambrian deposit later than the Treptichnus (Phycodes) pedum biosphere. It can be considered that the formation of Dongpo formation should be later than that of Sinian, and it is early Cambrian. The forming age of the underlying Luohuan formation and Dongpo formation should be the early Cambrian or the late Sinian (late or post-Ediacaran).
【学位授予单位】：贵州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.212.5;P535
[Abstract]:The Luohuan formation, which is located in the southern margin of North China platform and characterized by complex conglomerate deposits, has been paid close attention to since its naming. There has been no unified opinion as to whether or not it was a glacier and the age of its formation. The Dongpo formation above the complex conglomerate of Luohuan formation is generally a set of fine clastic rocks with high maturity, which is unconformable with the Cambrian strata based on biostratigraphy. On the basis of field profile investigation and statistical analysis of gravel data in the laboratory, it can be concluded that the special "upwelling and underwinding" phenomenon contained in layered and lamellar conglomerates is a falling stone structure of ice raft deposition. In particular, the "falling stone" phenomenon of micro-sand clastic is found, which can reflect the cold glacial environment at that time. In addition, other phenomena and evidences related to glaciation, such as boulder phenomenon and gravel morphology, in the strata of Luohuan formation, combined with the stratigraphic layer and distribution law, can be considered to be formed by glaciation. However, the fossils such as Skolithoso Arenicolitesus Treptichnus Palaeophycus-Planolites found in the Yudongpo formation indicate that the Dongpo formation is not lower than the first trace fossil belt of the early Cambrian and is a Cambrian deposit later than the Treptichnus (Phycodes) pedum biosphere. It can be considered that the formation of Dongpo formation should be later than that of Sinian, and it is early Cambrian. The forming age of the underlying Luohuan formation and Dongpo formation should be the early Cambrian or the late Sinian (late or post-Ediacaran).
【学位授予单位】：贵州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.212.5;P535
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