豫西汝州羅圈組雜礫巖及上覆東坡組的成因及時代探討
發(fā)布時間：2018-07-25 15:29
【摘要】：位于華北地臺南緣、以雜礫巖沉積為特征的羅圈組自命名起就一直倍受地質學界的關注。關于其是否為冰川成因以及形成時代的問題,一直沒有得出統(tǒng)一的意見。而羅圈組雜礫巖之上的東坡組,普遍為一套以成熟度較高的細碎屑巖為主的地層,該地層與具有生物地層依據的寒武紀地層呈不整合接觸關系。本文在野外剖面考察以及室內的礫石數據統(tǒng)計分析的基礎上,可以認為層狀及紋層狀雜礫巖中含有的特殊“上凸下繞”現象為冰筏沉積的墜石構造,特別是發(fā)現了微觀砂級碎屑的“墜石”現象,能夠反映當時為寒冷的冰川環(huán)境。加上羅圈組地層中其他與冰川作用相關的現象和證據,如漂礫現象,以及礫石的形態(tài)特征等,再結合地層本身的層位、分布規(guī)律,可以認為羅圈組應為冰川作用所形成。而于東坡組發(fā)現的Skolithos、Arenicolites、Treptichnus、Palaeophycus、Planolites等遺跡化石,表明東坡組不低于早寒武世的第一個遺跡化石帶,為晚于Treptichnus(Phycodes)pedum生物帶的寒武紀沉積�？烧J為東坡組的形成年代應晚于震旦紀,為寒武紀早期。而其下伏的羅圈組與東坡組整合接觸,形成時代應為寒武紀早期或震旦紀晚期(埃迪卡拉紀末期或之后)。
[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).
【學位授予單位】：貴州大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：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).
【學位授予單位】：貴州大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P588.212.5;P535
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