旺苍县鼓城乡唐家河剖面仙女洞组沉积环境精细研究

发布时间：2018-08-11 08:29

【摘要】：米仓山隆起区属于上扬子地台北缘的一部分,位于四川盆地北部川陕交界地区。米仓山区内寒武纪地层出露,岩性变化大。下寒武统由宽川铺组、郭家坝组、仙女洞组、阎王碥组和孔明洞组组成,主要为碎屑岩、碳酸盐岩和混积岩类,其中仙女洞组及相邻地层包括泥晶灰岩、多种类型鲕粒灰岩、(微)生物灰岩、砾屑灰岩和钙质砂泥岩等。根据实测剖面沉积物几何形态、沉积构造和粒度变化等宏微观特征,本文将米仓山区仙女洞组及相邻地层划分出11类沉积岩相,并通过各类沉积岩相代表的沉积环境以及各岩相之间的位置关系,进一步总结为4类沉积岩相组合,分别代表浅海陆棚、台缘斜坡、台缘丘滩和局限台地等沉积环境,再对其中的纵向序列进行研究,划分出多种沉积亚环境。米仓山区早寒武世仙女洞期的沉积环境总体可归结为毗邻古陆的连陆混积碳酸盐岩镶边台地—斜坡—陆棚沉积环境。本文通过区域背景研究,认为仙女洞组底部为台地边缘斜坡沉积,并拟出4种沉积岩相表征斜坡不同深度的沉积环境,后以变形条带、崩坍岩块和斜坡灰泥丘为特征,探讨出米仓山西南缘台缘斜坡变形构造形成机制,即同沉积断裂大背景之下由于重力因素等引发的滑塌变形,形成独具特色的似瘤状砾屑灰岩与滑塌角砾。通过对比分析全球早寒武世微生物及其分布规律,总结出米仓山区仙女洞组海相碳酸盐岩不同沉积环境、水体深度发育的三期不同类型的生物岩隆：斜坡藻丘、台缘藻丘和台缘滩后古杯丘,探讨微生物生存繁殖的水体环境差异,并归纳出不同灰泥丘各自的营造模式。
[Abstract]:The Mecang Mountain uplift is a part of the Taipei margin of the Upper Yangtze platform and is located in the northern Sichuan Basin at the junction of Sichuan and Shaanxi. The Cambrian strata are exposed and the lithology changes greatly in the Micang Mountain area. The Lower Cambrian is composed of the Kuanchuanpu formation, the Guojiaba formation, the Xiandong formation, the Yan Wangbin formation and the Kongming Cave formation, and is mainly composed of clastic rocks, carbonate rocks and migmatite, among which the Andromedan formation and adjacent strata include mudstone. Many types of oolitic limestone, (micro) biolimestone, gravel limestone and calcareous sand mudstone. According to the macro and micro characteristics of sediment geometry, sedimentary structure and grain size change in the measured section, 11 types of sedimentary lithofacies have been classified into the Xiandong formation and adjacent strata in Micang Mountain area in this paper. And through the sedimentary environment represented by various sedimentary lithofacies and the position relationship between each lithofacies, it is further summarized as four types of sedimentary lithofacies assemblages, representing the shallow sea shelf, the platform margin slope, the platform margin hill beach and the limited platform, respectively. Then the longitudinal sequence is studied and a variety of sedimentary subenvironments are divided. The sedimentary environment of the early Cambrian Fairy Cave in Micang Mountain area can be attributed to the rimmed platform slope shelf sedimentary environment adjacent to the ancient land. Based on the study of the regional background, it is considered that the bottom of the Xiadong formation is a platform margin slope deposit, and four sedimentary lithofacies are proposed to characterize the sedimentary environment of the slope at different depths, followed by a deformed strip, a collapsing rock block and a sloping mud mound. The forming mechanism of deformation structure of the slope in the southwestern margin of Mecang Mountain is discussed, that is, the landslide deformation caused by gravity factors under the background of the synsedimentary fault, forms unique nodular conglomerate limestone and sloughing breccia. By comparing and analyzing the microbes and their distribution in the global early Cambrian, three different types of biolith uplift in the Xiandong formation of Xiandong formation in Micang Mountain area, which are formed in different sedimentary environments and deep water bodies, are summarized, which are algae-dune on slopes. In this paper, the difference of water environment between algal dune of platform margin and ancient cup mound of backside beach of platform margin is discussed, and the construction mode of different plaster mound is concluded.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13

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