川西南地区灯影组微生物碳酸盐岩沉积环境分析

发布时间：2019-06-24 22:51

【摘要】：川西南地区位于中上扬子地台西南缘,该区灯影组发育了一套微生物碳酸盐岩沉积岩层。在野外实测剖面、钻井岩心观察和显微薄片鉴定的基础上,通过对先锋剖面及金石1井的地层特征、岩石学特征的研究,结合前人的研究成果,将该区灯影组地层划分为53层(包括0层):灯一段划分18层,以泥-粉晶白云岩最为发育;灯二段划分21层,以叠层石白云岩和豹斑状凝块石白云岩为主;灯三段划分14层,以层纹石白云岩和豹斑状凝块石白云岩为主。在地层划分的基础上,将研究区灯影组岩石类型划分为贫-非微生物白云岩类和微生物白云岩类两个大类,其中贫-非微生物白云岩类划分为颗粒白云岩和晶粒白云岩两类。根据微生物白云岩类的成分、结构和构造以及微生物含量的多少,微生物的生态学特征的差异,以及它们所提供给沉积物的物质组分、结构构造的不同,本文将区内灯影组微生物白云岩类又划分为10种类型,分别为:水平状纹层叠层石白云岩、波状纹层叠层石白云岩、丘状纹层叠层石白云岩、柱状纹层叠层石白云岩、锥状纹层叠层石白云岩、不规则状纹层叠层石白云岩、层纹石白云岩、豹斑状凝块石白云岩、散碎状凝块/砂屑微生物白云岩和核形石白云岩等。通过分析研究区灯影组微生物碳酸盐岩的C、O同位素特征、Mn2+、Fe2+微量元素绝对含量特征及阴极发光所反映的Mn2+、Fe2+相对含量,来判断其沉积环境。本文采用δ13C-Z值图解的方法对研究区微生物碳酸盐岩的沉积环境进行判断,认识到研究区微生物碳酸盐岩δ13C-Z值点处于海水成岩环境区间,而且研究区微生物碳酸盐岩中更富δ13C,Z值更高,其Z值在127.25~134.75之间,明显120,说明研究区内微生物碳酸盐岩沉积时的盐度很高,其沉积环境为海水(潮坪)环境。研究区微生物碳酸盐岩的阴极发光几乎都发光,且多为橙黄-橙红色,是因为Mn2+含量足,而Fe2+含量较少,并且Mn2+、Fe2+微量元素的绝对含量也证实这一结果,这反映了该区微生物碳酸盐岩的沉积环境中少有大气水补给Fe2+,其沉积环境应属于海水(潮坪)沉积环境。研究区灯影组微生物白云岩中主要发育叠层构造、凝块结构、微生物碎屑结构和核形石结构,这些组构特征是作为该区微生物白云岩沉积相识别及划分的重要标志。根据地球化学特征分析、阴极发光特征分析及室内微相分析的结果,对研究区灯影组地层进行了沉积相、亚相和微相的划分。研究区灯影组微生物碳酸盐岩地层中可识别出潮上带、潮间上带低能带、潮间下带高能带、潮下泻湖、潮下障壁滩、潮下低能带等6种沉积微相。6种沉积微相在时空上的有序组合,构成了研究区灯影组碳酸盐岩局限台地内的潮坪亚相。根据沉积相在纵向和横向上的变化,建立了该区灯影组微生物碳酸盐岩的沉积模式,相对海平面的海退-海侵-海退-海侵沉积旋回很好的控制了沉积相模式的演化,为该区的地质研究和油气勘探提供了重要的基础地质资料。
[Abstract]:The southwest of the upper Yangtze platform is located in the southwest of Sichuan, and a set of micro-microbial carbonate sedimentary rock is developed in the Dengying Formation. On the basis of field survey section, drilling core observation and micro-sheet identification, the formation characteristics and petrological characteristics of the pioneer section and the Jinshi 1 well are studied, and the formation of the Dengying Formation in this area is divided into 53 layers (including 0 layers) in combination with the previous research results. The first segment of the lamp is divided into 18 layers, and is the most developed by the mud-powder-crystal dolostone; the two sections of the lamp are divided into 21 layers, and the stone dolostone and the leopard-shaped aggregate stone dolomite are mainly divided into three sections; and the three sections of the lamp are divided into 14 layers, and the layer-like stone dolostone and the leopard-shaped aggregate stone-stone dolomite are the main. On the basis of the formation division, the types of rock types in the study area are divided into two broad categories of lean-non-microbial dolomite and microorganism dolostone, among which the lean-non-microbial dolostone is divided into two types: the granular dolostone and the grain dolomite. depending on the composition, structure and construction of the microbial dolomite, as well as the amount of microbial content, the difference in the ecological characteristics of the microorganism, and the material composition provided to the deposit, the structure of the structure is different, In this paper, the microbial dolostone in the light-shadow group in the region is divided into 10 types, namely, the horizontal-form layer-layer-layer-layer-layer-layer-layer stone dolostone, the wave-like-pattern-layer-layer-layer-layer-layer stone dolomite, the papular-like layer-layer-layer-layer-layer-layer stone dolostone, the columnar-type layer-layer-layer-layer-layer stone dolomite, the cone-shaped layer-layer-layer-layer-layer stone dolomite, Irregular laminas, stone dolostone, layer-like stone dolostone, leopard-like-shaped stone-stone dolostone, loose-broken clot/ sand-debris microbial dolomite and nuclear-shaped stone dolomite, etc. The sedimentary environment was determined by analyzing the characteristics of C, O isotope, the absolute content of Mn2 +, Fe 2 + and the relative content of Mn2 + and Fe 2 + as reflected by the cathode luminescence. In this paper, the sedimentary environment of the micro-organism carbonate in the study area is judged by using the method illustrated in the Figure 13C-Z value, and it is recognized that the 13C-Z value point of the microbial carbonate rock in the study area is in the sea-water diagenetic environment, and the more rich 13C and Z value in the microbial carbonate in the study area are higher. The Z-value is between 127.25 and 134.75. It is clear that the salinity of the micro-organism carbonate in the study area is high, and its sedimentary environment is the sea water (tidal flat) environment. The cathode luminescence of the micro-organism carbonate in the study area is almost all light, and is orange-orange-red, because the content of Mn2 + is sufficient, and the content of Fe2 + is less, and the absolute content of Mn2 + and Fe 2 + trace elements also confirms this result. This reflects that the sedimentary environment of the micro-organism carbonate in this area is rare for the supply of Fe 2 + in the atmosphere, and its sedimentary environment should belong to the sedimentary environment of the sea water (tidal flat). In the study area, the main developmental stack structure, the clot structure, the microbial debris structure and the core-shaped stone structure in the microbial dolomite of the Dengying Formation of the study area are the important marks for the identification and division of the sedimentary facies of the microbial dolomite in the area. According to the geochemical characteristics, the characteristics of the cathode luminescence and the results of the indoor microfacies analysis, the sedimentary facies, subfacies and microfacies are divided into the formation of the Dengying Formation in the study area. In the study area,6 sedimentary microfacies such as the upper belt, the upper belt, the high band, the lower lagoon, the lower barrier beach and the lower energy band can be identified in the micro-organism carbonate formation of the Dengying Formation of the study area.6 sedimentary microfacies are in an ordered combination in time and space. The tidal subfacies in the limited platform of the carbonate of the Dengying Formation in the study area are formed. According to the change of the sedimentary facies in the longitudinal direction and the transverse direction, the sedimentary model of the micro-organism carbonate in the Dengying Formation in this area is established, and the evolution of the sedimentary facies model is well controlled by the sea-back-transgression-transgression-transgressive sedimentary cycle of the sea level. It provides important basic geological data for geological research and oil and gas exploration in this area.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13

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