鄂尔多斯盆地上二叠统—中上三叠统沉积特征及古气候演化

发布时间：2018-01-03 00:35

本文关键词：鄂尔多斯盆地上二叠统—中上三叠统沉积特征及古气候演化　出处：《中国地质大学(北京)》2017年博士论文　论文类型：学位论文

【摘要】：鄂尔多斯盆地位于华北地台西缘,自古生代中晚期开始发育陆相沉积,其中二叠-三叠系在大部分地区发育完整且相对连续,是研究华北陆块二叠-三叠纪之交古气候和环境演化的重要区域。在二叠-三叠系界线之上发育一套红层,由于其缺少生物化石和标志层,研究难度大。本文以鄂尔多斯盆地上二叠统-中上三叠统为主要研究对象,借助显微镜、扫描电镜、主量、微量元素测定、X衍射矿物组成分析、TOC测定以及碳氧同位素分析等手段,通过11个野外露头剖面,367口井测井资料,27口钻井岩心观察,以古气候、古环境演化为主线,进行了层序地层、沉积相等方面的研究,总结了鄂尔多斯盆地二叠-三叠系界线上下的层序沉积序列,恢复了P/T界线上下的古气候环境演化,探讨了鄂尔多斯盆地红层的成因和成色机制,并最终厘定了鄂尔多斯盆地上二叠统-中上三叠统沉积相带的分布规律,建立了不同气候环境背景下的沉积相模式。本文以高分辨率层序地层学理论为依据,结合野外露头、钻井岩心以及测井资料将鄂尔多斯盆地上二叠统-中上三叠统划分为4个超长期旋回(SLSC1~SLSC4),13个长期旋回。通过地球化学分析认为晚二叠世至中晚三叠世鄂尔多斯盆地的气候环境存在显著变化。晚二叠世SLSC1(石千峰组)沉积时期氧化程度相对低,古气候相对温暖湿润;早三叠世SLSC2(刘家沟组与和尚沟组)属于强氧化环境,气候十分干旱炎热;而中三叠世SLSC3(纸坊组)氧化程度变弱,气温降低,转为半干旱半湿润的过渡性气候。中晚三叠世SLSC4(延长组长10~长7),湖平面上升到最高,盆地转变为温暖潮湿的气候和相对还原的环境。碳同位素分析结果显示,鄂尔多斯盆地陆相P/T界线上δ13CPDB存在显著负偏,与全球范围内的海相二叠-三叠系界线具有可对比性,说明在华北地台陆相P/T界线上同样存在气候突变和生物灭绝等重大地质事件的沉积记录。通过研究发现鄂尔多斯盆地的下三叠统刘家沟组与和尚沟组的红层是干旱炎热的气候和强氧化环境的沉积产物,以原生成因为主。其红色主要来自于作为染色剂的赤铁矿。石千峰组与纸坊组局部的紫红色红层也是在干旱气候下形成,但干旱程度不及早三叠世,因而其岩石内部含赤铁矿少,且保留一定的有机质和方解石。沉积岩出现不同的颜色主要是由于矿物组成不同,是盆地构造演化和气候环境变迁的结果。本文最终建立了层序地层格架内不同气候环境背景下的沉积相展布特征和沉积相模式。早三叠世干旱炎热气候背景下鄂尔多斯盆地发育河流-三角洲-滨湖沉积相,湖盆面积小、水体浅,河流-三角洲分布面积广,砂体为红色、呈分支状,类型单一,以曲流河-三角洲砂体为主。晚三叠世温暖潮湿气候条件下鄂尔多斯盆地湖盆面积扩张,水体变深,发育深湖和半深湖沉积相,并出现重力流沉积,曲流河、辫状河-三角洲砂体类型丰富,多呈连片状分布,厚度大、面积广。
[Abstract]:Ordos basin is located in the western margin of the North China platform, in the late Paleozoic continental sedimentary development began in two, Triassic in most areas and relatively complete continuous development, is an important area of the North China block two Triassic paleoclimate and environment evolution of Triassic. In two the Permian Triassic boundary developed on a red layer. Due to the lack of fossils and markers, and difficult to study. In this paper, Erdos basin two Permian - Triassic in three as the main research object, through the microscope, scanning electron microscope, the main content, determination of trace elements in mineral composition analysis, X diffraction, TOC and determination of carbon and oxygen isotope analysis, through 11 an outcrop, logging data of 367 wells, 27 wells with core observation, paleoclimate, paleoenvironment evolution, the sequence stratigraphy, sedimentary facies research, summed up the two - fold Erdos Basin Sequence sedimentary sequence of Triassic boundary of the restored paleo environmental evolution under the P/T on the line, the causes of the red basin Erdos and fineness mechanism, and finally determined the distribution of facies Erdos basin two Permian - three Permian sedimentary, sedimentary facies model is built in different climate environmental background. Based on the high resolution sequence stratigraphy theory, combining the outcrop, drilling core and well logging data Ordos basin two Permian - Triassic in three divided into 4 super long term cycle (SLSC1~SLSC4), 13 long term cycles. The results of geochemical analysis show that there are significant changes to the Late Permian in the evening of the three Ordos Triassic Basin climate. Late Permian SLSC1 (Shi Qianfeng group) during the deposition of the relatively low degree of oxidation, the climate is relatively warm and humid; Early Triassic (three SLSC2 group and Liu Jia Gou Shang Gou group) belongs to strong oxidation environment, the climate is very hot and dry; three in Triassic SLSC3 (Zhifanggou group) oxidation degree is weak, the temperature decreased, to semi arid and semi humid transitional climate. In the Late Triassic (three SLSC4, 7 10~ Long Chang) lake level rose to the highest, the basin into a warm and humid climate and relatively reducing environment. Carbon isotope analysis results show that Ordos basin continental Delta 13CPDB P/T line has significant negative bias, and the global scope of the two marine Triassic boundary can be compared, indicating sedimentary record in the North China platform continental P/ T boundary are also major geological events of climate mutation and biological extinction. Through the study found that Erdos basin under the three Triassic Liujiagou group and Heshanggou group of red layer is deposited hot dry climate and strong oxidizing environment, with the original generation. The main red for the Lord To come from the stain as hematite. Shiqianfeng Formation and Zhifanggou group of local red purple red layer is formed under the arid climate in the late three, but the degree of drought early Triassic, the rock containing hematite, calcite and organic matter and retain certain sedimentary rocks. There is the same color is mainly due to mineral composition is different, tectonic evolution and climate change results. This paper finally established the sedimentary facies in sequence stratigraphic framework in different climatic environment characteristics and sedimentary facies model. Three early Triassic hot dry climate background in Ordos Basin River delta sedimentary facies in Binhu. The lake area is small, shallow water, River Delta wide distribution area, sand body is red, was branched to a single type of meandering fluvial delta sand bodies. Three late Triassic under warm and humid climate Erdos Lake Basin The basin area expands, the water body deepens, the deep lake and semi deep lake sedimentary facies are developed, and the gravity flow deposits occur. The meandering river and braided river delta sand bodies are rich in types, and are mostly distributed in a contiguous way, with large thickness and wide area.

【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P532;P512.2

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