【作者】 时国；

【导师】 田景春；

【作者基本信息】 成都理工大学 ， 沉积学， 2010， 博士

【摘要】 南华北地区奥陶系以一套相对稳定的海相碳酸盐岩沉积为特征,多年来众多学者对其从各个方面进行了深入研究,在层序划分、沉积演化等方面取得了一系列成果。在油气勘探方面与相邻的鄂尔多斯盆地、北华北地区相比,虽然也有油气显示,但一直未获得重大的突破,这是由于一系列基础地质问题尚需深化、系统研究。为此,本论文在众多前人研究成果的基础上,以沉积学、层序地层学、岩溶学理论为指导,在对野外主干剖面实测、钻井岩心观察及测井资料综合分析的基础上,对南华北地区奥陶系进行系统深入的研究。在地层划分对比、沉积体系类型特征研究的基础上,开展层序地层学研究,首先识别出层序界面的物质表现形式有6种类型,分别为:不整合面、古喀斯特作用面、冲刷面、岩性岩相转换面、超覆面、最大海泛面。上述几种类型的层序界面可归结为3种成因类型:隆升侵蚀层序不整合界面、海侵上超层序不整合界面、陆上暴露层序不整合界面。在层序界面识别的基础上将奥陶系划分出3个超层序(SS1、SS2和SS3),进一步划分为9个三级层序(OSQ1-OSQ9),其中SS1超层序包括OSQ1和OSQ2两个三级层序,SS2超层序包括OSQ3、OSQ4、OSQ5、OSQ6和OSQ7五个三级层序,SS3超层序包括OSQ8和OSQ9两个三级层序。详细分析了层序地层单元的基本特征、叠置关系及空间分布规律,建立了研究区奥陶系的等时层序地层格架。对三级层序充填发育与构造层序的响应关系做了详细分析。OSQ1、OSQ2对应SS1超层序,反应了加里东运动Ⅰ幕,即怀远运动期盆地隆升速度较强,底界不整合起伏较大,盆地内部沉积速率小于沉降速率。OSQ3、OSQ4、OSQ5、OSQ6和OSQ7对应SS2超层序,为加里东运动Ⅱ幕的产物,该期受全球海平面上升影响,其隆升强度较Ⅰ幕要弱。OSQ8和OSQ9对应SS3超层序,对应于加里东运动Ⅲ幕强烈隆升的构造发展过程。以超层序体系域为单元,编制了研究区奥陶系超层序岩相古地理图,揭示了不同体系域期的层序岩相古地理特征及其演化。SS1海侵期主要沉积冶里组及亮甲山组下部地层,分布在温县-开封-商丘-永城-宿州一线以东北地区,为潮坪环境。SS1高位期沉积亮甲山组上部地层,沉积范围较冶里期进一步向北退缩,局限于商丘-永城-宿州以北的狭小地区,为局限台地的云坪环境。SS2海侵期沉积下马家沟组及上马家沟组下部一段地层,分布在渑池-汝州-霍邱一线以东北地区,主要为潮坪-局限台地环境。SS2高位期沉积上马家沟组二、三段地层,主要分布在登封-阜阳-灵璧一线以北地区,沉积环境更加局限,为潮坪-局限台地环境。强烈的构造隆升作用也为南华北地区奥陶系古岩溶发育提供了有利条件。通过野外露头剖面、钻井岩心观察及对测井资料的综合研究,奥陶系古岩溶表现为不整合面(风化壳)残积物、岩溶角砾、溶蚀孔洞缝等特征,主要发育于下奥陶统和奥陶系顶部。将奥陶系古岩溶划分为同生期、埋藏期和风化壳岩溶三种类型,不同类型岩溶受不同级别层序控制作用明显。其中同生期潮坪及台内滩型岩溶主要受高频旋回影响,粒内溶孔、铸模孔和粒间溶孔发育;同生期层间岩溶作用受三级层序影响明显,是膏溶角砾岩形成的主要因素;埋藏期岩溶主要受二级层序控制,有机溶蚀次生孔隙发育;风化壳岩溶发育程度和分布范围最广,主要受二级层序界面的形成控制。在上述基础上深入讨论了影响和控制层序格架内古岩溶发育的因素,其中构造、岩性、古气候和古地貌为主要因素。在综合分析古岩溶发育多种因素基础上,采用印模法首次对奥陶系两期风化壳岩溶古地貌进行了恢复。更多还原

【Abstract】 The Ordovician is a set of relatively stable marine carbonate rocks deposition around Southern North China. Over the years many scholars have studied the area from all aspects in detail, and so a series of achievements were made in the oil and gas exploration in the Erdos Basin and adjacent areas. Although there are oil and gas shows in this area, but not yet obtains the significant breakthrough in the oil gas exploration. According to the theory of sedimentology, sequence stratigraphy and karst, this thesis carried on systematic study of Ordovician sequence stratigraphy in the Southern North China, on the basis of comprehensive analysis of the main section of the field measured, drilling core observation and logging data. The material manifestations of sequence bottom interface have 6 types:unconformity,palaeo-karst active surfaces,erosion surface,lithology and lithofacies conversion surface,overlap area,maximum flooding surface.The several types of sequence boundaries can be attributed to three kinds of genetic types. Uplift erosion unconformity interface sequence,transgression unconformity on the super sequence interface,land exposure unconformity interface sequence. On the basis of the identification of sequence interface,to divide Ordovician into nine third-order sequences(OSQ1-OSQ9) and three super sequence (SS1, SS2 and SS3).This paper analyse in detail the sequence stratigraphic units of the basic features, overlay and spatial distribution of the study area, and established Ordovician isochronous sequence stratigraphic framework。We also analyse the three sequence filling sequence development and structural response relationship. It reflects I-stage that SS1 is corresponding to OSQ1 and OSQ2,when the basin was uplifting violently and the unconformity of bottom surface was obvious. It was the process of compensated basin that the internal of basin was depositing more slowly than that it was settling. It reflectedⅢ-stage that SS3 is corresponding to OSQ8 and OSQ9,when the basin was uplifting more violently.Using supersequence system as a unit, we have compiled 4 maps of lithofacies palaeogeography of supersequence of Ordovician system, and revealed the characteristics and evolutions of lithofacies palaeogeography of strata succession of different system tracts. SS1 transgression of the rule in groups and the main deposition Yeli lower part of the formation, which is located in the north-east region of Wen County-Kaifeng-Shangqiu–Yongchen -Suzhou, are in neritic tidal environment. SS1 high deposition Liangjiashan group of the upper strata, which range of deposition is further back to the north than Yeli and limited to the north of the small area of Shangqiu-Yongchen–Suzhou, is in a restricted cloud platform flat environment. SS2 transgression of sedimentary Lower Majiagou Formation and the lower part of a ground launched Majiagou, located in the northeast region of Mianchi-Ru Chou - Huoqiu, mainly from tidal flat-restricted platform environments. SS2 high deposition launched Majiagou of the second and third formation, mainly in north of Dengfeng - Fuyang - Lingbi, where sedimentary environment is more limited, is in the tidal flat - restricted platform environments.Strong tectonic uplift provide favorable conditions for the development of Ordovician paleokarst in the Southern North China. Through observing field outcrop section, drilling core and the study of logging data, Ordovician paleokarst is shown as unconformity (weathering crust) eluvium, karst breccia, dissolution hole joint and other characteristic. They are mainly developed in the lower Ordovician and Ordovician top. Ordovician paleokarst is divided into three types as syngenetic period, supergene period and burial period karst. Different types of karst are obvious controled by different levels of sequence.Which the types of syngenetic period tidal flat, lagoon and uchinada are affected mainly by high-frequency cycles, and develop intragranular dissolved pore, mould pore and intergranular dissolved pore. Supergene period interlayer karstification obviously affected by the third-order sequence,it is the main factor in the formation of gypsum breccia. Burial period karst controlled by the second-order sequence,and develop organic corrosion secondary pore. Weathering crust karst’s degree of development and distribution is the most widely,and it mainly controlled by the second-order sequence.This paper also discussed the impact and control factors of Ordovician karst, which tectonic, lithology, paleoclimate and paleogeomorphic are the main factors. In a comprehensive analysis based on multiple factors of the development of paleo karst, we adopted impression method to recover the paleogeomorphic Ordovician two weathering crust karst period.更多还原