【作者】 杨明；

【导师】 张梅生；

【作者基本信息】 吉林大学 ， 古生物学与地层学， 2018， 博士

【摘要】 辽宁兴城地区位于燕山裂陷槽东部边缘,中元古代时期发育有典型的华北地台型沉积建造,其中长城系岩石地层自下而上划分为:常州沟组、串岭沟组、团山子组和大红峪组,底部覆盖在新太古代绥中花岗岩之上。本文依托中国地质调查局《辽宁1:25万锦西市幅(K51C004001)区调修测》项目,对兴城地区中元古代长城系岩石地层特征进行较细致的研究,在团山子组顶部发现了古岩溶现象,可能是华北地台保存完好最古老的古岩溶事件。通过对该古岩溶的特征、类型、演化及成因等方面进行分析,讨论其地质意义。大红峪组不整合覆盖在团山子组之上,通过对其底部砾岩的分析,讨论其底界性质以及对地层划分和构造运动的意义。本文对兴城地区长城系岩石地层进行实测剖面,常州沟组、串岭沟组和团山子组的沉积较为连续,可与天津蓟县标准剖面进行对比,但大红峪组仅发育碎屑岩层,未见碳酸盐岩层出露。大红峪组在研究区主要分为三段:一段以灰白色巨厚层石英砂岩夹中薄层中粗粒长石石英砂岩为主,局部可见有凝灰质粉砂岩和沉凝灰岩,底部为硅质、铁质胶结石英砂岩质砾岩、花岗质砾岩、硅质角砾岩和复成分角砾岩;二段以灰绿色、黑绿色粉砂岩、粉砂质页岩夹青灰色薄板状中细粒石英砂岩为主,发育平行层理,页理发育,偶见波痕;三段为浅灰褐色厚层中粗粒含岩屑长石石英砂岩,夹灰白色薄层凝灰质砂岩。本文根据地层对比分析,重新厘定了原划分在1:20万区域地质调查报告中对于铁马山一带和磨盘山一带的地层划分。现将原划分在铁马山一带常州沟组的地层修订为大红峪组一段,原划分在串岭沟组的地层修订为大红峪组二、三段。磨盘山一带原划分在常州沟组的地层修订为大红峪组,原划分在大红峪组的地层修订为高于庄组。兴城地区团山子组顶部发育有古岩溶现象。古岩溶不整合面、裂隙、溶沟和溶蚀坑等特征明显,并被上覆大红峪组角砾岩填充。本文划分了4种与团山子组古岩溶有关的角砾岩和砾岩,并分析了填隙物的特征。根据该古岩溶特点,它发生于大红峪组沉积之前,属于表生环境下的局部古岩溶,并进一步划分了5个演化阶段。结合古岩溶的控制因素,分析了团山子组古岩溶的成因背景。兴城地区大红峪组不整合覆盖在其沉积之前的多个层位之上,底部砾岩成分复杂,各个剖面上的厚度和岩石类型有较大差异。本文详细描述了多个剖面上大红峪组底部砾岩的岩石学特征,分析其性质。根据剖面上砾岩的类型、特征和厚度,本文初步恢复了大红峪组早期古海岸地形特征。天津蓟县标准剖面上对于大红峪组底界的划分存在两种不同意见,即以“小白石英岩”还是“大白石英岩”为底界尚没有统一意见。本文根据团山子组顶部存在的古岩溶现象,证明大红峪组与团山子组之间存在明显的沉积间断现象。研究区大红峪组不整合于下伏的太古代花岗岩、常州沟组、串岭沟组和团山子组的多个层位之上,燕山裂陷槽内的多个地区也存在大红峪组与下伏地层的不整合现象。以上现象说明大红峪组与下伏地层存在明显的侵蚀间断,这与“小白石英岩”下存在10cm的砾岩现象是可以对比的。因此本文认为以“小白石英岩”为大红峪组底界是合理的。“兴城运动”一直是国内学者对于中元古代地层存在争议的问题之一。尽管国内学术界已经普遍认可燕山裂陷槽内多个地区大红峪组底部与下伏地层和太古代结晶基底的不整合现象,但多数人并不认为其属于一次地壳上升运动。本文详细研究了大红峪组底部不整合现象,划分出了异岩超覆不整合、单斜不整合和超覆不整合3种类型。本文认为异岩超覆不整合和超覆不整合代表了大红峪组沉积初期燕山海盆的逐渐扩大,而单斜不整合代表了海侵之前,兴城地区的地壳差异性升降运动。这种地壳运动的影响没有延伸到沉积盆地中心,仅在盆地边缘有明显表现。华北地台是Colombia超大陆的成员之一,古-中元古代时期发育燕山裂陷槽,吕梁运动之后开始接受盖层沉积。中元古代常州沟期—团山子期是燕山裂陷槽强烈断陷阶段,大红峪组期开始,裂陷槽进入较稳定的坳陷阶段。本文叙述的团山子组古岩溶事件以及“兴城运动”代表了燕山裂陷槽演化阶段的重要转折期。更多还原

【Abstract】 The Xingcheng area of Liaoning Province is located on the eastern edge of Yanshan Aulacogen,where developed the typical North China platform sedimentary formations during the Mesoproterozoic.The Changcheng System is composed of Changzhougou Formation,Chuanlinggou Formation,Tuanshanzi Formation and Dahongyu Formation from the bottom to the top,and overlaid on the Archean granite.Under the supported by the project of China Geological Survey < 1: 250000 Scale(K51C004001)Regional Geological Mapping Project of Jinxi City,Liaoning Province>,this paper makes a detailed study on the lithostratigraphic characteristics of the Changcheng System in the study area,and finds paleokarst phenomena at the top of the Tuanshanzi Formation,which is probably the oldest well preserved paleokarst event in the North China platform.According the analyzing on the characteristics,types,evolution and genesis of the Tuanshanzi paleokarst,the geological significance is discussed.The Dahongyu Formation unconformable overlaid on the Tuanshanzi Formation,and through the analyzing its bottom conglomerate,this paper discusses the nature of the bottom boundary and its significance of the stratigraphic division and the tectonic movement.In this paper,the stratigraphy of the Changcheng System in Xingcheng area is measured.The deposits of Changzhougou Formation,Chuanlinggou Formation and Guanshanzi Formation are continuous and can be correlated with the standard section of Jixian in Tianjin,but the Dahongyu Formation only developed clastic rocks without carbonate strata.The Dahongyu Formation is mainly divided into three members: the first is composed of gray-white thick bedded quartz sandstone with medium-thin layers of coarse-grained feldspar quartz sandstone,occasionally with the tuffaceous siltstone and sedimentary tuff,and the bottom are siliceous cemented quartz conglomerate,granitic conglomerate and siliceous breccia;the second is composed of gray-green,black-green siltstone,silty shale,and interebedded with bluish gray thin plate,medium fine-grained quartz sandstone with parallel bedding,lamellation and occasional wavemark;the third is composed of light gray-brown thick bedded feldspathic quartz sandstone with debris feldspar quartz sandstone and grayish thin-layer tuffaceous sandstone.Based on the stratigraphic correlation analysis,this paper redefines the stratigraphic division of the Tiemashan and Mopanshan areas in the original 1:200,000 regional geological survey report.In Tiemashan area the Changzhougou Formation is revised to the first member of the Dahongyu Formation and the Chuanlinggou Formation is revised to the second and third members of the Dahongyu Formation.In the area of Mopanshan Changzhougou Formation is revised to the Dahongyu Formation,and the Dahongyu Formation is revised to the Gaoyuzhuang Formation.Paleokarst occurred at the top of Tuanshanzi formation in Xingcheng area.The paleokarst unconformity surface,fissures,dissolution trenches and corrosion pits develop obviously,and are filled with breccia of the overlying Dahongyu Formation.In this paper,four types of breccia and conglomerate related to Tuanshanzi paleokarst are divided,and the characteristics of filling materials are analyzed.According to the characteristics of the paleokarst,it occurred before the deposit of the Dahongyu Formation,which belongs to the local paleokarst in the supergene environment.The evolution of paleokarst is further divided into five stages.Based on the controlling factors of paleokarst,this paper analyzed the origin background of Tuanshanzi paleokarst.The Dahongyu Formation in Xingcheng area unconformablely covers many layers before its deposition.The composition of conglomerate at the bottom is complex,and the thickness and characteristics in each section are quite different.This paper describes in detail the petrological characteristics of the bottom conglomerate of the Dahongyu Formation on several sections,and analyses their nature.According to the characteristics and thickness of the conglomerates in the sections,this paper preliminarily restores paleocoastal zone and paleotopographic features in the early deposit of the Dahongyu Formation in the study area.In the standard section of Jixian,Tianjin,there are two different views on the division of the bottom boundary of the Dahongyu formation.That is there is no unified opinion on the basis boundary of "small white quartz rock" or "big white quartz rock".According to the paleokarst phenomenon at the top of the Tuanshanzi Formation,it is proved that there is obvious sedimentary discontinuities between the Dahongyu Formation and the Tuanshanzi Formation.In the study area,the Dayongyu formation is unconformablely overlay on the Archean granite,Changzhougou Formation,Chuanlinggou Formation and Tuanshanzi Formation,and the unconformity between the Dahongyu Formation and the underlying strata also exists in many areas through the Yanshan Aulacogen.The above phenomena indicate that there are obvious erosion discontinuities between the Dahongyu Formation and the underlying strata,which can be cooperated with the conglomerate phenomenon with 10 cm under the "small white quartz rock".Therefore,it is reasonable to regard "small white quartz rock" as the bottom boundary of Dahongyu Formation.The "Xingcheng Movement" has always been one of the controversial issues for the Mesoproterozoic strata in China.Although the unconformity between the bottom of the Dahongyu Formation and the underlying strata and the Archean crystalline basement in many areas of the Yanshan Aulacogen has been generally recognized in domestic academia,most people do not consider it to be a crustal uplifting movement.In this paper,the bottom unconformity of Dahongyu Formation is studied in detail,and two types of unconformity are classified: heterogeneous overlying unconformity and monoclinic unconformity.It is considered that the heterogeneous overlying unconformity and overlying unconformity represents the gradual expansion of the Yanshan basin in the early sedimentary period of the Dahongyu Formation,while the monoclinic unconformity represents the differential crustal movement in Xingcheng region before the Dahongyu transgression.The influence of this crustal movement does not extend to the center of the sedimentary basin,and it is evident only at the margin of the basin.The North China platform is a part Colombian supercontinent,which develop the Yanshan Aulacogen during Paleo-Mesoproterozoic and the deposition begin after the Lvliang Movement.The Mesoproterozoic Changzhougou-Tuanshanzi period is the strong fault depression stage in Yanshan Aulacogen,and from the Dahongyu period,and the it enters the relatively stable depression stage.The paleokarst events of the Tuanshanzi Formation and the Xingcheng Movement represent an important turning point in the evolution of the Yanshanian Aulacogen.更多还原