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1.
鄂西宁乡式铁矿分布层位岩相特征与成因探讨 总被引：7，自引：0，他引：7
鄂西宁乡式铁矿分布广、规模大,尤以普遍发育赤铁矿鲕粒而独具特色。并且它一般赋存于加里东运动后第一个海浸沉积序列中由碎屑岩向碳酸盐岩过渡的层位,岩相古地理环境有明显的控制作用。本文铁矿层中赤铁矿鲕粒类型之繁多,结构之复杂,安全可与碳酸盐鲕粒相提并论,其成因亦非常相似,均为强烈搅动环境中机械沉积的产物。经波浪和潮汐水流的再次搬运富集。最后定们于中等一弱动荡环境或相地低凹摈滨相上部。 相似文献
2.
《International Geology Review》2012,54(8):736-753
Subtidal, intertidal, and supratidal carbonate facies are recognized in the Upper Jurassic (Kimmeridgian)-Upper Cretaceous (Cenomanian) peritidal carbonates of the Fele area (Western Taurides, Turkey). Vertical stacking patterns of these facies are of a cyclical character; shallowing upward is the trend of the cyclicity in these carbonate facies. In-situ karstic breccias, collapse breccias, caliche (laminar calcrete), “Microcodium” accretion, and root casts are structures commonly indicative of third-order sequence boundaries. However, mud cracks, solution pores or vugs, sheet cracks, loferites, and birds-eye structures are commonly delineated by parasequence boundaries. In-situ or collapse breccias can be genetically derived from sheet cracks, mud cracks, solution pores or vugs, and birds-eye structures with increasing exposure time. The use of such sedimentary structures in the recognition of sequence boundaries is highly practical in the ancient carbonate platforms of the world, inasmuch as the sequence boundaries, as demonstrated in this study, correlate with the eustatic sea level curves. 相似文献
3.
We investigate arrays of echelon cracks in rock (veins, joints, and dikes) formed by dilation. Individual cracks are interpreted as cross-sections of blade-like cracks at the leading edges of a parent fracture. Two morphological end members are distinguished as having straight or highly curved propagation paths as seen in such cross-sections. Bridges of rock between overlapping straight crack paths bend to accommodate crack dilation. Sigmoidal curvature of the bridges is achieved in a phase of increased dilation as the aspect ratio of bridges increases and their resistance to bending drops. Large bending strains within bridges may lead to cross fractures that link adjacent cracks. Good estimates of the dilation and shear displacement over arrays may be obtained directly from measurements of bridges. In contrast, the sigmoidal form of cracks of the other end member is caused by their curving propagation paths. These cracks may link as one crack tip intersects the adjacent crack wall. Some arrays of sigmoidal echelon cracks are associated with shear zones, but those analyzed here are not. 相似文献
4.
由侏罗系千佛岩组砂岩、泥岩及炭质页岩组成的软硬相间的互层边坡,受不同岩层工程特性的影响,开挖引起不同部位岩体产生拉裂、松弛及沿软弱结构面的蠕滑等变形。为分析地层岩性对边坡稳定性的影响,对侏罗系千佛岩组地层进行工程地质岩组划分,分为薄层泥岩与中薄层砂岩互层岩组、巨厚层砂岩夹中厚层砂岩和薄层泥岩岩组。在此基础上,通过对边坡岩体结构的详细研究,确定了控制边坡稳定性的结构面为层间软弱夹层,进而对边坡表层碎裂岩体、结构面组合形成的块体稳定性进行分析,结果表明,边坡浅层岩体整体稳定性差,局部处于极限平衡状态,深部岩体稳定性相对较好,边坡稳定性的岩体结构分析结果与边坡变形状况吻合。 相似文献
5.
冀中坳陷束鹿凹陷古近系沙河街组三段泥灰岩成因探讨 总被引：5，自引：3，他引：5
冀中坳陷束鹿凹陷中部古近系沙河街组三段下部（简称沙三下）泥灰岩属一类特殊的岩石类型组合，既非典型的碳酸盐岩，又非经典的碎屑岩。在进行了详细的岩心、薄片观察和各种分析化验资料的综合分析基础上，认识到研究区岩石为混积岩类，将混积岩（广义的）、混合沉积的概念和体系引入沉积物类型和岩相的划分中，为泥灰岩的科学定名提供了依据。据此对混积岩的类型进行了细致的划分，共划分出3大类型：结构混合、互层混合和夹层混合。每一类可以再细分为多种，其中结构混合包括①陆源组分为主的混积岩，②以内源组分为主的混积岩。互层混合成因的混积岩是最重要的岩石类型，本区所谓的纹层状泥晶灰岩大部分属于这一沉积类型，主要由灰质泥岩或泥灰岩与泥晶灰岩组成明暗相间的条带，有时含丰富的有机质。互层出现的形式是多种多样的，依据其岩石中原地组分和异地组分的含量不同，可进一步划分为4种类型。夹层混合沉积，表现为巨厚的碳酸盐岩质砾岩层夹前两类混积岩。构造、气候及物源等是控制混积岩形成的主要因素。 相似文献
6.
石西油田石炭系潜山火山岩油藏裂缝特征与分布 总被引：1，自引：0，他引：1
裂缝的发育情况对石西油田石炭系潜山火山岩油藏的勘探开发有重要作用。综合利用区域地质、岩心、常规测井、成像测井以及生产动态等资料对研究区裂缝特征及分布规律开展综合研究。研究表明:区内裂缝类型分为构造缝、风化缝、溶蚀缝、收缩缝,其中构造缝(剪切缝)和风化缝比较发育,裂缝总体发育规模中等,宽度较大,密度小,间距大;根据成像测井解释及构造解析,认为该区裂缝分为四期,其中海西运动中、晚期为主要的成缝期;裂缝主要受岩性、岩相、构造位置以及古地貌的控制;裂缝在纵向上主要分布在石炭系顶面以下25~150m范围内,在平面上主要位于断裂带附近、潜山构造高部位以及背斜长轴方向。 相似文献
7.
鄂尔多斯盆地延长组深水岩相发育特征及其石油地质意义 总被引：1，自引：0，他引：1
鄂尔多斯盆地湖盆中部地区三叠系延长组长7油层组广泛发育深水沉积。沉积物的粒度、沉积结构与构造、有机地球化学等特征研究表明,深水沉积岩可划分为四种岩相类型,分别为油页岩岩相、暗色泥岩岩相、砂质泥岩与泥质砂岩岩相和砂岩岩相。其中,油页岩岩相有机碳含量高,有机质类型好,测井曲线具有高阻、高伽马、低电位和时差跳跃频繁等特征;暗色泥岩岩相具有富含有机质、中低阻、中高伽马、高密度和高时差等特征;砂质泥岩与泥质砂岩岩相具有中电阻、低伽马、高密度、时差跳跃频繁等特征,泥质含量 20~70%;砂岩岩相表现出低的电阻、时差和伽马、泥质含量小于20%的特征,并刻画了各种深水岩相的剖面发育特征。深水斜坡带和湖底平原区的岩相组合存在较大的差异。深水岩相对非常规油气资源意义重大,其中油页岩岩相和暗色泥岩岩相为盆地中生界主力烃源岩,深水砂岩岩相是盆地大规模致密油的重要储集体,砂质泥岩与泥质砂岩岩相、暗色泥岩岩相富含丰富的页岩油资源,也具有潜在经济价值。 相似文献
8.
Relatively few studies have examined fault rock microstructures in carbonates. Understanding fault core production helps predict the hydraulic behaviour of faults and the potential for reservoir compartmentalisation. Normal faults on Malta, ranging from <1 m to 90 m displacement, cut two carbonate lithofacies, micrite-dominated and grain-dominated carbonates, allowing the investigation of fault rock evolution with increasing displacement in differing lithofacies. Lithological heterogeneity leads to a variety of deformation mechanisms. Nine different fault rock types have been identified, with a range of deformation microstructures along an individual slip surface. The deformation style, and hence type of fault rock produced, is a function of host rock texture, specifically grain size and sorting, porosity and uniaxial compressive strength. Homogeneously fine-grained micrtie-dominated carbonates are characterised by dispersed deformation with large fracture networks that develop into breccias. Alternatively, this lithofacies is commonly recrystallised. In contrast, in the coarse-grained, heterogeneous grain-dominated carbonates the development of faulting is characterised by localised deformation, creating protocataclasite and cataclasite fault rocks. Cementation also occurs within some grain-dominated carbonates close to and on slip surfaces. Fault rock variation is a function of displacement as well as juxtaposed lithofacies. An increase in fault rock variability is observed at higher displacements, potentially creating a more transmissible fault, which opposes what may be expected in siliciclastic and crystalline faults. Significant heterogeneity in the fault rock types formed is likely to create variable permeability along fault-strike, potentially allowing across-fault fluid flow. However, areas with homogeneous fault rocks may generate barriers to fluid flow. 相似文献
9.
塔中地区晚奥陶世碳酸盐台缘与台内沉积差异--定性和定量的碳酸盐岩微相综合分析 总被引：2，自引：2，他引：0
为揭示塔中地区东部的晚奥陶世镶边型碳酸盐台地边缘与台地内部的沉积差异,利用钻井岩芯及薄片资料,对良里塔格组开展了定性的和定量的碳酸盐岩微相分析研究。研究表明,台缘-台内沉积区发育9种微相类型（MF1~MF9）,不同颗粒岩类微相所代表的几种颗粒滩具有典型差别的粒度累积频率曲线样式。台地边缘主要发育各种高能颗粒滩的微相组合（MF1~MF4）,与台缘生物礁构成礁滩复合体;台地内部主要发育代表中-低能的潮坪-潟湖沉积的微相组合（MF5~MF9）。结合定量的粒度分析分析认为生屑砂屑颗粒灰岩微相（MF1）、生屑砾屑灰岩微相（MF2）和鲕粒颗粒灰岩微相（MF3）是冲流带（前滨）环境的产物,分别代表着台地边缘生屑滩、鲕粒滩和礁前砾屑滩沉积;球粒颗粒灰岩微相（MF5）为位于受障壁的台地内部、中等能量波浪控制的球粒滩;棘屑泥粒灰岩-漂浮岩微相（MF4）发育于台缘礁后的中-高能生屑滩。 相似文献
10.
根据岩性及其组合特征,本文将西藏北部安多—巴青地区侏罗纪含礁地层划分为流水成因的颗粒岩岩相、流水成因的碎屑岩岩相、复成因的泥晶—泥质灰岩岩相、生物及生物化学成因的障积岩岩相、生物及生物化学成因的粘结—障积岩岩相和生物及生物化学成因的骨架岩岩相等6大类型,计16种岩相。它们构成了潮坪相组合、台地浅滩相组合、开阔台地相组合和台地生物礁相组合共4种岩相组合,并由下而上有规律地形成2种岩相序列,即陆源碎屑与碳酸盐混合台地相序列和碳酸盐台地相序列。 相似文献
11.
The Formation and Distribution of the Marine Hydrocarbon Source Rock in the Tarim Basin, NW China 总被引：8，自引：7，他引：1
There are significant differences in type and distribution between marine source rock and continental source rock. According to the iithology, the Cambrian-Ordovician source rock in the Tarim basin is divided into two types： the carbonate source rock and the mud source rock. The two sets of source rocks are developed mainly in three sets of formations, Lower-Middle Cambrian carbonate source rock and mud source rock, Lower-Middle Ordovician mud source rock and Upper Ordovician lime mud source rock. The stratigraphic and areal distributions of the source rocks are controlled by the altitude and the sedimentary facies respectively. The mud source rock is developed in slope-semi deep sea environment. The source rock developed in the slope sedimentary environment is related with the anoxic environment and the one developed in semi deep sea has a close relationship with the up-flowing sea water. The carbonate source rock is developed mainly in platform slope of highstand systems tract and it is usually intimately associated with the salt rock. The Lower-Middle Cambrian carbonate source rock is developed mainly in the Bachu, Tazhong, Tangguzibasi and Yingmaili areas. The Lower-Middle Cambrian mud source rock is mainly developed in the areas east of the line of Kunan 1-Tadong 1. The Lower-Middle Ordovician mud source rock is developed mainly in the east slope of the Manjiaer depression. The carbonate source rock of Early Ordovician is developed mainly in the platform slope of highstand systems tract, such as the south margin of Tabei, the north slope of Tazhong, the Bachu area and Keping area. 相似文献
12.
Sourav Saha Anupam Ghosh Santanu Banerjee Pratul K. Saraswati Stuart D. Burley 《Journal of the Geological Society of India》2011,77(5):409-418
This study highlights lithofacies and biofacies characteristics of the open coast tidal flat near Daman on the eastern flank
of Gulf of Khambhat. Sedimentological and biological observation record six facies within the tidal flat area including older
beach, beach face, sand flat, mud flat/mixed flat, sand bar and beach rock. Distinct sedimentary structures, foraminiferal
assemblage and bioturbation intensity characterize each facies. A wide variety of wave and current generated sedimentary features
characterize the sand flat facies. Semiconsolidated sands of older beach running parallel the coastline at a level higher
than the present beach face possibly records the latest sea level highstand. The beach rock reflects early cementation of
sands in tropical environments. Foraminifera are widely distributed in sand flats, mixed flats and mud flats and grouped into
two biofacies — Ammonia-Elphidium-Quinqueloculina biofacies (sand flat and mixed flat) and Trochammina-Miliammina biofacies (mud flats). The beach face and sand bar facies contain forminifera reworked from sand flat and mud/mixed flat.
Seasonal variation in depositional style is marked by deposition of fresh mud deposited over large areas of the intertidal
flat during monsoon time, most of which is washed away by waves and current actions well before the onset of the next monsoon. 相似文献
13.
近年来,四川盆地西北部下二叠统栖霞组已成为油气勘探的热点和重点。但川北地区勘探程度较低,钻井和剖面资料较少,栖霞组岩石类型分类粗略,沉积模式尚存争议。故选取川北地区露头出露良好的小南海剖面,通过实测观察和室内岩石薄片鉴定,共识别出4类11种岩石类型,并在此基础上分析其岩石微相类型及沉积环境。结果表明:川北地区栖霞组为开阔台地相沉积,生物化石类型丰富,碳酸盐颗粒强烈泥晶化,发育相对低能的似球粒颗粒滩,有别于鲕粒滩和生物碎屑滩,为川北地区下二叠统栖霞组台地沉积模式提供了新的依据。似球粒浅滩的形成环境对进一步认识上扬子二叠纪古地理环境具有重要意义,可为川北地区在今后的勘探工作提供理论指导。此外,梁山组—栖霞组应为一个完整的三级层序,海平面变化是栖霞组沉积相横向迁移和纵向演化的主要控制因素。 相似文献
14.
Detailed study of Miocene carbonates in the Mediterranean region and their analogues on modern carbonate shelves (in the Mediterranean Sea, Brazil and other areas) reveals at least three major types of carbonate platform lithofacies in addition to the classic tropical coral reef (chlorozoan) lithofacies: (a) chloralgal lithofacies, similar to the chlorozoan, but without hermatypic corals; (b) rhodalgal lithofacies, characterized by abundant encrusting coralline algae; and (c) molechfor lithofacies, consisting of benthic foraminifers, molluscs, echinoids, bryozoans and barnacles. These carbonate lithofacies present complex distribution patterns seemingly related primarily to latitude and depth that control water temperature, although other factors (e.g., water circulation, river discharge, suspended sediment) controlling water salinity and temperature, nutrient content, light penetration, etc., also play important roles. Chloralgal and rhodalgal lithofacies can be considered two transitional terms between the two end-members: the chlorozoan lithofacies, which characterizes shallow tropical shelves; and the molechfor lithofacies, which characterizes colder and/or deeper areas. Detailed textural and sequential analysis are required for satisfactory interpretation of these lithofacies in ancient rocks. 相似文献
15.
The stratigraphic record of many cratonic carbonate sequences includes thick successions of stacked peritidal deposits. Representing accumulation at or near sea‐level, these deposits have provided insights into past palaeoenvironments, sea‐level and climate change. To expand understanding of carbonate peritidal systems, this study describes the geomorphology, sedimentology and stratigraphy of the tidal flats on the Crooked‐Acklins Platform, south‐east Bahamas. The Crooked Island tidal flats extend continuously for ca 18 km on the platformward flank of Crooked Island, reaching up to 2 km across. Tidal flats include four environmental zones with specific faunal and floral associations and depositional characteristics: (i) supratidal (continuous supratidal crust and pavement); (ii) upper intertidal, with the mangrove Avicennia germinans and the cyanobacteria Scytonema; (iii) lower intertidal (with the mangrove Rhizophora mangal) and (iv) non‐vegetated, heavily burrowed subtidal (submarine). These zones have gradational boundaries but follow shore‐parallel belts. Coring reveals that the thickness of this mud‐dominated sediment package generally is <2 m, with depth to Pleistocene bedrock gradually shallowing landward. The facies succession under much of the tidal flat includes a basal compacted, organic‐rich skeletal‐lithoclast lag above the bedrock contact (suggesting initial flooding). This unit grades upward into rhizoturbated skeletal sandy mud (subtidal) overlain by coarsening‐upward peloid‐foraminifera‐gastropod muddy sand (reflecting shallowing to intertidal elevations). Cores from landward positions include stacked thin indurated layers with autoclastic breccia, root tubules and fenestrae (interpreted as supratidal conditions). Collectively, the data reveal an offlapping pattern on this prograding low‐energy shoreline, and these Holocene tidal flats may represent an actualistic analogue for ancient humid progradational tidal flats. Nonetheless, their vertical facies succession is akin to that present beneath channelled belt examples, suggesting that facies successions alone may not provide unambiguous criteria for prediction of the palaeogeomorphology, lateral facies changes and heterogeneity in stratigraphic analogues. 相似文献
16.
Molar tooth (MT) structures are enigmatic, contorted millimetre‐ to decimetre‐long veins and spheroids of microcrystalline calcite that formed during very early diagenesis in Precambrian sediments. MT structures in the ca 2·6 Ga Monteville Formation are 600–800 Myr older than previously reported occurrences and establish that conditions necessary for MT genesis were met locally throughout much of the Precambrian. In the Monteville Formation, MT structures were formed shallow subtidally, extending to depths near storm wave base, in shale host sediments intercalated with storm‐generated carbonate sand lenses. They are filled with microcrystalline calcite and rare pyrite. Microcrystalline calcite identical to that in MT structures fills other pore space, including porosity between grains in carbonate sand lenses, moldic porosity in sand grains, sheet cracks in columnar stromatolites, and shallow cracks on sandy bedding planes. Relationships in the Monteville Formation demonstrate that microcrystalline CaCO3 precipitated in fluid‐filled cracks and pores; microcrystalline calcite characteristics, as well as the paucity of carbonate mud in host rocks, are inconsistent with injection of lime mud as the origin of MT structures. Locally, MT cracks were filled by detrital sediment before or during precipitation. Precipitation occurred in stages, and MT CaCO3 evolved from granular cores to a rigid mass of cores with overgrowths – allowing both plastic and brittle deformation of MT structures, as well as reworking of eroded MT structures as rigid clasts and lime mud. Crystal size distributions and morphology suggest that cores precipitated through nucleation, Ostwald ripening and size‐dependent crystal growth, whereas overgrowths formed during size‐independent crystal growth. 相似文献
17.
《Journal of Structural Geology》1999,21(8-9):1199-1207
This paper presents a new model of fault development in carbonate rocks involving a crack–seal–slip sequence. The structures of sheared calcite veins from the Les Matelles outcrop, Languedoc (S. France), and the observations used to construct this new model which integrates aspects of `crack–seal' evolution of calcite-filled veins with concepts of fault valve behaviour are described. In our model, hydraulic mode I reopening of an oblique pre-existing vein in an overall strike-slip stress regime is accompanied by precipitation of calcite, but significant fault slip cannot occur initially despite this obliquity because the ends of the pre-existing structure limit further reopening propagation beyond the tips. The rate of aligned calcite precipitation keeps pace with the rate of dilation of the structure, so that calcite cement essentially seals the system. Stress concentrations at the tips are allowed to rise with reopening until failure of the tip zone results in branch crack formation, triggering both slip along the vein and hydraulic pressure drop. This is followed by sealing within the branch cracks. Such a crack–seal–slip cycle may be repeated several times, as evidenced by fault-perpendicular calcite vein growth interlayered with calc-mylonite lamellae within these structures. Later cycles will become less pronounced because strength recovery of the sealed branch cracks does not regain the initial strength of the intact rock. This model could apply at various scales, and could be a mechanism for triggering earthquakes. 相似文献
18.
Carbonate buildups in the Flinders Ranges of mid-Early Cambrian age grew during a period of high archaeocyath diversity and are of two types: (1) low-energy, archaeocyath-sponge-spicule mud mounds, and (2) high-energy, archaeocyath-calcimicrobe (calcified microbial microfossil) bioherms. Mud mounds are composed of red carbonate mudstone and sparse to abundant archaeocyath floatstone, have a fenestral fabric, display distinct stromatactis, contain abundant sponge spicules and form structures up to 150m wide and 80 m thick. Bioherms are either red or dark grey limestone and occur as isolated small structures 2–20 m in size surrounded by cross-bedded calcarenites and calcirudites or as complexes of mounds and carbonate sands several hundreds of metres across. Red bioherms comprise masses of white Epiphyton with scattered archaeocyaths and intervening areas of archaeocyath-rich lime mudstone. Grey bioherms are complex intergrowths of archaeocyaths, encrusting dark grey Renalcis and thick rinds of fibrous calcite cement. The bioherms were prone to synsedimentary fracturing and exhibit large irregular cavities, up to 1.5 m across, lined with fibrous calcite. The buildups are isolated or in contiguous vertical succession. Mud mounds occur alone in low-energy, frequently nodular, limestone facies. Individual bioherms and bioherm complexes occur in high-energy on-shelf and shelf-margin facies. The two types also form large-scale, shallowing-upward sequences composed of basal (deep water) mud mounds grading upward into archaeocyath-calcimicrobe bioherm complexes and bioherms in cross-bedded carbonate sands. The uppermost sequence is capped by ooid grainstone and/ or fenestral to stromatolitic mudstone. The calcimicrobe and metazoan associations form the two major biotic elements which were to dominate reefs throughout much of subsequent Phanerozoic time. 相似文献
19.
20.
吉林南部通化二道江剖面新元古界万隆组臼齿构造及其沉积特征 总被引：1，自引：3，他引：1
吉林南部通化二道江剖面新元古界万隆组广泛发育缓坡碳酸盐岩沉积,其中发育的一种特殊的碳酸盐岩——臼齿碳酸盐岩,近年来引起了中国乃至世界各国地质学家的重视。通过对野外露头的详细观察和描述、室内薄片观察、扫描电镜、能谱分析等测试手段,揭示了二道江剖面万隆组的地层、岩石、臼齿构造(MT)及沉积岩相和沉积环境特征。臼齿构造是特指那些发育在前寒武纪细粒碳酸盐岩中有清晰边界、粒度在0·01mm左右的由等轴或多边形的微亮晶方解石组成的集合体,其形态可分为条带状构造、瘤状构造及棱角碎块状构造。臼齿构造的形成严格受沉积岩相和沉积环境的控制。万隆组由下而上可分为3段第1段下部为发育臼齿构造的纹层状泥晶灰岩、砂屑灰岩及风暴砾屑灰岩,为中—深缓坡沉积环境的产物;上部由浅缓坡相的泥灰岩、钙质页岩、砂屑灰岩与叠层石灰岩组成;第2段为厚层泥晶灰岩和粉屑泥晶灰岩、瘤状灰岩组成的深缓坡相沉积;第3段本剖面未出露。万隆组形成于缓坡沉积环境,其中浅缓坡相可分为4种岩相组合,中缓坡相可分为11种岩相组合,深缓坡相有6种岩相组合。 相似文献