Application of sequence stratigraphic concepts to the Upper Cretaceous Tununk Shale Member of the Mancos Shale Formation,south-central Utah: Parasequence styles in shelfal mudstone strata

Although sequence stratigraphic concepts have been applied extensively to coarse-grained siliciclastic deposits in nearshore environments, high-resolution sequence stratigraphic analysis has not been widely applied to mudstone-dominated sedimentary successions deposited in more distal hemipelagic to pelagic settings. To examine how sequence stratigraphic frameworks can be derived from the facies variability of mudstone-dominated successions, the Tununk Shale Member of the Mancos Shale Formation in south-central Utah (USA) was examined in detail through a combination of sedimentological, stratigraphic and petrographic methods. The Tununk Shale accumulated on a storm-dominated shelf during the second-order Greenhorn sea-level cycle. During this eustatic event, the depositional environment of the Tununk Shale shifted laterally from distal middle shelf to outer shelf, then from an outer shelf to an inner shelf environment. At least 49 parasequences can be identified within the Tununk Shale. Each parasequence shows a coarsening-upward trend via upward increases in silt and sand content, thickness and lateral continuity of laminae/beds, and abundance of storm-generated sedimentary structures. Variations in bioturbation styles within parasequences are complex, although abrupt changes in bioturbation intensity or diversity commonly occur across parasequence boundaries (i.e. flooding surfaces). Due to changes in depositional environments, dominant sediment supply and bioturbation characteristics, parasequence styles in the Tununk Shale show considerable variability. Based on parasequence stacking patterns, eleven system tracts, four depositional sequences and key sequence stratigraphic surfaces can be identified. The high-resolution sequence stratigraphic framework of the Tununk Shale reveals a hierarchy of stratal cyclicity. Application of sequence stratigraphic concepts to this thick mudstone-dominated succession provides important insights into the underlying causes of heterogeneity in these rocks over multiple thickness scales (millimetre-scale to metre-scale). The detailed sedimentological characterization of parasequences, system tracts and depositional sequences in the Tununk Shale provides conceptual approaches that can aid the development of high-resolution sequence stratigraphic frameworks in other ancient shelf mudstone successions.     

辽东本溪-桓仁地区古生界事件地层划分及特征

辽东本溪-桓仁地区古生界发育,是研究地层学、沉积学的典型地区.在简述事件地层学原理和地层事件概念,并对主要地质事件进行初步划分基础上,通过对本溪-桓仁地区1：5万区域地质调查、地层剖面测制研究,对该区古生界,根据地质事件的岩石记录,划分了构造上升和下降、海侵、缺氧、风暴、干燥炎热等6种事件地层单位,8个事件集群,并对各事件地层单位逐一描述,提出事件个体和事件集群、事件沉积层和事件集群沉积段的概念,并探讨了与沉积环境、层序地层的相关性.     

Basic geometrical models in geology: Werner's topological model

Werner's topological model is the most fundamental geometrical model in geology. It takes into account only order and continuity of geological bodies. Within this model, stratigraphic and geochronologic concepts of simultaneity, scale, stratigraphic units, facies, discordances, and so forth are defined, and algorithms for solving practical correlation problems may be worked out. Application of algorithms is illustrated by computer correlation of sections in East Kamchatka.     

Application of sequence and genetic stratigraphic concepts to Carboniferous coal-bearing strata: an example from the Black Warrior basin,USA

Carboniferous strata provide an excellent example on which to test the application of genetic stratigraphic and sequence stratigraphic concepts. Both approaches are employed in the evaluation of the coal-bearing strata of the Black Warrior basin, south-eastern USA. Bounding hiatal surfaces have been recognized in the succession of rock that includes the Mary Lee coal zone. Within the framework of genetic stratigraphy, one genetic sequence has been identified comprised of offlap (progradational and aggradational facies) and onlap (aggradational and transgressive facies) components. Seven parasequence sets have been delimited according to the concepts of sequence stratigraphy. These have been ascribed to transgressive, highstand and shelf margin systems tracts. The identification of components of these contrasting frameworks provide the basis for evaluating other Carboniferous strata. Correspondence to: R. A. Gastaldo     

沉积地层的结构分析──兼论1：5000区域地质调查中岩石地层研究的基本内容

近些年来，随着沉积学的新理论和新概念越来越多地渗入到地层学领域，岩石地层学也有了很大的进展。本文旨在从地层的沉积作用入手，讨论了地层的结构类型、分类及其地层的有序性。地层的沉积作用由垂向加积和侧向加积形成，并细分为４种类型的旋回沉积作用。现代岩石地层学的基本内容包括：（１）岩石地层单位的建立或厘定，（２）地层的成因，（３）地层的时代；（４）地层格架（岩石地层格架、年代地展格架和生物地层格架）等．岩石地层单位的确立是岩石地层学研究的基础，是建立在对地层的五个基本属性深入研究的基础上的：（１）岩石学特征，（２）生物学特征；（３）结构特征；（４）厚度和体态；（５）接触关系（地层单位顶、底和内部接触关系）。     

Geohistorical Stratigraphy and Stratigraphic Guides

A different understanding of the stratigraphic science methodology is considered. The classical geohistorical content of stratigraphy is set against the latest formal classification approach recorded in the International Stratigraphic Guide. Some provisions of the Stratigraphic Code of Russia and the International Stratigraphic Guide are studied. The described confrontation between the two concepts can be expressed by a formula: stratotype or limitotype.     

异整合面——古环境剧变的地层记录

异整合面是在区域(盆地尺度)或全球范围内发生根本性的、突然的、持续性的沉积相变而形成的地层界面.有别于传统的沉积学和地层学概念以沉积环境保持稳定或者缓慢连续变化为前提,异整合面强调古环境剧变事件在地层中的记录,它是不遵循瓦尔特相律的地层界面.陆相环境波动频繁、变化剧烈,容易发育异整合面,例如北美古近系绿河组、松辽盆地白...     

从地层记录的时空有序性解读地层学发展

自20世纪70年代以来,随着多重地层划分理论的提出和各种测试方法、手段的应用,一系列地层学分支学科开始出现。众多的地层学的分支学科极大地开阔了地层学研究领域,使地层学理论百家争鸣,向着多侧面、多层次和多尺度的方向发展,但较为专一的研究对象也使其趋向碎片化。因而,重新回顾地层学的发展历程,发现依据不同特征和属性建立的地层单位之间的关联,将趋向碎片化的地层学作为一个整体进行思考很有必要。就此从时空有序性的角度,系统总结和梳理了地层记录的不完备性、穿时性、旋回性、非渐变性和不可逆性。发现在地层记录中,尽管岩性变化、生物变化、物理变化和化学变化并不是严格地统一到时间变化中,但它们在时间和空间中的分布是有序和有规律的,是虽然不具备等时性但具备时间秩序性的沉积体。从下老上新的斯坦诺地层三定律,到空间上毗邻关系可以转化为时间上相随历史的瓦尔特相律,地层学不仅用上、下、左、右表达空间概念,也揭示其时间属性;不整合刚提出时仅仅是一个构造概念,是褶皱幕或造山幕导致的地层关系在空间上的不协调,但现今却包含了更多的时间属性,定义为地层记录的长时间缺失;地层旋回一开始是对地层重复性的描述,但随着第四纪米兰科维奇旋回的研究,证实它与沉积层序都是天文节律（时间）的产物。在复杂的地层记录中发现和恢复其有序的时空关系,揭示地层记录的时空有序性成为了地层学所有分支学科共同面临的主题,也使其相互交融。     

Archaean stromatolites of the Belingwe Greenstone Belt,Zimbabwe (Rhodesia)

The stromatolites of the Belingwe Greenstone Belt (approximately 2700 Ma old) are perhaps the best-developed Archaean stromatolites yet found. Exposures occur on two stratigraphic levels, both part of the “Bulawayan” in Rhodesian stratigraphic terminology (Wilson et al., 1978). The extensive outcrops show a wide variety of stromatolites, including forms similar to Baicalia, Conophyton, Irregularia and Stratifera. Many stromatolites occur in cyclic units, possibly reflecting periodic changes in lagoonal conditions. Associated sedimentary rocks were deposited in a very shallow-water environment and some display well-developed desiccation features. Currently held concepts concerning the evolution of stromatolites and their usefulness in biostratigraphy do not appear to be supported by the evidence from Belingwe.     

Geochemical－Sequence Stratigraphy and Its Application Prospects in Lake Basins

As a useful approach for hydrocarbon exploration,the sequence stratigraphy has been commonly accepted.The concepts of sequence and parasequence provide a state-of -the-artframe-work for studying the distribution and characters of depositional system,and analyzing the occurrence,distribution,characteristics of source,reservoir and seal-play elements.The newly-developed geochemical -sequence stratigraphy focuses mainly on the occurrence,distribution and characters of source rocks and reservoir hydrocarbons within a chronostratigraphic framework,Integrated with sequence wtratigraphy,geochemistry can be used to study the surce rock potential within a sequence wtratigraphic framework and to describe the characteristics of hydrocarbons accumulated in reservoirs,which were predicted by way of sequence stratigraphy.The concept of geochemical-sequence wtratigraphy was proposed by Peters et al.(2000).Constructing a reliable sequence stratigraphic framework is the basis of geochemical-sequence wtratigraphic study although it is not the main goal.High-resolution biomarker analysis is critrical to the construction of a geochemical-sequence stratigraphic model.The geochemical-stratigraphic study involves mainly:(1) the distribution and geochemical characteristics of source rocks with relative sea (lake)-level change;(3) to prodict if these reservoirs bear hydrocarbons and their geochemical features;(4) to be used to construct the time-stratigraphic framework.This paper also summarizes the lake basin types,and introduces their facies associatons,source potential and organic geochemical features.At the end,the authors offer some suggestions about how to carry out geochemical-sequence stratigraphic study in ladcustrine strata.     

沉积有机相的研究现状及其应用

沉积有机相是近年来国内外广泛运用于油气勘探的一种有效的研究方法。本文介绍了沉积有机相的概念、划分方案，及其在油气勘探、盆地分析和层序地层学中的应用，指出了沉积有机相与层序地层分析相结合对油气资源评价和预测烃源岩有广阔的发展前景。     

Vergence: an evaluation

Fold asymmetry is an independent concept distinct from facing. Fold vergence is a direction relating to the sense of asymmetry of folds. The complementary concept of cleavage vergence is defined allowing asymmetry to be used to locate major fold traces where no minor folds exist. Cleavage vergence is a valuable tool in complex structural terrains. Both concepts can be used singly or in combination to identify refolding. Vergence can define structural way-up where sedimentological or stratigraphic way-up cannot be recognised.     

Pleistocene stratigraphy in the southern Lower Mississippi Valley

Scientific inquiry into Pleistocene stratigraphy of the Lower Mississippi Valley (LMV) dates to early writings of European naturalists in the late 19th century. By the early 20th century, landscape evolution concepts, stratigraphic models, and regional syntheses had developed for most areas. The 1944 monograph of H.N. Fisk marks the advent of a predictive stratigraphic and landscape evolution model that links form and process to a predominantly glacioeustatic mechanism. The Fiskian model gained widespread acceptance, and decades passed before significant alternate models began to emerge. Revised stratigraphic and geomorphic concepts are presently developing from newly acquired environmental and engineering data. Present scenarios classify Pleistocene outcrop areas into erosional and constructional landscapes, and veneers of eolian, colluvial, fluvial, coastal, and marine origin can drape both types of surfaces.

The southern LMV and adjacent Gulf Coastal Plain (GCP) experienced significant landscape change during the Pleistocene. Late Tertiary (Pliocene?) to Early Pleistocene deposition of the Upland Complex was by streams with a high sand and gravel load relative to its mud load. The regional drainage network and fluvial system behavior was probably significantly different from the modern. Braided stream alluvial fan complexes received sediment from highland source areas adjacent to the LMV and the glaciated mid-continent. It is plausible that part of Upland Complex deposition predates initial glacial advances.

From Early to Middle Pleistocene, an erosional landscape formed during a dissection period that chiefly postdates soil formation on stable landscape positions of the Upland Complex. Slope evolution truncated a regionally extensive geosol in multiple phases, and parts of the erosion surface complex are graded to the oldest preserved constructional alluvial plains in present valleys. Toe and foot slope positions of the erosion surface complex and its correlative alluvial plains are presently delineated as the Intermediate Complex. Constructional landscapes formed at this time are sparsely preserved; Fisk's Montgomery Terrace in the Lower Red River Valley (LRRV) is the best preserved example. Influences on the development of erosion surfaces in the LMV are not well understood; however interactions of relative sea level fall, climate change, and epirogenic crustal movement are plausible factors.

From the latter part of Middle Pleistocene to the Holocene, there was widespread evolution of modern constructional landscapes. Constructional alluviation preserved lithofacies of mixed load, laterally accreting, meandering streams that developed over large areas of the southern LMV to form parts of the Prairie Complex. Lateral planation in valleys and stable rates of upland sediment generation were dominant processes during Prairie Complex deposition.

Pleistocene stratigraphic examples considered important by Fisk are still considered relevant to modern stratigraphic investigators. Presently, Pleistocene units of the southern LMV, the adjacent LRRV, and central GCP can be correlated only by relative stratigraphic relationships. Refined chronostratigraphic and paleoenvironmental models for these areas would help improve the understanding of the geomorphic influences on Quaternary landscape evolution in the region.     

Tectonic episodes of cratons: conflicting North American concepts

Over the past one hundred years North American geologists have been influenced by concepts of Earth history based on periodic events involving marked (‘Neocatastrophic’) changes and competing concepts involving steady-state (‘Uniformitanan’) behaviour. T.C. Chamberlin, a late 19th-/early 20th-Century exponent of a nonuniformitarian scenario of earth history, proclaimed ‘diastrophism as the ultimate basis of correlation’ - meaning that geological history is punctuated by orogenic paroxysms causing retreat of epicontinental waters to oceanic basins, creating segmentation of the stratigraphic and chronological record. At mid-Century James Gilluly gained wide support for the proposition that orogeny has followed a Uniformitarian, near-steady-state course. Accordingly, episodic diastrophism is a myth and cannot be the basis for periodic eustatic sea-level change, interregional unconformities, etc. In more recent decades two powerful new influences on geological thought have emerged. The global tectonic paradigm has forced upon us the realization that rearrangements of lithospheric plates are capable of changing the freeboard of continents. At the same time technological advances in the acquisition and processing of seismic-reflection data have been seized by receptive minds to organize the newly available stratigraphic imagery for application to the discipline of seismic stratigraphy which emphasizes the identification and correlation of unconformity-bounded successions of strata. Expansion of the methodology to the outcrop, beyond the limitations of seismic resolution, has brought about the flowering of the New Sequence Stratigraphy, doctrine that has deservedlyachieved wide application and acclaim. Practitioners of sequence stratigraphy, impressed by the distances over which unconformity-bounded stratal units can be correlated, hew to the belief that eustatic (commonly glacially engendered) sea-level change is the control. This paper examines evidence of tectonic episodes affecting cratons and their margins. These offer promise of a more satisfactory understanding of stratigraphic sequences and of the Earth history they represent. Consideration of these matters makes it inescapable that the elevation and subsidence of cratons (and their component basins and arches) reflect tectonic phenomena of the continental lithosphere quite independent of eustatic events.     

Zonal biostratigraphy in the solution of the fundamental and applied problems of geology

The problems of zonal stratigraphy of the early 21st century are discussed. The great advances achieved in recent years in using zones in geological practice are noted. At the same time, attention is drawn to the controversies existing in the interpretation of the concepts “biostratigraphic zone” and “chronozone,” in the methods of drawing the boundaries of such zones, and in the assessment of the spatial scale of zones and in the understanding of them as stratigraphic units.     

Estimation of the Mesozoic geological time scale

Geological time scales are constructed by combining the stratigraphic record with radiometric dates and their standard deviations. The stratigraphic record encompasses litho-, bio-, chrono-, and magnetostratigraphy. The statistical methods employed should embody concepts and data available for the systems considered. Recently, in order to estimate the ages of 31 Mesozoic stage boundaries, use was made of a database with chronostratigraphic classifications for 340 dates, biostratigraphic data including ammonite subzones, and information on seafloor spreading. This paper is primarily concerned with the propagation of errors through the successive steps of the data analysis. The following stepwise approach was taken for combining the different types of data: (1) maximum likelihood estimation with windows set around prior stage boundary estimates, (2) averaging of estimates with variable precision including magnetochronologic data, and (3) calibration by means of cubic smoothing splines assuming equal duration of ammonite subzones. The end product is a time-scale in which the stage boundary ages are accompanied by approximate 95 per cent confidence intervals.     

地球油气资源潜力是自然科学的基本问题

层序地层学自１９８７年问世以来，在国外如火如荼地发展起来，石油地质界对它的发展尤为关注。然而，在我国却显得举步维艰，进展缓慢。本文讨论了出现这种状况的起因：①不认识地震反射界面基本上是等时面；②认为地震／层序地层学是研究被动大陆边缘海相地层产生的，不适于非海相地层；③常规剖面中的地震反射频率和分辨率太低，不足以进行层序地层学研究；④层序地层学属纯理论科学，脱离油气勘探实际，采纳它的概念可能打气生产秩序。最后文章从正面阐述了开展层序地层学研究的必要性。     

古沙漠沉积及其层序单元—以鄂尔多斯白垩纪内陆古沙漠盆地为例

古沙漠是以风成沉积为特征的一种特殊环境的充填, 由于风成沉积与水成沉积机制不同, 目前以湖泛面为依据所开展的陆相湖盆层序地层研究的原则不能完全适用于古沙漠地层.分析讨论了基于地下潜水面为沉积基准面的古沙漠沉积作用过程及其控制因素, 探讨了古沙漠层序地层的构成及其单元的划分, 并提出了古沙漠成因地层及沉积学研究的有关概念和方法.      

二叠系-三叠系界线的事件地层学标志

<正> 传统的二叠-三叠系界线,是以喜马拉雅山的Otoceras层的底作为三叠系底界(Die-ner 1912)。70年代以来,国际上提出了多种方案(Waterhouse 1973,1976;Kozur 1977;Newell 1978),我国80年代出现了分歧意见(李子舜、姚建新1984;李子舜、詹立培等1986)。1986年在意大利举行的“西特提斯南阿尔卑斯的二叠系及二叠-三叠系界线国际     

华南泥盆系层序地层与岩石-年代地层界线间相关性探讨

以广西六景、象州大乐、桂林塘家湾及贵州独山与贵阳东北郊乌当剖面为例,在已有的地层、古生物、沉积相研究的基础上,开展了层序地层学研究.通过这项研究,认为那高岭组与莲花山组的界线是一年代地层、岩石地层及层序地层合一的界面;论证了大乐剖面应堂组的古琶段与贵州独山剖面的龙洞水组属于下泥盆统的可行性;总结了吉维特阶与艾菲尔阶间多处存在沉积间断面或沉积停滞面的客观事实,确认该界面为一符合实际又易于识别的自然界面,可作为D_2~2 /D_2~1的界面;讨论了存在于不同沉积相中的D_3/D_2界面,认为该界面置于D_2~2上部层序之上的海进体系域顶面,与以牙形类为准确立的界线很接近,但其更利于野外实际工作;对贵阳东北郊乌当剖面乌当组的归属提出疑问,并将其定为吉维特阶早期.