A QUANTITATIVE STUDY OF A SEQUENCE OF COAL-BEARING CYCLES IN THE NAMURIAN OF CENTRAL SCOTLAND, 1

Electronic computers have enabled the quantitative relationships between stratigraphic variables to be calculated for a sequence of Namurian (E1 zone) cycles deposited in a differentially subsiding basin east of Stirling. Despite their limitations, coefficients of correlation and linear regression equations provide a relatively simple means of expressing the relationships between critical variables and so provide a useful way in which various cyclically deposited sequences can be compared. All possible pairs chosen from eleven variables are investigated, including the total number and average thickness of cycles, total number of coals and total thicknesses of coal, sandstone and shale. These six variables all tend to show a linear relationship with total thickness of strata and hence net subsidence. A second part of this paper, to be published later, will examine the relationships between variables in more detail, using the technique of factor analysis.     

Cyclic sedimentation of the Karharbari Formation (Damuda Group), Talchir Gondwana basin, Orissa

The cyclic arrangement of lithofacies of the Karharbari Formation of the Damuda Group from a part of the Talchir Gondwana basin has been examined by statistical techniques. The lithologies have been condensed into five facies states viz. coarse-, medium-, fine-grained sandstones, shale and coal for the convenience of statistical analyses. Markov chain analysis indicates the arrangement of Karharbari lithofacies in form of fining upward cycles. A complete cycle consists of conglomerate or coarse-grained sandstone at the base sequentially succeeded by medium-and fine-grained sandstones, shale and coal at the top. The entropy analysis categorizes the Karharbari cycles into the C-type cyclicity, which is essentially a random sequence of lithologic states. Regression analysis undertaken in the present study indicates the existence of sympathetic relationship between total thickness of strata (net subsidence) and number and average thickness of sedimentary cycle and antipathic relationship between number and average thickness of sedimentary cycle. These observations suggest that cyclic sedimentation of the Karharbari Formation was controlled by autocyclic process by means of lateral migration of streams activated by intrabasinal differential subsidence, which operated within the depositional basin and the channels carrying coarse grade clastic sediments, which make the cycles thicker, tend to be more common in the areas of maximum subsidence. Clastic sediments issued from the laterally migrating rivers interrupted the cyclic sedimentation of the Karharbari Formation in many instances.     

Cyclic characteristics of coal-bearing sediments in the Bochumer Formation (Westphal A 2) Ruhrgebiet, Germany

Cyclic characteristics of the Bochumer coal measures have been studied statistically using first-order embedded Markov chain analysis on data from thirty-two boreholes. Separate tally matrices which were made for the Lower, Middle and Upper units by summing the tally matrices for all the boreholes, were used to produce various transition probability matrices, which were then subjected to the chi-square test. Results strongly suggest that the Bochumer succession was deposited by a Markovian mechanism, and that the sequence represents cyclic sedimentation. The preferential upward transition path for lithologic changes that can be derived in the total area and in individual logs is: coal\rightarrow shale\rightarrowsiltstone\rightarrowsandstone\rightarrowsiltstone\rightarrowrooty bed\rightarrowcoal. Among the noteworthy features are a two-way transition between siltstone and sandstone, which implies frequent interbedding of the two lithologies, and the transition, up out of siltstone to rooty beds. There are, however, minor variations, locally, either by way of subsidiary transitions or in the extent to which the above transitions can be followed. When tested for stationarity through time and space, the Markov chain analysis yields results which show the upward sequence of lithologic states (facies) to be stationary at individual localities, but non-stationary when the entire data are tested for the whole area. The relationship of the number of coal-bearing cycles to total thickness of strata and average thickness of coal-cycles is examined using linear regression. Significant positive relationships are present between the number of cycles and total thickness, and significant negative correlations occur between the number of cycles and their average thickness. The results of the study have been used to infer sedimentological evolution of the succession and sediment cyclicity. Environmentally, the Bochumer cycles fit suitably into the concept of deltaic cycles.     

The cyclic hierarchy of the 'Purbeckian' Sierra del Pozo Section, Lower Cretaceous (Berriasian), southern Spain

The lowermost Cretaceous (Berriasian) Sierra del Pozo Formation is divisible into metre‐scale cycles that are bundled in a four‐tiered hierarchy of cycles and cyclic sequences. At the smallest scale, sixth‐order cycles, thought to be the product of precessionally forced sea‐level fluctuations (c. 20 ka), average less than a metre in thickness, shallow upward and are bounded by surfaces where deeper facies abruptly overlie shallower facies. Bundles of sixth‐order cycles, called fifth‐order sequences, are recognized by two types of asymmetric patterns in facies distribution. First, more pronounced facies changes occur at sixth‐order cycle boundaries lower in a sequence, whereas smaller facies changes occur at cycle boundaries higher in a sequence. Secondly, subtidal marine limestones (i.e. biomicrites and biosparites) are the dominant facies lower in a cyclic sequence, whereas more restricted or shallower water facies (i.e. mud‐cracked microbial laminites, dolomites, shale and clay) are more predominant higher in a cyclic sequence. The bundling of sixth‐order cycles is explained as a product of periodic change (100 ka) in the eccentricity of the earth's orbit. The degree of orbital eccentricity modulates the magnitude of precessional sea‐level fluctuations, which in turn determine the relative facies contrasts at sixth‐order cycle boundaries. Larger scale fourth‐ and third‐order sequences are defined by similar patterns in facies contrast at successive sequence boundaries and by a change in predominant facies type from bottom to top. These patterns are explained as the product of 400 ka and 2 Ma periodic variations in the eccentricity of the earth's orbit. In summary, the strength of the precessional signal varies in consort with periodic changes in orbital eccentricity at three time scales producing a stacked hierarchy of cycles and sequences of cycles. Change in obliquity of the earth's axis may modulate the effects of the precessional signal and thereby modify patterns of preserved cyclic structure. This interpretation of cyclicity in the Sierra del Pozo section is markedly different from that of Jiménez de Cisneros & Vera (1993), who attributed all rock cycles to a single process (obliquity) even though the cycles they described varied in thickness from less than 1 m to more than 4 m. The cycles they described are shown here to be either precessional cycles or composite sets of precessional cycles (100 ka sequences). In this new hierarchical interpretation, ninety‐six 100 ka and twenty‐four 400 ka sequences are recognized, extending the time of deposition of the Sierra del Pozo section to more than 9·6 Ma.     

Depositional sequences in a foreland basin (north-western domain of the continental Duero basin,Spain)

The Cenozoic record of the north-western domain of the Duero basin is articulated at the surface through a set of continental depositional sequences called, from base to top, the Vegaquemada sequence, the Candanedo sequence, and the Barrillos sequence. These depositional sequences were deposited in continental sedimentary environments. The deposition of the first sequence occurred through a fluvial system with floodplains cut by low-sinuosity channels. The Vegaquemada sequence was developed between the Middle Eocene and the Early Agenian. The second sequence was formed by a set of highly efficient transport alluvial fans that evolved laterally towards fluvial systems with low-sinuosity fluvial channels and an extensive floodplain, where several types of palaeosols were formed. This sequence developed between the Early Agenian and the Late Vallesian. The third unit–the Barrillos sequence (between the Late Vallesian and the Turolian/Ruscinian transition), was generated by a set of highly efficient transport alluvial fans dominated by low-sinuosity fluvial channels.In subsurface geology, seismic and well data are used to rebuild the stratigraphic architecture. The two basal depositional sequences can be identified with two seismic units: the Palaeogene Seismic Unit (PgSU) and the Neogene Seismic Unit (NgSU), respectively. In the present work, we obtained the isovelocity, isochron, and isobath maps for the top and base of the two Cenozoic units. The Palaeozoic (PzSU) and Mesozoic (MzSU) seismic units are found under these two units. Through study of the logs of the various boreholes, it was only possible to analyse the upper 700 m of the Candanedo Sequence (NgSU), without encompassing the total thickness of the unit. Several middle-order sequences were differentiated, in general showing a sequential fining-upwards evolutionary character. Additionally, for the boreholes analysed two main types of electrofacies were identified, both representing fluvial channels and floodplain deposits.The north-western domain of the Duero basin is interpreted to have been formed in response to the tectonic uplifting of the Cantabrian Mountains since Middle-Eocene times. Integration of the data concerning the surface and subsurface geology in this domain reveals that this basin edge behaved as a foreland basin during Cenozoic stages. The foredeep, with a depth of 2800 m, is oriented east–west and has a sediment thickness of up to 3500 m. The forebulge is located in the southwestern zone and represents an area of basement uplifting in which a minimum thickness of materials from the Cenozoic depositional sequences has accumulated.     

Subsurface lithofacies analysis of the Fluvial Early Permian Warchha Sandstone, Potwar Basin, Pakistan

The Early Permian Warchha Sandstone is well preserved in subsurface in the Potwar Basin and the Punjab Plain of Pakistan. However, this succession is only exposed in the Salt Range, and within this region, only a modest number of the many outcrops are of sufficient quality to enable the preparation of lateral and vertical log profiles. From the subsurface, data from five wells drilled in the Salt Range and Potwar Basin have been analysed. Although they are of restricted coverage, these subsurface data — which take the form of gamma ray logs and well cuttings — provide a valuable addition to the outcrop dataset of the Warchha Sandstone as they provide useful information about vertical textural changes, type and thickness of bedding and the nature of sandbody contacts with underlying strata. Overall, the Warchha Sandstone succession is composed of repeated fining-upwards cycles indicative of a meandering fluvial succession. Sub-components of each cycle are themselves classified into six subsurface sedimentary facies. Through comparison with outcropping parts of the succession, the origin and significance of these subsurface facies can be related to specific architectural elements within the meandering fluvial system responsible for generating the Warchha Sandstone succession.     

High-resolution sequence stratigraphy of the Lower Triassic ‘Buntsandstein’ in the Netherlands and northwestern Germany

Detailed log correlations of the largely fluvio-lacustrine Lower Triassic Buntsandstein (Late Permian-Early Anisian), carried out on 80 wells in the Dutch onshore and offshore areas, can be linked to northwest-German high-resolution sequence stratigraphy. The correlations show that cyclic sedimentation occurred in large parts of the basin. Seven 1st-order sequences are recognised, namely the Main Claystone, Rogenstein, Volpriehausen, Detfurth, Hardegsen, Solling and Lower Röt Sequences. They are overlain by the lower part of the Upper Röt–Lower Muschelkalk Sequence. Distinct sequence boundaries have been identified at the bases of four sequences: Volpriehausen, Detfurth, Solling and Upper Röt. The higher-order sequences consist of fining-upwards cycles with a thickness of up to tens of metres. The sequences are laterally persistent and have a characteristic expression on gamma-ray and sonic logs. In the Lower Buntsandstein, they display a uniform character throughout most of the area, with only minor differences in thickness or lithology. NNE-oriented lows and swells were formed during deposition of the Volpriehausen, Detfurth and Hardegsen Sequences. Uplift prior to the deposition of the Solling Sequence caused deep erosion on the swells in the basin and minor erosion in the lows. The high-resolution sequences probably represent alternating, relatively wet and dry climatic periods, with a periodicity of about 100 000 years. An analysis of the sequences suggests that their reduced thickness on the swells is mainly the effect of erosion. This is supported by analyses of the accumulation patterns and rates.     

频谱分析法在识别米兰科维奇旋回及高频层序中的应用——以塔里木盆地塔中－巴楚地区下奥陶统鹰山组为例

在巴楚地区露头高频层序研究及塔中地区钻测井三级层序划分的基础上,对塔里木盆地塔中地区塔中162井和塔中43井下奥陶统鹰山组层序OSQ2的自然伽马能谱测井ln（Th/K）曲线进行了滤波处理、快速傅里叶变换处理、小波时频分析以及调谐处理,识别出具有米兰科维奇旋回特征的高频旋回。结果表明：斜度（黄赤交角）旋回最为明显,周期为37.0 ka,是以向上变浅为主的六级米级旋回的主要控制因素,其主旋回平均厚度在台地边缘相带的塔中162井及塔中43井中分别为4.55 m及3.97 m,在巴楚地区半局限-开阔台地相带中为2～4 m;95 ka的短偏心率周期是形成五级准层序的主要控制因素,而大致代表四级准层序组形成时限的413 ka长偏心率周期在地层记录中表现并不明显。据高频层序叠置关系分析及平均主旋回个数初步估算,塔中-巴楚地区下奥陶统鹰山组层序OSQ2的形成时限大约为4.92 Ma,塔中43井鹰山组层序OSQ2受后期构造隆升而被剥蚀约192  m。结合四级层序（准层序组）发育时限（413 ka）及其叠置关系,以及与其调谐的小波变换曲线特征,初步将塔中-巴楚地区鹰山组层序OSQ2划分出12个准层序组。自然伽马能谱测井ln（Th/K）曲线包含沉积古水深相对变化的信息,是反映气候变化生成的米兰科维奇旋回层序的良好指标。     

Deglaciation sequences in the Permo-Carboniferous Karoo and Kalahari basins of southern Africa: a tool in the analysis of cyclic glaciomarine basin fills

The Late Westphalian to Artinskian glaciomarine deposits of the Karoo and Kalahari basins of southern Africa consist of massive and stratified diamictite, mudrock with ice-rafted material, sandstone, silty rhythmite, shale and subordinate conglomerate forming a cyclic succession recognizable across both basins. A complete cycle comprises a resistant basal unit of apparently massive diamictite overlain by softer, bedded stratified diamictite, sandstone and mudrock with a total thickness of as much as 350 m. Four major cycles are observed each separated by bounding surfaces. Lateral facies changes are present in some cycles. The massive diamictites formed as aprons and fans in front of the ice-grounding line, whereas the stratified diamictites represent more distal debris-flow fans. The sandstones originated in different environments as turbidite sands, small subaqueous outwash channel sands and delta front sands. The rhythmites and mudrock represent blanket deposits derived from turbid meltwater plumes. Cycles represent deglaciation sequences which formed during ice retreat phases caused by eustatic changes in the Karoo and Kalahari basins. Evidence for shorter-term fluctuation of the ice margin is present within the major advance-retreat cycles. Hardly any sediment was deposited during lowstand ice sheet expansion, whereas a deglaciation sequence was laid down during a sea-level rise and ice margin retreat with the volume of meltwater and sediment input depending on temporary stillstands of the ice margin during the retreat phase. The duration of the cycles is between 9 and 11 Ma suggesting major global tectono-eustatic events. Smaller cycles probably linked to orbital forcing were superimposed on the longer-term events. A sequence stratigraphic approach using the stacking of deglaciation sequences with the ice margin advance phases forming bounding surfaces, can be a tool in the framework analysis of ancient glaciomarine basin fills.     

Cycle anatomy and variability in the storm-dominated type cincinnatian (Upper Ordovician): coming to grips with cycle delineation and genesis

Although parasequence and sequence are scale-independent terms, they are frequently applied only to specific scales of cycles. For example, meter-scale cycles are commonly assumed to be parasequences or PACs. In the Upper Ordovician Kope and Fairview Formations of northern Kentucky, we examined a succession of 50 meter-scale cycles that have been variously interpreted as deepening-upward, shallowing-upward, or showing no relationship with water depth. Our analysis shows that these cycles, characterized by shifts in storm-bed proximality, are highly variable in their thickness and internal construction. Most cycles are best considered high-frequency sequences, because deepening-upward intervals are common, and many cycles contain evidence of abrupt basinward shifts in facies as expected at sequence boundaries. A minority fit the parasequence model of shallowing-upward cycles bounded by flooding surfaces. Larger, 20 m scale cycles are defined by systematic thickening and thinning trends of meter-scale cycles. However, meter-scale cycles do not display any systematic trends in cycle anatomy as a function of position within the 20 m cycles or position within the Kope and Fairview Formations. The high cycle variability and the lack of systematic stratigraphic organization with respect to longer-term cyclicity reflect either the irregularity of relative sea-level changes, the poor recording of sea-level changes in this deep-water setting, or the generation of these cycles by climate-induced cyclicity in storm intensity. These three mechanisms would generate similar patterns at the outcrop scale, so it is not possible at the present to distinguish between them.     

利用米兰科维奇旋回划分柴达木盆地第四系层序地层

对柴达木盆地第四系自然伽马测井曲线的频谱分析结果表明, 地层中保存着厚度稳定的地层旋回.按柴达木盆地第四纪沉积速率0.87～0.90 m/ka计算,地层中保存的地层旋回厚度在厚度比值和沉积时间周期上都与米兰科维奇旋回周期一致,且主要受控于米兰科维奇旋回中的地轴倾斜度周期, 其引起的地层旋回厚度变化范围为25.0～36.1 m.据此采用Fischer图解法, 求取其可容纳空间变化曲线,以指导层序地层的正确划分.     

基于米氏旋回的黔西盘县上二叠统煤系高频层序研究

上二叠统记录了地质历史时期最大规模的生物灭绝事件和最深刻的环境变化。对上二叠统的层序地层格架进行精细 描绘,建立高分辨率的地层序列,是深入了解此次事件及其演化的基础和关键。基于钻测井、岩心观测及地球化学分析测 试结果等资料综合分析,并运用小波分析技术,对黔西盘县上二叠统煤系进行了米氏旋回的识别和划分,结果表明,研究 区上二叠统煤系记录了稳定的米兰科维奇旋回,天文轨道周期对其沉积过程具有明显影响,由长、短偏心率、地轴斜率和 岁差周期引起的地层旋回厚度分别为16.06~17.24 m、5.39~5.70 m、2.11~2.15 m、1.12~1.21 m,长偏心率周期对地层中沉积 旋回的控制和影响最强。对长、短偏心率周期进行滤波分析后,建立了上二叠统煤系“浮动”天文年代标尺,为约束同沉 积火山事件层（Tonstein） 的形成及其持续时限提供了年代学依据。以区域等时对比效果明显的长偏心率旋回为标尺,并结 合旋回沉积序列、旋回界面特征等,将上二叠统煤系划分为4个三级层序,并进一步划分为16个四级层序（对应于中期旋 回）,建立了研究区高频层序地层格架。     

Evaluation of the relative roles of global versus local sedimentary controls on Middle to Late Pleistocene formation of continental margin strata,Canterbury Basin,New Zealand

Determining the relative influence of eustasy versus local sedimentary processes on strata formation is a fundamental challenge in the study of continental margin stratigraphy. In this paper, the relative contribution of these factors on continental margin evolution during the Middle to Late Pleistocene is evaluated using samples from Integrated Ocean Drilling Program Expedition 317. Core‐logging, biostratigraphy and quantitative X‐ray diffraction mineralogy are used to delineate continental shelf sedimentary systems. Major lithological unconformities bound stratigraphic sequences that contain recurring compositional patterns and that resemble other examples of Middle to Upper Pleistocene sequences. However, a preliminary chronology suggests that sequence boundary formation cannot be linked ‘one to one’ with eustatic cycles and therefore these sequences can contain multiple ca 100 ka eustatic cycles. Smaller amplitude, higher frequency transitions in sediment composition are interpreted as stratigraphic sequences driven by more rapid perturbations in the interplay of accommodation and sediment supply; their stratigraphy is variable in time and across the shelf, suggesting a strong influence of local sedimentary forcing in their formation. Changes in sediment composition after the Middle Pleistocene Transition indicate that sediment transfer from onshore sources in the glaciated Southern Alps to the middle‐shelf occurred over a single 100 ka glacio‐eustatic cycle, with an additional 100 ka lag before the mineralogical signal was preserved on the outer‐shelf. This phenomenon is coincident with rapid shelf progradation in this basin, suggesting a causal relation between across‐shelf sediment transport and margin progradation. This is one of very few studies that provide insights at the core scale into the processes driving continental margin evolution during the Middle to Late Pleistocene. This work shows that compositional changes in mud‐dominated successions can lead to a sequence stratigraphic interpretation and the identification of high‐frequency sequences, which may not be possible using a conventional stratigraphic approach.     

扇三角洲高分辨率层序地层对比及砂体分布规律

笔者依据岩心、测井资料,通过岩性、电性对比,对胡状集油田沙三中亚段4～8油层组的扇三角洲相储层进行高分辨率层序地层研究,确立了不同级次旋回界面和旋回类型的识别特征,将研究层段分为1个长期旋回和6个中期旋回。依据中期旋回对砂体沉积的控制作用以及垂直、平行物源方向短期旋回与古地貌的变化关系,确定了短期旋回的对比原则和对比方法,建立了短期旋回对比格架。短期旋回地层在中期基准面旋回的不同时期的砂体分布特征差异明显,是造成储层层间和平面非均质性的主要原因,在细分油气开发层系时应区别对待。     

Relationship between Net Subsidence and Coal Cycle Parameters—A Statistical Appraisal from Subsurface Logs of Damuda Group,Talchir Gondwana Basin,India

Total thickness of strata and coal cycle parameters of the three formations, i.e. Karharbari, Barakar, and Barren Measures of the Damuda Group of the Talchir Gondwana basin were subjected to bivariate and multivariate statistical analyses. Polynomial regression lines were fitted to data sets consisting of total thickness of strata, number of coal cycles, and average thickness of coal cycles of the three formations of the Damuda Group. A significant direct relationship is observed between total thickness (net subsidence) of strata and number of coal cycles, while a significant inverse relationship exists between the number of coal cycles and their average thickness. Principal component and multiple regression analyses suggest that lithological parameters of the coal bearing strata reflect the dynamic of the basin subsidence. The sedimentary distributive mechanism in the form of lateral migration of streams or drainage diversion caused in response to differential subsidence of the depositional surface seem to be appropriate mechanisms for the development of coal cycles and peat swamps in the Talchir basin. Often during Karharbari sedimentation, peat accumulated in abandoned channels was scoured away by high energy migrating channels. On the other hand, Barakar peat swamps developed in a distal part of the flood plain, as a result of which many of the coal seams could be of appreciable thickness. The advent of arid climatic condition retarded the growth of vegetation to a larger extent that prevented profuse development of coal seams during the Barren Measures Formation.     

Palaeocurrent and palaeohydrologic analysis of some vertical profiles through a Cretaceous braided stream deposit, Banks Island, Arctic Canada

A study of directional variability has been carried out on five vertical profiles containing a total of approximately 195 superimposed planar crossbed sets. The latter are interpreted as the deposits of braid bars. Detailed measurements on one set revealed within-set variance of 93. Within river tract, between-bar variance was obtained by calculating a ten-point moving average for each profile, and subtracting the actual azimuth at each point from the moving average value. Variance at this level is 980, which compares closely with data obtained from modern braided streams. Variability in the moving average azimuth is interpreted as the result of meander migration in the entire channel system. Sinuosity can be estimated from this variability, using a geometrical approximation. It ranges from 1.03 to 1.13. Changes in stream competency with time are indicated by vertical changes in directional variance and set thickness. When accompanied by changes in mean azimuth, as in one of the present five profiles, the data suggest successive deposition by two distinct stream systems. A Markov chain analysis of the data sequence indicates a weak memory effect. Short sequences of bar deposits were formed by streams which varied little in orientation, and these are separated from one another by sequences showing random directional fluctuation. The hydrology of the Isachsen rivers was investigated using Schumm's (1968a, b, 1969, 1972) empirical relationships for modern rivers. Owing to inherent uncertainties in these relationships and a wide margin of error in the input data (principally associated with estimates of depth and width of the Isachsen streams), the results have a validity only at the order-of-magnitude level. Individual Isachsen rivers are estimated to have had drainage areas of between 5000 and 30,000 km²; this information is of use in reconstructions of palaeogeography and tectonic history.     

Cyclic sedimentation of the Barren Measures Formation (Damuda Group), Talchir Gondwana basin: Statistical appraisal from borehole logs

The succession of lithofacies of a part of the Barren Measures Formation of the Talchir Gondwana basin has been studied by statistical techniques. The lithologies have been grouped under five facies states viz coarse-, medium-, and fine-grained sandstones, shale and coal for statistical analyses. Markov chain analysis indicates the arrangement of Barren Measures lithofacies in the form of fining upward cycles. A complete cycle consists of conglomerate or coarse-grained sandstone at the base sequentially succeeded by medium-and fine-grained sandstones, shales and coal at the top. The entropy analysis puts the Barren Measures cycles into A-4 type cyclicity, which consists of different proportions of lower, upper and side truncated cycles of lithologic states. Regression analysis indicates a sympathetic relationship between total thickness of strata (net subsidence) and number of cycles and an antipathic relationship between average thickness and number of sedimentary cycles. The cyclic sedimentation of the Barren Measures Formation was controlled by autocyclic process which occurred due to the lateral migration of streams triggered by intrabasinal differential subsidence. In many instances, the clastic sediments from the laterally migrating rivers interrupted the cyclic sedimentation resulting in thinner cycles in areas where the number of cycles are more. Principal component and multivariate regression analyses suggest that the net subsidence of the basin is mostly controlled by the thickness of sandstones, shale beds and coal stringers.     

鄂尔多斯盆地上古生界高分辨率层序地层分析

按基准面旋回原理，将鄂尔多斯盆地上古生界本溪组（C2b)、太原组（P1t）、山西组(P1s)和下石盒子组（P1xs)划分为3个超长期、8个长期、19个中期和62个短期旋回层序：较为详细地介绍了各级别层序的结构类型、叠加样式和沉积演化序列；建立以长期旋回层序为年代地层框架，中期旋回层序为等时地层对比单元的层序的地层格架；并讨论高分辨率层序地层与天然气藏的关系。     

沉积旋回叠置形式的波形分析及旋回层序划分方法

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基于沉积相反演的砂砾岩体沉积期次精细划分与对比

砂砾岩体一般为多期发育、多次沉积的复合体,其内部结构非常复杂,对砂砾岩体沉积期次的精细划分与对比问题,国内外尚无很好的解决先例.本文提出了基于沉积相反演的砂砾岩体沉积期次精细划分方法.文章在岩芯观察和描述的基础上,用岩芯对成像测井资料进行刻度,建立研究区成像测并模式,并精确地识别出鲍马层序、高密度浊流序列和中扇辫状水道...