Shallow lacustrine delta front （SLDF） comprises mainly sheetlike subaqueous distributary channels （SDC） formed in shallow, gentle, and tectonically steady slope （Cai and Zhu, 2011）. SDC proves an important hydro...Shallow lacustrine delta front （SLDF） comprises mainly sheetlike subaqueous distributary channels （SDC） formed in shallow, gentle, and tectonically steady slope （Cai and Zhu, 2011）. SDC proves an important hydrocarbon reservoir type in the Daqing oilfield, Changqing oilfield, and the newly discovered Moxizhuang oilfield in Central Junggar Basin. However, SDC tends to prograde quickly and move laterally frequently,展开更多
The strata of Jurassic was divided into three tectonic sequences and eight se- quences of third rank,according to the developing feature of the tectonic inconformity and the transforming feature of the depositional sy...The strata of Jurassic was divided into three tectonic sequences and eight se- quences of third rank,according to the developing feature of the tectonic inconformity and the transforming feature of the depositional system tracts.Also the identification and the division of the base-level cycle of different period were carried through.Therefore three cycles of super period,eight cycles of long period,twenty-four cycles of middle period and some cycles of short period were identified.From the overall character of the coal-accu- mulation in the Mesozoic,we can see that the Yan'an formation is of the best nature of coal bearing.When the coal bearing systems of Jurassic were depositing,the Ordos area is the coal accumulating basin of terrene of large scale and located in the same tectonic unit.But the local structure of different part and the paleolandform are different in the basin which resulted in the difference of the depositional environment.So the layer number and the distribution of the thickness of the coal beds are different in the different part of the ba- sin.The coal-accumulating action migrated regularly along with the development,evolve- ment and migration of the depositional systems.The layer numbers of the coal beds, which can be mined,are more in the north and west fringe of the basin,whose distributing area is extensive,and they are more steady in the landscape orientation,also the total thickness is great.Therefore the nature of coal bearing and the coal-accumulating action of different part changed obviously in the space in Ordos area.展开更多
The recognition and contrast of bed sets in parasequence is difficult in terrestrial basin high-resolution sequence stratigraphy. This study puts forward new methods for the boundary identification and contrast of bed...The recognition and contrast of bed sets in parasequence is difficult in terrestrial basin high-resolution sequence stratigraphy. This study puts forward new methods for the boundary identification and contrast of bed sets on the basis of manifold logging data. The formation of calcareous interbeds, shale resistivity differences and the relation of reservoir resistivity to altitude are considered on the basis of log curve morphological characteristics, core observation, cast thin section, X-ray diffraction and scanning electron microscopy. The results show that the thickness of calcareous interbeds is between 0.5 m and 2 m, increasing on weathering crusts and faults. Calcareous interbeds occur at the bottom of a distributary channel and the top of a distributary mouth bar. Lower resistivity shale （4-5 Ω · m） and higher resistivity shale （〉 10Ω·m） reflect differences in sediment fountain or sediment microfacies. Reservoir resistivity increases with altitude. Calcareous interbeds may be a symbol of recognition for the boundary of bed sets and isochronous contrast bed sets, and shale resistivity differences may confirm the stack relation and connectivity of bed sets. Based on this, a high-resolution chronostratigraphic frame- work of Xi-1 segment in Shinan area, Junggar basin is presented, and the connectivity of bed sets and oil-water contact is confirmed. In this chronostratigraphic framework, the growth order, stack mode and space shape of bed sets are qualitatively and quantitatively described.展开更多
This comprehensive study establishes a novel high-resolution sequence stratigraphic framework for a shallow,warm,land-tied carbonate-rimmed shelf represented by the Ponta do Mel Formation.Integration of cores and cutt...This comprehensive study establishes a novel high-resolution sequence stratigraphic framework for a shallow,warm,land-tied carbonate-rimmed shelf represented by the Ponta do Mel Formation.Integration of cores and cuttings with seismic and well-log data provides the detailed subsurface stratigraphic framework encompassing two fourth-order genetic sequences.The high-resolution approach unveiled the step-by-step depositional and diagenetic evolution of the Ponta do Mel Formation at the fourth-order systems tracts scale and established the reservoir zonation.In each zone,the lateral contact between high-energy outer shelf and shelf rim potential reservoirs and low-energy inner shelf deposits constitutes critical reservoir heterogeneities that may affect production planning and development projects.Moreover,the reservoir scale enabled discussion on the controls on deposition,high-resolution sequence architecture,diagenesis,and insight into the zonation and characterisation of similar oil and gas reservoirs worldwide.展开更多
The phase change of lacustrine gravity flow deposition is fast and complex. In its reservoir division and correlation, the isochronous problem is very important. Taking the oil formation I of Es3 in Wuhaozhuang oilfie...The phase change of lacustrine gravity flow deposition is fast and complex. In its reservoir division and correlation, the isochronous problem is very important. Taking the oil formation I of Es3 in Wuhaozhuang oilfield as an example, through the analysis of stratigraphic drilling and logging data in the study area, according to the genetic types of different levels of base level cycle interfaces and the characteristics of high-resolution sequence stratigraphy, this paper subdivides the lacustrine gravity flow oil layer of lower Es3 in Wuhaozhuang Oilfield, divides it into four short-term base level cycle sequences, and establishes the high-resolution isochronous stratigraphic framework of this interval. It is found that the mid-term, short-term and ultra short-term base level cycles correspond to the oil formation, sand layer group and single layer in the oil layer correlation unit of the oilfield respectively. Based on this, the oil layer correlation unit of the interval is divided, and the sublayer correlation model is established according to the identification characteristics of the short-term base level cycle.展开更多
The sedimentary characteristics and their combination succession of the Permian in the Shandong nd Huainan-Huaibei coalfields are analyzed. The mid-and short-term stratigraphic base-level cycles are identified. High-r...The sedimentary characteristics and their combination succession of the Permian in the Shandong nd Huainan-Huaibei coalfields are analyzed. The mid-and short-term stratigraphic base-level cycles are identified. High-resolution sequences are divided based on the above results. The study shows that the stratigraphic base-level cyclic method is an efficient way in the determination of the high-resolution sequences, especially in the classification of tbe terrestrial and transitional depositional succession.展开更多
The study of sequence stratigraphy often focuses on shallow marine and shelf-edge regions,while research on deep-sea stratigraphic sequences remains relatively weak.This study,based on highresolution 3D seismic data a...The study of sequence stratigraphy often focuses on shallow marine and shelf-edge regions,while research on deep-sea stratigraphic sequences remains relatively weak.This study,based on highresolution 3D seismic data and drilling information,utilized sequence stratigraphy and seismic sedimentology as guidelines,and employed seismic interpretation methods to performed a division of deepsea stratigraphic sequences within the Romney 3D seismic survey area in the deep-water Taranaki Basin,New Zealand.Furthermore,it analyzed the characteristics of typical depositional systems and their associated controlling factors.The findings are as follows:(1)Based on seismic reflection termination relationships and seismic facies characteristics,four second-order sequence boundaries and nine thirdorder sequence boundaries were identified,resulting in the delineation of three second-order sequences and twelve third-order sequences in the basin.(2)Five seismic facies were recognized,corresponding to five typical sedimentary bodies:mass transport deposits(MTDs),deep-water channel,levee deposits,deltaic deposits,and pelagic deposits.However,due to the relatively thin sedimentary thickness of carbonate sediments,the seismic facies characteristics of carbonate sediments cannot be discerned in seismic data,but can be identified based on well data.Deltaic sediments mainly developed during the rift stage of the basin,while carbonate sediments formed during the transition from a passive to an active margin.Deep-water channel and levee deposits and MTDs emerged during the active margin stage,while pelagic deposits are ubiquitous in marine environments.(3)The uplift of New Zealand's interior and climate-driven erosion caused the resurgence of clastic sediments,which began to be transported to the deep sea,the seafloor topography would directly affect the movement path of sediment gravity flow,and sediment supply can affect the development and evolution of sedimentary systems.(4)Event deposits boundaries,such as erosional scour surfaces formed by channels and unconformities created by MTDs,can serve as boundaries for the division of deep-water stratigraphic sequences.This study proposes a method for delineating deep-water stratigraphic sequences using event deposits,particularly suitable under conditions where the influence of relative sea-level changes on deep-water deposits is relatively weak.This research not only enhances the understanding of deep-water depositional sequences but also provides a reference for studies on the evolution of deep-water deposition and its controlling factors in research areas with similar geological backgrounds worldwide.展开更多
Performing the high-resolution stratigraphic analysis may be challenging and time-consuming if one has to work with large datasets.Moreover,sedimentary records have signals of different frequencies and intrinsic noise...Performing the high-resolution stratigraphic analysis may be challenging and time-consuming if one has to work with large datasets.Moreover,sedimentary records have signals of different frequencies and intrinsic noise,resulting in a complex signature that is difficult to identify only through eyes-based analysis.This work proposes identifying transgressive-regressive(T-R)sequences from carbonate facies successions of three South American basins:(i)São Francisco Basin-Brazil,(ii)Santos Basin-Brazil,and(iii)Salta Basin-Argentina.We applied a hidden Markov model in an unsupervised approach followed by a Score-Based Recommender System that automatically finds medium or low-frequency sedimentary cycles from high-frequency ones.Our method is applied to facies identified using Fullbore Formation Microimager(FMI)logs,outcrop description,and composite logs from carbonate intervals.The automatic recommendation results showed better long-distance correlations between medium-to low-frequency sedimentary cycles,whereas the hidden Markov model method successfully identified high-resolution(high-frequency)transgressive and regressive systems tracts from the given facies successions.Our workflow offers advances in the automated analyses and construction of to lower-higher-rank stratigraphic framework and short to long-distance stratigraphic correlation,allowing for scale large-automated processing of the basin dataset.Our approach in this work fits the unsupervised learning framework,as we require no previous input of stratigraphical analysis in the basin.The results provide solutions for prospecting any sediment-hosted mineral resource,especially for the oil and gas industry,offering support for subsurface geological characterization,whether at the exploration scale or for reservoir zoning during production development.展开更多
Silicalites are extensively developed in the Liujiang Formation(Fm.)of the Frasnian in the Dianqiangui Basin and are often associated with carbonaceous shales.This stratigraphic combination represents a special sequen...Silicalites are extensively developed in the Liujiang Formation(Fm.)of the Frasnian in the Dianqiangui Basin and are often associated with carbonaceous shales.This stratigraphic combination represents a special sequence stratigraphy formed in special deep-water environments,which not only gives the shales unusual spatio-temporal distribution features,but also induces the shales in the Liujiang Fm.to frequently be rich in organic matter(OM).This study summarises the special deep-water sedimentary succession of the Liujiang Fm.,which is mainly distributed around synsedimentary faults,as well as establishing the sequence stratigraphic frameworks of the Liujiang Fm.in the west-east and southwest-northeast directions.Under the sequence stratigraphic frameworks,the spatio-temporal distribution features of the organic-rich shales of the Liujiang Fm.and the regional variations of the Liujiang Fm.were investigated.In addition,the rock components and OM occurrence states of the organic-rich shales were also observed and described in detail under the microscope.The results show that the organic-rich shales were formed temporally primarily during the third-order sea-level falling stage,developed spatially mainly on the east and west sides of the study area,as well as that the OM accumulation is closely related to tentaculitoids and seems to be influenced by a'biological pump'.展开更多
In view of the high accuracy and predictability, high-resolution sequence stratigraphy had been extensively applied to oil exploration and gotten prominent practicable results. This article takes the first layer, uppe...In view of the high accuracy and predictability, high-resolution sequence stratigraphy had been extensively applied to oil exploration and gotten prominent practicable results. This article takes the first layer, upper second submember, Shahejie （沙河街） Formation from Pucheng （濮城） oilfield as an example to analyze the application of high-resolution sequence stratigraphy in reservoir study on the basis of a comprehensive study of core log data. Firstly, facies analysis of this area reveals the corresponding terminal fan system occurring where sediment-laden streams decrease in size and vanish as a result of evaporation and transmission losses. The model includes a tripartite zonation of terminal fan into feeder, distributary, and basinal zones. Secondly, electrofacies were made by well-log analysis and then matched with sedimentary facies defined by core analysis. Four electrofacies characterizing the main sedimentary facies association and depositional environments within target area are defined （channel, lag deposit, lake or flood-plain, and overflow deposits）. Thirdly, related correlations based on high-resolution sequence stratigraphy were established. By observing the stacking arrangement of genetic sequences, different scales of stratigraphic cycle can be identified. Within scale and duration, the stratigraphic cycles are termed as genetic sequences, genetic sequence sets, and minor cycles.展开更多
Three third-order sequences and about one hundred high-frequency cycles or Milankovitchcycles within the Late Permian Changxingian to Early Triassic Griesbachian are identified in theMeishan Section of Changxing, Zhej...Three third-order sequences and about one hundred high-frequency cycles or Milankovitchcycles within the Late Permian Changxingian to Early Triassic Griesbachian are identified in theMeishan Section of Changxing, Zhejiang Province, southern China, the candidate stratotype sec-tion of the global Permo-Triassic boundary, based on a detailed study of the biological,ecological and high-resolution allochthonous cyclic events, microfacies and depositional systems.Furthermore, the stacking pattern of the depositional systems across various Changxingian andGriesbachian sedimentary facies of the Lower Yangtze and the sequence stratigraphic frameworkare outlined with the Meishan section as the principal section. In this paper the habitat types offossil biota are applied to semiquantitative palaeobathymetry and the study of relative sea levelchanges.展开更多
The Lower Permian Shanxi （山西） Formation is one of the main gas-bearing stratio graphic units in northeastern Ordos （鄂尔多斯） Basin, China. Based on an integrated investigation of well logs, cores, and outcrop, ...The Lower Permian Shanxi （山西） Formation is one of the main gas-bearing stratio graphic units in northeastern Ordos （鄂尔多斯） Basin, China. Based on an integrated investigation of well logs, cores, and outcrop, we delineated the sedimentary facies of the lower member of the Shanxi Formation and divided the succession into three third-order sequences from base to top as SQ1, SQ2, and SQ3. The lower region of Shanxi Formation was deposited in the following sedimentary facies or subfacies： subaqueous braided channel, subaqueous interdistributary, mouth bar, swamp and shelf in the Daniudi （~z~=J~） Gas Field and braided channel, and shelf and lake at Heidaigon （~J） outcrop. Braided-river deposits form the lowstand systems tract （LST） in each sequence. Braided channels mark the sequence boundaries at Heidaigou outcrop. A shelf and lake depositional environment with dark gray mudstone forms the transgressive systems tract （TST）. The location where dark gray mudstone first appears above the braided channel marks the first flooding surface （FFS）, and the end of that marks the maximum flooding surface （MFS）. The highstand systems tract （HST） deposits are fine-grained sediments with an aggradational parasequence at Heidaigou outcrop and swamp coalbed in the Daniudi Gas Field. Mouth-bar sand bodies in braided delta front, which form the LST in each sequence, form excellent reservoirs in the Daniudi Gas Field.展开更多
The Lower Cretaceous strata in the Kuqa Basin in Xinjiang are marked by a set of arid red beds. Several types of sedimentary fades can be identified in this set of arid red beds: mudstones of the plaza and intracontin...The Lower Cretaceous strata in the Kuqa Basin in Xinjiang are marked by a set of arid red beds. Several types of sedimentary fades can be identified in this set of arid red beds: mudstones of the plaza and intracontinental sebkha, aeolian sandstones, sandy conglomerates of the intermittent river, conglomerates of the pluvial fan, etc. These types of sedimentary facies constitute a typical desert system. Therefore, the Cretaceous strata in the Kuqa Basin provide a favorable condition for studies of sequence stratigraphic divisions of the desert system. With the rise and fall of the base level of the sedimentary basin, cyclicity is clearly revealed in stratigraphic records, which helps the identification of the third-order sequences. Based on the cyclicity in stratigraphic records, 5 third-order sequences can be found in the strata of the Early Cretaceous in the Kuqa Basin. These sequences comprise a second-order tectonic sequence. The primary feature of these third-order sequences is of an upward-fining sedimentary succession formed by a succession of 'coarse sediments of the alluvial system-fine sediments of the lake system'. The result of this study shows that aeolian sandstones are the best reservoirs of natural gas in the Cretaceous strata in the Kuqa Basin, and that the Kela-2 gas field is the first large gas field dominated by aeolian sandstone reservoirs in China.展开更多
In South China four depositional sequences are recognized in the upper part of Upper Devonian and Tournaisian. They are named SQ0 SQ1, SQ2 and SQ3 in ascending order. SQ0 is Strunian (uppermost Devonian), and the othe...In South China four depositional sequences are recognized in the upper part of Upper Devonian and Tournaisian. They are named SQ0 SQ1, SQ2 and SQ3 in ascending order. SQ0 is Strunian (uppermost Devonian), and the other three Tournaisian in age. These four depositional sequences appear to correlate fairly well with the four sequence recognized in Europe, North America and other areas. This may suggest that these sequences are synchronous depos- its resulted from the eustatic changes. The present study on sequence stratigraphy, biostratigraphy and event stratigraphy indicates that in neritic facies areas of South China, the Devonian-Carboniferous boundary, matching the boundary between Siphonodella praesulcata zone and S. sulcata zone in pelagic facies areas, is not only higher than the top of the Cystophrentis zone, but also higher than the top of the Devonian-Carboniferous boundary event bed. In neritic facies areas, the Devonian-Carbonifrerous boundary is marked by the most distinct transgressive surface within the Cystophrentiseudouralina interval zone, i. e. at the base of the TST of the SQ1. This boundary coincides with the top surface of the event bed resulted from the eustatic fall, and approximately corresponds to the basal part of Rseudouralina assemblage zone.展开更多
Sequence stratigraphical analysis was applied to the Upper Carboniferous-Lower Permian sedimentary succession of the northeastern Ordos Basin, north China based on data acquired from ten entire logging curves and eigh...Sequence stratigraphical analysis was applied to the Upper Carboniferous-Lower Permian sedimentary succession of the northeastern Ordos Basin, north China based on data acquired from ten entire logging curves and eight outcrops. The facies framework of the lithostratigraphical unit, the Taiyuan Formation comprises seven facies in two facies associations, varying from fluvio-delta to shelf-barrier islands. The facies are presented within a chronostratigraphical framework, linked by systems tract, which in turn are limited by flooding surfaces and sequence boundaries. Six third-order depositional sequences are recognised, bounded by six type 2 unconformities. An upwards-shallowing epicontinental sea sedimentary model is created, which consists of a sandstone, coal seam and carbonate succession.展开更多
Depositional sequences may be distinguished into six ranks of units as giga-, mega-, meso-, ortho-, sub- and micro-sequence, and are interpreted to be formed during the eustatic cycles with time-intervals of 500-6000 ...Depositional sequences may be distinguished into six ranks of units as giga-, mega-, meso-, ortho-, sub- and micro-sequence, and are interpreted to be formed during the eustatic cycles with time-intervals of 500-6000 Ma, 60-120 Ma, 30-40 Ma, 2-5 Ma, 0.1-0.4 Ma and 0.02-0.04 Ma respectively. All of them are thought to be essentially related to cosmological cycles, except the megasequence which may be caused by the long-term geothermal cycles on cratons. We deem that the depositional sequences, though often influenced variably by local tectonics and other factors, are primarily global and periodic in nature. We also hold that as one of the planets within the Galaxy, the earth must have been affected in various ways by other asteroids, and that the depositional sequences are merely the responses of the hydrosphere to the cosmological cycles in sedimentation.展开更多
The Qom Formation comprises Oligo-Miocene deposits from a marine succession distributed in the Central Basin of Iran. It is composed of five members designated as A-F. Little previous work exists on the sequence strat...The Qom Formation comprises Oligo-Miocene deposits from a marine succession distributed in the Central Basin of Iran. It is composed of five members designated as A-F. Little previous work exists on the sequence stratigraphy. Based on an integrated study of sequence stratigraphy with outcrop data, wells and regional seismic profiles, the Qom Formation is interpreted as a carbonate succession deposited in a mid.Tertiary back-arc basin. There are two second-order sequences （designated as SS1 and SS2） and five third-order sequences （designated as S1-S5）. Five distinct systems tracts including transgressive, highstand, forced regressive, slope margin and Iowstand have been recognized. The relationship between the sequences and lithologic sub-units has been collated and defined （S1 to S5 individually corresponding to A-C1, C2--C4, D-E, the lower and upper portions of F）; a relative sea level change curve and the sequence stratigraphic framework have been established and described in detail. The coincidence of relative sea level change between that of the determined back-arc basin and the world indicates that the sedimentary cycles of the Qom Formation are mainly controlled by eustatic cycles. The variable combination of the systems tracts and special tectonic-depositional setting causally underpin multiple sequence stratigraphic framework styles seen in the carbonates of the back-arc basin revealing： （1） a continental margin basin that developed some form of barrier, characterized by the development of multiple cycles of carbonate-evaporites; （2） a flat carbonate ramp, which occurred on the southern shelf formed by the lack of clastic supply from nearby magmatic islands plus mixed siliciclastics and carbonates that occurred on the northern shelf due to a sufficient clastics supply from the land; and （3） a forced regressive stratigraphic stacking pattern that occured on the southern shelf and in basin lows due to the uplifting of the southern shelf. Thick and widespread aggradational framework limestone usually occurs in the initial sequences （S1 and S3） of the supersequence, which led to preferential oil reservoir deposition but a lack of source and cap rocks, whereas the retrogradational and progradational framework limestone usually occurs in the later sequences （S2 and S4-S5） of the supersequence, which results in two perfect sets of source, reservoir and cap rock assemblies, so that the limestone in sub-member C2-C4 and the F-Member can be predicted as important objects for oil exploration.展开更多
Both the macroscopic feature and the sequence-stratigraphic position of the molar-tooth structure developed in the third member of the Gaoyuzhuang （高于庄） Formation at the Jixian （蓟县） Section in Tianjin （天津...Both the macroscopic feature and the sequence-stratigraphic position of the molar-tooth structure developed in the third member of the Gaoyuzhuang （高于庄） Formation at the Jixian （蓟县） Section in Tianjin （天津） can provide some useful information about its origin and can reveal some problems to be further researched in the future. The Mesoproterozoic Gaoyuzhuang Formation is a set of 1 600 m thick carbonate strata. This formation can be divided into four members. The first member is mainly made up of stromatolitic dolomites; the second is marked by a set of manganese dolomites; the third is mainly composed of lamina limestones with the development of molar-tooth strcutures; the fourth is a set of stromatolitic-lithoherm dolomites. According to lithofacies and its succession, several types of meter-scale cycles can be discerned in the Gaoyuzhuang Formation： the L-M type, the subtidal type and the peritidal type. There is a regularly vertical stacking pattern for meter-scale cycles in the third-order sequence. Therefore, the Mesoproterozoic Gaoyuzhuang Formation can be divided into 13 third-order sequences （SQ1 to SQ13 ） and can further be grouped into 4 second-order sequences. The third member is marked by lamina limestones and can be grouped into three third-order sequences （SQ9 to SQ11 ）. The molar-tooth structure is developed in the middle part of the third sequence, i.e. SQH , in the third member. Several features of this kind of molar-tooth structure reflect some features of carbonate sedimentation in the Precambrian, such as the particular configuration, abundant organic matter, and easy silication. Stromatolites are chiefly formed in a shallow tidal-flat environment; lamina are mainly formed in the shallow ramp and molar-tooth structures are mainly generated in a relatively more deep-water environment from the middle to the deep ramp. Therefore, similar to stromatolite and lamina, the molartooth structure might also be a kind of bio-sedimentation structure. This suggestion is based on macroscopic observation and the sedimentary-facies analysis of the molar-tooth structures from the sequencestratigraphic position. These features of Precambrian sedimentation also reveal the problem of Precambrian carbonate sedimentation. With more detailed study, a more practical solution for these problems may be obtained in the future.展开更多
The Upper Proterozoic glacigenous rocks in the southeastern margin of the Yangtze platform were accumulated in a glacially influenced marine environment with extension set- ting. Two type I depositional sequences have...The Upper Proterozoic glacigenous rocks in the southeastern margin of the Yangtze platform were accumulated in a glacially influenced marine environment with extension set- ting. Two type I depositional sequences have been identified in the glacioclastic sediments the their boundaries enhanced by both tectonism and the incision of glaciation. The lower sequence (SQ1), comprising Changan and Fulu formations (Guangxi Province), Jiangkou and Xiangmen formations(Hunan Province) and their equivalents, is bounded by erosional unconformities both at the base and on the top. The upper sequence (SQ2), composed mainly of Nantuo Formation and its equivalents, is confined by an erosional unconformity at the base and covered by an exposure surface of karstification on the top. The depositional systems tracts are difficult to be distinguished directly and mainly characterized by the variation in glacioclastic supplies. Two types of episodic parasequeuces can be identified in the glacigenous rocks and are related to the evolution of depositional systems tracts. Both the sequences and parasequences are caused by autocyclic mechanism. The present research shows that the Upper Proterozoic glacigenous deposits are of significance for the analysis of the tectonic evolution of the Late Precambrian basin in South China.展开更多
There are 9 major coal-accumulating periods during geological history in China,including the Early Carboniferous,Late Carboniferous-Early Permian,Middle Permian,Late Permian,Late Triassic,Early-Middle Jurassic,Early C...There are 9 major coal-accumulating periods during geological history in China,including the Early Carboniferous,Late Carboniferous-Early Permian,Middle Permian,Late Permian,Late Triassic,Early-Middle Jurassic,Early Cretaceous,Paleogene and Neogene.The coal formed in these periods were developed in different coal-accumulating areas(CAA)including the North China,South China,Northwest China,Northeast China,the Qinghai–Tibet area,and China offshore area.In this paper,we investigated depositional environments,sequence stratigraphy,lithofacies paleogeography and coal accumulation pattern of five major coal-accumulating periods including the Late Carboniferous to Middle Permian of the North China CAA,the Late Permian of the South China CAA,the Late Triassic of the South China CAA,the Early-Middle Jurassic of the North and Northwest China CAA,and the Early Cretaceous in the Northeast China CAA.According to distribution of the coal-bearing strata and the regional tectonic outlines,we have identified distribution range of the coal-forming basins,sedimentary facies types and coal-accumulating models.The sequence stratigraphic frameworks of the major coal-accumulating periods were established based on recognition of a variety of sequence boundaries.The distribution of thick coals and migration patterns of the coal-accumulating centers in the sequence stratigraphic framework were analyzed.The lithofacies paleogeography maps based on third-order sequences were reconstructed and the distribution of coal accumulation centers and coal-rich belts were predicted.展开更多
基金financially supported by National Natural Science Foundation of China(Grant No.41272159 and 41372123)
文摘Shallow lacustrine delta front （SLDF） comprises mainly sheetlike subaqueous distributary channels （SDC） formed in shallow, gentle, and tectonically steady slope （Cai and Zhu, 2011）. SDC proves an important hydrocarbon reservoir type in the Daqing oilfield, Changqing oilfield, and the newly discovered Moxizhuang oilfield in Central Junggar Basin. However, SDC tends to prograde quickly and move laterally frequently,
基金National Basis Research Program of China(2003CB214608)
文摘The strata of Jurassic was divided into three tectonic sequences and eight se- quences of third rank,according to the developing feature of the tectonic inconformity and the transforming feature of the depositional system tracts.Also the identification and the division of the base-level cycle of different period were carried through.Therefore three cycles of super period,eight cycles of long period,twenty-four cycles of middle period and some cycles of short period were identified.From the overall character of the coal-accu- mulation in the Mesozoic,we can see that the Yan'an formation is of the best nature of coal bearing.When the coal bearing systems of Jurassic were depositing,the Ordos area is the coal accumulating basin of terrene of large scale and located in the same tectonic unit.But the local structure of different part and the paleolandform are different in the basin which resulted in the difference of the depositional environment.So the layer number and the distribution of the thickness of the coal beds are different in the different part of the ba- sin.The coal-accumulating action migrated regularly along with the development,evolve- ment and migration of the depositional systems.The layer numbers of the coal beds, which can be mined,are more in the north and west fringe of the basin,whose distributing area is extensive,and they are more steady in the landscape orientation,also the total thickness is great.Therefore the nature of coal bearing and the coal-accumulating action of different part changed obviously in the space in Ordos area.
基金This paper is supported by the Main Project of the National Tenth Five-Year Plan .
文摘The recognition and contrast of bed sets in parasequence is difficult in terrestrial basin high-resolution sequence stratigraphy. This study puts forward new methods for the boundary identification and contrast of bed sets on the basis of manifold logging data. The formation of calcareous interbeds, shale resistivity differences and the relation of reservoir resistivity to altitude are considered on the basis of log curve morphological characteristics, core observation, cast thin section, X-ray diffraction and scanning electron microscopy. The results show that the thickness of calcareous interbeds is between 0.5 m and 2 m, increasing on weathering crusts and faults. Calcareous interbeds occur at the bottom of a distributary channel and the top of a distributary mouth bar. Lower resistivity shale （4-5 Ω · m） and higher resistivity shale （〉 10Ω·m） reflect differences in sediment fountain or sediment microfacies. Reservoir resistivity increases with altitude. Calcareous interbeds may be a symbol of recognition for the boundary of bed sets and isochronous contrast bed sets, and shale resistivity differences may confirm the stack relation and connectivity of bed sets. Based on this, a high-resolution chronostratigraphic frame- work of Xi-1 segment in Shinan area, Junggar basin is presented, and the connectivity of bed sets and oil-water contact is confirmed. In this chronostratigraphic framework, the growth order, stack mode and space shape of bed sets are qualitatively and quantitatively described.
基金support from Petrobras and the Programa de Pos-Graduacao em Geologia e Geofisica da Universidade Federal do Rio Grande do NorteWe are grateful to Gustavo Barros for his drafting skills.
文摘This comprehensive study establishes a novel high-resolution sequence stratigraphic framework for a shallow,warm,land-tied carbonate-rimmed shelf represented by the Ponta do Mel Formation.Integration of cores and cuttings with seismic and well-log data provides the detailed subsurface stratigraphic framework encompassing two fourth-order genetic sequences.The high-resolution approach unveiled the step-by-step depositional and diagenetic evolution of the Ponta do Mel Formation at the fourth-order systems tracts scale and established the reservoir zonation.In each zone,the lateral contact between high-energy outer shelf and shelf rim potential reservoirs and low-energy inner shelf deposits constitutes critical reservoir heterogeneities that may affect production planning and development projects.Moreover,the reservoir scale enabled discussion on the controls on deposition,high-resolution sequence architecture,diagenesis,and insight into the zonation and characterisation of similar oil and gas reservoirs worldwide.
文摘The phase change of lacustrine gravity flow deposition is fast and complex. In its reservoir division and correlation, the isochronous problem is very important. Taking the oil formation I of Es3 in Wuhaozhuang oilfield as an example, through the analysis of stratigraphic drilling and logging data in the study area, according to the genetic types of different levels of base level cycle interfaces and the characteristics of high-resolution sequence stratigraphy, this paper subdivides the lacustrine gravity flow oil layer of lower Es3 in Wuhaozhuang Oilfield, divides it into four short-term base level cycle sequences, and establishes the high-resolution isochronous stratigraphic framework of this interval. It is found that the mid-term, short-term and ultra short-term base level cycles correspond to the oil formation, sand layer group and single layer in the oil layer correlation unit of the oilfield respectively. Based on this, the oil layer correlation unit of the interval is divided, and the sublayer correlation model is established according to the identification characteristics of the short-term base level cycle.
文摘The sedimentary characteristics and their combination succession of the Permian in the Shandong nd Huainan-Huaibei coalfields are analyzed. The mid-and short-term stratigraphic base-level cycles are identified. High-resolution sequences are divided based on the above results. The study shows that the stratigraphic base-level cyclic method is an efficient way in the determination of the high-resolution sequences, especially in the classification of tbe terrestrial and transitional depositional succession.
基金the National Natural Science Foundation of China(Grant Nos.42077410 and 41872112).We acknowledge the insights and efforts of journal editor(Jie Hao)and three anonymous reviewers that improved the quality of the manuscript.
文摘The study of sequence stratigraphy often focuses on shallow marine and shelf-edge regions,while research on deep-sea stratigraphic sequences remains relatively weak.This study,based on highresolution 3D seismic data and drilling information,utilized sequence stratigraphy and seismic sedimentology as guidelines,and employed seismic interpretation methods to performed a division of deepsea stratigraphic sequences within the Romney 3D seismic survey area in the deep-water Taranaki Basin,New Zealand.Furthermore,it analyzed the characteristics of typical depositional systems and their associated controlling factors.The findings are as follows:(1)Based on seismic reflection termination relationships and seismic facies characteristics,four second-order sequence boundaries and nine thirdorder sequence boundaries were identified,resulting in the delineation of three second-order sequences and twelve third-order sequences in the basin.(2)Five seismic facies were recognized,corresponding to five typical sedimentary bodies:mass transport deposits(MTDs),deep-water channel,levee deposits,deltaic deposits,and pelagic deposits.However,due to the relatively thin sedimentary thickness of carbonate sediments,the seismic facies characteristics of carbonate sediments cannot be discerned in seismic data,but can be identified based on well data.Deltaic sediments mainly developed during the rift stage of the basin,while carbonate sediments formed during the transition from a passive to an active margin.Deep-water channel and levee deposits and MTDs emerged during the active margin stage,while pelagic deposits are ubiquitous in marine environments.(3)The uplift of New Zealand's interior and climate-driven erosion caused the resurgence of clastic sediments,which began to be transported to the deep sea,the seafloor topography would directly affect the movement path of sediment gravity flow,and sediment supply can affect the development and evolution of sedimentary systems.(4)Event deposits boundaries,such as erosional scour surfaces formed by channels and unconformities created by MTDs,can serve as boundaries for the division of deep-water stratigraphic sequences.This study proposes a method for delineating deep-water stratigraphic sequences using event deposits,particularly suitable under conditions where the influence of relative sea-level changes on deep-water deposits is relatively weak.This research not only enhances the understanding of deep-water depositional sequences but also provides a reference for studies on the evolution of deep-water deposition and its controlling factors in research areas with similar geological backgrounds worldwide.
文摘Performing the high-resolution stratigraphic analysis may be challenging and time-consuming if one has to work with large datasets.Moreover,sedimentary records have signals of different frequencies and intrinsic noise,resulting in a complex signature that is difficult to identify only through eyes-based analysis.This work proposes identifying transgressive-regressive(T-R)sequences from carbonate facies successions of three South American basins:(i)São Francisco Basin-Brazil,(ii)Santos Basin-Brazil,and(iii)Salta Basin-Argentina.We applied a hidden Markov model in an unsupervised approach followed by a Score-Based Recommender System that automatically finds medium or low-frequency sedimentary cycles from high-frequency ones.Our method is applied to facies identified using Fullbore Formation Microimager(FMI)logs,outcrop description,and composite logs from carbonate intervals.The automatic recommendation results showed better long-distance correlations between medium-to low-frequency sedimentary cycles,whereas the hidden Markov model method successfully identified high-resolution(high-frequency)transgressive and regressive systems tracts from the given facies successions.Our workflow offers advances in the automated analyses and construction of to lower-higher-rank stratigraphic framework and short to long-distance stratigraphic correlation,allowing for scale large-automated processing of the basin dataset.Our approach in this work fits the unsupervised learning framework,as we require no previous input of stratigraphical analysis in the basin.The results provide solutions for prospecting any sediment-hosted mineral resource,especially for the oil and gas industry,offering support for subsurface geological characterization,whether at the exploration scale or for reservoir zoning during production development.
基金financially supported by the Key R&D Program of Guangxi Zhuang Autonomous Region(2021AB30011)。
文摘Silicalites are extensively developed in the Liujiang Formation(Fm.)of the Frasnian in the Dianqiangui Basin and are often associated with carbonaceous shales.This stratigraphic combination represents a special sequence stratigraphy formed in special deep-water environments,which not only gives the shales unusual spatio-temporal distribution features,but also induces the shales in the Liujiang Fm.to frequently be rich in organic matter(OM).This study summarises the special deep-water sedimentary succession of the Liujiang Fm.,which is mainly distributed around synsedimentary faults,as well as establishing the sequence stratigraphic frameworks of the Liujiang Fm.in the west-east and southwest-northeast directions.Under the sequence stratigraphic frameworks,the spatio-temporal distribution features of the organic-rich shales of the Liujiang Fm.and the regional variations of the Liujiang Fm.were investigated.In addition,the rock components and OM occurrence states of the organic-rich shales were also observed and described in detail under the microscope.The results show that the organic-rich shales were formed temporally primarily during the third-order sea-level falling stage,developed spatially mainly on the east and west sides of the study area,as well as that the OM accumulation is closely related to tentaculitoids and seems to be influenced by a'biological pump'.
基金supported by the National Key Technology R&D Program (No. 2006BAC18B05)
文摘In view of the high accuracy and predictability, high-resolution sequence stratigraphy had been extensively applied to oil exploration and gotten prominent practicable results. This article takes the first layer, upper second submember, Shahejie （沙河街） Formation from Pucheng （濮城） oilfield as an example to analyze the application of high-resolution sequence stratigraphy in reservoir study on the basis of a comprehensive study of core log data. Firstly, facies analysis of this area reveals the corresponding terminal fan system occurring where sediment-laden streams decrease in size and vanish as a result of evaporation and transmission losses. The model includes a tripartite zonation of terminal fan into feeder, distributary, and basinal zones. Secondly, electrofacies were made by well-log analysis and then matched with sedimentary facies defined by core analysis. Four electrofacies characterizing the main sedimentary facies association and depositional environments within target area are defined （channel, lag deposit, lake or flood-plain, and overflow deposits）. Thirdly, related correlations based on high-resolution sequence stratigraphy were established. By observing the stacking arrangement of genetic sequences, different scales of stratigraphic cycle can be identified. Within scale and duration, the stratigraphic cycles are termed as genetic sequences, genetic sequence sets, and minor cycles.
文摘Three third-order sequences and about one hundred high-frequency cycles or Milankovitchcycles within the Late Permian Changxingian to Early Triassic Griesbachian are identified in theMeishan Section of Changxing, Zhejiang Province, southern China, the candidate stratotype sec-tion of the global Permo-Triassic boundary, based on a detailed study of the biological,ecological and high-resolution allochthonous cyclic events, microfacies and depositional systems.Furthermore, the stacking pattern of the depositional systems across various Changxingian andGriesbachian sedimentary facies of the Lower Yangtze and the sequence stratigraphic frameworkare outlined with the Meishan section as the principal section. In this paper the habitat types offossil biota are applied to semiquantitative palaeobathymetry and the study of relative sea levelchanges.
基金supported by the China National Key Research Project(No.2011ZX05009-002)the MOE Yangtze River Scholar and Innovative Team Program of China(No.IRT0864)
文摘The Lower Permian Shanxi （山西） Formation is one of the main gas-bearing stratio graphic units in northeastern Ordos （鄂尔多斯） Basin, China. Based on an integrated investigation of well logs, cores, and outcrop, we delineated the sedimentary facies of the lower member of the Shanxi Formation and divided the succession into three third-order sequences from base to top as SQ1, SQ2, and SQ3. The lower region of Shanxi Formation was deposited in the following sedimentary facies or subfacies： subaqueous braided channel, subaqueous interdistributary, mouth bar, swamp and shelf in the Daniudi （~z~=J~） Gas Field and braided channel, and shelf and lake at Heidaigon （~J） outcrop. Braided-river deposits form the lowstand systems tract （LST） in each sequence. Braided channels mark the sequence boundaries at Heidaigou outcrop. A shelf and lake depositional environment with dark gray mudstone forms the transgressive systems tract （TST）. The location where dark gray mudstone first appears above the braided channel marks the first flooding surface （FFS）, and the end of that marks the maximum flooding surface （MFS）. The highstand systems tract （HST） deposits are fine-grained sediments with an aggradational parasequence at Heidaigou outcrop and swamp coalbed in the Daniudi Gas Field. Mouth-bar sand bodies in braided delta front, which form the LST in each sequence, form excellent reservoirs in the Daniudi Gas Field.
基金This study was supported by the Ministry of Sciences and Technology of China(2001CB209100),
文摘The Lower Cretaceous strata in the Kuqa Basin in Xinjiang are marked by a set of arid red beds. Several types of sedimentary fades can be identified in this set of arid red beds: mudstones of the plaza and intracontinental sebkha, aeolian sandstones, sandy conglomerates of the intermittent river, conglomerates of the pluvial fan, etc. These types of sedimentary facies constitute a typical desert system. Therefore, the Cretaceous strata in the Kuqa Basin provide a favorable condition for studies of sequence stratigraphic divisions of the desert system. With the rise and fall of the base level of the sedimentary basin, cyclicity is clearly revealed in stratigraphic records, which helps the identification of the third-order sequences. Based on the cyclicity in stratigraphic records, 5 third-order sequences can be found in the strata of the Early Cretaceous in the Kuqa Basin. These sequences comprise a second-order tectonic sequence. The primary feature of these third-order sequences is of an upward-fining sedimentary succession formed by a succession of 'coarse sediments of the alluvial system-fine sediments of the lake system'. The result of this study shows that aeolian sandstones are the best reservoirs of natural gas in the Cretaceous strata in the Kuqa Basin, and that the Kela-2 gas field is the first large gas field dominated by aeolian sandstone reservoirs in China.
文摘In South China four depositional sequences are recognized in the upper part of Upper Devonian and Tournaisian. They are named SQ0 SQ1, SQ2 and SQ3 in ascending order. SQ0 is Strunian (uppermost Devonian), and the other three Tournaisian in age. These four depositional sequences appear to correlate fairly well with the four sequence recognized in Europe, North America and other areas. This may suggest that these sequences are synchronous depos- its resulted from the eustatic changes. The present study on sequence stratigraphy, biostratigraphy and event stratigraphy indicates that in neritic facies areas of South China, the Devonian-Carboniferous boundary, matching the boundary between Siphonodella praesulcata zone and S. sulcata zone in pelagic facies areas, is not only higher than the top of the Cystophrentis zone, but also higher than the top of the Devonian-Carboniferous boundary event bed. In neritic facies areas, the Devonian-Carbonifrerous boundary is marked by the most distinct transgressive surface within the Cystophrentiseudouralina interval zone, i. e. at the base of the TST of the SQ1. This boundary coincides with the top surface of the event bed resulted from the eustatic fall, and approximately corresponds to the basal part of Rseudouralina assemblage zone.
基金supported by the National Major Fundamental Research and Development Project of China(Grant No.2003CB214600)the State Key Program of National Natural Science of China(Grant No. 90814005)
文摘Sequence stratigraphical analysis was applied to the Upper Carboniferous-Lower Permian sedimentary succession of the northeastern Ordos Basin, north China based on data acquired from ten entire logging curves and eight outcrops. The facies framework of the lithostratigraphical unit, the Taiyuan Formation comprises seven facies in two facies associations, varying from fluvio-delta to shelf-barrier islands. The facies are presented within a chronostratigraphical framework, linked by systems tract, which in turn are limited by flooding surfaces and sequence boundaries. Six third-order depositional sequences are recognised, bounded by six type 2 unconformities. An upwards-shallowing epicontinental sea sedimentary model is created, which consists of a sandstone, coal seam and carbonate succession.
基金This paper is an outcome of the research programof sequence stratigraphy (SSLC) supported by the Stateac~sinn of ScienCe and
文摘Depositional sequences may be distinguished into six ranks of units as giga-, mega-, meso-, ortho-, sub- and micro-sequence, and are interpreted to be formed during the eustatic cycles with time-intervals of 500-6000 Ma, 60-120 Ma, 30-40 Ma, 2-5 Ma, 0.1-0.4 Ma and 0.02-0.04 Ma respectively. All of them are thought to be essentially related to cosmological cycles, except the megasequence which may be caused by the long-term geothermal cycles on cratons. We deem that the depositional sequences, though often influenced variably by local tectonics and other factors, are primarily global and periodic in nature. We also hold that as one of the planets within the Galaxy, the earth must have been affected in various ways by other asteroids, and that the depositional sequences are merely the responses of the hydrosphere to the cosmological cycles in sedimentation.
文摘The Qom Formation comprises Oligo-Miocene deposits from a marine succession distributed in the Central Basin of Iran. It is composed of five members designated as A-F. Little previous work exists on the sequence stratigraphy. Based on an integrated study of sequence stratigraphy with outcrop data, wells and regional seismic profiles, the Qom Formation is interpreted as a carbonate succession deposited in a mid.Tertiary back-arc basin. There are two second-order sequences （designated as SS1 and SS2） and five third-order sequences （designated as S1-S5）. Five distinct systems tracts including transgressive, highstand, forced regressive, slope margin and Iowstand have been recognized. The relationship between the sequences and lithologic sub-units has been collated and defined （S1 to S5 individually corresponding to A-C1, C2--C4, D-E, the lower and upper portions of F）; a relative sea level change curve and the sequence stratigraphic framework have been established and described in detail. The coincidence of relative sea level change between that of the determined back-arc basin and the world indicates that the sedimentary cycles of the Qom Formation are mainly controlled by eustatic cycles. The variable combination of the systems tracts and special tectonic-depositional setting causally underpin multiple sequence stratigraphic framework styles seen in the carbonates of the back-arc basin revealing： （1） a continental margin basin that developed some form of barrier, characterized by the development of multiple cycles of carbonate-evaporites; （2） a flat carbonate ramp, which occurred on the southern shelf formed by the lack of clastic supply from nearby magmatic islands plus mixed siliciclastics and carbonates that occurred on the northern shelf due to a sufficient clastics supply from the land; and （3） a forced regressive stratigraphic stacking pattern that occured on the southern shelf and in basin lows due to the uplifting of the southern shelf. Thick and widespread aggradational framework limestone usually occurs in the initial sequences （S1 and S3） of the supersequence, which led to preferential oil reservoir deposition but a lack of source and cap rocks, whereas the retrogradational and progradational framework limestone usually occurs in the later sequences （S2 and S4-S5） of the supersequence, which results in two perfect sets of source, reservoir and cap rock assemblies, so that the limestone in sub-member C2-C4 and the F-Member can be predicted as important objects for oil exploration.
基金This paper is financially supported by the National Natural Science Foundation of China (Nos .49802012 ,40472065) .
文摘Both the macroscopic feature and the sequence-stratigraphic position of the molar-tooth structure developed in the third member of the Gaoyuzhuang （高于庄） Formation at the Jixian （蓟县） Section in Tianjin （天津） can provide some useful information about its origin and can reveal some problems to be further researched in the future. The Mesoproterozoic Gaoyuzhuang Formation is a set of 1 600 m thick carbonate strata. This formation can be divided into four members. The first member is mainly made up of stromatolitic dolomites; the second is marked by a set of manganese dolomites; the third is mainly composed of lamina limestones with the development of molar-tooth strcutures; the fourth is a set of stromatolitic-lithoherm dolomites. According to lithofacies and its succession, several types of meter-scale cycles can be discerned in the Gaoyuzhuang Formation： the L-M type, the subtidal type and the peritidal type. There is a regularly vertical stacking pattern for meter-scale cycles in the third-order sequence. Therefore, the Mesoproterozoic Gaoyuzhuang Formation can be divided into 13 third-order sequences （SQ1 to SQ13 ） and can further be grouped into 4 second-order sequences. The third member is marked by lamina limestones and can be grouped into three third-order sequences （SQ9 to SQ11 ）. The molar-tooth structure is developed in the middle part of the third sequence, i.e. SQH , in the third member. Several features of this kind of molar-tooth structure reflect some features of carbonate sedimentation in the Precambrian, such as the particular configuration, abundant organic matter, and easy silication. Stromatolites are chiefly formed in a shallow tidal-flat environment; lamina are mainly formed in the shallow ramp and molar-tooth structures are mainly generated in a relatively more deep-water environment from the middle to the deep ramp. Therefore, similar to stromatolite and lamina, the molartooth structure might also be a kind of bio-sedimentation structure. This suggestion is based on macroscopic observation and the sedimentary-facies analysis of the molar-tooth structures from the sequencestratigraphic position. These features of Precambrian sedimentation also reveal the problem of Precambrian carbonate sedimentation. With more detailed study, a more practical solution for these problems may be obtained in the future.
文摘The Upper Proterozoic glacigenous rocks in the southeastern margin of the Yangtze platform were accumulated in a glacially influenced marine environment with extension set- ting. Two type I depositional sequences have been identified in the glacioclastic sediments the their boundaries enhanced by both tectonism and the incision of glaciation. The lower sequence (SQ1), comprising Changan and Fulu formations (Guangxi Province), Jiangkou and Xiangmen formations(Hunan Province) and their equivalents, is bounded by erosional unconformities both at the base and on the top. The upper sequence (SQ2), composed mainly of Nantuo Formation and its equivalents, is confined by an erosional unconformity at the base and covered by an exposure surface of karstification on the top. The depositional systems tracts are difficult to be distinguished directly and mainly characterized by the variation in glacioclastic supplies. Two types of episodic parasequeuces can be identified in the glacigenous rocks and are related to the evolution of depositional systems tracts. Both the sequences and parasequences are caused by autocyclic mechanism. The present research shows that the Upper Proterozoic glacigenous deposits are of significance for the analysis of the tectonic evolution of the Late Precambrian basin in South China.
基金This research was supported by the Project for the Survey of Land and Resources in China(1212010633901)National Natural Science Foundation of China(Grant No.41572090)。
文摘There are 9 major coal-accumulating periods during geological history in China,including the Early Carboniferous,Late Carboniferous-Early Permian,Middle Permian,Late Permian,Late Triassic,Early-Middle Jurassic,Early Cretaceous,Paleogene and Neogene.The coal formed in these periods were developed in different coal-accumulating areas(CAA)including the North China,South China,Northwest China,Northeast China,the Qinghai–Tibet area,and China offshore area.In this paper,we investigated depositional environments,sequence stratigraphy,lithofacies paleogeography and coal accumulation pattern of five major coal-accumulating periods including the Late Carboniferous to Middle Permian of the North China CAA,the Late Permian of the South China CAA,the Late Triassic of the South China CAA,the Early-Middle Jurassic of the North and Northwest China CAA,and the Early Cretaceous in the Northeast China CAA.According to distribution of the coal-bearing strata and the regional tectonic outlines,we have identified distribution range of the coal-forming basins,sedimentary facies types and coal-accumulating models.The sequence stratigraphic frameworks of the major coal-accumulating periods were established based on recognition of a variety of sequence boundaries.The distribution of thick coals and migration patterns of the coal-accumulating centers in the sequence stratigraphic framework were analyzed.The lithofacies paleogeography maps based on third-order sequences were reconstructed and the distribution of coal accumulation centers and coal-rich belts were predicted.
