An analysis of seismic data obtained through a cable route survey starting from the Qingdao coast to offshore has determined nine seismic units since Late Pleistocene. Correlation of the seismic data with Borehole Hj2...An analysis of seismic data obtained through a cable route survey starting from the Qingdao coast to offshore has determined nine seismic units since Late Pleistocene. Correlation of the seismic data with Borehole Hj2 confirms three eustatic events that occurred during the Late Quaternary and formed terrestrial units 2, 5 and 7. At the low sea level stage, paleo rivers highly developed, eroded previous strata, formed paleo valley, and left materials.展开更多
To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D sei...To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D seismic and drilling data,and reservoir sections are thoroughly investigated.Guided by the theory of sequence stratigraphy,the progradational sequence stratigraphic framework of the Yanchang Formation is systematically constructed to elucidate new deposition mechanisms in the depressed lacustrine basin,and it has been successfully applied to the exploration and development practices in the Qingcheng Oilfield.Key findings are obtained in three aspects.First,the seismic progradational reflections,marker tuff beds,and condensed sections of flooding surfaces in the Yanchang Formation are consistent and isochronous.Using flooding surface markers as a reference,a progradational sequence stratigraphic architecture is reconstructed for the middle-upper part of Yanchang Formation,and divided into seven clinoform units(CF1-CF7).Second,progradation predominantly occurs in semi-deep to deep lake environments,with the depositional center not always coinciding with the thickest strata.The lacustrine basin underwent an evolution of“oscillatory regression-progradational infilling-multi-phase superimposition”.Third,the case study of Qingcheng Oilfield reveals that the major pay zones consist of“isochronous but heterochronous”gravity-flow sandstone complexes.Guided by the progradational sequence stratigraphic architecture,horizontal well oil-layer penetration rates remain above 82%.The progradational sequence stratigraphic architecture and associated geological insights are more consistent with the sedimentary infilling mechanisms of large-scale continental depressed lacustrine basins and actual drilling results.The research results provide crucial theoretical and technical support for subsequent refined exploration and development of the Yanchang Formation,and are expected to offer a reference for research and production practice in similar continental lacustrine basins.展开更多
Indus basin hosts many significant mineral deposits like gypsum and cement raw materials, gemstones, iron, coal, marble, dimension and construction stones, petroleum and water resources, world class pink salt and othe...Indus basin hosts many significant mineral deposits like gypsum and cement raw materials, gemstones, iron, coal, marble, dimension and construction stones, petroleum and water resources, world class pink salt and other many minerals in different regions which need further exploitation and development. The construction of new water dams in different regions are vital (for availability of cheap electricity), because of available barren and fertile lands and wastage of water as flood. Further the installation of more cement industries in different regions of Indus Basin especially in middle Indus (Sulaiman Range where gypsum, clays and limestones can be available via belt) can increase export to receive more foreign exchange and make local cement cheap for the sustainable development of Pakistan. 31 stratigraphic sequential sections at different sections of Indus basins are presented to know the variation and local stratigraphy. Further here three new titanosaur taxa are being described. Saraikimasoom is based on snout;Gspsaurus, (Maojandino), Nicksaurus and Khanazeem are based on cranial, vertebral and appendicular elements;Balochisaurus, Marisaurus, Pakisaurus, and 3 new genera and species Imrankhanhero zilefatmi, Qaikshaheen masoomniazi and Ikqaumishan smqureshi based on vertebral and appendicular elements;and Sulaimanisaurus and Khetranisaurus based on only caudal vertebrae. Although Pakistani Titanosaurians seem to be proliferated found from one horizon of Vitakri Formation just below the K-Pg boundary they have a wide range of diagnostic features and key elements among titanosaurs which can be used for comparison and phylogenetic analyses with broad updated character data set of titanosaurs.展开更多
In recent years, with the development of terrestrial sequence stratigraphy, more attention has been focused on the study of the terrestrial lacustrine sequence stratigraphic model globally. Different viewpoints are pr...In recent years, with the development of terrestrial sequence stratigraphy, more attention has been focused on the study of the terrestrial lacustrine sequence stratigraphic model globally. Different viewpoints are preferred by researchers. Under the guidance of the theory of sequence stratigraphy, the findings of this paper indicate that climate is a major factor controlling the formation of the fourth-order sequence, based upon the study of the sequence stratigraphy in the Green River Formation of the Uinta basin in the USA. It also divides the fourth-order sequence in the terrestrial lacustrine basin into two system tracts： the wet （rising） half-cycle and the dry （falling） half- cycle, establishing a new-style fourth-order sequence stratigraphic model for the terrestrial lacustrine basin, that is, the climate-genetic sequence stratigraphic model. As a result, the theory of sequence stratigraphy is greatly enriched.展开更多
The East China Sea shelf basin is a key area for setting up the sea level changes of Cenozoic in the West Pacific. Based upon the characteristics of seismic reflection, the analysis of sequence stratigraphy and depos...The East China Sea shelf basin is a key area for setting up the sea level changes of Cenozoic in the West Pacific. Based upon the characteristics of seismic reflection, the analysis of sequence stratigraphy and depositional system, the high resolution chronostratigraphic framework has been set up by using the data of micropaleontologic biozone fossils. The relative sea level change curve has been set up by combining analysis of paleoecology, genetic facies, specific sedimentary structures and on lap recognized from the seismic profiles with study of geochemical characteristics. There are 4 2nd order basin cycles showing the long term sea level changes, and 22 3rd order cycles showing short term ones with relative changing ranges of 0-150 m. Transgression and regression showing long term sea level changes bear asymmetric feature, which indicates that the speed of transgression is faster than that of regression. There are a lot of differences when compared with Haq ’s curve. The sequence stratigraphic framework has also been set up and 3 tectonic sequences, 7 supersequences and 19 sequences have been subdivided for Tertiary in the East China Sea shelf basin. On the basis of detailed analysis of genetic facies and log facies, 9 sedimentary systems, 20 depositional assemblages and many genetic facies have also been recognized and investigated. Based on the studies mentioned above, the favorable source and reservoir facies of gas and petroleum are indicated.展开更多
A quantitative two-dimensional model of sequence stratigraphy is formulated to simulate the development of sequence architecture in sedimentary basins. The model takes into account sea level change, tectonic subsiden...A quantitative two-dimensional model of sequence stratigraphy is formulated to simulate the development of sequence architecture in sedimentary basins. The model takes into account sea level change, tectonic subsidence, compaction of sediments, flexural isostatic compensation, erosion and sedimentation. It may be used to test sequence stratigraphic model, to analyze the development of sequence architecture and sequence boundaries, and to predict facies distribution in basins. The computer model, combined with backstripping technique, is cali- brated to model the sedimentary filling of the Early Cretaceous Erlian basin and the Tertiary Yinggehai basin. The study shows that the development of high order sequences in the basins was closely related to the multiple stretching and inversion. The development of the progradational sequence set of the Yinghuang Formation in Yinggehai basin formed in synrift period was mainly controlled by a large amount of sediment input high fluctuation of sea level and gradual subsidence of the basin.展开更多
The Yitong graben is located in the northeastern segment of the Tertiary rift system in East China. The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on t...The Yitong graben is located in the northeastern segment of the Tertiary rift system in East China. The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on the southeastern side, with very thick marginal fan complexes indicating syntectonic sedimentation. The graben is infilled with Tertiary sediments up to 6 000 m thick, in which a series of different scaled hiatuses and tectonic inversion events have been discerned during hydrocarbon exploration. According to regional and local conformities, the basin infill may be divided into three tectonic sequences, among which the major sequence TS2 is further subdivided into three sequence sets and fourteen subsequences. Based on the sequence stratigraphic framework, depositional system tracts which are characterized by marginal fan complexes on both sides of basin and deep or shallow lacustrine deposits in the central part are reconstructed. The subsidence curves show that the graben had undergone several rapid subsidence episodes, which is interpreted to have been caused by multiple stretching of the lithosphere. Integrative analysis of the depositional structural features shows that the regional tectonic stress system experienced a transformation from dextral transformational shear through thermal subsidence to sinistral compressional shear with a general extensional setting. Extension and wrenching dominated the graben evolution and affected the depositional style in different evolutionary stages, the spatial configuration of depositional system and its relationship with unconformities. The conclusions have been applied with some successes to studying the reservoir and hydrocarbon source rock distribution and lithologic stratigraphic traps in this basin.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 architectural patterns of sedimentary succession are diverse in different depositionalbasins. The sedimentary architecture and geological condition of such basins asepicontinental sea, intraplate limnic basins, et...The architectural patterns of sedimentary succession are diverse in different depositionalbasins. The sedimentary architecture and geological condition of such basins asepicontinental sea, intraplate limnic basins, etc., differ cIearly from those of continentalmargin basin. Extension, complement and perfection of sequence stratigraphic models are needed in the studies of various depositional basins based on the classical sequence model. This paper, for this reason,expounds the thought, principles of sequence division, methodology and technology of the study of sequence stratigraphy in epicontinental and limnic basins.展开更多
A high-precision sedimentary environment study of the Lower Silurian Longmaxi Formation is an important subject for shale gas exploration and development in Sichuan Basin and its surrounding areas.On the basis of outc...A high-precision sedimentary environment study of the Lower Silurian Longmaxi Formation is an important subject for shale gas exploration and development in Sichuan Basin and its surrounding areas.On the basis of outcrops and drilling data,its isochronous stratigraphic framework was built according to a particular graptolite zone and an important marker bed,and lithofacies,paleontology,calcareous content,well logging,geochemistry and other geologic information were combined to describe the sedimentary microfacies of Longmaxi Formation and its stratigraphic sequence,sedimentary evolution process and high quality shale distribution features as follows:①with regional diachronism of the top and the bottom,the Longmaxi Formation is divided into two third-order sequences(SQ1 and SQ2),of which SQ1 is mainly an abyssal sedimentary assemblage deposited in the marine transgression period,and SQ2 is a bathyal to shallow sea sedimentary assemblage deposited in the marine regression period;②there are eight microfacies such as deep calcareous shelf and deep argillaceous shelf in this formation and the organic-rich shale was mainly deposited in the deep water area of SQ1;and③from SQ1 to SQ2,the depocenter moved from the depression area in southern-eastern to northern Sichuan Basin,but the central Sichuan uplift remained an underwater one.It is concluded from this study that:①shale gas production layers were mainly deposited in SQ1,the southern-eastern depression area was the depocenter in SQ1 and a shale gas enrichment area;and②black shale in northern Sichuan was deposited in late SQ2,with limited distribution and relatively insufficient exploration potential,but the potential of shale gas exploration in western Hubei area is between southern-eastern and northern Sichuan Basin.展开更多
The Jinshajiang belt, located between the Zhongzan and Qamdo massifs, preserves varied sediments representing different tectonic background. Those sediments outcrop in stratigraphic slices,not in continuous stratigrap...The Jinshajiang belt, located between the Zhongzan and Qamdo massifs, preserves varied sediments representing different tectonic background. Those sediments outcrop in stratigraphic slices,not in continuous stratigrapky. The stratigraphic slices of the passive continental margin are investigated by geologic mapping in Tuediug-Xiaruo, Northwestern Yunnan Province, and each of these slices is researched in age and sedimeutary environment. The stratigraphic successions of the passive continental margin are reconstructed. On the basis or new sequence, the evolutional history of the passive continental margin is divided into four stages: rift basin (D,-C,), complex continental margin basin (P1 ), residual hasin (P2-T2) and synorogenic basin (T3).展开更多
Yitong graben belongs to the north segment of the Tanlu fault belt .It was infilled with Eogene, Neogene and Quaternary clastic deposits, each Of them represents a distinct tectonic sequence.Six types of systems ass...Yitong graben belongs to the north segment of the Tanlu fault belt .It was infilled with Eogene, Neogene and Quaternary clastic deposits, each Of them represents a distinct tectonic sequence.Six types of systems association characteristics of distinct depositional systems and spatial disposition are identified in different evolutionary period of the graben.Sequence Stratigraphic framework of the graben is mainly controlled by structural framework,tectonic movement, sources supply, expanding and contracting cycle of lake, position of depositional center. The key factors are structural framework and tectonic movemeat.Through systematic analysis Of regional tectonic settings, it is recognized that Eogene tectonic sequence of Yitong graben was formed under tenso-shear regime. It includes four sequences indicating four tectonic events attributed to tectonic movement of marginal faults.Neogene tectonic sequence was formed under compresso-shear regime, which includes coarse clastic deposits with a thicknessof 0-500m.Pattern of in the Yitong graben indicates the asymmetrical subsisence of marginal faults along two sides and the complicated structural framework.展开更多
Based on the integrated study of the outcrops, the seismic, drilling and logging data of Lianglitage formation in central Tarim Basin, the sequence stratigraphic framework of the platform margin is built, and the Lian...Based on the integrated study of the outcrops, the seismic, drilling and logging data of Lianglitage formation in central Tarim Basin, the sequence stratigraphic framework of the platform margin is built, and the Lianglitage formation is divided into 3 third-order sequences. The vertical pattern and lateral distribution for carbonate reef-bank reservoir in sequence stratigraphic framework are analyzed. The reef-bank reservoir mainly developed in highstand system tract of sequence Ssq2, and distributed along the carbonate platform margin of the Middle-Late Ordovician in central Tarim Basin. The mudstone mound, organic reef, granule bank are vertically stacked. Laterally, the area of well shun3-shun4-shun2-shun6 are characterized by multiphase bank reservoir overlapping, and the area of well TZ82 -TZ44 - TZ161 -TZ24 - TZ26 are characterized by multiphase organic reef and bank overlapping. The reef-bank complexes in sequence Ssq2 are the main targets of exploration in central Tarim Basin.展开更多
The Fushan Depression is one of the petroliferous depressions in the Beibuwan Basin,South China Sea.Previous studies have preliminarily explored the origin and source of crude oils in some areas of this depression.Nev...The Fushan Depression is one of the petroliferous depressions in the Beibuwan Basin,South China Sea.Previous studies have preliminarily explored the origin and source of crude oils in some areas of this depression.Nevertheless,no systematic investigations on the classification and origin of oils and hy-drocarbon migration processes have been made for the entire petroleum system in this depression,which has significantly hindered the hydrocarbon exploration in the region.A total of 32 mudstone and 58 oil samples from the Fushan Depression were analyzed to definite the detailed oil-source correlation within the sequence and sedimentary framework.The organic matter of third member of Paleogene Liushagang Formation(Els(3))source rocks,both deltaic and lacustrine mudstone,are algal-dominated with high abundance of C_(23)tricyclic terpane and C_(30)4-methylsteranes.The deltaic source rocks occur-ring in the first member(Els_(1))and second member(Els_(2))of the Paleogene Liushagang Formation are characterized by high abundance of C_(19+20)tricyclic terpane and oleanane,reflecting a more terrestrial plants contribution.While lacustrine source rocks of Els_(1)and Els_(2)display the reduced input of terrige-nous organic matter with relatively low abundance of C 19+20 tricyclic terpane and oleanane.Three types of oils were identified by their biomarker compositions in this study.Most of the oils discovered in the Huachang and Bailian Els_(1)reservoir belong to group A and were derived from lacustrine source rocks of Els_(1)and Els_(2).Group B oils are found within the Els_(1)and Els_(2)reservoirs,showing a close relation to the deltaic source rocks of Els_(1)and Els_(2),respectively.Group C oils,occurring in the Els3 reservoirs,have a good affinity with the Els3 source rocks.The spatial distribution and accumulation of different groups of oils are mainly controlled by the sedimentary facies and specific structural conditions.The Els_(2)reservoir in the Yong'an area belonging to Group B oil,are adjacent to the source kitchen and could be considered as the favorable exploration area in the future.展开更多
This study reconstructed the paleo-uplift and depression pattern within the sequence stratigraphic framework of the Mid-Permian Maokou Formation,Sichuan Basin,investigated its tectono-sedimentary mechanisms and its co...This study reconstructed the paleo-uplift and depression pattern within the sequence stratigraphic framework of the Mid-Permian Maokou Formation,Sichuan Basin,investigated its tectono-sedimentary mechanisms and its control on paleogeomorphology and large-sale shoals based on analysis of outcrops,loggings and seismic data.The results show that the Maokou Formation comprises two third-order sequences,six fourth-order sequences(SSQ1-SSQ6),and four distinct slope-break zones developing progressively from north to south.Slope-break zones I-III in the northern basin,controlled by synsedimentary extensional faults,exhibited a NE-trending linear distribution with gradual southeastward migration.In contrast,slope-break zone IV in the southern basin displayed an arcuate distribution along the Emeishan Large Igneous Province(ELIP).The evolutions of these multistage slope-break zones governed the Mid-Permian paleogeomorphy in the Sichuan Basin transformations from a giant,north-dipping gentle slope(higher in the southwest than in the northeast)in the early-stage(SSQ1-SSQ2)to a platform(south)-basin(north)pattern in the middle-stage(SSQ3-SSQ5).Ultimately,a further depression zone developed in the southwestern basin during the late-stage(SSQ6),forming a paleo-uplift bounded by two depressions.The developments of the Mid-Permian paleogeomorphic configuration reflected the combined control by the rapid subduction of the Mianlüe Ocean and the episodic eruptions of the Emeishan mantle plume(or hot spots),which jointly facilitated the formation of extensive high-energy shoal facies belts along slope-break zones and around paleo-volcanic uplifts.展开更多
In this paper we discuss the timing of final closure of the Paleo-Asian Ocean based on the field investigations of the Carboniferous-Permian stratigraphic sequences and sedimentary environments in southeastern Inner M...In this paper we discuss the timing of final closure of the Paleo-Asian Ocean based on the field investigations of the Carboniferous-Permian stratigraphic sequences and sedimentary environments in southeastern Inner Mongolia combined with the geology of its neighboring areas. Studies show that during the Carboniferous-Permian in the eastern segment of the Tianshan-Hinggan Orogenic System, there was a giant ENE-NE-trending littoral-neritic to continental sedimentary basin, starting in the west from Ejinqi eastwards through southeastern Inner Mongolia into Jilin and Heilongjiang. The distribution of the Lower Carboniferous in the vast area is sparse. The Late Carboniferous or Permian volcanic-sedimentary rocks always unconformably overlie the Devonian or older units. The Upper Carboniferous-Middle Permian is dominated by llttoral-neritic deposits and the Upper Permian, by continental deposits. The Late Carboniferous-Permian has no trace of subduction-collision orogeny, implying the basin gradually disappeared by shrinking and shallowing. In addition, it is of interest to note that the Ondor Sum and Hegenshan ophiolitic melanges were formed in the pre-Late Silurian and pre-Late Devonian respectively, and the Solonker ophiolitic melange formed in the pre-Late Carboniferous. All the evidence indicates that the eastern segment of the Paleo-Asian Ocean had closed before the Late Carboniferous, and most likely before the latest Devonian （Famennian）.展开更多
Sandstone-type U mineral resources are among the important sources for nuclear energy.The U deposits in the Ordos Basin in China form part of the northern segment of the sandstone-hosted Central Asian Uranium MegaProv...Sandstone-type U mineral resources are among the important sources for nuclear energy.The U deposits in the Ordos Basin in China form part of the northern segment of the sandstone-hosted Central Asian Uranium MegaProvince.Two types of mineralizations are recognized in this basin:"phreatic permeable type"and"interlayer permeable type",both exhibiting features equivalent to roll-front subtypes.The"interlayer permeable type"is widely accepted as the dominant mineralization type for sandstone-type uranium deposits within large-scale basins,also designated as the"interlayer oxidation zone type",based on the horizontal color zoning model representing changing redox conditions.Here we synthesize data from several drill holes within the Ordos Basin,which suggest that major Mesozoic tectonic movements controlled the evolution of the sedimentary system in the basin.These tectonic movements contributed to the formation of three angular unconformities and four parallel unconformities as inferred from the stratigraphic relationships.In addition,other features such as vertical color zoning,paleo-channel controlled tabular or lentoid ore bodies(without roll-type)and a group interlayer horizontal zoning of altered minerals are also documented.Sequence stratigraphic analysis indicates that the Ordos Basin generally witnessed four cycles of water level variations during Mesozoic.During the variations,three high water level and three low water level events were recorded.Biological characteristics imply that the Ordos Basin went through multiple arid to humid climatic evolutions during Mesozoic.Combining the newly documented features with some novel concepts on the hydrodynamic mechanism for supergene ore-forming fluids,we propose a metallogenic model which invokes the importance of tectonic movements and water level fluctuations to explain the genesis of uranium deposits along the northern margin of the Ordos Basin.展开更多
The sequence stratigraphy of the Jurassic coal measures of northwestern China has been studied based on data from outcrop and borehole sections. Because of the geological background and the diversity of basin types, s...The sequence stratigraphy of the Jurassic coal measures of northwestern China has been studied based on data from outcrop and borehole sections. Because of the geological background and the diversity of basin types, such as isochronisms of coal seams and recognition of key sequence boundaries, it is rare to summarize and correlate sequence structure and framework. The types and recognition characteristics of the sequence boundaries of the Jurassic coal measures are revealed by comparing climatic characteristics, structural styles and the base level cycle. A total of five third-order sequences and 15 systems tracts have been subdivided and the sequence stratigraphic framework has been reconstructed confirming that the thick coals accumulated in the late stage of transgression system tracts of sequence I （SQ I） and sequence III （SQ III）. This idea is of important academic significance for instructing coal resources exploration, and enhancing geological effects of prospecting engineering. It is also of practical significance for guaranteeing construction of the large-scale coal production base in northwestern China, accelerating the westward development of the coal industry stratagem.展开更多
The Tanjianshan Group,which was previously divided into a,b,c and d formations,has been controversial for a long time.It mainly distributes in the northern margin of Qaidam Basin and is an important early Paleozoic gr...The Tanjianshan Group,which was previously divided into a,b,c and d formations,has been controversial for a long time.It mainly distributes in the northern margin of Qaidam Basin and is an important early Paleozoic greenschist facies metamorphic volcanic sedimentary rock formation.Detailed field investigation and zircon LA-ICPMS U-Pb dating of the key strata suggest that the original lower part of a Formation （a-1） versus the original middle upper of d Formation （d-3 and d-4）,the original upper part of a Formation （a-2） and b Formation versus the original lower part of d Formation （d-1 and d-2） of Tanjianshan Group are contemporaneous heterotopic facies volcanicclasolite deposit,respectively.The former formations formed during the middle-late Ordovician （463-458 Ma）,while the latter ones formed in the late Ordovician （about 445 Ma）.The original c formation of Tanjianshan Group,which formed after 430 Ma,is similar to the Maoniushan Formation of Kunlun Mountains and north Qaidam Basin.According to the rules of stratigraphic division and naming,new stratum formations of Tanjianshan Group are re-built and divided into Duancenggou （O1-2td）,Zhongjiangou （O2-3tz） and Xitieshan （O3tx） formations.The original c Formation is separated from Tanjianshan Group and is renamed as the Wuminggou Formation （S3-D1W）,which shows a discordant contact with underlying Tanjianshan Group and overlying Amunike Formation （D3a）.The zircon U-Pb age frequency spectrogram of Tanjianshan Group indicates three prominent peaks of 430 Ma,460 Ma and 908 Ma,which is consistent with the metamorphic and magmatic crystallization ages obtained from para-and orthogneisses in north Qaidam HP-UHP metamorphic belt,implying that strong Caledonian and Jinningian tectonic and magmatic events have ever happened in North Qaidam.展开更多
The Carboniferous Karashayi （卡拉沙依） Formation of Tarim basin formed in the epicontinental sea shelf environment where the evolution of basins is pediocratic. As an important reservoir-forming combination, the Car...The Carboniferous Karashayi （卡拉沙依） Formation of Tarim basin formed in the epicontinental sea shelf environment where the evolution of basins is pediocratic. As an important reservoir-forming combination, the Carboniferous Karashayi Formation consist of clastic rocks, carbonate rocks and gypsum rocks, which show clear sedimentary cyclicity. According to paleontology research and stratigraphic correlation, Karashayi Formation corresponds to Visean and Serpukhovian in international stratigraphic chart with a time limit about ±27 Ma. The sequence stratigraphic study for the Karashayi Formation is rough because of the difficulty to identify the unconformity surfaces. The current study mostly divides it into three or four 3rd sequences. However, this partition cannot meet the geological crossing correlation. At the theory aspect of sequence stratigraphy, the genesis of the 3rd sequence is also a disputed problem. Cyclostratigraphy study of the Natural Gamma-Ray Log, Spontaneous Potential Log and other logging curves has been taken out by spectrum analysis and wavelet analysis, etc.. For Well Shun6 and Well Zhongl in Tazhong （塔中） and neighbouring area, combined core observation and base level analysis, the Karashayi Formation was divided into 9 or 11 sequence stratigraphic units. Continuous constraints of each sequence is about ±2.40 Ma, corresponding to astronomical cycle formed by three parameters of Earth orbit. Accompanied by the historical division of 3rd sequences, the formation mechanism of 3rd sequences was possibly forced by the 2.4 Ma astro-nomical eccentricity cycles.展开更多
基金supported by the State‘863’Plan(No.2001AA602025)
文摘An analysis of seismic data obtained through a cable route survey starting from the Qingdao coast to offshore has determined nine seismic units since Late Pleistocene. Correlation of the seismic data with Borehole Hj2 confirms three eustatic events that occurred during the Late Quaternary and formed terrestrial units 2, 5 and 7. At the low sea level stage, paleo rivers highly developed, eroded previous strata, formed paleo valley, and left materials.
基金Supported by the National Science and Technology Major Project(2017ZX05001)CNPC Technology Project(2023YQX20111).
文摘To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D seismic and drilling data,and reservoir sections are thoroughly investigated.Guided by the theory of sequence stratigraphy,the progradational sequence stratigraphic framework of the Yanchang Formation is systematically constructed to elucidate new deposition mechanisms in the depressed lacustrine basin,and it has been successfully applied to the exploration and development practices in the Qingcheng Oilfield.Key findings are obtained in three aspects.First,the seismic progradational reflections,marker tuff beds,and condensed sections of flooding surfaces in the Yanchang Formation are consistent and isochronous.Using flooding surface markers as a reference,a progradational sequence stratigraphic architecture is reconstructed for the middle-upper part of Yanchang Formation,and divided into seven clinoform units(CF1-CF7).Second,progradation predominantly occurs in semi-deep to deep lake environments,with the depositional center not always coinciding with the thickest strata.The lacustrine basin underwent an evolution of“oscillatory regression-progradational infilling-multi-phase superimposition”.Third,the case study of Qingcheng Oilfield reveals that the major pay zones consist of“isochronous but heterochronous”gravity-flow sandstone complexes.Guided by the progradational sequence stratigraphic architecture,horizontal well oil-layer penetration rates remain above 82%.The progradational sequence stratigraphic architecture and associated geological insights are more consistent with the sedimentary infilling mechanisms of large-scale continental depressed lacustrine basins and actual drilling results.The research results provide crucial theoretical and technical support for subsequent refined exploration and development of the Yanchang Formation,and are expected to offer a reference for research and production practice in similar continental lacustrine basins.
文摘Indus basin hosts many significant mineral deposits like gypsum and cement raw materials, gemstones, iron, coal, marble, dimension and construction stones, petroleum and water resources, world class pink salt and other many minerals in different regions which need further exploitation and development. The construction of new water dams in different regions are vital (for availability of cheap electricity), because of available barren and fertile lands and wastage of water as flood. Further the installation of more cement industries in different regions of Indus Basin especially in middle Indus (Sulaiman Range where gypsum, clays and limestones can be available via belt) can increase export to receive more foreign exchange and make local cement cheap for the sustainable development of Pakistan. 31 stratigraphic sequential sections at different sections of Indus basins are presented to know the variation and local stratigraphy. Further here three new titanosaur taxa are being described. Saraikimasoom is based on snout;Gspsaurus, (Maojandino), Nicksaurus and Khanazeem are based on cranial, vertebral and appendicular elements;Balochisaurus, Marisaurus, Pakisaurus, and 3 new genera and species Imrankhanhero zilefatmi, Qaikshaheen masoomniazi and Ikqaumishan smqureshi based on vertebral and appendicular elements;and Sulaimanisaurus and Khetranisaurus based on only caudal vertebrae. Although Pakistani Titanosaurians seem to be proliferated found from one horizon of Vitakri Formation just below the K-Pg boundary they have a wide range of diagnostic features and key elements among titanosaurs which can be used for comparison and phylogenetic analyses with broad updated character data set of titanosaurs.
基金These research results are part of a key international cooperation project carried out during 2003 and 2005 and financially supported by SINOPEC.
文摘In recent years, with the development of terrestrial sequence stratigraphy, more attention has been focused on the study of the terrestrial lacustrine sequence stratigraphic model globally. Different viewpoints are preferred by researchers. Under the guidance of the theory of sequence stratigraphy, the findings of this paper indicate that climate is a major factor controlling the formation of the fourth-order sequence, based upon the study of the sequence stratigraphy in the Green River Formation of the Uinta basin in the USA. It also divides the fourth-order sequence in the terrestrial lacustrine basin into two system tracts： the wet （rising） half-cycle and the dry （falling） half- cycle, establishing a new-style fourth-order sequence stratigraphic model for the terrestrial lacustrine basin, that is, the climate-genetic sequence stratigraphic model. As a result, the theory of sequence stratigraphy is greatly enriched.
文摘The East China Sea shelf basin is a key area for setting up the sea level changes of Cenozoic in the West Pacific. Based upon the characteristics of seismic reflection, the analysis of sequence stratigraphy and depositional system, the high resolution chronostratigraphic framework has been set up by using the data of micropaleontologic biozone fossils. The relative sea level change curve has been set up by combining analysis of paleoecology, genetic facies, specific sedimentary structures and on lap recognized from the seismic profiles with study of geochemical characteristics. There are 4 2nd order basin cycles showing the long term sea level changes, and 22 3rd order cycles showing short term ones with relative changing ranges of 0-150 m. Transgression and regression showing long term sea level changes bear asymmetric feature, which indicates that the speed of transgression is faster than that of regression. There are a lot of differences when compared with Haq ’s curve. The sequence stratigraphic framework has also been set up and 3 tectonic sequences, 7 supersequences and 19 sequences have been subdivided for Tertiary in the East China Sea shelf basin. On the basis of detailed analysis of genetic facies and log facies, 9 sedimentary systems, 20 depositional assemblages and many genetic facies have also been recognized and investigated. Based on the studies mentioned above, the favorable source and reservoir facies of gas and petroleum are indicated.
文摘A quantitative two-dimensional model of sequence stratigraphy is formulated to simulate the development of sequence architecture in sedimentary basins. The model takes into account sea level change, tectonic subsidence, compaction of sediments, flexural isostatic compensation, erosion and sedimentation. It may be used to test sequence stratigraphic model, to analyze the development of sequence architecture and sequence boundaries, and to predict facies distribution in basins. The computer model, combined with backstripping technique, is cali- brated to model the sedimentary filling of the Early Cretaceous Erlian basin and the Tertiary Yinggehai basin. The study shows that the development of high order sequences in the basins was closely related to the multiple stretching and inversion. The development of the progradational sequence set of the Yinghuang Formation in Yinggehai basin formed in synrift period was mainly controlled by a large amount of sediment input high fluctuation of sea level and gradual subsidence of the basin.
文摘The Yitong graben is located in the northeastern segment of the Tertiary rift system in East China. The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on the southeastern side, with very thick marginal fan complexes indicating syntectonic sedimentation. The graben is infilled with Tertiary sediments up to 6 000 m thick, in which a series of different scaled hiatuses and tectonic inversion events have been discerned during hydrocarbon exploration. According to regional and local conformities, the basin infill may be divided into three tectonic sequences, among which the major sequence TS2 is further subdivided into three sequence sets and fourteen subsequences. Based on the sequence stratigraphic framework, depositional system tracts which are characterized by marginal fan complexes on both sides of basin and deep or shallow lacustrine deposits in the central part are reconstructed. The subsidence curves show that the graben had undergone several rapid subsidence episodes, which is interpreted to have been caused by multiple stretching of the lithosphere. Integrative analysis of the depositional structural features shows that the regional tectonic stress system experienced a transformation from dextral transformational shear through thermal subsidence to sinistral compressional shear with a general extensional setting. Extension and wrenching dominated the graben evolution and affected the depositional style in different evolutionary stages, the spatial configuration of depositional system and its relationship with unconformities. The conclusions have been applied with some successes to studying the reservoir and hydrocarbon source rock distribution and lithologic stratigraphic traps in this basin.
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.
文摘The architectural patterns of sedimentary succession are diverse in different depositionalbasins. The sedimentary architecture and geological condition of such basins asepicontinental sea, intraplate limnic basins, etc., differ cIearly from those of continentalmargin basin. Extension, complement and perfection of sequence stratigraphic models are needed in the studies of various depositional basins based on the classical sequence model. This paper, for this reason,expounds the thought, principles of sequence division, methodology and technology of the study of sequence stratigraphy in epicontinental and limnic basins.
基金State Key Basic Research and Development Program(No.973 Program)ProjectSpecial and Significant Project of Na-tional Key Science and Technology(No.2011ZX05018-001)National Strategic Petroleum Resources Area Selection and Evaluation Project(No.2009GYXQ15-01).
文摘A high-precision sedimentary environment study of the Lower Silurian Longmaxi Formation is an important subject for shale gas exploration and development in Sichuan Basin and its surrounding areas.On the basis of outcrops and drilling data,its isochronous stratigraphic framework was built according to a particular graptolite zone and an important marker bed,and lithofacies,paleontology,calcareous content,well logging,geochemistry and other geologic information were combined to describe the sedimentary microfacies of Longmaxi Formation and its stratigraphic sequence,sedimentary evolution process and high quality shale distribution features as follows:①with regional diachronism of the top and the bottom,the Longmaxi Formation is divided into two third-order sequences(SQ1 and SQ2),of which SQ1 is mainly an abyssal sedimentary assemblage deposited in the marine transgression period,and SQ2 is a bathyal to shallow sea sedimentary assemblage deposited in the marine regression period;②there are eight microfacies such as deep calcareous shelf and deep argillaceous shelf in this formation and the organic-rich shale was mainly deposited in the deep water area of SQ1;and③from SQ1 to SQ2,the depocenter moved from the depression area in southern-eastern to northern Sichuan Basin,but the central Sichuan uplift remained an underwater one.It is concluded from this study that:①shale gas production layers were mainly deposited in SQ1,the southern-eastern depression area was the depocenter in SQ1 and a shale gas enrichment area;and②black shale in northern Sichuan was deposited in late SQ2,with limited distribution and relatively insufficient exploration potential,but the potential of shale gas exploration in western Hubei area is between southern-eastern and northern Sichuan Basin.
文摘The Jinshajiang belt, located between the Zhongzan and Qamdo massifs, preserves varied sediments representing different tectonic background. Those sediments outcrop in stratigraphic slices,not in continuous stratigrapky. The stratigraphic slices of the passive continental margin are investigated by geologic mapping in Tuediug-Xiaruo, Northwestern Yunnan Province, and each of these slices is researched in age and sedimeutary environment. The stratigraphic successions of the passive continental margin are reconstructed. On the basis or new sequence, the evolutional history of the passive continental margin is divided into four stages: rift basin (D,-C,), complex continental margin basin (P1 ), residual hasin (P2-T2) and synorogenic basin (T3).
文摘Yitong graben belongs to the north segment of the Tanlu fault belt .It was infilled with Eogene, Neogene and Quaternary clastic deposits, each Of them represents a distinct tectonic sequence.Six types of systems association characteristics of distinct depositional systems and spatial disposition are identified in different evolutionary period of the graben.Sequence Stratigraphic framework of the graben is mainly controlled by structural framework,tectonic movement, sources supply, expanding and contracting cycle of lake, position of depositional center. The key factors are structural framework and tectonic movemeat.Through systematic analysis Of regional tectonic settings, it is recognized that Eogene tectonic sequence of Yitong graben was formed under tenso-shear regime. It includes four sequences indicating four tectonic events attributed to tectonic movement of marginal faults.Neogene tectonic sequence was formed under compresso-shear regime, which includes coarse clastic deposits with a thicknessof 0-500m.Pattern of in the Yitong graben indicates the asymmetrical subsisence of marginal faults along two sides and the complicated structural framework.
文摘Based on the integrated study of the outcrops, the seismic, drilling and logging data of Lianglitage formation in central Tarim Basin, the sequence stratigraphic framework of the platform margin is built, and the Lianglitage formation is divided into 3 third-order sequences. The vertical pattern and lateral distribution for carbonate reef-bank reservoir in sequence stratigraphic framework are analyzed. The reef-bank reservoir mainly developed in highstand system tract of sequence Ssq2, and distributed along the carbonate platform margin of the Middle-Late Ordovician in central Tarim Basin. The mudstone mound, organic reef, granule bank are vertically stacked. Laterally, the area of well shun3-shun4-shun2-shun6 are characterized by multiphase bank reservoir overlapping, and the area of well TZ82 -TZ44 - TZ161 -TZ24 - TZ26 are characterized by multiphase organic reef and bank overlapping. The reef-bank complexes in sequence Ssq2 are the main targets of exploration in central Tarim Basin.
基金funded by the South Oil Exploration and Development Company of PetroChina(2021-HNYJ-010).
文摘The Fushan Depression is one of the petroliferous depressions in the Beibuwan Basin,South China Sea.Previous studies have preliminarily explored the origin and source of crude oils in some areas of this depression.Nevertheless,no systematic investigations on the classification and origin of oils and hy-drocarbon migration processes have been made for the entire petroleum system in this depression,which has significantly hindered the hydrocarbon exploration in the region.A total of 32 mudstone and 58 oil samples from the Fushan Depression were analyzed to definite the detailed oil-source correlation within the sequence and sedimentary framework.The organic matter of third member of Paleogene Liushagang Formation(Els(3))source rocks,both deltaic and lacustrine mudstone,are algal-dominated with high abundance of C_(23)tricyclic terpane and C_(30)4-methylsteranes.The deltaic source rocks occur-ring in the first member(Els_(1))and second member(Els_(2))of the Paleogene Liushagang Formation are characterized by high abundance of C_(19+20)tricyclic terpane and oleanane,reflecting a more terrestrial plants contribution.While lacustrine source rocks of Els_(1)and Els_(2)display the reduced input of terrige-nous organic matter with relatively low abundance of C 19+20 tricyclic terpane and oleanane.Three types of oils were identified by their biomarker compositions in this study.Most of the oils discovered in the Huachang and Bailian Els_(1)reservoir belong to group A and were derived from lacustrine source rocks of Els_(1)and Els_(2).Group B oils are found within the Els_(1)and Els_(2)reservoirs,showing a close relation to the deltaic source rocks of Els_(1)and Els_(2),respectively.Group C oils,occurring in the Els3 reservoirs,have a good affinity with the Els3 source rocks.The spatial distribution and accumulation of different groups of oils are mainly controlled by the sedimentary facies and specific structural conditions.The Els_(2)reservoir in the Yong'an area belonging to Group B oil,are adjacent to the source kitchen and could be considered as the favorable exploration area in the future.
基金Supported by the Key projects of the PetroChina Joint Fund Under the National Natural Science Foundation of China(U23B20154,92255302)Science and Technology Cooperation Project of the Innovation Consortium between PetroChina and Southwest Petroleum University(2020CX010000)Open Fund of the Key Laboratory of Carbonate Reservoirs,China National Petroleum Corporation(RIPED-2024-JS-1804).
文摘This study reconstructed the paleo-uplift and depression pattern within the sequence stratigraphic framework of the Mid-Permian Maokou Formation,Sichuan Basin,investigated its tectono-sedimentary mechanisms and its control on paleogeomorphology and large-sale shoals based on analysis of outcrops,loggings and seismic data.The results show that the Maokou Formation comprises two third-order sequences,six fourth-order sequences(SSQ1-SSQ6),and four distinct slope-break zones developing progressively from north to south.Slope-break zones I-III in the northern basin,controlled by synsedimentary extensional faults,exhibited a NE-trending linear distribution with gradual southeastward migration.In contrast,slope-break zone IV in the southern basin displayed an arcuate distribution along the Emeishan Large Igneous Province(ELIP).The evolutions of these multistage slope-break zones governed the Mid-Permian paleogeomorphy in the Sichuan Basin transformations from a giant,north-dipping gentle slope(higher in the southwest than in the northeast)in the early-stage(SSQ1-SSQ2)to a platform(south)-basin(north)pattern in the middle-stage(SSQ3-SSQ5).Ultimately,a further depression zone developed in the southwestern basin during the late-stage(SSQ6),forming a paleo-uplift bounded by two depressions.The developments of the Mid-Permian paleogeomorphic configuration reflected the combined control by the rapid subduction of the Mianlüe Ocean and the episodic eruptions of the Emeishan mantle plume(or hot spots),which jointly facilitated the formation of extensive high-energy shoal facies belts along slope-break zones and around paleo-volcanic uplifts.
基金financially supported by the China Geological Survey(Grant No.12120115070302, 121201102000150009 and 12120115070301)
文摘In this paper we discuss the timing of final closure of the Paleo-Asian Ocean based on the field investigations of the Carboniferous-Permian stratigraphic sequences and sedimentary environments in southeastern Inner Mongolia combined with the geology of its neighboring areas. Studies show that during the Carboniferous-Permian in the eastern segment of the Tianshan-Hinggan Orogenic System, there was a giant ENE-NE-trending littoral-neritic to continental sedimentary basin, starting in the west from Ejinqi eastwards through southeastern Inner Mongolia into Jilin and Heilongjiang. The distribution of the Lower Carboniferous in the vast area is sparse. The Late Carboniferous or Permian volcanic-sedimentary rocks always unconformably overlie the Devonian or older units. The Upper Carboniferous-Middle Permian is dominated by llttoral-neritic deposits and the Upper Permian, by continental deposits. The Late Carboniferous-Permian has no trace of subduction-collision orogeny, implying the basin gradually disappeared by shrinking and shallowing. In addition, it is of interest to note that the Ondor Sum and Hegenshan ophiolitic melanges were formed in the pre-Late Silurian and pre-Late Devonian respectively, and the Solonker ophiolitic melange formed in the pre-Late Carboniferous. All the evidence indicates that the eastern segment of the Paleo-Asian Ocean had closed before the Late Carboniferous, and most likely before the latest Devonian （Famennian）.
基金supported by the National Basic Research Program (Grant No.2015CB453000)National Key R&D Program of China (Grant No.2018YFC0604200) both from Ministry of Science and Technology of the People’s Republic of China+1 种基金the International Geoscience Programme (IGCP675) which is a joint endeavor of UNESCO and IUGSthe Geological Survey Projects (Grant Nos. DD20160127,DD20160128) from China Geological Survey
文摘Sandstone-type U mineral resources are among the important sources for nuclear energy.The U deposits in the Ordos Basin in China form part of the northern segment of the sandstone-hosted Central Asian Uranium MegaProvince.Two types of mineralizations are recognized in this basin:"phreatic permeable type"and"interlayer permeable type",both exhibiting features equivalent to roll-front subtypes.The"interlayer permeable type"is widely accepted as the dominant mineralization type for sandstone-type uranium deposits within large-scale basins,also designated as the"interlayer oxidation zone type",based on the horizontal color zoning model representing changing redox conditions.Here we synthesize data from several drill holes within the Ordos Basin,which suggest that major Mesozoic tectonic movements controlled the evolution of the sedimentary system in the basin.These tectonic movements contributed to the formation of three angular unconformities and four parallel unconformities as inferred from the stratigraphic relationships.In addition,other features such as vertical color zoning,paleo-channel controlled tabular or lentoid ore bodies(without roll-type)and a group interlayer horizontal zoning of altered minerals are also documented.Sequence stratigraphic analysis indicates that the Ordos Basin generally witnessed four cycles of water level variations during Mesozoic.During the variations,three high water level and three low water level events were recorded.Biological characteristics imply that the Ordos Basin went through multiple arid to humid climatic evolutions during Mesozoic.Combining the newly documented features with some novel concepts on the hydrodynamic mechanism for supergene ore-forming fluids,we propose a metallogenic model which invokes the importance of tectonic movements and water level fluctuations to explain the genesis of uranium deposits along the northern margin of the Ordos Basin.
基金supported by the Major National S&T(Science and Technology) Program of China(2011ZX05009-002)the National Natural Science Foundation of China (41002049, 41030213)the Fundamental Research Funds for the Central Universities in China (2010YD09)
文摘The sequence stratigraphy of the Jurassic coal measures of northwestern China has been studied based on data from outcrop and borehole sections. Because of the geological background and the diversity of basin types, such as isochronisms of coal seams and recognition of key sequence boundaries, it is rare to summarize and correlate sequence structure and framework. The types and recognition characteristics of the sequence boundaries of the Jurassic coal measures are revealed by comparing climatic characteristics, structural styles and the base level cycle. A total of five third-order sequences and 15 systems tracts have been subdivided and the sequence stratigraphic framework has been reconstructed confirming that the thick coals accumulated in the late stage of transgression system tracts of sequence I （SQ I） and sequence III （SQ III）. This idea is of important academic significance for instructing coal resources exploration, and enhancing geological effects of prospecting engineering. It is also of practical significance for guaranteeing construction of the large-scale coal production base in northwestern China, accelerating the westward development of the coal industry stratagem.
基金funded by the National Natural Science Foundation of China (41173066, 41272110 and 41072070)Project Fund of Western Mining Corporation
文摘The Tanjianshan Group,which was previously divided into a,b,c and d formations,has been controversial for a long time.It mainly distributes in the northern margin of Qaidam Basin and is an important early Paleozoic greenschist facies metamorphic volcanic sedimentary rock formation.Detailed field investigation and zircon LA-ICPMS U-Pb dating of the key strata suggest that the original lower part of a Formation （a-1） versus the original middle upper of d Formation （d-3 and d-4）,the original upper part of a Formation （a-2） and b Formation versus the original lower part of d Formation （d-1 and d-2） of Tanjianshan Group are contemporaneous heterotopic facies volcanicclasolite deposit,respectively.The former formations formed during the middle-late Ordovician （463-458 Ma）,while the latter ones formed in the late Ordovician （about 445 Ma）.The original c formation of Tanjianshan Group,which formed after 430 Ma,is similar to the Maoniushan Formation of Kunlun Mountains and north Qaidam Basin.According to the rules of stratigraphic division and naming,new stratum formations of Tanjianshan Group are re-built and divided into Duancenggou （O1-2td）,Zhongjiangou （O2-3tz） and Xitieshan （O3tx） formations.The original c Formation is separated from Tanjianshan Group and is renamed as the Wuminggou Formation （S3-D1W）,which shows a discordant contact with underlying Tanjianshan Group and overlying Amunike Formation （D3a）.The zircon U-Pb age frequency spectrogram of Tanjianshan Group indicates three prominent peaks of 430 Ma,460 Ma and 908 Ma,which is consistent with the metamorphic and magmatic crystallization ages obtained from para-and orthogneisses in north Qaidam HP-UHP metamorphic belt,implying that strong Caledonian and Jinningian tectonic and magmatic events have ever happened in North Qaidam.
基金supported by the SINOPEC Forward Looking Project of China(No.YPH08114)Petrochemical Joint Fund (No.40839910)+1 种基金the Central University of Special Funds of China(No.CUGL120253)the Young Teacher Founding Project of China University of Geosciences(No. CUGQNL0826)
文摘The Carboniferous Karashayi （卡拉沙依） Formation of Tarim basin formed in the epicontinental sea shelf environment where the evolution of basins is pediocratic. As an important reservoir-forming combination, the Carboniferous Karashayi Formation consist of clastic rocks, carbonate rocks and gypsum rocks, which show clear sedimentary cyclicity. According to paleontology research and stratigraphic correlation, Karashayi Formation corresponds to Visean and Serpukhovian in international stratigraphic chart with a time limit about ±27 Ma. The sequence stratigraphic study for the Karashayi Formation is rough because of the difficulty to identify the unconformity surfaces. The current study mostly divides it into three or four 3rd sequences. However, this partition cannot meet the geological crossing correlation. At the theory aspect of sequence stratigraphy, the genesis of the 3rd sequence is also a disputed problem. Cyclostratigraphy study of the Natural Gamma-Ray Log, Spontaneous Potential Log and other logging curves has been taken out by spectrum analysis and wavelet analysis, etc.. For Well Shun6 and Well Zhongl in Tazhong （塔中） and neighbouring area, combined core observation and base level analysis, the Karashayi Formation was divided into 9 or 11 sequence stratigraphic units. Continuous constraints of each sequence is about ±2.40 Ma, corresponding to astronomical cycle formed by three parameters of Earth orbit. Accompanied by the historical division of 3rd sequences, the formation mechanism of 3rd sequences was possibly forced by the 2.4 Ma astro-nomical eccentricity cycles.
