Sedimentary architecture and distribution of intra-platform shoal in sequence framework of Permian Changxing Formation in central Sichuan Basin,SW China

Based on the comprehensive analysis of core, thin section, logging and seismic data, this study carried out the identification and comparison of Permian Changxing Formation sequences, clarified the typical sedimentary architectures of intra-platform shoal, investigated the vertical and horizontal development and distribution of intra-platform shoal in each sequence, and thus established the sedimentary evolution model of shoal body. The study results are reflected in four aspects.First, there are two complete third-order sequences(SQ1 and SQ2) in Changxing Formation in central Sichuan Basin. SQ1 is generally thick in the north and thin in the south, and SQ2 shows a thickness differentiation trend of “two thicknesses and three thinnesses”. Second, the Changxing Formation in central Sichuan Basin mainly develops intra-platform shoal, inter-shoal sea and intra-platform depression subfacies. In the vertical direction, the intra-platform shoal mainly presents two typical sedimentary sequences: stable superposed and high-frequency interbedded. Third, the stable superimposed sedimentary sequence is developed in the shoal belt at the edge of intra-platform depression, which is composed of two shoal-forming periods and located in the highstand systems tracts(HSTs) of SQ1 and SQ2. The high-frequency interbedded sedimentary sequence is developed in the southern shoal belt of intra-platform depression, which is composed of four shoal-forming periods and mainly located in the HST of SQ2. Fourth, during the SQ1 deposition, the intra-platform shoal was mainly developed at the edge of the intra-platform depression on the north side of the study area, and the inter-shoal sea subfacies was mainly developed on the south side. During the SQ2 deposition, the intra-platform shoal was widely developed in the area, forming two nearly parallel intra-platform shoal belts. The study results provide direction and ideas for exploration of Changxing Formation intra-platform shoal reservoirs in central Sichuan Basin.

Sequence Stratigraphy of the Jurassic Coal Measures in Northwestern China

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.

A Climatic Sequence Stratigraphic Model in the Terrestrial Lacustrine Basin:A Case Study of Green River Formation,Uinta Basin,USA

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.

Sequence Stratigraphic Modeling of Sedimentary Basin: Conceptual Model and Application to Erlian and Yinggehai Basins, China

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.

Tertiary Sea Level Changes and Sequence Stratigraphic Framework in East China Sea Shelf Basin

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.

Sequence Stratigraphy of Paleozoic in North Tarim Basin

The Paleozoic sequence stratigraphic system of North Tarim basin is established for the first time in this paper. The sequence stratigraphic system is composed of different orders of sequences, which includes 96 sequences, 31 supersequences, 9 supersequence sets and 4 megasequences. The characteristics of some important sequence boundaries are discussed and their time ranges are suggested, thus enhancing the precision of stratigraphic correlation in North Tarim basin.

Depositional Sequences of Yitong Graben (Eastern China) and Its Response to Transform-Extensional Processes

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.

Stratigraphic Sequence and Tectonic Evolution of Passive Continental Margin of Jinshajiang Belt in Northwestern Yunnan, China

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).

Geometric and Dynamical Characteristics of Sequences in Yitong Graben

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.

Study on Carbonate Sequence Stratigraphy of Ordovician in Northern Ordos Basin

The formation of carbonates is different from that of siliciclastics. The controlling factors, such as the in-situ production of carbonates the transport, local variation in depositional processes and the way of dispersal are unique to carbonates systems, and have resulted in the formation of a wide variety of stratal patterns. The authors believe that all the factors influencing the formation of carbonates, such as the evolution of carbonate platform, transgression and regression, drowning and exposing of the platform, should be taken into consideration during the study of carbonate sequence stratigraphy.This paper attempts to summarize the study procedure in outcrop sequence stratigraphy and to describe the integrated identification of condensed section, first flooding surface and maximum flooding surface, so that the framework of high-resolution sequence stratigraphy can be constructed. During the Sandokan in early Ordovician, a carbonate-siliciclastic ramp was developed in northern Ordos, which changed into a carbonate rimmed shelf or a distally steepened ramp during the Zhuozishan and Kelimoli. It was the break in the Wulalike and Middle Ordovician,changing the sedimentary setting into an aulacogen According to the basin evolution, the authors have established some different idealized models for depositional sequences and systems tracts.

A Glance on the Mineral Deposits and Stratigraphic Sequential Variations and Structures in Different Sections of Indus Basin (Pakistan): New Titanosaurian Sauropod Dinosaurs from the Latest Maastrichtian Vitakri Formation of Pakistan

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.

Carboniferous-Permian Stratigraphy and Sedimentary Environment of Southeastern Inner Mongolia,China:Constraints on Final Closure of the Paleo-Asian Ocean

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）.

Genesis of sandstone-type uranium deposits along the northern margin of the Ordos Basin,China

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.

Redefinition and Formation Age of the Tanjianshan Group in Xitieshan Region, Qinghai

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.

Simulation of the Subsidence and Deposition Processes of the Foreland Basin in the Southwestern Margin of Ordos

Characteristics of deformation in the thrust belt and sequence stratigraphic framework in the foreland basin, structural features of the basin margin, and the episodic thrusting are studied in this paper by combining the eastern Qilian thrust belt and the Late Triassic foreland basin on the southwestern margin of Ordos. On this basis, a geological model and a mechanical model of coupling mechanism were established for the pair of thrust belt and foreland basin, and the subsidence and deposition process of the foreland basin were simulated on given parameters.

Mesozoic “Red Beds” and its Evolution in the Hefei Basin

The Hefei Basin is the largest basin in the North China landmass with complete and well-preserved Mesozoic and Cenozoic strata. In the basin there developed a suite of extremely thick ＂red beds＂ in the Mesozoic. Owing to complex evolution processes and a lack of paleontological traces, there have been controversies regarding the division and correlation of this suite of red beds. Based on results obtained in recent years in drilling, seismic and surface geological investigations and in consideration of relationships between seismic sequences and regional tectonic events, as well as evidence in paleontology, petrology and isotopic dating, this paper preliminarily puts forward the following ideas about the sequence stratigraphic framework of the continental ＂red beds＂ in the Hefei Basin. （1） The Zhougongshan Formation and the Yuantongshan Formation have similar lithologic, geophysical and paleontological characteristics, so we incorporate them into a single formation, called the Yuantongshan Formation, and the original Zhougongshan and Yuantongshan Formations are regarded as the upper and the lower parts of the newly defined Yuantongshan Formation. Its age is the Middle Jurassic; （2） the Zhuxiang Formation belongs to the Upper Jurassic Series and （3） the age of the Xiangdaopu Formation is the Lower Cretaceous. Furthermore, signatures of depositional evolution are analyzed in the paper based on features of seismic reflection, outcrops and drilling data. The Early and Middle Jurassic is characterized by a foreland basin, which is influenced mainly by uplift and longitudinal compression of the Dabieshan Mountains; the Lower Jurassic System has a relatively small depositional area; the Middle Jurassic strata are distributed extensively over the whole basin, marking the summit of basin development; a flexure basin is characteristic of the Late Jurassic, manifesting a joint effect of the Dabieshan and Zhangbaling Mountains with the former being more significant. In the Early Cretaceous, the Xiangdaopu Formation was distributed in the Daqiao depression, evidently affected by extension of the Tanlu fault; in the Late Cretaceous, the Hefei Basin was subjected to dismembering and the Zhangqiao Formation was distributed in the east-west direction along the downthrown side of the fault.

Orbital Cycles Analysis and Its Genesis Significance for the Sequence Hierarchy:A Case Study of Carboniferous Karashayi Formation,Central Tarim Basin

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.

Sequence stratigraphy and depositional sequence interpretation:A case study of“George”Field,offshore Niger Delta,Nigeria

The seismic sequence stratigraphic analysis revealed four depositional sequences(DS-1,DS-2,DS-3 and DS-4).The accompanying systems tracts were interpreted and mapped in the study area based on the log motifs of the reference well and the spatial distribution of the recognized constrained surfaces:maximum flooding surfaces(MFSs),sequence boundaries(SBs)and transgressive surfaces(TSs)on the seismic data.Depositional systems in the study area comprise lowstand systems tracts(LSTs),transgressive systems tracts(TSTs)and highstand systems tracts(HSTs).The LSTs are represented by coeval facies dominated by deposition basinward of the shelf-edge during maximum regression and are characterized by shallow-water deposition from gravity flows and/or traction processes within the shelf-edge or canyon-head delta.The sediments associated with lowstand systems tracts recognized in the study area are the fluvial channel sands and slope fans(SF).The transgressive sand units were interpreted as shoreface sands deposited in the shelf region during rising sea levels.Highstand systems tracts are characterized by intervals of coarsening and shallowing upwards,with both fluvial and deltaic sands prograding laterally into neritic shales.In the study area,the units are very thick.The highstand and lowstand system tracts exhibit blocky log patterns and are associated with the reservoirs while the transgressive system tracts serve as seals to the reservoirs.The environment of sediments deposition in this area is delta plain,shelf,slope to toe of slope.

Tethyan evolution from early Paleozoic to early Mesozoic in southwest Yunnan

The Tethys orogenic belt in SW Yunnan constitutes a critical part of the expansive Tethys-Himalayan tectonic domain.The abundant,well-preserved geologic records make it an ideal area for studying the tectonic evolution of Proto-and Paleo-Tethys.In this paper,we focus on several major tectonic units in SW Yunnan and reconstruct the Tethyan evolution from the early Paleozoic to the early Mesozoic,based on stratigraphic,sedimentologic,and magmatic evidences.The recently discovered early Paleozoic Yunxian-Menghai ophiolitic belt in the Lincang Terrane situated east of the Changning-Menglian Belt represents the suture zone of the Proto-Tethys.The oceanic basin of Proto-Tehtys opened in the latest Neoproterozoic and subsequently began subducting in the late Miaolingian of the Cambrian(about 505 Ma).From the late Late Ordovician to the ealiest Silurian(about 450–442 Ma),the Proto-Tethys basin gradually closed resulting in the collision of the continental plates on both sides of the Proto-Tethyan ocean.The main collision stage occurred in the early Silurian(about 442–430 Ma)and the postcollision stage lasted from the mid-Silurian to the early Carboniferous(430–355 Ma).The earliest record of Paleo-Tethyan oceanic crust was generated in the late Devonian,and the ocean was then subducted in an eastward direction in the middle Late Carboniferous(about 310 Ma).The initial collision stage in the Paleo-Tethys took place at the end of the Permian(about 253Ma),and the main stage of the collision persisted into the early Ladinian(about 253–238 Ma).This was followed by postcollision extension from the late Ladinian to the early Jurassic(ca.238–196 Ma).We suggest that the opening of Paleo-Tethyan Ocean in SW Yunnan was a result of the extensional rift basin of the Proto-Tethys.Additionally,the activity of the Manxin mantle plume was likely a crucial factor in the rapid expansion of the Paleo-Tethyan Ocean.

The Cenozoic sedimentary environment and sedimentary filling evolution of Wan'an Basin in the western South China Sea

As one of the basins with extremely abundant oil and gas resources in South China Sea,the Wan'an Basin has attracted great attention from domestic and international geologists and hydrocarbon explorers.Currently,the sequence stratigraphic framework,distribution of sedimentary systems and sedimentary filling evolution of the Wan'an Basin are still not clear,consequently,it bring some difficulties for hydrocarbon exploration.Based on the palaeobios,well drilling,well logging,and seismic and other data,the sequence stratigraphic framework of the Wan'an Basin is established,and the sequence interfaces of T100,T60,T50,T40 and T30 in this study are identified.On this basis,the sedimentary environment and sedimentary filling evolution of the Wan'an Basin are systematically analyzed.The results show that the basin had experienced three tectonic evolution periods since Cenozoic,i.e.,the OligoceneeEarly Miocene extensional fault-depression period,Middle Miocene strike-slip reformation period and Late Miocene eQuaternary regional depression period.Thereinto,the provenance in the extensional faultdepression period(OligoceneeEarly Miocene)was mainly from the western uplift of the basin,where the deltaeshore-shallow lacustrineebathylimnetic sedimentary system during Early Oligocene and delta elittoral-neritic sedimentary system during Late OligoceneeEarly Miocene were developed respectively.The provenance during the strike-slip reformation period(Middle Miocene)was still mainly from the western uplift of the basin,where the deltaelittoral-neriticecarbonate platform sedimentary system was developed,and the carbonate platform began to develop abundantly.The provenance during the regional depression period(Late MioceneeQuaternary)is mainly supplied by input of the western distal large rivers,the deltaelittoral-shallow seaecarbonate platformebathyal sea sedimentary system was developed in the Late Miocene,and the shelf-margin deltaecontinental slopeebathyal sea sedimentary system was developed during Pliocene-Quaternary.Therefore,the Wan'an Basin has a favorable hydrocarbon resource potential.