Apatite(U-Th)/He and fission track dating and tectono-thermal history modeling were used to reconstruct the Meso-Cenozoic tectonic evolution of the Huangling paleo-uplift in the Middle Yangtze Block,South China.The te...Apatite(U-Th)/He and fission track dating and tectono-thermal history modeling were used to reconstruct the Meso-Cenozoic tectonic evolution of the Huangling paleo-uplift in the Middle Yangtze Block,South China.The tectono-thermal evolution showed different tectonic exhumation/subsidence processes in the tectonic evolution of the foreland basin.The apatite(U-Th)/He ages ranged from 31.3 to 77.8 Ma,recording the thermal events of the Cenozoic Himalayan movement and indicating progressive exhumation extending from the southeast to the northwest.The thermal information of the Mesozoic Yanshan movement period was recorded by the apatite fission track age with a pooled age of 93.8 to 147 Ma.The exhumation of the Huangling paleo-uplift began in the Late Jurassic.The tectono-thermal evolution was characterized by a rapid uplift during 140-115 Ma,subsidence during 115-60 Ma,a rapid uplift during 40-30 Ma,and a slow uplift from 30 Ma to the present.The western Hunan-Hubei Depression was exhumed in the Middle Jurassic,and the tectono-thermal evolution was characterized by a rapid uplift during 160-135 Ma,a slow uplift during 135-50 Ma,a rapid uplift during 50-25 Ma,and a slow uplift from 25 Ma to the present.This Cenozoic exhumation was a response to the far field effect of the eastward growth of the Tibetan Plateau.The Cretaceous basins exposed in the surrounding areas of the Huangling paleo-uplift(Zigui basin,Yichang slope,and Huaguoping synclinorium)are foreland basins formed by the bi-directional compression of the Qinling-Dabie orogenic belt and the Xuefengshan intracontinental deformation system.展开更多
Based on 2D and 3D seismic data,the latest drilling data and field outcrop data of the northern slope of the Central Sichuan paleo-uplift,the structural analysis method is used to analyze unconformity development char...Based on 2D and 3D seismic data,the latest drilling data and field outcrop data of the northern slope of the Central Sichuan paleo-uplift,the structural analysis method is used to analyze unconformity development characteristics and fault characteristics during the key structural transformation period,discussing the influence of the structural characteristics on the hydrocarbon accumulation of deep carbonate rocks.The results show that:(1)The two key unconformities of the Tongwan and Caledonian periods were primarily developed in deep carbonate rocks.Firstly,Tongwan’s unconformities are characterized by regional disconformities between the second and third members of the Dengying Formation,the top formation of the Sinian and the lower Cambrian,strips of which zigzag through the north and south sides of the study area.Secondly,the Caledonian unconformity is characterized by a regional unconformable contact between the lower Permian and the ower Paleozoic strata.From NE to SW,the age of the strata,which were subject to erosion,changes from new to old,the denudation distribution showing as a nose-shaped structure which inclines towards the ENE.(2)Boundary fault and transtensional strike-slip faults developed in the Sinian to Paleozoic strata.In profile,there are three types of structural styles:steep and erect,flower structures,’Y’and reversed’Y’type faults.In plane view,the Sinian developed extensional boundary faults extending in an almost NS direction,strike-slip faults developing and extending linearly in approximately EW,WNW and NE strikes in the Cambrian,with characteristically more in the south and less in the north.(3)The faults in the northern slope show obvious zonal deformations in transverse view as well as significant stages and stratified activity in a longitudinal direction.Among them,the activity of faults in the Sinian was the strongest,followed by the activity in the Cambrian period,the activity intensity of faults in the Permian period being the weakest.This fault activity can be divided into four periods:Sinian,Cambrian-Permian,the early Indosinian period and the late Indosinian-Himalayan period,the transtensional strikeslip faults being the products of oblique extensions of pre-existing weak zones in the Xingkai and Emei taphrogenesis,with a particular inheritance in the main faults.(4)Combined with hydrocarbon accumulation factors,it is considered that the epigenetic karstification of the Tongwan and Caledonian unconformities in the northern slope controlled the formation and distribution of carbonate karst reservoirs over a large area,also acting as a good pathway for oil and gas migration.The extensional faults developed at the margin of the NS trending rift,controlling the sag-platform sedimentary pattern in the Dengying Formation of the Sinian.Strike-slip faults in NE,WNW and ENE directions may control the microgeomorphological pattern inside the platform and intensify the differential distribution of grain beach facies.The multi-stage hereditary activity of strike-slip faults not only improved the porosity and permeability of the reservoirs,but also acted as the main channel of oil and gas migration,providing favorable conditions for the development of the current multi-layer gasbearing scenario in the northern slope of the Central Sichuan Basin.展开更多
ABSTRACT： Twenty unconformities, primarily superimposed types, were identified based on inter pretation of a 46 000 km seismic profile combined with data from over 40 drilling wells. These respec tively correspond to...ABSTRACT： Twenty unconformities, primarily superimposed types, were identified based on inter pretation of a 46 000 km seismic profile combined with data from over 40 drilling wells. These respec tively correspond to the main tectonic evolution stages and the boundaries between those stages. Re construction of the original depths of eroded strata was conducted for the Middle Caledonian, Early Hercynian, Late Hercynian, Indosinian, Early Yanshanian and Late Yanshanian unconformities using the virtual extrapolation of seismic reflection. Eroded strata thicknesses were also calculated for indi vidual periods and intervals. Based on the reconstructed data, in combination with data from research on sedimentary facies, a paleogeomorphological profile was constructed for different tectonic evolution stages of the basin during the Early Paleozoic. The profile indicates the presence of obvious regularity in the temporal and spatial evolution of these unconformities. Based on the characteristics of paleouplift evolution and postlayering reconstruction, the paleouplifts were divided into inherited （e.g., Tazhong （塔中）, residual （e.g., North Tarim） and active （e.g., Southwest Tarim and Bachu （巴楚） types. The huge North Tarim uplift represents a typical form of residual paleouplift. The Paleozoic strata in the upper layers of the uplift is in poor condition for reservoir accumulation and preservation; however, the Upper MesozoicCenozoic structural layer can form a secondary reservoir that is rela tively rich in oil and gas. Furthermore, the flank slope area of the uplift is always a key source for oil and gas collection and the most advantageous position for the formation of the original reservoir. The Tazhong paleouplift has been stable since its formation in the Late Ordovician, where petroleum accumulation has been distributed not only in the uplift, but also in the deep and slope belts of the uplift. Important breakthroughs in petroleum exploration of the slope break in the North Tazhong area datingback to the Paleozoic have further confirmed the enrichment of oil and gas in this type of uplift. The Southwest Tarim paleouplift is a buried type, which has given it favorable properties for hydrocarbon migration over a long time. An open question is whether the large amount of oil and gas accumulated here was transported to the current Bachu uplift.展开更多
Based on the outcrop survey,3D seismic data interpretation,drilling data analysis,the structural patterns and distribution of fault damage zones in carbonate strata of Tazhong Paleo-uplift were established to reveal t...Based on the outcrop survey,3D seismic data interpretation,drilling data analysis,the structural patterns and distribution of fault damage zones in carbonate strata of Tazhong Paleo-uplift were established to reveal the oil and gas enrichment law in the fault damage zones.The following findings were reached:(1)Through the filed survey,the fault damage zone system consists of fault core,damage zone with branch fault and fracture network.Affected by the active nature of the major faults,the fault damage zones differ in planar pattern and scale along the major faults.(2)3D seismic profiles reveal that there are three types of fault damage zones in carbonate strata in Tazhong paleo-uplift,strike-slip fault damage zones,thrust fault damage zones and superimposed fault damage zones.Featuring3 flowers and 3 root belts in vertical,the strike-slip fault damage zone can be subdivided into linear type,oblique type,feather type and horsetail type in plane.Thrust fault damage zones can be further divided into fault anticline type,anticline type and slope type.As the superimposition result of the above two kinds of fault damage zones,superimposed fault damage zones appear in three patterns,intersect type,encompassment type and penetrating type.(3)Cores from wells and geochemical data show oil and gas may migrate along the major fault and laterally.The feather type in strike-slip fault system,fault anticline type in thrust fault damage zone and intersect type in superimposed fault damage zone are possible sites for high production and efficiency wells.展开更多
Based on drilling data of JT1 and CS1,outcrop profiles and seismic data,the sedimentary pattern,space configuration of source-reservoir-cap combinations and paleouplift evolution characteristics of the Cambrian Lower ...Based on drilling data of JT1 and CS1,outcrop profiles and seismic data,the sedimentary pattern,space configuration of source-reservoir-cap combinations and paleouplift evolution characteristics of the Cambrian Lower Canglangpu Member in the central Sichuan paleouplift have been investigated to determine the favorable exploration zones.Controlled by Deyang-Anyue rift,the Lower Canglangpu Member features differential characteristics from east to west in sedimentary framework.In the west side of the Deyang-Anyue rift,this member is composed of clastic sediments,while in the east side of the Deyang-Anyue rift,it is fresh water shelf sediments,with grain beaches occurring along edges of the depressions,shelf and lagoon.Among the beaches,the dolomitic ones are mainly distributed around the depression edge and in the north of the lagoon.The beach sediments could become high quality reservoirs under the effect of karstification.Underlying the Lower Canglangpu Member is the widespread source rock of the Qiongzhusi Formation,so oil and gas generated by the Qiongzhusi Formation source rock can directly charge into the beach reservoirs.The sandy mudstone of the Upper Canglangpu Member can serve as the caprock of the Lower Canglangpu Member reservoir.The dolomitic beaches are located at the higher part of the paleo-uplift during the main accumulation period,with good hydrocarbon accumulation elements.Blocks PT1-CS1,HT1-GT2 and east GT2 are favorable exploration zones.展开更多
This paper depicts the distribution of the Wushenqi paleo-uplift in the Ordos Basin by using the latest drilling and seismic data, and analyzes the tectonic evolution of the paleo-uplift with the support of Bischke cu...This paper depicts the distribution of the Wushenqi paleo-uplift in the Ordos Basin by using the latest drilling and seismic data, and analyzes the tectonic evolution of the paleo-uplift with the support of Bischke curve and balanced section. The compressional Wushenqi paleo-uplift which developed in the Early Caledonian orogeny(Huaiyuan orogeny) is approximately a ellipse extending in S-N direction. Its long axis is about 194 km and short axis is about 55-94 km in nearly W-E direction. The denudation thickness and area of the Cambrian in the core are 170-196 m and 11 298 km^(2), respectively. It was mainly formed during the Huaiyuan orogeny according to the chronostratigraphic framework. It was in the embryonic stage in the Middle-Late Cambrian, denuded after developed obviously at the end of Late Cambrian. The paleo-uplift of the 3rd member of the Ordovician Majiagou Formation was reactivated and reduced in area. In the sedimentary period of the Ma 4 Member-pre-Carboniferous, the paleo-uplift experienced non-uniform uplift and denudation. It entered the stable period of burial and preservation in the Carboniferous and later period. The Wushenqi paleo-uplift was formed on the weak area of the basement and tectonic belts, into an compressional structure with irregular morphology, under the control of the non-coaxial compression in the south and north and the stress transmitted by the uplift in the basin. The Wushenqi paleo-uplift has a controlling effect on the sedimentary reservoirs and hydrocarbon accumulation.展开更多
Great breakthrough recently achieved in the SinianeLower Paleozoic gas exploration in the LeshaneLongnu¨si paleo-uplift,Sichuan Basin,has also made a common view reached,i.e.,large-scale paleo-uplifts will be the...Great breakthrough recently achieved in the SinianeLower Paleozoic gas exploration in the LeshaneLongnu¨si paleo-uplift,Sichuan Basin,has also made a common view reached,i.e.,large-scale paleo-uplifts will be the most potential gas exploration target in the deep strata of this basin.Apart from the above-mentioned one,the other huge paleo-uplifts are all considered to be the ones formed in the post-Caledonian period,the impact of which,however,has rarely ever been discussed on the SinianeLower Paleozoic oil and gas reservoir formation.In view of this,based on outcrops,drilling and geophysical data,we analyzed the SinianeLower Paleozoic tectonic setting and sedimentary background in the East Sichuan Basin,studied the distribution rules of reservoirs and source rocks under the control of paleo-uplifts,andfinally discussed,on the basis of structural evolution analysis,the conditions for the formation of SinianeLower Paleozoic gas reservoirs in this study area.The followingfindings were achieved.(1)The DazhoueKaijiang inherited uplift in NE Sichuan Basin which was developed before the Middle Cambrian controlled a large area of Sinian and Cambrian beach-facies development.(2)Beach-facies reservoirs were developed in the upper part of the paleo-uplift,while in the peripheral depression belts thick source rocks were developed like the Upper Sinian Doushantuo Fm and Lower Cambrian Qiongzhusi Fm,so there is a good sourceereservoir assemblage.(3)Since the Permian epoch,the DazhoueKaijiang paleo-uplift had gradually become elevated from the slope zone,where the Permian oil generation peak occurred in the slope or lower and gentle uplift belts,while the Triassic gas generation peak occurred in the higher uplift belts,both with a favorable condition for hydrocarbon accumulation.(4)The lower structural layers,including the Lower Cambrian and its underlying strata,in the East Sichuan Basin,are now equipped with a large-scale uplift with a simple structural configuration,above which a complete local structural trap was well developed with a good preserving condition.In conclusion,there are good forming conditions for hydrocarbon reservoirs in the SinianeLower Paleozoic strata in the DazhoueKaijiang paleo-uplift,East Sichuan Basin,in the higher parts of which the well-developed beach-facies reservoirs occupy an area of 8000 km2 and will be the next important gas exploration target in this basin.展开更多
Based on well horizon calibration,the typical seismic profiles in southwestern Tarim Basin were interpreted systematically,regional geological sections were established,and the regional denudation thickness of each te...Based on well horizon calibration,the typical seismic profiles in southwestern Tarim Basin were interpreted systematically,regional geological sections were established,and the regional denudation thickness of each tectonic period was restored.On this basis,the plane morphology maps of ancient structures of the Cambrian pre-salt dolomites in different periods were compiled,and the spatial distribution,development,evolution and migration of paleo-uplift in the late Early Paleozoic were analyzed.In the late Early Paleozoic,there existed a unified regional paleo-uplift widely distributed in southwestern Tarim Basin,which is called the southwestern Tarim plaeo-uplift.The“Tarim SW paleo-uplift”and“Hetian paleo-uplift”proposed in previous literatures are not independent,but the result of the spatio-temporal migration and evolution of the southwestern Tarim paleo-uplift identified in this paper.The southwestern Tarim paleo-uplift emerged at the end of Middle Ordovician,and took its initial shape with increased amplitude in the Late Ordovician.During the Silurian,the southwestern Tarim paleo-uplift rose steadily and expanded rapidly to the east,incorporating Pishan-Hetian and other areas,with the structural high locating in the Pishan-Hetian area.During the Devonian,the southwestern Tarim paleo-uplift began to shrink gradually,to a limited range in the Pishan-Hetian area in the southern part of the basin.During the Carboniferous,the southwestern Tarim paleo-uplift became an underwater uplift,that is,the paleo-uplift gradually died out.The southwestern Tarim paleo-uplift belongs to the forebulge of the southwestern Tarim foreland basin in the late Early Paleozoic,and its formation and evolution are related to the early Paleozoic orogeny of the West Kunlun orogenic belt in the south of the Tarim Basin.The migration of the southwestern Tarim paleo-uplift from the northwestern part of the southwestern Tarim Basin to the Pishan-Hetian area indicates the early Paleozoic orogenic process of the West Kunlun orogenic belt,which started in the western section at the end of Middle Ordovician and extended from west to east in a“scissor”style.The migration and evolution of the southwestern Tarim paleo-uplift controlled the development of unconformities at the end of Middle Ordovician,the end of Late Ordovician,and the end of Middle Devonian,and the spatial distribution of dissolved fracture-cave reservoirs in weathered crust below the unconformities in the southwest of Tarim Basin.The migration of the structural high of the southwestern Tarim paleo-uplift also played an important role in controlling the development of dissolved fracture-cave reservoirs in weathered crust.展开更多
Intra-platform carbonate mound-bank body reservoirs is an important type of oil and gas reservoirs in the Sichuan Basin,and paleo-uplift plays an important role in the scale formation process of scale intra-platform m...Intra-platform carbonate mound-bank body reservoirs is an important type of oil and gas reservoirs in the Sichuan Basin,and paleo-uplift plays an important role in the scale formation process of scale intra-platform mound-bank body reservoir.So far,however,the control action of paleo-uplift on the formation and distribution of intra-platform mound-bank body reservoirs has not been understood clearly enough,which restricts the oil and gas exploration progress of this type of reservoirs.In order to provide the basis for oil and gas exploration deployment,this paper analyzes the formation and evolution of four paleo-uplifts developed in the cratonic stage of the Sichuan Basin.On this basis,the genetic mechanisms and characteristics of scale intra-platform mound-bank body reservoirs are studied,and the characteristics and distribution of large-scale intra-platform reservoirs in the main series of strata are analyzed.And the following research results were obtained.First,the four paleo-uplifts developed in the Sichuan Basin plays an important constructive role in the formation of scale intra-platform mound-bank body reservoirs.Their control actions mainly include sedimentation and diagenesis.Along with the sea level change,they control the sedimentation scale and distribution range of intra-platform mound-bank body.They control the interlayer karstification and quasi-syngenetic dolomitization of intra-platform mound-bank body.And together with the late tectonic movement,they control the weathering crust karstification and fracturing of intra-platform mound-bank body.Second,Gaoshiti-Moxi paleo-uplift mainly controls the formation of the large-scale intra-platform mound-bank body reservoirs in the Sinian Dengying Formation and the Cambrian Longwangmiao Formation,Leshan-Longnüsi paleo-uplift mainly controls the formation of the scale intra-platform mound-bank body reservoir in the Cambrian Xixiangchi Formation and the Carboniferous Huanglong Formation,while Luzhou and Kaijiang paleo-uplifts mainly control the formation of the scale intra-platform mound-bank body reservoirs in the Triassic Jialingjiang Formation and Leikoupo Formation.Third,six sets of scale intra-platform reservoirs are developed in the Sichuan Basin.The intra-platform mound-bank body reservoirs of Dengying Formation and Longwangmiao Formation are mainly distributed in the core of paleo-uplift,and the other four sets are mainly distributed in the slope of paleo-uplift.In conclusion,these research results provide the geological basis for the prediction of scale intra-platform mound-bank body reservoirs in the Sichuan Basin and they are of important theoretical and practical significance.展开更多
Various types of paleo-uplifts with different characteristics are developed in the Tarim Basin.Previously,there were multiple opinions on the pale-uplifts origins and structural evolution,so the oil and gas exploratio...Various types of paleo-uplifts with different characteristics are developed in the Tarim Basin.Previously,there were multiple opinions on the pale-uplifts origins and structural evolution,so the oil and gas exploration ideas and deployment in the Tarim Basin were not developed smoothly.In this paper,regional seismic interpretation and structural analysis were carried out on the deep marine carbonate rocks in this basin based on the new seismic and drilling data.Then combined with the structural denudation results,the paleo-structural frameworks were reconstructed.And finally,the formation stage and main controlling factors of paleo-uplifts were discussed.It is shown that the Middle Ordovician is the key period when regional extension was converted to compression in this basin,so stratigraphic,sedimentary and structural differences occurred.Before the deposition of Yijianfang Fm in late Middle Ordovician,three carbonate paleo-uplifts(i.e.,the Northern,Central and SW Tarim paleo-uplifts)begun to appear,and they were all broad-folded paleo-uplifts of nearly E-W striking and were formed at the same stage.The distribution and development of the Phanerozoic uplifts in this basin are restricted by the Northern and Southern Tarim basement paleuplifts of nearly E-W striking which were developed during the Precambrian.It is indicated that all the three paleo-uplifts are compressional paleo-uplifts originated from the convergence of the southern plate margin based on the basement paleo-uplifts and they are all characterized by similar structural characteristics and inherited formation and evolution.The current differences of paleo-uplifts are controlled by multi-stage intense structural reformation since the Silurian.It is concluded that the oil and gas exploration potential is immense in the carbonate reservoirs of well-preserved deep paleo-structural zones in a larger area.展开更多
Since the Anyue Gasfield,located in the central Sichuan paleo-uplift of the Sichuan Basin,was discovered,great efforts have been made to work on natural gas exploration and discovery in the SinianeLower Paleozoic in t...Since the Anyue Gasfield,located in the central Sichuan paleo-uplift of the Sichuan Basin,was discovered,great efforts have been made to work on natural gas exploration and discovery in the SinianeLower Paleozoic in the north slope of present paleo-uplift which has similar depositional settings.It is verified by the breakthrough of natural gas exploration in the second Member of Upper Sinian Dengying Formation in the north slope of central Sichuan paleo-uplift by wildcat well PT1 and the new sign of natural gas exploration in the Canglangpu Formation of Lower Cambrian and the fourth Member of Dengying Formation by Well JT1 that there are also favorable conditions for the formation of large-scale gas province in the north slope.In order to determine the natural gas exploration potential of SinianeLower Paleozoic in the central Sichuan paleo-uplift and provide the guidance for the following exploration deployment,this paper analyzed the petroleum geological conditions of SinianeLower Paleozoic in the north slope.And the following research results were obtained.First,the marginal platform belts in the second and the fourth Member of Sinian Dengying Formation in the north slope are basically separated areally,and they are superior to the Gaoshiti-Moxi area in terms of marginal platform width and sedimentary thickness and are intrinsically advantageous in sedimentation.Second,compared with the Gaoshiti-Moxi area,the reservoirs of Sinian Dengying Formation in the north slope are better in reservoir conditions,and many sets of quality reservoirs are developed vertically in Siniane-Cambrian.Third,hydrocarbon accumulation elements of Sinian Dengying Formation are better allocated in the north slope.Lithological traps are developed with a larger cumulative area.Wells JT1 and PT1 verify that there is gas in the lithological trap of the fourth and the second Member of Dengying Formation and large-scale lithological gas reservoirs are developed in the slope setting.In conclusion,compared with the Gaoshiti-Moxi area,the Sinian-Lower Paleozoic in the north slope is superior in petroleum geological conditions and has the advantage of multi-layer stereoscopic exploration vertically,presenting a great natural gas exploration potential and promising exploration prospects,so it is a new important strategic zone of conventional natural gas exploration in the Sichuan Basin.展开更多
The Kulun region is located in the eastern Bainaimiao arc belt on the southeastern margin of the Central Asian Orogenic Belt(CAOB),adjacent to the North China Craton(NCC)to the south.This region records the closure of...The Kulun region is located in the eastern Bainaimiao arc belt on the southeastern margin of the Central Asian Orogenic Belt(CAOB),adjacent to the North China Craton(NCC)to the south.This region records the closure of the PaleoAsian Ocean during the Paleozoic to early Mesozoic and is key to study the tectonic evolution of the northern margin of the NCC.We conducted zircon U-Pb geochronology and Hf isotope analysis of volcanic-sedimentary and intrusive rocks in the Kulun region.The volcanic-sedimentary rocks were previously assigned an early Carboniferous age,but include volcanic rocks with ages of 267–266 Ma and sedimentary rocks with youngest detrital zircon age peaks of 265–244 Ma,which were intruded by a granite with an age of 242 Ma.This indicates that these rocks are actually middle Permian to Middle Triassic in age(267–242Ma)and correspond to the Qingfengshan and Liujiagou formations.Moreover,two volcanic rock samples have highεHf(t)values(+1.6 to+16.1)and relatively young two-stage Hf model ages(1095–327 Ma),indicating their sources associated with the CAOB.The age spectra and Hf isotopic characteristics of detrital zircons from the sedimentary rocks suggest that,during the middle Permian to Middle Triassic,the sedimentary provenance in the Kulun region was mainly the CAOB.However,by the Early Jurassic,the provenance changed to the NCC(i.e.,the Inner Mongolia Paleo-uplift,IMPU).This result,combined with the development of a series of conglomerates on the northern margin of the NCC in the Late Triassic(i.e.,Xingshikou,Xiaoyingzi,and Xiaohekou formations),indicates the Kulun region experienced an abrupt change in paleogeography during the Late Triassic,with the IMPU undergoing significant uplift and thus becoming the main sediment source in the Kulun region.Based on the Late Triassic alkaline igneous belt(235–215 Ma)in the IMPU,we speculate that this uplift was caused by detachment of the southward-subducting Paleo-Asian oceanic plate,which occurred in a post-orogenic extensional setting.The boundary between the NCC and CAOB(i.e.,the Bainaimiao arc belt)in the Kulun region is defined by the newly identified Paleoproterozoic granites(1.8 and 1.6 Ga)and our zircon geochronology and Hf isotope data.展开更多
The sedimentary environment of the Upper Triassic in the southeastern Sichuan Basin is obviously controlled by Luzhou paleo-uplift(LPU).However,the influence of paleo-uplift on the sedimentary patterns of the initial ...The sedimentary environment of the Upper Triassic in the southeastern Sichuan Basin is obviously controlled by Luzhou paleo-uplift(LPU).However,the influence of paleo-uplift on the sedimentary patterns of the initial stages of this period in the southeastern Sichuan Basin has not yet been clear,which has plagued oil and gas exploration and development.This study shows that there is a marine sedimentary sequence,which is considered to be the first member of Xujiahe Formation(T_(3)X^(1))in the southeastern Sichuan Basin.The development of LPU resulted in the sedimentary differences between the eastern and western Sichuan Basin recording T_(3)X^(1)and controlled the regional sedimentary pattern.The western part is dominated by marine sediments,but the eastern paleo-uplift area is dominated by continental sedimentation in the early stage of T_(3)X^(1),and it begins to transform into a marine sedimentary environment consistent with the whole basin in the late stage of the period recorded by the Xujiahe Formation.The evidences are as follows:(1)time series:based on the cyclostratigraphy analysis of Xindianzi section and Well D2,in the southeastern Sichuan Basin,the period of sedimentation of the Xujiahe Formation is about 5.9 Ma,which is basically consistent with the Qilixia section,eastern Sichuan basin,where the Xujiahe Formation is widely considered to be relatively complete;(2)distribution and evolution of palaeobiology:based on analysis of abundance evolution of major spore-pollen,many land plant fossils are preserved in the lower part of T_(3)X^(1),indicates the sedimentary environment of continental facies.In the upper part of T_(3)X^(1),the fossil of terrestrial plants decreased,while the fossil of marine and tidal environment appeared,this means that it was affected by the sea water in the late stages of T_(3)X^(1);(3)geochemistry:calculate the salinity of water from element indicates that the uplift area is continental sedimentary environment in the early stage of T_(3)X^(1),while the central and western areas of the basin are marine sedimentary environment.Until the late stage of T_(3)X^(1),the southeast of the basin gradually turns into marine sedimentary environment,consisting with the whole basin;(4)types of kerogen:type III kerogen representing continental facies was developed in the early stage of T_(3)X^(1)in the uplift area,and type II kerogen,representing marine facies,was developed in the late stage;while type II kerogenwas developed in the central and western regions of the basin as a whole in T_(3)X^(1).This study is of great significance for understanding of both stratigraphic division and sedimentary evolution providing theoretical support for the exploration and development of oil and gas.展开更多
基金funded by the National Natural Science Foundation of China(U2244208,42302138)China Postdoctoral Science Foundation(No.2020M733869)Science Foundation of China University of Petroleum,Beijing(No.2462023XKBH003).
文摘Apatite(U-Th)/He and fission track dating and tectono-thermal history modeling were used to reconstruct the Meso-Cenozoic tectonic evolution of the Huangling paleo-uplift in the Middle Yangtze Block,South China.The tectono-thermal evolution showed different tectonic exhumation/subsidence processes in the tectonic evolution of the foreland basin.The apatite(U-Th)/He ages ranged from 31.3 to 77.8 Ma,recording the thermal events of the Cenozoic Himalayan movement and indicating progressive exhumation extending from the southeast to the northwest.The thermal information of the Mesozoic Yanshan movement period was recorded by the apatite fission track age with a pooled age of 93.8 to 147 Ma.The exhumation of the Huangling paleo-uplift began in the Late Jurassic.The tectono-thermal evolution was characterized by a rapid uplift during 140-115 Ma,subsidence during 115-60 Ma,a rapid uplift during 40-30 Ma,and a slow uplift from 30 Ma to the present.The western Hunan-Hubei Depression was exhumed in the Middle Jurassic,and the tectono-thermal evolution was characterized by a rapid uplift during 160-135 Ma,a slow uplift during 135-50 Ma,a rapid uplift during 50-25 Ma,and a slow uplift from 25 Ma to the present.This Cenozoic exhumation was a response to the far field effect of the eastward growth of the Tibetan Plateau.The Cretaceous basins exposed in the surrounding areas of the Huangling paleo-uplift(Zigui basin,Yichang slope,and Huaguoping synclinorium)are foreland basins formed by the bi-directional compression of the Qinling-Dabie orogenic belt and the Xuefengshan intracontinental deformation system.
基金funded by the National Key Research and Development Program‘Deep Land Resources Exploration and Exploitation’special project(2017YFC0603106)the Project of Science and Technology Department of the Southwest Oil and Gas Field Company,Petrochina(20210301-02)。
文摘Based on 2D and 3D seismic data,the latest drilling data and field outcrop data of the northern slope of the Central Sichuan paleo-uplift,the structural analysis method is used to analyze unconformity development characteristics and fault characteristics during the key structural transformation period,discussing the influence of the structural characteristics on the hydrocarbon accumulation of deep carbonate rocks.The results show that:(1)The two key unconformities of the Tongwan and Caledonian periods were primarily developed in deep carbonate rocks.Firstly,Tongwan’s unconformities are characterized by regional disconformities between the second and third members of the Dengying Formation,the top formation of the Sinian and the lower Cambrian,strips of which zigzag through the north and south sides of the study area.Secondly,the Caledonian unconformity is characterized by a regional unconformable contact between the lower Permian and the ower Paleozoic strata.From NE to SW,the age of the strata,which were subject to erosion,changes from new to old,the denudation distribution showing as a nose-shaped structure which inclines towards the ENE.(2)Boundary fault and transtensional strike-slip faults developed in the Sinian to Paleozoic strata.In profile,there are three types of structural styles:steep and erect,flower structures,’Y’and reversed’Y’type faults.In plane view,the Sinian developed extensional boundary faults extending in an almost NS direction,strike-slip faults developing and extending linearly in approximately EW,WNW and NE strikes in the Cambrian,with characteristically more in the south and less in the north.(3)The faults in the northern slope show obvious zonal deformations in transverse view as well as significant stages and stratified activity in a longitudinal direction.Among them,the activity of faults in the Sinian was the strongest,followed by the activity in the Cambrian period,the activity intensity of faults in the Permian period being the weakest.This fault activity can be divided into four periods:Sinian,Cambrian-Permian,the early Indosinian period and the late Indosinian-Himalayan period,the transtensional strikeslip faults being the products of oblique extensions of pre-existing weak zones in the Xingkai and Emei taphrogenesis,with a particular inheritance in the main faults.(4)Combined with hydrocarbon accumulation factors,it is considered that the epigenetic karstification of the Tongwan and Caledonian unconformities in the northern slope controlled the formation and distribution of carbonate karst reservoirs over a large area,also acting as a good pathway for oil and gas migration.The extensional faults developed at the margin of the NS trending rift,controlling the sag-platform sedimentary pattern in the Dengying Formation of the Sinian.Strike-slip faults in NE,WNW and ENE directions may control the microgeomorphological pattern inside the platform and intensify the differential distribution of grain beach facies.The multi-stage hereditary activity of strike-slip faults not only improved the porosity and permeability of the reservoirs,but also acted as the main channel of oil and gas migration,providing favorable conditions for the development of the current multi-layer gasbearing scenario in the northern slope of the Central Sichuan Basin.
基金supported by the Key Program of National Natural Science Foundation of China (Nos. 41130422,40572067)
文摘ABSTRACT： Twenty unconformities, primarily superimposed types, were identified based on inter pretation of a 46 000 km seismic profile combined with data from over 40 drilling wells. These respec tively correspond to the main tectonic evolution stages and the boundaries between those stages. Re construction of the original depths of eroded strata was conducted for the Middle Caledonian, Early Hercynian, Late Hercynian, Indosinian, Early Yanshanian and Late Yanshanian unconformities using the virtual extrapolation of seismic reflection. Eroded strata thicknesses were also calculated for indi vidual periods and intervals. Based on the reconstructed data, in combination with data from research on sedimentary facies, a paleogeomorphological profile was constructed for different tectonic evolution stages of the basin during the Early Paleozoic. The profile indicates the presence of obvious regularity in the temporal and spatial evolution of these unconformities. Based on the characteristics of paleouplift evolution and postlayering reconstruction, the paleouplifts were divided into inherited （e.g., Tazhong （塔中）, residual （e.g., North Tarim） and active （e.g., Southwest Tarim and Bachu （巴楚） types. The huge North Tarim uplift represents a typical form of residual paleouplift. The Paleozoic strata in the upper layers of the uplift is in poor condition for reservoir accumulation and preservation; however, the Upper MesozoicCenozoic structural layer can form a secondary reservoir that is rela tively rich in oil and gas. Furthermore, the flank slope area of the uplift is always a key source for oil and gas collection and the most advantageous position for the formation of the original reservoir. The Tazhong paleouplift has been stable since its formation in the Late Ordovician, where petroleum accumulation has been distributed not only in the uplift, but also in the deep and slope belts of the uplift. Important breakthroughs in petroleum exploration of the slope break in the North Tazhong area datingback to the Paleozoic have further confirmed the enrichment of oil and gas in this type of uplift. The Southwest Tarim paleouplift is a buried type, which has given it favorable properties for hydrocarbon migration over a long time. An open question is whether the large amount of oil and gas accumulated here was transported to the current Bachu uplift.
基金Supported by the China National Science and Technology Major Project(2016ZX05004-004)
文摘Based on the outcrop survey,3D seismic data interpretation,drilling data analysis,the structural patterns and distribution of fault damage zones in carbonate strata of Tazhong Paleo-uplift were established to reveal the oil and gas enrichment law in the fault damage zones.The following findings were reached:(1)Through the filed survey,the fault damage zone system consists of fault core,damage zone with branch fault and fracture network.Affected by the active nature of the major faults,the fault damage zones differ in planar pattern and scale along the major faults.(2)3D seismic profiles reveal that there are three types of fault damage zones in carbonate strata in Tazhong paleo-uplift,strike-slip fault damage zones,thrust fault damage zones and superimposed fault damage zones.Featuring3 flowers and 3 root belts in vertical,the strike-slip fault damage zone can be subdivided into linear type,oblique type,feather type and horsetail type in plane.Thrust fault damage zones can be further divided into fault anticline type,anticline type and slope type.As the superimposition result of the above two kinds of fault damage zones,superimposed fault damage zones appear in three patterns,intersect type,encompassment type and penetrating type.(3)Cores from wells and geochemical data show oil and gas may migrate along the major fault and laterally.The feather type in strike-slip fault system,fault anticline type in thrust fault damage zone and intersect type in superimposed fault damage zone are possible sites for high production and efficiency wells.
基金Supported by the PetroChina Science and Technology Major Project(2016E-0602)。
文摘Based on drilling data of JT1 and CS1,outcrop profiles and seismic data,the sedimentary pattern,space configuration of source-reservoir-cap combinations and paleouplift evolution characteristics of the Cambrian Lower Canglangpu Member in the central Sichuan paleouplift have been investigated to determine the favorable exploration zones.Controlled by Deyang-Anyue rift,the Lower Canglangpu Member features differential characteristics from east to west in sedimentary framework.In the west side of the Deyang-Anyue rift,this member is composed of clastic sediments,while in the east side of the Deyang-Anyue rift,it is fresh water shelf sediments,with grain beaches occurring along edges of the depressions,shelf and lagoon.Among the beaches,the dolomitic ones are mainly distributed around the depression edge and in the north of the lagoon.The beach sediments could become high quality reservoirs under the effect of karstification.Underlying the Lower Canglangpu Member is the widespread source rock of the Qiongzhusi Formation,so oil and gas generated by the Qiongzhusi Formation source rock can directly charge into the beach reservoirs.The sandy mudstone of the Upper Canglangpu Member can serve as the caprock of the Lower Canglangpu Member reservoir.The dolomitic beaches are located at the higher part of the paleo-uplift during the main accumulation period,with good hydrocarbon accumulation elements.Blocks PT1-CS1,HT1-GT2 and east GT2 are favorable exploration zones.
基金Supported by the Major Science and Technology Project of PetroChina Changqing Oilfield Company (ZDZX2021-01)。
文摘This paper depicts the distribution of the Wushenqi paleo-uplift in the Ordos Basin by using the latest drilling and seismic data, and analyzes the tectonic evolution of the paleo-uplift with the support of Bischke curve and balanced section. The compressional Wushenqi paleo-uplift which developed in the Early Caledonian orogeny(Huaiyuan orogeny) is approximately a ellipse extending in S-N direction. Its long axis is about 194 km and short axis is about 55-94 km in nearly W-E direction. The denudation thickness and area of the Cambrian in the core are 170-196 m and 11 298 km^(2), respectively. It was mainly formed during the Huaiyuan orogeny according to the chronostratigraphic framework. It was in the embryonic stage in the Middle-Late Cambrian, denuded after developed obviously at the end of Late Cambrian. The paleo-uplift of the 3rd member of the Ordovician Majiagou Formation was reactivated and reduced in area. In the sedimentary period of the Ma 4 Member-pre-Carboniferous, the paleo-uplift experienced non-uniform uplift and denudation. It entered the stable period of burial and preservation in the Carboniferous and later period. The Wushenqi paleo-uplift was formed on the weak area of the basement and tectonic belts, into an compressional structure with irregular morphology, under the control of the non-coaxial compression in the south and north and the stress transmitted by the uplift in the basin. The Wushenqi paleo-uplift has a controlling effect on the sedimentary reservoirs and hydrocarbon accumulation.
基金supported by the PetroChina Major S&T Project"Field Test of Exploration and Development Technologies for Decp Marine Carbonate Reservoirs in Sichuan Basin"(No.:2014E-3208(GF))。
文摘Great breakthrough recently achieved in the SinianeLower Paleozoic gas exploration in the LeshaneLongnu¨si paleo-uplift,Sichuan Basin,has also made a common view reached,i.e.,large-scale paleo-uplifts will be the most potential gas exploration target in the deep strata of this basin.Apart from the above-mentioned one,the other huge paleo-uplifts are all considered to be the ones formed in the post-Caledonian period,the impact of which,however,has rarely ever been discussed on the SinianeLower Paleozoic oil and gas reservoir formation.In view of this,based on outcrops,drilling and geophysical data,we analyzed the SinianeLower Paleozoic tectonic setting and sedimentary background in the East Sichuan Basin,studied the distribution rules of reservoirs and source rocks under the control of paleo-uplifts,andfinally discussed,on the basis of structural evolution analysis,the conditions for the formation of SinianeLower Paleozoic gas reservoirs in this study area.The followingfindings were achieved.(1)The DazhoueKaijiang inherited uplift in NE Sichuan Basin which was developed before the Middle Cambrian controlled a large area of Sinian and Cambrian beach-facies development.(2)Beach-facies reservoirs were developed in the upper part of the paleo-uplift,while in the peripheral depression belts thick source rocks were developed like the Upper Sinian Doushantuo Fm and Lower Cambrian Qiongzhusi Fm,so there is a good sourceereservoir assemblage.(3)Since the Permian epoch,the DazhoueKaijiang paleo-uplift had gradually become elevated from the slope zone,where the Permian oil generation peak occurred in the slope or lower and gentle uplift belts,while the Triassic gas generation peak occurred in the higher uplift belts,both with a favorable condition for hydrocarbon accumulation.(4)The lower structural layers,including the Lower Cambrian and its underlying strata,in the East Sichuan Basin,are now equipped with a large-scale uplift with a simple structural configuration,above which a complete local structural trap was well developed with a good preserving condition.In conclusion,there are good forming conditions for hydrocarbon reservoirs in the SinianeLower Paleozoic strata in the DazhoueKaijiang paleo-uplift,East Sichuan Basin,in the higher parts of which the well-developed beach-facies reservoirs occupy an area of 8000 km2 and will be the next important gas exploration target in this basin.
基金Supported by the National Science and Technology Major Project(2017ZX005-008-01)Tarim Oilfield Company Project(041014120098).
文摘Based on well horizon calibration,the typical seismic profiles in southwestern Tarim Basin were interpreted systematically,regional geological sections were established,and the regional denudation thickness of each tectonic period was restored.On this basis,the plane morphology maps of ancient structures of the Cambrian pre-salt dolomites in different periods were compiled,and the spatial distribution,development,evolution and migration of paleo-uplift in the late Early Paleozoic were analyzed.In the late Early Paleozoic,there existed a unified regional paleo-uplift widely distributed in southwestern Tarim Basin,which is called the southwestern Tarim plaeo-uplift.The“Tarim SW paleo-uplift”and“Hetian paleo-uplift”proposed in previous literatures are not independent,but the result of the spatio-temporal migration and evolution of the southwestern Tarim paleo-uplift identified in this paper.The southwestern Tarim paleo-uplift emerged at the end of Middle Ordovician,and took its initial shape with increased amplitude in the Late Ordovician.During the Silurian,the southwestern Tarim paleo-uplift rose steadily and expanded rapidly to the east,incorporating Pishan-Hetian and other areas,with the structural high locating in the Pishan-Hetian area.During the Devonian,the southwestern Tarim paleo-uplift began to shrink gradually,to a limited range in the Pishan-Hetian area in the southern part of the basin.During the Carboniferous,the southwestern Tarim paleo-uplift became an underwater uplift,that is,the paleo-uplift gradually died out.The southwestern Tarim paleo-uplift belongs to the forebulge of the southwestern Tarim foreland basin in the late Early Paleozoic,and its formation and evolution are related to the early Paleozoic orogeny of the West Kunlun orogenic belt in the south of the Tarim Basin.The migration of the southwestern Tarim paleo-uplift from the northwestern part of the southwestern Tarim Basin to the Pishan-Hetian area indicates the early Paleozoic orogenic process of the West Kunlun orogenic belt,which started in the western section at the end of Middle Ordovician and extended from west to east in a“scissor”style.The migration and evolution of the southwestern Tarim paleo-uplift controlled the development of unconformities at the end of Middle Ordovician,the end of Late Ordovician,and the end of Middle Devonian,and the spatial distribution of dissolved fracture-cave reservoirs in weathered crust below the unconformities in the southwest of Tarim Basin.The migration of the structural high of the southwestern Tarim paleo-uplift also played an important role in controlling the development of dissolved fracture-cave reservoirs in weathered crust.
基金supported by the National Major Science and Technology Project“Development of large-scale oil/gas fields and coalbed methane”(No.2016ZX05007-002)。
文摘Intra-platform carbonate mound-bank body reservoirs is an important type of oil and gas reservoirs in the Sichuan Basin,and paleo-uplift plays an important role in the scale formation process of scale intra-platform mound-bank body reservoir.So far,however,the control action of paleo-uplift on the formation and distribution of intra-platform mound-bank body reservoirs has not been understood clearly enough,which restricts the oil and gas exploration progress of this type of reservoirs.In order to provide the basis for oil and gas exploration deployment,this paper analyzes the formation and evolution of four paleo-uplifts developed in the cratonic stage of the Sichuan Basin.On this basis,the genetic mechanisms and characteristics of scale intra-platform mound-bank body reservoirs are studied,and the characteristics and distribution of large-scale intra-platform reservoirs in the main series of strata are analyzed.And the following research results were obtained.First,the four paleo-uplifts developed in the Sichuan Basin plays an important constructive role in the formation of scale intra-platform mound-bank body reservoirs.Their control actions mainly include sedimentation and diagenesis.Along with the sea level change,they control the sedimentation scale and distribution range of intra-platform mound-bank body.They control the interlayer karstification and quasi-syngenetic dolomitization of intra-platform mound-bank body.And together with the late tectonic movement,they control the weathering crust karstification and fracturing of intra-platform mound-bank body.Second,Gaoshiti-Moxi paleo-uplift mainly controls the formation of the large-scale intra-platform mound-bank body reservoirs in the Sinian Dengying Formation and the Cambrian Longwangmiao Formation,Leshan-Longnüsi paleo-uplift mainly controls the formation of the scale intra-platform mound-bank body reservoir in the Cambrian Xixiangchi Formation and the Carboniferous Huanglong Formation,while Luzhou and Kaijiang paleo-uplifts mainly control the formation of the scale intra-platform mound-bank body reservoirs in the Triassic Jialingjiang Formation and Leikoupo Formation.Third,six sets of scale intra-platform reservoirs are developed in the Sichuan Basin.The intra-platform mound-bank body reservoirs of Dengying Formation and Longwangmiao Formation are mainly distributed in the core of paleo-uplift,and the other four sets are mainly distributed in the slope of paleo-uplift.In conclusion,these research results provide the geological basis for the prediction of scale intra-platform mound-bank body reservoirs in the Sichuan Basin and they are of important theoretical and practical significance.
基金Project supported by the National Major S&T Project(Grant No.2011ZX05004&2011ZX05003-004)the National Natural Science Fund Project(Grant No.41472103).
文摘Various types of paleo-uplifts with different characteristics are developed in the Tarim Basin.Previously,there were multiple opinions on the pale-uplifts origins and structural evolution,so the oil and gas exploration ideas and deployment in the Tarim Basin were not developed smoothly.In this paper,regional seismic interpretation and structural analysis were carried out on the deep marine carbonate rocks in this basin based on the new seismic and drilling data.Then combined with the structural denudation results,the paleo-structural frameworks were reconstructed.And finally,the formation stage and main controlling factors of paleo-uplifts were discussed.It is shown that the Middle Ordovician is the key period when regional extension was converted to compression in this basin,so stratigraphic,sedimentary and structural differences occurred.Before the deposition of Yijianfang Fm in late Middle Ordovician,three carbonate paleo-uplifts(i.e.,the Northern,Central and SW Tarim paleo-uplifts)begun to appear,and they were all broad-folded paleo-uplifts of nearly E-W striking and were formed at the same stage.The distribution and development of the Phanerozoic uplifts in this basin are restricted by the Northern and Southern Tarim basement paleuplifts of nearly E-W striking which were developed during the Precambrian.It is indicated that all the three paleo-uplifts are compressional paleo-uplifts originated from the convergence of the southern plate margin based on the basement paleo-uplifts and they are all characterized by similar structural characteristics and inherited formation and evolution.The current differences of paleo-uplifts are controlled by multi-stage intense structural reformation since the Silurian.It is concluded that the oil and gas exploration potential is immense in the carbonate reservoirs of well-preserved deep paleo-structural zones in a larger area.
基金supported by the National Major Science and Technology Project“Development of large-scale oil/gas fields and coalbed methane”(No.2016ZX05004-005)PetroChina Company Limited's Major Science and Technology Project“Key technology for achieving 30 BCM gas production and its application in Southwest Oil/Gas Field”(No.2016E-0602).
文摘Since the Anyue Gasfield,located in the central Sichuan paleo-uplift of the Sichuan Basin,was discovered,great efforts have been made to work on natural gas exploration and discovery in the SinianeLower Paleozoic in the north slope of present paleo-uplift which has similar depositional settings.It is verified by the breakthrough of natural gas exploration in the second Member of Upper Sinian Dengying Formation in the north slope of central Sichuan paleo-uplift by wildcat well PT1 and the new sign of natural gas exploration in the Canglangpu Formation of Lower Cambrian and the fourth Member of Dengying Formation by Well JT1 that there are also favorable conditions for the formation of large-scale gas province in the north slope.In order to determine the natural gas exploration potential of SinianeLower Paleozoic in the central Sichuan paleo-uplift and provide the guidance for the following exploration deployment,this paper analyzed the petroleum geological conditions of SinianeLower Paleozoic in the north slope.And the following research results were obtained.First,the marginal platform belts in the second and the fourth Member of Sinian Dengying Formation in the north slope are basically separated areally,and they are superior to the Gaoshiti-Moxi area in terms of marginal platform width and sedimentary thickness and are intrinsically advantageous in sedimentation.Second,compared with the Gaoshiti-Moxi area,the reservoirs of Sinian Dengying Formation in the north slope are better in reservoir conditions,and many sets of quality reservoirs are developed vertically in Siniane-Cambrian.Third,hydrocarbon accumulation elements of Sinian Dengying Formation are better allocated in the north slope.Lithological traps are developed with a larger cumulative area.Wells JT1 and PT1 verify that there is gas in the lithological trap of the fourth and the second Member of Dengying Formation and large-scale lithological gas reservoirs are developed in the slope setting.In conclusion,compared with the Gaoshiti-Moxi area,the Sinian-Lower Paleozoic in the north slope is superior in petroleum geological conditions and has the advantage of multi-layer stereoscopic exploration vertically,presenting a great natural gas exploration potential and promising exploration prospects,so it is a new important strategic zone of conventional natural gas exploration in the Sichuan Basin.
基金supported by the National Natural Science Foundation of China(Grant Nos.42102015&42288201)。
文摘The Kulun region is located in the eastern Bainaimiao arc belt on the southeastern margin of the Central Asian Orogenic Belt(CAOB),adjacent to the North China Craton(NCC)to the south.This region records the closure of the PaleoAsian Ocean during the Paleozoic to early Mesozoic and is key to study the tectonic evolution of the northern margin of the NCC.We conducted zircon U-Pb geochronology and Hf isotope analysis of volcanic-sedimentary and intrusive rocks in the Kulun region.The volcanic-sedimentary rocks were previously assigned an early Carboniferous age,but include volcanic rocks with ages of 267–266 Ma and sedimentary rocks with youngest detrital zircon age peaks of 265–244 Ma,which were intruded by a granite with an age of 242 Ma.This indicates that these rocks are actually middle Permian to Middle Triassic in age(267–242Ma)and correspond to the Qingfengshan and Liujiagou formations.Moreover,two volcanic rock samples have highεHf(t)values(+1.6 to+16.1)and relatively young two-stage Hf model ages(1095–327 Ma),indicating their sources associated with the CAOB.The age spectra and Hf isotopic characteristics of detrital zircons from the sedimentary rocks suggest that,during the middle Permian to Middle Triassic,the sedimentary provenance in the Kulun region was mainly the CAOB.However,by the Early Jurassic,the provenance changed to the NCC(i.e.,the Inner Mongolia Paleo-uplift,IMPU).This result,combined with the development of a series of conglomerates on the northern margin of the NCC in the Late Triassic(i.e.,Xingshikou,Xiaoyingzi,and Xiaohekou formations),indicates the Kulun region experienced an abrupt change in paleogeography during the Late Triassic,with the IMPU undergoing significant uplift and thus becoming the main sediment source in the Kulun region.Based on the Late Triassic alkaline igneous belt(235–215 Ma)in the IMPU,we speculate that this uplift was caused by detachment of the southward-subducting Paleo-Asian oceanic plate,which occurred in a post-orogenic extensional setting.The boundary between the NCC and CAOB(i.e.,the Bainaimiao arc belt)in the Kulun region is defined by the newly identified Paleoproterozoic granites(1.8 and 1.6 Ga)and our zircon geochronology and Hf isotope data.
基金supported by science and technology project of PetroChina Zhejiang Oilfield Company(grant numbers:zjyt-2021-kj-008).
文摘The sedimentary environment of the Upper Triassic in the southeastern Sichuan Basin is obviously controlled by Luzhou paleo-uplift(LPU).However,the influence of paleo-uplift on the sedimentary patterns of the initial stages of this period in the southeastern Sichuan Basin has not yet been clear,which has plagued oil and gas exploration and development.This study shows that there is a marine sedimentary sequence,which is considered to be the first member of Xujiahe Formation(T_(3)X^(1))in the southeastern Sichuan Basin.The development of LPU resulted in the sedimentary differences between the eastern and western Sichuan Basin recording T_(3)X^(1)and controlled the regional sedimentary pattern.The western part is dominated by marine sediments,but the eastern paleo-uplift area is dominated by continental sedimentation in the early stage of T_(3)X^(1),and it begins to transform into a marine sedimentary environment consistent with the whole basin in the late stage of the period recorded by the Xujiahe Formation.The evidences are as follows:(1)time series:based on the cyclostratigraphy analysis of Xindianzi section and Well D2,in the southeastern Sichuan Basin,the period of sedimentation of the Xujiahe Formation is about 5.9 Ma,which is basically consistent with the Qilixia section,eastern Sichuan basin,where the Xujiahe Formation is widely considered to be relatively complete;(2)distribution and evolution of palaeobiology:based on analysis of abundance evolution of major spore-pollen,many land plant fossils are preserved in the lower part of T_(3)X^(1),indicates the sedimentary environment of continental facies.In the upper part of T_(3)X^(1),the fossil of terrestrial plants decreased,while the fossil of marine and tidal environment appeared,this means that it was affected by the sea water in the late stages of T_(3)X^(1);(3)geochemistry:calculate the salinity of water from element indicates that the uplift area is continental sedimentary environment in the early stage of T_(3)X^(1),while the central and western areas of the basin are marine sedimentary environment.Until the late stage of T_(3)X^(1),the southeast of the basin gradually turns into marine sedimentary environment,consisting with the whole basin;(4)types of kerogen:type III kerogen representing continental facies was developed in the early stage of T_(3)X^(1)in the uplift area,and type II kerogen,representing marine facies,was developed in the late stage;while type II kerogenwas developed in the central and western regions of the basin as a whole in T_(3)X^(1).This study is of great significance for understanding of both stratigraphic division and sedimentary evolution providing theoretical support for the exploration and development of oil and gas.
