The Silurian in the Tarim Basin was deposited on the basement deformed by the Caledonian tectonic movements at the end of the Late Ordovician. The development and distribution of sedimentary sequences of the Early Sil...The Silurian in the Tarim Basin was deposited on the basement deformed by the Caledonian tectonic movements at the end of the Late Ordovician. The development and distribution of sedimentary sequences of the Early Silurian have been clearly controlled by the palaeogeomorphology of the Late Ordovician. Based on unconformity characteristics and distribution of erosion, several zones can be differentiated including a high uplifted erosion zone, a transitional slope zone and a depression zone. The central and west Tabei Uplift zones show high angular unconformity and intense erosion. The Tarim Basin in the late Ordovician shows characteristics of higher in the west, lower in the east while higher in the south, lower in the north. The Early Silurian mainly developed transgressive and highstand systems tracts on the whole, while the lowstand systems tract only developed partly below the slope break. The palaeogeomorphology controlled the elastic source supply and deposit distribution. Braided delta system and tidal flat-estuary system were deposited. The duration of uplifting of the Tazhong paleo- uplift was longer than that of the Tabei paleo-uplift, and deposition was later. This led to the lower and middle members of the Kepingtage Formation missing in that area. As a large-scale transgression occurred during the deposition period of the upper member of the Kepingtage Formation, sediment from the west of the basin was transported and deposited by tides and waves, forming tidal-marine debris systems above the uplift. Proximal alluvial fan and fan delta coarse elastic deposits developed in proximal uplift zone in the east and southeast of the basin, and braided delta put forward to the transitional zone between the edge of uplift and the sea. Large-scale tidal channel, sub-distributary channel and mouth bar of the delta front can form favorable reservoirs, and they are primary targets for oil and gas exploration. This research on sequence-depositional systems development and distribution controlled by palaeogeomorphology is significant in guiding the prediction of reservoir sandstones.展开更多
The reef-shoal depositional system of the Ordovician carbonate platform margin is well exposed in the Yijianfang （一间房） outcrop of the Bachn （巴楚） uplift region, which offers an advantageous condition to study ...The reef-shoal depositional system of the Ordovician carbonate platform margin is well exposed in the Yijianfang （一间房） outcrop of the Bachn （巴楚） uplift region, which offers an advantageous condition to study their paleoecology. Using a detailed field geologic survey and illustrated profiles of typical depositional systems, three types of genetic facies associations can be recognized in the reef-shoal depositional system： an organic reef, an organic shoal, and an upper slope. The organic reef is composed of three types of genetic facies （a reef base, a reef core, and fore-reef breccias）; the organic shoal is formed from five types of genetic facies （tide channels, fore-reef inner shoals, fore-reef outer shoals, back-reef inner shoals, and back-reef outer shoals）. The studies of the paleontological assemblage in each genetic facies of the depositional system indicate that the fauna preserved in each genetic facies are varied. The calathium, archaeoscyphia, bryozoan, and calcareous alga are well preserved in the organic reefs. The organisms preserved in the organic shoals are generally fragmented, while weil-preserved girvanella and nuia siberica with a content of about 15% in the back-reef outer shoals are the most characteristic and different from others. The sinoceras, trilobites, and gastropods are well preserved in the upper slope deposits. The studies will demonstrate that the reef-shoal complexes developed above the base of the fair-weather wave base and that the original hydrodynamic conditions for the reef core forming is the stronger and become more and more low-energy from the inner part to outer part of the organic shoals.展开更多
Uranium exploration breakthrough was extremely rare in an aeolian depositional system.In order to know the complicate characteristics of oxidation associated closely with uranium mineralization in the aeolian depositi...Uranium exploration breakthrough was extremely rare in an aeolian depositional system.In order to know the complicate characteristics of oxidation associated closely with uranium mineralization in the aeolian depositional system,petrology and mineralogy markers of the oxidation and its genetic mechanisms are identified and illustrated by fieldwork,thin section analysis and scanning electron microscopy test,based on 2 field outcrops in Zhenyuan County in the southwest of the Tianhuan depression in the Ordos Basin and the core of 2 wells in the north and south of Ordos Basin.The results showed:the typical macroscopic indicator of primary oxidation was the red fine sediments in the aeolian interdune with a thickness of 10-50 cm,and the microscopic characteristics of primary oxidation were the minerals such as hematite,ilmenite,and the irony matrix rich in fine-grained dolomite and biotite;the phreatic oxidation was manifested as the red sandstone with limonite horizontal layer with a thickness of 1-4 cm and a width of 60 cm-1 m,and the circular limonite nodules with a diameter of 3-7 cm,in which there was intergranular limonite cement;the interlayer oxidation was characterized by lenticular tongue and tapered red sandstone with a length of 1-10 m and a width of 10 cm-5m,in which detrital particles are coated with hematite and hematite was distributed inside the rhombus dolomite.The paleoclimate of the sedimentary period,the water-table movement and the pore and permeability conditions of the sand body were the key factors for the formation of different oxidation types in the aeolian depositional system.展开更多
Using analyses of the lithology,sequences,paleoenvironment,and tectonic setting,the depositional system of the Carboniferous Huanglong Formation in the eastern Sichuan Basin was identified.The lithological characteris...Using analyses of the lithology,sequences,paleoenvironment,and tectonic setting,the depositional system of the Carboniferous Huanglong Formation in the eastern Sichuan Basin was identified.The lithological characteristics of the Lower Member,Middle Member,and Upper Member were analyzed and classified.Before the use of carbon,oxygen,and strontium isotopes in the analysis,all of the geochemical data were tested for validity.On the basis of the Z values obtained from carbon and oxygen isotopes,the paleoenvironments of the three members were elucidated.Lower Member was dominantly an enclosed marine environment with intense evaporation and little freshwater input into the sea.Middle Member developed in a semi-enclosed to normal marine environment with many rivers.Upper Member was formed in a normal marine environment.The east Sichuan Basin was enclosed by paleouplifts before the deposition of the Huanglong Formation,forming a relatively enclosed depositional setting.Paleogullies developed in the Silurian strata that underlie the Carboniferous rocks;these paleogullies can be identified.On the basis of a comprehensive analysis,we propose that the Huanglong Formation developed in a platform system.Four microfacies were identified：supratidal flat,dolostone flat,grain shoal,and shelf microfacies.The high-permeability and high-porosity characteristics of the grain shoal microfacies are favorable for hydrocarbon accumulation,while the supratidal flat and shelf microfacies developed very few high-quality reservoirs.The paleogullies,in which increased amounts of grain shoal microfacies developed,controlled the distribution of high-quality reservoirs.展开更多
Based on drilling and seismic data, the Paleogene developed in Liaodong Bay can be divided into five third-order sequences bounded by six sequence boundaries. Through analyzing depositional systems in each sequence in...Based on drilling and seismic data, the Paleogene developed in Liaodong Bay can be divided into five third-order sequences bounded by six sequence boundaries. Through analyzing depositional systems in each sequence in detail, the Es-3 time was defined as fast rifting. During the deposition of the Es-3 member, the lake basin was continuous along the N-S direction but compartmentalized along the E-W direction by several N-S trending faults. Deposition was dominated by steep slope fans and fan deltas. The time of Es-2 and Es-1 was stable settling. The lake basin expanded substantially. The fan delta system and braided fluvial system were developed. Carbonate and clastic deposits were formed on the Liaoxi （west Liaohe） Rise. The time of Ed-3 time was again fast rifting. During this time, shale was deposited. In the time of Es-2, tectonic movement weakened. The basin was higher in the west and north, and lower in the east and south. A series of delta depositional systems were developed and smallscale slumping turbidite fans were present in semi-deep lake to deep lake. In the time of Ed-1, tectonic movement stopped. Flood plain deposition occurred. Finally the paper presents the characteristics of evolution and distribution of depositional systems both vertically and horizontally.展开更多
In the Karamay oilfield located on the northwestern margin of Junggar basin, Xinjiang, China, a large area of the Karamay Formation is exposed at outcrop in the northeast of the oilfield, a consequence of thrusting. T...In the Karamay oilfield located on the northwestern margin of Junggar basin, Xinjiang, China, a large area of the Karamay Formation is exposed at outcrop in the northeast of the oilfield, a consequence of thrusting. The Middle Triassic Karamay Formation in the outcrop area is a type of terrestrial third-order sequence, bounded by two easily recognizable sequence boundaries: a regional surface of angular unconformity (SB1) at the base and a regional unconformity (SB2) at the top. Within the Karamay Formation, two lacustrine expansion events can be recognized and be used to identify both the initial and the maximum lacustrine flooding surfaces. The two lacustrine flooding surfaces serve as references for the classification of this third-order sequence-Karamay Formation into the following three sedimentary successions: a lower lowstand systems tract (LST), a middle lacustrine-expanding systems tract (EST), and an upper highstand systems tract (HST). Different systems tracts are composed of different depositional system assemblages. In this paper, each depositional system is described in detail. The lowstand systems tract in the study area is characterized by incised valleys. At the base and on the margin of the incised valleys occur alluvial fan depositional systems, and in the upper and distal parts of the alluvial fan, low-sinuosity river depositional systems. The lacustrine-expanding systems tract consists of a lacustrine depositional system and a lacustrine delta depositional system, overlying the lower incised valley fills. The highstand systems tract is filled by a widespread lacustrine braided delta depositional system. The analysis of sequence stratigraphy in this paper serves the description of the spatial distribution of the reservoir. The depositional system analysis serves the description of the reservoir types. Field investigations of oil sandstone and oil seepage show that the Karamay Formation is composed of several types of reservoirs. However, two types of high quality reservoir occur both in the upper interval of the lowstand systems tract and in the lacustrine-expanding systems tract: gravelly low-sinuosity channel in the distal fans and sandy-gravelly distributary channel in the lacustrine delta plain.展开更多
It is a major continuous depocenter in Dalangtan area,western Qaidam basin since Early Cenozoic,which is most important Neogene salt deposits center in Qaidam basin.The Miocene Saline lake was developed firstly in
The Upper Eocene–Lower Oligocene Qianjiang Formation of the Jianghan Basin in central China consists of a 4700-m-thick lacustrine succession, containing 1800 m of halite deposits. The maximum thickness of the formati...The Upper Eocene–Lower Oligocene Qianjiang Formation of the Jianghan Basin in central China consists of a 4700-m-thick lacustrine succession, containing 1800 m of halite deposits. The maximum thickness of the formation is 4700 m, and includes 1800 m of halite. We have identified eight third-order depositional sequences based on pinch-out and onlap stratigraphic patterns in 2-D and 3-D seismic data and well logs. The basin evolved from a deep to shallow under-filled lake during the Eocene–Oligocene interval. The main rock types are dark mudstones, halite, and siltstone/sandstone in the depocenter, and alternating mudstone and gypsum in shallower areas. The vertical succession indicates a strong sedimentary cyclicity. Depositional facies indicate the presence of two lake system types. Halite developed in a saline lake system, whereas clastic sediments were deposited in freshwater lake systems. The alternating sediment types indicate that the basin cycled repeatedly between saline and freshwater lake systems. This cyclicity was caused by availability of accommodation space that was controlled by a combination of climate change, tectonic subsidence and sediment supply; notably, the highest frequency cycles occurred at Milankovitch timescales controlled by the Earth＇s orbital variations. The cyclic halite plays an important role in generating and preserving oil in the Qianjiang Formation of the Qianjiang depression.展开更多
Baise basin is a semi-graben type , pan-shaped faulted basin of Early Tertiary , in which carbonate lacustrine deposits and elastic lacustrine deposits developed . The assemblages of Gilbert-type delta-lakes ,littoral...Baise basin is a semi-graben type , pan-shaped faulted basin of Early Tertiary , in which carbonate lacustrine deposits and elastic lacustrine deposits developed . The assemblages of Gilbert-type delta-lakes ,littoral ,shallow and deep water fades are recognized . Based on grain size , the clastic lacustrine deposit systems can be grouped in three kinds of depositional sequences of progressive deposition : (1)from coarse to fine , (2)from fine to coarse and (3) from fine to coarse and then to fine agan . This was controlled mainly by hydrodynamic factor of lake bottom type .Lake shore was an important place for coal accumulation and peatmoor development . It had long time for coal accumulation and there was a very little amount of minerals into the basin ,and the thick coal layer and high quality coal developed m the zone where initial lake bottom was plan-like and the surface stream flow was weak .Peat accumulation advanced from the margin to the center of basin .Carbonate lakes contained much water ,very high preponderant contenis of coagel ,low inert contents and no fusinite in the coal .展开更多
To make clear about the sedimentary facies types and distribution of deep water sandstone reservoirs in Campos basin of Brazil,this paper researches the characteristics of deep-water sedimentary system in Campos basin...To make clear about the sedimentary facies types and distribution of deep water sandstone reservoirs in Campos basin of Brazil,this paper researches the characteristics of deep-water sedimentary system in Campos basin through the comprehensive analysis of drilling,logging and seismic data.There are 3 subfacies and 7 microfacies in the study area.There are 3 channels from south to north in Upper Cretaceous Maastrichtian,and the sedimentary incised valley and compound channels developed in micro-salt basin are the main deep water depositional types.The Paleocene to Eocene dominated by sedimentary incised valley and eroded compound channel deposits,also include 3 channel systems.From Oligocene to Miocene,the main deposition type is lobe,which is mainly distributed in central-north of the basin.Corresponding to deep water depositional stages,3 kinds of depositional models are found.From Turonian to Maastrichtian of Upper Cretaceous,with tectonic uplift,strong source material supply,and the negative topography produced by salt rock movement providing favorable accommodation for sand deposition,the depositional model was terrigenous direct feed mechanism with sedimentary incised valley and compound channels in micro salt basin.From Paleocene to Eocene,as the amplitude of tectonic uplift reached the maximum and the accompanied erosion peaked,accommodation space offered by micro salt basin was leveled up;the depositional model was terrigenous direct feed mechanism with sedimentary valley and incised compound channels.From Oligocene to Miocene,because of sable tectonics,sea level fluctuation is the main controlling factor for deep water deposition,so the depositional model was wide shelf indirect feed mechanism with bypass incised valley and lobe.The analysis of the characteristics and controlling factors of the 3 types deep-water sedimentary systems during 3 different stages in Campos Basin can provide valuable reference for the oil exploration in deep-water deposits in the Campos Basin and across the world.展开更多
With a comprehensive geological and geophysical data base,the Paleogene in the Liaodong Bay area,which consists of the Kongdian,Shahejie and Donghying Formations from the base to top,was divided into 4 second-order se...With a comprehensive geological and geophysical data base,the Paleogene in the Liaodong Bay area,which consists of the Kongdian,Shahejie and Donghying Formations from the base to top,was divided into 4 second-order sequences and 8 third-order sequences based on the characteristics of the se-quence boundaries. Each third-order sequence is subdivided into the lowstand,lake transgressive and highstand systems tracts. The Lowstand systems tract (LST) is mainly composed of progradational parasequence sets,while the lake transgressive systems tract (TST) largely consists of the retrograda-tional parasequence sets and the highstand systems tract (HST) is dominated by the progradational parasequence sets. The main types of depositional systems include the shallow lake,semi-deep lake,deep lake,delta,fan delta,braided fluvial delta and nearshore subaqueous fan. The braided fluvial delta and fan delta depositional systems are mainly confined to the sequences of the lower SEs4-Ek,SEs3 and SEs1+2,while the sequences of SEd3,SEd2 and SEd1 are dominated by the delta and nearshore subaqueous fan depositional systems with the latter being developed at the downthrown side of the basin-bounding fault in each sequence. The evolution of the depositional systems is always con-trolled by the paleo-tectonic setting and the ancient landform in the space and geological time. It is concluded that the most favorable reservoirs are distributed in the Liaoxi low uplift and the central Liaozhong sag.展开更多
In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is belie...In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is believed that the Upper Permian–Lower Triassic can be regarded as a long-term base-level cycle.Based on drilling data,characteristics of the lithology–electric property combination cyclicity,and the special lithology,the long-term base-level cycle was divided into five medium-term base-level cycles(MC1–MC5).On this basis,the Permian–Triassic sedimentary systems and their filling model were analyzed in accordance with the change of base-level cycle and transition of sedimentary environment,as well as characteristics of the drilling sedimentary facies and seismic facies.The results show that there were six sedimentary systems(fluvial,delta,tidal flat,open platform,restricted platform,and continental shelf)developed in the Upper Permian–Lower Triassic,the sedimentary systems were distributed such that the water was deep in the northwest and shallow in the southeast,and there were two base-level cycle filling models(a relatively stable tidal flat facies and a rapidly transgressive continental shelf facies to stable platform facies)developed in the Upper Permian–Lower Triassic.These models can provide a basis for evaluation of the Mesozoic–Paleozoic hydrocarbon geology in the South Yellow Sea Basin.展开更多
Gas chromatography-mass spectrometry(GC-MS)was used to analyze the pentacyclic triterpenoid distributions,specifically hopane and oleanane fingerprints,in 24 crude oil samples from the Niger Delta depobelts,with the a...Gas chromatography-mass spectrometry(GC-MS)was used to analyze the pentacyclic triterpenoid distributions,specifically hopane and oleanane fingerprints,in 24 crude oil samples from the Niger Delta depobelts,with the aim of defining the petroleum system,filling history,and the age of source rock producing these oils.The results indicate that the Niger Delta oils belong to a single fluvio-deltaic petroleum system,reflecting similar source organic facies and depositional environments.Geochemical parameters,including C29/C30hopane ratios,oleanane index,Ts/Tm,(Ts/(Ts+Tm)),moretane/C30hopane ratios,and C3222S/(22S+22R)ratios,suggest oxic conditions during source rock deposition and thermal maturity of the oils.The presence of terrigenous organic matter and complex filling history are also evident and influenced by multiple phases of sedimentation,and petroleum generation.A comparative plot of geologic time(Paleogene-Neogene age)and oleanane percentage composition show that the crude oils are constrained to the chronostratigraphic ages of their respective depobelts,demonstrating the potential of oleanane-derived parameters for relative dating of hydrocarbon sources,complementing traditional index fossil methods.展开更多
The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings.Natural boulders can be highly random and unpredictable.Consequently,boulder control...The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings.Natural boulders can be highly random and unpredictable.Consequently,boulder control during debris flows is crucial but difficult.Herein,an eco-friendly control system featuring anchoring natural boulders(NBs)with(negative Poisson's ratio)NPR anchor cables is proposed to form an NB-NPR baffle.A series of flume experiments are conducted to verify the effect of NB-NPR baffles on controlling debris flow impact.The deployment of NB-NPR baffles substantially influences the kinematic behavior of a debris flow,primarily in the form of changes in the depositional properties and impact intensities.The results show that the NB-NPR baffle matrix successfully controls boulder mobility and exhibits positive feedback on solid particle deposition.The NB-NPR baffle group exhibits a reduction in peak impact force ranging from 29%to 79%compared to that of the control group in the basic experiment.The NPR anchor cables play a significant role in the NB-NPR baffle by demonstrating particular characteristics,including consistent resistance,large deformation,and substantial energy absorption.The NB-NPR baffle innovatively utilizes the natural boulders in a debris flow gully by converting destructive boulders into constructive boulders.Overall,this research serves as a basis for future field experiments and applications.展开更多
Early Cambrian organic-rich shales in the Yangtze Plate are key shale gas exploration targets in China,but their sedimentary environments are not well understood.This lack of knowledge complicates the evaluation of th...Early Cambrian organic-rich shales in the Yangtze Plate are key shale gas exploration targets in China,but their sedimentary environments are not well understood.This lack of knowledge complicates the evaluation of these targets and associated risks.Assessing shale depositional environments is also challenging due to the fine-grained nature of the sediments and subtle compositional variations.Herein,marine black shales of the Lower Cambrian Shiyantou(SYT)Formation(Fm)and Yu'anshan(YAS)Fm are investigated through a series of experiment,including thin sections,scanning electron microscopy,and major and trace elements analysis.Results show that five lithofacies can be identified in the SYT and YAS shales:(1)calcareous mudstone;(2)wavy-laminated sand,silt,and clay bearing mudstone;(3)laminated and massive mudstone;(4)planar-laminated pyritic mudstone,and(5)thin bedded sand and siltstone.Average content of major elements SiO_(2),Al_(2)O_(3),MgO,Fe_(2)O_(3),K_(2)O,CaO,Na_(2)O,TiO_(2),P_(2)O_(5),and MnO of SYT Fm are 57.03%,12.74%,4.20%,3.97%,3.93%,3.35%,1.09%,0.68%,0.28%,and 0.05%,respectively.Average content of major elements SiO_(2),Al_(2)O_(3),MgO,Fe_(2)O_(3),K_(2)O,CaO,Na_(2)O,TiO_(2),P_(2)O_(5),and MnO of Yu'anshan Fm are 54.93%,14.52%,5.26%,6.00%,3.77%,3.88%,0.15%,0.63%,0.19%,and 0.10%,respectively.Samples from SYT Fm are enriched in Li,V,Cr,Co,Zr,Cs,and U relative to Upper Continental Crust(UCC)and most of shale samples from YAS Fm are enriched in Li,V,Co,and U relative to UCC.The marine black shales are deposited in dynamic anoxic to oxic environment in upper Yangtze Plate,which indicated the seabed had already oxidized in the Cambrian Stages 2 and 3.The Chemical Index of Alteration(CIA)values ranged 51.84–79.46 indicate a warm and humid climate in the 2 stages.These findings are consistent with the region's paleogeography and previous studies.They hold significance for sedimentologists,paleontologists,and other researchers involved in petroleum geology.展开更多
A comprehensive examination of detrital sandstone modes from the Sylhet Trough reveals a diverse range of sub-lithic to sub-feldspathic quartz arenites.Soil samples were gathered from Dupi Gaon(Jaintiapur)in Banglades...A comprehensive examination of detrital sandstone modes from the Sylhet Trough reveals a diverse range of sub-lithic to sub-feldspathic quartz arenites.Soil samples were gathered from Dupi Gaon(Jaintiapur)in Bangladesh,followed by a thorough analysis using field examination,X-ray diffraction(XRD),X-ray fluorescence(XRF),petrography,and heavy mineral concentration analyses.Field observations revealed the soil sample varying from white to yellowish to variegated,with thicknesses ranging from 15 cm to about 4 m,and exhibiting moderate softness.XRF analysis revealed significant SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3)levels in the samples,with zirconium(Zr)and copper(Cu)showing consistently high concentrations.XRD analysis identified quartz as predominant,along with muscovite,biotite,and accessory minerals like rutile and magnetite.Petrographic analysis highlighted quartz as dominant,with fractures suggesting tectonic influences,while heavy mineral separation techniques identified zircon,garnet,goethite,rutile,and magnetite.These findings provide insights into sediment provenance,depositional processes,and environ-mental conditions during the formation of the Dupi Tila Formation.The comprehensive geochemical data of the entire rock indicates that most of the sediments originated from felsic igneous sources,and also suggests a moderate to high level of weathering in the source region.Overall,the analyses suggested an in situ origin of the Dupi Tila Formation,with parent materials being predominantly detrital rather than authigenic,supported by the presence of detrital quartz and an assessment of the depositional environment,providing insights into the geological conditions of the era and potential modes of sediment transportation.展开更多
Although significant progress has been made in micromechanical characterization and upscaling of homogeneous materials,systematic investigations into deposition-controlled micro–macro rheological relationships in het...Although significant progress has been made in micromechanical characterization and upscaling of homogeneous materials,systematic investigations into deposition-controlled micro–macro rheological relationships in heterogeneous sedimentary soft rocks remain limited,particularly concerning timedependent viscous parameter upscaling.This study investigates six typical fluvial and lacustrine microfacies from the Ordos Basin,China,including riverbed lag,natural levee,floodplain lake,point bar,sheet sand,and shallow lake mud.Mineral composition and microstructure are characterized,and nanoindentation creep tests quantify viscoelastic properties.A micro–macro upscaling method that transforms the time-domain Burger model into the frequency domain and utilizes three traditional homogenization schemes:dilute approximation,Mori-Tanaka,and self-consistent methods,for comparative estimation of macroscopic rheological parameters is proposed.Microstructural analysis demonstrates distinct fabric patterns controlled by depositional energy.Floodplain lake and sheet sand microfacies show superior rheological stability due to dense quartz skeletons,whereas riverbed lag and shallow lake mud perform poorly,caused by skeleton relaxation and clay-dominated slip,respectively.The point bar microfacies exhibits a“rigid-soft hybrid”behavior,with high long-term stability but reduced transient stability.Comparatively,the frequency-domain upscaling framework developed in this study,incorporating the Mori-Tanaka scheme,demonstrates satisfactory agreement with experimental data,validating its capability to predict macroscopic viscoelastic properties from microstructural features.展开更多
The patterns of metal distribution and alteration zonation in magmatic-hydrothermal systems primarily focus on porphyry deposit and other closely associated types,such as skarn,epithermal and distal vein deposits(e.g....The patterns of metal distribution and alteration zonation in magmatic-hydrothermal systems primarily focus on porphyry deposit and other closely associated types,such as skarn,epithermal and distal vein deposits(e.g.,Zheng,2022;Hutchison et al.,2020;Cooke et al.,2011;Hedenquist et al.,1998).展开更多
The black shales of Wufeng and Longmaxi Formation(Late Ordovician-Early Silurian period)in Sichuan Basin are the main strata for marine shale gas exploration,which have a yearly shale gas production of 228×10^(8)...The black shales of Wufeng and Longmaxi Formation(Late Ordovician-Early Silurian period)in Sichuan Basin are the main strata for marine shale gas exploration,which have a yearly shale gas production of 228×10^(8)m^(3)and cumulative shale gas production of 919×10^(8)m^(3).According to the lithological and biological features,filling sequences,sedimentary structures and lab analysis,the authors divided the Wufeng/Guanyinqiao and Longmaxi Formations into shore,tidal flat,shoal,shallow water shelf and deep water shelf facies,and confirmed that a shallow water deposition between the two sets of shales.Although both Formations contain similar shales,their formation mechanisms differ.During the deposition of Wufeng shale,influenced by the Caledonian Movement,the Central Sichuan and Guizhou Uplifts led to the transformation of the Sichuan Basin into a back-bulge basin.Coinstantaneous volcanic activity provided significant nutrients,contributing to the deposition of Wufeng Formation black shales.In contrast,during the deposition of Longmaxi shale,collisions caused basement subsidence,melting glaciers raised sea levels,and renewed volcanic activity provided additional nutrients,leading to Longmaxi Formation black shale accumulation.Considering the basic sedimentary geology and shale gas characteristics,areas such as Suijiang-Leibo-Daguan,Luzhou-Zigong,Weirong-Yongchuan,and Nanchuan-Dingshan are identified as key prospects for future shale gas exploration in the Wufeng-Longmaxi Formations.展开更多
The lower member of Dalazi Formation is an important oil reservoir in the Songjiang Basin.Based on the research on its field-measured geological profiles,lithological combination characteristics and grain size distrib...The lower member of Dalazi Formation is an important oil reservoir in the Songjiang Basin.Based on the research on its field-measured geological profiles,lithological combination characteristics and grain size distribution characteristics,combined with the analysis of the spatial distribution characteristics,sedimentary structural characteristics and hydrodynamic conditions of the sediments in this member,nine sedimentary microfacies of the fan delta plain subfacies,fan delta front subfacies and littoral-shallow lacustrine subfacies have been identified.The study reveals that lower member of Dalazi Formation in the research area follows a fan delta–shallow lacustrine depositional model in the steep slope zone of a rift lake basin.The sediments primarily originate from the Pre-Mesozoic strata in the steep southeastern and eastern margins.The basin center migrated from the early Xiaoshahe area to the Yangmucun–Shenglicun area,and the sedimentary system gradually transitioned from fan delta to littoral-shallow lacustrine facies.展开更多
基金funded by the National Key Basic Research Program (973) (No. 2006CB202302)National Natural Science Foundation Program (No. 40372056)+1 种基金Fundamental Research Funds for the Central Universities(2010ZD07)the Frontier Research Project of Marine Facies (Evolution of the Tarim Basin and Surrounding Areaand Petroleum Resource Prospecting)
文摘The Silurian in the Tarim Basin was deposited on the basement deformed by the Caledonian tectonic movements at the end of the Late Ordovician. The development and distribution of sedimentary sequences of the Early Silurian have been clearly controlled by the palaeogeomorphology of the Late Ordovician. Based on unconformity characteristics and distribution of erosion, several zones can be differentiated including a high uplifted erosion zone, a transitional slope zone and a depression zone. The central and west Tabei Uplift zones show high angular unconformity and intense erosion. The Tarim Basin in the late Ordovician shows characteristics of higher in the west, lower in the east while higher in the south, lower in the north. The Early Silurian mainly developed transgressive and highstand systems tracts on the whole, while the lowstand systems tract only developed partly below the slope break. The palaeogeomorphology controlled the elastic source supply and deposit distribution. Braided delta system and tidal flat-estuary system were deposited. The duration of uplifting of the Tazhong paleo- uplift was longer than that of the Tabei paleo-uplift, and deposition was later. This led to the lower and middle members of the Kepingtage Formation missing in that area. As a large-scale transgression occurred during the deposition period of the upper member of the Kepingtage Formation, sediment from the west of the basin was transported and deposited by tides and waves, forming tidal-marine debris systems above the uplift. Proximal alluvial fan and fan delta coarse elastic deposits developed in proximal uplift zone in the east and southeast of the basin, and braided delta put forward to the transitional zone between the edge of uplift and the sea. Large-scale tidal channel, sub-distributary channel and mouth bar of the delta front can form favorable reservoirs, and they are primary targets for oil and gas exploration. This research on sequence-depositional systems development and distribution controlled by palaeogeomorphology is significant in guiding the prediction of reservoir sandstones.
基金supported by the SINOPEC Forward Looking Project of China (No. YPH08114)
文摘The reef-shoal depositional system of the Ordovician carbonate platform margin is well exposed in the Yijianfang （一间房） outcrop of the Bachn （巴楚） uplift region, which offers an advantageous condition to study their paleoecology. Using a detailed field geologic survey and illustrated profiles of typical depositional systems, three types of genetic facies associations can be recognized in the reef-shoal depositional system： an organic reef, an organic shoal, and an upper slope. The organic reef is composed of three types of genetic facies （a reef base, a reef core, and fore-reef breccias）; the organic shoal is formed from five types of genetic facies （tide channels, fore-reef inner shoals, fore-reef outer shoals, back-reef inner shoals, and back-reef outer shoals）. The studies of the paleontological assemblage in each genetic facies of the depositional system indicate that the fauna preserved in each genetic facies are varied. The calathium, archaeoscyphia, bryozoan, and calcareous alga are well preserved in the organic reefs. The organisms preserved in the organic shoals are generally fragmented, while weil-preserved girvanella and nuia siberica with a content of about 15% in the back-reef outer shoals are the most characteristic and different from others. The sinoceras, trilobites, and gastropods are well preserved in the upper slope deposits. The studies will demonstrate that the reef-shoal complexes developed above the base of the fair-weather wave base and that the original hydrodynamic conditions for the reef core forming is the stronger and become more and more low-energy from the inner part to outer part of the organic shoals.
基金supported by the National Key Research and Development Program of China (No.2018YFC0604202)from the Ministry of Science and Technology of China and the International Geosciences Program (No.IGCP675)
文摘Uranium exploration breakthrough was extremely rare in an aeolian depositional system.In order to know the complicate characteristics of oxidation associated closely with uranium mineralization in the aeolian depositional system,petrology and mineralogy markers of the oxidation and its genetic mechanisms are identified and illustrated by fieldwork,thin section analysis and scanning electron microscopy test,based on 2 field outcrops in Zhenyuan County in the southwest of the Tianhuan depression in the Ordos Basin and the core of 2 wells in the north and south of Ordos Basin.The results showed:the typical macroscopic indicator of primary oxidation was the red fine sediments in the aeolian interdune with a thickness of 10-50 cm,and the microscopic characteristics of primary oxidation were the minerals such as hematite,ilmenite,and the irony matrix rich in fine-grained dolomite and biotite;the phreatic oxidation was manifested as the red sandstone with limonite horizontal layer with a thickness of 1-4 cm and a width of 60 cm-1 m,and the circular limonite nodules with a diameter of 3-7 cm,in which there was intergranular limonite cement;the interlayer oxidation was characterized by lenticular tongue and tapered red sandstone with a length of 1-10 m and a width of 10 cm-5m,in which detrital particles are coated with hematite and hematite was distributed inside the rhombus dolomite.The paleoclimate of the sedimentary period,the water-table movement and the pore and permeability conditions of the sand body were the key factors for the formation of different oxidation types in the aeolian depositional system.
基金granted by the National Science and Technology Major Project(2011ZX05004-001)
文摘Using analyses of the lithology,sequences,paleoenvironment,and tectonic setting,the depositional system of the Carboniferous Huanglong Formation in the eastern Sichuan Basin was identified.The lithological characteristics of the Lower Member,Middle Member,and Upper Member were analyzed and classified.Before the use of carbon,oxygen,and strontium isotopes in the analysis,all of the geochemical data were tested for validity.On the basis of the Z values obtained from carbon and oxygen isotopes,the paleoenvironments of the three members were elucidated.Lower Member was dominantly an enclosed marine environment with intense evaporation and little freshwater input into the sea.Middle Member developed in a semi-enclosed to normal marine environment with many rivers.Upper Member was formed in a normal marine environment.The east Sichuan Basin was enclosed by paleouplifts before the deposition of the Huanglong Formation,forming a relatively enclosed depositional setting.Paleogullies developed in the Silurian strata that underlie the Carboniferous rocks;these paleogullies can be identified.On the basis of a comprehensive analysis,we propose that the Huanglong Formation developed in a platform system.Four microfacies were identified：supratidal flat,dolostone flat,grain shoal,and shelf microfacies.The high-permeability and high-porosity characteristics of the grain shoal microfacies are favorable for hydrocarbon accumulation,while the supratidal flat and shelf microfacies developed very few high-quality reservoirs.The paleogullies,in which increased amounts of grain shoal microfacies developed,controlled the distribution of high-quality reservoirs.
文摘Based on drilling and seismic data, the Paleogene developed in Liaodong Bay can be divided into five third-order sequences bounded by six sequence boundaries. Through analyzing depositional systems in each sequence in detail, the Es-3 time was defined as fast rifting. During the deposition of the Es-3 member, the lake basin was continuous along the N-S direction but compartmentalized along the E-W direction by several N-S trending faults. Deposition was dominated by steep slope fans and fan deltas. The time of Es-2 and Es-1 was stable settling. The lake basin expanded substantially. The fan delta system and braided fluvial system were developed. Carbonate and clastic deposits were formed on the Liaoxi （west Liaohe） Rise. The time of Ed-3 time was again fast rifting. During this time, shale was deposited. In the time of Es-2, tectonic movement weakened. The basin was higher in the west and north, and lower in the east and south. A series of delta depositional systems were developed and smallscale slumping turbidite fans were present in semi-deep lake to deep lake. In the time of Ed-1, tectonic movement stopped. Flood plain deposition occurred. Finally the paper presents the characteristics of evolution and distribution of depositional systems both vertically and horizontally.
文摘In the Karamay oilfield located on the northwestern margin of Junggar basin, Xinjiang, China, a large area of the Karamay Formation is exposed at outcrop in the northeast of the oilfield, a consequence of thrusting. The Middle Triassic Karamay Formation in the outcrop area is a type of terrestrial third-order sequence, bounded by two easily recognizable sequence boundaries: a regional surface of angular unconformity (SB1) at the base and a regional unconformity (SB2) at the top. Within the Karamay Formation, two lacustrine expansion events can be recognized and be used to identify both the initial and the maximum lacustrine flooding surfaces. The two lacustrine flooding surfaces serve as references for the classification of this third-order sequence-Karamay Formation into the following three sedimentary successions: a lower lowstand systems tract (LST), a middle lacustrine-expanding systems tract (EST), and an upper highstand systems tract (HST). Different systems tracts are composed of different depositional system assemblages. In this paper, each depositional system is described in detail. The lowstand systems tract in the study area is characterized by incised valleys. At the base and on the margin of the incised valleys occur alluvial fan depositional systems, and in the upper and distal parts of the alluvial fan, low-sinuosity river depositional systems. The lacustrine-expanding systems tract consists of a lacustrine depositional system and a lacustrine delta depositional system, overlying the lower incised valley fills. The highstand systems tract is filled by a widespread lacustrine braided delta depositional system. The analysis of sequence stratigraphy in this paper serves the description of the spatial distribution of the reservoir. The depositional system analysis serves the description of the reservoir types. Field investigations of oil sandstone and oil seepage show that the Karamay Formation is composed of several types of reservoirs. However, two types of high quality reservoir occur both in the upper interval of the lowstand systems tract and in the lacustrine-expanding systems tract: gravelly low-sinuosity channel in the distal fans and sandy-gravelly distributary channel in the lacustrine delta plain.
文摘It is a major continuous depocenter in Dalangtan area,western Qaidam basin since Early Cenozoic,which is most important Neogene salt deposits center in Qaidam basin.The Miocene Saline lake was developed firstly in
基金supported by the National Natural Science Foundation of China (No. 41322013)the Program for New Century Excellent Talents in Universities (No. NCET-110723)+2 种基金the National Key Basic Research Development Program of China (No. 2012CB822003)the Programme of Introducing Talents of Discipline to Universities (No. B14031)the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan) (No. CUG110611)
文摘The Upper Eocene–Lower Oligocene Qianjiang Formation of the Jianghan Basin in central China consists of a 4700-m-thick lacustrine succession, containing 1800 m of halite deposits. The maximum thickness of the formation is 4700 m, and includes 1800 m of halite. We have identified eight third-order depositional sequences based on pinch-out and onlap stratigraphic patterns in 2-D and 3-D seismic data and well logs. The basin evolved from a deep to shallow under-filled lake during the Eocene–Oligocene interval. The main rock types are dark mudstones, halite, and siltstone/sandstone in the depocenter, and alternating mudstone and gypsum in shallower areas. The vertical succession indicates a strong sedimentary cyclicity. Depositional facies indicate the presence of two lake system types. Halite developed in a saline lake system, whereas clastic sediments were deposited in freshwater lake systems. The alternating sediment types indicate that the basin cycled repeatedly between saline and freshwater lake systems. This cyclicity was caused by availability of accommodation space that was controlled by a combination of climate change, tectonic subsidence and sediment supply; notably, the highest frequency cycles occurred at Milankovitch timescales controlled by the Earth＇s orbital variations. The cyclic halite plays an important role in generating and preserving oil in the Qianjiang Formation of the Qianjiang depression.
文摘Baise basin is a semi-graben type , pan-shaped faulted basin of Early Tertiary , in which carbonate lacustrine deposits and elastic lacustrine deposits developed . The assemblages of Gilbert-type delta-lakes ,littoral ,shallow and deep water fades are recognized . Based on grain size , the clastic lacustrine deposit systems can be grouped in three kinds of depositional sequences of progressive deposition : (1)from coarse to fine , (2)from fine to coarse and (3) from fine to coarse and then to fine agan . This was controlled mainly by hydrodynamic factor of lake bottom type .Lake shore was an important place for coal accumulation and peatmoor development . It had long time for coal accumulation and there was a very little amount of minerals into the basin ,and the thick coal layer and high quality coal developed m the zone where initial lake bottom was plan-like and the surface stream flow was weak .Peat accumulation advanced from the margin to the center of basin .Carbonate lakes contained much water ,very high preponderant contenis of coagel ,low inert contents and no fusinite in the coal .
基金Supported by the China National Science and Technology Major Project(2017ZX05032-001)
文摘To make clear about the sedimentary facies types and distribution of deep water sandstone reservoirs in Campos basin of Brazil,this paper researches the characteristics of deep-water sedimentary system in Campos basin through the comprehensive analysis of drilling,logging and seismic data.There are 3 subfacies and 7 microfacies in the study area.There are 3 channels from south to north in Upper Cretaceous Maastrichtian,and the sedimentary incised valley and compound channels developed in micro-salt basin are the main deep water depositional types.The Paleocene to Eocene dominated by sedimentary incised valley and eroded compound channel deposits,also include 3 channel systems.From Oligocene to Miocene,the main deposition type is lobe,which is mainly distributed in central-north of the basin.Corresponding to deep water depositional stages,3 kinds of depositional models are found.From Turonian to Maastrichtian of Upper Cretaceous,with tectonic uplift,strong source material supply,and the negative topography produced by salt rock movement providing favorable accommodation for sand deposition,the depositional model was terrigenous direct feed mechanism with sedimentary incised valley and compound channels in micro salt basin.From Paleocene to Eocene,as the amplitude of tectonic uplift reached the maximum and the accompanied erosion peaked,accommodation space offered by micro salt basin was leveled up;the depositional model was terrigenous direct feed mechanism with sedimentary valley and incised compound channels.From Oligocene to Miocene,because of sable tectonics,sea level fluctuation is the main controlling factor for deep water deposition,so the depositional model was wide shelf indirect feed mechanism with bypass incised valley and lobe.The analysis of the characteristics and controlling factors of the 3 types deep-water sedimentary systems during 3 different stages in Campos Basin can provide valuable reference for the oil exploration in deep-water deposits in the Campos Basin and across the world.
基金Supported by Key Technologies Research and Development Program (Grant No.2001BA605A09-1)
文摘With a comprehensive geological and geophysical data base,the Paleogene in the Liaodong Bay area,which consists of the Kongdian,Shahejie and Donghying Formations from the base to top,was divided into 4 second-order sequences and 8 third-order sequences based on the characteristics of the se-quence boundaries. Each third-order sequence is subdivided into the lowstand,lake transgressive and highstand systems tracts. The Lowstand systems tract (LST) is mainly composed of progradational parasequence sets,while the lake transgressive systems tract (TST) largely consists of the retrograda-tional parasequence sets and the highstand systems tract (HST) is dominated by the progradational parasequence sets. The main types of depositional systems include the shallow lake,semi-deep lake,deep lake,delta,fan delta,braided fluvial delta and nearshore subaqueous fan. The braided fluvial delta and fan delta depositional systems are mainly confined to the sequences of the lower SEs4-Ek,SEs3 and SEs1+2,while the sequences of SEd3,SEd2 and SEd1 are dominated by the delta and nearshore subaqueous fan depositional systems with the latter being developed at the downthrown side of the basin-bounding fault in each sequence. The evolution of the depositional systems is always con-trolled by the paleo-tectonic setting and the ancient landform in the space and geological time. It is concluded that the most favorable reservoirs are distributed in the Liaoxi low uplift and the central Liaozhong sag.
基金Projects(41506080,41702162)supported by the National Natural Science Foundation of ChinaProjects(DD20160152,DD20160147,GZH200800503)supported by China Geological Survey+1 种基金Projects(XQ-2005-01,2009GYXQ10)supported by China Ministry of Land and ResourcesProject(201602004)supported by the Postdoctoral Innovation Foundation of Shandong Province,China
文摘In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is believed that the Upper Permian–Lower Triassic can be regarded as a long-term base-level cycle.Based on drilling data,characteristics of the lithology–electric property combination cyclicity,and the special lithology,the long-term base-level cycle was divided into five medium-term base-level cycles(MC1–MC5).On this basis,the Permian–Triassic sedimentary systems and their filling model were analyzed in accordance with the change of base-level cycle and transition of sedimentary environment,as well as characteristics of the drilling sedimentary facies and seismic facies.The results show that there were six sedimentary systems(fluvial,delta,tidal flat,open platform,restricted platform,and continental shelf)developed in the Upper Permian–Lower Triassic,the sedimentary systems were distributed such that the water was deep in the northwest and shallow in the southeast,and there were two base-level cycle filling models(a relatively stable tidal flat facies and a rapidly transgressive continental shelf facies to stable platform facies)developed in the Upper Permian–Lower Triassic.These models can provide a basis for evaluation of the Mesozoic–Paleozoic hydrocarbon geology in the South Yellow Sea Basin.
文摘Gas chromatography-mass spectrometry(GC-MS)was used to analyze the pentacyclic triterpenoid distributions,specifically hopane and oleanane fingerprints,in 24 crude oil samples from the Niger Delta depobelts,with the aim of defining the petroleum system,filling history,and the age of source rock producing these oils.The results indicate that the Niger Delta oils belong to a single fluvio-deltaic petroleum system,reflecting similar source organic facies and depositional environments.Geochemical parameters,including C29/C30hopane ratios,oleanane index,Ts/Tm,(Ts/(Ts+Tm)),moretane/C30hopane ratios,and C3222S/(22S+22R)ratios,suggest oxic conditions during source rock deposition and thermal maturity of the oils.The presence of terrigenous organic matter and complex filling history are also evident and influenced by multiple phases of sedimentation,and petroleum generation.A comparative plot of geologic time(Paleogene-Neogene age)and oleanane percentage composition show that the crude oils are constrained to the chronostratigraphic ages of their respective depobelts,demonstrating the potential of oleanane-derived parameters for relative dating of hydrocarbon sources,complementing traditional index fossil methods.
基金financial support from the National Natural Science Foundation of China(Grant No.41941018).
文摘The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings.Natural boulders can be highly random and unpredictable.Consequently,boulder control during debris flows is crucial but difficult.Herein,an eco-friendly control system featuring anchoring natural boulders(NBs)with(negative Poisson's ratio)NPR anchor cables is proposed to form an NB-NPR baffle.A series of flume experiments are conducted to verify the effect of NB-NPR baffles on controlling debris flow impact.The deployment of NB-NPR baffles substantially influences the kinematic behavior of a debris flow,primarily in the form of changes in the depositional properties and impact intensities.The results show that the NB-NPR baffle matrix successfully controls boulder mobility and exhibits positive feedback on solid particle deposition.The NB-NPR baffle group exhibits a reduction in peak impact force ranging from 29%to 79%compared to that of the control group in the basic experiment.The NPR anchor cables play a significant role in the NB-NPR baffle by demonstrating particular characteristics,including consistent resistance,large deformation,and substantial energy absorption.The NB-NPR baffle innovatively utilizes the natural boulders in a debris flow gully by converting destructive boulders into constructive boulders.Overall,this research serves as a basis for future field experiments and applications.
基金Supported by the National Natural Science Foundation of China(Nos.42130206,41302076)the Ministry of Science and Technology of the People’s Republic of China(MOST)Special Fund+1 种基金the State Key Laboratory of Continental Dynamics,Northwest University(No.201210128)the Major Scientific and Technological Projects of Changqing Oilfield(No.ZDZX-2021-03)。
文摘Early Cambrian organic-rich shales in the Yangtze Plate are key shale gas exploration targets in China,but their sedimentary environments are not well understood.This lack of knowledge complicates the evaluation of these targets and associated risks.Assessing shale depositional environments is also challenging due to the fine-grained nature of the sediments and subtle compositional variations.Herein,marine black shales of the Lower Cambrian Shiyantou(SYT)Formation(Fm)and Yu'anshan(YAS)Fm are investigated through a series of experiment,including thin sections,scanning electron microscopy,and major and trace elements analysis.Results show that five lithofacies can be identified in the SYT and YAS shales:(1)calcareous mudstone;(2)wavy-laminated sand,silt,and clay bearing mudstone;(3)laminated and massive mudstone;(4)planar-laminated pyritic mudstone,and(5)thin bedded sand and siltstone.Average content of major elements SiO_(2),Al_(2)O_(3),MgO,Fe_(2)O_(3),K_(2)O,CaO,Na_(2)O,TiO_(2),P_(2)O_(5),and MnO of SYT Fm are 57.03%,12.74%,4.20%,3.97%,3.93%,3.35%,1.09%,0.68%,0.28%,and 0.05%,respectively.Average content of major elements SiO_(2),Al_(2)O_(3),MgO,Fe_(2)O_(3),K_(2)O,CaO,Na_(2)O,TiO_(2),P_(2)O_(5),and MnO of Yu'anshan Fm are 54.93%,14.52%,5.26%,6.00%,3.77%,3.88%,0.15%,0.63%,0.19%,and 0.10%,respectively.Samples from SYT Fm are enriched in Li,V,Cr,Co,Zr,Cs,and U relative to Upper Continental Crust(UCC)and most of shale samples from YAS Fm are enriched in Li,V,Co,and U relative to UCC.The marine black shales are deposited in dynamic anoxic to oxic environment in upper Yangtze Plate,which indicated the seabed had already oxidized in the Cambrian Stages 2 and 3.The Chemical Index of Alteration(CIA)values ranged 51.84–79.46 indicate a warm and humid climate in the 2 stages.These findings are consistent with the region's paleogeography and previous studies.They hold significance for sedimentologists,paleontologists,and other researchers involved in petroleum geology.
文摘A comprehensive examination of detrital sandstone modes from the Sylhet Trough reveals a diverse range of sub-lithic to sub-feldspathic quartz arenites.Soil samples were gathered from Dupi Gaon(Jaintiapur)in Bangladesh,followed by a thorough analysis using field examination,X-ray diffraction(XRD),X-ray fluorescence(XRF),petrography,and heavy mineral concentration analyses.Field observations revealed the soil sample varying from white to yellowish to variegated,with thicknesses ranging from 15 cm to about 4 m,and exhibiting moderate softness.XRF analysis revealed significant SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3)levels in the samples,with zirconium(Zr)and copper(Cu)showing consistently high concentrations.XRD analysis identified quartz as predominant,along with muscovite,biotite,and accessory minerals like rutile and magnetite.Petrographic analysis highlighted quartz as dominant,with fractures suggesting tectonic influences,while heavy mineral separation techniques identified zircon,garnet,goethite,rutile,and magnetite.These findings provide insights into sediment provenance,depositional processes,and environ-mental conditions during the formation of the Dupi Tila Formation.The comprehensive geochemical data of the entire rock indicates that most of the sediments originated from felsic igneous sources,and also suggests a moderate to high level of weathering in the source region.Overall,the analyses suggested an in situ origin of the Dupi Tila Formation,with parent materials being predominantly detrital rather than authigenic,supported by the presence of detrital quartz and an assessment of the depositional environment,providing insights into the geological conditions of the era and potential modes of sediment transportation.
基金financially supported by the National Natural Science Foundation of China(No.42472334)DeepEarth Probe and Mineral Resources Exploration-National Science and Technology Major Project(No.2024ZD1004208)the China Postdoctoral Science Foundation(No.2025M771774)。
文摘Although significant progress has been made in micromechanical characterization and upscaling of homogeneous materials,systematic investigations into deposition-controlled micro–macro rheological relationships in heterogeneous sedimentary soft rocks remain limited,particularly concerning timedependent viscous parameter upscaling.This study investigates six typical fluvial and lacustrine microfacies from the Ordos Basin,China,including riverbed lag,natural levee,floodplain lake,point bar,sheet sand,and shallow lake mud.Mineral composition and microstructure are characterized,and nanoindentation creep tests quantify viscoelastic properties.A micro–macro upscaling method that transforms the time-domain Burger model into the frequency domain and utilizes three traditional homogenization schemes:dilute approximation,Mori-Tanaka,and self-consistent methods,for comparative estimation of macroscopic rheological parameters is proposed.Microstructural analysis demonstrates distinct fabric patterns controlled by depositional energy.Floodplain lake and sheet sand microfacies show superior rheological stability due to dense quartz skeletons,whereas riverbed lag and shallow lake mud perform poorly,caused by skeleton relaxation and clay-dominated slip,respectively.The point bar microfacies exhibits a“rigid-soft hybrid”behavior,with high long-term stability but reduced transient stability.Comparatively,the frequency-domain upscaling framework developed in this study,incorporating the Mori-Tanaka scheme,demonstrates satisfactory agreement with experimental data,validating its capability to predict macroscopic viscoelastic properties from microstructural features.
基金supported by the National Natural Science Foundation of China(Nos.42122012,U2444208)the Inner Mongolia Academician Project(No.2022-TZH03)the Fundamental Research Funds for the Central Universities(No.2652023001)。
文摘The patterns of metal distribution and alteration zonation in magmatic-hydrothermal systems primarily focus on porphyry deposit and other closely associated types,such as skarn,epithermal and distal vein deposits(e.g.,Zheng,2022;Hutchison et al.,2020;Cooke et al.,2011;Hedenquist et al.,1998).
基金supported by the project of the China Geological Survey(DD20221661).
文摘The black shales of Wufeng and Longmaxi Formation(Late Ordovician-Early Silurian period)in Sichuan Basin are the main strata for marine shale gas exploration,which have a yearly shale gas production of 228×10^(8)m^(3)and cumulative shale gas production of 919×10^(8)m^(3).According to the lithological and biological features,filling sequences,sedimentary structures and lab analysis,the authors divided the Wufeng/Guanyinqiao and Longmaxi Formations into shore,tidal flat,shoal,shallow water shelf and deep water shelf facies,and confirmed that a shallow water deposition between the two sets of shales.Although both Formations contain similar shales,their formation mechanisms differ.During the deposition of Wufeng shale,influenced by the Caledonian Movement,the Central Sichuan and Guizhou Uplifts led to the transformation of the Sichuan Basin into a back-bulge basin.Coinstantaneous volcanic activity provided significant nutrients,contributing to the deposition of Wufeng Formation black shales.In contrast,during the deposition of Longmaxi shale,collisions caused basement subsidence,melting glaciers raised sea levels,and renewed volcanic activity provided additional nutrients,leading to Longmaxi Formation black shale accumulation.Considering the basic sedimentary geology and shale gas characteristics,areas such as Suijiang-Leibo-Daguan,Luzhou-Zigong,Weirong-Yongchuan,and Nanchuan-Dingshan are identified as key prospects for future shale gas exploration in the Wufeng-Longmaxi Formations.
基金Supported by Jinchang City Level Science and Technology Plan Project(No.2023RC012).
文摘The lower member of Dalazi Formation is an important oil reservoir in the Songjiang Basin.Based on the research on its field-measured geological profiles,lithological combination characteristics and grain size distribution characteristics,combined with the analysis of the spatial distribution characteristics,sedimentary structural characteristics and hydrodynamic conditions of the sediments in this member,nine sedimentary microfacies of the fan delta plain subfacies,fan delta front subfacies and littoral-shallow lacustrine subfacies have been identified.The study reveals that lower member of Dalazi Formation in the research area follows a fan delta–shallow lacustrine depositional model in the steep slope zone of a rift lake basin.The sediments primarily originate from the Pre-Mesozoic strata in the steep southeastern and eastern margins.The basin center migrated from the early Xiaoshahe area to the Yangmucun–Shenglicun area,and the sedimentary system gradually transitioned from fan delta to littoral-shallow lacustrine facies.
