Objective The 5th member of the Ordovician Majiagou Formation in the southern Sulige gas field primarily consists of karst reservoirs， with proven reserves exceeding 100 billion cubic meters. However， during development， severe water production and complex gas-water relationships have been observed， and the distribution patterns and controlling factors of gas and water remain unclear， significantly constraining the release of the gas production potential of the region. Methods Based on formation water geochemical analysis， various chemical parameters （i.e.， Na⁺/Cl^-， desulfurization， Mg²⁺/Ca²⁺， Na⁺/Ca²⁺ and Na⁺ + Cl^-/Mg²⁺ coefficients） were analyzed to determine the formation environment of the water. The distribution patterns of gas and water were then studied by identifying the water-bearing intervals in individual wells， and by cross-well gas reservoir profile comparisons and the planar distribution of different formation water types. Finally， the controlling factors of gas-water distribution were explored in relation to the hydrocarbon source rock， karst reservoir heterogeneity and structural features. Results The total salinity of formation water （total dissolved solids） in the 5th member of the southern Sulige gas field is relatively concentrated （mean 83 598.7 mg/L）， with slightly acidic pH. The water type is predominantly CaCl₂， and exhibits low chloride-sodium coefficients， low desulfurization coefficients， low magnesium-calcium coefficients， low sodium-calcium coefficients and high metamorphism coefficients， all indicating good formation sealing favorable for gas reservoir preservation. These parameters show similar characteristics over the area， controlled by the karst reservoirs. The formation water is classified into three types， based on genetic differences， spatial distribution and reservoir properties： Type I （structural low-position water）， Type II （isolated lenticular water） and Type III （low-permeability trapped water）. Type I is mainly developed in karst areas， controlled by karst residual hill units， with a unified gas-water interface， and is the primary region for high-efficiency wells. Type II is sporadically distributed and influenced by the planar distribution of karst depressions and troughs， with moderate reservoir properties， representing a potentially favorable exploitation zone. Type III indicates poor reservoir properties. Conclusions The distribution of formation water is controlled by three factors： hydrocarbon source rock， karst reservoir heterogeneity and local structures within individual karst units. Insufficient hydrocarbon supply from the source rock is the fundamental reason for the development of formation water. The heterogeneity of the karst reservoir dictates the gas-water distribution pattern， and local structures have resulted in gas-water differentiation， with a unified gas-water interface within the same karst unit.

Objective The catastrophic failure of large submarine landslides can result in the deformation and destruction of thousands of square kilometers of seafloor， transporting hundreds to thousands of cubic kilometers of submarine sediments. This process dramatically reconstructs the seafloor topography of the continental shelf-slope region and has a profound impact on subsequent submarine sedimentation processes. Methods The topographic features of different large submarine landslides were qualitatively described using multibeam bathymetric and seismic reflection data， and the key geometric parameters of the submarine landslide top surface， such as area and volume， were quantitatively characterized. Based on the scale， morphological features， and formation mechanisms of the associated reliefs on the submarine landslide top surface， these landslides were separated into three categories： head evacuation zone， locally negative accommodation associated with internal fault systems， and locally negative accommodation associated with internal deformation blocks. The mechanisms of the three types of negative accommodation on the subsequent turbidity current system are then discussed separately. Results Firstly， the head evacuation zone is typically associated with hundreds to thousands of square kilometers of negative accommodation， which acts as a "funnel" during sediment transport along the continental margin， effectively capturing and concentrating subsequent turbidity currents while enhancing the transport efficiency of gravel and coarse sand and playing a crucial role in the accumulation of marine organic matter. Secondly， the striped negative accommodation associated with internal fault systems and the irregular negative accommodation associated with internal deformation blocks can regulate the sedimentation dynamics of subsequent turbidity currents， such as constraining flow direction， enhancing erosion intensity， and forcing channels to avulse. Finally， the negative accommodations associated with the submarine landslide top surface may produce synergistic effects， influencing the sediment filling and evolution of sedimentary basins and the distribution of sedimentary centers over millions of years. Conclusions The investigation of the morphological characteristics of submarine landslide top surfaces and their controlling effects on the subsequent turbidity currents sedimentary dynamic process can provide key geological information for clarifying the transport process of marginal sediments， identifying the distribution of sand-rich reservoirs in deep-sea sedimentary basins， and predicting the development range of catastrophic turbidity currents.

Objective The climate signals of the Danxia strata， a representative of Cretaceous continental red beds， offers key insights into red-bed sedimentation and Cretaceous geological events. Methods This study examined fine-grained clastic rocks in the Upper Cretaceous Danxia Basin， specifically the Second member and Fourth member of the Changba Formation and the Jinshiyan member of the Danxia Formation. Sedimentology， elemental and isotopic geochemistry were used to investigate the sedimentary environment and paleoclimate significance during key Upper Cretaceous stages （Cenomanian， Turonian， Campanian）. Results It was found that the fine-grained clastic rocks of these formations were deposited during a warm and humid climate phase， with suboxic to oxic water conditions. The water bodies were predominantly brackish， while localized high-salinity brackish and low-oxygen environments （e.g.， the Fourth member of the Changba Formation） were associated with lake shrinkage and climatic aridification. Water depth variations exhibit trends of initial contraction followed by expansion， gradual contraction， then initial expansion followed by contraction， which align with the changes in sedimentary facies and environment. Conclusions The Upper Cretaceous terrestrial sedimentary records of the Danxia Basin illustrate the climatic evolution of intermontane basins， shaped by global climate patterns of the Upper Cretaceous， as well as by significant influences from local topographic and geomorphic features.

Objective The cathodoluminescence （CL） characteristics of carbonate minerals are closely related to their major/trace and rare earth element （REE） contents. Existing studies primarily focus on the effects of Mn and Fe on CL， often neglecting the role of REEs. This study aims to investigate the influence of major/trace and rare earth elements on the CL characteristics of carbonate minerals， thereby providing geological evidence for inferring mineral genesis， depositional environments， and diagenetic processes. Methods CL and laser ablation inductively coupled plasma mass spectrometry （LA-ICP-MS） were used to test carbonate rock samples from the Lower and Middle Ordovician on the southern margin of the Ordos Basin. Statistical methods and classification algorithms were applied to analyze the test data， and common REE indicators were used to evaluate the properties of diagenetic fluids. Results The study reveals that matrix dolomite exhibits weak to moderate red luminescence under CL， with both zoned and uniform luminescence. Dolomite cements， with high Mn and Fe contents， are often zoned or non-luminescent. Analysis of variance （ANOVA） and Tukey's Honestly Significant Difference （HSD） post-hoc tests indicate that Fe， Mn， La， Ce， Pr， Nd， Sm， Eu， Gd， and Tb contents， and the Fe/Mn value significantly influence the CL of carbonate minerals. Non-luminescent and strongly luminescent groups are relatively easy to distinguish： non-luminescent minerals have Fe contents greater than 10，000×10^-6 or Mn contents less than 40×10^-6 . Additionally， the non-luminescent group with Fe contents over 10，000×10^-6 displays REE distribution patterns enriched in Middle Rare Earth Elements （MREE）， whereas the strongly luminescent group shows Light Rare Earth Elements （LREE） depletion and low Fe/Mn values. Using comprehensive dimensionality-reduced parameters of major/trace elements and REEs， in conjunction with Mn content， effectively distinguishes the extremely weakly luminescent， weakly luminescent， and moderately luminescent groups. The nature of diagenetic fluids during diagenesis impacts carbonate sediment composition， mineral content， and major/trace element and REE variations， directly influencing carbonate mineral CL. Conclusions By combining in situ major/trace element testing with various data processing methods， this study provides a more quantitative understanding of the impact of major/trace element and REE contents on CL intensity. These findings offer valuable insights for scholars studying the factors affecting CL.

Objective The Lower Triassic Feixianguan Formation in the Sichuan Basin contains thick oolitic beach reservoirs， which is the key layer of present oil and gas exploration. As the reserve strategic replacement field of the Sichuan Basin， the sedimentary system， reservoir properties and favorable zones in the Tieshanpo and Qilibei areas of the Feixianguan Formation are not clear， which restricts the potential deployment of oil and gas exploration in this area. Methods This study adopted comprehensive analysis of core， thin section， logging and seismic data to determine sedimentary facies types and the evolution of favorable reservoir zones in the region. Results In the study area， the Feixianguan Formation is a rimmed platform structure comprising five sedimentary facies： restricted platform， open platform， platform margin， slope and basin facies. The platform margin largely consists of oolitic beach development with obvious aggradational⁃lateral accretionary characteristics. These are mainly superimposed in the ssq2 to ssq4 periods vertically， with the largest in ssq2. Horizontally， the beach body was unstable and tended to migrate into the basin. The reservoir rock types are mainly （residual） oolitic limestone， （residual） oolitic dolomite and powder-fine crystalline dolomite. Conclusions The platform margin oolitic beach microfacies favors reservoir development in the Feixianguan Formation， and the porosity and permeability conditions are promising. well Po 5-well Poxi 1-well Po 2-well Po 1 in the Tieshanpo area and well Qilibei 1-well Qibei 102 in the Qilibei area are potentially favorable reservoir development zones. The spatial and temporal distribution and migration behavior of the beach bodies in the fourth-order sequence framework and the predicted favorable reservoir zones provide a basis for deepening the exploration and development of oolitic beach reservoirs in this region.

Objective During the Late Triassic depositional period of the Chang 7 member of the Yanchang Formation in the Ordos Basin， a set of continuously traceable shales was deposited， and the shale is currently the main stratigraphic strata for unconventional oil exploration and development. The laminated-type shale oil reservoir at the Chang 7₃ sub-member features fast lateral changing， which introduces problems such as unclear reservoir distribution， high exploration difficulty， and low drilling rate. Therefore， it is urgent to study and clarify the distribution pattern of laminated-type shale oil reservoirs. Methods First， through the latest three-dimensional （3D） seismic data， the stratigraphic dip flipping method was used to recover sedimentary paleogeomorphology. Then， we marked the seismic reflection of lacustrine mudstones， identified seismic stratigraphic comparison and division， and proposed four-stage progradational clinoforms and distribution patterns of shale oil reservoirs based on sedimentary paleogeomorphology. ［Results and Conclusions］ Combining seismic progradational sequences with palaeotopography of the lake basin， the distribution pattern of the Chang 7₃ sub-member shale oil reservoir and the genesis of shale oil gravity flow sedimentation have been clarified. The laminated-type shale oil reservoir in the Chang 7₃ sub-member is a gravity flow deposit developed on the lake paleo-uplift， located at the end of the progradational clinoforms， with poor connectivity and complex stacking relationships. In actual production， it should be explored as a "box body". The above perspective has assisted in the deployment of risky well locations and exploration discoveries for laminated-type shale oil reservoirs. It provides technical support for the scale and efficiency development of interbedded-type shale oil reservoirs.

Objective In this study， the effect of seasonal lake level changes on the sedimentary characteristics， growth process， and sedimentary architecture of the finger bar in shallow delta fronts is clarified. Methods Based on the modern mud and sand and hydrological data of finger bar in the Ganjiang Delta， sedimentary numerical simulation software Delft3D， which is commonly used in China and elsewhere， is used to conduct numerical simulation of the sedimentation of the finger bar under seasonal lake level changes and constant lake level conditions， comparing the differences in sedimentary architectures. Results The study shows that under seasonal lake level changes， the finger bar exhibit the following sedimentary architecture and growth evolution characteristics： （1） There are few finger bar， small curvature （average ~1.42）， long length （average ~9.2 km）， thick in the middle， and thin at the edge， with a thickness difference of 15.4 m. There is no evident confluence between the finger bar， presenting a plane combination style dominated by bird-foot shape. （2） The finger bar develop deep distributary channels， the natural levees are wide and thick， and the thickness of the single-stage accretionary body in the mouth bar is large. （3） The finger bar exhibit stable growth. During lake level drop， the finger bar undergo progradation， the distributary channels are mainly eroded-extended， and mouth bar deposits are formed at the front edge of the distributary channels. The distributary channels are also affected by the mouth bars and undergo diversion and breach， forming multiple terminal distributary channels， and the natural levees are almost undeveloped； during lake level rise， the finger bar undergo retrogradation， the erosion of the distributary channels is weak， the distributary channels are abandoned and optimized， and the natural levees on both sides of the distributary channels accumulate and continue to thicken. For constant lake level， the finger bar show the following sedimentary architecture and growth evolution characteristics： （1） There are many finger bar， with large curvature （average ~1.53）， short length （average ~7.2 km）， large overall thickness （maximum and minimum thickness differ by only 4.8 m）， and no evident topographic difference； multiple finger bar are constantly bifurcated and merged locally， forming a complex the finger bar network， and the plane combination style of the finger bar is mainly interlaced. （2） Deep distributary channels are developed in the finger bar， the single-stage accretion body of the estuary bar is thick， but the most important difference is that there is no natural levee deposition. （3） The growth process of the finger bar is relatively simple， with multiple the finger bar growing simultaneously， intertwining with each other， and finally forming an interlaced plane combination style. Conclusions Therefore， seasonal lake level change is an important formation condition for the finger bar at the front of shallow deltas， promoting the development of natural levees， improving the stability of distributary channels and the finger bar， and playing an important role in controlling the sedimentary architecture and growth process of the finger bar.

Objective In the middle and late stages of oil and gas field development， studying sand architecture is the key to accessing residual oil and enhancing recovery. Precise interpretation of similar outcrops provides a comparable prototype model for predicting underground reservoir architecture. Methods The shallow-water delta profiles of the Yan’an Formation in the Kaokaowusugou and Gulf Mining Industry in the Ordos Basin were the research objects. UAV oblique photography was used to obtain images of massive outcrops from which 3D digital outcrop models were established. Detailed interpretation of digital outcrop architecture was then carried out by combined field observation and indoor analysis. Results Developmental characteristics and evolutionary models of shallow-water delta front architecture during a time of rising lake levels were defined. When the lake level is low， mainly trunk-type distributary channels are developed， measuring 23.30-48.40 m wide × 0.89-1.81 m thick， with an average width-to-thickness ratio of 26.74. The sandbody superposition patterns are mainly overlay type. As the lake level rises， fork-type distributary channels， mouth bars， sand sheets and subaqueous distributary bays gradually develop. The width of the mouth bar is 53.90 m， thickness is 2.21 m， width-to-thickness ratio is 24.39， and the sandbody superposition patterns is mainly lateral splicing type. When the lake level is higher， mainly terminal-type distributary channels， mouth bars and sheet sand architectural units are developed. Terminal-type underwater distributary channels， which are isolated in muddy deposits， have widths ranging from 4.70 to 25.30 m， thickness from 0.40 to 1.03 m， and the width-to-thickness ratio from 11.75 to 24.56. Conclusions When the source supply of material is relatively stable， an increase in lake level enlarges the accommodation space. The architectural units evolve from trunk-type to terminal-type distributary channels， depositing mouth bars and sand sheets. The size of the sandbody decreases， but its width-to-thickness ratio increases. Overall， the ratio between sandstone and stratum thickness decreases， spatial connectivity decreases， and reservoir heterogeneity is enhanced.

Objective The Carnian Pluvial Episode （CPE） was a critical climatic perturbation in the Late Triassic， marked by a pronounced transition to warmer and more humid conditions. These environmental changes sub-stantially facilitated the accumulation of fine-grained sediments and the enrichment of organic matter. This study aims to elucidate the sedimentary and geochemical responses of Chang 7 member of the Yanchang Formation in the Ordos Basin to the CPE， by examining thick successions of organic-rich black shales. Methods A multi-proxy analytical approach was employed using core samples from well ZK903. Biomarker compounds serve as the principal dataset， supported by analyses of organic carbon isotopes， trace element geochemistry， and clay mineral assemblages. These proxies were used to reconstruct the paleoclimatic conditions， redox environment， paleosalinity， and organic matter sources across Chang 7 member to Chang 8 member. On this basis， an organic matter enrichment model was developed to interpret the basin’s response to the CPE. Results In the Ordos Basin， the Chang 7₃ submember records a distinct lithological transition from sandstone to black shale， signaling intensified influence from the CPE and progressively increasing organic matter accumulation. Geochemical proxies， including Sr/Cu and Sr/Rb ratios， together with clay mineral data， indicate a climatic shift from arid-hot to warm-humid conditions. Redox-sensitive parameters such as V/Cr and U/Th， along with biomarker ratios （Pr/Ph and Ts/（Ts+Tm））， point to a significant reduction in bottom-water oxygen levels during this interval. Additionally， increased Sr/Ba ratios and a higher gammacerane index （GI） suggest elevated precipitation and lake-level rise， which led to enhanced water column stratification and diminished vertical mixing. These conditions promoted the development of a freshwater， anoxic environment conducive to the preservation of organic matter. Notably， elevated values of ∑C{}_{{\mathrm{21}}^{-}} /∑C{}_{{\mathrm{22}}^{+}} and C₂₇/C₂₉ （ααα）R ratios in the Chang 7₃ interval indicate a shift in the biotic community structure， with a dominance of lower aquatic organisms， particularly algae， as the primary contributors to the organic matter pool. Conclusions The CPE exerted a profound influence on the paleoclimate and depositional dynamics of the study area. Enhanced thermal and hydrological conditions， in conjunction with lake stratification， promoted the accumulation of fine-grained sediments and created favorable conditions for both primary productivity and the preservation of organic matter. These factors jointly facilitated the formation of organic-rich black shales （oil shales） in the Yanchang Formation， underscoring the role of global climatic events in shaping regional hydrocarbon potential.

Objective The Late Triassic was a crucial period for the Mesozoic Qiangtang Basin evolution. However， the previous research concentrating on the sedimentology of the Upper Triassic strata is rare in the Qiangtang Basin， making it not conducive for elaborately analyzing the characterization of Late Triassic sedimentary evolution and predicting the distribution of source and reservoir rocks. Methods Based on the measured section， we synthesized the thin section， grain size of detrital particle， and typical primary sedimentary structure to identify the sedimentary facies of the Jiapila Formation， Bolila Formation， and Bagong Formation in the Jiang’ai Darina section and then establish the Late Triassic sedimentary evolution model in the central Qiangtang Basin. In addition， the whole-rock and clay minerals， physical properties， and total organic carbon （TOC） contents of sandstone and mudstone samples were analyzed to evaluate the characteristics of source and reservoir rocks. Results （1） In the Jiang’ai Darina section， the sedimentary facies of the Upper Triassic strata have experienced the evolution of the fan-delta facies → barrier-free coastal facies → carbonate ramp facies → neritic shelf facies → delta facies upward， and ten subfacies and eight microfacies were identified. （2） The Upper Triassic strata in the study area constitute an upward deepening transgressive succession and then a shallower regressive succession. The transgressive succession is mainly composed of the Jiapila Formation and Bolila Formation， whereas the regressive succession is primarily composed of the Bagong Formation. （3） The sandstone samples from the Jiapila Formation and Bagong Formation are ultra-low porosity and permeability reservoirs with secondary pores primarily. The mudstone samples of the Bagong Formation from the Jiang’ai Darina section are poor source rocks and non-source rocks， whereas they improve to the north （Woruoshan section）. We inferred that the depression between Jiang’ai Darina and Woruoshan may develop well source rocks and have a good exploration prospect based on the latest tectono-lithofacies paleogeographic data， but confirmation is required. Conclusions These results would provide a valuable reference for the researches of Late Triassic sedimentary-tectonic evolution and oil and gas resource evaluation in Qiangtang Basin.