To reduce the subjectivity in indicator weighting and the fuzziness of grading criteria in favorable area evaluation of tight sandstone reservoirs,we develop an integrated method that couples combined weighting with a normal cloud model,and apply it to the X subunit of the Member 3 of the Qingshankou Formation(Q3)in the Qianshen Block,southern Songliao Basin. First,subjective weights are derived from expert judgment using the Analytic Hierarchy Process(AHP). Objective weights are then obtained from the dataset using the CRITIC method. The two sets of weights are finally integrated to produce combined weights,improving both geological rationality and data-driven objectivity. Meanwhile,a normal cloud model is introduced to characterize uncertainty during grade assignment. Standard cloud parameters—expectation(E_x),entropy(E_n),and hyper-entropy(H_e)—are determined from the score intervals of evaluation grades under constraints of a boundary membership threshold,enabling a flexible mapping between evaluation grades and measured data. Results show that sedimentary facies belt,oil-bearing property,and effective thickness are the dominant controls on favorable areas,with combined weights of 0.253,0.182,and 0.124,respectively. Evaluation of 20 wells identifies 12 wells for Class Ⅰ,five wells for Class Ⅱ,and three wells for Class Ⅲ wells;the outcomes show 95% agreement with previous interpretations,with a Cohen’s kappa coefficient(κ)of 0.91. The method therefore provides a practical and reliable tool for favorable area evaluation of tight sandstone reservoirs.

The relative lake level is fundamental for constructing the sequence stratigraphy. However,considering the difficulty of ensuring the location of the lake level and the complexity of lacustrine rift basins,using traditional methods to establish the sequence stratigraphy is quite difficult. Thus,we introduced‘trajectory analysis’ in this study. We used well logging,lithological association,and seismic data to establish sequence stratigraphy of the lower part of the Second Member of Dongying Formation(corresponding to SQd₂)in the western part of Bozhong sag. Prograding sigmoidal clinoforms,prograding oblique clinoforms,small-scale mouth-shaped reflection,and parallel to sub-parallel reflection developed in SQd₂ of Bozhong sag. We interpreted four types of seismic reflection into three sedimentary systems,including river deltas,sub-lacustrine fans,and lakes. According to the direction of migration and the shape of shorelines,there are four types of shoreline trajectories identified,which are called ascending regression with convex-upward curvature(type-1),ascending regression with concave-upward curvature(type-2),descending regression with convex-upward curvature(type-3)and ascending transgression with concave-upward curvature(type-4),respectively. These four types of shoreline trajectories were related to the lowstand systems tract(LST),highstand systems tract(HST),falling stage systems tract(FSST),and transgressive systems tract(TST). Large-scale deltas developed during the late stage of SQd₂. The ascending regression with concave-upward curvature reflects the normal regression and large-scale deltas with‘thick topsets and thick foresets’ developed during this stage. Then,small-scale sub-lacustrine fans may develop due to gravity. The descending regression with convex-upward curvature is related to forced regression. During the stage,large-scale deltas with thin topsets and thick forestes developed. Thus,more sediment was transported into the deep lake,and large-scale sub-lacustrine fans were developed. In conclusion,we introduced‘trajectory analysis’ to divide an entire third-order sequence into four systems tracts. Then,we highlighted the importance of forced regression and the large-scale,rich sand sediment developed during this stage. Additionally,sub-lacustrine fans with relatively high sand ratios are always associated with rich-sandy deltas. The deltas and sub-lacustrine fans during the FSST are significant for reservoirs and lithologic traps.

The channel network structure of shallow delta is complex. In the previous studies on the morphological characterization of distributary channels,there was a lack of quantitative data support for the spatial continuity of river width. This paper focuses on the quantitative characterization of channel morphological parameters and studies the spatial continuous variation characteristics of the width of the distributary channels in the Ganjiang Delta,aiming to provide constraints on the spatial variation of channel width for reservoir configuration research,and then improve the reservoir configuration characterization method system. Based on the Google Earth Engine big data cloud computing platform,this paper improves the RivWidthCloud river width extraction algorithm,realizes the automated extraction of continuous width data of the Ganjiang Delta distributary channel,and reveals the spatial continuous variation law of the width of the distributary channel in the shallow delta plains. The results show that: (1)the river width data extracted after algorithm optimization have significant correlation with the measured values(R²=0.84),which verifies the reliability and applicability of this method in river morphology monitoring;(2)the seasonal variation of the width of the main branch of Gan River is significant(the average river width in the dry season is 444.85 m,and the average river width in the rainy season is 650.75 m,an increase of 46%),which is significantly higher than that of the other two tributary channels;(3)There is a significant spatial coupling relationship between channel width and bifurcation frequency: the width of the upstream section of the bifurcation mouth increases sharply,and the width of the secondary channel decreases significantly after bifurcation;(4)According to the continuous channel width curve(the trend line of continuous river width data points),the width data of the distributary channels has an overall decreasing trend towards the downstream of the delta,but still shows an oscillating change with multiple levels of fluctuations. (5)70% of the quasi-central-bar development areas present a width variation pattern of “wide beach head,narrow beach neck,and wider beach tail”,and the corresponding river channel width curve shows a three-stage feature of “high-low-higher”. The continuous river width quantification method provides a new tool for the study of modern delta sedimentation. The law of distributary channels scale variation revealed by it can provide a quantitative basis for fine characterization of the scale of distributary channels,geometric constraints for reservoir architecture modeling,compilation of small-scale sedimentary facies maps.

The Jiujialu Formation of the Lower Carboniferous in central Guizhou Province represents a significant bauxite-bearing stratigraphic unit in the region. This study aims to clarify the metallogenic geological setting and the dominant ore-forming processes of the bauxite deposits within the Jiujialu Formation in central Guizhou Province. Based on the theoretical framework of metallogenic sedimentology and supported by quantitative palaeogeographic reconstruction,the study employs an integrated approach combining petrology,sedimentology,and sedimentary geochemistry of the ore-bearing deposit to reconstruct the palaeoenvironment and explore the mechanisms of bauxite formation. The findings indicate that during the Early Carboniferous,central Guizhou Province was characterized by a nearshore karst peneplain depositional setting. The aluminous strata developed within a closed,karst-depression-controlled lacustrine-marsh wetland environment. The basal iron-rich section of the Jiujialu Formation represents Fe-enriched interval formed from relict slope deposits of ancient weathering crusts. The overlying clay-rich interval comprises dark clay rocks formed in transitional facies influenced by marine transgression or inundation. The middle aluminous section shows a regular vertical succession of lithofacies,including layered claystone,massive bauxite or bauxitic rock,pisolitic bauxite,clastic bauxite,and porous bauxite. This lithofacies assemblage reflects a metallogenic process combining both wetland sedimentation and subaerial leaching under subaerial exposure conditions. The deposition of Al-rich source rocks was followed by desiccation of the lacustrine-wetland system and the formation of a vadose leaching sequence under the influence of fluctuating groundwater levels. Based on these results,a metallogenic model for the bauxite deposits of the Jiujialu Formation in the Lower Carboniferous of central Guizhou Province is proposed.

The source-to-sink system(S2S)refers to the complete process of sediment erosion,transport,and deposition,in which sediments are generated from erosional landscapes,transported through routing systems,and ultimately deposited within depositional environments. Research on S2S not only advances our comprehensive understanding of Earth surface dynamics and their evolution,but also provides a geological basis and predictive models for identifying favorable sandbody distributions and guiding sedimentary mineral exploration and development. Based on a review of the history of S2S studies,this work highlights current research frontiers,including integrated perspectives on modern S2S systems,deep-time S2S systems and palaeogeographic reconstruction,characterization of S2S processes coupled with geomorphic-sedimentary evolution modeling,and applications of S2S theory in energy geology. Significant progress has been achieved in several aspects,such as classification of S2S systems and characterization of their main types,source-area attributes and sediment supply,sediment transport processes and signal propagation along routing systems,depositional processes(sandbody dispersal systems)and their controlling factors,quantitative characterization of S2S components(e.g.,the BQART model),and prediction of sandbody distribution. Finally,future research should place greater emphasis on the quantitative characterization of sediment transport and signal propagation of routing system,as well as predictive approaches for sandbody distribution.

Coal facies,referring to the sedimentary facies of coal,denote the original genetic type of coal,which is determined by the type of ancient peat swamp. After more than 70 years of development,coal facies research has achieved significant progress,with successive establishment of genetic parameters such as the Tissue Preservation Index(TPI),Gelification Index(GI),Groundwater Influence Index(GWI),and Vegetation Index(Ⅵ). Diessel classified coal facies types into dry forest swamp,wet forest swamp,marsh,and fen,using TPI-GI discrimination diagram. Chinese scholars have summarized the coal facies characteristics of major coal-accumulating periods in China: the Carboniferous-Permian coals in the North China coal-accumulating area are dominated by transition marsh-wet forest swamp facies;the Late Permian coals in the South China coal-accumulating area are mainly composed of transition marsh facies;the Early-Middle Jurassic coals in the Northwest China coal-accumulating area are characterized by the dominance of wet forest swamp-dry forest swamp facies;and the Early Cretaceous coals in the Northeast China coal-accumulating area are dominated by wet forest swamp facies. These characteristics reflect that significant differences exist in the types of coal-forming swamps,coal-forming plants,and paleoclimatic conditions across different coal-accumulating periods. With the discovery of unconventional resources such as deep coalbed methane and critical metals in coal-bearing series,the application of coal facies in the development of these resources has regained attention. Coal formed in different mires exhibit inherent differences in coal petrological and quality characteristics,and thus,the coal facies analysis can be applied to the evaluation of coal hydrocarbon generation potential,reservoir physical property analysis,and prediction of coal-associated resources. In recent years,with the deepening research on the sedimentary environment of coal-bearing series,mire evolution,and paleowildfire events,the rationality of using coal facies parameters such as TPI and GI as indicators for the sedimentary environment of coal-bearing series and coal has been questioned to a certain extent. The rationalization and standardized use of coal facies parameters urgently require discussion and resolution. For the sustainable development of coal facies research,future efforts should be focused on advancing the basic theories of coal facies analysis-especially the research on the genesis of macerals and modern peat mire environments and strengthening the application of coal facies analysis in practical production to better promote the utilization of mineral resources in coal-bearing series.

The global technically recoverable resources of shale oil are estimated at approximately 251.2 billion metric tons,derived from 157 organic-rich shale units across 116 basins. Internationally,shale oil exploration has largely focused on marine shale successions,whereas in China,lacustrine shales represent the primary target. The assessment of shale oil enrichment intervals is fundamentally governed by lithofacies palaeogeography. Lithofacies palaeogeographic reconstruction of lacustrine shale strata relies on quantitative datasets derived from outcrop,core,and geophysical analyses. Critical aspects of such reconstructions include considerations of temporal and spatial scales,single-factor analysis,and the application of conceptual depositional models. Recent progress in the study of shale laminae offers valuable single factors and diagnostic methods for interpreting depositional environments in palaeogeographic studies. Significant variations in reservoir properties and shale oil occurrence are observed among different lamina types. Consequently,palaeogeographic mapping based on lamina combinations and shale microfacies analysis represents an emerging research trend. Future research should aim to address the heterogeneous characteristics of lithofacies and organic matter distribution in lacustrine shale strata. Future studies should aim to resolve the heterogeneous distribution of lithofacies and organic matter in lacustrine shales,with priority given to: (1)delineating the spatial architecture of organic-rich shales within high-resolution chronostratigraphic frameworks,(2)characterizing mineral-organic composite structures,(3)establishing standardized microfacies classifications,and(4)developing depositional process simulations integrated with intelligent mapping techniques. An integrated approach combining modern sedimentological observations,sedimentary process simulations(both physical and numerical),organic petrology,and biomarker analysis is essential to reassess the sedimentary microfacies and organic enrichment mechanisms in lacustrine shale strata. This will facilitate the development of revised depositional models that accurately reflect the transport-deposition dynamics of fine-grained sediments,palaeotopographic constraints,and bioevolutionary context. By combining “inversion” and “forward modeling” methods and lever aging artificial intelligence technology,and incorporating key sweet-spot evaluation parameters,it is possible to quantitatively predict and intelligently map the spatiotemporal distribution of different lamina combinations. This methodology will allow for precise lithofacies palaeogeographic characterization of lacustrine shale strata and provide scientific guidance for the optimization of shale oil enrichment areas/layers.

The Earth’s evolutionary history has witnessed six major glaciations or glacial events,among which the earliest is believed to be the Pongola glaciation in South Africa,occurring approximately 2.9 billion years ago. A number of papers have been published on the last five major glaciations,yet understanding of the Pongola glacier remains limited. This raises key questions: did glaciation exist in the Archean,and how to identify it?By analyzing the characteristics of diamictites in the Mozaan Group(2.9 Ga)of the Pongola Supergroup in the Kaapvaal Craton,South Africa,this study summarizes the diagnostic markers of glacial deposits,and discusses whether the diamictites of the Archean Pongola Supergroup are glacial origin. Meanwhile,it aims to draw more attention from peers to the establishment and development of glacial sedimentology:a subdiscipline of event sedimentology in China. The Mesoarchean Pongola Supergroup is primarily distributed in the southeastern part of the Kaapvaal Craton and can be further divided into two groups: the Nsuze Group and the Mozaan Group. Petrological,sedimentological,and major/trace element geochemical analyses of the Mozaan Group diamictites support the interpretation of glacial origin. The Mozaan Group diamictites generally exhibit the following characteristics: (1)relatively thin thickness(<50 m);(2)massive mixed accumulation;(3)poor sorting and roundness of gravels;(4)gravels of varying particle sizes and compositions “floating” in a fine-grained matrix;(5)gravels with multiple sets of striations and polished surfaces;(6)quartz grains show elongation or deformation with silt-sized grains distributed around sandy grains in thin sections(referred to as a “nebular structure”);(7)dropstones developed in varves. Geochemical studies of elements reveal the following: the data points of Mozaan Group diamictites show a restricted distribution in the SiO₂/Al₂O₃ diagram,which is significantly different from the typical linear negative correlation observed in modern and ancient sediments that have undergone significant weathering and sorting;The distribution range of TiO₂/Al₂O₃ is also narrow,and the major element compositions are similar;The matrix of the diamictites is rich in total iron(Fe₂O₃(T))and shows a marked depletion of calcium(Ca)and sodium(Na). The mathematical inversion of measured δ¹⁸O and δ¹⁷O values in the diamictite and the underlying shale yields δ¹⁸O values of weathering water consistent with the isotopic characteristics of modern polar meteoric water,indicating cold climatic conditions. In addition,indicators such as the Chemical Index of Alteration(CIA)suggest that the Mozaan Group diamictites have barely experienced diagenetic alteration or chemical weathering,thus well representing the characteristics of their provenance. Therefore,the following glacial depositional model is proposed based on the above findings: during periods of low sea level,glaciers advanced along valleys toward the continental shelf. The till(glacial sediment)consisted of not only basal till,lateral till,and rock flour produced by glacial abrasion of the bedrock,but also rounded quartz grains mixed from shelf sands and fine-grained weathered materials derived from ferruginous mud. Some diamictites originated from the direct deposition of glacial sediments in periglacial zones and subsequent modification,characterized by a sharp contact between the diamictites and the underlying bedrock,with deformed layers present beneath parts of the diamictites. Another part of the thick diamictite layers,indicated by dropstones in the upper part,was transported by ice rafts to ice-distal glaciomarine environments.

The Eocene submarine fan channel system in the Rovuma Basin,East Africa,constitutes a significant case study for investigating the interaction between deep-water gravity flows and bottom currents. To address key scientific questions concerning the genetic types of individual channels and their distribution following differential reworking by bottom currents,this study systematically examines the genetic classification,spatial distribution,and mechanisms of bottom-current modification of single-channel systems in the lower Eocene strata of the region. Integrated analysis is based on core samples,well logging data,3D seismic datasets,and experimental results. The findings reveal the following: (1)The deep-water channel depositional system comprises four genetically distinct lithofacies—debris flow,turbidity current,bottom-current reworked,and hemipelagic drape deposits—which are further classified into 17 subtypes. Based on the relative abundance of gravity flow-related lithofacies,two primary types of single-channel systems are identified: debris flow-dominated fill channels and high-density turbidity current-dominated fill channels.(2)Debris flow-dominated fill channels are characterized by low width-to-depth ratios,sinuous geometries,and poorly developed levees. In contrast,high-density turbidity current-dominated fill channels exhibit straight to moderately sinuous morphologies,significantly higher width-to-depth ratios,and more pronounced levee development and thickness. Under the influence of bottom currents,both channel types display asymmetric cross-sectional profiles and lateral migration opposite to the direction of bottom-current flow. However,the high-density turbidity current-dominated channels exhibit greater asymmetry and more intense migration behavior.(3)Mechanistically,due to the high shear strength of debris flows,bottom-current reworking occurs primarily through “in-situ winnowing,” resulting in lenticular lithofacies containing internal traction structures. These channels show weak levee-channel asymmetry(average asymmetry index ≈1.35)and limited lateral migration(average migration index ≈0.65). Conversely,high-density turbidity currents,which possess lower shear strength,undergo “bulk reworking” of fine-grained suspended sediments by bottom currents. This process promotes the development of downcurrent-side lateral accretion deposits,leading to enhanced levee-channel asymmetry(average asymmetry index ≈2.5),increased confinement along the northern channel margins,and more pronounced migration against the bottom-current direction(average migration index ≈0.8). This study elucidates the differential response mechanisms of genetically distinct channel types to bottom-current interactions,offering critical insights for high-resolution characterization and targeted exploration of deep-water reservoirs.

The Triassic Lower Karamay Formation(T₂k₁)represents the primary target for petroleum exploration in the Xia 77 area,located on the northwest margin of Junggar Basin. Integrating data from drilling,core observations,well logging,and associated analytical experiments,this study applies fundamental principles of sedimentology to analyze the sedimentary facies architecture and evolutionary characteristics of the T₂k₁. The findings reveal the following: (1)The formation was deposited within a shallow-water fan delta system,which is subdivided into two main subfacies: the fan delta plain and the fan delta front. The fan delta front can be further classified into inner and outer front subfacies.(2)Within the fan delta plain,three gravity flow-dominated microfacies were identified: braided channels,floodplains,and debris flows. In the fan delta inner front,two traction flow-dominated microfacies are recognized—subaqueous distributary channels and subaqueous distributary bays. The fan delta outer front is characterized by three traction flow-induced microfacies: subaqueous distributary channels,subaqueous distributary bays,and mouth bars.(3)During the depositional period of the Lower Karamay Formation,the lake basin underwent a gradual deepening,transitioning from shallow to deeper water conditions. This hydrodynamic shift resulted in a regressive sedimentary sequence in response to overall lake transgression. Laterally,the progradational-to-retrogradational evolution of the system led to a northeastward backstepping of the fan delta plain,inner front,and outer front subfacies.