This study reconstructs the tectonic evolution and lithofacies palaeogeographic development of North Africa from the Cambrian to the Devonian through an integrated analysis of seismic,well-log,and core data. Emphasis is placed on evaluating how major tectonic events—interacting with eustatic sea-level fluctuations and climatic shifts—controlled sedimentary processes and basin architecture in the region. Results indicate that during the Cambrian-Ordovician,a depression basin dominated the western craton margin of the Tethys domain;progressive climatic cooling and continental glaciation led to the transition from braided fluvial systems to glaciogenic deposits. In the Silurian,rifting associated with the initial opening of the Paleo-Tethys Ocean triggered widespread marine transgression,resulting in the deposition of organic-rich shales in the Lower Silurian. Subsequent late Silurian regression facilitated the development of deltaic and fluvial systems. During the Devonian,the Hercynian orogeny profoundly reconfigured regional basin geometry,establishing a passive continental margin. Fluvial(braided and meandering)systems were progressively replaced by deltaic and shallow-marine environments;persistent bottom-water anoxia in the Late Devonian favored the accumulation and preservation of high-quality source rocks. Collectively,this work elucidates the synergistic controls exerted by tectonics,eustasy,and climate on the paleogeographic evolution of North Africa,identifies prospective hydrocarbon reservoir fairways,and provides a robust geological framework to guide future petroleum exploration.

The lacustrine carbonates of the Lower Cretaceous Barra Velha(BVE)Formation are important pre-salt oil and gas reservoirs in the deep-water Santos Basin in eastern Brazil,and their unique rock fabric characteristics have become the focus of academic attention. Over the past decade,numerous studies have been published on the fabric and genesis of these carbonates,yet controversies persist. Existing researches indicate that the in-situ carbonates of the BVE Formation mainly consist of calcite shrubs,calcite spherulites,and magnesium-rich clay minerals. There are opposing views on the genesis of the sedimentary fabric,whether it is microbial or chemical in origin,and correspondingly different classification schemes for the rocks. The deposition models also vary,including microbial deposition,chemical deposition,and travertine deposition. Since no obvious biological structures/substances have been identified so far,and the shrubs and spherulites exhibit fibrous crystal structures,an increasing number of studies support the view that chemical precipitation is the dominant process. However,it remains difficult to determine whether microbial and/or hydrothermal activity was involved. The comprehensive investigation of paleontological,autogenetic clay minerals and C-O-Sr isotopes shows that the sedimentary environment of BVE carbonates is a lake with high salt,high alkali and high evaporation,but the water temperature,water depth,material sources such as Mg-Si-Ca,carbonate formation stage or sedimentary and diagenetic superposition process and effect are still unclear. Based on the review of the relevant research progress,it is suggested that future studies should start from environmental medium parameters,material sources,and the origin of the main components,and carry out matched high-precision micro-fabric and in-situ major and trace elements,isotope analyses,as well as supporting experiments and numerical simulation,combined with modern investigation,macroscopic rock distribution,and dynamic system information on basin paleostructure and paleoclimate evolution,to unravel the enigma of the genesis of these carbonates together.

The Neoproterozoic represents a critical interval in the evolution of the Earth surface system,during which oceans transitioned from low-oxygen,microbially dominated conditions to a stratified and progressively oxygenated state,accompanied by profound reorganization of seawater chemistry and carbonate depositional systems. Marine dolomite cements,owing to their synsedimentary to early diagenetic modes of formation,have been widely used to reconstruct Neoproterozoic seawater chemistry;however,their formation mechanisms and principal controlling factors remain debated. This study synthesizes petrographic observations together with multiple geochemical proxies,including C,O,Sr,Mo,U,and Mg isotopes,from globally representative Neoproterozoic carbonate successions,to systematically evaluate the petrographic characteristics and paleoenvironmental significance of marine dolomite cements. The stratigraphic comparisons indicate that,despite regional variations in cement morphologies and isotopic compositions,the timing of dolomite precipitation and associated genetic patterns are broadly comparable,suggesting a dominant control by a common global seawater chemical background. Multi-isotopic records further demonstrate that Neoproterozoic seawater chemistry did not remain in a long-term steady state,but evolved dynamically in response to tectonic reorganization,glacial-interglacial oscillations,and variations in continental weathering fluxes. The widespread occurrence of dolomite therefore does not reflect a single,persistently existing “dolomite sea,”but instead records the episodic emergence of favorable chemical conditions during different tectonic-climatic stages. Dolomite precipitation windows are inferred to have been opened under a relatively elevated Mg/Ca background,when low sulfate concentrations,high alkalinity,and appropriate redox conditions acted in concert. Neoproterozoic tectonic-climatic processes modulated seawater end-member inputs and material cycling,allowing such precipitation windows to recur at the global scale and thereby accounting for the anomalous abundance of marine dolomite during this interval. This study systematically clarified the key controlling mechanisms of Neoproterozoic marine dolomite formation from a multi-scale and multi-isotope perspective,providing important constraints for reconstructing the chemical evolution of ancient oceans and understanding the co-evolution of the Earth’s surface system in deep time.

The diagenetic sequence and pore evolution of ancient carbonate rocks in deep or ultra-deep burial depth is one of the hot topical in reservoir evolution. Based on analysis of the petrographic, geochemical, and U-Pb dating of diagenesis minerals of the Dengying Formation at Chuanshen 1(CS1), Jinshi 1(JS1) and other wells, the authors has adopted the comparative methods, in which compare the matrix dolomites with different dolomite cements, as well as the other diagenetic minerals, occurred in cement or fillings in vugs & fractures with regard to the data of carbon, oxygen, and strontium isotopes, homogenization temperatures, U-Pb dating of dolomites and calcites, either in the Dengying Formation of Ediacaran, or Xianrendong Formation of the Early Cambrian, or Maokou Formation of Middle Permian. The diagenetic sequence has been reasonable modified: fibrous or fibrous growth→column fibrous or foliated or blade(length-fast cement) or dogtooth shaped→coarser fibrous or bundle shaped of marine cementation and bundle shaped cement or fasicular or radial dolomite cements. i.s botryoids or comb shell shaped or primary dolomite biomorphs of nanoscale spheroids→micro-stalactitic or vadose silt of meteoric cementation→cryptocrystalline or microcrystalline quartz(1^st)→fluorapatite, barite and fluorite(1^st)→semi-automorphic micro-crystalline dolomite→fine crystalline dolomite→fine and medium crystalline quartz(2^nd) or medium to coarse dolomite→Saddle dolomite(1^st)→medium to coarse crystalline calcite(1^st)→hydrocarbon discharge(episodes)→fluorite(continuous dissolution. 2^nd or 3^rd)+coarse calcite(2^nd)→coarse quartz(3^rd)+Galena+Sphalerite+Pyrite+Fluorite(4^th)+coarse calcite(3^rd)+coarse crystalline dolomite(or Saddle dolomite(2^nd)→pyrobitumens(pyrolysis or TSR, methane)→coarse calcite(4^th)+quartz(4^th); and the medium to coarse dolomite in some of the fractures or cavities is of early hot fluid dolomite origin, with relatively low ${\delta }^{13}{\mathrm{C}}_{\mathrm{P}\mathrm{D}\mathrm{B}}$(-1.78‰~-1.69‰) and ${\delta }^{18}{\mathrm{O}}_{\mathrm{P}\mathrm{D}\mathrm{B}}$(-9.28‰~-9.32‰) and moderate. homogenization temperatures(Th=130.9 ℃, 135.3 ℃, 116.6 ℃) and salinity(12.63wt% NaCl); the U-Pb Concordia Age of dolomite(D_Ⅱ-Ⅲ)is between 474.0±74.0 Ma to 482.0±56.0 Ma, By integrating analyses of burial history, the geological-time of dolomite(D_Ⅱ-Ⅲ) is mostly like to occur in the late Ediacaran to Cambrian(No later than Early Ordovician). The weak extension during the late Ediacaran to Cambrian period, interval by multiple episodes of tectonic compression and exhumation, provided the conditions for the meteoric water percolated downward along the faults or fractures, heated by deep circulation as well as mixing with formation water, lead to precipitate of dolomite. The diagenesis effect on pore evolution display that the early dolomite cementation developed in hot fluid had a smaller proportion and had little effect on pore reduction, in compared with diagenesis such as large-scale marine cementation, strong silicification, compaction, and dedolomitization.

The sedimentary environment of the Pinghu Formation in the BW area of the Xihu sag has long been controversial. In this study,19 mudstone samples were collected and analyzed for trace elements and rare earth elements(REEs)using two methods: conventional whole-rock total digestion and selective acetic acid extraction. Based on the geochemical data obtained,multiple proxies were integrated to systematically analyze the redox conditions,paleoclimatic characteristics,and paleosalinity evolution during the depositional period of the Pinghu Formation. The results show that: (1)Element concentrations obtained via acetic acid extraction are significantly lower than those from whole-rock digestion,but both methods reveal consistent elemental distribution patterns. Moreover,the acetic acid extraction method is proven to be more effective than conventional whole-rock digestion when applying specific elemental proxies to identify sedimentary environments,especially for distinguishing terrestrial and marine facies.(2)The redox conditions during the depositional period of the Pinghu Formation were predominantly suboxic to oxic,indicating a relatively oxidizing environment;paleoclimate and paleosalinity evolved concurrently,characterized by an initial warm and humid freshwater setting,which shifted to an arid and saline environment by the end of the early stage. This was followed by a transition to a warm and humid brackish setting in the middle stage,a return to arid and saline conditions by the mid-stage,and finally a return to a warm and humid freshwater environment in the late stage. In light of the sedimentary context of the study area,the synchronous variations in paleoclimate and paleosalinity are interpreted as recording four successive changes,collectively indicating at least two major marine transgressions during the depositional period of the Pinghu Formation. The above results have significant scientific guiding significance and application value for deepening oil and gas exploration in the Xihu sag of the East China Sea Shelf Basin.

Karstified carbonate geothermal reservoirs,characterized by high porosity-permeability and substantial development potential,represent a key target in deep geothermal exploration. The thick and strongly karstified Middle-Upper Cambrian carbonates of the Yuncheng Basin provide an ideal setting for investigating the genesis of deep karst reservoirs;however,the controlling mechanisms of reservoir development under multiphase tectonic-karst overprinting remain insufficiently constrained. In this study,outcrop observations,seismic data,cores,wireline logs,and casting thin sections,integrated with regional tectonic evolution and paleogeomorphic reconstruction,are used to systematically investigate lithologic and reservoir characteristics,diagenetic processes,karst types,and karstification stages of the Middle-Upper Cambrian carbonate succession. The results indicate that: (1)dominant lithologies include oolitic limestone,bioclastic limestone,stromatolitic and argillaceous limestone,and micro-to fine-crystalline dolostone,with reservoir space mainly comprising selective dissolution pores,bedding-parallel dissolution belts,and structural fractures;(2)three genetic categories of karstification and five major evolutionary stages are recognized,controlled by multiphase tectonic uplift,among which large exposure surfaces formed during the Huaiyuan,Late Caledonian,and Yanshanian events served as key loci for epigenetic karstification;(3)the karst reservoir initiated by synsedimentary to early diagenetic dissolution,significantly enlarged through three phases of superimposed epigenetic karstification,and was further modified by fracture-controlled burial dissolution,ultimately forming a composite system characterized by high porosity and strong connectivity. These results clarify the formation mechanisms of the Middle-Upper Cambrian karst geothermal reservoir in the Yuncheng Basin under multiphase karstification and tectonic evolution,and provide a robust theoretical basis for the prediction and evaluation of carbonate geothermal system. The findings also have important implications for geothermal exploration in North China and in analogous fault-depression basins.

The Kuqa Depression hosts extensively distributed Mesozoic coal-bearing strata,characterized by substantial coal seam thickness and relatively abundant deep coalbed methane(CBM)resources. This study focuses on the Jurassic Kezilenuer Formation coal-bearing strata of the Kuqa Depression. Relative to shallow CBM reservoirs,deep coal seams exhibit markedly complex geological characteristics—including well-developed partings,heterogeneous coal matrix structure,and coexistence of adsorbed and free gas phases—posing significant challenges for reliable logging-based gas content evaluation. Integrating core observations from deep coal intervals in the study area with conventional logging,borehole imaging,and nuclear magnetic resonance(NMR)logging data,this work systematically investigates the geological characteristics of deep coal rocks and develops a robust methodology for quantifying their gas content. Deep Jurassic coal rocks in the Kuqa Depression consistently display low natural gamma radiation,low bulk density,high electrical resistivity,high neutron porosity,and large acoustic transit time—distinctive petrophysical signatures corroborated by imaging logs,which reveal bright blocky and speckled textures. Macroscopically,coal seams of the Kezilenuer Formation are predominantly semi-bright to semi-dull,classified as medium-fixed-carbon,high-volatile,medium-low-ash,and ultra-low-moisture coals. Coal seams No.2 and No.3 within Member 4 of the Kezilenuer Formation represent the principal target intervals,with average thicknesses of 4.5 m and 6.2 m,respectively,and mean burial depths exceeding 4000 m. Imaging log analysis indicates that these deep coal rocks largely retain primary(undisturbed)structural integrity. Leveraging empirical correlations established between laboratory-measured gas composition/contents and corresponding logging response parameters,a region-specific logging evaluation model was developed for estimating both compositional parameters and total gas content in deep coal rocks. Calculated total gas contents range from 5.95 to 10.95 m³/t(mean: 9.5 m³/t),comprising an average adsorbed gas content of 7.12 m³/t and an average free gas content of 2.38 m³/t. Complementary analysis using the T₁-T₂ cross-plot derived from NMR logging further reveals that higher gas content is preferentially associated with intervals exhibiting elevated resistivity,higher fixed carbon content,and structurally stable coal matrices. Synthesizing coal seam identification,maceral and industrial component analyses,and quantitative gas content estimation,this study establishes an integrated evaluation framework—combining conventional logs,borehole imaging,and 2D NMR logging—for jointly assessing deep coalbed methane and shale gas potential,thereby supporting resource assessment,reserve estimation,and exploration decision-making.

Significant breakthroughs have been achieved in the Ordovician ultra-deep fault-controlled carbonate reservoirs in the Fuman area,Tarim Basin in recent years. This area is rich in oil and gas resources and has tremendous exploration potential,being one of the largest ultra-deep oilfields established in China at present. Nevertheless,the Fuman area has a deep burial depth and has undergone multiple tectonic evolution stages,leading to complex reservoir spaces and extremely strong heterogeneity. Thus,it is urgently necessary to clarify the characteristics of the reservoir spaces in the Yijianfang Formation of the study area and determine the types of reservoirs,establishing a logging identification method for reservoirs in a single well. Relying on geological data such as cores and thin sections,the petrological and reservoir space characteristics of the Yijianfang Formation were clarified,and four types of reservoirs were summarized: vug type,fracture type,fracture-vug type,and cave-type. With the aid of conventional logging and image logging data,the logging response characteristic chart of “conventional+imaging+pattern” was established. According to the image logging characteristics of different types of reservoirs,the technique of vug, cave and fracture stripping was utilized to achieve the identification of reservoirs in a single well and clarify the scale and physical property differences. The results indicate that the cave type reservoirs have a large scale and excellent physical properties,contributing mainly to oil and gas productivity. The fracture-vug type reservoirs have a medium scale and physical properties,serving as both an oil and gas migration channel and a storage space. The fracture type and vug type reservoirs have relatively poor scale and physical properties. Therefore,the cave type reservoirs are high-quality reservoirs in the study area and also the focus of current exploration and development. The research results provide a solution approach and technical support for the identifying Ordovician ultra-deep fault-controlled carbonate reservoirs in the Fuman area.

In the digital-intelligent era,disruptive technologies such as artificial intelligence and big data are driving sedimentology into its fourth research paradigm shift. This transformation profoundly reshapes its research philosophy and methodological system,which is critical not only for the disciplinary innovation of sedimentology itself but also for national strategic demands including energy security and ecological governance. To clarify the disciplinary evolution,core challenges,and proactive response strategies,this paper systematically reviews the intelligent development,problem typology,technological innovation,and application expansion of sedimentology. Results show that the intelligent evolution of sedimentology can be divided into four stages,with a fundamental shift from experience driven to data and knowledge dual driven mode. Based on the four major question types in natural science,sedimentology is confronted with a series of core propositions including the Soul Question,Mystery Question,Century Question,and Epochal Question,among which the mass slope coupling and heterogeneity of terrestrial reservoirs represent key breakthroughs. Currently,the application of AI in sedimentology is constrained by methodological conflicts,data fragmentation,and lagging theoretical development. To meet these challenges,sedimentology must break traditional mindsets,reject imitative research and empty conceptual innovation,and establish a new logic integrating theory,technology,and data. The deployment and optimization of AI models constitute the cornerstone of intelligent transformation,emphasizing fullcycle implementation: application deployment,realtime monitoring,and continuous iteration. Only by rooting in the disciplinary essence of sedimentology,deeply integrating AI with sedimentary dynamics,forming a closed loop of “data-simulation-verification”,strengthening interdisciplinary integration,and expanding frontier fields such as deep Earth,deep sea,and carbon neutrality,can sedimentology accomplish the leap from interpretive science to predictive and generative science and provide solid scientific support for national energy security and ecological civilization.

Four representative coal-bearing basins,including the Late Paleozoic North China epicontinental sea basin and the marginal sea basins of the South China Sea,were selected for a comparative analysis of the formation and evolutionary characteristics of autochthonous and allochthonous peat mires. The identification features for coal seams formed by autochthonous and allochthonous peat mires are proposed,and the differences between the two types of peat mires are summarized in terms of peat material accumulation,coal seam architecture,coal-interbed interfaces,and paleosol development. In addition,the characteristic attributes of allochthonous peat mires are elucidated. Research indicates that peat mires serve as the primary carriers of coal formation,represent a key type of sedimentary environment,and constitute a distinctive and significant feature of basin palaeogeography. Its significance and value lie in the following aspects: the attributes of sedimentary basins vary,and the palaeogeographic characteristics of autochthonous and allochthonous peat mires differ accordingly. The development and evolution of two mire types constitute important events in the evolution of coal-forming environments within basins;during the Late Paleozoic,frequent marine transgressions in the North China Basin not only suppressed peat mire development but also preserved peat material,producing a distinctive stratigraphic association in which marine transgressive layers are in direct contact with coal seams. The palaeogeography of transgression events represents a typical landscape of autochthonous peat mires;analysis of peat mire formation and evolution in the Huangxian terrestrial lacustrine faulted basin and the northern depression of the Pearl River Mouth Basin reveals that tectonic activity exerted a primary control on basin infill as well as on the development and evolution of peat mires. On steep slopes,unstable autochthonous mires were established,whereas stable autochthonous mires formed on gentle slopes. During critical stages of basin evolution,stable allochthonous mires developed in lacustrine or shallow-water settings,giving rise to the distinctive coal-oil shale assemblages.