Search Results (68)

Tracing the provenance and understanding the ore-forming processes of coastal zircon–titanium placers are important issues in placer research. The Wenchang area in Hainan Province is one of the important coastal zircon–titanium placer enrichment regions in China; however, the provenance, transport, and depositional mineralization mechanisms of these deposits remain poorly understood. In this study, systematic heavy mineral petrography, whole-rock major and trace element geochemical analyses, and zircon U–Pb dating were conducted on the zircon–titanium placer deposits in the coastal area of Wenchang to investigate their ore-forming processes. The results show that the zircon–titanium placers along the southeastern coast of Wenchang exhibit a gradual north–south transition in provenance, transport, and depositional mineralization mechanisms, and can accordingly be divided into Zone I (north) and Zone II (south). LA-ICP-MS zircon U–Pb dating reveals that zircons from the north (Zone I) are dominated by a major age population at 435.6 ± 2.2 Ma, with a subordinate age population at 155.1 ± 2.7 Ma. For the south (Zone II), previous data indicate that zircons yield ages predominantly in the ranges of 130–160 Ma and 230–260 Ma, with a minor group at 420–450 Ma, pointing to a provenance difference between the two zones. The northern zone (Zone I) is inferred to be characterized by proximal provenance and marine influence. The main sediment source is Paleozoic–Mesozoic granites in the Wenchang area and on both sides of the Qiongzhou Strait, with a possible minor contribution of distal detritus from the Pearl River drainage basin, introduced under the influence of currents in the Qiongzhou Strait. Heavy minerals were likely transported to the coast by rivers and wave erosion and subsequently enriched through repeated winnowing and sorting by high-energy waves and tides. The southern zone (Zone II) is characterized by multi-source convergence and mixed sedimentary mineralization. The sediments are interpreted to mainly derive from high-K granites in the Qiongzhong area, which were transported over long distances by the Wanquan River and other drainage systems and possibly mixed with Quaternary sediments and fine-grained detritus from the Pearl River basin carried by longshore currents. In the coastal environment, these materials were reworked by waves and tides and mixed with bioclastic debris, leading to ore enrichment. These results provide some basic data for a better understanding of the north–south variation and formation processes of the placers in this region, and may offer a useful reference for future exploration. Full article

“Shetaicui” is a distinctive quartzite jade from the Dashetai area of Inner Mongolia. Its green variety has attracted considerable academic attention because of its characteristic color and relatively high economic value, yet its color genesis and formation process remain poorly understood. Here, green “Shetaicui” was examined by petrographic observation, infrared and Raman spectroscopy, ultraviolet–visible (UV–Vis) absorption spectroscopy, colorimetric measurements, X-ray fluorescence spectroscopy (XRF), and electron probe microanalysis (EPMA). These methods were used to characterize its mineral composition and textures and investigate its color genesis and formation process. The results show that the jade is a fine-grained muscovite quartzite, whereas the wall rock is a fine-grained chlorite–quartz–muscovite schist. Coloration is mainly associated with Cr-bearing muscovite. Cr is the principal chromogenic element, whereas Fe contributes to coloration to a lesser extent. Pearson correlation analysis and multiple linear regression show that Cr₂O₃ is most strongly correlated with a* and C*, whereas FeO^T is most strongly correlated with L* and shows a weaker positive correlation with b*. Petrographic textures and mineral assemblages indicate that the jade and its wall rock underwent regional metamorphism broadly consistent with greenschist-facies conditions. Formation proceeded through three stages: sedimentary protolith formation, regional metamorphism, and jade formation during late fluid alteration. During regional metamorphism, quartz-rich sandy horizons formed a Qtz I-dominated pre-jade quartzite, whereas muddy horizons formed the chlorite–quartz–muscovite schist wall rock. Subsequent fluid alteration led to the formation of Cr-bearing muscovite and Qtz II within the pre-jade quartzite. Cr-bearing muscovite imparted the characteristic green coloration, completing the transformation of the pre-jade quartzite into “Shetaicui” jade. These results clarify the correlations between chromogenic elements and colorimetric parameters in green “Shetaicui” and provide petrographic and mineralogical evidence for this three-stage formation process. Full article

Fluvial sand bodies represent one of the most significant reservoir types in hydrocarbon exploration. Restricted by climatic conditions, sedimentary environments and the properties of provenance parent rocks, sedimentary characteristics and sand-body architectures exhibit substantial spatial variations across different river systems and along individual river segments. Research on modern sedimentary processes of the Weihe River provides critical insights for advancing continental fluvial sedimentology theories and reconstructing paleoriver sedimentary models for analogous basins. Integrating high-resolution satellite image interpretation combined with systematic field geological surveys across typical river reaches, this study systematically characterizes the spatial differentiation of river patterns, sedimentary signatures, sand-body architectures and their primary controlling factors within the Weihe Basin. The results reveal a distinct three-segment spatial differentiation pattern of fluvial styles in the Weihe Basin: braided rivers dominate the Baoji–Zhouzhi reach; low-sinuosity meandering rivers occur in the reach from Zhouzhi to Lintong; and high-sinuosity meandering rivers prevail in the downstream segments below Lintong. Unique hydrodynamic regimes associated with each river type control sedimentary partitioning and sand-body development. Braided rivers feature intense hydrodynamic force and coarse-grained sediments, with sedimentary assemblages consisting of gravelly channel deposits, mid-channel bars and floodplain deposits, which form thick stacked sand bodies via multi-stage sedimentary superimposition. Low-sinuosity meandering rivers possess moderate hydrodynamic energy and are dominated by sandy-gravel deposits, yielding a complete sedimentary succession composed of channel fills, point bars, natural levees and floodplains. High-sinuosity meandering rivers are characterized by weak hydrodynamic conditions and fine grain sizes dominated by sandstone and mudstone units, developing diverse sedimentary facies including channels, crevasse splays and oxbow lake deposits. The spatial heterogeneity of the sedimentary system across the Weihe Basin is synergistically controlled by the channel gradient, provenance attributes, sediment grain size and sediment concentration. This study clarifies the sedimentary evolutionary laws of modern rivers under semi-arid and semi-humid climatic conditions, enriches fundamental fluvial sedimentology theories, and supplies a modern sedimentary analog for paleoriver identification, paleoenvironmental reconstruction and hydrocarbon exploration targeting fluvial reservoir systems. Full article

Evaluating the sealing integrity of caprocks is critical for ensuring the long-term safety and containment efficiency of geological hydrocarbon reservoirs and CO₂ storage systems. In this study, we evaluated the caprock sealing capacity of the South Sea continental shelf using drill cutting samples collected from six wells across four structural blocks. Representative caprock intervals, consisting primarily of fine-grained sedimentary rocks, were identified based on well data and lithofacies information. Mercury Injection Capillary Pressure (MICP) analyses were performed to characterize pore structure and capillary sealing behavior. Results indicate that nanopores (<1 μm) dominate the pore system; however, pore size distributions exhibit significant heterogeneity. While B well samples displayed unimodal nanopore distributions, other wells showed bimodal or broad multiscale structures. As a result, MICP-derived Hg-air breakthrough pressures (P_b) varied considerably, ranging from 75 to 283 MPa. Notably, samples G-1 and J5-4 exhibited sealing capacities capable of retaining CO₂ column heights exceeding 5052 m, whereas sample J1-1 showed the lowest sealing performance. In the B well, a clear depth-dependent trend was observed: as depth increased from 2480 m to 3685 m, the critical pore diameter decreased from 13.66 nm to 7.57 nm, and breakthrough pressure increased from 95 MPa to 171 MPa. Subsequent quantitative XRD analysis, corrected for drilling-induced contamination, revealed that these deeper intervals are characterized by clay-rich (50.85–63.19%) and relatively ductile mineralogical compositions. These findings suggest that burial-related compaction within a consistently clay-rich, relatively ductile matrix may contribute to pore-throat refinement and enhanced relative capillary sealing capacity in the B well. Overall, the caprocks of the South Sea continental shelf show significant potential for geological hydrocarbon and CO₂ storage, though the observed spatial and depth-dependent heterogeneity underscores the necessity of well-specific site characterization. Full article

Recent exploration highlights the Gulong Sag as a promising target for tight oil in the Fuyu oil layer. However, the distribution of high-quality reservoirs remains poorly understood due to complex depositional and diagenetic controls, posing significant exploration risks. To address this, this study integrates petrological, mineralogical, and pore structure analyses to elucidate the genetic mechanisms of reservoir quality and identify favorable exploration targets. The sandstones are predominantly fine-grained lithic arkoses and feldspathic litharenites, characterized by abundant volcanic lithic clasts and muddy matrix. Four diagenetic facies were identified based on diagenetic assemblages and pore evolution. The chlorite pore-lining facies and moderate compaction–dissolution facies exhibit the highest reservoir quality (avg. porosity of 10.42% and 9.79%, respectively), benefiting from chlorite coatings that inhibited quartz overgrowth and intense dissolution that created secondary porosity. In contrast, the tightly compacted facies and carbonate-cemented facies represent unfavorable reservoirs (avg. porosity of 7.02% and 6.17%, respectively) due to the occlusion of pore throats by muddy matrix and early carbonate cements, respectively. The distribution of these facies is governed by the coupling of sedimentary environment and diagenetic alteration. Benefiting from superior sedimentary conditions and proximity to source rocks, the first member of the Fuyu oil layer developed extensive favorable facies (chlorite pore-lining facies and moderate compaction–dissolution facies), making it the primary exploration target. This study demonstrates how depositional compositions and diagenetic processes jointly control reservoir quality in tight sandstones, providing important insights for the exploration of analogous tight oil reservoirs. Full article

Sandstone-type uranium deposits represent one of the most significant uranium deposit types in China, predominantly hosted in Meso-Cenozoic sedimentary basins in the northern part of the country. Due to characteristics such as deep burial of orebodies, fine grain size of ores, and strong heterogeneity, traditional geological logging methods have limitations in rapidly and accurately identifying alteration minerals and mineralization indicator information. Core spectral technology (wavelength range approximately 400–2500 nm), particularly short-wave infrared spectroscopy (SWIR, 1300–2500 nm), enables rapid, non-destructive, and quantitative extraction of alteration mineral information from drill cores. This provides robust technical support for reconstructing metallogenic environments, delineating oxidation–reduction zones, and prospecting and prediction in sandstone-type uranium deposits. This review systematically examines the spectral absorption characteristics and geological significance of key alteration minerals (e.g., clay minerals, carbonate minerals, iron oxides, and hydrocarbon substances) in sandstone-type uranium deposits. It elaborates on the current application status of core spectral technology in sandstone-type uranium exploration within typical basins in northern China, such as the Ordos, Songliao, Erlian, and Qaidam Basins. These applications include alteration mineral mapping, oxidation–reduction zone delineation, and metallogenic fluid tracing. Due to the unique characteristics of host rock lithology, alteration mineral assemblages, and fluid properties in sandstone-type uranium deposits, the application of this technology also faces certain challenges, such as difficulties in spectral interpretation and insufficient accuracy in quantitative inversion. Integrating this technique with multiple methods, including petrography and X-ray diffraction (XRD), will facilitate more effective applications in both metallogenic research and prospecting practices for sandstone-type uranium deposits in northern China. Full article

A large number of low-resistivity and low-permeability reservoirs have been discovered in the deep Paleogene strata of the Wenchang Sag. These reservoirs are characterized by complex porosity–permeability relationships and difficulties in fluid property identification, which restrict the progress of exploration and development operations. However, existing reservoir studies mostly focus on either low-permeability or low-resistivity reservoirs, with relatively few investigations targeting this specific type. Using petrological analysis and physical property testing as the main methods, combined with sedimentary and diagenetic studies, this paper examines the characteristics and genesis of low-resistivity and low-permeability reservoirs in the Paleogene of the Wenchang Sag. The results show that the Paleogene reservoirs are dominated by lithic quartz sandstones, with secondary pores as the main reservoir space, consisting of medium–small pores and fine throats. Samples of the same grain size exhibit a favorable porosity–permeability correlation. Based on capillary pressure curve morphology, the reservoirs can be classified into three types: high mercury intrusion saturation with low displacement pressure, medium mercury intrusion saturation with medium displacement pressure, and medium mercury intrusion saturation with medium–high displacement pressure. The low porosity and permeability are mainly attributed to the fact that the reservoir rocks are primarily deposited in near-source braided fluvial delta underwater distributary channels, resulting in low compositional and textural maturity of sandstones. Strong compaction resistance leads to a significant reduction in primary pores during burial, and intergranular cement filling further deteriorates physical properties. On the other hand, rapid lithological changes and complex pore structures give rise to abundant isolated pores and poor connectivity, leading to high irreducible water saturation. Coupled with high formation water salinity, these factors collectively give rise to low-resistivity reservoirs in the study area. This study clarifies the formation mechanism of low-permeability and low-resistivity reservoirs in the Paleogene of the Wenchang Sag, providing guidance for reservoir evaluation in subsequent oil and gas exploration and serving as a reference for analogous areas. Full article

The Early Cretaceous Hongshanwan landform in the Lanzhou Basin hosts distinctive multicolored rhythmic sedimentary layers, yet the factors controlling their coloration remain debated. This study integrates mineralogical observations, whole-rock geochemistry, and detrital zircon U-Pb geochronology to investigate the controls on sediment coloration and basin evolution. Sharp and stratigraphically consistent color boundaries indicate that coloration was largely established during sedimentation and early diagenesis, with limited influence from late-stage weathering. Geochemical data suggest that the sediments were predominantly derived from intermediate-to-mafic igneous rocks under low-to-moderate chemical weathering and dominantly oxidizing conditions. Reddish-brown strata are mainly colored by fine-grained authigenic hematite formed during early diagenesis, whereas bluish-gray and pale-yellow layers inherit their colors from calcareous and mafic components with limited post-depositional alteration. Detrital zircon age distributions reveal three principal age populations (1322–1994 Ma, 331–376 Ma and 217–286 Ma), providing first-order constraints on provenance evolution and episodic sediment supply linked to multiple orogenic cycles in a back-arc foreland basin setting. Overall, the multicolored stratigraphy reflects a coupled influence of provenance composition, depositional redox state, diagenetic processes, and tectonic forcing, offering new insights into the origin and evolution of continental red-bed systems in inland basins of northern China. Full article

The Upper Permian marine shale of the inter-platform basin in the Nanpanjiang Basin are rich in organic matter, widely distributed, and relatively thick, indicating abundant resource potential for hydrocarbon exploration. To clarify the sedimentary condition and the variability of reservoir properties, the paleo-environment was reconstructed by using geochemical, mineralogical, rock-property, and pore-structure data. Building on a lithofacies classification, the development patterns of different shale lithofacies were revealed. Reservoir characteristics among lithofacies were compared using scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and low-temperature Nuclear Magnetic Resonance Cryoporometry (NMRC) experiments. A fractal analysis was performed based on NMR and NMRC data to quantify pore-scale heterogeneity, calculate fractal dimensions (D₁, D₂, and D_c), and evaluate the complexity of pore systems across lithofacies. Correlation analysis and redundancy analysis were applied to further explore the controlling factors of reservoir heterogeneity. The results showed that organic-rich shale in the Permian Linghao Formation occurred mainly in the 1st Member, with average total organic carbon (TOC) content of 2.57%, and the lower part of the 3rd Member (average TOC content 2.88%). In the 1st Member, high-carbon shale was deposited under humid conditions with intense weathering, abundant fine-grained clastic input from basin margins, strongly reducing (anoxic) bottom waters, vigorous phosphorus recycling, and moderate to low primary productivity. Using TOC and mineral composition, seven shale lithofacies were identified in the Linghao Formation, and their development patterns were established based on depositional paleo-environment characteristics and evolution. In the 1st Member, organic-rich shale was dominated by mixed lithofacies with moderate to high TOC. The paleo-environment exerted a primary control on reservoir properties, gas content, pore structure, and heterogeneity. The high-carbon lithofacies had the most favorable rock properties—higher porosity, greater pore volume, and higher gas content—and contained a larger proportion of well-developed organic pores. Fractal analysis revealed that seepage pores exhibited greater structural complexity than adsorption-related pores, with the high-carbon lithofacies showing the highest overall fractal dimensions and thus the strongest heterogeneity. Across the formation, higher clay content and TOC were the primary drivers of increased pore-scale heterogeneity, whereas greater feldspar and quartz contents tended to diminish it. Carbonates exerted a minor effect. Heterogeneity in adsorption pores exerted the strongest influence on differences among lithofacies. These results highlighted the utility of fractal analysis in quantitatively linking shale mineralogy and organic content to multiscale heterogeneity in inter-platform basin settings. Full article

Lacustrine fine-grained sediments commonly exhibit well-developed laminations, with significant variations in structural characteristics such as thickness and continuity, which are closely related to depositional environments and genetic processes. This paper focuses on the characteristics and formation mechanisms of the upper Es4 to lower Es3 members of the Shahejie Formation in the Dongying Sag. Through polarized light microscopy, field-emission environmental scanning electron microscopy (FE-SEM), electron probe microanalysis (EPMA), and X-ray diffraction (XRD), we systematically analyzed the types, characteristics, and genetic mechanisms of laminations in fine-grained sedimentary rocks. Results indicate that the mineral composition of these rocks is dominated by carbonates and clay minerals, allowing classification into calcareous and argillaceous mudstones. The types of laminae include calcareous laminae, argillaceous laminae, and silty laminae, which are formed by chemical precipitation, suspension settling, and low-density turbidity currents, respectively. The primary lamination associations are argillaceous–calcareous interbeds and argillaceous–silty interbeds, exhibiting rhythmic cyclicity. In the upper Es4 member, variations in climate, sediment supply, and seasonal factors caused fine-grained sediments to transition from flocculent suspension settling to chemical precipitation, forming periodic intercalations of argillaceous and calcareous laminae. In the lower Es3 member, seasonal turbidity currents triggered the deposition of normally graded silty layers and fine-silty laminae, followed by a return to suspension deposition, resulting in argillaceous–silty interbeds. This study reveals diverse transport and depositional mechanisms of fine-grained sediments under varying hydrodynamic conditions. It provides a new case for understanding the genesis of fine-grained sedimentary rocks and offers geological insights for shale oil exploration and development in the Dongying Sag. Full article

The mineralogical, geochemical, and statistical characteristics of recent fluvial deposits from the Brahmaputra–Jamuna River, Bangladesh, were examined to determine their provenance, transport dynamics, and depositional environment. Sediments were analyzed using X-ray diffraction (XRD), wavelength dispersive X-ray fluorescence (WD-XRF), field emission scanning electron microscopy (FE-SEM), and electron probe microanalysis (EPMA). Grain size analysis revealed a predominance of medium-to-fine sand (mean grain size 1.77–3.43 ϕ), with moderately well-sorted textures (sorting: 0.33–0.77 ϕ), mesokurtic to leptokurtic distributions, and skewness values ranging from −0.21 to +0.30. Mineralogical results show a high quartz content with minor feldspar, mica, zircon, rutile, and iron-bearing minerals. Geochemical data indicates high SiO₂ (63.39%–70.94%) and Al₂O₃ (12.25%–14.20%) concentrations and calculated chemical index of alteration (CIA) values ranging from 60.90 to 66.82. The microstructural study revealed angular to sub-angular grains with conchoidal fractures and stepped microcracks, indicating brittle deformation under high-energy conditions, which is consistent with short transport distances, limited sedimentary recycling, and a derivation from mechanically weathered source rocks. Multivariate analyses (PCA and K-means clustering) of grain size parameters reveal two distinct sedimentary regimes, namely Cluster 1 as finer-grained (2.36 ϕ), poorly sorted sediments, and Cluster 2 as coarser (2.98 ϕ), well-sorted deposits. Discriminant function values (Y₂: 78.82–119.12; Y₃: −6.01 to −2.56; V₁: 1.457–2.442; V₂: 1.409–2.323) highlight shallow water, fluvial/deltaic aspects, and turbidite depositional environments. These findings advance the understanding of sedimentary dynamics within large, braided river basins and support future investigations into the sustainable management of fluvial depositional environments. Full article

The Xujiahe Formation (FM) is a significant source rock layer in the Sichuan Basin. In recent years, a growing number of scholars believe that the shale gas potential of the Xujiahe Formation is equally substantial, with the first member of the formation being the richest resource. The deposition of Member (Mbr) 1 of Xujiahe FM represents the first and most extensive transgression event within the entire Xujiahe Formation. This study investigates the sedimentary environment and organic matter (OM) enrichment mechanisms of the dark mud shales in the Mbr1 of Xujiahe FM on the southeastern margin of the Sichuan Basin, utilizing methods such as elemental geochemistry and organic geochemistry analyses. The results indicate that these dark mud shales possess a relatively high OM abundance, averaging 2.20% and reaching a maximum of 6.22%. The OM is primarily Type II₂ to Type III. Furthermore, the paleoclimate during the Mbr1 period in the study area was warm and humid with lush aquatic vegetation. Intense weathering and ample precipitation transported large amounts of nutrients into the lacustrine/marine basin, promoting the growth and reproduction of algae and terrestrial plants. Correlation analysis between the Total Organic Carbon (TOC) content and various geochemical proxies in the Mbr1 mud shales suggests that OM enrichment in the study area was primarily controlled by the climate and sedimentation rate; substantial OM accumulation occurred only with abundant terrigenous OM input and a relatively high sedimentation rate. Redox conditions, primarily productivity, and terrigenous detrital input acted as secondary factors, collectively modulating OM enrichment. Event-driven transgressions also played an important role in creating conditions favorable for OM preservation. Synthesizing the influence of these multiple factors on OM enrichment, this study proposes two distinct composite models for OM enrichment, dominated by climate and sedimentation rate. Full article

The Lower Cretaceous Jiufotang Formation in the Fuxin Basin contains a proven petroleum system. However, its southern part remains underexplored due to limited drilling and fragmentary sedimentary studies. To address this issue, we conducted detailed sedimentological logging of the two typical outcrop sections, Pijiagou and Tanjiagou. Field observations, petrographic data, and grain-size analysis were integrated to decipher hydrodynamic conditions, calibrate microfacies associations, and reconstruct the sedimentary evolution through facies stacking pattern analysis. The results show that the Jiufotang Formation predominantly consists of calcareous fine-grained clastic rocks, with poorly sorted sandstones indicative of low-energy conditions. Sediment transport mechanisms include both traction and turbidity currents, with suspension being predominant. The succession records a depositional transition from fan-delta to lacustrine environments. Two subfacies, fan-delta front and shore-shallow lacustrine, were identified and subdivided into seven microfacies: subaqueous distributary channels, interdistributary bays, subaqueous levees, mouth bars, muddy shoals, sandy shoals, and carbonate shoals. The sedimentary evolution reflects an initial lacustrine transgression followed by regression, interrupted by multiple lacustrine-level fluctuations. The alternating depositional pattern of lacustrine and deltaic facies has formed complete source-reservoir-seal assemblages in the Jiufotang Formation in the study area, making it a potential favorable target for hydrocarbon accumulation. Full article

Fine-grained sedimentary rocks exhibit significant textural heterogeneity, often obscured by conventional grain size analysis techniques that require sample disaggregation. We propose a non-destructive, image-based grain size characterization workflow, utilizing stitched polarized thin-section photomicrographs, k-means clustering, and watershed segmentation algorithms. Validation against laser granulometry data indicates strong methodological reliability (absolute errors ranging from −5% to 3%), especially for particle sizes greater than 0.039 mm. The methodology reveals substantial internal heterogeneity within Es3 laminated shale samples from the Shahejie Formation (Bohai Bay Basin), distinctly identifying coarser siliceous laminae (grain size >0.039 mm, Φ < 8 based on Udden-Wentworth classification) indicative of high-energy depositional environments, and finer-grained clay-rich laminae (grain size <0.039 mm, Φ > 8) representing low-energy conditions. Conversely, massive mudstones exhibit comparatively homogeneous grain size distributions. Additionally, a multifractal analysis (Multifractal method) based on the S_50bi/S_50si ratio further quantifies spatial heterogeneity and pore-structure complexity, significantly enhancing facies differentiation and reservoir characterization capabilities. This method significantly improves facies differentiation ability, provides reliable constraints for shale oil reservoir characterization, and has important reference value for the exploration and development of the Bohai Bay Basin and similar petroliferous basins. Full article

The development of gravity flow sedimentology has improved our understanding of the physical properties of different types of gravity flow deposits, especially the advancement of various gravity flow models. Although studies of gravity flows have developed greatly, the linkage between different sub-facies and their reservoir properties is hindered by a lack of detailed sedimentary records. Here, integrated test data (including thin-section petrology, high-pressure mercury injection experiments, capillary pressure curve analysis, and scanning electron microscopy) are used to evaluate links between different types of gravity flows and their reservoir properties from the Late Triassic–Early Jurassic Anyao Formation, southeastern Paleo-Ordos Basin, China. The petrological and sedimentological data reveal two types of deep-water gravity flow deposits comprising sandy debris flow (SDF) and turbidity current (TC) deposits. Both are fine-grained lithic sandstones and form low-porosity and ultra-low permeability reservoirs. Secondary porosity, formed by the dissolution of framework grains, including feldspars and lithic fragments, dominates the pore types. This secondary porosity is widely developed in the Anyao Formation and formed by reaction with organic acids during burial (early mesodiagenesis). The associated mud rocks have reached the early mature stage of the oil window with Tmax of 442–448 °C. Compared with the turbidites, the sandy debris flows have higher framework grain content (87.9 vs. 84.8%), framework grain size (0.091 vs. 0.008 mm), porosity (6.97 vs. 3.44%), pore throat radius (0.102 vs. 0.025 μm), and permeability (0.025 vs. 0.005 mD) but are relatively poor in the sorting of framework grains and pore throat radii. The most important petrological factors affecting porosity and permeability of the SDF reservoirs are framework grain size and feldspar grain content, respectively, but those of the TC reservoirs are feldspar grain content and the maximum pore throat radius. Diagenetic dissolution of framework grains is the most important porosity-affecting factor for both SDF and TC reservoirs. Our multi-proxy study provides new insights into the links between gravity flow sub-facies and reservoir properties in the lacustrine deep-water environment. Full article