The Xiuyan impact crater is the only officially recognized impact crater in China, and its formation time remains unclear. In this study, we investigated the ages of Xiuyan impact crater lake sediments from a 99-m composite borehole using luminescence and radiocarbon dating. The results showed that all the radiocarbon ages were saturated and that the surface sediments in the crater lake were dated to ~331–334 ka. Furthermore, the luminescence ages of lake sediments at depths below approximately 37 m also appear to be saturated. The evolutionary history of the Xiuyan impact crater lake was reconstructed by incorporating sedimentological, geomorphological, and geochronological analyses. Based on the age-depth model results of luminescence ages above a depth of 37 m, it is suggested that the crater lake underwent several stages: initial formation at approximately 1201 ± 133 ka, subsequent filling with water and sediment, overflow, and eventual disappearance at ~331–334 ka.

Unconventional natural gas in deep coal measures has become an exploration and research hotspot in recent years. The exploration breakthrough of deep coalbed methane and tight sandstone gas in Daning-Jixian Block in the eastern Ordos Basin has revealed huge resource potential and commercial prospects in the deep Upper Paleozoic Carboniferous-Permian coal measures. However, the ambiguity of gas accumulation in deep coal measures has restricted exploration and development. Based on a series of tests for fluid inclusions, including petrographic observation, Raman spectroscopy analysis, and microthermometry, combined with the burial-thermal evolution history recovered from basin modeling, this study aims to clarify the timing of gas accumulation in deep coal measures. The results show four types of secondary fluid inclusions in the deep coal measure sandstone layers of Daning-Jixian Block, including CH₄-rich inclusions, C₂₊ hydrocarbons-bearing inclusions, CO₂-bearing inclusions, and aqueous inclusions. The main formation stage of fluid inclusions corresponded to the mesodiagenesis stage of the deep coal measure sandstone, and the coeval assemblages of fluid inclusions vary due to the recording of gas charging in different maturity stages of coal measure source rocks. This study suggests that tight sandstone gas accumulation in deep coal measures was a continuous charging process with one period-multiple episodes in Daning-Jixian Block, and occurred mainly during the Early Cretaceous (137−127 Ma BP). The results of this study contribute to further understanding of gas accumulation mechanisms in deep coal measures.

Complex hydrocarbon distributions characterize the Wenchang-A Sag. Systematic study of the geochemical characteristics of crude oil, natural gas and source rocks and their genetic relationship is still needs to be completed. The Rock-Eval, kerogen maceral, vitrinite reflectance, saturated hydrocarbon gas chromatography-mass spectrometry, natural gas components, carbon isotopes, and light hydrocarbon were performed. 1) Crude oil is classified based on four factors: wax content, the presence of C₂₇ diasteranes, the regular steranes αα20RC₂₇-αα20RC₂₈-αα20RC₂₉, and the bicadinanes characteristics. Class I crude oil has high wax and C₂₇ diasteranes. For Class II crude oil, the regular steranes are in ‘L’- shaped distribution, and the content of bicadinanes is shallow. Class III crude oil has soft wax and C₂₇ diasteranes, and regular steranes in the reverse ‘L’-shaped distribution, with a high peak degree of bicadinanes. For Class IV crude oil, regular steranes are in ‘V’-shaped distribution, with high peak bicadinane. 2) Class I crude oil comes from source rocks in area C. Class II crude oil comes from source rocks in areas D and E. Class III crude oil comes from areas A, and B. Class IV crude oil comes from source rocks in area A. 3) The source of natural gas in Group I is hydro propylene, and natural gas in Group II is humic. Natural gas in Group III is mixed. Groups I and II are kerogen cracking gas, and group III is a mixture of crude oil secondary cracking gas and kerogen cracking gas. Natural gas in Groups I and II mainly come from local source rocks, and Group III has mixed source characteristics. In the future, oil exploration can continue in Areas C and D, and more favorable areas for gas exploration are Areas C, D, and E.

Bedding fractures are among the key factors affecting the production efficiency of shale oil and gas, but relatively little research has been conducted on the effectiveness of bedding fractures. Based on field outcrops and drill cores from the Fuling area in the Sichuan Basin, this work discusses the development, filling, and opening characteristics of bedding fractures and their quantitative impact on physical properties. Multiple methods were employed, e.g., immersion testing, wet illumination, high-power microscanning, imaging logging identification and experimental measurement. The results indicate that the highest density reaches 437 fractures per meter, with apertures less than 0.5 µm being the majority. The average permeability of the shale samples with vertical bedding is 44.6 times that of the shale samples with parallel bedding, while the porosity exhibits less anisotropy. Many open bedding fractures with gas outlets in the core are shown by on-site immersion experiments and electron microscopy scanning experiments. Each dark stripe on the imaging logging map corresponds to a bedding fracture, and the thickness of the dark stripes corresponds to the aperture of the bedding fracture. There is no need to consider unfilled bedding fractures, as fractures filled with calcite veins and pyrite crystals can also become effective seepage channels because of the pores within the calcite veins and between the pyrite crystals. The utilization and transformation of bedding fractures during fracturing is one of the key steps in producing shale oil and gas. It is necessary to combine the in situ stress field, bedding fracture characteristics, and fracturability of shales to reasonably utilize bedding fractures to transform oil and gas reservoirs.

Surface soil materials from the Gobi Desert were sieved into fraction groups of 0.063–0.125, 0.125–0.25, 0.25–0.5, 0.5–1, and 1–2 mm. These samples were placed in a field for a physical weathering and dust deposition experiment. In the natural Gobi Desert environment, the dust-sized fractions (< 0.063 mm in diameter) produced by physical weathering and via dust deposition in the above groups were 1387 ± 124, 702 ± 70, 698 ± 47, 742 ± 101, and 769 ± 75 g·m⁻², respectively, from 18 October 2020 to 18 December 2021. Dust deposition during the same period was 611 ± 55 g·m⁻². For the same respective groups, 5.32 ± 0.76%, 0.58 ± 0.27%, 0.53 ± 0.18%, 0.80 ± 0.52%, and 0.98 ± 0.31% (by weight) of the bulk samples were weathered into dust-sized fractions during the experimental period. The physical weathering intensities were 23.95%, 14.96%, 8.90%, and 2.81% by weight for fraction groups of 2–4, 4–8, 8–16, and > 16 mm, respectively. The fine-grained materials of the gravel were more sensitive to physical weathering than coarse materials. In natural environments, the processes of dust deposition and physical weathering were key factors affecting the surface topographical equilibrium of the Gobi Desert and dust emission in Asia.

A sandy, braided river is a typical type of river that exists in ancient and modern alluvial plains and is inherent with significant seasonal water discharge variations. The variations play an important role in the depositional process and the formation of the sedimentary architecture of braided rivers. In this paper, a braided river outcrop along the Yellow River in Fugu is used to describe the effects of seasonal hydrodynamic variations on braided river sedimentary architecture. The results show that the braided channel network exhibits two different patterns during flood period and normal period. During flood periods, the main braided channels surrounding channel bars and the secondary braided channels distributed on the top of the channel bars coexist, forming a highly braided channel network. Migration of the main braided channels control the formation of middle channel bars and side bars. The generation and evolution of the secondary braided channels reformed the upper part of preexisting channel bars and produced affiliated bars along their flow path. During the normal period, water levels decrease, causing the secondary river channels to be abandoned and forming abandoned channels, and only the main braided channels stay active. In the long term sedimentation process, strong water flow during the flood period continuously erodes pre-existing sediments and forms new sediments, while weak water flow during the normal period can only reform the main braided channels and their adjacent channel bar sediments. Based on differences in sedimentary processes and associated hydrodynamic conditions, braided river sediments are divided into two combinations. The strong hydrodynamic combination includes main braided channels, middle channel bar, and side bar, while the weak hydrodynamic combination includes secondary braided channels, abandoned channels, and affiliated bars. The proportion of strong hydrodynamic combinations is much larger than that of weak hydrodynamic combinations. Based on this, we construct a braided river sedimentary architecture model that is helpful for the fine characterization of subsurface oil and gas reservoirs.

The hail size discrimination algorithm (HSDA) and its capacity to identify hail in Shandong Province are analyzed to satisfy the localized requirement by China’s S-band dual-polarization radars. A modified HSDA is obtained by using optimized membership function thresholds based on the statistics of Shandong hail data. The results are verified by a supercell storm process. 1) The modified HSDA improves the identification of large hail and giant hail. The results are consistent with the analysis of the scattering and polarization parameter characteristics of different-size hails, the dynamic and microphysical characteristics for supercell, and the real situation. 2) The horizontal and vertical hail-size distribution characteristics are consistent with the analysis about the growth process of larger hails and the precipitation particles filtering mechanisms in supercells. Small hail first forms at the suspension echo, then is injected into the larger hail growth area above the bounded weak echo area driven by updrafts, colliding with the abundant supercooled water in the K_DP column. Finally, large hail and giant hail fall near the direction of the updrafts to form a strong echo wall, and giant hail falls 6–12 km from the central updraft. 3) The maxima of the Z_DR and K_DP columns can be used to predict the hail-growth trend, which exceeds the −20°C isotherm for the heavy-hail growth stage at high-altitude in the supercell storm. When hail falls to the ground, the Z_DR column shortens and the K_DP column disappears, which provides the observation basis from polarimetric radars for the consumption of supercooled water by hail growth.

Climate change has significantly impacted the water resources and conservation area of the Yellow River basin. The Upper Yellow River basin (UYR), referring to the area above Lanzhou station on the Yellow River is the focus of this study, the runoff changes in the UYR would greatly impact the water resources in China. Most existing studies rely on a single hydrological model (HM) to evaluate runoff changes instead of multiple models and criteria. In terms of the UYR, outputs of the previous Coupled Model International Comparison Project (CMIP) are used as drivers of HMs. In this study, the weighted results of three HMs were evaluated using multiple criteria to investigate the projected changes in discharge in the UYR using the Shared Socioeconomic Pathways (SSPs) from CMIP6. The research’s key findings include the following. 1) Annual discharge in the UYR is expected to increase by 15.2%−64.4% at the end of the 21st century under the 7 SSPs. In the long-term (2081−2100), the summer and autumn discharge will increase by 18.9%−56.6% and 11.8%−70%, respectively. 2) The risk of flooding in the UYR is likely to increase in the three future periods (2021−2040, 2041−2060, 2081−2100) under all 7 SSPs. Furthermore, the drought risk will decrease under most scenarios in all three future periods. The verified HMs and the latest SSPs are applied in this study to provide basin-scale climate impact projections for the UYR to support water resource management.

Qinshui Basin possesses enormous deep coalbed methane (CBM) resources. Fine and quantitative description of coal reservoirs is critical for achieving efficient exploration and development of deep CBM. This study proposes a 3D geological modeling workflow that integrates three parts: geological data analysis, 3D geological modeling, and application of the model, which can accurately predict the favorable areas of CBM. Taking the Yushe-Wuxiang Block within the Qinshui Basin as a case study, lithology identification, sequence stratigraphy division, structural interpretation is conducted by integrating well logging, seismic, and drilling data. Six lithology types and regional structural characteristics of the Carboniferous-Permian coal-bearing strata are finely identified. Combining experimental testing on porosity and gas content and well testing on permeability, a 3D geological model that integrates the structural model, facies model, and property model was established. Utilizing this model, the total CBM resource volume in the study area was calculated to be 2481.3 × 10⁸ m³. Furthermore, the model is applied to predict the distribution ranges of four types of CBM favorable areas. The workflow is helpful to optimize well deployment and improve CBM resource evaluation, ultimately provide theoretical guidance for subsequent efficient exploration and development. Our study constitutes a reference case for assessing potential of CBM in other blocks due to the successful integration of multiple available of data and its practical applications.

Pressure mercury intrusion test is (MIP) one of the most commonly used methods to characterize pore-fracture structure. Here, we use the fractal dimension of the mercury intrusion curve to analyze the heterogeneity of pore and fracture distribution. Differing from the intrusive mercury curve, the extrusive curve provides a better representation of the seepage capacity of a reservoir. In this paper, the division method of sample types using both mercury invasive parameters (pore volume, pore volume percentage, porosity, permeability) and extrusive parameters (mercury removal efficiency) is discussed. The fractal dimension values of mercury intrusive and extrusive curves are calculated for all samples using the Menger, Thermodynamics, and Multifractal fractal models. Moreover, the fractal significance of the mercury withdrawal curve is examined. The results are as follows. 1) The samples can be divided into three types based on the mercury removal efficiency and total pore volume. Type A is characterized by lower total pore volume (< 0.08 cm³·g⁻¹) and removal efficiency (< 30%), type B has lower total pore volume (< 0.08 cm³·g⁻¹) and higher removal efficiency (> 30%), and type C has larger total pore volume (> 0.08 cm³·g⁻¹) and higher removal efficiency(> 30%). 2) Mercury removal efficiency does not correlate with the mineral composition or total pore volume, but it does show a clear positive correlation with pore volume in the range of 100 to 1000 nm. Unlike the Menger model, the mercury removal curve analyzed using the thermodynamics and multifractal model shows good fractal characteristics. 3) In contrast to the injective curves, the fractal dimension of mercury removal curves exhibits an obvious linear negative correlation with pore structure parameters and mercury removal efficiency. Moreover, the multifractal dimensions D₀–D₁₀ obtained from the mercury removal curves show a negative correlation with porosity and permeability. This indicates that fractal dimension based on the mercury extrusion curve can be used as a new parameter for characterizing pore-fracture structure heterogeneity.

The produced water from coalbed methane (CBM) wells contains abundant geochemical and microbiological information. The microbial communities in the produced water of 14 CBM wells from four coal-bearing synclines in Guizhou and Yunnan were successfully tested by using 16S rRNA amplicon sequencing technology. The results showed that the produced water contained a large number of archaea and bacteria. The bacteria mainly included the orders Bacteroidales and Clostridiales, accounting for 37.4% and 32.92%, respectively. The water contained more than 30 species of bacteria and 15 species of methanogens. Macellibacteroides was the dominant genus, followed by the genus Citrobacter. The methanogens mainly included the orders Methanobacteriales and Methanosarcinales, accounting for 57.46% and 26.49%, respectively. Methanobacterium was the dominant genus, followed by the genus Methanothrix. There were three kinds of metabolism: hydrogenotrophic methanogens, acetoclastic methanogens, and methylotrophic methanogens. The main influencing factors of archaea were coalbed properties, such as burial depth and R_o,max, while the influencing factors of bacteria were mainly the physical and chemical properties of groundwater, including Cl⁻, total dissolved solids, and HCO₃⁻. The microbial communities were segmented in the vertical direction of the coal measure strata, which can be consistent with the distribution characteristics of multiple superposed fluid systems, and the main microbial species in each section were preliminarily identified. Combining carbon and hydrogen isotopes of methane, and dissolved inorganic carbon stable carbon isotopes of produced water from CBM wells, the results showed that the microbial reduction in the Tucheng and Enhong synclines were strong and that there were obvious secondary biogases. A reduction in hydrogen-trophic methane bacteria is an important way to produce secondary biogases in the study area. These synclines are suitable to carry out microbially enhanced coalbed methane research, expanding and extending CBM stimulation technology in the later stage.

Pore volume/surface area and size distribution heterogeneity are two important parameters of pore structures, which restrict the gas-water-oil migration process in sandstone reservoirs. The fractal theory has been proved to be one of the most effective methods to quantify pore distribution heterogeneity. However, the dynamic variation of porosity and permeability due to fractal characteristics has been rarely studied. In this paper, physical properties, mineral composition, and pore distribution of 18 groups of sandstone samples were analyzed using scanning electron microscope (SEM) and high-pressure mercury injection tests. Then, Sierpinski model, Menger model, thermodynamic model, and multi-fractal model were used to calculate the fractal dimension of the pore volume. Thus, the relationship between fractal dimension and porosity/permeability variation rate, and pore compressibility were studied. The results are as follows. 1) All samples can be divided into three types based on pore volume (0.9 cm³∙g⁻¹) and mercury removal efficiency (35%), i.e., Type A (< 0.9 cm³∙g⁻¹and < 35%); Type B (> 0.9 cm³∙g⁻¹ and <35%); Type C ( > 0.9 cm³∙g⁻¹ and > 35%). 2) Four fractal models had poor applicability in characterizing fractal characteristics of different sample types. The fractal dimension by the Sierpinski model had a good linear correlation with that of other models. Pores with smaller volumes dominated the overall pore distribution heterogeneity by multi-fractal dimension. The pore diameter between 200−1000 nm and larger than 1000 nm was the key pore size interval that determined the fractal characteristics. 3) With the increase of confining pressures, porosity and permeability decreased in the form of a power function. The compressibility coefficient of typical samples was 0.002−0.2 MPa⁻¹. The compressibility of Types A and B was significantly higher than that of Type C, indicating that the total pore volume was not the key factor affecting the pore compressibility. The correlation of compressibility coefficient/porosity variation rate with pore volume (total and different size pore volume), fractal value and mineral component were not significant. This indicates that these three factors comprehensively restricted pore compression.

Mountain vegetation is highly sensitive to changes in climate. Currently, there is no consensus regarding the direction and magnitude of the spatial migration of mountain vegetation in response to climate change. Past studies have reported that climate change promotes upward or downward movement of plant species along an altitude gradient. Based on meteorological data and remote sensing images, this study analyzed the spatial distribution and dynamic trend of mountain altitudinal vegetation belts on the southern slope of the Tianshan Mountains over the past 30 years and discussed the climatic driving factors of these changes. The results showed that the forest belt in this area is unusual because it is embedded in the grassland belt in a patch-like manner and shows discontinuous changes or replacements along the vertical gradient. With the coexistence of warm humidification and warm drying on the southern slope of the Tianshan Mountains, the response of the upper and lower altitudes of the forest belt to climate change was similar, showing a trend of migration to higher-altitude areas. The main climatic factors affecting the migration of the upper and lower altitudes varied spatially. In general, the upper limit of the forest belt had a higher association with precipitation during the vegetative growth season, while the contribution of temperature-related factors to the lower limit of the forest belt was greater.

The sedimentary environment is inextricably linked to the macroscopic and microscopic characteristics of shale reservoirs, which influences shale gas accumulation significantly. This study discusses how the sedimentary environment affects the organic-matter-rich shale reservoirs that have been deposited in typical marine, marine-continental transitional, and continental basins in China. The following four aspects were analyzed including shale rock type and thickness distribution, organic matter abundance and distribution, mineral composition and pore structure, and kerogen type and hydrocarbon generation potential. From continental to marine facies, the sedimentary setting of shales with high organic content generally ranges from shore-shallow lakes to deep lakes, deltas, tidal flat lagoons, shallow sea shelves, and deep or semi-deep seas. In deeper water, the clay mineral content decreases, but the brittleness index and siliceous content increase with darker shale color. Thick shales mostly were deposited in deep or semi-deep lakes, delta fronts, prodeltas, tidal flat lagoons, and deep or semi-deep seas from continental to marine basins. The primary factors influencing organic matter enrichment in deep-sea and deep-lake shales are redox conditions and high biological productivity under favorable sedimentary environments, whereas favorable factors for organic matter enrichment in transitional facies include warm-humid palaeoclimates and abundant debris inputs. Continental shale is characterized by the presence of intergranular and intragranular pores, a low pore volume and specific surface area, and a high average pore size and hydrocarbon potential. The kerogen types are complex in continental shales, with type I in deep lake shales and type III in lakeshore shales. Transitional shales occur mostly in coal-bearing strata with type III organic content, medium pore sizes, and hydrocarbon generation potential. The high specific surface area and pore volume, small pore size, and high brittle mineral content of marine shale facilitate the production of dissolution pores. Marine shales are mainly kerogen type I–II₁ with relatively high maturity and low hydrocarbon production potential. By constructing an intrinsic link between the sedimentary environment and reservoir parameters, a sedimentary model of organic-rich shale under different depositional context should be summarized in the future, which can provide a foundation to analyze the geological circumstances of shale gas accumulation.