Search Results (745)

This study systematically investigates the lithofacies, sedimentary microfacies, vertical evolution, and spatial distribution of the braided river delta–shallow lacustrine carbonate mixed sedimentary rocks of the Upper Ganchaigou Formation in the Huatugou Oilfield of the Qaidam Basin, China. This study integrates data from field outcrops, core observations, thin section petrography, laboratory analyses, and well-logging interpretations. Based on these datasets, the sedimentary characteristics are identified, and a comprehensive sedimentary model is constructed. The results reveal that the study area contains five clastic facies, three types of mixed sedimentary facies, and ten sedimentary microfacies. Two distinct modes of mixed sedimentation are recognized: component mixing and stratigraphic mixing. A full lacustrine transgression–regression cycle is formed by the two types of mixed sedimentation characteristics, which exhibit noticeable differences in vertical evolution. Component mixing, which occurs in a mixed environment of continuous clastic supply and carbonate precipitation during the transgression, is the primary characteristic of the VIII–X oil formation. The mixed strata that make up the VI–VII oil formation show rhythmic interbedding of carbonate and clastic rocks. During the lacustrine regression, it shows the alternating sedimentary environment regulated by frequent variations in lacustrine levels. The planar distribution is affected by both intensity of sediment from the west and the changes in lacustrine level. During the lacustrine transgression, it is dominated by littoral-shallow lacustrine mixed beach bar and mixed sedimentary delta. On the other hand, during the lacustrine regression, it is dominated by laterally amalgamated sand bodies in the braided-river delta front. Based on this, a mixed sedimentary evolution model controlled by the coupling of “source–lacustrine level” is established. It offers a guide for reconstructing the sedimentary environment in basins that are similar to it and reveals the evolution path of mixed sedimentation in the short-axis source area of arid saline lacustrine basins. Full article

This paper presents a new, quick method for testing the content of magnetic forms of iron in organic soils. These forms are an important marker of changes occurring in the environment. This method is based on impedance spectroscopy of a measuring coil inside which the tested material is placed—the material serves as the core of the coil. Unlike EIS (electrochemical impedance spectroscopy), the new method does not use electrodes, is sensitive to magnetic forms of iron, and is non-contact (the measuring current does not flow through the tested material). The results of research on three materials, including brown peat and silt with plant detritus, are presented in this paper. The results showed that changes in the standardized components of the measuring coil impedance in the frequency range of 100–135 kHz enable the determination of the content of ferromagnetic iron oxide (Fe₃O₄). The proposed method is very sensitive to soil oxide content in the range of 0% to 8%. Additionally, elemental composition analysis was performed using ICP-AES (inductively coupled plasma–atomic emission spectroscopy), which allowed for comparison of iron and other metal content with impedance measurement results. The final results confirm the usefulness of impedance spectroscopy as a non-destructive method for studying sedimentary environments and assessing their mineral properties. Full article

As a tectonically stable and extensively superimposed basin situated in the North China Craton, the Ordos Basin hosts abundant reserves of oil, natural gas, and coal within its Paleozoic strata, rendering it a focal area in energy-related geological research. The basin’s evolutionary history provides a comprehensive record of key geological transitions—from an Early Paleozoic carbonate platform to Late Paleozoic marine–continental transitional deposits and ultimately to continental clastic sedimentation—largely governed by the regional tectonic dynamics associated with the North China Plate. This study presents a systematic review of the sedimentary and tectonic evolution of the Paleozoic sequence in the basin. Findings indicate that during the Early Paleozoic, the basin developed under a passive continental margin setting, characterized by widespread epicontinental marine carbonate deposition. By the Late Ordovician, subduction of the Qinqi Ocean triggered the Caledonian orogeny, resulting in regional uplift across the basin, widespread erosion, and a significant hiatus in Middle to Late Ordovician sedimentation, which facilitated the formation of paleo-weathered crust karst reservoirs. In the Late Paleozoic, the basin evolved into an intracratonic depression. From the Late Carboniferous to the Early Permian, the Hercynian tectonic event influenced the transformation from isolated rift basins to a broad epicontinental sea, leading to the deposition of critical coal-bearing strata within marine–continental transitional facies. Starting in the Middle Permian, the closure of surrounding oceanic domains induced widespread tectonic uplift, shifting the depositional environment to a terrestrial fluvial-lacustrine system and marking the termination of marine sedimentation in the region. Based on the comprehensive research findings, this study underscores that the superposition, inheritance, and interaction of multiple tectonic events are the primary controls on the paleogeographic architecture and sedimentary. Full article

The Pearl River Mouth Basin is a significant hydrocarbon basin in the northern part of the South China Sea, where deep hydrocarbon exploration has become increasingly important research in recent years. However, the current understanding of the source-to-sink and depositional systems of the Paleogene Zhuhai Formation is still limited, which restricts the exploration and discovery of large-scale sand bodies. Based on core observation, heavy mineral analysis, and well-seismic integrated analysis, this paper clarifies the development of a fan delta-tidal flat depositional and the source-to-sink systems of the Zhuhai Formation. The bedrock in the source region primarily consists of granite, Mesozoic sandstone, and tuff. The source region is divided into five parts (A1–A5), with seven main valleys (V1–V7) developed, supplying sediments to five depositional areas (S1–S5). Additionally, a fault-slope type coupled valley–fan depositional model is established for the study area, revealing the spatiotemporal distribution and main controlling factors of the fan delta system in a steeply dipping boundary fault environment. Catchment area, valley length, and cross-sectional area show a strong positive correlation with sedimentary system scale. Increased elevation difference enhances sediment transport potential energy, while reduced width-to-depth ratio strengthens hydrodynamic forces, promoting sedimentary sand body development and sedimentary system expansion. Full article

The Lower-Middle Jurassic Xishanyao Formation in the Nileke Sag of the Yili Basin contains substantial reserves of coal and coalbed methane (CBM). Elucidating its depositional evolution and the controlling factors of coal accumulation within a sequence-stratigraphic framework is crucial for guiding future exploration. This study integrates regional geological surveys, core observations, well-log analysis, and quantitative lithofacies statistics of the lower member to establish a sequence-stratigraphic framework and reconstruct the sedimentary paleogeography. Eleven minable coal seams are identified, exhibiting a depositionally controlled spatial thickness distribution. The coal is classified as low-rank bituminous (Rank I–II), characterized by high inertinite, low ash, medium-high volatile matter, and ultra-low sulfur content, indicating formation in a freshwater swamp influenced by seasonal droughts and floods. Three third-order sequences (SQ1–SQ3) are recognized. SQ2, deposited during peak transgression as a braided-river delta plain, provided the optimal environment for peat accumulation. In contrast, SQ3 is dominated by progradational deltas with coarser sediments, where coal accumulation weakened. The results demonstrate that coal accumulation was jointly controlled by tectonic subsidence (providing accommodation space), climate (causing peat oxidation and fine-clastic input), and sedimentation (with interdistributary bays on the delta plain being the most favorable sites). Coal accumulation in the Lower Xishanyao Member resulted from the coupling of tectonic, climatic, and sedimentary processes. This genetic model provides a theoretical basis for regional coal and CBM exploration. Full article

Studying sedimentary distribution in water reservoirs is essential to understand the depositional processes and develop sustainable environmental management strategies. Characterization of deposited sediments provides information about the sources of particulate matter, transport patterns and predominant deposition mechanisms in different compartments of the reservoir. This study aimed to evaluate active deposition processes and to improve the understanding of sedimentation in water reservoirs. In this case, the Espora hydroelectric power plant, located on the Corrente River, southwestern Goiás, Brazil, was employed as a model environment. Sediment cores were collected at 29 points along the reservoir, covering different aquatic compartments. Particle-size analysis of the sediments was performed based on established methodologies using textural classification to identify sedimentary facies. The results indicated the predominance of stream deposits (sandy material) in areas where water flow velocity was higher, and bed deposits, composed predominantly of clays and silts, in regions of lower water flow velocity and greater depth. Full article

The mechanisms of massive gold migration and enrichment are challenging issues in mineral deposit research. The evolution of the elements and structures of gold-bearing minerals is the key to revealing the mechanisms of gold enrichment and migration. The Sawayardun gold deposit has an ore reserve of 127 t located in the southwestern Tianshan, Xinjiang, China. It is an ideal place for studying the mechanisms of massive gold migration and precipitation. However, the occurrence and distribution of gold are unclear, preventing an understanding of the massive gold enrichment and precipitation mechanism in the Sawayardun gold deposit. Therefore, in this study, the microscopic structural characteristics and chemical compositions of sulfides and gold minerals in the deposit were comprehensively analyzed using scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) techniques. The mineralization evolution is divided into a metamorphosed sedimentary period and a hydrothermal mineralization period, with the latter further subdivided into four mineralization stages: the quartz–pyrite stage, the arsenopyrite–pyrite stage, the polymetallic sulfide stage, and the carbonate stage. EPMA analysis reveals no clear compositional trends among different pyrite generations. Arsenopyrite (Apy) is more enriched in Au and Sb than pyrite. Overall, arsenopyrite is S-rich and As-deficient. Compared to Apy2, Apy1 is enriched in Fe and S but depleted in As. Stibnite is closely associated with native gold and contains elevated Au (up to 3.63%). Invisible gold exists in a form that is visible at the micrometer-to-atomic scale within pyrite and is lattice-bound in arsenopyrite. Visible gold occurs as native grains in quartz fractures or within sulfides. The composition of pyrite indicates that the Sawayardun gold deposit formed in a reducing, medium-depth, meso-epithermal environment. Au extraction by Sb-rich melts, dissolution–reprecipitation, and adsorption by As-bearing pyrite were the primary mechanisms for Au migration and precipitation. This study contributes to understanding the enrichment and precipitation processes of gold in orogenic-gold deposits in southwestern Tianshan. Full article

The mineral matter in coal has great significance for geological evolution, and clean and fractional utilization. The Laochang mining area is one of the largest anthracite coal production bases in Southern China, and the most important coal energy base in Yunnan province, China. This study investigates the composition and mode of occurrence of mineral matter in the Laochang coals to reveal the sediment provenance, sedimentary environment, and hydrothermal fluids. The predominant minerals in the Laochang coals include oxide (quartz, anatase), clay (kaolinite, illite/smectite mixed layer), sulfide (pyrite, sphalerite), phosphate (xenotime, monazite, goyazite–gorceixite), and carbonate (calcite, dolomite, sideroplesite, siderite). The minerals in the Laochang coals are dominated by quartz (2.4~54.8%) and kaolinite (3.4~39.2%), followed by illite, smectite, muscovite, calcite, pyrite, and anatase. Quartz and dolomite in SB-7+8 coal have the highest proportions, reaching 54.8% and 17.3%. The modes of occurrence of minerals reflect that the Laochang coals are affected by the epigenetic hydrothermal fluids and seawater. The chalcophile elements Hg, Pb, Se, and Cr, and lithophile elements Li, Nb, Ta, Zr, Hf, and REY are slightly enriched in XB-3 coal, which is attributed to the intrusion of seawater and the supply of terrestrial detrital materials, respectively. REY is dominated by LREY, followed by MREY, and a lower level of HREY in the Laochang coals, which have a high fractionation degree. The REY enrichment H-type is influenced by the hydrothermal fluids. Based on the relationship between Al₂O₃ and TiO₂, Al₂O₃/TiO₂ and Nb/Yb, and the negative anomaly Eu, the detrital material in the erosion source area of the Laochang coal is derived from the Emeishan Large Igneous Province basalt and felsic–intermediate rocks. Full article

Black-odorous water pollution presents a serious threat to aquatic ecosystems and severely hinders the sustainable development of the ecological environment, as conventional remediation technologies often fall short in achieving the simultaneous removal of multiple pollutants. In this study, a novel composite remediation agent was developed by integrating microbial active components with modified clay minerals—sodium-modified zeolite (Na-Z) and magnesium–aluminum–lanthanum layered ternary hydroxides loaded onto sulfuric acid-modified bentonite (Mg-Al-La-LTHs@SBt)—through gel-embedding immobilization. This integrated system enabled the synergistic remediation of both overlying water and sediment pollutants. The modified clay minerals exhibited strong adsorption capacity for nitrogen and phosphorus compounds in the overlying water. Under 25 °C conditions, the composite agent achieved removal efficiencies of 58.14% for ammonium nitrogen (NH₄⁺-N) and 88.89% for total phosphorus (TP) while significantly reducing sedimentary organic matter and acid volatile sulfide (AVS). Notably, the agent retained substantial remediation efficacy even under low-temperature conditions (5 °C). High-throughput microbial community analysis revealed that the treatment enriched beneficial phyla (e.g., Proteobacteria) and beneficial genera (e.g., Thiobacillus) and suppressed sulfate-reducing groups (e.g., Desulfobacterota), promoting favorable nitrogen and sulfur transformations. These results provide a robust material and methodological basis for efficient, synergistic restoration of black-odorous water and the sustainable development of water resources. Full article

The Colombian Orinoquia was shaped within a tectonic and sedimentary framework linked to the uplift of the Andean cordilleras during the Oligocene–Miocene. This orogenic event generated two tectonic fronts and facilitated extensive fluvial sedimentation across a broad alluvial geosyncline. The present geomorphological configuration reflects the cumulative interaction of tectonic and erosional processes with Quaternary climatic dynamics, which together produced complex landscape assemblages characterized by plains with distinctive drainage patterns. To delineate and characterize geomorphological units, we employed multidimensional imagery and Machine Learning techniques within the Google Earth Engine platform. The classification model integrated dual polarizations of synthetic aperture radar (L-band) with key topographic variables including elevation, slope, aspect, convexity, and roughness. The analysis identified three major physiographic units: (i) the Foothills and the Floodplain, both dominated by fluvial environments; (ii) the High plains and Serranía de La Macarena (Macarena Mountain Range), where denudational processes predominate; and (iii) localized aeolian environments embedded within the Floodplain. These contrasting dynamics have generated a broad spectrum of landforms, ranging from terraces and alluvial fans in the Foothills to hills and other erosional features in La Macarena. The Floodplain, developed over a sedimentary depression, illustrates the combined action of fluvial and aeolian processes, whereas the High plains is characterized by rolling plains and peneplains formed through the uplift and erosion of Tertiary sediments. Such geomorphic heterogeneity underscores the interplay between tectonic activity, climatic forcing, and surface processes in shaping the Orinoquia landscape. The geomorphological classification using Random Forest demonstrated high effectiveness in discriminating units at a regional scale, with accuracy levels supported by confusion matrices and associated Kappa indices. Nevertheless, some degree of classificatory overlap was observed in fluvial environments, likely reflecting their transitional nature and complex sedimentary dynamics. Overall, this methodological approach enhances the objectivity of geomorphological analysis and establishes a replicable framework for assessing landform distribution in tropical sedimentary basins. Full article

This paper presents the results of a comprehensive study of a cuboid diamond of variety III according to the mineralogical classification of Y.L. Orlov, which was first discovered in Carnian (Upper Triassic) deposits of the Bulkur anticline in the northeastern Siberian platform. It is established that the crystal has a cubic shape with signs of intense dissolution and is characterized by a zonal–sectorial fibrous internal structure. The central area of the diamond is saturated with microinclusions. The studied cuboid diamond belongs to the IaAB type according to IR spectroscopy data. An accumulation of minerals, which is represented by chamosite (Fe-rich chlorite), quartz, and pyrite, as well as rare native metals (Fe, Cu, and Ag) and intermetallides (chromferide), is present on the diamond surface. The chemical composition and morphology of chamosite indicate its low-temperature hydrothermal–diagenetic origin (50–150 °C, pressure < 1 kbar) in the marine or lagoon sedimentary environment of the rift basin of the Siberian platform during the Triassic. The discovery of a diamond of variety III, characteristic of large industrial kimberlite pipes (Mir, Udachnaya, and Aikhal), in placers of the Leno-Anabar diamond-bearing subprovince indicates a possible unknown primary kimberlite source. Full article

Sedimentary dynamics in the Palamós Canyon are influenced by river inputs and storm resuspension, as well as by bottom trawling on the canyon flanks. In this study, we estimate recent sediment deposition patterns along the canyon axis using the excess activity concentration of the short-lived radiotracer ²³⁴Th (half-life of 24.1 days). Sediment cores were obtained at various locations along the canyon axis from a depth of approximately 800 m to 2100 m in June 2023 and August 2024. Excess ²³⁴Th (²³⁴Th_xs) was detected in all sampled sites with variable penetration depths (0.5–3.5 cm). ²³⁴Th_xs-derived estimations of mixing rates decreased downcanyon from up to 15.6 cm² y⁻¹ at the canyon head (~800 m) to negligible mixing at the canyon mouth (~2100 m). ²³⁴Th_xs inventories, a proxy of recent sediment deposition, were high (1800–3490 Bq m⁻²) at the canyon head and at the upper canyon (~1400 m) close to fishing grounds and decreased downcanyon (82–694 Bq m⁻²) at the lower canyon (~1800 m) and canyon mouth. Inventories varied 2-fold across years presumably attributed to enhanced riverine and bottom trawling sediment fluxes. Similar ²³⁴Th-derived sediment deposition patterns can be found in submarine canyons worldwide, highlighting the value of this radiotracer for sedimentary dynamics studies in such complex environments. Full article

The southern Korean Peninsula faces complex seismic challenges due to the concentration of critical infrastructure and the region’s unique intraplate tectonic environment. In this study, over 300 strong-motion records from 10 moderate-magnitude earthquakes were analyzed using data from 10 representative seismic stations. Acceleration response spectra, normalized by peak ground acceleration, were generated and systematically compared with international and domestic seismic design standards, including USNRC Regulatory Guide 1.60 and KBC 2016. The observed spectra frequently exceeded existing code requirements in the mid-to-high-frequency range critical for local infrastructure, indicating potential vulnerabilities in applying generic global standards to Korean conditions. Analysis of vertical-to-horizontal spectral ratios further revealed pronounced frequency dependence and amplification effects, especially in sedimentary basin sites. These findings underscore the importance of accounting for site-specific geological and seismic characteristics in the seismic design of critical infrastructure in Korea. The results advocate for the development of regionally calibrated, risk-informed seismic design frameworks and provide essential empirical data to support safer, more resilient infrastructure amid moderate but potentially hazardous earthquake activity. Full article

The depositional environment of the Machów Formation in the central part of the Carpathian Foredeep is still relatively poorly understood. Although lithological variability, facies diversity, and depositional history have been described in many publications, the paleoenvironment of sedimentation and the evolution of individual segments of the sedimentary basin are still not well known. The Miocene complex is difficult to recognize using standard seismic interpretation methods due to cumulative effects of depositional, erosional, and tectonic processes. Progress in science and technology offers new opportunities for the application of high-resolution methods of seismic data interpretation, such as seismostratigraphic interpretation, seismic facies analysis, and seismic geomorphology. The results of seismostratigraphic interpretation of the Machów Formation indicate the presence of numerous depositional sequences of varying thickness and spatial range. The interpretation enabled identification of various types of paleoenvironments, typical for both deeper basin zones (e.g., slope and basin floor fans) and coastal environments. Based on the research conducted, it was concluded that high-resolution 3D seismic data play an essential role in the detection and visualization of lithostratigraphic traps for hydrocarbons, which is important both in exploration and in determining hydrocarbon migration pathways. Full article

Coastal erosion poses a significant threat to global shorelines, exacerbated by anthropogenic pressures and climate change. The Sea of Azov, a shallow, semi-enclosed basin with coastlines composed of weakly consolidated sediments, represents a highly vulnerable and understudied hotspot for abrasion processes. This study provides a comprehensive, multi-decadal assessment of coastal retreat rates for the Sea of Azov by synergistically integrating long-term field observations with a multi-temporal analysis of satellite imagery from 1971 to 2022. We employed a diverse array of satellite data, including declassified CORONA, SPOT, Sentinel-2, and high-resolution Resurs-P imagery, which were processed and analyzed within a GIS framework using the Digital Shoreline Analysis System (DSAS). Our results quantify extreme coastal abrasion, revealing maximum retreat rates of 1.0–3.5 m/yr along the eastern Sea of Azov coast and specific sectors of Taganrog Bay. The spatiotemporal analysis identified the period of 2013–2014, marked by two major storms, as a peak of erosional activity across all coastal sectors. This study demonstrates that the spatial distribution of erosion is controlled by a convergence of high-energy wind-wave forcing, low geotechnical resistance of Quaternary sedimentary deposits, and unfavorable coastal morphometry. This research underscores the critical value of merging historical field data with modern geospatial technologies to establish baseline rates, identify erosion hotspots, and inform future coastal zone management strategies in vulnerable marine environments. Full article