Search Results (558)

Compound geological disaster chains pose major challenges for disaster prevention in mountainous regions due to their complex mechanisms and cascading impacts. This study investigates a landslide–debris flow–flash flood hazard chain that occurred on 21 July 2024 in the Xujia River catchment, Mianning County, Sichuan Province, China. This event is used as a representative case to improve the understanding of the formation and amplification mechanisms of breach-type debris flows through dynamic inversion constrained by sedimentary records. The objective is to reconstruct the evolution of the event and assess its downstream hazard extent. Post-disaster sedimentary and geomorphological records, including deposit distribution, channel aggradation, and flow traces, were systematically analyzed based on remote sensing interpretation, unmanned aerial vehicle surveys, and detailed field investigations. These sedimentary data were used as key constraints to estimate debris flow magnitude and mobility under different rainfall scenarios. A rainfall flood scenario-based estimation method was applied to quantify debris flow magnitude, and numerical simulations were conducted using the Rapid Mass Movement Simulation model to reproduce debris flow propagation and deposition processes. The results indicate that prolonged antecedent rainfall triggered slope failure in a tributary, leading to the accumulation of landslide-derived material and the formation of a temporary channel blockage. The subsequent breach of this blockage significantly amplified debris flow discharge, velocity, and sediment outflow, resulting in downstream hazard expansion. Simulation results constrained by sedimentary evidence show that peak discharge and solid material output under breach conditions were approximately three times higher than those of rainfall-driven scenarios under comparable rainfall frequencies. These findings demonstrate that sedimentary records provide critical constraints for the inversion of landslide debris flow disaster chain dynamics and highlight the effectiveness of post-disaster evidence based numerical assessment for hazard analysis and risk mitigation in debris flow-prone mountainous catchments. Full article

The shallow-buried abandoned Yellow River Delta (893–1855 AD) exhibits a distinctive geomorphic system shaped by coupled fluvial sediment reduction, climatic transition, and relative sea-level fluctuations, with its intact deposits recording key temperate delta evolution during climate change. Using four sediment cores, we applied optically stimulated luminescence (OSL) dating, sedimentary facies analysis, and grain-size techniques (C-M diagram, end-member modeling), integrated with geomorphic interpretation and historical data, to reconstruct the delta’s evolutionary sequence and clarify storm surge-driven geomorphic reworking and its diagnostic indicators. Results indicate that the delta’s evolution was governed by abrupt fluvial sediment loss, intensified storm dynamics, and relative sea-level rise. The 893 AD Yellow River avulsion triggered delta abandonment (893–1482 AD), driving a shift from a fluvially dominated muddy coast to a wave-controlled sandy system. Sandy deposits initially formed at M04A and prograded landward to M03A. During the Little Ice Age (1482–1855 AD), frequent storm surges further expanded and elevated these sandy accumulations, while weak sedimentation persisted in the inland depression (B03). This differential process generated a unique plain lowland–coastal highland system, a rare geomorphic type among large river deltas that differs from classic island–continent and barrier–lagoon systems. This study elucidates the phased response of temperate monsoon abandoned deltas to millennial-scale climate change, advances theories of multi-factor coupled delta evolution, and provides scientific support for coastal protection, stability assessment, and evolutionary prediction under global warming. Full article

High-salinity water environments, e.g., saline lacustrine basins and lagoons, represent significant sedimentary settings on Earth. They serve not only as crucial archives of paleoclimate and paleoenvironmental evolution but also as favorable realms for the development of high-quality hydrocarbon source rocks. Although traditional views suggested that high salinity inhibits biological activity and is thus detrimental to source rock formation; recent hydrocarbon discoveries in formations such as the Leikoupo Formation (Sichuan Basin) and Majiagou Formation (Ordos Basin) in China have confirmed the exceptional hydrocarbon generation potential of source rocks in such settings. Focusing on major sedimentary basins in China, this review synthesizes how high-salinity settings critically control the integrated “generation-storage” sequence of hydrocarbon source rocks. Research indicates that moderate salinity can promote blooms of halophilic microorganisms, e.g., algae, cyanobacteria, resulting in high primary productivity. Concurrently, salinity-driven stable water stratification creates a strongly reducing bottom water environment, which greatly facilitates the preservation of organic matter, establishing a synergistic enrichment model of “high productivity—excellent preservation.” Products of high-salinity environments, such as evaporites, e.g., gypsum, halite, can act as catalysts, lowering the activation energy for hydrocarbon generation and enhancing hydrocarbon yield. Additionally, associated organic salts provide supplementary material for hydrocarbon generation. Regarding reservoir quality, the laminated structures formed in high-salinity settings, combined with organic–inorganic synergistic diagenesis, e.g., dolomitization, organic acid dissolution, and hydrocarbon-generation overpressure, collectively shape high-quality reservoirs with significant heterogeneity. Despite important progress, challenges remain, including the quantitative analysis of primary factors controlling organic matter enrichment, the threshold of salinity inhibiting biological communities, and the prediction of strongly heterogeneous reservoirs. Saline settings serve as critical carbon sinks in the geological carbon cycle through high primary productivity, enhanced preservation conditions, and distinctive mineral assemblages, playing a particularly important role in the formation of hydrocarbon source rocks and long-term carbon sequestration. Future research should integrate modern saline lake observations with high-resolution characterization techniques to deepen the understanding of the formation mechanisms of high-salinity source rocks, aiming to provide theoretical guidance and exploration targets for petroleum systems in similar geological settings worldwide. Full article

The organic-rich shales of the Upper Ordovician–Lower Silurian Renheqiao Formation in Yunnan, China, represent a valuable target for understanding marine hydrocarbon systems and offshore oil and gas exploration. To decipher its organic matter (OM) accumulation patterns and offer perspectives relevant to the assessment of marine resources, this study employs an integrated petroleum geological, sedimentological, and palynological approach. Our findings indicate that organic-rich intervals (cumulative thickness 74–84.5 m) are concentrated in the R1–lower R6 and upper R6–R9 graptolite biozones, exhibiting high total organic carbon (TOC) content and graptolite reflectance values indicative of high to post-maturity thermal evolution, which confirms significant shale gas potential. Sedimentary evolution shows broad similarities with the Yangtze region’s Longmaxi Formation but with finer-scale differences. Due to its restricted paleogeographic setting on the Sibumasu Block, the Baoshan region responded to global sea-level changes with a lag, favoring sustained OM accumulation. Palynological analysis identified microphytoplankton, acritarchs, macroalgae, and animal-derived OM. Hydrocarbon-generating assemblages are divided into three stages: the first (R1–lower R6) and third (upper R6–R9) stages are favorable intervals with high TOC, dominated by microphytoplankton and acritarchs; the second stage (middle R6) shows lower enrichment, with increased macroalgae/animal-derived debris. Our analysis indicates that high abundances of primary producers (microphytoplankton/acritarchs) are strongly associated with organic enrichment. In contrast, higher abundances of secondary consumers (e.g., graptolites) show a significant negative correlation with TOC, suggesting their presence may coincide with conditions less favorable for accumulation or that they actively inhibit it. Full article

The Sinian (Ediacaran) Dengying Formation in the northeastern Sichuan Basin exhibits a significant exploration potential. Nevertheless, the great burial depth of carbonates in the Dengying Formation and the scarcity of drilling data have imposed constraints on in-depth investigations into the evolution of lithofacies paleogeography as well as the primary controlling mechanisms. Through integrated analysis of field outcrops, core and well logging data, the evolution of the lithofacies and paleogeography of the Dengying Formation in the northeastern Sichuan Basin was reconstructed by using 3D stratigraphic forward modeling. The study area is predominantly characterized by platform margin facies and restricted platform facies, comprising four subfacies including microbial (algal) mound, grain shoal, intershoal sea, and intraplatform depression. The microbial (algal) mound and grain shoal subfacies are primarily developed along the western and eastern platform margins, exhibiting a near north–south trend. Scattered mound–shoal complexes and intershoal sea occur within the platform, with localized intraplatform depression zone. During the depositional stage of the Dengying Formation, three primary paleogeomorphic units were developed including the platform margin topographic high zone, intraplatform gentle slope zone, and intraplatform depression zone. During the Deng-1 and Deng-3 periods, sea level rise increased accommodation space, leading to a gradual decline in carbonate productivity and limited development of the mound–shoal complexes. In contrast, during the Deng-2 and Deng-4 periods, sea level decreased, water depth decreased, and carbonate productivity was enhanced, resulting in extensive development of the mound–shoal complexes. The simulation results indicate that carbonate-producing ecosystems thrive when wind blows from 270° W (80% frequency) or 15° N (60% frequency); with an effective water depth of 10–20 m, the elevated carbonate productivity is conducive to the growth of biogenic calcification. Comprehensive analysis suggests that paleogeomorphology, eustatic fluctuations, and paleowind fields collectively control the distribution and evolution of the lithofacies in the Dengying Formation in the northeastern Sichuan Basin. Paleogeomorphology governs the types and distribution of sedimentary facies belts as well as the spatial arrangement of lithofacies. Eustasy determines the magnitude of mound–shoals and their lateral migration. Three-dimensional stratigraphic forward modeling offers a novel approach for reconstructing paleogeographic evolution of carbonate platforms and analyzing key controlling factors, while also enhancing our ability to predict the distribution patterns of mound–shoal complexes. Full article

A breakthrough has been achieved in shale gas exploration of the Lower Carboniferous Shale in the Yaziluo Rift Trough, Dianqiangui Basin, with Well SY-1 yielding a daily gas production of 1.1 × 10⁴ m³. To clarify the main controls and evolutionary patterns of shale pore structure, shale samples from different sedimentary environments were analyzed using TOC content, X-ray diffraction (XRD), low-pressure gas adsorption (CO₂ and N₂), and field emission-scanning electron microscopy (FE-SEM). The results show that shale from the basin sedimentary environment (BSE) exhibits the highest TOC, is dominated by siliceous minerals (quartz + feldspar), and contains minor carbonate minerals (calcite + dolomite). Shale from the upper slope sedimentary environment (USSE) has the lowest TOC and is rich in carbonate minerals. The lower slope sedimentary environment (LSSE) shows intermediate compositions. From BSE to USSE, pore volume and specific surface area decrease, while fracture development increases. A quantitative model for volumes of organic pores, clay mineral-associated pores, and brittle mineral-associated pores was established. Organic pores dominate in BSE shale (65.42%), followed by clay mineral-associated and brittle mineral-associated pores, while inorganic pores dominate in USSE shale (63%). Pore structure in BSE and LSSE is primarily controlled by TOC content, with pore volume and surface area increasing with TOC content, while mesopore development is influenced by organic matter type and mineral compositions. In USSE, pore structure is mainly governed by inorganic minerals, with clay minerals promoting pore volume and surface area development, whereas brittle minerals facilitate the preservation of macropores. Evolutionary models of pore development were established for these distinct sedimentary environments. Full article

The stratigraphic evolution of low-latitude carbonate platforms, highly sensitive to sea-level changes, is often poorly constrained due to limited core data and discontinuous depositional records. This study elucidates the evolution of the Meiji Atoll, a representative low-latitude platform in the southern South China Sea (SCS), since the late Miocene, using the reef-penetrating core (Well NK1) from Nansha Island. By integrating facies analysis, sequence stratigraphy, and geochemical proxies, we identified two third-order sequences (SQ1 and SQ2), each comprising transgressive (TST) and highstand (HST) systems tracts. Geochemical data indicate that TSTs were associated with enhanced upwelling and nutrient availability, fostering algal productivity, while HSTs were marked by subaerial exposure. The overall retrogradational stacking pattern of the atoll reflects a dominant control by long-term sea-level rise, superimposed by eustatic fluctuations. Our findings confirm that eustatic sea-level variations were a primary factor controlling the stratigraphic architecture and development of Cenozoic low-latitude carbonate systems. Full article

The Marnoso-arenacea basin (MaB) of the Northern Apennines represents one of the most significant lower–middle Miocene foredeep turbidite systems in the Mediterranean region. While the northern part of the basin (Emilia-Romagna Region) has been extensively investigated, the Umbrian portion remains less understood, particularly concerning high-resolution stratigraphic and structural frameworks. This study integrates detailed field mapping, physical stratigraphy, biostratigraphic data from calcareous nannofossils, and petrographic analyses of arenites and calcarenites to reconstruct the tectono-stratigraphic evolution of the MaB in the Umbrian portion of the basin. The basin is divided into three main tectono-stratigraphic units: Afra-Mt. Verde, Pietralunga–Gubbio–Valtopina and Mt. Vicino. The middle unit is detailed by means of stratigraphic architecture and sedimentary characteristics, which allow us to identify two distinct sub-units. Several carbonate and hybrid turbidite beds, including the Contessa megabed, serve as regional key markers, enabling robust stratigraphic correlations. Two mass-transport complexes (MTDs) have been identified and dated, revealing close relationships between sedimentation patterns and thrust propagation. Modal petrographic data indicate a mixed provenance, from the Alpine and Apennine regions, changing over time in response to tectonic segmentation. These findings enhance our understanding of the internal organization of the MaB and provide new insights into the foredeep’s paleogeography and tectono-sedimentary evolution during the Langhian–Serravallian stages. Full article

Understanding the Holocene environmental history of desert landscapes in northern China contributes to elucidating the mechanisms driving desertification in the mid-latitudes of the Northern Hemisphere (NH). Based on a systematic and comparative analysis on integrated paleoclimatic data from both China and the international community, this paper reviews the environmental evolution history of the Alashan Plateau since the Holocene, drawing upon sedimentary and proxy records from three major sandy deserts on the plateau—the Badanjilin, Tenggeli, Wulanbuhe Deserts. The results indicate that the Alashan Plateau experienced generally humid conditions during the early and middle Holocene, characterized by the development of high-level lakes; in contrast, the late Holocene was marked by aridity and intensified aeolian activity. For the three deserts on the plateau, the environmental evolution of the Tenggeli Desert during the early Holocene diverges from that of the other two. Meanwhile, the mid-Holocene drought event in the Badanjilin Deserts remains debated, centering on whether its spatial scale was local or regional across the plateau. The driving mechanism of environmental evolution in the study area can be fundamentally understood through the atmospheric and oceanic circulation systems, combined with solar insolation in the middle latitudes of NH. This interplay is comprehensively reflected by the interactions between the westerlies and the East Asian summer monsoon (EASM) across different periods. Responses of the Alashan Plateau’s climate to global change involve the combined effects of multiple factors, including the Westerlies, the EASM, the Atlantic-Pacific-Ocean (APO) circulation anomalies, the ‘third polar’ environmental effect of the Qinghai–Tibet Plateau, and the hydrological influence of the Yellow River, etc. The Holocene environmental evolution history of the study area was primarily shaped by climate patterns characterized by cold-dry and cold–wet (or temperate-moist) regimes. Understanding these patterns may provide insights for forecasting future climate trends in the Alashan Plateau under current global warming. Full article

In arid and semi-arid regions, the hydro-sedimentary processes responsible for reservoir siltation remain insufficiently studied. This study focuses on the Taskourt Dam, one of the major reservoirs in the Marrakech-Safi region in central Morocco. A 450 cm thick sediment core was collected from the reservoir to assess the impact of extreme flood variability on sediment dynamic. A multi-approach analysis was conducted, including sequence analysis, grain-size and bulk and clay mineralogy of the sediments. In addition, hydrological parameters, instantaneous discharge, historical variations in daily water volumes in the reservoir, spillway discharge volumes, and siltation rates were determined through bathymetric surveys. The aim is to identify and evaluate the dynamics of sedimentation evolution within the reservoir. The results highlight two major phases in the siltation history of the Taskourt reservoir. (1) From 2011 to 2016, the siltation rate experienced rapid growth, marked by several major flood events. This intense sedimentary dynamic is illustrated by an accumulation of 418 cm of sediments. The floods of 2014 and 2016 strongly contributed to the intensification of flow energy and to a significant sediment load during this period. (2) From 2017 to 2023, the siltation significantly slowed down, associated with a prolonged drought period. This trend is recorded by a limited sedimentary deposit of 32 cm in thickness. This study provides valuable insights for the development of integrated sediment management strategies, supporting sustainable reservoir operation and effective planning, particularly in similar contexts worldwide. Full article

The Transylvanian Basin is an intra-Carpathian sedimentary unit displaying complex tectonic and sedimentary evolution that started in the Late Cretaceous. This study presents a geotechnical characterization of three Paleogene lithostratigraphic units located in the northwestern part of the basin, i.e., Brebi, Mera, and Moigrad. These formations record the transition from marine carbonate facies to brackish and subsequently fluvial environments, controlled by tectonic uplifts, marine regressions, and fluctuations in sediment supply. A total of 583 soil samples were collected through geotechnical boreholes and analyzed in the laboratory according to EN ISO standards, assessing natural moisture content, bulk density, grain size distribution, Atterberg limits, carbonate content, unconfined compressive strength, and shear strength parameters. Characteristic values of these properties were determined based on probabilistic distributions. The analyzed formations exhibit well-differentiated lithological and geotechnical characteristics, primarily governed by the degree of plasticity and the presence of calcium carbonate. The Brebi Formation predominantly consists of medium-plasticity clays with highly to very highly carbonate content, indicating a partially cemented microstructure. The Mera Formation is mainly composed of high-plasticity clays having a variable content of carbonates, with frequent sandy intercalations, resulting in significant variability in mechanical properties. The Moigrad Formation consists of two distinct lithological complexes: a clay-rich complex composed of variably plastic calcareous clays spanning all four plasticity classes and a sandy unit made up of weakly cohesive sediments with a granular structure and locally developed carbonate microcementation. Full article

High-resolution single-channel Sparker (1 kJ) profiles have been carried out to reconstruct the seismo-stratigraphic architecture of a sector of the Campania–Latium Tyrrhenian margin (Southern Tyrrhenian Sea, Italy). Seven seismic lines between the Volturno river mouth and the southern Latium margin were processed in IHS Kingdom^® software (4.0) at the University of Sannio (Benevento, Italy) and interpreted at the CNR-ISMAR (Naples, Italy) using seismic- and sequence-stratigraphic criteria. The Sparker dataset refines correlations with previously interpreted Chirp profiles and improves the imaging of fault patterns and key stratigraphic markers. Several seismo-stratigraphic units displaced by normal faults were recognized. Unit 1 represents the acoustic substratum of the high-resolution record, whereas Unit 2 corresponds to a thick relict prograding wedge that thickens toward the Volturno river mouth. A mounded lowstand unit is interpreted as deposits related to the Volturno river delta/fan system. Volcanic units, including the Villa Literno volcanic complex and local volcanic edifices, are locally identified. Overall, the results show that Sparker processing and interpretation provide robust constraints on the stratigraphic architecture and Late Quaternary tectono-sedimentary evolution of deltaic continental shelves. In particular, while previous Chirp studies have effectively constrained the stratigraphic architecture of the Late Quaternary depositional sequence and the geometry of the NYT reflector, this study provides new insights about deeper progradational seismo-stratigraphic units and related volcanic deposits and their tectono-stratigraphic setting. Full article

This study presents a new 1:10,000 geological map of the Monte Bove area (northern Apennines), produced through an original field survey, which allows a detailed reconstruction of Jurassic tectono-sedimentary evolution. The area is characterized by three wedge-shaped structural highs that emerged from the basin floor due to extensional tectonics, following the demise of the Early Jurassic carbonate platform. Stratigraphic and geometric relationships indicate that these highs were already established by the earliest Pliensbachian, bounded by steep fault escarpments and locally mantled by condensed pelagic deposits. Through the Jurassic, the fault-bounded blocks were progressively buried by predominantly micritic pelagic sediments, with evidence of onlap, unconformities, and reworking. The new geological map allows precise delineation of fault geometries and depositional contacts, highlighting the importance of synsedimentary tectonics in shaping basin architecture and documenting a consistent structural trend. Full article

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

Along-slope bottom currents and down-slope (gravity-driven) turbidity currents coexist in the ocean and interact during their flow processes. The interaction between turbidity currents and bottom currents plays a crucial role in determining the lateral stacking of sediments and the direction of channel migration. Currently, there is ongoing debate regarding the migration direction, with two primary contrasting views: upstream migration versus downstream migration relative to the bottom current. However, due to the challenges in directly observing unidirectionally migrating channels in nature, the sedimentary hydrodynamics and underlying flow mechanisms remain poorly understood. In this study, we employ numerical simulations to systematically analyze the internal flow characteristics and depositional patterns within channels subjected to varying degrees of confinement. Our results demonstrate that variations in channel confinement influence the intensity of the interaction and the nature of the secondary flow, ultimately determining the spatial distribution of sediments. As confinement decreases, the migration pattern of a channel changes from negligible migration to migration in the downstream direction of the bottom current. Subsequently, it changes to migration in the upstream direction of the bottom current. This research provides a novel theoretical perspective for understanding the diametrically opposite migration directions of unidirectionally migrating channels and insights into the turbidity–bottom current interaction processes and the evolutionary mechanisms of deep-sea depositional geomorphology. Full article