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A synthesis of field geological and archaeological surveying, as well as near-surface stratigraphy, provides new insights into the late Quaternary history of this region. We find a long series of alluvial, colluvial, playa, and aeolian deposits that show a complicated history of changes in the late Quaternary climate and environment. In the current study, we summarize the results of a geoarchaeological study that focused on the entire range of landscapes and associated landforms along the fringe of the Libyan Plateau at Umm Dabadib, Kharga Oasis, in the Western Desert of Egypt. We also determined the distribution of the cultural materials of prehistoric sites in different geomorphic settings, including playas, wadis, and dune fields. [ABSTRACT FROM AUTHOR]

The Zeit sand reservoir is one of the most prolific formations at Northwestern side of the Gulf of Suez. In this research we will try to coordinate between electrical, petrophysical properties, dep-ositional environment and facies discrimination in order to evaluate the hydrocarbon potentiality of studied Zeit Formation. The statistical parameters for potassium (K), thorium (Th) and Th/U ratio contents have a general increase towards northwestern parts, whereas uranium (U) content has a general increase towards southeastern parts. The sandstone facies is distinguished from the other facies by its thorium content >4 ppm. U has high carbonate content (U ≽ 1 ppm). Rocks' electrical properties vary greatly depending on a number of factors. Electrical measurements were taken at frequencies range of (5 × 10−4 Hz–100 kHz) for fully saturated samples (clayey sandstone) with NaCl (20 gm/L). As salinity, clay content, and frequency increase, consequently does the electrical properties. The continental condition are present in northwestern part (back-sea) which is distinguished by high K percent, high Th, high Th/U ratio, and low U contents. Low K, Th, and Th/U ratio contents, with high U contents, characterize the marine depositional environment that existed around the east and southeastern parts (fore-sea coincide with the dipping of strata). Furthermore, the studied Zeit Formation has good petrophysi-cal properties that coincide with marine conditions. The middle and eastern parts (around ISS-94 and CSS-288) is a good reservoir (porosity 36%–39%, shale content <15%, hydrocarbon saturation 71%–92%, and net pay thickness 17–63 feet). [ABSTRACT FROM AUTHOR]

The Fraser River Delta (FRD) is a large sedimentary system and home to Metro Vancouver, situated within the unceded territories of several First Nations. This review provides an overview of the geological evolution of the FRD, connecting hydrodynamic processes with sedimentary deposits across its diverse environments, from the river to the delta slope. The study emphasizes the implications of sedimentation and delta evolution for natural hazards and coastal/delta management, pinpointing knowledge gaps. Comprising four main zones—river, delta plain, tidal flats, and delta slope—the FRD is subject to several natural hazards, including subsidence, flooding, earthquakes, liquefaction, and tsunamis. The delta plain, bordering the Fraser River's distributary channels, hosts tidal marshes and flats, including both active and abandoned areas. Active tidal flats like Roberts Bank and Sturgeon Bank receive sediment directly from the Fraser River, while abandoned tidal flats, like those at Boundary Bay and Mud Bay, no longer receive sediment. The tidal flats transition into the delta slope, characterized by sand in the south and mud in the north of the Main Channel. The FRD's susceptibility to hazards necessitates protective measures, with approximately 250 km of dykes shielding the delta plain from river floods and storm surges. Subsidence amplifies the impact of rising sea levels. Earthquakes in the region can induce tsunamis, submarine slope failures, and liquefaction of delta sediments, emphasizing the importance of incorporating sedimentation patterns and delta evolution into management strategies for sustainable urban development, habitat restoration, and coastal defence initiatives. [ABSTRACT FROM AUTHOR]

As sand moves across Earth's landscapes, the shapes of individual grains evolve, and microscopic textures accumulate on their surfaces. Because transport processes vary between environments, the shape and suite of microtextures etched on sand grains provide insights into their transport histories. For example, previous efforts to link microtextures to transport environments have demonstrated that they can provide important information about the depositional environments of rocks with few other indicators. However, such analyses rely on 1) subjective human description of microtextures, which can yield biased, error-prone results; 2) nonstandard lists of microtextures; and 3) relatively large sample sizes (>20 grains) to obtain reliable results, the manual documentation of which is extremely labor intensive. These drawbacks have hindered broad adoption of the technique. We address these limitations by developing a deep neural network model, SandAI, that classifies scanning electron microscope images of modern sand grains by transport environment with high accuracy. The SandAI model was developed using images of sand grains from modern environments around the globe. Training data encompass the four most common terrestrial environments: fluvial, eolian, glacial, and beach. We validate the model on quartz grains from modern sites unknown to it, and Jurassic-Pliocene sandstones of known depositional environments. Next, the model is applied to two samples of the Cryogenian Bråvika Member (of contested origin), yielding insights into periglacial systems associated with Snowball Earth. Our results demonstrate the robustness and versatility of the model in quickly and automatically constraining the transport histories recorded in individual grains of quartz sand. [ABSTRACT FROM AUTHOR]

Burrowed discontinuity surfaces associated with condensed fossil concentrations demarcate breaks (hiatuses) in the Phanerozoic marine sedimentary record. Such intervals may be difficult to interpret in view of complex anatomy and varied fossil signatures. Transformation of a discontinuity surface into a heavily burrowed 'pseudobreccia' may further complicate the record, but this issue has remained unexploited to date. The richly fossiliferous Cretaceous–Paleogene (Maastrichtian–Danian) boundary interval exposed in Poland provides opportunities to test the influence of burrow-generated pseudobreccia on the preservation of associated hiatal fossil concentrations. Here, we document pseudobreccia anatomy and fossil-sediment relationships by three-dimensional X-ray computed tomography imaging. In the pseudobreccia zone, we identify a distinctive assemblage of late Maastrichtian fossils, which underwent subsurface preparation by burrowers in a hitherto unreported ichno-taphonomic process. Recognition of pseudobreccia is a prerequisite for the interpretation of the stratigraphy, sedimentology and fossil record of such intervals, which is of special interest for periods of major biotic turnovers, like the end-Cretaceous mass extinction. [ABSTRACT FROM AUTHOR]

Fluvial networks are characterised by spatial and temporal transitions as geomorphic and ecological processes within these systems are mediated longitudinally by sediment and water fluxes which vary spatially in magnitude and variability. The aim of this special issue was to shed light on the nature of source-to-sink fluvial transitions associated with spatial and temporal variability in geomorphic and hydrological processes. We encouraged contributions that considered fluvial transitions at any spatial or temporal scale, and invited research that addressed the implications of such transitions. The number of submissions was limited, which was potentially indicative of the lack of field-based studies being conducted at a catchment- or source-to-sink scale. Two of the published submissions considered longitudinal transitions in sediment sources using a sediment finger-printing approach, while the remaining two articles combined traditional fluvial sedimentology techniques with optically stimulated luminescence chronology to deduce controls on river reach flood dynamics. As we enter a time of unprecedented human impact on the environment, there is a clear need for future research to focus on the catchment as a holistic unit as the interconnectedness of landscape pattern and process has implications for biodiversity, water quality, ecosystem service provision and thus catchment management. [ABSTRACT FROM AUTHOR]

Zones of alluviation at tributary – trunk confluences can act as sediment storage/transfer switches. Evaluating the temporal variation in tributary – trunk connectivity is key to understanding the origin, dynamics and residence time of tributary alluvial fill sequences, and determining relative and interacting effects of different drivers of landscape development. This paper evaluates processes and timescales of tributary (Prins River) – trunk (Touws River) connectivity at a site in the Little Karoo, as context for discussing sediment dispersal dynamics and implications for interpreting the landscape response to environmental change. An alluvial terrace in the tributary valley preserves a chronology (optically stimulated luminescence) of tributary valley alluviation that is regionally synchronous with valley alluviation in the upper Huis River and floodplain alluviation in the lower Touws and Groot rivers. A climatic shift within the Little Karoo at ~1000 years BP from relative aridity to relative humidity (and higher-energy rain-bearing circulation types) may have initiated widespread re-working of alluvial fills and the breaching of geomorphological buffers. Alternatively, there may be an intrinsic limit to sediment preservation potential associated with a regional floodplain cycling time of one to two thousand years. Longer archives are needed to contextualize fluvial responses to climatic variability in the region. [ABSTRACT FROM AUTHOR]

River deltas are ecologically critical landscape components and are responsible as habitats for millions of people, wildlife, and plant communities. Deltas store vast quantities of eroded nutrient‐rich sediment and play a significant role in water quality management through nutrient cycling and storage. Many studies have been conducted in marine and tidal delta environments that characterize the sedimentology and geomorphic characteristics of these relatively young landscapes. However, little work has been completed in even younger inland reservoir deltas. This study characterized the sediments and geomorphology of the growing delta forming at the outlet of the Des Moines River into Red Rock Reservoir in south‐central Iowa and discussed the implications of the lower delta sediment and topographic characteristics in terms of sediment and nutrient storage, and the potential impact of the delta on other hydroecological factors. We found that the ca. 30‐year‐old lower delta is storing up to 60% of the contributing watershed's eroded sediment and total carbon, with total sediment depths of ca. 9 m across the 755‐ha area. Further, we identified two major geomorphic landscape positions within the lower delta that were categorized as distributary channels and delta plains. Sedimentological differences in these microscale landscape positions were identified. Sand content was greater at lowest distributary channel elevations and at the highest plain elevations whereas silt dominated the elevation range between these two extremes. The zone of silt accumulation corresponds to the range in elevation associated with normal lake level management. The silt‐dominated area is regularly inundated and covered with a variety of emergent vegetation and is the zone of critical importance for waterbird habitat and nutrient‐processing capacity. [ABSTRACT FROM AUTHOR]

The formation age of the middle Yellow River and the existence of a northward‐flowing river have been fiercely debated. The age distribution of detrital zircon varied spatiotemporally and produced contradictory provenance interpretations. The Jinshaan Gorge, the main part of the middle Yellow River and key to studying fluvial evolution and clarifying disputes, developed its topography during the late Cenozoic. In this study, we systematically review the Cenozoic tectonic evolution of the North China Craton, perform detrital zircon U–Pb dating in the Neogene−Quaternary sediments and investigate the topography along the Jinshaan Gorge, and the sedimentology and chronological framework of these sediments. We propose that the Gorge of the middle Yellow River could have developed since the Neogene, controlled by the tectono‐geomorphologic evolution of the North China Craton in a dominantly extensional environment. No evidence supports a northward‐flowing river during the Early Pleistocene or even earlier in the Jinshaan Gorge. We attribute the provenance variations of the Cenozoic sediments to detrital mixing of diverse geological units, local and distant, and especially highlight the systematic provenance shift between the Neogene and Quaternary sediments caused by bedrock downcutting and recycling aeolian sediments. The increased 1.5−0.33 Ga component of the lower Yellow River during the Early Pleistocene was likely caused by enhanced loess accumulation and should not be individually used as a proxy for the Yellow River formation. We emphasize the significance of a comprehensive study of river evolution. Plain Language Summary: Three‐quarters of the Yellow River channel is located on the North China Craton, but the formation and evolution of the Yellow River have been usually attributed to the upper reaches due to the growth of the Tibetan Plateau. Geological units, such as aeolian deposits have a significant impact on the fluvial sediments of the Yellow River, and only systematic work can help unraveling their provenance and potential recycling. We have found that the tectonic evolution of the North China Craton between the rigid Ordos Block and the Lvliang Shan controlled the initial entrenchment of the Jinshaan Gorge in the middle Yellow River since the late or maybe the early Miocene. We have also revealed the complex spatial provenance changes of the fluvial sediments along the Yellow River and the systematic provenance shift between the Neogene and Quaternary sediments. At the same time, we emphasize the significance of an integrated study combining tectono‐geomorphic features, sedimentology and quantitative analysis, such as provenance, for the reconstruction of the river geological evolution. Key Points: The middle Yellow River has developed under the extensional tectonic evolution of the North China Craton since the CenozoicSystematic provenance shift between the Neogene and Quaternary sediments was caused by bedrock downcutting and aeolian depositionDetrital signal from the Tibetan Plateau cannot be transported to and detected in the lower Yellow River [ABSTRACT FROM AUTHOR]

Manned submersible dives in the northwest South China Sea encountered substantial amounts of plastic litter accumulated at the base of scours along the floor of a submarine canyon, which may associate with the depositional behaviors of turbidity currents. In this study, we conduct numerical simulations using field‐scale bathymetry to investigate the relationship between the canyon floor morphology, flow processes, and the locations and sizes of the plastic litter piles. The consistent deposition pattern caused by the numerical turbidity currents with different input parameters indicate that morphology of the canyon may exert a dominant influence on turbidite deposition. This is attributed to a significant reduction in shear velocity as simulated turbidity currents flowing through the scours on the canyon floor. Spatial correspondence between deposits of turbidity currents and plastic litter accumulation suggests that suspended sediments and plastic may undergo simultaneous dynamic processes during the transportation of turbidity currents. Plain Language Summary: The issue of marine plastic litter has attracted wide attention, particularly in terms of its transportation mechanisms and locations of accumulation on the ocean floor. Turbidity currents are subaqueous sediment‐gravity flows that can transport large amounts of sediment, nutrients and pollutants into the deep sea, yet there is sparse research on the dynamics of plastic litter transport under the control of turbidity currents, and its accumulation in the deep sea. Here, we present a series of numerical simulations of turbidity currents in a submarine canyon with various input parameters, when combined with observational data on topography and plastic litter distribution, confirm that turbidity currents constitute a plausible mechanism for the transport of plastic litter and for its accumulation in response to changes in flow associated with scours. In addition, we find that the concavity of the scours is also necessary for plastic litter accumulation, since it induces significant fluctuations in the shear velocity and the corresponding depositional process. Key Points: Numerical simulations were applied to investigate turbidity currents as a cause for plastic litter accumulations in a submarine canyonThe simulated turbidite deposits and observed plastic litter accumulations exhibit a strong spatial correspondenceThe morphology of the canyon floor may exert dominant influence on the plastic litter accumulations in submarine canyons [ABSTRACT FROM AUTHOR]

Glaciers and ice sheets are an integral part of Earth's system, advancing and retreating in response to changes in climate. Clues about the past, present and future behaviour of these ice masses are found throughout current and former glaciated landscapes. In this commentary, we outline recent scientific advances from a collection of articles in which geomorphological evidence is used to inform us about the behaviour of glaciers and ice sheets across a range of spatial (landform to continent) and temporal (seasons to millennia) scales. Through a diversity of approaches including field measurements, remote sensing and numerical modelling, these studies build on an extensive background literature to deepen our understanding of how ice flows, how glaciers and ice sheets respond to climate change, and of the processes of ice advance and retreat and the stability of the system. Further integration of knowledge across the fields of geomorphology and glaciology will have tangible benefits for managing the societal and environmental impacts of glacier change and for improved projections of sea‐level rise over the coming decades to centuries. [ABSTRACT FROM AUTHOR]

For exploring the regional distribution of continental reservoirs characterized by deep burial depth, intense compaction, high diagenesis, and tight reservoir pore space, the seismic sedimentology was analyzed in the Lower Jurassic strata in the hinterland of the Junggar Basin utilizing the sequence stratigraphy and the instantaneous phase, root mean square amplitude and frequency decomposition attributes extracted from flattened seismic data volume. Three sequences are identified, including SQ1, SQ2 and SQ3. From SQ1 to the transgressive systems tract of SQ2, sequences are dominated by fluvial sedimentary, while the highstand systems tract of SQ2 to SQ3 were dominated by deltaic sedimentary. The seismic attribute analysis exhibits consistent results which channels are recognizable and reliable. They are single-channel configurations to oxbow lakes, crevasse splay, and other fluvial microfacies during their migration and evolution. Rivers evolves from low curvature and wide riverbeds to high curvature and narrow riverbeds, before settling into medium-curvature and wide riverbeds. Additionally, there is a gradual shift in flow direction from south-north to northeast-southwest. The results can provide reference and guidance for utilizing seismic data to identify meandering rivers. [ABSTRACT FROM AUTHOR]

This study presents the findings of a comprehensive geotechnical and seismic site investigation conducted at Otuasega Town located in Bayelsa State within the Niger Delta region of Nigeria. Subsurface exploration involved advancing 10 boreholes to 30 m depth using hollow stem auger drilling. Continuous disturbed and undisturbed soil sampling was performed at 1.5 m intervals for detailed geotechnical testing. Laboratory tests on the recovered soil samples established the index properties, classification, densities and consistency limits of the stratified deposits. The subsurface profile comprised alternating layers of clay, silt and sand typical of deltaic sediments, with the clay fractions exhibiting medium to high plasticity. Shear wave velocity (Vs) profiling using Multichannel Analysis of Surface Waves (WASW) techniques categorised the site predominantly as Site Class C and D based on international standards. The Standard Penetration Test (SPT) N-values ranged from 5 to 10, indicating soft normally consolidated clay conditions typical of the Niger Delta region. Predictive empirical models developed from the field and lab data showed strong correlations for estimating key geotechnical parameters such as SPT blow count, Vs and liquefaction resistance. Ground response analyses using the Vs and SPT data indicated significant site amplification potential, with peak ground accelerations up to 1.5 times the bedrock motion. Liquefaction analysis based on the empirical SPT-based methods revealed a high potential for liquefaction in the sandy layers, especially under strong earthquake shaking. The study characterized the complex sedimentology and provided baseline information for seismic microzonation and site-specific ground response analyses to advance understanding of geohazards in this delta environment. [ABSTRACT FROM AUTHOR]

Quito (Ecuador) has a history of mudflow events from ravines that pose significant risks to its urban areas. Located close to the Pichincha Volcanic Complex, on 31 January 2022, the northwest and central parts of the city were hit by a mudflow triggered by unusual rainfall in the upper part of the drainage, with 28 fatalities and several properties affected. This research focuses on the affected area from collector overflow to the end, considering sedimentological characteristics and behavior through various urban elements. This study integrates the analysis of videos, images, and sediment deposits to understand the dynamics and impacts of the mudflow using a multidisciplinary approach. The methodology includes verifying multimedia materials using free software alongside the Large-Scale Particle Image Velocimetry (LSPIV) to estimate the kinematic parameters of the mudflow. The affected area, reaching a maximum distance of 3.2 km from the overflow point, was divided into four zones for a detailed analysis, each characterized by its impact level and sediment distribution. Results indicate significant variations in mudflow behavior across different urban areas, influenced by topographical and anthropogenic factors. Multimedia analysis provided insights into the mudflow's velocity and evolution as it entered urban areas. The study also highlights the role of urban planning and infrastructure in modifying the mudflow's distribution, particularly in the Northern and Southern Axes of its path, compared with a similar 1975 event, seven times larger than this. It also contributes to understanding urban mudflow events in Quito, offering valuable insights for disaster risk management in similar contexts. [ABSTRACT FROM AUTHOR]

Energetic conditions during storms cause major geomorphological changes in coastal environments and drive taphonomic transformations of coastal archaeological sites. Facing the emerging realities of modern climate change and sea-level rise, archaeologists have justifiably focused on erosional processes and the loss of cultural heritage. However, sedimentologists have long recognized that storm-forcing also involves significant (re)depositional processes and the formation of supratidal features. Geoarchaeological research at partially inundated Native American shell mound sites in Tampa Bay, Florida, integrated topobathymetric aerial LiDAR with sub-surface testing to reconstruct complex site-formation histories. These histories include reworking of cultural deposits by contemporary, recent-historical, and ancient storms, forming archaeological tempestites—sediment deposits that have been scoured from and/or deposited within archaeological contexts by storm-forcing. Using sedimentological, zooarchaeological, and radiometric data, as well as post-storm observations, we present methods for recognizing storm-driven redeposition in coastal-estuarine archaeological contexts and demonstrate the potential of archaeo-tempestites for improving archaeological and paleoenvironmental interpretation. Storm-reworking of estuarine shell mounds on the Florida Gulf Coast produces diagnostic signatures in stratigraphy, granulometry, organic content, and mollusk-composition. Ephemeral ground surfaces and overwashed sand-sheets provide suitable loci for radiometric dating of past storm events (14C and OSL). We discuss inter- and intra-site variation among regional archaeo-tempestites to better understand late-Holocene ecosystem transfer and the long-term effects of shell-bearing sites on inshore-estuarine ecological conditions. We consider the absorption of energetic forcing as part of the life-history or use-life of shell-bearing features and suggest that a broader study of Indigenous coastal terraforming may aid modern coastal protection and management efforts. [ABSTRACT FROM AUTHOR]

This study focuses on a detailed facies analysis of the PļaviÅas Formation (Upper Devonian, Lower Frasnian) and the interpretation of their sedimentary environments. The study area is located in the northwestern part of the Main Devonian Field, including the territory of Latvia and the southeastern part of Estonia. Facies analyses primarily rely on geological section documentation, macro-scale sample studies, and various methods, such as X-ray diffraction, X-ray fluorescence, total organic carbon analysis, biomarker analysis, and carbon and oxygen stable isotope analysis. Shallow-water sedimentation occurs across all studied areas of the Baltic Devonian Basin. The basin territory exhibits multiple areas with diverse hydrodynamic activities, leading to fluctuations in environmental energy levels during the study period. Notably, the lagoonal to tidal flat environment is particularly related to the northeastern part of the study area, especially within the SÄlija and Atzele members of the PļaviÅas Formation.

Quito (Ecuador) has a history of mudflow events from ravines that pose significant risks to its urban areas. Located close to the Pichincha Volcanic Complex, on 31 January 2022, the northwest and central parts of the city were hit by a mudflow triggered by unusual rainfall in the upper part of the drainage, with 28 fatalities and several properties affected. This research focuses on the affected area from collector overflow to the end, considering sedimentological characteristics and behavior through various urban elements. This study integrates the analysis of videos, images, and sediment deposits to understand the dynamics and impacts of the mudflow using a multidisciplinary approach. The methodology includes verifying multimedia materials using free software alongside the Large-Scale Particle Image Velocimetry (LSPIV) to estimate the kinematic parameters of the mudflow. The affected area, reaching a maximum distance of 3.2 km from the overflow point, was divided into four zones for a detailed analysis, each characterized by its impact level and sediment distribution. Results indicate significant variations in mudflow behavior across different urban areas, influenced by topographical and anthropogenic factors. Multimedia analysis provided insights into the mudflow’s velocity and evolution as it entered urban areas. The study also highlights the role of urban planning and infrastructure in modifying the mudflow’s distribution, particularly in the Northern and Southern Axes of its path, compared with a similar 1975 event, seven times larger than this. It also contributes to understanding urban mudflow events in Quito, offering valuable insights for disaster risk management in similar contexts.

Dedication to the memory of a colleague, Doctor of Geological and Mineralogical Sciences Valentin P. Tverdokhlebov, a well-known specialist in sedimentology and palaeogeography of the Late Permian and Triassic of the Eastern Russian Plate and Southern Urals, as well as taphonomy of vertebrate localities. Valentin Petrovich is a long-time head of the geological survey party investigating the stratigraphy of continental red-coloured strata, tectonics and placement of minerals in the Orenburg region. He co-authored a number of geological maps of the region. He participated in field work as a member of the joint Soviet-Mongolian palaeontological expedition in the Gobi Desert.

To solve the problems in restoring sedimentary facies and predicting reservoirs in loose gas-bearing sediment, based on seismic sedimentologic analysis of the first 9-component S-wave 3D seismic dataset of China, a fourth-order isochronous stratigraphic framework was set up and then sedimentary facies and reservoirs in the Pleistocene Qigequan Formation in Taidong area of Qaidam Basin were studied by seismic geomorphology and seismic lithology. The study method and thought are as following. Firstly, techniques of phase rotation, frequency decomposition and fusion, and stratal slicing were applied to the 9-component S-wave seismic data to restore sedimentary facies of major marker beds based on sedimentary models reflected by satellite images. Then, techniques of seismic attribute extraction, principal component analysis, and random fitting were applied to calculate the reservoir thickness and physical parameters of a key sandbody, and the results are satisfactory and confirmed by blind testing wells. Study results reveal that the dominant sedimentary facies in the Qigequan Formation within the study area are delta front and shallow lake. The RGB fused slices indicate that there are two cycles with three sets of underwater distributary channel systems in one period. Among them, sandstones in the distributary channels of middle-low Qigequan Formation are thick and broad with superior physical properties, which are favorable reservoirs. The reservoir permeability is also affected by diagenesis. Distributary channel sandstone reservoirs extend further to the west of Sebei-1 gas field, which provides a basis to expand exploration to the western peripheral area.

River bedforms and their deposits—fluvial cross strata— respond to floods. However, it is unclear if all floods are equally represented in cross strata. Here, using a series of physical experiments in which bedforms were subjected to equivalent flood magnitudes over varying durations, we demonstrate the existence of a lower bound on flood durations that are represented in cross strata. We show that the scour depths and preserved set thickness are indistinguishable from baseflow conditions when the rising‐limb duration of floods is shorter than the baseflow‐equilibrated bedform turnover timescale—time required to displace the volume of a single bedform at baseflow conditions. In contrast, scour depth and preserved set thickness distributions deviate from baseflow conditions when flood rising‐limb duration exceeds the baseflow‐equilibrated bedform turnover timescale, causing preferential preservation of falling‐limb bedform dynamics. Our work provides a previously unrecognized quantitative bound on flood durations that are represented in fluvial cross strata. Plain Language Summary: Bedforms are routinely found on sandy riverbeds and their deposits, called fluvial cross strata, are the fundamental building blocks of river deposits. It has long been hypothesized that bedforms respond to floods by changing their shape and speed. In addition, fluvial cross strata are hypothesized to record past floods, thus, providing a key window into past hydrologic variability. However, it is unclear if floods of all durations are equally likely to be represented in bedform morphology and fluvial cross strata. Here, we investigate how floods of different durations are recorded in fluvial cross strata using four physical experiments of bedform evolution. We examine changes in bedform morphology (height, length, speed) and preservation with floods of equal magnitude but varying durations and compare the results with a control experiment with steady water and sediment discharge. Our results reveal a previously unrecognized lower limit on preserved flood duration in cross strata, corresponding to the time required to move a single bedform one wavelength (turnover timescale) in baseflow conditions. Only floods with durations longer than the turnover timescale led to identifiable changes in bedform morphology and fluvial cross strata. These findings advance our ability to better interpret geological records of past floods. Key Points: Experiments show that baseflow‐equilibrated bedform turnover timescale sets the lower bound on preserved flood duration in cross strataFloods with a duration less than this lower bound do not cause a detectable change in preserved set thickness and scour‐depth distributionFloods with duration longer than the lower bound cause scour‐depth deepening and preferential preservation of falling‐limb deposits [ABSTRACT FROM AUTHOR]

The White Hills Gravel is the coarsest fluvial gravel within Victoria, southeastern Australia, and outcrops discontinuously across a substantial part (>35 000 km2) of this region. It overlies a major regional unconformity representing >300 Ma, and is dominated by conglomerate (61% of beds), with less abundant sandy lithofacies (36% of beds) and rare mudstones (3% of beds). The sedimentary characteristics of the basal conglomerates (e.g. thick bedding, common boulders, very poor sorting and in places chaotic appearance) indicate deposition by significant paleofloods, including debris floods, within braided streams that had similar flow directions to the modern drainage. Paleohydraulic calculations estimate that the paleofloods had discharges exceeding >7200 m3 s−1, over 25 times the largest recorded floods in the same valleys. These paleofloods were probably caused by exceptionally severe storm systems, consisting of many individual thunderstorms. Deposition of the White Hills Gravel has previously been attributed to the mid-Cretaceous uplift that affected southeastern Australia, but the maximum possible age of the formation (early Paleocene) is too young for this to be a viable explanation. Instead, the White Hills Gravel may have been deposited during a period of increased precipitation at the Paleocene–Eocene Thermal Maximum (ca 56 Ma), when an intensification of the hydrological system generated significant sediment responses within fluvial systems around the world. Modelling indicates that this climatic event had a substantial impact in Victoria, where increases in mean annual precipitation (50–60%) and the most extreme rainfall rates achieved by the strongest storms (60–70%) were some of the largest globally, and frequent and intense Atmospheric Rivers were an important part of the hydrological system. These factors, together with a period of disturbed vegetation cover, resulted in major paleofloods that could have deposited the coarse-grained conglomerates of the White Hills Gravel. KEY POINTS: The White Hills Gravel in central Victoria is dominated by conglomerate (∼61% of beds), with lesser sandstone (∼36% of beds) and rare mudstone (∼3% of beds). In valleys across the central Victorian Highlands, White Hills Gravel outcrops are characteristically elevated above the Calivil Formation, and in the Campaspe and Loddon valleys, the long profiles of both formations cross over downstream. There is no evidence of a tectonic origin for the formation; instead, the White Hills Gravel was most likely deposited in response to a sharp rise in precipitation. The very-coarse-grained base of the formation was deposited by major thunderstorm-generated paleofloods with discharges up to and exceeding 7200 m3 s−1 in small catchments. The White Hills Gravel may denote a significant fluvial response to climate modification across the Paleocene–Eocene Thermal Maximum. [ABSTRACT FROM AUTHOR]

Channel deposits from meandering rivers have proven to be far more complex than the well‐known lithofacies model consisting of coarse‐grained channel, gravelly channel‐lag and fine‐grained overbank deposits. Sharp bends in rivers are subject to different hydraulic processes than bends with lower curvatures, enabling erosion of inner banks and deposition of fine‐grained sediments in the outer bend, resulting in downstream migration of river bends. This phenomenon is known as counterpoint deposition, forming counterpoint bars. This research investigates whether scroll bars associated with a sharp bend in the Lower Rhine River, The Netherlands, are such a counterpoint‐bar deposit. A counterpoint bar is expected based on: (i) the surface morphology of the scroll bar; (ii) the confinement of the river course by an ice‐pushed ridge resulting in a sharp bend; and (iii) the archaeological context of successive Roman settlements atop the ice‐pushed ridge, potentially moving downstream with the migrating river bend. This hypothesis is tested through detailed borehole descriptions combined with optically stimulated luminescence dating, the latter being a novel approach to identifying counterpoint deposits. The deposits consist of clays and sandy clays with fine sand laminations, and sporadic larger sand bodies. Further upstream these deposits grade into channel deposits dominated by coarser sands with gravels. These lithologies are explained using earlier proposed mechanisms for counterpoint formation; substrata match those described in previously studied counterpoint deposits and their point bar counterparts. Optically stimulated luminescence dates indicate that the Lower Rhine River bend migrated downstream, confirming counterpoint deposition. A migration rate of 1.93 m/year was established through weighted linear regression. This study demonstrates the potential of optically stimulated luminescence dating to investigate counterpoint bar presence. The identified counterpoint bars and associated bend migration provide insight into meandering river dynamics that is crucial for river management and in aiding river restoration and rewilding initiatives. [ABSTRACT FROM AUTHOR]

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This paper presents the results of a detailed study of a deformed sequence of Late Devensian glacifluvial sands, gravels and diamictons exposed within river cliff sections cut by the Allt (river) Cuaich, northeast of Dalwhinnie in the Grampian Highlands of Scotland. Macroscale sedimentological and structural field observations are combined with micromorphological and microstructural analysis to investigate the ice-marginal processes which led to the deposition and subsequent deformation of these glacifluvial to glacilacustrine deposits. Sedimentological evidence indicates that water-lain deposits in the area are capped by till and record the eastward progradation of ice-proximal fans into water ponded by an ice margin that advanced up valley from the west/southwest. These glacifluvial/ice-marginal fan sequences were deformed and subsequently overridden by ice that advanced (at least 6 km) into the Cuaich catchment. A suite of similar, but undeformed ice-marginal fans and laminated glacilacustrine deposits were laid down during the subsequent withdrawal of ice down-valley. Microstructures present within the variably glacitectonised (folded, faulted) laminated sands, silts and clays reveal a complex history of local glacial readjustments in a dynamic ice-marginal aqueous setting. Brittle–ductile shearing, liquefaction and remobilisation, and extensional brittle faulting accompanied the deposition of an overlying till. A detailed model of brittle–ductile shearing and glacitectonite formation during the overriding of water-rich ice-marginal deposits involves initial proglacial thrusting and folding, followed by continued submarginal to subglacial brittle–ductile shearing and extensional faulting. The study supports growing evidence that in Scotland the British Ice Sheet underwent localised expansion towards the end of the main Late Devensian glaciation (Dimlington Stadial, 26–13 ka radiocarbon years BP). In addition, it clearly demonstrates that the complex polyphase deformation recorded by glacitectonised sequences may not simply be a product of intense subglacial deformation, but a result of progressive proglacial to submarginal deformation, followed by subglacial shear as the ice progressively overrides a preexisting sedimentary sequence. [ABSTRACT FROM AUTHOR]

A toxodontid (Notoungulata) specimen (CHN-UNLC-P-V-4) is the first fossil from the Paso de las Carretas Formation that crops out in the Río Quinto Basin (Neogene), to the east of San Luis city (Argentina). The geological study provides a new stratigraphic section and the position of sediments in the valley depocentre permits inferring an older age than that of the Río Quinto Formation, which implies an early Late Miocene age for the Paso de las Carretas Formation. This age agrees with the identified cf. Ocnerotherium intermedium (taxonomic determination supported by a phylogenetic analysis), as this species was recognised in the Chasicoan Stage/Age of San Luis Province. CHN-UNLC-P-V-4 includes a mandibular fragment with ventral extension, preserving m1–3, a symphysis fragment with incisors, and the partial upper tooth series. A body mass of ~ 1700 kg is estimated. The mandible is similar to that of Dinotoxodon and Gyrinodon, but teeth (mainly upper ones) approach CHN-UNLC-P-V-4 to O. intermedium. As the mandibular extension of this species was not established, but likely present and lower teeth have some differences, we maintain an open nomenclature for CHN-UNLC-P-V-4. The similar incisors to the holotype of ‘Neoadinotherium triangulatum’ supports the latter might belong to O. intermedium, as previously suggested. [ABSTRACT FROM AUTHOR]

The effect of microbial binding for the stabilization of steep carbonate slopes is well documented in Cenozoic examples but its significance and relationship with abiotic marine cements in Paleozoic reef systems and steep slopes is not clearly established. Here, samples from a Late Silurian (Ludlovian) reef complex are evaluated by using an integrated approach that involves petrographic and isotope analyses, cathodoluminescence microscopy, and environmental scanning electron microscopy. This study reveals the in situ production of mineral fabrics of microbial origins, including micrite, peloidal micrite with dendritic fabrics, meniscus, and bridge-like cements. This study stresses the leading role of microbes in the early lithification stages that led to the stabilization of Silurian steep carbonate slopes. These findings are further supported by the occurrence of fossilized microbes and extracellular polymeric substance. The micritic cements are the first step in the diagenetic paragenesis followed by abiotic fibrous and equant calcite cements whose stable isotope values are in concert with estimated values of calcite precipitated in equilibrium with Silurian seawater. Results from this project provide insights into the relationship between microbial binding and early abiotic marine cements in ancient reef systems and, further, provide evidence for a consortia of microbes that existed 440 Ma ago. [ABSTRACT FROM AUTHOR]

Lacustrine carbonates are a powerful archive of paleoenvironmental information but are susceptible to post‐depositional alteration. Microbial metabolisms can drive such alteration by changing carbonate saturation in situ, thereby driving dissolution or precipitation. The net impact these microbial processes have on the primary δ18O, δ13C, and Δ47 values of lacustrine carbonate is not fully known. We studied the evolution of microbial community structure and the porewater and sediment geochemistry in the upper ~30 cm of sediment from two shoreline sites at Green Lake, Fayetteville, NY over 2 years of seasonal sampling. We linked seasonal and depth‐based changes of porewater carbonate chemistry to microbial community composition, in situ carbon cycling (using δ13C values of carbonate, dissolved inorganic carbon (DIC), and organic matter), and dominant allochems and facies. We interpret that microbial processes are a dominant control on carbon cycling within the sediment, affecting porewater DIC, aqueous carbon chemistry, and carbonate carbon and clumped isotope geochemistry. Across all seasons and sites, microbial organic matter remineralization lowers the δ13C of the porewater DIC. Elevated carbonate saturation states in the sediment porewaters (Ω > 3) were attributed to microbes from groups capable of sulfate reduction, which were abundant in the sediment below 5 cm depth. The nearshore carbonate sediments at Green Lake are mainly composed of microbialite intraclasts/oncoids, charophytes, larger calcite crystals, and authigenic micrite—each with a different origin. Authigenic micrite is interpreted to have precipitated in situ from the supersaturated porewaters from microbial metabolism. The stable carbon isotope values (δ13Ccarb) and clumped isotope values (Δ47) of bulk carbonate sediments from the same depth horizons and site varied depending on both the sampling season and the specific location within a site, indicating localized (μm to mm) controls on carbon and clumped isotope values. Our results suggest that biological processes are a dominant control on carbon chemistry within the sedimentary subsurface of the shorelines of Green Lake, from actively forming microbialites to pore space organic matter remineralization and micrite authigenesis. A combination of biological activity, hydrologic balance, and allochem composition of the sediments set the stable carbon, oxygen, and clumped isotope signals preserved by the Green Lake carbonate sediments. [ABSTRACT FROM AUTHOR]

The Nonesuch Formation and related sedimentary units of the Oronto Group, southern Lake Superior region, midwestern United States, are commonly held to have been deposited in a lacustrine rift basin within interior continental Laurentia. Here, we present new sedimentologic and stratigraphic evidence that shows a marine influence on deposition. Tidally influenced shallow-marine sandstone and evaporitic, sandy and muddy tidal flat facies pass upward into fine-grained estuarine and sandy turbidite deposits, which are sharply overlain by mixed sandy and muddy tidal flat and floodplain deposits. These observations are evidence that the lower Oronto Group was deposited in an epeiric seaway, one of several such seaways that developed during the final amalgamation of Rodinia at a time of globally high sea level. Retrogradational-aggradational-pro-gradational-degradational stratal architecture records changes in the relative balance between generation of accommodation space and sedimentation rates, which we interpret to reflect the combined influence of Grenvillian Ottawan phase tectonic subsidence and thermal subsidence from earlier Midcontinent Rift magmatism. We use this revised stratigraphic framework to show that the geochemical proxies of the Nonesuch Formation are tied closely to sedimentary facies and reflect intrabasinal redox heterogeneity rather than global anoxia at the end-Mesoproterozoic. Further, our sedimentology shows that the microfossils recovered from the Nonesuch rocks are primarily associated with tidal flat facies. The combined influence of marine and local nonmarine conditions must be considered when invoking the Nonesuch Formation, or similar marine-influenced interior basin deposits, as global analogues. [ABSTRACT FROM AUTHOR]

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In the summer of 2021, Greece experienced significant forest fires and mega-fires across multiple regions, leading to human casualties and damage to the natural environment, infrastructure, livestock, and agriculture. The current study aims to assess the ecosystem condition in terms of the natural regeneration and soil conditions of an area burnt by a forest fire (2021), specifically in the Ancient Olympia region situated in West Peloponnese (Ilia Prefecture), Greece. A standardized field sampling methodology was applied to record natural regeneration at chosen sites where a forest fire had also previously occurred (in 2007), resulting in the natural re-growth of the Pinus halepensis forest. Furthermore, an analysis was conducted on the geochemical, mineralogical, and sedimentological properties of soils obtained from this location. The findings of the research demonstrate the decline in the established natural regeneration of the Pinus halepensis forest and the overall tree layer. Species characteristic of post-fire ecological succession were observed in the shrub and herb layers, displaying varying coverage. The examination of soil mineralogy, sedimentology, and geochemistry indicated that the soil characteristics in the area are conducive to either natural or artificial regeneration. Ultimately, recommendations for landscape rehabilitation strategies are provided to inform decision-making processes, considering future climate conditions. [ABSTRACT FROM AUTHOR]

Shallow marine shelf sedimentation is a hot and difficult topic in today's reservoir sedimentology research, and it is widely present in the world. The shallow marine shelf sedimentation is not only affected by complex hydrodynamic effects such as tides and waves, but also controlled by bottom tectonic features, forming a complex and varied sedimentation pattern. During the Middle Jurassic period, the northern part of West Siberian Basin was characterized by a shallow marine shelf sedimentary environment. In the central reion of this basin, a typical tectonic uplift zone developed, forming a tectonic background of "one uplift zone between two depressions". Simultaneously, the dominant influence of tides in the shallow marine shelf environment facilitated the formation of a typical shelf-type tidal delta sedimentation system in the Jurassic strata of the northern part of West Siberian Basin. This sedimentation constitutes a significant natural gas reservoir, and it is important to investigate the sedimentary evolution of shelf-type tidal deltas and to clarify the internal structure and distribution of sedimentary sand bodies and interlayers in shelf-type tidal deltas, which is the basis for the fine development of this type of reservoir. This paper takes the Jurassic strata in the Y region of northern part of West Siberian Basin as the research object, and conducts numerical simulation based on sedimentary dynamics for the shelf-type tidal delta sedimentation formed under the tectonic background of "one uplift zone between two depressions". In addition, tidal amplitude and initial water level were selected for different hydrodynamic factors to study the main controlling factors of shelf-type tidal delta sedimentation. The simulation results show that tidal amplitude is positively correlated with three-dimensional configuration characteristic parameters of the sedimentary sand bodies, and the development of tidal bars becomes more and more limited as the initial water level increases. This paper systematically investigates the sedimentary evolution of shelf-type tidal delta under the tectonic background of "one uplift zone between two depressions" by the sedimentary dynamics method, which deepens the understanding of the shelf-type tidal delta sedimentation process and provides a new thinking for the development of this sedimentary reservoir type (School of Geosciences China University of Petroleum (East China)). [ABSTRACT FROM AUTHOR]

Widespread sediment resuspension and transport processes on continental margins can modify deposits and influence the preservation of particulate organic carbon (POC) in marine sediments. However, it remains unclear how post‐depositional processes interact with physical mineral protection to affect the transport and fate of terrestrial POC along the river‐estuary‐shelf paths. Here, we synthesized literature data and newly obtained results from multiple analyses of sedimentology, mineralogy, and inorganic and organic geochemical tracers. Our goal was to quantitatively evaluate the impact of sediment reworking on the redistribution and further transformations of terrestrial POC at the Yangtze River‐ocean interface. Our results reveal that sediment resuspension resulting from physical forces along with mineral protection of phyllosilicates plays a crucial role in regulating the recycling and fate of terrestrial POC during its transport across the coastal ocean continuum. Physical processes lead to the resuspension of sequestered POC from suboxic/anoxic muddy sediments into the overlying water column. Concurrently, the interplay of energetic forcing and elevated oxygen levels has the potential to disrupt the organo‐mineral associations. The decrease in mineral‐carbon stabilization increases the likelihood that reactive POC inclusion/aggregation with minerals becomes accessible to surrounding microorganisms, making it susceptible to microbial/oxidative degradation. Consequently, mostly phyllosilicate‐protected 14C‐depleted POC (primarily soil‐derived) in <63 μm suspended sediment (>90% of the total mass) remains available for export and reburial in continental shelf sediments. The lateral transport of resuspended sediments from estuaries, previously underestimated, represents a potential contributor to the remobilized millennial‐aged POC components involved in active biogeochemical cycling on continental margins. Plain Language Summary: River‐dominated Ocean Margins (RiOMar) play a crucial role in the global biogeochemical cycling of organic carbon (OC) because they receive substantial riverine inputs of particulate matter and bound organic materials. Among the present‐day oceans, the largest repositories for OC burial are found in large river‐dominated estuaries and deltas. When disturbed, OC deposited in seafloor sediments can be converted to dissolved inorganic carbon—either releasing it as carbon dioxide into the atmosphere or sequestering it within marine sediments. This study found that sediment reworking and remobilization by physical forces within the Yangtze River Estuary contribute to the degradation and aging of particulate OC (POC). Such disturbed processes may reduce the potential for carbon storage in marine sediments. Repeated cycles of sediment setting and resuspension enhance the significance of residual aged terrestrial POC associated with phyllosilicate minerals. This alteration affects the distribution and quantity of fluvial POC before it reaches the coastal oceans. As estuaries are highly vulnerable to human pressures and widespread climate change, the resuspension of estuarine sediments is expected to be an essential factor influencing the long‐term preservation of OC in marine sediments. Key Points: Disruption of organo‐mineral associations by sediment reworking enhances the respiration and aging of terrestrial biosphere carbonDynamic resuspension/deposition loops in energetic estuaries modify the quality and quantity of riverine organic carbonRepeated cycles of particle deposition/resuspension within the estuary leave unreactive terrestrial carbon buried in the shelf depocenter [ABSTRACT FROM AUTHOR]

Low‐lying islands in tropical regions are vulnerable to near‐term sea‐level rise and hurricane‐induced flooding, with substantial human impact. These risks motivate researchers to elucidate the processes and timescales involved in the formation, growth and stabilization of coastlines through the study of Holocene shoreline dynamics. Little Ambergris Cay (Turks and Caicos Islands) is a low‐lying carbonate island that provides a case study in the nucleation and growth of such islands. This study investigates the sedimentology and radiocarbon chronology of the island's lithified sediments to develop a model for its history. The island's lithified rim encloses a tidal swamp populated by microbial mats and mangroves. Preliminary radiocarbon data supported a long‐standing inference that the island is Holocene in age. This study integrates petrographic, sedimentological and new radiocarbon data to quantify the age of the island and develop a model for its evolution. Results indicate that the ages of most lithified sediments on the island are <1000 cal yr bp, and the generation and lithification of carbonate sediment in this system supports coastline growth of at least 5 cm/year. The lithification of anthropogenic detritus was documented, consistent with other evidence that in recent centuries the lithified rim has grown by rates up to tens of centimetres per year. A unit of mid‐Holocene age was identified and correlated with a similar unit of early transgressive aeolianite described from San Salvador, The Bahamas. It is proposed that this antecedent feature played an important role in the nucleation and formation of the modern island. Results extend an established Bahamian stratigraphic framework to the south‐western extreme of the Lucayan archipelago, and highlight the dynamism of carbonate shorelines, which should inform forward‐looking mitigation strategies to increase coastal resiliency to sea‐level rise. These results inform interpretation of the palaeoenvironmental record of carbonate environments, underscoring their geologically rapid pace of lithification. [ABSTRACT FROM AUTHOR]

X-ray diffraction analyses (XRD) were performed on marine Palaeogene (Upper Eocene--Lower Oligocene) clay minerals from Central Germany (Schneidlingen 1/2018 research well). Geochemical and grain size analyses gave supporting information on eustatic controlled system tracts, transgressions, sediment supply and flow conditions during the time of sedimentation and served to structure the research well in the formations. Except for three transgressions, long-lasting steady flow conditions occurred in the forefield of the Central German Estuary ("Mitteldeutsches Ästuar" -- MdÄ). The clay mineral kaolinite could be identified as a delivery area indicator for the Central Saxon Hills ("Mittelsächsisches Hügelland"). The other studied clay minerals smectite, illite and chlorite indicate three cooling trends between or within the formations and the transition from a chemical to a physical weathering regime with the beginning of the Rupelsilt/-clay Subformation. Although there are hints for authigenic or early diagenetic influences, distinct changes within the clay mineral distribution describe prominent trends that correlate well with other insights from the sedimentation area. It has been shown be evidenced, that clay mineralogical studies of marine sediments from Central Germany can be used to determine source areas and climatic trends. [ABSTRACT FROM AUTHOR]

The sedimentary sequence of the Ninama Basin is associated with the latest phase of the continental Deccan volcanism of the Indian peninsula. It occurs as inter-, intratrappeans with a 39-m thick sequence comprising Sukhbhadar Formation and Ninama Limestone. The investigation aims to reconstruct its depositional setting based on the lithofacies and inorganic geochemistry to understand the influence of paleosalinity, paleoredox, paleodepth, provenance and paleoclimate on the sedimentation pattern. It is characterized by clastic and chemically formed rocks, including shale, mudstone, siltstone, sandstone and limestone. Facies analysis has revealed seven lithofacies, amongst which four are clastic facies, shale (SH), calcareous shale (CSH), silty mudstone (SM) and lithic greywacke (LGW), and three are carbonate facies, namely, grey-black limestone (GBL), cherty limestone (CL) and marlite (ML). Using geochemical analysis of major oxides and trace elements, ratios of Ca/(Ca+Fe), Sr/Ba, V/(V+Ni), V/Cr, Fe/(Ca+Mg), Ti/Al, Na/K, K/(Fe+Mg), CIA-K and MAP were determined and used to interpret and note the changes in the depositional system. The combined results of the lithofacies and geochemistry indicate that the deposition occurred in three phases. Phase 1 is characterized by high energy conditions in the shallow to moderate depth brackish-saline lake with oxic to dysoxic conditions; Phase 2 is characterized by anoxic deep fresh to the brackish water basin; and Phase 3 is characterized by semiarid conditions, saline, anoxic waters, high evaporation leading to shallowing of the lake, and low to moderate terrestrial input. This lacustrine basin in the paleotopographic low of the Deccan Volcanic Province is characterized by distinct lithology governed by various depositional parameters. A composite depositional model is constructed for the Ninama Basin, reflecting three phases of evolution that are dominantly controlled by the paleoenvironment. Research highlights: The present study focuses on lithofacies and inorganic geochemical analysis of Ninama paleolake sediments, Saurashtra intertrappeans, to interpret their paleosalinity, paleoredox, water depth, provenance, detrital influx, and paleoclimate. Phase 1 deposition was initiated in paleotopographic low of Deccan Traps, in an oxic–dysoxic, high-energy turbulent brackish water environment, in humid conditions. Phase 2 characterizes fine-grained clastic facies deposited in anoxic, fresh-brackish, deep lake waters in humid conditions. Phase 3 marks the shallowing, evident by carbonate facies with low-moderate terrestrial input deposited in saline and anoxic paleolake in semiarid conditions with high evaporation and low-moderate precipitation. The Deccan Traps have influenced the paleolake intertrappean sequence. [ABSTRACT FROM AUTHOR]

This study aims to address the problem of porosity preservation in the Mangahewa Formation of five main hydrocarbon fields covering onshore and offshore of the Taranaki Basin. An integrated reservoir characterization of the Middle to Late Eocene Mangahewa Formation is achieved through petrophysical evaluation, sedimentological and petrographical descriptions, and well log analysis methods. Petrophysical parameters (porosity and permeability) were acquired from the available core analysis and using mathematical equations to obtain other petrophysical matrices such as normalized porosity index (NPI) and reservoir quality index (RQI). Factors that affected Mangahewa reservoir were studied through thin-section microscopy and well-log analysis helped to measure the reservoir and hydrocarbon potentiality in the Mangahewa Formation. The Mangahewa Formation is dominated by sandstone and a range of marginal to shallow marine facies with varying hydraulic flow units (HFU). The Mangahewa Formation has a high positive correlation in porosity-permeability relationship and has a maximum of 4.67 μm RQI and 20.08 μm FZI (Well Kapuni-14) which reflect potential reservoir. The Mangahewa Formation observed from Wells Kapuni-14, Maui-A1G, McKee-16A, and Mokau-1 are dominated with 59.6%, 56.4%, 79.3%, and 68% of macro- and megapores, respectively. The presence of authigenic clay and calcite cement has greatly reduced the reservoir quality; however, primary and secondary pores are still observed within the Mangahewa sands. Moreover, well log analysis was carried out on four wells in Taranaki Basin, to run a qualitative and quantitative analysis of the Mangahewa reservoir. Eight potential reservoir zones were examined, revealing that the Mangahewa Formation has a very low shale volume of less than 6%, good effective porosity ranging between 11.0% and 13.3%, up to 36.2% of average water saturation and maximum of 69.8% average hydrocarbon saturation. In conclusion, from this comprehensive study, it can be deduced that the Mangahewa Formation possesses fair to good reservoir quality and hydrocarbon potentiality. [ABSTRACT FROM AUTHOR]

A multidisciplinary approach allowed the reconstruction of the shallow, highly complex Neogene lacustrine-type sedimentological interplay between the peri-Pannonian (sub)basin subsidence and its seafloor topography. The current study further discusses the mechanism of localized uplift and subsidence by analyzing depositional cycles of middle Miocene sediments drilled in a northwestern or shallower Toplica Basin depocenter (borehole BL4, depth up to 630 m; Central Serbia). Supported by recent constraints on a deeper basinal section of eastern and western subbasin depocenters, the composite study of the segmented Toplica Basin involved geological, sedimentological, mineralogical, inorganic, and organic geochemical analysis, as well as constraints on interchanging geodynamic drivers. The data were extracted from thirty-one selected samples from four sedimentary lithomembers: A, B, C, and D. The architecture of these deposits reflects an intricate pattern influenced by complex lake bottom and subsurface geology (dis)connecting the two depocenters. The investigated Neogene deposition, as a whole, was dominantly controlled by a lithospheric-scale extensional graben system (involving the Jastrebac core complex-type tectonic exhumation) developed on top of the underlying Serbo-Macedonian basement unit. The crustal extension allowed rapid material inflow from other exposed sequences of the juvenile basin, including the abutting surface exposures. During the initial stretching and basin subsidence stage, sediment inflow towards the eastern Toplica depocenter was hindered. The influx of surface-eroded material was interrupted by a natural "obstacle". In turn, such a configuration facilitated voluminous material transport into the western depocenter of the basin, thereby controlling the deposition of lithomembers A and B. After the deposition of lithomember B ceased, the "barrier", or likely intrabasinal structural high, contributed to a reversal of the former westward-directed transport. In that manner, the vertical movements of the structural high enabled material transfer typical for the eastern basin segment, consequently prompting a sedimentary development of the lithomembers C and D. In this context, mineralogical and geochemical differences between the sequences are used as tracers of depositional changes affected by tectonic events. Sequences of sand and gravel layers of upper lithomembers C and D pointed out that alluvial processes strongly influenced their depositional cycle. On the other hand, a more pronounced presence of sulfide minerals (pyrite concretions) in lithomembers A and B correlated with a calm and anoxic paleoenvironment. The elevated trend of mixed terrigenous and/or microbiologically reworked organic matter (higher carbon/nitrogen (C/N) ratio and terrigenous/aquatic (TAR) ratio, the lower sum of steroids/sum of hopanoids (S/H)) ratio, deposited under anoxic–dysoxic freshwater lacustrine conditions (higher pristane/phytane (Pr/Ph) ratio, absence of squalane (i -C 30) and β-carotane), is observed towards a shallower section of the borehole (lithomembers C and D). [ABSTRACT FROM AUTHOR]

To solve the problems in restoring sedimentary facies and predicting reservoirs in loose gas-bearing sediment, based on seismic sedimentologic analysis of the first 9-component S-wave 3D seismic dataset of China, a fourth-order isochronous stratigraphic framework was set up and then sedimentary facies and reservoirs in the Pleistocene Qigequan Formation in Taidong area of Qaidam Basin were studied by seismic geomorphology and seismic lithology. The study method and thought are as following. Firstly, techniques of phase rotation, frequency decomposition and fusion, and stratal slicing were applied to the 9-component S-wave seismic data to restore sedimentary facies of major marker beds based on sedimentary models reflected by satellite images. Then, techniques of seismic attribute extraction, principal component analysis, and random fitting were applied to calculate the reservoir thickness and physical parameters of a key sandbody, and the results are satisfactory and confirmed by blind testing wells. Study results reveal that the dominant sedimentary facies in the Qigequan Formation within the study area are delta front and shallow lake. The RGB fused slices indicate that there are two cycles with three sets of underwater distributary channel systems in one period. Among them, sandstones in the distributary channels of middle-low Qigequan Formation are thick and broad with superior physical properties, which are favorable reservoirs. The reservoir permeability is also affected by diagenesis. Distributary channel sandstone reservoirs extend further to the west of Sebei-1 gas field, which provides a basis to expand exploration to the western peripheral area. [ABSTRACT FROM AUTHOR]

The coupling relationship between shelf-edge deltas and deep-water fan sand bodies is a hot and cutting-edge field of international sedimentology and deep-water oil and gas exploration. Based on the newly acquired high-resolution 3D seismic, logging and core data of Pearl River Mouth Basin (PRMB), this paper dissected the shelf-edge delta to deep-water fan (SEDDF) depositional system in the Oligocene Zhuhai Formation of Paleogene in south subsag of Baiyun Sag, and revealed the complex coupling relationship from the continental shelf edge to deep-water fan sedimentation and its genetic mechanisms. The results show that during the deposition of the fourth to first members of the Zhuhai Formation, the scale of the SEDDF depositional system in the study area showed a pattern of first increasing and then decreasing, with deep-water fan developed in the third to first members and the largest plane distribution scale developed in the late stage of the second member. Based on the development of SEDDF depositional system along the source direction, three types of coupling relationships are divided, namely, deltas that are linked downdip to fans, deltas that lack downdip fans and fans that lack updip coeval deltas, with different depositional characteristics and genetic mechanisms. (1) Deltas that are linked downdip to fans: with the development of shelf-edge deltas in the shelf area and deep-water fans in the downdip slope area, and the strong source supply and relative sea level decline are the two key factors which control the development of this type of source-to-sink (S2S). The development of channels on the continental shelf edge is conducive to the formation of this type of S2S system even with weak source supply and high sea level. (2) Deltas that lack downdip fans: with the development of shelf edge deltas in shelf area, while deep water fans are not developed in the downdip slope area. The lack of "sources" and "channels", and fluid transformation are the three main reasons for the formation of this type of S2S system. (3) Fans that lack updip coeval deltas: with the development of deep-water fans in continental slope area and the absence of updip coeval shelf edge deltas, which is jointly controlled by the coupling of fluid transformation at the shelf edge and the "channels" in the continental slope area. [ABSTRACT FROM AUTHOR]

This paper contributes to an understanding of the tectono‐sedimentary evolution of the South Pyrenean foreland system by reviewing the chronostratigraphic framework of the basin infill in its eastern sector. Six sections are analysed and cross‐correlated to build a 6.5 km thick composite magnetostratigraphy that represents the complete record of the Cadí Nappe in the Ripoll Syncline. New and previous magnetostratigraphic sections are integrated with available biostratigraphy to provide a new age calibration of the sedimentary succession of the Cadí Nappe, encompassing from Palaeocene to Middle Lutetian age. The proposed correlation with the Geomagnetic Polarity Time Scale aims at best reconcile magnetostratigraphic data with the regional biochronology built on the marine Shallow Benthic Zonation (SBZ biozones), the continental mammalian biochronology (MP levels) and the newly collected charophyte data. A subsidence analysis was performed on the calibrated composite succession, resulting in two well‐defined intervals bounded by a hiatus. A Palaeocene to Early Eocene interval with low (11–21 cm/kyr) total subsidence rates, and an Early to Middle Eocene interval, characterised by high (70–75 cm/kyr) total subsidence rates. The detailed trends in both subsidence and sedimentation mark the development and evolution of the foreland depozones, from distal foreland depozones to foredeep and wedge‐top depozones, relative to the emplacement of the Pedraforca Nappe and Cadí Thrust Nappe. The most pronounced sedimentary shift in the Cadí Nappe occurred at 49 Ma, with the rapid drowning of the carbonate platforms and its transition into talus and deep basinal environments. Carbonate platforms collapsed and resedimented on the talus of the elongated trough, newly formed parallel to the orogenic front. This marked the onset of tectonic subsidence triggered by the submarine emplacement of the Lower Pedraforca Nappe. The emersion of the orogenic wedge drove the entry of siliciclastics, lagged by 1 Myr, into the Ripoll Trough. The foredeep filled rapidly (5.5 km thickness in less than 7 Myr) compared to other South Pyrenean regions, favoured by its semi‐enclosed palaeogeography. The emplacement of the Vallfogona Thrust as early as the Middle Lutetian (43 Ma) brought the Cadi Nappe into a wedge‐top setting. However, the Ripoll growth syncline continued acting as a temporary sink for alluvial sedimentation while a foredeep developed further south in the autochthonous Ebro Basin. The flexural response of the Iberian plate to the tectonic thickening of the Axial Zone counterbalanced for a period the local uplift of the Cadi Nappe, providing accommodation space for the top sediments filling the Ripoll Syncline. [ABSTRACT FROM AUTHOR]

Slopes adjacent to the Bahamian carbonate platform revealed a large variety of depositional processes. In this study, we present a synthesis summarizing 109,000 km2 of bathymetric and reflectivity data with ∼7,900 km of seismic lines and 311 m of sediment cores that were obtained over the last 50 years. These data are used to develop a conceptual model of sedimentation patterns on Quaternary carbonate slope systems and their interaction with the adjacent shallow‐water carbonate platforms. Our data highlight that during the Quaternary, factors controlling large‐scale sedimentation on Bahamian slopes have numerous similarities as they have higher sedimentation rates during interglacials. At a small scale, every slope has its own characteristics that are contemporary controlled by two main characteristics: (a) facies on the adjacent shallow‐water platform, and (b) the impact of shallow‐ and deep‐water currents. Large‐scale tectonics influence sediment deposition as it determines the position of the islands and impacts platform facies distribution. Plain Language Summary: The factors that allow sediment to be exported from carbonate platforms to the deep‐sea need discussion. To gain a better understanding of the processes involved, the sedimentary archives of the slopes connected to these carbonate platforms are consulted. The sediments encountered vary and range from grains finer than 20 μm to coarse sandy sediments, a few millimeters in size. To understand the different processes that export those different types of sediment, we analyze various slopes of the Bahamas, a well‐known pure carbonate platform system. We used both numerical data (bathymetry, reflectivity, seismic) and sediment samples from this area and compared those records for the different Bahamian slopes. We highlighted that every slope displays a different sediment record; for every slope transect the adjacent platform facies together with deep‐sea processes (currents) determine the sediment distribution. The processes that export and transport the sediments are of equal importance. Key Points: Main factors controlling Bahamian slope sedimentation are revisedNumerous data types acquired offshore were synthesizedOur data suggest a strong influence of platform fine‐grained concentration and currents on slope sedimentation models [ABSTRACT FROM AUTHOR]

Subaqueous paleoseismic studies used soft sediment deformation structures (SSDS) to discern the shaking strength of past earthquakes, as the deformation degree of SSDS related to Kelvin Helmholtz Instability evolves from disturbed lamination and folds to intraclast breccia with higher peak ground accelerations (PGA). We lack comparative studies of different sediment types with SSDS related to earthquakes from different seismogenic sources to comprehend how these factors modulate earthquake‐induced deformation. Here, we compile sediment records with seven earthquake‐triggered SSDS from 10 lakes with organic‐, carbonate‐, siliciclastic‐, and diatom‐rich sediment from three subduction zones and one collisional setting. We target basin sequences with slope angles <0.65° to reduce the influence of gravitational downslope stress. We find that even minimal increases in slope angle, maximal 1°, lead to higher deformation degrees and, for some earthquakes, SSDS are only present at >0.65°. Fine‐grained clastics enhance sediment susceptibility to deformation, whereas abundant diatoms reduce it, demonstrating the influence of composition. Deformation correlates best with PGA and the vicinity of the earthquakes, suggesting that high frequency shaking promotes deformation. In addition, deformation only occurs above a minimum magnitude dependent on sediment composition, and higher deformation degrees in our studied basin sedimentary sequences only above Mw 4.9 for all sediment types, suggesting that sufficient duration of shaking—magnitude correlates with duration—is essential for SSDS development. We advise taking multiple cores on gentle slopes to study SSDS—additional to basin cores—to resolve small magnitude local earthquakes and relative differences in frequency content of past events. Plain Language Summary: Earthquakes can deform sediment and store information on the shaking strength of past earthquakes within these structures. Therefore, studying deformation records can help society to understand the recurrence and magnitude of past earthquakes. To successfully apply this method, we need to understand exactly how seismic shaking interacts with the sediment on the lake floor. However, we lack studies investigating how sediment composition modulates deformation or which characteristics of an earthquake control deformation. To fill this knowledge gap, we compare the deformation records of 10 lakes with different sediment types caused by earthquakes with different shaking characteristics. Our data show that high concentrations of fine mineral grains within the sediment can ease earthquake‐triggered deformation, whereas abundant diatoms—a type of algae—makes sediment more resistant. Furthermore, we propose that mainly the high frequency component of seismic waves and sufficient duration of the earthquake are critical to deform sediment. We claim that deformations are a valuable addition to other sedimentological records of past earthquakes as they can resolve relative differences between the shaking characteristics of past earthquakes. Key Points: Sediment composition modulates sediment sensitivity to deformation as fine‐grained sediment increases and diatoms decrease sensitivityAside from strong seismic shaking, sufficient high frequency content and duration of seismic waves are a prerequisite for deformationFor paleoseismology, we advise taking multiple cores on gentle slopes to study deformations and in the flat basin to study event deposits [ABSTRACT FROM AUTHOR]

Estuary sedimentary sequences have been the focus of several papers in the last decades; however, the majority these papers were centered in mesotidal and macrotidal estuaries of the middle latitudes. This present paper studies, from a sedimentological point of view, the infilling of a microtidal, wave-dominated tropical estuary, where wide tidal flats, mangroves and sabkhas are developed. Somone Lagoon is a Senegalese protected environment, very rich from an ecological point of view and with a definitive touristic vocation. For this work, 14 piston cores were studied. Additionally, the grain size, calcium carbonate and organic matter contents of 61 sediment samples vertically distributed in these cores were analyzed. The distribution of facies and the vertical sequences of sediments show the influence of the tropical seasonal fluctuations of fluvial sediment supply and evaporation processes. A high degree of bioturbation and an elevated organic content can be interpreted as the result of a high capacity of retention of the organic material into the estuary influenced by the weak tidal currents typical of a microtidal regime. These processes, acting since the last Holocene invasion of sea level, caused an advanced state of infilling of this estuarine system where both flood tidal deltas and bay head deltas prograde above the fine facies of the central domain of the estuary. [ABSTRACT FROM AUTHOR]

The rapid retreat and fragmentation of Alpine glaciers is widely reported as humanity faces dramatic climate change in mountainous regions. This rapid change leads to changes in sedimentary processes, which are exposed in recently deglaciated regions. These Alpine glacier forefields offer a wide spectrum of settings through which the ancient sedimentary record can be interpreted. Glacial valley orientation, slope inclination and lithology, and plumbing of subglacial and englacial meltwater drainage all influence the immediate preservation potential of glacial sediments upon deposition. In this contribution, we explore the geomorphology and sedimentology of the Taschachferner (a valley glacier), presenting a new geological-geomorphological map. This small glacier drains an icefield in the Ötztal Alps, and its current ice margin lies at approximately 2550 m a.s.l. Thus far, the glacial sedimentology and its bedrock geology have not been subject to investigation. The bedrock geology is dominated by E-W striking units of paragneiss and amphibolite, and the latter exhibit a series of well-preserved striations together with meltwater-sculpted bedforms (p-forms). The lower region of the glacier can be divided into two parts: (i) a clean-ice part, on the northern valley side with a low, subdued profile and (ii) a debris-covered part at the southern valley side, covered with supraglacial debris. The valley margins are dominated by several generations of lateral moraines, the most prominent of which corresponds to the 1852 Little Ice Age Maximum. A well-developed “hanging sandur” is observed immediately in front of the ice margin. This consists of a series of sand and gravel bars cradled in the lee of an interpreted regional fault cross-cutting the bedrock. Sandur deposition is currently influenced and overprinted by dead ice, influencing the trajectory and location of river channels and gravel bars. This paper provides clear lessons regarding the distribution of ice-margin facies associations, which must be incorporated into models of glacier decay in the context of a rapidly warming climate.

The fine-grained Pennsylvanian Cane Creek Shale of the Paradox Formation, Paradox Basin, Utah exhibits relatively thin cyclic interbeds of contrasting lithologies including fine sandstone to siltstone, organic-rich carbonate and dolomitic mudstone, and evaporites. As such, it provides a unique opportunity to evaluate micro-facies and the fluid storage capacity potential of mixed fine-grained systems. Micro-facies descriptions were performed using core and petrographic analyses, including scanning electron microscopy with energy dispersive spectroscopy. The study leverages core-based porosity and permeability data, as well as previous core description. These data are used together to explore mineralogical depositional and diagenetic controls on porosity and permeability. Twelve micro-facies were described based on sedimentological textures, grain size, lithology, and mineralogy categorized into three groups: 1) sandstone to siltstone, 2) mudstone, and 3) evaporitic micro-facies. Sandstone to siltstone micro-facies exhibit variable porosity and permeability. Porosity connectivity is dependent on the degree of authigenic cementation and compaction that negatively impacts porosity. Mudstone micro-facies show less variability in porosity and permeability; and are characterized by carbonate content, organic-matter, and clay nanopores. The development of early carbonate grains maintains porosity in mudstone and dolomitic siltstone micro-facies. Evaporitic micro-facies represented by evaporitic sabkha-like conditions are characterized by pore-reducing anhydrite and halite cement. A diagenetic paragenetic sequence was developed to assess the timing and impact of mineralogy on reservoir quality. Early (eogenetic), Middle (mesogenetic), and Late (telogenetic) stages correspond with diagenetic stages and known tectonic basin events. Syndepositional dolomite and diagenetic illite/smectite authigenic cements are the main controls on reservoir quality and have opposing effects related to porosity and permeability by preserving early pore space or reducing porosity and permeability.

Paleoenvironmental and paleoecological aspects of the Río Loro Formation (Paleogene, northwestern Argentina) were analyzed. In the type locality, four main sedimentary facies were recognized. Facies 1 (coarse-grained to pebbly amalgamated sandstones) record sedimentation in braided channels. Facies 2 (structureless to faintly laminated mudstones) and Facies 3 (interbedded mudstones with sandstones) are ascribed to deposition in distal to proximal floodplain settings, respectively. Facies 4 (coarse to medium-grained sandstone) is interpreted as deposited in meandering channels. Insect trace fossils, ascribed to nesting structures, were recognised particularly in facies 1 and 4. The recognized facies were grouped in a main facies association which allows interpretating a deposition in a complex multi-channel fluvial system with relatively stable muddy floodplain areas. Within this system, seasonal humid to dryer conditions favored biota substrate colonization and soil-forming processes. Well-preserved mammalian and reptilian remains were recognized in sandy mudstone deposits of Facies 3, showing low weathering stages (mainly stages 1 and 2) and the absence of signs of abrasion. These aspects, along with the presence of some articulated remains and their integration with the paleoenvironmental framework, suggest that skeletal pieces suffered an early burial after partial disarticulation, possibly by splays during major floods. The inferred habits of some of the taxa recorded are consistent with proximity to freshwater sources, vegetated areas, and seasonality. This multidisciplinary approach contributes to the understanding of paleoenvironmental and paleontological attributes of the Río Loro Formation and represents a basis for future surveys on this unit and its remarkable fossil record.