Sediment Depositional Processes Research Articles

Research on the relationships between river erosion and sedimentation and energy loss in the Yangtze River Basin of China

River scour and siltation, inherently prolonged and multifaceted phenomena, profoundly impact the hydraulic conductivity and navigational safety of waterways, thereby rendering the precise forecasting of their fluctuations a paramount and unresolved challenge. This study embarks on a novel investigative trajectory by examining energy dissipation in rivers, specifically through the scrutiny of empirical hydrological records. Employing the principles of energy balance theory, this study elucidates the intricate connection between energy losses and sedimentation volumes in the upper reaches of the Yangtze River and at its confluence with the significant tributary, the Jialing River.Our findings diverge from conventional wisdom, revealing that standard metrics of energy loss, encompassing kinetic, potential, and total mechanical energies, along with momentum losses, inadequately characterize the complexity of sediment deposition processes. In contrast, we demonstrate that the loss of suspension power is a more indicative measure of sedimentation quantity. Through meticulous comparisons of various formulations for calculating suspension power, we identified a formula grounded in the concept of minimal available power dissipation in river systems that exhibits superior accuracy in correlating suspension power losses with sedimentation patterns in river sections. This formula's efficacy is further enhanced when considering aggregate suspension power dissipation under the influence of tributary inflows, enabling refined predictions of sedimentation variations along river segments. In conclusion, the insights derived from this meticulous research contribute significantly to the realm of river resource management and the pursuit of sustainable, high-quality aquatic ecosystem development.

Environmental Life Cycle Assessment of Innovative Ejectors Plant Technology for Sediment by-Pass in Harbours and Ports

Sedimentation is the natural process of sediment transportation and deposition in quiescent water conditions. Sedimentation can affect the functionality of ports, harbours and navigation channels by reducing water depth, making navigation difficult, if not impossible. Different solutions are available to guarantee infrastructure functionality against sedimentation, with maintenance dredging being the most widely adopted. Alternative technologies for dredging have been developed and tested to reduce the environmental concerns related to dredging operations. Among other solutions, applying a sediment by-pass system based on a jet pump emerged as one of the most promising. While the existing literature covers the techno-economic aspects of sediment by-pass systems, the environmental impacts must be better evaluated and assessed. This paper aims to resolve this gap by evaluating, through the ReCiPe2016 life cycle assessment (LCA) methodology, the environmental impact of an innovative sediment by-pass system called an “ejectors plant”. The LCA results are based on the demonstrator established in Cervia Harbour in Italy, which was extensively monitored for 15 months during its operation. This paper shows how energy consumption during the operation phase highly affects the considered midpoint and endpoint categories. For example, the GWP100 of the ejectors plant, considering the Italian electricity mix, equals 1.75 million tons of equivalent CO2 over 20 years, while under a low-carbon scenario, it is reduced to 0.17. In that case, material consumption in the construction phase becomes dominant, thus highlighting the importance of eco-innovation of ejectors plants to minimise oxidant formation. Finally, this paper compares the ejectors plant and traditional dredging through environmental LCA. The ejectors plant had a lower impact in all categories except for GWP-related categories. The sensitivity analysis showed how such a conclusion may be mitigated by considering different electricity mixes and maintenance dredging working cycles.

Multi-method luminescence dating of young aeolian dunes in the central Tibetan plateau

The environment of the Tibetan Plateau (TP) is extremely sensitive to global climate change, and the frequent aeolian activity on the central TP generates large amounts of dust with the result that the region has a major impact on regional and global environmental change. The extensive aeolian dunes on the central TP provide a direct and valuable archive of aeolian activity; however, the age and sediment deposition processes of these dunes are still poorly understood. Optically stimulated luminescence (OSL) dating, an effective method for dating aeolian sediments, has been used sparingly in the region. In this study, we applied quartz single-aliquot regenerative-dose (SAR) OSL, K-feldspar post-infrared infrared-stimulated luminescence (pIRIR), and single-grain K-feldspar pIRIR methods to determine the ages of two well-preserved sand dunes in the Lunpola (LD) and Tuotuohe (TTH) river basins in the central TP. Our results showed that the quartz OSL signal of the TTH dune was dim, while the LD dune quartz exhibited a higher OSL sensitivity than that of the TTH dune. The high recuperation observed could be attributed to the low signal-to-noise ratio of the OSL signals. The K-feldspar signal was bright and the pIR50IR170 signal could be used to date young dune samples in the central TP, whereas it could be affected by the residual dose, or incomplete bleaching in the TTH profile, resulting in age overestimation. The single-grain K-feldspar protocol had a good potential for dating the young TP dunes. Multi-method luminescence dating is recommended for the cross-checking of young dune samples with low OSL sensitivity in the TP. Our luminescence dating reveals that aeolian dunes in the central TP formed approximately 385 to 330 a and persisted to the present, possibly in response to climate change since the late stage of Little Ice Age (1400−1850 CE).

Structural changes and assembly mechanisms of microbial communities during rapid sedimentation of Yellow River sediments

Microbial communities are essential for the biogeochemical cycles in aquatic ecosystems. The effects of sediment depositional processes on the microbial community characteristics in the Yellow River have not been extensively studied at the in-situ macroscopic scale. Since the Yellow River diversion reservoir has the sedimentation pond, it can be used as a natural experimental area. This study investigated changes in microbial community structures, functions, and assembly mechanisms under sediment deposition by analysing 26 water and sediment samples. The results showed that during rapid sediment deposition, different community structures formed between the water body and the sediment (Analysis of similarities, P<0.01), and the variability between them increased with increasing water depth. Sediments are more closely associated with carbon, nitrogen, and sulfur cycling processes, while water is more closely associated with light reactions. Under changing sediment concentrations, the microbial community diversities, community compositions, and functions changed significantly. Actinobacteria and Cyanobacteria were the species responsible for the significant differences in the microbial communities in the water, with linear discriminant analysis scores of 4.478–4.724 and 4.427–5.007, respectively. Water temperature, NH4+-N, and electrical conductivity were the most critical factors that affected the microbial community structures. During the rapid deposition of sediments, microbial community assembly was dominated by stochastic process. This study may provide a reference for exploring the mechanism of microbial community changes in reservoirs under the dynamic hydrological conditions of the Yellow River.

Pattern Analysis of Periodic Sediment Elevation Data: A Decision Support Framework for Deposited Sediment Management in Coastal Environment

This research explores sediment deposition patterns in coastal areas by employing synthetic data representing wandering set and recurrent patterns, utilizing Fourier transformation and power-law analysis to characterize frequency content and scaling behavior. The study employs fundamental models to interpret observed patterns and investigates the relevance of Poincaré's theorem in understanding recurrent patterns. Leveraging Python-based computation systems and open-source satellite data, the findings reveal contrasting behaviors in power-law exponents between scenarios, with wandering set patterns exhibiting scale-free characteristics and recurrent patterns displaying structured frequency distributions. This holistic approach advances scientific knowledge on sediment dynamics, informing evidence-based decision-making for effective sediment management and coastal resilience planning. Through its methodology and insights, the research contributes to understanding sediment deposition processes, elucidating underlying mechanisms driving coastal sedimentation, and providing practical approaches for monitoring and studying sediment dynamics in coastal environments, ultimately enhancing strategies for coastal management and conservation.

Dynamic mechanism of check dams on evolution of river corridors based on UAV telemetry combined with numerical simulations

AbstractCheck dams are a critical soil and water conservation engineering measure in gullies that significantly influence erosion, transportation, and sediment accumulation. Check dams help reduce erosion in the upstream area, ignoring the off‐site erosion reduction capacity due to erosion dynamics, and it also alters the morphology of gullies. The morphology of the gully cross‐section from the head to the inlet of the gully is mainly “V” shaped, “V, U,” transitional shaped, “U” shaped and trapezoidal shaped. The construction of check dams can force the geomorphologic evolution of the sub‐watershed to accelerate the transition to “old age” and reduce the allocation of sediment initiation during field sub‐flooding, thus promoting sediment deposition processes. The percentage of downstream scour hours in watersheds where check dams were constructed was 0.65% and 0.80%, respectively, compared to 19.78% and 19.06% in watersheds where there are no check dams. The results reveal the role check dam constructions play in gully morphology evolution from a hydrodynamic perspective and fill the gaps in off‐site erosion reduction, providing theoretical support for assessing the role of check dams in soil and water conservation work.

Sediment connectivity as a key to understand geomorphic effects of the Storm Alex in two mountain catchments of the Mediterranean Alps (Italy)

The occurrence of extreme rainfall events over mountain catchments is likely to trigger mass failure processes on hillslopes and sediment transport within the channel network. Understanding the degree of linkage between the sediment sources and transfer pathways downstream is essential in those catchments where settlements are affected by hydro-geomorphic processes, in order to plan suitable interventions for risk mitigation. A recent storm (October 2020) named “Alex”, estimated to be an extratropical cyclone with a more than 100-year return period, hit the Mediterranean Alps at the border between Italy and France, triggering deadly landslides and flooding processes. This work focuses on two adjacent mountain catchments located in the Liguria region (Italy) which share the same outlet, where a small village was damaged by high-magnitude sediment transport and deposition processes during the storm. In order to analyze sediment dynamics at the catchment scale leading to severe damage to the urban settlements at the outlet, an integrated approach was used. Very high resolution (0.5 m) satellite imagery was employed to map the mass failure processes on the hillslopes with a visual interpretation. This dataset was then compared with a map of the Index of Connectivity created using the SedInConnect 2.3 software to characterize the pre-event structural connectivity in both catchments. The integration of these two datasets permitted understanding that debris slides evolving into debris flows downstream supplied most of the sediments to the channel network. These processes concentrated mainly in a specific catchment where hillslopes have the highest connectivity with the valley bottom. This outcome provided a clear evidence that inventory maps developed soon after an extreme event, coupled with sediment connectivity datasets, can provide relevant information for future land management and risk mitigation strategies. These can be exploited to prioritize structural interventions in specific areas, to reduce the connectivity or disconnect inhabited areas from the hydro-geomorphic systems and avoid future damage.

Numerical Analysis of Water–Sediment Flow Fields within the Intake Structure of Pumping Station under Different Hydraulic Conditions

The vortices, backflow, and siltation caused by sediment-laden flow are detrimental to the safe and efficient operation of pumping stations. To explore the effects of water–sediment two-phase flow on the velocity field, vorticity field, and sediment distribution within intake structures, field tests and numerical simulations were conducted in this study with consideration for the sediment concentration, flow rate, and start-up combination. We applied a non-contact laser scanner and ultrasonic Doppler velocimetry to obtain the field data and reverse modeling of the three-dimensional model of the intake structure under siltation. A multiphase flow model based on the Euler–Euler approach combined with the k-ε turbulence model was adopted for numerical simulation under 10 working conditions, and the reliability was verified with field data. The results indicate that sediment promotes the evolution of coaxial vortices into larger-scale spiral vortices along the water depth, and the process of sediment deposition is controlled by the range, intensity, and flow velocity of the backflow zone. Furthermore, the maximum volume fraction of the near-bottom sediment increased by 202.01% compared to the initial state. The increase in flow rate exacerbates the turbulence of the flow field. Although the increase in sediment concentration benefits the flow diffusion, it further promotes sediment deposition. This study provides a new idea for modeling complex surfaces and considers different operating conditions. It can serve as a scientific reference for the structural optimization and anti-siltation design of similar water-conservancy projects.

Estimating Sediment Yield at Sungai Pusu Watershed using Soil and Water Assessment Tool (SWAT) Model

Sediment yield is the net result of soil erosion and sediment deposition processes. In the watershed, sediment yields are dominantly determined by stream flow, drainage area, and channel size. Land-use activity conducted by human is one of the major contributions to the sediment yield in the watershed. The study area covered in this study is the Sungai Pusu which flows through International Islamic University Malaysia (IIUM). Significant amount of sediments is deposited in Sungai Pusu due to the improper land clearing activities that are taking place along the river’s main tributaries. As a result, the water quality of Sungai Pusu is rapidly deteriorating. Sediment yield estimation is crucial in order to design suitable measure to rehabilitate the river. The aim of this study is to estimate sediment yield at Sungai Pusu watershed using SWAT model. Remote sensing and Geographic Information System (GIS) were used to evaluate sedimentation over time in the Sungai Pusu watershed. The SWAT model was performed to simulate water balance, stream flow, and sediment yield. The annual sediment yield obtained by the model is 427-ton ha-1 year-1.

Westerly aridity in the western Tarim Basin driven by global cooling since the mid-Pleistocene transition

To explore the relationship between the global cooling, westerlies, and central Asian aridity, we report ∼1.1 Ma local sedimentary environment changes according to physical-chemical parameters from an 800-m core (KT11) from the Kashgar region in the western Tarim Basin, China. Grain size end-member (EM) modelling is employed to quantify the processes of sediment transport and deposition. Four end members with modal values of 272 μm, 144 μm, 45.6 μm and 12.7 μm were extracted and explained 97.9% of the variance in the grain size data, corresponding aeolian dynamics, river energies, delta development and pedogenesis/long-term suspension components transported by wind or water, respectively. Four dominant sedimentation types, including lacustrine facies, delta facies, fluvial facies, and aeolian dunes, were identified through lithology and grain size frequency curves. The 1.1 Ma sedimentary successions experienced delta deposits interbedded with fluvial and aeolian deposits and lacustrines (1.1–0.6 Ma), alternating fluvial and aeolian facies with the occurrence of deltas and lacustrines (0.6–0.15 Ma), and aeolian facies interbedded with deltas and fluvial facies (0.15 Ma-present). Stepwise drying sedimentary conditions and enhanced desertification indicated by increasing rubidium/strontium ratios and proportion of aeolian sands, and decreasing total organic carbon since the past 1.1 Ma, implied intensified westerlies, likely resulted from ice volume expansion and ongoing global cooling according to geological record comparison and simulations during the Last Glacial Maximum compared to preindustrial conditions, which may have controlled the expansion of the permanent deserts in inland Asia. These persistent drying trends and intensified westerly circulation in arid regions during glacial periods after the mid-Pleistocene Transition indicated by larger amplitudes of aeolian sand proportion than prior to 0.6 Ma are similar to those in the interior monsoonal Asia, where the larger-amplitude of median grain size indicated enhanced Asian winter monsoon intensity and drier glacials.

The interplay between siliciclastic and carbonate depositional systems: Maastrichtian to Danian basin‐floor sediments of the mid‐Norwegian Møre Basin

AbstractSource‐to‐sink sedimentary systems associated with volcanic rifted margins serve as important archives for basin development by recording lithospheric changes affecting the depositional systems. Distinguishing between sediment transport processes and their sediment source(s) can guide the interpretation of a basin's history, and thereby inform regional paleogeographic reconstructions. In this contribution, we integrate and utilize wireline geophysical logs, detailed petrographic observations from side‐wall cores, and seismic analysis to describe and decipher a Maastrichtian to Danian‐aged basin‐floor depositional system in the deep outer Møre Basin, mid‐Norwegian margin. Well 6302/6‐1 (Tulipan) is a spatially isolated borehole drilled in 2001 that penetrates Maastrichtian and younger strata. A succession of hitherto undescribed carbonates and sandstones in the outer Møre Basin was discovered. It is investigated for sediment transport, provenance, and depositional processes on the basin floor surrounded by structural highs and ridges. The strata from the lower parts form a basin‐floor apron consisting of redeposited carbonate sourced from a westerly sub‐aerial high. The apron transitions vertically from mixed siliciclastic and carbonate into a purely siliciclastic fan with intercalated sandstone and mudstone, providing a rare high‐resolution record of how depositional environments experience a complete shift in dominant processes. The development coincides with similar latest Cretaceous‐earliest Palaeocene sequences recorded south of this region (e.g., well 219/20‐1) and may have been influenced by regional uplift associated with the onset of magmatism in the Northeast Atlantic. This study improves our understanding of a late, pre‐breakup source‐to‐sink sedimentary system developed near the breakup axis of an infant ocean, and documents what is possibly the northernmost chalk deposit in the Chalk Group.

A Multifaceted Study of Wawa River, Esperanza, Agusan Del Sur, Philippines - Aquatic Macroinvertebrates, Water Quality, and Soil Particle Size Analysis

The diversity of macro-invertebrate species in specific aquatic habitats often assesses environmental stress caused by pollution. To find out interactions in various macro-invertebrates communities, different water quality parameters and soil particles of Wawa River, research was conducted on Wawa River, Esperanza Agusan del Sur. Samples of macro-invertebrates, water and soil were taken from three different river stations. A total of 13 taxa of various macro-invertebrates were identified from the area. Phylum Arthropoda constitutes 62% of the total population and 32% form Phylum Mollusca. There is a notable similarity in macroinvertebrate abundance across the three stations, but the maximum numbers were observed in downstream. Most of the water physicochemical parameters of Wawa River were within the normal range, suitable for the healthy growth of macro-invertebrates. Most of the three sampling stations have medium sand particles, indicating relatively stable sediment, suitable habitat availability, and ongoing sediment transport and deposition processes. Diversified populations of various macro-invertebrates confirm good ecological condition of the environment and water in the studied site especially ample concentration of DO in River. The documented data on macro-invertebrates in the studied site will provide a baseline for future research.

Dynamics of run‐off hydraulic characteristics during gully headcut erosion driven by head height

AbstractIn the granitic red soil hills region of South China, gully headcut erosion is considered one of the main processes in the development of gullies. However, the dynamics of run‐off hydraulic characteristics such as hydrodynamics and energy consumption during erosion have not been clarified. We investigated the effects of five headcut heights (25 to 125 cm) on hydrodynamic and energy consumption characteristics using field in situ water discharge scouring experiments. The results demonstrated that the flow velocity (V), Froude number (Fr), Reynolds number (Re), run‐off shear (τ) and run‐off power (ω) all indicate the upstream area (UA) &gt; gully bed (GB). Except for V and Fr, several other hydraulic parameters exhibited a trend of sandy soil layer &gt; red soil layer, and a fluctuating increase with increasing headcut height was observed in the GB. The jet velocity at the edge of the headcut (Vb), jet shear stress (τj), potential energy conversion (∆EP) and bottoming instantaneous kinetic energy (EKbottom) all increased exponentially with increasing headcut height by factors of 1.10 to 1.37, 1.16 to 2.00, 1.07 to 2.06 and 1.22 to 1.86, respectively. Except for ∆EP, all others performed a trend of sandy soil layer &gt; red soil layer. The energy consumption at the gully head (∆EH) and its contribution tended to significantly increase with increasing headcut height, and the ∆EH of sandy soil layer was 13.20% to 49.89% higher than that of red soil layer. When the headcut height was greater than 100 cm, the contribution of energy consumption exceeded 50%. In addition, the sediment deposition process throughout the system was significantly influenced by the hydraulic and jet characteristics, and energy consumption was positively correlated with soil loss. The study results contribute to a profound understanding of gully headcut erosion and its hydrodynamic mechanisms.

Using rare earth element tracers to investigate ridge slope erosion process in contour ridge system under extreme rainfall

Extreme rainfall is becoming more frequent and intense, which no doubt increases the risks and uncertainty of water erosion in widely-used contour ridge systems. Ridge slope erosion can increase the probability of contour failure occurrence and then induce contour ridge losing anti-erosion properties. However, there is little understanding of ridge slope erosive process controlled by contour ridge system responding to extreme rainfall. In this study, five rare earth elements were applied in different ridge segments and soil layers to monitor the successive development of ridge slope erosion process under extreme rainfall in contour ridge system. Simulated rainfall experiments at high rainfall intensity (100 mm h−1) lasting for 60 min were conducted in runoff plots with ridge tillage practices characterized by microtopography indices and ridge geometry indices. Results showed that three sub-processes were observed for ridge slope erosion, including inter-rill erosion, headward erosion, and rill erosion. Headward erosion mainly resulted from the break-point at ridge surface and sidewall collapse at ridge toe, and the pouring of ponding water in furrow greatly promoted rill development. Erosion rate was the largest during headward erosion process, and rill erosion contributed the most to eroded source. The dominated erosion process was transport-limited during inter-rill erosion process, and detachment-limited during headward and rill erosion processes. Sediment transport and deposition processes as well as their transformation occurred simultaneously after the development of headward erosion. Eroded sediment was mainly from the low part of ridge, which was transported by raindrop-impacted sheet flow or overflow. These findings provide better responding of agricultural tillage to global climate change and references for the development of physically-based erosion models.

Impact of land use/cover change (LUCC) on sediment connectivity in small watersheds based on a revised index algorithm

Soil erosion is an important cause of global land degradation and other ecological and environmental problems. Revealing the influence mechanism of land use/cover change (LUCC) on sediment yield can provide a scientific basis for efficient comprehensive and decision-making management of watersheds. As an important indicator of sediment yield and transport capacity, sediment connectivity has been widely studied in recent years. However, the existing index of sediment connectivity (IC) ignores the influence of upslope land use/cover on confluence and the corresponding changes in downslope sediment transport. Moreover, a formula describing the upslope and downslope components does not establish an effective correlation with existing soil erosion formulas. Therefore, the index is not closely related to the erosion process and does not reflect the physical process of sediment transport and sediment deposition. In addition, there have been few reports concerning the effect of LUCC on sediment connectivity inside (on-site impact) and outside (off-site impact) the changed patches. Consequently, by based on addition of the revised parameters of the effective confluence area (Ar) and the runoff velocity factor (v) of the sediment delivery distributed (SEDD) model, an improved sediment connectivity index (ICZQ) is proposed. The results indicate that ICZQ has a significant linear relationship with annual runoff depth or sediment yield modulus in small watersheds within 100 km2 in the Loess Plateau, except for feature years containing rainstorm events (daily rainfall exceeding 50 mm). Therefore, the runoff and sediment transport capacity of small watersheds can be characterized by ICZQ under the influence of LUCC and rainfall change. In 1982–2020, driven by LUCC with an enhancement in vegetation (forest and grass), the ICZQ decreased in 90% of the area and decreased by a significant or extremely significant level over 48% of the area. To better understand the effects of LUCC on sediment connectivity, we analyzed on-site and off-site impacts with rainfall remaining unchanged to control the variables. The contribution rates of the on-site and off-site impacts caused by LUCC on sediment connectivity in Lvergou were 61% and 39%, 48% and 52%, respectively, over two typical periods (1985–1990 and 2015–2020). Due to the large proportion that off-site impacts occupied in the sediment connectivity change, the impact of LUCC on sediment connectivity cannot be ignored, especially when the associated scale is relatively small. The present study provides a quantitative method for the optimization of land use/cover patterns, such as vegetation restoration in watersheds along with a reference for further revealing the impact mechanism of erosion and sediment yield in watersheds.

Synchronism of sediment erosion and deposition processes during high-turbidity events in a large shallow lake

High-turbidity events (HTEs) frequently occur in shallow lakes and can deeply influence lake ecosystems. However, the processes of sediment erosion and deposition are not fully understood. To investigate these processes, two investigative campaigns that integrate bed sediment measurements, sediment settling experiments, in-situ observations, or a hydrodynamics-sediment model were conducted to quantitatively study wind-induced HTEs in Lake Taihu, China. Cohesive sediments were massively entrained from the lakebed by wind waves when the wind speed exceeded its critical value of 7 m s−1, as estimated by water depth, triggering HTEs with turbidity waves of > 100 nephelometric turbidity units. The suspended sediment concentration was the net sediment flux of erosion (average: 5.9 mg m−2 s−1) and deposition (average: 5.5 mg m−2 s−1), which occurred synchronously for most of the HTEs and resulted in high temporal variation in suspended sediment concentration. This synchronism was determined by the critical erosional stress of lakebed sediments, which was spatially heterogeneous (0.017–0.055 N m−2) in a large lake. Equations for erosion and deposition processes were derived following the investigative campaigns and used to develop a cohesive sediment transport model for simulating HTEs in Lake Taihu. Simulations indicate that the synchronism of sediment erosion and deposition led to a near-lakebed turbid water layer during an HTE, which sustained the sediment lutocline in Lake Taihu. Further investigation should be conducted on the role of the near-lakebed turbid water layer during endogenous pollution in large eutrophic lakes.

The characteristics and origin of chlorite coats in the Oligocene gas sandstone reservoirs of the Upper Huagang Formation, Xihu Depression, East China Sea Shelf Basin

Clay coats are widespread in the Oligocene braided river channel sandstones in the Xihu Depression on the East China Sea Shelf Basin. High clay coat coverage in braided channel sandstones is typically associated with good reservoir quality. The morphology, origin and distribution of clay coats and their effect on reservoir quality in different braided channel facies are investigated by core description, core analysis and a series of petrographic techniques. The present clay coats consist of two parts, the inner and outer coats. The inner coats are mainly composed of illite and chlorite components. The inner illite coats are transformed from smectitic clay precursors, while the inner chlorite coats may originate from thermally driven recrystallization of Fe-rich clay precursors. The outer clay coats, composed of well-crystallized chlorite, are possibly the result of neoformation directly from Fe- and Mg-rich pore water. The distribution of inner clay coats is controlled by sediment transport and deposition processes. The inner illite coats that are better developed in terms of content and thickness typically form in low energy braided channels due to relatively less transport abrasion of the smectitic clay precursors. The inner chlorite coats are observed exclusively in high energy mud clast-rich braided channels. The abundance of mud clasts and Fe-rich clay precursors are likely derived from the intense erosion of adjacent overbank mudstones, which are enriched in flocculated fluvial Fe oxides and hydroxides. The high coverage outer chlorite coats tend to occur in high energy braided channels with well-developed primary pores, since they provide sufficient growth space for chlorite. High energy braided channels with relatively low ductile component content generally maintain better porosity and permeability, which facilitates the development of the outer chlorite coats, thereby preserving more pore space by inhibiting quartz cementation and promoting subsequent dissolution of unstable silicate minerals, further improving reservoir quality. The results of this study provide new insights into the prediction of chlorite-coated reservoir quality of gas fields in Xihu Depression while also being relevant to braided river sandstones having comparable depositional settings worldwide.

Numerical study on the influence of salt marsh plants on coastal wetland hydrodynamics and suspended sediment transport

Salt-marsh plants play important roles in the hydrodynamics and sediment transport and deposition processes in coastal regions. The Delft3D model was applied to quantify the influence of salt-marsh plants on the hydrodynamic characteristics and suspended sediment transport of a coastal wetland, and to reveal the contribution of plants in trapping sediment in the local area. Specifically, the spatial distributions of salt-marsh plants were acquired from remote sensing images and coupled with the Delft3D model. A comparison showed that the modeled results and observed data fit very well. The model results indicated that salt marsh plants had a negligible effect on tidal level, but they did significantly affect flow velocity and tidal flux, as indicated by the obvious slow-flow zones in vegetated belts. Phragmites australis attenuated the flow velocity more than Suaeda heteroptera. We also found that the suspended sediment concentration was lower in P. australis and S. heteroptera areas because the resistance created by vegetation prevented sediment from being resuspended and helped trap suspended sediment. Numerical experiments further confirmed that the suspended sediment flux was obviously different with and without vegetation. The interception of suspended sediment by salt marsh plants could reduce the suspended sediment by more than 60%.

Deglacial and Holocene sediment dynamics and provenances off Lancaster Sound: Implications for paleoenvironmental conditions in northern Baffin Bay

Since the last deglaciation, Baffin Bay between Greenland and Canada developed from an isolated marginal sea to a major Arctic-Atlantic throughflow closely linked to the North Atlantic circulation. While the initial steps of gateway openings through Lancaster Sound and Nares Strait to northern Baffin Bay are reasonably well documented, far less is known about related regional deglacial-to-Holocene changes in sediment sources and depositional processes due to a lack of continuous and well-dated paleoenvironmental records from northern Baffin Bay. Sedimentological, mineralogical, and radiogenic isotope data of the well-dated sediment core GeoB22336-4 from the mouth of Lancaster Sound provide new insights on the impacts of ice-sheet retreat and opening of the gateways to the Arctic Ocean on the depositional setting. Basal subglacial till deposits point to a grounded ice stream at the mouth of Lancaster Sound before ∼14.5 ka BP. Subsequent glaciomarine sedimentation is characterized by the input of ice-rafted detritus (IRD), bioturbation traces, and foraminifera shells. Decreasing sediment supply and input of IRD through time reflects a period of ice-sheet recession to predominantly land-terminating positions during the Early Holocene. Changes in radiogenic isotope signatures reveal the openings of Lancaster Sound between ∼10.4 and 9.9 ka BP and of Nares Strait between 8.5 and 8.2 ka BP, in alignment with earlier studies. The rapid mid-Holocene (up to ∼5.8 ka BP) deposition of fine-grained sediments is most likely caused by enhanced sea ice-rafted sediment input released under a strong West Greenland Current influence. Finally, a slight increase in IRD input during the last ∼2 ka BP is linked to the neoglacial re-advance of regional glaciers.

Residual rocky forms in the landscape of the Outer Carpathians (Silesian Beskid Mts, Poland) – geotourist and sedimentological case study

This study investigated residual landforms developed within of the flysch bedrock in the Outer Western Carpathians as sandstone-to-conglomeratic tors. The studied relic rocky forms are locally exposed on the valley slopes in the top and plateau parts of the Silesian Beskid Mts. The cognitive values of such relic landforms, especially in the context of their morphogenetic traits and shaping of their macro- and microrelief, are well known and described. In contrast to epigenetic processes, the sedimentological aspect of the origin of such siliciclastic rocky deposits is still subject to different approaches in terms of terminology and interpretation. Thus, the aim of this study is to describe the conditions of environmental settings and character of the sediment transport and deposition processes from gravity flows, and to present a depositional system model for such a variety of flysch deposits. This study also attempts to present geotourist and geoeducational attractiveness of the tors against the background of regional geodiversity, geoheritage, and geoprotection. The results yielded a synthetic morpho-litho-sedimentological and geotouristic specification of the rocky forms analysed. The residual rocky landforms are polygenic geomorphological elements developed as a consequence of multistage and different scale of morph-forming activity operating on the basis of litho-sedimentological and tectonic assumptions under the influence of denudation processes.