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In this article, we explore the submarine channel formation driven by the interaction of turbidity currents with an erodible bed. The theoretical analysis considers the three-dimensional continuity and momentum equations of the fluid phase, and the advection–diffusion and Exner equations of the solid phase. The governing equations are linearized by imposing periodic perturbations on the base flow. We study the response of both the base flow (profiles of velocity and suspended sediment concentration) and perturbations (growth rate and perturbation fields) to changes in key parameters related to the flow and sediment transport. The growth rate and the critical wavenumber are examined for a given quintet formed by the gravitational parameter, longitudinal bed slope, sediment concentration at the edge of the driving layer, Rouse number and erosion coefficient. The critical wavenumber reduces with an increase in gravitational parameter, longitudinal bed slope, sediment concentration at the edge of the driving layer and erosion coefficient, while it increases with the Rouse number. For the submarine channel formation, we identify the upper threshold values for the gravitational parameter, longitudinal bed slope, sediment concentration at the edge of the driving layer and erosion coefficient and the lower threshold value for the Rouse number. [ABSTRACT FROM AUTHOR]

In order to reduce the levitation energy consumption and increase the levitation air gap, a simulation study of the electrochemistry superconducting magnetic levitation system based on the H equation is proposed. Through finite element simulation, the magnetic field distribution, current distribution, force, and other characteristics of the magnetic suspension system in the superconducting gravimeter are obtained; the relationship between the force of the superconducting ball in the magnetic field and the height of the suspension body and the current of the suspension coil is analyzed; and the penetration rate, the magnetic gradient, penetration depth, and maximum magnetic induction intensity of the superconducting spherical surface of the single-coil electrochemistry superconducting magnetic levitation system are obtained by simulation calculation. Simulation results show that, at 1 s, we start to use 0.2 s, 0.4 s, 0.6 s, and 0.8 s time, respectively, to pass current into the floating coil until it reaches 4.4 A. The magnetic gradient of the electrochemistry superconducting magnetic levitation system using a single coil is too large to meet the requirements of gravity measurement, the penetration depth is much smaller than the thickness of the superconducting sphere, and the maximum magnetic field on the surface of the superconducting sphere is much smaller than the critical magnetic field value of the superconducting material, and no loss will occur. The critical magnetic field value of the superconducting sphere is much smaller than that of the superconducting sphere. The critical magnetic field value of the material will not quench, which verifies that the H equation can simulate the superconducting magnetic levitation system well and has a high simulation accuracy and efficiency. [ABSTRACT FROM AUTHOR]

In recent years, it has become a common understanding among researchers that one of the significant agents for forming a variety of submarine geomorphologies is turbidity currents that travel long distances, so-called long-runout turbidity currents. In this study, we present a mathematical model of the formation of cyclic steps due to long-runout turbidity currents based on the assumption that the highly concentrated layer near the bottom of the turbidity currents achieves an equilibrium state. The model uses the four governing equations: the momentum equation, the continuity equation, the diffusion/dispersion equation of suspended sediment, and the continuity equation of sediment on the bed (the Exner equation). We simplify the governing equations by ignoring the entrainment from ambient water since there is a distinct density interface above the highly concentrated lower layer of long-runout turbidity currents. We determine the dimensions of cyclic steps based on the solution. Agreement between the predictions and field observations turns out to be reasonable. [ABSTRACT FROM AUTHOR]

High‐resolution imagery of the morphological character of modern active turbidite systems are critical for understanding the complexity of turbidity current processes occurring on the seafloor. Here, we describe a 30 cm‐resolution autonomous underwater vehicle repeat bathymetric dataset that allows to significantly increase the geomorphological detail of crescentic bedforms in turbidite systems. This repeat imagery shows the erosion produced by dense basal layers at the base of turbidity currents, the inception of plunge pools, and the controls that hydraulic jump troughs have on subsequent flow path of weaker turbidity currents. Transverse small‐scale scours located in cyclic step troughs suggest that weak flows follow local relief, therefore explaining the wide variability of turbidity current flow indicators observed in outcrops. This imagery demonstrates that turbidite systems are formed by the superimposition of erosion surfaces and depositional patterns recording contrasted flow behavior and provides new views on turbidity current behavior in natural environments. Plain Language Summary: Turbidity currents transport large amounts of sediment, macro‐nutrients and carbon to the deep‐sea. During their passage, they generate a wide variety of bedforms from which these flows can be reconstructed. However, the lack of detailed and very high‐resolution imagery of these bedforms prevents detailed understanding of the 3D behavior of turbidity currents. In this paper, we describe a 30 cm‐resolution autonomous underwater vehicle repeat bathymetric dataset that allows to map very‐fine scale features of turbidity current bedforms. This repeat imagery reveals the erosion produced by the base of turbidity currents and shows the formation of new small‐scale scours linked to the currents. The data also reveals the effect of large turbidity currents on the subsequent path of smaller ones. This high‐resolution imagery allows to bridge the gap between observations on the modern seafloor and those observed in outcrops. Key Points: 30 cm resolution AUV repeat imagery (2019–2020) of active turbidity current bedformsDetailed imaging of seafloor erosion from basal parts of turbidity currents and of plunge pool inceptionTrough of bedforms believed to control subsequent flow path of weaker turbidity currents [ABSTRACT FROM AUTHOR]

Sediment, nutrients, organic carbon and pollutants are funnelled down submarine canyons from continental shelves by sediment-laden flows called turbidity currents, which dominate particulate transfer to the deep sea. Post-glacial sea-level rise disconnected more than three quarters of the >9000 submarine canyons worldwide from their former river or long-shore drift sediment inputs. Existing models therefore assume that land-detached submarine canyons are dormant in the present-day; however, monitoring has focused on land-attached canyons and this paradigm remains untested. Here we present the most detailed field measurements yet of turbidity currents within a land-detached submarine canyon, documenting a remarkably similar frequency (6 yr−1) and speed (up to 5–8 ms−1) to those in large land-attached submarine canyons. Major triggers such as storms or earthquakes are not required; instead, seasonal variations in cross-shelf sediment transport explain temporal-clustering of flows, and why the storm season is surprisingly absent of turbidity currents. As >1000 other canyons have a similar configuration, we propose that contemporary deep-sea particulate transport via such land-detached canyons may have been dramatically under-estimated. Powerful avalanches were recorded for the first time in an underwater canyon that lies 100 s of km from land. This challenges a long-held view and indicates > 1000 similar canyons worldwide actively pump sediment and pollutants into the deep-sea. [ABSTRACT FROM AUTHOR]

The late Eocene-early Oligocene paleoenviromental and paleoclimatic conditions in the southern Hellenic Thrace Basin (Lemnos Island, Northeast Aegean Sea) have been determined, based on planktonic and benthic foraminiferal analyses. One hundred thirty-nine mudstone samples were collected from representative outcrops that cover the entire stratigraphic record. The samples correspond to submarine fan (Ifestia, Panagia and Kaspaka sections) and shallow-marine deposits (Kaminia section). The analyses of calcareous nannoplankton and planktonic foraminifera indicate that sedimentation took place during the late Eocene to early Oligocene (Priabonian-Rupelian). The ratio of planktonic to benthic foraminifera, the paleobathymetry and the qualitative analysis of foraminifera support a regional shallowing-upward trend. The presence of Globobulimina suggests that dysoxic conditions prevailed the late Eocene, while the presence of paragloborotaliids, globigerinids and chiloguembelinids in the studied succession could be indicative of a gradual cooling event since the late Eocene. The Eocene/Oligocene boundary is characterized by well-oxygenated bottom waters, and the abundance of Catapsydrax unicavus and Paragloborotalia nana suggests a strong cooling event during the early Oligocene (O1 biozone). This decrease in water temperature is most likely linked to the global cold Oi1 event. The early Oligocene is characterized by oxic bottom-water redox conditions that were intermittently interrupted by shorter periods of dysoxic conditions. The occurrence of Bathysiphon indicates the passage of turbidity currents. The recognition of Chiloguembelina cubensis, P. nana and C. unicavus suggests high productivity over the range of the water column, most likely correlated with mixing water during the cold event Oi2. This study decrypted the global paleoenvironmental and paleoclimatic changes that influenced the southern Hellenic Thrace Basin during the Eocene/Oligocene transition. [ABSTRACT FROM AUTHOR]

Interplay of deep‐water sedimentary processes is responsible for building a myriad of features and deposits across mixed turbidite–contourite systems, from <5 cm beds to >200 km long sedimentary drifts. Investigations of the spatial and temporal variability of their sedimentary facies and facies associations is crucial to reveal the dynamics between along‐slope bottom currents and down‐slope turbidity currents, as well as their impact on drift construction and channel erosion. This study focuses on extensive modern mixed (turbidite–contourite) systems, developed across the continental rise of the Pacific margin of the Antarctic Peninsula. Nine sediment cores were sampled and analysed, through grain size and geochemical methods, to study the sedimentary facies at high‐resolution (ca 1 to 20 cm). Three main facies associations have been identified across distinct morphological features (i.e. mounded drifts and trunk channels), comprising intercalations of hemipelagites, bottom current reworked sands (which include fine to coarse‐grained contourites) and gravitational facies (turbidites and mass‐transport deposits). These facies associations reflect fluctuations of the background sedimentation, oscillations of the bottom‐current velocity and of the frequency of gravity‐driven currents. The sedimentary record features cyclic alternations during the Late Quaternary (>99 kyr), suggesting that variations between along‐slope bottom currents and down‐slope turbidity currents are strongly linked to glacial–interglacial cycles during Marine Isotope Stages 1 to 6. Sedimentary records affected by bottom currents on polar margins, such as those of the Antarctic Peninsula, are essential to decipher the facies and facies sequences of bottom‐current deposits, as the low degree of bioturbation throughout most of the sediments allows us to observe the original sedimentary structures, which are poorly preserved in similar deposits from other continental margins. [ABSTRACT FROM AUTHOR]

A series of constant-flux saline and turbidity current experiments were carried out, focusing on the coupling impact of bed roughness and permeability on current propagation, mixing, and turbulence characteristics. The distinct current propagation phases on RI (rough and impermeable) and RP (rough and permeable) beds are identified, respectively. Experimental results revealed that the intermittently undulating bed surface breaks the strict no-slip boundary, thus, increasing local current velocity near the bed, while its roughness reduces the current peak profile velocity. Interbed pores induced vertical fluid exchange, which synchronously decreases the current peak profile velocity and local velocity near the bed, causes the density profile to no longer follow a monotonous variation trend along with water depth. The larger bed surface roughness or the interbed porosity leads to the smaller upper TKE (turbulent kinetic energy) peak. The lower TKE peak is inversely proportional to the bed surface roughness of the RI beds, while it is proportional to the porosity of the RP bed. A rough bed surface intensifies the asymmetry of the mean velocity distribution around peak velocity resulting in a transfer barrier of turbulent momentum triggered by the interbed pores. On the RP bed, the cross-correlation function based on two-point statistics captures the spikes associated with pore-scale eddies locally, but under the RI condition, it only obtains the logical timescale characterizing the largest eddies of the current. The sediment deposition makes the turbidity current easier to separate from the RP and RI bed than the saline type, causing a consequence of growing the current height. [ABSTRACT FROM AUTHOR]

The suspension system of the EMS (Electro-Magnetic Suspension) medium-and-low-speed maglev train is affected by the eddy current effect when the train is in motion. This is a crucial problem related to the improvement of train operation speed. In this article, this phenomenon is analyzed and the method of suppressing the eddy current effect is put forward. Firstly, theoretical analysis and experimental verification are carried out. It is worth mentioning that the experimental data, which thoroughly show how the suspension current changes with the maglev train speed under the influence of the eddy current effect, are collected and published for the first time, which strongly confirms the accuracy of the theoretical analysis. Secondly, an improved scheme to suppress the influence of the eddy current effect is proposed from the perspective of the rail structure for the first time and simulation results verify the effectiveness of the improved scheme. This research makes important progress on the improvement of the rail used in the maglev train. [ABSTRACT FROM AUTHOR]

The delivery and burial of terrestrial particulate organic carbon (OC) in marine sediments is important to quantify, because this OC is a food resource for benthic communities, and if buried it may lower the concentrations of atmospheric CO2 over geologic timescales. Analysis of sediment cores has previously shown that fjords are hotspots for OC burial. Fjords can contain complex networks of submarine channels formed by seafloor sediment flows, called turbidity currents. However, the burial efficiency and distribution of OC by turbidity currents in river‐fed fjords had not been investigated previously. Here, we determine OC distribution and burial efficiency across a turbidity current system within Bute Inlet, a fjord in western Canada. We show that 62% ± 10% of the OC supplied by the two river sources is buried across the fjord surficial (30–200 cm) sediment. The sandy subenvironments (channel and lobe) contain 63% ± 14% of the annual terrestrial OC burial in the fjord. In contrast, the muddy subenvironments (overbank and distal basin) contain the remaining 37% ± 14%. OC in the channel, lobe, and overbank exclusively comprises terrestrial OC sourced from rivers. When normalized by the fjord's surface area, at least 3 times more terrestrial OC is buried in Bute Inlet, compared to the muddy parts of other fjords previously studied. Although the long‐term (>100 years) preservation of this OC is still to be fully understood, turbidity currents in fjords appear to be efficient at storing OC supplied by rivers in their near‐surface deposits. Plain Language Summary: Plants on land use CO2 from the atmosphere to produce organic carbon, which promotes their growth. Rivers transport organic carbon to the sea, where it is either eaten by fauna or buried in the seafloor, thus decreasing atmospheric CO2 levels on Earth over thousands to millions of years. Fjords are recognized as global organic carbon sinks; trapping 18 million tons of organic carbon in their seafloor sediments each year. However, the complex morphology of fjord seafloors was not considered in the calculation of this organic carbon flux. In this study, we determine the distribution and abundance of terrestrial organic carbon across a fjord (Bute Inlet, Canada), which contains a submarine channel network terminating onto a large accumulation of sand (called a lobe). We show that 62% of the organic carbon supplied by the two rivers connected to the fjord is buried across the fjord; the majority of this carbon being held in the lobe. In total, Bute Inlet buries at least 3 times more organic carbon per unit of surface area than other fjords previously studied. Submarine channels in fjords thus appear to promote the storage of land‐derived organic carbon in the seafloor, potentially impacting CO2 levels and food resources for marine fauna. Key Points: Bute Inlet, a river‐fed fjord incised by turbidity currents, has a contemporary terrestrial organic carbon burial efficiency of 62% ± 10%Sandy surficial deposits are responsible for 63% ± 14% of the total terrestrial organic carbon burial budget in Bute Inlet, but only cover 17% of the seafloor areaGlobal estimates based only on the muddy parts of fjords may significantly underestimate organic carbon burial rates by a factor >3 [ABSTRACT FROM AUTHOR]

The grain‐size distribution of sediment particles is an important aspect of the architecture of submarine fans and lobes. It governs depositional sand quality and reflects distribution of particulate organic carbon and pollutants. Documenting the grain‐size distribution of these deep‐marine sedimentary bodies can also offer us an insight into the flows that deposited them. Submarine lobes are commonly assumed to linearly fine from an apex, meaning there should be a proportional relationship between grain size and distance from the lobe apex. However, not much detailed quantitative work has been done to test this hypothesis. Exposure of a 5 km long dip‐section of basin‐floor lobes in Clinoform 12, Battfjellet Formation, Spitsbergen, enable the study of basinward grain‐size evolution in lobe deposits. Furthermore, the dataset allows testing if there are any documentable grain‐size differences between lobe sub‐environments. For this purpose, the palaeogeography of Clinoform 12 was reconstructed and the youngest lobe, which was exposed in all collected logs, chosen to be evaluated for its grain‐size trends. Photographed thin sections of 66 rock samples were analysed to obtain quantitative grain‐size distributions. The results show that fining of lobe deposits occurs predominantly in the most proximal and most distal parts of the lobe, while the intermediate lobe, which is dominated by lobe off‐axis deposits, is characterised by a relatively consistent grain‐size range. Lobe sub‐environments show statistically distinct grain‐size distributions from lobe axis to lobe fringe. An explanation for these trends is the interplay of capacity and competence‐driven deposition with the grain‐size stratification of the flows. The outcomes of this study help to better understand the proximal to distal evolution of turbidity currents and their depositional patterns. They also provide important insights in reservoir potential of basin‐floor fans at lobe scale. [ABSTRACT FROM AUTHOR]

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Lacustrine mudstones are usually considered as deposited dominantly through vertical suspension fallout in low-energy environments influenced by only occasional fine-grained turbulent flows, while the deposition of their marine counterpart have been increasingly documented to be subject to more complex and dynamic processes. To provide insights into the dynamic processes that transport and deposit mud in lacustrine settings, this study presents an integrated petrographic, sedimentological, geochemical, and sequence-stratigraphic analysis of an ancient lacustrine mudstone-dominated succession using outcrops of the Lucaogou Formation in the Junggar Basin. Detailed facies characterization has revealed seven facies associations, which show spatial and temporal variations within a stratigraphic framework and stack to form eight repetitive parasequence styles. Process-based sedimentological analysis allows the identification of multiple transport mechanisms in different depositional settings, which strongly suggests that mud in lake systems is commonly subject to multiple dynamic transport processes (i.e., sediment plumes, turbidity flows, hyperpycnal flows, and wind-driven bottom currents), rather than suspension fallout under overall quiet conditions. The differences in the expression of parasequence styles can be attributed to the combination of allogenic and autogenic processes, which systematically change with distances from the shoreline. It is important to note that river-floods can discharge large amounts of mud into the deep lake setting. The strong correlation between geochemical data and the distribution of facies generated by riverine processes indicates that in saltwater lakes terrigenous mud is mainly transported to the deep water by sediment plumes and turbidity flows, whereas in freshwater lakes it is transported primarily by hyperpycnal flows. This study demonstrates that the transport and depositional processes of lake mud are diverse and vary systematically in response to lake conditions and environmental changes. High-resolution petrographic and sedimentologic analysis is essential to identify these dynamic processes, which allows more critical and accurate interpretations of depositional conditions and long-term depositional trends in lake systems. • The Lucaogou Formation is shown to comprise a variety of facies, facies association and parasequence styles. • Sediment plume, turbidity current, hyperpycnal flow and wind-driven bottom current were revealed in lacustrine environment. • Transport process is governed by salinity: saltwater via sediment plume & turbidity current, freshwater via hyperpycnal flow. • The expression of parasequence style is controlled by allogenic and autogenic depositions at different distances offshore. • Organic-rich mudstones in the Lucaogou Formation were mainly transported and deposited under dynamic hydrological conditions. [ABSTRACT FROM AUTHOR]

Pockmarks are prominent morphological features formed by fluid escape at the seafloor that provide valuable information on past environmental conditions and ongoing sedimentary processes, and they are also biodiversity hotspots and pose potential hazards in marine environments. Crescentic pockmarks are widespread on the present seafloor of the western South China Sea margin, however, their formation mechanisms are still poorly constrained. Here, we have imaged and investigated 116 crescentic pockmarks based on multibeam bathymetry and three-dimensional seismic data to gain insights into their origin and development processes. Crescentic pockmarks show asymmetrical geometries in cross-section and their opening directions are mainly oriented NW to NNW. Morphological analysis shows the presence of two types of composite styles, and the ratios between their widths and lengths are approximately ∼0.47. Seismic profiles crossing the crescentic pockmarks illustrate that their position has a trend of downslope migration. Time slices extracted from seismic data reveal that they exhibit as circular depressions in the deep strata, while they become crescentic gradually towards the shallow strata. We consider that the crescentic pockmarks may evolve from deep circular pockmarks and the intensity of fluid escape has played a vital role in affecting their morphologies. Downslope migration of these pockmarks might be influenced by the downslope bottom currents and turbidity currents, leading to more deposition in their upstream side and erosion in the downstream counterpart. Our study demonstrates how bottom currents and gravity flows rework pockmarks' seafloor expression to form the crescentic morphologies. Hence, it provides a world-class morphological current indicator for other modern and paleo-pockmarks on continental margins worldwide. • 116 crescentic pockmarks are analyzed using bathymetric and 3D seismic data. • Variations in fluid supply determine the composite styles of crescentic pockmarks. • Crescentic pockmarks evolve from circular ones with transitional infilled forms. • Downslope bottom and/or turbidity currents likely cause their downslope migration. • The shape of crescentic pockmarks is a morphological current indicator. [ABSTRACT FROM AUTHOR]

Depositional events have a significant impact on the terrestrial redox conditions and provide evidence for studying the organic matter enrichment. The objective of this study was to evaluate the influence of volcanic and turbidity current events on benthic redox conditions during the Upper Triassic Chang 7 member (Ch7) of the Ordos Basin. To address these issues, the varying sedimentological settings, paleoredox conditions, and relationships between the redox environment and depositional events were investigated via sedimentary analysis of the profiles, microscopic analysis, organic geochemical analysis, and elemental geochemical data. The fine-grained sediments in the Chang 7 3 submember (Ch7 3) consist of abundant organic matter, collophanite, and framboidal pyrite. However, in the upper part of the Ch7 member, there was a decrease in organic matter, a decrease in the number of microorganisms, and an increase in pyrite size, indicating that the oxic environment is not favorable for organic matter enrichment. The element and geochemical proxies show similar vertical variations and redox changes. Volcanic activity can bring substantial amounts of material or elements to the basin. The enrichment of Hg and S exhibited considerable variation, ranging from 8.7 to 274.4 ppb and from 0.16 to 4.53 wt%, respectively, which influenced the organic matter accumulation through the flourishing and death of microorganisms and redox changes in the benthic environment of the terrestrial basin. As the lake basin shrinks, the Ti and Al contents increase with increasing frequency of turbidity current events, and the terrestrial debris transported to the lake basin gradually increases while carrying large amounts of oxygen and affecting sedimentation rates, contributing to the destruction of the reducing conditions of the benthic environment, subsequently, influencing organic matter accumulation. These results will be helpful in understanding the effect of multiple depositional events on organic matter enrichment in lacustrine basins. • Geochemical and sedimentary results suggest altered redox conditions. • Volcanic activity enhanced the redox conditions. • Turbidity current events influence dilution and biodegradation efficiency. [ABSTRACT FROM AUTHOR]

Submarine canyons are prominent features on continental margins, acting as major conduits for sediment transport primarily through turbidity currents. Understanding how these currents interact with complex canyon topographies is crucial for deciphering the canyon system evolution, yet challenging due to limited field observations. Focusing on a group of slope-confined canyons within the Pearl River Mouth Basin, northern South China Sea, this study integrates multibeam bathymetry, core analysis, and process-based Computational Fluid Dynamics (CFD) modeling to investigate the influence of realistic canyon topography on turbidity current dynamics and resulting sediment deposition. Analysis of core samples revealed a potential turbidite layer characterized by silts and sandy silts. Using these sediment information and bathymetric data, we conducted a series of three-dimensional CFD simulations. Our findings highlight the significant variability in turbidity current characteristics, particularly flow velocity and sediment concentration, within the canyon groups. This variability is primarily controlled by canyon head depth, the width-to-relief ratio, and slope gradients. Notably, the simulations revealed unique flow structures not typically observed in experimental settings, including unidirectional flows, small-scale helical flows, stacked and mixed flow cells, and flow separation and convergence across inter-canyon ridges. Our CFD simulations also revealed a distinct near-wall pattern of linear deposition of coarse-grained sediments, which is similar to the observed bathymetric changes between 2009 and 2017. Based on the consistent results, we propose a conceptual model wherein differential erosion, driven by oceanographic processes, plays a key role in shaping the observed linear depositional patterns. • Multiple data indicate the possibility of turbidity currents emerging in the canyons. • Flow diversity in canyon groups is controlled by geomorphic parameters of canyons. • Linear depositional patterns are probably caused by regional oceanographic processes. [ABSTRACT FROM AUTHOR]

Abstract The underpinning problems of deep-water facies still remain unresolved. (1) The Tb, Tc, and Td divisions of the turbidite facies model, with traction structures, are an integral part of the “Bouma Sequence” (Ta, Tb, Tc, Td, Te). However, deposits of thermohaline contour currents, wind-driven bottom currents, deep-marine tidal currents, and baroclinic currents (internal waves and tides) also develop discrete rippled units, mimicking Tc. (2) The application of “cut-out” logic of sequences, which was originally introduced for the “Bouma Sequence”, with sharp basal contacts and sandy divisions containing well-developed traction structures, to muddy contorts with gradational basal contacts and an absence of well-developed traction structures is incongruent. (3) The presence of five internal divisions and hiatus in the muddy contoured facies model is in dispute. (4) Intersection of along slope contour currents with down slope sediment-gravity flows, triggering hybrid flows, also develops traction structures. (5) The comparison of genuine hybrid flows with down slope flow transformation of gravity flows is inconsistent with etymology of the term “hybrid”. (6) A reexamination of the Annot Sandstone at the Peira Cava type locality in SE France fails to validate either the orthodoxy of five internal divisions of the “Bouma Sequence” or their origin by turbidity currents. For example, the “Ta” division is composed of amalgamated units with inverse grading and floating mudstone clasts, suggesting a mass-transport deposit (MTD). The “Tb” and “Tc” divisions are composed of double mud layers and sigmoidal cross bedding, respectively, which suggest a tidalite origin. (7) Although it was reasonable to introduce a simplistic “Bouma Sequence” in 1962, at a time of limited knowledge on deep-water processes, it is obsolete now in 2021 to apply this model to the rock record amid a wealth of new knowledge. (8) The disconnect between 12 observed, but questionable, modern turbidity currents and over 10,000 interpreted ancient turbidites defies the doctrine of uniformitarianism. This disconnect is attributed to routine application of genetic facies models, without a pragmatic interpretation of empirical data. (9) A suggested solution to these problems is to interpret traction structures in the sedimentary record pragmatically on the basis of empirical field and experimental evidence, without any built-in bias using facies models, such as the “Bouma Sequence”. (10) Until reliable criteria are developed to distinguish traction structures of each type of bottom currents based on uniformitarianism, a general term “BCRS” (i.e., bottom-current reworked sands) is appropriate for deposits of all four kinds of bottom currents.

[Display omitted] • General spatiotemporal evolution law of turbidity currents under different vegetation canopy morphologies was verified. • Leaf morphology is a key attribute influencing vegetation resistance for turbidity currents. • Correlation between turbidity momentum and suspended sediment transport decreases under complex conditions. Understanding the flow-vegetation-sediment feedback mechanism is critical for ecological restoration of gently sloped landscapes. Numerous simulation or laboratory experiments on turbidity currents over vegetation have revealed the important roles of vegetation canopy morphology and structure in this feedback mechanism. However, there is still a lack of analysis on the related physical processes. This study investigated the evolutionary characteristics and sediment transport and deposition patterns of turbidity currents with different sediment size distribution in vegetation patches of different canopy morphologies through lock-exchange experiments. The roles of vegetation leaf morphology and canopy structure were explored by varying the leaf morphology and vegetation density with turbidity currents prepared using sediment samples configured with different particle sizes, which are more compatible with natural conditions. The kinetic characteristics and sediment distribution of the turbidity currents over vegetation were simultaneously analyzed, providing a new perspective for updating the methodology in laboratory experiments. The major findings of this study can be summarized as follows: 1) the general spatiotemporal evolution law of turbidity currents is applicable to complex vegetation canopy morphology; 2) canopy structure dominated by leaf morphology is an important influencing factor that needs to be taken into account in the research on vegetation resistance; and 3) the correlation between turbidity current momentum and suspended sediment transport decreases under complex conditions, and coarse-grained suspended sediment tend to limit the movement of turbidity currents and major deposition distance of the sediment. These findings can provide theoretical support for conservation of floodplain soil and water and restoration of watershed ecology. [ABSTRACT FROM AUTHOR]

[Display omitted] • In the Carboniferous Junggar Basin, 16 deep-water facies were identified, categorized into five depositional element types. • Arc volcanism and submarine volcanism differentially influenced different depositional elements. • Volcanism is crucial in determining types, formation, and distribution of deep-water deposits. The Carboniferous sedimentary successions of the north-western and southern margins of the Junggar Basin in northwest China show a gradual vertical transition from deep- to shallow-marine depositional environments. Stratigraphically, these successions are composed of sedimentary and igneous lithologies (volcaniclastic), which record the closure and subduction of the remnants of the western Junggar and northern Tianshan oceanic basins that formed branches of the Paleo-Asian Ocean. In the current study, 16 facies and 7 facies associations related to sediment gravity flows were identified. These lithofacies associations collectively reflect five depositional elements, which include mass transport deposits, gravity flow channel deposits, lobe complex deposits, submarine volcanic ridge deposits, and submarine volcanic turbidite fans. Submarine and subaerial arc volcanism are shown to have controlled the characteristics of gravity flow sedimentation recorded in these successions. Island–arc volcanic material in the Junggar Basin is divided into three sources: erosion of the arc by fluvial systems, island–arc eruption materials, and submarine volcanism. Volcaniclastic deposits were transported into the deep-marine basin by submarine sediment gravity flows. These flows included turbidity currents, supercritical flows, gravel-rich debris flows, sandy debris flows, and muddy debris flows. Submarine vents generated lava flows that were deposited onto the abyssal plain and triggered subaqueous pyroclastic density flows. This study and its analysis of the characteristics and likely genesis of these gravity flow sediments improve the understanding of the dynamic relationship between volcanic activity and gravity flow sedimentation in near-arc basins. These findings provide a useful case-example of sediment gravity flow systems in island–arcs, which can be compared with and used as a relevant analog for other deposits in similar settings globally. [ABSTRACT FROM AUTHOR]

This study employs the large-eddy simulation (LES) method to investigate the interaction of submarine sediment flows with extensive shear behavior and ambient water. This method is validated with good accuracy by simulating the head velocity and evolution geometries of a submarine mud flow with non-Newtonian fluid characteristics and a submarine turbidity current with Newtonian fluid characteristics in inclined and regular lock-exchange flume experiments. This study finds that the violent mass transfer at the interface of the submarine sediment flow and seawater is caused by numerous eddies, which significantly alter the submarine sediment flow's geometry, resulting in varying degrees of undulation, including the deposition pattern of the submarine sediment flow tail. The acceleration zone, where the velocity of the submarine sediment flow increases significantly at this undulation, propels the sediment flow forward, supporting its long-distance transport. Furthermore, the turbulence and mass transport characteristics of submarine turbidity currents with low dynamic viscosity Newtonian fluid characteristics are stronger than those of submarine mud flows with high dynamic viscosity non-Newtonian fluid characteristics. Therefore, when submarine landslides develop into later stages, such as submarine turbidity currents with high velocity, large volume, and long run-out distance characteristics, more attention must be given to the mass transport process. • CFD modeling captures the evolution of submarine sediment flows with extensive shear behaviors. • Mechanisms behind density variation in evolving mud flows (non-Newtonian) and turbidity currents (Newtonian) are clarified. • Numerical reproduction successfully depicts complex physical processes in turbidity current evolution. • These processes encompass head, tail, and neck formation, vortex generation, density mixing, separation, shedding, and deposition. [ABSTRACT FROM AUTHOR]

Debris avalanche deposits are developed on slopes in various environments, including submarine volcanoes, continental volcanoes, continental slopes, and mountain ranges. In contrast, research is relatively scarce on the coarse-grained subaqueous debris avalanche deposits formed by the collapse of steep basin margins in continental small rift basins, which are controlled by tectonics. Through the interpretation of satellite imagery, field investigations, and the study of the morphological characteristics and internal structures of sediments, a massive debris avalanche event during the Early Cretaceous, Xiguayuan Formation of the Luanping Basin at the northern edge of the Yanshan tectonic belt on the North China Block, named the Wangying Debris Avalanche Deposit (WYDAD), has been identified and analyzed for its kinematics, dynamics, and long-runout mechanisms. The study reveals that based on sedimentology, internal structures, and basal characteristics, five different types of sedimentary morphologies can be identified from the source zone to the distal zone: convergent ridges and grooves (longitudinal expansion and lateral compression), transverse ridges and grooves (compression), longitudinal ridges and grooves (shearing and stretching), arcuate ridges and grooves (compression), and mixed sediments (radial extension). The grain size of coarse-grained debris avalanche deposits decreases with increasing transport distance and fragmentation due to jigsaw cracking, while matrix content increases. Additionally, the entrainment of fine-grained substrate and the mixing of lake waters during the transport of debris avalanches often evolve into secondary debris flows or high-density turbidity currents. Debris avalanches are likely primarily controlled by regional tectonic activity and volcanic action. Compared to subaerial debris avalanche deposits, the subaqueous WYDAD exhibits characteristics such as low fragmentation, smooth underwater terrain due to water resistance and buoyancy, and higher fluidity. The mechanism for the long-distance, high-speed transport of the WYDAD is explained by "hydroplaning" and high pore pressure generated by non-draining shear. This study provides insights into the transport processes of coarse-grained subaqueous debris avalanche deposits in continental rift basins. It verifies whether such sediments can serve as a primary sedimentary system for CCUS or potential resource storage. [ABSTRACT FROM AUTHOR]

Clinoforms are ubiquitous depositional surfaces in sedimentary systems. The quintessential shape, with a flat or gentle topset, sloping foreset, and gentle to flat bottomset, is recognizable in the smallest ripple to the kilometer high edges of the continents. Essentially the shape is one which develops with differential sedimentation away from a sedimentary source. Systematic decay of transport competence and/or sediment amount from a site favouring deposition, generates differential loading of a typically lens-shaped sedimentary body. The lithology, grain size, water depth, hydrodynamic factors, transport mechanisms, antecedent topography, relative sea level and sediment rate all interact to create different sizes, slopes and shapes. Meanwhile there are several fundamental similarities between clinoforms, even with the smallest bedwave features (ripples and dunes), despite forming under very different depositional conditions. All clinoforms are to some extent governed by accommodation and energy limiting factors (water agitation and/or flow regime), which controls their height, and by proxy influences slope angle. Lithology exerts a fundamental control, slopes can build to angle of repose, which is higher for coarser non-cohesive sediment, while cohesive sediment develops gentler slopes, and also fail at lower angles. Sediment at angle of repose create steep linear slopes, or slope segments, but conversely linear slopes on continental margins are extremely low angle, probably reflecting high sediment with little along-slope contrast and mud-dominance. Meanwhile clinothems of similar lithology display a wide range of foreset angles, indicating numerous additional controls. Sedimentation rate appears to exert significant control on slope steepness, with limited sedimentation promoting steeper slopes related to basinward thinning deposits. The observation of steeper slopes with greater depth is a response to deepening environments generating the effect of comparatively less sedimentation. Processes are important in controlling slope angle as tidal and wave reworking, debris flows, and overpressure and slope failure, typically create lower angles. Turbidity currents meanwhile are part of a dynamic depositional system which can both steepen or lower a slope. There are four basic clinoform shapes: concave, linear, convex, and sigmoidal. These develop in response to variations in sedimentation along the profile driven by erosion/bypass/factors limiting deposition/accumulation/waning sediment supply. Curvature tends to be an indication of along-slope contrast, such as between erosional and deposition, sandier and muddier lithology or higher and lower sedimentation. Sigmoidal clinothems, associated with more accommodation and higher trajectories, are typically shorter and steeper than concave clinothems. Decaying shear-zone agitation and/or reworking and erosion shapes the rounded rollover. Decaying sediment amount and carrying capacity shapes the ensuing curvature. Concave slopes, lacking topsets and associated with sharp rollovers and low angle trajectories, are often longer with lower angle than sigmoidal forms. Their formation is likely closely linked to increased lower slope accumulation through slope failure, bypass, and/or turbidity currents, but can also be from increased suspension-dominated deposition in smaller clinoforms. In this ripples differ, as the concave to sigmoidal transition is associated with higher energy and erosion rounding the crest, and unlike larger clinoforms, the concave is often steeper than the sigmoidal. [ABSTRACT FROM AUTHOR]

Sediment waves are subaqueous sedimentary figures belonging to the supercritical flow domain and are of growing interest to the scientific community and industry. They are ubiquitously observed on the seafloor of world's oceans, as well as in the stratigraphic record imaged by marine seismic datasets. In this study we focus on the Cenozoic strata offshore Ivory Coast, where giant sediment waves developed at the base of slope range in height and wavelength: 10–100 m and 1–6 km, respectively. Sediment waves fields in this study developed simultaneously and adjacent to wide, rectilinear valleys, filled by mass-transport deposits. Thus, sediment waves serve as a rare example of large-scale deep-water cyclic steps formed through phase transformation (water entrainment and dilution) of laminar debris flows. The lithological nature of sediment waves can be estimated through the observation of polygonal faulting affecting the sediment waves fields, which suggest a dominant abundance of fine-grained material (clay and silt-prone). This study also shows that wide submarine valleys flanked by sediment waves do not necessarily correspond to sand-prone depositional systems, and that their potential to hold reservoir units for hydrocarbon exploration or CO 2 storage should be evaluated with caution when in lower resolution datasets are used. • High resolution 3D seismic data reveal large scale sediment waves deposited adjacently of rectilinear MTD-filled valleys. • Sediment waves are formed through phase transformation (water entrainment and dilution) of laminar debris flows. • Sediment waves lithology appear to be largely dominated by fine grained material. [ABSTRACT FROM AUTHOR]

Hybrid event beds (HEBs) form important components of subaqueous sediment gravity flow models in deep-lacustrine sedimentary basins, largely due to their clay-rich nature meaning that they often form non-reservoir and/or baffles/barriers to fluid flow in the subsurface. Using examples from a typical deep-lacustrine basin, this study documents the sedimentary characteristics and distribution of HEBs and explores their effect on reservoir properties. To achieve this, a suite of drill cores and wireline data through a range of debrites, concentrated flow deposits, and turbidites are analyzed from Paleogene in the Bohai Bay Basin, China. The superposition and convergence of gravity flow deposits resulted in a complex spatial and temporal distribution and evolution of the HEBs in the study area. The majority of identified HEB types are interpreted to be associated with lobe deposition. However, slumping-induced HEBs are interpreted to be restricted to the proximal slump areas. Slump HEBs are interpreted to have formed through slumping and associated generation of sediment gravity flows, where HEBs formed through flow transformation of slumps into high-concentration flows (debris flows) and/or high-density turbidity currents in down-slope areas. Debris flow HEBs are interpreted to be formed by particle rearrangement through vertical settling during flow transformation within the subaqueous fans. The effects of relative buoyancy in debris flows, rearrangement of debris flow particles, muddy substrate erosion by turbidity currents, and slumping upon HEB development are discussed. The average porosity and permeability observed within reservoir intervals formed by gravity flow deposits are 17.8 % (ranging from 2 % to 25 %) and 126 mD (ranging from 3 mD to 816 mD), respectively. HEBs within the studied reservoir interval display low-porosity (<15 % on average) and low-permeability (<10 mD on average) values. The occurrence of HEBs within a reservoir increases the variation coefficient of permeability, quantity, and thickness of the interlayers and presents a significant heterogeneity. The results of this study are important to consider in the context of constructing reservoir models in deep-lacustrine reservoirs of the Bohai Bay Basin, and which can be applied to other lacustrine gravity flow deposits in sedimentary basins worldwide. • Four types of hybrid event beds (HEBs) are observed in lobes or proximal slumps. • The detailed sedimentary evolution of different HEBs is presented. • HEBs are mainly controlled by sediment supply and terrain in lacustrine basins. • HEBs exert negative influences on oil and gas accumulation and production. [ABSTRACT FROM AUTHOR]

Paleocene deposits of the Subbetic Zone (southern Spain) provide outstanding evidence of the influence of sea mountains on deep marine currents. This part of the Betic Cordillera External Zones corresponds to the distal and deepest area of the original basin, where hemipelagic sedimentation prevailed during most of the Turonian-early Lutetian interval. This sedimentation is recorded by the so-called Capas Rojas and Quipar-Jorquera formations, units up to 250 m and 425 m thick, respectively, predominantly consisting of marls and marl/limestone alternations. These units draped and smoothed an irregular submarine topography of fault-bounded Mesozoic carbonate blocks. Some of these blocks became uplifted and subaerially exposed after a mid-Danian tectonic episode, transforming the Subbetic Zone in an archipelago during the late Danian-early Selandian interval. The emerged blocks were colonized by Microcodium -producing terrestrial plants, Microcodium consisting of aggregates of submilimetric monocrystalline calcite grains. Massive resedimentation of these grains into depressed zones of the archipelago resulted in discrete accumulations up to 100 m thick but of comparatively modest extent (≤150 km2) of calcarenites rich in Microcodium remains. The study of one of these calcarenite units, the Olivares Formation, demonstrates that most of its constituent Microcodium remains were brought to the deep sea by turbidity currents, but were subsequently reworked by oscillatory and unidirectional bottom-currents. The analysis of the Capas Rojas Formation in its type section and surrounding areas, where Microcodium -rich calcarenites are absent, demonstrates that the Danian-Selandian succession is riddled with hiatuses, which resulted in a drastic thickness reduction of the interval. Clearly, the rugged sea floor topography resulting from the mid-Danian tectonic event enhanced the sedimentary transport capacity of bottom-currents that, in addition to piling-up Microcodium -rich calcarenites in restricted zones, disturbed the hemipelagic sedimentation elsewhere in the Subbetic Zone. From late Thanetian times onwards the background hemipelagic sedimentation typical of the Capas Rojas progressively resumed throughout the Subbetic Zone, recording the gradual abatement of the sea floor relief by protracted erosion and/or subsidence. • Change of the bathyal Subbetic to an archipelago recorded by redeposited Microcodium • Pre- and post-archipelago weak deep-sea currents favored hemipelagic deposition. • The archipelago rugged sea-floor topography boosted the strength of deep-sea currents. • Deep-sea currents reworked calciturbidites and created hiatuses in hemipelagites. [ABSTRACT FROM AUTHOR]

The sedimentology of upper flow regime bedforms represents an important research topic at the present. Deposits interpreted as those of supercritical flows are widely recognized in modern fan systems, but their recovery is challenging. Most of the sedimentological information has come from channel thalwegs but supercritical bedforms are also frequently downslope from the channel mouths. Such an environment has been identified in the Paola basin, where erosive and depositional cyclic steps have been imaged and identified in a sandy submarine lobe of the Amantea Fan. High-resolution sub-bottom profiles provide insight into the bedform internal architecture and their relationships with a frontally-confining ridge. For the first time, supercritical bedforms in a submarine lobe have been interpreted in two distinct positions: in the scour of an erosional cyclic step and in the stoss side of a depositional cyclic step. Coarse to medium-grained massive sand with flame structures, indicating rapid sediment fall-out and frequently associated with the occurrence of hydraulic jumps, has been identified in the scour and at the toe of the ridge. The latter represents an example of topographically induced hydraulic jumps driven by a frontal confinement. Top-cut-out medium to fine sands with tractive structures have been interpreted as the deposits related to the stoss side of a cyclic step or small-scale antidune superimposed on the cyclic step surface. The presented data broaden the understanding of the range of processes that are driven by the interaction between turbidity currents and seafloor topography and the dip of the slope. The recognition that topography influences the density structure and the degree of criticality of the flow and, consequently, the morphodynamics and facies of the relative deposits may help to explain sediment distribution and improve depositional models of fan lobes in confined settings. • Sedimentological information about supercritical bedforms in a frontally confined submarine lobe are provided. • Observations result from the interpretation of high-resolution seismic profiles and the analysis of five gravity cores. • Sedimentary structures, generally associated with hydraulic jumps, have been identified in scour fills and at the base of a ridge. • The topography influences the distribution of supercritical bedforms and the flow criticality. [ABSTRACT FROM AUTHOR]

This article presents the current state-of-the-art understanding of underwater dilative slope failure (breaching). Experimental investigations are reviewed, providing critical insights into the underlying physics of breaching and pointing out knowledge gaps, which underscore the need for further research. Besides, field observations at several locations across the globe are outlined, highlighting the hazard of breaching and the need for effective coastal management strategies to mitigate the associated risks. Furthermore, existing methods for analyzing and predicting the slope failure evolution are discussed and reflected upon, including analytical approaches and numerical models, ranging from simplified 1D models to advanced 3D coupled flow-soil approaches. Lastly, open questions are posed and key future directions are identified to enhance our understanding of the breaching failure. Overall, this review paper provides a valuable resource for researchers and decision makers involved in slope stability and flow slide risk assessment. • State-of-the-art knowledge of underwater dilative slope failure (breaching) is presented. • Knowledge gaps, and limitations in the existing breaching models are identified. • Key future directions are defined to enhance our understanding of breaching. [ABSTRACT FROM AUTHOR]

Submarine canyons are primary conduits for turbidity currents transporting terrestrial sediments, nutrients, pollutants and organic carbon to the deep sea. The concavity in the longitudinal profile of these canyons (i.e. the downstream flattening rate along the profiles) influences the transport processes and results in variations in turbidite thickness, impacting the transfer and burial of particles. To better understand the controlling mechanisms of canyon concavity on the distribution of turbidite deposits, here we investigate the variation in sediment accumulation as a function of canyon concavity of 20 different modern submarine canyons, distributed on global continental margins. In order to effectively assess the isolated impact of the concavity of 20 different canyons, a series of two-dimensional, depth-resolved numerical simulations are conducted. Simulation results show that the highly concave profile (e.g. Surveyor and Horizon) tends to concentrate the turbidite deposits mainly at the slope break, while nearly straight profiles (e.g. Amazon and Congo) result in deposition focused at the canyon head. Moderately concave profiles with a smoother canyon floor (e.g. Norfolk-Washington and Mukluk) effectively facilitate the downstream transport of suspended sediments in turbidity currents. Furthermore, smooth and steep upper reaches of canyons commonly contribute to sediment bypass (i.e. Mukluk and Chirikof), while low slope angles lead to deposition at upper reaches (i.e. Bounty and Valencia). At lower reaches, the distribution of turbidite deposits is consistent with the occurrence of hydraulic jumps. Under the influence of different canyon concavities, three types of deposition patterns are inferred in this study, and verified by comparison with observed turbidite deposits on the modern or paleo-canyon floor. This study demonstrates a potential difference in sediment transport efficiency of submarine canyons with different concavities, which has potential consequences for sediment and organic carbon transport through submarine canyons. • The impact of submarine canyon concavity on turbidite deposition was assessed. • Distribution of turbidite deposits varies with changes in canyon concavity. • Three distinct deposition patterns were identified. • The recognized deposition patterns align well with the observed turbidite deposits. [ABSTRACT FROM AUTHOR]

The article discusses a study which showed that dense heads can control turbidity current sediment transport and runout into the deep sea. Topics covered include turbidity currents' possible composition of heterogeneous flow regimes in both muddy and sandy systems, and the model's implications for geohazards with increased risk for seafloor infrastructure damage. Also noted are dense heads' domination of fluxes through submarine channel systems and likely control of their evolution.

We use high-resolution 3D reflection seismic data to constrain the strato-structural evolution of the transitional and compressional domains of a Late Cretaceous deep-water fold-and-thrust belt (DWFTB) system and its influence on the overlying Cenozoic megasequence in the Orange Basin, South Africa. Multiple shale detachment surfaces have given rise to 10 a complex structural framework, allowing for the redistribution of stress and strain, with progressive deformation and sedimentation. High-resolution 3D seismic data show that the compressional domain exhibits large-scale landward-dipping DWFTBs with faults mainly detaching the Turonian shale detachment surface. Thrust sheets are segmented along strike by extensive oblique-slip faults which extend from the transitional domain into the down-dip compressional domain. The transitional domain is imaged as a complex region containing listric normal, thrust, and oblique-slip faults. Many faults in the 15 transitional domain have been reactivated to detach onto an older Albian shale detachment surface at depth, transferring stress and distributing strain during gravitational sliding. Smaller, localized fold-and-thrust belts are subsequently formed in the down-dip compressional domain directly below the kilometre-scale DWFTB system between the upper Turonian and lower Albian shale detachment surface. Mass erosional processes of the Cenozoic are confined above the transitional domain including a large, roughly slope-perpendicular Oligocene submarine canyon formed by turbidity currents, and a smaller series 20 of slope-parallel, sinusoidal channel-like features in the Miocene formed by bottom currents. Normal and oblique-slip faults from the transitional domain have been reactivated to terminate at either one of the Oligocene or Miocene sequence boundaries. This, together with a present-day seafloor slump scar above a buried Late Cretaceous syncline, indicates how the stratigraphy and structural geometry of a buried DWFTB system controls fundamental sedimentary processes in an evolving continental margin. [ABSTRACT FROM AUTHOR]

Species distribution patterns in the Brazilian Marine Province (BMP) are extensively debated, nevertheless no study used a multi-taxa approach to investigate possible biotic distinctions and the role of environmental factors in determining biogeographical patterns in this province. Here, we compiled the largest distributional multi-taxa dataset in the southern Atlantic (2412 reef species) to address the following: (1) similarities among areas accounting for species composition and environmental characteristics; (2) the absolute species richness of nine taxonomic groups among geographical bins; and (3) how species biogeographical patterns are explained by the environmental similarities. We hypothesized sub-provinces' limits will be strongly correlated to environmental delimitations, being sea surface temperature a central component influencing biotic subdivision on the BMP. We found eight different geographical bins considering the environmental factors, while five considering species distributions. We also observed a latitudinal gradient of species richness for most taxa, some presenting a "mid-domain" shape pattern. Beta diversity among sub-provinces was low, and the nestedness component more important, indicating high connectivity along the BMP. Using a db-RDA, we demonstrated that environmental variables explained 64% of species clustering patterns, with sea surface temperature, water turbidity and current velocity explaining the biotic clustering of the Brazilian northeastern coast. Sub-provinces North and Abrolhos Bank were the most distinct areas regarding environmental and biotic data. Our study highlights the importance of using a multi-taxa approach to understand the relationship between biogeographical patterns, as well as its response to environmental and historical factors. [ABSTRACT FROM AUTHOR]

Renewable energy installations and energy storage solutions require significant quantities of critical raw materials such as nickel, cobalt and rare earth metals. The supply chains of these raw materials face many difficulties, such as the continuous decrease of mineral ore grades on land. In view of these complications, the motivation to search for new resources has grown, with the deep sea being seen as a potential source of these minerals. Polymetallic nodule mining generates turbidity currents, which could negatively impact the deep-sea environment. For that reason, we investigate this type of current experimentally and numerically in order to characterize the generated turbidity current. Various non-cohesive sediment types, i.e., different particle sizes, and different concentrations are tested using a lock-exchange set-up. Three sediment types (glass beads, silica sand and a 50/50 blend of glass beads and silica sand) with seven initial sediment concentrations are examined. Additionally, for the numerical work, a drift–flux modelling approach is used to simulate the performed lock-exchange experiments. The results show that the front velocities of the currents resulting from the three sediment types increases with increasing initial concentrations inside the lock regardless. Moreover, using the same initial concentration, the difference in front velocities between the generated currents of the three sediment types decreases as the initial concentration increases. When using an initial volumetric concentration of 2.5% and 3%, the difference in front velocities between the generated current of the three sediment types vanishes. Finally, by comparing the numerical and experimental results, the drift–flux model is proven to be a reliable numerical model for predicting the current. [ABSTRACT FROM AUTHOR]

The magnetic bearing–rotor system has the advantages of no mechanical friction and active vibration control. A magnetic bearing with redundant structures provides an effective method to apply fault-tolerant control to the magnetic bearing–rotor system. In this paper, in order to improve the robustness of a rotor suspended by a magnetic bearing with redundant structures, the harmonic current suppression approach is proposed. Firstly, the generation mechanism of harmonic current in the magnetic bearing–rotor system is analyzed. Secondly, on the basis of the current distribution theory of magnetic bearing with redundant structures, the linearization model of electromagnetic force is established. Then, the eight-pole symmetrical radial magnetic bearing is taken as the research object, and the control system model with a multi-excitation disturbance source is established under the condition of no coil failure. Lastly, considering the periodicity of disturbance signals, a repetitive controller that is suitable for magnetic bearing with redundant structures is proposed in this paper, Moreover, in order to verify the effectiveness of the proposed control strategy, we inserted the repetitive controller into the original controller applied to the magnetically levitated rotor with redundant structures, and the corresponding simulation was carried out. The results demonstrate that the repetitive control method proposed in this paper can effectively suppress the harmonic current and improve the suspension accuracy of the rotor supported by the magnetic bearing with redundant structures. [ABSTRACT FROM AUTHOR]

Organic matter burial in the deep-sea fan sediments is an important component of the long-term carbon cycle. Although there is increasing recognition of the importance of organic matter in deep-sea sediments, a major focus has been on mudstones, commonly interpreted as the background sediments, deposited by pelagic or hemipelagic vertical suspension fallout in low-energy fan environments. Emerging evidence suggests that relatively coarse-grained sediment gravity flow deposits (e.g., turbidites and hybrid event beds) can also store a significant quantity of organic carbon, implying that a wide range of depositional processes can result in the concentration and enrichment of organic matter in submarine fans. However, the role of these processes on carbon burial is still not fully understood. This review aims to discuss the impact of three widely documented deep-sea depositional mechanisms/processes, namely vertical suspension settling, grain-by-grain (incremental aggradation), and the en-masse deposition on distribution, burial, and preservation of organic matter in deep-marine deposits. Organic matter accumulated from slowly settling suspension in mud caps (Te or H5 divisions of turbidites and hybrid beds, respectively) is prone to higher oxidation compared to the carbon buried in sandy components of turbidity currents (Ta-Tc units) and hybrid beds (H2/H3 divisions). The burial of organic matter in sandy parts of the deposits has important implications for understanding the fundamental physical processes that control carbon accumulation and preservation in deep-marine rock record. [ABSTRACT FROM AUTHOR]

The Aladağ melange is located between Mesozoic Tauride carbonate platform units and the Late Cretaceous Pozantı-Karsantı ophiolite and its metamorphic sole. The melange comprises a lower, mainly sedimentary unit, composed of variably disrupted thrust sheets of deep-sea sediments, with a localized matrix of mass-flow and turbidity current deposits. The upper, volcanic-sedimentary melange comprises highly disrupted basalt-pelagic carbonate-radiolarite units, rarely associated with gravity-flow deposits. Tholeiitic to alkaline basalts in the melange range from N-MORB, to E-MORB and to OIB, and are dated as Middle Jurassic to Early Cretaceous using Radiolaria from interbedded pelagic sediments. Comparisons with accretionary melanges throughout southern Turkey and elsewhere indicate a similar geochemical pattern of variable 'enrichment', commonly coupled with a subduction influence (e.g. negative Nb, Ta anomalies). Geochemically, the subduction-influenced basalts are consistent with an oceanic island arc origin. However, the geological setting of Triassic basalts within some of the melanges (e.g. Mersin) is indicative of a rifted continental margin setting. The Mesozoic basalts within the Turkish melanges considered here erupted along the distal, outer northern margin of the Tauride continent, followed by Late Cretaceous subduction-accretion and supra-subduction zone ophiolite emplacement. Regional to global chemical comparisons suggest that the subduction influence could represent geochemical subduction inheritance rather than contemporaneous subduction. [ABSTRACT FROM AUTHOR]

Decadal time series of chlorophyll-a concentrations sampled at high and low frequencies are explored to study climate-induced changes on the processes inducing interannual variations in the Initiation of the Phytoplankton Growing Period (IPGP) in early spring. In this study, we specifically detail the IPGP in two contrasting French coastal ecosystems: the Bay of Brest and the Bay of Vilaine. A large interannual variability in the IPGP is observed in both ecosystems in connection with variations of environmental drivers (solar radiation, sea temperature, wind direction and intensity, precipitation, river flow, sea level, currents and turbidity). We show that the IPGP is delayed by around 30 days in 2019 in comparison with 2010. The use of a one-dimensional vertical model coupling hydrodynamics, biogeochemistry and sediment dynamics shows that the IPGP is generally dependent on the interaction between several drivers. Interannual changes are therefore not associated with a unique driver (such as increasing sea surface temperature). Extreme events also impact the IPGP. In both bays, IPGP is sensitive to cold spells and flood events. The interannual variability of the IPGP is significant and strongly conditioned, at the local scale, by a combination of several environmental parameters, with a larger sensitivity to sea temperature and light conditions, linked to the turbidity of the system. While both bays are hydrodynamically contrasted, the processes that modulate IPGP are similar. [ABSTRACT FROM AUTHOR]

Transport of continental shelf sediments to the deep ocean can be studied from displaced symbiont‐bearing larger benthic foraminifera found in turbidity current deposits. The larger benthic foraminifera habitat depth, physical characteristics and preservation serve as indicators for understanding sediment transport dynamics near the seabed and in the water column. Here, an experiment was designed to explore sediment transport in a closed flume system using simulated high current velocities. Shelf sediments from the Gulf of Eilat/Aqaba, dominated by Amphistegina papillosa and Operculina ammonoides, were subjected to 60 cm s−1 and 80 cm s−1 current velocities while collected in a 10 cm vertical sediment trap. Larger benthic foraminifera abundance, shell physical properties and preservation were analyzed and compared with the original bulk sediments. The experiment results showed that at 80 cm s−1 velocity, larger benthic foraminifera shells of all sizes and preservations are efficiently resuspended and transported in large quantities throughout the water column, as opposed to their transport as bedload by the lower velocity current. Larger benthic foraminifera shape also has a role in the transport distances and accumulation depths. Operculina ammonoides shells were found to be more portable, compared to Amphistegina papillosa, due to their flatter discoid shape. The results suggest that a threshold velocity of ca 80 cm s−1 was needed to generate the thick coarse deposits found in the Gulf of Eilat/Aqaba slope sedimentary record, which were previously suggested to be triggered by large magnitude seismic events. Lower velocities probably winnowed minor amounts of larger benthic foraminifera shells (with little or no coarser sediments) that were deposited as a thin sand layer may point to lower magnitude seismic triggers. In conclusion, larger benthic foraminifera shells are transported and deposited in accordance with their hydrodynamic properties, resulting in assemblage differentiation along the transport pathway. This study shows that the fossil biogenic composition in slope sediments includes valuable information on current velocities, transport dynamics and possible triggers in the geological record. [ABSTRACT FROM AUTHOR]

In the process of establishing a bearingless induction motor (BL-IM) traditional dynamic model, the magnetomotive force of rotor winding, the influence of suspension winding on torque, and the influence of torque winding on radial force are ignored. To solve the problem of insufficient accuracy in the traditional analytical model, based on fixed-pole rotor structure designed by the research group, which comprehensively considers the effect of suspension winding, torque winding, and rotor winding, an improved dynamic model is proposed. First, the spatial variation equation of air gap under rotor eccentricity is established, the composite magnetomotive force of three sets of windings according to the law of magnetic circuit is deduced, and the analytical model of magnetic coenergy in air gap is built. Second, using virtual displacement theorem to find partial derivative, the torque and radial force analytical model are obtained. Third, the improved BL-IM dynamic model is established. Finally, finite element analysis simulations based on controlled variable method prove the accuracy of improved dynamic model. The change trend of torque is verified with respect to suspension current, phase difference between suspension current and torque current, as well as rotor eccentricity. The change characteristics of radial force under no-load, load, and load disturbance are analyzed. In experiments, the controllers based on the traditional dynamic model and the improved dynamic model are compared and analyzed for speed, radial displacement, and centroid trajectory. The effectiveness of the improved dynamic accurate model is verified. [ABSTRACT FROM AUTHOR]

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Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Suri-Las Planchadas Volcanic-Sedimentary Complex (SPVSC), northwest of the Sierras Pampeanas in Argentina, comprises an Early to Middle Ordovician (Floian–Dapingian) submarine and subaerial succession with a variety of mafic to felsic volcanic lithofacies. These units include mafic to intermediate submarine massive-hyaloclastic lava flows, dacitic lavas, pyroclast-rich volcaniclastic deposits, intrusions of domes/sills and rhyodacitic—rhyolitic lavas. Along Las Planchadas hill a section of ~ 3 km thickness is exposed showing vertical and lateral variations. The lower part is dominated by massive, pillowed and basaltic to intermediate lavas, autobreccia and hyaloclastic facies, representing the beginning of the volcanic arc activity. The upper almost 2 km of the succession is dominated by subaqueous-resedimented volcaniclastic siltstones, sandstones and breccias with abundant pyroclastic components and rhyodacitic to rhyolitic lava-domes, sills and dykes. Tuff and ignimbrite lithoclasts, abundant shards and pumice fragments were determined in the resedimented deposits. Volcanism in the SPVSC started with submarine eruptions and progressively grew above the wave base, accompanied by a change from mafic to intermediate and felsic members. The eruptive pattern shifted from effusive to explosive, producing a large apron of syn-and post-eruptive volcaniclastic deposits of debris flows and turbidity currents. They are the evidence of variations in composition and volcanic styles and their development contributed to generate an apron surrounding the volcanoes. The apron prograded and aggraded with the evolution of the volcanism culminating in shallow water volcanogenic beds. The final phase was characterized by felsic subaerial or shallow subaqueous explosive volcanism. [ABSTRACT FROM AUTHOR]

Morphology is one of the principal driving forces governing the sedimentology and evolution of delta‐canyon‐fan systems. However, quantified and systematic studies of morphological controls are still very limited. This study applied hydraulic‐based stratigraphic forward modelling to investigate the impacts of morphological parameters on sediment budget partitioning and channel network of delta‐canyon‐fan systems on passive margins. A total of six sets of stratigraphic forward models are built using 47 initial bathymetries with six varying morphological parameters: shelf gradient; shelf width; slope gradient; canyon sinuosity; canyon depth; and basin gradient. The quantified relationships between morphological parameters and sedimentological parameters (dimensions, deposition/erosion volume/area, number of tributaries and slope channels) are investigated. The causes behind the relationships are explored by analyzing the response of qualified sedimentary features to morphological controls, such as grain‐size distribution, channel migration and sequence stratigraphic frame. The results suggest that low shelf gradient, low shelf width, high canyon gradient and low canyon sinuosity are beneficial for sediment budget partitioning into deep basins and turbidity currents to flow inside canyons. Low canyon depth also promotes sediment delivery but results in more channels on canyon flanks. For the delta, channel lateral migration increases then decreases with increasing shelf gradient due to the gradient threshold in determining channel sinuosity; delta size increases then stops increasing with increasing shelf width due to the shelf width threshold in determining the balance between accommodation and sediment supply. For the canyon, low canyon gradient, high canyon sinuosity and low canyon depth have similar effects on canyons, all resulting in significant channel translation and canyon widening but less canyon head retrogradation. This study improves the knowledge of controlling factors and sediment transport regime of a delta–canyon–fan system. Moreover, the observed relationships could provide semi‐quantitative guidelines to predict the dimensions of delta–canyon–fan systems and the distribution of hydrocarbon reservoirs. [ABSTRACT FROM AUTHOR]

Equilibrium sediment transport is the condition of zero net entrainment and deposition by sediment‐transporting flow (i.e. grade or regime). Here criteria for equilibrium sediment transport, or those used as proxies for equilibrium (for example, onset of erosion, onset of particle setting or suppression of turbulence) for dilute, suspended‐load‐dominated, turbidity currents, are tested against laboratory and natural data. The examined criteria are restricted to those describing flow over a bed of loose particulate material involving non‐cohesive sediment. Models include both monodisperse and polydisperse formulations that represent sediment non‐uniformity by using a single characteristic grain size or discretization of the grain‐size distribution, respectively. Analysis shows that a polydisperse‐type flux‐balance model, that equates erosional and depositional fluxes and where erosion is related to the power used to lift sediment mass from the bed (the 'Flow‐Power Flux‐Balance' model) provides predictions most consistent with observational data. Other equilibrium models tested, monodisperse or polydisperse, fail to predict realistic bed slopes and/or flow durations for concentrations, velocities and depths within limits for natural flows. Results of the Flow‐Power Flux‐Balance model are used to quantify sediment transport fields, equilibrium Shields numbers and slopes for turbidity currents of variable flow and particle properties. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the control method proposed in this paper is to address the problem of the poor anti-interference of the suspension winding current in the traditional bearingless induction motor (BL-IM) direct suspension force control process. Design/methodology/approach: A model predictive direct suspension force control of a BL-IM based on sliding mode observer is proposed in this paper. The model predictive control (MPC) is introduced to the traditional direct suspension force control to improve the anti-interference of the suspension current. A sliding mode flux linkage observer is designed and applied to the MPC system, which reduces the error of the parameter observation and improves the robustness of the system. The strategy is designed and implemented in the MATLAB/Simulink and the two-level AC speed regulation platform. Findings: The simulation and experimental results show that the performance of the BL-IM under the control method proposed in this paper is better than that under the traditional direct suspension force control, and the suspension performance of the motor and the anti-interference of the control system are improved. Originality/value: This study helps to improve the suspension performance of the motor and the anti-interference of the control system. [ABSTRACT FROM AUTHOR]

Sedimentological features of the Upper Cambrian–Middle Ordovician rocks exposed in eastern Taimyr in the Faddey Gulf area are discussed. The studied sections belong to the transitional facies zone located between the carbonate platform (Siberian Platform continuation) in the south and a relatively deep-water basin in the north. The studied deposits compose a genetically coherent sequence formed in the distal zone of the siliciclastic–carbonate ramp at a depth exceeding the storm wave base. The lower (Upper Cambrian–lowermost Ordovician) part of the sequence is represented by limestones, dolomitized carbonate siltstones, and sandstones with shale layers. The upper (Lower–Middle Ordovician) part of the studied interval is dominated by shales with thin layers of carbonate siltstones. The carbonate detritus was sourced from a shallow-water shelf located south of the studied sections. The siliciclastic admixture in carbonate siltstones and sandstones was sourced from an island in the northern part of the modern Siberian Platform. The sandy material was transported by storm bottom currents; the fine-grained particles, by surface currents and winds as particulates and suspension clouds in the bottom water. Carbonate sandstones with the typical turbidite sedimentary structures, common in the lower part of the section, were deposited by turbidity currents initiated by storms. At that time, a prominent break likely existed in the ramp profile. The predominant NE orientation of flute casts indicates the alongslope (or along the trough axis) transport of material by bottom currents. The ramp topography was leveled in the second half of the Early Ordovician and in the Middle Ordovician. [ABSTRACT FROM AUTHOR]

The flow field in the Toyama Deep-Sea Channel (TDSC) in the Japan Sea was investigated based on mooring observations. An asymmetric current system accompanying offshore and onshore currents over the east- and west-side slopes in the channel, respectively, is suggested. A bottom intensified flow characteristic was observed at the offshore stations in the Yamato Basin. The asymmetric current system in the channel is also suggested by the asymmetric distribution of water characteristics across the TDSC in Toyama Bay; a cold dense water mass with higher dissolved oxygen (DO) and higher transmittance (Tr) was found over the west-side slope of the channel, whereas a water mass with lower DO and lower Tr was distributed over the east-side slope, suggesting a turbidity current from the head of Toyama Bay. The currents facing the shallower depth on their right-hand-side, along with the density distribution in the TDSC, suggest a density current system under the influence of the earth's rotation. The dissolved oxygen concentration in the TDSC was significantly lower than that in the offshore region of the same temperature range. This suggests that the water mass over the west-side slope in the TDSC is a modified offshore water mass which experienced significant mixing with the low DO water mass over the east-side slope in the TDSC, probably due to strong shear between the offshore and onshore currents in the narrow channel. [ABSTRACT FROM AUTHOR]

The article explores the general stratigraphic notion of a gross incompleteness of sedimentary record may then extend down to the deposition time scale of a single turbidite. It mentions that deposition of a classic turbidite by a surge-type turbidity current, as envisaged by conceptual models, as widely considered a discrete event of continuous sediment accumulation at a falling rate by the gradually waning density flow.