Jeff Peakall’s research while affiliated with University of Leeds and other places

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Publications (201)


Fig. 3. Grain-size distribution plots. (A) The sediment trap at the M1 mooring site of Heijnen et 140
Fig. 4. Fourier transform infrared (FTIR) spectroscopy spectra and microscope photographs of 202
Fig. 5. (A-D) Core photographs and X-ray scans of the box-cores used in 210 Pb dating. (E-H) the 228
Fig. 6. Box plot for microfibre concentration and sediment depth for all push-cores. 244
Fig. 8. Photographs taken of seabed push-core sampling from the Remotely Operated Vehicle. (A) 293

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Untangling microfibres: Pervasive plastic pollution in submarine canyons
  • Preprint
  • File available

January 2025

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66 Reads

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Ian Kane

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Submarine canyons are important conduits for microplastic transport to the deep sea via turbidity currents. However, other near-bed oceanographic flows and sub-seafloor processes may play an important role in the transport and burial of microplastics. We use sediment push-cores for microplastic and sediment grain-size analysis from two transects across the Whittard Canyon, UK, to show that complex process-interactions control the transport and burial of microplastics and semi-synthetic microfibres in the thalweg and on the canyon flanks. Microplastic pollution is pervasive across the canyon at both transects, from the thalweg and from 500 m higher on the flanks, despite turbidity currents being confined to the canyon thalweg. Furthermore, we calculate sediment accumulation rates from 210Pb dating and show that microplastic concentrations remain similar at sediment depths down to 10 cm. This reveals that the huge global-increase in plastic production rates over time is not recorded, and that microplastics are present in sediments that pre-date the mass-production of plastic. The interaction of turbidity currents, deep-tidally-driven currents, and sub-seafloor processes shreds any potential signal that microplastics may provide as indicators of historical plastic production rates, which undermines the utility of microplastics as reliable markers of the onset of the Anthropocene.

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Fig. 3c. (A-B) Plots of non-dimensional maximum run-up distance and height of the density
Fig. 6. Numerical model results for the normalised maximum run-up height of turbidity
Fig. 7. Schematic diagram illustrating the characteristics of maximum run-up height potential
Challenging the turbidity current maximum run-up height paradigm

December 2024

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94 Reads

Turbidity currents are a primary mechanism for transporting sediments, pollutants, and organic carbon into the deep ocean. They are strongly influenced by seafloor topography because of their relative bulk density and associated gravitational influence being 3-4 orders of magnitude smaller than in terrestrial systems. Marked run-up of turbidity currents on slopes poses a hazard to seafloor infrastructure, and leads to distinctive depositional patterns, yet the prediction of run-up heights remains poorly understood because the present calculations are derived from 2D experimental configurations and/or numerical modelling and merely limited to scenarios in which the flow strikes the topographic barriers orthogonally. Here we present the results of 3D experiments in unconfined settings that are used to develop a new analytical model that improves the prediction of maximum run-up heights of turbidity currents that encounter topographic slopes of varying gradients and flow incidence angles. We show that existing predictive models based on 2D confined flows focusing on frontal topographic configurations underestimate the run-up heights of turbidity currents by approximately 15-40%. Experimental results highlight the importance of considering the energy contribution from internal pressure in the fluid, and lateral flow expansion and divergence in unconfined flows. Our findings reveal that intermediate slope gradients (ca. 30°) and (near-)perpendicular flow incidence angles generate the highest run-up heights, up to 3.3 times the flow thickness. Novel analytical models are presented subsequently for predicting maximum run-up height as a function of both the gradient and incidence angle, comparing the models to the newly observed data. Such models provide relatively more realistic estimates of run-up heights for flows on three-dimensional slopes typical of natural systems. These findings are critical for improving sediment transport models, predicting the distribution of sediments, pollutants, and organic carbon in deep-sea environments, assessing seafloor geohazards, and reconstructing ancient deep-water basin palaeogeographies.


Preservation of groove mark striae formed by armoured mud clasts: The role of armour sediment size and bed yield stress

September 2024

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93 Reads

Striated grooves in tool marks are common at the base of sandstones, especially in deep‐marine successions, but their use in physical‐process and environmental reconstruction is underdeveloped. To fill this gap in knowledge, striations in the central groove of chevron marks and in chevron‐less groove marks were formed in the laboratory by dragging tools armoured with silt, sand or gravel across muddy substrates. These experiments simulated the formation of striated grooves by armoured mud clasts carried at the base of quasi‐laminar and fully laminar debris flows, aiming to: (1) delineate the bed shear strengths for the formation of striated grooves at different armour sediment sizes; (2) examine how the preservation potential of striated grooves depends on clay bed rheology and size of armour sediment and (3) discuss how the pre‐lithification clay bed consolidation state and size of armour sediment can be reconstructed from striated grooves in the geological record. The experimental results revealed that tools with small‐diameter silt and sand armours dragged along soft beds lack striations or, at best, leave poorly defined striations, whereas firm beds and gravel armours exhibit well‐defined striations. The spacing of striations formed by gravel clasts corresponds well with the clast diameter, implying that striation spacing is a good proxy for the diameter of armoured gravel under natural conditions. In contrast, the spacing of striae formed by sand armours is greater than the grain diameter, suggesting that the spacing of fine striations can only be used to predict a maximum armour sand size. A comparison of different processes of formation of armoured mud clasts demonstrated that the armouring of mud clasts most probably happens after incorporation of the clasts by erosion into the head of the debris flow and subsequent movement across a loose sandy or gravelly bed surface.


Flow‐induced interfacial deformation structures ( FIDS ): Implications for the interpretation of palaeocurrents, flow dynamics and substrate rheology

July 2024

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155 Reads

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1 Citation

Sedimentology

Sole structures on the base of turbidites, and other bed types, are typically classified into scour marks and tool marks, such as flutes, grooves, skim marks and prod marks. Yet, there are a range of other common sole marks that are unrelated to scouring or tools, and whose origin is poorly understood. Prominent among these sole structures are longitudinal ridges and furrows, and ‘dinosaur leather’ structures associated with mud ripples. Herein, these features are described and it is argued that they are the product of deformation of the substrate during a sediment gravity flow event. In these flow‐induced interfacial deformation structures (FIDS), a soft cohesive substrate undergoes deformation in response to a buoyant force induced by the denser basal component of an overriding flow, and the flow interacts with this buoyant deformation through shear to remould the substrate. Variations in the relative strength of these buoyant and shear‐induced forces explain the wide range of FIDS that can form. This FIDS model reinterprets the formation of longitudinal ridges and furrows, which have previously been classified as scour marks, and explains their distinctive spatial patterns. Furthermore, the new model builds on the seminal work of Dżułyński and colleagues in the 1960s and 1970s, who identified that these structures contain key palaeocurrent information, and it is argued that such information is largely under‐utilized. Importantly, alongside their utility as palaeocurrent indicators, FIDS provide insights into the rheology of the substrate at the time of their formation, and thus the nature of basal flow conditions in the formative flows.


Evolving fill‐and‐spill patterns across linked early post‐rift depocentres control lobe characteristics: Los Molles Formation, Argentina

June 2024

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149 Reads

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6 Citations

Sedimentology

Inherited rift topography controls the sediment routing, timing of sand supply, and sedimentary linkage of early post‐rift depocentres. Exhumed examples of early post‐rift turbidite systems are rare and previous studies have examined the evolution of individual depocentres; in contrast, the detailed evolution of early post‐rift turbidite systems across multiple depocentres has never been documented. Current fill‐and‐spill models do not detail the stratigraphic architecture and evolution of sedimentological characteristics of multiple intraslope fans developed across topography, including bed type distributions. Here, the evolution of three intraslope fans that developed across two early post‐rift depocentres is documented along an 18 km long transect in the southern Neuquén Basin, Argentina. The relative chronology of sand supply in depocentres is constrained with new U–Pb ages, and sediment source areas with provenance analysis. The early post‐rift intraslope fans record progradation of the system and progressive sedimentary linkage of post‐rift depocentres, transverse to local syn‐rift structures, with sediment routing subparallel to the cratonic basin margin. The large‐scale stratigraphic architecture of intraslope fans indicates an evolution as a fill‐and‐spill system, with initial confinement through flow stripping and overspill to spillover with erosion and bypass across a transverse topographic high separating the depocentres. Changes in early post‐rift intraslope fan characteristics, including thickness, sandstone content, lobe complex stacking patterns, stratal termination patterns and bed type distribution, record changing confinement through time within a depocentre, and spatially across depocentres. The strong spatial and vertical stratigraphic variability of transitional flow deposits and hybrid event beds reflects enhanced erosion, sediment bypass and flow transformation across transverse relief between the two depocentres during the spillover phase. These findings advance current understanding of early post‐rift turbidite systems and refine fill‐and‐spill models, which will help the prediction of spatial and vertical changes in rock quality and connectivity in subsurface hydrocarbon reservoirs and CO 2 storage sites.


Evolution and architecture of an overbank in an ocean-facing canyon-fill.

May 2024

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105 Reads

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1 Citation

Submarine canyon-fills comprise substantial volumes of thin-bedded successions deposited by sediment gravity flows that are either stripped or overspill from adjacent channels into highly confined, topographically complex overbank settings. Here, we document the Punta Baja Formation, a rare example of an exhumed canyon-confined overbank succession with good 3D constraints from the Mesozoic Peninsular Ranges Forearc, Mexico. High-resolution sedimentary logging and drone-captured photogrammetric models reveal that the overbank was a highly dynamic environment, where different bed types point to a variety of flow transformations and complex topographical interactions that evolved through time. The lower overbank is characterised by variable bed thicknesses, grain-sizes and palaeocurrent directions, which point to a wide range of unfiltered flows that overspilled from channels. Thick sandstone beds contain distinct hummock-like bedforms, representing high energy combined flows that repeatedly deflected and reflected against the high relief canyon margin, suggesting complete confinement within the conduit. Locally, thinner beds are disrupted by slides, debrites and scour surfaces on the canyon floor. As the canyon system matured, constituent channels migrated laterally and aggraded. Here, the character of the overbank changes, developing distinct fining- and thinning-upward packages that decay in thickness and grain-size away from the channel axis. Packages are more mud-rich and beds contain mixed grain-size bedforms indicating smaller magnitude, rapidly decelerated transitional flows that failed to interact with the canyon margin. In more quiescent parts of the upper overbank, beds containing rhythmic bundles of silt-rich, mud-draped bedforms are interpreted to be the product of sediments reworked by internal tides. This is the first detailed study of fine-grained fills in an ancient ocean-facing submarine canyon. Canyon-confined overbanks offer a more diverse fill, with flow transformations that demonstrate a complex balance between erosion and deposition, and an absence of discrete internal levée or depositional terrace elements that have been identified in more distal confined overbank settings.


Unconfined turbidity current interactions with oblique slopes: deflection, reflection and combined-flow behaviours

May 2024

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31 Reads

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1 Citation

What is the nature of flow reflection, deflection and combined-flow behaviour when gravity flows interact with slopes? In turn, how do these flow dynamics control sedimentation on slopes? Here, these questions are addressed using physical experiments, with low-density unconfined gravity flows interacting with slopes of varying gradients, at a range of flow incidence angles. The present paradigm for gravity current interaction with slopes was based on experiments with high-density flows, conducted in narrow 2D flume tanks, in small (1 m2 planform) 3D tanks, or in large 3D tanks where flows can surmount the topography. Here, larger-scale physical experiments were undertaken in unconfined settings where the flow cannot surmount a planar topographic slope. The experiments show that the dominant flow-process transitions from divergence-dominated, through reflection-dominated to deflection-dominated as the flow incidence angle varies from 90° to 15° and the slope gradient changes from 20° to 40°. Also, patterns of velocity pulsing at the base of, and on, the slope vary as a function of both the flow incidence angle and slope gradient. Furthermore, in all configurations complex multidirectional combined flows are observed on, or at the base of, the slope, and are shown to vary spatially across the slope. The findings challenge the paradigm of flow deflection and reflection in existing flow-topography process models that has stood for three decades. A new process model for flow-slope interactions is presented, that provides new mechanics for the frequent observation of palaeocurrents from sole marks at high angles to those in the associated ripple division. Results provide insights into the formation and spatial distribution of distinctive combined-flow bedforms, sediment dispersal patterns, and process controls on onlap termination styles in deep-sea settings, which can be applied to refine interpretations of exhumed successions.


Unconfined gravity current interactions with orthogonal topography: Implications for combined-flow processes and the depositional record.

February 2024

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236 Reads

Turbidity current behaviour is affected by interactions with seafloor topography. Changes in flow dynamics will depend on the physiographic configuration of the topography (orientation and gradient), and the character of the incoming flow (magnitude and rheology). A better understanding of how unconfined turbidity currents interact with topography will improve interpretations of the stratigraphic record; we address this using 3D flume tank experiments with unconfined saline density currents interacting with a ramp orientated perpendicular to flow direction. The incoming flow parameters remained constant, whilst the slope angle was independently varied. On a 20 slope, super-elevation of the flow and flow stripping of the upper, dilute region of the flow occurred high on the slope surface. This resulted in a strongly divergent flow and the generation of complex multidirectional flows (i.e., combined flows). The super-elevation and extent of flow stripping decreased as the slope angle increased. At 30 and 40, flow reflection and deflection, respectively, are the dominant flow process at the base of slope, with the reflected or deflected flow interacting with the parental flow, and generating combined flows. Thus, complicated patterns of flow direction and behaviour are documented even on encountering simple topographies; a planar slope orientated perpendicular to flow direction. Combined flows in deep-water settings have been linked to the interaction of turbidity currents with topography and the formation of internal waves with a dominant oscillatory flow component. Here, combined flow occurs in the absence of an oscillatory component. A new process model for the formation and distribution of hummock-like bedforms in deep-marine systems is introduced. This bedform model is coupled to a new understanding of the mechanics of onlap styles (draping versus abrupt pinchout) and triggers for soft-sediment deformation processes to produce a spatial model of gravity-current interaction, and deposition, on slopes to support palaeogeographic reconstructions.


Unidirectional and combined transitional flow bedforms: Controls on process and distribution in submarine slope settings

February 2024

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146 Reads

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8 Citations

Sedimentology

Mixed grain‐size bedforms comprise alternating sand‐rich and poorly sorted mud‐rich laminae and bands. These bedforms have been identified in distal submarine settings formed underneath unidirectional flows. This study documents mixed grain‐size bedforms in a proximal submarine slope setting formed beneath both unidirectional and combined flows. Core and outcrop data with well‐constrained palaeogeographical context are used to describe two types of mixed grain‐size bedform. Type A bedforms comprise mud‐rich current ripples and low‐amplitude bed‐waves with alternating concave and planar sandstone–mudstone foresets that pass into mud‐rich troughs, and aggradational sinusoidal laminasets. Type B bedforms consist of sandstone–mudstone laminasets that comprise rounded, biconvex ripples with sigmoidal‐shaped foresets and swale and hummock‐like laminasets and banded sets. These bedforms occur in channel‐margin, internal‐levée and external‐levée, intraslope and disconnected lobe environments, and represent 27 to 63% by stratigraphic thickness of the studied successions. They are interpreted as deposits of clay‐rich transitional flows, whose depositional style is governed by the balance of cohesive and turbulent forces, and the rate of flow deceleration. Type B bedforms are further interpreted as combined transitional flow deposits, resulting from flow deflection and ponding processes by seabed topography. Upward and lateral transitions between different bedforms create distinct bedform sequences, demonstrating progressive spatio‐temporal transformations in flow properties and their topographic interactions. By using a well‐constrained palaeogeographical setting, mixed grain‐size bedforms are shown to be situated close to sites of erosion into muddy substrates, abrupt losses in confinement, and/or changes in slope gradient. These bedforms demonstrate that flow transformation and transitional flow behaviour are not restricted to distal submarine settings. Furthermore, mixed grain‐size bedforms are not a diagnostic criterion for bottom currents, because such flows cannot account for the high mud content in laminasets, or the interlamination of sand and mud.


Benthic biology influences sedimentation in submarine channel bends: Coupling of biology, sedimentation and flow

January 2024

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88 Reads

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2 Citations

Submarine channels are key features for the transport of flow and nutrients into deep water. Previous studies of their morphology and channel evolution have treated these systems as abiotic, and therefore assume that physical processes are solely responsible for morphological development. Here, a unique dataset is utilised that includes spatial measurements around a channel bend that hosts active sediment gravity flows. The data include flow velocity and density, alongside bed grain size and channel‐floor benthic macrofauna. Analysis of these parameters demonstrate that while physical processes control the broadest scale variations in sedimentation around and across the channel, benthic biology plays a critical role in stabilising sediment and trapping fines. This leads to much broader mixed grain sizes than would be expected from purely abiotic sedimentation, and the maintenance of sediment beds in positions where all the sediment should be actively migrating. Given that previous work has also shown that submarine channels can be biological hotspots, then the present study suggests that benthic biology probably plays a key role in channel morphology and evolution, and that these need to be considered both in the modern and when considering examples preserved in the rock record.


Citations (67)


... Elongate sedimentary structures at the base of sandstone beds have been used routinely for reconstructing palaeocurrent directions since the 19th century (Hall, 1843). Known generically as sole marks (Dżułyński & Sanders, 1962;Peakall et al., 2020Peakall et al., , 2024, these structures can be formed by: (a) flow-induced scouring, mostly resulting in flute marks (Crowell, 1955;Allen, 1968Allen, , 1984Dżułyński & Walton, 1965;Enos, 1969;Collinson et al., 2006); (b) flow-induced deformation of a soft substrate, generating, for example, longitudinal ridges and furrows (Craig & Walton, 1962;Dżułyński & Walton, 1965;Anketell et al., 1970) and 'dinosaur leather' structures (Chadwick, 1948) and (c) objects in the flow that interact with the substrate, forming continuous tool marks, for example, groove and chevron marks (Shrock, 1948;Kuenen & Sanders, 1956;Dunbar & Rodgers, 1957;Kuenen, 1957;Dżułyński & Ślączka, 1958;Dżułyński & Walton, 1963;Collinson et al., 2006) and discontinuous tool marks, for example, skip, skim and prod marks (Dżułyński & Ślączka, 1958;Wood & Smith, 1958;Dżułyński et al., 1959;Allen, 1984). Palaeocurrent direction can be reconstructed from asymmetrically shaped sole marks; these include flutes, 'scaled' longitudinal furrows (Craig & Walton, 1962;Dżułyński & Walton, 1965), chevron marks and prod marks. ...

Reference:

Preservation of groove mark striae formed by armoured mud clasts: The role of armour sediment size and bed yield stress
Flow‐induced interfacial deformation structures ( FIDS ): Implications for the interpretation of palaeocurrents, flow dynamics and substrate rheology
  • Citing Article
  • July 2024

Sedimentology

... The structure of many continental margins reflects a competition between the dynamics of mobile substrates (Hudec and Jackson, 2007;Soto et al., 2021) and the processes that control sediment transport and deposition (Pirmez et al., 2000;Prather, 2003;Straub and Mohrig, 2009;Mitchell et al., 2021;Privat et al., 2024). Here, mobile substrates include uncompacted shales (van Rensbergen et al., 1999;Dinc et al., 2023) and salt (Hudec and Jackson, 2007) that can undergo ductile deformation if an overburden exceeds a critical mass for geological time scales. ...

Evolving fill‐and‐spill patterns across linked early post‐rift depocentres control lobe characteristics: Los Molles Formation, Argentina
  • Citing Article
  • June 2024

Sedimentology

... Thus, mean-flow dissipation is relevant at the Reynolds numbers of all geophysical currents. The data from channel flow considered so far is all from smooth channels, and particulate gravity currents always flow over a rough bed, the roughness appearing at the particle scale and (for environmental currents) at the sales of benthic fauna and bed-forms Sen et al. 2017;Azpiroz-Zabala et al. 2024). A large body of research exists into flow over rough beds, see the recent review of Kadivar et al. (2021). ...

Benthic biology influences sedimentation in submarine channel bends: Coupling of biology, sedimentation and flow

... Hummocky bedding is multi-genetic and can form in a range of environments (Prave & Duke, 1990;Tinterri, 2011). Hummocky bedding can be found in storm-influenced shoreface and offshore settings (Walker et al., 1983), deltas (Mutti et al., 2000), as well as deep-marine slopes and basins in sediment gravity flow deposits (Prave & Duke, 1990;Mulder et al., 2009;Tinterri, 2011;Taylor et al., 2024). Hummocky bedding can form under a range of processes (Prave & Duke, 1990;Tinterri, 2011), though is frequently attributed to combined flow (Dumas & Arnott, 2006;Perillo et al., 2014;Taylor et al., 2024;Wu et al., 2024;Fig. ...

Unidirectional and combined transitional flow bedforms: Controls on process and distribution in submarine slope settings
  • Citing Article
  • February 2024

Sedimentology

... Despite the widespread anoxia, several studies have successfully tracked pulsed or pervasively oxic intermediate waters in the Mesoproterozoic ocean, making the ocean redox states of this time more enigmatic [6][7][8]18,19 . Distinct hypotheses have been put forward to interpret these mid-depth water oxygenation events, including fluctuating ocean oxygenations 7,19 , low oxygen consumption due to a weak biological pump 6,20 , and variations of ocean redox structures forced by climate dynamics 18 . ...

Dynamic redox and nutrient cycling response to climate forcing in the Mesoproterozoic ocean

... Cohesion limited sediment transport along the furrows (figure 4e), while enhancing lateral propagation of momentum. This is also observed in some Cambrian trace fossils (figure 1d), with the absence of rheological chevron marks [66] indicating the discrete nature of the sediments. This differs considerably from the results for submerged traces (figure 4f), which were characterized by negligible lateral contact forces (one order of magnitude smaller) and V-shaped cross-sections ( figure 4b,d). ...

On the origin of chevron marks and striated grooves, and their use in predicting mud bed rheology
  • Citing Article
  • October 2023

Sedimentology

... In addition to the timing of this deposit, evidence of onshore deposits (Bondevik et al., 2003;Dawson et al., 1988;Dawson and Smith, 2000), wave heights (A. Dawson et al., 2020;Hill et al., 2023;Woodroffe et al., 2023) and offshore flow velocities (Bondevik et al., 2024) of the Storegga tsunami on Shetland and Northern Scotland, leads us to propose that this event generated the deposit observed in this study. This proposal is supported further by the physical and geochemical characteristics of sub-units e12 and e13. ...

Resolving tsunami wave dynamics: Integrating sedimentology and numerical modelling

... This variability in This is non-peer reviewed preprint submitted to EarthArxiv 47 the contrast between the velocity, and the concentration and grainsize layers (e.g., Patacci et al., 760 2015). From experimental modelling of 2D gravity currents, internal wave formation has also 761 been observed to occur at a critical layer within the body of gravity currents, at the height of the 762 maximum internal velocity, thus suggesting the 'steady' body of gravity currents has inherent 763 instabilities in the form of internal waves and may not be as steady as first assumed (e.g., 764 Marshall et al., 2021Marshall et al., , 2023. Whether the same mechanism for internal wave generation (e.g., part, these are analogous to isotropic hummocky-cross stratification, although the absence of 800 cross-cutting relationships is in marked contrast to true HCS (Harms, 1969). ...

On the role of transverse motion in pseudo-steady gravity currents

Experiments in Fluids

... From the available 2N threads, each of the first N threads compute ϕ i (r) and ∂ϕ i (r)/∂r for a single i, and each of the next N threads compute ϕ j (s) and ∂ϕ j (s)/∂s for a single j. Next, the first N threads effect the inner summation corresponding to a fixed i for both terms of (30), and the next N threads similarly effect the inner summation for (31). ...

Multi-fidelity modelling of shark skin denticle flows: insights into drag generation mechanisms

... The Rossby number is defined as Ro=U/fL, with mean velocity U, Coriolis frequency f and length scale L. The Coriolis frequency f is defined as f = 2ωsin(ϕ), with angular velocity ω and latitude ϕ. While the influence of the Coriolis force on moats is still unknown, its influence on submarine channels that develop due to downslope flowing turbidity currents has been demonstrated (Cossu and Wells 2010;Wells and Cossu 2013;Allen et al., 2022). For submarine channels, field observations show a latitudinal dependence on sinuosity (Wells and Cossu 2013;Allen et al., 2022). ...

Latitudinal changes in submarine channel-levee system evolution, architecture and flow processes