Modeling of submarine cyclic steps: Controls on their formation, migration, and architecture

Kostic, Svetlana

doi:10.1130/ges00601.1

Cited by 139 publications

(205 citation statements)

References 64 publications

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“…Upslope-migrating crescent-shaped bedforms with wavelengths of tens to hundreds of meters are common in canyon and channel heads in both marine and freshwater locations worldwide (Figs 1, 2, 5; Paull et al 2010aPaull et al , 2013Kostic 2011;Girardclos et al 2012;Hill 2012;Covault et al 2014;Hughes Clarke et al 2012, 2014. Such crescentic bedforms can indeed be associated with supercritical flows, as illustrated by the most recent observations presented at the workshop by Hughes Clarke from the Squamish delta.…”

Section: (B) Supercritical-flow Dynamics and Depositsmentioning

confidence: 80%

“…However, features including top-cut-out Bouma sequences, backset bedding, facies associated with shallow scours, and rapid pinch-out of beds could be formed by cyclic steps within supercritical flows ( Fig. 6; Postma et al 2009;Cartigny et al 2011Kostic 2011;. Other bedforms in the supercritical regime include a variety of antidunes (Middleton 1965;Hand 1974;).…”

Section: (B) Supercritical-flow Dynamics and Depositsmentioning

confidence: 99%

“…Recent flume and numerical models indicate that supercritical flows can produce upstream-migrating asymmetric bedforms with a wide range of scales (Figs. 5, 6;Sun and Parker 2005;Kostic and Parker 2006;Fildani et al 2006;Spinewine et al 2009;Cartigny et al 2011;Kostic 2011;). They provide a potential explanation for bedforms seen in fjord-head deltas (Figs.…”

Section: (B) Supercritical-flow Dynamics and Depositsmentioning

confidence: 99%

“…What is the role of these bedforms in initiating, filling, and maintaining submarine channels and canyons Covault et al 2014)? The field of morphodynamics is exploring how flow structure and bed morphology may coevolve (Sun and Parker 2005;Kostic 2011;Parker 2013;. Are large sandy and gravelly bedforms in deeper-water channels (Wynn et al 2002) of similar origin?…”

Section: (B) Supercritical-flow Dynamics and Depositsmentioning

confidence: 99%

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Key Future Directions For Research On Turbidity Currents and Their Deposits

Talling

Allin

Armitage

et al. 2015

Journal of Sedimentary Research

163

117

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Turbidity currents, and other types of submarine sediment density flow, redistribute more sediment across the surface of the Earth than any other sediment flow process, yet their sediment concentration has never been measured directly in the deep ocean. The deposits of these flows are of societal importance as imperfect records of past earthquakes and tsunamogenic landslides and as the reservoir rocks for many deep-water petroleum accumulations. Key future research directions on these flows and their deposits were identified at an informal workshop in September 2013. This contribution summarizes conclusions from that workshop, and engages the wider community in this debate. International efforts are needed for an initiative to monitor and understand a series of test sites where flows occur frequently, which needs coordination to optimize sharing of equipment and interpretation of data. Direct monitoring observations should be combined with cores and seismic data to link flow and deposit character, whilst experimental and numerical models play a key role in understanding field observations. Such an initiative may be timely and feasible, due to recent technological advances in monitoring sensors, moorings, and autonomous data recovery. This is illustrated here by recently collected data from the Squamish River delta, Monterey Canyon, Congo Canyon, and offshore SE Taiwan. A series of other key topics are then highlighted. Theoretical considerations suggest that supercritical flows may often occur on gradients of greater than , 0.6u. Trains of up-slope-migrating bedforms have recently been mapped in a wide range of marine and freshwater settings. They may result from repeated hydraulic jumps in supercritical flows, and dense (greater than approximately 10% volume) near-bed layers may need to be invoked to explain transport of heavy (25 to 1,000 kg) blocks. Future work needs to understand how sediment is transported in these bedforms, the internal structure and preservation potential of their deposits, and their use in facies prediction. Turbulence damping may be widespread and commonplace in submarine sediment density flows, particularly as flows decelerate, because it can occur at low (, 0.1%) volume concentrations. This could have important implications for flow evolution and deposit geometries. Better quantitative constraints are needed on what controls flow capacity and competence, together with improved constraints on bed erosion and sediment resuspension. Recent advances in understanding dilute or mainly saline flows in submarine channels should be extended to explore how flow behavior changes as sediment concentrations increase. The petroleum industry requires predictive models of longer-term channel system behavior and resulting deposit architecture, and for these purposes it is important to distinguish between geomorphic and stratigraphic surfaces

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Section: (B) Supercritical-flow Dynamics and Depositsmentioning

confidence: 80%

Section: (B) Supercritical-flow Dynamics and Depositsmentioning

confidence: 99%

Section: (B) Supercritical-flow Dynamics and Depositsmentioning

confidence: 99%

Section: (B) Supercritical-flow Dynamics and Depositsmentioning

confidence: 99%

See 2 more Smart Citations

Key Future Directions For Research On Turbidity Currents and Their Deposits

Talling

Allin

Armitage

et al. 2015

Journal of Sedimentary Research

163

117

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“…Supercritical turbidity currents are defined by the densimetric Froude number, Fr d , exceeding unity (Fr d =U/√g'h, where U is velocity, g' is reduced gravitational acceleration, and h is depth of a current). Cyclic steps are long-wave (the ratio of wavelength to height is >>1), upstreammigrating bedforms, commonly with asymmetrical waveforms in cross section, which develop in regions with high gradients and slope breaks that promote repeated internal hydraulic jumps in an overriding turbidity current (Kostic, 2011). These bedforms have been documented in fieldscale observations combined with morphodynamic modeling (e.g., Fildani et al, 2006;Kostic, 2011;Covault et al, 2014), physical experiments (e.g., Spinewine et al, 2009), direct monitoring of turbidity currents (e.g., Hughes Clarke, 2016), and recently in outcrops .…”

Section: Submarine-channel Faciesmentioning

confidence: 99%

The Stratigraphic Record of Submarine-Channel Evolution

Covault¹,

Sylvester²,

Hubbard³

et al. 2016

TSR

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Is it appropriate to model turbidity currents with the three‐equation model?

Pähtz

2015

JGR Earth Surface

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The three-equation model (TEM) was developed in the 1980s to model turbidity currents (TCs) and has been widely used ever since. However, its physical justification was questioned because self-accelerating TCs simulated with the steady TEM seemed to violate the turbulent kinetic energy balance. This violation was considered as a result of very strong sediment erosion that consumes more turbulent kinetic energy than is produced. To confine bed erosion and thus remedy this issue, the four-equation model (FEM) was introduced by assuming a proportionality between the bed shear stress and the turbulent kinetic energy. Here we analytically proof that self-accelerating TCs simulated with the original steady TEM actually never violate the turbulent kinetic energy balance, provided that the bed drag coefficient is not unrealistically low. We find that stronger bed erosion, surprisingly, leads to more production of turbulent kinetic energy due to conversion of potential energy of eroded material into kinetic energy of the current. Furthermore, we analytically show that, for asymptotically supercritical flow conditions, the original steady TEM always produces self-accelerating TCs if the upstream boundary conditions ("ignition" values) are chosen appropriately, while it never does so for asymptotically subcritical flow conditions. We numerically show that our novel method to obtain the ignition values even works for Richardson numbers very near to unity. Our study also includes a comparison of the TEM and FEM closures for the bed shear stress to simulation data of a coupled Large Eddy and Discrete Element Model of sediment transport in water, which suggests that the TEM closure might be more realistic than the FEM closure.

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Modeling of submarine cyclic steps: Controls on their formation, migration, and architecture

Cited by 139 publications

References 64 publications

Key Future Directions For Research On Turbidity Currents and Their Deposits

Key Future Directions For Research On Turbidity Currents and Their Deposits

The Stratigraphic Record of Submarine-Channel Evolution

Is it appropriate to model turbidity currents with the three‐equation model?

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