Morphodynamics of submarine channel inception revealed by new experimental approach

Leeuw, Jan de; Eggenhuisen, Joris T.; Cartigny, Matthieu

doi:10.1038/ncomms10886

Cited by 83 publications

(122 citation statements)

References 40 publications

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“…Under a robust set of choices of slope and grain size, we find in numerical simulations that levees form bounding a channel of focused flow. It is not necessary to posit a preexisting scour or depression in the sediment base to observe the formation of these levees, in agreement with recent laboratory‐scale experiments of De Leeuw et al (). These levees have a characteristic right‐angled triangular shape and exhibit clear systematic variations with slope and grain size.…”

Section: Introductionsupporting

confidence: 87%

Levees Formed by Turbidity Currents: A Depth‐Averaged Modeling Treatment

Halsey

Kumar

2019

JGR Oceans

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The formation of levees with accompanying channels is a ubiquitous feature of turbidity flows both in submarine canyons and on submarine fans. We examine the latter situation using numerical and theoretical calculations based on a depth‐averaged model for subaqueous turbidity currents, introduced by Parker et al. (1986, https://doi.org/S0022112086001404) and reinterpreted by Halsey et al. (2017, https://doi.org/10.1002/2016JC012635). Using a novel similarity solution to these equations, applied to a two‐component sand/mud flow, we show that in a well‐defined limit levees form along rays emanating from the source of the flows, which in our case is the outlet of a submarine canyon. The width of the channel between the levees decreases as particle size increases and increases with increasing slope of the surface. The levees form with a characteristic right‐triangle shape, with the steep slope facing inward toward the channel. The levee height is comparable to the height of the turbidity flow. Levees form even in the absence of preexisting scour. We confirm these analytical results with numerical simulations of the depth‐averaged equations. Further downslope, the formation of levees seems to be inconsistent with an erosion law introduced by Garcia and Parker (1991, 10.1061/(ASCE)0733-9429(1991)117:4(414)), calling the applicability of this law to natural systems into question.

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Section: Introductionsupporting

confidence: 87%

Levees Formed by Turbidity Currents: A Depth‐Averaged Modeling Treatment

Halsey

Kumar

2019

JGR Oceans

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“…Flow confinement is an important process for channel initiation and it can be achieved by channel incision and levee construction (e.g., Straub and Mohrig 2009;Rowland et al 2010;Weill et al 2014;De Leeuw et al 2016). In addition to these studies, we suggest that flow confinement and channelization could also be a result of flowcapture processes.…”

Section: A Mechanism For Channel Initiationmentioning

confidence: 99%

The Role of Mass Wasting In the Progressive Development Of Submarine Channels (Espírito Santo Basin, Se Brazil)

Qin

Alves

Constantine

et al. 2017

Journal of Sedimentary Research

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ABSTRACT:A Pliocene-Quaternary submarine channel system, influenced by a localized mass wasting, is investigated in this work using high-resolution 3D seismic data from offshore Espírito Santo Basin, SE Brazil. Three abandoned channels, a channel belt and an mass-transport deposit (MTD) are recognized in the channel system within a confluence region confined by salt diapirs. In this confluence region, the cross-sectional area (CSA) of the channel system can be up to 1.2 km 2 , i.e., 4 to 10 times larger than CSA in other parts of the channel system. Such significant changes in the architecture and morphology of the channel system resulted from the interaction between mass-wasting processes and turbidity flows. We postulate that a basal erosional scar was created by mass-wasting processes and was filled with an MTD. This basal scar was then used as a preferential pathway for turbidity flows, which were captured by its headwall and lateral margins. The interpreted data shows that the captured turbidity flows greatly widened the basal scar, but caused only small modifications in scar height. Part of the MTD within the basal scar was removed downslope by turbidity flows, and was replaced by channel-fill deposits. This paper shows a flow-capture process occurred in a confluence region on continental slope. Basal scars can capture turbidity flows and facilitate flow channelization, which is a key process for submarine-channel initiation. The replacement of MTD by channel-fill deposits has profound implications for reservoir volumes and net-to-gross ratios in channel systems and partly depends on the turbidity-flows properties, such as their erosive ability and frequency. The more erosive and frequent flows are captured by the basal scar, the larger is the accommodation space created for succeeding sand-prone turbidites.

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“…Progress in understanding the response of a turbidity current to specific topographic features was hindered on the one hand by the difficulty of studying such flows in natural deep‐water settings and, on the other hand, by the scale limitation of laboratory flume‐tank experiments. Laboratory studies have been an important contribution as analogues for various flow phenomena, such as flow reflection (Kneller et al ., ), topographic ponding (Lamb et al ., , ; Violet et al ., ; Toniolo et al ., ; Patacci et al ., ), channel inception (Yu et al ., ; De Leeuw et al ., ) and flow behaviour in sinuous channels (Peakall et al ., ; Janocko et al ., ). While a crucial component for developing the core mathematical understanding for many aspects of flow processes, the dilute and extremely fine‐grained laboratory mini‐flows may fail to reveal some of the important hydraulic aspects of natural‐scale turbidity currents, such as the phenomena of internal reverse underflow and the hydraulic impact of large Kelvin–Helmholtz waves (Janocko et al ., ; Ge et al ., , ; see also discussion by Al‐Ja'Aidi, ).…”

Section: Introductionmentioning

confidence: 99%

Response of unconfined turbidity current to deep‐water fold and thrust belt topography: Orthogonal incidence on solitary and segmented folds

Howlett

Nemec

et al. 2019

Sedimentology

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Sea‐floor topography of deep‐water folds is widely considered to have a major impact on turbidity currents and their depositional systems, but understanding the flow response to such features was limited mainly to conceptual notions inspired by small‐scale laboratory experiments. High‐resolution three‐dimensional numerical experiments can compensate for the lack of natural‐scale flow observations. The present study combines numerical modelling of thrusts with fault‐propagation folds by Trishear3D software with computational fluid dynamics simulations of a natural‐scale unconfined turbidity current by MassFlow‐3D™ software. The study reveals the hydraulic and depositional responses of a turbidity current (ca 50 m thick) to typical topographic features that it might encounter in an orthogonal incidence on a sea‐floor deep‐water fold and thrust belt. The supercritical current (ca 10 m sec−1) decelerated and thickened due to the hydraulic jump on the fold backlimb counter‐slope, where a reverse overflow formed through current self‐reflection and a reverse underflow was issued by backward squeezing of a dense near‐bed sediment load. The reverse flows were re‐feeding sediment to the parental current, reducing its waning rate and extending its runout. The low‐efficiency current, carrying sand and silt, outran a downslope distance of >17 km with only modest deposition (<0·2 m) beyond the fold. Most of the flow volume diverted sideways along the backlimb to surround the fold and spread further downslope, with some overspill across the fold and another hydraulic jump at the forelimb toe. In the case of a segmented fold, a large part of the flow went downslope through the segment boundary. Preferential deposition (0·2 to 1·8 m) occurred on the fold backlimb and directly upslope, and on the forelimb slope in the case of a smaller fold. The spatial patterns of sand entrapment revealed by the study may serve as guidelines for assessing the influence of substrate folds on turbiditic sedimentation in a basin.

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Morphodynamics of submarine channel inception revealed by new experimental approach

Cited by 83 publications

References 40 publications

Levees Formed by Turbidity Currents: A Depth‐Averaged Modeling Treatment

Levees Formed by Turbidity Currents: A Depth‐Averaged Modeling Treatment

The Role of Mass Wasting In the Progressive Development Of Submarine Channels (Espírito Santo Basin, Se Brazil)

Response of unconfined turbidity current to deep‐water fold and thrust belt topography: Orthogonal incidence on solitary and segmented folds

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