Powerful turbidity currents driven by dense basal layers

Paull, C. K.; Talling, Peter J.; Maier, K. L.; Parsons, D.; Xu, Jingping; Caress, David W.; Gwiazda, R.; Lundsten, E. M.; Anderson, K.; Barry, James; Chaffey, M.; O’Reilly, Tom; Rosenberger, Kurt J.; Gales, J. A.; Kieft, Brian; McGann, Mary; Simmons, S.; McCann, Mike; Sumner, Esther J.; Clare, Michael; Cartigny, Matthieu

doi:10.1038/s41467-018-06254-6

Cited by 202 publications

(284 citation statements)

References 59 publications

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“…The first turbidity current removes this sediment, and as a result, no further turbidity currents are generated. Unconsolidated seafloor sediments have been observed in other active submarine channels (Curran et al, 2002;Lintern et al, 2016;Paull et al, 2018).…”

Section: How Do Dilute River Plumes Generate Turbidity Currents?mentioning

confidence: 96%

Direct Monitoring Reveals Initiation of Turbidity Currents From Extremely Dilute River Plumes

Hage

Cartigny

Sumner

et al. 2019

Geophysical Research Letters

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Rivers (on land) and turbidity currents (in the ocean) are the most important sediment transport processes on Earth. Yet how rivers generate turbidity currents as they enter the coastal ocean remains poorly understood. The current paradigm, based on laboratory experiments, is that turbidity currents are triggered when river plumes exceed a threshold sediment concentration of ~1 kg/m3. Here we present direct observations of an exceptionally dilute river plume, with sediment concentrations 1 order of magnitude below this threshold (0.07 kg/m3), which generated a fast (1.5 m/s), erosive, short‐lived (6 min) turbidity current. However, no turbidity current occurred during subsequent river plumes. We infer that turbidity currents are generated when fine sediment, accumulating in a tidal turbidity maximum, is released during spring tide. This means that very dilute river plumes can generate turbidity currents more frequently and in a wider range of locations than previously thought.

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Section: How Do Dilute River Plumes Generate Turbidity Currents?mentioning

confidence: 96%

Direct Monitoring Reveals Initiation of Turbidity Currents From Extremely Dilute River Plumes

Hage

Cartigny

Sumner

et al. 2019

Geophysical Research Letters

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“…Lowe, ; Baker et al., ), either during initial tractional sedimentation prior to the development of traction carpets (Lowe, ) or during bypass of the HDTC (Baker et al., ). Failure of the sediment bed in canyon systems has also been postulated to lead to the downstream formation of a high‐concentration basal layer beneath a turbidity current (Paull et al., ). Tractional sedimentation in sand‐rich HDTCs is typically dominated by upper‐stage plane beds and dune‐like bedforms, associated with a turbulent flow regime, prior to increasing sediment concentrations near the base leading to the development of traction carpets (Lowe, ).…”

Section: Tool Marksmentioning

confidence: 99%

“…Tractional sedimentation in sand‐rich HDTCs is typically dominated by upper‐stage plane beds and dune‐like bedforms, associated with a turbulent flow regime, prior to increasing sediment concentrations near the base leading to the development of traction carpets (Lowe, ). In a supercritical regime, high‐concentration basal layers have been postulated to develop over cyclic steps (Hughes Clarke, ; Paull et al., ). This initial turbulence‐driven tractional regime is highly unlikely to be able to maintain larger clasts in fixed positions and at a constant height within the flow, and thus form grooves, for the reasons discussed above for ‘low‐density turbidity currents’.…”

Section: Tool Marksmentioning

confidence: 99%

“…This initial turbulence‐driven tractional regime is highly unlikely to be able to maintain larger clasts in fixed positions and at a constant height within the flow, and thus form grooves, for the reasons discussed above for ‘low‐density turbidity currents’. In the postulated high‐concentration basal layers of Monterey Canyon, associated with upslope migrating bedforms, large ( ca 0.45 m diameter) spherical and cuboid instrumented ‘artificial‐clasts’ are observed to rotate within the flow, and are thought to be rafted in, or at the upper interface of, the dense layer (Paull et al., ). These ‘artificial‐clasts’ further suggest that clasts are not dragged in a fixed position at the base of high concentration basal layers.…”

Section: Tool Marksmentioning

confidence: 99%

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An integrated process‐based model of flutes and tool marks in deep‐water environments: Implications for palaeohydraulics, the Bouma sequence and hybrid event beds

et al. 2020

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Flutes and tool marks are commonly observed sedimentary structures on the bases of sandstones in deep-water successions. These sole structures are universally used as palaeocurrent indicators but, in sharp contrast to most sedimentary structures, they are not used in palaeohydraulic reconstructions or to aid prediction of the spatial distribution of sediments. Since Kuenen's famous 1953 paper, flutes and tool marks in deep-water systems have been linked to turbidity currents, as reflected in the standard Bouma sequence taught to generations of geologists. Yet, these structures present a series of unaddressed enigmas. Detailed field studies in the 1960s and early 1970s observed that flutes are typically associated with thicker, more proximal beds, whilst tools are generally prevalent in thinner, more distal, beds. Additionally, flutes and tool marks are rarely observed on the same surfaces, and flutes are seen to change downstream from larger wider parabolic to smaller narrower spindle-shaped forms. No model has been proposed that explains these field-based observations. This contribution undertakes a radical reexamination of the formative flow conditions of flutes and tool marks, and demonstrates that they are the products of a wide range of sediment gravity flows, from turbulent flows, through transitional clay-rich flows, to debris flows. Flutes are not solely the product of turbulent flows, but can continue to form in transitional flows. Grooves are shown to be formed by debris flows, slumps and slides, not turbidity currents, and in many cases the debris flows are linked to the debritic component of hybrid flows. Discontinuous tool marks, including skim (bounce) marks, prod marks and skip marks, are shown to be formed by transitional mud-rich flows. Consequently, the observed spatial distribution of flutes and tool marks can be explained by a progressive increase in flow cohesivity downstream. This model of flutes and tool marks dovetails with models of hybrid flows that predict such a longitudinal increase in flow cohesivity. However, some deposits show grooves preferentially associated with Bouma T A beds, and these are likely formed by flows transforming from higher to lower cohesion, and are present 1601 in basins where hybrid beds are absent or rare. The recognition that sole structures may have no genetic link to the later overlying turbidity current deposits, and can be formed by a wide range of flow types, indicates that the existing pictorial description of the Bouma sequence is incorrect. A modified Bouma sequence is proposed here that addresses these points. In utilizing the advances in fluid dynamics since Kuenen's pioneering research, this study demonstrates that it is possible to use flutes and tool marks to interpret flow type at the point of formation, the nature of flow transformations, and the mechanics of the basal layer. These advances suggest that it is then possible to predict the nature of deposit type down-dip. This new understanding, in combination with further testing in outcrop of t...

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“…Overall, such flows are unlikely to be successfully modeled by a depth-averaged approach, since they consist of two components with very different rheologies-an overlying dilute turbidity current, underlain by a dense component that is nowhere addressed in either the three-or four-equation model of Parker et al (1986). Note also that recent observational results from the Monterey Canyon indicate a region of enhanced concentration near the base of turbidity currents (Paull et al, 2018). This latter reference suggests that the floor of the Monterey Canyon may be easily liquefied by the stress imposed by an overlying turbidity current.…”

Section: 1029/2018jc014817mentioning

confidence: 99%

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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Powerful turbidity currents driven by dense basal layers

Cited by 202 publications

References 59 publications

Direct Monitoring Reveals Initiation of Turbidity Currents From Extremely Dilute River Plumes

Direct Monitoring Reveals Initiation of Turbidity Currents From Extremely Dilute River Plumes

An integrated process‐based model of flutes and tool marks in deep‐water environments: Implications for palaeohydraulics, the Bouma sequence and hybrid event beds

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

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