Upper flow regime bedforms on levees and continental slopes: Turbidity current flow dynamics in response to fine-grained sediment waves

Kostic, Svetlana

doi:10.1130/ges01015.1

Cited by 46 publications

(54 citation statements)

References 33 publications

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“…Coarse-grained sediment waves and bars have also been described from studies of the modern seafloor (Piper et al, 1985;Wynn et al, 2002;Paull et al, 2011;Gamberi et al, 2013;Kostic, 2014;Covault et al, 2017;Hage et al, 2018). These are typically larger than the bedforms described here, with wavelengths on the order of tens to hundreds of metres and heights from 1 to 10 m. These features are generally interpreted as antidunes or cyclic-steps formed under Froudesupercritical flow Postma and Cartigny, 2014).…”

Section: Comparison To Other Overbank Sand Bars and Bedformsmentioning

confidence: 58%

Supercritical flows overspilling from bypass‐dominated submarine channels and the development of overbank bedforms

McArthur

Kane²,

Bozetti

et al. 2019

The Depositional Record

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Overbank deposits of submarine channels are typically thin-bedded, fine-grained and predominantly characterized by a series of sedimentary structures interpreted to record a relatively simple history of waning flow. Here, a new type of bedform indicative of Froude-supercritical flow is reported from successions of thin-bedded turbidites interpreted as channel overbank deposits in the Upper Cretaceous Rosario Formation, Baja California, Mexico. A link is demonstrated between the development of overbank deposits in the form of depositional terraces or internal levees and contemporaneously active sediment transport, bypass and deposition of coarsergrained material in a channel. The overbank bedforms overlie an erosion surface and contain a suite of sedimentary structures indicative of initially Froude-supercritical flow conditions and a progressive waning of flow strength. In some cases, a stacked repetition of facies is interpreted to record a rejuvenation of flow energy. The characteristic sedimentary sequence observed is as follows: (a) long wavelength, low amplitude erosional surface with superimposed scours; (b) antidune backsets; (c) upper stage plane-parallel lamination; (d) subcritical climbing ripples; (e) supercritical climbing ripples; (f) lower stage planar laminated tops; (g) a sharp upper surface.The exact vertical sequence of sedimentary structures encountered varies depending on the point of observation with respect to the bedform crest and distance from the parent channel. The recognition of these distinctive bedforms allows for interpretation of sediment bypass and proximity to a channel thalweg. These bedforms have not hitherto been described and provide a further example of the range of flow processes operating in submarine channel-levee systems, which aids depositional environment interpretation in both subsurface and outcrop studies. K E Y W O R D SBaja California, deep-marine, Rosario Formation, slope channels, turbidity currents, Upper Cretaceous |McARTHUR eT Al.

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Section: Comparison To Other Overbank Sand Bars and Bedformsmentioning

confidence: 58%

Supercritical flows overspilling from bypass‐dominated submarine channels and the development of overbank bedforms

McArthur

Kane²,

Bozetti

et al. 2019

The Depositional Record

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“…3A) with wavy laminae and rare laminasets accreting countercurrent relate, respectively, to temporarily reduced aggradation under the unsteady hyperpycnal current (Best et al, 2005) and to local inversion of the flow field close to hydraulic jumps migrating upstream. Temporary decreases in Froude number may have led to superposed antidunes (e.g., set 2; Kostic, 2014). The depositional event may have lasted up to several days, as currently observed where exceptional floods generate long-lived underflows at river mouths (Mulder et al, 2003).…”

Section: Supercritical-flow Structures: Interpretationmentioning

confidence: 88%

Supercritical-flow structures on a Late Carboniferous delta front: Sedimentologic and paleoclimatic significance

Ventra

Cartigny

Bijkerk

et al. 2015

Geology

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Deposits of fluvial systems in highly seasonal tropical climates possess unique architectural and facies characters owing to a flood-prone regime alternating with lengthy periods of ineffective discharge. Distally linked deltaic successions should also feature distinctive attributes, with great potential to preserve the stratigraphic evidence of exceptional discharge events. We describe Late Carboniferous deltafront, valley-confined sandstones from the Pennine Basin (UK), originally deposited at paleoequatorial latitudes during final assembly of the Pangean megacontinent and characterized by giant sedimentary structures with repetitively sigmoidal geometry. Facies traits indicate geologically instantaneous deposition of a large sediment volume from a density current at sustained supercritical-flow conditions, leading to aggradation of cyclic steps, recently identified bedforms developing in high-energy flows and of which this is the first complete outcrop example. The lack of unconformable erosional surfaces and absence of different associated facies point to a single aggradational event during which the structures attained dimensions comparable to those indicated by seismic data sets from which they are remotely detected on modern seafloors. Cyclic-step formation in a deltaic setting suggests that Pangean megamonsoons could have triggered hydrologic events capable of imprinting sedimentologic signatures on shallow-marine deposits.

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“…Cyclic steps are long-wave bedforms created due to the instability of Froude-supercritical turbidity currents interacting with an erodible bed; they can be both net-erosional and netdepositional Fildani et al, 2006;Kostic and Parker, 2006;Kostic, 2014Kostic, , 2011Lamb et al, 2008;Tubau et al, 2015). The best studied example of cyclic steps from the present-day seafloor is located in the outer bend of the Shepard meander of the Monterey channel.…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Genesis and character of thin-bedded turbidites associated with submarine channels

Hansen

Callow

Kane

et al. 2015

Marine and Petroleum Geology

117

129

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Submarine channel related thin-bedded turbidites are deposited in environments such as external levees, internal levees, depositional terraces and at times of channel abandonment.Thin-bedded turbidites are defined as beds that are less than 10cm thick, but the described environments can at times contain beds up to 50cm thick which would be classified as medium or thick-bedded (Boggs, 2006). This paper addresses many examples of these environments from the modern seafloor, outcrop and the subsurface to suggest criteria that assist in the differentiation of levees and terraces from an architectural, sedimentological, M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 2 ichnological and hydrocarbon reservoir perspective. External levees confine channel belts and are elongate sedimentary deposits that are a product of over-spill of turbidity currents from the channel belt they confine. External levees often have predictable vertical, lateral and downstream changes but can commonly be modified by collapse of the inner external levee into the channel, collapse on the outer external levee, sediment waves, and interaction of external levees with topographic features such as other channels, other external levees, basin margins or previous slump/slide blocks, which can greatly modify the sand distribution within them.A combination of internal levees, depositional terraces and slide blocks of external levee sediment make up thin-bedded turbidites within channel belts. We differentiate between wedge shaped internal levees and topographically flat or subdued depositional terraces whose differing geometries and sand distribution reflect the fact that the flow processes involved in the formation of these deposits are different. The characteristic wedge shape of an internal levee requires sufficient space within the channel belt for the over-spilling current to decelerate and deposit the majority of its suspended sediment before reaching the bounding topography of the channel belt. In the case of depositional terraces the space available in the channel belt is insufficient for the current to deposit the majority of its sediment before reaching the bounding topography of the channel belt, creating confined sheet-like deposits.External levees, internal levees and depositional terraces have distinct sedimentological characteristics such as sand bed thickness trends and sedimentary structures that can be used to distinguish them. Together with sedimentological characteristics, in some systems these thin-bedded turbidite deposits contain distinctive trace fossil assemblages, where channel proximal deposits such as proximal external levees, internal levees and depositional terraces M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 3 can have much higher biodiversity than sand-rich channel axes and more mud-dominated outer external levees.The depositional sites for internal levees and depositional terraces within channel belts can be formed by various processes such as entrenchment, point bar accretion, meander bend cutoff, ...

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Upper flow regime bedforms on levees and continental slopes: Turbidity current flow dynamics in response to fine-grained sediment waves

Cited by 46 publications

References 33 publications

Supercritical flows overspilling from bypass‐dominated submarine channels and the development of overbank bedforms

Supercritical flows overspilling from bypass‐dominated submarine channels and the development of overbank bedforms

Supercritical-flow structures on a Late Carboniferous delta front: Sedimentologic and paleoclimatic significance

Genesis and character of thin-bedded turbidites associated with submarine channels

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