Submarine "Natural Levees"

Buffington, Edwin C.

doi:10.1086/625999

Cited by 45 publications

(21 citation statements)

References 5 publications

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“…They are a product of over-spill of turbidity currents from an adjacent channel and over time increase in relief above the channel floor, both due to levee aggradation and channel down-cutting; they also tend to prograde into the basin as the channel-lobe transition advances, so that levees commonly overlie lobes/frontal splays (or high amplitude reflection packets -HARPs -in seismic data (Manley et al, 1997)) (e.g. Buffington 1952;Piper & Normark 1983;Hiscott et al 1997;Normark & Damuth 1997;Piper & Deptuck 1997;Peakall et al 2000;Skene et al 2002;Deptuck et al 2003;Kane et al 2007;Meiburg & Kneller 2010;Kane & Hodgson 2011;Nakajima & Kneller 2012;Morris et al 2014). Due to the spatial deceleration of the over-spilling flow and the preferential deposition of coarser suspended sediment closer to the channel the external levee thickness tends to decrease away from the channel.…”

Section: External Leveesmentioning

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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Section: External Leveesmentioning

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 channels are ubiquitous geomorphological features of Earth's continental slopes and act as important conduits for the transfer of sediment from the shelf to deep ocean basins (Buffington, 1952;Menard, 1955;Komar, 1973;Peakall et al, 2000;Kneller, 2003;Babonneau et al, 2004). Their sedimentary record typically suggests prolonged periods of erosion, bypass and sediment transfer, which may leave an incomplete record within the channel (Stevenson et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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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“…The dynamics of turbidity current flow within submarine channels are significantly different to those of their subaerial counterparts (Peakall et al, 2000;Corney et al, 2006;Keevil et al, 2007;Mohrig and Buttles, 2007;Kane et al, 2008). In the submarine case, where the density contrast between the flow and the ambient fluid is much lower than that of open-channel flows, the flow may be significantly superelevated above the channel margins; consequently significant overspill occurs, building high-relief levees (e.g., Buffington, 1952;Menard, 1964;Komar, 1973;Hay et al, 1983;Piper and Normark, 1983;Hiscott et al, 1997;Peakall et al, 2000;Skene et al, 2002;Klaucke et al, 2004;Kane et al, 2007;Mohrig and Buttles, 2007). Levees may provide an uninterrupted depositional record in systems where the channel axis is dominated by bypass processes (e.g., Hiscott et al, 1997).…”

Section: Introductionmentioning

confidence: 99%