Spatial variability of prodeltaic undulations on the Guadalfeo River prodelta: support to the genetic interpretation as hyperpycnal flow deposits

Lobo, F. J.; Goff, John A.; Mendes, Isabel; Bárcenas, P.; Fernández-Salas, L.M.; Martín-Rosales, W.; Macías, Jorge; Río, Víctor Díaz del

doi:10.1007/s11001-014-9233-9

Cited by 19 publications

(9 citation statements)

References 56 publications

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“…Density flows can be triggered by a wide variety of processes in marine (Urgeles et al, 2007;Hughes Clarke et al, 2014;Lobo et al, 2015) and lacustrine deltaic settings (Girardclos et al, 2012;Turmel et al, 2015). The origin of density flows on delta fronts is often debated (Talling, 2014), especially in marine deltas where hyperpycnal currents are rarer than in lacustrine settings due to the density difference between oceans and rivers.…”

Section: Origin Of Density Flowsmentioning

confidence: 99%

“…The morphology of deltas as well as the presence of bedforms on their slopes depend on a wide range of factors, including the presence and behaviour of density currents originating from river floods and slope instability (Postma, 1990;Lai & Capart, 2007). Density currents at river mouths are common when there is a high volume of sediment discharge (Migeon et al, 2006;Warrick et al, 2013;Katz et al, 2015;Lobo et al, 2015;Turmel et al, 2015) and can propagate in many ways, depending on the density contrast between the inflowing water (river) and the freshwater or saltwater receiving basin. Hyperpycnal flows (underflows) can be generated when freshwater charged with sediment plunges to form sediment density flows (or density flows sensu Talling et al, 2012) in the receiving basin (Mulder & Syvitski, 1995).…”

Section: Introductionmentioning

confidence: 99%

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Morphological expression of bedforms formed by supercritical sediment density flows on four fjord‐lake deltas of the south‐eastern Canadian Shield (Eastern Canada)

et al. 2016

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High‐resolution swath bathymetry data collected in fjord‐lakes Pentecôte, Walker and Pasteur (eastern Québec, Canada) allowed imaging in great detail the deltas of four rivers in order to understand the factors controlling the formation and downslope evolution of bedforms present on their slopes. The morphometry and morphology of 199 bedforms reflect the behaviour of sediment density flows. The shape of the bedforms, mostly crescentic, and the relationships between their morphological properties indicate that they were formed by supercritical density flows and that they are cyclic steps. The crescentic shape suggests an upslope migration while the aspect ratios and increasing wavelengths with distance from the shore (and decreasing slopes) are compatible with a cyclic step origin. At the rollover point, the acceleration of the density flows on steep slopes produces tightly spaced hydraulic jumps and favours short wavelength and symmetrical bedforms. Further downslope, decreasing slopes and increasing specific discharge increase the wavelength and asymmetry of the bedforms. The wavelength and asymmetry are increased because density flows require longer distances to become supercritical again on lower slopes after each successive hydraulic jump. Bedform morphometry and morphology are used to reconstruct density flow behaviour downslope. Froude numbers are high near the rollover point and gradually decrease downslope as the slope becomes gentler. Conversely, the specific discharge and flow depth are low near the rollover point and gradually increase downslope as the flow either erodes sediments or becomes more dilute due to sediment deposition and water entrainment. The supercritical density flows are believed to be triggered mainly by hyperpycnal flows but some evidence of delta‐front slope failures is also observed. The differences in delta morphology and bedform development between the four deltas are linked to basin morphology and watershed hydrology, but also mainly to the fjord heritage of the lakes that allowed the focusing of sediment at the delta front.

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Section: Origin Of Density Flowsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Morphological expression of bedforms formed by supercritical sediment density flows on four fjord‐lake deltas of the south‐eastern Canadian Shield (Eastern Canada)

et al. 2016

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“…In addition, the river basins are located in the hottest, driest, and less vegetated regions of the Iberian Peninsula, providing greater sediment availability. These factors lead to significant episodes of sediment discharge, with values of sediment flux up to 630 kg/s [ Lobo et al , ]. In these cases, the formation of central river mouth bars is expected after flood events as the ones simulated in this work.…”

Section: Discussionmentioning

confidence: 67%

“…Their water discharges are low on a mean annual basis, but they exhibit a marked seasonal variability and the drainage basins have undergone numerous catastrophic floods in response to torrential rains [ Brázdil et al , ]. Examples of such deltas fed by torrential rivers were reported by Bárcenas et al [] along the coast of the Alboran Sea (western Mediterranean Basin), characterized by low wave energy and microtidal conditions [ Ortega‐Sánchez et al , ; Lobo et al , ]. A total of 12 deltaic systems were identified related to the following rivers: Güi, Torrox, Chillar, Jate, Seco, Verde, Guadalfeo, Gualchos, Haza de Trigo, Albuñol, Huarea, and the Adra river.…”

Section: Discussionmentioning

confidence: 99%

Effects of basin bottom slope on jet hydrodynamics and river mouth bar formation

Jiménez-Robles

Ortega-Sánchez

Losada

2016

J. Geophys. Res. Earth Surf.

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River mouth bars are strategic morphological units primarily responsible for the development of entire deltaic systems. This paper addresses the role of receiving basin slope in the hydrodynamics of an exiting sediment‐laden turbulent jet and in resulting mouth bar morphodynamics. We use Delft3D, a coupled hydrodynamic and morphodynamic numerical model, along with a theoretical formulation to reproduce the physics of the problem, characterized by a fluvially dominated inlet free of waves and tides. We propose an updated theoretical model with a slope‐dependent entrainment coefficient, showing that the rate at which ambient fluid is incorporated into a jet increases with higher basin slopes. Transient results reveal that the magnitude of a basin slope can alter the stability of a jet, favoring the formation of an unstable meandering jet. While a stable jet gives rise to “middle‐ground” bars accompanied by diverging channels, a “lunate” mouth bar results from unstable jets. Additional morphodynamic simulations demonstrate that the time required for mouth bar stagnation in its final position increases linearly with the basin slope. In contrast, the distance at which the mouth bar eventually forms decreases until reaching an asymptotic value for slopes higher than 2%. Moreover, the basin slope highly influences sedimentary processes responsible for bar formation: for milder slopes, progradation processes prevail, while in steeper basins aggradation is more relevant. Finally, the minimum relative water depth over a bar crest that forces the flow to bifurcate around a fully developed bar decreases with the basin slope.

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“…Fields of supercritical‐flow bedforms fed by flood‐prone river outflows have been documented along subaqueous portions of modern deltas in other areas of the Mediterranean (e.g. Urgeles et al., 2011; Lobo et al., 2015; Casalbore et al., 2017; Kostic et al., 2019). Outcrop examples have been recently reported from an ancient channel–lobe transition zone of a deep‐water delta, from Eocene continental‐slope successions of southern California (Ono & Plink‐björklund, 2018), in the Eocene of north‐eastern Spain (Postma et al., 2021), and in Plio‐Pleistocene base of scarp deposits exposed in a southern sector of the western margin of the Messina Strait (Longhitano, 2016; Chiarella et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

Coarse‐grained deltas approaching shallow‐water canyon heads: A case study from the Lower Pleistocene Messina Strait, Southern Italy

et al. 2021

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The tide-dominated Messina Strait (southern Italy) is a 3 km wide marine passageway, whose block-faulted borders form steep subaqueous zones incised by canyons and gullies. These erosional features retreat towards the shorelines and are often in direct connection with subaerial valley-bounded river deltas. High-energy density-flows generated by river floods periodically enter the canyon heads, attaining supercritical-flow regime and accreting large, upslope-migrating bedforms. Although these bedforms have been documented in recent studies, little attention has been paid to the definition of the type of delta entering canyon heads, the internal features of river-influenced deposits accumulated in the nearshore zone, and their interplay with tidal currents flowing axially to the strait. This study focuses on a Lower Pleistocene coarse-grained succession exposed along the north-eastern margin of the modern Messina Strait, investigated using conventional facies analysis and sedimentological logging, integrated with photogrammetric techniques and interpretation of drone-acquired imagery. Facies confinement between basement blocks suggests a subaqueous delta complex shed from the tectonically controlled margin of the ancient strait and entering shallowly submerged canyon heads. Basal breccias, conglomerates and pebbly sandstones exhibiting channel-form discontinuities and upslope dipping backsets are interpreted as cyclic-step and antidune deposits. Units composed of these facies are comprised between master erosional surfaces and tidal ravinement surfaces. The tidal ravinements suggest that canyon infill occurred during a major phase of sea-level rise, punctuated by minor falls and stillstands. These surfaces are overlain by mixed bioclastic-siliciclastic, arenitic, trough and planar cross-strata, representing dunes migrating roughly parallel to the palaeo-coastline and originated by tidal currents amplified by the narrowing of the ancient Messina Strait. Tidal-influenced sedimentation dominated over the fluvial-influenced processes during the late transgression, overfilling the canyon relief. The exceptionally good exposure of depositional architectures and facies characteristics is key to outline 2523

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Spatial variability of prodeltaic undulations on the Guadalfeo River prodelta: support to the genetic interpretation as hyperpycnal flow deposits

Cited by 19 publications

References 56 publications

Morphological expression of bedforms formed by supercritical sediment density flows on four fjord‐lake deltas of the south‐eastern Canadian Shield (Eastern Canada)

Morphological expression of bedforms formed by supercritical sediment density flows on four fjord‐lake deltas of the south‐eastern Canadian Shield (Eastern Canada)

Effects of basin bottom slope on jet hydrodynamics and river mouth bar formation

Coarse‐grained deltas approaching shallow‐water canyon heads: A case study from the Lower Pleistocene Messina Strait, Southern Italy

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