Morphology, age and sediment dynamics of the upper headwall of the Sahara Slide Complex, Northwest Africa: Evidence for a large Late Holocene failure

Li, Wei; Alves, Tiago Marcos; Urlaub, Morelia; Georgiopoulou, Aggeliki; Klaucke, Ingo; Wynn, Russell B.; Groß, Felix; Meyer, Mathias; Repschläger, Janne; Berndt, Christian; Krastel, Sebastian

doi:10.1016/j.margeo.2016.11.013

Cited by 30 publications

(38 citation statements)

References 67 publications

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“…From the limited cases reported in the literature, the Storegga Slide shows turbidite rates ranging from 7.8% to 10.4% (Haflidason et al, ), values that are similar to the turbidite rates calculated in this work. However, some major landslides do not show any associated turbidites (e.g., the Sahara Slide on the northwest African continental margin; Georgiopoulou et al, ; Li et al, ). In some steeper continental slopes, turbidite rates may be much larger than those reported in this work as turbidity currents often incorporate significant volumes of seafloor sediment.…”

Section: Discussionmentioning

confidence: 99%

“…The three latter processes are considered in the literature as generating the main components of mass‐transport deposits (MTDs) and can be identified on seismic data (e.g., Bull et al, ; Moscardelli & Wood, ). In addition, turbidites generated during slope failure are commonly observed on sediment cores as they cover very large areas of continental slopes and ocean basins (e.g., Li et al, ; Masson et al, ; Owen et al, ; Piper et al, ). Detailed estimates of the volume of MTDs (Vm; see Text S1 for the detailed terminology definition; Figure a) on seismic data, and morphological analyses of seafloor scars using multibeam bathymetric data, are key to calculate the residual volume of failed strata after their emplacement (Vr; Figure ) (e.g., Alves & Cartwright, ; Calvès et al, ; Lamarche et al, ; ten Brink et al, ; Vӧlker, ).…”

Section: Introductionmentioning

confidence: 99%

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True Volumes of Slope Failure Estimated From a Quaternary Mass‐Transport Deposit in the Northern South China Sea

Sun

Alves

et al. 2018

Geophysical Research Letters

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Submarine slope failure can mobilize large amounts of seafloor sediment, as shown in varied offshore locations around the world. Submarine landslide volumes are usually estimated by mapping their tops and bases on seismic data. However, two essential components of the total volume of failed sediments are overlooked in most estimates: (a) the volume of subseismic turbidites generated during slope failure and (b) the volume of shear compaction occurring during the emplacement of failed sediment. In this study, the true volume of a large submarine landslide in the northern South China Sea is estimated using seismic, multibeam bathymetry and Ocean Drilling Program/Integrated Ocean Drilling Program well data. The submarine landslide was evacuated on the continental slope and deposited in an ocean basin connected to the slope through a narrow moat. This particular character of the sea floor provides an opportunity to estimate the amount of strata remobilized by slope instability. The imaged volume of the studied landslide is ~1035 ± 64 km3, ~406 ± 28 km3 on the slope and ~629 ± 36 km3 in the ocean basin. The volume of subseismic turbidites is ~86 km3 (median value), and the volume of shear compaction is ~100 km3, which are ~8.6% and ~9.7% of the landslide volume imaged on seismic data, respectively. This study highlights that the original volume of the failed sediments is significantly larger than that estimated using seismic and bathymetric data. Volume loss related to the generation of landslide‐related turbidites and shear compaction must be considered when estimating the total volume of failed strata in the submarine realm.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

True Volumes of Slope Failure Estimated From a Quaternary Mass‐Transport Deposit in the Northern South China Sea

Sun

Alves

et al. 2018

Geophysical Research Letters

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“…These two surfaces may represent two unrelated events or represent different slip planes within a single landslide complex. Infill of Surface 1 prior to erosion by Surface 2 indicates several depositional episodes rather than different phases of the same event, similar to the Hinlopen Slide (Vanneste et al ., ) or the Sahara Slide Complex (Li et al ., ). If Surfaces 1 and 2 represent the basal shear surfaces that coalesce up‐dip into the headwall of a larger slide, this could be the characteristic of retrogressive erosional events (Piper et al ., ).…”

Section: Discussionmentioning

confidence: 97%

“…Failures can form a single submarine landslide or a composite landslide complex (e.g. Gee et al ., ; Antobreh & Krastel, ; Li et al ., ) with products of failure often treated as multiple separate events (MTDs) in seismic and outcrop data sets (e.g. Moscardelli et al ., ; Sobiesiak et al ., ; Ortiz‐Karpf et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Exhumed lateral margins and increasing flow confinement of a submarine landslide complex

et al. 2017

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Submarine landslides, including the basal shear surfaces along which they fail, and their subsequent infill, are commonly observed in modern seabed and seismic reflection data sets; their resultant relief impacts sediment routing and storage patterns on continental margins. Here, three stacked submarine landslides are documented from the Permian Ecca Group, Laingsburg depocentre, Karoo Basin, South Africa, including two superimposed lateral margins. The stratigraphic framework includes measured sections and correlated surfaces along a 3 km long, 150 m high outcrop. Two stacked 2·0 to 4·5 km wide and 90 m and 60 m deep erosion surfaces are recognized, with lateral gradients of 8° and 4°, respectively. The aim of this study was to understand the evolution of a submarine landslide complex, including: evolution of basal shear surfaces/zones; variation of infill confinement; and location of the submarine landslides in the context of basin‐scale sedimentation and degradation rates. Three stages of formation are identified: (i) failure of submarine landslide 1, with deposition of unconfined remobilized deposits; (ii) failure of submarine landslide 2, forming basal shear surface/zone 1, with infill of remobilized deposits and weakly confined turbidites; and (iii) failure of submarine landslide 3, forming basal shear surface/zone 2, with infill of remobilized deposits and confined turbidites, transitioning stratigraphically to unconfined deposits. The expression of basal shear varies laterally, from metres thick zones in silt‐rich strata to sharp stepped surfaces in sand‐rich strata. Faulting and rotation of overlying bedding suggest that the shear surfaces/zones were dynamic. Stacking of landslides resulted from multi‐phase slope failure, increasing down‐dip topography and confinement of infilling deposits. The failure slope was probably a low supply tilted basin margin evidenced by megaclast entrainment from underlying basin‐floor successions and the lack of channel systems. This study develops a generic model of landslide infill, as a function of sedimentation and degradation rates, which can be applied globally.

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“…The first scenario we may consider is that the Agadir Slide may be formed by a single-phase event but occurred along two basal shear surfaces (glide planes). Several previous studies have revealed that multiple mass wasting events can be triggered at the same time and amalgamate or erode each other (Moscardelli et al, 2006;Li et al, 2017). If this was the case for the Agadir Slide, the upper and lower headwall areas would have been generated simultaneously.…”

Section: Emplacement Processes Of the Agadir Slidementioning

confidence: 97%

The Agadir Slide offshore NW Africa: Morphology, emplacement dynamics, and potential contribution to the Moroccan Turbidite System

Krastel

Alves

et al. 2018

Earth and Planetary Science Letters

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A newly identified large-scale submarine landslide on the NW African margin (Agadir Slide) is investigated in terms of its morphology, internal architecture, timing and emplacement processes by using high-resolution multibeam bathymetry data, 2D seismic profiles and gravity cores. The Agadir Slide is located south of the Agadir Canyon at a water depth ranging from 500 m to 3500 m, with an estimated affected area of ~5500 km 2. The complex morphology of the Agadir Slide reveals two headwall areas and two slide fairways (Western and Central slide fairways). Volume calculations indicate that approximately 340 km 3 of sediment were accumulated downslope in the slide fairways (~270 km 3) and Agadir Canyon (~70 km 3). Novel stratigraphic correlations based on five gravity cores indicate an age of ~142±1 ka for the emplacement of the Agadir Slide. However, the emplacement dynamics of the Agadir Slide suggests it was developed in two distinct, successive stages. The presence of two weak layers (glide planes) is suggested as the major preconditioning factor for the occurrence of slope instability in the study area, and local seismicity related to fault activity and halokinesis likely triggered the Agadir Slide. Importantly, the Agadir Slide neither disintegrated into sediment blocks nor was transformed into turbidity currents. Its timing of emplacement does not correlate with any turbidites recorded downslope across the Moroccan Turbidite System.

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Morphology, age and sediment dynamics of the upper headwall of the Sahara Slide Complex, Northwest Africa: Evidence for a large Late Holocene failure

Cited by 30 publications

References 67 publications

True Volumes of Slope Failure Estimated From a Quaternary Mass‐Transport Deposit in the Northern South China Sea

True Volumes of Slope Failure Estimated From a Quaternary Mass‐Transport Deposit in the Northern South China Sea

Exhumed lateral margins and increasing flow confinement of a submarine landslide complex

The Agadir Slide offshore NW Africa: Morphology, emplacement dynamics, and potential contribution to the Moroccan Turbidite System

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