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Active continental margins are tectonic sites with complex sedimentary processes. Tectono–sedimentary interactions occur over geological time and determine the modern morphology of the margin. However, such interactions have been poorly documented in high‐latitude regions. This study focuses on deep‐water sedimentary systems on the South Shetland convergent margin, which is the only remaining active continental margin in Antarctica. Numerous gullies, 20 canyons and three contourite drifts are identified by interpreting bathymetry, oceanography and reflection seismic data. Heavy mineral contents of a gravity core, located at a downslope elongated mounded drift, show the asynchronous interplay of downslope and alongslope processes. The rest of the margin is dominated by turbidity currents. Variations in the slope gradient control thalweg profiles and sinuosity of canyons. Tectonic‐related morphology restricts the distribution of contourite drifts. Earthquakes triggered by underplating and tectonic compression may induce slope instability at the lower flank of the plastered drift. Tectonic uplift influences the amount of sediments transported by ice sheets and controls the shelf stacking pattern. The mixed turbidite–contourite system transitions to separated canyon and drift systems from passive to active continental margins under the influence of the tectonic‐related morphology. A systematic comparison has been made among several convergent margins with similar tectonic settings. Results suggest that submarine canyons on these shelf‐slope systems have similar morphological features and are comparable in size. Coarse sediment input and steep continental slopes (mean slope 7 to 10°) control the canyon morphology on these margins. Therefore, this research has important implications for furthering the current understanding of sedimentary systems on high‐latitude convergent margins and tectono–sedimentary interactions. [ABSTRACT FROM AUTHOR]

Well‐exposed, vertically dipping, glacially polished outcrops of the Neoproterozoic Windermere Supergroup in the southern Canadian Cordillera include basin‐floor deposits of the Upper Kaza Group overlain by slope channel complexes of the Isaac Formation. Within the 2·5 km thick Kaza and Isaac succession is an up to 360 m thick interval composed of diverse deep‐water stratal elements including scour and interscour deposits, distributary channels, fine‐grained turbidites, terminal splays, mass‐transport deposits, erosional and levéed channels and avulsion splays, which collectively were formed during the development of an ancient passive‐margin channel‐lobe system. The proportion and vertical and lateral arrangement of stratal elements reveal three distinct complexes. The lower complex, consisting mostly of distributary channels and small and large scours, is interpreted to represent the detachment of lobes from an upflow levéed channel, wherein a well‐developed channel‐lobe transition zone was formed by efficient, siliciclastic flows during a period of sustained transport bypass and limited deposition coincident with the onset of falling relative sea level. The middle, comparatively thicker and more sandstone‐rich complex, comprises distributary channel fills, fine‐grained turbidites and lesser terminal splays that are interspersed with small scours, capped by a slope levéed channel filled with coarser‐grained siliciclastic sediment. The abundance of basin‐floor elements suggests negligible separation between the levéed channel and lobe, and therefore a poorly‐developed channel‐lobe transition zone, resulting from inefficient, siliciclastic‐rich depositional flows that became dominant during lowstand and/or ensuing transgression. The stratal makeup of the upper complex resembles the lower detached complex, suggesting a return to efficient flows, and an abrupt change to mixed carbonate–siliciclastic sediments associated with highstand conditions. Accordingly, the stratigraphic architecture and stacking pattern of the Kaza–Isaac interval, which relate to the formation of multiple channel‐lobe transition zones, were controlled by temporal changes in sediment supply and flow characteristics during the long‐term progradation of the Laurentian continental margin. [ABSTRACT FROM AUTHOR]

The main factors controlling the bulk sedimentation in the region of the Mendeleev Rise and the adjacent part of the Arctic Ocean during the late Cenozoic were studied using a complex of geomorphological, lithological, and organic geochemical data. Samples for the study were collected during the cruises of the R/V Akademik Fedorov in 2000, 2005, and 2007 and icebreaker Kapitan Dranitsyn in 2012. Analysis of the group and molecular compositions of the dispersed organic matter (DOM) in bottom sediments has shown that the input of terrigenous sediments enriched with abrasion products of lithified rocks from the eastern source province determines the Holocene- Pleistocene sedimentation on the continental slope of the East Siberian Sea and in the Podvodnikov Basin. The individual characteristics of DOM of the late Cenozoic deposits from the underwater mountains of the Mendeleev Rise reflect the wide diversity of sedimentary sources and depositional conditions. Subaqueous erosion and redeposition of denudation products of source rocks and pre-Holocene sediments play an important part in sedimentation together with a terrigenous flow and ice transport. [ABSTRACT FROM AUTHOR]

The integrated interpretation of high-resolution multibeam bathymetry, seismic profiles and backscatter data in the S. Eufemia Gulf (SEG; Calabro-Tyrrhenian continental margin, south-eastern Tyrrhenian Sea) documents the relationship between postglacial fault activity and morpho-sedimentary processes. Three systems of active normal faults that affect the seafloor or the shallow subsurface, have been identified: 1) the S. Eufemia fault system located on the continental shelf with fault planes mainly oriented N26E-N40E; 2) the offshore fault system that lies on the continental slope off Capo Suvero with fault planes mainly oriented N28E-N60E; 3) the Angitola Canyon fault system located on the seafloor adjacent to the canyon having fault planes oriented N60E-N85E. The faults produce a belt of linear escarpments with vertical displacement varying from a few decimeters to about 12 m. One of the most prominent active structures is the fault F1 with the highest fault length (about 9.5 km). Two main segments of this fault are identified: a segment characterised by seafloor deformation with metric slip affecting Holocene deposits; a segment characterised by folding of the seafloor. A combined tectono-stratigraphic model of an extensional fault propagation fold is proposed here to explain such different deformation. In addition to the seabed escarpments produced by fault deformation, in the SEG, a strong control of fault activity on recent sedimentary processes is clearly observed. For example, canyons and channels frequently change their course in response to their interaction with main tectonic structures. Moreover, the upper branch of the Angitola Canyon shows straight flanks determined by fault scarps. Tectonics also determined different sediment accumulation rates and types of sedimentation (e.g., the accumulation of hanging wall turbidite deposits and the development of contourite deposits around the Maida Ridge). Furthermore, the distribution of landslides is often connected to main fault scarps and fluids are locally confined in the hanging wall side of faults and can escape at the seabed, generating pockmarks aligned along their footwall. • Active faults are imaged by multibeam bathymetry and seismic profiles. • Three main systems of faults affect the continental shelf and slope sectors. • A tectono-stratigraphic model of an extensional fault propagation fold is proposed. • Tectonic activity exerts a strong control on seabed morphology and recent processes. • Margin shaping results from the interplay between tectonic and non-tectonic factors. [ABSTRACT FROM AUTHOR]

Free gas is an important trigger of instability on continental slopes, and resulting mass-wasting strata can potentially form competent seals to hydrocarbon accumulations. This work uses two high-quality 3D seismic volumes to investigate fluid accumulations at the base of mass-transport deposits in the Pearl River Mouth Basin, South China Sea. In parallel, IODP/ODP borehole data are used to document the petrophysical character of mass-transport deposits formed in similar continental-slope environments to the South China Sea. The interpreted data show gas accumulations as comprising enhanced seismic reflections that are discordant, or vertically stacked, below mass-transport deposits with chaotic seismic facies. Gas was accumulated in basal shear zones of mass-transport deposits in response to differences in capillary pressure and porosity. Free gas in Zone A covers an area of at least 18 km 2 . In Zone B, the free gas is sub-circular in plan view and covers an area of 30.58 km 2 for a volume of sediment approaching 1.5 km 3 . This work is important as it shows that vertical migration of gas is not significant in mass-transport deposits from the Pearl River Mouth Basin, but up-dip migration along their basal shear zones is suggested in multiple locations. As a result, free gas can pinch-out laterally to extend 1–2 km beyond these same basal shear zones. As a corollary, we show that free gas accumulations below mass-transport deposits comprise an important geohazard and should be taken into account when drilling continental-slope successions in both the South China Sea and continental margins recording important mass wasting. Strata charged with free gas form weak layers, hinting at a novel trigger of retrogressive slope failures on continental slopes worldwide. [ABSTRACT FROM AUTHOR]

Several high-resolution 'SES 2000 deep' seismic profiles and a core of bottom sediments were obtained in cruises 33, 35, and 37 of the R/V Akademik Ioffe in the area of the Columbia channel (continental rise of Brazil, South America). The analysis of seismic facies and direct correlation of acoustic and lithological data indicates that sedimentation in this area is mostly controlled by the contour current of the Antarctic Bottom Water (AABW). The gravity flows from seamounts and continental slope only episodically contributed coarser material to the deposition of the muddy contourites. The mixed gravitite-contourite systems consisting of accumulative bodies (drifts) and erosion channels are the results of interaction of these sedimentation processes. [ABSTRACT FROM AUTHOR]

The Quaternary continental slope of the Baiyun Sag in northern South China Sea is characterized by a complex topography and abundant gravity flow sedimentation. High-resolution 3-D seismic data in this area allow for a detailed study of the seismic geomorphology and deep-water gravity flow depositional process. The Quaternary continental slope in the northern South China Sea is an above-graded slope. An intraslope basin lies within the above-grade continental slope. Slump, erosion, and deposition processes tend to develop a gentle topography and consequently a graded slope. The upper continental slope, which is above the slope equilibrium profile, is dominated by erosion and slumping. Slides, slumps and erosional channels are developed within this continental slope. The intraslope basin is located below the slope equilibrium profile and is potential accommodation space where sediments transported by gravity flows could be deposited, forming lobe aprons. Under the influence of gravity flow supply, gravity flow duration, continental slope topography, equilibrium profile, and accommodation, a slump-erosional channel-lobe depositional system is developed in the Quaternary continental slope in the Baiyun Sag. The deep-water gravity flow depositional process and the distribution of gravity flow sediments are greatly influenced by the continental slope topography, while the continental slope topography at the same time is reshaped by deep-water gravity flow depositional process and its products. The study of the interplay between the continental slope and gravity flow is helpful in predicting the distribution of the deep-water gravity flow sediments and the variation of sediment quality. [ABSTRACT FROM AUTHOR]

Abstract: Flemish Pass is a small, perched slope basin seaward of the Grand Banks on the eastern Canadian continental margin. Glacial ice crossed the Grand Banks to reach the upper continental slope during some Mid to Late Quaternary glaciations but terminated on the middle shelf, 200 km distant, at the last glacial maximum. This study investigates the effect of ice extent on slope sedimentation processes. Sediment in Flemish Pass comprises muds of hemipelagic and proglacial plume origin, minor thin-bedded turbidite sands, and thick-bedded mass-transport deposits (MTDs). A regional stratigraphy, based on 500 km of high-resolution seismic profiles and 60 piston cores up to 11 m long, was dated using 30 radiocarbon dates, the presence of Ash Zone II and oxygen isotope stratigraphy. This provided stratigraphic control for till tongues in water depths <600 m along the Grand Banks margin, recognized from oxygen isotope stage (OIS) 6 and locally from OIS 4. Five types of MTD deposited during OIS 4 and 6, were recognized from seismic-reflection data and related to ice sheet processes in the area. During OIS 2, when ice sheets did not reach the area, no MTDs are found in the basin, and the sedimentation rates decreased to ~2 mm/yr. The variation of sediment supply over the last 170 ka indicates a strong tie between the styles and rate of sedimentation in the basin and the presence of shelf-crossing ice. [Copyright &y& Elsevier]

Recent studies suggest that as much as half of the organic carbon (OC) undergoing burial in the sediments of tectonically active continental margins may be the product of fossil shale weathering. These estimates rely on the assumption that vascular plant detritus spends little time sequestered in intermediate reservoirs such as soils, freshwater sediments, and river deltas, and thus only minimally contributes to the extraneously old 14C ages of total organic matter often observed on adjacent shelves. Here we test this paradigm by measuring the Δ14C and δ13C values of individual higher plant wax fatty acids as well as the δ13C values of extractable alkanes isolated from the Eel River margin (California). The isotopic signatures of the long chain fatty acids indicate that vascular plant material has been sequestered for several thousand years before deposition. A coupled molecular isotope mass balance used to reassess the sedimentary carbon budget indicates that the fossil component is less abundant than previously estimated, with pre-aged terrestrial material instead composing a considerable proportion of all organic matter. If these findings are characteristic of other continental margins proximal to small mountainous rivers, then the importance of petrogenic OC burial in marine sediments may need to be reevaluated. [ABSTRACT FROM AUTHOR]

Echo character recorded on Chirp sub-bottom sonar data from offshore of SW Taiwan was analysed to examine and compare the sedimentary processes of adjacent passive and active continental margin settings. Seafloor echoes in the study area are classified into four types: (1) distinct echoes, (2) indistinct echoes, (3) hyperbolic echoes and (4) irregular echoes. Based on the mapped distribution of the echo types, the sedimentary processes offshore of SW Taiwan are different in the two tectonic settings. On the passive South China Sea (SCS) margin, slope failure is the main process on the upper continental slope, whereas turbidite deposits accumulate in the lower continental slope. In contrast, the submarine Taiwan orogenic wedge is characterized by fill-and-spill processes in intraslope basins on the upper slope, and mass-transport deposits are observed in the canyons and on the lower Kaoping slope. This difference is largely caused by the huge influx of terrigenous sediments into the submarine Taiwan orogenic wedge compared with the passive SCS continental margin. In the latter, loading and movement of the Taiwan orogenic wedge has had a significant effect on the seafloor morphology and has triggered retrogressive failures. Gas hydrate dissociation may have enhanced the slope failure processes at some locations. [ABSTRACT FROM AUTHOR]

We attempt here to quantify and model physiographic features off the central west coast of India in terms of power spectral exponent, amplitude parameter. We demonstrate that statistical analysis of multi-beam echo-sounder grid bathymetry data is able to characterise the outer shelf, upper slope, shelf margin basin and several structural rises in the region. A scatter diagram analysis shows that the seafloor data can be grouped into two distinct clusters. Distinctly different clustering patterns are observed over the structural rises, compared to the shelf, slope and basinal areas. This suggests different modes of formation for the members of these two clusters. In fact, the steep structural rises appear to be part of the NW–SE-trending coast-parallel Mid-Shelf Basement and Prathap ridges. These ridges are rift-induced volcanic emplacements on a stretched and thinned continental crust which probably formed during mid-Cretaceous times. [ABSTRACT FROM AUTHOR]

• We use seismic data to interpret the Quaternary sediments of the northern North Sea. • The lowermost Quaternary unit is interpreted as a turbidite-contourite deposit. • The East Shetland Platform was a major source area for coarse-grained sediments. • Fluvial-deltaic turbidites transition seaward into Shetland Drift contourites. • Contourites developed on the continental slope through the entire Quaternary. The thick sequence of Quaternary sediments preserved within the northern North Sea contains important information about the glacial history, palaeo-oceanographic conditions and slope stability of this region during the last 2.6 million years. The interplay between glacial, fluvial and contouritic processes can be determined from seismic stratigraphic studies. Here, seismic horizon, attribute and geomorphological interpretations of an extensive 2D seismic dataset (∼100,000 km2) and two 3D seismic cubes (∼18,400 km2) are integrated with lithological data from eight exploration wells to map sandy sedimentary units. Mapping of seismic horizons and facies reveals that, in addition to prograding glacial sediments derived from the Norwegian mainland, the Quaternary succession includes wedge-shaped units with prograding internal clinoforms building out from the East Shetland Platform, relatively flat-lying units of acoustically stratified sediments within the central northern North Sea, and aggrading to prograding units with low-amplitude internal reflections on the continental slope. The lowermost unit of Quaternary sediment is interpreted as an ∼800 km3 earliest Pleistocene (∼2.6 Ma) turbidite-contourite deposit, in which turbidites derived from a fluvial delta building out from the East Shetland Platform transition seaward into aggrading to prograding sediments of the Shetland Drift. The wedge-shaped units are intercalated with glacigenic sediments in the central northern North Sea, showing that the East Shetland Platform was a major source area for the delivery of coarse-grained sediments during the Early Pleistocene (∼2.6–0.8 Ma). The distribution of units of aggrading to prograding geometries suggests that contourites continued to develop on the continental slope, including on the North Sea trough-mouth fan, throughout the Quaternary. These interpretations constrain a new model for the Quaternary evolution of the northern North Sea that reconciles the development of the eastern and western sides of this margin, and shows the importance of fluvial-deltaic and contouritic sedimentation during periods of reduced glacigenic sediment input. Our model also provides a high-resolution analogue for the sedimentary architectures and seismic facies that can be produced by the interplay of down-slope and along-slope processes on other continental margins. [ABSTRACT FROM AUTHOR]

The morphology of divergent continental margins results from, amongst other things, rift processes, juxtaposition of oceanic, continental and transitional crust, and subsequent loading and shaping by sedimentary processes. Resulting morphologies have led to conventional classification of margin components into shelf, slope, rise and abyssal plain segments. Division of the inclined part of a continental margin into a slope and a rise; however, is challenging, due to complex geomorphologies and mixture of sedimentary processes. The rise, in particular, seems to elude specific criteria on which it might be uniquely identified, despite very specific criteria proposed in its original inception. This study seeks to develop a methodology on which the rise might be made more readily apparent. Solely diffusive behaviour of sediment flux should result in an exponential-shaped slope. This basic form is referred to as a graded shape. The continental rise, as a depositional body, conceptually should represent a departure from this shape, otherwise it cannot be morphologically distinguished from the continental slope. It is proposed that a graded slope represents the base-level condition for a margin that results from long-term diffusive sediment distribution due to a balance of processes of sediment input, transport, deposition, erosion and output. This study shows empirically that this base-level condition is mathematically predictable as an exponential decay curve with a constant exponent. To test this hypothesis, a 3D graded surface model slope that extends from the shelf break to the abyssal plain was produced for the Northwest Atlantic margin (NWAM) from Blake Outer Ridge to the northern tip of Labrador Sea. Removal of this model from measured bathymetry results in residual bathymetric anomalies that highlight graded, above-grade and below-grade segments of the margin. Nearly half of the margin by area (2 of 4.6 M km2) fits the graded curve model to within +/- 100 m. Above-grade segments total 1.9 M km2 and are mostly related to contourite deposition (e.g., Chesapeake Drift and Hatteras Outer Ridge) and submarine fan deposition (e.g., Laurentian Fan). Below grade segments (0.6 M km2) are related to erosion (e.g., Blake Escarpment) or non-deposition (e.g., Flemish Cap). There do not appear to be any consistent criteria in the form or distribution of residual bathymetric anomalies and associated sedimentary properties that allow ready distinction of the continental slope from the continental rise. Chesapeake Drift and Hatteras Outer Ridge are the largest anomalies along the entire margin, and yet it was on these features that the original concept of the continental rise was developed. The complexity of the margin, highlighted by this residual bathymetry technique, indicates the inadequacy of dividing a margin into long established components of slope, rise and abyssal plain. Classification of the margin according to grade seems more informative in terms of understanding its geomorphology, sediment distribution and geologic history. • Highly sedimented continental margins have a predictable graded exponential decay shape as their base-level condition. • Departures from grade may be due to over-supply (above-grade) or under-supply of sediment (below-grade). • Residual bathymetry derived by removal of predicted from measured bathymetry quantitatively identifies grade shape. • The continental rise was conceptualized on a highly anomalous above-grade region of the Northwest Atlantic margin. [ABSTRACT FROM AUTHOR]

The Piedra Buena Terrace (PBT), situated in the Patagonian continental slope, is swept by the vigorous flow of Antarctic-sourced bottom water masses, and intersected by a considerable submarine canyon system. It thus represents a world-class natural laboratory to investigate the sedimentary dynamics of deep-ocean settings influenced by both, along-slope, and down-slope sedimentary processes. In the framework of the Pampa Azul project, the PBT was surveyed with swath bathymetry and a high-resolution parametric sub-bottom seismic profiler and sampled at several locations with a 7 m long gravity corer. Through the integration of the acoustic data, grain size results from a sediment core and two AMS 14 C ages this work attempts to: (1) describe for the first time the detailed geomorphology of a poorly known region of the Patagonian continental slope; (2) depict the principal sub-surface seismic units, illustrating their internal structure, geometry, and distribution; (3) establish a correlation between sub-surface seismic facies and sediment deposits using the first age constraints for this region; (4) propose a model with the depositional history of the PBT, focusing on the interaction between along-slope and down-slope processes and seafloor morphology. The acquired bathymetric data imaged with unprecedent detail the geomorphology of the southern part of the PBT revealing the presence of a field of kilometric-sized, sub-circular, crater-like depressions, and a submarine canyon. The analyzed seismic sub-bottom profiles showed that the shallow sedimentary structure of the study area is represented by patchy-mounded deposits characterized by three distinctive features: cyclic stacks of two seismic facies (FA and FB), mounded shape, and preferential location northwards the morphological depressions and the submarine canyon. Integration of a seismic sub-bottom profile with one sediment core indicates that the alternation of seismic facies reflects variations in the hydrodynamic conditions. FA is related to a high to moderate energy medium with input of terrigenous material and FB is related to a low energy environment with a limited contribution of sediments from the continent. The patchy distribution, mounded shape and preferential location are associated with hydrodynamic processes occurring between the geomorphological features and the north-flowing Antarctic bottom currents, which result in the deposition of mounded contourites in the northern flank of depressions and hybrid along-slope down-slope deposits northwards a submarine canyon. The 14 C ages constrain the chronological framework of these sediments to the Late-Pleistocene. This is in contrast with previous investigations that have suggested much older ages (Late Miocene) for the sub-surface sediments of PBT. Finally, a conceptual model is here proposed to illustrate the Late Quaternary sediment depositional history of the PBT where the interaction between north-flowing bottom contouritic currents and seafloor relief played an important role in the deposition and preservation of sediments in this area. • Morphosedimentary study of the Piedra Buena Terrace (Patagonian Continental Margin). • The geomorphology of the Terrace is characterized by a field of kilometric crater-like depressions, and a submarine canyon. • Mounded-contouritic deposits build-up in the northern flank of crater-like depressions. • 14 C ages constrain the chronological frame of the shallow strata of the Piedra Buena Terrace to the Late Pleistocene. • Late-Quaternary sedimentation is controlled by seafloor heterogeneities, sea-level variations, and bottom currents intensity. [ABSTRACT FROM AUTHOR]

This study presents novel findings on the Pliocene and Quaternary evolution of the Gela Basin (Strait of Sicily, Mediterranean Sea), an area recording the interaction between tectonics, climate change at Milankovitch and sub-Milankovitch timescales, and dynamic water masses exchange between the eastern and western Mediterranean Sea. The calibration of seismic profiles with exploration boreholes allowed for the refining of the chronostratigraphic framework of the Gela Basin and highlighted the main phases of margin growth. Since the Pliocene, the margin has recorded the deposition of 100 m high shelf-edge clinothems, accompanied by sediment drifts on the slope and mass-transport deposits (MTDs), possibly triggered by seismic activity. Through the Plio-Quaternary the locus of deposition of sediment drifts migrated upslope due to a progressive shift of bottom currents. After the Middle Pleistocene Transition (MPT) the margin experienced an accelerated outbuilding with the deposition of a 700 m thick succession in only 0.8 Myr. At this time, a marked change in sedimentary architecture reflects the growth of shelf-edge clinothems and associated MTDs on the slope, and the spreading of contourite deposits over a broader and generally shallower area. Sediment flux to the basin and the intensity of bottom currents appear both paced at 100 kyr eccentricity orbital cycles. The growth of bottom current deposits on a large portion of the upper slope and outer shelf likely reflects constraints to the bottom current flow by the margin morphology, inherited from Miocene and Pliocene tectonics. Overall, a combination of long-term tectonic activity, climate change and shifts in oceanographic regime resulted in a complex along-strike variability of the margin morphology and stratigraphic architecture and affected where and when MTDs were emplaced. These conclusions show how climate cyclicity influence sediment supply which combined with margin morphology can promote slope instability in continental margins. • Evolution of the Gela Basin (Mediterranean Sea) during Plio-Quaternary investigated. • The outbuilding of the margin changed after the Middle Pleistocene Transition. • Contourite deposits play a key role in margin destabilization. • Clinothems and associated submarine landslides are paced at Milankovitch cyclicity. • Erosional unconformities act as glide planes for submarine landslides. [ABSTRACT FROM AUTHOR]

On continental margins, the upper slope to shelf break environment forms a critical region where sediment supply, hydrographic activity and gravitational processes determine how and when sediments are partitioned between the shallow- and deep-marine realm. On the SW Iberian margin, relatively few studies have addressed the dynamics of this region, although it holds key information regarding the link between the sedimentary evolution of the continental shelf and the contourite depositional system on the middle slope. This work therefore presents a high-resolution analysis of the morphological and stratigraphic expressions of late Quaternary (dominantly last glacial and present-day interglacial) sedimentary processes on the upper slope and shelf margin sector between 7° and 7°30' W. The integration of seismic, bathymetric and hydrographic data reveals the presence of alongslope processes and products (a bottom current-related plastered drift, moat, erosional surface and terrace, an internal wave-/tide-controlled sediment wave field), downslope (gravitational) processes and products (an upper slope – shelf margin valley system, slumps, debrites, gullies), neotectonic elements (diapirs) and fluid flow features (pockmarks, bright spots). The spatial distribution of these features indicates that the study area becomes increasingly alongslope-dominated towards the W, and oppositely, more downslope-dominated towards the E, because sediment supply to the latter area is enhanced under the dominant eastward dispersal of fluvially supplied sediments on the shelf. In addition, glacial-interglacial variations in the amount of sediments supplied to the shelf edge and the intensity of oceanographic processes in the study area also generate a distinct temporal variability, with glacial and interglacial intervals respectively recording principally downslope- and alongslope-controlled morphological elements. Finally, regardless of these overall spatial and temporal patterns, diapirism and fluid flow are inferred to locally destabilize sediments and induce small-scale mass wasting in the study area. These findings are not only relevant to the northern Gulf of Cadiz, but also to the general understanding of sedimentary dynamics and controls in mixed downslope- and alongslope-controlled upper slope to shelf margin settings worldwide. • Significant upper-slope morphological variability revealed off the Guadiana River. • Wide genetic diversity driven by along-/downslope processes, diapirism and gas flow. • Spatio-temporal patterns controlled by oceanographic variations and sediment supply. [ABSTRACT FROM AUTHOR]

A new basin-scale comprehensive view of contourite features, turbidite systems, and mass-wasting deposits comprising the Spanish and Moroccan margins and basins of the Alboran Sea has been achieved after a new detailed seismic stratigraphic analysis and the construction of sedimentary maps for the Pliocene and Quaternary sedimentary units. Multiple contourite systems were defined in this sea: i) the Intermediate Mediterranean contourite system (IMCS), formed under the action of the LMW on the Spanish continental margin; ii) the Deep Mediterranean contourite system (DMCS), formed under the action of the DMW and made up of contourites mostly found on the Moroccan margin and annex sub-basins; and iii) the Atlantic contourite system (ACS), shaped by the AW and its interfaces with the LMW and DMW on the uppermost continental slopes of both margins. The contourite features (drifts, moats, channels and terraces) coexist during the various stages of the Plio-Quaternary with turbidite systems showing different onsets and cessations in activity, and with mass-wasting deposits. In this work, the temporal and spatial distributions of contourite and turbidite systems can be considered as proxies to deduct the long-term impacts of bottom-current circulations and related processes, and ultimately allowed to decipher past bottom-current dynamics and the multiple factors controlling Plio-Quaternary sedimentation in the Alboran Sea. • Pliocene and Quaternary palaeogeographic reconstructions of the Alboran Sea • Contourites and turbidites allow characterizing palaeoceanographic process. • Tectonic uplift, local topography and palaeoclimate affect the sediment transport • Relevance for other Mediterranean marginal seas [ABSTRACT FROM AUTHOR]

The Baiyun Slide Complex is one of the largest submarine landslides on the northern margin of the South China Sea. Newly acquired high-resolution bathymetric data, 2D and 3D seismic data permitted the systematic investigation of the Baiyun Slide Complex in terms of its seafloor morphology and associated sedimentary processes. The headwall region of the Baiyun Slide Complex, located at a water depth between 1000 m and 1700 m, is U-shaped and opens towards the east. It was efficiently and almost completely evacuated, generating pronounced headwall and sidewall scarps. Submarine channels, sediment waves, migrating channels, sediment drifts and moats are observed within and around the headwall region, illustrating the effects of both downslope and along-slope sedimentary processes. Submarine channels are 16–37 km-long 800-1500 m-wide, and 20 to 50 m-deep. As a modern example of the interplay between slope instability and subsequent incision, submarine channels were generated after the formation of the Baiyun Slide scar to suggest intensified downslope sedimentary processes after the slope collapsed. The initiation and formation of these submarine channels result from the evacuation of the Baiyun Slide scar, which provided the necessary space of the continental slope to accommodate subsequent turbidity and mass wasting flows. Our results are an important example of how submarine landslides can influence erosional and depositional processes on continental margins. • Downslope and along-slope processes controlled the morphology of headwall region. • Erosive channels were initiated after the formation of the Baiyun Slide scar. • Downslope sedimentary processes were intensified after the slide scar formation. [ABSTRACT FROM AUTHOR]

The present-day morphology of the Le Danois Bank region has been investigated based on bathymetric and high to ultra-high resolution seismic reflection data. The involved bottom-current processes are associated with the Eastern North Atlantic Central Water, the Atlantic Mediterranean Water and the Labrador Sea Water. Sediments originating from various canyon systems along the Cantabrian Margin and the Asturias continental shelf are transported by downslope and alongslope processes towards the Le Danois intraslope basin. The background flow velocities of bottom currents are all below the threshold (8–10 cm/s) of generating plastered and mounded geometries of contourite drifts. However, bottom currents are locally accelerated (up to 25 cm/s) due to the presence of the Le Danois Bank and the Vizco High, creating a furrow and three moats and generating six plastered drifts, three elongated mounded and separated drifts at different depth intervals. The extension and distribution of the drifts are controlled by slope morphology and/or bottom current velocities. Unlike contourite drifts along other continental slopes, a single contourite drift (the Gijón Drift) with a lateral variation in drift geometry and internal structure indicates the interaction of bottom currents with different flow dynamics. Additionally, scouring of active bottom currents and rapid sedimentation rate of contourite drifts may be at the origin of slope instability events. Besides contourite drifts, internal waves may have induced the formation of sediment waves. In the Le Danois intraslope basin, multiple sedimentary processes work together and shape the present-day seafloor. Bottom currents are focused due to deflection on complex topographical obstacles within a relatively small basin setting, and create a wide variety of sedimentary features, including contourite drifts. The resulting sedimentary features thus have more frequent lateral variations, a feature typical for topographically constrained small basins. Image 1 • Present-day morphology of the Le Danois Bank region is shaped by alongslope, downslope and mixed processes. • Due to the morphological constraint of the Le Danois Bank and the Vizco High, bottom currents are more focused and strongly intensified (estimated acceleration up to 25 cm/s). • Contourite drifts are suggested to have specific geometries and shapes in topographically constrained small basins. • Contourite drifts have more frequent spatial variations in topographically constrained small basins. [ABSTRACT FROM AUTHOR]

Submarine mass movements may have profound effects on the morphology and stratigraphic architecture of continental margins. Furthermore, they can represent a threat to human life and infrastructures, and also have implications for hydrocarbon exploration/production. In polar regions, they are one of the predominant sedimentary processes on the continental slope. Exploration seismology has been widely employed to study masstransport deposits (landslides, glacigenic debris flows, mass flows, etc.), which are usually characterized by chaotic reflections. In this study, we analyse a seismic profile acquired in the southern part of the Storfjorden trough mouth fan (NW Barents Sea margin), showing the presence of two submarine mass-transport deposits (MTDs). A giant MTD (PLS-1) is located on the lower continental slope at 2.6–3 km depth, while a more recent MTD (PLS-2) occurs at 1.9–2.4 km depth. Velocity and attenuation seismic tomography, seismic attributes analyses and rock-physics models reveal distinct petrophysical properties for PLS-1 and PLS-2. Despite the known influence of burial depth(s), fluid flow content, and compaction on the internal character of MTDs, the two deposits studied here, in fact, show distinct petrophysical characteristics that reflect lithological variations - more than to any other control. These results suggest different source areas for the two MTDs. The inferred coarser sediment in PLS-1 indicates provenance from areas with abundant glacigenic debris flows, (such as the Bjørnøya Trough-Mouth Fan). Conversely, the finer, relatively fluid-rich sediments of PLS-2 that underwent little translation could have an origin in the area between trough-mouth fans. Here, slow-moving ice resulted in a relatively scarce release of subglacial debris at the shelf edge and the continental slope was subject to enhanced erosion and degradation with a comparatively higher production of relatively fine-grained turbidite flows. [ABSTRACT FROM AUTHOR]