There is still a great unawareness about the deep-water circulation in the NE-Central Atlantic since the Late Cretaceous. The morphology, sedimentary stacking pattern and distribution of contourite depositional systems have been widely used as paleoceanographic indicators, given clues about the relative velocity and pathways of bottom currents past-circulation. We present here evidence of a new contourite features developed in the NECentral Atlantic offshore Madeira Island between -3000 m and - 4950 m water depth. These features allowed us to define two Contourite Depositional Systems (CDSs). The dataset used in our work is composed of multichannel reflection seismic profiles and DSDP and ODP sites for the chronostratigraphic framework. The seismic stratigraphy analysis allowed the identification of six seismic units (U1-U6) and a sub-unit (U6a) separated by erosional discontinuities (D1-D6). The acoustic basement corresponds to oceanic crust located in the Cretaceous Magnetic Quite Zone (-120 Ma to 84 Ma), but basalts drilled at DSDP Site 136 near Madeira Island, indicate an age of about 106 Ma. Sedimentary deposits from seismic units are interpreted as pelagic (unit U1; Early Cretaceous); contourite (U2 to U6; Late Cretaceous to Quaternary); and mass transport deposits (U6a; Quaternary). These seismic units characterize the CDSs from Late Cretaceous (Campanian?), resting unconformably on pelagic sediments of probable Aptian to Santonian age. The CDS-1 (U2 to U4) was formed from Late Cretaceous (Campanian?) to Middle Miocene and the CDS-2 (U5 and U6) was deposited from Middle Miocene to Quaternary. They are bounded by major erosional surfaces and characterized by giant elongated mounded contourite drifts (Drift 1 and Drift 2, respectively). Presently, CDS-1 is inactive and buried by pelagic sediments. Conversely, CDS-2 outcrops between -3000 and 4800 m water depth on the lower slope of Madeira plateau. These results reveal that this region of the NE-Central Atlantic has been swept by long-term northward bottom currents. We propose that the most plausible water masses responsible for these bottom-currents and drifts generation have been the Southern Component Water (SCW) and more recently the Antarctic Bottom Water (AABW). Consequently, the onset of the first incursion of the SCW was near the end of Late Cretaceous, probably in the Campanian. Since the late Eocene, the AABW would have a dominant role in this region of the NE-Central Atlantic. Assuming that during cool periods, the AABW had a greater volume and circulated shallower than 4000 m, we hypothesized that CDS-2 has been mainly active during these periods. On the contrary, during warmer periods, the AABW circulates deeper (>4000 m) and thus contourite deposition associated with the AABW shifted to deeper water depths. Presently the CDS-2 can be considered as a relict feature. Therefore, the Madeira CDCs represents a unique and very promising sedimentary archive for reconstructing deep-water masses circu-lation and their variability in the NE-Central Atlantic since the end of Cretaceous through the Quaternary, where the oceanic seafloor irregularities have been key in controlling the water masses and bottom currents behavior.

The deep-water sedimentary processes and morphological features offshore Madeira Island, located in the Central-NE Atlantic have been scantly studied. The analysis of new multibeam bathymetry, echo-sounder profiles and few multichannel seismic reflection profiles allowed us to identify the main geomorphologies, geomorphic processes and their interplay. Several types of features were identified below 3800 m water depth, shaped mainly by i) the interplay between northward-flowing Antarctic Bottom Water (AABW) and turbidity currents and ii) interaction of the AABW with oceanic reliefs and the Madeira lower slope. Subordinate and localized geomorphic processes consist of tectono-magmatic, slope instability, turbidity currents and fluid migration. The distribution of the morphological features defines three regional geomorphological sectors. Sector 1 represents a deep-seafloor with its abyssal hills, basement highs and seamounts inherited from Early Cretaceous seafloor spreading. Sector 2 is exclusively shaped by turbidity current flows that formed channels and associated levees. Sector 3 presents a more complex morphology dominated by widespread depositional and erosional features formed by AABW circulation, and localized mixed contourite system developed by the interplay between the AABW circulation and WNW-ESE-flowing turbidite currents. The interaction of the AABW with abyssal hills, seamounts and basement ridges leads to the formation of several types of contourites: patch drifts, double-crest mounded bodies, and elongated, mounded and separated drifts. The patch drifts formed downstream of abyssal hills defining an previously unknown field of relatively small contourites. We suggest they may be a result of localized vortexes that formed when the AABW's flow impinges these oceanic reliefs producingthe erosional scours that bound these features. The bottom currents in the area are known to be too weak (1-2 cm s(-1)) to produce the patch drifts and scours. Therefore, we suggest that these features could be relics at present, having developed when the AABW was stronger than today, as during glacial/end of glacial stages.

Paleoceanographic studies of abyssal bottom currents are often complicated by low current speeds and sedimentation rates, resulting in sediment condensation or erosion. However, increased rates of erosion and deposition may occur where bottom current velocities change as they pass through deep marine gaps and gateways. Despite this, the depositional processes in these gateways and their paleoceanographic implications remain poorly understood. Based on new sedimentological, hydrological and geophysical (high resolution seismic and bathymetry) data from Discovery Gap (Azores-Gibraltar Fracture Zone) collected during the 43rd cruise of the R/V Akademik Nikolaj Strakhov in 2019, the key sedimentary processes occurring in the Late Quaternary have been determined. Two depressions with depths exceeding 5300 m in the centre and south of Discovery Gap have been identified, the latter filled with contouritic deposits. These depressions are separated by a roughly N-S trending central sill at 4860 m and a sediment filled terrace at 4720 m water depth. Elongated NE-SW trending highs and sills, are present in the north and south of the study area. Their importance in controlling the flow of water through Discovery Gap is determined by the presence of erosion at the base of these highs with adjacent sheeted or mounded contourite drifts. Pelagic, hemipelagic, reworked pelagic/hemipelagic and fine-grained contourite sedimentary facies have been identified. The sedimentary facies associations point to remarkable variability in the Antarctic Bottom Water (AABW), linked to glacial-interglacial changes, and its intermittent influence in Discovery Gap during the Quaternary. During glacial intervals (MIS 6, 4 and 2) and at their terminations there was enhanced bottom current activity coeval with higher terrigenous content, and increased carbonate dissolution. The results of this study improve our understanding of sedimentary processes in abyssal environments and highlight the value of the sedimentary record in deep marine gateways for interpreting the interaction of bottom water with abyssal morphology. Future work in other modern deep gaps is essential to shed more light on how deep gaps form and to fully reconstruct deep-water paleocirculation within oceanic basins.

The Sines Contourite Depositional System, located in the Southwest Portuguese Margin, is a central segment of the Iberian Contourite Depositional Complex, built under the influence of the Mediterranean Outflow Water (MOW). This work presents the onset and evolution of this system using multibeam bathymetry, multichannel seismic reflection lines, sediment cores and well data. Six seismic units of Late Miocene through Holocene age have been identified, which defined three evolutionary stages for drift construction: a) an onset and initial stage, from the Latest Miocene to the Late Pliocene (5.33-2.5 Ma), where a sheeted drift was built under a weak flowing MOW; b) a growing stage from the Early to Middle Quaternary (2.5-0.7 Ma), characterized by the deposition of a mounded drift in the south and a sheeted drift in the north, which is correlated with a strengthening of the MOW; and c) a maintenance stage between the Middle Pleistocene and Holocene (0.7 Ma - present), where the modern depositional and erosional contourite features developed associated with three intensification periods of the MOW at 0.7 Ma, 0.4 Ma and 20 ka. The development of the Sines Contourite Depositional System was constrained in the long-term by seafloor paleomorphologies inherited from the Mesozoic rifting phases of the Southwest Portuguese Margin. The NNW-SSE horsts and grabens built during the Mesozoic rifting provided accommodation for drift growth, with limited lateral migration, and locally enhanced the alongslope bottom-current. In short-term, environmental (climate and sea-level) fluctuations modulated changes in bottom-current density and intensity, determining sedimentary cycles in the depositional record, especially during the Quaternary. Our findings emphasize the occurrence of three main plastered morphologies throughout the seismic record, which were compared with other plastered drifts in different continental margins to establish a conceptual model.

We present a multidisciplinary study of the seismic stratigraphy, sedimentology, geochemistry and magnetism to characterize the Quaternary mass movement deposits (MMD) and the associated deformation in the Portimao Bank (Gulf of Cadiz, offshore SW Iberia). Two scales of approach have been applied. At large-scale (m to km) approach, were recognized and characterized a series of important and subsequent slide scars (tens of meters high) and MMD (the larger one with 10 km length) related to landslides, more prominent at Portimao Bank's southern flank. At small-scale (cm) approach, we point out on a piston core collected within a scar affected by MMD, a replication of the sedimentary column as evidenced by geochronological results and corroborated by sedimentology, geochemistry and magnetic data. Magnetic fabric data enabled the identification and characterization of the internal structure and deformation of MMD along the sedimentary column. For last, geochronology and the morphology of Portimao seamount are discussed in order to constraint the factors controlling MMD triggering. The multidisciplinary approach is useful in a better characterization of the MMD at different scales and improved the understanding of its dynamics.

The contourite depositional system (CDS) along the southwestern Iberian Margin (SIM), within the Gulf of Cadiz and offshore areas of western Portugal bear the unmistakable signal of Mediterranean Outflow Water (MOW) exiting the Strait of Gibraltar. This locality records key information concerning the effects of tectonic activity on margin sedimentation, the effects of MOW dynamics on Atlantic circulation, and how these factors may have influenced global climate. Over the last four decades, numerous studies have been conducted on the late Miocene, Pliocene and Quaternary sedimentary stacking pattern of Neogene basins along the SIM for both academic and resources exploration purposes. However, understanding of the region rests primarily on basic seismic stratigraphy calibrated with limited data from only a few exploration wells. The Integrated Ocean Drilling Program (IODP) Expedition 339 recently drilled five sites in the Gulf of Cadiz and two sites on the western Iberian margin. The integration of core and borehole data with other geophysical databases leads us to propose a new stratigraphic framework. Interpretation of IODP Exp. 339 data along with that from industry sources and onshore outcrop analysis helps refine our understanding of the SIM's sedimentary evolution. We identify significant changes in sedimentation style and dominant sedimentary processes, coupled with widespread depositional hiatuses along the SIM within the Cadiz, Sanlucar, Doñana, Algarve and Alentejo basins. Following the 4.5 Ma cessation of a previous phase of tectonic activity related to the Miocene–Pliocene boundary, tectonics continued to influence margin development, downslope sediment transport and CDS evolution. Sedimentary features indicate tectonic pulses of about 0.8–0.9 Ma duration with a pronounced overprint of ~ 2–2.5 Ma cycles. These more protracted cycles relate to the westward rollback of subducted lithosphere at the convergent Africa-Eurasia plate boundary as its previous NW–SE compressional regime shifted to a WNW–ESE direction. Two major compressional events affecting to the Neogene basins at 3.2–3 Ma and 2–2.3 Ma help constrain the three main stages of CDS evolution. The stages include: 1) the initial-drift stage (5.33–3.2 Ma) with a weak MOW, 2) a transitional-drift stage (3.2–2 Ma) and 3) a growth-drift stage (2 Ma-present time) with enhanced MOW circulation into the Atlantic and associated contourite development due to greater bottom-current velocity. Two minor Pleistocene discontinuities at 0.7–0.9 Ma and 0.3–0.6 Ma record the effects of renewed tectonic activity on basin evolution, appearing most prominently in the Doñana basin. Several discontinuities bounding major and minor units appear on seismic profiles. Quaternary records offer the clearest example of this, with major units of about 0.8–0.9 Ma and sub-units of 0.4–0.5 Ma. Sedimentation is controlled by a combination of tectonics, sediment supply, sea-level and climate. This research identifies time scales of tectonic controls on deep-marine sedimentation, specifically over periods of 2.5–> 0.4 Ma. Shorter-term climatic (orbital) mechanisms control sedimentation at time scales of ≤ 0.4 Ma. The role of bottom water circulation and associated processes in shaping the seafloor and controlling the sedimentary stacking pattern on continental margins has to be seriously reconsidered in future multidisciplinary studies. This is not only because of the common occurrence of sandy contourite deposits in deep water setting and their economic interest for hydrocarbon exploration, but principally because they archive the heartbeat of the interior Earth and therefore have important sedimentary and paleoceanographic implications.

VIII Simposio sobre el Margen Iberico Atlantico (MIA15), del 21 al 23 de septiembre de 2015, Malaga.-- 3 pages, 5 figures

The base of the Faro contouritic drift (IODP Site U1386) on the northern margin of the Gulf of Cádiz (Algarve margin) is characterized by two sequences of frequent gravity deposits with different ages and compositions. Among these gravity deposits, several relatively thick debrites (up to 12m) have been observed and studied in detail.Sedimentological analyses have been performed and because of non-turbulent behavior of debris flows, detailed micropaleontological studies could be realized. Planktonic foraminifera thus allowed establishing a detailed biostratigraphy of these deposits. Benthic foraminifer and ostracod assemblages were used to evaluate the origin of the sediment composing these debris flows and estimate their run-out distance.These debrites are dated from Early Pliocene and early Pleistocene, and were deposited in a mesobathyal environment. They comprise silty mud clasts and matrixes with sand content up to 34%. The Early Pliocene debrites are bioclast-rich whereas the Early Pleistocene debrite is enriched in terrigenous particles. The data indicates that these debrites were triggered on the continental shelf and traveled less than 100km, eroding the seafloor all along their path for the Early Pliocene debrites and only the first part of their path for the early Pleistocene debrite. Matrixes originate from failure areas whereas eroded sediments along the flow pathway are incorporated into the flow as clasts.High abundance of shelf fauna during the Early Pliocene and great supply of terrigenous particles from rivers during the early Pleistocene in the south-western Iberian margin have favored gravity flows from the continental shelf to the slope. The contouritic paleo-moat of the Faro drift has been a determining channeling feature for gravity flows along the Algarve margin during the early Pleistocene, testifying of the strong interaction between MOW circulation and down-slope processes. Tectonic and diapiric activities were significant during Early Pliocene and early Pleistocene on the Algarve margin and could have been triggering parameters of failures related to these debris flows.

Earthquakes and submarine landslides are recurrent and widespread manifestations of fault activity offshore SW Iberia. The present work tests the effects of sea-level rise on offshore fault systems using Coulomb stress change calculations across the Alentejo margin. Large-scale faults capable of generating large earthquakes and tsunamis in the region, especially NE–SW trending thrusts and WNW–ESE trending dextral strike-slip faults imaged at basement depths, are either blocked or unaffected by flexural effects related to sea-level changes. Large-magnitude earthquakes occurring along these structures may, therefore, be less frequent during periods of sea-level rise. In contrast, sea-level rise promotes shallow fault ruptures within the sedimentary sequence along the continental slope and upper rise within distances of <100 km from the coast. The results suggest that the occurrence of continental slope failures may either increase (if triggered by shallow fault ruptures) or decrease (if triggered by deep fault ruptures) as a result of sea-level rise. Moreover, observations of slope failures affecting the area of the Sines contourite drift highlight the role of sediment properties as preconditioning factors in this region.

Seamounts are first-order morphological elements on continental margins and in oceanic domains, which have been extensively researched over recent decades in all branches of oceanography. These features favour the development of several geological processes, and their study gives us a better understanding of their geological and morphological domains. The seamounts around Iberia are numerous and provide excellent examples of the geodiversity of these morphological elements. Here we present a compilation of 15 seamounts around the Iberian Peninsula. These seamounts have different origins related to the geodynamic evolution (volcanism, extensional or compressive tectonics, and diapirism) of the domains where they are located. The current configuration of their relief has been influenced by Neogene-Quaternary tectonics. Their positioning controls the current morpho-sedimentary processes in the basins and on the margins, and highlights the fact that downslope processes on seamount flanks (mass flows, turbidite flows, and landslides) and processes parallel to seamounts (contouritic currents) correspond to the major geological features they are associated with them. Biogenic structures commonly develop on the tops of seamounts where occasionally isolated shelves form that have carbonate-dominated sedimentation.

espanolPresentamos una vision sintetica de los patrones sedimentarios evolutivos de las plataformas continentales de la Peninsula Iberica, con un enfasis particular en las interpretaciones de estratigrafia secuencial propuestas y con el objetivo de realizar una comparacion entre los estilos de construccion de plataformas continentales en el Atlantico y el Mediterraneo. La mayor parte de las plataformas estudiadas muestran un claro predominio de los depositos progradantes desarrollados durante intervalos de descenso relativo y de bajo nivel del mar, lo cual es particularmente evidente en el registro sedimentario Plioceno-Cuaternario, reflejando el control primario de los cambios glacioeustaticos. Los depositos transgresivos y de alto nivel del mar previos al Ultimo Maximo Glacial parecen estar mejor representados en plataformas continentales influenciadas por los grandes cursos fluviales. Los depositos transgresivos postglaciales muestran una gran variabilidad espacial, cambiando lateralmente desde parasecuencias progradantes hasta extensas laminas arenosas. Por el contrario, los depositos de alto nivel del mar Holocenos muestran un caracter mas homogeneo, con desarrollo de cunas sedimentarias proximales y depocentros fangosos distales. Los diferentes estilos de crecimiento de las plataformas continentales atlanticas de Iberia resultan basicamente de la interaccion entre los regimenes deposicionales e hidrodinamicos, observandose una gradacion latitudinal de plataformas desde la plataforma erosiva del Mar Cantabrico a la plataforma deposicional del Golfo de Cadiz. Localmente, se identifican algunos sectores de la plataforma que no responden a este patron general, sino que su crecimiento esta controlado por rasgos morfo-estructurales (por ejemplo, los ambientes de rias y las plataformas atravesadas por accidentes tectonicos mayores). Los patrones de crecimiento de las plataformas mediterraneas de Iberia estan estrechamente relacionados con el aporte fluvial, diferenciandose dos estilos basicos: plataformas con alto aporte y plataformas con bajo aporte sedimentario. El estilo de bajo aporte sedimentario es el tipo mas frecuente, el cual puede mostrar una mayor complejidad en funcion de la existencia de canones submarinos y/o de rasgos morfoestructurales EnglishWe present a synthetic view of continental-shelf evolutionary patterns around the Iberian Peninsula, focusing on proposed sequence stratigraphy interpretations and attempting a comparison between Atlantic- and Mediterranean-type shelf-margin constructions. Most of the studied shelves show a dominance of regressive to lowstand deposition through successive progradations, particularly evident in the Pliocene-Quaternary, documenting the influence of glacio-eustasy. Transgressive to highstand development predating the Last Glacial Maximum seems to be favoured off major rivers, but the highest variability is seen during postglacial evolution. Transgressive deposits tend to show a higher spatial variability, ranging from prograded parasequences to extensive sand sheets. Holocene highstand deposits usually show a more homogeneous character, with development of proximal wedge-shaped deposits and a distal sheet-like deposition. Atlantic continental shelves off Iberia display three different types of shelf growth: depositional shelves, shelves with restricted progradation and erosional shelves. They result from the interplay between depositional and hydrodynamic regimes, with the occurrence of a latitudinal gradation from erosional shelves in the Cantabrian continental shelf to depositional shelves in the northern Gulf of Cadiz shelf. Some shelf sectors do not correspond to this general pattern, as shelf sedimentation is mainly controlled by morpho-structural features (e.g., ria environments and shelves crossed by major tectonic accidents). The Mediterranean continental shelves of Iberia show two basic types, high- versus low-supply shelves, and their growth patterns are mainly a response to the amount of fluvial supply. The low-supply style is clearly the most frequent type, and it may show further complexity according to the occurrence of submarine canyons and/or morpho-structural control.

Here we present a synthesis of bedforms and sediment types on the shelves surrounding the Iberian Peninsula and the Balearic Islands, after the integration several pieces of bathymetric, morphological and sedimentological datasets. The Iberian and Balearic shelves are divided into segments according to the largescale margin configuration, fluvial sediment supply and hydrodynamic regime. Their geological settings and large-scale sedimentation patterns place the investigated shelves into two broad categories: abrupt, steep and narrow sediment-starved shelves, illustrated by the Cantabrian shelf, and gentle, smooth and wide sediment-fed shelves, such as the shelves off some major flivial systems. An in-depth classification was subsequently attempted, based on morpho-sedimentary types. Under this approach, the Iberian and Balearic shelves can be classified as: (1) storm-dominated shelves, with erosional rocky floors, frequent abrasion surfaces and coarse-grained sediments; (2) current-dominated shelves, showing a good equilibriumbetween sediment fluxes and coastal and shallow ocean circulation, with laterally extensive muddy belts; (3) sediment supply-dominated shelves, where extensive subaqueous deltas develop off river mouths; and (4) wave-dominated shelves that occur off coastal stretches with minor and/or multiple fluvial sediment sources and enhanced littoral current.

Shelves from volcanic ocean islands result from the competition between two main processes, wave erosion that forms and enlarges them and volcanic progradation that reduces their dimension. In places where erosion dominates over volcanism, shelf width can be used as a proxy for the relative age of the subaerial volcanic edifices and reconstruction of their extents prior to erosion can be achieved. In this study, new multibeam bathymetry and high-resolution seismic reflection profiles are exploited to characterize the morphology of the insular shelves adjacent to each volcanic edifice of Terceira Island in order to improve the understanding of its evolution. Subaerial morphological and geological/stratigraphic data were also used to establish the connection between the onshore and offshore evolution. Shelf width contiguous to each main volcanic edifice is consistent with the known subaerial geological history of the island; most of the older edifices have wider shelves than younger ones. The shelf edge proved to be a very useful indicator in revealing the original extent of each volcanic edifice in plan view. Its depth was also used to reconstruct vertical movements, showing that older edifices like Serra do Cume-Ribeirinha, Guilherme Moniz, and Pico Alto have subsided while more recent ones have not. The morphology of the shelf (namely the absence/presence of fresh lava flow morphologies and several types of erosional, depositional, and tectonic features) integrated with the analysis of the coastline morphology allowed us to better constrain previous geological interpretations of the island evolution.

High-resolution morpho-bathymetric data at 1:200,000 scale obtained during the FAIVI cruise (2011) and the resulting geomorphologic map of the Terceira island offshore area (central Azores, Portugal) are presented for the first time. The uneven morphology around Terceira is primarily related to volcanic features, such as linear and cone-shaped eruptive centres and lava flows. Such features are mostly concentrated on volcanic ridges and are aligned along preferential axes, suggesting a strong interaction between tectonics and volcanic processes. The occurrence of active tectonics is also demonstrated by systems of faults cutting the seafloor to the north, east and south of the island. Mapped erosive-depositional features include an insular shelf located at < 150 m water depth (wd), small landslide headwalls, erosive scarps, channelized features and crescent-shaped bedforms. The presented map may represent the base for a first-order geo-hazard assessment.

The contourite drifts off southwest Iberia that formed as a result of the interaction of the Mediterranean Outflow Water (MOW) with the continental middle slope were studied in the Algarve margin using multichannel reflection seismic lines, oil-wells, piston cores, and a bathymetric compilation of four datasets. The seismostratigraphic interpretation of a dense array of oil industry seismic and stratigraphic correlation allowed the identification of five seismic units of Early Pliocene through Holocene in the Faro and Albufeira drifts and four correlative seismic units in the Lagos and Sagres drifts and three in the Portimão drift. A three-phased evolutionary model for the contourite formation is proposed. Firstly, a precursory phase of Pliocene age made up of sheeted drifts represents an initial phase of deposition under bottom-current activity that is correlated with the first stages of an enhanced MOW at about 3.5Ma. Secondly, the building up phase of Early Pleistocene age is related to a strengthening of the MOW close to the onset of the Northern Hemisphere glaciations at about 2.6Ma during which were deposited low-mounded drifts. Thirdly, the growing phase from Middle-Pleistocene through Holocene suggests the presence of a stronger MOW since the beginning of the Middle-Pleistocene Transition at about 1.3–1.0Ma, accounting for the deposition of mounded drifts and formation of the Álvares Cabral moat. Seismostratigraphic interpretation and isochron maps allowed for the establishment of the main oceanographic, climatic, morphologic and tectonic factors that controlled the drifts deposition: i) the Pliocene and Quaternary MOW circulation forced by climate changes; ii) the sea bottom topography inherited from the Late Miocene, mainly shaped by the Portimão, Lagos and Bartolomeu Dias canyons system; iii) the interaction between along-slope and down-slope processes since the Pliocene; and iv) Pliocene–Quaternary fault-activity and diapirism.

Multibeam swath bathymetry data from the Northwestern part of the Gulf of Cadiz revealed the existence of several intriguing kilometric crescentic depressions lying between −4300m and −4700m, never before reported to occur at such great depths. Morphological parameterization of these features, coupled with a detailed analysis of multi-channel and middle resolution seismic profiles, showed that these crescent-shaped features were formed due to the existence of specific time-recurrent interaction between: a) regional active thrusts, which portray the overall tectonic scenario in the area, and on top of which most crescentic depressions are carved; and b) tectonically induced scouring comprising localized erosion and simultaneous progradational sedimentation, produced by downslope currents of probable turbiditic origin. The obtained results also suggest a possible contribution of fluid migration and extrusion processes, such as mud volcanism and associated pockmark formation, besides gravity driven landslides and slumping, in the development of the studied crescentic depressions.