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European Geosciences Union General Assembly (2017. Viena), During the last decades several works have been carried out on the morphosedimentary processes driven by bottom-currents in several continental margins and abyssal plains worldwide. However these processes still remain poorly understood on deep-water settings and particularly around oceanic islands. This study is focused on the offshore of Madeira Island (Portugal), which is located in the Northeast Atlantic at about 700 km west of NW Africa., Estrutura de Missão para a Extensão da Plataforma Continental, Portugal, Instituto Dom Luiz, Portugal, Royal Holloway, University of London, Reino Unido, Universidade de Évora, Portugal, Instituto Hidrográfico, Portugal, Instituto Português do Mar e da Atmosfera, Portugal, GEOPHI Srl, Italia, Centro Oceanográfico de Málaga, Instituto Español de Oceanografía, España, Instituto Geológico y Minero de España, España

5th International Geologica Belgica Meeting, 26-29 January 2016, Mons, Belgium, We have investigated the origin of morphological depressions (circular-elliptical depressions, amphitheatre-shaped escarpments and valleys) on the Guadalquivir Bank uplifted area (Gulf of Cadiz middle slope). This work is based on swath bathymetry and high-and mid-resolution reflection seismic datasets. Depressions occur on the distal (depositional) sector of the Gulf of Cadiz Contourite Depositional System, which has been developed under the influence of the Mediterranean Outflow Water (MOW). The Guadalquivir Bank is a NE-oriented relief that was uplifted along the Neogene and Quaternary. It forms the southern limit of the Bartolomeu Dias and Faro Sheeted Drift (SD) plateaus that are separated by the NW-trending Diego Cao Contourite Channel. Circular-elliptical depressions occur on the Bartolomeu Dias SD plateau, aligned parallel to the rim of the Diego Cao Channel. Irregular, crescent-shaped depressions occur to the SE of the study area and a valley surrounds the Guadalquivir Bank. The origin of these features is interpreted as the result of the interplay between oceanographic, mass-wasting, tectonic and fluid-escape processes. Four stages define the development of these features: 1) Onset of a contourite mounded drift associated with a proto-Diego Cao moat originated by a weak MOW circulation as it interacted with the structural features of the Guadalquivir Bank during the Lower Pliocene; 2) Evolution to a more complex multi-crest drift and moat system, probably as a result of an enhanced MOW and increased deformation of the underlying structures during the Upper Pliocene-Early Quaternary; 3) Event of enhanced tectonic activity that provoked widespread mass-wasting events along middle slope sheeted drift plateaus during the Mid Pleistocene. It was recorded in a prominent erosive surface under the present-day Diego Cao channel western rim and numerous slide scars displaying amphitheatre shapes on the limits of the plateaus; 4) Final stage (Late Quaternary) when the MediterraneanIntermediate Branch started flowing towards the N-NW along the deep gateway that was opened as a result of the mass-wasting event and/or structural adjustments. The contourite system evolved, due to tectonic events, to the present-day channel and a complex separated drift that includes circular depressions. They result from the interaction between the bottom current and the irregular basal surface created by the slide scars. During this phase, crescent-shaped depressions were created, probably by the interplay between bottom currents and fluid escape processes, and the marginal valley around the Guadalquivir Bank resulted from current reworking of the irregular topography of contouritic deposits affected by slide scars

5th International Geologica Belgica Meeting, 26-29 January 2016, Mons, Belgium

VIII Simposio sobre el Margen Ibérico Atlántico (MIA15), del 21 al 23 de septiembre de 2015, Málaga.-- 3 pages, 5 figures, The effects of the Mediterranean Outflow Water (MOW) over a deep seafloor environment have been filmed with an ARGUS ROV system in the Cadiz Contourite Depositional System (Gulf of Cadiz, Spanish Atlantic). The new images, obtained in different erosional and depositional features of the system at depths between 500 and 700 m, state the capability of bottom currents to generate bedforms at different scales. The ROV system recorded a great variability of current-induced features, both longitudinal and transverse in different sub-environments dominated by gravel and sand to silty sand sediments: furrows, contouritic channels, terraces, and drift domains. The spatial distribution of the bedforms confirms the general westward decrease in energy of the MOW. But the bedform patterns reflect a great variability in the velocity and direction of the bottom current at local scale. This fact suggests a complex scenario characterized by the combination of different hydrodynamic processes action, This contribution has been supported through the MOWER (CTM 2012-39599-C03) and CONDRIBER (Ref. PTDC/GEO-GEO/4430/2012) projects

VIII Simposio sobre el Margen Ibérico Atlántico (MIA15), del 21 al 23 de septiembre de 2015, Málaga.-- 3 pages, 2 figures.-- This work is also a contribution to MOWER project CTM2012-39599-C03-02 (Spain), Contourite drifts are recognized as able to generate mass-transport deposits along Portuguese margins. It is important to understand the behavior of these depositional bodies and to which external factors they may be related to. Calcareous nannofossil assemblages are here described as an additional proxy to identify and correlate these disturbed sedimentary units. Core CO14-GC-06 contains a combination of extant (e.g. Gephyrocapsa muellerae, Calcidiscus leptoporus s.l. and Coccolithus pelagicus s.l.) and extinct taxa (reticulofenestrids and watznaueriales) which relative proportions are related to the ongoing major oceanographic processes that generate marine paleoproductivity and reworking. A unique nannofacies, a reticulofenestrid-rich chalk, was detected on one of the turbidite layers, leaving the question of determining its provenance, This work was supported by CONDRIBER project PTDC/GEO-GEO/4430/2012, funded by FCT Fundação para a Ciência e a Tecnologia

VIII Congreso Geológico de España, 17-19 de julio de 2012, Oviedo