Adelgazamiento de la corteza en el margen septentrional del Golfo de Cádiz

Refraction/wide angle seismic profiles acquired in 2000 during the Parsifal cruise across the Southportuguese Zone, the Algarve Basin and the South Iberian continental margin have allowed us to determine the crustal structure west of the Bank of Guadalquivir, which has been constrained by gravity modelling. According to the crustal model obtained, a crustal thinning of 11 km takes place from the shoreline to the Guadalquivir Bank area, where enhanced crustal attenuation has been found. Under the sedimentary cover, the velocity structure consists of a wedge-shaped upper crust with velocities between 5.8 and 5.9 km/s, characterised by a pronounced thickness variation. In the middle-lower crust, velocity increases from 6 to 7 km/s

First evidence of a main channel generated by the Mediterranean Outflow Water after its exit from the Gibraltar Strait

An extensive terrace comprising sandy sheeted drifts characterises the proximal sector (close to the Straits of Gibraltar) of the Contourite Depositional System (CDS) of the Gulf of Cadiz and the western continental margin of Portugal. A novel morphosedimentary study over this terrace has been executed based on new multibeam echosounder data, seismic profiles, and surficial sediments samples collected during the CONTOURIBER-1 Cruise (2010). Based on that study, an impressive large channel laterally connected with the central part of the Strait of Gibraltar (Camarinal Sill) has been identified. It is associated southwestward with a huge contourite levee (sand bank), which has been generated by overflow processes related to the Mediterranean Outflow Water (MOW). In the middle to the distal part of the terrace, there are other minor channels, erosional scour alignments and depositional features. The mapping of all these features coupled with CTD data allows to further understand the pathway and deceleration of the MOW, in addition to aid the conceptual identification of contourite terrace

Mud volcano development and tectonics in the Gulf of Cadiz

Se han identificado en el Golfo de Cádiz numerosas estructuras asociadas al escape de fluidos: volcanes de fango, montículos de fango con chimeneas carbonatadas y pockmarks. La mayor parte de los volcanes de fango se encuentran el el margen bético rifeño, a profundidades de 400-1400 m, y siguiendo una dirección NE-SW y NW-SE. Así mismo se han reconocido también algunos volcanes de fango dispersos en el talud inferior a profundidades de 2400-3900 m de profundidad. En el Golfo de Cádiz la actividad tectónica relacionada con el régimen compresivo general (NW-SE) constituye el principal factor de control en la migración de fluidos. La adquisición de perfiles sísmicos en el talud continental ha permitido cartografiar y caracterizar las estructuras tectónicas dominantes: cabalgamientos, fallas extensionales y fallas en dirección, así como diapiros y analizar su relación con el desarrollo de volcanes de fango en diferentes sectores del margen. Todas estas estructuras tectónicas han proporcionado vías de escape a fluidos y sedimentos sometidos a sobrepresión y han favorecido su migración a través de la columna sedimentaria para finalmente llegar a construir volcanes de fango.Numerous structures associated with fluid escape have been identified in the Gulf of Cadiz: mud volcanoes, carbonate-mud mounds bearing carbonate chimneys and pockmarks. Most of the mud volcanoes are found in the eastern domain of the Gulf of Cadiz, which corresponds to the Betic-Rifean Margin, at 400-1400 m depth, following NE-SW and NW-SE trends. Scattered mud volcanoes have also been recognized in the lower slope at 2400-3900 m depth. In the Gulf of Cadiz , structures related to the NW compressive regime represent the major control for fluid migration. Acquisition of seismic profiles along the continental slope allows us to map and characterize the dominant tectonic structures: thrust faults, extensional faults, strike-slip faults as well as diapirs and analyze its relationship with mud volcano development in different sectors of the margin. All these tectonic structures have provided escape pathways for overpressured material and fluids or have favoured the upwards fluid movement along the sedimentary column and eventually the build-up of mud volcanoes.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEMinisterio de Ciencia e Innovación (MICINN)EuroCOREEuroMARGINSCONSOLIDER-INGENIO 2010pu

Submarine geomorphology of the passage of Lanzarote (East Canary Islands region)

International Symposium on Marine Sciences (6º. 2018. Vigo)Centro Oceanográfico de Málaga, Instituto Español de Oceanografía, EspañaCentro oceanográfico de Cádiz, Instituto Español de Oceanografía, EspañaInstituto Geológico y Minero de España, EspañaFacultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, EspañaCentro Oceanográfico de Canarias, Instituto Español de Oceanografía, Españ

Morfología y tectónica del talud inferior del Golfo de Cádiz

Analysis of bathymetric and seismic reflection data allow us to characterize the processes and structures that generate seafloor morphological features in the lower continental slope and the transition to the abyssal plain of the Betic-Rif Margin. Several differences can be stablished in the lower slope and the transition to the Horseshoe and Sena Abyssal Plains. The lower slope in the Horseshoe sector shows an upper convex - lower concave profile and the transition to the abyssal plain is marked by a scarp related to the activity of a main NE-SW reverse fault. Whereas in the Sena sector the lower slope appears as a convex profile and the region boundary with the abyssal plain is determined by the position of the external front of the Allochthonous Betic-Rif Units

Ferromanganese Crust and Phosphorites Pan-European Predictivity Cartography: MINDeSEA project results

[EN] MINDeSEA is a project framed in GeoERA whose general objective is to obtain a metallogenetic study of the main types of mineral resources existing in the bottom of the European seas: hydrothermal sulphides, ferromanganese crusts, phosphorites, marine placers and polymetallic nodules. One of the specific objectives of the project is to develop databases and harmonized cartography of the mineral deposits of the seabed, the latter providing predictivity maps, among others.This research is a contribution to the project MINDeSEA (grant agreement no 731166), and has been partially funded by the Spain’s Recovery and Resilience Plan included in the MINECRITICAL project “Strategic critical metals for the energy transition” (C17.I7).Peer reviewe

New discoveries of mud volcanoes on the Moroccan Atlantic continental margin (Gulf of Cádiz): morpho-structural characterization

10th International Conference on Gas in Marine Sediments, 6-11 September 2010, Listvyanka, RussiaDuring the MVSEIS-08 cruise of 2008, ten new mud volcanoes (MVs) were discovered on the offshore Moroccan continental margin (Gulf of Cádiz) at water depths between 750 and 1,600 m, using multibeam bathymetry, backscatter imagery, high-resolution seismic and gravity core data. Mud breccias were recovered in all cases, attesting to the nature of extrusion of these cones. The mud volcanoes are located in two fields: the MVSEIS, Moundforce, Pixie, Las Negras, Madrid, Guadix, Almanzor and El Cid MVs in the western Moroccan field, where mud volcanoes have long been suspected but to date not identified, and the Boabdil and Al Gacel MVs in the middle Moroccan field. Three main morphologies were observed: asymmetric, sub-circular and flat-topped cone-shaped types, this being the first report of asymmetric morphologies in the Gulf of Cádiz. Based on morpho-structural analysis, the features are interpreted to result from (1) repeated constructive (expulsion of fluid mud mixtures) and destructive (gravity-induced collapse and submarine landsliding) episodes and (2) interaction with bottom currentsDivisión de Geología Marina, Instituto Geológico y Minero de España, EspañaCentro Oceanográfico de Málaga, Instituto Español de Oceanografía, EspañaFacultad de Ciencias del Mar, Universidad de Cádiz, EspañaFacultad de Ciencias Geológicas, Universidad Complutense de Madrid, Españ

Seafloor environments on Madrid and El Cid mud volcanoes (Moroccan continental margin of the Gulf of Cádiz)

Simposio sobre el Margen Ibérico Atlántico (9º. 2018. Coimbra, Portugal)More than 70 mud volcanoes (MVs) are identified along the continental margin of the Gulf of Cadiz,,although only a few have been thoroughly sampled and direct observed. This work is a contribution to the knowledge of the Gulf of Cadiz MVs Madrid and El Cid, located in the continental slope known as Western Moroccan Field over 1300 m water depth. On Madrid MV extensive crusts and mud breccia were observed. Nevertheless in El Cid MV, the rocky fragments are of smaller size and mud breccia has not been sampled/observed on the surface. In both MVs, coral reefs colonizing rocky fragments and covering seafloor of metric size have been observed.Departamento de Ciencias de la Tierrra, Universidad de Cádiz, EspañaCentro Oceanográfico de Málaga, Instituto Español de Oceanografía, EspañaCentro oceanográfico de Cádiz, Instituto Español de Oceanografía, EspañaInstituto Geológico y Minero de España, EspañaEstrutura de Missão para a Extensão da Plataforma Continental, Portuga

Identificación de riesgos geoambientales y su valoración en la zona de hundimiento del buque Prestige

Potential geological hazard assessment has been carried out in the area where the Prestige vessel was sunk using a broad database that comprises: multibeam, high and ultra-high resolution seismic profiles, gravity cores, onland seismicity stations and Ocean Bottom Seismometers (OBS). The main results of this study indicate that among the geologic factors that can be considered as potential hazards, four main categories can be differentiated based on their origin: morphologic, sedimentary, tectonic, and seismicity. Hazards of morphologic origin include steep gradients; the morphologic features suggest the occurrence of mass-wasting instabilities. Hazards of sedimentary origin also includes the occurrence of slope instability processes in form of single slides and a great variety of erosive and depositional gravity flows (debris and turbidity flows). Hazards of tectonic and seismic origin are important because the sinking area straddles the Calida Bank which is a structural seamount with a moderate tectonic activity that results in a latent seismicity of low to moderate magnitude. The interaction of these factors leads to consider to the risk as medium, and the degree of exposure of the bow and stern as high. Several general and specific recommendations are made in order to increase the geological and geophysics knowledgement in the Prestige sinking area and Spanish continental margins and deep sea areas. These recommendations also should be used to elaborate the options for reducing the hazard and loss