Comunidades de coralígeno ligadas a procesos diapíricos de la plataforma española del golfo de Cádiz

The Gulf of Cádiz (GoC) represents an important area of seepage activity and of biological diversity due to the tectonic activity and subsoil fluid mobility, as well as the confluence of Atlantic and Mediterranean water masses and organisms from both basins. Some circalittoral and bathyal areas of the GoC remain still unexplored and they could harbour interesting communities and species that may deserve protection. In summer 2013, a geological expedition carried out between San Fernando and Conil de la Frontera, at water depths between 40 and 55 m and 10 M from Cádiz detected complex coralligenous communities that may be linked to diapiric processes. These communities represent a well preserved 1170 habitat type (Reefs) of the Habitat Directive and also contain ca. 20 spp. of invertebrates that are included in European, National and Local (Andalusian) threatened species lists. The area should be included in the Natura 2000 network as it represents one of the few circalittoral coralligenous communities from Spanish waters of the GoC.Versión del edito

Estimation of shub height for fuel-type mapping combining airborne LiDAR and simultaneous color infrared ortho imaging

P. 341-348A fuel-type map of a predominantly shub-land area in central Portugal was generated for a fire research experimental site, by combining airborne light detection and ranging (LiDAR), and simultaneous color infrared ortho imaging. Since the vegetation canopy and the ground are too close together to be easily discerned by LiDAR pulses, standard of processing LiDAR data did not provide an accurate estimate of shrub heightS

The role of late Quaternary tectonic activity and sea-level changes on sedimentary processes interaction in the Gulf of Cadiz upper and middle continental slope (SW Iberia)

A morphological and seismic-stratigraphic analysis of the Gulf of Cadiz area near the Strait of Gibraltar is presented in this work, focused on the sedimentary evolution of the upper and proximal middle-continental slope since the Mid-Pleistocene. Based on the analysis of seismic reflection profiles and swath bathymetry data, this work analyses the close influence of the activity of buried and outcropping diapiric ridges and late Quaternary sea-level changes on the evolution of contouritic features related to the Mediterranean Outflow Water (MOW) and Eastern North Atlantic Central Water (ENACW), gravitational features and fluid-escape structures. The stratigraphic architecture reveals that, under active diapiric deformation, the upper slope plastered drift grew during low sea-level stages, when sediment supply was high and the ENACW swept the upper slope, contrasting with the present-day highstand situation dominated by northwest-trending MOW flow. The south-estward ENACW flow forced asymmetry and lateral migration of gullies incised in the plastered drift. Two evolutionary stages have been established: 1) After the Mid Pleistocene, activity of diapirs with a NE trend determined the location of the deepest depressions which were infilled by plastered contouritic drifts; 2) Between Late Quaternary and present, a drastic change of buried diapirs growth pattern and orientation to a NW trend enhanced slope-derived gravitational processes affecting the bottom current dynamics. Adjustments to tectonic changes led to a phase of plastered drift growth on the upper slope during which depocenters varied their distribution and orientation. In a long-term the structural control on sedimentation shows a northwestward displacement of deformation, resulting in an overall extension of the contourite depositional system to the NW. In a short-term, sea-level changes favored drift deposition, gullies incision and the strengthening of water masses. This work evidences the importance of tectonic deformation in sedimentation at recent time scales, and the twodirectional interplay between recent tectonic activity and bottom current dynamics.Versión del edito

Micro-morphologies, habitats and associated biodiversity in a fluid venting submarine structure using ROV underwater images: Mercator mud volcano (Gulf of Cádiz)

Mercator mud volcano has been explored by direct visual observations using a ROV at 350 to 370 m depth. Underwater images, taken mainly at the summit, have allowed characterizing the fluid venting environment, where different microforms, habitats and associated biota, with typical seepage components have been identified. Chemosynthetic bacterial communities were detected and sampled at the northeastern side of the summit at 350 m, next to pockmark-like depressions with diameters ranging 1 to 3 m, bioturbation marks, sediment mounds and authigenic carbonates of different sizes (0.1-5m length). Chemosynthesis-based communities were mainly composed by bacterial mats (patch diameter 10-30 cm), however some remains of cold seep chemosymbiotic bivalves (Lucinoma asapheus) were also found on the sediment. Habitat types at Mercator MV are influenced by oceanographic and sedimentation processes deposition and favouring fauna colonizing diverse substrate types, such as large sponges on slabs and sea-pens and annelids on soft bottoms

Morphology and characterisation of the relict facies on the internal continental shelf in the Gulf of Cadiz, between Ayamonte and Huelva (southern Iberian Peninsula)

The objectives of the present paper are the determination of the morphologic characteristics of the superficial Quaternary relict facies on the internal continental shelf in the Gulf of Cadiz, between Ayamonte and Huelva (southern Spain), their characterisation, and their evolution in the final phases of the last eustatic hemicycle. The study area extends from the mouth of the Guadiana River to the mouth of the Tinto-Odiel River, and from the 6 m isobath to the 56 m isobath. High-resolution seismic profiles (3.5 kHz and Geopulse, 175 J), sonographic profiles (SSS, 100 kHz), and bathymetric profiles (Echotrac sounder) were used in this study. Sediment samples were obtained using Van Veen and Shipek drags. Bathymetric, physiographic, lithologic and morphologic analyses were performed to determine the superficial sediment distribution, relict facies distribution, and thickness of the unconsolidated sediment cover. Analysis of the data obtained indicated that the relict facies beaches and coastal barriers associated with coastal spits located in the ancient outlets of the rivers. Relict facies were grouped into well-differentiated depths, indicating that their position on the continental shelf is influenced by the still-stands and the periods of rapid sea-level changes. The nature of the outcropping relict facies shows that their final configuration can be related to the shelf construction processes, as well as to the most important Holocene transgressive phases.Los objetivos de este trabajo son la determinación de las características morfológicas, la caracterización de las facies relictas cuaternarias superficiales y el estudio de su evolución con relación a las fases finales del último hemiciclo eustático en la plataforma continental interna del golfo de Cádiz, entre Ayamonte y Huelva. El área de estudio abarca desde la desembocadura del río Guadiana hasta la del río Tinto-Odiel y desde los 6 m hasta 56 m de profundidad. Se utilizó gran cantidad de material geofísico, en el que se encuentran perfiles sísmicos de alta resolución (3.5 kHz y Geopulse, 175 J), perfiles sonográficos y perfiles batimétricos, además de muestras de sedimentos obtenidas con dragas Van Veen y Shipek. Con esta información se han realizado análisis batimétricos, fisiográficos, litológicos y morfológicos, además de determinar la distribución de los sedimentos superficiales y de las facies relictas y de cuantificar la potencia de la cobertera sedimentaria. Con todos los datos obtenidos se ha determinado que las facies relictas son interpretadas como playas y cordones litorales asociados a flechas litorales situadas en las antiguas desembocaduras de los ríos. Las formas descritas están agrupadas en zonaciones batimétricas bien diferenciadas, lo que indica que su posición en la plataforma continental está influida por las paradas y etapas de movimiento rápido del nivel del mar. Las características de las facies relictas aflorantes indican que su configuración final puede estar relacionada con los procesos de edificación de la plataforma a partir de las mayores fases transgresivas holocenas.Instituto Español de Oceanografí

Seafloor deformation related to Quaternary tectonics in the Majorca Channel, Balearic Promontory (Western Mediterranean)

El análisis morfotectónico del sector central del Promontorio Balear, entre las islas de Ibiza y Mallorca, mediante batimetría multihaz y perfiles sísmicos de muy alta resolución ha permitido diferenciar varios rasgos morfológicos relacionados con la tectónica a dos escalas. Los elementos de gran escala, de dirección NE-SO, son: i) el escarpe Émile Baudot; ii) el monte submarino Émile Baudot, y iii) la alineación de montes submarinos Ausiàs March y Ses Olives. Los elementos de pequeña escala son: i) dos elevaciones longitudinales (ENE-OSO); ii) escarpes rectilíneos (NO-SE a NE-SO); iii) depresiones tectónicas (NNE SSO a NE-SO); y iv) alineaciones rectilíneas de pockmarks (NO-SE a NNE-SSO). Los elementos de mayor tamaño responden a la configuración estructural neógeno-cuaternaria. El escarpe Émile Baudot limita el Promontorio Balear y la cuenca oceánica del Mediterráneo Occidental. La alineación de montes submarinos Ausiàs March y Ses Olives está generada por una fase extensional, y el monte submarino Émile Baudot forma parte de una alineación volcánica NO-SE asociada a la Zona de Fractura de Ibiza. Los elementos de pequeña escala están relacionados con estructuras tectónicas activas que deforman las unidades sedimentarias del Cuaternario y el fondo marino. Las elevaciones longitudinales están generadas por pliegues anticlinales, mientras que el resto de estructuras están asociadas a la actividad de fallas normales de buzamiento alto.A morphotectonic analysis has been carried out between the islands of Ibiza and Majorca in the central sector of the Balearic Promontory using multibeam bathymetry and very high-resolution seismic profiles. Several morphological features related to tectonics at two different scales have been differentiated. The large-scale features have a NE-SW direction, they are: i) the Émile Baudot Escarpment; ii) the Émile Baudot seamount, and iii) the Ausiàs March and Ses Olives seamounts alignment. The differentiated small-scale elements are i) two longitudinal elevations (ENE-WSW); ii) rectilinear scarps (NW-SE to NE-SW); iii) tectonic depressions limited by one or two scarps (NNE-SSW to NE-SW), and iv) rectilinear pockmarks alignments (NW-SE to NNE-SSW). The largest elements respond to the Neogene-Quaternary structural configuration. The Émile Baudot escarpment is the limit between the Balearic Promontory and the Western Mediterranean oceanic basin. The alignment of the Ausiàs March and Ses Olives seamounts respond to the last extensional phase, and the Émile Baudot seamount forms part of a NW-SE volcanic alignment that could be associated with the Ibiza Fracture Zone. The smaller elements are related to active tectonic structures that deform Quaternary sedimentary units and the seafloor. The longitudinal elevations correspond to anticlinal folds, while the rest of the structures are associated to the activity of near vertical normal faults.En prens

Influencia de la tectónica cuaternaria sobre la morfología del talud continental de la región de Adra (Mar de Alborán septentrional)

El análisis de un mosaico batimétrico y de perfiles sísmicos de alta resolución ha permitido definir la geomorfología tectónica del Margen de Adra, sector norte del Mar de Alborán. Se han identificado cuatro tipos morfológicos relacionados con estructuras tectónicas: (i) Crestas longitudinales (N50-70); (ii) Escarpes lineales (N30, N55, N130, N165, N-S); (iii) Depresiones tectónicas (N130, N165, N-S), y (iv) Líneas de cambio de la pendiente (N130). Este esquema morfoestructural se relaciona con un cabalgamiento ciego (NO-SE) en el sector NO, y en el oriental con la falla de desgarre siniestra de La Serrata (NE-SO). Entre estas dos estructuras se ha desarrollado un sistema de fallas de desgarre diestras (NO-SE) que incluye a la Falla de Adra, y un corredor NNE-SSO constituido por fallas secundarias NNO-SSE. Además se han observado fallas inversas menores N-S que pueden ser consecuencia de la interferencia de los principales sistemas de fallas de la región con el Banco de Chella.The analysis of multibeam bathymetric data and high resolution seismic profiles has allowed us to define the tectonic geomorphology of the Adra margin, northern Alboran Sea. Four geomorphic tectonic-related structures have been analyzed: (i) Longitudinal ridges (N50-70); (ii) Linear scarps (N30, N55, N130, N165, N-S); (iii) Tectonic depressions (N130, N165, N-S), and (iv) Lines of changes in the slope gradient (N130). In the northwestern sector morphostructure is related to a blind thrust (NE-SW), which folds Quaternary units, and in the eastern sector is linked to the NE-SW sinistral strike slip fault of La Serrata (NE-SW). Between these two structures, a NW-SE dextral strike-slip fault system, including the Adra Fault, and a NNE-SSW highly deformed corridor constituted by secondary NNW-SSE faults have been developed. Minor high angle N-S reverse faults can be related to secondary deformation features, due mainly to the interference of Chella Bank and the regional main fault systems.Postprin