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The Iberian margin in the Gulf of Cádiz hosts a fluid venting area embedded into a contourite depositional drift and is a natural laboratory to study how multiple interacting processes shape the seafloor. A high-resolution morpho-sedimentary analysis, based on geophysical data, sediment samples and submarine imagery, has been carried out; the onset and evolution of the main geoforms are discussed; and the influence of geological, oceanographic and biogenic processes conditioning substrate types and benthic community distribution are evaluated. The interplay of geological (e.g., salt and shale diapirism, mud volcanism), oceanographic (e.g., water mass circulation, secondary circulation, vertical eddies, internal waves) and biogenic (e.g., methane derived authigenic carbonates formation, coral mound aggradations) processes drive the formation of a large variety of geoforms including, among others, contourite drifts, channels, diapiric ridges, mud volcanoes, pockmarks, and coral mounds. At a smaller scale, the interaction between massive and fluid extrusive, biogenic, and bottom current-related processes (both depositional and erosive) determines the distribution of substrate types and benthic communities, which have been classified as belonging to different biotopes.

34th International Association of Sedimentologists (IAS) Meeting of Sedimentology, Sedimentology to face societal challenges on risk, resources and record of the past, 10-13 September 2019, Rome.-- 1 page, The Garrucha and Almanzora are the northern tributaries of the submarine canyon system called Almanzora-Alías-Garrucha located in the Palomares continental margin (Southwestern Mediterranean Sea). The tributary system is deeply incised in the continental shelf that is 5 km wide and extends down to 100¿120 mwd, where the transition towards the upper continental slope starts.Multiple multibeam echosounder datasets were used to characterize this study area. 50 m resolution bathymetry data belonging to the Spanish General Secretariat of Fisheries (SGP) was merged with data recorded in the framework of the FAUCES project in order to produce high-resolution maps (10 to 2 m grid size resolution). The higher resolution data was recently collected onboard the vessel Sarmiento de Gamboa using an Atlas Hydrosweep DS and Kongsberg-Simrad EM2040 operated from the AUV AsterX. Accurate seafloor video imaging was recorded by an ARGUS ROV system. The Garrucha tributary erodes completely the continental shelf: its shallowest part reaches the infralittoral at 7-20 mwd. The Almanzora tributary is narrower and less incising: its head is located at 65¿90 m and affects the outer prodelta of the Almanzora River. In both cases a dense network of dendritic gullies along their flanks can be observed. After the convergence of the tributaries at 1100 mwd, the submarine canyon becomes wider and shows a meandering pattern. The ROV surveyed 7 nautical miles along the canyon axis at depths between 1100 and 1653 m. The images reveal a changing environment within this shelf-slope system. The ROV system recorded a great variability of depositional and erosive features such as sedimentary instabilities (isolated blocks, topples and falls) and bedforms. All these observations suggest that the tributary system funnel sediments from the coastline and shelf down to the deep sedimentary system, and also that the canyon system can act as a sediment source/reservoir in two ways: 1) sediment eroded from the canyon walls and 2) sediment released to the distal canyon after it has been temporarily deposited on the canyon floor

Tagoro, the youngest submarine volcano of the Canary Islands, erupted in 2011 South of El Hierro Island. Pre-existing sea floor and inhabiting biological communities were buried by the newly erupted material, promoting the appearance of new habitats. The present study pursues to describe the first metazoans colonizing different new habitats formed during the eruption and to create precedent on this field. Through dredge and remote operated vehicle samplings, five main habitat types have been detected based on the substrate type and burial status after the eruption. Inside the Tagoro volcanic complex (TVC), two new habitats are located in and around the summit and main craters—hydrothermal vents with bacterial mats and sulfurous-like fields mainly colonized by small hydrozoan colonies. Two other habitats are located downslope the TVC; new hard substrate and new mixed substrate, holding the highest biodiversity of the TVC, especially at the mixed bottoms with annelids (Chloeia cf. venusta), arthropods (Monodaeus couchii and Alpheus sp.), cnidarians (Sertularella cf. tenella), and molluscs (Neopycnodonte cochlear) as the first colonizers. An impact evaluation was done comparing the communities of those habitats with the complex and well-established community described at the stable hard substrate outside the TVC, which is constituted of highly abundant hydrozoans (Aglaophenia sp.), antipatharians (Stichopates setacea and Antipathes furcata), and colonizing epibionts (e.g., Neopycnodonte cochlear). Three years after the eruption, species numbers at Tagoro were still low compared to those occurring at similar depths outside the TVC. The first dominant species at the TVC included a large proportion of common suspension feeders of the circalittoral and bathyal hard bottoms of the area, which could have exploited the uncolonized hard bottoms and the post eruptive fertilization of water masses.

En el talud medio del golfo de Cádiz se desarrolla un sistema deposicional contornítico generado por la masa de Agua Mediterránea de Salida (Mediterranean Outflow Water; MOW) que interacciona con la topografía del fondo erosionando una serie de canales contorníticos en cuyos diques o levees se han identificados ondas sedimentarias oblicuas o paralelas a sus ejes. Estas ondas se han estudiado con mosaicos batimétricos adquiridos en varias campañas oceanográficas. Las ondas sedimentarias se encuentran entre 520 y 650 m de profundidad, sus longitudes axiales varían entre 360 m y 2400 m, sus alturas entre 3 m en posiciones alejadas del canal y 10 m en las ondas más proximales y sus longitudes de onda entre 175 y 600 m. Las velocidades de la MOW medida sobre estos campos de ondas oscilan entre 0,18 y 0,32 m/s. El origen de estas ondas podría explicarse por el desbordamiento de la parte superior del flujo canalizado, de forma que los cambios de dirección del canal harían que se “desprendiesen” las partes del flujo situadas por encima del canal, que iría perdiendo velocidad a medida que se separa de éste, justificándose así las direcciones de las ondas y la disminución de sus alturas a medida que aumenta la distancia al canal.

AMERICAN GEOPHYSICAL UNION

El objetivo principal del proyecto “Physico-chemical, biological and geological study of an underwater volcano in a degassing stage: Island of El Hierro”, (VULCANO-II) es estudiar, desde un punto de vista totalmente interdisciplinar, la fase de desgasificación activa del único volcán submarino monitoreado desde su nacimiento en aguas españolas. De esta forma, se pretende además, dar continuidad a los estudios multidisciplinares realizados sobre el volcán submarino de la isla de El Hierro en el contexto del proyecto del Plan Nacional VULCANO-I, (CTM2012-36317) y VULCANA (Vulcanología Canaria Submarina, IEO). Para ello, se realizará la monitorización de las propiedades físico-químicas, biológicas y geológicas del proceso eruptivo submarino de la isla de El Hierro y otros puntos sensibles, como el volcán de Enmedio entre Gran Canaria y Tenerife

The northeastern sector of the Gulf of Cadiz continental margin has been deeply studied the last two decades. The seafloor is characterized by the Gulf of Cadiz Contourite Depositional System, strong diapirism and seepage related to the mobility of the frontal units of the Gibraltar Arc. Since 2010 high resolution bathymetric data and high and very high resolution seismic reflection and parametric echosounder profiles have improved the resolution of the previous collected data set. These data allow to analyze the middle continental slope morphology and its shallow structure with the aim to know the active tectonic processes on the seafloor. Two types of structures have been considered: (a) anticline domes and (b) normal faults which produce linear scarps and tectonic depressions. The shallow tectonics in this region is mainly related to the high mobility of geological formations in the subsoil and their ductile mechanical behaviour. Versión del editor

The Passage of Lanzarote is an example of a wide oceanic corridor. It extends between the eastern Canary Islands and the Western Africa continental margin. Seafloor morphology of this passage has been analyzed with the aim to know the morphogenetic processes related to both the oceanography and the geology. Multibeam bathymetric data and high and very high resolution seismic profiles obtained in the SUBVENT2 cruise have been used. Five main morphological groups were analyzed: (a) Volcanic or diapiric submarine hills; (b) Tectonic features on the continental slope (linear scarps and a rhomboid-like depression) related to normal faults at the top of buried diapirs; (c) Giant circular depressions initially triggered by submarine venting at the top of diapirs; (d) Sedimentary instabilities and canyons (gullies, canyons, mass transport deposits) that are present specially on the Fuerteventura-Lanzarote ridge must be related to the high energy geological processes, both constructive and dismantling, associated to the evolution of these volcanic domains; and (e) Contouritic features both erosive (central channel, contourite channels) and depositional (mounded and plastered drifts) that occur in the central part of the bottom surface of the passage, and are generated by the interaction of the MW and the interface MW-AAIW with the seafloor. Versión del editor

The study of turbidity plumes developed in front of the river mouth, have an increasing scientific interest due to its contribution to infralittoral sediment transport and deposition. River plume evolution and deposition in submarine fans related to environmental constrains could be interpreted by the analysis of suspended particulate matter (SPM) retained during the filtering process. In this study, a new methodology approach to obtain quantitative results in sediment filters, using custom digital image processing techniques, is presented and some promising preliminary results are obtained. This procedure could avoid time-consuming during SPM analysis allowing an easy way to obtain fast and quantitative information, which might lead to a better interpretation and comprehension of factors involved in the evolution of riverine turbidity plumes. Versión del editor

The Gulf of Cadiz is located in the boundary of two lithospheric plates, this tectonic activity promote fluid rich hydrocarbon emissions from subsurface reservoirs and the formation of several mud volcanoes. The seabed and sedimentological heterogeneity, the complex oceanographic circulation, and the low fishing activity in certain areas may promote high biodiversity and complex habitats (habitat 1170 and 1180, Natura 2000). Environmental variables (fishing activity, substrate types, near bottom currents) and fauna collected with beam-trawl have been compared for several mud volcanoes and adjacent bottoms in order to understand the spatial distribution of both habitats and environmental/anthropogenic variables. The faunistic samples yielded high abundances, biomass and species richness in Gazul, Pipoca and Chica but low ones in Anastasya. In relation to environmental variables and fisheries activity, there is a strong correlation with the substrate type, depth, salinity and near-bottom current as primary variables influencing the distribution of habitats of different mud volcanoes. In this context, high species richness, abundance and biomass was found in areas with authigenic carbonates, coarse sediments, high near-bottom current speed, low salinities and low fishing activity.

The continental slope of the Canary Islands volcanic province is characterized by the occurrence of several seamounts and large landslides that have been widely documented. A detailed morphological study of the Echo seamount has been done by using multibeam bathymetry, backscatter data and very high resolution seismic profiles. The seamount shape, the occurrence of a flat summit and the presence of characteristics morphological features on the summit and along the flanks as volcanic cones, ridges, slides scars, gullies and channels, among others, have allowed establishing differences in its evolution. The analysis of these seamount features let to think that the seamount could be an oceanic island that becomes eroded and sank to its present depth. Recent geological processes observed at the base of the seamount let to establish different features and morpho-sedimentary units. They have been interpreted as the result of dismantling processes of the flanks although they have also related to the massive slope instabilities developed on the continental slope. Versión del editor

The evolutionary stages of the submarine delta off the Adra River are investigated in this study, under the context of climatic fluctuations entangled with increasing human activities and interventions in the drainage basins and adjacent shores during the Middle to Late Holocene. To achieve that goal, we used an extensive database comprising a set of bathymetric data covering different time slices, a dense grid of high-resolution seismic data and several sediment cores collected in the two submarine lobes of the Adra River delta. Two main evolutionary phases can be identified. The first one extended through most of the construction history and was mediated by major climatic events at the Mediterranean scale; this phase included three major progradational events occurring during the Mid Holocene, the Roman time and the Little Ice Age. The most recent phase is strongly determined by human modifications of the fluvial channels, and resulted in a drastic transformation of the submarine sedimentary environment. Versión del editor

Clinoforms constitute the basic building elements of continental margin growth. Submarine clinoforms are composed of three geometric elements: topset, foreset and bottomset. This study focuses on the determination of the distal termination of submarine deltaic clinoforms by using morphometric criteria and subsequent validation with stratigraphic, sedimentological and geochemical data. The mechanism and factors that potentially affect bottomset generation are also discussed. These criteria have been applied to the Guadalhorce River prodelta, an environment where advection and along-shore sediment transport prevail. We conclude that the seaward advance of the prodelta is prevented by the current velocity increase at the foot of the morphosedimentary feature. En prensa

Extrusive edifices and structural reliefs, catalogued as mounds and located on the seafloor to the west of Canary Islands were analyzed by acoustic data obtained with multibeam and parametric echosounders during several oceanographic expeditions. They were carried out at deep waters, from 4800 to 5200 m, and they have allowed characterizing 41 newly discovered submarine structures which occur either as isolated edifices or clustered mounds. These features have circular to elongated shapes with diameters of 2-24 km and relief heights of 10 to 250 m, showing different flank slopes of 2-50°. They generally display mounded forms and show morphological elements as ridges, near-circular rock outcrops, depressions and fault scarps together with mass flow and slide deposits located at the vicinity of the edifices. Two types of extrusive features are evidenced by the morphological and seismic data analyses, the first one probably corresponds to high velocity extrusions that reach the seafloor surface and the second one is probably formed by the combination of faulted structures and low velocity extrusions that produce singular domes in the shallower sedimentary records. Based on both analyses, extrusive phenomena represent the dominant mechanism for mound field evolution in the Canary lower slope region. Versión del editor

This work presents results from bioturbation intensity and trace fossil analysis of the piston core PC07, recovered at Portimão Bank during the MONTERA cruise in 2012. The aim was to investigate the potential of bioturbation analysis as an indicator for mass movement events. Bioturbation and trace fossil identification was complemented with results from sedimentological analysis (grain-size, carbonates, organic matter), measurements of magnetic fabric parameters (mass magnetic susceptibility and anisotropy of magnetic susceptibility), and AMS 14C dating. Considering the vertical zonation of bioturbation, magnetic fabric changes, sedimentology and AMS radiocarbon dating, two intervals were identified, Interval A (0-180 cm) and Interval B (180-356 cm), being the limit between them placed at 180-181cm. These intervals seem to replicate almost the same vertical zonation of bioturbation and the trend of carbonates and organic matter changes downcore. The magnetic fabric parameters (degree of anisotropy – Pj and shape – T of the magnetic susceptibility ellipsoid) show the major change at about 180 cm. Geochronological results indicate that the age of sediments in Interval A is 8590 yr BP (31-32 cm) and 14 300 yr BP (103-104 cm). Otherwise, ages in Interval B are the following: 5035 yr BP (181-182 cm), 8900±50 yr BP (219-220 cm), 18999±120 yr BP (303-305 cm). These results point to the emplacement of sediments of Interval A on top of youngest sediments of Interval due to landsliding. Since no internal deformation is seen, probably this indicates translational movement and short transport from the source. Versión del editor

Contourite drifts are one the main morphosedimentary features in the Alboran Sea and their sediments are important archives of the past oceanographic conditions and sedimentary processes. The end-member modelling approach lets to decompose multimodal grain-size distribution into genetically meaningful subpopulation that may be related to different sediment transport mechanisms and source areas. Three end-members have been identified in the contourite drift and moat system located at the southern side of the Dijbouti Ville seamount that have been interpreted in terms of sediment sources. Two end-members point to an eolian source and comprise fine silt (EM1) and coarse silt (EM2) as modal grain-sizes, characterized by high and low contents, respectively, of terrigenous elements (Al, Si, Ti and K). The third end-member (EM3) indicates a fluvial origin and is mainly defined by a clay modal grain-size of intermediate and homogeneous content in terrigenous elements. Downcore variation of the relative proportion of these EMs can be used to decipher paleocenographic and paleoclimatic conditions in the Alboran Sea. Versión del editor

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.

The construction and evolution of submarine deltaic deposits are influenced by a combination of allogenic and autogenic factors. Numerical simulation of turbidity currents are used to propose a morphodynamic model that quantifies the effect of the slope and river input variations on delta development/construction for the case of mountainous rivers subjected to a seasonal Mediterranean climate, such as those located in the northern shelf of the Alboran Sea. These simulations were performed by using both constant and variable rates of fluvial flows. Both theoretical and real bathymetric profiles were used in the simulations. The results indicate that both the river flow and the depositional basin slope are key features for the development of morphostratigraphic features of submarine deltas at different spatial scales. Versión del editor

New high-quality high-resolution bathymetric data along the northeastern slope of the Gulf of Cadiz continental margin reveals three gullies fields. The morphological and morphometric features of these gullies have been studied. The following morphometric variables have been measured in every gully in order to make a quantitative morphological analysis: width, depth, thalweg length, straight line length, area, sinuosity index, width/depth ratio, and stream order. The morphological characterization of the gullies suggests that these morphologies vary with the local physiography (concavity/convexity of the slope), the sediment transport efficiency, tectonic control and oceanographic regime. Versión del editor

The Guadalfeo and the Adra submarine deltas off the northern coast of the Alboran Sea have been built up under the direct influence of short and mountainous rivers. The area is subjected to strong climatic seasonality, with sporadic winter torrential floods and high summer aridity. In addition numerous anthropogenic activities have affected these systems, mostly during the last two centuries. In order to decode the influence of climatic variability and anthropogenic impacts on sediment supplies during the recent past, five sediment cores were collected from the Guadalfeo and Adra submarine deltas. Benthic foraminiferal and sedimentological analyses, combined with radiocarbon dating, were performed. The impact of torrential floods alternating with periods of low rainfall or dry periods were recorded in the Adra and Guadalfeo prodeltas. Periods with low abundance of benthic foraminifera and high amounts of coarse-grained sediments, were interpreted as the result of enhanced sediment supply to the shelf triggered by major flood events. On the other hand, periods with high amounts of fine-grained sediments and high abundances of colonizers and opportunistic foraminiferal species indicate the establishment of new environments with distinct ecological constraints. These environments were driven by lower sediment supplies during low rainfall or dry periods. The most recent sedimentation seems to reflect the human interventions in the rivers basins, such as deviation of the main river courses and dams construction, which reduced the sediment input and promoted the deposition of shallow-water submarine deltas. Versión del editor

The Gulf of Cadiz display a wide continental shelf at its northwestern part with a complex oceanographic circulation, large extensions with soft bottoms, diapiric ridges, mud volcanoes, channels, that promote geological and biological heterogeneity and also a wide variety of commercial resources that are exploited by an important fishing sector. Fisheries activity in this area has been studied using VMS and logbooks data during 2011. Fishing effort and captures maps for some important species (Nephrops norvegicus and Parapenaeus longirostris) have been developed for different areas which may be able to improve the spatial and quantitative information on fisheries, and implement measures to improve ecosystem management and conservation of the different vulnerable habitats of the Gulf of Cadiz

The seabed morphology and the sub-bottom characteristics of a sector of the Gulf of Cádiz continental slope have been analyzed from different data sets. The morphological characteristics, the type of sediments and dominant benthic species of Gazul mud volcano and adjacent areas have been studied. The morphological characteristics identified were grouped in fluid escape related features, bottom current features, mass movement features, structural features and biogenic related features. Additionally, dominant benthic species associated to fluid escape and seepage, hard substrates or soft bottoms have also been indicated in these features. A bottom current velocity analysis allowed relating the morphological features with the different sedimentary and oceanographic processes as well as the benthic habitats and that currently occur in the mud volcano and nearby areas. The major factor controlling these features and their associated benthic habitats is the interaction of deep water masses with the seafloor topography. At high velocities, authigenic carbonates can be exhumed and colonized by sessile suspensivorous species associated with hard substrates such as cold-water corals, anthipatarians and large sponges. Mounds and diapiric ridges are found on the depressions and they could be relict structures. Living corals have been found on raised zones, revealing different oceanographic condition and strong enough currents to favour the availability of nutrients and organic particles. Chemosymbiotic organisms are very scarce at the summit and old remains of Lucinoma asapheus indicating past higher seepage activity. Versión del editor

The Bay of Málaga is located in a biodiversity hotspot with high productivity that favors a wide variety of commercial and non-commercial species as well as fishing fleet types. Benthic and demersal fauna from circalittoral soft bottoms of this bay have been studied using a benthic dredge (8 sampling stations in December 2013) and an otter trawl (8 sampling stations on a seasonal basis). Sediment and water properties have also been studied in order to analyze their relationships with the benthic and demersal communities. A total of 287 spp. have been found, being molluscs and fishes the most diverse and abundant ones in the samples. A low number of species (44 spp.) were only collected with both sampling gears, indicating the importance on combining sampling methods in biodiversity studies. Benthic dredge samples displayed some differences in relation to depth and sediment types, whereas differences of otter trawl samples seemed to be more influenced by seasonal changes. SIMPER analyses indicated that temporal variation was due to seasonal changes of abundance of some species of commercial interest. This seasonal variability should be taken into account in further management of this area as a potential new Fisheries Reserve.

Five different groups of gullies have been distinguished along the northeastern slope of the Gulf of Cádiz using geostatistical analysis. A Grouping Analyst has been carried out to six morphological variables of the gullies: area, straight line length, width/depth ratio, width, depth and stream order. The spatial distribution of the identified five groups and their mean characteristics have allowed us to propose an evolutionary model for the two zones of the upper continental slope. This model is related to the local physiography, the sediment supply, the tectonic control and the oceanographic regime. Versión del editor

The Guadalfeo and the Adra submarine deltas off the northern coast of the Alboran Sea have been built up under the direct influence of short and mountainous rivers. The area is subjected to strong climatic seasonality, with sporadic winter torrential floods and high summer aridity. In addition numerous anthropogenic activities have affected these systems, mostly during the last two centuries. In order to decode the influence of climatic variability and anthropogenic impacts on sediment supplies during the recent past, five sediment cores were collected from the Guadalfeo and Adra submarine deltas. Benthic foraminiferal and sedimentological analyses, combined with radiocarbon dating, were performed. The impact of torrential floods alternating with periods of low rainfall or dry periods were recorded in the Adra and Guadalfeo prodeltas. Periods with low abundance of benthic foraminifera and high amounts of coarse-grained sediments, were interpreted as the result of enhanced sediment supply to the shelf triggered by major flood events. On the other hand, periods with high amounts of fine-grained sediments and high abundances of colonizers and opportunistic foraminiferal species indicate the establishment of new environments with distinct ecological constraints. These environments were driven by lower sediment supplies during low rainfall or dry periods. The most recent sedimentation seems to reflect the human interventions in the rivers basins, such as deviation of the main river courses and dams construction, which reduced the sediment input and promoted the deposition of shallow-water submarine deltas.

Advances in remotely-sensed techniques have revolutionized mapping methods and our understanding of the seabed environment. In particular, multibeam backscatter data nowadays allows developing quantitative studies on the composition of the seafloor, which represents an important baseline for habitat mapping. Usually, the acoustic response is considered as a direct proxy of sediment texture, but seepage could affect significantly this relationship. A multibeam data set from the Gulf of Cádiz, was grouped using an ISO-cluster analysis and results were compared with 80 ground-truthing stations taken inside and outside cold seepage areas. Results show significant differences between the acoustic response of sediments with the same texture depending on the presence/absence of fluid emissions. Understanding this relationship is necessary to make image-based backscatter classification that allows the production of sediment and habitat maps in areas with extensive fluid emissions such as the Gulf of Cádiz.

En este trabajo se ha analizado la morfología del fondo, las características sub-superficiales y las comunidades bentónicas en el complejo Hespérides, situado en el talud continental del Golfo de Cádiz, con el objetivo de entender su relación con los procesos geológicos y oceanográficos, así como la influencia sobre los hábitats que se generan. Se han detectado especies bentónicas asociadas a escapes de fluidos, a sustratos duros y blandos en diferentes zonas del complejo. Los sedimentos de brecha fangosa y los organismos quimiosimbióticos se localizan en la cima de los conos volcánicos asociados a una mayor actividad de emisión. Los carbonatos autigénicos en los flancos y la base del edificio están relacionados con una actividad de expulsión de fluidos moderada, siendo desenterrados por las corrientes de fondo y colonizados por especies de sustratos duros. Las depresiones en la base están formadas por procesos de colapso, debido a escapes de fluidos activos bajo la influencia de las corrientes profundas. En general, los principales factores que controlan la morfología y las comunidades bentónicas asociadas son los procesos relacionados con escapes de fluidos, aunque no hay que despreciar el efecto de los procesos gravitacionales y la acción de las masas de agua profunda. Seabed morphology, sub-bottom characteristics and benthic communities of the Hespérides volcanic complex, located in the continental slope of the Gulf of Cadiz, have been analyzed. The aim of this study is to characterize the morphological features, the geological processes and near-bottom water masses for understanding the relationships between the occurrence of this fluid venting related edifice and their associated biota. Additionally, dominant benthic species associated with seepage, hard substrates or soft bottoms have also been observed in different areas of the complex. Mud breccia sediments and chemosymbiotic metazoans are mainly located at the summit indicating a higher seepage activity. Authigenic carbonates on the flanks and the base of the volcanic structure are related to a moderate seepage activity, being exhumed by bottom currents and colonized by hard substrate associated species. Adjacent depressions are linked to collapse processes as a result of the interplay of active fluid escape and bottom current effects. In general, major factors controlling these features and their associated biota are mud flow and fluid-escaperelated processes, although other factors such as gravitational and deep water masses related processes are also involved. LIFE+ INDEMARES/CHICA y ATLAS (EU Horizon 2020), Grupo PAIDI RNM-328. SUBVENT (CGL2012-39524-C02-01). Versión del editor 0,0000

Se ha analizado la morfología del fondo, las características sub-superficiales y los hábitats bentónicos de un sector del talud continental del Golfo de Cádiz. El objetivo es reconocer los tipos morfológicos y los procesos geológicos y oceanográficos para entender la relación con dichos procesos, así como su influencia sobre los hábitats y las especies bentónicas asociadas. Se han estudiado las características morfológicas, el tipo de sedimento y las especies bentónicas dominantes en cuatro estructuras volcánicas y en los fondos marinos adyacentes. Los tipos morfológicos identificados se han agrupado en formas relacionadas con escapes de fluidos desde el subsuelo, con corrientes de fondo, con movimientos en masa, formas estructurales y biogénicas. Además, se han identificado las especies bentónicas dominantes y asociadas a escapes de fluidos, a sustratos duros (costras de carbonatos autigénicos) y a sustratos blandos. Los principales factores que controlan la morfología y las comunidades bentónicas asociadas son los procesos relacionados con escapes de fluidos, aunque existen otros procesos, como los gravitacionales, y las propiedades de las masas de agua profunda. Los sedimentos de brecha fangosa y los organismos quimiosimbióticos se localizan principalmente en la cima de los edificios volcánicos, indicando que la actividad de expulsión de fluidos podría ser elevada en algunos casos. La presencia de coladas de fango y cuerpos lóbulados sobre los flancos son indicativos de un proceso de extrusión que tuvo lugar en diferentes fases. Los carbonatos autigénicos se han localizado en los flancos y en la base de las estructuras volcánicas y están relacionados con una actividad de expulsión de fluidos moderada, siendo desenterrados por la actividad de las corrientes de fondo y colonizados por especies de sustratos duros. Las depresiones en las zonas adyacentes están formadas por procesos de colapso, debido a escapes de fluido activos y bajo la influencia de las corrientes profundas. Seabed morphology, sub-bottom characteristics and benthic habitats of a sector of the Gulf of Cadiz continental slope have been analyzed. The aim is to recognize morphological features, geological processes and near-bottom water masses for understanding the relationships between the occurrence of fluid venting related edifices and their associated habitats and benthic communities. Morphological characteristics, sediment types and dominant benthic species of four volcanic structures and their adjacent areas have been studied. Identified morphological characteristics were grouped in fluid escape related features, bottom current features, mass movement features, structural features and biogenic related features. Additionally, dominant benthic species associated with seepage, hard substrates (authigenic carbonates) or soft bottoms have also been found in these features. A major factor controlling these features and their associated biota is mud flow and fluid-escape-related processes, although other factors such as gravitational and deep water masses related processes are involved. Mud breccia sediments and chemosymbiotic metazoans are mainly located at the summit indicating a higher mud flow and seepage activity. The presence of mass flows deposits and mud lobes on the flanks are indicative of mud extrusion process in different phases. Authigenic carbonates on the flanks and the base of the volcanic structures are related to a moderate seepage activity, being exhumed by bottom currents and colonized by hard substrate associated species. Adjacent depressions are linked to collapse processes, where active fluid escape and bottom current effects have been identified. Proyectos LIFE+ INDEMARES/CHICA y ATLAS (EU Horizon 2020). Grupo PAIDI RNM-328. Proyecto SUBVENT (CGL2012-39524-C02-01) Versión del editor

En el presente trabajo se realiza un análisis de las morfologías de pequeña escala en los diferentes dominios de los deltas sumergidos (techo deltaico, frente deltaico y prodelta) en la plataforma continental del sureste de la Península Ibérica. El objetivo del estudio es comprender los procesos genéticos, en particular el papel jugado por los flujos energéticos de origen fluvial. Para alcanzar tal fin, se han interpretado datos batimétricos obtenidos con ecosondas multihaz (EM3000D y EM3002D) y perfiles de sísmica de alta resolución obtenidos con una ecosonda TOPAS (Topographic Parametric Sonar) y con Geopulse. Se han definido cinco tipos morfológicos de pequeña escala en los deltas sumergidos del área de estudio, que han sido clasificados en cuatro grupos genéticos: a) Morfologías deposicionales (campos de ondulaciones), b) Morfologías erosivas (canales), c) Morfologías gravitacionales (deslizamientos) y d) Morfologías antrópicas (montículos y surcos erosivos). En los topsets se desarrollan principalmente morfologías asociadas a procesos erosivos; en los foresets se identifican morfologías erosivas, gravitacionales y deposicionales; finalmente, en los bottomsets dominan los procesos de acumulación sedimentaria. La distribución espacial de dichas morfologías muestra una cierta uniformidad en los deltas estudiados, lo cual permite diferenciar áreas de alta energía (topsets y foresets) con predominio de procesos erosivos y gravitacionales, y áreas de baja energía (bottomsets) con predominio de procesos deposicionales. Esta distribución se interpreta como el resultado de la influencia principal de flujos transversales a los deltas sumergidos, posiblemente relacionados con corrientes hiperpicnales, favorecidos durante períodos de alta descarga fluvial asociados a precipitaciones intensas., An analysis of small-scale morphologies developed in the different domains of submerged deltas (topset, foreset and bottomset) on the continental shelf of the southeast of the Iberian Peninsula is performed in this paper. The aim of the study is to understand the genetic processes, in particular the role played by the fluvial flows. To achieve this goal, bathymetric data obtained with multibeam echosounders (EM3000D and EM3002D) and seismic profiles obtained with a high resolution TOPAS (Topographic Parametric Sonar) and a Geopulse seismic source have been interpreted. Five small-scale morphological types have been defined in the study area, which have been classified into four genetic groups: a) Depositional morphologies (undulations fields), b) erosive morphologies (channels), c) gravitational morphologies (slides) and d) anthropic morphologies (monticules and erosional furrows). Over the topsets, morphologies associated with erosive processes mainly occur; over the foresets, erosive, gravitational and depositional morphologies are identified; finally, the bottomsets are dominated by depositional processes. The spatial distribution of these morphologies shows a certain uniformity in the studied deltas, which allows to distinguish between high-energy areas (topsets and foresets) where erosion and gravitational processes are dominant, and low-energy areas (bottomsets) with dominance of depositional processes. This distribution is interpreted as the result of the main influence of flows crossing the submerged deltas, possibly related to hyperpycnal flows favored during periods of high river discharge triggered by torrential precipitations., MOSAICO (P06-RNM-01594), TESELA (P11-RMN-7069)

Las simulaciones numéricas de las corrientes de turbidez en zonas deltaicas se han usado para estudiar la morfología y la formación de las ondulaciones de los sistemas prodeltaicos del Mediterráneo occidental. Una serie de ondulaciones del fondo del mar elongadas y subparalelas a las líneas batimétricas se sitúan sobre los dominios medio y distal de las cuñas prodeltaicas asociadas a los ríos que desembocan en el margen norte del Mar de Alborán. En este estudio se han usado datos reales de ecosonda multihaz y muestras de sedimentos superficiales para su comparación con simulaciones numéricas, con el objetivo de proponer un modelo evolutivo de estas ondulaciones del fondo del mar. La morfología de las ondas está relacionada con variables del caudal de los sistemas fluviales y de la pendiente del fondo marino, y se comprueba tanto en datos de campo como en simulaciones matemáticas que para caudales altos y pendientes moderadas o bajas, las ondulaciones son anchas, largas, altas y puntiagudas. En cuanto al modelo evolutivo, se observa tanto en las simulaciones numéricas como en el registro sedimentario que las ondulaciones migran pendiente arriba durante su evolución, lo que nos lleva a pensar que estas formas son similares a antidunas asociadas con corrientes de turbidez descritas por otros autores. Por tanto, estas ondulaciones se pueden caracterizar como formas de fondo rítmicas que: a) están asociadas a un flujo supercrítico (número de Froude >1); y b) tienen una migración pendiente arriba. Esto es debido al salto hidráulico que se produce en el límite proximal y distal de las ondulaciones, de forma que en la parte proximal el flujo es subcrítico, produciéndose sedimentación neta, y en el límite distal el flujo es supercrítico, y por lo tanto, domina la erosión, por lo que el campo de ondulaciones migra pendiente arriba. Este modelo propuesto se observa tanto en las simulaciones numéricas como en los datos de campo. Numerical simulations of turbidity currents in deltaic areas have been used to study the morphology and the formation of the undulations of the western Mediterranean prodeltaic systems. A series of elongated and subparallel sea floor undulations are located on the middle and distal domains of the prodeltaic wedges. Those are associated with river mouths flowing into the northern margin of the Alboran Sea. For this study, we have used real multibeam echosounder data and surface sediment samples to be compared with numerical simulations. The main aim is to propose an evolutionary model of these seabed undulations. The morphology of the undulations is related to the river flow and seafloor slope. Both field data and mathematical simulations confirm that the undulations are wide, long, high and sharp for moderate and low slopes or high flow rates. Regarding the evolutionary model, it is observed in both the numerical simulations and the sedimentary record as the undulations migrate upslope during its evolution, which leads us to believe that these morphologies are similar to antidunes associated with turbidity currents described by other authors. Therefore, these undulations may be characterized as rhythmic bedforms that: a) are associated with a supercritical flow (Froude number> 1); and b) display an upslope migration. This is due to hydraulic jump that occurs in the proximal and distal limit of the undulations, so the flow is subcritical producing net sedimentation in the proximal part of the undulation and the flow is supercritical in the distal part of the undulations dominated by erosion, so the undulations field migrates upslope. This proposed model is observed in numerical simulations and field data. MOSAICO (P06-RNM-01594), TESELA (P11-RMN-7069) Versión del editor

Comunicación presentada al V Simposio Internacional de ciencias del Mar celebrado en alicante entre el 20 y el 22 de julio de 2016. Between October 2011 and March 2012 a submarine volcanic eruption took place at the offshore of El Hierro Island. The extensive study of the eruption and subsequent degassing process has allowed monitoring the newly generated volcanic edifice. Multibeam bathymetric has enabled building a digital high-resolution bathymetric model (grid 1x1 m). The preliminary analysis of the geomorphology of this volcanic eruption displays four main features: i) the edifice consists of a principal and a series of secondary cones distributed in NW-SE trend; ii) two escarpments NE-SW directed that partially match with inherited flanks of the previously existing valley; iii) three crests, one of them interpreted as the prolongation of a NE-SW scarp and the other as the head of gravitational instabilities of NE-SW and N-S direction at the main hill; and iv) mixed lava and dense pyroclastic flows extended from the volcanic edifice to the southwest and characterized by a high slope front, that probably represents the maximum distance reached by the main lava products. Versión del editor

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Las simulaciones numéricas de las corrientes de turbidez en zonas deltaicas se han usado para estudiar la morfología y la formación de las ondulaciones de los sistemas prodeltaicos del Mediterráneo occidental. Una serie de ondulaciones del fondo del mar elongadas y subparalelas a las líneas batimétricas se sitúan sobre los dominios medio y distal de las cuñas prodeltaicas asociadas a los ríos que desembocan en el margen norte del Mar de Alborán. En este estudio se han usado datos reales de ecosonda multihaz y muestras de sedimentos superficiales para su comparación con simulaciones numéricas, con el objetivo de proponer un modelo evolutivo de estas ondulaciones del fondo del mar. La morfología de las ondas está relacionada con variables del caudal de los sistemas fluviales y de la pendiente del fondo marino, y se comprueba tanto en datos de campo como en simulaciones matemáticas que para caudales altos y pendientes moderadas o bajas, las ondulaciones son anchas, largas, altas y puntiagudas. En cuanto al modelo evolutivo, se observa tanto en las simulaciones numéricas como en el registro sedimentario que las ondulaciones migran pendiente arriba durante su evolución, lo que nos lleva a pensar que estas formas son similares a antidunas asociadas con corrientes de turbidez descritas por otros autores. Por tanto, estas ondulaciones se pueden caracterizar como formas de fondo rítmicas que: a) están asociadas a un flujo supercrítico (número de Froude >1); y b) tienen una migración pendiente arriba. Esto es debido al salto hidráulico que se produce en el límite proximal y distal de las ondulaciones, de forma que en la parte proximal el flujo es subcrítico, produciéndose sedimentación neta, y en el límite distal el flujo es supercrítico, y por lo tanto, domina la erosión, por lo que el campo de ondulaciones migra pendiente arriba. Este modelo propuesto se observa tanto en las simulaciones numéricas como en los datos de campo., Numerical simulations of turbidity currents in deltaic areas have been used to study the morphology and the formation of the undulations of the western Mediterranean prodeltaic systems. A series of elongated and subparallel sea floor undulations are located on the middle and distal domains of the prodeltaic wedges. Those are associated with river mouths flowing into the northern margin of the Alboran Sea. For this study, we have used real multibeam echosounder data and surface sediment samples to be compared with numerical simulations. The main aim is to propose an evolutionary model of these seabed undulations. The morphology of the undulations is related to the river flow and seafloor slope. Both field data and mathematical simulations confirm that the undulations are wide, long, high and sharp for moderate and low slopes or high flow rates. Regarding the evolutionary model, it is observed in both the numerical simulations and the sedimentary record as the undulations migrate upslope during its evolution, which leads us to believe that these morphologies are similar to antidunes associated with turbidity currents described by other authors. Therefore, these undulations may be characterized as rhythmic bedforms that: a) are associated with a supercritical flow (Froude number> 1); and b) display an upslope migration. This is due to hydraulic jump that occurs in the proximal and distal limit of the undulations, so the flow is subcritical producing net sedimentation in the proximal part of the undulation and the flow is supercritical in the distal part of the undulations dominated by erosion, so the undulations field migrates upslope. This proposed model is observed in numerical simulations and field data., MOSAICO (P06-RNM-01594), TESELA (P11-RMN-7069)

Los hidratos de gas son compuestos cristalinos donde una molécula de gas, principalmente metano, queda atrapada en una red de moléculas de agua en forma de hielo. La importancia de los hidratos de gas en la naturaleza es muy alta ya que constituye una fuente alternativa de energía y a su vez juegan un papel importante en el delicado equilibrio del clima a nivel global y en los riesgos geológicos en el ámbito marino. La acción COST MIGRATE está diseñada con el fin de integrar la experiencia de un gran número de grupos de investigación europeos y agentes del sector para promover el desarrollo de conocimientos multidisciplinarios sobre el potencial de los hidratos de gas como fuente de energía en Europa. Dos de los objetivos de esta acción son realizar un inventario europeo de hidratos de gas explotables y evaluar los riesgos ambientales. En este trabajo se muestran los principales indicios de hidratos de gas en los márgenes europeos incluida la Península Ibérica, con una primera aproximación sobre el espesor y situación de la zona de estabilidad de hidratos de gas en el margen Ibérico. Gas hydrates are crystalline compounds where a molecule of gas, mainly methane, is trapped in a cage of icewater molecules. The importance of gas hydrates in nature is very high because it is an alternative source of energy and play a major role in the delicate balance of the global climate and in the marine geological risks. MIGRATE COST action is designed to integrate the experience of a large number of European research groups and industrial players to promote the development of multidisciplinary knowledge on the potential of gas hydrates as energy resource in Europe. Two of the objectives of the action aim to estimate the European inventory of exploitable gas hydrates and to assess environmental risks. In this work we show the occurrences of gas hydrates described in European margins including the Iberian Peninsula, with a first approximation on the thickness and location of the area of stability of gas hydrates in the Iberian margin. COST Action ES1405 (MIGRATE)