Three instrumented lines were installed on the continental slope and the basin of the Gulf of Valencia for thirteen months (May 2010 to June 2011) aiming to study particle fluxes and their relationship with environmental parameters. Total mass flux varied between 52 mg m−2 d−1 in the central part of the basin and 7199 mg m−2 d−1 in the northern slope sector. The main biogenic constituent was calcium carbonate (estimated fraction) representing more than 26% of the total flux, whereas organic matter and biogenic silica add together <10%. These percentages were similar to the proportional contents in the sea floor sediment and were mainly attributed to advection of particles from the Ebro shelf during wave resuspension events. The coincidence in the temporal variation of the Ebro River discharges with the total mass flux observed in the Gulf of Valencia suggests that the effect of river discharges >400 m−3 s−1 can be detected at least 155 km to the southwest. The temporal variation of satellite-derived chlorophyll-a abundance and organic matter flux indicated that biogenic material collected in the Gulf of Valencia is related to sea surface spring phytoplankton blooms developing in the northwestern Mediterranean. However, the temporal variation of biogenic silica corresponded better with the usual pattern of deep chlorophyll-a maxima reached during the fall season, suggesting that diatoms are a main component in subsurface phytoplankton blooms.

A sand ridge field with crests oriented NE–SW (52°) located between 55 and 85m water depth on the Valencia continental shelf (Spain) was mapped with multibeam swath bathymetry and characterized with seismic profiling and sediment sampling. Boundary-layer hydrodynamic measurements conducted over a sand ridge at 66m depth show evidence of wave and current sediment resuspension during a major storm event with a three-year recurrence period. From the measured intrawave sediment concentration profiles it is shown that the suspended sediment time evolution is related not only to mean currents but also to the wave field. The near-bottom shear stress generated during storm conditions reached around 1N/m2 and was able to resuspend and transport sandy and muddy sediments for more than 32h. The total suspended sediment transport in a layer of 1m above the bottom was around 4000kg per meter width and directed 160°.It is argued that these sand ridges were developed in a shallow environment and there is no evidence of present-day ridge migration or morphological degradation. It is hypothesized that sediment dynamics affecting sand ridges during storms favors the maintenance of their morphology.

The Palamós and the Cap de Creus submarine canyon heads were instrumented during two consecutive winters to study their respective role in the dynamics of the sediment transport on the northwestern Mediterranean Sea. Several events of dense shelfwater cascading (DSWC) were identified and compared among them. Sediment transport during DSWC at the Palamós canyon is significant during eastern and also northern storm events, but not related with river floods. However, the magnitude of transport events in the Palamós Canyon is one order of magnitude lower than in the Cap de Creus Canyon.

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.

Circulation patterns and sediment dynamics were studied over the Gulf of Valencia (GoV) continental slope during spring and winter 2011–2012. Two moorings were deployed at two locations; at 450m depth from February to May 2011, and at 572m depth from October 2011 to February 2012. At both mooring sites, observations were made of currents, temperature and near-bottom turbidity within the lowermost 80m above the seafloor. The temperature measurements allowed distinction of the different water masses and their temporal evolution. The fluctuations of the boundary between the Western Mediterranean Deep Water (WMDW) and the Levantine Intermediate Water (LIW) masses were monitored, and several intrusions of Western Mediterranean Intermediate Water (WIW) were observed, generally coinciding with changes in current direction. At both mooring sites, the currents generally maintained low velocities <10cms−1, with several pulses of magnitude increases >20cms−1, and few reaching up to 35cm s−1, associated with mesoscale eddies and topographic waves. The current direction was mainly towards the SSE on the first deployment and to the ESE on the second deployment. This second location was affected by a strong bottom offshore veering presumably generated by local topographic effects. Increases in suspended sediment concentrations (SSC) were observed repeatedly throughout the records, reaching values >3mgl−1. However, these SSC variations were uncorrelated with changes in velocity magnitude and direction and/or with temperature oscillations. Results presented in this paper highlight the complex relation between the hydrodynamics and sediment transport over the GoV continental slope, and suggest that other potential sediment resuspension mechanism not linked with current fluctuations, might play a key role in the present-day sedimentary dynamics. Resuspension due to bottom trawling appears to be the most plausible mechanism.

According to previous studies, the surface circulation of the Gulf of Valencia (GoV) is characterized by a convergence between the southwestward Northern Current carrying old Atlantic Waters (oAW) and the northward intrusions of recent Atlantic Waters (rAW) imported through the Ibiza Channel. This paper focuses on the distribution of the suspended sediment concentration in the GoV obtained from a dense grid of CTD observations in June 1995 during the oceanographic cruise MESO'95 (MESOscale processes). We evaluate the relation between currents, water masses and the nepheloid structure at the time of the survey. Results showed higher suspended sediment concentration (SSC) in the oAW than in the rAW. At the shelf-break depth, an important detachment of particulate matter was observed off Cap La Nao, extending seawards all across the Ibiza Channel. The presence of this intermediate nepheloid layer detachment indicates a preferential off-shelf sediment export at the southern end of the GoV, where the orientation of the continental margin changes, and oAW and rAW merge. On the continental slope, several nepheloid layers detachments were observed between 400 and 600m, where the Levantine Intermediate Water (LIW) interacts with the seafloor, suggesting the possible presence of internal waves causing sediment resuspension and/or maintaining particles in suspension in the mid-slope region. A bottom nepheloid layer was also observed at deeper locations along the central and southern part of the GoV continental slope, but not at the Ibiza Sill.

The Cap de Creus and the Palamós submarine canyon heads were instrumented during two consecutive winters to study their respective role in the dynamics of the sediment transport on the north-western Mediterranean Sea. Several events of dense shelf-water cascading (DSWC) were identified simultaneously at both canyons and compared between them. DSWC events were characterized by abrupt drops of temperature, increases of current speeds, and peaks of high suspended-sediment concentrations (SSC). Concentrations up to 170mg l−1 were recorded in both studied winters at the Cap de Creus Canyon coinciding with the first DSWC event of the winter concurrent with an eastern storm. Overall, the amount of sediment transported during the DSWC events was one order of magnitude greater at the Cap de Creus Canyon than at the Palamós Canyon. Results from this study have identified for the first time the presence of DSWC events also in the Palamós Canyon head, south of the Gulf of Lions (GoL), and corroborated previous findings that the Cap de Creus Canyon is the main pathway for DSWC and the associated sediment transport from the GoL down to the deeper regions of the north-western Mediterranean.