Concentración, enriquecimiento y distribución de metales pesados en sedimentos de la bahía de Tánger, Marruecos

The distribution, enrichment, and accumulation of heavy metals in the surface sediments of the Tangier Bay, Morocco, were investigated. Surface sediment samples from eleven locations in the Bay of Tangier were collected in 2007 and characterized for grain size, organic matter and metal content (e.g. Fe, Mn, Cr, Cu, Ni, Pb, Zn and Cd). The evaluation of the heavy metal contamination status of the bay showed minor enrichment by the enrichment factors (EF) calculation, corroborated by the metal pollution index (MPI). The results of a Pearson correlation showed high positive correlations among organic carbon and most metals (0.788 < r < 0.939) and cluster analysis grouped the stations inside the harbour (stations 1, 10 and 9) and in the vicinity of the principal rivers in the bay (stations 3 and 11), which showed the highest concentrations of metal content. The main sources of contamination are domestic and industrial effluents, which arise due to the lack of sewage treatment. However, these areas could not be classified as polluted when the data were compared with sediment quality guidelines (USEPA, 1997).Se ha investigado la distribución y acumulación de metales pesados en sedimentos superficiales de la bahía de Tánger, Marruecos. Se tomaron 11 muestras de sedimentos superficiales ubicadas en la bahía de Tánger durante el año 2007 y se analizaron los metales (Fe, Mn, Cr, Cu, Ni, Pb, Zn y Cd), materia orgánica y distribución granulométrica. El estado de contaminación por metales de la bahía, se evaluó mediante el cálculo del factor de enriquecimiento (EF) y en general mostró bajo enriquecimiento, corroborado por el uso del índice de polución metálica (MPI). Los resultados de la correlación de Pearson presentaron una correlación significativa importante entre el carbono orgánico y la mayoría de los metales (0.788 < r < 0.939). El análisis clúster agrupó las estaciones dentro del puerto (estaciones 1, 10 y 9) y en las proximidades de los ríos que desembocan en la bahía (estaciones 3 y 11), que mostraron la mayor concentración del contenido de metales. Las principales fuentes de contaminación fueron los efluentes domésticos e industriales, como consecuencia del escaso tratamiento de estos vertidos. Sin embargo, esta zona no puede ser clasificada como contaminada al comparar los datos con las normas de calidad de sedimentos (USEPA, 1997)

133,000 Years of Sedimentary Record in a Contourite Drift in the Western Alboran Sea: Sediment Sources and Paleocurrent Reconstruction

The Djibouti Ville Drift is part of a contourite depositional system located on the southern side of the Djibouti Ville Seamount in the Alboran Sea (Western Mediterranean). The sedimentary record of a core located in the drift deposits has been characterized to achieve the possible sediment sources for the Saharan dust supply and the paleocurrent variability related to Mediterranean intermediate waters for the last 133 kyr. Three end-member grain-size distributions characterize the sediment record transported by the bottom current to address the different aeolian populations, i.e., coarse EM1, silty EM2, and fine EM3. For these particles, the most likely source areas are the Saharan sedimentary basins and deserts, as well as the cratonic basins of the Sahara-Sahel Dust Corridor. The prevalence of these main source areas is shown in the core record, where a noticeable change occurs during the MIS 5 to MIS 4 transition. Some punctual sediment inputs from the seamount have been recognized during sea-level lowstand, but there is no evidence of fluvial supply in the drift deposits. The paleocurrent reconstruction allows the characterizing of the stadial and cold periods by large increases in the mean sortable silt fraction and UP10, which point to an enhanced bottom current strength related to intermediate water masses. Conversely, interglacial periods are characterized by weaker bottom current activity, which is associated with denser deep water masses. These proxies also recorded the intensified Saharan wind transport that occurred during interstadial/stadial transitions. All these results point to the importance of combining sediment source areas with major climatic oscillations and paleocurrent variability in palaeoceanographic sedimentary archives, which may help to develop future climate prediction models.Fil: López González, Nieves. Instituto Español de Oceanografía; EspañaFil: Alonso, Belén. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias del Mar; EspañaFil: Juan, Carmen. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias del Mar; EspañaFil: Ercilla, Gemma. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias del Mar; EspañaFil: Bozzano, Graziella. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cacho, Isabel. Universidad de Barcelona; EspañaFil: Casas, David. Instituto Geológico y Minero de España; EspañaFil: Palomino, Desirée. Instituto Español de Oceanografía; EspañaFil: Vázquez, Juan Tomás. Instituto Español de Oceanografía; EspañaFil: Estrada, Ferran. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias del Mar; EspañaFil: Bárcenas, Patricia. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias del Mar; EspañaFil: d’Acremont, Elia. Sorbonne Universités; FranciaFil: Gorini, Christian. Université Pierre et Marie Curie; Francia. Sorbonne University; FranciaFil: Moumni, Bouchta El. Université Abdelmalek Essaadi; Marrueco

133,000 Years of Sedimentary Record in a Contourite Drift in the Western Alboran Sea: Sediment Sources and Paleocurrent Reconstruction

The Djibouti Ville Drift is part of a contourite depositional system located on the southern side of the Djibouti Ville Seamount in the Alboran Sea (Western Mediterranean). The sedimentary record of a core located in the drift deposits has been characterized to achieve the possible sediment sources for the Saharan dust supply and the paleocurrent variability related to Mediterranean intermediate waters for the last 133 kyr. Three end-member grain-size distributions characterize the sediment record transported by the bottom current to address the different aeolian populations, i.e., coarse EM1, silty EM2, and fine EM3. For these particles, the most likely source areas are the Saharan sedimentary basins and deserts, as well as the cratonic basins of the Sahara-Sahel Dust Corridor. The prevalence of these main source areas is shown in the core record, where a noticeable change occurs during the MIS 5 to MIS 4 transition. Some punctual sediment inputs from the seamount have been recognized during sea-level lowstand, but there is no evidence of fluvial supply in the drift deposits. The paleocurrent reconstruction allows the characterizing of the stadial and cold periods by large increases in the mean sortable silt fraction and UP10, which point to an enhanced bottom current strength related to intermediate water masses. Conversely, interglacial periods are characterized by weaker bottom current activity, which is associated with denser deep water masses. These proxies also recorded the intensified Saharan wind transport that occurred during interstadial/stadial transitions. All these results point to the importance of combining sediment source areas with major climatic oscillations and paleocurrent variability in palaeoceanographic sedimentary archives, which may help to develop future climate prediction models

Reconstruction of the source areas for the aeolian dust deposited in the contourite drift associated with the submarine seamount Djibouti Ville (Alboran Sea)

Se ha realizado el estudio del registro sedimentario del drift contornítico asociado al monte submarino Villa de Djibouti (mar de Alborán, Mediterráneo occidental) con el fin de reconstruir las áreas fuente de polvo eólico desde el Pleistoceno Superior al Holoceno. Se han podido diferenciar tres end-members (EM1 grueso, EM2 limoso y EM3 fino) que caracterizan la distribución granulométrica de las principales poblaciones de polvo eólico. Las áreas fuente más probables de estas partículas son las cuencas sedimentarias y los desiertos, así como las cuencas cratónicas del corredor Sahara-Sahel, cuya prevalencia en el registro sedimentario experimenta un cambio durante la transición de MIS 5 a MIS 4. Se han reconocido algunos aportes puntuales del monte coincidiendo con periodos de bajada del nivel del mar, pero no se han encontrado evidencias de aportes fluviales en los depósitos contorníticosThe sedimentary record of the contourite drift associated with the Djibouti Ville seamount (Alboran Sea, western Mediterranean) has been studied to reconstruct the source areas of the aeolian dust from Late Pleistocene to Holocene. Three end-member grain-size distributions address for different aeolian populations (coarse EM1, silty EM2 and fine EM3). For these particles, the most probable source areas are the Saharan sedimentary basins and deserts as well as the cratonic basins of the Sahara-Sahel corridor, whose prevalence in the core record changes by the MIS 5 to MIS 4 transition. Some punctual sediment inputs from the seamount have been recognized during sea-level low-stand but there is no evidence for fluvial supply in the drift deposit

Djibouti Ville Drift (SW Mediterranean): Sedimentation and record of bottom-current fluctuations during the Pleistocene and Holocene

Seismic profiles and sedimentological data (bulk fraction) of two sediment cores recovered from the Djibouti Ville Drift (SW Mediterranean Sea) indicate that bottom currents have played a fundamental role in shaping the sediment drift. The deposits are composed of biogenous to mixed muddy and silty contourites. A grain size analysis of the terrigenous fraction together with mineralogical, magnetic susceptibility, 14C-AMS dating and stable oxygen isotope data have been analysed to reconstruct glacial and interglacial changes in the bottom currents during the last 133kyr. The sharp vertical grain size changes in the moat and drift indicate that there were substantial bottom current acceleration and deceleration events with faster flow speeds being registered in the moat environment. In sediments from glacial periods (MIS2, MIS3, and MIS6) and stadials 5b and 5d, there is a low carbonate content, high levels of terrigenous elements and paleocurrent proxy values suggest faster flows with the exception of MIS4. Deposits from the interglacial period (MIS1) and interstadials 5a, 5c and 5e, have a high carbonate content, low levels of terrigenous elements, and the paleocurrent proxy values indicate slower flows.Versión del edito

Actas del III Seminario Hispano-Marroquí (Algeciras, abril de 2011)

Actas del III Seminario Hispano-Marroquí (Algeciras, abril de 2011

Water mass footprints in uneven turbidite system development in the Alboran Sea

Multidisciplinary work between oceanography, geomorphology and sedimentology has uncovered evidence explaining the uneven development of the turbidite systems (TSs) in the Alboran Sea. Nine TSs have been mapped in the Spanish margin, ranging from sandy to mixed sand-mud fans, and which become sandier towards the Strait of Gibraltar; in contrast TSs do not develop in the Moroccan margin, where three canyons incise the continental slope but there is no TS formation. We interpret that the uneven development of TSs in the two margins and their variable architectures are conditioned by the interaction of alongslope with downslope processes. Two different interaction scenarios with varying intensities are proposed.Versión del edito

Seafloor Morphology and Processes in the Alboran Sea

The seafloor of the Alboran Sea reflects its complex tectonic, sedimentary, and oceanography dynamics as a consequence of the geological context, involving interaction between the Eurasian and African plates, and oceanographic context, as it is where the Atlantic and Mediterranean waters meet. Their physiography has a semi-enclosed configuration characterized by two margins (the Spanish Iberian and North Africa—mostly Moroccan margins) enclosing deep basins. Tectonic activity is mainly attested by folds and faults that predominantly affect the central and eastern seafloor sectors, as well as numerous seamounts and fluid-flow features (pockmarks, mud volcanoes, and diapirs) that dot the seafloor. The sedimentary and oceanographic processes allow us to distinctly define two principal environments in the Alboran Sea: the shallow proximal margin (continental shelf); and the deep distal margin (continental slope and base of the slope) with the adjacent sub-basins. The shelf mostly comprises prodeltaic and infralittoral prograding wedges, with local bedform fields, submarine valleys, and wave-cut terraces. Coastal and fluvio-marine sedimentary processes, acting since the last glacial period, are responsible for these features. The deep marine environment is characterised by the ubiquity of contourites, whose continuity is interrupted by turbidite systems, canyons, and landslides. The alongslope action of the Mediterranean waters and their interfaces with the Atlantic water has been the main process governing transport, seafloor reworking, and sedimentation of contourites. Mass-movement processes are responsible for the formation of: (1) turbidite systems—turbidity flows and mass flows were dominant during the last glacial sea-level lowstand, evolving to dilute gravity flows during present interglacial high stand; and (2) landslides—the main triggering factors comprising over-steepening, seismicity, under consolidation due to overpressure by interstitial fluids, stratigraphy, and high sedimentation rates. Locally, still-undetermined biological activity in the Spanish and coral activity in the Moroccan margin generated fields of mounded bioconstructions. The seafloor morphology of the Alboran Sea offers interesting clues for assessing the main potential geological hazards, with tectonic seismicity and landslides (as well as their related tsunamis) being some of the most important potential hazards affecting coastal populations. In addition, the seafloor morphology in combination with assemblages of habitat-forming species enables habitat identification and mapping.En prens

Submarine canyons and related features in the Alboran Sea: continental margins and major isolated reliefs

The analysis of a data set of multibeam bathymetry plus high resolution seismic and parametric profiles allow us to characterize the geomorphologic units on the Alboran Sea-floor as well as the evolution of morpho-sedimentary systems along the Pliocene and Quaternary, later than the main erosive Messinian event. Since the opening of the Gibraltar Straits, the sedimentary evolution of this basin has been controlled by the interchange of water masses between the Atlantic Ocean and the Mediterranean Sea. Basin physiography is also a consequence of the Pliocene-Quaternary compression which has progressively uplifted the sourrounding reliefs and deforms the interior and the margins of the basin. On this scenario, several submarine canyons and gullies have been developed in this basin which traverse especially the northern margin and the flanks of the Northern Alboran Ridge, without affecting the African margins. This fact must be related to the action of bottom contour currents which constitute the main morpho-sedimentary process. The influence of water masses distributed the sedimentary input carried by rivers and coming from the erosion of surrounding ranges. In the southern margin of this basin this influence is stronger and inhibits the development of transversal submarine canyons

The Strait of Gibraltar: submarine morphology, oceanogra- phic connections and evolution

32 pages, 10 figures[EN] The Strait of Gibraltar is a first-order physiographic feature between southern Iberia and northern Africa. It has been excavated over the Arc of Gibraltar in favor of a conjugated ENE-WSW and WNW-ESE fault system that have acted as weakness structures. The Strait was generated by erosive processes of the water masses coming from the Atlantic Ocean in the lower Pliocene, due to the rude and rapid flooding of the Alboran Sea basin. Once the flood stabilized the exchange and interaction of the Atlantic and Mediterranean water masses began as we know it today; the Atlantic water that circulates on the surface of the Strait towards the Alborán Sea, and the Mediterranean water masses that circulate in depth towards the Atlantic Ocean. The acceleration of the Atlantic and Mediterranean water masses in the Strait corridor has favored the development of erosive processes.These processeshave allowed the outcrops of the rocky substratum, the development of sedimentary instabilities and the generation of paleochannels, carbonate crusts and cold-water coral formations during the Pliocene and Quaternary. Likewise, the acceleration of the Mediterranean water masses on their way in and out of the Strait and their interaction with the sea floor have controlled sedimentation both in the Alborán Sea basin and in the Gulf of Cádiz, forming contouritic depositional systems[ES] El estrecho de Gibraltar es un rasgo fisiográfico de primer orden entre el sur de Iberia y el norte de África. Ha sido excavado sobre el Arco de Gibraltar a favor de un sistema de fallas conjugadas de direcciones ENE-OSO y ONO-ESE que han actuado como estructuras de debilidad. El Estrecho fue generado por procesos erosivos de las masas de agua procedentes del océano Atlántico en el Plioceno inferior, al producirse de forma brusca y rápida la inundación de la cuenca del mar de Alborán. Una vez estabilizada la inundación comenzó el intercambio y la interacción de las masas de agua atlántica y mediterránea tal y como hoy la conocemos: el agua atlántica que circula en la superficie del Estrecho hacia el mar de Alborán, y las masas de agua mediterráneas que transitan en profundidad hacia el océano Atlántico. La aceleración de las masas de agua atlántica y mediterránea en el corredor del Estrecho ha favorecido el desarrollo de procesos erosivos. Estos procesos han permitido los afloramientos del substrato rocoso, el desarrollo de inestabilidades sedimentarias, generación de paleocanales, costras carbonatas y formaciones coralígenas de aguas frías durante el Plioceno y el Cuaternario.Asimismo, la aceleración de las masas de agua mediterráneas en su camino de entrada y salida del Estrecho y su interacción con el suelo marino han controlado la sedimentación tanto en la cuenca del mar de Alborán como en el golfo de Cádiz, formando sistemas deposicionales contorníticosWith the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)Peer reviewe