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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)

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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.

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 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

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

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 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.

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.

The Guadalfeo submarine delta is located on the northern Alboran Sea shelf in the western Mediterranean Sea. The sedimentary dynamics of the deltaic system is governed by the discharge of one of the major rivers in this area draining the western sector of the near-coastal Sierra Nevada Mountains. The area is under the influence of a Mediterranean climate, with high spatial and temporal (i.e., inter- and intra-annual) rain variability. Major anthropogenic forcing affected the river system during the 1930’s, with the deviation of the main river channel 2.5 km to the west, to its present position. More recently, the construction of Béznar (1977-1985) and Rules (1993-2003) dams have also contributed to limit the amount of sediments exported to the deltaic system. In order to understand the interaction between river discharges and the evolution of the submarine delta at different timescales, sediment cores were collected off the ancient (core 13) and present-day (cores12 and 15) river courses. A chronological framework was performed and combined with sedimentological and benthic foraminiferal analyses. Radiocarbon dating of plant debris from the base of the cores indicates that the sedimentary record goes back 200 years. In core 13, the variations between coarse and fine fractions along the core and the upward increase of benthic foraminiferal population density, would indicate that deposition possibly occurred until the deviation of the main river course to its present position. In the lower part of core 12, the strong alternation between coarse and fine sediment textures and the variable amounts of benthic foraminiferal species are interpreted as the result of an active fluvial regime. The upper part, with high percentages of fine sediments and high values of population density, could be attributed to the stabilization of the river course in its present-day location. Core 15, located at 11 m water depth, showed the highest content of gravel in the lower part of the core, high contents of silt at two core depths and increased percentages of sand to the top, indicating the strong influence of human interventions in the river basin and consequent changes in the sediment supply to the Guadalfeo submarine delta. info:eu-repo/semantics/publishedVersion

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.

Benthic foraminifera have a wide distribution in space and time and also respond rapidly to environmental changes. The northern Alboran Sea is influenced by a torrential regime with sporadic, intense rainfalls and extended periods of aridity. In addition, anthropogenic activities such as river channel deviation have taken place during the last ca. 150 years. In order to understand the interaction between natural and anthropogenic impacts through time, shifts of most abundant benthic foraminiferal species, species richness and diversity indices were combined with sedimentological analyses and radiocarbon dating of sediment cores collected from the Adra shelf prodeltaic deposit, in the northern Alboran Sea. The strong variations of benthic foraminiferal assemblages involving significant population density changes occurred until ca. 1870 AD, and are interpreted as response to natural processes. Low population densities correlate with rainfall-driven periods of increased sediment supply to the shelf. In contrast, intervals with increased population densities, followed by a raise of successful colonizers and opportunistic species, indicate the establishment of an environment with new ecological constraints. After ca. 1870 AD, the impact of anthropogenic activities with the deviation of the main river course to the east, are responsible for a drastic reduction of sedimentation rates in the study area. info:eu-repo/semantics/publishedVersion

Continental shelves today find themselves largely submerged as a consequence of the sea-level rise in the last 20,000 years, the time since the Last Glacial Maximum (LGM), the period of maximum ice mass and minimum ocean volume within the Last Glacial Cycle. Their geomorphology, however, is far from controlled by marine processes alone. Shallow parts of the shelves were land during most of the past 120,000 years (the last full interglacial–glacial cycle), and deeper parts of the current shelves were coastal zones for most of that time, and this goes for older cycles too. To describe and understand the geomorphology of continental shelf drowned landscapes requires combining the knowledge on marine and terrestrial processes and to take into account both climatic and sea-level cyclicities in the larger picture of shelf evolution. With this special issue, we hope to interest the Geomorphology readership in the peculiarities of Continental Shelf Drowned Landscapes and their evolution during the youngest climatic–eustatic cycles. The special issue emerges from two international meetings organised in 2011. These were (i) the CMP-commission sponsored session on ‘Drowned landscapes and continental shelves during the last glacial cycles’ at the XVIII INQUA congress (21–27 July 2011) in Bern, Switzerland, and (ii) the 5th IGCP526 conference (13–16 Sept 2011) held in Sidney, British Columbia, Canada, on ‘Continental Shelves: Risks, Resources and Record of the Past’.