Guadalfeo and Adra submarine deltas evolution in response to sediment supply variations

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.info:eu-repo/semantics/publishedVersio

Benthic foraminiferal and sedimentological response to the evolution of the Adra submarine delta, northern Alboran Sea

The Adra submarine delta is located on the northern Alboran Sea shelf in the western Mediterranean Sea. The genesis of this deltaic system is associated with the discharges of the short and mountainous Adra River. The area is under the influence of a Mediterranean climate with sporadic winter torrential flows and increased summer aridity. Major anthropogenic activities in the river system occurred in 1872 AD, with the deviation of the main fluvial course to the east. The channel was silted up in 1910 AD as result of a flood event and relocated further west, at its present position. These artificial changes are reflected in the submarine morpho‐stratigraphy of the delta that is composed of two main lobes. In order to understand the interaction between river discharges and the evolution of the submarine delta at different timescales, two sediment cores were collected from both lobes. 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 250 years BP. The correlation of sediment cores with seismic records indicate that both cores penetrated the same seismic unit, deposited between ca. 1070 to ca. 1872 AD, under the direct influence of the ancient river course. The predominant sedimentary facies is sandy silt with intercalated sand layers. The uppermost core sections are pure sand. The number of benthic foraminifera is generally below 100 specimens per gram. The most abundant species in both cores are Ammonia tepida, Bolivina ordinaria, Nonionella stella, Reophax arctica and Textularia earlandi. The increases of sand and the low faunal density, followed by increased abundance of successful colonizers and opportunistic species, is interpreted as result of periods of high precipitation, and sediment supply to the shelf, and the subsequent establishment of an environment with new ecological constrains.info:eu-repo/semantics/publishedVersio

The Guadiaro-Baños contourite drifts (SW Mediterranean). A geotechnical approach to stability analysis

Two Quaternary plastered contourite drifts, with terraced and low-mounded morphologies, make up the continental slope and base-of-slope in the northwestern Alboran Sea, respectively, between the Guadiaro and Baños turbidite systems, close to the Strait of Gibraltar. Considering their significant lateral extent, the link between the contourite drift deposits and landslides may be particularly important for hazard assessment. The physical properties, composition and geometry of contourite drifts have been proposed as key factors in slope stability, although this relationship still needs to be better constrained. In this work, new in-situ geotechnical data (cone penetration tests; CPTu) has been combined with morphostratigraphic, sedimentological, and (laboratory) geotechnical properties to determine the stability of the Guadiaro-Baños drifts. For the depositional domains of both drifts, the resulting sedimentary and geotechnical model describes low-plasticity granular and silty sands on the erosive terraced domain that evolve seawards to silty and silty-clay deposits with a higher plasticity and uniform geomechanical properties. For the shallower coarse-grained contourite sediments, the cohesion (c') and internal friction angle (ϕ') values are 0–9 kPa and 46–30°, respectively, whereas for the distal fine contourites the undrained shear strength gradient (∇Su) is 2 kPa/m. These properties allow us to establish high factors of safety for all the scenarios considered, including seismic loading. Slope failure may be triggered in the unlikely event that there is seismic acceleration of PGA > 0.19, although no potential glide planes have been observed within the first 20 m below the seafloor. This suggests that the contourite drifts studied tend to resist failure better than others with similar sedimentary characteristics. The interplay of several processes is proposed to explain the enhanced undrained shear strength: 1) the geometry of the drifts, defined by an upper contouritic terrace and lower low-mounded shapes; 2) recurrent low-intensity earthquakes with insufficient energy to trigger landslides, favouring increased strength due to dynamic compaction; and 3) cyclic loading induced by solitons/internal waves acting on the sediment.En prens

Improving Scientific Knowledge of Mallorca Channel Seamounts (Western Mediterranean) within the Framework of Natura 2000 Network

The scientific exploration of Mallorca Channel seamounts (western Mediterranean) is improving the knowledge of the Ses Olives (SO), Ausias March (AM), and Emile Baudot (EB) seamounts for their inclusion in the Natura 2000 network. The aims are to map and characterize benthic species and habitats by means of a geological and biological multidisciplinary approach: high-resolution acoustics, sediment and rock dredges, beam trawl, bottom trawl, and underwater imagery. Among the seamounts, 15 different morphological features were differentiated, highlighting the presence of 4000 pockmarks, which are seafloor rounded depressions indicators of focused fluid flow escapes, usually gas and/or water, from beneath the seabed sediments. So far, a total of 547 species or taxa have been inventoried, with sponges, fishes, mollusks, and crustaceans the most diverse groups including new taxa and new geographical records. Up to 29 categories of benthic habitats have been found, highlighting those included in the Habitats Directive: maërl beds on the summits of AM and EB, pockmarks around the seamounts and coral reefs in their rocky escarpments as well as fields of Isidella elongata on sedimentary bathyal bottoms. Trawling is the main demersal fishery developed around SO and AM, which are targeted to deep water crustaceans: Parapenaeus longirostris, Nephrops norvegicus, and Aristeus antennatus. This study provides scientific information for the proposal of the Mallorca Channel seamounts as a Site of Community Importance and for its final declaration as a Special Area of Conservation

Endodontic regenerative treatment for internal radicular resorption using bio-ceramic material, case report

The internal resorption of the internal radicular conduct is a process than can be both physiological or pathological, being the osteoclasts, odontoclasts and dentinoclast responsible for said process. 49-year-old female patient, refers orthodontic treatment at age 20, attends a dental check-up due to pain when chewing. Dental organ (DO) #11 was diagnosed with internal root resorption and symptomatic, suppurative apical periodontitis. Treatment started performing an endodontic access and taking a conductometry reading with an apical foramen locator, using a precision hybrid instrumentation technique and applying hypochlorite irrigation, the intra-canal was medicated with chemically pure calcium hydroxide for 7 days. The canal obturation was repaired infiltrating a bio-ceramic material (BIO-C Sealer) followed by the placement of the single cone using a vertical condensation technique

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

Understanding the complex geomorphology of a deep sea area affected by continental tectonic indentation: the case of the Gulf of Vera (Western Mediterranean)

We present a multidisciplinary study of morphology, stratigraphy, sedimentology, tectonic structure, and physical oceanography to report that the complex geomorphology of the Palomares continental margin and adjacent Algerian abyssal plain (i.e., Gulf of Vera, Western Mediterranean), is the result of the sedimentary response to the Aguilas Arc continental tectonic indentation in the Eurasian–Africa plate collision. The inden tation is imprinted on the basement of the margin with elongated metamorphic antiforms that are pierced by igneous bodies, and synforms that accommodate the deformation and create a complex physiography. The basement is partially covered by Upper Miocene deposits sealed by the regional Messinian Erosive Surface characterized by palaeocanyons that carve the modern margin. These deposits and outcropping basement highs are then covered and shaped by Plio-Quaternary contourites formed under the action of the Light Intermediate and Dense Deep Mediterranean bottom currents. Even though bottom currents are responsible for the primary sedimentation that shapes the margin, 97% of this region's seafloor is affected by mass-movements that modified contourite sediments by eroding, deforming, faulting, sliding, and depositing sediments. Mass-movement processes have resulted in the formation of recurrent mass-flow deposits, an enlargement of the submarine canyons and gully incisions, and basin-scale gravitational slides spreading above the Messinian Salinity Crisis salt layer. The Polopo, Aguilas and Gata slides are characterized by an extensional upslope domain that shapes the continental margin, and by a downslope contractional domain that shapes the abyssal plain with diapirs piercing (hemi)pelagites/sheet-like turbidites creating a seafloor dotted by numerous crests. The mass movements were mostly triggered by the interplay of the continental tectonic indentation of the Aguilas Arc with sedimentological factors over time. The indentation, which involves the progressively southeastward tectonic tilting of the whole land-sea region, likely generated a quasi-continuous oversteepening of the entire margin, thus reducing the stability of the contourites. In addition, tectonic tilting and subsidence of the abyssal plain favoured the flow of the underlying Messinian Salinity Crisis salt layer, contributing to the gravitational instability of the overlying sediments over large areas of the margin and abyssal plain