Duarte D.,Portuguese Institute for the Sea and Atmosphere IPMA |
Magalhaes V.H.,Portuguese Institute for the Sea and Atmosphere IPMA |
Magalhaes V.H.,Instituto Dom Luiz Associated Laboratory IDL |
Terrinha P.,Portuguese Institute for the Sea and Atmosphere IPMA |
And 9 more authors.
Marine and Petroleum Geology | Year: 2017
Located on the West Iberian margin, between Cabo Carvoeiro and Cabo da Roca, the Estremadura Spur is a trapezoidal promontory elongated in an east-west direction, extending until the Tore seamount. Recently a field with more than 70 pockmarks was discovered in the NW region of the Estremadura Spur outer shelf (Lourinhã Monocline). Pockmarks are the seabed culminations of fluid migration through the sedimentary column and their characteristic seabed morphologies correspond to cone-shaped circular or elliptical depressions. The characterization of these features and the understanding of the associated fluid escape process are the main objectives of this work. Here we characterize these structures to understand their structural and stratigraphic control based on: 1) Seismic processing and interpretation of the high resolution 2D single-channel sparker seismic dataset, 2) Bathymetric and Backscatter interpretation and 3) ROV direct observation of the seafloor. The analysis of the seismic profiles allowed the identification of six seismic units, disturbed by the migration and accumulation of fluids. The Estremadura Spur outer shelf has been affected by several episodes of fluid migration and fluid escape during the Pliocene-Quaternary that are expressed by a vast number of seabed and buried pockmarks. At present, the pockmarks are mainly inactive, as the seabed pockmarks are covered by recent sediments. It is concluded that the migration of fluids to the seabed occurred over the Pliocene-Quaternary, as indicated by the buried pockmarks at different depths below the seabed. The vertical stacking of various pockmarks suggests a cyclical fluid flow activity that can possibly be the result of the eustatic sea level variations and the subsequent changes of the hydrostatic pressure. © 2017 Elsevier Ltd
Gomes-Pereira J.N.,University of The Azores |
Gomes-Pereira J.N.,LARSyS Associated Laboratory for Robotics and Systems in Engineering and Science |
Tojeira I.,Portuguese Task Group for the Extension of the Continental Shelf EMEPC
Marine Biodiversity | Year: 2014
We report the first in situ observations of a large Taningia danae Joubin, 1931, close to the seafloor at bathyal depths of 2,157 m. The observation was made in the subtropical northeast Atlantic Seine seamount during daytime on 29 September 2012, over a silt-covered seafloor (33°40.1142′N, 14°22.7301′W). Seawater temperature was 4.2 °C, salinity 35.40 ppt, oxygen saturation 50.87 Ox%, and pressure 2,178.29 dbar. Mantle length was estimated from imagery to be 65.3 cm (STD = 6.3). A repeated behaviour was observed every time the ROV approached: (1) swimming away from the ROV by flapping the fins twice (moving forward or backward), (2) gliding slightly inclined downward, until colliding against the seafloor, and (3) ascending obliquely or vertically in relation to the seafloor, finally evading the area moving upward using jet propulsion. These observations greatly extend the species depth range and document behaviour patterns. T. danae is able to explore beyond the mesopelagic zone where it has previously been reported. © 2013 Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg.
Tempera F.,University of The Azores |
Hipolito A.,University of The Azores |
Madeira J.,University of Lisbon |
Vieira S.,University of The Azores |
And 2 more authors.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2013
High-resolution datasets collected by multibeam and acoustic backscatter surveys were used to produce fine-scale seafloor nature and morpho-tectonic interpretations of the Condor seamount. Condor constitutes an elongated volcanic ridge that extends for 39. km and rises more than 1800. m from the surrounding seafloor. Constructive morphologies include (i) linear eruptive centres, (ii) volcanic cones with or without summit depressions, (iii) lava flows and (iv) hummocky sectors. Eruptive type is interpreted to vary with depth. On the deeper seamount extremities, the predominance of highly acoustically backscattering volcanic cones and hummocky terrain is interpreted to result from effusive eruptions not yet covered by sediment deposits. In contrast, the smoother relief of the central seamount flanks is interpreted as draping and infilling of the underlying effusive relief by (i) primary volcaniclastic deposits produced by explosive eruptions on the shallowest parts of the ridge, together with (ii) secondary volcanigenic sediments resulting from truncation of the seamount top by swell erosion and (iii) sediments resulting from biogenic production. A set of WNW-ESE to NW-SE trending volcano-tectonic structures are shown to control most of the fissural volcanism that formed the ridge. A network of NNW-SSE trending faults is identified on the sea-floor around Condor but they show little relation with the distribution of volcanic edifices or with post-emplacement dismantling of the seamount. These fault sets are related to the transtensional regime acting on the Azorean segment of the Eurasia-Nubia plate boundary. Erosional features include (i) palaeo wave-cut platforms on the seamount summit, (ii) landslide scars produced by lateral collapses of the NE and SW-facing flanks, (iii) gullies and turbidity current channels and (iv) mass-wasting deposits. Iceberg drag and bump marks are also identified on the seamount upper flanks, representing the first reference to such features in the Azores and an additional low latitude record. Given the lack of major erosional and tectonic dismantling, Condor is suggested to be a relatively young seamount. A revised factoring of eustatic, erosional and isostatic processes does not exclude that the summit may have been eroded as late as the Last Glacial Maximum. © 2013 Elsevier Ltd.
Pham C.K.,University of The Azores |
Pham C.K.,Laboratory of Robotics and Systems in Engineering and Science LARSyS |
Ramirez-Llodra E.,CSIC - Institute of Marine Sciences |
Ramirez-Llodra E.,Norwegian Institute for Water Research |
And 24 more authors.
PLoS ONE | Year: 2014
Anthropogenic litter is present in all marine habitats, from beaches to the most remote points in the oceans. On the seafloor, marine litter, particularly plastic, can accumulate in high densities with deleterious consequences for its inhabitants. Yet, because of the high cost involved with sampling the seafloor, no large-scale assessment of distribution patterns was available to date. Here, we present data on litter distribution and density collected during 588 video and trawl surveys across 32 sites in European waters. We found litter to be present in the deepest areas and at locations as remote from land as the Charlie-Gibbs Fracture Zone across the Mid-Atlantic Ridge. The highest litter density occurs in submarine canyons, whilst the lowest density can be found on continental shelves and on ocean ridges. Plastic was the most prevalent litter item found on the seafloor. Litter from fishing activities (derelict fishing lines and nets) was particularly common on seamounts, banks, mounds and ocean ridges. Our results highlight the extent of the problem and the need for action to prevent increasing accumulation of litter in marine environments. © 2014 Pham et al.
Braga-Henriques A.,University of The Azores |
Carreiro-Silva M.,University of The Azores |
Tempera F.,University of The Azores |
Porteiro F.M.,University of The Azores |
And 4 more authors.
Marine Biodiversity | Year: 2012
Observations of deep-sea homolids are becoming more common, but good-resolution imagery of these crabs in the natural environment is still scarce. Sixteen new in situ observations of Paromola cuvieri from various locations within the central and eastern groups of the Azores Archipelago (Northeast Atlantic) are described here based on video footage collected by two submersible vehicles. Crabs were found on coral gardens and deep-sea sponge aggregations, which are priority habitats of conservation importance under OSPARCOM. Diverse sessile megafauna were recorded (>59 taxa), including sponges, hydroids, corals, brachiopods, crinoids and oysters. Overall, 75% of the crabs were carrying live specimens of sessile invertebrates, mainly sponges and cold-water corals. Object selection shows to be a more complex process than previously thought, in which factors such as morphology, size and weight of objects and also palatability seem to be more important in the process of object selection than their availability. © 2011 Senckenberg, Gesellschaft für Naturforschung and Springer.