Chiocci, Francesco L. ... et al.-- Conferencia Internacional para conmemorar el 1er Aniversario d... more Chiocci, Francesco L. ... et al.-- Conferencia Internacional para conmemorar el 1er Aniversario de la erupcion submarina de El Hierro 2011-2012, 10-15 October 2012, El Pinar, El Hierro, Canary Islands, Spain
The Pliocene-Quaternary tectonic-sedimentary evolution of the NE Alboran Sea is established using... more The Pliocene-Quaternary tectonic-sedimentary evolution of the NE Alboran Sea is established using high-resolution seismic profiles. The Pliocene-Quaternary deposits resting upon an acoustic basement with a complex morphostrncture are stratigraphically made up of three seismic sequences whose facies, stratal patterns and nature of boundaries result from the interaction between sea-level changes, tectonics and physiographic configuration. During the Early Pliocene, a generalized synsedimentary transgression with extensive tectonic activity resulted in a homogeneous sedimentation deformed by extensional tectonic activity along two main fault systems (NE-SW and NW-SE). The sediment distribution was controlled by the pre-existing palaeotopography. During the Late Pliocene, a generalized synsedimentary regression with a N-S compressive tectonic activity favoured the development of a great variety of seismic facies related to the initiation of the Almeria turbidite system and the triggering of gravity mass-flow deposits. The deformation of these seismic facies was mainly controlled by the transcurrent NE-SW and NW-SE structures, and their distribution was related to the point source represented by the Almeria Canyon. During the Quaternary, the high-frequency sea-level oscillations coeval to NNW-SSE compressive tectonic activity resulted in the progradation of the margin, the occurrence of instability phenomena, and the sedimentary displacements of the Almeria turbidite system. An analysis of subsidence evolution shows an attenuation during the Pliocene-Quaternary, from a maximum of 342 m/m.y, to 160 m/m.y, for the total subsidence, and from a maximum of 196 to 116 m/m.y, for the tectonic subsidence.
A detailed analysis of the modern morphology, acoustic facies and architecture of the eastern Mag... more A detailed analysis of the modern morphology, acoustic facies and architecture of the eastern Magdalena Turbidite System has been based on multibeam bathymetry and backscatter data. In spite of the fact that the Magdalena Turbidite System developed in a tectonically active setting, its present architecture model is comprised of two tecto-sedimentary provinces: deformed-constructional and undeformed-erosive. The deformed province occurs where the deformed prism developed. This prism is characterised by structural highs and associated small-scale ridges and scarps. In this province, the Magdalena Turbidite System is constructional because sediment coming from the Colombian hinterland (via the Magdalena River and from coastal erosion) and sediment remobilised from the walls of the structural highs are transported trough canyons and gullies, and emplaced as gravity deposits into the deformed prism. In the undeformed province, by contrast, the Magdalena Turbidite System displays an architecture model similar to a passive continental margin, and is characterised by large-scale mass-flow deposits, leveed channel complexes, scars of slumps, and sediment waves. This province is presently erosive because the existing leveed channels are partially or totally destroyed and cannibalised by mass-flow deposits, cut by small-scale scars of slumps, and their morphology is subdued or modified by the formation of a sediment wave field.
The shelf-upper slope stratigraphy offshore and around the Guadalfeo River on the northern contin... more The shelf-upper slope stratigraphy offshore and around the Guadalfeo River on the northern continental margin of the Alboran Sea, Western Mediterranean Basin, has been defined through the interpretation of a grid of Sparker seismic profiles. We tried to identify evolutionary trends in shelf growth, as well as to determine the regional/ local factors that may modify the influence of glacio-eustatic fluctuations. Four major depositional sequences are identified in the sedimentary record by a detailed seismic interpretation, which defines three significant intervals of shelf-upper slope progradation, dominated by deposition of shelf-margin wedges, which resulted in uniform patterns of shelf-margin growth in response to significant sea-level falls. In contrast, the record of transgressive intervals is more variable, mainly as the result of distinct patterns of regressive-to-transgressive transitions. Major progradational wedges are internally composed of seawardprograding, landward-thinning wedges, interpreted to represent shelf-margin deltaic deposits. In contrast, the last aggradational interval is composed of shelf-prograding wedges that show distinct characteristics, in terms of seismic facies, morphology and distribution when compared with previous shelf-margin wedges. These shelf wedges are thought to represent the particular case of Regressive Systems or Shelf Margin Systems Tracts, and their development seems to be controlled by a drastic change in main depocenter location, which moved from the upper slope to the shelf during the Pleistocene. The stacking pattern of seismic units, the shallowness of the acoustic basement and the migration of the shelf break are used to infer spatial and temporal changes in tectonic subsidence-uplift rates, which interact with low-order glacio-eustatic changes. For much of the Pliocene-Quaternary, uplifted sectors alternated laterally with sectors experiencing more subsidence. Subsequently, a significant change from lateral outgrowth to vertical accretion is recognised. This stratigraphic change could be related to the combined influence of increased subsidence rates on the shelf and the onset of higher-frequency glacio-eustatic cyclicity after the Mid Pleistocene Revolution that occurred around 1 Ma.
This work provides a regional perspective on the links between glacial, glacimarine and marine se... more This work provides a regional perspective on the links between glacial, glacimarine and marine sedimentary processes occurring since the Last Glacial Maximum along the Central Bransfield Basin (Antarctic Peninsula), from shallow to deep areas, by combining information provided by gravity cores from shelf to deep basin settings, swath bathymetry and high-resolution reflection seismic and sub-bottom (TOPAS) profiles. Seven lithofacies have been identified. Their textural, compositional and X-radiographic characteristics, as well as their spatial distribution allow the differentiation of two stages of deposition, involving distinct sedimentary processes. The Last Glacial Maximum was characterised by subglacial deformation by the Antarctic Peninsula Ice Sheet as it reached its most extended position on the distal mid-slope platforms of the Central Bransfield Basin. Proglacial debris flows occurred on the external edges of the mid-slope platforms and lower slope. Since the last deglaciation, glacimarine (proglacial debris flows, glacimarine proglacial processes and turbid glacial meltwater) and open-marine sedimentary processes (turbidity currents, sliding and contour current activity) have predominated in the Central Bransfield Basin. Glacial cyclicity is the main factor controlling the sedimentary processes in the basin, but several secondary factors, including physiography, sediment entry points and oceanography, have been identified as local controls on the sediment distribution. The unusual physiography of the Central Bransfield Basin, where slope platforms form wide flat surfaces seaward from glacial troughs, is a key factor in the widespread occurrence of glacial and glacimarine processes on the entire continental margin.
We analyzed in detail the seabed morphology of the seamounts and surroundings on the Djibouti Mar... more We analyzed in detail the seabed morphology of the seamounts and surroundings on the Djibouti Marginal Shelf (northern Alboran Sea) using high resolution (Sparker) and very high resolution (TOPAS) seismic reflection profiles and multibeam bathymetry. The aim of the study was to determine the recent geological processes, and in particular the contouritic processes associated with Mediterranean waters. Six groups of morphologic features were defined: structural features (seamount cap, tectonic depressions), fluid dynamics-related features (pockmarks), mass-movement features (gullies, slides), bottom-current features (moats, scour marks, terraces, elongated and separated drifts, plastered drifts, confined drifts, sheeted drifts), mixed features (ridges) and bioconstructions (carbonate mounds). The main processes controlling feature formation are Late Cenozoic tectonic activity and the interaction of Mediterranean waters with the seafloor topography. Seamounts act as topographic barriers that affect the pathway and velocity of Mediterranean water flows, which are subdivided into strands that interact with the surrounding seafloor. Sedimentary instability and fluiddynamic processes play a minor role, and their occurrence is probably triggered by seismicity.
Seismic profiles and sedimentological data (bulk fraction) of two sediment cores recovered from t... more 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, 14 C-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.
Submarine Mass Movements and Their Consequences: 6th International Symposium, 2014
ABSTRACT The Quaternary stratigraphic architecture of seamounts and surrounding deposits in the e... more ABSTRACT The Quaternary stratigraphic architecture of seamounts and surrounding deposits in the eastern Alboran Sea reveals at least 53 stacked MTDs in the Pollux Bank, Sabinar Bank (Sabinar Platform and Western Sabinar), Maimonides Ridge, and Adra Ridge. These MTDs are grouped into two types based on their size: smallscale MTDs (length <5 km and thickness <18 ms) and large-scale MTDs (length >5 km and thickness >18 ms). The study of these deposits has allowed us to define a close relationship between size (thickness-length) and source area gradients. The frequency of MTD events has varied between 40 and 373 kyr throughout the Quaternary (1.8 Ma to present). Correlation between individual MTDs is difficult but could be done for at least one local MTD event between Sabinar Platform and Western Sabinar (Sabinar Bank); in addition, one regional MTD event has been recognized around all of the studied seamounts. These failure events could have been triggered by tectonically controlled seismicity at both regional and local scale.
New core data from a sediment–wave field on the Demerara Outer Ridge show that the waves are main... more New core data from a sediment–wave field on the Demerara Outer Ridge show that the waves are mainly built from turbidity currents that flow northwards down the Demerara margin. The contour currents circulating parallel and obliquely to the margin are apparently not as important to wave formation as previously proposed. Detailed analysis of the sedimentary facies of cores taken on the crest and flank of a sediment wave indicates that fine-grained turbiditic deposits are dominant. Hemipelagic/pelagic deposits are interbedded with the turbidites. Sediment redistribution by contour currents was only evidenced by the presence of peculiar clay mineral assemblages and microfaunal associations, as well as some sedimentary structures such as truncations and cross-bedding. The turbiditic processes were active during the Last Glacial. In contrast, the Holocene is characterised by pelagic sedimentation. A combination of seismic and core data suggests that the sediment waves result from predominantly turbiditic depositional processes interacting with minor contour currents and synsedimentary deformation processes.
The northern continental slope off the Ebro Delta has a badland topography indicating major slope... more The northern continental slope off the Ebro Delta has a badland topography indicating major slope erosion and mass movement of material that deposits sediment into a ponded lobe. The southern slope has a low degree of mass movement activity and slope valleys feed channel levee-complexes on a steep continental rise. The last active fan valley is V-shaped with little meandering and ils thalweg merges downstream with the Valencia Valley. The older and larger inactive channel-levee complex is smoother, U-shaped, and meanders more than the active fan valley.
The study of more than 500 single-and multichannel seismic records enabled the generation of a de... more The study of more than 500 single-and multichannel seismic records enabled the generation of a detailed palaeo-bathymetric map of the Messinian surface over most of the Alboran Basin, Western Mediterranean. This regional surface is characterized by several erosional features (channels, terraces and canyons) and topographic highs (structural, volcanic and diapiric in origin). The most prominent feature is the incised Zanclean Channel crossing the entire basin, its entrenchment having been associated with the opening of the Strait of Gibraltar and subsequent inflow of Atlantic waters. The incision depth of the channel is variable, suggesting local variations in the erosive capacity of the Atlantic inflow, conditioned mainly by the regional basin topography and the local presence of topographic highs. Adjacent to this channel along the Spanish and Moroccan margins, and near the Strait of Gibraltar, several submarine terraces developed at different depths suggest a pulsed flooding of the Alboran Basin. There could have been two major inflow phases of Atlantic water, one shortly before and another during the Zanclean flooding, the latter accompanied by periods of relative sea-level stillstands that enabled terrace development. Alternatively, these features were all generated during the main flooding evident and subsequent pulsed infilling of the basin.
A multiple Contourite Depositional System has been defined in the Plio-Quaternary sedimentary reg... more A multiple Contourite Depositional System has been defined in the Plio-Quaternary sedimentary register in the Alboran Sea. This multiple system formed by the Atlantic and the low density and high density Mediterranean Waters, which shaped the margins and basins since the opening of the Gibraltar Strait. Three different (paleo)circulation scenarios are proposed since then: the Atlantic water Flooding;the Pliocene circulation, characterized by immature low and high density Mediterranean waters and a strong countercurrent in the Western Basin; and the Quaternary circulation, characterized by tabular Mediterranean water masses with multiple current dynamics,an increasing influence of density contrasts, and climate shifts causing major vertical and horizontal displacements of their interfaces.
The interpretation of approximately 100 km of EM12 multibeam bathymetry and backscatter data toge... more The interpretation of approximately 100 km of EM12 multibeam bathymetry and backscatter data together with high resolution TOPAS profiles obtained during a transit over the Orinoco deep-sea fan, near the Barbados accretionary prism, shows that the braided drainage pattern seen on GLORIA images by Belderson et al. (1984)corresponds to wide (∼10 km), low relief (<5 m) channels, incised by numerous
Abstract: The Oligocene to Recent Agadir turbidite system occurs in the Agadir Basin, abutting ag... more Abstract: The Oligocene to Recent Agadir turbidite system occurs in the Agadir Basin, abutting against the continental margin off South Morocco (central eastern Atlantic). This system is part of the submarine drainage system linking back to the Anti-and High Atlas mountains ...
Morpho-seismic characterization of Quaternary mass movement deposits in the eastern sector of the... more Morpho-seismic characterization of Quaternary mass movement deposits in the eastern sector of the Alboran Sea (SW Mediterranean
The Ceuta Drift is an elongated-terrace feature (up to 100 km long, 28 km wide, 400 m relief, and... more The Ceuta Drift is an elongated-terrace feature (up to 100 km long, 28 km wide, 400 m relief, and 700 ms thick) located in the southwestern Alboran Sea, close to the Gibraltar Strait. It extends between 200 and 700 m water depth, parallel to the Moroccan slope. The drift stratigraphy is defined by the vertical stacking of at least five seismic units bounded by discontinuities: onlap and downlap surfaces at the bottom, and erosive surfaces at the top. Sedimentologically, the most recent deposits are defined by the vertical succesion, from bottom to top, of contouritic sandy muds, muds, and silty clays. The Ceuta Drift began to develop during the early Quaternary, when the pre-existing sea-floor morphology favoured the formation of an offshoot current system from the Mediterranean water masses. The action of this current together with sea-level changes have controlled the growth pattern of this drift.
Chiocci, Francesco L. ... et al.-- Conferencia Internacional para conmemorar el 1er Aniversario d... more Chiocci, Francesco L. ... et al.-- Conferencia Internacional para conmemorar el 1er Aniversario de la erupcion submarina de El Hierro 2011-2012, 10-15 October 2012, El Pinar, El Hierro, Canary Islands, Spain
The Pliocene-Quaternary tectonic-sedimentary evolution of the NE Alboran Sea is established using... more The Pliocene-Quaternary tectonic-sedimentary evolution of the NE Alboran Sea is established using high-resolution seismic profiles. The Pliocene-Quaternary deposits resting upon an acoustic basement with a complex morphostrncture are stratigraphically made up of three seismic sequences whose facies, stratal patterns and nature of boundaries result from the interaction between sea-level changes, tectonics and physiographic configuration. During the Early Pliocene, a generalized synsedimentary transgression with extensive tectonic activity resulted in a homogeneous sedimentation deformed by extensional tectonic activity along two main fault systems (NE-SW and NW-SE). The sediment distribution was controlled by the pre-existing palaeotopography. During the Late Pliocene, a generalized synsedimentary regression with a N-S compressive tectonic activity favoured the development of a great variety of seismic facies related to the initiation of the Almeria turbidite system and the triggering of gravity mass-flow deposits. The deformation of these seismic facies was mainly controlled by the transcurrent NE-SW and NW-SE structures, and their distribution was related to the point source represented by the Almeria Canyon. During the Quaternary, the high-frequency sea-level oscillations coeval to NNW-SSE compressive tectonic activity resulted in the progradation of the margin, the occurrence of instability phenomena, and the sedimentary displacements of the Almeria turbidite system. An analysis of subsidence evolution shows an attenuation during the Pliocene-Quaternary, from a maximum of 342 m/m.y, to 160 m/m.y, for the total subsidence, and from a maximum of 196 to 116 m/m.y, for the tectonic subsidence.
A detailed analysis of the modern morphology, acoustic facies and architecture of the eastern Mag... more A detailed analysis of the modern morphology, acoustic facies and architecture of the eastern Magdalena Turbidite System has been based on multibeam bathymetry and backscatter data. In spite of the fact that the Magdalena Turbidite System developed in a tectonically active setting, its present architecture model is comprised of two tecto-sedimentary provinces: deformed-constructional and undeformed-erosive. The deformed province occurs where the deformed prism developed. This prism is characterised by structural highs and associated small-scale ridges and scarps. In this province, the Magdalena Turbidite System is constructional because sediment coming from the Colombian hinterland (via the Magdalena River and from coastal erosion) and sediment remobilised from the walls of the structural highs are transported trough canyons and gullies, and emplaced as gravity deposits into the deformed prism. In the undeformed province, by contrast, the Magdalena Turbidite System displays an architecture model similar to a passive continental margin, and is characterised by large-scale mass-flow deposits, leveed channel complexes, scars of slumps, and sediment waves. This province is presently erosive because the existing leveed channels are partially or totally destroyed and cannibalised by mass-flow deposits, cut by small-scale scars of slumps, and their morphology is subdued or modified by the formation of a sediment wave field.
The shelf-upper slope stratigraphy offshore and around the Guadalfeo River on the northern contin... more The shelf-upper slope stratigraphy offshore and around the Guadalfeo River on the northern continental margin of the Alboran Sea, Western Mediterranean Basin, has been defined through the interpretation of a grid of Sparker seismic profiles. We tried to identify evolutionary trends in shelf growth, as well as to determine the regional/ local factors that may modify the influence of glacio-eustatic fluctuations. Four major depositional sequences are identified in the sedimentary record by a detailed seismic interpretation, which defines three significant intervals of shelf-upper slope progradation, dominated by deposition of shelf-margin wedges, which resulted in uniform patterns of shelf-margin growth in response to significant sea-level falls. In contrast, the record of transgressive intervals is more variable, mainly as the result of distinct patterns of regressive-to-transgressive transitions. Major progradational wedges are internally composed of seawardprograding, landward-thinning wedges, interpreted to represent shelf-margin deltaic deposits. In contrast, the last aggradational interval is composed of shelf-prograding wedges that show distinct characteristics, in terms of seismic facies, morphology and distribution when compared with previous shelf-margin wedges. These shelf wedges are thought to represent the particular case of Regressive Systems or Shelf Margin Systems Tracts, and their development seems to be controlled by a drastic change in main depocenter location, which moved from the upper slope to the shelf during the Pleistocene. The stacking pattern of seismic units, the shallowness of the acoustic basement and the migration of the shelf break are used to infer spatial and temporal changes in tectonic subsidence-uplift rates, which interact with low-order glacio-eustatic changes. For much of the Pliocene-Quaternary, uplifted sectors alternated laterally with sectors experiencing more subsidence. Subsequently, a significant change from lateral outgrowth to vertical accretion is recognised. This stratigraphic change could be related to the combined influence of increased subsidence rates on the shelf and the onset of higher-frequency glacio-eustatic cyclicity after the Mid Pleistocene Revolution that occurred around 1 Ma.
This work provides a regional perspective on the links between glacial, glacimarine and marine se... more This work provides a regional perspective on the links between glacial, glacimarine and marine sedimentary processes occurring since the Last Glacial Maximum along the Central Bransfield Basin (Antarctic Peninsula), from shallow to deep areas, by combining information provided by gravity cores from shelf to deep basin settings, swath bathymetry and high-resolution reflection seismic and sub-bottom (TOPAS) profiles. Seven lithofacies have been identified. Their textural, compositional and X-radiographic characteristics, as well as their spatial distribution allow the differentiation of two stages of deposition, involving distinct sedimentary processes. The Last Glacial Maximum was characterised by subglacial deformation by the Antarctic Peninsula Ice Sheet as it reached its most extended position on the distal mid-slope platforms of the Central Bransfield Basin. Proglacial debris flows occurred on the external edges of the mid-slope platforms and lower slope. Since the last deglaciation, glacimarine (proglacial debris flows, glacimarine proglacial processes and turbid glacial meltwater) and open-marine sedimentary processes (turbidity currents, sliding and contour current activity) have predominated in the Central Bransfield Basin. Glacial cyclicity is the main factor controlling the sedimentary processes in the basin, but several secondary factors, including physiography, sediment entry points and oceanography, have been identified as local controls on the sediment distribution. The unusual physiography of the Central Bransfield Basin, where slope platforms form wide flat surfaces seaward from glacial troughs, is a key factor in the widespread occurrence of glacial and glacimarine processes on the entire continental margin.
We analyzed in detail the seabed morphology of the seamounts and surroundings on the Djibouti Mar... more We analyzed in detail the seabed morphology of the seamounts and surroundings on the Djibouti Marginal Shelf (northern Alboran Sea) using high resolution (Sparker) and very high resolution (TOPAS) seismic reflection profiles and multibeam bathymetry. The aim of the study was to determine the recent geological processes, and in particular the contouritic processes associated with Mediterranean waters. Six groups of morphologic features were defined: structural features (seamount cap, tectonic depressions), fluid dynamics-related features (pockmarks), mass-movement features (gullies, slides), bottom-current features (moats, scour marks, terraces, elongated and separated drifts, plastered drifts, confined drifts, sheeted drifts), mixed features (ridges) and bioconstructions (carbonate mounds). The main processes controlling feature formation are Late Cenozoic tectonic activity and the interaction of Mediterranean waters with the seafloor topography. Seamounts act as topographic barriers that affect the pathway and velocity of Mediterranean water flows, which are subdivided into strands that interact with the surrounding seafloor. Sedimentary instability and fluiddynamic processes play a minor role, and their occurrence is probably triggered by seismicity.
Seismic profiles and sedimentological data (bulk fraction) of two sediment cores recovered from t... more 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, 14 C-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.
Submarine Mass Movements and Their Consequences: 6th International Symposium, 2014
ABSTRACT The Quaternary stratigraphic architecture of seamounts and surrounding deposits in the e... more ABSTRACT The Quaternary stratigraphic architecture of seamounts and surrounding deposits in the eastern Alboran Sea reveals at least 53 stacked MTDs in the Pollux Bank, Sabinar Bank (Sabinar Platform and Western Sabinar), Maimonides Ridge, and Adra Ridge. These MTDs are grouped into two types based on their size: smallscale MTDs (length <5 km and thickness <18 ms) and large-scale MTDs (length >5 km and thickness >18 ms). The study of these deposits has allowed us to define a close relationship between size (thickness-length) and source area gradients. The frequency of MTD events has varied between 40 and 373 kyr throughout the Quaternary (1.8 Ma to present). Correlation between individual MTDs is difficult but could be done for at least one local MTD event between Sabinar Platform and Western Sabinar (Sabinar Bank); in addition, one regional MTD event has been recognized around all of the studied seamounts. These failure events could have been triggered by tectonically controlled seismicity at both regional and local scale.
New core data from a sediment–wave field on the Demerara Outer Ridge show that the waves are main... more New core data from a sediment–wave field on the Demerara Outer Ridge show that the waves are mainly built from turbidity currents that flow northwards down the Demerara margin. The contour currents circulating parallel and obliquely to the margin are apparently not as important to wave formation as previously proposed. Detailed analysis of the sedimentary facies of cores taken on the crest and flank of a sediment wave indicates that fine-grained turbiditic deposits are dominant. Hemipelagic/pelagic deposits are interbedded with the turbidites. Sediment redistribution by contour currents was only evidenced by the presence of peculiar clay mineral assemblages and microfaunal associations, as well as some sedimentary structures such as truncations and cross-bedding. The turbiditic processes were active during the Last Glacial. In contrast, the Holocene is characterised by pelagic sedimentation. A combination of seismic and core data suggests that the sediment waves result from predominantly turbiditic depositional processes interacting with minor contour currents and synsedimentary deformation processes.
The northern continental slope off the Ebro Delta has a badland topography indicating major slope... more The northern continental slope off the Ebro Delta has a badland topography indicating major slope erosion and mass movement of material that deposits sediment into a ponded lobe. The southern slope has a low degree of mass movement activity and slope valleys feed channel levee-complexes on a steep continental rise. The last active fan valley is V-shaped with little meandering and ils thalweg merges downstream with the Valencia Valley. The older and larger inactive channel-levee complex is smoother, U-shaped, and meanders more than the active fan valley.
The study of more than 500 single-and multichannel seismic records enabled the generation of a de... more The study of more than 500 single-and multichannel seismic records enabled the generation of a detailed palaeo-bathymetric map of the Messinian surface over most of the Alboran Basin, Western Mediterranean. This regional surface is characterized by several erosional features (channels, terraces and canyons) and topographic highs (structural, volcanic and diapiric in origin). The most prominent feature is the incised Zanclean Channel crossing the entire basin, its entrenchment having been associated with the opening of the Strait of Gibraltar and subsequent inflow of Atlantic waters. The incision depth of the channel is variable, suggesting local variations in the erosive capacity of the Atlantic inflow, conditioned mainly by the regional basin topography and the local presence of topographic highs. Adjacent to this channel along the Spanish and Moroccan margins, and near the Strait of Gibraltar, several submarine terraces developed at different depths suggest a pulsed flooding of the Alboran Basin. There could have been two major inflow phases of Atlantic water, one shortly before and another during the Zanclean flooding, the latter accompanied by periods of relative sea-level stillstands that enabled terrace development. Alternatively, these features were all generated during the main flooding evident and subsequent pulsed infilling of the basin.
A multiple Contourite Depositional System has been defined in the Plio-Quaternary sedimentary reg... more A multiple Contourite Depositional System has been defined in the Plio-Quaternary sedimentary register in the Alboran Sea. This multiple system formed by the Atlantic and the low density and high density Mediterranean Waters, which shaped the margins and basins since the opening of the Gibraltar Strait. Three different (paleo)circulation scenarios are proposed since then: the Atlantic water Flooding;the Pliocene circulation, characterized by immature low and high density Mediterranean waters and a strong countercurrent in the Western Basin; and the Quaternary circulation, characterized by tabular Mediterranean water masses with multiple current dynamics,an increasing influence of density contrasts, and climate shifts causing major vertical and horizontal displacements of their interfaces.
The interpretation of approximately 100 km of EM12 multibeam bathymetry and backscatter data toge... more The interpretation of approximately 100 km of EM12 multibeam bathymetry and backscatter data together with high resolution TOPAS profiles obtained during a transit over the Orinoco deep-sea fan, near the Barbados accretionary prism, shows that the braided drainage pattern seen on GLORIA images by Belderson et al. (1984)corresponds to wide (∼10 km), low relief (<5 m) channels, incised by numerous
Abstract: The Oligocene to Recent Agadir turbidite system occurs in the Agadir Basin, abutting ag... more Abstract: The Oligocene to Recent Agadir turbidite system occurs in the Agadir Basin, abutting against the continental margin off South Morocco (central eastern Atlantic). This system is part of the submarine drainage system linking back to the Anti-and High Atlas mountains ...
Morpho-seismic characterization of Quaternary mass movement deposits in the eastern sector of the... more Morpho-seismic characterization of Quaternary mass movement deposits in the eastern sector of the Alboran Sea (SW Mediterranean
The Ceuta Drift is an elongated-terrace feature (up to 100 km long, 28 km wide, 400 m relief, and... more The Ceuta Drift is an elongated-terrace feature (up to 100 km long, 28 km wide, 400 m relief, and 700 ms thick) located in the southwestern Alboran Sea, close to the Gibraltar Strait. It extends between 200 and 700 m water depth, parallel to the Moroccan slope. The drift stratigraphy is defined by the vertical stacking of at least five seismic units bounded by discontinuities: onlap and downlap surfaces at the bottom, and erosive surfaces at the top. Sedimentologically, the most recent deposits are defined by the vertical succesion, from bottom to top, of contouritic sandy muds, muds, and silty clays. The Ceuta Drift began to develop during the early Quaternary, when the pre-existing sea-floor morphology favoured the formation of an offshoot current system from the Mediterranean water masses. The action of this current together with sea-level changes have controlled the growth pattern of this drift.
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