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11.
Ferran Estrada Gemma Ercilla Christian Gorini Bel��n Alonso Juan Tom��s V��zquez Daniel Garc��a-Castellanos Carmen Juan Andr��s Maldonado Abdellah Ammar Mohammed Elabbassi 《Geo-Marine Letters》2011,31(5-6):361-376
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. 相似文献
12.
Katrin Wendt-Potthoff Matthias KoschorreckMarta Diez Ercilla Javier Sánchez España 《Limnologica》2012,42(3):175-188
Microbial activity, abundance and biomass, and biogeochemical cycling of iron, sulphur and carbon were studied in the extremely acidic (pH 2.5-4.3), meromictic, nutrient-rich pit lake Cueva de la Mora in Spain. The goal was to find out (1) if the relatively high nutrient content influenced plankton abundance in the water column and alkalinity-producing microbial processes in the sediments compared to other acid pit lakes, and (2) if sediments in the shallow, mixed and the deep, stagnant parts of the lake exhibited differences in microbial activities and geochemical sediment composition related to meromixis. We hypothesised that redox cycling was more intense in the mixed part and higher amounts of reduced components would accumulate in the stagnant part. Especially phytoplankton biomass, CO2 production, and sulphate reduction were indeed higher than reported from typical acid pit lakes and were rather within the range of neutral or weakly acidic lakes, which can be attributed to the relatively high nutrient contents of Cueva de la Mora. Even in the monimolimnion, anaerobic processes occurred mainly in the sediments. Sediments from the mixed and stagnant parts of the lake differed markedly in their biogeochemistry. Mixolimnetic sediments showed high iron and sulphate reduction rates, and they appeared to undergo substantial recycling, as supported by reactive Fe, relation between gross sulphate reduction rate and net accumulation of reduced sulphur, and viable counts of iron and sulphur bacteria. Monimolimnetic sediments exhibited lower anaerobic microbial activities, and surprisingly they accumulated more Fe(II) than mixolimnetic sediments, but less reduced sulphur and carbon. This might be explained by a strong separation of the two water bodies, resulting in comparably less input of energy (light) and allochthonous matter into the monimolimnion. Regarding the total extent of alkalinity-generating microbial processes, their net effect is not sufficient to neutralise the lake within decades. 相似文献
13.
D. Casas G. Ercilla F. Estrada B. Alonso J. Baraza H. Lee 《Marine Georesources & Geotechnology》2013,31(4):253-278
Our investigation is centred on the continental slope of the Antarctic Peninsula and adjacent basin. Type of sediments, sedimentary stratigraphy, and physical and geotechnical characterization of the sediments have been integrated. Four different types of sediments have been defined: diamictons, silty and muddy turbidites, muddy, silty and muddy matrix embedded clast contourites. There is a close correspondence between the physical properties (density, magnetic susceptibility and p-wave velocity) and the texture and/or fabric as laminations and stratification. From a quantitative point of view, only a few statistical correlations between textural and physical properties have been found. Within the geotechnical properties, only water content is most influenced by texture. This slope, with a maximum gradient observed (20°), is stable, according to the stability under gravitational loading concepts, and the maximum stable slope that would range from 22° to 29°. Nevertheless, different instability features have been observed. Volcanic activity, bottom currents, glacial loading-unloading or earthquakes can be considered as potential mechanisms to induce instability in this area. 相似文献
14.
Multi-sensor core logger data and index properties were measured onboard the JOIDES resolution during ODP Leg 157 and compared with grain size distribution and carbonate contents measured in the on-shore laboratory. Cored sediments are similar in grain size, but very variable in carbonate content. Magnetic susceptibility clearly defines the volcanic turbidite layers, whereas GRAPE density and acoustic velocity help to define the coarser (silty) bases of some organic or calcareous turbidite layers. Index properties are mostly controlled by consolidation effects. 相似文献
15.
16.
Ercilla G Córdoba D Gallart J Gràcia E Muñoz JA Somoza L Vázquez JT Vilas F;Prestige Group 《Marine pollution bulletin》2006,53(5-7):208-219
The tanker Prestige sank off NW Iberia on the 19th November 2002. The stern and bow of the Prestige wreck are located on the southwestern edge of the Galicia Bank, at 3565 m and 3830 m water depths, respectively. This bank is a structural high controlled by major faults with predominant N-S, NNE-SSW, and NNW-SEE trends. It is characterized by moderate to low seismic activity. The faults have controlled the local depositional architecture, deforming, fracturing, relocating and distributing sediments since the Valangian (early Cretaceous). The Prestige sinking area corresponds to an asymmetric half-graben structure with a N-S trend, which conditions the present-day morphology. The faulted flank outcrops and its activity and erosion have favoured the occurrence of mass-movements (slumps, slump debris, mass-flows and turbidity currents), building valleys and depositional lobes. Nearsurface sediments comprise mostly terrigenous and biogenous turbiditic muds and sands with a minor presence of hemipelagic muds, except on the fault scarp where pelagites predominate. Potential geological hazards resulting from tectonic and sedimentary processes affect almost the entire Prestige sinking area. 相似文献
17.
F. J. Lobo A. Maldonado F. J. Hernández-Molina L. M. Fernández-Salas G. Ercilla B. Alonso 《Marine Geophysical Researches》2008,29(3):195-216
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 seaward-prograding, 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. 相似文献
18.
Francisco Javier Hern��ndez-Molina Dorrik A. V. Stow Estefan��a Llave Michele Rebesco Gemma Ercilla David Van Rooij Anxo Mena Juan-Tom��s V��zquez Antje H. L. Voelker 《Geo-Marine Letters》2011,31(5-6):285-300
Deep-water circulation is a critical part of the global conveyor belt that regulates Earth??s climate. The bottom (contour)-current component of this circulation is of key significance in shaping the deep seafloor through erosion, transport, and deposition. As a result, there exists a high variety of large-scale erosional and depositional features (drifts) that together form more complex contourite depositional systems on continental slopes and rises as well as in ocean basins, generated by different water masses flowing at different depths and at different speeds either in the same or in opposite directions. Yet, the nature of these deep-water processes and the deposited contourites is still poorly understood in detail. Their ultimate decoding will undoubtedly yield information of fundamental importance to the earth and ocean sciences. The international congress Deep-water Circulation: Processes & Products was held from 16?C18 June 2010 in Baiona, Spain, hosted by the University of Vigo. Volume 31(5/6) of Geo-Marine Letters is a special double issue containing 17 selected contributions from the congress, guest edited by F.J. Hernández-Molina, D.A.V. Stow, E. Llave, M. Rebesco, G. Ercilla, D. Van Rooij, A. Mena, J.-T. Vázquez and A.H.L. Voelker. The papers and discussions at the congress and the articles in this special issue provide a truly multidisciplinary perspective of interest to both academic and industrial participants, contributing to the advancement of knowledge on deep-water bottom circulation and related processes, as well as contourite sedimentation. The multidisciplinary contributions (including geomorphology, tectonics, stratigraphy, sedimentology, paleoceanography, physical oceanography, and deep-water ecology) have demonstrated that advances in paleoceanographic reconstructions and our understanding of the ocean??s role in the global climate system depend largely on the feedbacks among disciplines. New insights into the link between the biota of deep-water ecosystems and bottom currents confirm the need for this field to be investigated and mapped in detail. Likewise, it is confirmed that deep-water contourites are not only of academic interest but also potential resources of economic value. Cumulatively, both the congress and the present volume serve to demonstrate that the role of bottom currents in shaping the seafloor has to date been generally underestimated, and that our understanding of such systems is still in its infancy. Future research on contourites, using new and more advanced techniques, should focus on a more detailed visualization of water-mass circulation and its variability, in order to decipher the physical processes involved and the associations between drifts and other common bedforms. Moreover, contourite facies models should be better established, including their associations with other deep-water sedimentary environments both in modern and ancient submarine domains. The rapid increase in deep-water exploration and the new deep-water technologies available to the oil industry and academic institutions will undoubtedly lead to spectacular advances in contourite research in terms of processes, morphology, sediment stacking patterns, facies, and their relationships with other deep-marine depositional systems. 相似文献
19.
Ferran Estrada Jesús Galindo‐Zaldívar Juan Tomás Vázquez Gemma Ercilla Elia D'Acremont Belén Alonso Christian Gorini 《地学学报》2018,30(1):24-33
The Alboran Sea constitutes a Neogene–Quaternary basin of the Betic–Rif Cordillera, which has been deformed since the Late Miocene during the collision between the Eurasian and African plates in the westernmost Mediterranean. NNE–SSW sinistral and WNW–ESE dextral conjugate fault sets forming a 75° angle surround a rigid basement spur of the African plate, and are the origin of most of the shallow seismicity of the central Alboran Sea. Northward, the faults decrease their transcurrent slip, becoming normal close to the tip point, while NNW–SSE normal and sparse ENE–WSW reverse to transcurrent faults are developed. The uplifting of the Alboran Ridge ENE–WSW antiform above a detachment level was favoured by the crustal layering. Despite the recent anticlockwise rotation of the Eurasian–African convergence trend in the westernmost Mediterranean, these recent deformations—consistent with indenter tectonics characterised by a N164°E trend of maximum compression—entail the highest seismic hazard of the Alboran Sea. 相似文献
20.
Multi-sensor core logger data and index properties were measured onboard the JOIDES resolution during ODP Leg 157 and compared with grain size distribution and carbonate contents measured in the on-shore laboratory. Cored sediments are similar in grain size, but very variable in carbonate content. Magnetic susceptibility clearly defines the volcanic turbidite layers, whereas GRAPE density and acoustic velocity help to define the coarser (silty) bases of some organic or calcareous turbidite layers. Index properties are mostly controlled by consolidation effects. 相似文献