Person: Vegas Martínez, Ramón
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First Name
Ramón
Last Name
Vegas Martínez
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Area
Geodinámica Interna
Identifiers
3 results
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Item Nature and tectonic setting of the Guadalquivier Bank (Gulf of Cadiz, SW Iberian Peninsula)(Revista de la Sociedad Geológica de Espña, 2003) Vegas Martínez, Ramón; Medialdea, T.; Muñoz García, Mercedes; Díaz del Río, V.; Somoza, L.During two oceanographic cruises on the Guadalquivir Bank (continental slope of the southwestern Atlantic margin of the Iberian Peninsula), Variscan basement rocks were dredged, as well as, lithified hardground-related carbonate sediments containing Late Tortonian-Early Messinian foraminifers. Basement samples contained graywackes, shales, quartzites, basic volcanics, and metabasites in amphibolite facies. All these sedimentary and volcanic rocks can be attributed to the Volcano-Sedimentary Complex of the Pyrite Belt (South Portuguese Zone of the Iberian Variscan belt). This correlation is based on petrological similarities and the occurrence of low-grade metamorphism in prehnite-pumpellyite facies, identical to those defined in the Pyrite Belt. The metabasites have been correlated with the Beja-Acebuches Ophiolite Complex. These results have led us to consider two problems: the relationship between the Guadalquivir Bank and the South Portuguese Zone and the situation of this bank in the context of the Mesozoic evolution of the continental margin.The outcrop of these rocks on the middle slope of the Portuguese margin implies Variscan fold-and-thrust tectonics of greater intensity for the South Portuguese Zone, and the erosion of the Culm Group in the Guadalquivir Bank area. This erosion is explained by the uplift of the continental side of the transform fault that gave rise to the Mesozoic margin of the Southern Iberian Peninsula.Item Structure and evolution of the ‘‘Olistostrome’’ complex of the Gibraltar Arc in the Gulf of Cádiz (eastern Central Atlantic): evidence from two long seismic cross-sections(Marine geology, 2004) Medialdea Cela, Teresa; Vegas Martínez, Ramón; Somoza Losada, Luis; Vázquez Garrido, Juan Tomás; Maldonado López, Andrés; Díaz del Río Español, Víctor; Maestro González, Adolfo; Córdoba Barba, Diego; Fernández Puga, Mª CarmenReflection profiles characterize the structure and the upper Mesozoic to Cenozoic deposits of the Gulf of Ca´diz region. Two long ENE–WSW multichannel seismic lines (ca. 400–500 km long) are analyzed to study the evolution of the area from the continental shelf to the Horseshoe and Seine abyssal plains. The huge allochthonous deposits emplaced in this region (the socalled ‘‘Olistostrome’’ of the Gulf of Cadiz) are described in terms of three different domains on the basis of the seismic architecture, the main tectonic features and the nature of the basement, oceanic or continental. The eastern domain extends along the continental shelf and upper and middle slope and corresponds to the offshore extension of the Betic–Rifean external front. It is characterized by salt and shale nappes later affected by extensional collapses. The central domain develops along the lower slope between the Betic–Rifean front and the abyssal plains and is characterized by a change in dip of the allochthonous basal surface and the basement. The allochthonous masses were emplaced by a combined gravitational and tectonic mechanism. The northern boundary of this domain is marked by the occurrence of an outstanding WNW–ESE-trending thrust fault with a strike-slip component, termed here as the Gorringe–Horseshoe fault. The westernmost domain corresponds to the abyssal plains, where the distal emplacement of the allochthonous body takes place; it is characterized by thrust faults affecting both the sedimentary cover and the oceanic basement. The allochthonous masses show a less chaotic character and the thickness decreases notably. These domains represent different evolutionary steps in the mechanisms of emplacement of the allochthonous units. The eastern domain of the allochthonous units was emplaced as part of the pre-Messinian orogenic wedge related to the collision that gave rise to the Betic–Rifean Belt, whereas the allochthonous wedge of the central and western domains were emplaced later as a consequence of the NE–SW late Miocene compression that continues in present times.Item Tectonics and mud volcano development in the Gulf of Cádiz(Marine geology, 2009) Medialdea Cela, Teresa; Somoza Losada, Luis; Pinheiro, Luis Menezes; Fernández Puga, Mª Carmen; Vázquez Garrido, Juan Tomás; León Buendía, Ricardo; Ivanov, M.K.; Magalhaes, Vitor Hugo; Díaz del Río Español, Víctor; Vegas Martínez, RamónMany structures associated with fluid escape, including mud volcanoes, mud-carbonate mounds, pockmarks and slides, have been identified and characterized in the Gulf of Cádiz. Most of the mud volcanoes following NE–SW and NW–SE main trends are found at 350–2000 m depth in the eastern domain of the Gulf of Cádiz, which corresponds to the Betic–Rifean Margin. Scattered mud volcanoes have also been recognized on the lower slope at 2300–3900 m depth. The major tectonic structures are thrust faults, extensional faults, strikeslip faults and diapirs. All these tectonic structures have provided escape pathways for overpressured material and fluids or have favoured upward fluid movement along the sedimentary column and eventually the build up of mud volcanoes. In this work we present images of the mud volcano plumbing systems and the relationship between regional tectonics and mud volcano development. Seismic profiles acquired during the TASYO 2000 and MVSEIS/TTR-15 cruises are used to image and interpret the link between the mud volcano edifices and the subsurface tectonic structures.