Person:
Vegas Martínez, Ramón

First Name

Ramón

Last Name

Vegas Martínez

URI

https://hdl.handle.net/20.500.14352/84115

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Area

Geodinámica Interna

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Now showing 1 - 10 of 54

Estructura y evolución geodinámica del extremo noreste del margen continental catalán durante el Neógeno
(Acta geológica hispánica, 1994) Medialdea, T.; Vázquez, J.T.; Vegas Martínez, Ramón
A partir de la interpretación de una red de perfiles sísmicos de reflexión multicanal, se ha efectuado un estudio de la estructura y evolución geodinámica durante el Neógeno del margen continental noronental de la Península Ibérica, entre los cabos de Bagur y Creus. Las principales estructuras consisten en una serie de altos, fosas y semifosas que se encuentran asociadas a dos familias de fallas: NE-SO a N-S y NO-SE a ONO-ESE. En relación con esta última dirección destacan las fosas de Rosas y Bagur. Estas cuencas se encuentran rellenas por depósitos neógeno-cuatemarios, en los que ha sido posible diferenciar varias unidades (Unidad del Oligoceno (?)-Mioceno inferior, Unidad del Mioceno medio-Mioceno superior y Unidad del Pliocuaternario). Dentro de la evolución geodinámica propuesta para el área se pueden diferenciar dos etapas: la primera (Oligoceno superior-Burdigaliense), corresponde al periodo de "rifting" desarrollado en el Mediterráneo noroccidental, en el que la extensión se acomodó mediante un sistema de fallas normales (dirección NE-SO) y fallas transfer (dirección NO-SE). La segunda etapa (Tortoniense-actualidad) se caracteriza por un cierto bloqueo de los procesos extensionales sobre el sistema NE-SO, mientras que se favorece el movimiento tensional del sistema NO-SE.
Análisis de anomalías gravimétricas y modelación cortical 2D de la región volcánica del Campo de Calatrava (Ciudad Real, España)
(Geogaceta, 2014) Sentre Domingo, Miguel Ángel; Granja Bruña, José Luis; Vegas Martínez, Ramón; Sainz-Maza Aparicio, Sergio
La región volcánica de Campo de Calatrava se ha interpretado como un proceso de volcanismo intraplaca desarrollado durante el Neógeno. Se han propuesto dos modelos geodinámicos contrapuestos para explicar el origen de este volcanismo: a) un proceso de rifting en un contexto extensional con un adelgazamiento localizado de corteza; b) un proceso flexural de la litosfera en un contexto compresivo débil sin adelgazamiento de corteza. El análisis de las anomalías gravimétricas de Bouguer y una modelización gravimétrica 2D a escala cortical contribuyen a discriminar entre los modelos geodinámicos propuestos para el origen del volcanismo. Los modelos gravimétricos se han constreñido en base a los estudios sísmicos profundos existentes en la zona y a la cartografía geológica regional. Los modelos gravimétricos descartan un adelgazamiento cortical, lo que cuestiona el modelo de rifting abortado y apoyan la hipótesis alternativa del proceso flexural de la litosfera en régimen compresivo débil como origen del volcanismo bético.
Un modelo de evolución geotectónica para la Cadena Celtibérica
(Acta geológica hispánica, 1979) Álvaro, M.; Capote Del Villar, Ramón; Vegas Martínez, Ramón
An aulacogen model is given for the Celtibenan Chain in Eastern Spain that undenvent a final strong deformation due to comprensive events that took place not only in its associated geosyncline, the Betic Cordillera, but also in some adjacents areas e. g. the Pyrenees. The identificationof the aulacogen is basedon the stratigraphic, volcanic and tectonic records and on its charactenstics as an intracontinental chain of intermediate type.
Datación paleomagnética de la parte sur del dique de Messejana- Plasencia
(Geotemas, 2000) Palencia Ortas, Alicia; Osete López, María Luisa; Vegas Martínez, Ramón; Villasante Marcos, Víctor; Silva, Pedro F.; Fonseca, P.E.; Miranda Pantoja, José Miguel
A Paleomagnetic investigation of 11 sites across the southern part of Messejana-Plasencia dike has been carried out. The magnetic behaviour o f pilot samples indicates that thermal demagnetisation is more effective than alternating field cleaning (AF) in isolating the Characteristic Remanent Magnetisation (ChRM). Therefore thermal demagnetisation was systematically used with the remaining samples. The ChRM is well grouped. Most sites exhibit normal polarities with the exception of two sites, where samples with reversed polarities have been observed. The paleomagnetic pole derived from the sites is well defined, with values of Plat=72.5, Plong=243.7 and Al);=6.0. This coincides with the pole calculated in a previous investigation (Schott et at. 1981) o f the dike. It is also in agreement with Toarcian poles from the Iberian Range (Osete et al. 2000) and statistically different from the Oxfordian Pole obtained in the same region. Previous radiometric studies suggested that the age o f dike intrusion is 160-200Ma. Paleomagnetic data indicates that the age o f intrusion can be constrained between 180-200Ma.
Carboniferous subduction complex in the south portuguese zone coeval with basement reactivation and uplift in the Iberian Massif
(Cuadernos do Laboratorio Xeolóxico de Laxe, 1980) Vegas Martínez, Ramón
The formation of thick piles of flysch-like sediments needs the existence of narrowed seas, active denouement of neighbouring continents and generaHzed marginal subsidence. These conditions are present during the initial and final stages of Wilson's perceptive cycle. In this context, the Late Precambrian flysch of the Iberian Masslf must be related to the initial rifting, whilst the Culm of southwestern Iberia was accumulated during an episode of Upper Palaeozoic subduction that remained active after impingement of Iberia against North America. Culm sediment~ shed from the uplifted collision zone and fed into a remnant ocean that remained at the nonsutured southern border of Iberia. This model of synorogenic flysch formation has been described elsewhere for similar plate arrangements. On other grounds this model provides a framework that explains the different structural and magmatic trends of the Ossa-Morena Zone (near the active margin) in the context of the rest of the Massif (basement reactivation). In addition to this, it seems to support a partly primary origin for the Iberian arc versus a secondary origin.
Adelgazamiento de la corteza en el margen septentrional del Golfo de Cádiz
(Geotemas, 2004) Medialdea Cela, Teresa; Córdoba Barba, Diego; Vegas Martínez, Ramón; Dañobeitia, J.J.
Refraction/wide angle seismic profiles acquired in 2000 during the Parsifal cruise across the Southportuguese Zone, the Algarve Basin and the South Iberian continental margin have allowed us to determine the crustal structure west of the Bank of Guadalquivir, which has been constrained by gravity modelling. According to the crustal model obtained, a crustal thinning of 11 km takes place from the shoreline to the Guadalquivir Bank area, where enhanced crustal attenuation has been found. Under the sedimentary cover, the velocity structure consists of a wedge-shaped upper crust with velocities between 5.8 and 5.9 km/s, characterised by a pronounced thickness variation. In the middle-lower crust, velocity increases from 6 to 7 km/s.
A new 200 Ma paleomagnetic pole for Africa, and paleo-secular variation scatter from Central Atlantic Magmatic Province (CAMP) intrusives in Morocco (Ighrem and Foum Zguid dykes)
(Geophysical journal international, 2011) Palencia Ortas, Alicia; Ruiz Martínez, Vicente Carlos; Villalain, J.J.; Osete López, María Luisa; Vegas Martínez, Ramón; Touil, A.; Hafid, A.; McIntosh, G.; Hinsbergen, D.J.J. van; Torsvik, T. H.
Available apparent polar wander (APW) paths for the 200 Ma configuration of Pangea, just prior to the opening of the Central Atlantic Ocean, differ as much as 10o in arc length. Here, we add new data from northwest Africa for this time, obtained from the northeasttrending Foum-Zguid and Ighrem dykes (ca. 200 Ma). These dykes form part of the northern domain of the Central Atlantic Magmatic Province (CAMP), and crosscut the Anti-Atlas Ranges in Morocco, and compositionally correspond to quartz-normative tholeiites intruded in continental lithosphere shortly before the opening of the Central Atlantic Ocean. The Foum-Zguid dyke has been intensively studied, whereas the Ighrem dyke has received less scientific focus. We sampled both dykes for paleomagnetic investigation along 100 km of each dyke (12 sites for Foum-Zguid and 11 for Ighrem, 188 samples included in the final analyses). Rock magnetic experiments indicate a mixture of multidomain and single-domain magnetite and/or low-Ti titanomagnetite particles as the principal remanence carriers. In both dykes, the primary nature of the characteristic remanent magnetization is supported by positive contact tests, related to Fe-metasomatism or baked overprints of the corresponding sedimentary country rocks. The directions of the characteristic magnetization exhibit exclusively normal polarity. Site-mean virtual geomagnetic poles are differently grouped in each dyke, suggesting distinct geomagnetic secular variation records. The Foum-Zguid paleomagnetic pole (N = 12, PLat = 67.9◦N, PLon = 247.9◦E, κ = 125, A95 = 3.9◦) plots close to that of Ighrem (N = 11, PLat = 78.4◦N, PLon = 238.2◦E, κ = 47, A95 = 6.7◦), confirming those mineralogical and geochemical evidences supporting that they represent dissimilar magmatic stages. Virtual geomagnetic poles dispersion from both dykes (S = 10.5◦13.0◦ 8.1◦ ) is in line with those obtained from recent studies of a CAMP-related dyke in Iberia and results from CAMP lavas in the Argana basin. These three new estimates of paleosecular variation at low latitudes around the Triassic–Jurassic boundary are concordant with a recently proposed dispersion curve for the Jurassic but suggest a slightly lower geomagnetic scatter than considered so far. After combining results from both dykes, the resulting paleomagnetic pole (PLat = 73.0◦N, PLon = 244.7◦E, N = 23, κ = 55, A95 = 4.1◦) is statistically compared with existing and coeval African paleopoles, and with global synthetic 200 Ma running mean poles in northwest Africa coordinates.
Gravity modeling of the lithosphere in the Calatrava Volcanic Province (Spain): geodynamic implications
(Journal of iberian geology, 2015) Granja Bruña, José Luis; Vegas Martínez, Ramón; Sentre Domingo, M.A.; Muñoz Martín, Alfonso; Sainz-Maza Aparicio, S.
The origin of the intraplate volcanism in the Calatrava Volcanic Province (CVP) is controversial. On the basis of its geochemical signature, it has been ascribed to an “aborted” rift, implying lithospheric thinning. However, the volcanism occurred during the generalized Cenozoic NW−SE-oriented compressive tectonic regime. On the other hand, on the basis of evidence for its deep-seated origin, it has been linked to the existence of a baby-plume detached from an active megaplume below the Canary-Azores Islands and the western Mediterranean. In order to understand better the aforementioned geodynamic scenarios for the origin of the CVP, we address here the study of the lithosphere in the CVP and its vicinity by means of gravity analysis and 2+1/2D modeling. Gravity modeling results do not support the rifting model adopted for the intraplate volcanism occurred in the CVP because the crust shows a quasi-constant thickness. Density models suggest the existence of a sub-crustal, anomalous low-density block that could be underplated magmatic material at the base of the crust, suggesting that only a minor part of it intruded up into the crust and erupted. The localized magmatism of the CVP can be related to the combination of two factors: active, the gentle folding of the Iberian lithosphere and associated uplifting of the Variscan basement due to the NW-directed transmission of compressive stresses in the upper plate yielded by the subduction/collision in the south Iberian margin. The formation of the lithospheric folding in the Calatrava region results in a decrease of the pressure beneath the swell of the antiform that is likely to bring about basaltic magmatism below the swell; and one passive, the existence of a Variscan right-lateral shear band, which yields a weakened crust that facilitates the ascent of the magmatic materials. The relatively small volume, but large extension, of the volcanic outcrops could be associated with the preferential ascent of the magmas along the weakened crust of this NW−SE-trending Variscan shear band.
Investigaciones paleomagnéticas en la Zona Subbética
(Cuadernos de geología ibérica, 1988) Osete López, María Luisa; Freeman, R.; Vegas Martínez, Ramón
Se ha realizado un estudio palomagnético en la parte central de la Zona Subbética, en rocas volcánicas (pillow-lavas, material intrusivo y coladas de basaltos) y sedimentarias (calizas, margocalizas y calizas nodulosas de facies Ammonitico Rosso) de edad jurásica. Con objeto dc analizar las propiedades magnéticas de las rocas estudiadas se han determinado las curvas termomagnéticas de los materiales volcánicos y se han realizado experimentos sobre adquisición gradual de remanencia magnética isoterma y de desimanación de dos componentes isotermas ortogonales con las rocas sedimentarias. A pesar dc que el comportamiento magnético ha sido diferente en cada una de las litologías investigadas, en la mayoría de los casos ha sido posible aislar una componente magnética estable durante los procesos de lavado magnético. Los resultados obtenidos han sido comparados con las direcciones esperadas para Iberia estable y se ha observado una importante discrepancia en el valor de la declinación magnética. La desviación hacia el Este de la paleodeclinación encontrada en esta área indica que se han producido rotaciones horarias en la Zona Subbética.
La secuencia litoestratigráfica del Neoproterozoico-Cámbrico Inferior
(Geología de España, 2004) Rodríguez Alonso, M. D.; Díez Balda, M.A.; Perejón, Antonio; Pieren Pidal, Agustín Pedro; Liñán, Eladio; López Díaz, F.; Moreno, F.; Gámez Vintaned, J.A.; González Lodeiro, F.; Martínez Poyatos, D.; Vegas Martínez, Ramón; Vera, J.A.