Person: Muñoz Martín, Alfonso
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First Name
Alfonso
Last Name
Muñoz Martín
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Geodinámica, Estratigrafía y Paleontología
Area
Geodinámica Interna
Identifiers
6 results
Search Results
Now showing 1 - 6 of 6
Item Morphotectonics of the central Muertos thrust belt and Muertos Trough (northeastern Caribbean)(Marine Geology, 2009) Granja Bruña, José Luis; Ten Brink, Uri S.; Carbo Gorosabel, Andrés; Muñoz Martín, Alfonso; Gómez Ballesteros, MaríaMultibeam bathymetry data acquired during the 2005 Spanish R/V Hespérides cruise and reprocessed multichannel seismic profiles provide the basis for the analysis of the morphology and deformation in the central Muertos Trough and Muertos thrust belt. The Muertos Trough is an elongated basin developed where the Venezuelan Basin crust is thrusted under the Muertos fold-and-thrust belt. Structural variations along the Muertos Trough are suggested to be a consequence of the overburden of the asymmetrical thrust belt and by the variable nature of the Venezuelan Basin crust along the margin. The insular slope can be divided into three east–west trending slope provinces with high lateral variability which correspond to different accretion stages: 1) The lower slope is composed of an active sequence of imbricate thrust slices and closed fold axes, which form short and narrow accretionary ridges and elongated slope basins; 2) The middle slope shows a less active imbricate structure resulting in lower superficial deformation and bigger slope basins; 3) The upper slope comprises the talus region and extended terraces burying an island arc basement and an inactive imbricate structure. The talus region is characterized by a dense drainage network that transports turbidite flows from the islands and their surrounding carbonate platform areas to the slope basins and sometimes to the trough. In the survey area the accommodation of the ongoing east–west differential motion between the Hispaniola and the Puerto Rico–Virgin Islands blocks takes place by means of diffuse deformation. The asymmetrical development of the thrust belt is not related to the geological conditions in the foreland, but rather may be caused by variations in the geometry and movement of the backstop. The map-view curves of the thrust belt and the symmetry of the recesses suggest a main north–south convergence along the Muertos margin. The western end of the Investigator Fault Zone comprises a broad band of active normal faults which result in high instability of the upper insular slope.Item Geological evolution of the volcanic island La Gomera, Canary Islands, from analysis of its geomorphology(Marine geology, 2009) Llanes Estrada, María Pilar; Herrera, R.; Gómez, M.; Muñoz Martín, Alfonso; Acosta, Juan; Uchupi, E.; Smith, D.Erosion and landslide processes played an important role in shaping the geomorphology of the Canary Islands. But for the heavily eroded La Gomera Island, those processes have been unclear. We conducted an integrated study of its offshore extension, onshore geology, and links between them in order to determine the geomorphological evolution of the island relative to the rest of the archipelago. The characteristics of the island's barrancos and its interfluves have led us to differentiate four types of morphological areas whose fluvial networks are in different stages of evolution. Those barrancos offshore are interrupted by La Gomera's shelf, and its erosion has been much greater than for the rest of the Canary Islands. Such erosion is both a function of time and varied swell action. La Gomera's insular slope is carved by a system of submarine canyons and channels that have morphology indicative of turbidity current erosion. Many of the barrancos onshore and the canyons offshore have steps or knickpoints: some are the result of varied resistance to erosion, and others are explained by other mechanisms. A ridge whose crest is covered by cone-like shape structures is interpreted as of volcanic origin, with the particularity that it lacks onshore continuation, the opposite of what has been observed elsewhere in the Canary Islands. Also in contrast with the other islands of the archipelago, La Gomera's margin does not seem to have resulted from destructive mass wasting and the only offshore sign of catastrophic events are the presence of two embayments along La Gomera's northern shelf edge and a lobe structure on the insular apron at 3000 m depth. These features may be the remains of the catastrophic failures that took place on the island 9.4-8.7 Ma ago. Alternatively, they could be due to recent catastrophic failures on the upper slope due to sediment steeping. Since the conclusion of the main volcanic activity 4.0 Ma ago, La Gomera has been intensively eroded by gradual fluvial denudation and secondary failures. La Gomera's insular margin reveals much regarding its evolution, but more comprehensive studies including seismic and coring are needed to understand its whole geological history.Item Prospección hidrogeológica en zonas áridas de baja permeabilidad (Tifariti, Sahara Occidental) con el método EM de inducción(Geogaceta, 2009) Olaiz Campos, Antonio José; Muñoz Martín, Alfonso; Villarroya Gil, Fermín Ignacio; Lorenzo, Javier de; Castanedo, Cristina; Padín, AntónThe aim of this study is to evaluate electromagnetic induction methods to analyze low permeability rocks in desert areas, as a tool for groundwater surveying. We have focused the field work in large faults zones, previously mapped by satellite images and digital elevation models. This is because in low-permeability rocks (i.e. granites) the groundwater flow is mainly controlled by these discontinuities. The objective is to map the high conductivity zones and their geometry in depth. Obtained results allow us to identify well defined fractures with low apparent resistivities that are the most suitable areas to locate groundwater extractions.Item Oblique strain partitioning and transpression on an inverted rift: The Castilian Branch of the Iberian Chain(Tectonophysics, 2009) Vicente Muñoz, Gerardo De; Vegas Martínez, Ramón; Muñoz Martín, Alfonso; Wees, Jan Dierik van; Casas Sáinz, Antonio; Sopeña, Alfonso; Sánchez Moya, Yolanda; Arche, Alfredo; López Gómez, José; Olaiz Campos, Antonio José; Fernández Lozano, JavierThe Iberian Chain is a wide intraplate deformation zone formed by the tectonic inversion during the Pyrenean orogeny of a Permian –Mesozoic basin developed in the eastern part of the Iberian Massif. The N – S convergence between Iberia and Eurasia from the Late Cretaceous to the Lower Miocene times produced signi cant intraplate deformation. The NW –SE oriented Castilian Branch of the Iberian Chain can be considered as a “key zone ” where the proposed models for the Cenozoic tectonic evolution of the Iberian Chain can be tested. Structural style of basin inversion suggests mainly strike slip d–isplacements along previous NW –SE normal faults, developed mostly during the Mesozoic. To con rm this hypothesis, structural and basin evolution analysis, macrostructural Bouguer gravity anomaly analysis, detailed mapping and paleostress inversions have been used to prove the important role of strike slip deformation. In addition, we demonstrate that two main folding trends almost perpendicular (NE SW t–o E W an–d NW SE) w–ere simultaneously active in a wide transpressive zone. The two fold trends were generated by dierent mechanical behaviour, including buckling and bending under constrictive strain conditions. We propose that strain partitioning occurred with oblique compression and transpression during the Cenozoic.Item Aplicación del método electromagnético de inducción ligera para el análisis de la permeabilidad en medios fracturados (granito de “El Berrocal”, Sistema Central Español)(Geogaceta, 2009) Vicente, Raquel de; Muñoz Martín, Alfonso; Olaiz Campos, Antonio José; Antón López, Loreto; Vicente Muñoz, Gerardo DeFracture characterization in granites has been an important subject of study during these last years, by means of geological-structural cartography, hydrogeology and geochemical analysis. All these works have been carried out to investigate the hydromechanics and permeability in low-permeability rocks. In this study we apply a surface geophysical method in order to characterize the permeability of the fault zones affecting “El Berrocal” granite (Central System, Spain). The low-induction electromagnetic method (EM) gives us the apparent resistivity values of the rocks at a maximum depth, allowing us to differentiate between soil / altered rock from fresh granites. As the apparent resistivity depends on the granite alteration and/or the water content, this parameter allows to estimate the relative permeability of different fracture zones. The obtained results show that the high-permeability fractures are those that are larger ones which were active during Alpine deformation (Eocene-present).Item European continuous active tectonic strain–stress map(Tectonophysics, 2009) Olaiz Campos, Antonio José; Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo De; Vegas Martínez, RamónThis paper shows a new continuous strain–stress map for Europe obtained from the direct inversion of earthquake focal mechanisms calculated from the centroid tensor method. A total of 1608 focal mechanisms have been selected with several quality criteria from different catalogues (CMT Harvard, ETH, Med-Net, I.G.N. and I.A.G.) from 1973 to the present day. Values for the maximum horizontal shortening direction and brittle strain–stress regime defined by the k′ ratio (ey/ez, horizontal maximum/vertical strain) have been calculated following in Europe and Pannonian Basin the slip model of tri-axial deformation. The individual results including Dey and the shape of the active brittle strain ellipsoid have been interpolated to a final 15′ regular grid taking into account the relationship between the tectonic horizontal strain–stress value and the vertical load. Both continuous strain regime and maximum horizontal shortening (Dey) maps show a good correlation with the primary tectonic forces generated along the plate boundaries, plate kinematics and also some local perturbations related with main crustal heterogeneities and topography, as well as significant spatial variations in integrated crustal strength.