Person:
Muñoz Martín, Alfonso

First Name

Alfonso

Last Name

Muñoz Martín

URI

https://hdl.handle.net/20.500.14352/75220

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Department

Geodinámica, Estratigrafía y Paleontología

Area

Geodinámica Interna

Identifiers

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Now showing 1 - 8 of 8

La deformación alpina en el Sistema Central Español
(Geo-guías, Rutas geológicas por la Península Ibérica, Canarias, Sicilia y Marruecos, 2019) De Vicente Muñoz, Gerardo; Muñoz Martín, Alfonso; Olaiz, A.J.; Vegas, Ramón; Antón López, Loreto; Martín Velázquez, Silvia; Giner Robles, J.; Rodriguez Pascua, M.A.
La idea del origen compresivo del Sistema Central (SC) se debe a Birot y Solé Sabarís (1954) [1], antes del establecimiento del papel que la tectónica de placas juega en el desarrollo de las estructuras intraplaca. Sin embargo, sus observaciones de campo no fueron tenidas en cuenta y, durante mucho tiempo, el SC fue considerado como una estructura extensiva [2]. Los primeros modelos de estructura del SC, en un contexto compresivo intraplaca, fueron propuestos por Vegas y Suriñach (1987) [3], que calcularon un engrosamiento cortical de 5 km, mientras que Warburton y Álvarez (1989) [4] construyeron una sección transversal con el desarrollo de una tectónica de piel fina asociada a un detachment intracortical proveniente de las Béticas y con un acortamiento asociado de 50 km. Esta idea fue también propuesta con menos detalle para el sector portugués, pero en relación a un estilo tectónico de piel gruesa y un acortamiento menor [5]. No obstante, estos trabajos carecían de observaciones de campo. En concreto, la sección de Warburton y Álvarez adolece de numerosas inconsistencias. El estilo tectónico propuesto durante la celebración de la III reunión de la Comisión de Tectónica de la SGE, que es el que se tiene en cuenta hoy en día, fue el de una tectónica de piel gruesa, sin despegues en la cobertera, con la formación de cabalgamientos imbricados de piel fina con implicación del basamento y pop ups dentro del basamento varisco de direcciones NE-SO a E-O. El acortamiento asociado se calculó en un 14% (20 km) [6, 7].
Longest and still longer: The Messejana-Plasencia dyke and its links with later Alpine deformation belt in Iberia
(Tectonophysics, 2021) De Vicente Muñoz, Gerardo; Olaiz Campos, Antonio José; Muñoz Martín, Alfonso; Cunha, Pedro P.
The Messejana-Plasencia dyke (End-Triassic), NE-SW oriented, is the longest simple structure in Iberia (~500 km) and constitutes a first-order rheological discontinuity that crosses the entire crust. During the Alpine deformation, this discontinuity nucleated the Messejana-Plasencia left-lateral strike-slip fault and its related strike-slip deformation belt, consisting of a series of wide coalescent stepovers and small basins developed on the footwalls. Both structures can be followed from offshore of SW mainland Portugal to the central sector of the Spanish-Portuguese Central System. Using tectonic, geophysical, magnetic, and gravimetric analyses, our study demonstrated that it extends NE more than ~100 km below the continental sediments of the Duero Cenozoic Basin, until the Iberian Chain. We used a tectonostratigraphic analysis to determine the age of the wrench fault movement and that of the Spanish-Portuguese thrusts. In this range, the largest displacement during the Cenozoic occurred in the southern thrust of the Spanish sector of the Central System over the Madrid Cenozoic Basin, and NE-SW trending. This thrust displaces the Moho more than 10 km and probably joins the Messejana-lasencia strike-slip fault at depth. The deduced age movement for both is Oligocene-Lower-Middle Miocene, related to the intraplate stresses transmitted from the Pyrenean orogen towards its foreland. A strain partitioning process was then deduced for the simultaneous movement of both main Alpine faults in Central Iberia.
Waste dump erosional landform stability – a critical issue for mountain mining
(Earth surface processes and Landforms, 2017) Martín Moreno, Cristina; Duque, José F. Martín; Ibarra, José M. Nicolau; Muñoz Martín, Alfonso; Zapico, Ignacio
Mining is the largest producer of solid wastes which, when released to land or into waterways, can cause harmful environmental impacts. This is mostly due to fluvial erosion, which is highly increased in mountain areas, due to abrupt slopes. We have analysed this situation at a mountain watershed (192 ha), where steep mined sites and their waste dumps are the main source of sediment in a Natural Park. This problem was tackled by building gabion check dams downstream from the mined sites. We used the DEM of Differences (DoD) method to quantify erosion and sediment yield from three waste dumps (5 ha). Their topography and substrate properties were analysed to understand the erosion problem. The sediment trapped by the check dams was quantified by Electrical Resistivity Tomography. The rainfall characteristics triggering an episode that filled the check dams with sediment in the winter of 2009-2010, were studied to confirm whether it was a case of extreme precipitation conditions. The waste dumps sediment yield (353 ± 95 Mg ha-1 yr-1) suggests severe landform instability. Analysis of topographic and substrate properties confirmed long, steep slopes combined with highly erodible materials. The check dams proved to be inefficient in controlling sediment loads, as they had only functioned for four years of 31 of existence, having trapped 13000 ± 660 m3 of sediment, whereas we estimated that the waste dumps have yielded approximately three times more sediment for the same period. Rainfall analyses showed that neither intense nor extreme conditions (return period of 25-35 years) triggered the mobilization of 37 ± 2 Mg ha-1 in a month. This study highlights the fact that mining operations in similar mountainous settings, with equivalent waste dump construction and reclamation practices, are currently unfeasible. We conclude that landform stability cannot be achieved at this site without landform changes.
Echo-character distribution in the Cantabrian Margin and the Biscay Abyssal Plain
(Journal of maps, 2021) Maestro, Adolfo; Gallastegui, Alba; Moreta, Mercedes; Llave, Estefanía; Bohoyo, Fernando; Druet Vélez, María; Navas, Javier; Mink, Sandra; Fernández Sáenz, Fernando; Catalán, Manuel; Gómez Ballesteros, María; Muñoz Martín, Alfonso; Granja Bruña, José Luis
In 2003, 2006–2009, 2014 and 2015, seven oceanographic cruises were carried out onboard the Spanish R/V Hespérides in the Cantabrian Margin and the adjacent abyssal plains, covering anarea of 219,124 km2. Based on the combined analysis and interpretation of the bathymetric and reflectivity data obtained with multibeam echosounders (SIMRADEM12, EM120 and EM1002), and ultra-high-resolution reflection seismic records acquired with the SIMRAD TOPASPS18 parametric sounder, the mapping of the acoustic facies or echo-character at a scale of 1:1,200,000 has been carried out. Thirty types of echoes have been differentiated and gather into four main groups: Distinct, Irregular, Hyperbolic and Undulated. The echo-character depends on the acoustic response of the shallow sediment and these a bed morphology. Therefore, its analysis and characterization are basic for understanding recent and present-day sedimentary processes.
Análisis gravimétrico y magnético de estructuras diapíricas en el offshore de la cuenca de Asturias
(Geogaceta, 2021) Fuente Oliver, Miguel Ángel; Muñoz Martín, Alfonso; Olaiz Campos, J. A.; Zamora Valcarce, Gonzalo
En este trabajo se analizan mediante campos potenciales (gravimetría y magnetismo) las estructuras salinas interpretadas previamente en el offshore de la Cuenca de Asturias. Para ello se han realizado los mapas de anomalías y tres modelos en 2+3/4D GRAV/MAG con datos coincidentes con un cubo sísmico 3D adquirido por Repsol en 2008. El análisis cuantitativo de los mapas y la modelización en 2+3/4D ha permitido reinterpretar la estructura del basamento y de las estructuras salinas hasta ajustar la señal GRAV/MAG. Estas modificaciones son significativas por debajo de los niveles de evaporitas, destacando la necesidad de introducir menor cantidad de sal, y una reinterpretación de la geometría del techo del basamento.
3D crustal‑scale structure of the West Iberia margin: a novel approach to integrated structural characterization of passive margins
(Marine geophysical researches, 2021) Granado, Cristina; Muñoz Martín, Alfonso; Olaiz Campos, J. A.; Fernández, Oscar; Druet Vélez, María
Hyperextended margins are very heterogeneous along the entire length of the margin, so the definition of tectonic domains made exclusively from 2D seismic sections presents serious limitations. In this work we present an approach of the 3D crustal-scale structure of the West Iberia margin (WIM) by modelling eight lithospheric sections, using seismic, wells and gravity data. The continuous nature of gravity data allowed us to propose a new map of tectonic domains within the WIM. Maps of total horizontal (THD) and vertical gradients (dZ) of Bouguer anomaly have been calculated and compared with other criteria such as the crustal structure and thinning factor. This comparative analysis has been carried out on a section proposed as a model for the Western Iberian Margin (Tugend et al. in Tectonics, 2014; Cadenas et al. in Tectonics 37:758–785, 2018), and on four 2 + 1/2D gravimetric models transversal to the margin. The results point out a significant variation in the absolute values of Bouguer anomaly, thinning factor and crustal structure along the margin and, therefore, of the position of the different domain boundaries. Clear patterns that correlating the Bouguer anomaly signal and its derivatives to the tectonic domain are evidenced. Most significantly, the necking-zone and its transition to the hyperextended domain are characterized by high values of the THD of the Bouguer anomaly. The observed patterns in Bouguer anomaly and its derivatives provide a solid constraint for mapping the boundaries between different tectonic domains along the margin, even in those areas where limited deep seismic information could lead to uncertain interpretations. The results of this work can also inform on the general kinematics of the WIM.
Integrated perspective of the present–day stress and strain regime in Colombia from analysis of earthquake focal mechanisms and geodetic data
(The Geology of Colombia, 2020) Arcila, M.M.; Muñoz Martín, Alfonso; Gómez Tapias, Jorge; Pinilla-Pachón, Ana Oliva
Focal mechanism analysis is a powerful tool for analyzing the geodynamic context of broad and complex regions, such as northwestern South America. In this zone, a complex tectonic convergence occurs among the Caribbean, Nazca, and South American Plates. The orientations of the maximum horizontal shortening and the values of the brittle strain/stress regime (k’ ratio) are obtained based on the analysis of 617 centroid–moment tensors reported from 1976 to 2017 in the Global Centroid–Moment–Tensor Project. These results are complemented with an analysis of GPS velocities, which can be used to determine the surficial deformation and to compare it with the crustal deformation to define the stress field in Colombia, and to formulate a seismotectonic model. This model is characterized by the slow southeastwards displacement of the Caribbean Plate, the convergence of the Andean, Coiba, and Panamá Blocks in northwestern Colombia, and the westwards convergence of the Nazca Plate below the South American overriding Plate. The strain/stress regime maps also show different tectonic environments and large–scale geological heterogeneities.
Near surface geophysical analysis of the Navamuño depression (Sierra de Béjar, Iberian Central System): Geometry, sedimentary infill and genetic implications of tectonic and glacial footprint
(Geomorphology, 2018) Carrasco González, Rosa María; Turu, Valenti; Pedraza Gilsanz, Javier de; Muñoz Martín, Alfonso; Ros, Xavier; Sánchez Vizcaíno, Jesús; Ruiz Zapata, Blanca; Olaiz Campos, Antonio José; Herrero-Simon, Ramón
The geometric and genetic characterization of the Navamuño depression peatland system (Iberian Central System) is presented here using results from a geophysical survey. This depression is a ~30 ha pseudo-endorheic flat basin over granitic bedrock. Three geophysical techniques were used to map the subsurface geology, and identify and describe the infill sequence: shallow seismic refraction (SR), magnetic resonance sounding (MRS) and electrical resistivity measurements (VES and ERT). The three main geoelectrical layers (G1, G2, G3) identified in previous research, have also been identified in the present work. Using the data obtained in this new research we have been able to analyse these three geological layers in detail and reinterpret them. They can be grouped genetically into two sedimentary units: an ancient sedimentary body (G3), of unknown age and type, beneath an Upper Pleistocene (G2) and Holocene (G1) sedimentary infill. The facies distribution and geometry of the Upper Pleistocene was examined using the Sequence Stratigraphy method, revealing that the Navamuño depression was an ice-dammed in the last glacial cycle resulting in glaciolacustrine sedimentation. A highly permeable sedimentary layer or regolith exists beneath the glaciolacustrine deposits. Below 40 m depth, water content falls dramatically down to a depth of 80 m where unweathered bedrock may be present. The information obtained from geophysical, geological and geomorphological studies carried out in this research, enabled us to consider various hypotheses as to the origin of this depression. According to these data, the Navamuño depression may be explained as the result of a transtensional process from the Puerto de Navamuño strike-slip fault during the reactivation of the Iberian Central System (Paleogene-Lower Miocene, Alpine orogeny), and can be correlated with the pull-apart type basins described in these areas. The neotectonic activity of this fault and the icedammed processes in these areas during the Last Glacial Cycle (MIS2) were the main causes of recent sedimentary infill in this depression.