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 - 10 of 23

Glacial geomorphology of the High Gredos Massif: Gredos and Pinar valleys (Iberian Central System, Spain)
(Journal of Maps, 2020) Carrasco González, Rosa María; Soteres, Rodrigo L.; De Pedraza Gilsanz, Javier; Fernandez-Lozano, Javier; Turu, Valentí; López-Sáez, Jose Antonio; Karampaglidis, Theodoros; Granja Bruña, José Luis; Muñoz Martín, Alfonso
We present a detailed geomorphological map of the landform assemblages originated by the two major paleoglaciers of the Sierra de Gredos mountain range in the Spanish Iberian Central System. Based on previous works, our map focused on the features formed by Gredos and Pinar paleoglaciers during the last glaciation and subsequent glacial events. Based on a remote sensing analysis and exhaustive field surveys, we identified with great accuracy the local distribution of glacial, periglacial, mass movement, structural, fluvial, and lacustrine features. We recognized three main glacial geomorphological formations representing: (i) the maximum glacial extension reached (peripheral deposits); (ii) the culmination of glacial conditions (principal moraines) and (iii) the local glacial withdrawal (internal deposits). Our map offers a renewed spatial framework on which to conduct higher-resolution glacial chronologies, especially of Late Glacial and Holocene glacial activity, providing key information for performing future paleoclimatic reconstructions of the northern hemisphere mid-latitudes.
3D Spatial Distribution of Arsenic in an Abandoned Mining Area: A Combined Geophysical and Geochemical Approach
(Minerals, 2020) Ruiz Roso, Jesús; García Lorenzo, Mari Luz; Castiñeiras García, Pedro; Muñoz Martín, Alfonso; Crespo Feo, Elena
Abandoned mine wastes, containing high sulfide contents, are of particular concern because of the formation of acid mine drainage (AMD), becoming an active and harmful point source of potentially toxic elements (PTEs) to the environment. A detailed evaluation of the chemical and mineralogical composition of mining wastes is necessary to determine effective remediation actions. Due to the high amount of generated wastes as a result of mining and processing activities, the cost and time consumed for this characterization are limiting. Hence, efficient tools could be applied to predict the composition of these wastes and their spatial distribution. This study aims to determine the physico-chemical characterization of wastes from mining activities using geochemical and geophysical techniques. The obtained results, both geochemical and geophysical, allow us to locate areas with a high potential risk of contamination by As in an economic and simple way, and enable us to design detailed geochemical sampling campaigns. In addition, the fact that there are conductive fractures in depth suggests the possible circulation of contaminants through them as well as the preferential lines of circulation.
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.
Present-Day Crustal Stress Field from Gcmt Focal Mechanisms Based on the Slip Model.
(Conference Proceedings, 83rd EAGE Annual Conference & Exhibition, 2022) Olaiz Campos, J. A.; Muñoz Martín, Alfonso; De Vicente Muñoz, Gerardo
The Slip Model is applied to the Global Centroid Moment Tensor database to determine the present day state of stress. Thus, from each focal mechanism the horizontal shortening direction (Dey) and the shape factor of the strain ellipsoid (k`), defined as the relationship between the maximum horizontal shortening and the vertical axis, are calculated. Additionally, this method proposed the neoformed plane from the calculated nodal planes. In this study, to determine the stress configuration at crustal scale, only depths < 40 km are included. Focal mechanisms are grouped in reverse, strike-slip and normal, to analyse its distribution and to determine the b-parameter from Gutenberg-Richter law. Finally, global shape factor and horizontal shortening direction maps are presented.
Kink bands alpinos en rocas foliadas del basamento varisco del Sistema Central
(Geogaceta, 2021) De Vicente Muñoz, Gerardo; Muñoz Martín, Alfonso; Díez Fernández, Rubén; Olaiz Campos, J. A.
La asociación espacial y cinemática entre kink bands en rocas con foliación varisca y cabalgamientos alpinos en el basamento del Sistema Central, permiten deducir que los primeros tienen una edad cenozoica, y no varisca o tardivarisca. Sistemáticamente, la dirección de los ejes de los kinks es subparalela a los cabalgamientos. Se estudian tres afloramientos clave: El Cabalgamiento de Villares de Jadraque, el Cabalgamiento de Valdesotos y el Retrocabalgamiento de El Atazar.
Geophysical characterization of the El Cervunal kame complex (Sierra de Gredos, Iberian Central System): Insight of infill geometry and reconstruction of former glacial formations
(Journal of applied geophysics, 2021) Granja Bruña, José Luis; Turu, Valenti; Carrasco González, Rosa María; Muñoz Martín, Alfonso; Ros, Xavier; Fernández Lozano, Javier; Soteres, Rodrigo L.; Karampaglidis, Theodoros; López Saez, José Antonio; Pedraza Gilsanz, Javier de
Geological and geophysical studies in complex valley troughs provide a key record for the reconstruction of paleoenvironmental conditions during the Quaternary. Here we present a study of the sedimentary infill of the El Cervunal kame complex or El Cervunal trough (Sierra de Gredos, Iberian Central System) by means of a combined interpretation of near-surface geophysical techniques supported by geomorphological and borehole data. A set of 1D and 2D near-surface geophysical methods, including electrical (Vertical Electrical Sounding and 2D Electrical Resistivity Tomography), seismic (2D Seismic Tomography and 1D Refraction Microtremor) and Magnetic Resonance Sounding techniques, were used to test their applicability in providing better insight on the infill nature and geometry. Because of greater sensitivity and higher resolution and coverage achieved with resistivity methods, the electrical resistivity has proven to be the most informative physical parameter, while seismic and magnetic resonance methods were complementary. The sedimentary infill was classified into three geophysical units and five sub-units with their geological interpretation. Unit 1 consists of a postglacial sedimentary sequence and includes alluvial-plain and alluvial-fan deposits. Units 2 and 3 below the postglacial unit were interpreted as glacial sequences including kame (glacigenetic and fluvio-glacial) and morainic deposits, respectively. Subsoil information combined with the geomorphological data enabled the partial reconstruction of the map-view geometry of the morainic bodies at the El Cervunal trough. The results suggest a complex evolution of the study area where erosive-sedimentary processes dominate, but also structural factors should be considered. At least five well-differentiated stages can be established to explain the occurrence of the trough infill: pre-glacial, maximum glacial extension, trough obturation, glacial retreat and periglacial-postglacial.
Variscan inheritance induces Alpine upper crustal delamination in East Spanish–Portuguese Central System
(Tectonics, 2022) De Vicente Muñoz, Gerardo; Díez Fernández, Rubén; Olaiz Campos, Antonio José; Muñoz Martín, Alfonso
The Spanish–Portuguese Central System (SPCS) is an Alpine Mountain range with crystalline basement characterised by a two-layer rheological structure. This structure formed after primary (protolith) and secondary (tectonometamorphic) processes during the extensional collapse of the Variscan Orogen. The SPCS structure is usually controlled by foreland-directed thrusts and strike-slip faults. However, the eastern SPCS is dominated by NW-directed, imbricate backthrusts and lacks the main thrust directed to the foreland basin located southeast of the mountain range (Madrid Cenozoic Basin). The SPCS exhibits a crustal root (> 40 km depth) supporting SE-directed crustal-scale thrusting. Alpine backthrusts sole into an SE-dipping décollement within the Variscan basement. Variscan extension-related structures parallel the SE-dipping geometry of Alpine backthrusts, so they provided favourably oriented rheological weaknesses to accommodate Alpine shortening. Backthrusts geometry, their hanging wall position within the fault that raised the SPCS and gravity modelling support an Alpine crustal delamination process. Tectonic wedging and delamination of the more competent basement occurred in the footwall of Variscan extensional faults (Daurius domain), which enforced the shearing off of a rheologically weaker upper layer of the crust, located in the hanging wall of the Variscan extensional faults (Arriaca domain) by inverting Variscan extensional faults. This led to NW-directed incipient continental subduction of the weaker crust. Intraplate subduction and crustal delamination can be independent from lithosphere-scale inheritance and be conditioned by structural inheritance in the overlying crust. Alpine shortening for the Cretaceous cover is around 17.7 km (10.5% shortening), and 11 km (7%) for the upper-lower crust limit.
Magnetic anomalies of the NW Iberian continental margin and the adjacent abyssal plains
(Journal of maps, 2020) Druet Vélez, María; Catalán, Manuel; Martín Dávila, José; Martos, J.M.; Muñoz Martín, Alfonso; Granja Bruña, José Luis
The NW Iberian margin is a hyperextended continental margin, formed during the opening of the North Atlantic Ocean, where a subsequent partial tectonic inversion has undergone during the Alpine Orogeny. This succession of tectonic episodes determines the magnetic signature of the margin. The Spanish Exclusive Economic Zone Project has carried out seven one-month cruises between 2001 and 2009. To extend and densify the spatial coverage, we have used data from the World Digital Magnetic Anomaly Map. Here, we describe the methodology used for the acquisition and data processing of the magnetic field data. The use of diverse instrumentation, a non-complete external field’s cancelation, and the use of different magnetic core field models, contributed to the total error budget. To reduce it, we have used a leveling algorithm which minimizes all these contributions. Finally, a statistical analysis was applied using crossover residuals, showing a resolution better than 28 nT.
Geometry of the modelled freshwater/salt-water interface under variable-density-driven flow (Pétrola Lake, SE Spain)
(Hydrogeology Journal, 2022) Sanz, David; Valiente, Nicolás; Dountcheva, I.; Muñoz Martín, Alfonso; Cassiraga, E.; Gómez Alday, J.J.
Pétrola Lake in southeast Spain is one of the most representative examples of hypersaline wetlands in southern Europe. The rich ecosystem and environmental importance of this lake are closely associated with the hydrogeological behaviour of the system. The wetland is fed by the underlying aquifer with relatively fresh groundwater—1gL−1 of total dissolved solids (TDS)—with a centripetal direction towards the wetland. In addition, the high evaporation rates of the region promote an increase in the concentration of salts in the lake water, occasionally higher than 80 g L−1 TDS. The density difference between the superficial lake water and the regional groundwater can reach up to 0.25 g cm−3, causing gravitational instability and density-driven flow (DDF) under the lake bottom. The objective of this study was to gain an understanding of the geometry of the freshwatersaltwater interface by means of two-dimensional mathematical modelling and geophysical-resistivity-profile surveys. The magnitude and direction of mixed convective flows, generated by DDF, support the hypothesis that the autochthonous reactive organic matter produced in the lake by biomass can be transported effectively towards the freshwater–saltwater interface areas (e.g. springs in the lake edge), where previous research described biogeochemical processes of natural attenuation of nitrate pollution.
Geometría y modelado numérico de los cabalgamientos Alpinos y de los pliegues de propagación de falla asociados en el macizo de Honrubia-Sepúlveda (Sistema Central)
(Geotemas, 2024) Muñoz Cemillán, Alfonso; Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo De; Olaiz Campos, Antonio José
El sector de Honrubia-Sepúlveda (Norte del Sistema Central) se caracteriza por presentar una serie de cabalgamientos imbricados con basamento implicado y vergencia hacia el norte. Estos cabalgamientos desarrollan pliegues de propagación de falla en la cobertera mesozoica con flancos largos de bajo buzamiento hacia el sur (entre 2 y 5º). Dada la ausencia de datos en profundidad, y debido a su estilo “de piel fina con basamento implicado”, algunos autores interpretan la presencia de un nivel de despegue relativamente somero en profundidad. Para discutir esta estructura se han analizado y modelizado con el método de trishear uno de estos pliegues que presentan mejor desarrollo (Allmendinger, 1998). Los resultados de la modelización sugieren desechar la presencia de geometrías rampa-rellano, y la ausencia de un nivel de despegue común superficial para los cabalgamientos. Los resultados obtenidos también descartan otras geometrías de la rampa, como son las de un aumento del buzamiento de los cabalgamientos en profundidad, o rampas con geometrías lístricas. Los modelos que mejor explican la geometría del pliegue de propagación se generan mediante fallas inversas de buzamiento constante (entre 40 y 50º), valores de p/s entre 1.5 y 1.8 y ángulos de trishear estrechos (de unos 60º).