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
17 results
Search Results
Now showing 1 - 10 of 17
Item 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.Item 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, GerardoThe 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.Item 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.Item 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, AlfonsoThe 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.Item 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.Item 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 JoséEl 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).Item 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 LuisIn 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.Item The Prados del Cervunal morainic complex: Evidence of a MIS 2 glaciation in the Iberian Central System synchronous to the global LGM(Quaternary Science Reviews, 2023) Carrasco, R.M.; Turu, V.; Soteres, R. L.; Fernández-Lozano, J.; Karampaglidis, T.; Rodés, A.; Ros, X.; De Andrés De Pablo, Nuria; Granja Bruña, José Luis; Muñoz Martín, Alfonso; López-Sáez, J.A.; Braucher, R.; De Pedraza Gilsanz, Javier; Palacios Estremera, David; ASTER TeamThe area of Prados del Cervunal (PC) is an intra-morainic topographic depression located at 1800 m asl in the divide or interfluve between Garganta de Gredos and Garganta del Pinar valleys (Central Gredos; Iberian Central System, ICS). Both valleys, along with the adjacent Hoya Nevada, were occupied by glaciers during the Upper Pleistocene, leading to the development of the Prados del Cervunal moraine complexes studied in this work. Using cartographic methods and morphostratigraphic analysis, the three main glacial formations established in the Regional Chrono-Evolutionary Pattern for the ICS, Peripheral Deposits (PD), Principal Moraine (PM) and Internal Deposits (ID), have been identified and mapped in this area. The chronology of these formations has been implemented by Cosmic Ray Exposure (CRE) techniques using 10Be (new data) and 26Cl (previous data, recalculated in this work) in samples from morainic boulders. With these data, the following chrono-evolutionary sequence has been established: (stage 1) local-Maximum Ice Extent (MIE), dated in 25.0 ± 1.4 ka and corresponding to the maximum age obtained in these paleoglaciers; (stage 2) period of oscillations around the MIE, corresponding to the development of the PD Formation between ~25 ka and ~21 ka; (stage 3) period of readvance and stabilisation, dated after ~21 ka (average age obtained for the PD moraines attached to PM moraines) and previous to ~18 (minimum age obtained for a main crest of the PM formation); and (stage 4) onset of deglaciation dated around to ~18 ka (average of ages obtained for the first main crest of the ID formation). During the stages of maximum ice expansion, these three glaciers formed an Ice field whose tongues were interconnected on the PC flat by an ice transfluence system (stages 1 and 2, Plateau Glacier Period). In later stages, the ice masses were partitioned, giving rise to valley glaciers and large moraines forming morainic complexes like those of PC (stages 2, 3 and 4, Valley Glaciers Period). The local MIE and onset of deglaciation stages in this area show a good fit with the ages stablished to global level for the global Last Glacial Maximum (LGM) and the onset of the Last Glacial Termination (Termination I). They also show good correlation at local (with other areas of the ICS), peninsular (with other Iberian mountains) and continental (some areas of the Alps and mountains of Central Europe) level. Finally, this evolutionary sequence and its correlations allowed us to adjust and validate some units of the Regional Chrono-Evolutionary Pattern model and propose the Gredos-Pinar-Cabeza Nevada glacial system as benchmark for the glaciation of Marine Isotope Stage (MIS) 2 in the Iberian Peninsula.Item 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, GonzaloEn 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.Item 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, MaríaHyperextended 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.