Person:
Antón López, Loreto

First Name

Loreto

Last Name

Antón López

URI

https://hdl.handle.net/20.500.14352/82688

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Area

Geodinámica Interna

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Now showing 1 - 9 of 9

Iberia, a natural laboratory for the quantification of the large scale erosional response to the fluvial capture processes
(8º Congresso Nacional de Geomorfologia - Geomorfologia 2017, Congresso Nacional de Geomorfologia (8. 2017. Porto), 2017) Antón López, Loreto; Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo De; Alberto Gomes, António; Teixeira, José; Soares, Laura
Due to its geological location and diversity, Iberia is a key natural laboratory for the study of tectonic and geological processes. Within those it is especially suitable for the study of large-scale fluvial capture processes, and their influence on topography and landscape evolution. Nowadays, Iberia is characterized by the presence of highly elevated extensive flat surfaces (Iberian Mesetas). Those high plains correspond to planation surfaces developed mainly on Palaeozoic and Mesozoic rocks, and sedimentation surfaces of Neogene rocks. These last mostly represent the sedimentary deposits related to infill of the, formerly closed Foreland Basins. Three main rivers (Duero, Ebro and Tajo) which watersheds cover an area over 250 km2, drain almost half of the total Iberia surface. For these basins the development of the present-day drainage network was related to the opening of formerly closed fluvial systems, developed within ancient Cenozoic basins. In The Iberian Peninsula, the signature of that change in drainage conditions is still preserved in some areas, and can be studied through the analysis of longitudinal profiles shapes and the relief characterization. The analysis of present and former topography represents a powerful qualitative tool for a relative quantification of fluvial dissection and basin denudation, allowing to illustrate the spatial distribution of surface erosion, associated to the exorheic history of the basins. This work approaches the analysis of the denudation processes for the main formerly endorheic Iberian basins.
Mechanisms and age estimates of continental-scale endorheic to exorheic drainage transition: Douro River, Western Iberia
(Global and Planetary Change, 2019) Cunha, Pedro P.; Martins, António A.; Stokes, Martin; Cabral, Joao; Lopes, Fernando C.; Vicente Muñoz, Gerardo De; Pereira, Diamantino; Buylaert, Jan-Pieter; Murray, Andrew S.; Antón López, Loreto
In western Iberia, mechanisms that can explain the transition from endorheic to exorheic continental-scale drainage reorganization are foreland basin overspill, headwards erosion and capture by an Atlantic river, or a combination of both. To explore these, we have investigated the Portuguese sector of the Douro River, the locus of drainage reorganization. The Douro River is routed downstream through the weak sedimentary infill of the Douro Cenozoic Basin, after which the river cuts down through harder granitic and metamorphic rocks crossed by active fault zones, before reaching the Atlantic coast. We investigated the drainage reorganization using an integrated approach that combined remote sensing, field survey and geochronology, applied to Pliocene–Quaternary fluvial sediments and landforms. The older drainage record is documented by a series of high and intermediate landform levels comprising: (1) a high level (1000–500 m a.s.l.) faulted regional fluvial erosion surface, the North Iberian Meseta planation surface and the Mountains and Plateaus of Northern Portugal, recording the endorheic drainage of the Douro Cenozoic Basin; (2) a first inset level at 650–600 m a.s.l., comprising a broad fluvial surface developed onto a large ENE–WSW depression, interpreted as recording the initiation of the continental scale reorganization; and (3) an inset fluvial surface at 550–400 m a.s.l., corresponding to the establishment of the exorheic ancestral Douro valley. The younger drainage record comprises an entrenched fluvial strath terrace sequence of up to 9 levels (T9 = oldest), positioned at 246–242 m above the modern river base; T1 = youngest, positioned at +17–13 m. Levels T1 and T3 display localized fault offsets. The three lowest terrace levels (T3–T1) were dated using optically stimulated luminescence techniques with results ranging from >230–360 ka (T3), through 57 ka (T2) to 39–12 ka (T1). Fluvial incision rates of the younger terraces were quantified and temporally extrapolated to model the ages of the intermediate to high elevation levels of the early drainage record. Integration of incision data informs on the probable timing of the drainage reorganization and the initial adjustment, ~3.7–1.8 Ma. This was followed by acceleration of incision, producing the entrenched river terrace sequence developed via spatial and temporal variations in rock strength, uplift and cyclic cool-climate variability as the river adjusted to the Atlantic base level.
Datación de eventos tectónicos mediante integración de geocronología K-Ar y análisis de paleoesfuerzos en el Domo del Tormes
(Geotemas, 2004) Antón López, Loreto; Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo De; Galindo Francisco, María Del Carmen
The present paper deals with K-Ar absolute dating performed on three fault gouges structures selected across the geological structure known as the Domo del Tormes (Zamora-Salamanca, Spain). The dating performed on five clay samples, with grain size of 0,2-0,4mm and <0,2mm, provides ages from 210 ± 11 to 86,9 ± 4,3 Ma. The interpretation of the results obtained by both geocronological and fault population analysis methods contributed relevant data to ascertain the age of the various palaeostress fields defined in the study area, with maximum horizontal compression oriented E-W and NE-SW.
Alpine paleostress reconstruction and active faulting in western Iberia
(Central European Journal of Geosciences, 2010) Antón López, Loreto; Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo De
The study of intraplate tectonics is crucial for understanding the deformation within plates, far from active plate boundaries and associated stress transmission to the plate interiors. This paper examines the tectonic evolution of the Variscan basement at the western margin of the Cenozoic Duero basin. Located east of the Vilariça Fault System in NW Iberia, this intraplate zone is a relatively flat but elevated area with an intense NNE-SSW trending fault system and associated moderate seismicity. Although the area has played an important role in the Duero basin configuration, its Alpine to present-day tectonic evolution has not been well constrained. In order to characterize the successive paleostress fields, 1428 pairs of fault-striae were measured at 56 sites and two focal mechanisms were used. Stress inversion methods have been applied to analyze paleostress regimes. Results show the existence of three dominant maximum horizontal stress (Shmax) trends: N-S, NE-SW and E-W. Relative and absolute dating of the activated faults for each Shmax shows that the clearly predominant N-S paleostress field in the zone has been active since the Oligocene up to the present day; while a NE-SW stress field is found to have been active during the Cretaceous and an older E-W paleostress field was active in the earlier Alpine cycle (Late Triassic).
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 De
Fracture 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).
Análisis de la geometría en profundidad de fracturas conductoras en zonas de baja permeabilidad mediante tomografía eléctrica (El Berrocal, Sistema Central Español)
(Geogaceta, 2007) Muñoz Martín, Alfonso; Olaiz Campos, Antonio José; Vicente Muñoz, Gerardo De; Antón López, Loreto; Elorza, Francisco José; Vicente, Raquel de
The groundwater flow in zones of low permeability, as granites, is mainly associated with zones of fracture. For this reason the characterization of the fractures is fundamental, both in surface as in depth, and must integrate geological information (geological mapping, structural analysis), geophysics (mainly electrical and electromagnetic methods) and geochemistry (radon and others gases) with hydrogeology. In this work we analyze the geophysical response of a strike-slip fault zone by means of three 2D resistivity models. The objective is to investigate the presence of several conductive zones and their geometry in depth. The obtained results allow to control the geometry in depth of the fractures, the gaps between the different mapped traces along the fault zone as well as the thickness of landfill. All this information will be useful for the hidromechanical simulation of the massif, and to check the geometry and gas permeability calculated from emanometry.
Análisis de la fracturación y campos de paleoesfuerzos en el centrooeste de la Península Ibérica.
(Geotemas, 2004) Antón López, Loreto; Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo De
The Tormes Dome is a granitic massif emplaced during the Hercinian orogeny and later deformed by several posthercynian fracturation episodes. Three main paleostress fields have been obtained from stress inversion o f 1375 fault-slip data collected throughout the study area. The maximum horizontal stress (SHMAX) are oriented N-S, NE-SW and E-W with extensional and strike-slip stress regimes. Difficulties to determine age dating o f the three paleostress fields made necessary to enlarge the study area to the surrounding Cenozoic basins borders. In addition, geocronological information obtained form K-Ar dating o f fault gouges collected in the Tomes Dome has been used to establish the relative chronology of the three tectonic episodes from field data and determine their activity periods form Mesozoic to present time. An important result is that there is no relevant brittle tectonic activity associated with the recent NW-SE stress field in the western peninsula from Upper Miocene to the present times and some field evidences, as well as two focal mechanisms of earthquakes occurred in the area seem that in the Tormes Dome the recent stress field present an Shmax oriented N-S.
Seismicity and potencially active faults in the Northwest and Central-West Iberian Peninsula
(Journal of iberian geology, 2012) Martín-González, F.; Antón López, Loreto; Insua Arévalo, Juan Miguel; Vicente Muñoz, Gerardo De; Martínez Díaz, José Jesús; Muñoz Martín, Alfonso; Heredia, N.; Olaiz Campos, Antonio José
The Northwest and Central-West Iberian Peninsula configure an intraplate area far from the active plate boundaries, where the Variscan basement crops out extensively (Iberian Massif). This area of the Iberian Peninsula has been traditionally considered a seismically stable region; however, it presents a moderate intraplate seismicity which indicates the presence of active structures and the occurrence of potentially damaging earthquakes. The scarcity of Mesozoic and Cenozoic deposits makes very difficult to track the record of the more recent tectonic activity and the characterization of active tectonic structures within the Iberian Massif. Nevertheless the seismic sequences of 1995-1997 in Lugo (5.1 mb; IV) and 2003 in Zamora (4.2 Mw) provided important information about the orientation of the present stress tensor, and the distribution of the hypocenters informed about the rupture geometry of the fault planes. The present work integrates geological, geomorphological, structural, and seismological data in order to define the main potentially active faults in the region. Faults trending NE–SW to N–S are potentially active as strike-slip, in some cases with a reverse component, under a NW-SE to N–S compression. [RESUMEN] El Noroeste y Centro Oeste de la Peninsula Ibérica son parte de una región intraplaca alejada de los bordes de placa sísmicamente activos, donde aflora el basamento varisco (Macizo Ibérico). Esta región de la Península Ibérica ha sido tradicionalmente considerada sísmicamente estable; sin embargo, presenta una moderada sismicidad que indica la presencia de estructuras activas y terremotos potencialmente catastróficos. La escasez y dispersión de los depósitos Mesozoicos y Cenozoicos hace difícil identificar la actividad tectónica más reciente, así como la caracterización de las fallas potencialmente activas dentro del Macizo Iberico. Sin embargo la sismicidad de 1995 y 1997 en Lugo (5.1 mb) y de 2003 en Zamora (4.2 Mw) aportó importante información para determinar la orientación del tensor actual de esfuerzos. De igual modo, la orientación de las replicas aportó información sobre los planos de rotura. El presente trabajo integra datos geológicos, geomorfológicos, estructurales y sismotectónicos para definir las principales fallas potencialmente activas en la región. Las fallas con orientaciones NE-SW hasta N-S son potencialmente activas, bajo un tensor de esfuerzos de NW-SE a N-S, como fallas de desgarre y en algunas zonas con componente inversa.
Tensor actual de esfuerzos y fallas potencialmente activas en el Domo del Tormes (NO de Iberia)
(Geogaceta, 2006) Antón López, Loreto; Vicente Muñoz, Gerardo De
Located in the NW of the Iberian Peninsula, the Domo del Tormes is an intra-plate granitic domain made up of a Hercynian megastructure and traditionally considered of very low or null seismicity. The geology of the area makes difficult to determine the recent deformations and the characterization of neotectonic activity. The data compilation and further discussion of seismic activity in the area provide information on present day stress tensor orientation and the match of gravimetry, geological and structural data revealed a series of main anomalies related to faulting on a regional scale, defining some potentially active structures in the area.