Aproximación a la mecánica de los cabalgamientos en el contexto general de la deformación en el NW de la península Ibèrica

En la cadena herciniana del NW de la Peninsula Ibérica, las Zonas Cantábrica y Asturoccidental-leonesa proporcionan buenos ejemplos de cabalgamientos desarrollados en diferentes momentos en el transcurso de la secuencia deformacional. Así, en la Zona Asturoccidental-leonesa, al existir temperaturas y presiones de confinamiento relativamente elevadas, las rocas reaccionaron ante los esfuerzos de manera dúctil, originándose pliegues; al progresar la deformación, se alcanzó la resistencia de las rocas en algunos puntos y estas se fracturaron originándose cabalgamientos. Las fracturas cortan pues a plieguesanteriores y en consecuencia no se producen sobre planos de debilidad preexistentes. Debido a la gran resistencia que ofrecen las superfícies de fractura al deslizamiento, se asocian a ellas numerosas fracturas menores y otras estructuras a veces muy penetrativas. Por el contrario, en la Zona Cantábrica. La temperatura y la preslón de confinamiento fueron menores, lo cual debió dificultar la deformación dúctil y disminuyó probablemente la resistencia de las rocas. Por otro lado, se desarrolló una superfície de debilidad en las rocas debida a la existencia de una presión de fluidos alta y tal vez a la presencia de algunos niveles poco resistentes a la deformación. Todo ello condicionó el que se originase un despegue generalizado cuya ascensión mediante fallas lístricas dio lugar a mantos de tipo apalachense. Desaparecidas las condiciones quefavorecieron el emplazamiento de estos mantos, el acortamiento posterior se llevó a cabo por un proceso de plegamiento

A geological model for the management of subsurface data in the urban environment of Barcelona and surrounding area

The overdevelopment of cities since the industrial revolution has shown the need to incorporate a sound geological knowledge in the management of required subsurface infrastructures and in the assessment of increasingly needed groundwater resources. Additionally, the scarcity of outcrops and the technical difficulty to conduct underground exploration in urban areas highlights the importance of implementing efficient management plans that deal with the legacy of heterogeneous subsurface information. To deal with these difficulties, a methodology has been proposed to integrate all the available spatio-temporal data into a comprehensive spatial database and a set of tools that facilitates the analysis and processing of the existing and newly added data for the city of Barcelona (NE Spain). Here we present the resulting actual subsurface 3-D geological model that incorporates and articulates all the information stored in the database. The methodology applied to Barcelona benefited from a good collaboration between administrative bodies and researchers that enabled the realization of a comprehensive geological database despite logistic difficulties. Currently, the public administration and also private sectors both benefit from the geological understanding acquired in the city of Barcelona, for example, when preparing the hydrogeological models used in groundwater assessment plans. The methodology further facilitates the continuous incorporation of new data in the implementation and sustainable management of urban groundwater, and also contributes to significantly reducing the costs of new infrastructures.Peer ReviewedPostprint (published version

Structural geology and geophysics as a support to build a hydrogeologic model of granite rock

A method developed for low-permeability fractured media was applied to understand the hydrogeology of a mine excavated in a granitic pluton. This method includes (1) identifying the main groundwater-conducting features of the medium, such as the mine, dykes, and large fractures, (2) implementing this factors as discrete elements into a three-dimensional numerical model, and (3) calibrating these factors against hydraulic data (Martinez-Landa and Carrera 2006). A key question is how to identify preferential flow paths in the first step. Here, we propose a combination of several techniques. Structural geology, together with borehole sampling, geophysics, hydrogeochemistry, and local hydraulic tests aided in locating all structures. Integration of these data yielded a conceptual model of the site. A preliminary calibration of the model was performed against short-term (< 1 day) pumping tests, which facilitated the characterization of some of the fractures. The hydraulic properties were then used for other fractures that, according to geophysics and structural geology, belonged to the same families. Model validity was tested by blind prediction of a long-term (4 months) large-scale (1 km) pumping test from the mine, which yielded excellent agreement with the observations. Model results confirmed the sparsely fractured nature of the pluton, which has not been subjected to glacial loading-unloading cycles and whose waters are of Na-HCO3 type.Peer Reviewe

tomografia sismica de alta resolucion a lo largo del perfil sismico de IBERSEIS

International audienc

Mountain building processes during continent-continent collision in the Uralides

Since the early 1990's the Paleozoic Uralide Orogen of Russia has been the target of a significant research initiative as part of EUROPROBE and GEODE, both European Science Foundation programmes. One of the main objectives of these research programmes was the determination of the tectonic processes that went into the formation of the orogen. In this review paper we focus on the Late Paleozoic continent-continent collision that took place between Laurussia and Kazakhstania. Research in the Uralides was concentrated around two deep seismic profiles crossing the orogen. These were accompanied by geological, geophysical, geochronological, geochemical, and low-temperature thermochronological studies. The seismic profiles demonstrate that the Uralides has an overall bivergent structural architecture, but with significantly different reflectivity characteristics from one tectonic zone to another. The integration of other types of data sets with the seismic data allows us to interpret what tectonic processes where responsible for the formation of the structural architecture, and when they were active. On the basis of these data, we suggest that the changes in the crustal-scale structural architecture indicate that there was significant partitioning of tectonothermal conditions and deformation from zone to zone across major fault systems, and between the lower and upper crust. Also, a number of the structural features revealed in the bivergent architecture of the orogen formed either in the Neoproterozoic or in the Paleozoic, prior to continent-continent collision. From the end of continent-continent collision to the present, low-temperature thermochronology suggests that the evolution of the Uralides has been dominated by erosion and slow exhumation. Despite some evidence for more recent topographic uplift, it has so far proven difficult to quantify it. © 2008 Elsevier B.V. All rights reserved

A geological model for the management of subsurface data in the urban environment of Barcelona and surrounding area

The overdevelopment of cities since the industrial revolution has shown the need to incorporate a sound geological knowledge in the management of required subsurface infrastructures and in the assessment of increasingly needed groundwater resources. Additionally, the scarcity of outcrops and the technical difficulty to conduct underground exploration in urban areas highlights the importance of implementing efficient management plans that deal with the legacy of heterogeneous subsurface information. To deal with these difficulties, a methodology has been proposed to integrate all the available spatio-temporal data into a comprehensive spatial database and a set of tools that facilitates the analysis and processing of the existing and newly added data for the city of Barcelona (NE Spain). Here we present the resulting actual subsurface 3-D geological model that incorporates and articulates all the information stored in the database. The methodology applied to Barcelona benefited from a good collaboration between administrative bodies and researchers that enabled the realization of a comprehensive geological database despite logistic difficulties. Currently, the public administration and also private sectors both benefit from the geological understanding acquired in the city of Barcelona, for example, when preparing the hydrogeological models used in groundwater assessment plans. The methodology further facilitates the continuous incorporation of new data in the implementation and sustainable management of urban groundwater, and also contributes to significantly reducing the costs of new infrastructures.Peer Reviewe

URSEIS. Transecting the Uralide Orogen Database and state of the art

The Ural Mountains of central Russia separate the ancient core of Europe, the East European Craton, from the more easterly terranes of Siberia and Kazahkstan. Together with the Caledonian, Appalachian and Variscian orogenic belts, the Urals compose the Paleozoic framework of the old craton. Todays Mountains are largely a Tertiary feature. The Uralide orogen extends far eastwards, forming the basement of the Mesozoic hydrocarbon bearing formations of the West Siberian Basin. The 3000 km long mountain belt is a unique natural laboratory with many key features that are important for our understanding of Paleozoic collisional orogeny. Comparison of the Uralides with the other related Paleozoic orogens will provide new insight into the processes of pre-Mesozoic plate tectonics. The existing database indicates the Urals are remarkable for their preservation of a continental root, the orogen having apparently suffered less post-orogenic collapse than most other Paleozoic mountain belts. Nevertheless, extension must have contributed significantly to the preservation throughout the belt of some of the world's most complete ophiolites and island-arc volcanic suites (along with associated mineralizations), juxtaposed over very high-P blueschists and eclogites. Other Paleozoic orogens have been re-equilibrated to normal crustal thicknesses during late- to post-orogenic processes. Such mechanisms of uplift and extension are also demonstrated in young orogens (e.g. Himalaya, Alps). The existence or appearant preservation of a thickened crust beneath the Uralides represents a fundamental problem in the understanding of orogenic processes. The young history of the Urals, following extensive Mesozoic transgression and erosion, is of particular interest in view of the reportedly high (2mm/yr) uplift rates and widespread evidence of Tertiary (Recent?) tectonism. Historical seismicity is reported to be concentrated to the Middle Urals, apparently related to a compressional stress regime. Establishing the relationship of the crustal roots to deep structures in the subcrustal lithosphere and astenosphere and understanding the development of these major structures in time is fundamental for full interpretations of the dynamic evolution of the Urals. A wide range of new interdisciplinary investigations of the Uralide orogen are proposed here in the form of a collaborative European-American initiative, the scope of which has never been previously attempted for the continental lithosphere. Geoscientists from institutions all over Europe will work together with N.I.S. colleagues on key aspects of the mountain belt. COCORP-DEKORP type deep seismic reflection (CDP) profiles across the Southern Urals are a key experiment for relating shallow to deep structures. (orig.)Available from TIB Hannover: RR 6134(95/01) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); European Science Foundation (ESF), 67 - Strasbourg (France)DEGerman