62 research outputs found
La Geologia regional, clau de volta del mètode geològic
Des dels inicis de la geologia moderna, el mètode de treball impulsat per l'escola
werneriana dóna un paper fonamental a la geologia regional, tant pel que fa a la geologia històrica corn a la geologia causal o dels processos. El desenvolupament de la geologia regional porta al mapa geològic, des d'aleshores l'eina més estesa per comunicar, de manera sintètica, les informacions fenomenològiques de
caràcter regional. La geologia regional té avui una important presència en els diferents camps de la geologia i ocupa una posició clau en el mètode geològic, atès el caràcter essencialment històric i regional de la geologia. Constitueix un primer grau interpretatiu que es pot interpretar en termes de geologia històrica, explicar en termes de geologia causal o utilitzar-lo en la producció de teoria causal, amb la qual, en la progressió del pensament geològic manté una necessària relació iterativa.Since the early stages of modern geology, the
method developed by geologists of the wernerian
school has given a fundamental role to regional
geology in relation to both, historical geology and
causal or process geology. The development of
regional geology led to geological maps, since
then the most extended tool to sinthetically
communicate phenomenological informations
of regional nature. Nowadays, regional geology
is largely present in the different fields of geology,
and is a keystone of the geological method
because of the essentially historical and regional
nature of geology. It constitutes a first step in
geological interpretation which can be interpreted
in terms of historical geology, explained in terms
of causal geology, or be used in the production
of causal theory, with which it maintains a
necessary iterative relationship in the advance
of the geological thought.Desde los inicios de la geología moderna, el método de trabajo impulsado por la escuela
werneriana otorga un papel fundamental a la geología regional, tanto en relación a la geología histórica como a la geología causal o de los procesos. El desarrollo de la geología regional conduce al mapa geológico, desde entonces la herramienta más extendida para comunicar, de manera sintética, las informaciones fenomenológicas de carácter regional. La geología regional tiene hoy en día una importante presencia en los distintos campos de la geología y ocupa una posición clave en el
método geológico dado el carácter esencialmente histórico y regional de la geología. Constituye un primer escalón interpretativo que puede, a su vez, interpretarse en términos de geología histórica, explicarse en términos de geología
causal o utilizarlo en la producción de teoría causal, con la que, en el progreso del pensamiento geológico, mantiene una necesaria relación iterativa
Development of geology in Spain : a case study of a marginal science
Geology in Spain developed outside the mainstream of major geological ideas. Geology was introduced intothe country when it had already grown mature. The history of geology in Spain is series of initiatives aimedat aligning the country with the innovative currents taking place in the rest of Europe. This was accomplishedby different protagonists: state and private institutions during the Enlightenment, mining engineers in the 19thcentury, church and regional authorities in Catalonia in the last quarter of the 19th century and in the early years ofthe 20th century, and the university in the 20th century. The importance of the links with foreign geologists shouldnot be underestimated. Not until the 20th century did improvement in living standards and university expansionallow Spanish geology to attain the critical number of scientists needed to undertake quality research and achievefull integration into the international community
Estudio tectónico del Paleozoico inferior del Pirineo entre la Cerdaña y el río Ter (resumen)
El análisis estructural del domo del río Freser (Pirineos Orientales, España) permite poner de manifiesto una sucesión de tres fases de plegamiento hercinianas. Se describen las características de las mismas y se comparan con las descritas por otros autores en regiones vecinas
Precisiones acerca de la significación petrológica y estructural de las rocas gneísicas y cataclásticas del Maresme (prov. de Barcelona)
Se estudian pequeños afloramientos de rocas metamórficas y cataclásticas ubicadas en el granito herciniano de la Cadena Costera Catalana al NE de Barcelona. Tras una breve síntesis de las diversas ideas emitidas sobre la génesis de estas rocas se realiza un estudio comparativo de las mismas. De él se infiere la presencia de dos grupos de rocas de significación petrogenética y tectónica distinta: 1) Los gneises de Mataró, que resultan del metamorfismo polifásico progresivo herciniano de sedimentos del Paleozoico inferior y 2) las rocas cataelásticas de Caldetes, ligadas a deformaciones internas en el batolito del granito herciniano postectónico, acompañadas de transformaciones hidrotermales en mayor o menor grado.Small outcrops of metamorphic and cataclastic rocks, located in the Hercynian granite of the Catalan Litoral Ridge (NE from Barcelona) were studied. Following a brief examination of the previous ideas issued concerning the origin of these rocks, a comparative study has been made. As a result of the forementioned, the presence of two groups of rocks could be established, both having an individual petrogenetic and tectonic signification: 1) The Mataró Gneises outcome of a progressive and polyphasic metamorphism of Lower Paleozoic sedimentary rocks. 2) The Caldetes Cataclastic Rocks, are related to interna1 deformations within the hercynian late tectonic granite batholith, assisted in some extent by hydrothermalism
Sobre la compresión alpina en el sector central de las Cadenas Costeras Catalanas
Este trabajo tiene como finalidad el estudio de la compresión alpina en la cobertera mesozoica del sector central de las Cadenas Costeras Catalanas. A nivel microestructural se reconoce un giro de la dirección de compresión en el tiempo, de NW-SE -sincrónica del plegamiento de la cadena- a N-S y NE-W.Si una evolución similar es admitida a nivel del zócalo, puede explicarse la existencia, en los Catalánides, de fallas transversales levógiras. y dextrógiras. Finalmente se compara la evolución propuesta en el sector central de los Catalánides con la descrita por otros autores en la Cordillera Ibérica y los Pirineos, y se concluye que todo el ámbito NE del Bloque Ibérico ha sufrido una evolución homogénea de la compresión durante el Paleógeno
Precisions sobre la disposició estructural dels terrenys triàsics de Vallcarca (Barcelona)
The structural setting of the Buntsandstein outcrops located between the Mare de Déu del Coll church and Can Mora in Vallcarca (Barcelona), mapped by J. Almera in 1880,
is accurately determined.
The pulling down of buildings and some diggings out enables the observation of the structural relationship between the Triassic and the Paleozoic rocks.
The different outcrops are described and located (fig. 1), and it is established that wherever the contacts are exposed the Triassic rocks are thrusted by the Paleozoic materials.
The fault planes strike NNE-SSW dipping to the ESE and the few slickensides observed indicate a reverse slip (fig. 2). Taking into account the geometry of the outcrops we can conclude that we are dealing with a fault zone where the Hercynian rocks thrust the Triassic rocks and where the detailed structure shows a set of anastomosing fault planes, pinching in between slices of Triassic rocks
Origin of a restraining bend in an evolving strike-slip system : The Cenozoic As Pontes basin (NW Spain)
The As Pontes basin (12 km2), NW Iberian Peninsula, is bounded by a double restraining bend of a dextral strike-slip fault, which is related to the western onshore end of the Pyrenean belt. Surface and subsurface data obtained from intensive coal exploration and mining in the basin since the 1960s together with additional structural and stratigraphic sequence analysis allowed us to determine the geometric relationships between tectonic structures and stratigraphic markers. The small size of the basin and the large amount of quality data make the As Pontes basin a unique natural laboratory for improving our understanding of the origin and evolution of restraining bends. The double restraining bend is the end stage of the structural evolution of a compressive underlapping stepover, where the basin was formed. During the first stage (stepover stage), which began ca. 30 Ma ago (latest Rupelian) and lasted 3.4 My, two small isolated basins bounded by thrusts and normal faults were formed. For 1.3 My, the strike-slip faults, which defined the stepover, grew towards each other until joining and forming the double restraining bend, which bounds one large As Pontes basin (transition stage). The history of the basin was controlled by the activity of the double restraining bend for a further 3.4 My (restraining bend stage) and ended in mid-Aquitanian times (ca. 22 Ma)
An active zone characterized by slow normal faults, the northwestern margin of the València trough (NE Iberia): a review
The northwestern margin of the Valencia trough is an area of low strain characterized by slow normal faults and low to moderate seismicity. Since the mid 1990s this area has been the subject of a number of studies on active tectonic which have proposed different approaches to the location of active faults and to the calculation of the parameters that describe their seismic cycle. Fifty-six active faults have been found and a classification has been made in accordance with their characteristics: a) faults with clear evidence of large paleo-, historic or instrumental earthquakes (2/56); b) faults with evidence of accumulated activity during the Plio-Quaternary and with associated instrumental seismicity (7/56); c) faults with evidence of accumulated activity during the Plio-Quaternary and without associated instrumental seismicity (17/56); d) faults with associated instrumental seismicity and without evidence of accumulated activity during the Plio-Quaternary (30/56), and e) faults without evidence of activity or inactive faults. The parameters that describe the seismic cycle of these faults have been evaluated by different methods that use the geological data obtained for each fault except when paleoseismological studies were available. This classification can be applied to other areas with low slip faults because of the simplicity of the approaches adopted. This study reviews the different approaches proposed and describes the active faults located, highlighting the need a) to better understand active faults in slow strain zones through paleoseismological studies, and b) to include them in seismic hazard studies
La serie sísmica de Tivissa, 1845 (cadenas costeras catalanas): Los deslizamientos del barranco del Manou
La serie sísmica de Tivissa tuvo lugar durante la lluviosa década de 1840-1850, 21 días después de los aguaceros que ocasionaron graves inundaciones. La serie empezó el 30 de septiembre y finalizó el 14 de octubre. Los terremotos de mayor intensidad ocurrieron el 3 (IEMS-98=VI) y el 7 de octubre (IEMS-98=VI-VII). De acuerdo con la distribución de la información macrosísmica se propone un área epicentral para ambos terremotos entre Tivissa y Vandellòs. El sismo del 7 de octubre indujodeslizamientos de masa al Sur de Tivissa. La estratigrafía, la disposición estructural y la orografía facilitaron estos deslizamientos: tuvieron lugar en una secuencia de capas calcáreas, decimétricas, con interestratos centimétricos de margas que buzan en el mismo sentido que la pendiente de la vertiente del valle, pero menos que ésta, y que está afectada por diaclasas perpendiculares a la estratificación. Ello implica la existencia de masas rocosas aisladas por la estratificación y las diaclasas, susceptibles de deslizarse hacia el valle. El agua de los aguaceros que precedieron a los sismos infiltrada por las diaclasas podría haber facilitado el despegue a nivel de los interestratos margosos. Teniendo en cuenta los datos geológicos y sismológicos se discuten las posibles fuentes de estos terremotos
Variscan and Alpine structure of the hills of Barcelona: geology in an urban area
Line 9 of the underground railway is currently being constructed in Barcelona. This undertaking necessitates tunnelling through a number of hills that are mainly made up of Paleozoic rocks, which exhibit a complex structure due to the superposition of Variscan, Mesozoic, Paleogene, and Neogene structures. We present a geological map of the hills of Barcelona originally compiled at 1:5000 scale. Unpublished field notes from surveys carried out in the 1940s and in the early 1970s were crucial for drawing up this detailed map, which together with subsurface data from public works and our study of the few remaining outcrops, enabled us to provide fresh insights into the structure of this area. We also discuss the age of the structures on the basis of cross-cutting relationships and regional considerations. Our conclusions highlight the ongoing need for a geological survey of cities given that our understanding of their geology depends on impermanent outcrops and on the recovery of lost subsurface data. These considerations call for a suitable management of the geological information in urban areas with a complex geology for planning and developing safe infrastructures
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