Estratigrafía y petrología del subsuelo precuaternario del sector SW de la depresión de Barcelona (cadenas costeras catalanas, NE de Iberia)

Las numerosas obras de Ingeniería Civil que se han realizado en los últimos años en la depresión de Barcelona (ampliación del aeropuerto, ampliación del metro y AVE fundamentalmente) han permitido recabar mucha información sobre el subsuelo de esta área. En este trabajo se caracterizan las distintas unidades de subsuelo precuaternarias que aparecen en los numerosos sondeos realizados recientemente en la zona SW de la depresión de Barcelona. Se ha identificado un sustrato triásico formado por areniscas del Buntsandstein y dos unidades de edad Miocena, una basal de carácter continental y otra superior depositada en un ambiente marino. Todas estas unidades fueron fracturadas debido a una tectónica extensiva y, posteriormente, fueron fosilizadas en primer lugar por los sedimentos del Plioceno, que recubren la superficie de erosión messiniense, y finalmente, por el Cuaternario. El análisis de las distintas unidades permite obtener datos sobre la evolución paleogeográfica y tectónica de la depresión de Barcelona durante el Mioceno y el Plioceno.çCurrent building of civil Engineering infrastructures in the Barcelona plain and Llobregat delta (mainly metro and airport extension and high speed train) is providing new geological subsurface data to build better geologic models and understand the basin evolution. This work focuses on the pre-Quaternary units observed in cores. Based on petrographic analyses combined when it was possible with paleontological studies, we identified the lower Triassic Buntsandstein sandstone facies and Miocene continental and marine facies which appear compartmentalized due to extensive deformation. After this extensive episode, Pliocene and Quaternary sediments, which were deposited after the development of successive erosive surfaces, overlay the Triassic and Miocene units. The identification of these units enabled one to improve the interpretation of the tectonic and paleogeographic evolution of the Barcelona plai

Bajo la ciudad: roedores miocenos de muestras de sondeos del subsuelo de Barcelona

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Sequence Stratigraphy as a tool for water resources management in alluvial coastal aquifers: application to the Llobregat delta (Barcelona, Spain)

Most coastal aquifers undergo seawater intrusion. Mitigating this risk depends on a sound knowledge of flow mechanisms, well located and constructed wells, an effective management, suitable policies and the desire to conserve the aquifer. To this end, a comprehensive geological model is essential. The single most important question that the geological model should address is the degree and nature of the connection of the aquifer to the sea. Differences in the connection explain why apparently similar coastal aquifers display very different salinitzation behavior. Some aquifers salinize with moderate pumping (eg. Tordera and Llobregat deltas) whereas others sustain large extractions with lower vulnerability to seawater intrusion (eg. Ter delta). However, the characterization of such a connection is not easy given the lack of onshore-offshore geological mapping potential pathways for seawater contamination. This thesis is focused on sequence stratigraphy, which is necessary to understand the onshore-offshore aquifer connection, thus modifying the classical hydrogeological conceptual models. The methodology of sequence stratigraphy offers a perspective of delta architecture based on geological controls and processes. Sequence stratigraphic concepts are used in Western Mediterranean deltas in addition to local factors, such as subsidence, uplift and the rate of sediment supply to account for differences in Pleistocene stratigraphic patterns and aquifer preservation. These local factors exert an influence over the shape, slope and thickness of aquifers. Together with the width of the continental shelf, the presence of submarine canyons, faults and thin prodelta layers conditions vulnerability to seawater intrusion. The Quaternary Mediterranean shelf is characterized by high-frequency depositional sequences mainly composed of large-scale regressive wedges with poor or poorly preserved transgressive to highstand intervals. Although the Llobregat delta is an anomaly, it serves as a paradigm of deltaic architecture because of its well preserved transgressive and highstand intervals. The well preserved coarse transgressive deposits are important from hydrogeological point of view. They act as aquifers with high lateral continuity from onshore to offshore providing paths for seawater intrusion.The excellent preservation in the Llobregat delta may be a consequence of Quaternary growth faults, which caused high accommodation space, limiting the action of wave and storm events. The identification of different seismic units and deformation features along the coast makes it possible to distinguish two main morpho-structural sectors. These sectors can be influenced by tectonic movements, which may be intensified by sediment supply changes.Detailed sedimentological, age and paleontological (foraminifera and ostracods) data display a cyclic vertical pattern of facies, including a high degree of reworked sediments. Available ages together with high sediment preservation due to constant subsidence and sediment supply during sea level rises allow us to establish a chronostratigraphic framework. The most significant and widespread erosion were interpreted as occurring during gradual sea-level falls with a frequency of 100 Kyr. glacial-interglacial cycles. However, most of the regressive deposits display complex internal architectures, which suggest the imprint of higher-frequency cycles. The stacking pattern of the modern Holocene delta is controlled by changes in the relative sea-level and in the sediment supply. Paleofloods frequencies controlled by climatic changes and intensified by anthropic activity caused an important progradational pulses in the Llobregat delta and the channel switching with the rapid abandonment of the delta lobes

Geologia del Miocè del Pla de Barcelona

Peer ReviewedPostprint (published version

Estratigrafía y petrología del subsuelo precuaternario del sector SW de la depresión de Barcelona (cadenas costeras catalanas, NE de Iberia)

Las numerosas obras de Ingeniería Civil que se han realizado en los últimos años en la depresión de Barcelona (ampliación del aeropuerto, ampliación del metro y AVE fundamentalmente) han permitido recabar mucha información sobre el subsuelo de esta área. En este trabajo se caracterizan las distintas unidades de subsuelo precuaternarias que aparecen en los numerosos sondeos realizados recientemente en la zona SW de la depresión de Barcelona. Se ha identificado un sustrato triásico formado por areniscas del Buntsandstein y dos unidades de edad Miocena, una basal de carácter continental y otra superior depositada en un ambiente marino. Todas estas unidades fueron fracturadas debido a una tectónica extensiva y, posteriormente, fueron fosilizadas en primer lugar por los sedimentos del Plioceno, que recubren la superficie de erosión messiniense, y finalmente, por el Cuaternario. El análisis de las distintas unidades permite obtener datos sobre la evolución paleogeográfica y tectónica de la depresión de Barcelona durante el Mioceno y el Plioceno.çCurrent building of civil Engineering infrastructures in the Barcelona plain and Llobregat delta (mainly metro and airport extension and high speed train) is providing new geological subsurface data to build better geologic models and understand the basin evolution. This work focuses on the pre-Quaternary units observed in cores. Based on petrographic analyses combined when it was possible with paleontological studies, we identified the lower Triassic Buntsandstein sandstone facies and Miocene continental and marine facies which appear compartmentalized due to extensive deformation. After this extensive episode, Pliocene and Quaternary sediments, which were deposited after the development of successive erosive surfaces, overlay the Triassic and Miocene units. The identification of these units enabled one to improve the interpretation of the tectonic and paleogeographic evolution of the Barcelona plai