Tesis Doctorals - Departament - Dinàmica de la Terra i de l'Oceà

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Influence of Mesozoic structural inheritance on fault reactivation in the central Catalan Coastal Ranges (Catalan Margin, NW Mediterranean). Paleogene and Neogene tectonostratigraphic evolution
(Universitat de Barcelona, 2025-05-16) Marín Pérez, Miquel À.; Cabrera, Lluís; Ferrer García, J. Oriol (José Oriol); Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] The Catalan Coastal Ranges (CCR), located at the NE of the Iberian Peninsula is one of the alpine structural units that limit the Ebro Basin and it constitutes its southeastern boundary. Moreover, this unit is also the onshore portion of the continental margin that bounds the Valencia Trough to the NW. It is nowadays characterized by a NE-SW trending basin-and-range configuration that consists in series of ENE- to NE-striking blocks bounded by major faults displaying a right-stepping en-echelon pattern. The Alpine geological evolution of the CCR is complex and includes up to three main tectonic phases that shaped its distinguishing present-day configuration: (1) a multiepisodic extensional phase from the late Permian to the Aptian, (2) a compressional phase during the Paleogene, and (3) a latest Oligocene- middle Miocene extension. Within this scenario of superimposed tectonic phases, structural inheritance has been previously postulated as a key factor of control on the tectonic evolution of the area. This inheritance has often been related to two main aspects: the general idea of the control exerted by the Mesozoic basin configuration on the Cenozoic tectonic evolution of the area (i.e., the limits of the Mesozoic basin appear aligned to subsequent Paleogene and Neogene structural trends), alongside the proposed negative inversion of Paleogene contractional structures during the Neogene, facts that would explain the present-day configuration of the CCR. However, the particularities and extent of this structural inheritance including the mechanisms driving crustal deformation during contraction and basin formation were still under discussion. These mechanisms are believed to be key in the understanding of an area with potential multiple fault reactivations. While most of the recent studies offer fragmented interpretations, the present Ph.D. thesis covers the central domain of the CCR, between the El Camp Basin in the south to the northeast end of the Valles-Penedes Basin, aiming to provide a comprehensive reconstruction of its tectonic evolution from the Mesozoic to the present-day using a multidisciplinary approach. Special attention was paid to the Gaia-Montmell High for three main reasons. First, this area is characterized by its preserved Mesozoic succession, particularly the presence Jurassic and Cretaceous strata; second, the area would also correspond to the source of sediments of the well-preserved synorogenic successions deposited in the central part of the southeast margin of the Ebro Basin, the previous interpretation of which suggested the presence of a progressive unconformity that recorded the Paleogene tectonic evolution of the CCR; and third, the Gaia-Montmell High corresponds to the relay between two major Neogene structures, the Montmell-Valles Fault System (MVFS) and the El Camp Fault. These three factors make this area of the CCR an appropriate candidate for the proposed objectives. The research involved geological and geophysical analysis together with the review and integration of the available fluid-rock interactions studies in the region, thereby contributing to a refined geodynamic model of the region. The performed investigations comprised the analysis of field data from geological mapping, the collection of structural and stratigraphic data, gathering samples for magnetostratigraphic and provenance analysis, the acquisition of magnetotelluric (MT) data as well as the characterization of fault zones in the different sectors along MVFS. Structural and stratigraphic data (e.g., dip and orientation of bedding and faults) were used for the construction of three structural cross-sections at key locations: the Gaia-Montmell, the Marmellar, and the Cabra sections. MT data acquired along the Gaia-Montmell Section, alongside data from available exploratory wells, allowed the constraint and characterization of the structural styles present in the upper crust. This geological section was balanced via structural restoration techniques, the results of which illustrate the tectonic evolution of the area at two key time- steps: the end of the Late Jurassic-Early Cretaceous extension and the end of the Paleogene compression. Moreover, the magnetostratigraphic and provenance analysis performed in the southeast margin of the Ebro Basin allowed an accurate refinement of the ages of the studied Paleogene formations, hence allowing to constrain the timing of the synorogenic sedimentation and the identification of the source areas. Accordingly, these results made possible a precise reconstruction of the Paleogene compressional deformation. The Cenozoic tectonostratigraphic evolution of the central CCR was highly controlled by its Mesozoic structural inheritance. During the Mesozoic, the MVFS constituted the northwest limit of the Late Jurassic-Early Cretaceous Montmell-Garraf Basin. The northeastern limit of this basin would be located several kilometres north of the present-day Llobregat River valley as suggested by syn-tectonic Paleogene detrital sediments in the Ebro Basin margin next to this area. Moreover, this basin belonged to a larger basin system that included another ENE-trending, SE-dipping basement fault displaying a right-stepped en-echelon arrangement: the Barcelona Fault. Together, the Montmell-Garraf and the Barcelona basins conformed the proximal to, perhaps, the initial necking domain of the continental margin that separated the Ebro Block from the Alpine-Ligurian Tethys. Two successive episodes of tectonic inversion characterized the Cenozoic evolution of central CCR. The first one, related to the convergence between Iberia and Eurasia during the Paleogene, reactivated the MVFS as compressional. As a result, major NW-directed basement footwall shortcuts including the Gaia-El Camp Thrust developed. The precise timing of inversion and thrust emplacement during this period has been provided by the tectono-stratigraphic analysis involving provenance analysis and magnetostratigraphic dating performed in synorogenic sediments deposited in the SE margin of the Ebro Basin. These analyses reveal that the inversion of the Montmell-Valles Faults System started in the Bartonian and continued up to the late Priabonian, and that the emplacement of the Gaia-El Camp Thrust took place from early to late Priabonian. A rapid increase of the sedimentation rates characterized this second contractional pulse, followed by a decrease during late Priabonian, which can be interpreted as the prelude of the end of the Paleogene compressional phase in the area. The second episode of tectonic inversion occurred when the previously formed compressional structure during the Paleogene became reactivated as extensional during the Neogene. In the Gaia- Montmell High, this phase was characterized by a limited reactivation of the Montmell Fault and the transmission of the extension to the formation of a hangingwall short-cut: the Baix Penedes Fault. The reactivation of the Gaia-El Camp Thrust was also attested by the development of an array of extensional faults in the backlimb of the Carme-Cabra Anticline that corresponds to the NE-end of El Camp Fault. This episode of negative inversion resulted in the development of accommodation zones between the major faults characterized by the presence of relay ramps with breaching faults. The reactivation of the MVFS showed differences along strike during both phases of tectonic inversion. These differences appeared to be related to the decoupling of the deformation from surface to depth due to its interpreted kinked-planar geometry and the change of fault dip from >60º at surface to 30º at depth. The deeper and less dipping panels of the fault system were reactivated (as contractional during the Paleogene and as extensional during the Neogene), whereas the highly dipping shallower parts of the fault system only show localized reactivations. The ability of the Mesozoic faults to be reactivated and the spatial distribution of the deformation appear also influenced by differences the inherited fault rocks. The observations from fluid-rock interactions denote that, alongside the fault geometries, different rock-host lithologies (granites and siliciclastic metasediments in the north of the MVFS versus carbonate rocks in the central and southern sectors) controlled the type of mineral precipitation and cementation product of fluid circulation. These resulted in changes in the mechanical properties of the resulting fault rocks (gouge versus cemented breccias) along the fault trend, significantly controlling its reactivation. Tectonic inversion was effective in areas with non-cohesive fault gouge in the pre-existent fault core (areas with Paleozoic granites and siliciclastic metasediments characterized as host-rock), whereas fault reactivation appeared limited or even precluded in areas where the pre-existent damage zone was formed by highly cemented and cohesive breccias (areas with thick Mesozoic carbonate successions). The results of the present research and the multidisciplinary approach adopted herein offer a refined tectono-stratigraphic framework for the central Catalan Coastal Ranges from the Mesozoic to the present-day and provide a detailed interpretation of the influence of the Mesozoic structural inheritance. It emphasizes the importance of fault geometries and the effect of the lithological heterogeneities on the resulting mechanical properties of the inherited fault zones as key factors on fault reactivation and the transmission of the tectonic stresses in the studied area.
Contaminación por basuras marinas en ecosistemas costeros: análisis multiescalar de sus fuentes, dinámicas y riesgos asociados en manglares, playas y lagunas de Latinoamérica y el Caribe
(Universitat de Barcelona, 2025-06-27) Garcés Ordóñez, Ostin; Canals Artigas, Miquel; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[spa] La contaminación por basuras marinas es una problemática global que afecta a los ecosistemas marinos y costeros, provocando pérdida de biodiversidad, degradación ambiental y disminución de servicios ecosistémicos clave. En las zonas costeras, los ecosistemas de transición, como los manglares, las playas y las lagunas costeras, son particularmente vulnerables a este tipo de contaminación, ya que están expuestos tanto a fuentes terrestres como marinas, con basuras tanto de procedencia local como lejana. Su acumulación en zonas sensibles está influenciada por factores hidrodinámicos, antropogénicos y ecológicos, generando impactos negativos y riesgos ambientales. Comprender y generar conocimiento científico sobre estos mecanismos es esencial, ya que puede contribuir a la gestión ambiental y a la formulación de políticas públicas orientadas a soluciones desde la fuente y a la conservación de los ecosistemas. En América Latina y el Caribe, los ecosistemas costeros, de gran valor ecológico y socioeconómico, ofrecen un contexto ideal para generar conocimiento científico aplicable a la gestión ambiental y la formulación de políticas públicas. Esta tesis recopila cinco artículos de investigación y uno de revisión, centrados en la contaminación por basuras marinas en la región, a través de casos de estudio en manglares, playas y lagunas costeras, tanto en costas continentales como insulares. Se analizan las fuentes, la composición, las abundancias, los riesgos ambientales, y su relación con las condiciones ecológicas y antrópicas de cada entorno. El análisis se inicia con un enfoque amplio sobre macrobasuras en manglares y playas, continúa con un abordaje más específico sobre las botellas de plástico en asentamientos humanos y playas, y finaliza con estudios de microplásticos en lagunas costeras. Estas investigaciones identifican los principales factores que generan la contaminación por basura marina, en los cuales se requiere definir acciones y políticas específicas.
Monitoring floating microplastics in coastal wasters of the Western Mediterranean Sea
(Universitat de Barcelona, 2024-03-22) De Haan, William P.; Sanchez-Vidal, Anna; Canals Artigas, Miquel; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] Plastic waste is a global threat to ecosystems, especially in marine systems where most of the threats from plastics occur. The Mediterranean Sea is one of the most polluted basins due to marine litter, particularly plastics. Although there has been progress made since the first reports were published almost five decades ago, there are still open questions regarding the sources, distribution, and fate of plastics in the ocean and the Mediterranean Sea, and monitoring approaches are still far from being fully harmonized and operational. This Thesis is structured as a collection of five research articles that aim to evaluate the current state, properties, spatiotemporal trends, and sources of floating plastic waste, particularly microplastics, in coastal areas of the Western Mediterranean Sea. After a general introduction, the first study evaluates the current state and properties of floating microplastics in the NW and SW Mediterranean Sea. This study also evaluates the incorporation potential of microplastics into in-situ captures marine organic aggregates which may contribute to their export to the deep-sea. There is a need to expand our knowledge about the processes that determine the distribution and fate of plastics in nearshore coastal areas, where little data has been collected due to the limited accessibility of scientific platforms. Therefore, in the third study, we design and implement a novel net, the “Paddle trawl”, that can be towed from recreational rowing platforms that can be used in citizen science in nearshore coastal areas. This study provided the basis for the third study, where we applied this methodology to a large-scale citizen science project along nearshore areas (< 1 km) of the Catalan coast, which gives us insight into the spatiotemporal intra-annual variability and the properties of microplastics, as well as the factors that determine their distribution. Likewise, the fourth study focuses on monitoring microplastics but considers wider temporal scales to detect long-term trends. We make use of a regional backtracking model that gives us insight into the particular sources and the sources of spatiotemporal variability of microplastics along the coastal areas (1 – 4 km from shore) along the North Catalan coast. Finally, in the fifth study, an assessment of the concentrations, fluxes, and properties of artificial turf fibers is presented that evaluates the state of this particular type of plastic pollutant in surface waters of the NW Mediterranean Sea and rivers. It is important to continue expanding our knowledge of the processes that determine the distribution and fate of plastics, especially in nearshore coastal areas. The studies presented in this Thesis provide valuable insight into the current state of floating plastic waste in the Western Mediterranean Sea and offer new methodologies for monitoring and evaluating the impact of plastic waste in coastal areas.
Fluxos de partícules i metalls als marges continentals del sud-est de la península Ibèrica
(Universitat de Barcelona, 2024-01-26) Tarrés Mercader, Marta; Canals Artigas, Miquel; Sanchez-Vidal, Anna; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[cat] Les partícules que sedimenten en el medi marí tenen un paper clau en el cicle biogeoquímic d’un bon nombre d’elements i, per tant, són essencials per al funcionament de l’ecosistema. L’estudi dels fluxos de partícules permet entendre els processos que controlen la transferència de matèria i dels elements químics associats cap al fons marí, on poden quedar emmagatzemats per llargs períodes de temps. En aquest context, esclarir el transport de partícules als marges continentals, situats entre el continent i la conca profunda, és altament rellevant per millorar el coneixement sobre aitals processos i també per encarar no pas pocs reptes ambientals. Aquesta Tesi se centra en la dinàmica del transport de partícules sedimentàries als marges continentals dels golfs de Vera i d'Almeria, a la Mediterrània sud-occidental. Aquests marges estan entallats per un seguit de canyons submarins de característiques ben diverses. De tots ells, s’han investigat el canyó d’Escombreras, el sistema Garrucha-Almanzora i el canyó d’Almeria, i també el talús obert i el peu del talús. L’ús d’un conjunt de paràmetres indicatius, com la magnitud dels fluxos, la mida de gra, la composició elemental, i el contingut en metalls (Al, Fe, Ti, Co, Cu, Mn, Ni, Pb i Zn) i As, ha permès caracteritzar les partícules que sedimenten i els sediments del fons marí, i analitzar la dinàmica de les partícules, per determinar finalment els factors que regeixen llur variabilitat espacial i temporal. A aquest efecte, també s’han tingut en compte els forçaments externs, atmosfèrics i oceanogràfics, i les activitats antropogèniques susceptibles de condicionar la composició i el comportament de les partícules. En aquest context, l’ús de traçadors, com els isòtops del carboni i del Pb, i biomarcadors específics, pot ajudar a respondre a algunes preguntes rellevants: (i) Quin és l’origen i la composició de la matèria orgànica en uns marges continentals amb escasses aportacions fluvials, com els investigats? i (ii) Quina és la contribució del dipòsit de residus miners de la badia de Portmán, al sud de Múrcia i, especialment, de la seva extensió submarina, al flux de metalls cap al marge distal? La recerca efectuada constata que les tempestes, amb un augment de l’onatge i dels corrents, són els principals dinamitzadors del transport de sediments cap al marge profund. L’arribada de material de la plataforma continental resuspès explica, en gran mesura, la variabilitat temporal dels continguts de metalls i As als canyons submarins d’Escombreras i, sobretot, d’Almeria. Les tempestes també poden influir en l’origen i la composició i de la matèria orgànica exportada, com ho mostra el transport de detritus de Posidonia oceanica cap al canyó d’Escombreras. Les condicions ambientals abans i durant les tempestes modulen la magnitud i la composició dels fluxos de partícules. Entre aquestes condicions s’hi compten les característiques de la columna d’aigua, les aportacions fluvials i la producció primària. Les especificitats de cada tempesta, com ara la direcció i el règim d’onatge, la velocitat i la direcció dels corrents, i la seva durada, també afecten molt notablement a la remobilització, el transport i l’acumulació de partícules sedimentàries i matèria orgànica, en funció de la seva mida de gra, densitat i forma. Al peu del talús, a 2.500 m de profunditat, la producció primària és el factor principal de control dels fluxos de partícules. Certs forçaments antropogènics, com la pesca d’arrossegament de fons, també poden afavorir l’exportació de partícules, com s’ha comprovat al sistema de canyons de Garrucha-Almanzora. L’activitat industrial a la franja costanera propera deixa sentir tanmateix els seus efectes sobre la composició dels fluxos de partícules al marge continental profund, com ho demostra el cas concret del canyó d’Escombreras, en que una de les principals vies d’entrada de Pb antropogènic es produiria per la intermediació del transport atmosfèric. Els resultats obtinguts evidencien que les partícules sedimentàries són vectors de transferència de contaminants metàl·lics cap als canyons submarins i el marge continental profund, en sentit ampli. Aquesta Tesi demostra, per altra banda, la complexitat de les interaccions entre els factors i processos que governen la composició i la dinàmica dels fluxos de partícules i la sedimentació en els marges continentals i les conques pregones adjacents. També és una contribució al coneixement d’una àrea geogràfica encara poc estudiada. Els nous coneixements aportats poden ser útils per a una gestió informada i sostenible de l’ecosistema marí.
Multi-hazard assessment and risk management in volcanic islands
(Universitat de Barcelona, 2023-10-25) López Saavedra, Marta; Martí i Molist, Joan, 1957-; Pedrazzi, Dario; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] Our planet is impacted by diverse natural and human-induced events, including weather-related events (floods, droughts, forest fires, etc.) and geological events (landslides, earthquakes, volcanic eruptions, etc.). These events disrupt the geosphere and the biosphere. Understanding these hazards is crucial to anticipate and provide warnings to exposed populations. Interconnections between phenomena are being discovered, such as volcanic eruptions impacting the ocean, atmosphere, and climate. These events can lead to economic losses, fatalities, infrastructure destruction, and mental health burdens. The frequency and magnitude of these events, especially weather-related hazards, are increasing due to climate change. Preparation, information, and decision support systems are needed to mitigate their impact. Volcanic islands are highly vulnerable due to their isolation, fragile economies, and multi- hazard nature, being often the source of complex successions of disastrous events. Moreover, climate change exacerbates vulnerability by increasing the magnitude and frequency of these events, as well as contributing to rising sea levels. Anticipating and preparing for such events are crucial to ensuring safe and sustainable lifestyles. The island of Tenerife in the Canary Archipelago is an excellent example of where both cascading non-extreme and extreme hazards have occurred along its history and could occur again in the future. Both phonolitic and basaltic volcanic eruptions on Tenerife have occurred frequently during the Holocene. These eruptions cause ash falls, lava flows, and explosive projections of pyroclasts. They also generate seismic activity, risking damage to buildings and infrastructure, which adds to the tectonic seismicity experienced by the region, with a lower magnitude and intensity. Therefore, the probability of a volcanic eruption on the island in the next few years is not negligible. This is higher for basaltic eruptions along the rift zones, as they have been all the historical eruptions, which today could have a significant affectation on the surrounding areas, as most of them are now highly populated. However, the probability of an eruption from Teide is also high, assuming the level of current activity and the fact that its last eruption occurred 1,000 years ago. In this case, volcanic and associated hazards would be of much higher intensity and could affect mostly the northern side of the island, in particular the Icod and La Orotava valleys. In addition, annual floods and torrential episodes, triggered by storms, produce severe human and economic losses and affect cities like Santa Cruz de Tenerife and San Cristóbal de La Laguna. Sediment transport, debris flows, and rock falls occur during these events. The island also experiences phenomena such as Sahara haze, forest fires, and the possibility of tsunamis in the surrounding Atlantic Ocean. On the other hand, a cascading sequence involving a caldera-forming eruption, high-magnitude seismicity, mega-landslides and tsunamis occurred at least twice during the construction of this island and could occur again in the future. Its population growth and consequent urban expansion, especially focused on the construction of tourist infrastructure on the coast, lead to the population encroaching on areas with higher risk of these events. However, scientific knowledge and protocols mainly focus on individual hazards and risks. Predicting the outcomes of multi-hazard scenarios remains challenging. The multi-hazard concept emerged in the 1990s to address this issue. However, conflicting perspectives hinder its implementation in disaster reduction policies. This contribution presents a methodological development based on scientific knowledge for decision-making in vulnerable regions facing natural hazards, using Tenerife as a case study. To accomplish this, we first explored and clarified the issues surrounding the implementation of a multi-hazard perspective in disaster risk reduction strategies to understand the main challenges of this approach. Following this, a comprehensive long-term multi-hazard assessment was conducted for the island of Tenerife, covering both non-extreme and extreme events. For the former, a Bayesian-inferred Event Tree framework was applied to calculate the probabilities of natural hazards in Tenerife based on its historical event records from 1496 to 2020. On the other hand, to address the existing gap in risk management protocols regarding cascade effects for extreme events, we simulated the extent and potential impact of a multiple, extreme geohazard episode similar to the last recorded one that took place on the island of Tenerife around 180 ka. According to these analyses, the island is facing a high probability of future floods, which have caused the most significant human and economic losses to date in the island. Furthermore, a potential caldera-forming eruption in Teide could generate Pyroclastic Density Currents that would cover almost the entire island, along with high-magnitude seismic activity that could trigger large-scale landslides in the north resulting in tsunami waves reaching up to 200 meters in height. Land management based on long-term assessments of multiple hazards, as carried out here, is crucial to strengthen Tenerife's current risk mitigation plans. This will enable the sustainable development of the island through the sustainable use of currently exploited energy and material resources, as well as through a two-way relationship between sustainable tourism exploitation and the education of its population, both focused on the conservation of its geological heritage. All of this will contribute to increasing society's resilience to multiple hazards in the context of climate change, without having to forego the opportunities offered by volcanic regions like Tenerife. For this reason, this doctoral thesis emphasizes the importance of establishing a cross- cutting, climate change-oriented, socially inclusive, and scientifically based multi-hazard risk management system. This system should be aligned with the critical needs and solutions of society.
Aplicación de tecnologías avanzadas para la caracterización del depósito de vertidos mineros de la bahía de Portmán, Murcia (España)
(Universitat de Barcelona, 2023-05-19) Baza Varas, Andrea; Canals Artigas, Miquel; Frigola Ferrer, Jaime I.; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[spa] La afectación de ambientes costeros por vertidos mineros con altos contenidos metálicos procedentes de la explotación de sulfuros constituye un problema de alcance mundial. Aunque la mayoría de residuos mineros son almacenados y gestionados en tierra, en determinadas localidades buena parte de los mismos acaba llegando a las costas y al lecho marino, tanto directa —es decir, a propósito, puesto que representa una opción de vertido rápida y barata— como indirectamente. Esta Tesis Doctoral contribuye al conocimiento de los depósitos de vertidos mineros costeros y submarinos, más inaccesibles y mucho menos conocidos que los depósitos acumulados en tierra. Nos hemos centrado en el depósito de vertidos mineros de la bahía de Portmán en La Unión, Murcia, formado por la acumulación de unos 57 millones de toneladas de residuos vertidos a lo largo de 33 años (1957-1990) de actividad minera. En primer lugar, hemos abordado la caracterización multiparamétrica de los depósitos, mediante el análisis de testigos recuperados en la plataforma continental interna. Se han medido sistemáticamente las propiedades físicas (densidad, susceptibilidad magnética y velocidad de las ondas P) y geoquímicas (composición elemental) de los materiales, con el fin de determinar su variabilidad interna y documentar la evolución del área submarina afectada, así como las consecuencias medioambientales asociadas como, por ejemplo, la extinción local por enterramiento de las praderas de la fanerógama Posidonia oceanica, endémica del mar Mediterráneo. En segundo lugar, se examina el estado de oxidación de dos elementos químicos clave: el arsénico (As) y el azufre (S), valiéndonos para ello de un útil tan potente como el Sincrotrón ALBA. El primero, especialmente, tiene una gran relevancia ecotoxicológica. Sin descartar del todo la hipótesis clásica de que algunos minerales sulfurados del As poco estables presentes en el depósito de residuos, como el oropimente (As2S3) y el realgar (AsS), procediesen de las menas explotadas —para lo que sería también necesario que hubiesen sobrevivido al tratamiento por flotación ácida—, postulamos la hipótesis de la formación postdeposicional in situ, avalada por los datos proporcionados por el sincrotrón y por la presencia de compuestos orgánicos sulfurados en el mismo depósito, debidos a la actividad de bacterias sulfatoreductoras. La presencia de estos minerales en el depósito tiene importantes consecuencias en relación con la movilidad y la biodisponibilidad del As, puesto que su formación reduce la liberación de este elemento al medio circundante. Las contribuciones de esta Tesis Doctoral deberían ser tenidas en cuenta en la toma de decisiones por parte de los organismos competentes acerca de las posibles acciones de remediación ambiental. Algunas acciones ya fueron puestas en práctica desde la finalización de la actividad y de la acumulación de los vertidos mineros asociados (en tierra), pero fueron paralizadas debido a la gran controversia generada. Además, deberían incluirse también como posibles acciones la no actuación o una actuación blanda de remediación. Esta Tesis Doctoral aporta una nueva visión que suma posibilidades de actuación para la remediación ambiental de la zona. Al respecto, durante la elaboración de la Tesis Doctoral ha habido un intercambio fluido con la Demarcación de Costas de Murcia, del MITECO, la cual ha apoyado y facilitado en todo momento las investigaciones realizadas, incluso en lugares de acceso restringido. El caso de estudio de Portmán podría servir de referente para otros lugares del mundo —que no son pocos— afectados por problemáticas semejantes.
Afloraments fracturats digitalitzats. Avaluació de tècniques remotes en models DFN i aplicació de Machine Learning
(Universitat de Barcelona, 2023-02-23) Blanco Núñez, Laura; Muñoz, J. A.; Gratacós Torrà, Òscar; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] he ongoing digital transition results in millions of data points gathered every day. Within the context of geosciences, the use of digital remote sensing techniques is increasing. Machine learning techniques are interesting alternative to support the processing and interpretation of large amounts of collected data. The present industrial PhD focuses on the analysis of fractured outcrops using remote sensing techniques and machine learning with two specific objectives; (1) the evaluation of how representative are remote sensing techniques to identify fractures and subsequently represent them in discrete fracture network (DFN) models; and (2) the use of classification machine learning models in processes associated with fractured environments, such as block falls. METHODOLOGY: The first case study, evaluates remote techniques for data gathering (Terrestrial Laser Scanner (TLS) and Photogrammetry (SfM)). The experiment was carried out in active La Fou quarry in Barcelona. Fractures surfaces were reconstructed from a large number of remotely captured data (Santana et al., 2012; Geyer et al., 2015), the fractures network is characterized by multiple families (García-Sellés et al., 2018). With these results, and those collected with manual scanline techniques, three-dimensional (DFN) models are constructed. One model is built using data from each capture technique (DFNTLS, DFNSfM and DFNscan-line), where the main geometric properties of the fractures will be represented. Finally, the fracture trace maps are generated to calculate the porosity and permeability using aperture data for each of the scenarios. The second case study is aimed at automating the classification of block falls. The study area is located on the historically unstable Degotalls escarpments, close to the access road of the Monastery of Montserrat. Monitoring of these escarpments using periodic TLS scanning began in 2007, as a result of multiple falling block episodes starting back in 2001, which affected the Monastery car park (limiting access to the Sanctuary on several occasions). The methodology consists of aligning two scans or point clouds of the same outcrop, captured at two different times, aiming to detect clusters of differences between the scans. Subsequently, each cluster of differences is visually reviewed to identify and classify block falls. The methodology developed in this Thesis, incorporates machine learning algorithms to automate this last stage of identification and classification of fallen blocks. RESULTS: In the first case study, the main geometric properties for each fracture captured and processed are position, orientation, height, and length. These can be used to characterize fracture statistics such as spacing, intensity, P10, P20, P21 and P32, among others. For individual families are identified Family I WNW-ESE, Family II NNW/SSE, Family III, N-S and Family IV NE-SW. The technique with the highest number of characterised fractures was TLS with more than 52,000, followed by photogrammetry with 1,094 and finally scan-lines with 398 fractures measured. Fracture height and length are very variable, average values range from a few centimetres to 18m. TLS average lengths are less than one metre. The spacings between fractures in Family I have centimetric sizes and the rest of the families have more variable spacing from centimetric to 6m. Photogrammetry obtains values that sometimes double or triple the rest of the techniques. Furthermore, with the input of the fracture openings into the model, trace maps have been generated and porosity and permeability value of the fracture network has been obtained. In the three DFN models, the average porosity value obtained is between 5.4-5.7% and the average permeability values between 4x105 mD and 6.2x105mD. In the second case study, the results generated from the combination of 11 classifier algorithms and 15 resampling methods, allow us to identify the best predictive combination for the classification of fallen blocks, according to the temporal period and steepness. In Degotalls-E, from approximately 5,800 clusters identified by each monitoring, a 98% reduction is achieved in the number of clusters to be validated, between False Positives (FP) and True Positives (VP), understanding (VP) as the real block falls. In Degotalls-N the reduction would be 80.16% for a complete identification, while for identifying 96% of the real block drops, the reduction would be 90%, from a population of about 3,700 initial clusters. It is also important to note that the validation of the task by comparing high-resolution images has significantly increased the reliability of the results obtained. CONCLUSIONS AND THE WAY FORWARD: In the evaluation of the representativeness of using remote sensing techniques for the construction of DFN models, the results suggest that data captured and processed with remote techniques are represented in DFN models with very acceptable results. The remote sensing technique that more accurately approximates the outcrop depends on the geometric property that need to be captured and represented. The layout of the outcrop and fracture orientations also influence data capture. When analysing the results for permeability and porosity of the fracture network, similar values are obtained for all three DFN models. Consequently, the geometrical differences of the models by each technique do not greatly influence the estimation of these values, showing equivalent fracture models in the case of the Fou. The DFN models, which are currently obtained using remote sensors allow the uncertainties generated in the three- dimensional regional models to be characterized measured and reduced. This will be the obhect of further research both academic and industrial. Finally, the work carried out at Montserrat shows that the application of remote techniques in the field of digitisation and the identification of differences during the monitoring of outcrops is precise and of high resolution. This new methodology integrating machine learning algorithms for the identification and classification of fallen blocks demonstrates, especially in Degotalls-E, that applying this system generates acceptable results in terms of True Positive (VP), False Positive (FP) and False Negative (FN). This automation will eventually allow to implement a block drop alert system, with an integrated TLS device, which allows and facilitates the detection of precursors, involving an application of the technique used during the development of this thesis in the industrial world.
Holocene Climate variability in the Western Mediterranean Sea: an integrated oceanic and atmospheric perspective
(Universitat de Barcelona, 2022-02-17) Català i Caparrós, Albert; Cacho Lascorz, Isabel; Pena González, Leopoldo David; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] The Mediterranean region is very sensitive to modern climate variability. Located in a temperate subtropical climatic zone and surrounded almost entirely by large continental masses, the Mediterranean region climate and oceanography are largely controlled by the climatic variability of the subtropical and subpolar atmospheric systems. The western Mediterranean Sea exchanges seawater through the Strait of Gibraltar with the Atlantic Ocean, where inflowing surface waters from the Atlantic Ocean enter this region. In contrast, Mediterranean waters outflow into the Atlantic at depth, a net exchange of heat and salts that is very sensitive to present and past climatic changes. This thesis presents a new approach to studying and understanding past natural climatic variability of the Mediterranean region by analysing the changes in the ocean and the atmosphere during the Holocene. This thesis aims to improve our understanding of the mechanisms and climatic/oceanographic responses that have modulated the southern Iberian Peninsula climate during the last 11.700 years. In addition, relevant methodological advances in «state-of-the-art» geochemical tools are implemented here to study past hydrological changes and, for the first time, these methods are validated using a modern time series record in the Alboran Sea. This thesis has been built on four main key points: First, a new high-resolution deglacial and Holocene Sea Surface Temperature (SST) reconstruction is presented for the Alboran Sea (western Mediterranean), based on Mg/Ca ratios measured in the planktonic foraminifera Globigerina bulloides. This new SST record is evaluated by comparison with other Mg/Ca–SST records and previously published alkenone–SST reconstructions from the same region. The comparison shows a high degree of coherence between the different Mg/Ca–SST records but strong discrepancies compared to the alkenone– SST records. We argue that these discrepancies arise from differences in the sensitivity of the proxy–response to environmental changes. A working hypothesis in this thesis is that the discrepancy in SSTs reflects a resilience strategy of planktonic foraminifera G. bulloides, shifting its main growing season into the colder SST upwelling season (spring) thus explaining the shorter deglacial warming in Mg/Ca records compared to alkenones. Interestingly, Holocene short–term SST variability is larger in the Mg/Ca–SST record than in the alkenone–SST records. It is proposed that the larger Mg/Ca–SST variability reflects spring temperature variability, while the smoothed alkenone–SST variability represents averaged annual temperatures. The Mg/Ca–SST record differentiates the Holocene into three periods: (1) the Early Holocene (11.7 – 9 kyr BP) with the warmest SST values recorded; (2) the Middle Holocene (9 – 4.2 kyr BP) characterised by a continuous cooling trend that culminated in the coldest Holocene SST at around 4.2 kyr BP; (3) the Late Holocene (4.2 kyr BP to present) characterised by the lack of clear cooling/warming trends but enhanced millennial-scale variability. This SST evolution is discussed in the context of the changing physic-chemical properties of inflowing Atlantic surface water associated with changes in the North Atlantic circulation conditions as well as with regional hydrographical and atmospheric changes. It is proposed that a close mechanistic link between North Atlantic circulation patterns and the inflow of surface waters into the Mediterranean played a crucial role in controlling the Holocene climatic variability of this region. The second key point of this thesis is based on developing a new fast, efficient and reliable method to prepare lithogenic sediment samples for the radiogenic isotope analysis (87Sr/86Sr, 143Nd/144Nd, 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb). Two new methods are developed: the first is targeted to achieve a total digestion of the lithogenic fraction, whereas the second is aimed at separating and purifying the different isotopic systems (Sr, Nd, Pb) in the lithogenic fraction by using a one single pass chromatographic column with the DGA resin. The new chromatographic separation method for the Sr, Nd and Pb is developed in a single step using a controlled-pressure vacuum system applied to each column. The third key point of this thesis is based on a novel approach to studying the provenance of the lithic sediment fraction captured by a sediment trap between 1997 and 1998 in front of the Malaga coast. This sediment trap captured the sinking lithogenic particles in the Alboran Sea with an approximately bi-weekly resolution for a complete year; thus, an annual record of changes in the amount and nature of particles was obtained. A systematic provenance study is developed using isotope geochemistry techniques to characterise the source area of the lithogenic particles arriving in the Alboran Sea. In particular, the radiogenic isotopes of 87Sr/86Sr, 143Nd/144Nd, 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb were measured in the lithogenic sediment fraction, and the measured isotopic ratios signal were compared with the potential source areas and their corresponding isotopic endmember values. In this sense, due to the singular location of the Alboran Sea, lithogenic particles are typically introduced by both from fluvial discharges and/or atmospheric dust plumes from the Sahara desert. These new Sr and Nd isotope results clearly indicate that river discharge is the primary source of sediments arriving into the sediment traps. Even though there is evidence for a degree of presence of Saharan dust signal in all the samples, this endmember is generally significantly diluted by the sheer mass of sediments transported by rivers. Only during periods of the year with minimum river runoff, it is possible to clearly distinguish the Sahara isotopic signature in the lithogenic sediment samples. A comparison of the newly generated radiogenic isotope records with instrumental rainfall gauge records in Malaga and the Guadalhorce river discharges (located in front of the sediment trap) indicates that the observed variations in the isotopic composition of terrigenous materials (particularly Sr isotope ratios) are closely linked to the rainfall and river discharges. Therefore it is now possible to clearly differentiate through the 87Sr/86Sr ratio those events when the first rains occurred after the dry season (autumn and early winter), especially those associated to the torrential events and also those periods at the end of the rainy season followed by dry summer conditions (late winter to autumn). The fourth point takes advantage of the mechanistic changes described in the radiogenic isotope measurements in present-day sediment traps as a response to changes in rainfall patterns in the western Mediterranean Sea. Using these new results as a present-day analogue, it is possible now to extrapolate this isotopic mixing model to reconstruct past changes in rainfall patterns during the Holocene. With this goal in mind, in this thesis has been measured 87Sr/86Sr, 143Nd/144Nd, 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb isotope ratios in the lithogenic fraction of marine sediments, at the same core site located in the Alboran Sea where the Mg/Ca-SST were measured. By applying the radiogenic isotope mixing models developed for the sediment traps, it is shown that a relatively constant fluvial discharge source of sediments during the Holocene at this location. Moreover, the elemental composition of the bulk sediment measured on the XRF- core scanner is statistically treated using the principal component analyses. This treatment reveals that Zr and K are potentially affected by hydrological changes. Based on the new measurements of radiogenic isotopes in lithogenic sediments as well as bulk XRF analysis, we can clearly subdivide the Holocene into three main climatic periods as defined by changes in the rainfall patterns: (1) the Early Holocene (11.7 – 7.6 cal kyr BP), described as relatively constant rainfall regime, reduced erosion and transport of fluvial sediments towards the sea; (2) the Middle Holocene (7.6 – 4.2 cal kyr BP) which is described as a transitional period marked by a progressive increase in erosion and sediment transport by rivers, potentially as a response to a regional aridification increase and/or enhanced torrential character of the rains, reaching a maximum expression in the sedimentary record at around 4.2 cal kyr BP. (3) the Late Holocene period (4.2 – 0 cal kyr BP) is punctuated by stronger millennial-scale variability compared to the previous intervals. It is argued that this last period corresponds to the establishment of rainfall patterns analogue to present-day conditions.
Yacimientos de ámbar del Cretácico de la Cuenca del Maestrazgo: tafonomía, bioinclusiones y paleoecología
(Universitat de Barcelona, 2023-02-01) Álvarez Parra, Sergio; Delclòs Martínez, Xavier; Peñalver Mollá, Enrique; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[spa] El objetivo de esta Tesis Doctoral es el estudio de los yacimientos de ámbar de la Cuenca del Maestrazgo con foco en la tafonomía, el paleoambiente, el contenido paleobiológico y la paleoecología. En esta cuenca se ha hallado ámbar con bioinclusiones en cuatro yacimientos: Ariño (Albiense inferior), San Just (Albiense superior), Arroyo de la Pascueta (Albiense superior) y La Hoya (Cenomaniense inferior). Una línea de investigación principal ha sido el estudio tafonómico del ámbar del nivel AR-1 de Ariño. Este nivel se localiza en la Mina Santa María (Ariño, Teruel), se ha asignado a la Formación Escucha, se ha interpretado como una llanura pantanosa bajo un clima tropical o subtropical y ha proporcionado un rico y diverso registro fósil. Además, en este nivel se han diferenciado una capa inferior con piezas de ámbar de raíz in situ en relación con el lugar de producción de la resina, y una capa superior rica en ámbar aéreo con bioinclusiones. El registro de bioinclusiones del ámbar de Ariño incluye insectos de 11 órdenes diferentes, un fragmento de pluma de dinosaurio y pelo de mamífero. Las características tafonómicas del registro fósil del yacimiento de Ariño, correspondiente al nivel AR-1, han permitido tipificarlo como autóctono-parautóctono. Las peculiaridades geoquímicas y de conservación del ámbar de Ariño podrían apuntar hacia un paleoambiente en el que los árboles resiníferos vivieron bajo un fuerte estrés ambiental, quizás relacionado con encharcamientos o inundaciones seguidos de desecaciones de forma periódica. El estudio pluridisciplinar del registro fósil del yacimiento de Ariño ha proporcionado información clave sobre sus características paleoecológicas. Los yacimientos de ámbar de San Just (Utrillas, Teruel), Arroyo de la Pascueta (Rubielos de Mora, Teruel) y La Hoya (Cortes de Arenoso, Castellón) se han asignado al “Grupo Utrillas” y comparten características tafonómicas y paleoambientales. Los tres yacimientos se han interpretado como parautóctonos y sus paleoambientes se han relacionado con lagunas costeras bajo un clima árido. El ámbar de San Just es el más rico en bioinclusiones de la Cuenca del Maestrazgo, e incluye insectos de 12 órdenes diferentes y fragmentos de plumas de dinosaurio. Además, el yacimiento de San Just es la localidad tipo de 26 especies de artrópodos. Los ámbares de Arroyo de la Pascueta y La Hoya son pobres en bioinclusiones. Se han observado diferencias entre los registros de bioinclusiones de los ámbares de Ariño y San Just, probablemente debido a las diferencias en sus edades y paleoambientes. Se han identificado coocurrencias taxonómicas a nivel de especie en varios ámbares de la península ibérica, lo que puede indicar una posible conexión entre los bosques resiníferos de estas áreas. Como se ha indicado en investigaciones anteriores, los registros de bioinclusiones de los ámbares de la península ibérica en general, y de la Cuenca del Maestrazgo en particular, muestran coocurrencias de géneros de insectos con los ámbares del Barremiense del Líbano y del Cenomaniense de Myanmar. A partir de los análisis espectroscópicos y geoquímicos de los ámbares de la Cuenca del Maestrazgo se ha inferido que los árboles productores de resina en esta región durante la mitad del Cretácico pertenecieron a la familia de coníferas Araucariaceae. El Cretácico fue un periodo en el que se dieron las condiciones ambientales adecuadas para la producción en masa de resina, además del depósito de las piezas de resina resultantes, al menos en algunas regiones, como en la Cuenca del Maestrazgo durante la mitad del Cretácico. Los factores abióticos y bióticos implicados probablemente estuvieron interrelacionados. La aplicación de técnicas bioinformáticas en el estudio de la distribución de bosques resiníferos podría proporcionar nueva información sobre los factores clave involucrados en la producción en masa de resina.
Geophysical and geological characterization of fault-controlled geothermal systems: The Vallès Basin case of study
(Universitat de Barcelona, 2023-01-20) Mitjanas Colls, Gemma; Ledo Fernández, Juan José; Queralt i Capdevila, Pilar; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] Geothermal energy is a renewable source of energy that harnesses heat from the Earth's interior. Temperature increases with depth, defining the geothermal gradient, which can be variable depending on the geological context. The geological setting of western Europe favors a relatively high geothermal gradient that could be exploited to generate electricity or for its direct use, for example, for its application in industry, greenhouses, or heating systems. In each of these cases, geothermal could favor the community's energy independence and reduce the use of polluting energy sources. To appropriately exploit areas with a significant geothermal gradient, it is essential to know the origin of the temperature anomaly and the system's functioning. In this context, developing appropriate exploration methodologies and techniques is essential for its adequate and efficient use. This thesis develops a methodology focused on a geothermal system type characterized by being located in highly fractured zones. These fractures connect the surface with great depths, allowing the rapid ascent of deep fluids at high temperatures without giving them time to cool down. Specifically, this thesis applies this methodology to a study case located in the Vallès Basin, close to Barcelona city (NE Iberian Peninsula), where some localities, such as La Garriga and Caldes de Montbui towns, have thermal hot springs (60ºC and 70ºC, respectively). In particular, the methodology applied to study the Vallès Basin geothermal fractured system, is focused on two main cores, geophysical and geological techniques. Geophysical methods allow the characterization of the subsurface physical properties, reaching great depths without having to drill. For example, if the physical characteristics of the subsurface have enough contrast, they could allow distinguishing between different types of rocks, fractured zones, or if there is any fluid circulation. However, the geophysical results have to be complemented with other geoscientific studies in order to make a proper interpretation. In this case, this thesis includes a characterization of the area's geology, fracturing, and hydrology. Finally, the integration of the applied techniques has allowed the understanding of the origin and system's functioning, which is presented in the form of a 3D conceptual model, geological model, and temperature model. This innovative methodology, which integrates different geoscientific techniques at different scales, combining traditional techniques with novel digital tools, has facilitated the characterization of a geothermal system controlled by geological structures. Therefore, it is established as a methodical option to characterize systems of similar origin.
Salt Tectonics of the Offshore Tarfaya Basin (NW Africa): A Regional to Local Approach
(Universitat de Barcelona, 2022-12-01) Uranga Moran, Rodolfo Martín; Muñoz, J. A.; Ferrer García, J. Oriol (José Oriol); Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] Although there is certain consensus on the Middle Jurassic to Present evolution of the Central Atlantic, the Early Jurassic rift to drift transition stage is still under discussion. Through the interpretation of unpublished, recently acquired deep seismic reflection data, integrated with legacy 2D surveys from offshore Morocco, this thesis (Chapter 2) presents new evidences supporting a revised passive margin evolutionary model with focus on the rift to drift transition phase. Assuming evaporite deposition was synchronous along the margin, a northward propagation of rifting and breakup is interpreted, with salt deposited during the late crustal thinning stage in the Tarfaya and Agadir basins (Southern segment), during crustal thinning in the Agadir, Essaouira and Safi basins (Central segment), and during continental stretching in the Mazagan Plateau (Northern segment). Furthermore, structural inheritance from Paleozoic tectonic boundaries, such as the South Atlas Fault Zone, were reactivated as transfer zones during rifting separating segments with different crustal deformation styles and extensional rates. Finally, from Late Cretaceous times, the inherited Paleozoic and Mesozoic structural fabric controlled the localization of thick and thin-skinned tectonic inversion caused by the compressional events related to the convergence between the African and Eurasian plates. Chapter 3 from this thesis presents the key events that conditioned the evolution of the offshore Tarfaya Basin (SW Morocco). From Late Triassic to Early Jurassic times, salt was deposited with a basinward thickening wedge-shaped geometry on a narrow trough developed over thinned continental crust. During the Jurassic, salt withdrawal was probably triggered by local depocenters related to the progradational loading on the demised carbonate slope on a proximal setting in the central and northern areas of the Tarfaya Basin. Moreover, thermal subsidence might have led to the regional tilting of the salt basin probably playing an important role as triggering mechanism in the distal basin. During the Early Cretaceous, the progradation of the Tan-Tan Delta promoted a continued basinward expulsion of salt and the proximal extrusion of salt sheets. Finally, from Late Cretaceous to the Present-day, shortening related to the convergence between Africa and Eurasia resulted in thick-skin inversion and the rejuvenation of precursor salt structures. Finally, Chapter 4 of this thesis focuses on the effect of salt tectonics on seabed topography and how it controlled deep-water sedimentation in the Tarfaya Basin. The study area is subdivided in three structural domains: I (Proximal), II (Intermediate) and III (Distal), with distinctive characteristics. Domain I is characterized by secondary welded, buried salt sheets with counterregionally dipping feeders. Domain II is distinguished by contractionally rejuvenated diapirs and salt sheets and Domain III by passively growing diapirs actively deforming the modern seabed. During the Paleogene, the active growth of structures located in Domain I imposed a high paleotopographic relief blocking turbiditic flows sourced from the shelf. The Early Oligocene is characterized by continued active diapirism and a low sediment flux. This triggered the widespread deposition of mass transport deposits and the diversion of turbiditic channel- lobe systems. In contrast, the Late Oligocene is marked by the exhumation of the Atlas, Anti Atlas and Reguibat Shield systems which provided large amounts of sediments that bypassed the shelf and were deposited forming large turbiditic fans. The Miocene is characterized by sediment bypass from the shelf to deep-offshore settings and a gradual burial of the proximal salt structures that were ultimately secondary welded. The identified depositional systems evidence a progressive amalgamation of the different minibasins. The Plio-Quaternary evolution of the study area is marked by a second major orogenic pulse in the Atlas System resulting in an increase of onshore exhumation rates and sediment flux from the High Atlas, Anti Atlas and Reguibat Shield.
Sedimentology and sedimentary architecture of the Middle Ordovician Hawaz Formation in the subsurface of the Murzuq Basin (Libya)
(Universitat de Barcelona, 2022-10-14) Gil-Ortiz, Marc; Cabello López, Patricia; McDougall, Neil David; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] The Hawaz Formation is a Middle Ordovician siliciclastic succession which extends for hundreds of kilometres across North Africa. This thesis uses a subsurface-based approach, mainly utilizing well data, complemented by data from nearby outcrops, with the aim of gaining new insight into the oil-prone Hawaz Formation in the emergent hydrocarbon province of the Murzuq Basin (SW Libya). The limited lateral continuity of this formation, often truncated by the Late Ordovician glaciation unconformities, has always presented a challenge to the interpretation of this reservoir in terms of large-scale sedimentary architecture and facies connectivity. This investigation has required a high resolution description and interpretation of the sedimentology and sedimentary architecture of this succession in the subsurface of the north central part of the Murzuq Basin through two well-differentiated phases: 1) sedimentological description and interpretation of lithofacies and facies associations together with a sequence stratigraphic analysis of the succession; 2) basin-scale reservoir characterization in terms of vertical and lateral continuity of facies belts and paleogeographic reconstruction of this unit in the area of study. This research has resulted in the identification and characterisation of fifteen distinctive lithofacies, defined on the basis of lithology and internal fabric, mainly using core and microresistivity image log data, grouped into seven correlatable facies associations distributed in broad and laterally extensive facies belts deposited in a shallow marine, intertidal to subtidal environment. These facies associations are: 1) tidal flat; 2) subtidal complex; 3) abandoned subtidal complex; 4) middle to lower shoreface; 5) burrowed shelfal and lower shoreface; 6) burrowed inner shelf and; 7) shelfal storm sheets. Three main depositional sequences and their respective systems tracts have also been identified and interpreted as deposited mainly during transgressive and high relative sea level stages. On this basis, a genetic-based stratigraphic zonation scheme has been proposed as a tool to improve subsurface management of this reservoir unit. Facies analysis and sedimentological interpretation provided the basis for the reconstruction of the sedimentary architecture of the Hawaz Formation by means of eight correlation panels oriented along both sedimentological dip (NNW-SSE) and strike (WSW to ENE) and a series of Gross Depositional Environment (GDE) maps with the aim of providing insight into the lateral distribution of facies association belts and hence, distribution of potential reservoir geobodies, within the framework of a sequence stratigraphic-based zonation. The results of this study suggest that the Hawaz Formation was deposited in a relatively protected or embayed shoreline with multiple bays or estuaries as the main entry points for sediment into the basin, most likely partially influenced by the effects of pre-existing north- northwest to south-southeast Pan-African extensive faults controlling local accommodation space and reactivated during Ordovician times. Finally, the principal factors controlling the deposition of this succession were significantly different from most actualistic depositional models for modern subtidal to intertidal paralic environments. At least four processes or factors were key for the deposition of the Hawaz Formation and permitted us to better understand the fabric, lateral extension and distribution of this succession across the North African Platform and, indeed, in our area of study. These factors were: 1) a generalised lack of land flora during the Middle Ordovician; 2) a different global eustatic sea level scenario, during much of the Middle Ordovician, differing substantially from present-day icehouse period in terms of relative sea level and erosive potential in coastal settings; 3) a likely higher variation in tidal ranges reflecting the shorter Earth-Moon distance associated with the Lower Paleozoic times and finally; 4) distinctive Skolithos/Cruziana ichnofabric present in the Hawaz Formation compared to broader and more diversified ichnofacies in equivalent depostional settings at present times, which are no longer preserved in modern coastal environments due to the extinction of most organisms causing these bioturbation traces.
La Formación Caspe: análisis sedimentológico y estratigráfico de los depósitos fluviales del Oligoceno – Mioceno inferior del SE de la Cuenca del Ebro
(Universitat de Barcelona, 2022-10-24) Cuevas Martínez, José Luis; Cabrera, Lluís; Marzo, M.; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[spa] La Formación Caspe corresponde a las facies fluviales de los depósitos de un abanico fluvial de edad oligo-miocena, referido en la literatura como Sistema aluvial del Guadalope-Matarranya. Dicho sistema tuvo su área fuente en la Zona de Enlace entre el Sistema Ibérico y los Catalánides y distribuía sedimentos radialmente hacia el N, NE y NW a lo largo de una distancia de unos 90 -100 Km. Los problemas sedimentológicos planteados han sido determinar el origen de la segmentación en storeys en los depósitos de canal, en los cuales domina la morfologia de ribbon sandstone, determinar hasta qué punto los conjuntos canal-levee formaban cinturones aluviales sobreelevados y determinar la tipología de las antiguas redes fluviales. En relación con los procesos sedimentarios y el contexto paleogeográfico, otro de los problemas a resolver ha sido la determinación del régimen hídrico y el entorno paleoclimático. El estudio estratigráfico una primera parte, de síntesis del conocimiento previo, y una segunda parte en la que presentamos una serie magnetoestratigráfica, correspondiente a los 550 m más altos que se pueden medir en la Formación, la cual ha permitido correlacionar las partes medias del sistema aluvial con las series de sistema lacustre elaboradas por autores previos. Dicha serie abarca un lapso mínimo de unos 2 Ma entre los crones C7Ar y C6n.1n. El lapso mínimo que abarca la formación es de 6.429 Ma, entre la parte superior del Rupeliense y la inferior del Aquitaniense (crones C11n a C6n.1n). Los ribbon sandstones corresponden al depósito de cinturones de canales que desarrollaban levees de poco relieve y estaban sujetos a procesos de avulsión frecuente, inducidos por colmatación y reducción de capacidad. En estos cinturones, los canales se apilaban con un marcado componente vertical como resultado del acoplamiento entre la sedimentación en la llanura de inundación y en los canales. Dicho acoplamiento se ha caracterizado mediante el número de movilidad estratigráfica, el cual presenta valores próximos a los típicos para canales turbidíticos. Las relaciones entre ribbon sandstones adyacentes y los storeys que los forman muestran que cada sección vertical puede corresponder a la superposición de litosomas de relleno de canal que pueden presentar relaciones de divergencia y convergencia respecto de la sección observada, y pueden conectar con ribbon sandstones adyacentes. La conectividad entre litosomas de arenisca es mayor que la que puede deducirse a partir de la observación de secciones verticales. El régimen hídrico habría sido marcadamente discontinuo, en un contexto paleoclimático de árido a semiárido en la Cuenca del Ebro. Los caudales formativos muestran valores máximos significativamente superiores al régimen actual. El análisis de la arquitectura a escala kilométrica muestra que los ribbon sandstones se concentran verticalmente sobre superficies de extensión plurikilométrica, separadas por intervalos dominantemente pelíticos. El análisis de las secuencias formadas por los ribbon sandstones y el resto de litofacies relacionadas, combinado con la arquitectura indicada sugiere que la estratigrafía a escala de formación corresponde al apilamiento compensacional de lóbulos deposicionales de diversas escalas. Respecto a la ruta sedimentaria, la tasa de aporte de sedimento, y la extensión y evolución del área fuente han podido calcularse en base a balances de volumen. Los valores obtenidos son de un orden de magnitud inferiores a los de sistemas de edad equivalente en el margen sur pirenaico. La ruta sedimentaria conformaría un sistema altamente reactivo. Los controles alogénicos climáticos de zona proximal podrían manifestarse a dos escalas: a escala de tiempo de la oblicuidad (46 Ka) y a escalas de tiempo de la excentricidad (superiores a los 100 Ka). A escala de la oblicuidad, la distribución del sedimento en lóbulos deposicionales distorsionaría esta señal y la desconectaría del sistema lacustre. A escalas de tiempo superiores a la oblicuidad, las variaciones de la descarga de sedimento afectarían la totalidad del sistema.
Temporal Variability of Nepheloid Layer Structures on Continental Slope Environments: Natural and Anthropogenic Processes
(Universitat de Barcelona, 2022-02-17) Arjona Camas, Marta; Puig, Pere; Palanques Monteys, Albert; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] This Thesis aims to investigate the contribution of the deep-sea trawling activities, besides that of natural processes, to the sediment dynamics in different continental slope areas, particularly in the NW Mediterranean and the NE Pacific basins. The temporal and spatial variability of the water column turbidity structure in the Foix Canyon (NW Mediterranean) are studied by analysing two months of hydrographic profiles collected by an autonomous hydrographic profiler. The water column turbidity structure consists in intermediate nepheloid layers (INLS) developed between 300 and 500 m water depth and above the canyon rims, and INLs and near-bottom nepheloid layers (BNLs) confined inside the canyon between 650 and 800 m water depth. Data from fishing vessels positioning during the deployment period reveals that the presence and depths of the observed INLs and BNLs depend on the operating depths of bottom trawlers and on the specific fishing grounds being exploited by the local trawling fleet. This data strongly suggests that bottom trawling activities in the study area are the main driver of the turbidity increases observed in the water column. The spatial and temporal variations on the water column turbidity structure and near- bottom suspended sediment transport associated to both natural processes (storms, river floods, and dense shelf water cascading, DSWC) and bottom trawling activities are also analysed for three months in the Palamós Canyon (NW Mediterranean) using an autonomous hydrographic profiler and near-bottom instrumentation installed in a mooring, covering a trawling closure period, and an active trawling period. Periods of enhanced water turbidity during the trawling closure period are associated with storms and DSWC events, transporting turbid dense waters into the canyon. In absence of such energetic events, the water column remains unchanged, displaying the lowest suspended sediment concentrations of the recording period, until the trawling season began. INLs (250 and 350 m depth) and BNLs (> 500 m depth) are found at the water depths where trawling grounds from the Palamós Canyon are located. High near-bottom suspended sediment fluxes are sporadically registered during the trawling closure associated with a major wet eastern storm and a DSWC event, whereas smaller but more frequent increases in near-bottom suspended sediment fluxes are recorded during trawling activities. However, the continued bottom trawling activity, at least for 30 days of monitoring, produces an accumulated suspended sediment transport similar to that generated by a major DSWC event. Considering that bottom trawling in Palamós Canyon is practised on a daily basis throughout the year, except for the 2-month trawling closure period, a much larger contribution of anthropogenically derived suspended sediment transport can be expected. The temporal evolution of the hydrographic and nepheloid layer structure in the upper slope of Vancouver Island (British Columbia, Cascadia margin, NE Canadian Pacific) is also assessed by analysing four months of sensor data from the NEPTUNE observatory. The water column turbidity structure during the study period consists in surface nepheloid layers (SNLs) (<100 m depth) associated to primary and secondary productivity, INLs between 150 and 300 m depth at the shelf-break and upper slope domain, and BNLs developed at deeper continental slope regions (~400 m depth). Strong fall storms occurring during the monitored months seem to generate the more intense INLs found at shelf-break depths. However, not all the recorded INLs coincide with the more intense storms, indicating that other sediment resuspension mechanisms might be modulating these INL detachments. Results from this study suggest that, in combination with the regional currents, the presence of continuous fishing along the continental slope off Vancouver Island, contributes to the advection of suspended sediment particles, playing a major role in their transference along the margin as nepheloid layers.
Developing Advanced Photogrammetric Methods for Automated Rockfall Monitoring
(Universitat de Barcelona, 2022-03-17) Blanch Gorriz, Xabier; Guinau Sellés, Marta; Abellán Fernández, Antonio; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] In recent years, photogrammetric models have become a widely used tool in the field of geosciences thanks to their ability to reproduce natural surfaces. As an alternative to other systems such as LiDAR (Light Detection and Ranging), photogrammetry makes it possible to obtain 3D points clouds at a lower cost and with a lower learning curve. This combination has allowed the democratisation of this 3D model creation strategy. On the other hand, rockfalls are one of the geological phenomena that represent a risk for society. It is the most common natural phenomenon in mountainous areas and, given its great speed, its hazard is very high. This doctoral thesis deals with the creation of photogrammetric systems and processing algorithms for the automatic monitoring of rockfalls. To this end, 3 fixed camera photogrammetric systems were designed and installed in 2 study areas. In addition, 3 different workflows have been developed, two of which are aimed at obtaining comparisons of higher quality using photogrammetric models and the other focused on automating the entire monitoring process with the aim of obtaining automatic monitoring systems of low temporal frequency. The photogrammetric RasPi system has been designed and installed in the study area of Puigcercós (Catalonia). This very low-cost system has been designed using Raspberry cameras. Despite being a very low-cost and low-resolution system, the results obtained demonstrate its ability to identify rockfalls and pre-failure deformation. The HRCam photogrammetric system has also been designed and installed in the Puigcercós study area. This system uses commercial cameras and more complex control systems. With this system, higher quality models have been obtained that enable better monitoring of rockfalls. Finally, the DSLR system has been designed similarly to the HRCam system but has been installed in a real risk area in the Tajo de San Pedro in the Alhambra (Andalusia). This system has been used to constantly monitor the rockfalls affecting this escarpment. In order to obtain 3D comparisons with the highest possible quality, two workflows have been developed. The first, called PCStacking, consists of stacking 3D models in order to calculate the median of the Z coordinates of each point to generate a new averaged point cloud. This thesis shows the application of the algorithm both with ad hoc created synthetic point clouds and with real point clouds. In both cases, the 25th and 75th percentile errors of the 3D comparisons were reduced from 3.2 cm to 1.4 cm in synthetic tests and from 1.5 cm to 0.5 cm in real conditions. The second workflow that has been developed is called MEMI (Multi-Epoch and Multi-Imagery). This workflow is capable of obtaining photogrammetric comparisons with a higher quality than those obtained with the classical workflow. The redundant use of images from the two periods to be compared reduces the error to a factor of 2 compared to the classical approach, yielding a standard deviation of the comparison of 3D models of 1.5 cm. Finally, the last workflow presented in this thesis is an update and an automation of the method for detecting rockfalls from point-clouds carried out by the RISKNAT research group. The update has been carried out with two objectives in mind. The first is to transfer the entire working method to free licence (both language and programming), and the second is to include in the processing the new algorithms and improvements that have recently been developed. The automation of the method has been performed to cope with the large amount of data generated by photogrammetric systems. It consists of automating all the processes, which means that everything from the capture of the image in the field to the obtention of the rockfalls is performed automatically. This automation poses important challenges, which, although not completely solved, are addressed in this thesis. Thanks to the creation of photogrammetric systems, 3D model improvement algorithms and automation of the rockfall identification workflow, this doctoral thesis presents a solid and innovative proposal in the field of low-cost automatic monitoring. The creation of these systems and algorithms constitutes a further step in the unimpeded expansion of monitoring and warning systems, whose ultimate goal is to enable us to live in a safer world and to build more resilient societies to deal with geological hazards.
Caracterització espaciotemporal de la dinàmica d’allaus de neu majors al Pirineu català
(Universitat de Barcelona, 2021-12-10) Oller Figueras, Pere; Furdada i Bellavista, Glòria; Baeza Adell, Cristina; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[cat] Aquesta tesi té per objectiu avançar en el coneixement de la dinàmica de les allaus, i en concret, de les allaus majors, al Pirineu de Catalunya i, per extensió, als Pirineus, tot entenent per allau major l’allau la mida de la qual excedeix l’abast de les allaus habituals (freqüents), causant danys en cas que hi hagi infraestructures a la seva proximitat. La base del treball, i font de dades, és una base de dades d’allaus majors. Aquesta, parteix de la informació provinent d’enquestes a la població, del seguiment hivernal de l’activitat d’allaus, completada amb una cartografia realitzada a partir de fotointerpretació, amb inspeccions de camp d’estiu i d’hivern, i amb informació històrica-documental. D’aquest treball, s’han elaborat i publicat dos articles en revistes indexades. En l’article 1, els esdeveniments d’allaus majors de la base de dades van ser usats per quantificar la magnitud dels episodis en que es van produir. Per a tal finalitat, es va concebre un índex de l’activitat d’allaus majors (MAAMI). Aquest índex està basat en el nombre d’allaus majors registrades, la seva magnitud, i la seva freqüència estimada, en un període de temps determinat. Per tant, quantifica la magnitud d’un episodi d’allaus majors o hivern d’allaus majors. El treball ha permès reconstruir en detall els episodis majors dels hiverns 1995/96 a 2013/14. Per analitzar tot el segle XX, amb un conjunt de dades menys complert es va definir un índex simplificat SMAAMI. Amb menys precisió, es van obtenir els mateixos paràmetres a resolució de temporada hivernal al llarg del segle XX. L’anàlisi de l’extensió espacial dels diferents episodis ha permès conèixer millor i precisar la delimitació de les regions nivològiques establertes, i millorar el coneixement sobre els patrons atmosfèrics que causen els episodis majors i la seva interpretació climàtica. S’ha obtingut també la probabilitat d’ocurrència d’episodis que poden afectar a zones urbanitzades i, per tant, que suposen un risc. En l’article 2, les dades de la base de dades han estat usades per a ajustar el model empíric noruec α−β, que s’utilitza internacionalment per a calcular distàncies d’abast d’allaus “extremes”, aplicant el coneixement actual de l’activitat d’allaus majors per a tot el Pirineu català, i usant les eines actuals de cartografia. Això ha permès millorar significativament el primer model obtingut només per al Pirineu occidental català ja fa més de 25 anys. El model s’ha obtingut a partir d’una mostra de 97 esdeveniments d’allaus “extremes” que es van produir del final del segle XIX fins a l’inici del segle XXI. A partir de la Regressió Lineal Múltiple s’ha obtingut una equació usant 3 variables independents: pendent de la zona d’allaus (β), distància horitzontal (Hβ), i àrea de la zona de sortida (Azs), amb un considerable ajust (R2=0.81). La nova equació actualitzada prediu l’abast d’allaus per un període de retorn de l’ordre dels 100 anys. Per estudiar quines variables del terreny expliquen els valors extrems de la mostra d’allaus, es va realitzar una anàlisi comparativa de variables que influencien un major o menor abast. Seleccionant un conjunt més extrem d’allaus, es va observar que la mida de la zona d’allaus i l’orientació de la zona de sortida mostraven certa associació amb distàncies d’abast menors i majors a les predites amb el model. En resum, a partir d’una base de dades d’allaus majors en l’àmbit del Pirineu català, alimentada per dades d’allaus individuals, s’ha avançat en la caracterització dels episodis d’allaus majors, tant en la seva intensitat i causes com en la seva extensió geogràfica; per altra banda, gràcies a la utilització conjunta de les dades d’allaus majors, s’ha establert un model de càlcul que s’aplica a la predicció de l’abast d’allaus centenàries en zones d’allaus particulars. Els resultats obtinguts permeten avançar en el coneixement de la dinàmica de les allaus al Pirineu català i, per tant, en el coneixement de la perillositat i del risc que suposen.
Barremian charophytes from the Maestrat Basin: taxonomy, palaeoecology, palaeobiogeography and biostratigraphy
(Universitat de Barcelona, 2021-11-25) Pérez Cano, Jordi; Martín-Closas, Carles; Bover-Arnal, Telm; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] This thesis is focused on the taxonomical, biogeographical, palaeoecological and biostratigraphical characterization of the Barremian charophytes of the Maestrat Basin (Eastern Iberian Chain, Spain). Thirty-four charophyte taxa, including fructifications and thalli, which belong to the three families that co-existed during the Early Cretaceous, i.e., the Porocharaceae, the Characeae and the Clavatoraceae, were identified in two Barremian sections (Fredes and Herbers-Mas de Petxí). Twenty-six of them correspond to clavatoracean utricles, including Clavator grovesii var. jiuquanensis, which is herein firstly reported in the Iberian Chain. Similar clavatoracean richness is not found elsewhere, showing the importance of the Maestrat Basin as a hotspot for the clavatoracean species-richness during Barremian. New characters found in the clavatoracean utricles and thalli improved the knowledge on this important, mainly Cretaceous, family. The Echinochara lazarii utricle was reinterpreted as bilaterally symmetrical, rather than triradiated. This type of symmetry was previously unknown within genus Echinochara and in the whole subfamily Atopocharoidae, leading to a taxonomic emendation of this genus. This species was found attached to the thallus Charaxis spicatus allowing the reconstruction of the Echinochara whole-plant. The cortication of this thallus was reviewed and a new type of cortication, called double triplostichous cortication, was described. A second important result was the characterization of a gradualistic evolutionary lineage in Clavator calcitrapus. This lineage includes two anagenetic varieties, C. calcitrapus var. jiangluoensis and C. calcitrapus var. calcitrapus, linked by all possible intermediary morphotypes. This lineage has important biogeographic implications since the oldest variety had a subcosmopolitan range, while the second was endemic to Iberia. Finally, a previously unknown centripetal calcification pattern was found in the internodal cell of genus Munieria. This type of calcification is reminiscent of the one observed in the clavatoroid gyrogonites, providing further support to the hypothesis that this thallus belonged to the Clavatoraceae. The expanded sedimentary record of the Herbers-Mas de Petxí section and the abundance and diversity of charophyte remains found, provided a unique context, at least at European scale, to study the palaeoecology of charophyte species and the evolution of charophyte floras through the Barremian. Three sedimentary units, named from base to top Cantaperdius, Artoles and Morella formations, were analysed. Within these lithostratigraphic units, five charophyte associations were distinguished. 1) A charophyte association developed in freshwater lakes with low clastic input was found in the lower part of the Cantaperdius Formation and was mainly composed of Atopochara trivolvis var. triquetra, Clavator harrisii, Ascidiella stellata, and A. triquetra. Besides, Hemiclavator-rich populations were locally dominant. 2) An association characteristic of freshwater lakes with high clastic input mainly composed of Echinochara lazarii, Globator maillardii var. trochiliscoides, A. trivolvis var. triquetra, C. harrisii, Hemiclavator neimongolensis var. neimongolensis, and occasionally also Clavator calcitrapus. This association is mostly found in the upper part of the Cantaperdius Formation. 3) Porochara maestratica populations mainly thrived in low-clastic-influenced brackish settings; while 4) E. lazarii preferably thrived in clastic-influenced brackish settings. Both these brackish settings where abundant in the Artoles Formation. 5) The charophyte association developed in lakes formed in coastal mudflat to floodplain settings was mainly constituted by E. lazarii, A. trivolvis var. triquetra and var. trivolvis, and C. harrisii var. harrisii and var. reyi. This association is found in the Morella Formation. The environmental distribution of the associations recognized depended on the salinity, the clastic influence, and the depth. A new Barremian–early Aptian charophyte biostratigraphy is proposed. Two biozonations, European and Eurasian, were distinguished and correlated. Furthermore, these biozones were calibrated to the Geological Time Scale by means of strontium-isotope stratigraphy, enabling their correlation with the coeval marine realm. The European biostratigraphy is formed by two partial range biozones (characterized by the First Appearance Data, FAD), of index species that were endemic from the Western Tethyan Archipelago (extant Europe and North Africa): (1) Globator maillardii var. trochiliscoides (early Barremian) and (2) Ascidiella cruciata-Pseudoglobator paucibracteatus. The base of this latter biozone was calibrated with an oyster shell sample with an 87Sr/86Sr ratio of 0.707482, translating to a late early Barremian age, giving a total timespan of late early Barremian–early Aptian for this biozone. The Eurasian biozone is composed of three partial range biozones. (1) Atopochara trivolvis var. triquetra biozone is almost equivalent to the G. maillardii var. trochiliscoides biozone. (2) Hemiclavator neimongolensis var. neimongolensis biozone, which was calibrated with an oyster shell whose 87Sr/86Sr ratio is 0.707481 (late early Barremian). (3) The next biozone is defined by the FAD of Clavator grovesii var. jiuquanensis. Its base was dated with an oyster shell gathered 24.5 m below the FAD of the index species and its 87Sr/86Sr ratio is 0.707489 (late early Barremian). The FAD of C. grovesii var. corrugatus defines the next biozone. The biozonation described herein is intended to facilitate the correlation between different basins of the western Tethys, and between non-marine basins in whole Eurasia.
Paleoseismic transect across the Alhama de Murcia Fault and implications of a fault-based seismic hazard assessment for the Eastern Betics
(Universitat de Barcelona, 2021-10-25) Gómez Novell, Octavi; Ortuño Candela, Maria; García-Mayordomo, Julián; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] The Eastern Betics Shear Zone (EBSZ) is one of the most active fault systems in SE Spain. It has caused damaging earthquakes in historical times, including the 2011 Lorca earthquake, which evidenced that the regional hazard estimations needed revision. In this context, the available fault data is usually too local and, for some faults, reliable and representative parameters are still lacking. Such heterogeneity has usually hampered seismic hazard models based on geological data. This thesis aims to be a comprehensive study allowing to: i) complete the paleoseismic record and parameters of one of the most active faults in the EBSZ, the Alhama de Murcia Fault (AMF), and ii) include fault data in a probabilistic seismic hazard assessment (PSHA). The study is thus divided in two main parts. (A) a local study presenting a structural characterization and integral paleoseismic study in four sites across a complete transect of the AMF. (B) a regional fault-based PSHA of the EBSZ with the main faults as inputs to define complex fault rupture scenarios using the SHERIFS code. A) The structural characterization has been carried out in the two central segments of the AMF, Lorca-Totana and Totana-Alhama. In the former, five fault branches are identified with partitioning of the deformation. From N to S: N1-AMF (lateral), N2a and b-AMF (dip slip), S-AMF (lateral) and F-AMF (dip slip). The Totana-Alhama segment shows more diffuse deformation, where the most prominent structure is the Amarguillo Fault (AF), a N-S transtensional ramification. The paleoseismic survey has been carried out in eight paleoseismic trenches across four fault branches of the Lorca-Totana segment. We obtained one of the completest paleoearthquake records in Iberia with seventeen events for the last ~100 ka in S-AMF. The recurrence varies from 5.7±1.7 to 3.1±1.4 kyr for the last 73-18 ka in S-AMF and F-AMF. The time compatibility of the last five events in these branches suggests that they could rupture synchronously. The total net slip rate of the segment since 18 ka is 1.55 +0.14/-0.18 mm/yr, considerably higher than previous estimations. The slip rate evolution shows fluctuations over time (super-cycles), some of which coincide with patterns identified in nearby faults, inferring possible activity synchronicities. B) The fault-based PSHA suggests that multi-fault ruptures involving lengths of single to several whole faults of the EBSZ are feasible, contrary to the rupture of the whole system (~400 km). The hazard shows a clear control of the EBSZ faults, increasing the accelerations close to their traces with respect to area source PSHAs. The seismic hazard is dependent on the slip rates, as lower slip rate faults (Palomares fault; PF, or NE end of AMF) have negligible contribution. Our results for the 475-year return period are also more consistent with the accelerations reached in the 2011 Lorca event than the building code or national hazard map. For some faults, the lack of detailed paleoseismic studies can compromise the reliability of the hazard. This is a key discussion in the present study, marking the need for better constrained and reliable slip rates in the EBSZ. The integral paleoseismic study of the AMF has revealed to be a crucial step towards a more representative characterization of its paleoseismic parameters (slip rates, recurrence), and thus, of the EBSZ. Acquiring refined and reviewed paleoseismic data is key to improve seismic hazard evaluations. Hereby, further research should focus on poorly researched faults and on performing integrative studies in other EBSZ faults. The comprehensive approach followed, from paleoseismic data collection to PSHA, contributes to perform more critical interpretations of the seismic hazard, and aims to serve as a case example for other low-to-moderate seismicity regions.
Sediment routing systems of the Eocene Tremp-Jaca basin: Stratigraphic analysis and numerical models
(Universitat de Barcelona, 2021-02-12) Vinyoles i Busquets, Andreu; López Blanco, Miguel; Garcés Crespo, Miguel; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] The Eocene South-Pyrenean foreland basin provides a continuum of outcrops representing a Source to Sink sediment routing system from subaerial canyons to deep marine environments. On this context, the specific objective of this study is: (a) to contribute to the knowledge of the chronostratigraphy and the basin infill of the study area; (b) to analyze the evolution of the sedimentation rates on the Tremp-Jaca basin; and (c) to generate numerical models to (i) assess the sediment routing and sediment balance and, (ii) to evaluate the basin response to the propagation of climatic and tectonic signals. Two new magnetostratigraphic sections are built on the Tremp-Jaca basin; the Olsón (Ainsa basin) and the Yebra de Basa sections (Jaca basin). The Olsón section provides a late Lutetian to early Priabonian age for the Escanilla formation in the Ainsa basin, and the same age range is provided on the Yebra de Basa section for the strata encompassed between the Sabiñánigo sandstone and the Santa Orosia formation. The age constrains provided by these new sections and the data sorted from a systematic review of the literature have been used for an analysis of the sedimentation rates in the Tremp-Jaca basin. The studied sections were decompacted by backstripping to correct the differential burial compactions between the sections. This study shows that sedimentation rates may not show the expected variations related to depozone distribution. This lack of correlation between the depozones and the sedimentation rates are consequence of the lagged response to deformation front shifts and the complexity in the structure of the wedge-top. This complexity result in a widespread subsidence related to the emplacement of basement units in the hinterland. Also underfilled forelands may develop high sedimentation rates in the initial stages of wedge-top as basin gradients are a continuation to those developed in the previous foredeep phase. Sedimentation rates in overfilled areas are controlled by accommodation. In underfilled areas, the main control is clastic supply. During graded shelf regressive stages, maximum sedimentation rates are in foreset areas. In the transgressive stages, maximum sedimentation rates are at the topset. In out-of-grade periods, high sedimentation rates are in deep marine areas. The results obtained above have been used to feed forward stratigraphic models, using Dionisos software, to test and understand the different parameters affecting the sedimentary infill of the basin. A first model on the sediment routing systems of the Tremp-Jaca basin, based on the data from the sedimentation rates analysis, succeeds on reproducing the sedimentary routes that can be deduced from the paleocurrent patterns on the Tremp-Jaca basin, validating the inputted data. A second forward stratigraphic model, based on architectural and cyclostratigraphic analysis from previous works, determines that the high-frequency Milankovitch cyclicity of the Belsué-Atarés delta (Sierras Exteriores) is primarily forced from the sediment supply and secondary from the eustasy.
Numerical modeling of continental collision and intraplate deformation. Application to the Cenozoic geodynamic evolution of North Iberia
(Universitat de Barcelona, 2021-01-27) Valverde Pérez, Àngel; García-Castellanos, Daniel; Jiménez i Munt, Ivone; Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà
[eng] This thesis aims at improving the current understanding of the geodynamic controls on tectonic deformation during plate collision, using the Cenozoic evolution of Iberia as a case scenario. Despite the vast efforts during the last decades, there is a limited understanding today about what plate properties control the propagation of tectonic deformation towards the interior of tectonic plates. Meanwhile, the classic enigmas about the timing and the processes involved in the construction of the Iberian topography also persist: What is the origin of the high average elevation of the Iberian Peninsula? What is the quantitative contribution to topography induced by the intraplate tectonics of Iberia? How was this intraplate deformation in the middle of the Iberian microplate triggered? To answer these questions, I first gathered information about the tectonic events in Iberia during the Cenozoic from previous structural tectonic and geodynamic modelling publications. Continental collision with Eurasia in the north first gave rise to the uprising of the Pyrenean and Basque-Cantabrian chains. Deformation subsequently jumped southwards and formed the elevation of the interior mountain ranges. Meanwhile in the southern margin, the subduction of the Tethys oceanic lithosphere due to the Africa-Iberia convergence gave rise to the Betics and opened the Alborán Sea. The underlaying hypothesis of this thesis is that this succession can be reproduced via a geodynamic model giving the appropriate initial conditions that are in reasonable agreement with the geological setting during the early-Cenozoic Iberia. To this purpose, we carried out a series of high-resolution mechanical and thermomechanical numerical models with a state-of-the-art code named UNDERWORLD 2.0 (still under development at Univ. Melbourne). We first review fundamental ideas such as the patterns of deformation of the lithosphere predicted for converging continental margins, as well as the elevation of mountain ranges in a continental collision scenario. Then we investigate how the crustal deformation accommodates far from the continental margins, taking into account the mathematical equations and physical laws that govern the thermal field and rock deformation. Based on these, a series of mechanical numerical models are developed to explore the possible evolutionary scenarios after a continental collision. Two deformation end member models appear: double-vergence and crustal folding. While in the first one deformation concentrates near the axial collision zone where the orogen develops, in the second, deformation is transmitted farther from the initial contact between lithospheres. We compare these results with patterns of deformation seen in the Pyrenean mountain range as well as other natural scenarios where cortical folding occurs near a thrust failure like in the Zagros Chain in Iran. This thesis then focuses on a series of high-resolution 2D numerical models for the North-Central area of the Peninsula. These models aim at linking the Cenozoic evolution of the Cantabrian chain to that of the Central System and the Duero basin. Here, deformation and failure consider creep-like behavior and plasticity in a viscoplastic rheology. We test the hypothesis of the presence of a detachment level within the Variscan basement, at the lower crust, of limited srength and thus capable of transmitting deformation towards the interior, potentially leading to the rise of the Central System. An alternative tested hypothesis is that the entire lithosphere folded in response to the convergence between Iberia and Eurasia. Finally, we extend these 2D numerical models to the southern margin of Iberia to investigate how the approximation of Africa may have affected the distribution and timing of shortening in the different domains of the microplate, with particular emphasis on the topography and deformation of the Central System and adjacent basins.

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