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Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/222684
Influence of Mesozoic structural inheritance on fault reactivation in the central Catalan Coastal Ranges (Catalan Margin, NW Mediterranean). Paleogene and Neogene tectonostratigraphic evolution
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[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.
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MARÍN PÉREZ, Miquel à.. Influence of Mesozoic structural inheritance on fault reactivation in the central Catalan Coastal Ranges (Catalan Margin, NW Mediterranean). Paleogene and Neogene tectonostratigraphic evolution. [consulta: 30 de novembre de 2025]. [Disponible a: https://hdl.handle.net/2445/222684]