Recent and active deformation structures in the central-eastern sector of the Betic Cordillera and the Alboran Sea: indentation processes and roll-back

Type Thesis
Date 2022-05-24
Language English
Other localization http://hdl.handle.net/10481/75430
Author(s) Tendero Salmeron Victor1
University Universidad de Granada
Discipline Ciencias de la Tierra
Thesis supervisor Jesus Galindo Zaldivar
Thesis co-supervisor Ercilla Zarraga Gemma
Thesis co-supervisor D'Acremont Elia
Note ISBN: 9788411173520
Abstract

A multidisciplinary study that combines geology, geophysics and geodesy in an integrated land-sea approach is crucial for the analysis of the active and recent tectonic structures in the Alboran Sea and central-eastern Betic Cordillera. Such a study, presented in this Ph.D. Thesis, reveals new insights in the geodynamics of the Gibraltar Arc. The interaction between indentation tectonics caused by the Eurasia- Africa convergence and the active extension, and westwards displacement, related to subduction with roll-back, controls the active tectonics of the central Alboran Domain. To study these structures, geological, geodetical and geophysical methods have been applied, and marine and terrestrial data are integrated. In the central Alboran Sea indentation, the magnetic anomalies reveal large igneous intrusions related to the AlKaPeCa Domain rift that have conditioned the development of strike-slip faults and the indentation tectonics. In fact, these rigid bodies act as a backstop where the indenter of south Alboran Sea collides and has generated the Alboran Ridge. The magnetic anomalies also point to the inherited origin of the dextral Yusuf fault (north-eastern boundary of the indenter) and a very recent formation of the sinistral Al Idrissi fault zone (western boundary of the indenter). The southern termination of the Al Idrissi fault zone in the transtensional Nekor basin shows the interaction between the southwestwards motion of the Rif Cordillera and the indentation of the central Alboran Sea. The faults studied at the Al Hoceima Bay (Nekor basin) show a westward migration caused by the SW motion of the Rif. The deformation of the northern Alboran Sea is characterized by two conjugate sets of strike-slip faults that are propagating towards the coast. In the Campo de Dalías zone, the results of GNSS measurements show that the southern points of the GNSS network move WNW, while the northern ones move WSW. This zone is affected by normal-dextral faults with NW-SE orientation. Their dextral component, together with the GNSS results, implicate an influence of both the ENE-WSW extension, which is dominant in the central Betic, combined with the propagation of the tectonic indentation of the Alboran Sea. Thus, a transition zone can be defined in the western and northern boundaries of the Alboran Sea indentation. Such a transition happens between the indentation tectonics related to the continental collision in the central Alboran Sea, and the westwards motion with extension due to roll-back in the west Alboran Domain. In the eastern Betic, the active tectonics is marked by the transpressive and strike-slip faults of the Eastern Betic Shear Zone. A few of these faults, such as the Palomares one, are originated by the Águilas Arc indentation, where a rigid fragment of the Algerian crust collides with the deformed Betic Internal Zones. The gravity modeling next to the Palomares fault shows that the basin geometries are controlled by rotated synforms, whose fragmentation originated the Palomares fault during the indentation. In addition, the length of the Palomares fault is shorter than previously considered and it is constrained by the folding deformation. Consequently, it disrupts the continuity of the EBSZ. In addition, the data show a NW propagation of the Águilas Arc indentation. The high coupling in the eastern Betics between the Alboran Domain and the underlying Iberian crust favors the stress transmission towards the Iberian massif. This explains the strike-slip seismicity located inside the Iberian basement of the easternmost Guadalquivir foreland basin. Geophysical, seismological and geological data show a NNE-SSW sinistral fault in the Iberian basement and, combined with the compression structures located northwards, support an incipient indentation tectonics. The compression and strike-slip tectonics in the basement combined with the small westwards displacement at the surface, all point to an interaction between the collision tectonics of the eastern Betics and the roll-back in the central Betics. The boundary zone between areas affected by indentation tectonics and roll-back has variable features. Whilst in the Alboran Sea it is a transition zone, in the centraleastern Betics it manifests as a sharp boundary located west of the Águilas Arc indentation. Alternatively, in the Betic Cordillera, the boundary zone could be an area of progressive transition, eventually affected by other lithospheric processes related to the rupture of the slab between the western and eastern Betics. In the Guadalquivir foreland basin, transitional areas are also observed. The advancement of indentation, and the development of the Gibraltar Arc by roll-back processes, produces a progressive westwards migration of the boundary of the areas affected by these tectonic processes.

Abstract <p>El estudio multidisciplinar que combina geolog&iacute;a, geof&iacute;sica y geodesia e integra datos tierra-mar es crucial para el an&aacute;lisis de las estructuras tect&oacute;nicas activas y recientes del Mar de Albor&aacute;n y del sector centro-oriental de las B&eacute;ticas. Es el caso de esta tesis, que aporta nuevos datos sobre los procesos geodin&aacute;micos que afectan al Arco de Gibraltar. La interacci&oacute;n de indentaciones tect&oacute;nicas debidas a la convergencia Eurasia-&Aacute;frica y la extensi&oacute;n y movimiento al oeste relacionas con la subducci&oacute;n con roll-back controlan la tect&oacute;nica activa del sector central Dominio de Albor&aacute;n. Para su estudio se han combinado m&eacute;todos geol&oacute;gicos, geof&iacute;sicos y geod&eacute;sicos y se han integrado datos marinos y terrestres. En la indentaci&oacute;n del Mar de Albor&aacute;n, las anomal&iacute;as magn&eacute;ticas han revelado la presencia de grandes intrusiones &iacute;gneas relacionadas con el rift del Dominio AlKaPeCa, las cuales han condicionado el desarrollo de fallas de salto en direcci&oacute;n y la indentaci&oacute;n tect&oacute;nica. De hecho, esas intrusiones act&uacute;an como un tope contra el que colisiona el indentador del sur del Mar de Albor&aacute;n, generando la Cresta de Albor&aacute;n. Los resultados tambi&eacute;n apoyan el car&aacute;cter heredado de la falla dextra de Yusuf (borde noreste del indentador) y la formaci&oacute;n muy reciente de la zona de falla sinistra de Al Idrissi (borde occidental del indentador). La terminaci&oacute;n sur de Al Idrissi en la cuenca transtensiva de Nekor muestra la interacci&oacute;n entre el movimiento al suroeste del Rif y la indentaci&oacute;n del centro del Mar de Albor&aacute;n. Las fallas estudiadas en la Bah&iacute;a de Alhucemas (cuenca de Nekor) muestran una migraci&oacute;n al oeste causada por el movimiento al SO del Rif. La deformaci&oacute;n en el norte de Albor&aacute;n se caracteriza por dos sets de fallas conjugadas de salto en direcci&oacute;n que se propagan hacia la costa. En el Campo de Dal&iacute;as, los resultados de medidas de GNSS muestran que los puntos del sur se mueven hacia el ONO, mientras que los del norte se mueven hacia el OSO. En esta zona hay fallas NO-SE normales-dextras. Su componente dextro y los resultados de la red GNSS apuntan a la influencia de ambos procesos (la propagaci&oacute;n de la indentaci&oacute;n tect&oacute;nica del Mar de Albor&aacute;n y la extensi&oacute;n ENE-OSO de las B&eacute;ticas centrales) en las estructuras activas. As&iacute;, se puede definir una zona de transici&oacute;n en los m&aacute;rgenes norte y oeste de la indentaci&oacute;n del Mar de Albor&aacute;n entre los procesos de indentaci&oacute;n relacionados con la colisi&oacute;n continental en el centro del Mar de Albor&aacute;n y el movimiento al oeste debido al roll-back de la zona occidental. En las B&eacute;ticas orientales, la tect&oacute;nica activa est&aacute; caracterizada por transpresi&oacute;n y las fallas de salto en direcci&oacute;n de la Eastern Betic Shear Zone. Algunas de ellas, como la falla de Palomares, est&aacute;n generadas por la indentaci&oacute;n del Arco de &Aacute;guilas, en la que un fragmento r&iacute;gido de la corteza argelina colisiona con las deformadas Zonas Internas b&eacute;ticas. Sin embargo, los modelos de gravimetr&iacute;a de las cuencas adyacentes a la falla de Palomares se&ntilde;alan que las cuencas est&aacute;n formadas por sinformes rotados, cuya fragmentaci&oacute;n durante la indentaci&oacute;n gener&oacute; la falla de Palomares. Por tanto, la longitud de la falla de Palomares es menor, limitada por la deformaci&oacute;n y desplazamiento de los pliegues, y est&aacute; desconectada de la EBSZ. Los datos tambi&eacute;n muestran que la indentaci&oacute;n del Arco de &Aacute;guilas se propaga hacia el NO. Teniendo en cuenta que en las B&eacute;ticas orientales la corteza ib&eacute;rica est&aacute; desconectada del slab y adherida a las B&eacute;ticas, debe de haber un grado de acoplamiento alto entre ambas que favorece la transmisi&oacute;n de esfuerzos a Iberia. Esto explica la sismicidad con mecanismos focales de salto en direcci&oacute;n en el basamento ib&eacute;rico de la zona m&aacute;s oriental de la cuenca de antepa&iacute;s del Guadalquivir. Datos geof&iacute;sicos, s&iacute;smicos y geol&oacute;gicos muestran una falla NNE-SSO sinistra en el basamento que, combinada con las estructuras compresivas localizadas al norte, apoyan la existencia de una indentaci&oacute;n incipiente. La compresi&oacute;n y las fallas de salto en direcci&oacute;n del basamento, sumadas a los peque&ntilde;os desplazamientos al oeste de la superficie, indican una interacci&oacute;n de los procesos de colisi&oacute;n y transpresi&oacute;n que dominan las B&eacute;ticas orientales y el roll-back en las B&eacute;ticas centrales. El l&iacute;mite entre &aacute;reas afectadas por la tect&oacute;nica de indentaci&oacute;n y el roll-back es variable. Mientras en el Mar de Albor&aacute;n es una zona de transici&oacute;n, en el sector centro-oriental de las B&eacute;ticas parece ser un l&iacute;mite neto, al oeste de la indentaci&oacute;n del Arco de &Aacute;guilas. Alternativamente, en esa zona podr&iacute;a haber una transici&oacute;n progresiva, como en zonas de la cuenca del Guadalquivir, eventualmente afectada por otros procesos litosf&eacute;ricos relacionados con la ruptura del slab entre las B&eacute;ticas orientales y occidentales. El avance de la indentaci&oacute;n y el desarrollo del Arco de Gibraltar por procesos de roll-back generan una progresiva migraci&oacute;n al oeste de este l&iacute;mite entre &aacute;reas afectadas por diferentes procesos tect&oacute;nicos.</p>

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Tendero Salmeron Victor (2022). Recent and active deformation structures in the central-eastern sector of the Betic Cordillera and the Alboran Sea: indentation processes and roll-back. PhD Thesis, Universidad de Granada. https://archimer.ifremer.fr/doc/00777/88896/