Salt tectonics of the offshore tarfaya basin (nw africa): A regional to local approach
- Autores: Rodolfo Uranga Moran
- Directores de la Tesis: Josep Anton Muñoz i de la Fuente (dir. tes.), Josep Oriol Ferrer García (codir. tes.)
- Lectura: En la Universitat de Barcelona ( España ) en 2022
- Idioma: inglés
- Tribunal Calificador de la Tesis: Eduard Roca Abella (presid.), Antonio María Casas Sáinz (secret.), Leonardo Muñiz Pichel (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencias de la Tierra por la Universidad de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
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 Through the interpretation of unpublished, recently acquired deep seismic reflection data, integrated with legacy 2D surveys from offshore Morocco, this thesis (Chapter 2) presents new evidences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.
