Geology of the Eastern Prebetic Zone at the Jumilla region (SE Iberia)

<p>This article presents a geological map and cross-sections at 1:50,000 scale covering an area of 609 km² of the Eastern Prebetic Zone (SE Iberia). The structure of the studied area is characterized by an NW-directed fold-and-thrust belt and inactive salt diapirs that are parallel to the ENE- to NE-regional trend of the eastern Betic Cordillera. This regional trend is locally disrupted by the NW-trending Matamoros Basin, which is flanked by the active Jumilla and La Rosa diapirs. The geological map, the cross-sections and the outcrop observations support the hypothesis that the major Mesozoic rifting phase affecting the Eastern Prebetic Zone occurred during the Upper Jurassic to Santonian times coeval to the development of extensional basins in the Western Tethyan area. The proximal part of this passive margin was subsequently incorporated into the external part of the Betic thin-skinned fold-and-thrust belt. The Upper Cretaceous to Cenozoic tectonic evolution of the study area encompassed the following stages: a Campanian to Aquitanian NW-directed contraction; a Burdigalian to upper Miocene extensional reactivation of the main subsalt faults; and a Serravallian NW-directed contractional reactivation. In this scenario, the combined effect of the previous contractional reactivation of pre-existing salt structures together with the Miocene subsalt extension triggered passive salt extrusion of the La Rosa and Jumilla diapirs.</p

Mode of extension and final architecture of the south Angolan margins controlled by Precambrian lithospheric heterogeneity.

International audienceWe use offshore 2-3D seismic reflection and potential field data coupled with field work to investigate the control of lithospheric heterogeneity and shear zone rejuvenation on the mode of extension and the architectural segmentation of the southern Angola margins. The pre-rift basement is inherited from several Precambrian deformation events ended by the Pan-African/Brasiliano orogen that accreted four different age-dependent lithospheric domains with contrasted thickness, fabrics, thermal structure, and chemical composition. From north to south, the continental crust is composed of Neoproterozoic metapelites, Paleoproterozoic gneisses and migmatites and Archean greenstone belts pervasively intruded by TTG granitoids. The latter are compartmentalized by lithospheric-scale Archean – Paleoproterozoic shear zones with a general sub-vertical fabric. Upon extension, these pre-existing shear zones nucleated extensional deformation, focalized magmatism and accommodated different rates of extension and width of offshore rift domains. In the north, younger Neoproterozoic lithospheric domain deformed with a ductile behavior and multiple crustal detachments promoting lithospheric decoupling and a distributed extension, with late continental break-up. It favored the formation of a wide magma-poor margin where extension was accommodated by low-angle, seaward-dipping extensional faults and mantle-exhumation. To the south, Archean and Paleoproterozoic lithospheric domain with stronger and brittle strength profile promoted a more localized extensional deformation and favored an early lithospheric coupling and continental break-up. This ultimately led to the formation of a short margin with increased magmatic budget, where extension was accommodated by high-angle, landward-dipping extensional faults and mantle-exhumation. We demonstrate that the pre-rift heterogeneity of the lithosphere controlled the mode of extension during the rift and the along-strike variation of margin geometry. Moreover, the rejuvenation of Precambrian shear zones as extensional transverse fault zones also promoted the activation of lithospheric-scale thermal drains facilitating the emplacement of mantle-related melts into the upper crust

Geology of the Eastern Prebetic Zone at the Jumilla region (SE Iberia)

This article presents a geological map and cross-sections at 1:50,000 scale covering an area of 609 km2 of the Eastern Prebetic Zone (SE Iberia). The structure of the studied area is characterized by an NW-directed fold-and-thrust belt and inactive salt diapirs that are parallel to the ENE- to NE-regional trend of the eastern Betic Cordillera. This regional trend is locally disrupted by the NW-trending Matamoros Basin, which is flanked by the active Jumilla and La Rosa diapirs. The geological map, the cross-sections and the outcrop observations support the hypothesis that the major Mesozoic rifting phase affecting the Eastern Prebetic Zone occurred during the Upper Jurassic to Santonian times coeval to the development of extensional basins in the Western Tethyan area. The proximal part of this passive margin was subsequently incorporated into the external part of the Betic thin-skinned fold-and-thrust belt. The Upper Cretaceous to Cenozoic tectonic evolution of the study area encompassed the following stages: a Campanian to Aquitanian NW-directed contraction; a Burdigalian to upper Miocene extensional reactivation of the main subsalt faults; and a Serravallian NWdirected contractional reactivation. In this scenario, the combined effect of the previous contractional reactivation of pre-existing salt structures together with the Miocene subsalt extension triggered passive salt extrusion of the La Rosa and Jumilla diapirs

Papel de las fallas extensivas de piel gruesa pre-existentes en la deformación de piel fina afectando a un margen pasivo invertido con tectónica salina (Prebético oriental)

El Prebético de Jumilla (SE Iberia), se caracteriza por una deformación multiepisódica desde el Pérmico- Triásico hasta la actualidad. Esta evolución geodinámica incluye un episodio extensivo (Pérmico-Triásico al Cretácico Superior), una inversión tectónica (Paleoceno al Mioceno medio) y finalmente una extensión tardía (Mioceno superior hasta la Actualidad). En este trabajo se presenta una cartografía de detalle y un corte geológico apoyados por datos gravimétricos que muestran que el área se ha visto afectada por deformación de piel gruesa y deformación de piel fina. Este análisis multidisciplinar combinando datos estructurales, sedimentológicos y gravimétricos, revela que la deformación de piel gruesa está representada por un sistema de fallas de basamento extensivas con dirección NE-SO y otro ortogonal de dirección NNO-SSE. Mientras que en el bloque superior de la falla de basamento, se desarrollaron cuencas sinclinales sobre las evaporitas del Triásico Superior, un sistema de tectónica de piel fina con diapiros reactivos (salt-rollers) y fallas lístricas despegadas en el techo de estas evaporitas se desarrolló en el bloque inferior de estas fallas

Polyphased mesozoic rifting from the Atlas to the north-west Africa paleomargin.

24 pagesInternational audienceBased on the interpretation of geological maps, seismic reflection and well data complemented with a bibliographic compilation and field work in the Rif, we investigate the factors that control the rift initiation, its development and the formation of oceanic crust in NW Africa. From SE to NW, we examine the Western Sahara Atlas, the Tendrara, the Guercif, and the Rif basins, to establish their geodynamic evolution in relation with the Mesozoic formation of the Central Atlantic and Maghrebian Tethys oceans, respectively. The Triassic extension was diffuse and developed over Lower Carboniferous horst-and-graben structures formed in the NW passive margin of Gondwana and involved in the subsequent late Carboniferous – early Permian Variscan orogenic system; suggesting that, at the onset of the Triassic rifting, the lithosphere was thermally re-equilibrated and replaced by more fertile lithospheric mantle. Afterwards, extension resumed in the Atlas system during middle to late Pliensbachian and finished during Toarcian. In the Rif and Guercif basins, the extension began later, mainly during the Toarcian, climaxing during Middle Jurassic times with the exhumation along low-angle extensional faults of CAMP gabbroic bodies and the final mantle exhumation during Upper Jurassic in the Rif. The study evidences the prominent role of the Variscan structural and thermal inheritance on the subsequent deformation events. Accordingly, the Paleozoic inverted basins and horsts localized the Triassic extension. From that, the opening of the Central Atlantic and Maghrebian Tethys oceans activated, respectively, the SE (Atlas) and NW (Tethys) rifted segments of the weakened continental crust where the Jurassic extension was gradually distributed. This led to the final formation of an oceanic domain in the NW paleomargin of Africa