From ductile to brittle, late- to post-orogenic evolution of the Betic Cordillera: Structural insights from the northeastern Internal zones

Abstract

Abstract. -Relations between Alpine detachment-bounded metamorphic domes, crustal-scale strike-slip fault zones and sedimentary basins in the Internal zones of the Betic cordillera are still matter of debate. Current tectonic interpretations of these basins vary from late-orogenic extensional structures to compressional ones associated with strike-slip motions along major still active faults. Structural investigations including new field mapping, meso-scale faults recognition, palaeostress analysis of brittle small-scale faults systems were performed in the sedimentary cover of the Almanzora corridor and the Huércal-Overa basins, located either in the hanging wall unit of the Filabres extensional shear zone or at the termination of the Alhama de Murcia sinistral fault zone. In parallel, a detailed study of the ductile and the ductile-brittle deformation was carried out in the footwall unit of the Filabres extensional shear zone, in the NevadoFílabride complex. Three main brittle events were recognised in the basin cover including two extensional events that occurred prior to a weak tectonic inversion of the basin during a third, still active event. The first one, D1 b is characterized by the development a first stress regime consistent with~NW-SE extensional tectonics. Besides, the consistency between the latest ductile and the brittle kinematics for the Filabres extensional shear zone and the activity of meso-scale fault systems that primarily control the main SW-NE depocentres allow concluding to a top-to-the-NW continuum of strain during the final exhumation of the Nevado-Filábride complex. The resulting overall half-graben architecture of the basins is then related to the combination of the formation of the metamorphic domes that added a local control superimposed on the regional deformation. Indeed, after a consistent top-to-the-west shearing prevailing during most of the Nevado-Filábride exhumation, final exhumation stages were in turn, characterised by important kinematics changes with a subordinate top-to-the-NW sense of shear (D1 b ). The onset of sedimentation in the basins occurred shortly after the crossing of the ductile-brittle transition in the underlying metamorphic domes at ca. 14 Ma into SW-NE fault-bounded troughs. Tectonic subsidence was then maintained during D2 b while extensional kinematics changed to N-S or even locally to SSW-NNE. Extensional tectonics then lasted most of the Tortonian during the final tectonic denudation increments of the Sierra de los Filabres achieved at ca. 9-8 Ma. Intramontane basins are therefore genuinely extensional and clearly related to the latest exhumation stages of the Nevado-Filábride complex in the back-arc domain. Conversely, at ca. 8 Ma, basins started to record a~N-S to NNW-SSE compressional stress regime (D3 b ) and ceased to be active depocentres while shortening within the Internal zones then recorded only the Iberia/Africa convergence. The weak inversion of the basins however resulted either in the reactivation of originally extensional faults such ...

Subduction- and exhumation-related structures preserved in metaserpentinites and associated metasediments from the Nevado–Filábride Complex (Betic Cordillera, SE Spain)

“…Only when the rocks of the Nevado-Filábride Complex reached upper crustal conditions at 12-9 Ma was exhumation accommodated by brittle extensional detachments as described extensively by several authors (e.g., Augier et al, 2013;Do Couto et al, 2014;Galindo-Zaldívar et al, 1989;Jabaloy et al, 1993).…”

“…This has led to the redefinition of the Alborán Domain as only the two uppermost complexes (Alpujárride and Maláguide). The Nevado-Filábride Complex is now considered part of the Iberian Massif palaeomargin that was subducted below the allochthonous Alborán Domain just after the subduction of the Alpujárride Complex at 20 Ma, and accreted below the Alpujárride rocks during a late exhumation event (Augier et al, 2013;Behr and Platt, 2012;Booth-Rea et al, 2007Gómez-Pugnaire et al, 2004Platt et al, 2013). In this context, the structural evolution documented in this paper was related to the initiation of a subduction zone rather than the initial fabrics that develop within a subducted slab entering a subduction zone that may have been active for some period of time.…”

Tectonic inversion of an asymmetric graben: Insights from a combined field and gravity survey in the Sorbas basin

“…This later displays an overall half‐graben geometry accompanied by mesoscale to small‐scale synsedimentary normal faults. Its formation and its development have been associated with the exhumation of the NF metamorphic complex in the Sierra de Los Filabres metamorphic dome [ Augier et al ., ; Meijninger and Vissers , ; Augier et al ., ] (see Figure ). According to Augier et al .…”

“…Conversely, timing of the final exhumation stages in the greenschists facies conditions spans over the middle and the late Miocene (from 15 to 9 Ma) [ de Jong , ; Monié and Chopin , ; Johnson et al ., ; Augier et al ., ; Platt et al ., ; Vázquez et al ., ] through an ~E‐W regional‐scale extension [ Jabaloy et al ., ]. Final exhumation stages in the brittle regime at circa 13–12 Ma were accompanied by the development of extensional sedimentary basins such as the Huércal‐Overa basin [ Vissers et al ., ; Augier , ; Meijninger and Vissers , ; Augier et al ., ].…”

3D modelling of the Sorbas Basin (Spain): New constraints on the Messinian Erosional Surface morphology

“…2C). From Tortonian and up to, at least, the Sorbas Member, the series of the Sorbas Basin display a progressive decrease in fold amplitude; such feature most certainly results from an ongoing NeS compression active since the late Tortonian (Galindo-Zaldívar et al, 1993;Augier et al, 2013;Do Couto et al, 2014).…”