An evaporite‐bearing accretionary complex in the northern front of the Betic‐Rif orogen

Abstract

The Guadalquivir Accretionary Complex forms a largely oblique prism at the northern edge of the Betic‐Rif orogen, where Miocene sediments plus allochthonous evaporite‐bearing units were accreted during the displacement of the Alborán Domain toward the west. Traditional interpretations end the tectonic structuring of the Betic Cordillera at the present topographic front, beyond which gravitational and/or diapiric processes would predominate. However, this study shows pervasive tectonic deformation in the outer prism with coherent oblique shortening kinematics, which is achieved through an alternation of roughly N‐S arcuate thrust systems connected by E‐W transfer fault zones. These structures accord well with the geophysical models that propose westward rollback subduction. The main stage of tectonic activity occurred in the early‐middle Miocene, but deformation lasted until the Quaternary with the same kinematics. Evaporite rocks played a leading role in the deformation as evidenced by the suite of ductile structures in gypsum distributed throughout the area. S‐ and L‐ gypsum tectonites, scaly clay fabrics, and brittle fabrics coexist and consistently indicate westward motion (top to 290°), with subordinate N‐S contraction almost perpendicular to the transfer zones. This work reveals ductile tectonic fabrics in gypsum as a valuable tool to elucidate the structure and deformational history of complex tectonic mélanges involving evaporites above the décollement level of accretionary wedges.

Tectono‐Stratigraphic and Thermal Evolution of the Western Betic Flysch: Implications for the Geodynamics of South Iberian Margin and Alboran Domain

“…In the western Betic, Triassic sedimentary rocks are exposed in the Guadalquivir accretionary wedge (GAW) and in the chaotic complexes of the central and western Betic (Figure 4). The Buntsandstein facies is absent in the Subbetic and the sequence is restricted to Muschelkalk and Keuper facies (Martínez-García et al, 2017;Pérez-Valera et al, 2017) at the origin of the diapiric structures (Flinch & Soto, 2017). A detrital, continental to coastal Triassic facies is observed in the Malaguide which contrasts with Alpine-type carbonate-dominated series of the AJ (Martín-Algarra, 1987;Ortí et al, 2017).…”

“…Salt tectonics is known to be at the origin of several peculiar structural features observed in the western Betic (Flinch & Soto, 2017). The GAW represents an accretionary complex emplaced during the Miocene, from late Burdigalian to Tortonian, made of the Median and External Subbetic Zones and the Flysch Complex glided northward and emplaced in the Guadalquivir Basin (Pérez-Valera et al, 2017). It is made of a chaotic mélange comprising blocks of Meso-Cenozoic sediments in a matrix of Triassic clays and gypsum.…”

“…The apparent structural complexity of the GAW reflects diapiric events that occurred first on the Iberian paleomargin between late Cretaceous and Paleocene. These initial phase of salt mobilization was followed by the extrusion and spreading of salt sheets associated with north-propagating frontal thrust during the late Oligocene to early Miocene (Berástegui et al, 1998;Flinch et al, 1996;Flinch & Soto, 2017;Pérez-Valera et al, 2017;Vera, 2000). The dominant control by salt on the tectonics of the Subbetic is further indicated by (1) Triassic evaporites found resedimented in the Cretaceous-Paleocene, (2) the lack of Jurassic or lower Cretaceous strata that are otherwise present in the Subbetic, and (3) the identification of Cretaceous-Paleogene subbasins (Flinch & Soto, 2017).…”

Measurement of Road Surface Deformation Using Images Captured from UAVs

“…These units consist in a set of materials with a complex structure and diverse lithology, in which the following formations predominate: Triassic evaporites and shales, Cretaceous-Paleogene marls and clays, and Miocene loamy-clay sediments belonging to the Guadalquivir basin. In this area the Guadalquivir Units are represented by marls and clays overthrusted by thick stratigraphic successions of Jurassic limestones from Intermediante Betic Units, which form a prominent relief (Figure 1c) [65][66][67][68]. The contact is dotted with small alluvial fans, thick piedmont deposits and travertines, the last associated with springs at the foot of the Jurassic limestones.…”

“…The contact is dotted with small alluvial fans, thick piedmont deposits and travertines, the last associated with springs at the foot of the Jurassic limestones. In the study area the geological Guadalquivir Units outcrop [66]. These units consist in a set of materials with a complex structure and diverse lithology, in which the following formations predominate: Triassic evaporites and shales, Cretaceous-Paleogene marls and clays, and Miocene loamy-clay sediments belonging to the Guadalquivir basin.…”