Extension versus compression during the Miocene tectonic evolution of the Betic chain. Late folding of normal fault systems

Abstract

The westernmost part of the Mediterranean Alpine Belt is represented by the Betic‐Rif orogenic belt, around the Gibraltar Arc, which in turn surrounds the Alboran Basin. In the Betic Chain, early and middle Miocene crustal thinning of the Alboran basement is well established, as extensional low‐angle normal faults and detachment faults, developed in both ductile and brittle conditions, thinned a previously thickened crust. In the Alboran Domain of the central Betics, two main extensional episodes are evidenced: a Langhian one, with a north‐northwestward transport direction, followed by a west‐southwestward extension, Serravallian in age. Therefore all the units heretofore considered to be thrust nappes are, in reality, extensional units bounded by low‐angle normal faults. The cortical segment studied formed the basement of the Miocene Alboran Basin, in which progressively deeper basement units were covered by younger marine sediments as a result of extensional denudation processes. The age of these sediments clearly dates the faulting. The extensional evolution during the Miocene is much more complex than the past models suggest. During the upper Miocene, these extensional systems were folded as the result of a compressive regime, which allowed them to be well exposed. Compression in the Gibraltar Arc is nearly contemporaneous with extension, and the westward migration of the compression through its footwall is related with the extensional spreading.

The Tell-Rif orogenic system (Morocco, Algeria, Tunisia) and the structural heritage of the southern Tethys margin

“…They revealed large-scale extension associated with HT metamorphism (among others Fernandez et al, 2016;Negro et al, 2006;Platt and Whitehouse, 1999) and formation of crustal scale detachements (Augier et al, 2005;Caby et al, 2001;Crespo-Blanc et al, 1994;Jabaloy et al, 1993;Platt et al, 2005) producing deep unroofing during the Late OligoceneEarly Miocene, within the AlKaPeCa domain (Bruguier et al, 2009;Michard et al, 2006;Monié et al, 1992;Monié et al, 1994;Platt et al, 2003). This Miocene signal shows diachronous stages between the "AlKa" and "PeCa" domains, being older for the Peloritani and Calabria than for Alboran and the Kabylie basement (Michard et al, 2006;Platt et al, 2013 for the Betics-Rif-Tell data; Heymes et al, 2010;Rossetti et al, 2004Rossetti et al, , 2010 for the Peloritani-Calabria data).…”

Structural and kinematic constraints to the exhumation of the Alpujarride Complex (Central Betic Cordillera, Spain)

“…Comas et al, 1992;García-Dueñas et al, 1992) provides key issues for the timing and tectonic context of the brittle faulting affecting the Alpujarride Complex. In particular, Crespo-Blanc et al (1994) and Crespo-Blanc (1995) showed that extension liked to the Contraviesa fault system was active during Burdigalian-Langhian times (approximately 20.5-15 Ma, according to Berggren et al (1985)). Moreover, the lower Burdigalian generalised marine transgression in the inner part of the Gibraltar Arc suggests that the onset of extension in that region took place possibly at the Oligocene-Miocene boundary (Rodríguez-Fernández et al, 1999).…”

“…This faulting event is also responsible for the tectonic elision and thinning of the nappe sequences and can be thus referred to as the Early Miocene phases of the Alboran rifting. In particular, it can be tentatively ascribed to the Contraviesa extensional fault system of Crespo-Blanc et al (1994) for the style of deformation and the associated extension direction.…”

“…Comas et al, 1992;García-Dueñas et al, 1992;Martínez-Martínez and Azañón, 1997). The first, associated with a NNW-SSEtrending extension direction, corresponds to the Early Miocene in age Contraviesa fault system of Crespo-Blanc et al (1994), and the second corresponds to the Middle Miocene top-to-the-WSW Filabres extensional detachment system, whose sole detachment marks the Alpujarride/ Nevado-Filabride tectonic boundary (García-Dueñas et al, 1986;Platt and Vissers, 1989;García-Dueñas et al, 1992;Johnson et al, 1997;Martínez-Martínez et al, 2002). The final uplift of part of the Alboran Basin and its basement is due to a post-Tortonian to Present N-S to NW-SE compression, which produced folds (mainly kilometre-scale E-W-striking folds) and faults (high-angle normal and reverse faults and conjugate systems of strike-slip faults) (e.g.…”

“…Names of Alpujarride units are after Azañón et al (1994). Hanging-wall movement along D 4 faults according to García-Dueñas et al (1992), Crespo-Blanc et al (1994), Azañón and Crespo-Blanc (2000) and this work. The geological cross-section, modified after Azañón and Crespo-Blanc (2000), illustrates the tectonic setting of the Betic Cordillera in the study area and the control operated by the D 4 faulting episode on the present structural architecture of the Alpujarride Complex.…”