Regional correlations across the Internides-Externides front (northwestern Rif Belt, Morocco) during the Late Cretaceous-Early Burdigalian times: palaeogeographical and palaeotectonic implications

Abstract

New insights into the palaeogeographical evolution of the Rifian Internides and their external surroundings are inferred from six key stratigraphic successions selected across the Internides-Externides front. These successions span a time interval ranging from the late Cretaceous to the early Burdigalian. The main results are: (1) important lost palaeogeographical domains should be located during the late Cretaceous-Eocene between the present-day Ghomarides and the Dorsale Calcaire, on one hand, and between the Predorsalian units and the Flysch Trough as isolated carbonate platforms, on the other hand; (2) during the late Eocene-early Oligocene an extensional tectonic event, well marked in the Dorsale Calcaire, caused the collapse of these platforms and resulted in olistostromes and coarse-grained breccias in both the Predorsalian and the Btni Ider areas; (3) by the beginning of mid-Oligocene, an overturning contractional event in the Ghomarides resulted in the regional onset of the siliciclastic depositional regime throughtout these palaeogeographical areas; (4) during the Aquitanian-early Burdigalian, the stepwise return of pelagic deposition in the Ghomarides indicates extensional phases, whereas the homogenization of the same pelagic facies over the Dorsale Calcaire and its external surroundings may indicate that the previously distant palaeogeographical areas were brought nearer (i.e. just before large-scale thrusting).The Gibraltar arc consists of two juxtaposed structural domains: (1) the Internal Domain, (Internides) where the orogenic contractions started from Oligocene time and generally resulted in high-grade metamorphism, particularly in its innermost part; (2) the External Domain (Externides), where the outward migrating orogenic contractions during Miocene time progressively produced piggyback-foredeep basins and ramp-anticline structures. The culmination of these phenomena during the paroxysmal phase resulted in a high accretionary prism and successive large-scale gravitational processes (Chalouan et al. 2006).The Tertiary sedimentary filling within and/or close to these forming basins was differently interpreted in both domains. Whereas there is acceptance that the filling of the main flysch depocentres in the External Domain occurred shortly before the paroxysmal nappe emplacement, or even as syntectonic deposits, competing hypotheses were presented for the equivalent strata in the Internal domain. Some workers attempted to link them to postorogenic deposits transgressively sealing the paroxysmal structures (e.g. Durand-Delga et al. 1993), whereas others considered them as recording a near-continuous marine regime entirely predating the main orogenic events (e.g. Maat6 1996). Recently, detailed stratigraphic studies of the Oligo-Miocene cover were carried out in the Malaguides (Guerrera et al. 1993;Martin-Martin et al.

Origin and consequences of western Mediterranean subduction, rollback, and slab segmentation

“…In the Rif, Kabylides, and Peloritani Mountains, finally, a stack of nonmetamorphosed, rootless thrust sheets of Mesozoic‐Cenozoic carbonates (“Dorsale Calcaire” unit) is found, thrusted at the front of and structurally below the upper ALKAPECA units [ Michard et al ., ; Chalouan et al ., ]. The Dorsale Calcaire unit probably formed the sedimentary cover of part of the lower ALKAPECA units, which decoupled upon arrival in the subduction zone to form rootless nappes [ Frizon de Lamotte et al ., ; El Kadiri et al ., ].…”

Tectonic and stratigraphic evolution of the Western Alboran Sea Basin in the last 25 Myrs

“…2A; Torres-Roldán, 1979;Martínez-Martínez and Azañón, 1997;Michard et al, 2002). Located between the Malaguide/Ghomaride complex and the Flysch units, the Mesozoic-Paleogene Dorsale Calcaire represents the sedimentary cover of the inner Alboran domain (Chalouan and Michard, 2004;El Kadiri et al, 2006). Nevado-Filabride and Alpujarride/Sebtide complexes underwent a high-pressure (HP) and low-temperature (LT) metamorphism (Puga et al, 2000;López Sánchez-Vizcaíno et al, 2001;Martínez-Martínez et al, 2002a;Augier et al, 2005a).…”

“…As the latter is unlikely to reach the extension and thickness of SU1 (given the limited shape of the Maghrebian flysch klippe onshore), we opt for the Ghomaride complex. The Ghomaride unit is the topmost nappe composing the Alboran domain and mainly consist of slightly metamorphic Paleozoic successions (Chalouan, 1986) (Chalouan and Michard, 1990;Maaté et al, 2000;El Kadiri et al, 2006;Martín-Martín et al, 2006). The Ghomaride unit is separated from the Alpujarride-Sebtide by an extensional detachment (Chalouan and Michard, 1990).…”

The Betic-Rif Arc and Its Orogenic Hinterland: A Review

“…A thin and structurally incoherent zone called the pre-Dorsale developed along the external margin, characterized by deep-water Late Jurassic and Cretaceous sequences, including radiolarian cherts, and a Tertiary sequence transitional into the flysch units (De Wever et al 1985). Late Paleocene and late Eocene to Oligocene breccias and possible olistostromes in both the Dorsale and pre-Dorsale suggest Paleogene tectonism (El Kadiri et al 2006). In the western Betics, the Dorsale includes syntectonic breccias ascribed to the Aquitanian (Martín-Algarra & Estévez 1984).…”