A Lost Realm in the Internal Domains of the Betic‐Rif Orogen (Spain and Morocco): Evidence from Conglomerates and Consequences for Alpine Geodynamic Evolution

Abstract

The Malaguide-Ghomaride Complex is capped by Upper Oligocene-Aquitanian clastic deposits postdating early Alpine orogenesis but predating the main tectonic-metamorphic evolution, end of nappe emplacement, unroofing, and exhumation of the metamorphic units of the Betic-Rif Orogen. Two conglomerate intervals within these deposits are characterized by clasts of sedimentary, epimetamorphic, and mafic volcanic rocks derived from Malaguide-Ghomaride units and by clasts of acidic magmatic and orthogneissic rocks of unknown provenance, here studied. Magmatic rocks originated from late-Variscan two-mica cordierite-bearing granitoids and, subordinately, from aplitic dikes. Orthogneisses derive from similar plutonic rocks but are affected by an Alpine metamorphic overprint evolving from greenschist (T=510&j0;-530 degrees C and P=5-6 kbar) to low-temperature amphibolite facies (T>550&j0;C and P<3 kbar). Such a plutonic rock suite is unknown in any Betic-Rif unit or in the basement of the Alboran Sea, and the metamorphic evolution in the orthogneisses is different from (and older than) that of Alpujarride-Sebtide rocks to which they were formerly ascribed. Magmatic and metamorphic rocks very similar to those studied characterize the basements of some Kabylia and Calabria-Peloritani units. Therefore, the source area is a currently lost continental-crust realm of Calabria-Peloritani-Kabylia type, located to the ESE of the Malaguide-Ghomaride Domain and affected by a pre-latest Oligocene Alpine metamorphism. Increasingly active tectonics transformed this realm into rising areas from which erosion fed small subsiding synorogenic basins formed on the Malaguide-Ghomaride Complex. This provenance analysis demonstrates that all these domains constituted a single continental-crust block until Aquitanian-Burdigalian times, before its dispersal around nascent western Mediterranean basins.

Age of anatexis in the crustal footwall of the Ronda peridotites, S Spain

“…Middle Miocene (17-15 Ma) ages for the HP-LT metamorphic event in the Nevado-Filábride (López Sánchez-Vizcaíno et al, 2001;Platt et al, 2006) suggest that this complex is a slab of the Iberian margin that underthrusted the Alborán domain during the Early Miocene collision. The Maláguide complex (Blumenthal, 1930;Foucault and Paquet, 1971) is made of Early Paleozoic to Eocene rocks (Martín-Algarra et al, 2000). Although all materials are strongly deformed by thrusts and folds, Permo-Triassic to Eocene rocks appear unmetamorphosed and lie uncomformably on the pre-Permian basement.…”

Transformation of Andalusite to Kyanite in the Alpujarride Complex (Betic Cordillera, Southern Spain): Geologic Implications

“…This belt resulted from the Alpine collision between the Iberian, African, and Mesomediterranean plates formed during the Mesozoic breakup of the Pangea supercontinent (Martín-Algarra 1987;Guerrera et al 1993;Martín-Algarra et al 2009b). The orogenic belt was later fragmented during and after the Late Miocene, when the Western Mediterranean basins opened, thus producing the outward (foreland) migration of its fragments (Martín-Algarra et al 2000). One of these fragments constitutes the Betic Internal Zones, which, together with the Internal Zones of the Rif (Morocco) and the basement of the Alboran Sea, form the so-called Alboran Domain (Balanyà and García Dueñ as 1987).…”

“…1B) of (essentially) Miocene age (quite probably preceded by late Cretaceous to early Tertiary tectonometamorphic events; see Puga et al 2000Puga et al , 2002references therein). This stack was strongly thinned by mid-to late-Miocene orogenic extensional collapse (Balanyà et al 1993;Platt et al 1996Platt et al , 1998Platt et al , 2003Argles et al 1999a) coeval with the disintegration of the AlKaPeCa belt (Martín-Algarra et al 2000) and is unconformably covered by Burdigalian deposits (Viñ uela Group; fig. 1C with slightly different lithostratigraphy and metamorphic grade of Alpine age (Vera 2004;references therein).…”

Tectonic evolution of the Sicilian Maghrebian Chain inferred from stratigraphic and petrographic evidences of Lower Cretaceous and Oligocene flysch

“…The sedimentary succession of these internal sectors (the so-called "Dorsale Calcaire", sensu Fallot 1937) is almost the same along all the western peri-Mediterranean chains, between the Gibraltar and Calabria-Peloritani Arcs. The Rifian "Dorsale Calcaire" is often marked by a pronounced discontinuity because its Mesozoic portion (Triassic-Liassic Verrucano-like redbeds evolving to Lower Jurassic platform carbonates; Perrone et al 2006;Critelli et al 2008;Zaghloul et al 2009;Perri et al 2011Perri et al , 2013, related to the Tethyan rifting, usually lacks post-Toarcian to Upper Cretaceous deposits (Chalouan et al 2008) and, locally, it is topped by Eocene detrital Nummulitic limestones (Nold et al 1981;El Kadiri et al 2006), representing a depositional sequence post-dating an early Alpine compressive event (Maate 1996;Martin-Algarra et al 2000). Unconformable Oligocene turbidite deposits locally characterize the top of the succession (Olivier 1979;Durand-Delga & Fontboté 1980;Wildi 1983;Zaghloul et al 2005;Puglisi 2008); 2.…”