A lost realm in the internal domains of the Betic-Rif Orogen (Spain and Morocco): Evidence from conglomerates and consequences for Alpine geodynamic evolution

The Malaguide-Ghomaride Complex is capped by Upper Oligocene-Aquitanian ela stic deposits postdating early Alpine orogenesis but predating the main tec tonic-metamorphic evolution, end of nappe emplacement, unroofing, and exhum ation of the metamorphic units of the Betic-Rif Orogen. Two conglomerate in tervals within these deposits are characterized by clasts of sedimentary, e pimetamorphic, and mafic volcanic rocks derived from Malaguide-Ghomaride un its and by clasts of acidic magmatic and orthogneissic rocks of unknown pro venance, here studied. Magmatic rocks originated from late-Variscan two-mic a cordierite-bearing granitoids and, subordinately, from aplitic dikes. Ort hogneisses derive from similar plutonic rocks but are affected by an Alpine metamorphic overprint evolving from greenschist (T= 510 degrees-530 degree s C and P = 5-6 kbar) to low-temperature amphibolite facies (T> 550 degrees 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 i n the orthogneisses is different from (and older than) that of Alpujarride- Sebtide rocks to which they were formerly ascribed. Magmatic and metamorphi c rocks very similar to those studied characterize the basements of some Ka bylia and Calabria-Peloritani units. Therefore, the source area is a curren tly lost continental-crust realm of Calabria-Peloritani-Kabylia type, locat ed to the ESE of the Malaguide-Ghomaride Domain and affected by a pre-lates t Oligocene Alpine metamorphism. Increasingly active tectonics transformed this realm into rising areas from which erosion fed small subsiding synorog enic basins formed on the Malaguide-Ghomaride Complex. This provenance anal ysis demonstrates that all these domains constituted a single continental-c rust block until Aquitanian-Burdigalian times, before its dispersal around nascent western Mediterranean basins.