The onset of the syn-orogenic sedimentation in the Flysch Basin of the Sicilian Maghrebids: state of the art and new biostratigraphic constraints

The synorogenic deposits forming the uppermost part of the stratigraphic su ccessions of the Sicilide Units have been studied in order to recognize the tectogenetic phases in the Sicilian sector of the Maghrebian Chain. The Si cilide Units deposits sedimented in the Maghrebian Flysch Basin, which repr esents the southernmost of the oceanic branches separating, from the Late J urassic, the European and African plates and the microcontinents located be tween them. The study, focused on the Troina-Tusa Unit, has shown that it consists of p revalently marry-clayey foreland deposits, from Cretaceous to early Miocene age. Within the uppermost part of these deposits arenaceous beds appear, w hich mark the transitional boundary with two heteropically lying turbiditic formations. The first one (Tusa Tuffite Fm.) is characterized by volcanoar enitic layers, whereas the second one (Troina Sandstone Fm.) consists of ar kosic and lithic arkosic beds, interbedded with conglomerates and pelites. These two formations testify the onset of the foredeep stage in the Sicilid e Basin evolution, occurring through the replacement of the marry-clayey se diments by syn-orogenic turbiditic deposits. Contemporaneously, an active a ndesitic magmatic are supplies abundant epiclastic detritus to the internal areas of the basin. In the uppermost levels of the marry-clayey sediments microfloras indicate an age not older then Aquitanian. Coccoliths and foraminifera in the overly ing Tusa Tuffite and Troina Sandstone Fms, indicate an age not older than B urdigalian for the synorogenic turbiditic sediments. Therefore, these depos its are more recent than indicated up to now (upper Oligocene-middle Aquita nian), Consequently. the deformation of the Sicilide Basin, the consumption of the Maghrebian oceanic area and the following Africa-Europe continental collision must have occurred in late Burdigalian or during the Langhian. Biostratigraphic and field data show that there is no evidence, in the Sici lian sector of the Maghrebian Flysch Basin, of the meso-Alpine, Eocene-earl y Oligocene, tectogenetic phases, which have been recently re-proposed by s ome authors. They rather agree with the Aquitanian deformation of the more internal Peloritanian Domain. Moreover. they question the deformation age o f the Maghrebian External Domain contiguous to the Flysch Basin (Panormide and Imerese Zones). These latter must have been deformed not earlier than L anghian, or, more probably, during the Serravallian, later than what was th ought up to now. Finally, the new data indicate a synchronous deformation in the whole Maghr ebian Flysch Basin from the Calabria-Peloritani Are to the Rif and Eerie Co rdilleras.