The Lower Miocene volcaniclastic sedimentation in the Sicilian sector of the Maghrebian Flysch Basin: geodynamic implications

Abstract Volcaniclastic debris-rich formations, characterising the Troina–Tusa Unit in the Sicilian Maghrebian Chain, are examined. The Troina–Tusa Unit terrains sedimented in the Maghrebian Flysch Basin, which, from Jurassic to Early Miocene, constituted the southernmost branch of the Western Tethys, located between Africa and the Mesomediterranean Terrane margins. New field, biostratigraphic and petrographic data enable a reconstruction of the palaeogeographic and structural evolution of the Flysch Basin immediately before its deformation. All the studied formations transpired to be Burdigalian in age. The sandstone compositions, showing different source areas (magmatic arc, recycled orogen and continental block), indicate a provenance for the clastic material from a crystalline basement with an active volcanic arc, replaced by a remnant volcanic arc, which was rapidly completely eroded. The source area that has been considered is Sardinia, where Upper Oligocene–Aquitanian calc-alkaline volcanites are widespread, but the sedimentological characteristics and the Burdigalian age do not fit with this provenance. The Burdigalian calc-alkaline arc should be located on the internal side of the Troina–Tusa Basin, above the already stacked Peloritanian units. A migration of the volcanic activity, connected with the subduction plain roll-back, can be envisaged from the Sardinia Block to the Peloritanian Chain, this latter still docked to the Sardinia–Corsica massif

New biostratigraphic and petrographic data from the Poggio Carnaio Sandstone Fm (Val Marecchia Nappe): insights into the tectonic evolution of the Northern Apennines.

In the Northern Apennines, the Poggio Carnaio Sandstone Formation consists of sandy-clayey turbidites, cropping out in the northernmost corner of the Val Marecchia Nappe. The formation has been considered Oligocene in age and is commonly interpreted as an Epiligurian unit, unconformably deposited above the Val Marecchia Nappe during its transport towards the Adriatic foreland. The Poggio Carnaio Sandstone Fm rests on the Argille Varicolori Fm of the Val Marecchia Nappe, but field data do not allow it to be recognized wherever it abruptly replaces the pelagic sediments of the Argille Varicolori Fm, thus testifying to the foredeep evolution of the basin, or where it unconformably overlies this latter formation. Nannofossil assemblages are characterized by abundant reworked Cretaceous and Paleogene taxa and by some taxa, whose first occurrence is reported in the upper part of the NN4 Zone = upper part of the CN3 Zone. Therefore the formation must be considered not older than Langhian. Detrital modes of arenites revealed a quartz-feldspathic composition and the lithic component includes mainly metamorphic fragments and minor plutonic, sedimentary, ophiolithic and volcanic clasts. The presence of clasts of garnet, sillimanite, hornblende and glaucophane is significant. Biostratigraphic as well as petrographic data agree with the interpretation of the Poggio Carnaio Sandstone Fm as an Epiligurian succession. Rock fragments indicate source areas characterized by Ligurian-, Pennidic- and Australpine-type units. Sedimentary facies and textural features of arenites, revealing a rapid erosion and deposition of clasts in a basin close to the source area of the clastic supply, indicate that the Alps cannot be considered as the source area of these arenites, as frequently argued for many North-Apennine clastic formations. Ligurian-, Pennidic- and Australpine-type units were located close to the Poggio Carnaio Sandstone basin, probably representing the geometrically highest units of the Palaeo-Apennine Chain

Occurrence of upper Burdigalian silexite beds within the Beni Ider Flysch Fm. in the Ksar-es-Seghir area (Maghrebian Flysch Basin, Northern Rif, Morocco): stratigraphic correlations and geodynamic implications.

In the Maghrebian Chain, pelagic and turbiditic successions deposited on the oceanic crust of the Flysch Basin crop out from Gibraltar to Sicily, tectonically juxtaposed between the External and Internal Nappes. In the Rifian Maghrebids, the Mauretanian successions, deposited on the northern side of the basin and supplied by a >, are represented by the Tisirene and Beni Ider Nappes, the latter including at the top the turbiditic Beni Ider Flysch Formation. The age of the Beni Ider Flysch, important to constrain both the evolution to foredeep of the basin and the onset of the compressional deformation, is still highly debated because ages ranging from early Oligocene to early Burdigalian have been proposed. In the Dchar Foual area, some sections, characterized at the top by silexite beds, have been sampled. The lowermost beds furnished nannoplankton associations not older than Chattian (Zone CP19b), whereas the highest ones gave results not older than late Burdigalian (Zone CN3). The latter age fully agrees with ages found in the Betic Algeciras Flysch and in the Sicilian Troina-Tusa Flysch, as well as in the Sicilide successions of Southern Apennines. This late Burdigalian age represents a constraint that cannot be neglected in the reconstructions of the tectonic evolution of the Alpine Chains of the Western Mediterranean, from the Betic Cordillera to the Apennines

The Poggio del Carnaio Sandstones: age, petrography and importance for the reconstruction of the Northern Apennines evolution.

none5noneDI STASO A; S. PERROTTA; GUERRERA F; PERRONE V; TRAMONTANA MDI STASO, A; Perrotta, S.; Guerrera, F; Perrone, V; Tramontana, M