First U–Pb detrital zircon ages from Numidian sandstones in Southern Apennines (Italy): Evidences of African provenance

Abstract

Two samples of quartz-rich sandstones collected in the Numidian Flysch of Southern Apennines (Italy) have been studied to highlight the provenance of detritus using radiometric dating by LA-ICP-MS of detrital zircons and to compare the obtained ages with those of the Betic and Maghrebian Chains. The provenance of quartzose detritus from European or African Plates is still debated in these Chains, accordingly the ages of the detrital zircons can contribute significantly to discriminate the origin of the quartzose supply.The U–Pb zircon ages (n=47) vary from 3047±13Ma (Mesoarchean) to 516±19Ma (Cambrian). The predominance of Paleo-Proteozoic ages (2500–1600Ma) and the lack of Hercynian and Alpine ones suggest a provenance of the Numidian supply from North-African cratonic areas during the early–middle Langhian, when the Numidian successions of Southern Apennines were deposited. In addition, a cluster of ages at 773±24Ma and 668±12Ma in one sample and at 664±17Ma in the other sample, calculated on zircon domains with magmatic zoning, testify to an important contribution from Neo-proterozoic “granitic” rocks widely outcropping in the North-African Craton.The age data on detrital zircons from Numidian sandstones in Southern Apennines overlap those found in the Numidian sandstones widespread in the Betic Cordillera and in the Maghrebian Chain from south Spain to Sicily. This suggests that the entire depositional zone in which Numidian Flysch deposited, was fed from a southerly source represented by the African Craton where Archean, Proterozoic and Cambrian rocks widely crop out from the Atlantic coast to the Hoggar and Tibesti Massifs. Finally, it must be outlined that a Meso-Archean zircon age (3047Ma) has been found in the Numidian Flysch of the Southern Apennines whereas in the Numidian Flysch of the Maghrebian Chain, zircons older than Paleo-proterozoic (1840Ma) have not yet been found.