LA-ICP-MS U-Pb ages were collected on detrital zircons from two samples of sandstones belonging to Bifurto Formation (BF) (Southern Apennines, Italy). These rocks deposed on carbonatic Campano-Lucana platform are considered analogous for stratigraphic position and deposition age (Langhian time) to Numidian Flysh (NF) sandstones deposed in Lagonegro basin, both cropping out along the east area of the Apenninic chain (D’Errico et al., 2014). However BF arenites show a scarce textural maturity (high content of matrix, angular quartz grain presence, poor sorting) respect to FN typical ultramature sandstones, evidencing a certain variability within the “Numidian type“ deposits. This study mainly aims to suggest the provenance of quartzose detritus of Bifurto sandstones comparing their detrital zircon ages with those of the NF deposits. The age data collected on the Bifurto sandstones reveal zircon ages ranging from 2551±40 Ma to 425±9 Ma (fifty-seven concordant ages) and overlapping those of the zircons from NF sandstones (3047±13 Ma - 516±19 Ma) (Fornelli et al., 2015). In Bifurto sandstones two zircon ages at 450 and 425Ma are present whereas these ages are missing in typical numidian sandstones. Relevant is the absence of Hercynian and Alpine zircon ages in all analysed quartzose sandstone samples. In addition, the internal pattern zoning (mainly oscillatory zoning evidenced by SEM imaging technique) of the detrital zircons, in both cases, suggest a magmatic origin of the crystals with ages > 516-517 Ma, therefore a basement in which granitoids or meta-granitoids with ancient ages could be invoked for detritus provenance. A comparison of detritic zircon ages of the “Numidian Type” sandstones from Southern Apennines with those found in Numidian sandstones of Spain, Morocco, Algeria and Sicily (Thomas et al., 2010 and references therein) indicates similar provenance of detritus. The obtained data strengthen the interpretation that the entire area of the African Craton, extending from the Atlantic coast to the Hoggar and Tibesti Massifs, where Archean, Palaeoproterozoic and Cadomian-Panafrican rocks, not involved in the Hercynian or Alpine orogenetic cycles, are widely diffused (Gasquet et al., 2004), represented the common source area of the quartzose supply forming the Numidian successions both in the Maghrebian and Apenninic domains. This provenance is also supported by mineralogical and geochemical data on the Numidian mudstones having kaolinite composition (Mongelli, 2004) derived from weathered areas in which lateritic soils widely occurred. Summing up, even if the quartz rich sandstones outcropping in Central-Southern Italy have a younger deposition age (Langhian) with respect to that of Maghrebian Chain (Aquitanian), the signatures of detrital zircon ages are comparable indicating the same provenance area despite a certain delay in the supply of sediments.

U-Pb detrital zircon ages in "Numidian Type" sandstones from Southern Apennines (Southern Italy): inferences on supply provenance

Annamaria Fornelli;Francesca Micheletti;PERRONE, VINCENZO
2017

Abstract

LA-ICP-MS U-Pb ages were collected on detrital zircons from two samples of sandstones belonging to Bifurto Formation (BF) (Southern Apennines, Italy). These rocks deposed on carbonatic Campano-Lucana platform are considered analogous for stratigraphic position and deposition age (Langhian time) to Numidian Flysh (NF) sandstones deposed in Lagonegro basin, both cropping out along the east area of the Apenninic chain (D’Errico et al., 2014). However BF arenites show a scarce textural maturity (high content of matrix, angular quartz grain presence, poor sorting) respect to FN typical ultramature sandstones, evidencing a certain variability within the “Numidian type“ deposits. This study mainly aims to suggest the provenance of quartzose detritus of Bifurto sandstones comparing their detrital zircon ages with those of the NF deposits. The age data collected on the Bifurto sandstones reveal zircon ages ranging from 2551±40 Ma to 425±9 Ma (fifty-seven concordant ages) and overlapping those of the zircons from NF sandstones (3047±13 Ma - 516±19 Ma) (Fornelli et al., 2015). In Bifurto sandstones two zircon ages at 450 and 425Ma are present whereas these ages are missing in typical numidian sandstones. Relevant is the absence of Hercynian and Alpine zircon ages in all analysed quartzose sandstone samples. In addition, the internal pattern zoning (mainly oscillatory zoning evidenced by SEM imaging technique) of the detrital zircons, in both cases, suggest a magmatic origin of the crystals with ages > 516-517 Ma, therefore a basement in which granitoids or meta-granitoids with ancient ages could be invoked for detritus provenance. A comparison of detritic zircon ages of the “Numidian Type” sandstones from Southern Apennines with those found in Numidian sandstones of Spain, Morocco, Algeria and Sicily (Thomas et al., 2010 and references therein) indicates similar provenance of detritus. The obtained data strengthen the interpretation that the entire area of the African Craton, extending from the Atlantic coast to the Hoggar and Tibesti Massifs, where Archean, Palaeoproterozoic and Cadomian-Panafrican rocks, not involved in the Hercynian or Alpine orogenetic cycles, are widely diffused (Gasquet et al., 2004), represented the common source area of the quartzose supply forming the Numidian successions both in the Maghrebian and Apenninic domains. This provenance is also supported by mineralogical and geochemical data on the Numidian mudstones having kaolinite composition (Mongelli, 2004) derived from weathered areas in which lateritic soils widely occurred. Summing up, even if the quartz rich sandstones outcropping in Central-Southern Italy have a younger deposition age (Langhian) with respect to that of Maghrebian Chain (Aquitanian), the signatures of detrital zircon ages are comparable indicating the same provenance area despite a certain delay in the supply of sediments.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11586/206879
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