U-Pb detrital zircon ages from Gorgoglione Flysch sandstones (Southern Apennines, Italy): inferences on source area

LA-ICP-MS U-Pb ages were collected on detrital zircons from one sample of sandstone belonging to the Gorgoglione Flysch (GF) outcropping in Southern Apennines (Basilicata Region, Italy). The Gorgoglione Flysch represents a sedimentary siliciclastic succession having ≈1500 m thickness consisting of coarse-medium grained turbidites with mudstone layers. The deposition age of detritus was Langhian-Serravallian in a wedge-top basin belonging to the Southern Apennine Foreland Basin System (e.g. Lentini et al., 2002). GF sandstones show immature mineralogical composition and textural features. The composition varies from arkoses to lithic arkoses with some abundance of micas; the texture shows widespread siliciclastic and calcareous matrix and scarce cementation. The provenance studies on GF sandstones based on quantitative modal analysis, indicated a crystalline basement formed by continental crust rocks located in the eastern sectors of the Alpine Chain (Critelli & Loiacono, 1988). The prevalent granitoids and low grade metamorphic rocks occur in the crystalline basement as testified by nature of lithic fragments in GF sandstones. The detrital zircon radiometric dating through U-Pb spot analyses, tend to establish the ages of the source rocks supplying the sedimentation basin in Langhian-Serravallian times. The age data collected on nine detrital zircons selected by one sample of sandstone reveal twelve ages ranging from Neoproterozoic to Triassic ages and four Oligocene-Aquitanian ages. The oldest age (669±25 Ma) was measured on homogeneous luminescent zircon probably derived from metamorphites; a meaningful Carboniferous-Permian age cluster (n=10) ranging from 319±13 Ma to 262±4 Ma seem connected to zircons showing oscillatory magmatic zoning linked to granitoid and to recrystallized zircons in metamorphic conditions; one Triassic age (247±6 Ma) was measured on broken crystal whereas four sub-concordant ages (25±1 Ma to 23±9 Ma) are shown by two euhedral zircon crystals with regular oscillatory magmatic zoning. The preliminary dating of detrital zircons from GF sandstones seem to indicate a provenance of detritus from Hercynian magmatic and metamorphic rocks forming the Alpine chain but the presence of a younger magmatic component suggested that even igneous rocks connected to Oligocene magmatic activity were present in the source area