Detrital zircons from the Hronicum Carboniferous–Permian sandstones (Western Carpathians, Slovakia): depositional age and provenance
For the assessment of depositional age and provenance of the Hronicum Unit Pennsylvanian to Permian siliciclastic sediments, SIMS (SHRIMP) U–Pb analyses have been carried out on detrital zircons. To constrain the presumed provenance of the Hronicum Unit sediments five samples have been taken from two lithostratigraphic units, the Nižná Boca and the Malužiná formations. The detrital-zircon age spectrum demonstrates two prominent populations, the first, Late Pennsylvanian–Early Cisuralian (288–309 Ma) and the second, Famennian—Tournaisian (345–371 Ma). The probability density age peak at 297 Ma permits to estimate the maximum sedimentation age of the Nižná Boca Fm. to younger than Asselian and the beginning of the Malužiná Formation sedimentation has been assessed at least in Sakmarian. The sedimentation persisted, with the exception of a short break in the Wordian/Capitanian, through the Lopingian. Smaller zircon age clusters range within 446–541 Ma, with a dominance of the Cambrian detrital zircons (491–541 Ma). The Precambrian time-span is dominated by the two groups of detrital zircons; Ediacaran in the range of 545–612 Ma and Paleoproterozoic–Neoarchean ranging from 1.8 to 2.8 Ga. The documented zircon ages reflect derivation of the Hronicum sediments from the Variscan Western Carpathian crystalline basement, the Late Devonian/Early Mississippian magmatic arc. These data support close relations of the presumed Hronicum basement with the Armorican terranes and derivation from the Cadomian Belt, associated with the West African Craton during Neoproterozoic and Cambrian time.