Surface microtextures and new U–Pb dating of detrital zircons from the Eocene Strihovce sandstones in the Magura Nappe of the External Western Carpathians: implications for their provenance

Abstract

Heavy mineral morphological, chemical and isotopic features are strong discriminative parameters in provenance studies. This paper focuses on the micro-textural signatures of detrital zircon grains obtained by scanning electron microscope (SEM) and U–Pb geochronological dating from the Strihovce Formation sandstones of the Magura Nappe in the External Western Carpathians. Our focus provides an important contribution to understanding the provenance of these sedimentary rocks. Although the SEM images reveal few dissolution features, they highlight many marks of mechanical processes which occur during detrital zircon transport. The detrital zircon U–Pb ages range from Mesoarchean–Neoproterozoic through Cambrian to Permian and Late Cretaceous. The pronounced peak at approximately 480 Ma Ordovician indicates the culmination of the peri-Gondwanan magmatic event. In conjunction with Archean to Proterozoic zircon inheritance, it implies Cadomian affinity of the potential source terranes which supplied the Magura Basin. The approximate ages of 379 Ma for the Late Devonian peak and 264 Ma for the Permian relate to widespread magmatism and/or rhyolite volcanism. These sources could be associated with the Carpathian basement units and the Apuseni terranes of the Tisza/Dacia mega-units. Most importantly, the sub-hedral Proterozoic zircons may signal the input of ‘first-cycle’ material from relatively closer surroundings, including the South-Magura Ridge to the Magura Basin.