Pages: 243 - 249
Abstract: K/Ar dating of the potassium-magnesium sulphate minerals (langbeinite, polyhalite, and kainite) from Miocene evaporites of different stratigraphic formations and tectonic zones of the Carpathian Foredeep provides evidence that they have recrystallized at roughly the same time, and thus the ages of those minerals differ from the age of the hosting formations. The age of langbeinite from the Stebnyk mine (the host formation in Lower Miocene) indicates the recrystallization in the Middle Miocene (13.63–14.65 Ma), and the same age of langbeinite from the Kalush mine indicates that the host formation (the age of which is uncertain) is older than the Tyras “Suite” (which belongs to the NN6 Zone). The recrystallization was a response to three major tectonic events which affected the area: (1) beginning of the Carpathian nappe overthrusting in Ukraine (overthrust of the Outer Western Carpathians on the Carpathian Foredeep and of the Boryslav-Pokuttya and Sambir Zones on the Bilche-Volytsa Zone) and the related overheating, dated at 13.6–14.6 Ma; (2) final stage of overthrusting, origin of faults transverse to the Carpathian overthrust (11.4–12.6 Ma); (3) neotectonic movements and uplift (7.2–9.9 Ma). Thus, the evaporite minerals can be used to date the tectonic events in the regions of complex geological structure.
Keywords: Miocene, Carpathians, geochronology, evaporites, langbeinite, argonDownload PDF document