Unique carbonate sections of the Frasnian-Famennian stage boundary (F/F) in the geopark Toratau locality (the Ryauzyak and Sikaza rivers’ basin in the Western slope of the Southern Urals)
Peculiarities of conodonts and brachiopods change in a Frasnian-Famennian brachiopod coquina interval in classical carbonate sections of the Western Uralian Folded Zone in the Southern Urals are considered. In the Ryauzyak and Kuk-Karauk (Sikaza) sections, the boundary position is substantiated by conodonts at the bottom of the Barminsky horizon. It is established within a lithologically homogeneous brachiopod coquina by simultaneous emergence of the conodonts Palmatolepis triangularis Sann. and brachiopods Parapugnax markovskii (Yud.). The F/F boundary interval is subdivided into the Upper rhenana, linguiformis, Lower and Middle triangularis zones which are thoroughly characterized by means of conodonts and brachiopods. At the top of the Frasnian in all sections (linguiformis zone), a replacement of the palmatolepid biofacies with abundant taxa of the Palmatolepis genus by extremely poor monotaxonic icriodid biofacies is observed. This is probably due to changes in global sea levels and the Mass Extinction Event (Upper Kellwasser Event) at the F/F boundary.