Following last year’s successful restoration of the monument marking the world’s first global stratotype (GSSP) at Klonk near Suchomasty, the stratotype section itself was restored this year. Over the past twenty years, it had weathered and become buried under rock debris on Klonk’s steep slope, rendering it virtually inaccessible to the specialist community. With a few exceptions, the stratigraphic numbering had become illegible. Between 29 September and 2 October 2026, the main phase of the restoration of the boundary section between the Silurian and Devonian took place. Thanks to the dedicated work of the team members, the original scope of the restoration was exceeded many times over.
The rock outcrop is now again exposed from the strata above the Silurian–Devonian boundary downwards, stratigraphically approximately 1 m below the former ecavation, which has become part of a boundary section several metres wide. Layer No. 20, in the upper part of which the boundary between the Silurian and Devonian runs, is now exposed over a lateral extent of approximately 3 m. The strata have been provisionally numbered. The section will now be left to natural weathering and cleaning for approximately one month, after which it will be definitively numbered using special paint. In the coming years, therefore, only routine maintenance of the outcrop will be required as part of the standard upkeep of the Klonk National Nature Reserve, in collaboration with experts and the Český kras Protected Landscape Area Administration..
A huge thank you for their hard work in restoration one of the world’s most significant geological sections goes to Vojtěch Kovář, Štěpán Manda, Martina Nohejlová and Petra Tonarová from the Czech Geological Survey, Matěj Šilinger from the Museum of the Bohemian Karst in Beroun, Tomáš Kumpan from Masaryk University and his students (Ema Kohoutová, Nela Koudelková, Akhan Akhmetov, Marek Navrátil and Lukas Viceník), Jakub Vodička (Brdičkova university-affiliated primary school), Lucie Pařízková (Charles University) and, last but not least, Ladislav Slavík (Czech Academy of Sciences), acting chair of the International Subcommission on Devonian Stratigraphy. The online support was provided by Jindřich Hladil and Petr Štorch of the Czech Academy of Sciences. Aerial drone documentation of the Klonk slope, both before and after restoration, was carried out by Martin Kýhos and Barbora Kořínková of the Czech Geological Survey.
We would like to thank the village of Suchomasty and Vápenka Čertovy schody, a.s. for their generous support.
In respect of its being the location of the 'first global boundary stratotype section and point (GSSP)', Klonk Hill was included by the International Union of Geological Sciences (IUGS) in its assemblage of '100 geological heritage sites' around the world in a listing published in October 2022.
Further information on the GSSP at Klonk near Suchomasty is available at https://en.wikipedia.org/wiki/Klonk