Zavírka

Zavírka is a small yet scientifically remarkable natural monument located roughly one kilometer northeast of the village of Svojkovice, in the Rokycany District of the Plzeň Region, Czech Republic. Despite covering only 0.05 hectares, this site has drawn the attention of geologists and paleontologists across Europe as one of the country's most important Ordovician fossil localities.

What can visitors find here?

At the heart of the protected area is a partially exposed, nearly vertical rock face standing 2–3 meters high, rising along the left bank of the Chejlava stream (also known locally as Chýlava or Těškovský potok). The outcrop is composed of Paleozoic claystone shale, topped by younger Quaternary deposits. Above the exposed rock, a scree slope covered in spruce forest continues upward. The entire site sits at an elevation of 396–408 meters above sea level, within the Holoubkov Basin, part of the larger Hořovice Furrow geological depression.

Why is this site protected?

The monument owes its protected status to an exceptionally rich deposit of fossilized fauna belonging to the Klabava Formation, dating to the Czech Ordovician period. Zavírka is considered one of the richest known localities for fauna of the Corymbograptus v-similis biozone — a group of colonial marine organisms that drifted through ancient oceans hundreds of millions of years ago. It was here that the species Corymbograptus holubi was first scientifically described, making Zavírka the type locality (locus typicus) for this organism — a fixed reference point for researchers studying this group anywhere in the world.

The fossils preserved within the claystone shale allow scientists to reconstruct the conditions of the ancient sea that once covered this region during the Ordovician, more than 440 million years ago. To a casual visitor, the outcrop might look like an ordinary forested slope, but to a geologist it reads like an open book documenting the history of life in the oceans of prehistoric Europe.

Protection history

The site was formally declared a natural monument on September 5, 1989, by decision of the Rokycany District National Committee. Today it is administered by the Plzeň Regional Authority, although the underlying land remains privately owned. Zavírka is classified as an IUCN Category III protected area, meaning it is protected for a specific, unique natural feature — in this case, a scientifically significant geological outcrop — rather than for a broad ecosystem.

Frequently asked questions

Can you visit Zavírka? The site is accessible, but given its small size and scientific importance, visitors should take care not to disturb the outcrop, which is protected precisely because of its research value.

What makes this site special? Zavírka is the type locality (locus typicus) of the species Corymbograptus holubi — the exact place where this organism was first scientifically described, making it a permanent reference point for researchers worldwide.

How do you get to Zavírka? The natural monument lies about one kilometer northeast of the center of Svojkovice, on the left bank of the Chejlava stream, at an elevation of just under 400 meters above sea level.

Are there other natural attractions nearby? Zavírka sits within the Holoubkov Basin and the Hořovice Furrow, a geologically rich region known for numerous outcrops documenting the history of Paleozoic seas in this part of the Czech Republic.