Klonk is a national nature monument in the

Bohemian Karst Bohemian or Bohemians may refer to: *Anything of or relating to Bohemia Beer * National Bohemian, a brand brewed by Pabst * Bohemian, a brand of beer brewed by Molson Coors Culture and arts * Bohemianism, an unconventional lifestyle, origin ...

Protected Landscape Area in the

Czech Republic The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...

. It lies in the northern part of the municipality of

Suchomasty Suchomasty is a municipality and village in Beroun District in the Central Bohemian Region of the Czech Republic. It has about 500 inhabitants. Administrative parts The village of Borek is an administrative part of Suchomasty. History The first ...

, approximately south of

Beroun Beroun (; german: Beraun) is a town in the Central Bohemian Region of the Czech Republic. It has about 20,000 inhabitants. It lies at the confluence of the Berounka and Litavka rivers. Beroun creates a conurbation with Králův Dvůr, former p ...

. It is globally recognized as a geologically important location due to the presence of the

Global Boundary Stratotype Section and Point A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. The effort to define GSSPs is conducted ...

(GSSP) marking the boundary between

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleoz ...

and

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...

periods. The boundary was set based on the first appearance of the

graptolite Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian ( Miaolingian, Wuliuan) through t ...

'' Monograptus uniformis'' in the bed number 20. The stratotype was ratified on the 8th of February 1972 by the

International Union of Geological Sciences The International Union of Geological Sciences (IUGS) is an international non-governmental organization devoted to international cooperation in the field of geology. About The IUGS was founded in 1961 and is a Scientific Union member of the Int ...

Montreal Montreal ( ; officially Montréal, ) is the second-most populous city in Canada and most populous city in the Canadian province of Quebec. Founded in 1642 as '' Ville-Marie'', or "City of Mary", it is named after Mount Royal, the triple- ...

as the first formally accepted GSSP.

History

The positioning of the boundary between Silurian and Devonian has been a matter of discussion since the 19th century. The so-called hercynian question was resolved only after the ratification of the GSSP in 1972. The monument was declared as a protected area in 1977.

IUGS geological heritage site

In respect of its being the location of the 'first global boundary stratotype section and point (GSSP)', Klonk Hill was included by the

(IUGS) in its assemblage of 100 'geological heritage sites' around the world in a listing published in October 2022. The organisation defines an IUGS Geological Heritage Site as ''"a key place with geological elements and/or processes of international scientific relevance, used as a reference, and/or with a substantial contribution to the development of geological sciences through history."''

Geology

Klonk is a rocky slope by the right bank of Suchomastský brook. It contains two formations of upper Silurian ( Kopanina formation, Požáry formation) and one formation of lower Devonian ( Lochkov formation named for the nearby ' Lochkov profile'). Kopanina formation is represented by calcareous

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especiall ...

s, Požáry formation by gray tabular

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...

s and bioclastic limestones can be found in Lochkov formation. The boundary beds are intact, without disturbance by tectonic processes, there are no facial changes and the profile is made of one continuous sequence. There are various paleontologically significant objects, apart from the already mentioned graptolites it is possible to find the

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the ...

'' Warburgella rugulosa'' typical for the base of Devonian period, the conodont '' Icriodus wolschmidti'' and the

chitinozoan Chitinozoa (singular: chitinozoan, plural: chitinozoans) are a group of flask-shaped, organic walled marine microfossils produced by an as yet unknown organism. Common from the Ordovician to Devonian periods (i.e. the mid-Paleozoic), the millime ...

'' Agnochitina chlupaci''. Various other

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...

s can be found in the profile, such as

bivalves Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

gastropods The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. The ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipedes, isopoda, isopods, barnacles, copepods, ...

s and

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, w ...

s. Apart from animals, remains of terrestrial flora can also be found in the beds, namely the genus '' Cooksonia''. Soils are rather undeveloped, only close above the brook in the lower part of the slope clayey screes can be found. There is a unique monument representing the geological boundary set by international agreement. It was built in 1977 by academic sculptor Jiří Novotný.

Flora and fauna

Various plant communities can be found at Klonk. The vicinity of the brook is characterized by human planted vegetation, for example the common alder (''Alnus glutinosa''), European ash (''Fraxinus excelsior'') or Canadian poplar (''Populus x canadensis)'', in the lower parts of the slope are the remains of scree forests with dominant sycamore. Shady limestones by the brook are a favourable location for a number of rare bryophytes, such as the craven featherwort (''Pedinophyllum interruptu''m) or beech feather-moss (Eurhynchium crassinervum). Most of the slope is covered by vegetation which is not native to the location – black pine (''Pinus nigra)'',

European larch ''Larix decidua'', the European larch, is a species of larch native to the mountains of central Europe, in the Alps and Carpathian Mountains as well as the Pyrenees, with disjunct lowland populations in northern Poland and southern Lithuania. It ...

(''Larix decidua''),

black locust ''Robinia pseudoacacia'', commonly known in its native territory as black locust, is a medium-sized hardwood deciduous tree, belonging to the tribe Robinieae of the legume family Fabaceae. It is endemic to a few small areas of the United States ...

(''Robinia pseudoaccacia'') and

Norway spruce ''Picea abies'', the Norway spruce or European spruce, is a species of spruce native to Northern, Central and Eastern Europe. It has branchlets that typically hang downwards, and the largest cones of any spruce, 9–17 cm long. It is very close ...

(''Picea abies''). The original community of oak-hornbeam forests ( sessile oak (''Quercus petraea''),

common hornbeam ''Carpinus betulus'', the European or common hornbeam, is a species of tree in the birch family Betulaceae, native to Western Asia and central, eastern, and southern Europe, including southern England. It requires a warm climate for good growth, ...

(''Carpinus betulus''), field maple (''Acer campestre'')) can only be found in the upper parts of the profile. The formerly woodless areas tend to be covered by bushes of dog-rose (''Rosa canina''),

blackthorn ''Prunus spinosa'', called blackthorn or sloe, is a species of flowering plant in the rose family Rosaceae. The species is native to Europe, western Asia, and regionally in northwest Africa. It is locally naturalized in New Zealand, Tasmania, ...

(''Prunus spinosa'') and common dogwood (''Cornus sanguinea''), atop the hill we may find an area of xerothermic grasslands such as

spotted knapweed ''Centaurea stoebe'', the spotted knapweed or panicled knapweed, is a species of ''Centaurea'' native to eastern Europe, although it has spread to North America, where it is considered an invasive species. It forms a tumbleweed, helping to increa ...

(Centaurea stoebe) and hairy oxytropis (''Oxytropis pilosa''). Klonk is the nesting place for a number of birds, among others the

grey wagtail The grey wagtail (''Motacilla cinerea'') is a member of the wagtail family, Motacillidae, measuring around 18–19 cm overall length. The species looks somewhat similar to the yellow wagtail but has the yellow on its underside restricted to ...

(''Motacilla cinerea''),

Eurasian sparrowhawk The Eurasian sparrowhawk (''Accipiter nisus''), also known as the northern sparrowhawk or simply the sparrowhawk, is a small bird of prey in the family Accipitridae. Adult male Eurasian sparrowhawks have bluish grey upperparts and orange-barr ...

(''Accipited nisus'') or the

common buzzard The common buzzard (''Buteo buteo'') is a medium-to-large bird of prey which has a large range. A member of the genus '' Buteo'', it is a member of the family Accipitridae. The species lives in most of Europe and extends its breeding range acr ...

(''Buteo buteo''). Most of the fauna here is represented by invertebrates, however apart from other areas of the Bohemian karst it is somewhat poorer in

molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ...

. Vertebrate fauna is represented by

red fox The red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the Order (biology), order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe ...

(''Vulpes vulpes)'',

European badger The European badger (''Meles meles''), also known as the Eurasian badger, is a badger species in the family Mustelidae native to almost all of Europe. It is classified as least concern on the IUCN Red List as it has a wide range and a large stab ...

(''Meles meles''), wood mouse (''Apodemus sylvaticus'') and other, usually common species.

Protection plan

The goal of the protection plan is to secure the important geological profile and preserve it for future study. Klonk is mainly threatened by amateur palaeontologists who expect a rich locality, however the location is important mainly due to microfossils. Another threat is the overgrowing of vegetation, which has been successfully removed mechanically and by herbicides in the past. The removal of unwanted vegetation should also help the return of the original vegetation, which used to be strongly influenced by pasture. Plans for the future include marking of borders of the protected area in order to facilitate management, since it lies on parts of two private properties. The profile is currently closed to the public not only to protect it, but also to avoid injuries of visitors on the steep slope.

Educational trail

The location is a part of long geological educational trail, which also leads through adjacent areas of importance such as Lom na Kobyle, Zlatý kůň, Koda and others. Individual localities aren't necessarily related and it is thus possible to travel only through certain segments of the trail. The trail is suitable even for cyclists and the information boards are in Czech with English abstract.

References

* {{cite web, url=http://www.stratigraphy.org/sildev.htm , title=GSSP for the Silurian - Devonian Boundary , last=Ogg , first=James , access-date=2006-07-02 , archive-url=https://web.archive.org/web/20060618104054/http://www.stratigraphy.org/sildev.htm , archive-date=2006-06-18 , url-status=dead Geography of the Czech Republic Stratigraphy of Europe First 100 IUGS Geological Heritage Sites