Lochkovský profil National Nature Monument

The Lochkovský Profile is a geological profile of international significance which documents the development in the Upper Silurian and Lower Devonian periods.
 
The national nature monument lies in the parishes of Lochkov and Radotín on the south-western outskirts of the city of Prague. The monument covers an area of 39.1ha at elevations of 240-340 metres above sea level.
 
The oldest positions in the geological profile are exposed in the easternmost section of Lochkovský profil NNM. These are dark-grey calcareous shales which contain concretions of dark fine-grained limestones in places, and occasionally contain fossilized graptolite and ostracode fauna. These shales are of Silurian age and belong to the middle position of the Kopanina Formation. The lower boundary of these shales is of tectonic origin, as they were carried along the Koda reverse-slip fault to lie on a bench of cephalopod limestone which also belongs to the Kopanina Formation, but to its upper positions. The calcareous shales from the middle positions of the Kopanina Formation are overlain by a 4-metre-thick position of massive limestones with a predominance of fossilized cephalopods and molluscs. These massive limestones can best be seen in the Lochkov Profile at the Mramorový lom – Marble Quarry. Above the massive limestone we can see a 60-metre-high complex of strata of dark-grey, fine-grained limestones which are interbedded with positions of dark-grey calcareous shales, which belong to the Požáry Formation of Upper Silurian age. The whole sequence of the Požáry Strata can be observed in the part of the Lochkov Profile called “U topolů – At the Poplars”, which is situated in a cutting on the route of the former narrow-guage railway. The “U topolů” locality is a key profile of the boundary between the Silurian and the Devonian in the Prague Basin (Barrandien) to the world stratotype of this boundary at Klonk near Suchomasty. The Požáry Formation is rich in fossils of many species of predominantly marine invertebrate fauna. Above the Požáry Formation we can find a 180cm-thick bed of crinoid limestones, which belong to the Lochkov level of Lower Devonian age. The actual boundary between the Silurian and the Devonian was determined on the basis of the first occurrence of the trilobite Warburgella rugosa in the base of this bench, in the layers which lithologically reflect the Požáry Formation. Light-grey, fine-grained limestones with bodies of shale can be found above the bed of crinoid limestone.
 
As we move up through this layer the shale positions become less frequent. Some of limestone positions also contain hornfels. At Lochkovský profil NNM, these Lochkov limestones are strongly folded. The Lochkov limestones of Lower Devonian age are then overlain by Slivenec limestones which belong to the Prag level. These Slivenec limestones are rose-green to grey-green in colour and rich in crinoids and other fauna types. Above the Slivenec limestones at the “U topolů” profile we can see tuberous, grey, fine-grained Dvorecko-Prokopské limestones. However, in the Cikánka Quarry the Slivenec limestones are overlain by red-brown coloured Řeporyje limestones, which only differ in colour from the Dvorecko-Prokopský limestones.
 
The Lochkovský profil NNM has been studied scientifically and in great detail and serves as a testing ground for comparative stratigraphical, biostratigraphical, palaeontological and correlational research.
 
The most valuable flora can be found on the rocky steppe enclaves and includes the feather-grasses Stipa joannis and Stipa capillata, the Bohemian small pasque flower (Pulsatilla pratensis subsp. bohemica) and the aster - Aster amellus. Lochkovský profil NNM is also an extremely valuable zoological locality with rare thermophilous fauna of steppe gastropods, pentatomid bugs, beetles, butterflies and spiders. Lochkovský profil NNM is a proposed Site of Community Importance for the occurrence of the Jersey tiger moth (Callimorpha quadripunctaria).