Dalejský profil National Nature Monument

The Dalejský Profile documents the geological development of the older Palaeozoic formations of the Upper Ordovician, Silurian and Lower Devonian geological periods.
 
The national nature monument lies in the parishes of Řeporyje, Stodůlky and Holyně on the south-western edge of the city of Prague. The protected area was declared in 1982 on an area of 23.6ha at elevations of 285-345 metres above sea level.
 
The Dalejský Profile includes the artificially-exposed rocks which were left behind by limestone quarrying in several shelf quarries, which contain a number of significant stratigraphical and palaeontological localities. The abandoned Mušlovka limestone quarry is the most significant of these localities. Limestone from the Kopanina Formation, which was used to make powdered lime, was quarried here until the 1930s. After this quarrying was ended the floor of the quarry was filled with waste materials from other nearby quarries. The Mušlovka quarry (Mussel Quarry) was named by the local people for the quantity of fossils found here and this later became the official name. In the quarry we can see the classical boundary between the limestone positions of the Kopanina and Požáry Formations from the Upper Silurian period. Brownish and greenish strongly calcareous tuffite shales with concretions are exposed in the north-western wall of the quarry and these shales also contain contiguous bodies of firm, fine-grained, dark-grey limestones with pyrites. These are the lower layers of the Kopanina Formation. A massive bench of light-grey biodetritic limestone can be found in the left-hand side of the north-eastern wall of the quarry, with thinly-layered grey limestones with thin lenses of calcareous shales overlaying them. All of these limestones belong to the Kopanina Formation, which contain an abundance of fossils of various kinds of Palaeozoic marine invertebrate fauna, such as cephalopods, molluscs, gastropods, graptolites and brachiopods. The upper sections of the Mušlovka quarry walls are built of dark-grey, thinly platy limestone, with lenses of calcareous shales, which belong to the lower part of the Požáry Formation from the uppermost Silurian.
 
The so-called „Lobolite Cliff“, which is the western wall of the Černý lom – Black Quarry is another significant palaeontological locality within Dalejský profil NNM. The upper positions of the Požáry Strata are exposed here. However, these layers are strongly disturbed and crumbling as a result of weathering and have a secondary yellowish and rusty colouring. This cliff is famous for the quantity of extremely well-preserved remains of sea lilies (Crinoidea), especially their stems, ball-shaped flotation chambers – known as lobolites and occasionally their crowns, which have been uncovered here.
 
Dalejský profil NNM is not only of stratigraphical and paleontological importance but also for its rare and unusual flora. Xerophilous and thermophilous rocky steppe biotopes can be found on and around the limestone and diabase outcrops with the critically endangered early star of Bethlehem (Gagea bohemica) and earth-star fungus Geastrum pouzarii. Unfortunately, most of the territory is overgrown by false acacias (Robinia pseudoacacia) and Austrian pines (Pinus nigra).
 
To maintain access to the geological profiles and to support the rocky steppe biotopes it is necessary to remove woody growths regularly from parts of the Dalejský Profile, especially in the Mušlovka and Černý lom quarries.