Where is the site located?
GPS: 49° 57′ 48.83″ N, 15° 38′ 6.31″ E
The site lies in the northern part of the Iron Mountains National Geopark, in an area where the mountain range of the Iron Mountains passes to the flat region of the East Bohemian Table. The ridge at this site is formed by spectacular, highly resistant rocks, now exposed by old quarries.
What is the geological position of the site?
The site is located in the Bohemian Massif, in the marginal area of the Central Bohemian Region, where Paleozoic sedimentary rocks are exposed. The original rocks were deposited in the Ordovician sea.
What happened at this site in the past?
– 470 million years
In the Ordovician, early in the second period of the Paleozoic era, this area was lying on the Southern Hemisphere. It was a part of a shallow sea not far from the supercontinent of Gondwana. The climate was probably temperate to cold, with marked fluctuations, which controlled the changes in sea level. The sea was colonized by invertebrates, the best known representatives of which were trilobites, brachiopods, bivalves and cephalopods. The kingdom of plants was represented by primitive organisms, such as algae.
What does the site display today?
Rocks collectively known as the Lipoltice Formation have been preserved in a narrow strip in the area among the villages of Jankovice, Lipoltice and Horní Raškovice. These rocks date to the earliest Ordovician. They enter a wider rock complex preserved since Paleozoic times – the so-called Chrudim Paleozoic. In fact, the original rocks were unconsolidated marine sediments: various sands, occasionally with a high proportion of siliceous mass, muds and gravels. These deposits were brought into the sea from the adjacent land. Later, they became affected by further geological processes, which turned them into solid rocks mostly grey in colour but locally reddish- to rusty-coloured by iron compounds. Sands were changed for sandstones and quartzites, muds were changed for shales and siltstones, and gravels were changed for conglomerates (pebbles are visible in the rock). The dips of sedimentary strata were also altered by orogenic processes. The original flat-lying sediments were bent and fractured into thin slices by the effect of high pressures. In the near vicinity of the town of Přelouč, they now form the Přelouč syncline. Together with the older Cambrian sediments, they display a concave-upward structure.
The ridge at this site is formed by resistant quartzite, intercalated with beds of conglomerate and sandy shale. It poses a mere relict of the Ordovician sediments: any softer sediments were abraded through geological time and removed.
What was affected by man?
Quartzite at this site was utilized by our ancestors as excellent material for the production of millstones. From this area, millstones were supplied to the whole Bohemian Kingdom. The boom of millstone extraction dates to the 17th century; since then, their production diminished and the quarries were finally abandoned. Most of the quarries became subsequently flooded by groundwater, giving rise to deep pools (Návesní, Bezedná, Ovčí jáma etc.), which became an important source of water. A quarry at the southern limit of the village was still active in the 1960s, producing stone for construction purposes in this area.
What was discovered?
The near vicinity of the village of Horní Raškovice is also influenced by the past activities of man. They created romantic, cliff-lined pools. The potential of a far-view site was beneficial for the construction of the Barborka lookout tower and the establishment of a rest area. The lookout tower was opened in 2004, and the educational trail named “Raškovice quarriesˮ originated in 2005. This trail takes the visitors around the village up to the Vysoká skála Cliff and back.
“The Iron Mountains – a geologically significant region” project of 2014
An information panel was manufactured within the project of “The Iron Mountains – a geologically significant region”. It was installed at the western limit of the Horní Raškovice village near a local road leading to the Vysoká skála Cliff, in the proximity of the Barborka lookout tower.