Prvohory (paleozoikum)

site 14

Where is the site located?

GPS: 49° 54′ 11.86″ N, 15° 45′ 9.03″ E

The site lies in the central part of the Iron Mountains National Geopark, in about a midpoint of the gentle northeastern slope of the Iron Mountains, which is inclined towards Chrudim.

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 resistant Paleozoic rocks are exposed. These rocks enclose proofs of the activity of ancient organisms. Their present appearance is a result of the action of water and frost through geological ages.

What happened at this site in the past?

− 470 million years

In the Ordovician, 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 inhabited mostly by invertebrates, the best known representatives of which were trilobites, brachiopods, worms, bivalves and cephalopods.

- 1.8 million years

In the Pleistocene, the older epoch of the Quaternary period, this area was lying on the Northern Hemisphere, being a part of the Eurasian Plate. The essential climatic feature is the alternation of cold periods (glacials) with massive spread of ice sheets and much warmer and more humid periods (interglacials). Cyclic climatic oscillations induced very dynamic changes on the earth surface. Intervals of intense destruction repeatedly alternated with intervals of accumulation, which gave rise to the present relief.

What does the site display today?

Near vicinity of the village of Rabštejn is formed by Paleozoic rocks, called the Míčov Formation. These rocks date to the Mid 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 and muds. These became affected by later geological processes, which turned them into solid rocks mostly grey or beige in colour. Sands were changed for sandstones and quartzites, muds were changed for siltstones and shales. The dips of sedimentary strata were also altered by orogenic processes. The original flat-lying sediments were bent and fractured into thin slices which were thrust upon one another. They now form the so-called Vápenný Podol syncline.

The Míčov Formation is composed of dark shales and by the Skalka conglomerates mostly light grey in colour. The latter are resistant rocks which underwent contact metamorphism (i.e., they were changed by the heat transmitted from the near magmatic body of the Železné hory pluton). They commonly contain light to white quartz veins, which healed fractures in the rock.

In the area between Mladoňovice and Slatiňany, quartzites form several elevations elongated in the direction SW–NE.

The Markovice Gorge was formed along the Markovický potok Stream. Its right-hand slopes display outcrops of the Skalka quartzites. The outcrop series is ended by a rocky spur supporting the Rabštejnek Castle. A closer look of the outcrop series would reveal geomorphological phenomena resulting from the action of water, frost and vegetation. These include frost-riven cliffs produced by blocky disintegration of the original rock mass, boulder and talus streams passing to boulder fields – accumulations of angular boulders fallen to cliff bases.

What was affected by man?

The steep rocky spur in the forested gorge of the Markovický potok Stream was used for the construction of the Rabštejnek Castle by our ancestors. The history of the castle dates back to the 14th century. The castle itself, located on a cliff, consisted of a square tower with a platform, and a two-storey palace of an irregular quadrangle ground plan. Settlement under the castle with a moat and a mound probably contained wooden agricultural buildings.

The castle was abandoned in the 16th century and became degraded. In the early 19th century, low walls were the only remains preserved. In the latter half of the 19th century, two rooms in the castle ruin were adapted on the order of the Prince of Auersperg; they were utilized for hunting in the adjacent game preserve.

The castle is now ruined again. It heavily suffered from the 2008 storm, during which several trees outside the castle were uprooted and damaged the castle walls.

This romantic spot has been also a long-lasting destination for the tramping movement, practicing unrestrained stay in wild nature.

What was discovered?

The Skalka quartzites lately became subject to paleontological studies, and traces after activities of Ordovician organisms – trace fossils, or ichnofossils – were discovered here.
These traces can be distinguished in outcrops as darker, almost vertical smears or tubes (when their longitudinal section is preserved). Occasionally, they have the character of tiny hollows on bedding planes (when their transverse section is preserved). They belong to the ichnogenus Skolithos . These features are interpreted by the paleontologists as fossil dwelling burrows (tunnels) produced by Ordovician organisms on sea bottom .

The study of trace fossils is critical in such rock types which do not allow the preservation of body fossils. Then, trace fossils become a significant key to the study of geological history of a particular region.

“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 erected about 100 m to the northeast of the Rabštejnek Castle ruin, near a forest road which is used as a tourist-marked green trail between Rabštejn and the Čejkovice crossroads.