site 13

Where is the site located?

GPS: 49°53’37.09″ N, 15°44’17.07″ 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 fascinating Paleozoic rocks are exposed. These rocks enclose proofs of the activity of ancient organisms.

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.

What does the site display today?

The area of the village of Deblov 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 under high pressures, now displaying a concave-upward structure of the so-called Vápenný Podol syncline. Within this structure, the youngest rocks have been preserved in its centre, passing to progressively older sediments towards the margins.

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). In the field, they form elevations elongated in the SW–NE direction.

What was affected by man?

Landscape around this site is characterized by very old bedrock. This was subjected to long-lasting erosion. By now, it has been abraded, levelled and covered with younger sedimentary rocks. Occurrences of natural rock outcrops are therefore very important from the viewpoint of geosciences. The outcrops unfortunately concentrate to forests, and soon become overgrown by vegetation and poorly accessible. Vegetation occasionally completely obscures the geological phenomena. It is therefore important to discover such outcrops in the field and take appropriate measures for their preservation.

What was discovered?

Trace fossils after ancient organisms, called ichnofossils by the experts, occur in the hard Skalka quartzites of the Chrudim Paleozoic. They were observed as early as in the late 19th century (Krejčí and Helmhacker, 1881) and described as long tubes called “scolitusˮ. Once again, they became attractive for the scientists at the end of the 20th century and the beginning of the 21st century. At the site of Deblov, a unique striated bedding plane has been preserved with perfectly visible trace fossils. Tube- or straw-shaped structures can be seen even by a layman. They represent traces after crawling or boring. Some of them are traces after simple dwelling burrows of ancient organisms comparable to the present sea worms who also build their dwellings in sea bottom.

Trace fossils are classified into the so-called ichnogenera by the experts. They bear specific names. This site yielded representatives of ichnogenera Pragichnus, Phycodes and Skolithos.

“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 placed near the local road at the southern limits of Deblov. The geosite itself lies some 450 m further south, being accessible by a tarmac road leading to the end of the forest and beyond, towards the top of Chocholka elevation. The bedding plane preserved at the outcrop has been cleaned from native vegetation and washed by jet water (GPS: 49°53’25.94″ N, 15°44’24.67″ E).

Cross sections of tunnels of the genus Skolithos (Daniel Smutek)