Where is the site located?
GPS: 49° 51′ 13.27″ N, 15° 58′ 17.69″ E
The area lies in the eastern part of the Iron Mountains National Geopark. The northern environs of Skutíčko, forming a prominent forested slope, lies on the curved margin of the East Bohemian Table. The area between Vrbatův Kostelec in the west and Svatoanenské Valley in the east provides a view of spectacular rocky outcrops. This area reminds of the effort of our ancestors to extract coal.
What is the geological position of the site?
The site is located in the Bohemian Massif, in the marginal area of the Bohemian Cretaceous Basin. The text below will focus on rocks created by the last sea flooding in Late Cretaceous times at the end of the Mesozoic.
What happened at this site in the past?
– 95 million years
In the course of the Mesozoic, the supercontinent of Pangea fell apart into separate tectonic plates, which drifted atop the elastic asthenosphere. In the latest Mesozoic, this area was lying on the Northern Hemisphere, becoming a part of the Eurasian Plate. The climate was very warm, controlled by the greenhouse effect which induced a progressive rise of global sea level. Flooding occurred over a large portion of dry land, first by freshwaters of rivers and lakes. Later on, a large part of the Bohemian Massif became a part of a shallow sea passage.
This site was located in a shallow near-shore zone, colonized by ancient vegetation both on dry land and in water. Waters were dominated by the representatives of molluscs, fishes and amphibians.
What does the site display today?
The northern environs of Skutíčko is formed by Upper Cretaceous sediments pertaining to the Bohemian Cretaceous Basin. This basin has been preserved approximately in the central part of the Bohemian Massif from northern Bohemia across central Bohemia to eastern Bohemia, in a region subsided along faults of the so-called Elbe Zone. The southern environs of Skutíčko is formed by much older magmatic rocks of the Železné hory plutonic complex, which originated in the Late Paleozoic and is represented by the Skuteč granite (granodiorite).
This area displays the oldest Upper Cretaceous sediments of Cenomanian age (the first age of Upper Cretaceous), first in the freshwater development, called the Peruc Member.
This unit consists of fine grey sediments – siltstone and claystone with coalified organic matter passing to thin coal seams, and of sandstone (consolidated sediments formed from deposited sand).
These are overlain by solid, light yellowish-grey pillar-jointed sandstone of the Korycany Member. It is composed of quartz grains held together by clayey, calcareous matrix, and also contains grains of greenish mineral glauconite, which originates in marine environment. These units have been preserved in relatively high thicknesses, locally reaching 60 to 70 m – the largest occurrence at the foot of the Iron Mountains. They most probably fill an extensive pre-Cretaceous depression.
On your way further north, you come across another formation overlying the Peruc and Korycany Members. It is much different, being composed of fine, consolidated sediments: calcareous to marly siltstone. It is younger – Lower Turonian in age (Turonian is the second age of Upper Cretaceous). Its characteristic property – tendency to jointing – explains the name given to this rock by the stonemasons: opoka.
Our journey is actually a journey from a seashore to the centre of a deepening sea basin: the thickness of the sediments gradually increases and their particle size decreases. The present setting also results from tectonic forces affecting the sediments during their geological history. These forces induced bending of originally flat-lying strata and their disintegration into separate blocks. The sediments were also altered by subsequent erosion of the area, which resulted in their removal or in their exhumation at specific sites, such as in river valleys.
What was affected by man?
The occurrences of dark grey to black carbonaceous claystone and coal among Vrbatův Kostelec, Skutíčko and Přibylov have been noted by our ancestors as early as in the early 19th century. They are embedded in light sandstones. The first written record of a manually excavated test pit with coal finds at precinct 695 by the road dates to the year 1804. It was followed by several attempts for coal mining coordinated, among others, by the Rychmburk Farm administration, by the “Mining Co-operative of the Citizens of Skutečˮ, by a pharmacist from Třebechovice pod Orebem, or by invited German miners. These mining attempts were always finally terminated due to the low yield. Minor shafts and galleries were excavated. Moreover, a mine accident occurred during shaft excavation in 1860. Two miners died, probably of suffocation.
Traces after mining activities have been present until these days, being limited to backfilled shafts and cavities carved in sandstone cliffs at entrances to former galleries.
What was discovered?
In the late 19th century and early 20th century, mining activities allowed the scientists to describe finds of natural materials, which are now inaccessible. As has been documented by the scientists, thin beds of coal with high lustre and conchoidal fracture were present in coal-bearing intervals. They reminded of asphalt with their appearance. Carbonaceous claystones on spoil tips were found to contain fragments of ferns and minute, more-or-less transparent pieces of amber – petrified resin of Upper Cretaceous conifers. Finds of nodules of amber were also reported (formerly, the were called “succiniteˮ), reaching the size of a childʼs head. They were dark brown, honey-coloured or brownish hyacinth-coloured.
“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 in the centre of the Skutíčko village. Outcrops of Upper Cretaceous rocks are located about 800 m to the north and northwest.