Paleozoic ENG
Paleozoic era spans from 539 to 252 million years ago. It is commonly divided into Early Paleozoic encompassing Cambrian, Ordovician, Silurian, and Devonian, and Late Paleozoic encompassing Carboniferous and Permian periods.
Early Paleozoic
Cambrian
In the Cambrian period, the supercontinent Rhodinia disintegrated into several smaller blocks. The area of Central Europe (the Bohemian Massif) was located in the temperate zone of the southern hemisphere at the margin of the new continent called Gondwana. The planet saw emergence of the first multicellular fauna capable of creating hard skeletons or shells for better protection from predators and harsh conditions. This period yielded trilobites, brachiopods, crinoids, and cephalopods as well. There are also known rare finds of soft-bodied organisms (annelids, arthropods, crustaceans, and the oldest chordates) from Canada and China. In our country, Cambrian sediments are found particularly in Barradien and the Iron Mountains, as well as in the Krkonoše Mts.
Ordovician
Ordovician is considered one of the coldest periods in the Earth’s history. Vast amounts of water were frozen in glaciers, which caused a decrease in the global sea level by several dozen metres. The Bohemian Massif was situated rather deep in the sea close to the southern continent, Gondwana, where black graptolitic shales were deposited. The faunas of it include graptolites, conodonts, trilobites, molluscs, brachiopods, fishes, and cephalopods as well. Ordovician floras consist of red algae (rhodophyta) only. Rocks of this period are found particularly in Barradien and the Iron Mountains. Recently, uniquely preserved Ordovician fauna was also discovered near Železný Brod.
Silurian
The Silurian period is typical for warming climate and an increasing of the global sea level. The Bohemian Massif was still located in the southern hemisphere near Gondwana, which was slowly shifting northwards. Sedimentation still involved prevalently black shales and limestones. Silurian fauna, especially graptolites, conodonts, anthozoa, stromatoporoidea, crinoids, nautili, and orthoceras used to be preserved excellently. On land, the first vascular plants (psilophyta) appeared. Silurian rocks are found particularly in Barradien and the Iron Mountains; in the Krkonoše Piedmont, graptolitic shales are found near Poniklá village.
Devonian
During the Devonian period the collision of continents Gondwana and Laurussia was started, causing important rock-forming processes called the Variscan Orogeny. The region of our present territory was located in the tropical zone, in shallow warm sea with favourable conditions for corals, stromatoporoids, and algae creating reefs, as well as for cephalopods, crinoids, conodonts, and brachiopods. There are known the oldest fishes, and on the land first amphibians as well. Devonian is also typical for first vascular plants, including clubmosses, horsetails, ferns, as well as the oldest gymnosperms. Devonian rocks are found particularly in Barradien, the Iron Mountains, and in Moravia; certain areas around the Krkonoše yield folded layers containing lenses of metamorphic Devonian limestones and shales.