In the early Paleozoic, the Geopark territory was flooded by sea. It was probably reaching considerable depths, as suggested by rocks of the Krkonoše–Jizera Crystalline Complex in the Železný Brod area.

The original deep-sea claystones and siltstones, later metamorphosed, are now preserved as phyllites (roofing slates). Their schistosity planes are identical with the original bedding planes, which is favourable for the preservation of abundant fossils, documenting Ordovician age of these rocks. Based on the latest research, the rich assemblage of trace fossils was extended by body fossils. Body fossils in such form are world-unique as fossils become preserved only very exceptionally in metamorphic rocks.
In the late Paleozoic, in Carboniferous and Permian times, a series of continental sedimentary basins was formed in the eastern part of the Geopark. They were filled with extensive lakes and vegetated with dense mire forests. Numerous streams were bringing detrital material into the basins, now forming up to 3500 m thick successions of arkosic conglomerates, sandstones, siltstones and claystones, locally with tuffitic admixture. Fossils were preserved in many horizons in these rocks, comprising mainly imprints of various plants, insects, fishes and other faunas. Moreover, the surroundings of Nová Paka is famous for rich occurrences of petrified plant stems – the so-called “silicified woods”. These fossils represent unique, three-dimensional remains after tropical swamp forests of that time.

Created 18.2.2020 14:54:11 - updated 28.2.2020 22:43:36 | read 334x | sprokesova