Owing to several periods with favourable conditions for sediment deposition and fossilization of plant and animal remains, the Geopark boasts of high numbers of fossils in its territory. Fossils preserved in metamorphic rocks of Lower Paleozoic age are unique in global scale, although many others are of scientific importance, too.
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.
Bohemian Cretaceous Basin, which covers a large part of the Geopark territory, is the largest sedimentary basin in the Czech Republic.
Cenozoic sediments (only Quaternary sediments are present) are relatively poor in fossil remains.