Cretaceous Sea ENG

Approximately 100 million years ago, in the middle of Cretaceous period, the sea reached our territory. The cause of this sea level rise was a big increase on the global temperature as a result of the massive greenhouse effect affecting the planet due to increased volcanic activity accompanying the disintegration of the Pangea. The results of this disintegration were formation of oceanic ridges and bulging of the seabed, so the sea level was about 350 metres higher compared to the present state. The shallow warm sea full of nutrients, which flooded a big part of Europe, provided very favourable conditions for life and development of many kinds of animals. Abundant groups were bivalves, oysters, and sponges, as well as echinoderms, arthropods, corals, cephalopods, fishes, sharks, etc. Large amounts of fine-grained siliceous sandstone sedimented on the bottom of the sea together with agrillite, marlite, and limestone; calcareous sediments and small reefs were formed at the shores and in the surf zones. In our territory, Cretaceous deposits are abundant and are found in a large area from Moravia to Northern Bohemia. The fossil record is commonly very rich, documenting the great biodiversity of the contemporary ecosystems. Cretaceous rocks also cover the majority of the Geopark. Their most noticeable form are the sandstone rock towns around Jičín and Turnov, but we can find many other sites rich on marine fauna fossils, particularly in the basement of sandstone towns. The finds also include big colonies of oysters and sponges, sea urchins, bivalves, ammonoids, echinoderms, and shark teeth.