The Cretaceous biogenic structures created in Triassic sandstones (Devět Křížů at Červený Kostelec, NE Bohemia, Czech Republic)
Bulletin of Geosciences, volume 74, issue 3;
pages: 335 - 342;
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Tabularly jointed white sandstones at the Devět Křížů Quarry change gradually into overlying yellowish sandstones with strong bioturbation and the intensity of bioturbation increases towards the base of the Cretaceous. The sandstones are overlaid by weakly lithified oligomictic glauconitic conglomerates of the lower part of the Korycany Formation (Upper Cretaceous). All the biogenic structures (i.e. tunnels, tunnel/shaft systems, three-dimensional boxworks and shafts of the ichnogenera Thalassinoides
and ?root canals) are opened on the erosional plane of the marine Upper Cretaceous. For this reason, we assume that the bioturbation, though it affected the Triassic substrate, is Upper Cretaceous in age, and all the rocks of the Devět Křížů Sandstone were deposited during a sole non-marine sedimentary cycle in the Middle or Upper Triassic.