International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

Ichnology of the Cretaceous Oceanic Red Beds (Outer Western Carpathians, Czech Republic)

Pages: 233 - 250

Authors: RADEK MIKULAS, PETR SKUPIEN, MIROSLAV BUBIK, ZDENEK VASICEK

Abstract: Large differences in the intensity and overall character of bioturbational structures were found in five facies containing hemipelagic red beds. Red beds (CORB) of the Godula facies of the Silesian Unit and their equivalents (mostly not red) in the Kelc facies of the Silesian Unit and the CORB in the non-calcareous sediments of the Raca Unit display a very low degree of bioturbation. The CORB facies of the Raca Unit, containing calcareous intercalations, displays a very high degree of bioturbation as expressed by a high ichnofabric index. They contain trace fossils Chondrites, Zoophycos, Planolites, Thalassinoides, Palaeophycus, Teichichnus and Phycosiphon. The supply of food obviously acted as the controlling factor. The “calcareous” facies of the CORB of the Raca Unit has a considerably higher proportion of sand-dominated interbeds and also carbonates than the non-calcareous facies. This (especially the presence of carbonates) suggests a relative proximity of food-rich environments and an easy transport of nutrition-rich substrate by turbidite currents into the basin directly, not only by periodical fall-out of dead plankton (which is probably responsible for the rhythmicity of poor colonization horizons in weakly bioturbated units).

Keywords: Upper Cretaceous, Western Carpathians, hemipelagic, ichnofossils, ichnofabric, red beds

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