Ichnofabrics of the Upper Cretaceous fine-grained rocks from the Stołowe Mountains (Sudetes, SW Poland)

Abstract

Upper Cretaceous fine-grained rocks (the "Plänermergel") from the Stołowe Mountains are in general strongly bioturbated. The sections studied (180 m thick), located in the southern part of the mountains, are dominated by mudstones, marlstones and siltstones; sandstones, partly unbioturbated, are subordinate. The entire sequence shows a succession of ichnofabrics, which reflects a transgressive-regressive cycle (Cenomanian) and a regressive cycle (lower to middle/upper? Turonian). The trace fossil assemblage contains nine ichnogenera: Asterosoma, Cylindrichnus, Ophiomorpha, Palaeophycus, Phycosiphon, Planolites, Taenidium, Teichichnus, and Thalassinoides. Three basic types of ichnofabrics have been recognized: Ophiomorpha, Thalassinoides and Phycosiphon, all representing fully marine ichnofacies. The first two of these belong to the Cruziana ichnofacies, indicating the offshore zone, and the third one probably to the Zoophycos ichnofacies indicating a quiet shelfal setting below storm wave base.