Abstract
The Upper Cretaceous chalk of northern Europe is a pure calcitic, pelagic deposit which appears to be totally bioturbated in almost all cases. Trace fossils are abundant but there is no single association of trace fossils that can characterize all chalk. In the Maastrichtian chalk sequences of Denmark alone there are at least four ichnofacies (trace fossil associations): (A) a Zoophycos-dominated ichnofacies in fine-grained white chalk; (B) a Thalassinoides-dominated ichnofacies in white or gray chalk with a higher content of macrofaunal bioclasts; (C) a Planolites-dominated ichnofacies in slightly marly chalk, which seems to indicate a thixotropic substrate; (D) a hardground ichnofacies dominated by Entobia, Gastrochaenolites, and Trypanites. Several additional ichnofacies occur in the chalks of England, France, Belgium and the Netherlands that cannot be observed in Denmark: (E) nodular chalks, developed by numerous generations of Thalassinoides; (F) phosphatic chalks, characterized by pelletfilled Teichichnus and « Thalassinoides; (G) chalk marls, containing extremely abundant Chondrites; (H) calcarenitic tuffeau, containing locally abundant Ophiomorpha.
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