Ichnofabrics of the Upper Cretaceous marlstones in the Opole region, southern Poland

Abstract

Two basic types of ichnofabrics occur in the marlstone-dominated Turonian-Coniacian deposits in the Opole region, namely the Thalassinoides and Chondrites ichnofabrics. Trace fossils (Chondrites, Ophiomorpha, Palaeophycus, Phycosiphon, Planolites, Taenidium, Teichichnus, Thalassinoides, Trichichnus) indicate the Cruziana ichnofacies. In the Thalassinoides ichnofabric, the trace fossils occur almost entirely against a totally bioturbated background, indicating relatively well-oxygenated sediments. In the Chondrites ichnofabric, trace fossils are smaller and the background is almost entirely bioturbated. Only in the lower part of the Odra quarry section, primary lamination is locally preserved. Generally, the Chondrites ichnofabric indicates less oxygenated and possibly deeper sediments than the Thalassinoides ichnofabric. Occurrence of the Chondrites ichnofabric in the Lower Turonian and Upper Lower Coniacian can be related to widely known anoxic events