The cyclic Rørdal Member – a new lithostratigraphic unit of chronostratigraphic and palaeoclimatic importance in the upper Maastrichtian of Denmark

Researchers have identified the Rørdal Member, a new lithostratigraphic unit within the upper Maastrichtian chalk of Denmark, marking a significant early late Maastrichtian cooling event. This cyclic chalk-marl unit, approximately 10 meters thick, is distinct from surrounding pure white chalks and is recognized across multiple boreholes and outcrops, including Stevns Klint and the Rørdal quarry in Aalborg. The study leverages coccolith and brachiopod data to place the member within specific nannofossil and brachiopod zones, confirming its lower upper Maastrichtian age. Isotope analysis further supports its role as a basinwide isochronous marker, offering valuable insights into palaeoclimatic shifts during this period.

Surlyk, F., Stemmerik, L., Ahlborn, M., Harlou, R., Lauridsen, B. W., Thibault, N., Rasmussen, S. L., Schovsbo, N., & Sheldon, E. (2010). The cyclic Rørdal Member – a new lithostratigraphic unit of chronostratigraphic and palaeoclimatic importance in the upper Maastrichtian of Denmark. Bulletin of the Geological Society of Denmark, 58, 89–98. https://doi.org/10.37570/bgsd-2010-58-07