The Gresten Klippen Zone is an individual geological unit, mainly outcropping at the northern rim of the Northern Calcareous Alps. It is best exposed between the Enns Valley in the west and the Vienna Forest in the east. It contains a rock sequence ranging from Early Jurassic to Early Cretaceous, including sandstones, various limestones, breccias and radiolarites. The late Early Cretaceous–Paleogene is represented by the Buntmergel Formation. A sandstone block from the latter yields well-preserved planktonic foraminiferids which allow an assignment to the Early Eocene (E-7 Zone). The low density currents which deposited the parallel laminated sandstones originated in the lower shelf-middle slope.