The Grünbach Formation is an Austrian geological formation that dates to the lower Campanian age of the Late Cretaceous. it forms part of the Gosau Group, and represents a marine regression event, representing a coastal/brackish environment, being underlain by the marine carbonate and overlain by the deep marine siliciclastic . The main lithology is clay, marl, siltstone and sandstone, with a minor conglomerate component. Coal seams have also been noted. It is notable for its fossils including those of dinosaurs and plants.