microbial population growth cycle. The local manganese ore is, in reality, a Mn-ore series of stromatolite with a volcanic tuff component, that was later transformed by diagenetic processes. The modern analog of this environment of the Úrkút Manganese Ore basinal deposits would be flourishing Prokaryotic bacteria colonies located in submarine vent systems, normally related with remnants of proto-rifts or failed rift systems on continental crust in a submarine environment. The local environments are interpreted as hydrothermal vent systems of cooler temperatures. Fossils Bivalves Brachiopoda The dominant group are the Terebratulids, while Strophomenids play a significant role. While the Brachiopods and Gastropods are more abundant on the underlying Hiertlaz Formation, but also continuous on the Úrkút and Épleny quarries. In the very rich fauna of the local seamount slope the orders Terebratulida and Rhynchonellida play an equally important role, but the basin areas are characterized by a low-diversity fauna dominated by large terebratulids. Gastropoda Cephalopoda Actinopterygii Fungi Palynology Fossil Wood References Geologic formations of Hungary Jurassic System of Europe Toarcian Stage Limestone formations Paleontology in Hungary