Devonian

Devonian The fourth of the six periods of the Palaeozoic Era, about 416–359.2 Ma ago, and the first period of the Upper Palaeozoic Sub-Era. In Europe there are both marine and continental facies present, the latter being commonly known as the Old Red Sandstone. Although originally described from the type area in Devon, the marine Devonian is subdivided stratigraphically into stages established in the exceptionally fossiliferous deposits of the Ardennes in Belgium. These stages are the Gedinnian (416–411.2 Ma ago), Siegennian (411.2–400 Ma ago), and Emsian (400–390 Ma ago) of the Lower Devonian, the Eifelian (also called Couvinian, 390–380 Ma ago) and Givetian (380–375 Ma ago) of the Middle Devonian, and the Frasnian (375–370 Ma ago) and Famennian (370–359.2 Ma ago) of the Upper Devonian. The subdivision of the marine deposits is based on lithologies and the presence of an abundant invertebrate fauna including goniatites (Ammonoidea) and spiriferid brachiopods (Spiriferida). The continental Old Red Sandstone deposits contain a fauna of jawless fish and plants belonging to the primitive psilophyte group. As a result of the Caledonian orogeny ( mountain-building episode) of late Silurian times, much of the British Isles was covered with continental red-bed facies.