Devonian

Devonian The fourth of the six periods of the Palaeozoic Era and the first of the Upper Palaeozoic Sub-era. It began about 480.5 Ma ago and ended about 362.5 Ma ago. 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 (408–401 Ma), Siegennian (401–394 Ma), and Emsian (394–387 Ma) of the Lower Devonian, the Eifelian (387–380 Ma) and Givetian (380–374 Ma) of the Middle Devonian, and the Frasnian (374–367 Ma) and Famennian (367–360 Ma) 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 of late Silurian times, much of the British Isles was covered with continental red-bed facies. Fossils of vascular plants are abundant in Devonian beds; the Rhynie chert flora (Middle Devonian) consists of well-preserved psilophytes.