LUDLOW SERIES

the third of four main divisions (in ascending order) comprising the Silurian System; it represents all those rocks on a global basis deposited during the Ludlow Epoch, some 421 to 414 million years ago. The name is derived from the type district, located immediately west of the town of Ludlow in Shropshire, Eng., where about 350 m (1,150 feet) of siltstone and limestone strata occur. The base of the Ludlow Series was formally defined in 1980 on authority of the International Commission on Stratigraphy (International Union of Geological Sciences) with a global stratotype section and point (GSSP) in the quarry at Pitch Coppice on the south side of the Ludlow-Wigmore Road, 4 km (2.5 miles) southwest of Ludlow. The boundary point is coincident with the base of the Lower Elton Formation, which is equated with the base of the graptolite biozone Neodiversograptus nilssoni. Among the shelly fauna typical of the Ludlow Seriesfound in places as widely separated as the Midwestern United States and the Altai Mountains of Russiaare many species of brachiopods belonging to the genus Kirkidium. The top of the Ludlow Series is defined by the base of the overlying Pridoli Series. The Ludlow Series is divided into two worldwide stages: the Gorstian and Ludfordian stages.