Clun Forest (Welsh: Coedwig Colunwy[1]) is a remote, rural area of open pastures, moorland and mixed deciduous/coniferous woodland in the southwest part of the English county of Shropshire and also just over the border into Powys, Wales.
Originally flat-lying these strata have been folded into two structural basins both centred on the Clun valley; one to the east, and one to the west of Newcastle.
The two basins are separated by an anticline which runs north–south through Newcastle along what is referred to as the Clun Forest Disturbance.
The central areas of both basins are characterised by the mudstones and sandstones of the Clun Forest Formation, a unit of latest Silurian (Pridoli) age.
beneath this and forming a roughly concentric outcrop are the calcareous siltstones of the Cefn Einion Formation.