The Clwyd Limestone Group is a stratigraphic unit (a defined sequence of rock layers) of Chadian to Brigantian age (Lower Carboniferous) found in north Wales.
[1] Its most extensive outcrop is along the length of the Clwydian Range, immediately to the east of its crest, between Llandegla and Prestatyn.
A further though more fragmented outcrop extends in an arc along the western margins of the Vale of Clwyd north from Rhyd-y-meudwy, west of Ruthin and then northwest to meet the coast at Llanddulas.
The outcrop also extends southwards from Llandegla to form an impressive scarp at Creigiau Eglwyseg north of Llangollen and south again, to the west of Oswestry to Llanymynech Hill on the Powys/Shropshire border.
The outcrop south of Llandegla comprises only the Leete, Cefn Mawr and Minera units.