Within Pembrokeshire the Carboniferous Limestone forms the spectacular coastal cliffs at St Govan's Head along from which are features such as Huntsman's Leap and the Green Bridge of Wales, a natural arch. It forms prominent headlands such as those of Stackpole Head and Lydstep Point and the cliffs at Tenby. A narrow, intensely quarried outcrop runs inland from Carmarthen Bay through Carmarthenshire from Kidwelly, entering the Brecon Beacons National Park at Llandyfan and extending westwards through the Black Mountain to Cribarth above the upper Swansea Valley. It is here referred to as the ‘north crop' as distinct from a sub-parallel outcrop, the ‘south crop' which defines the southern rim of the South Wales Coalfield. The outcrop continues through Ystradfellte to Pontneddfechan, Penderyn and Pontsticill. It then runs near the southern margin of the national park via Trefil and the Llangattock escarpment to Blorenge where it turns southwards. A very narrow ‘east crop' and ‘south crop' run by Cwmbran and north of Cardiff. It turns west again to meet Swansea Bay at Porthcawl. West of the bay, the rock forms the renowned southern coast of Gower between Mumbles Head and Worms Head. There are further occurrences in the Vale of Glamorgan, both inland and on the coast.