page_title: St Brides Major (community)
section_title: Limestone Downs
hierarchical_section_title: St Brides Major (community) / Geology and Landscape / Limestone Downs
caption_attribution_description: English: B4265 - Pant St Brides The "back road" to Bridgend is rather twisty - hence the many warnings
context_page_description: St Brides Major is a community on the western edge of the Vale of Glamorgan, South Wales. Its largest settlement is the village of St Brides Major, and also includes the villages of Ogmore-by-Sea and Southerndown, and the hamlets of Ogmore Village, Castle-upon-Alun, Heol-y-Mynydd, Norton and Pont-yr-Brown It is notable for coastal geology and scenery, limestone downlands and fossilised primitive mammals, sea cliffs and beaches, two Iron Age hillforts, three medieval castle sites, two stepping stone river crossings and a clapper bridge. Three long distance paths cross the community. It is the western limit of the Vale of Glamorgan Heritage Coast, and has a visitor centre and tourist facilities.
context_section_description: Ogmore Down occupies the northern part of the community, and is a large area of common grazing land. Irregular boundaries to the unenclosed land show where medieval encroachments occurred, and the northeastern part of the common, near Ogmore Village, is now the Southerndown Golf Club, a championship standard golf course, laid out in 1904. The steep valley sides above the River Ewenny are wooded, but most of the unenclosed common is limestone heath grassland, notable for high brown fritillary butterflies. South of Ogmore Down are two hills just over 100 metres (330 ft) above sea level. To the west is Beacons Down (101 metres (331 ft)), and to the east, separated by the St Brides Gorge, is Old Castle Down (102 metres (335 ft)). Old Castle Down is a 79-hectare (200-acre) SSSI, designated for both its Carboniferous limestone geology and the range of grassland habitats that support rare wildflowers and invertebrates. Duchy Quarry, a disused quarry on the eastern slopes of the hill, above the Alun Gorge, reveals the particular geological feature of the SSSI. The Carboniferous limestone acquired deep cracks and fissures, which then filled up with Jurassic sediments in which are found fossilised remains of reptiles and primitive mammals. Most notable was the 1949 discovery of teeth of the Morganucodon.
caption: B4265 through St Brides Gorge, between Beacons Down and Old Castle Down
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