
Southerndown Coast is a
Site of Special Scientific Interest
A Site of Special Scientific Interest (SSSI) in Great Britain, or an Area of Special Scientific Interest (ASSI) in the Isle of Man and Northern Ireland, is a conservation designation denoting a protected area in the United Kingdom and Isle ...
(SSSI) in
St Brides Major community, in the
Vale of Glamorgan
The Vale of Glamorgan ( ), locally referred to as ''The Vale'', is a Principal areas of Wales, county borough in the South East Wales, south-east of Wales. It borders Bridgend County Borough to the west, Cardiff to the east, Rhondda Cynon Taf t ...
, South Wales. It forms part of the
Glamorgan Heritage Coast
The Glamorgan Heritage Coast is a stretch of coastline in the Vale of Glamorgan, South Wales, UK.
The Glamorgan Heritage Coast lies between Ogmore-by-Sea and St Athan (with Nash Point at its midpoint) on the South Wales coast. There is a Herit ...
, bordered by the
Monknash Coast to the southeast. The nearby villages are
Southerndown
Southerndown is a village in the Vale of Glamorgan, in south Wales. It is southwest of Bridgend, and within the St Brides Major (community), St Brides Major community, close to Llantwit Major and Ogmore-by-Sea. It is mostly known for its beach ...
and
Ogmore-by-Sea
Ogmore-by-Sea (Welsh language, Welsh: ''Aberogwr'', meaning "Mouth of the River Ogmore") is a seaside village in St Brides Major (community), St Brides Major community in the Vale of Glamorgan, Wales. It lies on the western limit of the Glamorg ...
. The SSSI extends over 5 kilometres (3 miles) of south-west facing coastline, with rocky limestone cliffs, broad beaches and deeply fissured
wave-cut platform
A wave-cut platform, shore platform, coastal bench, or wave-cut cliff is the narrow flat area often found at the base of a sea cliff or along the shoreline of a lake, bay, or sea that was created by erosion. Wave-cut platforms are often most obvi ...
s.
Southerndown Coast SSSI

The stretch of shore, cliff, cliff-top, and several short, steep valleys, are designated an SSSI for their geological and botanical value.
[www.ccgc.gov.uk sssi sites: southerndown coast]
accessed 5 November 2013 The cliffs expose the Jurassic
geological strata and some of the underlying
Carboniferous Limestone, the latter dating from between 359 and c. 330 million years ago. By the
Triassic
The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...
period, 200 million years ago, the Carboniferous rocks had already been tilted and eroded.
[ A new deposition phase created more sedimentary rocks, including a red Triassic conglomerate, and a creamy white ]Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
limestone known as Sutton Stone, a freestone much sought-after for carved stonework, and so widely quarried where it occurs.[ The SSSI is in two parts. The northern section is the wave-cut platform alongside Ogmore-by-Sea. The southern section, with a short gap, covers both the intertidal areas and the cliffs and grassy cliff-tops of Dunraven Bay, Trwyn y Witch headland and the valleys and shoreline of Cwm Mawr and Cwm Bach.][ The whole length of the SSSI is traversed by the South Wales section of the ]Wales Coast Path
The Wales Coast Path () is a designated long-distance trail which follows, or runs close to, the coastline of Wales.
Launched in 2012, the footpath is long and was heralded as the first dedicated coast path in the world to cover the entire len ...
.Wales Coast Path: South Wales Coast and Severn Estuary
Accessed 10 November 2013
Geology
Geological SSSIs are selected to protect sites that display one or more geological features. Three geological features are noted for this site as being of particular significance:–
*Alluvial fan deposits of Triassic sediments where they were deposited onto the eroded Carboniferous Limestone surface.
*Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
intrusion of mineralised fluids into the basal breccia
Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix.
The word has its origins in the Italian language ...
, Carboniferous limestone and Triassic
The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...
rocks. Veins of calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...
, baryte
Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate (Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...
and galena
Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver.
Galena is one of the most abundant and widely distributed sulfide minerals. It crysta ...
are found within the coastal cliffs and outcrops.
*The gradual change in deposition characteristics from water's edge (littoral
The littoral zone, also called litoral or nearshore, is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely i ...
) deposits through to the deeper water marine deposits can be seen south-east of Black Rocks. The cliffs and foreshore show this transition better than anywhere in Britain,[link to Southerndown Coast SSSI citation sheet, first cited, 1965]
. Countryside Council for Wales. Accessed 7 November 2013.
Places to look for these geological features include:-
*Triassic/Carboniferous unconformity and fan deposit: , SS8610675135.
Accessed 5 November 2013
*Fossils in the limestone pavement: , SS8648674600.[
*The Carboniferous unconformity, karstic fill and mineralised veins: , SS8656174529.][
*Triassic conglomerates show well at, SS8661474441.][
* A former quarry and lead mine: , SS8691274277.][
*Deep fissures in the Limestone pavement create blowholes. Overlying this are layers of Sutton Stone outcrops, and thinner banded limestone of the Southerndown beds: , SS8708574122.]
Botany
The cliff-top grassland is species-rich, with a range of plant communities. Where the limestone is at the surface, calcareous
Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines.
In zoology
''Calcare ...
wildflowers are abundant, notably quaking grass
''Briza'' is a genus of annual and perennial plants in the grass family, native to northern temperate regions of Eurasia, North Africa, and certain islands in the Atlantic.
The group is generally referred to as the quaking grasses because the ...
, rock-rose and wild thyme
''Thymus serpyllum'', known by the common names of Breckland thyme, Breckland wild thyme, wild thyme, creeping thyme, or elfin thyme, is a species of flowering plant in the mint family, Lamiaceae. It is a low, usually prostrate subshrub formin ...
. Other localities have neutral, deeper soil and cowslips, dog-violets and bird's foot trefoil
''Lotus corniculatus'' is a flowering plant in the pea family Fabaceae. Common names include common bird's-foot trefoil, eggs and bacon, birdsfoot deervetch, and just bird's-foot trefoil (a name also often applied to other ''Lotus'' spp.). It ha ...
are common. Nearer the sea, salt spray gives a maritime grassland community, including red fescue
''Festuca rubra'' is a species of grass known by the common name red fescue, creeping red fescue or the rush-leaf fescue. It is widespread across much of the Northern Hemisphere and can tolerate many habitats and climates. It is best adapted to w ...
, sea carrot and buck's-horn plantain.[
]
See also
*
*Old Castle Down
Old Castle Down is a Site of Special Scientific Interest between St Brides Major and Ewenny in the Vale of Glamorgan, south Wales.
The Countryside Council for Wales states that the site has been categorised as a Site of Special Interest "...for a ...
(Neighbouring SSSI)
References
{{coord, 51.458, -3.634, name=Southerndown Coast, display=title, region:GB_type:landmark
Sites of Special Scientific Interest in the Vale of Glamorgan
Coast of the Vale of Glamorgan
Beaches of the Vale of Glamorgan