Carreg Dwfn (also referred to as Careg Dwfn and Carregydwfn and referred to also as Careg-y-dwfan. ) is a hill four miles southeast of

Llandeilo Llandeilo () is a town and community in Carmarthenshire, Wales, situated at the crossing of the River Towy by the A483 on a 19th-century stone bridge. Its population was 1,795 at the 2011 Census. It is adjacent to the westernmost point of the B ...

and just to the south of the village of

Trap A trap is a mechanical device used to capture or restrain an animal for purposes such as hunting, pest control, or ecological research. Trap or TRAP may also refer to: Art and entertainment Films and television * ''Trap'' (2015 film), Fil ...

in the county of

Carmarthenshire Carmarthenshire ( cy, Sir Gaerfyrddin; or informally ') is a county in the south-west of Wales. The three largest towns are Llanelli, Carmarthen and Ammanford. Carmarthen is the county town and administrative centre. The county is known as ...

, south

Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...

. It lies at the western extremity of the

Brecon Beacons National Park The Brecon Beacons National Park ( cy, Parc Cenedlaethol Bannau Brycheiniog) is one of three national parks in Wales, and is centred on the Brecon Beacons range of hills in southern Wales. It includes the Black Mountain (range), Black Mountain ...

and

Fforest Fawr Geopark Fforest Fawr Geopark is a Geopark in the Brecon Beacons National Park, south Wales. It is the first designated Geopark in Wales having gained membership of both the European Geoparks Network and the UNESCO-assisted Global Network of National ...

. Its summit at is towards the eastern end of a rocky east-west-aligned ridge.

Geology

The hill is formed from the coarse

Twrch Sandstone The Marros Group is the name given to a suite of rocks of Namurian age laid down during the Carboniferous Period in South Wales. These rocks were formerly known as the Millstone Grit Series but are now distinguished from the similar but geographi ...

(formerly known as the Basal Grit) laid down during the

Namurian The Namurian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 326 and 313 Ma (million years ago). It is a subdivision of the Carboniferous system or period and the regional Silesian series. The Namurian is ...

stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...

of the

Carboniferous period The Carboniferous ( ) is a Period (geology), geologic period and System (stratigraphy), system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago (Myr, Mya), to the beginning of the Permian Period, ...

. It is defined by faults to east and west. There are a handful of disused

gritstone Gritstone or grit is a hard, coarse-grained, siliceous sandstone. This term is especially applied to such sandstones that are quarried for building material. British gritstone was used for millstones to mill flour, to grind wood into pulp for pa ...

quarries on the southern slope of the hill. Quarrying rights at these sites were stopped by the

Brecon Beacons National Park Authority The Brecon Beacons National Park ( cy, Parc Cenedlaethol Bannau Brycheiniog) is one of three national parks in Wales, and is centred on the Brecon Beacons range of hills in southern Wales. It includes the Black Mountain ( cy, Y Mynydd Du) in ...

in 2008. To its north is the large Craigyrodyn Quarry which worked the

Carboniferous Limestone Carboniferous Limestone is a collective term for the succession of limestones occurring widely throughout Great Britain and Ireland that were deposited during the Dinantian Epoch of the Carboniferous Period. These rocks formed between 363 and ...

outcrop which parallels the narrow band of Twrch Sandstone running west to east through the region. Glacial striae on rock surfaces high on the hill record that during the ice age, glacial ice travelled obliquely across it towards the southwest though lower down, to the south, the ice is recorded as moving more or less from east to west.Strahan, A. et al. 1907 ''The Geology of the South Wales Coalfield Part VII: the country around Ammanford'' (memoir to sheet 230 of the Geological Survey) HMSO, London p199

Access

Carreg Dwfn is designated as open country under the provisions of the CRoW Act 2000. Public footpaths run around the western, northern and eastern sides.

External links

images of Carreg Dwfn and surrounding area on Geograph website

References

{{coord, 51.8382, -3.9530, type:mountain_region:GB, display=title Mountains and hills of Carmarthenshire Black Mountain (hill)