Garreg Las
Encyclopedia
Garreg Las is a subsidiary summit of Fan Brycheiniog
in the Brecon Beacons National Park in the county of Carmarthenshire
, south Wales
. Its summit sits towards the northern end of a broad north-south ridge, Esgair Hir ("long ridge"), at 635 metres (2,083.3 ft) above sea level. The hill is sometimes referred to as Twyn Swnd.
A subsidiary top just over 1 kilometre (0.621372736649807 mi) to the north of the main summit is Carreg yr Ogof, whose name ("rock of the cave") reflects its limestone geology
. Its top, at 585 metres (1,919.3 ft) above sea level, is crowned by a trig point
.
, a coarse sandstone (formerly known as the Basal Grit) of the Marros Group
(formerly the Millstone Grit
Series) which was laid down during the Carboniferous period. Wrapped around its northern and western flanks is a narrow band of Carboniferous Limestone
which gives rise to a karst
landscape. The Twrch Fechan Fault defines its eastern margin and brings Old Red Sandstone
rocks into contact with the limestone on this flank. A number of major shakeholes in the Basal Grit adorn these eastern flanks, one of which, known as 'Pwll Cynrig' is flooded.
s known as Carnau'r Garreg Las. A further cairn, known as Carn y Gigfran, lies a few hundred metres to the north of Carreg yr Ogof.
. A bridleway approaches the hill from Llanddeusant
to the north and is followed in part by the Beacons Way which runs from Llangadog
to Abergavenny
and which continues southwards over the hill.
Fan Brycheiniog
Fan Brycheiniog is the highest peak in the Black Mountain region of the Brecon Beacons National Park in South Wales. It is just inside the county of Powys, and also within the Fforest Fawr Geopark designated in 2005 in recognition of the area's geological heritage.The Beacons Way, a waymarked long...
in the Brecon Beacons National Park in the county of Carmarthenshire
Carmarthenshire
Carmarthenshire is a unitary authority in the south west of Wales and one of thirteen historic counties. It is the 3rd largest in Wales. Its three largest towns are Llanelli, Carmarthen and Ammanford...
, south Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
. Its summit sits towards the northern end of a broad north-south ridge, Esgair Hir ("long ridge"), at 635 metres (2,083.3 ft) above sea level. The hill is sometimes referred to as Twyn Swnd.
A subsidiary top just over 1 kilometre (0.621372736649807 mi) to the north of the main summit is Carreg yr Ogof, whose name ("rock of the cave") reflects its limestone geology
Geology of South Wales
South Wales is an area with many features of outstanding interest to geologists, who have for long used the area for University field trips.This varied and accessible region has provided a written record of geological interest going back to the 1100s when Giraldus Cambrensis noted pyritous shales...
. Its top, at 585 metres (1,919.3 ft) above sea level, is crowned by a trig point
Trig point
A triangulation station, also known as a triangulation pillar, trigonometrical station, trigonometrical point, trig station, trig beacon or trig point, and sometimes informally as a trig, is a fixed surveying station, used in geodetic surveying and other surveying projects in its vicinity...
.
Geology
Garreg Las is formed from the Twrch SandstoneMarros Group
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 geographically separate rock sequences of the Pennines and...
, a coarse sandstone (formerly known as the Basal Grit) of the Marros Group
Marros Group
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 geographically separate rock sequences of the Pennines and...
(formerly the Millstone Grit
Millstone Grit
Millstone Grit is the name given to any of a number of coarse-grained sandstones of Carboniferous age which occur in the Northern England. The name derives from its use in earlier times as a source of millstones for use principally in watermills...
Series) which was laid down during the Carboniferous period. Wrapped around its northern and western flanks is a narrow band of Carboniferous Limestone
Carboniferous limestone
Carboniferous Limestone is a term used to describe a variety of different types of limestone occurring widely across Great Britain and Ireland which were deposited during the Dinantian epoch of the Carboniferous period. They were formed between 363 and 325 million years ago...
which gives rise to a karst
KARST
Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
landscape. The Twrch Fechan Fault defines its eastern margin and brings Old Red Sandstone
Old Red Sandstone
The Old Red Sandstone is a British rock formation of considerable importance to early paleontology. For convenience the short version of the term, 'ORS' is often used in literature on the subject.-Sedimentology:...
rocks into contact with the limestone on this flank. A number of major shakeholes in the Basal Grit adorn these eastern flanks, one of which, known as 'Pwll Cynrig' is flooded.
Archaeology
On the summit are two prehistoric cairnCairn
Cairn is a term used mainly in the English-speaking world for a man-made pile of stones. It comes from the or . Cairns are found all over the world in uplands, on moorland, on mountaintops, near waterways and on sea cliffs, and also in barren desert and tundra areas...
s known as Carnau'r Garreg Las. A further cairn, known as Carn y Gigfran, lies a few hundred metres to the north of Carreg yr Ogof.
Access
The hill is entirely classed as open country and therefore freely available to walkersHillwalking
In the British Isles, the terms hillwalking or fellwalking are commonly used to describe the recreational outdoor activity of walking on hills and mountains, often with the intention of visiting their summits...
. A bridleway approaches the hill from Llanddeusant
Llanddeusant, Carmarthenshire
Llanddeusant is a community in the Black Mountain region of the Brecon Beacons National Park in Carmarthenshire, Wales. It is about 5 miles southeast of Llangadog....
to the north and is followed in part by the Beacons Way which runs from Llangadog
Llangadog
Llangadog is a community located in Carmarthenshire, Wales, which includes the villages of Llangadog, Bethlehem and Capel Gwynfe. A notable local landscape feature is Y Garn Goch with two Iron Age hill forts....
to Abergavenny
Abergavenny
Abergavenny , meaning Mouth of the River Gavenny, is a market town in Monmouthshire, Wales. It is located 15 miles west of Monmouth on the A40 and A465 roads, 6 miles from the English border. Originally the site of a Roman fort, Gobannium, it became a medieval walled town within the Welsh Marches...
and which continues southwards over the hill.