Narrow Vein Mudstone Formation | |
---|---|
Stratigraphic range: Hirnantian | |
Type | Group |
Unit of | Abercorris Group |
Underlies | Garnedd-Wen Formation |
Overlies | Broad Vein Mudstone Formation |
Thickness | 400 metres (1,300 ft) to 560 metres (1,840 ft) |
Lithology | |
Primary | Mudstone |
Other | Slate |
Location | |
Coordinates | 52°40′33″N3°49′23″W / 52.6757°N 3.8230°W |
Region | Mid Wales |
Country | Wales |
Extent | Dinas Mawddwy to Tywyn |
The Narrow Vein Mudstone Formation (commonly known as the Narrow Vein) is an Ordovician lithostratigraphic group (a sequence of rock strata) in Mid Wales. The rock of the formation is silty, homogeneous or finely-laminated mudstone. It generally a medium blue colour. This formation has been commercially quarried as slate in several locations along its length. The formation is between 400 metres (1,300 ft) and 560 metres (1,840 ft) thick and runs from Dinas Mawddwy south-west to Cardigan Bay at Tywyn. [1]
The formation is exposed in a number of locations in Mid Wales where glacial valleys cut across it. It is especially visible in the quarries along its length
The Narrow Vein is one of the two major slate veins in Mid Wales that were commercially quarried. Narrow Vein rock is generally more splittable than Broad Vein rock and was often used to make roofing slates. [2]
The Narrow Vein was quarried in the following locations:
The Corris Railway is a narrow gauge preserved railway based in Corris on the border between Merionethshire and Montgomeryshire in Mid-Wales.
Aberllefenni quarry is the collective name of three slate quarries, Foel Grochan, Hen Gloddfa and Ceunant Ddu, located in Cwm Hengae, just to the west of Aberllefenni, Gwynedd, North Wales. It was the longest continually operated slate mine in the world until its closure in 2003. Foel Grochan is the quarry on the north side of the valley, facing Ceunant Ddu and Hen Gloddfa on the south; all three were worked as a single concern throughout their history. Rock was mainly extracted underground, though all three quarries had open pits as well.
Ratgoed quarry was the northernmost of the slate quarries served by the Corris Railway. It is one mile north of Aberllefenni in Gwynedd, Mid Wales, on the western side of Mynydd Llwydiarth. The quarry primarily worked the Narrow Vein, though it also produced some Broad Vein slates.
Bryn Eglwys quarry was a slate quarry and mine near Abergynolwyn, in Merionethshire, Wales. More than 300 men worked at the site, making it the principal employer in the area. Two veins of slate, known as the Broad Vein and the Narrow Vein, were worked. The geology continues eastwards towards Corris and Dinas Mawddwy, and westwards towards Tywyn. It was one of many quarries that worked these veins.
The Hendre-Ddu Tramway was a 1 ft 11 in narrow gauge industrial railway built in 1874 in Mid-Wales to connect the Hendre-Ddu slate quarry to Aberangell station on the Mawddwy Railway. It consisted of a main line 3+1⁄2 miles (5.6 km) long and several branch lines and spurs serving other quarries, local farms and the timber industry.
The Abercorris quarry was a slate quarry worked between the mid-1840s and the early 1950s. It was located at Corris Uchaf about 5 miles north of Machynlleth, in Gwynedd, north-west Wales. The quarry was connected to the Corris Railway via the Upper Corris Tramway which carried its products to the Cambrian Railways at Machynlleth for distribution. It worked the Narrow Vein.
Dinorwic quarry is a large former slate quarry, now home to the Welsh National Slate Museum, located between the villages of Llanberis and Dinorwig in Wales. At its height at the turn of the century, it was the second largest slate quarry in Wales, after the neighbouring Penrhyn quarry near Bethesda. Dinorwic covered 700 acres (283 ha) consisting of two main quarry sections with 20 galleries in each. Extensive internal tramway systems connected the quarries using inclines to transport slate between galleries. Since its closure in 1969, the quarry has become the site of the National Slate Museum, a regular film location, and an extreme rock climbing destination.
The Mawddwy Railway was a rural line in the Dyfi Valley in mid-Wales that connected Dinas Mawddwy with a junction at Cemmaes Road railway station on the Newtown and Machynlleth Railway section of the Cambrian Railways.
The Cwt y Bugail quarry is a former slate quarry located east of Blaenau Ffestiniog in Wales. It was first worked as a trial pit around 1840. Continuous production began in 1863 and continued until closure in 1961. The quarry was connected to the Ffestiniog Railway at Duffws Station via the Rhiwbach Tramway.
Aberangell railway station was an intermediate railway station on the Mawddwy Railway which ran from Cemmaes Road to Dinas Mawddy in the Welsh county of Merionethshire. The station was opened by the Mawddwy Railway in 1867 and closed to all goods traffic in 1908. The railway re-opened in 1911 with all services run by the Cambrian Railways. It was amalgamated into the Great Western Railway in 1923 as part of the grouping of British railways, and remained open to passenger and freight traffic until 1931 and 1952, respectively. The station was the transshipment point between the branch and the Hendre Ddu Tramway.
The Dyfi hills are a range situated in the southernmost area of Snowdonia, bounded by the River Dyfi on the east and south sides, by the Afon Dulas on the west and the Afon Cerist to the north. They lie to the west of the Aran Fawddwy range, north-east of the Tarren y Gesail range and are a subgroup of the Cadair Idris group.
The Ratgoed Tramway was a 2 ft 3 in gauge horse-worked tramway that connected the remote Ratgoed Quarry with the Corris Railway at Aberllefenni. It was 1.75 miles (2.82 km) long.
The Nant Ceiswyn is a small river in Mid Wales. It flows from the northern flank of Mynydd Dolgoed down to Pont Cymerau, north-east of Aberllefenni. Here it joins the Nant Llwydiarth to form the Afon Dulas that flows south to the Afon Dyfi. There was an ancient bridge at Pont Cymerau.
Cymerau quarry was a slate quarry served by the Ratgoed Tramway, a horse-worked section of the Corris Railway. It is located about half a mile north of Aberllefenni in Merioneth, North Wales, on the eastern side of the isolated Cwm Ceiswyn. It worked the Narrow Vein, the highest-quality slate vein in the Abercorris Group.
The Abercwmeiddaw quarry was a slate quarry that operated between the 1840s and 1938. It was located at Corris Uchaf about 5 miles (8.0 km) north of Machynlleth, in Gwynedd, north-west Wales. The quarry was connected to the Corris Railway via the Upper Corris Tramway which carried its products to the Cambrian Railways at Machynlleth for distribution.
Minllyn quarry was a slate quarry near Dinas Mawddwy in Wales that opened before 1793 and continued working intermittently until 1925. The quarry is located on the western flank of Foel Dinas.
The Broad Vein Mudstone Formation is an Ordovician lithostratigraphic group in Mid Wales. The rock of the formation is silty mudstone, intensely bioturbated in places. It varies in colour from a pale to a medium blue. This formation has been commercially quarried as slate in several locations along its length. The formation is between 400 metres (1,300 ft) and 560 metres (1,840 ft) thick and runs from Dinas Mawddwy south-west to Cardigan Bay at Tywyn.
The Nod Glas Formation is an Ordovician lithostratigraphic group in Mid Wales. The rock of the formation is made up of pyritous, graptolitic mudstone that is generally black in colour. It weathers to a soft, very well cleaved and coal-like material. The formation runs from Conwy in the north, down to Cardigan Bay in the area around Aberdyfi and Tywyn, though it is not a continuous over this area.
Dolgoch slate quarry was a slate quarry in Mid Wales, approximately halfway between Bryn-crug and Abergynolwyn. The quarry was named after a nearby stream, the Nant Dolgoch. 'Dol goch' is Welsh for 'red meadow'.