Ogwen Group | |
---|---|
Stratigraphic range: Arenig to Caradoc Ordovician | |
Type | Group |
Sub-units | Allt Llwyd and Wig Bach formations, Nant Ffrancon Subgroup (which includes Llanengan and St Tudwal's formations), Cwm Eigiau, Allt Fawr Rhyolitic Tuff, Dwyfach and Nod Glas formations |
Overlies | Mawddach Group, Rhobell Volcanic Group |
Thickness | variable, more than 2 km |
Lithology | |
Primary | mudstones, siltstones |
Other | sandstones, tuffs, oolitic ironstones |
Location | |
Region | northwest Wales |
Country | Wales |
Type section | |
Named for | Ogwen Valley |
The Ogwen Group is an Ordovician lithostratigraphic group (a sequence of rock strata) in Gwynedd, north-west Wales. The name is derived from Ogwen Valley, a locality in Snowdonia where it outcrops.
The rocks occur throughout Llŷn and eastwards into Snowdonia within Gwynedd. [1]
The Group consists of about 1000 m thickness (in the Pwllheli area) of mudstones and siltstones with some basal sandstones together with tuffs and oolitic ironstones laid down during the Arenig and Caradoc epochs of the Ordovician Period. [2] The Nant Ffrancon subgroup alone exceeds 2km thickness in central Snowdonia. The subgroup as itself been classed as both a formation and a group at times. [3]
The Glyderau are a mountain group in Snowdonia, North Wales. The name derives from the highest peaks in the range, Glyder Fawr and Glyder Fach. According to Sir Ifor Williams, the word "Glyder" derives from the Welsh word "Cludair", meaning a heap of stones.
The Carneddau are a group of mountains in Snowdonia, Wales. They include the largest contiguous areas of high ground in Wales and England, as well as six or seven of the highest peaks in the country—the Fifteen Peaks. The range also encloses a number of lakes such as Llyn Cowlyd and Llyn Eigiau, and the Aber Falls waterfall. It is delimited by the Irish Sea to the north, the Conwy valley to the east, and by the A5 road from Betws-y-Coed to Bethesda to the south and west. The area covers nearly 200 square kilometres (77 sq mi), about 10% of the area of Snowdonia. The area is bordered by three main roads—the A55, the A5 to the south and the A470 to the east.
Glyder Fawr is a mountain in Snowdonia, Wales, the highest peak in the Glyderau range at just over 1,000 metres, having had its height recalculated in 2010 using GPS. It is the fifth-highest mountain in Wales and has several walking and scrambling routes leading to its summit. According to Sir Ifor Williams, the word "Glyder" derives from the Welsh word "Gludair", meaning a heap of stones.
ˈ The Afon Ogwen is a river in north-west Wales draining from some of the greatest peaks in Snowdonia before discharging to the sea on the eastern side of Bangor, Gwynedd.
The Nant Ffrancon Pass in Snowdonia, North Wales, is the long steady climb of the A5 road between Bethesda, Gwynedd, and Llyn Ogwen in Conwy. The summit at 312 metres (1,024 ft) is at Pont Wern-gof, about one-third of a mile beyond the eastern end of Llyn Ogwen. From here the road descends through Nant y Benglog to Capel Curig and through to Betws-y-Coed. The A5 is the Holyhead to London trunk road, which was re-engineered by Thomas Telford between 1810 and 1826. The original road through the Nant Ffrancon was constructed by Lord Penrhyn in the late 18th century, and at Capel Curig in 1801 he built a coaching inn, which is now Plas y Brenin, the UK National Mountaineering Centre.
The Drefach Group is an Ordovician lithostratigraphic group in west Wales. The name is derived from the village of Drefach near Meidrim in Carmarthenshire. The Group comprises the Mydrim Shales Formation, the Mydrim Limestone Formation, the Hendre Shales Formation, Asaphus Ash Formation and at its base, the underlying Felin-wen Formation.
The Fishguard Volcanic Group is an Ordovician lithostratigraphic group in west Wales. The name is derived from the town of Fishguard in Pembrokeshire. This assemblage of rocks has also been referred to as the Fishguard Volcanic Series or Fishguard Volcanic Complex. These rocks are believed to be the source of the 'bluestones' which form a part of the well-known prehistoric monument of Stonehenge in southern England.
The Llanbedrog Volcanic Group is an Ordovician lithostratigraphic group in northwest Wales. The name is derived from the village of Llanbedrog on the Llyn Peninsula where the strata are exposed.
The Snowdon Volcanic Group is an Ordovician lithostratigraphic group in Snowdonia, north-west Wales. The name is derived from Snowdon, the highest peak in Wales where it outcrops. This assemblage of rocks has also been referred to as the Snowdon Volcanic Series.
The Llewelyn Volcanic Group is an Ordovician lithostratigraphic group in Snowdonia, north-west Wales. The name is derived from Carnedd Llewelyn, the highest peak in the Carneddau range where it outcrops.
The Harlech Grits Group is a lower to middle Cambrian lithostratigraphic group in northwest Wales. The name is derived from the town of Harlech in Gwynedd.
The Mawddach Group is a middle to upper Cambrian lithostratigraphic group in Gwynedd, Wales. The name is derived from the river known as the Afon Mawddach.
The Sherwood Sandstone Group is a Triassic lithostratigraphic group which is widespread in Britain, especially in the English Midlands. The name is derived from Sherwood Forest in Nottinghamshire which is underlain by rocks of this age. It has economic importance as the reservoir of the Morecambe Bay gas field, the second largest gas field in the UK.
Graig Goch is a 586m high hill in the Gwynedd area in Wales and lying within Snowdonia National Park. The hill falls within the communities of Llanfihangel-y-Pennant and Corris, the summit being located in the former. The hill takes the form of a NE-SW aligned ridge with a broad top which rise to subsidiary tops either side of the main summit. These are the 540m+ top of Mynydd Cedris and the 504m top of Mynydd Rugog. The hill’s most notable feature is the large cliff which stretches the length of its northwestern face overlooking Tal-y-llyn, in part a major rock-slope failure.
The Dent Group is a group of Upper Ordovician sedimentary and volcanic rocks in north-west England. It is the lowermost part of the Windermere Supergroup, which was deposited in the foreland basin formed during the collision between Laurentia and Avalonia. It lies unconformably on the Borrowdale Volcanic Group. This unit was previously known as the Coniston Limestone Group or Coniston Limestone Formation and should not be confused with the significantly younger Coniston Group.
Lôn Las Ogwen is a 17.7 km (11.0 mi) cycle route in the National Cycle Network which runs south from the NCN 5 at Porth Penrhyn on the north coast of Wales to Llyn Ogwen in Snowdonia. Lôn Las is Welsh for "blue lane".
This article describes the geology of the Cairngorms National Park, an area in the Highlands of Scotland designated as a national park in 2003 and extended in 2010. The Cairngorms National Park extends across a much wider area than the Cairngorms massif itself and hence displays rather more varied geology.
The geology of Snowdonia National Park in North Wales is dominated by sedimentary and volcanic rocks from the Cambrian and Ordovician periods with intrusions of Ordovician and Silurian age. There are Silurian and Cenozoic sedimentary rocks on the park's margins. The succession was intensely faulted and folded during the Caledonian Orogeny. The region was uplifted as the North Atlantic Ocean opened during the Cenozoic. The current mountainous landscape arises from repeated glaciations during the Quaternary period.
The Holy Island Group is a sequence of metasedimentary rocks of Cambro-Ordovician age found in northern and western Anglesey and the adjacent Holy Island in North Wales. It comprises four formations; a lower South Stack Formation, an overlying Holyhead Formation, a succeeding Rhoscolyn Formation and an uppermost New Harbour Formation. The South Stack Formation outcrops on Holy Island, between Holyhead and South Stack and at Rhoscolyn, and also inland on Anglesey itself between Mynydd Mechell and Carreglefn. The Holyhead and Rhoscolyn formations are restricted to the Holyhead Mountain and Rhoscolyn areas of Holy Island. The New Harbour Formation, which previously enjoyed 'Group' status, is some 2km thick and conformably overlies the Rhoscolyn Formation. It extends across much of northern and western Anglesey and Holy Island.