In geology

Geology

Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

, the Llandovery Group refers to the lowest division of the Silurian period

Silurian

The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...

 (Upper Silurian) in Britain

Great Britain

Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

. It is named after the town of Llandovery

Llandovery

Llandovery is a market town in Carmarthenshire, Wales, lying on the River Tywi and the A40 road.The town is served by Llandovery railway station, where there is a park and ride to Llanelli and Shrewsbury via the Heart of Wales Line...

 in 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...

, although Charles Lapworth

Charles Lapworth

Charles Lapworth was an English geologist.-Biography:He was born at Faringdon in Berkshire and educated as a teacher at the Culham Diocesan Training College near Abingdon, Oxfordshire. He moved to the Scottish border region, where he investigated the previously little-known fossil fauna of the area...

 had proposed the name Valentian (from the Roman British province of Valentia

Valentia (Roman Britain)

Valentia was the name of a consular northern province of Roman Britain.-History:Count Theodosius set up Valentia in 369 AD as part of his reorganisation of Britain following the Great Conspiracy, and probably named it after the reigning emperors, Valentinian and Valens.Ammianus tells of how the...

) for this group in 1879. It includes the Tarannon Shales (1000-1500 ft.), Upper Llandovery

Llandovery

Llandovery is a market town in Carmarthenshire, Wales, lying on the River Tywi and the A40 road.The town is served by Llandovery railway station, where there is a park and ride to Llanelli and Shrewsbury via the Heart of Wales Line...

 and May Hill Sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

 (800 ft.), Lower Llandovery, (600-1500 ft.)

The Lower Llandovery rocks consist of conglomerate

Conglomerate (geology)

A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...

s, sandstones and slaty beds. At Llandovery they rest upon Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 rocks. These rocks occur with a narrow crop in Pembrokeshire

Pembrokeshire

Pembrokeshire is a county in the south west of Wales. It borders Carmarthenshire to the east and Ceredigion to the north east. The county town is Haverfordwest where Pembrokeshire County Council is headquartered....

, which curves round through Llandovery, and in the Rhayader

Rhayader

Rhayader is a market town and community in Powys, Mid Wales. It has a population of 2,075, and is the first town on the banks of the River Wye, from its source on the Plynlimon range of the Cambrian Mountains....

 district they reach a considerable thickness. They also occur in Ceredigion

Ceredigion

Ceredigion is a county and former kingdom in mid-west Wales. As Cardiganshire , it was created in 1282, and was reconstituted as a county under that name in 1996, reverting to Ceredigion a day later...

 and 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...

.

The Upper Llandovery has local lenticular developments of shelly limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 (Norbury

Norbury

Norbury is a town in the London Borough of Croydon, also crossing the London Borough of Merton. It shares the postcode London SW16 with nearby Streatham. Norbury is south of Charing Cross.-History:...

, Hollies and Pentamerus

Pentamerus

Pentamerus is a prehistoric genus of brachiopod that lived from the Silurian to the Middle Devonian in Asia, Europe, and North America.-External links:* in the Paleobiology Database...

 limestones). It occurs with a narrow outcrop in Carmarthenshire at the base of the Silurian, disappearing beneath the Old Red Sandstone westward to reappear in Pembrokeshire; north-eastward the outcrop extends to the Long Mynd

Long Mynd

The Long Mynd in Shropshire, England, is a part of the Shropshire Hills Area of Outstanding Natural Beauty. It is south of the county town Shrewsbury, and has an area of over 22 square kilometres , most of which takes the form of a heathland plateau. Most of the land on the Long Mynd is owned by...

, which the conglomerate wraps round. As it is followed along the crop it rests upon the Lower Llandovery, Caradog, Llandeilo

Llandeilo

Llandeilo is a town in Carmarthenshire, Wales, situated at the crossing of the River Towy by the A483 on a 19th century stone bridge. Its population is 1,731.The town is served by Llandeilo railway station on the Heart of Wales Line.- Early history :...

, Cambrian

Cambrian

The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...

 and pre-Cambrian rocks. The fossils include the trilobites Phacops caudata, Encrinurus punctatus and Calymene blumenbachis; the brachiopods Pentamerus oblongus, Orthis calligramma and Atrypa reticularis; the corals Favosites

Favosites

Favosites is an extinct genus of tabulate coral characterized by polygonal closely packed corallites . The walls between corallites are pierced by pores which allowed transfer of nutrients between polyps....

and Lindostroemia; and the zonal graptolites Rastriles maximus and Monograptus spinigerus.

The Tarannon shales, grey and blue slates, designated by Adam Sedgwick

Sedgwick

Sedgwick may refer to:-Places:United Kingdom* Sedgwick, Cumbria, England* Sedgwick, West Sussex, EnglandUnited States* Sedgwick, Arkansas* Sedgwick, Colorado* Sedgwick, Kansas* Sedgwick, Maine* Sedgwick, Wisconsin* Sedgwick County, Colorado...

 the Paste Rock, is traceable from Conwy

Conwy

Conwy is a walled market town and community in Conwy County Borough on the north coast of Wales. The town, which faces Deganwy across the River Conwy, formerly lay in Gwynedd and prior to that in Caernarfonshire. Conwy has a population of 14,208...

 into Carmarthenshire; in Ceredigion, there are gritty beds; and in the neighbourhood of Builth, soft dark shales. The group is poor in fossils, with the exception of graptolites; of these Cyrtograptus grayae and Monograptus exiguus are zonal forms. The Tarannon group is represented by the Rhayader Pale Shales in Powys

Powys

Powys is a local-government county and preserved county in Wales.-Geography:Powys covers the historic counties of Montgomeryshire and Radnorshire, most of Brecknockshire , and a small part of Denbighshire — an area of 5,179 km², making it the largest county in Wales by land area.It is...

; in the Moffat Silurian belt in south Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 by a thick development, including the Hawick

Hawick

Hawick is a town in the Scottish Borders of south east Scotland. It is south-west of Jedburgh and south-southeast of Selkirk. It is one of the farthest towns from the sea in Scotland, in the heart of Teviotdale, and the biggest town in the former county of Roxburghshire. Hawick's architecture is...

 rocks and Ardwell

Ardwell

Ardwell is a village in the Scottish unitary council area of Dumfries and Galloway. It lies on the shores of Luce Bay in the southern part of the Rhins of Galloway. The A716 road to Drummore or the Mull of Galloway passes through the village...

 Beds, and the Queensberry Group or Gala; in the Girvan

Girvan

Girvan is a burgh in Carrick, South Ayrshire, Scotland, with a population of about 8000 people. Originally a fishing port, it is now also a seaside resort with beaches and cliffs. Girvan dates back to 1668 when is became a municipal burgh incorporated by by charter...

 area, by the Drumyork Flags, Bargany Group and Penkill Group; and in Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

 by the Treveshilly Shales of Strangford Lough

Strangford Lough

Strangford Lough, sometimes Strangford Loch, is a large sea loch or inlet in County Down, Northern Ireland. It is separated from the Irish Sea by the Ards Peninsula. The name Strangford is derived ; describing the fast-flowing narrows at its mouth...

, and the shales of Salterstown, Co. Louth.

The Upper and Lower Llandovery rocks are represented in descending order by the Pale Shales, Graptolite Shales, Grey Slates and Corwen Grit of Meirionnydd

Meirionnydd

Meirionnydd is a coastal and mountainous region of Wales. It has been a kingdom, a cantref, a district and, as Merionethshire, a county.-Kingdom:...

 and Denbighshire

Denbighshire

Denbighshire is a county in north-east Wales. It is named after the historic county of Denbighshire, but has substantially different borders. Denbighshire has the distinction of being the oldest inhabited part of Wales. Pontnewydd Palaeolithic site has remains of Neanderthals from 225,000 years...

. In the Lake district the lower part of the Stockdale shales (Skelgill beds) is of Llandovery age. In the Girvan area to the north their place is taken by the Camregan, Shaugh Hill and Mullock Hill groups. In Ireland the Llandovery rocks are represented by the Anascaul Slates of the Dingle promontory, by the Owenduff and Gowlaun Grits, Co. Galway, by the Upper Pomeroy Beds, by the Uggool and Ballaghaderin Beds, Co. Mayo, and by rocks of this age in Coalpit Bay and Slieve Felim Mountains.

Economic deposits in Llandovery rocks include slate pencils (Teesdale

Teesdale

Teesdale is a dale, or valley, of the east side of the Pennines in England. Large parts of Teesdale fall within the North Pennines Area of Outstanding Natural Beauty - the second largest AONB in England and Wales. The River Tees rises below Cross Fell, the highest hill in the Pennines, and its...

), building stone, flag-stone, road metal and lime.