The Carreg Cennen Disturbance is a zone of geological faults and folds

Fold (geology)

The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in...

 in south and mid 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...

 which forms a part of both the Church Stretton Fault Zone and the Welsh Borderlands Fault System. To the southwest it is known as the 'Llandyfaelog Disturbance'.

These structures which stretch from 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....

 to Shropshire

Shropshire

Shropshire is a county in the West Midlands region of England. For Eurostat purposes, the county is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. It borders Wales to the west...

 are thought to have originated during the Caledonian Orogeny

Caledonian orogeny

The Caledonian orogeny is a mountain building era recorded in the northern parts of the British Isles, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occurred from the Ordovician to Early Devonian, roughly...

 or mountain-building period.

Influence on the landscape

It is most impressively revealed at Carreg Cennen

Carreg Cennen

Castell Carreg Cennen is a castle near the River Cennen , in the village of Trapp, four miles south of Llandeilo in Carmarthenshire, Wales. The castle's location has been described as spectacular, due to its position above a limestone precipice.- Description :Carreg Cennen Castle consists of a...

  itself where the mediaeval castle sits perched atop a 90m cliff 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 is caught up within a faulted block sitting between two arms of the Disturbance. It is probably also responsible for the alignment of the Afon Cennen

Afon Cennen

The Afon Cennen is a river in the county of Carmarthenshire, south Wales. It rises on the northern slopes of the Black Mountain to the east of the summit of Tair Carn Uchaf and flows north to Blaencennen Farm, then westwards past Carreg Cennen Castle, continuing through the village of Trap where it...

 to the west of this location where the river follows the line of the fault for over 2.5 mi / 4 km.

The Caledonian Orogeny

The Carreg Cennen Disturbance is one of the more southerly geological features within Britain which can be described as following the Caledonoid trend. The phrase describes a suite of major northeast-southwest oriented geological structures

Geological structure of Great Britain

The geological structure of Great Britain is complex, resulting as it does from a long and varied geological history spanning more than two billion years...

 associated with the closure of the former Iapetus Ocean

Iapetus Ocean

The Iapetus Ocean was an ocean that existed in the Neoproterozoic and Paleozoic eras of the geologic timescale . The Iapetus Ocean was situated in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia...

 in the middle Palaeozoic era and giving rise to the Caledonian Orogeny. The Neath Disturbance

Neath Disturbance

The Neath Disturbance is a geological structure which stretches across south Wales from Swansea Bay northeastwards as far as Hereford in western England. It comprises a series of both faults and associated folds which were active during the mountain-building period known as the Variscan orogeny...

 and the Cribarth Disturbance

Cribarth Disturbance

The Cribarth Disturbance is a geological structure forming a lineament which stretches across south Wales from Swansea up the Swansea Valley then northeastwards to Brecon and beyond. It comprises both a series of faults and associated folds which were active during the mountain-building period...

 are similar features also found in south Wales. The Bala Fault

Bala Fault

Bala Fault is a SW-NE trending geological fault in Wales that extends offshore into Cardigan Bay. In the offshore area it is a major normal fault and forms the bounding structure to the Cardigan Bay Basin, with a fill including about 2500 m of Lias Group. At its northeastern end it links to the...

, Menai Strait Fault, Southern Uplands Fault

Southern Uplands Fault

The Southern Uplands Fault is a fault in Scotland that runs from Girvan to Dunbar on the East coast. It marks the southern boundary of the Scottish Midland Valley....

, Highland Boundary Fault

Highland Boundary Fault

The Highland Boundary Fault is a geological fault that traverses Scotland from Arran and Helensburgh on the west coast to Stonehaven in the east...

 and Great Glen Fault

Great Glen Fault

The Great Glen Fault is a long strike-slip fault that runs through its namesake the Great Glen in Scotland. However, the fault is actually much longer and over 400 million years old.-Location:...

are other major Caledonoid structures of Britain.