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Glossary of geological terms

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Cae’r Mynach Formation / Ffurfiant Cae’r Mynach

A succession of sandstones, siltstones and mudstones laid down during the upper part of the Ludlow Epoch of the Silurian Period.

Cainozoic or Kainozoic / Cainosoig

Literally ‘recent life’ – the era of geological time which followed the Mesozoic and began at the start of the Palaeogene Period 66 million years ago.

Caledonian Mountains / Mynyddoedd Caledonaidd

A former range of mountains – possibly of Himalayan size – raised up during the Caledonian Orogeny. The range ran through Scotland and northern England, through Scandinavia and the northeastern United States. Sand, mud and pebbles eroded from them formed the Old Red Sandstone.

Caledonian Orogeny / Orogeni Caledonaidd

Mountain-building period which lasted from the Ordovician to the Devonian arising from the closure of the former Iapetus Ocean.  It deformed the Silurian and Ordovician rocks of Fforest Fawr Geopark.

Caledonides / Gwregys Orogenig Caledonaidd

The rocks and geological structures associated with the Caledonian Orogeny.

Cambrian / Cambriaidd

Geological period which lasted 56 million years from 541 to 485 million years ago.  See geological timescale.

Caradocian or Caradoc Series / Cyfres Caradog

Epoch of the Silurian Period. See Silurian timechart.

Carboniferous / Carbonifferaidd

Geological period which lasted 60 million years from 359 to 299 million years ago. See geological timescale.

Carboniferous Limestone / Calchfaen Carbonifferaidd

The suite of limestones which were deposited during the Carboniferous Period and comprised of several different limestone formations, each of different origin.

Carboniferous Limestone Series / Cyfres y Calchfaen Carbonifferaidd

Subdivision of the Carboniferous Period during which the main limestones were deposited. See geological timescale.

Carreg Cennen Disturbance / Cylchfa Ffawtio-plygu Carreg Cennen

Linear zone comprising geological faults and folds stretching from Carmarthen Bay to the Sennybridge area from where it continues north-eastwards as the Church Stretton Fault Zone (see below). It forms a part of the Welsh Borderland Fault System.

Cennen Beds / Gwelyau Cennen

A succession of rocks laid down at the end of the Ludlow Epoch of the Silurian Period.

Cerig Formation / Ffurfiant Cerrig

Set of mudstones of Telychian age within the Silurian Period.

Church Stretton Fault Zone / Cylchfa Ffawtio Church Stretton

Linear zone comprising geological faults and folds stretching from Church Stretton to the Sennybridge area, continuing south-westwards as the Carreg Cennen Disturbance.

Cil-yr-ychen Limestone / Calchfaen Cilyrychen

Thick formation of limestone deposited during the Carboniferous Period.

Clint

See Limestone pavement

Coal Measures / Haenau Glo

Traditional subdivision of the Carboniferous Period. See Carboniferous timechart.

Coed Wenallt Beds / Gwelyau Coed Wenallt

A succession of rocks laid down during the Ludlow Epoch of the Silurian Period.

Cretaceous / Cretasig

Geological period which lasted 79 million years from 145 to 66 million years ago. See geological timescale.

Cribarth Disturbance / Cylchfa Ffawtio-plygu’r Cribarth

Linear zone comprising geological faults and folds stretching from Abercraf area through the mountain which gives it its name and on north-eastwards as the Cribarth Fault towards Brecon.

Crug Limestone / Calchfaen Crug

A limestone formation deposited during the Caradoc Epoch of the Ordovician Period.

Cumbriense Sandstone / Tywodfaen Cumbriense

A thin sandstone laid down during the Namurian Stage of the upper Carboniferous Period and prominent in the Ystradfellte area.

Cwm Graig Ddu Formation / Ffurfiant Cwm Graig Ddu

Mudstone laid down during the Ludlow Epoch of the Silurian Period.