This is a list of the named geological faults affecting the rocks of Wales. See the main article on faults for a fuller treatment of fault types and nomenclature but in brief, the main types are normal faults, reverse faults, thrusts or thrust faults and strike-slip faults. Many faults may have acted as both normal faults at one time and as reverse or thrust faults at another and may or may not have also incorporated some degree of strike-slip movement too. Fault zones, fault belts and fault complexes typically describe assemblages of faults which have a common origin and history and whose alignments tend to be sub-parallel to one another.
There are also a number of 'disturbances', notably in South Wales. These linear features are a combination of faults and folds - the relative importance of faulting and folding varying along the length of each disturbance.
Key to tables Column 1 indicates the name of the fault. Note that different authors may use different names for the same fault or a section of it. Conversely the same name may be applied to more than one fault, particularly in the case of smaller faults which are widely separated. Names are as they appear in the literature and do not necessarily conform to the commonly accepted modern spelling or form of the place-names with which they are associated. Column 2 indicates the OS grid reference of the approximate midpoint of certain faults. Note that the mapped extent of a fault may not accurately reflect its actual extent. Column 3 indicates the county in which the fault occurs. Some traverse two or more counties of course. Column 4 indicates on which sheet, if any, of the British Geological Survey's 1:50,000 / 1" scale geological map series of England and Wales, the fault is shown and named (either on map/s or cross-section/s or both). Also listed are a handful of BGS maps at other scales, where the fault is both shown and named. Column 5 indicates a selection of publications in which references to the fault may be found. See references section for full details of publication.
Alphabetical lists of faults
A Fault name OS map refCountyBGS map sheetbook referencesAber Dinlle FaultGwyneddBrenchley & Rawson 2006Aber FaultGlamorganshireE&W 248Aber Richard FaultE&W 194; 210Aberbeeg FaultMem E&W 232Aberdaron FaultGwyneddE&W 133Abergwesyn FaultE&W 196, 212Abertillery FaultE&W 249Mem E&W 232Abertridwr FaultGlamorganshireE&W 249Acorn FaultE&W 230Afon Banwy FaultPowysE&W 150Afon Ganol FaultClwydMem E&W 95/107Afon Saint FaultGwyneddE&W 133Allt y Crib FaultE&W 163Allt y Grug FaultE&W 230Alyn Valley FaultE&W 108Anafon FaultGwyneddE&W 106Arthog - Caerdeon FaultE&W 149Axton FaultFlintshireE&W 96
B Fault name OS map refCountyBGS map sheetbook referencesBala - Llanelidan FaultSmith et al. 2005Bala FaultE&W 135; 136Bala Fault ZoneUK (south) 625KBeddgelert FaultGwyneddE&W 119Beech Hill FaultMonmouthshireUsk-Cwm:25KBelmont FaultClwydMem E&W 95/107Benton FaultPembrokeshireE&W 228Brenchley & Rawson 2006Berach FaultE&W 230Berw FaultAngleseyBrenchley & Rawson 2006Berw Fault ComplexAngleseyBrenchley & Rawson 2006Bethel FaultGlamorganshireE&W 247Bettws FaultE&W 230Bettws Newydd FaultMem E&W 232Blaenavon FaultMonmouthshireE&W 232Blaenhirwaun ThrustE&W 230Blaen Onneu FaultE&W 232Bodafon ThrustAngleseyBrenchley & Rawson 2006Bodelwyddan FaultDenbighshireE&W 95; 107Mem E&W 95/107Box FaultGlamorganshireE&W 247Bristol Channel Fault ZoneBristol ChannelBronnant FaultCeredigionE&W 178; 210; 211Bronnant Fault ZoneCeredigionE&W 194; 195Brothers FaultGlamorganshireE&W 247Brwynd OverthrustE&W 163Bryn Eglwys FaultE&W 120Brenchley & Rawson 2006Bryn Morgan ThrustE&W 230Bryn Posteg FaultE&W 164Bryn Rhys FaultClwydMem E&W 95/107Brynderi FaultMonmouthshireMem E&W 233/250Bryneglwys FaultE&W 121Bryngwili FaultE&W 230Bryngwyn FaultGlamorganshireE&W 230; 247Bryn-y-maen FaultDenbighshireE&W 95Bwlchgwyn FaultE&W 108Bylchau FaultDenbighshireE&W 107Mem E&W 95/107
C Fault name OS map refCountyBGS map sheetbook referencesCae Parc FaultGlamorganshireE&W 247Caerdeon Bodlyn FaultMerionethshireE&W 135Caergwrle FaultE&W 108Caerleon FaultMonmouthshireE&W 249; Usk-Cwm:25KCaerphilly FaultGlamorganshireE&W 249Camdwr FaultE&W 163Capel Garmon FaultClwydE&W 107Mem E&W 95/107Cardigan - Fishguard Fault BeltPembrokeshireE&W 210Carmel Fault (Powys)PowysE&W 179Carmel Fault (Carmarthenshire)CarmarthenshireE&W 230Carmel Head ThrustUK (south) 625KBrenchley & Rawson 2006Carreg Maen Taro FaultE&W 232Carrog Valley FaultCeredigionE&W 178Cascade OverthrustE&W 163Castell FaultE&W 163Mem E&W 165/151Cefn FaultClwydMem E&W 95/107Cefncynfal FaultPowysMem E&W 165/1051Cefn Bryn ThrustGlamorganshireE&W 246Cefn Crib FaultGlamorganshireE&W 249Cefn FaultE&W 107Cefn Garw FaultMonmouthshireMem E&W 233/250Cefn Ila FaultMonmouthshireUsk-Cwm:25KE&W 232Cefnamwlch-Rhiw FaultGwyneddE&W 134Ceibwr Bay FaultE&W 193Ceidio FaultAngleseyBrenchley & Rawson 2006Ceunant FaultE&W 149Chapel FaultE&W 231Chepstow FaultMonmouthshireMem E&W 233/250Church Stretton Fault SystemBrenchley & Rawson 2006Church Stretton Fault ZoneE&W 213Mem E&W 165/151Cilfeigan FaultMonmouthshireE&W 249; Usk-Cwm:25KClaerwen FaultE&W 179Clochaenog FaultClwydMem E&W 95/107Clwyd FaultSmith et al. 2005Clydach Bridge FaultMonmouthshireE&W 232Clywedog FaultE&W 164Clytha FaultE&W 232Coalbrook FaultE&W 230Coed Hir FaultE&W 231Coed Ithel FaultMonmouthshireMem E&W 233/250Coedycerrig FaultE&W 232Coed-y-paen FaultMonmouthshireE&W 249; Usk-Cwm:25KConwy Valley Fault/Conway Valley FaultGwyneddE&W 106Mem E&W 95/107Copper Works FaultGlamorganshireE&W 247Cors-bol FaultAngleseyBrenchley & Rawson 2006Craig Twrch FaultE&W 212Craiglaseithin FaultGwyneddE&W 135/149Craignant - Milton FaultSmith et al. 2005Craignant FaultSmith et al. 2005Craig-y-beri FaultE&W 137Craig-y-glyn FaultE&W 137Creigydd FaultMonmouthshireE&W 249; Usk-Cwm:25KCribarth FaultE&W 213Crick FaultMonmouthshireMem E&W 233/250Cross Ash FaultMonmouthshireMem E&W 233/250Crychan FaultPowysE&W 196, 213Crychan Fault BeltE&W 213Cwm Cayo Brook FaultMonmouthshireMem E&W 233/250Cwm Cynnen FaultE&W 211Cwm Dockin FaultE&W 165Cwm Dwfnant FaultE&W 196Cwm Earl FaultE&W 165Cwm Felin FaultGlamorganshireE&W 247Cwm Llwyd FaultE&W 230Cwm Pennant FaultBrenchley & Rawson 2006Cwm Pit FaultGlamorganshireE&W 247Cwm Sylwi FaultE&W 149; 163Cwmcarvan FaultMonmouthshireMem E&W 233/250Cwmdockin FaultPowysMem E&W 151/165Cwm-dows FaultGlamorganshireE&W 249Cwmgwineu FaultGlamorganshireE&W 247Cwmllynfell FaultE&W 230Cwm-Mawr FaultE&W 196Cwmmawr ThrustE&W 230Cwmneol FaulE&W 231Cymmer FaultGlamorganshireE&W 248Cynheidre ThrustE&W 230Cynllaith FaultE&W 137
D Fault name OS map refCountyBGS map sheetbook referencesDaren Ddu FaultGlamorganshireE&W 249Daron FaultGwyneddE&W 133Denbigh FaultClwydE&W 107Mem E&W 95/107Dinas Fault (Powys)PowysE&W 231Dinas Fault (Glams)GlamorganshireE&W 248Dinorwic FaultGwyneddE&W 106Dip Fach FaultE&W 231Dolforwyn FaultE&W 165Mem E&W 151/165Dolwar FaultPowysE&W 150Dowlais Fault (Mons)MonmouthshireE&W 231; 232Dowlais Fault (Glams)GlamorganshireE&W 249Duffryn FaultGlamorganshireE&W 230, 247Dulas FaultE&W 196Dulas Gap FaultDenbighshireE&W 95; 107Mem E&W 95/107Dyffryn Maelor FaultClwydMem E&W 95/107Dyfi Valley FaultPowysE&W 150Dyfnant FaultPowysE&W 150Dyfngwm FaultE&W 164Dylife Esgairgaled FaultE&W 164Dylife FaultE&W 164Dynant FaultE&W 230Dysynni FaultE&W 149Dyto FaultClwydMem E&W 95/107
E Fault name OS map refCountyBGS map sheetbook referencesEast Llangerniew FaultClwydE&W 107Mem E&W 95/107Efailnewydd FaultGwyneddE&W 134Eglwysbach FaultClwydMem E&W 95/107Energlyn FaultGlamorganshireE&W 249Erroxhill FaultPembrokeshireE&W 228
F Fault name OS map refCountyBGS map sheetbook referencesFelin Arw FaultGlamorganshireE&W 248Ferry FaultGlamorganshireE&W 247Flint FaultE&W 108Forge OverthrustE&W 149; 163
G Fault name OS map refCountyBGS map sheetbook referencesGadlys FaultGlamorganshireE&W 231; 248Gardeners FaultGlamorganshireE&W 230; 247Garth - Llanwrtyd Fault BeltE&W 212Garth FaultE&W 196, 213Garth Ferry FaultAngleseyBrenchley & Rawson 2006Garth Hill OverthrustGlamorganshireE&W 249Gelli FaultGlamorganshireE&W 249Gelligaer FaultGlamorganshireE&W 249Gelli-goch OverthrustE&W 149; 163Giant's Grave FaultGlamorganshireE&W 247Glan Hafren FaultE&W 165Mem E&W 151/165Glanalders FaultE&W 179Glandyfi FaultE&W 163Glaslyn Valley FaultBrenchley & Rawson 2006Glyn Ceiriog FaultE&W 121Glyn FaultMonmouthshireE&W 249; Usk-Cwm:25KGlyn Valley FaultE&W 135Glyn Wallis FaultE&W 230Glyncorrwg FaultGlamorganshireE&W 231; 248Gnoll FaultGlamorganshireE&W 247Gop FaultFlintshireE&W 95Mem E&W 95/107Gors FaultGlamorganshireE&W 230, 247Gorsedd Bran FaultClwydMem E&W 95/107Gorseinon FaultGlamorganshireE&W 247Great Ewloe FaultE&W 108Greenland FaultMonmouthshireE&W 232Gresford FaultE&W 121Grib FaultE&W 230Groes FaultClwydE&W 107Mem E&W 95/107Grovesend FaultGlamorganshireE&W 230; 247Guilsfield FaultPowysE&W 150, 151Mem E&W 151/165Gwaynynog FaultClwydE&W 107Mem E&W 95/107Gwern-ddu FaultMonmouthshireMem E&W 233/250Gwespyr FaultFlintshireE&W 96Gwili FaultGlamorganshireE&W 230, 247Gwrych Castle FaultDenbighshireE&W 95; 107Mem E&W 95/107Gyrnos FaultE&W 231
H Fault name OS map refCountyBGS map sheetbook referencesHafan FaultE&W 163Hawarden FaultE&W 108Hendre FaultE&W 230Highgate FaultPowysE&W 164; 165Mem E&W 151/165Hirwaun No 1 FaultE&W 231Hirwaun No 2 FaultE&W 231Hirwaun No 2a FaultE&W 231Hirwaun No 3 FaultE&W 231Hudnalls FaultMonmouthshireMem E&W 233/250
I, J, K Fault name OS map refCountyBGS map sheetbook referencesItton FaultMonmouthshireMem E&W 233/250John Grey's FaultGlamorganshireE&W 247Keepers Lodge FaultE&W 230Kilkenny FaultGlamorganshireE&W 231; 249King's Wood FaultMonmouthshireMem E&W 233/250Kinmel Park FaultDenbighshireE&W 95Mem E&W 95/107
L Fault name OS map refCountyBGS map sheetbook referencesLeeswood FaultE&W 108Little Mill FaultE&W 232Llanbadoc FaultMonmouthshireE&W 232; Usk-Cwm:25KLlancayo FaultMonmouthshireE&W 233Mem E&W 233/250Llandrindod - Pen-y-waun Fault BeltE&W 213Llandyfan FaultE&W 230Llandynan FaultE&W 121Llanegryn FaultE&W 149Llanelidan FaultE&W 121Llanerchyraur FaultE&W 164Llanerfyl FaultPowysE&W 150Llanfabon FaultGlamorganshireE&W 231; 249Llanfrechfa FaultMonmouthshireE&W 249; Usk-Cwm:25KLlangattock FaultMem E&W 233/250Llanglydwen FaultE&W 210; 211Llangollen - Llantysilio - Aqueduct FaultSmith et al. 2005Llangollen FaultE&W 121Llangwm FaultMonmouthshireMem E&W 233/250Llangynidr FaultMem E&W 232Llanhilleth FaultGlamorganshireE&W 249Llannefydd FaultClwydE&W 107Mem E&W 95/107Llanrhaeadr FaultClwydE&W 107Mem E&W 95/107Llantysilio FaultE&W 121Llanvair Discoed FaultMonmouthshireMem E&W 233/250Llanvair FaultMonmouthshireE&W 250Llanvapley FaultMem E&W 232Llanvihangel FaultMonmouthshireMem E&W 233/250Llanwonno FaultGlamorganshireE&W 248Llanwrtyd FaultE&W 196Llanwrtyd FaultE&W 213Llechwedd FaultE&W 164Llethir FaultE&W 230Llety Wilws FaultE&W 230Llwyn Celyn FaultE&W 230Llwyn FaultE&W 165Llyfnant FaultE&W 163Llysfaen FaultDenbighshireE&W 95Mem E&W 95/107Longoaks FaultGlamorganshireE&W 247Lunnon FaultGlamorganshireE&W 247
M Fault name OS map refCountyBGS map sheetbook referencesMaen FaultClwydMem E&W 95/107Maes-gwyn (or Maes Gwyn) FaultClwydE&W 107Mem E&W 95/107Marian Ffrith (or Marianffrith) FaultFlintshireE&W 95Mem E&W 95/107Mathern FaultMonmouthshireMem E&W 233/250Mawddach FaultE&W 149Melai FaultClwydMem E&W 95/107Menai Strait Fault SystemBrenchley & Rawson 2006Merthyr Church FaultGlamorganshireE&W 231; 249Meusydd FaultE&W 230Minera Fault BeltE&W 121Minffordd FaultBrenchley & Rawson 2006Mochras FaultMerionethshireE&W 135; 49Brenchley & Rawson 2006Moelfre FaultMerionethshireE&W 135Moel-Gilau FaultGlamorganshireE&W 248Montgomery FaultPowysMem E&W 151/165Morfa FaultGlamorganshireE&W 247, 248Morlais FaultGlamorganshireE&W 247Mount Pleasant FaultE&W 230Mynydd Bach FaultE&W 195Mynydd Bodrochwyn FaultClwydMem E&W 95/107
N