# List of geological faults of Wales

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 | County | BGS map sheet | book references |
| Aber Dinlle Fault | Gwynedd | | Brenchley & Rawson 2006 |
| Aber Fault | Glamorganshire | E&W 248 | |
| Aber Richard Fault | | E&W 194; 210 | |
| Aberbeeg Fault | | | Mem E&W 232 |
| Aberdaron Fault | Gwynedd | E&W 133 | |
| Abergwesyn Fault | | E&W 196, 212 | |
| Abertillery Fault | | E&W 249 | Mem E&W 232 |
| Abertridwr Fault | Glamorganshire | E&W 249 | |
| Acorn Fault | | E&W 230 | |
| Afon Banwy Fault | Powys | E&W 150 | |
| Afon Ganol Fault | Clwyd | | Mem E&W 95/107 |
| Afon Saint Fault | Gwynedd | E&W 133 | |
| Allt y Crib Fault | | E&W 163 | |
| Allt y Grug Fault | | E&W 230 | |
| Alyn Valley Fault | | E&W 108 | |
| Anafon Fault | Gwynedd | E&W 106 | |
| Arthog - Caerdeon Fault | | E&W 149 | |
| Axton Fault | Flintshire | E&W 96 | |

### B

| Fault name | County | BGS map sheet | book references |
| Bala - Llanelidan Fault | | | Smith et al. 2005 |
| Bala Fault | | E&W 135; 136 | |
| Bala Fault Zone | | UK (south) 625K | |
| Beddgelert Fault | Gwynedd | E&W 119 | |
| Beech Hill Fault | Monmouthshire | Usk-Cwm:25K | |
| Belmont Fault | Clwyd | | Mem E&W 95/107 |
| Benton Fault | Pembrokeshire | E&W 228 | Brenchley & Rawson 2006 |
| Berach Fault | | E&W 230 | |
| Berw Fault | Anglesey | | Brenchley & Rawson 2006 |
| Berw Fault Complex | Anglesey | | Brenchley & Rawson 2006 |
| Bethel Fault | Glamorganshire | E&W 247 | |
| Bettws Fault | | E&W 230 | |
| Bettws Newydd Fault | | | Mem E&W 232 |
| Blaenavon Fault | Monmouthshire | E&W 232 | |
| Blaenhirwaun Thrust | | E&W 230 | |
| Blaen Onneu Fault | | E&W 232 | |
| Bodafon Thrust | Anglesey | | Brenchley & Rawson 2006 |
| Bodelwyddan Fault | Denbighshire | E&W 95; 107 | Mem E&W 95/107 |
| Box Fault | Glamorganshire | E&W 247 | |
| Bristol Channel Fault Zone | Bristol Channel | | |
| Bronnant Fault | Ceredigion | E&W 178; 210; 211 | |
| Bronnant Fault Zone | Ceredigion | E&W 194; 195 | |
| Brothers Fault | Glamorganshire | E&W 247 | |
| Brwynd Overthrust | | E&W 163 | |
| Bryn Eglwys Fault | | E&W 120 | Brenchley & Rawson 2006 |
| Bryn Morgan Thrust | | E&W 230 | |
| Bryn Posteg Fault | | E&W 164 | |
| Bryn Rhys Fault | Clwyd | | Mem E&W 95/107 |
| Brynderi Fault | Monmouthshire | | Mem E&W 233/250 |
| Bryneglwys Fault | | E&W 121 | |
| Bryngwili Fault | | E&W 230 | |
| Bryngwyn Fault | Glamorganshire | E&W 230; 247 | |
| Bryn-y-maen Fault | Denbighshire | E&W 95 | |
| Bwlchgwyn Fault | | E&W 108 | |
| Bylchau Fault | Denbighshire | E&W 107 | Mem E&W 95/107 |

### C

| Fault name | County | BGS map sheet | book references |
| Cae Parc Fault | Glamorganshire | E&W 247 | |
| Caerdeon Bodlyn Fault | Merionethshire | E&W 135 | |
| Caergwrle Fault | | E&W 108 | |
| Caerleon Fault | Monmouthshire | E&W 249; Usk-Cwm:25K | |
| Caerphilly Fault | Glamorganshire | E&W 249 | |
| Camdwr Fault | | E&W 163 | |
| Capel Garmon Fault | Clwyd | E&W 107 | Mem E&W 95/107 |
| Cardigan - Fishguard Fault Belt | Pembrokeshire | E&W 210 | |
| Carmel Fault (Powys) | Powys | E&W 179 | |
| Carmel Fault (Carmarthenshire) | Carmarthenshire | E&W 230 | |
| Carmel Head Thrust | | UK (south) 625K | Brenchley & Rawson 2006 |
| Carreg Maen Taro Fault | | E&W 232 | |
| Carrog Valley Fault | Ceredigion | E&W 178 | |
| Cascade Overthrust | | E&W 163 | |
| Castell Fault | | E&W 163 | Mem E&W 165/151 |
| Cefn Fault | Clwyd | | Mem E&W 95/107 |
| Cefncynfal Fault | Powys | | Mem E&W 165/1051 |
| Cefn Bryn Thrust | Glamorganshire | E&W 246 | |
| Cefn Crib Fault | Glamorganshire | E&W 249 | |
| Cefn Fault | | E&W 107 | |
| Cefn Garw Fault | Monmouthshire | | Mem E&W 233/250 |
| Cefn Ila Fault | Monmouthshire | Usk-Cwm:25K | E&W 232 |
| Cefnamwlch-Rhiw Fault | Gwynedd | E&W 134 | |
| Ceibwr Bay Fault | | E&W 193 | |
| Ceidio Fault | Anglesey | | Brenchley & Rawson 2006 |
| Ceunant Fault | | E&W 149 | |
| Chapel Fault | | E&W 231 | |
| Chepstow Fault | Monmouthshire | | Mem E&W 233/250 |
| Church Stretton Fault System | | | Brenchley & Rawson 2006 |
| Church Stretton Fault Zone | | E&W 213 | Mem E&W 165/151 |
| Cilfeigan Fault | Monmouthshire | E&W 249; Usk-Cwm:25K | |
| Claerwen Fault | | E&W 179 | |
| Clochaenog Fault | Clwyd | | Mem E&W 95/107 |
| Clwyd Fault | | | Smith et al. 2005 |
| Clydach Bridge Fault | Monmouthshire | E&W 232 | |
| Clywedog Fault | | E&W 164 | |
| Clytha Fault | | E&W 232 | |
| Coalbrook Fault | | E&W 230 | |
| Coed Hir Fault | | E&W 231 | |
| Coed Ithel Fault | Monmouthshire | | Mem E&W 233/250 |
| Coedycerrig Fault | | E&W 232 | |
| Coed-y-paen Fault | Monmouthshire | E&W 249; Usk-Cwm:25K | |
| Conwy Valley Fault/Conway Valley Fault | Gwynedd | E&W 106 | Mem E&W 95/107 |
| Copper Works Fault | Glamorganshire | E&W 247 | |
| Cors-bol Fault | Anglesey | | Brenchley & Rawson 2006 |
| Craig Twrch Fault | | E&W 212 | |
| Craiglaseithin Fault | Gwynedd | E&W 135/149 | |
| Craignant - Milton Fault | | | Smith et al. 2005 |
| Craignant Fault | | | Smith et al. 2005 |
| Craig-y-beri Fault | | E&W 137 | |
| Craig-y-glyn Fault | | E&W 137 | |
| Creigydd Fault | Monmouthshire | E&W 249; Usk-Cwm:25K | |
| Cribarth Fault | | E&W 213 | |
| Crick Fault | Monmouthshire | | Mem E&W 233/250 |
| Cross Ash Fault | Monmouthshire | | Mem E&W 233/250 |
| Crychan Fault | Powys | E&W 196, 213 | |
| Crychan Fault Belt | | E&W 213 | |
| Cwm Cayo Brook Fault | Monmouthshire | | Mem E&W 233/250 |
| Cwm Cynnen Fault | | E&W 211 | |
| Cwm Dockin Fault | | E&W 165 | |
| Cwm Dwfnant Fault | | E&W 196 | |
| Cwm Earl Fault | | E&W 165 | |
| Cwm Felin Fault | Glamorganshire | E&W 247 | |
| Cwm Llwyd Fault | | E&W 230 | |
| Cwm Pennant Fault | | | Brenchley & Rawson 2006 |
| Cwm Pit Fault | Glamorganshire | E&W 247 | |
| Cwm Sylwi Fault | | E&W 149; 163 | |
| Cwmcarvan Fault | Monmouthshire | | Mem E&W 233/250 |
| Cwmdockin Fault | Powys | | Mem E&W 151/165 |
| Cwm-dows Fault | Glamorganshire | E&W 249 | |
| Cwmgwineu Fault | Glamorganshire | E&W 247 | |
| Cwmllynfell Fault | | E&W 230 | |
| Cwm-Mawr Fault | | E&W 196 | |
| Cwmmawr Thrust | | E&W 230 | |
| Cwmneol Faul | | E&W 231 | |
| Cymmer Fault | Glamorganshire | E&W 248 | |
| Cynheidre Thrust | | E&W 230 | |
| Cynllaith Fault | | E&W 137 | |

### D

| Fault name | County | BGS map sheet | book references |
| Daren Ddu Fault | Glamorganshire | E&W 249 | |
| Daron Fault | Gwynedd | E&W 133 | |
| Denbigh Fault | Clwyd | E&W 107 | Mem E&W 95/107 |
| Dinas Fault (Powys) | Powys | E&W 231 | |
| Dinas Fault (Glams) | Glamorganshire | E&W 248 | |
| Dinorwic Fault | Gwynedd | E&W 106 | |
| Dip Fach Fault | | E&W 231 | |
| Dolforwyn Fault | | E&W 165 | Mem E&W 151/165 |
| Dolwar Fault | Powys | E&W 150 | |
| Dowlais Fault (Mons) | Monmouthshire | E&W 231; 232 | |
| Dowlais Fault (Glams) | Glamorganshire | E&W 249 | |
| Duffryn Fault | Glamorganshire | E&W 230, 247 | |
| Dulas Fault | | E&W 196 | |
| Dulas Gap Fault | Denbighshire | E&W 95; 107 | Mem E&W 95/107 |
| Dyffryn Maelor Fault | Clwyd | | Mem E&W 95/107 |
| Dyfi Valley Fault | Powys | E&W 150 | |
| Dyfnant Fault | Powys | E&W 150 | |
| Dyfngwm Fault | | E&W 164 | |
| Dylife Esgairgaled Fault | | E&W 164 | |
| Dylife Fault | | E&W 164 | |
| Dynant Fault | | E&W 230 | |
| Dysynni Fault | | E&W 149 | |
| Dyto Fault | Clwyd | | Mem E&W 95/107 |

### E

| Fault name | County | BGS map sheet | book references |
| East Llangerniew Fault | Clwyd | E&W 107 | Mem E&W 95/107 |
| Efailnewydd Fault | Gwynedd | E&W 134 | |
| Eglwysbach Fault | Clwyd | | Mem E&W 95/107 |
| Energlyn Fault | Glamorganshire | E&W 249 | |
| Erroxhill Fault | Pembrokeshire | E&W 228 | |

### F

| Fault name | County | BGS map sheet |
| Felin Arw Fault | Glamorganshire | E&W 248 |
| Ferry Fault | Glamorganshire | E&W 247 |
| Flint Fault | | E&W 108 |
| Forge Overthrust | | E&W 149; 163 |

### G

| Fault name | County | BGS map sheet | book references |
| Gadlys Fault | Glamorganshire | E&W 231; 248 | |
| Gardeners Fault | Glamorganshire | E&W 230; 247 | |
| Garth - Llanwrtyd Fault Belt | | E&W 212 | |
| Garth Fault | | E&W 196, 213 | |
| Garth Ferry Fault | Anglesey | | Brenchley & Rawson 2006 |
| Garth Hill Overthrust | Glamorganshire | E&W 249 | |
| Gelli Fault | Glamorganshire | E&W 249 | |
| Gelligaer Fault | Glamorganshire | E&W 249 | |
| Gelli-goch Overthrust | | E&W 149; 163 | |
| Giant's Grave Fault | Glamorganshire | E&W 247 | |
| Glan Hafren Fault | | E&W 165 | Mem E&W 151/165 |
| Glanalders Fault | | E&W 179 | |
| Glandyfi Fault | | E&W 163 | |
| Glaslyn Valley Fault | | | Brenchley & Rawson 2006 |
| Glyn Ceiriog Fault | | E&W 121 | |
| Glyn Fault | Monmouthshire | E&W 249; Usk-Cwm:25K | |
| Glyn Valley Fault | | E&W 135 | |
| Glyn Wallis Fault | | E&W 230 | |
| Glyncorrwg Fault | Glamorganshire | E&W 231; 248 | |
| Gnoll Fault | Glamorganshire | E&W 247 | |
| Gop Fault | Flintshire | E&W 95 | Mem E&W 95/107 |
| Gors Fault | Glamorganshire | E&W 230, 247 | |
| Gorsedd Bran Fault | Clwyd | | Mem E&W 95/107 |
| Gorseinon Fault | Glamorganshire | E&W 247 | |
| Great Ewloe Fault | | E&W 108 | |
| Greenland Fault | Monmouthshire | E&W 232 | |
| Gresford Fault | | E&W 121 | |
| Grib Fault | | E&W 230 | |
| Groes Fault | Clwyd | E&W 107 | Mem E&W 95/107 |
| Grovesend Fault | Glamorganshire | E&W 230; 247 | |
| Guilsfield Fault | Powys | E&W 150, 151 | Mem E&W 151/165 |
| Gwaynynog Fault | Clwyd | E&W 107 | Mem E&W 95/107 |
| Gwern-ddu Fault | Monmouthshire | | Mem E&W 233/250 |
| Gwespyr Fault | Flintshire | E&W 96 | |
| Gwili Fault | Glamorganshire | E&W 230, 247 | |
| Gwrych Castle Fault | Denbighshire | E&W 95; 107 | Mem E&W 95/107 |
| Gyrnos Fault | | E&W 231 | |

### H

| Fault name | County | BGS map sheet | book references |
| Hafan Fault | | E&W 163 | |
| Hawarden Fault | | E&W 108 | |
| Hendre Fault | | E&W 230 | |
| Highgate Fault | Powys | E&W 164; 165 | Mem E&W 151/165 |
| Hirwaun No 1 Fault | | E&W 231 | |
| Hirwaun No 2 Fault | | E&W 231 | |
| Hirwaun No 2a Fault | | E&W 231 | |
| Hirwaun No 3 Fault | | E&W 231 | |
| Hudnalls Fault | Monmouthshire | | Mem E&W 233/250 |

### I,J,K

| Fault name | County | BGS map sheet | book references |
| Itton Fault | Monmouthshire | | Mem E&W 233/250 |
| John Grey's Fault | Glamorganshire | E&W 247 | |
| Keepers Lodge Fault | | E&W 230 | |
| Kilkenny Fault | Glamorganshire | E&W 231; 249 | |
| King's Wood Fault | Monmouthshire | | Mem E&W 233/250 |
| Kinmel Park Fault | Denbighshire | E&W 95 | Mem E&W 95/107 |

### L

| Fault name | County | BGS map sheet | book references |
| Leeswood Fault | | E&W 108 | |
| Little Mill Fault | | E&W 232 | |
| Llanbadoc Fault | Monmouthshire | E&W 232; Usk-Cwm:25K | |
| Llancayo Fault | Monmouthshire | E&W 233 | Mem E&W 233/250 |
| Llandrindod - Pen-y-waun Fault Belt | | E&W 213 | |
| Llandyfan Fault | | E&W 230 | |
| Llandynan Fault | | E&W 121 | |
| Llanegryn Fault | | E&W 149 | |
| Llanelidan Fault | | E&W 121 | |
| Llanerchyraur Fault | | E&W 164 | |
| Llanerfyl Fault | Powys | E&W 150 | |
| Llanfabon Fault | Glamorganshire | E&W 231; 249 | |
| Llanfrechfa Fault | Monmouthshire | E&W 249; Usk-Cwm:25K | |
| Llangattock Fault | | | Mem E&W 233/250 |
| Llanglydwen Fault | | E&W 210; 211 | |
| Llangollen - Llantysilio - Aqueduct Fault | | | Smith et al. 2005 |
| Llangollen Fault | | E&W 121 | |
| Llangwm Fault | Monmouthshire | | Mem E&W 233/250 |
| Llangynidr Fault | | | Mem E&W 232 |
| Llanhilleth Fault | Glamorganshire | E&W 249 | |
| Llannefydd Fault | Clwyd | E&W 107 | Mem E&W 95/107 |
| Llanrhaeadr Fault | Clwyd | E&W 107 | Mem E&W 95/107 |
| Llantysilio Fault | | E&W 121 | |
| Llanvair Discoed Fault | Monmouthshire | | Mem E&W 233/250 |
| Llanvair Fault | Monmouthshire | E&W 250 | |
| Llanvapley Fault | | | Mem E&W 232 |
| Llanvihangel Fault | Monmouthshire | | Mem E&W 233/250 |
| Llanwonno Fault | Glamorganshire | E&W 248 | |
| Llanwrtyd Fault | | E&W 196 | |
| Llanwrtyd Fault | | E&W 213 | |
| Llechwedd Fault | | E&W 164 | |
| Llethir Fault | | E&W 230 | |
| Llety Wilws Fault | | E&W 230 | |
| Llwyn Celyn Fault | | E&W 230 | |
| Llwyn Fault | | E&W 165 | |
| Llyfnant Fault | | E&W 163 | |
| Llysfaen Fault | Denbighshire | E&W 95 | Mem E&W 95/107 |
| Longoaks Fault | Glamorganshire | E&W 247 | |
| Lunnon Fault | Glamorganshire | E&W 247 | |

### M

| Fault name | County | BGS map sheet | book references |
| Maen Fault | Clwyd | | Mem E&W 95/107 |
| Maes-gwyn (or Maes Gwyn) Fault | Clwyd | E&W 107 | Mem E&W 95/107 |
| Marian Ffrith (or Marianffrith) Fault | Flintshire | E&W 95 | Mem E&W 95/107 |
| Mathern Fault | Monmouthshire | | Mem E&W 233/250 |
| Mawddach Fault | | E&W 149 | |
| Melai Fault | Clwyd | | Mem E&W 95/107 |
| Menai Strait Fault System | | | Brenchley & Rawson 2006 |
| Merthyr Church Fault | Glamorganshire | E&W 231; 249 | |
| Meusydd Fault | | E&W 230 | |
| Minera Fault Belt | | E&W 121 | |
| Minffordd Fault | | | Brenchley & Rawson 2006 |
| Mochras Fault | Merionethshire | E&W 135; 49 | Brenchley & Rawson 2006 |
| Moelfre Fault | Merionethshire | E&W 135 | |
| Moel-Gilau Fault | Glamorganshire | E&W 248 | |
| Montgomery Fault | Powys | | Mem E&W 151/165 |
| Morfa Fault | Glamorganshire | E&W 247, 248 | |
| Morlais Fault | Glamorganshire | E&W 247 | |
| Mount Pleasant Fault | | E&W 230 | |
| Mynydd Bach Fault | | E&W 195 | |
| Mynydd Bodrochwyn Fault | Clwyd | | Mem E&W 95/107 |

### N

| Fault name | County | BGS map sheet | book references |
| Nant Cerrig Fault | Clwyd | | Mem E&W 95/107 |
| Nant Dyar Fault | | | Mem E&W 232 |
| Nant Marl Fault | | E&W 230 | |
| Nant y Fedw Fault | | E&W 196 | |
| Nant-Figillt Fault | | E&W 108 | |
| Nantmor Fault | Gwynedd | E&W 119 | |
| Nantygwrdy Fault | | E&W 164 | |
| Nantyricket Fault | | E&W 164 | |
| Nedern Fault | Monmouthshire | | Mem E&W 233/250 |
| Nercwys - Nant-Figillt Fault Zone | | E&W 108 | |
| New House Thrust | | E&W 165 | |
| Newcastle Fault | Monmouthshire | | Mem E&W 233/250 |
| Newlands Thrust | Glamorganshire | E&W 247, 248 | |
| Newmarket Fault | Clwyd | | Mem E&W 95/107 |
| Newton Fault | Glamorganshire | E&W 247 | |
| Newmarket Fault | Flintshire | E&W 95 | |
| Newport Sands Fault | | E&W 193; 210 | |
| Nicholaston Fault | Glamorganshire | E&W 247 | |

### O

| Fault name | County | BGS map sheet | book references |
| Ochr-y-cefn Fault | Clwyd | | Mem E&W 95/107 |
| Ogof Cadno Fault | | E&W 193 | |
| Ogof Fault | | E&W 163 | |
| Olway Brook Fault | Monmouthshire | | Mem E&W 233/250 |

### P,Q

| Fault name | County | BGS map sheet | book references |
| Palleg Fault | | E&W 230 | |
| Palmer's Lake Overthrusts | Pembrokeshire | E&W 244/5 | |
| Pant Fault | Denbighshire | E&W 95 | Mem E&W 95/107 |
| Pant-y-fotty Fault | Clwyd | | Mem E&W 95/107 |
| Paper Mill Fault | | E&W 108 | |
| Parc Postyn Fault | Clwyd | | Mem E&W 95/107 |
| Pared Fault | Gwynedd | E&W 133 | |
| Parwyd Fault | Gwynedd | E&W 133 | |
| Pendaren Fault | Glamorganshire | E&W 249 | |
| Penffordd Fault | Pembrokeshire | E&W 210 | |
| Pengam Fault | Glamorganshire | E&W 249 | |
| Pennal Fault | | E&W 149; 150; 163 | |
| Penrhiwfelen Fault | Glamorganshire | E&W 247 | |
| Penterry Fault | Monmouthshire | | Mem E&W 233/250 |
| Pentre Clwydau Fault | | E&W 231 | |
| Pentre Felin Fault | Clwyd | | Mem E&W 95/107 |
| Pentre Llanharan Thrust | Glamorganshire | E&W 248 | |
| Pentremawr Lag Fault | Carmarthenshire | E&W 229 | |
| Pentre Tafarn-y-fedw Fault | Clwyd | | Mem E&W 95/107 |
| Pentwyn Fault (Mons) | Monmouthshire | E&W 249 | |
| Pentwyn Fault (Glams) | Glamorganshire | E&W 249 | |
| Pen-y-castell Fault | Glamorganshire | E&W 231, 248 | |
| Penydarren Fault | | E&W 231 | |
| Pen-y-Fan Fault | Monmouthshire | E&W 232 | |
| Pen-y-llan Fault | Monmouthshire | E&W 249; Usk-Cwm:25K | |
| Pen-y-parc Fault | Monmouthshire | E&W 249; Usk-Cwm:25K | |
| Plas Isaf Fault | Glamorganshire | E&W 247 | |
| Pont Morlais Fault | | E&W 230 | |
| Pontarsais Fault | | E&W 212 | |
| Pont-y-ddol Fault | Clwyd | | Mem E&W 95/107 |
| Pontypool Road Fault | Monmouthshire | E&W 232 | |
| Port Eynon Thrust | Glamorganshire | E&W 246 | |
| Portskewett Hill Fault | | | Mem E&W 233/250 |
| Prestatyn Fault | Clwyd | E&W 95 | Mem E&W 95/107 |
| Pwllau Bach Fault | | E&W 231 | |
| Pwllmawr Fault | Glamorganshire | E&W 247 | |
| Pwll-meyric Fault | Monmouthshire | | Mem E&W 233/250 |

### R

| Fault name | County | BGS map sheet | book references |
| Ramsey Fault | Pembrokeshire | E&W 209 | |
| Rassau Fault | | | Mem E&W 232 |
| Reservoir Fault | Monmouthshire | | Mem E&W 233/250 |
| Rhadyr Fault | Monmouthshire | Usk-Cwm:25K | Mem E&W 232 |
| Rhaiadr Fault | | E&W 137 | |
| Rhiw Fault | Glamorganshire | E&W 249 | |
| Rhiw Gwraidd Fault | | E&W 179 | |
| Rhobell Fracture | | | Brenchley & Rawson 2006 |
| Rhos Fault | Glamorganshire | E&W 231; 232; 249 | |
| Rhuallt Fault | Flintshire | E&W 95 | Mem E&W 95/107 |
| Rhydding Fault | Glamorganshire | E&W 230; 247 | |
| Rhyd Sion Wynn Fault | Clwyd | | Mem E&W 95/107 |
| Rhyd-y-creua Fault | Clwyd | | Mem E&W 95/107 |
| Rhymney Fault | | | Mem E&W 232 |
| Ritec Fault | Pembrokeshire | | Brenchley & Rawson 2006 |
| Road Uchaf Fault? | | | Brenchley & Rawson 2006 |
| Rock Park Fault | | E&W 196 | |
| Rockfield Fault | Monmouthshire | | Mem E&W 233/250 |

### S

| Fault name | County | BGS map sheet | book references |
| Sarn-Abersoch Thrust | Gwynedd | E&W 134 | |
| Sawdde Fault | | E&W 212 | |
| Severn Valley Fault Belt | | E&W 151 | Toghill P. 2006 |
| Siamber Wen Fault | Denbighshire | E&W 95; 107 | Mem E&W 95/107 |
| Sirhowy Fault | Monmouthshire | E&W 232 | |
| Six Pit Fault | Glamorganshire | E&W 247 | |
| Soflen Fault | Clwyd | E&W 107 | Mem E&W 95/107 |
| Soughton Fault | | E&W 108 | |
| St Arvans Fault | Monmouthshire | | Mem E&W 233/250 |
| St Brides Fault | Monmouthshire | | Mem E&W 233/250 |
| Stradey Fault | Carmarthenshire | E&W 229 | |
| Strumble Head Fault | Pembrokeshire | E&W 210 | |
| Swansea Fault | Glamorganshire | E&W 247 | |
| Swansea Valley Fault | | E&W 213 | |
| Syddyn Fault | Carmarthenshire | E&W 229 | |

### T

| Fault name | County | BGS map sheet | book references |
| Tafalog Fault | Powys | E&W 150 | |
| Taipellaf Fault | Clwyd | | Mem E&W 95/107 |
| Talgarth Fault | Monmouthshire | | Mem E&W 233/250 |
| Tal-y-coed Fault | Monmouthshire | | Mem E&W 233/250 |
| Tal-y-llyn Fault | | E&W 149 | |
| Tanant Fault | | E&W 137 | |
| Teifi Fault | | E&W 212 | |
| Tintern Fault | Monmouthshire | | Mem E&W 233/250 |
| Tirdonkin Fault | Glamorganshire | E&W 247 | |
| Tonfannau Fault | | E&W 149 | |
| Trafle Fault | Glamorganshire | E&W 247 | |
| Trawsfynydd - Cwm Bowyd Fault | | | Brenchley & Rawson 2006 |
| Trawsfynydd Fault | | MW&M:250K, E&W 135 | |
| Tredegar Fault | Monmouthshire | E&W 231; 232 | |
| Tre-fal-du Fault | Monmouthshire | | Mem E&W 233/250 |
| Trelleck Common Fault | Monmouthshire | | Mem E&W 233/250 |
| Trelleck Fault | Monmouthshire | | Mem E&W 233/250 |
| Tremadog Thrust Zone | | | Brenchley & Rawson 2006 |
| Tre-'r-ddol Fault | | E&W 163 | |
| Trevethin Fault | Glamorganshire, Monmouthshire | E&W 232; 249 | |
| Trinant Fault | Glamorganshire | E&W 249 | |
| Tumble Fault | | E&W 230 | |
| Tweedle Fault | | E&W 231 | |
| Twrch Fechan Fault | | E&W 230 | |
| Twyn Sych Fault | | E&W 231 | |
| Ty Llwyd Fault | | E&W 230 | |
| Ty Mawr Fault | Clwyd | | Mem E&W 95/107 |
| Tyn-y-caeau Fault (Denb) | Denbighshire | E&W 95 | Mem E&W 95/107 |
| Ty'n-y-caeau Fault (Mons) | Monmouthshire | E&W 249; Usk-Cwm:25K | |

### U,V

| Fault name | County | BGS map sheet | book references |
| Upper Artro Fault | Merionethshire | E&W 135 | |
| Usk Fault | Monmouthshire | | Mem E&W 233/250 |
| Vale of Clwyd Fault | Denbighshire | E&W 121; 95 | Mem E&W 95/107 |
| Van Fault | | E&W 164 | |

### W,X,Y,Z

| Fault name | County | BGS map sheet | book references |
| Warren Fault | | E&W 230 | |
| Welsh Borderland Fault | | | Smith et al. 2005 |
| Welsh Borderland Fault System | | UK (south) 625K | Brenchley & Rawson 2006 |
| Wenallt Fault | | E&W 164 | |
| Werf Fault | | E&W 231 | |
| West Llangerniew Fault | Clwyd | E&W 107 | Mem E&W 95/107 |
| Weston Madoc Fault | | E&W 165 | |
| Wonastow Fault | Monmouthshire | | Mem E&W 233/250 |
| Wrexham Fault | | E&W 121 | |
| Yspytty Ifan Fault | | E&W 120 | |
| Ystwyth Fault | | E&W 179 | Mem E&W 151/165 |

## List of Disturbances

The following named features comprise both faulting and folding;
table of named disturbances :
| Disturbance name | County | BGS map sheet |
| Caerbryn Disturbance | Carmarthenshire | E&W 230 |
| Carreg Cennen Disturbance | Carmarthenshire | E&W 230 |
| Clun Forest Disturbance | | |
| Cribarth Disturbance | Powys | E&W 230, 231 |
| Llandyfaelog Disturbance | Carmarthenshire | E&W 231 |
| Llannon (or Llanon) Disturbance | Carmarthenshire | E&W 230 |
| Neath Disturbance | | E&W 231 |
| Pontyclerc Disturbance | Carmarthenshire | E&W 230 |
| Saron Disturbance | Carmarthenshire | E&W 230 |
| Trimsaran Disturbance | | |