Group or Formation | Period | Notes |
Aber Mawr Shale | Ordovician | |
Afon Ffinnant Formation | Ordovician | |
Allt Ddu Formation | Ordovician | |
Aran Volcanic Group/Llyn y Gafr Formation | Ordovician | |
Bala Group/Rhiwlas Formation | Ordovician | |
Black Rock Limestone | Carboniferous | |
Blaencediw Formation | Ordovician | |
Bod Deiniol Formation | Ordovician | |
Bodeidda Mudstone | Ordovician | |
Bronydd Formation | Silurian | |
Bryn Siltstone Formation | Ordovician | |
Builth Volcanic | Ordovician | |
Camnant Mudstone | Ordovician | |
Carmarthen Formation | Ordovician | |
Carmarthen Group/Afon Ffinnant Formation | Ordovician | |
Carnedd Iago Formation | Ordovician | |
Crychan Formation | Silurian | |
Cwm Felin Boeth Formation | Ordovician | |
Cymerig Limestone | Ordovician | |
Cyrn Formation | Ordovician | |
Dolhir Formation | Ordovician | |
Dyserth Quarry Limestone | Carboniferous | |
Elton Beds | Silurian | |
Ffestiniog Flag Formation | Cambrian | |
Ffestiniog Flags | Cambrian | |
Foel Formation | Carboniferous | |
GelliFormation | Ordovician | |
Glyn Formation | Ordovician | |
Glyn Gower Formation | Ordovician | |
GraigFormation | Ordovician | |
Gronant Formation | Carboniferous | |
Haverford Formation | Ordovician | |
Haverford Mudstone | Silurian | |
Hells Mouth Grits | Cambrian | |
High Tor Limestone | Carboniferous | |
Hirnant Limestone | Ordovician | |
Hope Shale | Ordovician | |
Hughley Shale | Silurian | |
Hunts Bay Oolite Formation | Carboniferous | |
Leete Limestone | Carboniferous | |
Llanarmon Limestone | Carboniferous | |
Llandudno Pier Dolomite Formation | Carboniferous | |
Llanelly Formation | Carboniferous | |
Llanfallteg Formation | Ordovician | |
Llanfawr Mudstone | Ordovician | |
Llwyn Formation | Carboniferous | |
Lower Flaxley Beds | Silurian | |
Lower Longhope Beds | Silurian | |
Lower Old Red Sandstone Group/Downtonian Formation | Silurian | |
Ludlow Series Group/Whitcliffe Formation | Silurian | |
Mawddach Group/DolFormation | Ordovician | |
May Hill Sandstone Formation | Silurian | |
Mercia Mudstone | Triassic | |
Middle Elton Formation | Silurian | |
Milford Haven Formation | Silurian | |
Moel Hiraddug Limestone | Carboniferous | |
Nant Ffrancon Formation | Ordovician | |
Nant Hir Formation | Ordovician | |
Nant Hir Group/Derfel Limestone | Ordovician | |
Ogof Hen Formation | Ordovician | |
Onny Shale | Ordovician | |
PenFormation | Silurian | |
Plas Uchaf Formation | Ordovician | |
Pont y Fenni Formation | Ordovician | |
Pontyfenni Formation | Ordovician | |
Quartz Conglomerate | Devonian | |
Rhiwlas Limestone Formation | Ordovician | |
Senni bed Formation | Devonian | |
Senni Beds | Devonian | |
Sholeshook Limestone | Ordovician | |
Slade and Redhill Mudstone | Ordovician | |
Spring Quarry Limestone | Carboniferous | |
St. Maughan's Formation | Devonian | |
Sully Beds | Triassic | |
Sutton Formation | Jurassic | |
Sutton stone Formation | Jurassic | |
Trefawr Formation | Silurian | |
Treiorwerth Formation | Ordovician | |
TyFormation | Silurian | |
Upper Blaisdon Beds | Silurian | |
Upper Flaxley Beds | Silurian | |
Upper Longhope Beds | Silurian | |
Wenallt Formation | Ordovician | |
Wenlock Shale | Silurian | |
Wilsonia Shales Formation | Silurian | |
Woolhope Limestone | Silurian | |