# List of fossiliferous stratigraphic units in Wales

This is a list of fossiliferous stratigraphic units in Wales.
| Group or Formation | Period |
| 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 |