| Aber Mawr Formation | |
| Type: | Geological formation |
| Age: | Arenig |
| Period: | Floian |
| Prilithology: | Mudstone |
| Otherlithology: | Tuff, debrite |
| Namedfor: | Aber Mawr Bay, Ramsey Island |
| Country: | Wales |
| Underlies: | Porth Lauog Formation |
| Thickness: | >215m (705feet) |
| Extent: | Ramsey Island |
The Aber Mawr Formation is a geological formation in Wales. It preserves fossils dating back to the Arenig Series of the Ordovician period.[1]