| Penarth Group | |
|---|---|
| Stratigraphic range: | |
 Cut face of Cotham Marble, from the Lilstock Formation, showing the stromatolitic structures resembling a landscape | |
| Type | Group |
| Sub-units | Westbury Formation, Lilstock Formation |
| Underlies | Lias Group |
| Overlies | Mercia Mudstone Group |
| Thickness | from 0 to more than 12m |
| Lithology | |
| Primary | mudstone |
| Other | limestone, sandstone |
| Location | |
| Country | Great Britain, Ireland |
| Extent | widespread |
| Type section | |
| Named for | Penarth |
The Penarth Group is a Rhaetian age (Triassic) lithostratigraphic group (a sequence of rock strata) which is widespread in Britain. It is named from the seaside town of Penarth near Cardiff in south Wales where strata of this age are exposed in coastal cliffs southwards to Lavernock Point. This sequence of rocks was previously known as the Rhaetic or Rhaetic Beds.[1]