Ballagan Formation
| Ballagan Formation | |
|---|---|
| Stratigraphic range: Tournaisian–Visean | |
Exposure of alternating siltstone and dolomite layers of the Ballagan Formation in the bank of Tarras Water | |
| Type | Formation |
| Unit of | Inverclyde Group |
| Underlies | Clyde Sandstone Formation |
| Overlies | Kinnesswood Formation |
| Area | Central Lowlands, Northern England |
| Thickness | ~900 m |
| Lithology | |
| Primary | mudstone, cementstone, siltstone |
| Other | sandstone |
| Location | |
| Region | Scotland |
| Country | United Kingdom |
| Type section | |
| Named for | Ballagan Glen |
| Named by | Browne, 1980 |
The Ballagan Formation is a geologic formation in Scotland and England. It preserves fossils dating back to the early part of the Carboniferous period (Tournaisian – early Visean). Its name comes from the "Ballagan Beds" of Ballagan Glen, near Strathblane, which has a good example of this geological formation.
The Ballagan Formation was historically known as the Cementstone Group, but more recently it has been placed as the middle formation of the Inverclyde Group. This change was motivated by the recognition that the youngest parts of the Devonian Upper Old Red Sandstone (now known as the Kinnesswood Formation) were geologically continuous with the lowest parts of the Lower Carboniferous Calciferous Sandstone Measures (now known as the Ballagan and Clyde Sandstone formations). This interval of Devonian-Carboniferous overlap was named the Inverclyde Group, and the cementstone-rich "drab beds" in the middle of the group were renamed to the Ballagan Formation. In Lothian, the Ballagan and Clyde Sandstone formations are sometimes known as the Tyninghame Formation.