Fig. 2. The South Wales and Pembrokeshire Coalfields, and the localities used for primary data collection.

Pennant Formation geology is outlined after Jones and Hartley³⁵. The stratigraphic column shows the five Members of the Pennant Formation, modified from Waters et al.⁷², and Barclay⁷³ with age data from the British Geological Survey Geological Timechart. The localities are colour-coded by Member.