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BISHOPSTON VALLEY

Entering the Bishopston Valley from Pwlldu

The underlying geology is Carboniferous limestone, resulting in classic karst features at the surface. The Bishopston Pill disappears and reappears a number of times along the length of the valley, creating caves with magical names such as Guzzle Hole.

The stream disappears underground near Barlands Quarry, leaving the stream-bed and ford below St. Teilo’s Church dry except in periods of high rainfall. There is a rock exposure of the Namurian limestone here. Just south of this is a vast pit with sheer walls and a sink hole in its bottom. A little way along from this, the stream-bed is obviously only infrequently flooded and the valley itself is narrow and gorge-like.

On the opposite side of the valley from Guzzle Hole is Long Ash Mine, an adit around 60m in length, which was abandoned in 1854. This produced lead and silver from a lode formed by mineralisation along a fault. It was never extensively worked, probably due to its tendency to flood. A short distance further up the dry floor of the valley from the mine is the entrance to Guzzle Hole where you can see the stream running underground.