Geology - Resources

Perhaps the most useful guide for those wanting to know more about the geology of our valley is the volume “Geological Excursions in Powys” by N.H. Woodcock and M.G. Bassett (National Museum of Wales, 1993). This describes most of the rocks of the region as a sequence of themed chapters, each discussing the geology of a specific area – and usually of a specific period – as can be seen by following a route through the area. Chapter 14 describes the Devonian sequence and discusses the geology of the Senni bed exposures in detail.

Another excellent source is the short guide “Classic Landforms of the Brecon Beacons” by Richard Shakesby of Swansea University. This explains many of the more striking landforms of the Beacons, including some very close to Senni, and describes how they formed, with particular emphasis on the effects of the glaciations.

Finally, although it is not yet published, we eagerly await the release of the new British Geological Survey 1:50000 scale map of the area around Senni which was mapped in 2003-4. This will be accompanied by a monograph describing the geology of the area and presenting new evidence, especially about the Quaternary and Holocene – the glaciations and deposits laid down in this current interglacial period.

Geological maps of the Senni Valley, including the large-scale 1/50,000 map of the Brecon area [Brecon (B&Sup) (1), E213BSUPF(1)], @ £13.50, are available from the British Geological Survey.