Ffordd Coed Dol-Fawr
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Geology & landscape
Geological Period: Silurian
Description
Description Cuttings and natural outcrops along the northern side of this forestry track provide excellent exposures of a thinly layered sequence of sandstones, siltstones and mudstones of lower Silurian age. These are contorted by a series of folds produced by intense crustal compression during the Caledonian mountain building episode. These exemplify with particular clarity the structural characteristics of this area which, in geological terms, lies on the south-west side of the Plynlimon Dome. Folds range in scale from a few centimetres to hundreds of metres and are associated with a well developed cleavage (closely spaced parallel fractures). The fold hinges are often horizontal, but are sometimes inclined at more than 40 degrees. This may be related to the form of the major structure of the Plynlimon Dome itself, but is the subject of current research and remains to be fully explained. At one locality a second generation cleavage cuts across the earlier structures, providing a notable occurrence of this rare feature. This site provides outstanding exposures of geological structures characteristic of west-central Wales and displays many features of interest, with great potential for future research. Remarks: The site is owned by the Forestry Commission.