Jointing along the Swansea Valley Disturbance between Clydach and Hay-on-Wye, South Wales

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SummaryAlong the length of the Swansea Valley Disturbance, from Clydach (near Swansea) to Hay-on-Wye (Herefordshire), 4 main joint sets are developed. They are NE—SW, NW—SE, N—S and E—W in trend. On the NW and SE sides of the main fault zone only the N—S and E—W sets tend to be developed, whereas within this fault zone only the NE—SW and NW—SE sets are found. It is suggested that the NE—SW and NW—SE sets are shear joints developed at the same time as the main fault zone and the N—S and E—W sets have been developed in response to the release of residual strain energy after the end of the Variscan orogeny.