It runs north, parallel to the A4069 road, for over 4 km from near Brynaman to meet the Carreg Cennen Disturbance near Brest Cwm Llwyd.
[1] It moved as a sinistral (left lateral) strike-slip fault during the Variscan Orogeny.
Together with the Llwyn Celyn Fault it formed a left-stepping offset that created a pull apart structure, which preserved the Cwm Llwyd Outlier of Namurian rocks.
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