"The Bwa Du Fault is of regional importance as one of the best-exposed major faults on Anglesey. It is expressed as a 15m-wide gully between the ruggedly exposed yellow quartzite of the Rhoscolyn Formation to its SE and the lower-lying cliffs of the green-grey schists of the New Harbour Formation to its NW. The fault zone has a trend of 120° and a steep, near vertical, dip. The complex faulting and juxtaposition of the Rhoscolyn Formation (South Stack Group) with the New Harbour Group of Precambrian rocks, together with later small-scale folds in the schist, make this an exciting research site and excellent teaching material for students." visit http://www.geomon.co.uk/