AbstractIn recent years the folding and cleavage seen in the Aberystwyth Grits has been ascribed to downslope movement in soft unlithified sediment, not to tectonic forces. A detailed examination of folded beds in a small part of the outcrop was undertaken to test this theory. It is concluded that the folding and cleavage was initiated by movement from a rising tectonic ridge, but that the sediments may not have been completely lithified at the time of folding.