Slump-fold and palaeoslope orientations in Upper Silurian rocks, North Wales

Abstract

AbstractSilurian mudstones and siltstones in the region south of Colwyn Bay, North Wales, contain numerous ‘disturbed beds’, with folds, fabrics, and other features resulting from pre-lithification deformation at or near to the sea floor. Orientation data are presented for slump folds in four areas of Ludlow rocks where the exposure allows three-dimensional measurement. The data show considerable scatter, perhaps reflecting an irregular slope morphology, and the palaeoslope inferred for each of the areas is slightly differently orientated. In general, however, the palaeoslope directions indicate that the slumps moved not eastwards, along the axis of the Denbigh Trough, as most recently suggested, but down the southern flanks of a gentle, intra-basinal swell.