Geograph - photograph every grid square

Folded and cracked strata below Allt Wen

One of the fold axes in this area is buried below the surface on the left hand side. The curved section of the fold has cracked off the vertical limb in this exposed section of the fold.

Allt Wen, the northern end of the coastal cliff south of Aberystwyth, is a remarkable geological site. A number of micro-folds only a few metres across with nearly parallel vertical limbs have been exposed on a wave-cut platform at the base of the cliff. The exact sequence of events that have taken place here is still debated, but it is thought that during the Caledonian orogeny 400Ma ago, freshly deposited layers of sediment became pressurised and folded before they were fully lithified and thus more deformable. There are also quartz veins parallel with the bedding in some places. It is thought that they were pressed into the fresh sediment before the folding took place. For more details, see the Geological Conservation Review's site report Link .