You should never go for a walk in the country and come back empty-handed. Metaphorically speaking, of course. We went for a quick ramble yesterday up around the parking area at Bwlch-gwynt (the col on the Preseli ridge used by the main road). In the brief pause between fronts, we splashed and squelched our way around on the sodden grasslands for a while, and got rather wet -- but I discovered two things.
One, that the little tor called Carn Fach, at about 390m, is distinctly ice-moulded, and looks as if it might have been affected by overriding Late Devensian glacier ice.
Some answers and yet more questions. Does the trim line (either at 420m or 340m) represent the highest Late Devensian ice surface elevation in this part of west Wales? Or was the ice surface initially higher, with the trimline traces belonging to later oscillations or readvances of the ice front with different glaciological conditions? And what were the interactions with the Preseli ice cap?
Another trip up to Bwlch-gwynt is clearly required.