This is one of the glacial erratics collected from the till at Rhosyfelin. It's a mudstone pebble about 10 cms long -- probably derived from the Ordovician mudstones and shales which are common along the North Pembrokeshire coastal strip -- and which are also found among the volcanic rocks of the Fishguard Volcanic Series. This pebble has got a number of smoothed glacial facets on it, with a fresher breakage on the right-hand corner and some nice striations running in various directions.
I'm still not at all sure that the archaeologists (or the geologists working with them) recognize the presence of till and fluvio-glacial deposits at this site -- although I am quite mystified as to what else these very prominent deposits might be called. In the talks by Prof MPP and colleagues the pre-Holocene sediments have been notable for not being mentioned at all.......
Gosh, Brian, did you take the trouble to smuggle this 10 - centimetre long glacial erratic mudstone pebble through Swedish customs just so you could photograph and Blog it to us all?? Phenomenological!! Intrepid! Great stuff!
ReplyDeleteNothing so complicated, Tony. It was in my batch of photos from the last visit -- only just got round to examining them properly.......
ReplyDeleteIt was strange to travel across the Netherlands the other day, and to stay in Amersfoort, which gave its name to an interstadial, and to pass through Hengelo, which also gave its name to a climatic event recorded in the Dutch Pleistocene sequence.