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Wednesday, 8 January 2014

Interglacial raised beach exposed at Abermawr -- for the first time ever


Sorry this is such a fuzzy photo -- but it's a long-distance shot, hand-held, taken in a strong wind!  Actually it's quite a historic photo --it's the first time the interglacial (Ipswichian) raised beach has ever been seen at Aber-mawr, on the west side of the Pen Caer Peninsula in North Pembrokeshire.  I knew it was there, of course, but all previous studies of the Pleistocene sequence of deposits at Abermawr -- going back to the 1800's -- have failed to record it.  I worked here quite intensively in 1962-1965 and never saw it once, even after storms that caused cliff collapses and cleaned up the cliff face.

At last, after the dramatic events of the past stormy week, cliff falls have revealed the strip of rounded pebbles sitting on a bedrock bench (probably a part of the raised beach rock platform) in the eastern corner of the bay.  The deposits are sealed beneath a thick layer of broken debris and pseudo-stratified head -- dating from the early part of the Devensian glaciation when the climate was cold but not glacial.

By the way, there are other sites in Pembrokeshire where the Ipswichian raised beach is clearly visible beneath later deposits -- and this new discovery confirms a well-established Pleistocene stratigraphy for West Wales.

7 comments:

Dave Maynard said...

How long do you think these things will be visible? It would be worth documenting them.

Still trying to get to Newport and Poppit at low tide.

Dave

chris johnson said...

Very interesting to see these pictures. I wonder what is to see in the river valleys as a lot of flooding has been happening I hear. At Rhosyfelin I wonder how high the river is?

I am often reminded of the little museum at Cenarth where you can see photos of a great flood a few decades back. It exceeds my imagination to see the sheer height and scale of that river at that time.

Very curious if any professional archaeologist can explain how it is possible to do secure dating on the Rhosyfelin campsite given its location.

BRIAN JOHN said...

Dave -- I expect the new exposures to be visible for a long time. In the summer, when the rocks are dry, it will be possible to scramble up and take a good look at the raised beach exposure.

Tim Holt-Wilson said...

Great! Only a Quaternary geologist's or geomorphologist's heart could beat more strongly with the intellectual and aesthetic pleasure of such a sight. I have taken the liberty of tweeting the news:
‏@tim_holt_wilson
Interglacial raised beach at Abermawr nicely revealed by recent storms - http://brian-mountainman.blogspot.co.uk/2014/01/interglacial-raised-beach-exposed-at.html @QuaternaryRA_UK #geodiversity #Wales

BRIAN JOHN said...

Thanks Tim -- hope the geomorphological twitterati are delighted with the news!!

TonyH said...

Have alerted my brother, who likes studying and exploring the landscape and is a former photography lecturer, of this news at Abermawr, not far from his home above Trefin.

Jon Morris said...

Very curious if any professional archaeologist can explain how it is possible to do secure dating on the Rhosyfelin campsite given its location.

Not a professional archaeologist, so can't really comment, but I guess you would have to keep mum about such encounters and probably get a room off-site if things went beyond the dating phase.