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Tuesday, 22 August 2017

Erratics from Newport beach

There have been some very low tides recently, and on a walk the other day I found a large exposure of rounded pebbles on an outcrop of till, very close to the outermost end of the river channel.  This was very close to the old Lifeboat Station at Cwm.  These pebbles are clearly derived from the till, but the rounding is modern -- every now and again this area is exposed and subjected to quite violent wave action.  This is a photo of some of the pebbles collected:

The bulk of the pebbles exposed just now are sandstones, gritstone and shales -- many of these are typical of the Ordovician sediments in this general area, and from the eastern part of Cardigan Bay -- in Ceredigion.  But there are a lot of these igneous pebbles too, which I refer to as porphyritic volcanics, and they sure as eggs are not local.  To my untrained eye they look as if they might have come from the Ramsey Island volcanic outcrops, but an origin there is very unlikely -- so I suggest that they have come from either the Harlech Dome, from the Snowdon volcanic zone, or maybe even from the Lake District.   Maybe from all of these areas...........

I'm intrigued by how similar this assortment is to the pebbles which Sid Howells is looking at from Flat Holm.  Some of those, of course, COULD have come from Ramsey Island, since an origin there would accord with what we know about directions of ice movement.

This is a photo which I published earlier, of some of the Flat Holm erratic pebbles:

All advice on what these latest pebbles from Newport are, and where they might have come from, gratefully received.......

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