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Wednesday, 22 February 2017

Devensian till at the Blue Lagoon, Abereiddi

One does not often see exposures of Devensian till on the north Pembrokeshire coast, except in valleys and bays where till is often found as a "plug".  However, there is a splendid exposure at Abereiddi, near the famous flooded quarry called the Blue Lagoon.  Above are a couple of photos.

As we can see, the clifftop till is here about 3m thick, resting on broken shale bedrock.  The till is full of rounded, striated and faceted cobbles and erratics.  The matrix is clay-rich, but more gravelly in patches.  There is some iron-staining, but by and large the larger stones are fresh in appearance, just as they are in all of the other Devensian till exposures in North Pembrokeshire.

I'm not making any particularly new point here.  This is just for the record.......


MoA said...

What are the clasts?

BRIAN JOHN said...

The usual mixture of shales, blackish mudstones, sandstones, grits, quartzites, dolerite, lumps of quartz, and some that look like volcanics. Didn't have much time to examine the sections properly --my wife and friends were in a hurry to keep going! But I didn't notice anything unusual.

TonyH said...

My brother lives fairly nearby, over in Trefin direction, so I've seen the till.