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Monday, 13 February 2017

Llandre Gravel Quarry -- where is the Penfro Till?


 The flooded Llandre Gravel Quarry, not far from Clynderwen, well inside the "Devensian ice-free area".  Gravels (heavily iron-stained) can be seen in the exposures on two sides of the quarry.  There us no current exposure of till.

Not long ago I  put up a post about the Penfro Till Formation, and wondered where its type locality is really located and just how old it is.  Is it, indeed, just one formation,or are assorted tills of various ages all lumped together rather unreliably?  I am beginning to suspect that the latter is the case.

https://brian-mountainman.blogspot.co.uk/2017/02/penfro-till-formation.html

I called in to have a look at the quarry today  -- it's very close to the road, near a big animal shed belonging to Llandre Egremont Farm and a few hundred metres north of the point where the road passes under the Gelli railway bridge. Grid reference:  SN 092202.  I wasn't able to achieve much, and I couldn't dig away at the gravels without risking life and limb........ but the gravels are at least 3m thick and are heavily iron-stained. But they do not appear to be anything like as rotten as the gravels exposed at Llangolman.  I'm not even sure that they are fluvioglacial -- they look like river gravels to me -- with most pebbles under 5 cm in diameter and with just a few larger clasts.  I think the gravel pit is cut into a remnant of an old river terrace with its top no more than 2m above the present valley floor.  I would hesitate, therefore, to give this site any great geomorphological significance, or assume that it will help us in unravelling the Ice Age history of this area.  I'll take a look at it again in the summer, when hopefully it will be dry enough for me to do a bit more work on the gravel faces.

Higher up the slope, adjacent to the animal sheds, there is an exposure of rotted bedrock and slope deposits or head -- but no gravels or till.

This is certainly not a good enough site to be a type locality for anything.  I might revise that judgment in due course, once I have hoofed about a bit more.

Postscript

I have discovered another gravel pit, at SN093203, about 300m from the one described above.  It's at an altitude of c 44m, on a broad spur above the river valley.  Let's call it Llandre No 2 quarry -- I shall go and check it out.......

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