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Wednesday, 1 February 2017

Penfro Till Formation


I'm increasingly intrigued -- and concerned -- about something labelled as "The Penfro Till Formation" in the official stratigraphic lexicon.  This label is applied to all of the glacial deposits lying outside the supposed Devensian limit in South Wales -- we have done several posts on this.  According to Prof David Bowen, this formation is a part of the "Albion Glacigenic Group".  I'm not sure where the type section is supposed to be -- it might be Pencoed in Glamorgan, and it might just be West Angle Bay in Pembrokeshire, or the old gravel pit at Llandre, near Clynderwen.  All of the glacial and fluvioglacial deposits in the south Pembrokeshire Devensian "ice-free" area are included.  These are well shown on the BGS mapping -- this is a small scale map and one enlarged section:



Apart from the smaller exposures shown on these maps, there are two extensive ones -- let's call them the Clynderwen Gravels and the Templeton Till.  I need to get at them in order to describe them properly........

In this discission we need to include the Llangolman deposits already described on this blog:

https://brian-mountainman.blogspot.co.uk/2014/10/pre-devensian-glacial-deposits-south-of.html
https://brian-mountainman.blogspot.co.uk/2015/04/llangolman-gravel-pit-angian-fluvio.html
https://brian-mountainman.blogspot.co.uk/2015/01/if-ever-there-was-case-for-osl-dating.html
https://brian-mountainman.blogspot.co.uk/2014/12/fluvio-glacial-gravels-around.html
https://brian-mountainman.blogspot.co.uk/2014/12/ancient-till-at-llangolman.html

The signs are that many -- if not all -- of these deposits are heavily weathered, and look different from the fresh glacial and fluvioglacial deposits of north and west Pembrokeshire.  But are they all of the same age?  Could some of them date from the Wolstonian glaciation and some from the Anglian?

https://brian-mountainman.blogspot.co.uk/2017/01/time-to-bring-wolstonian-in-from-cold.html

Whaever the truth of the matter,  we need much better field research and cosmogenic dating before the matter of the "Penfro Till Formation" can be sorted out.

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