The Penfro Till Formation -- a geological myth

This is the BGS map of till units in Great Britain; the "minimal till" area (shown in red) to the south of the presumed Devensian limit in Wales is labelled as the "Penfro Till Formation"........

Here we go again. Having expressed my despair, many times on this blog, about the tendency in archaeological circles to accept myths and fantastic speculations as established truths, I have to express my frustration about the same sort of thing happening in geology.

I was looking at the BGS lexicon today, and was very disappointed to see that the entry for the Penfro Till formation is unchanged, in spite of strong concerns about its reliability as a label:

https://brian-mountainman.blogspot.com/2017/02/penfro-till-formation.html
https://brian-mountainman.blogspot.com/2017/02/llandre-gravel-quarry-where-is-penfro.htmlhttps://brian-mountainman.blogspot.com/2019/01/the-curse-of-lithostratigraphy.html

https://www.bgs.ac.uk/lexicon/lexicon.cfm?pub=POTI

As I have pointed out before on this blog, and in correspondence with the BGS, if we look at the definitive entry for this "ancient till" in the lexicon, under the Albion Glacigenic Group as the "parent unit", we find that the type localities are West Angle Bay and Llandre Quarry in Pembrokeshire. That is an extraordinary error on the part of the geologists, since there is NO ancient till exposed at either site, and the sands and gravels at West Angle are demonstrably Devensian -- and therefore have nothing to do with the Albion Glacigenic Group.

https://brian-mountainman.blogspot.com/2017/03/the-west-angle-enigma-3-two-tills-or-one.html

The critical central part of the West Angle exposure. Here we see the erosional contact between the older deposits (partly interglacial) to the south and the younger (partly glacial) deposits to the north. Dixon, Bowen and others might not have seen this contact clearly, and so they assumed (erroneously) that some glacial deposits are older than the grey silt and clay series.

This is the West Angle stratigraphy:

10. Made ground and soil -- modern
9. Dark red stratified horizon -- late glacial (Devensian / Holocene transition
8. Dark red diamicton (non-stratified) -- Late Devensian glaciation (LGM)
7. Orange silt and clay series -- Ipswichian interglacial dune slack environment (freshwater)
6. Grey silt and clay series -- ditto
5. Peat and peaty silt -- ditto
4. Stony grey silts -- up to 1.5 m thick -- ditto (includes some slope breccia material?)
3. Ferruginous bedded sands and gravels -- up to 1.5 m thick -- Ipswichian shoreline deposits?
2. Rounded pebbles / beach shingle in a sandy and gravelly matrix -- up to 1.8 m thick -- Ipswichian raised beach
1. Sand layer -- more than 1 m thick -- Ipswichian sandy beach

There are admittedly some glaciofluvial gravels at Llandre that might be old, but neither DQB nor anybody else has ever published a full description of them, and there is nothing at the site to tie the gravels into a regional stratigraphic sequence.

Type localities need to be stable, accessible and clearly tied into a regional stratigraphy. Llandre is useless as a type locality for anything; if West Angle is used as a type locality for anything, it should be for the Devensian or the Ipswichian, and most definitely not for the Penfro Formation or the Anglian glaciation.

The error is compounded by reference to Pencoed, where the glacigenic deposits are also assumed (without hard evidence) to be pre-Ipswichian in age.  This is unfortunate, to put it mildly, because in the BGS memoir for the country around Bridgend, written more than 30 years ago, Wilson et al (1990) argue quite strongly that the Ewenny and Pencoed glaciogenic deposits are probably NOT related to the Penfro Till Formation of the Albion Glacigenic Group, but are probably of Late Devensian age.  I tend to agree with them on that, and think it rather strange that within the BGS the right hand appears not to know what the left hand is doing.

Wilson, D, Davies, J R, Fletcher, C J N and Smith,
M. 1990. Geology of the South Wales Coalfield, Part
VI, the country around Bridgend. Memoir of the British
Geological Survey, Sheet 261 and 262 (England and Wales)
Second edition

https://pubs.bgs.ac.uk/publications.html?pubID=B01835

Anyway, I have written yet again to the BGS with a request that the lexicon entry for the Penfro Till Formation should be scrapped -- or at the very least completely rewritten.   Don't hold your breath -- within the BGS things are measured in millions of years........

See also:

http://nora.nerc.ac.uk/id/eprint/21121/1/IR10041.pdf

ENTWISLE, D C, WILDMAN, G. 2010. Creation of the Till Thematic Layer. British Geological Survey Internal Report, IR/10/041. 14pp.

The correspondents for Wales are shown as David Wilson and Jon Merritt