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Saturday, 11 February 2023

Preseli -- trimlines, tors and the LGM




My new article published in Quaternary Newsletter is currently available via a direct link to the QRA web site -- but that may not remain open for very long, and I have now added the article to Researchgate as well.  It's the proof version, identical to the published version except for the in-house formatting style.

Was there a Late Devensian ice-free corridor in Pembrokeshire?

https://www.researchgate.net/publication/368426571_Was_there_a_Late_Devensian_ice-free_corridor_in_Pembrokeshire

Citation:
Brian John. 2023. Was there a Late Devensian ice-free corridor in Pembrokeshire? Quaternary Newsletter 158, pp 5-16.

https://www.qra.org.uk/uploads/documents/QN%20158.%20Feb%202023.pdf

One of the articles with which mine is most severely at odds is this one, by Prof Neil Glasser and colleague:

Glasser, N.F. et al. (2018). Late Devensian deglaciation of south-west Wales from luminescence and cosmogenic isotope dating. Jnl of Quaternary Science 33 (7) (2018), pp 804-818.

https://www.researchgate.net/publication/326994378_Late_Devensian_deglaciation_of_south-west_Wales_from_luminescence_and_cosmogenic_isotope_dating_LATE_DEVENSIAN_DEGLACIATION_OF_SOUTH-WEST_WALES

In it, the authors refer quite specifically to the LGM maximum ice edge position being located along the north face of Mynydd Preseli, with a string of "unglaciated rock tors" to the south of it.  

Quote: ".......the north of the Preseli Mountains.......formed the local southern limit of the Irish Sea Ice Stream advance into the region." (p 4)

So we have a fundamental disagreement here -- and I imagine that this will not be resolved until there is a comprehensive cosmogenic dating programme on the rock surfaces or tors and rocky summits like Carn Meini, Carn Alw, Carn Goedog, Carningli and Carn Enoch.


The map showing LGM ice edge positions in North Pembrokeshire and Ceredigion, after Glasser et al.  Note the ice edge position indicated at bottom left of the map.  Clearly, further work is required to sort things out........


Carn Enoch, on Dinas Mountain, on the upland overlooking Cardigan Bay.  Glaciated, or not glaciated, during the LGM?






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