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Wednesday 3 October 2018

Was there a proglacial lake on the Somerset Levels?

From Patton et al, 2017

This is an interesting reconstruction of the Fleuve Manche Basin, which is assumed to have collected vast quantities of meltwater during the wastage phase of the two big linked ice sheets that affected northern Europe -- the Fennoscandian Ice Sheet (FIS) and the Celtic Ice Sheet (CIS) -- this latter was called the "British and Irish Ice Sheet (BIIS) in the past.......

https://www.eurekalert.org/multimedia/pub/144059.php

https://reader.elsevier.com/reader/sd/pii/S0277379117302068?token=5415399C90699A2A3C8EFEDBE4DE12E8A66EF22B972C248193F17554317A8ACC2DF9B316B6E53402082F1B93C36DE460

The meltwater torrents after 23,000 years BP must have flowed more or less in the directions indicated -- since water has to flow perpendicular to the edge of the ice sheet and the surface contours.  But the North Sea Basin was a dip in the landscape, so a vast lake must have existed there, which then overflowed southwards and south-westwards.

I know this is just a model, but look at southern England.  The ice sheet edge (effectively the edge of the Welsh Ice Cap) is shown to the east of the Bristol Channel and the Severn Estuary,  with pro-glavial lakes ponded up in the Somerset Lowlands and the the north of the Mendips.  These lakes are shown overflowing not into the Bristol Channel, but southwards towards the English Channel coast, reaching the coast to the west of the Isle of Wight.   This is not a new idea -- there have been discussions for many years about glacial lakes, overflow channels and dry gaps in the territory to the west and south of the Wiltshire Downs.    I need to examine the evidence again......

The other interesting thing to come out of this model is the possibility of glacier ice affecting both the Mendips and the Cotswolds.  We have devoted some space on this blog in the past to the matter of ice on the Mendips, but the Cotswolds are much more difficult to work out.  Watch this space........



This model is supposed to portray the situation as it might have been in the Late Devensian -- but as I have said many times on this blog, Devensian modelling is also a pretty good guide to what went on in the Anglian Glaciation as well.





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