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Saturday, 1 October 2011

The forgotten glaciation

Astute observers will note that the latest map of ice limits, by Gibbard and Clark, shows THREE glaciations affecting the southern parts of Great Britain.  Probably there have been others too, but these are the ones that we need to match up with the evidence on the ground.
So what of the Saalian / Wolstonian Glaciation?  Well, it was pretty big -- and occurred around 150,000 years ago.

One problem is that it's pretty difficult to unravel it from the earlier Anglian Glaciation and the later Devensian -- except in the East Midlands, where three different ice limits (quite widely spaced) are represented in the sediment sequences.

But the line is very generalised -- and Gibbard and Clark have got it totally screwed up across Wales.  A glacial limit running across from the Welsh Borders in mid-Wales down to Carmarthen Bay just does not make sense glaciologically.  If there was ice over the high plateaux of Mid Wales there must also have been ice over the Brecon Beacons and the uplands of the South Wales Coalfield.  So the Saalian limit was certainly much further to the south.  But where?  More work to be done, chaps.......

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