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Thursday, 30 June 2016

Britice Project revises Devensian ice margins


For years I have been arguing that the Devensian ice margin shown on BRITICE maps is all wrong, since it defies glaciological logic and does not accord with the evidence on the ground.  Now, at last, it seems that common sense is breaking out.  The latest version of the map (dated 2016) is shown below.


Nothing much has changed in the Celtic Sea sector, but in the outer reaches of the Bristol Channel the ice margin has been moved sharply eastwards to incorporate Chris Rolfe's work on the glaciation of Lundy Island, the work of John Hiemstra and others on Gower,  and maybe even my work on this blog, where I have pointed out that the ice limit shown in Pembrokeshire was all wrong, and that Cadey Island appears to have been glaciated in the Devensian.  It's only a matter of time before the BRITICE team (led by Prof Chris Clark) come to recognize that Devensian ice probably did affect parts of the coast of Devon and Cornwall as well.

The ice lobe occupying the Celtic Sea looks much more sensible now, since as I have repeatedly pointed out, you do not get narrow elongated lobes of ice in unconstrained situations.

Things now start to get rather interesting, particularly in South Pembrokeshire, where it has always been assumed that the surface glacial deposits are probably Anglian rather than Devensian in age.  But the area is now shown on the 2016 BRITICE map as having been glaciated in the Devensian.  Watch this space.......

4 comments:

TonyH said...

I was a bit puzzled, or maybe I misunderstood a recent Blog remark you made about Prof Chris Clark: did you, or did you not state that he is not a glaciologist? I know you've had indirect spats with him in the relatively recent past, over what he said to his then Sheffield University colleague, Prof Parker Pearson (who notoriously doesn't on principle liaise with glaciologists, at least about Preseli, Stonehenge and the bluestones). Please could you clarify.

BRIAN JOHN said...

Chris is not a glaciologist -- he is a glacial geomorphologist. He lectures on glaciology, just as I did at one time. But I doubt very much that he would call himself a glaciologist, if asked!! His publications show that his prime research interest is in the effect of ice on the landscape, and not in the physics of ice. Incidentally, I would not call myself a glaciologist either, even though I have a reasonable grasp of how glaciers work......

TonyH said...

The 2nd map, to me at least, isn't too clear with regards to the the Devensian ice margin and Lundy Island & also Caldey Island.

BRIAN JOHN said...

The outer red line - labelled a major zonal limit -- represents the maximum extent of the Devensian Irish Sea Glacier.