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Monday, 23 January 2012

Another Preseli Ice Cap Image


This is another image of the Preseli Ice Cap, from the modelling work reported by Henry Patton and colleagues in 2011.  This shows the picture as it MIGHT have been around 23,850 years ago, with cold-based (thin) ice over the main Preseli ridge and with a few small patches elsewhere as well.  One of these patches is on Carningli -- assumed to have done nothing to the landscape.  Danny McCarroll and colleagues have said:

“East of the proposed ice limit, the western Preseli Hills (Mynydd Carningli) show no evidence of glaciation” (McCarroll et al., 2010)

Oh yes they do, chaps.  There are ice-moulded slabs on Carningli (very near the summit) and also morainic debris on the flanks of the upland.  So the ice was maybe not so cold in the Devensian, and it was certainly capable of affecting the landscape in a number of different ways.  But the complicating factor here is that the Irish Sea ice was coming in from the NW, and extending some way beyond the red line marked on the map.  So there may have been some mixing of Irish Sea Glacier ice and local ice  -- exactly as we see in Greenland today, where big ice streams exist right next to upland ice caps.

The red point shows the sampling point for the cosmogenic dates given by Mc Carroll and others --  as I have previously argued, those dates are wrong.  I'm pretty sure they are INHERITED dates.  More work needed.  We'll get there in the end.

That's the nice thing about models -- they give you something to work on and argue about......

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