The extent of the Late Devensian Celtic Sea Ice Lobe

One of the nice things about a blog such as this is that I can report on new research, praise it, question it, or just raise interesting questions that it throws up.  I have reported on several occasions over the past few months on the excellent papers now appearing from the BRITICE-Chrono team and others; their work is transforming our knowledge of both Late Devensian chronology and ice extent.

And I can play about, free of constraints, in suggesting new models that seem to me to fit newly reported evidence and emerging scenarios.  These models may not last long, but who cares anyway?  If they help others to crystallise out their own ideas and evolve more accurate models that fit more closely with evidence on the ground (and on the sea bed), that's fine by me.......

As the geomorphologists who read this blog will know, I have had concerns for a long time about the strange ice lobe shown in many Devensian ice edge reconstructions as flowing southwards past the Isles of Scilly, but with no constraints on either its western or eastern edges.  This lobe is shown by the thin red line on the map above.

The new research work suggests that the ice of the Irish Sea Ice Stream probably extended c 500 km to the SSW of St George's Channel, with a grounding line very close to the continental platform edge.   Praeg and other authors have been rather cautious in portraying the full extent of the ice, so on the map above I have done it for them,  with the outermost thick red line on the map.  I have also added likely flowlines for the glacier.  I cannot accept the flowlines of some other authors, who have shown ice flowing parallel to the ice edge;  ice always flows perpendicular to the ice edge, except in constrained environments like troughs.   There are no troughs on this seafloor platform, and thus no constraints.

So there we are then.  This is a very big ice lobe, approx 500 km x 300 km in extent.  On its eastern flank, it must have come into contact with the west-facing cliffs of Cornwall and Devon.  It brushed the northern and western coasts of the Isles of Scilly, and I think there is a fair chance that it also extended well to the SE of Scilly towards the tip of Brittany, maybe pushing a little way into the English Channel.  A lot of adjustments may well be needed on this south-eastern flank of the lobe, because the sand ridges described by Scourse, Praeg and others do not seem to align with the proposed directions of ice flow.  Wouldn't it be fun is somebody was to find traces of till on the outer coast to the west of Brest?  I have walked that coast and have seen nothing, but one never knows........  Watch this space..............