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Sunday 21 October 2018

Isles of Scilly -- new paper now published

This new peer-reviewed paper is now published, unfortunately with a serious mistake in it!  Figure 11, the crucial map showing the revised glacial limit, has had the bottom inadvertently chopped off it while it was being resized in the editorial process.  The map above is the correct one!


Brian John, 2018. EVIDENCE FOR EXTENSIVE ICE COVER ON THE ISLES OF SCILLY. Quaternary Newsletter Vol. 146, October 2018, pp 3-27.


Previous studies of the Quaternary sediments on the Isles of Scilly have suggested that the ice of the Late Devensian Irish Sea Glacier impinged upon the north coasts of the islands but that it did not extend much further south. There is also disagreement in the literature about whether any earlier glacial episode affected the islands, although a number of researchers have noted the presence of erratic cobbles in pre-Devensian raised beaches. The new field research, based in part upon examinations of exposures that might not have been available to earlier researchers, shows that erratic cobbles and pebbles are common in raised beaches and in early and middle Devensian brecciated slope deposits around all of the island coasts. The most parsimonious explanation is that they have come from disaggregated glacial deposits dating from at least one glacial episode (Anglian?) during which the islands were completely inundated by ice. Furthermore, coherent diamictons similar to those found on the north coasts of the islands, and in western and southern Pembrokeshire, are also found on the coasts of St Mary’s and St Agnes islands, indicating that the Devensian ice cover was more extensive than previously suggested. It appears that ice from the Celtic Sea pressed into the archipelago from the north-west and west, with lobes fingering into sounds and straits which are currently below sea-level. The diamictons, rich in striated and faceted erratic cobbles and pebbles from many different lithologies, do not appear to be primary tills; they are suggestive of an ice-margin environment in which disaggregation and redistribution of glacial and glaciofluvial sediments has occurred. The new interpretation of Late Glacial Maximum ice extent is consistent with other recent work which places the limit of the Irish Sea / Celtic Sea ice lobe around 250 km south-west of the Isles of Scilly, near the Celtic Sea shelf edge.


You should be able to access the article here:

It can also be downloaded as a PDF.

The article was based on old-fashioned field observations during a week-long visit to the islands in 2016.  What I now hope is that some other researchers who have access to the full research facilities of various university departments will re-visit at least some of my sites and will confirm or dispute my suggestions and conclusions............

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