Stonehenge and the Ice Age: Till characteristics and nomenclature

If you have ever wondered about diamictons and tills, and all things related to glacial deposition, you can always read the text by David Sugden and myself (if you can get a copy!) or --if you are short of time -- just take a look at this. It's a fascinating little web site, with great illustrations:

https://web.viu.ca/earle/geol305/Glacial%20Tills.pdf

I have always subscribed to the view that if something looks like a till, it probably is a till -- and that it is probably NOT an ancient deposit redistributed or rearranged under periglacial conditions over many thousands of years. I am a man who likes his Occam's Razor; the most parsimonious explanation of things is always what I look for, unless I am dragged away from it by something unexpected or spectacular. The spat about the Caldey Island "diamicton" comes to mind..........

Since I have worked in so many glacier snout environments characterised by complete chaos, I am even rather sceptical about giving different till types names -- but I suppose there are always those who like to classify things. I am equally cautious about the significance of fabric analyses, given that what happened here may not really have anything to do with what happened there, or a bit above, or a bit below. In a chaotic ice wastage environment, anything can happen, and usually does. Where a glacier is melting away, in a "dead ice environment", the environment is far from dead -- it becomes highly dynamic and mobile, with slumps and slides all over the place and a vast amount of sediment redistribution. In these environments, field workers sometimes lose their lives when fragile ice bridges collapse without warning and where debris is suddenly mobilised on a steep melting ice slope. If you happen to be standing in the wrong place at the wrong time time, too bad........

But some principles do apply. We do have lodgement tills in Pembrokeshire, in the exposures of clay-rich Irish Sea tills at Abermawr, Mwnt, Whitesands, Druidston and elsewhere -- and in those exposures we can see deformation features and much else besides, if we subject the till to "micro-fabric analyses."

Elsewhere, and above the lodgement tills, we find something much more akin to chaos, in what was referred to in the old days as "rubble drift" -- patches of flow till, intermittent and discontinuous beds of sands and gravels, some blocks of incorporated frost-shattered slope breccia, and both subglacial and supraglacial meltout tills. The tills that I have been describing on the Pembrokeshire coast, from multiple locations, have been emplaced in these rather chaotic environments at a time of catastrophic ice wastage -- I doubt that any of them have accumulated by lodgement on a glacier bed.