How much do we know about Stonehenge? Less than we think. And what has Stonehenge got to do with the Ice Age? More than we might think. This blog is mostly devoted to the problems of where the Stonehenge bluestones came from, and how they got from their source areas to the monument. Now and then I will muse on related Stonehenge topics which have an Ice Age dimension...
THE BOOK
Some of the ideas discussed in this blog are published in my new book called "The Stonehenge Bluestones" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
To order, click HERE
Some of the ideas discussed in this blog are published in my new book called "The Stonehenge Bluestones" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
To order, click HERE
Wednesday 8 January 2014
The Joy of Stratigraphy
When I was studying geology, the bit that I really enjoyed was stratigraphy, since it was all perfectly logical and chimed in well with those old fellows Hutton, Darwin etc etc. The storms at Abermawr have freshened up the stratigraphic succession in the cliff face, and I was able to get some classic photos yesterday.........
ABERMAWR NORTH.
The top photo shows -- in order of deposition: at the base, rough broken "rubble drift" interpreted as an accumulation of early and Middle Devensian frost-shattered debris in slope deposits, derived from the old cliff line which is still hidden. There are some big angular blocks in it from cliff falls etc. Above that is the Irish Sea till, a very fine-grained lodgement till accumulated as the Irish Sea Glacier flowed across the area in the late Devensian -- around 20,000 years ago. The base of the Irish Sea till is coloured red because oxidation processes have been at work -- from water percolating UPWARDS from the permeable deposits beneath. There is another stained layer on top of the till, but that is mixed up with ice wastage products (flow-tills) and meltwater deposits.
The photo below shows the Lower Devensian slope deposit of angular bedrock rubble, incorporating (in the centre of the photo) a beautiful reddish-coloured erratic which must have been derived from old (Anglian) glacial deposits in the vicinity. We see similar erratics incorporated in Early Devensian periglacial accumulations at Whitesands and elsewhere.
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