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...
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Monday, 3 May 2010
More about the moraine
Here it is -- a very broad area at grid ref SN046372 with a litter of sub-angular and rounded boulders of all sizes -- including many of fine-grained local dolerite but many more that are extremely coarse-grained. I don't think I have ever seen an outcrop of such rock anywhere in this area. I have taken samples.
This is an erratic of whitish rhyolite (probably from one of the outcrops to the N or NW) surrounded by much coarser dolerite boulders.
And this is the area with the hawthorn tree which is NOT moraine -- look at the different texture, colour and appearance of the boulders and rock slabs.
I think this moraine is plastered over a wide area in a broad depression above and below the 250m contour. It extends all the way down to Pont Ceunant, where the till is exposed in a river cutting. Higher up the slope from the area where the pics were taken, there is an area of hummocky terrain -- the vegetation is so thick that it is difficult to determine whether these hummocks are original depositional features, or created as a result of dissection and stream action.
The boulder surfaces on the moraine are very heavily weathered. That's a bit surprising -- if the moraine was placed here in the Devensian, around 20,000 years ago, I'm not sure I would expect quite such heavy weathering........
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