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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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