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Monday, 6 December 2010

Bluestone fragments "not from South Wales"

I've reported on this before, but it now appears that the Sheffiled Univ team led by MPP has accepted that the bluestone fragments near the Cursus (identified by Rob Ixer and Vin Davies) are not from South Wales.....

Bluestone chips between Fargo Plantation and the Cursus
In 1947 J.F.S. Stone found chips of South Welsh ‘bluestone’ (rhyolite and metamorphic
sandstone but not Preseli dolerite) close to the southern edge of the Cursus, just east of
Fargo Plantation. In 2006 a concentration of igneous rocks was localised by test-pitting
to within a small flint scatter immediately outside the Cursus ditch but initial petrological
identification indicates that these new finds are not from South Wales.

By Mike Parker Pearson, Josh Pollard, Colin Richards, Julian Thomas, Chris Tilley and
Kate Welham with Mike Allen, Wayne Bennett, David Field, Charly French, Neil
Linford, Andy Payne, Dave Robinson and Clive Ruggles,
Sheffield University 2010


Robert Langdon said...

That's very interesting Brian!!

Is any of the Stonehenge circle 'remains' - Rhyolite, or has no-one looked that closely??

So where are they from??- one would imagine that if the ice sheet 'drop off' theory is correct it was two different periglacials? or could it be two different quarries!

Does the fact that theses are 'chips' show that these may have been 'worked' and are not whole?

I remember seeing periglacial marks in an excavation in The Avenue in a NE direction - which indicated the Anglian Ice sheet came from that direction - so is there a bluestone crop in that direction?

If your theory is correct then the Devensian must have come in from the NW - ie wales - but the isostatic centre is Scotland - which would have pushed them to Cornwall??


BRIAN JOHN said...

This isn't really news -- the info has been around for a while. There's lots of rhyolite; have a look at my list here from 9th Nov:
No quarries, but lots of different sources -- as you would expect with a collection of glacial erratics.

Periglacial marks? If they are periglacial, they have nothing to do with glacier ice.

The form of the British ice sheet is now pretty well known for the Devensian -- see my post dated 6 December 2009. Jim Scourse's work suggests that the Devensaian ice reached much further south -- as far as the Scilly Isles. He may well be right..... but I don't like the naff shape of his glacier, which seems to me to defy glaciological principles..

Anonymous said...

Most of the test pit material was 19th 20th cent.
But there are a few South Wales echte bluestones. 5/6?
The detailed results are being written up.
GCU In two minds.
Rhyolite/shymolite 100s of bits high hundreds.

BRIAN JOHN said...

Look forward to seeing it in print. Rhyolite / shymolite? Is that the Brynberian stuff, or something else again?

Anonymous said...

Less Brynberian more Beth din.
GCU In two minds.