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Tuesday, 18 October 2011

Rhosyfelin geology

The BGS has made available for public use, via its fantastic web site, a full geological map of the UK at a 1:50,000 scale.  It's superimposed on the Google imagery, so you can get to wherever you want and find out what the geology is......  you can even click on a site and get a description of the rock type.

http://maps.bgs.ac.uk/geologyviewer_google/googleviewer.html


 

Above is an extract from the map showing the Rhosyfelin - Pont Saeson area.  The site of the famous "bluestone quarry" is slap in the centre of the photo, where the minor road has a distinct Z-bend.  The pinky-purple colour shows the extent of Fishguard Volcanics, which also sweep from here towards the NW, with a number of outcrops on the northern flanks of Carningli and Dinas Mountain.

The green colours represent sedimentary rocks -- for the most part Ordovician shales in this area.

The Fishguard Volcanics in this area are rhyolite lavas and ashes with considerable internal variation, which leads Rob Ixer and Richard Bevins to think they can tie down some of the Stonehenge fragments to specific locations at Craig Rhosyfelin with great accuracy.  We have already had some discussions as to whether you can tie down particular fragments to a location with an accuracy of +/- 2m!! 

We await with interest their paper on this matter....

5 comments:

Geo Cur said...

It's been available for quite a few weeks, yet another web dream come true .

BRIAN JOHN said...

We get there in the end! I just had a notification from QRA about it. But it is certainly very useful indeed........

David St. F. Evans said...

Brian,
BGS Lexicon also shows that Flat Holme and Steep Holme Islands consist of the same bedrock as the Weston-super-Mare area.
Damn it ---- that's ruined another promising theory of mine, and I was going to include the Isle of Man.

David St. F.

BRIAN JOHN said...

You could always try Caldey, Ramsey, Skomer and Skokholm.....

David St. F. said...

Da iawn Brian, seren aur i chi.

I went to Caldey Island,
On the last day of July.
I left my pants and vest down there
I hope they're bloody dry!



What majestic poetry.