THE BOOK
Some of the ideas discussed in this blog are published in my book called "The Bluestone Enigma" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
To order, click
HERE

Thursday, 3 July 2014

How did Palaeozoic building stones get to Glastonbury?


Glastonbury Tribunal -- reputedly built in the 1400's

I came across this interesting snippet in Hugh Prudden's excellent notes on the geology of Somerset -- suggesting that some of the building stone used in the older buildings of Glastonbury has come from Palaeozoic outcrops -- maybe from the Quantocks, Brendon Hills and Exmoor.  These of course lie to the west of Glastonbury, and if the Irish Sea Glacier ever did reach Glastonbury (as I have speculated more than once), it might -- just might -- have picked up Palaeozoic erratics on the way through.  I don't know whether any more accurate provenancing has ever been done -- can anybody enlighten us?

18.  GLASTONBURY ST 5138 
Junction Bed-Yeovil Sands-Holocene formations-landforms

Erosion has separated this outlier of Yeovil Sands from the main escarpment which can be seen some 26 km to the east.  The intervening vale is Lower Lias clays.  To the north are the Mendip Hills and, to the west, the Rhaetic Beds and Blue Lias of the Polden Hills.  On a clear day the Palaeozoic massifs of the Quantocks, Brendon Hills and Exmoor can be seen.  Fluvial and marine deposits of sand, clay, gravel and peat underlie the Somerset Moors and Levels which extend to the Bristol Channel.  This is, perhaps, the best place for a comprehensive view of Somerset. The Junction Bed limestone, which includes the marlstone Rock Bed, forms a marked bench.  The main street in Glastonbury has a rich variety of Palaeozoic and Jurassic building stones.  The Abbey ruins have Doulting Stone facings with a core of Blue Lias.and Marlstone.  



The Quantocks

 The Brendon Hills

Exmoor


7 comments:

Myris of Alexandria said...

Ah without my geological map I think the Palaeozoic rocks are Upper Palaeozoic namely Carboniferous and Devonian, whereas apart from the elephant in the circle all the Palaeozoic rocks associated with Stonehenge are Lower Palaeozoic namely Ordovician the Lower Palaeozoic sandstone may be Cambrian.
So not a lot of help.
The Mendips have tiny Devonian outcrops it is almost totally Carb. and Permo-Trias.
M

Constantinos Ragazas said...

Brian,

What is that circular feature in the Exmoor photo? Natural or man-made?

Kostas

BRIAN JOHN said...

Man-made, Kostas. Lots of Iron Age and earlier features on Exmoor...

BRIAN JOHN said...

Kostas:

Furzebury Brake -- presumed Iron Age:

http://www.exmoorher.co.uk/hbsmr-web/record.aspx?UID=MSO7577-Furzebury-Brake-East-Myne-Camp-Selworthy

Constantinos Ragazas said...

Brian,

Thanks for the link. From the link and photos, the site includes an inner bank with an outer ditch .

"There is no sign of an outer enclosure, and the site commands no special view. Thus it is 'reasonably certain that the site was chosen for its defensive advantage by natives, not for lookout by a Roman Commander'. "

But like Stonehenge, there is no 'defensive advantage' for an inner bank with an outer ditch.

Kostas

BRIAN JOHN said...

Of course there is. There would be no point at all in building an outer bank and an inner ditch, would there?

Constantinos Ragazas said...

Brian,

There would be no point at all in building any bank or ditch outer or inner, imho!

Kostas