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Wednesday 13 November 2013

Another mighty capstone

Thanks to Phil Morgan for this message and photos:

I've attached two recent photos of the Cotswold-Severn Class Neolithic burial chamber known as Tinkinswood, located 6 miles west-south-west of Cardiff Civic Centre, just off Duffryn Lane which runs south from the village of St. Nicholas on the main A48, Cardiff to Bridgend road, (ST 09219 73313, or 51.451506, -3.307679).
Cadw provide a good write up if you Google 'Tinkinswood Burial Chamber'.
Some sources say the chamber is made of mudstone, however, to my eye it looks to be a limestone, which, if correct, would require transport for some considerable distance for the closest source of limestone is at the village of St. Nicholas, about 0.7 miles due north of Tinkinswood.
Either way, measurements show that the capstone has dimensions of 6.1m long, with a width increasing from 2.8m to 4.5m, a depth of 0.95m, and a volume of about 21 cubic metres. This volume would give the capstone a mass of 43 to 57 tonnes.

As Phil says, the prevailaing view is that the capstone is made of local mudstone -- that's what it looks like to me, from Phil's high-definition photo.  It's doubful that it was transported anywhere -- it seems to have been used where it was found.  Maybe it wasn't even raised -- which means that the tomb builders simply excavated beneath it, inserting smaller stones as props every now and then as they dug away beneath it and took the spoil away via the area which is now referred to as the walled forecourt.

I've never visited this one -- but it does look rather splendid.


chris johnson said...

Very good to see photos of new sites.

Recently we discussed excarnation. This is a classic case of capstone close to the ground

geocur said...

If the capstone had been quarried where it was to be erected we might expect to find evidence of the quarry pit ,such as has been suggested but not confirmed at Pentre Ifan , but there has been no mention of any pit directly below the capstone despite the extensive Ward excavation . Further there is a suggestion of pre-cairn stone structure below the capstone plus a more likely site for the mudstones at the nearby “quarry “ .

Phil M said...

A question for the audience:

An accurate measurement of the slope angle of the capstone at Tinkinswood shows it to be 7 degrees off horizontal. A mile down the road from Tinkinswood is a second, Cotswold-Severn Class chamber, at St. Lythans, which also has a slope angle of 7 degrees.
Recently Brian posted a painting of the Pentre Ifan burial chamber which showed a slope angle of about 7 degrees, (nice painting).

Any views on whether this is coincidental or intentional?

geocur said...

Pentre Ifan and Tinkinswood are more than 70 miles apart and two different types of monument . Much closer to Tinkinswood is Maesyfelin (less than mile ) where the angle of the capstone looks almost level from some angles . Closer to Pentre Ifan spatially and typologically is Carreg Coetan (3 miles ) which looks to be at an even jauntier angle than PI ,Trellyffaint is 4 miles and is almost horizontal ,Llech y Dribedd (4 miles ) is difficult as the capstone is level at seen on the side stones but the top looks like it is greater than 7 degrees .
I’m sure the angles of the capstones are intentional within the physical and architectural constraints but they do vary from area to area and within areas .