|It's quite dull to point this out, as their flutiness is perhaps why they're so appealing today, but it may well be that these lovely fluted stones were not in their lovely fluted state when they were erected. Here are some gleanings from an article about the circle's excavation in 2008.
The stone is thought to come from an outcrop of Fell Sandstone at NT935437, east of here. The stones must have been dressed there, or at least away from the circle, as when the site was excavated, no tell-tale bits were found.
The grooves are called 'rillenkarren' and are caused when wind and water erodes the stone. But the direction the grooves run in, parallel to the bedding plane, suggests they developed after the stones were put up. Because if they'd been chosen for their rillishness in situ, the grooves would probably run the other way compared to the bedding plane.
The waists of the stones are said to be as a result of physical erosion too (maybe animals plus weathering), although the general shape of narrow bottomed / wide topped was probably part of the deliberate shaping.
Another point is that if Beckensall's cup marks are man-made, they must have been put on there post-dressing of the stones, and therefore be unusually dateable.
Roughly a fifth of the stones' heights are hidden beneath the ground, which because it doesn't seem like very much, led the authors of the article to speculate whether the 'waists' of the stones were actually caused by erosion at a former ground level.
And a last point, that although the stones mostly have two flatter faces and two narrow sides, the builders of the circle didn't seem to orientate them in a consistent way (for example, in/out of the circle, or towards a point of the compass). But it may be they 'relied upon some lost factor of the landscape we cannot know'. Indeed.
Much more besides in: 'The Excavation of Duddo Stone Circle, Northumberland' by B Edwards, R Miket, and R Bishop (2011): Proceedings of the Prehistoric Society 77, pp321-353.
Posted by Rhiannon
1st January 2014ce
Edited 1st January 2014ce