Hi Ryaner,

It certainly does look loke a natural marking, very well spotted!

Any idea what the stuff is in the bottom right hand corner of the photo Tom linked to? Am I seeing things? It looks like paintbrushes and some sort of pigment to me, green in a whole pot with brush or finger marks in it and blue in a broken one. Hope you managed to disturb whoever was about to use it.

Rune

I think these things - I call them 'seams and shoulders' have been chipped out. On a tough sandstone they don't weather much. The orthodox view is that they are natural and caused by free rocks scratching against each other in the glacial drift. Look in the 'terminus' of the groove for a small carved feature that looks like nostrils.