> Quite simply, could the "tail" on some cup and rings be an event marker – the position of a shadow cast by a wooden
> gnomon inserted into the central hole at a particular time of day and time of year?

if that was the case, I don't think the cups would have "smoothed off" edges, they'd have very straight vertical edges and would be deeper, to hold up the stake in the centre

also, what about sites with multiple cup-marks around a central large cup-mark? I know a theory can't be applied to ALL rock art though

Cheers
Andy