Thank you to Eds for putting this onto the Gardom Standing Stone site which led me to follow the archaeology on the internet. There was a programme by the University of Sheffield from late 1990s exploring the landscape but a lot of the links seem to be missing ....
Another link here gives a history to the wide range of prehistory on Gardom Edge, plus I note a healthy booklist should you want to follow it up.

http://www.thefreelibrary.com/Gardom's+Edge%3a+a+landscape+through+time.-a084341473

As to the shadow casting of stones, it is perfectly feasible but as a theory I knew it could be pulled apart, talk about pigeons and cats.
And whilst on the subject of animals, how did all those bunnies come to inhabit the centre of Newcastle?