Black-white pairs

Here are two rock piles from central Carlisle, along with interpretations of their design. Piles with a black and white pair seem common in Carlisle but I have not seen many outside of this town. Here is a third from a different site in Carlisle, the Benfield A land. [Thanks Tim Fohl for the photo.]
For some reason I was thinking of black-white pairs in rock piles; and thought I would switch topics and show some pictures of them. Here is one from Falmouth, MA. It may not be the same thing.