The origins of Rocky Brook Stirling MA

On Sunday, before I got stopped by the police, I was driving slowly eastward on Upper North Row in Stirling and, coming into a dip in the road (around A), I saw a rock pile off to my right. So I parked and hopped out to take a quick picture.
Once there I thought I would go just a little further into the white pine saplings and surprise! There is a genuine "cairn" - big game.
A little further downstream was a humbler example:
And those were the only two like that I saw. I did not explore in all directions though, since there were houses.

Also along the stream, some of the piles were effigy-like.
And here also was the example of the rock-on-rock with black crystals, (near B):

Finally, at C, on the hill shoulder, there were a few wedged rocks and some low piles that might suggest lines of site.
I don't know what to conclude about the wide variety of rock pile types we see here. The brook is certainly getting a send-off.

Because I was accosted by the police on returning to my car, I did not get a chance to explore all around the little swamp north of the road or on the hill above the word "North". I should go back.