Along the stone fence - a small rock pile site with piles on boulders and a few non-descript ground piles

This is another place on Nagog Hill, Acton. I went in one conservation land entrance and then stayed to the left as much as I could behind the fields and houses. I expected to find something but, as usual when you first see a rock pile site, you don't quite believe it:
Was this a bit of the stone wall spilling over onto an adjacent boulder? To the far right of the picture is another rock. On closer inspection this one is too far from the wall.
I figured this to be a ceremonial pile. And there was yet another in the background. As I went along next to the stone wall, the first time I passed, I caught maybe one more rock pile on the ground. Something like this:
And like this:
I detect lighter colored single rocks in these low ground piles. I think of this as "grave" feature, although I never really know.

This place, along the stone wall is a strip of land maybe 20 yards wide between the wall and a wetland it faces to the southeast. When I explored more carefully there were possibly ten piles in there. There are three or perhaps four visible in this picture:
I am not sure of the function of this site. With grave-like piles and piles supported up on boulders.