A wet spot and small rock pile site in Fitchburg, MA

I went to explore one of the pieces of Fitchburg State Forest, east of Pearl Hill. There was no major find but I did see several small sites at different wet spots on top of the hill. In each case there seemed to be something going on with uprights plates of rust brown rock. In some cases there was also something going on with quartz or white feldspar.

Here are some pictures from the first of these small sites. There was an outcrop next to a wet spot. At the top of the outcrop I saw this.From there I could see down into the wet spot, which was loosely filled with mountain laurel, and I could see what looked like an old pile in there:
Note the vertical piece of brown rock.

And as I looked around I saw a few others:
Here is a view of the spot.
It is my impression that the flat plat of rock in the first photo was lined up more or less with the direction, to the right in the picture, towards which the water is flowing - which would be something like west or southwest.
I walked right through the state forest from one side to the other before I came to this place. It was in back of a farm, and there were what looked like some pretty "agrarian" structures very close by. Still I cannot give up on the idea that this is a ceremonial site. With the cluster of piles, within the laurel, and with the rock piles built from so few rocks, they seem to coexist with the farm.