Near Tadmuck Swamp Westford

I was was exploring just south of Rt 495 near where a brook begins leading into Tadmuck swamp and -hey- there is a rock pile:
And I looked around and saw maybe five or so other low ground piles. Here is another before I cleaned it and after. Before:
After:There were maybe five or so piles like this - low, on the ground, non-descript. They are on the west edge of a little wetland. A few feet further north were some larger tumbled piles with more ambiguous structure:
This last one is looking southeast over the wetland.

Then slightly further back from the water near the larger structures were some "small piles with big rocks". Here is one:
Note the large vertical flake leaning up against the larger rock.

An then this next one which looked more like a traditional pile with a pointer rock (picture does not do it justice). So this is an interesting and different little site with a bit of structure: a cluster of low non-descript piles near the wetland's edge. Larger tumbled down 'piles' and some small piles with big rocks. All about 50 yards from the nearest house and with the sound of the highway not too distant. I thought perhaps the piles were not all part of the same impulse, the low ground ones being built at a place already sanctified by the larger piles. But who knows? It is a unique small site.