?

I have hundreds of acres in NYstate. I have lots of rock piles on the side of a rolling hill. Most of the these are about 300 square feet, cleary human in origion, and most rocks are larger then a human could carry comfortably. I also have half a dozen larger piles on top of the hill or more. I assumed these were framer stacked, but my metal detector indicates this likely predates farmers (Absolutly no fences found, and no metal scrap? etc). The land is too asidic for grasses, and blueberry and scrub fluffy ground cover blankets the hill. Then I noticed all the stacks on the side of the hill are where the ferns grow, and where water leaks out of the mountain, even during the dry days of july. For the record, even the old logging ruts have horse-shoe nails, etc, that get lost along the trail, so, anyplace where modern man gets involved, leaves metal scrap. On the next mountain, my neighbor found a slate indian arrowhead, which is super clean (not suprising). ?? Then I was thinking the ascidic nature of the hill has kept modern man off of this property likely ever since the indians discovered columbus. It's just unusable for anything except hunting, logging, etc. Although the yotes and birds love it and call it home. Also note, all rockpiles from field clearning has lots of metal around the rock piles, and It's not the place for metal detecting (too much metal junk). Any ideas?