Sherrod Loop structure mystery

I stumbled upon this pit on the upper end of Sherrod Loop. Scattered about were four large flat topped stones resembling in size and shape those used to support water towers. I corresponded with Tom Klinger and he is as puzzled as I am on what might have been here. Anyone have any ideas, or better yet - actual knowledge?

The upper photo shows one of the large stones adjacent to the pit. The lower photo shows three of the stones trailing into the distance starting near the corner of the pit with the last one among the distant trees. I saw no other large stones but did no digging, so others could be covered up for all I know.