it was out about 2 hours into the woods I went to today . It looks like an old wooden foundation I can tell the area is swamp but is dry at the moment ANY THOUGHTS!!? The dimensions are about 10x10 with 4 ft berm around it .
The reason why I believe it's man made is the posts are in a square and are in the middle of a ringed earthen berm with two entry or exit points on each end
....Hard to tell as I haven't explored your state BUT I've seen similar in 7 western States , sometimes with wood, others rock or masonry. Certainly this one has not been maintained ! Try MAGNET FISHING there !