Unlimited mind,
There is a show on tonite Wed. 7/15/09 on PBS called Time Team America and they are investigating an ancient site in South Carolina that is said to be the oldest know North America site. It may be connected to your site in some way. I am taping the show and will let you know what they found if the show is not on in your area. I am so excited about your find and can't wait for more info. Here is the web page for the show.
http://www.pbs.org/opb/timeteam/
I think you can watch the show online if you can't see it tonight.