Do you think it's kaolin clay? I have some in my tower garden, it's also often called "builders clay". A friend here had an entire front yard of it, not solid like red clay at all....lots of organic amendments has made it pretty nice stuff, however I do not think it's acidic, I think it is chalky.

It wasn't there last year, so I doubt it's clay. Maybe it's time to spend some time on the UGA extension website.