Alrighty, I'll offer a word in case it helps.
Due to local climate, soil ( or lack of ) and flora ( fire wood availability )..true fire rock middens may be very small to non existant ( blown away ) in the south BUT...
Hearthrocks are a good marker ....just a different type of cooking system...Limestone gets a very prominent red
coloration when exposed to high heat.
If you can spot these type of rock 'camps' then look closer for flint flakes.
I found the page on cooking stones . http://www.texasbeyondhistory.net/st-plains/nature/images/cookstone%20.html. It is very helpful thanks . The best luck i have had is following creeks and looking into the banks. I found a cash of guadeloupe scrapers that way. they were about 15ft. down in a 30ft. bank .