Carbon dating is good up to 50kya, i.e. anything an archeologist is likely to be involved with. There's a separate issue dating things around 2500 BP called the

Carbon dating is good up to 50kya, i.e. anything an archeologist is likely to be involved with. There's a separate issue dating things around 2500 BP called the Hallstatt plateau, but the slave trade this paper is looking at happened more recently than either of these (400 BP max). The problem is that carbon dating doesn't give you very good localization because it's generated by atmospheric sources. Strontium is almost exclusively of geological origin and the ratio varies a lot, so you can build a good map with it.