[Coyoteman]

BTW, here's another question (tee hee).

For radiometric dating, recall that one of the crevo threads recently posted an article about a naturally occurring uranium-based chain reaction in Africa...this by definition would screw up isotope ratios in the immediate vicinity of the reaction, as well as any places to which the fission by-products or matrix got washed downstream.

How common an occurrence is that? Is it enough to worry about dating of any fossils or local geographical strata?

This is not my specialty, so my answer will not be as precise nor necessarily as correct as for radiocarbon dating.

The materials they date in Africa are not the fossils themselves but the volcanic layers which are often found above or below the fossil-bearing layers. Volcanic layers are suitable for dating by the various forms of radiometric dating. I believe I remember that the uranium problem does not occur in those volcanic layers, but this is far from my area of specialty.

As an additional source of dating, the fossil-bearing layers usually contain animal and plant fossils as well. Some of the species are unique to certain layers, and once those layers are dated in one location, those relative dates can be applied to other locations.

Hope this helps.

[grey_whiskers]

Yes, it helped. It's just that I only heard of the natural atomic piles last week, so it was new to *me*.

I therefore jumped to the conclusion that nobody else had thought about it either :-)

Thanks for your patient answers...

Cheers!