Questions about Xenoliths and dating

I believe there is a topic somewhere, that is fairly specific to the KBS tuff. Unfortunately, I'm currently unable to track it down.In short, the KBS tuff was a water laid tuff. A rather hybrid volcanic/sedimentary rock. As such, it contained significant contamination from older materials. These contaminants might be considered xenoliths, but I think that would be extending the definition outside of the usual definition.The contaminents were determined and painstakingly removed from the sample, and a quality dating was the result.Note: I post this not having read the cited materials. I suspect such is covered in them. I have a Talk Origins reference filed away somewhere, if anyone wishes to demand such. Or you could just go to Talk Origins (or Google) and do a search for "KBS tuff"MooseAdded by edit: D'oh, you supplied a good Talk Origins reference. It in turn supplied the reference I was thinking of, Radiometric Dating and the Geological Time Scale.This message has been edited by minnemooseus, 12-01-2005 02:55 PM