Re: Rb/Sr Dating

GRMorton@aol.com
Sat, 23 Sep 1995 16:45:06 -0400

Jim Foley wrote:
>>I think Glenn got it slightly wrong. Using multiple rocks is fine, *if*
you have good reason to believe that they were formed at the same time. A
geologist should normally be able to determine if that is the case. Austin is
apparently using rocks that are "demonstrably not cogenetic" (the words of
Brent Dalrymple, a radio-dating expert). That violates the assumptions of
isochron dating, and means that any resulting date is meaningless.<<

And David Tyler took me to task for the same point. My position came
ultimately from Dalrymple so if Dalrymple is wrong, I am wrong. And I want
to correct what I said about "different rocks" I should have used to the
term "cogenetic".

When someone like Dalrymple says that the method used is flawed, I have to
listen because he is an expert in the field.

glenn