>> Jim foley says, "The above book devotes less than 2 pages to this topic,
>> but there are surely many whole books about it."
>> He is absolutely right. However, the index fossils are widely used and, to
>> the best of my knowledge, not one book is written about them.
Maybe not one whole book (I wouldn't know), but surely any
biostratigraphy text goes into considerable detail on them.
>> They seem to be used and no rules are given as to how to determine which
>> fossils are index fossils. Except if they appear to be short lived, then
>> they are.
No rules? The book I listed gave a number of criteria for useful index
fossils. Being short-lived (geologically speaking) was only one of
them.
>> If we do not take them seriously as "proof," then no harm done, but
>> they are crucial.
Proof of what??? It's merely an empirical observation that some fossils
are more useful for correlation than others.
(We need Glenn back. He must know a lot more about this than I do)
-- Jim Foley Symbios Logic, Fort Collins, COJim.Foley@symbios.com (303) 223-5100 x9765 I've got a plan so cunning you could put a tail on it and call it a weasel. -- Edmund Blackadder