The above book devotes less than 2 pages to this topic, but there are
surely many whole books about it.
>>>>> On Thu, 11 Jan 1996 11:17:46 -0600, rta@TIGGER.STCLOUD.MSUS.EDU
>>>>> (Russell T. Arndts) said:
>> Apparently, I am not making my point. My guess is that what substitutes
>> for rules is merely that an index fossil must fit the paradigm. For
>> example, one characteristic is that a useful index fossil must have seemed
>> to have lived for a short period of time.
Yes, but so what? Just because a species is not an index fossil doesn't
mean that it breaks the paradigm (you mean evolution?).
>> If it is found with fossil species [including other index fossils] thought
>> to have existed for over 150 million years, it would not be used as an
>> index fossil. This sounds like cyclic to me reasoning to me.
It doesn't matter if it's found with other fossils that have a much
greater time range; of course that will happen. What does matter is
it's relationship with other index fossils. If another index fossil is
found in the same strata that was thought to be from a totally different
time period, something would have to give. That apparently doesn't
happen.
>> There are no independant proofs that a particular index fossil lived for
>> merely 10 million years.
>> Thus any rules to prove that the fossil species existed for only 10 million
>> years would be obviously weak.
I don't understand what "rules" you mean. Observation has shown that
most species are limited to a small interval of the geologic column.
Whether that interval lasted 1 or 10 million years can only be shown by
other methods.
The stratigraphic column provides relative dates. We can say, for
example, that a particular assemblage fits into the late Jurassic.
Geologists two centuries ago were able to discern many different faunas,
which always appeared in the same order. This does not rely on or
assume evolution; the broad details were in place well before Darwin
published, subsequent work has merely refined the details.
Once we have a relative column, you can then test radiometric dating
against it. For example, you can date different sites thought to have
the same age for stratigraphic reasons. Or you can date different
layers at the same place, and see if deeper layers are radiometrically
older. You can do this even if radiometric tests are only accurate 50%
of the time (an underestimate); you just do plenty of tests and see
where the results cluster.
-- 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