Re: Precambrian geology

Jonathan Clarke (
Wed, 24 Mar 1999 07:35:20 +1100

Greetings Allen

Allen Roy wrote:

> > From: Jonathan Clarke <>
> > Precambrian rocks, like younger successions, consist of sedimentary,
> > igneous rocks, and metamorphic rocks. For the most part, these closely
> > resemble younger rocks and thus have formed by similar processes. The
> > main difference is that they lack shelly fossils. If they were formed
> > by completely different processes, why this similarity?
> The line between preflood and flood rocks is hazy and may or may not be at
> the uniformitarian interpretive division of Precambrain. What may appear
> to be a good dividing line in one area on the globe may not be the best
> interpretation at another.

Many YECs appear to use that definition. If you don't, that is fine, but what
sort of criteria do you use that can be used in the field or laboratory to
discriminate between pre, syn, and post flood successions? You haven't given
anything in this paragraph or the following one that a geologist can use in the
real world.

> It is possible that some sedimentary and most granetic type rocks are
> preflood. However, metamorphic rocks are likely considered to have become
> that way because of flood catastrophe tectonic forces. Other igneous
> rockes are likely deposited during the flood. Thus formation before,
> during or after the flood catastrophe are likely to have occured by similar
> processes. The differences may be the rates at which deposition occurred
> during the flood catastrophe.
> > A similar question is posed by supposed by "post flood" rocks, whether
> > you hold that flood sedimentation ended in the Carboniferous, Permian,
> > Cretaceous, Paleogene, or Pliocene. In each case the rocks "post flood"
> > are very similar to older rocks and contain evidence for similar
> > formative processes operating "post flood" as those supposedly operating
> > during the flood (and, for that matter "pre flood" in the Precambrian).
> > Once again, why the similarity?

> Similarity in deposition is a matter of interpretation not necessarily a
> matter of evidence. And, it is possible that all the evidence we see in
> the rocks is of catastrophic deposition and none of slow deposition. But
> that the reason for the evidence being interpreted as slow is because of
> the force fit of uniformitarian interpretation upon the evidence.

You haven't answered my question, instead you have only avoided it.

But to address you comments, what is your point, exactly? Everything is
interpretation, sure. But there is a difference between careful interpretation
and constrained speculation. There is no a priori reason for preferring
"catastrophic" or "uniformitarian" explanations. What matters is the evidence
of the rocks themselves. That is why some rock units are interpreted as the
results of catastrophic processes and others as the results of slow processes.
Geological processes came to be generally seen in the 18th and early 19th
century as the result of slow processes because the evidence demanded it, not
because of forcing some "uniformitarian" framework onto it.

> > Another way to ask these questions is "What unique features exist in
> > Cambrian to Carboniferous?Permian?Paleogene/Pliocene rocks that shows
> > they must have been formed in a global flood"?
> By the same token, what unique features exist in the ....... rocks that
> shows that they must have been formed over vast periods of time? The
> answer is in interpretation according to one's paradigm.

You seem once again to be avoiding answering my question by saying it is all a
matter of interpretation according to paradigm. However I refuse to believe
that rocks are geological ink blots into which we read what we want! Your
strong interpretation of Kuhn's paradigm model is quite unwarranted. There
must be evidence one way of the other, otherwise we might as well all be potato

Do you actually believe that the geological record is such that we can
understand the past? To put it another way, can we determine how rocks are
formed from their own evidence? If you say yes, we can the discuss how
individual rock units can be interpreted. if not, then there is no point. We
could discuss philosophy of science to establish why you believe this, but not
actual evidence and its interpretation.

> Allen

God Bless