Re: Precambrian geology (1)

Jonathan Clarke (
Sat, 27 Mar 1999 17:16:52 +1100

Greetings Allen

Once again there is a longish post which I will respond to in two parts. In
this one I will discuss your comments on stratigraphy and flood deposits. In
the next I will discuss history of geology.

Allen Roy wrote:

> > From: Jonathan Clarke <>
> > Allen Roy wrote:
> > > 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.
> Flood models are still in development and just exactly where the begining
> and ending lines would be is still debated. In general, for the beginning,
> rocks that have fossils are usually considered flood deposition, however,
> some exceptions may be noted. The Archaeic or Precambrian are thought to
> be post-creation week and pre-flood deposition.
> Another point would be something like the great unconformity and the
> interpreted high energy Tapeats sandstone deposition at Grand Canyon. The
> idea being that the flood catastrophe began with high energy events (like
> asteroid impacts).
> The ending is even more debated than the beginning. I tend to think that
> most Tertiary deposition is post-flood. Anything that is associated with
> tectonic movement would be flood deposition.
> That is about as specific as I can get at this point.

"Archaeic" - do you mean "Archaean" - and "Precambrian" have precise
definitions. Do you agree with these definitions? "Precambrian" is a
biostratigraphic term which now has radiometric ages assigned to. "Archaean"
is based on radiometric ages. Are you saying you believe that biostratigraphy
works and that radiometric dates are consistent? if not, why use these terms?

The same with terms like "Tertiary". Rocks are called this on the basis of
either biostratigraphy or radiometric ages. If you use terms like this you are
implying you agree that they are internally consistent. If you don't believe
this - why use them?

I hope this is not too pointed but: "That is about as specific as I can get at
this point." Why is that? constraints of time and space? Because you do not
know? or because you don't want to say?

God Bless