On Wed, 20 Nov 1996, Glenn Morton wrote:
> Now, the Diecke bentonite is a bentonite which is wide spread
through out the eastern US., from Michigan, to Alabama to New York.
It is the same bentonite as the Big Bentonite that covers large parts
of Europe. The Deicke bentonite is the largest volcanic eruption
ever. Let me cite Huff et al, ...
>
> This event allows one to know that the beds in Europe were the
identical time in America. The only reason anyone reading this is
just now learning of it is because Creationists don't know enough
geology to even be aware of things like this. Thus,they don't talk
about them.
I used to use this bentonite as evidence for correlation. However, a
paper in _Geology_ (I think it was last year) provided geochemical
evidence against the US / Europe link. I can't supply a reference
now, but I'll look it up.
GM:
> >> Third, there is occassionally depositional patterns which can be
correlated across these basins. The tertiary has more clastic
deposition than almost any other period... The Pennsylvanian
strata all over the world is very cyclic in nature. ... Finally,
chemicals can be correlated. The majority of the Coal is found
in carboniferous strata. Banded iron formations are only found
at the bottom of the pile in the pre-cambrian.The iridium anomaly
at the top of the Cretaceous appears to be a world-wide
event. Ratios of sulfur isotopes can be correlated around the world
> >>
> >> These types of correlations from basin to basin help tell what
rock is to be correlated with what rock.
DT:
> >These are all reasonable approaches to correlation, although a
number of these generalised correlations only really emerge one the
rocks are reexamined in the light of the Geological Column
concept.
GM:
> No. The are the order that the rocks are found in undisturbed
basins. The data is mere observation of order and lithology.
We observe rock units - no problem. Do we observe "Tertiary" rocks?
No - we observe rocks which we interpret as Tertiary in the sequence.
Once we have done our correlations, patterns emerge. This is the
point I am making here. Or take the Iridium anomaly - there are
Iridium spikes at horizons other than the K/T boundary, but we would
not be wise to insist on the geochemical correlation and say they are
all at the same correlatable horizon. The K/T anomaly is a
conclusion which emerges after the horizon has been identified in the
sequence.
DT:
> >I would suggest that more is needed to establish time-equivalence.
> >Here are some possibilities:
> >(a) Orogenies. Major deformation events in earth history have
> >occured: lower-lying rocks exhibit folding, etc., and are overlain
by relatively undeformed strata. This establishes a time sequence
and correlation proceeds by linking together rocks in the same
orogenic belt.
GM:
> There are hundreds of bentonites throughout the geological column.
These can be used to correlate separate basins.
Yes, this is a valid tool for time correlation. For example, certain
bentonites in England and Germany have the same chemistry, and permit
time correlation across large areas.
DT: ...
> >(c) Large-scale unconformities. Whilst unconformities are
pervasive in the rock record, there are some which stand out. The
Cambrian unconformity marks the base of the rock record which carries
hard-bodied fossils.
GM:
> I am not an expert in that part of the column, but my understanding
is that this last statement is no longer true. I am going to give you
a non-scientific reference, since it has been a while since I have
studied that area. see "When Life Exploded," TIME Dec 4, 1995, p.
773-774.
>
> I just found a scientific source, see John P. Grotzinger, Samuel A.
Bowring, Beaverly Z. Saylor and Alan J. Kaufman, "Biostratigraphic
and Geochronologic Constraints on Early Animal Evolution," Science
270, Oct. 27, 1995, p. 603-604 (598-604).
Thanks. I'll follow this up.
Best wishes,
*** From David J. Tyler, CDT Department, Hollings Faculty,
Manchester Metropolitan University, UK.
Telephone: 0161-247-2636 ***