Re: Resurrection of the Quaternary (was RE: Precisely Dating The KT Boundary)

[don ohmes <d_ohmes@yahoo.com>]

Then the iridium layer that marks the end-Cretaceous boundary can by convention 
be designated as zero on the time spectrum of iridum layers. If it is useful to 
sequence all Ir layers, older Ir layers could be negative numbers and more 
recent events be positive. This would make any revisions made necessary by new 
data less confusing. I am not  proposing that all geologic time be sequenced by 
iridium layers, or that the iridium layer is indicative of causation, only that 
the _term_ accepted by concensus as replacement for "K/T" (et al), be one that 
would NEVER need revision. Is one little rock in the sea of Babel too much to 
ask?

Don

----- Original Message ----
From: David Marjanovic <david.marjanovic@gmx.at>
To: DML <dinosaur@usc.edu>
Sent: Thursday, September 7, 2006 4:24:40 PM
Subject: Re: Resurrection of the Quaternary (was RE: Precisely Dating The KT 
Boundary)

Combined comments:

> Bad, BAD Cenozoic stratigraphers! We let you get away with too much for 
> too long! And now you want a period (or Sub-Era) whose
> boundaries are NOT CONGRUENT with Stage boundaries!?!?

Oh, they are congruent with stage boundaries (Piacenzan-Gelasian). However, 
they still aren't congruent with epoch boundaries (it's within the 
Pliocene). Apparently the terrestrial and the marine Quarternary Researchers 
used the term in different ways, and here we get the marine one, based on 
the start of the ice age series...

> I thought "P" was for "Permian". Wouldn't it be the K/Pg boundary? (Or
> why not just the M/C boundary?)

Because C is the Carboniferous... :-Â

> Is the global Iridium layer unique? If so, I suggest "IL" as a substitute 
> for "K/T" to avoid future modifications to stratigraphic nomenclature. Or, 
> if not unique, but sufficiently unusual, then "IL1, 2, 3...". This assumes 
> of course that no forward-looking scientists are going to change the names 
> of the elements...

More and more such iridium-enriched layers are being discovered (IIRC all of 
them associated with at least stage boundaries and extinction events). The 
numbering would have to be revised all the time, or become very confusing.

No, iridium is not going to change the way e. g. columbium became niobium.