Paleonet: Mesozoic-Cenozoic ...

[Dr. Peter Paul Smolka]

On Wed, 13 Dec 2006, leigh van valen wrote:

> Date: Wed, 13 Dec 2006 12:24:15 -0600
> From: leigh van valen <leigh at uchicago.edu>
> Reply-To: A listserver system for paleontologists. <paleonet at nhm.ac.uk>
> To: A listserver system for paleontologists. <paleonet at nhm.ac.uk>
> Subject: Re: Paleonet: Mesozoic-Cenozoic ...
> 
> Leo, Sandy wrote:
>
>  Ladies & Gentlemen -- just one question.  Why is the base of the
> Quaternary placed in the Pliocene?  -- A. Leo
> 
> 
> Well, remember that a couple of decades ago the Pliocene was being
> nibbled away from both ends at a more or less linear rate.  It seems not
> to have entirely disappeared yet, but it may still be in
> predator-infested country.  Is there a Pliocene Defense Association?
> 
> (Yes, I realize that letting the Quaternary overlap the Pliocene means
> that no one except Quaternarians, which I'll try not to confuse with
> quaternions, need use 'Quaternary', especially if the Holocene gets
> incorporated into the Pleistocene.)


As the "overlap question" appears to be of some interest:

I understood the discussions within the SNS such that

a) the Quaternary consists (will consist) now of Gelasian-Holocene (=
the great climate change around 2.6 also reflected).

b) implicitely (not outspoken) other boundaries are accordingly
(= base Quaternary=base Gelasian = implicite new top Pliocene).

The primary units, as based on GSSPs, remain as they are (G,P,H).

Only the grouping changes.

The Pliocene will then be quite short (e.g. 5.1x to 2.6x Ma).
With about from "end of Messinian", also climatically, to beginning
of large NH glaciations it is not only stratigraphically but
environmentally easy to remember.

I am not sure whether a "top Pliocene" issue was discussed explicitely
following the initiation of the discussion by van Coevering
(= I have to look it up in the e-mails).
I understood it implicitely as such (P/Q boundary, so to say).

c) Thus, as a Quaternary as sub-era will (most likely) exist
there is a unit between base Quaternary and top Cretaceous, e.g
grouping these times "to something" makes sense.
Thus: I understood that the
Tertiary (e.g. K-T as initially asked, see about the last
sentence of Prof. Hilgen) is (factually) not abandoned.

E.g. with Gelasian-Holocene = Q grouping Paleocene-Pliocene = T
appears natural.

Formulated with a polite smile (addressing those who do not
favor a unit of Tertiary):
When one thinks of the Rupelium for example one definitely does
not have a feel like a "Quaternary" (Gelasian-Holocene) world
(environment). One also does not have a feel like "it is part
of the Cretaceous world". So having Tertiary as "overall unit"
between base Q and top C is in my opinion the most natural if one
has a Q.

The contribution of van Coevering was a valuable contribution to
scientific discussion: E.g. a constructive suggestion to change
some perspective. The definition itsself is an ICS issue, e.g.
voting there including considering recommendations (such as the
INQUA vote).

Until that I would say: It is K-T around 65 Ma.

**************************

To the other issues: (change at 3.5 Ma etc., remarks of Michael Styzen,
Piacencian/Zanclian):

The 2.6 Ma change can be seen marine and terrestrial; it is
almost _the_ change in this time. Thus personally I was quite happy
that the discussion which started with a "big bang" (suggestion
to abandon the Quaternary and Tertiary) arrived at a new view about
the base of the Quaternary, e.g. 2.6 Ma (grouping Gelasian-Holocene,
leaving the Vrica GSSP as it is and so forth).

With a polite smile: Calling the INQUA after abandoning the Q(u)
the Gelasian-Holocene Assoc. would appear unusual.

In fact: The "new" definition of base Q is closer to the earliest one
(18xx or early 19xx): Base Q is the time with the great NH glaciations.

Within the Pliocene itsself, depending on the place, various changes
can be seen as well: The closing Isthmus of Panama for example
is even visible in paleotemperature-records (SSTs of DSDP/ODP sites)
of the NW Atlantic around 4 Ma (and such a change also elsewhere).
The shoaling itsself starts of course earlier.

To formulate compact:
The "later part of the Upper Plicocene" appears sometimes warmer
"before it "really cools down".

Thus seeing "in between" (around 3.5 Ma) environmental changes
fits well. I can remember my own PhD work (1986-1988) where even
in the old DSDP Site 407 (Western flank Reykjanes Ridge) there had been
a temperature drop at about this time. At that time we experimented with
various approaches to assess neogene paleotemperatures. In the
retrospective we might have continued to use almost all.

To avoid any confusion I really have to look up from sample to sample
where (when) the cold interval _at that place_ (DSDP-407) was.

In other sites there are "warm" "Mid Pliocene" samples.

So: It is a fascinating time with lots of environmental changes.

Environmental changes are one thing, clock adjustments another:

The clock-ticks (GSSPs, possibly patterns of paleointensity curves)
are one thing. The meaning of them is worldwide the same (_that_ time at
which at the place of GSSP (name1) species (name2) (definition-terms,
such as appeared/disappeared).

The Berggren term (Berggren around 1995) of "transfering the meaning"
in this context, I found really useful.

With this framework almost established now the nice part becomes more
easy:

Analyzing environmental changes (formulated compact) "worldwide
synchronously" (including the propagation of environments, including
times where in some regions "nothing happened").

I would thus not prefer new subdivisions (GSSPs, see the sometimes
reactivated discussion on a "Mid Pliocene").

The readjustment of the Quaternary (base Gelasian or base Pleistocene)
was one thing leaving the definitions (GSSPs) as they are.

Around 3.5 Ma we have already the Piacencian/Zanclian boundary
("_around_ 3.5" not "_at_ 3.5", I have to look up the details).
I personally think that what you have seen at 3.5 Ma might be
the same process that lead to the Piac./Zancl. change
(either synchronous or propagating: Paleointensities will most
likely show).

All lines are written in a polite and pleasant mood. If some term,
due to compactness, might appear harsh, it really is not intended.

Deduced from those (DSDP) and ODP sites with a high sample density:

I expect for the Pliocene and the Miocene the same variability
as we have seen in the Quaternary: right now high-res
is beyond the capabilities
of counted/estimated faunas and resulting SSTs, e.g. sample-density.
With better technology being in our reach, it might be a question of
letter sending, even foram-determination might be done technologically.

> 
> Incidentally, I've used Pg for many years, and not because I was born in
> a Year of the Pig.  Really.
> 
> -Leigh
> 
With a polite smile: Suidae 
can possibly be observed from some Oligocene time on
(vertebrates are not my field)... and when the rats appeared I don t
know.

Best regards

Peter

> -----Original Message-----
> From: paleonet-bounces+atleo=sandia.gov at nhm.ac.uk
> [mailto:paleonet-bounces+atleo=sandia.gov at nhm.ac.uk] On Behalf Of Dr.
> Peter Paul Smolka
> Sent: Tuesday, December 12, 2006 11:12 AM
> To: paleonet at nhm.ac.uk
> Subject: Paleonet: Mesozoic-Cenozoic ...
>
> Dear interested,
>
> Prof. Harris referred regarding the K-T discussion to Prof.
> van Coevering, possibly regarding his contribution to this issue.
>
> Following a vivid discussion (and other suggestions by Aubry et al.)
> there had been a meeting of the Subcommission on Neogene Stratigraphy in
> Leuven (with previous discussions / questionaires within the SNS,
> coordinated by Prof. Hilgen, chair of the SNS).
>
> His report on the Leuven meeting is as follows:
>
>
> ---------- Forwarded message ----------
> Date: Fri, 14 Oct 2005 09:59:25 +0200
>
> ( ... )
>
> Q: Quaternary
> T: Tertiary
> N: Neogene
>
> (asterisks by me)
> Between the asterisks: The e-mail of Prof. Hilgen, chair of the SNS.
> ************************
> Dear members of the SNS,
>
> ( ... )
>
> In Leuven I presented the point of view of the SNS. I stated that the
> problem does not only concern the definition of the Q but also that of
> the N and pointed at the imbalance in this respect in the composition of
> the Task Force that was installed last year to come up with
> recommendations for solving the Q issue before the Leuven meeting. I
> further presented the outcome of the SNS 3rd questionnaire and stated
> that SNS was willing to accept the compromise solution as formulated in
> the Aubry et al. paper. That is also my personal point of view because
> this option seems the only solution that might be acceptable for both
> communities as well as for a wider stratigraphic community.
>
> The Task Force installed last year came up with the following
> recommendations before the Leuven meeting:
> 1) That the Quaternary is to be recognized as a formal
> chronostratigraphic/ geochronological unit.
> 2) That the lower boundary of the Quaternary will coincide with the base
> of the Gelasian Stage and thus be defined by the Gelasian GSSP.
> 3) That the Quaternary will have the rank of either a. System/Period and
> will be at the top of the Neogene System/Period, with its lower boundary
> marking the top of a shortened Neogene, or b. Sub-erathem/Sub-era and
> will be correlative with the upper part of the Neogene System/Period
>
> The different options under 3 were voted upon by the ICS voting
> membership (ICS board and chairs of the subcommissions) and the only
> option that received a
> (clear) majority of votes was the option with a subdivision of the
> Cenozoic in Paleogene and Neogene Periods and the Quaternary maintained
> as Subera with its base at 2.6 Ma (i.e. the "compromise" solution
> presented in Aubry et al., 2005). This option clearly leaves open the
> possibility for a revival of the Tertiary as a Subera preceeding the Q.
>
> This decision of course is not final yet. The outcome of the voting is
> now forwarded to the IUGS and INQUA. I will keep you informed about the
> continuing story of the Q definition.
>
>
> Best wishes,
> Frits Hilgen
> ************************
>
> I hope this helps.
>
> Lucy Edwards drove my attention to an apparent trend that more people
> appear to regard the van Coevering contribution, which is perfectly
> valid as contribution to scientific discussions, as "official" (and thus
> final) version (she recommended me to google it myself, I trust her
> data).
>
> This is by no means any criticism at valued researchers (such as Prof.
> van Coevering).
>
> It is only a hint to the difference between a contribution to a
> discussion and a final official version.
>
> Possibly some people who apply K-P misunderstood the contribution to
> scientific discussion as "official version".
>
> See the procedure following the SNS meeting.
>
> Best regards
>
> Peter
>

**********************************************************************
Dr. Peter P. Smolka
University Muenster
Geological Institute
Corrensstr. 24
D-48149 Muenster

Tel.: +49/251/833-3989   +49/2533/4401
Fax:  +49/251/833-3989   +49/2533/4401
E-Mail: smolka at uni-muenster.de
E-Mail: PSmolka at T-Online.de
**********************************************************************

**********************************************************************
Dr. Peter P. Smolka
University Muenster
Geological Institute
Corrensstr. 24
D-48149 Muenster

Tel.: +49/251/833-3989   +49/2533/4401
Fax:  +49/251/833-3989   +49/2533/4401
E-Mail: smolka at uni-muenster.de
E-Mail: PSmolka at T-Online.de
**********************************************************************