Wednesday, October 7, 2009

First Pluto, now the Pliocene!

Fascinating stuff from The Paleoantrhopology Society:

Dear Fellow Paleoanthropologists:

We write to bring your attention to a matter which impacts strongly on all our research. You may be aware that in recent years, there has been a push by some Quaternary stratigraphers to redefine the Pliocene-Pleistocene boundary from its accepted position at ca. 1.8 Ma (the start of the Calabrian Stage of the Mediterranean stratigraphic sequence) to a level close to 2.6 Ma (start of the Gelasian Stage), 800,000 years older. This increases the length of the Pleistocene by 45% and makes the Early Pleistocene 70% of the epoch. The argument for this change was that it is a better fit to the paleoclimatic conception of the Quaternary. The International Commission on Stratigraphy ruled in favor of the change, and it was formally approved by the parent body of ICS, the International Union of Geological Sciences.

This change moves into the "Early Pleistocene" numerous important paleoanthropological horizons and events, such as Gona (with the earliest known stone tools); levels between 2.6-1.8 Ma at Hadar, the Middle Awash and the Turkana Basin; Kanjera; and some South African site units [e.g., Sterkfontein, Taung and perhaps parts of Swartkrans and Kromdraai], rendering all recent literature (including our textbooks) at odds with the new definition. Concomitantly, the Olduvai paleomagnetic subchron would no longer lie near the Pliocene-Pleistocene boundary, which would instead correlate closely to the Gauss-Matuyama geomagnetic boundary. This action violates 60 years of consistent terminology, based on the 1948 decision by the International Geological Congress to equate the base of the Pleistocene to the base of the Calabrian (since dated to ca. 1.8 Ma).

Stability is the watchword of global accord in chronostratigraphy, as it is in zoological nomenclature, but this action will cause massive instability in our field, among others.

Our view is two-fold:

1) there was no attempt to obtain feedback from the paleoanthropological (or really paleontological) community, although we use the concept of a Pliocene-Pleistocene boundary constantly (and consistently); it really was pushed through quickly by INQUA representatives who acted politically but not collegially.

2) there has been a definition in place for 60 years which included historical, paleontological and climatological underpinnings; the proposed change is comparable to changing the holotype of a species (e.g., Homo habilis) because the original was not perfect, and a better one has been found later; definitions are fixed, and we work around them. Moreover, the IUGS has ruled that no further discussion of this problem may be heard for 10 years, thus undemocratically preventing any response.

We have prepared a formal petition to the IUGS and other international scientific bodies, which a number of colleagues have already "signed" (electronically). We submit this petition for your consideration here. If you wish to sign it, you may do so by clicking on the "I agree to sign" button on the Paleoanthropology Society website, where we have also posted a number of publications related to this situation. Note that the Society is not taking a position on this argument, merely offering a means for us to contact and inform you.

Thank you for your consideration of our request.

Sincerely, Eric Delson and John Van Couvering
Visit The Robert J. Sawyer Web Site


At October 08, 2009 1:26 AM , Blogger Marcelof said...

Now you have to update Calculating God :D

At October 08, 2009 12:11 PM , Blogger Ron Friedman said...

Unfortunately, I don’t know enough about geological periods, nor am I a Paleoanthropologist, to make an intelligent decision for or against a definition change.

Also, I’m not sure adding consistency by changing Pluto’s status from a planet to a dwarf planet (and elevating Ceres to the same rank) was a bad idea. Sometimes it’s better to be consistent with our definitions, instead of clanging to ancient / legacy definitions.

Another example for such a change was the migration from Imperial to Metric system.


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