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Re: Volcanism, impacts and mass extinctions conference in London



I still can't find abstracts, does anyone know if they are available
anywhere?

I think everyone would probably agree that it is wholly plausible that the
Deccan Traps may have been causing global climate change that stressed the
biota, and that the Chicxulub impact therefore was able to wipe out
weakened groups, like non-avian dinosaurs, where other impacts did not. I
certainly could accept that. The latest Maastrichtian does show maybe 2 or
3 degrees of ocean warming, and the Danian has an unstable, fluctuating,
climate. 

The problem for this hypothesis is that there is a HUGE body of work which
seems to show, instead, low extinction rates for the maybe two million
years of eruptions before the K-T, and near-instantaneous extinctions at
the impact moment, followed immediately by global forest collapses. The
climate fluctuations don't seem to hit the highs and lows seen in the rest
of the Cretaceous or at the PETM.

More than quantity is the quality, of multiple sites across North America
where sedimentary resolution is extremely high, some of which show
palynological extinction rates of 30% instantaneously, and then only a
single fern species growing for thousands of years after that. Globally at
this same precise moment we see forest collapses. In Australia 3 plants go
extinct, in New Zealand 2, and in Patagnoia 10%. After this instantaneous
event, correlated with silica spherules, clay, and soot, all of these
locales show pioneer plant communities of far lower diversity. The signal
seems clear, strong, and cosmopolitan, and none of these conclusions rely
on one or a handful of outlier sites.

In other words, the Deccan Traps hypothesis must also be falsifiable, and
it seems like that work has been done. I cite Nichols and Johnson, Plants
and the K-T Event, 2008. They used extyreme methodological rigor to
exclude artifacts like the Signor - Lipps effect, which can create a false
impression of stepwise extinctions and declining diversity right before a
sudden extinction.

The Volcanic faction has very good points to make, and everyone should
read them. In earth history, flood basalts always correlate with mass
extinctions and impacts really don't (or, at least, it is almost never
possible to prove they did). But in Biology every rule has exceptions.

It is still possible, though, that we will find definitive (definitely not
re-worked) evidence of non-avian dinosaurs persisting past the K-T. I
would bet that the Southern Hemisphere is the most likely place for that.
That might change the story in the public imagination, but it might not
overturn the conclusion that it was the impact that really brought on the
Cenozoic.

Jason Brougham
Senior Principal Preparator
American Museum of Natural History
jaseb@amnh.org
(212) 496 3544





On 3/30/13 1:41 PM, "Ben Creisler" <bcreisler@gmail.com> wrote:

>From: Ben Creisler
>bcreisler@gmail.com
>
>
>The British Natural History Museum just hosted a conference about mass
>extinctions related to volcanism and impacts. The circular with talk
>titles is available online but I haven't found the abstracts.
>
>http://massextinction.princeton.edu/sites/default/files/pdfs/Final%20Circu
>lar.pdf
>
>
>At least one news story from the conference has been reported so far:
>
>http://news.discovery.com/earth/biggest-dino-killer-volcano-vs-asteroid-13
>0327.htm
>
>http://science.nbcnews.com/_news/2013/03/28/17503180-volcano-eruption-theo
>ry-gains-backing-in-dinosaur-extinction?lite