[meteorite-list] Meteor Theory Gets Rocky Ride From Dinosaur Expert

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Tue May 24 18:24:10 2005
Message-ID: <4293A963.1834AB97_at_bhil.com>

Hi,

    As all us Chicxulub controversy fans know, Keller's conclusions are criticized by a lot of other
Chicxulub investigators. It wouldn't be called a controversy otherwise, now would it? This one seems
to be particularly hot. There is detectable emotion in it, glaring right through the scientific
"detachment."
    For my fellow Chicxulub fans, I recommend the following website by one of her her chiefest critics:
<http://www.geo.vu.nl/~smit/csdp/debates.htm>
    Not only is it blunt and refreshingly direct, but it contains a lot of data. Take that famous core
about which so much argument is expended. It all seems pretty abstract to me, with no idea of what such
a core looks like. This site links to a giant photo page where you can look through that core in great
detail. Great presentation.
    The site also details the human controversy, paper by paper, speech by speech, with links to all of
them, and there is a solid criticism of the news coverage of this controversy, too.
    Don't mistake me, this is not a "balanced" presentation -- this is the other side of the argument.
But it's both impressive and entertaining. In fact, it looks more like a news webpage than the usual
"scientific" page.
    Myself, I don't see how a time delay between the impact and the extinction "proves" that the rock
didn't do it. Now, if you could prove that the dinos disappeared before the rock arrived, that would be
different kettle of saurians!
    Of course, the critics say that it is Keller's age estimate (300,000 years) that is in error, not
the existence or thickness of the layer. Dating by sedimentation rate is notoriously tricky. If this
website is right, it's not the only mistake she's made.
    Chicxulub fans, take a look at it if you haven't seen it before.


Sterling K. Webb
----------------------------------------------------------
Ron Baalke wrote:

> http://www.nature.com/news/2005/050523/full/050523-2.html
>
> Meteor theory gets rocky ride from dinosaur expert
> Rex Dalton
> Nature
> 24 May 2005
>
> US palaeontologist amasses data against Mexican crater hypothesis.
>
> The widely held theory that a particular meteorite strike on Mexico
> wiped out the dinosaurs is under sharp attack, again.
>
> The asteroid that created the Chicxulub crater in the Yucatan peninsula
> in Mexico arrived too early to have caused the Cretaceous-Tertiary mass
> extinction, according to evidence given on 23 May at an American
> Geophysical Union conference in New Orleans, Louisiana.
>
> A team led by palaeontologist Gerta Keller of Princeton University, New
> Jersey, reported that a sediment core drilled in east Texas emphatically
> confirms a study that the group released two years ago. Sediments of
> glass sprayed out by the Chicxulub impact are separated from fossils
> killed during the mass extinction by a 300,000-year gap, they argue.
>
> "I believe this is the mortal wound for the Chicxulub theory," says
> Keller. Scientists should mount a search for the crater left by the
> meteorite that was really responsible for the mass extinction, she adds.
>
> Many geophysicists remain unswayed. Sean Gulick of the University of
> Texas at Austin doubts the report because it means another huge asteroid
> must have hit the Earth in the same era, about 65 million years ago.
> "The odds of that are highly unlikely," said Gulick, who chaired the
> Chicxulub symposium at the conference.
>
> However, some sedimentologists are being persuaded by the core
> specimens. Paul Wignall of the University of Leeds in Britain calls
> Keller's evidence "quite convincing", although he didn't attend the
> meeting.
>
> Original thought
>
> Two years ago, Keller stunned a symposium at an American Geophysical
> Union meeting in Nice, France, with an analysis of a section of a
> 1,500-metre core drilled in the Yucatan, only 60 kilometres from the
> Chicxulub crater.
>
> The Yucatan core, called Yaxcopoil-1, was the result of an international
> project designed to provide the most advanced record of events at the
> Cretaceous-Tertiary boundary. But it was beset by strife over access to
> the core and subsequent interpretations (see 'Hot Tempers, Hard Core
> <http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v425/n6953/full/425013a_fs.html>').
>
> Keller claimed the crater preceded mass extinction by 300,000 years[1].
> Her critics say the sediment layers she sees are actually rubble
> from collapsing crater walls. But her team argues that palaeomagnetic
> dating and minute fossil analysis rules this out.
>
> Northern exposure
>
> To settle the dispute, Keller drilled 2,000 kilometres north of the
> crater to get a sedimentary view unaffected by backwash.
>
> The Brazos River Valley, Texas, is widely accepted as the best location
> to check Chicxulub impact debris from afar. In March, three
> 50-metre-deep holes were drilled near the small town of Rosebud to
> extract sediment from the time of the mass extinction.
>
> >From a 2-metre section of the best core, the Keller team charted what
> they say shows the 300,000-year gap. First, there is a 2
> centimetre-thick layer of altered glass called bentonite that is the
> ejected material from the Chicxulub impact. About 50 centimetres above
> that lie sediments beds from the tsunami set off by the asteroid.
> Finally, a full 1.2 metres above these beds, there is the detritus of
> the mass extinction, represented by fossils of tiny plants and animals
> that died.
>
> The National Science Foundation has given Keller US$40,000 to drill
> another core in autumn 2006. This one will be on the opposite side of
> the Chicxulub crater, some 7,800 kilometres south near the city of
> Recife in Brazil. Keller hopes to find evidence that will finally quiet
> her critics.
>
> References
>
> 1. Keller G., et al. Proc. Natl. Acad. Sci. USA, 101. 3753 - 3758
> (2004).
>
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Received on Tue 24 May 2005 06:23:31 PM PDT