Plankton undermine dino extinction theory - April 27, 2009
Posted for Rex Dalton
The plankton record doesn’t lie. And again it is showing that the meteor that created the Chicxulub impact crater in Mexico didn’t cause the Cretaceous/Tertiary [KT] mass extinction, says Gerta Keller – the Princeton University paleontologist whose group has been a primary questioner of the widely accepted theory that the asteroid wiped out the dinosaurs and most life 65 million years ago.
As researchers were wrapping up last week’s European Geosciences Union meeting in Vienna, Austria, the Keller group is publishing an article April 27 online in the Journal of the Geological Society, London, [JGSL 166, 393-411 2009 doi: 10.1144/0016-76492008-116] on its latest data in support of its view that the impact occurred 300,000 years before the KT mass extinction. Keller’s work also is among research discussed last weekend at a post-EGU workshop on Austrian geological sections of the KT.
The article focuses on stratigraphy in northeastern Mexico, in particular a site called El Penon outside Monterrey in the state of Nuevo Leon that is about 1,200 kilometres from the impact location on the Yucatan Peninsula. At El Penon, Keller and colleagues located a line of the spherules reflecting blast material from the Yucatan impact. Looking above and below this spherule-laced section, Keller checked the fossil record of foraminifera that are used to chart life around mass extinctions.
Below the spherule line, they found 52 foraminifera species – and above the line after the impact the same 52 species were abundant. “We found not a single species went extinct as a result of the Chicxulub impact,” says Keller. This means the Chicxulub impact couldn’t have been the sole event causing the extinction, she says.
This supports earlier research she and colleagues reported six years ago showing the Chicxulub impact was 300,000 years before the KT extinction. That research was based on sediments and plankton from a core drilled into the Yucatan impact crater, which showed life records through the period when the extinction occurred and the asteroid hit.
At the US National Science Foundation that has funded Keller’s research, there is considerable support. Richard Lane, a director of earth sciences, says, “Keller and colleagues continue to amass detailed stratigraphic information supporting new thinking about the Chicxulub impact and the mass extinction. The two may not be linked after all.”
But the Keller research was expected to be greeted with more skepticism at the Austrian workshop attended by researchers who have disputed her findings for years. However, she is so convinced she says her group now will focus entirely on the Deccan Traps lava fields of India as the source of deadly gases that caused the KT extinction – a theory that is gaining proponents.
“We have amassed an enormous and convincing database on the age and biotic effects of the Chicxulub impact, from Mexico to Texas,” says Keller. “No substantial counter data has been produced by anyone. From now on, we will focus on Deccan volcanism.”
Image: computer-generated gravity map of the Chicxulub Crater / Virgil L. Sharpton, University of Alaska, Fairbanks
Comments
First of all, forams are deep sea species that would be relatively unaffected by the impact, and we know that numerous higher lifeforms did survive the impact event.
Secondly, weren't the Deccan traps a result of antipodal effects of the impact itself? One would expect that the cumulative effects of the volcanism would take on the order of 100,000 years to kick in anyways, and it would take some time for those effects to percolate down to the foram level as well.
Posted by: Thomas Lee Elifritz | April 27, 2009 07:08 PM
That's interesting, because as I was at the Smithsonian a couple of weeks ago and their exhibition said that the foraminifera went from ~50 groups to about 3. Could there have been a delay while environmental effects worked their way down to the forams?
Posted by: Mona Albano | April 29, 2009 06:36 AM
What bothers me about this whole thing is that multiple papers have been published against the Chicxulub event leading to dinosaur extinction...all by the same author, Gerta Keller. These type of people make a name for themselves, rather than try to come up with a scenario that includes all the evidence, not just cherry-picked data. As others have said, the Deccan events could have been antipodal explosions related to the crater impact...and yes, why would we expect microscopic species to go extinct, anyway? Clearly, there is a lot of self-congratulation going on here, but not a lot of consideration for multiple viewpoints.
Posted by: Robert | April 29, 2009 09:28 AM