[meteorite-list] More Than a Meteor Likely Killed Dinosaurs 65 Million Years Ago

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Oct 17 14:13:17 2006
Message-ID: <200610171813.LAA20745_at_zagami.jpl.nasa.gov>

http://www.nsf.gov/news/news_summ.jsp?cntn_id=108103&org=NSF&from=news

National Science Foundation Press Release 06-150

More Than a Meteor Likely Killed Dinosaurs 65 Million Years Ago

Growing evidence shows a series of natural events caused extinction
October 17, 2006

Growing evidence shows that the dinosaurs and their contemporaries were
not wiped out by the famed Chicxulub meteor impact alone, according to a
paleontologist who says multiple meteor impacts, massive volcanism in
India and climate changes culminated in the end of the Cretaceous Period.

The Chicxulub impact may have been the lesser and earlier of a series of
meteor impacts and volcanic eruptions that pounded life on Earth for
more than 500,000 years, say Princeton University paleontologist Gerta
Keller and her collaborators Thierry Adatte from the University of
Neuchatel, Switzerland, and Zsolt Berner and Doris Stueben from
Karlsruhe University in Germany.

A final, much larger and still unidentified impact 65.5 million years
ago appears to have been the last straw, said Keller, exterminating
two-thirds of all species in one of the largest mass extinction events
in the history of life. It's that impact - not Chicxulub - that left the
famous extraterrestrial iridium layer found in rocks worldwide that
marks the impact that finally ended the Age of Reptiles, Keller believes.

"The Chicxulub impact alone could not have caused the mass extinction,"
said Keller, "because this impact predates the mass extinction."

Keller is scheduled to present that evidence at the annual meeting of
the Geological Society of America (GSA) in Philadelphia, on Tuesday,
October 24, 2006.

"Chicxulub is one of thousands of impact craters on Earth's surface and
in its subsurface," said H. Richard Lane, program director in the
National Science Foundation (NSF) Division of Earth Sciences, which
funded the research. "The evidence found by Keller and colleagues
suggests that there is more to learn about what caused the major
extinction event millions of years ago, and the demise of the dinosaurs
at the end of the Cretaceous."

Marine sediments drilled from the Chicxulub crater itself, as well as
from a site in Texas along the Brazos River and from outcrops in
northeastern Mexico, reveal that Chicxulub hit Earth 300,000 years
before the mass extinction. Microscopic marine animals were left
virtually unscathed, said Keller.

"In all these localities we can analyze their microfossils in the
sediments directly above and below the Chicxulub impact layer, and
cannot find any significant biotic effect," said Keller. "We cannot
attribute any specific extinctions to this impact."

The story that seems to be taking shape, according to Keller, is that
Chicxulub, though violent, actually conspired with the prolonged and
gigantic volcanic eruptions of the Deccan Flood Basalts in India, as
well as with climate change, to nudge species towards the brink. They
were then pushed over with a second large meteor impact.

The Deccan volcanism released vast amount of greenhouse gases into the
atmosphere over a period of more than a million years leading up to the
mass extinction. By the time Chicxulub struck, the oceans were already
3-4 degrees warmer, even at the bottom, Keller said.

"On land it must have been 7-8 degrees warmer," she said. "This
greenhouse warming is well-documented. The temperature rise was rapid
over about 20,000 years, and it stayed warm for about 100,000 years,
then cooled back to normal well before the mass extinction."

Where's the crater? "I wish I knew," said Keller.

Scheduled Presentations at the Geological Society of America meeting in
Philadelphia:

"Chixculub Impact and the K/T Mass Extinction"

Pennsylvania Convention Center: 105 AB

Tuesday, 24 October, 2:50 p.m.

"K/T Mass Extinction and the Lilliput Effect: Consequences of Impacts,
Volcanism and Climate Change"

Pennsylvania Convention Center

Wednesday, 25 October, 11:45 a.m.

-NSF-

Media Contacts
Cheryl Dybas, NSF (703) 292-7734 cdybas_at_nsf.gov
Ann Cairns, GSA (303) 357-1056 acairns_at_geosociety.org

Related Websites
Talk: Chixculub Impact and the K/T Mass Extinction:
http://www.nsf.gov/news/longurl.cfm?id=14
Talk: K/T Mass Extinction: Consequences of Impacts:
http://www.nsf.gov/news/longurl.cfm?id=15

The National Science Foundation (NSF) is an independent federal agency
that supports fundamental research and education across all fields of
science and engineering, with an annual budget of $5.58 billion. NSF
funds reach all 50 states through grants to nearly 1,700 universities
and institutions. Each year, NSF receives about 40,000 competitive
requests for funding, and makes nearly 10,000 new funding awards. The
NSF also awards over $400 million in professional and service contracts
yearly.
Received on Tue 17 Oct 2006 02:13:14 PM PDT