[meteorite-list] Black Gold-- Chicxulub Tea

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Wed, 07 May 2008 11:39:45 -0400
Message-ID: <67j3245km9e28illkh3fqit2d4mqvdl62t_at_4ax.com>

http://www.abc.net.au/science/articles/2008/05/07/2238200.htm?site=science&topic=latest

Dinosaur killer may have struck oil

The dinosaur-killing Chicxulub meteor might have ignited an oilfield rather than
forests when it slammed into the Gulf of Mexico 65 million years ago, say
geologists.

Smoke-related particles found in sediments formed at the time of the impact are
strikingly similar to those created by modern high-temperature coal and oil
burning, as opposed to forest fires, says Professor Simon Brassell of Indiana
University.

He and colleagues from Italy and the UK publish their report on the discovery in
the May issue of the journal Geology.

Evidence of some sort of large burn that may have changed the world's climate at
the end of the Cretaceous has been around since the 1980s.

But scientists can't agree on just what sort of fire it was.

"It seemed like [vegetation] wildfires were the easiest solution," recalls
geochemist Professor Wendy Wolbach of DePaul University, who worked on evidence
of the fires at the time.

There was even the discovery of retene, a chemical released by cone-bearing
trees when they burn in forest fires today.

But that was before the Chicxulub crater had been identified.

What's more, Wolbach says, it has never been certain that the fires were global,
as some have suggested.

For one thing, there has never been a lot of fossil charcoal found from that
time, which would be expected if there had been so much vegetation burning.

"There isn't enough charcoal to account for that," says Brassell.

Particles of carbon
What he and his colleagues have found instead are particles called cenospheres,
which resemble the sooty output of industrial coal and oil burning, he says.

When cenospheres are found, they are usually associated with what's called fly
ash, which is man-made.

"In many places the presence of such material is taken as evidence as the
presence of human activities," says Brassell.

And since the Cretaceous-Tertiary boundary is about 65 million years too early
for humans and their coal-fired Industrial Revolution, something else had to be
burning fossil fuels.

Brassell and his team suggest that the Chicxulub meteor crashed into oily shales
of the Gulf of Mexico, which caused the oil in the rocks to vaporise and ignite
in the air, making cenospheres in the process.

Today the large oil fields that edge right up to the Chicxulub structure testify
to the ample supply of oil available to burn 65 million years ago.

Oil there today
It's even likely the impact itself was responsible for the fracturing and
heating of the rocks in that region and allowing the oil to collect into the
large pools that are found there today, Brassell says.

The bottom line, says Wolbach, is that the Chicxulub impact and its aftermath
were probably a lot more complicated than is sometimes portrayed.

"The retene seems to suggest that at least some wildfires burned," says Wolbach.
"I think it's probably a combination."

Tags: astronomy-space, chemistry, dinosaurs, earth-sciences, geology,
palaeontology
Received on Wed 07 May 2008 11:39:45 AM PDT