[meteorite-list] Dinosaur-Era Forest Fires Studied - Possible Link To Manson Impact Crater

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:22:38 2004
Message-ID: <200306131932.MAA24381_at_zagami.jpl.nasa.gov>

http://www.billingsgazette.com/index.php?id=1&display=rednews/2003/06/13/build/wyoming/32-old-fire.inc

Dinosaur-era forest fires studied
By MIKE STARK
Billings Gazette (Wyoming)
June 13, 2003

CODY, Wyo. -- The cracked and arid landscapes of Wyoming had a different
look 70 million years ago.

An inland sea covered a large chunk of the state, and leathery dinosaurs
tromped through lush, marshy areas and sandy beaches.

But today's ranchers and yesterday's reptiles shared at least one natural
force that shaped their surroundings: wildfires.

Scientists are just beginning to look at the role of prehistoric wildfires,
and one of the best places to learn about them is northern Wyoming,
according to Marilyn Wegweiser, an assistant professor of geology at Georgia
College and State University in Milledgeville, Ga.

Wegweiser, who does much of her fieldwork in Wyoming and Montana, spoke at
the Buffalo Bill Historical Center in Cody earlier this week.

Four years ago, while she was teaching a geology class in the Bighorn Basin,
Wegweiser stumbled across pieces of charcoal sprinkled with bits of ancient
bone. At first, the objects seemed out of place as Wegweiser tried to
understand where they had come from. It dawned on her a short time later.

"I thought, 'I'm walking around in a very, very old forest fire,' " she
said.

Wegweiser was quickly drawn to the idea of wildfire sweeping across the
landscape 70 million years ago.

She soon found further evidence of paleo-wildfires in Wyoming, including
dinosaur bones and trees in Elk Basin that were cooked in a fire so hot that
all of the organic matter was burned off and the rest was preserved for many
millions of years.

"They haven't really changed since the day it occurred," Wegweiser said.
"That's really cool."

She found pieces of one dinosaur, possibly a meat-eater, that died either in
a wildfire or within two weeks of a fire, she said. The heat could have been
from 650 degrees Celsius to 1,200 degrees, she said.

"The barbecue was on," she said. "Either way, it didn't get out."

So what caused wildfires back then?

Lightning was certainly a factor, she said. Active volcanoes could have
played a role, too. But Wegweiser theorizes about another option.

Around the same time of the ancient fires in Wyoming, a meteorite estimated
to be about 2 miles across came screaming into the atmosphere at 43,000 mph
and crashed into what is now Manson, Iowa. The crater is more than 5 miles
deep and 20 miles in diameter.

"It sucked to be you if you were underneath it," she said.

No doubt the meteor launched an enormous cloud of debris into the atmosphere
and sent huge waves from the eastern edge of the inland sea, but Wegweiser
also said the meteor may have sent sparks into what is now Wyoming, touching
off large fires.

Some scientists have theorized that the Manson meteor, estimated to have hit
74 million years ago, roughly coincides in time with the extinction of the
dinosaurs, but Wegweiser and others believe that the animals were already on
their way out when the meteor hit.

As most residents know, prehistoric Wyoming was home to plenty of
meat-eating and vegetarian dinosaurs, including triceratops and
tyrannosaurus.

"They were all alive when this part of the basin might have burned,"
Wegweiser said.

Evidence of the paleo-wildfires could play an important role in
understanding where and when certain animals inhabited this area. Ancient
objects preserved by fire can be mapped, temperature and duration of
wildfires can be determined and information about climate conditions from
millions of years ago can be found, she said.

But so far, Wegweiser has only pawed through about three square miles in the
Bighorn Basin looking for evidence of paleo-wildfires.

She plans on continuing to search for the prehistoric fires and other
artifacts. Wyoming is a gold mine for researchers digging up the past, she
said.

Just last year, Wegweiser found the first evidence of a duck-billed
dinosaur, called the edmontonosaurus, that no one knew ever inhabited this
area. She has also found dinosaur tracks and even preserved dinosaur skin.
Received on Fri 13 Jun 2003 03:32:30 PM PDT