[meteorite-list] Missouri Meteorite Strike Zone Pinpointed In Research

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:30:00 2004
Message-ID: <200309271711.KAA21970_at_zagami.jpl.nasa.gov>

http://www.news-leader.com/today/0927-Meteorites-176462.html

Meteorite strike zone pinpointed in research

A grant for more extensive drilling could bolster extinction theory.

Mike Penprase
News-Leader (Springfield, Missouri)
September 27, 2003
  
Osceola - They never knew what hit them.

Denizens of the shallow sea covering much of Missouri more than 300 million
years ago were slammed by a meteorite 1,200 feet across and moving five times
faster than a bullet, leaving a geological puzzle to solve in what is now
St. Clair and Hickory counties, Kevin Evans said Friday as he and more than
100 fellow geologists and students searched for signs of that mighty collision.

In a bit of poetic justice, ocean dwellers called blastoids got blasted into
extinction, joked one member of what was described as the largest field trip
ever held by the Association of Missouri Geologists.

But Evans was serious about the implications of the research, bolstering
extinction theories based on meteorite strikes and letting astronomers know
what a strike from a small meteorite might do.

"We think we've got something kind of interesting here," Evans said of what
is called the Weau-bleau-Osceola Structure.

Rock formations thousands drive past every day on Missouri 13 and Missouri
82 got a going-over from hammer-wielding field-trip participants, who were
attending the association's 50th annual meeting in Springfield.

Sites on the highways and at an Ash Grove Aggregate quarry drew superlatives
from the geologists as Evans recounted how he and fellow researchers discovered what may be the concentric rings of uplifted rock signifying what could
be one of the largest meteorite strike zones in the United States.

"It will make a good story," Evans said, perhaps good enough to lure outside
help.

The next step in the project is to try for a National Science Foundation grant
to finance further research, he said while the clink of hammers against rock
echoed at the quarry.

The story began when Evans used computer software to join four maps together
and discovered the ring formations around Weaubleau Creek.

The research team theorizes the meteor strike created a crater 12 miles wide
and more than 1,000 feet deep at ground zero. It would have dwarfed a nuclear
bomb blast, Evans said.

Some of the evidence is just south of the quarry, where researchers point out
signs that the area was one of several strike zones along the 38th Parallel,
running from Kansas to Illinois.

Twisted and mixed formations of what should have been neatly horizontal layers
of sedimentary rock may support the belief that something big hit the Ozarks
millions of years before dinosaurs were on the scene.

While the Missouri Department of Transportation has helped the team by
drilling three test holes in July along Missouri 13, a grant would enable
the team to do more extensive drilling, along with other research, Evans said.

It could take years to gather enough evidence to make an airtight conclusion,
Evans said, but the rewards were immediate for students like Scott Sowers.

A road cut on Missouri 82 swarmed over by the geologists surrendered a prize
for the SMS student: an "Osceola round rock" or "Weaubleau egg," a spherical
stone so common it can be found in the walls of stone structures in the area.

They're evidence a meteorite hit, turning rock into liquid that cooled as
airborne spheres before falling back to Earth, the researchers contend.

"This is my first rock of the day, and I'm excited about it," Sowers said of
the softball-size stone.

Other students gathered discs from prehistoric plants called crinoids and
others hacked rocks to get pieces of iron pyrite.

Most of them also gathered up bits of breccia, speckled rock consisting of
sharp bits of hard rock embedded in softer rock such as sandstone.

That rock and quartz, which tests show were shattered by an immense force,
are other bits of evidence the SMS team uses to advance its theory,
contending a meteorite strike was so violent it shattered rock into tiny
bits, embedding them in what eventually turned to stone.

Retired geologist and ground zero resident Gordon Kinney said he was
excited, too.

Until he read about the SMS team's theory, he had no idea he was living on
a cliff that's part of a meteorite strike zone.

"I thought, holy cow, we're right the middle of it," he said.

He tried to determine whether there was anything unusual about the area he
lives in years ago, but wasn't able to find precise enough maps to draw a
conclusion, Kinney said.

"I don't think there was any clue," he said.

Retired geology professor Dick Gentile said he doesn't believe there are
any clues supporting the SMS team's theory.

At one point, he seemed to try to generate a debate at the quarry with
Evans and fellow researcher Chuck Rovey.

That's just part of the scientific method in which evidence supports
theories, except that there's rarely enough evidence to turn a theory
indisputably into fact, he explained later.

Gentile thinks other forces created the area's jumbled geology.

Unless pieces of meteorite are found, theories such as cryptovolcanic
activity — in effect, the surfacing of superheated gasses and liquid
rock without a volcano — are just as valid, he said.

"You've got evidence for both," he said. "As it is in geology, there's not
enough evidence for either side to silence the other side."

Missouri Department of Natural Resources chief park naturalist George
Kastler said he hasn't made up his mind about the SMS scientists' theory,
but he knows that once they start publishing scientific articles, the
debate will intensify.

"This will stir some debate," he said. "I think there should be some good
discussions."
Received on Sat 27 Sep 2003 01:10:59 PM PDT