[meteorite-list] Uvlade Texas Crater Contorversy

From: E. L. Jones <jonee_at_meteoritecentral.com>
Date: Sun Jan 16 17:41:29 2005
Message-ID: <41EAED8E.1080108_at_epix.net>

To save the list from the inane registration process at MySanantonio.com
site here is the article:
*
Will 'Rosetta Stone' prove Uvalde crater? *

* Web Posted: 01/16/2005 12:00 AM CST *

* Zeke MacCormack
San Antonio Express-News *

UVALDE ? The origin of a 2-mile-wide depression outside this town has
been debated for decades, but a local scientist now claims to have solid
evidence that it's a meteorite crater.

Bobby Graham rests his case on a rock, measuring roughly 3 feet by 2
feet, he found in October off U.S. 83 about 15 miles south of the city.

He's convinced that the object he calls "the Uvalde Crater Rosetta
Stone" was part of the ground where a 300-foot wide meteorite crashed to
Earth some 30 million years ago.

"I've got the goods," said Graham, 74, who took on the mystery after
retiring from Sandia National Laboratories, a federal nuclear weapons
facility, in 1996.

But other scientists are awaiting the results of further investigations
of the rock, including core sampling and microscopic inspections, before
reaching any conclusions.

Graham said swirls on the top of the 150-pound caramel-colored rock
suggest it was once molten. Its middle features small "teardrops" of
stone, some tinged in red, and the bottom is normal native sandstone.

Its varied features reflect the changes the rock underwent in a split
second upon impact, "when all the extreme temperature and pressure was
involved," said Graham, whose specialty during his 38-year career at
Sandia was the effects of high-pressure shock compression.

He'll present his findings in March at the Lunar and Planetary Science
Conference in Houston.

"It's not just fascinating; it's important, scientifically, to the world
to understand these craters," Graham said. "We're sending spacecraft to
look at craters all over the solar system, but we can learn things here,
too."

He predicts scientists and tourists alike will flock to see the unusual
rock, which will anchor a display at the city's new library on what may
prove to be the fourth known meteorite crater in Texas.

Joining him in addressing the Houston conference will be William
Feathergail "Feather" Wilson, a geologist who, with son Douglas, is
credited with identifying the purported crater in 1979 while on a field
trip with Trinity University students.

"In this area, the rocks are deformed in an extreme fashion, stuff is
upside down, it's blown out and there's a lot of folding," said Wilson,
a Bandera County resident.

He says Graham's analysis of the Rosetta Stone bolsters the theory ? on
which the scientific community has waffled ? that a meteorite created
the 1,500-foot depression, which has since been filled in.

"I've always believed it (was a meteorite crater) because we couldn't
come up with any other conclusion," said Wilson, who first reported his
findings in Geology magazine in 1979.

The site was included but later removed from the "Earth Impact Data
Base" maintained by the Planetary and Space Science Center at the
University of New Brunswick, Canada.

It was delisted because deformed quartz found there ? which supported
the meteorite strike theory ? was later found far away, Wilson said.

If proven to be a crater, Wilson said, "it's important from the
standpoint that out of the 130 to 150 craters on Earth, almost all of
those have been found in hard rocks. Very few have been found in soft
water-saturated sedimentary rocks" like those around Uvalde.

Fred Horz, who's familiar with craters from running a NASA experimental
impact lab, is convinced that a meteorite hit caused the crater, but he
said Wilson's extensive investigation ? which included use of seismic
mapping ? was more convincing than Graham's rock.

"All of the rock strata all over southern Texas are basically
flat-laying deposits," he said. "In this area, for some reason, they are
severely fragmented and broken up and even demonstrably transported."

After traveling to see the rock last month, Horz didn't shy from sharing
some good-natured differences of opinion with Graham.

"It's just a question of interpretation. He sees impact melts and I
don't," Horz said. "I don't see shocked rocks."
Received on Sun 16 Jan 2005 05:41:18 PM PST