[meteorite-list] Scientists Preuse Unearthed Cores From Ancient Chesapeake Bay Crater

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed Mar 22 21:17:44 2006
Message-ID: <200603221826.k2MIQTT24857_at_zagami.jpl.nasa.gov>

http://www.timesdispatch.com/servlet/Satellite?pagename=RTD%2FMGArticle%2FRTD_BasicArticle&%09s=1045855935235&c=MGArticle&cid=1137834861822&path=!health!healthology

Scientists peruse unearthed cores from ancient Chesapeake Bay crater
Dozens from around the world converge on N.Va. for samples

BY A.J. HOSTETLER
RICHMOND TIMES-DISPATCH (Virginia)
March 22, 2006

RESTON -- In a former federal printing plant, Belgium geologist Philippe
Claeys hovered over the tables of rocks, some 600 million years old,
hoping to find traces of an asteroid.

Claeys was among dozens of scientists from around the globe descending
on the U.S. Geological Survey this week to select samples of a
1.1-mile-long core, much of it granite, unearthed last fall from the
ancient crater under the Chesapeake Bay.

He and about two dozen other scientists from Finland, Austria, Germany,
Estonia and elsewhere strolled Monday through the one-time printing
plant filled with open boxes of cores. In an atmosphere of a silent
auction, they wrote their names on slips of clear Mylar and tucked them
beside the desired rocks for project officials to sort through and
distribute later.

They were drawn to the USGS headquarters by the remains of what
geologists say was a fiery, 2-mile-wide space rock that blasted into
coastal Virginia more than 35 million years ago, carving a hole that
quickly filled with tons of water, rubble and debris.

"The only thing you could do to simulate the conditions of the impact is
a nuclear blast," said Greg Gohn, the USGS project leader.

Claeys, from the Free University of Brussels, wants to identify the
cause of the crater without setting off a nuclear explosion. He suspects
that the bay was a bystander to a major collision in the asteroid belt
between Mars and Jupiter.

Debris from that collision, he says, might have bombarded the Earth not
just in the Chesapeake Bay but in Siberia, Canada and possibly other
sites where craters from about the same time frame have been found.

"What we have so far is pointing to an asteroid," he said.

He plans to study the ratio of platinum-related elements, a telltale
sign of a meteorite, in the Virginia cores. Comparing that with the
ratio found in other craters of the same age could nail the culprit here
in Virginia.

"Something that happens in the asteroid belt, between Mars and Jupiter,
can, in a short geologic time frame . . . send a whole bunch of large
projectiles towards Earth," he said. "That's a little bit scary. We
don't know when that's going to happen again."

Two of the crater project's principal investigators, Uwe Reimold of
Germany's Humboldt University and Christian Koeberl of the University of
Vienna, worked side by side, conferring over the samples. Moving slowly
from table to table, they scrutinized the mostly gray and tan rock for
samples to investigate the physical processes involved in creating
impact craters and how the rock was altered chemically.

Koeberl said he was convinced that new data from a much younger and
well-preserved crater in Ghana would help them interpret the crater
centered on Virginia's Eastern Shore.

They left a long trail of Mylar slips. Each scientist was limited to 150
requests.

Both assisted in the drilling last fall, which ran nearly continuously
in Northampton County near Cheriton for almost three months to remove
5,795 feet of cores.

The USGS paired with the International Continental Scientific Drilling
Program and NASA on the nearly $1.5 million project to dig into the
basement of the 53-mile-wide crater. The crater's epicenter is Cape Charles.

Scientists expect the cores to reveal more about the effects the
prehistoric impact had on the region's geology and water supply and to
help better estimate the space rock's speed, size and energy as it
slammed into the seabed. Other scientists will study samples of ancient
water found in the cores that had been trapped in the crater's depths by
the impact's aftermath.

The crater is the largest of its kind in the U.S. and the
seventh-largest in the world. It is 1,000 feet beneath the lower part of
the bay, surrounding peninsulas and the intercontinental shelf of the
Atlantic Ocean.

The USGS plans to return this spring to the drill site to core the top
412 feet to complete the record.
Received on Wed 22 Mar 2006 01:26:29 PM PST