[meteorite-list] Deepest Core Samples Yet Pulled From Chesapeake Bay Crater

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Dec 5 11:53:02 2005
Message-ID: <200512051651.jB5GpUF20359_at_zagami.jpl.nasa.gov>

http://home.hamptonroads.com/stories/story.cfm?story=96415&ran=187009

Deepest core samples yet pulled from Bay crater
By DIANE TENNANT
The Virginian-Pilot
December 5, 2005

An attempt to drill more than a mile into an ancient impact crater under
the Chesapeake Bay ended Sunday morning, a little short of the goal.

Rock samples from 5,795 feet below ground were pulled from the ground at
about 7:45 a.m. Scientists from the U.S. Geological Survey endured
gusting winds and rain to collect the last of the boxes of core samples
- tubes of rock and sediment - that will be studied in labs around the
world.

"I think it's a clear success," said Greg Gohn of the USGS, one of four
principal investigators .

The drilling project, in the soybean fields of a privately owned farm
north of Cape Charles, was the deepest look ever taken into the
Chesapeake Bay impact crater, which was created 35 million years ago,
when an asteroid or comet traveling between 15 and 40 miles per second
slammed into a shallow sea that covered much of the East Coast. The
resulting crater is at least a mile deep and about 56 miles across. The
center lies under Cape Charles, and the edges lie under parts of Norfolk
and Virginia Beach, the Peninsula and the Middle Peninsula.

Studies on the crater have focused largely on groundwater. The crater
disrupts the normal layers of freshwater aquifers in the region, either
trapping saltwater or allowing it to penetrate farther inland than would
be expected.

Eight holes had already been drilled into outer parts of the crater to
collect core samples. The deepest of those was 2,699 feet, less than
half of the latest effort, which had aimed for 7,218 feet.

Seven science teams and 118 scientists from around the world are
involved in the project. The teams plan to examine such things as
immediate environmental effects of the impact, long-term effects and
geophysics such as temperature and density of rocks. Biologists also are
searching for microbes that can survive extreme conditions.

It is believed that when the crater formed, tsunamis topped the
Appalachian Mountains and bounced off Europe, wildfires raged along the
East Coast and sand was melted into glass beads that were carried
thousands of miles away by the wind.

Drilling began in mid-September and ran 24 hours a day for nearly three
months. When it ended, it was 1,423 feet short of the goal. Several
hundred feet of granite slowed the drillers.

Still, scientists were pleased with the results. The crater is buried
beneath more than 1,000 feet of sediment at that location. Samples were
taken of those sediments as well as rock that was melted by the heat of
the impact, found at more than 4,000 feet under ground.

The last core brought to the surface contained pegmatite, a rock that is
similar to granite but full of large crystals of quartz, garnet and
other minerals.

The deep drilling project was funded in part by the International
Continental Scientific Drilling Program, a consortium of science
agencies in 13 countries, including China, Canada, Germany and South
Africa. In the United States, the National Science Foundation is the
funding partner.

Analysis of the samples is expected to take months . The first results
will probably be published in scientific journals 12 to 18 months from now.
Received on Mon 05 Dec 2005 11:51:26 AM PST