The vault.
The sediments at the bottom of the lake in Northen Quebec's Pingualuit Crater hold unmatched clues to North America's climate record.
Credit: Robert Fréchette / ARK; (inset) University of Arkansas
Posted on 12/15/2007 3:43:24 PM PST by neverdem
The vault.
The sediments at the bottom of the lake in Northen Quebec's Pingualuit Crater hold unmatched clues to North America's climate record.
Credit: Robert Fréchette / ARK; (inset) University of Arkansas
SAN FRANCISCO, CALIFORNIA--A million years ago, a large meteorite smashed into what is now northern Quebec and created a crater that may become an unprecedented repository of data with which to study long-term climate change, researchers reported here this week at a meeting of the American Geophysical Union.
Canada and the northern United States are dotted with tens of thousands of lakes, most of them formed by meltwater at the end of the last ice age about 12,000 years ago. Sediments at the bottom of those lakes hold chemical and biological evidence of how the planet's climate has varied for even longer periods, over many ice ages and interglacial cycles, and how those variations have affected the local ecosystems. But almost all of these sediments have been bulldozed repeatedly by glaciers as the giant rivers of ice have advanced and retreated over the last 2 million years, scrambling the geological record.
Pingualuit Crater in northern Quebec seems to have escaped this fate. Its 3.7-kilometer-wide, nearly circular lake not only is deep enough--nearly 270 meters--to have avoided the glacial pummeling but also has remained sequestered from any other body of water during its entire history. So the sediment that has collected on the lake's bottom has preserved a pristine record of the climate and biological activity in the lake for more than a million years--much longer than any similar climate data source currently available. Until recently, however, the technology necessary to retrieve samples from the bottom, without disturbing the samples or contaminating the lake's ultraclear water, did not exist.
So, paleolimnologist Sonja Hausmann of the University of Arkansas, Fayetteville, and colleagues employed a new type of coring rig devised specifically for obtaining delicate samples. Last May, after trekking across the then-frozen lake on foot without the aid of potentially polluting snowmobiles or sled dogs, the team deployed the bottom-dwelling rig, which is suspended from a Kevlar cable, and spent 2 weeks carefully extracting cores from the top 10 meters of Pingualuit's estimated 150 meters of sediment. Those samples are beginning to provide a treasure trove of data going back at least 250,000 years.
"We think the samples span at least two [interglacial] cycles," Hausmann says. They include diatoms--microscopic algae whose silicate shells can provide exquisite historical portraits of the lake's water quality and climatic conditions--as well as trace metals and pollen that have fallen from the atmosphere. Other records can be compiled from sources such as the ice cores in Greenland and the sea beds, she says, but the Pingualuit cores are the only ones available from the North American land that contain the skeletal remains of climate-sensitive algae.
"Collecting this core was no small endeavor," says paleolimnologist John Smol of Queen's University in Kingston, Canada. "Many of us had previously assumed that the last Ice Age had obliterated older sediment records," he says, but Pingualuit's cores show that "there is a remarkable history book still present."
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CC/GW potential seems very interesting.
Wow! What a cool lake!
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I am surprised the global warmers don’t use the melting of the glaciers over the great lakes region just 14,000 years ago as evidence of man made global warming.
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Seems to me that glaciers would have pushed debris into the lake despite the fact they didn’t scour the bottom.
Wow I have dived and swam some blue holes before yet never seen such a large ice hole........but then we are talking global warming an AlGore......:o)
Isn’t this the same region that is infested with diamond mines ?
That is a strange looking structure. Must have been buried in ice or sediment that disappeared when the glacier moved on.
This one does kind of jump up and down yelling "I'm a meteorite impact!", doesn't it?
That’s right, unless the crater was blown right through the ice and the lip was too substantial for the ice to climb over so it flowed around instead.
The only other thing I can think of is pretty unlikely. The center of the outflow of glacial ice would need to be dead center over the lake.
Lakes here in the permafrost develop from sinkholes and fill in from dust and various living things. That crater appears to have been covered to considerable depth and the soil is now in Indiana after the glacier melted leaving bedrock. It has been exposed for much too short a time for erosion or vegetation to do serious work.
There have been about 8 major warm/cool cycles, but many smaller ones. The earth changes quite a lot. Every time a major volcano erupts [Tambora, Toba, Katmai], a meteor strikes like the dinosaurs 65 mya.
Thanks for posting. I’ve never heard of the lake nor the coring project. It will be very interesting to see the results of their research.
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