Researchers find 'needle in a haystack' as lakebed yields microscopic clues about submerged archeological sites
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After drilling for clues under the bed
of a lake in south-eastern Ontario, a McMaster researcher has turned
up evidence of human activity that has been submerged since water
covered it thousands of years ago.
Lisa Sonnenburg, an instructor in the School of Geography & Earth
Sciences, led a team that found tiny flakes of stone left behind in
tool making that took place on land that now forms part of the bottom
of Rice Lake, near Peterborough, Ontario.
The discovery is significant because it represents the first use of
such accumulations of stone chips, called microdebitage, to pinpoint
underwater archeological sites.
"I was excited when I first saw it under the microscope, but of
I had to make sure I was seeing what I was actually seeing," says
Sonnenburg. "Everyone had told me, 'You're not going to find anything.
You're looking for a needle in a haystack.' Lo and behold, we found
the needle in the haystack."
Sonnenburg collaborated with colleagues Joe Boyce and Ed Reinhardt,
also of the School of Geography and Earth Sciences. Their research, is
published online in the journal Geology.
Water levels at Rice Lake have fallen and risen in the 10,000 years
since the glaciers receded, Sonnenburg explains. Once the ice was
gone, the lake became a magnet for human settlement, and today its
shores are rich in archeological evidence.
Sonnenburg said researchers at nearby dry-land sites such as
Mounds had suggested it was possible that settlements had existed on
adjacent land that was later flooded.
She and her team first mapped out the lakebed using scanning
technology to search for likely sites.
Then they drilled out and carefully examined 16 core samples taken
from selected points around a 10 km section of the lake.
In three of the core samples, they discovered small flakes of stone
tiny deposits with large implications. Under an electron microscope,
the fragments showed the marks of being worked by humans, suggesting
the flakes had come from tool making, and establishing microdebitage
as a new source of evidence in underwater archeology.
This summer, Sonnenburg is using similar methods as she
in a larger project that is mapping underwater structures in Lake
Huron, also believed to have been used by humans before they were
McMaster University, one of four Canadian universities listed among
the Top 100 universities in the world, is renowned for its innovation
in both learning and discovery. It has a student population of 23,000,
and more than 140,000 alumni in 128 countries.
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