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Rice Lake, Ontario, Canada. Image: Atkinson, Creative Commons Attribution-ShareAlike 3.0 License.Rice Lake, Ontario, Canada. Image: Atkinson, Creative Commons Attribution-ShareAlike 3.0 License.

Canadian lake yields microscopic clues about submerged archaeological sites

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After drilling for evidence 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 recovered tiny flakes of stone left behind in tool making which took place on dry land that now lies beneath the waters of Rice Lake, near Peterborough, Ontario.

The discovery is significant because it represents the first use of utilising  geological coring and microdebitage collection, to pinpoint underwater archaeological sites.

Micro-debitage is evidence of human activity; in this case, flakes of quartz resulting from making stone tools.  More than 150 flakes found in core samples provide evidence of paleo-Indian activity in the area 9,000 years ago.

Images of microdebitage from the cores (image: Lisa Sonnenburg)

Images of microdebitage and comparitive material from the cores. 1. Microdebitage from McIntyre Site. 2. Microdebitage from RIL 10 3. Experimental obsidian microdebitage 4. Close-up of microdebitage showing feathered edges and unidirectional striations 5. Close-up of microdebitage showing thinned edge and unidirectional conchoidal fractures 6. Close-up of microdebitage showing thinned edge, and unidirectional striations 7. Naturally occurring angular quartz grain from RIL 10 8. Naturally occurring angular quartz grain from RIL 10 9. Naturally occurring angular quartz grain from RIL 10 (image: Lisa Sonnenburg)

“I was excited when I first saw it under the microscope, but of course 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.’ … 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 archaeological evidence.

Coring on the lake. Dr. Joe Boyce, Dr. Ed Reinhardt and Gillian Krezoski (MSc) of the School of Geography and Earth Sciences. (image: Lisa Sonnenburg)

Coring on the lake. Dr. Joe Boyce, Dr. Ed Reinhardt and Gillian Krezoski (MSc) of the School of Geography and Earth Sciences. (image: Lisa Sonnenburg)

Sonnenburg said researchers at nearby dry-land sites such as Serpent Mounds had suggested it was possible that settlements had existed on adjacent land that was later flooded. She and her team first mapped 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 huge 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 archaeology.

This summer, Sonnenburg is using similar methods as she participates in a larger project that is mapping underwater structures in Lake Huron, in areas also believed to have been used by humans before they were submerged.

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