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Efforts will map ridge in Lake Huron

June 3, 2010
Patty Ramus

The Thunder Bay National Marine Sanctuary and the University of Michigan have been collaborating to conduct sonar mapping of a ridge in Lake Huron, as part of a U-M research project that involves looking for evidence of early hunters at the lake bottom.

Since Thursday of last week, National Oceanic and Atmospheric Administration personnel, sanctuary staff and researchers from U-M have been conducting multi-beam sonar mapping of the the Alpena-Amberley Ridge about 60 miles off shore near the Canadian border. The data collected will be developed into a detailed map of the lake bottom and this information will be utilized for a variety of purposes by U-M, the sanctuary and other agencies, said John O'Shea, U-M professor of anthropology.

According to O'Shea, the overall project is focused on the Alpena-Amberley Ridge which is a geological formation that stretches across Lake Huron and is roughly 10 miles wide. Between 7,500 and 9,900 years ago this feature would have been dry land and divided the Lake Huron basin into two distinct lakes, with the lake levels themselves being about 300 feet lower than the present day.

The researchers hypothesized the ridge would have provided a corridor for caribou migration and early hunters would set up near the ridge to ambush them during their migrations. In the arctic, stone constructions have been found that were erected by caribou hunters to channel animals into certain kill areas. The researchers decided to explore the lake bottom to look for evidence of these hunters.

"We got some high risk research funding ... from the (National Science Foundation) to do some initial work and we actually found a series of structures that are virtually identical to what you see in the arctic," O'Shea said.

Their initial findings were published by the Proceedings of the National Academy of Sciences in April 2009. U-M began talking with the marine sanctuary about conducting a multi-beam sonar survey to create the detailed map. Several people, in particular state and federal fisheries researchers, are interested in the data. The fisheries researchers would be able to use it as they build new models for predicting fish populations, O'Shea said.

"There will be a lot of uses beyond archaeology," he said.

The sanctuary and U-M received a joint grant through the NOAA ocean exploration program to conduct the survey and process the data. The area being surveyed is in the sanctuary's potential boundary expansion area and there's a potential for finding new sinkholes or shipwrecks, which is part of the sanctuary's interest in the data, said Russ Green, sanctuary deputy superintendent.

"The sanctuary just... wants a map of this area so we kind of know what's out there and what the topography's like," he said.

Green said the sanctuary has contracted with a company to process the data. O'Shea said once the data has been processed the researchers will begin to determine if there are any intact occupation sites. They plan to do more work with underwater remotely operated vehicles and work with the sanctuary to include divers on key targets later this summer. The sonar mapping is expected to be completed on Monday.

"It's a long-term project and there are a lot of layers to it," O'Shea said.

Patty Ramus can be reached via e-mail at or by phone at 358-5687.



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