A team of archaeologists uncover what might be the oldest intact site of human activity on two continents, located near Walker (Minnesota, USA). Thor Olmanson is director of the Leech Lake Heritage Sites program and is the project's principal investigator. This fall, he and David Mather, National Register Archaeologist for the state's Historic Preservation Office, invited geologists, soil scientists, fellow archaeologists and other scientists to investigate the site. "As the natural response is skepticism, everyone who came was ready to debunk the site," said Olmanson. "And, so far, they have left convinced that this is something different, something that needs to be looked at more closely" he said.
     As the glaciers began to recede, approximately 15,000 years ago, an ice-free "oasis" developed in this part of the state. There was an access from the southeast to this relatively stable environment which was habitable at least part of the year, although surrounded by glaciers. The ancient people visiting the site near Walker probably consisted of extended family groups, often up to 15 individuals, Olmanson explained. They selected certain types of stones, flaked off just enough from the pebbles and cobbles to make sharp tools. They used the tools to prepare plants for food as well as the animals that they had killed or scavenged. Organic materials they used, such as bone, wood, and fibers, have not survived.
     A dense lens lies beneath today's land surface and effectively capped or 'encapsulated' the debris that the group of hunters left behind. After the glaciers melted, the area became dry and warm. Winds deposited fine sand atop of the glacial materials. Over the centuries, the debris left at the site was covered, and left intact, until it was discovered by chance.
     Because no organic materials, such as bone, appear to have survived in the acidic soils at the site, conventional carbon dating of the site is not possible. The preliminary dating of the site is based on the location of the stone tools within the glacial deposits. Future work should include use of other absolute dating methods are possible, recommended Colleen Wells, field director for the Leech Lake Heritage Sites program. Wells proposes using a dating technique known as Optically Stimulated Luminescence (OSL) which measures the last time that buried sand grains were exposed to sunlight.
     The excavation is carried by a full crew of archaeologists, geologists and field staff. This year, a group from Oxford University is visiting. Twelve lucky people were selected through annual lottery to help the working archaeologists continue the excavation of the site.
     
Source: The Pilot-Independent (24 January 2007)