Using a new application of absolute dating technology, Michigan State University researchers found Lake Michigan’s northern coastal dunes to be younger than previously thought.
In a new book by William Lovis, MSU Museum curator, Alan Arbogast, MSU geography chair, and G. William Monaghan, Indiana University geoarchaeologist, new evidence estimates that the major interval of dune building along Lake Michigan’s northern coast occurred between 3,500 and 2,000 years old. This is compared to eastern Lake Michigan’s southern dunes, which began to form about 5,000 years ago.
Using traditional radiocarbon dating of the northern dunes wasn’t a viable option because organic material left in the sand was limited. OSL dating, however, accurately determines when sand grains were last exposed to light or when they were buried in the growing dunes. Using Optically Stimulated Luminescence dating, they were able to come up with the improved age estimate.
Dunes harbor an abundance of quartz grains, which contain micro-fissures, tiny cracks that trap electrons released from decaying radioactive isotopes. Knowing this fact, the team kept quartz-rich sand samples in the dark and re-exposed them to light in order to measure radioactivity in the quartz and date how long the sand had been buried.
“This was truly an interdisciplinary team effort, and we’re excited to have this technique in our toolbox,” Arbogast said.
Along with new data on Michigan dunes’ age, the study showed a significant dune growth period occurring as recently as 1,000 years ago. The results have given archaeologists insight into how archaeological sites are buried and preserved along Lake Michigan, as well as provided a better understanding of dune management throughout the Great Lakes
Future research hopes to answer why so few dunes exist from 5,000 years ago, why the dunes were active during the specific period 1,000 years ago and how climate change will impact dunes.
The book, “The Geoarchaeology of Lake Michigan Coastal Dunes,” was published by the Michigan Department of Transportation through Michigan State University Press.