A team of researchers collected soil samples from LSU’s Campus Mounds Monday to conduct dating tests that could resolve the long-standing debate about their age.
The project employs optically stimulated luminescence, a method never before used on the mounds, to determine when grains of sand were last exposed to sunlight.
Led by LSU doctoral student Reilly Corkran, the team includes state archaeologist Chip McGimsey, Tad Britt from the National Park Service and specialists in soil science and geology from LSU and beyond.
Researchers drilled two cores into each mound using 2.5-inch barrels to extract sediment layers, ensuring the process would not harm the structures.
“One core goes all the way to the bottom,” McGimsey said. “If you can get a sample from the surface where they were starting to build the mounds that would give you a good idea of exactly when mound construction started.”
Britt, the chief of archeology at the NPS National Center for Preservation Technology and Training explained, “When they dumped a basket of soil while building the mounds and covered up the next layer, they were setting the clock.”
Samples will be sent to a lab in the Netherlands, where geochronologist Liz Chamberlain will conduct OSL analysis. OSL could confirm whether the structures are as old as 11,000 years — a claim made by LSU researcher Brooks Ellwood.
“The controversy is that, while this is one of the earliest man-made structures in the Americas, there is a discrepancy over the date,” Britt said. “In the ’80s, ’90s and 2000s, most of the dates came out to about 6,000 years ago. Brooks Ellwood analyzed cores … and deduced that the mounds were actually 11,000 years old.”
In addition to dating the mounds, the project aims to reconstruct the ancient environment of the Gulf Coast.
“The landscape has changed dramatically from then,” Britt said. “We’re trying to recreate what the landscape looked like before they built the mounds up through today.”
The team, including LSU geomorphologist Korey Konsoer and University of Kansas geoarchaeologist Rolfe Mandel, will analyze particles in the recovered soil, such as pollen and grain size, to piece together the environmental history and further understand the site’s landscape.
Their aim is to not only pinpoint the mounds’ age but also paint a clearer picture of the lives and activities of their builders.
“Much like the stadium, this is a ceremonial place where people would have gathered,” Britt said.
While the Chitimacha Tribe of Louisiana is integral to the project, according to Britt, they could not be present on site.
