Mammoth Site in South Dakota is far older than previously thought
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Researchers in South Dakota re-dated the Mammoth Site, a location containing the remains of over 60 Columbian mammoths, and determined the animals lived over 160,000 years ago.
The site, discovered in 1974, previously had dates suggesting the mammoths died around 26,000 years ago. Jim Mead of Mammoth Site and the University of Arizona questioned these dates, seeking a new method to determine the site’s age.
Traditional radiocarbon dating proved unreliable because the mammoth bones lacked collagen and the bone mineral, apatite, absorbed carbon from groundwater, resetting the age. Scientists then turned to luminescence dating, which measures radiation absorbed by sediment grains since their last exposure to sunlight. They sampled sand surrounding the mammoth remains, finding the feldspar grains within revealed the site was significantly older than previously believed, between 160,000 and 232,000 years old.
The team acknowledges some uncertainty in the dating, noting one sample yielded a result 40,000 years younger than others, and plans to use additional methods like uranium-thorium dating to confirm their findings. Understanding the true age of the Mammoth Site will help researchers reconstruct the environment and evolution of large mammals in the Black Hills region of South Dakota, providing a longer record of the area’s natural history.
The lowest layers of the sinkhole remain unexcavated, potentially holding even more discoveries.
