Ancient mounds in America

In the middle of Louisiana State University’s campus stand two earthen mounds, each c.5.5m tall. The LSU Campus Mounds have long been known to be among the c.800 mounds created by ancient indigenous communities in this region, but archaeological investigations recently published in the American Journal of Science ( have shed new light on the history of their construction, and revealed that one of them may be the earliest known man-made structure in the Americas still standing today. By collecting and dating sediment cores from both mounds, researchers were able to discover that construction first began on the southern mound (Mound B) as early as c.11,000 years ago, with the creation of Mound A starting later, c.9,500 years ago, and work on both mounds continuing in multiple phases over several millennia.

Layers of ash from burnt reed and cane plants as well as burnt mammal bones identified in the sediment cores indicate that the mounds were the site of a series of large, hot fires – too hot for cooking – which were probably associated with ceremonial or cremation activities. The researchers also noted that the crests of the two mounds were built on an alignment close to 8° east of north, corresponding, perhaps deliberately, to the point where one of the brightest stars in the night sky, Arcturus, may have risen above the horizon c.7,600 years ago, during the mounds’ final phases of construction (c.8,000 to c.5,500 years ago).

Images: LSU
Text: Amy Brunskill 
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