The Louisiana State University campus is likely home to the oldest known man-made structures in North America

New research reveals more information about Louisiana Point out University (LSU) campus mounds, including discovery of charred mammal bone fragments thousands of years old and a coordinated alignment of the two mounds towards one of the brightest stars in the night sky. This new information offers greater insight into the oldest known human constructions in North America.

The two large grassy mounds of approximately 20 feet tall, on the LSU campus, are among the tallest 800 man-made hill-like mounds in Louisiana , built by ancient indigenous peoples. While many mounds in the area have been destroyed, the LSU campus mounds have been preserved and are listed on the National Register of Historic Places.

“There is nothing known that is man-made and that ancient that still exists today in North America except for the mounds,” said Professor Emeritus Brooks Ellwood of LSU’s Department of Geology and Geophysics, who has led this study, published in the American Journal of Science by Yale University.

He and his colleagues collected sediment cores from the two mounds located on the LSU campus on extensive from Dalrymple Generate to learn more about them. Cores revealed layers of ash from burnt reeds and canes, as well as burnt osteons. Radiocarbon dating of the layers of material indicates that the mounds were built over thousands of years. These finds show that people started building the first mound about 11 20 year. The scientists believe the sediments from the southern mound, which they named “Mound B,” were taken from a location just behind LSU’s Hill Memorial Library because there is a large depression in the ground. The mound was built over a few thousand years, layer by layer, to about half its current height.

The layers of ash and bone fragments Charred microscopic traces may indicate that the mound was used for ceremonial purposes, including the burning of reeds and sugar cane to make large hot fires that would have been too hot for cooking. Scientists don’t know what kind of mammals were cremated or why. However, they found numerous charred microscopic bone fragments, known as osteons, the building blocks of large mammalian bones, in the ash beds of the two mounds on the LSU campus.

Then, approximately 8 200 years ago, South Mound B was abandoned. Tree roots found in the 8 200 year old sediment layer indicate that the mound was not used for approximately 1 000 year. Also about 8 200 years ago, the northern hemisphere experienced a major climatic event with a sudden drop in average temperatures of about 35 degrees Fahrenheit, which lasted approximately 160 years.

“We don’t know not why they abandoned the mounds approximately 8 200 years ago, but we do know that their environment changed suddenly and dramatically, which may have affected many facets of their daily lives,” Ellwood said.

Then there are approximately 7 500 years ago, the natives began building a new mound just north of the first mound. However, this time they took mud from the floodplain where the entrance to LSU’s Tiger Stadium currently stands, which at the time was an estuary. With this mud, they built the second mound, “Mound A”, layer by layer, up to approximately half of its current height. Mound A contains water-saturated mud, which liquefies when stirred. As a result, mound A is unstable and degrading, which is why it’s essential to stay away from mounds to preserve them.

According to new layer scans of sediments and their age, it appears that the Aboriginal peoples cleared the first abandoned Mound B and began building it to its present height before completing Mound A. Both mounds were completed approximately 6 000 years old and are of similar height.

The crests of the two mounds are aligned along an azimuth that is approximately 8.5 degrees east of true north. According to LSU astronomer and study co-author Geoffrey Clayton, approximately 6 000 years ago, the red giant star Arcturus would rise from ‘about 8.5 degrees east of north in the night sky, which means it would have lined up along the crests of the two mounds on the LSU campus. Arcturus is one of the brightest stars that can be seen from Earth.

“The people who built the mounds, approximately 6 000 years, coordinated the orientation of the buildings to align with Arcturus, seen in the night sky at that time,” Ellwood said.

Yet there is more to learn and discover about these archaeological treasures on the LSU campus.

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