30 JANUARY 2023 WorldWide Drilling Resource® Sediment Cores Reveal Louisiana State University Campus Mounds to be Oldest Man-Made Structures in North America Adapted from Information by Louisiana State University (LSU) On LSU’s campus in Baton Rouge, two large grassy mounds about 20 feet tall are among more than 800 man-made, hill-like mounds built by ancient indigenous people in Louisiana. While many mounds in the region have been destroyed, the LSU Campus Mounds have been preserved and are listed on the National Register of Historic Places. A new study revealed more information about these mounds and offered insights about the structures’ long history. “There’s nothing known that is man-made and this old still in existence today in North America, except the mounds,” said LSU Department of Geology and Geophysics Professor Emeritus Brooks Ellwood, who led this study. Ellwood and colleagues collected sediment cores from the mounds to learn more about them. The cores revealed layers of ash from burned reed and cane plants, as well as burned mammal bones. Radiocarbon dating of the layers of material indicated the mounds were built over thousands of years. These findings show people began to build the first mound about 11,000 years ago. Scientists believe sediment for the southern mound, which they’ve named “Mound B,” was taken from a location immediately behind LSU’s Hill Memorial Library, because there is a large depression in the ground there. The mound was built up over a few thousand years, layer by layer, to about half of its current height. Layers of ash and tiny pieces of mammal bones may indicate the mound was used for ceremonial purposes, which included burning reed and cane plants to make large, hot fires that would have been too hot for cooking. Scientists are not certain what type of mammals were cremated or why; however, they found many microscopic, charred bone fragments, known as osteons, the building blocks of large mammal bones, in the ash beds in both of the LSU Campus Mounds. Around 8200 years ago, Mound B was abandoned. Tree roots found in the 8200-year-old sediment layer indicate the mound was not used for about 1000 years. Around the same time, the northern hemisphere experienced a major climate event with temperatures suddenly dropping on average by about 35 degrees Fahrenheit, which lasted about 160 years. “We don’t know why they abandoned the mounds around 8200 years ago, but we do know their environment changed suddenly and dramatically, which may have affected many aspects of their daily life,” explained Ellwood. Then, around 7500 years ago, indigenous people began to build a new mound just to the north of the first mound. However, this time, they took mud from the floodplain where the entrance to LSU’s Tiger Stadium is currently located, which at that time was an estuary. With this mud, they built the second mound, “MoundA,” layer by layer, to about half of its current height. MoundAcontains mud saturated with water, which liquefies when agitated. As a result, Mound A is unstable and degrading, which is why it is critical to stay off the mounds to preserve them. According to new analyses of sediment layers and their ages, it looks like indigenous people cleared the abandoned first-built Mound B and began to build it up to its current height before ENV Sediment Cont’d on page 32. Blasting by: The Southern African Institute of Mining and Metallurgy Drilling and Blasting Short Course February 22-23 ~ ONLINE phone: +27-11-538-0237 www.saimm.co.za Foundations by: The International Association of Foundation Drilling (ADSC) Super T School February 14-16 ~ Southlake, TX phone: 469-359-6000 www.adsc-iafd.com Education Connection by: Pile Driving Contractors Assn & Pile Dynamics, Inc. Seminar on Deep Foundation Integrity Testing and Wave Equation Analysis February 27 ~ Orlando, FL High Strain Dynamic Foundation Testing Workshop & Proficiency Test February 28 & March 1 ~ Orlando, FL phone: 904-215-4771 www.piledrivers.org More education opportunities during events can be found by clicking here online at: worldwidedrillingresource.com
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