Explained the mysterious disappearance of the ancient Americans
Scientists from the University of Illinois at Urbana-Champaign and Tulane University in New Orleans studied remains of settlements of the native Americans who lived in the XIII century ad and were builders of mounds.
The researchers believe that the residents left their village, situated on the coast of Louisiana, due to the ingress of salt water into freshwater reservoirs. About it reported in a press release on the website at the University of Illinois.
Ancient people built mounds in North America since 4500 BC. In the XIII century in the lower part of the valley of the Mississippi river formed the culture of Placemen, which mounds had ceremonial significance and were part of temple complexes. Native Americans lived only in areas with access to resource-rich waterways that could support the existence of relatively large settlements. For example, in Grand Caillou, located in the Delta of the Mississippi river, in its heyday, had a population of 500 people, but eventually the place was abandoned.
The researchers conducted radiocarbon and optical Dating and isotopic analysis of samples of sediments and pottery found during archaeological excavations. It turned out that the mounds consist of three layers, wherein the upper and lower clay, and in the middle is less durable ground. This structure makes durable mound. The hill was erected on river sediments, which were about a meter higher than the surrounding land, which also contributed to the preservation of the mound.
The results of Dating of the charcoal showed that the settlers left Grand Caillou around 1400.
Analysis of the ratio of carbon isotopes, it became clear that the area gradually became unfit for human habitation due to the penetration of saline water and declining reserves of fresh water.