Two distinct sediment layers have formed in the lake every summer and winter over tens of thousands of years.
The researchers collected roughly 70-metre core samples from the lake and painstakingly counted the layers to come up with a direct record stretching back 52,000 years.
Although it sometimes requires taking minute samples of an object, even that damage may be unacceptable for some artifacts.
In conventional dating methods, scientists remove a small sample from an object, such as a cloth or bone fragment.Various geologic, atmospheric and solar processes can influence atmospheric carbon-14 levels.Since the 1960s, scientists have started accounting for the variations by calibrating the clock against the known ages of tree rings.Funding for this project is provided by the National Science Foundation, the National Center for Preservation Technology and Training, and Texas A&M University. With more than 161,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. The American Chemical Society is a nonprofit organization chartered by the U.
Marine records, such as corals, have been used to push farther back in time, but these are less robust because levels of carbon-14 in the atmosphere and the ocean are not identical and tend shift with changes in ocean circulation.