Before the publication of this new research, the longest and most important radiocarbon dating records came from such marine sediments or cave formations, but these needed to be corrected.

At last, the cores from Lake Suigetsu provide a more complete, direct record of radiocarbon from the atmosphere without the need for further correction.

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'Such changes can be very significant when you are trying to examine human responses to climate that are often dated by other methods, such as through layer counting from the Greenland ice cores.

For the first time we have a more accurate calibrated time-scale, which will allow us to answer questions in archaeology that we have not had the resolution to address before.' ________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________ Generally, researchers use a composite record called Int Cal to determine the ages of objects, based on their radiocarbon measurements.

'In most cases the radiocarbon levels deduced from marine and other records have not been too far wrong.

However, having a truly terrestrial record gives us better resolution and confidence in radiocarbon dating,' said Professor Ramsey.

In the field, you get to help excavate the Haynie site, a Chaco outlier, with two Chaco-period great houses.

In the lab, you will handle thousand-year-old artifacts and help us understand a defining time in Pueblo Indian culture.

Many of the layers were too fine to be distinguished by the naked eye, so the researchers used a microscope, as well as a method called X-ray fluorescence that identifies chemical changes along the core.

A record of year-to-year changes in radiocarbon levels in the atmosphere, such as those found in a sediment core, must be 'anchored' in time by assigning some part of it an absolute age.

At least some of the articles have been updated or revised specifically for the Discovery edition.