[3] In late 2009, the journal Radiocarbon announced agreement on the INTCAL09 standard, which extends a more accurate calibration curve to 50,000 years.

[4][5] The results of research on varves in Lake Suigetsu, Japan announced in 2012 realised this aim.

"It also allows us to look at the differences between the atmosphere and oceans and study the implications for our understanding of the marine environment as part of the global carbon cycle.

[9] The water is anoxic (deoxygenated) preventing the growth of organisms and due to seasonal variations it is usually but not always possible to distinguish the annual deposits visually.

It has taken almost twenty years to overcome the consequent problems, using multiple cores and new detection techniques to complete the sequence.