Argon argon dating
Our editors will review what you’ve submitted and determine whether to revise the article.
Join Britannica's Publishing Partner Program and our community of experts to gain a global audience for your work! This dating method is based upon the decay of radioactive potassium-40 to radioactive argon-40 in minerals and rocks; potassium-40 also decays to calcium-40.
It has also been indispensable in other early east African sites with a history of volcanic activity such as Hadar, Ethiopia.
The K-Ar method continues to have utility in dating clay mineral diagenesis.
For shorter timescales, it is likely that not enough Argon 40 will have had time to accumulate in order to be accurately measurable.
K-Ar dating was instrumental in the development of the geomagnetic polarity time scale.
Both flame photometry and mass spectrometry are destructive tests, so particular care is needed to ensure that the aliquots used are truly representative of the sample.
One archeological application has been in bracketing the age of archeological deposits at Olduvai Gorge by dating lava flows above and below the deposits.In these materials, the decay product Ar is not trapped by the rock while it is liquid (molten), but starts to accumulate when the rock solidifies (recrystallises).