Potassium argon dating advantages
Due to the long half-life, the technique is most applicable for dating minerals and rocks more than 100,000 years old.For shorter timescales, it is unlikely that enough argon-40 will have had time to accumulate in order to be accurately measurable.One archeological application has been in bracketing the age of archeological deposits at Olduvai Gorge by dating lava flows above and below the deposits.
The geomagnetic polarity time scale was calibrated largely using K–Ar dating.
Ar atoms are able to diffuse through and escape from molten magma because most crystals have melted and the atoms are no longer trapped.
Entrained argon—diffused argon that fails to escape from the magma—may again become trapped in crystals when magma cools to become solid rock again.
Potassium is a common element found in many materials, such as micas, clay minerals, tephra, and evaporites.
In these materials, the decay product Ar is able to escape the liquid (molten) rock, but starts to accumulate when the rock solidifies (recrystallizes).