Potassium argon and argon argon dating
Lava flows that lie above and below rock beds with ancient human fossils are a good—and true—example.The mineral sanidine, the high-temperature form of potassium feldspar, is the most desirable.Results in the potassium-argon dating program at Berkeley are reported.Geologically well-classified authigenic sediments ranging from Miocene (12 m.y.) to Givetian (285 m.y.) have been analyzed utilizing equipment designed to date materials of low radiogenic argon content.
The site also must be geologically meaningful, clearly related to fossil-bearing rocks or other features that need a good date to join the big story.What simplifies things is that potassium is a reactive metal and argon is an inert gas: Potassium is always tightly locked up in minerals whereas argon is not part of any minerals. So assuming that no air gets into a mineral grain when it first forms, it has zero argon content.