Lava flows that lie above and below rock beds with ancient human fossils are a good—and true—example.
This work was supported in part by AEC contract number AT(11-1)-101 and in part by National Science Foundation grant number G-208.
Any alteration or fracturing means that the potassium or the argon or both have been disturbed.
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.
Geologists have used this method to date rocks as much as 4 billion years old.
It is based on the fact that some of the radioactive isotope of Potassium, Potassium-40 (K-40) ,decays to the gas Argon as Argon-40 (Ar-40).
It has been proposed that significant core radioactivity (1-2 TW) may be caused by high levels of U, Th, and K.
ABSTRACT: Electromagnetic surveys of the crust and upper mantle underlying the Western Canada Sedimentary Basin have revealed two conductivity anomalies that are arguably related to Paleoproterozoic tectonic processes, recording a signature diagnostic of euxinic (foreland?
) basin succession and perhaps defining a deep-marine transtensional basin.
For every 100 K-40 atoms that decay, 11 become Ar-40.
It makes up 0.012% (120 ppm) of the total amount of potassium found in nature.