These isochron “ages” range from 841.5±164 Ma (whole-rock K-Ar) to 1375±170 Ma (mineral Sm-Nd).Each method appears to yield concordant “ages” internally between whole rocks and minerals. It is therefore argued that only changing radioisotope decay rates in the past could account for these discordant isochron “ages” for the same geologic event. Furthermore, these data are consistent with alpha decay having been
accelerated more than beta decay, and with the longer the present half-life
the greater being the acceleration factor.
When a whole rock isochron
and a mineral isochron agree, one has very strong evidence that the system
has not been disturbed and that the isotopic date is genuine.But there are still disagreements between