Creation rock dating
Other measurements, some as low as 0.5 MY, were said to be anomalously young.
These were explained as possible overprinting by an alkaline-rich hot water infusion.
One is the Carbon-14 system used for dating fragments of once-living organisms.
It's never used for non-organic samples, and almost never even attempted if the sample is thought to be much older than about 50,000 years.
Because mammal bones had been found below this stratum, they said these dates were obviously in error because of "the possible presence of extraneous argon derived from inclusions of pre-existing rocks." Even though the rock looked good, anything older than 5 MY was obviously wrong in view of their knowledge of the "sequence of evolutionary development." Meanwhile a team from the University of California at Berkeley, led by G. Curtis, analyzed several KBS pumice rocks and found some that were around 1.6 MY and some that were about 1.8 MY.
Reasons given usually involved detrital intrusion, leakage or leaching of some of the isotopes in the sample, and sometimes the initial isotopic content of the sample.
For K-Ar dates, it's easy to blame argon loss if the reported age is too short, or argon absorption if it's too long.
Studies have been made of submarine basalt rocks of known recent age near Hawaii. Yet it was found beneath a layer of the volcanic KBS Tuff that had an accepted radiometric date of 2.6 MY (millions of years old).
Leakey declared that the skull was 2.9 MY, and said that it "fits no previous models of human beginnings." It was named KNM-ER-1470 (for Kenya National Museum, East Rudolf, #1470).