Radiometric dating of detrital minerals in sedimentary rocks gives
Nontechnical readers can skip the box-figures, however, without losing much.
Experimental Errors The methods that give ancient ages produce almost as many "wrong" answers as "right" ones.
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.
And, of course, the public doesn't usually hear of these wrong answers.
In almost every case of a discrepancy, the fossil dates were accepted as correct. Woodmorappe quoted one researcher as saying: In general, dates in the 'correct ball park' are assumed to be correct and are published, but those in disagreement with other data are seldom published nor are discrepancies fully explained.2 When these reports did discuss the possible causes of errors, they used words such as "possibly," "perhaps," "probably," "may have been," etc.
Most radiometric arguments were said to favor the 2.6 MY date, but the paleontological arguments favored the 1.8 MY date-(that is where the skull would best fit evolutionary theory).
And final agreement came only after paleontologists had agreed on fossil correlations involving two species of extinct pigs. Commenting on this method of selecting rock samples for radiometric dating, Lubenow asks: The question arises, "How does one know when one has good samples for dating?
Marvin Lubenow gives a good description of the ten years of controversy surrounding the dating of this skull.4 In the first attempt at dating the KBS Tuff, Fitch and Miller analyzed the raw rocks, and got dates ranging from 212 to 230 MY-the Triassic period, vastly older than expected.
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.
One is the Carbon-14 system used for dating fragments of once-living organisms.