Eos, Transactions American Geophysical Union

Polonium halos



I welcome York's contribution [York, 1979] to the exchange of views concerning the possible existence and potential cosmological implications of polonium halos in Precambrian granites [Damon, 1979; Gentry, 1979], but I must take exception to some omissions from his comments about my results on Po halos.

York seems to regard even the existence of Po halos as only tentative. But notwithstanding the uncertainties, his article leans heavily toward the proposition that Po halos do exist, at least in micas. York's thesis is that Po halos are most probably explainable within the accepted framework because the interlocking nature of various radiometric dating techniques provides powerful evidence that conventional geochronology is correct. York faults me for ignoring this internal consistency. Contrary to his understanding, I do not ignore these data. But neither do I accept the idea that the presumed agreement between techniques is really coercive evidence for the correctness of the uniformitarian assumption which undergirds the present model. There was no discussion of the 238U206Pb ratios [Gentry et al., 1976], which raise significant questions about the accepted geochronological scheme.