Call for an improved set of decay constants for geochronological use

The accuracy of radioisotopic ages is, at present, limited by the accuracy of radioactive decay constants. A literature survey reveals that decay cons tants used in geo- and cosmochronology usually are assigned uncertainties o f ca. 1% but that then are very much larger unaccounted discrepancies betwe en decay constants reported by different "counting groups" as well as diffe rences between results derived from counting experiments and from the compa rison of ages obtained on the same samples by utilizing different radioacti ve clocks. An extension and partial revision of the decay constants recomme nded in 1976 for adoption in geo- and cosmochronology by the International Union of Geological Sciences (IUGS) appears both desirable and feasible, gi ven the analytical improvements of the last 20 years. We call for a concert ed effort to achieve improvements in the near future. For this it will be n ecessary to rigorously evaluate counting biases in counting determinations, initial daughter contamination for ingrowth experiments, and the existence of truly "point-like" geological events for age comparison approaches. Cop yright (C) 2001 Elsevier Science Ltd.