Project Details Recommendations for Isotope Data in the Geosciences-II

Project No.:
Start Date:
01 October 2013
End Date:


Update and harmonize recommendations on decay constants (half-lives) and radioactive isotopes. Resolve issues dealing with the definition of the year with representatives of the IUPAP, BIPM and IAU.

See earlier project 2006-016-1-200


The inter-Union project “Recommendations for isotope Data in the Geosciences-II”(RIDIG2) strives to provide an authoritative recommendation based on a critical reevaluation of data on half-lives and decay schemes of long-lived radioactive nuclides used by the geological and planetary science communities. Uncertainty analyses will follow ISO/GUM procedures. A specific goal of the project is reconcile current inconsistencies between values used in geological and planetary science on the one hand and those used in the nuclear physics and chemistry communities on the other. Phase II (2013-2015) focuses on these four nuclides used in geochronology 40K, 87Rb, 176Lu and 187Re.

The previous publication in PAC (2011, Vol. 83, No. 5, pp. 1159-1162; on the definition of the year raised issues, which are under continuing discussion with Stephen Lea (IUPAP), Felicitas Arias (BIPM) and Nicole Capitaine (IAU).

The Joint International Union of Geological Sciences (IUGS)/IUPAC Task Group on Isotope Geochronology recommends isotope data in the geosciences. It deals with the evaluation of radioactive half-life data for long-lived nuclides that are used for the geological dating of materials. It is also working to resolve issues dealing with the definition of the year with representatives of the BIPM, IUPAP and the IAU.


Feb 2020 update – The Task Group is presently working on the evaluation of data on the two isotopes of samarium which are most relevant for geochronological applications, namely 146Sm and 147Sm. A draft report on the recommendations has been prepared. After a considerable length of time, the reviews of the samarium manuscript are back. Editorial discussions with the Geochimica et Cosmochimica Acta journal are underway at present.

Page last update 21 Feb 2020