Methods in high-precision geochronology

U-Pb isotope dilution thermal ionization mass spectrometry (ID-TIMS) geochronology is often coined the "gold-standard" in geochronology. This is because 1) the decay constants of U are better known than any other long-lived parent nuclide, 2) the dual decay of 238U and 235U allow the evaluation of closed-system behavior, 3) because the standard, or tracer, against which ages are calculated can be calibrated with high precision and accuracy, and 4) because the mass spectrometry can be carried out with a high degree of precision and accuracy. Despite these benefits, there are significant improvements being made to both the U-Pb ID-TIMS method and its intercalibration with other dating methods. Much of my own work in this regard has been carried out as part of the NSF-funded EARTHTIME network, whose goals are (in part) to forge a community based initiattive arriving at intercalibration between different dating methods at the 0.1% level or better. Details of this initiative can be found here: