High-precision Intercalibration of U-Pb and Ar-Ar geochronometers
22 Oct 04 - 24 Oct 04- Endicott House, MIT, Dedham, MA

Convened by:
Samuel A. Bowring (MIT)
Paul R. Renne (Berkeley Geochronology Center and UC Berkeley)
Randall Parrish (NIGL, UK)
Introduction to the Theme of the Workshop
In the past five years, the precision of both 40Ar/39Ar and U-Pb geochronology has steadily improved with recent advances potentially allowing us to address questions previously out of reach. There is great potential for the application of these techniques to determining accurate and precise absolute ages thus yielding previously unattainable insights into rates of geological processes and the development of a fully consistent, robust and highly resolved geological timescale. It is now common in modern laboratories to determine both 40Ar/39Ar and U-Pb dates to 0.1% precision or better when not considering external sources of error. However, given the significantly improved analysis, interlaboratory and inter-decay-scheme differences are now clearly apparent, in some cases being more than 1%, e.g., several million years in the mid-Paleozoic. These discrepancies can lead to major uncertainties when comparing dates obtained using the two systems, which in turn can lead to incorrect geological inferences, for example the potential linking of extinction events with geological events or bolide impacts. With the proposed advent of the EARTHTIME project as a mechanism for developing a highly calibrated timescale in the next decade, it is essential that our community make a serious effort to eliminate interlaboratory bias and reducing systematic errors by: 1) developing a standardized set of analytical protocols; and 2) establishing a widely agreed upon set of mineral and isotopic standards for interlaboratory comparison; such an approach will permit the full evaluation of inter-decay-scheme bias and allow for the confident integration of U-Pb and 40Ar/39Ar geochronology applied to the calibration of the geological timescale. These efforts will be of enormous benefit to all of the earth sciences that rely on accurate chronometry.

For additional information please see the .pdf

Get the report from our first meeting (October, 2003) in .pdf format here.

EARTHTIME is supported by the National Science Foundation.