Workshop: High-precision Intercalibration of U-Pb and Ar-Ar Geochronometers

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

EAR-0443866 Bowring 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. This award will fund a two-day workshop to be held at MIT the weekend of October 15th or 22nd 2004 that will bring together representatives of the major laboratories worldwide involved in both 40Ar/39Ar and U-Pb geochronology to discuss problems and solutions to interlaboratory differences and to develop further a plan to move forward with increased precision and accuracy in geochronology. This will include having participants analyze and report both U-Pb and 40Ar/39Ar standard data at this meeting. The joining of both the U-Pb and 40Ar/39Ar communities at this workshop will provide a foundation for a focused effort toward understanding and resolving the issue of inter-decay system bias and allowing confident application of both chronometers to the calibration of the geological timescale. ***