The main focused of my research is on applying and technically improving the 40Ar/39Ar dating method and in applying the method to multi-disciplinary geologic studies across the Geologic Timescale. My research has been primarily on the extreme ends of the Geologic Timescale, morphologic, stratigraphic, and volcanic hazard studies on young (< ~3 Ma) basaltic volcanic rocks, thermochronology of large basaltic intrusions, and on the age of meteorites. I am currently involved in a volcanic hazard assessment at the Idaho National Laboratory and the risk assessment of the proposed site for the Advanced Small Modular Reactor test facility.

Additional projects include the dating several different types of meteorites.  I am particularly interested in studying shock induced transition of plagioclase-to-maskelynite, commonly observed in the Martian shergottites, and the effect of impact shock on the 40Ar/39Ar geochronometer.

The technical projects involve the improvements in accuracy and precision of Ar isotopic measurements are 1) determine the cause(s) of significant inter-laboratory inconsistencies between the relative ages of two of commonly used 40Ar/39Ar mineral standards, Fish Canyon (FC, ~28.2 Ma) and Alder Creek (AC, ~1.19 Ma). 2) development of a new noble-gas ion-source.


  • B.A. from the University of California, Berkeley (1980)
  • M.S. from Stanford University (1984)
  • Ph.D. University of California, Berkeley (1996)
  • Lamont-Doherty Earth Observatory as a Senior Staff Associate from 1997 - 2002


Research Interests