Research Integration of high-precision geochronology, paleontology, and stratigraphy to determine the age of major events for life. For example, dating the end-Permian mass extinction through U-Pb analysis of zircon from volcanic ash beds, with the goal of determining the cause of the extinction. Developing techniques necessary to produce temporal constraints with uncertainties of better than 0.1%, including production of tracer solutions and characterization of zircon age standards that are being distributed worldwide for the purposes of inter-laboratory calibration. Obtaining high-precision dates from small fragments of accessory minerals (zircon, monazite, titanite) that were characterized for composition and zoning by micro-beam methods. Examples of the goals of this work are determining rates of silicic magma generation and the timing of metamorphic events.