Colloquium: Noah M. McLean

Noah M. McLean, Assistant Professor, Department of Geology, University of Kansas

Abstract:  - U-Pb geochronology is the most precise and accurate way to tell time in the geologic record.  It’s used to calibrate the geologic timescale, evaluate the timing, pace, and causes of mass extinctions, explore rates of biologic evolution, and track the growth and evolution of our continents and orogenic systems over time.  The last decade has seen dramatic advances in the precision of U-Pb age measurements, expanding the scope of the geologic problems it can inform.  This talk will explore three new techniques for improving the accuracy of U-Pb dates and the uncertainties used to interpret them.  Tracing U-Pb dates back to first principles illuminates and quantifies sources of systematic uncertainty, including from historical assumptions about uranium isotopes that can now be revised.  Experimental petrology can help settle old, persistent questions about how U and Th partition between silicate melts and the mineral zircon, the single biggest uncertainty in dating samples that are less than about five million years old.  The results from both can become inputs to improved statistical algorithms and implemented in free open-source software that helps geochronologists and the wider community accurately visualize and understand U-Pb data, facilitating data interpretation and pointing the way toward new approaches for further sharpening this important chronometer.