Luminescense Specialist Joins Survey

Sébastien Huot of the Université du Québec á Montréal, Canada, joined the Illinois State Geological Survey team in May 2011 through an international laboratory exchange program. Huot specializes in luminescence dating and gamma-ray spectrometry. He received his Ph.D. in 2007 from Denmark under the supervision of Andrew Murray and is now a postdoctoral research fellow in Michel Lamothe's luminescence dating laboratory at the Université du Québec á Montréal. Sébastien helped ISGS researchers establish the long sequence of luminescence measurements on quartz grains with a reference check on feldspar contamination so that individual aliquots can be rejected if contaminated by trace amounts of feldspar grains. Because optically stimulated luminescence (OSL) dating of glacial sediments is an important application for ISGS geologists, Sébastien helped them establish the procedure for analyzing partially bleached samples, which is to analyze fewer than 20 instead of more than 1,000 quartz grains for each aliquots. For gamma spectrometer methods, he helped ISGS scientists lower the background radiation by 60 times and reduce "dead counting time" from 0.5 to 0.01%, which fundamentally increases the counting efficiency. This efficiency is very important because the lab measures a very low abundance of uranium, thorium, and potassium isotopes in geological sediments. The OSL dating procedure has moved one large step forward in providing accurate dating of Illinois' sediments.