Geosciences and Environmental Change Science Center
August 31, 2016
Chemical abrasion-SIMS (CA-SIMS) U-Pb dating of zircon from the late Eocene Caetano caldera, Nevada
By Kathryn Watts, Matthew Coble, Jorge Vazquez, Christopher Henry, Joe Colgan (GECSC), and David John. Published in Chemical Geology.
Upon crystallization, zircon (a nearly ubiquitous mineral in felsic igneous rocks) incorporates uranium from its host magma, while strongly excluding lead. It thus provides a robust record of radiogenic lead accumulation from uranium decay—unless lead is "lost" from the zircon after it forms. To mitigate lead loss, chemical abrasion can be used to dissolve away damaged parts of the zircon grain. This is widely done in conjunction with thermal ionization mass spectrometry (in which the whole zircon is dissolved) but this study is the first to employ it in conjunction with secondary ion mass spectrometry (in which a small spot on the zircon is selected for dating). Results indicate that lead loss can affect zircons as young as 34 Ma, and that chemical abrasion can partly, although not completely, mitigate the problem.
August 19, 2016
Total belowground carbon flux in subalpine forests is related to leaf area index, soil nitrogen, and tree height
By Erin Berryman (GECSC), Michael Ryan, John Bradford, Todd Hawbaker (GECSC), and Richard Birdsey. Published in Ecosphere.
In forests, total belowground carbon flux is a large component of the carbon budget and represents a critical pathway for delivery of plant carbon to soil. This study looked for predictable patterns of total belowground carbon flux with measured variability in leaf area index, soil nitrogen, and tree height across three different subalpine forests in the Rocky Mountains. The results, which varied in support among the relationships studied, can aid with estimates of forest soil respiration and total belowground carbon flux across landscapes, using spatially explicit forest data such as national inventories or remotely sensed data products.
August 16, 2016
GECSC Geologist Natalie Kehrwald was invited by the National Academy of Sciences to present her work on melting glaciers to Hollywood writers and directors as part of the Science & Entertainment Exchange. The goal of this exchange is to incorporate accurate science into entertainment media and to show the wonder and adventure of science in narratives. Natalie discussed her work with Adventurers and Scientists for Conservation, a nonprofit organization that recruits members of the outdoor adventure community to help gather data.
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