December 20th Speaker

Dr. Roberta L. Rudnick, University of California Santa Barbara (UCSB), will be presenting
"Glacial diamictites and the evolving continental crust"

Dr. Roberta L. Rudnick / December Speaker


Most of Earth’s heat-producing elements are in the continental crust, particularly the upper crust. Thus, defining the upper crust composition is crucial for understanding the distribution of these elements that are responsible for powering mantle convection and plate tectonics. In order to constrain the composition of the upper continental crust and provide uncertainties on that composition, we analyzed the fine-grained matrix of more than 100 samples of glacial diamictites. These samples span both space and time, with depositional ages ranging from 2.9 Ga to 300 Ma. Systematic changes in the composition of the diamicrites document the rise of atmospheric oxygen and a change in bulk composition of subaerial crust from mafic-dominated in the Archean, to a more felsic composition from the Neoproterozoic onwards. This fundamental change in composition likely reflects the emergence of plate tectonics in the Late Archean. 

Dr. Roberta L. Rudnick / December Speaker

Speaker Biography

Roberta L. Rudnick is a Distinguished Professor in the Department of Earth Science at the University of California, Santa Barbara. Prior to joining the UCSB faculty in 2016 she held Professorial appointments at the University of Maryland and at Harvard University. Dr. Rudnick received her B.S. in Geology at her local public university (Portland State University) and an M.S. from Sul Ross State University in Alpine, Texas. She received her Ph.D. in Geochemistry from the Australian National University in 1988, after which she was an Alexander von Humboldt Fellow at the Max-Planck Institute for Chemistry in Mainz, West Germany, and a Research Fellow at the Research School of Earth Sciences at the Australian National University. Her research focuses on the origin and evolution of the continents, including the underlying mantle lithosphere, as well as lithium isotope geochemistry.

CGS Dinner/ Tuesday, November 15th, 2022

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