Daniel H. Rothman, Ph.D.
Lorenz Center and Department of Earth, Atmospheric, and Planetary Sciences
Massachusetts Institute of Technology
September 28, 2012
2:00 - 3:00 pm
Livak Ballroom, Dudley H. Davis Student Center
Summary
The end-Permian extinction is associated with a mysterious disruption to Earth's carbon cycle. Here we identify causal mechanisms via three observations. First, we show that geochemical signals indicate an incipient singular blow-up of the marine inorganic carbon reservoir, coincident with the extinction and consistent with the evolutionary expansion of a new microbial metabolic pathway. Second, we show that the fast acetoclastic pathway in {\em Methanosarcina}, limited by nickel and responsible for most modern biogenic methane, emerged at a time statistically indistinguishable from the extinction. Finally, we show that nickel concentrations in South China sediments increased sharply at the extinction, probably as a consequence of massive Siberian volcanism and enabling the blow-up. Collectively, these results suggest that a specific microbial innovation instigated Earth's greatest mass extinction.
Speaker Bio
Daniel H. Rothman is a theoretical geophysicist who has contributed widely to the understanding of the organization of the natural environment. His work has resulted in fundamental advances in subjects ranging from seismology and fluid flow to biogeochemistry and paleobiology. He has also made significant contributions to research in statistical physics. Much of his recent interests focus on the dynamics of Earth's carbon cycle. Rothman received his AB in applied mathematics from Brown University in 1979 and his PhD in geophysics from Stanford University in 1986. He has been a member of the faculty of the Department of Earth, Atmospheric, and Planetary Sciences at MIT since 1986, and has held visiting appointments at the University of Chicago, Ecole Normale Superieure, and Harvard's Radcliffe Institute for Advanced Study, among others. Rothman is co-founder of the Lorenz Center at MIT, a privately funded interdisciplinary research center devoted to learning how climate works.