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Biological Signatures in Clumped Isotopes of O2


May 19, 2015, noon - 1 p.m.
Slichter 3843

Presented By:
Jeanine Ash
UCLA

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Even in the decades prior to Urey's 1947 "birth of stable isotope geochemistry", Earth scientists were interested in the oxygen isotopic composition of the atmosphere and water. In this talk, I'll discuss atmospheric oxygen isotopes and the biosphere from first a historic perspective and then through the lens of photochemical and terrarium experiments we've undertaken. In a closed-system terrarium experiment, we demonstrate that biological oxygen (O2) cycling drives the clumped-isotope composition of O2 away from isotopic equilibrium. Our model of the system suggests that unique biological signatures are present in clumped isotopes of O2—and not formation temperatures. Photosynthetic O2 is depleted in 18O18O and 17O18O relative to a stochastic distribution of isotopes, unlike at equilibrium, where heavy-isotope pairs are enriched. Similar signatures may be widespread in nature, offering new tracers of biological and geochemical cycling.