Scientific Objectives and Lab Approach
My research group uses stable isotope geochemistry to study different aspects of the Earth system, focusing mainly on the junction of geology, biology, and climate. Our motivations are simple: We seek to learn more about the Earth system, to develop methods for studying the Earth system, and to provide students with solid scientific training by carrying out these objectives.
Topics we have worked on include the history of the East Asian monsoons, the global expansion of C4 vegetation during the late Neogene, paleoenvironments of human evolution, and seawater paleotemperature and isotopic reconstruction during the late Paleozoic and Mesozoic.
Most of our research centers on the development and interpretation of new isotopic methods and datasets. We take a 'hands on' approach, often designing new methods, building custom equipment, and developing models, theory, and mathematics to carry out our research objectives.
Triple oxygen isotope compositions of CO2 and carbonates We recently solved the analytical problem of making high-precision triple oxygen isotope measurements on CO2 and carbonates (Passey et al., 2014, GCA). This opens the door to a wealth of new applications, ranging from animal (paleo)ecology, paleoaridity, and reconstruction of deep-time pCO2 / carbon cycling. Using the new methods, Huanting Hu (PhD '16) is studying the triple oxygen isotope compositions of dinosaurian eggshells as a basis for reconstructing Mesozoic carbon cycle dynamics and CO2 levels. Haoyuan Ji (PhD '16) initiated a study of recent soil and lacustrine carbonates, seeking to find out whether evidence of evaporation and aridity can be retrieved with this measurement. Ian Winkelstern (current postdoc) will be further exploring the triple oxygen isotope systematics of lakes.
Solid-state clumped isotope reordering We now have a fairly good understanding of the basics of this exciting new shallow crustal geothermometer / geospeedometer based on solid-state diffusion of C and O in carbonate minerals (e.g., Passey and Henkes, 2012, EPSL; Henkes et al., 2014, GCA; Stolper and Eiler, 2016, Am. J. Sci.), and exciting applications are emerging (e.g., Shenton et al., 2015, GSA Bulletin; Lloyd et al., 2016, GCA). Dana Brenner (current PhD student at Johns Hopkins) is addressing the important 'unknown' of how water and pressure influence reordering kinetics. Dana is also conducting 'computational reordering' experiments in order to gain a better understanding of reordering kinetics.
Benjamin H. Passey ** University of Michigan ** Department of Earth and Environmental Sciences