Research

Current Projects:

CERG examines Cenozoic climatic and biotic changes in a variety of places. One recent project in Montana examined the role of climatic and environmental change in driving biotic and ecological changes using a combination of stable isotope geochemistry, paleosol geochemistry, and phytolith extraction. That project built 40 Myr record of climatic and biotic changes, with a focus on critical transitions including the Eocene-Oligocene transition, the Oligocene-Miocene transition, and the spread to ecological dominance by the grasses during the Miocene. The Montana Site Project was funded by NSF Award #1024535.

Soil and Lake Biogeochemistry and Proxy Development

One of key outstanding questions is how the terrestrial biosphere will respond to global climatic change. To address this question, CERG uses a variety of isotopic and elemental geochemical tools to examine nutrient and element cycling. Phytoliths are also extracted to look at short-term paleoecological changes in modern soils. This combination of approaches also makes it possible to derive proxy relationships for key environmental variables such as precipitation and temperature that can be applied to paleosols to reconstruct paleoclimate. A part of this work focused on modern microbial mat systems was funded by NSF Award #1035595. Other support has come from NSF Award #1415543 to rebuild the ICP labs at UM with new whole rock and micro-trace elemental capabilities.

Precambrian Paleoenvironments and Life on Land

Precambrian paleosols and clastic sediments often preserve MISS (microbially-induced sedimentary structures) and organic matter that makes it possible to reconstruct what life on land was like during the Precambrian. In addition, the chemical composition of paleosols may also be used to reconstruct the atmospheric pCO2. These results are then put into atmospheric chemistry models to understand better the role of both trace atmospheric gases and of physical factors such as albedo, continental growth, and water vapor. The project was funded by NSF Award #1050760.

Stable Isotope Ecology of Conifers

Conifers are both widespread today and have been common in the geologic record for much of the past 200 million years, but how they cycle carbon and how they respond to different moisture regimes are relatively poorly understood. Ongoing work on extant and historical (e.g., herbarium) samples from the start industrial revolution through modern timescan be used to parse out the separate roles of atmospheric (Suess effect) and climatic changes. Support for this project was from the Margaret and Herman Sokol Fund.

Mesozoic Paleoenvironments and Nutrient Cycling

The later part of the Mesozoic represents the transition to modern environments. Ongoing work is focused on the Western Interior Seaway as well as on the Deccan Traps of India, where the role of tectonic and volcanic processes in shaping plant evolution and terrestrial paleoenvironments is being investigated. Work in this area was previously funded by the American Chemical Society (#53845-ND8) and the NSF (Award #1388295).

Warm Periods in Cenozoic Climate and Biotic Response

Current research in this area is focused on the early Eocene climatic optimum (53-50 Ma ago). Along with colleagues from the University of Wisconsin, the University of Minnesota, the University of Arizona, North Carolina State University, Northern Arizona University, Boise State, and Binghamton University, we are taking a multi-pronged approach to collecting a high-resolution (sub-Milankovitch) paleoclimatic and paleoenvironmental record from the lacustrine (Green River Fm.) and floodplain (Wasatch Fm.) parts of the Greater Green River Basin in Wyoming. In addition, my group is focusing on using microbialites as potential CO2 recorders, an approach that we’ve used previously with Mesoproterozoic microbialites. This work is currently funded by the NSF (Award #1812949).