We investigate the elemental and isotopic composition of geological and biological materials to address a wide variety of environmental and geological problems.  Research topics vary widely, and include the development of new biomarker and isotopic methods to reconstruct the Earth’s climate, geochemical and isotopic reconstructions of the Earth’s carbon and water cycles, isotopic investigations of atmospheric pollution and the nitrogen cycle, geochronological studies of tectonic processes, events, and weathering, and the kinetics of elements and isotope exchange in fluid systems. Through these studies, we develop novel methods to assess biogeochemical, climatic, and lithospheric processes on Earth and other planetary bodies.