Our research to this point focuses on at least one of the three topics above. We are geochemists, and our tool of choice is heavy metal stable isotopes. We study heavy metal isotopes in a variety of settings and sample types. We have been spending a lot of time lately studying isotope cycles in settings that are very rare today but that were common on ancient Earth. We like studying old sedimentary rocks because they hold the secrets of Earth's past environments. Among other things, these rocks can tell us about the history of molecular oxygen (O2) on Earth, and what role, if any, this history played in the evolution of life.