The history of life is known by its records: body fossils, burrows, and tracks, and the fractionation of heavy and light isotopes between geological and biological materials. Microorganisms play an important role in the creation — and destruction — of all these records during initial deposition, early diagenesis, and lithification. However, modern analogs suggest that microbial ecological structure may be particularly critical in the formation of ancient phosphate-rich sedimentary deposits ("phosphorites"). Phosphorites are among the most robust paleobiological records, often containing exquisitely preserved fossil organisms and being associated with major ecological and climatological transitions in geologic time. But are they representative of global perturbations to biogeochemical cycling? Or local factors that selected for particular microbial communities? In reconstructing the depositional setting and diagenetic history of different ancient phosphorite deposits at regional, local, and microscopic scales, we can test hypotheses about the relationship between microbial ecology and phosphorite formation. This talk will focus on the view through the phosphorite taphonomic window at the Precambrian-Cambrian Boundary, but hey! It's impossible to talk phosphorite without also talking a little bit about dinosaur poop.

Cecilia B. Sanders, Ph.D., is currently a Blaustein Postdoctoral Fellow at Johns Hopkins University in Baltimore, MD. She received her Ph.D. in geobiology and her MS in planetary sciences from Caltech in 2022 and 2018, respectively. Her research interests include all aspects of the origins and evolution of life on Earth and other worlds. She is particularly interested in the mechanisms by which paleoenvironmental and paleobiological information enter the geologic record, a subject to which she applies all of the tools of sedimentary geology, mineral spectroscopy, and stable isotope geochemistry. Her favorite mineral is troilite, mostly because it is fun to say.

For the zoom information; please contact Rey Garduño (rgarduno@stanford.edu)