by Dr. David Johnston (Harvard/EPS)

Abstract:

The story of Earth's biological and chemical evolution is locked within the geological record of marine sedimentary rocks. Drafting that evolutionary narrative, however, requires a means of accessing and calibrating these rock records. Traditional approaches lean heavily elements like carbon and the relative abundance of its isotopes to reconstruct paleo-environments  and, most notably the history of atmospheric O₂. More recently, sulfur and iron based storylines have emerged in complement to that of carbon. The collection, and more importantly the parallel analysis of these three element cycles presents a great opportunity to further sharpen our understanding of Earth history and atmospheric oxygen. As direct O₂ proxies remain elusive to absent, proxy development and calibration remains the best vehicle. Developing new tools to recapitulate this story is therefore at the core of my research.

This seminar will cover three parallel research trajectories that all speak to Paleozoic O₂ levels.  This narrative will touch on everything from protein-level sulfur isotope fractionations, through to database approaches and novel isotope systematics.  For a quick primer on our lab’s philosophy, have a peak at the cartoon on the Johnston Lab Website