We are patterns that emerge from natural processes.  Ourselves, our world, the universe evolve from intricate interactions across space and through time.  My interests focus on interpreting processes from patterns, mostly patterns in rocks, to understand interactions between life and environment. 

My science is grounded in carbonate stratigraphy, petrography, and geochemistry.  Field work, accompanied by laboratory analyses, allows me to track changes in ancient environments through space and time on scales of microns to thousands of kilometers, of seconds to billions of years. A primary research focus for my career has been to constrain the chemistry of the oceans and atmosphere about 2.5 billion years ago, just prior to the oxidation of Earth's atmosphere.  Cyanobacteria provided the molecular oxygen.  Did they first evolve at this time?  Did they proliferate?  How did Earth's environment buffer the extent of oxidation?  Some of the specific questions I focus on include how molecular oxygen was distributed in environments, balances of sources and sinks of oxidants, and interactions among environmental changes, the biosphere and microbial evolution. 

These questions lead to much broader questions of how one interprets the members and ecology of ancient microbial communities from their sparse remains in rocks.  What bacteria were present and what were they doing?  Wrestling with these questions leads down many interesting paths.  One of the most promising is the study of biofilm morphology in mobile, filamentous bacteria.  By studying natural communities, performing experiments on filamentous cyanobacteria, and modeling the aggregate behavior of interacting sticks and threads, we are starting to demonstrate that very specific aspects of biofilm morphology are due exclusively to the shape and style of motion of constituent bacteria.  The apparent universality of these relationships point the way toward interpreting behaviors in microbial communities that lived 2.5 billion years ago.  In addition, the patterns that emerge from these systems may be uniquely biological and independent of the detailed biochemistry of life; they may be morphological biosignatures one could expect in microbial communities on other planets, signatures we could find in rocks on Mars.