We are developing new geochemical criteria for distinguishing between iron formations oxidized by oxgyen, UV light, and anaerobic photosynthetic bacteria in experimental iron-oxidizing systems. Those criteria are being used to probe the 3.26-billion-year-old Manzimnyama Jaspillite, one of the oldest well-preserved oxide facies banded iron formations. For comparison, we are applying the same criteria to the 3.42-billion-year-old Buck Reef Chert, which shows no evidence of primary iron oxidation. Fieldwork is conducted in the Barberton greenstone belt of South Africa.

This work has application in examining the history of the evolution of microbial photosynthesis. Specifically, we expect to be able to use our results to identify major evolutionary milestones in the transition from anoxygenic to oxygenic photosynthesis.