COG3

Faculty, McGill University

Title: Biogenic magnetite as biosignature: Implications for the search for life and paleoclimate

Abstract: The investigation of the ultrastructure and nature of the reaction at the molecular level occurring at the interface between inorganic and organic phases is essential to understanding the processes and pathways that lead to the nucleation and growth of biogenic magnetite. This provides valuable insight into the role of biology in geochemical cycles. Magnetofossils, remnants of biogenic magnetite, as archives of life history and environmental information can be used (i) as biosignatures in ancient terrestrial and extraterrestrial geological systems, (ii) to understand the origin and evolution of life and the biosphere, and (iii) to provide information for reconstructing paleoenvironments and paleoclimates. Studying the processes that lead to the formation of intra- and extracellular magnetite by bacteria will improve the mineralogical and geochemical criteria to distinguish between biogenic and non-biogenic magnetite. In this talk, I will present experimental results of magnetite formation by a variety of bacteria under different environmental conditions as well as magnetofossils collected from a wide range of sediments. I will also discuss the newly discovered giant biogenic magnetite and identification of their origin in the PETM, which provides a unique opportunity to shed new light on the paleoenvironmental conditions during this time as well as having implications for the consequences of man-made global warming during the “Anthropocene” (the present age of global time) as the PETM is an ideal analogue for the present.