Investigating the formation of biogenic magnetite and the preservation of magnetofossils: implications for biosignatures and paleoenvironments

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Using an interdisciplinary approach that integrates mineralogy, biogeochemistry and microbiology and the application of electron microscopy, I investigate processes that lead to the formation of biominerals and characterize their chemical and isotopic composition, crystal morphology and mineral structure. In general, by understanding the processes and pathways of biomineralization, we gain valuable insight into the role of biology in geochemical cycles. Biominerals 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. My current research program is directed towards investigating magnetite crystals produced by bacteria in order to improve the mineralogical and geochemical criteria to distinguish between biogenic and non-biogenic magnetite. This is accomplished by (1) analyzing the newly discovered giant biogenic magnetite present within sediments of the Paleocene-Eocene Thermal Maximum (PETM) and their relationship to other Fe minerals such as glauconite, and (2) studying the structural details of magnetosomes from both cultured magnetotactic bacteria and magnetic bacteria collected from freshwater lakes and marine habitats as well as their magnetite fossils (i.e., magnetofossils). As the PETM is characterized as an extreme global warming event where temperatures increased by about 5 to 9°C over an interval of 180 ky at about 55.5 Ma, investigation of the biogenic magnetite in the PETM may shed new light on the paleoenvironmental conditions of this period. It also has implications for the possible 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.