EESS talk on "Sub-micrometer pyrites in stromatolites recorded isotopic fingerprints of microbial activities through time "


Event details

Date and time 16.03.2021 12:1513:00  
Place and room
Speaker Dr Johanna Marin Carbonne, Tenure Track Assistant Professor, Institute of Earth Sciences (ISTE), Faculty of Geosciences and Environment, UNIL
Category Conferences - Seminars
The identification of microbial signatures preserved in the geological record is crucial for understanding life evolution in the Early Earth. Iron and sulfur isotope composition offer the most direct means to track the biogeochemical cycling of these elements through time, but their joint use as biomarker of specific metabolic activity has been relatively limited to date. Archean stromatolites and modern microbialites contain small sulfides, that can be formed either by abiotic processes (reaction between H2S and Fe(II)) or by metabolic activity like microbial sulfate reduction (MSR) or dissimilatory iron reduction (DIR). We have developed a microscale approach using correlative microscopy, SIMS and NanoSIMS analyses. In situ Fe and S isotope analyses as well as high-resolution mineralogy of pyrites in Archean stromatolites from the Tumbiana Formation (2.7 Ga, Australia) and microbialites from Atexcac Lake (Mexico) and Cayo Coco Lagoon (Cuba) reveal well-preserved primary microbial signature inherited from biomineralization process. This microscale approach allows us to distinguish microbial signatures from late overprints in the geological record but also provide implications on the evolution of redox conditions as well as on sulfate concentration evolution through time. 

Short biography:
Dr Johanna Marin Carbonne graduated from the National School of Geology in Nancy (France) in 2006. The same year, she obtained another Masters in geosciences, planetology and cosmochemistry. In 2009, she successfully obtained her PhD at the Petrographic and Geochemical Research Center (CRPG, Nancy) with a thesis entitled "Silicon and oxygen isotopic composition of Precambrian cherts: paleo environmental implications".
Between 2010 and 2014, Johanna Marin Carbonne spent two post-doctoral periods, one at UCLA between 2010 and 2012, and the second at the Institut de physique du globe, attached to the University of Paris Diderot before being appointed assistant professor at the 'Jean Monnet University in Saint-Etienne in France and attached to the Magmas and Volcanoes Laboratory of Clermont-Ferrand. She is currently a recipient of an European grant, ERC Starting Grant, obtained for the period 2018-2023 for her STROMATA project. This project aims to define new biogenicity tracers through the study of micropyrites associated with organic matter in old stromatolites and is hosted at the UNIL in Lausanne, at the Institute of Earth Sciences where she is assistant tenure track professor.

Her research aims to quantitatively reconstruct the surface conditions of the early Earth and to better understand the evolution of life during this period.Her research foIt combines a detailed mineralogy approach associated with high spatial resolution analyzes of traditional and non-traditional stable isotopes by Secondary Ion Mass Spectrometry, SIMS. 

Practical information

  • General public
  • Free
  • This event is internal


  • EESS - IIE



Stromatolite Early Life isotope geochemistry geobiology