Stromatolites constitute amongst the oldest traces of life on Earth (more than 3.4 billion years old) and provide a unique fossil archive spanning nearly all of geological time. My objective is to investigate the signatures preserved in stromatolites, with a focus on their potential as biosignature archives. My research lies at the interface between geochemistry, mineralogy, paleoenvironmental reconstruction and astrobiology, aiming to decipher the complex interplay between biological processes and abiotic sedimentary structures.
Keywords
Origin of life • Biosignatures • Stromatolites • Microbialites • Paleoenvironments • Collections
Researchinterest
I explore the diversity, morphology, and evolution of microbialites through time and space. I am particularly interested in how these structures inform us about early life, paleoenvironmental conditions, and the resilience of microbial ecosystems on Earth.
My research focuses on the geochemical characterization of modern and ancient stromatolites to reconstruct paleoenvironmental conditions in both local or global context. I analyze their stable isotope content (δ¹³C, δ¹⁸O), and certain redox-sensitive tracers (Fe, Mn, U, V, Mo), as well as rare earth elements (REE).
My research also investigates stromatolite morphology, mineralogy, and internal lamination textures – particularly through cyclostromatostratigraphy, an emerging field that explores potential rhythmic growth patterns and their environmental drivers.
By combining these approaches, I aim to understand the relationship between microbial processes and abiotic controls in forming organo-sedimentary structures from micro- to macro-scales across deep geological time.
Stromatolitecollection
According to my scientific approach, stromatolites can be defined as “lithified sedimentary structures, deposited in various aqueous environments, and characterized by structured lamination from an initiation surface under the combined influence of microbial communities and environmental factors”.
During my PhD, I assembled a reference microbialite collection at the Muséum national d’Histoire naturelle in Paris, now open to the scientific community. This curated archive spans from the Precambrian to the Quaternary and supports comparative research on microbialite formation across time and environments.
https://doi.org/10.60520/IEDA/113109
If you are interested in collaborating on any subject related to stromatolites (geomicrobiology, geochemistry, paleoenvironment, evolution, diagenesis...), you need powder samples, photos, general information, etc., please let me know ! It would be a real pleasure to bring this collection to life.
Currenttopics
My current focus is on developing multi-parameter frameworks to help distinguish biogenic from abiotic laminated structures – a crucial step not only for understanding early life on Earth, but also for identifying potential biosignatures on other planets.
We develop AI-assisted image analysis tools to distinguish between biotic and abiotic structures in various laminated rocks using microscopy, high-resolution X-ray tomography (µCT), and micro-X-ray fluorescence (µXRF) images.
We are currently working on a segmentation pipeline for the extraction of morphometric descriptors of lamination patterns, along with other valuable features such as porosity or mineralogical contrasts, allowing for the construction of multi-layered descriptors for each sample.
All these parameters are embedded into a global feature framework, which integrates chemical, textural, and morphological features. By training machine learning algorithms on both well-characterized biogenic structures and abiotic analogs, we aim to build a robust classifier capable of biogenicity assessment.
Keypublications
- Fogret L., Sansjofre P., Lalonde S.V. 2024. Geochemistry of Carbonate Microbialites through Time and Space: Insights from the Microbialite Collection of the Muséum National d’Histoire Naturelle (MNHN), France. Chemical Geology 662: 122239. https://doi.org/10.1016/j.chemgeo.2024.122239.
- Fogret L., Sansjofre P., Lalonde S.V. 2024. Geochemical Dataset Associated with the National Museum of Natural History Microbialite Collection, Paris, Version 1.0. Interdisciplinary Earth Data Alliance (IEDA). https://doi.org/10.60520/IEDA/113109.
- Caumartin J., Benzerara K., Havas R., Thomazo C., Fogret L., Betancourt V., Tavera R., Doisneau B., Jézéquel D., López-García P. 2025. Huntite [CaMg3(CO3)4], a Rare Carbonate Phase Formed during Early Diagenesis in Modern Microbialites. ACS Earth and Space Chemistry 9 (6): 1544–65. https://doi.org/10.1021/acsearthspacechem.5c00022.
- dos Santos R.F., Sansjofre P., Nogueira A.C.R., Crockford P.W., Uhlein G.J., Fogret L., Pereira F.S., Romero G.R., Lalonde S.V. 2024. Rare Earth Elements as Indicators of Post-Marinoan (∼635 Ma) Paleoceanographic Changes from the Amazon Craton. Precambrian Research 413: 107575. https://doi.org/10.1016/j.precamres.2024.107575.