MIT EAPS Directory

Julien Alleon

Postdoctoral Associate

Research Description

The early life fossil record is based upon a limited number of often controversial graphitic microfossils. The main complication resides in the poor preservation of organic biosignatures in the (meta)sedimentary rock record. Biodegradation and fossilization processes, as well as the increase of temperature and pressure conditions during burial diagenesis and metamorphism inevitably alter the original biochemical signatures of organic molecules. Thus, at a certain stage, biogenic and abiotic organics may become very difficult to distinguish.

My research combines characterization of natural samples using advanced spectroscopic techniques (STXM-based XANES & Raman microspectroscopies) and simulation of fossilization processes in the laboratory to investigate the potential preservation of microorganism molecular biosignatures in ancient rocks.

Publications

Alleon J., Bernard S., Le Guillou C., Daval D., Skouri-Panet F., Kuga M., Robert F. (2017). Organic molecular heterogeneities can withstand diagenesis. Scientific Reports 7, 1508. doi:10.1038/s41598-017-01612-8

Alleon J., Bernard S., Le Guillou C., Marin-Carbonne J., Pont S., Beyssac O., McKeegan K. D., Robert F. (2016). Molecular preservation of 1.88 Ga Gunflint organic microfossils as a function of temperature and mineralogy. Nature Communications 7, 11977. doi:10.1038/ncomms11977

Alleon J., Bernard S., Le Guillou C., Daval D., Skouri-Panet F., Pont S., Delbes L., Robert F. (2016). Early entombment within silica minimizes the molecular degradation of microorganisms during advanced diagenesis. Chemical Geology 437, 98-108. doi:10.1016/j.chemgeo.2016.05.034

Alleon J., Bernard S., Remusat L., Robert F. (2015). Estimation of nitrogen-to-carbon ratios of organics and carbon materials at the submicrometer scale. Carbon 84, 290-298. doi:10.1016/j.carbon.2014.11.044

Contact Information

Office

E25-601

Education

PhD in Biogeochemistry, National Museum of Natural History, Paris, France (2012-2015)
Master’s degree in Geochemistry, European Institute for Marine Studies, Plouzané, France (2010-2012)