title: Patterns of metal distribution in hypersaline microbialites during early diagenesis: Implications for the fossil record.
abstract: The use of metals as biosignatures in the fossil stromatolite record requires understanding of the processes controlling the initial metal(loid) incorporation and diagenetic preservation in living microbialites. Here, we report the distribution of metals and the organic fraction within the lithifying microbialite of the hypersaline Big Pond Lake (Bahamas). Using synchrotron-based X-ray microfluorescence, confocal, and biphoton microscopies at different scales (cm-μm) in combination with traditional geochemical analyses, we show that the initial cation sorption at the surface of an active microbialite is governed by passive binding to the organic matrix, resulting in a homogeneous metal distribution. During early diagenesis, the metabolic activity in deeper microbialite layers slows down and the distribution of the metals becomes progressively heterogeneous, resulting from remobilization and concentration as metal(loid)-enriched sulfides, which are aligned with the lamination of the microbialite. In addition, we were able to identify globules containing significant Mn, Cu, Zn, and As enrichments potentially produced through microbial activity. The similarity of the metal(loid) distributions observed in the Big Pond microbialite to those observed in the Archean stromatolites of Tumbiana provides the foundation for a conceptual model of the evolution of the metal distribution through initial growth, early diagenesis, and fossilization of a microbialite, with a potential application to the fossil record.
authors.affiliation: Geobiosphère Actuelle & Primitive, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, CNRS, Paris, France.|Dipartimento di Scienze Chimiche e Geologiche, Università di Modena e Reggio Emilia, Modena, Italy.
authors.forename: M C
authors.initials: MC
authors.lastname: Sforna
authors.affiliation: Geobiosphère Actuelle & Primitive, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, CNRS, Paris, France.|Synchrotron Soleil, Gif-sur-Yvette, France.
authors.forename: M
authors.initials: M
authors.lastname: Daye
authors.affiliation: Geobiosphère Actuelle & Primitive, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, CNRS, Paris, France.
authors.forename: P
authors.initials: P
authors.lastname: Philippot
authors.affiliation: Synchrotron Soleil, Gif-sur-Yvette, France.
authors.forename: A
authors.initials: A
authors.lastname: Somogyi
authors.affiliation: Geomicrobiologie, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, CNRS, Paris, France.
authors.forename: M A
authors.initials: MA
authors.lastname: van Zuilen
authors.affiliation: Synchrotron Soleil, Gif-sur-Yvette, France.
authors.forename: K
authors.initials: K
authors.lastname: Medjoubi
authors.affiliation: Geomicrobiologie, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, CNRS, Paris, France.
authors.forename: E
authors.initials: E
authors.lastname: Gérard
authors.affiliation: Synchrotron Soleil, Gif-sur-Yvette, France.
authors.forename: F
authors.initials: F
authors.lastname: Jamme
authors.affiliation: Department of Geological Sciences, Stockholms Universitet, Stockholm, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Dupraz
authors.affiliation: Center for Biomechanics and Biocalorimetry, University of Basel, Basel, Switzerland.
authors.forename: O
authors.initials: O
authors.lastname: Braissant
authors.affiliation: Societe Suisse des Explosifs SA, Brig, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Glunk
authors.affiliation: Department of Marine Sciences, University of Connecticut, Groton, CT, USA.
authors.forename: P T
authors.initials: PT
authors.lastname: Visscher
mesh_terms: D001444:Bahamas; D002623:Chemistry Techniques, Analytical; D004783:Environmental Microbiology; D005580:Fossils; D008670:Metals / Q000032:analysis*; D064307:Microbiota; D054712:Salinity
chemical_list: D008670:Metals