Preservation in microbial mats: mineralization by a talc-like phase of a fish embedded in a microbial sarcophagus

Miguel Iniesto (1) , Nina Zeyen (2) , Ana I López-Archilla (1) , Sylvain Bernard (2) , Angela Buscalioni (3) , M. Carmen Guerrero (1) , Karim Benzerara (2)

1 Departamento de Ecología
2 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
3 Departamento de Biología

Microbial mats have been repeatedly suggested to promote early fossilization of macroorganisms. Yet, experimental simulations of this process remain scarce. Here, we report results of 5 year-long experiments performed onfish carcasses to document the influence of microbial mats on mineral precipitation during early fossilization. Carcasses were initially placed on top of microbial mats. After 2 weeks, fish became coated by the mats forming a compact sarcophagus, which modified the microenvironment close to the corpses. Our results showed that these conditions favored the precipitation of a poorly crystalline silicate phase rich in magnesium. This talc-like mineral phase has been detected in three different locations within the carcasses placed in microbial mats for more than 4 years: (1) within inner tissues, colonized by several bacillary cells; (2) at the surface of bones of the upper face of the corpse buried in the mat; and (3) at the surface of several bones such as the dorsal fin which appeared to be gradually replaced by the Mg-silicate phase. This mineral phase has been previously shown to promote bacteria fossilization. Here we provide first experimental evidence that such Mg-rich phase can also be involved in exceptional preservation of animals.

Mots clés: Mg-silicate biomineralization; fish preservation; fossilization; microbial mat; experimental taphonomy

Domaines: Paléontologie; Microbiologie et Parasitologie

Miguel Iniesto, Nina Zeyen, Ana I López-Archilla, Sylvain Bernard, Angela Buscalioni, et al.. Preservation in microbial mats: mineralization by a talc-like phase of a fish embedded in a microbial sarcophagus. Frontiers in Earth Science, 2015, 3, pp.51. ⟨10.3389/feart.2015.00051⟩. ⟨hal-01741622⟩