The Formation and Preservation of Synechococcus elongatus Cell Molds in Simulated Silica Sinter: Implications for the Identification of Microfossils
Résumé
Siliceous sinters that precipitate around modern hot spring systems are able to fossilize the indigenous microbial communities, forming molds that accurately outline the shape of the microorganisms. Over time, the biomass decays, and only silica molds or their infill may remain as evidence of the former living cells. However, little is known regarding the fidelity of such silica molds in terms of size and morphology, and the preservation of critical parameters for the identification of ancient silicified microorganisms by silica molds remains untested. Here we report experiments examining the formation of microbial molds of the cyanobacterium Synechococcus elongatus in silica gel. We demonstrate that post-depositional processes, primarily desiccation, are crucial for obtaining accurate and robust molds, and that initial desiccation acts to strengthen cell molds against further alteration. However, all silica gel treatments systematically created preservational biases (changes in size, additional structures) that may be misleading and may complicate the identification of fossil microorganisms
Mots clés
early diagenesis
microfossils
silica gel
siliceous sinter
silicification
Synechococcus elongatus
taphonomy
YELLOWSTONE-NATIONAL-PARK
IN-SITU SILICIFICATION
ACID-BASE PROPERTIES
HOT-SPRING SINTER
KENYA RIFT-VALLEY
BLUE-GREEN-ALGAE
NEW-ZEALAND
MICROBIAL SILICIFICATION
NORTH-ISLAND
CYANOBACTERIAL SILICIFICATION