IN-SITU SILICIFICATION OF AN ICELANDIC HOT-SPRING MICROBIAL MAT - IMPLICATIONS FOR MICROFOSSIL FORMATION

Transmission electron microscopy and energy-dispersive x-ray analysis revealed that filamentous phototrophic bacteria resembling Chloroflexu s aurantiacus underwent rapid silicification in an Icelandic hot sprin g microbial mat. The mineralization associated with the cells occurred both extracellularly, within and on the external sheaths of the bacte ria, and intracellularly, within the cytoplasm. The exceptional preser vation of the bacterial sheaths is due to the presence of distinct min eral nucleation sites. This results in the production of silica casts of the bacteria, which bear a striking resemblance to microbial remain s in ancient microfossil assemblages.