Silicified Biota in High-Altitude, Geothermally Influenced Ignimbrites at El Tatio Geyser Field, Andean Cordillera (Chile)

Abstract

Biofilms and filamentous communities provided favorable sites for silica precipitation on deeply weathered ignimbrites that make up the substrate at the hydrothermal field of El Tatio (Andean Cordillera, Chile). The amorphous silica encrustation enabled the preservation of a variety of biotic and abiotic features. An integrated study based on optical/scanning electron microscopy and molecular methods of totally to partially silicified microbial communities and biofilms allowed a comparative evaluation of the microfacies and the microbial diversity in the siliceous sinters produced by the digression of a little braided stream departing from a hot spring pool. This study showed useful convergent identifications of certain groups of microbes, such as filamentous cyanobacteria attributed to the genera Phormidium and Rivularia. Together with these microbes, other presumably initial colonizers, such as the halophilic and thermophilic pennate diatoms Nitzschia and Synedra, were widely present and could have contributed to the formation of biofilms and mucus that, as potential home to early silicification, could have contributed to the preservation of microbiologically derived morphologies.