Rapid in situ silicification of microbes at Loburu hot springs, Lake Bogoria, Kenya Rift Valley

Microbial mats, located along the margins of hot-spring pools and outflow channels at Lake Bogoria, Kenya, are commonly silicified forming friable laminated crusts. Columnar microstromatolites composed of silica and calcite are also forming at several springs in sites of oscillating water level or spray. Silicification of the microbes involves impregnation of organic tissue by very fine amorphous silica particles and encrustation by small (< 2 mu m) silica spheroids. Rapid silicification of the microbes, which may begin while some are still alive, can preserve sheaths and in some examples, the filaments, capsules and cells. Although this provides evidence of their general morphology, the biological features that are required for taxonomic identifications are commonly poorly preserved. The silica precipitation results mainly from evaporative concentration and rapid cooling of spring waters that have been drawn upward through the mats and microstromatolites by capillary processes. Almost all the silica at the Loburu springs nucleates on microbial substrates. This affinity of silica for functional groups on microbial surfaces contributes to the rapid silicification of the microbes and their preservation in modern and ancient cherts.