INVESTIGATIONS BY CONFOCAL SCANNING LASER MICROSCOPY ON MODERN MICROBIAL MATS, AND COMPARISON WITH 2.9 GA OLD BACTERIAL TEXTURES FROM THE PONGOLA SUPERGROUP, SOUTH AFRICA

Microbial mats are dense, organic layers that are formed predominantly by benthic cyanobacteria. In tropical marine carbonate environments, the microbes induce chemical precipitation, which results in stromatolite formation. In contrast, in siliciclastic marine regimes, the microbes interact with physical sedimentary processes. This biotic-physical interaction influences the development of characteristic microbial mat textures.

The aim of this study was to document those textures of siliciclastic microbial mats. Until recently, modern and fossil microbial mats have exclusively been examined in thin sections, which document any textures only in two dimensions. In contrast, confocal scanning laser microscopy (CSLM) gives a three dimensional view of bacterial microstructures.

First, we investigated modern microbial mats that we collected at the east coast of the USA. We then compared the microbial mat fabrics with fossil bacterial textures from the 2.9 Ga Pongola Supergroup, South Africa. We elucidate (i) the differences in mat textures with respect to selective taphonomic processes that lead to the preservation of the ancient bacterial textures. We (ii) show the morphological differences between bacterial filaments and abiogenic textures, eg. of hydrothermal veins.