Turbulent lifestyle: Benthic cyanobacteria forming ichnofossils from the Archean to today

Today, extensive microbial mats predominantly composed of cyanobacteria colonize widely the modern sandy coast lines. The benthic microbiota respond to the physical sediment dynamics caused by hydraulic reworking of the deposits by biostabilization, baffling and trapping, as well as binding. This biotic–physical interaction originates characteristic microbially induced sedimentary structures (MISS) that differ greatly from both purely physical structures and from stromatolites. Studies conducted on modern MISS are the key for understanding equivalent fossil structures that occur in shallow-marine sandstones of all Earth ages.

Wrinkle structures, mat chips, and roll-up structures are most commonly found. Examples stem from the Ordovician of the Montagne Noire, France, the Neoproterozoic of the Nama Group, Namibia, as well as from various Archean locations. A unique assemblage of a multitude of exceptionally preserved MISS can be found in the 2.9-Ga-old Pongola Supergroup, South Africa. The ‘Nhlazatse Section' includes ‘erosional remnants and pockets', ‘multidirected ripple marks', ‘polygonal oscillation cracks', ‘gas domes', and many more. The structures record 4 different mat facies, each one is typical for a specific tidal zone. The microbial mat structures are preserved in situ, and are consistent with the MISS constructed today by benthic cyanobacteria. Possibly we can conclude that benthic cyanobacteria have been highly diverse already that time, and could have originated much earlier.