The strange structures, observable in these rocks, are called algal oncoids and are the result of the deposition of concentric layers of calcium carbonate around fragments of shells or rock, by cyanobacteria. These structures are still being formed today on seabeds characterized by the influence of waves or strong currents. In the Carnic Alps they are located in the Lower Permian of the Val Dolce Formation (the Austrian Grenzland Formation).

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Panorama across the peat bog of the Grotta di Attila