Microbial carbonate

Marine worm holes


These coloured circles are almost certainly marine worm holes, and the dark mass from which they spring is an encrustation of calcite precipitated in bacterial mucilage.


It is a gruesome thought, but in the lower Carnian age (approximately 235 million years ago), the Dolomite seas were rich in mucilaginous bacteria;


entire mountains such as the Saddle or Sassolungo are nothing less than gigantic castles of bacterial encrustations, with a few other fossils (sponges, corals, the odd shell) that make a minimal contribution to the volume of the rocks.Today the situation is different. Environments such as those where these bacteria proliferated are now colourful coral reefs. We live in a fortunate time, and the Triassic sea, if we could see it as it was, would look like something from another planet.



Name: Microbialite
Classification: Chemical sedimentary rock, microbial boundstone
Mineral composition: Calcite
Fossils: thrombolytic microbialites
Location: Giau Pass, Mount Cernera (46°28’22.0″N12°04’30.1″E)
Formation: San Cassiano formation
Era: Lower Carnian (approximately 235 million years ago)
Depositional environment: Carbonate substructure, microbial reef