Name: Microbialite
Classification: Chemical sedimentary rock, microbial boundstone
Mineral composition: Calcite
Fossils:thrombolytic microbialites
Location: Giau Pass, Mount Cernera (46°28'22.0"N 12°04'30.1"E)
Formation: San Cassiano formation
Era: Lower Carnian (approximately 235 million years ago)
Depositional environment:Carbonate substructure, microbial reef

CARBONATO MICROBIALE IMC_0060

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.

 

GALLERY