Stromatolites are laminated calcareous structures
caused mainly by nonskeletal algae (generally cyanobacteria; blue-green
and green algae) that date back to the early Precambrian.
biosedimentary in origin, and resulting from the
interaction of filamentous and coccoid algae, which are in the form of
"algal-mats" and physical sedimentary processes.
perform a sediment stabilizing role by mechanically
trapping and binding sediment particles on organic films.
The result is a well laminated stromatolite and
oncolites or a poorly laminated structure and clotted fabrics.
Microbial mats cover the sediments of Shark Bay, Australia;
Courtesy of www.ggl.ulalval.ca