Sedimentary rocks dating Scene from chatterly
Cyanobacteria use water, carbon dioxide, and sunlight to create their food.
Fluctuations in metazoan population and diversity may not have been the only factor in the reduction in stromatolite abundance.
Laguna Bacalar in Mexico's southern Yucatán Peninsula in the state of Quintana Roo, has an extensive formation of living giant microbialites (that is, stromatolites or thrombolites).
The microbialite bed is over 10 km (6.2 mi) long with a vertical rise of several meters in some areas.
This may be a protective mechanism that affords evolutionary benefit to the colony in harsh environments where mechanical forces act to tear apart the microbial mats.
Thus these sometimes elaborate structures, constructed by microscopic organisms working somewhat in unison, are a means of providing shelter and protection from a harsh environment.
Lichen stromatolites are a proposed mechanism of formation of some kinds of layered rock structure that are formed above water, where rock meets air, by repeated colonization of the rock by endolithic lichens.