Abstract:
Nowadays, it is universally accepted that the majority of carbonate sediments accumulate under the direct or indirect influence of biota. The carbonate material is deposited in a purely biogenic way in the form of skeletal remains of organisms. A significant share of it is produced biochemically. The consumption of CO2 by algae and cyanobacteria increases pH and creates a geochemical medium that favors the transformation of soluble calcium bicarbonate into insoluble carbonate. The pseudobiogenic mechanism of carbonate material fixation represents a peculiar variety of this process: a favorable medium is created around an organism, and the latter is covered by a thin carbonate crust conserving the organism's morphology. Such a mode of carbonate precipitation is characteristic of calcibiontic forms of Cyanophyceae: Epiphyton, Markovella, Renalcis, and others.