SOME FEATURES OF THE EVOLUTION OF BENTHOGENE CARBONATE FORMATIONS

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.