Features of calcareous algae mineralization at the transition to the Phanerozoic Biosphere

In this paper we discuss the mineralization features of Vendian-Early Paleozoic algae, preserved in several varieties: silicified, organic-walled, calcified, and sometimes partially phosphatized. Amongst these, the calcified taxa of the Chlorophyta and Rhodophyta divisions were dominant. Calcareous algae were subjected to mineralization twice: the primary structure arose during their lifetime, while the second carbonate cover formed as a result of calcium deposition on the dead thalli by bacterial-cyanobacterial associations acting as catalysts. In cases when algal fossils are found in localities near ore deposits, their porous carbonate envelope can change color depending on the prevalent chemical elements in the solution.