Abstract(#br)Comprehensive studies of ash material from buried archaeological objects of different ages and from incinerated modern plants suggest that carbonates are produced in the course of the organic matter incineration. Highly soluble potassium carbonate (K 2 CO 3 , potash) is formed together with difficulty soluble calcium carbonate (CaCO 3 , calcite), and, as a rule, the content of the latter in the ash is higher than the content of potash. It is important that calcium carbonate can be preserved in the buried state for a long time. The pyrogenic formation of carbonates is a phenomenon that is not taken into account by researchers studying natural and anthropogenic soils. It is particularly important for buried soils and habitation deposits, as it leads to their alkalization and to... the accumulation of secondary carbonates in the layers affected by pyrogenesis. The role of this process in natural systems is discussed, and the stability of pyrogenic carbonates in soils of different geographic zones is analyzed.