The results of analysis of organic matter from nodular phosphorites and their host bituminous argillites of the Lower-Middle Cambrian Kuonamka Formation of the Siberian Platform are reported. The organic matter of the both formations have similar, mainly planktonic origin. However, the organic matter from phosphorites is characterized by some specific features (enhanced content of organic sulfur, lower hydrogen index, lower concentration of paramagnetic centers, peculiarities of saturated hydrocarbon content) interpreted as the result of later microbial activity on the final stages of phosphate genesis.
