It has been established that the basement rocks of the Lower Maeotian section are characterized by the greatest variation in the chemical and isotopic composition of OM, while the carbonate rocks are more similar. It was revealed that the initial OM accumulated mainly under reducing conditions, but has some differences in its composition: for example, in the rocks of the Senkina and Sharabay bays it is an algal-cyanobacterial substance, and in the rocks of the Shirokaya bay it has a large contribution of the microbial component and the introduction of humus material. It was found that the isotopic composition of Corg has a strong variability (–19.27…–33.72 ‰), but most of the samples are in the range of –22.1…–24.93 ‰. It has been established that the 13Сcarb and 13Сorg isotopic curves in the studied rocks reflect their deviations both towards lighter and towards heavier values. The general direction of the isotopic composition, with some variations, nevertheless tends to be isotopically heavier towards the upper part of the sections. It was revealed that the litho-mineral-geochemical specificity of the sections reflects significant changes in sedimentation conditions, generally associated with fluctuations in the temperature and salt composition of waters, and bioproductivity. It is proposed to use such accessory minerals as zircon, monazite, ilmenite as an indicator of mud paleovolcanism.