The object of our research is the Kazantip Cape (Kerch Peninsula, Crimea). Its attraction is a ring-shaped rock massif composed of bryozoans previously considered to be a reef structure growing on the limbs ofrisingbrachyanticline about 8 million years ago. Application of complex of investigating methods show that clay deposits underlying bryozoan structure are composed of expandable mixed-layered minerals, smectite, kaolinite, chlorite, illite with accessory minerals (zircon, monazite, ilmenite). These clays are the result of eruption of fossilized analogue of mud volcano. This process was accompanied by unloading of cold gas-fluid seepage. Specific mineralization (barite, celestine, strontianite, authigenic minerals of rare-earth elements and manganese) of bryozoan’s bioherms indicates that the seep process continued even after the waning of mud volcanism.