In the right-bank part of the Saratov Region, a section of terrigenous and carbonate rocks has been determined to underlie the ≪sponge≫ horizon conventionally dated back to the Santonian. The maximum thickness of the marls, constituting a substantial portion of the section, occurs in the western part of the region. Field description is presented alongside with the correlation scheme of the recognized stratified intervals in the three joined Ozerki objects and the results of petromagnetic and magnetic-mineralogical examinations in the carbonate rock interval.