Widespread “camouflaged” pyroclastics including smectite, illite-smectite and heulandite are detected in the upper jurassic– lower cretaceous deposits of the Ulyanovsk-Saratov basin. Moreover, volcanic glasses are found in several stratigraphic units. The quantity of pyroclastic material in the study section (17–72%) is probably related to volcanic input in the basin. Concentrations of the trace and rare earth elements point to a predominantly acid source of ash material, except the Promzino and Ulyanovsk black shale formations linked to the mixed andesite-basaltic and felsic sources.