Greenish clays often occur as thin layers in Early Cretaceous shallow-water carbonatesediments of Istria where they mark the top of fining upwards sequences. When they showevidence of subaerial exposure and pedogenesis they are considered paleosols. The claymineralogical composition is as follow: (1) randomly oriented I/S mixed layer, (2) regularlyoriented I/S mixed layer, (3) illitic material, (4) kaolinite and (5) chlorite. The insoluble limestoneresidue situated immediately below the greenish clays is dominated by smectite, and also containskaolinite and illitic material. The very high smectite content in the insoluble residue is probablythe result of additions of volcanic dust during carbonate sedimentation. That clay mineralcomposition in the pelitic material clearly indicates the influence of both pedogenic and diageneticprocesses. It may also indicate additional volcanic dust contribution before and during thesubaerial exposure. Greenish clays often occur as thin layers in Early Cretaceous shallow-water carbonate fractions of Istria where they mark the top of fining upwards sequences. When they show the pattern of subaerial exposure and pedogenesis they are considered paleosols. The claymineralogical composition is as follows: (1) randomly (3) illitic material, (4) kaolinite and (5) chlorite. The insoluble limestoneresidue situated immediately below the greenish clays is dominated by smectite, and also containskaolinite and illitic material. The very high smectite content in the insoluble residue is probably the result of additions of volcanic dust during carbonate sedimentation. That clay mineralcomposition in the pelitic material clearly indicates the influence both bottle and diagenetic processes. It may also indicate additional volcanic dust contribution before and during the subaerial exposure.