Clay min er als in cave sed i ments and terra rossa soils in the Montagnola Senese karst mas sif ( It aly ) Francesco IACOVIELLO

Red dish mud-rich sed i ments are com mon in sev eral karst ar eas, in the form of red sur face soils and clastic cave in fill ings. The or i gin and sig nif i cance of red sur face soils have been much de bated over re cent years, while clastic mud-rich sed i ments in cave en vi ron ments have re ceived less at ten tion from geoscientists. The ge netic re la tion ship be tween these two ma te ri als still re mains un cer tain. Be cause these sed i ments are mainly com posed of fine-grained ma te ri als, their study has been gen er ally fo cused on the clay frac tion only. This pa per com pares the clay frac tion of red sur face soils and mud-rich cave sed i ments in the Montagnola Senese karst mas sif. Pre vi ous stud ies have dem on strated that, in this area, red cave muds orig i nate from the ero sion of the sim i larly red sur face soils, that were sub se quently re-de pos ited in the cave en vi ron ment. De spite these well-es tab lished ge netic re la tions, no ta ble dif fer ences in the clay frac tion of these two ma te ri als have been rec og nized in the pres ent study. These dif fer ences are likely to be at trib ut able to the dif fer ent grades of pedogenetic weath er ing that af fected the two ma te ri als. This study dem on strates that the ge netic re la tion ship be tween mud-rich cave sed i ments and red sur face soils can be mis in ter preted when only the clay min eral frac tion is con sid ered.