Physical and Microbiological Analysis of Sandstone Deterioration in the Argentine Jesuit Missions

Mainly cyanobacteria, but also algae and fungi, were identified on the Jesuit missions San Ignacio Mini, Loreto, Santa Maria and Santa Ana, in NE Argentina. Many organisms were deeply pigmented, indicative of stressful conditions. San Ignacio samples of itacuru rock showed higher colonization and biodiversity, related to higher porosity allowing entry of water and nutrients. Sandstone from other locations was arenitous, containing 95% silicates. Physicochemical analyses suggested mobilization of ions, particularly Fe, from within the stone to the surface. This intense deteriorating colonization, together with climatic weathering, transforms the sandstone to a protosoil, for growth of bryophytes and higher plants.