LICHENIC ALTERATION AND MINERALIZATION IN CALCAREOUS MONUMENTS OF NORTHEASTERN SPAIN

Biodeterioration processes on three Spanish calcareous monuments (Scip io's Tower, Olerdola Wall, and the Naveta d'Es Tudons) were investigat ed. Scipio's Tower and Olerdola Wall, both located in Catalonia, were built with blocks of bioclastic packstones (foraminifera, bivalves, ga stropods, red algae, echinoderms) of the Langhian (Middle Miocene) Age . The Naveta d'Es Tudons, located on the island of Menorca, was constr ucted with blocks made up of bioclastic packstones, partially dolomiti zed and dedolomitized, and is of Miocene Age. The main organisms that inhabited these three monuments were lichens [mainly Dirina massiliens is Durieu et Mont, Verrucaria nigrescens Pers., Caloplaca aurantia (Pe rs.) Hellb., Caloplaca velana (Massal.) Du Rietz, Caloplaca erythrocar pa (Pers.) Zw., Petractis thelotremalla (Bagl.) Vezda, and Strigula ca learea Bricaud et Roux], which caused the main alteration of the rock. The distributions of these lichens were determined and their actions on the stone were studied by different techniques. From the samples st udied, a general and complete alteration profile was proposed and desc ribed. In this profile from the external area of the stone to tire una ltered substratum, five zones were distinguished: lichen thallus, micr ocorrosion surface, altered zone, transition zone, and finally the una ltered zone or substratum. A model of evolution of these zones was als o developed. Some structures found in tire different zones of these pr ofiles were morphologically described and filaments and spheres were i dentified. In the fame way, some diagenetic products found in these zo nes were described and related to tire processes that originated them. An interpretation of these structures and products and their relation to organisms and microorganisms was attempted.