Petrografía, procedencia y alterabilidad del material pétreo utilizado en la construcción del Monasterio de San Millán de la CogoIIa, Yuso (s.XVI-XVIl), La Rioja

Abstract

A catalogue of the stone material employed for the construction of the San Millán de la CogoIIa Monastery (Yuso) has been undertaken. The characterization of the rocks has enabled us to explain the provenance of the most part of the stones from several quarries very close to the monastery. We have also compared the different degree of alteration of the stone material. Whereas the brecciated limestones from Jurassic age employed for the construction of all the main walls and columns of the monastery, have a very resistant behaviour to weathering, the Tertiary sandstones and coarse-crystalline evaporites (gypsum) were destined to archs, archivolts, cornices and ornamental pieces and appear largely affected by dissolution processes showing a high degree of decomposition, particularly in the northern and western façades of the building.

The evaporitic material has been specially conflictive with respect to the restoration works carried out the last year on this historic monastery