Geoscientific Approach to Diagnosis of Weathering Damage on Prehispanic Sandstone Monument Piedra Pintada de Aipe, Colombia

Rock art is a common cultural manifestation throughout Colombia. Here the Painted Stone of Aipe represents a striking archaeological evidence as an outstanding masterpiece of pre-Hispanic rock art. Several pectorals of different shapes are observed as a central motif used by the pre-Hispanic communities of Quimbaya, Tairona and the southern tribes. In addition to the pectorals, the stylized devil or monkey is seen in various combinations along with nose rings, fishhooks, bead necklaces, pendants, and rattles, among others. The substrate of the Aipe Painted Stone is a yellowish sandstone of oval shape and the low-relieve carvings are mainly on the longer SE-side of the stone block. This study aims to assess the different decay phenomena affecting the ~500-year old pre-Hispanic rock art carved on the sandstone block which is at an altitude of 370m on a main road near the Magdalena River. The artwork has important conservation problems mainly due to weathering creating a complex set of mechanical, chemical and biological processes on the rock. In the sandstone, the ~0,1 mm quartz-grains (45%) and foraminifers (15%) are mainly cemented by cryptocrystalline SiO₂; also phases like phosphates, clays, micas, opaques and a high open porosity of 15 % occur, enhancing chemical dissolution and precipitation of Fe-oxides. Among the main identified deterioration agents are water flows and humidity changes, solar radiation, abrasion caused by dust and sand carried by the often strong wind, internal pressure variations due to temperature variations and salt migration, plants and microorganisms, but also anthropic interventions.