Geomorphological Context and Weathering Processes of the Rock Art Shelters of La Tunita (Sierra de Ancasti, Northwest Argentina)

Abstract

This study analyzes the geomorphological context, weathering processes, and evolution of granitic shelters bearing rock art in the Parque Arqueológico Provincial La Tunita (Sierra de Ancasti, Northwest Argentina), a key repository of Aguada Culture pictographs (ca. 600–900 AD). The research pursued four main objectives: (i) to characterize the spatial location and geomorphological setting of the principal shelters; (ii) to generate a three‐dimensional record of the cavities in relation to the distribution of pictographs; (iii) to identify inherited morphologies and ongoing degradative processes; and (iv) to propose a geomorphological evolutionary model for the area. Methodological procedures combined systematic photogrammetric recording with the production of 3D models. Weathering diagnosis was supported by X‐ray diffraction (XRD) to determine lithological composition, alteration products, and patinas, complemented by petrographic thin sections. The evolutionary model indicates that megatafoni and vault morphologies correspond to forms developed through prolonged weathering under warm–humid conditions. The tafoni interiors show vaults and ribs, some of which display higher resistance to uniaxial compression (RCU) than the surrounding rock. Active weathering results from the combined influence of humidity, salts, and biological/anthropic agents. Weathering fronts, gypsum and calcite neoformation, together with capillary humidity, partially affect the pictographs. Physical disintegration—granular disaggregation and exfoliation—is concentrated in overhangs and block supports, where compressive stress and water infiltration through fractures compromise the edges of certain paintings.