An Approach to Identify and Understand the Main Processes of Weathering that Suffer the Pre-Hispanic STELAE Located in the CALAKMUL Biosphere Reserve in Campeche, Mexico

Oxpemul is an archaeological site with pre-Hispanic legacy located in the Calakmul biosphere reserve in Mexico. The stelae in this site have important epigraphic records of the Mayan culture. However, this information can be lost due to weathering processes that these structures undergo. In this work, ion chromatography analysis of ions extracted from samples obtained in situ using cotton poultices was used to discuss the weathering processes involved in four stelae located in Oxpemul. The plots of Ca(2+)vs SO42-, (Ca2+ + Mg2+) vs HCO3- and Ca(2+)vs HCO3- and the mineral phases found by x-ray diffraction (XRD) revealed that the dissolution of carbonates from the limestone and the recrystallization processes of these phases are the main weathering processes that occur in the stelae. Furthermore, it was found that the hydrolysis of silicates by cation exchange reactions to form montmorillonite contributes to the weathering process. The presence of oxalate crystals found by XRD and electron microscopy revealed that biodeterioration reactions also contribute to the weathering of the stelae. This is the first study carried out to identify and understand the weathering processes that occur in these stelae. This information could be useful to establish strategies for preserving, conserving, and restoring these vestiges.