New chronological framework for Zapotec architecture at Las Mesillas, Oaxaca, Mexico: Integrating radiocarbon and luminescence dating

San Pedro Martir Quiechapa, a municipality in the southern highlands of Oaxaca, preserves evidence of landscape engineering by the ancient Zapotec civilization. At Las Mesillas, the municipality's largest archaeological site, terraced hillsides and monumental architectural complexes reveal the intensive reshaping of the landscape. Architectural phases show cycles of infilling, resurfacing, and reconfiguration that reflect ritual renewal practices and long-term ceremonial investment in the site. To establish the chronology of construction at Las Mesillas, we applied luminescence dating techniques to sediments sealed beneath two excavated architectural contexts, Operation A and B. Coarse quartz grains were extracted from the sediment and analyzed using a single-grain Optically Stimulated Luminescence (OSL) protocol, while coarse feldspar grains were analyzed using a multi-grain post-Infrared-Infrared luminescence (pIR-IRSL) protocol. Three radiocarbon dates were obtained from charcoals contained in the sediment. The integrated radiocarbon and luminescence-based chronology from Operations A and B reveals a sequence of construction, renovation, and reuse at Las Mesillas from the 1st century BCE through the 11th century CE, from the Terminal Formative through the Early Postclassic periods. Renovations of both the summit and terrace during the 10th-11th centuries CE indicate coordinated planning and continued participation in broader Mesoamerican sociopolitical networks.