Deciphering the construction of the ancient city of Palenque and its effects on the landscape

The ancient city of Palenque, in the Mayan territory, was established in a strategic position between the piedmont of the Sierra de Chiapas and the alluvial plain of the Michol River. The city became prominent during the Classic period (250–900 AD), when landscape modifications were carried out at different scales and with varying degrees of intensity during its construction. In this work, we present a combined study of natural and urban soils together with technogenic materials and geomorphological analysis based on LiDAR survey. The natural soils and Technosols (backfills) properties were determined to uncover different aspects of the soil memory about the environment. The geomorphological approach revealed various landscape modifications, including terrain leveling, the construction of structures, and the diversion of rivers and streams. Due to the diversion, changes in the water and sediment supply caused the modification of the alluvial fan configuration as well as the location of the travertine outcrops. Regarding the pre-Palenque soil cover, our study has demonstrated the presence of yellowish, sandy-silty soils derived from Cretaceous sandstones around the site, which is also present beneath the constructions. This soil distribution differs from that of nearby archaeological sites, where limestone produces Rendzinas and Luvisol-like soils. Our study showed the use of similar materials at different construction stages in the backfills (bones, shells, limestones, stucco, ceramics, charcoal, soil, and travertine); however, there were differences in their proportions. The initial stage, dated to 200–350 AD (based on a radiocarbon date from organic matter in the buried paleosol underlying the studied building), was characterized by the primary use of soil fragments. The final stages documented a significant use of limestone and travertine.