Impacts of Mayan land use on Laguna Tuspán watershed (Petén, Guatemala) as seen through clay and ostracode analysis

This work presents a high resolution, multi-proxy study of 'Maya clays' in lacustrine sediments from Laguna Tuspán, near the archaeological site of La Joyanca. Micropaleontological (ostracodes), mineralogical (clay minerals) and geochemical (bulk elemental composition and stable isotopes in organic carbon) records reveal three different phases of soil erosion throughout the last 5300 years. The oldest phase from 5281 to 2998 cal yr BP (i.e. 3331 - 1048 BC) is characterized by successive natural and moderate soil erosion deposits which follow climatic variations recorded in the American tropical belt. The time interval between 2998 and 1281 cal yr BP (i.e. 1048 BC and AD 661) contains four distinct erosional layers which, according to clay mineralogy, are indicative of both increased erosion of the regolith and strong soil loss. The most recent, also the most massive, deposit of Maya clay ends around 1281 cal yr BP (AD 661), that is some 200 years before the so-called 'Maya collapse' in the Petén area. Recent archeological fieldwork studies indicate that a population mobility took place into the city of La Joyanca from its hinterland by the early Late Classic Period (ca. AD 600), that is, at the end or just after this erosion episode, and well before the occurrence of the Terminal Classic-Postclassic (AD 800-1250) drastic climatic changes. Shifts in environmental management by the local society and timing of urbanization may explain environmental changes better than droughts per se.