A Bayesian AMS ¹⁴C chronology of the Classic Maya Center of Uxbenká, Belize

Archaeologists require precise chronologies of cultural change to understand the nature and timing, and causes and effects, of ecological and social transformations. The Uxbenká Archaeological Project (UAP) has made chronology building a main goal, employing epigraphic data, artifact seriation, and high-precision AMS ¹⁴C dating. With more than 60 ¹⁴C dates with measurement errors below ±25 ¹⁴C yr, primarily on single charcoal specimens, Uxbenká may be the most intensively dated Classic Period site in the tropical Maya Lowlands. Here we take the next step, combining this rich chronometric dataset with associated stratigraphic information in OxCal's Bayesian framework to generate a high-resolution chronology of Uxbenká's early development and expansion in southern Belize. We show how archaeologists may take advantage of complex architectural stratigraphy to constrain broad calibrated ranges during the Classic Period, and to estimate dates for observed construction events that can not be directly dated (e.g., clearing/leveling plazas, laying plaster floors, renovating/rebuilding structural elements). Our analysis confirms the antiquity of the ceremonial Stela Plaza (Group A), where first construction is estimated between 60 cal BC and cal AD 220 and is associated with a Pre-Classic structure obscured by later construction and reorientation of the group to a N-S alignment ca. AD 150-310. The analysis also indicates initial leveling and construction at plaza Group B from cal AD 60-310 and Group D from cal AD 20-240, both earlier than previously assumed. Though Late Classic contexts are not as well represented by direct dates, architectural modifications are documented at all three plaza groups after AD 550, including the extensive plastering, laying paving stones, and construction of facades on existing structures. The resulting chronology revises our previous thinking on the mode of settlement and development of Classic Maya society at Uxbenká and indicates specific areas of investigation to elucidate events in the Late and Terminal Classic at the site, including political and social fragmentation and the abandonment of the urban core late in the Classic Period.