FP-XRF ANALYSIS OF ARCHAEOLOGICAL SEDIMENTS FROM VISTA ALEGRE, QUINTANA ROO, MEXICO

Vista Alegre is a small island on the north coast of the Yucatan Peninsula, set amongst mangroves at the southern edge of Holbox Lagoon. Architectural features such as a pyramid and defensive wall mark it as an important maritime trading settlement for the northern Maya lowlands, with evidence of occupation from the Preclassic period until Spanish contact (c. 8^th century BCE-16^th century CE). The island is bounded by shallow bays to the east and west, which are thought to have been maintained in antiquity to provide harbor for the canoes of the coastal trade routes.

In 2016, archeologists opened a series of 1m x 1m test excavations in an East-West transect across the island, reaching depths of up to 3.97m before encountering bedrock. This depth of sediment accumulation is considered anomalous for the region, which is characterized by poorly developed soil profiles overlaying a recently emerged (c. 18,000 years BP) carbonate platform. The island’s localized high volume of sediment deposition is therefore thought to be the result, in part, of anthropogenic processes such as dredging, filling, and leveling.

During the 2016 excavations, sediment samples were collected from each archaeological level, as well as each visually determined sedimentary strata. This study employs field-portable X-ray fluorescence (FP-XRF) to analyze the geochemistry of these samples, in order to develop a geochemical signature for the strata encountered during excavation. Three 120-second measurements were collected for each sample at both the 15kV and 40kV settings. Preliminary data analysis has involved the generation of inter-correlation matrices of samples from the transect’s three centermost excavations. Significant correlations (r = 0.95 or greater) have been observed among 15kV data between Ti and Ba, as well as Mn and Fe. A significant negative correlation exists between Ca and Si. The 40kV measurements display significant correlations between Fe and Co, Fe and Rb, and Rb and Y.

These correlations allow us to select analytes to develop a geochemical signature for each sample. A cross-section of chemofacies from each test excavation unit will then be constructed to investigate intra- and inter-test unit variability. This will provide insight into the natural and cultural formation processes that created this ancient Maya port.