SAK LU’UM: ANCIENT MAYA INTERACTIONS WITH ENVIRONMENTAL GYPSUM (Invited Presentation)

Gypsum is a dominant component of the Icaiche Formation underlying a good deal of the Yucatan Peninsula. This gypsum affected the overall distribution of ancient Maya settlement in two principal ways: 1) by affecting the potability of groundwater in some areas, and 2) by contributing to the development of large-scale dissolution features (bajos) in the landscape. In areas where groundwater was readily accessible by the Maya, high gypsum content was repellent to population concentration. Bajos are typically at least seasonally inundated and settlement directly within these depressions was highly restricted. However, bajo edges were attractive places for urbanization because of the possibilities present for rain water capture and storage, the existence of aprons of colluvial soils, and, in some places, for wetland agriculture. Soils within bajos interiors tend to have high gypsum content, probably reflecting a combination of exposure of geologic gypsum via weathering and erosion, capillary precipitation with soils, and, in some instances alluvial precipitation. An intriguing possibility exists that the Maya used gypsum as an agricultural amendment in heavy clay soils. The Maya were sufficiently interested in gypsum to quarry it in significant quantities in some areas. Known ancient uses for gypsum include as a plaster, as a substrate for painting, as a varnish, and the carving of alabaster vessels.