117-12 Geochemical Records of Environmental Change and Human Activity During the Classic Maya Period at Cenote Xcach

Abstract:

During the Classic Period (200-950 CE), the ancient Maya civilization underwent substantial environmental stress from deforestation, erosion and drought across the  Yucatán region and population growth. Although anthropogenic environmental degradation and socio-political instability have been proposed as drivers of this shift, critical geographic gaps remain between these regions. Here we present organic bulk and biomarker data from a high-resolution sediment core from Cenote Xcach, a previously unstudied lake located in the northern Yucatán lowlands. We employed a multi-proxy geochemical approach to reconstruct human occupation and agricultural activity at Xcach. Stable isotopes of nitrogen (δ¹⁵N) and total organic carbon-to-nitrogen (TOC:TN) ratios were used to determine changes in organic matter source to the lake. These data were coupled with phosphorus (P), mercury (Hg), and fecal stanol abundances, which reflect lake productivity, the cultural use of cinnabar-based vermilion pigment, and human population change, respectively. Phosphorus and Hg concentrations exhibit strong positive relationships with bulk δ¹⁵N values. A pronounced δ¹⁵N enrichment (ca. 4‰) during the Classic Period coincides with elevated P concentrations, consistent with increased nutrient loading associated with human wastewater inputs, agricultural fertilization, and/or slash-and-burn land management. Following this peak, declining δ¹⁵N values during the post-Classic period correspond with a marked increase in TOC ratios (>10), indicating a transition toward greater terrestrial organic matter input and forest regrowth after possible site depopulation. Together, these complementary proxies document a sequence of intensified land use, elevated demographic pressure, and subsequent ecological recovery. Ongoing analysis of charcoal abundances and coprostanol concentrations will further constrain the timing and magnitude of population change, agricultural practices, and fire activity at this minimally studied site, adding to the complexity of environmental pressures on the Classic Maya prior to the Terminal Collapse.

Geological Society of America Abstracts with Programs. Vol. 58, No. 5, 2026

doi: 10.1130/abs/2026AM-21912

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