Comparison of Historical and Speleothem (Paleo)climate Records from Northwest Yucatán (Mexico)

Paleoclimate studies on the Yucatán Peninsula, Mexico, are important for understanding relationships between past climate change and ancient Maya cultural evolution. The Postclassic Maya capital of Mayapán is a site of interest for such studies,  given that evidence of repeated drought conditions corresponded to times of violent conflict, from ~1400 to 1450 CE (Kennett et al., 2022), just before site abandonment in ~1450 and prior to the protracted Spanish conquest of the Yucatán region from 1527 to 1697 CE. As part of further efforts to identify past droughts in northwest Yucatán, we studied a new stalagmite from Cenote Ch’en Mul, located directly beneath the archaeological site of Mayapán. The upper 120 mm section of stalagmite MAYA-22-7 is chronologically constrained by five uranium-series dates between 1618 ± 23 (2σ) and 2001 ± 11, and grew at a near-constant rate of 0.3 mm/yr. Stable isotopes (ẟ18O and ẟ13C) of calcite were measured every 0.1 mm along the upper section growth axis and compared with Colonial-period records of known droughts, famines, and population declines (Hoggarth et al., 2017). 

The ẟ18O and ẟ13C records capture abrupt increases (1-2 ‰ above baseline), coincident (±5 years) with some of the historical records of extreme drought. One notable example includes ẟ18O values 1.0 ‰ above baseline from 1767 to 1770 CE, indicative of an extended dry period contemporaneous with the “Great Famine” of 1765 to 1773. That dry interval is described in historic records as having been characterized by drought, locusts, famine, widespread epidemics, and mortality, which caused a 39 % population reduction (Hoggarth et al., 2017). Evidence for severe drought is replicated for the interval 1765-1768 in a nearby speleothem record from Belize (Kennett et al., 2012). Furthermore, ẟ13C values demonstrate distinct 2 ‰ shifts, from -10 to -8 ‰, and frequent (3-5 year) repeated oscillations, indicating a strong, rapid response of the overlying ecosystem’s carbon budget to climate variability, perhaps related to the El Niño/Southern Oscillation (ENSO). Ultimately, in combination with other local and regional paleoclimate records, study of MAYA-22-7 will help assess the reliability of stalagmite records to capture historic droughts with high temporal accuracy, document patterns of climate variability (e.g., ENSO-related changes), and track land-use change across cultural transitions, while contributing to our understanding of human-climate-environment interactions in the Maya Lowlands.