An ultra-high-resolution seasonal-scale stalagmite palaeoclimate record from the Yucatán peninsula, spanning the Maya Terminal Classic period.

It has now been over 25 years since stable isotope data from lake sediment cores was first used to provide quantitative evidence of increased aridity in the Yucatán peninsula during the Maya Terminal Classic period (c.800-1000CE); a time in which Maya civilisation underwent major societal shifts and depopulations, frequently termed the Classic Maya Collapse. While palaeoclimatic evidence of reduced precipitation during the Terminal Classic from sediments and, more recently, speleothems is now plentiful, the degree of uncertainty in their chronology and proxy interpretation has precluded analysis of the precise link between decadal and sub-decadal scale drought events and the abandonment of individual Maya archaeological sites on similar timescales.

We present a sub-seasonal-resolution stable isotope record from the stalagmite Tecoh06-1, from Tzabnah Cave (near Tecoh, Yucatán), which spans 185 years of the Terminal Classic. By utilising a prior visual layer count and milling at varying resolution to yield 10-20 samples per lamina, we here record seasonal-scale annual fluctuations in both δ¹⁸O and δ¹³C. With each lamina confirmed to be annual, we have developed a known-duration record which can be temporally fixed by conventional U/Th dating, greatly reducing the associated degree of chronological uncertainty. This is the first local palaeoclimate dataset to record seasonality through the Terminal Classic, and additionally it replicates a lower-resolution record from the same cave, published by Medina-Elizalde et al. (2010), to a satisfactory degree over the sampled period.

Using this palaeoseasonal record we can now reliably characterise the multiple decadal-scale intervals wherein precipitation remained low year-round. These intervals would have likely been those with the most significant detrimental impact on Maya agriculture and society.