Preprints
https://doi.org/10.5194/bg-2023-63
https://doi.org/10.5194/bg-2023-63
12 Apr 2023
 | 12 Apr 2023
Status: this preprint is currently under review for the journal BG.

Past fire dynamics inferred from polycyclic aromatic hydrocarbons and monosaccharide anhydrides in a stalagmite from the archaeological site of Mayapan, Mexico

Julia Homann, Niklas Karbach, Stacy A. Carolin, Daniel H. James, David Hodell, Sebastian F. M. Breitenbach, Ola Kwiecien, Mark Brenner, Carlos Peraza Lope, and Thorsten Hoffmann

Abstract. Speleothems (cave stalagmites) contain inorganic and organic substances that can be used to infer past changes in local and regional paleoenvironmental conditions. Specific biomarkers can be employed to elucidate the history of past fires, caused by interactions among climate, regional hydrology, vegetation, humans, and fire activity. We conducted a simple solid-liquid extraction on pulverised carbonate samples to prepare them for analysis of 16 polycyclic aromatic hydrocarbons (PAHs) and three monosaccharide anhydrides (MAs). The preparation method requires only small samples (0.5 1.0 g); PAHs and MAs were measured by GC-MS and LC-HILIC-MS, respectively. Detection limits range from 0.05–2.1 ng for PAHs and 0.01–0.1 ng for MAs. We applied the method to 10 samples from a ~400-year-old stalagmite from Cenote Ch'en Mul, at Mayapan, the largest Postclassic Maya capital of the Yucatán Peninsula. We found a strong correlation (r=0.75, p < 0.05) between the major MA (levoglucosan) and non-alkylated PAHs (Σ15). We investigated multiple diagnostic PAH and MA ratios and found that although not all were applicable as paleo-fire proxies, ratios that combine PAHs with MAs are promising tools for identifying different fire regimes and inferring the type of fuel burned. In the 1950s and 1960s, levoglucosan and Σ15 concentrations roughly doubled compared to other times in the last 400 years, suggesting greater fire activity at Mayapan during these two decades. The higher concentrations of fire markers may be due to land clearance at the site and explorations of the cave by the Carnegie Institution archaeologists.

Julia Homann et al.

Status: open (extended)

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Julia Homann et al.

Julia Homann et al.

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Short summary
Cave stalagmites contain substances that can be used to reconstruct past changes in the local and regional environmental conditions. We used two classes of biomarkers (polycyclic aromatic hydrocarbons and monosaccharide anhydrides) to detect the presence of fire and to also explore changes in fire regime (e.g. fire frequency, intensity, and fuel source). We tested our new method on a stalagmite from Mayapan, a large Maya city on the Yucatán Peninsula.
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