A Late Holocene Record of Precipitation Changes from Western Guatemala Inferred from Lacustrine Carbonate-Based Stable Isotopes

Guatemala is a drought-sensitive country that experiences varying amounts of precipitation in response to Atlantic and Pacific Ocean influences. A 5.5 m, finely-laminated sediment core from Lake San Francisco in the Huehuetenango province was collected in order to reconstruct precipitation changes over the last ~5,500 years at a decadal-scale resolution. An age-depth model was developed based on 7 radiocarbon ages of charcoal as well as ²¹⁰Pb dating of surface sediments. Authigenic carbonates preserved in the sediment record provide an archive of lake-water isotopic variability in response to climate driven changes in hydrologic balance. Modern surface water isotope data taken from lakes throughout the region indicate evaporative enrichment relative to meteoric water. Carbonate-based stable isotope records from closed-basin lakes like San Francisco will thus record changes in the ratio between evaporation and precipitation, with high δ¹⁸O reflecting drier conditions while lower δ¹⁸O values indicate periods of increased hydrologic balance. Our data suggest relatively dry conditions within the region between 2-5 ka BP, with the driest period lasting from ~3.2 to ~4.2 ka. A shift to wetter conditions began at ~2 ka and persisted until the past century. The detailed stratigraphy and well-resolved age model exhibited by the San Francisco record indicate a high potential to produce detailed paleoclimate data from Western Guatemala.