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Over the last glacial cycle, climate variations in the Neotropics were related to diverse forcing mechanisms whose understanding has been limited because of the scarcity of continuous long records. Here we use high‐resolution charcoal particle accumulation, inorganic carbon precipitation and magnetic susceptibility data from Lake Chalco, located in high‐altitude tropical central Mexico, to assess the fire regimes and drought periods between ∼85 and 10.8k cal a BP. Overall, drought intervals were characterized by high carbonate deposition and were contemporary with high spring insolation. Most of the high fire activity periods were coupled with droughts, whereas some of them seem to have responded to volcanic activity in the basin. Periods of more fire activity during the latest part of Marine Isotope Stage 3 were associated with a long interval of higher spring insolation. Increase in drought frequency during 47–27k cal a BP were possibly linked to a more active Laurentide Ice Sheet influencing the oceanic and atmospheric controls of the tropical climatic system. In fact, Chalco and Cariaco records show similar millennial‐scale trends, suggesting a role of the Intertropical Convergence Zone in modulating moisture availability in the region.

A high-resolution 14C chronology for the Teopancazco archaeological site in the Teotihuacan urban center of Mesoamerica was generated by Bayesian analysis of 33 radiocarbon dates and detailed archaeological information related to occupation stratigraphy, pottery and archaeomagnetic dates. The calibrated intervals obtained using the Bayesian model are up to ca. 70% shorter than those obtained with individual calibrations. For some samples, this is a consequence of plateaus in the part of the calibration curve covered by the sample dates (2500 to 1450 14C yr BP). Effects of outliers are explored by comparing the results from a Bayesian model that incorporates radiocarbon data for two outlier samples with the same model excluding them. The effect of outliers was more significant than expected. Inclusion of radiocarbon dates from two altered contexts, 500 14C yr earlier than those for the first occupational phase, results in ages calculated by the model earlier than the archaeological records. The Bayesian chronology excluding these outliers separates the first two Teopancazco occupational phases and suggests that ending of the Xolalpan phase was around cal AD 550, 100 yr earlier than previously estimated and in accordance with previously reported archaeomagnetic dates from lime plasters for the same site.

We inferred millennial-scale climate variations and paleohydrological conditions in the northern sector of the American tropics for 30.3–5.5 cal ka BP using geochemical characteristics of sediments from Lake Chalco in central Mexico. The sediment sequence is chronologically constrainedwith three tephra and nine radiocarbon dates. Temporal variations in titanium, total inorganic carbon, total organic carbon/titanium ratio, carbon/nitrogen ratio, and silica/titanium ratio indicate changes in runoff, salinity, productivity, and sources. Higher concentrations of Ti indicate more runoff during latest Marine Isotope Stage (MIS) 3 (30.3–28.6 cal ka BP). Runoff was lower during the last glacial maximum (LGM; 23–19 cal ka BP) than during the Heinrich 2 event (26–24 cal ka BP). The interval of reduced runoff continued up to 17.5 cal ka BP but increased during the Bølling/Allerød. Trends of decreasing runoff and increasing salinity are observed throughout MIS 1. Lake Chalco received less runoff during the LGM compared to deglaciation, opposite the trend of other North American tropical records. Different amounts of rainfall at different sites are possibly due to shifts in the position of the Intertropical Convergence Zone, changes in the size of the Altlanticwarmpool, and varying sea-surface temperatures of the Atlantic and Pacific oceans

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