Abstract

We inferred hydrological changes in Lake Petén Itzá (Guatemala) during Marine Isotope Stages (MIS) 3-2 using geochemical (Ti, Ca/Ti+Al+Fe ratio and Mn/Fe) and mineralogical (carbonates, gypsum, quartz, clay) data from sediment core PI-2 to reconstruct changes in runoff, lake evaporation, organic matter sources and potential oxic/anoxic conditions associated with variations in water-level during the last ~59 cal ka BP. Early MIS3 (57.0–52.5 cal ka BP) was dominated by relatively wet conditions, higher lake primary productivity and anoxic waters, which persisted into the subsequent interval (52.5–39.0 cal ka BP), except for two periods of possible low water-level at 52 and 46 cal ka BP when our data suggest higher evaporation, high terrestrial organic matter input and persistent oxic conditions. Towards the end of MIS3 and start of MIS2 (39.0–23.0 cal ka BP), lake evaporation increased considerably, as did inputs of terrestrial organic matter, and waters became more oxic as water-levels dropped and the site moved from the hypolimnion to the epilimnion. These conditions reversed during the Last Glacial Maximum (23.0–18.0 cal ka BP) when runoff and lake productivity increased and waters again became anoxic as a result of rising water-levels. Refining the age-depth model for the Site PI-2 also allowed the correlation to Greenland Interstadials (GI14-2), Greenland Stadial (GS14-2) and Heinrich Stadials (HS5-1). HS and GS were characterized by increases in Ca/Ti+Al+Fe ratios and gypsum content generally indicative of drier conditions. GS13, 9 and 5 showed the driest conditions associated with the contemporaneous establishment of HS5-3, respectively. In contrast, GI show high Ti values which suggests relatively greater runoff and overall wetter conditions compared with GS and HS, with the most marked GI peaks between 40 and 30 cal ka BP. This runoff variability is in accord with shifts in the average position of the Intertropical Convergence Zone and strength of the Atlantic Meridional Oceanic Circulation during the Late Pleistocene.

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