Hydrological and climate variability in the northern Neotropics during the Late Quaternary

Lake Petén Itzá preserves a sedimentary record spanning the last 413 ka BP, offering insights into past climate and environmental changes of lowland Central America. This record is crucial for understanding past climate changes in the region due to its extensive temporal coverage and the lake’s position at the convergence of various climate drivers, such as the Intertropical Convergence Zone (ITCZ) and the Caribbean Low-Level Jet (CLLJ). The lake also holds significant cultural, environmental, and ecological value, but currently is highly vulnerable to climate change. In 2006, the International Continental Scientific Drilling Program (ICDP) drilled seven cores at different lake locations, whose variability in length and temporal coverage provide a comprehensive dataset for analyzing paleoclimate data across different timescales. This doctoral dissertation investigates the hydroclimate response of lowland Central America using Lake Petén Itzá sediments combined with inorganic (XRF data) and organic (bulk-geochemical, Rock-Eval, and biomarker data) proxies and supported by pollen and mineralogy data, to understand environmental changes and their potential climate drivers across geological time. Firstly, a new chronology established for the oldest sediments allowed us to detect glacial-interglacial cycles corresponding to Marine Isotope Stages (MIS) 11 to 5 (413-70 ka BP). Our data suggest a clear response of wet environments during the warm periods of MIS11 and MIS9 and dry conditions during MIS10, both influenced by the latitudinal migration of the ITCZ and the CLLJ. A hiatus between 304 and 147 ka BP indicates the absence of sediments deposited during MIS8, MIS7, and the beginning of MIS6. After 147 ka BP, wet conditions with high lake levels and Pinus and Quercus forests were reconstructed for the end of MIS6, linked to moisture input from cold fronts originating in higher latitudes. During MIS5 and part of MIS4 (130-70 ka BP), an increase in Moraceae and relatively dry environments marked the beginning of the penultimate interglacial, characterized by potential millennial-scale moisture variability. Secondly, this doctoral work focused on the MIS3 to MIS2 (59-15 ka BP) to analyze millennial-scale hydroclimate variations associated with Dansgaard-Oeschger (D-O) and Heinrich Stadials (HS). During the cold phases of the D-O (Greenland Stadials; GS), the environment was dominated by dry conditions, which intensified during the HS, aligning with high fire activity and previous temperature reductions of 5 to 10°C compared to the present. Conversely, during the warm phases of the D-O (Greenland Interstadials; GI), the environment experienced wet conditions, low evaporation, and anoxic bottom waters. In this study, we propose that the ITCZ had a greater influence on millennial-scale precipitation variations in lowland Central America, while the CLLJ more significantly affected precipitation on orbital scales, causing reduced rainfall during the Last Glacial Maximum (LGM). Thirdly, the first comprehensive record of organic matter content and lipid-based temperature over the late Pleistocene to Holocene (last 27 kyr) is presented, detailing changes in primary productivity and the influence of lake level variations and runoff on Lake Petén Itzá. Enhanced aquatic primary productivity is observed during humid periods like the LGM and Early Holocene, while dry periods such as HS1 and the Younger Dryas show low organic matter content dominated by terrestrial sources. Human settlement led to increased aquatic productivity around 3 ka ago. Additionally, temperature reconstructions using the MBT’5Me lipid paleothermometer suggest average temperatures of 20.8°C during the LGM and 25.4°C during the warmest Early Holocene peak with a deglacial temperature increase by 4°C. Finally, an extensive review of 155 paleoclimate sites in the northern Neotropics was conducted for the first time to understand the role of different climate drivers and the response of various regions from MIS11 to LGM. This review highlights the importance of obtaining more continental records from MIS11 to MIS6, as well as the complexity of the interaction of different climate drivers from MIS5 to LGM. It also emphasizes the high regionalization in environmental responses, potentially influenced by the continentality and altitude of the records. This work significantly advances the understanding of Lake Petén Itzá’s climate history and its broader implications for the northern Neotropics, laying a foundation for future paleoclimate studies in the region.