Palaeohydrological reconstruction in the high plain of Bogotá (Colombian, Eastern Cordillera) using plant wax n-alkane biomarkers and compound-specific stable hydrogen isotope (δDwax) analysis.

Understanding the mechanisms of past climatic variability allows refining the prediction of how the biologic systems respond to the forthcoming climatic changes. Although palaeoclimatical studies have previously been conducted in the Eastern Cordillera of Colombia, we have a very weakly constrained understanding of Pleistocene/Holocene palaeohydroclimatic dynamics in northern tropical South America. This study presents new reconstructions of past hydrological variability using stable hydrogen isotope proxies. The goal was to gain new insights into long-term climate forcing mechanisms in high altitude tropical environments within and surrounding the Bogotá Basin. Stable hydrogen isotope compositions of leaf waxes (δDwax), retrieved from three sediment cores, are used as a palaeohydrological proxy for the last ~ 18,080 years. To refine interpretations of the δDwax, superficial soils were also analysed over a range of modern climatic and ecological settings. The δDwax records register a significant climatic transition from drier conditions at ~ 11,300 cal. yr. BP. This was followed by a wetter trend after ~ 9,400 cal. yr. BP. Relatively dry climate characterised the mid-Holocene from ~ 7,500 cal. yr. BP. During mid- to late-Holocene transition, a distinct positive shift of δDwax is recorded in all three records, implying a marked reduction of rainfall coeval with the globally-recognised "4.2 kyr. BP event". δDwax values indicate that the climate became more humid into the late-Holocene. During the last ~ 2,500 cal. yr. BP, the δDwax signals showed a notable increase variability, indicating the alternating of abrupt dry-wet events. Overall, these δDwax records show evidence for a distinct relationship between northern South America and South America south of the equator during late-Pleistocene and the Holocene. These findings support previous hydroclimate studies linked to precession-driven changes in solar insolation. Millennial-scale climate variability in the Northern Hemisphere associated with the latitudinal displacements of the ITCZ, as well as the influence of the ENSO phenomenon controlling hydroclimate variability, was identified in these new records.