Holocene environmental changes in the Ugii Nuur basin, Mongolia

In this study we investigate the Holocene environmental evolution of the Ugii Nuur basin in the Orkhon Valley, central Mongolia, in order to gain a better understanding of the climate and landscape dynamics of the steppe region in Central Asia. We assess terrestrial and lake sediments using mineralogical, geochemical and statistical techniques and provide absolute chronologies by radiocarbon datings and infra-red stimulated luminescence datings including fading correction. Our findings and their discussion in a broader regional context show that there is a Mid Holocene climate optimum. The shift towards warmer and wetter conditions involved changes from Aeolian dynamics of sand mobilization to loess-like sediment accumulation owing to the establishment of dust-trapping vegetation. Between 4 and 2.8 ka BP we track a decline in moisture supply which is then followed by relatively humid conditions until today. We infer that the region is sensitive to changes of the westerlies dynamics. In addition, we conclude that the Late Holocene was characterized by favorable climatic conditions that probably were an important prerequisite for the repetitive colonization of the Orkhon Valley throughout the last 3000 years.