C01_P09

Improving radiocarbon based chronologies in semi-arid regions using paleomagnetic secular variations – a case study from Mongolian high-altitude lakes

Strobel P¹, Haberzettl T², Struck J¹, Salazar G³, Szidat S³, Nowaczyk N⁴, Bazarradnaa E⁵,  Zech R¹, Bliedtner M¹

¹Institute of Geography, Friedrich Schiller University Jena, Jena, Germany, ²Physical Geography, Institute for Geography and Geology, University of Greifswald, Greifswald, Germany, ³Department of Chemistry, Biochemistry and Pharmaceutical Sciences and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland, ⁴Section Climate Dynamics and Landscape Evolution, GFZ German Research Centre for Geosciences, Potsdam, Germany, ⁵Institute of Plant and Agricultural Sciences, Mongolian University of Life Sciences, Darkhan, Mongolia

The paleoenvironmental evolution of semi-arid Mongolia is not well understood so far. To some degree, this is because chronologies in the region are often imprecise limiting the reliability of paleoenvironmental reconstructions. Most chronologies rely on a limited number of ¹⁴C-dates on bulk organic material, which comprises aquatic and terrestrial organic material potentially effected by “hard water” and “pre-ageing” effects. However, it is often impossible to disentangle both effects and resulting age-offsets lead to an overestimation of the true sedimentation age. To overcome these issues, paleomagnetic secular variations (PSV) can be a valuable independent chronological control tool to evaluate and refine ¹⁴C-based chronologies in semi-arid regions.

Here we present a chronological approach including ¹⁴C dating of different sediment compounds and PSV from Lake Khar Nuur, which is located in the Mongolian Altai Mountains. While ¹⁴C-ages of aquatic macrofossils are stratigraphically consistent, ¹⁴C-ages of bulk organic material show partly age-offsets due to pre-aging and sediment relocation. However, we cannot exclude that both compounds are additionally affected by a hard water effect resulting in a general overestimation of the true depositional age. Therefore, analyses of PSV are currently in progress and will be compared to the recently established PSV record from the high-altitude Lake Shireet Naiman Nuur (Bliedtner et al., 2022), which is located in the Mongolian Khangai Mountains and has a very precise chronological control. Comparison of the two ¹⁴C independent PSV records will allow to evaluate and potentially refine our ¹⁴C-based chronology at Lake Khar Nuur.