EGU2020-16577, updated on 26 Oct 2020
https://doi.org/10.5194/egusphere-egu2020-16577
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Calibration and paleohydrological application of compound-specific isotope analyses (δ13Cwax, δ2Hwax and δ18Osugar) in semi-arid/arid Mongolia

Julian Struck1, Marcel Bliedtner1, Paul Strobel1, Gerhard Daut1, Jens Schumacher2, Lucas Bittner3, Birgit Plessen4, Bruno Glaser5, Björn Klaes6, Enkhtuja Bazarradnaa7, Gary Salazar8, Sönke Szidat8, Michael Zech3, and Roland Zech1
Julian Struck et al.
  • 1Institute of Geography, Physical Geography, Friedrich-Schiller-University Jena, Jena, Germany (julian.struck@uni-jena.de)
  • 2Institute of Mathematics, Friedrich-Schiller-University Jena, Jena, Germany
  • 3Institute of Geography/ Physical Geography with focus on paleoenvironmental research, Dresden University of Technology, Dresden, Germany
  • 4Climate Dynamics and Landscape Evolution Section, GFZ German Research Centre for Geosciences, Potsdam, Germany
  • 5Institute of Agronomy and Nutritional Sciences, Soil Biogeochemistry, Martin-Luther University Halle-Wittenberg, Halle (Saale), Germany
  • 6Department of Geology, University of Trier, Trier, Germany
  • 7Institute of Plant and Agricultural Sciences, Mongolian University of Life Sciences, Darkhan Uul, Mongolia
  • 8Department of Chemistry and Biochemistry and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland

Several lake sediment studies have investigated the Holocene climate history in Mongolia using pollen, organic and inorganic elemental analyses. However, these studies come to very different conclusions. Isotope analyses, particularly compound-specific carbon, hydrogen and oxygen isotopic composition of leaf wax n-alkanes (δ13Cwax, δ2Hwax) and hemicellulose sugars (δ18Osugar) are increasingly used for paleoenvironmental and -hydrological reconstructions and might have great potential to address the controversies in Mongolia.

Here we present a regional calibration of δ13Cwax, δ2Hwax and δ18Osugar on topsoils along a distinct climate gradient in semi-arid/arid Mongolia. δ13Cwax significantly correlates with aridity indicating variations in water use efficiency. The apparent fractionation (Ɛapp) of δ2Hwax and δ18Osugar is nearly constant at -131 ± 13‰ for Ɛn-C29/p, -148 ± 11‰ for Ɛn-C31/p and 40.8 ± 1.9‰ for Ɛsugar/p, respectively. δ2Hwax (n-C29 and n-C31) and δ18Osugar thus, reflect the isotopic composition of precipitation, which in turn is controlled by atmospheric circulation systems bringing moisture to continental Mongolia, i.e. the interaction between the Westerlies and the Asian Summer Monsoon. Therefore, we applied regionally calibrated δ13Cwax, δ2Hwax and δ18Osugar isotopes, as well as well-established sedimentological and geochemical proxies and δ13Corg, δ13Ccarb, δ18Ocarb on a 160 cm long gravity core from Lake Telmen (Central Mongolia) that covers 4,110 +350/‑340 cal. a BP.

Low terrestrial input (e.g. low Al, Fe, K, Sr) suggests decreased runoff and points to overall dryer conditions in the area around Lake Telmen between 4,110 +350/‑340 and 3,040 +610/‑400 cal. a BP. Those findings are in line with positive δ2Hn-C23, δ18Osugar and δ18Ocarb, which indicate enhanced lake water evaporation. From 3,040 +610/‑400 to 1,360 +230/‑220 cal. a BP, high terrestrial input and more negative δ2Hn-C23, δ18Osugar and δ18Ocarb values indicating more humid conditions. This is in line with seismic results which reveal distinct subaqueous cliffs and an extreme lake level rise beginning at ~ 2,000 cal. a BP. Drier conditions and low lake levels occurred between 1,360 +230/‑220 and 700 +210/‑180 cal. a BP and are indicated by low Ca/Mg ratios and a distinct enrichment in 13Cwax, 2Hwax,18Osugar and 18Ocarb. From 700 +210/‑180 cal. a BP onwards, drier conditions continue but the terrestrial input increases possibly reflecting anthropogenic impact.

How to cite: Struck, J., Bliedtner, M., Strobel, P., Daut, G., Schumacher, J., Bittner, L., Plessen, B., Glaser, B., Klaes, B., Bazarradnaa, E., Salazar, G., Szidat, S., Zech, M., and Zech, R.: Calibration and paleohydrological application of compound-specific isotope analyses (δ13Cwax, δ2Hwax and δ18Osugar) in semi-arid/arid Mongolia, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16577, https://doi.org/10.5194/egusphere-egu2020-16577, 2020