EGU21-12836
https://doi.org/10.5194/egusphere-egu21-12836
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Climatic variations during the Holocene inferred from radiocarbon and stable carbon isotopes in a high-alpine cave

Caroline Welte1,2, Jens Fohlmeister3,4, Melina Wertnik1,2, Lukas Wacker1, Bodo Hattendorf5, Tim Eglinton2, and Christoph Spötl6
Caroline Welte et al.
  • 1ETHZ, Laboratory of Ion Beam Physics, Physics, Zürich, Switzerland (cwelte@phys.ethz.ch)
  • 2ETHZ, Geological Institute, Erdwissenschaften, Zürich, Switzerland (cwelte@phys.ethz.ch)
  • 3Potsdam Institute for Climate Impact Research, Telegrafenberg, 14473 Potsdam, Germany
  • 4GFZ German Research Centre for Geosciences, Section 'Climate Dynamics and Landscape Development', 14473 Potsdam, Germany
  • 5Laboratory of Inorganic Chemistry, D-CHAB, ETHZ, Vladimir-Prelog Weg 1, 8093 Zurich, Switzerland
  • 6Institute of Geology, University of Innsbruck, Innrain 52f, 6020 Innsbruck, Austria

Laser ablation coupled online to accelerator mass spectrometry [1] allows analyzing the radiocarbon (14C) concentration in carbonate samples in a fast and spatially resolved manner. This novel technique can provide 14C data at a spatial resolution comparable to that of stable carbon isotope measurements and, thus, can help to interpret δ13C signatures. In this work, we analyzed δ13C and 14C of a Holocene stalagmite from the high-alpine Spannagel Cave (Austria). Combined δ13C and 14C profiles allow identifying three growth periods : (i) the period > 8 ka BP exhibits relatively low δ13C values with small variability combined with a comparably high dead carbon fraction (dcf) of around 60%. This points towards C contributions of an old organic carbon reservoir in the karst potentially mobilized due to the warm climatic conditions of the early Holocene. (ii) Between 3.8 and 8 ka BP, a strong variability in δ13C with values from -8 to +1‰ and a generally lower dcf was observed. The δ13C variability was most likely caused by changes in gas exchange processes in the cave, which are induced by reduced drip rates as derived from lower stalagmite growth rates. Additionally, the lower dcf indicates that the OM reservoir contributed less to stalagmite growth in this period possibly as a result of reduced precipitation or because the OM reservoir became exhausted. (iii) In the youngest section between 2.4 and 3.8 ka BP, comparably stable and low δ13C values combined with an increasing dcf reaching up to 50% are again hinting towards a contribution of an aged organic carbon reservoir in the karst.

[1] C. Welte, et al., (2016). Anal. Chem., 88, 8570– 8576.

How to cite: Welte, C., Fohlmeister, J., Wertnik, M., Wacker, L., Hattendorf, B., Eglinton, T., and Spötl, C.: Climatic variations during the Holocene inferred from radiocarbon and stable carbon isotopes in a high-alpine cave, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12836, https://doi.org/10.5194/egusphere-egu21-12836, 2021.

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