Climatic variations during the Holocene inferred from radiocarbon and stable carbon isotopes in speleothems from a high-alpine cave
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Published:2021-10-19
Issue:5
Volume:17
Page:2165-2177
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ISSN:1814-9332
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Container-title:Climate of the Past
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language:en
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Short-container-title:Clim. Past
Author:
Welte CarolineORCID, Fohlmeister Jens, Wertnik Melina, Wacker LukasORCID, Hattendorf BodoORCID, Eglinton Timothy I., Spötl ChristophORCID
Abstract
Abstract. Rapid and continuous analysis of radiocarbon (14C) concentration in
carbonate samples at spatial resolution down to 100 µm has been made
possible with the new LA-AMS (laser ablation accelerator mass spectrometry)
technique. This novel approach can provide radiocarbon data at a spatial
resolution similar to that of stable carbon (C) isotope measurements by
isotope ratio mass spectrometry of micromilled samples and, thus, can help
to interpret δ13C signatures, which otherwise are difficult to
understand due to numerous processes contributing to changes in the C-isotope
ratio. In this work, we analyzed δ13C and 14C on the
Holocene stalagmite SPA 127 from the high-alpine Spannagel Cave (Austria).
Both proxies respond in a complex manner to climate variability. Combined
stable carbon and radiocarbon profiles allow three growth
periods characterized by different δ13C signatures to be identified: (i) the
period 8.5 to 8.0 ka is characterized by relatively low δ13C
values with small variability combined with a comparably high radiocarbon
reservoir effect (expressed as dead carbon fraction, dcf) of around 60 %.
This points towards C contributions of host rock dissolution and/or from an
“old” organic matter (OM) reservoir in the karst potentially mobilized due
to the warm climatic conditions of the early Holocene. (ii) Between 8 and
3.8 ka there was a strong variability in δ13C with values ranging from
−8 ‰ to +1 ‰ and a generally lower dcf. The δ13C variability is most likely caused by changes in C exchange between
cave air CO2 and dissolved inorganic carbon in drip water in the cave,
which are induced by reduced drip rates as derived from reduced 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 meteoric precipitation or because it was exhausted. (iii) In the
youngest section between 3.8 and 2.4 ka, comparably stable and low
δ13C values, combined with an increasing dcf reaching up to
50 % again, hint towards a contribution of an aged OM reservoir in the
karst. This study reveals the potential of combining high-resolution
14C profiles in speleothems with δ13C records in order to
disentangle climate-related C dynamics in karst systems.
Publisher
Copernicus GmbH
Subject
Paleontology,Stratigraphy,Global and Planetary Change
Reference69 articles.
1. Bajo, P., Borsato, A., Drysdale, R., Hua, Q., Frisia, S., Zanchetta, G.,
Hellstrom, J., and Woodhead, J.: Stalagmite carbon isotopes and dead carbon
proportion (DCP) in a near-closed-system situation: An interplay between
sulphuric and carbonic acid dissolution, Geochim. Cosmochim. Ac.,
210, 208–227, 2017. 2. Bar-Matthews, M., Ayalon, A., Kaufman, A., and Wasserburg, G. J.: The
Eastern Mediterranean paleoclimate as a reflection of regional events: Soreq
cave, Israel, Earth Planet Sc. Lett., 166, 85–95, 1999. 3. Benavente, J., Vadillo, I., Carrasco, F., Soler, A., Linan, C., and Moral,
F.: Air Carbon Dioxide Contents in the Vadose Zone of a Mediterranean Karst,
Vadose Zone J., 9, 126–136, 2010. 4. Bergel, S. J., Carlson, P. E., Larson, T. E., Wood, C. T., Johnson, K. R.,
Banner, J. L., and Breecker, D. O.: Constraining the subsoil carbon source
to cave-air CO2 and speleothem calcite in central Texas, Geochim.
Cosmochim. Ac., 217, 112–127, 2017. 5. Breecker, D. O., Payne, A. E., Quade, J., Banner, J. L., Ball, C. E., Meyer,
K. W., and Cowan, B. D.: The sources and sinks of CO2 in caves under mixed
woodland and grassland vegetation, Geochim. Cosmochim. Ac., 96,
230–246, 2012.
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