Climatic variations during the Holocene inferred from radiocarbon and stable carbon isotopes in a high-alpine cave
- Journal Article
Rights / licenseCreative Commons Attribution 4.0 International
A novel technique making use of laser ablation coupled online to accelerator mass spectrometry (LA-AMS) allows analyzing the radiocarbon (14C) concentration in carbonate samples continuously at high spatial resolution within very short analysis times. This new technique can provide radiocarbon data similar to the spatial resolution of stable carbon (C) isotope measurements by isotope-ratio mass spectrometry (IRMS) and, thus, can help to interpret δ13C signatures, which otherwise are difficult to understand due to numerous processes contributing to changes in C-isotope changes ratios. In this work we analyzed δ13C and 14C on the Holocene stalagmite SPA 127 from the high-alpine Spannagel Cave (Austria). Combined stable carbon and radiocarbon profiles allow to identify three growth periods characterized by different δ13C signatures: (i) the period > 8 ka BP 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 3.8–8 ka BP a strong variability in δ13C reaching values from −8 to +1 ‰ with a generally lower dcf was observed. The δ13C variability is most likely caused by changes in gas exchange processes 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 is contributing less to stalagmite growth in this period possibly as a result of reduced precipitation or because it is exhausted. (iii) In the youngest section between 2.4–3.8 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 OM reservoir in the karst. Show more
Journal / seriesClimate of the Past Discussions
Organisational unit03868 - Eglinton, Timothy I. / Eglinton, Timothy I.
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