Radiocarbon Calibration using Speleothems II - Soil carbon-climate interaction
Final Report Abstract
The Radiocarbon in Speleothem project began with two goals: (1) to develop an atmospheric radiocarbon calibration using speleothems, and (2) to understand the variable dead carbon fraction (DCF)—the proportion of host-rock-derived carbon. We achieved the first goal with a full-glacial-period ¹⁴C record, but no speleothem with a stable DCF was found, highlighting that DCF variability is driven mainly by soil processes rather than atmospheric changes. Attempts to use Mg/Ca as a proxy for soil carbon transport proved more complex than expected, leading to a second project phase focused on modeling soil dynamics' influence on radiocarbon variability. This phase combined geochemical data and modeling, using speleothems from Turkey, Yemen, Puerto Rico, and Mexico, covering the past 40,000 years. DCF values ranged from 5– 65%, showing significant ¹⁴C variability unlinked to trace elements or stable isotopes. Two key drivers emerged: soil carbon concentration and system openness during dissolution—processes not traceable with other proxies. While the project did not yield a global radiocarbon calibration, it supported numerous theses, generated valuable data, and led to the development of a carbon transfer model integrating soil-carbon-climate dynamics. Despite progress, results from Hulu Cave (China)—showing a uniquely low and stable DCF— could not be replicated. Hulu appears to be a rare, possibly singular, case, raising doubts about its suitability as a global ¹⁴C reference. Reproducing such a record remains a key challenge.
Publications
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Climate-induced speleothem radiocarbon variability on Socotra Island from the Last Glacial Maximum to the Younger Dryas. Climate of the Past, 16(1), 409-421.
Therre, Steffen; Fohlmeister, Jens; Fleitmann, Dominik; Matter, Albert; Burns, Stephen J.; Arps, Jennifer; Schröder-Ritzrau, Andrea; Friedrich, Ronny & Frank, Norbert
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HEIDELBERG RADIOCARBON LAB – ESTABLISHING A NEW CARBON DIOXIDE EXTRACTION LINE FOR CARBONATE SAMPLES. Radiocarbon, 63(3), 915-924.
Therre, S.; Proß, L.; Friedrich, R.; Trüssel, M. & Frank, N.
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Using the triple proxy δ13C–radiocarbon–major and trace elements to understand stalagmite stable carbon composition in Madagascar. Chemical Geology, 608, 121044.
Voarintsoa, Ny Riavo G. & Therre, Steffen
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Simultaneous U and Th isotope measurements for U-series dating using MCICPMS. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 539, 169-178.
Kerber, Inga Kristina; Arps, Jennifer; Eichstädter, René; Kontor, Fabian; Dornick, Christoph; Schröder-Ritzrau, Andrea; Babu, Athulya; Warken, Sophie & Frank, Norbert
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The role of Northern Hemisphere summer insolation for millennial-scale climate variability during the penultimate glacial. Communications Earth & Environment, 4(1).
Fohlmeister, Jens; Luetscher, Marc; Spötl, Christoph; Schröder-Ritzrau, Andrea; Schröder, Birgit; Frank, Norbert; Eichstädter, René; Trüssel, Martin; Skiba, Vanessa & Boers, Niklas
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Technical note: “U–Th Analysis” – open-source software dedicated to MC-ICP-MS U-series data treatment and evaluation. Geochronology, 7(1), 1-13.
Kerber, Inga Kristina; Kontor, Fabian; Mielke, Aaron; Warken, Sophie & Frank, Norbert
