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Denudation and weathering rates of carbonate lithologies from meteoric 10Be/9Be ratios

During the past decades, cosmogenic nuclides, such as in-situ produced 10Be, evolved as state-of-the-art tool to quantify millennial-scale denudation in quartz-rich landscapes. However, applications of cosmogenic nuclides to carbonate-dominated lithologies are still rare, even though carbonate dissolution is a major weathering process that may compensate anthropogenically elevated CO2 levels over centennial-millennial timescales.

Recent advances in quantifying carbonate erosion have been made using cosmogenic 36Cl and of carbonate weathering using dissolved loads (e.g.[1],[2]). As these integrate over two distinct time-scales we developed a method that records such rates simultaneously: the cosmogenic meteoric 10Be over 9Be ratio (10Be/9Be). We adapted a framework[3] combining a known atmospheric flux tracer, meteoric 10Be (T1/2=1.4 My), with stable 9Be, a trace released from rocks by weathering, to the limestone-dominated French Jura Mountains. We analyzed water, soil, sediment, and bedrock for 10Be/9Be, major/trace elements, and Sr and C isotopes, to quantify i) Be contribution from carbonate vs. silicate minerals and ii) from primary vs. secondary carbonate phases, iii) solid-solute load partitioning, and iv) deep (sediment) vs. surficial (soils) weathering and erosion. Our results indicate average denudation rates of 300 t/km2/yr, denudation being dominated by weathering flux (W/D ratios of 0.7-0.97), and a consistently higher contribution from deep weathering. These rates agree to decadal-scale denudation rates from combined suspended and dissolved fluxes within < 2x which highlights the great potential of this method for future Earth’s surface studies.

[1]Ott et al., JGR-ES, 2019.

[2]Ben-Asher et al., GSA-Bull., 2021.

[3]von Blanckenburg, F, Bouchez, J. and Wittmann, H., EPSL, 2012.


Hella Wittmann1, Julien Bouchez2, Damien Calmels3, Jerome Gaillardet2, Daniel Frick1, Nicole Stroncik1, Georges Aumaître4, Didier Bourlès4, Karim Keddadouche4, Friedhelm von Blanckenburg5
1Helmholtz Centre Potsdam GFZ German Research Centre for Geoscience, Germany; 2Université de Paris, Institut de physique du globe de Paris, France; 3Université Paris-Saclay, Laboratoire GEOPS, CNRS, Orsay, France; 4Aix-Marseille Univ., CNRS, IRD, INRA, Coll France, CEREGE, Technopôle de l’Environnement Arbois-Méditerranée, Aix-en-Provence, France; 5Helmholtz Centre Potsdam GFZ German Research Centre for Geoscience, Germany;Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
GeoMinKöln 2022