| Abstrakt: |
Knowledge of the rates of carbonate rock denudation, the relative apportionment of chemical weathering versus physical erosion, and their sensitivity to climate, vegetation, and tectonics is essential for disclosing feedbacks within the carbon cycle and the functioning of karst landscapes that supply important services to humans. Currently, however, for carbonate lithologies, no method exists that allows to simultaneously partition denudation into erosion and weathering fluxes at spatial scales ranging from soil to watersheds. To determine total denudation rates in carbonate landscapes from an individual soil or river sample, we adapted a published framework that combines cosmogenic meteoric 10Be as an atmospheric flux tracer with stable 9Be that is released from rocks by weathering, to the limestone‐dominated French Jura Mountains. By analyzing water, soil, sediment, travertine, and bedrock for 10Be/9Be, major and trace elements, carbon stable isotopes and radiogenic strontium, we quantified contributions of Be from primary versus secondary carbonate phases and its release during weathering from carbonate bedrock versus silicate impurities. We calculated partitioning of Be between solids and solutes, and rates of catchment‐wide (from sediment) and point source (from soil) denudation, weathering and erosion. Our results indicate that average denudation rates are 300–500 t/km2/yr. Denudation is dominated by weathering intensity (W/D) ratios of >0.92, and a non‐negligible contribution from deeper (below soil) weathering. Our rates agree to within less than a factor of two with decadal‐scale denudation rates from combined suspended and dissolved fluxes, highlighting the substantial potential of this method for future Earth surface studies. Carbonate rocks, constituting about 10% of the terrestrial Earth’s surface, play a crucial role in the short‐term carbon cycle by absorbing atmospheric CO2and forming karst landscapes. These landscapes, supporting 10% of the global population with vital services, remain poorly understood due to a lack of tools for assessing erosion and weathering rates. In our study of the French Jura Mountains, we utilized a novel method involving the isotope ratio of 10Be/9Be from the cosmogenic meteoric 10Be, raining onto Earth from the atmosphere at a specific rate, and the stable trace element 9Be released from rocks by weathering, to measure erosion, weathering, and total denudation. Our results indicate an annual soil and sediment erosion of 300–500 tons per square kilometer, with 90% attributed to rock dissolution (weathering) and 10% to physical erosion. A non‐trivial fraction of weathering appears to happen deep (below soil). Our new rates agree closely with rates estimated independently from suspended and dissolved river loads. As such, they demonstrate the considerable potential of the 10Be/9Be technique as a rate meter at Earth’s surface. Denudation rates from 10Be/9Be in a carbonate landscape agree within a factor of 2 with rates from suspended and dissolved river loadsMeteoric 10Be/9Be‐derived carbonate denudation is dominated by weathering (>0.9 W/D)A non‐negligible contribution in denudation originates in deeper (below soil) weathering Denudation rates from 10Be/9Be in a carbonate landscape agree within a factor of 2 with rates from suspended and dissolved river loads Meteoric 10Be/9Be‐derived carbonate denudation is dominated by weathering (>0.9 W/D) A non‐negligible contribution in denudation originates in deeper (below soil) weathering |
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