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Controls on Physical and Chemical Denudation in a Mixed Carbonate-Siliciclastic Orogen
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  • Erica D Erlanger,
  • Jeremy Caves Rugenstein,
  • Aaron Bufe,
  • Vincenzo Picotti,
  • Sean Willett
Erica D Erlanger
GFZ Potsdam, GFZ Potsdam

Corresponding Author:ederlanger@gmail.com

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Jeremy Caves Rugenstein
Max Planck Institute for Meteorology, Max Planck Institute for Meteorology
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Aaron Bufe
1GFZ German Research Center for Geosciences, 1GFZ German Research Center for Geosciences
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Vincenzo Picotti
ETH Zurich, ETH Zurich
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Sean Willett
ETH Zurich, ETH Zurich
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Mixed siliciclastic and carbonate active orogens are common on Earth’s surface, yet most studies have focused on physical erosion and chemical weathering in silicate-rich landscapes. Relative to purely siliciclastic landscapes, the response of erosion and weathering to uplift may differ in mixed-lithology regions. However, our knowledge of weathering and erosion in mixed carbonate-silicate lithologies is limited and thus our understanding of the mechanistic coupling between uplift, chemical weathering, and the carbon cycle. Here, we partition the denudation fluxes into erosion and weathering fluxes of carbonates and silicates in the Northern Apennine Mountains of Italy—a mixed siliciclastic-carbonate active orogen—using dissolved solutes, the fraction of carbonate sand in sediments, and existing 10Be denudation rates. Erosion fluxes are generally an order of magnitude higher than weathering fluxes and dominate total denudation. The contribution of carbonate and silicate minerals to erosion varies between lithologic units, but weathering fluxes are systematically dominated by carbonates. Silicate weathering may be limited by reaction rates, whereas carbonate weathering may be limited by acidity of the rivers that drain the orogen. Precipitation of secondary calcite from super-saturated streams leads to the loss of up to 90% of dissolved Ca2+ from carbonate-rich catchments. Thus, in the weathering zone, [Ca2+] is exceptionally high, likely driven by high soil pCO2; however, re-equilibration with atmospheric pCO2 in rivers converts solutes back into solid grains that become part of the physical denudation flux. Limits on weathering in this landscape therefore differ between the subsurface weathering zone and what is exported by rivers.
Aug 2021Published in Journal of Geophysical Research: Earth Surface volume 126 issue 8. 10.1029/2021JF006064