Preprints
https://doi.org/10.5194/egusphere-2022-1376
https://doi.org/10.5194/egusphere-2022-1376
 
03 Jan 2023
03 Jan 2023
Status: this preprint is open for discussion.

Erosion and weathering in carbonate regions reveal climatic and tectonic drivers of carbonate landscape evolution

Richard F. Ott1,2, Sean F. Gallen3, and David Helman4,5 Richard F. Ott et al.
  • 1Department of Earth Sciences, ETH Zurich, Zurich, Switzerland
  • 2Earth Surface Geochemistry, GFZ German Research Centre for Geosciences, Potsdam, Germany
  • 3Department of Geosciences, Colorado State University, Fort Collins, US
  • 4Department of Soil and Water Sciences, Institute of Environmental Sciences, Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel
  • 5The Advanced School for Environmental Studies, The Hebrew University of Jerusalem, Jerusalem, Israel

Abstract. Carbonate rocks are highly reactive and presumably have higher ratios of chemical weathering to total denudation relative to most other rock types. Their chemical reactivity affects the first-order morphology of carbonate-dominated landscapes and their climate sensitivity. However, there have been few efforts to quantify the partitioning of denudation into mechanical erosion and chemical weathering in carbonate landscapes such that their sensitivity to changing climatic and tectonic conditions remains elusive. Here, we compile bedrock and catchment-average cosmogenic calcite-36Cl denudation rates and compare them to weathering rates from the same regions. Local bedrock denudation and weathering rates are comparable, ~20–40 mm/ka, whereas catchment-average denudation rates are ~2.7 times higher. This discrepancy is 5 times lower compared to silicate-rich rocks illustrating that elevated weathering rates make denudation more spatially uniform in carbonate-dominated landscapes. Catchment-average denudation rates correlate well with topographic relief and hillslope gradient, and moderate correlations with runoff can be explained by concurrent increases in weathering rate. Comparing denudation rates with weathering rates shows that mechanical erosion processes contribute ~50 % of denudation in southern France and ~70 % in Greece and Israel. Our results indicate that the partitioning between largely slope-independent chemical weathering and slope-dependent mechanical erosion varies based on climate and tectonics and impacts the landscape morphology. In humid, slowly uplifting regions, carbonates are associated with low-lying, flat topography because slope-independent chemical weathering dominates denudation. In contrast, in arid climates with rapid rock uplift rates, carbonate rocks form steep mountains that facilitate rapid, slope-dependent mechanical erosion required to compensate for inefficient chemical weathering and runoff loss to groundwater systems. This result suggests that carbonates represent an end-member for interactions between climate, tectonics, and earth materials.

Richard F. Ott et al.

Status: open (until 14 Feb 2023)

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Richard F. Ott et al.

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Short summary
We compile data on carbonate denudation, the sum of mechanical erosion and chemical weathering, from cosmogenic nuclides and use them in conjunction with weathering data to constrain the partitioning of denudation into erosion and weathering. We show how carbonate erosion and weathering respond to different climatic and tectonic conditions and find that variations in denudation partitioning can be used to explain the vastly different morphology of carbonate landscapes on Earth.