Title: Quantifying carbonate denudation from cosmogenic 36Cl and climatic and tectonic controls on carbonate landscape evolution

Richard F Ott1,2, Sean F Gallen3, David Helman4,5

1Department of Earth Sciences, ETH Zurich, Zurich, Switzerland; 2Earth Surface Geochemistry, German Centre for Geoscience Research, Potsdam, Germany; 3Department of Geosciences, Colorado State University, Fort Collins, US; 4Department of Soil and Water Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel; 5Advanced School for Environmental Studies, The Hebrew University of Jerusalem, Jerusalem, Israel

Event: GeoKarlsruhe 2021

Date: 2021

DOI: 10.48380/dggv-n2w0-3p85

Quantifying carbonate denudation and the partitioning between chemical and mechanical surface lowering in karstic areas is challenging. Here we present a compilation of 36Cl denudation rates from alluvial samples in the Mediterranean and combine these with chemical weathering rates derived from water chemistry and satellite-dervied runoff data. We calculate mechanical erosion as the difference between the total denudation from cosmogenic 36Cl measurements and the chemical weathering rates. Our results show a dominance of mechanical erosion in Mediterranean carbonate regions. We observe a strong scaling between mechanical erosion, catchment steepness and total denudation rate, but a weak scaling with chemical weathering. This implies that slope dependent erosion gets progressively more important with increasing denudation rates and therefore is linked to tectonic uplift.

Significant amounts of chemical weathering can bias cosmogenic denudation rate measurements. Therefore, we investigate this potential bias for the calculation of 36Cl denudation rates in the reported Meditteranean sites, but find a limited influence.

These findings support a conceptual model of a dissolution speed limit in carbonates due to available water and acid such that areas of high local uplift require substantial mechanical erosion to balance uplift and form steep slopes. In contrast, areas experiencing low uplift rates with sufficient water availability (e.g. humid climate) can balance uplift entirely with dissolution resulting in subdued carbonate landscapes. This feedback explains why Meditterranean carbonate mountains are often high and steep compared to oher rock units, whereas carbonates in humid temperate climates form the subdued parts of the landscape.

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