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

Abstract

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.

Aeolian dust accretion outpaces erosion in the formation of Mediterranean alpine soils. New evidence from the periglacial zone of Mount Olympus, Greece

“…Even though we did not estimate the dissolution rate of Mount Olympus bedrock metacarbonates and the elemental composition of the insoluble residue, we consider that the fine earth (silt and clay) contents of MK and TZ interbedded layers, which average 10% and 25%, respectively, cannot be derived only by carbonate dissolution and/or by isovolumetric replacement of calcite. Küfmann (2008), Krklec et al (2022) and Ott et al (2023) propose carbonate bedrock dissolution rates between ⁓0.23, 0.15 and 0.4 cm ka −1 , respectively, which for the postglacial (12.5 ka BP to present) alpine soil formation on Mount Olympus imply ⁓5 cm of carbonate loss to soil formation, a value too low to explain the observed thickness of MK and TZ interbedded layers and of the PM soil as a result of residual clay accumulation alone. Our direct observations of episodic Sahara dust deposition on the snowpack of Mount Olympus (Figure 3) provide undisputable evidence of Sahara dust accretion on PM soil.…”

Modeling Cosmogenic Nuclides in Transiently Evolving Topography and Chemically Weathering Soils

“…Here, ∆ x and ∆ y are the grid point lengths in the x and y directions, and ∆ t is the duration of the timestep. Thus far, few studies have accounted for enrichment or depletion of the host mineral in cosmogenic nuclide‐based estimates of basin‐averaged denudation rate, but recent work in carbonate landscapes underscores the importance of doing so (Ott et al., 2022, 2023). In Section 3, we show the implications of neglecting chemical erosion in point‐based and basin‐averaged estimates of denudation rate.…”

Morpho-tectonics of transpressional systems: insights from analog modeling

“…Muscovite 40 Ar/ 39 Ar dates are older outside this valley at around 250 -425 Ma (van der Lelij et al, 2016). Cosmogenic radionuclide dating (Ott et al, 2023) and low-temperature thermochronology (Pérez-Consuegra et al, 2022) from the central and western Colombian Andes (Figure 10c) show the highest erosion/denudation rates in the lofted Cauca valley (1 km elevation) along the Romeral-Cauca fault systems. Though perhaps coincidentally, we note that the trend of the main valley in each natural prototype supports the observed differences between the final configurations of the presented high and low erosion models.…”