Form, Process and Evolution of Carbonate Hillslopes in sub-Humid Climate

This research deciphered key controls on the evolution of carbonate hillslopes across the sub-humid Eastern Mediterranean climate, including the influence of climate, chemical weathering, soil transport efficiency and dust flux. It yielded three joint publications in Q1 journals.

Our study utilized geochemical analysis of immobile elements, grain size analysis, cosmogenic nuclides, numerical modeling and high-resolution topographic data. Regolith and bedrock were sampled at seven carbonate study sites, across a prominent north-to-south gradient in both rainfall (250 to 900 mm yr-1) and dust flux. Numerical simulations were performed to estimate soil transport efficiency utilizing five cinder cones along the Golan Heights, where dust flux and chemical weathering are negligible and the initial topographic conditions are well constrained.

The soil creep efficiency coefficient (K) was found to be negatively correlated with mean annual rainfall between 600 to 1000 mm as increasing vegetation cover stabilizes the regolith. The K vs. rainfall dependency displays a hump at 400-600 mm/yr. Analysis of soil pit samples in carbonate hillslopes suggest that dust fraction in the soil decreases from nearly 100% of the fine regolith material in the southern sites to less than 10% in the northern sites and is positively correlated with modern measurements of dust deposition rates. Chemical weathering increases with mean annual rainfall from 5-25% in the arid south to 45-60% in the wetter sub-humid north. Hilltop denudation rates obtained using cosmogenic 36Cl show a prominent increase with mean annual rainfall. Using a novel mass balance, we predict hilltop curvature across our study sites and demonstrate that it is similar to the observed curvature.

The results of this study demonstrate that chemical weathering and dust flux play a profound role in hillslope morphology. Moreover, the mean annual rainfall is a key factor in carbonate hillslope evolution - it correlates with chemical depletion, denudation rates and soil creep efficiency.