Comparison of regolith physical and chemical characteristics with geophysical data along a climate and ecological gradient, Chilean Coastal Cordillera (26 to 38° S)

Abstract

Abstract. We combine geophysical observations from ground-penetrating radar (GPR) with regolith physical and chemical properties from pedons excavated in four study areas spanning 1300 km of the climate and ecological gradient in the Chilean Coastal Cordillera. Our aims are the following: (1) to relate GPR observations to depth-varying regolith physical and weathering-related chemical properties in adjacent pedons and (2) to evaluate the lateral extent to which these properties can be extrapolated along a hillslope using GPR observations. Physical observations considered include regolith bulk density and grain size distribution, whereas chemical observations are based on major and trace element analysis. Results indicate that visually determined pedolith thickness and the transition from the B to C horizons generally correlate with maximums in the 500 and 1000 MHz GPR envelope profiles. To a lesser degree, these maximums in the GPR envelope profiles agree with maximums in weathering-related indices such as the chemical index of alteration (CIA) and the chemical index of mass transfer (τ) for Na. Finally, we find that upscaling from the pedon to hillslope scale is possible with geophysical methods for certain pedon properties. Taken together, these findings suggest that the GPR profiles down hillslopes can be used to infer lateral thickness variations in pedolith horizons in different ecologic and climate settings, and to some degree the physical and chemical variations with depth.

Effect of rock uplift and Milankovitch timescale variations in precipitation and vegetation cover on catchment erosion rates

“…As the study areas exhibit similar granitoid lithology, the erosional parameters (Table A1) are kept uniform for both the study areas. However, parameters based on climate conditions, namely soil production rate (Schaller et al, 2018), MAP, and vegetation cover (Schmid et al, 2018) The porosity (0.2) used in this study is lower than the usual range for soil (0.3-0.4), as sediment produced as a result of weathering in the study areas is a mixture of fine-and coarse-grained regolith (Schaller et al, 2020). Manning's numbers for bare soil and reference vegetation cover are the same as used by Schmid et al (2018).…”

Effects of seasonal variations in vegetation and precipitation on catchment erosion rates along a climate and ecological gradient: insights from numerical modeling

“…Together, these study areas span ∼ 1300 km of the Coastal Cordillera. These study areas are chosen for their steep climate and ecological gradient from north (arid environment with small to no shrubs) to south (humid-temperate environment with evergreen mixed forests) (Schaller et al, 2020). The study areas are part of the German-Chilean priority research program EarthShape (https://www.earthshape.…”

Effects of seasonal variations in vegetation and precipitation on catchment erosion rates along a climate and ecological gradient: Insights from numerical modelling

“…Together, these study areas span ~1,300 km distance of the Coastal Cordillera. These study areas are chosen for their steep climate and ecological gradient from North (arid environment with small shrubs) to South (humid temperate environment with evergreen mixed forests) (Schaller et al, 2020). The study areas are part of the German-Chilean priority research program EarthShape (www.earthshape.net) and ongoing research efforts within these catchments.…”