Comparison of regolith physical and chemical characteristics with geophysical data along a climate and ecological gradient, Chilean Coastal Cordillera (26 to 38° S)
2020
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.
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