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Abstract
Observing the subsurface architecture of the deep Critical Zone (CZ), which lies beyond the uppermost layer of accessible soil, is a complex but crucial task. Near-surface geophysics offers an alternative to accessing the deep CZ at scales relevant to fluid, nutrient and gas transport. As geophysical instruments are sensitive to different subsurface physical properties, their combination can enhance insight into CZ architecture. However, the agreement between and complementarity of multiple geophysical techniques has not been widely assessed for CZ-related questions. This study employed geophysics to image a highly weathered lateritic hill rich in iron oxides developed from Archean granite within the Avon River Critical Zone Observatory, Western Australia. Data gathered from an electrical resistivity tomography (ERT) and horizontal-to-vertical-spectral-ratio (HVSR) passive seismic transect were used to visualise CZ architecture through specific resistivity values and ambient noise contrasts. Both techniques revealed a notable degree of lateral variability consistent with the formation of the ~3–4 m thick duricrust-capped hilltop, the creation of gullies in the sodic material of the pallid zone exposed along the slope and the deposition of ~11 m thick colluvial sediment at the foot slope. Calculated bedrock depth was consistent between the HVSR and ERT instruments along the hilltop plateau but varied from ~23 m to 31 m on the slope and 32 m to 39 m at the foot slope, respectively. Overall, the vertical variation depicted by the ERT, including the differentiation of two layers within the lateritic weathering profile - the pallid zone and saprolite – made up for the inaccuracy of the HVSR technique in depicting layers of similar composition. Moreover, the HVSR method clearly depicted bedrock depth, overcoming the partial masking of the bedrock by saline groundwater in the ERT model. The complementarity of these two methods allowed the development of a detailed conceptual model of subsurface CZ architecture within a saline lateritic weathering profile.
Original language | English |
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Pages (from-to) | 5186-5201 |
Number of pages | 16 |
Journal | Earth Surface Processes and Landforms |
Volume | 49 |
Issue number | 15 |
Early online date | 19 Nov 2024 |
DOIs | |
Publication status | Published - Dec 2024 |
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Dive into the research topics of 'Combining electrical resistivity tomography and passive seismic to characterise the subsurface architecture of a deeply weathered lateritic hill within the Avon River critical zone observatory'. Together they form a unique fingerprint.Projects
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Founding an Australian Critical Zone Observatory Network
Thompson, S. (Investigator 01), Leopold, M. (Investigator 02), Beringer, J. (Investigator 03), De Kauwe, M. (Investigator 04), Andersen, M. (Investigator 05), Chittleborough, D. (Investigator 06), Farkas, J. (Investigator 07), Meyer, W. (Investigator 08), Marshall, A. (Investigator 09) & Cleverly, J. (Investigator 10)
ARC Australian Research Council
1/03/21 → 28/02/25
Project: Research