Groundwater Exploration Using AEM in Structurally Complex, Inverted Sedimentary Basins and Paleovalleys, Kimberley Regio

Abstract

Summary Airborne electromagnetics (AEM) has successfully mapped and characterised groundwater systems in a range of landscapes and geological settings in the East Kimberley Region of north-western Australia. The AEM data enabled rapid imaging of key elements of hydrogeological systems in near-surface Cenozoic paleovalley, alluvial fan and colluvial sediments, and in underlying tectonically-inverted sedimentary basins. Rapid mapping and assessment of groundwater systems, MAR targets and salinity hazards involved the integration of AEM data with Ground Magnetic Resonance (GMR), seismic reflection, drilling and pump tests, borehole geophysics, soils, regolith, geological and structural mapping, and hydrogeological and hydrochemical investigations. AEM survey design was aided by the use of spatio-temporal analysis of Landsat data to identify areas of potential surface-groundwater interaction. A suite of equivalent 1D AEM inversion models produced comparable images of the sub-surface hydrostratigraphy and faults. However, 2.5D inversions produced different solutions in key locations. 3D inversions were subsequently performed, and drilling and tectonic analysis was used to assess all AEM inversion models. Recognising zones of structural complexity was important in the successful development of appropriate AEM inversion strategies and models. Overall, the success of groundwater system mapping has been due to the use of AEM within a broader, inter-disciplinary, multi-physics project framework.