<p>This study presents a hydrogeological framework for subsurface aquifers in the Horn River Basin (HRB), Canada, providing critical insights for water resource management related to regional shale gas development. We analyzed airborne transient electromagnetic (ATEM) data from ten profiles using a quasi-2D laterally constrained inversion (LCI) to model subsurface electrical resistivity patterns. The results consistently identify an extensive, highly conductive layer (0–10 Ω·m), which is interpreted as a weathered and fractured portion of the Cretaceous Buckinghorse Formation. The high conductivity is attributed to the combined effects of the formation’s clay-rich lithology and, critically, high porewater salinity. This interpretation of a saline, non-potable shallow aquifer system is strongly supported by a convergence of evidence, including the shale’s marine origin, consistency with regional hydrogeochemical data, and a pronounced resistivity contrast with overlying units. This conductive layer is typically situated between a surficial layer of intermediate-resistivity glacial till and an underlying, similarly resistive layer of unweathered Cretaceous bedrock. Significant variations in the depth, thickness, and surface exposure of the conductive layer were observed across the profiles. These are interpreted as the result of a complex interplay between Cenozoic tectonic uplift, subsequent glacial and deltaic erosion, and depositional history. Areas of surface exposure, particularly in deltaic settings, indicate a higher potential for groundwater-surface water interaction and also highlight potential geotechnical risks associated with the weathered, clay-rich shale. This study demonstrates the utility of ATEM and LCI in unraveling complex hydrogeological systems and provides an essential, data-driven model for sustainable resource management in the HRB.</p>