NUMERICAL AND HYDROGEOPHYSICAL MODEL OF MOUNT TOONDINA IMPACT CRATER, SOUTH AUSTRALIA

Mount Toondina, located on the Great Artesian Basin (GAB), South Australia, is a meteorite impact crater which contains several current and former groundwater discharge features. Aerial photographs and field survey data indicate that water was flowing from several springs as recent as twenty years ago. A key feature of the site is the ring of freshwater vegetation that is surrounded by a saline gibber plain on the outer areas of the ring and a tufa salt flat in the interior. Geophysical site surveys include resistivity, gravity and seismic data used to constrain a hydrogeophysical model for the site. Fluid chemistry and geological mapping was used along with the geophysical data to constrain FEFLOW models to test hydrogeological conceptual models of the permeability structure of Mount Toondina. The numerical results suggest that the spring system is controlled by advective flow from the subsurface artesian aquifer to the ring of vegetation around the perimeter of the impact structure. Additionally, the numerical results suggest that flow is influenced by free convective processes. The field data and FEFLOW model results will be used to better manage flora and fauna in the Mount Toondina area and to provide insight about groundwater flow on other impact craters.