Oodjuongari – A possible impact crater in the Beetaloo Sub-basin

The Oodjuongari Structure (-16.636, 134.205), seen on aeromagnetic data as a circular feature (Figures 2, 3a and 5), and traversed by four 2D seismic reflection profiles (Figures 6 and 7), is interpreted as a possible impact crater concealed by superficial Cainozoic strata. There is no surface expression of the structure which is located within the Beetaloo Sub-basin and overlying Georgina Basin, although small streams appear to deviate around the feature (Figure 3b). The structure appears to be circular on the aeromagnetic data and has a maximum diameter of 5 km. It has similar size and aeromagnetic signature to the Foelsche impact structure located 275 km to the east (Haines & Rawlings, 2002). In both cases the pronounced circular aeromagnetic feature appears to be related to a circular disruption of flat-lying mafic volcanics, which are the Mid-Cambrian Antrim Plateau Volcanics at Oodjuongari. If the Oodjuongari Structure is an impact structure, the 5 km diameter would be consistent with a complex crater with a central uplift.