Unsuccessful exploration in the central Polda Trough region for possible potash deposits formed within pre-Permian red beds has involved the drilling of a 1398 m deep exploratory/stratigraphic hole (Kilroo 1/83KD1A) plus the acquisition of a limited extent gravity survey (along 4 north-south traverses totalling 110 line km) to investigate the structure of the [informally named] Colton sub-basin. Interpretation of the gravity data showed a narrow east-west trending trough lying just south of Mount Wedge, with its steep southern margin marked by a single fault or zone of faulting. The depth to top of crystalline basement within this part of the trough was calculated as being around 2.5 km, but a scarcity of density petrophysical data for its contained Jurassic and Palaeozoic sediments, and the fact that such basement is probably granitic, made this result seem doubtful.