83 open rotary reconnaissance holes totalling 3577.5 m, and 1 PQ diamond corehole to 45.5 m depth, were drilled 85 km west of Tarcoola, to investigate if sedimentary uranium deposits occur buried there in association with fluvial Tertiary palaeochannels incised into Proterozoic and Archaean basement. Minor, patchy radiometric anomalies were found within the north-south running Wynbring Palaeochannel and its tributaries, occurring at the base of the near-surface oxidation zone, mostly in lignitic paludal clays (best result 2060 cps in hole TW108, corresponding to an estimated grade of 0.1% U3O8 over a 0.4 m interval). The main palaeochannel was shown to have a width of 1.4 to 3 km, and to have cut down as much as 74 m into the basement. However, the radiometric anomalies occur at shallow depths (generally less than 20 m), at or near the top of the carbonaceous part of the channel fill sequence, and coinciding with the contemporary water table. Analysis of the drillhole cuttings samples for uranium and thorium have demonstrated that the palaeochannel sediments' U content does not relate directly with their radiometric log response, since the logged radiometric peaks vary in magnitude for sediment intervals having similar assay values. The peaks' locations coincide with high U values, though, indicating a limited separation of radioactive daughter elements. Radioactivity in Precambrian basement source rocks sampled in outcrop at 12 sites was found to be due to higher Th content.