TARGET: Possible sedimentary uranium, leached from crystalline rocks of the Musgrave Block and concentrated in sediments of the Eromanga Basin, in settings associated with the basal Mesozoic unconformity. EXPLORATION: 1:80 000 scale photogeological mapping was followed by rotary mud drilling of 52 open vertical holes totalling 5522 m, wireline geophysical logging with SP, resistivity and gamma ray tools, and geochemical assaying of 13 drill cuttings samples for Cu, U, Se and V. As part of a hydrochemical survey, 7 groundwater samples were analysed for uranium, radon-222, radium-226, bicarbonates, sulphates, total dissolved solids, and chemical oxygen demand. RESULTS: Drilling down to the Jurassic-Proterozoic unconformity revealed two palaeovalleys trending NNE and separated by a basement ridge. These valleys are filled with Upper Jurassic fluviatile sediments and lower Cretaceous marine clays, which unconformably overly folded ?Adelaidean or ?Cambrian siltstones. The Jurassic sediments are interbedded, carbonaceous and pyritic sandstones and clays, overlying a very pyritic quartz pebble basal conglomerate. In places these reduced sediments show abnormal radioactivity, with kicks recorded on logs from holes AL21 to AL56: the strongest gamma ray log anomaly, recorded over a 0.76 m thick interval in drillhole AL50, was equivalent to 195 ppm U308.