A strong total count radiometric anomaly (to 10 x background) was encountered on the western shoreline of Lake Torrens, about 20 miles south-east of Andamooka, during the course of reconnaissance aerial radiometric surveying. Detailed tests to identify the cause of the anomaly have indicated that the type of radioactivity detected is due to short-lived radon 222 produced from radium 226, this latter, longer-lived radionuclide evidently now being trapped within a lakeside ferruginous crust overlying polygonally jointed, flat-lying quartzite bedrock. The water-soluble radium has presumably been tranported to the current site over some time, and therefore may lie well distant from its point of origin as a decay product of a parent primary or secondary uranium deposit. Exploratory drilling is planned over the area of maximum radioactivity.