DATE: Thursday 16 October 1990 at 5.15 pm VENUE: Rugby Club, Crane Place, Sydney SPEAKER: Professor W. K. Fletcher, Department of Geological Sciences, University of British Columbia. TOPIC: "Interpretation of Exploration Geochemical Data: Background and Threshold." Professor Fletcher is undertaking a Distinguished Lecture Series under the auspices of the Association of Exploration Geochemists. He will be discussing the concept of threshold values as applied to exploration geochemical surveys. In addition to statistical evaluation, Professor Fletcher will consider the practical undertaking of soil and sediment surveys with respect to the media sampled, observations and data manipulation required to successfully discriminate between background and anomalous concentrations.