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Until recently very little in situ stress data have been available from the UK

Thermal conductivity measurements were carried out on over 400 samples from Tertiary and Cretaceous sediments and Jurassic basalts during Ocean Drilling Program Leg 123 in the Argo Abyssal Plain, North West Australia. Ship-board physical property measurements were obtained from cores over the same intervals, and petrophysical wireline logs were run. New algorithms are demonstrated relating thermal conductivity to matrix grain type and porosity, derived only from wireline log data. Comparison with heat flows calculated using high-resolution temperature measurements at Site 765 suggest that thermal conductivities predicted from wireline logs can be used to estimate heat flow. This implies that existing exploration and production wells in which high resolution temperature measurements and thermal conductivities have not been measured could still be used to prepare regional maps of heat flow variation.

StepwiseThe principal advantage of the 40Ar/39Ar dating method lies in the stepwise degassing technique. Despite the widespread use of the technique, each worker seems to adopt an individual criterion of choice, as to how the data should be treated, so as to extract the maximum amount of information from it.It was considered desirable to make a detailed analysis of the data taken during a number of stepwise degassing experiments to decide upon the most useful treatment of results.The basic principles of the technique are reviewed, and a method of data analysis is presented, which enables a detailed study of the argon liberation characteristics of the sample to be made. It also allows the age of the sample to be determined, such that no direct correction is made for atmospheric contaminant 40Ar. This avoids the fundamental assumption that all "Ar, used to make this correction, is of atmospheric origin. * Present address: Water Resources Board, Reading Bridge House, Reading RG1 8PS t Received in original form 1971 August 2 449 1 450 N. Robin Brereton 2. The behaviour of argon in a mineral