Gamma ray spectrometric techniques have been used for the determination of uranium, thorium and potassium contents from cores selected at 3 to 4 m intervals from a 600 m deep borehole in sedimentary formations and the results compared with a similarly detailed examination of heat flow, and some physical properties, from the same borehole.The results indicate a broad positive correlation between thermal resistivity and some of the radio-element parameters and between heat flow and heat production. The heat production variations down the borehole are not quantitatively sufficient to explain the observed heat flow variations. The uranium series appears to be in radioactive equilibrium even in those sections where the uranium content is low, the porosity relatively high and the heat flow low; it is therefore concluded that the depletion of uranium is due to an ancient rather than a recent leaching process and that it is unlikely that the heat flow variations along the borehole are due to existing or recent underground waterflows. Long term geochemical reactions are now thought to be the most likely explanation of the heat flow variations.

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