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Downhole measurements

Heat flow

Five APCT-3 downhole temperature measurements in Hole U1334B ranged from 2.82°C at 32.2 m to 5.09°C at 106.2 m (Table T33), giving a geothermal gradient of 33.0°C/km (Fig. F36). The bottom water temperature was 1.457°C, based on the average of the minimum temperature in the five APCT-3 temperature profiles. Thermal conductivity under in situ conditions was estimated from laboratory-determined thermal conductivity using the method of Hyndman et al. (1974) (see "Physical properties" in the "Methods" chapter). The calculated in situ values are up to 2.2% below the measured laboratory values. Thermal resistance was then calculated by cumulatively adding the inverse of the in situ thermal conductivity values over depth intervals downhole (Fig. F36). A heat flow of 31.6 mW/m2 was obtained from the linear fit between temperature and thermal resistance (Fig. F36) (Pribnow et al., 2000), which is an intermediate value compared to nearby sites in the global heatflow database.