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doi:10.2204/iodp.proc.307.203.2009

In situ temperature measurements and thermal conductivities

In situ temperature measurements obtained during Expedition 307 were made with the Adara advanced piston corer temperature tool (APCT) (Blum, 1997). The APCT fits into the cutting shoe of the advanced piston corer and can therefore be used to measure sediment temperatures during regular piston coring. The tool consists of a platinum resistance-temperature device calibrated over a temperature range of 0°–30°C. After penetration, the sensor records a pulse of frictional heating, which decays while the tool remains in the formation for 10–15 min. Sampling rates of 5 s per measurement were used during Expedition 307. The extrapolation of the frictional heating pulse to equilibrium temperature generally accounts for the nominal accuracy of 0.1°C. However, overall uncertainty may be much larger if the probe does not remain stationary during the measurement period.

Thermal conductivity was measured in intervals where downhole temperature measurements were taken, using whole-round cores and the needle probe method in full-space configuration during Expedition 307. On board the R/V JOIDES Resolution, the Teka TK04 measurement system is used, which employs a transient linear source method with a needle probe that is inserted into the soft sediment (Von Herzen and Maxwell, 1959). The TK04 uses an automated routine to find the conductivity by least-squares fitting to the measured temperature-time series, with an accuracy of 5% and a precision of 5%.

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