The ADARA tool was deployed to collect in-situ temperature data at 113.7 mbsf in Hole 898A (ADARA depth is based on the sub-bottom depth of the bottom of the APC core barrel). The WSTP tool was deployed to collect in-situ temperature data at 177.4 and 225.6 mbsf in Hole 898A (WSTP depth is based on the sub-bottom depth of the bottom of the previous core barrel). We did not use the WSTP measurement at 225.6 mbsf because after insertion of the tool the temperature profile did not show a normal decay toward equilibrium. This suggests that the tool was moved after insertion.
Interpretation of data from the ADARA tool deployed at 113.7 mbsf yielded a bottom-water temperature of 2.0° ±0.1°C and an in-situ temperature of 6.8° ±0.1°C (error estimates for bottom-water and in-situ temperatures are informed guesses; Fig. 31). We estimated the bottom-water temperature by averaging the observed temperature between 2100 and 2900 s, when the tool was stopped just above the seafloor. The in-situ temperature was extrapolated by using 3465 s as the insertion time and by modeling the data over the interval from 3560 to 4240 s.
Analyses of the WSTP measurements at 177.4 mbsf yielded a bottom-water temperature of 3.7° ±0.1°C (we address the inconsistent bottom-water temperatures below) and an in-situ temperature of 10.9° ±0.1°C (Fig. 32). The bottom-water temperature was obtained by averaging temperature readings between 1950 and 2100 s, when the tool was stopped just above the seafloor. The in-situ temperature was extrapolated by using 3643 s as the insertion time and by modeling the data over the interval from 3661 to 3905 s. The shape of the temperature data curve suggests that the tool was inserted cleanly and also that the tool was stationary during the measurement.
The two measurements yield different estimates of bottom-water temperature. We attribute this difference to a calibration problem in the ADARA instrument. Temperature differences recorded by this instrument are likely to be more accurate than each absolute temperature. We corrected for this difference by shifting the bottom-water and in-situ temperatures recorded by the ADARA by an amount that brings the two bottom-water temperature measurements into agreement. In Table 14, therefore, we have increased the ADARA in-situ measurement by 1.7°C. This shift makes the in-situ temperature at 113.7 mbsf, 8.5° ± 0.1°C. When the ADARA instrument number 11 is next recalibrated it may be possible to improve these estimates.
The slope of a linear least-squares fit of the temperature to depth (Table 14) yields an estimate of 41 ±2 mK/m (95% confidence level) for the temperature gradient in the upper 177 mbsf at Site 898. The slope of a linear least-squares fit of the temperature to vertically integrated thermal resistivity (Table 14) yields an estimate of 61 ±2 mW/m2 (95% confidence level) for the heat flow (see "Explanatory Notes" chapter, this volume).