A WSTP tool was deployed to collect in-situ temperature data at 122.4, 170.6, and 218.7 mbsf in Hole 900A (WSTP depth is based on the depth of the bottom of the previous cored interval). The general shape of the temperature vs. time curves for each deployment suggests that the tools were inserted in a single movement and were stationary during the measurements. The individual temperature measurements showed much more scatter about the typical cooling curve than is usual (Fig. 48B, Fig. 49, Fig. 50B). We suspect that this was a problem with the tool, but do not think that it renders the measurements invalid.
Analyses of the WSTP measurements at 122.4 mbsf, obtained immediately prior to Core 149-900A-15R, yielded a bottom-water temperature of 3.8 ± 0.1°C and an in-situ temperature of 10.2 ± 0.1°C (Fig. 48). The bottom-water temperature was obtained by averaging temperature readings between 2400 and 2900 s, when the tool had stopped just above the seafloor. The in-situ temperature was estimated by using 3171 s as the insertion time and by modeling the temperature decay over the interval from 3202 to 3770 s.
Analyses of the WSTP measurements at 170.6 mbsf, obtained immediately prior to Core 149-900A-20R, yielded a bottom-water temperature of 3.8 ± 0.1°C and an in-situ temperature of 12.2 ± 0.1°C (Fig. 49). The bottom-water temperature was obtained by averaging temperature readings between 2000 and 2200 s, when the tool had stopped just above the seafloor. The in-situ temperature was estimated by using 3250 s as the insertion time and by modeling the temperature decay over the interval from 3281 to 4150 s.
Analyses of the WSTP measurements at 218.7 mbsf, obtained immediately prior to Core 149-900A-25R, yielded a bottom-water temperature of 3.8 ± 0.1°C and an in-situ temperature of 14.4 ± 0.1°C (Fig. 50). The bottom-water temperature was obtained by averaging temperature readings between 2200 and 2400 s, when the tool had stopped just above the seafloor. The in-situ temperature was estimated by using 3198 s as the insertion time and by modeling the temperature decay over the interval from 3289 to 4023 s.
The slope of a linear least-squares fit of the temperature to depth (Table 18) yields an estimate of 49 ± 3 mK/m (95% confidence level) for the temperature gradient in the upper 218 mbsf at Site 900. The slope of a linear least-squares fit of the temperature to vertically integrated thermal resistivity (Table 18), yields an estimate of 59 ± 8 mW/m2 (95% confidence level) for the heat flow (see "Explanatory Notes" chapter, this volume).