Six downhole tools were employed at Site 1227: the Adara temperature shoe, the DVTP, the DVTP-P, the WSTP, the APC-M, and the PCS. The results of the temperature and pressure measurements at Site 1227 are described in the first two sections below. Results of other tools are briefly mentioned in the last section.
Five determinations of temperature were made at Site 1227 using the Adara APC temperature tool, the DVTP, and the WSTP. All three of the downhole temperature records were either of poor quality or deviated from the values expected from the Leg 112, Site 684 data. Table T8 summarizes the deployments and the observed problems. Figure F22 shows the data from the two DVTP deployments at 81.6 and 110.1 mbsf. Both records show considerable small-scale oscillations and double peaks when the tool is first pushed into the sediments. The record from 81.6 mbsf (after Core 201-1227A-9H) lasts for only 5 min before the temperature jumps up and again decays for the remainder of the 10-min deployment. The record for the lower thermistor from 110.1 mbsf (after Core 201-1227A-12H) is too noisy to be fit and provides only an upper bound on in situ temperature.
The results of the DVTP temperature estimates are displayed in Figure F22. In situ temperatures were estimated by extrapolation of the station data using thermal conductivities measured on adjacent cores to correct for the frictional heating on penetration as described in "Downhole Tools" in the "Explanatory Notes" chapter. Because of the overall poor quality of the Site 1227 downhole temperature data, the results from Site 684 are given in the summary table and were included in the thermal gradient estimate.
The combined in situ temperatures of Sites 1227 and 684 define a gradient of 0.0492°C/m in the upper 110 m of the sediment column (Fig. F23). Extrapolating the temperatures using this gradient yields a value of 16.4°C at the bottom of Hole 1227A (160 mbsf). Multiplying the gradient by an average thermal conductivity of 0.76 W/(m·K) (Fig. F20A) yields a conductive heat flow estimate of 37.3 mW/m2 at Site 1227. This result is slightly higher than the value of 31 mW/m2 obtained for Site 684 by the Leg 112 Shipboard Scientific Party (1988).
Comparing lithology from locations that produced good and bad temperature decay profiles showed some differences that may be used to optimize future DVTP deployments. The better DVTP deployment at 81.6 mbsf occurred between cores composed of clay and nannofossil-bearing diatom ooze (Cores 201-1227A-9H and 10H). These fine-grained sediments are similar to those from Site 1225 and 1226, where the acquired temperature data were excellent. In contrast, the second deployment location at 100.1 mbsf occurred between cores of pyrite and diatom-rich silty clays with sand-sized particles (Cores 201-1227A-12H and 13H). These sediments were significantly more coarse grained than those cored from above and below the better deployment (see "Density and Porosity" in "Physical Properties"). Accumulation of gravel in the base of the hole does not appear to differ between the two deployments. Both locations had ~40 cm of gravel at the top of the subsequent core. Another aspect of Site 1227 that may be important is the shallow 423-m water depth compared to >3000 m at Sites 1225 and 1226. The increased noise in the data may be due to the greater influence of heave or currents on the tool in shallow water. It appears that for deployments in shallow water the best strategy may be to choose fine-grained intervals for the deployments.
The DVTP-P was deployed once at Site 1227 at a depth of 132 mbsf (after Core 201-1227A-14H). The record displayed in Figure F24 shows a relatively noise-free signal with the expected sharp pressure increase when the tool was pushed into the sediments. Within 2 min, the pressure dropped to the value initially recorded at the base of the hole. A pressure signal equivalent to in situ hydrostatic pressure with relatively little noise was recorded during the remainder of the 30-min deployment. The rapid return to hydrostatic pressure suggests that the sealing of the formation around the tool was poor. The abrupt drop in pressure for one data value after 40 s is probably due to suction when the tool is pulled upward by heave of the drill string.
A sample of bottom water was collected with the WSTP at 10 m above the seafloor. Quality assessed using a lithium tracer indicated only 4% dilution of the bottom-water sample by the water in the sampling tube. The APC-M tool was deployed in Hole 1227A continuously from Cores 201-1227A-4H through 5H and in Hole 1227D continuously from Cores 201-1227D-1H through 7H. The recovered data from this run showed that the tool and data logger functioned correctly. The data from the APC-M tool will be analyzed postcruise.
Both the PCS and FPC tools were deployed between 128 and 132 mbsf, but neither run was successful. The PCS core never closed. The FPC tool only recovered a handful of pebbles and shell hash.