Of Sites 1110 through 1113, temperature measurements were made only at Site 1111. An open-hole temperature measurement was made within Hole 1111A using the Davis-Villinger Temperature Probe (DVTP) lowered on the wireline. The probe was held within the open hole at 91 mbsf for 20 min. In situ formation temperature measurements were obtained before taking Cores 180-1111A-13X and 15X using the DVTP at probe-tip depths of 117.2 and 136.5 mbsf, respectively. The measured mudline temperature was 2.4ºC.
For the open-hole measurement at 91 mbsf, downhole equilibrium temperature was approximated by plotting temperature as a function of ln[t/(t-s)], where t is the total time elapsed since the drill bit penetrated that depth, and s is the total time elapsed between the initial penetration and the cessation of circulation (Fig. F30). The line was then extrapolated to infinite time (where ln[t/(t-s)] = 0). Equilibrium formation temperatures for the in situ measurements were estimated using the CONEFIT program (see "Explanatory Notes" chapter). These estimates of equilibrium temperature used thermal conductivity of 0.9 W·m-1·ºC-1, based on the available core data (see "Physical Properties").
Resulting estimated temperatures are shown on Figure F31. Near-seafloor temperatures (4.0º and 2.8ºC) were estimated at 94 and 117.2 mbsf, indicating movement of bottom water into the formation. It was not possible to verify whether bottom-water invasion was drilling induced or naturally occurring. Naturally occurring fluid flow requires a high permeability conduit to the seafloor, and it would need to be very recent for the high temperature difference (12.5ºC) between 117.2 and 136.5 mbsf to be preserved. Calculations using one-dimensional thermal transport suggest that thermal conduction would significantly reduce this gradient in less than 100 yr.
With the assumption that the low temperatures at 94 and 117.2 mbsf are transient anomalies, we estimated the large-scale thermal gradient for Hole 1111A based on mudline temperature and the temperature at 136.5 mbsf (Fig. F31). The resulting thermal gradient is 0.095ºC·m-1 (95ºC·km-1), similar to that at Site 1108. The computed heat flow is 86 mW·m-2, using the measured thermal conductivity of 0.9 W·m-1·ºC-1.