- Ti
= To
+ Q
(dZ / k) = To
+ {Q 
i
2 [(Zi+1
- Zi)
/ (ki+1
- ki)]}
/ 1000,
Temperature measurements were taken at two Prydz Bay drill sites (Sites 1165 and 1167) to determine the downhole and areal variation in heat flow and thermal gradient. The discrete measurements were made with the temperature tool, which is located in the coring shoe of the APC, during piston-coring operations. The components include a platinum temperature sensor and a data logger. The platinum resistance temperature device is calibrated for temperatures ranging from -20° to 100°C, with a resolution of 0.01°C. In operation, the adapted coring shoe is mounted on a regular APC barrel and lowered down the pipe by wireline. The tool is typically held for 5-10 min in the mudline to equilibrate with bottom-water temperatures and then lowered to the bottom of the drill string. Standard APC techniques are used, with the core barrel being fired into the sediment using hydraulic pressure. The Adara temperature tool (and APC barrel) remains in the sediment for 10-15 min to obtain a temperature record. This provides a sufficiently long transient record for extrapolation to a steady-state temperature. The nominal accuracy of the temperature measurement is ~0.1°C.
These temperature data were then combined with the measured thermal conductivity data from the core samples (see "Physical Properties") to calculate the heat flow and thermal gradients at each site. Assuming a predominantly conductive thermal regime, the heat flow can be determined by plotting the measured temperature vs. thermal resistance of the sedimentary section (Langseth and Takami, 1992). Fourier's Law for one-dimensional vertical heat conduction can be expressed by
where Q = heat flow (mW/m2), k = thermal conductivity (W/[m·°C]), and (dT / dZ) is the thermal gradient (°C/km). If a steady-state system is assumed and Q is constant with depth, then Q can be combined with measured conductivity to give an expression of temperature variation with depth over the entire intersected sedimentary section:
(dZ / k) = To
+ {Q i
2 [(Zi+1
- Zi)
/ (ki+1
- ki)]}
/ 1000,
where Ti = the temperature (°C) at depth Zi (m), To = seafloor temperature, and ki = the discrete measured thermal conductivity (W/[m·°C]).
