Geothermal properties at DSDP Hole 90-587 and Site 90-588

A new WHOI heat flow instrument was successfully used in conjunction with the hydraulic piston corer to obtain temperature-time records for three depths at DSDP Site 587. In order to arrive at an estimate for in situ, steady-state temperature, these data are applied to a two-dimensional theoretical formulation that describes the cooling behaviour of an annular cylinder surrounded by sediment. An average heat flow of 56.9 mW/m**2 is computed from the resulting temperature profile. This value is in close agreement with the theoretical heat flux of 53.0 mW/m**2 determined from the general heat flow-age relationship. The temperature profile at Site 587 is nonlinear. Examination of the effects of sudden changes in bottom water temperature and upward movement of pore fluid fails to provide convincing solutions to the cause of this nonlinearity. Knowing sediment permeability and extending the theoretical data analysis to three dimensions would improve our ability to understand the geothermal environment at this location.