The heat.flow/basement depth relation, which favors the simple thermal boundary layer model, will be tested to determine if it actually is applicable to older oceanic areas. To document this, heat flow will be documented in the Late Jurassic ocean floor of western Gulf of Mexico using both heat.flow measurements acquired during a proposed R/V Gyre cruise and also analyzing the radioactivity of DSDP 90 and 91 sites to determine the effect of radiogenic heat from 10 km of sediments on the surface heat flux. Seismic refraction and reflection data will be used to compute the water.loaded basement and the possible effect of thinner.than.normal crust on this depth.
