ABSTRACT

We characterize heat flux through two diapiric salt features in deep (> 1080 m) water on the Texas continental slope. Sediment stratigraphy and salt top morphology, delineated by a previous single channel seismic reflection survey (Beckley and Behrens, this volume), provide inferences on the two salt structures; one is a cylindrical stock about 5 km in diameter and the other is a sub-circular salt tongue about 10 km in diameter. 74 heat flow measurements show large-scaled, positive anomalies (factor of two to three relative to the values off salt of 32 mW/m2) over the two features. Variation of the heat flow coincides with the thickness variation of the salt that is inferred from the seismic records. We believe that these anomalies mainly reflect the high thermal conductivity of the salt and give major constraints on geometry of the salt bodies. Our three-dimensional, steady state thermal model provides estimates on the feeder depths of the two salt features. Analyses are also made on the secondary thermal effects such as (1) differential sedimentation, (2) salt movement, and (3) unknown fluid migration. (1) and (2) based on the seismic stratigraphy suggest that these effects alone can produce a significant positive anomaly (probably 20%) and should be reflected in thermal modeling. The episodic nature of (3) does not seem to produce persistent, large-scaled thermal anomalies.