HALOKINESIS IN THE JURASSIC OF THE SOUTHE AST BASIN (FRANCE) - EVIDENCE FOR A THERMAL ANOMALY IN THE DEEP TRIASSIC ROCKS

In the SE basin, a first major halokinesis of Triassic formations at C allovo-Oxfordian times along basement faults is synchronous with the t rapping of dense fluids at minimum P-T conditions of similar to 260 de grees-400 degrees C and similar to 1.8 kbar (Edon et al., 1994). Maxim um conductive temperatures were modelled in the sedimentary pile at th e Upper Callovian before halokinesis. Calculations show that pressures similar to 1.8 kbar were reached at the base of the collapsed Triassi c rocks for a value of the offset similar to the present one. Temperat ures, however, are always lower than the minimum values given by fluid inclusions. The existence of a convective thermal anomaly in the deep Triassic rocks at this time is demonstrated. Part of the carbonic com ponent in the diapiric fluids, injected from below along basement faul ts, could have caused heat transfer, and favoured the abrupt salt upli ft.