ASSUMPTIONS AND OBSERVATIONS IN TECTONIC MODELING OF RIFT BASINS - SOME IMPLICATIONS OF THERMO-ISOSTASY, STRESS AND RHEOLOGY FOR INTRABASINAL STRUCTURE

There has been a multitude of studies showing to what extent alteratio ns in fundamental tectonic assumptions and/or modelling parameters can affect predictions on how extensional sedimentary basins evolve. Howe ver, that little is known about how mantle processes initiate lithosph eric rifting/extension and affect basin evolution limits the extent to which improvements in tectonic modelling assumptions and parameter re solution can lead to a better understanding of intrabasinal or reservo ir development processes. The tectonic heat budget appears to be const rained by empirical means (with the aid of kinematic models) without t he necessity of a thorough understanding of the dynamic processes invo lved in basin formation. Nevertheless, the thermal coupling of tectoni c model with intrabasinal development is sensitive to the choice of se diment thermal conductivities, An important, but often neglected, tect onic modelling 'parameter' to resolve is when the state of stress chan ges through time as a result of the interaction of all the known and u nknown tectonic processes actively affecting the basin-lithosphere sys tem. The occurrence of (geologically) short-lived episodes of rapid ba sin subsidence may be a response to a change in the tectonic setting, regardless of the relative sense of change of the ambient stress field . Recent theoretical studies suggest the same may be true for the evol ution of salt diapirs. (C) 1996 Elsevier Science Ltd.