Abstract

The mechanical history of a small extensional basin is closely linked to the thermal evolution of the lithosphere. An assumption about one (either the mechanical or the thermal history) will restrict the conclusions reached regarding the other. In this study, the relationship between these two primary controls on extensional basin behaviour is evaluated to demonstrate the need for constraints on forward models of basin evolution. The sensitivity of forward models to variations in two-dimensional conductive heat transfer, effective flexural rigidity, extension (β) factor, and lateral extent of stretching and sedimentation on the resulting geometry, subsidence history, and basin heat flux is assessed. Our results indicate that the amount and distribution of crustal extension cannot be inferred from the final basin geometry. The variability in mechanical response possible for most basin environments allows the development of indistinguishable basin geometries and subsidence histories from quite different original extension patterns. Therefore, basin geometry and subsidence history will not uniquely determine the stretching and thermal history of a particular basin.

Although the nature of the mechanical response of the lithosphere (local or regional compensation, elastic or viscous behaviour) normally must be assumed, the thermal history and crustal structure can be partially constrained by using existing techniques. Examination of basin sediments can also help to constrain the timing of initial subsidence and changes in basin geometry through time.